JP2001115019A - Aqueous solvent solution of polyimide precursor and oriented liquid crystal film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous solvent solution of a polyimide precursor free from polyamic acid. SOLUTION: The aqueous solvent solution of a polyimide precursor is produced by dissolving a compound expressed by general formula (1) (R1 is a bivalent organic group) and a compound expressed by general formula (2) (R2 is a tetravalent organic group; R3 and R4 are each H or a 1-12C alkyl) in an aqueous solvent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous solution of a polyimide precursor obtained by dissolving an acid anhydride and a diamine in water in an unreacted state, and to a polyimide film and a liquid crystal alignment film produced from the solution.

[0002]

2. Description of the Related Art Polyimides are usually obtained by thermally or chemically dehydrating a polyamic acid obtained by ring-opening polyaddition of a diamine and a dianhydride of a tetracarboxylic acid to obtain imidization. be able to. Polyimide has excellent heat resistance, solvent resistance, mechanical properties, electrical properties, etc.
It is used as a film or molded body in various fields such as electronics, machinery, aerospace, etc.In particular, coatings using polyimide are used as semiconductors, liquid crystal alignment films, protective films for electronic components, insulating films, etc. There is much demand. The coating agent using a polyimide, a polyamic acid that is a precursor of the polyimide, N-
Precursors dissolved in organic solvents such as methyl-2-pyrrolidone and N, N-dimethylacetamide, and solution systems in which polyimides obtained by dehydrating and ring-closing (imidizing) polyamic acid are dissolved in organic solvents. Is done. Solution-based coating agents have excellent storage stability, and the polyimide film has the advantage that it can be obtained by drying the coating film and firing it at a relatively low temperature. However, a film obtained from a solution-based coating agent has a disadvantage of poor solvent resistance. Further, generally, there are many polyimides which are hardly soluble or insoluble in an organic solvent, and there is a problem that the number of polyimides which can be used for a solvent-based coating agent is small. By the way, in order to obtain a polyimide soluble in an organic solvent, it is necessary to give special consideration to the molecular structure in the process of synthesizing the polyimide. For these reasons, when obtaining a polyimide film, a precursor-based coating agent is often used. Films obtained from precursor-based coatings have the advantage of very high solvent resistance. But,
Since the conventional precursor coating agent employs a special organic solvent as a dispersion medium, it can be applied only to a substrate which is not affected by the organic solvent. In addition, in order to imidize the polyamic acid, after drying the coating film, 300
It must be fired at a high temperature of at least ℃ for a long time. In addition, because polyamic acids are susceptible to hydrolysis,
Conventional precursor coating agents are liable to be degraded with time and lack storage stability.

[0003]

SUMMARY OF THE INVENTION One of the objects of the present invention is to eliminate the disadvantages of conventional polyimide precursor-based coating agents without losing their advantages, to provide excellent storage stability, and to attack the substrate. Another object of the present invention is to provide a new type of polyimide precursor aqueous solvent solution that can obtain a polyimide film by firing at a relatively low temperature. Another object of the present invention is to provide a polyimide film or a liquid crystal alignment film obtained by using the above-mentioned polyimide precursor aqueous solvent solution.

[0004]

SUMMARY OF THE INVENTION The polyimide precursor aqueous solvent solution according to the present invention comprises a conventional polyimide precursor-based coating agent comprising a polyamic acid which is a reaction product of a diamine and an acid anhydride in a special organic solvent. In contrast to the solution, a diamine represented by the following general formula (1) and a tetracarboxylic acid or a derivative thereof represented by the following general formula (2) are dissolved in an aqueous solvent.

Embedded image (In the formula, R ¹ represents a divalent organic group.)

Embedded image (In the formula, R ² represents a tetravalent organic group, and R ³ and R ⁴ each independently represent hydrogen or an alkyl group having 1 to 12 carbon atoms.)

