Liquid crystal display device and electronic apparatus

According to an aspect, a liquid crystal display device includes a first substrate, a second substrate, a liquid crystal layer, a first electrode, and a second electrode. The first electrode includes an electrode base portion extending in a first direction, and a plurality of comb tooth portions extending in a second direction different from the first direction and protruding from the electrode base portion with a certain distance interposed therebetween. At least one of the first substrate and the second substrate includes a light-blocking part that reduces intensity of light passing therethrough at a position overlapping with at least one of the center of the comb tooth portion and the center between the adjacent comb tooth portions in a direction perpendicular to the first substrate.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application claims priority to Japanese Priority Patent Application JP 2014-098531 filed in the Japan Patent Office on May 12, 2014, the entire content of which is hereby incorporated by reference.

BACKGROUND

1. Technical Field

The present invention relates to a liquid-crystal display device provided with liquid crystals and to an electronic apparatus including the liquid-crystal display device provided with liquid crystals.

2. Description of the Related Art

There have been developed systems (modes) for driving liquid crystals, including a liquid crystal driving system that uses an electric field generated in a vertical direction between substrates, that is, a vertical electric field. Examples of a liquid crystal display device that drives liquid crystals using a vertical electric field include, but are not limited to, vertical-electric-field liquid crystal display devices provided with a twisted nematic (TN) system, a vertical alignment (VA) system, an electrically controlled birefringence (ECB) system, etc. As disclosed in Japanese Patent Application Laid-open Publication No. 2008-52161 (JP-A-2008-52161), there has also been developed a liquid crystal driving system that uses an electric field generated in a direction parallel to substrates (horizontal direction), that is, a horizontal electric field. Examples of a liquid crystal display device that drives liquid crystals using a horizontal electric field include, but are not limited to, horizontal-electric-field liquid crystal display devices provided with a fringe field switching (FFS) system, an in-plane switching (IPS) system, etc.

In the IPS mode, a first electrode and a second electrode are provided on the same layer, and an electric field is generated mainly in a direction parallel to the substrate surface. This configuration makes it difficult for the electric field to be generated in an area on the first electrode, thereby making it difficult for liquid-crystal molecules in the area to be driven.

In the FFS mode, a pixel electrode and a common electrode overlap in a direction perpendicular to the substrate surface with a dielectric film interposed therebetween, and an electric field extending mainly in a direction oblique to the substrate surface or a parabolic electric field (also referred to as a fringe electric field) is generated. This makes it easy for liquid-crystal molecules in an area on the pixel electrode to be driven. In other words, the FFS mode can provide a higher aperture ratio than the IPS mode does.

The horizontal-electric-field liquid crystal display device generates an electric field between the first electrode and the second electrode in a direction parallel to the substrate, thereby rotating the liquid crystal molecules in a plane parallel to the substrate surface. The liquid crystal display device uses a change in the light transmittance corresponding to the rotation of the liquid crystal molecules, thereby performing display. Such horizontal-electric-field liquid crystal display devices are required to achieve a higher response speed of the liquid crystals.

Japanese Patent Application Laid-open Publication No. 2013-109309 (JP-A-2013-109309) discloses a liquid crystal display device achieving a higher response speed of liquid crystals.

In the liquid crystal display device disclosed in JP-A-2013-109309, although the response speed of the liquid crystals is improved in the whole pixels, there is an area in which the liquid crystal molecule hardly move even when voltage is applied, and improvement in contrast is desired.

For the foregoing reasons, there is a need for a liquid crystal display device and an electronic apparatus that improve the contrast of entire pixels while improving the response speed of the entire pixels to further improve display quality in a plane.

SUMMARY

According to an aspect, a liquid crystal display device includes a first substrate, a second substrate arranged to be opposed to the first substrate, a liquid crystal layer arranged between the first substrate and the second substrate, a first electrode arranged between the first substrate and the liquid crystal layer, and a second electrode arranged at a position opposed to the first electrode. The first electrode includes an electrode base portion extending in a first direction, and a plurality of comb tooth portions extending in a second direction different from the first direction and protruding from the electrode base portion with a certain distance interposed therebetween. At least one of the first substrate and the second substrate includes a light-blocking part that reduces intensity of light passing therethrough at a position overlapping with at least one of the center of the comb tooth portion and the center between the adjacent comb tooth portions in a direction perpendicular to the first substrate.

According to another aspect, an electronic apparatus includes a liquid crystal display device, and a control device that supplies input signals to the liquid crystal display device. The liquid crystal display device includes a first substrate, a second substrate arranged to be opposed to the first substrate, a liquid crystal layer arranged between the first substrate and the second substrate, a first electrode arranged between the first substrate and the liquid crystal layer; and a second electrode arranged at a position opposed to the first electrode. The first electrode includes an electrode base portion extending in a first direction, and a plurality of comb tooth portions extending in a second direction different from the first direction and protruding from the electrode base portion with a certain distance interposed therebetween. At least one of the first substrate and the second substrate includes a light-blocking part that reduces intensity of light passing therethrough at a position overlapping with at least one of the center of the comb tooth portion and the center between the adjacent comb tooth portions in a direction perpendicular to the first substrate.

DETAILED DESCRIPTION

Exemplary embodiments according to the present invention are described below in greater detail with reference to the accompanying drawings. The contents described in the embodiments are not intended to limit the present invention. Components described below include components easily conceivable by those skilled in the art and components substantially identical therewith. Furthermore, the components described below can be appropriately combined. The disclosure is given by way of example only. Various changes and modifications made without departing from the spirit of the present invention and easily conceivable by those skilled in the art are naturally included in the scope of the present invention. The drawings may possibly illustrate the width, the thickness, the shape, and the like of each unit more schematically than the actual aspect to simplify the explanation. These elements, however, are given by way of example only and are not intended to limit interpretation of the invention. In the specification and the figures, components similar to those previously described with reference to a preceding figure are denoted by like reference numerals, and overlapping explanation thereof will be appropriately omitted.

FIG. 1is a block diagram of an exemplary system configuration of a liquid-crystal display device according to the embodiment. A liquid-crystal display device1is a transmissive liquid-crystal display device and includes a display panel2and a driver IC3. Flexible printed circuits (FPCs), which are not illustrated, transmit an external signal to the driver IC3or drive electric power for driving the driver IC3. The display panel2includes a translucent insulation substrate such as a glass substrate11, a display area21, a horizontal driver (a horizontal drive circuit)23, and a vertical driver (a vertical drive circuit)22. The display area21is provided on the surface of the glass substrate11and is formed of a number of pixels each including a liquid-crystal cell arranged in a matrix (rows and columns). The glass substrate11includes a first substrate and a second substrate. In the first substrate, a number of pixel circuits each including an active element (e.g., a transistor) are arranged in a matrix. The second substrate is arranged facing the first substrate with a certain gap interposed therebetween. The gap between the first substrate and the second substrate is maintained to the certain gap by photo spacers arranged at respective positions on the first substrate. The gap between the first substrate and the second substrate is sealed with liquid crystals.

Exemplary system configuration of the liquid-crystal display device

The display panel2includes the display area21, the driver IC3having functions of an interface (I/F) and a timing generator, the vertical driver22, and the horizontal driver23on the glass substrate11.

In the display area21, sub-pixels Vpix that include the liquid crystal layer have a matrix (row-and column) structure in which units each forming one pixel on display are arranged in m rows×n columns. In the present specification, a row indicates a pixel row including N sub-pixels Vpix arrayed in a direction. A column indicates a pixel column including M sub-pixels Vpix arrayed in a direction orthogonal to the direction in which the sub-pixels Vpix included in the row are arrayed. The values of M and N are determined depending on display resolution in the vertical direction and that in the horizontal direction, respectively. In the display area21, with respect to the array of M-by-N sub-pixels Vpix, scanning lines241,242,243. . .24Mare arranged for each row and signal lines251,252,253. . .25Nare arranged for each column. In the embodiment, the scanning lines241,242,243. . .24Mmay be collectively referred to as a scanning line24, whereas the signal lines251,252,253. . .25Nmay be collectively referred to as a signal line25. In the embodiment, any scanning line of the scanning lines241,242,243. . .24Mmay be expressed as a scanning line24α+1(0≦α≦M), whereas any signal line of the signal lines251,252,253. . .25Nmay be expressed as a signal line25β+1(0≦β≧N).

