JPH10111514A - Forming method of liquid crystal orienting film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a liquid crystal orienting film from a flat and uniform coating film having excellent adhesion property to a substrate by applying and backing a specified polyimide precursor resin on a transparent electrode to form a polymide precursor and/or polyimide resin and then forming a specified solvent-soluble polymide resin film thereon. SOLUTION: A polyimide precursor resin film expressed by formula I is applied and baked to form a polymiode precursor and/or polyimide resin film on a transparent electrode on a substrate. Then a solvent-soluble polyimide resin film expressed by formula II is formed thereon and the resin film surface is subjected to orientation treatment. In formula I, R<1> is a quadrivalent org. group which constitutes tetracarboxylic acid, etc., R<2> is a bivalent org. group which constitutes diamine, and m is a positive integer. In formula II, R<3> is a quadrivalent group which constitutes tetracarboxylic acid, etc., R<4> is a bivalent org. group which constitutes diamine, and (n) is a positive integer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a liquid crystal alignment film in a liquid crystal display device, and more particularly, to a method for forming a liquid crystal alignment film having excellent electrical characteristics of a liquid crystal cell and excellent adhesion to a substrate. It relates to a forming method.

[0002]

2. Description of the Related Art In practice, polyimide resins are often used exclusively for liquid crystal alignment films. However, conventionally, an alignment treatment agent such as a polyimide solution is applied to a substrate surface with a transparent electrode by a method such as spin coating or transfer printing. After that, the surface is generally rubbed to be used as a liquid crystal alignment film. That is, generally, a single layer of polyimide was formed on a substrate and subjected to an alignment treatment such as rubbing to be used as a liquid crystal alignment film.

However, in recent liquid crystal display devices, not only the control of the uniaxial alignment and the tilt alignment angle of the liquid crystal molecules but also the provision of an alignment film material excellent in the electrical characteristics of the liquid crystal device and the adhesion to the device substrate are provided. It is becoming necessary. In the prior art, for example, in controlling the tilt orientation angle of liquid crystal, a polyimide resin precursor disclosed in Japanese Patent Publication No. 6-25834, a dicarboxylic acid having a diamine and an alkyl group having 6 to 20 carbon atoms, or a derivative thereof. There is a method using a liquid crystal alignment treating agent containing a diimide compound precursor precursor which is a compound obtained by reacting the compound. Thereby, the tilt orientation angle of the liquid crystal can be adjusted almost arbitrarily. However, this method does not always satisfy the electrical characteristics of the liquid crystal element. On the other hand, it is known that an excellent voltage holding characteristic can be obtained by using a polyimide material disclosed in Japanese Patent Application Laid-Open No. 2-287324.

[0004] Furthermore, Japanese Patent Application No. 7-24017 filed by the applicant of the present application discloses that a polyimide resin containing a plurality of components is used to exhibit a high and stable tilt orientation angle and a voltage holding characteristic. It is disclosed that a liquid crystal element which is high and has little charge accumulation can be provided. However, such a liquid crystal alignment treating agent containing a plurality of components has a problem that a sufficiently uniform resin film cannot always be obtained depending on the composition due to the compatibility of the components.

[0005]

As described above, the characteristics of a liquid crystal alignment film in a recent liquid crystal display element include not only control of uniaxial alignment and tilt alignment angle of liquid crystal molecules but also electrical property of the liquid crystal element at the same time. It has become necessary to provide an alignment film material having excellent properties and adhesion to a substrate. That is,
It is an object of the present invention to control the uniaxial orientation and the tilt orientation angle of a liquid crystal, and to provide a liquid crystal element having a high charge retention characteristic, a small charge accumulation, a flat and uniform coating film, and an excellent adhesion to a substrate. An object of the present invention is to provide a method for forming a film.