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The polyimide precursor aqueous solvent solution of the present invention generally comprises a diamine represented by the general formula (1) and a tetracarboxylic acid or a derivative thereof represented by the general formula (2) in substantially equimolar amounts. To dissolve in an aqueous solvent as a dispersion medium. And in an aqueous solvent,
It is presumed that the compound of the general formula (1) and the compound of the general formula (2) form a salt with the former amino group being —NH ₃ ⁺ and the latter carboxyl group being —COO—. This salt is considered to be the identity of the polyimide precursor. The polyimide precursor aqueous solvent solution of the present invention does not contain any amic acid units or imide groups.

The diamine represented by the general formula (1) includes aliphatic diamines, aromatic diamines, and aliphatic aromatic diamines. Examples of the aliphatic diamine include 1,2-diaminoethane, 1,2-diaminopropane, 1,3-diaminopropane, 1,4-diaminobutane, 1,3-diaminopentane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 1,11-diaminoundecane, 1,12-diaminododecane, 2- Methyl-1,5-diaminopentane, 4,4-dimethylheptamethylenediamine, di (aminomethyl) cyclohexane, diaminodicyclohexylmethane, diaminodicyclohexyl ether, diaminocyclohexane, diaminohexahydrodiphenyl, isophoronediamine, m-
Xylylenediamine, p-xylylenediamine aminopropyl-terminated dimethylsiloxane oligomer, and the like. Examples of the aliphatic aromatic diamine include 4-aminobenzylamine. And, for the aromatic diamine, for example, p-phenylenediamine, m-phenylenediamine, 2,4-diaminotoluene, 2,6-
Diaminotoluene, 3,5-diaminotoluene, 1,4
-Diaminonaphthalene, 1,5-diaminonaphthalene,
1,8-diaminonaphthalene, 2,3-diaminonaphthalene, 2,6-diaminonaphthalene, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylmethane, 2,
2′-diaminodiphenylethane, 4,4′-diaminodiphenylethane, 4,4′-diaminodiphenylsulfone, 4,4′-diaminodiphenylsulfide,
3,3'-diaminobenzophenone, 3,4'-diaminobenzophenone, 4,4'-diaminobenzophenone, 4,4'-diaminoazobenzene, 2,4'-diaminobiphenyl, 3,3'-4,4'- Diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 1,2-diaminoanthraquinone, 1,4-diaminoanthraquinone, 1,5-diaminoanthraquinone, 2,6-diaminoanthraquinone, 2,7- Diaminofluorene, 4,4'-diaminotriphenylmethane, 4,4'-diaminobenzanilide, 5-amino-
1- (4′-aminophenyl) 1,3,3-trimethylindane, 6-amino-1- (4′-aminophenyl)
-1,3,3-trimethylindane, 2,2-bis [4
-(4-aminophenoxy) phenyl] propane, 2,
2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane, 2,2-bis (4-aminophenyl] hexafluoropropane, 2,2-bis [4-
(4-aminophenoxy) phenyl] sulfone, 1,3
-Bis (3-aminophenyl] benzene, 1,3-bis (4-aminophenyl] benzene, 1,4-bis (4-
Aminophenyl] benzene, 9,9-bis (4-aminophenyl) -10-hydroanthracene, 9,9-bis (4-aminophenyl) fluorene, 4,4′-methylene-bis (2-chloroaniline), 2,2 ', 5,5'
-Tetrachloro-4,4'-diaminobiphenyl, 2,
2 ', 5,5'-tetrachloro-4,4'-diamino-
5,5'-dimethoxybiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 4,4 '-(p-
Phenyleneisopropylidene) bisaniline, 4,4 '
-(M-phenyleneisopropylidene) bisaniline,
2,2′-bis [4- (4-amino-2-trifluoromethylphenoxy) phenyl] hexafluoropropane, 4,4′-diamino-2,2′-bis (trifluoromethyl) biphenyl, 4,4 '-Bis [(4-amino-2-trifluoromethyl) phenoxy] octafluorobiphenyl, 4,4'-diamino-3-dodecyldiphenyl ether, 1-dodecanoxy-2,4-diaminobenzene, 1,1-bis ( 4-aminophenyl) cyclohexane, 2,2-bis [4- (4-aminophenoxy) phenyl] octane and the like. Here, the aliphatic diamine means a compound in which two carbons in the organic group R ¹ directly bonded to an amino group in the formula (1) are each an aliphatic carbon, and the aromatic diamine is the same as the aromatic diamine. Refers to an aliphatic carbon, and an aliphatic aromatic diamine refers to ^one in which one of two carbons in an organic group R ¹ directly connected to an amino group is an aliphatic carbon and the other is an aromatic carbon. To tell. The aliphatic diamines, aromatic diamines, and aliphatic aromatic diamines exemplified above can be used alone or in combination of two or more, and different diamines can be used in combination. However, the use of an aliphatic diamine is preferred because a polyimide film can be obtained by firing at a relatively low temperature and for a short time.

