JP2008216985A - Liquid crystal aligning agent, liquid crystal alignment layer and liquid crystal display element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal aligning agent which is excellent in image sticking characteristics irrespective of kinds of electrodes constituting a liquid crystal display element, and to provide a liquid crystal alignment layer obtained from the liquid crystal aligning agent, and the liquid crystal display element equipped with the liquid crystal alignment layer. <P>SOLUTION: The liquid crystal aligning agent includes: 100 weight part of a polymer having an imide bond unit and an amic acid bond unit; and at least 5 weight part of a compound including an intramolecular epoxy group and represented by formula (I-3), (here, R is a divalent organic group). The ratio of the number of the amic acid bond unit to the total sum of the number of the imide bond units and the amic acid bond units is 60-95%. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a liquid crystal aligning agent, a liquid crystal alignment film, and a liquid crystal display element. More specifically, the present invention relates to a liquid crystal aligning agent having good image sticking characteristics regardless of the type of electrodes constituting the liquid crystal display element, a liquid crystal alignment film obtained from the liquid crystal aligning agent, and a liquid crystal display element including the film.

Conventionally, a cell of a sandwich structure is formed by forming a nematic liquid crystal layer having positive dielectric anisotropy between two substrates having a liquid crystal alignment film formed on the surface via a transparent conductive film, There is known a TN liquid crystal display element having a TN (Twisted Nematic) type liquid crystal cell in which the major axis of liquid crystal molecules is continuously twisted by 90 degrees from one substrate toward the other substrate.
Further, the addition of a chiral agent achieves a state in which the major axis of the liquid crystal molecules is continuously twisted between the substrates by 180 degrees or more, and an STN (Super Twisted Nematic) type liquid crystal display element utilizing the birefringence effect generated thereby. Is also present. More recently, a homeotropically aligned nematic liquid crystal layer having negative dielectric anisotropy between opposing substrates and a cholesteric liquid crystal layer in which the helical axis is parallel to the substrate normal are formed. A guest-host type reflective liquid crystal display element in which a dye is added to the above has also been developed. The alignment of the liquid crystal in these liquid crystal display elements is usually expressed by a liquid crystal alignment film subjected to a rubbing treatment. Here, as a material for the liquid crystal alignment film constituting the liquid crystal display element, polyimide, polyamide, polyester, and the like are conventionally known. In particular, polyimide is used in many liquid crystal display elements because of its excellent heat resistance, affinity with liquid crystals, mechanical strength, and the like.

  Recently, studies have been made on improving display quality such as higher definition of liquid crystal display elements and lowering power consumption, and the range of use of liquid crystal display elements is expanding. In particular, reflective or transflective liquid crystal display elements that can maintain high display quality when used outdoors are used in mobile terminals, so that various metal electrodes (hereinafter referred to as reflective electrodes) are used to exhibit the function of reflecting external light. Is used. However, a liquid crystal display element having a reflective electrode has a problem that image sticking is more likely to occur than a conventional transmission type liquid crystal display element, and the liquid crystal alignment film is required to have a sticking characteristic higher than the level conventionally required. It was.

  An object of the present invention is to provide a liquid crystal aligning agent that provides a liquid crystal alignment film having excellent image sticking characteristics regardless of the type of electrodes constituting the liquid crystal display element.

  Still another object of the present invention is to provide the liquid crystal alignment film and a liquid crystal display device including the same.

  Still other objects and advantages of the present invention will become apparent from the following description.

  According to the present invention, the above objects and advantages of the present invention include, firstly, an imide bond unit represented by the following formula (I-1) and an amic acid bond unit represented by the following formula (I-2). The polymer has 100 parts by weight, wherein the ratio of the amic acid bond unit to the total number of bond units of the imide bond unit and the amic acid bond unit is 60 to 95 mol%, and contains an epoxy group in the molecule This is achieved by a liquid crystal aligning agent comprising at least 5 parts by weight of a compound represented by the following formula (I-3) (hereinafter referred to as “specific epoxy compound”).

(Wherein P ¹ is a tetravalent organic group and Q ¹ is a divalent organic group.)

(Wherein P ² is a tetravalent organic group and at least 30 mol% of a tetravalent organic group derived from pyromellitic dianhydride and 1,2,3,4-cyclobutanetetracarboxylic dianhydride) 1,2-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,3- Dichloro-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-tetramethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride and 1,2,4 consists tetravalent organic radical derived from at least one tetracarboxylic dianhydride selected from the group consisting of 5-cyclohexanetetracarboxylic dianhydride, and Q ² is a divalent organic group.)

(Here, R is a divalent organic group.)

  According to the present invention, the above objects and advantages of the present invention are secondly achieved by a liquid crystal alignment film formed from the liquid crystal aligning agent of the present invention.

  According to the present invention, thirdly, the above objects and advantages of the present invention are achieved by a liquid crystal display device comprising the liquid crystal alignment film of the present invention.

The liquid crystal alignment film formed by the liquid crystal aligning agent of the present invention has excellent image sticking characteristics as compared with conventional alignment films, and includes a TN liquid crystal display element, an STN liquid crystal display element, a reflective liquid crystal display element, and a transflective liquid crystal display element. For example, it can be suitably used for constituting various liquid crystal display elements.
The liquid crystal display element of the present invention can be effectively used in various devices, and is suitably used as a display device for, for example, a desk calculator, a wristwatch, a table clock, a mobile phone, a counting display board, a word processor, a personal computer, and a liquid crystal television. Can be used.

  Hereinafter, the present invention will be described in detail.

