WO2018122936A1 - Liquid crystal aligning agent, liquid crystal alignment film and liquid crystal display element - Google Patents

Abstract

Provided are: a liquid crystal aligning agent for obtaining an alignment film that is suitable for photo-alignment and enables the achievement of good afterimage characteristics without producing bright dots even if used for negative liquid crystals; a liquid crystal alignment film; and a liquid crystal display element. A liquid crystal aligning agent which contains at least one polymer (A) that is selected from the group consisting of polyimide precursors having a structural unit represented by formula (1) and a structural unit represented by formula (2) and imidized polymers of the polyimide precursors. In the formulae, the symbols are as defined in the description.

Description

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

The present invention relates to a liquid crystal aligning agent suitable for a photo-alignment method treatment, a liquid crystal aligning film obtained from the liquid crystal aligning agent, and a liquid crystal display element using the liquid crystal aligning film.

Liquid crystal display elements used for liquid crystal televisions, liquid crystal displays, and the like are usually provided with a liquid crystal alignment film for controlling the alignment state of the liquid crystals. As the liquid crystal alignment film, a polyimide-based liquid crystal alignment film obtained by applying a polyimide precursor such as polyamic acid (polyamic acid) or a liquid crystal aligning agent mainly composed of a soluble polyimide solution to a glass substrate or the like and baking it is mainly used. Yes. At present, according to the most widespread industrial method, this liquid crystal alignment film is rubbed in one direction with a cloth of cotton, nylon, polyester or the like on the surface of the polyimide liquid crystal alignment film formed on the electrode substrate. It is produced by performing a so-called rubbing process.

The photo-alignment method has an advantage that it can be produced by an industrially simple manufacturing process as a rubbing-less alignment treatment method. In a liquid crystal display element of an IPS drive method or a fringe field switching (hereinafter referred to as FFS) drive method, By using the liquid crystal alignment film obtained by the alignment method, the performance of the liquid crystal display element can be improved as compared to the liquid crystal alignment film obtained by the rubbing treatment method. Therefore, it attracts attention as a promising liquid crystal alignment method.

However, the liquid crystal alignment film obtained by the photo-alignment method has a problem that anisotropy with respect to the alignment direction of the polymer film is smaller than that by the rubbing treatment. If the anisotropy is small, sufficient liquid crystal orientation cannot be obtained, and problems such as occurrence of afterimages occur when a liquid crystal display element is formed. As a method for increasing the anisotropy of a liquid crystal alignment film obtained by a photo-alignment method, it has been proposed to remove a low molecular weight component generated by cutting the main chain of the polyimide by light irradiation after light irradiation.

Japanese Unexamined Patent Publication No. 9-297313 Japanese Unexamined Patent Publication No. 2011-107266

In the IPS drive type and FFS drive type liquid crystal display elements, a positive type liquid crystal is conventionally used. By using a negative type liquid crystal, it is possible to reduce the transmission loss at the upper part of the electrode and improve the contrast. It is. When used in an IPS driving type or FFS driving type liquid crystal display element using a liquid crystal alignment film obtained by the photo-alignment method and a negative liquid crystal, it is expected to have higher display performance than a conventional liquid crystal display element.

However, as a result of examination by the inventors of the present application, in the case of a liquid crystal display element using a negative liquid crystal, a liquid crystal alignment film by photo-alignment has a problem of causing a display defect due to a high incidence of display defects (bright spots). I understood.
An object of the present invention is to provide a liquid crystal alignment suitable for a photo-alignment process for obtaining a liquid crystal alignment film for a photo-alignment method in which no bright spots are generated and good afterimage characteristics are obtained even when a negative liquid crystal is used. It is in providing the liquid crystal display element which comprises an agent, the liquid crystal aligning film obtained from this liquid crystal aligning agent, and this liquid crystal aligning agent.

As a result of extensive research, the present inventor has found that a liquid crystal aligning agent containing a polyimide polymer having a specific structure is effective for achieving the above object, and has completed the present invention.

The gist of the present invention is as described below.
1. It contains at least one polymer (A) selected from the group consisting of a polyimide precursor having structural units represented by the following formula (1) and the following formula (2) and an imidized polymer of the polyimide precursor. A liquid crystal aligning agent characterized by that.

(In the formula (1), equation (2), _{X 1} and _{X 2 are} each independently a tetravalent organic group, _{R 1} and _{R 2} are each independently a hydrogen atom, or carbon atoms An alkyl group having 1 to 4; A ₁ , A ₂ , A ₃ , and A ₄ are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; and Z ₁ , Z ₂ , Z ₃ , And Z ₄ are each independently a hydrogen atom, a halogen atom, or an alkyl group having 1 to 4 carbon atoms, and n is an integer of 1 to 4).

According to the present invention, even when a negative liquid crystal is used, a bright alignment point that can be suppressed in the photo-alignment treatment method can be suppressed, and a liquid crystal alignment film having high irradiation sensitivity and good afterimage characteristics can be obtained. The liquid crystal aligning agent suitable for can be provided. By providing a liquid crystal alignment film obtained from such a liquid crystal aligning agent, a highly reliable liquid crystal display element without display defects can be provided.

<Specific polymer>
As described above, the liquid crystal aligning agent of the present invention is selected from the group consisting of a polyimide precursor having a structural unit represented by the above formula (1) and the above formula (2) and an imidized polymer of the polyimide precursor. At least one polymer (also referred to as a specific polymer (A)).
In Formula (1) and Formula (2), R ₁ and R ₂ are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. From the viewpoint of ease of imidization by heating, a hydrogen atom or a methyl group is particularly preferable. X ₁ and X ₂ are tetravalent organic groups. A structure capable of imparting anisotropy by a reaction such as decomposition or isomerization upon irradiation with ultraviolet rays is preferable, and at least one selected from the group consisting of structures represented by the following formulas (X1-1) to (X1-9) It is more preferable that

In the formula (X1-1), R ₃ , R ₄ , R ₅ , and R ₆ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, An alkynyl group or a phenyl group, which may be the same or different. From the viewpoint of liquid crystal orientation, R ₃ , R ₄ , R ₅ , and R ₆ are preferably a hydrogen atom, a halogen atom, a methyl group, or an ethyl group, and more preferably a hydrogen atom or a methyl group. Specific examples of the structure of the formula (X1-1) include structures represented by the following formulas (X1-10) to (X1-11). From the viewpoint of liquid crystal alignment and sensitivity, (X1-11) is particularly preferable.

In Formula (1) and Formula (2), A ₁ , A ₂ , A ₃ , and A ₄ are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. From the viewpoint of liquid crystal orientation, a hydrogen atom or a methyl group is preferable, and a hydrogen atom is more preferable.
In formula (1) and formula (2), Z ₁ , Z ₂ , Z ₃ , and Z ₄ are each independently a hydrogen atom, a halogen atom, or an alkyl group having 1 to 4 carbon atoms. From the viewpoint of liquid crystal orientation, a hydrogen atom, a halogen atom, or a methyl group is preferable. n is an integer of 1 to 4.

In the specific polymer (A), the proportion of the structural unit represented by the above formula (1) is 10 to 50 mol% with respect to 1 mol of all the structural units from the viewpoint of liquid crystal orientation and suppression of bright spots. Is more preferable, and more preferably 30 to 50 mol%.
In the specific polymer (A), the content ratio of the structural unit represented by the above formula (2) is 20 to 20 parts per 1 mole of all the structural units from the viewpoint of liquid crystal orientation and suppression of bright spots. 90 mol% is preferable, and more preferably 20 to 50 mol%.

The specific polymer (A) has a structural unit represented by the following formula (3) in addition to the structural units represented by the above formulas (1) and (2) from the viewpoint of the mechanical strength of the alignment film. It is preferable.

Wherein (3), _{X 3} has _the same meaning as _{X 1} and _{X 2} in the above formula, including preferred examples (1) and (2). R ₃ is synonymous with the above R ₁ and R ₂ including preferred examples. Y ₁ is at least one selected from the group consisting of structures represented by the following formulas [1d-1] to [1d-7].

In the above formulas [1d-1] to [1d-7], D is a tert-butoxymethoxycarbonyl group. n ₁ to n ₅ are each independently an integer of 1 to 5.
More specific examples of Y ₁ include the following formulas [1d1-1] to [1d1-6].

In the above [1d1-1] to [1d1-6], D is a tert-butoxymethoxycarbonyl group.
The content ratio of the structural unit represented by the formula (3) is preferably 10 to 50 mol%, more preferably 20 to 30 mol% with respect to 1 mol of all the structural units of the specific polymer (A). is there.

The specific polymer (A) has, in addition to the structural units represented by the above formulas (1) to (3), a polyimide precursor containing a structural unit represented by the following formula (4) and the polyimide precursor. You may do it.

In formula (4), R ₄ has the same meaning as R ₁ in formula (1), including preferred examples. A ₅ and A ₆ , including preferred examples, are synonymous with A ₁ and A _{2 in} the above formula (1). X is a tetravalent organic group, and its structure is not particularly limited.
Specific examples include the above formulas (X1-1) to (X1-9) or the following formulas (X-9) to (X-42). From the viewpoint of availability of the compound, X includes X1-1 to X1-9, X-17, X-25, X-26, X-27, X-28, X-32, or X-39. . In addition, tetracarboxylic dianhydrides having an aromatic ring structure are preferable from the viewpoint of obtaining a liquid crystal alignment film in which residual charges accumulated by a DC voltage can be quickly relaxed, and X is X-26, X-27, X -28, X-32, X-35, or X-37 is more preferred.

In the above formula (4), Y is a divalent organic group, and its structure is not particularly limited. Specific examples of Y ₂ include the following formulas (Y-1) to (Y-84).

In order to improve the liquid crystal alignment, Y is preferably a highly linear structure. As specific examples, Y-7, Y-43 to Y-48, Y63, or Y-71 to Y-76 are more preferable. Y-77 to Y-84 are more preferable because a liquid crystal alignment film can be obtained in which the residual charge accumulated by the DC voltage is quickly relaxed.

