JP7533470B2 - Liquid crystal alignment agent, liquid crystal alignment film, and liquid crystal display element - Google Patents

Description

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.

Conventionally, various driving methods have been developed for liquid crystal display elements, with different electrode structures and physical properties of the 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, and FFS (Finge Field Switching) type. These liquid crystal display elements generally have a liquid crystal alignment film for aligning the liquid crystal molecules.

Known materials for liquid crystal alignment films include polymers such as polyamic acid, polyamic acid ester, polyimide, and polyamide. Currently, the liquid crystal alignment film that is most widely used industrially is produced by rubbing the surface of a film formed on an electrode substrate using a polymerizable composition containing the above polymer in one direction with a cloth such as cotton, nylon, or polyester, a process known as rubbing.

Rubbing is an industrially useful method that is simple and has excellent productivity. However, as liquid crystal display elements become more powerful, precise, and larger, various problems arise, such as scratches on the alignment film surface, dust generation, effects of mechanical force and static electricity, and non-uniformity within the alignment treatment surface.

As an alternative to rubbing treatment, a photo-alignment method is known in which liquid crystal alignment ability is imparted by irradiation with polarized radiation. As liquid crystal alignment treatments using the photo-alignment method, methods utilizing photoisomerization reactions, photocrosslinking reactions, photodecomposition reactions, etc. have been proposed (see Non-Patent Document 1). Patent Document 1 proposes using a polyimide film having an alicyclic structure such as a cyclobutane ring in the main chain for the photo-alignment method.

The above-mentioned photoalignment method is a rubbing-less alignment treatment method that can be produced using an industrially simple manufacturing process, and is also attracting attention as a promising liquid crystal alignment treatment method because it is expected to improve the contrast and viewing angle characteristics of liquid crystal display elements using IPS and FFS drive methods compared to liquid crystal alignment films obtained using rubbing treatment methods.

Japanese Patent Application Publication No. 9-297313

"Liquid Crystal Photo-Alignment Film" Kidowaki, Ichimura, Functional Materials, November 1997, Vol. 17, No. 11, pp. 13-22

In recent years, the scope of use of liquid crystal display elements has expanded, and liquid crystal display elements may be used for long periods of time in high temperature and high humidity environments or in environments exposed to light irradiation. A liquid crystal alignment film is required to be able to withstand use in such harsh environments, and a high voltage retention rate is one of its important characteristics. However, according to the findings of the present inventors, it has become clear that in the case of photo-alignment methods in which chemical changes are caused by irradiation with radiation or the like, the voltage retention rate tends to decrease. In addition, it has become clear that when alignment ability is imparted by the photo-alignment method, the liquid crystal alignment property is insufficient, and image sticking becomes a problem, for example, in liquid crystal display elements using an IPS driving method or an FFS driving method.

Therefore, the present invention aims to provide a liquid crystal alignment agent for obtaining a liquid crystal display element that has a high voltage retention rate and good liquid crystal alignment properties even in harsh environments, even in the case of alignment treatment using a photo-alignment method that causes chemical changes due to exposure to radiation, etc., and that can suppress burn-in that occurs in liquid crystal display elements using an IPS drive system or an FFS drive system, a liquid crystal alignment film obtained from the liquid crystal alignment agent, a liquid crystal display element having the liquid crystal alignment film, and further, a new compound for use in the liquid crystal alignment agent.

但し、Ｒは、水素原子又はメチル基である。ベンゼン環上の任意の水素原子は、ヒドロキシ基、ハロゲン原子、炭素数１～６のアルキル基、炭素数１～６のアルコキシ基、又はフッ素原子を含有する炭素数１～６の１価の有機基により置換されていてもよい。 As a result of intensive research, the present inventors have found that the above object can be achieved by a liquid crystal alignment agent containing, as an additive, an aromatic compound having a specific chemical structure as shown below, and have completed the present invention.
The present invention relates to a liquid crystal aligning agent characterized by containing an aromatic compound having two or more structures represented by the following formula (1), a liquid crystal alignment film obtained from the liquid crystal aligning agent, a liquid crystal display element having the liquid crystal alignment film, and further, a novel compound used in the liquid crystal aligning agent.

