JP5691610B2 - Composition for forming liquid crystal alignment film, liquid crystal alignment film, and liquid crystal display element - Google Patents

Description

  The present invention relates to a composition for forming a liquid crystal alignment film, a liquid crystal alignment film, and a liquid crystal display element.

  Since liquid crystal display elements have advantages such as low power consumption and easy miniaturization and flattening, they range from small liquid crystal display devices such as mobile phones to large screen liquid crystal display devices such as liquid crystal televisions. Widely used.

  The display mode of the liquid crystal display device includes, for example, Twisted Nematic type (TN type), Super Twisted Nematic type (STN type), In-Plane Switching type (IPS type), Vertical Alignment type, etc. It has been known. In any display mode, since the alignment state of the liquid crystal molecules is controlled by the liquid crystal alignment film, the characteristics of the liquid crystal alignment film and the composition for forming the liquid crystal alignment film used as the material of the liquid crystal alignment film are This contributes to the development of the characteristics of the display element.

  Among these display modes, the IPS type has a horizontal electric field system in which two electrodes for driving a liquid crystal are arranged in a comb-like shape on one substrate, and an electric field parallel to the substrate surface is generated to control liquid crystal molecules. It is. For example, JP-A-5-505247 discloses that this lateral electric field type liquid crystal display device is excellent in wide viewing angle characteristics. Japanese Patent Application Laid-Open No. 9-80424 discloses a technique for further improving the wide viewing angle characteristics by applying an optical compensation film to the lateral electric field type liquid crystal display element.

  In recent years, in addition to the above-described technology, a higher display quality is desired for this horizontal electric field type liquid crystal display element. In order to realize high display quality, it is necessary to increase the response speed of liquid crystal and improve contrast. In order to exhibit such characteristics in a liquid crystal display element, it is required that the retardation value of the liquid crystal alignment film is large. The

  However, a liquid crystal alignment film having a large retardation value that sufficiently exhibits such characteristics is not provided, and development of a liquid crystal display element that realizes high display quality is desired.

JP-A-5-505247 Japanese Patent Laid-Open No. 9-80424

  The present invention has been made based on the above circumstances, and provides a liquid crystal alignment film having a large retardation value, a liquid crystal display element that realizes a high display quality including the liquid crystal alignment film, and a liquid crystal of a lateral electric field type It aims at providing the composition for liquid crystal aligning film formation which can form a display element and the said liquid crystal aligning film.

（式（１）中、Ｘは置換されてもよい２価の芳香族基である。Ｕ^１及びＵ^２は、それぞれ独立に、単結合、−Ｏ−、−ＣＯＯ−又は−ＯＣＯ−である。） The invention made to solve the above problems is
At least selected from the group consisting of a polyamic acid obtained by reaction of tetracarboxylic dianhydride and a diamine compound containing at least the diamine represented by the following formula (1), and a polyimide formed by dehydrating and ring-closing this polyamic acid. It is the composition for liquid crystal aligning film formation containing 1 type of polymer.

(In formula (1), X is a divalent aromatic group which may be substituted. U ¹ and U ² are each independently a single bond, —O—, —COO— or —OCO—. .)

  Since the composition for forming a liquid crystal alignment film has a polymer having a specific structure as described above, a liquid crystal alignment film having a large retardation value can be formed. As the retardation value increases, the interaction between the liquid crystal alignment film and the liquid crystal increases, and the force with which the liquid crystal alignment film aligns the liquid crystals in the alignment direction becomes stronger. When this force is strong, when the liquid crystal driven by applying an electric field is released from the electric field, the force for returning the liquid crystal to the orientation orientation becomes strong, and as a result, the response speed of the liquid crystal is increased.

  As the tetracarboxylic dianhydride, 2,3,5-tricarboxycyclopentylacetic acid dianhydride, 3,5,6-tricarboxy-2-carboxymethylnorbornane-2: 3,5: 6-dianhydride, 2,4,6,8-tetracarboxybicyclo [3.3.0] octane-2: 4,6: 8-dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, and pyro It is preferable to include at least one selected from the group consisting of merit acid dianhydrides, and X is preferably a 1,4-phenylene group or a naphthylene group. By including such a specific compound as tetracarboxylic dianhydride and using X as such a specific group, a polyamic acid serving as a component of a composition for forming a liquid crystal alignment film having desired characteristics can be obtained.

  The liquid crystal alignment film of the present invention formed from the composition for forming a liquid crystal alignment film has a large retardation value. When the liquid crystal alignment film is applied to, for example, a horizontal electric field type liquid crystal display element, the response speed of the liquid crystal is high. And the black level in the dark state is increased to improve the contrast. As a result, high display quality can be realized.

  In the liquid crystal display element of the present invention, the display mode is preferably a lateral electric field mode. When the liquid crystal alignment film having the above characteristics is applied to a horizontal electric field type liquid crystal display element, the characteristics are maximized.

  As described above, the liquid crystal alignment film formed from the composition for forming a liquid crystal alignment film of the present invention has a large retardation value. When the liquid crystal alignment film is applied to a liquid crystal display element of a horizontal electric field method, The response speed is increased, and the black level in the dark state is increased to improve the contrast. As a result, high display quality can be realized.

  Hereinafter, embodiments of the present invention will be described in detail.

(Composition for forming liquid crystal alignment film)
The composition for forming a liquid crystal alignment film of the present invention comprises a polyamic acid obtained by a reaction between a tetracarboxylic dianhydride and a diamine compound containing at least the compound represented by the above formula (1), and dehydrating the polyamic acid. It contains at least one polymer selected from the group consisting of polyimides formed by ring closure, and may further contain optional components as necessary. Since the composition for forming a liquid crystal alignment film has a polymer having a specific structure as described above, a liquid crystal alignment film having a large retardation value can be formed. Hereinafter, each component will be described in detail.

(Tetracarboxylic dianhydride)
Examples of tetracarboxylic dianhydrides used for the synthesis of polyamic acid include aliphatic tetracarboxylic dianhydrides, alicyclic tetracarboxylic dianhydrides, aromatic tetracarboxylic dianhydrides, and the like. In addition to these, tetracarboxylic dianhydrides described in Japanese Patent Application No. 2009-157556 can be used. These tetracarboxylic dianhydrides may be used alone or in combination of two or more.

  Examples of the aliphatic tetracarboxylic dianhydride include butanetetracarboxylic dianhydride.

Examples of the alicyclic tetracarboxylic dianhydride include 1,2,3,4-cyclobutanetetracarboxylic 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-8-methyl-5- (tetrahydro-2,5-dioxo-3-furanyl) -naphtho [1,2-c] furan-1,3-dione, 3-oxabicyclo [3.2.1] Octane-2,4-dione-6-spiro-3 ′-(tetrahydrofuran-2 ′, 5′-dione), 5- (2,5-dioxotetrahydro-3-furanyl) -3-methyl-3-cyclohexene -1,2-dicarboxylic acid Water, 3,5,6-tricarboxy-2-carboxymethylnorbornane-2: 3,5: 6-dianhydride, 2,4,6,8-tetracarboxybicyclo [3.3.0] octane- 2: 4,6: 8-dianhydride, 4,9-dioxatricyclo [5.3.1.0 ^2,6 ] undecane-3,5,8,10-tetraone and the like.

