TWI615440B - Liquid crystal alignment agent, liquid crystal alignment film, liquid crystal display device - Google Patents

Abstract

The present invention provides a liquid crystal alignment agent capable of manufacturing a highly reliable liquid crystal display element. The liquid crystal alignment agent contains at least one polymer (A) selected from the group consisting of polyamidic acid, polyamidate, and polyimide, and a polyfunctional block having an aromatic ring. Isocyanate compound (B-1).

Description

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

The present invention relates to a liquid crystal alignment agent, a liquid crystal alignment film, and a liquid crystal display element, and in particular, to a technology for improving the reliability of a liquid crystal display element.

In the past, liquid crystal display devices have developed various driving methods such as an electrode structure or the physical properties of liquid crystal molecules used. For example, Twisted Nematic (TN) or Super Twisted Nematic (STN) are known. Type, Vertical Alignment (VA), Multi-domain Vertical Alignment (MVA), In-Plane Switching (IPS), Fringe Field Switching (FFS) ), Optically Compensated Bend (OCB) and other liquid crystal display elements. These liquid crystal display elements have a liquid crystal alignment film for aligning liquid crystal molecules. The liquid crystal alignment film is made of polymers such as polyamic acid, polyimide, polyamidate, polyester, and polyorganosiloxane. Among them, various properties such as heat resistance, mechanical strength, and affinity for liquid crystals are used. On the positive side, polyamidic acid or polyimide is usually used.

In recent years, liquid crystal display elements have been used not only in display devices such as personal computers as before, but also in various types such as liquid crystal televisions or car navigation systems, mobile phones, smartphones, and information displays. use. In addition, a liquid crystal display element is required to have a highly reliable element that can withstand long-term use, and a variety of liquid crystal alignment agents that satisfy the above-mentioned requirements have been proposed (for example, refer to Patent Documents 1 and 2). Patent Documents 1 and 2 disclose liquid crystal alignment agents that contain not only polyfluorene imine having a carboxyl group as a polymer component, but also a primary amino group having a primary amine group and a nitrogen-containing aromatic heterocyclic ring. A primary amine compound bonded to an aliphatic hydrocarbon group is used as an additive.

[Prior Art Literature]

[Patent Literature]

[Patent Document 1] International Publication No. 2008/013285

[Patent Document 2] International Publication No. 2009/084665

The requirements for the high performance of liquid crystal display elements have been further increased. Liquid crystal alignment films require liquid crystal alignment films that have less deterioration and deterioration after long-term use than the previous liquid crystal alignment films, and which can appropriately exhibit the performance as liquid crystal alignment films. .

This invention is made in view of the said subject, The main objective is to provide the liquid crystal aligning agent which can improve the reliability of a liquid crystal display element. Another object is to provide a highly reliable liquid crystal display element.

The present inventors conducted intensive research in order to accomplish the problems of the conventional technology as described above, and as a result, found that the specific problems can be solved by including a specific compound in the liquid crystal alignment agent as an additive, and the present invention has been completed. Specifically, the present invention provides the following liquid crystal alignment agent, liquid crystal alignment film, and liquid crystal display element.

One aspect of the present invention is to provide a liquid crystal alignment agent, comprising: at least one polymer (A) selected from the group consisting of polyamidic acid, polyamidate, and polyimide; and And a polyfunctional block isocyanate compound (B-1) having an aromatic ring.

One aspect of the present invention is to provide a liquid crystal alignment film formed using the liquid crystal alignment agent described above. Then, another aspect of the present invention is to provide a liquid crystal display element including the liquid crystal alignment film.

According to the liquid crystal alignment agent of the present invention, by including the compound (B-1) as an additive component, a liquid crystal display element capable of obtaining a low voltage retention after a long period of use and having a small decrease in voltage retention rate can be formed. Liquid crystal alignment film.

Hereinafter, each component contained in the liquid crystal aligning agent of this invention, and other components arbitrarily mix | blended as needed are demonstrated.

<Polymer (A)>

The liquid crystal alignment agent of the present invention contains, as a polymer component, at least one polymer (A) selected from the group consisting of polyamidic acid, polyamidate, and polyimide.

[Polyamic acid]

Polyamic acid (hereinafter also referred to as "polyamino acid (A)") as the polymer (A) of the present invention can be obtained by, for example, reacting a tetracarboxylic dianhydride with a diamine.

(Tetracarboxylic dianhydride)

Examples of the tetracarboxylic dianhydride used to synthesize the polyamic acid (A) of the present invention include aliphatic tetracarboxylic dianhydride, alicyclic tetracarboxylic dianhydride, and aromatic tetracarboxylic dianhydride. As specific examples of these tetracarboxylic dianhydrides, examples of the aliphatic tetracarboxylic dianhydride include 1, 2, 3, 4-butane tetracarboxylic dianhydride, and the like; and examples of the alicyclic tetracarboxylic dianhydride include : 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 2,3,5-tricarboxycyclopentylacetic dianhydride, 1,3,3a, 4,5,9b-hexahydro-5- (Tetrahydro-2,5-dioxo-3-furyl) -naphtho [1,2-c] furan-1,3-dione, 1,3,3a, 4,5,9b-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- Furyl) -3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, 3,5,6-tricarboxy-2-carboxymethylnorbornane-2: 3,5: 6-di Anhydride, 2,4,6,8-tetracarboxybicyclo [3.3.0] octane-2: 4,6: 8-dianhydride, 4,9-dioxatricyclo [5.3.1.0 ^2,6 ] Monoalkane-3,5,8,10-tetraketone, cyclohexanetetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, etc .; Examples of aromatic tetracarboxylic dianhydride include pyromellitic dianhydride Other than that, tetracarboxylic dianhydride described in Japanese Patent Laid-Open No. 2010-97188 can be used. The tetracarboxylic dianhydrides may be used alone or in combination of two or more.

It is preferable that the tetracarboxylic dianhydride used for synthesize | combining polyamic acid (A) is an alicyclic tetracarboxylic dianhydride from the point which has good solubility or transparency with respect to a solvent. Among them, it is more preferable to include at least one selected from the group consisting of the following tetracarboxylic dianhydrides (hereinafter also referred to as "specific tetracarboxylic dianhydrides"): 2,3,5-tricarboxycyclopentylacetic acid Dianhydride, 1,3,3a, 4,5,9b-hexahydro-5- (tetrahydro-2,5-dioxo-3-furyl) -naphtho [1,2-c] furan-1 , 3-dione, 1,3,3a, 4,5,9b-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: 8-dianhydride, 1,2,4, 5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride and 1,2,3,4-cyclobutanetetracarboxylic dianhydride; particularly preferred At least one of the group consisting of the following tetracarboxylic dianhydrides (hereinafter also referred to as "specific tetracarboxylic dianhydrides"): 2,3,5-tricarboxycyclopentylacetic dianhydride, 2,4, 6,8-tetracarboxybicyclo [3.3.0] octane-2: 4,6: 8-dianhydride, 1,2,3,4-cyclobutane tetra Carboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride and 1,2,3,4-cyclopentanetetracarboxylic dianhydride.

The tetracarboxylic dianhydride used for synthesizing polyamic acid is preferably 20 mol% or more of the specific tetracarboxylic dianhydride, and more preferably the tetracarboxylic dianhydride used for synthesis. The content is 50 mol% or more, and particularly preferably 80 mol% or more.

(Diamine)

Examples of the diamine used for synthesizing the polyamidic acid (A) of the present invention include aliphatic diamines, alicyclic diamines, aromatic diamines, and diamine organosiloxanes. As specific examples of these diamines, examples of the aliphatic diamine include m-xylylenediamine, 1,3-propanediamine, tetramethylenediamine, pentamethylenediamine, and hexamethylenediamine. Examples of the alicyclic diamine include 1,4-diaminocyclohexane, 4,4'-methylenebis (cyclohexylamine), and 1,3-bis (aminomethyl) cyclohexyl. Examples of the aromatic diamine include p-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfide, and 1,5-diamine Naphthalene, 2,2'-dimethyl-4,4'-diaminobiphenyl, 4,4'-diamino-2,2'-bis (trifluoromethyl) biphenyl, 2,7- Diaminofluorene, 4,4'-diaminodiphenyl ether, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 9,9-bis (4-amino Phenyl) fluorene, 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane, 2,2-bis (4-aminophenyl) hexafluoropropane, 4,4 ' -(P-phenylene diisopropylidene) bisaniline, 4,4 '-(m-phenylene diisopropylidene) bisaniline, 1,4-bis (4-aminophenoxy) benzene, 4,4'-bis (4-aminophenoxy) biphenyl, 2,6-diaminopyridine, 3,4-diaminopyridine, 2,4-diaminopyrimidine, 3,6-di Aminoacridine, 3,6-diaminooxazole, N-methyl-3 , 6-diaminooxazole, N-ethyl-3,6-diaminooxazole, N-phenyl-3,6-diaminooxazole, N, N'-bis (4-amino (Phenyl) -benzidine, N, N'-bis (4-aminophenyl) -N, N'-dimethylbenzidine, 1,4-bis- (4-aminophenyl) -pyrazine , 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-indene-6-amine, 3,5-diaminobenzoic acid, cholesteryloxy-3,5-diaminobenzene, bile Sterenyloxy-3,5- Diaminobenzene, cholesteryloxy-2,4-diaminobenzene, cholesteryloxy-2,4-diaminobenzene, 3,5-diaminobenzoic acid cholesteryl Ester, Cholesteryl 3,5-diaminobenzoate, Lanostyl 3,5-diaminobenzoate, 3,6-Bis (4-aminobenzyloxy) cholesterol Stearyl, 3,6-bis (4-aminophenoxy) cholestane, 4- (4'-trifluoromethoxybenzyloxy) cyclohexyl-3,5-diaminobenzyl Acid ester, 4- (4'-trifluoromethylbenzyloxy) cyclohexyl-3,5-diaminobenzoate, 1,1-bis (4-((aminophenyl) formyl) Phenyl) -4-butylcyclohexane, 1,1-bis (4-((aminophenyl) methyl) phenyl) -4-heptylcyclohexane, 1,1-bis ( 4-((aminophenoxy) methyl) phenyl) -4-heptylcyclohexane, 1,1-bis (4-((aminophenyl) methyl) phenyl) -4- ( 4-heptylcyclohexyl) cyclohexane, 2,4-diamino-N, N-diallylaniline, 4-aminobenzylamine, 3-aminobenzylamine, and the following formula ( D-1)

