TWI856190B - Liquid crystal alignment agent, liquid crystal alignment film and liquid crystal display element - Google Patents

Abstract

The present invention provides a liquid crystal alignment agent, a liquid crystal alignment film, and a liquid crystal display element. The liquid crystal alignment agent is used to obtain a liquid crystal display element that has a high voltage retention rate even when the alignment treatment is performed by a photoalignment method that causes chemical changes by irradiation with radiation or the like, and has good liquid crystal alignment properties, and can suppress the afterimages that occur in IPS or FFS liquid crystal display elements. The liquid crystal alignment agent is characterized by containing an aromatic compound having a structure represented by two or more of the following formula (1). (R is a hydrogen atom or a methyl group; any hydrogen atom on the benzene ring may be substituted by a hydroxyl group, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a monovalent organic group having 1 to 6 carbon atoms containing a fluorine atom).

Description

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

The present invention relates to a liquid crystal alignment agent, a liquid crystal alignment film obtained from the liquid crystal alignment agent, a liquid crystal display element using the liquid crystal alignment film, and a novel compound used in the liquid crystal alignment agent.

In the past, various driving methods have been developed for liquid crystal display elements, which differ in electrode structure or physical properties of liquid crystal molecules used, and various display elements are known, such as TN (Twisted Nematic) type, STN (Super Twisted Nematic) type, VA (Vertical Alignment) type, IPS (In-Plane Switching) type, FFS (Fringe Field Switching) type, etc. These liquid crystal display elements generally have a liquid crystal alignment film for aligning liquid crystal molecules.

As materials for liquid crystal alignment films, polymers such as polyamic acid or polyamic acid ester, polyimide, polyamide, etc. are known. Currently, the most popular liquid crystal alignment film in industry is produced by rubbing the surface of a film formed of a polymerizable composition containing the above polymers on an electrode substrate in one direction with a cloth such as cotton, nylon, polyester, etc., so-called rubbing treatment.

Friction treatment is a simple and highly productive industrial method. However, as liquid crystal display devices become more high-performance, high-precision, and large-scale, there are various problems such as scratches on the surface of the alignment film caused by friction treatment, dust, mechanical force or static electricity, and unevenness within the alignment treatment surface.

As a method to replace the rubbing treatment, a photo-alignment method is known, which gives liquid crystal alignment ability by irradiating polarized radiation. The liquid crystal alignment treatment by the photo-alignment method is proposed to utilize photoisomerization reaction, photocrosslinking reaction, photodecomposition reaction, etc. (refer to non-patent document 1). Patent document 1 proposes that a polyimide film having an alicyclic structure such as a cyclobutane ring in the main chain is used for the photo-alignment method.

As a frictionless alignment method, the optical alignment method can be produced by an industrially simple process. In addition, in IPS drive or FFS drive liquid crystal display elements, it is expected that the contrast or viewing angle characteristics of the liquid crystal display element will be improved compared to the liquid crystal alignment film obtained by the friction treatment method. Therefore , it has attracted attention as a promising liquid crystal alignment treatment method.

Patent document 1: Japanese Patent Publication No. 9-297313 Non-patent document

Non-patent document 1: "Liquid crystal optical alignment film" Kidowaki, Ichimura, Functional Materials, November 1997, Vol. 17, No. 11, pp. 13-22

Invent the problem you want to solve

In recent years, the use range of liquid crystal display elements has been further expanded, and liquid crystal display elements are sometimes used for a long time in high temperature and high humidity environments or in environments exposed to light. As a liquid crystal alignment film, it is required to withstand use in such harsh environments, and in particular, a high voltage retention rate has become one of the important characteristics. However, according to the knowledge and understanding of the inventors of this case, in the case of the photo-alignment method that causes chemical changes by irradiation with radiation, there is a clear tendency for the voltage retention rate to decrease. In addition, in the case of imparting alignment ability by performing the photo-alignment method, it is obvious that the liquid crystal alignment is insufficient, or afterimages become a problem in, for example, liquid crystal display elements of the IPS drive method or the FFS drive method.

Therefore, the object of the present invention is to provide a liquid crystal alignment agent, a liquid crystal alignment film obtained from the liquid crystal alignment agent, a liquid crystal display element having the liquid crystal alignment film, and a novel compound for a liquid crystal alignment agent, wherein the liquid crystal alignment agent is used to obtain a liquid crystal display element having a high voltage retention rate and good liquid crystal alignment even when the alignment treatment is performed by a photoalignment method that causes chemical changes by irradiation with radiation or the like, and can suppress the afterimage that occurs in a liquid crystal display element of an IPS drive or FFS drive method. Means of Solving the Problem

The inventors of the present invention have repeatedly and diligently examined and found that the above-mentioned problem can be achieved by using a liquid crystal alignment agent containing an aromatic compound having a specific chemical structure shown below as an additive, and finally completed the present invention. The present invention is a liquid crystal alignment agent, a liquid crystal alignment film obtained from the liquid crystal alignment agent, a liquid crystal display element having the liquid crystal alignment film, and a novel compound used in the liquid crystal alignment agent. The liquid crystal alignment agent is characterized by containing an aromatic compound having a structure shown by two or more of the following formula (1). However, R is a hydrogen atom or a methyl group; any hydrogen atom on the benzene ring may be substituted by a hydroxyl group, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a monovalent organic group having 1 to 6 carbon atoms and containing a fluorine atom.

According to the present invention, a liquid crystal alignment agent, a liquid crystal alignment film obtained from the liquid crystal alignment agent, a liquid crystal display element having the liquid crystal alignment film, and a novel compound for the liquid crystal alignment agent can be provided. The liquid crystal alignment agent is used to obtain a liquid crystal display element that has a high voltage retention rate and good liquid crystal alignment even when an alignment treatment is performed by a photoalignment method that causes chemical changes by irradiation with radiation, etc., and can suppress afterimages in a harsh environment, especially in an IPS drive mode or a FFS drive mode.

Embodiment of the invention: Aromatic compound of formula (1)

The liquid crystal alignment agent of the present invention is characterized by containing an aromatic compound having a structure represented by two or more of the following formula (1) (hereinafter referred to as the aromatic compound of formula (1)).

In the above formula (1), R represents a hydrogen atom or a methyl group. Any hydrogen atom on the benzene ring may be substituted by a hydroxyl group, a halogen atom, an alkyl group having 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, or a monovalent organic group having 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, and having a fluorine atom. Here, examples of the monovalent organic group having a fluorine atom include trifluoromethyl, trifluoroethyl, trifluoromethoxy, trifluoroethoxy, and the like.

In the liquid crystal alignment agent of the present invention, by containing the aromatic compound of the above formula (1) as an additive, as specifically demonstrated in the embodiments described below, a liquid crystal alignment film in a liquid crystal display element can be obtained that has a high voltage retention rate in a harsh environment and good liquid crystal alignment even when the alignment treatment is performed by a photoalignment method that causes chemical changes by irradiation with radiation or the like. Although the mechanism may not be clear, it is believed to be roughly as follows. In the alignment treatment caused by the photoalignment method, for example, the surface of a film-like object formed by the liquid crystal alignment agent on the surface of the substrate is irradiated with high-energy UV light that is polarized to be roughly straight. However, at this time, due to the irradiation of UV light, decomposition products of organic substances constituting the film-like object are generated, which become impurities that cause the voltage retention rate in the liquid crystal alignment film to decrease, and therefore it is believed that the voltage retention rate of the liquid crystal alignment film is decreased. However, in the liquid crystal alignment agent of the present invention, when the above impurities are generated by irradiation with UV light, since the aromatic compound of the above formula (1) has a functional group that can react with the impurities, the impurities contained in the obtained liquid crystal alignment film can be reduced by reacting with the impurities that cause the voltage retention rate to decrease. Therefore, the liquid crystal alignment film obtained by the liquid crystal alignment agent of the present invention is considered to maintain a high voltage retention rate. In addition, the aromatic compound of the above formula (1) contained in the liquid crystal alignment agent of the present invention has a highly planar structure, so it does not hinder the liquid crystal alignment of the obtained liquid crystal alignment film, and it is considered that a liquid crystal alignment film with high liquid crystal alignment can be obtained. Therefore, in the IPS driving method or the FFS driving method, even if the liquid crystal display element is driven for a long time, the liquid crystal returns to the same state as before driving, so it is considered that a liquid crystal display element with less afterimages can be obtained.

