Patent ID: 12253765

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention are described with reference to the drawings. However, the present invention can be implemented in many different aspects, and should not be construed as being limited to the description of the following embodiment. For the sake of clarifying the explanation, the drawings may be expressed schematically with respect to the width, thickness, shape, and the like of each part compared to the actual aspect, but this is only an example and does not limit the interpretation of the present invention. For this specification and each drawing, elements similar to those described previously with respect to the previous drawing may be given the same reference sign (or a number followed by a, b, etc.) and a detailed description may be omitted as appropriate. The terms “first” and “second” appended to each element are a convenience sign used to distinguish them and have no further meaning except as otherwise explained.

As used herein, where a member or region is “on” (or “below”) another member or region, this includes cases where it is not only directly on (or just under) the other member or region but also above (or below) the other member or region, unless otherwise specified. That is, it includes the case where another component is included in between above (or below) other members or regions.

Structure of Liquid Crystal Display Device

The present embodiment discloses, as an example, a MIP (Memory in Pixel) type liquid crystal display device that includes a memory circuit for storing data in each pixel.

FIG.1shows the configuration of a liquid crystal display device100. The liquid crystal display device100includes a pixel array106in which pixels105are arranged. The pixel array106is arranged, for example, on a transparent glass substrate. In this embodiment, the array substrate102refers to the substrate on which the pixel array106is arranged. The array substrate102is arranged with a drive circuit to drive the pixel array106. The drive circuit includes a vertical driver108, a horizontal driver110and a driver IC112. These drive circuits are arranged on the array substrate102in the region outside the pixel array106.

The pixel array106is arranged with an arbitrary number (m rows and n columns) of pixels105in a matrix in the row and column directions. The pixel array106has a plurality of scanning signal lines116extending in the row direction and a plurality of data signal lines118extending in the column direction, corresponding to the array of pixels105.

The pixel105includes a plurality of sub-pixels.FIG.1shows an aspect in which a pixel105includes a first sub-pixel104A, a second sub-pixel104B, and a third sub-pixel104C. As described later, the liquid crystal display device100displays images in area gradations, so that one sub-pixel includes a plurality of pixel electrodes.FIG.1shows that the first sub-pixel104A includes a first pixel electrode120A, a second pixel electrode120B, and a third pixel electrode120C. The second sub-pixel104B and the third sub-pixel104C also have a similar configuration.

The vertical driver108outputs scanning signals to the scanning signal lines116arranged in the pixel array106. The pixels105arranged in the pixel array106are selected row by row, and each sub-pixel104A, sub-pixel104B, and sub-pixel104C of the selected pixel105is in the signal write state, and data signals (video signals) are written from the data signal line118. The vertical driver108operates to sequentially output selection pulses to a plurality of scanning signal lines116, so that data signals are written every one frame. The vertical driver108can also operate to rewrite the data of the pixel105assigned to a specific area by addressing it in row units.FIG.1shows a configuration in which the vertical driver108is arranged on both sides of the pixel array106, but this arrangement is not limited to this example, and the vertical driver108may be arranged only on either the left or right side of the pixel array106.

The horizontal driver110outputs data signals output from the driver IC112to the data signal lines118. The horizontal driver110includes a multiplexer circuit and selects the plurality of data signal lines118and outputs data signals. Various methods can be selected as the writing method of data signals by the horizontal driver110, such as the line sequential method, which writes data signals simultaneously to the plurality of pixels105lined up in the row selected by the vertical driver108, and the point sequential method, which writes data signals one by one in sequence in pixel units in the plurality of pixels105lined up in the selected row.

The driver IC112is, for example, made of a semiconductor integrated circuit and mounted on the array substrate102. For example, the driver IC112may be mounted on the array substrate102in a COG (Chip on Glass) method or mounted on the flexible printed circuit board114in a COF (Chip on Film) method as shown. The driver IC112outputs data signals for displaying images to the horizontal driver110, and outputs timing signals to the vertical driver108to synchronize with the data signals.

