Patent Application
20240324309
One embodiment of the present invention relates to a display apparatus. One embodiment of the present invention relates to a method for manufacturing a display apparatus.
Note that one embodiment of the present invention is not limited to the above technical field. Examples of a technical field of one embodiment of the present invention disclosed in this specification and the like include a semiconductor device, a display apparatus, a light-emitting apparatus, a power storage device, a memory device, an electronic device, a lighting device, an input device, an input/output device, a driving method thereof, and a manufacturing method thereof. A semiconductor device refers to any device that can function by utilizing semiconductor characteristics.
In recent years, higher-resolution display panels have been required. Examples of devices that require high-resolution display panels include a smartphone, a tablet terminal, and a laptop computer. Furthermore, higher resolution has been required for a stationary display apparatus such as a television device or a monitor device along with an increase in definition. An example of a device required to have the highest resolution is a device for virtual reality (VR) or augmented reality (AR).
Examples of a display apparatus that can be used for a display panel include, typically, a liquid crystal display apparatus, a light-emitting apparatus including a light-emitting element such as an organic EL (Electro Luminescence) element (also referred to as an organic EL device) or a light-emitting diode (LED), and electronic paper performing display by an electrophoretic method or the like.
For example, the basic structure of an organic EL element is a structure where a layer containing a light-emitting organic compound is interposed between a pair of electrodes. By applying voltage to this element, light emission can be obtained from the light-emitting organic compound. A display apparatus using such an organic EL element does not need a backlight that is necessary for a liquid crystal display apparatus and the like; thus, a thin, lightweight, high-contrast, and low-power display apparatus can be achieved. Patent Document 1, for example, discloses an example of a display apparatus using an organic EL element.
Patent Document 2 discloses a display apparatus using an organic EL device for VR.
In a display apparatus, in order to improve the light extraction efficiency, a structure in which light emission emitted from a light-emitting device is extracted through a microlens is employed. Patent Document 3 discloses a method for forming a microlens using a radiation-sensitive resin composition.
An object of one embodiment of the present invention is to provide a display apparatus with high display quality. An object of one embodiment of the present invention is to provide a highly reliable display apparatus. An object of one embodiment of the present invention is to provide a display apparatus that can easily achieve a higher resolution. An object of one embodiment of the present invention is to provide a display apparatus having both high display quality and a high resolution. An object of one embodiment of the present invention is to provide a display apparatus with low power consumption.
An object of one embodiment of the present invention is to provide a display apparatus having a novel structure or a method for manufacturing the display apparatus. An object of one embodiment of the present invention is to provide a method for manufacturing the above-described display apparatus with high yield. An object of one embodiment of the present invention is to alleviate at least one of problems of the conventional technique.
Note that the description of these objects does not preclude the existence of other objects. Note that one embodiment of the present invention does not have to achieve all the objects. Note that objects other than these can be derived from the description of the specification, the drawings, the claims, and the like.
One embodiment of the present invention is a display apparatus including a first pixel, a second pixel provided adjacent to the first pixel, a first insulating layer, and a second insulating layer over the first insulating layer. The first pixel includes a first pixel electrode, a first EL layer covering the first pixel electrode, a third insulating layer in contact with part of a top surface of the first EL layer, and a common electrode over the first EL layer and the third insulating layer. The second pixel includes a second pixel electrode, a second EL layer covering the second pixel electrode, a fourth insulating layer in contact with part of a top surface of the second EL layer, and the common electrode over the second EL layer and the fourth insulating layer. The first insulating layer is in contact with a top surface and a side surface of the third insulating layer, a top surface and a side surface of the fourth insulating layer, a side surface of the first EL layer, and a side surface of the second EL layer. At least part of the second insulating layer is provided to be sandwiched between an end portion of the side surface of the first EL layer and an end portion of the side surface of the second EL layer. Each of the first insulating layer, the third insulating layer, and the fourth insulating layer contains an inorganic material. The second insulating layer contains an acrylic resin, and the second insulating layer has a tapered side surface and a convex shaped top surface. A taper angle of the tapered side surface of the second insulating layer is less than 90°, and the common electrode overlaps with the second insulating layer.
Another embodiment of the present invention is a display apparatus including a first pixel, a second pixel provided adjacent to the first pixel, a first insulating layer, and a second insulating layer over the first insulating layer. The first pixel includes a first pixel electrode, a first EL layer covering the first pixel electrode, a third insulating layer in contact with part of a top surface of the first EL layer, and a common electrode over the first EL layer and the third insulating layer. The second pixel includes a second pixel electrode, a second EL layer covering the second pixel electrode, a fourth insulating layer in contact with part of a top surface of the second EL layer, and the common electrode over the second EL layer and the fourth insulating layer. The first EL layer includes a first light-emitting layer and a first functional layer over the first light-emitting layer, and the second EL layer includes a second light-emitting layer and a second functional layer over the second light-emitting layer. Each of the first functional layer and the second functional layer contains a first compound. The first compound is an organic compound having a heteroaromatic ring skeleton including one selected from a pyridine ring, a diazine ring, and a triaxine ring, and a bicarbazole skeleton or an organic compound having a condensed heteroaromatic ring skeleton including a pyridine ring or a diazine ring, and a bicarbazole skeleton. The glass transition temperature of the first compound is higher than or equal to 100° C. and lower than or equal to 180° C. The first insulating layer is in contact with a top surface and a side surface of the third insulating layer, a top surface and a side surface of the fourth insulating layer, a side surface of the first EL layer, and a side surface of the second EL layer. Each of the first insulating layer, the third insulating layer, and the fourth insulating layer contains an inorganic material. The second insulating layer contains an organic material. The second insulating layer has a tapered side surface and a convex shaped top surface in a cross-sectional view. A taper angle of the tapered side surface of the second insulating layer is less than 90°, and the common electrode overlaps with the second insulating layer.
In the above, each of the first pixel electrode and the second pixel electrode preferably has a tapered shape in a cross-sectional view of the display apparatus, and the taper angles of the tapered side surfaces of the first pixel electrode and the second pixel electrode are preferably less than 90°.
In the above, each of the first insulating layer, the third insulating layer, and the fourth insulating layer preferably contains aluminum oxide.
In the above, part of the second insulating layer preferably overlaps with the first pixel electrode and another part of the second insulating layer preferably overlaps with the second pixel electrode.
In the above, each of the top surface of the first EL layer, the top surface of the second EL layer, and the top surface of the second insulating layer preferably includes a region in contact with the common electrode.
In the above, the first pixel preferably includes a common layer provided between the first EL layer and the common electrode. The second pixel preferably includes the common layer provided between the second EL layer and the common electrode. Each of the top surface of the first EL layer, the top surface of the second EL layer, and the top surface of the second insulating layer preferably includes a region in contact with the common layer.
In the above, a layer containing silicon is preferably provided between the second insulating layer and the first insulating layer.
In the above, each of the first functional layer and the second functional layer is preferably a hole-blocking layer.
One embodiment of the present invention is a manufacturing method for a display apparatus, including a step of forming a first pixel electrode, a first EL layer covering the first pixel electrode, a first insulating layer in contact with a top surface of the first EL layer, a second pixel electrode, a second EL layer covering the second pixel electrode, and a second insulating layer in contact with a top surface of the second EL layer, a step of depositing a third insulating layer to cover the first EL layer, the first insulating layer, and the second insulating layer, a step of performing surface treatment on the third insulating layer using a silylating agent, a step of applying a photosensitive resin composition containing an acrylic resin onto the third insulating layer, a step of exposing part of the resin composition to visible light or ultraviolet rays, a step of performing development to remove part of the resin composition to form a fourth insulating layer, a step of performing first heat treatment to make a side surface of the fourth insulating layer in a tapered shape and make a top surface of the fourth insulating layer in a convex shape, a step of removing parts of the first insulating layer, the second insulating layer, and the third insulating layer to expose the top surface of the first EL layer and the top surface of the second EL layer, and a step of forming a common electrode to cover the first EL layer, the second EL layer, and the fourth insulating layer.
In the above, hexamethyldisilazane is preferably used in surface treatment of the third insulating layer.
Another embodiment of the present invention is a method for manufacturing a display apparatus, including a step of forming a first pixel electrode, a first EL layer covering the first pixel electrode, a first insulating layer in contact with a top surface of the first EL layer, a second pixel electrode, a second EL layer covering the second pixel electrode, a second insulating layer in contact with a top surface of the second EL layer, a step of depositing a third insulating layer to cover the first EL layer, the first insulating layer, and the second insulating layer, a step of applying a photosensitive organic resin onto the third insulating layer, a step of performing a first light exposure to expose part of the organic resin to visible light or ultraviolet rays, a step of performing development to remove part of the organic resin to form a fourth insulating layer, a step of performing first heat treatment to make a side surface of the fourth insulating layer in a tapered shape and make a top surface of the fourth insulating layer in a convex shape, a step of removing parts of the first insulating layer, the second insulating layer, and the third insulating layer to expose the top surface of the first EL layer and the top surface of the second EL layer, and a step of forming a common electrode to cover the first EL layer, the second EL layer, and the fourth insulating layer. The first EL layer includes at least a first light-emitting layer and a first functional layer over the first light-emitting layer. The second EL layer includes at least a second light-emitting layer and a second functional layer over the second light-emitting layer. Each of the first functional layer and the second functional layer includes a first compound having glass transition temperature higher than or equal to 100° C. and lower than or equal to 180° C.
In the above, the first compound is preferably an organic compound having a heteroaromatic ring skeleton including one selected from a pyridine ring, a diazine ring, and a triaxine ring and a bicarbazole skeleton or an organic compound having a condensed heteroaromatic ring skeleton including a pyridine ring or a diazine ring and a bicarbazole skeleton.
In the above, it is preferable that the first EL layer and the second EL layer be formed by a photolithography method and the display apparatus include a region in which a distance between the first EL layer and the second EL layer is less than or equal to 8 μm.
In the above, aluminum oxide is preferably deposited as the third insulating layer by an ALD method.
In the above, second heat treatment is preferably performed before the first light exposure, and second heat treatment is preferably performed at a temperature higher than or equal to 70° C. and lower than or equal to 120° C.
In the above, a second light exposure is preferably performed before first heat treatment and irradiation with visible light or ultraviolet rays at greater than 0 mJ/cm2 and less than or equal to 500 mJ/cm2 is preferably performed in the second light exposure. In the above, the second light exposure is preferably performed in a nitrogen atmosphere.
In the above, first heat treatment is preferably performed at a temperature higher than or equal to 70° C. and lower than or equal to 130° C.
In the above, third heat treatment is preferably performed after first heat treatment and third heat treatment is preferably performed at a temperature higher than or equal to 80° C. and lower than or equal to 100° C.
According to one embodiment of the present invention, a display apparatus with high display quality can be provided. Alternatively, a highly reliable display apparatus can be provided. A display apparatus that can easily achieve a higher resolution can be provided. A display apparatus with both high display quality and a high resolution can be provided. A display apparatus with low power consumption can be provided.
According to one embodiment of the present invention, a display apparatus having a novel structure or a method for manufacturing a display apparatus can be provided. A method for manufacturing the above-described display apparatus with high yield can be provided. According to one embodiment of the present invention, at least one of problems of the conventional technique can be at least alleviated.
Note that the description of these effects does not preclude the existence of other effects. Note that one embodiment of the present invention does not need to have all the effects. Note that effects other than these can be derived from the description of the specification, the drawings, the claims, and the like.
Embodiments will be described below with reference to the drawings. Note that the embodiments can be implemented with many different modes, and it will be readily understood by those skilled in the art that modes and details thereof can be changed in various ways without departing from the spirit and scope thereof. Thus, the present invention should not be construed as being limited to the description of embodiments below.
Note that in structures of the invention described below, the same reference numerals are commonly used for the same portions or portions having similar functions in different drawings, and a repeated description thereof is omitted. Furthermore, the same hatch pattern is used for the portions having similar functions, and the portions are not especially denoted by reference numerals in some cases.
Note that in each drawing described in this specification, the size, the layer thickness, or the region of each component is exaggerated for clarity in some cases. Thus, they are not limited to the illustrated scale.
Note that in this specification and the like, ordinal numbers such as “first” and “second” are used in order to avoid confusion among components and do not limit the number.
In this specification and the like, a display apparatus may be rephrased as an electronic device.
In this specification and the like, a display panel that is one embodiment of a display apparatus has a function of displaying (outputting) an image or the like on (to) a display surface. Thus, the display panel is one embodiment of an output device.
In this specification and the like, a substrate of a display panel to which a connector such as an FPC (Flexible Printed Circuit) or a TCP (Tape Carrier Package) is attached, or the substrate on which an IC is mounted by a COG (Chip On Glass) method or the like is referred to as a display panel module, a display module, or simply a display panel or the like in some cases. In this specification and the like, a display panel module, a display module, or a display panel is referred to as a display apparatus in some cases.
In this specification and the like, the term “film” and the term “layer” can be interchanged with each other. For example, in some cases, the term “conductive layer” and the term “insulating layer” can be interchanged with the term “conductive film” and the term “insulating film”, respectively.
In this specification and the like, a device manufactured using a metal mask or an FMM (fine metal mask) is sometimes referred to as a device having an MM (metal mask) structure. In addition, in this specification and the like, a device manufactured without using a metal mask or an FMM is sometimes referred to as a device having an MML (metal maskless) structure.
In this specification and the like, a hole or an electron is sometimes referred to as a “carrier”. Specifically, a hole-injection layer or an electron-injection layer may be referred to as a “carrier-injection layer”, a hole-transport layer or an electron-transport layer may be referred to as a “carrier-transport layer”, and a hole-blocking layer or an electron-blocking layer may be referred to as a “carrier-blocking layer”. Note that in some cases, the above-described carrier-injection layer, carrier-transport layer, and carrier-blocking layer cannot be distinguished from each other depending on the cross-sectional shape, properties, or the like. Furthermore, one layer may have two or three functions of the carrier-injection layer, the carrier-transport layer, and the carrier-blocking layer in some cases.
In this specification and the like, a light-emitting device (also referred to as a light-emitting element) includes an EL layer between a pair of electrodes. The EL layer includes at least a layer containing a light-emitting substance (also referred to as a light-emitting layer). Examples of layers (also referred to as functional layers) in the EL layer include a light-emitting layer, carrier-injection layers (a hole-injection layer and an electron-injection layer), carrier-transport layers (a hole-transport layer and an electron-transport layer), and carrier-blocking layers (a hole-blocking layer and an electron-blocking layer). In this specification and the like, a light-receiving device (also referred to as a light-receiving element) includes at least an active layer that functions as a photoelectric conversion layer between a pair of electrodes. In this specification and the like, one of the pair of electrodes may be referred to as a pixel electrode and the other may be referred to as a common electrode.
In this embodiment, a display panel of one embodiment of the present invention is described with reference to
One embodiment of the present invention is a display panel including a display portion capable of full-color display. The display portion includes a first subpixel and a second subpixel that emit light of different colors. The first-subpixel includes a first light-emitting device that emits blue light and the second subpixel includes a second light-emitting device that emits light of a color different from the color of light emitted by the first light-emitting device. At least one kind of material is different between the first light-emitting device and the second light-emitting device; for example, the light-emitting devices contain different light-emitting materials. That is, light-emitting devices for different emission colors are separately formed in the display panel of one embodiment of the present invention.
A structure in which light-emitting layers in light-emitting devices of different colors (for example, blue (B), green (G), and red (R)) are separately formed or separately patterned is sometimes referred to as an SBS (Side By Side) structure. The SBS structure allows optimization of materials and structures of light-emitting devices and thus can extend freedom of choice of the materials and the structures, which makes it easy to improve the luminance and the reliability.
In the case of manufacturing a display panel including a plurality of light-emitting devices emitting light of different colors, light-emitting layers emitting light of different colors each need to be formed into an island shape. Note that in this specification and the like, the term “island shape” refers to a state where two or more layers formed using the same material in the same step are physically separated from each other. For example, “island-shaped light-emitting layer” means a state where the light-emitting layer and its adjacent light-emitting layer are physically separated from each other.
For example, an island-shaped light-emitting layer can be deposited by a vacuum evaporation method using a metal mask (also referred to as a shadow mask). However, this method causes a deviation from the designed shape and position of an island-shaped light-emitting layer due to various influences such as the accuracy of the metal mask, the positional deviation between the metal mask and a substrate, a warp of the metal mask, and the vapor-scattering-induced expansion of outline of the deposited film; accordingly, it is difficult to achieve high resolution and a high aperture ratio of the display apparatus. In addition, the outline of the layer may blur during vapor deposition, whereby the thickness of an end portion may be reduced. That is, the thickness of the island-shaped light-emitting layer may vary from area to area. In the case of manufacturing a display panel with a large size, high definition, or high resolution, the manufacturing yield might be reduced because of low dimensional accuracy of the metal mask and deformation due to heat or the like.
In a method for manufacturing a display panel of one embodiment of the present invention, a first layer (also referred to as an EL layer or part of an EL layer) including a light-emitting layer emitting light of a first color is formed over an entire surface, and then a first mask layer is formed over the first layer. Then, a first resist mask is formed over the first mask layer and the first layer and the first mask layer are processed using the first resist mask, so that the first layer is formed into an island shape. Next, in a manner similar to that for the first layer, a second layer (also referred to as an EL layer or part of an EL layer) including a light-emitting layer emitting light of a second color is formed into an island shape using a second mask layer and a second resist mask.
In this specification and the like, a mask film and a mask layer are each positioned above at least a light-emitting layer (specifically, a layer processed into an island shape among layers included in an EL layer) and has a function of protecting the light-emitting layer in the manufacturing step. Note that in this specification and the like, the mask film may be referred to as a sacrificial film, and the mask layer may be referred to as a sacrificial layer.
In the case of processing the light-emitting layer into an island shape, a conceivable structure is such that the light-emitting layer is processed by performing a photolithography method directly on the light-emitting layer. In that case, damage to the light-emitting layer (e.g., processing damage) might significantly degrade the reliability. In view of the above, in the manufacture of the display panel of one embodiment of the present invention, a mask layer or the like is preferably formed over a functional layer above the light-emitting layer (e.g., a carrier-blocking layer, a carrier-transport layer, or a carrier-injection layer, more specifically, a hole-blocking layer, an electron-transport layer, or an electron-injection layer), followed by the processing of the light-emitting layer and the functional layer into an island shape. Such a method provides a highly reliable display apparatus. A functional layer between the light-emitting layer and the mask layer can inhibit the light-emitting layer from being exposed on the outermost surface during the manufacturing step of the display apparatus and can reduce damage to the light-emitting layer.
Here, in the case of performing processing by a photolithography method, for example, the EL layers might suffer from various kinds of damage due to heating at the time of a photo mask (also referred to as a resist mask) formation and exposure to a chemical solution or an etching gas at the time of photo mask processing or removal. In the case where a mask layer is provided over the EL layer, the EL layer might be affected by heating, a chemical solution, an etching gas, or the like in depositing, processing, and removing the mask layer.
In addition, when steps after deposition of the EL layer are performed at temperature higher than the upper temperature limit of the EL layer, deterioration of the EL layer proceeds, which might result in a decrease in the emission efficiency and reliability of the light-emitting device.
Thus, in one embodiment of the present invention, the upper temperature limit of a compound contained in the light-emitting device is preferably higher than or equal to 100° C. and lower than or equal to 180° C., further preferably higher than or equal to 120° C. and lower than or equal to 180° C., still further preferably higher than or equal to 140° C. and lower than or equal to 180° C.
Examples of indicators of the upper temperature limit are the glass transition point, the softening point, the melting point, the thermal decomposition temperature, and the 5% weight loss temperature. For example, as an indicator of the upper temperature limit of a layer included in the EL layer, a glass transition point of a material contained in the layer can be used. In the case where the layer is a mixed layer formed of a plurality of materials, a glass transition point of a material contained in the highest proportion can be used, for example. Alternatively, the lowest temperature among the glass transition points of the materials may be used.
In particular, the upper temperature limit of the functional layers provided over the light-emitting layer is preferably high. It is further preferable that the upper temperature limit of the functional layer provided over and in contact with the light-emitting layer be high. When the functional layer has high heat resistance, the light-emitting layer can be effectively protected and less damaged.
In addition, it is particularly preferable that the upper temperature limit of the light-emitting layer be high. In this case, the light-emitting layer can be inhibited from being damaged by heating and being decreased in emission efficiency and lifetime.
Increasing the upper temperature limit of the light-emitting device can increase the reliability of the light-emitting device. Furthermore, the allowable temperature range in the manufacturing process of the display apparatus can be widened, thereby improving the manufacturing yield and the reliability.
In the case where the light-emitting layer is processed into an island shape, a layer positioned below the light-emitting layer (e.g., a carrier-injection layer or a carrier-transport layer, more specifically, a hole-injection layer, a hole-transport layer, or the like) is preferably processed into an island shape with the same pattern as the light-emitting layer. Processing a layer positioned below the light-emitting layer into an island shape with the same pattern as the light-emitting layer can reduce a leakage current (sometimes referred to as a horizontal-direction leakage current, a horizontal leakage current, or a lateral leakage current) that might be generated between adjacent subpixels. For example, in the case where a hole-injection layer is shared by adjacent subpixels, a horizontal leakage current might be generated due to the hole-injection layer. In contrast, in the display apparatus of one embodiment of the present invention, the hole-injection layer can be processed into an island shape with the same pattern as the light-emitting layer; hence, a horizontal leakage current between adjacent subpixels is not substantially generated or a horizontal leakage current can be extremely small.
As described above, the island shaped EL layers manufactured in the method for manufacturing a display panel of one embodiment of the present invention are formed not by using a metal mask having a fine pattern but by processing an EL layer deposited over the entire surface. Accordingly, a high-resolution display panel or a display panel with a high aperture ratio, each of which has been difficult to achieve, can be obtained. Moreover, EL layers can be formed separately for the respective colors, enabling the display panel to perform extremely clear display with high contrast and high display quality. In addition, a mask layer provided over an EL layer can reduce damage to the EL layer in the manufacturing process of the display panel, increasing the reliability of the light-emitting device.
It is difficult to reduce the distance between adjacent light-emitting devices to less than 10 μm with a formation method using a fine metal mask, for example. However, the method using a photolithography method according to one embodiment of the present invention can shorten the distance between adjacent light-emitting devices, adjacent EL layers, or adjacent pixel electrodes to less than 8 μm, less than or equal to 5 μm, less than or equal to 3 μm, less than or equal to 2 μm, less than or equal to 1.5 μm, less than or equal to 1 μm, or even less than or equal to 0.5 μm, for example, in a process over a glass substrate. Using a light exposure apparatus for LSI can further shorten the distance between adjacent light-emitting devices, adjacent EL layers, or adjacent pixel electrodes to less than or equal to 500 nm, less than or equal to 200 nm, less than or equal to 100 nm, or even less than or equal to 50 nm, for example, in a process over a Si wafer. Accordingly, the area of a non-light-emitting region that could exist between two light-emitting devices can be significantly reduced, and the aperture ratio can be close to 100%. For example, the display apparatus of one embodiment of the present invention can achieve an aperture ratio higher than or equal to 40%, higher than or equal to 50%, higher than or equal to 60%, higher than or equal to 70%, higher than or equal to 80%, or higher than or equal to 90%; that is, an aperture ratio lower than 100%.
Increasing the aperture ratio of the display apparatus can improve the reliability of the display apparatus. Specifically, with reference to the lifetime of a display apparatus including an organic EL device and having an aperture ratio of 10%, a display apparatus having an aperture ratio of 20% (that is, two times the aperture ratio of the reference) has a lifetime approximately 3.25 times as long as that of the reference, and a display apparatus having an aperture ratio of 40% (i.e., four times the aperture ratio of the reference) has a lifetime approximately 10.6 times as long as that of the reference. Thus, the density of current flowing in the organic EL device can be reduced with increasing aperture ratio, and accordingly the lifetime of the display apparatus can be increased. The display apparatus of one embodiment of the present invention can have a higher aperture ratio and thus can have higher display quality. Furthermore, the display apparatus of one embodiment of the present invention has excellent effect that the reliability (especially the lifetime) can be significantly improved with increasing aperture ratio.
Furthermore, a pattern (also referred to as a processing size) of the EL layer itself can be made much smaller than that in the case of using a metal mask. For example, in the case of using a metal mask for forming EL layers separately, a variation in the thickness occurs between the center and the edge of the EL layer. This causes a reduction in an effective area that can be used as a light-emitting region with respect to the area of the EL layer. In contrast, in the above manufacturing method, a film deposited to have a uniform thickness is processed, so that island-shaped EL layers can be formed to have a uniform thickness. Accordingly, even in a fine pattern, almost the whole area can be used as a light-emitting region. Consequently, a display panel having both high resolution and a high aperture ratio can be manufactured.
In addition, in a method for manufacturing a display panel of one embodiment of the present invention, it is preferable that a layer including a light-emitting layer (that can be referred to as an EL layer or part of an EL layer) be formed over an entire surface, and then a mask layer be formed over the EL layer. Next, it is preferable that a resist mask be formed over the mask layer, and the EL layer and the mask layer be processed using the resist mask, whereby an island-shaped EL layer be formed.
Provision of a mask layer over an EL layer can reduce damage to the EL layer during a manufacturing step of the display panel and increase the reliability of the light-emitting device.
Each of the above-described first layer and the second layer includes at least a light-emitting layer and preferably consists of a plurality of layers. Specifically, each of the first layer and the second layer preferably includes one or more layers over the light-emitting layer. A layer included between the light-emitting layer and the mask layer can inhibit the light-emitting layer from being exposed on the outermost surface during the manufacturing process of the display panel and can reduce damage to the light-emitting layer. Thus, the reliability of the light-emitting device can be increased. Thus, the first layer and the second layer each preferably include the light-emitting layer and a carrier-blocking layer (a hole-blocking layer or an electron-blocking layer) or a carrier-transport layer (an electron-transport layer or a hole-transport layer) over the light-emitting layer.
Note that it is not necessary to form all layers included in the EL layers separately for the respective light-emitting devices emitting light of different colors, and some layers of the EL layers can be deposited in the same step. Examples of layers (also referred to as functional layers) in the EL layer include a light-emitting layer, carrier-injection layers (a hole-injection layer and an electron-injection layer), carrier-transport layers (a hole-transport layer and an electron-transport layer), and carrier-blocking layers (a hole-blocking layer and an electron-blocking layer). In the method for manufacturing a display panel of one embodiment of the present invention, after some layers included in the EL layer are formed into an island shape separately for each color, the mask layer is removed at least partly; then, the other remaining layers included in the EL layers (referred to as a common layer in some cases) and a common electrode (also referred to as an upper electrode) are formed (as a single film) to be shared by the light-emitting devices of different colors. For example, a carrier-injection layer and a common electrode can be formed so as to be shared by the light-emitting devices of the respective colors.
Meanwhile, the carrier-injection layer is often a layer having relatively high conductivity in the EL layer. Thus, when the carrier-injection layer is in contact with a side surface of any layer of the EL layer formed into an island shape or a side surface of the pixel electrode, the light-emitting device might be short-circuited. Note that also in the case where the carrier-injection layer is provided in an island shape and the common electrode is formed to be shared by the light-emitting devices of different colors, the light-emitting device might be short-circuited when the common electrode is in contact with the side surface of the EL layer or the side surface of the pixel electrode.
In view of the above, the display panel of one embodiment of the present invention includes an insulating layer that covers at least a side surface of an island-shaped light-emitting layer. The insulating layer may cover part of a top surface of the island-shaped light-emitting layer. Note that the side surface of the island-shaped light-emitting layer here refers to the plane that is not parallel to the substrate (or the surface where the light-emitting layer is formed) among the interfaces between the island-shaped light-emitting layer and other layers. The side surface is not necessarily one of a planar plane and a curved plane in an exactly mathematical perspective.
This can inhibit at least some layers of the island-shaped EL layers and the pixel electrodes from being in contact with the carrier-injection layer or the common electrode. Hence, a short circuit of the light-emitting device is inhibited, and the reliability of the light-emitting device can be increased.
In addition, the insulating layer preferably has a function of a barrier insulating layer against at least one of water and oxygen. Alternatively, the insulating layer preferably has a function of inhibiting the diffusion of at least one of water and oxygen. Alternatively, the insulating layer preferably has a function of capturing or fixing (also referred to as gettering) at least one of water and oxygen.
Note that in this specification and the like, a barrier insulating layer refers to an insulating layer having a barrier property. A barrier property in this specification and the like refers to a function of inhibiting diffusion of a particular substance (also referred to as having low permeability). Alternatively, a barrier property refers to a function of capturing or fixing (also referred to as gettering) a particular substance.
When the insulating layer has a function of the barrier insulating layer or a gettering function, entry of impurities (typically, at least one of water and oxygen) that would diffuse into the light-emitting devices from the outside can be inhibited. With this structure, a highly reliable light-emitting device, furthermore, a highly reliable display panel can be provided.
The display panel of one embodiment of the present invention includes a pixel electrode functioning as an anode; an island-shaped hole-injection layer, an island-shaped hole-transport layer, an island-shaped light-emitting layer, an island-shaped hole-blocking layer, and an island-shaped electron-transport layer that are provided in this order over the pixel electrode; an insulating layer provided to cover side surfaces of the hole-injection layer, the hole-transport layer, the light-emitting layer, the hole-blocking layer, and the electron-transport layer; an electron-injection layer provided over the electron-transport layer; and a common electrode that is provided over the electron-injection layer and functions as a cathode.
Alternatively, the display panel of one embodiment of the present invention includes a pixel electrode functioning as a cathode; an island-shaped electron-injection layer, an island-shaped electron-transport layer, an island-shaped light-emitting layer, an island-shaped electron-blocking layer, and an island-shaped hole-transport layer that are provided in this order over the pixel electrode; an insulating layer provided to cover side surfaces of the electron-injection layer, the electron-transport layer, the light-emitting layer, the electron-blocking layer, and the hole-transport layer; a hole-injection layer provided over the hole-transport layer; and a common electrode that is provided over the hole-injection layer and functions as an anode.
