Patent Grant
11960174
The present invention relates to a semiconductor device, a liquid crystal display device and an electronic appliance. In particular, the present invention relates to a liquid crystal display device and an electronic appliance that control molecular orientation of liquid crystal molecules by generation of an electrical field parallel to a substrate.
As for a liquid crystal display device, there are a vertical electrical field type in which an electrical field vertical to a substrate is applied to liquid crystal and a transverse electrical field type in which an electrical field parallel to a substrate is applied to liquid crystal. A liquid crystal display device of a transverse electrical field type is superior in a viewing angle characteristic to that of a vertical electrical field type.
As a method for controlling a gray scale by generating an electrical field parallel to a substrate (transverse electrical field) to move liquid crystal molecules in a plane parallel to the substrate, there are an IPS (In-Plane Switching) mode and an FFS (Fringe-Field Switching) mode.
An IPS liquid crystal display device is provided with two interdigitated electrodes (also referred to as comb teeth-shaped electrodes or comb-shaped electrodes) over one of a pair of substrates. A transverse electrical field is generated by a potential difference between these electrodes (one of interdigitated electrodes is a pixel electrode and the other is a common electrode), which moves liquid crystal molecules in a plane parallel to the substrate.
An FFS liquid crystal display device is provided with a second electrode over one of a pair of substrates, and a first electrode over the second electrode. The first electrode has a slit (opening pattern), and the second electrode has a plate shape (planar shape to cover most slits of the first electrodes). A transverse electrical field is generated by a potential difference between these electrodes (one of the first electrode and the second electrode is a pixel electrode and the other is a common electrode), which moves liquid crystals in a plane parallel to the substrate.
That is, the liquid crystal molecules which are oriented parallel to the substrate (so-called homogeneous orientation) can be controlled in a direction parallel to the substrate; therefore, a viewing angle is increased.
Conventionally, a pixel electrode or a common electrode has been a light-transmissive conductive film; therefore, it has been formed of ITO (indium tin oxide) (Patent Document 1: Japanese Published Patent Application No. 2000-89255).
As described above, the pixel electrode or the common electrode has been a light-transmissive conductive film; therefore, it has been formed of ITO conventionally. Accordingly, the number of manufacturing steps and masks, and manufacturing cost have been increased.
An object of the present invention is to provide a semiconductor device, a liquid crystal display device, and an electronic appliance each having a wide viewing angle, which is manufactured through a smaller number of steps using less masks at low cost compared with a conventional device.
A liquid crystal display device of the present invention includes a substrate, and a transistor and a liquid crystal element that are formed over the substrate. Further, a semiconductor film of the transistor and a pixel electrode or a common electrode of the liquid crystal element are films formed in the same step.
Note that the liquid crystal element is only necessary to be capable of rotating a molecular orientation of liquid crystal molecules controlling the amount of light generally in direction parallel to the substrate by a transverse electrical field generated due to a potential difference between the pixel electrode and the common electrode provided to connect between pixels of a plurality of pixels in a pixel portion.
According to a structure of a liquid crystal display device of the present invention, a transistor and a liquid crystal element provided with a first electrode and a second electrode are provided over a substrate, and the first electrode includes a film in the same layer as a semiconductor layer of the transistor.
According to another structure of a liquid crystal display device of the present invention, a first electrode, a second electrode, and a transistor are provided over a substrate, and the first electrode includes a film in the same layer as a semiconductor layer of the transistor. A molecular orientation of liquid crystal molecules in a liquid crystal layer is changed depending on a potential difference between the first electrode and the second electrode.
According to another structure of a liquid crystal display device of the present invention, in the above structure, the first electrode is a comb-teeth shaped electrode, and the second electrode is a plate-like electrode.
According to another structure of a liquid crystal display device of the present invention, a transistor and a liquid crystal element provided with a first electrode, a second electrode, and a third electrode are provided over a substrate, and the first electrode or the second electrode includes a film in the same layer as a semiconductor layer of the transistor. The second electrode and the third electrode are electrically connected.
According to another structure of a liquid crystal display device of the present invention, a transistor and a liquid crystal element provided with a first electrode and a second electrode are provided over a substrate, and the first electrode and the second electrode each include a film in the same layer as a semiconductor layer of the transistor.
According to another structure of a liquid crystal display device of the present invention, a first electrode, a second electrode, and a transistor are provided over a substrate, and the first electrode and the second electrode each include a film in the same layer as a semiconductor layer of the transistor. A molecular orientation of liquid crystal molecules in a liquid crystal layer is changed depending on a potential difference between the first electrode and the second electrode.
According to another structure of a liquid crystal display device of the present invention, a first electrode, a second electrode, a third electrode, and a transistor are provided over a substrate, and the first electrode includes a film in the same layer as a semiconductor layer of the transistor. A molecular orientation of liquid crystal molecules in a liquid crystal layer is changed by an electrical field generated due to a potential difference between the first electrode and the second electrode, and an electrical field generated due to a potential difference between the first electrode and the third electrode.
According to another structure of a liquid crystal display device of the invention, in the above structure, the first electrode and the second electrode are comb teeth-shaped electrodes.
According to another structure of a liquid crystal display device of the invention, in the above structure, the first electrode and the second electrode are comb teeth-shaped electrodes, and the third electrode is a plate-like electrode.
An electronic appliance of the present invention includes the liquid crystal display device having any of the above structures for a display portion.
A switch used in the present invention may be any switch such as an electrical switch or a mechanical switch. That is, it may be anything as long as it can control a current flow and is not limited to a particular type. It may be, for example, a transistor, a diode (PN diode, PIN diode, Schottky diode, diode-connected transistor, or the like), a thyristor, or a logic circuit configured with them. Therefore, in the case of using a transistor as a switch, polarity (conductivity) thereof is not particularly limited because the transistor operates as a simple switch. However, when an off current is preferred to be small, a transistor of polarity with a small off current is preferably used. For example, a transistor which has an LDD region or a multi-gate structure has a small off current. Further, it is desirable that an n-channel transistor be employed when the potential of a source terminal of the transistor operating as a switch is closer to a low potential side power source (Vss, GND, 0 V or the like), and a p-channel transistor be employed when a potential of the source terminal is closer to a high potential side power source (Vdd or the like). This helps the switch operate efficiently since the absolute value of the gate-source voltage of the transistor can be increased.
It is to be noted that a CMOS switch can also be applied by using both n-channel and p-channel transistors. In the case of such a CMOS switch, a current can be applied when a switch of either the p-channel transistor or the n-channel transistor is conductive, which helps the switch operate efficiently. For example, even when a voltage of an input signal to a switch is either high or low, an appropriate voltage can be outputted. In addition, a voltage amplitude value of a signal for turning on or off a switch can be made small; therefore, power consumption can be lowered. It is to be noted that when a transistor is used as a switch, the transistor includes an input terminal (one of a source terminal and a drain terminal), an output terminal (the other of the source terminal and the drain terminal), and a terminal for controlling conduction (gate terminal). On the other hand, when a diode is used as a switch, there is the case where a terminal for controlling conduction is not included. Thus, the number of wirings for controlling terminals can be reduced.
Note that in the present invention, the description “being connected” includes the case where elements are electrically connected, the case where elements are functionally connected, and the case where elements are directly connected. Accordingly, in the configurations disclosed by the present invention, other elements may be interposed between elements having a predetermined connecting relation. For example, one or more elements which enable an electrical connection (for example, a switch, a transistor, a capacitor, an inductor, a resistor, or a diode) may be provided between a certain portion and a certain portion. In addition, one or more circuits which enable a functional connection may be provided between connection, such as a logic circuit (for example, an inverter, a NAND circuit, or a NOR circuit), a signal converter circuit (for example, a DA converter circuit, an AD converter circuit, or a gamma correction circuit), a potential level converter circuit (for example, a power supply circuit such as a booster circuit or a step-down circuit, or a level shifter circuit for changing a potential level of an H signal or an L signal), a voltage source, a current source, a switching circuit, or an amplifier circuit (for example, a circuit which can increase the signal amplitude, the amount of current, or the like, such as an operational amplifier, a differential amplifier circuit, a source follower circuit, or a buffer circuit), a signal generating circuit, a memory circuit, or a control circuit. Alternatively, the elements may be directly connected without other elements or other circuits interposed therebetween. Note that when elements are connected without other elements or circuits interposed therebetween, such elements are described as “being directly connected” in this specification. On the other hand, when elements are described as “being electrically connected”, the following cases are included: the case where such elements are electrically connected (that is, connected with other elements interposed therebetween), the case where such elements are functionally connected (that is, connected with other circuits interposed therebetween), and the case where such elements are directly connected (that is, connected without other elements or other circuits interposed therebetween).
Note that various modes besides a liquid crystal element can be applied to a display element. For example, a display medium in which contrast is changed by an electromagnetic effect can be used, such as an EL element (organic EL element, inorganic EL element, EL element containing organic material and inorganic material), an electron emitting element, a liquid crystal element, an electronic ink, a light diffraction element, a discharging element, a digital micromirror device (DMD), a piezoelectric element, or a carbon nanotube. It is to be noted that an EL panel type display device using an EL element includes an EL display; a display device using an electron emitting element includes a field emission display (FED), an SED type flat panel display (Surface-conduction Electron-emitter Display), and the like; a liquid crystal panel type display device using a liquid crystal element includes a liquid crystal display; a digital paper type display device using an electronic ink includes electronic paper; a display device using a light diffraction element includes a grating light valve (GLV) type display; a PDP (Plasma Display Panel) type display using a discharging element includes a plasma display; a DMD panel type display device using a micromirror element includes a digital light processing (DLP) type display device; a display device using a piezoelectric element includes a piezoelectric ceramic display; a display device using a carbon nanotube includes a nano emissive display (NED); and the like.
Note that in the present invention, various types of transistors can be applied to a transistor. Therefore, types of transistors which can be applied are not limited to a certain type. For example, a thin film transistor (TFT) including a non-single crystalline semiconductor film typified by amorphous silicon or polycrystalline silicon can be applied. With use of them, following advantages can be provided: such transistors can be manufactured at a low manufacturing temperature, can be manufactured at low cost, and can be formed over a large substrate, and transistors that can transmit light can be manufactured by being formed over a light-transmissive substrate. In addition, a MOS transistor, a junction transistor, a bipolar transistor, a transistor formed using a semiconductor substrate or an SOI substrate, or the like can be employed. With use of them, transistors with few variations, transistors with a high current supply capability, or transistors with a small size can be manufactured, and a circuit with low power consumption can be constructed. Further, a transistor including a compound semiconductor such as ZnO, a-InGaZnO, SiGe, or GaAs, or a thin film transistor obtained by thinning such compound semiconductors can be employed. Accordingly, such transistors can be manufactured at a low manufacturing temperature, can be manufactured at a room temperature, and can be formed directly on a low heat-resistant substrate such as a plastic substrate or a film substrate. A transistor or the like formed by an ink-jet method or a printing method may also be employed. With use of them, such transistors can be manufactured at a room temperature, can be manufactured at a low vacuum, and can be manufactured using a large substrate. In addition, since such transistors can be manufactured without use of a mask (reticle), the layout of the transistors can be easily changed. A transistor including an organic semiconductor or a carbon nanotube, or other transistors can be applied as well. With use of them, the transistors can be formed over a substrate which can be bent. Note that a non-single crystalline semiconductor film may include hydrogen or halogen. In addition, various types of substrates can be applied to a substrate provided with transistors are formed without limitation to a certain type. With use of them, transistors may be formed using, for example, a single crystalline substrate or an SOI substrate, a glass substrate, a quartz substrate, a plastic substrate, a paper substrate, a cellophane substrate, a stone substrate, a stainless steel substrate, or a substrate made of a stainless steel foil. In addition, after formation of transistors over a substrate, the transistors may be transposed onto another substrate. With use of the aforementioned substrates, transistors with excellent properties and with low power consumption can be formed, and thus, a device that is not easily broken or have high heat resistance can be formed.
A transistor can have various structures without limitation to a certain structure. For example, a multi-gate structure having two or more gate electrodes may be used. With the multi-gate structure, channel regions are connected in series; therefore, a plurality of transistors are connected in series. With the multi-gate structure, an off current can be reduced, and the withstand voltage of the transistor can be increased, which improves reliability. In addition, even if a drain-source voltage fluctuates when the transistor operates in a saturation region, drain-source current does not fluctuate very much, and stable characteristics can be provided. In addition, a structure in which gate electrodes are formed above and below a channel may be used. With the use of the structure in which gate electrodes are formed above and below the channel, a channel region is enlarged so that the amount of current flowing therethrough is increased, or a depletion layer can be easily formed, so that the S value is decreased. Further, when the gate electrodes are provided above and below the channel, a plurality of transistors are connected in parallel.
Further, a gate electrode may be provided above or below the channel. Either a staggered structure or an inversely staggered structure may be employed. A channel region may be divided into a plurality of regions, or connected in parallel or in series. Further, a source electrode or a drain electrode may overlap with a channel (or a part of it), thereby preventing a charge from being accumulated in a part of the channel and being unstable operation. Further, an LDD region may be provided. By providing an LDD region, an off current can be reduced and reliability can be improved by improving the withstand voltage of a transistor, and further stable characteristics can be obtained since a drain-source current does not change so much even when a drain-source voltage changes in the operation in a saturation region.
It is to be noted in the present invention that one pixel corresponds to the smallest unit of an image. Accordingly, in the case of a full color display device formed of color elements of R (red), G (green), and B (blue), one pixel is formed of a dot of an R color element, a dot of a G color element, and a dot of a B color element. It is to be noted that color elements are not limited to three colors, and may be formed of more than three colors or a color other than RGB. For example, RGB to which white is added (RGBW) or RGB to which one or more colors selected from yellow, cyan, magenta, emerald green, vermilion, and the like are added can be employed. Alternatively, a similar color to at least one of RGB may be added to RGB, for example, R, G, B1, and B2 may be employed. Although B1 and B2 are both blue, they have slightly different frequencies. By using such a color element, a more realistic image can be displayed and power consumption can be reduced. It is to be noted that one pixel may include a plurality of dots of certain color elements of a certain color. In this case, each of the plurality of dots of the color elements may each have a different size of region which contributes to display. Further, a gray scale may be expressed by controlling each of the plurality of dots of the color elements. This method is referred to as an area gray scale method. Alternatively, the viewing angle may be expanded by supplying each of a plurality of dots of a certain color elements with a slightly different signal.
It is to be noted in the present invention that pixels may be arranged in matrix. Here, the case where pixels are arranged in matrix corresponds to the case where pixels are arranged on a straight line or a jagged line in vertical direction and transverse direction. Therefore, the case where pixels are arranged in matrix also corresponds to the case where pixels are arranged in the form of stripes or the case where dots of three color elements are arranged in what is called a delta pattern or in a Bayer pattern when full color display is carried out using the three color elements (for example, RGB). It is to be noted that color elements are not limited to three colors and may be more than three colors, for example, RGBW (W is white) or RGB to which one or more of yellow, cyan, magenta, and the like are added. The dots of the color elements may have different sizes of a display regions. Accordingly, reduction in power consumption and longer lifetime of a display element can be achieved.
Note that a transistor is an element having at least three terminals of a gate, a drain, and a source. The transistor has a channel region between a drain region and a source region, and can supply a current through the drain region, the channel region, and the source region. Here, since the source and the drain of the transistor may change depending on the structure, the operating conditions, and the like of the transistor, it is difficult to define which is a source or a drain. Therefore, in the present invention, a region functioning as a source or a drain may not be called the source or the drain. In such the case, for example, one of the source and the drain may be called a first terminal and the other terminal may be called a second terminal. Note also that a transistor may be an element having at least three terminals of a base, an emitter, and a collector. In this case also, one of the emitter and the collector may be similarly called a first terminal and the other terminal may be called a second terminal.
A gate wiring (also referred to as a scan line, a gate line, a gate signal line, or the like) means a wiring for connecting between gate electrodes of pixels, or a wiring for connecting a gate electrode to another wiring.
However, there is a portion functioning as both a gate electrode and a gate wiring. Such a region may be called either a gate electrode or a gate wiring. That is, there is a region where a gate electrode and a gate wiring cannot be clearly distinguished from each other. For example, in the case where a channel region overlaps with an extended gate wiring, the overlapped region functions as both a gate wiring and a gate electrode. Accordingly, such a region may be called either a gate electrode or a gate wiring.
In addition, a region formed of the same material as a gate electrode and connected to the gate electrode may also be called a gate electrode. Similarly, a region formed of the same material as a gate wiring and connected to the gate wiring may also be called a gate wiring. In a strict sense, such a region may not overlap with a channel region, or may not have a function of connecting to another gate electrode. However, there is a region formed of the same material as a gate electrode or a gate wiring and connected to the gate electrode or the gate wiring due to precision or the like in manufacturing. Accordingly, such a region may also be called either a gate electrode or a gate wiring.
In a multi-gate transistor, for example, a gate electrode of one transistor is often connected to a gate electrode of another transistor with use of a conductive film which is formed of the same material as the gate electrode. Since such a region is a region for connecting a gate electrode to another gate electrode, it may be called a gate wiring, while it may also be called a gate electrode since a multi-gate transistor can be considered as one transistor. That is, a region which is formed of the same material as a gate electrode or a gate wiring and connected thereto may be called either the gate electrode or the gate wiring. In addition, for example, a part of a conductive film which connects a gate electrode and a gate wiring may also be called either a gate electrode or a gate wiring.
Note that a gate terminal means a part of a gate electrode or a part of a region which is electrically connected to the gate electrode.
It is to be noted that a source includes a source region, a source electrode, and a source wiring (also referred to as source line, source signal line, or the like), or a part of them. A source region corresponds to a semiconductor region which contains a lot of P-type impurities (boron, gallium, or the like) or N-type impurities (phosphorus, arsenic, or the like). Therefore, a region containing a small amount of P-type impurities or N-type impurities, that is, an LDD (Lightly Doped Drain) region is not included in a source region. A source electrode corresponds to a conductive layer of a part which is formed of a different material from a source region and electrically connected to the source region. However, a source electrode may be referred to as a source electrode including a source region. A source wiring corresponds to a wiring for connecting source electrodes of pixels and connecting a source electrode and another wiring.
However, there is a part which functions as a source electrode and also as a source wiring. Such a region may be referred to as a source electrode or a source wiring. That is, there is a region which cannot be specifically determined as a source electrode or a source wiring. For example, when there is a source region overlapping a source wiring which is extended, the region functions as a source wiring and also as a source electrode. Therefore, such a region may be referred to as a source electrode or a source wiring.
Further, a portion which is formed of the same material as a source electrode and connected to the source electrode may be referred to as a source electrode as well. A portion which connects one source electrode and another source electrode may also be referred to as a source electrode as well. Further, a portion overlapping a source region may be referred to as a source electrode. Similarly, a region which is formed of the same material as a source wiring and connected to the source wiring may be referred to as a source wiring. In a strict sense, such a region may not have a function to connect to another source electrode. However, there is a region which is formed of the same material as a source electrode or a source wiring and connected to a source electrode or a source wiring due to a manufacturing margin and the like. Therefore, such a region may also be referred to as a source electrode or a source wiring.
Also, for example, a conductive film of a portion which connects a source electrode and a source wiring may be referred to as a source electrode or a source wiring.
It is to be noted that a source terminal corresponds to a part of a source region, a source electrode, or a region electrically connected to a source electrode.
It is to be noted that as for a drain, the similar thing to a source can be applied.