The liquid crystal aligning agent of this invention consists of a polymer which has an imide bond unit and an amic acid bond unit formed by reaction of tetracarboxylic dianhydride and diamine. The imide bond unit and the amic acid bond unit may be contained in the same polymer or in different polymers.
The ratio of the amic acid bond unit to the total number of bond units of the imide bond unit and the amic acid bond unit is 60 to 95 mol%. If it is less than 60 mol%, the image sticking property may be inferior, and if it exceeds 95 mol%, the liquid crystal orientation may be inferior.
A polyamic acid composed of an amic acid bond unit is obtained by ring-opening polyaddition of a tetracarboxylic dianhydride and a diamine compound, and a polyimide is usually obtained by dehydrating and ring-closing a polyamic acid. The partially imidized polymer can be usually obtained by a method of synthesizing a block copolymer by bonding an amic acid prepolymer and an imide prepolymer.

<Polyamic acid and polyimide>
[Tetracarboxylic dianhydride]
P ² in the above formula (I-2) is a tetravalent organic group derived from at least 30 mol% of pyromellitic dianhydride and 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 2-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,3-dichloro-1, 2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-tetramethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride and 1,2,4,5-cyclohexane It consists of a tetravalent organic group derived from at least one tetracarboxylic dianhydride selected from the group consisting of tetracarboxylic dianhydrides.

P ² in the above formula (I-2) may contain a tetravalent organic group derived from other tetracarboxylic dianhydrides other than those described above. Examples of such other tetracarboxylic dianhydrides include butanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 3,3 ′, 4,4 ′. -Dicyclohexyltetracarboxylic dianhydride, 2,3,5-tricarboxycyclopentylacetic acid dianhydride, 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-7-methyl-5- (tetrahydro-2,5-dioxo- 3-furanyl)- [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, 1,3,3a, 4,5,9b-hexahydro-5,8-dimethyl-5- (tetrahydro-2,5-dioxo-3 -Furanyl) -naphtho [1,2-c] -furan-1,3-dione, 3,5,6-tricarboxynorbornane-2-acetic acid dianhydride, 2,3,4,5-tetrahydrofurantetracarboxylic acid Dianhydride, 1,3,3a, 4,5,9b-hexahydro-5-ethyl-5- (tetrahydro-2,5-dioxo-3-furanyl) -naphtho [1,2-c] -furan-1 , 3-dione, 1,3,3a, 4,5,9b-hexahi Dro-7-ethyl-5- (tetrahydro-2,5-dioxo-3-furanyl) -naphtho [1,2-c] -furan-1,3-dione, 1,3,3a, 4,5,9b Hexahydro-8-ethyl-5- (tetrahydro-2,5-dioxo-3-furanyl) -naphtho [1,2-c] -furan-1,3-dione, 5- (2,5-dioxotetrahydrofura Nyl) -3-methyl-3-cyclohexene-1,2-dicarboxylic dianhydride, bicyclo [2.2.2] -oct-7-ene-2,3,5,6-tetracarboxylic dianhydride 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-tricarboxy-2-carboxymethyl norbornane -2: 3,5: 6-dianhydride, 4,9-dioxatricyclo [5.3.1.0 ^{2 , 6} ] Undecane-3,5,8,10-tetraone, aliphatic and alicyclic tetracarboxylic dianhydrides such as compounds represented by the following formulas (I) and (II);

(Wherein R ¹ and R ³ represent a divalent organic group having an aromatic ring, R ² and R ⁴ represent a hydrogen atom or an alkyl group, and a plurality of R ² and R ⁴ are the same. But it may be different.)
3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenylsulfonetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride Anhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyl ether tetracarboxylic dianhydride, 3,3 ′, 4,4′-dimethyldiphenyl Silane tetracarboxylic dianhydride, 3,3 ′, 4,4′-tetraphenylsilane tetracarboxylic dianhydride, 1,2,3,4-furantetracarboxylic dianhydride, 4,4′-bis (3,4-dicarboxyphenoxy) diphenyl sulfide dianhydride, 4,4′-bis (3,4-dicarboxyphenoxy) diphenylsulfone dianhydride, 4,4′-bis (3,4-dicarboxyphenoxy) ) Gife Nylpropane dianhydride, 3,3 ′, 4,4′-perfluoroisopropylidenediphthalic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,2 ′, 3 , 3′-biphenyltetracarboxylic dianhydride, bis (phthalic acid) phenylphosphine oxide dianhydride, p-phenylene-bis (triphenylphthalic acid) dianhydride, m-phenylene-bis (triphenylphthalic acid) Dianhydride, bis (triphenylphthalic acid) -4,4'-diphenyl ether dianhydride, bis (triphenylphthalic acid) -4,4'-diphenylmethane dianhydride, ethylene glycol-bis (anhydro trimellitate) ), Propylene glycol-bis (anhydro trimellitate), 1,4-butanediol-bis (anhydro trimellitate), 1,6-he Sundiol-bis (anhydro trimellitate), 1,8-octanediol-bis (anhydro trimellitate), 2,2-bis (4-hydroxyphenyl) propane-bis (anhydro trimellitate), Aromatic tetracarboxylic dianhydrides such as compounds represented by the following formulas (1) to (4) can be exemplified. These may be used alone or in combination of two or more.

Of these, butanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 5- (2, 5-Dioxotetrahydrofural) -3-methyl-3-cyclohexene-1,2-dicarboxylic dianhydride, bicyclo [2.2.2] -oct-7-ene-2,3,5,6-tetra Carboxylic dianhydride, 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-tricarboxy-2-carboxynorbornane-2: 3,5: 6-2 Anhydride, 4,9- Oxatricyclo [5.3.1.0 ^{2, 6]} undecane -3,5,8,10- tetraone, 2,2 ', 3,3'-biphenyltetracarboxylic dianhydride, the formula (I) Among the compounds represented by formula (5), the compound represented by each of the following formulas (5) to (7) and the compound represented by the following formula (8) among the compounds represented by the above formula (II) are good. It is preferable from the viewpoint of exhibiting excellent liquid crystal orientation.