As the aromatic compound of the above formula (1), a compound represented by the following formula (b1) is preferred. In the above formula (b1), R is the same as in the above formula (1); n is an integer of 2 to 6, when n is 2, A represents a single bond or a divalent linking group, and when n is 3 to 6, A represents an n-valent organic group.

Examples of the n-valent organic group include an n-valent alkyl group, an n-valent heteroatom-containing group including a group having a heteroatom between carbon atoms of the alkyl group or at the terminal of the alkyl group, and an n-valent organic group in which a part or all of the hydrogen atoms in the above-mentioned alkyl group and heteroatom-containing group are substituted with a substituent. Examples of the divalent linking group in A include a divalent alkyl group, a divalent heteroatom-containing group including a group having a heteroatom between carbon atoms of the alkyl group or at a terminal of the alkyl group, a divalent linking group in which a part or all of the hydrogen atoms possessed by the above alkyl group and heteroatom-containing group are substituted with a substituent, -S(=O) ₂ -, -CO-, -O-, -S-, -NR-CO- (R represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms), and -NR-CO-NR- (R represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms).

Examples of the n-valent alkyl group include alkanes such as methane, ethane, propane, and butane; alkenes such as ethylene, propylene, butene, and pentene; alkynes such as acetylene, propyne, butyne, and pentyne; cycloalkanes such as cyclopropane, cyclobutane, cyclopentane, cyclohexane, norbornane, and adamantane; cyclopropene, cyclobutene, cyclopentene, cyclohexene, norbornane, and adamantane; Alicyclic hydrocarbons having 3 to 30 carbon atoms such as cycloolefins such as camphene, aromatic hydrocarbons having 6 to 30 carbon atoms such as benzene, toluene, xylene, mesitylene, naphthalene, methylnaphthalene, dimethylnaphthalene, anthracene, and hydrocarbons in which a part of the carbon-carbon bonds of the above chain hydrocarbons are replaced by the above alicyclic hydrocarbons or aromatic hydrocarbons, and n-valent groups obtained by removing n hydrogen atoms from hydrocarbons. Examples of divalent hydrocarbon groups include divalent groups obtained by removing two hydrogen atoms from hydrocarbons exemplified as the above n-valent hydrocarbon groups.

As the above-mentioned group having a heteroatom, for example, there can be cited a group having at least one selected from the group consisting of an oxygen atom, a nitrogen atom, a silicon atom, a phosphorus atom, and a sulfur atom. If specific examples are listed, there can be cited -O-, -NR- (R represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms), -CO-, -S-, -CO-, and a group combining these. Among them, -O- is preferred.

As the above substituent, for example, there can be cited halogen atoms such as fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, etc.; alkoxy groups such as methoxy groups, ethoxy groups, propoxy groups, etc.; alkoxycarbonyl groups such as methoxycarbonyl groups, ethoxycarbonyl groups, etc.; alkoxycarbonyloxy groups such as methoxycarbonyloxy groups, ethoxycarbonyloxy groups, etc.; cyano groups, nitro groups, etc. In the above formula (b1), n is preferably 2, and A is preferably a single bond or a divalent linking group.

The divalent linking group is preferably a group having a structure represented by the following formula (a-1) or (a-2). In the above formulae (a-1) and (a-2), R ₁ , R _1' , R ₂ , and R _2' each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, preferably 1 or 2 carbon atoms; m1 and m2 each independently represent an integer of 1 to 18, preferably 1 to 6; and n represents an integer of 1 to 6, preferably 1 to 4. In addition, "*" represents a bond.

The molecular weight of the aromatic compound of the above formula (1) is preferably 2000 or less, more preferably 1500 or less, from the viewpoint of improving the reactivity with the decomposition product generated by the photo-alignment method. On the other hand, from the viewpoint of suppressing the sublimation of the aromatic compound due to the burning, the molecular weight of the aromatic compound is preferably 150 or more, more preferably 200 or more.

Preferred examples of the aromatic compound of the above formula (1) include compounds selected from the group consisting of the following formulas (b-1) to (b-7). The compounds of the following formulas (b-1) to (b-4) are novel compounds not disclosed in previous literature.

<Polymer> The liquid crystal alignment agent of the present invention containing the aromatic compound of the above formula (1) contains a polymer capable of aligning liquid crystals, similar to the known ones, but the polymer is not particularly limited as long as it has the ability to align liquid crystals. Examples of the polymer include polyimide precursors, polyimides of imide compounds of polyimide precursors, acrylic polymers, methacrylic polymers, acrylamide polymers, methacrylamide polymers, polystyrene, polysiloxane, polyamide, polyester, polyurethane, polycarbonate, polyurea, polyphenol (phenolic varnish resin), maleimide polymers, and polymers into which compounds having isocyanuric acid skeletons and tris-ion skeletons are introduced. The polymer can be used alone or in combination of two or more.

As raw materials for producing these polymers, the following can be cited. When the polymer is a polyimide precursor or polyimide such as polyamic acid, polyamic acid ester, etc., it is at least one tetracarboxylic acid component selected from tetracarboxylic acid or its derivatives and diamine; When the polymer is a (meth)acrylic acid polymer, it is (meth)acrylic acid or its derivatives, (meth)acrylic acid ester or its derivatives; when the polymer is a (meth)acrylamide polymer, it is (meth)acrylamide or its derivatives;

When the polymer is polystyrene, it is styrene or its derivatives; when the polymer is polysiloxane, it is a silane compound having a methoxy group or an ethoxy group; when the polymer is polyamide, it is at least one dicarboxylic acid component selected from dicarboxylic acids and their derivatives and a diamine component; When the polymer is polyester, it is at least one dicarboxylic acid component selected from dicarboxylic acids and their derivatives and a diol component;

When the polymer is a polyurethane, it is an isocyanate and a compound and a compound having a hydroxyl group; when the polymer is a polycarbonate, it is a bisphenol derivative and phosgene or a phosgene equivalent (for example, trichlorophosgene) or diphenyl carbonate; When the polymer is a polyurea, it is a diisocyanate derivative and a diamine component; when the polymer is a maleimide polymer, it is a copolymer of a maleimide derivative alone or with styrene; When the polymer is a polymer into which a compound having an isocyanuric acid skeleton or a tris-indium skeleton is introduced, it is a compound having an isocyanuric acid skeleton or a tris-indium skeleton.

<Polyimide polymer> The polymer contained in the liquid crystal alignment agent of the present invention is preferably one or more polymers selected from the group consisting of polyimide precursors and polyimides which are imides of polyimide precursors (hereinafter also referred to as polyimide polymers) from the viewpoint of the practicality as a liquid crystal alignment agent and the mechanical and electrical properties of the coating film. The above-mentioned polyimide polymer can be produced by a known method. For example, polyamide as a polyimide precursor is obtained by subjecting a tetracarboxylic acid component formed by tetracarboxylic dianhydride or its derivatives to a polymerization (condensation) reaction with a diamine component, and polyimide is obtained by subjecting the polyimide precursor to imidization.

<Tetracarboxylic acid component> Polyamides as polyimide precursors include, for example, those obtained from tetracarboxylic acid components containing aromatic, aliphatic or alicyclic tetracarboxylic dianhydrides. Here, aromatic tetracarboxylic dianhydrides are acid dianhydrides obtained by dehydrating four carboxyl groups within the molecule, which contain at least one carboxyl group bonded to an aromatic ring. Aliphatic tetracarboxylic dianhydrides are acid dianhydrides obtained by dehydrating four carboxyl groups bonded to a chain hydrocarbon structure. However, it is not necessary to be composed of only a chain hydrocarbon structure, and a part of it may have an alicyclic structure or an aromatic ring structure.

In addition, alicyclic tetracarboxylic dianhydride is an acid dianhydride obtained by dehydrating four carboxyl groups in the molecule, including at least one carboxyl group bonded to an alicyclic structure. However, none of these four carboxyl groups is bonded to an aromatic ring. In addition, it is not necessary to be composed only of an alicyclic structure, and a part of it may have a chain hydrocarbon structure or an aromatic ring structure.

The polyamide of the present invention is preferably obtained from a tetracarboxylic acid component including tetracarboxylic dianhydride represented by the following formula (2).

In the above formula (2), X is preferably a structure selected from the following (x-1) to (x-13).

