JPH11258613A - Substrate for liquid crystal panel and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow the part except part to be sufficiently rubbed and uniformly aligned so that the spacers are not damaged by the rubbing processing by forming micro spacers composed of photosensitive resin being longitudinally almost in the same direction as the rubbing direction. SOLUTION: Spacer, extending in the direction in which a rubbing direction 102 of a substrate, on which spacers are to be formed, and a longitudinal direction 301 of the spacers almost matches with each other, are formed on a non- picture element part. Since a non-electrode part has a width of approximately 15-30 μm, the spacers are arranged so as to stay within this space. Elliptic, rhombic, parallelogram, straight forms are exemplified as examples of preferred forms of spacers. In such a manner, the spacers are relaxed in pressurization even if rubbed, so they are not shaved nor toppled. Moreover, the area of shaded part with respect to a rubbing method disappears. An alignment restriction force in the neighborhood of the spacers is also in the direction of extending the spacer wall and an abnormal alignment state is not induced.

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 used as a home, office and industrial information display terminal. More specifically, the present invention relates to a shape of a substrate spacing support member for holding a gap between a pair of substrates.

[0002]

2. Description of the Related Art Liquid crystal displays are widely used as display units for notebook computers because of their characteristics of low power consumption and space saving. In recent years, the size has increased,
It is expected that products with a size of 15 inches to 21 inches are being manufactured, and will gradually replace CRTs (Cathod Ray Tubes) used in desktop personal computers and televisions. Liquid crystal displays for desktops include nematic liquid crystal driven by thin film transistors (TFTs) and ferroelectric liquid crystal (FLC).
Crystal) or antiferroelectric liquid crystal (AFLC: Anti-F)
erroelectric Liquid Crystal).
These differ in the principle of display and the driving method, but the structure in which liquid crystal is sandwiched between a pair of glass substrates (liquid crystal panel frame) does not change in any liquid crystal display.

[0003] The distance between a pair of substrates of a TFT-driven display, which is the object of the present invention, is constant within a range of approximately 3 to 6 µm, but must be as uniform as possible. For this purpose, a method of dispersing a spherical or rod-shaped substrate spacing support member called spacer beads between the substrates has been adopted. The spacer beads are made of glass or resin, are dispersed in an appropriate solvent, and are applied and dried on a substrate. The coating and drying process is susceptible to static electricity and foreign matter. As a result, if the spacer beads are agglomerated or unevenly distributed, the spacing between the substrates becomes uneven and the display quality deteriorates. As the size of the liquid crystal panel increases, it becomes more difficult to spray the liquid crystal panel uniformly. In addition, since the spacer beads are only floating in the gap between the substrates, the spacing between the substrates is easily deformed and changed by an external pressure. However, such a problem also occurs that the spacer moves when the liquid crystal flows. . Still another problem is that if the spacer is located on a display pixel because the position of the spacer cannot be controlled, that portion is blanked out.

[0004] As a means for removing the disadvantages of the spacer bead dispersing method, there is disclosed a technique in which a fine member is formed by photolithography to form a spacer, or further, a pair of substrates is completely bonded through these. (For example, JP-A-63-50817, JP-B-2-36930, JP-A-4-255826, JP-A-7-84267, etc.). According to these techniques, a substrate spacing support member (hereinafter, referred to as a non-pixel portion) is selectively provided.
This is synonymous with a spacer), and the uniformity of the substrate spacing is excellent. Since it is fixed on the substrate, it does not move, and the substrate can be washed, so that the yield at the time of cell production is extremely excellent.

To bond a pair of substrates, first, an alignment film is formed on the substrates, and then a photosensitive resin having a desired thickness is applied thereon. After that, it is exposed and developed using a mask having an appropriate pattern and dried. By this step, a photosensitive resin pattern having a desired thickness, that is, a spacer member can be formed. When the substrate having the spacer member and the other substrate are kept in close contact with each other for about one hour in an environment of about 150 to 170 ° C., the two substrates are completely bonded. This is because, at a high temperature, the photosensitive resin chemically interacts with polyimide, which is a material for an alignment film, and exhibits strong adhesiveness. Both positive and negative photosensitive resins can be used. Any shape of the spacer, such as a point shape and a linear shape, can be considered. Although the application of the polyimide solution for orientation is possible even after the spacer is formed, the polyimide is repelled depending on the material of the spacer member or the spacer is dissolved by the solvent, and there is a problem in the uniformity of the application, and there is no general versatility. If both substrates are to be bonded, there is a serious weakness in that polyimide is placed on the top of the spacer and does not bond.