The tetracarboxylic acid represented by the general formula (2) or a derivative thereof includes, for example, pyromellitic acid, naphthalene-1,4,5,8-tetracarboxylic acid,
Naphthalene-2,3,6,7-tetracarboxylic acid, 2,
2 ', 3,3'-biphenyltetracarboxylic acid, 3,
3 ', 4,4'-biphenyltetracarboxylic acid, 2,
3,5,6-biphenyltetracarboxylic acid, 2,2 ′,
3,3′-benzophenonetetracarboxylic acid, 2,3
3 ′, 4′-benzophenonetetracarboxylic acid, 3,
3 ′, 4,4′-benzophenonetetracarboxylic acid,
3,3 ′, 4,4′-diphenylethertetracarboxylic acid, 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic acid, 3,3 ″, 4,4 ″ -terphenyltetracarboxylic acid, perylene -3,4,9,10-tetracarboxylic acid, phenanthrene-1,8,9,10-tetracarboxylic acid, anthracene-2,3,6,7-tetracarboxylic acid, p-benzoquinone-2,3,5 , 6-tetracarboxylic acid, azobenzene-3,3 ', 4,4'-
Tetracarboxylic acid, 2,2-bis (3,4-dicarboxyphenyl) propane, 2,2-bis (2,3-dicarboxyphenyl) propane, 1,1-bis (2,3-dicarboxyphenyl) Ethane, 1,1-bis (3,4-
Dicarboxyphenyl) ethane, bis (2,3-dicarboxyphenyl) methane, bis (3,4-dicarboxyphenyl) methane, 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane, thiophene-
2,3,4,5-tetracarboxylic acid, furan-2,3
4,5-tetracarboxylic acid, pyridine-2,3,5,6
-Tetracarboxylic acid, 4,4'-bis (3,4-dicarboxyphenoxy) diphenylsulfone, 4,4'-
Bis (3,4-dicarboxyphenoxy) diphenylpropane, 3,3 ′, 4,4′-perfluoroisopropylidene diphthalic acid, butane-1,2,3,4-tetracarboxylic acid, pentane-1,2 , 4,5-tetracarboxylic acid, cyclobutane-1,2,3,4-tetracarboxylic acid, cyclopentane-1,2,3,4-tetracarboxylic acid, cyclohexane-1,2,3,4-tetracarboxylic acid Acid, 2,3,5-tricarboxycyclopentylacetic acid,
3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalene succinic acid, bicyclo [2.2.2]-
Oct-7-ene-2,3,5,6-tetracarboxylic acid, 2,3,4,5-tetrahydrofurantetracarboxylic acid, 3,5,6-tricarboxynorbornane-2-
Acetic acid, 1,3,3a, 4,5,9b-hexahydro-5
-(Tetrahydro-2,5-dioxo-3-furanyl)
-Naphtho- [1,2-c] -furan-1,3-dione,
1,3,3a, 4,5,9b-Hexahydro-5-methyl-5- (tetrahydro-2,5-dioxo-3-furanyl) -naphtho- [1,2-c] -furan-1,3- Dione, 1,3,3a, 4,5,9b-hexahydro-8
-Methyl-5- (tetrahydro-2,5-dioxo-3
-Furanyl) -naphtho- [1,2-c] -furan-1,
3-dione, 5- (2,5-dioxotetrahydrofural) -3-methyl-3-cyclohexene-1,2-dicarboxylic acid, and the like. These tetracarboxylic acids and derivatives thereof can be used alone or in combination of two or more. The case where R ³ and R ⁴ in the general formula (2) are hydrogen is a tetracarboxylic acid, and derivatives thereof include:
Tricarboxylic acid monoesters in which one of R ³ or R ⁴ is hydrogen and the other is an alkyl group, and dicarboxylic acid diesters in which both R ³ and R ⁴ are substituted with an alkyl group are included. When R ³ or R ⁴ in the general formula (2) is an alkyl group, the alkyl group preferably has 1 to 12 carbon atoms, and among them, a methyl group or an ethyl group is preferred. This is preferable in that a precursor aqueous solvent solution can be produced at low cost. Further, dicarboxylic acid diesters in which R ³ and R ⁴ are substituted with an alkyl group having the same carbon number are preferable because they can be easily obtained by reacting a dicarboxylic acid of tetracarboxylic acid with an alcohol. That is, preferred tetracarboxylic acids and derivatives thereof are tetracarboxylic acid, dicarboxylic acid dimethyl ester, and dicarboxylic acid diethyl ester. Among the above-mentioned four preferable tetracarboxylic acids and derivatives thereof, it is particularly preferable to use aromatic tetracarboxylic acids and derivatives thereof in that high heat resistance can be imparted to the finally obtained polyimide film. Here, the aromatic tetracarboxylic acid and its derivative are represented by the general formula (2)
The compound in which the organic group R ² has at least one aromatic ring.