In the above formulae (x-1) to (x-13), R ¹ to R ⁴ each independently represent 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, a monovalent organic group having 1 to 6 carbon atoms and having a fluorine atom, or a phenyl group. R ⁵ and R ⁶ each independently represent a hydrogen atom or a methyl group. j and k each independently represent an integer of 0 or 1. _{A 1} and A ₂ each independently represent a single bond, -O-, -CO-, -COO-, phenylene group, -SO ₂ -, or -CONH-. Two A ₂ 's may be the same or different. *1 is a bond to one of the anhydride groups, and *2 is a bond to the other anhydride group).

The above formula (x-1) is particularly preferably selected from the group consisting of the following formulas (x1-1) to (x1-6). In the above formulae (x1-1) to (x1-6), *1 represents a bond to one of the anhydride groups, and *2 represents a bond to another anhydride group.

As a more specific example of the above formulas (x-12) and (x-13), the following formulas (x-14) to (x-29) can be cited. In addition, the "*" in the formula represents the bonding position. The amount of the tetracarboxylic dianhydride or its derivative represented by the formula (2) is preferably 60-100 mol%, more preferably 80-100 mol%, and even more preferably 90-100 mol%, based on 1 mol of the total tetracarboxylic acid component reacting with the diamine component.

<Diamine Component> The diamine component used for producing the polyimide precursor is not particularly limited, but is preferably a diamine component containing a diamine represented by the following formula (3).

In the above formula (3), _A1 represents an alkylene group having 2 to 14 carbon atoms, or a group substituted by -O-, -CO-, -OCO-, or -COO- under the condition that at least one of the _-CH2- groups in the alkylene group is discontinuous. _A1 is preferably an alkylene group having 2 to 12 carbon atoms, or a group substituted by -O-, -CO-, -OCO-, or -COO- under the condition that at least one of the _-CH2- groups in the alkylene group is discontinuous, and more preferably an alkylene group having 2 to 10 carbon atoms, or a group substituted by -O-, -CO-, -OCO-, or -COO- under the condition that at least one of the _-CH2- groups in the alkylene group is discontinuous. _A2 represents a halogen atom, a hydroxyl group, an amine group, a thiol group, a nitro group, a phosphate group, or a monovalent organic group having 1 to 20 carbon atoms. When _A2 exists in plural numbers, _A2 may be the same or different. a is an integer of 0 to 4, and when a exists in plural numbers, a may be the same or different. b and c are each independently an integer of 1 or 2, and d is an integer of 0 or 1.

As the diamine represented by the above formula (3), diamines represented by the following formulas (3d-1) to (3d-9) are preferred. (In formulas (3d-8) and (3d-9), the two m's may be the same or different).

As the diamine represented by the above formula (3), the diamine represented by the following formula (3-1) to formula (3-12) is more preferred.

The amount of the diamine represented by the formula (3) is preferably 60-100 mol%, more preferably 80-100 mol%, and even more preferably 90-100 mol%, based on 1 mol of the total diamine components reacting with the tetracarboxylic acid component.

The polyimide polymer used in the present invention may have at least one nitrogen-containing structure (hereinafter also referred to as nitrogen-containing structure) selected from the group consisting of nitrogen-containing heterocyclic rings (excluding imide rings possessed by polyimide), diamine groups, and tertiary amine groups, from the viewpoint of improving the voltage retention of the obtained liquid crystal alignment film. The polyimide polymer having a nitrogen-containing structure can be obtained by using a monomer having a nitrogen-containing structure, such as a diamine having a nitrogen-containing structure, as at least a part of the raw materials.

Examples of the nitrogen-containing heterocyclic ring include pyrrole, imidazole, pyrazole, triazole, pyridine, pyrimidine, phthalimide, pyrrolidine, indole, benzimidazole, purine, quinoline, isoquinoline, naphthyridine, quinoxaline, phthalimide, triiron, carbazole, acridine, piperidine, piperidine, pyrrolidine, and hexamethyleneimine. Among them, pyridine, pyrimidine, pyrrolidine, piperidine, piperidine, quinoline, carbazole, or acridine is preferred.

The secondary amine group and the tertiary amine group which the diamine having a nitrogen-containing structure may have are represented by, for example, the following formula (n). In the above formula (n), R represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms; "*" represents a bond to the hydrocarbon group. Examples of the monovalent hydrocarbon group of R in the above formula (n) include alkyl groups such as methyl, ethyl, and propyl; cycloalkyl groups such as cyclohexyl; and aromatic groups such as phenyl and methylphenyl. R is preferably a hydrogen atom or a methyl group.

Specific examples of the diamine having a nitrogen-containing structure include 2,6-diaminopyridine, 3,4-diaminopyridine, 2,4-diaminopyrimidine, 3,6-diaminocarbazole, N-methyl-3,6-diaminocarbazole, 1,4-bis(4-aminophenyl)-piperidinium, 3,6-diaminoacridine, N-ethyl-3,6-diaminocarbazole, N-phenyl-3,6-diaminocarbazole, N,N'-bis(4-aminophenyl)-benzidine, N,N'-bis(4-aminophenyl)-N,N'-dimethylbenzidine, 4,4'-diaminodiphenylamine, N,N-bis(4-aminophenyl)-methylamine, and compounds represented by the following formulas (z-1) to (z-18).

From the viewpoint of improving the voltage retention of the liquid crystal display element, the usage ratio of the diamine having a nitrogen-containing structure is preferably 1 mol% or more, more preferably 2 mol% or more, relative to the total amount of the diamine used in the synthesis. Furthermore, the usage ratio is preferably 90 mol% or less, more preferably 80 mol% or less.

The polyimide polymer used in the present invention may also contain other diamines other than the diamines described above. Examples of other diamines are given below, but the present invention is not limited thereto. 4-(2-(methylamino)ethyl)aniline, 4-(2-aminoethyl)aniline, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ketone, 4,4'-diaminodiphenyl ether, diamines having photo-alignment groups such as diamines represented by the following formulas (g-1) to (g-9), 1-(4-aminophenyl)-1,3,3-trimethyl-1H-indane-5-amine, 1-(4-aminophenyl)-2,3-dihydro-1, 3,3-trimethyl-1H-inden-6-amine, diamines containing carboxyl groups such as 3,5-diaminobenzoic acid, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, bis[4-(4-aminophenoxy)phenyl]ether, 4,4'-bis(4-aminophenoxy)biphenyl, 1,4-diaminonaphthalene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 2,7-diaminonaphthalene, 2,2'-bis[4-(4-aminophenoxy)phenyl]ether [phenoxy)phenyl]propane, 2,2'-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2'-bis(4-aminophenyl)propane, diamines having a urea bond such as diamines represented by the following formulas (u-1) to (u-3), diamines having an amide bond such as diamines represented by the following formulas (u-4) to (u-7), 2-(2,4-diaminophenoxy)ethyl methacrylate, 2,4-diamino-N,N-diallylaniline, etc. A diamine having a photopolymerizable group at the end, a diamine having a steroid skeleton such as cholesteryloxy-3,5-diaminobenzene, cholesteryloxy-3,5-diaminobenzene, cholesteryloxy-2,4-diaminobenzene, 3,5-diaminobenzoic acid cholesteryl ester, 3,5-diaminobenzoic acid cholesteryl ester, 3,5-diaminobenzoic acid lanostanyl ester, 3,6-bis(4-aminobenzyloxy)cholestane, a diamine represented by the following formula (V-1) to (V-6),

(In formula (u-7), the two m's may be the same or different).

(In formula (V-6), the two k can be the same or different).