(In the formula (D-1), X ^I and X ^II are each independently a single bond, -O-, -COO-, or -OCO-, and R ^I and R ^II are each independently an alkane group having 1 to 3 carbon atoms. Base, a is 0 or 1, b is an integer from 0 to 2, c is an integer from 1 to 20, and n is 0 or 1, where a and b are not 0 at the same time.)

Compounds shown, etc .; Examples of the diaminoorganosiloxane include 1,3-bis (3-aminopropyl) -tetramethylsiloxane, etc .; in addition, Japanese Patent Laid-Open The diamine described in 2010-97188. Other diamines may be used alone or in combination of two or more of them.

The divalent group represented by "-X ^I- (R ^I -X ^II ) _n- " in the formula (D-1) is preferably an alkanediyl group having 1 to 3 carbon atoms, * -O-, * -COO- or * -OC ₂ H ₄ -O- (wherein the bond marked with "*" is bonded to the diaminophenyl group). Specific examples of the group "-C _c H _{2c + 1} " include, for example, methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, and n-nonyl. , N-decyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, n-octadecyl, n-19 Alkyl, n-icosyl and the like. The two amino groups in the diaminophenyl group are preferably located at the 2,4-position or the 3,5-position with respect to the other groups.

Specific examples of the compound represented by the formula (D-1) include, for example, compounds represented by the following formulae (D-1-1) to (D-1-5).

[Molecular weight regulator]

When synthesizing polyamic acid, a terminal-modified polymer can be synthesized by using an appropriate molecular weight modifier while using the tetracarboxylic dianhydride and diamine as described above. By forming the terminal-modified polymer, it is possible to further improve the coatability (printability) of the liquid crystal alignment agent without impairing the effects of the present invention.

Examples of the molecular weight modifier include acid monoanhydrides, monoamine compounds, and monoisocyanate compounds. Specific examples of these compounds include, for example, maleic anhydride, maleic anhydride, Phthalic anhydride, itaconic anhydride, n-decylsuccinic anhydride, n-dodecylsuccinic anhydride, n-tetradecylsuccinic anhydride, n-hexadecylsuccinic anhydride, etc .; monoamine compounds such as Examples include aniline, cyclohexylamine, n-butylamine, n-pentylamine, n-hexylamine, n-heptylamine, and n-octylamine. Examples of the monoisocyanate compound include phenyl isocyanate, naphthyl isocyanate, and the like.

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

[Synthesis of Polyamic Acid]

The use ratio of the tetracarboxylic dianhydride and the diamine provided for the synthesis reaction of the polyamidic acid of the present invention is preferably 1 equivalent to the amine group of the diamine, and the acid anhydride group of the tetracarboxylic dianhydride becomes 0.2 to 2 equivalent The ratio is more preferably a ratio of 0.3 to 1.2 equivalents.

The synthesis reaction of the polyamic acid is preferably performed in an organic solvent. The reaction temperature at this time is preferably -20 ° C to 150 ° C, and more preferably 0 ° C to 100 ° C. The reaction time is preferably from 0.1 to 24 hours, and more preferably from 0.5 to 12 hours.

Examples of the organic solvent include aprotic polar solvents, phenol-based solvents, alcohols, ketones, esters, ethers, halogenated hydrocarbons, and hydrocarbons. As specific examples of these organic solvents, examples of the aprotic polar solvent include N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidone, and N-ethyl-2-pyrrolidone. , N, N-dimethylacetamide, N, N-dimethylformamide, dimethylmethylene, γ-butyrolactone, tetramethylurea, hexamethylphosphonium triamine, etc .; Examples of the phenol-based solvent include phenol, m-cresol, xylenol, and halogenated phenol. Examples of the alcohol include methanol, ethanol, isopropanol, cyclohexanol, ethylene glycol, propylene glycol, and 1,4. -Butanediol, triethylene glycol, ethylene glycol monomethyl ether, and the like; examples of the ketone include: acetone, methyl Ethyl ketone, methyl isobutyl ketone, cyclohexanone and the like; examples of the ester include ethyl lactate, butyl lactate, methyl acetate, ethyl acetate, butyl acetate, and methoxypropionate , Ethyl ethoxypropionate, diethyl oxalate, diethyl malonate, isoamyl propionate, isoamyl isobutyrate, etc .; examples of the ether include diethyl ether, ethylene glycol Methyl ether, ethylene glycol ether, ethylene glycol-n-propyl ether, ethylene glycol-isopropyl ether, ethylene glycol-n-butyl ether, ethylene glycol dimethyl ether, ethylene glycol 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, Diisoamyl ether and the like; examples of the halogenated hydrocarbon include dichloromethane, 1,2-dichloroethane, 1,4-dichlorobutane, trichloroethane, chlorobenzene, o-dichlorobenzene, etc .; Examples of the hydrocarbon include hexane, heptane, octane, benzene, toluene, xylene and the like.

Among these organic solvents, one or more selected from the group consisting of an aprotic polar solvent and a phenol-based solvent (organic solvent of the first group), or an organic solvent selected from the first group is preferably used. And a mixture of one or more of them with 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 use ratio of the organic solvent in the second group is preferably 50% by weight or less, and more preferably 40% by weight, with respect to the total amount of the organic solvent in the first group and the organic solvent in the second group. Hereinafter, it is particularly preferably 30% by weight or less. It is preferable that the usage-amount (a) of an organic solvent is 0.1 weight%-50 weight% with respect to the total amount (a + b) of a reaction solution, and the total amount (b) of a tetracarboxylic dianhydride and a diamine.

In the manner described above, a reaction solution obtained by dissolving polyamidic acid (A) was obtained. The reaction solution may be directly provided to the preparation of the liquid crystal alignment agent, or the polyamic acid (A) contained in the reaction solution may be isolated and then provided to the preparation of the liquid crystal alignment agent, or the isolated polyfluorene may be provided. The acid (A) is purified and then provided to the preparation of the liquid crystal alignment agent. After dehydration of poly (amino acid) (A) In the case of polyimide, the reaction solution may be directly provided to the dehydration ring-closing reaction, or the polyamido acid (A) contained in the reaction solution may be isolated and then provided to the dehydration ring-closing reaction, or The isolated polyamidic acid (A) may be purified and then provided to a dehydration ring-closure reaction. Isolation and purification of the polyamic acid (A) can be performed according to a known method.

[Polyurethane]

The polyamidate (hereinafter also referred to as polyamidate (A)) as the polymer (A) can be obtained, for example, by the following method: [I] Polyimide obtained by the synthesis reaction A method for synthesizing amidinic acid (A) with a hydroxyl-containing compound, a halide, an epoxy-containing compound, etc .; [II] a method for reacting a tetracarboxylic acid diester with a diamine; and [III] A method of reacting a tetracarboxylic diester dihalide with a diamine, and the like.

Here, examples of the hydroxyl-containing compound used in the method [I] include alcohols such as methanol, ethanol, and propanol; and phenols such as phenol and cresol. Examples of the halide include methyl bromide, bromoethane, bromooctadecane, methyl chloride, octadecyl chloride, 1,1,1-trifluoro-2-iodoethane, and the like. Examples of the compound include propylene oxide. The tetracarboxylic acid diester used in the method [II] can be obtained, for example, by ring-opening a tetracarboxylic dianhydride using the alcohol. The tetracarboxylic acid diester dihalide used in the method [III] can be obtained by reacting the tetracarboxylic acid diester obtained in the above manner with an appropriate chlorinating agent such as thionyl chloride. Examples of the diamine used in the method [II] and the method [III] include diamines used when synthesizing polyamidic acid (A). In addition, the polyamidate (A) may have only the amidate structure, or may be a partial esterified product in which the amidate structure and the amidate structure coexist.