The liquid crystal display device1receives a master clock, a horizontal synchronizing signal, and a vertical synchronizing signal, which are external signals from the outside. These signals are supplied to the driver IC3. The driver IC3converts the level of the master clock, the horizontal synchronizing signal, and the vertical synchronizing signal at voltage amplitude of an external power source into a level at voltage amplitude of an internal power source required for driving the liquid crystals. Thus, the driver IC3generates a master clock, a horizontal synchronizing signal, and a vertical synchronizing signal. The driver IC3supplies the generated master clock, the generated vertical synchronizing signal, and the generated horizontal synchronizing signal to the vertical driver22and the horizontal driver23. The driver IC3generates a common potential to be supplied to pixels in common to a common electrode COM for each sub-pixel Vpix, which will be described later, and supplies the common potential to the display area21.

The vertical driver22sequentially samples and latches, in one horizontal period, display data output from the driver IC3in synchronization with a vertical clock pulse. The vertical driver22sequentially outputs and supplies the latched digital data of one line as a vertical scanning pulse to the scanning lines24m,24m+1,24m+2. . . of the display area21. Thus, the vertical driver22sequentially selects sub-pixels Vpix row by row. The vertical driver22, for example, outputs the digital data to the scanning lines24m,24m+1,24m+2. . . from the top of the display area21, that is, the upper side in the vertical scanning, to the bottom of the display area21, that is, the lower side in the vertical scanning. Alternatively, the vertical driver22may output the digital data to the scanning lines24m,24m+1,24m+2. . . from the bottom of the display area21, that is, the lower side in the vertical scanning, to the top of the display area21, that is, the upper side in the vertical scanning in order.

The horizontal driver23is supplied with 6-bit digital video data Vsig of R (red), G (green), and B (blue), for example. The horizontal driver23writes display data to the sub-pixels Vpix of the row selected in the vertical scanning performed by the vertical driver22in units of a pixel, a plurality of pixels, or all the pixels via the signal line25.

In the liquid crystal display device1, continuous application of a direct current (DC) voltage with the same polarity to the liquid crystal elements may possibly deteriorate resistivity (resistance value specific to the substance) and the like of the liquid crystals. To suppress deterioration in the resistivity (resistance value specific to the substance) and the like of the liquid crystals, the liquid crystal display device1employs a driving method for reversing the polarity of video signals at a certain period based on the common potential of drive signals.

Some types of methods for driving a liquid crystal display panel are known, including a line inversion driving method, a dot inversion driving method, and a frame inversion driving method. The line inversion driving method is a method for reversing the polarity of video signals at a time period of 1H (H represents a horizontal period) corresponding to one line (one pixel row). The dot inversion driving method is a method for alternately reversing the polarity of video signals for pixels vertically and horizontally adjacent to each other. The frame inversion driving method is a method for reversing the polarity of video signals to be written to all the pixels in one frame corresponding to one screen with the same polarity at a time. The liquid crystal display device1may employ any one of the driving methods described above.

FIG. 2is a circuit diagram illustrating a drive circuit that drives pixels in the liquid crystal display device according to the embodiment. In the display area21, wiring of the signal lines25n,25n+1,25n+2and the scanning lines24m,24m+1,24m+2are formed, for example. The signal lines25n,25n+1,25n+2supply pixel signals to thin film transistor (TFT) elements Tr in respective sub-pixels Vpix as display data. The scanning lines24m,24m+1,24m+2drive respective TFT elements Tr. The signal lines25n,25n±1,25n+2extend on a plane parallel to the surface of the glass substrate11described above and supply the pixel signals for displaying an image on the sub-pixels Vpix. Each of the sub-pixels Vpix includes the TFT element Tr and a liquid crystal capacitor LC. The TFT element Tr is formed of a thin film transistor, and specifically of an n-channel metal oxide semiconductor (MOS) TFT in this example. One of the source and the drain of the TFT element Tr is coupled to the corresponding one of the signal lines25n,25n+1,25n+2, the gate thereof is coupled to the corresponding one of the scanning lines24m,24m+1,24m+2, and the other of the source and the drain thereof is coupled to one end of the liquid crystal capacitor LC. The one end of the liquid crystal capacitor LC is coupled to the other of the source and the drain of the TFT element Tr, whereas the other end thereof is coupled to the corresponding common electrode COM.

The sub-pixel Vpix is coupled to other sub-pixels Vpix belonging to the same row in the display area21by the corresponding one of the scanning lines24m,24m+1,24m+2. The scanning lines24m,24m+1,24m+2are coupled to the vertical driver22and are supplied with the vertical scanning pulses of scanning signals from the vertical driver22. The sub-pixel Vpix is further coupled to other sub-pixels Vpix belonging to the same column in the display area21by the corresponding one of the signal lines25n,25n+1,25n+2. The signal lines25n,25n+1,25n+2are coupled to the horizontal driver23and are supplied with pixel signals from the horizontal driver23. The sub-pixel Vpix is further coupled to the other sub-pixels Vpix belonging to the same column in the display area21by the corresponding common electrode COM. The common electrodes COM are coupled to the driver IC3, and are supplied with drive signals from the driver IC3.

The vertical driver22illustrated inFIG. 1applies vertical scanning pulses to the gate of the TFT element Tr of the sub-pixels Vpix via the scanning lines24m,24m+1,24m+2illustrated inFIG. 2. Thus, the vertical driver22sequentially selects a row (a horizontal line) out of the rows of the sub-pixels Vpix arranged in a matrix in the display area21as a target of display drive. The horizontal driver23illustrated inFIG. 1supplies pixel signals to the respective sub-pixels Vpix forming each horizontal line sequentially selected by the vertical driver22via the corresponding one of the signal lines25n,25n+1,25n+2illustrated inFIG. 2. These sub-pixels Vpix perform display of the horizontal line in accordance with the supplied pixel signals. The driver IC3applies drive signals, thereby driving common electrodes COM in each drive electrode block including a certain number of common electrodes COM.

As described above, the vertical driver22in the liquid crystal display device1performs driving so as to sequentially scan the scanning lines24m,24m+1,24m+2, thereby sequentially selecting a horizontal line. The horizontal driver23in the liquid crystal display device1supplies the pixel signals to the sub-pixels Vpix belonging to the horizontal line, thereby performing display of the horizontal line. In performing the display operation, the driver IC3applies the drive signals to the common electrode COM corresponding to the horizontal line.

A control device4includes, for example, a central processing unit (CPU)41serving as an arithmetic unit and a storage device42serving as a memory, and can implement various functions by executing computer programs using such hardware resources. Specifically, the control device4reads out a computer program stored in the storage device42to be loaded on the memory, and causes the CPU41to execute a command included in the computer program loaded on the memory. The control device4then performs control so that the driver IC3can handle an image to be displayed on the display panel2as information of image input gradation depending on a command execution result by the CPU41. A backlight6irradiates the display panel2with light according to a control signal of the control device4, and allows light to be incident on the entire surface of the display area21. The backlight6includes, for example, a light source and a light guide plate that guides light output from the light source to be emitted to the back surface of the display panel2. The backlight6includes a plurality of light sources arranged in a direction along one side of the display area21, and an amount of light from each light source may be independently controlled. Accordingly, the backlight6can cause light to be incident on part of the display panel2due to the light emitted from only part of the light sources. In the embodiment, the backlight6arranged on the back surface side of the display panel2is used as the light source of the liquid crystal display device1. Alternatively, the light source may be a front light arranged on the front surface side of the display panel2.

The display area21includes a color filter. The color filter includes a grid-shaped black matrix76aand apertures76b. The black matrix76ais formed to cover the outer periphery of the sub-pixel Vpix as illustrated inFIG. 2. In other words, the black matrix76ais arranged at a boundary between the sub-pixels Vpix that are two-dimensionally arranged and thus is formed into a grid shape. The black matrix76ais made of a material having a high light absorption rate. The aperture76bserves as an aperture formed by the grid shape of the black matrix76aand is arranged at a position corresponding to the sub-pixel Vpix. As described above, the black matrix76ais a light-blocking part (a second light-blocking part) having a light blocking property that surrounds the aperture of the sub-pixel Vpix.

The aperture76bincludes color areas colored with three colors of red (R), green (G), and blue (B), for example. In the color filter, the color areas of the color filter in the three colors of red (R), green (G), and blue (B) are periodically arrayed on the respective apertures76b, for example. Thus, the color areas in the three colors of R, G, and B correspond to the respective sub-pixels Vpix illustrated inFIG. 2and serve as a pixel Pix as a set.

The color filter may be made by a combination of other colors as long as it is colored differently. Typically, the luminance of the color area of green (G) is higher than that of the color areas of red (R) and blue (B). The display area may be provided with no color filter, resulting in production of white color. Alternatively, the color filter may be made of a transmissive resin to produce a white color.

