JPS6146933A - Production of liquid crystal display element - Google Patents

Abstract

PURPOSE:To produce a liquid crystal display having no orientation defects by forming an oriented film of polyimide or polyamide imide onto a uniaxially stretched polyester film having a small extinction ratio and good uniformity of film thickness and rubbing the same with a polyurethane foam having specific properties. CONSTITUTION:The uniaxially stretched polyester film having within + or -3 deg. extinction ratio and within 1mu film thickness fluctuation distribution is used for the substrate of the liquid crystal display element. The solvent soluble polyimide or polyimide amide is coated on such substrate in the form of a solvent such as dimethyl formamide which does not dissolve the polyester film to form the oriented film. The oriented film is then subjected to the rubbing treatment by the polyurethane foam having 20-50% repellent elasticity and 10-50 deg. surface hardness measured by an ASKER C-TYPE rubber hardness meter. The liquid crystal display element which has a small tilt angle, obviates coloring within an optional visual angle under high duty and has excellent moisture resistance is thus obtd.

Description

[Detailed Description of the Invention] The present invention relates to a method of manufacturing a liquid crystal display device using a plastic transparent substrate, and in particular, a manufacturing method that is suitable for manufacturing a dynamic drive device that enables high duty cycle. Regarding.

A liquid crystal display element is a liquid crystal display element in which a liquid crystal material is sealed between two substrates provided with an electrode pattern, and the liquid crystal material is electro-optically modulated by applying a signal voltage to the electrodes to display characters, figures, etc. This is to display the following information. Although inorganic glass has been used as this substrate, liquid crystal display elements using plastic substrates are attracting attention from the viewpoint of thinning and weight reduction, strength, and manufacturing cost reduction.

Liquid crystal display elements using this plastic substrate are usually
It is manufactured by forming an electrode pattern of segment electrodes or common electrodes on a plastic substrate, then subjecting the substrate surface to alignment treatment, and then sealing a liquid crystal substance between two opposing substrates. Conventionally, the orientation process is

This has been done by coating an alignment agent such as organic silane on a substrate to form an alignment film, and then subjecting it to a rubbing treatment. The rubbing process has basically been adapted from the method used for glass substrates, using a brush made of paper tubes or metal cylinders with fibers such as nylon, or fibrous rubbing materials such as cotton cloth. This has been carried out by rubbing the surface of the alignment film in a certain direction with a certain pressure.

However, when a fibrous material for glass substrates is used in the alignment process of liquid crystal display elements whose substrates are made of plastic, uniform alignment cannot be achieved due to differences in the smoothness, flatness, flexibility, etc. of the substrates. No processing is performed, and orientation defects such as rubbing marks, reverse twist, and reverse tilt are likely to occur.

There was a drawback that it was difficult to obtain products with good display.

Furthermore, organic silane and nylon/epoxy/organotitanate reaction products (see Japanese Patent Application Laid-open No. 14220/1983), which have been conventionally used as alignment films for plastic substrates, can be processed at temperatures below 150°C. However, it has poor heat resistance and a small tilt angle, making it unsatisfactory for manufacturing high-duty liquid crystal display elements.

An object of the present invention is to provide a method for manufacturing a liquid crystal display element using a plastic substrate that has excellent alignment performance, provides high display quality, and is capable of increasing duty.

That is, the following (a) # of the liquid crystal display element of the present invention:
It is characterized by including steps (b) and (C).

(a) Extinction angle within ±3 degrees, film thickness distribution within 1 μm 1
A process in which an axially stretched polyester film is used as a substrate and an electrode pattern is formed on this substrate.

(b) forming an alignment film by applying solvent-soluble polyimide or its precursor or polyimide amide to a substrate;
Surface hardness is 10 as measured by rubber hardness tester Asker-C type.
The process of rubbing with polyurethane foam at ~50 degrees The present invention will be described in more detail below.

A polyester film such as polyethylene phthalate is used as the substrate. This film needs to be a uniaxially stretched polyester film with an extinction angle of within ±3 degrees and a film thickness distribution of within 1 μm. When a biaxially stretched polyester film is used, optical anisotropy occurs due to the stretching axis, and the entire display surface is colored in rainbow colors due to the birefringence of the liquid crystal, deteriorating the display quality. In uniaxially stretched film.

However, the coloration seen with biaxially stretched film disappears.

Depending on the method of disposing the polyester film and the angle at which it is viewed, streak-like coloring may occur and the visual characteristics may deteriorate. Extinction angle ±3
Such coloring can also be prevented by keeping the temperature within .

In addition, when the film thickness unevenness of a uniaxially stretched polyester film becomes large, anisotropy of the optical axis occurs and the display performance is extremely deteriorated. Therefore, the film thickness needs to have a thickness distribution of 1 μm or less.

