JP2006003476A - Liquid crystal aligning agent and liquid crystal display element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal aligning agent by a rubbing treatment of which an alignment property of liquid crystal molecules is certainly imparted and with which a liquid crystal display element provided with a liquid crystal alignment layer having excellent liquid crystal alignment controllability is obtainable. <P>SOLUTION: The liquid crystal aligning agent consists of a polyimide including an imide repeating unit derived from 4,4'-diamino-2 (or 3), 2' (or 3') diaminobiphenyl and a tetracarboxylic acid dianhydride, and that derived from cyclohexane bis (methylamine) and a tetracarboxylic acid dianhydride, wherein the sum of the imide repeating units is 50 mol % or more of the total repeating units. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid crystal aligning agent used for forming a liquid crystal alignment film of a liquid crystal display element. More specifically, the present invention relates to a liquid crystal aligning agent that provides a liquid crystal alignment film that has good storage stability, excellent coating properties, and excellent alignment properties for liquid crystal display elements.

  Currently, as a liquid crystal display element, a liquid crystal alignment film made of polyamic acid, polyimide, or the like is formed on the surface of a substrate on which a transparent conductive film is provided to form a liquid crystal display element substrate. A nematic liquid crystal layer having positive dielectric anisotropy is formed in a cell having a sandwich structure so that the major axis of the liquid crystal molecules is continuously twisted 90 degrees from one substrate to the other. A TN type liquid crystal display element having a so-called TN type (Twisted Nematic) liquid crystal cell is known.

  Further, STN (Super Twisted Nematic) type liquid crystal display elements have been developed that have higher contrast than TN type liquid crystal display elements and have less viewing angle dependency. This STN type liquid crystal display element uses nematic liquid crystal blended with a chiral agent which is an optically active substance as liquid crystal, and the major axis of liquid crystal molecules is continuously twisted over 180 degrees between substrates. The birefringence effect generated by the above is utilized.

  In addition, a horizontal electric field type liquid crystal display element is known in which two electrodes for driving a liquid crystal are arranged in a comb shape on one substrate, an electric field parallel to the substrate surface is generated, and liquid crystal molecules are controlled. The alignment of the liquid crystal in these liquid crystal display elements is usually expressed by a liquid crystal alignment film subjected to a rubbing treatment.

  As a liquid crystal display element different from the above, a liquid crystal display element having a vertical alignment type liquid crystal cell in which liquid crystal molecules having negative dielectric anisotropy are aligned perpendicular to a substrate is known. In such a liquid crystal display element, the alignment of the liquid crystal is usually controlled by a liquid crystal alignment film formed of a liquid crystal alignment agent containing a polymer such as polyamic acid or soluble polyimide.

  A first object of the present invention is to provide a liquid crystal aligning agent capable of providing a liquid crystal display element having a liquid crystal alignment film having liquid crystal molecule alignment ability reliably imparted by rubbing treatment and having excellent liquid crystal alignment. There is.

  A second object of the present invention is to provide a liquid crystal aligning agent capable of constituting a liquid crystal display element provided with a liquid crystal alignment film having excellent coatability.

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

The above objects and advantages of the present invention are primarily represented by the following formulas (A) and (B) having both repeating units represented by the following formulas (A) and (B). It is achieved by a liquid crystal aligning agent characterized by containing a polyimide whose total of repeating units is 50 mol% or more of all repeating units contained in the polyimide.

（式中、Ｒは４価の有機基である）

(Wherein R is a tetravalent organic group)

Secondly, the above objects and advantages of the present invention are achieved by a liquid crystal display device comprising a liquid crystal alignment film obtained from the liquid crystal aligning agent of the present invention.

  According to the liquid crystal aligning agent of this invention, when it is set as a liquid crystal aligning film, a reliable liquid crystal aligning film suitable for liquid crystal display elements can be obtained regardless of process conditions such as rubbing conditions.

  Furthermore, a liquid crystal display element having a liquid crystal alignment film formed using the liquid crystal aligning agent of the present invention is excellent in liquid crystal alignment and can be used effectively in various devices, such as a desk calculator, a wristwatch, a table clock, and a coefficient display board. It is suitably used for display devices such as mobile phones, word processors, personal computers, liquid crystal data projectors, and liquid crystal televisions.