[0006]

When a photosensitive resin spacer is formed by a photolithography method in a TFT-driven liquid crystal panel, the following problem occurs depending on the shape. First, a polyimide film for liquid crystal alignment is applied on the stripe-shaped electrode group, and a spacer is formed with a photosensitive resin. After that, a rubbing process is generally performed. A rubbing treatment may be performed before the spacer is formed. However, during the development process using an alkaline solution, the polyimide surface is deteriorated by hydrolysis or a thin resist remaining film is left, so that the alignment of the liquid crystal is reduced. Therefore, disclination often occurs easily around the electrode edge. Therefore, it is a desirable process to perform a rubbing treatment after performing a treatment such as rinsing after the development. In this case, depending on the shape of the spacer, if there is a convex portion of about 3 to 5 μm, the upper portion may be cut off if the top portion is strongly rubbed with a cloth, or may fall down or collapse in severe cases. Alternatively, when the thickness of the spacer is increased, the shaded portion is not rubbed and the orientation cannot be imparted, or the existence of the spacer itself lowers the orientation.

The present invention has been made in view of the above. It is an object of the present invention to provide a liquid crystal panel substrate and a liquid crystal panel having spacers in which the spacers are not damaged as much as possible by the rubbing treatment and portions other than the spacers are sufficiently rubbed to provide a uniform alignment state.

[0008]

In the liquid crystal panel substrate according to the first aspect of the present invention, fine spacers made of a photosensitive resin having a longitudinal direction substantially in the same direction as the rubbing direction are formed. A liquid crystal panel substrate characterized by the above-mentioned. The liquid crystal panel substrate according to claim 2, wherein the height of the finely shaped spacer is in the range of 2.5 μm to 5 μm, and a liquid crystal suitable for a liquid crystal panel mainly using a nematic liquid crystal. This is a panel substrate. According to a third aspect of the present invention, there is provided a substrate for a liquid crystal panel, wherein a spacer having a fine shape is formed on an alignment film for liquid crystal alignment. By this procedure, the alignment film can be uniformly applied without being affected by the solvent contained in the alignment film, regardless of the material of the spacer member. A liquid crystal panel according to a fourth aspect of the present invention is a liquid crystal panel in which a pair of both substrates holds a nematic liquid crystal in a liquid crystal panel frame completely adhered via a spacer.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. In general, a liquid crystal cell is manufactured by laminating a pair of substrates on each of which a stripe-shaped transparent electrode is formed such that the transparent electrodes are orthogonal to each other. A liquid crystal cell for driving the TFT includes one substrate on which a large number of TFTs in a matrix are formed,
The other substrate having a planar electrode is laminated and manufactured. In any case, fine spacers are formed on one of the substrates using a photosensitive resin as a gap support member. The upper and lower rubbing directions are not the same (parallel) but oppose to form an angle of about 90 degrees when viewed from one substrate side. Specifically, as shown in FIG.
2 is rubbed. This is because the directions 103 and 104 in which the electrode lines of the upper and lower substrates extend are parallel to the sides of the rectangle, and rubbing in the diagonal direction has the effect of reducing the angle dependence of the displayed image in the right, left, up and down directions. At this time, rubbing is performed on the striped electrodes from an oblique direction.

Therefore, even if a spacer is formed at a place other than a display pixel, the above-described problem occurs depending on the shape, and it is necessary to appropriately select the shape. In the present invention, a spacer extending in a direction in which the rubbing direction 102 of the substrate on which the spacer is formed substantially coincides with the longitudinal direction 301 of the spacer is formed in the non-pixel portion (see FIG. 2). Since the width of the non-electrode portion is generally about 15 to 30 μm, the non-electrode portion is arranged so as to fit within this. Examples of preferred shapes include, for example, elliptical, rhombic, parallelogram, and linear spacers as shown in FIG. In this way, even if rubbing is performed, the pressure applied to the spacers is reduced, so that the spacers are not scraped or fall. Further, there is no area of a portion which is hidden by the rubbing method. The alignment regulating force in the vicinity of the spacer is also in the extending direction of the spacer wall, and an abnormal alignment state is not induced. Of course, if the bottom area of the spacer is large, it is possible to increase the symmetry of the shape, but this depends on the area of the non-pixel portion. As the height of the spacer increases, the amount of shaving increases. However, in the experiment conducted by the present inventor, there was no problem up to about 8 μm in the shape shown in FIG.

Hereinafter, an embodiment will be described.

[0012]

<Example 1> First, two transparent rectangular glass substrates were prepared, and ITO (indium tin) was formed by sputtering.
oxide) was deposited to a thickness of 2000 Å. One of the substrates is etched by a conventional photolithography method to form a striped ITO (indium tin oxidized) having a line width of 270 Å and a pitch of 300 Å.
e) A transparent electrode group was formed. Each was fired at 250 degrees for 1 hour. The use of a flat electrode on one side simulates a TFT-driven liquid crystal display element. Of course, both may be formed as striped electrodes and opposed to be orthogonal to each other.

