JPH09265097A - Composition for liquid crystal alignment film, liquid crystal alignment film, liquid crystal holding substrate and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polyimide oriented film without causing defective orientation due to mechanical or thermal stress by using a specified amt. of an arom. diamine having a methylene group on the principal chain. SOLUTION: At the time of producing a compsn. for a liq. crystal alignment film contg. polyamic acid obtd. by allowing an arom. diamine to react with tetracarboxylic acid anhydride, an arom. diamine having a methylene group on the principal chain is used by 10-55mol% of the arom. diamine. A bendable structure is introduced into the structure of the principal chain of polyimide and mechanical or thermal stress applied to a film to be oriented by treatment after film formation, especially by rubbing is easily relieved. The film is efficiently oriented and liq. crystal orienting property is improved. The pref. amt. of the arom. diamine having a methylene group on the principal chain is 10-50mol%, especially 10-30mol%.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a composition for liquid crystal alignment film, a liquid crystal alignment film, a liquid crystal sandwiching substrate and a liquid crystal display device.

[0002]

2. Description of the Related Art Conventionally, as an alignment film for a liquid crystal display device,
For example, the aromatic polyimide obtained by subjecting 4,4'-diaminodiphenyl ether and pyromellitic dianhydride to a condensation reaction (see Japanese Patent Publication No. 55-10180), and recently, transparency of display elements or liquid crystal To obtain a high pretilt angle, a polyimide obtained by subjecting a diamine having a perfluoroalkyl group and a tetracarboxylic acid having an alicyclic structure or a derivative thereof to a condensation reaction (see JP-A-63-259515), 2 , 2-bis [4- (4-aminophenoxy) phenyl] octane and pyromellitic dianhydride are subjected to a condensation reaction to obtain an aromatic polyimide (see JP-A-64-25126) and the like. There is.

[0003]

In spite of various measures taken in this way, alignment failure may occur due to mechanical stress or thermal stress applied during the film-forming process, especially the rubbing process. there were. The present invention
It is an object of the present invention to provide a polyimide alignment film that does not cause alignment failure due to mechanical stress or thermal stress, and a composition for obtaining this alignment film.

[0004]

The present invention provides a composition for liquid crystal alignment film containing a polyamic acid obtained by reacting an aromatic diamine with a tetracarboxylic acid anhydride, wherein 10 to 55 mol of the aromatic diamine is used. % Is an aromatic diamine having a methylene group on the main chain, which is a composition for a liquid crystal alignment film.

Using this composition for a liquid crystal alignment film, a polyimide layer is formed by coating, drying and dehydration ring closure on a substrate, and then the polyimide layer is rubbed to obtain a liquid crystal alignment film. In addition, a liquid crystal alignment film is formed on the surface on which the electrodes are formed to form a liquid crystal sandwich substrate, and a liquid crystal is sandwiched between two liquid crystal sandwich substrates to form a liquid crystal display element.

Since 10 to 55 mol% of the aromatic diamine is an aromatic diamine having a methylene group on the main chain, a bendable structure is introduced into the polymer main chain structure of polyimide to form an alignment film. It becomes easy to relieve the mechanical and thermal stress applied to the alignment film in the subsequent treatment, especially the rubbing treatment. Therefore, it is considered that the alignment film is efficiently subjected to the alignment treatment and is effective in improving the alignment property.

In order to ease the stress by introducing a bendable structure into the polymer main chain structure, the number of moles of the aromatic diamine having a methylene group on the main chain is 10 mol% of the diamine used in the reaction. The above is necessary. On the other hand, the introduction of a methylene group on the main chain lowers the glass transition point of the polyimide and deteriorates the thermal stability, so the number of moles of the aromatic diamine having a methylene group on the main chain is used for the reaction. The content of diamine is 55 mol% or less. From the viewpoint of the balance between stress relaxation and thermal stability, the aromatic diamine having a methylene group on the main chain is
It is preferably 10 to 50 mol%, and most preferably 10 to 30 mol%.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION When the methylene groups on the main chain are continuous as shown in Chemical formula 1, n is preferably 16 or less, more preferably 14 or less, most preferably 12 or less. preferable. When n is large, the heat resistance of the obtained polyimide becomes poor.