[Polyimide]

Polyimide (hereinafter also referred to as "polyimide (A)") as the polymer (A) can be dehydrated by ring-closing the polyamidoacid (A) synthesized in the manner described above. Obtained by amination.

The polyfluorene imine (A) may be a complete fluorinated imide obtained by dehydrating and ring-locking all the fluorinated acid structures of the polyfluorinated acid (A) as a precursor thereof, or may be only fluorinated A part of the amine acid structure undergoes dehydration and ring closure to partially coexist the fluorene acid structure and the fluorene imine ring structure. The polyfluorene imine (A) preferably has a hydrazone imidization rate of 30% or more, more preferably 50% to 99%, and particularly preferably 60% to 99%. The fluorene imidization ratio is a total of the number of fluorene imine structures and the number of fluorene imine ring structures with respect to the polyfluorene imine, and the ratio of the number of fluorene imine ring structures is expressed as a percentage. Here, a part of the fluorene imine ring may be an isofluorene ring.

The dehydration ring closure of the polyamic acid (A) is preferably performed by a method of heating the polyamino acid (A), or dissolving the polyamino acid (A) in an organic solvent, and in the solution A method of adding a dehydrating agent and a dehydrating closed-loop catalyst, and heating if necessary. Among these, the latter method is preferably used.

In the method for adding a dehydrating agent and a dehydrating ring-closing catalyst to the solution of polyamic acid (A), the dehydrating agent may be 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 mol to 20 mol with respect to 1 mol of the phosphonic acid structure of the polyamic acid (A). Examples of the dehydration ring-closing catalyst include tertiary amines such as pyridine, trimethylpyridine, dimethylpyridine, and triethylamine. The amount of the dehydration ring-closing catalyst used is preferably 0.01 to 10 mol relative to 1 mol of the dehydrating agent used. Examples of the organic solvent used in the dehydration ring-closing reaction include the organic solvents exemplified as the organic solvent for synthesizing the polyamic acid (A). The reaction temperature of the dehydration ring-closing reaction is preferably 0 ° C to 180 ° C, and more preferably 10 ° C to 150 ° C. The reaction time is preferably 1.0 to 120 hours, and more preferably 2.0 to 30 hours.

A reaction solution containing polyfluoreneimine (A) was obtained in the above manner. The reaction solution may It can be directly supplied to the preparation of liquid crystal alignment agent, or the dehydrating agent and dehydration ring-closing catalyst can be removed from the reaction solution and then provided to the preparation of the liquid crystal alignment agent, or polyimide (A) can be isolated and then provided to the liquid crystal alignment agent. Alternatively, the isolated polyfluorene imine (A) may be purified and then provided to the preparation of the liquid crystal alignment agent. These purification operations can be performed according to a known method. The method for synthesizing polyamidoimine (A) is not limited to the method described above. For example, the method can also be carried out by polyamidoimidation of polyamidate (A).

The polyamidic acid, polyamidate, and polyimide obtained as the polymer (A) in the above manner preferably have 10 mPa when they are made into a solution having a concentration of 10% by weight. s ~ 800mPa. The compound having a solution viscosity of s is more preferably 15 mPa. s ~ 500mPa. The solution viscosity of the compound. In addition, the solution viscosity (mPa.s) of the polymer (A) means that the polymer (A) is prepared using a good solvent (for example, γ-butyrolactone, N-methyl-2-pyrrolidone, etc.). The polymer solution having a concentration of 10% by weight is a value obtained by measuring at 25 ° C using an E-type viscometer (trade name).

Moreover, it is preferable that the weight average molecular weight of polystyrene conversion measured by gel permeation chromatography with respect to the polyamic acid, a polyamic acid ester, and a polyimide as said polymer (A) is 500- 100,000, more preferably 1,000 to 50,000.

<Block isocyanate compound (B)>

Examples of the additional component include a polyfunctional block isocyanate compound (B) (hereinafter also simply referred to as "compound (B)"). Here, the "block isocyanate compound" means that a compound (isocyanate compound) having an isocyanate group (-NCO) is reacted with a blocking agent such as a compound having an active hydrogen or an active methylene compound, and is at room temperature. Become an inert compound. The "active hydrogen" refers to a hydrogen atom bonded to an atom other than a carbon atom, and preferably refers to a bonding energy. Hydrogen atoms below the carbon-hydrogen bond of polymethylene.

The compound (B) may be a low-molecular compound obtained by a reaction between a polyfunctional isocyanate compound and a blocking agent, or may be a polyisocyanate obtained by polymerizing a polyfunctional isocyanate compound and a blocking agent. Polymer compound obtained by reaction. The compound (B) is preferably a low-molecular compound, and examples thereof include a compound represented by the following formula (b-1).

(In the formula (b-1), R ¹ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 6 carbon atoms, X ¹ is an n-valent organic group having 1 to 30 carbon atoms, and X ² is a monovalent hydrocarbon group having 1 to 30 carbon atoms. Organic group; n is an integer from 2 to 6; wherein multiple R ¹ in the formula may be the same or different, and multiple X ² may be the same or different.)

The compound (B) is preferably a polyfunctional block isocyanate compound (B-1) having an aromatic ring from the viewpoint that the effect of lowering the performance of the liquid crystal alignment film accompanying long-term use is not properly obtained, Specifically, a compound represented by the following formula (b1-1) is preferred.

(In the formula (b1-1), X ¹¹ is an n-valent organic group having an aromatic ring; R ¹ , X ² and n have the same meanings as the formula (b-1).)

Examples of the monovalent hydrocarbon group having 1 to 6 carbon atoms in the formula R ¹ include a chain hydrocarbon group, an alicyclic hydrocarbon group, and an aromatic hydrocarbon group. Herein, the "chain hydrocarbon group" as used in this specification refers to a hydrocarbon group that does not include a cyclic structure in the main chain, and is composed of only a chain structure. Among them, the chain structure may be linear or branched. The so-called "alicyclic hydrocarbon group" refers to a hydrocarbon group containing only an alicyclic hydrocarbon structure and having no aromatic ring structure. However, it does not necessarily need to consist only of the structure of an alicyclic hydrocarbon, and also includes the hydrocarbon group which has a chain structure in a part. The "aromatic hydrocarbon group" refers to a hydrocarbon group containing an aromatic ring structure as a ring structure. However, it does not necessarily need to consist only of an aromatic ring structure, and may include a chain structure or an alicyclic hydrocarbon structure in part.

As specific examples of R ¹ , examples of the chain hydrocarbon group include an alkyl group having 1 to 6 carbon atoms such as methyl, ethyl, propyl, butyl, and pentyl; and a carbon number such as vinyl, propenyl, and butenyl. Alkenyl groups of 1 to 6; alkynyl groups of 1 to 6 carbons such as ethynyl and propynyl, etc. These chain hydrocarbon groups may be linear or branched. Examples of the alicyclic hydrocarbon group include cyclopentyl and cyclohexyl. Examples of the aromatic hydrocarbon group include phenyl.

In the chain hydrocarbon group, R ¹ is preferably a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and more preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. In particular, when R ¹ is a hydrogen atom, it is preferable from the viewpoint that X ^{2 is} easily detached from the compound by heat treatment and an isocyanate group is easily regenerated.

Examples of the n-valent organic group having 1 to 30 carbon atoms in X ¹ include a hydrocarbon group such as a chain hydrocarbon group, an alicyclic hydrocarbon group, and an aromatic hydrocarbon group, or the introduction of -O-,-between carbon-carbon bonds in the hydrocarbon group. Functional groups such as COO-, -CO-, -NHCO-, -S-, -NH-, and groups having a heterocyclic ring. Each of these groups may have a substituent such as a halogen atom (for example, a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom) or an alkoxy group.

Examples of the n-valent chain hydrocarbon group include methane, ethane, propane, butane, pentane, hexane, heptane, octane, nonane, decane, dodecane, tetradecane, dioxane, and the like. Groups with 1 to 30 carbon atoms such as decadecane to remove n hydrogen atoms, etc .; Groups to remove n hydrogen atoms from olefins with 1 to 30 carbon atoms, such as ethylene, propylene, butene, pentene, etc .; A group for removing n hydrogen atoms from an alkyne having 1 to 30 carbon atoms such as acetylene and methylacetylene, and the like may be linear or branched. In addition, examples of the n-valent alicyclic hydrocarbon group include a group that removes n hydrogen atoms from an alicyclic hydrocarbon having 3 to 30 carbon atoms, such as cyclopropane, cyclopentane, cyclohexane, and methylcyclohexane; Examples of the n-valent aromatic hydrocarbon group include aromatic hydrocarbons having 5 to 30 carbon atoms such as benzene, toluene, xylene, mesitylene, ethylbenzene, biphenyl, diphenylmethane, diphenylethane, naphthalene, and anthracene. Groups for removing n hydrogen atoms in a hydrocarbon, etc .; n-valent groups having a heterocyclic ring include, for example, n-valent groups for removing n hydrogen atoms from a heterocyclic ring, structures including a chain structure or an alicyclic hydrocarbon, and heterocyclic rings. N-valent basis of the structure, etc.

