JP2008151945A - Liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display having proper display quality. <P>SOLUTION: The liquid crystal display device has an active area DSP constituted of pixels in a matrix state and a light-shielding area SLD surrounding the active area, and comprises an array substrate AR having a pixel electrode EP in each pixel, a counter substrate CT having a counter electrode ET, extending from the active area to at least a part of the light-shielded area, and a liquid crystal layer LQ held in between the array substrate and the counter substrate. A first pixel electrode EP1 disposed in a pixel of the column along one side of the active area has a shape different from and an area larger than those of a second pixel electrode EP2 in a pixel in other columns of the active area, and has an extended portion toward the light-shielded area. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device having a transmissive display function for displaying an image by selectively transmitting backlight light.

  A liquid crystal display device having a transmissive display function includes a transmissive liquid crystal display panel and a backlight unit that illuminates the liquid crystal display panel from the back. The liquid crystal display panel has a configuration in which a liquid crystal layer is held between a pair of substrates, and has an active area for displaying an image and a light-shielding area surrounding the active area.

  Each pixel constituting the active area is provided with a pixel electrode, and a color display type liquid crystal display device is also provided with a color filter. Further, between the pixels in the active area, a light shielding layer (black matrix) is arranged as in the light shielding area. The counter electrode is disposed so as to cover the color filter, and extends not only to the active area but also to the outside of the active area (that is, at least a part of the light shielding area) in consideration of the misalignment between the substrates.

  In the liquid crystal display device having such a configuration, when a voltage of the liquid crystal layer is applied, a vertical electric field substantially parallel to the normal direction of the liquid crystal display panel is formed between the pixel electrode of each pixel and the counter electrode. . At this time, the pixels arranged at the end of the active area are affected by an oblique electric field formed in addition to the vertical electric field. That is, an oblique electric field inclined with respect to the normal line of the liquid crystal display panel is formed between the counter electrode extending to the light shielding area and the pixel electrode disposed at the end of the active area.

  Due to the interaction between the oblique electric field and the vertical electric field, the pixels at the edge of the active area may cause alignment defects (disclination) of the liquid crystal molecules contained in the liquid crystal layer. Such a poor alignment causes a so-called light leakage such that the backlight passes through the liquid crystal layer regardless of the voltage applied to the liquid crystal layer in the transmissive liquid crystal display panel, which causes deterioration of display quality. Become.

  According to the liquid crystal display element of Patent Literature 1, by providing the counter electrode with a notch portion that faces the outside of the peripheral edge of the pixel electrode on the upstream side in the alignment processing direction of the alignment film thereon. It is disclosed that an oblique electric field that causes disclination does not occur in the vicinity of the edge of the pixel electrode on the upstream side in the alignment processing direction.

According to the liquid crystal display panel of Patent Document 2, a first substrate including a display electrode and an alignment film, a second substrate including a counter electrode and an alignment film, and a liquid crystal between the first substrate and the second substrate. A sealing portion for encapsulating molecules, an insulating film is provided on the pixel portion where the display electrode and the counter electrode face each other, and the pretilt angle of the liquid crystal molecules in the pixel portion is the pretilt of the liquid crystal molecules in the non-pixel portion It is disclosed to make it lower than the corner.
Japanese Patent Laid-Open No. 9-311349 JP-A-8-328006

  In the liquid crystal display device as described above, in particular, a TN (twisted nematic) mode normally white configuration (that is, maximum transmittance (white) when no voltage is applied to the liquid crystal layer, and a predetermined voltage is applied to the liquid crystal layer) In some cases, the minimum transmittance (which is sometimes black)), when black is displayed (that is, when a voltage is applied), a linear light leakage (disclination line) occurs along one edge of the active area, resulting in a bright line. There is a need to improve display quality.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a liquid crystal display device having a good display quality.