Viewed from a direction orthogonal to the front surface, the scanning line24and the signal line25in the display area21are arranged at an area overlapping with the black matrix76a. In other words, the scanning line24and the signal line25are hidden behind the black matrix76aviewed from a direction orthogonal to the front surface. As described above, the black matrix76ais a light-blocking part (a second light-blocking part) having a light blocking property arranged to be opposed to the scanning line24or the signal line25. The display area21has the aperture76bin each area in which no black matrix76ais arranged.

As illustrated inFIG. 2, the scanning lines24m,24m+1,24m+2are arranged at regular intervals, and the signal lines25n,25n+1,25n+2are also arranged at regular intervals. Adjacent scanning lines24do not necessarily have a regular interval therebetween, and adjacent signal lines25do not necessarily have a regular interval therebetween either. The sub-pixels Vpix are arranged facing each other in the same direction at the respective areas sectioned by the proximate scanning lines24m,24m+1,24m+2and the proximate signal lines25n,25n+1,25n+2.

FIG. 3is a plan view for explaining the pixels in the liquid crystal display device according to the embodiment.FIG. 4is a schematic diagram illustrating a sectional view along the line A1-A2ofFIG. 3. As illustrated inFIGS. 3 and 4, in the embodiment, one direction along a plane of the liquid crystal display device1(the display panel2illustrated inFIG. 1) is assumed to be an X-direction, a direction orthogonal to the X-direction is assumed to be a Y-direction, and a direction orthogonal to the X-Y plane is assumed to be a Z-direction. In each sub-pixel Vpix, the aperture76bis formed on the lower side in the vertical scanning (lower side inFIG. 3). The TFT element Tr is arranged on the left on the upper side in the vertical scanning (upper side inFIG. 3). A contact90H is formed on the right on the upper side in the vertical scanning (upper side inFIG. 3). The contact90H is used to couple a pixel electrode to a drain electrode90of the TFT element Tr. The drain of the TFT element Tr includes part of a semiconductor layer (an active layer) and the drain electrode90. Similarly, the source of the TFT electrode Tr includes another part of the semiconductor layer (active layer) and a source electrode91. Color filters76R,76G, and76B are formed by periodically arraying the color areas of the color filters in the three colors of red (R), green (G), and blue (B) on the respective apertures76b, for example. Thus, the color areas49R,49G, and49B in the three colors of R, G, and B illustrated inFIG. 3are formed in the respective sub-pixels Vpix illustrated inFIG. 2.

As illustrated inFIG. 4, the liquid crystal display device1includes a pixel substrate (the first substrate)70A, a counter substrate (the second substrate)70B arranged facing the surface of the pixel substrate70A in a direction perpendicular thereto, and a liquid crystal layer70C inserted between the pixel substrate70A and the counter substrate70B. The surface of the pixel substrate70A on the side opposite to the liquid crystal layer70C is provided with the backlight6. Photo spacers (not illustrated) maintain a gap between the pixel substrate70A and the counter substrate70B to a certain gap.

In the embodiment, an electric field (a horizontal electric field) is generated between a first electrode31and a second electrode32laminated in a direction (the Z-direction) perpendicular to the surface of a TFT substrate71of the pixel substrate70A and in a direction parallel to the TFT substrate71. As a result, the liquid crystal molecules in the liquid crystal layer70C rotate in a plane parallel to the substrate surface. The liquid crystal display device1uses a change in the light transmittance corresponding to the rotation of the liquid crystal molecules, thereby performing display. The second electrode32illustrated inFIG. 4is the pixel electrode, whereas the first electrode31is the common electrode COM, for example. As illustrated inFIG. 4, a first orientation film73ais provided between the liquid crystal layer70C and the pixel substrate70A, whereas a second orientation film73bis provided between the liquid crystal layer70C and the counter substrate70B.

The counter substrate70B includes a glass substrate72and the light-blocking black matrix76aformed on one surface of the glass substrate72. The black matrix76afaces the liquid crystal layer70C in a direction perpendicular to the pixel substrate70A. In the liquid crystal display device1according to the embodiment, the aperture76balso includes a light-blocking part76chaving a light blocking property in the same layer as the black matrix76a. The light-blocking part76cis in the same layer as the black matrix76a, and thereby can be formed of the same material as the black matrix76awithout additional processes. A position of the light-blocking part76cwill be described later.

The pixel substrate70A includes the TFT substrate71serving as a circuit substrate. The scanning line24millustrated inFIG. 3is formed on the TFT substrate71. A gate electrode93is electrically coupled to the scanning line24m. While the scanning line24mand the gate electrode93are formed in different layers inFIGS. 3 and 4, the scanning line24mand the gate electrode93may be integrally formed.

A semiconductor layer92containing amorphous silicon (a-Si) forming the TFT element Tr is formed in an upper layer of the gate electrode93. The semiconductor layer92is coupled to the source electrode91forming the TFT element Tr. The source electrode91is an electric conductor and is electrically coupled to a part of the semiconductor layer92. The source electrode91is electrically coupled to the signal line25nillustrated inFIG. 3(not illustrated inFIG. 4). The semiconductor layer92is coupled to the drain electrode90forming the TFT element Tr. The drain electrode90is electrically coupled to another part of the semiconductor layer92. While the signal line25nand the source electrode91are formed in different layers inFIG. 3, the signal line25nand the source electrode91may be integrally formed. The semiconductor layer92may contain LTPS (Low temperature Polysilicon) or oxide instead of amorphous silicon.

In the liquid crystal display device1according to the embodiment, the aperture76balso includes therein a light-blocking part76dhaving a light blocking property in the same layer as the source electrode91or the drain electrode90. The light-blocking part76dis included in the pixel substrate70A. A material of the light-blocking part76dis the same as that of the source electrode91or the drain electrode90that is wiring for causing the first electrode31or the second electrode32to work. Due to this, a forming pattern of the light-blocking part76dhas high accuracy, and additional processes are not required. A position of the light-blocking part76dwill be described later. The liquid crystal display device1according to the embodiment may include at least one of the light-blocking part76cand the light-blocking part76dillustrated inFIG. 4.

An insulation layer74is formed of laminated insulation films, which are an insulation film741between the scanning line24mand the semiconductor layer92, an insulation film742between the semiconductor layer92and the signal line25n, an insulation film743between the signal line25nand the second electrode32, and an insulation film744between the second electrode32and the first electrode31, for example. The insulation films741,742,743, and744may be made of the same insulation material, or any one thereof may be made of a different insulation material. For example, the insulation film743is made of an organic insulation material such as a polyimide resin and the other insulation films (insulation films741,742, and744) are made of an inorganic insulation material such as silicon nitride and silicon oxide.

The contact90H made of a conductive metal is formed in what is called a contact hole. The contact90H couples the drain electrode90and the second electrode32. The first electrode31serves as the common electrode COM and is supplied with a common potential to be supplied to the pixels in common. The first electrode31and the second electrode32are translucent electrodes made of a translucent conductive material (a translucent conductive oxide) such as indium tin oxide (ITO).

FIG. 5is a schematic diagram for explaining a relation between the shape of the first electrode and the aperture according to the embodiment. As illustrated inFIG. 5, the first electrode31has a comb teeth shape formed by slits S that are areas with no conductive material provided. The first electrode31includes a plurality of comb tooth portions131protruding from an electrode base portion132extending in the Y-direction. The comb tooth portions131include comb tooth portions131aand comb tooth portions131b. The comb tooth portions131aand the comb tooth portions131bextend in opposite directions from the electrode base portion132. The comb tooth portions131aprotrude from the electrode base portion132with a certain distance interposed therebetween. Similarly, the comb tooth portions131bprotrude from the electrode base portion132with a certain distance interposed therebetween. From each electrode base portion132, the comb tooth portions131aextend in the X-direction, whereas the comb tooth portions131bextend in a direction opposite to the X-direction. Similarly to the comb tooth portions131aor the comb tooth portions131b, the electrode base portion132is made of translucent conductive material (translucent conductive oxide) such as indium tin oxide (ITO).