In terms of reactivity with a carboxyl group of the polymer (A), X ^{1 in the} group is preferably an n-valent aromatic hydrocarbon group having 5 to 30 carbon atoms or an n-valent group having a heterocyclic ring. , of formula (b-1) in the group ^{"* -NR 1 -CO-X 2} ( wherein, * represents a bond to X is ^1)" is preferably bonded to an aromatic ring or a heterocyclic ring. The aromatic ring is particularly preferably a benzene ring.

In terms of improving reactivity with a carboxyl group possessed by the polymer (A), X ¹ is preferably an n-valent organic group having an aromatic ring, that is, X ¹¹ , and more specifically, 5 to 30 carbon atoms An n-valent aromatic hydrocarbon group or an n-valent group having an aromatic heterocyclic ring. X ¹¹ is 30 or less in carbon number, preferably 3 to 20 in carbon number, and more preferably 3 to 15 in carbon number.

The n-valent aromatic hydrocarbon group having 5 to 30 carbon atoms in X ¹ and X ¹¹ is preferably an n-valent group removing n hydrogen atoms from the ring portion of the aromatic hydrocarbon having 5 to 30 carbon atoms. In this case, it may be a group in which n hydrogen atoms are removed from the same ring, or a group in which n hydrogen atoms are removed in total from a plurality of rings.

In the n-valent group having an aromatic heterocyclic ring among X ¹ and X ¹¹ , the aromatic heterocyclic ring is preferably a nitrogen-containing aromatic heterocyclic ring having a nitrogen atom in the ring portion. Specific examples include a pyridine ring, a pyrimidine ring, a pyrazine ring, a pyridazine ring, a triazine ring, and the like, and a pyridine ring, a pyrimidine ring, or a triazine ring is more preferable. The number of aromatic heterocycles included in X ¹ and X ¹¹ is not particularly limited, and may be one or two or more. The n-valent group having an aromatic heterocyclic ring is preferably an n-valent group obtained by removing n hydrogen atoms from the ring portion of the aromatic heterocyclic ring. In this case, the group may be a group in which n hydrogen atoms are removed from the same heterocyclic ring, or a group in which n hydrogen atoms are removed in total from a plurality of heterocyclic rings may be used.

In terms of the degree of cross-linking of the polymer (A) and the ease of acquisition, n is preferably an integer of 2 to 4, more preferably 2 or 3, and particularly preferably 2.

Examples of the monovalent organic group having 1 to 30 carbon atoms in X ² include a hydrocarbon group such as a chain hydrocarbon group, an alicyclic hydrocarbon group, and an aromatic hydrocarbon group, or a carbon-carbon bond in the hydrocarbon group, or a formula (b Groups in which functional groups such as -O-, -COO-, -CO-, -NHCO-, -S-, -NH- and the like are introduced at positions adjacent to the carbonyl group in -1). Each of these groups may have a substituent such as a halogen atom (for example, a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom) or an alkoxy group. Specific examples of the monovalent hydrocarbon group in X ² include the groups and the like exemplified in the description of R ¹ .

In terms of reducing the amount of “HX ² ” remaining in the reaction system due to the regeneration of isocyanate groups caused by heating, X ² is preferably 1 to 6 carbon atoms, and more preferably 1 to 6 carbon atoms. 4.

Examples of X ² include groups represented by the following formulae (x2-1) to (x2-7).

[Chemical 5]

(In the formulae (x2-1) to (x2-7), R ² , R ⁵ , R ⁶ , R ^7, and R ⁹ are each independently a monovalent hydrocarbon group; R ³ and R ⁴ are each independently a monovalent hydrocarbon group. Or the group "-OR ¹⁰ " (where R ¹⁰ represents a monovalent hydrocarbon group); R ⁸ is a monovalent aromatic hydrocarbon group; m is an integer from 2 to 11; "*" represents a bonding bond with a carbonyl group.)

Specific examples of the monovalent hydrocarbon group of R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ^9, and R ¹⁰ include the groups exemplified as the monovalent hydrocarbon group of R ¹ . R ² to R ¹⁰ are each preferably 1 to 30 carbon atoms.

m is preferably an integer of 3 to 8, and more preferably an integer of 4 to 6.

For a small impact on the film departing from the characteristics of X ² to bring the groups, X ² is preferably the formula (X2-1) a group represented. R ² X ² is preferably a monovalent hydrocarbon group having a carbon number of 1 to 30 carbon atoms and more preferably a monovalent hydrocarbon group having 1 to 30. From the viewpoint of reducing the remaining amount in the reaction system of "HX ² " generated with the regeneration of the isocyanate group, the monovalent chain hydrocarbon group of R ² is preferably 1 to 10 carbon atoms, and more preferably 1 to 10 carbon atoms. 6 is particularly preferably 1 to 4, and particularly preferably an alkyl group having 1 to 4 carbon atoms.

Preferable specific examples of X ² include, for example, groups represented by the following formulae (x2-1-1) to (x2-7-1).

[Chemical 6]

(In the formula, "*" represents a bonding bond with a carbonyl group.)

Specific examples of the compound (B) include, for example, compounds represented by the following formulae (b-1-1) to (b-1-11). The compound (B) may be used alone or in combination of two or more.

[Chemical 8]

The compounding ratio of the compound (B) is preferably 0.1 to 50 parts by weight, and more preferably 0.5 to 30 parts by weight, with respect to 100 parts by weight of the entire amount of the polymer component contained in the liquid crystal alignment agent. It is particularly preferably 1 to 20 parts by weight.

In addition, in the case where a film is formed using the liquid crystal alignment agent of the present invention, X ² is dissociated from the compound (B) due to heating (post-baking) during film formation, and an isocyanate group is further formed, and The regenerated isocyanate group reacts with a carboxyl group of the polymer (A) to form a crosslinked structure.

The content ratio of the block isocyanate group (-NR ¹ -CO-X ² ) in the liquid crystal alignment agent is preferably 0.01 equivalent to 1.0 with respect to 1 equivalent of the carboxyl group of the polymer (A) in the liquid crystal alignment agent. The ratio of equivalents is more preferably a ratio of 0.1 to 1.0 equivalents.

The compounding ratio of the compound (B-1) is preferably 0.1 to 50 parts by weight, and more preferably 0.5 parts by weight with respect to 100 parts by weight of the entire amount of the polymer component contained in the liquid crystal alignment agent. -30 parts by weight, particularly preferably 1 to 20 parts by weight.

<Other ingredients>

The liquid crystal aligning agent of this invention may contain other components other than the said polymer (A) and the said compound (B) as needed. Examples of the other component include polymers other than the polymer (A), compounds having at least one epoxy group in the molecule (hereinafter referred to as "epoxy-containing compounds"), functional silane compounds, and the like .

[Other polymers]

The other polymers can be used to improve solution properties or electrical properties. Examples of the other polymers include polyorganosiloxane, polyester, polyamide, cellulose derivatives, polyacetals, polystyrene derivatives, and poly (styrene-phenylcis-butene difluorene). Amine) derivatives, poly (meth) acrylates, and the like.

When other polymers are added to the liquid crystal alignment agent, the blending ratio of the other polymers is preferably 50% by weight or less, and more preferably 0.1% to 40% by weight, relative to the total polymer amount in the composition. % Is particularly preferably 0.1% by weight to 30% by weight.

[Epoxy-containing compound]

The epoxy-containing compound can be used to improve the adhesion or electrical characteristics of the liquid crystal alignment film to the substrate surface. 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, 2,2-dibromo neopentyl glycol diglycidyl ether 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-diglycidyl-benzylamine, N, N-diglycidyl-aminomethyl Cyclohexane, N, N-diglycidyl-cyclohexylamine and the like are preferred compounds. Other examples of the epoxy group-containing compound include an epoxy group-containing polyorganosiloxane described in International Publication No. 2009/096598.

When these epoxy compounds are added to the liquid crystal alignment agent, the compounding ratio of the epoxy compound is preferably 40 parts by weight or less with respect to 100 parts by weight of the total polymer contained in the liquid crystal alignment agent, and more preferably It is 0.1 to 30 parts by weight.