Preferably, P ² is 30 to 70 mol% of a tetravalent organic group derived from pyrrolemetic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2-dimethyl-1,2 , 3,4-cyclobutanetetracarboxylic dianhydride, 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,3-dichloro-1,2,3,4-cyclobutane From tetracarboxylic dianhydride, 1,2,3,4-tetramethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride and 1,2,3,4-cyclohexanetetracarboxylic dianhydride It consists of 30 to 70 mol% of tetravalent organic groups derived from at least one tetracarboxylic dianhydride selected from the group or tetravalent organic groups derived from other tetracarboxylic dianhydrides.
Further, as the tetracarboxylic dianhydride constituting P ¹ in the above formula (I-1), unlike the case where the tetracarboxylic dianhydride described above for the polyamic acid is a polyamic acid, it is used without any limitation. .

[Diamine compound]
Examples of the diamine compound used for the synthesis of polyamic acid or polyimide include p-phenylenediamine, m-phenylenediamine, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylethane, and 4,4′-diaminodiphenyl sulfide. 4,4′-diaminodiphenyl sulfone, 3,3′-dimethyl-4,4′-diaminobiphenyl, 4,4′-diaminobenzanilide, 4,4′-diaminodiphenyl ether, 1,5-diaminonaphthalene, 2, , 2′-dimethyl-4,4′-diaminobiphenyl, 5-amino-1- (4′-aminophenyl) -1,3,3-trimethylindane, 6-amino-1- (4′-aminophenyl) -1,3,3-trimethylindane, 3,4'-diaminodiphenyl ether, 3,3'-diaminoben Phenone, 3,4′-diaminobenzophenone, 4,4′-diaminobenzophenone, 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, 1,4-bis (4-aminophenoxy) Benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 9,9-bis (4-aminophenyl) -10-hydroanthracene, 2,7-diamino Fluorene, 9,9-dimethyl-2,7-diaminofluorene, 9,9-bis (4-aminophenyl) fluorene, 4,4′-methyl -Bis (2-chloroaniline), 2,2 ′, 5,5′-tetrachloro-4,4′-diaminobiphenyl, 2,2′-dichloro-4,4′-diamino-5,5′- Dimethoxybiphenyl, 3,3′-dimethoxy-4,4′-diaminobiphenyl, 1,4,4 ′-(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′-trifluoromethoxybenzoyloxy) cyclohexyl-3,5-diaminobenzene Aromatic diamines such as Nzoates;
1,1-metaxylylenediamine, 1,3-propanediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, 4,4-diaminoheptamethylenediamine, 1 , 4-diaminocyclohexane, isophoronediamine, tetrahydrodicyclopentadienylenediamine, hexahydro-4,7-methanoindanylene methylenediamine, tricyclo [6.2.1.0 ^2,7 ] -undecylenedimethyldiamine, 4 Aliphatic and cycloaliphatic diamines such as 1,4′-methylenebis (cyclohexylamine), 1,3-bis (aminomethyl) cyclohexane, 1,4-bis (aminomethyl) cyclohexane;
2,3-diaminopyridine, 2,6-diaminopyridine, 3,4-diaminopyridine, 2,4-diaminopyrimidine, 5,6-diamino-2,3-dicyanopyrazine, 5,6-diamino-2,4 -Dihydroxypyrimidine, 2,4-diamino-6-dimethylamino-1,3,5-triazine, 1,4-bis (3-aminopropyl) piperazine, 2,4-diamino-6-isopropoxy-1,3 , 5-triazine, 2,4-diamino-6-methoxy-1,3,5-triazine, 2,4-diamino-6-phenyl-1,3,5-triazine, 2,4-diamino-6-methyl -S-triazine, 2,4-diamino-1,3,5-triazine, 4,6-diamino-2-vinyl-s-triazine, 2,4-diamino-5-phenylthiazole, 2,6- Aminopurine, 5,6-diamino-1,3-dimethyluracil, 3,5-diamino-1,2,4-triazole, 6,9-diamino-2-ethoxyacridine lactate, 3,8-diamino-6 Phenylphenanthridine, 1,4-diaminopiperazine, 3,6-diaminoacridine, bis (4-aminophenyl) phenylamine, 3,6-diaminocarbazole, N-methyl-3,6-diaminocarbazole, N-ethyl -3,6-diaminocarbazole, N-phenyl-3,6-diaminocarbazole, N, N'-di (4-aminophenyl) -benzidine, and each of the following formulas (III) to (VI) A diamine having two primary amino groups and a nitrogen atom other than the primary amino group in the molecule, such as a compound;

(In the formula, R ⁵ represents a monovalent organic group having a ring structure containing a nitrogen atom selected from pyridine, pyrimidine, triazine, piperidine and piperazine, and X represents a divalent organic group.)

(Wherein X represents a divalent organic group having a ring structure containing a nitrogen atom selected from pyridine, pyrimidine, triazine, piperidine and piperazine, R ⁶ represents a divalent organic group, and a plurality of X May be the same or different.)
Monosubstituted phenylenediamine represented by the following formula (V); diaminoorganosiloxane represented by the following formula (VI);

(Wherein R ⁷ represents a divalent organic group selected from —O—, —COO—, —OCO—, —NHCO—, —CONH— and —CO—, and R ⁸ represents a steroid skeleton, A monovalent organic group having a group selected from a fluoromethyl group and a fluoro group or an alkyl group having 6 to 30 carbon atoms is shown.)

