JPH11228823A - Composition for liquid crystal, oriented film, production of liquid crystal oriented film, liquid crystal oriented film, liquid crystal clamping substrate and liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composition for liquid crystal oriented film hardly exhibiting a viscosity change, provide a method for producing the liquid crystal oriented film, and obtain the liquid crystal oriented film from the composition, a liquid crystal clamping substrate having the oriented film and a liquid crystal display element. SOLUTION: In a composition for liquid crystal oriented film containing a resin for the liquid crystal oriented film and a solvent, 10-80 wt.% of the solvent is N,N-dimethylacetamide. The production of the liquid crystal oriented film is to apply the composition for the liquid crystal oriented film onto a surface on which a resin layer is formed by heating and drying, then rubbing the resin layer. The liquid crystal display element is obtained by installing an electrode on the side facing to the liquid crystal on a liquid crystal clamping substrate and forming the liquid oriented film obtained from the composition for the liquid crystal oriented film on the substrate and electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a composition for a liquid crystal alignment film, a method for producing a 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, N-methyl-2-pyrrolidone (Japanese Patent Application Laid-Open No.
JP-A-1-177440), γ-butyrolactone (JP-A-1-295226, etc.) and 2-butoxyethanol (butyl cellosolve) (JP-A-6-3497).
No. 9) is generally used. Particularly, 2-butoxyethanol is used to ensure good printability.

Usually, a printing method is used to form an alignment film. As the size of a liquid crystal display element increases, wettability at the time of printing is improved, and repelling and shrinkage of a liquid after printing are prevented. A solvent having a low surface tension is added to ensure good printability.

[0004] Solvents having a low surface tension include N-methyl-2-pyrrolidone (surface tension of 41 dyn / cm) and γ-butyrolactone (surface tension of 43.9 dyn / cm), which are solvents used in liquid crystal alignment film compositions. 2-butoxyethanol (surface tension of 27.4 dyn / cm), which has a lower surface tension than that of (2) and is compatible with these solvents.

However, with the recent high quality of liquid crystal display elements, unevenness in film thickness during printing has influenced display characteristics, and it has become necessary to ensure good printability. ing. Since 2-butoxyethanol, which is usually used to ensure good printability, has a hydroxyl group, it decomposes polyimide or polyamide used in the composition for a liquid crystal alignment film by solvolysis to cause a decrease in viscosity. In order to prevent this, it was necessary to store frozen at a low temperature of -5 ° C or lower.

Further, since the printing of the liquid crystal alignment film is performed at room temperature, there is a possibility that the viscosity may decrease during use. Therefore, it is necessary to leave the liquid crystal alignment film composition at room temperature for 24 hours or more continuously. Could not. Therefore, in order to ensure good printability, it is necessary to control the viscosity of the liquid crystal alignment film composition and frequently finely adjust the conditions of the liquid crystal alignment film printing machine depending on the viscosity.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned drawbacks of the prior art, and a composition for a liquid crystal alignment film which does not easily cause a change in viscosity, a method for producing a liquid crystal alignment film, and a liquid crystal alignment film obtained from this composition. Another object of the present invention is to provide a liquid crystal sandwiching substrate having the alignment film and a liquid crystal display element.

[0008]

The present invention relates to a composition for a liquid crystal alignment film containing a resin for a liquid crystal alignment film and a solvent,
The present invention relates to a composition for a liquid crystal alignment film, wherein 10% to 80% by weight of a solvent is N, N-dimethylacetamide. The present invention also relates to the above composition for a liquid crystal alignment film, wherein the resin for a liquid crystal alignment film is a polyimide resin. The present invention also provides
On the surface of the liquid crystal sandwiching substrate on which the electrodes are formed, apply the composition for a liquid crystal alignment film described above, heat and dry to form a resin layer, and then rub the resin layer to form a liquid crystal alignment film. Related to manufacturing method. The present invention also relates to a liquid crystal alignment film formed from any one of the above liquid crystal alignment film compositions.
The present invention also relates to a liquid crystal sandwiching substrate having any one of the above liquid crystal alignment films. The present invention also relates to a liquid crystal display device in which an electrode is provided on a liquid crystal sandwiching substrate on a side facing the liquid crystal, and a liquid crystal alignment film obtained from any of the above-described compositions for a liquid crystal alignment film is formed on the substrate and the electrode. .