It is to be noted in the present invention that a semiconductor device corresponds to a device including a circuit having a semiconductor element (transistor, diode, or the like). Further, a semiconductor device may be a general device which can function by utilizing semiconductor characteristics.
Further, a display device corresponds to a device including a display element (liquid crystal element, EL element, or the like). It is to be noted that a display device may be a main body of a display panel in which a plurality of pixels including display elements such as liquid crystal elements or EL elements and a peripheral driver circuit for driving the pixels are formed over the same substrate. Further, a display device may include a peripheral driver circuit disposed over a substrate by wire bonding or a bump, that is, a so-called chip on glass (COG). Furthermore, a display device may include the one provided with a flexible printed circuit (FPC) or a printed wiring board (PWB) (IC, resistor, capacitor, inductor, transistor, or the like). Moreover, a display device may include an optical sheet such as a polarizing plate or a retardation film. In addition, a backlight unit (such as a light guide plate, a prism sheet, a diffusion sheet, a reflection sheet, a light source (an LED, a cold-cathode tube, or the like)) may be included.
A light emitting device corresponds to a display device including a self-light emitting display element such as an EL element or an element used for an FED in particular. A liquid crystal display device corresponds to a display device including a liquid crystal element.
It is to be noted in the present invention that when it is described that an object is formed on another object, it does not necessarily mean that the object is in direct contact with the another object. In the case where the above two objects are not in direct contact with each other, still another object may be interposed therebetween. Accordingly, when it is described that a layer B is formed on a layer A, it means either the case where the layer B is formed in direct contact with the layer A, or the case where another layer (such as a layer C or a layer D) is formed in direct contact with the layer A, and then the layer B is formed in direct contact with the another layer. In addition, when it is described that an object is formed over or above another object, it does not necessarily mean that the object is in direct contact with the another object, and another object may be interposed therebetween. Accordingly, when it is described that a layer B is formed over or above a layer A, it means either the case where the layer B is formed in direct contact with the layer A, or the case where another layer (such as a layer C or a layer D) is formed in direct contact with the layer A, and then the layer B is formed in direct contact with the another layer. Similarly, when it is described that an object is formed below or under another object, it means either the case where the objects are in direct contact with each other or not in contact with each other.
Therefore, a liquid crystal display device with a wide viewing angle and low manufacturing cost compared with a conventional device can be provided.
Although the present invention is fully described by way of embodiment modes and embodiments with reference to the accompanying drawings, it is to be understood that various changes and modifications will be apparent to those skilled in the art. Therefore, unless such changes and modifications depart from the spirit and the scope of the present invention, they should be construed as being included therein.
First, brief description is made of a structure of a display panel of Embodiment Mode 1 of the present invention.
In the display panel of Embodiment Mode 1 of the present invention, a liquid crystal layer is sandwiched between a first substrate and a second substrate provided so as to face the first substrate.
A pixel portion of a display panel of Embodiment Mode 1 of the present invention is formed over a first substrate. The pixel portion includes a plurality of wirings (hereinafter referred to as signal lines) that are supplied with a signal (hereinafter referred to as a video signal) for expressing a gray scale and a plurality of wirings (hereinafter referred to as scan lines) that selects a pixel to which the video signal is written.
In the pixel portion, a plurality of pixels are arranged in matrix corresponding to the scan lines and the signal lines. Each pixel is connected to any one of the scan lines and any one of the signal lines. Each pixel includes at least one transistor and a pixel electrode.
The transistor of each pixel is provided in the vicinity of intersection of the scan line and the signal line. The transistor controls charge and discharge of a charge to the pixel electrode of each pixel.
Further, each pixel includes a liquid crystal element in which a molecular orientation of liquid crystal molecules in a liquid crystal layer is changed depending on a potential difference between the pixel electrode provided independently for each pixel and a common electrode provided to connect between pixels of a plurality of pixels in the pixel portion.
As the liquid crystal layer, a ferroelectric liquid crystal (FLC), a nematic liquid crystal, a smectic liquid crystal, a liquid crystal which is to be homogeneously oriented, a liquid crystal which is to be homeotropically oriented, or the like can be used.
An electrical field is generated by a potential difference between the pixel electrode and the common electrode. The electrical field includes many transverse components that are parallel to the first substrate (that is, parallel to the pixel electrode and the common electrode). A change of the molecular orientation of liquid crystal molecules means rotation of a liquid crystal molecule in a plane parallel to the first substrate (that is, in a plane parallel to the pixel electrode and the common electrode).
It is to be noted that, in this specification, “rotation in a plane parallel to an electrode” includes parallel rotation which includes discrepancy invisible to the human eye. In other words, “rotation in a plane parallel to an electrode” also includes rotation which mainly includes vector components in a plane direction but also includes a few vector components in a normal direction in addition to the vector components in the plane direction.
For example, an IPS liquid crystal display device includes pixel electrodes 9201 and common electrodes 9202 over a substrate 9200 as shown in
An FFS liquid crystal display device includes common electrodes 9302 over a substrate 9300 and pixel electrodes 9301 over the common electrode 9302 as shown in
Furthermore, a liquid crystal display device for which an IPS mode and an FFS mode are combined includes second common electrode 9403 over a substrate 9400 and pixel electrodes 9401 and first common electrodes 9402 over the second common electrode 9403 as shown in
Thus, it is allowed as long as the molecular orientation of the liquid crystal molecules controlling the amount of light can be rotated in a parallel direction with respect to the substrate by a transverse electrical field generated due to a potential difference between the pixel electrode and the common electrode. Therefore, electrodes having various shapes can be used as the pixel electrode and the common electrode. That is, liquid molecules tilt in an electrical field direction when a transverse electrical field is generated due to a potential difference between the pixel electrode and the common electrode, whereby the liquid crystal layer may transmit light (such a display device is referred to as a display device of a normally black mode) or the liquid crystal layer may transmit no light (such a display device is referred to as a display device of a normally white mode).
For example, as for an electrode shape seen from above the substrate, a interdigitated electrode (also referred to as a comb teeth-shaped electrode or a comb-shaped electrode), an electrode provided with a slit (opening), or an electrode covering an entire surface (also referred to as a plate-like electrode) can be used as each of the pixel electrode and the common electrode.
Examples of electrode shapes seen from above the substrate are shown in
In
In
In
In
In
In
In
In
Note that these are examples of electrode shapes, and the present invention is not limited thereto.
Thus, in this specification, a comb teeth-shaped electrode includes an electrode having a shape in which in a branch portion of an electrode, one end of a branch is connected to an end of another branch adjacent to the branch. An electrode provided with a slit includes an electrode having a shape in which in a branch portion of an electrode, both ends of adjacent branches are connected. A plate-like electrode includes an electrode extending across regions of a plurality of branches of the other electrodes.
Further, a cross-sectional shape of the pixel electrode and the common electrode may be a concave-convex shape, a meandering shape or a planar shape. In the case where the pixel electrode or the common electrode is used as an reflective film of a reflective liquid crystal display panel or a semi-transmissive liquid crystal display panel, the cross-sectional shape of the pixel electrode or the common electrode is a concave-convex shape or a meandering shape, whereby outside light can be reflected diffusely by the pixel electrode or the common electrode. Therefore, luminance can be improved and at the same time, mirroring reflection can be prevented. Note that various combinations can be applied to the shape of the pixel electrode and the shape of the common electrode.
It is to be node that in the reflective liquid crystal display panel or the semi-transmissive liquid crystal display panel, an insulating film may be made to function as a light scattering layer by formation of a concave-convex surface of the insulating film in a reflection region or addition of particles for scattering light in the insulating film. Thus, even if the reflective film does not have a concave-convex surface, mirroring reflection can be prevented, so that an electrical field having components in a desired direction component can be formed easily for a liquid crystal layer when the pixel electrode or the common electrode is used as the reflective film.
Further, a film for adjusting thickness of a liquid crystal layer may be arranged in the semi-transmissive liquid crystal display panel in order to thin thickness of the liquid crystal layer (so-called cell gap) between a portion which reflects light to perform display (reflection region) and a portion which transmits light from a backlight or the like to perform display (transmission region).
Note that in the case of the reflective liquid crystal display panel or the semi-transmissive liquid crystal display panel, the path length of light passing through the liquid crystal layer does not vary significantly depending on a portion in one pixel. Therefore, an insulating film for adjusting thickness of the liquid crystal layer (cell gap) is not necessarily arranged.
Note that a direction in which liquid crystal molecules tilt when a transverse electrical field generated due to a potential difference between the pixel electrode and the common electrode is deviated from the electrical field direction, whereby a liquid crystal display panel with higher responsivity can be provided. Further, responsivity between intermediate gray scales may be enhanced by provision of a so-called overdrive circuit that is a control circuit for driving liquid crystal molecules at a high speed.
Note that shapes of the pixel electrode and the common electrode are devised, whereby so-called multi-domain orientation may be achieved. That is to say, when a transverse electrical field is generated in the liquid crystal layer due to a potential difference between the pixel electrode and the common electrode, the liquid crystal molecules are set to tilt in a plurality of directions. Thus, variation of color tones depending on a viewing angle may be reduced. In that case, it is set that the pixel electrode and the common electrode are electrodes each provided with a boomerang-shaped slit or a zigzag slit, or branch portions of the electrodes each have a boomerang shape or a zigzag shape. Accordingly, variation of color tones depending on a viewing angle can be extremely small; therefore, a liquid crystal display panel with high chromatic purity and high contrast ratio can be provided.
For the pixel electrode or the common electrode, films formed in the same step as a film used for a semiconductor layer (a semiconductor film functioning as a channel, a source, or a drain) of the transistor is used. Note that for at least a part of the pixel electrode or the common electrode, films formed in the same step as a film used for the semiconductor layer of the transistor may be used.
For the semiconductor layer of the transistor, a non-single crystalline semiconductor film (including an amorphous semiconductor film and a polycrystalline semiconductor film) typified by an amorphous semiconductor and a polycrystalline semiconductor (also referred to as polysilicon) can be used. Alternatively, a compound semiconductor film of ZnO, a-InGaZnO or the like may be used. A non-single crystalline semiconductor film may contain hydrogen or halogen. That is to say, a non-single crystalline semiconductor film or a compound semiconductor film is used also for at least a part of the pixel electrode or the common electrode.
Note that the semiconductor layer of the transistor desirably has thickness such that light is transmitted. Preferably, the semiconductor layer of the transistor has thickness of 10 nm to 100 nm, more preferably, 45 nm to 60 nm. Further, a non-single crystalline semiconductor film or a compound semiconductor film each having thickness approximately equal to that of the semiconductor layer of the transistor is preferably used also for at least a part of the pixel electrode or the common electrode.
Films formed in the same step as a film used for the semiconductor layer of the transistor each have a light-transmitting property; therefore, it is preferably used for the pixel electrode or the common electrode of the transmissive liquid crystal display panel, and a part of the pixel electrode or the common electrode of the semi-transmissive liquid crystal display panel. It is needless to say that they may be used for the pixel electrode or the common electrode of the reflective liquid crystal display panel.
Films formed in the same step means a plurality of films formed by separation of a stretch of film after formation of the stretch of film. The films formed in the same step are also referred to as films in the same layer. Therefore, when even films arranged over a stretch of film are in different layers if they are not formed in the same step, the films.
In other words, a stretch of film is formed by a chemical vapor deposition (CVD) method, a sputtering method, a vacuum evaporation method or a spin-coating method and the film is patterned, so that films in the same layer can be formed.
Note that patterning is to process a film shape, which means forming a film pattern by a photolithography technique (including, for example, forming a contact hole in photosensitive acrylic and processing photosensitive acrylic into a spacer), forming a mask pattern by a photolithography technique and etching with use of the mask pattern, or the like. That is, in the patterning step, a part of film is selectively removed.
The films in the same layer include those with different thicknesses or components.
For example, in the case of patterning films in the same layer, thickness of a mask pattern is controlled and the mask pattern is isotropically etched, thereby the films in the same layer can have different thicknesses or may include films containing different components by addition of impurities into a part of the films in the same layer.
Further, all of the films formed in the same step may be formed over a stretch of film, or some of the films formed in the same step may be formed over films in different layers.
That is, a bottom film contact with a first film and a second film formed in the same step is not limited.
Note that the above description is made of a main structure of the liquid crystal display panel of Embodiment Mode 1 of the present invention; however, the present invention is not limited to this. That is, a polarizing plate, a retardation film, a color filter, a backlight, a scan line driver circuit for supplying a signal to a scan line, a signal line driver circuit for supplying a signal to a signal line, and the like may be included.
For a backlight light source, a fluorescent lamp (a cold-cathode fluorescent tube or a hot-cathode fluorescent tube), a light-emitting diode, a CRT, an EL (inorganic or organic), an incandescent lamp, or the like can be used as appropriate. Also, a combination of a light guide plate, a reflector, a light source, a diffusion sheet, a reflection sheet, and the like can be a backlight.
That is, the liquid crystal display device described in this embodiment mode includes a substrate, and a transistor and a liquid crystal element that are formed over the substrate. Further, a semiconductor layer of the transistor and a pixel electrode or a common electrode of the liquid crystal element are films formed in the same step.
Note that the semiconductor layer of the transistor may be a part of the pixel electrode or the common electrode of the liquid crystal element. In other words, the pixel electrode and the common electrode of the liquid crystal element may have a stacked-layer structure of the semiconductor layer of the transistor and another conductive film.
Note that the liquid crystal element may rotate a molecular orientation of liquid crystal molecules controlling amount of light generally in a parallel direction with respect to the substrate by a transverse electrical field generated due to a potential difference between the pixel electrode and the common electrode provided to connect between pixels of a plurality of pixels in a pixel portion.
Further, the liquid crystal display panel of Embodiment Mode 1 of the present invention is described in detail.
A transistor, a first electrode to be a pixel electrode of a liquid crystal element, and a second electrode to be a common electrode of the liquid crystal element are formed over a first substrate. Note that in this specification, the first substrate over which the transistor, the first electrode, and the second electrode are formed is referred to as a circuit substrate. In addition, in a liquid crystal display panel, the circuit substrate and the second substrate (counter substrate) provided so as to face the circuit substrate are attached to each other, and a liquid crystal layer is interposed therebetween. Note that the first electrode to be the pixel electrode of the liquid crystal element and the second electrode to be the common electrode of the liquid crystal element may also be formed over the counter substrate.
Subsequently, a structure of a circuit substrate, which is applicable to the liquid crystal display panel of Embodiment Mode 1 of the present invention, is described below.
First, description is made of a first structure of the circuit substrate of Embodiment Mode 1 of the present invention.
Note that
The circuit substrate of
The circuit substrate of
The first electrode 6101 and the second electrode 6102 each have a comb-teeth shape, and are arranged so that branch portions of the electrodes are alternate. Note that in
Next, description is made of a second structure of the circuit substrate of Embodiment Mode 1 of the present invention.
Next, description is made of a third structure of the circuit substrate of Embodiment Mode 1 of the present invention.
Next, description is made of a fourth structure of the circuit substrate of Embodiment Mode 1 of the present invention.
Next, description is made of a fifth structure of the circuit substrate of Embodiment Mode 1 of the present invention.
Next, description is made of a sixth structure of the circuit substrate of Embodiment Mode 1 of the present invention.
Next, description is made of a seventh structure of the circuit substrate of Embodiment Mode 1 of the present invention.
Next, description is made of an eighth structure of the circuit substrate of Embodiment Mode 1 of the present invention.
Next, description is made of a ninth structure of the circuit substrate of Embodiment Mode 1 of the present invention.
Next, description is made of a tenth structure of the circuit substrate of Embodiment Mode 1 of the present invention.
Next, description is made of an eleventh structure of the circuit substrate of Embodiment Mode 1 of the present invention.
Next, description is made of a twelfth structure of the circuit substrate of Embodiment Mode 1 of the present invention.
Next, description is made of a thirteenth structure of the circuit substrate of Embodiment Mode 1 of the present invention.
Next, description is made of a fourteenth structure of the circuit substrate of Embodiment Mode 1 of the present invention.
Next, description is made of a fifteenth structure of the circuit substrate of Embodiment Mode 1 of the present invention.
Next, description is made of a sixteenth structure of the circuit substrate of Embodiment Mode 1 of the present invention.
A shape of the projection 7702 is reflected, whereby a concave-convex shape is formed on a surface of the conductive film 7701. Using the projection 7702 makes it easy to adjust great height differences of concavity and convexity and the number of concavity and convexity.
Next, description is made of a seventeenth structure of the circuit substrate of Embodiment Mode 1 of the present invention.
A shape of the projection 7802 is reflected, whereby a concave-convex shape is formed on a surface of the conductive film 7801. Using the projection 7802 makes it easy to adjust great height differences of concavity and convexity and the number of concavity and convexity.
Next, description is made of an eighteenth structure of the circuit substrate of Embodiment Mode 1 of the present invention.
A shape of the projection 7902 is reflected, whereby a concave-convex shape is formed on a surface of the conductive film 7901. Using the projection 7902 makes it easy to adjust great height differences of concavity and convexity and the number of concavity and convexity.
Next, description is made of a nineteenth structure of the circuit substrate of Embodiment Mode 1 of the present invention.
A shape of the projection 8001 is reflected, whereby a concave-convex shape is formed on a surface of the second electrode 7201. Using the projection 8001 makes it easy to adjust great height differences of concavity and convexity and the number of concavity and convexity.
Next, description is made of a twentieth structure of the circuit substrate of Embodiment Mode 1 of the present invention.
Next, description is made of a twenty-first structure of the circuit substrate of Embodiment Mode 1 of the present invention.
Next, description is made of a twenty-second structure of the circuit substrate of Embodiment Mode 1 of the present invention.
Next, description is made of a twenty-third structure of the circuit substrate of Embodiment Mode 1 of the present invention.
Next, description is made of a twenty-fourth structure of the circuit substrate of Embodiment Mode 1 of the present invention. The twenty-fourth structure is described with reference to a cross sectional view of a circuit substrate in
Next, description is made of a twenty-fifth structure of the circuit substrate of Embodiment Mode 1 of the present invention. The twenty-fifth structure is described with reference to a cross sectional view of a circuit substrate in
Next, description is made of a twenty-sixth structure of the circuit substrate of Embodiment Mode 1 of the present invention. The twenty-sixth structure is described with reference to a cross sectional view of a circuit substrate in
Next, description is made of a twenty-seventh structure of the circuit substrate of Embodiment Mode 1 of the present invention. The twenty-seventh structure is described with reference to a cross sectional view of a circuit substrate in
A shape of the projection 8601 is reflected, whereby a concave-convex shape is formed on a surface of the conductive film 8602. Using the projection 8601 makes it easy to adjust great height differences of concavity and convexity and the number of concavity and convexity.
Next, description is made of a twenty-eighth structure of the circuit substrate of Embodiment Mode 1 of the present invention. The twenty-eighth structure is described with reference to a cross sectional view of a circuit substrate in
A shape of the projections 8611 is reflected, whereby a concave-convex shape is formed on a surface of the conductive film 8612. Using the projections 8611 makes it easy to adjust great height differences of concavity and convexity and the number of concavity and convexity.
Next, description is made of a twenty-ninth structure of the circuit substrate of Embodiment Mode 1 of the present invention. The twenty-ninth structure is described with reference to a cross sectional view of a circuit substrate in
The shape of the projection 8621 is reflected, whereby a concave-convex shape is formed on a surface of the second electrode 8622. Using the projection 8621 makes it easy to adjust great height differences of concavity and convexity and the number of concavity and convexity.
