New diamines

Abstract

To provide a liquid crystal aligning agent for producing a liquid crystal alignment film for optical alignment which is free from bright spots and provides good afterimage characteristics even when a negative liquid crystal is used, and to provide the liquid crystal alignment film, and a novel diamine that serves as a material for a liquid crystal display element.SOLUTION: A diamine disclosed herein is represented by the following formula. (In the formula, R1 and R2 independently represent a single bond, -O-, -S-, -NR12-, ester bond, amide bond, thioester bond, urea bond, carbonate bond, or a carbamate bond, R12 represents a hydrogen atom or a methyl group, and A represents an alkylene group having 1 or 2 carbon atoms.)SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a liquid crystal aligning agent used in the production of a liquid crystal display element, a liquid crystal alignment film obtained from the liquid crystal aligning agent, and a novel diamine serving as a raw material for a liquid crystal display element having the liquid crystal alignment film. [Background technology]

[0002] The photo-alignment method is an industrially simple manufacturing process as a rubbing-less alignment treatment method. In particular, in liquid crystal display elements using the IPS (In-Plane-Switching) driving method or the FFS (Flinge field Switching) driving method, the use of a liquid crystal alignment film obtained by the above photo-alignment method is expected to improve the contrast and viewing angle characteristics of the liquid crystal display element compared to a liquid crystal alignment film obtained by a rubbing treatment method (Patent Document 1). This makes it possible to improve the performance of the liquid crystal display element, and the method is attracting attention as a promising liquid crystal alignment treatment method.

[0003] However, the liquid crystal alignment film obtained by the photo-alignment method has a problem that the anisotropy in the alignment direction of the polymer film is smaller than that obtained by rubbing. If the anisotropy is small, sufficient liquid crystal alignment cannot be obtained, and when the liquid crystal display element is formed, problems such as the generation of an afterimage occur (Non-Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 9-297313 [Non-patent literature]

[0005] [Non-Patent Document 1] "Liquid Crystal Photo-Alignment Film" Functional Materials, Vol. 17 (1997), No. 11, pp. 13-22 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to suppress the occurrence of afterimages after AC driving due to insufficient anisotropy in the alignment direction of a liquid crystal alignment film obtained by a photoalignment method. [Means for solving the problem]

[0007] The present inventors have conducted extensive research to solve the above problems and have completed the present invention. A liquid crystal aligning agent comprising at least one polymer selected from the group consisting of a polyimide precursor having a structure represented by the following formula (1) in its main chain and an imidized polymer of the polyimide precursor: [ka] In the formula, R1 and R2 each independently represent a single bond, -O-, -S-, or -NR 12 -, ester bond, amide bond, thioester bond, urea bond, carbonate bond, or carbamate bond. 12 is a hydrogen atom or a methyl group. A is an alkylene group having 1 or 2 carbon atoms. B1 and B2 have the same structure and are divalent organic groups selected from the following structures. [ka] In the formula, R4 is an alkylene group having 1 to 5 carbon atoms, and R5 is a hydrogen atom, a methyl group, a hydroxyl group, or a methoxy group. Effect of the Invention

[0008] By using the liquid crystal aligning agent of the present invention, it is possible to obtain a liquid crystal alignment film that has high liquid crystal alignment properties and can suppress the occurrence of AC afterimages. It is not entirely clear why the above-mentioned effects are obtained by using the liquid crystal alignment agent of the present invention, but it is presumed that this is because the chemical structure of the diamine used as the raw material of the polymer that constitutes the liquid crystal alignment material is rigid and has a symmetrical structure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] <Specific structure> The main chain of the polymer constituting the liquid crystal aligning agent of the present invention contains the specific structure represented by the above formula (1) (hereinafter, also referred to as the specific structure). [ka] In the above formula (1), R1 and R2 each independently represent a single bond, -O-, -S-, or -NR 12 -, ester bond, amide bond, thioester bond, urea bond, carbonate bond, or carbamate bond, and R 12 is a hydrogen atom or a methyl group. A is an alkylene group having 1 or 2 carbon atoms. B1 and B2 have the same structure and are divalent organic groups selected from the following structures. By having B1 and B2 have the same structure, a liquid crystal alignment film having high liquid crystal alignment properties can be obtained.

[0010] [ka] In the above formula, R4 is an alkylene group having 1 to 5 carbon atoms. R5 is a hydrogen atom, a methyl group, a hydroxyl group, or a methoxy group.

[0011] In the above formula (1), R1 and R2 are each preferably a single bond, -O-, -S-, -NR 12 -, an ester bond or an amide bond is preferred, and -O- is particularly preferred. 12 From the viewpoint of liquid crystal alignment, A is preferably a hydrogen atom or a methyl group. Also, A is preferably an alkylene group having a carbon chain length of 2 from the viewpoint of liquid crystal alignment. From the viewpoint of liquid crystal alignment, B1 and B2 are preferably a biphenylene group. In the above formula, from the viewpoint of liquid crystal alignment, R4 is preferably an alkylene group having 1 to 3 carbon atoms, and R5 is preferably a hydrogen atom or a methyl group. The specific structure is preferably contained in the diamine, which is the raw material of the polyimide precursor. Specific examples of the diamine having the specific structure include, but are not limited to, the following diamines. The polyimide precursor is preferably obtained by polymerizing a diamine component containing at least one diamine selected from the following diamines with a tetracarboxylic acid component. [ka]

[0012] [ka] (R5 is defined as above.)

[0013] [ka] In the above formula, R5 and R 12 are the same as defined above, including preferred examples of each.

[0014] The diamine having the above specific structure is preferably a diamine having amino groups bonded to both ends of the above specific structure, and among these, the following diamines are preferred from the viewpoints of alignment and reduction of bright spots when used in a liquid crystal display device. [ka] In the above formula, R1, R2, and A are as described above, including preferred examples of each. As the diamine having the above specific structure, the following diamines are particularly preferred. [ka]

[0015] <Polymer> The polyimide precursor constituting the liquid crystal aligning agent of the present invention contains a structural unit of the following formula (2). [ka]

[0016] X1 is at least one selected from the group consisting of structures represented by the following formulae (X1-1) and (X1-2): Among these, the following formula (X1-2) is preferred from the viewpoint of liquid crystal alignment properties. [ka]

[0017] Y1 is a divalent organic group represented by formula (1). R3 is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. Specific examples include a methyl group, an ethyl group, a propyl group, an i-propyl group, an n-butyl group, an i-butyl group, an s-butyl group, a t-butyl group, an n-pentyl group, etc. From the viewpoint of ease of imidization by heating, R3 is preferably a hydrogen atom or a methyl group.

