JP7673778B2 - New diamines - Google Patents

Description

The present invention relates to a liquid crystal alignment agent used in the manufacture of liquid crystal display elements, a liquid crystal alignment film obtained from the liquid crystal alignment agent, and a novel diamine that is a raw material for liquid crystal display elements having the liquid crystal alignment film.

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 liquid crystal display elements, and is attracting attention as a promising liquid crystal alignment treatment method.

However, the liquid crystal alignment film obtained by the photoalignment method has a problem in that the anisotropy in the orientation 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 film is used as a liquid crystal display element, problems such as the generation of afterimages occur (Non-Patent Document 1).

Japanese Patent Application Publication No. 9-297313

"Liquid Crystal Photo-Alignment Film" Functional Materials, Vol. 17 (1997), No. 11, pp. 13-22

The objective of the present invention is to suppress the occurrence of residual images after AC driving due to insufficient anisotropy in the alignment direction of the liquid crystal alignment film obtained by the photoalignment method.

式中、Ｒ_１及びＲ_２は、それぞれ独立して、単結合、－Ｏ－、－Ｓ－、－ＮＲ_１２－、エステル結合、アミド結合、チオエステル結合、ウレア結合、カーボネート結合、又はカルバメート結合である。Ｒ_１２は、水素原子、又はメチル基である。Ａは炭素数１又は２のアルキレン基である。Ｂ_１及びＢ_２は同じ構造を有し、かつ下記構造から選ばれる２価の有機基である。

式中、Ｒ_４は、炭素数１～５のアルキレン基である。Ｒ_５は水素原子、メチル基、ヒドロキシ基又はメトキシ基である。 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:

In the formula, R ₁ and R ₂ are each independently a single bond, -O-, -S-, -NR ₁₂ -, an ester bond, an amide bond, a thioester bond, a urea bond, a carbonate bond, or a carbamate bond. R ₁₂ is a hydrogen atom or a methyl group. A is an alkylene group having 1 or 2 carbon atoms. _{B 1} and B ₂ have the same structure and are divalent organic groups selected from the following structures:

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.

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.

上記式（１）において、Ｒ_１及びＲ_２は、それぞれ独立して、単結合、－Ｏ－、－Ｓ－、－ＮＲ_１２－、エステル結合、アミド結合、チオエステル結合、ウレア結合、カーボネート結合、又はカルバメート結合であり、Ｒ_１２は、水素原子又はメチル基である。Ａは炭素数１又は２のアルキレン基である。Ｂ_１及びＢ_２は、同じ構造を有し、かつ下記構造から選ばれる２価の有機基である。Ｂ_１とＢ_２は同じ構造を有することにより、高い液晶配向性を有する液晶配向膜を得ることができる。 <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).

In the above formula (1), R ₁ and R ₂ are each independently a single bond, -O-, -S-, -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. B ₁ and B ₂ have the same structure and are divalent organic groups selected from the following structures. By having B ₁ and B ₂ have the same structure, a liquid crystal alignment film having high liquid crystal alignment properties can be obtained.

上記式中、Ｒ_４は、炭素数１～５のアルキレン基である。Ｒ_５は水素原子、メチル基、ヒドロキシ基又はメトキシ基である。）

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.

In the above formula (1), from the viewpoint of liquid crystal alignment, R ₁ and R ₂ are preferably a single bond, -O-, -S-, -NR ₁₂ -, an ester bond or an amide bond, and more preferably -O-. From the viewpoint of liquid crystal alignment, R ₁₂ is preferably a hydrogen atom or a methyl group. From the viewpoint of liquid crystal alignment, A is preferably an alkylene group having a carbon chain of 2.
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. From the viewpoint of liquid crystal alignment, _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.

（Ｒ_５は、前記と同定義である。）

( _R5 is defined as above.)

上記式において、Ｒ_５及びＲ_１２は、それぞれの好ましい例も含めて、前記と同定義である。

In the above formula, _R5 and _R12 are defined as above, including preferred examples thereof.