Hereinafter, the present invention will be described in detail. The polyimide used in the present invention can be obtained by dehydrating and ring-closing a polyamic acid obtained by reacting a tetracarboxylic dianhydride and a diamine compound in an organic solvent. Two or more of these polyimides may be used together.
<Polyamic acid and polyimide>
[Tetracarboxylic dianhydride]
Examples of the tetracarboxylic dianhydride used for the synthesis of the polyamic acid that is a polyimide precursor include butanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1, 2-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,3-dichloro-1, 2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-tetramethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclo Pentanetetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 3,3 ′, 4,4′-dicyclohexyltetracarboxylic dianhydride, 2,3,5 Tricarboxycyclopentylacetic acid dianhydride, 3,5,6-tricarboxynorbornane-2-acetic acid dianhydride, 2,3,4,5-tetrahydrofurantetracarboxylic dianhydride, 1,3,3a, 4,5 , 9b-Hexahydro-5 (tetrahydro-2,5-dioxo-3-furanyl) -naphtho [1,2-c] -furan-1,3-dione, 1,3,3a, 4,5,9b-hexahydro -5-methyl-5 (tetrahydro-2,5-dioxo-3-furanyl) -naphtho [1,2-c] -furan-1,3-dione, 1,3,3a, 4,5,9b-hexahydro -5-ethyl-5 (tetrahydro-2,5-dioxo-3-furanyl) -naphtho [1,2-c] -furan-1,3-dione, 1,3,3a, 4,5,9b-hexahydro -7-methyl-5 (teto Lahydro-2,5-dioxo-3-furanyl) -naphtho [1,2-c] -furan-1,3-dione, 1,3,3a, 4,5,9b-hexahydro-7-ethyl-5 ( Tetrahydro-2,5-dioxo-3-furanyl) -naphtho [1,2-c] -furan-1,3-dione, 1,3,3a, 4,5,9b-hexahydro-8-methyl-5 ( Tetrahydro-2,5-dioxo-3-furanyl) -naphtho [1,2-c] -furan-1,3-dione, 1,3,3a, 4,5,9b-hexahydro-8-ethyl-5 ( Tetrahydro-2,5-dioxo-3-furanyl) -naphtho [1,2-c] -furan-1,3-dione, 1,3,3a, 4,5,9b-hexahydro-5,8-dimethyl- 5 (tetrahydro-2,5-dioxo-3-furanyl) -naphtho [ , 2-c] -furan-1,3-dione, 5- (2,5-dioxotetrahydrofural) -3-methyl-3-cyclohexene-1,2-dicarboxylic dianhydride, bicyclo [2,2 , 2] -Oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, 3-oxabicyclo [3.2.1] octane-2,4-dione-6-spiro-3 ′ -(Tetrahydrofuran-2 ', 5'-dione), aliphatic and alicyclic tetracarboxylic dianhydrides such as compounds represented by the following formulas (I) and (II);

（式中、Ｒ¹およびＲ³は、芳香環を有する２価の有機基を示し、Ｒ²およびＲ⁴は、水素原子またはアルキル基を示し、複数存在するＲ²およびＲ⁴は、それぞれ同一でも異なっていてもよい。）

(Wherein R ¹ and R ³ represent a divalent organic group having an aromatic ring, R ² and R ⁴ represent a hydrogen atom or an alkyl group, and a plurality of R ² and R ⁴ are the same. But it may be different.)

Pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenylsulfone tetracarboxylic dianhydride, 1,4,5, 8-naphthalene tetracarboxylic dianhydride, 2,3,6,7-naphthalene tetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyl ether tetracarboxylic dianhydride, 3,3 ′, 4,4′-dimethyldiphenylsilanetetracarboxylic dianhydride, 3,3 ′, 4,4′-tetraphenylsilanetetracarboxylic dianhydride, 1,2,3,4-furantetracarboxylic dianhydride 4,4′-bis (3,4-dicarboxyphenoxy) diphenyl sulfide dianhydride, 4,4′-bis (3,4-dicarboxyphenoxy) diphenylsulfone dianhydride, 4,4′-bi (3,4-Dicarboxyphenoxy) diphenylpropane dianhydride, 3,3 ′, 4,4′-perfluoroisopropylidenediphthalic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic acid Dianhydride, bis (phthalic acid) phenylphosphine oxide dianhydride, p-phenylene-bis (triphenylphthalic acid) dianhydride, m-phenylene-bis (triphenylphthalic acid) dianhydride, bis (triphenyl) Phthalic acid) -4,4'-diphenyl ether dianhydride, bis (triphenylphthalic acid) -4,4'-diphenylmethane dianhydride, ethylene glycol-bis (anhydrotrimellitate), propylene glycol-bis (an Hydrotrimellitate), 1,4-butanediol-bis (anhydrotrimellitate), 1,6-hexa Diol-bis (anhydro trimellitate), 1,8-octanediol-bis (anhydro trimellitate), 2,2-bis (4-hydroxyphenyl) propane-bis (anhydro trimellitate), below Aromatic tetracarboxylic dianhydrides such as compounds represented by formulas (1) to (4) can be given. These may be used alone or in combination of two or more.

