CN103113901A

CN103113901A - Liquid crystal aligning agent, liquid crystal alignment film and liquid crystal display device

Info

Publication number: CN103113901A
Application number: CN2012103572450A
Authority: CN
Inventors: 内山克博; 野口峻一
Original assignee: JSR Corp
Current assignee: JSR Corp
Priority date: 2011-11-16
Filing date: 2012-09-21
Publication date: 2013-05-22
Anticipated expiration: 2032-09-21
Also published as: JP2013127597A; CN103113901B; KR20130054125A; JP5929566B2; TWI532764B; KR101928350B1; TW201321433A

Abstract

The invention provides a liquid crystal aligning agent, a liquid crystal alignment film and a liquid crystal display device. The liquid crystal aligning agent contains: A, at least one polymer (a) selected from groups consisted of polyamic acid and polyimide, wherein the polyamic acid is obtained by reacting tetracarboxylic dianhydride with diamine, and the polyimide is obtained by dehydrating the polyamic acid so as to close ring; B, an antioxidant (b); C, at least one solvent (c) selected from groups consisted of 1,3-dimethyl-2-imidazolidinone, N-ethyl-2-pyrrolidinone, and a compound represented by a formula (1).

Description

Liquid crystal alignment agent, liquid crystal alignment film and liquid crystal display element

Technical Field

The present invention relates to a liquid crystal aligning agent, a liquid crystal alignment film, and a liquid crystal display device, and more particularly, to a liquid crystal aligning agent having good printability and being used to obtain a liquid crystal display device having good electrical characteristics after being driven for a long time, and a liquid crystal alignment film and a liquid crystal display device manufactured using the liquid crystal aligning agent.

Background

A horizontally aligned liquid crystal display element such as a Twisted Nematic (TN) mode, an In-Plane Switching (IPS) mode, or a Fringe Field Switching (FFS) mode, or a vertically aligned liquid crystal display element such as a Vertical Alignment (VA) mode has been known as a liquid crystal display element. These liquid crystal display elements include a liquid crystal alignment film for aligning liquid crystal molecules. In general, polyamic acid or polyimide is used as a material of a liquid crystal alignment film in view of good properties such as heat resistance, mechanical strength, and affinity with liquid crystal.

In recent years, liquid crystal display elements have been used not only in display terminals such as personal computers as in the past, but also in various applications such as liquid crystal televisions, car navigation systems, cellular phones, smart phones, and information displays. With the increase in the number of uses, the liquid crystal display element is used under severer conditions than ever before in terms of driving time and the like. Therefore, as a liquid crystal display element, there is a demand for less reduction in display quality (less reduction in electrical characteristics) even when continuous driving is performed for a long time, and various liquid crystal aligning agents for obtaining such a liquid crystal display element have been proposed (for example, see patent document 1 or patent document 2).

Documents of the prior art

Patent document

Patent document 1: japanese patent application laid-open No. 2010-97188

Patent document 2: japanese patent application laid-open No. 2010-156934

However, in the liquid crystal display element, deterioration with use cannot be avoided as in the case of other polymer materials. Further, among the deterioration, particularly serious is oxidative deterioration which occurs from energy such as ultraviolet light or heat as a starting point. On the other hand, in recent years, for example, as in information displays and the like, liquid crystal display elements are often driven for a long time, and in this case, due to progress of oxidation degradation, electrical characteristics of the liquid crystal display elements are likely to be degraded, and display quality is likely to be degraded. Therefore, in order to suppress oxidative deterioration of the liquid crystal display element, it is considered to include an antioxidant as an additive in the liquid crystal aligning agent. However, when the liquid crystal aligning agent contains an antioxidant, a problem occurs in that printability is lowered.

Disclosure of Invention

The present invention has been made in view of the above problems, and a main object thereof is to provide a liquid crystal aligning agent which has good printability and can obtain a liquid crystal display device which can maintain good electrical characteristics even after being driven for a long time, and a liquid crystal alignment film and a liquid crystal display device which are produced using the liquid crystal aligning agent.

The present inventors have made intensive studies to achieve the above-mentioned problems of the prior art, and as a result, have found that the above-mentioned problems can be solved by preparing a liquid crystal aligning agent by dissolving a polymer component and an antioxidant in a specific solvent, and have completed the present invention. Specifically, the present invention provides the following liquid crystal aligning agent, liquid crystal alignment film, and liquid crystal display device.

One aspect of the present invention provides a liquid crystal aligning agent, which is characterized by comprising: A) at least one polymer (a) selected from the group consisting of polyamic acid obtained by reacting tetracarboxylic dianhydride with diamine and polyimide obtained by subjecting the polyamic acid to dehydration ring-closure; B) an antioxidant (b); C) at least one solvent (c) selected from the group consisting of 1, 3-dimethyl-2-imidazolidinone, N-ethyl-2-pyrrolidone, and a compound represented by the following formula (1);

in the formula (1), R¹And R²Each independently represents a hydrogen atom, a hydrocarbon group having 1 to 6 carbon atoms, or a 1-valent group containing-O-between carbon-carbon bonds of the hydrocarbon group, R¹And R²Or may be bonded to each other to form a ring structure; r³Is an alkyl group having 1 to 6 carbon atoms.

According to the liquid crystal aligning agent of the present invention, since the antioxidant (b) is contained, peroxy radicals or hydroperoxides generated in the liquid crystal or in the liquid crystal alignment film can be complemented or decomposed in the liquid crystal display element manufactured by using the liquid crystal aligning agent. This can suppress the oxidation degradation of the liquid crystal display element and maintain the electrical characteristics well even after the liquid crystal display element is driven for a long time. In particular, since the liquid crystal aligning agent of the present invention uses the specific solvent (c), the printability is good even when the agent contains an antioxidant.

In one aspect of the liquid crystal aligning agent of the present invention, the content of the solvent (c) is 5% by weight or more of the entire solvent. In this case, the printability can be improved.

Further, as another aspect, the tetracarboxylic dianhydride preferably comprises 2, 3, 5-tricarboxycyclopentylacetic acid dianhydride and 2, 4, 6, 8-tetracarboxybicyclo [3.3.0] octane-2: 4,6: at least one compound selected from 8-dianhydrides. When the tetracarboxylic dianhydride is the above-mentioned specific compound, the solubility of the polymer (a) in the solvent (c) becomes better, and the printability can be made better.

As one aspect of the liquid crystal aligning agent of the present invention, it is preferable that the antioxidant (b) is at least one selected from the group consisting of a compound having a hindered amine structure and a compound having a hindered phenol structure. By using the above-mentioned specific compound as an antioxidant, it is possible to suppress as much as possible a decrease in electrical characteristics caused by long-term driving of a liquid crystal display element.

Further, an aspect of the present invention is to provide a liquid crystal alignment film formed from the liquid crystal aligning agent described above, and a liquid crystal display device including the liquid crystal alignment film. In a liquid crystal display element comprising the liquid crystal alignment film, electrical characteristics can be well maintained even after long-term driving.

Detailed Description

Liquid crystal aligning agent

The liquid crystal aligning agent comprises at least one polymer (a) selected from the group consisting of polyamic acid obtained by reacting tetracarboxylic dianhydride and diamine and polyimide obtained by dehydrating and ring-closing the polyamic acid, and an antioxidant (b), and is obtained by dissolving the polymer (a) and the antioxidant (b) in a solvent. Hereinafter, the liquid crystal aligning agent of the present invention will be described in detail.

With respect to the polymer (a)

Polyamic acid

Tetracarboxylic acid dianhydride

Examples of the tetracarboxylic dianhydride used for synthesizing the polyamic acid in the present invention include aliphatic tetracarboxylic dianhydride, alicyclic tetracarboxylic dianhydride, and aromatic tetracarboxylic dianhydride. As specific examples of these, it is possible to,

examples of the aliphatic tetracarboxylic acid dianhydride include 1, 2, 3, 4-butanetetracarboxylic acid dianhydride;

examples of the alicyclic tetracarboxylic acid dianhydride include 1, 2, 3, 4-cyclobutanetetracarboxylic acid dianhydride, 2, 3, 5-tricarboxycyclopentylacetic acid dianhydride, 1, 3, 3a, 4, 5, 9 b-hexahydro-5- (tetrahydro-2, 5-dioxo-3-furyl) -naphtho [1, 2-c ] furan-1, 3-dione, 1, 3, 3a, 4, 5, 9 b-hexahydro-8-methyl-5- (tetrahydro-2, 5-dioxo-3-furyl) -naphtho [1, 2-c ] furan-1, 3-dione, 3-oxabicyclo [3.2.1] octane-2, 4-dione-6-spiro-3 '- (tetrahydrofuran-2', 5' -dione), 5- (2, 5-dioxotetrahydro-3-furanyl) -3-methyl-3-cyclohexene-1, 2-dicarboxylic anhydride, 3, 5, 6-tricarboxyl-2-carboxymethylnorbornane-2: 3,5: 6-dianhydride, 2, 4, 6, 8-tetracarboxylic bicyclo [3.3.0] octane-2: 4,6: 8-dianhydride, 4, 9-dioxatricyclo [5.3.1.02, 6] undecane-3, 5, 8, 10-tetraone, cyclohexane tetracarboxylic dianhydride, etc.;

examples of the aromatic tetracarboxylic acid dianhydride include pyromellitic acid dianhydride; in addition, tetracarboxylic dianhydrides described in Japanese patent application laid-open No. 2010-97188 can be used. The tetracarboxylic dianhydrides mentioned above may be used singly in1 kind or in combination of 2 or more kinds.