In the formula, R is a hydrogen atom or a methyl group, and any hydrogen atom on the benzene ring may be substituted with 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, even in the case of alignment treatment using a photo-alignment method in which a chemical change occurs due to exposure to radiation or the like, a liquid crystal alignment agent for obtaining a liquid crystal display element that has a high voltage retention rate and good liquid crystal alignment properties even in harsh environments, and in particular can suppress burn-in even in the IPS drive system or FFS drive system, a liquid crystal alignment film obtained from the liquid crystal alignment agent, a liquid crystal display element having the liquid crystal alignment film, and further a novel compound for use in the liquid crystal alignment agent are provided.

<Aromatic compound of formula (1)>
The liquid crystal aligning agent of the present invention is characterized in that it contains an aromatic compound having two or more structures represented by the following formula (1) (hereinafter, sometimes referred to as an 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 with 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 containing a fluorine atom. Examples of the monovalent organic group having a fluorine atom include a trifluoromethyl group, a trifluoroethyl group, a trifluoromethoxy group, and a trifluoroethoxy group.

In the liquid crystal aligning agent of the present invention, by containing the aromatic compound of the above formula (1) as an additive, as specifically illustrated in the examples described later, even in the case of alignment treatment by a photoalignment method in which a chemical change occurs due to irradiation with radiation, etc., a liquid crystal alignment film in a liquid crystal display element having a high voltage holding ratio and good liquid crystal alignment property under harsh environments can be obtained. Although the mechanism is not necessarily clear, it is generally considered as follows.
In the alignment treatment by the photo-alignment method, for example, the surface of a film-like material formed from a liquid crystal alignment agent on the surface of a substrate is irradiated with nearly linearly polarized high-energy UV light. In this case, the irradiation of UV light produces decomposition products of the organic matter that constitutes the film-like material, which become impurities that cause a decrease in the voltage retention rate in the liquid crystal alignment film, and thus it is believed that the voltage retention rate of the liquid crystal alignment film is reduced.
However, in the liquid crystal aligning agent of the present invention, when the above-mentioned impurities are generated by irradiation with UV light, the aromatic compound of the above formula (1) has a functional group capable of reacting with the impurities, and this reacts with the impurities that cause a decrease in the voltage holding ratio, thereby reducing the impurities contained in the obtained liquid crystal alignment film. Therefore, the liquid crystal alignment film obtained from the liquid crystal aligning agent of the present invention is believed to maintain a high voltage holding ratio.
In addition, since the aromatic compound of the formula (1) contained in the liquid crystal alignment agent of the present invention has a highly planar structure, it is believed that the liquid crystal alignment of the resulting liquid crystal alignment film is not hindered, and a liquid crystal alignment film having high liquid crystal alignment properties can be obtained. Therefore, in the IPS driving method or FFS driving method, even when the liquid crystal display element is driven for a long time, the liquid crystal returns to the same state as before the driving, and it is believed that a liquid crystal display element with less image sticking can be obtained.

上記式（ｂ１）において、Ｒは、上記式（１）における場合と同義である。ｎは、２～６の整数であり、ｎが２の場合、Ａは、単結合又は２価の連結基を表し、ｎが３～６の場合、Ａはｎ価の有機基を表す。 The aromatic compound of the above formula (1) is preferably a compound represented by the following formula (b1).

In the above formula (b1), R has the same meaning 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 hydrocarbon group, an n-valent heteroatom-containing group containing a group having a heteroatom between the carbon atoms of the hydrocarbon group or at the end of the hydrocarbon group, and an n-valent organic group in which some or all of the hydrogen atoms of the hydrocarbon group and the heteroatom-containing group are substituted with substituents.
Examples of the divalent linking group for A include divalent hydrocarbon groups, divalent heteroatom-containing groups containing a group having a heteroatom between the carbon atoms of the hydrocarbon group or at the end of the hydrocarbon group, divalent linking groups in which some or all of the hydrogen atoms of the hydrocarbon group and heteroatom-containing group have been substituted with substituents, -S(═O) ₂ -, -CO-, -O-, -S-, -NR-CO- (R represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms), -NR-CO-NR- (R represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms), and the like.

