JPH08201826A - Liquid crystal display element - Google Patents

Abstract

PURPOSE: To provide a liquid crystal display element with less numerical aperture, excellent picture quality and a wide angle of visibility as a result of no bending and movement of a discrimination line and no need for an extremely large width of shield film. CONSTITUTION: A liquid crystal display element has a pair of electrodes constituting one picture element, at least one of which is given different orientation treatments to be divided into two areas where respective liquid crystal sections with different oriented conditions exist. A portion 5 with no electrode is provided on the electrode 3 located in the rising direction of a liquid crystal director so that the liquid crystal director coincides with a boundary for dividing a portion rising toward an each other separating direction.

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 element, and more particularly to a liquid crystal display element which provides a wide field of view by providing a plurality of regions on a substrate.

[0002]

2. Description of the Related Art A liquid crystal display element provided with a plurality of regions for the purpose of widening the viewing angle is disclosed in JP-A-57-18673.
5, JP-A-60-212142, JP-A-6
3-106624, JP-A-64-88520, JP-A-1-245223, and JP-A-5-203.
951 and the like. The main idea is to divide one pixel into a plurality of regions and define the alignment directions of the liquid crystal in different regions so as to complement each other in the viewing angle dependence. As a method of defining the alignment direction of the liquid crystal, there is a method of oblique vapor deposition of a silicon oxide film, a method of rubbing a thin film of a polyimide resin, and a method of rubbing a polyimide thin film is widely used because of the simplicity of the process. The polyimide resin used here is, for example, JP-A-61-479.
32, JP-A-6-148650, and SE-7311, manufactured by Nissan Kagaku Co., Ltd.
There is AL1051 made by Japan Synthetic Rubber.

In order to divide one pixel into a plurality of regions, it is necessary to change the rubbing direction within one pixel. A specific method for doing so is Japanese Patent Laid-Open No. Sho 60.
No. 211422, No. 5-203951, and the like. For example, Japanese Patent Laid-Open No. 60-212142
In the publication, a part of the pixel is protected by a photoresist layer after the first rubbing, the second rubbing is performed, and then the operation of peeling off the photoresist layer is repeated. Dividing into multiple regions is mentioned. Furthermore, JP-A-5-173137,
Japanese Unexamined Patent Publication No. 5-203951 discloses that one substrate is subjected to a split alignment treatment, the other substrate is subjected to a uniform alignment treatment over the entire surface, and the pretilt angle of the substrate subjected to the divided alignment treatment is determined over the uniform alignment treatment. By making the pretilt angle of the substrate subjected to
It is described that the orientation of the liquid crystal layer on the substrate that has been subjected to the division alignment treatment becomes dominant, and the division alignment can be performed with a small number of steps.

[0004]

When the division orientation is performed by such a method, a disclination line is always generated at the division boundary, and light is leaked from the disclination line, which lowers the contrast. Invite. Therefore, in order to maintain a high contrast, it is necessary to shield this part from light, but if the light-shielding part becomes too thick, the aperture ratio will decrease and the screen will become dark, so it is desirable that the light-shielding part be as thin as possible. If the disclination line is properly fixed at the division boundary position, this light shielding part can be thin, but when actually creating a panel driven by thin film transistors, mainly due to the influence of the lateral electric field, the disc There is a problem that the line is largely bent at the edge of the pixel and a thick light-shielding portion is required to shield the light from the edge, resulting in a large reduction in the aperture ratio.

Further, a phenomenon has been observed in which the disclination line moves when a voltage is applied. This movement of the disclination line was observed as an afterimage, deteriorating the performance of the display element.

An object of the present invention is to provide a liquid crystal display device having a wide field of view, which realizes stable divisional alignment and eliminates a phenomenon such as an afterimage that deteriorates the display performance.