The first orientation film73adescribed above is subjected to orientation processing in an orientation direction ORI (a first orientation direction) illustrated inFIGS. 3 and 5such that the liquid crystal molecules have a certain initial orientation in the X-direction. The second orientation film73bis subjected to orientation processing in a direction (a second orientation direction) antiparallel to the orientation direction ORI of the first orientation film73a. The orientation directions of the first orientation film73aand the second orientation film73bare antiparallel to each other. As described above, the comb tooth portions131aextend in the X-direction, and the comb tooth portions131bextend in the direction opposite to the X-direction. The orientation direction ORI is parallel to the direction in which the comb tooth portions131aor the comb tooth portions131bextend. The orientation direction ORI is considered to be parallel as long as it is sufficiently parallel to maintain the rotation direction of liquid crystal molecules LCM illustrated inFIG. 9, which will be described later. More specifically, the orientation direction ORI allows a manufacturing error of 0 degree or greater to 0.5 degree or less. To provide a certain orientation to the liquid crystal molecules, the following orientation films may be used: an orientation film formed by performing rubbing on an organic film such as a polyimide; or an optical orientation film that can be provided with a specific liquid-crystal orientation capability by irradiating the film with light such as ultraviolet rays. In this way, according to the embodiment, the first orientation film73aand the second orientation film73bare subjected to rubbing treatment to have the certain initial orientation. However, a method of providing an initial orientation to the first orientation film73aand the second orientation film73bis not limited to the rubbing treatment. The first orientation film73aand the second orientation film73bmay be formed by using a material having optical orientation to have the certain initial orientation.

FIG. 6is a schematic diagram for explaining a relation between the shape of the first electrode and a shaded position according to the embodiment. The black matrix76aonly needs to shade the sub-pixel Vpix to the position of a width76h1aillustrated inFIG. 6, thereby hiding the contact90H. An electric field applied to the endmost slit Sw between the comb tooth portion131bclosest to the edge of the aperture76band the contact90H has different distribution from that of an electric field applied to the slit S between adjacent comb tooth portions131aor between adjacent comb tooth portions131b. If the black matrix76ashades the sub-pixel Vpix to the position of a width76h1billustrated inFIG. 6to hide the contact90H and more than half of the endmost slit Sw, the rate of change in the transmittance of the endmost slit Sw can be made closer to that of the slit S. Alternatively, if the black matrix76ashades the sub-pixel Vpix to the position of a width76h1cillustrated inFIG. 6to hide the contact90H and the endmost slit Sw, it is not necessary to consider the difference between the rates of change in the transmittance of the endmost slit Sw and the slit S. This structure can make luminance in the aperture76buniform.

FIG. 7is an explanatory diagram for explaining orientation of the liquid crystals in a state where no voltage to generate an electric field between the first electrode and the second electrode is applied in the liquid crystal display device according to the embodiment.FIG. 8is a schematic diagram illustrating a sectional view along the line B1-B2ofFIG. 7.FIG. 9is an explanatory diagram for explaining orientation of the liquid crystals in a state where the voltage to generate an electric field between the first electrode and the second electrode is applied in the liquid crystal display device according to the embodiment.FIG. 10is a schematic diagram illustrating a sectional view along the line C1-C2ofFIG. 9.FIG. 11is a schematic diagram for explaining in detail the shape of the first electrode in the pixel according to the embodiment.

As described above, the first orientation film73ais subjected to orientation processing in the orientation direction ORI illustrated inFIGS. 3 and 5such that the liquid crystal molecules have a certain initial orientation in the X-direction. In a case where no voltage to generate an electric field between the first electrode31and the second electrode32is applied, the long-axis direction of liquid crystal molecules Lcm in the liquid crystal layer70C tends to be aligned parallel to the direction in which the comb tooth portions131aand the comb tooth portions131bextend as illustrated inFIG. 7. As a result, the liquid crystal molecules Lcm are initially oriented parallel to the direction in which the comb tooth portions131aand the comb tooth portions131bextend at neighboring areas of a right long side131R and a left long side131L of the comb tooth portions131aand the comb tooth portions131bfacing each other in the width direction of the slit S. The liquid crystal molecules Lcm illustrated inFIG. 8are initially oriented along the orientation direction ORI and upward with respect to the orientation direction ORI so as to have a pretilt angle θp with respect to the surface of the TFT substrate71.

When a voltage to generate an electric field between the first electrode31and the second electrode32is applied, the liquid crystal molecules Lcm rotate in a liquid-crystal rotation direction LCQ as illustrated inFIG. 9. In other words, the liquid-crystal rotation direction LCQ is a direction of twist or rotation of the liquid crystals in the X-Y plane. The liquid crystal molecules Lcm positioned at the neighboring area of the right long side131R and those at the neighboring area of the left long side131L are affected by electric fields in opposite directions and thus are likely to rotate in opposite directions.

As described above, when a voltage is applied to the first electrode31and the second electrode32, in the liquid crystal layer70C of the liquid crystal display device1according to the embodiment, the liquid crystal molecules Lcm in the neighboring area of the right long side131R rotate in a direction opposite to a rotating direction of those in the neighboring area of the left long side131L. The right long side131R is one of the sides of adjacent comb tooth portions131a(131b) facing the slit S in the width direction thereof, whereas the left long side131L is the other of the sides. The liquid crystal molecules Lcm respond to a change in the electric field between the first electrode31and the second electrode32at higher speed in the liquid crystal display device1according to the embodiment than in the FFS-mode liquid crystal display device disclosed in JP-A-2008-52161. As a result, the liquid crystal display device1according to the embodiment achieves a higher response speed.

The response speed is a speed at which the transmittance of the liquid crystals is shifted between certain levels when a voltage is applied to the first electrode31and the second electrode32. In other words, the response speed is specified by a time required to shift the transmittance from a state where no voltage is applied (for example, transmittance=0) to a state where a voltage is applied (transmittance=1) or a time required to shift the transmittance from the state where a voltage is applied to the state where no voltage is applied.

When a voltage to generate an electric field between the first electrode31and the second electrode32is applied, the long-axis direction of the liquid crystal molecules Lcm rotates in a plane (X-Y plane) parallel to the surface of the pixel substrate70A (TFT substrate71) and changes also in the Z-direction as illustrated inFIG. 10. The first electrode31and the second electrode32are arranged facing each other in a direction perpendicular to the surface of the pixel substrate70A (TFT substrate71). Therefore, the electric field generated between the first electrode31and the second electrode32serves as a fringe electric field passing through the slits S. The fringe electric field causes the long axis of the liquid crystal molecules Lcm to rotate in the liquid-crystal rotation directions LCQ (clockwise and counterclockwise) in the X-Y plane illustrated inFIG. 9and to rise in the direction (Z-direction) perpendicular to the surface of the pixel substrate70A (TFT substrate71). The liquid-crystal rotation directions LCQ may possibly be mixed at the center area of the slits S.

As illustrated inFIG. 10, the long-axis direction of the liquid crystal molecules Lcm has an angle θp2larger than the pretilt angle θp in a slit area Rs between the comb tooth portions131b. The long-axis direction of the liquid crystal molecules Lcm has an angle θp1opposite to the pretilt angle θp in a slit area Ls between the comb tooth portions131a. The long-axis direction of the liquid crystal molecules Lcm in the slit area Ls is less likely to rise and may have lower orientation stability than the long-axis direction of the liquid crystal molecules Lcm in the slit area Rs does.

By specifying the shape of the first electrode31more finely as illustrated inFIG. 11, it is possible to increase the responsiveness of the liquid crystal display device1according to the embodiment. As illustrated inFIG. 11, L0represents a total slit length between the electrode base portions132in the X-direction, for example. L1represents a comb tooth protrusion length of the comb tooth portions131ain the X-direction. The comb tooth protrusion length L1corresponds to a length from a position x1of a tip131afof the comb tooth portions131ato a protrusion start position x0in the electrode base portion132. Similarly, L2represents a comb tooth protrusion length of the comb tooth portions131bin the X-direction. The comb tooth protrusion length L2corresponds to a length from a position x1of a tip131bfof the comb tooth portions131bto a protrusion start position x0in the electrode base portion132. The width of the tip131afof the comb tooth portions131aand the tip131bfof the comb tooth portions131bin the Y-direction is w1. The total slit length L0is preferably set to a value equal to or greater than 10 μm to a value equal to or smaller than 60 μm, for example. The total slit length L0is more preferably set smaller than 40 μm, specifically to 20 μm, for example. In the liquid crystal display device1according to the embodiment, a decrease in the total slit length L0increases the orientation stability of the liquid crystals, whereas an increase in the total slit length L0increases the luminance.

As described above, the liquid crystal molecules Lcm in the slit area Ls inFIG. 10may possibly be less likely to rise in the long-axis direction than those in the slit area Rs in the long-axis direction and have lower orientation stability than those in the slit area Rs do. To make the slit area Ls smaller than the slit area Rs, the comb tooth protrusion length L1illustrated inFIG. 11is made smaller than the comb tooth protrusion length L2of the comb tooth portions131bpositioned on the upstream of the comb tooth portions131ain the orientation direction ORI. Thus, the liquid crystal display device1according to the embodiment can increase the orientation stability.

The width w1of the tip131afof the comb tooth portions131aand the tip131bfof the comb tooth portions131bin the Y-direction is set to a value equal to or greater than 2 μm to a value equal to or smaller than 5 μm, for example. Setting the width w1to a smaller value can increase the response speed.

