JP4858686B2 - Liquid crystal alignment agent, liquid crystal alignment film, and liquid crystal display element - Google Patents

Description

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

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

Up to now, studies have been made on improving display quality, such as higher definition of liquid crystal display elements, and lowering power consumption. As a result, remarkable progress has been made as a high-performance display element. Liquid crystal display elements having a high retention rate and high reliability have been developed. However, in recent years, in addition to the conventional transmission type, the range of use of liquid crystal display elements such as a reflection type and a semi-transmission type has been expanded. As a result, the required performance for liquid crystal alignment films has become increasingly severe. In particular, demands for image sticking characteristics have become severe in a low-voltage drive type liquid crystal display element aiming at low power consumption, and it cannot be said that the performance of a conventional liquid crystal display element is sufficient. Among liquid crystal alignment films composed of polyamic acid, which is a precursor of conventional polyimide, and imide-based polymers having a structure obtained by dehydrating and cyclizing it, a liquid crystal display element is formed using the liquid crystal alignment film. When prepared, there were many having problems in image sticking characteristics even if the liquid crystal alignment ability was excellent and a sufficient voltage holding ratio was obtained.
Japanese Patent Laid-Open No. 2001-228481

  An object of the present invention is to provide a liquid crystal aligning agent comprising a polyamic acid useful as a liquid crystal aligning film and an imidized polymer, and giving a liquid crystal aligning film having good image sticking characteristics while exhibiting a high voltage holding ratio. There is to do.

  Another object of the present invention is to provide a liquid crystal alignment film obtained from the liquid crystal aligning agent and having excellent performance as described above.

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

  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, according to the present invention, firstly represented by the following formula (I):

Here, P is the following formula (a):

A tetravalent group represented by the following formulas (b) to (f):

In combination with at least one tetravalent group selected from the group consisting of tetravalent groups represented by each of the following formulas, and Q is the following formula (g):

A divalent group represented by:
A polyamic acid having a repeating unit represented by formula (I), and an imidized polymer of a polyamic acid having no repeating unit represented by the above formula (I), and the total number of bonding units of the amic acid bonding unit and the imide bonding unit The number of amic acid binding units based on 30-90%,
This is achieved by a liquid crystal aligning agent characterized in that.

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

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

The liquid crystal alignment film formed by the liquid crystal aligning agent of the present invention has excellent image sticking characteristics as compared with conventional alignment films, and is a TN liquid crystal display element, STN liquid crystal display element, reflective liquid crystal display element, and transflective liquid crystal display element. It can be suitably used to construct various liquid crystal display elements.
The liquid crystal display element of the present invention can be effectively used in various devices, and is suitable for display devices such as desk calculators, watches, table clocks, mobile phones, counting display boards, word processors, personal computers, and liquid crystal televisions. Can be used.

  Hereinafter, the present invention will be described in detail.

The liquid crystal aligning agent in this invention contains the imidation polymer of the polyamic acid which has a repeating unit represented by the said formula (I), and the polyamic acid which does not have the repeating unit represented by the said formula (I).
The polyamic acid is obtained by ring-opening polyaddition of a tetracarboxylic dianhydride and a diamine compound, and the imidized polymer is usually obtained by dehydrating and ring-closing the polyamic acid.

<Polyamic acid and imidized polymer>
[Tetracarboxylic dianhydride]
The tetravalent organic group represented by P in the repeating unit (amic acid unit) represented by the above formula (I) of the polyamic acid and the corresponding tetravalent organic in the repeating unit (imide unit) of the imidized polymer. The groups are all groups derived from tetracarboxylic dianhydride. These tetravalent organic groups are not the same but different. In other words, a tetravalent organic group (P) derived from a tetracarboxylic dianhydride constituting an amic acid bond unit and a tetravalent organic group derived from a tetracarboxylic dianhydride constituting an imide bond unit; Is different. P in the formula (I) is at least one selected from the group consisting of a tetravalent organic group represented by the following formula (i) and a tetravalent group represented by each of the following formulas (ii) to (vi). And have.