The tetracarboxylic dianhydride used for synthesizing the polyamic acid preferably contains an alicyclic tetracarboxylic dianhydride in terms of good solubility in a solvent. Furthermore, the alicyclic tetracarboxylic dianhydride is preferably selected from the group consisting of 2, 3, 5-tricarboxycyclopentylacetic dianhydride, 1, 3, 3a, 4, 5, 9 b-hexahydro-5- (tetrahydro-2, 5-dioxo-3-furyl) -naphtho [1, 2-c ] furan-1, 3-dione, 1, 3, 3a, 4, 5, 9 b-hexahydro-8-methyl-5- (tetrahydro-2, 5-dioxo-3-furyl) -naphtho [1, 2-c ] furan-1, 3-dione, 2, 4, 6, 8-tetracarboxybicyclo [3.3.0] octane-2: 4,6: at least one selected from the group consisting of 8-dianhydride and 1, 2, 3, 4-cyclobutanetetracarboxylic dianhydride, and particularly preferably 2, 3, 5-tricarboxycyclopentylacetic acid dianhydride and 2, 4, 6, 8-tetracarboxybicyclo [3.3.0] octane-2: 4,6: at least any one of 8-dianhydrides.

The tetracarboxylic dianhydride comprises 2, 3, 5-tricarboxycyclopentylacetic acid dianhydride and 2, 4, 6, 8-tetracarboxybicyclo [3.3.0] octane-2: 4,6: in the case of at least one of 8-dianhydrides, the total content of these compounds is preferably 10 mol% or more, more preferably 20 mol% to 100 mol%, and still more preferably 50 mol% to 100 mol%, based on the total amount of tetracarboxylic dianhydride used in the synthesis of polyamic acid.

Diamines

Examples of the diamine used for synthesizing the polyamic acid in the present invention include aliphatic diamines, alicyclic diamines, aromatic diamines, and diaminoorganosiloxanes. These diamines may be used alone in1 kind or in combination of 2 or more kinds. Specific examples of the diamine include 1, 1-m-xylylenediamine, 1, 3-propylenediamine, butylenediamine, pentylenediamine, and hexylenediamine;

examples of the alicyclic diamine include 1, 4-diaminocyclohexane, 4' -methylenebis (cyclohexylamine), 1, 3-bis (aminomethyl) cyclohexane, and the like;

examples of the aromatic diamine include p-phenylenediamine, 4 '-diaminodiphenylmethane, 4' -diaminodiphenyl sulfide, 1, 5-diaminonaphthalene, 2 '-dimethyl-4, 4' -diaminobiphenyl, 2 '-bis (trifluoromethyl) -4, 4' -diaminobiphenyl, 2, 7-diaminofluorene, 4 '-diaminodiphenyl ether, 2-bis [4- (4-aminophenoxy) phenyl ] propane, 9-bis (4-aminophenyl) fluorene, 2-bis [4- (4-aminophenoxy) phenyl ] hexafluoropropane, 2-bis (4-aminophenyl) hexafluoropropane, 4' - (p-phenylenediisopropylidene) bisaniline, and mixtures thereof, 4, 4 '- (m-phenylenediisopropylidene) dianiline, 1, 4-bis (4-aminophenoxy) benzene, 4' -bis (4-aminophenoxy) biphenyl, 2, 6-diaminopyridine, 3, 4-diaminopyridine, 2, 4-diaminopyrimidine, 3, 6-diaminoacridine, 3, 6-diaminocarbazole, N-methyl-3, 6-diaminocarbazole, N-ethyl-3, 6-diaminocarbazole, N-phenyl-3, 6-diaminocarbazole, N '-bis (4-aminophenyl) -benzidine, N' -bis (4-aminophenyl) -N, N '-dimethylbenzidine, 1, 4-bis- (4-aminophenyl) -piperazine, 1, 4-bis (4-aminophenyl) -piperazine, 2, 6-diaminopyridine, 3, 6-diaminoacridine, 3, 6-diaminocarbazole, N' -bis (4-aminophenyl) -benzidine, 1- (4-aminophenyl) -2, 3-dihydro-1, 3, 3-trimethyl-1H-inden-5-amine, 1- (4-aminophenyl) -2, 3-dihydro-1, 3, 3-trimethyl-1H-inden-6-amine, 3, 5-diaminobenzoic acid, cholestanyloxy-3, 5-diaminobenzene, cholestanyloxy-2, 4-diaminobenzene, cholestanyl 3, 5-diaminobenzoate, lanostanyl ester, lanostanyl 3, 5-diaminobenzoate, and mixtures thereof, 3, 6-bis (4-aminobenzoyloxy) cholestane, 3, 6-bis (4-aminophenoxy) cholestane, 4- (4 '-trifluoromethoxybenzoyloxy) cyclohexyl-3, 5-diaminobenzoate, 4- (4' -trifluoromethylbenzoyloxy) cyclohexyl-3, 5-diaminobenzoate, 1-bis (4- ((aminophenyl) methyl) phenyl) -4-butylcyclohexane, 1-bis (4- ((aminophenyl) methyl) phenyl) -4-heptylcyclohexane, 1-bis (4- ((aminophenoxy) methyl) phenyl) -4-heptylcyclohexane, 1-bis (4- ((aminophenyl) methyl) phenyl) -4- (4-heptylcyclohexyl) cyclohexane, 2, 4-diamino-N, N-diallylaniline, 4-aminobenzylamine, 3-aminobenzylamine, and a compound represented by the following formula (A-1), and the like:

in the formula, X^IAnd X^IIAre each a single bond, -O-, -COO-or-OCO-, R^IIs an alkanediyl group having 1 to 3 carbon atoms, a is 0 or 1, b is an integer of 0 to 2, c is an integer of 1 to 20, and n is 0 or 1. Wherein a and b are not both 0;

examples of the diaminoorganosiloxane include 1, 3-bis (3-aminopropyl) -tetramethyldisiloxane, and diamines described in Japanese patent application laid-open No. 2010-97188 may be used.

-X in the above formula (A-1)^I-(R^I-X^II)_nThe 2-valent group represented by- "is preferably an alkanediyl group having 1 to 3 carbon atoms,^*-O-、^*-COO-or^*-O-C₂H₄-O- (wherein, appended with "^*The bond of "is bonded to a diaminophenyl group). radical-C_cH_2c+1Specific examples of "include methyl, ethyl, n-propyl, n-butyl and n-butylPentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, n-octadecyl, n-nonadecyl, n-eicosyl and the like. Relative to the radical "X^I"in particular, the 2 amino groups of the diaminophenyl group are preferably located in the 2, 4-or 3, 5-positions.

Specific examples of the compound represented by the above formula (A-1) include compounds represented by the following formulae (A-1-1) to (A-1-3), respectively.

The diamine used for synthesizing the polyamic acid in the present invention preferably contains 30 mol% or more of an aromatic diamine (diamine in which an amino group is bonded to an aromatic ring) with respect to all of the diamines, more preferably 50 mol% or more, and particularly preferably 80 mol% or more.

In addition, when a polyamic acid contained in the liquid crystal aligning agent for vertical alignment is synthesized, a diamine having a pretilt component is preferably used as the other diamine in order to impart good vertical alignment. Specifically, examples of the diamine having a pretilt component include dodecyloxy-2, 4-diaminobenzene, tetradecyloxy-2, 4-diaminobenzene, pentadecyloxy-2, 4-diaminobenzene, hexadecyloxy-2, 4-diaminobenzene, octadecyloxy-2, 4-diaminobenzene, dodecyloxy-2, 5-diaminobenzene, tetradecyloxy-2, 5-diaminobenzene, pentadecyloxy-2, 5-diaminobenzene, hexadecyloxy-2, 5-diaminobenzene, octadecyloxy-2, 5-diaminobenzene, cholestanyloxy-3, 5-diaminobenzene, cholestanyloxy-2, 4-diaminobenzene, cholestyryloxy-2, 4-diaminobenzene, cholestanyl 3, 5-diaminobenzoate, cholestenonyl 3, 5-diaminobenzoate, lanostanyl 3, 5-diaminobenzoate, 3, 6-bis (4-aminobenzoyloxy) cholestane, 3, 6-bis (4-aminophenoxy) cholestane, 4- (4 '-trifluoromethoxybenzoyloxy) cyclohexyl-3, 5-diaminobenzoate, 4- (4' -trifluoromethylbenzoyloxy) cyclohexyl-3, 5-diaminobenzoate, 1-bis (4- ((aminophenyl) methyl) phenyl) -4-butylcyclohexane, 1-bis (4- ((aminophenyl) methyl) phenyl) -4-heptylcyclohexane, dihydrocholestyryl-3, 5-diaminobenzoate, dihydrocholestyryl-3, 6-bis (4-aminobenzoyl) cholestyryl, cholestyryl-3, 5-bis (4-trifluoromethylbenzoyl-4-amino) phenyl-4-, 1, 1-bis (4- ((aminophenoxy) methyl) phenyl) -4-heptylcyclohexane, 1-bis (4- ((aminophenyl) methyl) phenyl) -4- (4-heptylcyclohexyl) cyclohexane, a diamine represented by the above formula (A-1), and the like. In addition, 1 kind of diamine having a pretilt component may be used alone or 2 or more kinds may be used in combination.