[0006]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, completed the present invention. That is, according to the present invention, the transparent electrode formed on the substrate has the general formula (1)

[0007]

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Wherein R ¹ is a tetravalent organic group forming a tetracarboxylic acid or a derivative thereof, R ² is a divalent organic group forming a diamine, and m is a positive integer. A polyimide precursor resin film represented by formula (2) is applied and baked to form a polyimide precursor and / or polyimide resin film, and then, on the polyimide precursor and / or polyimide resin film, a general formula (2)

[0009]

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Wherein R ³ is a tetravalent organic group constituting a tetracarboxylic acid or a derivative thereof, R ⁴ is a divalent organic group constituting a diamine, and n is a positive integer. The present invention relates to a method for forming a liquid crystal alignment film, comprising forming a solvent-soluble polyimide resin film represented by the formula (1) and then subjecting the surface of the solvent-soluble polyimide resin film to an alignment treatment.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The kind of the polyimide precursor resin represented by the general formula (1) is not particularly limited. In forming this resin film, the baking temperature after application on the substrate can be selected in the range of 50 ° C. to 350 ° C., and particularly in the range of 100 ° C. to 250 ° C. to obtain the effect of the present invention. Is preferred. The film thickness is 100
Practically preferred is ~ 3000 Angstroms, especially 200-2000 Angstroms.

The polyimide precursor resin can be obtained by reacting and polymerizing tetracarboxylic dianhydride or its derivative and diamine in a polar solvent. The tetracarboxylic dianhydride used in the synthesis of the polyimide precursor is not particularly limited, but specific examples thereof include the following.

Aromatic tetracarboxylic acids such as pyromellitic acid, benzophenonetetracarboxylic acid, biphenyltetracarboxylic acid and naphthalenetetracarboxylic acid and their dianhydrides, dicarboxylic acid diacid halides thereof, cyclobutanetetracarboxylic acid, cyclobutane Alicyclic tetracarboxylic acids such as pentanetetracarboxylic acid and cyclohexanetetracarboxylic acid and dianhydrides thereof, dicarboxylic acid diacid halides thereof, and aliphatic tetracarboxylic acids such as butanetetracarboxylic acid and dianhydrides thereof And dicarboxylic acid diacid halides.

These tetracarboxylic acids or derivatives thereof may be used alone or in combination of two or more. Further, specific examples of the diamine used for synthesizing the polyimide precursor resin represented by the general formula (1) include the following, but the present invention is not particularly limited thereto. . p-phenylenediamine 1,4-bis (4-aminophenyl) benzene 4,4'-diaminobiphenyl 3,3'-dimethyl-4,4'-diaminobiphenyl 3,3'-dimethoxy-4,4'-diamino Biphenyl 3,3'-dihydroxy-4,4'-diaminobiphenyl 3,3'-dichloro-4,4'-diaminobiphenyl 3,3'-dicarboxy-4,4'-diaminobiphenyl 4,4'-bis (4-aminophenoxy) biphenyl diaminodiphenylmethane, diaminodiphenyl ether, 2,2-diaminodiphenylpropane, 4,4′-
Diaminodiphenyl sulfone, diaminobenzophenone, 1,3-bis (4-aminophenoxy) benzene,
1,4-bis (4-aminophenoxy) benzene, 4,
4'-di (4-aminophenoxy) diphenylsulfone, 2,2-bis [4- (4-aminophenoxy) phenyl] propane 1,1,1,3,3,3-hexafluoro-2,2-bis Aromatic diamines such as [4- (4-aminophenoxy) phenyl] propane; alicyclic diamines such as diaminodicyclohexylmethane, diaminodicyclohexyl ether, and diaminocyclohexane; 1,2-diaminoethane; 1,3-diaminopropane; And aliphatic diamines such as 1,4-diaminobutane and 1,6-diaminohexane. Furthermore,

[0015]

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(L is an integer of 1 to 10). Further, in order to increase the tilt angle of the liquid crystal, 4,4′-diamino-3-dodecyldiphenyl ether 1-dodecanoxy-2,4-diaminobenzene, 1,1
-Bis (4-aminophenyl) cyclohexane A long-chain alkyl group having 6 to 20 carbon atoms, such as 2,2-bis [4- (4-aminophenoxy) phenyl] octane, or a diamine having a cycloalkyl group You can use it. In addition, one of these diamines
Species or a mixture of two or more species can be used.