(In the above formulae (V-1) to (V-6), ^Xv1 to ^Xv4 and ^Xp1 to ^Xp2 each independently represent -( _CH2 ) _a- (a is an integer of 1 to 15), -CONH-, -NHCO-, -CON( _CH3 )-, _-NH- , -O-, _-CH2O- , _-CH2OCO- , -COO- or -OCO-; ^Xv5 represents -O-, _-CH2O- , -CH2OCO-, -COO- or -OCO-; Xa represents _{a single bond, -O-, -NH-, -O-(CH2)m-O-, -C(CH3)2-, -CO-, -(CH2)m-, -SO2-, -OC(CH3)2- , -CO- ( CH2 ) m- , -NH- ( CH2 ) m-} , _-SO2 -(CH ₂ ) _m -, -CONH-(CH ₂ ) _m -, -CONH-(CH ₂ ) _m -NHCO-, -COO-(CH ₂ ) _m -OCO-, -CONH-, -NH-(CH ₂ ) _m -NH- or -SO ₂ -(CH ₂ ) _m -SO ₂ -; m is an integer of 1 to 8; R ^v1 to R ^v4 , R ^1a to R ^1b each independently represents an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, or an alkoxyalkyl group having 2 to 20 carbon atoms), a diamine having a siloxane bond such as 1,3-bis(3-aminopropyl)-tetramethyldisiloxane, a diamine having a group "-N(D)-" (D represents a protective group that is detached by heating and replaced by a hydrogen atom, preferably a tert-butyloxycarbonyl group) of the following formulas (5-1) to (5-11), Diamines having an oxazoline structure such as formula (Ox-1) to (Ox-2), 1-(4-(2,4-diaminophenoxy)ethoxy)phenyl)-2-hydroxy-2-methylacetone, 2-(4-(2-hydroxy-2-methylpropionyl)phenoxy)ethyl-3,5-diaminobenzoate, 4,4-diaminodiphenyl ketone, 3,4'-diaminodiphenyl ketone and the like having a free radical polymerization initiator function.

(Boc represents tert-butoxycarbonyl).

<Production method of polyamide> The polyamide used as the polyimide precursor of the present invention can be produced by the following method. Specifically, it can be synthesized by reacting the above-mentioned tetracarboxylic acid component and the above-mentioned diamine component in the presence of an organic solvent at -20~150℃, preferably 0~50℃, for 30 minutes to 24 hours, preferably 1~12 hours (polycondensation). The organic solvent used in the above reaction is preferably N,N-dimethylformamide, N-methyl-2-pyrrolidone or γ-butyrolactone in view of the solubility of the monomer and the polymer, and two or more of these can also be mixed and used. The concentration of the polymer is preferably 1 to 30% by mass, more preferably 5 to 20% by mass, from the viewpoint of preventing the polymer from precipitating and easily obtaining a high molecular weight product.

The polyamine obtained by the above reaction can be recovered by injecting the reaction solution into a weak solvent while stirring the reaction solution sufficiently to precipitate the polyamine. Alternatively, after several precipitations, washing with a weak solvent, and drying at room temperature or with heat, a purified polyamine powder can be obtained. The weak solvent is not particularly limited, and water, methanol, ethanol, hexane, butyl cellulose, acetone, toluene, etc. can be cited.

When the polyimide precursor is a polyamic acid ester, it can be produced by known methods such as (1) a method of esterifying a polyamic acid obtained from a tetracarboxylic dianhydride and a diamine; (2) a method of reacting a tetracarboxylic acid diester dichloride with a diamine; or (3) a method of polycondensing a tetracarboxylic acid diester with a diamine.

The polyimide precursor can be prepared by using a suitable terminal blocking agent together with a tetracarboxylic acid derivative and a diamine as described above to obtain a terminal-blocked polymer. As the terminal blocking agent, for example, there can be mentioned acid anhydrides or di-tert-butyl dicarbonate such as maleic anhydride, nadic anhydride, phthalic anhydride, itaconic anhydride, cyclohexanedicarboxylic anhydride, 3-hydroxyphthalic anhydride, trimellitic anhydride, etc.; monoamine compounds such as aniline, 2-aminophenol, 3-aminophenol, 4-aminosalicylic acid, 5-aminosalicylic acid, 6-aminosalicylic acid, 2-aminobenzoic acid, 3-aminobenzoic acid, 4-aminobenzoic acid; monoisocyanate compounds such as ethyl isocyanate, phenyl isocyanate, naphthyl isocyanate, etc., etc. The amount of the terminal blocking agent used is preferably 40 mol parts or less, more preferably 30 mol parts or less, based on 100 mol parts in total of the diamine components used.

<Production method of polyimide> The polyimide used in the present invention can be produced by imidizing a polyamic acid or a polyamic acid ester as a polyimide precursor by a known method. For example, when producing polyimide from polyamic acid, it is simple to add a catalyst to a solution of polyamic acid obtained by the reaction of a diamine component and a tetracarboxylic acid component for (chemical) imidization. The imidization can be carried out by stirring the polymer to be imidized in an organic solvent in the presence of an alkaline catalyst and an acid anhydride.

As the organic solvent, the solvent used in the above-mentioned polymerization reaction can be used. As the alkaline catalyst, pyridine, triethylamine, trimethylamine, tributylamine, trioctylamine, etc. can be mentioned. Among them, pyridine is preferred because it has a moderate alkalinity required for the reaction to proceed. In addition, as the acid anhydride, acetic anhydride, trimellitic anhydride, pyromellitic anhydride, etc. can be mentioned. Among them, if acetic anhydride is used, it is easier to purify after the reaction.

The temperature for the imidization reaction is -20~140℃, preferably 0~100℃, and the reaction time can be 1~100 hours. The amount of alkaline catalyst is 0.5~30 mole times of the amide group, preferably 2~20 mole times, and the amount of acid anhydride is 1~50 mole times of the amide group, preferably 3~30 mole times. The imidization rate of the obtained polymer can be controlled by adjusting the amount of catalyst, temperature, and reaction time. Moreover, the imidization rate mentioned in this specification is the ratio of the imide group to the total amount of the imide group and carboxyl group (or its derivative) derived from tetracarboxylic dianhydride or its derivative. In the polyimide, the imidization rate does not necessarily need to be 100%, and can be adjusted arbitrarily according to the use or purpose. The imidization rate of the polyimide used in the present invention is preferably 20-100%, and more preferably 50-99%.

The solution of polyimide obtained as described above can be injected into a weak solvent while stirring to precipitate the polymer. After several precipitations and washing with a weak solvent, a refined polyimide powder can be obtained by drying at room temperature or with heat. The weak solvent is not particularly limited, but methanol, acetone, hexane, butyl cellulose, heptanone, methyl ethyl ketone, methyl isobutyl ketone, ethanol, toluene, benzene, etc. can be cited.

The molecular weight of the polyimide precursor and polyimide prepared as described above is preferably 2,000-500,000 in weight average molecular weight, more preferably 5,000-300,000, and particularly preferably 10,000-100,000. Also, the number average molecular weight is preferably 1,000-250,000, more preferably 2,500-150,000, and particularly preferably 5,000-50,000.

<Liquid crystal alignment agent> The liquid crystal alignment agent of the present invention has a form in which an aromatic compound of the above formula (1) is added to a solution in which a polymer having the ability to align liquid crystals is dissolved in a solvent. The content (concentration) of the polymer contained in the liquid crystal alignment agent of the present invention can be appropriately changed by setting the thickness of the coating to be formed, but from the point of view of forming a uniform and defect-free coating, it is preferably 1% by mass or more, and from the point of view of the storage stability of the solution, it is preferably 10% by mass or less. In addition, the content (concentration) of the aromatic compound of the above formula (1) added to the liquid crystal alignment agent of the present invention is preferably 0.1 to 5% by mass, more preferably 0.15 to 5% by mass, and particularly preferably 0.2 to 5% by mass. In addition, the content of the aromatic compound of the above formula (1), which is the total content of the above polymer and the aromatic compound of the above formula (1) contained in the liquid crystal alignment agent, is preferably 1-15% by mass, more preferably 2-10% by mass, and particularly preferably 2-8% by mass.

The solvent used for the liquid crystal alignment agent of the present invention is not particularly limited as long as it is a solvent that dissolves the aromatic compound of the above formula (1) and the above polymer. Specific examples are listed below. For example, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, dimethyl sulfoxide, γ-butyrolactone, 1,3-dimethyl-2-imidazolidinone, methyl ethyl ketone, cyclohexanone, cyclopentanone, 3-methoxy-N,N-dimethylpropaneamide or 4-hydroxy-4-methyl-2-pentanone, the solvents shown in the following formulas [D-1] to [D-3], etc. can be cited.

(In formula [D-1], ^D1 represents an alkyl group having 1 to 3 carbon atoms, in formula [D-2], ^D2 represents an alkyl group having 1 to 3 carbon atoms, and in formula [D-3], ^D3 represents an alkyl group having 1 to 4 carbon atoms). The solvent in the present invention is particularly preferably N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, γ-butyrolactone, 3-methoxy-N,N-dimethylpropaneamide or 1,3-dimethyl-2-imidazolidinone (hereinafter, these are also referred to as good solvents).