The total amount of the diamines having a pretilt component is preferably 5 mol% or more, more preferably 10 mol% or more, based on all the diamines.

Molecular weight regulator

When a polyamic acid is synthesized, a terminal-modified polymer may be synthesized by using an appropriate molecular weight modifier together with the tetracarboxylic dianhydride and the diamine described above. By forming the terminal-modified polymer, the coating property (printability) of the liquid crystal aligning agent can be further improved without impairing the effect of the present invention.

Examples of the molecular weight modifier include acid monoanhydrides, monoamine compounds, and monoisocyanate compounds. Specific examples of these compounds include maleic anhydride, phthalic anhydride, itaconic anhydride, n-decylsuccinic anhydride, n-dodecylsuccinic anhydride, n-tetradecylsuccinic anhydride, and n-hexadecylsuccinic anhydride;

examples of the monoamine compound include aniline, cyclohexylamine, n-butylamine, n-pentylamine, n-hexylamine, n-heptylamine, n-octylamine, and the like;

examples of the monoisocyanate compound include phenyl isocyanate and naphthyl isocyanate.

The use ratio of the molecular weight modifier is preferably 20 parts by weight or less, more preferably 10 parts by weight or less, based on 100 parts by weight of the total of the tetracarboxylic dianhydride and the diamine used.

Synthesis of Polyamic acid

The ratio of the tetracarboxylic dianhydride to the diamine used in the synthesis reaction of the polyamic acid of the present invention is preferably 0.2 to 2 equivalents, more preferably 0.3 to 1.2 equivalents, of the acid anhydride group of the tetracarboxylic dianhydride to 1 equivalent of the amino group of the diamine.

The synthesis reaction of the polyamic acid is preferably carried out in an organic solvent. The reaction temperature in this case is preferably-20 to 150 ℃ and more preferably 0 to 100 ℃. The reaction time is preferably 0.1 to 24 hours, more preferably 0.5 to 12 hours.

Examples of the organic solvent include aprotic polar solvents, phenols and derivatives thereof, alcohols, ketones, esters, ethers, halogenated hydrocarbons, and hydrocarbons.

Specific examples of the organic solvent include N-methyl-2-pyrrolidone, 1, 3-dimethyl-2-imidazolidinone, N-ethyl-2-pyrrolidone, N-dimethylacetamide, N-dimethylformamide, dimethyl sulfoxide, γ -butyrolactone, tetramethylurea, hexamethylphosphoric triamide, and a compound represented by the following formula (1);

examples of the phenol derivatives include m-cresol, xylenol, and halogenated phenol;

examples of the alcohol include methanol, ethanol, isopropanol, cyclohexanol, ethylene glycol, propylene glycol, 1, 4-butanediol, triethylene glycol, and ethylene glycol monomethyl ether;

examples of the ketone include acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone;

examples of the ester include ethyl lactate, butyl lactate, methyl acetate, ethyl acetate, butyl acetate, methyl methoxypropionate, ethyl ethoxypropionate, diethyl oxalate, and diethyl malonate;

examples of the ether include diethyl ether, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol n-propyl ether, ethylene glycol isopropyl ether, ethylene glycol n-butyl ether, ethylene glycol dimethyl ether, ethylene glycol ethyl ether acetate, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, and tetrahydrofuran;

examples of the halogenated hydrocarbon include dichloromethane, 1, 2-dichloroethane, 1, 4-dichlorobutane, trichloroethane, chlorobenzene, and o-dichlorobenzene;

examples of the hydrocarbon include hexane, heptane, octane, benzene, toluene, xylene, isoamyl propionate, isoamyl isobutyrate, and diisoamyl ether.

Among these organic solvents, it is preferable to use one or more selected from the group consisting of aprotic polar solvents and phenols and derivatives thereof (organic solvents of the first group), or a mixture of one or more selected from the group consisting of organic solvents of the first group and one or more selected from the group consisting of alcohols, ketones, esters, ethers, halogenated hydrocarbons and hydrocarbons (organic solvents of the second group). In the latter case, the ratio of the organic solvent of the second group to the total amount of the organic solvent of the first group and the organic solvent of the second group is preferably 50% by weight or less, more preferably 40% by weight or less, and still more preferably 30% by weight or less.

The amount of the organic solvent (a) used is preferably as follows: the total amount (b) of the tetracarboxylic dianhydride and the diamine is 0.1 to 50 wt% based on the total amount (a + b) of the reaction solution.

Thus, a reaction solution obtained by dissolving the polyamide acid was obtained. The reaction solution can be directly supplied to the preparation of the liquid crystal alignment agent, or the polyamic acid contained in the reaction solution can be isolated and then supplied to the preparation of the liquid crystal alignment agent, or the isolated polyamic acid can be purified and then supplied to the preparation of the liquid crystal alignment agent. In the case of producing a polyimide by subjecting a polyamic acid to dehydration ring closure, the reaction solution may be directly subjected to dehydration ring closure, the polyamic acid contained in the reaction solution may be isolated and then subjected to dehydration ring closure, or the isolated polyamic acid may be purified and then subjected to dehydration ring closure. Isolation and purification of the polyamic acid can be carried out according to a known method.

Polyimide and synthesis of polyimide

The polyimide contained in the liquid crystal aligning agent of the present invention can be obtained by subjecting the polyamic acid synthesized as described above to dehydration ring closure to imidize the same.

The polyimide may be a complete imide product obtained by dehydration ring closure of all the amic acid structures of the polyamic acid as a precursor thereof, or may be a partial imide product obtained by dehydration ring closure of only a part of the amic acid structures and coexistence of the amic acid structure and the imide ring structure. The polyimide in the present invention has an imidization ratio of preferably 30% or more, more preferably 50% to 99%, and still more preferably 60% to 99%. The imidization ratio is a ratio of the number of imide ring structures to the total of the number of amic acid structures and the number of imide ring structures of the polyimide expressed in percentage. Here, a part of the imide ring may be an imide ring.

The dehydration ring-closing of the polyamic acid is preferably carried out by the following method: a method of heating the polyamic acid; or a method in which the polyamic acid is dissolved in an organic solvent, and a dehydrating agent and a dehydration ring-closing catalyst are added to the solution, followed by heating as necessary. Among them, the latter method is preferably used.

In the method of adding the dehydrating agent and the dehydration cyclization catalyst to the polyamic acid solution, the dehydrating agent may be, for example, an acid anhydride such as acetic anhydride, propionic anhydride, or trifluoroacetic anhydride. The amount of the dehydrating agent to be used is preferably 0.01 to 20 moles based on 1 mole of the amic acid structure of the polyamic acid. As the dehydration ring-closure catalyst, tertiary amines such as pyridine, collidine, lutidine and triethylamine can be used. The dehydration ring-closing catalyst is preferably used in an amount of 0.01 to 10mol based on 1 mol of the dehydrating agent used. Examples of the organic solvent used in the dehydration ring-closure reaction include organic solvents exemplified as organic solvents used in the synthesis of polyamic acid. The reaction temperature of the dehydration ring-closure reaction is preferably 0 to 180 ℃, more preferably 10 to 150 ℃. The reaction time is preferably 1.0 to 120 hours, more preferably 2.0 to 30 hours.

This was carried out to obtain a reaction solution containing polyimide. The reaction solution may be directly supplied to the preparation of the liquid crystal aligning agent, or may be supplied to the preparation of the liquid crystal aligning agent after the dehydrating agent and the dehydration ring-closing catalyst are removed from the reaction solution, or may be supplied to the preparation of the liquid crystal aligning agent after the polyimide is isolated, or may be supplied to the preparation of the liquid crystal aligning agent after the isolated polyimide is purified. These purification operations may be carried out according to known methods.

Solution viscosity of Polymer

The polyamic acid and polyimide obtained as described above preferably have a solution viscosity of 10 to 800mPa · s, more preferably 15 to 500mPa · s, when prepared as a solution having a concentration of 10% by weight. The solution viscosity (mPa · s) of the polymer is a value measured at 25 ℃ using an E-type rotational viscometer for a 10 wt% polymer solution prepared using a good solvent for the polymer (e.g., γ -butyrolactone, N-methyl-2-pyrrolidone, 1, 3-dimethyl-2-imidazolidinone, N-ethyl-2-pyrrolidone, etc.).

The polyamic acid and polyimide preferably have a weight average molecular weight (Mw) of 1,000 to 500,000, particularly preferably 2,000 to 300,000, in terms of polystyrene as measured by Gel Permeation Chromatography (GPC), and the ratio (Mw/Mn) of Mw to the number average molecular weight (Mn) in terms of polystyrene as measured by Gel Permeation Chromatography (GPC) is preferably 15 or less, particularly preferably 10 or less. By setting the molecular weight to such a range, good alignment and stability of the liquid crystal display element can be ensured.

Regarding the antioxidant (b)

The liquid crystal aligning agent of the present invention contains an antioxidant (b) as an additive. The antioxidant (b) functions as a radical extender or a peroxide decomposer for deactivating peroxy radicals or hydroperoxides generated from energy such as ultraviolet light or heat. When such an antioxidant (b) is contained in the liquid crystal alignment film, in the case where a peroxy radical or a hydroperoxide is generated in the liquid crystal of the liquid crystal display element or in the liquid crystal alignment film with the long-term use of the liquid crystal display element, the group or the compound is invalidated, and the decrease in the electrical characteristics of the liquid crystal display element due to the peroxy radical or the like is suppressed.