[0018] Z1 and Z2 are each independently a hydrogen atom, or an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or an alkynyl group having 2 to 10 carbon atoms, which may have a substituent. Specific examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a t-butyl group, a hexyl group, an octyl group, a decyl group, a cyclopentyl group, a cyclohexyl group, and a bicyclohexyl group. Examples of the alkenyl group include those in which one or more CH2-CH2 structures present in the above alkyl groups are replaced with a CH=CH structure. Specific examples of the alkenyl group include a vinyl group, an allyl group, a 1-propenyl group, an isopropenyl group, a 2-butenyl group, a 1,3-butadienyl group, a 2-pentenyl group, a 2-hexenyl group, a cyclopropenyl group, a cyclopentenyl group, and a cyclohexenyl group. Examples of the alkynyl group include those in which one or more CH2-CH2 structures present in the above alkyl groups are replaced with a C≡C structure. Specific examples include an ethynyl group, a 1-propynyl group, and a 2-propynyl group.

[0019] The above alkyl group, alkenyl group, and alkynyl group may have a substituent, and may further form a ring structure depending on the substituent. Here, the formation of a ring structure by a substituent means that the substituents are bonded to each other or to a part of the parent skeleton to form a ring structure. Examples of the substituent include a halogen group, a hydroxyl group, a thiol group, a nitro group, an aryl group, an organooxy group, an organothio group, an organosilyl group, an acyl group, an ester group, a thioester group, a phosphate ester group, an amide group, an alkyl group, an alkenyl group, and an alkynyl group. The halogen group includes a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom. The aryl group includes a phenyl group, which may be further substituted with the other substituents described above.

[0020] The organooxy group can have a structure represented by -OR. The Rs may be the same or different, and examples thereof include the alkyl group, alkenyl group, alkynyl group, and aryl group described above. These Rs may further be substituted with the substituents described above. Specific examples include a methoxy group, an ethoxy group, a propyloxy group, a butoxy group, a pentyloxy group, a hexyloxy group, a heptyloxy group, and an octyloxy group. The organothio group can have a structure represented by -SR. Examples of R include the alkyl group, alkenyl group, alkynyl group, and aryl group described above. These R groups may be further substituted with the substituents described above. Specific examples include a methylthio group, an ethylthio group, a propylthio group, a butylthio group, a pentylthio group, a hexylthio group, a heptylthio group, and an octylthio group.

[0021] The organosilyl group may have a structure represented by -Si-(R)3. The R may be the same or different, and may be the alkyl group, alkenyl group, alkynyl group, aryl group, etc., as described above. These R may be further substituted with the substituents described above. Specific examples include a trimethylsilyl group, a triethylsilyl group, a tripropylsilyl group, a tributylsilyl group, a tripentylsilyl group, a trihexylsilyl group, a pentyldimethylsilyl group, and a hexyldimethylsilyl group. The acyl group may have a structure represented by -C(O)-R. Examples of R include the alkyl group, alkenyl group, and aryl group described above. These R groups may be further substituted with the substituents described above. Specific examples include a formyl group, an acetyl group, a propionyl group, a butyryl group, an isobutyryl group, a valeryl group, an isovaleryl group, and a benzoyl group.

[0022] The ester group can have a structure represented by -C(O)OR or -OC(O)-R. Examples of R include the above-mentioned alkyl group, alkenyl group, alkynyl group, aryl group, etc. These R may be further substituted with the above-mentioned substituent. The thioester group can have a structure represented by -C(S)OR or -OC(S)-R. Examples of R include the above-mentioned alkyl group, alkenyl group, alkynyl group, aryl group, etc. These R may be further substituted with the above-mentioned substituent. The phosphate ester group can have a structure represented by -OP(O)-(OR)2. The Rs may be the same or different, and examples thereof include the above-mentioned alkyl groups, alkenyl groups, alkynyl groups, and aryl groups. These Rs may further be substituted with the above-mentioned substituents.

[0023] The amide group may have a structure represented by -C(O)NH2, -C(O)NHR, -NHC(O)R, -C(O)N(R)2, or -NRC(O)R. The R may be the same or different, and may be, for example, the alkyl group, alkenyl group, alkynyl group, and aryl group described above. These R may be further substituted with the substituent described above. Examples of the aryl group include the same aryl groups as those described above, which may be further substituted with other substituents as described above. Examples of the alkyl group include the same alkyl groups as those described above. The alkyl group may be further substituted with other substituents as described above. Examples of the alkenyl group include the same alkenyl groups as those described above. This alkenyl group may be further substituted with other substituents as described above. Examples of the alkynyl group include the same alkynyl groups as those described above. This alkynyl group may be further substituted with other substituents as described above.

[0024] Generally, introduction of a bulky structure may reduce the reactivity of the amino group or the liquid crystal alignment property, so Z1 and Z2 are more preferably a hydrogen atom or an alkyl group having 1 to 5 carbon atoms which may have a substituent, and particularly preferably a hydrogen atom, a methyl group, or an ethyl group. The structural unit represented by the above formula (2) is preferably contained in an amount of 20 to 100 mol % based on all structural units, and from the viewpoint of liquid crystal alignment, it is particularly preferably 30 to 100 mol %.

[0025] <Other structural units> When the polymer constituting the liquid crystal aligning agent of the present invention contains a structural unit other than the structural unit of the above formula (2), the structural unit is represented by the following formula (3). [ka] The definitions of R3, Z1 and Z2 are the same as those in formula (2) above.

[0026] X2 is a tetravalent organic group, and Y2 is a divalent organic group. X2 is a tetravalent organic group derived from a tetracarboxylic acid derivative, and its structure is not particularly limited. In the polyimide precursor, X2 may be a mixture of two or more types. Specific examples of X2 include structures of the following formulas (X-1) to (X-44).

[0027] [ka]

[0028] [ka]

[0029] [ka]

[0030] [ka]

[0031] R to R in the above formula (X-1) 11 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 having 2 to 6 carbon atoms, or a phenyl group. 11 However, if it has a bulky structure, it may deteriorate the liquid crystal alignment property, so a hydrogen atom, a methyl group or an ethyl group is more preferable, and a hydrogen atom or a methyl group is particularly preferable.

