JPH06265903A - Color liquid crystal display device and its production - Google Patents

Abstract

PURPOSE:To provide the color liquid crystal display device of a C-TN system which is wide in the optimum visual angle region of a display contrast and is uniform and stable over the entire part of a screen. CONSTITUTION:Respective pixel regions are bisected and are subjected to orientation treatments in such a manner that the optimum visual angle directions of the contrasts respectively in the one region of a pair of the divided region R and the other region vary. As a result, the regions in the optimum visual angle directions of the contrast of the display device are widened. The orientation treatments are executed in such a manner that the helix directions 4 of the respective liquid crystal layers 1 in a pair of the divided regions are the same and, therefore, the change in the helix directions 4 of the liquid crystal layer 1 with lapse of time is small and the good characteristics of the contrasts are stably maintained. Further, the stability in various places of the helix directions 4 are improved by adding a cholesteric liquid crystal to these regions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a word processor,
The present invention relates to a color liquid crystal display device used for a laptop computer display, an AV display, and the like, and a manufacturing method thereof.

[0002]

2. Description of the Related Art A twisted nematic (hereinafter abbreviated as TN) mode of liquid crystal has a higher contrast than other display modes such as a dynamic scattering (DS) mode and a guest host (GH) mode. Have been widely used for display devices for OA and AV. However, the TN mode has a large visual angle dependency, and the display contrast greatly changes depending on the viewing direction.

For example, in a TN liquid crystal panel in which the surface of one of the substrates of the liquid crystal panel is rubbed from the upper left to the lower right, and the surface of the other substrate is rubbed from the lower left to the upper right, the center is at 6 o'clock of the clock. The display contrast is highest when observed from the 1/4 quadrant in the range of ± 45 °, but it is difficult to obtain high display contrast in the other quadrants.

As a method for improving the viewing angle dependence of the TN mode liquid crystal, Compl having two rising angles of liquid crystal molecules with respect to the substrate surface, that is, pretilt angles.
elementary Twisted Nematic
An LCD (hereinafter abbreviated as C-TN) has been proposed.
(K. Takatori et al., JAPAN
DISPLAY 92, pp. 591) FIG. 5 shows one picture element region in this C-TN type liquid crystal display device. FIG. 5A shows a schematic plan configuration showing the rubbing processing direction of this one picture element portion, and FIG. 5B shows FIG.
The cross section of (a) is shown.

In this liquid crystal display device, liquid crystal is sandwiched between a base substrate and a counter substrate, and each picture element is divided into two regions. As shown in the figure, one is A
The area and the other area are areas B. The dotted arrow in FIG. 5A indicates the rubbing direction of the base substrate surface, and the solid arrow indicates the rubbing direction of the counter substrate surface.

When liquid crystal is sealed between the two substrates, the twist direction in the liquid crystal layer is determined by the pretilt angle defined by the rubbing state of the base substrate surface and the rubbing state of the counter substrate surface. In the case of this example, the area A of each picture element has a left-handed twist structure, and the area B has a right-handed twist structure. Then, in each picture element region, two quadrants indicated by X in FIG.
The best display contrast is obtained when observing from the range of ± 45 ° centered on the 3 o'clock direction of the clock in the region and from the range of ± 45 ° centered on the 6 o'clock direction of the clock in the B region.

Therefore, in each picture element area, one picture element is divided into two, and the pair of divided areas have different twisting directions in which good contrast can be obtained. By doing so, the entire contrast characteristic is averaged, so that a wide viewing angle characteristic can be obtained.

The above-mentioned conventional example is devised based on such a principle.

[0009]

In the above conventional example, as shown in FIG. 5, the twisting directions of the liquid crystal are different in each of the two regions in one picture element. Therefore, as shown in FIG. Two types of minute regions having a right twist structure and a left twist structure coexist in the liquid crystal display panel.

