Patent Application
20250081748
One embodiment of the present invention relates to a display device, a display module, and an electronic device. One embodiment of the present invention relates to a method for manufacturing a display device.
Note that one embodiment of the present invention is not limited to the above technical field. Examples of the technical field of one embodiment of the present invention include a semiconductor device, a display device, a light-emitting apparatus, a power storage device, a memory device, an electronic device, a lighting device, an input device (e.g., a touch sensor), an input/output device (e.g., a touch panel), a method for driving any of them, and a method for manufacturing any of them.
Recent display devices have been expected to be applied to a variety of uses. Usage examples of large-sized display devices include a television device for home use (also referred to as TV or television receiver), digital signage, and a PID (Public Information Display). In addition, a smartphone and a tablet terminal each including a touch panel, and the like, are being developed as portable information terminals.
Furthermore, display devices have been required to have higher resolution. As devices requiring high resolution display devices, for example, devices for virtual reality (VR), augmented reality (AR), substitutional reality (SR), or mixed reality (MR) have been actively developed.
Light-emitting apparatuses including light-emitting devices (also referred to as light-emitting elements) have been developed as display devices, for example. Light-emitting devices (also referred to as EL devices or EL elements) utilizing electroluminescence (hereinafter referred to as EL) have features such as ease of reduction in thickness and weight, high-speed response to input signals, and driving with a constant DC voltage power source, and have been used in display devices.
Patent Document 1 discloses a display device using an organic EL device (also referred to as organic EL element) for VR.
One object of one embodiment of the present invention is to provide a highly reliable display device. Another object of one embodiment of the present invention is to provide a high-resolution display device. Another object of one embodiment of the present invention is to provide a high-definition display device. Another object of one embodiment of the present invention is to provide a display device with high display quality.
Another object of one embodiment of the present invention is to provide a method for manufacturing a highly reliable display device. Another object of one embodiment of the present invention is to provide a method for manufacturing a high-resolution display device. Another object of one embodiment of the present invention is to provide a method for manufacturing a high-definition display device. Another object of one embodiment of the present invention is to provide a method for manufacturing a display device with high display quality. Another object of one embodiment of the present invention is to provide a method for manufacturing a display device with high yield.
Note that the description of these objects does not preclude the existence of other objects. One embodiment of the present invention does not need to achieve all these objects. Other objects can be derived from the description of the specification, the drawings, and the claims.
One embodiment of the present invention is a display device which includes a first light-emitting device, a second light-emitting device positioned adjacent to the first light-emitting device, and a first insulating layer; the first light-emitting device includes a first pixel electrode, a first EL layer over the first pixel electrode, and a common electrode over the first EL layer; the second light-emitting device includes a second pixel electrode, a second EL layer over the second pixel electrode, and the common electrode over the second EL layer; part of a side surface of the first EL layer and part of a side surface of the second EL layer are positioned to face each other; part of the first insulating layer is positioned at a position interposed between a side end portion of the first EL layer and a side end portion of the second EL layer; another part of the first insulating layer overlaps with part of a top surface of the first EL layer or part of a top surface of the second EL layer; the first light-emitting device emits blue light; the second light-emitting device emits light of a color different from that from the first light-emitting device; the first EL layer includes a first light-emitting unit over the first pixel electrode, a first charge-generation layer over the first light-emitting unit, and a second light-emitting unit over the first charge-generation layer; and the second EL layer includes a third light-emitting unit over the second pixel electrode.
In the above, a structure may be employed in which a second insulating layer that covers an end portion of the first pixel electrode is included.
In the above, a structure may be employed in which a second insulating layer that covers an end portion of the first pixel electrode and an end portion of the second pixel electrode is included.
Another embodiment of the present invention is a display device which includes a first light-emitting device, a second light-emitting device, a third light-emitting device, and a first insulating layer; the first light-emitting device is positioned adjacent to the second light-emitting device and the third light-emitting device; the first light-emitting device includes a first pixel electrode, a first EL layer over the first pixel electrode, and a common electrode over the first EL layer; the second light-emitting device includes a second pixel electrode, a second EL layer over the second pixel electrode, and the common electrode over the second EL layer; the third light-emitting device includes a third pixel electrode, a third EL layer over the third pixel electrode, and the common electrode over the third EL layer; any two selected from part of a side surface of the first EL layer, part of a side surface of the second EL layer, and part of a side surface of the third EL layer are positioned to face each other; part of the first insulating layer is positioned at a position interposed between any two selected from a side end portion of the first EL layer, a side end portion of the second EL layer, and a side end portion of the third EL layer; another part of the first insulating layer overlaps with part of a top surface of the first EL layer, part of a top surface of the second EL layer, or part of a top surface of the third EL layer; the first light-emitting device emits blue light; the second light-emitting device emits red light; the third light-emitting device emits green light; the first EL layer includes a first light-emitting unit over the first pixel electrode, a first charge-generation layer over the first light-emitting unit, and a second light-emitting unit over the first charge-generation layer; the second EL layer includes a third light-emitting unit over the second pixel electrode; and the third EL layer includes a fourth light-emitting unit over the third pixel electrode, a second charge-generation layer over the fourth light-emitting unit, and a fifth light-emitting unit over the second charge-generation layer.
In the above, a structure may be employed in which a second insulating layer that covers an end portion of the first pixel electrode and an end portion of the third pixel electrode is included.
In the above, a structure may be employed in which a second insulating layer that covers an end portion of the first pixel electrode, an end portion of the second pixel electrode, and an end portion of the third pixel electrode is included.
In the above, the first insulating layer preferably includes a first layer and a second layer over the first layer, the first layer preferably includes an inorganic material, and the second layer preferably includes an organic material.
In the above, the common electrode is preferably positioned over the second layer.
One embodiment of the present invention can provide a highly reliable display device.
One embodiment of the present invention can provide a high-resolution display device. One embodiment of the present invention can provide a high-definition display device. One embodiment of the present invention can provide a display device with high display quality.
One embodiment of the present invention can provide a method for manufacturing a highly reliable display device. One embodiment of the present invention can provide a method for manufacturing a high-resolution display device. One embodiment of the present invention can provide a method for manufacturing a high-definition display device. One embodiment of the present invention can provide a method for manufacturing a display device with high display quality. One embodiment of the present invention can provide a method for manufacturing a display device with high yield.
Note that the description of these effects does not preclude the existence of other effects. One embodiment of the present invention does not necessarily have all these effects. Other effects can be derived from the description of the specification, the drawings, and the claims.
Embodiments will be described in detail with reference to the drawings. Note that the present invention is not limited to the following description, and it will be readily appreciated by those skilled in the art that modes and details of the present invention can be modified in various ways without departing from the spirit and scope of the present invention. Thus, the present invention should not be construed as being limited to the description in the following embodiments.
Note that in structures of the invention described below, the same portions or portions having similar functions are denoted by the same reference numerals in different drawings, and description thereof is not repeated. The same hatching pattern is used for portions having similar functions, and the portions are not denoted by specific reference numerals in some cases.
The position, size, range, or the like of each component illustrated in drawings does not represent the actual position, size, range, or the like in some cases for easy understanding. Thus, the disclosed invention is not necessarily limited to the position, size, range, or the like disclosed in the drawings.
Note that the term “film” and the term “layer” can be interchanged with each other depending on the case or the circumstances. For example, the term “conductive layer” can be replaced with the term “conductive film”. As another example, the term “insulating film” can be replaced with the term “insulating layer”.
In this specification and the like, a device formed using a metal mask or an FMM (a fine metal mask or a high-resolution metal mask) may be referred to as a device having an MM (metal mask) structure. In this specification and the like, a device manufactured without using a metal mask or an FMM may be referred to as a device having an MML (a metal maskless) structure.
In this specification and the like, a structure where at least light-emitting layers of light-emitting devices having different emission wavelengths are separately formed 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 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 the above-described carrier-injection layer, carrier-transport layer, and carrier-blocking layer cannot be clearly distinguished from each other on the basis of the cross-sectional shape, properties, or the like in some cases. 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 (a light-emitting element) includes an EL layer between a pair of electrodes. The EL layer includes at least a light-emitting layer. Examples of the 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 functioning as a photoelectric conversion layer between a pair of electrodes.
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, the term “island-shaped light-emitting layer” refers to a state where the light-emitting layer and its adjacent light-emitting layer are physically separated from each other.
Note that in this specification and the like, a tapered shape indicates a shape in which at least part of the side surface of a structure is inclined to a substrate surface. For example, a tapered shape preferably includes a region where an angle formed by the inclined side surface and the substrate surface (such an angle is also referred to as a taper angle) is less than 90°. Note that the side surface of the component and the substrate surface are not necessarily completely flat and may be substantially flat with a slight curvature or substantially flat with slight unevenness.
Note that in this specification and the like, a sacrificial layer is 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 process. Note that in this specification and the like, a sacrificial layer may be referred to as a mask layer.
In this embodiment, a display device of one embodiment of the present invention will be described with reference to
A display device of one embodiment of the present invention includes light-emitting devices of different emission colors, which are separately formed, and can perform full-color display.
In the case of manufacturing a display device 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.
For example, an island-shaped light-emitting layer can be formed by a vacuum evaporation method using a metal 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 low 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 formed film; accordingly, it is difficult to achieve high resolution and a high aperture ratio of the display device. In addition, the outline of the layer might blur during evaporation, so that the thickness of an end portion might be reduced. That is, the thickness of the island-shaped light-emitting layer formed using a metal mask may vary from area to area. In the case of manufacturing a display device 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 view of this, in manufacture of the display device of one embodiment of the present invention, fine patterning of a light-emitting layer is performed by a photolithography method without a shadow mask such as a metal mask. Specifically, pixel electrodes are formed for the respective subpixels, and then a light-emitting layer is formed across the pixel electrodes. After that, the light-emitting layer is processed by a photolithography method, so that one island-shaped light-emitting layer is formed per pixel electrode. Thus, the light-emitting layer can be divided for the respective subpixels, so that island-shaped light-emitting layers can be formed for the respective subpixels.
In the case of processing the light-emitting layer into an island shape, a structure is possible where processing is performed by a photolithography method directly on the light-emitting layer. In the case of the above structure, damage to the light-emitting layer (e.g., processing damage) might significantly degrade the reliability. In view of this, in manufacture of the display device of one embodiment of the present invention, a method is preferably employed in which a sacrificial layer (also referred to as a mask layer, a protective layer, or the like) is formed over a functional layer (e.g., a carrier-blocking layer, a carrier-transport layer, a carrier-injection layer, or the like) positioned above the light-emitting 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 device. A functional layer provided between the light-emitting layer and the sacrificial layer can inhibit the light-emitting layer from being exposed on the outermost surface during the manufacturing process of the display device and can reduce damage to the light-emitting layer.
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, a carrier-transport layer, a carrier-blocking 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.
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 formed in the same step. In the manufacturing method of the display device of one embodiment of the present invention, some layers included in the EL layer are formed into an island shape separately for each color, and then at least part of the sacrificial layer is removed. After that, other layers (sometimes referred to as common layers) included in the EL layers and a common electrode (also referred to as an upper electrode) are formed so as to be shared by the light-emitting devices of different colors (formed as one film). For example, the carrier-injection layer and the common electrode can be formed so as to be shared by the light-emitting devices of different 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 formed into 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.
Thus, the display device of one embodiment of the present invention includes an insulating layer covering at least the side surface of the island-shaped EL layer. The insulating layer preferably covers part of the top surface of the island-shaped EL layer.
This can inhibit some layers below the light-emitting layer of the island-shaped EL layers and the pixel electrodes covered by the island-shaped EL layers 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 a cross-sectional view, an end portion of the insulating layer preferably has a tapered shape with a taper angle of less than 90°. In this case, step disconnection of the common layer and the common electrode provided over the insulating layer can be prevented. Consequently, it is possible to inhibit a connection defect due to step disconnection. Alternatively, an increase in electrical resistance caused by local thinning of the common electrode due to level difference can be inhibited.
Note that in this specification and the like, disconnection refers to a phenomenon in which a layer, a film, or an electrode is disconnected because of the shape of the formation surface (e.g., a level difference).
As described above, the island-shaped EL layers manufactured by the method for manufacturing a display device of one embodiment of the present invention are formed not by using a fine metal mask but by processing an EL layer formed over the entire surface. Accordingly, a high-resolution display device or a display device with a high aperture ratio, which has been difficult to achieve, can be manufactured. Moreover, light-emitting layers can be formed separately for the respective colors, enabling the display device to perform extremely clear display with high contrast and high display quality. Moreover, providing the sacrificial layer over the light-emitting layer can reduce damage to the light-emitting layer in the manufacturing process of the display device, resulting in an increase in 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 of one embodiment of the present invention can shorten the distance between adjacent light-emitting devices, the distance between adjacent EL layers, or the distance between adjacent pixel electrodes to 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 1.5 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, the distance between adjacent EL layers, or the distance between 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, in the display device of one embodiment of the present invention, the 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% and lower than 100% can be achieved.
Note that increasing the aperture ratio of the display device can improve the reliability of the display device. Specifically, with reference to the lifetime of a display device including an organic EL device and having an aperture ratio of 10%, a display device 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 device having an aperture ratio of 40% (that is, 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 through the organic EL device to obtain a certain display can be reduced with an increasing aperture ratio, and accordingly the lifetime of the display device can be increased. The display device of one embodiment of the present invention can have a higher aperture ratio and thus can have higher display quality. Furthermore, the display device 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 of the island-shaped EL layer itself (also referred to as processing size) can be made much smaller than that in the case of using a fine metal mask. For example, in the case of using a metal mask for forming EL layers separately into island shapes, a variation in the thickness of the pattern occurs between the center and the edge of the pattern, which causes a reduction in an effective area that can be used as a light-emitting region with respect to the area of the entire EL layer. In contrast, in the above manufacturing method, a film formed 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. Thus, a display device having both high resolution and a high aperture ratio can be manufactured. Furthermore, the display device can be reduced in size and weight.
Specifically, for example, the display device of one embodiment of the present invention can have 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.
Furthermore, a light-emitting device that emits light with a relatively short wavelength, such as blue light, tends to cause deterioration of luminance or the like more easily than a light-emitting device that emits light with a relatively long wavelength, such as red light. Thus, a light-emitting device that emits blue light in a display device of the present invention employs a tandem structure (a structure including a plurality of light-emitting units) for improved reliability of the light-emitting device and the display device. Furthermore, a light-emitting device that emits red light employs a single structure (a structure including only one light-emitting unit) for a simplified manufacturing process, so that the yield in a manufacturing process of the display device can be increased. As a light-emitting device that emits green light, a single structure or a tandem structure is selected as appropriate.
Note that in the present invention, a tandem structure is employed at least for a light-emitting device having the lowest reliability and the light-emitting device is not limited to the blue-light-emitting device. For example, in the case where a green-light-emitting device has the lowest reliability, a blue-light-emitting device may have a single structure and a green-light-emitting device may have a tandem structure.
Each of the light-emitting units included in the tandem structure includes at least one light-emitting layer. Each of the light-emitting units may also 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. A charge-generation layer (also referred to as an intermediate layer) is preferably provided between the light-emitting units.
In this embodiment, cross-sectional structures of the display device of one embodiment of the present invention are mainly described, and a method for manufacturing the display device of one embodiment of the present invention will be described in detail in Embodiment 4.
The top surface shape of the subpixel illustrated 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.
The range of the circuit layout for forming the subpixels is not limited to the range of the subpixels illustrated in
Although the subpixels 11R, 11G, and 11B have the same or substantially the same aperture ratio (can also be referred to as the same size or the same size of a light-emitting region) in
The pixel 110 illustrated in
In this specification and the like, the row direction is referred to as X direction and the column direction is referred to as Y direction in some cases. The X direction and the Y direction intersect with each other and are, for example, orthogonal to each other (see
Although the top view (can also be referred to as the plan view) of
As shown in
Although
The display device of one embodiment of the present invention can have any of the following structures: a top-emission structure where light is emitted in a direction opposite to the substrate where the light-emitting device is formed, a bottom-emission structure where light is emitted toward the substrate where the light-emitting device is formed, and a dual-emission structure where light is emitted toward both surfaces.
The layer 101 including transistors can employ a stacked-layer structure where 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. Specifically, it is preferable 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 in its composition, and a nitride oxide refers to a material that contains more nitrogen than oxygen in its composition. 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 transistors will be described later in Embodiment 6.
The light-emitting device 130R emits red (R) light, the light-emitting device 130G emits green (G) light, and the light-emitting device 130B emits blue (B) light.
In this specification and the like, a blue (B) wavelength range is greater than or equal to 400 nm and less than 490 nm, and blue (B) light has at least one emission spectrum peak in the wavelength range. A green (G) wavelength range is greater than or equal to 490 nm and less than 580 nm, and green (G) light has at least one emission spectrum peak in the wavelength range. A red (R) wavelength range is greater than or equal to 580 nm and less than 700 nm, and red (R) light has at least one emission spectrum peak in the wavelength range.
As the light-emitting device, for example, 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 fluorescent light (a fluorescent material), a substance that emits phosphorescent light (a phosphorescent material), a substance that exhibits thermally activated delayed fluorescence (a thermally activated delayed fluorescence (TADF) material), and an inorganic compound (e.g., a quantum dot material). In addition, an LED (Light Emitting Diode) such as a micro LED can also be used as the light-emitting device.
The light-emitting device can emit infrared, red, green, blue, cyan, magenta, yellow, or white light, for example. Furthermore, the color purity can be increased when the light-emitting device has a microcavity structure.
Embodiment 2 can be referred to for the structure and materials of the light-emitting device.
One of a 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 sometimes described below as an example. Note that Embodiment 2 can be referred to for the details of structures and materials of the pixel electrode and the common electrode.
The light-emitting device 130R includes a pixel electrode 111R over the insulating layer 255c, an island-shaped layer 113R over the pixel electrode 111R, a common layer 114 over the island-shaped layer 113R, and a common electrode 115 over the common layer 114. In the light-emitting device 130R, the layer 113R and the common layer 114 are collectively referred to as an EL layer in some cases.
The light-emitting device 130G includes a pixel electrode 111G over the insulating layer 255c, an island-shaped layer 113G over the pixel electrode 111G, the common layer 114 over the island-shaped layer 113G, and the common electrode 115 over the common layer 114. In the light-emitting device 130G, the layer 113G and the common layer 114 are collectively referred to as an EL layer in some cases.
The light-emitting device 130B includes a pixel electrode 111B over the insulating layer 255c, an island-shaped layer 113B over the pixel electrode 111B, the common layer 114 over the island-shaped layer 113B, and the common electrode 115 over the common layer 114. In the light-emitting device 130B, the layer 113B and the common layer 114 are collectively referred to as an EL layer in some cases.