Next, description is made of a thirtieth structure of the circuit substrate of Embodiment Mode 1 of the present invention. The thirtieth structure is described with reference to a cross sectional view of a circuit substrate in
Next, description is made of a thirty-first structure of the circuit substrate of Embodiment Mode 1 of the present invention. The thirty-first structure is described with reference to a cross sectional view of a circuit substrate in
Next, description is made of a thirty-second structure of the circuit substrate of Embodiment Mode 1 of the present invention. The thirty-second structure is described with reference to a cross sectional view of a circuit substrate in
Thus, circuit substrates having various structures can be applied to the liquid crystal display panel of Embodiment Mode 1 of the present invention.
Further, a main structure of a liquid crystal display panel in the case where the circuit substrate described above and a counter substrate are attached to each other is described below.
Description is made of a structure of the circuit substrate of the liquid crystal display panel shown in
An orientation film 8803 is formed over the first electrode 8801 and the second electrode 8802. Then, a retardation film 8804 is provided on a surface of the substrate 8800, on which the first electrode 8801 and the second electrode 8802 are not formed, and a polarizing plate is provided outside the retardation film 8804.
Next, description is made of a structure of the counter substrate of the liquid crystal display panel shown in
Note that color filters and a light-shielding layer (black matrix), or any of them may be provided for an insulating film formed over a circuit substrate, or for a part of the insulating film. By provision of the color filter or the light-shielding layer over the circuit substrate, a margin of alignment with the counter substrate can be improved.
In the liquid crystal display panel shown in
Note that like the display panel shown in
Needless to say that the first electrode 8801 and the second electrode 8802 are not necessary to be formed directly on the substrate 8800. As shown in
Further, as shown in
Description is made of a structure of a liquid crystal display panel of Embodiment Mode 2 of the present invention.
In the liquid crystal display panel of Embodiment Mode 2, a first insulating film is provided over a first substrate; a semiconductor layer of a transistor, and a first electrode and a second electrode of a liquid crystal element are provided over the first insulating film; a second insulating film is provided so as to cover the semiconductor layer of the transistor, and the first electrode and the second electrode of the liquid crystal element; a gate electrode is provided over the semiconductor layer of the transistor with the second insulating film interposed therebetween; a third insulating film is provided so as to cover the gate electrode and the second insulating film; a hole (contact hole) is formed in the third insulating film and the second insulating film; and a wiring formed over the third insulating film is connected to the semiconductor layer of the transistor through the hole. A surface of the first substrate, which is provided with the transistor, is attached to the second substrate. A liquid crystal layer is provided between the first substrate and the second substrate.
Note that the semiconductor layer of the transistor is a film formed in the same layer as the first electrode and the second electrode of the liquid crystal element.
Further, each of the first electrode and the second electrode of the liquid crystal element is an electrode having a slit or a comb-shaped electrode.
A base insulating film (the first insulating film 101) is formed over a substrate 100 in order to prevent impurities from diffusing from the substrate 100. The substrate 100 can be formed of an insulating substrate such as a glass substrate, a quartz substrate, a plastic substrate, or a ceramic substrate, or of a metal substrate, a semiconductor substrate, or the like. The first insulating film 101 can be formed by a CVD method or a sputtering method. For example, a silicon oxide film, a silicon nitride film, a silicon oxynitride film, or the like formed by a CVD method using SiH4, N2O, and NH3 as a source material can be applied. Alternatively, a stacked layer of them may be used. It is to be noted that the first insulating film 101 is provided to prevent impurities from diffusing from the substrate 100 into the semiconductor layer. In the case where the substrate 100 is formed of a glass substrate or a quartz substrate, it is not necessary to provide the first insulating film 101.
A semiconductor layer (channel formation regions 102a, an impurity region 102b, an impurity region 102c and an impurity region 102d) of a transistor 111, and a pixel electrode (first electrode 102e) and a common electrode (second electrode 1021) that control molecular orientation of the liquid crystal molecules are formed over the first insulating film 101. The channel formation regions 102a, the impurity region 102b, the impurity region 102c, the impurity region 102d, the first electrode 102e and the second electrode 102f are non-single crystalline semiconductor films (for example, polysilicon films), which are formed in the same step.
In the case where the transistor 111 is an n-channel transistor, an impurity element such as phosphorus or arsenic is introduced into the impurity region 102b, the impurity region 102c and the impurity region 102d, whereas in the case where the transistor 111 is a p-channel transistor, an impurity element such as boron is introduced into the impurity region 102b, the impurity region 102c, and the impurity region 102d.
Further, the impurity element introduced into the impurity region 102b, the impurity region 102c, and the impurity region 102d may also be introduced into the first electrode 102e and the second electrode 102f. The resistance of the first electrode 102e and the second electrode 102f is lowered when an impurity is introduced thereto, which is preferable for each of the first electrode 102e and the second electrode 102f to function as an electrode.
The first electrode 102e and the second electrode 102f each have thickness of, for example, 45 nm to 60 nm, and have sufficiently high light transmittance. In order to further improve the light transmittance, it is desirable to set thickness of the first electrode 102e and the second electrode 102f to be 40 nm or less.
The semiconductor layer (the channel formation region 102a, the impurity region 102b, the impurity region 102c, and the impurity region 102d) of the transistor 111, and the first electrode 102e and the second electrode 102f that control molecular orientation of the liquid crystal molecules are formed in the same step. In this case, the number of steps can be reduced, so that the manufacturing cost can be reduced. In addition, it is desirable that impurity elements of the same type be introduced into the impurity region 102b, the impurity region 102c, and the impurity region 102d; and the first electrode 102e and the second electrode 102f. This is because when the impurity elements of the same type are introduced, the impurity elements can be introduced without a problem even if the impurity region 102b, the impurity region 102c, and the impurity region 102d; and the first electrode 102e and the second electrode 102f are located close to each other, so that dense layout becomes possible. It is desirable to add impurity elements of only one of a p type and an n type because the manufacturing cost can be low compared with the case in which impurity elements of different types are introduced.
A gate insulating film (second insulating film 103) is formed over the semiconductor layer of the transistor 111, and the first electrode 102e and the second electrode 102f. In
Two gate electrodes 104 are formed over the channel formation region 102a of the transistor 111 with the second insulating film 103 interposed therebetween. For the gate electrodes 104, an aluminum (Al) film, a copper (Cu) film, a thin film containing aluminum or copper as a main component, a chromium (Cr) film, a tantalum (Ta) film, a tantalum nitride (TaN) film, a titanium (Ti) film, a tungsten (W) film, a molybdenum (Mo) film, or the like can be used.
An interlayer insulating film (third insulating film 105) is formed over the second insulating film 103 and the gate electrodes 104. The third insulating film 105 preferably has a stacked-layer structure. For example, a protective film and a planarization film may be stacked in this order. For the protective film, an inorganic insulating film is suitable. As an inorganic insulating film, a silicon nitride film, a silicon oxide film, a silicon oxynitride film, or a film formed by stacking these layers can be used. For a planarization film, a resin film is suitable. As a resin film, polyimide, polyamide, acrylic, polyimide amide, epoxy or the like can be used.
A signal line (wiring 106) is formed over the third insulating film 105. The wiring 106 is connected to the impurity region 102c through a hole (contact hole) formed in the third insulating film 105. As the wiring 106, a titanium (Ti) film, an aluminum (Al) film, a copper (Cu) film, an aluminum film containing Ti, or the like can be used. Preferably, copper having low resistance is used.
A first orientation film 107 is formed over the wiring 106 and the third insulating film 105. Then, a liquid crystal layer 108, a second orientation film 109 and a substrate 110 are provided over the first orientation film 107. That is, the liquid crystal layer 108 is interposed between the first orientation film 107 and the second orientation film 109. That is, the second orientation film 109 is formed over the substrate 110, and a surface of the substrate 110, on which the second orientation film 109 is formed, and a surface of the substrate 100, on which the first orientation film 107 is formed, are attached to each other. The liquid crystal layer 108 is provided between the first orientation film 107 and the second orientation film 109.
Description is made of a structure of a liquid crystal display panel of Embodiment Mode 3 of the present invention.
In the liquid crystal display panel of Embodiment Mode 3, a second electrode of a liquid crystal element is provided over a first substrate; a first insulating film is provided so as to cover the second electrode of the liquid crystal element; a semiconductor layer of a transistor, and a first electrode of the liquid crystal element are provided over the first insulating film; a second insulating film is provided so as to cover the semiconductor layer of the transistor, and the first electrode of the liquid crystal element; a gate electrode is provided over the semiconductor layer of the transistor with the second insulating film interposed therebetween; a third insulating film is provided so as to cover the gate electrode and the second insulating film; a hole (contact hole) is formed in the third insulating film and the second insulating film; and a wiring formed over the third insulating film is connected to the semiconductor layer of the transistor through the hole. A surface of the first substrate, which is provided with the transistor, is attached to the second substrate. A liquid crystal layer is provided between the first substrate and the second substrate.
Note that the semiconductor layer of the transistor is a film formed in the same layer as the first electrode of the liquid crystal element.
Further, the first electrode of the liquid crystal element is an electrode having a slit or a comb-shaped electrode, and the second electrode of the liquid crystal element is a plate-like electrode.
For the common electrode (second electrode 102f) in
The second electrode 301 may be either a conductive film having reflectivity or a conductive film having a light-transmitting property. As a conductive film having reflectivity, a metal film such as an aluminum (Al) film, a copper (Cu) film, a thin film containing aluminum or copper as a main component, a chromium (Cr) film, a tantalum (Ta) film, a tantalum nitride (TaN) film, a titanium (Ti) film, a tungsten (W) film, and a molybdenum (Mo) film are given. As a conductive film having a light-transmitting property, a transparent conductive film such as an indium tin oxide (ITO) film, an indium zinc oxide (IZO) film, an indium tin oxide containing silicon oxide (ITSO) film, a zinc oxide (ZnO) film, and a cadmium tin oxide (CTO) film are given. In the case where the second electrode 301 is a conductive film having reflectivity, the liquid crystal display panel of Embodiment Mode 3 of the present invention is a reflective liquid crystal display panel, whereas in the case where the second electrode 301 is a conductive film having a light-transmitting property, the liquid crystal display panel of Embodiment Mode 3 of the present invention is a light-transmissive liquid crystal display panel.
Description is made of a structure of a liquid crystal display panel of Embodiment Mode 4 of the present invention.
In the liquid crystal display panel of Embodiment Mode 4, a second electrode of a liquid crystal element is provided over a first substrate; a conductive film having reflectivity, which has smaller area than the second electrode, is provided over the second electrode of the liquid crystal element; a first insulating film is provided so as to overlap the second electrode of the liquid crystal element and the conductive film; a semiconductor layer of a transistor, and a first electrode of the liquid crystal element are provided over the first insulating film; a second insulating film is provided so as to cover the semiconductor layer of the transistor, and the first electrode of the liquid crystal element; a gate electrode is provided over the semiconductor layer of the transistor with the second insulating film interposed therebetween; a third insulating film is provided so as to cover the gate electrode and the second insulating film; a hole (contact hole) is formed in the third insulating film and the second insulating film; and a wiring formed over the third insulating film is connected to the semiconductor layer of the transistor through the hole. A surface of the first substrate, which is provided with the transistor, is attached to the second substrate. A liquid crystal layer is provided between the first substrate and the second substrate.
Note that the semiconductor layer of the transistor is a film formed in the same layer as the first electrode of the liquid crystal element.
Further, the first electrode of the liquid crystal element is an electrode having a slit or a comb-shaped electrode, and the second electrode of the liquid crystal element is a plate-like electrode.
In the liquid crystal display panel of Embodiment Mode 4 of the present invention, the second electrode 301 is preferably a conductive film having a light-transmitting property. As a conductive film having a light-transmitting property, a transparent conductive film such as an indium tin oxide (ITO) film, an indium zinc oxide (IZO) film, an indium tin oxide containing silicon oxide (ITSO) film, a zinc oxide (ZnO) film, and a cadmium tin oxide (CTO) film are given. The conductive film 401 is preferably a conductive film having reflectivity. As a conductive film having reflectivity, a metal film such as an aluminum (Al) film, a copper (Cu) film, a thin film containing aluminum or copper as a main component, a chromium (Cr) film, a tantalum (Ta) film, a tantalum nitride (TaN) film, a titanium (Ti) film, a tungsten (W) film, and a molybdenum (Mo) film are given.
The liquid crystal display panel of Embodiment Mode 4 of the present invention is suitable for a semi-transmissive liquid crystal display panel.
Description is made of a structure of a liquid crystal display panel of Embodiment Mode 5 of the present invention.
In the liquid crystal display panel of Embodiment Mode 5, a second electrode of a liquid crystal element is provided over a first substrate; a first insulating film is provided so as to overlap the second electrode of the liquid crystal element; a semiconductor layer of a transistor, and a first electrode of the liquid crystal element are provided over the first insulating film; a second insulating film is provided so as to overlap the semiconductor layer of the transistor, and the first electrode the liquid crystal element; a gate electrode is provided over the semiconductor layer of the transistor with the second insulating film interposed therebetween; a third insulating film is provided so as to overlap the gate electrode and the second insulating film; a hole (contact hole) is formed in the third insulating film and the second insulating film; and a wiring formed over the third insulating film is connected to the semiconductor layer of the transistor through the hole. A surface of the first substrate, which is provided with the transistor, is attached to the second substrate. A liquid crystal layer is provided between the first substrate and the second substrate.
Note that the semiconductor layer of the transistor is a film formed in the same layer as the first electrode of the liquid crystal element.
Further, each of the first electrode and the second electrode of the liquid crystal element is an electrode having a slit or a comb-shaped electrode, and branch portions thereof are provided alternately.
For the common electrode (second electrode 102f) in
The second electrode 501 may be either a conductive film having reflectivity or a conductive film having a light-transmitting property. As a conductive film having reflectivity, a metal film such as an aluminum (Al) film, a copper (Cu) film, a thin film containing aluminum or copper as a main component, a chromium (Cr) film, a tantalum (Ta) film, a tantalum nitride (TaN) film, a titanium (Ti) film, a tungsten (W) film, or a molybdenum (Mo) film is given. As a conductive film having a light-transmitting property, a transparent conductive film such as an indium tin oxide (ITO) film, indium zinc oxide (IZO) film, an indium tin oxide containing silicon oxide (ITSO) film, a zinc oxide (ZnO) film, or a cadmium tin oxide (CTO) film is given. The liquid crystal display panel of Embodiment Mode 3 of the present invention is either a reflective liquid crystal display panel or a light-transmissive liquid crystal display panel. In the case where the second electrode 301 is a conductive film having reflectivity, a reflective liquid crystal display panel is preferable, whereas in the case where the second electrode 301 is a conductive film having a light-transmitting property, a light-transmissive liquid crystal display panel is preferable.
In Embodiment Modes 2 to 5, description is made of a structure of the liquid crystal display panel, in which a gate electrode is provided over the semiconductor layer of the transistor in the transistor formed over the substrate, that is, a structure of a liquid crystal display panel having a so-called top-gate transistor. In this embodiment mode, description is made of a structure of a liquid crystal display panel, in which a gate electrode is provided below the semiconductor layer of the transistor in the transistor formed over the substrate, that is, a structure of a liquid crystal display panel having a so-called bottom-gate transistor.
In the liquid crystal display panel of Embodiment Mode 6, a gate electrode is provided over a first substrate; a first insulating film is provided so as to cover the gate electrode; a semiconductor layer of a transistor is provided over the gate electrode with the first insulating film interposed therebetween, and a first electrode and a second electrode of a liquid crystal element are provided over the substrate with the first insulating film interposed therebetween; a second insulating film is provided so as to cover the semiconductor layer of the transistor, and the first electrode and the second electrode of the liquid crystal element; a hole (contact hole) is formed in the second insulating film; and a wiring formed over the second insulating film is connected to the semiconductor layer of the transistor through the hole. A surface of the first substrate, which is provided with the transistor, is attached to the second substrate. A liquid crystal layer is provided between the first substrate and the second substrate.
Note that the semiconductor layer of the transistor is a film formed in the same layer as the first electrode and the second electrode of the liquid crystal element.
Further, each of the first electrode and the second electrode of the liquid crystal element is an electrode having a slit or a comb-shaped electrode, and branch portions thereof are provided alternately.
Two gate electrodes 201 are formed over a substrate 200. As the substrate 200, an insulating substrate such as a glass substrate, a quartz substrate, a plastic substrate; or a ceramic substrate, a metal substrate, a semiconductor substrate, or the like can be used. As the gate electrodes 201, an aluminum (Al) film, a copper (Cu) film, a thin film containing aluminum or copper as a main component, a chromium (Cr) film, a tantalum (Ta) film, a tantalum nitride (TaN) film, a titanium (Ti) film, a tungsten (W) film, a molybdenum (Mo) film, or the like can be used.
A gate insulating film (first insulating film 202) is formed so as to cover the gate electrodes 201. As the first insulating film 202, a silicon oxide film, a silicon nitride film, a silicon oxynitride film, or the like formed by a CVD method or a sputtering method can be used.
A semiconductor layer (channel formation regions 203a, an impurity region 203b, an impurity region 203c, and an impurity region 203d) of a transistor 210, and a first electrode 203e and a second electrode 203f that control molecular orientation of the liquid crystal molecules are formed over the first insulating film 202. The channel formation regions 203a, the impurity region 203b, the impurity region 203c, the impurity region 203d, the first electrode 203e, and the second electrode 203f are non-single crystalline semiconductor films (for example, polysilicon films), which are formed in the same step.
In the case where the transistor 210 is an n-channel transistor, an impurity element such as phosphorus or arsenic is introduced into the impurity region 203b, the impurity region 203c and the impurity region 203d, whereas in the case where the transistor 210 is a p-channel transistor, an impurity element such as boron is introduced into the impurity region 203b, the impurity region 203c, and the impurity region 203d.
Further, the impurity element introduced into the impurity region 203b, the impurity region 203c, and the impurity region 203d may also be introduced into the first electrode 203e and the second electrode 203f. The resistance of the first electrode 203e and the second electrode 203f is lowered when an impurity is introduced thereto, which is preferable for each of the first electrode 203e and the second electrode 203f to function as an electrode.
The first electrode 203e and the second electrode 203f each have thickness of, for example, 45 nm to 60 nm, and have sufficiently high light transmittance. In order to further improve the light transmittance, it is desirable to make thickness of the first electrode 203e and the second electrode 203f be 40 nm or less.
The semiconductor layer (the channel formation region 203a, the impurity region 203b, the impurity region 203c, and the impurity region 203d) of the transistor 210, and the first electrode 203e and the second electrode 203f that control molecular orientation of the liquid crystal molecules are formed in the same step. Thus, the number of steps can be reduced, so that the manufacturing cost can be reduced. In addition, it is desirable that impurity elements of the same type be introduced into the impurity region 203b, the impurity region 203c, and the impurity region 203d; and the first electrode 203e and the second electrode 203f. This is because when the impurity elements of the same type are introduced, the impurity elements can be introduced without a problem even if the impurity region 203b, the impurity region 203c, and the impurity region 203d; and the first electrode 203e and the second electrode 203f are located close to each other, so that dense layout becomes possible. It is desirable to add impurity elements of either p-type or n-type because the manufacturing cost can be low compared with the case in which impurity elements of different types are introduced.