A liquid crystal display device according to an aspect of the present invention includes:
A liquid crystal display device having an active area constituted by matrix-like pixels and a light-shielding area surrounding the active area,
A first substrate having a pixel electrode in each pixel;
A second substrate having a counter electrode extending from the active area to at least a part of the light shielding area;
A liquid crystal layer held between the first substrate and the second substrate,
The first pixel electrodes arranged in the pixels of the column along one end side of the active area have a different shape from the second pixel electrodes arranged in the pixels of the other column in the active area and are more than the second pixel electrodes. It has a large area and has an extended portion extending to the light shielding area side.

  According to the present invention, a liquid crystal display device with good display quality can be provided.

  A liquid crystal display device according to an embodiment of the present invention will be described below with reference to the drawings.

  As shown in FIGS. 1 and 2, the color display type liquid crystal display device is an active matrix type liquid crystal display device and includes a transmissive liquid crystal display panel LPN. The liquid crystal display panel LPN includes an array substrate (first substrate) AR, a counter substrate (second substrate) CT disposed opposite to the array substrate AR, and a space between the array substrate AR and the counter substrate CT. And a liquid crystal layer LQ held in the liquid crystal layer LQ.

  The liquid crystal display device is opposite to the first optical element OD1 provided on the outer surface opposite to the surface holding the liquid crystal layer LQ of the array substrate AR and the surface holding the liquid crystal layer LQ of the counter substrate CT. The second optical element OD2 provided on the outer surface of the first optical element is provided. Further, the liquid crystal display device includes a backlight unit BL that illuminates the liquid crystal display panel LPN from the first optical element OD1 side.

  The liquid crystal display panel LPN includes an active area DSP that displays an image and a light shielding area SLD that surrounds the active area DSP. The active area DSP is composed of a plurality of pixels PX arranged in an m × n matrix.

  The array substrate AR is formed using an insulating substrate 10 having optical transparency such as a glass plate. That is, the array substrate AR includes, in the active area DSP, m × n pixel electrodes EP arranged in each pixel PX, and n scanning lines Y (Y1 to Y1) extending along the row direction of each pixel PX. Yn), m signal lines X (X1 to Xm) extending along the column direction of the respective pixels PX, the corresponding scanning lines Y and the corresponding signal lines X are arranged in the respective pixels PX in a region including the intersection. M × n switching elements W and the like.

  The switching element W is composed of, for example, an n-channel thin film transistor, and includes a semiconductor layer 12 made of polysilicon or amorphous silicon. In the present embodiment, the switching element W includes a semiconductor layer 12 made of polysilicon. The semiconductor layer 12 has a source region 12S and a drain region 12D on both sides of the channel region 12C. The semiconductor layer 12 is covered with a gate insulating film 14.

  The gate electrode WG of the switching element W is connected to the scanning line Y (or formed integrally with the scanning line Y). Both the gate electrode WG and the scanning line Y are disposed on the gate insulating film 14. These gate electrodes WG and scanning lines Y are covered with an interlayer insulating film 16.

  The source electrode WS and the drain electrode WD of the switching element W are disposed on both sides of the gate electrode WG on the interlayer insulating film 16. The source electrode WS is connected to the signal line X (or formed integrally with the signal line X) and is in contact with the source region 12S of the semiconductor layer 12. The drain electrode WD is connected to the pixel electrode EP and is in contact with the drain region 12D of the semiconductor layer 12. These source electrode WS, drain electrode WD, and signal line X are covered with an organic insulating film 18.

  The pixel electrode EP is disposed on the organic insulating film 18 and is electrically connected to the drain electrode WD. The pixel electrode EP is formed of a light-transmitting conductive member such as indium tin oxide (ITO) or indium zinc oxide (IZO). The pixel electrodes EP corresponding to all the pixels PX are covered with the alignment film 20.

  On the other hand, the counter substrate CT is formed using an insulating substrate 30 having optical transparency such as a glass plate. That is, the counter substrate CT includes a color filter layer 34 disposed corresponding to each pixel and a black matrix (light shielding layer) BM disposed between adjacent pixels in the active area DSP.