  When the specific example of the tetracarboxylic dianhydride used for each repeating unit is shown, as the tetracarboxylic dianhydride constituting the amic acid unit, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, And pyromellitic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, used in combination therewith, 3, 3 ', 4,4'-benzophenone tetracarboxylic dianhydride and 3,3', 4,4'-biphenyl ether tetracarboxylic dianhydride. Moreover, as a tetracarboxylic dianhydride which comprises an imide unit, 2,3,5-tricarboxycyclopentyl acetic acid dianhydride and 1,3,3a, 4,5,9b-hexahydro-5- (Tetrahydro-2,5-dioxo-3-furanyl) -naphtho [1,2-c] -furan-1,3-dione.

  Examples of other tetracarboxylic dianhydrides used in the synthesis of polyamic acid or polyimide include, for example, butanetetracarboxylic 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-cyclohexanetetra Carboxylic dianhydride, 3,3 ′, 4,4′-dicyclohexyltetracarboxylic dianhydride, 3,5,6-tricarboxynorbornane-2-acetic dianhydride, 2, , 4,5-tetrahydrofurantetracarboxylic dianhydride, 1,3,3a, 4,5,9b-hexahydro-5-ethyl-5 (tetrahydro-2,5-dioxo-3-furanyl) -naphtho [1, 2-c] -furan-1,3-dione, 1,3,3a, 4,5,9b-hexahydro-7-methyl-5 (tetrahydro-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 [1,2-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), Compounds represented by formulas (II) and (III) Aliphatic and cycloaliphatic tetracarboxylic dianhydrides;

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

  Of these, butanetetracarboxylic dianhydride, 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 5- (2,5-dioxotetrahydrofural) -3-methyl-3-cyclohexene-1,2-dicarboxylic dianhydride, bicyclo [ 2.2.2] -Oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, 3-oxabicyclo [3.2.1] octane-2,4-dione-6-spiro -3 ′-(tetrahydrofuran-2 ′, 5′-dione), compounds represented by the following formulas (5) to (7) among the compounds represented by the above formula (II), and the above formula (III) Of the compounds to be prepared, the following formula (8 In the compounds represented from the viewpoint that it is possible to express the good liquid crystal orientation.

[Diamine compound]
The divalent organic group represented by Q in the repeating unit (amic acid unit) represented by the above formula (I) of the polyamic acid and the corresponding divalent organic in the repeating unit (imide unit) of the imidized polymer. All groups are groups derived from diamine compounds. These divalent organic groups are not the same but different. In other words, the divalent organic group (Q) derived from the diamine compound constituting the amic acid bond unit is different from the divalent organic group derived from the diamine compound constituting the imide bond unit. Q in the above formula (I) is a divalent organic group represented by the following formula (vii).

  That is, the diamine compound that gives the divalent organic group (Q) is 4,4'-diaminodiphenyl ether. As a diamine compound constituting the imide bond unit, for example, 2,2'-trifluoromethyl-4,4'-diaminobiphenyl can be mentioned as a preferable one.

Examples of other diamine compounds used for the synthesis of the polyamic acid or polyimide include p-phenylenediamine, m-phenylenediamine, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylethane, and 4,4′-. Diaminodiphenyl sulfide, 4,4′-diaminodiphenyl sulfone, 3,3′-dimethyl-4,4′-diaminobiphenyl, 4,4′-diaminobenzanilide, 1,5-diaminonaphthalene, 2,2′-dimethyl -4,4'-diaminobiphenyl, 5-amino-1- (4'-aminophenyl) -1,3,3-trimethylindane, 6-amino-1- (4'-aminophenyl) -1,3 3-trimethylindane, 3,4'-diaminodiphenyl ether, 3,3'-diaminobenzophenone, 3,4'-dia Nobenzophenone, 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-bis (2-chloroaniline), 2,2 ′, 5,5′-tetrachloro-4, '-Diaminobiphenyl, 2,2'-dichloro-4,4'-diamino-5,5'-dimethoxybiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 1,4,4'-( p-phenyleneisopropylidene) bisaniline, 4,4 ′-(m-phenyleneisopropylidene) bisaniline, 2,2′-bis [4- (4-amino-2-trifluoromethylphenoxy) phenyl] hexafluoropropane, 4 , 4′-Diamino-2,2′-bis (trifluoromethyl) biphenyl, 4,4′-bis [(4-amino-2-trifluoromethyl) phenoxy] -octafluorobiphenyl, 4- (4′- Aromatic diamines such as trifluoromethoxybenzoyloxy) cyclohexyl-3,5-diaminobenzoate;
1,1-metaxylylenediamine, 1,3-propanediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, 4,4-diaminoheptamethylenediamine, 1 , 4-diaminocyclohexane, isophoronediamine, tetrahydrodicyclopentadienylenediamine, hexahydro-4,7-methanoindanylene methylenediamine, tricyclo [6.2.1.0 ^2,7 ] -undecylenedimethyldiamine, 4 Aliphatic and cycloaliphatic diamines such as 4,4'-methylenebis (cyclohexylamine);
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 (IV) to (V) A diamine having one primary amino group and a nitrogen atom other than the primary amino group;