The liquid crystal alignment agent of the present invention may contain a solvent (also called a weak solvent) that can improve the coating properties or surface smoothness of the liquid crystal alignment film when the liquid crystal alignment agent is applied. Such weak solvents are preferably 1-80% by mass of the total solvent contained in the liquid crystal alignment agent, preferably 10-80% by mass, and more preferably 20-70% by mass.

Specific examples of weak solvents are listed below. Ethanol, isopropanol, 1-butanol, 2-butanol, isobutanol, tert-butanol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, isopentanol, tert-pentanol, 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-propylene glycol, 1,3-propylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 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, propylene carbonate Ethyl ester, 2-(methoxymethoxy)ethanol, butyl cellulose, ethylene glycol monoisoamyl ether, ethylene glycol monohexyl ether, 2-(hexyloxy)ethanol, furfuryl alcohol, diethylene glycol, propylene glycol, 1-butoxy-2-propanol, 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, butyl cellulose acetate, ethylene glycol monoacetate, ethylene glycol diacetate, diethylene glycol monoethyl ether acetate, diacetone alcohol, propylene glycol diacetate, diisoamyl ether, diethylene glycol monobutyl ethyl 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 acetate monoethyl ether, methyl pyruvate, ethyl pyruvate, methyl 3-methoxypropionate, methyl 3-ethoxypropionate, ethyl 3-methoxypropionate, 3-ethoxypropionic acid, 3-methoxypropionic acid, propyl 3-methoxypropionate, butyl 3-methoxypropionate, n-propyl lactate, n-butyl lactate, isoamyl lactate, diisobutyl ketone, ethyl carbitol or the solvents represented by the above formula [D-1] to [D-3], etc. Among them, butyl cellulose, 1-butoxy-2-propanol, butyl cellulose acetate, dipropylene glycol monomethyl ether, diacetone alcohol, diethylene glycol diethyl ether, diisoamyl ether, propylene glycol diacetate, diisobutyl ketone, ethyl carbitol or dipropylene glycol dimethyl ether are preferably used.

The liquid crystal alignment agent of the present invention may include a crosslinking compound having an epoxy group, an isocyanate group, an oxycyclobutyl group or a cyclocarbonate group, a crosslinking compound having at least one substituent selected from the group consisting of a hydroxyl group, a hydroxyalkyl group and a lower alkoxyalkyl group, or a crosslinking compound having a polymerizable unsaturated bond (but excluding the aromatic compound of formula (1)). It is preferred that there are two or more of these substituents or polymerizable unsaturated bonds in the crosslinking compound. The crosslinking compound may also be a combination of two or more types. As specific examples of preferred crosslinking compounds, the compounds shown in the following formulas (CL-1) to (CL-11) can be cited. The content of the crosslinking compound in the liquid crystal alignment agent of the present invention is preferably 0.1-150 parts by mass, more preferably 0.1-100 parts by mass, relative to 100 parts by mass of the polymer.

Furthermore, the liquid crystal alignment agent of the present invention may contain a compound that can improve the uniformity of the thickness or the surface smoothness of the film obtained by coating. As the compound, fluorine-based surfactants, silicone-based surfactants, non-ionic surfactants, etc. can be cited. More specifically, for example, Eftop EF301, EF303, EF352 (above, manufactured by Mitsubishi Materials Electronics Co., Ltd.), Megaface F171, F173, R-30 (above, manufactured by DIC), Fluorad FC430, FC431 (above, manufactured by 3M), Asahi Guard AG710, Surflon S-382, SC101, SC102, SC103, SC104, SC105, SC106 (above, manufactured by AGC), etc. can be cited.

Furthermore, in the liquid crystal alignment agent, as a compound that promotes charge transfer in the liquid crystal alignment film and promotes the decharge of the device, a nitrogen-containing heterocyclic amine represented by formula [M1] to formula [M156] published in [0194] to [0200] of International Publication WO2011/132751 (published on October 27, 2011) can also be added. This amine can be directly added to the liquid crystal alignment agent, but it is preferably added after being made into a solution with a concentration of 0.1 to 10% by mass, and more preferably 1 to 7% by mass. This solvent is not particularly limited as long as it can dissolve the specific polymer.

<Liquid crystal alignment film and liquid crystal display element> The liquid crystal alignment film of the present invention is a film obtained by applying the above-mentioned liquid crystal alignment agent on a substrate, drying it, and firing it. As a substrate, if it is a substrate with high transparency, it is not particularly limited, and a glass substrate, a silicon nitride substrate, an acrylic substrate, or a plastic substrate such as a polycarbonate substrate can be cited. A substrate formed with an ITO electrode for driving the liquid crystal is preferred from the point of view of simplifying the process. In a reflective liquid crystal display element, if it is a substrate with only one side, an opaque material such as a silicon wafer can also be used, and a light-reflecting material such as aluminum can also be used in the electrode at this time.

As a method of coating the liquid crystal alignment agent on the substrate and forming a film, screen printing, lithography, flexographic printing, inkjet method or spray method can be cited. Among them, the coating and film forming method using the inkjet method can be preferably used. After the liquid crystal alignment agent is coated on the substrate, the solvent can be evaporated to form a film (film) by heating means such as a hot plate, a heat circulation oven or an IR (infrared) oven. The drying and firing steps after coating the liquid crystal alignment agent can be selected at any temperature and time. Usually, in order to fully remove the contained solvent, it is fired at 50-180°C for 1-10 minutes, or in order to further perform thermal imidization, it can be fired at 150-300°C for 5-120 minutes. If the film after firing is too thin, the reliability of the liquid crystal display element may be reduced, so it is preferably 5-300nm, and more preferably 10-200nm.

As the alignment treatment method of the liquid crystal alignment film obtained by the liquid crystal alignment agent of the present invention, a friction treatment method may be used, but a light alignment treatment method is preferably used. As a light alignment treatment method, a method of irradiating the surface of the above-mentioned film-like object with radiation deflected in a certain direction, preferably firing at a temperature of 150~250°C according to the circumstances, to give liquid crystal alignment (also called liquid crystal alignment ability) can be cited. As radiation, ultraviolet light or visible light with a wavelength of 100~800nm can be used. Among them, ultraviolet light with a wavelength of 100~400nm is preferred, and ultraviolet light with a wavelength of 200~400nm is more preferred.

Furthermore, when irradiating radiation, in order to improve the liquid crystal alignment, the substrate having the above-mentioned film-like object can be irradiated while being heated at 50~250℃. The irradiation amount of the above-mentioned radiation is preferably 1~10,000mJ/ ^cm2 . Among them, 100~5,000mJ/ ^cm2 is preferred. The above-mentioned liquid crystal alignment film prepared in this way can stabilize and align the liquid crystal molecules in a certain direction. Furthermore, the liquid crystal alignment film that has been irradiated with polarized radiation by the above method can be treated with water or a solvent, or the liquid crystal alignment film that has been irradiated with radiation can be heated.

As the solvent used in the above-mentioned contact treatment, if it is a solvent that dissolves the decomposition product generated from the film by irradiation of radiation, it is not particularly limited. As a specific example, water, methanol, ethanol, 2-propanol, acetone, methyl ethyl ketone, 1-methoxy-2-propanol, 1-methoxy-2-propanol acetate, butyl celoxy, ethyl lactate, methyl lactate, diacetone alcohol, 3-methoxy methyl propionate, 3-ethoxy ethyl propionate, propyl acetate, butyl acetate, cyclohexyl acetate, etc. can be cited. Among them, from the point of versatility or the safety of the solvent, water, 2-propanol, 1-methoxy-2-propanol or ethyl lactate are preferred. Water, 1-methoxy-2-propanol or ethyl lactate are more preferred. The solvent can be one type, or two or more types can be combined.

As the above-mentioned contact treatment, immersion treatment or spray treatment (also called spray treatment) can be cited. The treatment time of such treatment is preferably 10 seconds to 1 hour from the point of view of efficiently dissolving the decomposition products generated from the film-like material by irradiation with radiation. Among them, it is preferably to carry out immersion treatment for 1 to 30 minutes. In addition, the solvent during the above-mentioned contact treatment may be at room temperature or heated, but is preferably 10 to 80°C. Among them, 20 to 50°C is preferred. In addition, from the point of view of the solubility of the decomposition products, ultrasonic treatment or the like may be carried out as needed.