## STR1 ## - (CH _{2) n} - Examples of such aromatic diamines, 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 1,2
Bis [4-aminophenoxy] ethane, 1,3-bis [4-aminophenoxy] propane, 1,4-bis [4
-Aminophenoxy] butane, 1,5-bis [4-aminophenoxy] pentane, di [2- (4-aminophenoxy) ethyl] ether, 1,2-bis [2- (4-aminophenoxy) ethoxy] ethane , Di (2- (2-
[4-aminophenoxy] ethoxy) ethyl) ether, 1,2-bis [4-aminophenyl] ethane, di (4-diamino-3methylphenyl) methane, di (4-
Diamino-3,5-dimethylphenyl) methane, di (4
-Diamino-3-ethyl-5-methylphenyl) methane, di (4-diamino-3,5-diethylphenyl) methane and the like can be mentioned, and these can be used in combination of two or more kinds.

The diamine other than the aromatic diamine having a methylene group on the main chain is not particularly limited, and 4,4'-diaminodiphenyl ether and 1,4-
Diaminobenzene, 1,4-diamino-2,3,5,6
-Tetramethylbenzene, 2,2-bis (4- (4-aminophenoxy) phenyl) propane, 2,2-bis (4- (4-aminophenoxy) phenyl) -1,1,
1,3,3,3-hexafluoropropane, 1,8-diaminooctane and the like can be mentioned, and these can be used in combination of two or more kinds.

The tetracarboxylic dianhydride to be reacted with the diamine includes pyromellitic dianhydride, methylpyromellitic dianhydride, dimethylpyromellitic dianhydride and di (trifluoromethyl) pyromellitic dianhydride. , 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride, 5,5'-dimethyl-3,3', 4,4'-
Biphenyltetracarboxylic dianhydride, p- (3,4-
Dicarboxyphenyl) benzene dianhydride, 3,3 ′,
4,4'-tetracarboxydiphenyl ether dianhydride, 2,3,3 ', 4'-tetracarboxydiphenyl ether dianhydride, 3,3', 4,4'-tetracarboxybenzophenone dianhydride, 1,4 5,7-tetracarboxynaphthalene dianhydride, 1,2,5,6-tetracarboxynaphthalene dianhydride, 3,3 ′, 4,4 ′
-Tetracarboxydiphenylmethane dianhydride, 2,2
-Bis (3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis (3,4-dicarboxyphenyl)
-1,1,1,3,3,3-hexafluoropropane dianhydride, 3,3 ', 4,4'-tetracarboxydiphenyl sulfone dianhydride, 3,4,9,10-tetracarboxyperylene dianhydride Anhydride, 3,3 ', 4,4'-ethylene glycol bis (phenyl) tetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4- Examples thereof include cyclobutanetetracarboxylic dianhydride and 1,2,3,4-butanetetracarboxylic dianhydride, and these may be used in combination of two or more kinds.

An aromatic diamine having a methylene group on its main chain, a diamine other than an aromatic diamine having a methylene group on its main chain, and a tetracarboxylic dianhydride are dissolved in an inert solvent and reacted. It is polyamic acid.

At this time, the total number of moles of the aromatic diamine having a methylene group on the main chain, the total number of moles of diamines other than the aromatic diamine having a methylene group on the main chain, and the tetracarboxylic dianhydride. It is preferable that the total number of moles is approximately equal to the number of moles and the reaction is performed.

