JP2780184B2 - Alignment film and liquid crystal device - Google Patents

Description

The present invention relates to a method for forming an alignment film of a liquid crystal cell for a liquid crystal display.

[Prior Art] In recent years, the development of liquid crystal display technology has been remarkable, and application to liquid crystal televisions and the like has become possible. As shown in FIG. 1, the liquid crystal display comprises a substrate 11 having two transparent electrodes 12, a liquid crystal 14, and an alignment film 13.
Is made up of

In the case of active matrix driving used in a liquid crystal television, since pixels are driven independently, there was no problem with the conventional technology regarding the alignment technology. However, in this case, there is a disadvantage that the yield is low and the cost is high.

On the other hand, according to the simple matrix driving method, there is a possibility that the cost may be reduced, so that an alternative to the active method is considered.

These alternative technologies are called SBE system, NTN system and the like.

The important point of this technology is that the liquid crystal molecules of the conventional liquid crystal display are twisted by 90 degrees or more, but twisted by 180 degrees or more.

For this reason, it is necessary to allow the liquid crystal molecules to be tilted at least 5 degrees with respect to the substrate to release the distortion due to excessive twisting. One of the methods of standing at least 5 degrees is a method using an alignment film.

A conventional method of forming an alignment film in which liquid crystal molecules are twisted by 180 degrees or more has been a method of applying a single-component polyimide resin.

[Problems to be Solved by the Invention] In order to optimize the contrast of the liquid crystal display, the angle between the liquid crystal molecules and the substrate must be optimized according to the type of liquid crystal and the twist angle of the liquid crystal.

However, the angle with the substrate could not be arbitrarily changed because a single component was used.

Further, even if an attempt is made to change by multiple components, it was impossible to change it widely because there was no component that would greatly change the angle with the substrate with a single component.

[Means for Solving the Problems] The alignment film of the present invention is (1) an alignment film formed from an alignment agent containing two kinds of polyamic acid compounds, and one polyamic acid compound has the following structural formula. It is characterized by having.

(However, n is a positive integer, and R represents hydrogen or an alkyl group.) The liquid crystal device of the present invention is a liquid crystal device in which liquid crystal is sealed between a pair of substrates via a spacer. An alignment film formed from an alignment agent containing an acid compound is formed on the pair of substrates, and one polyamic acid compound has the following structural formula.

(However, n represents a positive integer, and R represents hydrogen or an alkyl group.) The following compounds are considered as the polyamic acid which is a precursor of the polyimide alignment film having a low angle with the substrate.

(Herein, n is a positive integer.) Such a polyamic acid compound can be produced by reacting a tetracarboxylic anhydride with a diamine-based compound as a raw material, and can be considered variously in addition to the raw material of the compound.

For example, as tetracarboxylic anhydride, hexafluoropropylidene diphthalic anhydride, biphenyltetracarboxylic anhydride, and as diamine compound, m-phenylenediamine, m-xylenediamine, 1,6-diaminohexane, Bis -M (manufactured by Mitsui Petrochemical) and Bis-P (manufactured by Mitsui Petrochemical) can be considered.

Drying, baking conditions, rubbing conditions, and the like can be directly applied to the conditions for forming a conventional polyimide-based alignment film.

Coating methods include spin coating, dipping,
Both the casting method and the brush coating method can be used, but the spin coating method is excellent.

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

The angle of the liquid crystal molecules with respect to the substrate can be varied from several degrees (0 to 5 degrees) by changing the mixing ratio of the two-component polyamic acid.
Can be changed freely up to 20 degrees. Additivity is substantially established between the angle between the liquid crystal molecules and the substrate achieved by mixing and the angle achieved by the two components before mixing.

 Hereinafter, the present invention will be described in detail with reference to examples.

[Example] (Example 1) A 10 wt% N-methylpyrrolidone solution was prepared by mixing two kinds of polyamic acids having the following structural formulas at the ratio shown in Table 1, and was used as an aligning agent 1-5. In addition, the numerical value of a table shows the ratio of weight.

These alignment agents are spin-coated at 1500 rpm
m and applied to a substrate with a transparent electrode. The substrate was dried at 90 ° C. for 2 hours, and baked at 200 ° C. for 2 hours.

After firing, the substrate was transferred at a feed rate of 0.6 m / min under a rotating body having a diameter of 80 mm with nylon fibers planted on a surface rotating at a rotation speed of 400 rpm, and subjected to a rubbing treatment. The substrate obtained in this manner is set so that the rubbing direction is 220 degrees, and a liquid crystal cell is assembled through a 12-micron spacer. A liquid crystal (manufactured by Merck, ZLI2214)
Was filled, and the angle between the liquid crystal molecules and the substrate was measured by a magnetic field alignment method. The results shown in Table 2 were obtained.

The same treatment was carried out using a 10% by weight solution of N-methylpyrrolidone consisting of only polyamic acid 1 and polyamic acid 2, and the measured results were 20.1 degrees and 1.2 degrees.

(Example 2) A 10% by weight dimethylformamide solution in which two kinds of polyamic acids having the following structural formulas were mixed at the ratio shown in Table 3 was prepared, and used as an aligning agent 6-10. In addition, the numerical value of a table shows the ratio of weight.

The rotation speed of these alignment agents was 2,000 rp by spin coating.
m and applied to a substrate with a transparent electrode. The substrate was dried at 90 ° C. for 2 hours, and baked at 200 ° C. for 2 hours.

After firing, the substrate was transferred at a feed rate of 0.6 m / min under a rotating body having a diameter of 80 mm with nylon fibers planted on a surface rotating at a rotation speed of 400 rpm, and subjected to a rubbing treatment. A liquid crystal cell (ZLI2214 manufactured by Merck) is assembled through a 12-micron spacer so that the rubbing direction of the substrate thus obtained is 220 degrees, and the liquid crystal (ZLI2214 Merck) is filled. Was measured, and the results in Table 4 were obtained.

The same treatment was performed using a 10% by weight dimethylformamide solution consisting of only polyamic acid 1 and polyamic acid 3, and the measured results were 20.0 degrees and 0.2 degrees.

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

[Effects of the Invention] As described above, according to the present invention, it is not necessary to prepare an alignment agent according to the type of liquid crystal, the angle of twist, and the like, and it is possible to cope with all by preparing two types of polyamic acids. Has an effect.

[Brief description of the drawings]

 FIG. 1 is a conceptual diagram of a liquid crystal display. 11 ... Substrate 12 ... Electrode 13 ... Alignment film 14 ... Liquid crystal

Claims (2)

(57) [Claims] An alignment film formed from an alignment agent containing two kinds of polyamic acid compounds, wherein one of the polyamic acid compounds has the following structural formula. (However, n is a positive integer, R is hydrogen or an alkyl group) 2. In a liquid crystal device in which liquid crystal is sealed between a pair of substrates via a spacer, an alignment film formed from an alignment agent containing two kinds of polyamic acid compounds is formed on the pair of substrates. Wherein one polyamic acid compound has the following structural formula. (However, n is a positive integer, R represents hydrogen or an alkyl group)