JPS6410812B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides means for improving the quality of initial homogeneous alignment, which can be used in liquid crystal display devices that require liquid crystal molecules to be homogeneously aligned in an initial state (unexcited state). This invention relates to a liquid crystal holding substrate.

Conventionally, as a means to improve the homogeneous alignment of liquid crystal molecules in the initial state, methods include forming an obliquely vapor-deposited film of silicon oxide or the like on a substrate, forming a film of various surface treatment agents, organic polymers, etc. A method of rubbing the film is known. However, each of these known methods has drawbacks as described below.

That is, the orientation ability of an obliquely vapor deposited film such as silicon oxide differs depending on the type of liquid crystal material, and there are some liquid crystal materials that do not provide orientation at all. This is a very serious problem when using a mixture of various liquid crystals to improve the temperature characteristics or electro-optical characteristics of the liquid crystal. In addition, in the method of forming a film of various surface treatment agents, organic polymers, etc. and then rubbing the film, the heat resistance of the film is low, so the film deteriorates due to heating during device assembly, resulting in a decrease in orientation. Most of them have drawbacks such as smearing, etc., and only heat-resistant organic polymer films such as polyimide have good heat resistance of orientation regulating force. However, these known polyimide polymer films have poor adhesion to the substrate surface, resulting in partial peeling of the coating during rubbing, resulting in poor orientation such as the formation of domains. There was a drawback that this occurred.

The present inventors conducted studies to eliminate the above-mentioned drawbacks of the prior art, and as a result, they arrived at the present invention. That is, the present invention allows the molecular axis of liquid crystal to be aligned parallel to the substrate surface and in the characteristic direction of the substrate surface, regardless of the liquid crystal material, and this liquid crystal alignment regulating force has excellent heat resistance.
Furthermore, by improving the resistance to rubbing, it is possible to provide a liquid crystal display device that is stable over time, has a long life, and has high performance without imposing restrictions on the assembly of liquid crystal display elements.

In the present invention, an electrode is provided on the side facing the liquid crystal on a liquid crystal holding substrate, and a carboxylic acid anhydride, a diamine and a general formula (In the formula, R is a divalent hydrocarbon group, and R ₁ and R ₂ are monovalent hydrocarbon groups.) The present invention relates to a liquid crystal holding substrate formed with a polyimide silane polymer coating obtained by dehydration and ring closure.

Polyamic acid, which is a precursor of the polyimidosilane polymer used in the present invention, is synthesized by the reaction of carboxylic acid anhydride, diamine, and diaminosilane. These reactions are carried out under anhydrous conditions, preferably at 50°C.
or at a lower temperature.

The reaction ratio of the carboxylic anhydride, diamine and diaminosilane is preferably such that the number of moles of the carboxylic acid anhydride is equal to the number of moles of the diamine and diaminosilane. This reaction is carried out in the presence of a solvent such as dimethylformamide, dimethylacetamide, dimethylsulfoxide, N-methylpyrrolidone, or the like.

Examples of the carboxylic anhydride include pyromellitic anhydride, 2,3,6,7-naphthalenetetracarboxylic anhydride, 3,3',4,4'-diphenyltetracarboxylic anhydride, 1,2, 5,6-naphthalenetetracarboxylic anhydride, 2,2',3,
3'-diphenyltetracarboxylic anhydride, thiophene-2,3,4,5-tetracarboxylic anhydride, 2,2-bis(3,4-biscarboxyphenyl)propane anhydride, 3,4- Dicarboxyphenylsulfone anhydride, berylene-3,4,9,
10-tetracarboxylic anhydride, bis(3,4-dicarboxyphenyl)ether anhydride, 3,3',
4,4'-benzophenonetetracarboxylic anhydride and the like are used.

Examples of the diamine include m-phenylenediamine, p-phenylenediamine, m-xylenediamine, p-xylenediamine, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 3,3 '-Dimethyl-4,4'-diaminodiphenylmethane, 3,3',5,5'-tetramethyl-4,4'-diaminodiphenylmethane,
2,2'-bis(4-aminophenyl)propane
4,4'-methylene dianiline, benzidine, 4,
4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfone, 1,5-diaminonaphthalene, 3,3'-dimethylbenzidine, 3,
3′-dimethoxybenzidine, 2,4-bis(β-
Amino-tert-butyl)toluene, bis(4-β
-amino-tert-butylphenyl) ether,
1,4-bis(2-methyl-4-aminobentyl)benzene and the like are used.