<Method for producing polyamic acid ester>
The polyamic acid ester which is a polyimide precursor used in the present invention can be synthesized by the method (1), (2) or (3) shown below.
(1) When synthesizing from polyamic acid The polyamic acid ester can be synthesized by esterifying a polyamic acid obtained from tetracarboxylic dianhydride and diamine.
Specifically, the polyamic acid and the esterifying agent are reacted in the presence of an organic solvent at −20 ° C. to 150 ° C., preferably 0 ° C. to 50 ° C., for 30 minutes to 24 hours, preferably 1 to 4 hours. Can be synthesized.

The esterifying agent is preferably one that can be easily removed by purification, and N, N-dimethylformamide dimethyl acetal, N, N-dimethylformamide diethyl acetal, N, N-dimethylformamide dipropyl acetal, N, N-dimethylformamide Dineopentyl butyl acetal, N, N-dimethylformamide di-t-butyl acetal, 1-methyl-3-p-tolyltriazene, 1-ethyl-3-p-tolyltriazene, 1-propyl-3-p -Tolyltriazene, 4- (4,6-dimethoxy-1,3,5-triazin-2-yl) -4-methylmorpholinium chloride and the like. The amount of the esterifying agent used is preferably 2 to 6 molar equivalents per 1 mol of the polyamic acid repeating unit.

The solvent used in the above reaction is preferably N, N-dimethylformamide, N-methyl-2-pyrrolidone, or γ-butyrolactone from the solubility of the polymer, and these may be used alone or in combination. The concentration at the time of synthesis is preferably 1 to 30% by mass, and more preferably 5 to 20% by mass from the viewpoint that polymer precipitation is unlikely to occur and a high molecular weight product is easily obtained.

(2) Case of reaction of tetracarboxylic acid diester dichloride and diamine The polyamic acid ester can be synthesized from tetracarboxylic acid diester dichloride and diamine.
Specifically, tetracarboxylic acid diester dichloride and diamine in the presence of a base and an organic solvent at −20 ° C. to 150 ° C., preferably 0 ° C. to 50 ° C., for 30 minutes to 24 hours, preferably 1 to 4 hours. It can be synthesized by reacting.

As the base, pyridine, triethylamine, 4-dimethylaminopyridine and the like can be used, but pyridine is preferable because the reaction proceeds gently. The addition amount of the base is preferably 2 to 4 times the molar amount of the tetracarboxylic acid diester dichloride from the viewpoint of easy removal and high molecular weight.
The solvent used in the above reaction is preferably N-methyl-2-pyrrolidone or γ-butyrolactone in view of the solubility of the monomer and polymer, and these may be used alone or in combination. The polymer concentration at the time of synthesis is preferably 1 to 30% by mass and more preferably 5 to 20% by mass because polymer precipitation is unlikely to occur and a high molecular weight product is easily obtained. In order to prevent hydrolysis of the tetracarboxylic acid diester dichloride, the solvent used for the synthesis of the polyamic acid ester is preferably dehydrated as much as possible, and it is preferable to prevent mixing of outside air in a nitrogen atmosphere.

(3) Case of reaction of tetracarboxylic acid diester and diamine Polyamic acid ester can be synthesized by polycondensation of tetracarboxylic acid diester and diamine.
Specifically, tetracarboxylic acid diester and diamine in the presence of a condensing agent, a base, and an organic solvent at 0 ° C. to 150 ° C., preferably 0 ° C. to 100 ° C., for 30 minutes to 24 hours, preferably 3 to 15 It can be synthesized by reacting for a time.
Examples of the condensing agent include triphenyl phosphite, dicyclohexylcarbodiimide, 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide hydrochloride, N, N′-carbonyldiimidazole, dimethoxy-1,3,5-triazide. Nylmethylmorpholinium, O- (benzotriazol-1-yl) -N, N, N ′, N′-tetramethyluronium tetrafluoroborate, O- (benzotriazol-1-yl) -N, N , N ′, N′-tetramethyluronium hexafluorophosphate, (2,3-dihydro-2-thioxo-3-benzoxazolyl) phosphonate diphenyl, and the like. The addition amount of the condensing agent is preferably 2 to 3 times the molar amount of the tetracarboxylic acid diester.

As the base, tertiary amines such as pyridine and triethylamine can be used. The amount of the base added is preferably 2 to 4 moles relative to the diamine component because it can be easily removed and a high molecular weight product can be easily obtained.
In the above reaction, the reaction proceeds efficiently by adding Lewis acid as an additive. As the Lewis acid, lithium halides such as lithium chloride and lithium bromide are preferable. The addition amount of the Lewis acid is preferably 0 to 1.0 times mol with respect to the diamine component.

Among the methods for synthesizing the three polyamic acid esters, since a high molecular weight polyamic acid ester is obtained, the synthesis method (1) or (2) is particularly preferable.
The polyamic acid ester solution obtained as described above can be polymerized by pouring into a poor solvent while stirring well. Precipitation is performed several times, and after washing with a poor solvent, a purified polyamic acid ester powder can be obtained at room temperature or by heating and drying. Although a poor solvent is not specifically limited, Water, methanol, ethanol, hexane, butyl cellosolve, acetone, toluene etc. are mentioned.

<Method for producing polyamic acid>
The polyamic acid which is a polyimide precursor used in the present invention can be synthesized by the following method.
Specifically, tetracarboxylic dianhydride and diamine are reacted in the presence of an organic solvent at −20 ° C. to 150 ° C., preferably 0 ° C. to 50 ° C. for 30 minutes to 24 hours, preferably 1 to 12 hours. Can be synthesized.

The organic solvent used in the above reaction is preferably N, N-dimethylformamide, N-methyl-2-pyrrolidone, or γ-butyrolactone from the solubility of the monomer and polymer, and these may be used alone or in combination of two or more. . The concentration of the polymer is preferably 1 to 30% by mass and more preferably 5 to 20% by mass because the polymer does not easily precipitate and a high molecular weight body is easily obtained.
The polyamic acid obtained as described above can be recovered by precipitating the polymer by pouring into the poor solvent while thoroughly stirring the reaction solution. Moreover, the powder of polyamic acid refine | purified by performing precipitation several times, washing | cleaning with a poor solvent, and normal temperature or heat-drying can be obtained. Examples of the poor solvent include water, methanol, ethanol, hexane, butyl cellosolve, acetone, toluene and the like.

<Production method of polyimide>
The polyimide used in the present invention can be produced by imidizing the polyamic acid ester or polyamic acid. When a polyimide is produced from a polyamic acid ester, chemical imidization in which a basic catalyst is added to a polyamic acid solution obtained by dissolving the polyamic acid ester solution or the polyamic acid ester resin powder in an organic solvent is simple. Chemical imidization is preferable because the imidization reaction proceeds at a relatively low temperature and the molecular weight of the polymer does not easily decrease during the imidization process.

Chemical imidation can be performed by stirring the polyamic acid ester to be imidized in an organic solvent in the presence of a basic catalyst. As an organic solvent, the solvent used at the time of the polymerization reaction mentioned above can be used. Examples of the basic catalyst include pyridine, triethylamine, trimethylamine, tributylamine, trioctylamine and the like. Of these, triethylamine is preferred because it has sufficient basicity to allow the reaction to proceed.
The temperature for carrying out the imidization reaction is −20 ° C. to 140 ° C., preferably 0 ° C. to 100 ° C., and the reaction time is preferably 1 to 100 hours. The amount of the basic catalyst is 0.5 to 30 moles, preferably 2 to 20 moles, of the amic acid ester group. The imidation ratio of the resulting polymer can be controlled by adjusting the amount of catalyst, temperature, and reaction time. Since the added catalyst remains in the solution after the imidation reaction, the obtained imidized polymer is recovered by the means described below and redissolved in an organic solvent to obtain a liquid crystal aligning agent. It is preferable.

When manufacturing a polyimide from a polyamic acid, chemical imidation which adds a catalyst to the solution of the said polyamic acid obtained by reaction with a diamine component and tetracarboxylic dianhydride is simple. Chemical imidization is preferable because the imidization reaction proceeds at a relatively low temperature and the molecular weight of the polymer is unlikely to decrease during the imidization process.
Chemical imidation can be performed by stirring a polymer to be imidized in an organic solvent in the presence of a basic catalyst and an acid anhydride. As an organic solvent, the solvent used at the time of the polymerization reaction mentioned above can be used. Examples of the basic catalyst include pyridine, triethylamine, trimethylamine, tributylamine, trioctylamine and the like. Of these, pyridine is preferable because it has an appropriate basicity for proceeding with the reaction. Examples of the acid anhydride include acetic anhydride, trimellitic anhydride, pyromellitic anhydride, and the like. Among them, use of acetic anhydride is preferable because purification after completion of the reaction is facilitated.

The temperature for carrying out the imidization reaction is −20 ° C. to 140 ° C., preferably 0 ° C. to 100 ° C., and the reaction time can be 1 to 100 hours. The amount of the basic catalyst is 0.5 to 30 mol times, preferably 2 to 20 mol times the amic acid group, and the amount of the acid anhydride is 1 to 50 mol times, preferably 3 to 30 mol times the amic acid group. Is double. The imidation ratio of the resulting polymer can be controlled by adjusting the amount of catalyst, temperature, and reaction time.
In the solution after the imidation reaction of polyamic acid ester or polyamic acid, the added catalyst and the like remain, so the obtained imidized polymer is recovered by the means described below, and redissolved in an organic solvent. Thus, the liquid crystal aligning agent of the present invention is preferable.

The polyimide solution obtained as described above can be polymerized by pouring into a poor solvent while stirring well. Precipitation is performed several times, and after washing with a poor solvent, a purified polyamic acid ester powder can be obtained at room temperature or by heating and drying.
The poor solvent is not particularly limited, and examples thereof include methanol, acetone, hexane, butyl cellosolve, heptane, methyl ethyl ketone, methyl isobutyl ketone, ethanol, toluene, and benzene.