The hole-injection layer or the electron-injection layer and the like often have relatively high conductivity in the EL layer. Since the side surfaces of these layers are covered with the insulating layer in the display panel of one embodiment of the present invention, these layers can be inhibited from being in contact with the common electrode or the like. Hence, a short circuit of the light-emitting device is inhibited, and the reliability of the light-emitting device can be increased.
The insulating layer that covers the side surface of the island-shaped EL layer may have a single-layer structure or a stacked-layer structure.
For example, an insulating layer having a single-layer structure using an inorganic material can be used for a protective insulating layer for the EL layer. This leads to higher reliability of the display panel. The protective insulating layer preferably partly covers part of a top surface of the EL layer. In such a case, a formed structure may have the mask layer remaining between the top surface of the EL layer and the protective insulating layer in some cases. The mask layer is preferably an insulating layer formed using an inorganic material like the protective insulating layer.
In the case where the insulating layer having a stacked-layer structure is used, a first layer of the insulating layer, which is formed in contact with the EL layer, is preferably formed using an inorganic insulating material. In particular, the first layer is preferably formed by an atomic layer deposition (ALD) method, by which damage due to deposition is small. Alternatively, an inorganic insulating layer is preferably formed by a sputtering method, a chemical vapor deposition (CVD) method, or a plasma-enhanced chemical vapor deposition (PECVD) method, which have higher deposition speed than an ALD method. In that case, a highly reliable display panel can be manufactured with high productivity. The second layer of the insulating layer is preferably formed using an organic material to fill a concave portion formed by the first layer of the insulating layer.
For example, an aluminum oxide film formed by an ALD method can be used as the first layer of the insulating layer, and an organic resin film can be used as the second layer of the insulating layer. For the organic resin, a photosensitive resin composition containing an acrylic resin is preferably used, for example.
In the case where the side surface of the EL layer and the organic resin film are in direct contact with each other, the EL layer might be damaged by an organic solvent or the like that might be contained in the organic resin film. When an inorganic insulating film such as an aluminum oxide film formed by an ALD method is used as the first layer of the insulating layer, a structure can be employed in which the organic resin film and the side surface of the EL layer are not in direct contact with each other. Thus, the EL layer can be inhibited from being dissolved by the organic solvent, for example.
In addition, in the cross-sectional view of the display apparatus, the second layer of the insulating layer preferably has a tapered shape with a taper angle θ1. The taper angle θ1 is an angle formed by the side surface of the second layer of the insulating layer and the substrate surface. The taper angle θ1 is less than 90°, preferably less than or equal to 60°, and further preferably less than or equal to 45°.
Note that in this specification and the like, a tapered shape refers to a shape such that at least part of a side surface of a component is inclined with respect to the substrate surface or the surface where the component is formed. For example, a tapered shape preferably includes a region where the angle between the inclined side surface and the substrate surface or the surface where a component is formed (such an angle is also referred to as a taper angle) is less than 90°. Note that the side surface of the component, the substrate surface, and the formation surface are not necessarily completely planar and may be substantially planar with a slight curvature or with slight unevenness.
When the end portion of the side surface of the second layer in the insulating layer has such a forward tapered shape, the common layer and the common electrode provided over the end portion of the side surface of the second layer can be deposited without disconnection, local thinning, or the like, so that good coverage can be obtained. This can improve the in-plane uniformity of the common layer and the common electrode, so that the display quality of the display apparatus can be improved.
In the above-described structure, the top surface of the second layer of the insulating layer preferably includes a convex curved surface shape in a cross-sectional view of the display apparatus. The convex shape of the top surface of the second layer of the insulating layer preferably has a shape that expands gradually toward the center. When the second layer of the insulating layer has such a shape, the common layer and the common electrode can be deposited with good coverage.
It is preferable that one end portion of the second layer of the insulating layer overlap with the first pixel electrode and the other end portion of the second layer of the insulating layer overlap with the second pixel electrode. With such a structure, the end portion of the second layer of the insulating layer can be formed over a substantially planar region of the EL layer. Thus, the tapered shape of the second layer of the insulating layer is relatively easy to form by processing.
In the display panel of one embodiment of the present invention, it is not necessary to provide an insulating layer that covers the end portion of the pixel electrode between the pixel electrode and the EL layer; thus, the distance between adjacent light-emitting devices can be made extremely small. As a result, higher resolution or higher definition of the display panel can be achieved. In addition, a mask for forming the insulating layer is not needed, resulting in a reduction in the manufacturing costs of the display panel.
Furthermore, light emitted from the EL layer can be extracted efficiently with a structure where an insulating layer covering the end portion of the pixel electrode is not provided between the pixel electrode and the EL layer, i.e., a structure where an insulating layer is not provided between the pixel electrode and the EL layer. Thus, the display panel of one embodiment of the present invention can significantly reduce the viewing angle dependence. A reduction in the viewing angle dependence leads to an increase in visibility of an image on the display panel. For example, in the display panel of one embodiment of the present invention, the viewing angle (the maximum angle with a certain contrast ratio maintained when a screen is seen from an oblique direction) can be greater than or equal to 100° and less than 180°, preferably greater than or equal to 150° and less than or equal to 170°. Note that the above viewing angle refers to that in both the vertical direction and the horizontal direction.
The pixel 110 illustrated in
In this specification and the like, the row direction and the column direction are sometimes referred to as the X direction and the Y direction, respectively. The X direction and the Y direction intersect with each other and are, for example, orthogonal to each other (see
Although the top view of
As illustrated in
Although
The display panel of one embodiment of the present invention can have any of the following structures: a top-emission structure in which light is emitted in a direction opposite to the substrate where the light-emitting device is formed, a bottom-emission structure in which light is emitted toward the substrate where the light-emitting device is formed, and a dual-emission structure in which light is emitted toward both surfaces.
The layer 101 including a transistor can employ a stacked-layer structure in which a plurality of transistors are provided over a substrate and an insulating layer is provided to cover these transistors, for example. The insulating layer over the transistors may have a single-layer structure or a stacked-layer structure. In
As each of the insulating layer 255a, the insulating layer 255b, and the insulating layer 255c, a variety of inorganic insulating films such as an oxide insulating film, a nitride insulating film, an oxynitride insulating film, and a nitride oxide insulating film can be suitably used. As each of the insulating layer 255a and the insulating layer 255c, an oxide insulating film or an oxynitride insulating film, such as a silicon oxide film, a silicon oxynitride film, or an aluminum oxide film, is preferably used. As the insulating layer 255b, a nitride insulating film or a nitride oxide insulating film, such as a silicon nitride film or a silicon nitride oxide film, is preferably used. More specifically, it is preferred that a silicon oxide film be used as the insulating layer 255a and the insulating layer 255c, and a silicon nitride film be used as the insulating layer 255b. The insulating layer 255b preferably has a function of an etching protective film.
Note that in this specification and the like, oxynitride refers to a material that contains more oxygen than nitrogen, and nitride oxide refers to a material that contains more nitrogen than oxygen. For example, in the case where silicon oxynitride is described, it refers to a material that contains more oxygen than nitrogen in its composition. In the case where silicon nitride oxide is described, it refers to a material that contains more nitrogen than oxygen in its composition.
Structure examples of the layer 101 including a transistor will be described in Embodiment 3 and Embodiment 4.
The light-emitting devices 130a, 130b, and 130c emit light of different colors. Preferably, the light-emitting devices 130a, 130b, and 130c are a combination of light-emitting devices emitting light of three colors, red (R), green (G), and blue (B), for example.
As the light-emitting devices 130a, 130b, and 130c, a light-emitting device such as an OLED (Organic Light Emitting Diode) or a QLED (Quantum-dot Light Emitting Diode) is preferably used. Examples of a light-emitting substance contained in the light-emitting device include a substance that emits fluorescence light (a fluorescent material), a substance that emits phosphorescent light (a phosphorescent material), an inorganic compound (a quantum dot material and the like), a substance that exhibits thermally activated delayed fluorescence (a thermally activated delayed fluorescent (TADF) material), and the like. As the TADF material, a material in which the singlet and triplet excited states are in thermal equilibrium may be used. Since such a TADF material has a short emission lifetime (excitation lifetime), it inhibits a reduction in the emission efficiency of a light-emitting device in a high-luminance region.
The light-emitting device includes an EL layer between a pair of electrodes. The EL layer includes at least a light-emitting layer. In this specification and the like, one of the pair of electrodes may be referred to as a pixel electrode and the other may be referred to as a common electrode.
One of the pair of electrodes of the light-emitting device functions as an anode and the other electrode functions as a cathode. The case where the pixel electrode functions as an anode and the common electrode functions as a cathode is described below as an example in some cases.
Each of the end portions of the pixel electrode 111a, the pixel electrode 111b, and the pixel electrode 111c preferably has a tapered shape. Here, the taper angle on each side surface of the pixel electrode 111a, the pixel electrode 111b, and the pixel electrode 111c is less than 90°, preferably less than or equal to 60°, and further preferably less than or equal to 45°. When the end portion of these pixel electrode has the tapered shape, a first layer 113a, a second layer 113b, or a third layer 113c provided along the side surface of the pixel electrode also has a tapered shape. When the side surface of the pixel electrode is tapered, coverage with an EL layer provided along the side surface of the pixel electrode can be improved. The pixel electrodes having tapered side surfaces are preferred because a foreign matter (such as dust or particles) mixed during the manufacturing process can be easily removed by treatment such as cleaning.
The light-emitting device 130a includes a pixel electrode 111a over the insulating layer 255c, an island-shaped first layer 113a over the pixel electrode 111a, a common layer 114 over the island-shaped first layer 113a, and a common electrode 115 over the common layer 114. In the light-emitting device 130a, the first layer 113a and the common layer 114 can be collectively referred to as an EL layer.
The light-emitting device 130b includes a pixel electrode 111b over the insulating layer 255c, an island-shaped second layer 113b over the pixel electrode 111b, the common layer 114 over the island-shaped second layer 113b, and the common electrode 115 over the common layer 114. In the light-emitting device 130b, the second layer 113b and the common layer 114 can be collectively referred to as an EL layer.
The light-emitting device 130c includes a pixel electrode 111c over the insulating layer 255c, an island-shaped third layer 113c over the pixel electrode 111c, the common layer 114 over the island-shaped third layer 113c, and the common electrode 115 over the common layer 114. In the light-emitting device 130c, the third layer 113c and the common layer 114 can be collectively referred to as an EL layer.
There is no particular limitation on the structure of the light-emitting device in this embodiment, and the light-emitting device can have a single structure or a tandem structure.
In this embodiment, the island-shaped layers provided in the EL layers included in the light-emitting devices are referred to as the first layer 113a, the second layer 113b, and the third layer 113c, and the layer shared by the plurality of light-emitting devices is referred to as the common layer 114. Note that in this specification and the like, the first layer 113a, the second layer 113b, and the third layer 113c are collectively referred to as EL layers, not including the common layer 114.
The first layer 113a, the second layer 113b, and the third layer 113c each at least include a light-emitting layer. Preferably, the first layer 113a, the second layer 113b, and the third layer 113c include a red-light-emitting layer, a green-light-emitting layer, and a blue-light-emitting layer, respectively, for example.
Each of the first layer 113a, the second layer 113b, and the third layer 113c may include one or more of a hole-injection layer, a hole-transport layer, a hole-blocking layer, a charge-generation layer, an electron-blocking layer, an electron-transport layer, and an electron-injection layer.
For example, each of the first layer 113a, the second layer 113b, and the third layer 113c may include a hole-injection layer, a hole-transport layer, a light-emitting layer, and an electron-transport layer in this order. In addition, an electron-blocking layer may be provided between the hole-transport layer and the light-emitting layer. In addition, a hole-blocking layer may be provided between the electron-transport layer and the light-emitting layer. Furthermore, an electron-injection layer may be provided over the electron-transport layer.
The first layer 113a, the second layer 113b, and the third layer 113c may include an electron-injection layer, an electron-transport layer, a light-emitting layer, and a hole-transport layer in this order, for example. In addition, a hole-blocking layer may be provided between the electron-transport layer and the light-emitting layer. In addition, an electron-blocking layer may be provided between the hole-transport layer and the light-emitting layer. Furthermore, a hole-injection layer may be provided over the hole-transport layer.
In this manner, the first material layer 113a, the second material layer 113b, and the third material layer 113c each preferably include a light-emitting layer and a carrier-transport layer (a hole-transport layer or an electron transport layer) over the light-emitting layer. Alternatively, the first layer 113a, the second layer 113b, and the third layer 113c each preferably include a light-emitting layer and a carrier-blocking layer (a hole-blocking layer or an electron-blocking layer) over the light-emitting layer. Alternatively, the first layer 113a, the second layer 113b, and the third layer 113c each preferably include a light-emitting layer, a carrier-blocking layer over the light-emitting layer, and a carrier-transport layer over the carrier-blocking layer. Since the surfaces of the first layer 113a, the second layer 113b, and the third layer 113c are exposed in the manufacturing step of the display panel, providing one or both of the carrier-transport layer and the carrier-blocking layer over the light-emitting layer inhibits the light-emitting layer from being exposed on the outermost surface, so that damage to the light-emitting layer can be reduced. Thus, the reliability of the light-emitting device can be increased.
The upper temperature limit of the compounds contained in the first layer 113a, the second layer 113b, and the third layer 113c is preferably higher than or equal to 100° C. and lower than or equal to 180° C., further preferably higher than or equal to 120° C. and lower than or equal to 180° C., still further preferably higher than or equal to 140° C. and lower than or equal to 180° C. For example, the glass transition point (Tg) of these compounds is preferably higher than or equal to 100° C. and lower than or equal to 180° C., further preferably higher than or equal to 120° C. and lower than or equal to 180° C., still further preferably higher than or equal to 140° C. and lower than or equal to 180° C.
In particular, the upper temperature limit of the functional layer provided over the light-emitting layer is preferably high. It is further preferable that the upper temperature limit of the functional layer provided on and in contact with the light-emitting layer be high. When the functional layer has high heat resistance, the light-emitting layer can be effectively protected and less damaged.
The functional layer provided over the light-emitting layer preferably includes an organic compound having a heteroaromatic ring skeleton including one selected from a pyridine ring, a diazine ring, and a triazine ring and a bicarbazole skeleton or an organic compound having a condensed heteroaromatic ring skeleton including a pyridine ring or a diazine ring and a bicarbazole skeleton, and Tg of the organic compound is higher than or equal to 100° C. and lower than or equal to 180° C., preferably higher than or equal to 120° C. and lower than or equal to 180° C., further preferably higher than or equal to 140° C. and lower than or equal to 180° C. The functional layer using such an organic compound can have one or both of a function as a hole-blocking layer and a function as an electron-transport layer. Note that the functional layer using such an organic compound is not limited to be provided on the upper side (upper electrode side) of the light-emitting layer, and may be provided on the lower side (lower electrode side) of the light-emitting layer.
Specific examples of the organic compounds include 2-{3-[3-(9-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}dibenzo[f,h]quinoxaline (abbreviation: 2mPCCzPDBq), 2-{3-[2-(9-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}dibenzo[f,h]quinoxaline (abbreviation: 2mPCCzPDBq-02), 9-[3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-9′-phenyl-3,3′-bi-9H-carbazole (abbreviation: mPCCzPTzn), 9-[3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-9′-phenyl-2,3′-bi-9H-carbazole (abbreviation: mPCCzPTzn-02), 9-[4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-9′-phenyl-3,3′-bi-9H-carbazole (abbreviation: PCCzPTzn), 9-(4,6-diphenyl-1,3,5-triazin-2-yl)-9′-phenyl-3,3′-bi-9H-carbazole (abbreviation: PCCzPTzn), 9-[3-(4,6-diphenyl-pyrimidin-2-yl)phenyl]-9′-phenyl-3,3′-bi-9H-carbazole (abbreviation: 2PCCzPPm), 9-(4,6-diphenyl-pyrimidin-2-yl)-9′-phenyl-2,3′-bi-9H-carbazole (abbreviation: 2PCCzPm), 9-(4,6-diphenylpyrimidin-2-yl)-9′-phenyl-3,3′-bi-9H-carbazole (abbreviation: 2PCCzPm-02), 4-(9′-phenyl[2,3′-bi-9H-carbazol]-9-yl)benzofuro[3,2-d]pyrimidine (abbreviation: 4PCCzBfpm-02), and 4-{3-[3-(9-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}benzo[h]quinazoline, and the like.
The upper temperature limit of the light-emitting layer is preferably high. In this case, the light-emitting layer can be inhibited from being damaged by heating and being decreased in emission efficiency and lifetime.
The light-emitting layer contains a light-emitting substance (also referred to as a light-emitting organic compound, a guest material, or the like) and an organic compound (also referred to as a host material or the like). Since the content of the organic compound is higher than that of the light-emitting substance in the light-emitting layer, Tg of the organic compound can be used as an indicator of the upper temperature limit of the light-emitting layer.
For example, a light-emitting layer exhibiting any of the colors from blue to green can include a light-emitting substance and a first organic compound. The first organic compound preferably includes a condensed heteroaromatic ring skeleton. The first organic compound preferably includes an anthracene skeleton, a benzanthracene skeleton, a dibenzanthracene skeleton, a chrysene skeleton, a naphthalene skeleton, a phenanthrene skeleton, or a triphenylene skeleton. Tg of the first organic compound is preferably higher than or equal to 100° C. and lower than or equal to 180° C., further preferably higher than or equal to 120° C. and lower than or equal to 180° C., still further preferably higher than or equal to 140° C. and lower than or equal to 180° C.
Specific examples of the first organic compound include 9-(1-naphthyl)-10-[4-(2-naphthyl)phenyl]anthracene (abbreviation: αN-βNPAnth), 2,9-di(1-naphthyl)-10-phenylanthracene (abbreviation: 2αN-αNPhA), 9-(1-naphthyl)-10-[3-(1-naphthyl)phenyl]anthracene (abbreviation: αN-mαPAnth), 9-(2-naphthyl)-10-[3-(1-naphthyl)phenyl]anthracene (abbreviation: βN-mαPAnth), 9-(2-naphthyl)-10-[3-(2-naphthyl)phenyl]anthracene (abbreviation: βN-mβNPAnth), 9-(1-naphthyl)-10-[4-(1-naphthyl)phenyl]anthracene (abbreviation: αN-αNPAnth), 9-(2-naphthyl)-10-[4-(2-naphthyl)phenyl]anthracene (abbreviation: βN-βNPAnth), 2-(1-naphthyl)-9-(2-naphthyl)-10-phenylanthracene (abbreviation: 2αN-βNPAnth), and the like.
A light-emitting layer exhibiting any of the colors from green to yellow can include a light-emitting substance and a second organic compound, for example. The second organic compound preferably includes a heteroaromatic ring skeleton including one selected from a pyridine ring, a diazine ring, and a triazine ring. As the heteroaromatic ring skeleton, the second organic compound preferably includes a condensed heteroaromatic ring skeleton including a diazine ring such as a benzofuropyrimidine (Bfpm) skeleton, a phenanthrofuropyrazine (Pnfpr) skeleton, a naphthofuropyrazine (Nfpr) skeleton, a naphthofuropyrimidine (Nfpm) skeleton, a phenanthrofuropyrimidine (Pnfpm) skeleton, a benzofuropyrazine (Bfpr) skeleton, a pyrimidine skeleton, a quinazoline skeleton, a benzoquinazoline skeleton, a quinoxaline skeleton, a benzoquinoxaline skeleton, or a dibenzo[f,h]quinoxaline skeleton. In addition, Tg of the second organic compound is preferably higher than or equal to 100° C. and lower than or equal to 180° C., further preferably higher than or equal to 120° C. and lower than or equal to 180° C.
The second organic compound preferably includes either one or both of a first skeleton having one selected from a triazine skeleton, a triphenylene skeleton, a dibenzo[f,h]quinoxaline skeleton, a benzofuropyrimidine (Bfpm) skeleton, a phenanthrofuropyrazine (Pnfpr) skeleton, a naphthofuropyrazine (Nfpr) skeleton, a naphthofuropyrimidine (Nfpm) skeleton, a phenanthrofuropyrimidine (Pnfpm) skeleton, a benzofuropyrazine (Bfpr) skeleton, a benzofuropyridine (Bfpy) skeleton, a phenanthrofuropyridine (Pnfpy) skeleton, a naphthofuropyridine (Nfpy) skeleton, a pyrimidine skeleton, a pyridine skeleton, a quinoline skeleton, a benzoquinoline skeleton, a quinazoline skeleton, a benzoquinazoline skeleton, a quinoxaline skeleton, a benzoquinoxaline skeleton, a triazatriphenylene skeleton, a tetraazatriphenylene skeleton, a hexaazatriphenylene skeleton, and a phenanthroline skeleton, and a second skeleton having one selected from a diarylamine skeleton, a carbazole skeleton, an indole skeleton, a pyrrole skeleton, a benzocarbazole skeleton, a dibenzocarbazole skeleton, an indolocarbazole skeleton, an indenocarbazole skeleton, a dibenzofuran skeleton, a furan skeleton, a benzofuran skeleton, a benzonaphthofuran skeleton, a bisnaphthofuran skeleton, a benzothiophene skeleton, a dibenzothiophene skeleton, and a thiophene skeleton. Also in that case, Tg of the second organic compound is preferably higher than or equal to 100° C. and lower than or equal to 180° C., further preferably higher than or equal to 120° C. and lower than or equal to 180° C.
Specific examples of the second organic compound include 4,8-bis[3-(dibenzothiophen-4-yl)phenyl]benzofuro[3,2-d]pyrimidine (abbreviation: 4,8mDBtP2Bfpm), 8-(1,1′:4′,1″-terphenyl-3-yl)-4-[3-(dibenzothiophen-4-yl)phenyl]-benzofuro[3,2-d]pyrimidine (abbreviation: 8mpTP-4mDBtPBfpm), 4,8-bis[3-(dibenzofuran-4-yl)phenyl][1]benzofuro[3,2-d]pyrimidine, and 4,8-bis[3-(9H-carbazol-9-yl)phenyl[1]benzofuro[3,2-d]pyrimidine (abbreviation: 4,8mCzP2Bfpm), and the like.
The light-emitting layer exhibiting any of the colors from green to yellow may include a third organic compound in addition to the light-emitting substance and the second organic compound. The third organic compound preferably has a π-electron rich heteroaromatic ring skeleton such as a carbazole, a 3,3′-bicarbazole skeleton, or a 2,3′-bicarbazole skeleton, or a condensed aromatic hydrocarbon ring. Tg of the third organic compound is preferably higher than or equal to 100° C. and lower than or equal to 180° C., further preferably higher than or equal to 120° C. and lower than or equal to 180° C. Note that a nitrogen atom of carbazole, a 3,3′-bicarbazole skeleton, or a 2,3′-bicarbazole skeleton preferably has a bond with a substituted or unsubstituted aryl group having 6 to 30 carbon atoms.
Note that specific examples of the third organic compound include 9-(2-naphthyl)-9′-phenyl-9H-3,3′-bicarbazole (abbreviation: PNCCP), 9-(3-biphenyl)-9′-(2-naphthyl)-3,3′-bi-9H-carbazole (abbreviation: βNCCmBP), 9-(4-biphenyl)-9′-(2-naphthyl)-3,3′-bi-9H-carbazole (abbreviation: βNCCBP), 9,9′-di-2-naphthyl-3,3′-9H,9′H-bicarbazole (abbreviation: BisβNCz), 9-(2-naphthyl)-9′-[1,1′:4′,1″-terphenyl]-3-yl-3,3′-9′H-bicarbazole, 9-(2-naphthyl)-9′-[1,1′:3′,1″-terphenyl]-3-yl-3,3′-9H,9′H-bicarbazole, 9-(2-naphthyl)-9′-[1,1′:3′,1″-terphenyl]-5′-yl-3,3′-9H,9′H-bicarbazole, 9-(2-naphthyl)-9′-[1,1′:4′,1″-terphenyl]-4-yl-3,3′-9H,9′H-bicarbazole, 9-(2-naphthyl)-9′-[1,1′: 3′,1″-terphenyl]-4-yl-3,3′-9H,9′H-bicarbazole, 9-(2-naphthyl)-9′-(triphenylen-2-yl)-3,3′-9H,9′H-bicarbazole, 9-phenyl-9′-(triphenylen-2-yl)-3,3′-9H,9′H-bicarbazole (abbreviation: PCCzTp), 9,9′-bis(triphenylen-2-yl)-3,3′-9H,9′H-bicarbazole, 9-(4-biphenyl)-9′-(triphenylen-2-yl)-3,3′-9H,9′H-bicarbazole, and 9-(triphenylen-2-yl)-9′-[1,1′: 3′,1″-terphenyl]-4-yl-3,3′-9H,9′H-bicarbazole, the like.
For example, the light-emitting layer exhibiting any colors from red to yellow can include a light-emitting substance and a fourth organic compound. The fourth organic compound preferably has a heteroaromatic ring skeleton that includes one selected from a pyridine ring, a diazine ring, and a triazine ring. As the heteroaromatic ring skeleton, the fourth organic compound preferably includes the condensed heteroaromatic ring skeleton including a diazine ring such as a dibenzo[f,h]quinoxaline skeleton, a benzofuropyrimidine (Bfpm) skeleton, a phenanthrofuropyrazine (Pnfpr) skeleton, a naphthofuropyrazine (Nfpr) skeleton, a naphthofuropyrimidine (Nfpm) skeleton, a phenanthrofuropyrimidine (Pnfpm) skeleton, a benzofuropyrazine (Bfpr) skeleton, a pyrimidine skeleton, a quinazoline skeleton, a benzoquinazoline skeleton, a quinoxaline skeleton, or a benzoquinoxaline skeleton. Tg of the fourth organic compound is preferably higher than or equal to 100° C. and lower than or equal to 180° C., further preferably higher than or equal to 120° C. and lower than or equal to 180° C. In particular, the fourth organic compound has a condensed heteroaromatic ring skeleton having a quinoxaline skeleton or a quinazoline skeleton and Tg is preferably higher than or equal to 100° C. and lower than or equal to 180° C., further preferably higher than or equal to 120° C. and lower than or equal to 180° C. The fourth organic compound preferably includes either one or both of a first skeleton having one selected from a triazine skeleton, a triphenylene skeleton, a dibenzo[f,h]quinoxaline skeleton, a benzofuropyrimidine (Bfpm) skeleton, a phenanthrofuropyrazine (Pnfpr) skeleton, a naphthofuropyrazine (Nfpr) skeleton, a naphthofuropyrimidine (Nfpm) skeleton, a phenanthrofuropyrimidine (Pnfpm) skeleton, a benzofuropyrazine (Bfpr) skeleton, a benzofuropyridine (Bfpy) skeleton, a phenanthrofuropyridine (Pnfpy) skeleton, a naphthofuropyridine (Nfpy) skeleton, a pyrimidine skeleton, a pyridine skeleton, a quinoline skeleton, a benzoquinoline skeleton, a quinazoline skeleton, a benzoquinazoline skeleton, a quinoxaline skeleton, a benzoquinoxaline skeleton, a triazatriphenylene skeleton, a tetraazatriphenylene skeleton, a hexaazatriphenylene skeleton, and a phenanthroline skeleton and a second skeleton having one selected from a diarylamine skeleton, a carbazole skeleton, an indole skeleton, a pyrrole skeleton, a benzocarbazole skeleton, a dibenzocarbazole skeleton, an indolocarbazole skeleton, an indenocarbazole skeleton, a dibenzofuran skeleton, a furan skeleton, a benzofuran skeleton, a benzonaphthofuran skeleton, a bisnaphthofuran skeleton, benzothiophene, dibenzothiophene, and a thiophene skeleton. Also in that case, Tg of the fourth organic compound is preferably higher than or equal to 100° C. and lower than or equal to 180° C., further preferably higher than or equal to 120° C. and lower than or equal to 180° C.
Specific examples of the fourth organic compound include 11-[(3′-dibenzothiophen-4-yl)biphenyl-3-yl]phenanthro[9′,10′:4,5]furo[2,3-b]pyrazine (abbreviation: 11mDBtBPPnfpr), 12-(9′-phenyl-3,3′-bi-9H-carbazol-9-yl)phenanthro[9′,10′:4,5]furo[2,3-b]pyrazine (abbreviation: 12PCCzPnfpr), 9-[(3′-9-phenyl-9H-carbazol-3-yl)biphenyl-4-yl]naphtho[1′,2′:4,5]furo[2,3-b]pyrazine (abbreviation: 9pmPCBPNfpr), 9-(9′-phenyl-3,3′-bi-9H-carbazol-9-yl)naphtho[1′,2′:4,5]furo[2,3-b]pyrazine (abbreviation: 9PCCzNfpr), 10-(9′-phenyl-3,3′-bi-9H-carbazol-9-yl)naphtho[1′,2′:4,5]furo[2,3-b]pyrazine (abbreviation: 10PCCzNfpr), 9-[3′-(6-phenylbenzo[b]naphtho[1,2-d]furan-8-yl)biphenyl-3-yl]naphtho[1′,2′:4,5]furo[2,3-b]pyrazine (abbreviation: 9mBnfBPNfpr), 9-{3-[6-(9,9-dimethylfluoren-2-yl)dibenzothiophen-4-yl]phenyl}naphtho[1′,2′:4,5]furo[2,3-b]pyrazine (abbreviation: 9mFDBtPNfpr), 9-[(3′-(6-phenyldibenzothiophen-4-yl)biphenyl-3-yl]naphtho[1′,2′:4,5]furo[2,3-b]pyrazine (abbreviation: 9mDBtBPNfpr-02), 9-[3-(9′-phenyl-3,3′-bi-9H-carbazol-9-yl)phenyl]naphtho[1′,2′:4,5]furo[2,3-b]pyrazine (abbreviation: 9mPCCzPNfpr), and the like.
The light-emitting layer exhibiting any of the colors from yellow to red may include the above-described third organic compound in addition to the light-emitting substance and the fourth organic compound.