  The color filter layer 34 is formed of colored resins colored in mutually different colors, and the red color filter disposed in the red pixel PXR of the active area DSP, the green color filter disposed in the green pixel PXG, and the blue pixel PXB. A blue color filter disposed on the surface. The black matrix BM is formed of a coloring material with extremely low transmittance, such as a black resin or a colored metal material. When the black matrix BM is formed using a black resin, the peripheral light shielding layer arranged in a frame shape so as to surround the active area DSP in the light shielding area SLD may be simultaneously formed using the same black resin. .

  Further, the counter substrate CT includes a counter electrode ET disposed so as to cover the color filter layer 34 in the active area DSP. The counter electrode ET is disposed so as to face the pixel electrode EP corresponding to the plurality of pixels PX. The counter electrode ET is formed of a light-transmissive conductive member such as ITO. The counter electrode ET is covered with an alignment film 36.

  When the counter substrate CT and the array substrate AR as described above are arranged so that the alignment film 20 and the alignment film 36 face each other, a predetermined gap is formed by a spacer (not shown) arranged therebetween. Is done. The liquid crystal layer LQ is composed of a liquid crystal composition including liquid crystal molecules sealed in a gap formed between the alignment film 20 of the array substrate AR and the alignment film 36 of the counter substrate CT.

  The alignment film 20 and the alignment film 36 are rubbed, and in the state where no voltage is applied to the liquid crystal layer LQ, the liquid crystal molecules are arranged depending on the rubbing direction of these alignment films. As shown in FIG. 1, when the liquid crystal display panel LPN is viewed from the 3 o'clock direction, the alignment films 20 are aligned with respect to the 6 o'clock direction in order to align the liquid crystal display panel LPN in the 3 o'clock viewing angle direction so that gradation inversion does not occur. The rubbing direction of the alignment film 36 is 45 degrees with respect to the 6 o'clock direction, and the rubbing directions of the alignment film 20 and the alignment film 36 are substantially orthogonal to each other. With such a configuration, the twist angle of the liquid crystal molecules in the liquid crystal layer LQ is set to 94 degrees.

  The first optical element OD1 and the second optical element OD2 control the polarization state of light passing through the first optical element OD1 and the second optical element OD2. That is, the first optical element OD1 and the second optical element OD2 include polarizing plates each having a transmission axis and an absorption axis in directions orthogonal to a predetermined direction within each main surface. These polarizing plates are arranged, for example, so that their transmission axes are substantially orthogonal to each other.

  With such a configuration, a liquid crystal display device having a TN mode normally white configuration is provided.

  The liquid crystal display panel LPN having the above-described configuration includes the first connection portion 31 and the second connection portion 32 that are disposed outside the active area DSP. The first connection portion 31 has a plurality of electrode pads that can be connected to a driving IC chip that functions as a signal supply source. The second connection portion 31 has a plurality of connection terminals that can be connected to a flexible printed circuit (FPC) board that functions as a signal supply source.

  In the example shown in FIG. 1, the first connection portion 31 and the second connection portion 32 are provided in the extension portion ARA of the array substrate AR that extends outward from the end portion CTA of the counter substrate CT. In the array substrate AR, n scanning lines Y are drawn out of the active area DSP and connected to the first connection portion 31. Similarly, m signal lines X are also drawn from the active area DSP to the outside and connected to the first connection portion 31.

  The n scanning lines Y are sequentially supplied with scanning signals (drive signals) from a scanning line driver (not shown). Further, every time the switching elements W in each row are turned on by the scanning signal, video signals (drive signals) are supplied to the m signal lines X from a signal line driver (not shown). Thereby, the pixel electrode EP of each row is set to a pixel potential corresponding to the video signal supplied via the corresponding switching element W.