[0032] In formula (3), Y2 is a divalent organic group derived from diamine, and the structure is not particularly limited. Specific examples of the structure of Y2 include the following (Y-1) to (Y-118). [ka]

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[0044] [ka]

[0045] [ka]

[0046] [ka]

[0047] [ka]

[0048] [ka]

[0049] (In formula (Y-109), m and n are each independently an integer of 1 to 11, and m+n is an integer of 2 to 12; in formula (Y-114), h is an integer of 1 to 3; and in formulas (Y-111) and (Y-117), j is an integer of 0 to 3.) The polyimide precursor used in the present invention is obtained by the reaction of a diamine component with a tetracarboxylic acid derivative, and examples of the polyimide precursor include polyamic acid and polyamic acid ester.

[0050] <Polyimide precursor (polyamic acid)> The polyamic acid, which is the polyimide precursor used in the present invention, is produced by the following method. Specifically, the compound can be synthesized by reacting a tetracarboxylic dianhydride with a diamine in the presence of an organic solvent at −20 to 150° C., preferably 0 to 50° C., for 30 minutes to 24 hours, preferably 1 to 12 hours.

[0051] The reaction between the diamine component and the tetracarboxylic acid component is usually carried out in an organic solvent. The organic solvent used in this case is not particularly limited as long as it dissolves the generated polyimide precursor. Specific examples of the organic solvent used in the reaction are listed below, but are not limited to these examples. For example, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, γ-butyrolactone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide, or 1,3-dimethyl-imidazolidinone can be mentioned. In addition, when the polyimide precursor has high solubility, methyl ethyl ketone, cyclohexanone, cyclopentanone, 4-hydroxy-4-methyl-2-pentanone, or the organic solvents represented by the following formulae [D-1] to [D-3] can be used.

[0052] [ka] In formula [D-1], D 1 represents an alkyl group having 1 to 3 carbon atoms, and in formula [D-2], D 2 represents an alkyl group having 1 to 3 carbon atoms, and in formula [D-3], D 3 represents an alkyl group having 1 to 4 carbon atoms.

[0053] These solvents may be used alone or in combination. Furthermore, even if the solvent does not dissolve the polyimide precursor, it may be mixed with the above-mentioned solvent to the extent that the generated polyimide precursor does not precipitate. Furthermore, since moisture in the solvent inhibits the polymerization reaction and further causes hydrolysis of the generated polyimide precursor, it is preferable to use a solvent that has been dehydrated and dried. The concentration of the polyamic acid polymer in the reaction system is preferably from 1 to 30% by mass, and more preferably from 5 to 20% by mass, from the viewpoints that precipitation of the polymer is unlikely to occur and a high molecular weight polymer is easily obtained.

[0054] The polyamic acid obtained as described above can be recovered by injecting the reaction solution into a poor solvent while thoroughly stirring it to precipitate the polymer. In addition, the precipitation can be carried out several times, washed with a poor solvent, and then dried at room temperature or by heating to obtain a purified polyamic acid powder. The poor solvent is not particularly limited, but examples thereof include water, methanol, ethanol, hexane, butyl cellosolve, acetone, and toluene.

[0055] <Polyimide precursor (polyamic acid ester)> The polyamic acid ester, which is a polyimide precursor used in the present invention, can be produced by the following production method (1), (2) or (3).

[0056] (1) Manufacturing from polyamic acid The polyamic acid ester can be produced by esterifying the polyamic acid produced as described above. Specifically, the polyamic acid can be produced by reacting the polyamic acid with an esterifying agent in the presence of an organic solvent at −20 to 150° C., preferably 0 to 50° C., for 30 minutes to 24 hours, preferably 1 to 4 hours.

[0057] The esterification agent is preferably one that can be easily removed by purification, and examples of the esterification agent include 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, etc. The amount of the esterification agent to be added is preferably 2 to 6 molar equivalents relative to 1 mole of the repeating unit of the polyamic acid.

[0058] Examples of organic solvents include N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, γ-butyrolactone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide, and 1,3-dimethyl-imidazolidinone. In addition, when the polyimide precursor has high solubility in the solvent, methyl ethyl ketone, cyclohexanone, cyclopentanone, 4-hydroxy-4-methyl-2-pentanone, or the solvents represented by the formulas [D-1] to [D-3] can be used. These solvents may be used alone or in combination. Furthermore, even if the solvent does not dissolve the polyimide precursor, it may be mixed with the above-mentioned solvent to the extent that the generated polyimide precursor does not precipitate. Furthermore, since moisture in the solvent inhibits the polymerization reaction and further causes hydrolysis of the generated polyimide precursor, it is preferable to use a solvent that has been dehydrated and dried.

[0059] The solvent used in the above reaction is preferably N,N-dimethylformamide, N-methyl-2-pyrrolidone, or γ-butyrolactone from the viewpoint of the solubility of the polymer, and these may be used alone or in combination of two or more. The concentration during production is preferably 1 to 30% by mass, more preferably 5 to 20% by mass, from the viewpoints that the polymer is less likely to precipitate and a high molecular weight product is easily obtained.

[0060] (2) When produced by reacting a tetracarboxylic acid diester dichloride with a diamine Polyamic acid esters can be prepared from tetracarboxylic acid diester dichlorides and diamines. Specifically, it can be produced by reacting a tetracarboxylic acid diester dichloride with a diamine in the presence of a base and an organic solvent at −20 to 150° C., preferably 0 to 50° C., for 30 minutes to 24 hours, preferably 1 to 4 hours.

[0061] As the base, pyridine, triethylamine, 4-dimethylaminopyridine, etc. can be used, but pyridine is preferred because the reaction proceeds mildly. The amount of base added is preferably 2 to 4 times the molar amount of tetracarboxylic acid diester dichloride, because it is an amount that can be easily removed and a high molecular weight product can be easily obtained. The solvent used in the above reaction is preferably N-methyl-2-pyrrolidone or γ-butyrolactone in terms of the solubility of the monomer and polymer, and these may be used alone or in combination of two or more. The polymer concentration during production is preferably 1 to 30% by mass, more preferably 5 to 20% by mass, in terms of preventing polymer precipitation and facilitating the production of a high molecular weight polymer. In addition, in order to prevent hydrolysis of the tetracarboxylic acid diester dichloride, the solvent used in the production of the polyamic acid ester is preferably as dehydrated as possible, and is preferably used in a nitrogen atmosphere to prevent the inclusion of outside air.