[Functional silane compound]

The functional silane compound can be used for the purpose of improving the printability of a liquid crystal alignment agent. use. Examples of such a functional silane compound include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 2-aminopropyltrimethoxysilane, and 2-aminopropyl Triethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxy Silane, 3-ureidopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, N-ethoxycarbonyl-3-aminopropyltrimethoxysilane, N-triethoxy Silylpropyltriethylene triamine, 10-trimethoxysilyl-1,4,7-triazadecane, 9-trimethoxysilyl-3,6-diazanonylacetic acid Ester, 9-trimethoxysilyl-3,6-diazanonanoic acid methyl ester, N-benzyl-3-aminopropyltrimethoxysilane, N-phenyl-3-aminopropyltrimethyl Oxysilane, glycidyloxymethyltrimethoxysilane, 2-glycidyloxyethyltrimethoxysilane, 3-glycidyloxypropyltrimethoxysilane, and the like.

When these functional silane compounds are added to the liquid crystal alignment agent, the blending ratio of the functional silane compounds is preferably 2 parts by weight or less, and more preferably 0.02 parts by weight to 100 parts by weight of the total polymer. 0.2 parts by weight.

In addition to the above-mentioned compounds, a compound having at least one oxetanyl group in the molecule, an antioxidant, or the like may be used as the other component.

[Solvent]

The liquid crystal alignment agent of the present invention is prepared as a liquid obtained by dispersing or dissolving the polymer (A), the block isocyanate compound (B) as an additional component, and other components used as necessary in an appropriate organic solvent.状 组合 物。 Composition.

Examples of the organic solvent used include N-methyl-2-pyrrolidone, γ-butyrolactone, γ-butyrolactam, N, N-dimethylformamide, and N, N-dimethylethyl Phenylamine, 4-hydroxy-4-methyl-2-pentanone, ethylene glycol monomethyl ether, butyl lactate, butyl acetate, methyl methoxypropionate, ethyl ethoxypropionate, ethylene glycol Alcohol methyl ether, ethylene glycol ether, ethylene glycol-n-propyl ether, ethylene glycol-isopropyl ether, ethylene glycol -N-butyl ether (butyl cellosolve), ethylene glycol dimethyl ether, ethylene glycol ether acetate, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol monomethyl ether, diethyl ether Diethylene glycol monoethyl ether, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diisobutyl ketone, isoamyl propionate, isoamyl isobutyrate, diisoamyl ether, Ethylene carbonate, propylene carbonate, etc. These solvents can be used alone or in combination of two or more.

The solid content concentration (the ratio of the total weight of components other than the solvent of the liquid crystal alignment agent to the total weight of the liquid crystal alignment agent) in the liquid crystal alignment agent of the present invention is appropriately selected in consideration of viscosity, volatility, and the like, and is preferably selected. The range is 1% to 10% by weight. That is, the liquid crystal alignment agent of the present invention is applied to the surface of the substrate in a manner described later, and it is preferable to perform heating to form a coating film that is a liquid crystal alignment film or a coating film that is a liquid crystal alignment film. At this time, when the solid content concentration is less than 1% by weight, the film thickness of the coating film becomes too small, and it is difficult to obtain a good liquid crystal alignment film. On the other hand, when the solid content concentration exceeds 10% by weight, the film thickness of the coating film becomes too large, and it is difficult to obtain a good liquid crystal alignment film. In addition, there are some cases where the viscosity of the liquid crystal alignment agent increases and the coating property decreases. tendency.

A particularly preferred range of the solid content concentration varies depending on the method used when the liquid crystal alignment agent is applied to the substrate. For example, when the spinner method is used, the solid content concentration (the ratio of the total weight of all components other than the solvent in the liquid crystal alignment agent to the total weight of the liquid crystal alignment agent) is particularly preferably 1.5% to 4.5% by weight. Range. In the case of using the printing method, it is particularly preferable to set the solid content concentration to a range of 3% to 9% by weight, and thereby set the solution viscosity to 12 mPa. s ~ 50mPa. The range of s. In the case of using the inkjet method, it is particularly preferable to set the solid content concentration to a range of 1% to 5% by weight, and thereby set the solution viscosity to 3 mPa. s ~ 15mPa. The range of s. The temperature when preparing the liquid crystal alignment agent of the present invention is preferably 10 ° C ~ 50 ° C, more preferably 20 ° C to 30 ° C.

<Liquid crystal alignment film and liquid crystal display element>

The liquid crystal alignment film of the present invention is formed by using the liquid crystal alignment 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 alignment agent. The driving mode of the liquid crystal display element is not particularly limited, and can be applied to various driving modes such as TN type, STN type, IPS type, FFS type, VA type, MVA type, Polymer Sustained Alignment (PSA) type and the like.

The liquid crystal display element of the present invention can be produced, for example, by a method including the following steps (1) to (3). Step (1) uses different substrates depending on the required driving mode. Step (2) and step (3) are common to each driving mode.

[Step (1): Formation of Coating Film]

First, the liquid crystal alignment agent of the present invention is coated on 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, VA type, MVA type, or PSA type liquid crystal display element, two substrates provided with a patterned transparent conductive film are used as a pair, and each substrate The formation surface of the transparent conductive film is preferably coated with the liquid crystal alignment agent of the present invention by an offset printing method, a spin coating method, a roll coater method, or an inkjet printing method, respectively. Here, the substrate can be, for example, glass such as float glass, soda glass, or polyethylene terephthalate, polybutylene terephthalate, polyether, polycarbonate, or poly (alicyclic olefin). ) And other plastic transparent substrates. As the transparent conductive film provided on one side of the substrate, a NESA film (registered trademark of PPG, USA) containing tin oxide (SnO ₂ ), and indium oxide-tin oxide (In ₂ O ₃ -SnO ₂ ) can be used. Indium tin oxide (ITO) film and the like. In order to obtain a patterned transparent conductive film, for example, a method of forming a pattern by using light and etching after forming a patternless transparent conductive film, and a method of using a mask having a desired pattern when forming a transparent conductive film can be used. When the liquid crystal alignment agent is applied, in order to improve the adhesion between the substrate surface and the transparent conductive film and the coating film, a surface on which the coating film is formed on the substrate surface may be pre-coated with a functional silane compound, a functional titanium compound, or the like. Pre-processing.

After the liquid crystal alignment agent is applied, it is preferable to perform preheating (prebaking) for the purpose of preventing sagging of the applied alignment agent. The pre-baking temperature is preferably 30 ° C to 200 ° C, more preferably 40 ° C to 150 ° C, and particularly preferably 40 ° C to 100 ° C. The pre-baking time is preferably 0.25 minutes to 10 minutes, and more preferably 0.5 minutes to 5 minutes. Then, a sintering (post-baking) step is performed for the purpose of completely removing the solvent, and also for the purpose of thermally fluorinating the sulfamic acid structure present in the polymer as necessary. The calcination temperature (post-baking temperature) at this time is preferably 80 ° C to 300 ° C, and more preferably 120 ° C to 250 ° C. The post-baking time is preferably 5 minutes to 200 minutes, and more preferably 10 minutes to 100 minutes. The film thickness of the film formed in the above manner is preferably 0.001 μm to 1 μm, and more preferably 0.005 μm to 0.5 μm.

(1-2) In the case of manufacturing an IPS-type or FFS-type liquid crystal display element, the electrode formation surface is provided on the substrate provided with an electrode including a transparent conductive film or a metal film patterned in a comb-tooth shape, and is not provided. The liquid crystal aligning agent of the present invention is coated on one side of the electrodes facing the substrate, and then each coated surface is heated to form a coating film. About the material of the substrate and the transparent conductive film used at this time, the coating method, the heating conditions after coating, the patterning method of the transparent conductive film or metal film, the pre-treatment of the substrate, and the preferred film thickness of the formed coating film Is the same as (1-1). As the metal film, for example, a film containing a metal such as chromium can be used.

In any of the cases (1-1) and (1-2), a coating film that becomes an alignment film is formed by applying a liquid crystal alignment agent on a substrate and then removing an organic solvent. In this case, the polymer contained in the liquid crystal alignment agent of the present invention is polyamic acid, or polyamic acid ester, or In the case of a fluorene imidized polymer having a fluorinated imine ring structure and a fluorinated acid structure, a dehydration ring-closing reaction may be performed by further heating after the coating film is formed to form a more fluorinated coating film.

[Step (2): Rubbing treatment]

When manufacturing a TN-type, STN-type, IPS-type, or FFS-type liquid crystal display element, the following rubbing treatment is performed: using a roller wound with a cloth containing fibers such as nylon, rayon, and cotton, the steps ( The coating film formed in 1) was rubbed in a fixed direction. Thereby, the alignment ability of the liquid crystal molecules is imparted to the coating film to form a liquid crystal alignment film. On the other hand, in the case of manufacturing a VA-type liquid crystal display element, the coating film formed in the step (1) may be directly used as a liquid crystal alignment film, or the coating film may be subjected to a rubbing treatment. In addition, the liquid crystal alignment film after the rubbing treatment may be further subjected to the following treatments: a process of changing the pretilt angle of a part of the liquid crystal alignment film by irradiating a part of the liquid crystal alignment film with ultraviolet rays; After the etchant film, the rubbing treatment is performed in a direction different from the previous rubbing treatment, and then the resist film is removed; thereby the liquid crystal alignment film has different liquid crystal alignment capabilities in each region. In this case, the visual field characteristics of the obtained liquid crystal display element can be improved.