An interlayer insulating film (second insulating film 204) is formed over the first insulating film 202 and the semiconductor layer (the channel formation region 203a, the impurity region 203b, the impurity region 203c, and the impurity region 203d) of the transistor 210, and the first electrode 203e and the second electrode 203f that control molecular orientation of the liquid crystal molecules. The second insulating film 204 preferably has a stacked-layer structure. For example, a protective film and a planarization film may be stacked in this order. For the protective film, an inorganic insulating film is suitable. As an inorganic insulating film, a silicon nitride film, a silicon oxide film, a silicon oxynitride film, or a film formed by stacking these layers can be used. For a planarization film, a resin film is suitable. As a resin film, polyimide, polyamide, acrylic, polyimide amide, epoxy, or the like can be used.
A signal line (wiring 205) is formed over the second insulating film 204. The wiring 205 is connected to the impurity region 203c through a hole (contact hole) formed in the second insulating film 204. As the wiring 205, a titanium (Ti) film, an aluminum (Al) film, a copper (Cu) film, an aluminum film containing Ti, or the like can be used. Preferably, copper which has low resistance may be used.
A first orientation film 206 is formed over the wiring 205 and the second insulating film 204. Then, a liquid crystal layer 207, a second orientation film 208, and a substrate 209 are provided over the first orientation film 206. That is, the liquid crystal layer 207 is interposed between the first orientation film 206 and the second orientation film 208. That is, the second orientation film 208 is formed over the substrate 209, and a surface of the substrate 209, on which the second orientation film 208 is formed, and a surface of the substrate 200, on which the first orientation film 206 is formed, are attached to each other. The liquid crystal layer 207 is provided between the first orientation film 206 and the second orientation film 208.
Description is made of a structure of a liquid crystal display panel of Embodiment Mode 7 of the present invention.
In the liquid crystal display panel of Embodiment Mode 7 of the present invention, a gate electrode and a second electrode of a liquid crystal element are provided over a first substrate; a first insulating film is provided so as to cover the gate electrode and the second electrode of the liquid crystal element; a semiconductor layer of a transistor is provided over the gate electrode with the first insulating film interposed therebetween, and a first electrode of the liquid crystal element is provided over the second electrode of the liquid crystal element with the first insulating film interposed therebetween; a second insulating film is provided so as to cover the semiconductor layer of the transistor, and the first electrode of the liquid crystal element; a hole (contact hole) is formed in the second insulating film; and a wiring formed over the second insulating film is connected to the semiconductor layer of the transistor through the hole. A surface of the first substrate, which is provided with the transistor, is attached to the second substrate. A liquid crystal layer is provided between the first substrate and the second substrate.
Note that the semiconductor layer of the transistor is a film formed in the same layer as the first electrode of the liquid crystal element.
Further, the first electrode of the liquid crystal element is an electrode having a slit or a comb-shaped electrode, and the second electrode of the liquid crystal element is a plate-like electrode.
For the common electrode (second electrode 203f) in
The second electrode 601 may be either a conductive film having reflectivity or a conductive film having a light-transmitting property. As a conductive film having reflectivity, a metal film such as an aluminum (Al) film, a copper (Cu) film, a thin film containing aluminum or copper as a main component, a chromium (Cr) film, a tantalum (Ta) film, a tantalum nitride (TaN) film, a titanium (Ti) film, a tungsten (W) film, or a molybdenum (Mo) film is given. As a conductive film having a light-transmitting property, a transparent conductive film such as an indium tin oxide (ITO) film, indium zinc oxide (IZO) film, an indium tin oxide containing silicon oxide (ITSO) film, a zinc oxide (ZnO) film, or a cadmium tin oxide (CTO) film is given. In the case where the second electrode 601 is a conductive film having reflectivity, the liquid crystal display panel of Embodiment Mode 7 of the present invention is a reflective liquid crystal display panel, whereas in the case where the second electrode 601 is a conductive film having a light-transmitting property, the liquid crystal display panel of Embodiment Mode 7 of the present invention is a light-transmissive liquid crystal display panel.
Description is made of a structure of a liquid crystal display panel of Embodiment Mode 8 of the present invention.
In the liquid crystal display panel of Embodiment Mode 8 of the present invention, a gate electrode and a second electrode of a liquid crystal element are provided over a first substrate; a conductive film having reflectivity, which has smaller area than the second electrode of the liquid crystal element, is provided over the second electrode of the liquid crystal element; a first insulating film is provided so as to cover the gate electrode, the second electrode of the liquid crystal element, and the conducive film; a semiconductor layer of a transistor is provided over the gate electrode with the first insulating film interposed therebetween, and a first electrode of the liquid crystal element is provided over the second electrode of the liquid crystal element with the first insulating film interposed therebetween; a second insulating film is provided so as to cover the semiconductor layer of the transistor, and the first electrode of the liquid crystal element; a hole (contact hole) is formed in the second insulating film; and a wiring formed over the second insulating film is connected to the semiconductor layer of the transistor through the hole. A surface of the first substrate, which is provided with the transistor, is attached to the second substrate. A liquid crystal layer is provided between the first substrate and the second substrate.
Note that the semiconductor layer of the transistor is a film formed in the same layer as the first electrode of the liquid crystal element.
Further, the first electrode of the liquid crystal element is an electrode having a slit or a comb-shaped electrode, and the second electrode of the liquid crystal element is a plate-like electrode.
In the liquid crystal display panel of Embodiment Mode 8 of the present invention, the second electrode 601 is preferably a conductive film having a light-transmitting property. As a conductive film having a light-transmitting property, a transparent conductive film such as an indium tin oxide (ITO) film, an indium zinc oxide (IZO) film, an indium tin oxide containing silicon oxide (ITSO) film, a zinc oxide (ZnO) film, or a cadmium tin oxide (CTO) film is given. The conductive film 401 is preferably a conductive film having reflectivity. As a conductive film having reflectivity, a metal film such as an aluminum (Al) film, a copper (Cu) film, a thin film containing aluminum or copper as a main component, a chromium (Cr) film, a tantalum (Ta) film, a tantalum nitride (TaN) film, a titanium (Ti) film, a tungsten (W) film, or a molybdenum (Mo) film is given.
The liquid crystal display panel of Embodiment Mode 8 of the present invention is suitable for a semi-transmissive liquid crystal display panel.
Description is made of a structure of a liquid crystal display panel of Embodiment Mode 9 of the present invention.
The liquid crystal display panel of Embodiment Mode 9 of the present invention has a structure in which the second electrode 601 and the conductive film 701 are formed using one mask. Specifically, the second electrode 601 and the conductive film 701 are formed with use of a mask called halftone or gray tone, in which thickness of a resist is varied depending on a region. Accordingly, a manufacturing process can be simplified, and the number of masks (the number of reticles) can be reduced.
In the liquid crystal display panel of Embodiment Mode 9 of the present invention, a first conductive film and a second electrode of a liquid crystal element are provided over a first substrate; a gate electrode is provided over the first conductive film; a second conductive film having reflectivity, which has smaller area than the second electrode of the liquid crystal element, is provided over the second electrode of the liquid crystal element; a first insulating film is provided so as to cover the gate electrode, the second electrode of the liquid crystal element, and a second conducive film; a semiconductor layer of a transistor is provided over the gate electrode with the first insulating film interposed therebetween, and a first electrode of the liquid crystal element is provided over the second electrode of the liquid crystal element with the first insulating film interposed therebetween; a second insulating film is provided so as to cover the semiconductor layer of the transistor, and the first electrode of the liquid crystal element; a hole (contact hole) is formed in the second insulating film; and a wiring formed over the second insulating film is connected to the semiconductor layer of the transistor through the hole. A surface of the first substrate, which is provided with the transistor, is attached to the second substrate. A liquid crystal layer is provided between the first substrate and the second substrate.
Note that the semiconductor layer of the transistor is a film formed in the same layer as the first electrode of the liquid crystal element.
Further, the first conductive film is a film formed in the same layer as the second electrode of the liquid crystal element, and the gate electrode is a film formed in the same layer as the second conductive film.
Further, the first electrode of the liquid crystal element is an electrode having a slit or a comb-shaped electrode, and the second electrode of the liquid crystal element is a plate-like electrode.
In the liquid crystal display panel of Embodiment Mode 9 of the present invention, it is preferable that the second electrode 601 and the conductive film 801 be formed in the same step, and the conductive film 701 and the gate electrode 201 be formed in the same step.
As for formation of them, a first conductive film to be the second electrode 601 and the conductive film 801 is formed first, and a second conductive film to be the gate electrode 201 and the conductive film 701 is formed thereover. Then, a resist film is formed over the second conductive film, and the resist film is exposed to light using a exposure mask having a light-shielding portion by which exposure light is shielded and a semi-transmissive portion through which exposure light partially passes. Subsequently, development is performed to form a first resist pattern having two film thicknesses and a second resist pattern having an almost uniform thickness. The first conductive film and the second conductive film are etched using the first resist pattern and the second resist pattern to be separated to be almost the same patterns as the first resist pattern and the second resist pattern. The first resist pattern and the second resist pattern are ashed or etched to form a third resist pattern and a fourth resist pattern respectively.
The separated second conductive film is etched using the third resist pattern and the fourth resist pattern as masks. Accordingly, a pattern of the second conductive film etched using the third resist pattern becomes smaller than a pattern of the first conductive film. That is, the second conductive film etched using the third resist pattern can be used as the conductive film 701.
Description is made of a structure of a liquid crystal display panel of Embodiment Mode 10 of the present invention.
In the liquid crystal display panel of Embodiment Mode 10 of the present invention, a gate electrode and a second electrode of a liquid crystal element are provided over a first substrate; a first insulating film is provided so as to cover the gate electrode, the second electrode of the liquid crystal element, and the conducive film; a semiconductor layer of a transistor is provided over the gate electrode with the first insulating film interposed therebetween, and a first electrode of the liquid crystal element is provided over the second electrode of the liquid crystal element with the first insulating film interposed therebetween; a second insulating film is provided so as to cover the semiconductor layer of the transistor, and the first electrode of the liquid crystal element; a hole (contact hole) is formed in the second insulating film; and a wiring formed over the second insulating film is connected to the semiconductor layer of the transistor through the hole. A surface of the first substrate, which is provided with the transistor, is attached to the second substrate. A liquid crystal layer is provided between the first substrate and the second substrate.
Note that the semiconductor layer of the transistor is a film formed in the same layer as the first electrode of the liquid crystal element.
Further, each of the first electrode and the second electrode of the liquid crystal element is an electrode having a slit or a comb-shaped electrode.
For the common electrode (second electrode 102f) in
The second electrode 901 may be either a conductive film having reflectivity or a conductive film having a light-transmitting property. As a conductive film having reflectivity, a metal film such as an aluminum (Al) film, a copper (Cu) film, a thin film containing aluminum or copper as a main component, a chromium (Cr) film, a tantalum (Ta) film, a tantalum nitride (TaN) film, a titanium (Ti) film, a tungsten (W) film, or a molybdenum (Mo) film is given. As a conductive film having a light-transmitting property, a transparent conductive film such as an indium tin oxide (ITO) film, indium zinc oxide (IZO) film, an indium tin oxide containing silicon oxide (ITSO) film, a zinc oxide (ZnO) film, or a cadmium tin oxide (CTO) film is given. The liquid crystal display panel of Embodiment Mode 10 of the present invention is either a reflective liquid crystal display panel or a light-transmissive liquid crystal display panel. In the case where the second electrode 901 is a conductive film having reflectivity, a reflective liquid crystal display panel is preferable, whereas in the case where the second electrode 901 is a conductive film having a light-transmitting property, a light-transmissive liquid crystal display panel is preferable.
Description is made of a structure of a liquid crystal display panel of Embodiment Mode 11 of the present invention.
In this embodiment mode, description is made of a structure in which the liquid crystal display panel is provided with a polarizing plate or a polarizing film.
In a first structure of the liquid crystal display panel of Embodiment Mode 11, which corresponds to a liquid crystal display panel of Embodiment Mode 2 using a polarizing plate, a first insulating film is provided over a first substrate; a semiconductor layer of a transistor, and a first electrode and a second electrode of a liquid crystal element are provided over the first insulating film; a second insulating film is provided so as to cover the semiconductor layer of the transistor, and the first electrode and the second electrode of the liquid crystal element; a gate electrode is provided over the semiconductor layer of the transistor with the second insulating film interposed therebetween; a third insulating film is provided so as to cover the gate electrode and the second insulating film; a hole (contact hole) is formed in the third insulating film and the second insulating film; and a wiring formed over the third insulating film is connected to the semiconductor layer of the transistor through the hole. A surface of the first substrate, which is provided with the transistor, is attached to a second substrate. A liquid crystal layer is provided between the first substrate and the second substrate.
Note that the semiconductor layer of the transistor is a film formed in the same layer as the first electrode and the second electrode of the liquid crystal element.
Further, each of the first electrode and the second electrode of the liquid crystal element is an electrode having a slit or a comb-shaped electrode.
Here, the liquid crystal display panel of Embodiment Mode 11 of the present invention has a polarizing plate or a polarizing film. The polarizing plate may be provided on an outer surface (a surface on which the liquid crystal layer is not provided) of the first substrate and an outer surface (a surface on which the liquid crystal layer is not provided) of the second substrate, or the polarizing film may be provided over or below the third insulating film or an inner surface (a surface on which the liquid crystal layer is provided) of the second substrate.
In a second structure of the liquid crystal display panel of Embodiment Mode 11 of the present invention, which corresponds to the liquid crystal display panel of Embodiment Mode 3 of the present invention using a polarizing plate, a second electrode of a liquid crystal element is provided over a first substrate; a first insulating film is provided so as to cover the second electrode of the liquid crystal element; a semiconductor layer of a transistor, and a first electrode of the liquid crystal element are provided over the first insulating film; a second insulating film is provided so as to cover the semiconductor layer of the transistor, and the first electrode the liquid crystal element; a gate electrode is provided over the semiconductor layer of the transistor with the second insulating film interposed therebetween; a third insulating film is provided so as to cover the gate electrode and the second insulating film; a hole (contact hole) is formed in the third insulating film and the second insulating film; and a wiring formed over the third insulating film is connected to the semiconductor layer of the transistor through the hole. A surface of the first substrate, which is provided with the transistor, is attached to a second substrate. A liquid crystal layer is provided between the first substrate and the second substrate.
Note that the semiconductor layer of the transistor is a film formed in the same layer as the first electrode of the liquid crystal element.
Further, the first electrode of the liquid crystal element is an electrode having a slit or a comb-shaped electrode, and the second electrode of the liquid crystal element is a plate-like electrode.
Here, the liquid crystal display panel of Embodiment Mode 11 of the present invention has a polarizing plate or a polarizing film. The polarizing plate may be provided on an outer surface (a surface on which the liquid crystal layer is not provided) of the first substrate and an outer surface (a surface on which the liquid crystal layer is not provided) of the second substrate, or the polarizing film may be provided over or below the third insulating film or an inner surface (a surface on which the liquid crystal layer is provided) of the second substrate.
In a third structure of the liquid crystal display panel of Embodiment Mode 11 of the present invention, which corresponds to the liquid crystal display panel of Embodiment Mode 4 of the present invention using a polarizing plate, a second electrode of a liquid crystal element is provided over a first substrate; a conductive film having reflectivity, which has smaller area than the second electrode of the liquid crystal element, is provided over the second electrode of the liquid crystal element; a first insulating film is provided so as to cover the second electrode of the liquid crystal element and the conductive film; a semiconductor layer of a transistor, and a first electrode of the liquid crystal element are provided over the first insulating film; a second insulating film is provided so as to cover the semiconductor layer of the transistor, and the first electrode of the liquid crystal element; a gate electrode is provided over the semiconductor layer of the transistor with the second insulating film interposed therebetween; a third insulating film is provided so as to cover the gate electrode and the second insulating film; a hole (contact hole) is formed in the third insulating film and the second insulating film; and a wiring formed over the third insulating film is connected to the semiconductor layer of the transistor through the hole. A surface of the first substrate, which is provided with the transistor, is attached to a second substrate. A liquid crystal layer is provided between the first substrate and the second substrate.
Note that the semiconductor layer of the transistor is a film formed in the same layer as the first electrode of the liquid crystal element.
Further, the first electrode of the liquid crystal element is an electrode having a slit or a comb-shaped electrode, and the second electrode of the liquid crystal element is a plate-like electrode.
Here, the liquid crystal display panel of Embodiment Mode 11 of the present invention has a polarizing plate or a polarizing film. The polarizing plate may be provided on an outer surface (a surface on which the liquid crystal layer is not provided) of the first substrate and an outer surface (a surface on which the liquid crystal layer is not provided) of the second substrate, or the polarizing film may be provided over or below the third insulating film or an inner surface (a surface on which the liquid crystal layer is provided) of the second substrate.
In a fourth structure of the liquid crystal display panel of Embodiment Mode 11, which corresponds to the liquid crystal display panel of Embodiment Mode 5 using a polarizing plate, a second electrode of a liquid crystal element is provided over a first substrate; a first insulating film is provided so as to cover the second electrode of the liquid crystal element; a semiconductor layer of a transistor, and a first electrode of the liquid crystal element are provided over the first insulating film; a second insulating film is provided so as to cover the semiconductor layer of the transistor, and the first electrode of the liquid crystal element; a gate electrode is provided over the semiconductor layer of the transistor with the second insulating film interposed therebetween; a third insulating film is provided so as to cover the gate electrode and the second insulating film; a hole (contact hole) is formed in the third insulating film and the second insulating film; and a wiring formed over the third insulating film is connected to the semiconductor layer of the transistor through the hole. A surface of the first substrate, which is provided with the transistor, is attached to the second substrate. A liquid crystal layer is provided between the first substrate and the second substrate.
Note that the semiconductor layer of the transistor is a film formed in the same layer as the first electrode of the liquid crystal element.
Further, each of the first electrode and the second electrode of the liquid crystal element is an electrode having a slit or a comb-shaped electrode, and branch portions thereof are provided alternately.
Here, the liquid crystal display panel of Embodiment Mode 11 of the present invention has a polarizing plate or a polarizing film. The polarizing plate may be provided on an outer surface (a surface on which the liquid crystal layer is not provided) of the first substrate and an outer surface (a surface on which the liquid crystal layer is not provided) of the second substrate, or the polarizing film may be provided over or below the third insulating film or an inner surface (a surface on which the liquid crystal layer is provided) of the second substrate.
In a fifth structure of the liquid crystal display panel of Embodiment Mode 11, which corresponds to the liquid crystal display panel of Embodiment Mode 6 using a polarizing plate, a gate electrode is provided over a first substrate; a first insulating film is provided so as to cover the gate electrode; a semiconductor layer of a transistor is provided over the gate electrode with the first insulating film interposed therebetween, and a first electrode and a second electrode of a liquid crystal element are provided over the first substrate with the first insulating film interposed therebetween; a second insulating film is provided so as to cover the semiconductor layer of the transistor, and the first electrode and the second electrode of the liquid crystal element; a hole (contact hole) is formed in the second insulating film; and a wiring formed over the second insulating film is connected to the semiconductor layer of the transistor through the hole. A surface of the first substrate, which is provided with the transistor, is attached to a second substrate. A liquid crystal layer is provided between the first substrate and the second substrate.
Note that the semiconductor layer of the transistor is a film formed in the same layer as the first electrode and the second electrode of the liquid crystal element.
Further, each of the first electrode and the second electrode of the liquid crystal element is an electrode having a slit or a comb-shaped electrode, and branch portions thereof are provided alternately.