  Examples of the aromatic tetracarboxylic dianhydride include pyromellitic dianhydride.

  Of these tetracarboxylic dianhydrides, alicyclic tetracarboxylic dianhydrides and aromatic tetracarboxylic dianhydrides are preferred, 2,3,5-tricarboxycyclopentylacetic dianhydride, 1,2, 3,4-cyclobutanetetracarboxylic dianhydride, 3,5,6-tricarboxy-2-carboxymethylnorbornane-2: 3,5: 6-dianhydride, 2,4,6,8-tetracarboxybicyclo [3.3.0] Octane-2: 4,6: 8-dianhydride and pyromellitic dianhydride are more preferable, 2,3,5-tricarboxycyclopentylacetic acid dianhydride, 1,2,3 , 4-cyclobutanetetracarboxylic dianhydride and pyromellitic dianhydride are particularly preferable. When tetracarboxylic dianhydride contains said preferable compound, the polyamic acid used as the material of the composition for liquid crystal aligning film formation which has a desired characteristic can be obtained.

  When 2,3,5-tricarboxycyclopentylacetic acid dianhydride is used in combination with other tetracarboxylic dianhydrides, 2,3,5-tricarboxycyclopentylacetic acid dianhydride in all tetracarboxylic dianhydrides The content of is preferably 30 mol% or more, more preferably 50 mol% or more.

(Diamine compound)
As a diamine compound used for the synthesis | combination of a polyamic acid, the diamine represented by the said Formula (1) is included at least, and other diamine may be used together as needed.

In the above formula (1), X is a divalent aromatic group which may be substituted. Examples of the divalent aromatic group include a 1,2-phenylene group, a 1,3-phenylene group, a 1,4-phenylene group, a biphenyl-4,4′-diyl group, a naphthylene group, and an anthracenediyl group. It is done. U ¹ and U ² are each independently a single bond, —O—, —COO— or —OCO—.

  Examples of the substituent for X include a halogen atom, a hydroxyl group, a nitro group, a cyano group, a carboxyl group, a cycloalkyl group, an aryl group, an alkoxy group, an acyl group, an acyloxy group, an alkoxycarbonyl group, and a haloalkyl group.

  As the diamine represented by the formula (1), a compound represented by the following formula is preferred.

(Other diamines)
Examples of other diamines that may be included in the diamine compound together with the diamine represented by the above formula (1) include aliphatic diamines, alicyclic diamines, diaminoorganosiloxanes, and aromatic diamines. In addition to these, tetracarboxylic dianhydrides described in Japanese Patent Application No. 2009-157556 can be used.

  Examples of the aliphatic diamine include 1,1-metaxylylenediamine, 1,3-propanediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, and the like.

  Examples of the alicyclic diamine include 1,4-diaminocyclohexane, 4,4′-methylenebis (cyclohexylamine), 1,3-bis (aminomethyl) cyclohexane, and the like.

  Examples of the diaminoorganosiloxane include 1,3-bis (3-aminopropyl) -tetramethyldisiloxane.

  Examples of the aromatic diamine include p-phenylenediamine, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenyl sulfide, 1,5-diaminonaphthalene, 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-aminophenyl) fluorene, 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane, 2,2-bis (4-aminophenyl) hexafluoro Propane, 4,4 ′-(p-phenylenediisopropylidene) bisaniline, 4,4 ′-(m-pheny 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-diaminoacridine, 3,6-diaminocarbazole, N-methyl-3,6-diaminocarbazole, N-ethyl-3,6-diaminocarbazole, N-phenyl-3,6-diaminocarbazole N, N′-bis (4-aminophenyl) -benzidine, N, N′-bis (4-aminophenyl) -N, N′-dimethylbenzidine, 1,4-bis- (4-aminophenyl)- Piperazine, 3,5-diaminobenzoic acid, dodecanoxy-2,4-diaminobenzene, tetradecanoxy-2,4-diamy Benzene, pentadecanoxy-2,4-diaminobenzene, hexadecanoxy-2,4-diaminobenzene, octadecanoxy-2,4-diaminobenzene, dodecanoxy-2,5-diaminobenzene, tetradecanoxy-2,5-diaminobenzene, pentadecanoxy-2 , 5-diaminobenzene, hexadecanoxy-2,5-diaminobenzene, octadecanoxy-2,5-diaminobenzene, cholestanyloxy-3,5-diaminobenzene, cholestenyloxy-3,5-diaminobenzene, cholestanyloxy- 2,4-diaminobenzene, cholestenyloxy-2,4-diaminobenzene, cholestanyl 3,5-diaminobenzoate, cholestenyl 3,5-diaminobenzoate, lanostannyl 3,5-diaminobenzoate, 3,6-bi (4-aminobenzoyloxy) cholestane, 3,6-bis (4-aminophenoxy) cholestane, 4- (4′-trifluoromethoxybenzoyloxy) cyclohexyl-3,5-diaminobenzoate, 4- (4 ′ -Trifluoromethylbenzoyloxy) cyclohexyl-3,5-diaminobenzoate, 1,1-bis (4-((aminophenyl) methyl) 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, - diallyl aniline, 4-amino-benzylamine, diamines represented by 3-amino-benzylamine and the following formula (2).

(In Formula (2), Y is a C1-C3 alkanediyl group, -O-, -COO-, or -OCO-. A is 0 or 1. b is an integer of 0-2. C is an integer from 1 to 20.)

In said formula (2), Y is a C1-C3 alkanediyl group. Examples of the alkyl group having 1 to 3 carbon atoms include a methanediyl group, an ethanediyl group, and an n-propanediyl group. In the above formula (2), as the C _c H _{2c + 1} group, for example, linear or branched, methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group Decyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, eicosyl group and the like. In the above formula (2), the diaminophenyl group is preferably a 2,4-diaminophenyl group or a 3,5-diaminophenyl group.

  Examples of the diamine represented by the above formula (2) include compounds represented by the following formulas (2-1) to (2-5). In the above formula (2), it is preferable that a and b are not 0 simultaneously.

  Of these other diamines, aromatic diamines are preferred, and p-phenylenediamine, 4,4′-diaminodiphenylmethane, 2,2′-dimethyl-4,4′-diaminobiphenyl, 4,4′-diamino-2. , 2′-bis (trifluoromethyl) biphenyl, 4,4′-diaminodiphenyl ether, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-amino) Phenoxy) phenyl] hexafluoropropane, 2,2-bis (4-aminophenyl) hexafluoropropane, 4,4 ′-(p-phenylenediisopropylidene) bisaniline, 4,4 ′-(m-phenylenediisopropylidene) ) Bisaniline, 1,4-bis (4-aminophenoxy) benzene, 4,4′-bis (4-aminophen) Xyl) biphenyl, 3,5-diaminobenzoic acid, 3,6-bis (4-aminobenzoyloxy) cholestane, 3,6-bis (4-aminophenoxy) cholestane, 4- (4'-trifluoromethoxybenzoy) Roxy) cyclohexyl-3,5-diaminobenzoate, 4- (4′-trifluoromethylbenzoyloxy) cyclohexyl-3,5-diaminobenzoate, [3- (4-aminobenzoyl) oxyphenyl] 4-aminobenzoate More preferred are p-phenylenediamine, 4,4′-diaminodiphenylmethane, and [3- (4-aminobenzoyl) oxyphenyl] 4-aminobenzoate.