The flexible printed circuit board114is connected to the array substrate102. The data signals and control signals input to the driver IC112are input from an external controller (not shown) via the flexible printed circuit board114.

FIG.2shows the first sub-pixel circuit122A and the second sub-pixel circuit122B included in the sub-pixel104, the first pixel electrode120A connected to the first sub-pixel circuit122A, the second pixel electrode120B connected to the second sub-pixel circuit122B and the third pixel electrode120C. The liquid crystal display device100according to the present embodiment is mainly a reflective display device, and the first pixel electrode120A, the second pixel electrode120B and the third pixel electrode120C are reflective electrodes. The liquid crystal display device100is a gradation display device that represents gradation by the area gradation method, in which the first pixel electrode120A, second pixel electrode120B, and third pixel electrode120C are area-weighted by the first pixel electrode120A, second pixel electrode120B and third pixel electrode120C.

FIG.2shows an example of the sub-pixel104applicable to area gradation. The sub-pixel104includes the first pixel electrode120A, the second pixel electrode120B and the third pixel electrode120C having the same area. The sub-pixel104has the first pixel electrode120A in the center and the second pixel electrode120B and the third pixel electrode120C on both sides (above and below when viewed in the column direction).

The sub-pixel104includes a first sub-pixel circuit122A and the second sub-pixel circuit122B. The first sub-pixel circuit122A is connected to the first pixel electrode120A, while the second sub-pixel circuit122B is connected to the second pixel electrode120B and the third pixel electrode120C. That is, the same drive voltage is applied to the second pixel electrode120B and the third pixel electrode120C. In this way, the area ratio of the sub-pixel104is weighted to the area of the first pixel electrode120A, with the second pixel electrode120B and the third pixel electrode120C as a pair of pixel electrodes to which a voltage is applied, resulting in a pixel electrode area ratio of 1:2.

The first sub-pixel circuit122A is configured to apply the drive voltage to the first pixel electrode120A, while the second sub-pixel circuit122B applies the drive voltage to the second pixel electrode120B and the third pixel electrode120C, as such, although the first sub-pixel circuit122A is divided into three pixel electrodes, the sub-pixel104can be regarded as substantially having two pixel electrodes with different areas. Each pixel electrode of each sub-pixel104A, sub-pixel104B, and sub-pixel1040included in the pixel105is arranged so that the first pixel electrode120A is arranged in the center and the second pixel electrode120B and the third pixel electrode120C are arranged on both sides. This arrangement enables the center of gravity of each tone with respect to the center of gravity of one pixel to be aligned.

As shown inFIG.2, the first sub-pixel circuit122A includes a first switching element126A, a second switching element126B, a third switching element126C, and a first latch circuit124A. The first switching element126A is, for example, a thin-film transistor, a gate is connected to the scanning signal line116, and one of the input/output terminals consisting of a source and a drain is connected to the data signal line118. When a scanning signal is applied to the gate from the scanning signal line116, the first switching element126A is turned on and the data signal is input to the first latch circuit124A from the data signal line118. The output signal of the first latch circuit124A controls the on/off state of the second and third switching elements126B,126C. The second switching element126B is arranged between the first control signal line128A, in which a control signal of the same polarity as the voltage of the counter electrode138(refer toFIG.3) is applied, and the output node Nout1of the first pixel circuit122A. The third switching element126C is arranged between the second control signal line128B, in which a control signal of the opposite phase of the first control signal line128A is applied. and the output node Nout1. The first latch circuit124A is connected to the first power line130A. in which a high potential power supply voltage is applied. and the second power line130B in which a low potential power supply voltage is applied.

One of the second switching element126B and the third switching element126C is turned on and the other is turned off according to the polarity of the voltage held by the first latch circuit124A. One input/output terminal of the second switching element126B is connected to one input/output terminal of the third switching element126C, and the node is the output node Nout1of the first sub-pixel circuit122A, which is connected to the first pixel electrode120A.