Examples of n-valent hydrocarbon groups include chain hydrocarbons having 1 to 30 carbon atoms, such as alkanes such as methane, ethane, propane, and butane; alkenes such as ethylene, propylene, butylene, and pentene; alkynes such as ethyne, propyne, butyne, and pentyne; alicyclic hydrocarbons having 3 to 30 carbon atoms, such as cycloalkanes such as cyclopropane, cyclobutane, cyclopentane, cyclohexane, norbornane, and adamantane; cycloalkenes such as cyclopropene, cyclobutene, cyclopentene, cyclohexene, and norbornene; aromatic hydrocarbons having 6 to 30 carbon atoms, such as benzene, toluene, xylene, mesitylene, naphthalene, methylnaphthalene, dimethylnaphthalene, and anthracene; and hydrocarbons in which some of the carbon-carbon bonds of the chain hydrocarbons have been replaced with the above-mentioned alicyclic hydrocarbons or aromatic hydrocarbons. Examples of the divalent hydrocarbon group include divalent groups obtained by removing two hydrogen atoms from the above-mentioned examples of the n-valent hydrocarbon groups.

Examples of the group having a heteroatom include groups having at least one atom selected from the group consisting of an oxygen atom, a nitrogen atom, a silicon atom, a phosphorus atom, and a sulfur atom. Specific examples include -O-, -NR- (wherein R represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms), -CO-, -S-, -CO-, and combinations of these. Of these, -O- is preferred.

Examples of the substituent include halogen atoms such as a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom; alkoxy groups such as a methoxy group, an ethoxy group, and a propoxy group; alkoxycarbonyl groups such as a methoxycarbonyl group and an ethoxycarbonyl group; alkoxycarbonyloxy groups such as a methoxycarbonyloxy group and an ethoxycarbonyloxy group; a cyano group, a nitro group, and the like.
In the above formula (b1), n is preferably 2, and A is preferably a single bond or a divalent linking group.

上記式（ａ－１）、（ａ－２）中、Ｒ_１、Ｒ_１’、Ｒ_２、Ｒ_２’は、それぞれ独立に、水素原子又は炭素数１～４、好ましくは炭素数１又は２のアルキル基を表す。ｍ１及びｍ２は、それぞれ独立に、１～１８、好ましくは１～６の整数である。ｎは１～６、好ましくは１～４の整数である。また、「＊」は結合手を表す。 The divalent linking group is preferably one having a structure represented by the following formula (a-1) or (a-2).

In the above formulas (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. n represents an integer of 1 to 6, preferably 1 to 4. In addition, "*" represents a bond.

The aromatic compound of the above formula (1) preferably has a molecular weight of 2000 or less, more preferably 1500 or less, in order to enhance reactivity with decomposition products generated by the photoalignment method. On the other hand, in order to suppress sublimation of the aromatic compound due to firing, 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 the prior art.

<Polymer>
The liquid crystal aligning agent of the present invention containing the aromatic compound of the above formula (1) contains a polymer capable of aligning liquid crystals, similar to known ones, but such a polymer is not particularly limited as long as it has the ability to align liquid crystals.
Examples of such polymers include polyimide precursors, polyimides which are imidized products of polyimide precursors, acrylic polymers, methacrylic polymers, acrylamide polymers, methacrylamide polymers, polystyrene, polysiloxanes, polyamides, polyesters, polyurethanes, polycarbonates, polyureas, polyphenols (novolac resins), maleimide polymers, and polymers into which a compound having an isocyanuric acid skeleton or a triazine skeleton has been introduced. Such polymers can be used alone or in combination of two or more.