[0062] (3) Production from tetracarboxylic acid diester and diamine The polyamic acid ester can be produced by polycondensation of a tetracarboxylic acid diester and a diamine. Specifically, the compound can be produced by reacting a tetracarboxylic acid diester with a diamine in the presence of a condensing agent, a base, and an organic solvent at 0 to 150° C., preferably 0 to 100° C., for 30 minutes to 24 hours, preferably 3 to 15 hours.

[0063] The condensing agent may be triphenyl phosphite, dicyclohexylcarbodiimide, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, N,N'-carbonyldiimidazole, dimethoxy-1,3,5-triazinylmethylmorpholinium, 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)diphenylphosphonate, etc. The amount of the condensing agent added is preferably 2 to 3 times the molar amount of the tetracarboxylic acid diester.

[0064] The base may be a tertiary amine such as pyridine, triethylamine, etc. The amount of base added is preferably 2 to 4 times the molar amount of the diamine component, since it is an amount that can be easily removed and a high molecular weight substance can be easily obtained. In the above reaction, the reaction can be efficiently carried out by adding a Lewis acid as an additive. The Lewis acid is preferably a lithium halide such as lithium chloride or lithium bromide. The amount of Lewis acid added is preferably 0 to 1.0 times the molar amount of the diamine component.

[0065] Among the above three methods for producing a polyamic acid ester, the above method (1) or (2) is particularly preferred since it gives a high molecular weight polyamic acid ester. The polyamic acid ester solution obtained as described above can be poured into a poor solvent while being thoroughly stirred to precipitate the polymer. Precipitation is carried out several times, washed with a poor solvent, and then dried at room temperature or by heating to obtain a purified polyamic acid ester powder. The poor solvent is not particularly limited, but examples thereof include water, methanol, ethanol, hexane, butyl cellosolve, acetone, and toluene.

[0066] <Polyimide> The polyimide used in the present invention can be produced by imidizing the above-mentioned polyamic acid ester or polyamic acid. When producing a polyimide from a polyamic acid ester, a simple method is chemical imidization in which a basic catalyst is added to a polyamic acid ester solution or a polyamic acid solution obtained by dissolving a polyamic acid ester resin powder in an organic solvent. Chemical imidization is preferred 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.

[0067] Chemical imidization can be carried out by stirring the polyamic acid ester to be imidized in an organic solvent in the presence of a basic catalyst. The organic solvent can be the solvent used in the polymerization reaction described above. Examples of the basic catalyst include pyridine, triethylamine, trimethylamine, tributylamine, and trioctylamine. Among them, triethylamine is preferred because it has sufficient basicity to promote the reaction. The temperature when carrying out the imidization reaction is -20 to 140°C, preferably 0 to 100°C, and the reaction time is preferably 1 to 100 hours. The amount of the basic catalyst is 0.5 to 30 times by mole, preferably 2 to 20 times by mole, the amount of the amic acid ester group. The imidization rate of the obtained polymer can be controlled by adjusting the amount of the catalyst, the temperature, the reaction time, etc. Since the added catalyst and the like remain in the solution after the imidization reaction, it is preferable to recover the obtained imidized polymer by the means described below and re-dissolve it in an organic solvent to obtain the liquid crystal aligning agent of the present invention.

[0068] When producing polyimide from polyamic acid, a simple method is chemical imidization in which a catalyst is added to a solution of polyamic acid obtained by reacting a diamine component with a tetracarboxylic dianhydride. Chemical imidization is preferred 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 imidization can be carried out by stirring the polyamic acid to be imidized in an organic solvent in the presence of a basic catalyst and an acid anhydride. The organic solvent can be the solvent used in the polymerization reaction described above. Examples of the basic catalyst include pyridine, triethylamine, trimethylamine, tributylamine, and trioctylamine. Among these, pyridine is preferred because it has a suitable basicity for promoting the reaction. Examples of the acid anhydride include acetic anhydride, trimellitic anhydride, and pyromellitic anhydride. Among these, acetic anhydride is preferred because it is easy to purify after the reaction is completed.

[0069] The temperature during the imidization reaction is -20 to 140°C, preferably 0 to 100°C, and the reaction time is preferably 1 to 100 hours. The amount of the basic catalyst is 0.5 to 30 times by mole, preferably 2 to 20 times by mole, the amic acid group, and the amount of the acid anhydride is 1 to 50 times by mole, preferably 3 to 30 times by mole, the amic acid group. The imidization rate of the resulting polymer can be controlled by adjusting the amount of the catalyst, temperature, reaction time, etc.

[0070] Since the added catalyst and the like remain in the solution after the imidization reaction of the polyamic acid ester or polyamic acid, it is preferable to recover the obtained imidized polymer by the means described below and re-dissolve it in an organic solvent to obtain the liquid crystal aligning agent of the present invention. The polyimide solution obtained as described above can be poured into a poor solvent while being thoroughly stirred to precipitate the polymer. The precipitation is carried out several times, and after washing with a poor solvent, the polymer can be dried at room temperature or by heating to obtain a purified polyimide powder. The poor solvent is not particularly limited, but examples thereof include methanol, acetone, hexane, butyl cellosolve, heptane, methyl ethyl ketone, methyl isobutyl ketone, ethanol, toluene, and benzene.

[0071] <Liquid crystal alignment agent> The liquid crystal aligning agent of the present invention contains at least one polymer selected from the group consisting of polyimide precursors having a specific structure in the main chain and imidized polymers of the polyimide precursors. The molecular weight of the polymer is preferably 2,000 to 500,000 in weight average molecular weight (Mw), more preferably 5,000 to 300,000, and even more preferably 10,000 to 100,000. The number average molecular weight (Mn) is preferably 1,000 to 250,000, more preferably 2,500 to 150,000, and even more preferably 5,000 to 50,000.

[0072] The concentration of the polymer in the liquid crystal aligning agent of the present invention can be appropriately changed depending on the thickness of the coating film to be formed, but it is preferably 1% by mass or more from the viewpoint of forming a uniform and defect-free coating film, and is preferably 10% by mass or less from the viewpoint of storage stability of the solution. The concentration of the polymer is preferably 2 to 7% by mass.