In this specification and the like, in the EL layers included in the light-emitting devices, the island-shaped layer provided in each light-emitting device is referred to as the layer 113B, the layer 113G, or the layer 113R, and the layer shared by the plurality of the light-emitting devices is referred to as the common layer 114. Note that in this specification and the like, the layer 113R, the layer 113G, and the layer 113B are sometimes referred to as island-shaped EL layers, EL layers formed in an island shape, or the like, in which case the common layer 114 is not included.
The layer 113R, the layer 113G, and the layer 113B each have an island shape after being processed by a photolithography method. At each of end portions of the layer 113R, the layer 113G, and the layer 113B, an angle between the top surface and the side surface is approximately 90°. By contrast, an organic film formed using a fine metal mask or the like has a thickness that tends to gradually decrease with decreasing distance to the end portion, and the top surface has a slope shape in the range of greater than or equal to 1 μm and less than or equal to 10 μm, for example; thus, such an organic film has a shape whose top surface and side surface cannot be easily distinguished from each other.
The top and side surfaces of each of the layer 113R, the layer 113G, and the layer 113B are clearly distinguished from each other. Accordingly, as for the layer 113R and the layer 113G which are adjacent to each other, part of the side surface of the layer 113R and part of the side surface of the layer 113G are positioned to face each other. This applies to any combination of the layer 113R, the layer 113G, and the layer 113B.
In this manner, the layer 113R, the layer 113G, and the layer 113B are isolated from each other. When the EL layer is provided in an island shape for each light-emitting device, a leakage current between adjacent light-emitting devices can be inhibited. Thus, it is possible to prevent crosstalk due to unintended light emission, so that a display device with extremely high contrast can be achieved. In particular, a display device having high current efficiency at low luminance can be achieved.
End portions of the pixel electrode 111R, the pixel electrode 111G, and the pixel electrode 111B each preferably have a tapered shape. Specifically, the end portions of the pixel electrode 111R, the pixel electrode 111G, and the pixel electrode 111B each preferably have a tapered shape with a taper angle less than 90°. In the case where the end portions of the pixel electrodes each have a tapered shape, each of the layer 113R, the layer 113G, and the layer 113B provided along the side surfaces of the pixel electrodes reflects the tapered shape. When the side surface of the pixel electrode has a tapered shape, coverage with the EL layer provided along the side surface of the pixel electrode can be improved.
Note that the pixel electrodes 111R, 111G, and 111B are collectively referred to as a pixel electrode 111 in some cases.
As a material for forming the pixel electrode 111, a metal, an alloy, an electrically conductive compound, a mixture thereof, and the like can be used as appropriate. Specific examples include In—Sn oxide (indium tin oxide, also referred to as ITO), In—Si—Sn oxide (also referred to as ITSO), In—Zn oxide (indium zin oxide), In—W—Zn oxide, an alloy containing aluminum (an aluminum alloy) such as an Al—Ni—La (an alloy of aluminum, nickel, and lanthanum), and an Ag—Pd—Cu (an alloy of silver, palladium, and copper, also referred to as APC). In addition, it is possible to use a metal such as aluminum (Al), magnesium (Mg), 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 an element belonging to Group 1 or Group 2 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 metal, the alloy, the electrically conductive compound, the mixture thereof, and the like described above may be stacked as appropriate to form the pixel electrode 111.
In
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 device 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 device. For example, in the display device of one embodiment of the present invention, the viewing angle (the maximum angle with a certain contrast ratio maintained when the 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.
In this embodiment, as illustrated in
The blue-light-emitting device tends to cause a decrease in reliability (e.g., deterioration of luminance) more easily than a light-emitting device with a long wavelength (e.g., a red-light-emitting device). Thus, the light-emitting device 130B in a display device of the present invention employs a tandem structure for improved reliability of the light-emitting device 130B and the display device. Furthermore, each of the light-emitting device 130R and the light-emitting device 130G employs a single structure for a simplified manufacturing process, so that the yield in the manufacturing process of the display device can be increased.
The layer 113R, the layer 113G, and the layer 113B each include at least a light-emitting layer. The layer 113R includes a light-emitting layer emitting red light, and the layer 113G includes a light-emitting layer emitting green light. In other words, the layer 113R contains a light-emitting material emitting red light, and the layer 113G contains a light-emitting material emitting green light.
The layer 113R and the layer 113G may each 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, the layer 113R and the layer 113G may each 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 layer 113R and the layer 113G may each 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.
Thus, the layer 113R and the layer 113G each preferably include a light-emitting layer and a carrier-transport layer (an electron-transport layer or a hole-transport layer) over the light-emitting layer. Alternatively, the layer 113R and the layer 113G 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 layer 113R and the layer 113G 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 layer 113R and the layer 113G are exposed in the manufacturing process of the display device, 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 layer 113B includes a plurality of light-emitting units and a charge-generation layer. Each of the light-emitting units includes at least one light-emitting layer. Here, as described above, the light-emitting device 130B preferably emits light having at least one emission spectrum peak in a blue (B) wavelength range (greater than or equal to 400 nm and less than 490 nm). Thus, at least one of the plurality of the light-emitting layers included in the layer 113B preferably emits light having at least one emission spectrum peak in the blue (B) wavelength range. Note that one or more of the plurality of the light-emitting layers included in the layer 113B may emit light having no emission spectrum peak in the blue (B) wavelength range. That is, a structure in which light emitted from the plurality of the light-emitting layers included in the layer 113B overlaps with each other to form blue (B) light may be employed. Here, at least one of the plurality of the light-emitting layers included in the layer 113B preferably includes a light-emitting material that emits blue light.
Each of the light-emitting units may also 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. The charge-generation layer is preferably provided between the light-emitting units.
For example, the layer 113B illustrated in
Here, a light-emitting layer of the light-emitting unit 113B1 and a light-emitting layer of the light-emitting unit 113B3 may be formed using the same light-emitting material or different light-emitting materials. In the case where different light-emitting materials are used, the light-emitting materials for the light-emitting units are selected such that light emitted from the light-emitting layer of the light-emitting unit 113B1 and light emitted from the light-emitting layer of the light-emitting unit 113B3 overlap with each other to form the blue (B) light. For example, one of the light-emitting layer of the light-emitting unit 113B1 and the light-emitting layer of the light-emitting unit 113B3 can be formed using a light-emitting material that emits blue light, and the other can be formed using a light-emitting material that emits blue-green light.
For example, the light-emitting unit 113B1 may include a hole-injection layer, a hole-transport layer, a light-emitting layer, and an electron-transport layer in this order, and the light-emitting unit 113B3 may include 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. Moreover, 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 of the light-emitting unit 113B3.
For example, the light-emitting unit 113B1 may include an electron-injection layer, an electron-transport layer, a light-emitting layer, and a hole-transport layer in this order, and the light-emitting unit 113B3 may include an electron-transport layer, a light-emitting layer, and a hole-transport layer in this order. In addition, a hole-blocking layer may be provided between the electron-transport layer and the light-emitting layer. Moreover, 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 of the light-emitting unit 113B3. In that case, the charge-generation layer 113B2 is preferably provided as appropriate.
The light-emitting unit 113B3 preferably includes a light-emitting layer and a carrier-transport layer (an electron-transport layer or a hole-transport layer) that is over the light-emitting layer. Alternatively, the light-emitting unit 113B3 preferably includes a light-emitting layer and a carrier-blocking layer (a hole-blocking layer or an electron-blocking layer) that is over the light-emitting layer. Further alternatively, the light-emitting unit 113B3 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 light-emitting unit 113B3 is exposed in the manufacturing process of the display device, providing one or both of the carrier-transport layer and the carrier-blocking layer over each 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.
Furthermore, as illustrated in
Here, the layer 113G includes a plurality of light-emitting units and a charge-generation layer. Each of the light-emitting units includes at least one light-emitting layer. Here, as described above, the light-emitting device 130G preferably emits light having at least one emission spectrum peak in a green (G) wavelength range (greater than or equal to 490 nm and less than 580 nm). Thus, at least one of the plurality of the light-emitting layers included in the layer 113G preferably emits light having at least one emission spectrum peak in the green (G) wavelength range. Note that one or more of the plurality of the light-emitting layers included in the layer 113G may emit light with no emission spectrum peak in the green (G) wavelength range. That is, a structure in which light emitted from the plurality of the light-emitting layers included in the layer 113G overlaps with each other to form the green (G) light may be employed. Here, at least one of the plurality of the light-emitting layers included in the layer 113G preferably includes a light-emitting material that emits green light.
Each of the light-emitting units may also 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. The charge-generation layer is preferably provided between the light-emitting units.
For example, the layer 113G illustrated in
Here, a light-emitting layer of the light-emitting unit 113G1 and a light-emitting layer of the light-emitting unit 113G3 may be formed using the same light-emitting material or different light-emitting materials. In the case where different light-emitting materials are used, the light-emitting materials of the light-emitting units are selected such that light emitted from the light-emitting layer of the light-emitting unit 113G1 and light emitted from the light-emitting layer of the light-emitting unit 113G3 overlap with each other to form the green (G) light.
For example, the light-emitting unit 113G1 may include a hole-injection layer, a hole-transport layer, a light-emitting layer, and an electron-transport layer in this order, and the light-emitting unit 113G3 may include 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. Moreover, 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 of the light-emitting unit 113G3.
For example, the light-emitting unit 113G1 may include an electron-injection layer, an electron-transport layer, a light-emitting layer, and a hole-transport layer in this order, and the light-emitting unit 113G3 may include an electron-transport layer, a light-emitting layer, and a hole-transport layer in this order. In addition, a hole-blocking layer may be provided between the electron-transport layer and the light-emitting layer. Moreover, 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 of the light-emitting unit 113G3. In that case, the charge-generation layer 113G2 is preferably provided as appropriate.
The light-emitting unit 113G3 preferably includes a light-emitting layer and a carrier-transport layer (an electron-transport layer or a hole-transport layer) that is over the light-emitting layer. Alternatively, the light-emitting unit 113G3 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. Further alternatively, the light-emitting unit 113B3 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 light-emitting unit 113G3 is exposed in the manufacturing process of the display device, providing one or both of the carrier-transport layer and the carrier-blocking layer over each 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.
As described above, the light-emitting device 130G and the light-emitting device 130B employs a tandem structure for improved reliability of the light-emitting device 130G and the light-emitting device 130B and the display device. Furthermore, the light-emitting device 130R employs a single structure for a simplified manufacturing process, so that the yield in the manufacturing process of the display device can be increased.
The upper temperature limits of the compounds contained in the layer 113R, the layer 113G, and the layer 113B are each 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. Note that in the present invention, the upper temperature limits of the compounds contained in the layer 113R, the layer 113G, and the layer 113B are not limited to the above ranges. It is also possible to use the layer 113R, the layer 113G, and the layer 113B that contain compounds whose upper temperature limits are lower than or equal to 100° C. in accordance with the design of the light-emitting devices.
In particular, the upper temperature limits of the functional layers provided over the light-emitting layer are 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 damage to the light-emitting layer can be reduced.
In addition, 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 material, 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 light-emitting layer contains more organic compound than light-emitting substance, Tg of the organic compound can be used as an indicator of the upper temperature limit of the light-emitting layer.
As illustrated in
Furthermore, as described above, when the end portion of the layer 113R is positioned outside the end portion of the pixel electrode 111R, a distance between the light-emitting region of the EL layer (i.e., a region overlapping with the pixel electrode) and the end portion of the EL layer can be increased. Accordingly, variations in characteristics of the light-emitting device can be inhibited, and the reliability of the light-emitting device can be suppressed.
Note that although the pixel electrode 111R and the layer 113R are described above, the same applies to the pixel electrode 111G and the layer 113G and the pixel electrode 111B and the layer 113B.
The common layer 114 provided over the layer 113R, the layer 113G, and the layer 113B includes an electron-injection layer or a hole-injection layer, for example. 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 130R, 130G, and 130B.
The common electrode 115 over the common layer 114 is shared by the light-emitting devices 130R, 130G, and 130B. 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
Alternatively, as illustrated in
As illustrated in
As the insulating layer 136, an inorganic insulating film or an organic insulating film can be used. In the case where an inorganic insulating film is used as the insulating layer 136, an inorganic insulating film that is usable for the insulating layer 125 described later may be used. In the case where an organic insulating film is used as the insulating layer 136, an organic insulating film that is usable for the insulating layer 127 described later may be used.
Although
In that case, the insulating layer 136 is preferably provided so as not to be in contact with the pixel electrode 111R and the pixel electrode 111G. This makes it possible to provide the insulating layer 136 without a reduction in the aperture ratio of the light-emitting devices 130R and 130G.
Also in the case where the light-emitting device 130G and the light-emitting device 130B have a tandem structure as illustrated in
Also in the case where the light-emitting device 130G and the light-emitting device 130B have a tandem structure as illustrated in
In that case, the insulating layer 136 is preferably provided so as not to be in contact with the pixel electrode 111R. This makes it possible to provide the insulating layer 136 without a reduction in the aperture ratio of the light-emitting device 130R.
In
In
In the case where end portions are aligned or substantially aligned with each other and the case where top surface shapes are the same or substantially the same, it can be said that outlines of stacked layers at least partly overlap with each other in a top view. 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 inward from the lower layer or the upper layer is positioned outward from the lower layer; such a case is also represented by the expression “end portions are substantially aligned with each other” or “top surface shapes are substantially the same”.
The side surfaces of the layer 113R, the layer 113G, and the layer 113B are each covered with the insulating layer 125. The insulating layer 127 overlaps with the side surfaces of the layer 113R, the layer 113G, and the layer 113B with the insulating layer 125 therebetween. In other words, the insulating layer 125 and the insulating layer 127 are provided so as to be interposed between two selected from a side end portion of the layer 113R, a side end portion of the layer 113G, and a side end portion of the layer 113B.
The top surfaces of the layer 113R, the layer 113G, and the layer 113B are each partly covered with the sacrificial layer 118. The insulating layer 125 and the insulating layer 127 overlap with part of the top surfaces of the layer 113R, the layer 113G, and the layer 113B with the sacrificial layers 118 therebetween. Note that the top surface of each of the layer 113R, the layer 113G, and the layer 113B is not limited to the top surface of a flat portion overlapping with the top surface of the pixel electrode, and can include the top surfaces of the inclined portion and the flat portion which are positioned outside the top surface of the pixel electrode.
When the side surface and part of the top surface of each of the layer 113R, the layer 113G, and the layer 113B are covered with at least one of the insulating layer 125, the insulating layer 127, and the sacrificial layer 118, the common layer 114 (or the common electrode 115) can be inhibited from being in contact with the side surfaces of the pixel electrodes 111R, 111G, and 111B and the layers 113R, 113G, and 113B and thus inhibit a short circuit of the light-emitting device. In particular, since the charge-generation layer 113B2 of the layer 113B is a layer having relatively high conductivity, the side surface of the charge-generation layer 113B2 is preferably covered with at least one of the insulating layer 125, the insulating layer 127, and the sacrificial layer 118. Using the structure described above can increase the reliability of the light-emitting device.
Although
The insulating layer 125 is preferably in contact with the side surfaces of the layer 113R, the layer 113G, and the layer 113B. When the insulating layer 125 is configured to be in contact with the layer 113R, the layer 113G, and the layer 113B, film separation of the layer 113R, the layer 113G, and the layer 113B can be prevented. When the insulating layer 125 is in close contact with the layer 113B, the layer 113G, or the layer 113R, the effect of fixing or bonding the adjacent layer 113B and the like by the insulating layer 125 is obtained. Thus, the reliability of the light-emitting device can be increased. The manufacturing yield of the light-emitting device can be increased.
As illustrated in
In the example illustrated in
In
The insulating layer 127 is provided over the insulating layer 125 to fill a depressed portion of the insulating layer 125. The insulating layer 127 can be configured to overlap with the side surface and part of the top surface of each of the layer 113R, the layer 113G, and the layer 113B with the insulating layer 125 therebetween. The insulating layer 127 preferably covers at least part of a side surface of the insulating layer 125.
The insulating layer 125 and the insulating layer 127 can fill a space between adjacent island-shaped layers, whereby unevenness with a large level difference 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. Consequently, the coverage with the carrier-injection layer, the common electrode, and the like can be increased.
The common layer 114 and the common electrode 115 are provided over the layer 113R, the layer 113G, the layer 113B, the sacrificial 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 level difference due to a region where the pixel electrode and the island-shaped EL layer are provided and a region where the pixel electrode and the island-shaped EL layer are not provided (a region between the light-emitting devices) is caused. In the display device of one embodiment of the present invention, the level difference can be planarized with 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 step disconnection. Alternatively, an increase in electrical resistance caused by local thinning of the common electrode 115 due to level difference can be inhibited.
The top surface of the insulating layer 127 preferably has a shape with higher flatness; however, it may include a projecting portion, a convex surface, a concave surface, or a depressed portion. For example, the top surface of the insulating layer 127 preferably has a smooth convex shape with high flatness.
Next, examples of materials of the insulating layer 125 and the insulating layer 127 are 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 either 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. In particular, when an inorganic insulating film such as an aluminum oxide film, a hafnium oxide film, or a silicon oxide film that is formed by an atomic layer deposition (ALD) method is used as the insulating layer 125, it is possible to form the insulating layer 125 that has 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. Alternatively, the insulating layer 125 preferably has a function of inhibiting diffusion of at least one of water and oxygen. Alternatively, the insulating layer 125 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 125 has a function of a barrier insulating layer or a gettering function, entry of impurities (typically, at least one of water and oxygen) that might diffuse into the light-emitting devices from the outside can be inhibited. With this structure, a highly reliable light-emitting device and a highly reliable display device can be provided.
The insulating layer 125 preferably has a low impurity concentration. In this case, deterioration of the EL layer due to entry of impurities from the insulating layer 125 into the EL layer 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.
Note that for the insulating layer 125 and the sacrificial layers 118B, 118G, and 118R, the same material can be used. In this case, the boundary between the insulating layer 125 and any of the sacrificial layers 118B, 118G, and 118R is unclear and thus the layers cannot be distinguished from each other in some cases. Thus, the insulating layer 125 and any of the sacrificial layers 118B, 118G, and 118R are sometimes observed as one layer. In other words, in some cases, one layer is observed as being provided in contact with the side surface and part of the top surface of each of the layer 113R, the layer 113G, and the layer 113B and the insulating layer 127 is observed as covering at least part of the side surface of the one layer.
The insulating layer 127 provided over the insulating layer 125 has a planarization function for unevenness with a large level difference on the insulating layer 125 formed between adjacent light-emitting devices. In other words, the insulating layer 127 has an effect of improving the planarity of the 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, and for example, a photosensitive resin composite containing an acrylic resin is preferably used. 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.