After the above contact treatment, it is preferred to perform cleaning (also called rinsing) or calcining using a low-boiling point solvent such as water, methanol, ethanol, 2-propanol, acetone or methyl ethyl ketone. At this time, either rinsing or calcining can be performed, or both can be performed. The calcining temperature is preferably 150~300℃. Among them, 180~250℃ is preferred, and 200~230℃ is more preferred. In addition, the calcining time is preferably 10 seconds to 30 minutes. Among them, 1~10 minutes is preferred. For the heat treatment of the above-mentioned radiation-irradiated coating, it is preferably set at 50~300℃ for 1~30 minutes, and more preferably at 120~250℃ for 1~30 minutes.

The liquid crystal alignment film of the present invention is suitable as a liquid crystal alignment film for a liquid crystal display element of a transverse electric field mode such as an IPS mode or an FFS mode from the viewpoint of obtaining a high liquid crystal alignment property, and is particularly suitable as a liquid crystal alignment film for a liquid crystal display element of an FFS mode. The liquid crystal display element is obtained by preparing a liquid crystal cell by a known method after obtaining a substrate with a liquid crystal alignment film obtained from the liquid crystal alignment agent of the present invention, and using the liquid crystal cell. As an example of a method for preparing a liquid crystal cell, a liquid crystal display element of a passive matrix structure is described. In addition, it can also be a liquid crystal display element of an active matrix structure in which a switching element such as a TFT (Thin Film Transistor) is provided on each pixel portion constituting an image display.

Specifically, transparent glass substrates are prepared, a common electrode is set on one substrate, and a segment electrode is set on the other substrate. These electrodes can be, for example, ITO electrodes, patterned to display the desired image. Then, an insulating film is set on each substrate in a manner covering the common electrode and the segment electrode. The insulating film can be, for example, a SiO ₂ -TiO ₂ film formed by a sol-gel method.

Next, a liquid crystal alignment film is formed on each substrate, and one substrate is stacked on another substrate so that the liquid crystal alignment film surfaces face each other and are bonded to the periphery with a sealant. In order to control the gap between the substrates, spacers are usually mixed in advance in the sealant, and preferably, spacers for controlling the gap between the substrates are also pre-spread in the surface portion where the sealant is not provided. In a part of the sealant, an opening that can be filled with liquid crystal from the outside is provided. Next, the liquid crystal material is injected into the space surrounded by the two substrates and the sealant through the opening provided in the sealant, and then the opening is sealed with a bonding agent. During the injection, a vacuum injection method can be used, or a method using a capillary phenomenon in the atmosphere can be used. The liquid crystal material can be either a positive liquid crystal material or a negative liquid crystal material, but a negative liquid crystal material is preferred. Next, the polarizing plates are installed. Specifically , a pair of polarizing plates are attached to the surfaces of the two substrates on the opposite sides to the liquid crystal layer.

The following examples are given to illustrate the present invention in more detail, but the present invention is not limited thereto. The abbreviations of the following compounds and the methods for determining the properties are as follows. <Solvent> DMF: N,N-dimethylformamide, NMP: N-methyl-2-pyrrolidone GBL: γ-butyrolactone, BCS: butyl cylosurfactone <Diamine> DA-1: 1,2-bis(4-aminophenoxy)ethane DA-2: N-tert-butoxycarbonyl-N-(2-(4-aminophenyl)ethyl)-N-(4-aminobenzyl)amine DA-3: p-phenylenediamine, DA-4: refer to the following formula (DA-4) DA-5: 4,4'-diaminodiphenylamine DA-6: 4,4'-diaminodiphenylmethane

＜Tetracarboxylic dianhydride＞

＜Additives＞

T-1 to T-4 are novel compounds not disclosed in the literature, and their synthesis methods are described in detail in the following Synthesis Examples 1 to 4.

< ^1H -NMR measurement> Apparatus: Fourier transform superconducting nuclear magnetic resonance apparatus (FT-NMR) "AVANCE III" (manufactured by BRUKER) 500 MHz. Solvent: deuterated chloroform ( _CDCl3 ) or deuterated N,N-dimethylsulfoxide ([ _D6 ]-DMSO). Standard substance: tetramethylsilane (TMS).

(Synthesis Example 1) Synthesis of [T-1]:

In a 1L four-necked flask, 4,4'-biphenyldiboronic acid (22.5 g, 93 mmol), 3-chloro-2-methyl-1-propene (95.1 g, 1050 mmol), Najera catalyst I (0.244 g, 0.3 mmol), tetrabutylammonium bromide (13.5 g, 42 mmol), potassium carbonate (116.1 g, 840 mmol), DMF (250 g) and pure water (13 g) were added and stirred at 130°C. After the reaction was completed, the reaction solution was poured into ethyl acetate (1000 g), neutralized with 1N aqueous hydrochloric acid solution (1000 g), and then washed with pure water (1000 g). The obtained organic layer was concentrated and the obtained crude product was separated by silica gel column chromatography (eluent: hexane only) to obtain 4.7 g of a white solid. The solid was confirmed to be [T-1] by the ¹ H-NMR results shown below. ¹ H-NMR (500 MHz, [D ₆ ]-DMSO): δ7.57-7.60 (d, 4H), 7.25-7.27 (d, 4H), 4.80-4.81 (m, 2H), 4.76-4.77 (m, 2H), 3.34 (s, 4H), 1.65 (s, 6H)

(Synthesis Example 2) Synthesis of [T-2]:

In a 1L four-necked flask, add 2,6-dimethylphenol (50.0 g, 409 mmol), 3-chloro-2-methyl-1-propene (37.0 g, 409 mmol), potassium carbonate (84.8 g, 613 mmol), potassium iodide (6.80 g, 41 mmol) and DMF (500 g), and stir at 80°C. After the reaction is completed, pour the reaction system into ethyl acetate (500 g), and wash the organic layer with pure water (1500 g). The obtained organic layer is concentrated, and the obtained crude product is separated by silica gel column chromatography (eluent: hexane only), thereby obtaining 66.6 g of [T-2-1].

[T-2-1] (66.6 g, 378 mmol) and N,N-dimethylaniline (300 g) were added to a 1L four-necked flask and stirred at 180°C. After the reaction was completed, the reaction system was poured into ethyl acetate (1000 g), and the organic layer was washed with 1N aqueous hydrochloric acid solution (1000 g) and then with pure water (1000 g). The organic layer was concentrated to obtain 66.6 g of [T-2-2].

[T-2-2] (17.3 g, 98 mmol), 1,2-bis(toluenesulfonyloxy)ethane (18.5 g, 50 mmol), potassium carbonate (20.7 g, 150 mmol) and DMF (170 g) were added to a 500 mL four-necked flask and stirred at 80°C. After the reaction was completed, the reaction system was poured into ethyl acetate (500 g) and the organic layer was washed with pure water (1000 g). The obtained organic layer was concentrated and the crude product was separated by silica gel column chromatography (eluent: ethyl acetate/hexane = 1/30 (volume ratio)) to obtain 10.0 g of a transparent liquid. From the results of ¹ H-NMR shown below, it was confirmed that this liquid was [T-2]. ¹ H-NMR (500MHz, CDCl ₃ ): δ6.83(s, 4H), 4.78-4.79(m, 2H), 4.72-4.73(m, 2H), 4.09(s, 4H), 3.20(s, 4H), 2.30(s, 12H), 1.67(s, 6H)

(Synthesis Example 3) Synthesis of [T-3]:

In a 500 mL four-necked flask, 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenol (18.9 g, 86 mmol), 1,2-bis(toluenesulfonyloxy)ethane (15.9 g, 43 mmol), potassium carbonate (17.8 g, 129 mmol) and DMF (190 g) were added and stirred at 80° C. After the reaction was completed, potassium carbonate was removed by filtering the reaction system, and the filtrate was poured into ethyl acetate (1000 g), and the organic layer was washed with pure water (2000 g). The obtained organic layer was concentrated, and ethanol (60 g) was added to the crude product, followed by reslurry washing at room temperature to obtain 14.0 g of [T-3-1].

In a 500 mL four-necked flask, [T-3-1] (13.5 g, 29 mmol), 3-chloro-2-methyl-1-propene (39.4 g, 435 mmol), Najera catalyst I (0.071 g, 0.09 mmol), tetrabutylammonium bromide (3.73 g, 12 mmol), potassium carbonate (32.1 g, 232 mmol), DMF (100 g) and pure water (25 g) were added and stirred at 130°C.