Examples of the antioxidant (b) include a compound having a hindered amine structure, a compound having a hindered phenol structure, a compound having an alkyl phosphate structure (phosphorus-based antioxidant), a compound having a thioether structure (sulfur-based antioxidant), and a mixture thereof (blended antioxidant).

As the antioxidant (b) to be used, a compound having a hindered amine structure, a compound having a hindered phenol structure, or a mixture thereof is preferable (hereinafter, also referred to as a specific antioxidant). When such a specific antioxidant is used, the electrical characteristics of the liquid crystal display element can be maintained well after the liquid crystal display element is driven for a long time, as compared with a case where an antioxidant other than the specific antioxidant (for example, a phosphorus-based antioxidant or a sulfur-based antioxidant) is used. That is, the light resistance of the liquid crystal display element can be further improved.

Specifically, as the compound having a hindered amine structure, a compound represented by the following formula (d1) can be suitably used, and as the compound having a hindered phenol structure, a compound represented by the following formula (d2) can be suitably used.

In the formula (d1), R⁴Is a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aralkyl group having 7 to 13 carbon atoms, a1, 3-dioxobutyl group or a1, 4-dioxobutyl group. Wherein R is⁴Can also be used to remove the R⁴The resulting 2-valent group having 1 hydrogen atom forms part of the molecular chain. R⁵～R⁸Each independently an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms or an aralkyl group having 7 to 13 carbon atoms. X¹Is a single bond, an oxygen atom, a carbonyl group,^**-(CH₂)_n-O- (n is an integer of 1 to 4) or^**-CONH-，X²～X⁵Each independently is a single bond, a carbonyl group,^**-CH₂-CO-or^**-CH₂-CH (OH) -. Wherein,^**represents a bond to the piperidine ring.^*Representing a key.

In the formula (d2), R⁹The hydrocarbon group has 4 to 16 carbon atoms, or a group containing at least one of "-O-" and "-S-" between carbon-carbon bonds of the hydrocarbon group. R¹⁰Is a hydrogen atom or a hydrocarbon group having 1 to 16 carbon atoms, and a is an integer of 0 to 3. Wherein, in the case where a is 2 or 3, a plurality of R¹⁰Independently have the above definitions.^*Representing a key.

R in relation to the above formula (d1)⁴Examples of the alkyl group having 1 to 20 carbon atoms include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, and nonadecyl groups.

Examples of the aryl group having 6 to 20 carbon atoms include phenyl, 3-fluorophenyl, 3-chlorophenyl, 4-isopropylphenyl, 4-n-butylphenyl, 3-chloro-4-methylphenyl, 4-pyridyl, 2-phenyl-4-quinolyl, 2- (4 '-tert-butylphenyl) -4-quinolyl, 2- (2' -thienyl) -4-quinolyl and the like;

examples of the aralkyl group having 7 to 13 carbon atoms include benzyl group and phenethyl group.

R⁵～R⁸The alkyl group having 1 to 6 carbon atoms, the aryl group having 6 to 12 carbon atoms and the aralkyl group having 7 to 13 carbon atoms of (A) are listed as R⁴In the description, the alkyl group having 1 to 6 carbon atoms, the aryl group having 6 to 12 carbon atoms and the aralkyl group having 7 to 13 carbon atoms are exemplified as the group.

In the above formula (d1), the formula is represented by "-X¹-R⁴Examples of the group "represented by" include methyl, ethyl, n-propyl, isopropyl, n-butyl, 2-butyl, isobutyl, tert-butyl, methoxy, ethoxy, propoxy, butoxy and pentyloxy, octyloxy, formyl, acetyl, phenyl, benzyl, 1, 3-dioxobutyl, 1, 4-dioxobutyl, 4-pyridylcarbonyl, benzoyl, 2-phenyl-4-quinolyl, 2- (4 '-tert-butylphenyl) -4-quinolyl, 2- (2' -thienyl) -4-quinolyl, a group represented by the formula "-CONH-Ph (wherein Ph is phenyl, 3-fluorophenyl, 3-chlorophenyl, 4-isopropylphenyl, 4-n-butylphenyl or 3-chloro-4-methylphenyl)", and the like.

R4 may form a part of the molecular chain as a 2-valent group excluding 1 hydrogen atom from the carbon atoms. In this case, "-X¹-R⁴Examples of the "2-valent group" include "-X¹-R⁴"is a group formed by removing 1 hydrogen atom from each of the 1-valent groups exemplified in the description of the group represented by the formula (I).

In the above formula (d1), "-X²-R⁵”、“-X³-R⁶”、“-X⁴-R⁷”、“-X⁵-R⁸Examples of the group "include methyl, ethyl, n-propyl, isopropyl, n-butyl, 2-butyl, isobutyl, tert-butyl, phenyl, benzyl and benzoylA group such as a 4-formylbenzoyl group, a 2-hydroxy-2-phenylethyl group, a 2-oxo-2- (3, 4, 5-trimethoxyphenyl) ethyl group and the like. Additionally, "-X²-R⁵”、“-X³-R⁶”、“-X⁴-R⁷"and" -X⁵-R⁸"may be the same or different.

R in relation to the above formula (d2)⁹Examples of the hydrocarbon group having 4 to 16 carbon atoms include aliphatic hydrocarbon groups, alicyclic hydrocarbon groups, and aromatic hydrocarbon groups. Specific examples of the aliphatic hydrocarbon group include the above-mentioned R⁴In the description of (1), a group exemplified as an alkyl group having 4 to 16 carbon atoms; examples of the alicyclic hydrocarbon group include cyclopentyl, cyclohexyl, norbornyl, isobornyl and the like, adamantyl, tricyclodecyl and the like; examples of the aromatic hydrocarbon group include a phenyl group, a fluorophenyl group, a chlorophenyl group, a benzyl group, and a phenethyl group. And, R⁹The hydrocarbon group having 4 to 16 carbon atoms may contain 1-valent group of at least any one of "-O-" and "-S-" at least 1 to 1 carbon atom between carbon-carbon bonds.

As R⁹Preferable specific examples thereof include t-butyl, 1-methylpentadecyl, 1-ethylpentadecyl, octylthiomethyl, decylthiomethyl, dodecylthiomethyl and tetradecylthiomethyl.

As R¹⁰The hydrocarbon group having 1 to 16 carbon atoms of (A) may include the above-mentioned R in addition to methyl, ethyl, n-propyl, isopropyl and the like⁹The groups exemplified in the description of (1).

R¹⁰The bonding position(s) is not particularly limited, but is preferably ortho-position with respect to the phenolic hydroxyl group or R⁹The former is more preferable.

As R¹⁰Preferable specific examples of (B) include methyl, ethyl, tert-butyl, 1-methylpentadecyl and 1-ethylpentadecyl.

Commercially available antioxidants (b) can also be used. Specific examples of such compounds include commercially available products of compounds having an amine structure such as Adekastab LA-52, LA-57, LA-63, LA-68, LA-72, LA-77, LA-81, LA-82, LA-87, LA-402, LA-502 (manufactured by Adeka, Inc., above), CHIMASSORB119, CHIMASSORB2020, CHIMASSORB944, TINUVIN622, TINUVIN123, TINUVIN144, TIVIN NU 765, TINUVIN770, TINUVIN111, TINUVIN783, and TINUVIN791 (manufactured by BASF corporation, above);

examples of commercially available products of compounds having a phenol structure include Adekastab AO-20, Adekastab AO-30, Adekastab AO-40, Adekastab AO-50, Adekastab AO-60, Adekastab AO-80, Adekastab AO-330 (manufactured by ADEKA Co., Ltd.), IRGANOX1010, IRGANOX1035, IRGAOX1076, IRGANOX1098, IRGANOX1135, IRGANOX1330, IRGA1726, IRGANOX1425, IRGANOX1520, IRGANOX245, IRGANOX259, IRGANOX3114, IRGANOX3790, IRGANOX5057, IRGANOX565, IRGAOD 295 (manufactured by BASF Japan Co., Ltd.), and the like;

examples of commercially available phosphorus antioxidants include Adekastab PEP-4C, AdekastabPEP-8, Adekastab PEP-36, HP-10, 2112 (manufactured by ADEKA), IRGAFOS168, GSY-P101 (manufactured by Sakai chemical industry Co., Ltd.), IRGAFOS168, IRGAFOS12, IRGAFOS126, IRGAFOS38, and IRGAFOS P-EPQ (manufactured by BASFJapan);

commercially available sulfur antioxidants include, for example, Adekastab AO-412, Adekastab AO-503 (manufactured by ADEKA Co., Ltd.), IRGANOX PS 800, IRGANOX PS 802 (manufactured by BASF Japan Co., Ltd.), and the like;

examples of commercially available products containing an antioxidant include Adekastab A-611, Adekastab A-612, Adekastab A-613, Adekastab AO-37, Adekastab AO-15, Adekastab AO-18, and Adekastab 328 (manufactured by ADEKA Co., Ltd.), TINUVIN111, TINUVIN783, and TINUVIN791 (manufactured by BASF Japan Co., Ltd.). Further, the antioxidant (b) may be used alone in1 kind or in combination of 2 or more kinds.