This has a serious problem in terms of reliability as shown below. For example, when a long-term reliability test such as a high-temperature high-humidity storage test or a high-temperature aging test is performed, the region of the right helix structure or the left helix structure, whichever is more stable, is dominant, and the other Overwhelms the area of twist structure. Then, the balance between the region of the left-handed twist structure and the region of the right-handed twist structure is lost, and the good contrast region is changed, for example, in one of the 3 o'clock direction and the 6 o'clock direction of the timepiece. Therefore, there is a problem that good viewing angle characteristics cannot be uniformly obtained on the entire screen.

The present invention has been made to solve the above problems, and suppresses the viewing angle dependence of a C-TN type liquid crystal display device, and a good display contrast is uniformly obtained over the entire screen. An object of the present invention is to provide a display device and a manufacturing method thereof.

[0012]

A color liquid crystal display device according to the present invention includes a pair of substrates arranged to face each other, a color filter formed on one of the pair of substrates, and a space between the pair of substrates. In a color liquid crystal display device having a sandwiched liquid crystal, each picture element area of the pair of substrates is divided into two, and one and the other of the pair of divided picture element areas are oriented in different directions. A color liquid crystal display device in which the natural twist direction of the liquid crystal is defined as one of the left and right directions, and cholesteric liquid crystal is added according to the natural twist direction of the liquid crystal. According to the above, the above object is achieved.

Further, in the method for manufacturing a liquid crystal display device of the present invention, a pair of substrates arranged to face each other, a color filter formed on one of the pair of substrates, and a pair of substrates are sandwiched between the substrates. In the color liquid crystal display device having a liquid crystal, each of the picture element regions of the pair of substrates is divided into two, and one and the other of the pair of divided picture element regions are oriented in different directions. The natural twist direction of the liquid crystal is defined as one of the left and right directions,
A method of manufacturing a color liquid crystal display device in which a cholesteric liquid crystal is added according to the natural twist direction, the method comprising a step of applying a polymer film on one substrate surface of the pair of substrates; A step of aligning the film surface in a predetermined first direction, a step of applying a photoresist to the entire surface of the polymer film, and a photo process opening in only one area of each of the two divided pixel areas. A step of providing a portion, a step of aligning one substrate surface of the pair of substrates in a direction opposite to the first direction, a step of peeling the photoresist, and a surface of the other substrate of the pair of substrates. A step of applying a polymer film on the top, a step of orienting the surface of the polymer film in a predetermined second direction, a step of applying a photoresist to the entire surface of the polymer film, and a pair divided into two parts. Only one of the picture element areas of A step of providing an opening in the process, a step of orienting the other substrate surface of the pair of substrates in a direction opposite to the second direction, a step of peeling the photoresist, and a step of attaching the pair of substrates. A method of manufacturing a color liquid crystal display device including a step of additionally filling a liquid crystal, by which the above object is achieved.

[0014]

In the present invention, each picture element region is divided into two in the color liquid crystal display device. The inner surface of the base substrate is formed so that the optimum viewing angle direction of the display contrast in each of the one area and the other area of the pair of divided areas is different and the natural twist direction of the liquid crystal in each area is the same. And the inner surface of the counter substrate is oriented.

With respect to the pair of divided areas, the optimum viewing angle direction of the display contrast in each area is different, so that the area in the optimum viewing angle direction with good contrast of the display device is widened. At the same time, since the twisting directions of the respective divided regions are aligned in one direction, there is almost no change over time in the natural twisting direction of the liquid crystal of the entire display device.

Further, by adding the cholesteric liquid crystal in accordance with the natural twist direction of the liquid crystal at this time, the local change of the natural twist direction of the liquid crystal due to the unevenness of the substrate surface or the cleanliness is suppressed.

[0017]

EXAMPLES Examples of the present invention will be described below.

