JPS63100426A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To obtain a liquid crystal display element which is free from a disturbance in orientation and blurring of characters after a deterioration test even if the element is subjected to a heat treatment at a low temp. by using a heat- treated film of a compsn. consisting of specific polyamic acid, colloidal silica, and tertiary amine compd. as an oriented film. CONSTITUTION:The oriented film is formed of the heat-treated film consisting of the polyamic acid having the structural unit expressed by formula I, the tertiary amine compd. and the colloidal silica. In formula I, R1 is a trivalent or tetravelent org. group, R2 is a divalent org. group, (m) is 1 or 2. The tertiary amine has the effect of dispersing silica uniformly into the polyimide film and to improve the transparency of the film and has the catalytic effect to accelerate imide ring closure. The silica has the effect of capturing the solvent and ionic impurities remaining in a slight amt. in the oriented film as a result of the heat treatment effected at the low temp. and to prevent diffusion. The liquid crystal display element which is free from the disturbance in the orientation and the blurring of the characters after the deterioration treatment in spite of the heat treatment at the low temp. is thereby obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal display element, and more particularly to a liquid crystal display element using a specific alignment control film.

[Prior Art] Conventionally, liquid crystal display elements, especially nematic liquid crystal display elements that operate under the action of an electric field and utilize an electro-optic effect, have been manufactured using inorganic materials such as vapor-deposited films of silicon oxide, and organic polymer materials such as polyimide. was known as an orientation control film.

Although inorganic materials have advantages such as having no factors that adversely affect liquid crystals when in contact with liquid crystals and having good heat resistance, they have the disadvantage of high manufacturing costs.

For this reason, organic polymer materials, which are superior in mass production and therefore have low manufacturing costs, are currently the mainstream.

Among organic polymer materials, polyimide can be cited as a material that forms an alignment film with relatively excellent alignment properties. For example, it is obtained by coating polyamic acid, which is a polyimide precursor obtained by condensation of pyromellitic dianhydride and 4°4°-diaminodiphenyl ether as described in JP-A No. 51-65960, and then ring-closing it by heating. Polyimide has fairly good orientation uniformity and durability in deterioration tests. However, many polyimides, typified by polyimides obtained from pyromellitic dianhydride and diaminodiphenyl ether, are
This method requires an imide ring-closing temperature of 50° C., and there is a problem in that the substrate (glass) is damaged due to thermal strain during this heat treatment step.

In addition, to prevent damage to the substrate, the imide ring-closing temperature was set to 2.
When lowered to 50℃, deterioration test (70℃, 95%RH, 1
00 hours), the orientation was disturbed and there was a problem that characters were blurred.

[Problems to be Solved by the Invention] It is an object of the present invention to solve the above-mentioned problems and provide a liquid crystal display element in which imide ring closure can be performed at low temperatures and alignment is not disturbed in a deterioration test.

[Means for solving the problem] (1) In a liquid crystal display element having a liquid crystal alignment film on a substrate on which a transparent electric bridge is formed, the alignment film has A, a general formula, where R1 is Trivalent or tetravalent organic group, R2 is 2
The valent organic group, m, is 1 or 2. This is a liquid crystal display element characterized in that it is formed of a heat-treated film comprising a polyamic acid having the structural unit [I] represented by B, a tertiary amine compound, and C, colloidal silica.

In the present invention, the polyamic acid having the structural unit [I] refers to a polymer having a structure represented by the general formula described above and having an imide ring or other cyclic structure (Ishitoshi, polyimide polymer ).

In the above structural unit [I], R is a trivalent or tetravalent organic group having at least two or more carbon atoms. In view of the heat resistance of the polyimide polymer, R1 preferably has a structure in which the bond to the carbonyl group of the polymer main chain is directly formed through an aromatic ring or an aromatic heterocycle. Therefore,
R1 is preferably a trivalent or tetravalent group containing an aromatic ring or an aromatic heterocycle and having 6 to 30 carbon atoms.

A more preferable specific example of R1 is -o--o-
o-o-, -o-sO=÷.

(In the formula, the bond represents a bond with the carbonyl group of the polymer main chain, and the carboxyl group is located at the ortho position to the bond, but this bond is not shown in the above structural formula).