  When using the said other diamine together, as content of the diamine represented by the said Formula (1) in a diamine compound, 0.1 mol% or more is preferable, 1 mol%-50 mol% are more preferable, 5 mol%-35 mol % Is particularly preferred.

(Method for synthesizing polyamic acid)
A polyamic acid is obtained by reacting a tetracarboxylic dianhydride and a diamine compound containing a diamine represented by the above formula (1).

  The content of tetracarboxylic dianhydride is preferably 0.2 to 2 equivalents, preferably 0.3 to 2 equivalents of an acid anhydride group of tetracarboxylic dianhydride with respect to 1 equivalent of amino group of the diamine compound. 1.2 equivalents are more preferred.

  The synthesis reaction is preferably performed in an organic solvent. The reaction temperature is preferably −20 ° C. to 150 ° C., more preferably 0 ° C. to 100 ° C. The reaction time is preferably 0.1 hour to 24 hours, more preferably 0.5 hour to 12 hours.

  Examples of the organic solvent include aprotic polar solvents, phenol and derivatives thereof, alcohols, ethers, halogenated hydrocarbons, hydrocarbons and the like. These organic solvents may be used alone or in combination of two or more.

  Examples of the aprotic polar solvent include amides, ketones, esters, and other aprotic polar solvents.

  Examples of amides include N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide and the like.

  Examples of ketones include acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone.

  Examples of esters include ethyl lactate, butyl lactate, methyl acetate, ethyl acetate, butyl acetate, methyl methoxypropionate, ethyl ethoxypropionate, diethyl oxalate, diethyl malonate, γ-butyrolactone, isoamylpropio Nate, isoamyl isobutyrate and the like.

  Examples of other aprotic polar solvents include dimethyl sulfoxide, tetramethyl urea, hexamethyl phosphortriamide and the like.

  Examples of the phenol derivative include m-cresol, xylenol, halogenated phenol and the like.

  Examples of alcohols include methyl alcohol, ethyl alcohol, isopropyl alcohol, cyclohexanol, ethylene glycol, propylene glycol, 1,4-butanediol, triethylene glycol, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, and diethylene glycol monoethyl ether. Can be mentioned.

  Examples of ethers include diethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol di-n-propyl ether, ethylene glycol di-i-propyl ether, ethylene glycol di-n-butyl ether, and ethylene glycol. Examples include monoethyl ether acetate, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, tetrahydrofuran, and diisopentyl ether.

  Examples of halogenated hydrocarbons include dichloromethane, 1,2-dichloroethane, 1,4-dichlorobutane, trichloroethane, chlorobenzene, o-dichlorobenzene, and the like.

  Examples of hydrocarbons include hexane, heptane, octane, benzene, toluene, xylene and the like.

  Of these organic solvents, aprotic polar solvents are preferable, and N-methyl-2-pyrrolidone and γ-butyrolactone are more preferable.

  The polyamic acid solution obtained after the reaction may be used for the preparation of the composition for forming a liquid crystal alignment film as it is, and after the polyamic acid contained in the reaction solution is isolated, it is used for the preparation of the composition for forming a liquid crystal alignment film. Alternatively, the isolated polyamic acid may be purified and then used for preparing a composition for forming a liquid crystal alignment film. Examples of the method for isolating the polyamic acid include a method of pouring a reaction solution into a large amount of a poor solvent and drying a precipitate obtained under reduced pressure, and a method of distilling the reaction solution under reduced pressure using an evaporator. Examples of the method for purifying the polyamic acid include a method in which the isolated polyamic acid is dissolved again in an organic solvent and precipitated with a poor solvent, and a method in which the step of distilling off the organic solvent or the like with an evaporator is performed once or a plurality of times. .

(Polyimide)
A polyimide is obtained by dehydrating and ring-closing the polyamic acid to imidize it.

The polyimide may be a completely imidized product in which all of the amic acid structure of the precursor polyamic acid has been dehydrated and cyclized, and only a part of the amic acid structure may be dehydrated and cyclized to form an amic acid structure and an imide. It may be a partially imidized product in which a ring structure coexists. At this time, a part of the imide ring may be an isoimide ring. The imidation ratio in the polyimide is preferably 30% or more, more preferably 40% or more, and particularly preferably 50% or more. The imidization rate in polyimide is determined by pouring the polyimide solution into pure water, drying the obtained precipitate under reduced pressure at room temperature, dissolving in deuterated dimethyl sulfoxide, and using tetramethylsilane as a reference material at room temperature. ¹ H-NMR was measured and determined from the obtained ¹ H-NMR spectrum by the formula represented by the following formula (3).

Imidation ratio (%) = {1- (A ¹ / A ² ) × α} × 100 (3)

In formula (3), A ¹ is the peak area (10 ppm) derived from the proton of the NH group. A ² is the peak area derived from other protons. α is the number ratio of other protons to one NH group proton in the polyamic acid.

(Polyimide synthesis method)
As a method for synthesizing polyimide, for example, (i) a method of heating a polyamic acid (hereinafter sometimes referred to as “method (i)”), (ii) a polyamic acid is dissolved in an organic solvent, Examples include a method of adding a dehydrating agent and a dehydrating ring-closing catalyst, and heating as necessary (hereinafter, also referred to as “method (ii)”), a method based on a dehydrating ring-closing reaction of polyamic acid.

(Method (i))
As reaction temperature in method (i), 50 to 200 degreeC is preferable and 60 to 170 degreeC is more preferable. When the reaction temperature is less than 50 ° C., the dehydration ring-closing reaction does not proceed sufficiently, and when the reaction temperature exceeds 200 ° C., the molecular weight of the resulting polyimide may decrease. The reaction time is preferably 1.0 hour to 24 hours, more preferably 1.0 hour to 12 hours.

  The polyimide obtained in the method (i) may be used as it is for the preparation of the composition for forming a liquid crystal alignment film, or may be used for the preparation of the composition for forming a liquid crystal alignment film after isolating the polyimide. After purifying the obtained polyimide or purifying the obtained polyimide, it may be used for preparing the composition for forming a liquid crystal alignment film.

(Method (ii))
Examples of the dehydrating agent in the method (ii) include acid anhydrides such as acetic anhydride, propionic anhydride, and trifluoroacetic anhydride.

  The content of the dehydrating agent is appropriately selected depending on the desired imidization rate, but is preferably 0.01 mol to 20 mol with respect to 1 mol of the amic acid structure of the polyamic acid.

  Examples of the dehydration ring closure catalyst in the method (ii) include pyridine, collidine, lutidine, triethylamine and the like.

  The content of the dehydration ring closure catalyst is preferably 0.01 mol to 10 mol with respect to 1 mol of the dehydrating agent contained. In addition, the imidation rate can be increased as the content of the dehydrating agent and the dehydrating ring-closing agent is increased.