[0007]

According to the present invention, different alignment treatments are applied to at least one of a pair of electrodes constituting one pixel to divide it into two or more portions, and the divided portions have different alignment states. When realizing different liquid crystal divisions and applying a voltage, to the electrodes in the direction in which the director of the liquid crystal rises,
A liquid crystal display element is characterized in that a portion without electrodes is provided in a direction that coincides with a boundary of a division process of a portion where the directors of the liquid crystal stand in a direction away from each other. As a result, the electric field is generated in the direction that promotes the division orientation, and the disclination line is fixed at the division position. As a result, it is possible to prevent the phenomenon that the disclination line bends and the phenomenon that the disclination line moves due to driving, and it is possible to prevent the reduction of the aperture ratio and the deterioration of the display performance due to the afterimage.

[0008]

When the split orientation is realized, the method disclosed in JP-A-60-2114 is used.
As disclosed in Japanese Unexamined Patent Application Publication No. 22-22, and Japanese Patent Application Laid-Open No. 5-203951, a PR process using a resist is used. 1
After the rubbing for the second time, a part of the alignment film is protected with a resist, and after rubbing for the second time, the resist is stripped with a stripping solution. There are also two types of methods, that is, a method of similarly performing division processing on the facing substrate and a method of not performing division processing. When the division treatment is not performed, in most cases, the alignment film is applied and rubbed in one direction. Alternatively, JP-A-4
As described in JP-A-7520, after the alignment film is applied, polarized light may be irradiated to perform the alignment treatment.

Whatever method is used, the direction of the director of the liquid crystal must have a portion schematically arranged in the middle of the panel gap at the division boundary. When a disclination line is generated at the boundary of this division and a voltage is applied to drive it, a lateral electric field is generated, so that the phenomenon that the disclination line bends from the division boundary occurs.
Further, it may be connected to a disclination line generated in another place of the pixel, and it is observed as an afterimage, resulting in deterioration of image quality. In particular, when the rubbing is performed so that the director arrangement is located at the center of the pixel, it becomes a very serious problem.

At this time, if the electrode in the direction in which the director of the liquid crystal rises, that is, the electrode on the upper side in FIG. The lines of electric force between the two act in a direction to fix the disclination, so that the disclination is extremely stable. Therefore, it is possible to prevent the disclination line from moving, and to prevent deterioration in image quality such as an afterimage. Further, since the disclination line is fixed along the portion where there is no electrode, it is possible to prevent the disclination line from being bent by a lateral electric field. Since the light-shielding film can be used to prevent light leakage from the disclination line, it is possible to minimize the decrease in the aperture ratio. In particular, if the notches of the electrodes are formed in stripes or rectangles, the reduction in aperture ratio can be reduced. The light-shielding film may be provided on either of the pair of electrode substrates, but it is preferable to provide the light-shielding film on the substrate which has been subjected to the split alignment treatment, because alignment is easy, especially when only one of the substrates is split and aligned.

Further, when the director arrangement as shown in FIG. 1 is carried out at a place other than the inside of the pixel, the shading of the disclination line is not a serious problem, but the movement of the disclination line does not occur. There is a problem, and better image quality can be obtained by fixing the disclination line.

Here, for convenience of description, a method of rubbing the same alignment film on one substrate by using a resist pattern was described. However, different alignment films are painted and divided regardless of organic or inorganic. The same effect can be obtained when the orientation is realized or when the divided orientation is realized by another method.

Further, in particular, when only one of the substrates is subjected to the divisional alignment treatment, as described in Japanese Patent Application No. 6-79089, the region in which the pretilt angle becomes large has a splay type alignment. Although it is more advantageous to fix the disclination line, the effect of the present invention is strong and the influence of the size of the pretilt angle is great if it is limited to the disclination on the division boundary of the pixel central portion. It was confirmed that he would not receive it. Furthermore, here, an example in which one pixel is divided into two regions has been described, but the same can be said when dividing into three or more regions.

[0014]

EXAMPLES The present invention will be described in detail below with reference to examples.