In the case of manufacturing a PSA liquid crystal display device, the following step (3) may be directly performed using the coating film formed in the step (1), or a simple method may be used to control the collapse of liquid crystal molecules. The purpose of the alignment division method is to perform weak rubbing treatment.

[Step (3): Construction of Liquid Crystal Cell]

(3-1) A liquid crystal cell is produced by preparing two substrates on which a liquid crystal alignment film is formed as described above, and arranging liquid crystal between the two substrates disposed opposite to each other. In order to manufacture a liquid crystal cell, the following two methods are mentioned, for example. First, the first method is a previously known method. In this method, firstly, two substrates are arranged to face each other through a gap (cell gap) so that the liquid crystal alignment films face each other, and the peripheral portions of the two substrates are bonded using a sealant. The liquid crystal cell can be manufactured by filling and filling liquid crystals into divided cell gaps and sealing the injection holes. The second method is a method called a One Drop Fill (ODF) method. In this method, for example, a UV-curable sealant is applied to a predetermined portion of one of the two substrates on which the liquid crystal alignment film is formed, and further, the liquid crystal alignment film is added dropwise to predetermined positions on the liquid crystal alignment film. After the liquid crystal, another substrate is bonded to the liquid crystal alignment film so as to face each other. Then, the liquid crystal is spread on the entire surface of the substrate, and then the entire surface of the substrate is irradiated with ultraviolet light to harden the sealant, thereby manufacturing a liquid crystal cell. In any case, it is desirable to remove the liquid crystal filling by slowly heating the liquid crystal cell manufactured as described above to a temperature at which the liquid crystal used becomes an isotropic phase, and then slowly cooling to room temperature. Mobile orientation at the time.

As the sealant, for example, an epoxy resin containing a hardener and alumina balls as a spacer can be used. Examples of the liquid crystal include a nematic liquid crystal and a smectic liquid crystal. Among them, a nematic liquid crystal is preferred. For example, a Schiff base liquid crystal and an oxidation couple can be used. Nitrogen (azoxy) liquid crystal, biphenyl liquid crystal, phenylcyclohexane liquid crystal, ester liquid crystal, terphenyl liquid crystal, biphenyl cyclohexane liquid crystal, pyrimidine liquid crystal, dioxane liquid crystal, bicyclooctane Based liquid crystal, cubic liquid crystal and the like. In addition, the following substances may be added to these liquid crystals and used, for example, cholesterol liquid crystals such as cholesteryl chloride, cholesteryl nonanoate, and cholesteryl carbonate. ; Chiral agents sold under the trade names "C-15" and "CB-15" (Merck); p-decyloxymethylene-p-amino-2-methylbutyl Ferroelectric liquid crystals such as p-decyloxybenzylidene-p-amino-2-methylbutylcinnamate and the like.

(3-2) When manufacturing a PSA type liquid crystal display element, a liquid crystal cell is constructed in the same manner as described in (3-1), except that a photopolymerizable compound is injected or dropped together with the liquid crystal. Then, the liquid crystal cell is irradiated with light while a voltage is applied between the conductive films included in the pair of substrates. The voltage applied here may be, for example, a DC voltage or an AC voltage of 5V to 50V. In addition, as the light to be irradiated, for example, ultraviolet rays including visible light with a wavelength of 150 nm to 800 nm and visible rays may be used, and ultraviolet rays including light having a wavelength of 300 to 400 nm are preferred. As a light source for irradiating light, for example, a low-pressure mercury lamp, a high-pressure mercury lamp, a deuterium lamp, a metal halide lamp, an argon resonance lamp, a xenon lamp, an excimer laser, and the like can be used. In addition, the ultraviolet rays in the preferable wavelength region can be obtained by a method in which a light source is used in combination with, for example, a filter, a diffraction grating, and the like. The irradiation amount of light is preferably 1,000 J / m ² or more and less than 200,000 J / m ² , and more preferably 1,000 J / m ² to 100,000 J / m ² .

Then, 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. Examples of the polarizing plate attached to the outer surface of the liquid crystal cell include a polarizing plate formed by sandwiching a polarizing film called an “H film” with a protective cellulose acetate film or a polarizing plate including the H film itself. "H film" is a polarizing film formed by absorbing iodine while extending the orientation of polyvinyl alcohol. In addition, when the coating film is subjected to a rubbing treatment, the two substrates are arranged facing each other such that the rubbing directions in the respective coating films form a predetermined angle with each other, for example, orthogonal or anti-parallel.

The liquid crystal display element of the present invention can be effectively applied to various devices, for example, it can be used in clocks, portable game consoles, word processors, notetype personal computers, and car navigation systems. (car navigation system), camcorder, personal digital assistant (PDA), digital camera, mobile phone, smart phone, various monitors, LCD TV and other display devices.

[Example]

Hereinafter, the present invention will be further specifically described by examples, but the present invention is not limited to these examples.

In the following examples and comparative examples, the following methods were used to measure the polyimide imidization ratio of the polymer solution, the solution viscosity of the polymer solution, the weight average molecular weight of the polymer, and the epoxy equivalent.

[Perylene imidation rate of polyimide]

A solution of polyfluoreneimide was poured into pure water, and the resulting precipitate was sufficiently dried under reduced pressure at room temperature, and then dissolved in deuterated dimethylsulfine, and tetramethylsilane was used as a reference substance at room temperature. ¹ H- NMR measurement ^{(1 H-Nuclear magnetic resonance,} 1 H-NMR). Based on the obtained ¹ H-NMR spectrum, the fluorene imidization ratio [%] was determined by the following formula (1).

醯 Imination ratio [%] = (1-A ¹ / A ² × α) × 100 ... (1)

(In formula (1), A ¹ is the peak area of NH-derived protons appearing near the chemical shift of 10 ppm, A ² is the peak area of other protons, and α is the precursor of other protons relative to the polymer. (Polyamic acid) Proportion of the number of one proton of the NH group.)

[Solution viscosity of polymer solution]

Using a predetermined solvent, for a solution prepared with a polymer concentration of 10% by weight, the solution viscosity of the polymer solution was measured at 25 ° C using an E-type rotary viscometer [mPa. s].

[Polymer average molecular weight]

The weight average molecular weight is a polystyrene conversion value measured by gel permeation chromatography under the following conditions.

Column: made by Tosoh (stock), TSKgelGRCXLII (trade name)

Solvent: Tetrahydrofuran

Temperature: 40 ° C

Pressure: 68kgf / cm ²

[Epoxy equivalent]

The epoxy equivalent was measured by the hydrochloric acid-methyl ethyl ketone method described in Japanese Industrial Standard C 2105 (JIS C 2105).

<Synthesis of Polymer (A)>

[Synthesis Example 1: Synthesis of Polyfluorene (PI-1)]

22.4 g (0.1 mol) of 2,3,5-tricarboxycyclopentylacetic dianhydride as tetracarboxylic dianhydride, 8.6 g (0.08 mol) of p-phenylenediamine as diamine, and 3,5- 10.5 g (0.02 mol) of cholesteryl diaminobenzoate, dissolved in 166 g of N-methyl-2-pyrrolidone (NMP), and reacted at 60 ° C. for 6 hours to obtain polyamine 20 % By weight solution. A small amount of the obtained polyamic acid solution was added, and NMP was added to prepare a solution having a polyamic acid concentration of 10% by weight. The viscosity of the solution was 90 mPa. s.

Then, NMP was added to the obtained polyamic acid solution to prepare a solution having a polyamic acid concentration of 7% by weight, 11.9 g of pyridine and 15.3 g of acetic anhydride were added, and a dehydration ring-closure reaction was performed at 110 ° C. for 4 hours. After the dehydration ring-closing reaction, the solvent in the system is replaced with a new NMP (by this operation, the pyridine and acetic anhydride used in the dehydration ring-closing reaction are removed from the system; the same applies hereinafter), thereby obtaining the amidine 26% by weight solution of polyimide (PI-1) with a rate of about 68%. A small amount of the obtained polyimide solution was added, and NMP was added to prepare a solution having a polyimide concentration of 10% by weight. The measured solution viscosity was 45 mPa. s.

[Synthesis Example 2: Synthesis of polyimide (PI-2)]

22.5 g (0.1 mol) of 2,3,5-tricarboxycyclopentylacetic dianhydride as tetracarboxylic dianhydride and 10.7 g (0.07 mol) of 3,5-diaminobenzoic acid as diamine Cholesteryloxy-2,4-diamine 7.35 g (0.015 mol) of benzene and 6.94 g (0.015 mol) of the compound represented by the formula (D-1-5) were dissolved in 190 g of NMP and reacted at 60 ° C for 6 hours to obtain 20% by weight solution of polyamic acid. A small amount of the obtained polyamic acid solution was added, and NMP was added to prepare a solution having a polyamic acid concentration of 10% by weight. The viscosity of the solution was 80 mPa. s.

