JP2002229047A - Liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the aperture rate of the area between a pixel electrode and a counter electrode, i.e., the so-called ineffective region when the ineffective area is present. SOLUTION: In each pixel area wherein the pitch DP of dots arranged in a matrix form on the liquid crystal side of one of substrates arranged opposite each other across liquid crystal is 150 μm (DP<=219 μm), the pixel electrode and counter electrode are formed; and each electrode is composed of three electrodes in total, i.e., two counter electrodes and one pixel between them and three bent parts are formed in respective extending directions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display, and more particularly to a so-called in-plane switching method.

[0002]

2. Description of the Related Art A so-called in-plane switching type liquid crystal display device is provided with a pixel electrode which generates an electric field in a pixel region on one side of a transparent substrate through a liquid crystal. An electrode is formed, and the liquid crystal has a configuration in which light transmittance is controlled by an electric field having a component substantially parallel to the transparent substrate in the electric field.

Such a liquid crystal display device has excellent so-called wide viewing angle characteristics, and a portion where light can pass through liquid crystal in each pixel region is a region between a pixel electrode and a counter electrode. Therefore, it is known that an improvement in aperture ratio is desired.

Further, such a liquid crystal display device has a disadvantage that the color tone changes when observed from directions opposite to each other with respect to the vertical direction of the display surface, so that the direction of the electric field generated in each pixel region is changed. It has become known to form different regions. This is a so-called multi-domain method, and specifically, a pixel electrode and a counter electrode are formed in a zigzag shape along their extending direction.

[0005]

However, in the liquid crystal display device of the lateral electric field type employing the multi-domain system, the bent portion of the pixel electrode formed in a zigzag shape and the bent portion of the counter electrode also formed in a zigzag shape are used. Since the direction of the electric field generated in the region between the portions is complicated, it is difficult to drive the liquid crystal to transmit light, and an ineffective region that does not substantially contribute to the improvement of the aperture ratio is formed. Will be done.

The present invention has been made in view of such circumstances, and an object thereof is to provide a liquid crystal display device having a configuration in which the aperture ratio is improved as much as possible despite the existence of the invalid area. It is in.

[0007]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

[0008] The liquid crystal display device according to the present invention includes, for example,
Dot pitch DP arranged in a matrix on the liquid crystal side of one of the substrates opposed to each other via the liquid crystal
Is formed in each pixel region set in the range of 150 μm <DP ≦ 219 μm, and each of the electrodes has two counter electrodes disposed with one pixel electrode interposed therebetween. It is composed of a total of three electrodes,
It is characterized in that three bent portions are formed in each extending direction.

In the liquid crystal display device configured as described above, one pixel electrode and two opposing electrodes are arranged in one pixel, and when a so-called multi-domain is adopted,
It has been confirmed that the maximum aperture ratio can be obtained by setting the bent portions of each of the three electrodes to be three as compared with the other number.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the liquid crystal display device according to the present invention will be described below with reference to the drawings. << Equivalent Circuit >> FIG. 2 is an equivalent circuit diagram showing one embodiment of the liquid crystal display device according to the present invention. The figure is a circuit diagram, but is drawn corresponding to an actual geometric arrangement. In the figure, there is a transparent substrate SUB1, which is arranged to face another transparent substrate SUB2 via a liquid crystal.

On the liquid crystal side surface of the transparent substrate SUB1,
Gate signal line G extending in the x direction and juxtaposed in the y direction in the figure
L and a drain signal line DL that is insulated from the gate signal line GL, extends in the y direction and is arranged in the x direction, and a rectangular region surrounded by each of the signal lines is a pixel region. The display unit AR is configured by a set of these pixel regions.

Although not shown in the figure, a thin film transistor TFT driven by the supply of a scanning signal (voltage) from one gate signal line GL is provided in each pixel region.
And a pixel electrode PIX to which a video signal (voltage) is supplied from one drain signal line DL via the thin film transistor TFT, and a counter electrode CT for generating an electric field between the pixel electrode PIX and the pixel electrode PIX. I have.

The counter electrode CT is formed by being connected to a counter voltage signal line CL that travels in the x direction in the figure through substantially the center of the pixel region. Therefore, the counter voltage signal line CL runs in the display area AR. In the figure, they are formed so as to extend in the x direction and be juxtaposed in the y direction.

One end of each gate signal line GL extends to one side (left side in the figure) of the transparent substrate, and the extending portion is connected to a vertical scanning circuit V composed of a semiconductor integrated circuit mounted on the transparent substrate SUB1. One end of each drain signal line DL also extends to one side (upper side in the figure) of the transparent substrate SUB1, and the extending portion is a semiconductor integrated circuit mounted on the transparent substrate SUB1. Video signal driving circuit H comprising
e.

One end (right side in the figure) of each counter voltage signal line CL is connected to a common connection line extending to one side (upper side in the figure) of the transparent substrate SUB. A counter voltage signal is supplied.