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

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

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

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

(In the formula, y is an integer of 2 to 12, and z is an integer of 1 to 5.)
Among these, p-phenylenediamine, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenyl sulfide, 1,5-diaminonaphthalene, 2,7-diaminofluorene, 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-amino) Phenyl) hexafluoropropane, 4,4 ′-(p-phenylenediisopropylidene) bisaniline, 4,4 ′-(m-phenylenediisopropylidene) bisaniline, 1,4-cyclohexanediamine, 4,4′-methylenebis ( (Cyclohexylamine), 1,4-bis (4-aminophenoxy) benzene, 4,4′-bis ( -Aminophenoxy) biphenyl, 4- (4'-trifluoromethoxybenzoyloxy) cyclohexyl-3,5-diaminobenzoate, compounds represented by the above formulas (9) to (13), 2,6-diaminopyridine, 3,4-diaminopyridine, 2,4-diaminopyrimidine, 3,6-diaminoacridine, a compound represented by the following formula (14) among the compounds represented by the above formula (IV), and the above formula (V) Of the compounds represented, the compounds represented by the following formula (15) and the compounds represented by the following formulas (VI) are preferably compounds represented by the following formulas (16) to (21).

[Synthetic reaction of polyamic acid]
The ratio of the tetracarboxylic dianhydride and the diamine compound used for the polyamic acid synthesis reaction is such that the acid anhydride group of the tetracarboxylic dianhydride is 0.1 relative to 1 equivalent of the amino group contained in the diamine compound. A ratio of 2 to 2 equivalents is preferable, and a ratio of 0.3 to 1.2 equivalents is more preferable.
The synthetic reaction of polyamic acid is preferably carried out in an organic solvent under a temperature condition of -20 to 150 ° C, more preferably 0 to 100 ° C. Here, the organic solvent is not particularly limited as long as it can dissolve the synthesized polyamic acid. For example, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, dimethyl sulfoxide And aprotic polar solvents such as γ-butyrolactone, tetramethylurea and hexamethylphosphortriamide; and phenolic solvents such as m-cresol, xylenol, phenol and halogenated phenol. The amount of the organic solvent used (a) is such that the total amount (b) of the tetracarboxylic dianhydride and the diamine compound is 0.1 to 30% by weight with respect to the total amount (a + b) of the reaction solution. It is preferable that

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

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

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

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

[Logarithmic viscosity of polymer]
The value of the polyamic acid and imidized polymer obtained as described above and their logarithmic viscosity (η _ln ) is preferably 0.05 to 10 dl / g, more preferably 0.05 to 5 dl / g.
The value of the logarithmic viscosity (η _ln ) in the present invention is determined by measuring the viscosity at 30 ° C. for a solution having a concentration of 0.5 g / 100 ml using N-methyl-2-pyrrolidone as a solvent. ).