Here, the liquid crystal display panel of Embodiment Mode 11 of the present invention has a polarizing plate or a polarizing film. The polarizing plate may be provided on an outer surface (a surface on which the liquid crystal layer is not provided) of the first substrate and an outer surface (a surface on which the liquid crystal layer is not provided) of the second substrate, or the polarizing film may be provided over or below the second insulating film or an inner surface (a surface on which the liquid crystal layer is provided) of the second substrate.
In a sixth structure of the liquid crystal display panel of Embodiment Mode 11 of the present invention, which corresponds to the liquid crystal display panel of Embodiment Mode 7 of the present invention using a polarizing plate, a gate electrode and a second electrode of a liquid crystal element are provided over a first substrate; a first insulating film is provided so as to cover the gate electrode and the second electrode of the liquid crystal element; a semiconductor layer of a transistor is provided over the gate electrode with the first insulating film interposed therebetween, and a first electrode of the liquid crystal element is provided over the second electrode of the liquid crystal element with the first insulating film interposed therebetween; a second insulating film is provided so as to cover the semiconductor layer of the transistor, and the first electrode of the liquid crystal element; a hole (contact hole) is formed in the second insulating film; and a wiring formed over the second insulating film is connected to the semiconductor layer of the transistor through the hole. A surface of the first substrate, which is provided with the transistor, is attached to a second substrate. A liquid crystal layer is provided between the first substrate and the second substrate.
Note that the semiconductor layer of the transistor is a film formed in the same layer as the first electrode of the liquid crystal element.
Further, the first electrode of the liquid crystal element is an electrode having a slit or a comb-shaped electrode, and the second electrode of the liquid crystal element is a plate-like electrode.
Here, the liquid crystal display panel of Embodiment Mode 11 of the present invention has a polarizing plate or a polarizing film. The polarizing plate may be provided on an outer surface (a surface on which the liquid crystal layer is not provided) of the first substrate and an outer surface (a surface on which the liquid crystal layer is not provided) of the second substrate, or the polarizing film may be provided over or below the second insulating film or an inner surface (a surface on which the liquid crystal layer is provided) of the second substrate.
In a seventh structure of the liquid crystal display panel of Embodiment Mode 11 of the present invention, which corresponds to the liquid crystal display panel of Embodiment Mode 8 of the present invention using a polarizing plate, a gate electrode and a second electrode of a liquid crystal element are provided over a first substrate; a conductive film having reflectivity, which has smaller area than the second electrode of the liquid crystal element, is provided over the second electrode of the liquid crystal element; a first insulating film is provided so as to cover the gate electrode, the second electrode of the liquid crystal element, and the conducive film; a semiconductor layer of a transistor is provided over the gate electrode with the first insulating film interposed therebetween, and a first electrode of the liquid crystal element is provided over the second electrode of the liquid crystal element with the first insulating film interposed therebetween; a second insulating film is provided so as to cover the semiconductor layer of the transistor, and the first electrode of the liquid crystal element; a hole (contact hole) is formed in the second insulating film; and a wiring formed over the second insulating film is connected to the semiconductor layer of the transistor through the hole. A surface of the first substrate, which is provided with the transistor, is attached to a second substrate. A liquid crystal layer is provided between the first substrate and the second substrate.
Note that the semiconductor layer of the transistor is a film formed in the same layer as the first electrode of the liquid crystal element.
Further, the first electrode of the liquid crystal element is an electrode having a slit or a comb-shaped electrode, and the second electrode of the liquid crystal element is a plate-like electrode.
Here, the liquid crystal display panel of Embodiment Mode 11 of the present invention has a polarizing plate or a polarizing film. The polarizing plate may be provided on an outer surface (a surface on which the liquid crystal layer is not provided) of the first substrate and an outer surface (a surface on which the liquid crystal layer is not provided) of the second substrate, or the polarizing film may be provided over or below the second insulating film or an inner surface (a surface on which the liquid crystal layer is provided) of the second substrate.
In an eighth structure of the liquid crystal display panel of Embodiment Mode 11 of the present invention, which corresponds to the liquid crystal display panel of Embodiment Mode 9 of the present invention using a polarizing plate, a first conductive film and a second electrode of a liquid crystal element are provided over a first substrate; a gate electrode is provided over the first conductive film; a second conductive film having reflectivity, which has smaller area than the second electrode of the liquid crystal element, is provided over the second electrode of the liquid crystal element; a first insulating film is provided so as to cover the gate electrode, the second electrode of the liquid crystal element, and the second conducive film; a semiconductor layer of a transistor is provided over the gate electrode with the first insulating film interposed therebetween, and a first electrode of the liquid crystal element is provided over the second electrode of the liquid crystal element with the first insulating film interposed therebetween; a second insulating film is provided so as to cover the semiconductor layer of the transistor, and the first electrode of the liquid crystal element; a hole (contact hole) is formed in the second insulating film; and a wiring formed over the second insulating film is connected to the semiconductor layer of the transistor through the hole. A surface of the first substrate, which is provided with the transistor, is attached to the second substrate. A liquid crystal layer is provided between the first substrate and the second substrate.
Note that the semiconductor layer of the transistor is a film formed in the same layer as the first electrode of the liquid crystal element.
Further, the first conductive film is a film formed in the same layer as the second electrode of the liquid crystal element, and the gate electrode is a film formed in the same layer as the second conductive film.
Further, the first electrode of the liquid crystal element is an electrode having a slit or a comb-shaped electrode, and the second electrode of the liquid crystal element is a plate-like electrode.
Here, the liquid crystal display panel of Embodiment Mode 11 of the present invention has a polarizing plate or a polarizing film. The polarizing plate may be provided on an outer surface (a surface on which the liquid crystal layer is not provided) of the first substrate and an outer surface (a surface on which the liquid crystal layer is not provided) of the second substrate, or the polarizing film may be provided over or below the second insulating film or an inner surface (a surface on which the liquid crystal layer is provided) of the second substrate.
In a ninth structure of the liquid crystal display panel of Embodiment Mode 11 of the present invention, which corresponds to the liquid crystal display panel of Embodiment Mode 10 of the present invention using a polarizing plate, a gate electrode and a second electrode of a liquid crystal element are provided over a first substrate; a first insulating film is provided so as to cover the gate electrode and the second electrode of the liquid crystal element; a semiconductor layer of a transistor is provided over the gate electrode with the first insulating film interposed therebetween, and a first electrode of the liquid crystal element is provided over the second electrode of the liquid crystal element with the first insulating film interposed therebetween; a second insulating film is provided so as to cover the semiconductor layer of the transistor, and the first electrode of the liquid crystal element; a hole (contact hole) is formed in the second insulating film; and a wiring formed over the second insulating film is connected to the semiconductor layer of the transistor through the hole. A surface of the first substrate, which is provided with the transistor, is attached to the second substrate. A liquid crystal layer is provided between the first substrate and the second substrate.
Note that the semiconductor layer of the transistor is a film formed in the same layer as the first electrode of the liquid crystal element.
Further, each of the first electrode and the second electrode of the liquid crystal element is an electrode having a slit or a comb-shaped electrode.
Here, the liquid crystal display panel of Embodiment Mode 11 of the present invention has a polarizing plate or a polarizing film. The polarizing plate may be provided on an outer surface (a surface on which the liquid crystal layer is not provided) of the first substrate and an outer surface (a surface on which the liquid crystal layer is not provided) of the second substrate, or the polarizing film may be provided over or below the second insulating film or an inner surface (a surface on which the liquid crystal layer is provided) of the second substrate.
First, a structure in which a polarizing plate is provided on an outer side of a substrate is described in detail. That is, the polarizing plate is provided on a surface opposite to a surface over which an orientation film is formed. The liquid crystal display panels described in Embodiment Modes 1 to 10 each can be provided with a polarizing plate; however, in this embodiment mode, specific description is made taking as examples the case where a polarizing plate is provided in the structure of
Next, a structure in which a polarizing film is provided on an inner side of a substrate is described in detail. That is, the polarizing film is provided on a surface over which an orientation film is formed. The liquid crystal display panels described in Embodiment Modes 1 to 10 each can be provided with a polarizing film; however, in this embodiment mode, specific description is made taking as examples the case where a polarizing film is provided in the structure of
Next, description is made of a structure in which a polarizing film is provided on an inner side of a substrate, and a polarizing plate is provided on an outer side of the substrate. Specifically, the polarizing film is provided on a surface over which an orientation film is formed, and the polarizing plate is provided on a surface opposite to a surface over which the orientation film is formed. The liquid crystal display panels described in Embodiment Modes 1 to 10 each can be provided with a polarizing plate; however, in this embodiment mode, description is made taking as examples the case where a polarizing plate is provided in the structure of
Description is made of a structure of a liquid crystal display panel of Embodiment Mode 12 of the present invention.
In this embodiment mode, description is made of a structure of a liquid crystal display panel provided with a reflective electrode including a concave-convex shape. The liquid crystal display panel of this embodiment mode can reflect outside light diffusely; therefore, luminance of display can be improved and at the same time, mirroring reflection can be prevented. Note that the structure described in this embodiment mode can be appropriately applied to the liquid crystal display panels described in Embodiment Modes 1 to 11 as long as the structure includes a reflective electrode.
Alternatively, as shown in
Alternatively, as shown in
Alternatively, as shown in
Alternatively, as shown in
Description is made of a structure of a liquid crystal display panel of Embodiment Mode 13 of the present invention.
In this embodiment mode, description is made of a structure of a liquid crystal display panel in which thickness of a liquid crystal layer is not uniform but is partially varied. In the case of the liquid crystal display panel of this embodiment mode, visibility can be improved by adjustment of thickness of the liquid crystal layer.
That is because the liquid crystal layer has refractive index anisotropy so that a polarization state of light is changed depending on a traveling distance of light in the liquid crystal layer. Accordingly, an image cannot be displayed correctly. Therefore, it is necessary to adjust the polarization state of light. As a method for adjusting the polarization state, thickness of the liquid crystal layer (a so-called cell gap) in a portion where display is performed by reflection of light (reflection region) may be thinned so that the distance becomes not too long when light passes through the reflection region twice as compared to a transmission region.
It is preferable that thickness of the liquid crystal layer in the reflection region be half of thickness of the liquid crystal layer in the transmission region. Here, description “to be half” also includes the amount of discrepancy that cannot be recognized by human eyes.
It is to be noted that light does not enter only from a direction vertical to the substrate, that is, a normal direction, and light also enters obliquely in many cases. Therefore, with all cases considered, traveling distances of light may be almost the same in both the reflection region and the transmission region. Therefore, thickness of the liquid crystal layer in the reflection region is preferably almost greater than or equal to one-third and less than or equal to two-thirds of thickness of the liquid crystal layer in the transmission region.
In order to thin thickness of the liquid crystal layer (so-called cell gap), a film for adjusting thickness may be arranged.
The film can be easily formed when the film for adjusting thickness is arranged on a substrate side provided with an electrode of a liquid crystal element. In other words, various films are formed on the substrate side provided with the electrode of the liquid crystal element. Therefore, the film for adjusting thickness may be formed using these films, and thus there are few difficulties when a film is formed. In addition, it becomes also possible to form the film for adjusting thickness in the same step as a film having another function. Therefore, a process can be simplified and the cost can be reduced.
Note that the film for adjusting thickness of the liquid crystal layer may be provided on a counter substrate side.
When the film for adjusting thickness of the liquid crystal layer is arranged on the counter substrate side, the electrodes of the liquid crystal element can be arranged in the same plane (even when slight deviation is caused due to a wiring of a lower layer and an electrode, if the deviation is extremely smaller than that caused due to thickness of the film for adjusting thickness of the liquid crystal layer described in this embodiment mode, the deviation is included in the same plane) in both the reflection region and the transmission region. Therefore, distances between the pixel electrode and the common electrode can be almost the same in the transmission region and in the reflection region. A direction, a distribution, intensity, and the like of an electric field are changed depending on a distance between electrodes. Therefore, when the distances between the electrodes are almost the same, electric fields applied to the liquid crystal layer can be almost the same in the reflection region and the transmission region; thus, it is possible to precisely control the liquid crystal molecule. In addition, since degrees of liquid crystal molecule rotation are almost the same in the reflection region and the transmission region, an image can be displayed with almost the same gray scale in the case of display as a transmission type and in the case of display as a reflection type.
In addition, the film for adjusting thickness of the liquid crystal layer can cause a disordered orientation mode of the liquid crystal molecule in the vicinity thereof, and a defect such as disclination is possibly generated. However, when the film for adjusting thickness of the liquid crystal layer is arranged over the counter substrate, the film for adjusting thickness can be apart from the electrode of the liquid crystal element. Accordingly, a low electric field is applied, thereby preventing a disordered orientation mode of the liquid crystal molecule and a hard-to-see screen.
Further, only a color filter, a black matrix, and the like are formed over the counter electrode; thus, the number of steps is small. Accordingly, even when the film for adjusting thickness of the liquid crystal layer is formed over the counter substrate, the yield is not easily reduced. Even if a defect is generated, not so much manufacturing cost is wasted because of the small number of steps and inexpensive cost.
It is to be noted that in the case where the film for adjusting thickness of the liquid crystal layer is formed over the counter substrate, the film for adjusting thickness of the liquid crystal layer may contain a particle which serves as a scattering material so as to improve luminance by diffusing light. The particle is formed using a light-transmissive resin material which has a different refractive index from a base material forming a gap-adjusting film (for example, an acrylic resin). When the film for adjusting thickness of the liquid crystal layer contains the particle as described above, light can be scattered, and contrast and luminance of a display image can be improved.
In a liquid crystal display device of the present invention having the above structure, a viewing angle is wide, a color is not often changed depending on an angle at which a display screen is seen, and an image that is favorably recognized both outdoors in sunlight and dark indoors (or outdoors at night) can be provided.
In a region where display is performed by reflection of light (reflection region), the fourth insulating film 2801 is provided to adjust thickness of the liquid crystal layer 108. By provision of the fourth insulating film 2801, thickness of the liquid crystal layer 108 in the reflection region can be thinned as compared to thickness of the liquid crystal layer 108 in a transmission region. In other words, the liquid crystal layer on an upper side of the fourth insulating film 2801, that is, the liquid crystal layer on an upper side of the conductive film 401, has a thinner film thickness out of the liquid crystal layer 108 on an upper side of the second electrode 301.
Note that since the fourth insulating film 2801 scarcely has refractive index anisotropy, a polarization state is not changed even when light passes therethrough. Therefore, the presence or absence, thickness, or the like of the fourth insulating film 2801 does not have a significant effect.
Note that even if the fourth insulating film 2801 is not formed over the third insulating film 105, it is only necessary that thickness of the liquid crystal layer 108 on an upper side of the conductive film 401 be thinner out of the liquid crystal layer on an upper side of the second electrode 301. Therefore, as shown in
Next,
In a region where display is performed by reflection of light (reflection region), the third insulating film 2901 is provided to adjust thickness of the liquid crystal layer 207. By provision of the third insulating film 2901, thickness of the liquid crystal layer 207 in the reflection region can be thinned as compared to thickness of the liquid crystal layer 207 in a transmission region. In other words, the liquid crystal layer on an upper side of the third insulating film 2901, that is, the liquid crystal layer on an upper side of the conductive film 701, has a thinner film thickness out of the liquid crystal layer 207 on an upper side of the second electrode 601.
Note that since the third insulating film 2901 scarcely has refractive index anisotropy, a polarization state is not changed even when light passes therethrough. Therefore, the presence or absence, thickness, or the like of the third insulating film 2901 does not have a significant effect.
Note that even if the third insulating film 2901 is not formed over the second insulating film 204, it is only necessary that thickness of the liquid crystal layer 207 on an upper side of the conductive film 701 be thinner out of the liquid crystal layer 207 on an upper side of the second electrode 601. Therefore, as shown in
Next,
In a region where display is performed by reflection of light (reflection region), the third insulating film 3001 is provided to adjust thickness of the liquid crystal layer 207. By provision of the third insulating film 3001, thickness of the liquid crystal layer 207 in the reflection region can be thinned as compared to thickness of the liquid crystal layer 207 in a transmission region. In other words, the liquid crystal layer 207 on an upper side of the third insulating film 3001, that is, the liquid crystal layer 207 on an upper side of the conductive film 701, has a thinner film thickness out of the liquid crystal layer 207 on an upper side of the second electrode 601.
Note that since the third insulating film 3001 scarcely has refractive index anisotropy, a polarization state is not changed even when light passes therethrough. Therefore, the presence or absence, thickness, or the like of the third insulating film 3001 does not have a significant effect.
Note that even if the third insulating film 3001 is not formed over the second insulating film 204, it is only necessary that thickness of the liquid crystal layer on an upper side of the conductive film 701 be thinner out of the liquid crystal layer on an upper side of the second electrode 601. Therefore, as shown in
Description is made of a structure of a liquid crystal display panel of Embodiment Mode 14 of the present invention.
In this embodiment mode, description is made of a structure in which the liquid crystal display panel is provided with a retardation film.
First, a structure in which a retardation film is provided on an outer side of a substrate. Specifically, the retardation film is provided on a surface opposite to a surface on which an orientation film is formed. The liquid crystal display panels described in Embodiment Modes 1 to 13 each can be provided with a retardation film; however, description is made taking as examples the case where a retardation film is provided in the structure of
Next, a structure is described, in which a retardation film is provided on an inner side of a substrate. Specifically, the retardation film is provided on a surface opposite to a surface on which an orientation film is formed. In a semi-transmissive liquid crystal display panel, the retardation film has a phase difference in a portion on the reflection region, and the retardation film has approximately zero phase difference in a portion on the transmission region.
Description is made of a structure of a liquid crystal display panel of Embodiment Mode 15 of the present invention.
In Embodiment Modes 1 to 14, in the case where the pixel electrode and the common electrode are not formed from conductive films in the same layer, the pixel electrode is provided nearer the liquid crystal layer than the common electrode; however, in this embodiment mode, description is made of a structure of a liquid crystal display panel in which the common electrode is provided nearer the liquid crystal layer than the pixel electrode.
Description is made of a structure of a liquid crystal display panel of Embodiment Mode 16 of the present invention.
In this embodiment mode, description is made of a structure of a liquid crystal display panel for which a so-called IPS mode and a so-called FFS mode are combined.
In the case of the IPS mode, an electrical field almost parallel to a substrate surface is generated due to a potential difference between electrodes, so that liquid crystal molecules are rotated almost parallel to the substrate surface. In the case of the FFS mode, a width between electrodes is reduced as compared to in the IPS mode, and an oblique electrical field is utilized to control an orientation of liquid crystal molecules. Then, in the liquid crystal display panel of Embodiment Mode 16 of the present invention, one pixel includes a display region of the IPS mode and a display region of the FFS mode.
The common electrode (second electrode 4301) in
The common electrode (second electrode 4401) in
Description is made of a pixel layout to which a basic structure of the liquid crystal display panel of Embodiment Mode 1 of the present invention is applied.
Note that
The pixel portion of the display panel of Embodiment 1 of the present invention includes a plurality of signal lines (first wirings 106a in the pixel of
Further, in the pixel portion, a plurality of pixels are arranged in matrix corresponding to the scan lines and the signal lines, and each pixel is connected to any one of the scan lines and any one of the signal lines.
Each pixel includes at least one transistor (the transistor 111 in the pixel of
The semiconductor layer (a semiconductor film functioning as a channel formation region, a source region, and a drain region) of the transistor 111 and the first electrode 102e of each pixel are a stretch of film.