In the polyimide precursor aqueous solvent solution of the present invention, the dispersion medium is an aqueous solvent. The aqueous solvent means water alone or a mixed solvent composed of water and at least one hydrophilic organic solvent, provided that the compounds represented by the general formulas (1) and (2) and the salts thereof can be dissolved therein. There is no particular limitation. The mixed solvent generally contains water at 10% by mass or more, preferably 20% by mass or more, and more preferably 30% by mass or more. When a mixed solvent is used, alcohols, glycols, ketones,
Esters, ethers, amide solvents and the like can be used. Examples of such organic solvents include methyl alcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol, butanol, cyclohexanol, ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, , 3-butanediol, 1,5-pentanediol, 2-methyl-2,4-pentanediol, glycerin, diethylene glycol, triethylene glycol,
2-methoxyethanol, 2-ethoxyethanol, 2
-Isopropoxyethanol, 2-butoxyethanol, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, propylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, diethylene glycol mono Isopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, ethylene glycol monoisobutyl ether,
Diethylene glycol monoisobutyl ether, diethylene glycol monohexyl ether, ethylene glycol monoallyl ether, acetone, methyl ethyl ketone, dioxane, tetrahydrofuran, trioxane,
Examples thereof include 1,2-dimethoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, and N, N-dimethylformamide. Particularly preferred aqueous solvents in the present invention include water alone, water / methanol, water / ethanol, water / isopropanol, water / dimethoxyethane, water / methoxyethanol, and the like.

As described above, the polyimide precursor aqueous solvent solution of the present invention is prepared by dispersing and dissolving the compound of the general formula (1) and the compound of the general formula (2) in the above-mentioned aqueous solvent. Can be. In this case, the procedure for adding each compound to the aqueous solvent is not particularly limited. Ideally, the quantitative relationship between the compound of the general formula (1) and the compound of the general formula (2) to be dissolved in the aqueous solvent is 1: 1 in molar ratio. However, as long as the compound of the general formula (2) is dissolved in the aqueous solvent at a ratio of 0.8 to 1.2 moles per mole of the compound of the general formula (1), the solution is a polyimide precursor. It can be used as an aqueous solvent solution. Incidentally, when the ratio of the compound of the general formula (1) and the compound of the general formula (2) dissolved in the aqueous solvent deviates from the above-mentioned ratio range, a polyimide film having a sufficient degree of polymerization may not be obtained. There is. The concentration of the above compound in the polyimide precursor aqueous solvent solution of the present invention is not particularly limited, but is usually 1 to 60% by weight based on the total amount of the compound of the general formula (1) and the compound of the general formula (2). And more preferably in the range of 2 to 50% by weight. 1% by weight
If it is less than 60%, the film-forming property may be deteriorated. The temperature at the time of preparing the polyimide precursor aqueous solvent solution is -20 ° C.
To 100 ° C, more preferably 0 ° C to 60 ° C. When the temperature is lower than −20 ° C., the compound forming the polyimide precursor may be precipitated, and when the temperature is higher than 100 ° C., the compound may be imidized in the liquid.