  Incidentally, as shown in FIG. 3, in the active area DSP, the color filters 34 (R, G, B) are arranged corresponding to the pixels PX of the respective colors. In the light shielding area SLD, a light shielding layer (black matrix) SL is disposed. In the light shielding area SLD, the color filters 34 (R, G, B) are arranged for the purpose of ensuring a gap equivalent to that of the active area DSP. In the example shown in FIG. 3, in the light shielding area SLD, a plurality of color filters 34 (R, G, B) are arranged at the same pitch as the color filters arranged in each pixel PX.

  In the liquid crystal display device having such a configuration, as shown in FIG. 4, with respect to the pixels PXE (that is, the blue pixels PXB) arranged in a row along one side of the active area DSP, the normal direction of the liquid crystal display panel LPN In addition to the vertical electric field along the vertical axis, it is affected by an oblique electric field formed.

  That is, the counter electrode ET extends from the active area DSP to at least a part of the light shielding area SLD in consideration of misalignment when the array substrate AR and the counter substrate CT are bonded to each other. For this reason, an oblique electric field inclined with respect to the normal line of the liquid crystal display panel LPN is formed between the counter electrode ET arranged in the light shielding area SLD and the pixel electrode EP of the pixel PXE arranged at the end of the active area. The

  In particular, in a liquid crystal display device adopting a normally white TN mode, when a predetermined voltage is applied to the liquid crystal layer in black display, in addition to the vertical electric field between the pixel electrode and the counter electrode that should be originally formed, Such an oblique electric field is generated. For this reason, due to the interaction between the vertical electric field and the oblique electric field, alignment defects of the liquid crystal molecules included in the liquid crystal layer LQ occur in the pixel PXE at the end of the active area (that is, a reverse tilt domain is formed). In a position where such an orientation failure occurs, the backlight light from the backlight unit BL passes through the liquid crystal display panel LPN and is visually recognized as a bright line near the boundary B between the active area DSP and the light shielding area SLD. Will be.

  Therefore, in this embodiment, as shown in FIGS. 5 to 7, the pixel electrodes (here, the first pixel electrodes EP1) arranged in the columns of pixels PXE along one end of the active area DSP are in the active area. The pixel electrode has a shape different from that of a pixel electrode (here, the second pixel electrode EP2; for example, a pixel electrode arranged in a pixel in a column adjacent to the pixel PXE) disposed in a pixel of another column in the DSP, and the second pixel electrode It has an area larger than EP2 and has an extension EX extending to the light shielding area SLD side.

  That is, in the column direction in which the signal line X extends, pixels of the same color are arranged, and striped color filters are arranged corresponding to the pixel columns composed of these pixels. In the example shown in FIG. 6, the pixel PXE disposed at one end of the active area DSP is a blue pixel, and a striped blue color filter extending in the column direction corresponding to a pixel column composed of these blue pixels. 34B is arranged. In the example shown here, in the active area DSP, a red pixel column, a green pixel column, and a blue pixel column are arranged in that order along the row direction.

  The first pixel electrode EP1 arranged corresponding to the pixel PXE is larger in size than the other pixels PX, for example, the second pixel electrode EP2 arranged corresponding to the green pixel PXG in the adjacent green pixel column. In particular, the width along the row direction is different, and the width L1 is larger than the width L2 of the second pixel electrode EP2. The first pixel electrode EP1 extends from the active area DSP over the boundary B to the light shielding area SLD. That is, in the first pixel electrode EP1, a portion extending to the light shielding area SLD side from the width L2 of the second pixel electrode EP2 corresponds to the extending portion EX.

  With such a configuration, it is possible to shift the position where the alignment defect may occur due to the influence of the oblique electric field from the active area DSP to the light shielding area SLD. Therefore, even if an alignment defect occurs in the liquid crystal layer LQ due to the electric field between the first pixel electrode EP1 and the counter electrode ET, the first pixel electrode EP1 extends sufficiently long into the light shielding area SLD. Therefore, the influence remains in the light shielding area, and the influence on the active area DSP can be reduced. For this reason, it is possible to prevent the occurrence of light leakage at one end of the active area, and it is possible to obtain a good display quality.