The transparent substrate SUB2 includes a vertical scanning circuit V
In addition, it is disposed to face the transparent substrate SUB1 so as to avoid a region where the semiconductor circuit constituting the video signal driving circuit He is mounted, and has an area smaller than that of the transparent substrate SUB1.

The fixing of the transparent substrate SUB2 to the transparent substrate SUB1 is performed by a sealing material SL formed around the transparent substrate SUB2.
Also has a function of sealing the liquid crystal between the transparent substrates SUB1 and SUB2.

<< Pixel Configuration >> FIG. 3 is a plan view showing an embodiment of the configuration of each pixel region on the transparent substrate SUB1 side, and shows the configuration within the dotted frame in FIG. FIG. 4 is a diagram of FIG.
FIG. 5 is a sectional view taken along line IV-IV, and FIG. 5 is a sectional view taken along line VV in FIG. In the figure, first, a transparent substrate S
A gate signal line GL (the upper signal line in the figure is not shown) is formed on the liquid crystal side surface of the UB1 and extends in the x direction in the figure and is juxtaposed in the y direction. Each of these gate signal lines GL
As described above, a region surrounded by and a drain signal line DL described later is a pixel region.

Between the gate signal lines GL, the counter voltage signal lines CL run parallel to the gate signal lines GL, that is, substantially in the middle of the pixel region in the x direction in the drawing.
Are formed. The counter voltage signal line CL is formed of, for example, the same material and in the same layer as the gate signal line GL.

The counter voltage signal line CL is formed integrally with a counter electrode CT. The counter electrode CT extends, for example, three in each of the upper and lower directions (the y direction in the drawing) with the counter voltage signal line CL interposed therebetween. Is formed.

Each of these counter electrodes CT is formed in a zigzag shape along the extending direction so that the color tone does not change even if the display surface is observed at a different viewing angle, which is called a so-called multi-domain system. The details will be described later on the pixel electrode PI
This will be described in relation to X. And these gate signal lines G
An insulating film GI made of, for example, a SiN film is formed so as to cover L and the counter voltage signal line CL (counter electrode CT) (see FIGS. 4 and 5).

This insulating film GI functions as an interlayer insulating film between the gate signal line GL and the counter voltage signal line CL for the drain signal line DL described later, and the gate insulating film for the thin film transistor TFT described later. Function as
The capacitor Cst described later has a function as a dielectric film.

Further, an i-type (intrinsic: conductivity-type-determining impurity) made of, for example, a-Si is not doped on the upper surface of the insulating film GI at a portion overlapping the gate signal line GL at the lower left of the pixel region in the drawing. ) Is formed.

The semiconductor layer AS is formed by forming a drain electrode SD2 and a source electrode SD1 on the upper surface thereof, thereby forming a semiconductor layer of a MIS type thin film transistor TFT using a part of the gate signal line GL as a gate electrode. It is.

The source electrode SD1 and the drain electrode SD2 of the thin film transistor TFT are formed simultaneously with the drain signal line DL formed on the insulating film GI.

That is, a drain signal line DL extending in the y direction in the figure and arranged in parallel in the x direction is formed (the signal line on the right side in the figure is not shown).
Is formed so as to extend to the upper surface of the semiconductor layer AS, so that the extending portion is a thin film transistor TFT.
Is formed as the drain electrode SD2.

A source electrode SD1 is simultaneously formed on the semiconductor layer AS while being separated from the drain electrode SD2. The source electrode SD1 is formed integrally with the pixel electrode PIX.

This pixel electrode PIX is located in the pixel area as shown in FIG.
It is formed between the counter electrodes CT so as to extend in the direction. Three counter electrodes CT are formed as described above,
There are two pixel electrodes PIX formed between them.

Each pixel electrode PIX is referred to as a so-called multi-domain system, and is formed in a zigzag shape along the extending direction so that the color tone does not change even when observed at different viewing angles with respect to the display surface. .

That is, the pixel electrode PIX and the counter electrode CT
A region in which the direction of the electric field generated between the electrodes is made different is formed by making each of the electrodes zigzag along the extending direction.

In this embodiment, each pixel electrode PI
In the case of X, one bent portion is formed on the counter voltage signal line CL, and two bent portions are formed at equal intervals along the extending direction in the up-down direction, so that a total of five bent portions are provided. It has become.

Each counter electrode CT is a pixel pixel electrode PI
Because of the arrangement in parallel with X, each counter electrode CT
Also has a total of five bends at locations corresponding to the pixel electrodes PIX.

The counter electrode CT of each counter electrode CT adjacent to the drain signal line DL is connected to the drain signal line D.
A function to shield the electric field from L from not terminating on the pixel electrode PIX side is provided, so that the line width is formed large, and the side on the side of the drain signal line DL is straight along the drain signal line DL. It has a shape formed into a shape.

That is, the counter electrode CT adjacent to the drain signal line DL is different from the other counter electrodes CT in that only the side on the pixel electrode PIX side is formed in a zigzag shape, and the electrodes extend along the extending direction. It has a shape that varies in width.