Of these, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,3-dimethyl-1, 2,3,4-cyclobutanetetracarboxylic dianhydride, 1,3-dichloro-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-tetramethyl-1,2 , 3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 3,3 ′ , 4,4'-dicyclohexyltetracarboxylic dianhydride, 2,3,5-tricarboxycyclopentylacetic acid dianhydride, 3,5,6-tricarboxynorbornane-2-acetic acid dianhydride, 2,3,4 , -Tetrahydrofurantetracarboxylic dianhydride, 1,3,3a, 4,5,9b-hexahydro-5 (tetrahydro-2,5-dioxo-3-furanyl) -naphtho [1,2-c] -furan-1 , 3-dione, 1,3,3a, 4,5,9b-hexahydro-5-methyl-5 (tetrahydro-2,5-dioxo-3-furanyl) -naphtho [1,2-c] -furan-1 , 3-dione, 1,3,3a, 4,5,9b-hexahydro-5-ethyl-5 (tetrahydro-2,5-dioxo-3-furanyl) -naphtho [1,2-c] -furan-1 , 3-dione, 1,3,3a, 4,5,9b-hexahydro-7-methyl-5 (tetrahydro-2,5-dioxo-3-furanyl) -naphtho [1,2-c] -furan-1 , 3-dione, 1,3,3a, 4,5, b-Hexahydro-7-ethyl-5 (tetrahydro-2,5-dioxo-3-furanyl) -naphtho [1,2-c] -furan-1,3-dione, 1,3,3a, 4,5 9b-Hexahydro-8-methyl-5 (tetrahydro-2,5-dioxo-3-furanyl) -naphtho [1,2-c] -furan-1,3-dione, 1,3,3a, 4,5 9b-Hexahydro-8-ethyl-5 (tetrahydro-2,5-dioxo-3-furanyl) -naphtho [1,2-c] -furan-1,3-dione, 1,3,3a, 4,5 9b-Hexahydro-5,8-dimethyl-5 (tetrahydro-2,5-dioxo-3-furanyl) -naphtho [1,2-c] -furan-1,3-dione, 5- (2,5-dione) Oxotetrahydrofural) -3-methyl-3-cyclohexene- 1,2-dicarboxylic dianhydride, bicyclo [2,2,2] -oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, 3-oxabicyclo [3.2.1 ] Octane-2,4-dione-6-spiro-3 ′-(tetrahydrofuran-2 ′, 5′-dione), among the compounds represented by the above formula (I), the following formulas (5) to (7): Of the compounds represented by the formula (II) and the compound represented by the formula (II), a compound represented by the following formula (8) is preferred, and 2,3,5-tricarboxycyclopentylacetic acid dianhydride is particularly preferred.

[Diamine compound]
The diamine compound used for the synthesis of the polyamic acid which is a precursor of the polyimide is 4,4′-diamino-2,2′-dimethylbiphenyl, 4,4′-diamino-2,3′-dimethylbiphenyl, 4, 4'-diamino-3,3'-dimethylbiphenyl, 1,2-cyclohexanebis (methylamine), 1,3-cyclohexanebis (methylamine) and 1,4-cyclohexanebis (methylamine). These are used in such a ratio that the total of the repeating units represented by the above formulas (A) and (B) is 50 mol% or more with respect to all the repeating units in the polymer. The said diamine compound can be used by 1 type (s) or 2 or more types.

Moreover, the diamine compound which may be used together with said diamine compound in the ratio which the sum total of the repeating unit represented by each of said formula (I) and (B) will be 50 mol% or less with respect to all the repeating units in a polymer. For example, p-phenylenediamine, m-phenylenediamine, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylethane, 4,4′-diaminodiphenyl sulfide, 4,4′-diaminodiphenylsulfone, 4 , 4′-diaminobenzanilide, 4,4′-diaminodiphenyl ether, 1,5-diaminonaphthalene, 5-amino-1- (4′-aminophenyl) -1,3,3-trimethylindane, 6-amino- 1- (4′-aminophenyl) -1,3,3-trimethylindane, 3,4′-diaminodiphenyl Ether, 3,3′-diaminobenzophenone, 3,4′-diaminobenzophenone, 4,4′-diaminobenzophenone, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [ 4- (4-aminophenoxy) phenyl] hexafluoropropane, 2,2-bis (4-aminophenyl) hexafluoropropane, 2,2-bis [4- (4-aminophenoxy) phenyl] sulfone, 1,4 -Bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 9,9-bis (4-aminophenyl) -10- Hydroanthracene, 2,7-diaminofluorene, 9,9-bis (4-aminophenyl) fluorene, 4,4'-methylene- (2-chloroaniline), 2,2 ′, 5,5′-tetrachloro-4,4′-diaminobiphenyl, 2,2′-dichloro-4,4′-diamino-5,5′-dimethoxybiphenyl 3,3′-dimethoxy-4,4′-diaminobiphenyl, 1,4,4 ′-(p-phenyleneisopropylidene) bisaniline, 4,4 ′-(m-phenyleneisopropylidene) bisaniline, 2,2 ′ -Bis [4- (4-amino-2-trifluoromethylphenoxy) phenyl] hexafluoropropane, 4,4'-diamino-2,2'-bis (trifluoromethyl) biphenyl, 4,4'-bis [ Aromatic diamines such as (4-amino-2-trifluoromethyl) phenoxy] -octafluorobiphenyl;