Next, a polyimide solution HL1110 (manufactured by Hitachi Chemical Co., Ltd.) for liquid crystal alignment is applied to both substrates, dried and dried.
An alignment film having a thickness of 0 Å was formed. Next, a negative photosensitive resin MR83 (manufactured by Tokyo Ohka Co., Ltd.) was applied to a thickness of 4.5 μm on a substrate having a planar electrode, and dried at 90 ° C. for 30 minutes. Thereafter, exposure and development were performed using a mask having a spacer pattern shown in FIG. 3, and drying was performed at about 140 ° C. for about 1 hour. As a result, a flat diamond-shaped spacer as shown in FIG. 3 was formed. The major axis of the spacer was 40 μm, the single axis was 10 μm, and the ratio was 4: 1. Thereafter, the substrate on which the spacer was formed was rubbed three times in the same direction in parallel with the extending direction of the spacer. The other substrate was subjected to a rubbing treatment so as to be in the rubbing direction shown in FIG.

The pair of substrates was aligned with each other so as to fit in the gap between the stripe-shaped electrodes opposed by the spacer, the gap between the substrates was reduced, and both substrates were brought into close contact with each other.
When the substrate was kept in a 160 ° C. oven for 1 hour and cooled, the two substrates were completely bonded by the photosensitive spacer. The periphery of the liquid crystal panel frame except for the opening for liquid crystal penetration was sealed with an epoxy resin, and then left at about 90 ° to obtain a liquid crystal panel frame with a reinforced periphery. When a nematic liquid crystal (ZLI4536: manufactured by Merck) was penetrated into the liquid crystal panel frame and cooled again from the liquid state, no abnormal alignment state including the periphery of the spacer was found at all. Even when an appropriate electrode was selected and a driving signal was applied, disclination did not occur at the edge of one of the linear electrodes. The same result was obtained even when the thickness of the spacer was about 6 μm. Even when a pressure of 40 Newtons per unit area was applied to the liquid crystal panel, the display state was not disturbed.

Comparative Example 1 A liquid crystal panel frame was manufactured in the same procedure as in Example 1, and the same liquid crystal was permeated. However, unlike the first embodiment, the shape of the spacer is rectangular (30 μm × 15
μm), and the longitudinal direction is the same as the extending direction of the stripe electrode. In this case, since the rubbing is performed diagonally, the shaded portion of the spacer has a width of about 20 μm and the orientation state is different from the surrounding. Further, it was recognized that disclination occurred at the electrode edge in the portion close to the shadow during driving, light leakage occurred, and the contrast was reduced. In addition, as a photosensitive resin, not only a negative photosensitive resin but also a positive photosensitive resin can be used. However, the positive type is crushed when pressure is applied at a high temperature, and a desired cell gap cannot be obtained. Therefore, it can be used when a pair of substrates is not used as a spacer and bonded.

[0016]

According to the present invention, since the alignment polyimide is first applied, the alignment film is applied uniformly. The formed spacer member will not be deformed or fall down due to rubbing. Rubbing is performed uniformly over the entire substrate because there is little area behind the spacer member as viewed from the rubbing direction. Therefore, even if there is a convex portion, occurrence of alignment disorder and disclination is suppressed. Since the polyimide films on both substrates are flexibly and firmly bonded via the spacer member, a liquid crystal panel having excellent impact resistance can be manufactured.

[0017]

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a rubbing direction and an electrode direction of upper and lower substrates.

FIG. 2 is an explanatory view showing an example of the shape of spacers and arranging them between electrode lines (non-pixel portions).

FIG. 3 is an explanatory diagram illustrating an example of a spacer member shape.

[Explanation of symbols]

 101, 102 Rubbing direction 103, 104 Electrode direction 301 Longitudinal direction of spacer

Claims (4)

[Claims] 1. A liquid crystal panel substrate comprising fine spacers made of a photosensitive resin having a longitudinal direction substantially in the same direction as the rubbing direction. 2. The liquid crystal panel substrate according to claim 1, wherein the height of the fine spacer is in a range of 2.5 μm to 5 μm. 3. The liquid crystal panel substrate according to claim 1, wherein said fine spacer is formed on an alignment film for liquid crystal alignment. 4. A nematic liquid crystal is held in a liquid crystal panel frame in which the liquid crystal panel substrate according to any one of claims 1 to 3 and a counter electrode-attached substrate are bonded via the fine spacer. A liquid crystal display device characterized by the above-mentioned.