A polyimide precursor is obtained by reacting and polymerizing a tetracarboxylic dianhydride or a derivative thereof with a diamine. In this case, a tetracarboxylic dianhydride is generally used as the tetracarboxylic acid derivative used. The molar ratio of tetracarboxylic dianhydride to diamine is 0.8
To 1.2 is preferred. As in the ordinary polycondensation reaction, the degree of polymerization of the produced polymer increases as the molar ratio approaches 1.

If the degree of polymerization is too low, the strength of the polyimide coating film is insufficient, and if the degree of polymerization is too high, the workability at the time of forming the polyimide coating film may deteriorate. Therefore,
The degree of polymerization of the product in this reaction is 0.05 to 5.0 dl / g (at a temperature of 3) in terms of reduced viscosity of the polyimide precursor solution.
0.5 g / dl in N-methylpyrrolidone at 0 ° C)
It is preferred that

The method of reacting and polymerizing the tetracarboxylic dianhydride with the diamine is not particularly limited.
In general, a polyimide precursor is synthesized by reacting tetracarboxylic dianhydride with a diamine in an organic polar solvent such as N-methylpyrrolidone. The reaction temperature at that time is from -20 ° C to 1
Any temperature of 50 ° C, preferably -5 ° C to 100 ° C, can be selected.

Further, as a polymerization method of the polyimide precursor, a usual solution method is preferable. Specific examples of the solvent used in the solution polymerization method include N, N-dimethylformamide,
Examples thereof include N, N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam, dimethylsulfoxide, tetramethylurea, pyridine, dimethylsulfone, hexamethylphosphoramide, and butyrolactone. These may be used alone or as a mixture. Further, even if the solvent does not dissolve the polyimide precursor, the solvent may be used in addition to the above solvent within a range where a uniform solution can be obtained.

For the purpose of further improving the adhesion to the substrate, an additive such as a coupling agent can be added to the obtained resin solution. Next, a solvent having a repeating unit of the general formula (2) of the present invention to be coated on a resin film obtained by applying and firing a solution containing the polyimide precursor resin represented by the general formula (1) A soluble polyimide resin and a method for forming the resin film will be described.

The method for obtaining a solvent-soluble polyimide resin having a repeating unit of the general formula (2) is not particularly limited, but generally, a tetracarboxylic acid or a derivative thereof is reacted with a diamine and polymerized to form a polyimide precursor. ,
Subsequently, it can be obtained by dehydration ring-closing imidization. Also,
In forming this solvent-soluble polyimide resin film,
Baking after applying a solution containing the solvent-soluble polyimide resin on a resin film formed by applying and baking a solution containing the polyimide precursor resin represented by the general formula (1) on a substrate. The temperature can be selected in the range of 50 to 350 ° C., but is particularly preferably in the range of 100 to 250 ° C. in order to obtain the effects of the present invention. The film thickness is 100
Practically preferred is ~ 3000 Angstroms, especially 200-2000 Angstroms.

The tetracarboxylic acid and its derivative constituting R ³ in the general formula (2) are not particularly limited as long as the solubility of the obtained polyimide resin in the organic solvent is not impaired. Specific examples thereof include the following, but the present invention is not particularly limited thereto. Aromatic tetracarboxylic acids such as pyromellitic acid, benzophenonetetracarboxylic acid, biphenyltetracarboxylic acid and naphthalenetetracarboxylic acid and their dianhydrides and dicarboxylic acid diacid halides, cyclobutanetetracarboxylic acid, cyclopentanetetracarboxylic Alicyclic tetracarboxylic acids such as acid, cyclohexanetetracarboxylic acid and 3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalenesuccinic acid, dianhydrides thereof, and dicarboxylic diacids thereof Examples thereof include halides, aliphatic tetracarboxylic acids such as butanetetracarboxylic acid, and dianhydrides thereof, and dicarboxylic acid diacid halides thereof. Of these, alicyclic tetracarboxylic acids and dianhydrides thereof, dicarboxylic acid diacid halides thereof, aliphatic tetracarboxylic acids and dianhydrides thereof, dicarboxylic acid diacid halides and the like are preferable. In particular, 3, 4
-Dicarboxy-1,2,3,4-tetrahydro-1-
Alicyclic tetracarboxylic acids such as naphthalene succinic acid, dianhydrides thereof, and dicarboxylic acid diacid halides are preferred.