(In the formula, R ⁹ represents a hydrocarbon group having 1 to 12 carbon atoms, and a plurality of R ⁹ may be the same or different, p is an integer of 1 to 3, and q is 1 to 20) Is an integer.)
Examples include compounds represented by the following formulas (9) to (13). These diamine compounds can be used alone or in combination of two or more.

(In the formula, y is an integer of 2 to 12, and z is an integer of 1 to 5.)
Among these, p-phenylenediamine, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenyl sulfide, 1,5-diaminonaphthalene, 2,7-diaminofluorene, 4,4′-diaminodiphenyl ether, 2, 2-bis [4- (4-aminophenoxy) phenyl] propane, 9,9-bis (4-aminophenyl) fluorene, 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane, 2 , 2-bis (4-aminophenyl) hexafluoropropane, 4,4 ′-(p-phenylenediisopropylidene) bisaniline, 4,4 ′-(m-phenylenediisopropylidene) bisaniline, 1,4-cyclohexanediamine 4,4′-methylenebis (cyclohexylamine), 1,4-bis (4-amino) Enoxy) benzene, 4,4′-bis (4-aminophenoxy) biphenyl, 4- (4′-trifluoromethoxybenzoyloxy) cyclohexyl-3,5-diaminobenzoate, 1,3-bis (aminomethyl) cyclohexane , Compounds represented by the above formulas (9) to (13), 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, N′-di (4-aminophenyl) -benzidine Of the compounds represented by the formula (III), a compound represented by the following formula (14), a compound represented by the formula (IV) Compounds represented by the following formulas (16) to (21) Among the compounds represented by and a compound represented by the formula (V) by the following equation (15) of the object is preferable.

[Synthetic reaction of polyamic acid]
The ratio of the tetracarboxylic dianhydride and the diamine compound used for the polyamic acid synthesis reaction is such that the acid anhydride group of the tetracarboxylic dianhydride is 0.1 relative to 1 equivalent of the amino group contained in the diamine compound. A ratio of 5 to 2 equivalents is preferable, and a ratio of 0.7 to 1.2 equivalents is more preferable.
The synthetic reaction of polyamic acid is preferably carried out in an organic solvent under a temperature condition of -20 to 150 ° C, more preferably 0 to 100 ° C. Here, the organic solvent is not particularly limited as long as it can dissolve the synthesized polyamic acid. For example, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, dimethyl sulfoxide And aprotic polar solvents such as γ-butyrolactone, tetramethylurea and hexamethylphosphortriamide; and phenolic solvents such as m-cresol, xylenol, phenol and halogenated phenol. The amount of the organic solvent used (a) is such that the total amount (b) of the tetracarboxylic dianhydride and the diamine compound is 0.1 to 30% by weight with respect to the total amount (a + b) of the reaction solution. It is preferable that

[Poor solvent]
For the organic solvent, alcohol, ketone, ester, ether, halogenated hydrocarbon, hydrocarbon and the like, which are poor solvents for polyamic acid, can be used in combination as long as the polyamic acid to be produced does not precipitate. Specific examples of the poor solvent include, for example, methyl alcohol, ethyl alcohol, isopropyl alcohol, cyclohexanol, ethylene glycol, propylene glycol, 1,4-butanediol, triethylene glycol, ethylene glycol monomethyl ether, ethyl lactate, butyl lactate, Acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methyl acetate, ethyl acetate, butyl acetate, methyl methoxypropionate, ethyl ethoxypropionate, diethyl oxalate, diethyl malonate, diethyl ether, ethylene glycol methyl ether, ethylene Glycol ethyl ether, ethylene glycol-n-propyl ether, ethylene glycol-i-propyl ether, ethylene glycol-n- Chill 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, tetrahydrofuran, dichloromethane, 1,2-dichloroethane, 1 , 4-dichlorobutane, trichloroethane, chlorobenzene, o-dichlorobenzene, hexane, heptane, octane, benzene, toluene, xylene, isoamylpropionate, isoamylisobutyrate, diisopentyl ether and the like.

  As described above, a reaction solution obtained by dissolving polyamic acid is obtained. Then, the reaction solution is poured into a large amount of poor solvent to obtain a precipitate, and the precipitate is dried under reduced pressure, or the reaction solution is distilled off under reduced pressure with an evaporator to obtain a polyamic acid. Further, the polyamic acid can be purified by dissolving the polyamic acid again in an organic solvent and then precipitating it with a poor solvent, or performing the step of evaporating under reduced pressure with an evaporator once or several times.

[Polyimide]
The polyimide constituting the liquid crystal aligning agent of the present invention can be prepared by dehydrating and ring-closing the polyamic acid as described above. The polyimide used in the present invention may be partially dehydrated and ring-closed with an imidization rate of less than 100%. The “imidation ratio” here is a value representing the ratio of the repeating unit having an imide ring or an isoimide ring as a percentage in all repeating units of the polymer. An alignment agent containing an imidized polymer having an imidization ratio of 20 to 100% can be evaluated as having a high voltage holding ratio, particularly when used in a TFT type device. The polyamic acid is dehydrated and closed by (i) a method of heating the polyamic acid, or (ii) dissolving the polyamic acid in an organic solvent, adding a dehydrating agent and a dehydrating ring-closing catalyst to this solution, and heating as necessary. By the method.
The reaction temperature in the method of heating the polyamic acid (i) is preferably 50 to 200 ° C, more preferably 60 to 170 ° C. If the reaction temperature is less than 50 ° C., the dehydration ring-closure reaction does not proceed sufficiently, and if the reaction temperature exceeds 200 ° C., the molecular weight of the imidized polymer obtained may decrease.