1,3-propanediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, 4,4-diaminoheptamethylenediamine, 1,4-diaminocyclohexane, isophoronediamine, Tetrahydrodicyclopentadienylenediamine, hexahydro-4,7-methanoindanylene methylenediamine, tricyclo [6.2.1.0 ^2,7 ] -undecylenedimethyldiamine, 4,4'-methylenebis (cyclohexylamine) Aliphatic and alicyclic diamines such as 2,5-norbornanebis (methylamine), 2,6-norbornanebis (methylamine), 2,7-norbornanebis (methylamine);
2,3-diaminopyridine, 2,6-diaminopyridine, 3,4-diaminopyridine, 2,4-diaminopyrimidine, 5,6-diamino-2,3-dicyanopyrazine, 5,6-diamino-2,4 -Dihydroxypyrimidine, 2,4-diamino-6-dimethylamino-1,3,5-triazine, 1,4-bis (3-aminopropyl) piperazine, 2,4-diamino-6-isopropoxy-1,3 , 5-triazine, 2,4-diamino-6-methoxy-1,3,5-triazine, 2,4-diamino-6-phenyl-1,3,5-triazine, 2,4-diamino-6-methyl -S-triazine, 2,4-diamino-1,3,5-triazine, 4,6-diamino-2-vinyl-s-triazine, 2,4-diamino-5-phenylthiazole, 2,6- Aminopurine, 5,6-diamino-1,3-dimethyluracil, 3,5-diamino-1,2,4-triazole, 6,9-diamino-2-ethoxyacridine lactate, 3,8-diamino-6 2 in the molecule such as phenylphenanthridine, 1,4-diaminopiperazine, 3,6-diaminoacridine, bis (4-aminophenyl) phenylamine and compounds represented by the following formulas (III) to (IV) A diamine having one primary amino group and a nitrogen atom other than the primary amino group;

（式中、Ｒ⁵は、ピリジン、ピリミジン、トリアジン、ピペリジンおよびピペラジンから選ばれる窒素原子を含む環構造を有する１価の有機基を示し、Ｘは２価の有機基を示す。）

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

（式中、Ｘは、ピリジン、ピリミジン、トリアジン、ピペリジンおよびピペラジンから選ばれる窒素原子を含む環構造を有する２価の有機基を示し、Ｒ⁶は２価の有機基を示し、複数存在するＸは、同一でも異なっていてもよい。）

Wherein X represents a divalent organic group having a ring structure containing a nitrogen atom selected from pyridine, pyrimidine, triazine, piperidine and piperazine, R ⁶ represents a divalent organic group, and a plurality of X May be the same or different.)

Mono-substituted phenylenediamines represented by the following formula (V); diaminoorganosiloxanes represented by the following formula (VI);

（式中、Ｒ⁷は、−Ｏ−、−ＣＯＯ−、−ＯＣＯ−、−ＮＨＣＯ−、−ＣＯＮＨ−および−ＣＯ−から選ばれる２価の有機基を示し、Ｒ⁸は、ステロイド骨格、トリフルオロメチル基およびフルオロ基から選ばれる基を有する１価の有機基または炭素数６〜３０のアルキル基を示す。）

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

（式中、Ｒ⁹は炭素数１〜１２の炭化水素基を示し、複数存在するＲ⁹は、それぞれ同一でも異なっていてもよく、ｐは１〜３の整数であり、ｑは１〜２０の整数である。）

(Wherein R ⁹ represents a hydrocarbon group having 1 to 12 carbon atoms, and a plurality of R ⁹ may be the same or different, p is an integer of 1 to 3, and q is 1 to 20) Is an integer.)

Examples thereof include compounds represented by the following formulas (9) to (21). These diamine compounds can be used alone or in combination of two or more.

（式中、ｙは２〜１２の整数であり、ｚは１〜５の整数である。）

(In the formula, y is an integer of 2 to 12, and z is an integer of 1 to 5.)

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

  The polyamic acid synthesis reaction is preferably performed in an organic solvent under a temperature condition of −20 ° C. to 150 ° C., more preferably 0 to 100 ° C.

  The organic solvent is not particularly limited as long as it can dissolve the synthesized polyamic acid. Aprotic polar solvents such as 1-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, dimethylsulfoxide, γ-butyrolactone, tetramethylurea, hexamethylphosphortriamide; m-cresol And phenolic solvents such as xylenol, phenol and halogenated phenol. The amount of organic solvent used (α) is such that the total amount (β) of tetracarboxylic dianhydride and diamine compound is 0.1 to 30% by weight with respect to the total amount (α + β) of the reaction solution. It is preferable that

  In addition, alcohols, ketones, esters, ethers, halogenated hydrocarbons, hydrocarbons, etc., which are poor solvents for polyamic acid, are used in combination with the organic solvent as long as the resulting polyamic acid does not precipitate. be able to. Specific examples of such poor solvents include, for example, methyl alcohol, ethyl alcohol, isopropyl alcohol, cyclohexanol, 4-hydroxy-4-methyl-2-pentanone, ethylene glycol, propylene glycol, 1,4-butanediol, triethylene glycol. , Ethylene glycol monomethyl ether, ethyl lactate, butyl lactate, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methyl acetate, ethyl acetate, butyl acetate, methyl methoxypropionate, ethyl ethoxypropionate, diethyl oxalate, malon Acid diethyl, diethyl ether, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol-n-propyl ether, ethylene glycol-i Propyl ether, ethylene glycol-n-butyl ether, ethylene glycol dimethyl ether, ethylene glycol ethyl ether acetate, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, tetrahydrofuran, dichloromethane 1,2-dichloroethane, 1,4-dichlorobutane, trichloroethane, chlorobenzene, o-dichlorobenzene, hexane, heptane, octane, benzene, toluene, xylene and the like.