Note that specific examples of the third organic compound include N-(1,1′-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine (abbreviation: PCBBiF), or N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]bis(9,9-dimethyl-9H-fluoren-2-yl)amine (abbreviation: PCBFF), N-(1,1′-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-4-amine, N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-yl)-9,9-dimethyl-9H-fluoren-4-amine, N-(1,1′-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-diphenyl-9H-fluoren-2-amine, N-(1,1′-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-diphenyl-9H-fluoren-4-amine, N-(1,1′-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-spirobi(9H-fluoren)-4-amine, N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-N-[1,1′:3′,1″-terphenyl-4-yl]-9,9-dimethyl-9H-fluoren-2-amine, N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-N-[1,1′:4′,1″-terphenyl-4-yl]-9,9-dimethyl-9H-fluoren-2-amine, and the like.
The first layer 113a, the second layer 113b, and the third layer 113c include a first light-emitting unit, a charge-generation layer, and a second light-emitting unit, for example. Preferably, the first layer 113a, the second layer 113b, and the third layer 113c include two or more light-emitting units that emit red light, two or more light-emitting units that emit green light, and two or more light-emitting units that emit blue light, for example.
The second light-emitting unit preferably includes the light-emitting layer and a carrier-transport layer (an electron-transport layer or a hole-transport layer) over the light-emitting layer. The second light-emitting unit preferably includes a light-emitting layer and a carrier-blocking layer (a hole-blocking layer or an electron-blocking layer) over the light-emitting layer. The second light-emitting unit preferably includes a light-emitting layer, a carrier-blocking layer over the light-emitting layer, and a carrier-transport layer over the carrier-blocking layer. Since the surface of the second light-emitting unit is exposed in the manufacturing step of the display panel, providing one or both of the carrier-transport layer over the light-emitting layer inhibits the light-emitting layer from being exposed on the outermost surface, so that damage to the light-emitting layer can be reduced. Thus, the reliability of the light-emitting device can be increased. Note that in the case where three or more light-emitting units are provided, the uppermost light-emitting unit preferably includes a light-emitting layer and one or both of a carrier-transport layer and a carrier-blocking layer over the light-emitting layer.
The common layer 114 includes, for example, an electron-injection layer or a hole-injection layer. Alternatively, the common layer 114 may include a stack of an electron-transport layer and an electron-injection layer, and may include a stack of a hole-transport layer and a hole-injection layer. The common layer 114 is shared by the light-emitting devices 130a, 130b, and 130c.
The common electrode 115 is shared by the light-emitting devices 130a, 130b, and 130c. The common electrode 115 shared by the plurality of light-emitting devices is electrically connected to a conductive layer 123 provided in the connection portion 140 (see
Note that
The protective layer 131 is preferably included over the light-emitting devices 130a, 130b, and 130c. Providing the protective layer 131 can improve the reliability of the light-emitting device. The protective layer 131 may have a single-layer structure or a stacked-layer structure of two or more layers.
There is no limitation on the conductivity of the protective layer 131. As the protective layer 131, at least one type of an insulating film, a semiconductor film, and a conductive film can be used.
The protective layer 131 including an inorganic film can inhibit deterioration of the light-emitting device by inhibiting oxidation of the common electrode 115 and inhibiting entry of impurities (e.g., moisture and oxygen) into the light-emitting device, for example; thus, the reliability of the display panel can be improved.
As the protective layer 131, an inorganic insulating film such as an oxide insulating film, a nitride insulating film, an oxynitride insulating film, or a nitride oxide insulating film can be used, for example. Examples of the oxide insulating film include a silicon oxide film, an aluminum oxide film, a gallium oxide film, a germanium oxide film, an yttrium oxide film, a zirconium oxide film, a lanthanum oxide film, a neodymium oxide film, a hafnium oxide film, and a tantalum oxide film. Examples of the nitride insulating film include a silicon nitride film and an aluminum nitride film. Examples of the oxynitride insulating film include a silicon oxynitride film and an aluminum oxynitride film. Examples of the nitride oxide insulating film include a silicon nitride oxide film and an aluminum nitride oxide film. In particular, the protective layer 131 preferably includes a nitride insulating film or a nitride oxide insulating film, and further preferably includes a nitride insulating film.
As the protective layer 131, an inorganic film containing In—Sn oxide (also referred to as ITO), In—Zn oxide, Ga—Zn oxide, Al—Zn oxide, indium gallium zinc oxide (In—Ga—Zn oxide, also referred to as IGZO), or the like can also be used. The inorganic film preferably has high resistance, specifically, higher resistance than the common electrode 115. The inorganic film may further contain nitrogen.
When light emitted from the light-emitting device is extracted through the protective layer 131, the protective layer 131 preferably has a high visible-light-transmitting property. For example, ITO, IGZO, and aluminum oxide are preferable because they are each inorganic materials having a high visible-light-transmitting property.
The protective layer 131 can be, for example, a stacked-layer structure of an aluminum oxide film and a silicon nitride film over the aluminum oxide film, or a stacked-layer structure of an aluminum oxide film and an IGZO film over the aluminum oxide film. Such a stacked-layer structure can inhibit entry of impurities (e.g., water and oxygen) into the EL layers side.
Furthermore, the protective layer 131 may include an organic film. For example, the protective layer 131 may include both an organic film and an inorganic film. Examples of an organic material that can be used for the protective layer 131 include organic insulating materials or the like that can be used for the insulating layer 127 described later.
The protective layer 131 may have a stacked-layer structure of two layers which are formed by different formation methods. Specifically, the first layer of the protective layer 131 may be formed by an ALD method, and the second layer of the protective layer 131 may be formed by a sputtering method.
In
In
In
As the mask layer 118, one or more kinds of inorganic films such as a metal film, an alloy film, a metal oxide film, a semiconductor film, an organic insulating film, and an inorganic insulating film can be used, for example. As the mask layer, a variety of inorganic insulating films that can be used as the protective layer 131 can be used. For example, an inorganic insulating material such as aluminum oxide, hafnium oxide, or silicon oxide can be used.
As illustrated in
In
Covering the side surface of the pixel electrode with the EL layer can inhibit contact between the pixel electrode and the common electrode 115; thus, a short circuit in the light-emitting device can be inhibited. Furthermore, the distance between the light-emitting region (i.e., the region overlapping with the pixel electrode) in the EL layer and the end portion of the EL layer can be increased. The end portion of the first layer 113a, the end portion of the second layer 113b, and the end portion of the third layer 113c include a portion that may be damaged in the manufacturing process of the display apparatus. Avoiding the use of the portion for the light-emitting region, variation in characteristics of the light-emitting device can be inhibited, and the reliability can be increased.
The side surfaces of the first layer 113a, the second layer 113b, and the third layer 113c are covered with the insulating layer 127 and the insulating layer 125. Part of the top surfaces of the first layer 113a, the second layer 113b, and the third layer 113c is covered with the insulating layer 127, the insulating layer 125, and the mask layer 118. Thus, the common layer 114 (or the common electrode 115) can be inhibited from being in contact with the side surfaces of the pixel electrodes 111a, 111b, and 111c, the first layer 113a, the second layer 113b, and the third layer 113c, whereby a short circuit of the light-emitting device can be inhibited. Thus, the reliability of the light-emitting device can be increased.
The insulating layer 125 preferably covers at least one of the side surfaces of the island-shaped EL layers, and further preferably covers both of the side surfaces of the island-shaped EL layers. The insulating layer 125 can be in contact with the side surface of each island-shaped EL layers.
In
The insulating layer 127 is provided over the insulating layer 125 to fill a concave portion in the insulating layer 125. The insulating layer 127 can overlap with part of the top surfaces or the side surfaces of the first layer 113a, the second layer 113b, and the third layer 113c (in other words, the insulating layer 127 can cover the side surfaces) with the insulating layer 125 therebetween.
The insulating layer 125 and the insulating layer 127 can fill a space between adjacent island-shaped layers, whereby large unevenness of the formation surfaces of the layers (e.g., the carrier-injection layer and the common electrode) provided over the island-shaped layers can be reduced and the formation surfaces can be more planar. Thus, the coverage with the carrier-injection layer, the common electrode, and the like can be increased and disconnection of the carrier-injection layer, the common electrode, and the like can be inhibited.
The common layer 114 and the common electrode 115 are provided over the first layer 113a, the second layer 113b, the third layer 113c, the mask layer 118, the insulating layer 125, and the insulating layer 127. At the stage before the insulating layer 125 and the insulating layer 127 are provided, a step due to a region where the pixel electrode and the EL layer are provided and a region where the pixel electrode and the EL layer are not provided (a region between the light-emitting devices) is caused. In the display panel of one embodiment of the present invention, unevenness can be reduced by including the insulating layer 125 and the insulating layer 127, and the coverage with the common layer 114 and the common electrode 115 can be improved. Consequently, it is possible to inhibit a connection defect due to disconnection. Alternatively, an increase in electrical resistance, which is caused by a reduction in thickness of the common electrode 115 locally due to the step, can be inhibited.
In order to improve the planarity of a surface where the common layer 114 and the common electrode 115 are formed, the top surface of the insulating layer 127 preferably has a shape with higher planarity and may have a convex portion, a convex surface, a concave surface, or a concave portion. For example, the top surface of the insulating layer 127 preferably has a smooth convex shape with high planarity.
The insulating layer 125 can be provided in contact with the island-shaped EL layer. Thus, peeling of the island-shaped EL layer can be prevented. When the insulating layer 125 and the island-shaped EL layer are in close contact with each other, an effect of fixing adjacent island-shaped EL layers by or attaching the adjacent island-shaped EL layers to the insulating layer 125 can be attained. Thus, the reliability of the light-emitting device can be increased. The manufacturing yield of the light-emitting device can be increased.
Here, the insulating layer 125 has a region in contact with the side surface of the island-shaped EL layer and functions as a protective insulating layer of the EL layer. With the insulating layer 125, entry of impurities (such as oxygen and moisture) from the side surface of the island-shaped EL layer into its inside can be inhibited, and thus a highly reliable display panel can be obtained.
Note that in the display apparatus of one embodiment of the present invention, the insulating layer 127 is provided over the insulating layer 125 to fill the concave portion formed by the insulating layer 125. Moreover, the insulating layer 127 is provided between the island-shaped EL layers. In other words, the display apparatus of one embodiment of the present invention employs a process in which island-shaped EL layers are formed and then the insulating layer 127 is formed to overlap with an end portion of the island-shaped EL layer (hereinafter referred to as a process 1). As a process different from the process 1, there is a process (hereinafter referred to as a process 2) in which a pixel electrode is formed in an island shape, an insulating film (also referred to as a bank or a structure body) that covers an end portion of the pixel electrode is formed, and then an island-shaped EL layer is formed over the pixel electrode and the insulating film.
The process 1 is preferable to the process 2 because of having a wider margin. Specifically, the process 1 has a wider margin for the accuracy of alignment of different patterning steps than the process 2 and can provide display apparatuses with few variations. Since the method for manufacturing the display apparatus of one embodiment of the present invention is based on the process 1, a display apparatus with few variations and high display quality can be provided.
Next, an example of a material and formation method for the insulating layer 125 and the insulating layer 127 is described.
The insulating layer 125 can be formed using an inorganic material. As the insulating layer 125, an inorganic insulating film such as an oxide insulating film, a nitride insulating film, an oxynitride insulating film, or a nitride oxide insulating film can be used, for example. The insulating layer 125 may have a single-layer structure or a stacked-layer structure. Examples of the oxide insulating film include a silicon oxide film, an aluminum oxide film, a magnesium oxide film, an indium gallium zinc oxide film, a gallium oxide film, a germanium oxide film, an yttrium oxide film, a zirconium oxide film, a lanthanum oxide film, a neodymium oxide film, a hafnium oxide film, and a tantalum oxide film. Examples of the nitride insulating film include a silicon nitride film and an aluminum nitride film. Examples of the oxynitride insulating film include a silicon oxynitride film and an aluminum oxynitride film. Examples of the nitride oxide insulating film include a silicon nitride oxide film and an aluminum nitride oxide film. In particular, aluminum oxide is preferably used because it has high selectivity with respect to the EL layer in etching and has a function of protecting the EL layer when the insulating layer 127 to be described later is formed. An inorganic insulating film such as an aluminum oxide film, a hafnium oxide film, or a silicon oxide film is formed by an ALD method as the insulating layer 125, whereby the insulating layer 125 can have few pinholes and an excellent function of protecting the EL layer. The insulating layer 125 may have a stacked-layer structure of a film formed by an ALD method and a film formed by a sputtering method. The insulating layer 125 may have a stacked-layer structure of an aluminum oxide film formed by an ALD method and a silicon nitride film formed by a sputtering method, for example.
The insulating layer 125 preferably has a function of a barrier insulating layer against at least one of water and oxygen. The insulating layer 125 preferably has a function of inhibiting the diffusion of at least one of water and oxygen. The insulating layer 125 preferably has a function of capturing or fixing (also referred to as gettering) at least one of water and oxygen.
When the insulating layer 125 has a function of the barrier insulating layer or a gettering function, entry of impurities (typically, at least one of water and oxygen) that would diffuse into the light-emitting devices from the outside can be inhibited. With this structure, a highly reliable light-emitting device, and furthermore, a highly reliable display panel can be provided.
The insulating layer 125 preferably has a low impurity concentration. Accordingly, degradation of the EL layer, which is caused by entry of impurities into the EL layer from the insulating layer 125, can be inhibited. In addition, when the impurity concentration is reduced in the insulating layer 125, a barrier property against at least one of water and oxygen can be increased. For example, the insulating layer 125 preferably has one of a sufficiently low hydrogen concentration and a sufficiently low carbon concentration, desirably has both of them.
The insulating layer 125 can be formed by a sputtering method, a CVD method, a pulsed laser deposition (PLD) method, an ALD method, or the like. The insulating layer 125 is preferably formed by an ALD method achieving good coverage.
When the substrate temperature at the time when the insulating layer 125 is formed is increased, the formed insulating layer 125, even with a small thickness, can have a low impurity concentration and a high barrier property against at least one of water and oxygen. Thus, the substrate temperature is preferably higher than or equal to 60° C., further preferably higher than or equal to 80° C., still further preferably higher than or equal to 100° C., yet still further preferably higher than or equal to 120° C. Meanwhile, the insulating layer 125 is formed after formation of an island-shaped EL layer, and it is preferable that the insulating layer 125 be formed at a temperature lower than the upper temperature limit of the EL layer. Thus, the substrate temperature is preferably lower than or equal to 200° C., further preferably lower than or equal to 180° C., still further preferably lower than or equal to 160° C., still further preferably lower than or equal to 150° C., yet still further preferably lower than or equal to 140° C.
Examples of indicators of the upper temperature limit are the glass transition point, the softening point, the melting point, the thermal decomposition temperature, and the 5% weight loss temperature. The upper temperature limit of the EL layer can be, for example, any of the above temperatures, preferably the lowest temperature thereof.
As the insulating layer 125, an insulating film is preferably formed to have a thickness greater than or equal to 3 nm, greater than or equal to 5 nm, or greater than or equal to 10 nm and less than or equal to 200 nm, less than or equal to 150 nm, less than or equal to 100 nm, or less than or equal to 50 nm.
The insulating layer 127 provided over the insulating layer 125 has a function of reducing large unevenness of the insulating layer 125 formed between adjacent light-emitting devices. In other words, the insulating layer 127 brings an effect of improving the planarity of a surface where the common electrode 115 is formed.
As the insulating layer 127, an insulating layer containing an organic material can be suitably used. As the organic material, a photosensitive organic resin is preferably used; for example, a photosensitive resin composition containing an acrylic resin may be used. The viscosity of the material of the insulating layer 127 is greater than or equal to 1 cP and less than or equal to 1500 cP, and is preferably greater than or equal to 1 cP and less than or equal to 12 cP. By setting the viscosity of the material of the insulating layer 127 in the above range, the insulating layer 127 having a tapered shape, which is to be described later, can be formed relatively easily. Note that in this specification and the like, an acrylic resin refers to not only a polymethacrylic acid ester or a methacrylic resin, but also all the acrylic polymer in a broad sense in some cases.
Note that the organic material usable for the insulating layer 127 is not limited to the above as long as the insulating layer 127 has a tapered side surface as described later. For the insulating layer 127, an acrylic resin, a polyimide resin, an epoxy resin, an imide resin, a polyamide resin, a polyimide-amide resin, a silicone resin, a siloxane resin, a benzocyclobutene-based resin, a phenol resin, precursors of these resins, or the like can be used in some cases, for example. Alternatively, an organic material such as polyvinyl alcohol (PVA), polyvinylbutyral, polyvinylpyrrolidone, polyethylene glycol, polyglycerin, pullulan, water-soluble cellulose, an alcohol-soluble polyamide resin, or the like can be employed for the insulating layer 127 in some cases. As the photosensitive resin, a photoresist can be used in some cases. As the photosensitive resin, a positive material or a negative material can be used in some cases.
The insulating layer 127 may be formed using a material absorbing visible light. When the insulating layer 127 absorbs light emitted by the light-emitting device, leakage of light (stray light) from the light-emitting device to adjacent light-emitting device through the insulating layer 127 can be inhibited. Thus, the display quality of the display panel can be improved. Since no polarizing plate is required to improve the display quality of the display panel, the weight and thickness of the display panel can be reduced.
Examples of the material absorbing visible light include a material containing a pigment of black or any other color, a material containing a dye, a light-absorbing resin material (e.g., polyimide), and a resin material that can be used for color filters (a color filter material). Using a resin material obtained by stacking or mixing color filter materials of two or three or more colors is particularly preferred to enhance the effect of blocking visible light. In particular, mixing color filter materials of three or more colors enables the formation of a black or nearly black resin layer.
For example, the insulating layer 127 can be formed by a wet film formation method such as spin coating, dipping, spray coating, ink-jetting, dispensing, screen printing, offset printing, a doctor blade coating method, slit coating, roll coating, curtain coating, or knife coating. Specifically, an organic insulating film that is to be the insulating layer 127 is preferably formed by spin coating.
In addition, the insulating layer 127 is formed at a temperature lower than the upper temperature limit of the EL layer. The typical substrate temperature in the formation of the layer 127 is lower than or equal to 200° C., preferably lower than or equal to 180° C., further preferably lower than or equal to 160° C., still further preferably lower than or equal to 150° C., yet still further preferably lower than or equal to 140° C.
Here, a structure of the insulating layer 127 and the vicinity thereof will be described with reference to
As illustrated in
As illustrated in
The taper angle θ1 of the insulating layer 127 is less than 90°, preferably less than or equal to 60°, and further preferably less than or equal to 45°. Such a forward tapered shape of the end portion of the side surface of the insulating layer 127 can inhibit disconnection, local thinning, or the like from occurring in the common layer 114 and the common electrode 115 which are provided over the end portion of the side surface of the insulating layer 127, leading to film formation with good coverage. Accordingly, in-plane uniformity of the common layer 114 and the common electrode 115 can be improved, which enables the display quality of the display apparatus to be improved.
As illustrated in
The insulating layer 127 is formed in a region between two EL layers (e.g., in
As illustrated in
In the region 139, by forming the insulating layer 127 and the like in the above manner, a disconnected portion and a locally thinned portion can be prevented from being formed in the common layer 114 and the common electrode 115 from the substantially planar region of the first layer 113a to the substantially planar region of the second layer 113b. Thus, between the light-emitting devices, a connection defect caused by the disconnected portion and an increase in electric resistance caused by the locally thinned portion can be inhibited from occurring in the common layer 114 and the common electrode 115. Accordingly, the display quality and the reliability of the display apparatus of one embodiment of the present invention can be improved.
As already described above, the pixel electrode preferably has a tapered side surface. In this case, the EL layer can have a tapered portion in a cross-sectional view of the display apparatus. For example, as illustrated in
As illustrated in
When a photosensitive organic insulating film is used as the insulating film to be the insulating layer 127, for example, the insulating film to be the insulating layer 127 might be irradiated with ultraviolet rays in a light exposure step. Thus, the EL layer is also irradiated with ultraviolet rays, and the EL layer is damaged in some cases.
In contrast, by providing a light-blocking film having a property of blocking ultraviolet rays (to be processed into the light-blocking layer 135 later), even when irradiation with ultraviolet rays is performed in the above-described light exposure step, ultraviolet rays for irradiation of the EL layer can be reduced and the EL layer can be inhibited from being damaged. Specifically, the above light-blocking film may have a light-blocking property with respect to ultraviolet rays of at least a certain wavelength as the light for irradiation of the insulating film to be the insulating layer 127 in the light exposure step of the insulating film to be the insulating layer 127. Thus, the display apparatus of one embodiment of the present invention can be a highly reliable display apparatus.
Note that in the light exposure step of the insulating film to be the insulating layer 127, in the case where the insulating film to be the insulating layer 127 is irradiated with visible light, the above light-blocking film may have a light-blocking property with respect to visible light. Specifically, in the light exposure step of the insulating film to be the insulating layer 127, the above light-blocking film may have a light-blocking property with respect to visible light of at least a certain wavelength as the light for irradiation of the insulating film.
In the light exposure step of the light-blocking film to the insulating film to be the insulating layer 127, for example, the above light-blocking film has a function of absorbing or reflecting light of part of a wavelength of light irradiated to the insulating film to be the insulating layer 127. For example, in the light exposure step of the insulating film to be the insulating layer 127, the above light-blocking film has a transmittance of light of at least part of the wavelengths of light irradiated to the insulating film to be the insulating layer 127 is less than or equal to 50%, preferably less than or equal to 10%, further preferably less than or equal to 1%, still further preferably less than or equal to 0.1%.
The light-blocking layer 135 can be formed between adjacent light-emitting devices by processing the light-blocking film by an etching method or the like after the formation of the insulating layer 127. The light-blocking layer 135 preferably has a function of absorbing or reflecting light with a certain wavelength as the light emitted from the light-emitting device. Accordingly, stray light of light emitted from the light-emitting device can be inhibited, and the display quality of the display apparatus can be improved.
An insulating layer can be used as the light-blocking layer 135; however, without being limited thereto, a conductive layer or a semiconductor layer may be used, for example. Since the light-blocking layer 135 can be formed by processing the light-blocking film by an etching method or the like as described above, the light-blocking layer 135 preferably has a favorable processing property by an etching method or the like.
For the light-blocking layer 135, a material containing a Group 14 element, for example, silicon such as amorphous silicon, carbon, or germanium can be used. For example, the light-blocking layer 135 may be formed using a metal; molybdenum, titanium, tantalum, tungsten, aluminum, copper, chromium, neodymium, scandium, or an alloy containing any of these metals can be used. As the light-blocking layer 135, a nitride containing any of the above metals (e.g., titanium nitride, chromium nitride, molybdenum nitride, or tungsten nitride), or an oxide containing any of the above metals as its component (e.g., titanium oxide, chromium oxide, molybdenum oxide, or tungsten oxide) can be used.
The thickness of the light-blocking layer 135 is preferably greater than or equal to 3 nm or greater than or equal to 5 nm and less than or equal to 200 nm, less than or equal to 150 nm, less than or equal to 100 nm, less than or equal to 50 nm, or less than or equal to 10 nm.
Here, in the display apparatus of one embodiment of the present invention, the light-blocking layer 135 is provided over the insulating layer 125. This can prevent the light-blocking layer 135 from being in contact with the EL layer. Thus, the range of choices for materials of the light-blocking layer 135 can be widened. For example, a material that may damage the EL layer when in contact with the EL layer can be used for the light-blocking layer 135. Furthermore, a method in which the EL layer is exposed at the time of forming the light-blocking layer 135 may cause damage to the EL layer can be used to form the light-blocking layer 135. Furthermore, a material having conductivity, such as a metal, can be used for the light-blocking layer 135. Note that in the case where a material that does not cause damage to the EL layer even when in contact with the EL layer and has an insulating property is used for the light-blocking layer 135, for example, the display apparatus of one embodiment of the present invention can have a structure without including the insulating layer 125.
When the angle of the tapered portion is less than 90°, the tapered portion is easily irradiated with ultraviolet rays or the like in the light exposure step of the insulating film to be the insulating layer 127 as compared with the case where the angle of the tapered portion is greater than or equal to 90°. When the light-blocking film to be the light-blocking layer 135 is provided in the display apparatus of one embodiment of the present invention, even a tapered portion of the EL layer can be inhibited from being irradiated with ultraviolet rays, and damage to the EL layer can be inhibited. As described above, the display apparatus of one embodiment of the present invention can improve the coverage of the pixel electrode with the EL layer and can inhibit the EL layer from being damaged in the manufacturing step. Thus, the display apparatus of one embodiment of the present invention can be a highly reliable display apparatus.
As illustrated in
Like the insulating layer 127, the protruding portion 116 preferably has a tapered side surface in a cross-sectional view of the display apparatus. The taper angle of the protruding portion 116 is less than 90°, preferably less than or equal to 60°, further preferably less than or equal to 45°, still further preferably less than or equal to 20°. The taper angle of the protruding portion 116 is smaller than the taper angle θ1 of the insulating layer 127 in some cases. When the protruding portion 116 has such a forward tapered shape, the common layer 114 and the common electrode 115 provided over the protruding portion 116 can be formed with good coverage, without disconnection or the like.
The insulating layer 125 may include a region (hereinafter, referred to as a depression portion 133) that has a smaller thickness than another portion (e.g., a portion overlapping with the insulating layer 127) in the protruding portion 116. Depending on the thickness of the insulating layer 125, for example, the insulating layer 125 in the protruding portion 116 disappears and the depression portion 133 is formed to reach the sacrificial layer 118b in some cases.
Although all of the thicknesses of the first layer 113a to the third layer 113c are shown as equal in
For example, when the third layer 113c emits light with the longest wavelength and the second layer 113b emits light with the shortest wavelength, the third layer 113c can have the largest thickness and the second layer 113b can have the smallest thickness. Note that without limitation to this, the thicknesses of the EL layers can be adjusted in consideration of the wavelengths of light emitted by the light-emitting elements, the optical characteristics of the layers included in the light-emitting elements, the electrical characteristics of the light-emitting elements, and the like.
In the display panel of this embodiment, the distance between the light-emitting devices can be narrowed. Specifically, the distance between the light-emitting devices, the distance between the EL layers, or the distance between the pixel electrodes can be less than 10 μm, less than or equal to 8 μm, less than or equal to 5 μm, less than or equal to 3 μm, less than or equal to 2 μm, less than or equal to 1 μm, less than or equal to 500 nm, less than or equal to 200 nm, less than or equal to 100 nm, less than or equal to 90 nm, less than or equal to 70 nm, less than or equal to 50 nm, less than or equal to 30 nm, less than or equal to 20 nm, less than or equal to 15 nm, or less than or equal to 10 nm. In other words, the display panel of this embodiment includes a region where the distance between two adjacent island-shapes EL layers is less than or equal to 1 μm, preferably less than or equal to 0.5 μm (500 nm), further preferably less than or equal to 100 nm.
A light-blocking layer may be provided on the surface of the substrate 120 on the resin layer 122 side. A variety of optical members can be arranged on the outer side of the substrate 120. Examples of the optical members include a polarizing plate, a retardation plate, a light diffusion layer (e.g., a diffusion film), an anti-reflective layer, and a light-condensing film. Furthermore, an antistatic film inhibiting the attachment of dust, a water repellent film suppressing the attachment of stain, a hard coat film inhibiting generation of a scratch caused by the use, an impact-absorbing layer, or the like may be provided as a surface protective layer on the outer side of the substrate 120. For example, a glass layer or a silica layer (a SiOx layer) is preferably provided as the surface protective layer to inhibit the surface contamination and generation of a scratch. The surface protective layer may be formed using DLC (diamond like carbon), aluminum oxide (AlOx), a polyester-based material, a polycarbonate-based material, or the like. For the surface protective layer, a material having high visible-light transmittance is preferably used. The surface protective layer is preferably formed using a material with high hardness.
For the substrate 120, glass, quartz, ceramics, sapphire, a resin, a metal, an alloy, a semiconductor, or the like can be used. The substrate on the side from which light from the light-emitting device is extracted is formed using a material which transmits the light. When a material having flexibility is used for the substrate 120, the flexibility of the display panel can be increased. Furthermore, a polarizing plate may be used as the substrate 120.
For the substrate 120, any of the following can be used, for example: polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), a polyacrylonitrile resin, an acrylic resin, a polyimide resin, a polymethyl methacrylate resin, a polycarbonate (PC) resin, a polyethersulfone (PES) resin, polyamide resins (e.g., nylon and aramid), a polysiloxane resin, a cycloolefin resin, a polystyrene resin, a polyamide-imide resin, a polyurethane resin, a polyvinyl chloride resin, a polyvinylidene chloride resin, a polypropylene resin, a polytetrafluoroethylene (PTFE) resin, an ABS resin, and cellulose nanofiber. Glass that is thin enough to have flexibility may be used for the substrate 120.
Note that in the case where a circularly polarizing plate overlaps with the display panel, a highly optically isotropic substrate is preferably used as the substrate included in the display panel. A highly optically isotropic substrate has a low birefringence (in other words, a small amount of birefringence).
The absolute value of a retardation (phase difference) of a highly optically isotropic substrate is preferably less than or equal to 30 nm, further preferably less than or equal to 20 nm, still further preferably less than or equal to 10 nm.
Examples of the film having high optical isotropy include a triacetyl cellulose (TAC, also referred to as cellulose triacetate) film, a cycloolefin polymer (COP) film, a cycloolefin copolymer (COC) film, and an acrylic film.
In the case where a film is used for the substrate and the film absorbs water, the shape of the display panel might be changed, e.g., creases are generated. Thus, for the substrate, a film with a low water absorption rate is preferably used. For example, the water absorption rate of the film is preferably 1% or lower, further preferably 0.1% or lower, further preferably 0.01% or lower.
For the resin layer 122, a variety of curable adhesives such as a photocurable adhesive like an ultraviolet curable adhesive, a reactive curable adhesive, a thermosetting adhesive, and an anaerobic adhesive can be used. Examples of these adhesives include an epoxy resin, an acrylic resin, a silicone resin, a phenol resin, a polyimide resin, an imide resin, a PVC (polyvinyl chloride) resin, a PVB (polyvinyl butyral) resin, and an EVA (ethylene vinyl acetate) resin. In particular, a material with low moisture permeability, such as an epoxy resin, is preferable. Alternatively, a two-liquid-mixture-type resin may be used. An adhesive sheet or the like may be used.