A monoamine compound, a dicarboxylic acid and a derivative thereof can be added to the polyimide precursor aqueous solvent solution of the present invention in order to control the degree of polymerization of the finally obtained polyimide, improve physical properties, and the like. The monoamine compound to be added is not particularly limited. For example, n-butylamine, n-pentylamine, n-hexylamine, n-heptylamine, n-octylamine, n-nonylamine, n-decylamine, n-undecylamine N-dodecylamine, n-tridecylamine, n-tetradecylamine, n-pentadecylamine, n-hexadecylamine, n-heptadecylamine, n-octadecylamine, n-eicosylamine, cyclohexylamine,
Aniline and the like can be used. As the dicarboxylic acid and its derivative, for example, maleic acid, phthalic acid, nadic acid and their monoesters can be added. As the monoester, an alkyl ester having 1 to 12 carbon atoms is preferable, and among them, a methyl ester and an ethyl ester are preferable. Further, the polyimide precursor aqueous solvent solution of the present invention, if necessary, a surfactant for adjusting the surface tension of the solution, a catalyst for accelerating the imidization reaction, an adhesion promoter, polyvinyl Alcohol, partially acetalized polyvinyl alcohol, polyacrylamide, polyethylene glycol, polyacrylic acid, water-soluble polymers such as carboxymethyl cellulose, and other additives may be added.

The polyimide precursor aqueous solvent solution of the present invention is applied to a substrate, dried and fired to give a polyimide film. This polyimide film may be used together with the base material, may be separated from the base material and used alone, or may be transferred to another base material and used.
The substrate is not particularly limited, and any of glass, ceramic, concrete, plastic, metal, semiconductor, wood, paper, leather and the like can be used as the substrate. The shape of the substrate may be any of a powder, a line, a plane, a curved surface, and a three-dimensional shape. As a specific example of the flat base material,
For example, a glass substrate, a plastic substrate, an aluminum foil, a copper foil, a metal substrate such as a stainless steel belt or a stainless steel drum, a semiconductor substrate such as silicon, and the like can be given. The polyimide precursor aqueous solvent solution of the present invention can also be applied to a substrate with a transparent electrode used for a liquid crystal display device. In this case, since the dispersion medium of the polyimide precursor aqueous solvent solution of the present invention is an aqueous solvent, even when a plastic substrate is used, the concern that the substrate is chemically eroded can be reduced. As the plastic substrate,
Specifically, polyethylene, polypropylene, poly (4
Polyolefin such as methylpentene-1), polyimide, polyamideimide, polyamide, polyetherimide, polyetheretherketone, polyetherketone, polyketonesulfide, polyethersulfone, polysulfone, polyphenylenesulfide, polyphenyleneoxide, polyethyleneterephthalate, poly Examples include films formed from cellulose-based plastics such as butylene terephthalate, polyethylene naphthalate, polyacetal, polycarbonate, polyarylate, acrylic resin, polyvinyl alcohol, polypropylene, and triacetyl cellulose; epoxy resins; and phenolic resins.