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

[Synthesis of polyimide]
The polyimide constituting the liquid crystal aligning agent of the present invention can be synthesized by dehydrating and ring-closing the polyamic acid. The polyamic acid is dehydrated and closed by (i) a method of heating the polyamic acid, or (ii) dissolving the polyamic acid in an organic solvent, adding a dehydrating agent and a dehydrating ring-closing catalyst to this solution, and heating as necessary. By the method.

  The reaction temperature in the method of heating the polyamic acid (i) is preferably 50 to 200 ° C, more preferably 60 to 170 ° C. 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.

  On the other hand, in the method (ii) of adding a dehydrating agent and a dehydrating ring-closing catalyst to the polyamic acid solution, an acid anhydride such as acetic anhydride, propionic anhydride, or trifluoroacetic anhydride is used as the dehydrating agent. Can do. Although the usage-amount of a dehydrating agent is based on the desired imidation rate, it is preferable to set it as 0.01-20 mol with respect to 1 mol of repeating units of a polyamic acid. Moreover, as a dehydration ring closure catalyst, tertiary amines, such as a pyridine, a collidine, a lutidine, a triethylamine, can be used, for example. However, it is not limited to these. The amount of the dehydration ring-closing catalyst used is preferably 0.01 to 10 mol with respect to 1 mol of the dehydrating agent used. The imidation rate can be increased as the amount of the above dehydrating agent and dehydrating ring-closing agent increases. Examples of the organic solvent used in the dehydration ring-closing reaction include the organic solvents exemplified as those used for the synthesis of polyamic acid. And reaction temperature of dehydration ring closure reaction becomes like this. Preferably it is 0-180 degreeC, More preferably, it is 10-150 degreeC. Moreover, a polyimide can be refine | purified by performing operation similar to the purification method of a polyamic acid with respect to the reaction solution obtained in this way.

  In the polyimide according to the present invention, 50 mol% or more of all repeating units are occupied by the total repeating units represented by the above formulas (A) and (B). The total repeating unit is a repeating unit represented by each of the formulas (a) and (b) and an imide repeating unit different from these repeating units (at least one of a diamine compound and tetracarboxylic dianhydride is different) and It is composed of amic acid repeating units corresponding to these repeating units.

[End-modified polymer]
The polyimide used in the present invention may be a terminal-modified type having a controlled molecular weight. By using this terminal-modified polymer, the coating characteristics of the liquid crystal aligning agent can be improved without impairing the effects of the present invention. Such a terminal-modified polymer can be synthesized by adding a monofunctional compound such as an acid monoanhydride, a monoamine compound, or a monoisocyanate compound to the reaction system when synthesizing a polyamic acid. . 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 monoamine compounds include aniline, cyclohexylamine, n-butylamine, n-pentylamine, n-hexylamine, n-heptylamine, n-octylamine, n-nonylamine, n-decylamine, and n-undecylamine. N-dodecylamine, n-tridecylamine, n-tetradecylamine, n-pentadecylamine, n-hexadecylamine, n-heptadecylamine, n-octadecylamine, n-eicosylamine, etc. Can do. Examples of the monoisocyanate compound include phenyl isocyanate and naphthyl isocyanate.

[Logarithmic viscosity of polymer]
The polyamic acid and polyimide obtained as described above preferably have a logarithmic viscosity (η _ln ) of 0.05 to 10 dl / g, more preferably 0.05 to 5 dl / g.

The value of the logarithmic viscosity (η _ln ) is determined by measuring the viscosity at 30 ° C. with respect to a solution having a concentration of 0.5 g / 100 ml using N-methyl-2-pyrrolidone as a solvent. It is required.

[Liquid crystal aligning agent]
The liquid crystal aligning agent of the present invention is constituted by dissolving the above polyimide in an organic solvent.

  The temperature at the time of preparing the liquid crystal aligning agent of this invention becomes like this. Preferably it is 0 to 200 degreeC, More preferably, it is 20 to 60 degreeC.

  Examples of the organic solvent include 1-methyl-2-pyrrolidone, γ-butyrolactone, γ-butyrolactam, N, N-dimethylformamide, N, N-dimethylacetamide, 4-hydroxy-4-methyl-2-pentanone, Ethylene glycol monomethyl ether, butyl lactate, butyl acetate, methyl methoxypropionate, ethyl ethoxypropionate, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol-n-propyl ether, ethylene glycol-i-propyl ether , Ethylene glycol-n-butyl ether (butyl cellosolve), ethylene glycol dimethyl ether, ethylene glycol ethyl ether acetate, diethylene glycol dimethyl ether, diethylene glycol Examples thereof include coal diethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether acetate, and diethylene glycol monoethyl ether acetate.