A slit pitch (an array pitch) p between adjacent comb tooth portions131ais equal to an array pitch between adjacent comb tooth portions131b. The tip131afof the comb tooth portions131aand the tip131bfof the comb tooth portions131bare arranged alternately in the Y-direction. With this structure, the right long side131R of the comb tooth portions131aand the right long side131R of the comb tooth portions131bare aligned in the X-direction as illustrated inFIG. 9. With this structure, the left long side131L of the comb tooth portions131aand the left long side131L of the comb tooth portions131bare also aligned in the X-direction as illustrated inFIG. 9. As a result, the liquid-crystal rotation directions LCQ in which the liquid crystal molecules Lcm rotate are the same direction viewed in the X-direction, thereby stabilizing the rotation behavior of the liquid crystal molecules Lcm. Because a decrease in the slit pitch p increases the response speed, the slit pitch p is preferably set smaller than 9 μm.

The gap between the tip131afof the comb tooth portions131aand the tip131bfof the comb tooth portions131billustrated inFIG. 11corresponds to a width W in the X-direction of a communicating aperture extending in the Y-direction. The width W is preferably set to a smaller value. The width W of the communicating aperture in the X-direction is set to 7 μm or smaller, for example, and more preferably to 4 μm or smaller. The width W of the communicating aperture in the X-direction may be set to 0 or smaller. In a case where W=0 is satisfied, for example, the tip131afof the comb tooth portions131aand the tip131bfof the comb tooth portions131bare aligned in the Y-direction. In this case, the tips are arranged with gaps interposed therebetween in the Y-direction, whereby a plurality of slits S communicate with one another. In a case where W<0 is satisfied, the tip131afof the comb tooth portions131aand the tip131bfof the comb tooth portions131benter into respective slits S adjacent thereto in the X-direction. In other words, the comb tooth portions131aand the comb tooth portion131bare alternately engaged.

The width of the comb tooth portions131ain the Y-direction at the protrusion start position x0in the electrode base portion132is represented by w2and is larger than the width w1of the tip131afof the comb tooth portions131ain the Y-direction. Thus, the comb tooth portions131ahave a trapezoidal shape. A long side131al1and a long side131al2of the comb tooth portions131aare oblique to a reference direction of a virtual line131acpassing through the center of the comb tooth portions131a(X-direction in which the comb tooth portions131aextend) by an angle θ. Setting the angle θ larger than 0.5 degree can facilitate alignment of the liquid-crystal rotation directions LCQ in which the liquid crystal molecules Lcm rotate, thereby stabilizing the behavior of the liquid crystal molecules Lcm. The shape of the comb tooth portions131ahas been exemplified as a trapezoidal shape such that the left and the right sides at least partially have obliquity opposite to each other with respect to the extending direction. The shape of the comb tooth portions131ais not limited thereto. The obliquity of the left and the right sides of the comb tooth portions131awith respect to the extending direction may be different between a base area closer to the base portion and a tip area away from the base portion.

Similarly, the width of the comb tooth portions131bin the Y-direction at the protrusion start position x0in the electrode base portion132is represented by w2and is larger than the width w1of the tip131bfof the comb tooth portions131bin the Y-direction. Thus, the comb tooth portions131bhave a trapezoidal shape. A long side131bl1and a long side131bl2of the comb tooth portions131bare oblique to a reference direction of a virtual line131bcpassing through the center of the comb tooth portions131b(X-direction in which the comb tooth portions131bextend) by an angle θ. Setting the angle θ larger than 0.5 degree can facilitate alignment of the liquid-crystal rotation directions LCQ in which the liquid crystal molecules Lcm rotate, thereby stabilizing the behavior of the liquid crystal molecules Lcm. Because the liquid-crystal rotation directions LCQ are aligned in lines adjacent to each other in the X-direction and on the X-direction line in the liquid crystal display device1according to the embodiment, high orientation stability can be achieved. The shape of the comb tooth portions131bhas been exemplified as a trapezoidal shape such that the left and the right sides at least partially have obliquity opposite to each other with respect to the extending direction. The shape of the comb tooth portions131bis not limited thereto. The obliquity of the left and the right sides of the comb tooth portions131bwith respect to the extending direction may be different between a base area closer to the base portion and a tip area away from the base portion.

When the comb tooth protrusion length L1of the comb tooth portions131aor the comb tooth protrusion length L2of the comb tooth portions131bis increased, it is necessary to increase the angle θ. An increase in the angle increases the difference between the width w1and the width w2, resulting in limitation on the slit pitch p. In a case where the angle θ is 0.5 degree or greater to 1.0 degree or less, for example, the comb tooth protrusion length L1of the comb tooth portions131aor the comb tooth protrusion length L2of the comb tooth portions131bis preferably set to 45 μm or smaller.

Because the electrode base portion132does not contribute to transmission of light, a width D1of the electrode base portion132in the X-direction (a direction orthogonal to the extending direction of the electrode base portion132) is preferably set to a smaller value. The width D1is preferably set larger than 0 μm and equal to or smaller than 4 μm. Setting the width D1larger than 0 μm can increase the conductivity, whereas setting the width D1equal to or smaller than 4 μm can suppress decrease in the transmittance. In a case where the width D1is larger than 0 μm and equal to or smaller than 4 μm and where the comb tooth protrusion length L1of the comb tooth portions131aor the comb tooth protrusion length L2of the comb tooth portions131bis 45 μm or smaller, the display area21can serve as a high-definition screen of 160 pixels per inch (ppi) or higher. In a case where the width w1is 0.5 for example, the width w2is preferably set to 1 μm or larger to ensure the quality throughout the comb tooth protrusion length L1of the comb tooth portions131aor the comb tooth protrusion length L2of the comb tooth portions131b.

As described above, setting the slit pitch p to a smaller value can increase the response speed. A decrease in the slit pitch p, however, increases the width of the comb tooth portions131aor the comb tooth portions131bin the Y-direction, for example, resulting in an increase in the area that does not contribute to transmission of light. The transmittance can be effectively increased by an increase in the comb tooth protrusion length L1of the comb tooth portions131aor the comb tooth protrusion length L2of the comb tooth portions131b. However, the increase in the length can possibly make alignment of the liquid-crystal rotation directions LCQ, in which the liquid crystal molecules Lcm rotate, difficult, resulting in instability in the behavior of the liquid crystal molecules Lcm.

FIG. 12is a schematic diagram for explaining in detail a transmission ineffective area according to the embodiment.FIG. 13is a schematic diagram illustrating a disclination line of the first electrode according to the embodiment. In the embodiment, a boundary between clockwise rotation and counterclockwise rotation of the liquid crystals is referred to as disclination. Due to this structure, first comb tooth portions131aand second comb tooth portions131bare opposed to each other with a transmission ineffective area np interposed therebetween. The transmission ineffective area np is an area which includes no translucent conductive material. Even when a voltage is applied to the first electrode31, the liquid crystal molecules Lcm hardly move in the transmission ineffective area np. As a result, the transmittance is reduced in the transmission ineffective area np. The liquid crystals hardly move also in a region overlapping with the electrode base portion132. Therefore, each of the comb tooth protrusion lengths L1and L2illustrated inFIG. 11is a transmission effective interval Em in the X-direction in which the liquid crystal molecules Lcm effectively rotate even if a voltage is applied to the first electrode31.

As illustrated inFIG. 13, a disclination line dc1in which the liquid crystal molecules hardly move even if a voltage is applied to the first electrode31is likely to be generated at the center of the first comb tooth portion131a, the center of the second comb tooth portion131b, the center between adjacent first comb tooth portions131a, and the center between adjacent second comb tooth portions131b. As illustrated inFIGS. 12 and 13, the first electrode31is configured such that the tip131afof the first comb tooth portion131aand the tip131bfof the second comb tooth portion131bare alternately arranged in the Y-direction. Due to this, orientations AXI of the liquid crystal molecules Lcm are the same in a line LQ1. The orientations AXI of the liquid crystal molecules Lcm are the same also in a line LQ2. As a result, the disclination line dc1generated at the center of the first comb tooth portion131aand the disclination line dc1generated at the center between the adjacent second comb tooth portions131bare connected to make the disclination line dc1easier to be seen. The disclination line dc1generated at the center of the second comb tooth portion131band the disclination line dc1generated at the center between the adjacent first comb tooth portions131aare connected to make the disclination line dc1easier to be seen. As described above, the first electrode31illustrated inFIG. 13includes many disclination lines dc1, and a period of change in transmittance in the Y-direction is shortened.