  Examples of the organic solvent used in the method (ii) include organic solvents similar to those exemplified as those used for the synthesis of polyamic acid.

  The reaction temperature in method (ii) is preferably 0 ° C to 180 ° C, more preferably 10 ° C to 150 ° C. The reaction time is preferably 1.0 hour to 120 hours, more preferably 2.0 hours to 30 hours. By setting the reaction conditions in the above range, the dehydration ring-closing reaction proceeds sufficiently, and the molecular weight of the resulting polyimide can be made appropriate.

  In the method (ii), a reaction solution containing polyimide is obtained. This reaction solution may be used as it is for the preparation of a composition for forming a liquid crystal alignment film, or may be used for the preparation of a composition for forming a liquid crystal alignment film after removing the dehydrating agent and the dehydration ring-closing catalyst from the reaction solution. May be used for preparing a composition for forming a liquid crystal alignment film, or may be used for preparing a composition for forming a liquid crystal alignment film after purifying the isolated polyimide. Examples of a method for removing the dehydrating agent and the dehydrating ring-closing catalyst from the reaction solution include a solvent replacement method. Examples of the polyimide isolation method and purification method include the same methods as those exemplified as the polyamic acid isolation method and purification method.

  The polyamic acid or polyimide contained in the composition for forming a liquid crystal alignment film may be a terminal-modified type. By using the terminal-modified polymer, the coating characteristics of the composition for forming a liquid crystal alignment film can be further improved without impairing the effects of the present invention.

  Such a terminal-modified polymer can be obtained by adding a molecular weight modifier to a polymerization reaction system when synthesizing a polyamic acid. Examples of molecular weight regulators include acid monoanhydrides, monoamine compounds, monoisocyanate compounds, and the like.

  Examples of the acid monoanhydride include maleic anhydride, phthalic anhydride, itaconic anhydride, n-decyl succinic anhydride, n-dodecyl succinic anhydride, n-tetradecyl succinic anhydride, n- Examples include hexadecyl succinic anhydride.

  Examples of the monoamine compound include aniline, cyclohexylamine, n-butylamine, n-pentylamine, n-hexylamine, n-heptylamine, n-octylamine, n-nonylamine, n-decylamine, n-undecylamine, Examples include n-dodecylamine, n-tridecylamine, n-tetradecylamine, n-pentadecylamine, n-hexadecylamine, n-heptadecylamine, n-octadecylamine, and n-eicosylamine.

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

  As a usage-amount of a molecular weight regulator, 20 mass parts or less are preferable with respect to a total of 100 mass parts of tetracarboxylic dianhydride and diamine compound used when synthesize | combining a polyamic acid, and 10 mass parts or less are more preferable. .

  The viscosity is preferably 20 mPa · s to 800 mPa · s, and more preferably 30 mPa · s to 500 mPa · s when measured with a polyamic acid solution or a polyimide solution having a concentration of 10% by mass. The viscosity (mPa · s) was measured at 25 ° C. using an E-type rotational viscometer using a predetermined solvent.

(Optional component)
The liquid crystal alignment film-forming composition can contain other components such as other polymers, epoxy compounds, and functional silane compounds as long as the desired effects are not impaired.

(Other polymers)
By containing other polymers, the solution characteristics of the liquid crystal compounding agent and the electric characteristics of the liquid crystal alignment film formed by the liquid crystal compounding agent are improved.

  Examples of the other polymer include polymers other than the polyamic acid and polyimide. For example, the polymer is obtained by reacting a tetracarboxylic dianhydride and a diamine compound not containing the diamine represented by the above formula (1). Polyamic acid (hereinafter sometimes referred to as “other polyamic acid”), polyimide obtained by dehydrating and ring-closing this polyamic acid (hereinafter sometimes referred to as “other polyamic acid”), polyamic acid ester , Polyester, polyamide, polysiloxane, cellulose derivative, polyacetal, polystyrene derivative, polystyrene-phenylmaleimide derivative, poly (meth) acrylate, and the like. Among these, other polyamic acids and other polyimide acids are preferable, and other polyamic acids are more preferable.

  As content of another polymer, 50 mass% or less is preferable with respect to all the polymers, 0.1 mass%-40 mass% are more preferable, 0.1 mass%-30 mass% are especially preferable.

(Epoxy compound)
By containing an epoxy compound, the rigidity and electrical characteristics of the liquid crystal alignment film formed by the liquid crystal compounding agent are improved.

  Examples of the epoxy 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, glycerin diglycidyl ether, trimethylolpropane triglycidyl ether, 2,2-dibromoneopentyl glycol diglycidyl ether, N, N, N ′, N′-tetraglycidyl-m-xylenediamine, 1,3- Bis (N, N-diglycidylaminomethyl) cyclohexane, N, N, N ′, N′-tetraglycidyl-4,4′-diaminodiphenyl Tan, N, N-diglycidyl - benzylamine, N, N-diglycidyl - aminomethyl cyclohexane, N, N-diglycidyl - cyclohexylamine, and the like.

  As for content of an epoxy compound, 40 mass parts or less are preferable with respect to 100 mass parts of all the polymers, and 0.1 mass part-30 mass parts are more preferable.

(Functional silane compound)
The functional silane compound is contained for the purpose of improving the adhesion between the obtained liquid crystal alignment film and the substrate.

  Examples of the functional silane compound 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-aminopropyltri Methoxysilane, N-ethoxycarbonyl-3-aminopropyltriethoxysilane, N-triethoxysilylpropyltriethylenetriamine, N-trimethoxysilylpropyltriethylenetriamine, 10-trimethoxysilyl-1,4,7 Triazadecane, 10-triethoxysilyl-1,4,7-triazadecane, 9-trimethoxysilyl-3,6-diazanonyl acetate, 9-trimethoxysilyl-3,6-diazanonyl acetate, 9-triethoxy Silyl-3,6-diazanonyl acetate, methyl 9-trimethoxysilyl-3,6-diazananoate, methyl 9-triethoxysilyl-3,6-diazananoate, N-benzyl-3-aminopropyltrimethoxysilane N-benzyl-3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-phenyl-3-aminopropyltriethoxysilane, glycidoxymethyltrimethoxysilane, glycidoxymethyltri Ethoxysilane, 2-glycidoxyethyltrimethoxy Run, 2-glycidoxyethyl triethoxysilane, 3-glycidoxypropyl trimethoxysilane, 3-glycidoxypropyl triethoxysilane, and the like.

  2 mass parts or less are preferable with respect to 100 mass parts of all polymers, and, as for content of a functional silane containing compound, 0.02 mass part-0.2 mass part are more preferable.

(Method for producing composition for forming liquid crystal alignment film)
The composition for forming a liquid crystal alignment film is obtained by dehydrating and ring-closing a polyamic acid obtained by a reaction between a tetracarboxylic dianhydride and a diamine compound containing at least a diamine represented by the following formula (1). At least one polymer selected from the group consisting of polyimides, and if necessary, an optional component is dissolved or dispersed by mixing in an organic solvent.

  Examples of the organic solvent that can be used in the production of the composition for forming a liquid crystal alignment film include aprotic polar solvents, ketones, esters, ethers, diethylene glycol monoalkyl acetates, and the like. These organic solvents may be used alone or in combination of two or more.