  The solid content concentration in the liquid crystal aligning agent of the present invention is selected in consideration of viscosity, volatility, etc., but is preferably in the range of 1 to 10% by weight. That is, the liquid crystal aligning agent of the present invention is applied to the substrate surface to form a coating film that becomes a liquid crystal alignment film. When the solid content concentration is less than 1% by weight, the coating film thickness is When the solid content concentration exceeds 10% by weight, the film thickness of the coating film becomes excessive and a good liquid crystal alignment film cannot be obtained. In addition, the viscosity of the liquid crystal aligning agent increases, resulting in poor coating characteristics.

  The liquid crystal aligning agent of the present invention may contain a functional silane-containing compound or an epoxy compound from the viewpoint of improving the adhesion to the substrate surface within a range that does not impair the intended physical properties. Examples of such functional silane-containing compounds include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 2-aminopropyltrimethoxysilane, 2-aminopropyltriethoxysilane, and N- (2-aminoethyl). -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-ureidopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, N-ethoxycarbonyl-3-amino Propyltrimethoxysilane, N-ethoxycarbonyl-3-aminopropyltriethoxysilane, N-triethoxysilylpropyltriethylenetriamine, N-trimethoxysilylpropyltriethylenetriamine, 10-trimethoxysilyl- , 4,7-triazadecane, 10-triethoxysilyl-1,4,7-triazadecane, 9-trimethoxysilyl-3,6-diazanonyl acetate, 9-triethoxysilyl-3,6-diazanonyl acetate N-benzyl-3-aminopropyltrimethoxysilane, N-benzyl-3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-phenyl-3-aminopropyltriethoxysilane, N -Bis (oxyethylene) -3-aminopropyltrimethoxysilane, N-bis (oxyethylene) -3-aminopropyltriethoxysilane, etc. can be mentioned. Examples of such epoxy compounds 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, and 1,6-hexane. Diol diglycidyl ether, glycerin diglycidyl ether, 2,2-dibromoneopentyl glycol diglycidyl ether, 1,3,5,6-tetraglycidyl-2,4-hexanediol, N, N, N ′, N′— Tetraglycidyl-m-xylenediamine, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, N, N, N ′, N′-tetraglycidyl-4,4 ′ Diaminodiphenylmethane, 3- (N-Ariru N Gurishijiru) aminopropyltrimethoxysilane, 3- (N, N-diglycidyl) and aminopropyl trimethoxy silane can be cited.

[Liquid crystal display element]
The liquid crystal display element of the present invention can be produced, for example, by the following method.
(1) The liquid crystal aligning agent of the present invention is applied to one surface of a substrate provided with a patterned transparent conductive film by a method such as a roll coater method, a spinner method, or a printing method, and then the coated surface is heated. Thus, a coating film is formed. As the substrate, for example, glass such as float glass or soda glass; a transparent substrate made of a plastic such as polyethylene terephthalate, polybutylene terephthalate, polyethersulfone, or polycarbonate can be used. As the transparent conductive film provided on one surface of the substrate, an NESA film (registered trademark of PPG, USA) made of tin oxide (SnO ₂ ), an ITO film made of indium oxide-tin oxide (In ₂ O ₃ —SnO ₂ ), etc. Can be used. For patterning these transparent conductive films, a photo-etching method or a method using a mask in advance is used. When applying the liquid crystal aligning agent, in order to further improve the adhesion between the substrate surface and the transparent conductive film and the coating film, a functional silane-containing compound or a functional titanium-containing compound is previously applied to the surface of the substrate. You can also The heating temperature after application of the liquid crystal aligning agent is preferably 80 to 300 ° C, more preferably 120 to 250 ° C. The film thickness of the formed coating film is preferably 0.001-1 μm, more preferably 0.005-0.5 μm.
(2) A rubbing process is performed in which the formed coating film surface is rubbed in a certain direction with a roll wound with a cloth made of a fiber such as nylon, rayon, or cotton. Thereby, the orientation ability of a liquid crystal molecule is provided to a coating film, and it becomes a liquid crystal aligning film.