The method of applying the polyimide precursor aqueous solvent solution of the present invention on a substrate is not particularly limited, and a known method,
For example, spin coating, bar coating, roll coating, printing, immersion pulling, curtain coating,
A Meyer bar coating method, a doctor blade method, a knife coating method, a die coating method, a gravure coating method, a microgravure coating method, an offset gravure coating method, a lip coating method, a spray coating method, or the like can be arbitrarily adopted. Of course, it can also be applied with a brush or brush.
The polyimide precursor aqueous solvent solution applied on the substrate with a desired film thickness is then dried. The drying temperature cannot be specified unconditionally because it is preferable to appropriately select according to the type of diamine or tetracarboxylic acid or a derivative thereof contained in the solution, the configuration of the aqueous solvent, etc., but it is usually room temperature or higher and 200 ° C. or lower. Preferably, a temperature of 50 ° C. or more and 150 ° C. or less is selected. Drying may be performed at a constant temperature or may be performed while increasing the temperature stepwise. By baking the dried coating film, diamine and tetracarboxylic acid or a derivative thereof are imidized, and a polyimide film can be obtained. The firing temperature is not particularly limited.
The temperature is preferably from 00 ° C to 400 ° C, and from 120 ° C to 35 ° C.
0 ° C or lower is more preferable, and 150 ° C or higher and 300 ° C or lower is further preferable. At 100 ° C. or lower, imidization may not proceed, and at 400 ° C. or higher, thermal decomposition may occur. The drying and firing may be performed almost simultaneously by devising the drying and firing processes. The surface of the polyimide film thus obtained can be washed with water or an organic solvent as needed. The polyimide film obtained from the polyimide precursor aqueous solvent solution of the present invention is a heat-resistant film, a liquid crystal alignment film, an insulating film such as a semiconductor or a capacitor, a retardation film, an optical waveguide, an optical element such as a diffraction element, a sealing material, Heat-resistant adhesives, solar cell coatings,
It can be used as a gas separation membrane, reverse osmosis membrane, ultrafiltration membrane, etc., and also can be used as a coating material for electric wires, fibers, paper, woven fabric, nonwoven fabric, etc. In addition, the polyimide precursor aqueous solvent solution of the present invention can be used as a film-forming material in the fields of electronics, semiconductors, machinery, aerospace, and the like. In particular, the polyimide film of the present invention can be preferably used as a liquid crystal alignment film. The polyimide film obtained from the polyimide precursor aqueous solvent solution of the present invention can be used as it is for a liquid crystal alignment film, but a good liquid crystal alignment film can be obtained by further performing an alignment treatment on the film. The method of the alignment treatment is not particularly limited, and a known method, for example, a rubbing method, a stretched polymer film method, a microgroove method, a transfer method, a light irradiation method, or the like can be adopted. The liquid crystal display device using the polyimide film of the present invention for the liquid crystal alignment film, when preparing the polyimide film, because there is no severe heat history of high temperature and long time, less damage to the color filter, etc., advantageous conditions Thus, a liquid crystal display device can be manufactured.

[0013]