上記式中、Ｒ_１、Ｒ_２、Ａは、それぞれの好ましい例を含めて、上記したとおりである。上記特定構造を有するジアミンとしては、なかでも、以下のジアミンが好ましい。

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.

In the above formula, R ₁ , R ₂ 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.

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

_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.

_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.

Z ₁ and Z ₂ 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 CH ₂ -CH ₂ 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. The alkynyl group includes those in which one or more CH ₂ -CH ₂ structures present in the alkyl group are replaced with a C≡C structure, specifically, an ethynyl group, a 1-propynyl group, a 2-propynyl group, etc.

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.

The organooxy group can have a structure represented by -O-R. The R's may be the same or different, and examples thereof include the alkyl group, alkenyl group, alkynyl group, and aryl group described above. These R's 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 -S-R. 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.

The organosilyl group may have a structure represented by -Si-(R) ₃ . The R may be the same or different, and may be, for example, 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 can 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.

The ester group can have a structure represented by -C(O)O-R or -OC(O)-R. Examples of R include the above-mentioned alkyl group, alkenyl group, alkynyl group, and aryl group. These R groups may be further substituted with the above-mentioned substituents.
The thioester group can have a structure represented by -C(S)O-R or -OC(S)-R. Examples of R include the above-mentioned alkyl group, alkenyl group, alkynyl group, and aryl group. These R groups may be further substituted with the above-mentioned substituents.
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 aforementioned alkyl groups, alkenyl groups, alkynyl groups, and aryl groups. These Rs may be further substituted with the aforementioned substituents.

The amide group can have a structure represented by -C(O)NH ₂ , -C(O)NHR, -NHC(O)R, -C(O)N(R) ₂ , or -NRC(O)R. 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 be further substituted with the above-mentioned substituents.
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.

Generally, introduction of a bulky structure may decrease the reactivity of the amino group or the liquid crystal alignment property. Therefore, _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 present 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 %.

Ｒ_３、Ｚ_１及びＺ_２の定義は、上記式（２）におけるのと同じである。 <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).

The definitions of R ₃ , Z ₁ and Z ₂ are the same as in formula (2) above.

_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).

R ₈ to R ₁₁ in the above formula (X-1) 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. If R ₈ to R ₁₁ have a bulky structure, there is a possibility that the liquid crystal alignment property is deteriorated, 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.

In formula (3), _Y2 is a divalent organic group derived from a diamine, and the structure thereof is not particularly limited. Specific examples of the structure of _Y2 include the following (Y-1) to (Y-118).

(In formula (Y-109), m and n each independently represent an integer of 1 to 11, and m+n represents an integer of 2 to 12; in formula (Y-114), h represents an integer of 1 to 3; and in formulas (Y-111) and (Y-117), j represents 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.

<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.

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 reaction is not particularly limited as long as it dissolves the generated polyimide precursor. Specific examples of organic solvents 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 may be mentioned.
In addition, when the polyimide precursor has high solubility, methyl ethyl ketone, cyclohexanone, cyclopentanone, 4-hydroxy-4-methyl-2-pentanone, or an organic solvent represented by the following formulas [D-1] to [D-3] can be used.

式［Ｄ－１］中、Ｄ^１は炭素数１～３のアルキル基を示し、式［Ｄ－２］中、Ｄ^２は炭素数１～３のアルキル基を示し、式［Ｄ－３］中、Ｄ^３は炭素数１～４のアルキル基を示す。

In formula [D-1], D ¹ represents an alkyl group having 1 to 3 carbon atoms, 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.

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.

The polyamic acid obtained as described above can be recovered by injecting the reaction solution into a poor solvent while stirring it thoroughly 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 include water, methanol, ethanol, hexane, butyl cellosolve, acetone, and toluene.

<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).

(1) Production from polyamic acid A 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.

The esterification agent is preferably one that can be easily removed by purification, and examples of such agents 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, and 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride. The amount of esterification agent added is preferably 2 to 6 molar equivalents per mole of the repeating unit of polyamic acid.

Examples of the organic solvent 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.

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 precipitation of the polymer is unlikely to occur and that it is easy to obtain a high molecular weight product.