These tetracarboxylic acids or derivatives thereof may be used alone or in combination of two or more. Specific examples of the diamine in the repeating unit (2) constituting the solvent-soluble polyimide represented by the general formula (2) are not particularly limited as long as the organic solvent solubility of the obtained polyimide resin is not impaired. Specific examples thereof include the following, but the present invention is not particularly limited thereto. p-phenylenediamine 1,4-bis (4-aminophenyl) benzene 4,4'-diaminobiphenyl 3,3'-dimethyl-4,4'-diaminobiphenyl 3,3'-dimethoxy-4,4'-diamino Biphenyl 3,3'-dihydroxy-4,4'-diaminobiphenyl 3,3'-dichloro-4,4'-diaminobiphenyl 3,3'-dicarboxy-4,4'-diaminobiphenyl 4,4'-bis (4-aminophenoxy) biphenyl diaminodiphenylmethane, diaminodiphenyl ether, 2,2-diaminodiphenylpropane, 4,4′-
Diaminodiphenyl sulfone, diaminobenzophenone, 1,3-bis (4-aminophenoxy) benzene,
1,4-bis (4-aminophenoxy) benzene, 4,
4'-di (4-aminophenoxy) diphenylsulfone, 2,2-bis [4- (4-aminophenoxy) phenyl] propane 1,1,1,3,3,3-hexafluoro-2,2-bis Aromatic diamines such as [4- (4-aminophenoxy) phenyl] propane; alicyclic diamines such as diaminodicyclohexylmethane, diaminodicyclohexyl ether, and diaminocyclohexane; 1,2-diaminoethane; 1,3-diaminopropane; And aliphatic diamines such as 1,4-diaminobutane and 1,6-diaminohexane. Furthermore,

[0025]

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(J is an integer of 1 to 10). Further, in order to increase the liquid crystal tilt alignment angle, R ^{4 in the} repeating unit constituting the solvent-soluble polyimide represented by the general formula (2) is used. As a diamine having a long-chain alkyl group having 6 to 20 carbon atoms, or
Diamines having a cyclalkyl group can be used. Specific examples thereof include the following, but the present invention is not particularly limited thereto. That is, 4,4'-diamino-3-dodecyldiphenyl ether 1-dodecanoxy-2,4-diaminobenzene, 1,1
-Bis (4-aminophenyl) cyclohexane A long-chain alkyl group having 6 to 20 carbon atoms, such as 2,2-bis [4- (4-aminophenoxy) phenyl] octane, or a diamine having a cycloalkyl group Can be mentioned. Also, one or more of these diamines can be used in combination.

Although the method for producing the polyimide resin of the present invention is not particularly limited, generally, the molar ratio of tetracarboxylic acid or a derivative thereof to diamine is 0.50 to 1: 1.
Reaction polymerization in an organic solvent in the range of 00 or 2.00 to 1.01 results in a reduced viscosity of 0.05 to 5.0 dl / g (in N-methyl-2-pyrrolidone at a temperature of 30 ° C., a concentration of 0.5
g / dl) of a polyimide resin precursor, followed by dehydration and ring closure to obtain a polyimide resin.

The reaction polymerization temperature of the tetracarboxylic acid or a derivative thereof with the diamine may be any temperature of -20 to 150 ° C, but is preferably in the range of -5 to 100 ° C. Further, as a polymerization method of the polyimide resin precursor, a solution method is usually suitable. Specific examples of the solvent used in the solution polymerization method include N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-
Examples thereof include pyrrolidone, N-methylcaprolactam, dimethylsulfoxide, tetramethylurea, pyridine, dimethylsulfone, hexamethylphosphoramide, and butyrolactone.