Next, a transparent electrode such as an indium oxide film or a tin oxide film is formed in a predetermined pattern on this polyester film. Here, prior to this formation, it is preferable to heat-treat the polyester film at a temperature of 130 to 160°C to prevent thermal deformation in a subsequent process.

Next, solvent-soluble polyimide or polyamide-imide is coated on the substrate on which the electrode pattern is formed, and
By heating and baking at 0 to 155°C, an alignment film having a thickness of 500 to 3,000 layers is formed. Specific examples of solvent-soluble polyimide or its precursor or polyimide amide include:
For example, there is a polymer produced by reacting polymer bismaleimide and benzyl oxime shown by the following repeating unit disclosed in JP-A No. 56-52722, and DA-
5ND, CBN-D, Hitachi Chemical's P I X-140
0, HL-1100, etc. As the solvent, a polar solvent such as dimethylformamide or 2-methylpyrrolidone is used. Since these solvents have strong polar groups, they dissolve films such as polyether sulfone and polycarbonate, but do not dissolve uniaxial polyester films.

Application methods include blade application, dipping, spray method, spinner application, screen printing, etc.
Any conventional method can be used.

Next, this alignment film is subjected to a rubbing treatment.

In the rubbing process, the impact resilience is 20 to 50% 1 surface hardness (
A polyurethane foam having a hardness (measured with a rubber hardness meter Asker-C type) of 10° to 50° is used.

Further, it is more preferable to have a rebound resilience of 30 to 40% and a surface hardness of 15 to 40 degrees. Rubbing is 10
It is appropriate to perform the rubbing at a rubbing pressure of about 50 g/aJ, and the number of times of rubbing is preferably about 2 to 5 times.

A liquid crystal display element is obtained by sealing a liquid crystal material between the substrates subjected to horizontal alignment treatment in this manner.

■-By forming an alignment film of polyimide or polyamideimide on uniaxially stretched polyester and rubbing this alignment film with polyurethane foam, alignment defects such as reverse twist and chilled 〇-lines will not occur. A liquid crystal display element having sufficient alignment properties can be obtained.

Furthermore, by controlling the extinction angle and film thickness distribution of the uniaxially stretched polyester film, monochromatic coloring can be prevented and excellent display quality can be obtained.

Embarrassment According to the manufacturing method of the present invention, it is possible to drive a matrix with a uniform orientation, a high duty matrix of 1/16. A liquid crystal display element with a high temperature can be obtained.

Example 1 A substrate with a transparent electrode formed on a uniaxially stretched polyester film with an extinction angle of 1.5 degrees and a film thickness unevenness of ±1 μm or less was used, and a soluble polyimide solution (Nissan Chemical Co., Ltd.
Co., Ltd., DA-5ND) was applied and heat treated at 150° C. for 1 hour to form an alignment film of approximately 2000 layers. This alignment film is made of polyurethane foam (repulsion resilience 40%, hardness 30%).
Rubbing treatment was performed using a pressure of 50 g/a1.

After applying a divinylbenzene copolymer with a thickness of 8 μm onto one substrate using a spinner, the other substrate printed with a sealing adhesive was bonded to produce a liquid crystal cell. A nematic liquid crystal (ZLT-2460 manufactured by Merck & Co., Ltd.) was sealed in this to create a liquid crystal element.

Comparative Example 1 A liquid crystal device was produced in the same manner as in Example 1, except that a uniaxially stretched polyester film with a thickness unevenness of 3 μm was used.

Comparative Example 2 A liquid crystal element was manufactured by repeating the same operations as in Example 1 except that a cotton cloth was used for rubbing treatment at a pressure of 50 g/d or higher.

The liquid crystal devices obtained as described above were evaluated for orientation, domain generation, and coloring, and the results are shown in Table 1.

Table 1: When the same treatment as in Example 1 was performed except that an epoxy-nylon-organotitanate mixed system was used as the alignment agent, reverse tilt occurred.

Furthermore, although various rubbing conditions were investigated, reverse tilt was not improved under any conditions.

Claims (1)

[Claims] 1. (a) Extinction angle within ±3 degrees, film thickness distribution within 1 μm 1.
(b) forming an alignment film by applying solvent-soluble polyimide or its precursor or polyimide amide to the substrate; (c) forming an alignment film on the substrate using an axially stretched polyester film as a substrate; The alignment film has a rebound resilience of 20 to 50% and a surface hardness of 10 to 5 as measured with a rubber hardness meter Asker C type.
A method for manufacturing a liquid crystal display element, comprising a step of rubbing with 0 degree polyurethane foam.