The liquid crystal display device100according to the present embodiment is applied with a vertically aligned (VA: Vertical Alignment) liquid crystal, the counter electrode138(refer toFIG.3) is arranged to face the first pixel electrode120A, the second pixel electrode120B, and the third pixel electrode120C with the liquid crystal layer in between. When a predetermined common voltage is applied to the counter electrode138, a voltage of the same polarity as or opposite polarity to the common voltage is applied to the first pixel electrode120A from the first sub-pixel circuit122A as the above drive voltage. In other words, a voltage of the same polarity or the opposite polarity as the common voltage is output from output node Nout1by turning on one of the second switching element126B and the third switching element126C according to the voltage based on the data signal held by the first latch circuit124A.

The second sub-pixel circuit122B includes the same circuit configuration as the first sub-pixel circuit122A and operates in the same method. The output node Nout2of the second sub-pixel circuit122B is connected to the second pixel electrode120B and the third pixel electrode120C and outputs a voltage of the same polarity or opposite polarity as the common voltage to these two pixel electrodes.

FIG.3shows the cross-sectional structure of the first pixel electrode120A and the second pixel electrode120B and the boundary of these electrodes as a partial cross-sectional structure of the pixel array106of the liquid crystal display device100. The liquid crystal display device100includes the array substrate102and the opposing substrate132. The array substrate102and the opposing substrate132are arranged to face each other with the liquid crystal layer142in between.FIG.3shows a structure in which the first pixel electrode120A and the second pixel electrode120B are arranged on the array substrate102and the counter electrode138is arranged on the counter substrate132.

FIG.3also schematically shows a structure in which the first pixel electrode120A is connected to the switching element126-1(corresponding to the second switching element126B or the third switching element126C shown inFIG.2) and the second pixel electrode120B is connected to the switching element126-2. The first pixel electrode120A and the second pixel electrode120B are arranged on an insulating layer146. The first pixel electrode120A is connected to a connecting wiring148-1by a contact hole formed in the insulating layer146, and the second pixel electrode120B is connected to a connecting wiring148-2by a contact hole formed in the insulating layer146. The connecting wiring148-1is an intermediate wiring that connects the switching element126-1to the first pixel electrode120A, and the connecting wiring148-2is an intermediate wiring that connects the switching element126-2to the second pixel electrode120B.

The fillers150-1,150-2may be disposed on the first pixel electrode120A and the second pixel electrode120B to prevent the formation of steps at the contact holes formed in the insulating layer146. The fillers150-1,150-2can planarize the recesses formed by the contact holes and prevent orientation disorder of the liquid crystal molecules in this area.

The first and second pixel electrodes120A,120B are reflective electrodes and are formed by a metal film, while the reflective electrode may be formed by a plurality of conductive films of different materials. For example, the first pixel electrode120A and the second pixel electrode120B may be formed from the first conductive layers152-1,152-2that are connected to the connecting wiring148-1,148-2and the second conductive layers153-1,153-2, which are arranged on top of the first conductive layers152-1,152-2to cover the fillers150-1,150-2. The first conductive layers152-1,152-2are preferably formed of a transparent conductive material such as ITO (Indium Tin Oxide), and the second conductive layers153-1,153-2are preferably formed of a light-reflective metal film such as aluminum. These materials can be combined to ensure a suitable electrical connection between the first pixel electrode120A and the second pixel electrode120B and the connecting wirings148-1,148-2, so that they can function as reflective electrodes. The structure of the first and second pixel electrodes120A,120B may align the edges of the second conductive layers153-1,153-2with the edges of the first conductive layers152-1,152-2, or the edges of the upper second conductive layers153-1,153-2may be set back from the edges of the lower first conductive layers152-1,152-2as shown inFIG.3.

A color filter layer134, an overcoat layer136, and the counter electrode138are arranged on the counter substrate132. The counter electrode138is formed of a transparent conductive film such as ITO and has a size that extends over the entire pixel array106. A first opening154A is arranged in a region where the counter electrode138overlaps the first pixel electrode120A, and a second opening154B is arranged in a region where the counter electrode138overlaps the second pixel electrode120B.