The raw materials for producing these polymers include the following.
When the polymer is a polyimide precursor or polyimide such as polyamic acid or polyamic acid ester, at least one tetracarboxylic acid component selected from tetracarboxylic acids or derivatives thereof and a diamine;
When the polymer is a (meth)acrylic polymer, it is (meth)acrylic acid or a derivative thereof, or a (meth)acrylic acid ester or a derivative thereof; when the polymer is a (meth)acrylamide polymer, it is (meth)acrylamide or a derivative thereof;

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

When the polymer is a polyurethane, an isocyanate, a compound, and a compound having a hydroxyl group; when the polymer is a polycarbonate, a bisphenol derivative and phosgene or a phosgene equivalent (e.g., trichlorophosgene) or diphenyl carbonate;
When the polymer is a polyurea, it is a bisisocyanate derivative and a diamine component; when the polymer is a maleimide polymer, it is a maleimide derivative alone or copolymerized with styrene;
In the case where the polymer is a polymer into which a compound having an isocyanuric acid skeleton or a triazine skeleton has been introduced, the compound has an isocyanuric acid skeleton or a triazine skeleton.

<Polyimide Polymer>
As the polymer contained in the liquid crystal aligning agent of the present invention, from the viewpoints of practicality as a liquid crystal aligning agent and mechanical and electrical properties of the coating film, one or more polymers selected from the group consisting of polyimide precursors and polyimides which are imidized products of polyimide precursors (hereinafter, also referred to as polyimide-based polymers) are preferred.
The polyimide polymer can be produced by a known method. For example, a polyamic acid, which is a polyimide precursor, can be obtained by a polymerization (condensation) reaction between a tetracarboxylic acid component made of a tetracarboxylic dianhydride or a derivative thereof and a diamine component, and a polyimide can be obtained by imidizing the polyimide precursor.

<Tetracarboxylic acid component>
The polyamic acid, which is a polyimide precursor, may be, for example, one obtained from a tetracarboxylic acid component containing an aromatic, aliphatic, or alicyclic tetracarboxylic acid dianhydride. Here, the aromatic tetracarboxylic acid dianhydride is an acid dianhydride obtained by intramolecular dehydration of four carboxyl groups, including at least one carboxyl group bonded to an aromatic ring. The aliphatic tetracarboxylic acid dianhydride is an acid dianhydride obtained by intramolecular dehydration of four carboxyl groups bonded to a chain hydrocarbon structure. However, it is not necessary for the polyamic acid dianhydride to be composed only of a chain hydrocarbon structure, and it may have an alicyclic structure or an aromatic ring structure as a part of it.

An alicyclic tetracarboxylic dianhydride is an acid dianhydride obtained by intramolecular dehydration of four carboxyl groups, including at least one carboxyl group bonded to an alicyclic structure, provided that none of the four carboxyl groups are bonded to an aromatic ring.
In addition, it is not necessary for the structure to be composed solely of an alicyclic structure, and it may also have a chain hydrocarbon structure or an aromatic ring structure as a part thereof.

The polyamic acid of the present invention is preferably one obtained from a tetracarboxylic acid component containing a 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 formulas (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 a fluorine atom, or a phenyl group.
^R5 and ^R6 each independently represent a hydrogen atom or a methyl group. j and k each independently represent an integer of 0 or 1. _A1 and _A2 each independently represent a single bond, -O-, -CO-, -COO-, phenylene, _-SO2- , or -CONH-. The two _A2s may be the same or different. *1 is a bond bonded to one acid anhydride group, and *2 is a bond bonded to the other acid anhydride group.)

上記式（ｘ１－１）～（ｘ１－６）において、＊１は一方の酸無水物基に結合する結合手を表し、また、＊２は他方の酸無水物基に結合する結合手を表す。 The above formula (x-1) is preferably one 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 bonded to one acid anhydride group, and *2 represents a bond bonded to the other acid anhydride group.

上記式（２）で表されるテトラカルボン酸二無水物若しくはその誘導体の使用量は、ジアミン成分と反応させる全テトラカルボン酸成分１モルに対して、６０～１００モル％含むことが好ましく、８０～１００モル％がより好ましく、９０～１００モル％がさらに好ましい。 Preferred specific examples of the above formulae (x-12) and (x-13) include the following formulae (x-14) to (x-29), in which "*" represents a bonding position.