FIG. 14is a schematic diagram for explaining in detail the transmission ineffective area according to a first modification of the embodiment.FIG. 15is a schematic diagram illustrating the disclination line of the first electrode according to the first modification of the embodiment. As illustrated inFIGS. 14 and 15, in the first electrode31according to the first modification of the embodiment, a plurality of first comb tooth portions131aland first comb tooth portions131asalternately protrude from the electrode base portion132at a certain distance from each other. A plurality of second comb tooth portions131bland second comb tooth portions131bsalternately protrude from the electrode base portion132at a certain distance from each other.

As illustrated inFIG. 15, in the area in which the first comb tooth portions131alare adjacent to the first comb tooth portions131asin the width direction of the slit S, the liquid crystal molecules Lcm in the neighboring areas of respective adjacent long sides are oblique to the X-direction in opposite directions. In the area in which the first comb tooth portions131alare adjacent to the second comb tooth portions131blin the width direction of the slit S, the liquid crystal molecules Lcm in the neighboring areas of respective adjacent long sides are oblique to the X-direction in the same direction. In the area in which the second comb tooth portions131blare adjacent to the second comb tooth portions131bsin the width direction of the slit S, the liquid crystal molecules Lcm in the neighboring areas of respective adjacent long sides are oblique to the X-direction in opposite directions. Due to this, when the neighboring areas of two right long sides arranged in a line in the X-direction and the neighboring areas of two left long sides arranged in a line in the X-direction are viewed from one of the adjacent electrode base portions132toward the other one thereof, the liquid crystal molecules are arranged in opposite directions, the same direction, and opposite directions, in order. The liquid crystal molecules Lcm in the respective neighboring areas of the left long side of the first comb tooth portion131aland the left long side of the second comb tooth portion131blwhich are arranged in a line in the X-direction are oblique to the X-direction in opposite directions. The liquid crystal molecules Lcm in the respective neighboring areas of the right long side of the first comb tooth portion131aland the right long side of the second comb tooth portion131blwhich are arranged in a line in the X-direction are oblique to the X-direction in opposite directions. The liquid crystal molecules Lcm in the respective neighboring areas of the left long side of the first comb tooth portion131asand the left long side of the second comb tooth portion131bswhich are arranged in a line in the X-direction are oblique to the X-direction in opposite directions. The liquid crystal molecules Lcm in the respective neighboring areas of the right long side of the first comb tooth portion131asand the right long side of the second comb tooth portion131bswhich are arranged in a line in the X-direction are oblique to the X-direction in opposite directions. Accordingly, the disclination line dc1generated at the center of the second comb tooth portion131band the disclination line dc1generated at the center between the adjacent first comb tooth portions131aare separated from each other. In this way, in the first electrode31illustrated inFIG. 15, a decrease in transmittance of the disclination line dc1is suppressed, and a period of change in the transmittance in the Y-direction is lengthened. The liquid crystal display device1according to the first modification of the embodiment can thus improve the transmittance in addition to providing excellent properties such as a fast response and a wide viewing angle.

FIG. 16is an explanatory diagram illustrating light transmittance distribution due to the disclination line of the first electrode according to a comparative example.FIG. 17is an explanatory diagram illustrating a positional relation between the light transmittance distribution due to the disclination line of the first electrode according to the embodiment and the light-blocking part.FIGS. 16 and 17both represent the area in which the liquid crystal molecules move when a voltage is applied to the first electrode31as a white area, and represents the disclination line dc1and the transmission ineffective area np as a black area. The disclination line dc1and the transmission ineffective area np have a contrast different from that of the area in which light is blocked with the black matrix76a. For example, the white area illustrated inFIG. 16has a contrast of 0.1:200 (black:white). The black area including the disclination line dc1and the transmission ineffective area np has a contrast of 0.1:0.1 (black:white). On the other hand, the area in which light is blocked with the black matrix76ahas a contrast of 0.001:0.001 (black:white). As a result, the contrast of the whole sub-pixels is about 1:1300 (black:white).

The liquid crystal display device1according to the embodiment includes, as illustrated inFIG. 4, at least one of the light-blocking part76cand the light-blocking part76d. As illustrated inFIG. 17, when the black area of the disclination line dc1is overlapped with at least one of the light-blocking part76cand the light-blocking part76d, the black area of the light-blocking area generated by at least one of the light-blocking part76cand the light-blocking part76dshows a contrast close to the contrast of the area in which light is blocked with the black matrix76a. The black area of the light-blocking area generated by the light-blocking part76cand the light-blocking part76dhas a contrast of 0.001:0.001 (black:white). As a result, the contrast of the whole sub-pixels can be made close to about 1:2000 (black:white). For example, the width of the black area of the disclination line dc1is about half or below the width of the comb tooth portion, or about half or below the width of the slit S. In addition to the light-blocking part76cor the light-blocking part76dillustrated inFIG. 17, another light-blocking part may overlap with the transmission ineffective area np. Another light-blocking part can intersect with the light-blocking part76cor the light-blocking part76dto make the black area of the light-blocking area have a grid shape.

The liquid crystal display device1according to the embodiment includes at least one of the light-blocking part76cand the light-blocking part76dillustrated inFIG. 4for reducing intensity of light passing therethrough at a position overlapping with the center of the first comb tooth portion131aand the center between the adjacent first comb tooth portions131ain a direction perpendicular to the first substrate. The liquid crystal display device1according to the embodiment also includes at least one of the light-blocking part76cand the light-blocking part76dillustrated inFIG. 4for reducing intensity of light passing therethrough at a position overlapping with the center of the second comb tooth portion131band the center between the adjacent second comb tooth portions131bin a direction perpendicular to the first substrate. Accordingly, as illustrated inFIG. 17, at least one of the light-blocking part76cand the light-blocking part76dcan overlap with the black area of the disclination line dc1. As a result, the contrast of the whole sub-pixels can be improved. As illustrated inFIG. 17, the light-blocking part76cand the light-blocking part76dare arranged both at the center of the first comb tooth portion131aand at the center between the adjacent first comb tooth portions131a. The arrangement of the light-blocking part76cand the light-blocking part76dis not limited thereto. The light-blocking part may be arranged at least at any of the center of the first comb tooth portion131aand the center between the adjacent first comb tooth portions131a. As exemplified in the arrangement of the light-blocking part76cand the light-blocking part76d, the light-blocking part may be formed on both of the TFT substrate71serving as the first substrate and the glass substrate72serving as the second substrate, or formed on any one of the first substrate and the second substrate.

As in the liquid crystal display device1according to the first modification of the embodiment, when the respective tips131afand131bfof the first comb tooth portion131aand the second comb tooth portion131bextending from the adjacent electrode base portions132are opposed to each other at a distance, at least one of the light-blocking part76cand the light-blocking part76dillustrated inFIG. 4for reducing intensity of light passing therethrough may be provided at a position overlapping with the center of the first comb tooth portion131ain a direction perpendicular to the first substrate. Accordingly, as illustrated inFIG. 17, at least one of the light-blocking part76cand the light-blocking part76dcan overlap with the black area of the disclination line dc1. The number of disclination lines dc1of the first electrode31according to the first modification of the embodiment is smaller than that of disclination lines dc1illustrated inFIG. 13, so that transmittance can be further improved.

As illustrated inFIGS. 13 and 15, the present inventors have found that, in a case where an interval between the disclination lines dc1is 1, a decrease in the interval1increases the response speed. The interval1is not necessarily a fixed interval as long as an average value of intervals1is equal to or smaller than a certain value (hereinafter, referred to as an average interval1). The average interval1may be equal to or smaller than 10 μm, for example.

Similarly, the present inventors have found that a decrease in the transmission effective interval Em also increases the response speed. The transmission effective interval Em is not necessarily a fixed interval as long as an average value of transmission effective intervals Em is equal to or smaller than a certain value (hereinafter, referred to as an average transmission effective interval Em). The average transmission effective interval Em may be equal to or smaller than 10 μm, for example.

In this way, the liquid crystal display device1according to the embodiment and the first modification improves the contrast of the sub-pixels Vpix while improving the response speed of the entire pixels Pix to further improve display quality in the plane.

Manufacturing Method

The method for manufacturing the liquid crystal display device1according to the embodiment includes the following process, for example. A manufacturing apparatus performs a first substrate preparation process to prepare a glass substrate, which is a translucent substrate, as the TFT substrate71of the pixel substrate (first substrate)70A.