The first pixel electrode120A and the second pixel electrode120B are reflective electrodes and reflect external light incident from the opposing substrate132. That is, the external light passes through the color filter layer134, the transparent overcoat layer136, the counter electrode138, and the liquid crystal layer142, and is reflected by the first pixel electrode120A and the second pixel electrode120B, and the reflected light is emitted from the counter substrate132following a reverse route from that of incident light. The presence or absence of reflected light and its intensity reflected from the opposing substrate132is controlled by the orientation state of the liquid crystal molecules144in the liquid crystal layer142.

As shown inFIG.3, the pixel array106includes a reflective region RR formed by the first pixel electrode120A and the second pixel electrode120B and a transmissive region TR between the first pixel electrode120A and the second pixel electrode120B. The transmissive region TR is defined as the region between the edge of the second conductive layer (metal film)153-1, which makes up the first pixel electrode120A, and the edge of the second conductive layer (metal film)153-2, which makes up the second pixel electrode120B. A backlight160is disposed on a back side of the array substrate102(opposite side of a surface on which the first pixel electrode120A and the second pixel electrode120B are arranged) in the liquid crystal display device100. The liquid crystal display device100has the function of displaying images by means of reflective electrodes while emitting light from the backlight160through the transmissive region TR, which assists in the display luminance of the images. For example, it is difficult to display a bright image in dark areas using only the reflective mode, but combining this with the transmissive mode makes it possible to display images brighter.

The liquid crystal display device100according to this embodiment is not arranged with a light-shielding layer that hides the region between pixels. Therefore, it is also important to control the orientation of liquid crystal molecules in the transmissive region TR between the first pixel electrode120A and the second pixel electrode120B.

Although the alignment film is not shown inFIG.3, the array substrate102and the opposing substrate132are disposed with a vertically oriented film. The vertical alignment film keeps the liquid crystal molecules144vertically oriented when no voltage is applied between the first pixel electrode120A and the second pixel electrode120B and the counter electrode138. That is, a long axis of the liquid crystal molecules144is oriented such that it is standing perpendicular to the substrate surface of the array substrate102. When a predetermined voltage is applied between the first pixel electrode120A and the second pixel electrode120B and the counter electrode138, the long axis of the liquid crystal molecules144tilts from vertical to horizontal (transverse) and is oriented horizontally when the maximum voltage is applied.FIG.3schematically shows that since electric fields are not formed at the edges of the first opening154A and second opening154B in the counter electrode138, the liquid crystal molecules at the regions overlapping these openings remain vertically oriented, while the liquid crystal molecules around these openings are obliquely oriented between the horizontally oriented liquid crystal molecules and those that remain vertically oriented.

FIG.4shows a planar schematic diagram of a pixel array as a comparative example in which a plurality of pixel electrodes202are arranged in a matrix in the X-axis and Y-axis directions shown in the figure. The pixel electrode202shown inFIG.4is square in a plan view. The dotted circle overlapping the pixel electrode202indicates the openings206of the counter electrode204.FIG.4shows an arrangement in which a spacer208is disposed in the region surrounded by the four pixel electrodes202.

FIG.4shows the direction of orientation of liquid crystal molecules at each location by arrows, with an electric field formed between the pixel electrode and the counter electrode. As shown inFIG.3, the liquid crystal molecules are oriented radially around the openings206when a potential difference is generated between the pixel electrode202and the counter electrode204. The liquid crystal molecules are oriented radially on the pixel electrode202, but in the region between the pixel electrodes, the liquid crystal molecules oriented from both sides interfere with each other, resulting in an unstable orientation state. As a result, as shown inFIG.4, the region DR near the center of one side of the pixel electrode202and between the neighboring pixel electrodes202is a region that induces orientation disorder (disclination) of the liquid crystal molecules. As shown inFIG.4, the regions DR are generated between the pixel electrodes arrayed in a matrix-like pattern, and if this orientation disorder occurs in many regions DR, it may be visible to the user as a display irregularity on the entire screen.