<Liquid crystal aligning agent>
The liquid crystal aligning agent used in the present invention has a form of a solution in which the specific polymer (A) is dissolved in an organic solvent. The molecular weight of the specific polymer (A) is preferably 2,000 to 500,000 in terms of weight average molecular weight, more preferably 5,000 to 300,000, still more preferably 10,000 to 100,000. . The number average molecular weight is preferably 1,000 to 250,000, more preferably 2,500 to 150,000, and still more preferably 5,000 to 50,000.
The concentration of the polymer in the liquid crystal aligning agent can be appropriately changed according to the setting of the thickness of the coating film to be formed, but is preferably 1% by weight or more because a uniform and defect-free coating film is formed. 10% by weight or less is preferable from the viewpoint of stability.

The solvent used for the liquid crystal aligning agent of this invention will not be specifically limited if it is a solvent (it is also called a good solvent) in which a specific polymer (A) is dissolved. Specific examples of good solvents are given below.
For example, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, dimethyl sulfoxide, γ-butyrolactone, 1,3-dimethyl-imidazolidinone, methyl ethyl ketone Cyclohexanone, cyclopentanone, 4-hydroxy-4-methyl-2-pentanone, and the like. Of these, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, and γ-butyrolactone are preferably used.

Furthermore, when the solubility of the specific polymer (A) in the solvent is high, solvents represented by the following formulas [D-1] to [D-3] are preferable.

In formulas [D-1] to [D-3], D ¹ represents an alkyl group having 1 to 3 carbon atoms, D ² represents an alkyl group having 1 to 3 carbon atoms, and D ³ represents 1 to ³ carbon atoms. 4 alkyl groups).
The content of the good solvent in the liquid crystal aligning agent is preferably 20 to 99% by mass of the total solvent, more preferably 20 to 90% by mass, and particularly preferably 30 to 80% by mass.
The liquid crystal aligning agent can contain a solvent (also referred to as a poor solvent) that improves the coating properties and surface smoothness of the liquid crystal aligning film when the liquid crystal aligning agent is applied. These poor solvents are preferably 1 to 80% by mass, more preferably 10 to 80% by mass, and particularly preferably 20 to 70% by mass based on the total amount of the solvent contained in the liquid crystal aligning agent.

Specific examples of the poor solvent are given below.
Ethanol, isopropyl alcohol, 1-butanol, 2-butanol, isobutyl alcohol, tert-butyl alcohol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, isopentyl alcohol, tert- Pentyl alcohol, 3-methyl-2-butanol, neopentyl alcohol, 1-hexanol, 2-methyl-1-pentanol, 2-methyl-2-pentanol, 2-ethyl-1-butanol, 1-heptanol, 2 -Heptanol, 3-heptanol, 1-octanol, 2-octanol, 2-ethyl-1-hexanol, cyclohexanol, 1-methylcyclohexanol, 2-methylcyclohexanol, 3-methylcyclohexanol, 1,2-ethanediol , , 2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 2- Methyl-2,4-pentanediol, 2-ethyl-1,3-hexanediol, dipropyl ether, dibutyl ether, dihexyl ether, dioxane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, 1,2- Butoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol dibutyl ether, 2-pentanone, 3-pentanone, 2-hexanone, 2-hepta , 4-heptanone, 3-ethoxybutyl acetate, 1-methylpentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, ethylene glycol monoacetate, ethylene glycol diacetate, propylene carbonate, ethylene carbonate 2- (methoxymethoxy) ethanol, ethylene glycol monobutyl ether, ethylene glycol monoisoamyl ether, ethylene glycol monohexyl ether, 2- (hexyloxy) ethanol, furfuryl alcohol, diethylene glycol, propylene glycol, propylene glycol monobutyl ether, 1- (Butoxyethoxy) propanol, propylene glycol monomethyl ether acetate, dipropylene glycol, dipropiate Lenglycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol dimethyl ether, tripropylene glycol monomethyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, ethylene glycol monoacetate , Ethylene glycol diacetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, 2- (2-ethoxyethoxy) ethyl acetate, diethylene glycol acetate, triethylene glycol, triethylene glycol monomethyl ether, triethylene glycol mono Ethyl ether, methyl lactate Ethyl lactate, methyl acetate, ethyl acetate, n-butyl acetate, propylene glycol monoethyl ether, methyl pyruvate, ethyl pyruvate, methyl 3-methoxypropionate, methyl ethyl 3-ethoxypropionate, ethyl 3-methoxypropionate , 3-ethoxypropionic acid, 3-methoxypropionic acid, propyl 3-methoxypropionate, butyl 3-methoxypropionate, methyl lactate, ethyl lactate, n-propyl lactate, n-butyl lactate, isoamyl lactate Alternatively, the formula [D-1] to the formula [D-3].

Of these, 1-hexanol, cyclohexanol, 1,2-ethanediol, 1,2-propanediol, propylene glycol monobutyl ether, ethylene glycol monobutyl ether or dipropylene glycol dimethyl ether are preferable.
The liquid crystal aligning agent of the present invention includes at least one substituent selected from the group consisting of a crosslinkable compound having an epoxy group, an isocyanate group, an oxetane group or a cyclocarbonate group, a hydroxyl group, a hydroxyalkyl group and a lower alkoxyalkyl group. It is preferable to introduce a crosslinkable compound having a crosslinkable compound or a crosslinkable compound having a polymerizable unsaturated bond. It is necessary to have two or more of these substituents and polymerizable unsaturated bonds in the crosslinkable compound.

Examples of the crosslinkable compound having an epoxy group or an isocyanate group include bisphenolacetone glycidyl ether, phenol novolac epoxy resin, cresol novolac epoxy resin, triglycidyl isocyanurate, tetraglycidylaminodiphenylene, tetraglycidyl-m-xylenediamine, tetra Glycidyl-1,3-bis (aminoethyl) cyclohexane, tetraphenyl glycidyl ether ethane, triphenyl glycidyl ether ethane, bisphenol hexafluoroacetodiglycidyl ether, 1,3-bis (1- (2,3-epoxypropoxy)- 1-trifluoromethyl-2,2,2-trifluoromethyl) benzene, 4,4-bis (2,3-epoxypropoxy) octafluorobiphenyl Triglycidyl-p-aminophenol, tetraglycidylmetaxylenediamine, 2- (4- (2,3-epoxypropoxy) phenyl) -2- (4- (1,1-bis (4- (2,3-epoxy) Propoxy) phenyl) ethyl) phenyl) propane or 1,3-bis (4- (1- (4- (2,3-epoxypropoxy) phenyl) -1- (4- (1- (4- (2,3 -Epoxypropoxy) phenyl) -1-methylethyl) phenyl) ethyl) phenoxy) -2-propanol and the like.

The crosslinkable compound having an oxetane group is a compound having at least two oxetane groups represented by the following formula [4A].

Specific examples include crosslinkable compounds represented by the formulas [4a] to [4k] published on pages 58 to 59 of International Publication No. WO2011 / 132751 (published on October 27, 2011).

The crosslinkable compound having a cyclocarbonate group is a crosslinkable compound having at least two cyclocarbonate groups represented by the following formula [5A].

Specific examples include crosslinkable compounds represented by the formulas [5-1] to [5-42] described on pages 76 to 82 of International Publication No. WO2012 / 014898 (published on 2.2.2.2012).
Examples of the crosslinkable compound having at least one substituent selected from the group consisting of a hydroxyl group and an alkoxyl group include an amino resin having a hydroxyl group or an alkoxyl group, such as a melamine resin, a urea resin, a guanamine resin, and a glycoluril. -Formaldehyde resin, succinylamide-formaldehyde resin or ethylene urea-formaldehyde resin. Specifically, a melamine derivative, a benzoguanamine derivative, or glycoluril in which a hydrogen atom of an amino group is substituted with a methylol group, an alkoxymethyl group, or both can be used. The melamine derivative or benzoguanamine derivative can exist as a dimer or a trimer. These preferably have an average of 3 to 6 methylol groups or alkoxymethyl groups per triazine ring.

Examples of the melamine derivative or benzoguanamine derivative include MX-750, which has an average of 3.7 substituted methoxymethyl groups per triazine ring, and an average of 5.8 methoxymethyl groups per triazine ring. MW-30 (manufactured by Sanwa Chemical Co., Ltd.) and Cymel 300, 301, 303, 350, 370, 771, 325, 327, 703, 712 and the like methoxymethylated melamine, Cymel 235, 236, Methoxymethylated butoxymethylated melamine such as 238, 212, 253, 254, butoxymethylated melamine such as Cymel 506, 508, carboxyl group-containing methoxymethylated isobutoxymethylated melamine such as Cymel 1141, Cymel 1123, etc. Methoxymethylated ethoxyme Benzomethylamine, methoxymethyl butoxymethylated benzoguanamine such as Cymel 1123-10, butoxymethylated benzoguanamine such as Cymel 1128, carboxymethyl-containing methoxymethylated ethoxymethylated benzoguanamine such as Cymel 1125-80 Cyanamide).

Examples of glycoluril include butoxymethylated glycoluril such as Cymel 1170, methylolated glycoluril such as Cymel 1172, and methoxymethylolated glycoluril such as Powderlink 1174.
Examples of the benzene or phenolic compound having a hydroxyl group or an alkoxyl group include 1,3,5-tris (methoxymethyl) benzene, 1,2,4-tris (isopropoxymethyl) benzene, 1,4-bis ( sec-butoxymethyl) benzene or 2,6-dihydroxymethyl-p-tert-butylphenol.
More specifically, the crosslinkable compounds represented by the formulas [6-1] to [6-48] described in pages 62 to 66 of International Publication No. WO2011 / 132751 (published on 10.27.2011) can be mentioned.