The counter voltage signal line C of the pixel electrode PIX
The overlapping portion with L is formed so as to have a relatively large area, and the storage capacitor element Cst having the insulating film GI as a dielectric film is formed here.

The storage capacitance element Cst is provided for storing the video signal supplied to the pixel electrode PIX for a long time when the thin film transistor TFT is turned off. Then, the transparent substrate SU thus formed is formed.
A protective film PSV made of, for example, a SiN film is formed on the surface of B1.
Are formed (see FIGS. 4 and 5). This protective film PS
V is mainly formed to avoid direct contact of the thin film transistor TFT with the liquid crystal LC. Further, an alignment film (not shown) is formed on the surface of the protective film PSV, and determines the initial alignment direction of the liquid crystal molecules that are in direct contact with the alignment film.

On the other hand, a black matrix BM is formed on the surface on the liquid crystal LC side of the transparent substrate SUB2 opposed to the liquid crystal LC. It is formed around each pixel area, and is formed so as to be separated from other adjacent pixel areas. In other words, each pixel region is formed in a shape in which an opening is formed at a central portion excluding the periphery.

The black matrix BM is provided mainly for shielding external light to the thin film transistor TFT and for improving the contrast.
A color filter FIL is formed so as to cover the opening of the black matrix BM. For example, the color filter FIF has a band shape having a common color for each pixel arranged in parallel in the y direction in the figure, and each of the red (R), green (G), and blue (B) color filters FIL in the x direction in the figure.
Are sequentially repeated and arranged side by side.

A flattening film OC made of, for example, a resin layer is formed so as to cover the black matrix BM and the color filter FIL, so that steps due to the black matrix BM and the color filter FIL do not appear on the surface. Has become. And the flat film OC
An alignment film (not shown) is formed on the surface of the liquid crystal, and determines the initial alignment direction of liquid crystal molecules that are in direct contact with the alignment film.

<< Consideration of Invalid Region and Electrode Spacing >> The liquid crystal display device having the above-described structure is composed of the pixel electrode PIX and the counter electrode CT.
Between them, an electric field is generated in the direction of their shortest distance. That is, an electric field is generated between the upper pixel electrode PIX and the counter electrode CT in the direction of 90 ° with respect to the extending direction of the upper and lower pixel electrodes PIX and P in FIG. An electric field is generated between the counter electrodes CT in a direction at 90 ° to the extending direction of the electrodes.

This means that, for the pixel electrode PIX having a divergent angle of the angle θ at the bent portion, + (90 ° − θ /
2), and the counter electrode C in the direction of-(90 ° -θ / 2).
An area where an electric field is generated between T and T is formed.

However, between the bent portion of the pixel electrode PIX and the bent portion of the counter electrode CT (near the x-direction line), the direction of the electric field is not determined in any of the above directions, and the liquid crystal cannot be driven as prescribed. , An area with insufficient luminance is formed (this area is defined as an invalid area in this specification).

As shown in detail in FIG. 6, the ineffective area extends from the vertex of the convex portion on the side of the other electrode (for example, the counter electrode CT) facing one electrode (for example, the pixel electrode PIX). The region NUL is formed as a divergent pattern over the periphery of the concave portion on the side of the electrode.

Therefore, from the viewpoint of improving the aperture ratio,
The smaller the area of the invalid area NUL, the better.
We have come to think that the area of L may have some relationship between the distance (electrode interval) between the pixel electrode PIX and the counter electrode CT.

Therefore, the pixel electrode PIX and the counter electrode CT
With the electrode spacing of 10.4 μm, 13.4 μm, 1
7.9 μm, and each of the pixel electrodes PI
An X and a counter electrode CT having a bent portion were prepared.

On the other hand, the pixel electrode PIX and the counter electrode CT are
The electrode spacing is 10.4 μm, 13.4 μm, 17.9
The pixel electrode PIX and the counter electrode CT each having no bent portion, in other words, those in which each electrode is formed to extend linearly, were prepared.

In the case of the pixel electrode PIX and the counter electrode CT formed in a straight line, the electric fields generated therebetween are all in the same direction, and it goes without saying that the above-described configuration does not generate the invalid area NUL at all. .

From this, the distance between the electrodes is 10.4 μm.
With a bent portion, and the interval between the electrodes is 10.4
The luminance in white display of each of those having a thickness of μm and having no bent portion was measured, and the amount represented by the following equation (1) was calculated.

## EQU00001 ## (Brightness in a configuration with a bent portion) / (Brightness in a configuration with a bent portion) (1)

In this case, those having a bent portion in each electrode and those not having a bent portion in each electrode differ only in the electrode interval, and have other conditions such as the size of the pixel region, the width of the electrode, the electrode width, and the like. And the number of pieces were the same.

For this reason, the value calculated from the above equation (1) indicates the rate of decrease in luminance due to the occurrence of an invalid area, and as shown in the following equation (2), the value corresponds to the area of the pixel area. , The area of the invalid area can be calculated.