As illustrated in
The pixel 110 illustrated in
The subpixels 110a, 110b, 110c, and 110d can include light-emitting devices that emit light of different colors. As the subpixels 110a, 110b, 110c, and 110d, for example, subpixels of four colors of R, G, B, and W, subpixels of four colors of R, G, B, and Y, subpixels of four colors of R, G, B, and IR, and the like can be given.
The display panel of one embodiment of the present invention may include a light-receiving device in the pixel.
Three of the four subpixels included in the pixel 110 illustrated in
As the light-receiving device, a pn or pin photodiode can be used, for example. The light-receiving device functions as a photoelectric conversion device (also referred to as a photoelectric conversion element) that detects light entering the light-receiving device and generates electric charge. The amount of electric charge generated from the light-receiving device depends on the amount of light entering the light-receiving device.
It is particularly preferable to use an organic photodiode including a layer containing an organic compound as the light-receiving device. An organic photodiode, which is easily made thin, lightweight, and large in area and has a high degree of freedom for shape and design, can be used in a variety of display panels.
In one embodiment of the present invention, organic EL devices are used as the light-emitting devices, and an organic photodiode is used as the light-receiving device. The organic EL devices and the organic photodiode can be formed over the same substrate. Thus, the organic photodiode can be incorporated in the display panel including the organic EL devices.
The light-receiving device includes at least an active layer that functions as a photoelectric conversion layer between a pair of electrodes. In this specification and the like, one of the pair of electrodes may be referred to as a pixel electrode and the other may be referred to as a common electrode.
One of the pair of electrodes of the light-receiving device functions as an anode, and the other electrode functions as a cathode. The case where the pixel electrode functions as an anode and the common electrode functions as a cathode is described below as an example. When the light-receiving device is driven by application of reverse bias between the pixel electrode and the common electrode, light entering the light-receiving device can be detected and electric charge can be generated and extracted as current. Alternatively, the pixel electrode may function as a cathode and the common electrode may function as an anode.
A manufacturing method similar to that of the light-emitting device can be employed for the light-receiving device. An island-shaped active layer (also referred to as a photoelectric conversion layer) included in the light-receiving device is formed by processing a film that is to be the active layer and formed over the entire surface, not by using a fine metal mask; thus, the island-shaped active layer can be formed to have a uniform thickness. In addition, a mask layer provided over the active layer can reduce damage to the active layer in the manufacturing step of the display panel, increasing the reliability of the light-receiving device.
As illustrated in
The structure of the light-emitting device 130a is as described above.
The light-receiving device 150 includes a pixel electrode 111d over the insulating layer 255c, a fourth layer 113d over the pixel electrode 111d, the common layer 114 over the fourth layer 113d, and the common electrode 115 over the common layer 114. The fourth layer 113d includes at least an active layer.
Here, the fourth layer 113d includes at least an active layer, preferably includes a plurality of functional layers. Examples of the functional layers include carrier-transport layers (a hole-transport layer and an electron-transport layer) and carrier-blocking layers (a hole-blocking layer and an electron-blocking layer). One or more layers are preferably included over the active layer. A layer included between the active layer and the mask layer can inhibit the active layer from being exposed on the outermost surface during the manufacturing step of the display panel and can reduce damage to the active layer. Accordingly, the reliability of the light-receiving device 150 can be increased. Thus, the fourth layer 113d preferably includes an active layer and a carrier-blocking layer (a hole-blocking layer or an electron-blocking layer) or a carrier-transport layer (an electron-transport layer or a hole-transport layer) over the active layer.
The fourth layer 113d is provided in the light-receiving device 150, not in the light-emitting device. Note that the functional layer other than the active layer in the fourth layer 113d may include the same material as the functional layer other than the light-emitting layers in the first layer 113a to the third layer 113c. The common layer 114 is a continuous layer shared by the light-emitting device and the light-receiving device.
Here, a layer shared by the light-receiving device and the light-emitting device might have different functions in the light-emitting device and the light-receiving device. In this specification, the name of a component is based on its function in the light-emitting device in some cases. For example, a hole-injection layer functions as a hole-injection layer in the light-emitting device and functions as a hole-transport layer in the light-receiving device. Similarly, an electron-injection layer functions as an electron-injection layer in the light-emitting device and functions as an electron-transport layer in the light-receiving device. A layer shared by the light-receiving device and the light-emitting device may have the same function in both the light-emitting device and the light-receiving device. The hole-transport layer functions as a hole-transport layer in both the light-emitting device and the light-receiving device, and the electron-transport layer functions as an electron-transport layer in both the light-emitting device and the light-receiving device.
The mask layer 118a is positioned between the first layer 113a and the insulating layer 125, and a mask layer 118d is positioned between the fourth layer 113d and the insulating layer 125. The mask layer 118a is a remaining part of the mask layer provided over the first layer 113a at the time of processing the first layer 113a. The mask layer 118d is a remaining part of a mask layer provided in contact with a top surface of the fourth layer 113d at the time of processing the fourth layer 113d, which is a layer including the active layer. The mask layer 118a and the mask layer 118d may contain the same material or different materials.
As illustrated in
In the display panel including the light-emitting device and the light-receiving device in each pixel, the pixel has a light-receiving function, which enables detection of a contact or approach of an object while an image is displayed. For example, all the subpixels included in the display panel can display an image; alternatively, some of the subpixels can emit light as a light source, some of the rest of the subpixels can detect light, and the other subpixels can display an image.
In the display panel of one embodiment of the present invention, the light-emitting devices are arranged in a matrix in a display portion, and an image can be displayed on the display portion. Furthermore, the light-receiving devices are arranged in a matrix in the display portion, and the display portion has one or both of an image capturing function and a sensing function in addition to an image displaying function. The display portion can be used as an image sensor or a touch sensor. That is, by detecting light with the display portion, an image can be captured or the approach or contact of an object (e.g., a finger, a hand, or a pen) can be detected. Furthermore, in the display panel of one embodiment of the present invention, the light-emitting devices can be used as a light source of the sensor. Accordingly, a light-receiving portion and a light source do not need to be provided separately from the display panel; hence, the number of components of an electronic device can be reduced. For example, a fingerprint authentication device, a capacitive touch panel for scroll operation, or the like is not necessarily provided separately from the electronic device. Thus, with the use of the display panel of one embodiment of the present invention, the electronic device can be provided with reduced manufacturing cost.
In the display panel of one embodiment of the present invention, when an object reflects (or scatters) light emitted from the light-emitting devices included in the display portion, the light-receiving devices can detect reflected light (or scattered light); thus, image capturing or touch detection is possible even in a dark place.
When the light-receiving devices are used as an image sensor, the display panel can capture an image using the light-receiving devices. For example, the display panel of this embodiment can be used as a scanner.
For example, data on biological information such as a fingerprint or a palm print can be obtained with use of the image sensor. That is, a biometric authentication sensor can be incorporated in the display panel. When the display panel incorporates a biometric authentication sensor, the number of components of an electronic device can be reduced as compared to the case where a biometric authentication sensor is provided separately from the display panel; thus, the size and weight of the electronic device can be reduced.
In the case where the light-receiving devices are used as the touch sensor, the display panel can detect an approach or contact of an object with the use of the light-receiving devices.
The display panel of one embodiment of the present invention can have one or both of an image capturing function and a sensing function in addition to an image displaying function. Thus, the display panel of one embodiment of the present invention can be regarded as being highly compatible with the function other than the display function.
Next, materials that can be used for the light-emitting device and the light-receiving device will be described.
A conductive film transmitting visible light is used as the electrode through which light is extracted, which is either the pixel electrode or the common electrode. A conductive film that reflects visible light is preferably used as the electrode through which light is not extracted. In the case where a display panel includes a light-emitting device emitting infrared light, a conductive film transmitting visible light and infrared light is used as the electrode through which light is extracted, and a conductive film reflecting visible light and infrared light is preferably used as the electrode through which light is not extracted.
A conductive film transmitting visible light may be used also as the electrode through which light is not extracted. In that case, this electrode is preferably provided between a reflective layer and the EL layer. In other words, light emitted by the EL layer may be reflected by the reflective layer to be extracted from the display panel.
As a material that forms the pair of electrodes (the pixel electrode and the common electrode) of the light-emitting device and the light-receiving device, a metal, an alloy, an electrically conductive compound, a mixture thereof, and the like can be used as appropriate. Specific examples include indium tin oxide (In—Sn oxide, also referred to as ITO), In—Si—Sn oxide (also referred to as ITSO), indium zinc oxide (In—Zn oxide), In—W—Zn oxide, an alloy containing aluminum (an aluminum alloy) such as an alloy of aluminum, nickel, and lanthanum (Al—Ni—La), and an alloy of silver, palladium, and copper (Ag—Pd—Cu, also referred to as APC). In addition, it is possible to use a metal such as aluminum (Al), titanium (Ti), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), gallium (Ga), zinc (Zn), indium (In), tin (Sn), molybdenum (Mo), tantalum (Ta), tungsten (W), palladium (Pd), gold (Au), platinum (Pt), silver (Ag), yttrium (Y), or neodymium (Nd) or an alloy containing an appropriate combination of any of these metals. It is also possible to use a Group 1 element or a Group 2 element in the periodic table, which is not described above (e.g., lithium (Li), cesium (Cs), calcium (Ca), or strontium (Sr)), a rare earth metal such as europium (Eu) or ytterbium (Yb), an alloy containing an appropriate combination of any of these elements, graphene, or the like.
The light-emitting device preferably employs a microcavity structure. Thus, one of the pair of electrodes of the light-emitting device preferably includes an electrode having properties of transmitting and reflecting visible light (a transflective electrode), and the other preferably includes an electrode having a property of reflecting visible light (a reflective electrode). When the light-emitting device has a microcavity structure, light obtained from the light-emitting layer can be resonated between the electrodes, whereby light emitted from the light-emitting device can be intensified.
The transflective electrode can have a stacked-layer structure of a reflective electrode and an electrode having a property of transmitting visible light (also referred to as a transparent electrode).
The transparent electrode has a light transmittance higher than or equal to 40%. For example, an electrode having a visible light (light at a wavelength longer than or equal to 400 nm and shorter than 750 nm) transmittance higher than or equal to 40% is preferably used in the light-emitting device. The visible light reflectivity of the transflective electrode is higher than or equal to 10% and lower than or equal to 95%, preferably higher than or equal to 30% and lower than or equal to 80%. The visible light reflectivity of the reflective electrode is higher than or equal to 40% and lower than or equal to 100%, preferably higher than or equal to 70% and lower than or equal to 100%. These electrodes preferably have a resistivity lower than or equal to 1×10−2 Ωcm.
The light-emitting layer contains a light-emitting material (also referred to as a light-emitting substance). The light-emitting layer can contain one or more kinds of light-emitting substances. As the light-emitting substance, a substance whose emission color is blue, violet, bluish violet, green, yellowish green, yellow, orange, red, or the like is appropriately used. Alternatively, as the light-emitting substance, a substance that emits near-infrared light can be used.
Examples of the light-emitting substance include a fluorescent material, a phosphorescent material, a TADF material, and a quantum dot material.
Examples of a fluorescent material include a pyrene derivative, an anthracene derivative, a triphenylene derivative, a fluorene derivative, a carbazole derivative, a dibenzothiophene derivative, a dibenzofuran derivative, a dibenzoquinoxaline derivative, a quinoxaline derivative, a pyridine derivative, a pyrimidine derivative, a phenanthrene derivative, and a naphthalene derivative.
Examples of a phosphorescent material include an organometallic complex (particularly an iridium complex) having a 4H-triazole skeleton, a 1H-triazole skeleton, an imidazole skeleton, a pyrimidine skeleton, a pyrazine skeleton, or a pyridine skeleton; an organometallic complex (particularly an iridium complex) having a phenylpyridine derivative including an electron-withdrawing group as a ligand; a platinum complex; and a rare earth metal complex.
The light-emitting layer may contain one or more kinds of organic compounds (e.g., a host material and an assist material) in addition to the light-emitting substance (guest material). As one or more kinds of organic compounds, one or both of a hole-transport material and an electron-transport material can be used. Alternatively, as one or more kinds of organic compounds, a bipolar material or a TADF material may be used.
The light-emitting layer preferably includes a phosphorescent material and a combination of a hole-transport material and an electron-transport material that easily forms an exciplex, for example. Such a structure makes it possible to efficiently obtain light emission using ExTET (Exciplex-Triplet Energy Transfer), which is energy transfer from an exciplex to a light-emitting substance (a phosphorescent material). When a combination of materials is selected so as to form an exciplex that exhibits light emission whose wavelength overlaps with the wavelength of a lowest-energy-side absorption band of the light-emitting substance, energy can be transferred smoothly and light emission can be obtained efficiently. With this structure, high efficiency, low-voltage driving, and a long lifetime of a light-emitting device can be achieved at the same time.
In addition to the light-emitting layer (the active layer in the fourth layer 113d), each of the first layer 113a, the second layer 113b, the third layer 113c, and the fourth layer 113d may further include a layer containing any of a substance with a high hole-injection property, a substance with a high hole-transport property, a hole-blocking material, a substance with a high electron-transport property, a substance with a high electron-injection property, an electron-blocking material, a substance with a bipolar property (a substance with a high electron-transport property and a high hole-transport property), and the like.
Either a low molecular compound or a high molecular compound can be used for the light-emitting device and the light-receiving device, and an inorganic compound may also be included. Each layer included in the light-emitting device can be formed by a method such as an evaporation method (including a vacuum evaporation method), a transfer method, a printing method, an inkjet method, or a coating method.
For example, each of the first layer 113a, the second layer 113b, the third layer 113c, and the fourth layer 113d may include one or more of a hole-injection layer, a hole-transport layer, a hole-blocking layer, an electron-blocking layer, an electron-transport layer, and an electron-injection layer.
As the common layer 114, one or more of a hole-injection layer, a hole-transport layer, a hole-blocking layer, an electron-blocking layer, an electron-transport layer, and an electron-injection layer can be used. For example, a carrier-injection layer (a hole-injection layer or an electron-injection layer) may be formed as the common layer 114. Note that the light-emitting device does not necessarily include the common layer 114.
Each of the first layer 113a, the second layer 113b, and the third layer 113c preferably includes a light-emitting layer and a carrier-transport layer over the light-emitting layer. Accordingly, the light-emitting layer is inhibited from being exposed on the outermost surface in the manufacturing step of the display panel 100, so that damage to the light-emitting layer can be reduced. Thus, the reliability of the light-emitting device can be increased.
The hole-injection layer is a layer injecting holes from an anode to the hole-transport layer, and a layer containing a material with a high hole-injection property. Examples of a material with a high hole-injection property include an aromatic amine compound and a composite material containing a hole-transport material and an acceptor material (electron-accepting material).
The hole-transport layer transports holes injected from the anode by the hole-injection layer, into the light-emitting layer. The hole-transport layer is a layer containing a hole-transport material. As the hole-transport material, a substance having a hole mobility higher than or equal to 1×10−6 cm2/Vs is preferable. Note that other substances can also be used as long as they have a property of transporting more holes than electrons. As the hole-transport material, materials with a high hole-transport property, such as a π-electron rich heteroaromatic compound (e.g., a carbazole derivative, a thiophene derivative, and a furan derivative) and an aromatic amine (a compound having an aromatic amine skeleton), are preferable.
The electron-blocking layer is provided in contact with the light-emitting layer. The electron-blocking layer has a hole-transport property and contains a material capable of blocking electrons. Any of the materials having an electron-blocking property among the above hole-transport materials can be used for the electron-blocking layer.
The electron-blocking layer has a hole-transport property, and thus can also be referred to as a hole-transport layer. A layer having an electron-blocking property among the hole-transport layers can also be referred to as an electron-blocking layer.
The electron-transport layer transports electrons injected from the cathode by the electron-injection layer, into the light-emitting layer. The electron-transport layer is a layer containing an electron-transport material. A substance with an electron mobility higher than or equal to 1×10−6 cm2/Vs is preferable as the electron-transport material. Note that other substances can also be used as long as they have a property of transporting more electrons than holes. As the electron-transport material, it is possible to use a material with a high electron-transport property, such as a metal complex having a quinoline skeleton, a metal complex having a benzoquinoline skeleton, a metal complex having an oxazole skeleton, a metal complex having a thiazole skeleton, an oxadiazole derivative, a triazole derivative, an imidazole derivative, an oxazole derivative, a thiazole derivative, a phenanthroline derivative, a quinoline derivative having a quinoline ligand, a benzoquinoline derivative, a quinoxaline derivative, a dibenzoquinoxaline derivative, a pyridine derivative, a bipyridine derivative, a pyrimidine derivative, or a π-electron deficient heteroaromatic compound such as a nitrogen-containing heteroaromatic compound.
The hole-blocking layer is provided in contact with the light-emitting layer. The hole-blocking layer has an electron-transport property and contains a material capable of blocking holes. Any of the materials having a hole-blocking property among the above electron-transport materials can be used for the hole-blocking layer.
The hole-blocking layer has an electron-transport property, and thus can also be referred to as an electron-transport layer. A layer having a hole-blocking property among the electron-transport layers can also be referred to as a hole-blocking layer.
The electron-injection layer is a layer injecting electrons from the cathode to the electron-transport layer and a layer containing a material with a high electron-injection property. As the material with a high electron-injection property, an alkali metal, an alkaline earth metal, or a compound thereof can be used. As the material with a high electron-injection property, a composite material containing an electron-transport material and a donor material (an electron-donating material) can also be used.
For the electron-injection layer, an alkali metal, an alkaline earth metal, or a compound thereof, such as lithium, cesium, ytterbium, lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaFx, where x is a given number), 8-(quinolinolato)lithium (abbreviation: Liq), 2-(2-pyridyl)phenolatolithium (abbreviation: LiPP), 2-(2-pyridyl)-3-pyridinolato lithium (abbreviation: LiPPy), 4-phenyl-2-(2-pyridyl)phenolatolithium (abbreviation: LiPPP), lithium oxide (LiOx), or cesium carbonate can be used, for example. In addition, the electron-injection layer may have a stacked-layer structure of two or more layers. In the stacked-layer structure, for example, lithium fluoride can be used for the first layer and ytterbium can be used for the second layer.
Alternatively, the electron-injection layer may be formed using an electron-transport material. For example, a compound having an unshared electron pair and an electron deficient heteroaromatic ring can be used as the electron-transport material. Specifically, a compound having at least one of a pyridine ring, a diazine ring (a pyrimidine ring, a pyrazine ring, and a pyridazine ring), and a triazine ring can be used.
Note that the lowest unoccupied molecular orbital (LUMO) level of the organic compound having an unshared electron pair is preferably greater than or equal to −3.6 eV and less than or equal to −2.3 eV. In general, the highest occupied molecular orbital (HOMO) level and the LUMO level of an organic compound can be estimated by CV (cyclic voltammetry), photoelectron spectroscopy, optical absorption spectroscopy, inverse photoelectron spectroscopy, or the like.
For example, 4,7-diphenyl-1,10-phenanthroline (abbreviation: BPhen), 2,9-di(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline (abbreviation: NBPhen), diquinoxalino[2,3-a:2′,3′-c]phenazine (abbreviation: HATNA), 2,4,6-tris[3′-(pyridin-3-yl)biphenyl-3-yl]-1,3,5-triazine (abbreviation: TmPPPyTz), or the like can be used for the organic compound having an unshared electron pair. Note that NBPhen has a higher glass transition temperature (Tg) than BPhen and thus has high heat resistance.
In the case of manufacturing a tandem light-emitting device, a charge-generation layer (also referred to as an intermediate layer) is provided between two light-emitting units. The intermediate layer has a function of injecting electrons into one of the two light-emitting units and injecting holes to the other when voltage is applied between the pair of electrodes.
For the charge-generation layer, for example, a material that can be used for the electron-injection layer, such as lithium, can be suitably used. For the charge-generation layer, for example, a material that can be used for the hole-injection layer can be suitably used. As the charge-generation layer, a layer containing a hole-transport material and an acceptor material (electron-accepting material) can be used. As the charge-generation layer, a layer containing an electron-transport material and a donor material can be used. Forming such a charge-generation layer can inhibit an increase in the driving voltage that would be caused by stacking light-emitting units.
The active layer in the fourth layer 113d includes a semiconductor. Examples of the semiconductor include an inorganic semiconductor such as silicon and an organic semiconductor including an organic compound. This embodiment describes an example in which an organic semiconductor is used as the semiconductor included in the active layer. The use of an organic semiconductor is preferable because the light-emitting layer and the active layer can be formed by the same method (e.g., a vacuum evaporation method) and thus the same manufacturing apparatus can be used.
As the active layer, a pn or pin photodiode can be used, for example. An n-type semiconductor material and a p-type semiconductor material that can be used for the active layer are described below. The n-type semiconductor material and the p-type semiconductor material may be formed as layers to be stacked or may be mixed to form one layer.
Examples of an n-type semiconductor material contained in the active layer include electron-accepting organic semiconductor materials such as fullerene (e.g., C60 and C70) and fullerene derivatives. Other examples of fullerene derivatives include [6,6]-Phenyl-C71-butyric acid methyl ester (abbreviation: PC70BM), [6,6]-Phenyl-C61-butyric acid methyl ester (abbreviation: PC60BM), and 1′,1″,4′,4″-Tetrahydro-di[1,4]methanonaphthaleno[1,2:2′,3′,56,60:2″,3″][5,6]fullerene-C60 (abbreviation: ICBA).
Another example of an n-type semiconductor material includes a perylenetetracarboxylic derivative such as N,N′-dimethyl-3,4,9,10-perylenetetracarboxylic diimide (abbreviation: Me-PTCDI).
Another example of an n-type semiconductor material includes 2,2′-(5,5′-(thieno[3,2-b]thiophene-2,5-diyl)bis(thiophene-5,2-diyl))bis(methan-1-yl-1-ylidene)dimalononitrile (abbreviation: FT2TDMN).
Other examples of an n-type semiconductor material include a metal complex having a quinoline skeleton, a metal complex having a benzoquinoline skeleton, a metal complex having an oxazole skeleton, a metal complex having a thiazole skeleton, an oxadiazole derivative, a triazole derivative, an imidazole derivative, an oxazole derivative, a thiazole derivative, a phenanthroline derivative, a quinoline derivative, a benzoquinoline derivative, a quinoxaline derivative, a dibenzoquinoxaline derivative, a pyridine derivative, a bipyridine derivative, a pyrimidine derivative, a naphthalene derivative, an anthracene derivative, a coumarin derivative, a rhodamine derivative, a triazine derivative, and a quinone derivative.
Examples of a p-type semiconductor material contained in the active layer include electron-donating organic semiconductor materials such as copper(II) phthalocyanine (CuPc), tetraphenyldibenzoperiflanthene (DBP), zinc phthalocyanine (ZnPc), tin phthalocyanine (SnPc), quinacridone, and rubrene.
Examples of a p-type semiconductor material include a carbazole derivative, a thiophene derivative, a furan derivative, and a compound having an aromatic amine skeleton. Other examples of a p-type semiconductor material include a naphthalene derivative, an anthracene derivative, a pyrene derivative, a triphenylene derivative, a fluorene derivative, a pyrrole derivative, a benzofuran derivative, a benzothiophene derivative, an indole derivative, a dibenzofuran derivative, a dibenzothiophene derivative, an indolocarbazole derivative, a porphyrin derivative, a phthalocyanine derivative, a naphthalocyanine derivative, a quinacridone derivative, a rubrene derivative, a tetracene derivative, a polyphenylene vinylene derivative, a polyparaphenylene derivative, a polyfluorene derivative, a polyvinylcarbazole derivative, and a polythiophene derivative.
The HOMO level of the electron-donating organic semiconductor material is preferably shallower (higher) than the HOMO level of the electron-accepting organic semiconductor material. The LUMO level of the electron-donating organic semiconductor material is preferably shallower (higher) than the LUMO level of the electron-accepting organic semiconductor material.
Fullerene having a spherical shape is preferably used as the electron-accepting organic semiconductor material, and an organic semiconductor material having a substantially planar shape is preferably used as the electron-donating organic semiconductor material. Molecules of similar shapes tend to aggregate, and aggregated molecules of similar kinds, which have molecular orbital energy levels close to each other, can increase a carrier-transport property.
For the active layer, a high molecular compound such as Poly[[4,8-bis[5-(2-ethylhexyl)-2-thienyl]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl]-2,5-thiophenediyl[5,7-bis(2-ethylhexyl)-4,8-dioxo-4H,8H-benzo[1,2-c:4,5-c′]dithiophene-1,3-diyl]] polymer (abbreviation: PBDB-T) or a PBDB-T derivative, which functions as a donor, can be used. For example, a method in which an acceptor material is dispersed to PBDB-T or a PBDB-T derivative can be used.
For example, the active layer is preferably formed by co-evaporation of an n-type semiconductor and a p-type semiconductor. Alternatively, the active layer may be formed by stacking an n-type semiconductor and a p-type semiconductor. The active layer may contain a mixture of three or more kinds of materials. For example, a third material may be mixed with an n-type semiconductor material and a p-type semiconductor material in order to extend the wavelength range. In this case, the third material may be a low molecular compound or a high molecular compound.
As the functional layer other than the active layer, the light-receiving device may further include a layer containing a substance with a high hole-transport property, a substance with a high electron-transport property, a substance with a bipolar property (a substance with a high electron-transport property and a high hole-transport property), or the like. Without limitation to the above, the light-receiving device may further include a layer containing a substance with a high hole-injection property, a hole-blocking material, a material with a high electron-injection property, an electron-blocking material, or the like. Layers other than the active layer in the light-receiving device can be formed using a material that can be used for the light-emitting device, for example.
As the hole-transport material or the electron-blocking material, a high molecular compound such as poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonic acid) (PEDOT/PSS), or an inorganic compound such as a molybdenum oxide or copper iodide (CuI) can be used, for example. As the electron-transport material or the hole-blocking material, an inorganic compound such as zinc oxide (ZnO), or an organic compound such as polyethylenimine ethoxylate (PEIE) can be used. The light-receiving device may include a mixed film of PEIE and ZnO, for example.
Next, an example of a method for manufacturing the display panel 100 illustrated in
Thin films included in the display panel (e.g., insulating films, semiconductor films, and conductive films) can be formed by a sputtering method, a CVD method, a vacuum evaporation method, a PLD method, an ALD method, or the like. Examples of a CVD method include a PECVD method and a thermal CVD method. As an example of the thermal CVD method, a metal organic chemical vapor deposition (MOCVD) method can be given.
Alternatively, thin films included in the display panel (e.g., an insulating films, a semiconductor films, and a conductive film) can be formed by a method such as spin coating, dipping, spray coating, ink-jetting, dispensing, screen printing, offset printing, a doctor knife method, slit coating, roll coating, curtain coating, or knife coating.
Specifically, for manufacture of the light-emitting device, a vacuum process such as an evaporation method and a solution process such as a spin coating method or an inkjet method can be used. Examples of an evaporation method include physical vapor deposition methods (PVD methods) such as a sputtering method, an ion plating method, an ion beam evaporation method, a molecular beam evaporation method, and a vacuum evaporation method, and a chemical vapor deposition method (CVD method). Specifically, functional layers (e.g., a hole-injection layer, a hole-transport layer, a light-emitting layer, an electron-transport layer, and an electron-injection layer) included in the EL layer can be formed by a method such as an evaporation method (e.g., a vacuum evaporation method), a coating method (e.g., a dip coating method, a die coating method, a bar coating method, a spin coating method, or a spray coating method), or a printing method (e.g., an inkjet method, a screen printing (stencil) method, an offset printing (planography) method, a flexography (relief printing) method, a gravure printing method, or a micro-contact printing method).
Thin films included in the display panel can be processed by a photolithography method or the like. Alternatively, thin films may be processed by a nanoimprinting method, a sandblasting method, a lift-off method, or the like. Alternatively, island-shaped thin films may be directly formed by a film formation method using a shielding mask such as a metal mask.
There are the following two typical methods of a photolithography method. In one of the methods, a resist mask is formed over a thin film that is to be processed, the thin film is processed by etching or the like, and then the resist mask is removed. In the other method, a photosensitive thin film is formed and then processed into a desired shape by light exposure and development.
As the light used for light exposure in the photolithography method, for example, an i-line (with a wavelength of 365 nm), a g-line (with a wavelength of 436 nm), an h-line (with a wavelength of 405 nm), or combined light of any of them can be used. Alternatively, ultraviolet rays, KrF laser light, ArF laser light, or the like can be used. In addition, light exposure may be performed by liquid immersion exposure technique. As the light used for light exposure, extreme ultraviolet (EUV) light or X-rays may also be used. Instead of the light used for the light exposure, an electron beam can also be used. It is preferable to use EUV light, X-rays, or an electron beam because they can perform extremely minute processing. Note that in the case of performing light exposure by scanning of a beam such as an electron beam, a photomask is not necessarily used.
For etching of thin films, a dry etching method, a wet etching method, a sandblasting method, or the like can be used.
First, as illustrated in
Next, as illustrated in
As illustrated in
The above-described structure that can be used for the pixel electrode can be used for the pixel electrodes 111a, 111b, and 111c. The pixel electrodes 111a, 111b, and 111c can be formed by a sputtering method or a vacuum evaporation method, for example.
Each of the end portions of the pixel electrodes 111a, 111b, and 111c preferably has a tapered shape. This can improve the coverage with the layers formed over the pixel electrodes 111a, 111b, and 111c and improve the manufacturing yield of the light-emitting devices.
Here, hydrophobization treatment is preferably performed on the pixel electrodes 111a, 111b, and 111c. Through hydrophobization treatment, hydrophilic properties of the surfaces to be processed can be changed into hydrophobic properties, or hydrophobic properties of the surfaces to be processed can be enhanced. By performing hydrophobization treatment on the pixel electrodes, adhesion between the pixel electrodes and the first layer 113A formed later can be increased, so that film peeling can be inhibited. Note that hydrophobization treatment is not necessarily performed.