  On the other hand, in the method (ii) of adding a dehydrating agent and a dehydrating ring-closing catalyst to the polyamic acid solution, an acid anhydride such as acetic anhydride, propionic anhydride, or trifluoroacetic anhydride is used as the dehydrating agent. Can do. The amount of the dehydrating agent used is preferably 0.01 to 20 mol relative to 1 mol of the polyamic acid repeating unit. Moreover, as a dehydration ring closure catalyst, tertiary amines, such as a pyridine, a collidine, a lutidine, a triethylamine, can be used, for example. However, it is not limited to these. The amount of the dehydration ring-closing catalyst used is preferably 0.01 to 10 mol with respect to 1 mol of the dehydrating agent used. In addition, as an organic solvent used for dehydration ring closure reaction, the organic solvent illustrated as what is used for the synthesis | combination of a polyamic acid can be mentioned. And the reaction temperature of dehydration ring closure reaction becomes like this. Preferably it is 0-180 degreeC, More preferably, it is 10-150 degreeC. Moreover, a polyimide can be refine | purified by performing operation similar to the purification method of polyamic acid with respect to the reaction solution obtained in this way.

Method for measuring imidation rate of imidized polymer After imidized polymer was dried under reduced pressure at room temperature, it was dissolved in deuterated dimethyl sulfoxide, and ¹ H-NMR was measured at room temperature using tetramethylsilane as a reference substance. It can obtain | require by the type | formula shown by (ii).
Imidation ratio (%) = (1-A ¹ / A ² × α) × 100 ------ (ii)
A ¹ : NH group proton-derived peak area (10 ppm)
A ² : Peak area derived from other protons α: Number ratio of other protons to one proton of NH group in polymer precursor (polyamic acid)

<End-modified polymer>
The polyamic acid, the polyimide, and the partially imidized block polymer may be of a terminal modified type in which the molecular weight is adjusted. By using this terminal-modified polymer, the coating characteristics of the liquid crystal aligning agent can be improved without impairing the effects of the present invention. Such a terminal-modified type can be synthesized by adding an acid monoanhydride, a monoamine compound, a monoisocyanate compound or the like to the reaction system when synthesizing the polyamic acid. Here, as the acid monoanhydride, for example, maleic anhydride, phthalic anhydride, itaconic anhydride, n-decyl succinic anhydride, n-dodecyl succinic anhydride, n-tetradecyl succinic anhydride , N-hexadecyl succinic anhydride and the like. Examples of monoamine compounds include aniline, cyclohexylamine, n-butylamine, n-pentylamine, n-hexylamine, n-heptylamine, n-octylamine, n-nonylamine, n-decylamine, and n-undecylamine. N-dodecylamine, n-tridecylamine, n-tetradecylamine, n-pentadecylamine, n-hexadecylamine, n-heptadecylamine, n-octadecylamine, n-eicosylamine, etc. Can do. Examples of the monoisocyanate compound include phenyl isocyanate and naphthyl isocyanate.

<Solution viscosity>
The polymer used in the aligning agent of the present invention preferably has a viscosity of 20 to 800 mPa · s, and has a viscosity of 30 to 500 mPa · s, when a 10% by weight solution is obtained. It is more preferable.
In addition, the solution viscosity (mPa * s) of the polymer was measured at 25 degreeC using the E-type rotational viscometer about the solution diluted to the solid content concentration of 10 weight% using the predetermined | prescribed solvent.

<Liquid crystal aligning agent>
The liquid crystal aligning agent of this invention is comprised by the said polymer and the other component added arbitrarily being normally dissolved and contained in the organic solvent. In the polymer constituting the liquid crystal aligning agent of the present invention, the molar ratio of the imide bond unit represented by the formula (I-1) to the amic acid bond unit represented by the formula (I-2) is 40. : 60-5: 95.
As an organic solvent which comprises the liquid crystal aligning agent of this invention, the solvent illustrated as what is used for the synthesis reaction of a polyamic acid can be mentioned. Moreover, the poor solvent illustrated as what can be used together in the case of the synthesis reaction of a polyamic acid can also be selected suitably, and can be used together.

Particularly preferred organic solvents used in the liquid crystal aligning agent of the present invention include N-methyl-2-pyrrolidone, γ-butyrolactone, γ-butyrolactam, N, N-dimethylformamide, N, 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-i-propyl ether, ethylene glycol-n-butyl ether (butyl cellosolve), ethylene glycol dimethyl ether, ethylene glycol ethyl ether acetate, diethylene glycol di Examples thereof include methyl ether, diethylene glycol diethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, isoamyl propionate, isoamyl isobutyrate, and diisopentyl ether. These can be used alone or in admixture of two or more. A particularly preferable solvent composition is a composition obtained by combining the above-mentioned solvents, wherein no polymer is precipitated in the aligning agent, and the surface tension of the aligning agent is in the range of 25 to 40 mN / m. It is.