On the other hand, in the region U surrounded by the edges of the four pixel electrodes202, the liquid crystal molecules are equally oriented from four or eight directions, and since the electric field is not generated in this region, the orientation state is relatively stable. The orientation of liquid crystal molecules is controlled by the effect of the spacer208in the region where the spacer208is disposed, and the disclination is less likely to occur. While the region DR is affected by the liquid crystal molecules oriented on each electrode, it is at a distance from the region U, where the orientation of the liquid crystal molecules is stable, when viewed at the level of the liquid crystal molecules, and these are the factors causing the unstable orientation state.

The liquid crystal display device100according to this embodiment is used for displaying images, with the region between pixels acting as the transmissive region TR. If disclination occurs in the regions DR as shown inFIG.4, the image quality may be adversely affected. It is possible to prevent the formation of disclination and suppress the degradation of image quality when the liquid crystal display device100is arranged with the configuration of pixel electrodes shown in the following embodiments.

First Embodiment

FIG.5is a plan view showing the configuration of pixel array106.FIG.5shows an arrangement in which the pixel104includes three sub-pixels, and the first pixel electrode120A, the second pixel electrode120B, and the third pixel electrode120C are arranged correspondingly. The pixel104includes the first pixel circuit122A and the second pixel circuit122B shown inFIG.2. The first pixel electrode120A is sandwiched between the second pixel electrode120B and the third pixel electrode120C.

As shown inFIG.5, the first pixel electrode120A has a shape in which three or four corners are notched in relation to the square shape shown inFIG.4. Since the corners of the first pixel electrode120A have a notched shape, the length of one side is shorter than in the square shape. Such a shape can be otherwise expressed as a shape in which, the corners of the pixel electrodes concerned are brought closer to the center of each side in comparison with a virtual square formed by extending the sides parallel to the array direction of the pixel electrodes in each pixel electrode. The pixel array106is a matrix array of pixel electrodes of such shapes in the X-axis and Y-axis directions shown in the figure.

As shown inFIG.5, the first pixel electrode120Aa, the second pixel electrode120Ba, and the third pixel electrode120Ca arranged in the first sub-pixel104A all have a shape in which the corners are notched. In other words, the pixel electrodes arranged in the sub-pixel have a shape including an end notch (cutoff corner). The first pixel electrode120Ab, second pixel electrode120Bb, and third pixel electrode120Cb arranged in the second sub-pixel104B, and the first pixel electrode120Ac, second pixel electrode120Bc, and third pixel electrode120Cc arranged in the third sub-pixel104C also have similar shapes. Accordingly, the spacing (gap) in the region W surrounded by the first pixel electrode120Aa, the first pixel electrode120Ab, the second pixel electrode120Ba, and the second pixel electrode120Bb is much wider than in the region U shown inFIG.4.FIG.5also shows the arrangement of the spacer156in the region between pixels surrounded by the first pixel electrode120Ab, the first pixel electrode120Ac, the second pixel electrode120Bc, and the second pixel electrode120Bc. The corners of the first pixel electrode120Ab, the first pixel electrode120Ac, the second pixel electrode120Bc, and the second pixel electrode120Bc that surround the spacer156are not notched on the spacer156side, and each corner is shaped to protrude toward the spacer156.

FIG.6schematically shows the orientation of the liquid crystal molecules during the formation of the electric field in the pixel array106shown inFIG.5by means of arrows. As described with reference toFIG.4, the liquid crystal molecules are oriented radially with the opening154in the counter electrode138as the center. At the region DR where the edges of the pixel electrodes120are adjacent to each other, the liquid crystal molecules are oriented so that they collide from both sides, as in the example shown inFIG.4. However, as shown inFIG.6, since the region W surrounded by the first pixel electrode120Aa, the first pixel electrode120Ab, the second pixel electrode120Ba, and the second pixel electrode120Bb, except for the position where the spacer156is installed, the regions DR are close to the region W. The region U shown inFIG.4is basically a region where disclination does not occur, and the same can be said for the region W, which can be considered as an enlarged version of the region U. As shown inFIG.6, the distance between the region W and the regions DR is smaller than the distance between the region U and the regions DR shown inFIG.4. In this way, when there is an area (region W in the present embodiment) where the arrangement of the liquid crystal molecular is stable, the liquid crystal molecules around the area will increase their stability due to the influence of the liquid crystal molecules in the region W. As a result, the instability of the liquid crystal molecules can be resolved and the occurrence of disclination can be suppressed.