Hydrophobization treatment can be performed by fluorine modification of the pixel electrodes, for example. The fluorine modification can be performed by, for example, treatment or heat treatment using a fluorine-containing gas, plasma treatment in an atmosphere of a fluorine-containing gas, or the like. As the fluorine-containing gas, a fluorine gas such as a fluorocarbon gas can be used, for example. As the fluorocarbon gas, a low carbon fluoride gas such as a carbon tetrafluoride (CF4) gas, a C4F6 gas, a C2F6 gas, a C4F8 gas, or a C5F8 gas can be used, for example. Moreover, as the fluorine-containing gas, a SF6 gas, a NF3 gas, a CHF3 gas, or the like can be used, for example. Alternatively, a helium gas, an argon gas, a hydrogen gas, or the like can be added to any of the above gases as appropriate.
In addition, treatment using a silylating agent is performed on the surfaces of the pixel electrodes after plasma treatment is performed in a gas atmosphere containing a Group 18 element such as argon, so that the surfaces of the pixel electrodes can have hydrophobic properties. As the silylating agent, hexamethyldisilazane (HMDS), trimethylsilylimidazole (TMSI), or the like can be used. Alternatively, treatment using a silane coupling agent is performed on the surfaces of the pixel electrodes after plasma treatment is performed in a gas atmosphere containing a Group 18 element such as argon, so that the surfaces of the pixel electrodes can have hydrophobic properties.
Plasma treatment on the surfaces of the pixel electrodes in a gas atmosphere containing a Group 18 element such as argon can apply damage to the surfaces of the pixel electrodes. Accordingly, a methyl group included in the silylating agent such as HMDS is likely to bond to the surfaces of the pixel electrodes. Moreover, silane coupling due to the silane coupling agent is likely to occur. As described above, treatment using a silylating agent or a silane coupling agent performed on the surfaces of the pixel electrodes after plasma treatment in a gas atmosphere containing a Group 18 element such as argon enables the surfaces of the pixel electrodes to have hydrophobic properties.
Treatment using the silylating agent, the silane coupling agent, or the like can be performed by application of the silylating agent, the silane coupling agent, or the like by a spin coating method or a dipping method, for example. Treatment using the silylating agent, the silane coupling agent, or the like can also be performed by forming a film containing the silylating agent, a film containing the silane coupling agent, or the like over the pixel electrodes and the like by a gas phase method, for example. In a gas phase method, first, a material containing the silylating agent, a material containing the silane coupling agent, or the like is volatilized so that the silylating agent, the silane coupling agent, or the like is included in the atmosphere. Next, a substrate where the pixel electrodes and the like are formed is put in the atmosphere. Accordingly, a film containing the silylating agent, the silane coupling agent, or the like can be formed over the pixel electrodes, so that the surfaces of the pixel electrodes can have hydrophobic properties.
The first layer 113A is a layer to be the first layer 113a later. Thus, the first layer 113A can have the above-described structure that can be employed for the first layer 113a. The first layer 113A can be formed by a method such as an evaporation method (including a vacuum evaporation method), a transfer method, a printing method, an inkjet method, or a coating method. The first layer 113A is preferably formed by an evaporation method. A premix material may be used in the deposition by an evaporation method. Note that in this specification and the like, a premix material is a composite material in which a plurality of materials are combined or mixed in advance.
As described above, a material having high heat resistance is used for the light-emitting device of the display apparatus of one embodiment of the present invention. Specifically, the upper temperature limit of the compounds contained in the first layer 113A is preferably higher than or equal to 100° C. and lower than or equal to 180° C., further preferably higher than or equal to 120° C. and lower than or equal to 180° C., still further preferably higher than or equal to 140° C. and lower than or equal to 180° C. Thus, the reliability of the light-emitting device can be increased. In addition, the upper limit of the temperature that can be applied in the manufacturing process of the display apparatus can be increased. Thus, the range of choices of the materials and the formation method of the display apparatus can be widened, thereby improving the manufacturing yield and the reliability.
As the first mask layer 118A and the second mask layer 119A, a film that is highly resistant to the process conditions for the first layer 113A, a second layer 113B and a third layer 113C to be formed later, and the like, specifically, a film having high etching selectivity with EL layers, is used.
The first mask layer 118A and the second mask layer 119A can be formed by a sputtering method, an ALD method (including a thermal ALD method and a PEALD method), a CVD method, or a vacuum evaporation method, for example. The first mask layer 118A, which is formed over and in contact with the EL layer, is preferably formed by a formation method that causes less damage to the EL layer than a formation method for the second mask layer 119A. For example, the first mask layer 118A is preferably formed by an ALD method or a vacuum evaporation method rather than a sputtering method.
The first mask layer 118A and the second mask layer 119A are formed at a temperature lower than the upper temperature limit of the EL layer. The substrate temperature at the time of forming the first mask layer 118A and the second mask layer 119A is typically lower than or equal to 200° C., preferably lower than or equal to 150° C., further preferably lower than or equal to 120° C., still further preferably lower than or equal to 100° C., yet still further preferably lower than or equal to 80° C.
Examples of indicators of the upper temperature limit are the glass transition point, the softening point, the melting point, the thermal decomposition temperature, and the 5% weight loss temperature. The upper temperature limit of each of the first layer 113A to the third layer 113C (i.e., the first layer 113a to the third layer 113c) can be any of these temperatures, preferably the lowest temperature.
As described above, a material having high heat resistance is used for the light-emitting device of the display apparatus of one embodiment of the present invention. Thus, the substrate temperature at the time of forming a mask film can be higher than or equal to 100° C. and lower than or equal to 180° C., higher than or equal to 120° C. and lower than or equal to 180° C., or higher than or equal to 140° C. and lower than or equal to 180° C. For example, an inorganic insulating film formed at a higher temperature can be denser and have a higher barrier property. Thus, by depositing the mask film at such a temperature, damage to the first layer 113A can be further reduced, and the reliability of the light-emitting device can be increased.
The first mask layer 118A and the second mask layer 119A are preferably films that can be removed by a wet etching method. Using a wet etching method can reduce damage to the first layer 113A in processing of the first mask layer 118A and the second mask layer 119A, compared to the case of using a dry etching method.
The first mask layer 118A is preferably a film having high etching selectivity with the second mask layer 119A.
In the method for manufacturing a display panel of this embodiment, it is desirable that the layers (e.g., the hole-injection layer, the hole-transport layer, the light-emitting layer, and the electron-transport layer) included in the EL layer not be easily processed in the step of processing the mask layers, and that the mask layers not be easily processed in the steps of processing the layers included in the EL layer. In consideration of the above, the materials and a processing method for the mask layers and processing methods for the EL layer are preferably selected.
Although this embodiment describes an example where the mask layer is formed to have a two-layer structure of the first mask layer and the second mask layer, the mask layer may have a single-layer structure or a stacked-layer structure of three or more layers.
As the first mask layer 118A and the second mask layer 119A, it is preferable to use an inorganic film such as a metal film, an alloy film, a metal oxide film, a semiconductor film, or an inorganic insulating film, for example.
For each of the first mask layer 118A and the second mask layer 119A, it is possible to use a metal material such as gold, silver, platinum, magnesium, nickel, tungsten, chromium, molybdenum, iron, cobalt, copper, palladium, titanium, aluminum, yttrium, zirconium, or tantalum or an alloy material containing any of the metal materials, for example. It is particularly preferable to use a low-melting-point material such as aluminum or silver. The use of a metal material capable of blocking ultraviolet rays for one or both of the first mask layer 118A and the second mask layer 119A is preferable, in which case the EL layer can be inhibited from being irradiated with ultraviolet rays and deteriorating.
For each of the first mask layer 118A and the second mask layer 119A, a metal oxide such as In—Ga—Zn oxide can be used. As the first mask layer 118A or the second mask layer 119A, an In—Ga—Zn oxide film can be formed by a sputtering method, for example. Furthermore, indium oxide, In—Zn oxide, In—Sn oxide, indium titanium oxide (In—Ti oxide), indium tin zinc oxide (In—Sn—Zn oxide), indium titanium zinc oxide (In—Ti—Zn oxide), indium gallium tin zinc oxide (In—Ga—Sn—Zn oxide), or the like can be used. Alternatively, indium tin oxide containing silicon or the like can also be used.
In addition, in place of gallium described above, an element M (M is one or more kinds selected from aluminum, silicon, boron, yttrium, copper, vanadium, beryllium, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, magnesium, and the like) may be used.
As each of the first mask layer 118A and the second mask layer 119A, any of a variety of inorganic insulating films that can be used as the protective layer 131 can be used. In particular, an oxide insulating film is preferable because its adhesion to the EL layer is higher than that of a nitride insulating film. For example, an inorganic insulating material such as aluminum oxide, hafnium oxide, or silicon oxide can be used for each of the first mask layer 118A and the second mask layer 119A. As the first mask layer 118A or the second mask layer 119A, an aluminum oxide film can be formed by an ALD method, for example. The use of an ALD method is preferable, in which case damage to a base (in particular, the EL layer or the like) can be reduced.
For example, an inorganic insulating film (e.g., an aluminum oxide film) formed by an ALD method can be used as the first mask layer 118A, and an inorganic film (e.g., an In—Ga—Zn oxide film, an aluminum film, or a tungsten film) formed by a sputtering method can be used as the second mask layer 119A.
Note that the same inorganic insulating film can be used for both the first mask layer 118A and the insulating layer 125 that is to be formed later. For example, an aluminum oxide film formed by an ALD method can be used for both the first mask layer 118A and the insulating layer 125. Here, the same deposition conditions may be used for the first mask layer 118A and the insulating layer 125. For example, when the first mask layer 118A is formed under conditions similar to those of the insulating layer 125, the first mask layer 118A can be an insulating layer having a high barrier property against at least one of water and oxygen. Note that without limitation to this, different deposition conditions may be employed for the first mask layer 118A and the insulating layer 125.
A material dissolvable in a solvent that is chemically stable with respect to at least a film on the outermost side of the first layer 113A may be used for one or both of the first mask layer 118A and the second mask layer 119A. Specifically, a material that will be dissolved in water or alcohol can be suitably used. In forming a film of such a material, it is preferable to apply the material dissolved in a solvent such as water or alcohol by a wet film formation method and then perform heat treatment for evaporating the solvent. At this time, heat treatment is preferably performed in a reduced-pressure atmosphere, in which case the solvent can be removed at a low temperature in a short time and thermal damage to the EL layer can be reduced accordingly.
Each of the first mask layer 118A and the second mask layer 119A may be formed by a wet film formation method such as spin coating, dipping, spray coating, ink-jetting, dispensing, screen printing, offset printing, a doctor knife method, slit coating, roll coating, curtain coating, or knife coating.
Each of the first mask layer 118A and the second mask layer 119A may be formed using an organic material such as polyvinyl alcohol (PVA), polyvinyl butyral, polyvinylpyrrolidone, polyethylene glycol, polyglycerin, pullulan, water-soluble cellulose, or an alcohol-soluble polyamide resin.
Next, a resist mask 190a is formed over the second mask layer 119A as illustrated in
The resist mask may be formed using either a positive resist material or a negative resist material.
The resist mask 190a is provided at a position overlapping with the pixel electrode 111a. One island-shaped pattern is preferably provided for one subpixel 110a as the resist mask 190a. Alternatively, one band-like pattern for a plurality of subpixels 110a aligned in one column (aligned in the Y direction in
Here, when the resist mask 190a is formed such that the end portion of the resist mask 190a is positioned outward from the end portion of the pixel electrode 111a, the end portion of the first layer 113a to be formed later can be positioned outward from the end portion of the pixel electrode 111a.
Note that the resist mask 190a is preferably provided also at a position overlapping with the connection portion 140. This can inhibit the conductive layer 123 from being damaged during the manufacturing step of the display panel.
Then, as illustrated in
In an etching of the second mask layer 119A, an etching condition with high selectivity is preferably employed so that the first mask layer 118A is not removed by the etching. Since the EL layer is not exposed in processing the second mask layer 119A, the range of choices of the processing method is wider than that for processing the first mask layer 118A. Specifically, deterioration of the EL layer can be further inhibited even when a gas containing oxygen is used as an etching gas in processing the second mask layer 119A.
After that, the resist mask 190a is removed. The resist mask 190a can be removed by ashing using oxygen plasma, for example. Alternatively, an oxygen gas and any of CF4, C4F8, SF6, CHF3, Cl2, H2O, BCl3, and a noble gas (also referred to as a rare gas) such as He may be used. Alternatively, the resist mask 190a may be removed by wet etching. At this time, the first mask layer 118A is positioned on the outermost surface and the first layer 113A is not exposed; thus, the first layer 113A can be inhibited from being damaged in the step of removing the resist mask 190a. In addition, the range of choices of the method for removing the resist mask 190a can be widened.
Next, as illustrated in
The first mask layer 118A and the second mask layer 119A can be processed by a wet etching method or a dry etching method. The first mask layer 118A and the second mask layer 119A are preferably processed by anisotropic etching.
Using a wet etching method can reduce damage to the first layer 113A in processing of the first mask layer 118A and the second mask layer 119A, compared to the case of using a dry etching method. In the case of using a wet etching method, it is preferable to use a developer, an aqueous solution of tetramethylammonium hydroxide (TMAH), dilute hydrofluoric acid, oxalic acid, phosphoric acid, acetic acid, nitric acid, a chemical solution containing a mixed solution thereof, or the like, for example.
In the case of using a dry etching method, deterioration of the first layer 113A can be inhibited by not using a gas containing oxygen as the etching gas. In the case of using a dry etching method, it is preferable to use a gas containing CF4, C4F8, SF6, CHF3, Cl2, H2O, or BCl3 or a noble gas (also referred to as a rare gas) such as He as the etching gas, for example.
For example, when an aluminum oxide film formed by an ALD method is used as the first mask layer 118A, the first mask layer 118A can be processed by a dry etching method using CHF3 and He. In the case where an In—Ga—Zn oxide film formed by a sputtering method is used as the second mask layer 119A, the second mask layer 119A can be processed by a wet etching method using diluted phosphoric acid. Alternatively, the mask layer 119A may be processed by a dry etching method using CH4 and Ar. Alternatively, the second mask layer 119A can be processed by a wet etching method using diluted phosphoric acid. In the case where a tungsten film formed by a sputtering method is used as the second mask layer 119A, the second mask layer 119A can be processed by a dry etching method using a combination of CF4 and O2, a combination of CSF6 and O2, a combination of CF4, Cl2, and O2, or a combination of CF6, Cl2, and O2.
Next, as illustrated in
Thus, as illustrated in
The first layer 113a covers the top surface and the side surface of the pixel electrode 111a and thus, the subsequent steps can be performed without exposure of the pixel electrode 111a. When the end portion of the pixel electrode 111a is exposed, corrosion might occur in the etching step or the like. A product generated by corrosion of the pixel electrode 111a might be unstable; for example, the product might be dissolved in a solution in wet etching and might be scattered in an atmosphere in dry etching. The product dissolved in a solution or scattered in an atmosphere might be attached to a surface to be processed, the side surface of the first layer 113a, and the like, which adversely affects the characteristics of the light-emitting device or forms a leakage path between the light-emitting devices in some cases. In a region where the end portion of the pixel electrode 111a is exposed, adhesion between layers in contact with each other might be lowered, which might be likely to cause peeling of the first layer 113a or the pixel electrode 111a.
Accordingly, with the structure in which the first layer 113a covers the top surface and the side surface of the pixel electrode 111a, for example, the yield of the light-emitting device can be improved and the display quality of the light-emitting device can be improved.
Note that part of the first layer 113A may be removed using the resist mask 190a. Then, the resist mask 190a may be removed.
The first layer 113A is preferably processed by anisotropic etching. In particular, anisotropic dry etching is preferably used. Alternatively, wet etching may be used.
In the case of using a dry etching method, deterioration of the first layer 113A can be inhibited by not using a gas containing oxygen as the etching gas.
A gas containing oxygen may be used as the etching gas. When the etching gas contains oxygen, the etching rate can be increased. Thus, the etching can be performed under a low-power condition while an adequately high etching rate is maintained. Thus, damage to the first layer 113A can be inhibited. Furthermore, attachment of a reaction product generated in the etching can be inhibited.
In the case of using a dry etching method, it is preferable to use a gas containing one or more kinds of H2, CF4, C4F8, SF6, CHF3, Cl2, H2O, BCl3, and a noble gas (also referred to as a rare gas) such as He and Ar as the etching gas, for example. Alternatively, a gas containing oxygen and at least one of the above is preferably used as the etching gas. Alternatively, an oxygen gas may be used as the etching gas. Specifically, for example, a gas containing H2 and Ar or a gas containing CF4 and He can be used as the etching gas. As another example, a gas containing CF4, He, and oxygen can be used as the etching gas.
Through the above steps, regions of the first layer 113A, the first mask layer 118A, and the second mask layer 119A that do not overlap with the resist mask 190a can be removed.
Then, as illustrated in
As illustrated in
The second layer 113B is a layer to be the second layer 113b later. The second layer 113b emits light of a color different from that of light emitted by the first layer 113a. Structures, materials, and the like that can be used for the second layer 113b are similar to those for the first layer 113a. The second layer 113B can be formed by a method similar to that for the first layer 113A.
The first mask layer 118B can be formed using a material that can be used for the first mask layer 118A. The second mask layer 119B can be formed using a material that can be used for the second mask layer 119A.
Next, a resist mask 190b is formed over the second mask layer 119B as illustrated in
The resist mask 190b is provided at a position overlapping with the pixel electrode 111b. The resist mask 190b may be provided also at a position overlapping with the region to be the connection portion 140 later.
Next, steps similar to those described with reference to
Accordingly, as illustrated in
Next, as illustrated in
As illustrated in
The third layer 113C is a layer to be the third layer 113c later. The third layer 113c emits light of a color different from those of light emitted by the first layer 113a and the second layer 113b. Structures, materials, and the like that can be used for the third layer 113c are similar to those for the first layer 113a. The third layer 113C can be formed by a method similar to that for the first layer 113A.
The first mask layer 118C can be formed using a material that can be used for the first mask layer 118A. The second mask layer 119C can be formed using a material that can be used for the second mask layer 119A.
Next, a resist mask 190c is formed over the second mask layer 119C as illustrated in
The resist mask 190c is provided at a position overlapping with the pixel electrode 111c. The resist mask 190c may be provided also at a position overlapping with the region to be the connection portion 140 later.
Next, steps similar to those described with reference to
Accordingly, as illustrated in
Note that the side surfaces of the first layer 113a, the second layer 113b, and the third layer 113c are preferably perpendicular or substantially perpendicular to their formation surfaces. For example, the angle between the formation surfaces and these side surfaces is preferably greater than or equal to 60° and less than or equal to 90°.
When the EL layers are processed by a photolithography method as described above, the distance between pixels can be shortened to be less than or equal to 8 μm, less than or equal to 5 μm, less than or equal to 3 μm, less than or equal to 2 μm, or less than or equal to 1 μm. Here, the distance between pixels can be specified by the distance between facing end portions of two adjacent layers among the first layer 113a, the second layer 113b, and the third layer 113c, for example. The distance between pixels is shortened in this manner, whereby a display apparatus with high resolution and a high aperture ratio can be provided.
Subsequently, the mask layers 119a, 119b, and 119c are removed as illustrated in
Note that a structure may be employed in which the step of forming an insulating film 125A is performed without removal of the mask layers 119a, 119b, and 119c.
The step of removing the mask layers can be performed by a method similar to that for the step of processing the mask layers. In particular, using a wet etching method can reduce damage to the first layer 113a, the second layer 113b, and the third layer 113c in removing the mask layers, as compared to the case of using a dry etching method.
The mask layers may be removed by being dissolved in a solvent such as water or alcohol. Examples of alcohol include ethyl alcohol, methyl alcohol, isopropyl alcohol (IPA), and glycerin.
After the mask layers are removed, drying treatment may be performed to remove water included in the EL layer and water adsorbed on the surface of the EL layer. For example, heat treatment in an inert gas atmosphere or a reduced-pressure atmosphere can be performed. Heat treatment can be performed with a substrate temperature higher than or equal to 50° C. and lower than or equal to 200° C., preferably higher than or equal to 60° C. and lower than or equal to 150° C., further preferably higher than or equal to 70° C. and lower than or equal to 120° C. Employing a reduced-pressure atmosphere is preferable, in which case drying at a lower temperature is possible.
Next, as illustrated in
The insulating film 125A is a layer to be the insulating layer 125 later. Thus, the insulating film 125A can be formed using a material that can be used for the insulating layer 125. As the insulating film 125A, an inorganic insulating film can be formed by an ALD method, an evaporation method, a sputtering method, a CVD method, or a PLD method, for example. The thickness of the insulating film 125A is preferably greater than or equal to 3 nm, greater than or equal to 5 nm, or greater than or equal to 10 nm and less than or equal to 200 nm, less than or equal to 150 nm, less than or equal to 100 nm, or less than or equal to 50 nm.
The insulating film 125A, which is formed in contact with the side surface of the EL layer, preferably is deposited by a formation method that causes less damage to the EL layer. In addition, the insulating film 125A is formed at a temperature lower than the upper temperature limit of the EL layer. The substrate temperature at the time of forming the insulating film 125A is preferably higher than or equal to 60° C., higher than or equal to 80° C., higher than or equal to 100° C., or higher than or equal to 120° C. and lower than or equal to 200° C., lower than or equal to 180° C., lower than or equal to 160° C., lower than or equal to 150° C., or lower than or equal to 140° C. Note that the steps after the formation of the insulating film 125A are also performed at a temperature lower than the upper temperature limit of the EL layer.
As described above, a material with high heat resistance is used for the light-emitting device of the display apparatus of one embodiment of the present invention. Thus, the substrate temperature at the time of forming the insulating film 125A can be higher than or equal to 100° C. and lower than or equal to 180° C., higher than or equal to 120° C. and lower than or equal to 180° C., or higher than or equal to 140° C. and lower than or equal to 180° C. For example, an inorganic insulating film formed at a higher temperature can be denser and have a higher barrier property. Thus, by depositing the insulating film 125A at such a temperature, damage to the first layer 113a, the second layer 113b, and the third layer 113c can be further reduced, and the reliability of the light-emitting device can be increased.
As the insulating film 125A, an aluminum oxide film is preferably formed by an ALD method, for example. The use of an ALD method is preferable, in which case damage by the film formation is reduced and a film with good coverage can be formed. Here, the insulating film 125A can be formed using a material similar to those for the mask layers 118a, 118b, and 118c and a method similar to that for the mask layers 118a, 118b, and 118c. In that case, a boundary between the insulating film 125A and the mask layers 118a, 118b, and 118c might be unclear.
As illustrated in
As described later, the insulating layer 127 including a photosensitive organic resin is formed in contact with a top surface of the insulating film 125A. Therefore, the top surface of the insulating film 125A preferably has a high affinity with respect to a photosensitive organic resin (e.g., a photosensitive resin composition containing an acrylic resin) to be the insulating layer 127. To improve the affinity, the top surface of the insulating film 125A is preferably made to be hydrophobic (or more hydrophobic) by performing surface treatment. For example, treatment is preferably performed using a silylating agent such as hexamethyldisilazane (HMDS). When the top surface of the insulating film 125A is made to be hydrophobic in this manner, the insulating layer 127a can be formed with favorable adhesiveness. Note that above-described hydrophobization treatment may be performed as surface treatment.
Next, as illustrated in
The insulating layer 127a is a film to be the insulating layer 127 in a later step, and the above-described organic material can be used for the insulating layer 127a. As the organic material, a photosensitive organic resin is preferably used; for example, a photosensitive resin composition containing an acrylic resin may be used. The viscosity of the insulating layer 127a is preferably greater than or equal to 1 cP and less than or equal to 1500 cP, further preferably greater than or equal to 1 cP and less than or equal to 12 cP. When the viscosity of the insulating layer 127a is within the above range, the insulating layer 127 having a tapered shape as illustrated in
The insulating layer 127a is preferably formed using a resin composition containing a polymer, an acid-generating agent, and a solvent, for example. The polymer is formed using one or more kinds of monomers and has a structure in which one or more kinds of structural units (also referred to as structure units) are repeated regularly or irregularly. As the acid-generating agent, one or both of a compound that generates acid by light irradiation and a compound that generates acid by heating can be used. The resin composition may further contain one or more of a photosensitive agent, a sensitizer, a catalyst, an adhesive additive, an interface active agent, and an antioxidant. As such a resin composition, for example, the resin composition described in Patent Document 3 (Japanese Published Patent Application No. 2020-101659) can be suitably used. For example, the resin composition can include a quinonediazide compound as the acid generator.
There is no particular limitation on the formation method for the insulating layer 127a, and for example, the insulating layer 127a can be formed using a wet film formation method such as spin coating, dipping, spray coating, ink-jetting, dispensing, screen printing, offset printing, doctor blade coating, slit coating, roll coating, curtain coating, or knife coating. In particular, the insulating layer 127a is preferably formed by spin coating.
Heat treatment is preferably performed after the application of the insulating layer 127a. Heat treatment is performed at a temperature lower than the upper temperature limit of the EL layer. The substrate temperature in heat treatment is higher than or equal to 50° C. and lower than or equal to 200° C., preferably higher than or equal to 60° C. and lower than or equal to 150° C., and further preferably higher than or equal to 70° C. and lower than or equal to 120° C. Accordingly, the solvent contained in the insulating layer 127a can be removed.
As described above, a material with high heat resistance is used for the light-emitting device of the display apparatus of one embodiment of the present invention. Thus, the substrate temperature in heat treatment after the application of the insulating layer 127a can be higher than or equal to 100° C. and lower than or equal to 180° C., higher than or equal to 120° C. and lower than or equal to 180° C., or higher than or equal to 140° C. and lower than or equal to 180° C.
Next, as illustrated in
When a visible light or ultraviolet rays is used for light exposure, the visible light or ultraviolet rays preferably include an i-line (wavelength: 365 nm). Furthermore, visible light including the g-line (wavelength: 436 nm), the h-line (wavelength: 405 nm), or the like may be used.
Here, when a barrier insulating layer against oxygen (e.g., an aluminum oxide film) is provided as one or both of the mask layer 118 (the mask layers 118a, 118b, and 118c) and the insulating film 125A, diffusion of oxygen into the EL layer can be reduced. In particular, when the EL layer is irradiated with light (visible light or ultraviolet rays), an organic compound contained in the EL layer is brought into an excited state and a reaction with oxygen contained in the atmosphere is promoted in some cases. Specifically, when the EL layer is irradiated with light (visible light or ultraviolet rays in an oxygen-containing atmosphere, oxygen might be bonded to the organic compound contained in the EL layer. When one or both of the mask layer 118 and the insulating film 125A are provided over the EL layer, bonding of oxygen in the atmosphere to the organic compound contained in the EL layer 113 can be suppressed.
Although
In the case where the light-blocking film 135A is provided over the insulating film 125A as illustrated in
In a light exposure to the insulating layer 127a, the EL layer which is formed to have a tapered portion is irradiated with the above-described visible light or ultraviolet rays easily compared to the EL layer in which the portion corresponding to the tapered portion in a cross-sectional view of a display apparatus is formed perpendicularly, for example. Thus, providing the light-blocking film 135A can reduce damage to the EL layer due to the above-described visible light or ultraviolet rays even in the tapered portion. Thus, a display apparatus having higher reliability can be manufactured.
Next, as illustrated in
Next, as illustrated in
Here, when a barrier insulating layer against oxygen (e.g., an aluminum oxide film) is provided as one or both of the mask layer 118 (the mask layers 118a, 118b, and 118c) and the insulating film 125A, diffusion of oxygen into the EL layer can be reduced. In particular, when the EL layer is irradiated with light (visible light or ultraviolet rays), an organic compound contained in the EL layer is brought into an excited state and a reaction with oxygen contained in the atmosphere is promoted in some cases. Specifically, when the EL layer is irradiated with light (visible light or ultraviolet rays in an oxygen-containing atmosphere, oxygen might be bonded to the organic compound contained in the EL layer. When one or both of the mask layer 118 and the insulating film 125A are provided over the EL layer, bonding of oxygen in the atmosphere to the organic compound contained in the EL layer 113 can be suppressed.
Here, irradiation with visible light or ultraviolet rays in
In the case where the light-blocking film 135A is provided over the insulating film 125A as illustrated in
Here, when a barrier insulating layer against oxygen (e.g., an aluminum oxide film) is provided as one or both of the mask layer 118 (the mask layers 118a, 118b, and 118c) and the insulating film 125A, diffusion of oxygen into the EL layer can be reduced. In particular, when the EL layer is irradiated with light (visible light or ultraviolet rays), an organic compound contained in the EL layer is brought into an excited state and a reaction with oxygen contained in the atmosphere is promoted in some cases. Specifically, when the EL layer is irradiated with light (visible light or ultraviolet rays in an oxygen-containing atmosphere, oxygen might be bonded to the organic compound contained in the EL layer. When one or both of the mask layer 118 and the insulating film 125A are provided over the EL layer, bonding of oxygen in the atmosphere to the organic compound contained in the EL layer 113 can be suppressed.
Next, heat treatment is performed as illustrated in
As described above, a material with high heat resistance is used for the light-emitting device of the display apparatus of one embodiment of the present invention. Thus, the substrate temperature in heat treatment can be higher than or equal to 100° C. and lower than or equal to 180° C., higher than or equal to 120° C. and lower than or equal to 180° C., or higher than or equal to 140° C. and lower than or equal to 180° C.
Like the insulating layer 127 illustrated in
Here, it is preferable that the insulating layer 127 be reduced so that one end portion thereof overlaps with the pixel electrode 111a and the other end portion thereof overlaps with the pixel electrode 111b. Alternatively, it is preferable that one end portion overlaps with the pixel electrode 111b and the other end portion overlaps with the pixel electrode 111c in the insulating layer 127. Alternatively, it is preferable that one end portion of the insulating layer 127 overlap with the pixel electrode 111c and the other end portion of the insulating layer 127 be reduced so as to overlap with the pixel electrode 111a. With such a structure, an end portion of the insulating layer 127 can be formed over a substantially flat region of the first layer 113a (the second layer 113b). Thus, the tapered shape of the insulating layer 127 is relatively easy to process as described above.