[Liquid crystal aligning agent]
The liquid crystal aligning agent of the present invention is constituted by dissolving and containing the polyamic acid and the imidized polymer in an organic solvent. In the polymer constituting the liquid crystal aligning agent of the present invention, the number of amic acid bond units accounts for 30 to 90% based on the total number of bond units of polyamic acid bond units and imide bond units, and the number of imide bond units is Used to account for 10-70%.
As an organic solvent which comprises the liquid crystal aligning agent of this invention, the same thing as the solvent illustrated as what is used for the synthesis reaction of a polyamic acid can be mentioned. In addition, the same poor solvents exemplified as those that can be used together in the synthesis reaction of the polyamic acid can be appropriately selected and used together.
The solid content concentration in the liquid crystal aligning agent of the present invention is selected in consideration of viscosity, volatility and the like. Preferably it is the range of 1-10 weight%. That is, the liquid crystal aligning agent of the present invention is applied to the substrate surface to form a coating film that becomes a liquid crystal alignment film. When the solid content concentration is less than 1% by weight, the film thickness of this coating film is too small. It is difficult to obtain a good liquid crystal alignment film. When the solid content concentration exceeds 10% by weight, it is difficult to obtain a good liquid crystal alignment film because the film thickness is excessive, and the viscosity of the liquid crystal aligning agent is increased, so that the coating properties tend to be inferior. Moreover, the temperature at the time of preparing the liquid crystal aligning agent of this invention, Preferably, it is 0 to 200 degreeC, More preferably, it is 20 to 60 degreeC.

The liquid crystal aligning agent for forming the liquid crystal alignment film of the present invention contains a compound having at least one epoxy group in the molecule (hereinafter also referred to as “epoxy group-containing compound”) from the viewpoint of improving the adhesion to the substrate surface. It is preferable that Examples of the epoxy group-containing compound include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6- Hexanediol diglycidyl ether, glycerin diglycidyl ether, 2,2-dibromoneopentyl glycol diglycidyl ether, 1,3,5,6-tetraglycidyl-2,4-hexanediol, N, N, N ′, N ′ - tetraglycidyl -m- xylene diamine, 1,3-bis (N, N-diglycidyl aminomethyl) cyclohexane, N, N, N ', N' - -4,4'- tetraglycidyl Gia Minodiphenylmethane and the like can be mentioned as preferable ones. The compounding ratio of these epoxy group-containing compounds is preferably 40 parts by weight or less, more preferably 0.1 to 15 parts by weight with respect to 100 parts by weight of the total weight of the polyamic acid and the imidized polymer.

Moreover, the liquid crystal aligning agent of this invention may contain the functional silane containing compound. Examples of such functional silane-containing compounds include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 2-aminopropyltrimethoxysilane, 2-aminopropyltriethoxysilane, and N- (2-aminoethyl). -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-ureidopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, N-ethoxycarbonyl-3-amino Propyltrimethoxysilane, N-ethoxycarbonyl-3-aminopropyltriethoxysilane, N-triethoxysilylpropyltriethylenetriamine, N-trimethoxysilylpropyltriethylenetriamine, 10-trimethoxysilyl- , 4,7-triazadecane, 10-triethoxysilyl-1,4,7-triazadecane, 9-trimethoxysilyl-3,6-diazanonyl acetate, 9-triethoxysilyl-3,6-diazanonyl acetate N-benzyl-3-aminopropyltrimethoxysilane, N-benzyl-3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-phenyl-3-aminopropyltriethoxysilane, N -Bis (oxyethylene) -3-aminopropyltrimethoxysilane, N-bis (oxyethylene) -3-aminopropyltriethoxysilane, etc. can be mentioned.
The blending ratio of these functional silane-containing compounds is preferably 40 parts by weight or less with respect to 100 parts by weight of the total weight of the polyamic acid and the imidized polymer.