The solid content concentration in the liquid crystal aligning agent of the present invention is selected in consideration of viscosity, volatility and the like. Preferably it is the range of 1-10 weight%. That is, the liquid crystal aligning agent of the present invention is applied to the substrate surface to form a coating film that becomes a liquid crystal alignment film. When the solid content concentration is less than 1% by weight, the coating film thickness is When the solid content concentration exceeds 10% by weight, it is difficult to obtain a good liquid crystal alignment film because the film thickness is excessive. The viscosity of the aligning agent increases, resulting in poor coating properties.
The particularly preferable solid content concentration range varies depending on the method used when the liquid crystal aligning agent is applied to the substrate. For example, when the spinner method is used, the range of 1.5 to 4.5% by weight is particularly preferable. In the case of the printing method, it is particularly preferable that the solid content concentration is in the range of 3 to 9% by weight, and thereby the solution viscosity is in the range of 12 to 50 mPa · s. In the case of the ink jet method, it is particularly preferable that the solid content concentration is in the range of 1 to 5% by weight, and thereby the solution viscosity is in the range of 3 to 15 mPa · s.
The temperature at which the liquid crystal aligning agent of the present invention is prepared is preferably 0 ° C to 200 ° C, more preferably 20 ° C to 60 ° C.

  The liquid crystal aligning agent that forms the liquid crystal aligning film of the present invention needs to contain a specific epoxy compound. Preferred specific epoxy compounds include, for example, N, N, N ′, N′-tetraglycidyl-m-xylenediamine, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, and the like. . The compounding ratio of these epoxy group-containing compounds is 5 parts by weight or more, preferably 10 to 30 parts by weight with respect to 100 parts by weight of the polymer.

Moreover, the liquid crystal aligning agent of this invention may contain the functional silane containing compound. Examples of such functional silane-containing compounds include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 2-aminopropyltrimethoxysilane, 2-aminopropyltriethoxysilane, and N- (2-aminoethyl). -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-ureidopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, N-ethoxycarbonyl-3-amino Propyltrimethoxysilane, N-ethoxycarbonyl-3-aminopropyltriethoxysilane, N-triethoxysilylpropyltriethylenetriamine, N-trimethoxysilylpropyltriethylenetriamine, 10-trimethoxysilyl- , 4,7-triazadecane, 10-triethoxysilyl-1,4,7-triazadecane, 9-trimethoxysilyl-3,6-diazanonyl acetate, 9-triethoxysilyl-3,6-diazanonyl acetate N-benzyl-3-aminopropyltrimethoxysilane, N-benzyl-3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-phenyl-3-aminopropyltriethoxysilane, N -Bis (oxyethylene) -3-aminopropyltrimethoxysilane, N-bis (oxyethylene) -3-aminopropyltriethoxysilane, etc. can be mentioned.
The blending ratio of these functional silane-containing compounds is preferably 2 parts by weight or less, more preferably 0.2 parts by weight or less with respect to 100 parts by weight of the polymer.

<Liquid crystal display element>
The liquid crystal display element obtained using the liquid crystal aligning agent of this invention can be manufactured, for example with the following method.

(1) The liquid crystal aligning agent of the present invention is applied to one surface of a substrate provided with a patterned transparent conductive film by a method such as a roll coater method, a spinner method, a printing method, an ink jet method, etc. Is heated to form a coating film. Here, as the substrate, for example, glass such as float glass or soda glass; a transparent substrate made of plastic such as polyethylene terephthalate, polybutylene terephthalate, polyethersulfone, polycarbonate, alicyclic polyolefin, or the like can be used. As a transparent conductive film provided on one surface of the substrate, an NESA film (registered trademark of PPG, USA) made of tin oxide (SnO ₂ ), an ITO film made of indium oxide-tin oxide (In ₂ O ₃ —SnO ₂ ), etc. For patterning these transparent conductive films, a photo-etching method or a method using a mask in advance is used. When applying the liquid crystal aligning agent, in order to further improve the adhesion between the substrate surface and the transparent conductive film and the coating film, a functional silane-containing compound, a functional titanium-containing compound, or the like is previously applied to the surface of the substrate. You can also After applying the liquid crystal aligning agent, preheating (pre-baking) is preferably performed for the purpose of preventing dripping of the applied aligning agent. The pre-baking temperature is preferably 30 to 200 ° C, more preferably 40 to 150 ° C, and particularly preferably 40 to 100 ° C. Thereafter, a baking (post-baking) step is performed for the purpose of completely removing the solvent and heat imidizing the polyamic acid. The firing (post-bake) temperature is preferably 80 to 300 ° C, more preferably 120 to 250 ° C. In this way, the liquid crystal aligning agent of the present invention containing a polyamic acid forms a coating film that becomes a liquid crystal aligning film by removing the organic solvent after coating, and further proceeds with dehydration ring closure by further heating. An imidized liquid crystal alignment film can also be used. The film thickness of the liquid crystal alignment film to be formed is preferably 0.001 to 1 μm, and more preferably 0.005 to 0.5 μm.

(2) A rubbing process is performed in which the formed coating film surface is rubbed in a certain direction with a roll wound with a cloth made of a fiber such as nylon, rayon, or cotton. Thereby, the orientation ability of liquid crystal molecules is imparted to the coating film to form a liquid crystal orientation film.
Further, by partially irradiating the liquid crystal alignment film formed of the liquid crystal alignment agent of the present invention with ultraviolet rays as disclosed in, for example, JP-A-6-222366 and JP-A-6-281937. A resist film is partially formed on the surface of the liquid crystal alignment film that has been subjected to a treatment for changing the pretilt angle or a rubbing treatment as disclosed in JP-A-5-107544, which is different from the previous rubbing treatment. The visibility characteristics of the liquid crystal display element can be improved by removing the resist film after performing the rubbing treatment in the direction and changing the liquid crystal alignment ability of the liquid crystal alignment film.