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 may be used, for example. Alternatively, for the insulating layer 127, it is possible to use an organic material such as polyvinyl alcohol (PVA), polyvinyl butyral, polyvinylpyrrolidone, polyethylene glycol, polyglycerin, pullulan, water-soluble cellulose, or an alcohol-soluble polyamide resin. A photoresist may be used as the photosensitive resin. As the photosensitive organic resin, either a positive material or a negative material may be used.
The insulating layer 127 may be formed using a material absorbing visible light. When the insulating layer 127 absorbs light from the light-emitting device, leakage of light (stray light) from the light-emitting device to the adjacent light-emitting device through the insulating layer 127 can be inhibited. Thus, the display quality of the display device can be improved. Since the display quality of the display device can be improved without using a polarizing plate in the display device, the weight and thickness of the display device can be reduced.
Examples of the material absorbing visible light include a material containing a pigment of black or the like, a material containing a dye, a resin material with a light-absorbing property (e.g., polyimide), and a resin material that can be used for a color filter (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 preferable to enhance the effect of blocking visible light. In particular, mixing color filter materials of three or more colors makes it possible to form a black or nearly black resin layer.
Next, a structure of the insulating layer 127 and the vicinity thereof will be described with reference to
As illustrated in
The insulating layer 127 is formed in a region between two island-shaped EL layers (e.g., a region between the layer 113R and the layer 113G in
As illustrated in
The taper angle θ1 of the insulating layer 127 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°. When the end portion of the insulating layer 127 has such a forward tapered shape, the common layer 114 and the common electrode 115 that are provided over the insulating layer 127 can be formed with favorable coverage, thereby inhibiting step disconnection, local thinning, or the like. Consequently, the in-plane uniformity of the common layer 114 and the common electrode 115 can be increased, so that the display quality of the display device can be improved.
As illustrated in
As illustrated in
As illustrated in
The taper angle θ2 of the insulating layer 125 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°.
As illustrated in
The taper angle θ3 of the sacrificial layer 118G 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°. When the sacrificial layer 118G has such a forward tapered shape, the common layer 114 and the common electrode 115 that are provided over the sacrificial layer 118G can be formed with favorable coverage.
The end portion of the sacrificial layer 118B and the end portion of the sacrificial layer 118G are each preferably positioned outward from the end portion of the insulating layer 125. In that case, unevenness of the surface where the common layer 114 and the common electrode 115 are formed is reduced, and coverage with the common layer 114 and the common electrode 115 can be improved.
Although the details will be described in Embodiment 4, when the insulating layer 125 and the sacrificial layer 118 are collectively etched, the insulating layer 125 and the sacrificial layer 118 below the end portion of the insulating layer 127 are eliminated by side etching and accordingly a cavity is formed in some cases. The cavity causes unevenness in the formation surface of the common layer 114 and the common electrode 115, so that step disconnection is likely to occur in the common layer 114 and the common electrode 115. Thus, the etching treatment is performed in two separate steps with heat treatment performed between the two etching steps, whereby even when a cavity is formed by the first etching treatment, the cavity can be filled with the insulating layer 127 deformed by the heat treatment. Since the second etching treatment is for etching a thinner film, the amount of side etching decreases, a void is less likely to be formed, and even if a void is formed, it can be extremely small. Thus, generation of unevenness in the formation surface of the common layer 114 and the common electrode 115 can be inhibited, and accordingly step disconnection of the common layer 114 and the common electrode 115 can be inhibited. Since the etching treatment is performed twice in this manner, the taper angle θ2 and the taper angle θ3 are different from each other in some cases. The taper angle θ2 and the taper angle θ3 may be the same. Furthermore, the taper angle θ2 and the taper angle θ3 may each be smaller than the taper angle θ1.
The insulating layer 127 may cover at least part of the side surface of the sacrificial layer 118R and at least part of the side surface of the sacrificial layer 118G. For example,
Also in
As illustrated in
Note that the insulating layer 127 does not necessarily overlap with the top surface of the pixel electrode. As illustrated in
As illustrated in
As illustrated in
To form a structure in which the insulating layer 127 includes a concave surface in its center portion as illustrated in
Note that a method for forming a concave surface in the center portion of the insulating layer 127 is not limited to the above method. For example, an exposed portion and a half-exposed portion may be formed separately with the use of two photomasks. Alternatively, the viscosity of the resin material used for the insulating layer 127 may be adjusted; specifically, the viscosity of the material used for the insulating layer 127 may be less than or equal to 10 cP, preferably greater than or equal to 1 cP and less than or equal to 5 cP.
Although not illustrated, the concave surface in the center portion of the insulating layer 127 is not necessarily continuous, and may be disconnected between adjacent light-emitting devices. In this case, part of the insulating layer 127 in the center portion of the insulating layer 127 illustrated in
As described above, in each of the structures illustrated in
The protective layer 131 is preferably provided over the light-emitting devices 130R, 130G, and 130B. 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 preventing 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 device 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. Specific examples of these inorganic insulating films are as listed in the description of the insulating layer 125. 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 (ITO), In—Zn oxide, Ga—Zn oxide, Al—Zn oxide, In—Ga—Zn oxide (indium gallium zinc oxide or 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 inorganic materials having a high visible-light-transmitting property.
The protective layer 131 can employ, 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 layer. 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 that can be used for the insulating layer 127.
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.
A light-blocking layer may be provided on a surface of the substrate 120 on the resin layer 122 side. Moreover, a variety of optical members can be provided 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 inhibiting 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 (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 a 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 that transmits the light. When a flexible material is used for the substrate 120, the flexibility of the display device can be increased and a flexible display can be provided. Furthermore, a polarizing plate may be used as the substrate 120.
For the substrate 120, it is possible to use 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, cellulose nanofiber, and the like. Glass that is thin enough to have flexibility may be used as the substrate 120.
In the case where a circularly polarizing plate overlaps with the display device, a highly optically isotropic substrate is preferably used as the substrate included in the display device. 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 films 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.
When a film is used for the substrate and the film absorbs water, the shape of the display device 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, a film with a water absorption rate lower than or equal to 1% is preferably used, a film with a water absorption rate lower than or equal to 0.1% is further preferably used, and a film with a water absorption rate lower than or equal to 0.01% is still further preferably used.
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
Although
The lens array 133 may include a convex surface facing the substrate 120 side or a convex surface facing the light-emitting device side.
The lens array 133 can be formed using at least one of an inorganic material and an organic material. For example, a material containing a resin can be used for the lens. Moreover, a material containing at least one of an oxide and a sulfide can be used for the lens. As the lens array 133, a microlens array can be used, for example. The lens array 133 may be directly formed over the substrate or the light-emitting device; alternatively, a lens array separately formed may be bonded thereto.
As illustrated in
Providing the coloring layer so as to overlap with the light-emitting device is preferable because external light reflection can be greatly reduced. When the light-emitting device has a microcavity structure, external light reflection can be further reduced. As described above, when one, preferably both of the coloring layer and the microcavity structure are employed, external light reflection can be sufficiently reduced even without using an optical member such as a circular polarizing plate for the display device. When a circular polarizing plate is not used for the display device, decay of light emission from the light-emitting device can be inhibited and thus the outcoupling efficiency of the light-emitting device can be increased. Thus, the power consumption of the display device can be reduced.
Coloring layers of different colors preferably include a region where they overlap with each other. The region where the coloring layers of different colors overlap with each other can function as a light-blocking layer. This can further reduce reflection of external light.
As illustrated in
As illustrated in
For the insulating layer 134, one or both of an inorganic insulating film and an organic insulating film can be used. The insulating layer 134 may have either a single-layer structure or a stacked-layer structure. For the insulating layer 134, a material that can be used for the protective layer 131 can be used, for example. Light emitted from the light-emitting device is extracted through the insulating layer 134, so that the insulating layer 134 preferably has a high visible-light-transmitting property.
In
In the example of
In
Unlike in
Although
The subpixels 11R, 11G, 11B, and 11S can be configured to include light-emitting devices emitting light of different colors. The subpixels 11R, 11G, 11B, and 11S are subpixels of four colors of R, G, B, and W, subpixels of four colors of R, G, B, and Y, or subpixels of four types of R, G, B, and IR, for example.
The display device 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, a pn-type or pin-type photodiode can be used as the light-receiving device. 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 charge. The amount of charge generated from the light-receiving device depends on the amount of light entering the light-receiving device.
The light-receiving device can detect one or both of visible light and infrared light. In the case of detecting visible light, for example, one or more of blue light, violet light, bluish violet light, green light, yellowish green light, yellow light, orange light, red light, and the like can be detected. Infrared light is preferably detected because an object can be detected even in a dark place.
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 employed in a variety of display devices.
In one embodiment of the present invention, an organic EL device is used as the light-emitting device, and an organic photodiode is used as the light-receiving device. The organic EL device and the organic photodiode can be formed over the same substrate. Thus, the organic photodiode can be incorporated in the display device using the organic EL device.
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.
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 sacrificial layer provided over the active layer can reduce damage to the active layer in the manufacturing process of the display device, increasing the reliability of the light-receiving device.
Embodiment 3 can be referred to for the structure and materials of the light-receiving device.
As illustrated in
The structures of the light-emitting devices 130R and 130B are as described above.
The light-receiving device 150 includes a pixel electrode 111S over the insulating layer 255c, a layer 113S over the pixel electrode 111S, the common layer 114 over the layer 113S, and the common electrode 115 over the common layer 114. The layer 113S includes at least an active layer.
Here, the layer 113S includes at least an active layer, preferably includes a plurality of functional layers. Examples of the functional layer 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). In addition, one or more layers are preferably provided over the active layer. A layer between the active layer and the sacrificial layer can inhibit the active layer from being exposed on the outermost surface during the manufacturing process of the display device and can reduce damage to the active layer. Accordingly, the reliability of the light-receiving device 150 can be improved. Thus, the layer 113S 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 layer 113S is a layer that is provided in the light-receiving device 150 and is not in the light-emitting devices. Note that the functional layer other than the active layer included in the layer 113S may include the same material as the functional layer other than the light-emitting layer included in each of the layers 113R, 113G, and 113B. Meanwhile, the common layer 114 is a continuous layer shared by the light-emitting devices and the light-receiving device.
Here, a layer used in common to 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. In addition, a layer shared by the light-receiving device and the light-emitting device might have the same function in the light-emitting device and the light-receiving device. For example, 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.
Like the layer 113R and the like, it is preferable that the layer 113S be provided to cover the pixel electrode 111S and be in contact with the insulating layer 255c around the pixel electrode 111S.
The sacrificial layer 118R is positioned between the layer 113R and the insulating layer 125, and a sacrificial layer 118S is positioned between the layer 113S and the insulating layer 125. The sacrificial layer 118R is a remaining portion of the sacrificial layer provided over the layer 113R when the layer 113R is processed. The sacrificial layer 118S is a remaining portion of a sacrificial layer provided in contact with the top surface of the layer 113S at the time of processing the layer 113S, which is a layer including the active layer. The sacrificial layer 118B and the sacrificial layer 118S may include the same material or different materials.
Although
The subpixel 11S may have a higher aperture ratio than at least one of the subpixels 11R, 11G, and 11B. The wide light-receiving area of the subpixel 11S can make it easy to detect an object in some cases. For example, in some cases, the aperture ratio of the subpixel 11S is higher than the aperture ratio of each of the other subpixels depending on the resolution of the display device and the circuit structure or the like of the subpixel.
The subpixel 11S may have a lower aperture ratio than at least one of the subpixels 11R, 11G, and 11B. A small light-receiving area of the subpixel 11S leads to a narrow image-capturing range, inhibits a blur in a capturing result, and improves the definition. Accordingly, high-resolution or high-definition image capturing can be performed, which is preferable.
As described above, the subpixel 11S can have a detection wavelength, resolution, and an aperture ratio that are suitable for the intended use.
In the display device of one embodiment of the present invention, each light-emitting device includes an island-shaped EL layer, which can inhibit generation of leakage current between the subpixels. Thus, it is possible to prevent crosstalk due to unintended light emission, so that a display device with extremely high contrast can be achieved.
In the display device of one embodiment of the present invention, a tandem structure is employed at least for a light-emitting device that emits blue light. With such a structure, the reliability of a blue-light-emitting device whose luminance or the like easily deteriorates can be improved. Moreover, when the reliability of the blue-light-emitting device is improved, the reliability of the display device can be improved. Furthermore, a red-light-emitting device employs a single structure for a simplified manufacturing process, so that the yield in the manufacturing process of the display device can be increased.
When the insulating layer having a tapered end portion is provided between adjacent island-shaped EL layers, it is possible to inhibit generation of step disconnection and formation of a locally thinned portion in the common electrode at the time of forming the common electrode. Thus, a connection defect due to a disconnected portion and an increase in electrical resistance due to a locally thinned portion can be inhibited from being caused in the common layer and the common electrode. Consequently, the display device of one embodiment of the present invention achieves both high resolution and high display quality.
This embodiment can be combined with the other embodiments as appropriate. In this specification, in the case where a plurality of structure examples are described in one embodiment, the structure examples can be combined as appropriate.
In this embodiment, a structure example of a light-emitting device that can be used in a display device of one embodiment of the present invention is described.
The light-emitting device 550R has a structure in which one light-emitting unit 512R_1 is provided between a pair of electrodes (an electrode 501 and an electrode 502). Similarly, the light-emitting device 550G has a structure in which one light-emitting unit 512G_1 is provided. The light-emitting device 550B has a structure in which a light-emitting unit 512B_1, a charge-generation layer 531, and a light-emitting unit 512B_2 are provided between a pair of electrodes. That is, in the display device 500, the light-emitting device 550R and the light-emitting device 550G each have a single structure, and the light-emitting device 550B has a tandem structure as in the display device 100 and the like illustrated in
The electrode 501 functions as a pixel electrode and is provided in every light-emitting device. The electrode 502 functions as a common electrode and is shared by a plurality of light-emitting devices.
As illustrated in
The light-emitting device 550B includes a layer 525 between the light-emitting unit 512B_2 and the electrode 502. The light-emitting device 550R includes the layer 525 between the light-emitting unit 512R_1 and the electrode 502. The light-emitting device 550G includes the layer 525 between the light-emitting unit 512G_1 and the electrode 502. In this manner, the layer 525 can be shared by a plurality of light-emitting devices like the electrode 502. In this case, the layer 525 can be referred to as a common layer. By providing one or more common layers for a plurality of light-emitting devices in this manner, the manufacturing process can be simplified, resulting in a reduction in manufacturing cost.
Note that without limitation to the above, the layer 525 may be provided for each of the light-emitting devices 550R, 550G, and 550B. In that case, the layer 525 can be regarded as part of the light-emitting unit 512B_2, the light-emitting unit 512R_1, and the light-emitting unit 512G_1.
In the case where the electrode 501 functions as an anode and the electrode 502 functions as a cathode, the layer 521 includes, for example, a layer containing a substance with a high hole-injection property (a hole-injection layer). The layer 522 includes, for example, one or both of a layer containing a substance with a high hole-transport property (a hole-transport layer) and a layer containing a substance with a high electron-blocking property (an electron-blocking layer). The layer 524 includes, for example, one or both of a layer containing a substance with a high electron-transport property (an electron-transport layer) and a layer containing a substance with a high hole-blocking property (a hole-blocking layer). The layer 525 includes, for example, a layer containing a substance with a high electron-injection property (an electron-injection layer).
In the case where the electrode 501 functions as an anode, the electrode 501 is electrically connected to a wiring to which an anode potential is supplied (hereinafter referred to as an anode wiring). Here, the same anode wiring may be electrically connected to the electrodes 501 of the light-emitting devices 550R, 550G, and 550B. Alternatively, the electrodes 501 of the light-emitting devices 550R and 550G each having a single structure may be electrically connected to an anode wiring which is in a wiring system different from that for the wiring to which the electrode 501 of the light-emitting device 550B having a tandem structure is electrically connected.
In the case where the electrode 501 functions as a cathode and the electrode 502 functions as an anode, for example, the layer 521 includes an electron-injection layer, the layer 522 includes one or both of an electron-transport layer and a hole-blocking layer, the layer 524 includes one or both of a hole-transport layer and an electron-blocking layer, and the layer 525 includes a hole-injection layer.
Note that the light-emitting unit 512B_1 and the light-emitting unit 512B_2 may be the same or different in the structure (material, thickness, or the like) of the layer 522, the light-emitting layer 523B, and the layer 524. For example, a light-emitting material that emits blue light may be used for the light-emitting layer 523B of the light-emitting unit 512B_1, and a light-emitting material that emits blue-green light may be used for the light-emitting layer 523B of the light-emitting unit 512B_2.
In the case of manufacturing a light-emitting device having a tandem structure, two light-emitting units are stacked with the charge-generation layer 531 therebetween. The charge-generation layer 531 includes at least a charge-generation region. The charge-generation layer 531 has a function of injecting electrons into one of the light-emitting unit 512B_1 and the light-emitting unit 512B_2 and injecting holes into the other when voltage is applied between the electrode 501 and the electrode 502.
The light-emitting layer 523R included in the light-emitting device 550R contains a light-emitting substance (also referred to as a light-emitting material) that emits red light, a light-emitting layer 523G included in the light-emitting device 550G contains a light-emitting substance that emits green light, and a light-emitting layer 523B included in the light-emitting device 550B contains a light-emitting substance that emits blue light. Note that the light-emitting device 550R and the light-emitting device 550G have a structure in which the light-emitting unit 512B_1 included in the light-emitting device 550B is replaced with the light-emitting layer 523R and the light-emitting layer 523G, respectively, and the other components are similar to those of the light-emitting device 550B.
Note that the structure (material, thickness, and the like) of each of the layer 521, the layer 522, the layer 524, and the layer 525 may be the same between the light-emitting devices of two or more colors or among the light-emitting devices of all colors, or different from one another among the light-emitting devices of all colors.
A structure in which a plurality of light-emitting units are connected in series through the charge-generation layer 531 as in the light-emitting device 550B is referred to as a tandem structure in this specification. In contrast, a structure in which one light-emitting unit is provided between a pair of electrodes as in the light-emitting device 550R and the light-emitting device 550G is referred to as a single structure. Note that the tandem structure may be referred to as a stack structure. The tandem structure enables a light-emitting device capable of high-luminance light emission. Furthermore, a tandem structure allows the amount of current needed for obtaining the same luminance to be reduced as compared to the case of using a single structure; thus, the light-emitting device can have higher reliability.
