JPH0651317A - Treatment of oriented film and liquid crystal display element produced by using this method - Google Patents

Abstract

PURPOSE:To provide a uniform display free from display defects by devising a method for setting the curing temp. of an oriented film. CONSTITUTION:This method is constituted to prevent various kinds of the display defects not by specifying the conventional setting of the curing temp. of the oriented film but by setting optimum curing conditions stepwise in respective stages. For example, the oriented film is subjected to a thermal curing treatment at a low temp. at which a rubbing property is good; thereafter, the oriented film is thermally cured at a high temp. and is subjected to a washing treatment. As a result, the excellent liquid crystal display element free from flaws and fibrous dust at the time of the rubbing treatment, free from stain-like traces after the washing treatment and free from the display defects is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating an alignment film and a liquid crystal display device manufactured by using the method.

[0002]

2. Description of the Related Art In recent years, various display defects remain as a problem in the display uniformity of liquid crystal panels. In particular, dust generated during the process becomes linear scratches corresponding to the rotation direction of the rubbing roller during the rubbing process.

Further, fibrous dust or the like adheres to the surface of the alignment film after rubbing, resulting in gap unevenness and threshold unevenness.
Therefore, conventionally, a display defect caused by dust before and after the rubbing process has been a problem.

[0004]

However, in the conventional constitution, the alignment film curing temperature has an effect on the scratches of the rubbing treatment at the low temperature curing, but the alignment film surface after the cleaning operation has stain marks. Remain and the imidization ratio in the plane of the alignment film is not constant, resulting in display unevenness.

On the other hand, high temperature curing is effective for cleaning the surface of the alignment film after the rubbing treatment, but many scratch marks are generated during rubbing.

Unfortunately, there is no alignment film curing temperature at which both problems can be solved at the same time. Therefore, it is very difficult to eliminate display defects.

The present invention solves the conventional problems, and an object of the present invention is to provide a method for treating an alignment film free from display defects due to dust and a liquid crystal display device manufactured using the same.

[0008]

In order to solve the above problems, the present invention is characterized in that the alignment film curing heat treatment is performed in several steps.

[0009]

The present invention prevents various display defects by setting the optimum curing conditions for each process in several steps, rather than keeping the conventional setting of the curing temperature of the alignment film constant.

For example, by performing a heat curing treatment at a low temperature with a good rubbing property, a heat curing treatment at a high temperature, and a cleaning treatment, scratches and fibrous dust during the rubbing treatment are eliminated, and stain marks after the cleaning treatment are removed. Disappears.

With the structure of the present invention, an excellent liquid crystal display element free from display defects due to dust and an alignment film can be cured.

[0012]

[Examples] Details will be described below.

Two substrates were prepared by forming a transparent electrode of indium tin oxide (hereinafter referred to as an ITO electrode) on a glass substrate.

An aromatic polyamic acid solution (2204 manufactured by Chisso Petrochemical Co., Ltd.) was applied onto each of the substrates by a spinner.

After preliminary curing heat treatment at 80 ° C. for 15 minutes, 20
0 ° C. (FIG. 1-A), 1 hour heat curing treatment (where the imidization ratio is less than 50%, but the imidization ratio suitable for rubbing is usually 20% to 50%). .)
A polyimide alignment film was formed.

Next, the alignment film surface of each substrate was subjected to an alignment treatment by a usual rubbing method so as to form a liquid crystal display device having a 240 ° twist structure.

After that, a heat curing treatment (imidization ratio: 50% or more) was performed at 240 ° C. (FIG. 1-C) for 1 hour to wash the alignment film surface.

Next, a seal resin (Structbond manufactured by Mitsui Toatsu) was screen-printed around the one-sided substrate alignment film by a conventional method in order to bond the two substrates.

After that, in order to keep the distance between the substrates uniform, spacers of 6 μm (Micropearl manufactured by Sekisui Fine Chemical Co., Ltd.) on the orientation film surface of the other substrate have a density of about 120 pieces /
After spraying in square millimeters, both substrates were laminated so that the alignment film surface was on the inside, and vacuum-packed using a heat-resistant vacuum pack bag to make the gap uniform.

At this time, the ITO electrodes on the upper and lower substrates are arranged so as to be exposed to the outside. The nematic liquid crystal material (for STN: ZLI manufactured by Merck & Co., Inc.)
A liquid crystal display device was obtained by the usual vacuum injection method.

As a result of lighting display, an excellent liquid crystal display element having no linear scratches due to rubbing treatment, no stain marks after washing operation, and no fibrous dust due to rubbing treatment is obtained. It was realized.

[0022]

INDUSTRIAL APPLICABILITY As described above, the present invention provides an excellent method for treating an alignment film, which realizes the absence of display defects such as scratch marks after rubbing treatment and stain marks after cleaning treatment. The manufactured liquid crystal display device can be provided.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the curing temperature of the alignment film of the present invention and the imidization ratio.

[Explanation of symbols]

 A Curing temperature of 30% imidization ratio (good rubbing property) B Curing temperature of 50% imidization ratio C Curing temperature of 70% imidization ratio (good cleaning treatment)

Claims (5)

[Claims] 1. A polyimide-based alignment film solution is applied to or printed on a surface of a substrate having a transparent electrode, and then a heat-curing process is performed at the stage of performing a heat-curing process.
After that, a method for treating an alignment film is characterized in that it is heat-cured at a high temperature. 2. The method for treating an alignment film according to claim 1, wherein the surface of the alignment film which has been heat-cured at a high temperature is washed. 3. An alignment film which has been heat-cured at a temperature lower than an imidization ratio of 50% is subjected to a rubbing treatment, and then the alignment film is heat-cured at a temperature of an imidization ratio of 50% or higher. A characteristic method for treating an alignment film. 4. The method for treating an alignment film according to claim 3, wherein the surface of the alignment film which is heat-cured at a temperature at which the imidization ratio is 50% or more is washed. 5. A liquid crystal display device manufactured by using the method for treating an alignment film according to claim 1.