A region projecting from the second wiring 104c functions as the gate electrode 104a, and the semiconductor layer overlapping with the gate electrode 104 includes the channel formation region of the transistor 111. Further, one of the impurity region 102b and the impurity region 102c functions as a source of the transistor 111, and the other functions as a drain thereof. Note that the transistor 111 has a so-called dual-gate structure (in which two gate electrodes are arranged alongside over the semiconductor layer); however, the present invention is not limited to this. Alternatively, a multi-gate structure in which three or more gate electrodes are arranged alongside over the semiconductor layer or a so-called single-gate structure (in which one gate electrode is provided for one transistor) may be employed. In the case of the single-gate structure, the impurity region 102d is omitted.
In the transistor 111, the impurity region 102c to be one of a source and a drain is connected to the first wiring 106a through a contact hole, and the first electrode 102e and the impurity region 102b to be the other of the source and the drain are a stretch of film.
In
Further, the second electrode 102f is a film formed in the same step as the semiconductor layer of the transistor 111 and the first electrode 102e. The second electrode 102f is provided to electrically connect between pixels of a plurality of pixels through the third wiring 106b, at the same time, electrically connected to the fourth wiring 104b that is arranged in parallel with and separate from the second wiring 104c.
Note that in
The liquid crystal display panel of Embodiment 1 of the present invention is allowed as long as the semiconductor layer of the transistor 111, the first electrode 102e, and the second electrode 102f are films formed in the same step.
Further, shapes of the first electrode 102e and the second electrode 102f are not limited to the shapes shown in
Note that although
Next, more specific description is made of the structure of the liquid crystal display panel of Embodiment 1 of the present invention with reference to
A base insulating film (the first insulating film 101) is formed over the substrate 100 in order to prevent impurities from diffusing from the substrate 100. The substrate 100 can be formed of an insulating substrate such as a glass substrate, a quartz substrate, a plastic substrate, or a ceramic substrate, or of a metal substrate, a semiconductor substrate, or the like. The first insulating film 101 can be formed by a CVD method or a sputtering method. For example, a silicon oxide film, a silicon nitride film, a silicon oxynitride film, or the like formed by a CVD method using SiH4, N2O, and NH3 as a source material can be applied. Alternatively, a stacked layer of them may be used. It is to be noted that the first insulating film 101 is provided to prevent impurities from diffusing from the substrate 100 into the semiconductor layer. In the case where the substrate 100 is formed of a glass substrate or a quartz substrate, the first insulating film 101 is not necessary to be provided. It is also to be noted that when a silicon nitride film is used as the first insulating film 101, the entry of the impurities is prevented effectively. On the other hand, when a silicon oxide film is used as the first insulating film 101, trapping of an electric charge or hysteresis of electric characteristics is not caused even if the first insulating film 101 is in direct contact with the semiconductor layer. Therefore, it is more preferable that a stacked-layer film in which a silicon nitride film and a silicon oxide film are stacked in this order over the substrate 100 be used as the first insulating film 101.
The semiconductor layer (the channel formation region 102a, the impurity region 102b, the impurity region 102c, and the impurity region 102d) of the transistor 111, and the first electrode 102e and the second electrode 102f that control molecular orientation of the liquid crystal molecules are formed over the first insulating film 101. The channel formation region 102a, the impurity region 102b, the impurity region 102c, the impurity region 102d, the first electrode 102e, and the second electrode 102f are, for example, polysilicon films, which are formed in the same step.
In the case where the transistor 111 is an n-channel transistor, an impurity element such as phosphorus or arsenic is introduced into the impurity region 102b, the impurity region 102c and the impurity region 102d, whereas in the case where the transistor 111 is a p-channel transistor, an impurity element such as boron is introduced into the impurity region 102b, the impurity region 102c and the impurity region 102d.
Further, the impurity element introduced into the impurity region 102b, the impurity region 102c and the impurity region 102d may also be introduced into the first electrode 102e and the second electrode 102f. The resistance of the first electrode 102e and the second electrode 102f is lowered since an impurity is introduced thereto, which is preferable for each of the first electrode 102e and the second electrode 102f to function as an electrode.
The first electrode 102e and the second electrode 102f each have thickness of, for example, 45 nm to 60 nm, and have sufficiently high light transmittance. In order to further improve the light transmittance, it is desirable to set thickness of the first electrode 102e and the second electrode 102f to be 40 nm or less.
Each of the first electrode 102e and the second electrode 102f may be an amorphous silicon film or an organic semiconductor film. In that case, an amorphous silicon film or an organic semiconductor film is used for the semiconductor layer of the transistor 111.
The semiconductor layer (the channel formation region 102a, the impurity region 102b, the impurity region 102c and the impurity region 102d) of the transistor 111, and the first electrode 102e and the second electrode 102f that control molecular orientation of the liquid crystal molecules are formed in the same step. In this case, the number of steps can be reduced, so that the manufacturing cost can be reduced. In addition, it is desirable that impurity elements of the same type be introduced into the impurity region 102b, the impurity region 102c, the impurity region 102d, the first electrode 102e and the second electrode 102f. This is because when the impurity elements of the same type are introduced, the impurity elements can be introduced without a problem even if the impurity region 102b, the impurity region 102c, the impurity region 102d, the first electrode 102e and the second electrode 102f are located close to each other, so that dense layout becomes possible. It is desirable to add impurity elements of either P-type or N-type because the manufacturing cost can be low compared with the case in which impurity elements of different types are introduced.
A gate insulating film (second insulating film 103) is formed over the semiconductor layer of the transistor 111, the first electrode 102e, and the second electrode 102f. In
Two gate electrodes 104a are formed over the channel formation region 102a of the transistor 111 with the second insulating film 103 interposed therebetween. In addition, a gate wiring (the first wiring 104b) and an auxiliary wiring (the second wiring 104c) are formed over the second insulating film 103. The second wiring 104c and the gate electrode 104a are a stretch of film, and the second wiring 104c is formed in the same step as the first wiring 104b and the gate electrode 104a. Also, for each of the gate electrode 104a, the first wiring 104b, and the second wiring 104c, an aluminum (Al) film, a copper (Cu) film, a thin film containing aluminum or copper as a main component, a chromium (Cr) film, a tantalum (Ta) film, a tantalum nitride (TaN) film, a titanium (Ti) film, a tungsten (W) film, a molybdenum (Mo) film, or the like can be used.
An interlayer insulating film (third insulating film 105) is formed over the second insulating film 103, the gate electrodes 104a, the first wiring 104b, and the second wiring 104c. The third insulating film 105 preferably has a stacked-layer structure in which a protective film and a planarization film may be stacked in this order. For the protective film, an inorganic insulating film is suitable. As an inorganic insulating film, a silicon nitride film, a silicon oxide film, a silicon oxynitride film, or a film formed by stacking these films can be used. For a planarization film, a resin film is suitable. As a resin film, polyimide, polyamide, acrylic, polyimide amide, epoxy or the like can be used.
A signal line (a third wiring 106a) and a connection wiring (a fourth wiring 106b) are formed over the third insulating film 105. The third wiring 106a is connected to the impurity region 102c through holes (contact holes) formed in the third insulating film 105 and the second insulating film 103, and the fourth wiring 106b is connected to the second electrode 102f through holes formed in the third insulating film 105 and the second insulating film 103 and also connected to the first wiring 104b through the hole formed in the third insulating film 105. For each of the third wiring 106a and the fourth wiring 106b, a titanium (Ti) film, an aluminum (Al) film, a copper (Cu) film, an aluminum film containing Ti, or the like can be used. Preferably, copper having low resistance may be used.
The first orientation film is formed over the third wiring 106a, the fourth wring 106b, and the third insulating film 105. Then, a surface of the substrate 100, on which the first orientation film is formed, and a surface of the counter substrate, on which the second orientation film is formed, are provided so as face each other, and the liquid crystal layer is provided between the substrate 100 and the counter substrate. Thus, the liquid crystal display panel of Embodiment 1 of the present invention is completed.
A manufacturing method of a liquid crystal display device of Embodiment 1 of the present invention is described. First, the first insulating film 101 is formed over the substrate 100. Subsequently, a semiconductor film such as a polysilicon film or an amorphous silicon film is formed over the first insulating film 101. A resist pattern (not shown) is formed over the semiconductor film. Then, the semiconductor film is selectively etched with use of the resist pattern as a mask. In such a manner, the semiconductor film (the channel formation region 102a, the impurity region 102b, the impurity region 102c, and the impurity region 102d), the first electrode 102e, and the second electrode 102f are formed in the same step. After that, the resist pattern is removed thereafter.
The second insulating film 103 is formed over the semiconductor film (the channel formation region 102a, the impurity region 102b, the impurity region 102c, and the impurity region 102d), the first electrode 102e, the second electrode 102f, and the first insulating film 101. The second insulating film 103 is, for example, a silicon oxynitride film or a silicon oxide film, and formed by a plasma CVD method. Note that the second insulating film 103 may be formed of a silicon nitride film, or a multilayer film containing silicon nitride and silicon oxide. Then, a conductive film is formed over the second insulating film 103 and is patterned. Thus, two gate electrodes 104a are formed over the channel formation region 102a with the second insulating film 103 interposed therebetween. In addition, the first wiring 104b and the second wiring 104c are formed at the same time as the gate electrode 104a.
Note that as the conductive film, a film formed of aluminum (Al), nickel (Ni), tungsten (W), molybdenum (Mo), titanium (Ti), tantalum (Ta), neodymium (Nd), platinum (Pt), gold (Au), silver (Ag), or the like; a film formed of an alloy thereof; or a stacked-layer film thereof can be used. Alternatively, a silicon (Si) film to which an N-type impurity is introduced may be used.
Subsequently, impurities are added to the impurity region 102b, the impurity region 102c, and the impurity region 102d with use of the gate electrode 104a, a resist pattern (not shown), and the like as masks. Accordingly, impurities are included in the impurity region 102b, the impurity region 102c, and the impurity region 102d. Note that an N-type impurity element and a P-type impurity element may be added individually, or an N-type impurity element and a P-type impurity element may be added concurrently in a specific region. It is to be noted that in the latter case, an additive amount of one of an N-type impurity element and a P-type impurity element is set to be larger than that of the other.
Further, an impurity element may be added to the first electrode 102e and the second electrode 102f in a step of forming the impurity regions. Thus, the first electrode 102e and the second electrode 102f can be formed concurrently with the impurity region 102b, the impurity region 102c, and the impurity region 102d. Therefore, the number of steps can be prevented from being increased, so that the manufacturing cost can be reduced.
Note that an impurity elements may be added to the impurity regions before formation of the gate electrode 104a, for example, before or after formation of the second insulating film 103. At that time, the impurity element may be added to the first electrode 102e. Also in this case, addition of the impurity element to the impurity region 102b, the impurity region 102c, and the impurity region 102d can be conducted at the same time as addition of the impurity element to the first electrode 102e and the second electrode 102f. Accordingly, the manufacturing cost of the liquid crystal display panel can be reduced.
The third insulating film 105 is formed. Contact holes are formed in the third insulating film 105 and the second insulating film 103. Subsequently, a conductive film (such as a metal film) is formed over the third insulating film 105 and in the contact holes. Then, the conductive film is patterned, in other words, selectively removed. Thus, the third wiring 106a and the fourth wiring 106b are formed. Note that as the conductive film, a film formed of aluminum (Al), nickel (Ni), tungsten (W), molybdenum (Mo), titanium (Ti), tantalum (Ta), neodymium (Nd), platinum (Pt), gold (Au), silver (Ag), or the like; a film formed of an alloy thereof; or a stacked-layer film thereof can be used. Alternatively, a silicon (Si) film to which an N-type impurity is introduced may be used.
Subsequently, the first orientation film is formed, and liquid crystal is sealed between the first orientation film and a counter substrate on which the second orientation film is formed. Thus, the liquid crystal display panel is formed.
According to Embodiment 1 in the present invention, in the liquid crystal display panel in which the alignment orientation of the liquid crystal is controlled by the IPS mode, the first electrode 102e and the second electrode 102f are formed of a polysilicon film to which an impurity is introduced, and formed in the same step as the semiconductor layer (the source, the drain, and the channel formation region) of the transistor. Therefore, the number of manufacturing steps and the manufacturing cost can be reduced compared with the case in which the common electrode is formed of ITO.
Although the fourth wiring 106b is provided in the same layer as the third wiring 106a in this embodiment, the fourth wiring 106b may be provided in another wiring layer (for example, in the same layer as the first wiring 104b or the second wiring 104c). In addition, the second insulating film 103 is not necessarily formed over the whole surface.
The first wiring 104b may be formed in the same layer as the third wiring 106a. In this case, the first wiring 104b may be arranged parallel to the second wiring 104c, and the first wiring 104b and the second wiring 104c may be formed in the same layer only in a portion in which the third wiring 106a and the first wiring 104b are intersected.
Although a so-called top gate transistor in which a gate electrode is provided above a channel formation region is described in this embodiment, the present invention is not particularly limited thereto. A so-called bottom gate transistor in which the gate electrode is provided below the channel formation region or a transistor having a structure in which gate electrodes are provided over and below a channel formation region may be formed.
Note that a capacitor for holding a potential difference between the first electrode 102e and the second electrode 102f may be provided.
For example, as shown in
Further, as shown in
Further, as shown in
Note that each of the first wiring 106a, the second wiring 104c, the third wiring 106b, and the fourth wiring 104b is formed to have one element or a plurality of elements selected from a group of aluminum (Al), tantalum (Ta), titanium (Ti), molybdenum (Mo), tungsten (W), neodymium (Nd), chromium (Cr), nickel (Ni), platinum (Pt), gold (Au), silver (Ag), copper (Cu), magnesium (Mg), scandium (Sc), cobalt (Co), zinc (Zn), niobium (Nb), silicon (Si), phosphorus (P), boron (B), arsenic (As), gallium (Ga), indium (In), tin (Sn), and oxygen (O), a compound or an alloy material including one or a plurality of the elements selected from the group as a component (for example, Indium Tin Oxide (ITO), Indium Zinc Oxide (IZO), Indium Tin Oxide containing silicon oxide (ITSO), zinc oxide (ZnO), aluminum neodymium (Al—Nd), or magnesium silver (Mg—Ag)), a substance in which these compounds are combined, or the like. Alternatively, each of the first wiring 106a, the second wiring 104c, the third wiring 106b, and the fourth wiring 104b is formed to have a compound of silicon and the above-described material (silicide) (for example, aluminum silicon, molybdenum silicon, or nickel silicide) or a compound of nitrogen and the above-described material (for example, titanium nitride, tantalum nitride, or molybdenum nitride). Note that a large amount of n-type impurities (for example, phosphorus) or p-type impurities (for example, boron) may be included in silicon (Si). The impurities are included, thereby conductivity is improved and behavior similar to a normal conductor is exhibited. Accordingly, each of the first wiring 106a, the second wiring 104c, the third wiring 106b, and the fourth wiring 104b can be easily utilized as a wiring or an electrode. Silicon may be single crystalline silicon, polycrystalline silicon (polysilicon), or amorphous silicon. With use of single crystalline silicon or polycrystalline silicon, resistance can be reduced. With use of amorphous silicon, it can be manufactured with a simple manufacturing process. Since aluminum or silver has high conductivity, signal delay can be reduced. In addition, aluminum or silver is easily etched and patterned, so that minute processing can be performed. Since copper has high conductivity, signal delay can be reduced. Molybdenum is preferable because it can be manufactured without generation of a problem that a material causes a defect even when molybdenum is in contact with semiconductor oxide such as ITO or IZO or silicon, patterning and etching are easily performed, and heat resistance is high. Titanium is preferable because it can be manufactured without generation of a problem that a material causes a defect even when titanium is in contact with semiconductor oxide such as ITO or IZO or silicon, and heat resistance is high. Tungsten is preferable because heat resistance is high. Neodymium is preferable because heat resistance is high. In particular, it is preferable to use an alloy of neodymium and aluminum because heat resistance is improved and a hillock is hardly generated in aluminum. Silicon is preferable because it can be formed at the same time as a semiconductor film included in a transistor, and heat resistance is high. Indium Tin Oxide (ITO), Indium Zinc Oxide (IZO), Indium Tin Oxide containing silicon oxide (ITSO), zinc oxide (ZnO), and silicon (Si) are preferable because these materials have light-transmitting properties and can be used for a portion which transmits light. For example, these materials can be used for a pixel electrode or a common electrode.
Note that a wiring or an electrode may be formed of the above-described material with a single-layer structure or a multi-layer structure. By formation of the wiring or the electrode with a single-layer structure, a manufacturing process can be simplified; the number of days for a process can be reduced; and cost can be reduced. Alternatively, by formation of the wiring or the electrode with a multi-layer structure, an advantage of each material is taken and a disadvantage thereof is reduced so that a wiring or an electrode with high performance can be formed. For example, by inclusion of a material with low resistance (for example, aluminum) in a multi-layer structure, resistance in the wiring can be reduced. In addition, by inclusion of a material with high heat resistance, for example, by employment of a stacked-layer structure in which a material with low heat resistance and having a different advantage is sandwiched with materials with high heat resistance, heat resistance in the wiring or the electrode as a whole can be improved. For example, it is preferable that a stacked-layer structure be employed in which a layer containing aluminum is sandwiched with layers including molybdenum or titanium. Further, when there is a portion which is in direct contact with a wiring, an electrode, or the like formed of another material, they may be adversely affected each other. For example, in some cases, one material enters the other material and changes property thereof, so that an original purpose cannot be achieved; there occurs a problem in manufacturing, so that normal manufacturing cannot be performed. In such the case, a certain layer is sandwiched or covered with different layers, thereby the problem can be solved. For example, when Indium Tin Oxide (ITO) is to be in contact with aluminum, it is preferable to interpose titanium or molybdenum therebetween. Moreover, when silicon is to be in contact with aluminum, it is preferable to interpose titanium or molybdenum therebetween.
It is preferable that a material with heat resistance higher than that of a material used for the first wiring 106a be used for the second wiring 104c. This is because the second wiring 104c is often disposed in a higher-temperature state in a manufacturing process.
It is preferable that a material with resistance lower than that of a material used for the second wiring 104c be used for the first wiring 106a. This is because although only a signal of a binary value of an H signal and an L signal is supplied to the second wiring 104c, an analog signal is supplied to the first wiring 106a to contribute to display. Therefore, it is preferable to use a material with low resistance for the first wiring 106a so as to supply an accurate signal.
Although the fourth wiring 104b is not necessarily provided, a potential of a common electrode in each pixel can be stabilized by provision of the fourth wiring 104b. Note that although the fourth wiring 104b is provided in almost parallel to the second wiring 104b in
Note that the fourth wiring 104b is preferably provided in almost parallel to a gate line because an aperture ratio can be increased and layout can be efficiently performed.
Next, description is made of a pixel layout to which a basic structure of the liquid crystal display panel of Embodiment Mode 1 of the present invention is applied.
Note that
The pixel portion of the display panel of Embodiment 2 of the present invention includes a plurality of signal lines (first wirings 205a in the pixel of
Further, in the pixel portion, a plurality of pixels are arranged in matrix corresponding to the scan lines and the signal lines, and each pixel is connected to any one of the scan lines and any one of the signal lines.
Each pixel includes at least one transistor (the transistor 210 in the pixel of
The semiconductor layer (a semiconductor layer functioning as a channel formation region, a source region, and a drain region) of the transistor 210 and the first electrode 203e of each pixel are a stretch of film.