Since the polyimide resin represented by the general formula (2) is soluble in a solvent, a polyimide precursor obtained by reacting tetracarboxylic dianhydride with a diamine is directly imidized in a solution to form a solvent. A soluble polyimide solution can be obtained. When a polyimide precursor is converted into polyimide in a solution, a method of dehydrating and cyclizing by heating is usually employed. The ring closing temperature by this heat dehydration is 100 ° C to 350 ° C, preferably 120 ° C to 25 ° C.
Any temperature of 0 ° C. can be selected.

As another method of converting the polyimide precursor into polyimide, the ring can be chemically closed using a known dehydration ring closing catalyst. The polyimide solution obtained in this manner can be used as it is, or the polyimide solution is precipitated and isolated in a poor solvent such as methanol or ethanol, and the polyimide powder is used. Can be done. The solvent to be redissolved is not particularly limited as long as it can dissolve the obtained polyimide resin. Examples thereof include 2-pyrrolidone, N-methylpyrrolidone, N-ethylpyrrolidone, and N-ethylpyrrolidone.
-Vinylpyrrolidone, N, N-dimethylacetamide,
N, N-dimethylformamide, γ-butyrolactone and the like can be mentioned.

Even a solvent which does not dissolve the polymer by itself can be used in addition to the above solvents as long as the solubility is not impaired. Examples include ethyl cellosolve, butyl cellosolve, ethyl carbitol, butyl carbitol, ethyl carbitol acetate, ethylene glycol and the like. Also, JP-A-7
Solvents disclosed in JP-A-109438, JP-A-7-228839 and the like can also be used.

For the purpose of improving the mechanical strength of the liquid crystal alignment film, an additive such as a coupling agent can be added to the obtained resin solution. In the method of forming a liquid crystal alignment film according to the present invention, a polyimide precursor resin solution represented by the general formula (1) is coated on a transparent electrode and fired to form a polyimide precursor and / or a polyimide-containing resin film. Then, a solvent-soluble polyimide resin represented by the general formula (2) is applied on the polyimide precursor and / or the polyimide resin film, and heated and fired to form a polyimide resin layer. The surface is subjected to an alignment treatment such as a rubbing treatment, and can be used as a liquid crystal alignment film. If the resin layer is turned upside down and the solvent-soluble polyimide resin is used as the lower layer, the effect of the present invention on the charge retention characteristics and charge storage characteristics of the liquid crystal element cannot be obtained.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

[0034]

【Example】

Example 1 20.02 g of 4,4'-diaminodiphenyl ether
(0.1 mol) in N-methylpyrrolidone (NMP) 2
Dissolved in 30 g, and 9.60 g (0.05 mol) of cyclobutanetetracarboxylic dianhydride and 10.90 (0.05 mol) g of pyromellitic dianhydride were added thereto.
The reaction was carried out at room temperature for 4 hours, and the reduced viscosity was 0.9 dl / g (concentration of 0.
5 g / dl) of a polyimide precursor was obtained. This solution was diluted with NMP to a solid concentration of 6% to obtain a polyimide precursor solution (A-1).

3,4-dicarboxy-1,2,3,4-
30.03 g (0.1 mol) of tetrahydro-1-naphthalene succinic dianhydride (hereinafter abbreviated as TDA), 9.72 g (0.09 mol) of p-phenylenediamine, 1
-Hexadecanoxy-2,4-diaminobenzene 3.4
8 g (0.01 mol) in 245 g of NMP at room temperature
The mixture was reacted for 0 hour to prepare a polyimide precursor intermediate solution. To 50 g of this polyimide precursor intermediate solution, 10.8 g of acetic anhydride and 5.0 g of pyridine were added as imidization catalysts, and reacted at 50 ° C. for 3 hours to prepare a polyimide resin solution. This solution was poured into 500 ml of methanol, and the obtained white precipitate was separated by filtration and dried to obtain a white polyimide resin powder. The reduced viscosity ηsp / c of the obtained polyimide resin was 0.43 dl / g (0.5% by weight NMP solution, 30 ° C.).