Subsequently, the manufacturing apparatus forms the scanning line24mand the gate electrode93on the TFT substrate71. The manufacturing apparatus then forms an insulation film741between the scanning line24mand the gate electrode93, and the semiconductor layer92to be formed, on the TFT substrate71. The manufacturing apparatus then forms the layer of the source electrode91, the drain electrode90, and the semiconductor layer92, for example. The manufacturing apparatus then forms an insulation film742between the semiconductor layer92and the signal line25nto be formed. The manufacturing apparatus then forms the signal line25nand couples the signal line25nto the source electrode91. The manufacturing apparatus then forms an insulation film743between the signal line25nand the second electrode32to be formed.

Subsequently, the manufacturing apparatus forms the second electrode32serving as a pixel electrode by sputtering or etching, for example. The manufacturing apparatus then couples the drain electrode90and the second electrode32via the conductive contact90H. The thickness of the second electrode32is 10 nm or greater to 100 nm or less, for example. The manufacturing apparatus then forms the insulation film744on the second electrode32by plasma-enhanced chemical vapor deposition (CVD), for example.

Subsequently, the manufacturing apparatus forms the first electrode31by sputtering or etching, for example. The manufacturing apparatus then couples the first electrode31to the driver IC3such that the first electrode31functions as the common electrode COM. The thickness of the first electrode31is 10 nm or greater to 100 nm or less, for example. The first electrode31is formed into a comb teeth shape with the slits S. The manufacturing apparatus then forms the first orientation film73a, which is obtained by performing processing in the orientation direction ORI on a polymeric material such as a polyimide, on the first electrode31. Thus, the manufacturing apparatus performs the manufacturing process of the first substrate.

The manufacturing apparatus performs a second substrate preparation process to prepare a glass substrate, which is a translucent substrate, as the glass substrate72of the counter substrate (second substrate)70B.

The manufacturing apparatus forms the layer of the color filters76R,76G, and76B and the black matrix76aon the glass substrate72and then forms an overcoat layer and the like on the layer. The manufacturing apparatus then forms the second orientation film73b, which is obtained by performing processing antiparallel (in an opposite direction) to the orientation direction ORI on a polymeric material such as a polyimide, on the overcoat layer. Thus, the manufacturing apparatus performs the manufacturing process of the second substrate. The color filters76R,76G, and76B, and the black matrix76amay be arranged on the TFT substrate71instead of the glass substrate72. That is, the light-blocking part having a light blocking property that covers each aperture of the color filters76R,76G, and76B may be formed at least on any of the glass substrate72(second substrate) and the TFT substrate71(first substrate). The light-blocking part arranged at the center of the comb tooth portion or the center between the comb tooth portions may also be formed in the same layer as the light-blocking part covering each aperture of the color filters76R,76G, and76B formed on any of the glass substrate72(second substrate) and the TFT substrate71(first substrate).

The manufacturing apparatus causes the pixel substrate70A and the counter substrate70B to face each other. The manufacturing apparatus injects liquid crystals between the substrates and seals the liquid crystal section with a frame edge, thereby forming the liquid crystal layer70C. The back surface of the pixel substrate70A is provided with a polarizing plate and the backlight6, whereas the front surface thereof is provided with a polarizing plate and the like. The driver IC3is coupled to an electrode terminal on the frame edge. Thus, the liquid crystal display device1is manufactured.

While the embodiment uses amorphous silicon (a-Si) as the semiconductor layer92forming the TFT element Tr, it is not limited thereto. The embodiment may use polycrystalline silicon (poly-Si) as the semiconductor layer92. The embodiment may use another semiconductor material (for example, germanium (Ge)) instead of silicon or a material obtained by adding another material to silicon (for example, silicon germanium (SiGe)). The embodiment may use an oxide semiconductor material as the semiconductor layer92. Examples of the oxide semiconductor material include, but are not limited to, an oxide semiconductor material including indium (In), etc.

In the embodiment, the TFT element Tr is a bottom gate TFT in which the gate electrode93is provided below the semiconductor layer92. The embodiment may use a top gate TFT in which the gate electrode93is provided above the semiconductor layer92if possible. In the case of using a top gate TFT as the TFT element Tr, the manufacturing apparatus manufactures: the semiconductor layer92, the scanning line24mand the gate electrode93, and the signal line25nin this order; or the semiconductor layer92, the signal line25n, and the scanning line24mand the gate electrode93in this order, instead of the manufacturing process described above.

The liquid crystal display device1according to a second modification of the embodiment will be described.FIG. 18is a schematic diagram illustrating a modification of the sectional view along the line A1-A2ofFIG. 3as the liquid crystal display device according to the second modification of the embodiment. Components identical to those described in the embodiment are denoted by like reference numerals, and overlapping explanation thereof will not be repeated.

The liquid crystal display device1according to the second modification of the embodiment generates an electric field (a horizontal electric field) between the first electrode31and the second electrode32laminated in a direction (Z-direction) perpendicular to the surface of the TFT substrate71of the pixel substrate70A and in a direction parallel to the TFT substrate71. As a result, liquid crystal molecules in the liquid crystal layer70C rotate in a plane parallel to the substrate surface. The liquid crystal display device1uses a change in the light transmittance corresponding to the rotation of the liquid crystal molecules, thereby performing display. The second electrode32illustrated inFIG. 18is the common electrode COM, whereas the first electrode31is the pixel electrode, for example. The first electrode31is coupled to the drain electrode90via the conductive contact90H, for example. The first electrode31is sectioned by each area of the sub-pixel Vpix and has an independent pattern electrically insulated from the first electrode31in an area of the sub-pixel Vpix adjacent thereto. The liquid crystal display device1according to the embodiment exhibits the same advantage in both of the embodiment and the second modification.

The liquid crystal display device1according to a third modification of the embodiment will be described.FIG. 19is a schematic diagram for explaining the modification of a relation between the shape of the first electrode and the aperture as the liquid crystal display device according to the third modification of the embodiment. Components identical to those described in the embodiment are denoted by like reference numerals, and overlapping explanation thereof will not be repeated.

The first electrode31includes the comb tooth portions131protruding from the electrode base portion132extending in the X-direction. The comb tooth portions131include the comb tooth portions131aand the comb tooth portions131bextending in opposite directions from the electrode base portion132. Adjacent comb tooth portions131aprotrude from the electrode base portion132with a certain distance interposed therebetween. Similarly, adjacent comb tooth portions131bprotrude from the electrode base portion132with a certain distance interposed therebetween. From each electrode base portion132, the comb tooth portions131aextend in the Y-direction, whereas the comb tooth portions131bextend in a direction opposite to the extending direction of the comb tooth portions131ain the Y-direction.

The first orientation film73ais subjected to orientation processing in the orientation direction ORI illustrated inFIG. 19such that the liquid crystal molecules have a certain initial orientation in the Y-direction. The second orientation film73bis subjected to orientation processing antiparallel to the orientation direction ORI of the first orientation film73a. The orientation directions ORI of the first orientation film73aand the second orientation film73bare antiparallel to each other. As described above, the comb tooth portions131aextend in the Y-direction, and the comb tooth portions131bextend in the direction opposite to the Y-direction. The orientation direction ORI is parallel to the direction in which the comb tooth portions131aand the comb tooth portions131bextend. The orientation direction ORI is considered to be parallel as long as it is sufficiently parallel to maintain the rotation direction of liquid crystal molecules LCM illustrated inFIG. 9. More specifically, the orientation direction ORI allows a manufacturing error of 0 degree or greater to 0.5 degree or less. The liquid crystal display device1according to the embodiment exhibits the same advantage in both of the embodiment and the third modification.

The liquid crystal display device1according to a fourth modification of the embodiment will be described.FIG. 20is a plan view for explaining the pixel as the liquid crystal display device according to the fourth modification of the embodiment.FIG. 21is a schematic diagram illustrating a sectional view along the line E1-E2ofFIG. 20. Components identical to those described in the embodiment are denoted by like reference numerals, and overlapping explanation thereof will not be repeated.

As illustrated inFIG. 20, the semiconductor layer92is polycrystalline silicon (poly-Si) forming the TFT element Tr. The semiconductor layer92is a double-gate transistor forming a channel with two areas.

As illustrated inFIGS. 20 and 21, the liquid crystal display device1according to the fourth modification of the embodiment generates an electric field (a horizontal electric field) between the first electrode31and the second electrode32laminated in a direction (Z-direction) perpendicular to the surface of the TFT substrate71of the pixel substrate70A in a direction parallel to the TFT substrate71. As a result, liquid crystal molecules in the liquid crystal layer70C rotate in a plane parallel to the substrate surface. The liquid crystal display device1uses a change in the light transmittance corresponding to the rotation of the liquid crystal molecules, thereby performing display. The second electrode32illustrated inFIG. 21is the common electrode COM, whereas the first electrode31is the pixel electrode, for example. The first electrode31is coupled to the conductive drain electrode90, for example. The first electrode31is sectioned by each area of the sub-pixel Vpix and has an independent pattern electrically insulated from the first electrode31in an area of the sub-pixel Vpix adjacent thereto.