  Examples of the aprotic polar solvent include N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, γ-butyrolactone, γ-butyrolactam and the like.

  Examples of ketones include 4-hydroxy-4-methyl-2-pentanone and diisobutyl ketone.

  Examples of the esters include butyl lactate, butyl acetate, methyl methoxypropionate, ethyl ethoxypropionate, isoamyl propionate, isoamyl isobutyrate, ethylene carbonate, propylene carbonate, and the like.

  Examples of ethers include ethylene glycol monomethyl ether, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol-n-propyl ether, ethylene glycol-i-propyl ether, ethylene glycol-mono-n-butyl ether, ethylene glycol dimethyl ether, Examples include ethylene glycol ethyl ether acetate, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and diisopentyl ether.

  Examples of the diethylene glycol monoalkyl acetate include diethylene glycol monomethyl ether acetate and diethylene glycol monoethyl ether acetate.

  The solid content concentration in the composition for forming a liquid crystal alignment film is appropriately selected in consideration of viscosity, volatility, coating method, and the like, but is preferably 1% by mass to 10% by mass. By setting the solid content concentration in the above range, the film thickness of the liquid crystal alignment film formed from the liquid crystal alignment film forming composition is appropriate, and as a result, a good liquid crystal alignment film can be obtained. Also, the coating workability is improved. As described above, the preferred solid content concentration range varies depending on the application method of the composition for forming a liquid crystal alignment film. For example, the spinner method is preferably 1.5% by mass to 4.5% by mass, and the printing method is preferable. 3 mass%-9 mass% are preferable, and it is preferable to make the viscosity in these concentration ranges into the range of 12 mPa * s-50 mPa * s. The solid content concentration in the ink jet method is preferably 1% by mass to 5% by mass, and the viscosity in this concentration range is preferably in the range of 3 mPa · s to 15 mPa · s.

  As temperature at the time of preparing the said composition for liquid crystal aligning film formation, 10 to 50 degreeC is preferable and 20 to 30 degreeC is more preferable.

(Liquid crystal alignment film)
The liquid crystal alignment film of the present invention is formed from the liquid crystal alignment film forming composition and has a large retardation value. When the liquid crystal alignment film is applied to, for example, a horizontal electric field type liquid crystal display element, the response speed of the liquid crystal is high. And the black level in the dark state is increased to improve the contrast. As a result, high display quality can be realized.

(Method for producing liquid crystal alignment film)
As a manufacturing method of the said liquid crystal display element, the manufacturing method which has a coating-film formation process (1) and a rubbing process process (2), for example is mentioned.

(Coating film formation process (1))
In the coating film forming step (1), first, the composition for forming a liquid crystal alignment film is applied onto a substrate, and then the coating surface is heated to form a coating film. In addition, the preferable application | coating method of the use substrate, the composition for liquid crystal aligning film formation, and the heating temperature after application | coating of the composition for liquid crystal aligning film formation are suitably selected by the desired display mode.

  Examples of the material for the substrate include glass such as float glass and soda glass; and plastics such as polyethylene terephthalate, polybutylene terephthalate, polyethersulfone, polycarbonate, and poly (alicyclic olefin).

  The substrate is patterned into a comb shape using a pair of a conductive film forming surface of a substrate provided with a transparent conductive film patterned in a comb shape and a substrate not provided with a conductive film facing the substrate. The composition for forming a liquid crystal alignment film is preferably applied to the conductive film forming surface of the substrate provided with the transparent conductive film and the one surface of the substrate (counter substrate) not provided with the conductive film, preferably by a printing method or a spinner method. Or it coats by the inkjet method, respectively, Then, each coating surface is heated, and a coating film is formed.

Examples of the transparent conductive film include a NESA film (USPPG, registered trademark) made of tin oxide (SnO ₂ ), an ITO film made of indium oxide-tin oxide (In ₂ O ₃ —SnO ₂ ), and the like. As a method of obtaining a patterned transparent conductive film, for example, after forming a transparent conductive film without a pattern, a method of forming a pattern by photo-etching, and a method of using a mask having a desired pattern when forming the transparent conductive film Etc.

  When applying the composition for forming a liquid crystal alignment film, in order to further improve the adhesion between the substrate surface and the transparent conductive film and the coating film, the surface of the substrate surface on which the coating film is formed is functionalized as a pretreatment. It is preferable to apply a silane compound, a functional titanium compound or the like in advance.

  As heating temperature after apply | coating the composition for liquid crystal aligning film formation, 80 to 300 degreeC is preferable and 120 to 250 degreeC is more preferable. The heating time is preferably 1 minute to 60 minutes, and more preferably 10 minutes to 30 minutes. The film thickness of the coating film to be formed is preferably 10 nm to 1,000 nm, and more preferably 50 nm to 500 nm.

  As described above, the composition for forming a liquid crystal alignment film is heated after application to remove the organic solvent to form a coating film. However, when the composition for forming a liquid crystal alignment film contains polyimide, It is good also as a more imidized coating film by advancing the dehydration ring closure reaction by further heating after film formation.

(Rubbing process (2))
In the rubbing treatment step (2), a rubbing treatment is performed in which the coating surface formed as described above is rubbed in a certain direction with a roll wound with a cloth made of fibers such as nylon, rayon, and cotton. Thereby, the said coating film provides the orientation ability of a liquid crystal molecule to a coating film, and forms a liquid crystal aligning film.

  Further, with respect to the liquid crystal alignment film formed as described above, a treatment for 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, or the surface of the liquid crystal alignment film A resist film is formed on a part of the substrate, and a rubbing process is performed in a direction different from the previous rubbing process, and then the resist film is removed so that the liquid crystal alignment film has a different liquid crystal alignment ability for each region. Thus, it is possible to improve the visibility characteristics of the liquid crystal display element obtained.

(Liquid crystal display element)
The liquid crystal display element of the present invention includes the liquid crystal alignment film formed as described above. The liquid crystal alignment film of the present invention formed from the composition for forming a liquid crystal alignment film has a large retardation value. When the liquid crystal alignment film is applied to, for example, a horizontal electric field type liquid crystal display element, the response speed of the liquid crystal is high. And the black level in the dark state is increased, so that the contrast is improved. As a result, high display quality can be realized.

  Specifically, in the liquid crystal display element of the present invention, two substrates having the liquid crystal alignment film formed on the surface thereof are arranged opposite to each other on the liquid crystal alignment film side through a sealant provided at the periphery of the substrate. The liquid crystal is filled between these two substrates.

(Manufacturing method of liquid crystal display element of horizontal electric field type)
When the liquid crystal alignment film is applied to a horizontal electric field type liquid crystal display element, the characteristics are maximized. Examples of the method for producing the horizontal electric field type liquid crystal display element include the following steps.

  A liquid crystal cell is manufactured by preparing two substrates on which the liquid crystal alignment film is formed as described above, and disposing a liquid crystal between the two substrates opposed to each other. Here, when the rubbing treatment is performed on the coating film, the two substrates are disposed to face each other so that the rubbing directions in the respective coating films are at a predetermined angle, for example, orthogonal or antiparallel.