[0073] The organic solvent (hereinafter also referred to as a good solvent) that dissolves the polymer and is contained in the liquid crystal aligning agent used in the present invention is not particularly limited as long as the polymer can be uniformly dissolved in the organic solvent. Examples of the solvent include N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, dimethylsulfoxide, γ-butyrolactone, 1,3-dimethyl-imidazolidinone, methyl ethyl ketone, cyclohexanone, cyclopentanone, and 4-hydroxy-4-methyl-2-pentanone. Of these, it is preferable to use N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, or γ-butyrolactone. Furthermore, when the polymer of the present invention has high solubility in a solvent, it is preferable to use the solvents represented by the above formulas [D-1] to [D-3]. The content of the good solvent in the liquid crystal aligning agent of the present invention is preferably 20 to 99% by mass of the total solvent contained in the liquid crystal aligning agent, more preferably 20 to 90% by mass, and more preferably 30 to 80% by mass.

[0074] The liquid crystal aligning agent of the present invention can use a solvent (also called a poor solvent) that improves the coating property and surface smoothness of the liquid crystal alignment film when the liquid crystal aligning agent is applied. Specific examples of poor solvents are as follows. For example, 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, ethanol, 2-ethyl-1-hexanol, cyclohexanol, 1-methylcyclohexanol, 2-methylcyclohexanol, 3-methylcyclohexanol, 1,2-ethanediol, 1,2-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-heptanone, 4-heptanone, 3-ethoxybutyl acetate, 1-methylpentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, ethylene glycol monoethyl ether, noacetate, 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,Dipropylene glycol 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 mono Examples of the solvent include methyl ether, triethylene glycol monoethyl ether, methyl lactate, ethyl lactate, methyl acetate, ethyl acetate, n-butyl acetate, propylene glycol monoethyl ether acetate, 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, and the solvents represented by the formulas [D-1] to [D-3].

[0075] Of these, 1-hexanol, cyclohexanol, 1,2-ethanediol, 1,2-propanediol, propylene glycol monobutyl ether, ethylene glycol monobutyl ether, and dipropylene glycol dimethyl ether are preferred. The content of these poor solvents is preferably 1 to 80% by mass of the total solvent contained in the liquid crystal aligning agent, more preferably 10 to 80% by mass, and more preferably 20 to 70% by mass.

[0076] In addition to the above, the liquid crystal aligning agent of the present invention may contain a polymer other than the polymer of the present invention, a dielectric or conductive substance for the purpose of changing the electrical properties such as the dielectric constant or conductivity of the liquid crystal alignment film, a silane coupling agent for the purpose of improving the adhesion between the liquid crystal alignment film and the substrate, a crosslinking compound for the purpose of increasing the hardness or denseness of the film when made into a liquid crystal alignment film, and an imidization accelerator for the purpose of efficiently proceeding with imidization by heating the polyimide precursor when baking the coating film.

[0077] <Liquid crystal alignment film> The liquid crystal alignment film of the present invention is a film obtained by applying the liquid crystal alignment agent to a substrate, drying and baking. The substrate to which the liquid crystal alignment agent is applied is not particularly limited as long as it is a highly transparent substrate, and glass substrates, silicon nitride substrates, acrylic substrates, polycarbonate substrates and other plastic substrates can be used, and from the viewpoint of simplifying the process, it is preferable to use a substrate on which an ITO electrode or the like for driving liquid crystal is formed. In addition, in a reflective liquid crystal display element, an opaque material such as a silicon wafer can be used for only one substrate, and in this case, a light-reflecting material such as aluminum can be used for the electrode.

[0078] Examples of the method for applying the liquid crystal aligning agent of the present invention include a spin coating method, a printing method, and an ink jet method. The drying and baking process after applying the liquid crystal alignment agent can be performed at any temperature and time. Usually, in order to sufficiently remove the organic solvent contained, the drying temperature is preferably 50 to 120°C, and the drying time is preferably 1 to 10 minutes. The baking temperature is preferably 150 to 300°C, and the baking time is preferably 5 to 120 minutes. The thickness of the film after firing is not particularly limited, but if it is too thin, the reliability of the liquid crystal display element may be impaired, so the thickness is preferably 5 to 300 nm, more preferably 10 to 120 nm.

[0079] The method of photo-alignment treatment of the liquid crystal alignment film includes irradiating the coating film surface with radiation polarized in a certain direction, and optionally further heat-treating at a temperature of 150 to 250°C to impart liquid crystal alignment ability. As the radiation, ultraviolet rays and visible light having a wavelength of 100 to 800 nm can be used. Among these, ultraviolet rays having a wavelength of 100 to 400 nm are preferred, and those having a wavelength of 200 to 400 nm are particularly preferred. In order to improve the liquid crystal alignment property, the coating film substrate may be irradiated with radiation while being heated at 50 to 250°C. The radiation dose is 1 to 10,000 mJ / cm. 2 is preferable, and 100 to 5,000 mJ / cm 2 The liquid crystal alignment film prepared as described above can stably align liquid crystal molecules in a certain direction. The higher the extinction ratio of the polarized UV light, the more preferable it is, since this allows for higher anisotropy to be imparted. Specifically, the extinction ratio of linearly polarized UV light is preferably 10:1 or greater, and more preferably 20:1 or greater.

[0080] The film irradiated with polarized radiation may then be contact-treated with a solvent containing at least one selected from water and organic solvents. The solvent used in the contact treatment is not particularly limited as long as it dissolves the decomposition product generated by light irradiation. 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, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, propyl acetate, butyl acetate, and cyclohexyl acetate. Two or more of these solvents may be used in combination. From the viewpoint of versatility and safety, at least one selected from the group consisting of water, 2-propanol, 1-methoxy-2-propanol, and ethyl lactate is more preferable. Water, 2-propanol, or a mixed solvent of water and 2-propanol is particularly preferable.

[0081] In the present invention, examples of the contact treatment between the film irradiated with polarized radiation and a solution containing an organic solvent include immersion treatment and spray treatment, and a treatment that brings the film into sufficient contact with the liquid is preferred. Among these, a method of immersing the film in a solution containing an organic solvent for preferably 10 seconds to 1 hour, more preferably 1 to 30 minutes, is preferred. The contact treatment may be performed at room temperature or with heating, and is preferably performed at 10 to 80°C, more preferably 20 to 50°C. If necessary, a means for enhancing contact, such as ultrasonic waves, may be used. After the contact treatment, in order to remove the organic solvent in the solution used, either rinsing with a low boiling point solvent such as water, methanol, ethanol, 2-propanol, acetone, or methyl ethyl ketone and / or drying may be performed.