From the viewpoint of achieving both the suppression of the oxidation degradation of the liquid crystal display element and the improvement of the printability, the content of the antioxidant (b) is preferably 0.01 to 10 parts by weight, more preferably 0.01 to 5 parts by weight, and particularly preferably 0.1 to 3 parts by weight, based on 100 parts by weight of the polymer (a).

With respect to the solvent

The liquid crystal aligning agent of the present invention is formed by dissolving the polymer (a) and the antioxidant (b) in a solvent. The liquid crystal aligning agent of the present invention contains at least one solvent (c) selected from the group consisting of 1, 3-dimethyl-2-imidazolidinone, N-ethyl-2-pyrrolidone, and a compound represented by the following formula (1). The solvent (c) has high solubility in polyamic acid or polyimide and a high boiling point. By using such a solvent (c), in printing for printing the liquid crystal aligning agent on the substrate, volatilization of the solvent from the printer is suppressed, and the polymer component and the antioxidant are less likely to be deposited on the printer, resulting in good printability.

In the formula (1), R¹And R²Each independently represents a hydrogen atom, a hydrocarbon group having 1 to 6 carbon atoms, or a 1-valent group containing-O-between carbon-carbon bonds of the hydrocarbon group, R¹And R²They may be bonded to each other to form a ring structure. R³Is an alkyl group having 1 to 6 carbon atoms;

r of formula (1)¹And R²The hydrocarbon group having 1 to 6 carbon atoms may be saturated or unsaturated. And, R¹And R²The carbon-carbon single bond of the hydrocarbon group having 1 to 6 carbon atoms may contain "-O-". As R¹And R²Specific examples of the "O" group include, for example, an alkyl group having 1 to 6 carbon atoms, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, and a group containing an "-O" group between carbon-carbon bonds of these groups. In the formula (1), R¹And R²May be the same or different from each other.

Examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, and a hexyl group.

Examples of the alicyclic hydrocarbon group include cyclopentyl and cyclohexyl; examples of the aromatic hydrocarbon group include a phenyl group and the like.

R¹And R²May also be bonded to R¹And R²The bonded nitrogen atoms together form a ring. R¹、R²Examples of the ring bonded to each other include a pyrrolidine ring and a piperidine ring. Further, a 1-valent chain hydrocarbon group such as a methyl group may be bonded to these rings.

R¹And R²Preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and more preferably a hydrogen atom or a methyl group.

R³The alkyl group having 1 to 6 carbon atoms may be straight or branched, and specifically, R is mentioned¹And R²The alkyl group having 1 to 6 carbon atoms is exemplified as the group in the description. Wherein R is³An alkyl group having 1 to 4 carbon atoms can be preferably used.

Specific examples of the compound represented by the above formula (1) include 3-methoxy-N, N-dimethylpropionamide, 3-butoxy-N, N-dimethylpropionamide, 3-hexyloxy-N, N-dimethylpropionamide, isopropoxy-N-isopropyl-propionamide, N-butoxy-N-isopropyl-propionamide, and the like. Among these compounds, 3-methoxy-N, N-dimethylpropionamide and 3-butoxy-N, N-dimethylpropionamide can be preferably used.

As the solvent (c), 1 kind of the above exemplified compounds can be used alone or 2 or more kinds can be used in combination. Among them, a solvent in which 1 or 2 or more kinds of 1, 3-dimethyl-2-imidazolidinone, N-ethyl-2-pyrrolidone, 3-methoxy-N, N-dimethylpropionamide, and 3-butoxy-N, N-dimethylpropionamide are combined is particularly preferably used.

From the viewpoint of suppressing the deposition of the polymer (a) or the antioxidant (b) during printing and improving the printability, the solvent (c) is preferably used in an amount of 5 wt% or more, more preferably 10 wt% or more, based on the total amount of the solvents contained in the liquid crystal aligning agent. In addition, the upper limit of the content of the solvent (c) is preferably 90% by weight or less, more preferably 70% by weight or less, and even more preferably 50% by weight or less, based on the total amount of the solvent contained in the liquid crystal aligning agent, from the viewpoint of reducing the residual amount of the solvent in the formed liquid crystal alignment film and improving the electrical characteristics.

As the solvent used for the preparation of the liquid crystal aligning agent of the present invention, other solvents than the above-mentioned solvent (c) can be used. Examples of the other solvent include N-methyl-2-pyrrolidone, γ -butyrolactone, γ -butyrolactam, N-dimethylformamide, N-dimethylacetamide, 4-hydroxy-4-methyl-2-pentanone, ethylene glycol monomethyl ether, butyl lactate, butyl acetate, methyl methoxypropionate, ethyl ethoxypropionate, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol N-propyl ether, ethylene glycol isopropyl ether, ethylene glycol N-butyl ether (butyl cellosolve), ethylene glycol dimethyl ether, ethylene glycol ethyl ether acetate, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, dipropylene glycol monomethyl ether (DPM), diisobutyl ketone, isoamyl propionate, and mixtures thereof, Isoamyl isobutyrate, diisoamyl ether, ethylene carbonate, propylene carbonate, and the like. These organic solvents may be used alone or in combination of 2 or more.

Other ingredients

The liquid crystal aligning agent of the present invention contains the polymer (a), the antioxidant (b) and the solvent as described above, and may contain other components as needed. Examples of the other component include polymers other than the specific polymer, compounds having at least one epoxy group in the molecule (hereinafter referred to as "epoxy group-containing compounds"), functional silane compounds, and the like.

Other polymers

The other polymers mentioned above may be used to improve solution characteristics or electrical characteristics. Examples of the other polymer include polyamic acid ester, polyester, polyamide, polysiloxane, cellulose derivative, polyoxymethylene, polystyrene derivative, poly (styrene-phenylmaleimide) derivative, poly (meth) acrylate, and the like.

When another polymer is added to the liquid crystal aligning agent, the blending ratio thereof is preferably 50% by weight or less, more preferably 0.1% by weight to 40% by weight, and still more preferably 0.1% by weight to 30% by weight, based on the amount of all the polymers in the composition.

Compounds containing epoxy groups

The compound containing epoxy group can be used for improving the adhesion of the liquid crystal alignment film and the surface of the substrate. Examples of the epoxy group-containing compound include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1, 6-hexanediol diglycidyl ether, glycerol diglycidyl ether, trimethylolpropane triglycidyl ether, 2-dibromoneopentyl glycol diglycidyl ether, N, N, N ', N ' -tetraglycidyl-m-xylylenediamine, 1, 3-bis (N, N-diglycidylaminomethyl) cyclohexane, N, N, N ', N ' -tetraglycidyl-4, 4 ' -diaminodiphenylmethane, N, N-diglycidylbenzylamine, N, N-diglycidylaminomethyl cyclohexane, N, N-diglycidylaminomethylcyclohexane, and mixtures thereof, N, N-diglycidyl-cyclohexylamine and the like are preferable epoxy compounds.

Further, as an example of the compound containing an epoxy group, an epoxy group-containing polyorganosiloxane described in the international publication No. 2009/096598 can be used.

When these epoxy compounds are added to the liquid crystal aligning agent, the blending ratio thereof is preferably 40 parts by weight or less, and more preferably 0.1 to 30 parts by weight, based on 100 parts by weight of the total of the polymers contained in the liquid crystal aligning agent.

Functional silane compound

The functional silane compound can be used for improving the printing performance of the liquid crystal aligning agent. Examples of such functional silane compounds include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 2-aminopropyltrimethoxysilane, 2-aminopropyltriethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-ureidopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, N-ethoxycarbonyl-3-aminopropyltrimethoxysilane, N-ethoxycarbonyl-3-aminopropyltriethoxysilane, N-triethoxysilylpropyltriethoxysilane, N-trimethoxysilylpropyltriethoxysilane, N-aminopropyltriethoxysilane, N-aminopropyltrimethoxysilane, N-aminopropyltriethoxysilane, N-hydroxysilane, N-allyltrimethoxysilane, N-hydroxysilane, N-, 10-trimethoxysilyl-1, 4, 7-triazodecane, 10-triethoxysilyl-1, 4, 7-triazodecane, 9-trimethoxysilyl-3, 6-diazanonylacetate, 9-triethoxysilyl-3, 6-diazanonylacetate, methyl 9-trimethoxysilyl-3, 6-diazanonanoate, methyl 9-triethoxysilyl-3, 6-diazanonanoate, N-benzyl-3-aminopropyltrimethoxysilane, N-benzyl-3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-propyltrimethoxysilane, N-propyltriethoxysilane, N-propyltrimethoxysilane, N-ethyl, N-phenyl-3-aminopropyltriethoxysilane, glycidoxymethyltrimethoxysilane, glycidoxymethyltriethoxysilane, 2-glycidoxyethyltrimethoxysilane, 2-glycidoxyethyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, etc.

When these functional silane compounds are added to the liquid crystal aligning agent, the blending ratio thereof is preferably 2 parts by weight or less, more preferably 0.02 to 0.2 parts by weight, based on 100 parts by weight of the total of the polymers.