  In order to manufacture a liquid crystal cell, the following two methods are mentioned, for example. The first method is a conventionally known method. First, 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 together using a sealant, and the substrate surface and the seal are bonded. A liquid crystal cell can be manufactured by sealing the injection hole after injecting and filling the liquid crystal into the cell gap partitioned by the agent.

  The second method is a method called the One Drop Fill method (ODF method). For example, an ultraviolet light curable sealing material is applied to a predetermined location on one of the two substrates on which the liquid crystal alignment film is formed, and liquid crystal is dropped on the liquid crystal alignment film surface. A liquid crystal cell can be manufactured by bonding the other substrate so that the liquid crystal alignment films face each other, and then irradiating the entire surface of the substrate with ultraviolet light to cure the sealant.

  Regardless of which method is used, the liquid crystal cell produced as described above is further heated to a temperature at which the liquid crystal used takes an isotropic phase, and then gradually cooled to room temperature, so that the flow alignment during liquid crystal injection is achieved. It is desirable to remove. Then, by attaching a polarizing plate to the outer surface of the liquid crystal cell, the horizontal electric field type liquid crystal display element can be obtained.

  As a sealing agent, the epoxy resin etc. which contain the aluminum oxide sphere as a hardening | curing agent and a spacer are mentioned, for example.

  Examples of the liquid crystal include nematic liquid crystal and smectic liquid crystal. Among these, 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, biphenyl cyclohexane liquid crystal, pyrimidine liquid crystal, dioxane liquid crystal, Bicyclooctane liquid crystal, cubane liquid crystal and the like can be mentioned. In addition, these liquid crystals include, for example, cholesteric liquid crystals such as cholestyl chloride, cholesteryl nonate, cholesteryl carbonate; chiral agents (Merck, C-15, CB-15); p-decyloxybenzylidene-p-amino-2- A ferroelectric liquid crystal such as methylbutyl cinnamate may be further added.

  As a polarizing plate bonded to the outer surface of the liquid crystal cell, for example, a polarizing plate in which a polarizing film called “H film” that absorbs iodine while stretching and aligning polyvinyl alcohol is sandwiched between cellulose acetate protective films or H Examples thereof include a polarizing plate made of the film itself.

  EXAMPLES Hereinafter, although this invention is explained in full detail based on an Example, this invention is not interpreted limitedly based on description of this Example.

(Synthesis of diamine represented by the above formula (1))
[Synthesis Example 1]
Bis (4-aminophenyl) terephthalate was synthesized according to the following reaction scheme.

  In a nitrogen atmosphere, put 1,200 mL of methylene chloride in a 3 L three-necked flask, mix 1 mol (203.02 g) of terephthaloyl chloride and 2.2 mol (306.04 g) of 4-nitrophenol, and stir at room temperature with pyridine. 3 mol (237.3 g) was slowly added dropwise. Thereafter, the reaction solution was stirred and reacted for 3 hours by reflux. After returning to room temperature, the precipitate obtained by the reaction was separated by filtration, and the precipitate was washed with a 3% by mass hydrochloric acid aqueous solution, 3% by mass sodium hydrogen carbonate solution and distilled water in this order. Intermediate 1 (334.82 g) was obtained by vacuum-drying at 12 ° C. for 12 hours. Under a nitrogen atmosphere, 0.05 mol (20.42 g) of Intermediate 1 and 0.5 mol (112.83 g) of tin (II) chloride dihydrate and 500 mL of γ-butyrolactone were mixed in a 1 L three-necked flask, The reaction was stirred for 2 hours at ° C. To the reaction solution, 4 L of γ-butyrolactone was added and washed with a 2 mol / L potassium fluoride aqueous solution. 6 L of ethyl acetate was added to the obtained organic solvent phase and washed with distilled water. The organic solvent phase was concentrated on a rotary evaporator. The solid obtained by concentration was placed in a 2 L eggplant flask, and 400 mL of methanol was added and stirred. The solid was separated by suction filtration, and the obtained solid was vacuum-dried at 60 ° C. for 12 hours to obtain the desired diamine, bis (4-aminophenyl) terephthalate (12.64 g).

[Synthesis Example 2]
Bis (4-aminophenyl) -2,6-naphthalenedicarboxylate was synthesized according to the following reaction scheme.

  Under a nitrogen atmosphere, a 300 mL eggplant flask was mixed with 0.1 mol (21.62 g) of 2,6-naphthalenedicarboxylic acid, 80 mL of thionyl chloride, and 0.2 mL of N, N-dimethylformamide and stirred at 80 ° C. for 5 hours to react. I let you. After returning the reaction solution to room temperature, the remaining thionyl chloride was removed with a water flow aspirator. 1,200 mL of methylene chloride was added and washed with distilled water. The organic solvent phase was dried with magnesium sulfate. Magnesium sulfate was filtered off, and the organic solvent phase was concentrated on a rotary evaporator. The obtained concentrated liquid was transferred to a 2 L three-necked atmosphere under a nitrogen atmosphere, mixed with 0.22 mol (30.6 g) of 4-nitrophenol and 1,000 mL of methylene chloride, and stirred at room temperature with 0.3 mol of pyridine ( 23.73 g) was slowly added dropwise. Thereafter, the reaction solution was stirred for 6 hours by reflux to react. The precipitate obtained by the reaction after returning to room temperature was filtered off, and the precipitate was washed with 3% by mass hydrochloric acid solution, 3% by mass sodium hydrogen carbonate solution and distilled water, and vacuum-dried at 60 ° C. for 12 hours. went. The obtained solid was transferred to a 500 mL eggplant flask, 300 mL of tetrahydrofuran was added, and the mixture was stirred with reflux for 1 hour. The temperature was returned to room temperature, and the solid was separated by filtration. The obtained solid was dried at 60 ° C. for 12 hours to obtain 22.26 g of Intermediate 3. Under a nitrogen atmosphere, 0.03 mol (18.34 g) of intermediate 3 and 0.4 mol (90.26 g) of tin (II) chloride dihydrate and 400 mL of γ-butyrolactone were mixed in a 1 L three-necked flask. The reaction was stirred for 2 hours at ° C. After the reaction, 400 mL of ethyl acetate was added and washed with a 2 mol / L potassium fluoride aqueous solution and distilled water in this order. The obtained organic solvent phase was concentrated by a rotary evaporator. The resulting purified composition was purified by silica gel column chromatography (developing solvent, tetrahydrofuran: hexane = 2: 1) to obtain the desired diamine, bis (4-aminophenyl) 2,6-naphthalenedicarboxylate (6.7 g). 4 was obtained.