[0051]

## EQU2 ## {(brightness in a configuration with a bent portion) / (brightness in a configuration with a bent portion)} × area of pixel region (2) Such an operation is performed when the distance between the electrodes is 13.4 μm. Between the electrode having a bent portion and the electrode having an interval of 13.4 μm and not having a bent portion, and the one having an electrode interval of 17.9 μm and having a bent portion, and A graph as shown in FIG. 1 is obtained by plotting the relationship between the electrode spacing and the ineffective area and performing fitting by an approximate expression by performing the same operation for the electrode having a spacing of 17.9 μm and having no bent portion. I got

In the above-mentioned work, the above equations (1) and (2) are calculated by so-called optical measurement, a picture of the pixel area is taken, and after reading as an image by a scanner, the invalid area NU is calculated by software.
It was also performed by so-called photographic measurements to quantify the area of L.

From the graph shown in FIG. 1, when the horizontal axis represents the electrode spacing g and the vertical axis represents the invalid area S, as shown in the following equations (3) and (4):

S = 0.3027 × g ² (3) For photo measurement

S = 0.2875 × g ² (4) In the case of optical measurement, it is clear that the characteristic shown by the quadratic curve is obtained.

From this graph, it has been found that the area of the invalid area NUL has a certain relationship with the electrode interval. For example, when it is desired to keep the area of the invalid area NUL below a certain value, the pixel electrode PIX and the It is possible to determine what value or less the electrode spacing with the counter electrode CT is.

Further, irrespective of the value of the electrode interval between the pixel electrode PIX and the counter electrode CT, the following equation (5) is obtained.
If the relationship of (6) is satisfied, the invalid area NUL
Can be set to the minimum, and the inconvenience due to the existence of the invalid area NUL can be suppressed. Therefore, the aperture ratio can be improved.

[0056]

S ≦ 0.3027 × g ² (5) In case of photo measurement

S ≦ 0.2875 × g ² (6) In the case of optical measurement

<< Reduction of Reduction of Aperture Ratio by Invalid Region >> As described above, in the multi-domain system, there is a disadvantage that the aperture ratio is reduced due to the existence of the invalid region NUL. For this reason, in this embodiment, as shown in FIG.
The light-shielding film IL is formed on a line connecting each bent portion between the IX and the counter electrode CT, and the direction of the generated electric field is made constant to reduce the area of the invalid region NUL.

In FIG. 7, the counter electrode CT of the pixel electrode PIX is shown.
A side of the counter electrode CT is bent so as to have a convex shape, and a side of the counter electrode CT that is bent so that a side of the counter electrode CT on the side of the pixel electrode PIX is concave. Is formed radially around the concave portion of the pixel electrode PIX from the point (1).

In this case, with respect to the pixel electrode PIX having a spread angle of the angle θ at the bent portion, + (90 ° −θ) with respect to a reference line (x-direction line) in a direction that divides the angle θ into two. /
2) and the electric field generated between the counter electrode CT in the direction of-(90 ° -θ / 2) can be made to be in a fixed direction, and the area of the invalid region NUL can be reduced. Become like

In this case, the ineffective area can be reduced by the light shielding film IL. However, since the light shielding film IL itself directly affects the reduction of the aperture ratio, the area of the light shielding film IL is larger than the area of the invalid area NUL. It is also preferable to form them smaller. By doing so, the light shielding film IL
This is because the reduction of the aperture ratio due to the invalid area NUL can be reduced.

It goes without saying that the shape of the light shielding film IL is not necessarily limited to the shape as shown in FIG. For example, as shown in FIG.
The band-shaped light-shielding film IL may be arranged on a line connecting the bent portion of IX to the bent portion of the counter electrode CT.

When the light-shielding film IL has a band-like pattern,
The value of the width can be determined according to the distance between the pixel electrode PIX and the counter electrode CT. This is because the size of the invalid area NUL between the electrode PIX and the counter electrode CT is related to the distance between the pixel electrode PIX and the counter electrode CT.

In this case, as described above, since the aperture ratio of the strip-shaped light-shielding film IL is reduced by itself, the strip-shaped light-shielding film IL has a smaller area than the invalid area NUL. Is preferably determined.
For this reason, it is preferable that the width of the band-shaped light-shielding film IL is not more than 0.25 times as large as the distance between the pixel electrode PIX and the counter electrode CT.

That is, the pixel electrode PIX and the counter electrode CT
Is 5 μm, 10 μm, 15 μm, 20
In the case of μm, 25 μm, and 30 μm, the width of the light-shielding film IL is 1.25 μm or less, 2.5 μm or less, respectively.
75 μm or less, 5 μm or less, 6.25 μm or less, 7.5
It is preferably not more than μm.

<< Relationship Between Number of Electrodes, Number of Bent Portions, and Aperture Ratio >> The above-described pixel configuration shows one embodiment. For example, the number of pixel electrodes PIX and counter electrodes CT, or the bent portions of these electrodes are used. It is needless to say that various modes can be obtained by changing the number and the like. Here, for each element that can be changed in the above-described pixel configuration,
As shown in FIG. 9, the symbols of the respective elements are defined below.