An object of the present invention is to improve the printability of the composition for a liquid crystal alignment film. The N, N-dimethylacetamide used in the present invention is used in a solvent of 10 or less to sufficiently lower the surface tension. Preferably, it is used in an amount of at least% by weight. In addition, since the liquid crystal alignment film is usually cured at a temperature of 180 ° C. or higher, the boiling point of the mixed solvent is preferably set to 170 ° C. or higher to prevent the alignment film surface from being roughened due to rapid volatilization of the solvent during the curing. Boiling point solvent (boiling point 166 ° C)
Is preferably used at 80% by weight or less of the solvent.

Since the N, N-dimethylacetamide used in the present invention has a sufficiently low surface tension of 32 dyn / cm, there is no end group of an alcoholic hydroxyl group such as 2-butoxyethanol which is usually used for improving printability. Therefore, a decrease in viscosity during storage can be suppressed. N, N-dimethylacetamide is a good solvent for polyimide resins and polyamide resins.

The other solvent is not particularly limited as long as it dissolves the resin contained in the composition for a liquid crystal alignment film. As described above, a polar solvent having a high boiling point, for example, a solvent having a boiling point of 150 ° C. or more, is used. Preferably, for example, N-methyl-2
One or more of pyrrolidone, N, N-dimethylformamide, dimethylsulfoxide, sulfolane and the like are used. These are all good solvents for the polyimide resin and the polyamide resin.

The resin contained in the composition for a liquid crystal alignment film of the present invention is not particularly limited as long as it functions as a liquid crystal alignment film, and polyimide resins such as polyimide, polyamide imide, polyether imide, and polyimide silicon are used. A polyimide resin such as a polyimide resin precursor such as polyamic acid corresponding to these, or a polyamide resin such as polyamide or polyetheramide is preferable.

The resin used in the present invention is preferably a polyimide resin or a precursor thereof, and is obtained by reacting a diamine compound and a tetracarboxylic dianhydride in a solvent. It is desirable that the diamine compound and the tetracarboxylic dianhydride are reacted in substantially equimolar amounts.

Examples of the diamine compound include 1,4-diaminobenzene, 1,3-diaminobenzene, 1,2-diaminobenzene, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, and 3,3 '.
-Diaminodiphenyl ether, 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, 1,4-diaminocyclohexane, 1,3-diaminocyclohexane, 1,8 -Diaminooctane, 1,6
-Diaminohexane and the like, and these can be used in combination of two or more.

As diaminosilicon, the following general formula (I)

Embedded image (Wherein, R ¹ and R ² each independently represent a carbon number of 1 to 3)
Alkyl group substituted phenylene group which may have a group, represents a divalent hydrocarbon group such as an alkylene group having 1 to 3 carbon atoms which may each be the same or different, R ³
And R ⁴ represent a monovalent hydrocarbon group such as a phenyl group which may have an alkyl group having 1 to 3 carbon atoms as a substituent, an alkyl group having 1 to 5 carbon atoms, and are the same or different. And m is an integer of 1 or more). Diaminosilicon is preferably used in an amount of 0 to 80% by weight, particularly preferably 0 to 50% by weight, based on the total amount of the diamine compound.

The tetracarboxylic dianhydride includes pyromellitic dianhydride, methyl pyromellitic dianhydride, dimethyl pyromellitic dianhydride, 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'-tetra Carboxydiphenyl ether dianhydride, 2,3
3 ', 4'-tetracarboxydiphenyl ether dianhydride, 3,3', 4,4'-tetracarboxybenzophenone dianhydride, 1,4,5,7-tetracarboxynaphthalene dianhydride, 1,2,5 2,6-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'-tetracarboxydiphenylsulfone dianhydride, 3,4,9,10-tetracarboxyperylene dianhydride, 3,3', 4,4'-ethylene glycol bis (phenyl) tetra Carboxylic dianhydride, 1,
2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-butanetetracarboxylic dianhydride and the like, These may be used in combination of two or more.