Examples of the crosslinkable compound having a polymerizable unsaturated bond include trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol penta (meth) acrylate, and tri (meth) acryloyloxyethoxytrimethylol. Crosslinkable compounds having three polymerizable unsaturated groups in the molecule such as propane or glycerin polyglycidyl ether poly (meth) acrylate, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, tetraethylene glycol di (Meth) acrylate, polyethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, butylene glycol Rudi (meth) acrylate, neopentyl glycol di (meth) acrylate, ethylene oxide bisphenol A type di (meth) acrylate, propylene oxide bisphenol type di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, glycerin Di (meth) acrylate, pentaerythritol di (meth) acrylate, ethylene glycol diglycidyl ether di (meth) acrylate, diethylene glycol diglycidyl ether di (meth) acrylate, diglycidyl phthalate di (meth) acrylate or hydroxypivalic acid neo Crosslinkable compounds having two polymerizable unsaturated groups in the molecule, such as pentyl glycol di (meth) acrylate, in addition, 2-hydroxyethyl (meth) acrylate 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 2-phenoxy-2-hydroxypropyl (meth) acrylate, 2- (meth) acryloyloxy-2-hydroxypropyl phthalate, 3-chloro-2 Crosslinkability having one polymerizable unsaturated group in the molecule such as hydroxypropyl (meth) acrylate, glycerin mono (meth) acrylate, 2- (meth) acryloyloxyethyl phosphate ester or N-methylol (meth) acrylamide Compounds and the like.

Furthermore, a compound represented by the following formula [7A] can also be used.

(In the formula [7A], E ₁ represents a group selected from the group consisting of a cyclohexane ring, a bicyclohexane ring, a benzene ring, a biphenyl ring, a terphenyl ring, a naphthalene ring, a fluorene ring, an anthracene ring or a phenanthrene ring; ₂ represents a group selected from the following formula [7a] or [7b], and n represents an integer of 1 to 4.

The above is an example of a crosslinkable compound, but is not limited thereto. Moreover, the crosslinkable compound used for a liquid crystal aligning agent may be 1 type, or may combine 2 or more types.

The content of the crosslinkable compound in the liquid crystal aligning agent is preferably 0.1 to 150 parts by mass with respect to 100 parts by mass of all the polymer components. Among these, in order for the crosslinking reaction to proceed and to exhibit the desired effect, the amount is preferably 0.1 to 100 parts by mass with respect to 100 parts by mass of all the polymer components. More preferred is 1 to 50 parts by mass.

The liquid crystal aligning agent of this invention can use the compound which improves the uniformity of the film thickness of a liquid crystal aligning film at the time of apply | coating a liquid crystal aligning agent, and surface smoothness.
Examples of the compound that improves the film thickness uniformity and surface smoothness of the liquid crystal alignment film include fluorine-based surfactants, silicone-based surfactants, and nonionic surfactants.
More specifically, for example, F-top EF301, EF303, EF352 (above, manufactured by Tochem Products), MegaFuck F171, F173, R-30 (above, manufactured by Dainippon Ink), Florard FC430, FC431 (or more) And Asahi Guard AG710, Surflon S-382, SC101, SC102, SC103, SC104, SC105, SC106 (above, manufactured by Asahi Glass Co., Ltd.).

The amount of the surfactant used is preferably 0.01 to 2 parts by mass, more preferably 0.01 to 1 part by mass with respect to 100 parts by mass of all the polymer components contained in the liquid crystal aligning agent.
Furthermore, the liquid crystal aligning agent is published on pages 69 to 73 of International Publication No. WO2011 / 132751 (published on 10.27.2011) as a compound that promotes charge transfer in the liquid crystal alignment film and promotes charge release of the device. It is also possible to add nitrogen-containing heterocyclic amine compounds represented by the formulas [M1] to [M156]. The amine compound may be added directly to the liquid crystal aligning agent, but it is preferable to add the amine compound after forming a solution having a concentration of 0.1 to 10% by mass, preferably 1 to 7% by mass. The solvent is not particularly limited as long as the specific polymer (A) is dissolved.

The liquid crystal aligning agent of the present invention includes, in addition to the above-mentioned poor solvent, crosslinkable compound, resin film or compound that improves the film thickness uniformity and surface smoothness of the liquid crystal aligning film, and a compound that promotes charge removal. As long as the effects of the invention are not impaired, a polymer other than the polymer described in the present invention, a silane coupling agent for the purpose of improving the adhesion between the alignment film and the substrate, and further when firing the coating film An imidization accelerator for the purpose of efficiently progressing imidization by heating of the polyimide precursor may be added to.

<Liquid crystal alignment film and liquid crystal display element>
The liquid crystal alignment film is a film obtained by applying the above liquid crystal aligning agent to a substrate, drying and baking. The substrate to which the liquid crystal aligning agent of the present invention is applied is not particularly limited as long as it is a highly transparent substrate, and a plastic substrate such as an acrylic substrate or a polycarbonate substrate can be used together with a glass substrate or a silicon nitride substrate. At that time, it is preferable to use a substrate on which an ITO electrode or the like for driving the liquid crystal is used from the viewpoint of simplification of the process. In the reflective liquid crystal display element, an opaque material such as a silicon wafer can be used as long as it is only on one side of the substrate, and a material that reflects light such as aluminum can be used for the electrode in this case.

A method for applying the liquid crystal aligning agent is not particularly limited, but industrially, a method of performing screen printing, offset printing, flexographic printing, an inkjet method, or the like is common. Other coating methods include a dipping method, a roll coater method, a slit coater method, a spinner method, or a spray method, and these may be used depending on the purpose.
After the liquid crystal aligning agent is applied onto the substrate, the solvent can be evaporated by a heating means such as a hot plate, a thermal circulation oven, or an IR (infrared) oven to form a liquid crystal alignment film. Arbitrary temperature and time can be selected for the drying and baking steps after applying the liquid crystal aligning agent of the present invention. Usually, a condition of baking at 50 to 120 ° C. for 1 to 10 minutes and then baking at 150 to 300 ° C. for 5 to 120 minutes is mentioned in order to sufficiently remove the contained solvent. If the thickness of the liquid crystal alignment film after baking is too thin, the reliability of the liquid crystal display element may be lowered, and thus it is preferably 5 to 300 nm, and more preferably 10 to 200 nm.

The method for aligning the liquid crystal alignment film obtained from the liquid crystal aligning agent of the present invention may be a rubbing method, but the photo alignment method is preferred. As a preferred example of the photo-alignment treatment method, the surface of the liquid crystal alignment film is irradiated with radiation deflected in a certain direction, and in some cases, preferably, a heat treatment is performed at a temperature of 150 to 250 ° C. And a method of imparting (also referred to as liquid crystal alignment ability). As the radiation, ultraviolet rays or visible rays having a wavelength of 100 to 800 nm can be used. Among these, ultraviolet rays having a wavelength of preferably 100 to 400 nm, more preferably 200 to 400 nm are preferable.

Further, in order to improve the liquid crystal alignment, the substrate coated with the liquid crystal alignment film may be irradiated with radiation while heating at 50 to 250 ° C. The irradiation amount of the radiation is preferably 1 ~ 10,000mJ / cm ^2, more preferably 100 ~ 5,000mJ / cm ^2. Thus, the liquid crystal alignment film can stably align liquid crystal molecules in a certain direction.
A higher extinction ratio of polarized ultraviolet rays is preferable because higher anisotropy can be imparted. Specifically, the extinction ratio of linearly polarized ultraviolet light is preferably 10: 1 or more, and more preferably 20: 1 or more.

Further, the liquid crystal alignment film irradiated with polarized radiation can be subjected to contact treatment using water or a solvent by the above method.
The solvent used for the contact treatment is not particularly limited as long as it is a solvent that dissolves a decomposition product generated from the liquid crystal alignment film by irradiation with radiation. Specific examples include water, methanol, ethanol, 2-propanol, acetone, methyl ethyl ketone, 1-methoxy-2-propanol, 1-methoxy-2-propanol acetate, butyl cellosolve, ethyl lactate, methyl lactate, diacetone alcohol, 3- Examples thereof include methyl methoxypropionate, ethyl 3-ethoxypropionate, propyl acetate, butyl acetate or cyclohexyl acetate. Of these, water, 2-propanol, 1-methoxy-2-propanol or ethyl lactate is preferable, and water, 1-methoxy-2-propanol or ethyl lactate is more preferable in view of versatility and solvent safety. A solvent may be used alone or in combination of two or more.

Examples of the above-described contact treatment, that is, treatment of water or a solvent on the liquid crystal alignment film irradiated with polarized radiation includes immersion treatment and spray treatment (spray treatment). The time for these treatments is preferably 10 seconds to 1 hour, and preferably immersion treatment for 1 to 30 minutes, from the viewpoint of efficiently dissolving the decomposition products generated from the liquid crystal alignment film by radiation. In addition, the solvent for the contact treatment may be heated at normal temperature, but is preferably 10 to 80 ° C. Of these, 20 to 50 ° C. is preferable. In addition, from the viewpoint of the solubility of the decomposition product, ultrasonic treatment or the like may be performed as necessary.

After the contact treatment, it is preferable to perform rinsing (also referred to as rinsing) with a low boiling point solvent such as water, methanol, ethanol, 2-propanol, acetone, or methyl ethyl ketone, and baking of the liquid crystal alignment film. At that time, either one of rinsing and firing, or both may be performed. The firing temperature is preferably 150 to 300 ° C, more preferably 180 to 250 ° C, and particularly preferably 200 to 230 ° C. The firing time is preferably 10 seconds to 30 minutes, more preferably 1 to 10 minutes.

The liquid crystal alignment film of the present invention is suitable as a liquid crystal alignment film for a horizontal electric field type liquid crystal display element such as an IPS mode or an FFS mode, and is particularly useful for an FFS mode liquid crystal display element. The liquid crystal display element is obtained using a liquid crystal cell by preparing a liquid crystal cell by a known method after obtaining a substrate with a liquid crystal alignment film obtained from the liquid crystal aligning agent of the present invention.
As an example of a method for manufacturing a liquid crystal cell, a liquid crystal display element having a passive matrix structure will be described as an example. Note that an active matrix liquid crystal display element in which a switching element such as a TFT (Thin Film Transistor) is provided in each pixel portion constituting the image display may be used.