After the reaction was completed, the reaction solution was poured into ethyl acetate (600 g) and washed with pure water (1200 g). The obtained organic layer was concentrated and the crude product was separated by silica gel column chromatography (eluent: ethyl acetate/hexane = 1/30 (volume ratio)) to obtain 1.6 g of a white solid. From the results of ¹ H-NMR shown below, it was confirmed that this solid was the target [T-3]. ¹ H-NMR (500MHz, CDCl ₃ ): δ7.09-7.11(d, 4H), 6.87-6.89(d, 4H), 4.78-4.79(m, 2H), 4.70-4.71(m, 2H), 4.30(s, 4H), 3.26(s, 4H), 1.67(s , 6H)

(Synthesis Example 4) Synthesis of [T-4]:

In a 500 mL four-necked flask, 2,6-dimethylphenol (25.0 g, 205 mmol), allyl bromide (29.8 g, 246 mmol), potassium carbonate (42.5 g, 308 mmol) and DMF (250 g) were added and stirred at 80°C. After the reaction was completed, the reaction system was poured into ethyl acetate (300 g), and the organic layer was washed with pure water (600 g) and concentrated to obtain 30.8 g of [T-4-1].

In a 500 mL four-necked flask, [T-4-1] (30.8 g, 190 mmol) and N,N-dimethylaniline (200 g) were added and stirred at 180°C. After the reaction was completed, the reaction system was poured into ethyl acetate (500 g), and the organic layer was washed with 1 N aqueous hydrochloric acid solution (500 g) and pure water (500 g), and the organic layer was concentrated to obtain 30.3 g of [T-4-2].

In a 500 mL four-necked flask, [T-4-2] (30.3 g, 187 mmol), 1,2-bis(toluenesulfonyloxy)ethane (34.4 g, 93 mmol), potassium carbonate (38.6 g, 279 mmol) and DMF (360 g) were added and stirred at 80°C. After the reaction was completed, the reaction system was poured into ethyl acetate (1000 g) and the organic layer was washed with pure water (2000 g). The obtained organic layer was concentrated and the crude product was separated by silica gel column chromatography (eluent: ethyl acetate/hexane = 1/80 (volume ratio)) to obtain 18.7 g of a transparent liquid. From the results of ¹ H-NMR shown below, it was confirmed that this liquid was the target [T-4]. ^1. ₂₂ (s, 12H)

<Viscosity measurement method> Use E-type viscometer TVE-22H (manufactured by Toki Sangyo Co., Ltd.) with a sample volume of 1.1 mL, conical rotor TE-1 (1°34’, R24), and a temperature of 25°C for measurement.

<Measurement method of molecular weight> The number average molecular weight (Mn) and weight average molecular weight (Mw) were calculated as polyethylene glycol and polyethylene oxide equivalent values by measurement using a GPC (normal temperature gel permeation chromatography) apparatus. GPC apparatus: Shodex (GPC-101), column: Shodex (KD803, KD805 in series), column temperature: 50°C, eluent: N,N-dimethylformamide (as additive, lithium bromide monohydrate (LiBr・H ₂ O) is 30 mmol/L, phosphoric acid-anhydrous crystals (o-phosphoric acid) is 30 mmol/L, tetrahydrofuran (THF) is 10 ml/L), flow rate: 1.0 ml/min. Standard samples for calibration curve preparation: TSK standard polyethylene oxide (weight average molecular weight (Mw) of about 900,000, 150,000, 100,000, 30,000) and POLYMER manufactured by Tosoh Corporation Polyethylene glycol manufactured by LABORATORIES (peak molecular weight (Mp) of approximately 12,000, 4,000, and 1,000). In order to avoid peak overlap, the measurement was performed on two samples, one of which was a mixture of four samples of 900,000, 100,000, 12,000, and 1,000, and the other was a mixture of three samples of 150,000, 30,000, and 4,000.

<Method for determination of imidization ratio> 20 mg of polyimide powder was placed in an NMR sample tube (NMR sample tube standard, φ5 (manufactured by Kusano Scientific Co., Ltd.)), dimethyl sulfoxide (DMSO-d ₆ , 0.05% TMS (tetramethylsilane) mixture) (0.53 mL) was added, and ultrasonic waves were applied to completely dissolve it. The solution was measured for 500 MHz proton NMR using a Fourier transform superconducting nuclear magnetic resonance device (FT-NMR) "AVANCE III" (manufactured by BRUKER). The imidization rate is determined by using the proton from the structure that does not change before and after imidization as the reference proton, and the peak accumulation value of this proton and the peak accumulation value of the proton from the NH group of the acylamidin that appears around 9.5ppm~10.0ppm, and is calculated by the following formula. Imidization rate (%) = (1-α・x/y) × 100 In the above formula, x is the peak accumulation value of the proton from the NH group of the acylamidin, y is the peak accumulation value of the reference proton, and α is the ratio of the number of reference protons to the number of protons of the NH group of the acylamidin in the case of polyacylamidin (acylamidization rate is 0%).

(Synthesis Example 5) In a 100 mL four-necked flask equipped with a stirring device and a nitrogen inlet tube, weigh DA-1 (3.91 g, 16.0 mmol), DA-2 (2.19 g, 6.41 mmol), DA-3 (0.519 g, 4.80 mmol) and DA-4 (1.54 g, 4.81 mmol), add NMP (46.2 g), and stir while supplying nitrogen to dissolve. While stirring this diamine solution, add CA-1 (5.70 g, 25.4 mmol) and CA-2 (1.20 g, 4.80 mmol), and further add NMP (39.1 g) so that the solid content concentration becomes 15 mass %, and stir at 40°C for 24 hours to obtain a polyamide solution (A) (viscosity: 450 mPa・s). The molecular weight of polyamine is Mn=11,200 and Mw=26,900.

(Synthesis Example 6) In a 100 mL four-necked flask equipped with a stirring device and a nitrogen inlet tube, DA-5 (5.10 g, 25.6 mmol) and DA-6 (1.27 g, 6.41 mmol) were taken, NMP (36.1 g) was added, and the mixture was dissolved by stirring while nitrogen was supplied. CA-2 (4.00 g, 16.0 mmol) and CA-3 (4.42 g, 15.0 mmol) were added while stirring the diamine solution, and NMP (47.7 g) was further added so that the solid content concentration became 15% by mass. The mixture was stirred at 50°C for 24 hours to obtain a polyamine solution (B) (viscosity: 904 mPa・s). The molecular weight of the polyamine was Mn=14,600 and Mw=37,500.

(Synthesis Example 7) In a 100 ml four-necked flask equipped with a stirring device and a nitrogen inlet tube, weigh the obtained polyamide solution (A) (30 g), add NMP (15.0 g), and stir for 30 minutes. Add acetic anhydride (4.89 g) and pyridine (1.51 g) to the obtained polyamide solution, heat at 50°C for 2 hours and 30 minutes to perform chemical imidization. The obtained reaction solution is added to methanol (154 mL) while stirring, and the precipitate is filtered and then washed with methanol (154 mL) 3 times. The obtained resin powder is dried at 60°C for 12 hours to obtain a polyimide resin powder (A). The imidization rate of the polyimide resin powder is 64%, Mn=9,900, Mw=20,000.

(Synthesis Example 8) In a 100 mL Erlenmeyer flask, weigh the polyimide resin powder (A) (3.00 g) obtained in Synthesis Example 7, add NMP (22.0 g) so that the solid content concentration becomes 12%, and stir at 70°C for 24 hours to dissolve it, thereby obtaining a polyimide solution (A).

(Example 1) In a 100 mL Erlenmeyer flask, weigh the polyimide solution (A) (3.80 g) obtained in Synthesis Example 8 and the polyamide solution (B) (4.56 g) obtained in Synthesis Example 6, add T-1 (0.114 g), NMP (1.64 g), GBL (6.00 g) and BCS (4.00 g), and stir at room temperature for 3 hours to obtain a liquid crystal alignment agent (1). In this liquid crystal alignment agent, no abnormalities such as turbidity or precipitation were observed, confirming that it was a uniform solution.

(Examples 2 to 5) Except that T-2, T-3, T-4 or T-5 were used instead of T-1, the liquid crystal alignment agents (2) to (5) of Examples 2 to 5 were obtained by the same method as Example 1. In these liquid crystal alignment agents (2) to (5), no abnormalities such as turbidity or precipitation were observed, and they were confirmed to be uniform solutions.