In the display device of one embodiment of the present invention, a tandem structure is employed at least for the light-emitting device 550B that emits blue light. With such a structure, the reliability of a blue-light-emitting device whose luminance or the like easily deteriorates can be improved. Moreover, when the reliability of the blue-light-emitting device 550B is improved, the reliability of the display device can be improved. Furthermore, the red-light-emitting device 550R employs a single structure for a simplified manufacturing process, so that the yield in the manufacturing process of the display device can be increased.
The light-emitting device 550R, the light-emitting device 550G, and the light-emitting device 550B have an SBS structure in which at least light-emitting layers are separately formed for light-emitting devices. 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.
The display device 500 of one embodiment of the present invention employs a light-emitting device with a tandem structure and has the SBS structure. Thus, the display device can have both the advantage of a tandem structure and the advantage of an SBS structure. In the light-emitting device 550B included in the display device 500 illustrated in
Furthermore, as illustrated in
The display device 500 illustrated in
When the number of stacked light-emitting units is increased in the above manner, luminance obtained from the light-emitting device with the same amount of current can be increased in accordance with the number of stacked layers. Moreover, increasing the number of stacked light-emitting units can reduce the amount of current needed for obtaining the same luminance; thus, power consumption of the light-emitting device can be reduced in accordance with the number of stacked layers.
Next, materials that can be used for the light-emitting device will be described.
A conductive film that transmits visible light is used as the electrode through which light is extracted, which is either the electrode 501 or the electrode 502. 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 device includes a light-emitting device emitting infrared light, a conductive film that transmits visible light and infrared light is preferably used as the electrode through which light is extracted, and a conductive film that reflects visible light and infrared light is preferably used as the electrode through which light is not extracted.
A conductive film that transmits visible light may be used as an electrode through which light is not extracted. In that case, the electrode is preferably provided between a reflective layer and the light-emitting unit that is the closest to the reflective layer. In other words, light emitted from the light-emitting device may be reflected by the reflective layer to be extracted from the display device.
As a material that forms the pair of electrodes of the light-emitting device, a metal, an alloy, an electrically conductive compound, a mixture thereof, and the like can be used as appropriate. Specific examples of the material include metals such as aluminum, magnesium, titanium, chromium, manganese, iron, cobalt, nickel, copper, gallium, zinc, indium, tin, molybdenum, tantalum, tungsten, palladium, gold, platinum, silver, yttrium, and neodymium, and an alloy containing any of these metals in appropriate combination. Other examples of the material include In—Sn oxide (indium tin oxide or ITO), In—Si—Sn oxide (ITSO), In—Zn oxide (indium zinc oxide), and In—W—Zn oxide. Other examples of the material include an alloy containing aluminum (aluminum alloy), such as an alloy of aluminum, nickel, and lanthanum (Al—Ni—La), and an alloy containing silver, such as an alloy of silver and magnesium and an alloy of silver, palladium, and copper (APC). Other examples of the material include an element that belongs to Group 1 or Group 2 of the periodic table, which is not described above (e.g., lithium, cesium, calcium, or strontium), a rare earth metal such as europium or ytterbium, an alloy containing an appropriate combination of these elements, and graphene. The metal, the alloy, the electrically conductive compound, the mixture thereof, and the like described above may be stacked as appropriate to form the pair of electrodes (the pixel electrode and the common electrode) of the light-emitting device.
For example, in the case where the electrode 501 is used as a pixel electrode, a stacked conductive film in which a titanium film, an aluminum film, a titanium film, and an ITO film are stacked in this order may be used as the electrode 501. Alternatively, a stacked conductive film in which an APC film and an ITO film are stacked may be used as the electrode 501. For example, in the case where the electrode 502 is used as the common electrode, a stacked conductive film in which an alloy film of magnesium and aluminum and an ITO film are stacked in this order may be used. Note that in the above, an ITSO film may be used instead of the ITO film.
The light-emitting devices preferably employ a microcavity structure. Thus, one of the pair of electrodes included in the light-emitting device is preferably an electrode having properties of transmitting and reflecting visible light (a transflective electrode), and the other is preferably an electrode having a property of reflecting visible light (a reflective electrode). In other words, a transflective electrode is preferably used as the electrode through which light is extracted, which is either the electrode 501 or the electrode 502, and a reflective electrode is preferably used as the electrode through which light is not extracted. 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.
A conductive film that transmits visible light may be provided on the light-emitting layer side of the transflective electrode or on the light-emitting layer side of the reflective electrode. Here, the conductive film that transmits visible light functions as an optical adjustment layer. In that case, the conductive film that transmits visible light can also have a function of a pixel electrode or a common electrode.
The light transmittance of the transparent electrode is higher than or equal to 40%. For example, an electrode having a visible light (light with wavelengths greater than or equal to 400 nm and less than 750 nm) transmittance higher than or equal to 40% is preferably used as the transparent electrode of the light-emitting device. The transflective electrode has a visible light reflectance 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 reflective electrode has a visible light reflectance 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 less than or equal to 1×10−2 Ωcm.
The light-emitting device includes at least the light-emitting layer. The light-emitting device may further include, as a layer other than the light-emitting layer, a layer containing 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, an electron-blocking material, a substance with a high electron-injection property, a substance with a bipolar property (a substance with a high electron-transport property and a high hole-transport property), or the like. For example, the light-emitting device can 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 in addition to the light-emitting layer.
Either a low molecular compound or a high molecular compound can be used in the light-emitting device, and an inorganic compound may also be included. Each layer included in the light-emitting device can be formed by any of the following methods: an evaporation method (including a vacuum evaporation method), a transfer method, a printing method, an inkjet method, a coating method, and the like.
The light-emitting layer contains one or more kinds of light-emitting substances. As the light-emitting substance, a substance that exhibits an emission color of blue, violet, bluish violet, green, yellowish green, yellow, orange, red, or the like is used as appropriate. Alternatively, a substance that emits near-infrared light can be used as the light-emitting substance.
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 (a guest material). As one or more kinds of organic compounds, one or both of a substance with a high hole-transport property (a hole-transport material) and a substance with a high electron-transport property (an electron-transport material) can be used. As the hole-transport material, it is possible to use a material with a high hole-transport property that can be used for the hole-transport layer and will be described later. As the electron-transport material, it is possible to use a material with a high electron-transport property that can be used for the electron-transport layer and will be described later. 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 to form an exciplex that exhibits light emission whose wavelength overlaps with the wavelength of the 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, the high efficiency, low-voltage driving, and long lifetime of the light-emitting device can be achieved at the same time.
The hole-injection layer is a layer injecting holes from an anode to a hole-transport layer and 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).
As the hole-transport material, it is possible to use a material with a high hole-transport property that can be used for the hole-transport layer and will be described later.
As the acceptor material, an oxide of a metal belonging to any of Group 4 to Group 8 of the periodic table can be used, for example. Specific examples include molybdenum oxide, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, tungsten oxide, manganese oxide, and rhenium oxide. Among these, molybdenum oxide is especially preferable because it is stable in the air, has a low hygroscopic property, and is easy to handle. An organic acceptor material containing fluorine can be used. Alternatively, an organic acceptor material such as a quinodimethane derivative, a chloranil derivative, or a hexaazatriphenylene derivative can be used.
As the material with a high hole-injection property, a material that contains a hole-transport material and the above-described oxide of a metal belonging to Group 4 to Group 8 of the periodic table (typically, molybdenum oxide) may be used, for example.
The hole-transport layer transports holes injected from the anode by the hole-injection layer, to the light-emitting layer. The hole-transport layer is a layer containing a hole-transport material. The hole-transport material preferably has a hole mobility of higher than or equal to 1×10−6 cm2/Vs. Note that other substances can be also used as long as the substances have a hole-transport property higher than an electron-transport property. As the hole-transport material, a material with a high hole-transport property, such as a π-electron rich heteroaromatic compound (e.g., a carbazole derivative, a thiophene derivative, or a furan derivative) or an aromatic amine (a compound having an aromatic amine skeleton), is 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, to the light-emitting layer. The electron-transport layer is a layer containing an electron-transport material. The electron-transport material preferably has an electron mobility of higher than or equal to 1×10−6 cm2/Vs. Note that other substances can be also used as long as the substances have an electron-transport property higher than a hole-transport property. As the electron-transport material, any of the following materials with a high electron-transport property can be used, for example: 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, and 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.
An electron-injection layer is a layer injecting electrons from a cathode to an electron-transport layer and 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 (electron-donating material) can also be used.
The difference between the lowest unoccupied molecular orbital (LUMO) level of the material with a high electron-injection property and the work function value of the material used for the cathode is preferably small (specifically, smaller than or equal to 0.5 eV).
The electron-injection layer can be formed using, for example, 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. The electron-injection layer may have a stacked-layer structure of two or more layers. The stacked-layer structure can be, for example, a structure where lithium fluoride is used for the first layer and ytterbium is used for the second layer.
The electron-injection layer may contain 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 LUMO level of the organic compound having an unshared electron pair is preferably higher than or equal to −3.6 eV and lower 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), 2,2′-(1,3-phenylene)bis(9-phenyl-1,10-phenanthroline) (abbreviation: mPPhen2P), 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 as 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.
As described above, the charge-generation layer includes at least a charge-generation region. The charge-generation region preferably contains an acceptor material, and for example, preferably contains a hole-transport material and an acceptor material which can be used for the above-described hole-injection layer.
The charge-generation layer preferably includes a layer containing a material with a high electron-injection property. The layer can also be referred to as an electron-injection buffer layer. The electron-injection buffer layer is preferably provided between the charge-generation region and the electron-transport layer. Providing the electron-injection buffer layer can lower an injection barrier between the charge-generation region and the electron-transport layer; thus, electrons generated in the charge-generation region can be easily injected into the electron-transport layer.
The electron-injection buffer layer preferably contains an alkali metal or an alkaline earth metal, and for example, can contain an alkali metal compound or an alkaline earth metal compound. Specifically, the electron-injection buffer layer preferably contains an inorganic compound containing an alkali metal and oxygen or an inorganic compound containing an alkaline earth metal and oxygen, further preferably contains an inorganic compound containing lithium and oxygen (lithium oxide (Li2O) or the like). Alternatively, a material that can be used for the electron-injection layer can be suitably used for the electron-injection buffer layer.
The charge-generation layer preferably includes a layer containing a material with a high electron-transport property. The layer can also be referred to as an electron-relay layer. The electron-relay layer is preferably provided between the charge-generation region and the electron-injection buffer layer. In the case where the charge-generation layer does not include an electron-injection buffer layer, the electron-relay layer is preferably provided between the charge-generation region and the electron-transport layer. The electron-relay layer has a function of preventing interaction between the charge-generation region and the electron-injection buffer layer (or the electron-transport layer) and smoothly transferring electrons.
A phthalocyanine-based material such as copper (II) phthalocyanine (abbreviation: CuPc) or a metal complex having a metal-oxygen bond and an aromatic ligand is preferably used for the electron-relay layer.
Note that the charge-generation region, the electron-injection buffer layer, and the electron-relay layer cannot be clearly distinguished from each other on the basis of the cross-sectional shapes, characteristics, or the like in some cases.
Note that the charge-generation layer may contain a donor material instead of an acceptor material. For example, the charge-generation layer may include a layer containing an electron-transport material and a donor material, which can be used for the electron-injection layer.
When two light-emitting units are stacked, providing the charge-generation layer between the light-emitting units can suppress an increase in driving voltage.
Note that there is no particular limitation on the light-emitting material of the light-emitting layer in the display device 500 illustrated in
For another example, the display device in
For the display device of one embodiment of the present invention, a structure may be employed in which fluorescent materials are used for all the light-emitting layers included in the light-emitting devices 550R, 550G, and 550B or a structure may be employed in which phosphorescent materials are used for all the light-emitting layers included in the light-emitting devices 550R, 550G, and 550B.
The display device in
This embodiment can be combined with the other embodiments as appropriate.
In this embodiment, a light-receiving device that can be used for the display device of one embodiment of the present invention and a display device having a light-emitting and light-receiving function will be described.
As illustrated in
The active layer 767 functions as a photoelectric conversion layer.
In the case where the lower electrode 761 is an anode and the upper electrode 762 is a cathode, the layer 766 includes one or both of a hole-transport layer and an electron-blocking layer. The layer 768 includes one or both of an electron-transport layer and a hole-blocking layer. In the case where the lower electrode 761 is a cathode and the upper electrode 762 is an anode, the structures of the layer 766 and the layer 768 are interchanged.
Next, materials that can be used for the light-receiving device will be described.
Either a low molecular compound or a high molecular compound can be used for the light-receiving device, and an inorganic compound may also be contained. Each layer included in the light-receiving device 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 active layer included in the light-receiving device 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 where 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.
Examples of an n-type semiconductor material included in the active layer include electron-accepting organic semiconductor materials such as fullerene (e.g., C60 fullerene and C70 fullerene) and fullerene derivatives. Examples of the fullerene derivative include [6,6]-phenyl-C71-butyric acid methyl ester (abbreviation: PC71BM), [6,6]-phenyl-C61-butyric acid methyl ester (abbreviation: PC61BM), and 1′,1″,4′,4″-tetrahydro-di[1,4]methanonaphthaleno[1,2:2′,3′,56,60:2″,3″][5,6]fullerene-C60 (abbreviation: ICBA).
Other examples of an n-type semiconductor material include perylenetetracarboxylic acid derivatives such as N,N′-dimethyl-3,4,9,10-perylenetetracarboxylic diimide (abbreviation: Me-PTCDI) and 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 (abbreviation: CuPc), tetraphenyldibenzoperiflanthene (abbreviation: DBP), zinc phthalocyanine (abbreviation: ZnPc), tin (II) phthalocyanine (abbreviation: SnPc), quinacridone, and rubrene.
Other 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 the 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.
Three or more kinds of materials may be mixed in the active layer. 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. The third material may be a low molecular compound or a high molecular compound.
In addition to the active layer, the light-receiving device may further include a layer including 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 including 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 included in the light-receiving device can be formed using a material that can be used for the light-emitting device.
As the hole-transport material or the electron-blocking material, a high molecular compound such as poly(3,4-ethylenedioxythiophene)/polystyrenesulfonic acid (abbreviation: PEDOT/PSS), or an inorganic compound such as 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.
In the display device 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 a target (e.g., a finger, a hand, or a pen) can be detected.
Furthermore, in the display device of one embodiment of the present invention, the light-emitting device can be used as a light source of the sensor. In the display device of one embodiment of the present invention, when an object reflects (or scatters) light emitted from the light-emitting device included in the display portion, the light-receiving device can detect reflected light (or scattered light); thus, image capturing or touch detection is possible even in a dark place.
Accordingly, a light-receiving portion and a light source do not need to be provided separately from the display device; hence, the number of components of an electronic device can be reduced. For example, a biometric authentication device, a capacitive touch panel for scroll operation, or the like does not need to be provided separately from the electronic device. Thus, with the use of the display device of one embodiment of the present invention, the electronic device can be provided with reduced manufacturing cost.
Specifically, the display device of one embodiment of the present invention includes a light-emitting device and a light-receiving device in a pixel. In the display device of one embodiment of the present invention, an organic EL device is used as the light-emitting device, and an organic photodiode is used as the light-receiving device. The organic EL device and the organic photodiode can be formed over the same substrate. Thus, the organic photodiode can be incorporated in the display device using the organic EL device.
In the display device including a light-emitting device and a light-receiving device in each pixel, the pixel has a light-receiving function; thus, the display device can detect a contact or approach of an object while displaying an image. For example, all the subpixels included in the display device can display an image; alternatively, some of the subpixels can emit light as a light source, and the other subpixels can display an image.
In the case where the light-receiving device is used as an image sensor, the display device can capture an image with the use of the light-receiving device. For example, the display device of this embodiment can be used as a scanner.
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 can be performed using the image sensor.
For example, an image of the periphery, surface, or inside (e.g., fundus) of an eye of a user of a wearable device can be captured using the image sensor. Thus, the wearable device can have a function of detecting one or more selected from blinking, movement of an iris, and movement of an eyelid of the user.
The light-receiving device can be used for 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.
Here, the touch sensor or the near touch sensor can detect the 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 device 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 device. For example, the display device is preferably capable of detecting an object when the distance between the display device 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. With this structure, the display device can be operated without an object directly contacting with the display device. In other words, the display device can be operated in a contactless (touchless) manner. With the above structure, the display device can have a reduced risk of being dirty or damaged, or can be operated without the object directly contacting with a dirt (e.g., dust or a virus) attached to the display device.
The refresh rate can be variable in the display device of one embodiment of the present invention. 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 device, 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. For example, when the refresh rate of the display device is 120 Hz, the driving frequency of the touch sensor or the near touch sensor can be higher than 120 Hz (can typically be 240 Hz). With this structure, low power consumption can be achieved, and the response speed of the touch sensor or the near touch sensor can be increased.
The display device 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. One or more of 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 including neither a switch nor 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 in contact with the display device 100 as illustrated in
Alternatively, the display device may have a function of detecting an object that is approaching (is not in contact with) the display device as illustrated in
This embodiment can be combined with any of the other embodiments as appropriate.
In this embodiment, a method for manufacturing a display device of one embodiment of the present invention will be described with reference to
Thin films included in the display device (e.g., insulating films, semiconductor films, and conductive films) can be formed by a sputtering method, a chemical vapor deposition (CVD) method, a vacuum evaporation method, a pulsed laser deposition (PLD) method, an ALD method, or the like. Examples of a CVD method include a plasma-enhanced CVD (PECVD) method and a thermal CVD method. As one example of the thermal CVD method, a metal organic chemical vapor deposition (MOCVD: Metal Organic CVD) method can be given.
Alternatively, thin films included in the display device (e.g., insulating films, semiconductor films, and conductive films) 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 knife method, slit coating, roll coating, curtain coating, or knife coating.
Specifically, for manufacturing the light-emitting device, a vacuum process such as an evaporation method and a solution process such as a spin coating method or an ink-jet 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 hole-blocking layer, a light-emitting layer, an electron-blocking layer, an electron-transport layer, an electron-injection layer, and a charge-generation 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 device can be processed by a photolithography method or the like. Alternatively, the 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 two typical methods of a photolithography method. In one of the methods, a resist mask is formed over a thin film 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 deposited and then processed into a desired shape by light exposure and development.
As light for light exposure in a photolithography method, it is possible to use the i-line (wavelength: 365 nm), the g-line (wavelength: 436 nm), the h-line (wavelength: 405 nm), or light in which the i-line, the g-line, and the h-line are mixed, for example. Alternatively, ultraviolet rays (also referred to as ultraviolet light), KrF laser light, ArF laser light, or the like can be used. Light exposure may be performed by liquid immersion light exposure technique. As the light used for light exposure, extreme ultraviolet (EUV) light or X-rays may also be used. Furthermore, instead of the light used for light exposure, an electron beam can be used. Extreme ultraviolet light, X-rays, or an electron beam is preferably used, in which case extremely minute processing can be performed. Note that a photomask is not needed when light exposure is performed by scanning with a beam such as an electron beam.