Examples include, but are not limited to, the following.

Further, in the polymer having the structural unit [1], R1 may be composed of only one type among these, or may be a copolymer composed of two or more types.

Particularly desirable R1 is (however, in the formula, the definition of the bond is the same as above).

In the above structural unit [I], R2 is an organic group of 2fi[fi having at least two or more carbon atoms, but from the viewpoint of heat resistance when used as a polyimide polymer, it is difficult to combine it with the amide group of the polymer main chain. Those having a structure in which the bond is directly formed from an aromatic ring or an aromatic heterocycle are preferred. Therefore,
R2 is preferably a divalent group containing an aromatic ring or an aromatic heterocycle and having 6 to 30 carbon atoms.

Preferred specific examples of R2 include (in the formula, the bond represents a bond with the amide group of the main chain). Further, these may have substituents such as a 7-mino group, an amide group, a carboxyl group, a sulfonamide group, etc., as long as they do not adversely affect the heat resistance of the polyimide polymer. Particularly preferred examples of those having each of these substituents are listed below.

In the polymer having the structural unit [11], R2 may be composed of only one type among these, or may be a copolymer composed of two or more types.

Furthermore, in order to improve the adhesiveness of the polyimide polymer, it is also possible to copolymerize an aliphatic group having a siloxane structure as R2 within a range that does not reduce the heat resistance. Preferred specific examples are listed.

Specific examples of polymers containing structural unit [I] as main components include pyromellitic dianhydride and 4,4'-diaminodiphenyl ether, pyromellitic dianhydride and 3.3', 4.4'- Benzophenone tetracarboxylic acid and 4,4°-diaminodiphenyl ether, 3.3',4,4°-benzophenonetetracarboxylic dianhydride and 4,4°-diaminodiphenyl ether, 3
．． 3°, 4.4-biphenyltetracarboxylic dianhydride and 4.4-diaminodiphenyl ether, 3.3°, 4
, 4-biphenyltetracarboxylic dianhydride and 3.
3',4,4°-benzophenonetetracarboxylic dianhydride and 4,4°-diaminodiphenyl ether, pyromellitic dianhydride and 3,3°-diaminodiphenylsulfone, pyromellitic dianhydride and 3,3 °,4,4°-benzophenonetetracarboxylic dianhydride and 3,3°- or 4,4°-)diaminodiphenylsulfone, 3.3
',A,/l°-benzophenonetetracarboxylic dianhydride and 3,3°-(or 4,4°-)diaminodiphenylsulfone, 3.3',4.4°-biphenyltetracarboxylic dianhydride and 3.3'-(or 4.4'-)diaminodiphenylsulfone, 3.3°, 4. , lo-biphenyltetracarboxylic dianhydride and 3.3', 4.4°-benzophenonetetracarboxylic dianhydride and 3.3'-(or 4.4
'-) Diaminodiphenylsulfone, pyromellitic dianhydride and 4,4°-diaminodiphenyl ether and bis(3-aminopropyl)tetramethyldisiloxane, pyromellitic dianhydride and 3.3',4.4- Benzophenone tetracarboxylic dianhydride and 4,4-diaminodiphenyl ether and bis(3-aminopropyl)tetramethyldisiloxane, 3.3°, 4,4-benzophenone tetracarboxylic dianhydride and 4,4-diaminodiphenyl ether and bis(3-aminopropyl)tetramethyldisiloxane, 3.3°, 4,4°-biphenyltetracarboxylic dianhydride and 4,4°-diaminodiphenyl ether and bis(3-aminopropyl)tetramethyldisiloxane , 3.3°, 4,4°-biphenyltetracarboxylic dianhydride and 3.3', 4.4-benzophenonetetracarboxylic dianhydride, 4.4-diaminodiphenyl ether and bis(3-aminopropyl) Tetramethyldisiloxane, pyromellitic dianhydride and 3,3'-(or 4,4°-
) diaminodiphenylsulfone and bis(3-aminopropyl)tetramethyldisiloxane, pyromellitic dianhydride and 3,3',4,4'-benzophenonetetracarboxylic dianhydride and 3,3°-(or 4 .4'-
) diaminodiphenylsulfone and bis(3-aminopropyl)tetramethyldisiloxane, 3.3°, 4.4'-benzophenonetetracarboxylic dianhydride and 3.3'-(or a, a'-)diaminodiphenyl Sulfone and bis(3-aminopropyl)tetramethyldisiloxane, 3.3°, 4,4°-biphenyltetracarboxylic dianhydride and 3.3′-(or 4,4°-)diaminodiphenylsulfone and bis (3-Aminopropyl)tetramethyldisiloxane, 3.3°, a, a'-biphenyltetracarboxylic dianhydride and 3,3°, 4,4-benzophenonetetracarboxylic dianhydride and 3.3' A polyamic acid synthesized from -(or 4,4°-)diaminodiphenylsulfone, bis(3-aminopropyl)tetramethyldisiloxane, etc. is preferably used.