The amount of the tetracarboxylic dianhydride represented by the above formula (2) or a derivative thereof used is preferably 60 to 100 mol %, more preferably 80 to 100 mol %, and even more preferably 90 to 100 mol %, based on 1 mol of the total tetracarboxylic acid components to be reacted with the diamine components.

<Diamine component>
The diamine component used in the production of the polyimide precursor is not particularly limited, but a diamine component containing a diamine represented by the following formula (3) is preferred.

In the above formula (3), A ₁ represents an alkylene group having 2 to 14 carbon atoms, or a group in which at least one of the -CH ₂ - groups in the alkylene is replaced with -O-, -CO-, -OCO- or -COO- while not being consecutive. _{A 1} is more preferably an alkylene group having 2 to 12 carbon atoms, or a group in which at least one of the -CH ₂ - groups in the alkylene is replaced with -O-, -CO-, -OCO- or -COO- while not being consecutive, and even more preferably an alkylene group having 2 to 10 carbon atoms, or a group in which at least one of the -CH ₂ - groups in the alkylene is replaced with -O-, -CO-, -OCO- or -COO- while not being consecutive.
_A2 represents a halogen atom, a hydroxyl group, an amino group, a thiol group, a nitro group, a phosphate group, or a monovalent organic group having 1 to 20 carbon atoms. When a plurality of _A2s are present, _A2s may be the same or different. a is an integer of 0 to 4, and when a plurality of as are present, 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.

（式（３ｄ－８）および（３ｄ－９）において、２つのｍは同一でも異なってもよい。） As the diamine represented by the above formula (3), diamines represented by the following formulas (3d-1) to (3d-9) are preferable.

(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), diamines represented by the following formulas (3-1) to (3-12) are more preferable.

The amount of diamine represented by the above formula (3) used is preferably 60 to 100 mol%, more preferably 80 to 100 mol%, and even more preferably 90 to 100 mol%, per mole of the total diamine components to be reacted 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 a nitrogen-containing heterocycle (excluding the imide ring of polyimide), a secondary amino group, and a tertiary amino group, from the viewpoint of increasing the voltage retention rate of the resulting liquid crystal alignment film. A polyimide polymer having a nitrogen-containing structure can be obtained by using a monomer having a nitrogen-containing structure, for example, a diamine having a nitrogen-containing structure, as at least a part of the raw material.

Examples of the nitrogen-containing heterocycle include pyrrole, imidazole, pyrazole, triazole, pyridine, pyrimidine, pyridazine, pyrazine, indole, benzimidazole, purine, quinoline, isoquinoline, naphthyridine, quinoxaline, phthalazine, triazine, carbazole, acridine, piperidine, piperazine, pyrrolidine, and hexamethyleneimine. Of these, pyridine, pyrimidine, pyrazine, piperidine, piperazine, quinoline, carbazole, and acridine are preferred.

上記式（ｎ）において、Ｒは、水素原子又は炭素数１～１０の１価の炭化水素基を表す。「＊」は、炭化水素基に結合する結合手を表す。
上記式（ｎ）中のＲの１価の炭化水素基としては、例えば、メチル基、エチル基、プロピル基等のアルキル基；シクロヘキシル基等のシクロアルキル基；フェニル基、メチルフェニル基等のアリール含有基等が挙げられる。Ｒは、好ましくは水素原子又はメチル基である。 The secondary amino group and tertiary amino group that the diamine having a nitrogen-containing structure may have are represented, for example, by 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 bonded to the hydrocarbon group.
Examples of the monovalent hydrocarbon group represented by R in the above formula (n) include alkyl groups such as methyl, ethyl, and propyl groups, cycloalkyl groups such as cyclohexyl groups, and aryl-containing groups such as phenyl and methylphenyl groups. R is preferably a hydrogen atom or a methyl group.