As shown inFIG.6, it is preferable that the length Cf of the notched corner of the first pixel electrode120Aa be ⅕ to ¼ of the length of one side Ls when the corner is not notched. This notched length Cf is the same for the other pixel electrodes120. If the notch is larger than the above range, an area of the pixel electrode120will be reduced and the display luminance in a reflective mode will be greatly reduced. If the notch is smaller than the above range by too much, it is not desirable because the effect of suppressing the disclination will be less effective.

On the other hand, there is no need to form the notched corners in the region where the spacer156shown inFIG.6is arranged since the orientation of the liquid crystal molecules is regulated by the spacer156, as explained with reference toFIG.4. Therefore, as shown inFIG.5andFIG.6, the pixel array106can include regions where the spacing (the gap) between edges of the pixel electrodes diagonally facing each other (regions where the corners of the pixel electrodes are notched) is wide and regions where the spacing between edges of the pixel electrodes diagonally facing each other (regions where spacers are arranged) is relatively narrow.

As shown in this embodiment, it is possible to suppress the disclination that occurs in the inter-pixel region where the pixel electrodes120are adjacent to each other vertically or horizontally by widening the spacing between the ends of the four pixel electrodes120diagonally facing each other. Specifically, it is possible to increase the spacing between the edges of the four pixel electrodes120by notching the corners of the pixel electrodes120, thereby suppressing the occurrence of disclination. As a result, orientation disorder of liquid crystal molecules can be suppressed in the region between pixels that are displayed in a transmissive mode, and the degradation of picture quality can be reduced.

The liquid crystal display device100according to this embodiment includes memory circuits (latch circuit124) that store data signals in the sub-pixels104, and can display images based on the data signals stored in the memory circuits. The sub-pixel104includes three pixel electrodes (first sub-pixel105A, second sub-pixel105B, and third sub-pixel105C) which are formed of reflective electrodes, and the gradation is expressed by area gradation using these reflective electrodes. The liquid crystal display device100according to this embodiment can be combined with the display of images not only in the reflective mode but also in the transmissive mode, in which the region between sub-pixels is used as the transmissive region TR to transmit the light of the backlight160. In this case, as shown inFIG.5, an area of the transmissive region TR can be expanded by notching the corners of each pixel electrode120so that the distance between the edges of the diagonally facing pixel electrodes120widens, thereby increasing the luminance of the displayed image. As shown inFIG.3, it is preferable that the elements, wiring, etc. that form the pixel circuit are arranged on the lower layer of the pixel electrodes, and that these elements are laid out so that they do not overlap the transmissive region TR as much as possible. Such a layout, in addition to notching the corners of the pixel electrodes, can expand the real area of the transmissive region TR, thus increasing the brightness of the display in the transmissive mode.

Second Embodiment

The shape of the pixel electrodes is not limited to the shape shown in the first embodiment, and may have other different shapes as long as the spacing between diagonally facing pixel electrodes is widened. This embodiment shows an example in which the shape of the pixel electrodes differs from the first embodiment. In the following explanation, the focus will be on the portions that differ from the first embodiment.