(2) Production by Reaction of Tetracarboxylic Acid Diester Dichloride with Diamine A polyamic acid ester can be produced from a tetracarboxylic acid diester dichloride and a diamine.
Specifically, the compound 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.

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 the 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 a mixture 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 precipitation of the polymer 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.

(3) Production from a Tetracarboxylic Acid Diester and a Diamine A 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.

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, or the like. The amount of the condensing agent added is preferably 2 to 3 times the molar amount of the tetracarboxylic acid diester.

As the base, a tertiary amine such as pyridine, triethylamine, etc. The amount of the base added is preferably 2 to 4 times the molar amount of the diamine component, from the viewpoints that it is an amount that can be easily removed and that 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.

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.

<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.

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 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 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.

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.

The temperature for 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.

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.

<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.

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

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. In particular, it is preferably 20 to 90% by mass. More preferably, it is 30 to 80% by mass.

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 listed below.
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, 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 monoacetate, ethylene glycol diacetate, propylene carbonate, ethylene carbonate, 2-(methoxy methoxy)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 Examples of the solvent include ether acetate, diethylene glycol monobutyl ether acetate, 2-(2-ethoxyethoxy)ethyl acetate, diethylene glycol acetate, triethylene glycol, triethylene glycol monomethyl 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] above.

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 alignment agent, more preferably 10 to 80% by mass, and even more preferably 20 to 70% by mass.

In addition to the above, the liquid crystal alignment 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 and density of the film when made into a liquid crystal alignment film, and an imidization accelerator for the purpose of efficiently promoting imidization by heating the polyimide precursor when baking the coating film.

<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 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.

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 steps 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 therein, 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.

As a method of photo-alignment treatment of the liquid crystal alignment film, a method of irradiating the coating film surface with radiation polarized in a certain direction, and optionally further performing a heat treatment at a temperature of 150 to 250°C to impart liquid crystal alignment ability can be mentioned. As the radiation, ultraviolet rays and visible light having a wavelength of 100 to 800 nm can be used. Among them, 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 addition, 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 preferably 1 to 10,000 mJ/ ^cm2 , and particularly preferably 100 to 5,000 mJ/ ^cm2 . 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 since it is possible to impart higher anisotropy. Specifically, the extinction ratio of linearly polarized UV light is preferably 10:1 or more, and more preferably 20:1 or more.

The film irradiated with polarized radiation may then be contacted with a solvent containing at least one selected from water and an organic solvent.
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.

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 the 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, or drying, or both, may be performed.

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 be decomposed. Therefore, the heating time is preferably from 10 seconds to 30 minutes, and more preferably from 1 to 10 minutes.

<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.

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 may 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 may be, for example, a film made of SiO ₂ -TiO ₂ 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.

Next, liquid crystal material is injected into the space surrounded by the two substrates and the sealant through an opening provided in the sealant. This 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 may be 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.

The above-mentioned sealant may contain an inorganic filler for the purpose of improving adhesion, moisture resistance, etc. Examples of inorganic fillers that can be used include, but are not limited to, 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. Two or more of the above-mentioned inorganic fillers may be mixed and used.

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

なお、式中、Ｆｍｏｃは、9-フルオレニルメチルオキシカルボニル基を表し、Ｂｏｃは、ｔ－ブトキシカルボニル基を表す。

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

[ ^1H NMR]
Apparatus: Fourier transform superconducting nuclear magnetic resonance spectrometer (FT-NMR) INOVA-400 (Varian) 400 MHz
Solvent: deuterated dimethylsulfoxide (DMSO- _d6 )
Standard substance: tetramethylsilane (TMS)
Number of times of accumulation: 8 or 32

[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.

[Preparation of Liquid Crystal Cell]
A liquid crystal cell having the structure of an FFS mode liquid crystal display element was prepared.
First, a substrate with electrodes was prepared. The substrate was a rectangular glass plate measuring 30 mm x 50 mm and having a thickness of 0.7 mm. An ITO electrode having a solid pattern was formed on the substrate as a first layer, which constitutes an opposing electrode. A SiN (silicon nitride) film formed by a CVD method was formed as a second layer on the first layer opposing electrode. The thickness of the second layer SiN film was 500 nm, and it functions as an interlayer insulating film. A comb-shaped pixel electrode formed by patterning an ITO film as a third layer was arranged on the second layer 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 opposing electrode and the third layer pixel electrode were electrically insulated by the action of the second layer SiN film.