For etching of thin films, a dry etching method, a wet etching method, a sandblast method, or the like can be used.
First, the insulating layer 255a, the insulating layer 255b, and the insulating layer 255c are formed in this order over the layer 101 including transistors. Next, the pixel electrodes 111R, 111G, and 111B and the conductive layer 123 are formed over the insulating layer 255c (
Note that depressed portions are sometimes formed on a surface of the insulating layer 255c that does not overlap with any of the pixel electrodes 111R, 111G, and 111B and the conductive layer 123.
In the case where the insulating layer 136 is provided as illustrated in
Next, the pixel electrode is preferably subjected to hydrophobic treatment. The hydrophobic treatment can change the property of the surface of a processing target from hydrophilic to hydrophobic, or can improve the hydrophobic property of the surface of the processing target. The hydrophobic treatment for the pixel electrode can improve the adhesion between the pixel electrode and a film to be formed in a later step (here, a film 113b), thereby inhibiting film separation. Note that the hydrophobic treatment is not necessarily performed.
The hydrophobic treatment can be performed by fluorine modification of the pixel electrode, 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. A fluorine gas can be used as the fluorine-containing gas, and for example, a fluorocarbon gas can be used. 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, an SF6 gas, an 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 silylation agent is performed on the surface of the pixel electrode after plasma treatment is performed in a gas atmosphere containing a Group 18 element such as argon, so that the surface of the pixel electrode can become hydrophobic. As the silylation agent, hexamethyldisilazane (HMDS), trimethylsilylimidazole (TMSI), or the like can be used. Alternatively, treatment using a silane coupling agent is performed on the surface of the pixel electrode after plasma treatment is performed in a gas atmosphere containing a Group 18 element such as argon, so that the surface of the pixel electrode can become hydrophobic.
Plasma treatment on the surface of the pixel electrode in a gas atmosphere containing a Group 18 element such as argon can apply damage to the surface of the pixel electrode. Accordingly, a methyl group included in the silylation agent such as HMDS is likely to bond to the surface of the pixel electrode. Moreover, silane coupling due to the silane coupling agent is likely to occur. As described above, treatment using a silylation agent or a silane coupling agent performed on the surface of the pixel electrode after plasma treatment in a gas atmosphere containing a Group 18 element such as argon enables the surface of the pixel electrode to become hydrophobic.
The treatment using the silylation agent, the silane coupling agent, or the like can be performed by application of the silylation agent, the silane coupling agent, or the like by a spin coating method or a dipping method, for example. The treatment using the silylation agent, the silane coupling agent, or the like can also be performed by forming a film containing the silylation agent, a film containing the silane coupling agent, or the like over the pixel electrode and the like by a gas phase method, for example. In a gas phase method, first, a material containing the silylation agent, a material containing the silane coupling agent, or the like is vaporized so that the silylation agent, the silane coupling agent, or the like is included in the atmosphere. Next, a substrate where the pixel electrode and the like are formed is put in the atmosphere. Accordingly, a film containing the silylation agent, a film containing the silane coupling agent, or the like can be formed over the pixel electrode, so that the surface of the pixel electrode can become hydrophobic.
Then, the film 113b to be the layer 113B later is formed over the pixel electrodes (
As illustrated in
Note that a material having high heat resistance is preferably used for the light-emitting device. Specifically, the upper temperature limit of a compound included in the film 113b 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 device can be increased. Thus, the range of choices of the materials and the formation method of the display device can be widened, thereby improving the manufacturing yield and the reliability.
The film 113b1, the film 113b2, and the film 113b can be formed by an evaporation method, specifically a vacuum evaporation method, for example. The film 113b1, the film 113b2, and the film 113b may be formed by a method such as a transfer method, a printing method, an inkjet method, or a coating method.
Next, over the film 113b3 and the conductive layer 123, a sacrificial film 118b that is to be the sacrificial layer 118B later and a sacrificial film 119b that is to be the sacrificial layer 119B later are sequentially formed (
Although this embodiment describes an example where the sacrificial film is formed to have a two-layer structure of the sacrificial film 118b and the sacrificial film 119b, the sacrificial film may have a single-layer structure or a stacked-layer structure of three or more layers.
Providing a sacrificial layer over the film 113b can reduce damage to the film 113b in the process of manufacturing the display device and increase the reliability of the light-emitting device.
As the sacrificial film 118b, a film highly resistant to the processing conditions of the film 113b, specifically, a film having high etching selectivity with respect to the film 113b is used. For the sacrificial film 119b, a film having high etching selectivity with respect to the sacrificial film 118b is used.
The sacrificial film 118b and the sacrificial film 119b are formed at a temperature lower than the upper temperature limit of the film 113b. The typical substrate temperatures in formation of the sacrificial film 118b and the sacrificial film 119b are each 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., and yet still further preferably lower than or equal to 80° C.
Examples of indicators of the upper temperature limit include a glass transition point, a softening point, a melting point, a thermal decomposition temperature, and a 5% weight loss temperature. The upper temperature limits of the film 113b, a film 113g, and a film 113r (i.e., the layers 113B, 113G, and 113R) can each be any of the above temperatures that are indicators of the upper temperature limit, preferably the lowest temperature among the temperatures.
In the case where a material with high heat resistance is used for the light-emitting device, the substrate temperature at the time of forming the sacrificial film can be higher than or equal to 100° C., higher than or equal to 120° C., or higher than or equal to 140° C. For example, an inorganic insulating film formed at a higher film-formation temperature can be a film that is denser and has a higher barrier property. Thus, forming the sacrificial film at such a temperature can further reduce damage to the film 113b and improve the reliability of the light-emitting device.
As the sacrificial film 118b and the sacrificial film 119b, it is preferable to use a film that can be removed by a wet etching method. Using a wet etching method can reduce damage to the film 113b in processing the sacrificial film 118b and the sacrificial film 119b, as compared to the case of using a dry etching method.
The sacrificial film 118b and the sacrificial film 119b can be formed by a sputtering method, an ALD method (including a thermal ALD method or a PEALD method), a CVD method, or a vacuum evaporation method, for example. Alternatively, the aforementioned wet film formation method may be used for the formation.
Note that the sacrificial film 118b, which is formed over and in contact with the film 113b, is preferably formed by a formation method that causes less damage to the film 113b than a formation method for the sacrificial film 119b. For example, the sacrificial film 118b is preferably formed by an ALD method or a vacuum evaporation method rather than a sputtering method.
As the sacrificial film 118b and the sacrificial film 119b, it is possible to use one or more of a metal film, an alloy film, a metal oxide film, a semiconductor film, an organic insulating film, and an inorganic insulating film, for example.
For the sacrificial film 118b and the sacrificial film 119b, 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. A metal material capable of blocking ultraviolet rays is preferably used for one or both of the sacrificial film 118b and the sacrificial film 119b, in which case the film 113b can be inhibited from being irradiated with ultraviolet rays and deterioration of the film 113b can be inhibited.
A metal film or an alloy film is preferably used as one or both of the sacrificial film 118b and the sacrificial film 119b, in which case the film 113b can be inhibited from being damaged by plasma and deterioration of the film 113b can be inhibited. Specifically, the film 113b can be inhibited from being damaged by plasma in a step using a dry etching method, a step performing ashing, or the like. It is preferable to use a metal film such as a tungsten film or an alloy film as the sacrificial film 119b in particular.
For the sacrificial film 118b and the sacrificial film 119b, a metal oxide such as In—Ga—Zn oxide, 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 indium tin oxide containing silicon can be used.
In addition, in place of gallium described above, the element M (M is one or more selected from aluminum, silicon, boron, yttrium, copper, vanadium, beryllium, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, cobalt, and magnesium) may be used. In particular, M is preferably one or more selected from gallium, aluminum, and yttrium.
As the sacrificial film, a film including a material having a light-blocking property with respect to light, particularly ultraviolet rays, can be used. For example, a film having a reflecting property with respect to ultraviolet rays or a film absorbing ultraviolet rays can be used. Although a variety of materials, such as a metal having a light-blocking property with respect to ultraviolet rays, an insulator, a semiconductor, and a metalloid, can be used as the material having a light-blocking property, a film capable of being processed by etching is preferable, specifically, a film having good processability is preferable because part or the whole of the sacrificial film is removed in a later step.
For example, a semiconductor material such as silicon or germanium can be used as a material with a high affinity for the semiconductor manufacturing process. Alternatively, an oxide or a nitride of the semiconductor material can be used. Alternatively, a non-metallic material such as carbon or a compound thereof can be used. Alternatively, a metal, such as titanium, tantalum, tungsten, chromium, or aluminum, or an alloy containing one or more of them can be given. Alternatively, an oxide containing the above-described metal, such as titanium oxide or chromium oxide, or a nitride such as titanium nitride, chromium nitride, or tantalum nitride can be used.
The use of a film including a material having a light-blocking property with respect to ultraviolet rays for the sacrificial film can inhibit the EL layer from being irradiated with ultraviolet rays in a light exposure step or the like. The EL layer is inhibited from being damaged by ultraviolet rays, so that the reliability of the light-emitting device can be improved.
Note that the film including a material having a light-blocking property with respect to ultraviolet rays can have the same effect even when used as a material for the insulating film 125A that is described later.
As the sacrificial film 118b and the sacrificial film 119b, 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 film 113b 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 the sacrificial film 118b and the sacrificial film 119b. As the sacrificial film 118b and the sacrificial film 119b, an aluminum oxide film can be formed by an ALD method, for example. The use of an ALD method is preferable because damage to a base (in particular, the EL layer) 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 sacrificial film 118b, and an inorganic film (e.g., an In—Ga—Zn oxide film, a silicon film, or a tungsten film) formed by a sputtering method can be used as the sacrificial film 119b.
Note that the same inorganic insulating film can be used as both the sacrificial film 118b 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 as both the sacrificial film 118b and the insulating layer 125. Here, for the sacrificial film 118b and the insulating layer 125, the same film-formation condition may be used or different film-formation conditions may be used. For example, when the sacrificial film 118b is formed under conditions similar to those of the insulating layer 125, the sacrificial film 118b can be an insulating layer having a high barrier property against at least one of water and oxygen. Meanwhile, the sacrificial film 118b is a layer most or all of which is to be removed in a later step, and thus is preferably easy to process. Thus, the sacrificial film 118b is preferably formed with a substrate temperature lower than the substrate temperature at the time of formation of the insulating layer 125.
An organic material may be used for one or both of the sacrificial film 118b and the sacrificial film 119b. For example, as the organic material, a material that can be dissolved in a solvent chemically stable with respect to at least the uppermost film of the film 113b may be used. Specifically, a material that can 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, the heat treatment is preferably performed under 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 film 113b can be accordingly reduced.
The sacrificial film 118b and the sacrificial film 119b may each be formed using an organic resin such as polyvinyl alcohol (PVA), polyvinyl butyral, polyvinylpyrrolidone, polyethylene glycol, polyglycerin, pullulan, water-soluble cellulose, an alcohol-soluble polyamide resin, or a fluorine resin like perfluoropolymer.
For example, an organic film (e.g., a PVA film) formed by an evaporation method or the above wet film formation method can be used as the sacrificial film 118b, and an inorganic film (e.g., a silicon nitride film) formed by a sputtering method can be used as the sacrificial film 119b.
Note that as described in Embodiment 1, part of the sacrificial film sometimes remains as a sacrificial layer in the display device of one embodiment of the present invention.
Next, a resist mask 190B is formed over the sacrificial film 119b (
The resist mask 190B may be formed using either a positive resist material or a negative resist material.
The resist mask 190B is provided so as to cover the pixel electrode 111B. That is, in the top view, an end portion of the resist mask 190B is positioned outward from the end portion of the pixel electrode 111B. The resist mask 190B is preferably provided also at a position overlapping with the conductive layer 123. This can inhibit the conductive layer 123 from being damaged during the manufacturing process of the display device. Note that the resist mask 190B may not be provided over the conductive layer 123.
As illustrated in the cross-sectional view taken along Y1-Y2 in
Next, part of the sacrificial film 119b is removed using the resist mask 190B, so that the sacrificial layer 119B is formed (
The sacrificial film 118b and the sacrificial film 119b can be processed by a wet etching method or a dry etching method. The sacrificial film 118b and the sacrificial film 119b are preferably processed by anisotropic etching.
Using a wet etching method can reduce damage to the film 113b in processing the sacrificial film 118b and the sacrificial film 119b, as 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, or a mixed solution containing two or more of these acids, for example. In the case of employing a wet etching method, a mixed acid chemical solution containing water, phosphoric acid, diluted hydrofluoric acid, and nitric acid may be used. A chemical solution used for the wet etching treatment may be alkaline or acid.
Since the film 113b is not exposed in processing the sacrificial film 119b, the range of choices of the processing method is wider than that for processing the sacrificial film 118b. Specifically, deterioration of the film 113b can be further inhibited even when a gas containing oxygen is used as an etching gas for processing the sacrificial film 119b.
In the case of using a dry etching method for processing the sacrificial film 118b, deterioration of the film 113b 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 sacrificial film 118b, the sacrificial film 118b can be processed by a dry etching method using CHF3 and He or CHF3, He, and CH4. In the case where an In—Ga—Zn oxide film formed by a sputtering method is used as the sacrificial film 119b, the sacrificial film 119b can be processed by a wet etching method using a diluted phosphoric acid. Alternatively, the sacrificial film 119b may be processed by a dry etching method using CH4 and Ar. Alternatively, the sacrificial film 119b can be processed by a wet etching method using a diluted phosphoric acid. When a tungsten film formed by a sputtering method is used as the sacrificial film 119b, the sacrificial film 119b can be processed by a dry etching method using a combination of SF6, CF4, and O2 or a combination of CF4, Cl2, and O2.
The resist mask 190B can be removed by ashing using oxygen plasma, for example. Alternatively, an oxygen gas and any of CF4, C4F8, SF6, CHF3, Cl2, H2O, BCl3, or a noble gas (a rare gas) such as He may be used. Alternatively, the resist mask 190B may be removed by wet etching. At this time, the sacrificial film 118b is positioned on the outermost surface, and the film 113b is not exposed; thus, the film 113b can be inhibited from being damaged in the step of removing the resist mask 190B. In addition, the range of choices of the method for removing the resist mask 190B can be widened.
Next, the film 113b is processed to form the layer 113B. For example, part of the film 113b is removed using the sacrificial layer 119B and the sacrificial layer 118B as a hard mask, so that the layer 113B is formed (
Accordingly, as illustrated in
Here, when the film 113b is processed, the surface of the pixel electrodes 111R and the surface of the pixel electrode 111G are exposed to an etching gas, an etchant, or the like. On the other hand, the surface of the pixel electrode 111B is not exposed to an etching gas, an etchant, or the like. As described above, in the light-emitting device of the color formed first, the surface of the pixel electrode is not damaged by the etching process, whereby the interface between the pixel electrode and the EL layer can be kept in a favorable state.
The film 113b is preferably processed by anisotropic etching. Anisotropic dry etching is particularly preferable. Alternatively, wet etching may be used. Although not illustrated in
In the case of using a dry etching method, deterioration of the film 113b can be inhibited by not using a gas containing oxygen as the etching gas.
Alternatively, a gas containing oxygen may be used as the etching gas. When the etching gas contains oxygen, the etching rate can be increased. Accordingly, the etching can be performed under a low-power condition while an adequately high etching rate is maintained. Thus, damage to the film 113b can be reduced. Furthermore, a defect such as attachment of a reaction product generated at 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 (a rare gas) such as He and Ar as the etching gas, for example. Alternatively, a gas containing oxygen and one or more kinds 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. For another example, a gas containing CF4, He, and oxygen can be used as the etching gas. As another example, a gas containing H2 and Ar and a gas containing oxygen can be used as the etching gas.
A dry etching apparatus including a high-density plasma source can be used as the dry etching apparatus. As the dry etching apparatus including a high-density plasma source, an inductively coupled plasma (ICP) etching apparatus can be used, for example. Alternatively, a capacitively coupled plasma (CCP) etching apparatus including parallel plate electrodes can be used. The capacitively coupled plasma etching apparatus including parallel plate electrodes may have a structure in which a high-frequency voltage is applied to one of the parallel plate electrodes. Alternatively, a structure may be employed in which different high-frequency voltages are applied to one of the parallel plate electrodes. Alternatively, a structure may be employed in which high-frequency voltages with the same frequency are applied to the parallel plate electrodes. Alternatively, a structure may be employed in which high-frequency voltages with different frequencies are applied to the parallel plate electrodes.
Here, the layer 113B is provided to cover the pixel electrode 111B. When the layer 113B covers the top and side surfaces of the pixel electrode 111B, the following steps can be performed without exposing the pixel electrode 111B. When the end portions of the pixel electrode 111B are exposed, corrosion might occur in the etching step or the like. A product generated by corrosion of the electrode 111B might be unstable; for example, the product is liable to be dissolved in a solution in wet etching or to be diffused in an atmosphere in dry etching. The product dissolved in a solution or diffused in an atmosphere might be attached to a surface to be processed, the side surface of the layer 113B, and the like, which may adversely affect the characteristics of the light-emitting device or may form a leakage path between the plurality of light-emitting devices. In a region where the end portion of the pixel electrode 111B is exposed, the adhesion between contacting layers is lowered, which may be likely to facilitate film separation of the layer 113B or the pixel electrode 111B.
Thus, when the layer 113B covers the top and side surfaces of the pixel electrode 111B, the yield and characteristics of the light-emitting device can be improved, for example.
Damage caused by plasma or the like may be given to the end portion of the layer 113B at the time of processing of the film 113b or in a later step. The end portion of the layer 113B and the vicinity thereof are not used for light emission; thus, such regions are less likely to adversely affect the characteristics of the light-emitting device even when being damaged. Meanwhile, the light-emitting region of the layer 113B is covered with the sacrificial layer, and thus is not exposed to plasma and plasma damage is sufficiently reduced. The sacrificial layer is preferably provided to cover not only the top surface of a flat portion of the layer 113B overlapping with the top surface of the pixel electrode 111B, but also top surfaces of an inclined portion and a flat portion of the layer 113B that are positioned outside the top surface of the pixel electrode 111B. A portion of the layer 113B with reduced damage in the manufacturing process is used as the light-emitting region in this manner; thus, a light-emitting device having high emission efficiency and a long lifetime can be achieved.
In the region corresponding to the connection portion 140, a stacked-layer structure of the sacrificial layer 118B and the sacrificial layer 119B remains over the conductive layer 123.