(Embodiment 1) Embodiment 1 of the present invention will be described with reference to FIG. FIG. 1A is a schematic plan view showing a rubbing direction of one picture element portion of the color liquid crystal display device according to the first embodiment, and FIG. 1B is a picture element region of FIG. The cross section of the corresponding liquid crystal layer 1 is shown. This liquid crystal layer 1 is a base substrate 2
And a counter substrate 3, and one picture element is divided into two plane regions. As shown in FIG. 1A, one is an area A (a left area on the paper) and the other is an area B (a right area on the paper). The dotted arrow in FIG. 1A indicates the rubbing direction of the contact surface of the base substrate 2 with the liquid crystal layer 1, and the solid arrow indicates the rubbing direction of the contact surface of the counter substrate 3 with the liquid crystal layer 1.

In each area of the picture element divided into two,
In the area A, the contact surface of the base substrate 2 with the liquid crystal layer 1 is rubbed from the lower left to the upper right. The counter substrate 3 is rubbed on the contact surface with the liquid crystal layer 1 from the lower left to the upper right. In the area B of the picture element, the contact surface of the base substrate 2 with the liquid crystal layer 1 is rubbed from the upper left to the lower right,
The counter substrate 3 is rubbed from the lower right to the upper left.

Next, the base substrate 2 and the counter substrate 3 are bonded together, and the liquid crystal 1 is sealed therein. At the interface between the liquid crystal 1 and the substrate, the pretilt angle of the liquid crystal 1 is defined by the rubbing direction, and thus the twist direction 4 of the liquid crystal is inevitably determined.

As described above, according to the above-described alignment treatment in the first embodiment, the area in the optimum viewing angle direction of the area A becomes an area of ± 45 ° centering on the 3 o'clock direction of the timepiece, and the area in the optimum viewing angle direction of the area B is in the optimum viewing angle direction. The area is an area of ± 45 ° centered on the 6 o'clock direction of the watch. Further, the natural twist direction 4 of the liquid crystal 1 in the A area and the B area of each picture element has a left twist structure. As a result, the range in the optimum viewing angle direction where the contrast is good is widened, and this state is uniformly realized on the entire surface of the substrate.

However, it is very difficult to accurately control the pretilt angle over a wide area in a large substrate. This is because the pretilt angle changes due to subtle unevenness and cleanliness of the substrate, and an initial stable twist structure cannot be obtained. Therefore, in Example 1, a method is adopted in which a fixed amount of cholesteric liquid crystal is added to the liquid crystal material to forcibly impart a unidirectional twisted structure to the liquid crystal.

Next, a method of manufacturing the liquid crystal display panel according to the present invention will be described. 4A to 4F show the manufacturing process. All the figures are shown in the direction of viewing the cross section of the substrate.

First, as shown in FIG. 4A, an alignment film 9 is formed in the entire pixel region on the upper surface of the substrate 8 on which the electrodes are formed. A polymer film such as polyimide is used as the alignment film 9. Specifically, Optomer AL manufactured by Nippon Synthetic Rubber Co., Ltd.
1051, 2061, 4552, other, Nissan Chemical Co., Ltd., Sun Ever 100, 120, 130, 15
Examples include low temperature firing polyimides such as 0, 2170, and 4110. In Example 1, Optomer AL1051 manufactured by Nippon Synthetic Rubber Co., Ltd. was used.

After coating the polyimide film on the substrate by the spinner, baking is performed at a temperature of 200 ° C. for 1 hour.

After that, by rubbing the surface of the polyimide film 9 from the upper left to the lower right by the roller 10, a first microgroup is formed on the surface of the polyimide film 9. This state is the state shown in FIG.

A photoresist 12 is applied over the entire surface of the substrate 8 which has been subjected to the first alignment treatment. After the photoresist 12 is applied, exposure and development are performed using a predetermined photomask so that an opening is formed in the left area of each picture element, that is, the area A. This is the state shown in FIG.

Then, as shown in FIGS. 3D and 3E, the substrate 8 is rotated, and the polyimide film on the region A of the substrate which is opened and exposed on the surface is rubbed from the upper left to the lower right. Give.

Finally, as shown in FIG. 3F, after the rubbing process, the photoresist is peeled off.