As the inert solvent, it is not necessary to dissolve all of the above-mentioned monomers, but it is preferable to dissolve the produced polyamic acid, for example, N-methyl-2-pyrrolidone, N, N-dimethylformamide. , N, N-dimethylacetamide, dimethyl sulfoxide, tetramethyl sulfone, 1,4-dioxane and the like are used alone or in combination. In addition to these solvents, a solvent for improving coatability on a glass substrate can be added before or after the reaction. As these solvents, for example, butyl cellosolve, butyl cellosolve acetate, xylene, toluene and the like are used.

The polyamic acid obtained by the reaction is 100 to
A polyimide is obtained by heating to 400 ° C. and / or chemical treatment with a dehydrating agent such as acetic anhydride. An electrode is provided on the liquid crystal sandwich substrate on the side facing the liquid crystal, and a liquid crystal alignment film obtained from the liquid crystal alignment film composition is formed on the substrate and the electrode to obtain a liquid crystal display element.

To form the polyimide layer of the present invention on the liquid crystal substrate, the solution of the polyamic acid produced by the above reaction is applied to a glass substrate on which a transparent electrode such as ITO (Indium Tin Oxide) is formed in advance. After drying, dehydration and ring closure, a polyimide layer is formed. As a coating method, a dipping method, a printing method, a spraying method or the like is used. The dehydration ring-closing temperature can be arbitrarily selected in the range of 100 to 400 ° C, preferably 150 to 300 ° C. The heating time is 1 minute to 6 hours, preferably 1
Minutes to 3 hours.

The polyimide layer thus formed is used as a liquid crystal alignment film by rubbing the surface. A liquid crystal display device can be obtained by a known method using a liquid crystal display substrate having a liquid crystal alignment film.

[0017]

The present invention will be described below with reference to examples.

Example 1 4,4'-diaminodiphenylmethane 4.0 g (0.0
2 mol) and 1,4-diamino-2,3,5,6-tetramethylbenzene 13.1 g (0.08 mol), N-methyl-2-pyrrolidone 221 g was added and sufficiently stirred, and then pyromellitic When 21.8 g (0.10 mol) of acid dianhydride was added and reacted at 20 ° C. for 8 hours, it became a pale yellow viscous liquid. Adjust the viscosity of this solution to 640 ×
It is coated on a glass substrate on which an ITO transparent electrode is formed so as to have 200 dots, and heated at 250 ° C. for 30 minutes to remove the solvent and dehydrate and ring-close the polyamic acid to a thickness of 60 n.
m polyimide layer was formed. Next, the surface of this polyimide layer was rubbed to obtain a liquid crystal sandwich substrate. The two liquid crystal sandwich substrates were combined so that the rubbing directions were anti-parallel so that the polyimide layers faced each other, and an epoxy sealant (trade name EN-1000 manufactured by Hitachi Chemical Co., Ltd.) was used around the substrates. ), And the cell was assembled. A liquid crystal (using a trade name ZLI-2293 manufactured by Merck & Co., Inc.) was enclosed in the assembled cell to form a liquid crystal cell, and the pretilt angle was measured. As a result, the pretilt angle was 3.1 °. In addition, a cell was assembled in the same manner by making the two liquid crystal sandwich substrates into a 90 ° twist, and a chiral agent (using Merck's trade name CB-15 was used) was added to the assembled cell. Liquid crystal (trade name ZLI-2293 manufactured by Merck & Co., Inc.) was enclosed.
The obtained liquid crystal display element showed good alignment.

Example 2 Di (4-diamino-3-ethyl-5-methylphenyl)
Methane 14.1 g (0.05 mol) and 1,4-diamino-2,3,5,6-tetramethylbenzene 8.2 g
(0.05 mol) N-methyl-2-pyrrolidone 324
After adding g and stirring sufficiently, 21.8 g (0.10 mol) of pyromellitic dianhydride was added and reacted at 25 ° C. for 12 hours, resulting in a pale yellow viscous liquid. Using this solution, a liquid crystal cell was obtained and the pretilt angle was measured in the same manner as in Example 1 except that the temperature of solvent removal and the dehydration ring closure of the polyamic acid was 270 ° C. and the time was 1 hour. It was 3 °. In the same way, 90 °
A twisted liquid crystal display device was formed. The liquid crystal display element showed good alignment.