In the present invention, the general formula (In the formula, R is a divalent hydrocarbon group, and R ₁ and R ₂ are monovalent hydrocarbon groups.) Diaminosilanes represented by the formula are used, examples of which include di(aminopropoxy)dimethylsilane, etc. di(aminoalkoxy)dialkylsilane such as di(aminoalkoxy)dialkylsilane, di(aminoethoxy)diphenylsilane, di(aminophenoxy)dialkylsilane such as di(aminophenoxy)diethylsilane, di(aminophenoxy) such as di(aminophenoxy)diphenylsilane, etc. ) diallylsilanes, di(aminoalkoxy)alkylarylsilanes such as di(aminoethoxy)methylphenylsilane, etc.

It is preferable to use aromatic compounds as the above-mentioned carboxylic acid anhydride, diamine, and diaminosilane from the viewpoint of heat resistance.

Two or more of the above carboxylic acid anhydrides, diamines, and diaminosilanes may be used in combination.

The above diaminosilane is obtained, for example, by reacting dichlorosilane and hydroxylamine using a titanium alkoxide such as tetraisopropoxytitanium as a catalyst.

The amount of diaminosilane is preferably 0.1 to 50 mol% based on the total amount of diamine and diaminosilane from the viewpoint of adhesiveness, heat resistance, and stability.

Coating the above polyamic acid onto the substrate and electrodes involves coating the polyamic acid with dimethylformamide,
A 0.01 to 40% by weight solution of dimethylacetamide, dimethylsulfoxide, N-methylpyrrolidone, etc. is applied by a dip method, spinner method, spray method, printing method, brush coating method, or the like. 100℃~400℃ after application preferably 250℃
A polyimide silane-based polymer coating is obtained by heat-treating at a temperature of .degree. C. to 350.degree. C. to dehydrate and ring-close the polyamic acid.

Hereinafter, the present invention will be specifically explained with reference to Examples and Comparative Examples.

Example 0.1 mol of di(aminopropoxy)diphenylsilane, 0.9 mol of 4,4'-diaminodiphenyl ether and 3,3'4,
4'-Benzophenonetetracarboxylic anhydride 1.0
A 15% by weight N-methylpyrrolidone solution of polyamic acid, which is a precursor of a polyimidosilane polymer obtained by condensing moles, was applied using a spinner to a glass substrate on which an indium oxide electrode was formed. After coating, ring closure was performed by heating at 300° C. for 1 hour to form a polyimide silane polymer film with a thickness of 1000 Å. Thereafter, the coating was rubbed with gauze in a certain direction, but no peeling occurred in the polyimide silane polymer coating. Furthermore, when a liquid crystal display cell was produced using a pair of substrates having the above-mentioned rubbed polyimide silane polymer film, the alignment was very good.

Di(aminopropoxy)diphenylsilane used in the above examples was synthesized by the following method. Diphenyldichlorosilane (manufactured by Shin-Etsu Chemical)
KBM202) 122.2g and propanolamine 75.1g
were reacted at 70°C for 30 minutes using 0.1% by weight of tetraisopropoxytitanium based on the total amount of both as a catalyst. The temperature was then raised to 85°C to remove methanol, a reaction by-product, to obtain di(aminopropoxy)diphenylsilane as a product.

Comparative Example: Polyimide obtained by condensing 1.0 mol of 4,4'-diaminodiphenyl ether and 1.0 mol of 3,3'4,4'-benzophenonetetracarboxylic acid anhydride in N-methylpyrrolidone. A 15% by weight N-methylpyrrolidone solution of polyamic acid as a precursor was treated in the same manner as in the above example to form a polyimide film with a thickness of 1000 Å. Thereafter, when a rubbing process was performed in the same manner as in the above embodiment, some peeling occurred from the substrate. Furthermore, when a liquid crystal display cell was produced using a pair of substrates having the above-mentioned rubbed polyimide film, poor alignment was observed in some parts.

As shown in the Examples and Comparative Examples, the polyimide silane polymer coating exhibits very good adhesion to the substrate and can withstand all kinds of rubbing treatment conditions. Furthermore, since the heat resistance of the liquid crystal alignment regulating force is extremely excellent, it is possible to provide a liquid crystal display device that is stable over time, has a long life, and has high characteristics without imposing restrictions on the assembly of liquid crystal elements.

Claims (1)

[Claims] 1. An electrode is provided on the side facing the liquid crystal on a liquid crystal holding substrate, and a carboxylic acid anhydride, a diamine and a general formula are provided on the substrate and the electrode. (In the formula, R is a divalent hydrocarbon group, and R ₁ and R ₂ are monovalent hydrocarbon groups.) Polyimide silane obtained by dehydrating and ring-closing polyamic acid obtained by reacting diaminosilane represented by the formula A liquid crystal holding substrate formed with a polymer film.