The first and second rubbing processes are similarly performed on the counter substrate 3. First, after applying polyimide and optomer 1051 on the substrate 8 with a spinner, 200 ° C.
Firing is performed at the temperature of 1 hour. And the polyimide film 9
A first rubbing process is performed by rubbing the surface from the lower left to the upper right.

Further, a photoresist 12 is applied on the entire surface of the substrate 8 which has been subjected to the first alignment treatment. After application, A for each picture element
Exposure and development are performed using a predetermined photomask so that an opening is formed in the region.

The counter substrate 3 is rotated and the second rubbing process is performed from the lower right to the upper left. After the rubbing process,
Peel off the photoresist.

Then, the two substrates 2 and 3 are attached so that the surfaces subjected to the rubbing treatment face each other,
The liquid crystal 1 is sealed between the two substrates 2 and 3. Liquid crystal molecule 7
The spontaneous twist direction of the liquid crystal molecules 7 induced from the upper and lower pretilt angles is the left twist direction (counterclockwise), and the cholesteric liquid crystal that matches this direction is added.

As the nematic liquid crystal of the base liquid crystal material,
Merck, ZLI-3367, ZLI-13532 /
1, ZLI-3401 / 1, ZLI-4714, etc., but in Example 1, ZLI-3367 is used,
As the cholesteric liquid crystal, S-811 manufactured by Merck & Co. was used. The amount of cholesteric liquid crystal added is 0.2 wt%.

(Embodiment 2) First, as in Embodiment 1, an alignment film is formed on the entire surface of a pixel region on a base substrate on which electrodes are formed. As the alignment film, a polyimide film was used as in Example 1.

After forming the alignment film, a first rubbing process is performed on the surface of the base substrate from the upper right to the lower left. A photoresist is applied on the entire surface of the base substrate that has been subjected to the first alignment treatment, and exposure and development are performed using a predetermined photomask so that an opening is formed in the left side area of each picture element, that is, the A area. Then, the substrate is rotated, and the second rubbing process is performed from the lower left to the upper right.

On the other hand, for the counter substrate, after forming a polyimide film, a first rubbing process is performed from the upper left to the lower right. Then, after applying a photoresist on the entire surface of the substrate, exposure and development are performed using a predetermined photomask so that an opening is formed in the area A. Then, this substrate is rotated, and the second rubbing process is performed from the upper right to the lower left. Then, the two substrates are bonded together so that their alignment film forming surfaces face each other, and liquid crystal is sealed between the substrates. As the liquid crystal material, the same liquid crystal material as in Example 1 is used.

For each of the two divided picture element regions, the optimum viewing angle direction is ± 45 ° around the 3 o'clock direction in the A region and ± 45 ° around the 9 o'clock direction in the B region. Each area is different. 2 and 3
As shown in, the twist direction 4 of the liquid crystal is the same clockwise (clockwise) direction in each region.

Next, the evaluation test method for the reliability of the liquid crystal display panel manufactured by the method of the present invention and the result thereof will be shown.

The high temperature and high humidity standing test was conducted at a temperature of 80 ° C. under 95
% RH (relative humidity), high temperature aging test is 80
At a temperature of ° C, a rectangular wave of 5 V and 32 Hz was added.

Table 1 shows the results of performing these two types of reliability tests on the liquid crystal display panel according to the present invention and the liquid crystal display panel manufactured by the conventional method.

In Table 1, the evaluation of the level of the alignment state observed by a microscope is shown by ◯, Δ, and ×. The contents of the evaluation are as follows.

◯: Good TN orientation is shown, and almost no change in orientation is observed.

Δ: A level in which a region in which the orientation is slightly reversed appears and an orientation change is observed.

X: indicates a level at which the orientation inversion remarkably appears over a very wide range.