Examples of the reaction solvent include N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, γ-butyrolactone, dimethylsulfoxide, tetramethylsulfone, and the like.
One or more kinds such as 1,4-dioxane are used. 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, butyl cellosolve, butyl cellosolve acetate, xylene, toluene and the like are used.

The reaction is preferably carried out at 80 ° C. or lower, particularly preferably at 0 to 50 ° C. This produces polyamic acid. The polyamic acid may be partially imidized, and these are collectively referred to as a polyimide resin precursor. Therefore, the reaction temperature is 250 ° C.
Temperature may be increased. The polyimide precursor is preferably soluble in the solvent of the composition for a liquid crystal alignment film. This precursor is completely imidized into a polyimide resin when forming a liquid crystal alignment film-forming resin layer on a substrate, that is, when applying a composition for a liquid crystal alignment film and drying by heating. Is preferred. Further, if the polyimide resin precursor is soluble in the solvent for the liquid crystal alignment film composition, in advance,
It can be imidized. The imidization includes thermal imidization in which the above reaction is carried out at 120 to 250 ° C. and chemical imidization in which the reaction is carried out in the presence of a dehydrating agent. As the dehydrating agent, acid anhydrides such as acetic anhydride, propionic anhydride, and benzoic anhydride, and carbodiimide compounds such as dicyclohexylcarbodiimide are preferable. preferable. At this time, pyridine, isoquinoline, trimethylamine, aminopyridine, imidazole and the like can be used as a dehydration catalyst as required. The dehydration catalyst is preferably used in an amount of 1 to 8 mol per 1 mol of tetracarboxylic dianhydride.

In the present invention, N, N-dimethylacetamide may be used from the time of synthesizing the resin used for the composition for a liquid crystal alignment film, or the viscosity of the composition for a liquid crystal alignment film may be adjusted for coating. In carrying out, N, N-dimethylacetamide may be added.

After the composition for a liquid crystal alignment film of the present invention is applied, it is preferably dried at 100 to 400 ° C. to form a resin layer. An electrode is provided on the liquid crystal sandwiching substrate on the side facing the liquid crystal, and a liquid crystal alignment film obtained from a liquid crystal alignment film composition is formed on the substrate and the electrode to form a liquid crystal display device.

The liquid crystal alignment film of the present invention is formed on a liquid crystal substrate by applying the above-mentioned composition for a liquid crystal alignment film to, for example, an ITO (Individual).
um Tin Oxide) is applied on a substrate such as a glass substrate on which a transparent electrode is formed, and then heated to form a resin layer. The heating temperature is preferably in the range of 100 to 400C, more preferably in the range of 150 to 300C. The heating time is preferably 1 minute to 6 hours, more preferably 1 minute to 3 hours.

The resin 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.

[0023]

Since the composition for a liquid crystal alignment film of the present invention contains N, N-dimethylacetamide having a low surface tension in the solvent component, wettability to a substrate during coating is improved. Further, since it is possible to contain only a good solvent of a polyimide resin or a polyamide resin which is a resin component of the liquid crystal alignment film composition in the solvent, the viscosity stability in such a combination of the resin and the solvent is reduced. Get better.

[0024]

The present invention will be described below with reference to examples. Example 1 2,4 g of 4,4'-diaminodiphenyl ether
(0.1 mol) to 237 g of N-methyl-2-pyrrolidone
, And after stirring sufficiently, pyromellitic dianhydride 2
1.8 g (0.1 mol) was added and reacted at 20 ° C. for 8 hours to obtain a pale yellow viscous polyimide solution. After adjusting the viscosity of this solution, N-methyl-2-pyrrolidone
1 g and 397.1 g of N, N-dimethylacetamide were added, and a composition for a liquid crystal alignment film having a resin concentration of 5% and a viscosity of 30 mPa · s containing N, N-dimethylacetamide at 50% by weight of a solvent was prepared.