Specific examples of diamines having a nitrogen-containing structure include, for example, 2,6-diaminopyridine, 3,4-diaminopyridine, 2,4-diaminopyrimidine, 3,6-diaminocarbazole, N-methyl-3,6-diaminocarbazole, 1,4-bis-(4-aminophenyl)-piperazine, 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 increasing the voltage retention rate of the liquid crystal display element, the proportion of the diamine having a nitrogen-containing structure used is preferably 1 mol% or more, more preferably 2 mol% or more, based on the total amount of diamine used in the synthesis. The proportion is preferably 90 mol% or less, more preferably 80 mol% or less.

The polyimide polymer used in the present invention may contain other diamines in addition to the diamines described above. Examples of other diamines are given below, but the present invention is not limited to these.
4-(2-(methylamino)ethyl)aniline, 4-(2-aminoethyl)aniline, 4,4'-diaminodiphenylmethane, 4,4'-diaminobenzophenone, 4,4'-diaminodiphenylether, diamines having a photoalignment group such as diamines represented by the following formulas (g-1) to (g-9), 1-(4-aminophenyl)-1,3,3-trimethyl-1H-indan-5-amine, 1-(4-aminophenyl)-2,3-dihydro ... H-inden-6-amine, carboxyl group-containing diamines 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-amino photopolymerizable compounds such as 2,4-diamino-N,N-diallylaniline, 2,2'-bis[4-(aminophenoxy)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, and 2,4-diamino-N,N-diallylaniline Diamines having a polymerizable group at their terminals, diamines having a steroid skeleton such as cholestanyloxy-3,5-diaminobenzene, cholestenyloxy-3,5-diaminobenzene, cholestanyloxy-2,4-diaminobenzene, cholestanyl 3,5-diaminobenzoate, cholestanyl 3,5-diaminobenzoate, lanostannyl 3,5-diaminobenzoate, and 3,6-bis(4-aminobenzoyloxy)cholestane, diamines represented by the following formulae (V-1) to (V-6),

（式（ｕ―７）において、２つのｍは同一でも異なってもよい。）

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

（式（ｖ―６）において、２つのｋは同一でも異なってもよい。）

(In formula (v-6), two k's may be the same or different.)

(In the above formulas (V-1) to (V-6), X ^v1 to X ^v4 and X ^p1 to X ^p2 each independently represent -(CH ₂ ) _a - (a is an integer of 1 to 15), -CONH-, -NHCO-, -CON(CH ₃ )-, -NH-, -O-, -CH ₂ O-, -CH ₂ OCO-, -COO-, or -OCO-; X ^v5 represents -O-, -CH ₂ O-, -CH ₂ OCO-, -COO-, or -OCO-; Xa represents a single bond, -O-, -NH-, -O-(CH ₂ ) _m -O-, -C(CH ₃ ) ₂ -, -CO-, -(CH ₂ ) _m -, -SO ₂ -, -O-C(CH ₃ ) _{R v1} to R v4 represent -NH-(CH ₂ ) _m -, -SO _{2 -} (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 -} , and m is an integer of ^{1 to} 8. Each of ^1b 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; diamines having a siloxane bond such as 1,3-bis(3-aminopropyl)-tetramethyldisiloxane; and groups having "-N(D)-" such as those of the following formulas (5-1) to (5-11) (D represents a protecting group which is eliminated by heating and is replaced with a hydrogen atom, and is preferably a tert-butoxycarbonyl group). diamines having an oxazoline structure such as those represented by the following formulas (Ox-1) to (Ox-2); diamines having a radical polymerization initiator function such as 1-(4-(2,4-diaminophenoxy)ethoxy)phenyl)-2-hydroxy-2-methylpropanone, 2-(4-(2-hydroxy-2-methylpropanoyl)phenoxy)ethyl-3,5-diaminobenzoate, 4,4-diaminobenzophenone, and 3,4'-diaminobenzophenone.

（Ｂｏｃはｔ－ブトキシカルボニル基を表す。）

(Boc represents a t-butoxycarbonyl group.)