(3) Two substrates on which the liquid crystal alignment film is formed as described above are manufactured, and the two substrates are separated by a gap (cell gap) so that the rubbing directions in the respective liquid crystal alignment films are orthogonal or antiparallel. ), And the periphery of the two substrates are bonded together using a sealant, and liquid crystal is injected and filled in the cell gap defined by the substrate surface and the sealant, and the injection hole is sealed. A liquid crystal cell is constructed. And a liquid crystal display element is obtained by arrange | positioning a polarizing plate to the outer surface of a liquid crystal cell, ie, the transparent substrate side which comprises a liquid crystal cell.
Here, as the sealing agent, for example, an epoxy resin containing a curing agent and aluminum oxide spheres as a spacer can be used.

Examples of the liquid crystal include nematic liquid crystal and smectic liquid crystal. Among them, nematic liquid crystal is preferable. For example, Schiff base liquid crystal, azoxy liquid crystal, biphenyl liquid crystal, phenyl cyclohexane liquid crystal, ester liquid crystal, terphenyl liquid crystal. Liquid crystals, biphenylcyclohexane liquid crystals, pyrimidine liquid crystals, dioxane liquid crystals, bicyclooctane liquid crystals, cubane liquid crystals, and the like can be used. Further, for these liquid crystals, for example, cholesteric liquid crystals such as cholestyl chloride, cholesteryl nonate, cholesteryl carbonate, and chiral agents such as those sold under the trade names “C-15” and “CB-15” (manufactured by Merck). Etc. can also be used. Furthermore, a ferroelectric liquid crystal such as p-decyloxybenzylidene-p-amino-2-methylbutylcinnamate can also be used.
Further, as a polarizing plate to be bonded to the outer surface of the liquid crystal cell, a polarizing film or an H film in which a polarizing film called an H film that absorbs iodine while sandwiching and stretching polyvinyl alcohol is sandwiched between cellulose acetate protective films. The polarizing plate which consists of itself can be mentioned.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. The image sticking and imidization rate in the examples and comparative examples were evaluated by the following methods.

[Burn in]
A direct current of 5.0 V was applied to the liquid crystal display element for 20 hours, and a residual DC voltage was determined by a flicker-erasing method for the voltage remaining in the liquid crystal cell immediately after the direct current voltage was cut off. The case where the value of the residual DC voltage was 0.1 V or less was judged as good, and the case other than that was judged as bad.

[Method for measuring imidization rate of imidized polymer]
The imidized polymer was dried at room temperature under reduced pressure, then dissolved in deuterated dimethyl sulfoxide, and ¹ H-NMR was measured at room temperature using tetramethylsilane as a reference substance, and determined by the formula shown by the following formula (ii). .
Imidation ratio (%) = (1-A ¹ / A ² × α) × 100 ------ (ii)
A ¹ : NH group proton-derived peak area (10 ppm)
A ² : Peak area derived from other protons α: Number ratio of other protons to one proton of NH group in polymer precursor (polyamic acid)

[Solution viscosity]
The solution viscosity (mPa · s) of the polymer was measured at 25 ° C. using an E-type rotational viscometer for a solution diluted to a solid concentration of 10% by weight using a predetermined solvent.

Synthesis example 1
191 g (0.85 mol) of 2,3,5-tricarboxycyclopentylacetic acid dianhydride as tetracarboxylic dianhydride and 1,3,3a, 4,5,9b-hexahydro-8-methyl-5- (tetrahydro -2,5-dioxo-3-furanyl) naphtho [1,2-c] furan-1,3-dione 47 g (0.15 mol), p-phenylenediamine 91 g (0.85 mol) as a diamine compound, bis 25 g (0.10 mol) of aminopropyltetramethyldisiloxane, 25 g (0.040 mol) of 3,6-bis (4-aminobenzoyloxy) cholestane, and 2.8 g (0.030 mol) of aniline as a monoamine -Methyl-2-pyrrolidone was dissolved in 4,500 g and reacted at 60 ° C. for 6 hours. Next, 30 g of the obtained polyamic acid was dissolved in 570 g of N-methyl-2-pyrrolidone, 23 g of pyridine and 18 g of acetic anhydride were added, and dehydration ring closure was performed at 110 ° C. for 4 hours. After the imidization reaction, the solvent in the system was replaced with new γ-butyrolactone (pyridine and acetic anhydride used for the imidization reaction were removed from the system in this operation), and the solid content concentration was 10% by weight ( About 120 g of an imidized polymer solution (hereinafter referred to as “polyimide (A-1)”) having a solution viscosity of γ-butyrolactone solution of 65 mPa · s and an imidization ratio of about 95% was obtained.

Synthesis example 2
109 g (0.50 mol) of pyromellitic dianhydride as tetracarboxylic dianhydride, 98 g (0.50 mol) of 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 4,4 as diamine compound -200 g (1.0 mol) of diaminodiphenyl ether was dissolved in 230 g of N-methyl-2-pyrrolidone and 2,060 g of γ-butyrolactone, reacted at 40 ° C for 3 hours, and then 1,350 g of γ-butyrolactone was added. About 3,590 g of a polyamic acid (this is referred to as polyamic acid (B-1)) solution having a solid viscosity of 10% by weight and a solution viscosity of 200 mPa · s was obtained.

Synthesis example 3
1,2,3,4-cyclobutanetetracarboxylic dianhydride 98 g (0.50 mol) as tetracarboxylic dianhydride, 109 g (0.50 mol) pyromellitic dianhydride, 4,4 as diamine compound 198 g (1.0 mol) of '-diaminodiphenylmethane was dissolved in 230 g of N-methyl-2-pyrrolidone and 2,060 g of γ-butyrolactone, reacted at 40 ° C. for 3 hours, and then 1,350 g of γ-butyrolactone was added. Thus, about 3,600 g of a polyamic acid solution having a solid content concentration of 10% by weight and a solution viscosity of 125 mPa · s (hereinafter referred to as polyamic acid (B-2)) was obtained.