0.6 g of this powder was dissolved in 9.4 g of γ-butyrolactone to obtain a solvent-soluble polyimide resin solution (B-1) having a solid concentration of 6%. Next, the polyimide precursor solution (A-1) was diluted with NMP and sufficiently stirred to obtain a uniform solution having a total solid content of 4%. The resulting solution (A-1)
Was spin-coated on a glass substrate with a transparent electrode at 3500 rpm and baked at 250 ° C. for 60 minutes to obtain a polyimide film having a thickness of 800 A.

Further, a soluble polyimide resin solution (B-
1) was diluted with γ-butyrolactone and sufficiently stirred to obtain a uniform solution having a total solid content of 2%. The obtained solution was spin-coated on the polyimide film at 3500 rpm,
Baking was performed at 0 ° C. for 60 minutes to form a soluble polyimide film.
After rubbing this coating film with a cloth, two substrates on which a polyimide film was formed in the same manner as above in order to measure the electrical characteristics of the liquid crystal cell, and a 6 μ spacer was sprayed on the film surface, and then the rubbing direction was measured. The liquid crystal (Merck)
MLC-2003) to form a 90 ° twist liquid crystal cell. Observation of the alignment state of the liquid crystal cell with a polarizing microscope confirmed that the liquid crystal cell had a uniform alignment without any defect. When the voltage holding ratio of this liquid crystal cell was measured, it showed a high value of 98% at 23 ° C. and 80% at 90 ° C. In addition, 30 Hz / ± 3 in which DC 3 V is superimposed on this cell.
V rectangular wave is applied for 60 minutes at 23 ° C.
The residual voltage remaining in the liquid crystal cell immediately after turning off V was measured by an optical flicker elimination method.
And the charge accumulation was small.

Further, the polyimide resin film formed on the substrate was sufficiently rubbed, but no peeling of the film from the substrate surface was observed, indicating good adhesion.

Example 2 20.02 g of 4,4'-diaminodiphenyl ether
(0.1 mol) in N-methylpyrrolidone (NMP) 2
Dissolved in 37 g of pyromellitic dianhydride.
4 (0.1 mol) g was added and reacted at room temperature for 4 hours to obtain a polyimide having a reduced viscosity of 1.0 dl / g (concentration of 0.5 g / dl in N-methyl-2-pyrrolidone at a temperature of 30 ° C.). A precursor was obtained.

In the same manner as in Example 1, the polyimide precursor solution (A-2) was diluted with NMP and sufficiently stirred to obtain a uniform solution having a total solid content of 4%. This solution was spin-coated on a glass substrate with a transparent electrode at 3500 rpm,
The resultant was baked at 60 ° C. for 60 minutes to obtain a polyimide film having a thickness of 800 A. Next, using the solvent-soluble polyimide resin solution (B-1) prepared in Example 1, a liquid crystal cell was prepared in the same manner as in Example 1 below. The voltage holding ratio is 97% at 23 ° C., 9
The value is as high as 82% at 0 ° C., and the residual voltage is 0.1 V
And a low value. Also, no peeling due to rubbing was observed, indicating good adhesion.

Example 3 20.02 g of 4,4'-diaminodiphenyl ether
(0.1 mol) in N-methylpyrrolidone (NMP) 1
70 g, cyclobutanetetracarboxylic dianhydride (19.61 g, 0.1 mol) was added thereto, and the mixture was reacted at room temperature for 4 hours to obtain a reduced viscosity of 1.0 dl / g (temperature 3).
0.5 g / N-methyl-2-pyrrolidone at 0 ° C.
dl) A polyimide precursor was obtained.

Thereafter, the polyimide precursor solution (A-3) was diluted with NMP and sufficiently stirred in the same manner as in Example 1 to obtain a uniform solution having a total solid content of 4%. This solution was spin-coated at 3500 rpm on a glass substrate with a transparent electrode,
/ 60 minutes to obtain a polyimide film having a thickness of 800A.
Next, using the solvent-soluble polyimide resin solution (B-1) prepared in Example 1, a liquid crystal cell was prepared in the same manner as in Example 1 below. As a result, the voltage holding ratio was 97 at 23 ° C.
%, A high value of 82% at 90 ° C., and a low residual voltage of 0.4 V.