Further, by partially irradiating the liquid crystal alignment film formed of the liquid crystal alignment agent of the present invention with ultraviolet rays as disclosed in, for example, JP-A-6-222366 and JP-A-6-281937. A resist film is partially formed on the surface of the liquid crystal alignment film that has been subjected to a treatment for changing the pretilt angle or a rubbing treatment as disclosed in JP-A-5-107544, which is different from the previous rubbing treatment. The visibility characteristics of the liquid crystal display element can be improved by removing the resist film after performing the rubbing treatment in the direction and changing the liquid crystal alignment ability of the liquid crystal alignment film.
(3) One substrate on which the liquid crystal alignment film is formed as described above and one substrate on which the transparent conductive film is not patterned are prepared, and the rubbing direction in each liquid crystal alignment film is orthogonal or antiparallel. The two substrates are arranged to face each other with a gap (cell gap) between them, and the peripheral portions of the two substrates are bonded together using a sealant, and the substrate surface and the inside of the cell gap defined by the sealant A liquid crystal cell is constructed by injecting and filling liquid crystal into the substrate and sealing the injection hole. A polarizing plate is disposed on the outer surface of the liquid crystal cell, that is, on the other surface side of each substrate constituting the liquid crystal cell, and the polarization direction thereof coincides with or is orthogonal to the rubbing direction of the liquid crystal alignment film formed on one surface of the substrate. A liquid crystal display element is obtained by pasting together.

  Here, as the sealing agent, for example, an epoxy resin containing a curing agent and aluminum oxide spheres as a spacer can be used.

  Examples of the liquid crystal include nematic liquid crystal and smectic liquid crystal. Among them, nematic liquid crystal is preferable. For example, Schiff base liquid crystal, azoxy liquid crystal, biphenyl liquid crystal, phenyl cyclohexane liquid crystal, ester liquid crystal, terphenyl liquid crystal. Liquid crystals, biphenylcyclohexane liquid crystals, pyrimidine liquid crystals, dioxane liquid crystals, bicyclooctane liquid crystals, cubane liquid crystals, and the like can be used. Further, for these liquid crystals, for example, cholesteric liquid crystals such as cholestyl chloride, cholesteryl nonate, cholesteryl carbonate, and chiral agents such as those sold under the trade names “C-15” and “CB-15” (manufactured by Merck). Etc. can also be used. Furthermore, a ferroelectric liquid crystal such as p-decyloxybenzylidene-p-amino-2-methylbutylcinnamate can also be used.

  Further, as a polarizing plate to be bonded to the outer surface of the liquid crystal cell, a polarizing film or an H film in which a polarizing film called an H film that absorbs iodine while sandwiching and stretching polyvinyl alcohol is sandwiched between cellulose acetate protective films. The polarizing plate which consists of itself can be mentioned.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. The imidation ratio of the polymers and the storage stability of the liquid crystal aligning agent, the transparency of the liquid crystal alignment film, the rubbing resistance, the orientation of the prepared liquid crystal display element, and the voltage holding ratio are as follows. The method was evaluated.

[Imidation rate]
After the polyimide was dried under reduced pressure at room temperature, it was dissolved in deuterated dimethyl sulfoxide, and ¹ H-NMR was measured at room temperature using tetramethylsilane as a reference substance, and determined by the formula represented by the following formula (II).

Imidation ratio (%) = (1−A ¹ / A ² × α) × 100 (II)
A ¹ : Peak area derived from NH group protons (10 ppm)
A ² : Peak area derived from other protons α: Number ratio of other protons to one proton of NH group in polymer precursor (polyamic acid)

[Storage stability of liquid crystal alignment agent]
A liquid crystal aligning agent prepared with a predetermined composition was stored in a 40 ° C. storage for one month. If the aligning agent after one month was uniformly dissolved, it was evaluated as “◯”.

[Printability test of liquid crystal alignment agent]
The polymer was dissolved in a mixed solvent of γ-butyrolactone / N-methylpyrrolidone / butyl cellosolve (77/3/20 (weight ratio)) to obtain a solution having a solid content concentration of 4% by weight. The liquid crystal aligning agent of this invention was prepared by filtering. The liquid crystal aligning agent is applied to the transparent electrode surface of the glass substrate with a transparent electrode made of an ITO film using a liquid crystal alignment film printer (manufactured by Nissha Printing Co., Ltd.) and dried on a hot plate at 80 ° C. for 1 minute. The film was dried on a hot plate at 180 ° C. for 20 minutes to form a film having an average film thickness of 600 Å. This substrate was observed with a microscope with a magnification of 20 times, and the quality of the printability was determined by the presence or absence of printing unevenness and pinholes.

[Orientation of liquid crystal]
The presence / absence of an abnormal domain when the voltage was turned on / off (applied / released) to the liquid crystal display element was observed with a polarizing microscope, and the case where there was no abnormal domain was determined as “good”.

[Voltage holding ratio of liquid crystal display element]
A voltage of 5 V was applied to the liquid crystal display element with an application time of 60 microseconds and a span of 16.7 milliseconds, and then the voltage holding ratio after 16.7 milliseconds from the release of application was measured. The measuring apparatus used was VHR-1 manufactured by Toyo Corporation.