The tertiary amine compound in the present invention has the following general formula [A] (where R3, R4, and R5 are hydrocarbon groups having 1 to 30 carbon atoms, and each of R3 to R5 has the same It can contain various substituents and bonding groups, and those represented by n is 1, 2.3 are preferably used.

Preferred specific examples include trimethylamine, triethylamine, trilopropylamine, trilopropylamine, methyldiethylamine, dimethyl-〇-propylamine, N,N-dibutyl-2-ethylhexylamine, N-methyldiallylamine, and 3-dimethylamine. Brovanol, N-isobutylgetanolamine, dimethyl-3-dimethoxypropylamine, N,N,N',N'-tetramethyl-1
, 2-diaminoethane, N, N, N', N'-tetramethyldiaminopropane, N, N, N', N'-tetraallyl-1,4-diaminobutane, N, N, N', 14°
-Pentamethyldiethylenetriamine, N,N-dimethylbenzylamine, dimethylaminoacetaldehyde diethyl acetal, 2-dimethylaminoethyl acetate, dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, diethylaminoethyl methacrylate, diethylaminoethyl acrylate, etc. but not limited to.

In particular, when a highly basic aliphatic tertiary amine is used, 1
This is preferable because the transparency of 111 is further improved.

Particularly preferred specific examples include, but are not limited to, triethylamine, tripropylamine, tributylamine, 2-dimethylaminoethyl acetate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl acrylate, diethylaminoethyl acrylate, etc. Not done.

These compounds may be used alone or in combination
It may be used as a mixture of more than one species.

In addition, primary amines, secondary amines, quaternary amines, and organic basic compounds such as pyridine derivatives and imidazole derivatives may be used within the range that does not adversely affect coating properties, solution stability, and coating film transparency. may be added.

The amount of tertiary amine added is preferably 0.3 to 4.0 equivalents, more preferably 0.5 to 3.0 equivalents, based on the carboxyl group of the polyamic acid. It is better to add O. If the amount is less than the lower limit, the effect of promoting imide ring closure will not be sufficiently observed, and if the amount is more than the upper limit, A or B.

The viscosity stability of the composition consisting of C becomes worse during storage.

The colloidal silica used in the present invention is a colloidal solution of high molecular weight silicic anhydride. One example of this is commercially available silica sol, and the dispersion medium is usually water, but organosilica sol dispersed in an organic solvent is also commercially available (for example, 03CA manufactured by Catalysts & Chemicals Co., Ltd.).
L).

Silica sol dispersed in an organic solvent is prepared by replacing water, which is a dispersion medium of an aqueous silica sol, with an organic solvent.

Replacement of the dispersion medium can be carried out by adding an organic solvent to the aqueous silica sol and distilling off the water. Depending on the type of solvent, lower alcohol may be added,
In some cases, the surface of the silica particles is partially esterified.

From the viewpoint of compatibility with polyamic acid, organosilica sol dispersed in a separate solvent is desirable. Particularly preferred is an organosilica sol dispersed in an aprotic polar solvent such as dimethylformamide, dimethylacetamide, or N-methyl-2-pyrrolidone, which is a solvent for polyamic acid.

Further, other colloidal silica that can be used in the present invention includes colloidal silica synthesized from alkyl silicate, and in this case, a long-life effect of the liquid crystal display element can be expected.

Here, the alkyl silicate refers to the general formula Si (OR
>4 (wherein R is a hydrocarbon having 1 to 15 carbon atoms).