Specifically, a transparent glass substrate is prepared, a common electrode is provided on one substrate, and a segment electrode is provided on the other substrate. These electrodes can be ITO electrodes, for example, and are patterned so as to display a desired image. Next, an insulating film is provided on each substrate so as to cover the common electrode and the segment electrode. The insulating film can be, for example, a SiO ₂ —TiO ₂ film formed by a sol-gel method.
Next, a liquid crystal alignment film is formed on each substrate, the other substrate is overlaid on one substrate so that the liquid crystal alignment film faces each other, and the periphery is bonded with a sealant. In order to control the substrate gap, a spacer is usually mixed in the sealant, and it is preferable to spray a spacer for controlling the substrate gap on the in-plane portion where no sealant is provided. A part of the sealant is provided with an opening that can be filled with liquid crystal from the outside.

Next, a liquid crystal material is injected into the space surrounded by the two substrates and the sealing agent through the opening provided in the sealing agent, and then the opening is sealed with an adhesive. For the injection, a vacuum injection method may be used, or a method utilizing capillary action in the atmosphere may be used. As the liquid crystal material, either a positive liquid crystal material or a negative liquid crystal material may be used, but a negative liquid crystal material is preferable. Next, a polarizing plate is installed. Specifically, a pair of polarizing plates is attached to the surfaces of the two substrates opposite to the liquid crystal layer.
As described above, by using the liquid crystal aligning agent of the present invention, it is possible to obtain a liquid crystal aligning film that suppresses afterimages due to AC driving and has both adhesiveness with the sealing agent and the base substrate. In particular, it is useful for a liquid crystal alignment film for photo-alignment treatment obtained by irradiating polarized radiation.

The present invention will be described in more detail with reference to the following examples, but the present invention should not be construed as being limited thereto.
The abbreviations and measurement methods of the compounds used below are as follows.
NMP: N-methyl-2-pyrrolidone, BCS: Butyl cellosolve DA-1: 1,2-bis (4-aminophenoxy) ethane
DA-2: 1,3-bis (4-aminophenoxy) propane DA-3: p-phenylenediamine DA-6: 4- (2- (methylamino) ethyl) aniline

[viscosity]
The viscosity of the polyamic acid ester and the polyamic acid solution was measured using an E-type viscometer TVE-22H (manufactured by Toki Sangyo Co., Ltd.), a sample amount of 1.1 mL, cone rotor TE-1 (1 ° 34 ′, R24), temperature 25 Measured at ° C.
[Molecular weight]
The molecular weight of the polyamic acid ester is measured by a GPC (room temperature gel permeation chromatography) apparatus, and is a number average molecular weight (hereinafter also referred to as Mn) and a weight average molecular weight (hereinafter also referred to as Mw) in terms of polyethylene glycol and polyethylene oxide. Was calculated.
GPC device: manufactured by Shodex (GPC-101)
Column: manufactured by Shodex (series of KD803 and KD805)
Column temperature: 50 ° C
Eluent: N, N-dimethylformamide (as additives, lithium bromide-hydrate (LiBr · H ₂ O) 30 mmol / L, phosphoric acid / anhydrous crystals (o-phosphoric acid) 30 mmol / L, tetrahydrofuran) (THF) is 10 ml / L)
Flow rate: 1.0 ml / min Standard sample for preparing calibration curve: TSK standard polyethylene oxide (weight average molecular weight (Mw) of about 900,000, 150,000, 100,000, 30,000) manufactured by Tosoh Corporation, and polymer laboratory Polyethylene glycol manufactured by the company (peak top molecular weight (Mp) of about 12,000, 4,000, 1,000). In order to avoid the overlapping of peaks, the measurement was performed by mixing four types of 900,000, 100,000, 12,000, and 1,000, and three types of 150,000, 30,000, and 4,000. Two samples of mixed samples are measured separately.

[Measurement of imidization rate]
20 mg of polyimide powder is put into an NMR sample tube (NMR sampling tube standard, φ5 (manufactured by Kusano Kagaku)) and deuterated dimethyl sulfoxide (DMSO-d6, 0.05% TMS (tetramethylsilane) mixture) (0.53 ml) ) Was added and completely dissolved by applying ultrasonic waves. This solution was measured for proton NMR at 500 MHz with an NMR measuring instrument (JNW-ECA500) (manufactured by JEOL Datum). The imidation rate is determined based on protons derived from structures that do not change before and after imidation as reference protons, and the peak integrated value of these protons and proton peaks derived from NH groups of amic acid that appear in the vicinity of 9.5 ppm to 10.0 ppm. It calculated | required by the following formula | equation using the integrated value.
Imidization rate (%) = (1−α · x / y) × 100
In the above formula, x is the proton peak integrated value derived from the NH group of the amic acid, y is the peak integrated value of the reference proton, and α is the NH of the amic acid in the case of polyamic acid (imidation rate is 0%). This is the ratio of the number of reference protons to one group proton.

[Anisotropy of alignment film]
Measurement was performed using a liquid crystal alignment film evaluation system “Ray Scan Lab H” (LYS-LH30S-1A) manufactured by Moritex Corporation. The polyimide film having a thickness of 100 nm was irradiated with ultraviolet rays through a polarizing plate, and the magnitude of anisotropy with respect to the alignment direction of the obtained alignment film was measured.

[Production of liquid crystal cell]
A liquid crystal cell having a configuration of a fringe field switching (FFS) mode liquid crystal display element is manufactured.
First, a substrate with electrodes was prepared. On a glass substrate having a length of 30 mm, a width of 0 mm, and a thickness of 0.7 mm, an ITO electrode having a solid pattern constituting a counter electrode as a first layer is formed. On the counter electrode of the first layer, a SiN (silicon nitride) film formed by the CVD method is formed as the second layer. The second layer SiN film has a thickness of 500 nm and functions as an interlayer insulating film. On the second SiN film, a comb-like pixel electrode formed by patterning an ITO film as the third layer is arranged to form two pixels, a first pixel and a second pixel. ing. The size of each pixel is 10 mm long and about 5 mm wide. At this time, the first-layer counter electrode and the third-layer pixel electrode are electrically insulated by the action of the second-layer SiN film.

The pixel electrode of the third layer has a comb-like shape configured by arranging a plurality of electrode elements having a dogleg shape whose central portion is bent. The width in the short direction of each electrode element is 3 μm, and the distance between the electrode elements is 6 μm. Since the pixel electrode forming each pixel is formed by arranging a plurality of bent-shaped electrode elements in the central portion, the shape of each pixel is not rectangular, but in the central portion like the electrode elements. It has a shape that bends and resembles a bold “Koji”. Each pixel is divided into upper and lower portions with a central bent portion as a boundary, and has a first region on the upper side of the bent portion and a second region on the lower side.

When the first region and the second region of each pixel are compared, the formation directions of the electrode elements of the pixel electrodes constituting them are different. That is, when the rubbing direction of the liquid crystal alignment film described later is used as a reference, the electrode element of the pixel electrode is formed to form an angle of + 10 ° (clockwise) in the first region of the pixel, and the pixel in the second region of the pixel. The electrode elements of the electrode are formed so as to form an angle of −10 ° (clockwise). That is, in the first region and the second region of each pixel, the directions of the rotation operation (in-plane switching) of the liquid crystal induced by the voltage application between the pixel electrode and the counter electrode are mutually in the substrate plane. It is comprised so that it may become a reverse direction.

Next, after filtering the obtained liquid crystal aligning agent through a 1.0 μm filter, the prepared substrate with electrodes and a glass substrate having a columnar spacer with a height of 4 μm on which an ITO film is formed on the back surface, It applied by spin coat application. After drying on an 80 ° C. hot plate for 5 minutes, baking was carried out in a hot air circulating oven at 230 ° C. for 20 minutes to form a coating film having a thickness of 100 nm. This coating film surface was irradiated with linearly polarized ultraviolet light having a wavelength of 254 nm with an extinction ratio of 10: 1 or more via a polarizing plate. This substrate is immersed in at least one solvent selected from water and an organic solvent for 3 minutes, then immersed in pure water for 1 minute, and heated on a hot plate at 150 ° C. to 300 ° C. for 5 minutes to provide a liquid crystal alignment film A substrate was obtained. The two substrates are combined as a set, a sealant is printed on the substrate, and the other substrate is bonded so that the liquid crystal alignment film faces and the alignment direction is 0 °, and then the sealant is added. An empty cell was produced by curing. Liquid crystal MLC-7026-100 (manufactured by Merck & Co., Inc.) was injected into this empty cell by a reduced pressure injection method, and the injection port was sealed to obtain an FFS drive liquid crystal cell. Thereafter, the obtained liquid crystal cell was heated at 110 ° C. for 1 hour and allowed to stand overnight before being used for each evaluation.

[Afterimage evaluation by long-term AC drive]
A liquid crystal cell having the same structure as the liquid crystal cell used for the above-described afterimage evaluation was prepared.
Using this liquid crystal cell, an AC voltage of ± 5 V was applied for 120 hours at a frequency of 60 Hz in a constant temperature environment of 60 ° C. Thereafter, the pixel electrode and the counter electrode of the liquid crystal cell were short-circuited and left as it was at room temperature for one day.
After leaving, the liquid crystal cell is placed between two polarizing plates arranged so that the polarization axes are orthogonal, and the backlight is turned on with no voltage applied so that the brightness of the transmitted light is minimized. The arrangement angle of the liquid crystal cell was adjusted. Then, the rotation angle when the liquid crystal cell was rotated from the angle at which the second region of the first pixel became darkest to the angle at which the first region became darkest was calculated as an angle Δ. Similarly, in the second pixel, the second region and the first region were compared to calculate a similar angle Δ.