Synthesis example 1
224.17 g (1 mol) of 2,3,5-tricarboxycyclopentylacetic acid dianhydride as tetracarboxylic dianhydride and 106.15 g (0 of 2,2′-dimethyl-4,4′-diaminobiphenyl as diamine compound) 0.5 mol) and 71.13 g (0.5 mol) of 1,3-cyclohexanebis (methylamine) were dissolved in 4500 g of N-methyl-2-pyrrolidone and reacted at 60 ° C. for 6 hours. The reaction solution was then poured into a large excess of methyl alcohol to precipitate the reaction product. Thereafter, it was washed with methyl alcohol and dried at 40 ° C. under reduced pressure for 15 hours to obtain 360 g of a polyamic acid having a logarithmic viscosity of 0.75 dl / g (referred to as “polyamic acid (A1)”). 30 g of the resulting polyamic acid was dissolved in 570 g of N-methyl-2-pyrrolidone, 23.4 g of pyridine and 18.1 g of acetic anhydride were added, and dehydration was carried out at 110 ° C. for 4 hours, followed by precipitation, washing, Vacuum drying was performed to obtain 18.0 g of polyimide having a logarithmic viscosity of 0.80 dl / g and an imidization ratio of 88% (hereinafter referred to as “polyimide (B1)”).
Synthesis Examples 2 to 10 and Comparative Synthesis Examples 1 to 3
Except that tetracarboxylic dianhydride and diamine were changed to the compounds shown in Table 1, the same procedures as in Synthesis Example 1 were performed to obtain polyimides B2 to B10 and b1 to b2 having logarithmic viscosities and imidization ratios shown in Table 1. .

The diamine compounds and tetracarboxylic dianhydrides in Table 1 are as follows.
<Diamine compound>
D1: 1,3-cyclohexanebis (methylamine)
D2: 1,4-cyclohexanebis (methylamine)
D3: Diamine represented by the above formula (16) D4: Diamine represented by the above formula (17) D5: 3,3′-dimethyl-4,4′-diaminobiphenyl D6: 2,2′-dimethyl-4 , 4′-Diaminobiphenyl D7: p-phenylenediamine D8: 4,4′-methylenedianiline

<Tetracarboxylic dianhydride>
T1: 2,3,5-tricarboxycyclopentyl acetic acid dianhydride T2: 1,3,3a, 4,5,9b-hexahydro-8-methyl-5- (tetrahydro-2,5-dioxo-3-furanyl) Naphtho [1,2-c] -furan-1,3-dione

Example 1
2 g of the polyimide (B1) obtained in Synthesis Example 1 is dissolved in γ-butyrolactone to obtain a solution having a solid concentration of 4% by weight, and this solution is filtered through a filter having a pore size of 1 μm to prepare the liquid crystal aligning agent of the present invention. did. The storage stability and printability of the obtained liquid crystal aligning agent were evaluated. The results are shown in Table 2.

The liquid crystal aligning agent is applied on a transparent conductive film made of an ITO film provided on one surface of a glass substrate having a thickness of 1 mm using a spinner (rotation speed: 2000 rpm, application time: 1 minute), and at 200 ° C. By drying for 1 hour, a film having a dry film thickness of 0.05 μm was formed. A rubbing machine having a roll in which a rayon cloth was wound around this film was subjected to a rubbing treatment at a roll rotation speed of 400 rpm, a stage moving speed of 3 cm / second, and a hair foot pushing length of 0.4 mm. The liquid crystal alignment film-coated substrate was dipped in isopropyl alcohol for 1 minute and then dried on a hot plate at 100 ° C. for 5 minutes. Next, after applying an epoxy resin adhesive containing aluminum oxide spheres having a diameter of 5.5 μm to the outer edges of the pair of transparent electrode substrates having the liquid crystal alignment film of the liquid crystal alignment film coated substrate, the liquid crystal alignment film surfaces are relatively The adhesive was cured by overlapping and pressing. Next, a nematic liquid crystal (MLC-6221, manufactured by Merck & Co., Inc.) is filled between the substrates through the liquid crystal injection port, and then the liquid crystal injection port is sealed with an acrylic photo-curing adhesive, and polarizing plates are formed on both sides of the substrate. Were laminated to prepare a liquid crystal display element. The voltage holding ratio and orientation of the obtained liquid crystal display element were evaluated. The results are also shown in Table 2.
Examples 2-10, Comparative Examples 1-2
A liquid crystal aligning agent was prepared in the same manner as in Example 1 except that the polyimide or polyamic acid shown in Table 2 was used, and a liquid crystal display device was prepared and evaluated. The evaluation results are shown in Table 2.

Claims (4)

It contains a polyimide having both repeating units represented by the following formulas (A) and (B), and the total of the repeating units represented by the formulas (A) and (B) The liquid crystal aligning agent characterized by being 50 mol% or more of a repeating unit.

(Wherein R is a tetravalent organic group) The liquid crystal aligning agent of Claim 1 by which R is represented by a following formula (c).

The repeating unit represented by the above formula (A) is in the range of 50 to 95 mol% of all repeating units of the polymer, and the repeating unit represented by the above formula (B) is 5 to 5 of all repeating units of the polymer. The liquid crystal aligning agent of Claim 1 or 2 which exists in the range of 50 mol%. A liquid crystal display element comprising a liquid crystal alignment film formed from the liquid crystal aligning agent according to claim 1.