<Method of producing polyamic acid>
The polyamic acid, which is a polyimide precursor used in 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 to 150° C., preferably 0 to 50° C., for 30 minutes to 24 hours, preferably 1 to 12 hours (polycondensation).
The organic solvent used in the above reaction is preferably N,N-dimethylformamide, N-methyl-2-pyrrolidone, or γ-butyrolactone in terms of the solubility of the monomer and polymer, and two or more of these may be mixed for use. The concentration of the polymer 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 a high molecular weight product is easily obtained.

The polyamic acid obtained by the above reaction can be precipitated and recovered by injecting the reaction solution into a poor solvent while stirring it thoroughly. 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.

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

The polyimide precursor may be a terminal-capped polymer obtained by using an appropriate terminal-capping agent together with the above-mentioned tetracarboxylic acid derivative and diamine during the production thereof.
Examples of the end-capping agent include acid monoanhydrides such as maleic anhydride, nadic anhydride, phthalic anhydride, itaconic anhydride, cyclohexanedicarboxylic anhydride, 3-hydroxyphthalic anhydride, and trimellitic anhydride; di-tert-butyl dicarbonate; monoamine compounds such as aniline, 2-aminophenol, 3-aminophenol, 4-aminosalicylic acid, 5-aminosalicylic acid, 6-aminosalicylic acid, 2-aminobenzoic acid, 3-aminobenzoic acid, and 4-aminobenzoic acid; and monoisocyanate compounds such as ethyl isocyanate, phenyl isocyanate, and naphthyl isocyanate.
The proportion of the end-capping agent used is preferably 40 parts by mol or less, and more preferably 30 parts by mol or less, per 100 parts by mol of the total of the diamine components used.

<Method of producing polyimide>
The polyimide used in the present invention can be produced by imidizing a polyimide precursor, a polyamic acid or a polyamic acid ester, by a known method.
For example, when producing a polyimide from a polyamic acid, it is convenient to carry out (chemical) imidization by adding a catalyst to a solution of a polyamic acid obtained by reacting a diamine component with a tetracarboxylic acid component. The imidization can be carried out by stirring the polymer to be imidized in an organic solvent in the presence of a basic catalyst and an acid anhydride.

As the organic solvent, the solvent used in the polymerization reaction described above can be used. As the basic catalyst, pyridine, triethylamine, trimethylamine, tributylamine, trioctylamine, etc. can be mentioned. Among them, pyridine is preferred because it has an appropriate basicity to advance the reaction. As the acid anhydride, acetic anhydride, trimellitic anhydride, pyromellitic anhydride, etc. can be mentioned. Among them, acetic anhydride is preferred because it makes purification after the reaction is completed easier.

The temperature during the imidization reaction is -20 to 140°C, preferably 0 to 100°C, and the reaction time is 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, the temperature, and the reaction time.
The imidization ratio in this specification refers to the ratio of imide groups to the total amount of imide groups derived from tetracarboxylic dianhydride or its derivatives and carboxyl groups (or its derivatives). In polyimides, the imidization ratio does not necessarily have to be 100%, and can be adjusted as desired depending on the application or purpose. The imidization ratio of the polyimide used in the present invention is preferably 20 to 100%, more preferably 50 to 99%.

The polyimide solution obtained as described above can be poured into a poor solvent while stirring to precipitate the polymer. The precipitation is carried out several times, washed with a poor solvent, and then 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.

The molecular weight of the polyimide precursor and polyimide produced as described above is preferably 2,000 to 500,000, more preferably 5,000 to 300,000, and even more preferably 10,000 to 100,000, in terms of weight average molecular weight. The number average molecular weight is preferably 1,000 to 250,000, more preferably 2,500 to 150,000, and even more preferably 5,000 to 50,000.

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

The solvent used in the liquid crystal aligning 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 given below.
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-2-imidazolidinone, methyl ethyl ketone, cyclohexanone, cyclopentanone, 3-methoxy-N,N-dimethylpropanamide, 4-hydroxy-4-methyl-2-pentanone, and the solvents represented by the following formulae [D-1] to [D-3].