[0082] Furthermore, the membrane that has been contact-treated with the solvent may be heated at 150°C or higher for the purpose of drying the solvent and reorienting the molecular chains in the membrane. The heating temperature is preferably 150 to 300°C. The higher the temperature, the more the reorientation of the molecular chains is promoted, but if the temperature is too high, there is a risk of decomposition of the molecular chains. Therefore, the heating temperature is more preferably 180 to 250°C, and particularly preferably 200 to 230°C. If the heating time is too short, the effect of reorienting the molecular chains may not be obtained, whereas if it is too long, the molecular chains may decompose. Therefore, the heating time is preferably from 10 seconds to 30 minutes, and more preferably from 1 to 10 minutes.

[0083] <Liquid crystal display element> The liquid crystal display element of the present invention is obtained by preparing a substrate having a liquid crystal alignment film formed from the liquid crystal aligning agent of the present invention, and then preparing a liquid crystal cell by a known method, and using the cell to form an element. As an example of a method for fabricating a liquid crystal cell, a liquid crystal display element having a passive matrix structure will be described below as an example. However, a liquid crystal display element having an active matrix structure in which a switching element such as a TFT (Thin Film Transistor) is provided in each pixel portion constituting an image display may also be used.

[0084] First, transparent glass substrates are prepared, and a common electrode is provided on one substrate, and a segment electrode is provided on the other substrate. These electrodes can be, for example, ITO electrodes, 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 film made of SiO2-TiO2 formed by the sol-gel method. Next, the liquid crystal alignment film of the present invention is formed on each substrate. Next, one substrate is superimposed on the other substrate so that the alignment film surfaces face each other, and the periphery is bonded with a sealant. In order to control the gap between the substrates, it is usually preferable to mix a spacer into the sealant. It is also preferable to scatter spacers for controlling the gap between the substrates even in the in-plane portion where the sealant is not provided. In addition, an opening that can be filled with liquid crystal from the outside is usually provided in a part of the sealant.

[0085] Next, liquid crystal material is injected into the space surrounded by the two substrates and the sealant through an opening in the sealant. The opening is then sealed with an adhesive. The injection may be performed using a vacuum injection method or a method utilizing capillary action in the atmosphere. Next, polarizing plates are installed. Specifically, a pair of polarizing plates are attached to the surfaces of the two substrates opposite the liquid crystal layer. Through the above steps, the liquid crystal display element of the present invention is obtained. In the present invention, the sealing agent is, for example, a resin that has a reactive group such as an epoxy group, an acryloyl group, a methacryloyl group, a hydroxy group, an allyl group, an acetyl group, etc., and is cured by ultraviolet irradiation or heating. In particular, it is preferable to use a curable resin system that has both reactive groups, an epoxy group and a (meth)acryloyl group.

[0086] The above-mentioned sealing agent may be blended with an inorganic filler for the purpose of improving adhesion, moisture resistance, etc. The inorganic filler that can be used is not particularly limited, but specifically includes spherical silica, fused silica, crystalline silica, titanium oxide, titanium black, silicon carbide, silicon nitride, boron nitride, calcium carbonate, magnesium carbonate, barium sulfate, calcium sulfate, mica, talc, clay, alumina, magnesium oxide, zirconium oxide, aluminum hydroxide, calcium silicate, aluminum silicate, lithium aluminum silicate, zirconium silicate, barium titanate, glass fiber, carbon fiber, molybdenum disulfide, asbestos, etc. Preferred are spherical silica, fused silica, crystalline silica, titanium oxide, titanium black, silicon nitride, boron nitride, calcium carbonate, barium sulfate, calcium sulfate, mica, talc, clay, alumina, aluminum hydroxide, calcium silicate, aluminum silicate, etc. The above-mentioned inorganic fillers may be used in a mixture of two or more kinds. EXAMPLES

[0087] The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto. In the following, the abbreviations of compounds and the measuring methods of each property are as follows. NMP: N-methyl-2-pyrrolidone, BCS: Butyl cellosolve

[0088] [ka]

[0089] [ka]

[0090] [ka] In the formula, Fmoc represents a 9-fluorenylmethyloxycarbonyl group, and Boc represents a t-butoxycarbonyl group.

[0091] [ 1 H NMR] Equipment: Fourier transform superconducting nuclear magnetic resonance (FT-NMR) INOVA-400 (Varian) 400MHz Solvent: Deuterated dimethyl sulfoxide (DMSO-d6) Standard substance: Tetramethylsilane (TMS) Number of times: 8 or 32

[0092] [viscosity] The viscosity of the polyimide and polyamic acid solutions was measured using an E-type viscometer (VE-22H, manufactured by Toki Sangyo Co., Ltd.) with a sample amount of 1.1 mL, a cone rotor TE-1 (1°34′, R24), and a temperature of 25°C.

[0093] [Preparation of liquid crystal cells] A liquid crystal cell having the structure of an FFS mode liquid crystal display element was fabricated. First, a substrate with electrodes was prepared. The substrate was a rectangular glass plate measuring 30 mm x 50 mm and 0.7 mm thick. An ITO electrode with a solid pattern was formed on the substrate as the first layer, which constituted the counter electrode. A SiN (silicon nitride) film formed by CVD was formed on the first layer of the counter electrode as the second layer. The thickness of the second layer of the SiN film was 500 nm, and it functions as an interlayer insulating film. A comb-shaped pixel electrode formed by patterning the ITO film as the third layer was arranged on the second layer of the SiN film, forming two pixels, a first pixel and a second pixel. The size of each pixel was 10 mm long and about 5 mm wide. At this time, the first layer of the counter electrode and the third layer of the pixel electrode were electrically insulated by the action of the second layer of the SiN film.

[0094] The pixel electrode in the third layer has a comb-like shape composed of multiple electrode elements arranged in a "L" shape with the center bent at an internal angle of 160°. The width of each electrode element in the short direction is 3 μm, and the distance between the electrode elements is 6 μm. Since the pixel electrode forming each pixel is composed of multiple electrode elements arranged in a "L" shape with a bent center, the shape of each pixel is not rectangular, but has a shape similar to a bold "L" shape that is bent in the center like the electrode elements. Each pixel is divided into upper and lower parts by the bent part in the center, and has a first region above the bent part and a second region below the bent part.