Synthesis example 4
1,2,3,4-cyclobutanetetracarboxylic dianhydride 98 g (0.50 mol) as tetracarboxylic dianhydride, 109 g (0.50 mol) pyromellitic dianhydride, 2,2 as diamine compound '-Dimethyl-4,4'-diaminobiphenyl (212 g, 1.0 mol) was dissolved in N-methyl-2-pyrrolidone (230 g) and γ-butyrolactone (2,060 g) and reacted at 40 ° C. for 3 hours. 1,350 g of butyrolactone was added to obtain about 3,600 g of a polyamic acid (this polyamic acid (B-3)) solution having a solution viscosity of 220 mPa · s at a solid concentration of 10% by weight.

Synthesis example 5
196 g (1.0 mol) of 1,2,3,4-cyclobutanetetracarboxylic dianhydride as tetracarboxylic dianhydride and 212 g (1 of 2,2′-dimethyl-4,4′-diaminobiphenyl as diamine compound) 0.0 mol) was dissolved in N-methyl-2-pyrrolidone (370 g) and γ-butyrolactone (3,300 g) and reacted at 40 ° C. for 3 hours, and the solution viscosity was 160 mPa · s polyamic acid (this was polyamic acid (B-4)) About 3,700 g of solution was obtained.

Example 1
The polyimide (A-1) obtained in Synthesis Example 1 and the polyamic acid (B-1) obtained in Synthesis Example 2 were mixed with γ-butyrolactone so that polyimide: polyamic acid = 20: 80 (weight ratio). / N-methyl-2-pyrrolidone / butyl cellosolve mixed solvent (weight ratio 71/17/12), and N, N, N ′, N′-tetraglycidyl-m-xylenediamine was added to 100 parts by weight of the polymer. On the other hand, a solution having a solid content concentration of 3.5% by weight was dissolved by 20 parts by weight, and after sufficient stirring, this solution was filtered using a filter having a pore size of 1 μm to prepare the liquid crystal aligning agent of the present invention. The liquid crystal aligning agent was applied onto a transparent conductive film made of an ITO film provided on one surface of a glass substrate having a thickness of 1 mm using a spinner (rotation speed: 2500 rpm, application time: 1 minute), and 200 A film having a dry film thickness of 0.08 μm was formed by drying at 0 ° C. for 1 hour. A rubbing machine having a roll in which a rayon cloth was wound around this film was subjected to a rubbing treatment at a roll rotation speed of 400 rpm, a stage moving speed of 3 cm / second, and a hair foot pushing length of 0.4 mm. Next, it was ultrasonically cleaned in ultrapure water for 1 minute and dried in a 100 ° C. clean oven for 10 minutes. Next, after applying an epoxy resin adhesive containing aluminum oxide spheres having a diameter of 5.5 μm to the outer edges of the pair of transparent electrodes / transparent electrode substrates having the liquid crystal alignment film of the liquid crystal alignment film coated substrate, the liquid crystal alignment film The adhesive was cured by overlapping and pressing so that the surfaces were opposed. Next, a nematic liquid crystal (MLC-6221, manufactured by Merck & Co., Inc.) is filled between the substrates through the liquid crystal injection port, and then the liquid crystal injection port is sealed with an acrylic photocuring adhesive, and polarizing plates are formed on both sides of the substrate. Were laminated to prepare a liquid crystal display element. The image sticking of the obtained liquid crystal display element was evaluated. The liquid crystal aligning agent obtained in the present invention exhibited a low residual DC voltage of 0.1 V or less.

Examples 2-6 and Comparative Examples 1-8
Polyimide (A-1) obtained in Synthesis Example 1, polyamic acids (B-1) to (B-4) obtained in Synthesis Examples 2 to 5, and N, N, N ′, N′-tetraglycidyl -M-xylenediamine or 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane was dissolved in a mixed solvent containing γ-butyrolactone as a main component to obtain a solution having a solid content concentration of 3.5% by weight. The liquid crystal aligning agent of the present invention was prepared by filtering the solution through a filter having a pore size of 1 μm. Using each of the liquid crystal alignment agents thus adjusted, a film was formed on the substrate surface in the same manner as in Example 1, and a liquid crystal display element was produced using the substrate on which the liquid crystal alignment film was formed. The burn-in was evaluated. The results are shown in Table 1.

Claims (3)

100 parts by weight of a polymer having an imide bond unit represented by the following formula (I-1) and an amic acid bond unit represented by the following formula (I-2), wherein the imide bond unit and the amic acid bond The ratio of the amic acid bond unit to the total number of bond units of the unit is 60 to 95 mol%, and at least 5 parts by weight of the compound represented by the following formula (I-3) containing an epoxy group in the molecule A liquid crystal aligning agent characterized by comprising.

(Wherein P ¹ is a tetravalent organic group and Q ¹ is a divalent organic group.)

(Wherein P ² is a tetravalent organic group and at least 30 mol% of a tetravalent organic group derived from pyromellitic dianhydride and 1,2,3,4-cyclobutanetetracarboxylic dianhydride) 1,2-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,3- Dichloro-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-tetramethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride and 1,2,4 consists tetravalent organic radical derived from at least one tetracarboxylic dianhydride selected from the group consisting of 5-cyclohexanetetracarboxylic dianhydride, and Q ² is a divalent organic group.)

(Here, R is a divalent organic group.) The liquid crystal aligning film formed from the liquid crystal aligning agent of Claim 1. A liquid crystal display element comprising the liquid crystal alignment film according to claim 2.