JPH02223919A - Formation of oriented film - Google Patents

Abstract

PURPOSE:To optimize the angle with a substrate in correspondence to the kind of a liquid crystal and the helix angle of the liquid crystal and to improve the contrast of a liquid crystal display body to an optimum state by applying a soln. prepd. by dissolving specific two kinds of diamines and tetracarboxylic anhydride on the substrate with transparent electrodes, then subjecting the coating to drying, calcining and rubbing treatments. CONSTITUTION:The soln. prepd. by dissolving the diamine compd. exhibiting the constitutional formula expressed by formula I, other diamine compd. and the tetracarboxylic anhydride is applied on the substrate and thereafter, the coating is subjected to the drying and calcining, then to the rubbing. In the formula I, R denotes hydrogen or alkyl group. Since the oriented film consists of a polyimide resin, the film has the excellent heat resistance which is the characteristic of the polyimide. The angle of the liquid crystal molecules with the substrate can be changed as desired from 0 to 5 deg. up to 22 deg. by changing the mixing ratio of the diamine compd. of the two components and the need for preparing orienting agents to meet with the kind, helix angle, etc., of the liquid crystal is eliminated. Dealing with all cases is possible in this way by preparing two kinds of the diamines and the tetracarboxylic anhydride.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing an alignment film for a liquid crystal cell for a liquid crystal display.

[Conventional technology]

In recent years, the development of liquid crystal display technology has been remarkable, and it has become possible to apply it to liquid crystal televisions and the like. As shown in Fig. 1, this liquid crystal display consists of a substrate (11) with two transparent electrodes (12) and a liquid crystal (
14) and an alignment film (13).

In the case of active matrix drive used in LCD televisions, the pixels are driven independently, so there was no problem with conventional alignment technology. However, in this case, there is a drawback that the yield is low and the cost is high.

On the other hand, the simple matrix drive method is considered to be an alternative to the active method because it may be cheaper.

These alternative technologies are called SBE method, NTN method, etc.

The important point of this technology is that the liquid crystal molecules in conventional liquid crystal displays are twisted at 90 degrees, but are twisted at more than 180 degrees.

For this reason, it is necessary to make the liquid crystal molecules tilt at an angle of 5 degrees or more with respect to the substrate to release distortion caused by excessive twisting. One of the methods to make the angle 5 degrees or more is to use an alignment film.

The conventional method for creating an alignment film that twists liquid crystal molecules by 180 degrees or more is to apply a single-component polyimide resin.

[Problem to be solved by the invention]

In order to achieve the best contrast of a liquid crystal display, the angle with the substrate must be optimized depending on the type of liquid crystal and the twist angle of the liquid crystal.

However, since a single component was used, it was not possible to arbitrarily change the angle with the substrate.

Even if an attempt was made to change the angle using multiple components, it was impossible because there was no single component that could significantly change the angle with the substrate.

[Means to solve the problem]

The present invention was made to improve such drawbacks of the conventional alignment film, and is made by dissolving a diamine compound (1) having the following structural formula, another diamine compound (2), and a tetracarboxylic acid anhydride. After applying the solution, it is dried, baked, and then rubbed.

(However, R represents hydrogen or an alkyl group.) As the diamine compound (2), the following compounds can be considered.

1, 4.4'-diaminodiphenyl ether 2,
4.4'-diaminodiphenylmethane 3, p-
phenylenediamine 4, m-phenylenediamine 5, m-xylenediamine 6, 4,4'-diaminothylbenne 7, L4-diaminocyclohexane 8, L
6-diamithexane 9, Bis-M (manufactured by Mikata Petrochemical Co., Ltd.) 10°B1
5-P (manufactured by Mikata Petrochemical Co., Ltd.) Such a compound is just one example, and various other compounds can be considered as the diamine compound (2) in addition to the above compounds.

Various types of tetracarboxylic anhydride can be considered, such as pyromellitic anhydride, benzophenonetetracarboxylic anhydride, hexafluoropropylidene cyphthalic anhydride, and biphenyltetracarboxylic anhydride.

As for drying, firing conditions, rubbing conditions, etc., conventional conditions for producing a polyimide alignment film can be applied as they are.

As a coating method, any of the spin-coding method, dipping method, casting method, spacing method, etc. is possible, but the spin-coding method is superior.

[For production]

According to the method for producing an alignment film of the present invention, since the alignment film is made of polyimide resin, it has excellent heat resistance, which is a characteristic of polyimide.