As described above, in the cross-sectional view taken along Y1-Y2 in
As described above, in one embodiment of the present invention, the sacrificial layer 119B is formed in the following manner: the resist mask 190B is formed over the sacrificial film 119b, and part of the sacrificial film 119b is removed using the resist mask 190B. After that, part of the film 113b is removed using the sacrificial layer 119B as a hard mask, so that the layer 113B is formed. Thus, it can be said that the layer 113B is formed by processing the film 113b by a photolithography method. Note that part of the film 113b may be removed using the resist mask 190B. Then, the resist mask 190B may be removed.
Next, the pixel electrode is preferably subjected to hydrophobic treatment. In processing of the film 113b, the surface state of the pixel electrode changes to a hydrophilic state in some cases. The hydrophobic treatment for the pixel electrode can improve the adhesion between the pixel electrode and a film to be formed in a later step (here, the film 113g), thereby inhibiting film separation. Note that the hydrophobic treatment is not necessarily performed.
Next, the film 113g to be the layer 113G later is formed over the pixel electrodes 111R and 111G and the sacrificial layer 119B (
Next, over the film 113g, a sacrificial film 118g to be the sacrificial layer 118G later and a sacrificial film 119g to be a sacrificial layer 119G later are formed in this order, and then a resist mask 190G is formed (
The resist mask 190G is provided to cover the pixel electrode 111G. That is, in the top view, an end portion of the resist mask 190G is positioned outward from the end portion of the pixel electrode 111G.
Next, part of the sacrificial film 119g is removed using the resist mask 190G, so that the sacrificial layer 119G is formed (
Next, the film 113g is processed to form the layer 113G. For example, part of the film 113g is removed using the sacrificial layer 119G and the sacrificial layer 118G as a hard mask to form the first layer 113G (
Here, in processing of the film 113g, the surface of the pixel electrode 111R is exposed to an etching gas, an etchant, or the like. On the other hand, the surface of the pixel electrode 111B and the surface of the pixel electrode 111G are not exposed to an etching gas, an etchant, or the like. That is, the surface of the pixel electrode in the light-emitting device of the color formed second is exposed in one etching step, and the surface of the pixel electrode in the light-emitting device of the color formed third is exposed in two etching steps. Thus, an island-shaped EL layer of a light-emitting device in which the surface state of a pixel electrode is more likely to affect its characteristics is preferably formed earlier. As a result, the characteristics of the light-emitting device of each color can be improved.
Accordingly, as illustrated in
Next, the pixel electrode is preferably subjected to hydrophobic treatment. In processing of the film 113g, the surface state of the pixel electrode changes to a hydrophilic state in some cases. The hydrophobic treatment for the pixel electrode can improve the adhesion between the pixel electrode and a film to be formed in a later step (here, the film 113r), thereby inhibiting film separation. Note that the hydrophobic treatment is not necessarily performed.
Next, the film 113r to be the layer 113R later is formed over the pixel electrode 111R and the sacrificial layers 119G and 119B (
The film 113r (to be the layer 113R later) includes a light-emitting material that emits red light.
The film 113r can be formed by a method similar to a method that can be employed for forming the film 113g.
Next, over the film 113r, a sacrificial film 118r to be the sacrificial layer 118R later and a sacrificial film 119r to be a sacrificial layer 119R later are formed in this order, and then a resist mask 190R is formed (
The resist mask 190R is provided to cover the pixel electrode 111R. That is, in the top view, an end portion of the resist mask 190R is positioned outward from the end portion of the pixel electrode 111R.
Then, part of the sacrificial film 119r is removed using the resist mask 190R, so that the sacrificial layer 119R is formed. The sacrificial layer 119R remains over the pixel electrode 111R. After that, the resist mask 190R is removed. Next, part of the sacrificial film 118r is removed using the sacrificial layer 119R as a mask, so that the sacrificial layer 118R is formed. Here, the sacrificial layer 119R and the sacrificial layer 118R are provided to cover the pixel electrode 111R. That is, in the top view, the end portion of the sacrificial layer 119R and the end portion of the sacrificial layer 118R are positioned outward from the end portion of the pixel electrode 111R.
Next, the film 113r is processed to form the layer 113R. For example, part of the film 113r is removed using the sacrificial layer 119R and the sacrificial layer 118R as a hard mask, so that the layer 113R is formed (
Accordingly, as illustrated in
Note that side surfaces of the layer 113B, the layer 113G, and the layer 113R are preferably perpendicular or substantially perpendicular to their formation surfaces. For example, the angles between the formation surfaces and these side surfaces are preferably greater than or equal to 60° and less than or equal to 90°.
As described above, the distance between adjacent two layers among the layer 113B, the layer 113G, and the layer 113R formed by a photolithography method can be shortened to 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 can be determined by, for example, the distance between facing end portions of adjacent two layers among the layer 113B, the layer 113G, and the layer 113R. When the distance between the island-shaped EL layers is shortened in this manner, a display device with high resolution and a high aperture ratio can be provided.
As described above, when the tandem structure is employed at least for a light-emitting device that emits blue light, the reliability of the blue-light-emitting device whose luminance or the like easily deteriorates can be improved. Furthermore, when the reliability of the blue-light-emitting device is improved, the reliability of the display device can be improved. Furthermore, a red-light-emitting device employs a single structure for a simplified manufacturing process, so that the yield in the manufacturing process of the display device can be increased.
As described above, after the layer 113B including a light-emitting material emitting blue light is formed into an island shape, the layer 113G and the layer 113R each including a light-emitting material emitting light with a longer wavelength than blue light are formed into island shapes. Thus, the blue-light-emitting device can be inhibited from having an increased driving voltage and a shortened lifetime. In addition, the light-emitting device of each color can emit light at high luminance. Furthermore, an increase in the driving voltage of the light-emitting device of each color can be suppressed. Furthermore, the lifetime of the light-emitting device of each color can be longer and the reliability of the display device can be improved.
Note that the present invention is not limited thereto, and the order of forming the layer 113B, the layer 113G, and the layer 113R may be determined as appropriate. The order of forming the layer 113B, the layer 113G, and the layer 113R may be the order of the layer 113B, the layer 113R, and the layer 113G, the order of the layer 113G, the layer 113B, and the layer 113R, the order of the layer 113G, the layer 113R, and the layer 113B, the order of the layer 113R, the layer 113G, and the layer 113B, or the order of the layer 113R, the layer 113B, and the layer 113G.
Then, the sacrificial layers 119B, 119G, and 119R are preferably removed (
Although this embodiment describes an example in which the sacrificial layers 119B, 119G, and 119R are removed, the sacrificial layers 119B, 119G, and 119R are not necessarily removed. For example, in the case where the sacrificial layers 119B, 119G, and 119R each contain the aforementioned material having a light-blocking property with respect to ultraviolet rays, the process preferably proceeds to the next step without removing the sacrificial layers, in which case the island-shaped EL layers can be protected from ultraviolet rays.
The step of removing the sacrificial layers can be performed by a method similar to that for the step of processing the sacrificial layers. In particular, the use of a wet etching method can reduce damage to the layer 113B, the layer 113G, and the layer 113R at the time of removing the sacrificial layers compared with the case of using a dry etching method.
In the case where a metal film or an alloy film is used as each of the sacrificial layers 119B, 119G, and 119R, the sacrificial layers 119B, 119G, and 119R can inhibit plasma damage to the EL layers. Thus, film processing can be performed by a dry etching method in the steps before the removal of the sacrificial layers 119B, 119G, and 119R. On the other hand, in the step of removing the sacrificial layers 119B, 119G, and 119R and in the steps after the removal, the film inhibiting plasma damage to the EL layers is not present; thus, film processing is preferably performed by a method that does not use plasma, such as a wet etching method.
The sacrificial layer 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 sacrificial layers are removed, drying treatment may be performed to remove water contained in the layer 113B, the layer 113G, and the layer 113R and water adsorbed onto the surfaces of the layer 113B, the layer 113G, and the layer 113R. For example, heat treatment in an inert gas atmosphere such as a nitrogen atmosphere or a reduced-pressure atmosphere can be performed. The heat treatment can be performed at 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. A reduced-pressure atmosphere is preferably employed, in which case drying at a lower temperature is possible.
Next, the insulating film 125A to be the insulating layer 125 later is formed to cover the pixel electrodes, the layer 113B, the layer 113G, the layer 113R, the sacrificial layer 118B, the sacrificial layer 118G, and the sacrificial layer 118R (
As described later, the insulating film 127a is formed in contact with the top surface of the insulating film 125A. Thus, the top surface of the insulating film 125A preferably has high adhesion to a resin composite (e.g., a photosensitive resin composite containing an acrylic resin) that is used for the insulating film 127a. To improve the adhesion, the top surface of the insulating film 125A is preferably hydrophobized (or the hydrophobicity is improved) by surface treatment. For example, the treatment is preferably performed using a silylating agent such as hexamethyldisilazane (HMDS). By hydrophobizing the top surface of the insulating film 125A in this manner, the insulating film 127a can be formed with high adhesion. Note that the above-described hydrophobization treatment may be performed as the surface treatment.
Then, the insulating film 127a is formed over the insulating film 125A (
The insulating film 125A and the insulating film 127a are preferably formed by a formation method that causes less damage to the layer 113B, the layer 113G, and the layer 113R. In particular, the insulating film 125A, which is formed in contact with the side surfaces of the layer 113B, the layer 113G, and the layer 113R, is preferably formed by a formation method that causes less damage to the layer 113B, the layer 113G, and the layer 113R than the method for forming the insulating film 127a.
The insulating film 125A and the insulating film 127a are formed at a temperature lower than the upper temperature limits of the layer 113B, the layer 113G, and the layer 113R. When the insulating film 125A is formed at a high substrate temperature, the formed film, even with a small thickness, can have a low impurity concentration and a high barrier property against at least one of water and oxygen.
The insulating film 125A and the insulating film 127a are preferably formed at a substrate temperature 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.
When a material with high heat resistance is used for the light-emitting device, the substrate temperature at the time of forming the insulating film 125A and the insulating film 127a can be higher than or equal to 100° C., higher than or equal to 120° C., or higher than or equal to 140° C. For example, an inorganic insulating film formed at a higher film-formation temperature can be a film that is denser and has a higher barrier property. Thus, forming the insulating film 125A at such a temperature can further reduce damage to the layer 113B, the layer 113G, and the layer 113R and improve the reliability of the light-emitting device.
As the insulating film 125A, an insulating film is preferably formed within the above substrate temperature range 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 film 125A is preferably formed by an ALD method, for example. An ALD method is preferably used, in which case film formation damage can be reduced and a film with good coverage can be formed. As the insulating film 125A, for example, an aluminum oxide film is preferably formed by an ALD method.
Alternatively, the insulating film 125A may be formed by a sputtering method, a CVD method, or a PECVD method that provides a higher film formation speed than an ALD method. In that case, a highly reliable display device can be manufactured with high productivity.
The insulating film 127a is preferably formed by the aforementioned wet film formation method. For example, the insulating film 127a is preferably formed by spin coating using a photosensitive resin, specifically, a photosensitive resin composite containing an acrylic resin.
Heat treatment (also referred to as pre-baking) is preferably performed after formation of the insulating film 127a. The heat treatment is performed at a temperature lower than the upper temperature limits of the layer 113B, the layer 113G, and the layer 113R. The substrate temperature in the heat treatment is preferably higher than or equal to 50° C. and lower than or equal to 200° C., further preferably higher than or equal to 60° C. and lower than or equal to 150° C., still further preferably higher than or equal to 70° C. and lower than or equal to 120° C. Accordingly, a solvent contained in the insulating film 127a can be removed.
Next, the insulating film 127a is partly exposed to light by irradiating part of the insulating film 127a with visible light or ultraviolet rays (
Note that the width of the insulating layer 127 to be formed later can be controlled by the region exposed to light here. In this embodiment, the insulating layer 127 is processed so as to include a portion overlapping with the top surface of the pixel electrode (
Light used for light exposure preferably includes the i-line (wavelength: 365 nm). Furthermore, light used for the exposure may include at least one of the g-line (wavelength: 436 nm) and the h-line (wavelength: 405 nm).
Although
Next, as illustrated in
Note that a step of removing a development residue (what is called a scum) may be performed after development. For example, the residue can be removed by ashing using oxygen plasma. A step for removing a residue may be performed after each development step described below.
Etching may be performed to adjust the surface level of the insulating layer 127b. The insulating layer 127b may be processed by ashing using oxygen plasma, for example.
Note that after development and before post-baking, light exposure may be performed on the entire substrate, by which the insulating layer 127b is irradiated with visible light or ultraviolet rays. The energy density for the light exposure is preferably greater than 0 mJ/cm2 and less than or equal to 800 mJ/cm2, further preferably greater than 0 mJ/cm2 and less than or equal to 500 mJ/cm2. Performing such light exposure after development can improve the transparency of the insulating layer 127b in some cases. In addition, the insulating layer 127b can be changed into a tapered shape at low temperature in some cases.
By contrast, when light exposure is not performed on the insulating layer 127b, the shape of the insulating layer 127b can be easily changed or the insulating layer 127 can be easily changed into a tapered shape in a later process in some cases. Thus, it is sometimes preferable not to perform light expose on the insulating layer 127b after the development.
After that, heat treatment (also referred to as post-baking) is performed. As illustrated in
As illustrated in
Next, as illustrated in
The etching treatment can be performed by dry etching or wet etching. Note that the insulating film 125A is preferably formed using a material similar to those for of the sacrificial layers 118B, 118G, and 118R, in which case the etching treatment can be performed collectively.
In the case of performing dry etching, a chlorine-based gas is preferably used. As the chlorine-based gas, any of Cl2, BCl3, SiCl4, CCl4, and the like can be used alone or two or more of the gases can be mixed and used. Moreover, an oxygen gas, a hydrogen gas, a helium gas, an argon gas, or the like or a mixture of two or more of the gases can be added to the chlorine-based gas as appropriate. By employing dry etching, the thin regions of the sacrificial layers 118B, 118G, and 118R can be formed with a favorable in-plane uniformity.
In the case of performing dry etching, a by-product or the like generated by the dry etching is sometimes deposited on the top and side surfaces of the insulating layer 127b, for example. Thus, a component contained in the etching gas, a component contained in the insulating film 125A, components contained in the sacrificial layers 118B, 118G, and 118R, or the like might be contained in the insulating layer 127 in the completed display device.
The etching treatment is preferably performed by wet etching. Using a wet etching method can reduce damage to the layer 113B, the layer 113G, and the layer 113R, as compared to the case of using a dry etching method. For example, the wet etching can be performed using an alkaline solution or the like. For example, for wet etching of an aluminum oxide film, it is preferable to use an aqueous solution of tetramethyl ammonium hydroxide (TMAH) that is an alkaline solution. In this case, the wet etching can be performed by a puddle method. In the case of employing a wet etching method, a mixed acid chemical solution containing water, phosphoric acid, diluted hydrofluoric acid, and nitric acid may be used. A chemical solution used for the wet etching treatment may be alkaline or acid.
As described above, providing the insulating layer 127, the insulating layer 125, the sacrificial layer 118B, the sacrificial layer 118G, and the sacrificial layer 118R can inhibit the common layer 114 and the common electrode 115 between the light-emitting devices from having connection defects due to a disconnected portion and an increase in electric resistance due to a locally thinned portion. Thus, the display quality of the display device of one embodiment of the present invention can be improved.
After part of the layer 113B, the layer 113G, and the layer 113R are exposed, additional heat treatment may be performed. The heat treatment can remove water contained in the EL layer, water adsorbed onto the surface of the EL layer, and the like. In addition, the heat treatment changes the shape of the insulating layer 127 in some cases. Specifically, the insulating layer 127 may be extended to cover at least one of the end portion of the insulating layer 125, the end portions of the sacrificial layers 118B, 118G, and 118R, and the top surfaces of the layer 113B, the layer 113G, and the layer 113R. For example, the insulating layer 127 may have a shape illustrated in
Here, when the insulating layer 125 and the sacrificial layer are collectively etched after the post-baking, the insulating layer 125 and the sacrificial layer below the end portion of the insulating layer 127 disappear due to side etching and accordingly a cavity is formed in some cases. The cavity causes unevenness in the formation surface of the common layer 114 and the common electrode 115, so that step disconnection is likely to occur in the common layer 114 and the common electrode 115. To avoid this, the etching treatment for the insulating layer 125 and etching treatment for the sacrificial layer are preferably performed separately before and after the post-baking.
A method for performing the etching treatment for the insulating layer 125 and the etching treatment for the sacrificial layer separately before and after the post-baking is described below with reference to
Next, as illustrated in
The first etching treatment can be performed by dry etching or wet etching.
As illustrated in
As illustrated in
Although the sacrificial layers 118B, 118G, and 118R are thinned in
Although
Next, post-baking is performed. As illustrated in
The first etching treatment does not remove the sacrificial layers 118B, 118G, and 118R completely to make the thinned sacrificial layers 118B, 118G, and 118R remain, thereby preventing the layer 113G, the layer 113G, and the layer 113R from being damaged by the heat treatment and deteriorating. Thus, the reliability of the light-emitting device can be improved.
Next, as illustrated in
The end portion of the insulating layer 125 is covered with the insulating layer 127.
By using a method in which etching is performed before and after post-baking in this manner, even when a cavity is formed by side etching of the insulating layer 125 and the sacrificial layer in the first etching treatment, the subsequent post-baking can make the insulating layer 127 fill the cavity. After that, since the second etching treatment etches the thinned sacrificial layer, the amount of side etching is small and thus a cavity is not easily formed, and even if a cavity is formed, it can be extremely small. Thus, the flatness of the formation surfaces of the common layer 114 and the common electrode 115 can be improved.
Note that as illustrated in
The second etching treatment is preferably performed by wet etching. Using a wet etching method can reduce damage to the layer 113B, the layer 113G, and the layer 113R, as compared to the case of using a dry etching method. The wet etching can be performed using an alkaline solution or the like.
There may be a limitation on an apparatus and a method that can be used for the etching treatment of the insulating film 125A. For example, the etching treatment of the insulating film 125A is preferably performed by a puddle method using a development apparatus and a development solution because the above-described first etching treatment is performed before post-baking. This allows the insulating film 125A to be processed without providing a new apparatus in addition to the apparatuses used for light exposure, development, and post-baking. For example, in the case where an aluminum oxide film is used as the insulating film 125A, the insulating film 125A can be processed by wet etching using a developer including TMAH. In the case of employing a wet etching method, a mixed acid chemical solution containing water, phosphoric acid, diluted hydrofluoric acid, and nitric acid may be used. A chemical solution used for the wet etching treatment may be alkaline or acid.