Note that in the case where the side surface of the insulating layer 127 can be processed into a tapered shape only by the heat treatment illustrated in
Heat treatment is further preferably performed after the side surface of the insulating layer 127 is processed into a tapered shape. The heat treatment can remove water contained in the EL layer, water adsorbed onto the surface of the EL layer, and the like. For example, heat treatment in an inert gas atmosphere or a reduced-pressure atmosphere can be performed. Heat treatment can be performed at a substrate temperature higher than or equal to 80° C. and lower than or equal to 230° C., preferably higher than or equal to 80° C. and lower than or equal to 200° C., further preferably higher than or equal to 80° C. and lower than or equal to 130° C., still further preferably higher than or equal to 80° C. and lower than or equal to 100° C. Heat treatment is preferably performed in a reduced-pressure atmosphere, in which case dehydration at a lower temperature is possible. Note that the temperature range of heat treatment is preferably set as appropriate in consideration of the upper temperature limit of the EL layer. In consideration of the upper temperature limit of the EL layer, temperatures from 80° C. to 100° C. are particularly preferable in the above temperature range.
Etching may be performed so that the surface level of the insulating layer 127 is adjusted. The insulating layer 127 may be processed by ashing using oxygen plasma, for example.
Then, as illustrated in
The mask layers 118a, 118b, and 118c may be removed in a step that is different from or the same as a step of removing the insulating film 125A. The mask layers 118a, 118b, and 118c and the insulating film 125A are preferably films that are formed using the same material, for example, in which case they can be removed in the same step. For the mask layers 118a, 118b, and 118c and the insulating film 125A, insulating films are preferably formed by an ALD method, and aluminum oxide films are further preferably formed by an ALD method, for example.
As illustrated in
The insulating layer 125 (and the insulating layer 127) is (are) provided to cover the side surfaces and parts of the top surfaces of the pixel electrodes 111a, 111b, and 111c, the first layer 113a, the second layer 113b, and the third layer 113c. This inhibits the side surfaces of these layers from being in contact with a film to be formed later, thereby inhibiting a short circuit in the light-emitting device. In addition, damage to the first layer 113a, the second layer 113b, and the third layer 113c in later steps can be inhibited.
The step of removing the mask layers can be performed by a method similar to that for the step of processing the mask layers. For the mask layers 118a, 118b, and 118c, a method similar to the method usable in the step of removing the mask layers 119a, 119b, and 119c can be used. In addition, a removal step of the insulating film 125A can be performed in a manner similar to that of the mask layer.
In the case where the light-blocking film 135A is provided over the insulating film 125A, part of the light-blocking film 135A is removed before the processing of the insulating film 125A, so that the light-blocking layer 135 is formed. After that, the light-blocking layer 135 can be provided between the insulating layer 125 and the insulating layer 127 as illustrated in
The light-blocking film 135A can be processed by a dry etching method, for example. In that case, a gas containing one or more of SF6, CF4, HBr, Cl2, BCl3, H2, O2, and a noble gas such as Ar or He is preferably used as the etching gas, for example.
Note that in the case where the light-blocking film 135A, the insulating film 125A, and the mask layer 118 can be processed by the same etching conditions, for example, all the light-blocking film 135A, the insulating film 125A, and the mask layer 118 can be processed in the same step.
Then, as illustrated in
In
Note that the common layer 114 may be provided in the connection portion 140 depending on the level of the conductivity of the common layer 114. With such a structure, the connection portion 140 in which the conductive layer 123 is electrically connected to the common electrode 115 through the common layer 114 can be formed as illustrated in
Materials that can be used for the common layer 114 are as described above. The common layer 114 can be formed by an evaporation method (including a vacuum evaporation method), a transfer method, a printing method, an inkjet method, a coating method, or the like. The common layer 114 may be formed using a premix material.
The common layer 114 is provided to cover the top surfaces of the first layer 113a, the second layer 113b, and the third layer 113c and the top surface and the side surface of the insulating layer 127. Here, in the case where the common layer 114 has high conductivity and the insulating layers 125 and 127 are not provided, a short circuit in the light-emitting device might be caused when the common layer 114 is in contact with any of the side surfaces of the pixel electrodes 111a, 111b, and 111c, the first layer 113a, the second layer 113b, and the third layer 113c. However, in the display panel of one embodiment of the present invention, the insulating layers 125 and 127 cover side surfaces of the first layer 113a, the second layer 113b, and the third layer 113c, and the first layer 113a, the second layer 113b, and the third layer 113c cover side surfaces of the pixel electrodes 111a, 111b, and 111c, respectively. Thus, the common layer 114 having high conductivity can be inhibited from being in contact with the side surface of these layers, and a short circuit of the light-emitting device can be inhibited. Thus, the reliability of the light-emitting device can be increased.
Since a space between the first layer 113a and the second layer 113b and a space between the second layer 113b and the third layer 113c are filled with the insulating layers 125 and 127, the formation surface of the common layer 114 has a smaller step and higher planarity than the formation surface of the case where the insulating layers 125 and 127 are not provided. Thus, the coverage with the common layer 114 can be increased.
Then, the common electrode 115 is formed over the common layer 114 and the conductive layer 123 as illustrated in
A mask for defining a deposition area (also referred to as an area mask, a rough metal mask, or the like) may be used in the formation of the common electrode 115. Alternatively, the mask is not necessarily used in the formation of the common electrode 115; in that case, a film to be the common electrode 115 may be formed and may be processed with the use of a resist mask or the like subsequently.
Materials that can be used for the common electrode 115 are as described above. The common electrode 115 can be formed by a sputtering method or a vacuum evaporation method, for example. Alternatively, the common electrode 115 may be a stack of a film formed by an evaporation method and a film formed by a sputtering method.
After that, the protective layer 131 is formed over the common electrode 115. Furthermore, the substrate 120 is bonded to the protective layer 131 with the resin layer 122, whereby the display panel 100 illustrated in
Materials and deposition methods that can be used for the protective layer 131 are as described above. Examples of methods for depositing the protective layer 131 include a vacuum evaporation method, a sputtering method, a CVD method, and an ALD method. The protective layer 131 may have a single-layer structure or a stacked-layer structure.
In the above manner, the above-described display panel 100 can be manufactured.
In a display panel of one embodiment of the present invention, each subpixel includes an island-shaped EL layer, which can inhibit generation of leakage current between the subpixels. When a stacked-layer structure body of an inorganic insulating layer and an organic resin film is provided between the light-emitting devices as described above, a disconnection portion and a locally thinned portion can be inhibited from being formed in the common layer and the common electrode positioned over the stacked-layer structure body. Thus, a connection defect caused by the disconnected portion and an increase in electric resistance caused by the locally thinned portion can be inhibited from occurring in the common layer and the common electrode. Consequently, the display apparatus of one embodiment of the present invention achieves both high resolution and high display quality.
In the display panel of one embodiment of the present invention, increasing the upper temperature limit of the light-emitting device can increase the reliability of the light-emitting device. Furthermore, the allowable temperature range in the manufacturing process of the display apparatus can be widened, thereby improving the manufacturing yield and the reliability.
This embodiment can be combined with the other embodiments as appropriate.
In this embodiment, a display panel of one embodiment of the present invention is described with reference to
In this embodiment, pixel layouts different from that in
Examples of a top surface shape of the subpixel include polygons such as a triangle, a tetragon (including a rectangle and a square), and a pentagon; polygons with rounded corners; an ellipse; and a circle. Here, the top surface shape of the subpixel corresponds to the top surface shape of a light-emitting region of the light-emitting device.
The pixel 110 illustrated in
The pixel 110 illustrated in
Pixels 124a and 124b illustrated in
The pixels 124a and 124b illustrated in
In a photolithography method, as a pattern to be formed by processing becomes finer, the influence of light diffraction becomes more difficult to ignore; accordingly, the fidelity in transferring a photomask pattern by light exposure is degraded, and it becomes difficult to process a resist mask into a desired shape. Thus, a pattern with rounded corners is likely to be formed even with a rectangular photomask pattern. Consequently, the top surface of a subpixel can have a polygonal shape with rounded corners, an elliptical shape, a circular shape, or the like.
Furthermore, in the method for manufacturing the display panel of one embodiment of the present invention, the EL layer is processed into an island shape with the use of a resist mask. A resist film formed over the EL layer needs to be cured at a temperature lower than the upper temperature limit of the EL layer. Thus, the resist film is insufficiently cured in some cases depending on the upper temperature limit of the material of the EL layer and the curing temperature of the resist material. An insufficiently cured resist film may have a shape different from a desired shape by processing. As a result, the top surface of the EL layer may have a polygonal shape with rounded corners, an elliptical shape, a circular shape, or the like. For example, when a resist mask with a square top surface is intended to be formed, a resist mask with a circular top surface may be formed, and the top surface of the EL layer may be circular.
Note that to obtain a desired top surface shape of the EL layer, a technique of correcting a mask pattern in advance so that a transferred pattern agrees with a design pattern (an OPC (Optical Proximity Correction) technique) may be used. Specifically, with the OPC technique, a pattern for correction is added to a corner portion or the like of a figure on a mask pattern.
Also in the pixel 110 illustrated in
As illustrated in
The pixels 110 illustrated in
The pixels 110 illustrated in
The pixel 110 illustrated in
The pixel 110 illustrated in
The pixels 110 illustrated in
The display panel of one embodiment of the present invention may include a light-receiving device in the pixel.
Three of the four subpixels included in the pixel 110 illustrated in
For example, the subpixels 110a, 110b, and 110c may be subpixels of three colors of R, G, and B, and the subpixel 110d may be a subpixel including a light-receiving device.
Pixels illustrated in
The pixel illustrated in
The subpixel R includes a light-emitting device that emits red light. The subpixel G includes a light-emitting device that emits green light. The subpixel B includes a light-emitting device that emits blue light.
The subpixel PS includes a light-receiving device. There is no particular limitation on the wavelength of light detected by the subpixel PS. The subpixel PS can have a structure capable of detecting one or both of infrared light and visible light.
Pixels illustrated in
The layout of the subpixels R, G, and B illustrated in
At least one of the subpixel X1 and the subpixel X2 preferably includes the light-receiving device (i.e., the subpixel PS).
Note that the pixel layout including the subpixel PS is not limited to the structures illustrated in
The subpixel X1 or the subpixel X2 can include a light-emitting device that emits infrared light (IR), for example. In this case, the subpixel PS preferably detects infrared light. For example, with one of the subpixel X1 and the subpixel X2 used as a light source, reflected light of light emitted by the light source can be detected by the other of the subpixel X1 and the subpixel X2 while an image is displayed using the subpixels R, G, and B.
A structure including a light-receiving device can be used for both the subpixel X1 and the subpixel X2. In this case, the wavelength ranges of light detected by the subpixel X1 and the subpixel X2 may be the same, different, or partially the same. For example, one of the subpixel X1 and the subpixel X2 may mainly detect visible light while the other may mainly detect infrared light.
The light-receiving area of the subpixel X1 is smaller than the light-receiving area of the subpixel X2. A smaller light-receiving area leads to a narrower image-capturing range, inhibits a blur in a captured image, and improves the definition. Thus, the use of the subpixel X1 enables higher-resolution or higher-definition image capturing than the use of the light-receiving device included in the subpixel X2. For example, image capturing for personal authentication with the use of a fingerprint, a palm print, the iris, the shape of a blood vessel (including the shape of a vein and the shape of an artery), a face, or the like is possible by using the subpixel X1.
The light-receiving device included in the subpixel PS preferably detects visible light, and preferably detects one or more of blue light, violet light, bluish violet light, green light, greenish yellow light, yellow light, orange light, red light, and the like. The light-receiving device included in the subpixel PS may detect infrared light.
In the case where the subpixel X2 has a structure including the light-receiving device, the subpixel X2 can be used in a touch sensor (also referred to as a direct touch sensor), a near touch sensor (also referred to as a hover sensor, a hover touch sensor, a contactless sensor, or a touchless sensor), or the like. The wavelength of light detected by the subpixel X2 can be determined as appropriate depending on the application purpose. For example, the subpixel X2 preferably detects infrared light Thus, a touch can be detected even in a dark place.
Here, a touch sensor or a near touch sensor can detect an approach or contact of an object (e.g., a finger, a hand, or a pen).
The touch sensor can detect an object when the display panel and the object come in direct contact with each other. The near touch sensor can detect an object even when the object is not in contact with the display panel. For example, the display panel is preferably capable of detecting an object when the distance between the display panel and the object is greater than or equal to 0.1 mm and less than or equal to 300 mm, preferably greater than or equal to 3 mm and less than or equal to 50 mm. This structure enables the display panel to be operated without direct contact of an object, that is, enables the display panel to be operated in a contactless (touchless) manner. With the above-described structure, the display panel can have a reduced risk of being dirty or damaged, or can be operated without the object directly touching a dirt (e.g., dust or a virus) attached to the display panel.
The refresh rate of the display panel of one embodiment of the present invention can be variable. For example, the refresh rate is adjusted (adjusted in the range from 1 Hz to 240 Hz, for example) in accordance with contents displayed on the display panel, whereby power consumption can be reduced. The driving frequency of the touch sensor or the near touch sensor may be changed in accordance with the refresh rate. In the case where the refresh rate of the display panel is 120 Hz, for example, the driving frequency of the touch sensor or the near touch sensor can be higher than 120 Hz (typically 240 Hz). This structure reduces power consumption and increases the response speed of the touch sensor or the near touch sensor.
The display panel 100 illustrated in
The functional layer 355 includes a circuit for driving a light-receiving device and a circuit for driving a light-emitting device. A switch, a transistor, a capacitor, a resistor, a wiring, a terminal, and the like can be provided in the functional layer 355. Note that in the case where the light-emitting device and the light-receiving device are driven by a passive-matrix method, a structure not provided with a switch or a transistor may be employed.
For example, after light emitted from the light-emitting device in the layer 357 including the light-emitting device is reflected by a finger 352 that touches the display panel 100 as illustrated in
Alternatively, the display panel may have a function of detecting an object that is close to (i.e., not touching) the display panel as illustrated in
In the display panel of this embodiment, an image of the periphery of an eye, the surface of the eye, or the inside (fundus or the like) of the eye of a user of a wearable device can be captured with the use of the light-receiving device. Therefore, the wearable device can have a function of detecting one or more selected from a blink, movement of an iris, and movement of an eyelid of the user.
As described above, the pixel composed of the subpixels each including the light-emitting device can employ any of a variety of layouts in the display panel of one embodiment of the present invention. The display panel of one embodiment of the present invention can have a structure in which the pixel includes both a light-emitting device and a light-receiving device. Also in this case, any of a variety of layouts can be employed.
This embodiment can be combined with the other embodiments as appropriate.
In this embodiment, display panels of embodiments of the present invention are described with reference to
The display panel of this embodiment can be a high-resolution display panel. Accordingly, the display panel in this embodiment can be used for display portions of information terminals (wearable devices) such as watch-type and bracelet-type information terminals and display portions of wearable devices capable of being worn on a head, such as a VR device like a head-mounted display and a glasses-type AR device.
The display panel of this embodiment can be a high-definition display panel or a large-sized display panel. Accordingly, the display panel of this embodiment can be used for display portions of electronic devices such as a digital camera, a digital video camera, a digital photo frame, a mobile phone, a portable game console, a portable information terminal, and an audio reproducing device, in addition to display portions of electronic devices with a relatively large screen, such as a television device, a desktop or laptop personal computer, a monitor of a computer and the like, digital signage, and a large game machine such as a pachinko machine.
The display module 280 includes a substrate 291 and a substrate 292. The display module 280 includes a display portion 281. The display portion 281 is a region of the display module 280 where an image is displayed, and is a region where light from pixels provided in a pixel portion 284 described later can be seen.
The pixel portion 284 includes a plurality of pixels 284a arranged periodically. An enlarged view of one pixel 284a is illustrated on the right side in
The pixel circuit portion 283 includes a plurality of pixel circuits 283a arranged periodically.
One pixel circuit 283a is a circuit that controls light emission of three light-emitting devices included in one pixel 284a. One pixel circuit 283a may be provided with three circuits for controlling light emission of the respective light-emitting devices. For example, the pixel circuit 283a can include at least one selection transistor, one current control transistor (driving transistor), and a capacitor for one light-emitting device. In this case, a gate signal is input to the gate of the selection transistor, and a source signal is input to the source of the selection transistor. With such a structure, an active-matrix display panel is achieved.
The circuit portion 282 includes a circuit for driving the pixel circuits 283a in the pixel circuit portion 283. For example, one or both of a gate line driver circuit and a source line driver circuit are preferably included. In addition, at least one of an arithmetic circuit, a memory circuit, a power supply circuit, and the like may be included.
The FPC 290 functions as a wiring for supplying a video signal, a power supply potential, or the like to the circuit portion 282 from the outside. An IC may be mounted on the FPC 290.
The display module 280 can have a structure in which one or both of the pixel circuit portion 283 and the circuit portion 282 are stacked below the pixel portion 284; thus, the aperture ratio (the effective display area ratio) of the display portion 281 can be significantly high. For example, the aperture ratio of the display portion 281 can be higher than or equal to 40% and lower than 100%, preferably higher than or equal to 50% and lower than or equal to 95%, further preferably higher than or equal to 60% and lower than or equal to 95%. Furthermore, the pixels 284a can be arranged extremely densely and thus the display portion 281 can have an extremely high resolution. For example, the pixels 284a are preferably arranged in the display portion 281 with a resolution higher than or equal to 2000 ppi, preferably higher than or equal to 3000 ppi, further preferably higher than or equal to 5000 ppi, still further preferably higher than or equal to 6000 ppi, and lower than or equal to 20000 ppi or lower than or equal to 30000 ppi.
Such a display module 280 has an extremely high resolution, and thus can be suitably used for a VR device such as a head-mounted display or a glasses-type AR device. For example, even with a structure where the display portion of the display module 280 is seen through a lens, pixels of the extremely-high-resolution display portion 281 included in the display module 280 are inhibited from being perceived when the display portion is enlarged by the lens, so that display providing a high sense of immersion can be performed. Without being limited thereto, the display module 280 can be suitably used for electronic devices including a relatively small display portion. For example, the display module 280 can be favorably used in a display portion of a wearable electronic device, such as a watch.
The display panel 100A illustrated in
The substrate 301 corresponds to the substrate 291 in
The transistor 310 is a transistor including a channel formation region in the substrate 301. As the substrate 301, a semiconductor substrate such as a single crystal silicon substrate can be used, for example. The transistor 310 includes part of the substrate 301, a conductive layer 311, low-resistance regions 312, an insulating layer 313, and an insulating layer 314. The conductive layer 311 functions as a gate electrode. The insulating layer 313 is positioned between the substrate 301 and the conductive layer 311 and functions as a gate insulating layer. The low-resistance region 312 is a region where the substrate 301 is doped with an impurity, and functions as one of a source and a drain. The insulating layer 314 is provided to cover the side surface of the conductive layer 311.
An element isolation layer 315 is provided between two adjacent transistors 310 to be embedded in the substrate 301.
An insulating layer 261 is provided to cover the transistor 310, and the capacitor 240 is provided over the insulating layer 261.
The capacitor 240 includes a conductive layer 241, a conductive layer 245, and an insulating layer 243 positioned therebetween. The conductive layer 241 functions as one electrode of the capacitor 240, the conductive layer 245 functions as the other electrode of the capacitor 240, and the insulating layer 243 functions as a dielectric of the capacitor 240.
The conductive layer 241 is provided over the insulating layer 261 and is embedded in an insulating layer 254. The conductive layer 241 is electrically connected to one of the source and the drain of the transistor 310 through a plug 271 embedded in the insulating layer 261. The insulating layer 243 is provided to cover the conductive layer 241. The conductive layer 245 is provided in a region overlapping with the conductive layer 241 with the insulating layer 243 therebetween.
The insulating layer 255a is provided to cover the capacitor 240, the insulating layer 255b is provided over the insulating layer 255a, and the insulating layer 255c is provided over the insulating layer 255b.
As each of the insulating layer 255a, the insulating layer 255b, and the insulating layer 255c, a variety of inorganic insulating films such as an oxide insulating film, a nitride insulating film, an oxynitride insulating film, and a nitride oxide insulating film can be suitably used. As each of the insulating layer 255a and the insulating layer 255c, an oxide insulating film or an oxynitride insulating film, such as a silicon oxide film, a silicon oxynitride film, or an aluminum oxide film, is preferably used. As the insulating layer 255b, a nitride insulating film or a nitride oxide insulating film, such as a silicon nitride film or a silicon nitride oxide film, is preferably used. Specifically, it is preferable that a silicon oxide film be used as each of the insulating layer 255a and the insulating layer 255c and a silicon nitride film be used as the insulating layer 255b. The insulating layer 255b preferably has a function of an etching protective film. Although this embodiment describes an example in which a concave portion is provided in the insulating layer 255c, a concave portion is not necessarily provided in the insulating layer 255c.
The light-emitting device 130R, the light-emitting device 130G, and the light-emitting device 130B are provided over the insulating layer 255c.
Since the first layer 113a, the second layer 113b, and the third layer 113c are separated and are apart from each other in the display panel 100A, crosstalk generated between adjacent subpixels can be inhibited while the display panel has high resolution. Accordingly, the display panel can have high resolution and high display quality.
An insulator is provided in a region between adjacent light-emitting devices. In
The mask layer 118a is positioned over the first layer 113a in the light-emitting device 130R, the mask layer 118b is positioned over the second layer 113b in the light-emitting device 130G, and the mask layer 118c is positioned over the third layer 113c in the light-emitting device 130B.
Each of a pixel electrode 111a, a pixel electrode 111b, and a pixel electrode 111c of the light-emitting device is electrically connected to one of the source and the drain of the transistor 310 through a plug 256 embedded in the insulating layer 255a, the insulating layer 255b, and the insulating layer 255c, the conductive layer 241 embedded in the insulating layer 254, and the plug 271 embedded in the insulating layer 261. The level of the top surface of the insulating layer 255c is equal to or substantially equal to the level of the top surface of the plug 256. A variety of conductive materials can be used for the plugs.
The protective layer 131 is provided over the light-emitting device 130R, the light-emitting device 130G, and the light-emitting device 130B. The substrate 120 is bonded to the protective layer 131 with the resin layer 122. Embodiment 1 can be referred to for details of the light-emitting devices and the components thereover up to the substrate 120. The substrate 120 corresponds to the substrate 292 in
An insulating layer covering an end portion of the top surface of the pixel electrode 111a is not provided between the pixel electrode 111a and the first layer 113a. An insulating layer covering an end portion of the top surface of the pixel electrode 111b is not provided between the pixel electrode 111b and the second layer 113b. Thus, the distance between adjacent light-emitting devices can be extremely shortened. Accordingly, the display panel can have high resolution or high definition.
Although the display panel 100A includes the light-emitting devices 130R, 130G, and 130B in this example, the display panel of this embodiment may further include a light-receiving device.
The display panel illustrated in
The display panel 100B illustrated in
In the display panel 100B, a substrate 301B provided with the transistor 310B, the capacitor 240, and the light-emitting devices is bonded to a substrate 301A provided with the transistor 310A.
Here, an insulating layer 345 is preferably provided on the bottom surface of the substrate 301B. An insulating layer 346 is preferably provided over the insulating layer 261 provided over the substrate 301A. The insulating layers 345 and 346 are insulating layers functioning as protective layers and can inhibit diffusion of impurities into the substrate 301B and the substrate 301A. For the insulating layers 345 and 346, an inorganic insulating film that can be used for the protective layer 131 or an insulating layer 332 can be used.
The substrate 301B is provided with a plug 343 that penetrates the substrate 301B and the insulating layer 345. An insulating layer 344 is preferably provided to cover a side surface of the plug 343. The insulating layer 344 functions as a protective layer and can inhibit diffusion of impurities into the substrate 301B. For the insulating layer 344, an inorganic insulating film that can be used for the protective layer 131 can be used.
A conductive layer 342 is provided under the insulating layer 345 on the rear surface of the substrate 301B (the surface opposite to the substrate 120). The conductive layer 342 is preferably provided to be embedded in an insulating layer 335. The bottom surfaces of the conductive layer 342 and the insulating layer 335 are preferably planarized. Here, the conductive layer 342 is electrically connected to the plug 343.
Over the substrate 301A, a conductive layer 341 is provided over the insulating layer 346. The conductive layer 341 is preferably provided to be embedded in an insulating layer 336. The top surfaces of the conductive layer 341 and the insulating layer 336 are preferably planarized.
The conductive layer 341 and the conductive layer 342 are bonded to each other, whereby the substrate 301A and the substrate 301B are electrically connected to each other. Here, improving the flatness of a plane formed by the conductive layer 342 and the insulating layer 335 and a plane formed by the conductive layer 341 and the insulating layer 336 allows the conductive layer 341 and the conductive layer 342 to be bonded to each other favorably.
The conductive layer 341 and the conductive layer 342 are preferably formed using the same conductive material. For example, a metal film containing an element selected from Al, Cr, Cu, Ta, Ti, Mo, and W, a metal nitride film containing the above element as a component (a titanium nitride film, a molybdenum nitride film, or a tungsten nitride film), or the like can be used. Copper is particularly preferably used for the conductive layer 341 and the conductive layer 342. In that case, it is possible to employ Cu-to-Cu (copper-to-copper) direct bonding technique (a technique for achieving electrical continuity by connecting Cu (copper) pads).
The display panel 100C illustrated in
As illustrated in
The display panel 100D illustrated in
A transistor 320 is a transistor that contains a metal oxide (also referred to as an oxide semiconductor) in a semiconductor layer where a channel is formed (i.e., an OS transistor).
The transistor 320 includes a semiconductor layer 321, an insulating layer 323, a conductive layer 324, a pair of conductive layers 325, an insulating layer 326, and a conductive layer 327.
A substrate 331 corresponds to the substrate 291 in
The insulating layer 332 is provided over the substrate 331. The insulating layer 332 functions as a barrier layer that inhibits diffusion of impurities such as water and hydrogen from the substrate 331 into the transistor 320 and release of oxygen from the semiconductor layer 321 to the insulating layer 332 side. As the insulating layer 332, for example, a film in which hydrogen or oxygen is less likely to diffuse than in a silicon oxide film, such as an aluminum oxide film, a hafnium oxide film, or a silicon nitride film, can be used.
The conductive layer 327 is provided over the insulating layer 332, and the insulating layer 326 is provided to cover the conductive layer 327. The conductive layer 327 functions as a first gate electrode of the transistor 320, and part of the insulating layer 326 functions as a first gate insulating layer. An oxide insulating film such as a silicon oxide film is preferably used as at least part of the insulating layer 326 that is in contact with the semiconductor layer 321. The top surface of the insulating layer 326 is preferably planarized.
The semiconductor layer 321 is provided over the insulating layer 326. The semiconductor layer 321 preferably includes a metal oxide (also referred to as an oxide semiconductor) film having semiconductor characteristics. The pair of conductive layers 325 are provided over and in contact with the semiconductor layer 321 and function as a source electrode and a drain electrode.
An insulating layer 328 is provided to cover the top and side surfaces of the pair of conductive layers 325, the side surface of the semiconductor layer 321, and the like, and an insulating layer 264 is provided over the insulating layer 328. The insulating layer 328 functions as a barrier layer that inhibits diffusion of impurities such as water and hydrogen from the insulating layer 264 and the like into the semiconductor layer 321 and release of oxygen from the semiconductor layer 321. As the insulating layer 328, an insulating film similar to the insulating layer 332 can be used.
An opening reaching the semiconductor layer 321 is provided in the insulating layer 328 and the insulating layer 264. The insulating layer 323 that is in contact with the side surfaces of the insulating layer 264, the insulating layer 328, and the conductive layer 325, and the top surface of the semiconductor layer 321, and the conductive layer 324 are embedded in the opening. The conductive layer 324 functions as a second gate electrode, and the insulating layer 323 functions as a second gate insulating layer.
The top surface of the conductive layer 324, the top surface of the insulating layer 323, and the top surface of the insulating layer 264 are subjected to planarization treatment to be level with each other or substantially level with each other, and an insulating layer 329 and an insulating layer 265 are provided to cover these layers.
The insulating layer 264 and the insulating layer 265 each function as an interlayer insulating layer. The insulating layer 329 functions as a barrier layer that inhibits diffusion of impurities such as water and hydrogen from the insulating layer 265 and the like into the transistor 320. As the insulating layer 329, an insulating film similar to the insulating layer 328 and the insulating layer 332 can be used.
A plug 274 electrically connected to one of the pair of conductive layers 325 is provided so as to be embedded in the insulating layer 265, the insulating layer 329, and the insulating layer 264. Here, the plug 274 preferably includes a conductive layer 274a that covers the side surface of an opening in the insulating layer 265, the insulating layer 329, the insulating layer 264, and the insulating layer 328 and part of the top surface of the conductive layer 325, and a conductive layer 274b in contact with the top surface of the conductive layer 274a. In this case, a conductive material through which hydrogen and oxygen are less likely to diffuse is preferably used for the conductive layer 274a.
The display panel 100E illustrated in
The description of the display panel 100D can be referred to for the transistor 320A, the transistor 320B, and the components around them.
Although the structure where two transistors including an oxide semiconductor are stacked is described, the present invention is not limited thereto. For example, three or more transistors may be stacked.
The display panel 100F illustrated in
The insulating layer 261 is provided to cover the transistor 310, and a conductive layer 251 is provided over the insulating layer 261. An insulating layer 262 is provided to cover the conductive layer 251, and a conductive layer 252 is provided over the insulating layer 262. The conductive layer 251 and the conductive layer 252 each function as a wiring. An insulating layer 263 and the insulating layer 332 are provided to cover the conductive layer 252, and the transistor 320 is provided over the insulating layer 332. The insulating layer 265 is provided to cover the transistor 320, and the capacitor 240 is provided over the insulating layer 265. The capacitor 240 and the transistor 320 are electrically connected to each other through the plug 274.