(Synthesis of polyamic acid and polyimide)
[Synthesis Example 3] Synthesis of (A-1) 113 g (0.50 mol) of 2,3,5-tricarboxycyclopentylacetic acid dianhydride as tetracarboxylic dianhydride and [3- (4-aminobenzoyl) as a diamine compound ) Oxyphenyl] 4-aminobenzoate 17 g (0.05 mol, Iwatani Gas Chemical Co., Ltd.) and p-phenylenediamine 495 g (0.45 mol) are dissolved in 1,600 g of γ-butyrolactone and reacted at 60 ° C. for 6 hours. A solution containing polyamic acid was obtained. Next, 1,800 g of γ-butyrolactone was added to the obtained polyamic acid solution, 200 g of pyridine and 150 g of acetic anhydride were added, and a dehydration ring closure reaction was performed at 110 ° C. for 4 hours. After the dehydration ring closure reaction, concentration and dilution in the system were repeated twice, and then a predetermined amount of γ-butyrolactone was added to obtain 1,800 g of a solution containing 10% by mass of polyimide (A-1) having an imidization ratio of about 83%. Got.

[Synthesis Example 4] Synthesis of (A-2) 112 g (0.50 mol) of 2,3,5-tricarboxycyclopentylacetic acid dianhydride as tetracarboxylic dianhydride and bis (4-aminophenyl) terephthalate as diamine compound 35 g (0.10 mol) and 43 g (0.40 mol) of p-phenylenediamine are dissolved in 1,700 g of N-methyl-2-pyrrolidone and reacted at 60 ° C. for 6 hours to obtain a solution containing polyamic acid. It was. Next, 1,900 g of N-methyl-2-pyrrolidone was added to the obtained polyamic acid solution, 200 g of pyridine and 150 g of acetic anhydride were added, and dehydration ring closure reaction was performed at 110 ° C. for 4 hours. After the dehydration cyclization reaction, the solvent in the system was replaced with γ-butyrolactone, and then concentrated to obtain 1,900 g of a solution containing 10% by mass of polyimide (A-2) having an imidization ratio of about 86%. .

[Synthesis Example 5] Synthesis of (A-3) 112 g (0.50 mol) of 2,3,5-tricarboxycyclopentylacetic acid dianhydride as tetracarboxylic dianhydride and bis (4-aminophenyl)-as a diamine compound By dissolving 60 g (0.15 mol) of 2,6-naphthalenedicarboxylate and 38 g (0.35 mol) of p-phenylenediamine in 1,900 g of N-methyl-2-pyrrolidone and reacting at 60 ° C. for 6 hours, A solution containing polyamic acid was obtained. Next, 2,100 g of N-methyl-2-pyrrolidone was added to the obtained polyamic acid solution, 200 g of pyridine and 150 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 substituted with γ-butyrolactone and then concentrated to obtain 2,100 g of a solution containing 10% by mass of polyimide (A-3) having an imidization ratio of about 84%. .

[Synthesis Example 6] Synthesis of (A-4) 101 g (0.45 mol) of 2,3,5-tricarboxycyclopentylacetic acid dianhydride as tetracarboxylic dianhydride and 11 g of pyromellitic dianhydride (0. 05 mol), [3- (4-aminobenzoyl) oxyphenyl] 4-aminobenzoate 52 g (0.15 mol, Iwatani Gas Chemical Co., Ltd.), p-phenylenediamine 11 g (0.1 mol) and 4,4′- Diaminodiphenylmethane 50 g (0.25 mol) was dissolved in 2,000 g of γ-butyrolactone and reacted at 60 ° C. for 6 hours to obtain a solution containing polyamic acid. Next, 2,250 g of N-methyl-2-pyrrolidone was added to the obtained polyamic acid solution, 200 g of pyridine and 150 g of acetic anhydride were added, and dehydration ring closure reaction was performed at 110 ° C. for 4 hours. After the dehydration ring closure reaction, the system was repeatedly concentrated and diluted twice, and then a predetermined amount of γ-butyrolactone was added to obtain 2,250 g of a solution containing 10% by weight of polyimide (A-4) having an imidization ratio of about 84%. Got.

[Synthesis Example 7] Synthesis of (A-5) 67 g (0.3 mol) of 2,3,5-tricarboxycyclopentylacetic acid dianhydride as a tetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic 29 g (0.15 mol) of acid dianhydride, 11 g (0.05 mol) of pyromellitic dianhydride, and 52 g (0.15 mol, 0.13-mol) of [3- (4-aminobenzoyl) oxyphenyl] 4-aminobenzoate as a diamine compound Iwatani Gas Chemical Co., Ltd.), 11 g (0.1 mol) of p-phenylenediamine and 50 g (0.25 mol) of 4,4′-diaminodiphenylmethane were dissolved in 2,000 g of γ-butyrolactone and reacted at 60 ° C. for 6 hours. A solution containing polyamic acid was obtained. Next, 2,250 g of N-methyl-2-pyrrolidone was added to the obtained polyamic acid solution, 200 g of pyridine and 150 g of acetic anhydride were added, and dehydration ring closure reaction was performed at 110 ° C. for 4 hours. After the dehydration cyclization reaction, the system was repeatedly concentrated and diluted twice, and then a predetermined amount of γ-butyrolactone was added to give 2,200 g of a solution containing 10% by weight of polyimide (A-5) having an imidization ratio of about 82%. Got.

[Synthesis Example 8] Synthesis of (A-6) 111 g (0.50 mol) of 2,3,5-tricarboxycyclopentylacetic acid dianhydride as tetracarboxylic dianhydride and 54 g (0. 5 mol) was dissolved in 1,500 g of N-methyl-2-pyrrolidone and reacted at 60 ° C. for 6 hours to obtain a solution containing polyamic acid. Next, 1,650 g of N-methyl-2-pyrrolidone was added to the obtained polyamic acid solution, 200 g of pyridine and 150 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 γ-butyrolactone, and then concentrated to obtain 1,650 g of a solution containing 10% by mass of polyimide (A-6) having an imidation ratio of about 89%. .

[Synthesis Example 8] Synthesis of (A-7) 102 g (0.45 mol) of 2,3,5-tricarboxycyclopentylacetic acid dianhydride as tetracarboxylic dianhydride and 11 g of pyromellitic dianhydride (0. 05 mol), 27 g (0.25 mol) of p-phenylenediamine as a diamine compound and 50 g (0.25 mol) of 4,4′-diaminodiphenylmethane were dissolved in 1,700 g of N-methyl-2-pyrrolidone, and the mixture was heated at 60 ° C. for 6 hours. By making it react, the solution containing a polyamic acid was obtained. Next, 1,900 g of N-methyl-2-pyrrolidone was added to the obtained polyamic acid solution, 200 g of pyridine and 150 g of acetic anhydride were added, and 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 γ-butyrolactone and then concentrated to obtain 1,900 g of a solution containing 10% by mass of polyimide (A-7) having an imidization ratio of about 85%. .

(Preparation of composition for forming liquid crystal alignment film)
[Example 1]
To the solution containing the polyimide (A-1), γ-butyrolactone and ethylene glycol mono-n-butyl ether are added, and N, N, N ′, N′-tetraglycidyl-4,4′- is added as an epoxy compound. Diaminodiphenylmethane (molecular weight of about 400) is added in an amount of 5 parts by mass with respect to 100 parts by mass of the imidized polymer contained in the solution, and the weight ratio of γ-butyrolactone to ethylene glycol-n-butyl ether is 80:20. A solution having a partial concentration of 4% by mass was obtained. This solution was filtered using a filter having a pore size of 1 μm to prepare a composition for forming a liquid crystal alignment film.