Here, wet etching is preferably performed by a method that consumes a small amount of etchant; for example, a puddle method is preferred. Note that the etching area of the insulating film 125A in the connection portion 140 is extremely larger than the etching area of the insulating film 125A in the display portion. Thus, in the connection portion 140, a limitation for supply of the etchant is caused in the puddle method, for example, and the etching rate is likely to be lower than that in the display portion. The difference in etching rate between the display portion and the connection portion 140 causes a problem of unstable processing of the insulating film 125A. For example, when the etching time is determined in accordance with the etching rate in the connection portion 140, the insulating film 125A in the display portion may be etched excessively. When the etching time is determined in accordance with the etching rate in the display portion, the insulating film 125A in the connection portion 140 may remain without being sufficiently etched. Meanwhile, in a method for constantly supplying a new liquid so as not cause a difference in etching rate (e.g., a spin method), a large amount of etchant is consumed.
In view of the above, light exposure and development of the insulating film 127a in the connection portion 140 may be performed separately from light exposure and development of the insulating film 127a in the display portion. This allows the etching conditions (e.g., etching time) of the insulating film 125A in the connection portion 140 to be controlled independently from those in the display portion, thereby inhibiting both excess etching of the insulating film 125A in the display portion and insufficient etching of the insulating film 125A in the connection portion 140, so that the insulating film 125A can be processed into a desired shape.
Next, a process of the case where light exposure and development of the insulating film 127a in the display portion are performed separately from light exposure and development of the insulating film 127a in the connection portion 140 is described with reference to
After the insulating film 127a is formed (
Next, the region of the insulating film 127a exposed to light is removed by development. Thus, the insulating film 127a is formed in the whole display portion and a region surrounding the conductive layer 123 (
There is no particular limitation on the development method, and a dip method, a spin method, a puddle method, a vibration method, or the like can be employed. Note that in order to stabilize the etching rate, a method in which new liquid is constantly supplied is preferably employed. Alternatively, a method in which supply and holding (development) of liquid are repeated (also referred to as a step puddle method) is preferably employed. The step puddle method is preferable because liquid consumption can be reduced and the etching rate can be stabilized as compared to the method in which new liquid is constantly supplied.
Next, etching treatment is performed using the insulating film 127a as a mask to remove part of the insulating film 125A in the connection portion 140 and thin part of the sacrificial layer 118B. In the connection portion 140, a surface of the thinned portion of the sacrificial layer 118B is exposed (
A method that can be used for the first etching treatment can be employed for the etching treatment.
In the etching treatment performed on the connection portion 140, the etching treatment is stopped when the sacrificial layer 118B is thinned before the sacrificial layer 118B is completely removed. The sacrificial layer 118B in the connection portion 140 is processed also in etching treatment described later. When the sacrificial layer 118B is completely removed in the etching treatment at this stage, the insulating film 125A and the sacrificial layer below the end portion of the insulating layer 127 disappear due to side etching in the subsequent etching treatment, which might cause a cavity. When the sacrificial layer 118B remains over the conductive layer 123 in this manner, excess etching of the sacrificial layer 118B and damage of the conductive layer 123 can be prevented in a later process.
Note that depending on the thickness of the insulating film 125A and the thickness of the sacrificial layer 118B, the etching treatment may be stopped after only part of the insulating film 125A is thinned. In the case where the insulating film 125A is formed using a material similar to that for the sacrificial layer 118B and accordingly the boundary between the insulating film 125A and the sacrificial layer 118B is unclear, whether the insulating film 125A is removed or thinned and whether the sacrificial layer 118B is thinned cannot be determined in some cases.
Next, light exposure is performed in the display portion (
Next, the region of the insulating film 127a exposed to light is removed by development, so that the insulating layer 127b is formed (
Next, as illustrated in
Note that the process of the etching treatment illustrated in
At the stage of
After that, the above-described post-baking and second etching treatment are performed, whereby the insulating layer 125 and the insulating layer 127 can be formed.
As described above, light exposure and development of a film to be the insulating layer 127 in the connection portion 140 are performed separately from light exposure and development of the film in the display portion, whereby the processing conditions of the film to be the insulating layer 125 in the connection portion 140 can be controlled independently from those in the display portion. As a result, the insulating layer 125 can be processed into a desired shape to reduce defects in manufacturing the display device.
Note that a difference in etching rate between the connection portion 140 and the display portion can be sufficiently small in some cases depending on the apparatus, the method, and the like of the etching treatment. Furthermore, a difference between the etching area of the insulating film 125A in the connection portion 140 and the etching area of the insulating film 125A in the display portion can be sufficiently small in some cases depending on the layout of the connection portion 140 and the insulating layer 127b, and the like. In such a case, light exposure and development of the insulating film 127a for the display portion and the connection portion 140 are preferably performed in the same process, as illustrated in
Next, the common layer 114 and the common electrode 115 are formed in this order over the insulating layer 127, the layer 113B, the layer 113G, and the layer 113R (
The common layer 114 can be formed by an evaporation method (including a vacuum evaporation method), a transfer method, a printing method, an ink-jet method, a coating method, or the like.
The common electrode 115 can be formed by a sputtering method or a vacuum evaporation method, for example. Alternatively, a film formed by an evaporation method and a film formed by a sputtering method may be stacked.
Examples of methods for forming the protective layer 131 include a vacuum evaporation method, a sputtering method, a CVD method, and an ALD method.
As described above, in the manufacturing method of a display device in this embodiment, the island-shaped layer 113B, the island-shaped layer 113G, and the island-shaped layer 113R are formed not by using a fine metal mask but by processing a film formed over the entire surface; thus, the island-shaped layers can be formed to have a uniform thickness. Consequently, a high-resolution display device or a display device with a high aperture ratio can be obtained. Furthermore, even when the resolution or the aperture ratio is high and the distance between subpixels is extremely short, contact between the layer 113B, the layer 113G, and the layer 113R can be inhibited in adjacent subpixels. Accordingly, generation of leakage current between subpixels can be inhibited. Thus, it is possible to prevent crosstalk due to unintended light emission, so that a display device with extremely high contrast can be achieved.
As described above, when a tandem structure is employed at least for a light-emitting device that emits blue light, the reliability of a blue-light-emitting device whose luminance or the like easily deteriorates can be improved. Moreover, when the reliability of the blue-light-emitting device is improved, the reliability of the display device can be improved. Furthermore, a red-light-emitting device employs a single structure for a simplified manufacturing process, so that the yield in the manufacturing process of the display device can be increased.
This embodiment can be combined with the other embodiments as appropriate.
In this embodiment, a display device of one embodiment of the present invention is described with reference to
In this embodiment, pixel layouts different from the layout in
The top surface shape of the subpixel illustrated in the drawings in this embodiment corresponds to the top surface shape of a light-emitting region (or a light-receiving region).
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.
The range of the circuit layout of the subpixels is not limited to the range of the subpixels illustrated in the drawings and circuits may be placed outside the subpixels.
The pixel 110 illustrated in
The pixel 110 illustrated in
Pixels 124a and 124b illustrated in
The pixels 124a and 124b illustrated in
In
For example, in each pixel illustrated in
In a photolithography method, as a pattern to be processed 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 has a polygonal shape with rounded corners, an elliptical shape, a circular shape, or the like in some cases.
Furthermore, in the method for manufacturing the display device of one embodiment of the present invention, the EL layer is processed into an island shape using 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 after being processed. 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 whose top surface has a square shape is intended to be formed, a resist mask whose top surface has a circular shape may be formed, and the top surface of the EL layer may have a circular shape.
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 (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.
As illustrated in
The pixels 110 illustrated in
The pixels 110 illustrated in
The pixel 110 illustrated in
The pixel 110 illustrated in
The pixel 110 illustrated in
The pixels 110 illustrated in
The subpixels 110a, 110b, 110c, and 110d can include light-emitting devices emitting light of different colors. The subpixels 110a, 110b, 110c, and 110d can be subpixels of four colors of R, G, B, and white (W), subpixels of four colors of R, G, B, and Y, or subpixels of R, G, B, and infrared light (IR), for example.
In the pixels 110 illustrated in
The pixel 110 may include a subpixel including a light-receiving device.
In the pixels 110 illustrated in
In the pixels 110 illustrated in
There is no particular limitation on the wavelength of light detected by the subpixel S including a light-receiving device. The subpixel S can have a structure where one or both of visible light and infrared light are detected.
As illustrated in
The pixel 110 illustrated in
The pixel 110 illustrated in
In the pixels 110 illustrated in
In the pixels 110 illustrated in
In the pixels 110 illustrated in
In a pixel including the subpixels R, G, B, IR, and S, while an image is displayed using the subpixels R, G, and B, reflected light of infrared light emitted from the subpixel IR that is used as a light source can be detected by the subpixel S.
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 device of one embodiment of the present invention. The display device of one embodiment of the present invention can have a structure where 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 any of the other embodiments as appropriate.
In this embodiment, display devices of embodiments of the present invention are described with reference to
The display device of this embodiment can be a high-resolution display device. Accordingly, the display device of 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 that can be worn on the head, such as a VR device like a head-mounted display (HMD) and a glasses-type AR device.
The display device of this embodiment can be a high-definition display device or a large-sized display device. Accordingly, the display device 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 or 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 emitted 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 of
The pixel circuit portion 283 includes a plurality of pixel circuits 283a arranged periodically.
One pixel circuit 283a is a circuit that controls driving of a plurality of elements included in one pixel 284a. One pixel circuit 283a can be provided with three circuits each controlling light emission of one light-emitting device. 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 a gate of the selection transistor, and a source signal is input to a source of the selection transistor. Thus, an active-matrix display device is achieved.
The circuit portion 282 includes a circuit for driving the pixel circuits 283a in the pixel circuit portion 283. For example, the circuit portion 282 preferably includes one or both of a gate line driver circuit and a source line driver circuit. The circuit portion 282 may also include at least one of an arithmetic circuit, a memory circuit, a power supply circuit, and the like.
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 where one or both of the pixel circuit portion 283 and the circuit portion 282 are stacked below the pixel portion 284; hence, 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 greater than or equal to 40% and less than 100%, preferably greater than or equal to 50% and less than or equal to 95%, further preferably greater than or equal to 60% and less than or equal to 95%. Furthermore, the pixels 284a can be arranged extremely densely and thus the display portion 281 can have 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 extremely high resolution, and thus can be suitably used for a VR device such as an HMD 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 prevented 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 for a display portion of a wearable electronic device, such as a wrist watch.
The display device 100A illustrated in
The substrate 301 corresponds to the substrate 291 in
The transistor 310 includes 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 between these conductive layers. 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.
Note that a conductive layer surrounding the outer surface of the display portion 281 (or the pixel portion 284) is preferably provided in at least one layer of the conductive layers included in the layer 101 including transistors. The conductive layer can be referred to as a guard ring. By providing the conductive layer, elements such as a transistor and a light-emitting device can be inhibited from being broken by high voltage application due to ESD (electrostatic discharge) or charging caused by a step using plasma.
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. The light-emitting device 130R, the light-emitting device 130G, and the light-emitting device 130B are provided over the insulating layer 255c.
The sacrificial layer 118R is positioned over the layer 113R included in the light-emitting device 130R, the sacrificial layer 118G is positioned over the layer 113G included in the light-emitting device 130G, and the sacrificial layer 118B is positioned over the layer 113B included in the light-emitting device 130B. Here, the layer 113B has a tandem structure. As a result, the reliability of the light-emitting device 130B and the display device can be improved. The layer 113R has a single structure. The layer 113G may have a single structure or a tandem structure.
The pixel electrode 111R, the pixel electrode 111G, and the pixel electrode 111B are each electrically connected to one of the source and the drain of the transistor 310 through a plug 256 embedded in the insulating layer 243, 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 top surface of the insulating layer 255c and the top surface of the plug 256 are level or substantially level with each other. 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 attached onto the protective layer 131 with the resin layer 122. Embodiment 1 can be referred to for the details of components ranging from the light-emitting devices to the substrate 120. The substrate 120 corresponds to the substrate 292 in
The display devices illustrated in
The light-receiving device 150 includes the pixel electrode 111S, the layer 113S, the common layer 114, and the common electrode 115 which are stacked. Embodiment 1 and Embodiment 3 can be referred to for the details of the display device including the light-receiving device.
As illustrated in
In
Alternatively, the substrate 120 may be provided with the lens array 133 and bonded onto the protective layer 131 with the resin layer 122. By providing the lens array 133 for the substrate 120, the heat treatment temperature in the formation step of the lens array 133 can be increased.
The display device 100B illustrated in
In the display device 100B, a substrate 301B provided with the transistor 310B, the capacitor 240, and the light-emitting devices is attached 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 function 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 described later 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 the 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. As the insulating layer 344, an inorganic insulating film that can be used as 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.
A conductive layer 341 is provided over the insulating layer 346 over the substrate 301A. The conductive layer 341 is preferably provided to be embedded in the 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 attached to each other favorably.
The conductive layer 341 and the conductive layer 342 are preferably formed using the same conductive material. For example, it is possible to use a metal film including an element selected from Al, Cr, Cu, Ta, Ti, Mo, and W, or a metal nitride film including any of the above elements as a component (a titanium nitride film, a molybdenum nitride film, or a tungsten nitride film). In particular, copper is preferably used for the conductive layer 341 and the conductive layer 342. In that case, it is possible to employ Cu—Cu (copper-to-copper) direct bonding (a technique for achieving electrical continuity by connecting Cu (copper) pads).
The display device 100C illustrated in
As illustrated in
The display device 100D illustrated in
A transistor 320 is a transistor (hereinafter, also referred to as an OS transistor) that includes a metal oxide having semiconductor characteristics (also referred to as an oxide semiconductor) in its semiconductor layer where a channel is formed.
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 can prevent 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 film having semiconductor characteristics (also referred to as an oxide semiconductor). The pair of conductive layers 325 is provided over and in contact with the semiconductor layer 321 and functions 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 can prevent 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 planarized so as to be level 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 function as interlayer insulating layers. The insulating layer 329 functions as a barrier layer that can prevent diffusion of impurities such as water and hydrogen from the insulating layer 265 or the like into the transistor 320. For 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 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 covering the side surface of an opening formed 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. For the conductive layer 274a, a conductive material that does not easily allow diffusion of hydrogen and oxygen is preferably used.
The display device 100E illustrated in
The display device 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 to the structure. For example, three or more transistors may be stacked.
The display device 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 for driving the pixel circuit (a gate line driver circuit or a source line driver 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 or the like can be formed directly under the light-emitting device; thus, the display device can be downsized as compared to the case where the driver circuit is provided around a display region.
In the display device 100G, a substrate 152 and a substrate 151 are attached to each other. In
The display device 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 the connection portions 140 may 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 device 100G illustrated in
The light-emitting devices 130R, 130G, and 130B each have a structure similar to the stacked-layer structure illustrated in
The light-emitting device 130R includes a conductive layer 112R, a conductive layer 126R over the conductive layer 112R, and a conductive layer 129R over the conductive layer 126R. All of the conductive layers 112R, 126R, and 129R 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 the conductive layer 112G, the conductive layer 126G over the conductive layer 112G, and the conductive layer 129G over the conductive layer 126G.
The light-emitting device 130B 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 conductive layer 112R is connected to the conductive layer 222b included in the transistor 205 through an opening provided in the insulating layer 214. An end portion of the conductive layer 126R is positioned outward from an end portion of the conductive layer 112R. The end portion of the conductive layer 126R and an end portion of the conductive layer 129R 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 112R and the conductive layer 126R, and a conductive layer functioning as a transparent electrode can be used as the conductive layer 129R.
Detailed description of the conductive layers 112G, 126G, and 129G of the light-emitting device 130G and the conductive layers 112B, 126B, and 129B of the light-emitting device 130B is omitted because these conductive layers are similar to the conductive layers 112R, 126R, and 129R of the light-emitting device 130R.
Depressed portions are formed with the conductive layers 112R, 112G, and 112B so as to cover the openings provided in the insulating layer 214. A layer 128 is embedded in each of the depressed portions.
The layer 128 has a planarization function for the depressed portions of the conductive layers 112R, 112G, and 112B. The conductive layers 126R, 126G, and 126B electrically connected to the conductive layers 112R, 112G, and 112B, respectively, are provided over the conductive layers 112R, 112G, and 112B and the layer 128. Thus, regions overlapping with the depressed portions of the conductive layers 112R, 112G, and 112B 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. Specifically, the layer 128 is preferably formed using an insulating material and is particularly preferably formed using an organic insulating material. For the layer 128, an organic insulating material that can be used for the insulating layer 127 can be used, for example.
Top and side surfaces of the conductive layers 126R and 129R are covered with the layer 113R. Similarly, top and side surfaces of the conductive layers 126G and 129G are covered with the layer 113G, and top and side surfaces of the conductive layers 126B and 129B are covered with the layer 113B. Accordingly, regions provided with the conductive layers 126R, 126G, and 126B 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 surface and part of the top surface of each of the layer 113B, the layer 113G, and the layer 113R are covered with the insulating layers 125 and 127. The sacrificial layer 118B is positioned between the layer 113B and the insulating layer 125. The sacrificial layer 118G is positioned between the layer 113G and the insulating layer 125, and the sacrificial layer 118R is positioned between the layer 113R and the insulating layer 125. The common layer 114 is provided over the layer 113B, the layer 113G, the layer 113R, and the insulating layers 125 and 127, and the common electrode 115 is provided over the common layer 114. The common layer 114 and the common electrode 115 are each a continuous film provided to be shared by a plurality of light-emitting devices.
The protective layer 131 is provided over the light-emitting devices 130R, 130G, and 130B. The protective layer 131 and the substrate 152 are bonded to each other with an adhesive layer 142. The substrate 152 is provided with a light-blocking layer 117. A solid sealing structure, a hollow sealing structure, or the like can be employed to seal the light-emitting devices. In
The protective layer 131 is provided at least in the display portion 162, and preferably provided to cover the entire display portion 162. The protective layer 131 is preferably provided to cover not only the display portion 162 but also the connection portion 140 and the circuit 164. It is also preferable that the protective layer 131 be provided to extend to an end portion of the display device 100G. Meanwhile, a connection portion 204 has a portion not provided with the protective layer 131 so that the FPC 172 and a conductive layer 166 are electrically connected to each other.
The connection portion 204 is provided in a region of the substrate 151 not overlapping with the substrate 152. In the connection portion 204, the wiring 165 is electrically connected to the FPC 172 through the conductive layer 166 and a connection layer 242. In the shown example, the conductive layer 166 has a stacked-layer structure of a conductive film obtained by processing the same conductive film as the conductive layers 112R, 112G, and 112B, a conductive film obtained by processing the same conductive film as the conductive layers 126R, 126G, and 126B, and a conductive film obtained by processing the same conductive film as the conductive layers 129R, 129G, and 129B. On the top surface of the connection portion 204, the conductive layer 166 is exposed. Thus, the connection portion 204 and the FPC 172 can be electrically connected to each other through the connection layer 242.