[0046]

[Table 1]

As can be seen from Table 1, according to the liquid crystal display panel of the present invention, the twisted directions of the liquid crystal are aligned in one direction even after a lapse of time, and the alignment state is very stable. I was able to get

[0048]

As described above in detail, in the present invention, each picture element region of the color liquid crystal display device is divided into two, and the direction of the alignment treatment is changed in each of the divided regions, and the respective regions are changed. Since the viewing angle directions in which the contrast is good are different from each other, the area in the viewing angle direction in which the contrast is good is wide and uniform in the entire panel.

Since this alignment treatment is also a treatment in which the twisting directions of the liquid crystals in the pair of divided picture element regions are the same, the twisting direction of the liquid crystal in the entire panel is either left or right. The direction remains unchanged and does not change over time. Therefore, the above-mentioned display characteristic that the region with good contrast in the viewing angle direction is wide and is uniformly realized is stably maintained.

Further, by adding a cholesteric liquid crystal corresponding to the twist direction of the liquid crystal defined by the above processing, the twist direction can be stabilized.

[Brief description of drawings]

FIG. 1 is a diagram showing one picture element region of a C-TN type LCD according to the present invention. (A) is a plan view and (b) is a sectional view.

FIG. 2 is a diagram showing one picture element region of a C-TN type LCD according to the present invention. (A) is a plan view and (b) is a sectional view.

FIG. 3 is a plan view showing a twist direction of a pixel region of a C-TN type LCD according to the present invention. .

FIG. 4 is a manufacturing process diagram of a C-TN type LCD according to the present invention.

FIG. 5 is a picture element area of a conventional C-TN type LCD.
(A) is a plan view and (b) is a sectional view.

FIG. 6 is a plan view showing a twist direction of a pixel region of a conventional C-TN type LCD.

[Explanation of symbols]

 1 Liquid Crystal Layer (Liquid Crystal) 2 Base Substrate 3 Counter Substrate 4 Twisting Direction 5 Alignment Treatment Direction of Inner Surface of Base Substrate 6 Alignment Treatment Direction of Inner Surface of Counter Substrate 7 Liquid Crystal Molecule 8 Substrate 9 Alignment Film (Polyimide Film) 10 Roller 11 Rubbed Alignment film 12 photoresist

Claims (2)

[Claims] 1. A color liquid crystal display device comprising a pair of substrates arranged to face each other, a color filter formed on one of the pair of substrates, and a liquid crystal sandwiched between the pair of substrates. Each pixel region of each of the pair of substrates is divided into two, and one and the other of the pair of divided pixel regions are subjected to alignment treatment in different directions, and the natural twist direction of the liquid crystal is either left or right. A color liquid crystal display device which is defined in one direction and to which a cholesteric liquid crystal is added according to the natural twist direction of the liquid crystal. 2. A color liquid crystal display device comprising a pair of substrates arranged to face each other, a color filter formed on one of the pair of substrates, and a liquid crystal sandwiched between the pair of substrates. Each of the picture element regions of the pair of substrates is divided into two, and one and the other of the pair of divided picture element regions are oriented in different directions, and the natural twist direction of the liquid crystal is left and right. A method for manufacturing a color liquid crystal display device, wherein the color liquid crystal display device is defined in any one direction, and a cholesteric liquid crystal is added according to the natural twist direction, wherein a polymer is provided on a surface of one of the pair of substrates. A step of applying a film, a step of orienting the surface of the polymer film in a predetermined first direction, a step of applying a photoresist to the entire surface of the polymer film, and a pair of picture element regions divided into two parts. One territory Only in the photo process, an opening is provided by a photo process, a substrate surface of one of the pair of substrates is oriented in a direction opposite to the first direction, a step of removing the photoresist, A step of applying a polymer film on the other substrate surface of the substrate, a step of orienting the polymer film surface in a predetermined second direction, and a step of applying a photoresist to the entire surface of the polymer film. A step of forming an opening by a photo process in only one of the pair of divided pixel regions, and the other substrate surface of the pair of substrates is oriented in a direction opposite to the second direction. A method of manufacturing a color liquid crystal display device, which includes a step, a step of peeling the photoresist, and a step of bonding the pair of substrates to each other and enclosing a liquid crystal.