Next, NMP was added to the obtained polyamic acid solution to prepare a solution having a polyamic acid concentration of 7% by weight, 15.7 g of pyridine and 20.3 g of acetic anhydride were added, and a dehydration ring-closure reaction was performed at 110 ° C. for 4 hours. After the dehydration ring-closing reaction, the solvent in the system was replaced with a new NMP to obtain a solution containing 26% by weight of polyfluorene imine (PI-2) with a ratio of about 80%. A small amount of the obtained polyimide solution was added, and NMP was added to prepare a solution having a polyimide concentration of 10% by weight. The measured solution viscosity was 40 mPa. s.

[Synthesis Example 3: Synthesis of Polyimide (PI-3)]

18.7 g (0.075 moles) of 2,4,6,8-tetracarboxybicyclo [3.3.0] octane-2,4,6: 8-dianhydride as tetracarboxylic dianhydride and 1,2,3 4,4-cyclobutanetetracarboxylic dianhydride 4.90 g (0.025 mole), diamine 3,5-diaminobenzoic acid 10.7 g (0.07 mole), and 1,3-diamino-4- {4- [trans-4- (trans-4-n-pentylcyclohexyl) cyclohexyl] phenoxy} benzene (the compound represented by the formula (D-1-2)) 13.1 g (0.03 mo Ear), dissolved in 190 g of NMP, and reacted at 60 ° C. for 6 hours to obtain a solution containing 20% by weight of polyamic acid. A small amount of the obtained polyamic acid solution was added, and NMP was added to prepare a solution having a polyamic acid concentration of 10% by weight. The viscosity of the solution was 85 mPa. s.

Then, NMP was added to the obtained polyamic acid solution to prepare a solution having a polyamic acid concentration of 7% by weight, 9.5 g of pyridine and 12.3 g of acetic anhydride were added, and a dehydration ring-closure reaction was performed at 110 ° C. for 4 hours. After the dehydration ring-closing reaction, the solvent in the system was replaced with a new NMP to obtain a solution containing 26% by weight of polyfluorene imine (PI-3) having a hydrazone imidization rate of approximately 65%. A small amount of the obtained polyimide solution was added, and NMP was added to make a polyimide concentration of 10 weight. % Solution, the viscosity of the solution was 45mPa. s.

[Synthesis Example 4: Synthesis of polyimide (PI-4)]

110 g (0.50 mole) of 2,3,5-tricarboxycyclopentylacetic dianhydride as tetracarboxylic dianhydride and 1,3,3a, 4,5,9b-hexahydro-8-methyl-5 -(Tetrahydro-2,5-dioxo-3-furyl) naphtho [1,2-c] furan-1,3-dione 160 g (0.50 mole), p-phenylenediamine as diamine 91g (0.85 mole), 1,3-bis (3-aminopropyl) tetramethyldisilaxane 25g (0.10 mole) and 3,6-bis (4-aminobenzyloxy) ) 25 g of cholestane (0.040 mol) and 1.4 g (0.015 mol) of aniline as a monoamine, dissolved in 960 g of NMP, and reacted at 60 ° C. for 6 hours, thereby obtaining polyamine-containing Solution. A small amount of the obtained polyamic acid solution was added, and NMP was added to prepare a solution having a polyamic acid concentration of 10% by weight. The viscosity of the solution was 60 mPa. s.

Then, 2,700 g of NMP was added to the obtained polyamic acid solution, 390 g of pyridine and 410 g of acetic anhydride were added, and a dehydration ring-closure reaction was performed at 110 ° C for 4 hours. After the dehydration ring-closing reaction, the solvent in the system was replaced with a new γ-butyrolactone, thereby obtaining a solution containing 15% by weight of polyfluorene imine (PI-4) with a fluorene imidization rate of about 95%. About 2,500g. A small amount of this solution was divided and NMP was added to prepare a solution having a polyimide concentration of 10% by weight. The viscosity of the solution was 70 mPa. s.

[Synthesis Example 5: Synthesis of polyimide (PI-5)]

22.4 g (0.1 mole) of 2,3,5-tricarboxycyclopentylacetic acid dianhydride as tetracarboxylic dianhydride, 8.6 g (0.08 mole) of p-phenylenediamine as diamine, 4,4 ' -Diaminodiphenylmethane 2.0g (0.01 mole) and 4,4'-diamino-2,2'-bis (trifluoromethyl) biphenyl 3.2g (0.01 mole), dissolved in 324g In NMP, a reaction was carried out at 60 ° C. for 4 hours to obtain a solution containing 10% by weight of polyamic acid.

Next, 360 g of NMP was added to the obtained polyamic acid solution, 39.5 g of pyridine and 30.6 g of acetic anhydride were added, and a dehydration ring-closure reaction was performed at 110 ° C. for 4 hours. After the dehydration closed-loop reaction, The solvent in the system was replaced with a new NMP to obtain a solution containing 10% by weight of polyfluorene imine (PI-5) having a fluorination rate of about 93%. A small amount of the obtained polyfluorene imine solution was collected and the viscosity of the solution was 30 mPa. s.

[Synthesis Example 6: Synthesis of polyfluorene (PI-6)]

22.4 g (0.1 mol) of 2,3,5-tricarboxycyclopentylacetic dianhydride as tetracarboxylic dianhydride and 12.2 g (0.08 mol) of 3,5-diaminobenzoic acid as diamine And 9.80 g (0.02 mol) of cholesteryloxy-2,4-diaminobenzene, dissolved in 178 g of NMP, and reacted at 60 ° C. for 6 hours to obtain 20% by weight of polyamino acid. Solution. A small amount of the obtained polyamic acid solution was added, and NMP was added to prepare a solution having a polyamic acid concentration of 10% by weight. The viscosity of the solution was 80 mPa. s.

Then, NMP was added to the obtained polyamic acid solution to prepare a solution having a polyamic acid concentration of 7% by weight, 11.9 g of pyridine and 15.3 g of acetic anhydride were added, and a dehydration ring-closure reaction was performed at 110 ° C. for 4 hours. After the dehydration ring-closing reaction, the solvent in the system was replaced with a new NMP to obtain a solution containing 26% by weight of polyfluorene imine (PI-6) having a hydrazone imidization rate of approximately 65%. A small amount of the obtained polyimide solution was added, and NMP was added to prepare a solution having a polyimide concentration of 10% by weight. The measured solution viscosity was 40 mPa. s.

[Synthesis Example 7: Synthesis of polyorganosiloxane (APS-1)]

In a reaction vessel including a stirrer, a thermometer, a dropping funnel, and a reflux cooling tube, 100.0 g of 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 500 g of methyl isobutyl ketone, and triethyl 10.0 g of amines were mixed at room temperature. Then, after 30 minutes, 100 g of deionized water was added dropwise from a dropping funnel, and the reaction was performed at 80 ° C. for 6 hours while stirring under reflux. After the reaction, the organic layer was taken out and washed with a 0.2% by weight ammonium nitrate aqueous solution until the washed water became neutral, and then the solvent and water were distilled off under reduced pressure, thereby obtaining a viscous transparent liquid. Epoxy polyorganosiloxane (EPS-1). When ¹ H-NMR analysis was performed on this epoxy-group-containing polyorganosiloxane (EPS-1), a chemical shift (δ) = 3.2 ppm was obtained, and a peak based on epoxy groups was obtained as a theoretical intensity, and the reaction was confirmed. No side reaction of the epoxy group was generated. The weight-average molecular weight Mw of the obtained epoxy-group-containing polyorganosiloxane was 3,500, and the epoxy equivalent was 180 g / mole.

Next, in a 200 mL three-necked flask, 10.0 g of epoxy-containing polyorganosiloxane (EPS-1), 30.28 g of methyl isobutyl ketone as a solvent, and 4-dodecyloxybenzoic acid were charged. 3.98 g and 0.10 g of UCAT 18X (trade name, manufactured by San-Apro) was used as a catalyst, and the reaction was performed at 100 ° C. for 48 hours while stirring. After completion of the reaction, the solution obtained by adding ethyl acetate to the reaction mixture was washed three times with water, and the organic layer was dried with magnesium sulfate, and then the solvent was distilled off to obtain a liquid crystal-oriented polyorganosiloxane (APS-1). 9.0g. The weight average molecular weight Mw of the obtained polymer was 9,900.

<Example 1>

[Preparation of liquid crystal alignment agent]

In a solution containing polyimide (PI-1) as the polymer (A), 5 parts by weight of the compound represented by the formula (b-1-1) is added to 100 parts by weight of the polymer. The NMP solution was used as the block isocyanate compound (B), and the solution composition was NMP: BC (butyl cellosolve) = 50: 50 (weight ratio), and the solid content concentration was 6.0 weight%. This solution was filtered using a filter having a pore size of 1 μm, thereby preparing a liquid crystal alignment agent (S1).