A region projecting from the second wiring 201c functions as the gate electrode 201a, and the semiconductor layer overlapping with the gate electrode 201a includes the channel formation region of the transistor 210. Further, one of the impurity region 203b and the impurity region 203c functions as a source of the transistor 210, and the other functions as a drain thereof. Note that the transistor 210 has a so-called dual-gate structure (in which two gate electrodes are arranged alongside over the semiconductor layer); however, the present invention is not limited thereto. Alternatively, a multi-gate structure in which three or more gate electrodes are arranged alongside over the semiconductor layer or a so-called single-gate structure (in which one gate electrode is provided for one transistor) may be employed. In the case of the single gate structure, the impurity region 203d is omitted.
In the transistor 210, the impurity region 203c to be one of a source and a drain is connected to the first wiring 205a through a contact hole, and the first electrode 203e and the impurity region 203b to be the other of the source and the drain are a stretch of film.
In
Further, the second electrode 203f is a film formed in the same step as the semiconductor layer of the transistor 210 and the first electrode 203e. The second electrode 203f is provided to electrically connect between pixels of a plurality of pixels through the third wiring 201b, at the same time, electrically connected to the fourth wiring 205b that is arranged in parallel with and separate from the second wiring 201c.
Note that in
The liquid crystal display panel of Embodiment 2 of the present invention is allowed as long as the semiconductor layer of the transistor 210, the first electrode 203e, and the second electrode 203f are films formed in the same step.
Further, shapes of the first electrode 203e and the second electrode 203f are not limited to the shapes shown in
Note that although
Next, more specific description is made of the structure of the liquid crystal display panel of Embodiment 2 of the present invention with reference to
A gate electrode 201a, a gate wiring (the third wiring 201b) and an auxiliary wiring (the second wiring 201c) are formed over the substrate 200. The second wiring 201c and the gate electrode 201a are a stretch of film, and the second wiring 201c is formed in the same step as the first wiring 201b and the gate electrode 201a. Also, for each of the gate electrode 201a, the first wiring 201b, and the second wiring 201c, an aluminum (Al) film, a copper (Cu) film, a thin film containing aluminum or copper as a main component, a chromium (Cr) film, a tantalum (Ta) film, a tantalum nitride (TaN) film, a titanium (Ti) film, a tungsten (W) film, a molybdenum (Mo) film, or the like can be used.
A gate insulating film (first insulating film 202) is formed over the gate electrode 201a, the first wiring 201b, and the second wiring 201c. In
A semiconductor layer (a channel formation region 203a, an impurity region 203b, an impurity region 203c, and an impurity region 203d) of a transistor 210, and a first electrode 203e and a second electrode 203f that control molecular orientation of the liquid crystal molecules are formed over the first insulating film 202. The channel formation region 203a, the impurity region 203b, the impurity region 203c, the impurity region 203d, the first electrode 203e, and the second electrode 203f are, for example, polysilicon films, which are formed in the same step. The substrate 200 can be formed of an insulating substrate such as a glass substrate, a quartz substrate, a plastic substrate, or a ceramic substrate, or of a metal substrate, a semiconductor substrate, or the like.
In the case where the transistor 210 is an n-channel transistor, an impurity element such as phosphorus or arsenic is introduced into the impurity region 203b, the impurity region 203c, and the impurity region 203d. In the case where the transistor 210 is a p-channel transistor, an impurity element such as boron is introduced into the impurity region 203b, the impurity region 203c and the impurity region 203d.
Further, the impurity element introduced into the impurity region 203b, the impurity region 203c, and the impurity region 203d may also be introduced into the first electrode 203e and the second electrode 203f. The resistance of the first electrode 203e and the second electrode 203f is lowered, since an impurity is introduced thereto, which is preferable for each of the first electrode 203e and the second electrode 203f to function as an electrode.
The first electrode 203e and the second electrode 203f each have thickness of, for example, 45 nm to 60 nm, and have sufficiently high light transmittance. In order to further improve the light transmittance, it is desirable to set thickness of the first electrode 203e and the second electrode 203f to be 40 nm or less.
Each of the first electrode 203e and the second electrode 203f may be an amorphous silicon film or an organic semiconductor film. In that case, an amorphous silicon film or an organic semiconductor film is used for the semiconductor layer of the transistor 210.
The semiconductor layer (the channel formation region 203a, the impurity region 203b, the impurity region 203c, and the impurity region 203d) of the transistor 210, and the first electrode 203e and the second electrode 203f that control molecular orientation of the liquid crystal molecules are formed in the same step. In this case, the number of steps can be reduced, so that the manufacturing cost can be reduced. In addition, it is desirable that impurity elements of the same type be introduced into the impurity region 203b, the impurity region 203c, the impurity region 203d, the first electrode 203e, and the second electrode 203f. This is because when the impurity elements of the same type are introduced, the impurity elements can be introduced without a problem even if the impurity region 203b, the impurity region 203c, the impurity region 203d, the first electrode 203e, and the second electrode 203f are provided close to each other, so that dense layout becomes possible. It is desirable to add impurity elements of either P-type or N-type because the manufacturing cost can be low compared with the case in which impurity elements of different types are introduced.
An interlayer insulating film (second insulating film 204) is formed over the first insulating film 202, the semiconductor layer (the channel formation region 203a, the impurity region 203b, the impurity region 203c, and the impurity region 203d) of the transistor 210, and the first electrode 203e and the second electrode 203f. The second insulating film 204 preferably has a stacked-layer structure in which a protective film and a planarization film are stacked in this order. For the protective film, an inorganic insulating film is suitable. As an inorganic insulating film, a silicon nitride film, a silicon oxide film, a silicon oxynitride film, or a film formed by stacking these films can be used. As a planarization film, a resin film is suitable. For a resin film, polyimide, polyamide, acrylic, polyimide amide, epoxy, or the like can be used.
A signal line (a third wiring 205a) and a connection wiring (a fourth wiring 205b) are formed over the second insulating film 204. The third wiring 205a is connected to the impurity region 203c through holes (contact holes) formed in the second insulating film 204 and the first insulating film 202. The fourth wiring 205b is connected to the first wiring 201b through a hole formed in the second insulating film 204 and the first insulating film 202, and also connected to the second wiring 203f through the hole formed in the second insulating film 204. For each of the third wiring 205a and the fourth wiring 205b, a titanium (Ti) film, an aluminum (Al) film, a copper (Cu) film, an aluminum film containing Ti, or the like can be used. Preferably, copper having low resistance may be used.
The first orientation film is formed over the third wiring 205a, the fourth wring 205b, and the second insulating film 204. Then, a surface of the substrate 200, on which the first orientation film is formed, and a surface of the counter substrate, on which the second orientation film is formed, are provided so as face each other, and the liquid crystal layer is provided between the substrate 200 and the counter substrate. Thus, the liquid crystal display panel of Embodiment 2 of the present invention is completed.
Next, a manufacturing method of a liquid crystal display device of Embodiment 2 of the present invention is described. First, a conductive film is formed over the substrate 200, and is patterned. Thus, two gate electrodes 201a are formed. In addition, the first wiring 201b and the second wiring 201c are formed at the same time as the gate electrode 201a.
Note that as the conductive film, a film formed of aluminum (Al), nickel (Ni), tungsten (W), molybdenum (Mo), titanium (Ti), tantalum (Ta), neodymium (Nd), platinum (Pt), gold (Au), silver (Ag), or the like; a film formed of an alloy thereof; or a stacked-layer film thereof can be used. Alternatively, a silicon (Si) film to which an N-type impurity is introduced may be used.
The gate insulating film (first insulating film 202) is formed so as to cover the gate electrode 201a, the first wiring 201b, and the second wiring 201c. The first insulating film 202 is, for example, a silicon oxynitride film or a silicon oxide film, and formed by a plasma CVD method. Note that the first insulating film 202 may be formed of a silicon nitride film, or a multilayer film containing silicon nitride and silicon oxide.
Subsequently, a semiconductor film such as a polysilicon film or an amorphous silicon film is formed over the first insulating film 202, and a resist pattern (not shown) is formed over this semiconductor film. With use of this resist pattern as a mask, the semiconductor film is selectively etched. Thus, the semiconductor film (the channel formation region 203a, the impurity region 203b, the impurity region 203c, and the impurity region 203d), the first electrode 203e, and the second electrode 203f are formed in the same step. After that, the resist pattern is removed.
Subsequently, impurities are added to the impurity region 203b, the impurity region 203c, and the impurity region 203d. Accordingly, impurities are included in the impurity region 203b, the impurity region 203c, and the impurity region 203d. Note that an N-type impurity element and a P-type impurity element may be added individually, or an N-type impurity element and a P-type impurity element may be added concurrently in a specific region. It is to be noted that in the latter case, an additive amount of one of an N-type impurity element and a P-type impurity element is set to be larger than that of the other.
Further, an impurity element may be added to the first electrode 203e and the second electrode 203f in a step of forming the impurity regions. Thus, the first electrode 203e and the second electrode 203f can be formed concurrently with the impurity region 203b, the impurity region 203c, and the impurity region 203d. Therefore, the number of steps can be prevented from being increased, so that the manufacturing cost can be reduced.
The second insulating film 204 is formed over the semiconductor film (the channel formation region 203a, the impurity region 203b, the impurity region 203c, and the impurity region 203d), the first electrode 203e, the second electrode 203f, and the first insulating film 202. The second insulating film 204 is, for example, a silicon oxynitride film or a silicon oxide film, and formed by a plasma CVD method. Note that the second insulating film 204 may be formed of a silicon nitride film, or a multilayer film containing silicon nitride and silicon oxide.
Holes (contact holes) are formed in the second insulating film 204. Subsequently, a conductive film (such as a metal film) is formed over the second insulating film 204 and in the contact holes. Then, the metal film is patterned. Thus, the third wiring 205a and the fourth wiring 205b are formed. Note that as the conductive film, a film formed of aluminum (Al), nickel (Ni), tungsten (W), molybdenum (Mo), titanium (Ti), tantalum (Ta), neodymium (Nd), platinum (Pt), gold (Au), silver (Ag), or the like; a film formed of an alloy thereof; or a stacked-layer film thereof can be used. Alternatively, silicon (Si) into which an N-type impurity is introduced may be used.
Subsequently, the first orientation film is formed, and liquid crystal is sealed between the first orientation film and a counter substrate on which the second orientation film is formed. Thus, the liquid crystal display panel is formed.
According to Embodiment 2 in the present invention, in the liquid crystal display device in which the orientation of the liquid crystal is controlled by the IPS mode, the first electrode 203e and the second electrode 203f are formed of a polysilicon film to which an impurity is introduced, and formed in the same step as the semiconductor layer (the source, the drain, and the channel formation region) of the transistor. Therefore, the number of manufacturing steps and the manufacturing cost can be reduced compared with the case in which the common electrode is formed of ITO.
Although a so-called top gate transistor in which the gate electrode is provided above the channel formation region is described in this embodiment, the present invention is not particularly limited thereto. A so-called bottom gate transistor in which the gate electrode is provided below the channel formation region or a transistor having a structure in which the gate electrodes are provided over and below the channel formation region may be formed.
Note that a capacitor for holding a potential difference between the first electrode 203e and the second electrode 203f may be provided.
For example, as shown in
Further, as shown in
Further, as shown in
Note that each of the first wiring 205a, the second wiring 201c, the third wiring 201b, and the fourth wiring 205b is formed to have one element or a plurality of elements selected from a group of aluminum (Al), tantalum (Ta), titanium (Ti), molybdenum (Mo), tungsten (W), neodymium (Nd), chromium (Cr), nickel (Ni), platinum (Pt), gold (Au), silver (Ag), copper (Cu), magnesium (Mg), scandium (Sc), cobalt (Co), zinc (Zn), niobium (Nb), silicon (Si), phosphorus (P), boron (B), arsenic (As), gallium (Ga), indium (In), tin (Sn), and oxygen (O), a compound or an alloy material including one or a plurality of the elements selected from the group as a component (for example, Indium Tin Oxide (ITO), Indium Zinc Oxide (IZO), Indium Tin Oxide containing silicon oxide (ITSO), zinc oxide (ZnO), aluminum neodymium (Al—Nd), or magnesium silver (Mg—Ag)), a substance in which these compounds are combined, or the like. Alternatively, each of the first wiring 205a, the second wiring 201c, the third wiring 201b, and the fourth wiring 205b is formed to have a compound of silicon and the above-described material (silicide) (for example, aluminum silicon, molybdenum silicon, or nickel silicide) or a compound of nitrogen and the above-described material (for example, titanium nitride, tantalum nitride, or molybdenum nitride). Note that a large amount of n-type impurities (for example, phosphorus) or p-type impurities (for example, boron) may be included in silicon (Si). The impurities are included, thereby conductivity is improved and behavior similar to a normal conductor is exhibited. Accordingly, each of the first wiring 205a, the second wiring 201c, the third wiring 201b, and the fourth wiring 205b can be easily utilized as a wiring or an electrode. Silicon may be single crystalline silicon, polycrystalline silicon (polysilicon), or amorphous silicon. With use of single crystalline silicon or polycrystalline silicon, resistance can be reduced. With use of amorphous silicon, it can be manufactured with a simple manufacturing process. Since aluminum or silver has high conductivity, signal delay can be reduced. In addition, aluminum or silver is easily etched and patterned, so that minute processing can be performed. Since copper has high conductivity, signal delay can be reduced. Molybdenum is preferable because it can be manufactured without generation of a problem that a material causes a defect even when molybdenum is in contact with semiconductor oxide such as ITO or IZO or silicon, patterning and etching are easily performed, and heat resistance is high. Titanium is preferable because it can be manufactured without generation of a problem that a material causes a defect even when titanium is in contact with semiconductor oxide such as ITO or IZO or silicon, and heat resistance is high. Tungsten is preferable because heat resistance is high. Neodymium is preferable because heat resistance is high. In particular, it is preferable to use an alloy of neodymium and aluminum because heat resistance is improved and a hillock is hardly generated in aluminum. Silicon is preferable because it can be formed at the same time as a semiconductor film included in a transistor, and heat resistance is high. Indium Tin Oxide (ITO), Indium Zinc Oxide (IZO), Indium Tin Oxide containing silicon oxide (ITSO), zinc oxide (ZnO), and silicon (Si) are preferable because these materials have light-transmitting properties and can be used for a portion which transmits light. For example, these materials can be used for a pixel electrode or a common electrode.
Note that a wiring or an electrode may be formed of the above-described material with a single-layer structure or a multi-layer structure. By formation of the wiring or the electrode with a single-layer structure, a manufacturing process can be simplified; the number of days for a process can be reduced; and cost can be reduced. Alternatively, by formation of the wiring or the electrode with a multi-layer structure, an advantage of each material is taken and a disadvantage thereof is reduced so that a wiring or an electrode with high performance can be formed. For example, by inclusion of a material with low resistance (for example, aluminum) in a multi-layer structure, resistance in the wiring can be reduced. In addition, by inclusion of a material with high heat resistance, for example, by employment of a stacked-layer structure in which a material with low heat resistance and having a different advantage is sandwiched with materials with high heat resistance, heat resistance in the wiring or the electrode as a whole can be improved. For example, it is preferable that a stacked-layer structure be employed in which a layer containing aluminum is sandwiched with layers including molybdenum or titanium. Further, when there is a portion which is in direct contact with a wiring, an electrode, or the like formed of another material, they may be adversely affected each other. For example, in some cases, one material enters the other material and changes property thereof, so that an original purpose cannot be achieved; there occurs a problem in manufacturing, so that normal manufacturing cannot be performed. In such the case, a certain layer is sandwiched or covered with different layers, thereby the problem can be solved. For example, when Indium Tin Oxide (ITO) is to be in contact with aluminum, it is preferable to interpose titanium or molybdenum therebetween. Moreover, when silicon is to be in contact with aluminum, it is preferable to interpose titanium or molybdenum therebetween.
It is preferable that a material with heat resistance higher than that of a material used for the first wiring 205a be used for the second wiring 201c. This is because the second wiring 201c is often disposed in a higher-temperature state in a manufacturing process.
It is preferable that a material with resistance lower than that of a material used for the second wiring 201c be used for the first wiring 205a. This is because although only a signal of a binary value of an H signal and an L signal is supplied to the second wiring 201c, an analog signal is supplied to the first wiring 205a to contribute to display. Therefore, it is preferable to use a material with low resistance for the first wiring 205a so as to supply an accurate signal.
Although the third wiring 201b is not necessarily provided, a potential of a common electrode in each pixel can be stabilized by provision of the third wiring 201b. Note that although the third wiring 201b is provided in almost parallel to the second wiring 201c in
Note that the third wiring 201b is preferably provided in almost parallel to the second wiring 201c because an aperture ratio can be increased and layout can be efficiently performed.
First, a brief structure of a liquid crystal panel is described with reference to
In the liquid crystal panel shown in
As shown by the liquid crystal panel in
Note that by provision of the scan line input terminals 9903 on both the right side and the left side of the substrate 9900, the pixels 9902 can be arranged in a highly dense state.
In addition, by provision of the signal line input terminal 9904 on one of the up side and the bottom side of the substrate 9900, a frame of the liquid crystal panel can be small, or a region of the pixel portion 9901 can be large.
For each of the pixels 9902 in the pixel portion 9901, a first terminal of the switching element is connected to the signal line, and a second terminal thereof is connected to the pixel electrode layer, whereby each of the pixels 9902 can be independently controlled by a signal inputted externally. Note that on and off of the switching element are controlled by a signal supplied to the scan line.
Note that as described above, a single crystalline substrate, an SOI substrate, a glass substrate, a quartz substrate, a plastic substrate, a paper substrate, a cellophane substrate, a stone substrate, a stainless steel substrate, a substrate made of a stainless steel foil, or the like can be used as the substrate 9900.
Also, as described above, a transistor, a diode (such as a PN diode, a PIN diode, a Schottky diode, or a diode-connected transistor), a thyristor, a logic circuit configured with them, or the like can be used for the switching element.
In the case where a TFT is used for the switching element, a gate of the TFT is connected to the scan line, the first terminal thereof is connected to the signal line, and the second terminal thereof is connected to the pixel electrode layer. Therefore, each of the pixels 9902 can be independently controlled by a signal inputted externally.
Note that the scan line input terminal 9903 may be provided on one of the right side and the left side of the substrate 9900. By provision of the scan line input terminal 9903 on one of the right side and the left side of the substrate 9900, the frame of the liquid crystal panel can be small, or the region of the pixel portion 9901 can be large.
The scan lines extended from the one scan line input terminal 9903 and the scan lines extended from the other scan line input terminal 9903 may be common.
Note that the signal line input terminals 9904 may be provided on both the up side and the bottom side of the substrate 9900. By provision of the signal line input terminals 9904 on both the up side and the bottom side of the substrate 9900, the pixels 9902 can be arranged in a highly dense state.
Further, a capacitor may be further formed for the pixel 9902. In the case where a capacitor is formed for the pixel 9902, a capacitor line may be formed over the substrate 9900. In the case where a capacitor line is formed over the substrate 9900, it is set that a first electrode of the capacitor is connected to the capacitor line, and a second electrode thereof is connected to the pixel electrode layer. Meanwhile, in the case where the capacitor line is not formed over the substrate 9900, it is set that the first electrode of the capacitor is connected to the scan line of another pixel 9902 than the pixel 9902 for which the capacitor is provided, and the second electrode thereof is connected to the pixel electrode layer.