If R has a large number of carbon atoms, the amount of silica produced will decrease, so R is more preferably a hydrocarbon having 1 to 3 carbon atoms.

From the viewpoint of safety for the human body, tetraethyl silicate represented by S i (OCH2CH3)4 is particularly preferred as the alkyl silicate.

Colloidal silica synthesized from alkyl silicate used in the present invention is produced by hydrolysis condensation of alkyl silicate. For example, tetraethyl silicate is added to a mixture of methanol and aqueous ammonia, and then hydrolysis condensation is performed. Then, a suitable dispersion medium is added and methanol and ammonia are distilled off. Regarding the temperature conditions during distillation, it is preferable to carry out the distillation at a low temperature, for example, at a temperature of 60° C. or lower, in order to prevent agglomeration of colloidal silica.

As the dispersion medium, an organic solvent is preferable from the viewpoint of compatibility with polyamic acid. In particular, dimethylacetamide, dimethylformamide, N-methyl-
Aprotic polar solvents such as 2-pyrrolidone are preferred, more preferably N-methyl-2-pyrrolidone.

The concentration of colloidal silica synthesized from alkyl silicate can be adjusted by adjusting the amount of dispersion medium added.
A range of 0 wt% is preferred, but it is not limited to this range.

The amount of colloidal silica added, 5 (wt%) is 1 to 6Q (
vt%) is preferred, and more preferably 5 to 5Q (wt
%) is good. In addition, the amount of colloidal silica added is 3 (wt
%) is given by the following formula.

5i02 amount (0) S (wt%) = x
100Si02 amount (g) + polyamic acid amount (()) When adding less than the lower limit, the effect of improving properties is not significant, and when adding more than the upper limit, the coating film forming ability is poor. Become.

Next, an example of a method for manufacturing a liquid crystal display element according to the present invention will be described.

The polyamic acid having the structural unit [I] in the present invention is preferably produced by reacting a diamine and a tetracarboxylic dianhydride in an organic solvent at a temperature of about 15°C to 50°C for several hours.

A tertiary amine compound and colloidal silica are added to and mixed with the resulting polymer solution, the viscosity and concentration are adjusted with a diluent, and the solution is filtered before use.

Examples of organic solvents and diluents used in this reaction are:
Examples include aprotic polar solvents such as N-methyl-2-pyrrolidone and N,N-dimethylacetamide.

Next, it is coated on the glass substrate provided with the S i 02 layer and the conductive layer by a method such as a spin coating method, and then heat-treated to form a heat-treated film according to the present invention.

It is usually applied to a film thickness of around 1000, and
Heat treatment is performed at a temperature of 300°C to 300°C for 30 to 60 minutes. The alignment film can be obtained by lightly rubbing the heat-treated film with a cotton cloth or the like. The two substrates thus obtained are combined to create a cell.

As the liquid crystal sealed in the liquid crystal display element, any known liquid crystal may be appropriately selected. It may be a nematic type liquid crystal or a ferroelectric smectic type liquid crystal.

In the manner described above, the liquid crystal display element of the present invention can be obtained.

[Function] The present invention uses a heat-treated film of the polyamic acid and co-composition of the structural unit [I] as an alignment film, so that even after heat treatment at a low temperature, alignment disturbance and force are dispersed after a deterioration test. It has the effect of improving the transparency of the membrane and the catalytic effect of promoting imide ring closure.

Further, since silica is heat-treated at a low temperature, it has the effect of capturing trace amounts of solvent and ionic impurities remaining inside the alignment film and preventing their diffusion.

In general, when colloidal silica synthesized from alkyl silicate is used, metal impurities and halides are not mixed in, so when a heat-treated film of a composition containing this is used as an alignment film, metal impurities and halides are not mixed in. Because halides do not seep into the liquid crystal,
It is expected that the lifespan of liquid crystal display elements will be extended.

[Effects of the Invention] The present invention uses a heat-treated film of a composition consisting of polyamic acid of structural unit N], colloidal silica, and a tertiary amine compound as an alignment film, so that it does not deteriorate even when heat-treated at a low temperature. After the test, it is possible to obtain a liquid crystal display element free from alignment disturbances and character smearing.