The angle of the liquid crystal molecules with respect to the substrate can be freely changed from several degrees (0 to 5 degrees) to 22 degrees by changing the mixing ratio of the two diamine compounds.

There is almost no additivity between the angle between the liquid crystal molecules and the substrate achieved by an alignment film made of a mixture of two types of diamine compounds and the angle achieved by an alignment film made of each diamine and tetracarboxylic anhydride. It works.

Hereinafter, the present invention will be explained in detail with reference to Examples.

[Example 1] 10 weight percent N-
A methylpyrrolidone solution was prepared and used as alignment agent 1-5.

Note that the numerical values in the table indicate weight percentages.

Diamine 1 Diamine 2 H, N () (XH2 Tetracarboxylic Anhydride H Table 1 manufactured by Luk N4) was filled, and the angle between the liquid crystal molecules and the substrate was determined by the magnetic field alignment method, and the results shown in Table 2 were obtained. Ta.

Table 2 These alignment agents were rotated at a rotation speed of 1500 using the spin code method.
It was applied onto a substrate with a transparent electrode at rpm.

This substrate was dried at 90 degrees Celsius for 2 hours and then fired at 200 degrees Celsius for 2 hours.

After firing, this substrate was transferred under a rotating body with a diameter of 80 mm whose surface was flocked with nylon fibers, which was rotating at a speed of 400 rprr+ at a feed rate of 0.6 m/min, and subjected to a rubbing treatment. did.

The rubbing direction of the thus obtained substrate was 220 degrees, and a liquid crystal cell was assembled via a 12 micron spacer. Similar treatment was carried out using a 10 weight percent N-methylpyrrolidone solution containing tetracarboxylic anhydride 3, and the measured results were 22 degrees and 2 degrees, respectively.

[Example 2] A 10% by weight dimethylformamide solution was prepared by mixing two types of diamines having the following structural formulas in the proportions shown in Table 3, and used as alignment agent 6-10.

Note that the numerical values in the table indicate weight percentages.

Diamine 4 Diamine 5 H2N +0+N H2 Tetracarboxylic anhydride 6 Table 3 Assemble a liquid crystal cell via a 12 micron spacer, liquid crystal (ZLI2214 manufactured by Merck iL)
When the angle between the liquid crystal molecules and the substrate was measured using a magnetic field alignment method, the results shown in Table 4 were obtained.

Table 4 These alignment agents were rotated at a rotation speed of 2000 using the spin code method.
It was applied onto a substrate with a transparent electrode at rpm.

This substrate was dried at 90 degrees Celsius for 2 hours and then baked at 2 degrees Celsius for 2 hours.

After firing, this substrate was fed at a feed rate of 0. At 6 meters/minute,
The sample was transferred under a rotating body having a diameter of 80 mm and having a surface covered with nylon fibers, which was rotating at a rotational speed of 400 rprr+, and was subjected to a rubbing treatment.

The substrate thus obtained was subjected to the same treatment using a 10% by weight dimethylformamide solution prepared from diamine 4 and tetracarboxylic anhydride 6 and diamine 5 and tetracarboxylic anhydride 6, with a rubbing direction of 220. However, the measured results were 24 degrees and 3 degrees, respectively.

Although the embodiments have been described above, the present invention is not limited to the above embodiments, but can be broadly applied to other raw materials, solvents, coating conditions, drying, and firing conditions.

〔Effect of the invention〕

As described above, according to the present invention, there is no need to prepare an alignment agent according to the type of liquid crystal, twist angle, etc., and by preparing two types of diamine and tetracarboxylic acid anhydride, it is possible to deal with all types. have

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of a liquid crystal display. 11 ・ 12 Φ 13 dispute 14 ・ ・Substrates, electrodes, alignment films, liquid crystals and above Applicant Seiko Epson Co., Ltd. Agent Patent attorney Kizobe Suzuki (1 other person) &'l! '
4 Chi J1

Claims (1)

[Claims] A liquid crystal cell for a liquid crystal display comprising a substrate with a transparent electrode, an alignment film coated on the substrate, a spacer, and a liquid crystal,
A solution containing a diamine compound (1) having the following structural formula, a diamine compound (2) different from the compound, and a tetracarboxylic anhydride (3) is applied to a substrate with a transparent electrode, and then dried and baked, A method for creating an alignment film characterized by performing a rubbing treatment. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (However, R means hydrogen or an alkyl group.)