[Evaluation of bright spot of liquid crystal cell (contrast)]
The bright spot of the liquid crystal cell produced above was evaluated. Evaluation of the bright spot of the liquid crystal cell was performed by observing the liquid crystal cell with a polarizing microscope (ECLIPSE E600WPOL) (manufactured by Nikon Corporation). Specifically, the number of bright spots confirmed by observing the liquid crystal cell with a polarizing microscope in which the liquid crystal cell was installed in crossed Nicol and the magnification was 5 times was counted. ”And more than that,“ bad ”.

<Synthesis Example 1>
In a 50 mL four-necked flask equipped with a stirrer and a nitrogen inlet tube, 0.81 g (3.30 mmol) of DA-1, 0.57 g (2.20 mmol) of DA-2, and 0.36 g of DA-3 ( 3.30 mmol) and 0.84 g (2.20 mmol) of DA-4 were added, 29.99 g of NMP was added, and the mixture was stirred and dissolved while feeding nitrogen. While stirring this diamine solution, 2.35 g (10.51 mmol) of 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride was added, and the solid content concentration became 12% by mass. Thus, 6.40 g of NMP was added and stirred at room temperature for 24 hours to obtain a polyamic acid solution (A). The viscosity of this polyamic acid solution at a temperature of 25 ° C. was 316 mPa · s. Moreover, the molecular weight of this polyamic acid was Mn = 13230 and Mw = 29550.

<Synthesis Example 2>
In a 50 mL four-necked flask equipped with a stirrer and a nitrogen inlet tube, 0.5-1 g (2.20 mmol) DA-1, 0.85 g (3.30 mmol) DA-2, and 0.36 g DA-3 ( 3.30 mmol) and 0.84 g (2.20 mmol) of DA-4 were added, 30.17 g of NMP was added, and the mixture was stirred and dissolved while feeding nitrogen. While stirring this diamine solution, 2.35 g (10.51 mmol) of 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride was added, and the solid content concentration became 12% by mass. In this way, 6.34 g of NMP was added and stirred at room temperature for 24 hours to obtain a polyamic acid solution (B). The viscosity of this polyamic acid solution at a temperature of 25 ° C. was 356 mPa · s. Moreover, the molecular weight of this polyamic acid was Mn = 14120 and Mw = 31210.

<Synthesis Example 3>
In a 50 mL four-necked flask equipped with a stirrer and a nitrogen inlet tube, 0.81 g (3.60 mmol) DA-1, 0.31 g (1.20 mmol) DA-2, 0.52 g DA-3 ( 4.80 mmol) and 0.96 g (2.40 mmol) of DA-4 were added, 30.64 g of NMP was added, and the mixture was stirred and dissolved while feeding nitrogen. While stirring this diamine solution, 2.57 g (11.46 mmol) of 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride was added, and the solid content concentration became 12% by mass. Thus, 7.74 g of NMP was added and stirred at room temperature for 24 hours to obtain a polyamic acid solution (C). The viscosity of this polyamic acid solution at a temperature of 25 ° C. was 336 mPa · s. Moreover, the molecular weight of this polyamic acid was Mn = 13410 and Mw = 30110.

<Synthesis Example 4>
In a 50 mL four-necked flask equipped with a stirrer and a nitrogen introduction tube, DA-1 0.54 g (2.20 mmol), DA-2 0.57 g (2.20 mmol), DA-3 0.48 g ( 4.40 mmol), 0.88 g (2.20 mmol) of DA-4 was added, 28.27 g of NMP was added, and the mixture was stirred and dissolved while feeding nitrogen. While stirring this diamine solution, 2.35 g (10.51 mmol) of 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride was added, and the solid content concentration became 12% by mass. Thus, 7.03 g of NMP was added and stirred at room temperature for 24 hours to obtain a polyamic acid solution (D). The viscosity of this polyamic acid solution at a temperature of 25 ° C. was 366 mPa · s. Moreover, the molecular weight of this polyamic acid was Mn = 14530 and Mw = 36150.

<Synthesis Example 5>
In a 50 mL four-necked flask equipped with a stirrer and a nitrogen inlet tube, 0.91 g (3.90 mmol) of DA-1, 0.67 g (2.60 mmol) of DA-2, and 0.70 g of DA-3 ( 6.50 mmol), 26.76 g of NMP were added, and the mixture was stirred and dissolved while feeding nitrogen. While stirring the diamine solution, 2.78 g (12.42 mmol) of 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride was added, and the solid content concentration became 12% by mass. Thus, 10.71 g of NMP was added and stirred at room temperature for 24 hours to obtain a polyamic acid solution (E). The viscosity of this polyamic acid solution at a temperature of 25 ° C. was 301 mPa · s. Moreover, the molecular weight of this polyamic acid was Mn = 11990 and Mw = 25310.

<Synthesis Example 6>
In a 50 mL four-necked flask equipped with a stirrer and a nitrogen inlet tube, 0.81 g (3.30 mmol) of DA-1, 0.57 g (2.20 mmol) of DA-2, and 0.36 g of DA-3 ( 3.30 mmol) and 0.75 g (2.20 mmol) of DA-5 were added, 28.55 g of NMP was added, and the mixture was stirred and dissolved while feeding nitrogen. While stirring this diamine solution, 2.35 g (10.51 mmol) of 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride was added, and the solid content concentration became 12% by mass. Thus, 6.93 g of NMP was added and stirred at room temperature for 24 hours to obtain a polyamic acid solution (F). The viscosity of this polyamic acid solution at a temperature of 25 ° C. was 350 mPa · s. Moreover, the molecular weight of this polyamic acid was Mn = 15220 and Mw = 31850.

<Synthesis Example 7>
In a 50 mL four-necked flask equipped with a stirrer and a nitrogen inlet tube, 0.81 g (3.60 mmol) of DA-1, 0.65 g (6.00 mmol) of DA-3, and 0.96 g of DA-4 ( 2.40 mmol) was taken, 28.57 g of NMP was added, and the mixture was stirred and dissolved while feeding nitrogen. While stirring this diamine solution, 2.57 g (11.46 mmol) of 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride was added, and the solid content concentration became 12% by mass. As above, 8.49 g of NMP was added and stirred at room temperature for 24 hours to obtain a polyamic acid solution (G). The viscosity of this polyamic acid solution at a temperature of 25 ° C. was 386 mPa · s. Moreover, the molecular weight of this polyamic acid was Mn = 16530 and Mw = 37220.

<Synthesis Example 8>
Take 1.59 g (6.50 mmol) of DA-1 and 0.70 g (6.50 mmol) of DA-3 and add 26.34 g of NMP to a 50 mL four-necked flask with a stirrer and a nitrogen inlet tube. The mixture was stirred and dissolved while feeding nitrogen. While stirring the diamine solution, 2.78 g (12.42 mmol) of 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride was added, and the solid content concentration became 12% by mass. Thus, 10.86 g of NMP was added and stirred at room temperature for 24 hours to obtain a polyamic acid solution (H). The viscosity of this polyamic acid solution at a temperature of 25 ° C. was 310 mPa · s. Moreover, the molecular weight of this polyamic acid was Mn = 13310 and Mw = 26210.

<Synthesis Example 9>
1.68 g (6.50 mmol) of DA-2, 0.70 g (6.50 mmol) of DA-3 and 27.39 g of NMP were added to a 50 mL four-necked flask equipped with a stirrer and a nitrogen inlet tube. The mixture was stirred and dissolved while feeding nitrogen. While stirring the diamine solution, 2.78 g (12.42 mmol) of 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride was added, and the solid content concentration became 12% by mass. In this way, 10.48 g of NMP was added and stirred at room temperature for 24 hours to obtain a polyamic acid solution (I). The viscosity of this polyamic acid solution at a temperature of 25 ° C. was 322 mPa · s. Moreover, the molecular weight of this polyamic acid was Mn = 14430 and Mw = 29950.

<Synthesis Example 10>
Take 1.46 g (13.50 mmol) of DA-3 and 0.36 g (1.50 mmol) of DA-6 and add 20.88 g of NMP to a 50 mL four-necked flask equipped with a stirrer and a nitrogen inlet tube. The mixture was stirred and dissolved while feeding nitrogen. While stirring the diamine solution, 3.21 g (14.33 mmol) of 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride was added, and the solid content concentration became 12% by mass. In this way, 15.98 g of NMP was added and stirred at room temperature for 24 hours to obtain a polyamic acid solution (J). The viscosity of this polyamic acid solution at a temperature of 25 ° C. was 344 mPa · s. Moreover, the molecular weight of this polyamic acid was Mn = 14430 and Mw = 34850.

<Synthesis Example 11>
2.69 g (11.00 mmol) of DA-1 was added to a 50 mL four-necked flask equipped with a stirrer and a nitrogen introduction tube, and 30.90 g of NMP was added, and the mixture was stirred and dissolved while feeding nitrogen. While stirring this diamine solution, 2.35 g (10.51 mmol) of 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride was added, and the solid content concentration became 12% by mass. As such, 6.07 g of NMP was added and stirred at room temperature for 24 hours to obtain a polyamic acid solution (K). The viscosity of this polyamic acid solution at a temperature of 25 ° C. was 367 mPa · s. Moreover, the molecular weight of this polyamic acid was Mn = 17110 and Mw = 33310.

<Example 1>
15.00 g of the 12% by mass polyamic acid solution (A) obtained in Synthesis Example 1 was placed in a 100 ml Erlenmeyer flask, 9.00 g of NMP and 6.00 g of BCS were added, and the mixture was mixed at 25 ° C. for 8 hours. (1) was obtained. This liquid crystal aligning agent was confirmed to be a uniform solution without any abnormality such as turbidity and precipitation.