Furthermore, when a heat-treated film of a composition containing colloidal silica synthesized from an alkyl silicate is used, it is expected that the life of the liquid crystal display element will be extended.

[Example code] The present invention will be explained based on examples.

Examples 1 to 5 110 g of diaminodiphenyl ether was dissolved in 278 g of N-methylpyrrolidone to prepare an amine solution. pyromellitic anhydride 120Q to dimethylacetamide 30Q
Disperse in 8g and then add methylpyrrolidone 184Q
was added and dissolved to obtain an acid solution. By adding an acid solution to an amine solution and reacting at 60"C for 3 hours, 30
A solution (A) of 60 poise at .degree. C. was obtained.

A tertiary amine compound as shown in Table 1 was added to the solution (A) in an amount equivalent to the polyamic acid, and γ-aminopropyltriethoxysilane was added to the solution (A) as an adhesion improver.
5g was added and mixed. Colloidal silica dispersed in tomethyl-2-pyrrolidone (manufactured by Catalysts Kasei Kogyo Co., Ltd., trade name 03CAL) was added in the amount shown in Table 1, and mixed with tomethyl-2-pyrrolidone to adjust the viscosity to 5 cps at 25°C. 2-
It was diluted with pyrrolidone and filtered to obtain a coating solution.

It was coated on a glass substrate with an In2O3 transparent electrode using a spinner and heated at 250° C. for 1 hour to form a film with a thickness of 1000 μm. An alignment film was formed by rubbing in a certain direction with a cotton cloth. The polyimide in the sealed portions of the two glass substrates thus obtained was removed by plasma etching, and then sealed using epoxy resin to form cells. Next, thick-type nematic liquid crystal was injected, and a liquid crystal display element was completed. After being left in an atmosphere of 70° C. and 95% RH for 100 hours, the light was turned on and the occurrence of bleeding was examined. The results are shown in Table 1.

Comparative Example 1 The same procedure as in Example 1 was carried out except that the tertiary amine compound and colloidal silica were not added.

The results are shown in Table 1.

Comparative Example 2 The same procedure as in Example 1 was carried out except that no colloidal silica was added. The results are shown in Table 1.

Comparative Examples 3 to 4 In Example 1, instead of the tertiary amine compound, diallylamine (secondary amine) and primary n-butylamine (
However, a uniform coating film could not be obtained and a liquid crystal display element could not be formed.

As is clear from the above, the liquid crystal display element of the present invention has two
Under the heat treatment condition of 50°C, it shows good characteristics even after the deterioration test.

Examples 6 to 10 Examples 1 to 5 were carried out in the same manner as in Examples 1 to 5, except that the colloidal silica in Examples 1 to 5 was changed to colloidal silica synthesized from an alkyl silicate described below.

The implementation conditions and results are shown in Table 2.

As a result of metal analysis of the polymer solution of Example 7, sodium ions were 0.3 pDm or less, and chlorine ions were 'ippm.
It was below. This is on the same level as a polymer solution that does not contain colloidal silica, and is found to be an amount that does not adversely affect insulation and reliability.

As is clear from Table 2, compositions using colloidal silica synthesized from alkyl silicate retain good properties even after deterioration tests, and are substantially free of sodium ions and chloride ions. Reliability can be definitely improved compared to those using colloidal silica.

(Synthesis of colloidal silica) 100 parts of methanol, ammonia water (ammonia concentration 2
5%>10 parts of tetraethylsilicate are added with stirring at 30°C. After standing in this state for 60 minutes, 15 parts of N-methyl-2-pyrrolidone was added, and then treated under reduced pressure at 60°C to distill off ammonia, alcohol and water, and a transparent silica sol containing N-methyl-2-pyrrolidone as a solvent was obtained. obtain.

Claims (1)

[Claims] (1) In a liquid crystal display element that has a liquid crystal alignment film on a substrate on which transparent electrodes are formed, the alignment film has a general formula ▲ mathematical formula, chemical formula, table, etc. ▼・・・・・・［I
] (However, in the formula, R_1 is a trivalent or tetravalent organic group, R_2
is a divalent organic group, and m is 1 or 2. 1. A liquid crystal display element comprising a heat-treated film comprising a polyamic acid having a structural unit [I] represented by B, a tertiary amine compound, and C, colloidal silica.