The pixel electrodes in the third layer have a comb-like shape consisting of multiple electrode elements arranged in a "L" shape with the central portion 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. Because the pixel electrodes that form each pixel are arranged in multiple electrode elements with a "L" shape bent in the 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 central bend, and has a first region above the bent part and a second region below the bent part.

Next, the obtained liquid crystal alignment agent was filtered through a filter with a pore size of 1.0 μm, and then applied by spin coating to the above-prepared electrode-attached substrate and a glass substrate having a columnar spacer with a height of 4 μm and 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 circulation oven at 230 ° C. to form a coating film with a thickness of 100 nm. The coating surface was irradiated with polarized ultraviolet light at 500 mJ / cm ² to perform an alignment treatment, and a substrate with a liquid crystal alignment film was obtained. The liquid crystal alignment film formed on the electrode-attached substrate was aligned so that the direction that equally divides the inner angle of the pixel bend portion and the alignment direction of the liquid crystal were orthogonal, 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 and the alignment direction of the liquid crystal on the second substrate coincided when a liquid crystal cell was produced. The above two substrates were combined into one set, a sealant was printed on one 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 prepare an empty cell. Liquid crystal MLC-3019 (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.

[Evaluation of image lag due to long-term AC driving]
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. Thereafter, the pixel electrode and the counter electrode of the liquid crystal cell were shorted, and the liquid crystal 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 angle Δ of the liquid crystal cell obtained above was evaluated as "X" when it 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°.

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

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 the mixture was 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 for dissolution, 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).

Synthesis of Compound [DA-5] Compound [1] (40.2 g) and 5% palladium carbon (4.0 g) were added to dimethylformamide (800 g), and the mixture was stirred at 60° C. under a hydrogen atmosphere for 19 hours. After nitrogen replacement, 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 an amount 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).

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

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

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

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

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

(Comparative Example 1)
In 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 stirred overnight with a magnetic stirrer to obtain a liquid crystal alignment agent (AL-1).

(Comparative Example 2)
In 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 stirred overnight with a magnetic stirrer to obtain a liquid crystal alignment agent (AL-2).

(Comparative Example 3)
In 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 stirred overnight with a magnetic stirrer to obtain a liquid crystal alignment agent (AL-3).

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).

Example 2
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 in a 50 mL Erlenmeyer flask containing a stirrer. 3.50 g of NMP and 4.50 g of BCS were added, 0.75 g of a 10% NMP solution of AD-1, and 0.113 g of AD-2 were added, and the mixture was 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.

(Comparative Example 4)
The liquid crystal alignment agent (AL-1) obtained in Comparative Example 1 was subjected to an 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 produced using the liquid crystal alignment agent (AL-1) as described above, and an afterimage evaluation by long-term AC driving was carried out 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.

(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 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 0.11 degrees.

(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.

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 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 0.05 degrees.

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 for 30 minutes in an IR oven at a temperature of 230° C., and an imidized film with a thickness of 100 nm was obtained. When the state of the baked film was confirmed, it was confirmed that there was no unevenness or repelling and that the film was formed uniformly.

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

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 (2)

A diamine represented by the following formula:

(In the formula, R ₁ and R ₂ have the same structure and are selected from the group consisting of a single bond, -O-, -S-, and -NR ₁₂ -, R ₁₂ is a hydrogen atom or a methyl group, and A is an alkylene group having 2 carbon atoms.) 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 .

(In the formula, R ₁ and R ₂ have the same structure and are selected from the group consisting of a single bond, -O-, -S-, and -NR ₁₂ -, R ₁₂ is a hydrogen atom or a methyl group, and A is an alkylene group having 2 carbon atoms. _{B 1} and B ₂ have the same structure and are divalent organic groups selected from the following structures.)