The composition for a liquid crystal alignment film was prepared by adding two 640 ×
It is applied on a glass substrate on which an ITO transparent electrode is formed so as to be 200 dots, and heated at 250 ° C. for 30 minutes to remove the solvent and dehydrate the polyamic acid to form a ring having a thickness of 60.
A nm polyimide layer was formed. The surfaces of the polyimide layers on these two glass substrates are rubbed to obtain a liquid crystal sandwiching substrate as a liquid crystal alignment film, and the two polyimide layers are combined so that the rubbing directions are orthogonal to each other,
The cell is assembled by sealing the periphery with an epoxy sealant EN-1000 (trade name of Hitachi Chemical Co., Ltd.), and a liquid crystal to which a chiral agent CB-15 (trade name by Merck) is added so as to form a 90 ° twist. ZLI-1132 (trade name, manufactured by Merck & Co., Inc.) was sealed therein to produce a TN-type liquid crystal display device.

This liquid crystal display element showed good alignment without unevenness when observed by visual observation. When the composition for a liquid crystal alignment film was applied to the above-mentioned glass substrate using an alignment film printing apparatus manufactured by Hitachi Chemical Co., Ltd., there was no cissing in the coating film, no foreign matter, no coating unevenness by visual observation, and good printing. Showed sex. When the composition for a liquid crystal alignment film was stored in a refrigerator at 7 ° C., the viscosity after 6 months was 28 mPa · s, which was almost the same as that immediately after the production.

Comparative Example 1 After the viscosity of the polyimide solution of Example 1 was adjusted, 279.2 g of N-methyl-2-pyrrolidone and 278 g of 2-butoxyethanol were added.
A composition for a liquid crystal alignment film having a resin content of 5% by weight and a viscosity of 30 mPa · s was prepared. Using the composition for a liquid crystal alignment film, a polyimide layer was formed in the same manner as in Example 1.
No unevenness in film thickness was observed in this polyimide layer. Further, the TN type liquid crystal display element prepared by the same method as in Example 1 showed good alignment without any unevenness by visual lighting observation. When the composition for a liquid crystal alignment film in this example was printed with an alignment film printing device manufactured by Hitachi Chemical Co., Ltd., good printability was exhibited. However, the composition for a liquid crystal alignment film used in this example was 7
When stored in a refrigerator at ℃, the viscosity after one month was 23 mPa ·
s and decreased compared to immediately after fabrication.

Comparative Example 2 After the viscosity of the polyimide solution of Example 1 was adjusted, 557.2 g of N-methyl-2-pyrrolidone was added, and N-methyl-2 was added.
A composition for a liquid crystal alignment film having a resin concentration of 5% containing 35% by weight of a pyrrolidone solvent and a viscosity of 30 mPa · s was prepared. Using the composition for a liquid crystal alignment film, a polyimide layer was formed in the same manner as in Example 1, but this polyimide layer showed unevenness in film thickness. Further, the TN-type liquid crystal display element produced by the same method showed unevenness in visual lighting observation. When the composition for a liquid crystal alignment film in this example was printed with an alignment film printing device manufactured by Hitachi Chemical Co., Ltd., the printability was not good. When the composition for a liquid crystal alignment film used in this example was stored in a refrigerator at 7 ° C., the viscosity after 6 months was 29 mPa · s,
The viscosity was almost the same as immediately after the production.

Example 2 N, N, was added to 5.4 g (0.05 mol) of paraphenylenediamine.
After adding 40.2 g of -methyl-2-pyrrolidone and 40.2 g of N, N-dimethylacetamide and sufficiently stirring, 14.7 g of 3,3 ', 4,4'-biphenyltetracarponic dianhydride ( 0.05 mol) and reacted at 30 ° C. for 10 hours to obtain a pale yellow viscous polyimide solution. After adjusting the viscosity of this solution, 31.2 g of N-methyl-2-pyrrolidone and 24% of N, N-dimethylacetamide were added.
5.6 g was added, and a liquid crystal alignment film composition having a resin concentration of 6% and a viscosity of 45 mPa · s containing N, N-dimethylacetamide at 80% by weight of the solvent was prepared.