The transistor 320 can be used as a transistor included in the pixel circuit. The transistor 310 can be used as a transistor included in the pixel circuit or a transistor included in a driver circuit (a gate line driver circuit or a source line driver circuit) for driving the pixel circuit. The transistor 310 and the transistor 320 can also be used as transistors included in a variety of circuits such as an arithmetic circuit and a memory circuit.
With such a structure, not only the pixel circuit but also the driver circuit and the like can be formed directly under the light-emitting devices; thus, the display panel can be downsized as compared with the case where a driver circuit is provided around a display region.
In the display panel 100G, a substrate 152 and a substrate 151 are bonded to each other. In
The display panel 100G includes a display portion 162, the connection portion 140, a circuit 164, a wiring 165, and the like.
The connection portion 140 is provided outside the display portion 162. The connection portion 140 can be provided along one or more sides of the display portion 162. The number of connection portions 140 can be one or more.
As the circuit 164, a scan line driver circuit can be used, for example.
The wiring 165 has a function of supplying a signal and power to the display portion 162 and the circuit 164. The signal and power are input to the wiring 165 from the outside through the FPC 172 or input to the wiring 165 from the IC 173.
The display panel 100G illustrated in
The light-emitting devices 130R, 130G, and 130B each have the stacked-layer structure illustrated in
Since the first layer 113a, the second layer 113b, and the third layer 113c are separated from each other in the display panel 100G, crosstalk generated between adjacent subpixels can be inhibited while the display panel has high resolution. Accordingly, the display panel can have high resolution and high display quality.
The light-emitting device 130R includes a conductive layer 112a, a conductive layer 126a over the conductive layer 112a, and a conductive layer 129a over the conductive layer 126a. All of the conductive layers 112a, 126a, and 129a can be referred to as pixel electrodes, or one or two of them can be referred to as pixel electrodes.
The light-emitting device 130G includes a conductive layer 112b, a conductive layer 126b over the conductive layer 112b, and a conductive layer 129b over the conductive layer 126b.
The light-emitting device 130B includes a conductive layer 112c, a conductive layer 126c over the conductive layer 112c, and a conductive layer 129c over the conductive layer 126c.
The conductive layer 112a is connected to the conductive layer 222b included in the transistor 205 through an opening provided in the insulating layer 214. The end portion of the conductive layer 126a is positioned on the outer side of the end portion of the conductive layer 112a. The end portion of the conductive layer 126a and the end portion of the conductive layer 129a are aligned or substantially aligned with each other. For example, a conductive layer functioning as a reflective electrode can be used as the conductive layer 112a and the conductive layer 126a, and a conductive layer functioning as a transparent electrode can be used as the conductive layer 129a.
Detailed description of the conductive layers 112b, 126b, and 129b of the light-emitting device 130G and the conductive layers 112c, 126c, and 129c of the light-emitting device 130B is omitted because these conductive layers are similar to the conductive layers 112a, 126a, and 129a of the light-emitting device 130R.
The conductive layers 112a, 112b, and 112c are formed to cover the openings provided in the insulating layer 214. A layer 128 is embedded in each of concave portions of the conductive layers 112a, 112b, and 112c.
The layer 128 has a planarization function for the concave portions of the conductive layers 112a, 112b, and 112c. The conductive layers 126a, 126b, and 126c electrically connected to the conductive layers 112a, 112b, and 112c, respectively, are provided over the conductive layers 112a, 112b, and 112c and the layer 128. Thus, regions overlapping with the concave portions of the conductive layers 112a, 112b, and 112c can also be used as the light-emitting regions, increasing the aperture ratio of the pixels.
The layer 128 may be an insulating layer or a conductive layer. Any of a variety of inorganic insulating materials, organic insulating materials, and conductive materials can be used for the layer 128 as appropriate. In particular, the layer 128 is preferably formed using an insulating material.
An insulating layer containing an organic material can be suitably used for the layer 128. For the layer 128, an acrylic resin, a polyimide resin, an epoxy resin, a polyamide resin, a polyimide-amide resin, a siloxane resin, a benzocyclobutene-based resin, a phenol resin, a precursor of any of these resins, or the like can be used, for example. A photosensitive resin can also be used for the layer 128. As the photosensitive resin, a positive photosensitive material or a negative photosensitive material can be used.
When a photosensitive resin is used, the layer 128 can be formed through only light-exposure and development processes, reducing the influence of dry etching, wet etching, or the like on the surfaces of the conductive layers 112a, 112b, and 112c. When the layer 128 is formed using a negative photosensitive resin, the layer 128 can sometimes be formed using the same photomask (light-exposure mask) as the photomask used for forming the opening in the insulating layer 214.
The top and side surfaces of the conductive layer 126a and the top and side surfaces of the conductive layer 129a are covered with the first layer 113a. Similarly, the top surface and side surfaces of the conductive layer 126b and the top and side surfaces of the conductive layer 129b are covered with the second layer 113b. Moreover, the top and side surfaces of the conductive layer 126c and the top and side surfaces of the conductive layer 129c are covered with the third layer 113c. Accordingly, regions provided with the conductive layers 126a, 126b, and 126c can be entirely used as the light-emitting regions of the light-emitting devices 130R, 130G, and 130B, increasing the aperture ratio of the pixels.
The side surfaces of the first layer 113a, the second layer 113b, and the third layer 113c are covered with the insulating layers 125 and 127. The mask layer 118a is positioned between the first layer 113a and the insulating layer 125. The mask layer 118b is positioned between the second layer 113b and the insulating layer 125, and the mask layer 118c is positioned between the third layer 113c and the insulating layer 125. The common layer 114 is provided over the first layer 113a, the second layer 113b, the third layer 113c, and the insulating layers 125 and 127. The common electrode 115 is provided over the common layer 114. The common layer 114 and the common electrode 115 are each one continuous film shared by the plurality of light-emitting devices.
The protective layer 131 is provided over each of the light-emitting devices 130R, 130G, and 130B. The protective layer 131 covering the light-emitting devices can inhibit an impurity such as water from entering the light-emitting devices, and increase the reliability of the light-emitting devices.
The protective layer 131 and the substrate 152 are bonded to each other with an adhesive layer 142. A solid sealing structure, a hollow sealing structure, or the like can be employed to seal the light-emitting devices. In
The conductive layer 123 is provided over the insulating layer 214 in the connection portion 140. An example is described in which the conductive layer 123 has a stacked-layer structure of a conductive film obtained by processing the same conductive film as the conductive layers 112a, 112b, and 112c; a conductive film obtained by processing the same conductive film as the conductive layers 126a, 126b, and 126c; and a conductive film obtained by processing the same conductive film as the conductive layers 129a, 129b, and 129c. The end portion of the conductive layer 123 is covered with the mask layer 118a, the insulating layer 125, and the insulating layer 127. The common layer 114 is provided over the conductive layer 123, and the common electrode 115 is provided over the common layer 114. The conductive layer 123 and the common electrode 115 are electrically connected to each other through the common layer 114. Note that the common layer 114 is not necessarily formed in the connection portion 140. In this case, the conductive layer 123 and the common electrode 115 are directly and electrically connected to each other.
The display panel 100G has a top-emission structure. Light emitted by the light-emitting device is emitted toward the substrate 152. For the substrate 152, a material having a high visible-light-transmitting property is preferably used. The pixel electrode contains a material that reflects visible light, and a counter electrode (the common electrode 115) contains a material that transmits visible light.
A stacked-layer structure including the substrate 151 and the components thereover up to the insulating layer 214 corresponds to the layer 101 including transistors in Embodiment 1.
The transistor 201 and the transistor 205 are formed over the substrate 151. These transistors can be manufactured using the same material in the same process.
An insulating layer 211, an insulating layer 213, an insulating layer 215, and the insulating layer 214 are provided in this order over the substrate 151. Part of the insulating layer 211 functions as a gate insulating layer of each transistor. Part of the insulating layer 213 functions as a gate insulating layer of each transistor. The insulating layer 215 is provided to cover the transistors. The insulating layer 214 is provided to cover the transistors and has a function of a planarization layer. Note that the number of gate insulating layers and the number of insulating layers covering the transistors are not limited and may each be one or two or more.
A material through which impurities such as water and hydrogen do not easily diffuse is preferably used for at least one of the insulating layers covering the transistors. This allows the insulating layer to function as a barrier layer. Such a structure can effectively inhibit diffusion of impurities into the transistors from the outside and increase the reliability of a display panel.
An inorganic insulating film is preferably used as each of the insulating layer 211, the insulating layer 213, and the insulating layer 215. As the inorganic insulating film, a silicon nitride film, a silicon oxynitride film, a silicon oxide film, a silicon nitride oxide film, an aluminum oxide film, or an aluminum nitride film can be used, for example. A hafnium oxide film, an yttrium oxide film, a zirconium oxide film, a gallium oxide film, a tantalum oxide film, a magnesium oxide film, a lanthanum oxide film, a cerium oxide film, a neodymium oxide film, or the like may be used. A stack including two or more of the above insulating films may also be used.
An organic insulating layer is suitable as the insulating layer 214 functioning as a planarization layer. Examples of materials that can be used for the organic insulating layer include an acrylic resin, a polyimide resin, an epoxy resin, a polyamide resin, a polyimide-amide resin, a siloxane resin, a benzocyclobutene-based resin, a phenol resin, and precursors of these resins. The insulating layer 214 may have a stacked-layer structure of an organic insulating layer and an inorganic insulating layer. The uppermost layer of the insulating layer 214 preferably has a function of an etching protective layer. Accordingly, a concave portion can be inhibited from being formed in the insulating layer 214 at the time of processing the conductive layer 112a, the conductive layer 126a, the conductive layer 129a, or the like. Alternatively, a concave portion may be formed in the insulating layer 214 at the time of processing the conductive layer 112a, the conductive layer 126a, the conductive layer 129a, or the like.
Each of the transistor 201 and the transistor 205 includes a conductive layer 221 functioning as a gate, the insulating layer 211 functioning as a gate insulating layer, a conductive layer 222a and the conductive layer 222b functioning as a source and a drain, a semiconductor layer 231, the insulating layer 213 functioning as a gate insulating layer, and a conductive layer 223 functioning as a gate. Here, a plurality of layers obtained by processing the same conductive film are shown with the same hatching pattern. The insulating layer 211 is positioned between the conductive layer 221 and the semiconductor layer 231. The insulating layer 213 is positioned between the conductive layer 223 and the semiconductor layer 231.
There is no particular limitation on the structure of the transistors included in the display panel of this embodiment. For example, a planar transistor, a staggered transistor, an inverted staggered transistor, or the like can be used. A top-gate or a bottom-gate transistor structure may be employed. Alternatively, gates may be provided above and below the semiconductor layer where a channel is formed.
The structure in which the semiconductor layer where a channel is formed is interposed between two gates is used for the transistor 201 and the transistor 205. The two gates may be connected to each other and supplied with the same signal to drive the transistor. Alternatively, a potential for controlling the threshold voltage may be supplied to one of the two gates and a potential for driving may be supplied to the other to control the threshold voltage of the transistor.
There is no particular limitation on the crystallinity of a semiconductor material used for the transistors, and any of an amorphous semiconductor and a semiconductor having crystallinity (a microcrystalline semiconductor, a polycrystalline semiconductor, a single crystal semiconductor, or a semiconductor partly including crystal regions) may be used. A semiconductor having crystallinity is preferably used, in which case degradation of the transistor characteristics can be inhibited.
The semiconductor layer of the transistor preferably includes a metal oxide (also referred to as an oxide semiconductor). That is, a transistor including a metal oxide in its channel formation region (hereinafter, also referred to as an OS transistor) is preferably used for the display panel of this embodiment.
As the oxide semiconductor having crystallinity, a CAAC (c-axis aligned crystalline)-OS, an nc (nanocrystalline)-OS, and the like can be given.
Alternatively, a transistor using silicon in its channel formation region (a Si transistor) may be used. As silicon, single crystal silicon, polycrystalline silicon, amorphous silicon, and the like can be given. In particular, a transistor containing low-temperature polysilicon (LTPS) in its semiconductor layer (hereinafter also referred to as an LTPS transistor) can be used. The LTPS transistor has high field-effect mobility and favorable frequency characteristics.
With the use of Si transistors such as LTPS transistors, a circuit required to be driven at a high frequency (e.g., a source driver circuit) can be formed on the same substrate as the display portion. Thus, external circuits mounted on the display panel can be simplified, and costs of components and mounting cost can be reduced.
An OS transistor has extremely higher field-effect mobility than a transistor containing amorphous silicon. In addition, the OS transistor has an extremely low leakage current between a source and a drain in an off state (hereinafter, also referred to as off-state current), and charge accumulated in a capacitor that is connected in series to the transistor can be retained for a long period. Furthermore, power consumption of the display panel can be reduced with the use of an OS transistor.
The off-state current value per micrometer of channel width of the OS transistor at room temperature can be lower than or equal to 1 aA (1×10−18 A), lower than or equal to 1 zA (1×10−21 A), or lower than or equal to 1 yA (1×10−24 A). Note that the off-state current value per micrometer of channel width of a Si transistor at room temperature is higher than or equal to 1 fA (1×10−15 A) and lower than or equal to 1 pA (1×10−12 A). In other words, the off-state current of an OS transistor is lower than that of a Si transistor by approximately ten orders of magnitude.
To increase the emission luminance of the light-emitting device included in the pixel circuit, the amount of current fed through the light-emitting device needs to be increased. For this, it is necessary to increase the source-drain voltage of a driving transistor included in the pixel circuit. Since an OS transistor has a higher withstand voltage between the source and the drain than a Si transistor, a high voltage can be applied between the source and the drain of the OS transistor. Accordingly, when an OS transistor is used as the driving transistor included in the pixel circuit, the amount of current flowing through the light-emitting device can be increased, so that the emission luminance of the light-emitting device can be increased.
When transistors operate in a saturation region, a change in source-drain current with respect to a change in gate-source voltage can be smaller in an OS transistor than in a Si transistor. Accordingly, when an OS transistor is used as the driving transistor in the pixel circuit, the amount of current flowing between the source and the drain can be set minutely by a change in gate-source voltage; hence, the amount of current flowing through the light-emitting device can be controlled. Accordingly, the number of gray levels in the pixel circuit can be increased.
Regarding saturation characteristics of a current flowing when transistors operate in a saturation region, even in the case where the source-drain voltage of an OS transistor increases gradually, a more stable current (saturation current) can be fed through the OS transistor than through a Si transistor. Thus, by using an OS transistor as the driving transistor, a stable current can be fed through light-emitting devices even when the current-voltage characteristics of the EL devices vary, for example. In other words, when the OS transistor operates in the saturation region, the source-drain current hardly changes with an increase in the source-drain voltage; hence, the emission luminance of the light-emitting device can be stable.
As described above, with the use of an OS transistor as a driving transistor included in the pixel circuit, it is possible to achieve “inhibition of black floating”, “increase in emission luminance”, “increase in gray level”, “inhibition of variation in light-emitting devices”, and the like.
The semiconductor layer preferably contains indium, M (M is one or more selected from gallium, aluminum, silicon, boron, yttrium, tin, copper, vanadium, beryllium, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, and magnesium), and zinc, for example. Specifically, M is preferably one or more selected from aluminum, gallium, yttrium, and tin.
It is particularly preferable that an oxide containing indium (In), gallium (Ga), and zinc (Zn)(also referred to as IGZO) be used for the semiconductor layer. Alternatively, it is preferable to use an oxide containing indium, tin, and zinc. Alternatively, it is preferable to use an oxide containing indium, gallium, tin, and zinc. Alternatively, an oxide containing indium (In), aluminum (Al), and zinc (Zn) (also referred to as IAZO) is preferably used for the semiconductor layer. Alternatively, an oxide containing indium (In), aluminum (Al), gallium (Ga), and zinc (Zn) (also referred to as IAGZO) is preferably used for the semiconductor layer.
When the semiconductor layer is an In-M-Zn oxide, the atomic ratio of In is preferably higher than or equal to the atomic ratio of M in the In-M-Zn oxide. Examples of the atomic ratio of the metal elements in such an In-M-Zn oxide include In:M:Zn=1:1:1 or a composition in the neighborhood thereof, In:M:Zn=1:1:1.2 or a composition in the neighborhood thereof, In:M:Zn=1:3:2 or a composition in the neighborhood thereof, In:M:Zn=1:3:4 or a composition in the neighborhood thereof, In:M:Zn=2:1:3 or a composition in the neighborhood thereof, In:M:Zn=3:1:2 or a composition in the neighborhood thereof, In:M:Zn=4:2:3 or a composition in the neighborhood thereof, In:M:Zn=4:2:4.1 or a composition in the neighborhood thereof, In:M:Zn=5:1:3 or a composition in the neighborhood thereof, In:M:Zn=5:1:6 or a composition in the neighborhood thereof, In:M:Zn=5:1:7 or a composition in the neighborhood thereof, In:M:Zn=5:1:8 or a composition in the neighborhood thereof, In:M:Zn=6:1:6 or a composition in the neighborhood thereof, and In:M:Zn=5:2:5 or a composition in the neighborhood thereof. Note that a composition in the neighborhood includes the range of ±30% of an intended atomic ratio.
For example, when the atomic ratio is described as In:Ga:Zn=4:2:3 or a composition in the neighborhood thereof, the case is included where Ga is greater than or equal to 1 and less than or equal to 3 and Zn is greater than or equal to 2 and less than or equal to 4 with In being 4. When the atomic ratio is described as In:Ga:Zn=5:1:6 or a composition in the neighborhood thereof, the case is included where Ga is greater than 0.1 and less than or equal to 2 and Zn is greater than or equal to 5 and less than or equal to 7 with In being 5. When the atomic ratio is described as In:Ga:Zn=1:1:1 or a composition in the neighborhood thereof, the case is included where Ga is greater than 0.1 and less than or equal to 2 and Zn is greater than 0.1 and less than or equal to 2 with In being 1.
The transistor included in the circuit 164 and the transistor included in the display portion 162 may have the same structure or different structures. One structure or two or more types of structures may be employed for a plurality of transistors included in the circuit 164. Similarly, one structure or two or more types of structures may be employed for a plurality of transistors included in the display portion 162.
All of the transistors included in the display portion 162 may be OS transistors or all of the transistors included in the display portion 162 may be Si transistors; alternatively, some of the transistors included in the display portion 162 may be OS transistors and the others may be Si transistors.
For example, when both an LTPS transistor and an OS transistor are used in the display portion 162, the display panel can have low power consumption and high drive capability. Note that a structure where an LTPS transistor and an OS transistor are used in combination is referred to as LTPO in some cases. Note that as a more preferable example, it is preferable to use an OS transistor as a transistor or the like functioning as a switch for controlling electrical continuity between wirings and an LTPS transistor as a transistor or the like for controlling current.
For example, one of the transistors included in the display portion 162 functions as a transistor for controlling a current flowing through the light-emitting device and can be referred to as a driving transistor. One of a source and a drain of the driving transistor is electrically connected to the pixel electrode of the light-emitting device. An LTPS transistor is preferably used as the driving transistor. Accordingly, the amount of current flowing through the light-emitting device can be increased in the pixel circuit.
Another transistor included in the display portion 162 functions as a switch for controlling selection and non-selection of the pixel and can be referred to as a selection transistor. A gate of the selection transistor is electrically connected to a gate line, and one of a source and a drain thereof is electrically connected to a source line (signal line). An OS transistor is preferably used as the selection transistor. Accordingly, the gray level of the pixel can be maintained even with an extremely low frame frequency (e.g., 1 fps or less); thus, power consumption can be reduced by stopping the driver in displaying a still image.
As described above, the display panel of one embodiment of the present invention can have all of a high aperture ratio, high resolution, high display quality, and low power consumption.
Note that the display panel of one embodiment of the present invention has a structure including the OS transistor and the light-emitting device having an MML (metal maskless) structure. With this structure, the leakage current that might flow through the transistor and the leakage current that might flow between adjacent light-emitting devices (also referred to as lateral leakage current, side leakage current, or the like) can be extremely low. With the structure, a viewer can notice any one or more of the image crispness, the image sharpness, a high chroma, and a high contrast ratio in an image displayed on the display panel. When the leakage current that might flow through the transistor and the lateral leakage current that might flow between light-emitting devices are extremely low, display with little leakage of light at the time of black display can be achieved.
A transistor 209 and a transistor 210 each include the conductive layer 221 functioning as a gate, the insulating layer 211 functioning as a gate insulating layer, the semiconductor layer 231 including a channel formation region 231i and a pair of low-resistance regions 231n, the conductive layer 222a connected to one of the pair of low-resistance regions 231n, the conductive layer 222b connected to the other of the pair of low-resistance regions 231n, an insulating layer 225 functioning as a gate insulating layer, the conductive layer 223 functioning as a gate, and the insulating layer 215 covering the conductive layer 223. The insulating layer 211 is positioned between the conductive layer 221 and the channel formation region 231i. The insulating layer 225 is positioned at least between the conductive layer 223 and the channel formation region 231i. Furthermore, an insulating layer 218 covering the transistor may be provided.
Meanwhile, in the transistor 210 illustrated in
A connection portion 204 is provided in a region of the substrate 151 where the substrate 152 does not overlap. In the connection portion 204, the wiring 165 is electrically connected to the FPC 172 through a conductive layer 166 and a connection layer 242. An example is illustrated in which the conductive layer 166 has a stacked-layer structure of a conductive film obtained by processing the same conductive film as the conductive layers 112a, 112b, and 112c, a conductive film obtained by processing the same conductive film as the conductive layers 126a, 126b, and 126c, and a conductive film obtained by processing the same conductive film as the conductive layers 129a, 129b, and 129c. The conductive layer 166 is exposed on the top surface of the connection portion 204. Thus, the connection portion 204 and the FPC 172 can be electrically connected to each other through the connection layer 242.
A light-blocking layer 117 is preferably provided on a surface of the substrate 152 that faces the substrate 151. The light-blocking layer 117 can be provided between adjacent light-emitting devices, in the connection portion 140, and in the circuit 164, for example. A variety of optical members can be arranged on the outer surface of the substrate 152.
The material that can be used for the substrate 120 can be used for each of the substrate 151 and the substrate 152.
The material that can be used for the resin layer 122 can be used for the adhesive layer 142.
As the connection layer 242, an anisotropic conductive film (ACF), an anisotropic conductive paste (ACP), or the like can be used.
A display panel 100H illustrated in
Light emitted by the light-emitting device is emitted toward the substrate 151 side. For the substrate 151, a material having a high visible-light-transmitting property is preferably used. In contrast, there is no limitation on the light-transmitting property of a material used for the substrate 152.
The light-blocking layer 117 is preferably formed between the substrate 151 and the transistor 201 and between the substrate 151 and the transistor 205.
The light-emitting device 130R includes the conductive layer 112a, the conductive layer 126a over the conductive layer 112a, and the conductive layer 129a over the conductive layer 126a.
The light-emitting device 130G includes the conductive layer 112b, the conductive layer 126b over the conductive layer 112b, and the conductive layer 129b over the conductive layer 126b.
A material having a high visible-light-transmitting property is used for each of the conductive layers 112a, 112b, 126a, 126b, 129a, and 129b. A material reflecting visible light is preferably used for the common electrode 115.
Although
As illustrated in
As illustrated in
The top surface of the layer 128 may include one or both of a convex surface and a concave surface. The number of convex surfaces and the number of concave surfaces included in the top surface of the layer 128 are not limited and can each be one or more.
The height of the top surface of the layer 128 and the level of the top surface of the conductive layer 112a may be equal to or substantially equal to each other, or may be different from each other. For example, the height of the top surface of the layer 128 may be either lower or higher than the height of the top surface of the conductive layer 112a.
A display panel 100J illustrated in
The light-receiving device 150 includes a conductive layer 112d, a conductive layer 126d over the conductive layer 112d, and a conductive layer 129d over the conductive layer 126d.
The conductive layer 112d is connected to the conductive layer 222b included in the transistor 205 through an opening provided in the insulating layer 214.
The top and side surfaces of the conductive layer 126d and the top and side surfaces of the conductive layer 129d are covered with a fourth layer 113d. The fourth layer 113d includes at least an active layer.
The side surface of the fourth layer 113d is covered with the insulating layers 125 and 127. A mask layer 118d is positioned between the fourth layer 113d and the insulating layer 125. The common layer 114 is provided over the fourth layer 113d and the insulating layers 125 and 127, and the common electrode 115 is provided over the common layer 114. The common layer 114 is a continuous film provided to be shared by the light-receiving device and the light-emitting devices.
For example, the pixel layout described in Embodiment 1 with reference to
This embodiment can be combined with the other embodiments as appropriate.
In this embodiment, a structure example of a transistor that can be used in the display panel of one embodiment of the present invention will be described. Specifically, the case of using a transistor containing silicon in a semiconductor where a channel is formed will be described.
One embodiment of the present invention is a display panel including a light-emitting device and a pixel circuit. For example, three kinds of light-emitting devices emitting light of red (R), green (G), and blue (B) are included, whereby a full-color display panel can be achieved.
Transistors containing silicon in their semiconductor layers where channels are formed are preferably used as all transistors included in the pixel circuit for driving the light-emitting device. As silicon, single crystal silicon, polycrystalline silicon, amorphous silicon, and the like can be given. In particular, a transistor containing low-temperature polysilicon (LTPS) in its semiconductor layer (hereinafter also referred to as an LTPS transistor) is preferably used. The LTPS transistor has high field-effect mobility and favorable frequency characteristics.
With the use of transistors containing silicon, such as LTPS transistors, a circuit required to be driven at a high frequency (e.g., a source driver circuit) can be formed on the same substrate as the display portion. Thus, external circuits mounted on the display panel can be simplified, whereby costs of components and mounting costs can be reduced.
It is preferable to use a transistor containing a metal oxide (hereinafter also referred to as an oxide semiconductor) in its semiconductor layer where a channel is formed (hereinafter such a transistor is also referred to as an OS transistor) as at least one of the transistors included in the pixel circuit. An OS transistor has extremely higher field-effect mobility than a transistor containing amorphous silicon. In addition, an OS transistor has an extremely low leakage current between a source and a drain in an off state (hereinafter, also referred to as off-state current), and charge accumulated in a capacitor that is connected in series to the transistor can be retained for a long period. Furthermore, power consumption of the display panel can be reduced with the use of an OS transistor.
When an LTPS transistor is used as one or more of the transistors included in the pixel circuit and an OS transistor is used as the rest, the display panel can have low power consumption and high driving capability. In a more favorable example, it is preferable that an OS transistor be used as a transistor functioning as a switch for controlling electrical continuity between wirings and an LTPS transistor be used as a transistor for controlling current.
For example, one of the transistors included in the pixel circuit functions as a transistor for controlling current flowing through the light-emitting device and can be referred to as a driving transistor. One of a source and a drain of the driving transistor is electrically connected to the pixel electrode of the light-emitting device. An LTPS transistor is preferably used as the driving transistor. In this case, the amount of current flowing through the light-emitting device can be increased in the pixel circuit.
Another transistor included in the pixel circuit functions as a switch for controlling selection and non-selection of the pixel and can be referred to as a selection transistor. A gate of the selection transistor is electrically connected to a gate line, and one of a source and a drain thereof is electrically connected to a source line (signal line). An OS transistor is preferably used as the selection transistor. Accordingly, the gray level of the pixel can be maintained even with an extremely low frame frequency (e.g., 1 fps or less); thus, power consumption can be reduced by stopping the driver in displaying a still image.
More specific structure examples will be described below with reference to drawings.
The display portion 404 includes a plurality of pixels 430 arranged in a matrix. The pixels 430 each include a subpixel 405R, a subpixel 405G, and a subpixel 405B. The subpixel 405R, the subpixel 405G, and the subpixel 405B each include a light-emitting device functioning as a display device.
The pixel 430 is electrically connected to a wiring GL, a wiring SLR, a wiring SLG, and a wiring SLB. The wiring SLR, the wiring SLG, and the wiring SLB are electrically connected to the driver circuit portion 402. The wiring GL is electrically connected to the driver circuit portion 403. The driver circuit portion 402 functions as a source line driver circuit (also referred to as a source driver), and the driver circuit portion 403 functions as a gate line driver circuit (also referred to as a gate driver). The wiring GL functions as a gate line, and the wiring SLR, the wiring SLG, and the wiring SLB each function as a source line.
The subpixel 405R includes a light-emitting device that emits red light. The subpixel 405G includes a light-emitting device that emits green light. The subpixel 405B includes a light-emitting device that emits blue light. Thus, the display panel 400 can perform full-color display. Note that the pixel 430 may include a subpixel including a light-emitting device emitting light of another color. For example, the pixel 430 may include, in addition to the three subpixels, a subpixel including a light-emitting device emitting white light, a subpixel including a light-emitting device emitting yellow light, or the like.
The wiring GL is electrically connected to the subpixel 405R, the subpixel 405G, and the subpixel 405B arranged in a row direction (an extending direction of the wiring GL). The wiring SLR, the wiring SLG, and the wiring SLB are electrically connected to the subpixels 405R, the subpixels 405G, and the subpixels 405B (not illustrated) arranged in a column direction (an extending direction of the wiring SLR and the like), respectively.
A gate of the transistor M1 is electrically connected to the wiring GL, one of a source and a drain of the transistor M1 is electrically connected to the wiring SL, and the other thereof is electrically connected to one electrode of the capacitor C1 and a gate of the transistor M2. One of a source and a drain of the transistor M2 is electrically connected to a wiring AL, and the other of the source and the drain of the transistor M2 is electrically connected to one electrode of the light-emitting device EL, the other electrode of the capacitor C1, and one of a source and a drain of the transistor M3. A gate of the transistor M3 is electrically connected to the wiring GL, and the other of the source and the drain of the transistor M3 is electrically connected to a wiring RL. The other electrode of the light-emitting device EL is electrically connected to a wiring CL.