(Comparative Example 1) In a 100 mL Erlenmeyer flask, weigh the polyimide solution (A) (3.80 g) obtained in Synthesis Example 8 and the polyamide solution (B) (4.56 g) obtained in Synthesis Example 6, add NMP (1.64 g), GBL (6.00 g) and BCS (4.00 g), and stir at room temperature for 3 hours to obtain a liquid crystal alignment agent (6).

(Comparative Example 2) Except for using T-6 instead of T-1, a liquid crystal alignment agent (7) was obtained by the same method as in Example 1. In addition, in the liquid crystal alignment agents (6) and (7) obtained in the above-mentioned Comparative Examples 1 and 2, no abnormalities such as turbidity or precipitation were observed, and it was confirmed that they were uniform solutions.

(Example 6) The liquid crystal alignment agent (1) obtained in Example 1 was filtered through a filter with an aperture of 1.0 μm, and then coated on a glass substrate with a transparent electrode by spin coating. After drying on a hot plate at 80°C for 2 minutes, the coated surface was irradiated with 0.25 J/ ^cm2 of ultraviolet light with a wavelength of 254 nm and an extinction ratio of 26:1 through a polarizing plate, and then calcined in a hot air circulation oven at 230°C for 20 minutes to obtain a substrate with a liquid crystal alignment film with a film thickness of 100 nm. The two substrates obtained above were grouped together, and spacers with a diameter of 6 μm were spread on the liquid crystal alignment film surface of one of the substrates. A sealant was printed on this substrate, and another substrate was attached in such a way that the liquid crystal alignment film faces each other and the alignment direction becomes 0°, and then the sealant was hardened to make a hollow cell. In this hollow cell, liquid crystal MLC-7026-100 (Merck) was injected by the reduced pressure injection method, and the injection port was sealed to obtain a liquid crystal cell. The initial alignment of the liquid crystal cell was confirmed, and the flow alignment was not confirmed, and the alignment was good. This cell was heat-treated at 120°C for 60 minutes to make a liquid crystal cell.

[Evaluation method of liquid crystal alignment] Use a polarizing microscope (manufactured by NIKON, ECLIPSE E600 POL) to observe the liquid crystal alignment state in the liquid crystal cell produced by the above procedure. The liquid crystal alignment that can be confirmed and has no flow alignment is judged as "good", and the liquid crystal alignment that cannot be confirmed and has flow alignment is judged as "bad".

[Determination of voltage retention rate] After aging the above-mentioned liquid crystal cell by placing it on a backlight for 5 days, a 1V voltage was applied for 60μs at a temperature of 60°C, and the voltage after 500ms was measured. The voltage that could be maintained was calculated as the voltage retention rate. In the determination of the voltage retention rate, VHR-1 manufactured by Dongyang Technology Co., Ltd. was used. The result showed that the voltage retention rate of the alignment film formed by the liquid crystal alignment agent (1) at 60°C was 61.7%.

(Examples 7-10, Comparative Examples 3-4) Except that the liquid crystal alignment agent shown in Table 1 was used instead of the liquid crystal alignment agent (1), the liquid crystal cells were prepared in the same manner as in Example 6, and the liquid crystal alignment and voltage retention were evaluated. Table 1 shows the liquid crystal alignment and voltage retention of each obtained liquid crystal cell.

As shown in Table 1, it is confirmed that in Examples 6 to 10 in which additives (T-1) to (T-5) are added, the liquid crystal orientation is not reduced and the voltage holding ratio is improved compared to Comparative Example 3 in which these additives are not added and Comparative Example 4 in which an additive (T-6) different from the aromatic compound of the present invention is added.

In addition, the entire contents of the specification, patent scope, and abstract of Japanese Patent Application No. 2019-184619 filed on October 7, 2019 are cited here and incorporated as a disclosure of the specification of the present invention.

Claims (20)

A liquid crystal alignment agent, characterized by containing an aromatic compound having a structure represented by two or more of the following formula (1);

(R is a hydrogen atom or a methyl group; any hydrogen atom on the benzene ring may be substituted by a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a monovalent organic group having 1 to 6 carbon atoms containing a fluorine atom). The liquid crystal alignment agent of claim 1, wherein the aromatic compound is a compound represented by the following formula (b1);

(R is the same as in formula (1); n is an integer of 2 to 6. When n is 2, A represents a single bond or a divalent linking group. When n is 3 to 6, A represents an n-valent organic group). As in claim 2, the liquid crystal alignment agent, wherein n in the aforementioned formula (b1) is 2, and A represents a single bond or a divalent connecting group. The liquid crystal alignment agent of claim 2 or 3, wherein in the aforementioned formula (b1), the divalent linking group when n is 2 is a group represented by the following formula (a-1) or (a-2);

(R ₁ , R _1′ , R ₂ , and R _2′ each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; m1 and m2 each independently represent an integer of 1 to 18; n is an integer of 1 to 6; and “*” represents a bond). A liquid crystal alignment agent as claimed in any one of claims 1 to 3, wherein the aromatic compound is a compound with a molecular weight of less than 2000. The liquid crystal alignment agent of any one of claims 1 to 3, wherein the aromatic compound is selected from the group consisting of the following formulae (b-1) to (b-4) and (b-6);

For a liquid crystal alignment agent as in any one of claims 1 to 3, the content of the aforementioned aromatic compound is 0.1 to 5% by mass relative to the total amount of the liquid crystal alignment agent. The liquid crystal alignment agent of any one of claims 1 to 3 further contains a polymer capable of aligning liquid crystals. The liquid crystal alignment agent of any one of claims 1 to 3 contains at least one polymer selected from the group consisting of a polyimide precursor and an imide compound of the polyimide precursor. The liquid crystal alignment agent of claim 9, wherein the polyimide precursor is obtained using a tetracarboxylic acid component containing tetracarboxylic dianhydride represented by the following formula (2);

(X represents a structure selected from the following (x-1) to (x-13));

(R ¹ to R ⁴ each independently represents 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, a monovalent organic group having 1 to 6 carbon atoms containing a fluorine atom, or a phenyl group; R ⁵ and R ⁶ each independently represent a hydrogen atom or a methyl group; j and k each independently represent an integer of 0 or 1; A ₁ and A ₂ each independently represent a single bond, -O-, -CO-, -OCO-, phenylene group, -COO-, -SO ₂ -, or -CONH-; two A _2's may be the same or different; *1 is a bond to one of the anhydride groups, and *2 is a bond to the other anhydride group). The liquid crystal alignment agent of claim 10, wherein the aforementioned (x-1) is selected from the group consisting of the following formulas (x1-1) to (x1-6);

(*1 is the bond to one of the anhydride groups, *2 is the bond to the other anhydride group). The liquid crystal alignment agent of claim 9, wherein the polyimide precursor is obtained by using a diamine component containing a diamine represented by the following formula (3);

( _A1 represents an alkylene group having 2 to 14 carbon atoms, or a group substituted by -O-, -CO-, -OCO- or -COO- under conditions such that at least one _-CH2- of the alkylene group is discontinuous; _A2 represents a halogen atom, a hydroxyl group, an amine group, a thiol group, a nitro group, a phosphate group or a monovalent organic group having 1 to 20 carbon atoms; when _A2 exists in plural, _A2 may be the same or different; a is an integer of 0 to 4; when a exists in plural, a may be the same or different; b and c are each independently an integer of 1 or 2, and d is an integer of 0 or 1). The liquid crystal alignment agent of claim 12, wherein the diamine represented by the aforementioned formula (3) is selected from the group consisting of the following formulas (3-1) to (3-12);

As in claim 9, the liquid crystal alignment agent, wherein the aforementioned polyimide precursor is obtained using a diamine component, and the diamine component comprises a diamine having at least one nitrogen-containing structure selected from the group consisting of a nitrogen-containing heterocyclic ring (but excluding the imide ring of the polyimide), a diamine group, and a tertiary amine group. A method for manufacturing a liquid crystal alignment film, which comprises applying a liquid crystal alignment agent as described in any one of claims 1 to 14 on a substrate, firing the substrate, and irradiating the obtained film with polarized radiation. A method for manufacturing a liquid crystal alignment film as claimed in claim 15, wherein the sintering is performed at a temperature of 150-250°C. A liquid crystal alignment film, which is formed by a liquid crystal alignment agent as described in any one of claims 1 to 14. A liquid crystal display element having a liquid crystal alignment film as claimed in claim 17. For example, the liquid crystal display element in claim 18 is an IPS drive mode or a FFS drive mode. An aromatic compound selected from any one of the group consisting of the following formulas (b-1) to (b-4);