DP (V): indicates the pitch (dot pitch) in the y direction of the pixel area. To be precise, it is a dimension from a certain portion of one pixel region arranged adjacent to the y direction to a corresponding portion of the other pixel region.

DP (H): indicates the pitch of the pixel area in the x direction. In this embodiment, １ ／ of the dot pitch
The dimensions are as follows. In other words, the width of the three pixel areas, that is, the pixel area for red (R), the pixel area for green (G), and the pixel area for blue (B), which are arranged adjacent to each other in the x direction, is the dot. It corresponds to the pitch.

Ne: Indicates the number of electrodes. This is the total number of the pixel electrodes PIX, the counter electrodes CT (excluding those arranged adjacent to the drain signal lines DL), and the counter electrodes CT (those arranged adjacent to the drain signal lines DL). In FIG. 9, the number is five.

Ne ′: the number of electrodes, in this case, the total number of pixel electrodes PIX and counter electrodes CT (excluding those arranged adjacent to the drain signal line DL). Therefore, in relation to the above Ne, Ne ′ = Ne−2.
Has the relationship In FIG. 9, the number is three.

Nb: Indicates the number of bent portions in the electrode. Since the pixel electrode PIX and the counter electrode CT are arranged in parallel, in other words, by moving one of the electrodes in parallel (moving in the x direction in FIG. 9), the side becomes the side of the other electrode. It is designed to be stacked. For this reason, the number of bent portions of each electrode is the same. Therefore, Nb mentioned here is the pixel electrode PI
This is the number of bent portions of one (and one) of the electrodes X and the counter electrode CT.

Although five bent portions of the electrode are shown in FIG. 9, it is counted as four in the following description. A portion where an ineffective region is not formed, that is, a bent portion (1) of an electrode overlapping with the counter voltage signal line CL.
Book).

Wd indicates the line width of the drain signal line DL. The drain signal line DL is, for example, a gate signal line GL.
In some cases, the line width is narrowed at the intersection with the signal line, but here, the line width of a portion not intersecting with another signal line is referred to.
In this embodiment, for example, Wd is set to 7.5 μm.

Wc: Indicates the line width of the counter voltage signal line CL. The counter voltage signal line CL is, for example, a drain signal line D
Although the line width may be narrowed at the intersection with L,
Here, it refers to the line width of a portion running in the pixel area. In addition,
In this embodiment, for example, Wc = 20 μm.

Wg: Indicates the line width of the gate signal line GL. The line width of the gate signal line GL may be narrowed at an intersection with the drain signal line DL or the like, but here, the line width of a portion not intersecting with the drain signal line DL is referred to. In this embodiment, for example, Wg is set to 23 μm.

We: The line width of the pixel electrode PIX and the line width of the counter electrode CT (excluding those arranged adjacent to the drain signal line DL). These electrodes PIX, CT are
In order to improve the aperture ratio, it is preferable to make the width as narrow as possible, and therefore, each is formed as substantially the same line width.

Since the counter electrode CT arranged adjacent to the drain signal line DL has a function of shielding the electric field from the drain signal line DL, the above-mentioned pixel electrode P
The line width is set larger than IX and the counter electrode CT (excluding those arranged adjacent to the drain signal line DL).

Wsh (min): Wsh (min) is the width of the portion showing the minimum width of the width of the counter electrode CT arranged adjacent to the drain signal line DL. In this embodiment, for example, Wsh (min) is set to 9 μm.

Wsh (max): Wsh (max) is the width of the portion showing the maximum width of the width of the counter electrode CT arranged adjacent to the drain signal line DL.

Since the side of the counter electrode CT on the side of the drain signal line DL is formed in a straight line, Wsh (max) = Wsh (mi) in relation to Hcs described later.
n) + Hcs × tan10 ° holds.

Ge: Indicates the distance between the pixel electrode PIX and the counter electrode CT. More precisely, it indicates the separation distance at the bent portion of each electrode.

In other words, as described above, each electrode is moved in parallel (moved in the x direction in FIG. 9) so that one side of the electrode overlaps the one side of the adjacent electrode. Thus, the Ge can be grasped as a moving distance in that case.

Gdc: Indicates a separation distance between the drain signal line DL and the counter electrode CT adjacent to the drain signal line DL. In the case of this embodiment, for example, Gdc = 1.2
5 μm. In a region between the drain signal line DL and the counter electrode CT adjacent to the drain signal line DL, for example, light leakage due to a backlight occurs. Therefore, the value is usually set to be small. Depending on the value set, the aperture ratio will be affected.

Ggc: Gate signal line GL and counter electrode CT
3 shows a separation distance between the drain signal line DL and an adjacent one. In the case of this embodiment, for example, Ggc = 10
μm. This Ggc also affects the aperture ratio depending on the value to which it is set.