Examples of the other component include, in addition to the above, a compound having at least one propylene oxide group in the molecule (hereinafter referred to as "a propylene oxide group-containing compound") and the like. Specific examples of the glycidyl group-containing compound include 1, 4-bis { [ (3-ethyl-3-glycidyl) methoxy ] methyl } benzene (ARONE oxoetane OXT-121(XDO)), bis [2- (3-glycidyl) butyl ] ether (ARONE oxoetane OXT-221(DOX)), and 1, 4-bis [ (3-ethylglycidyl-3-yl) methoxy ] benzene (HQOX).

The concentration of the solid in the liquid crystal aligning agent of the present invention (the ratio of the total weight of the components excluding the solvent in the liquid crystal aligning agent to the total weight of the liquid crystal aligning agent) may be appropriately selected in consideration of viscosity, volatility, and the like, and is preferably in the range of 1 to 10 wt%. That is, when the liquid crystal aligning agent of the present invention is applied to the surface of a substrate and heated, as described later, to form a coating film as a liquid crystal alignment film or a coating film to be a liquid crystal alignment film, the film thickness of the coating film becomes too small to obtain a good liquid crystal alignment film when the solid content concentration is less than 1% by weight. On the other hand, when the solid content concentration exceeds 10% by weight, the film thickness of the coating film becomes too large to obtain a good liquid crystal alignment film, and the viscosity of the liquid crystal alignment agent increases to deteriorate the coating properties.

The range of the particularly preferable solid content concentration varies depending on the method used when the liquid crystal aligning agent is coated on the substrate. For example, when the spin coating method is used, the solid content concentration is particularly preferably in the range of 1.5 to 4.5 wt%. When the printing method is used, it is particularly preferable that the solid content concentration is in the range of 3 to 9% by weight, so that the solution viscosity is in the range of 12 to 50mPa · s. In the case of using the ink jet method, it is particularly preferable to set the solid content concentration in the range of 1 to 5% by weight so that the solution viscosity is in the range of 3 to 15mPa · s.

The temperature for preparing the liquid crystal aligning agent of the present invention is preferably 10 to 50 ℃ and more preferably 20 to 30 ℃.

Liquid crystal alignment film and liquid crystal display device

The liquid crystal alignment film of the present invention may be formed of the liquid crystal aligning agent prepared as described above. The liquid crystal display element of the present invention includes a liquid crystal alignment film formed using the liquid crystal aligning agent of the present invention. The liquid crystal display device of the present invention is applicable to a horizontal alignment mode such as IPS mode, TN mode, STN mode, and FFS mode, and also applicable to a vertical alignment mode such as VA mode.

The method for producing the liquid crystal display device of the present invention is explained below, and the method for producing the liquid crystal alignment film of the present invention is also explained in the explanation. The liquid crystal display element of the present invention can be manufactured, for example, by the following steps (1) to (3). Step (1) uses different substrates depending on the desired mode of operation. The step (2) and the step (3) are commonly used in each operation mode.

Step (1): formation of coating film

First, the liquid crystal aligning agent of the present invention is applied to a substrate, and then the coated surface is heated to form a coating film on the substrate.

(1-1) in the case of manufacturing a TN-type, STN-type, or VA-type liquid crystal display element, a pair of two substrates each provided with a patterned transparent conductive film is used, and the liquid crystal aligning agent of the present invention is applied to each transparent conductive film-forming surface thereof by an offset printing method, a spin coating method, a roll coating method, or an ink-jet printing method, and then each applied surface is heated (preferably two-stage heating including preheating (prebaking) and baking (postbaking)) to form a coating film. Here, as the substrate, glass such as float glass or soda glass; transparent substrates comprising plastics such as polyethylene terephthalate, polybutylene terephthalate, polyethersulfone, polycarbonate, and poly (alicyclic olefin). As the transparent conductive film provided on one surface of the substrate, a transparent conductive film containing tin oxide (SnO) can be used₂) The NESA film (manufactured by PPG, USA, registered trademark) contains indium oxide-tin oxide (In)₂O₃-SnO₂) An ITO film of (2). To obtain patterned transparent conductive films, e.g.Available are: a method of forming a pattern by photolithography after forming a transparent conductive film without a pattern; a method of using a mask having a desired pattern when forming the transparent conductive film. In the case of applying the liquid crystal aligning agent, the surface of the substrate on which the coating film is to be formed may be subjected to a pretreatment of previously applying a functional silane compound, a functional titanium compound, or the like, in order to improve the adhesion between the substrate surface and the transparent conductive film and the coating film.

After the liquid crystal aligning agent is applied, preheating (prebaking) is preferably performed in order to prevent the applied aligning agent from sagging or the like. The prebaking temperature is preferably from 30 ℃ to 200 ℃, more preferably from 40 ℃ to 150 ℃, and particularly preferably from 40 ℃ to 100 ℃. The prebaking time is preferably 0.25 to 10 minutes, more preferably 0.5 to 5 minutes. Thereafter, the solvent is completely removed, and a calcination (post-baking) step is performed for the purpose of thermal imidization of the amic acid structure present in the polymer, if necessary. The calcination (postbaking) temperature is preferably from 80 ℃ to 300 ℃, more preferably from 120 ℃ to 250 ℃. The post-baking time is preferably 5 minutes to 200 minutes, more preferably 10 minutes to 100 minutes. As described above, the film thickness of the formed film is preferably 0.001 to 1 μm, and more preferably 0.005 to 0.5. mu.m.

(1-2) in the case of producing an IPS type or FSS type liquid crystal display device, the liquid crystal aligning agent of the present invention is applied to an electrode-formed surface of a substrate provided with an electrode (the electrode includes a transparent conductive film or a metal film patterned into a comb-tooth shape) and one surface of an opposing substrate not provided with an electrode, and then each of the applied surfaces is heated to form a coating film. The materials of the substrate and the transparent conductive film used in this case, the coating method, the heating condition after coating, the method for patterning the transparent conductive film or the metal film, the pretreatment of the substrate, and the preferable film thickness of the formed coating film are the same as those in the above (1-1). As the metal film, for example, a film containing a metal such as chromium can be used.

In both cases (1-1) and (1-2), the liquid crystal aligning agent is applied to the substrate, and the organic solvent is removed to form a coating film serving as an alignment film. In this case, when the polymer contained in the liquid crystal aligning agent of the present invention is polyamic acid or an imidized polymer having an imide ring structure and an amic acid structure, the polymer may be further heated after the formation of the coating film to perform a dehydration ring-closing reaction, thereby forming a coating film which is further imidized.

Step (2): rubbing treatment

In the case of manufacturing a TN-type, STN-type, IPS-type, or FFS-type liquid crystal display element, the following rubbing treatment is performed: the coating film formed in the above step (1) is rubbed in a fixed direction by a roller wound with a cloth containing fibers such as nylon, rayon, cotton, or the like. This imparts the alignment ability of the liquid crystal molecules to the coating film, thereby forming a liquid crystal alignment film. On the other hand, in the case of producing a VA-type liquid crystal display element, the coating film formed in the above-mentioned step (1) may be used as it is as a liquid crystal alignment film, or may be subjected to a rubbing treatment.

In addition, the liquid crystal alignment film formed as described above may also be subjected to the following treatment so that the liquid crystal alignment film has a different liquid crystal alignment capability in each region: a process of changing a pretilt angle of a partial region of the liquid crystal alignment film by irradiating ultraviolet rays to the partial region; or a process of forming a resist film on a part of the surface of the liquid crystal alignment film, rubbing the film in a direction different from that of the rubbing process, and then removing the resist film. In this case, the viewing characteristics of the resulting liquid crystal display element can be improved.

And (3): construction of liquid Crystal cell

A liquid crystal cell was manufactured by preparing 2 substrates on which the liquid crystal alignment films were formed as described above, and disposing liquid crystal between the 2 substrates disposed in opposition to each other. Here, when the coating films are rubbed, the 2 substrates are disposed so that the rubbing directions of the respective coating films are at a predetermined angle, for example, orthogonal or antiparallel to each other.

In the production of the liquid crystal cell, for example, the following 2 methods are exemplified.

The first method is a method known since the past. First, 2 substrates were arranged to face each other with a gap (cell gap) therebetween so that the liquid crystal alignment films face each other, the peripheral portions of the 2 substrates were bonded to each other with a sealant, a liquid crystal was injected and filled into the cell gap defined by the substrate surfaces and the sealant, and then the injection hole was sealed, thereby manufacturing a liquid crystal cell.

The second method is a method called ODF (One Drop Fill) method. For example, an ultraviolet curable sealing material is applied to a predetermined position on one of the 2 substrates on which the liquid crystal alignment film is formed, liquid crystal is dropped onto predetermined portions on the liquid crystal alignment film surface, the other substrate is attached so that the liquid crystal alignment film faces each other, the liquid crystal is spread over the entire surface of the substrate, and then ultraviolet light is irradiated to the entire surface of the substrate to cure the sealing material, whereby a liquid crystal cell can be manufactured.

In the case of using any method, it is preferable that the liquid crystal cell manufactured as described above is further heated to a temperature at which the liquid crystal used becomes an isotropic phase, and then gradually cooled to room temperature, thereby removing the flow alignment at the time of filling the liquid crystal.

Next, a polarizing plate is bonded to the outer surface of the liquid crystal cell to obtain the liquid crystal display element of the present invention.

For example, an epoxy resin containing a curing agent and alumina balls as spacers can be used as the sealant.