Although the liquid crystal panel shown in
Note that the driver IC 10001 may be formed over a single-crystalline semiconductor substrate, or may have a circuit formed of a TFT over a glass substrate.
Note that for the liquid crystal panel shown in
Also, as shown in
The scan line driver circuit 9905 and the signal line driver circuit 9906 are formed of a plurality of n-channel transistors and p-channel transistors. It is to be noted that they may be formed of only n-channel transistors or p-channel transistors.
Subsequently, specific description is made of the pixel 9902 with reference to circuit diagrams of
A pixel 9902 of
Note that the wiring 10104, the wiring 10105, and the wiring 10106 are a signal line, a scan line, and a capacitor line, respectively.
The wiring 10104 is supplied with an analog voltage signal (video signal). It is to be noted that the video signal may be a digital voltage signal or a current signal.
The wiring 10105 is supplied with an H-level or L-level voltage signal (scan signal). Note that the H-level voltage signal is a voltage with which the transistor 10101 can be turned on, and the L-level voltage signal is a voltage with which the transistor 10101 can be turned off.
The wiring 10106 is supplied with a certain power source voltage. It is to be noted that a pulse signal may be supplied to the wiring 10106.
Description is made of operation of the pixel 9902 of
Next, when the wiring 10105 is at an L level, the transistor 10101 is turned off, and the wiring 10104, the second electrode of the liquid crystal element 10102, and the second electrode of the capacitor 10103 are electrically disconnected. However, the capacitor 10103 holds the potential difference between the wiring 10106 and the video signal; therefore, the second electrode of the capacitor 10103 can hold a similar potential to the video signal.
Thus, the pixel 9902 of
Note that as is not shown, the capacitor 10103 is not always necessary if the liquid crystal element 10102 has a capacitor component with which the video signal can be held.
Note that as shown in
As shown in
A liquid crystal display device having a liquid crystal panel is described with reference to
First, the liquid crystal display device shown in
Note that the liquid crystal panel 10307 can be similar to that described in another embodiment. Further, description is made of the liquid crystal panel of this embodiment having an active-type structure where each pixel is provided with a switching element; however, the liquid crystal display panel of
A structure of the backlight unit 10301 is described. The backlight unit 10301 is structured to include a diffuser plate 10302, a light guide plate 10303, a reflector plate 10304, a lamp reflector 10305, and a light source 10306. For the light source 10306, a cold cathode tube, a hot cathode tube, a light-emitting diode, an inorganic EL, an organic EL, or the like is used, and the light source 10306 has a function of emitting light if necessary. The lamp reflector 10305 has a function of effectively leading fluorescence to the light guide plate 10303. The light guide plate 10303 has a function of leading light to the entire surface by total reflection of fluorescence. The diffuser plate 10302 has a function of reducing variations in luminance, and the reflector plate 10304 has a function of reusing light leaked under the light guide plate 10303.
Note that by provision of a prism sheet between the diffuser plate 10302 and the second polarizer containing layer 10309 in the liquid crystal display device of this embodiment, luminance of a screen of the liquid crystal panel can be improved.
A control circuit for adjusting luminance of the light source 10306 is connected to the backlight unit 10301. A signal is supplied from the control circuit, whereby luminance of the light source 10306 can be adjusted.
The second polarizer containing layer 10309 is provided between the liquid crystal panel 10307 and the backlight unit 10301, and the first polarizer containing layer 10308 is provided on an opposite side of the liquid crystal panel 10307, on which the backlight unit 10301 is not provided.
Note that in the case where the liquid crystal element of the liquid crystal panel 10307 is driven in the IPS mode or the FFS mode, the first polarizer containing layer 10308 and the second polarizer containing layer 10309 may be provided so as to be in a cross nicol state or a parallel nicol state.
A retardation film may be provided between the liquid crystal panel 10307 and one or both of the first polarizer containing layer 10308 and the second polarizer containing layer 10309.
Note that a slit (lattice) 10310 is provided between the second polarizer containing layer 10309 and the backlight unit 10301 as shown in
The slit 10310 with an opening that is arranged on the backlight unit side transmits light that is incident from the light source to be a striped shape. Then, the light is incident on a display device portion. This slit 10310 can make parallax in both eyes of a viewer who is on the viewing side. The viewer sees only a pixel for the right eye with the right eye and only a pixel for a left eye with the left eye simultaneously. Therefore, the viewer can see three-dimensional display. That is, in the display device portion, light given a specific viewing angle by the slit 10310 passes through each pixel corresponding to an image for the right eye and an image for the left eye, whereby the image for the right eye and the image for the left eye are separated in accordance with different viewing angles, and three-dimensional display is performed.
An electronic appliance such as a television device or a mobile phone is manufactured using a liquid crystal display device of
A specific structure of a backlight is described with reference to
As shown in
As shown in
As shown in
Further, as shown in
Further, the light-emitting diode (W) 10502 which emits white light may be used in combination with the light-emitting diodes (LED) 10503, 10504, and 10505 of RGB colors.
Note that in the case of having the light-emitting diodes of RGB colors, the light-emitting diodes sequentially emit light in accordance with time by application of a field sequential mode, thereby color display can be performed.
Using a light-emitting diode is suitable for a large display device since luminance is high. Further, purity of RGB colors is high; therefore, a light-emitting diode has excellent color reproducibility as compared to a cold cathode tube. In addition, an area required for arrangement can be reduced; therefore, a narrower frame can be achieved when a light-emitting diode is applied to a small display device.
Further, a light source is not necessarily provided as the backlight unit shown in
An example of a polarizer containing layer (also referred to as a polarizing plate or a polarizing film) is described with reference to
A polarizing film 10800 of
The PVA polarizing film 10803 has a function of generating light in only a certain oscillation direction (linear polarized light). In specific, the PVA polarizing film 10803 contains a molecule (polarizer) in which lengthwise electron density and widthwise electron density are greatly different from each other. The direction of the molecules in which lengthwise electron density and widthwise electron density are greatly different from each other is uniformed, thereby the PVA polarizing film 10803 can form linear polarization.
For example, as for the PVA polarizing film 10803, a polymer film of polyvinyl alcohol is doped with an iodine compound and the PVA film is pulled in a certain direction, thereby a film in which iodine molecules are aligned in a certain direction can be obtained. Then, light which is parallel to the major axis of the iodine molecule is absorbed by the iodine molecule. Alternatively, a dichroic dye may be used instead of iodine for high durability use and high heat resistance use. It is desirable that the dye be used for liquid crystal display devices which need to have durability and heat resistance, such as an in-car LCD or an LCD for a projector.
When the PVA polarizing film 10803 is sandwiched by films to be base materials (the first substrate film 10802 and the second substrate film 10804) from the both sides, the reliability can be improved. Alternatively, the PVA polarizing film 10803 may be sandwiched by triacetylcellulose (TAC) films with high transparency and high durability. The substrate film and the TAC film function as protective films of the polarizer contained in the PVA polarizing film 10803.
The adhesive layer 10805 which is to be attached to a glass substrate of a liquid crystal panel may be attached to one of the substrate films (the substrate film 10804). The adhesive layer 10805 may be formed by application of an adhesive on one of the substrate films (the substrate film 10804). Furthermore, the adhesive layer 10805 may be provided with the mold release film 10806 (separate film).
The other substrate film (substrate film 10802) is provided with a protective film.
A hard coating scattering layer (anti-glare layer) may be provided on the surface of the polarizing film 10800. The surface of the hard coating scattering layer has minute concavity and convexity that is formed by an AG treatment; therefore, the hard coating scattering layer has an anti-glare function of scattering external light and can prevent reflection of external light in the liquid crystal panel and the surface reflection.
Furthermore, a plurality of optical thin layers with different refractive indexes may be layered (referred to as anti-reflection treatment or AR treatment) on the surface of the polarizing film 10800. The plurality of layered optical thin layers with different refractive indexes can reduce reflectivity on the surface by an effect of interference of light.
Operation of each circuit included in a liquid crystal display device is described with reference to
In the pixel portion 10605, a plurality of pixels are included and switching elements are provided in an intersecting region of a signal line 10612 and a scan line 10610. By the switching elements, application of a voltage to control tilt of liquid crystal molecules can be controlled. Such a structure where switching elements are provided in respective intersecting regions is referred to as an active type. The pixel portion of the present invention is not limited to such an active type, and may have a passive type structure instead. The passive type can be formed by a simple process, since each pixel does not have a switching element.
The driver circuit portion 10608 includes a control circuit 10602, a signal line driver circuit 10603, and a scan line driver circuit 10604. The control circuit 10602 to which a video signal 10601 is inputted has a function to control a gray scale in accordance with display content of the pixel portion 10605. Therefore, the control circuit 10602 inputs a generated signal to the signal line driver circuit 10603 and the scan line driver circuit 10604. When a switching element is selected through the scan line 10610 in accordance with the scan line driver circuit 10604, a voltage is applied to a pixel electrode in a selected intersecting region. The value of this voltage is determined in accordance with a signal inputted from the signal line driver circuit 10603 through a signal line.
Further, in the control circuit 10602, a signal to control power supplied to a lighting unit 10606 is generated, and the signal is inputted to a power source 10607 of the lighting unit 10606. The backlight unit described in the aforementioned embodiment can be used for the lighting unit. Note that the lighting unit includes a front light besides a backlight. A front light is a platy light unit formed of an illuminant and a light guiding body, which is attached to a front side of a pixel portion and illuminates the whole area. By such a lighting unit, the pixel portion can be evenly illuminated with low power consumption.
Further, as shown in
Further, as shown in
The signal line driver circuit 10603, the scan line driver circuit 10604, and the pixel portion 10605 as described above can be formed of semiconductor elements provided over one substrate. The semiconductor element can be formed using a thin film transistor provided over a glass substrate. In this case, a crystalline semiconductor film may be applied to the semiconductor element. The crystalline semiconductor film can constitute a circuit included in a driver circuit portion, since it has high electrical characteristics, in particular, mobility. Further, the signal line driver circuit 10603 and the scan line driver circuit 10604 may be mounted on a substrate with use of an IC (Integrated Circuit) chip. In this case, an amorphous semiconductor film can be applied to a semiconductor element in a pixel portion.
A liquid crystal display module is described with reference to
The second polarizer containing layer 10707 is provided between the circuit substrate 10700 and a backlight that is a light source. Also, the first polarizer containing layer 10706 is provided over the counter substrate 10701. On the other hand, an absorption axis of the second polarizer containing layer 10707 and an absorption axis of the first polarizer containing layer 10706 provided on the viewing side are arranged to be in a cross nicol state.
The stack of the second polarizer containing layer 10707 and the first polarizer containing layer 10706 is bonded to the circuit substrate 10700 and the counter substrate 10701. In addition, a retardation film may be stacked to be interposed between the stack of polarizer containing layers and the substrate. Furthermore, the first polarizer containing layer 10706 on the viewing side may be subjected to a reflection prevention treatment as necessary.
Moreover, optical response speed of a liquid crystal display module gets higher by reduction of the cell gap of the liquid crystal display module. In addition, the optical response speed can also get higher by decrease of the viscosity of a liquid crystal material. The increase in response speed is particularly advantageous when a pixel pitch in a pixel region of a liquid crystal display module of a TN mode is 30 μm or less. Also, further increase in response speed is possible by an overdrive method in which an applied voltage is increased (or decreased) for a moment.
The overdriving is described with reference to
The overdriving is a technique for increasing this response speed. In specific, this is a method as follows: first, Vo that is a larger voltage than Vi is applied to the element for a certain time to increase the response speed of the output luminance and the luminance is made close to the objective output luminance Lo, and then, the input voltage is returned to Vi. The input voltage and the output luminance at this time are shown by an input voltage 2 and an output luminance 2, respectively. As seen from the graph, the time which the output luminance 2 takes before reaching the objective luminance Lo is shorter than that of the output luminance 1.
It is to be noted that, although the case where the output luminance changes positively with respect to the input voltage is described with reference to
A circuit for realizing the above driving is described with reference to
First, the input video signal Gi is inputted to the coding circuit 9801 and encoded. In other words, the input video signal Gi is converted from an analog signal to a digital signal with an appropriate bit number. After that, the converted digital signal is inputted to the frame memory 9802 and the correction circuit 9803 in each. A video signal of the previous frame which has been held in the frame memory 9802 is also inputted to the correction circuit 9803 at the same time. Then, video signals that are corrected from the video signal of the frame and the video signal of the previous frame in the correction circuit 9803 according to a numeric value table that is prepared beforehand are outputted. At this time, an output switching signal may be inputted to the correction circuit 9803 and the corrected video signal and the video signal of the frame may be switched to be outputted. Next, the corrected video signal or the video signal of the frame is inputted to the DA converter circuit 9804. Further, the output video signal Go which is an analog signal of a value in accordance with the corrected video signal or the video signal of the frame is outputted. In this manner, the overdriving can be realized.
Next, the case where an input video signal Gi is a signal of a digital value and an output video signal Go is also a signal of a digital value is described with reference to
The input video signal Gi is a digital signal, and first, inputted to the frame memory 9812 and the correction circuit 9813 in each. A video signal of the previous frame which has been held in the frame memory 9812 is also inputted to the correction circuit 9813 at the same time. Then, video signals that are corrected from the video signal of the frame and the video signal of the previous frame in the correction circuit 9813 according to a numeric value table that is prepared beforehand are outputted. At this time, an output switching signal may be inputted to the correction circuit 9813 and the corrected video signal and the video signal of the frame may be switched to be outputted. In this manner, the overdriving can be realized.
It is to be noted that a combination of the numeric value table for obtaining a corrected video signal is the product of the number of gray scales, which 1 SF may take, and the number of gray scales, which 2 SF may take. The smaller the number of this combination, the more preferable, since data amount to be stored in the correction circuit 9813 becomes small. In this embodiment mode, in halftone before the subframe displaying a light image reaches the maximum luminance, the luminance of a dark image is 0; and after the subframe displaying a light image reaches the maximum luminance and until the maximum gray scale is displayed, the luminance of a light image is constant; therefore, the number of this combination can be significantly small. Accordingly, when the driving method of a display device of the present invention is carried out in combination with the overdriving, a great effect can be obtained.
It is to be noted that the overdrive circuit of the present invention includes the case where the input video signal Gi is an analog signal and the output video signal Go is a digital signal. In this case, the DA converter circuit 9804 may be omitted from the circuit shown in
The scanning backlight is described with reference to
A change in luminance of each cold cathode tube when scanning is described with reference to
The driving method of a display device shown in
It is preferable that the backlight luminance in a period with low luminance be approximately the same as the maximum luminance of the subframe in which a dark image is inserted. In specific, it is preferable that the luminance be the maximum luminance Lmax1 of 1 SF in the case where a dark image is inserted in 1 SF, and the maximum luminance Lmax2 of 2 SF in the case where a dark image is inserted in 2 SF.
It is to be noted that LEDs may be used as a light source of the scanning backlight. A scanning backlight in this case is as shown in
The high frequency driving is described with reference to
The display device of the present invention can be applied to various electronic appliances, specifically a display portion of electronic appliances. The electronic appliances include cameras such as a video camera and a digital camera, a goggle-type display, a navigation system, an audio reproducing device (a car audio component stereo, an audio component stereo, or the like), a computer, a game machine, a portable information terminal (a mobile computer, a mobile phone, a mobile game machine, an electronic book, or the like), an image reproducing device having a recording medium (specifically, a device for reproducing a recording medium such as a digital versatile disc (DVD) and having a display for displaying the reproduced image) and the like.
In recent years, the need to grow in size of a display has been increased. In accordance with the enlargement of a display, rise in price becomes a problem. Therefore, an object is to reduce the manufacturing cost as much as possible and to provide a high quality product at as low price as possible. A display using the display device of the present invention for the display portion 101103 can be reduced in cost.
In recent years, in accordance with advance in performance of a digital camera and the like, competitive manufacturing thereof has been intensified. Thus, it is important to provide a higher-performance product at as low price as possible. A digital camera using the display device of the present invention for the display portion 101202 can be reduced in cost.
In recent years, a mobile phone is provided with a game function, a camera function, an electronic money function, or the like, and the need for a high-value added mobile phone has been increased. Further, the high definition display has been required. The mobile phone using the display device of the present invention for the display portion 101803 can be reduced in cost.
Thus, the present invention can be applied to various electronic appliances.
As described above, an electronic appliance according to the present invention is completed by incorporation of a liquid crystal display device of the present invention into a display portion. Such an electronic appliance of the present invention can display an image that is favorable both indoors and outdoors. In particular, an electronic appliance such as a camera or an image pickup device which is often used outdoors and indoors can fully exert advantageous effects, such as a wide viewing angle and less color-shift depending on an angle at which a display screen is seen, both indoors and outdoors.
In this embodiment, an application example where a display panel of the present invention is used is described by illustration of an application mode. A display panel of the present invention may be incorporated in a moving object, a structure, or the like.
Note that the position for setting a display panel of the present invention is not limited to a glass door of a train car body as shown in
Another application example of a moving object incorporating a display device using a display panel of the present invention is described with reference to
Note that the position for setting a display panel of the present invention is not limited to a front portion of a car body as shown in
Another application example of a moving object incorporating a display device using a display panel of the present invention is described with reference to
Note that the position for setting a display panel of the present invention is not limited to the ceiling of the airplane body 11701 shown in
Although this embodiment has illustrated a train car body, a car body, and an airplane body as exemplary moving objects, the present invention is not limited to these, and can be applied to motorbikes, four-wheeled vehicles (including cars, buses, and the like), trains (including monorails, railroads, and the like), ships and vessels, and the like. By employment of a display panel of the present invention, manufacturing cost of a display panel can be reduced, as well as a moving object having a display medium with an excellent operation can be provided. In addition, since images displayed on display panels incorporated in a moving object can be switched all at once by an external signal, in particular, the present invention is quite advantageous to be applied to advertisement display boards for unspecified number of customers, or information display boards in an emergency.
An example where a display panel of the present invention is applied to a structure is described with reference to
The display panels 11402 shown in
Another example where a display panel of the present invention is applied to a structure is described with reference to
The position for setting a display panel of the present invention is not limited to the sidewall of the prefabricated bath unit 11601 shown in
Although this embodiment has illustrated a telephone pole, a prefabricated bath unit, and the like as exemplary structures, this embodiment is not limited to these, and can be applied to any structures which can incorporate a display panel. By application of the display device of the present invention, manufacturing cost of a display device can be reduced, as well as a moving object having a display medium with an excellent operation can be provided.
This application is based on Japanese Patent Application serial no. 2006-155471 filed in Japan Patent Office on 2 Jun. 2006, the entire contents of which are hereby incorporated by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-155471 | Jun 2006 | JP | national |
The instant application is a Continuation of U.S. application Ser. No. 16/151,710 filed on Oct. 4, 2018, which is a Continuation of U.S. application Ser. No. 14/102,858 filed on Dec. 11, 2013, now U.S. Pat. No. 10,095,070, which is a Continuation of U.S. application Ser. No. 13/795,173 filed on Mar. 12, 2013, now U.S. Pat. No. 8,610,862, which is a Continuation of U.S. application Ser. No. 12/909,237 filed on Oct. 21, 2010, now U.S. Pat. No. 8,537,318, which is a Continuation of U.S. application Ser. No. 11/806,148 filed on May 30, 2007, now U.S. Pat. No. 7,847,904, which claims priority under 35 U.S.C. 119 to the Japanese Application No. 2006-155471 filed on Jun. 2, 2006 in Japan.
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