The first orientation film73ais subjected to orientation processing in the orientation direction ORI such that the liquid crystal molecules have a certain initial orientation in the X-direction. The second orientation film73bis subjected to orientation processing antiparallel to the orientation direction ORI of the first orientation film73a. The orientation directions of the first orientation film73aand the second orientation film73bare antiparallel to each other.

Similarly to the liquid crystal display device1according to the embodiment, in the liquid crystal layer70C of the liquid crystal display device1according to the fourth modification of the embodiment, applying a voltage to the first electrode31and the second electrode32rotates the liquid crystal molecules in the neighboring area of the right long side131R and those in the neighboring area of the left long side131L in opposite directions. The right long side131R is one of the sides of adjacent comb tooth portions131cfacing each other in the width direction of the slit S, whereas the left long side131L is the other of the sides. Thus, the liquid crystal molecules respond to a change in the electric field between the first electrode31and the second electrode32at higher speed in the liquid crystal display device1according to the fourth modification of the embodiment than in the FFS-mode liquid crystal display device disclosed in JP-A-2008-52161. As a result, the liquid crystal display device1according to the fourth modification of the embodiment achieves a higher response speed.

Similarly to the comb tooth protrusion length L2of the comb tooth portions131b, in a case where a comb tooth protrusion length of the comb tooth portions131cincreases, it is necessary to increase the angle θ. An increase in the angle increases the difference between the width w1and the width w2, resulting in limitation on the slit pitch p. In a case where the angle θ is 0.5 degree or greater to 1.0 degree or less, for example, the comb tooth protrusion length of the comb tooth portions131cis preferably set to 45 μm or smaller.

Because the electrode base portion132does not contribute to transmission of light, the width D1of the electrode base portion132in the X-direction (direction orthogonal to the extending direction of the electrode base portion132) is preferably set to a smaller value. The width D1is preferably set to a value larger than 0 μm and equal to or smaller than 4 μm. Setting the width D1larger than 0 μm can increase the conductivity, whereas setting the width D1equal to or smaller than 4 μm can suppress a decrease in the transmittance. In a case where the width D1is larger than 0 μm and equal to or smaller than 4 μm and where the comb tooth protrusion length of the comb tooth portions131cis 45 μm or smaller, the display area21can serve as a high-definition screen of 160 ppi or higher. In a case where the width w1is 0.5 for example, the width w2is preferably set to 1 μm or larger to ensure the quality throughout the comb tooth protrusion length of the comb tooth portions131c.

In the liquid crystal display device1according to the fourth modification of the embodiment, the aperture76balso includes the light-blocking part76ehaving a light blocking property in the same layer as the source electrode91or the drain electrode90. A light-blocking part76eis provided to the pixel substrate70A. A material of the light-blocking part76eis the same as that of the source electrode91or the signal line25—that is wiring for causing the first electrode31or the second electrode32to work. A light-blocking part76fis provided to the pixel substrate70A. A material of the light-blocking part76fis the same as that of the scanning line24—that is wiring for causing the first electrode31or the second electrode32to work. Due to this, a forming pattern of the light-blocking part76eor the light-blocking part76fhas high accuracy, and does not require additional processes. A position of the light-blocking part76ccorresponds to the disclination line dc1described above. The liquid crystal display device1according to the fourth modification of the embodiment includes at least one of the light-blocking part76c, the light-blocking part76e, and the light-blocking part76ffor reducing intensity of light passing therethrough at a position overlapping with the center of the first comb tooth portion131cand the center between the adjacent first comb tooth portions131cin a direction perpendicular to the first substrate. As a result, the contrast of the whole sub-pixels can be improved. It is sufficient that the liquid crystal display device1according to the embodiment includes at least one of the light-blocking part76c, the light-blocking part76e, and the light-blocking part76fillustrated inFIG. 21. As illustrated inFIG. 21, the light-blocking part76eand the light-blocking part76fare arranged both at the center of the first comb tooth portion131cand at the center between the adjacent first comb tooth portions131c. The arrangement of the light-blocking part76eand the light-blocking part76fis not limited thereto. The light-blocking part may be arranged at least at any of the center of the first comb tooth portion131cand the center between the adjacent first comb tooth portions131c. As exemplified in the arrangement of the light-blocking part76eand the light-blocking part76f, the light-blocking part may be formed on both of the TFT substrate71serving as the first substrate and the glass substrate72serving as the second substrate, or formed on any one of the first substrate and the second substrate.

As described above, setting the slit pitch p to a smaller value can increase the response speed. A decrease in the slit pitch p, however, increases the width of the comb tooth portions131cin the Y-direction, for example, resulting in an increase in the area that does not contribute to transmission of light. Even when the liquid crystal display device1according to the fourth modification of the embodiment has an aspect of the fourth modification, the device exhibits the same advantage as that of the embodiment.

Evaluation Example

The following describes evaluation results of a first evaluation example to a third evaluation example. The present invention is not limited to these evaluation examples.FIG. 22is an explanatory diagram for explaining a relation between the response speed of the pixel and an average interval between the disclination lines in a first evaluation example of the liquid crystal display unit according to the embodiment. In a case where a reference response time Tf is 1 assuming that the average interval1between adjacent disclination lines dc1is infinity and voltage is off under the same conditions of an aperture width and a cell thickness d of the sub-pixels Vpix in the first evaluation example, simulated are relative values of a response time t when voltage is off with respect to the reference response time when the average interval1is each of 2 μm, 3 μm, 5 μm, 10 μm, 20 μm, and 100 μm.FIG. 22illustrates a simulation result. As illustrated inFIG. 22, when the average interval1is equal to or smaller than 10 μm, the liquid crystal display device1can accelerate the response time t when voltage is off. As a result, the liquid crystal display device1can accelerate the response speed of the liquid crystals.

FIG. 23is an explanatory diagram for explaining a relation between the response speed of the pixel and the average transmission effective interval in a second evaluation example of the liquid crystal display unit according to the embodiment. In a case where the reference response time Tf is 1 assuming that the average transmission effective interval Em is infinity and voltage is off, simulated are the relative values of the response time when voltage is off with respect to the average interval reference response time while changing the average transmission effective interval Em for respective cases where the average interval1is each of 3 μm and 100 μm.FIG. 23illustrates a simulation result. As illustrated inFIG. 23, when the average transmission effective interval Em is equal to or smaller than 10 μm, the liquid crystal display device1can accelerate the response time when voltage is off.

Application Examples

The following describes application examples of the liquid crystal display device1explained in the embodiment and the modifications thereof with reference toFIGS. 24 and 25.FIGS. 24 and 25are diagrams illustrating an example of an electronic apparatus to which the liquid crystal display device according to the embodiment is applied. The liquid crystal display device1according to the embodiment is applicable to electronic apparatuses of all fields, such as car navigation systems as illustrated inFIG. 24, television apparatuses, digital cameras, notebook personal computers, portable electronic apparatuses including mobile phones as illustrated inFIG. 25, or video cameras. In other words, the liquid crystal display device1according to the embodiment is applicable to electronic apparatuses of all fields that display video signals received from the outside or video signals generated inside thereof as an image or video. The electronic apparatus includes a control device4(refer toFIG. 1) that supplies video signals to the liquid crystal display device and controls the operation of the liquid crystal display device.

An electronic apparatus illustrated inFIG. 24is a car navigation device to which the liquid crystal display device1according to the embodiment and the modifications thereof is applied. The liquid crystal display device1is arranged on a dashboard300inside an automobile. Specifically, the liquid crystal display device1is arranged on the dashboard300and between a driver seat311and a passenger seat312. The liquid crystal display device1of the car navigation device is utilized to display navigation, display a music operation screen, reproduce and display a movie, or the like.

An electronic apparatus illustrated inFIG. 25operates as a mobile computer, a multifunctional mobile phone, a mobile computer capable of making a voice call, or a mobile computer capable of performing communications to which the liquid crystal display device1according to the embodiment and the modifications thereof is applied. The electronic apparatus is a portable information terminal, which may be called a smartphone or a tablet terminal. The portable information terminal includes a display unit562on the surface of a housing561, for example. The display unit562includes the liquid crystal display device1according to the embodiment and the modifications thereof and a touch detecting function (what is called a touch panel) that can detect external proximity objects.

The embodiment is not limited to the above description. The components of the above embodiment encompass a component easily conceivable by those skilled in the art, substantially the same component, and what is called an equivalent. The components can be variously omitted, replaced, and modified without departing from the gist of the embodiment.