[0095] Next, the obtained liquid crystal alignment agent was filtered through a filter with a pore size of 1.0 μm, and then spin-coated onto the above-prepared electrode-attached substrate and a glass substrate having a 4 μm-high columnar spacer with an ITO film formed on the back side. After drying for 2 minutes on a hot plate at 80°C, it was baked for 30 minutes in a hot air circulating oven at 230°C to form a coating film with a thickness of 100 nm. Polarized ultraviolet light was irradiated on the coating surface at 500 mJ / cm. 2 The substrate was irradiated with light so that the liquid crystal alignment film was aligned to obtain a substrate with a liquid crystal alignment film. The liquid crystal alignment film formed on the substrate with the electrodes was aligned so that the direction that equally divides the inner angle of the pixel bend portion was perpendicular to the alignment direction of the liquid crystal, and the liquid crystal alignment film formed on the second glass substrate was aligned so that the alignment direction of the liquid crystal on the first substrate was the same as the alignment direction of the liquid crystal on the second substrate when the liquid crystal cell was fabricated. The above two substrates were combined into a set, a sealant was printed on the substrate, and the other substrate was attached so that the alignment direction of the liquid crystal alignment film faces each other was 0°, and then the sealant was cured to fabricate an empty cell. The liquid crystal MLC-3019 (manufactured by Merck) 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. The obtained liquid crystal cell was then heated at 110°C for 1 hour and left overnight before being used for image retention evaluation.

[0096] [Evaluation of image lag due to long-term AC drive] Using the above liquid crystal cell, an AC voltage of ±5 V at a frequency of 30 Hz was applied for 120 hours in a constant temperature environment of 60° C. After that, the pixel electrode and the counter electrode of the liquid crystal cell were shorted, and the cell was left at room temperature for one day. After leaving it, the liquid crystal cell was placed between two polarizing plates arranged so that the polarization axes were perpendicular to each other, and the backlight was turned on with no voltage applied, and the arrangement angle of the liquid crystal cell was adjusted so that the brightness of the transmitted light was minimized. Then, the rotation angle when the liquid crystal cell was rotated from the angle at which the second region of the first pixel was the darkest to the angle at which the first region was the darkest was calculated as the angle Δ. Similarly, the second region and the first region of the second pixel were compared, and the same angle Δ was calculated. Then, the average value of the angle Δ values ​​of the first pixel and the second pixel was calculated as the angle Δ of the liquid crystal cell. The liquid crystal cell obtained above was rated as "X" when the angle Δ was 0.15° or more, as "△" when it was less than 0.15° and 0.1° or more, and as "◯" when it was less than 0.1°.

[0097] (Synthesis Example 1: Synthesis of DA-5) DA-5 was synthesized according to the following procedure. [ka]

[0098] Synthesis of compound [1] Ethylene glycol ditosylate (40.6 g, 110 mmol), 4-hydroxy-4'-nitrobiphenyl (49.5 g), and potassium carbonate (37.8 g) were added to dimethylformamide (500 g) and stirred at 80 ° C for 23 hours. After cooling to room temperature, the mixture was poured into pure water (1000 g) and stirred to precipitate crystals. The crystals were filtered, the residue was slurry washed with methanol (500 g), filtered, and the residue was dried to obtain a crude product (47.6 g). Dimethylformamide (333 g) was added to the crude product, which was then heated to 100 ° C to dissolve, and then methanol (333 g) was added and cooled to precipitate crystals. After filtration, the residue was dried to obtain compound [1] (yield: 40.2 g, yield: 80%, yellow crystals). 1H-NMR(400MHz, DMSO-d6, δppm):8.28(d, 4H, J = 9.2 Hz), 7.95(d, 4H, J = 9.2 Hz), 7.80(d, 4H, J = 9.2 Hz), 7.17(d, 4H, J = 9.2 Hz), 4.44(s, 4H).

[0099] Synthesis of compound [DA-5] Compound [1] (40.2 g) and 5% palladium carbon (4.0 g) were added to dimethylformamide (800 g) and stirred at 60°C under a hydrogen atmosphere for 19 hours. After replacing with nitrogen, dimethylformamide (680 g) was added and the diamine was dissolved by heating at 130°C. The catalyst was filtered while hot, and the filtrate was partially concentrated to a content of 813 g. Dimethylformamide (60 g) was added and dissolved at 120°C, and then methanol (838 g) was added and cooled to precipitate crystals. After filtration, the residue was dried to obtain compound [DA-5] (yield: 33.6 g, yield: 96%, ocher crystals). 1H-NMR(400MHz, DMSO-d6, δppm):7.46(d, 4H, J = 8.8 Hz), 7.29(d, 4H, J = 8.8 Hz), 7.00(d, 4H, J = 8.8 Hz), 6.61(d, 4H, J = 8.8 Hz), 5.13(br, 4H), 4.32(s, 4H).

[0100] (Synthesis Example 2) 1.30g (12.0mmol) of DA-1, 2.93g (12.0mmol) of DA-2, and 2.05g (6.00mmol) of DA-6 were weighed into a 100mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and then 77g of NMP was added and dissolved by stirring while supplying nitrogen. 6.19g (27.6mmol) of DAH-1 was added while stirring this diamine solution, and NMP was further added so that the solid concentration became 12% by mass, and the mixture was stirred at 40℃ for 12 hours to obtain a solution of polyamic acid (PAA-1) (viscosity: 340mPa s).

[0101] (Synthesis Example 3) In a 100mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, 1.17g (10.8mmol) of DA-1, 3.46g (10.8mmol) of DA-3, and 1.84g (5.39mmol) of DA-6 were weighed out, and then 75g of NMP was added and dissolved by stirring while supplying nitrogen. 5.57g (24.8mmol) of DAH-1 was added while stirring this diamine solution, and further NMP was added so that the solid concentration became 12% by mass, and the mixture was stirred at 40℃ for 12 hours to obtain a solution of polyamic acid (PAA-2) (viscosity: 340mPa s).

[0102] (Synthesis Example 4) In a 200mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, 1.17g (10.8mmol) of DA-1, 4.43g (10.8mmol) of DA-4, and 1.84g (5.39mmol) of DA-6 were weighed out, and then 83g of NMP was added and dissolved by stirring while supplying nitrogen. 5.75g (25.7mmol) of DAH-1 was added while stirring this diamine solution, and further NMP was added so that the solid concentration became 12% by mass, and the mixture was stirred at 40℃ for 12 hours to obtain a solution of polyamic acid (PAA-3) (viscosity: 360mPa s).

[0103] (Synthesis Example 5) 0.56g (5.18mmol) of DA-1, 2.06g (5.20mmol) of DA-5, and 0.89g (2.61mmol) of DA-6 were weighed into a 100mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and then 39g of NMP was added and dissolved by stirring while supplying nitrogen. 2.68g (12.0mmol) of DAH-1 was added while stirring this diamine solution, and further NMP was added so that the solid concentration became 12 mass%, and the mixture was stirred at 40℃ for 12 hours to obtain a solution of polyamic acid (PAA-4) (viscosity: 215mPa s).