[Examples 2-5 and Comparative Examples 1-2]
The polymers used were A-2 (Example 2), A-3 (Example 3), A-4 (Example 4), A-5 (Example 5), and A-6 (Comparative Example 1), respectively. The liquid crystal alignment film forming compositions of Examples 2 to 5 and Comparative Examples 1 to 2 were prepared in the same manner as in Example 1 except that A-7 (Comparative Example 2) was used.

(Manufacture of liquid crystal alignment film)
[Examples 6 to 10 and Comparative Examples 3 to 4]
The compositions for forming liquid crystal alignment films of Examples 1 to 5 and Comparative Examples 1 to 2 were applied by a spinner method onto a transparent conductive film made of an ITO film provided on one surface of a glass substrate having a thickness of 1 mm. The coating film having a film thickness of about 100 nm was formed by drying on the hot plate for 15 minutes. For this coating film, a rubbing machine having a roll wrapped with a rayon cloth is subjected to a rubbing treatment under the conditions of a roll rotation speed of 1000 rpm, a stage moving speed of 2 cm / sec, and a hair foot indentation length of 0.4 mm. A liquid crystal alignment film was obtained by imparting liquid crystal alignment ability to the coating film. This substrate was ultrasonically cleaned in ultrapure water for 1 minute, and then dried in a clean oven at 100 ° C. for 10 minutes to obtain a substrate having a liquid crystal alignment film. This liquid crystal aligning film was made into Examples 6-10 and Comparative Examples 3-4, respectively.

(Manufacture of horizontal electric field type liquid crystal display elements)
[Examples 11 to 15 and Comparative Examples 5 to 6]
The composition for forming liquid crystal alignment films of Examples 1 to 5 and Comparative Examples 1 and 2 prepared as described above was applied by a spinner on a glass substrate having a thickness of 1 mm and having a chromium electrode provided in a comb shape on one side. And it heated for 10 minutes on a 230 degreeC hotplate, and formed the coating film with a film thickness of about 800 mm. Using a rubbing machine having a roll around which a nylon cloth is wound on the formed coating surface, the roll rotation speed is 1,000 rpm, the stage moving speed is 25 mm / second, and the length of pushing the hair foot is 0.4 mm. A rubbing treatment was performed to give liquid crystal alignment ability. Further, this substrate was ultrasonically cleaned in ultrapure water for 1 minute and dried in a 100 ° C. clean oven for 10 minutes to produce a substrate having a liquid crystal alignment film on the surface having comb-like chrome electrodes. Separately, a coating film of the composition for forming a liquid crystal alignment film is formed on one surface of a glass substrate having a thickness of 1 mm that does not have an electrode in the same manner as described above, and a rubbing treatment is performed, followed by washing and drying. A substrate having a liquid crystal alignment film on one side was produced. Subsequently, an epoxy resin adhesive containing aluminum oxide spheres having a diameter of 5.5 μm is applied to the outer edge of the surface having the liquid crystal alignment film subjected to the rubbing treatment so that the rubbing direction in each liquid crystal alignment film is antiparallel. Two substrates were placed opposite to each other with a gap between them, and the outer edge portions were brought into contact with each other and pressed to cure the adhesive. Next, after filling a nematic liquid crystal (Merck, MLC-2042) between a pair of substrates from the liquid crystal injection port, the liquid crystal injection port is sealed with an acrylic photo-curing adhesive, and further on both sides of the outside of the substrate. By laminating the polarizing plate, a transverse electric field type liquid crystal display element was obtained. Such horizontal electric field type liquid crystal display elements were designated as Examples 11 to 15 and Comparative Examples 5 to 6, respectively.

(Evaluation)
Retardation (nm) was measured about the board | substrate which has a liquid crystal aligning film of Examples 6-10 and Comparative Examples 3-4. Further, the minimum relative transmittance (%) of the liquid crystal alignment films in the horizontal electric field type liquid crystal display elements of Examples 11 to 15 and Comparative Examples 5 to 6 was evaluated.

(Measurement of retardation)
Retardation (nm) was measured using a Layscan from Scanex. A retardation value of 0.025 nm or more was considered good, and a retardation value of less than 0.025 nm was regarded as bad. The results are shown in Table 1.

(Minimum relative transmittance measurement)
Using a device in which a polarizer and an analyzer are arranged between the light source and the light amount detector, the minimum relative transmittance (%) represented by the following formula (4) was measured. The black level in the dark state is represented by the minimum relative transmittance of the liquid crystal display element. In the horizontal electric field method, the smaller the black level in the dark state, the better the contrast. A sample having a minimum relative transmittance of less than 0.5% was considered good, and a sample having a minimum relative transmittance of 0.5% or more was judged defective. The results are shown in Table 2.

Minimum relative transmittance (%) = (β−B ⁰ ) / (B ¹⁰⁰ −B ⁰ ) × 100 (4)

In the formula, B ⁰ is a light transmission amount under blank Nicols. B ¹⁰⁰ is a blank and is a transmission amount of light under paranicol. β is a minimum amount of light transmission between the polarizer and the analyzer under the crossed Nicols and the liquid crystal display element is minimized.

  As is clear from the results in Tables 1 and 2, the liquid crystal display element having this liquid crystal alignment film has a liquid crystal response because the retardation value is larger and the minimum relative transmittance is smaller than in the comparative example. It was found that the speed was increased and the contrast was also improved, resulting in high display quality.

  The liquid crystal alignment film formed from the composition for forming a liquid crystal alignment film of the present invention has a large retardation value, and when the liquid crystal alignment film is applied to a horizontal electric field type liquid crystal display element, the response speed of the liquid crystal is increased. In addition, the contrast is improved by increasing the black level in the dark state, and as a result, high display quality can be realized. Therefore, the liquid crystal display element can be widely used as a moving image display device from a small liquid crystal display device such as a mobile phone to a large screen liquid crystal display device such as a liquid crystal television.

Claims (5)

At least selected from the group consisting of a polyamic acid obtained by reaction of tetracarboxylic dianhydride and a diamine compound containing at least a diamine represented by the following formula (1), and a polyimide formed by dehydrating and ring-closing this polyamic acid. Contains one polymer,
As the tetracarboxylic dianhydride, 2,3,5-tricarboxycyclopentylacetic acid dianhydride, 3,5,6-tricarboxy-2-carboxymethylnorbornane-2: 3,5: 6-dianhydride, Group consisting of 2,4,6,8-tetracarboxybicyclo [3.3.0] octane-2: 4,6: 8-dianhydride and 1,2,3,4-cyclobutanetetracarboxylic dianhydride A composition for forming a liquid crystal alignment film , comprising at least one selected from pyromellitic dianhydride .

(In Formula (1), X is a divalent aromatic group which may be substituted. U ¹ and U ² are each independently —COO— or —OCO— .)   The composition for forming a liquid crystal alignment film according to claim 1, wherein X is a phenylene group or a naphthylene group. The liquid crystal aligning film formed from the composition for liquid crystal aligning film formation of Claim 1 or Claim 2 . A liquid crystal display element provided with the liquid crystal aligning film of Claim 3 . The liquid crystal display element according to claim 4 , wherein the display mode is a horizontal electric field method.