<Examples 2 to 6>
The liquid crystal aligning agent (2) was obtained in the same manner as in Example 1 except that 12% by mass of the polyamic acid solutions (B) to (F) obtained in Synthesis Examples 2 to 6 were used. To (6) were obtained. All of these liquid crystal aligning agents were confirmed to be uniform solutions without any abnormality such as turbidity and precipitation.

<Comparative Examples 1 to 5>
The liquid crystal aligning agent (7) was obtained in the same manner as in Example 1 except that 12% by mass of the polyamic acid solutions (G) to (K) obtained in Synthesis Examples 7 to 11 were used. To (11) were obtained. All of these liquid crystal aligning agents were confirmed to be uniform solutions without any abnormality such as turbidity and precipitation.

(Example 7)
The liquid crystal aligning agent (1) obtained in Example 1 was filtered through a 1.0 μm filter, and then spin-coated on a 30 mm × 40 mm ITO substrate. After drying on an 80 ° C. hot plate for 2 minutes, baking was performed in a hot air circulation oven at 230 ° C. for 14 minutes to form a coating film having a thickness of 100 nm. The surface of the coating film was irradiated with a linearly polarized ultraviolet ray having a wavelength of 254 nm with an extinction ratio of 26: 1 via a polarizing plate, and the height of anisotropy with respect to the alignment direction of the obtained liquid crystal alignment film was measured. In anisotropy value 1.31 in dose is 100 / cm ² in the UV, anisotropy value at 150 mJ / cm ² at 3.10, the anisotropy at 200 mJ / cm ² The value was 2.25. The irradiation amount of the ultraviolet ray having the highest anisotropy was 150 mJ / cm ² , and was the optimum irradiation condition in the photo-alignment treatment.

(Example 8)
The liquid crystal aligning agent (2) obtained in Example 2 was filtered through a 1.0 μm filter, and then spin-coated on a 30 mm × 40 mm ITO substrate. After drying on an 80 ° C. hot plate for 2 minutes, baking was performed in a hot air circulation oven at 230 ° C. for 14 minutes to form a coating film having a thickness of 100 nm. The surface of the coating film was irradiated with a linearly polarized ultraviolet ray having a wavelength of 254 nm with an extinction ratio of 26: 1 via a polarizing plate, and the height of anisotropy with respect to the alignment direction of the obtained liquid crystal alignment film was measured. In anisotropy value 0.43 in the irradiation amount is 50 mJ / cm ² of the ultraviolet, anisotropy value at 100 mJ / cm ² at 3.53, the anisotropy at 150 mJ / cm ² The value was 3.26. The irradiation amount of the ultraviolet ray having the highest anisotropy was 150 mJ / cm ² , and was the optimum irradiation condition in the photo-alignment treatment.

Example 9
The liquid crystal aligning agent (3) obtained in Example 3 was filtered through a 1.0 μm filter, and then spin-coated on a 30 mm × 40 mm ITO substrate. After drying on an 80 ° C. hot plate for 2 minutes, baking was performed in a hot air circulation oven at 230 ° C. for 14 minutes to form a coating film having a thickness of 100 nm. The surface of the coating film was irradiated with a linearly polarized ultraviolet ray having a wavelength of 254 nm with an extinction ratio of 26: 1 via a polarizing plate, and the height of anisotropy with respect to the alignment direction of the obtained liquid crystal alignment film was measured. The anisotropy value when the UV irradiation dose is 200 mJ / cm ² is 2.24, the anisotropy value at 300 mJ / cm ² is 3.41, and the anisotropy value at 400 mJ / cm ² . The value was 1.51. The irradiation amount of the ultraviolet ray having the highest anisotropy was 300 mJ / cm ² , and was the optimum irradiation condition in the photo-alignment treatment.

(Example 10)
The liquid crystal aligning agent (4) obtained in Example 4 was filtered through a 1.0 μm filter, and spin-coated on a 30 mm × 40 mm ITO substrate. After drying on an 80 ° C. hot plate for 2 minutes, baking was performed in a hot air circulation oven at 230 ° C. for 14 minutes to form a coating film having a thickness of 100 nm. The surface of the coating film was irradiated with a linearly polarized ultraviolet ray having a wavelength of 254 nm with an extinction ratio of 26: 1 via a polarizing plate, and the height of anisotropy with respect to the alignment direction of the obtained liquid crystal alignment film was measured. The anisotropy value when the UV irradiation dose is 100 mJ / cm ² is 1.15, the anisotropy value at 200 mJ / cm ² is 2.30, and the anisotropy value at 300 mJ / cm ² is 300 mJ / cm ² . The value was 2.26. The irradiation amount of the ultraviolet ray having the highest anisotropy was 200 mJ / cm ² , and was the optimum irradiation condition in the photo-alignment treatment.

(Example 11)
The liquid crystal aligning agent (5) obtained in Example 5 was filtered through a 1.0 μm filter, and spin-coated on a 30 mm × 40 mm ITO substrate. After drying on an 80 ° C. hot plate for 2 minutes, baking was performed in a hot air circulation oven at 230 ° C. for 14 minutes to form a coating film having a thickness of 100 nm. The surface of the coating film was irradiated with a linearly polarized ultraviolet ray having a wavelength of 254 nm with an extinction ratio of 26: 1 via a polarizing plate, and the height of anisotropy with respect to the alignment direction of the obtained liquid crystal alignment film was measured. The dose of the ultraviolet light at 4.29 anisotropy value at 100 mJ / cm ^2, anisotropy value at 150 mJ / cm ² at 5.23, the anisotropy at 200 mJ / cm ² The value was 3.00. The irradiation amount of the ultraviolet ray having the highest anisotropy was 150 mJ / cm ² , and was the optimum irradiation condition in the photo-alignment treatment.

(Example 12)
The liquid crystal aligning agent (6) obtained in Example 6 was filtered through a 1.0 μm filter, and then spin-coated on a 30 mm × 40 mm ITO substrate. After drying on an 80 ° C. hot plate for 2 minutes, baking was performed in a hot air circulation oven at 230 ° C. for 14 minutes to form a coating film having a thickness of 100 nm. The surface of the coating film was irradiated with a linearly polarized ultraviolet ray having a wavelength of 254 nm with an extinction ratio of 26: 1 via a polarizing plate, and the height of anisotropy with respect to the alignment direction of the obtained liquid crystal alignment film was measured. In anisotropy value 2.76 in dose is 100 mJ / cm ² of the ultraviolet, anisotropy value at 150 mJ / cm ² at 4.87, the anisotropy at 200 mJ / cm ² The value was 4.01. The irradiation amount of the ultraviolet ray having the highest anisotropy was 150 mJ / cm ² , and was the optimum irradiation condition in the photo-alignment treatment.

(Comparative Example 6)
The liquid crystal aligning agent (7) obtained in Comparative Example 1 was filtered through a 1.0 μm filter, and then spin-coated on a 30 mm × 40 mm ITO substrate. After drying on an 80 ° C. hot plate for 2 minutes, baking was performed in a hot air circulation oven at 230 ° C. for 14 minutes to form a coating film having a thickness of 100 nm. The surface of the coating film was irradiated with linearly polarized ultraviolet light having a wavelength of 254 nm with an extinction ratio of 26: 1 via a polarizing plate, and the degree of anisotropy with respect to the alignment direction of the obtained liquid crystal alignment film was measured. The dose of the ultraviolet light in anisotropic value 2.02 at 100 mJ / cm ^2, in anisotropy value 2.87 at 200 mJ / cm ^2, the anisotropy at 300 mJ / cm ² The value was 2.51. The irradiation amount of the ultraviolet ray having the greatest anisotropy was 200 mJ / cm ² , and was the optimum irradiation condition in the photo-alignment treatment.

(Comparative Example 7)
The liquid crystal aligning agent (8) obtained in Comparative Example 2 was filtered through a 1.0 μm filter, and then spin-coated on a 30 mm × 40 mm ITO substrate. After drying on an 80 ° C. hot plate for 2 minutes, baking was performed in a hot air circulation oven at 230 ° C. for 14 minutes to form a coating film having a thickness of 100 nm. The surface of the coating film was irradiated with linearly polarized ultraviolet light having a wavelength of 254 nm with an extinction ratio of 26: 1 via a polarizing plate, and the degree of anisotropy with respect to the alignment direction of the obtained liquid crystal alignment film was measured. The dose of the ultraviolet light in the anisotropy value 5.02 at 100 mJ / cm ^2, anisotropy value at 150 mJ / cm ² at 7.37, the anisotropy at 200 mJ / cm ² The value was 6.40. The irradiation amount of the ultraviolet ray having the largest anisotropy was 150 mJ / cm ² , and was the optimum irradiation condition in the photo-alignment treatment.

(Comparative Example 8)
The liquid crystal aligning agent (9) obtained in Comparative Example 3 was filtered through a 1.0 μm filter, and then spin-coated on a 30 mm × 40 mm ITO substrate. After drying on an 80 ° C. hot plate for 2 minutes, baking was performed in a hot air circulation oven at 230 ° C. for 14 minutes to form a coating film having a thickness of 100 nm. The surface of the coating film was irradiated with linearly polarized ultraviolet light having a wavelength of 254 nm with an extinction ratio of 26: 1 via a polarizing plate, and the degree of anisotropy with respect to the alignment direction of the obtained liquid crystal alignment film was measured. The dose of the ultraviolet light at 4.11 anisotropy value at 50 mJ / cm ^2, anisotropy value at 100 mJ / cm ² at 5.78, the anisotropy at 150 mJ / cm ² The value was 4.55. The irradiation amount of the ultraviolet ray having the greatest anisotropy was 100 mJ / cm ² , and was the optimum irradiation condition in the photo-alignment treatment.