The liquid crystal includes nematic liquid crystal and smectic liquid crystal, and among them, nematic liquid crystal is preferable, and for example, schiff base liquid crystal, azoxy liquid crystal, biphenyl liquid crystal, phenylcyclohexane liquid crystal, ester liquid crystal, terphenyl liquid crystal, biphenylcyclohexane liquid crystal, pyrimidine liquid crystal, dioxane liquid crystal, bicyclooctane liquid crystal, cubic alkane liquid crystal and the like can be used. In addition, the following compounds may be added to these liquid crystals for use, for example: cholesteric liquid crystals such as cholesteryl chloride, cholesteryl nonanoate and cholesteryl carbonate; chiral agents commercially available under the trade names "C-15", "CB-15" (manufactured by Merck); ferroelectric liquid crystals such as p-decyloxybenzylidene-p-amino-2-methylbutyl cinnamate and the like.

Examples of the polarizing plate attached to the outer surface of the liquid crystal cell include a polarizing plate in which a polarizing film called an "H film" (a polarizing film in which iodine is absorbed while polyvinyl alcohol is stretched and aligned) is sandwiched between cellulose acetate protective films, and a polarizing plate including the H film itself.

The liquid crystal display element of the present invention can be effectively applied to various devices, for example, to display devices such as clocks, portable game machines, word processors, notebook computers, car navigation systems, camcorders, Personal Digital Assistants (PDAs), digital cameras, mobile phones, smart phones, various displays, liquid crystal televisions, information displays, and the like.

Examples of the invention

The present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

The solution viscosity of each polymer solution and the imidization ratio of polyimide in the synthesis examples can be measured by the following methods.

Solution viscosity of Polymer solution

The solution viscosity [ mPas ] of the polymer solution was measured at 25 ℃ with a rotary viscometer E using a predetermined solvent to prepare a solution having a polymer concentration of 10% by weight.

Imidization ratio of polyimide

Adding polyimide solution into pure water, drying the obtained precipitate at room temperature under reduced pressure, dissolving in deuterated dimethyl sulfoxide, and measuring at room temperature with tetramethylsilane as reference substance¹H-NMR. According to what is obtained¹H-NMR spectrum, the imidization rate [% ] was determined by the following numerical formula (1)]。

Imidization rate [% ]]＝(1-A¹/A²×α)×100...(1)

In the formula (1), A¹Is the peak area of a proton derived from an NH group appearing in the vicinity of a chemical shift of 10ppm, A²Is a peak area derived from other protons, and α is a number ratio of the other protons to 1 proton of an NH group in the precursor (polyamic acid) of the polymer.

Synthesis of Polymer (a)

Polymerization example 1: synthesis of polyimide (PI-1)

22.4g (0.1 mol) of 2, 3, 5-tricarboxycyclopentylacetic dianhydride (TCA) as tetracarboxylic dianhydride, 2.2g (0.02 mol) of p-Phenylenediamine (PDA) as diamine, 7.6g (0.05 mol) of 3, 5-Diaminobenzoic Acid (DAB), 10.5g (0.02 mol) of cholestanyl 3, 5-diaminobenzoate (HCDA), and 4.9g (0.01 mol) of cholestanyl oxy-2, 4-diaminobenzene (HCODA) were dissolved in 190g of N-methyl-2-pyrrolidone (NMP) and reacted at 60 ℃ for 6 hours to obtain a polyamic acid solution containing 20 wt%. The polyamic acid solution thus obtained was added with NMP to give a solution having a polyamic acid concentration of 10% by weight, and the solution viscosity was measured to be 88mPa · s.

Next, 442g of NMP was added to the obtained polyamic acid solution, and 11.9g of pyridine and 15.3g of acetic anhydride were added to conduct a dehydration ring-closure reaction at 110 ℃ for 4 hours. After the dehydration ring-closure reaction, the solvent in the system was replaced with fresh NMP (pyridine and acetic anhydride used in the dehydration ring-closure reaction were removed to the outside of the system by this operation, the same applies hereinafter), whereby a solution containing polyimide (PI-1) having an imidization rate of 26% by weight of about 65% was obtained. A small amount of the obtained polyimide solution was collected, NMP was added thereto to prepare a solution having a polyimide concentration of 10% by weight, and the solution viscosity was measured to be 55 mPas.

Polymerization example 2: synthesis of polyimide (PI-2)

22.5g (0.1 mol) of TCA as tetracarboxylic dianhydride, 4.3g (0.04 mol) of PDA as diamine, 3.1g (0.02 mol) of DAB, 5.2g (0.01 mol) of HCDA and 14.9g (0.03 mol) of HCODA were dissolved in 200g of NMP and reacted at 60 ℃ for 6 hours to obtain a solution containing 20 wt% of polyamic acid. The solution viscosity of the obtained polyamic acid solution was 60mPa · s, which was measured by adding NMP to a solution having a polyamic acid concentration of 10 wt%.

Then, 464g of NMP was added to the obtained polyamic acid solution, and 7.9g of pyridine and 10.3g of acetic anhydride were added to conduct a dehydration ring-closure reaction at 110 ℃ for 4 hours. After the dehydration ring-closure reaction, the solvent in the system was replaced with fresh NMP to obtain a solution containing polyimide (PI-2) having an imidization rate of about 51% at 26 wt%. A small amount of the obtained polyimide solution was collected, NMP was added thereto to prepare a solution having a polyimide concentration of 10% by weight, and the solution viscosity was measured to be 39 mPas.

Polymerization example 3: synthesis of polyimide (PI-3)

2, 4, 6, 8-Tetracarboxybicyclo [3.3.0] octane-2 as a tetracarboxylic dianhydride: 4,6: 24.9g (0.10 mol) of 8-dianhydride (BODA), 2.2g (0.02 mol) of PDA as a diamine, 7.6g (0.05 mol) of DAB, 10.4g (0.02 mol) of HCDA and 4.9g (0.01 mol) of HCODA were dissolved in 200g of NMP and reacted at 60 ℃ for 6 hours to obtain a solution containing 20 wt% of polyamic acid. The solution viscosity of the obtained polyamic acid solution was 70mPa · s, which was measured by adding NMP to a solution having a polyamic acid concentration of 10 wt%.

Then, 464g of NMP was added to the obtained polyamic acid solution, and 11.8g of pyridine and 15.3g of acetic anhydride were added to conduct a dehydration ring-closure reaction at 110 ℃ for 4 hours. After the dehydration ring-closure reaction, the solvent in the system was replaced with fresh NMP to obtain a solution containing polyimide (PI-3) having an imidization rate of about 63% by weight of 26%. A small amount of the obtained polyimide solution was collected, NMP was added thereto to prepare a solution having a polyimide concentration of 10% by weight, and the solution viscosity was measured to be 53 mPas.

Polymerization example 4: synthesis of polyimide (PI-4)

22.4g (0.10 mol) of TCA as tetracarboxylic dianhydride, 6.5g (0.06 mol) of PDA as diamine, 4.0g (0.02 mol) of 4, 4' -diaminodiphenylmethane (DDM), 5.2g (0.01 mol) of HCDA and 4.9g (0.01 mol) of HCODA were dissolved in 172g of NMP and reacted at 60 ℃ for 6 hours to obtain a solution containing 20 wt% of polyamic acid. The solution viscosity of the obtained polyamic acid solution was 101mPa · s, which was measured by adding NMP to a solution having a polyamic acid concentration of 10 wt%.

Next, 400g of NMP was added to the obtained polyamic acid solution, and 10.3g of pyridine and 13.3g of acetic anhydride were added to conduct a dehydration ring-closure reaction at 110 ℃ for 4 hours. After the dehydration ring-closure reaction, the solvent in the system was replaced with fresh NMP to obtain a solution containing polyimide (PI-4) having an imidization rate of about 55% at 26 wt%. A small amount of the obtained polyimide solution was collected, NMP was added thereto to prepare a solution having a polyimide concentration of 10% by weight, and the solution viscosity was measured to be 65 mPas.

Polymerization example 5: synthesis of polyimide (PI-5)

A polyamic acid solution was obtained in the same manner as in polymerization example 1, except that 1, 3-dimethyl-2-imidazolidinone (DMI) was used instead of NMP. The polyamic acid solution thus obtained was added with DMI to give a solution having a polyamic acid concentration of 10% by weight, and the solution viscosity was measured to be 90 mPas.

Next, the resultant polyamic acid solution was used to synthesize polyimide. A solution containing polyimide (PI-5) having an imidization rate of about 66% by weight of 26% was obtained by synthesizing the polyimide in the same manner as in the polymerization example 1, except that DMI was used instead of NMP. A small amount of the obtained polyimide solution was taken out, and DMI was added thereto to prepare a solution having a polyimide concentration of 10% by weight, and the solution viscosity was measured to be 56 mPas.

Polymerization example 6: synthesis of polyimide (PI-6)

A polyamic acid solution was obtained in the same manner as in polymerization example 2 except that N-ethyl-2-pyrrolidone (NEP) was used instead of NMP. The solution viscosity of the obtained polyamic acid solution was 59 mPas, which was measured by adding NEP to a 10 wt% polyamic acid solution.