Example 1 After washing the TFT substrate, a polyimide (manufactured by Nissan Kagaku: trade name SE-7210) that gives a high pretilt angle was spin-coated and baked at 200 ° C. for 1 hour. After rubbing using a rubbing device, a resist (trade name: OFPR-800 manufactured by Tokyo Ohka Kogyo Co., Ltd.)
C) is spin coated to a thickness of 1 μm,
It was baked for 0 minutes. All pixels were exposed and developed using a stripe pattern mask covering half of one pixel, rinsed with pure water, and then dried at 75 ° C. for 20 minutes. When the pattern was observed using an optical microscope, a resist pattern was formed on half of one pixel for all pixels. Next, using a rubbing device, rubbing was performed in the opposite direction to the first rubbing. The directions of the first and second rubbing are as shown in FIG. (Here, it was set so that the first rubbing was in the 8 direction and the second rubbing was in the 7 direction.) To remove the resist, the substrate was treated with ethyl lactate for 2 minutes, and then,
It was rinsed with pure water and dried at 110 ° C. for 30 minutes to obtain a main substrate. After observing the glass substrate on which the ITO film was formed as the counter substrate for observing the disclination, using the photoresist process and the wet etching process, the direction in which the directors of the liquid crystal are separated from each other among the division boundaries of the TFT substrate is used. The part that stands up,
That is, in FIG. 2, a rectangular slit having a width of 6 μm and a length equal to the lateral width of one pixel is formed in ITO at a position corresponding to the division boundary of the central portion of the pixel. Polyimide (AL-1051, manufactured by Japan Synthetic Rubber Co., Ltd.) that gives a low pretilt angle was spin-coated on this substrate, baked at 200 ° C. for 1 hour, and rubbed. A panel was prepared by bonding the two substrates thus prepared with an adhesive through a spherical spacer so that the gap was 6 μm and the rubbing directions of the upper and lower substrates were perpendicular to each other. At this time, as described later, the pretilt angle of the part where the resist remained was smaller than that of the part where the resist did not remain, but the part where the resist remained was spray type TN deformation and the resist did not remain. The substrates were bonded to each other to form a panel so that the bent portion was subjected to a normal TN type deformation. The relationship of rubbing directions is as shown in FIG. A normal nematic liquid crystal in which the left chiral material was dissolved was injected into this panel, and the injection port was sealed.

A driving voltage was applied to the prepared panel and the alignment state of the liquid crystal was observed with a polarization microscope. As a result, good split orientation was confirmed at any drive voltage,
And the disclination line in the center of the pixel is ITO
It is fixed neatly at the slit part of
It did not move due to changes in drive voltage. Further, the width of the disclination line was within 12 μm, and the width of the stripe for shielding light was 12 μm, which was sufficient, and the reduction of the aperture ratio was within the allowable range.

Next, for reference, the pretilt angles of the portion where the resist of the polyimide (SE-7210) giving a high pretilt angle was left and the portion where it was not left were exactly the same as when the above TN cell was prepared. To meet the conditions
An anti-parallel cell was prepared under each condition and measured by the crystal rotation method. As a result, the pretilt angle of the portion where the resist remained was 4.1 °, and the pretilt angle of the portion where the resist remained was 6.3.
Was asked. Further, the pretilt angle of the polyimide (AL-1051) giving a low pretilt angle was measured under the same conditions as those used for manufacturing the TN cell to prepare an anti-parallel cell and using the crystal rotation method. As a result, the pretilt angle was determined to be 1 °.

(Comparative Example 1) In the same manner as in Example 1, the entire surface of the counter substrate I
The experiment was conducted on the substrate with TO. As a result, the disclination line at the center of the pixel is greatly bent at the edge of each pixel, and the stripes for shading do not completely stop at 12 μm, and when trying to shade all the disclinations, the aperture ratio decreases significantly. confirmed.
In addition, it was found that in some pixels, the disclination line moved and was connected to the disclination lines of other pixels, and the disclination line remained in the pixel as it was, causing afterimages or burning. .