(Comparative Example 9)
The liquid crystal aligning agent (10) obtained in Comparative Example 4 was filtered through a 1.0 μm filter, and then spin-coated on a 30 mm × 40 mm ITO substrate. After drying on an 80 ° C. hot plate for 2 minutes, baking was performed in a hot air circulation oven at 230 ° C. for 14 minutes to form a coating film having a thickness of 100 nm. The surface of the coating film was irradiated with linearly polarized ultraviolet light having a wavelength of 254 nm with an extinction ratio of 26: 1 via a polarizing plate, and the degree of anisotropy with respect to the alignment direction of the obtained liquid crystal alignment film was measured. The dose of the ultraviolet light in anisotropic value 1.60 at 400 mJ / cm ^2, in anisotropy value 1.78 at 600 mJ / cm ^2, the anisotropy at 800 mJ / cm ² The value was 1.33. The irradiation amount of the ultraviolet ray having the greatest anisotropy was 600 mJ / cm ² , and was the optimum irradiation condition in the photo-alignment treatment.

(Comparative Example 10)
The liquid crystal aligning agent (11) obtained in Comparative Example 5 was filtered through a 1.0 μm filter, and then spin-coated on a 30 mm × 40 mm ITO substrate. After drying on an 80 ° C. hot plate for 2 minutes, baking was performed in a hot air circulation oven at 230 ° C. for 14 minutes to form a coating film having a thickness of 100 nm. The surface of the coating film was irradiated with linearly polarized ultraviolet light having a wavelength of 254 nm with an extinction ratio of 26: 1 via a polarizing plate, and the degree of anisotropy with respect to the alignment direction of the obtained liquid crystal alignment film was measured. The anisotropy value at 5.5 mJ / cm ² of the UV irradiation is 5.54, the anisotropy value at 100 mJ / cm ² is 7.34, and the anisotropy value at 200 mJ / cm ² . The value was 6.40. The irradiation amount of the ultraviolet ray having the greatest anisotropy was 100 mJ / cm ² , and was the optimum irradiation condition in the photo-alignment treatment.

(Example 13)
After the liquid crystal aligning agent (1) obtained in Example 1 is filtered through a 1.0 μm filter, the prepared substrate with electrodes and a columnar spacer with a height of 4 μm on which an ITO film is formed on the back surface are provided. It apply | coated to the glass substrate by spin coat application | coating. After drying on an 80 ° C. hot plate for 5 minutes, baking was carried out in a hot air circulating oven at 230 ° C. for 20 minutes to form a coating film having a thickness of 100 nm. The surface of the coating film was irradiated with 150 mJ / cm ² of linearly polarized UV light having a extinction ratio of 26: 1 through a polarizing plate at 150 mJ / cm ² and then heated on a hot plate at 230 ° C. for 14 minutes to obtain a substrate with a liquid crystal alignment film Got. The two substrates are combined as a set, a sealant is printed on the substrate, and the other substrate is bonded so that the liquid crystal alignment film faces and the alignment direction is 0 °, and then the sealant is added. An empty cell was produced by curing. Liquid crystal MLC-7026-100 (manufactured by Merck & Co., Inc.) was injected into this empty cell by a reduced pressure injection method, and the injection port was sealed to obtain an FFS drive liquid crystal cell. Thereafter, the obtained liquid crystal cell was heated at 110 ° C. for 1 hour and left to stand for evaluation of afterimages by long-term AC driving. The value of the angle Δ of this liquid crystal cell after long-term AC driving was 0.08 degrees. Further, as a result of observing the bright spots in the cell, the number of bright spots was less than 10, which was favorable.

(Example 14)
The same method as in Example 13 except that the liquid crystal aligning agent (1) obtained in Example 1 was irradiated with polarized ultraviolet light, then immersed in 2-propanol for 3 minutes, and then immersed in pure water for 1 minute. Thus, an FFS drive liquid crystal cell was produced. This FFS drive liquid crystal cell was subjected to afterimage evaluation by long-term AC drive. The value of the angle Δ of this liquid crystal cell after long-term AC driving was 0.10 degrees. Further, as a result of observing the bright spots in the cell, the number of bright spots was less than 10, which was favorable.

(Examples 15 to 19)
Each coating film having a thickness of 100 nm was formed in the same manner as in Example 13 except that the liquid crystal aligning agents (2) to (6) obtained in Examples 2 to 6 were used. Each of these coating surfaces was irradiated with a linearly polarized ultraviolet ray having a wavelength of 254 nm with an extinction ratio of 26: 1 through a polarizing plate at an irradiation amount (unit: mJ / cm ² ) described in Table 1 below. Except for the above, a substrate with a liquid crystal alignment film and then each FFS drive liquid crystal cell were prepared in the same manner as in Example 13, and afterimage evaluation was performed by long-term alternating current drive. Table 1 shows the value of the angle Δ of each liquid crystal cell after long-term AC driving and the results of observation of the bright spots in the cell. In addition, the number of luminescent spots was evaluated as good when it was less than 10, and the number of luminescent spots as 10 or more was evaluated as defective.

(Comparative Examples 11 to 15)
Each coating film having a thickness of 100 nm was formed in the same manner as in Example 13 except that the liquid crystal aligning agents (7) to (11) obtained in Comparative Examples 1 to 5 were used. Each of these coating surfaces was irradiated with a linearly polarized ultraviolet ray having a wavelength of 254 nm with an extinction ratio of 26: 1 through a polarizing plate at an irradiation amount (unit: mJ / cm ² ) described in Table 1 below. Except for the above, a substrate with a liquid crystal alignment film and then each FFS drive liquid crystal cell were prepared in the same manner as in Example 13, and afterimage evaluation was performed by long-term alternating current drive. Table 1 shows the value of the angle Δ of each liquid crystal cell after long-term AC driving and the results of observation of the bright spots in the cell. In addition, the number of luminescent spots was evaluated as good when it was less than 10, and the number of luminescent spots as 10 or more was evaluated as defective.

With the liquid crystal aligning agent of the present invention, even when a negative liquid crystal is used, a bright spot due to a decomposition product derived from the liquid crystal aligning film generated during the photo-alignment treatment does not occur, and a liquid crystal aligning film having good afterimage characteristics can be obtained. I can do it. Therefore, the liquid crystal alignment film obtained from the liquid crystal aligning agent of the present invention has few bright spots that cause a decrease in contrast, and reduces afterimages caused by alternating current driving in liquid crystal display elements of the IPS driving method and the FFS driving method. Thus, an IPS driving type or FFS driving type liquid crystal display element having excellent afterimage characteristics can be obtained. Therefore, it can be used in a liquid crystal display element that requires high display quality.

Claims (12)

1. It contains at least one polymer (A) selected from the group consisting of a polyimide precursor having structural units represented by the following formula (1) and the following formula (2) and an imidized polymer of the polyimide precursor. A liquid crystal aligning agent characterized by that.
   

   

   (In the formula (1), equation (2), _{X 1} and _{X 2 are} each independently a tetravalent organic group, _{R 1} and _{R 2} are each independently a hydrogen atom, or carbon atoms An alkyl group having 1 to 4; A ₁ , A ₂ , A ₃ , and A ₄ are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; and Z ₁ , Z ₂ , Z ₃ , And Z ₄ are each independently a hydrogen atom, a halogen atom, or an alkyl group having 1 to 4 carbon atoms, and n is an integer of 1 to 4).
2. The content ratio of the structural unit represented by the formula (1) is 10 to 50 mol% with respect to 1 mol of all the structural units of the polymer (A), and the structure represented by the formula (2) The liquid crystal aligning agent according to claim 1, wherein the content ratio of the units is 20 to 90 mol% with respect to 1 mol of all the structural units of the polymer (A).
3. In formula (1), formula (2), and formula (3), X ₁ , X ₂ and X ₃ are selected from the group consisting of structures represented by the following formulas (X1-1) to (X1-9) The liquid crystal aligning agent according to claim 1, wherein the liquid crystal aligning agent is at least one kind.
   

   

   (In Formula (X1-1), R ₃ , R ₄ , R ₅ , and R ₆ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkenyl group having 2 to 6 carbon atoms. , An alkynyl group or a phenyl group, which may be the same or different.)
4. The liquid crystal aligning agent according to any one of claims 1 to 3, wherein the polymer (A) has a structural unit represented by the following formula (3) as a structural unit other than the formula (1) and the formula (2).
   

   

   (Equation (3), _{X 3} are each _{independently} at least one selected from the group consisting of structures represented by the formula (X1-1) ~ (X1-9), R 3 is hydrogen An atom or an alkyl group having 1 to 4 carbon atoms, and Y ₁ is at least one selected from the group consisting of structures represented by the following formulas [1d-1] to [1d-7].
   

   

   (In the formulas [1d-1] to [1d-7], D is a tert-butoxymethoxycarbonyl group, and n1 to n5 are each independently an integer of 1 to 5.)
5. 5. The liquid crystal alignment according to any one of 1 to 4 above, wherein the content ratio of the structural unit represented by the formula (3) is 10 to 50 mol% with respect to 1 mol of all the structural units of the polymer (A). Agent.
6. In Formula (1), Formula (2), and Formula (3), X ₁ , X _2, and X ₃ are at least one selected from the group consisting of structures represented by Formula (X1-1) above Item 6. The liquid crystal aligning agent according to any one of Items 1 to 5.
7. Equation (1) is selected from the group consisting of structural formula (2), and that in the formula _(3), X 1, _{X 2} and _{X 3} are represented by the following formula (X1-10) and (X1-11) 7. The liquid crystal aligning agent according to claim 1, wherein the liquid crystal aligning agent is at least one kind.
   

   
8. The liquid crystal aligning agent according to any one of claims 1 to 7, wherein in the formulas (1), (2), and (3), X ₁ , X _2, and X ₃ are the formula (X1-11).
9. A liquid crystal alignment film obtained by irradiating a film obtained by applying and baking the liquid crystal aligning agent according to any one of claims 1 to 8 with polarized ultraviolet rays.
10. A liquid crystal alignment film obtained by an ink jet method using the liquid crystal aligning agent according to any one of claims 1 to 8.
11. A liquid crystal display element having the liquid crystal alignment film according to claim 9.
12. The liquid crystal display element according to claim 11, wherein the liquid crystal is a negative liquid crystal material.