Next, the resultant polyamic acid solution was used to synthesize polyimide. A solution containing polyimide (PI-6) having an imidization rate of about 49% by weight of 26% was obtained by synthesizing the polyimide in the same manner as in the polymerization example 2 except that NEP was used instead of NMP. A small amount of the obtained polyimide solution was collected, NEP was added thereto to prepare a polyimide solution having a polyimide concentration of 10% by weight, and the solution viscosity was measured to be 38 mPas.

Preparation of liquid Crystal alignment agent

Example 1

To a solution containing 100 parts by weight of the synthesized polyimide (PI-1), 3 parts by weight of IRGANOX1010 (manufactured by BASF Japan) as an antioxidant, NMP as a solvent, ethylene glycol mono-n-butyl ether (BC) and 1, 3-dimethyl-2-imidazolidinone (DMI) were added based on 100 parts by weight of the polyimide (PI-1) to prepare a solution having a solvent composition of NMP: BC: DMI of 30: 50: 20 (weight ratio) and a solid content of 6.5 wt%. The solution was filtered through a filter having a pore size of 1 μm to prepare a liquid crystal aligning agent.

Examples 2 to 14, and comparative examples 1 to 7

Liquid crystal aligning agents were prepared in the same manner as in example 1, except that the compositions of the polyimide, antioxidant and solvent used were changed as described in table 1 below.

Evaluation of printability

The respective liquid crystal aligning agents prepared above were evaluated for printability. Evaluation was performed in the following manner. First, each of the prepared liquid crystal aligning agents was applied to the transparent electrode surface of a glass substrate having a transparent electrode including an ITO film, using a liquid crystal alignment film printer (manufactured by japan office press, Angstromer, model "S40L-532) under the condition that the amount of the liquid crystal aligning agent applied to the anilox roller was 20 drops (about 0.2g) in a reciprocating manner. Coating on the substrate was performed 20 times using a new substrate at 1 minute intervals.

Next, the liquid crystal aligning agent was dispensed (single pass) onto the anilox roller at 1 minute intervals, and this operation (hereinafter referred to as idle operation) was performed 10 times in total (during this time, printing on the glass substrate was not performed) while the anilox roller was brought into contact with the printing plate at each time. The idling operation is not performed in a normal manufacturing process of the liquid crystal display device, but is performed intentionally in a severe condition to perform an operation of printing the liquid crystal aligning agent on the substrate.

After 10 idle runs, main printing was performed using a glass substrate. In the main printing, 5 substrates were put at 30-second intervals after idling, and each of the substrates coated with the liquid crystal aligning agent was heated (prebaked) at 80 ℃ for 1 minute to remove the solvent, and then heated (postbaked) at 200 ℃ for 10 minutes to form a coating film having a film thickness of about 80 nm. The pattern edge portion (the outer peripheral portion of the printed pattern) of the coating film was observed with a microscope at a magnification of 20 to evaluate the printability. Evaluation was performed in such a manner that the case where no precipitate (considered to be polyimide and antioxidant) was observed since the first main printing after idle operation was good (o), the case where no precipitate was observed in the first main printing after idle operation but was not observed when the first main printing was performed 5 times was good (Δ), and the case where precipitate was observed even after the first main printing was repeated 5 times was poor (x). The evaluation results are shown in table 1 below. In addition, experiments show that: in a liquid crystal aligning agent having good printability, precipitates are good (disappear) when continuously charged into a substrate.

The printability of the liquid crystal aligning agent was evaluated by performing the same operations as described above except that the number of times of idle operation was changed to 15 times, 20 times, and 25 times, respectively. The evaluation results are also shown in table 1 below.

Manufacture of liquid crystal display element

Production example 1

The liquid crystal aligning agent of example 1 prepared above was applied to the transparent electrode surface of a glass substrate having a thickness of 1mm and provided with a transparent electrode comprising an ITO film by a spinner, and prebaked at 80 ℃ for 1 minute on a hot plate. Next, the pre-baked substrate was post-baked at 210 ℃ for 30 minutes. Thus, a liquid crystal alignment film having a thickness of about 80nm was formed. This operation was repeated to obtain a pair (2 pieces) of substrates having liquid crystal alignment films. Next, in one of the pair of substrates, an epoxy adhesive containing alumina balls having a diameter of 5.5 μm was applied to the outer edge of the surface having the liquid crystal alignment film, and then the surfaces were stacked so that the liquid crystal alignment films were opposed to each other and pressure-bonded to cure the adhesive. Next, a nematic liquid crystal (MLC-6608, manufactured by merck) was filled between the pair of substrates from the liquid crystal injection port, and then the liquid crystal injection port was sealed with an acrylic photo-curing adhesive, thereby manufacturing a liquid crystal cell.

Production examples 2 to 14, and comparative production examples 1 to 7

Liquid crystal cells were produced in the same manner as in production example 1, except that the liquid crystal aligning agent used was changed to the liquid crystal aligning agents of examples 2 to 14 and comparative examples 1 to 7.

Evaluation of light resistance

After applying a voltage of 5V at 70 ℃ for an application time of 60 microseconds and a span of 167 milliseconds to each of the liquid crystal cells manufactured as described above, a voltage holding ratio after releasing the application for 167 milliseconds was measured by VHR-1 manufactured by Toyang technologies. The value thereof was taken as the initial voltage holding ratio VHR1 [% ]. Next, the liquid crystal cell after VHR1 measurement was irradiated with light for 650 hours using a weather tester using a carbon arc as a light source. The voltage holding ratio of the liquid crystal cell after light irradiation was measured by the same method as described above. This value was defined as the voltage holding ratio VHR2 [% ] after light irradiation. The decrease Δ VHR [% ] in the voltage holding ratio before and after light irradiation was determined according to the following formula (2), and light resistance was evaluated using Δ VHR. The results are shown in table 1 below. The smaller Δ VHR indicates the better light fastness.

ΔVHR[％]＝VHR1-VHR2...(2)

[ Table 1]

Note that the symbols for the solvent composition and the antioxidant in table 1 are as follows.

a: n-methyl-2-pyrrolidone (NMP)

b: ethylene glycol mono-n-butyl ether (BC)

c: gamma-butyrolactone (GBL)

d: 1, 3-dimethyl-2-imidazolidinone (DMI)

e: N-Ethyl-2-pyrrolidone (NEP)

f: 3-methoxy-N, N-dimethylpropionamide

g: 3-butoxy-N, N-dimethylpropionamide

F-1: IRGANOX1010 (phenolic antioxidant)

F-2: adekastab LA-72 (amine antioxidant)

F-3: TINUVIN622 (amine antioxidant)

F-4: IRGAFOS12 (phosphorus antioxidant)

F-5: IRGANOX PS 800 (Sulfur antioxidant)

F-6: adekastab AO-40 (phenolic antioxidant)

As shown in table 1, the liquid crystal display devices all used the liquid crystal aligning agents of the examples had good light resistance. Among them, when hindered amine-based or hindered phenol-based antioxidants are used as the antioxidants (examples 1 to 4, 6, and 8 to 14), the decrease in voltage holding ratio before and after long-term light irradiation is as small as 2.1% to 3.1%, and the light resistance is particularly good.

In the liquid crystal aligning agent of the example, regarding the printability, no precipitate was observed from the 1 st main printing in the main printing after 10 times of idling. When the number of idle operations was increased to 20 or 25 times, precipitates were observed from the 1 st main printing, but the precipitates disappeared when the 5 main printing was completed. From these results, it can be seen that: the liquid crystal aligning agent of the example hardly generates precipitates during printing and has good printability.

On the other hand, in the case where the antioxidant is not contained in the comparative examples (comparative examples 1, 2, and 5), although the printability is good, the decrease in the voltage holding ratio due to long-term light irradiation is as large as 9.3% to 12.3%, and the light resistance is not so good. In addition, in the case where the solvent (c) was not contained although the antioxidant was contained (comparative examples 3, 4, 6, and 7), precipitates were observed in the main printing after 10 times of idling, and when the number of times of idling was increased to 15, precipitates were observed in all of the 5 main printing, and the printability was not good.

Claims

1. A liquid crystal aligning agent is characterized by comprising:

A) at least one polymer (a) selected from the group consisting of polyamic acid obtained by reacting tetracarboxylic dianhydride with diamine, and polyimide obtained by subjecting the polyamic acid to dehydration ring closure;

B) an antioxidant (b); and

C) at least one solvent (c) selected from the group consisting of 1, 3-dimethyl-2-imidazolidinone, N-ethyl-2-pyrrolidone, and a compound represented by the following formula (1),

2. The liquid crystal aligning agent according to claim 1, wherein: the content of the solvent (c) is 5% by weight or more of the whole solvent.

3. The liquid crystal aligning agent according to claim 1 or 2, wherein: the polymer (a) is prepared by using a copolymer comprising 2, 3, 5-tricarboxycyclopentylacetic dianhydride and 2, 4, 6, 8-tetracarboxybicyclo [3.3.0] octane-2: 4,6: at least one compound selected from 8-dianhydrides is synthesized as the tetracarboxylic acid dianhydride.

4. The liquid crystal aligning agent according to claim 1 or 2, wherein: the antioxidant (b) is at least one selected from the group consisting of a compound having a hindered amine structure and a compound having a hindered phenol structure.

5. A liquid crystal alignment film is characterized in that: formed using the liquid crystal aligning agent according to any one of claims 1 to 4.

6. A liquid crystal display element, characterized in that: comprising the liquid crystal alignment film according to claim 5.