[0104] (Synthesis Example 6) 3.83g (19.2mmol) of DA-7 and 1.43g (4.79mmol) of DA-8 were weighed out into a 100mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, then 78g of NMP was added and stirred to dissolve while supplying nitrogen. 6.56g (22.2mmol) of DAH-2 was added while stirring this diamine solution, and NMP was further added so that the solid concentration became 12% by mass. The mixture was stirred at 70℃ for 20 hours to obtain a solution of polyamic acid (PAA-5) (viscosity: 420mPa s).

[0105] Comparative Example 1 Into a 50 mL Erlenmeyer flask containing a stirrer, 6.25 g of the polyamic acid solution (PAA-1) obtained in Synthesis Example 2 was weighed out. Next, 3.50 g of NMP and 4.5 g of BCS were added, and the mixture was stirred overnight with a magnetic stirrer to obtain a liquid crystal alignment agent (AL-1).

[0106] Comparative Example 2 Into a 50 mL Erlenmeyer flask containing a stirrer, 6.25 g of the polyamic acid solution (PAA-2) obtained in Synthesis Example 3 was weighed out. Next, 3.50 g of NMP and 4.5 g of BCS were added, and the mixture was stirred overnight with a magnetic stirrer to obtain a liquid crystal alignment agent (AL-2).

[0107] Comparative Example 3 Into a 50 mL Erlenmeyer flask containing a stirrer, 6.25 g of the polyamic acid solution (PAA-3) obtained in Synthesis Example 4 was weighed out. Next, 3.50 g of NMP and 4.5 g of BCS were added, and the mixture was stirred overnight with a magnetic stirrer to obtain a liquid crystal alignment agent (AL-3).

[0108] Example 1 In a 50 mL Erlenmeyer flask containing a stirrer, 6.25 g of the polyamic acid solution (PAA-4) obtained in Synthesis Example 5 was weighed out. Next, 3.50 g of NMP and 4.5 g of BCS were added and stirred overnight with a magnetic stirrer to obtain a liquid crystal alignment agent (AL-4).

[0109] Example 2 In a 50 mL Erlenmeyer flask containing a stirrer, 2.50 g of the polyamic acid solution (PAA-4) obtained in Synthesis Example 5 and 3.75 g of the polyamic acid solution (PAA-5) obtained in Synthesis Example 6 were taken. 3.50 g of NMP and 4.50 g of BCS were added, and 0.75 g of a 10% NMP solution of AD-1 and 0.113 g of AD-2 were added and stirred overnight with a magnetic stirrer to obtain a liquid crystal alignment agent (AL-5). The stability of AL-5 during frozen storage was confirmed by storing it in a -20°C environment. It was confirmed that there was no precipitation after one month of frozen storage and that the filterability was also good.

[0110] Comparative Example 4 The liquid crystal alignment agent (AL-1) obtained in Comparative Example 1 was subjected to the afterimage evaluation by long-term AC driving as described above. That is, a liquid crystal cell having the configuration of an FFS mode liquid crystal display element was prepared as described above using the liquid crystal alignment agent (AL-1), and the afterimage evaluation by long-term AC driving was performed on this FFS driving liquid crystal cell. As a result, the value of the angle Δ of this liquid crystal cell after long-term AC driving was 0.16 degrees.

[0111] Comparative Example 5 An FFS drive liquid crystal cell was produced in the same manner as in Comparative Example 4, except that the liquid crystal alignment agent (AL-2) obtained in Comparative Example 2 was used. As a result of carrying out an afterimage evaluation by long-term AC drive on this FFS drive liquid crystal cell, the value of the angle Δ of this liquid crystal cell after long-term AC drive was 0.11 degrees.

[0112] Comparative Example 6 An FFS drive liquid crystal cell was produced in the same manner as in Comparative Example 4, except that the liquid crystal alignment agent (AL-3) obtained in Comparative Example 3 was used. As a result of carrying out an afterimage evaluation by long-term AC driving on this FFS drive liquid crystal cell, the value of the angle Δ of this liquid crystal cell after long-term AC driving was 0.17 degrees.

[0113] Example 3 An FFS drive liquid crystal cell was produced in the same manner as in Comparative Example 4, except that the liquid crystal alignment agent (AL-4) obtained in Example 1 was used. As a result of carrying out an afterimage evaluation by long-term AC drive on this FFS drive liquid crystal cell, the value of the angle Δ of this liquid crystal cell after long-term AC drive was 0.05 degrees.

[0114] Example 4 The two-component polymer blend liquid crystal alignment agent (AL-5) obtained in Example 2 was filtered through a filter with a pore size of 1.0 μm, spin-coated on a glass substrate with a transparent electrode, and dried on a hot plate at a temperature of 80° C. for 2 minutes. After that, it was baked in an IR oven at a temperature of 230° C. for 30 minutes to obtain an imidized film with a thickness of 100 nm. When the state of the baked film was checked, it was confirmed that the film was formed uniformly without unevenness or repelling.

[0115] The results of the afterimage evaluation by long-term AC driving for the liquid crystal alignment agents of Comparative Examples 4 to 6 and Example 3 are summarized in Table 1. [Table 1]

[0116] The entire contents of the specification, claims, and abstract of Japanese Patent Application No. 2018-209060, filed on November 6, 2018, are hereby incorporated by reference as the disclosure of the specification of the present invention.

Claims

1. A diamine represented by the following formula: 【Chemistry 1】 (In the formula, R １ and R ２ have the same structure, and are each independently a single bond, —O—, —S—, —NR １２ -, and R １２ is a hydrogen atom or a methyl group, and A is an alkylene group having 2 carbon atoms.

2. At least one polymer selected from the group consisting of a polyimide precursor having a structure represented by the following formula (1) in its main chain and an imidized polymer of the polyimide precursor, The polyimide precursor is obtained by a polymerization reaction between a diamine component and a tetracarboxylic acid component, A polymer, wherein the diamine component comprises the diamine of claim 1. 【Chemistry 1】 (In the formula, R １ and R ２ have the same structure, and are each independently a single bond, —O—, —S—, —NR １２ -, and R １２ is a hydrogen atom or a methyl group, and A is an alkylene group having 2 carbon atoms. １ and B ２ is a divalent organic group having the same structure and selected from the following structures: 【Chemistry 2】

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