For example, the protective layer 131 is formed over the entire surface of the display device 100G and then a region of the protective layer 131 overlapping with the conductive layer 166 is removed, so that the conductive layer 166 can be exposed.
A stacked-layer structure of at least one organic layer and a conductive layer may be provided over the conductive layer 166, and the protective layer 131 may be provided over the stacked-layer structure. Then, a peeling trigger (a portion that can be a trigger of peeling) may be formed in the stacked-layer structure using a laser or a sharp cutter (e.g., a needle or a utility knife) to selectively remove the stacked-layer structure and the protective layer 131 thereover, so that the conductive layer 166 may be exposed. For example, the protective layer 131 can be selectively removed when an adhesive roller is pressed to the substrate 151 and then moved relatively while being rolled. Alternatively, an adhesive tape may be attached to the substrate 151 and then peeled. Since the adhesion between the organic layer and the conductive layer or between the organic layers is low, separation occurs at the interface between the organic layer and the conductive layer or in the organic layer. Thus, a region of the protective layer 131 overlapping with the conductive layer 166 can be selectively removed. Note that when the organic layer or the like remain over the conductive layer 166, the remaining organic layer or the like can be removed by an organic solvent or the like.
As the organic layer, it is possible to use at least one of the organic layers (a layer functioning as a light-emitting layer, a carrier-blocking layer, a carrier-transport layer, or a carrier-injection layer) used for the layer 113B, the layer 113G, and the layer 113R, for example. The organic layer may be formed concurrently with or provided separately from the layer 113B, the layer 113G, and the layer 113R. The conductive layer can be formed using the same step and the same material as those for the common electrode 115. An ITO film is preferably formed as the common electrode 115 and the conductive layer, for example. In the case where a stacked-layer structure is used for the common electrode 115, at least one of the layers included in the common electrode 115 is provided as the conductive layer.
The top surface of the conductive layer 166 may be covered with a mask so that the protective layer 131 is not provided over the conductive layer 166. As the mask, a metal mask (area metal mask) or a tape or a film having adhesiveness or attachability may be used. The protective layer 131 is formed while the mask is placed and then the mask is removed, so that the conductive layer 166 can be kept exposed even after the protective layer 131 is formed.
With such a method, a region not provided with the protective layer 131 can be formed in the connection portion 204, and the conductive layer 166 and the FPC 172 can be electrically connected to each other through the connection layer 242 in the region.
The conductive layer 123 is provided over the insulating layer 214 in the connection portion 140. In the illustrated example, the conductive layer 123 has a stacked-layer structure of a conductive film obtained by processing the same conductive film as the conductive layers 112R, 112G, and 112B; a conductive film obtained by processing the same conductive film as the conductive layers 126R, 126G, and 126B; and a conductive film obtained by processing the same conductive film as the conductive layers 129R, 129G, and 129B. The end portion of the conductive layer 123 is covered with the sacrificial layer 118B, 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. It is possible that the common layer 114 is not formed in the connection portion 140. In that case, the conductive layer 123 and the common electrode 115 are in direct contact with each other to be electrically connected to each other.
The display device 100G has a top-emission structure. Light emitted from the light-emitting device is emitted toward the substrate 152 side. For the substrate 152, a material having a high visible-light-transmitting property is preferably used. The pixel electrode includes a material reflecting visible light, and the counter electrode (the common electrode 115) includes a material transmitting visible light.
A stacked-layer structure ranging from the substrate 151 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 step.
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 that does not easily allow diffusion of impurities such as water and hydrogen is preferably used for at least one of the insulating layers that cover the transistors. Thus, the insulating layer can function as a barrier layer. This structure can effectively inhibit diffusion of impurities into the transistors from the outside and improve the reliability of the display device.
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, an aluminum nitride film, or the like 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 also 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 outermost layer of the insulating layer 214 preferably has a function of an etching protective layer. Accordingly, a depressed portion can be inhibited from being formed in the insulating layer 214 in processing the conductive layer 112R, the conductive layer 126R, the conductive layer 129R, or the like. Alternatively, a depressed portion may be provided in the insulating layer 214 in processing the conductive layer 112R, the conductive layer 126R, the conductive layer 129R, 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 a 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 device 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 bottom-gate transistor structure may be employed. Alternatively, gates may be provided above and below the semiconductor layer where a channel is formed.
The transistor 201 and the transistor 205 employ a structure where the semiconductor layer where a channel is formed is provided between two gates. 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, a single crystalline semiconductor, and a semiconductor having crystallinity other than single crystal (a microcrystalline semiconductor, a polycrystalline semiconductor, or a semiconductor partly including crystal regions) may be used. A single crystal semiconductor or 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 having semiconductor characteristics (an oxide semiconductor). That is, a transistor including a metal oxide in its channel formation region (an OS transistor) is preferably used for the display device of this embodiment.
Examples of the metal oxide that can be used for the semiconductor layer include indium oxide, gallium oxide, and zinc oxide. The metal oxide preferably includes two or three selected from indium, an element M, and zinc. The element M is one or more kinds selected from gallium, aluminum, silicon, boron, yttrium, tin, copper, vanadium, beryllium, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, cobalt, and magnesium. Specifically, the element M is preferably one or more kinds selected from aluminum, gallium, yttrium, and tin.
It is particularly preferable that an oxide containing indium (In), gallium (Ga), and zinc (Zn) (IGZO) be used as the metal oxide used for the semiconductor layer. Alternatively, it is preferable to use an oxide containing indium, tin, and zinc (also referred to as ITZO (registered trademark)). Further alternatively, it is preferable to use an oxide containing indium, gallium, tin, and zinc. Alternatively, it is preferable to use an oxide containing indium (In), aluminum (Al), and zinc (Zn) (also referred to as IAZO). Further alternatively, it is preferable to use an oxide containing indium (In), aluminum (Al), gallium (Ga), and zinc (Zn) (also referred to as IAGZO).
In the case where the metal oxide used for 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, in the case where the atomic ratio is described as In:Ga:Zn=4:2:3 or a composition in the neighborhood thereof, a 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. In addition, in the case where the atomic ratio is described as In:Ga:Zn=5:1:6 or a composition in the neighborhood thereof, a 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. In addition, in the case where the atomic ratio is described as In:Ga:Zn=1:1:1 or a composition in the neighborhood thereof, a 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 semiconductor layer may include two or more metal oxide layers having different compositions. For example, a stacked-layer structure of a first metal oxide layer having In:M:Zn=1:3:4 [atomic ratio] or a composition in the neighborhood thereof and a second metal oxide layer having In:M:Zn=1:1:1 [atomic ratio] or a composition in the neighborhood thereof and being formed over the first metal oxide layer can be favorably employed. In particular, gallium or aluminum is preferably used as the element M.
For another example, a stacked-layer structure of one selected from indium oxide, indium gallium oxide, and IGZO, and one selected from IAZO, IAGZO, and ITZO (registered trademark) may be employed.
As the oxide semiconductor having crystallinity, a CAAC (c-axis aligned crystalline)-OS, an nc (nanocrystalline)-OS, and the like are given.
Alternatively, a transistor including silicon in a channel formation region (a Si transistor) may be used. Examples of silicon include single crystal silicon, polycrystalline silicon, and amorphous silicon. In particular, a transistor including 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 a Si transistor such as an LTPS transistor, 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. This allows simplification of an external circuit mounted on the display device and a reduction in component cost and mounting cost.
An OS transistor has much higher field-effect mobility than a transistor using 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, the power consumption of the display device can be reduced with use of the OS transistor.
To increase the emission luminance of the light-emitting device included in a pixel circuit, it is necessary to increase the amount of current flowing through the light-emitting device. For that purpose, the source-drain voltage of the driving transistor included in the pixel circuit needs to be increased. 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. Thus, with use of an OS transistor as a driving transistor included in the pixel circuit, the amount of current flowing through the light-emitting device can be increased, resulting in an increase in emission luminance of the light-emitting device.
When a transistor operates in a saturation region, a change in source-drain current relative 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 included in the pixel circuit, 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 current flowing when a transistor operates in a saturation region, even in the case where the source-drain voltage of an OS transistor increases gradually, more stable current (saturation current) can be made flow through an OS transistor than through a Si transistor. Thus, with use of an OS transistor as a driving transistor, current can be made flow stably through the light-emitting device, for example, even when a variation in current-voltage characteristics of the EL device occurs. 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 use of an OS transistor as the driving transistor included in the pixel circuit, it is possible to achieve “inhibition of black blurring”, “increase in emission luminance”, “increase in the number of gray levels”, “inhibition of variation in light-emitting devices”, and the like.
The transistors included in the circuit 164 and the transistors included in the display portion 162 may have the same structure or different structures. A plurality of transistors included in the circuit 164 may have the same structure or two or more kinds of structures. Similarly, a plurality of transistors included in the display portion 162 may have the same structure or two or more kinds of structures.
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 device can have low power consumption and high drive capability. A structure where an LTPS transistor and an OS transistor are used in combination is referred to as LTPO in some cases. As a more suitable example, a structure where the OS transistor is used as a transistor or the like functioning as a switch for controlling continuity and discontinuity between wirings, and the LTPS transistor is used as a transistor or the like for controlling current, can be given.
For example, one transistor included in the display portion 162 functions as a transistor for controlling current flowing through the light-emitting device and can also 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. Thus, current flowing through the light-emitting device in the pixel circuit can be increased.
In contrast, another transistor included in the display portion 162 functions as a switch for controlling selection and non-selection of a pixel and can also 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 device 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 device 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. This structure can significantly reduce the leakage current that might flow through a transistor, and the leakage current that might flow between adjacent light-emitting devices (also referred to as a lateral leakage current, a side leakage current, or the like). With the structure, a viewer can observe 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 device. Note that when the leakage current that might flow through a transistor and the lateral leakage current between light-emitting devices are extremely low, light leakage or the like (what is called black blurring) that might occur in black display can be reduced as much as possible.
In particular, in the case where a light-emitting device having the MML structure employs the above-described SBS structure, a layer provided between light-emitting devices (for example, also referred to as an organic layer or a common layer which is shared by the light-emitting devices) is isolated; accordingly, side leakage can be prevented or be made extremely low.
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
The light-blocking layer 117 is preferably provided on the surface of the substrate 152 on the substrate 151 side. 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.
Any of the materials that can be used for the substrate 120 can be used for each of the substrate 151 and the substrate 152.
Any of the materials 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 device 100H illustrated in
Light emitted from 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 112R, the conductive layer 126R over the conductive layer 112R, and the conductive layer 129R over the conductive layer 126R.
The light-emitting device 130B includes a conductive layer 112B, a conductive layer 126B over the conductive layer 112B, and a 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 112R, 112B, 126R, 126B, 129R and 129B. A material reflecting visible light is preferably used for the common electrode 115.
Although not illustrated in
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 two or more.
The level of the top surface of the layer 128 and the level of the top surface of the conductive layer 112R may be equal to or substantially equal to each other, or may be different from each other. For example, the level of the top surface of the layer 128 may be lower or higher than the level of the top surface of the conductive layer 112R.
A display device 100J illustrated in
The light-receiving device 150 includes a conductive layer 112S, a conductive layer 126S over the conductive layer 112S, and a conductive layer 129S over the conductive layer 126S.
The conductive layer 112S 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 126S and the top and side surfaces of the conductive layer 129S are covered with the layer 113S. The layer 113S includes at least an active layer.
The side surface and part of the top surface of the layer 113S are covered with the insulating layers 125 and 127. The sacrificial layer 118S is positioned between the layer 113S and the insulating layer 125. The common layer 114 is provided over the layer 113S 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.
The display device 100J can employ any of the pixel layouts that are described in Embodiment 5 with reference to
This embodiment can be combined with any of the other embodiments as appropriate.
In this embodiment, electronic devices of one embodiment of the present invention will be described with reference to
Electronic devices of this embodiment each include the display device of one embodiment of the present invention in a display portion. The resolution and definition of display device of one embodiment of the present invention can be easily increased. Thus, the display device 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 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 electronic devices with a relatively large screen, such as a television device, a desktop or notebook personal computer, a monitor of a computer or the like, digital signage, and a large game machine such as a pachinko machine.
In particular, the display device of one embodiment of the present invention can have high resolution, and thus can be suitably used for an electronic device including 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 capable of being worn on a head, such as a VR device like a head-mounted display, a glasses-type AR device, and an MR device.
The definition of the display device 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, the definition is preferably 4K, 8K, or higher. The pixel density (resolution) of the display device 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. The use of the display device having one or both of such high definition and high resolution can further increase realistic sensation, sense of depth, and the like for personal use such as portable use and home use of electronic devices. There is no particular limitation on the screen ratio (aspect ratio) of the display device of one embodiment of the present invention. For example, the display device 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 sensing, detecting, or measuring force, displacement, position, speed, acceleration, angular velocity, rotational frequency, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, electric power, radiation, flow rate, humidity, gradient, oscillation, a smell, or infrared rays).
The electronic device in this embodiment can have a variety of functions. For example, the electronic device can have a function of displaying a variety of information (a still image, a moving image, a text image, and the like) 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 device of one embodiment of the present invention can be used for the display panels 751. Thus, the electronic device can perform display with extremely high resolution.
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 an image signal or the like can be supplied by the wireless communication device. Note that instead of the wireless communication device or in addition to the wireless communication device, a connector to which a cable for supplying an image signal and a power supply potential can be connected 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 touch on the outer surface of the housing 721. A tap operation or a slide operation, for example, by the user can be detected with the touch sensor module, whereby a variety of processing can be executed. For example, processing such as a pause or a restart of a moving image can be executed by a tap operation, and processing such as fast forward and fast rewind can be executed by a slide operation. The touch sensor module is provided in each of the two housings 721, whereby the range of the operation can be increased.
A variety of touch sensors can be used for the touch sensor module. For example, any of touch sensors of various types such as a capacitive type, a resistive type, an infrared type, an electromagnetic induction type, a surface acoustic wave type, and an optical type can be employed. 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. 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 device of one embodiment of the present invention can be used for the display portions 820. Thus, the electronic device can perform display with extremely high resolution. This enables a user to feel high sense of immersion.
The display portions 820 are provided at a position 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 portion 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 cover a plurality of fields of view, such as a telescope field of view and a wide field of view.
Although an example including the image-capturing portion 825 is described here, a range sensor (hereinafter, also referred to as a sensing portion) that is capable of measuring a distance from an object may be provided. That is, the image-capturing portion 825 is one mode 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. With the use of images obtained by the camera and images obtained by the distance image sensor, more pieces of 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, a structure including the vibration mechanism can be employed for any one or more of the display portion 820, the housing 821, and the wearing portion 823. Thus, without additionally using an audio device such as headphones, earphones, or a speaker, the user can enjoy images and sounds 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 an image signal from an image output device or the like, electric power for charging a 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 have 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 illustrated in
The electronic device may include an earphone portion. The electronic device 700B illustrated 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 device 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 placed 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.
The display device of one embodiment of the present invention can be used as the display panel 6511. Thus, an extremely lightweight electronic device can be obtained. Since the display panel 6511 is extremely thin, the battery 6518 with high capacity can be mounted while an increase in thickness of the electronic device is suppressed. 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 the pixel portion, whereby an electronic device with a narrow bezel can be obtained.
The display device 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 where 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 by wire or wirelessly 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 device of one embodiment of the present invention can be used for the display portion 7000.
Digital signage 7300 illustrated in
The display device of one embodiment of the present invention can be used for the display portion 7000 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 the display portion 7000 attracts more attention, so that the effectiveness of the advertisement can be increased, for example.
A touch panel is preferably used in the display portion 7000, in which case intuitive operation by a user is possible in addition to display of an image or a moving image on the display portion 7000. 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 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 device of one embodiment of the present invention can be used for the display portion 9001 in
The electronic devices illustrated in
The electronic devices illustrated in
This embodiment can be combined with any of the other embodiments as appropriate.
11B: subpixel, 11G: subpixel, 11R: subpixel, 11S: subpixel, 100A: display device, 100B: display device, 100C: display device, 100D: display device, 100E: display device, 100F: display device, 100G: display device, 100H: display device, 100J: display device, 100: display device, 101: layer, 110a: subpixel, 110b: subpixel, 110c: subpixel, 110d: subpixel, 110e: subpixel, 110: pixel, 111B: pixel electrode, 111G: pixel electrode, 111R: pixel electrode, 111S: pixel electrode, 111: pixel electrode, 112B: conductive layer, 112G: conductive layer, 112R: conductive layer, 112S: conductive layer, 113B: layer, 113b: film, 113G: layer, 113g: film, 113R: layer, 113r: film, 113S: layer, 114: common layer, 115: common electrode, 117: light-blocking layer, 118B: sacrificial layer, 118b: sacrificial film, 118G: sacrificial layer, 118g: sacrificial film, 118R: sacrificial layer, 118r: sacrificial film, 118S: sacrificial layer, 118: sacrificial layer, 119B: sacrificial layer, 119b: sacrificial film, 119G: sacrificial layer, 119g: sacrificial film, 119R: sacrificial layer, 119r: sacrificial film, 120: substrate, 122: resin layer, 123: conductive layer, 124a: pixel, 124b: pixel, 125A: insulating film, 125: insulating layer, 126B: conductive layer, 126G: conductive layer, 126R: conductive layer, 126S: conductive layer, 127a: insulating film, 127b: insulating layer, 127: insulating layer, 128: layer, 129B: conductive layer, 129G: conductive layer, 129R: conductive layer, 129S: conductive layer, 130B: light-emitting device, 130G: light-emitting device, 130R: light-emitting device, 131: protective layer, 132a: mask, 132b: mask, 132B: coloring layer, 132G: coloring layer, 132R: coloring layer, 132: mask, 133: lens array, 134: insulating layer, 136: insulating layer, 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, 190B: resist mask, 190G: resist mask, 190R: 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, 500: display device, 501: electrode, 502: electrode, 512B_1: light-emitting unit, 512B_2: light-emitting unit, 512B_3: light-emitting unit, 512G_1: light-emitting unit, 512G_2: light-emitting unit, 512R_1: light-emitting unit, 521: layer, 522: layer, 523B: light-emitting layer, 523G: light-emitting layer, 523R: light-emitting layer, 524: layer, 525: layer, 531: charge-generation layer, 550B: light-emitting device, 550G: light-emitting device, 550R: light-emitting device, 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, 761: lower electrode, 762: upper electrode, 765: layer, 766: layer, 767: active layer, 768: layer, 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, 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 control, 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 |
|---|---|---|---|
| 2021-208827 | Dec 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2022/062034 | 12/12/2022 | WO |