Comparative Example 1 The polyimide precursor solution prepared in Example 1 was diluted with NMP to a solid concentration of 4% to obtain a polyimide precursor solution (A). Using only this polyimide precursor solution, a polyimide film was formed on a glass substrate with a transparent electrode, and a liquid crystal cell was prepared in the same manner as in Example 1. As a result, the residual voltage showed a low value of 0.3 V, but the voltage holding ratio was as low as 80% at room temperature and 40% at 90 ° C., and a high voltage holding ratio and a low charge accumulation characteristic were obtained. Did not.

Comparative Example 2 0.6 g of the solvent-soluble polyimide powder obtained in Example 1 was γ
-Solvent-soluble polyimide resin solution (B) having a solid content of 4% dissolved in 14.6 g of butyrolactone was obtained. Using only this solvent-soluble polyimide solution (B), a polyimide film was formed on a glass substrate with a transparent electrode.
A liquid crystal cell was prepared in the same manner as described above. As a result, the voltage holding ratio was as high as 99% at room temperature and 90% at 90 ° C., but the residual voltage showed a large value of 1.0 V, and a high voltage holding ratio and low charge accumulation characteristics were obtained. Did not. When the rubbing was performed strongly, the film was peeled off from the substrate, and did not show sufficient adhesion.

Comparative Example 3 A polyimide precursor solution (A-5) was prepared by diluting the polyimide precursor solution prepared in Example 2 to a solid concentration of 4% with NMP.
I got Using only this polyimide precursor solution, a polyimide film was formed on a glass substrate with a transparent electrode, and a liquid crystal cell was prepared in the same manner as in Example 1. As a result, the residual voltage showed a low value of −0.2 V, but the voltage holding ratio was as low as 78% at room temperature and 40% at 90 ° C. I couldn't.

Comparative Example 4 A polyimide precursor solution (A-5) was prepared by diluting the polyimide precursor solution prepared in Example 3 to a solid concentration of 4% with NMP.
I got Using only this polyimide precursor solution, a polyimide film was formed on a glass substrate with a transparent electrode, and a liquid crystal cell was prepared in the same manner as in Example 1. As a result, the residual voltage was 1.4 V, the voltage holding ratio was 90% at room temperature, and 90 ° C.
, And was as low as 40%, and a low charge accumulation characteristic and a high voltage holding ratio could not be obtained.

[0047]

According to the method for forming a liquid crystal alignment film according to the present invention, it is possible to obtain a liquid crystal device having excellent characteristics such as a voltage holding ratio and a charge storage characteristic, and to obtain a sufficient adhesion to a substrate. It is possible to obtain a liquid crystal element having excellent characteristics and to produce the liquid crystal element more efficiently.

Claims (3)

[Claims] A transparent electrode formed on a substrate has a general formula (1) (Wherein R ¹ is a tetravalent organic group constituting a tetracarboxylic acid or a derivative thereof, R ² is a divalent organic group constituting a diamine, and m is a positive integer). A solution containing the polyimide precursor resin to be applied is applied and baked to form a polyimide precursor and / or polyimide resin film, and then, on the polyimide precursor and / or polyimide resin film, the general formula (2) 2] (In the formula, R ³ is a tetravalent organic group constituting a tetracarboxylic acid or a derivative thereof, R ⁴ represents a divalent organic group constituting a diamine, and n is a positive integer.) Forming a solvent-soluble polyimide resin film to be formed and then subjecting the surface of the solvent-soluble polyimide resin film to an alignment treatment. 2. A solvent-soluble polyimide resin of the formula (2), wherein R ³ contains a tetravalent organic group constituting an alicyclic or aliphatic tetracarboxylic acid or a derivative thereof. The method for forming a liquid crystal alignment film according to claim 1, which is a resin. 3. The solvent-soluble polyimide resin represented by the general formula (2), wherein R ³ is 3,4-dicarboxy-1,2,2,3.
3. The method for forming a liquid crystal alignment film according to claim 1, wherein the solvent is a solvent-soluble polyimide resin containing a tetravalent organic group constituting 3,4-tetrahydro-1-naphthalene succinic acid or a derivative thereof.