Hcs: Indicates the height (length) of the bent portion of each electrode. The height of the bent portion of this electrode is DP
(V), Wg, Cgs, Nb, the following equation (7)

(DP (V) −Wg−Ggc × 2) / (Nb + 1) (7)

The dot pitch DP (V) of each pixel region in the display section of the liquid crystal display device and the width W of the drain signal line DL
When d, the width We of the pixel electrode PIX and the counter electrode CT, and the number Nb of the bent portions of each electrode are determined, the distance (electrode interval) Ge between the pixel electrode PIX and the counter electrode CT can be expressed by the following equation (8). Become.

[0086]

[Equation 8] {DP (H) −Wd−Gdc × 2-Wsh (min) −Wsh (max) −We × Ne ′} / (Ne−1) (8) From this equation (8) It can be seen that the electrode spacing Ge is basically a function of the number of electrodes (Ne) and the number of electrode refractions (Nb). This is because Wsh (Max) is a function of Nb.

The area between the pixel electrode PIX and the counter electrode CT (corresponding to Ge) directly affects the aperture ratio. In this case, the existence of the above-mentioned invalid area which does not contribute to the aperture ratio is taken into account (that is, the invalid area). In the same manner as in the other regions), the aperture ratio can be expressed by the following equation (9).

Here, it is assumed that the aperture ratio shown in the following equation includes the invalid area. If the aperture ratio shown in the following equation (9) can be maximized, even if the invalid area exists. This also means that the substantial aperture ratio can be made larger than the aperture ratio in other embodiments.

[0089]

[Expression 9] {Ge × (DP (V) -Wg-Ggc-2-Wc)} / {DP (V) × DP (H)} (9) where dot pitch DP (V) In the case where = 297 μm, the change in the aperture ratio when the number of electrodes, the number of electrode refractions, and the electrode spacing are respectively changed is shown in a graph from the calculations by the above equations (8) and (9), and FIG. 10 is obtained.

In FIG. 10, the horizontal axis shows the electrode spacing (μm), and the vertical axis shows the aperture ratio (%). Each characteristic curve is obtained for each number of electrodes, and each characteristic curve indicates that the aperture ratio varies depending on the number of times of electrode refraction.

As is clear from this figure, in order to obtain the maximum aperture ratio, it is desirable that the number of electrodes is seven and the number of times of bending is two. But in this case,
It can be seen that the electrode spacing must be about 28.7 μm.

At present, the maximum value of the voltage of the video signal from the video signal drive circuit He is 7.45 V. In order to sufficiently drive the liquid crystal by the electric field generated between the pixel electrode PIX and the counter electrode CT. The maximum value of the electrode spacing must be 17.9 μm, in other words, it is desirable to set the electrode spacing to 17.9 μm or less from the viewpoint of avoiding an increase in power consumption.

From this, when trying to obtain the maximum aperture ratio, as is clear from FIG.
In this case, it is desirable that the number of times of bending is four. As described above, when the dot pitch DP (V) is predetermined, in order to obtain the maximum aperture ratio, there may be an optimum value for the number of electrodes formed in each pixel region and the number of times of bending. , FIG.

Therefore, it is clear that the optimum number of electrodes and the number of times of bending can be determined by the dot pitch DP (V) set to various values, and FIG. 11 is a graph showing this relationship. .

In FIG. 11, the horizontal axis indicates the dot pitch (μm) in the range of 150 μm to 450 μm, and the vertical axis indicates the number of times of bending and the aperture ratio (%). Then, a characteristic curve of the optimal number of electrodes at a dot pitch within a certain range and the aperture ratio at the number of bending times is shown.

From this graph, in order to obtain the maximum aperture ratio in the range of the selected dot pitch,
The number of electrodes and the number of refractions can be determined, and the results are shown in FIG.

That is, as shown in FIG. 12, it is desirable that the number of electrodes be three and the number of bends be three when the dot pitch DP (V) is in the range of 150 <DP (V) ≦ 219. Dot pitch DP (V) is 219 <DP
In the range of (V) ≦ 237, it is preferable that the number of electrodes is three and the number of bending times is two. Dot pitch DP
When (V) is in the range of 237 <DP (V) ≦ 246, it is preferable that the number of electrodes is three and the number of times of bending is one. Dot pitch DP (V) is 246 <DP (V) ≦ 3
In the range of 54, it is desirable that the number of electrodes is three and the number of bending is one.

The dot pitch DP (V) is 354 <DP
In the range of (V) ≦ 363, it is desirable that the number of electrodes is five and the number of bending is four. Further, it is desirable that the number of electrodes is five and the number of bending times is three in a range where the dot pitch DP (V) is 363 <DP (V) ≦ 378. Further, if the dot pitch DP (V) is 378 <DP
In the range of (V) ≦ 450, it is desirable that the number of electrodes is seven and the number of bending is six.

In the above-described pixel configuration (FIG. 3), the counter voltage signal line CL is formed so as to run in the center of the pixel. However, it is needless to say that the same effect can be obtained even when the counter voltage signal line CL is formed close to the gate signal line GL, that is, when the counter voltage signal line CL is formed at one end of the pixel electrode PIX and the counter electrode CT. Nor.