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

(1) The liquid crystal aligning agent of the present invention is applied to one surface of a substrate provided with a patterned transparent conductive film by a method such as a roll coater method, a spinner method, a printing method, an ink jet method, etc. Is heated to form a coating film. Here, as the substrate, for example, a 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 a transparent conductive film provided on one surface of the substrate, an NESA film (registered trademark of PPG, USA) made of tin oxide (SnO ₂ ), an ITO film made of indium oxide-tin oxide (In ₂ O ₃ —SnO ₂ ), etc. For patterning these transparent conductive films, a photo-etching method or a method using a mask in advance is used. When applying the liquid crystal aligning agent, in order to further improve the adhesion between the substrate surface and the transparent conductive film and the coating film, a functional silane-containing compound, a functional titanium-containing compound, or the like is previously applied to the surface of the substrate. You can also The heating temperature after application of the liquid crystal aligning agent is, for example, 80 to 300 ° C, and preferably 120 to 250 ° C. The liquid crystal aligning agent of the present invention containing a polyamic acid forms a coating film that becomes an alignment film by removing the organic solvent after coating. It can also be a membrane. 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 liquid crystal molecules is imparted to the coating film to form a liquid crystal orientation film.
Further, by partially irradiating the liquid crystal alignment film formed of the liquid crystal alignment agent of the present invention with ultraviolet rays as disclosed in, for example, JP-A-6-222366 and JP-A-6-281937. A resist film is partially formed on the surface of the liquid crystal alignment film that has been subjected to a treatment for changing the pretilt angle or a rubbing treatment as disclosed in JP-A-5-107544, which is different from the previous rubbing treatment. The visibility characteristics of the liquid crystal display element can be improved by removing the resist film after performing the rubbing treatment in the direction and changing the liquid crystal alignment ability of the liquid crystal alignment film.

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

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

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

[Imidation rate]
From the peak area ratio of absorption near 1381 cm ⁻¹ (C—N—C bending vibration = absorption of imide bond) and absorption near 1503 cm ⁻¹ (absorption of amic acid bond) in FT-IR measurement, The imidization rate was calculated by
Imidation ratio = {α ₁ / (α ₁ + α ₂ )} × 100 (%)
α _1: 1381cm ^-1 vicinity of the absorption peak area alpha _2: peak area of absorption around 1503cm ^-1 Incidentally, alpha ₂ is the absorption in the vicinity of 1303cm ^-1 but was heated for 10 minutes on a hot plate at 300 ° C. The coating The value obtained by calculating the peak area as 0.

[Voltage holding ratio]
A voltage of 5 V was applied to the liquid crystal display element with an application time of 60 microseconds and a span of 167 milliseconds, and then the voltage holding ratio after 167 milliseconds from the release of application was measured. The measuring apparatus used was VHR-1 manufactured by Toyo Corporation. The case where the voltage holding ratio was 90% or more was judged as good, and the other cases were judged as bad.

[Burn-in test]
A cell having an ITO electrode as shown in FIG. 1 is produced. A DC voltage of 6.0 V was applied to electrode A and a DC voltage of 0.5 V was applied to electrode B at room temperature for 24 hours. After releasing the stress, DC voltage of 0.1 to 5.0V is applied to electrodes A and B in increments of 0.1V. The image sticking characteristics were determined based on the luminance difference between the electrodes A and B at each voltage. When the luminance difference was small, it was judged that the burn-in characteristic was good (◯), and when the luminance difference was large, the burn-in characteristic was bad (x).

Synthesis example 1
2,3,5-tricarboxycyclopentylacetic acid dianhydride 112.09 g (0.50 mol) and 1,3,3a, 4,5,9b-hexahydro-8-methyl-5 as tetracarboxylic dianhydride (Tetrahydro-2,5-dioxo-3-furanyl) naphtho [1,2-c] furan-1,3-dione 157.15 g (0.50 mol), and diamine compound 94.62 g (0 875 mol), 32.02 g (0.10 mol) of 2,2′-trifluoromethyl-4,4′-diaminobiphenyl and 6.43 g of 3,6-bis (4-aminobenzoyloxy) cholestane. 01 mol), and 8.09 g (0.03 mol) of n-octadecylamine as a monoamine was dissolved in 4500 g of N-methyl-2-pyrrolidone. ℃ In the reaction was allowed to proceed 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 380 g of a polyamic acid having a logarithmic viscosity of 0.80 dl / g. 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, The pressure was reduced to obtain 18.6 g of polyimide having a logarithmic viscosity of 0.78 dl / g (referred to as “polyimide (A-1)”).