A data potential is supplied to the wiring SL. A selection signal is supplied to the wiring GL. The selection signal includes a potential for bringing a transistor into a conducting state and a potential for bringing a transistor into a non-conducting state.
A reset potential is supplied to the wiring RL. An anode potential is supplied to the wiring AL. A cathode potential is supplied to the wiring CL. In the pixel 405, the anode potential is a potential higher than the cathode potential. The reset potential supplied to the wiring RL can be set such that a potential difference between the reset potential and the cathode potential is lower than the threshold voltage of the light-emitting device EL. The reset potential can be a potential higher than the cathode potential, a potential equal to the cathode potential, or a potential lower than the cathode potential.
The transistor M1 and the transistor M3 each function as a switch. For example, the transistor M2 functions as a transistor for controlling current flowing through the light-emitting device EL. For example, it can be said that the transistor M1 functions as a selection transistor and the transistor M2 functions as a driving transistor.
Here, it is preferable to use LTPS transistors as all of the transistor M1 to the transistor M3. Alternatively, it is preferable to use OS transistors as the transistor M1 and the transistor M3 and to use an LTPS transistor as the transistor M2.
Alternatively, OS transistors may be used as all of the transistor M1 to the transistor M3. In that case, an LTPS transistor can be used as at least one of a plurality of transistors included in the driver circuit portion 402 and a plurality of transistors included in the driver circuit portion 403, and OS transistors can be used as the other transistors. For example, OS transistors can be used as the transistors provided in the display portion 404, and LTPS transistors can be used as the transistors provided in the driver circuit portion 402 and the driver circuit portion 403.
As the OS transistor, a transistor including an oxide semiconductor in its semiconductor layer where a channel is formed can be used. The semiconductor layer preferably contains indium, M (M is one or more selected from gallium, aluminum, silicon, boron, yttrium, tin, copper, vanadium, beryllium, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, and magnesium), and zinc, for example. Specifically, M is preferably one or more selected from aluminum, gallium, yttrium, and tin. In particular, IGZO is preferably used for a semiconductor layer of the OS transistor. Alternatively, it is preferable to use an oxide containing indium, tin, and zinc. Further alternatively, it is preferable to use an oxide containing indium, gallium, tin, and zinc.
A transistor using an oxide semiconductor having a wider band gap and smaller carrier density than silicon can achieve an extremely low off-state current. Thus, such a low off-state current enables long-term retention of charge accumulated in a capacitor that is connected to the transistor in series. Therefore, it is particularly preferable to use a transistor including an oxide semiconductor as the transistor M1 and the transistor M3 each of which is connected to the capacitor C1 in series. The use of the transistor including an oxide semiconductor as each of the transistor M1 and the transistor M3 can inhibit leakage of charge retained in the capacitor C1 through the transistor M1 or the transistor M3. Furthermore, since charge retained in the capacitor C1 can be retained for a long time, a still image can be displayed for a long time without rewriting data in the pixel 405.
Note that although the transistor is illustrated as an n-channel transistor in
The transistors included in the pixel 405 are preferably formed to be arranged over the same substrate.
Note that transistors each including a pair of gates overlapping with each other with a semiconductor layer therebetween can be used as the transistors included in the pixel 405.
In the transistor including a pair of gates, the same potential is supplied to the pair of gates electrically connected to each other, which brings advantage that the transistor can have a higher on-state current and improved saturation characteristics. A potential for controlling the threshold voltage of the transistor may be supplied to one of the pair of gates. Furthermore, when a constant potential is supplied to one of the pair of gates, the stability of the electrical characteristics of the transistor can be improved. For example, one of the gates of the transistor may be electrically connected to a wiring to which a constant potential is supplied or may be electrically connected to a source or a drain of the transistor.
The pixel 405 illustrated in
The pixel 405 illustrated in
Cross-sectional structure examples of a transistor that can be used in the display panel described above are described below.
The transistor 410 is provided over a substrate 401 and contains polycrystalline silicon in its semiconductor layer. For example, the transistor 410 corresponds to the transistor M2 in the pixel 405. In other words,
The transistor 410 includes a semiconductor layer 411, an insulating layer 412, a conductive layer 413, and the like. The semiconductor layer 411 includes a channel formation region 411i and low-resistance regions 411n. The semiconductor layer 411 contains silicon. The semiconductor layer 411 preferably contains polycrystalline silicon. Part of the insulating layer 412 functions as agate insulating layer. Part of the conductive layer 413 functions as agate electrode.
Note that the semiconductor layer 411 can include a metal oxide exhibiting semiconductor characteristics (also referred to as an oxide semiconductor). In this case, the transistor 410 can be referred to as an OS transistor.
The low-resistance region 411n is a region containing an impurity element For example, in the case where the transistor 410 is an n-channel transistor, phosphorus, arsenic, or the like is added to the low-resistance region 411n. Meanwhile, in the case where the transistor 410 is a p-channel transistor, boron, aluminum, or the like is added to the low-resistance region 411n. In addition, in order to control the threshold voltage of the transistor 410, the above-described impurity may be added to the channel formation region 411i.
An insulating layer 421 is provided over the substrate 401. The semiconductor layer 411 is provided over the insulating layer 421. The insulating layer 412 is provided to cover the semiconductor layer 411 and the insulating layer 421. The conductive layer 413 is provided at a position that is over the insulating layer 412 and overlaps with the semiconductor layer 411.
An insulating layer 422 is provided to cover the conductive layer 413 and the insulating layer 412. A conductive layer 414a and a conductive layer 414b are provided over the insulating layer 422. The conductive layer 414a and the conductive layer 414b are each electrically connected to the low-resistance region 411n in the opening portion provided in the insulating layer 422 and the insulating layer 412. Part of the conductive layer 414a functions as one of a source electrode and a drain electrode and part of the conductive layer 414b functions as the other of the source electrode and the drain electrode. An insulating layer 423 is provided to cover the conductive layer 414a, the conductive layer 414b, and the insulating layer 422.
The conductive layer 431 functioning as a pixel electrode is provided over the insulating layer 423. The conductive layer 431 is provided over the insulating layer 423 and is electrically connected to the conductive layer 414b through an opening provided in the insulating layer 423. Although not illustrated here, an EL layer and a common electrode can be stacked over the conductive layer 431.
The conductive layer 415 is provided over the insulating layer 421. The insulating layer 416 is provided to cover the conductive layer 415 and the insulating layer 421. The semiconductor layer 411 is provided such that at least the channel formation region 411i overlaps with the conductive layer 415 with the insulating layer 416 therebetween.
In the transistor 410a illustrated in
Here, to electrically connect the first gate electrode to the second gate electrode, the conductive layer 413 is electrically connected to the conductive layer 415 through an opening portion provided in the insulating layer 412 and the insulating layer 416 in a region not illustrated. To electrically connect the second gate electrode to a source or a drain, the conductive layer 415 is electrically connected to the conductive layer 414a or the conductive layer 414b through an opening portion provided in the insulating layer 422, the insulating layer 412, and the insulating layer 416 in a region not illustrated.
In the case where LTPS transistors are used as all of the transistors included in the pixel 405, the transistor 410 illustrated in
Described below is an example of a structure including both a transistor containing silicon in its semiconductor layer and a transistor containing a metal oxide in its semiconductor layer.
Structure example 1 described above can be referred to for the transistor 410a. Although an example using the transistor 410a is illustrated here, a structure including the transistor 410 and the transistor 450 or a structure including all the transistor 410, the transistor 410a, and the transistor 450 may alternatively be employed.
The transistor 450 is a transistor including metal oxide in its semiconductor layer. The structure in
Moreover,
The transistor 450 includes a conductive layer 455, the insulating layer 422, a semiconductor layer 451, an insulating layer 452, a conductive layer 453, and the like. Part of the conductive layer 453 functions as a first gate of the transistor 450, and part of the conductive layer 455 functions as a second gate of the transistor 450. In this case, part of the insulating layer 452 functions as a first gate insulating layer of the transistor 450, and part of the insulating layer 422 functions as a second gate insulating layer of the transistor 450.
The conductive layer 455 is provided over the insulating layer 412. The insulating layer 422 is provided to cover the conductive layer 455. The semiconductor layer 451 is provided over the insulating layer 422. The insulating layer 452 is provided to cover the semiconductor layer 451 and the insulating layer 422. The conductive layer 453 is provided over the insulating layer 452 and includes a region overlapping with the semiconductor layer 451 and the conductive layer 455.
An insulating layer 426 is provided to cover the insulating layer 452 and the conductive layer 453. A conductive layer 454a and a conductive layer 454b are provided over the insulating layer 426. The conductive layer 454a and the conductive layer 454b are electrically connected to the semiconductor layer 451 in opening portions provided in the insulating layer 426 and the insulating layer 452. Part of the conductive layer 454a functions as one of a source electrode and a drain electrode and part of the conductive layer 454b functions as the other of the source electrode and the drain electrode. The insulating layer 423 is provided to cover the conductive layer 454a, the conductive layer 454b, and the insulating layer 426.
Here, the conductive layer 414a and the conductive layer 414b electrically connected to the transistor 410a are preferably formed by processing the same conductive film as the conductive layer 454a and the conductive layer 454b. In
Moreover, the conductive layer 413 functioning as the first gate electrode of the transistor 410a and the conductive layer 455 functioning as the second gate electrode of the transistor 450 are preferably formed by processing the same conductive film.
In the structure in
Note that in this specification and the like, the expression “top surface shapes are substantially the same” means that at least outlines of stacked layers partly overlap with each other. For example, the case of processing the upper layer and the lower layer with the use of the same mask pattern or mask patterns that are partly the same is included. However, in some cases, the outlines do not completely overlap with each other and the upper layer is positioned on an inner side of the lower layer or the upper layer is positioned on an outer side of the lower layer; such cases are also represented by the expression “top surface shapes are substantially the same”.
Although the example in which the transistor 410a corresponds to the transistor M2 and is electrically connected to the pixel electrode is shown here, one embodiment of the present invention is not limited thereto. For example, a structure in which the transistor 450 or the transistor 450a corresponds to the transistor M2 may be employed. In that case, the transistor 410a corresponds to the transistor M1, the transistor M3, or another transistor.
This embodiment can be combined with the other embodiments as appropriate.
In this embodiment, a light-emitting device that can be used for the display panel according to one embodiment of the present invention will be described.
As illustrated in
The structure including the layer 4420, the light-emitting layer 4411, and the layer 4430, which are provided between a pair of electrodes, can function as a single light-emitting unit, and the structure in
Note that the structure where a plurality of light-emitting layers (light-emitting layers 4411, 4412, and 4413) are provided between the layer 4420 and the layer 4430 as illustrated in
A structure in which a plurality of light-emitting units (an EL layer 786a and an EL layer 786b) are connected in series with a charge-generation layer 4440 therebetween as illustrated in
In
Alternatively, light-emitting materials that emit light of different colors may be used for the light-emitting layer 4411, the light-emitting layer 4412, and the light-emitting layer 4413. White light emission can be obtained when the light-emitting layer 4411, the light-emitting layer 4412, and the light-emitting layer 4413 emit light of complementary colors. A color filter (also referred to as a coloring layer) may be provided as the layer 785 illustrated in
In
Note that also in
A structure in which light-emitting devices of different emission colors (e.g., blue (B), green (G), and red (R)) are separately formed is referred to as an SBS (Side By Side) structure in some cases.
The emission color of the light-emitting device can be red, green, blue, cyan, magenta, yellow, white, or the like depending on the material that constitutes the EL layer 786. Furthermore, the color purity can be further increased when the light-emitting device has a microcavity structure.
The light-emitting device that emits white light preferably contains two or more kinds of light-emitting substances in the light-emitting layer. To obtain white light emission, two or more kinds of light-emitting substances are selected such that their emission colors are complementary. For example, when an emission color of a first light-emitting layer and an emission color of a second light-emitting layer are complementary colors, the light-emitting device can be configured to emit white light as a whole. The same applies to a light-emitting device including three or more light-emitting layers.
The light-emitting layer preferably contains two or more light-emitting substances that emit light of R (red), G (green), B (blue), Y (yellow), O (orange), and the like. Alternatively, a light-emitting layer preferably contains two or more light-emitting substances each of which emits light containing two or more of spectral components of R, G, and B.
This embodiment can be combined with the other embodiments as appropriate.
In this embodiment, electronic devices of one embodiment of the present invention are described with reference to
Electronic devices of this embodiment each include the display panel of one embodiment of the present invention in a display portion. The display panel of one embodiment of the present invention can be easily increased in resolution and definition and can achieve high display quality. Thus, the display panel of one embodiment of the present invention can be used for a display portion of a variety of electronic devices.
Examples of the electronic devices include electronic devices with a relatively large screen, such as a television device, a desktop or laptop personal computer, a monitor of a computer or the like, digital signage, and a large game machine such as a pachinko machine; a digital camera; a digital video camera; a digital photo frame; a mobile phone; a portable game machine; a portable information terminal; and an audio reproducing device.
In particular, a display panel of one embodiment of the present invention can have high resolution, and thus can be favorably used for an electronic device having a relatively small display portion. Examples of such an electronic device include watch-type and bracelet-type information terminal devices (wearable devices) and wearable devices worn on the head, such as a VR device like a head-mounted display, a glasses-type AR device, and an MR (Mixed Reality) device.
The definition of the display panel of one embodiment of the present invention is preferably as high as HD (number of pixels: 1280×720), FHD (number of pixels: 1920×1080), WQHD (number of pixels: 2560×1440), WQXGA (number of pixels: 2560×1600), 4K (number of pixels: 3840×2160), or 8K (number of pixels: 7680×4320). In particular, a definition of 4K, 8K, or higher is preferable. The pixel density (resolution) of the display panel of one embodiment of the present invention is preferably 100 ppi or higher, further preferably 300 ppi or higher, further preferably 500 ppi or higher, further preferably 1000 ppi or higher, still further preferably 2000 ppi or higher, still further preferably 3000 ppi or higher, still further preferably 5000 ppi or higher, yet further preferably 7000 ppi or higher. With the use of such a display panel having one or both of high definition and high resolution, the electronic device can provide higher realistic sensation, sense of depth, and the like in personal use such as portable use and home use. There is no particular limitation on the screen ratio (aspect ratio) of the display panel of one embodiment of the present invention. For example, the display panel is compatible with a variety of screen ratios such as 1:1 (a square), 4:3, 16:9, and 16:10.
The electronic device in this embodiment may include a sensor (a sensor having a function of measuring force, displacement, position, speed, acceleration, angular velocity, rotational frequency, distance, light, liquid, magnetism, temperature, a chemical substance, sound, time, hardness, electric field, current, voltage, electric power, radiation, flow rate, humidity, gradient, oscillation, odor, or infrared rays).
The electronic device in this embodiment can have a variety of functions, for example, a function of displaying a variety of information (e.g., a still image, a moving image, and a text image) on the display portion, a touch panel function, a function of displaying a calendar, date, time, and the like, a function of executing a variety of software (programs), a wireless communication function, and a function of reading out a program or data stored in a recording medium.
Examples of a wearable device that can be worn on a head are described with reference to
An electronic device 700A illustrated in
The display panel of one embodiment of the present invention can be used as the display panels 751. Thus, the electronic devices are capable of performing ultrahigh-resolution display.
The electronic device 700A and the electronic device 700B can each project images displayed on the display panels 751 onto display regions 756 of the optical members 753. Since the optical members 753 have a light-transmitting property, a user can see images displayed on the display regions, which are superimposed on transmission images seen through the optical members 753. Accordingly, the electronic device 700A and the electronic device 700B are electronic devices capable of AR display.
In the electronic device 700A and the electronic device 700B, a camera capable of capturing images of the front side may be provided as the image capturing portion. Furthermore, when the electronic device 700A and the electronic device 700B are provided with an acceleration sensor such as a gyroscope sensor, the orientation of the user's head can be sensed and an image corresponding to the orientation can be displayed on the display regions 756.
The communication portion includes a wireless communication device, and a video signal and the like can be supplied by the wireless communication device. Instead of or in addition to the wireless communication device, a connector that can be connected to a cable for supplying a video signal and a power supply potential may be provided.
The electronic device 700A and the electronic device 700B are provided with a battery so that they can be charged wirelessly and/or by wire.
A touch sensor module may be provided in the housing 721. The touch sensor module has a function of detecting a touch on the outer surface of the housing 721. Detecting a tap operation, a slide operation, or the like by the user with the touch sensor module enables various types of processing. For example, a video can be paused or restarted by a tap operation, and can be fast-forwarded or fast-reversed by a slide operation. When the touch sensor module is provided in each of the two housings 721, the range of the operation can be increased.
Various touch sensors can be applied to the touch sensor module. For example, any of touch sensors of the following types can be used: a capacitive type, a resistive type, an infrared type, an electromagnetic induction type, a surface acoustic wave type, and an optical type. In particular, a capacitive sensor or an optical sensor is preferably used for the touch sensor module.
In the case of using an optical touch sensor, a photoelectric conversion device (also referred to as a photoelectric conversion element) can be used as a light-receiving device (also referred to as a light-receiving element). One or both of an inorganic semiconductor and an organic semiconductor can be used for an active layer of the photoelectric conversion device.
An electronic device 800A illustrated in
The display panel of one embodiment of the present invention can be used in the display portions 820. Thus, the electronic devices are capable of performing ultrahigh-resolution display. Such electronic devices provide an enhanced sense of immersion to the user.
The display portions 820 are positioned inside the housing 821 so as to be seen through the lenses 832. When the pair of display portions 820 display different images, three-dimensional display using parallax can be performed.
The electronic device 800A and the electronic device 800B can be regarded as electronic devices for VR The user who wears the electronic device 800A or the electronic device 800B can see images displayed on the display portions 820 through the lenses 832.
The electronic device 800A and the electronic device 800B preferably include a mechanism for adjusting the lateral positions of the lenses 832 and the display portions 820 so that the lenses 832 and the display portions 820 are positioned optimally in accordance with the positions of the user's eyes. Moreover, the electronic device 800A and the electronic device 800B preferably include a mechanism for adjusting focus by changing the distance between the lenses 832 and the display portions 820.
The electronic device 800A or the electronic device 800B can be mounted on the user's head with the wearing portions 823.
The image capturing portion 825 has a function of obtaining information on the external environment. Data obtained by the image capturing portion 825 can be output to the display portion 820. An image sensor can be used for the image capturing portion 825. Moreover, a plurality of cameras may be provided so as to support a plurality of fields of view, such as a telescope field of view and a wide field of view.
Although an example where the image capturing portions 825 are provided is shown here, a range sensor capable of measuring a distance between the user and an object (hereinafter also referred to as a sensing portion) just needs to be provided. In other words, the image capturing portion 825 is one embodiment of the sensing portion. As the sensing portion, an image sensor or a distance image sensor such as LIDAR (Light Detection and Ranging) can be used, for example. By using images obtained by the camera and images obtained by the distance image sensor, more information can be obtained and a gesture operation with higher accuracy is possible.
The electronic device 800A may include a vibration mechanism that functions as bone-conduction earphones. For example, any one or more of the display portion 820, the housing 821, and the wearing portion 823 can employ a structure including the vibration mechanism. Thus, without additionally requiring an audio device such as headphones, earphones, or a speaker, the user can enjoy video and sound only by wearing the electronic device 800A.
The electronic device 800A and the electronic device 800B may each include an input terminal. To the input terminal, a cable for supplying a video signal from a video output device or the like, power for charging the battery provided in the electronic device, and the like can be connected.
The electronic device of one embodiment of the present invention may have a function of performing wireless communication with earphones 750. The earphones 750 include a communication portion (not illustrated) and has a wireless communication function. The earphones 750 can receive information (e.g., audio data) from the electronic device with the wireless communication function. For example, the electronic device 700A in
The electronic device may include an earphone portion. The electronic device 700B in
Similarly, the electronic device 800B illustrated in
The electronic device may include an audio output terminal to which earphones, headphones, or the like can be connected. The electronic device may include one or both of an audio input terminal and an audio input mechanism. As the audio input mechanism, a sound collecting device such as a microphone can be used, for example. The electronic device may have a function of what is called a headset by including the audio input mechanism.
As described above, both the glasses-type device (e.g., the electronic device 700A and the electronic device 700B) and the goggles-type device (e.g., the electronic device 800A and the electronic device 800B) are preferable as the electronic device of one embodiment of the present invention.
The electronic device of one embodiment of the present invention can transmit information to earphones by wire or wirelessly.
An electronic device 6500 illustrated in
The electronic device 6500 includes a housing 6501, a display portion 6502, a power button 6503, buttons 6504, a speaker 6505, a microphone 6506, a camera 6507, a light source 6508, and the like. The display portion 6502 has a touch panel function.
The display panel of one embodiment of the present invention can be used for the display portion 6502.
A protection member 6510 having a light-transmitting property is provided on a display surface side of the housing 6501, and a display panel 6511, an optical member 6512, a touch sensor panel 6513, a printed circuit board 6517, a battery 6518, and the like are provided in a space surrounded by the housing 6501 and the protection member 6510.
The display panel 6511, the optical member 6512, and the touch sensor panel 6513 are fixed to the protection member 6510 with an adhesive layer (not illustrated).
Part of the display panel 6511 is folded back in a region outside the display portion 6502, and an FPC 6515 is connected to the part that is folded back. An IC 6516 is mounted on the FPC 6515. The FPC 6515 is connected to a terminal provided on the printed circuit board 6517.
A flexible display of one embodiment of the present invention can be used as the display panel 6511. Thus, an extremely lightweight electronic device can be achieved. Since the display panel 6511 is extremely thin, the battery 6518 with high capacity can be mounted without an increase in the thickness of the electronic device. Moreover, part of the display panel 6511 is folded back so that a connection portion with the FPC 6515 is provided on the back side of a pixel portion, whereby an electronic device with a narrow bezel can be achieved.
The display panel of one embodiment of the present invention can be used for the display portion 7000.
Operation of the television device 7100 illustrated in
Note that the television device 7100 has a structure in which a receiver, a modem, and the like are provided. A general television broadcast can be received with the receiver. When the television device is connected to a communication network with or without wires via the modem, one-way (from a transmitter to a receiver) or two-way (between a transmitter and a receiver or between receivers, for example) data communication can be performed.
The display panel of one embodiment of the present invention can be used for the display portion 7000.
Digital signage 7300 illustrated in
The display panel of one embodiment of the present invention can be used for the display portion 7000 illustrated in each of
A larger area of the display portion 7000 can increase the amount of information that can be provided at a time. The larger display portion 7000 attracts more attention, so that the effectiveness of the advertisement can be increased, for example.
The use of a touch panel in the display portion 7000 is preferable because in addition to display of a still image or a moving image on the display portion 7000, intuitive operation by a user is possible. Moreover, for an application for providing information such as route information or traffic information, usability can be enhanced by intuitive operation.
As illustrated in
It is possible to make the digital signage 7300 or the digital signage 7400 execute a game with the use of the screen of the information terminal 7311 or the information terminal 7411 as an operation means (controller). Thus, an unspecified number of users can join in and enjoy the game concurrently.
Electronic devices illustrated in
The display apparatus of one embodiment of the present invention can be used for the display portion 9001 in
The electronic devices illustrated in
The details of the electronic devices illustrated in
This embodiment can be combined with the other embodiments as appropriate.
AL: wiring, CL: wiring, GL: wiring, PS: subpixel, RL: wiring, SL: wiring, SLB: wiring, SLG: wiring, SLR: wiring, 100A: display panel, 100B: display panel, 100C: display panel, 100D: display panel, 100E: display panel, 100F: display panel, 100G: display panel, 100H: display panel, 100J: display panel, 100: display panel, 101: layer, 110a: subpixel, 110b: subpixel, 110c subpixel, 110d: subpixel, 110: pixel, 111a: pixel electrode, 111b: pixel electrode, 111c: pixel electrode, 111d: pixel electrode, 112a: conductive layer, 112b: conductive layer, 112c: conductive layer, 112d: conductive layer, 113A: first layer, 113a: first layer, 113B: second layer, 113b: second layer, 113C: third layer, 113c: third layer, 113d: fourth layer, 114: common layer, 115: common electrode, 116: protruding portion, 117: light-blocking layer, 118a: mask layer, 118A: first mask layer, 118b: mask layer, 118B: first mask layer, 118c: mask layer, 118C: first mask layer, 118d: mask layer, 118: mask layer, 119a: mask layer, 119A: second mask layer, 119b: mask layer, 119B: second mask layer, 119c: mask layer, 119C: second mask layer, 120: substrate, 122: resin layer, 123: conductive layer, 124a: pixel, 124b: pixel, 125A: insulating film, 125: insulating layer, 126a: conductive layer, 126b: conductive layer, 126c: conductive layer, 126d: conductive layer, 127a: insulating layer, 127b: insulating layer, 127: insulating layer, 128: layer, 129a: conductive layer, 129b: conductive layer, 129c: conductive layer, 129d: conductive layer, 130a: light-emitting device, 130B: light-emitting device, 130b: light-emitting device, 130c: light-emitting device, 130G: light-emitting device, 130R: light-emitting device, 131: protective layer, 132: mask, 133: depression portion, 135: light-blocking layer, 135A: light-blocking film, 137a: tapered portion, 137b: tapered portion, 139: region, 140: connection portion, 142: adhesive layer, 150: light-receiving device, 151: substrate, 152: substrate, 153: insulating layer, 162: display portion, 164: circuit, 165: wiring, 166: conductive layer, 172: FPC, 173: IC, 190a: resist mask, 190b: resist mask, 190c: resist mask, 201: transistor, 204: connection portion, 205: transistor, 209: transistor, 210: transistor, 211: insulating layer, 213: insulating layer, 214: insulating layer, 215: insulating layer, 218: insulating layer, 221: conductive layer, 222a: conductive layer, 222b: conductive layer, 223: conductive layer, 225: insulating layer, 231i: channel formation region, 231n: low-resistance region, 231: semiconductor layer, 240: capacitor, 241: conductive layer, 242: connection layer, 243: insulating layer, 245: conductive layer, 251: conductive layer, 252: conductive layer, 254: insulating layer, 255a: insulating layer, 255b: insulating layer, 255c: insulating layer, 256: plug, 261: insulating layer, 262: insulating layer, 263: insulating layer, 264: insulating layer, 265: insulating layer, 271: plug, 274a: conductive layer, 274b: conductive layer, 274: plug, 280: display module, 281: display portion, 282: circuit portion, 283a: pixel circuit, 283: pixel circuit portion, 284a: pixel, 284: pixel portion, 285: terminal portion, 286: wiring portion, 290: FPC, 291: substrate, 292: substrate, 301A: substrate, 301B: substrate, 301: substrate, 310A: transistor, 310B: transistor, 310: transistor, 311: conductive layer, 312: low-resistance region, 313: insulating layer, 314: insulating layer, 315: element isolation layer, 320A: transistor, 320B: transistor, 320: transistor, 321: semiconductor layer, 323: insulating layer, 324: conductive layer, 325: conductive layer, 326: insulating layer, 327: conductive layer, 328: insulating layer, 329: insulating layer, 331: substrate, 332: insulating layer, 335: insulating layer, 336: insulating layer, 341: conductive layer, 342: conductive layer, 343: plug, 344: insulating layer, 345: insulating layer, 346: insulating layer, 347: bump, 348: adhesive layer, 351: substrate, 352: finger, 353: layer, 355: functional layer, 357: layer, 359: substrate, 400: display panel, 401: substrate, 402: driver circuit portion, 403: driver circuit portion, 404: display portion, 405B: subpixel, 405G: subpixel, 405R: subpixel, 405: pixel, 410a: transistor, 410: transistor, 411i: channel formation region, 411n: low-resistance region, 411: semiconductor layer, 412: insulating layer, 413: conductive layer, 414a: conductive layer, 414b: conductive layer, 415: conductive layer, 416: insulating layer, 421: insulating layer, 422: insulating layer, 423: insulating layer, 426: insulating layer, 430: pixel, 431: conductive layer, 450a: transistor, 450: transistor, 451: semiconductor layer, 452: insulating layer, 453: conductive layer, 454a: conductive layer, 454b: conductive layer, 455: conductive layer, 700A: electronic device, 700B: electronic device, 721: housing, 723: wearing portion, 727: earphone portion, 750: earphone, 751: display panel, 753: optical member, 756: display region, 757: frame, 758: nose pad, 772: lower electrode, 785: layer, 786a: EL layer, 786b: EL layer, 786: EL layer, 788: upper electrode, 800A: electronic device, 800B: electronic device, 820: display portion, 821: housing, 822: communication portion, 823: wearing portion, 824: control portion, 825: image capturing portion, 827: earphone portion, 832: lens, 4411: light-emitting layer, 4412: light-emitting layer, 4413: light-emitting layer, 4420: layer, 4421: layer, 4422: layer, 4430: layer, 4431: layer, 4432: layer, 4440: charge-generation layer, 6500: electronic device, 6501: housing, 6502: display portion, 6503: power button, 6504: button, 6505: speaker, 6506: microphone, 6507: camera, 6508: light source, 6510: protection member, 6511: display panel, 6512: optical member, 6513: touch sensor panel, 6515: FPC, 6516: IC, 6517: printed circuit board, 6518: battery, 7000: display portion, 7100: television device, 7101: housing, 7103: stand, 7111: remote controller, 7200: laptop personal computer, 7211: housing, 7212: keyboard, 7213: pointing device, 7214: external connection port, 7300: digital signage, 7301: housing, 7303: speaker, 7311: information terminal, 7400: digital signage, 7401: pillar, 7411: information terminal, 9000: housing, 9001: display portion, 9002: camera, 9003: speaker, 9005: operation key, 9006: connection terminal, 9007: sensor, 9008: microphone, 9050: icon, 9051: information, 9052: information, 9053: information, 9054: information, 9055: hinge, 9101: portable information terminal, 9102: portable information terminal, 9103: tablet terminal, 9200: portable information terminal, 9201: portable information terminal
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-120393 | Jul 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2022/056369 | 7/11/2022 | WO |