Example 3 4,4'-diaminodiphenylmethane 6.0 g (0.0
3 mol) and 2,2-bis (4- (4-aminophenoxy) phenyl) -1,1,1,3,3,3-hexafluoropropane 36.3 g (0.07 mol) in N-methyl- After adding 316 g of 2-pyrrolidone and stirring sufficiently,
10.9 g (0.05 mol) of pyromellitic dianhydride and 16.1 g (0.05 mol) of 3,3 ′, 4,4′-tetracarboxybenzophenone dianhydride were added and reacted at 30 ° C. for 5 hours. Then, it became a pale yellow viscous liquid. A liquid crystal cell was obtained using this solution in the same manner as in Example 2, and the pretilt angle was measured and found to be 4.3 °.
Further, a 90 ° twist liquid crystal display element was formed by the same method. The liquid crystal display element showed good alignment.

COMPARATIVE EXAMPLE 1 217 g of N-methyl-2-pyrrolidone was added to 16.4 g (0.10 mol) of 1,4-diamino-2,3,5,6-tetramethylbenzene, and after sufficiently stirring, Add 21.8 g (0.10 mol) of pyromellitic dianhydride and add 2
After reacting at 0 ° C. for 8 hours, it became a pale yellow viscous liquid. When a liquid crystal display element was produced using this solution in the same manner as in Example 2, defective alignment occurred.

Comparative Example 2 Di (4-diamino-3-ethyl-5-methylphenyl)
Methane 16.9 g (0.06 mol) and 1,4-diamino-2,3,5,6-tetramethylbenzene 6.6 g
N-methyl-2-pyrrolidone 332 (0.04 mol)
After adding g and stirring sufficiently, 21.8 g (0.10 mol) of pyromellitic dianhydride was added and reacted at 25 ° C. for 12 hours, resulting in a pale yellow viscous liquid. When a liquid crystal display element was produced using this solution in the same manner as in Example 2, defective alignment occurred.

Comparative Example 3 51.9 g (0.10 mol) of 2,2-bis (4- (4-aminophenoxy) phenyl) -1,1,1,3,3,3-hexafluoropropane was added with N-. Methyl-2-pyrrolidone (359 g) was added, and after sufficiently stirring, 10.9 g (0.05 mol) of pyromellitic dianhydride and 3,3 ',
4,4'-Tetracarboxybenzophenone dianhydride 1
When 6.1 g (0.05 mol) was added and the mixture was reacted at 30 ° C. for 5 hours, it became a pale yellow viscous liquid. When a liquid crystal display element was produced using this solution in the same manner as in Example 2, defective alignment occurred.

[0024]

When a liquid crystal alignment film is formed from the composition for liquid crystal alignment film of the present invention and a liquid crystal display device is prepared using a liquid crystal display substrate having this liquid crystal alignment film, the alignment property becomes good and good. It is possible to obtain a liquid crystal display element having excellent display quality.

Claims (4)

[Claims] 1. In a composition for a liquid crystal alignment film containing a polyamic acid obtained by reacting an aromatic diamine and a tetracarboxylic acid anhydride, 10 to 55 mol% of the aromatic diamine is a methylene group on the main chain. A composition for liquid crystal alignment film, which is an aromatic diamine having 2. A liquid crystal alignment film obtained by applying the composition for liquid crystal alignment film according to claim 1 to a substrate, drying and dehydration ring closure to form a polyimide layer, and then rubbing the polyimide layer. 3. A liquid crystal sandwich substrate having the liquid crystal alignment film according to claim 2 formed on the surface on which the electrodes are formed. 4. A liquid crystal display device having a liquid crystal sandwiched between the liquid crystal sandwich substrates according to claim 3.