In this case, the pattern in which the bent portions of the pixel electrode PIX and the counter electrode CT are not positioned in the formation region of the counter voltage signal line CL. Counter voltage signal line CL
Is formed on one end side of the pixel electrode PIX and the counter electrode CT, the number of bent portions of each electrode is counted as five.

Further, the above-described pixel has its pixel electrode PI
Both X and the counter electrode CT extend in the y direction in the figure, but are not limited to this, and
Needless to say, the present invention can be applied to a configuration extending in the direction.

[0102]

As is apparent from the above description,
ADVANTAGE OF THE INVENTION According to the liquid crystal display device by this invention, when there exists a so-called invalid area | region between a pixel electrode and a counter electrode, it becomes possible to make it the structure which improved the aperture ratio as much as possible.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between an electrode interval and an ineffective area area of a liquid crystal display device according to the present invention.

FIG. 2 is a plan view showing one embodiment of the entire liquid crystal display device according to the present invention.

FIG. 3 is a plan view showing one embodiment of a pixel of the liquid crystal display device according to the present invention.

FIG. 4 is a sectional view taken along line IV-IV in FIG.

FIG. 5 is a sectional view taken along line VV in FIG. 3;

FIG. 6 is a diagram for explaining an invalid area generated between electrodes in a pixel.

FIG. 7 is a main part plan view showing another embodiment of the liquid crystal display device according to the present invention.

FIG. 8 is a main part plan view showing another embodiment of the liquid crystal display device according to the present invention.

FIG. 9 is a diagram for explaining a portion of each part for deriving a calculation formula.

FIG. 10 is a graph showing a relationship between an electrode interval and an aperture ratio in a pixel.

FIG. 11 is a graph showing the relationship between the number of electrodes, the number of refractions thereof, and the aperture ratio in a selected dot pitch range.

FIG. 12 is a table showing the relationship between the number of electrodes for obtaining the maximum aperture ratio and the number of refractions in a selected dot pitch range.

[Explanation of symbols]

SUB: transparent substrate, GL: gate signal line, DL: drain signal line, CL: counter voltage signal line, PIX: pixel electrode,
CT: counter electrode, TFT: thin film transistor, NUL:
Invalid area, IL: light shielding film.

Continued on front page F-term (reference) 2H092 GA13 GA14 GA26 JA24 JA41 JB51 NA07 PA08 5C094 AA10 BA03 BA43 CA19 EA04 EA07 JA08

Claims (14)