(Embodiment 2) In exactly the same manner as in Embodiment 1, only the magnitudes of the pretilt angles of the splay type TN deformation region and the normal TN deformation region are reversed.
That is, the part where the resist remains is the normal TN type deformation, and the part where the resist is not present is the spray type T
Substrates were attached so as to be N-deformed, and other conditions were exactly the same as in Example 1 to prepare a panel and perform an experiment. That is, in this case, rubbing was performed so that the first rubbing of the TFT substrate was in the direction 7 in FIG. 2 and the second rubbing was in the direction 8. As a result, good division orientation was confirmed at any drive voltage, and the disclination line at the center of the pixel was fixed neatly to the slit portion of ITO, that is, the division boundary, and did not move due to changes in drive voltage. It was The width of the disclination line was within 6 μm, and the width of the stripe for shielding light was 6 μm, which was sufficient, and the reduction of the aperture ratio was within the allowable range.

(Comparative Example 2) In exactly the same manner as in Example 2, I was formed on the entire surface of the counter substrate without cutting the ITO.
The experiment was conducted on the substrate with TO. As a result, although not as remarkable as in Comparative Example 1, in some pixels, the disclination at the center of the pixel was slightly bent at the edge of the pixel, and when the stripe for shading was 12 μm, the disclination was at the edge of the pixel. The phenomenon that the line protruded was seen.

(Embodiment 3) In the same manner as in Embodiment 1, TF
The T substrate side was subjected to a split orientation treatment to obtain a main substrate. The relationship between the rubbing directions is shown in FIG. In this case, the rubbing order does not have a great influence, but the direction 7 in FIG.
The first rubbing of the substrate, the direction of 8 is the second rubbing of the TFT substrate, and the direction of 9 facing each other is the second and first rubbing of the counter substrate. Further, as in Example 1, on the glass substrate on which the ITO film was formed as the counter substrate for observing the disclination, a part of the division boundary of the TFT substrate that rises in a direction in which the directors of the liquid crystal face each other, That is,
At the position corresponding to the center of the pixel, the width is 6 μm and the length is 1
A rectangular slit having the same width as the pixel was formed in the ITO. After that, a split alignment process was performed in the same manner as the TFT substrate of Example 1 to obtain a counter substrate. The relationship of rubbing directions is as shown in FIG. The two substrates created in this way should have a gap of 6 μm, and the rubbing directions of the upper and lower substrates should be at right angles to each other, and
Each of the divided areas was set so as to undergo a normal TN type deformation, and a panel was prepared by bonding with an adhesive through a spherical spacer. In the same manner as in Example 1, a normal nematic liquid crystal in which the left chiral material was dissolved was injected into this panel,
The injection port was sealed, a drive voltage was applied, and the alignment state of the liquid crystal was observed with a polarization microscope. As a result, good division orientation was confirmed at any drive voltage, and the disclination line in the center of the pixel was fixed neatly to the slit portion of ITO, that is, the division boundary, and did not move due to changes in drive voltage. It was Further, the width of the disclination line was within 6 μm, and the width of the stripe for shielding light was 6 μm, which was sufficient, and the reduction of the aperture ratio was within the allowable range.

(Comparative Example 3) In exactly the same manner as in Example 3, I was formed on the entire surface of the counter substrate without cutting the ITO.
The experiment was conducted on the substrate with TO. As a result, in some pixels, the disclination at the center of the pixel is slightly bent at the edge of the pixel, and the stripe for light shielding is 12 μm.
At m, the phenomenon of the disclination line protruding at the edge of the pixel was seen.

(Example 4) An experiment was carried out in the same manner as in Example 2 except that only the alignment film giving a high pretilt was replaced with Nissan Chemical Co., Ltd., trade name RN-715. In the case of this alignment film, the magnitude relationship between the pretilt angles of the portion where the resist was left and the portion where the resist was not left was SE-.
Since it is the reverse of 7210, the reverse is the case, that is, the larger pretilt angle is the splay type TN deformation,
An experiment was conducted in the same manner as in Example 2 except that the smaller pretilt angle caused normal TN deformation. As a result, just as in Example 1, good split orientation was confirmed at any drive voltage,
And the disclination line in the center of the pixel is ITO
It is fixed neatly at the slit part of
It did not move due to changes in drive voltage. Further, the width of the disclination line was within 10 μm, and the width of the stripe for shielding light was 12 μm, which was sufficient, and the reduction of the aperture ratio was within the allowable range.