EXAMPLES Examples will be described below, but the present invention is not limited to these examples. In addition, each analysis method used in the Example is as follows. (Infrared spectrometry) FT / IR-7000 manufactured by JASCO was used. (Film thickness measurement) Surface shape measuring device Dek manufactured by Japan Vacuum Engineering Co., Ltd.
tk 3030ST type was used. Example 1 4.01 g of 1,12-diaminododecane (20 mmo
l) and 6.20 g of diethyl ester of pyromellitic acid
(20 mmol) was dissolved at 50 ° C. in an aqueous solvent composed of 50 g of water and 50 g of ethanol, and cooled to room temperature to obtain a polyimide precursor solution. This polyimide precursor solution,
It was applied to a 1.1 mm thick glass substrate by spin coating, dried at 60 ° C. for 10 minutes, and baked at 200 ° C. for 10 minutes to imidize. As a result of infrared spectroscopy of the fired film, polyimide characteristic peaks were observed at 1774 and 1716 cm ^-1 as shown in FIG. 1, indicating that the film was a polyimide film. The thickness of the polyimide film was measured and found to be 0.5 μm. The polyimide film was immersed in water, isopropanol and acetone for 1 hour, but no change was observed. Example 2 In the same manner as in Example 1, 1,6-diaminohexane
32 g (20 mmol) of dimethyl ester of 3,3 ′, 4,4′-benzophenonetetracarboxylic acid 7.73
g (20 mmol) was dissolved at 50 ° C. in an aqueous solvent composed of 30 g of water and 50 g of ethanol, and cooled to room temperature to obtain a polyimide precursor solution. This polyimide precursor solution was applied to a glass substrate having a thickness of 1.1 mm by a spin coating method, dried at 60 ° C. for 10 minutes, and baked at 200 ° C. for 10 minutes to imidize. As a result of infrared spectroscopic measurement of the fired film, polyimide characteristic peaks were observed at 1775 and 1714 cm ^-1 as shown in FIG. 2, indicating that the film was a polyimide film. The thickness of the polyimide film was measured and found to be 0.6 μm. The polyimide film was immersed in water, isopropanol and acetone for 1 hour, but no change was observed. Example 3 As in Example 1, 1,9-diaminononane 3.1
7 g (20 mmol) and pyromellitic acid 5.08 g (2
0 mmol) was dissolved in an aqueous solvent composed of 50 g of water and 50 g of isopropanol at 50 ° C., and cooled to room temperature to obtain a polyimide precursor solution. This polyimide precursor solution is applied to a glass substrate having a thickness of 1.1 mm by spin coating, dried at 60 ° C. for 10 minutes, and baked at 250 ° C. for 10 minutes.
It was imidized. As a result of infrared spectroscopic measurement of the fired film, characteristic peaks of polyimide were observed at 1774 and 1714 cm ⁻¹ , indicating that the film was a polyimide film. The thickness of the polyimide film was measured and found to be 0.5 μm. The polyimide film was immersed in water, isopropanol and acetone for 1 hour, but no change was observed. Example 4 The polyimide precursor solution used in Example 1 was coated to a thickness of 75
A μm polyethylene terephthalate (PET) film (HSL-PET manufactured by Teijin) was applied by a bar coating method, dried at 60 ° C. for 10 minutes, and baked at 200 ° C. for 10 minutes to imidize. As a result of infrared spectroscopic measurement of the fired film, characteristic peaks of polyimide were observed at 1774 and 1716 cm ⁻¹ , indicating that the film was a polyimide film. The thickness of the polyimide film was measured and found to be 0.5 μm. The polyimide film was immersed in water, isopropanol and acetone for 1 hour, but no change was observed. Example 5 Two polyimide films on the glass substrate produced in Example 1 were rubbed with a rayon cloth, and the rubbing directions were antiparallel using a 5 μm spacer, and were bonded together.
Liquid crystal (ZLI-4792 manufactured by Merck) was injected to prepare a liquid crystal cell. Observation of the alignment state of the liquid crystal cell with a polarizing microscope confirmed that the liquid crystal cell was uniformly aligned over the entire surface.

[0014]

The polyimide precursor aqueous solvent solution of the present invention is obtained by dissolving a diamine compound, a tetracarboxylic acid or a derivative thereof in an aqueous solvent, and does not contain polyimide or polyamic acid. Since the dispersion medium is an aqueous solvent, it is extremely useful because it can reduce damage to the substrate on which the dispersion medium is applied and can also consider the environment. In addition, since the polyimide film obtained from the polyimide precursor aqueous solvent solution does not receive a severe heat history, if this is used for the liquid crystal alignment film, it is possible to reduce damage to the base material used during liquid crystal production. Can be. In addition, the above-mentioned polyimide film has excellent solvent resistance.

[Brief description of the drawings]

FIG. 1 is a diagram showing a result of infrared spectroscopy measurement in Example 1 of the present invention.

FIG. 2 is a diagram showing a result of infrared spectroscopy measurement in Example 2 of the present invention.

Claims (5)

[Claims] An aqueous solution of a polyimide precursor obtained by dissolving a compound represented by the following general formula (1) and a compound represented by the following general formula (2) in an aqueous solvent. Embedded image (In the formula, R ¹ represents a divalent organic group.) (In the formula, R ² represents a tetravalent organic group, and R ³ and R ⁴ each independently represent hydrogen or an alkyl group having 1 to 12 carbon atoms.) 2. The polyimide precursor aqueous solvent solution according to claim 1, wherein the compound represented by the general formula (1) is an aliphatic diamine. 3. The polyimide precursor aqueous solvent solution according to claim 1, wherein the compound of the general formula (2) is an aromatic tetracarboxylic acid or a derivative thereof. 4. A polyimide film produced from the polyimide precursor aqueous solvent solution according to claim 1. 5. A liquid crystal alignment film produced from the polyimide precursor aqueous solvent solution according to claim 1.