FIG.7is a plan view of the arrangement of the pixel electrodes of the pixel array106in this embodiment. The pixel array106includes a first sub-pixel104A, a second sub-pixel104B, and a third sub-pixel104C. The first sub-pixel104A includes a first pixel electrode120Aa, a second pixel electrode120Ba, and a third pixel electrode120Bc. The second sub-pixel104B and the third sub-pixel104C have the same configuration. As shown inFIG.7, a shape of the first pixel electrode120Ab is asymmetric with respect to the second pixel electrode120Bb and the second pixel electrode120Cb, which are adjacent to the top and bottom, and with respect to the first pixel electrode120Aa and the first pixel electrode120Ca, which are arranged on the left and right. While the shape of each pixel electrode has this asymmetric relationship, the region where the spacer156is not disposed is similar to the extended region W shown inFIG.6where the spacing (gap) between the edges of the four diagonally facing pixel electrodes (for example, first pixel electrode120Aa, first pixel electrode120Ab, second pixel electrode120Ab, second pixel electrode120Bb) is wider than that of when rectangular pixel electrodes are arranged at the same pitch. Furthermore, the shape of the pixel electrodes in itself may be horizontally or/and vertically asymmetrical.

As shown in the inset ofFIG.7, one side of the first pixel electrode120Aa has one portion L2that bends away from the edge of the adjacent second pixel electrode120B from the middle of one portion L1that extends in a straight line. That is, the first pixel electrode120Aa has a first portion (L1A) parallel to the Y-axis direction and a second portion (L2A) intersecting the Y-axis and X-axis directions. The first pixel120Ab adjacent to the first pixel electrode120Aa has a first portion (L1B) parallel to the Y-axis direction and a second portion (L2B) intersecting the Y-axis and X-axis directions. The first pixel electrode120Aa and the second pixel electrode120Ab are arranged so that the first portion (L1A) and the second portion (L2A) of the outer peripheral edges are adjacent to each other in the X-axis direction and the second portion (L2B) and the first portion (L1B) are adjacent to each other in the X-axis direction. The first portion (L1A) and second portion (L2B), whose outer edges are adjacent to each other, are non-parallel, and the second portion (L2A) and first portion (L1B) are parallel. In other words, each edge forming the contour of the first pixel electrode120Aa does not extend in a straight line from one end to the other, but has a contour shape that bends in the middle of the straight portion and is non-parallel to a side of the adjacent first pixel electrode120Ab. Such a shape and arrangement are the same for the second pixel electrode120Ba and the third pixel electrode120Ca.

Similar to the pixel electrodes shown in the first embodiment, the edges of the pixel electrodes adjacent to the spacer156do not have an odd shape, and the corners of each pixel electrode protrude toward the spacer156.

According to the pixel electrode shape shown inFIG.7, it is possible to widen the distance between the diagonally opposite edges of the four pixel electrodes. As a result, as in the first embodiment, it is possible to prevent the disclination that occurs in the region between pixels where the pixel electrodes are adjacent to each other vertically or horizontally. As a result, orientation disorder of liquid crystal molecules can be prevented in the region between pixels that are displayed in a transmissive mode, the degradation of picture quality can be reduced, and the picture quality can be improved.

Third Embodiment

This embodiment shows an example of a pixel electrode with a shape different from the first embodiment and the second embodiment.

FIG.8is a plan view of the arrangement of pixel electrodes of the pixel array106in this embodiment. The pixel array106includes a first sub-pixel104A, a second sub-pixel104B, and a third sub-pixel104C. The first sub-pixel104A includes a first pixel electrode120Aa, a second pixel electrode120Ba, and a third pixel electrode120Ca. The second sub-pixel104B and the third sub-pixel104C have similar pixel electrode configurations. As shown inFIG.8, the first pixel electrode120Aa has a shape of a rectangle (for example, a square) with a notch1201in the central portion of each side. In other words, the first pixel electrode120Aa according to this embodiment has at least one side adjacent to the neighboring pixel electrode (for example, the second pixel electrode120Ba), and the center of one of the sides has an outer edge that bends towards the inner side of the first pixel electrode120Aa. The second pixel electrode120Ba and the third pixel electrode120Ca have similar shapes.