Synthesis example 2
2,3,5-tricarboxycyclopentylacetic acid dianhydride 112.09 g (0.50 mol) and 1,3,3a, 4,5,9b-hexahydro-8-methyl-5 as tetracarboxylic dianhydride (Tetrahydro-2,5-dioxo-3-furanyl) naphtho [1,2-c] furan-1,3-dione 157.15 g (0.50 mol), 81.65 g (0 .755 mole), 2,2′-trifluoromethyl-4,4′-diaminobiphenyl 32.02 g (0.10 mole), bisaminopropyltetramethyldisiloxane 24.85 g (0.10 mole) and 3, 19.28 g (0.03 mol) of 6-bis (4-aminobenzoyloxy) cholestane and 2.79 g (0.03 mol) of aniline as a monoamine Le), was dissolved in N- methyl-2-pyrrolidone 4500 g, was reacted for 6 hours at 60 ° C.. 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 370 g of polyamic acid having a logarithmic viscosity of 0.77 dl / g. 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, The pressure was reduced to obtain 20.3 g of polyimide having a logarithmic viscosity of 0.79 dl / g (referred to as “polyimide (A-2)”).

Synthesis example 3
1,2,3,4-cyclobutanetetracarboxylic dianhydride 95.06 g (0.50 mol) and pyromellitic dianhydride 109.06 g (0.50 mol) as a tetracarboxylic dianhydride, a diamine compound As a result, 200.24 g (1.0 mol) of 4,4′-diaminodiphenyl ether was dissolved in 4500 g of N-methyl-2-pyrrolidone and reacted at 40 ° C. for 3 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 410 g of a polyamic acid having a logarithmic viscosity of 0.95 dl / g (referred to as “polyamic acid (B-1)”).

Synthesis example 4
2,3,5-tricarboxycyclopentylacetic acid dianhydride 112.08 g (0.5 mol) and 1,3,3a, 4,5,9b-hexahydro-8-methyl-5 as tetracarboxylic dianhydride 157.15 g (0.5 mol) of (tetrahydro-2,5-dioxo-3-furanyl) naphtho [1,2-c] furan-1,3-dione, 95.71 g of p-phenylenediamine (0 865 mol), 24.85 g (0.1 mol) of bisaminopropyltetramethyldisiloxane and 12.86 g (0.02 mol) of 3,6-bis (4-aminobenzoyloxy) cholestane, and N- 8.09 g (0.03 mol) of octadecylamine was 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 340 g of polyamic acid having a logarithmic viscosity of 0.84 dl / g. 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, The pressure was reduced to obtain 17.4 g of polyimide having a logarithmic viscosity of 0.65 dl / g (referred to as “polyimide (A-3)”).

Synthesis example 5
224.17 g (1.0 mol) of 2,3,5-tricarboxycyclopentylacetic acid dianhydride as tetracarboxylic dianhydride, 95.16 g (0.88 mol) of p-phenylenediamine as a diamine compound, and cholesteryl- 7.842 g (0.015 mol) of 3,5-diaminobenzoate was 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 400 g of a polyamic acid having a logarithmic viscosity of 0.75 dl / g (referred to as “polyamic acid B-2”). 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, The pressure was reduced to obtain 19.2 g of polyimide having a logarithmic viscosity of 0.78 dl / g (referred to as “polyimide (A-4)”).

Synthesis Example 6
196.12 g (1.0 mol) of 1,2,3,4-cyclobutanetetracarboxylic dianhydride as tetracarboxylic dianhydride and 2,2′-dimethyl-4,4′-diaminobiphenyl 212 as diamine compound .3 g (1.0 mol) was dissolved in 4500 g of N-methyl-2-pyrrolidone and reacted at 40 ° C. for 3 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 390 g of a polyamic acid having a logarithmic viscosity of 0.91 dl / g (referred to as “polyamic acid (B- 2 )”).