[Manufacture of liquid crystal cell]

Using the liquid crystal alignment film printer (manufactured by Japan Photo Printing Co., Ltd.), the prepared liquid crystal alignment agent (S1) was coated on the transparent electrode surface of a glass substrate with a transparent electrode containing an ITO film at 80 ° C. After heating (pre-baking) on a hot plate for 1 minute to remove the solvent, it was heated (post-baking) on a hot plate at 210 ° C. for 30 minutes to form a coating film having an average film thickness of 80 nm.

For this coating film, a friction machine having a roll wound with rayon cloth was used at a roll speed of 500. The rubbing treatment was performed at rpm, a platform moving speed of 3 cm / sec, and a gross indentation length of 0.4 mm to impart alignment ability to the liquid crystal. Then, ultrasonic cleaning was performed in ultrapure water for 1 minute, and then dried in a 100 ° C clean oven for 10 minutes, thereby obtaining a substrate having a liquid crystal alignment film. This operation was repeated to obtain a pair of (two) substrates having a liquid crystal alignment film.

Next, the pair of substrates were respectively coated on the outer edges of the surfaces having the liquid crystal alignment film with an epoxy resin adhesive added with alumina balls having a diameter of 5.5 μm, and then the liquid crystal alignment films were faced to overlap. Crimp to harden the adhesive. Next, a nematic liquid crystal (Merck, MLC-6221 (trade name)) 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 light-curing adhesive to produce a liquid crystal. unit.

[Evaluation of Reliability of Liquid Crystal Alignment Film]

With respect to the obtained liquid crystal cell, a voltage of 5V was applied at an application time of 60 microseconds and a span of 167 milliseconds, and then the voltage retention rate (VHR1) after 167 milliseconds after the release of the application was measured. Next, the liquid crystal cell was left to stand in an 80 ° C oven under a light emitting diode (LED) lamp for 200 hours, and then left at room temperature to naturally cool to room temperature. After cooling, a voltage of 5V was applied to the liquid crystal cell at an application time of 60 microseconds and a span of 167 milliseconds, and then the voltage retention rate (VHR2) after 167 milliseconds after the release of the application was measured. As the measurement device, "VHR-1" (trade name) manufactured by Toyo Technica (KK) was used. The change rate (ΔVHR) of the voltage holding ratio (VHR) at this time was calculated by the following formula (2), and the reliability of the liquid crystal alignment film was evaluated based on the ΔVHR.

△ VHR [%] = (VHR1-VHR2) / (VHR1) × 100 ... (2)

The evaluation was performed as follows: The case where ΔVHR was 0% or more and less than 0.4% was evaluated as "excellently good (◎)", and the case where 0.4V or more and less than 1.5% was evaluated as reliability. "Good (○)", a case where 1.5% or more and 2.0% or less was evaluated as a reliability "may (△)", and a case where it was more than 2.0% was evaluated as a reliability "bad (x)". As a result, ΔVHR of the liquid crystal cell was 0.5 [%], and reliability was good.

<Examples 2 to 9 and Comparative Example 1>

A liquid crystal alignment agent (S2) to a liquid crystal alignment agent (S9) and a liquid crystal were prepared in the same manner as in Example 1 except that the types and amounts of the polymer component and the additive component used were changed as described in Table 1 below. Alignment agent (R1). In addition, in the same manner as in Example 1, the reliability of the liquid crystal cell was evaluated separately for the prepared liquid crystal alignment agent. These results are shown in Table 1 below.

In Table 1, the "amount" in the polymer component column indicates each formulation ratio (parts by weight) to 100 parts by weight with respect to the entire amount of the polymer component contained in the liquid crystal alignment agent. In addition, the "addition amount" in the additive column indicates a blending ratio (parts by weight) to 100 parts by weight with respect to the entire amount of the polymer component in the liquid crystal alignment agent. The abbreviations of the additives in Table 1 have the following meanings.

Add-1: the compound represented by the formula (b-1-1)

Add-2: a compound represented by the formula (b-1-2)

Add-3: Compound represented by the following formula (m-1)

As shown in Table 1, in Examples 1 to 9, ΔVHR was as small as less than 1.0%, and the reliability of the liquid crystal display element was "good". In contrast, in Comparative Example 1, the ΔVHR was as large as 2.9%, and the reliability was "poor".

<Examples 10 to 13 and Comparative Example 2>

A liquid crystal alignment agent (S10) to a liquid crystal alignment agent (S13) and a liquid crystal were prepared in the same manner as in Example 1 except that the types and amounts of the polymer component and the additive component used were changed as described in Table 2 below. Alignment agent (R2). In addition, in the same manner as in Example 1, the reliability of the liquid crystal cell was evaluated separately for the prepared liquid crystal alignment agent. These results are shown in Table 2 below.

In Table 2, the "amount" in the polymer component column and the "added amount" in the additive column The values are the same as those in Table 1. The abbreviations of the additives in Table 2 have the following meanings.

Add-4: the compound represented by the formula (b-1-9)

Add-5: the compound represented by the formula (b-1-10)

Add-6: a compound represented by the following formula (m-2)

Add-7: the compound represented by the formula (b-1-11)

As shown in Table 2, in Examples 10 to 12, the ΔVHR was as small as 0.2% or less, and the reliability of the liquid crystal display element was evaluated as "especially good". In addition, in Example 13, the ΔVHR was 1.8%, which was an evaluation of reliability “may”. On the other hand, in Comparative Example 2, the ΔVHR was as high as 2.5%, and the reliability was "poor".

Claims (12)

A liquid crystal alignment agent comprising: at least one polymer (A) selected from the group consisting of polyamidic acid, polyamidate, and polyimide; and a polyfunctional intercalation having an aromatic ring. A segment isocyanate compound (B-1) in which the block isocyanate compound (B-1) is a compound represented by the following formula (b1-1),

In the formula (b1-1), R ¹ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 6 carbon atoms, X ¹¹ is an n-valent organic group having an aromatic ring, and X ² is a chain hydrocarbon group selected from 1 to 30 carbon atoms. 1, a alicyclic hydrocarbon group having 1 to 30 carbon atoms, and a monovalent hydrocarbon group in an aromatic hydrocarbon group having 1 to 30 carbon atoms, or between carbon-carbon bonds in the hydrocarbon group, or the same as in formula (b1-1) A group in which a functional group selected from -O-, -COO-, -CO-, -NHCO-, -S-, and -NH- is introduced at a position adjacent to the carbonyl group, and the group may have a group selected from a halogen atom and Substituent of alkoxy group; n is an integer of 2 to 6; among them, a plurality of R ¹ in the formula may be the same or different, and a plurality of X ² may be the same or different. The liquid crystal alignment agent according to item 1 of the scope of patent application, wherein X ¹¹ is an n-valent aromatic hydrocarbon group having 5 to 30 carbon atoms or an n-valent group having an aromatic heterocyclic ring. The liquid crystal alignment agent according to item 1 or item 2 of the scope of patent application, wherein X ¹¹ is an n-valent group from which n hydrogen atoms are removed from a ring portion of an aromatic hydrocarbon having 5 to 30 carbon atoms. The liquid crystal alignment agent according to item 1 or item 2 of the scope of patent application, wherein X ¹¹ is an n-valent organic group having an aromatic heterocyclic ring. The liquid crystal alignment agent according to item 4 of the scope of patent application, wherein X ¹¹ is an n-valent group in which n hydrogen atoms are removed from a ring portion of an aromatic heterocyclic ring. The liquid crystal alignment agent according to item 1 or item 2 of the patent application scope, wherein X ² is a group “* -OR ² ” (where R ² is a monovalent hydrocarbon group having 1 to 30 carbon atoms, “* "Represents a bonding bond to a carbonyl group). The liquid crystal alignment agent according to item 6 of the scope of patent application, wherein R ² is a monovalent chain hydrocarbon group having 1 to 30 carbon atoms. The liquid crystal alignment agent according to item 1 or item 2 of the scope of patent application, wherein X ¹¹ is an n-valent organic group having 3 to 15 carbon atoms having an aromatic ring. The liquid crystal alignment agent according to item 1 or item 2 of the patent application scope, wherein the block isocyanate compound (B-1) is 100 parts by weight relative to the entire amount of the polymer component contained in the liquid crystal alignment agent. ) Is contained in an amount of 0.1 to 50 parts by weight. The liquid crystal alignment agent according to item 1 or item 2 of the scope of the patent application, which contains at least one of a polyamic acid and a polyimide obtained by reacting a tetracarboxylic dianhydride with a diamine as said Polymer (A), the tetracarboxylic dianhydride comprises a member selected from the group consisting of 2,3,5-tricarboxycyclopentylacetic dianhydride, 2,4,6,8-tetracarboxybicyclo [3.3.0] octane- 2: 4,6: 8-dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, and 1,2,3 At least one of the group consisting of 4,4-cyclopentanetetracarboxylic dianhydride. A liquid crystal alignment film is formed by using the liquid crystal alignment agent according to any one of claims 1 to 10 of a patent application range. A liquid crystal display element includes the liquid crystal alignment film according to item 11 of the scope of patent application.