For reference, the polyimide (RN-
715) Anti-parallel cells were created under each condition so that the pretilt angles of the part where the resist was left and the part where the resist was not left were exactly the same as those for the above TN cell, and the crystal rotation was performed. It was measured by the method. As a result, the pretilt angle of the portion where the resist remained was determined to be 12 °, and the pretilt angle of the portion where the resist did not remain was determined to be 9 °.

(Embodiment 5) In the same manner as in Embodiment 2, the TFT substrate is changed to the usual one except that a light-shielding film having a width of 12 μm for shielding the disclination is provided in the center of the pixel only in the TFT substrate. , Conducted an experiment. As a result, good split orientation was realized, and the disclination line did not protrude from the light shielding film.

(Embodiment 6) In the same manner as in Embodiment 2, an experiment was conducted by changing only the shape of the notch of the ITO substrate on the opposite side from a rectangular shape to a stripe having a width of 6 μm and no border. As a result, good split orientation was realized, the width of the disclination line was within 6 μm, and the light-shielding film had a width of 10 μm, and the decrease in aperture ratio was within an allowable range.

(Embodiment 7) In the same manner as in Embodiment 1, only the rubbing direction is changed as shown in FIG.
An experiment was conducted. At this time, the direction 7 in FIG. 4 is the first rubbing of the TFT substrate, and the direction 8 is the second rubbing. Here, since the director arrangement as shown in FIG. 1 occurs not at the center of the pixel but at the end of the pixel, the ITO of the counter substrate in this portion was cut as in the first embodiment. As a result, good divisional orientation was realized, and the phenomenon that the disclination line was properly fixed and protruded into the pixel, and that the disclination line of another pixel was connected to cause the burn-in did not occur.

Comparative Example 4 A cell was prepared and evaluated in exactly the same manner as in Example 7 without making a cut in the ITO substrate. As a result, depending on the pixel, a disclination line protruded into the pixel. There was a phenomenon that it was observed as burn-in due to being connected to the disclination line of other pixels.

[0029]

As described above, according to the present invention, stable divisional alignment can be obtained, especially the disclination line in the central portion of the pixel is stable, and the width of the light shielding film can be reduced,
A liquid crystal display device having a wide viewing angle could be produced with high contrast without lowering the aperture ratio.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a configuration of the present invention.

FIG. 2 is a schematic diagram showing a rubbing direction.

FIG. 3 is a schematic diagram showing a rubbing direction.

FIG. 4 is a schematic diagram showing a rubbing direction.

[Explanation of symbols]

 1 TFT substrate subjected to orientation treatment 2 Glass substrate on the opposite side 3 ITO film 4 Polyimide orientation film 5 Incision of ITO 6 Liquid crystal molecules 7 Rubbing direction of TFT substrate 8 Rubbing direction of TFT substrate 9 Rubbing direction of opposite substrate

Claims (3)

[Claims] 1. At least one electrode of a pair of electrodes constituting one pixel is subjected to different alignment treatments in order to divide it into two or more parts, and each divided part has a liquid crystal section having a different alignment state. In the liquid crystal display element, a part without an electrode, which coincides with the boundary direction of the division process of the part where the director of the liquid crystal rises in the direction away from each other, is placed on the electrode where the director of the liquid crystal rises when a voltage is applied. A liquid crystal display device having. 2. The liquid crystal display element according to claim 1, wherein the portion having no electrode is a stripe or a rectangle. 3. The liquid crystal display element according to claim 1, wherein a light-shielding film is provided on the boundary of the divisional alignment on at least one of the pair of electrode substrates.