Example 1
The polyimide (A-1) obtained in Synthesis Example 1 and the polyamic acid (B-1) obtained in Synthesis Example 3 were mixed with γ-butyrolactone so that polyimide: polyamic acid = 20: 80 (weight ratio). / N-methyl-2-pyrrolidone / butyl cellosolve mixed solvent (weight ratio 71/17/12) and polymerized N, N, N ′, N ′,-tetraglycidyl-4,4′-diaminodiphenylmethane 2 parts by weight with respect to 100 parts by weight was dissolved to obtain a solution having a solid content concentration of 3.5% by weight. After sufficient stirring, the solution was filtered using a filter having a pore diameter of 1 μm to prepare the liquid crystal aligning agent of the present invention. . Imidation rate The liquid crystal aligning agent was applied onto a transparent conductive film made of an ITO film provided on one surface of a glass substrate having a thickness of 1 mm using a spinner (rotation speed: 2500 rpm, application time: 1 minute), A film having a dry film thickness of 0.08 μm was formed by drying at 200 ° C. for 1 hour. When the imidization rate of this film was measured, the imidation rate was 52%. 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 electrodes / transparent electrode substrates having the liquid crystal alignment film of the liquid crystal alignment film coated substrate, the liquid crystal alignment film The adhesive was cured by overlapping and pressing so that the surfaces were opposed. Next, a nematic liquid crystal (MLC-6221, manufactured by Merck & Co., Inc.) is filled between the substrates through the liquid crystal injection port, and then the liquid crystal injection port is sealed with an acrylic 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 of the obtained liquid crystal display element was evaluated. The liquid crystal aligning agent obtained in the present invention showed a high voltage holding ratio of 99% or more. Moreover, when the image sticking test was conducted, good results were shown.

Examples 2 and 3 and Comparative Examples 1 to 3
Polyimide obtained in Synthesis Example 2~6 (A-2) ~ ( A-4), the polyamic acid (B-1) ~ (B- 2), and N, N, N ', N ', - tetraglycidyl -4,4'-diaminodiphenylmethane was dissolved in a mixed solvent containing γ-butyrolactone as a main component to obtain a solution having a solid content concentration of 3.5%, and this solution was filtered with a filter having a pore size of 1 μm. The liquid crystal aligning agent was adjusted. Using each of the liquid crystal aligning agents thus adjusted, a film was formed on the substrate surface in the same manner as in Example 1, and a liquid crystal display element was produced using the substrate on which the liquid crystal aligning film was formed. . Then, voltage holding ratio and image sticking characteristics were evaluated. The results are shown in Table 1.

Explanatory drawing which shows arrangement | positioning of the electrodes A and B of the cell used for the burn-in test

Claims (5)

Formula (I)

Here, P is the following formula (a):

A tetravalent group represented by the following formulas (b) to (f):

In combination with at least one tetravalent group selected from the group consisting of tetravalent groups represented by each of the following formulas, and Q is the following formula (g):

A divalent group represented by:
A polyamic acid having a repeating unit represented by formula (I), and an imidized polymer of a polyamic acid having no repeating unit represented by the above formula (I), and the total number of bonding units of the amic acid bonding unit and the imide bonding unit The number of amic acid binding units based on 30-90%,
A liquid crystal aligning agent characterized by that. When the imidized polymer is a tetravalent group derived from tetracarboxylic dianhydride, 2,3,5-tricarboxycyclopentylacetic acid dianhydride and 1,3,3a, 4,5,9b-hexahydro-8- Contains a tetravalent group derived from each of methyl-5- (tetrahydro-2,5-dioxo-3-furanyl) naphtho [1,2-c] furan-1,3-dione and derived from a diamine compound The liquid crystal aligning agent of Claim 1 containing the bivalent group derived from 2,2'- trifluoromethyl-4,4'-diaminobiphenyl as a bivalent group to do. The liquid crystal aligning agent of Claim 1 or 2 which further contains the compound which has an at least 1 epoxy group in a molecule | numerator with 0.1-15 weight part with respect to 100 weight part of total weight of a polyamic acid and an imidation polymer. . The liquid crystal aligning film formed from the liquid crystal aligning agent in any one of Claims 1-3. A liquid crystal display device comprising the liquid crystal alignment film according to claim 4.

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