As explained with reference toFIG.4, the disclination occurs in the center of the inter-electrode region sandwiched between one side of the pixel electrode and one side of the adjacent pixel electrode (region DR). Each pixel electrode120shown inFIG.8has a notch1201in the center of each side, which contributes to form a region where the electric field is not generated or is significantly small in the center, that makes the orientation of the liquid crystal molecules stable in the region, and the orientation of the liquid crystal molecules around the region relatively stable as well. As a result, the orientation of liquid crystal molecules in the same position as the region DR shown inFIG.4is stabilized and the occurrence of disclination is prevented as much as possible. In other words, it is possible to form a region that approximates the region where the pixel electrodes face each other diagonally (for example, region W shown inFIG.6) by arranging the notch in the center of each side of the rectangular pixel electrode shown by the dotted line inFIG.8, and the occurrence of disclination is reduced.

AlthoughFIG.8shows a structure in which notches1201are formed on each opposing side between adjacent pixel electrodes, the notches1201may be formed only on one of the opposing sides.

According to the shape of the pixel electrodes shown inFIG.8, even if disclination occurs in the region between the pixel electrodes, the region where it occurs can be fixed and the orientation of the liquid crystal molecules can be stabilized. As a result, orientation disorder (fluctuation) of liquid crystal molecules can be prevented even in the region between pixels that are displayed in a transmissive mode, and the degradation of image quality can be prevented, thereby improving the image quality.

Fourth Embodiment

This embodiment differs from the first to third embodiments in that the form of the counter electrode is different.

FIG.9shows a plan view of the counter electrode138of the liquid crystal display according to this embodiment. As shown inFIG.9, the counter electrode138is arranged to overlap the pixel electrodes120. The counter electrode138is arranged with slits158in the region overlapping the pixel electrodes120. The slit158has a shape extending outward from a center portion of the region overlapping the pixel electrode120in a plan view. When the pixel electrode120is square, the slit158has a cross shape so that it extends toward each side of the pixel electrode120. Further, the slit158has a shape in which the tip of the cross shape is bifurcated into two. In other words, the slit158has the shape of a Y-shaped pattern that extends outward from the center of the region overlapping the pixel electrode120and is combined to connect at the center.

The liquid crystal molecules change orientation according to the intensity of the electric field between the pixel electrode120and the counter electrode138. Although the counter electrode138has a shape that extends over the entire pixel array106, an opening (a slit in this embodiment) is arranged in the region overlapping the pixel electrode120, so that the electric field is concentrated at the periphery of the slit158. The slit158shown inFIG.9extends to a region where the tip extends toward the outer edge of the pixel electrode120(the center of one side), allowing the region where the orientation of the liquid crystal molecules is stable to be formed near the center of each side, rather than in the center of the pixel electrode120.

A region is formed where the orientation of the liquid crystal molecules is stable in the vicinity of the region between pixels, thereby preventing the occurrence of disclination, by arranging the counter electrode138with the slit158having such a shape. As a result, orientation disorder (fluctuation) of liquid crystal molecules is reduced even in the region between pixels that are displayed in a transmissive mode, which can prevent the degradation of image quality and improve the image quality. In addition, the slit158has the shape extending in multiple directions from the center, which allows the liquid crystal molecules to be oriented in each direction, which also improves the viewing angle.

The shape of the slit158shown inFIG.9is an example and is not limited to the shape shown in the figure. The slit may have other shapes as long as it is capable of forming a region where the electric field is concentrated in the central region of the outer edge of the pixel electrode.

Each embodiment described above as embodiments of the present invention may be combined as appropriate to the extent that they do not contradict each other. Based on the liquid crystal display device of each embodiment, any addition, deletion, or design change of components, or any addition, omission, or change of conditions of processes made by a person skilled in the art as appropriate, is also included in the scope of the invention as long as it has the gist of the invention.

Other advantageous effects different from the advantageous effects provided by each of the embodiments described above, which are obvious from the description herein or which can be easily foreseen by those skilled in the art, are naturally considered to be provided by the present invention.