Example 1 using this liquid crystal alignment film composition
When a polyimide layer was formed in the same manner as in the above, no unevenness in film thickness was observed in this polyimide layer. Further, the TN type liquid crystal display element prepared by the same method as in Example 1 showed good alignment without any unevenness by visual lighting observation. The composition for a liquid crystal alignment film in this example was applied to a glass substrate using an alignment film printing apparatus manufactured by Hitachi Chemical Co., Ltd.
And good printability was exhibited. When the composition for a liquid crystal alignment film used in this example was stored in a freezer at −18 ° C., the viscosity after 6 months was 43 mPa · s, and there was almost no change in the viscosity immediately after the preparation.

Example 3 207.6 g of N-methyl-2-pyrrolidone was added to 20.5 g (0.2 mol) of 2,2-bis (4-aminophenoxyphenyl) propane, and the mixture was sufficiently stirred.
16.4 g (0.2 mol) of 3 ', 4,4'-benzophenonetetracarponic dianhydride was added and reacted at 25 ° C for 6 hours to obtain a pale yellow viscous polyimide solution. After adjusting the viscosity of this solution, N-methyl-2-pyrrolidone 17
1.2 g and 42.1 g of N, N-dimethylacetamide were added, and N, N-dimethylacetamide was added to 10% by weight of the solvent.
A composition for a liquid crystal alignment film having a resin content of 8% and a viscosity of 60 mPa · s was prepared.

Example 1 using this liquid crystal alignment film composition
A polyimide layer is formed in the same manner as described above, rubbed to a 240 degree twist, and then assembled with the polyimide layer facing each other to assemble a combination cell. A chiral agent CB-15 (a product of Merck) is formed to a 240 degree twist ) Was added, and an STN type liquid crystal display device was produced. This liquid crystal display element showed good alignment without unevenness by visual lighting observation.
When the composition for a liquid crystal alignment film in this example was applied to a glass substrate with an alignment film printing device manufactured by Hitachi Chemical Co., Ltd.,
As in Example 1, good printability was exhibited. When the composition for a liquid crystal alignment film used in this example was stored in a freezer at −18 ° C., the viscosity after 6 months was 58 mPa · s, which was almost the same as that immediately after the preparation.

[0033]

When a liquid crystal alignment film is formed from the composition for a liquid crystal alignment film of the present invention and a liquid crystal display device is manufactured using a liquid crystal display substrate having the liquid crystal alignment film, printability and workability are good. And, since it is possible to obtain a liquid crystal display device of good display quality, the composition for a liquid crystal alignment film of the present invention,
It is preferably used for a liquid crystal display element of high display quality.

Claims (6)

[Claims] 1. A liquid crystal alignment film composition comprising a liquid crystal alignment film resin and a solvent, wherein 10% to 80% by weight of the solvent is N, N-dimethylacetamide. 2. The composition for a liquid crystal alignment film according to claim 1, wherein the resin for a liquid crystal alignment film is a polyimide resin. 3. A method for applying a composition for a liquid crystal alignment film according to claim 1 on a surface of a liquid crystal sandwiching substrate on which an electrode is formed, heating and drying to form a resin layer, and then rubbing the resin layer. Characteristic manufacturing method of liquid crystal alignment film. 4. A liquid crystal alignment film formed from the liquid crystal alignment film composition according to claim 1. 5. A liquid crystal sandwiching substrate having the liquid crystal alignment film according to claim 4. 6. A liquid crystal display in which an electrode is provided on the liquid crystal sandwiching substrate on the side facing the liquid crystal, and a liquid crystal alignment film obtained from the composition for a liquid crystal alignment film according to claim 1 or 2 is formed on the substrate and the electrode. element.