  In the embodiment described above, the effect of reducing the influence of the oblique electric field increases as the width along the row direction of the first pixel electrode EP1 arranged corresponding to the pixel PXE increases. Accordingly, it was confirmed that the effect of sufficiently reducing the influence of the oblique electric field can be obtained by setting the width (L1-L2) of the extended portion EX to 10 microns or more.

  In each pixel PX, the pixel electrode EP is disposed between two adjacent scanning lines. That is, the pixel electrode EP is disposed between a self-scanning line that supplies a scanning signal to the switching element W of its own pixel and an adjacent scanning line that supplies a scanning signal to the switching element of a pixel adjacent in the column direction. Yes. In the example shown in FIG. 5, the first pixel electrode EP1 is disposed between the adjacent scanning line Y1 and the own scanning line Y2.

  In such a configuration, during black display, the vertical electric field between the first pixel electrode EP1 and the counter electrode ET may be affected by the electric field from the adjacent scanning line Y1 in addition to the oblique electric field. For this reason, it is desirable that the extending portion EX of the first pixel electrode EP1 has a shape in which the adjacent scanning line Y1 side is formed wider than the self scanning line Y2 side. In the example shown in FIG. 5, in the extension portion EX, the width on the self-scanning line Y2 side is 13 microns, whereas the width on the adjacent scanning line Y1 side is set to 23 microns.

  With such a configuration, it is difficult to be affected by an electric field from an adjacent scanning line, and a better display quality can be obtained.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the components without departing from the gist of the invention in the stage of implementation. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

FIG. 1 schematically shows a configuration of a liquid crystal display device according to an embodiment of the present invention. FIG. 2 is a diagram schematically showing a cross-sectional structure of the liquid crystal display device shown in FIG. 1 (a cross-sectional structure for one pixel in the liquid crystal display panel). FIG. 3 is a cross-sectional view schematically showing a configuration example when light leakage occurs around the active area in the liquid crystal display device shown in FIG. FIG. 4 is a diagram for explaining a mechanism of light leakage in the liquid crystal display device shown in FIG. FIG. 5 is a plan view schematically showing a configuration example of the liquid crystal display device according to the embodiment of the present invention. FIG. 6 is a cross-sectional view schematically showing a structure when the liquid crystal display panel of the configuration example shown in FIG. 5 is cut along line AA. FIG. 7 is a diagram showing the alignment state of the liquid crystal layer in the liquid crystal display device having the configuration example shown in FIG.

Explanation of symbols

LPN ... Liquid crystal display panel AR ... Array substrate CT ... Counter substrate LQ ... Liquid crystal layer BL ... Backlight unit DSP ... Active area SLD ... Shading area PX ... Pixel EP ... Pixel electrode (EP1 ... First pixel electrode, EP2 ... Second pixel electrode)
Y ... Scanning line X ... Signal line W ... Switching element BM ... Black matrix ET ... Counter electrode SL ... Light shielding layer

Claims (3)

A liquid crystal display device having an active area constituted by matrix-like pixels and a light-shielding area surrounding the active area,
A first substrate having a pixel electrode in each pixel;
A second substrate having a counter electrode extending from the active area to at least a part of the light shielding area;
A liquid crystal layer held between the first substrate and the second substrate,
The first pixel electrodes arranged in the pixels of the column along one end side of the active area have a different shape from the second pixel electrodes arranged in the pixels of the other column in the active area and are more than the second pixel electrodes. A liquid crystal display device having a large area and an extending portion extending toward a light shielding area. The first substrate includes a plurality of scanning lines extending along a row direction of each pixel and a plurality of signal lines X extending along a column direction of each pixel;
The first pixel electrode is disposed between two adjacent scan lines,
The liquid crystal display device according to claim 1, wherein the extending portion has a shape in which the other scanning line side is formed wider than the one scanning line side.   The liquid crystal display device according to claim 1, wherein the extending portion has a width of 10 microns or more.

Images