[Claims] 1. A pixel region in which a dot pitch DP arranged in a matrix on the liquid crystal side of one of the substrates opposed to each other via a liquid crystal is set in a range of 150 μm <DP ≦ 219 μm. A pixel electrode and a counter electrode are formed, and each of the electrodes is composed of a total of three electrodes in which two counter electrodes are arranged with one pixel electrode interposed therebetween, and each extending direction Wherein three bent portions are formed in the liquid crystal display device. 2. A method according to claim 1, wherein a dot pitch DP arranged in a matrix on the liquid crystal side of one of the substrates disposed opposite to each other with the liquid crystal therebetween is set in a range of 150 μm <DP ≦ 219 μm. A pixel electrode and a counter electrode are formed in a zigzag pattern in a direction in which the pixel electrode extends, and each of the electrodes includes a total of three electrodes in which two counter electrodes are arranged with one pixel electrode interposed therebetween. A liquid crystal display device, wherein six ineffective regions for light transmission are formed between the bent portion of the pixel electrode and the bent portion of the counter electrode. 3. In each pixel region in which a dot pitch DP arranged in a matrix on the liquid crystal side of one of the substrates opposed to each other via a liquid crystal is set within a range of 219 μm <DP ≦ 237 μm, A pixel electrode and a counter electrode are formed, and each of the electrodes is composed of a total of three electrodes in which two counter electrodes are arranged with one pixel electrode interposed therebetween, and each extending direction Wherein two bent portions are formed in the liquid crystal display device. 4. A pixel region in which a dot pitch DP arranged in a matrix on the liquid crystal side of one of the substrates disposed opposite to each other with a liquid crystal therebetween is set in a range of 219 μm <DP ≦ 237 μm. A pixel electrode and a counter electrode are formed in a zigzag pattern in a direction in which the pixel electrode extends, and each of the electrodes includes a total of three electrodes in which two counter electrodes are arranged with one pixel electrode interposed therebetween. A liquid crystal display device, wherein four ineffective regions for light transmission are formed between the bent portion of the pixel electrode and the bent portion of the counter electrode. 5. A method according to claim 1, wherein one of the substrates disposed opposite to each other with the liquid crystal therebetween has a dot pitch DP arranged in a matrix on the liquid crystal side of one of the substrates in a range of 237 μm <DP ≦ 246 μm. A pixel electrode and a counter electrode are formed, and each of the electrodes is composed of a total of three electrodes in which two counter electrodes are arranged with one pixel electrode interposed therebetween, and each extending direction Wherein one bent portion is formed in the liquid crystal display device. 6. A pixel region in which the dot pitch DP arranged in a matrix on the liquid crystal side of one of the substrates opposed to each other via a liquid crystal is set in a range of 237 μm <DP ≦ 246 μm. A pixel electrode and a counter electrode are formed in a zigzag pattern in a direction in which the pixel electrode extends, and each of the electrodes includes a total of three electrodes in which two counter electrodes are arranged with one pixel electrode interposed therebetween. A liquid crystal display device, wherein two ineffective regions for light transmission between the bent portion of the pixel electrode and the bent portion of the counter electrode are formed. 7. In each pixel region in which a dot pitch DP arranged in a matrix on the liquid crystal side of one of the substrates opposed to each other via a liquid crystal is set within a range of 246 μm <DP ≦ 354 μm, A pixel electrode and a counter electrode are formed, and each of the electrodes includes a total of five electrodes in which the pixel electrode and the counter electrode are alternately arranged with the counter electrode on both sides, and each of the electrodes extends A liquid crystal display device having five bent portions formed in directions. 8. A pixel region in which a dot pitch DP arranged in a matrix on the liquid crystal side of one of the substrates opposed to each other via a liquid crystal is set within a range of 246 μm <DP ≦ 354 μm. A pixel electrode and a counter electrode are formed in a zigzag pattern in the direction in which the pixel electrode extends, and each of the electrodes comprises a total of five electrodes in which the pixel electrode and the counter electrode are alternately arranged with the counter electrode on both sides. A liquid crystal display device comprising: a liquid crystal display; and 20 formed ineffective regions for light transmission between the bent portion of the pixel electrode and the bent portion of the counter electrode. 9. A pixel region in which a dot pitch DP arranged in a matrix on the liquid crystal side of one of the substrates opposed to each other via a liquid crystal is set in a range of 354 μm <DP ≦ 363 μm. A pixel electrode and a counter electrode are formed, and each of the electrodes includes a total of five electrodes in which the pixel electrode and the counter electrode are alternately arranged with the counter electrode on both sides, and each of the electrodes extends A liquid crystal display device comprising: four bent portions formed in directions. 10. A pixel region in which a dot pitch DP arranged in a matrix on the liquid crystal side of one of the substrates disposed opposite to each other via a liquid crystal is set in a range of 354 μm <DP ≦ 363 μm. A pixel electrode and a counter electrode are formed in a zigzag pattern in the direction in which the pixel electrode extends, and each of the electrodes comprises a total of five electrodes in which the pixel electrode and the counter electrode are alternately arranged with the counter electrode on both sides. A liquid crystal display device comprising: a liquid crystal display; and 16 formed ineffective regions for light transmission between the bent portion of the pixel electrode and the bent portion of the counter electrode. 11. A pixel area in which a dot pitch DP arranged in a matrix on the liquid crystal side of one of the substrates opposed to each other via a liquid crystal is set in a range of 363 μm <DP ≦ 378 μm. A pixel electrode and a counter electrode are formed, and each of the electrodes includes a total of five electrodes in which the pixel electrode and the counter electrode are alternately arranged with the counter electrode on both sides, and each of the electrodes extends A liquid crystal display device, wherein three bent portions are formed in a direction. 12. A pixel region in which the dot pitch DP arranged in a matrix on the liquid crystal side of one of the substrates opposed to each other via a liquid crystal is set in a range of 363 μm <DP ≦ 378 μm. A pixel electrode and a counter electrode are formed in a zigzag pattern in the direction in which the pixel electrode extends, and each of the electrodes comprises a total of five electrodes in which the pixel electrode and the counter electrode are alternately arranged with the counter electrode on both sides. A liquid crystal display device comprising: a liquid crystal display; and 12 formed ineffective regions for light transmission between the bent portion of the pixel electrode and the bent portion of the counter electrode. 13. A pixel region in which a dot pitch DP arranged in a matrix on the liquid crystal side of one of the substrates disposed opposite to each other via a liquid crystal is set in a range of 378 μm <DP ≦ 450 μm. A pixel electrode and a counter electrode are formed, and each of the electrodes includes a total of seven electrodes in which the pixel electrode and the counter electrode are alternately arranged with the counter electrode on both sides, and each of the electrodes extends A liquid crystal display device having six bent portions formed in directions. 14. A pixel region in which the dot pitch DP arranged in a matrix on the liquid crystal side of one of the substrates opposed to each other via a liquid crystal is set in a range of 378 μm <DP ≦ 450 μm. A pixel electrode and a counter electrode are formed in a zigzag pattern in the direction in which the pixel electrode extends, and each of the electrodes includes a total of seven electrodes in which the pixel electrode and the counter electrode are alternately arranged with the counter electrode on both sides. A liquid crystal display device comprising: a liquid crystal display; and 30 formed ineffective regions for light transmission between the bent portion of the pixel electrode and the bent portion of the counter electrode.