（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）。
本発明における溶媒は、なかでも、Ｎ－メチル－２－ピロリドン、Ｎ－エチル－２－ピロリドン、γ－ブチロラクトン、３－メトキシ－Ｎ，Ｎ－ジメチルプロパンアミド、又は１，３－ジメチル－２－イミダゾリジノン（以下、これらを良溶媒ともいう。）が好ましい。

(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).
Of these, the solvent in the present invention is preferably N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, γ-butyrolactone, 3-methoxy-N,N-dimethylpropanamide, 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 poor solvent) that improves the coating properties and surface smoothness of the liquid crystal alignment film when the liquid crystal alignment agent is applied. These poor solvents preferably account for 1 to 80% by mass of the total solvent contained in the liquid crystal alignment agent. Of these, 10 to 80% by mass is more preferable. More preferably, it is 20 to 70% by mass.

Specific examples of poor solvents are given below: ethanol, isopropyl alcohol, 1-butanol, 2-butanol, isobutyl alcohol, tert-butyl alcohol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, isopentyl alcohol, tert-pentyl alcohol, 3-methyl-2-butanol, neopentyl alcohol, 1-hexanol, 2-methyl-1-pentanol, 2-methyl-2-pentanol, 2-ethyl-1- Butanol, 1-heptanol, 2-heptanol, 3-heptanol, 1-octanol, 2-octanol, 2-ethyl-1-hexanol, cyclohexanol, 1-methylcyclohexanol, 2-methylcyclohexanol, 3-methylcyclohexanol, 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, hexanediol, 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-(methoxymeth) 2-(hexyloxy)ethanol, butyl cellosolve, 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 cellosolve acetate, ethylene glycol monoacetate, ethylene glycol diacetate, diethylene glycol monoethyl ether acetate, diacetone alcohol, propylene Examples of the solvent include glycol diacetate, diisopentyl ether, 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 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 formulas [D-1] to [D-3].
Of these, it is preferable to use butyl cellosolve, 1-butoxy-2-propanol, butyl cellosolve acetate, dipropylene glycol monomethyl ether, diacetone alcohol, diethylene glycol diethyl ether, diisopentyl ether, propylene glycol diacetate, diisobutyl ketone, ethyl carbitol, or dipropylene glycol dimethyl ether.

本発明の液晶配向剤における架橋性化合物の含有量は、全ての重合体１００質量部に対して、０．１～１５０質量部が好ましく、０．１～１００質量部がより好ましい。 The liquid crystal aligning agent of the present invention may contain a crosslinkable compound having an epoxy group, an isocyanate group, an oxetanyl group or a cyclocarbonate group, a crosslinkable compound having at least one substituent selected from the group consisting of a hydroxy group, a hydroxyalkyl group and a lower alkoxyalkyl group, or a crosslinkable compound having a polymerizable unsaturated bond (excluding the aromatic compound of formula (1)). It is preferable that the crosslinkable compound has two or more of these substituents or polymerizable unsaturated bonds. Two or more types of crosslinkable compounds may be combined. Specific examples of preferred crosslinkable compounds include compounds represented by the following formulas (CL-1) to (CL-11).

The content of the crosslinkable compound in the liquid crystal aligning agent of the present invention is preferably 0.1 to 150 parts by mass, more preferably 0.1 to 100 parts by mass, based on 100 parts by mass of all the polymers.

The liquid crystal aligning agent of the present invention may contain a compound that improves the uniformity of the thickness and the surface smoothness of the film-like material obtained by applying the agent.
Examples of such compounds include fluorine-based surfactants, silicone-based surfactants, nonionic surfactants, etc. More specific examples include EFTOP EF301, EF303, EF352 (all manufactured by Mitsubishi Materials Electronic Chemicals Co., Ltd.), Megafac F171, F173, R-30 (all manufactured by DIC Corporation), Fluorad FC430, FC431 (all manufactured by 3M), Asahiguard AG710, Surflon S-382, SC101, SC102, SC103, SC104, SC105, SC106 (all manufactured by AGC), etc.

Furthermore, the liquid crystal alignment agent may contain nitrogen-containing heterocyclic amines represented by formulas [M1] to [M156], which are listed in paragraphs [0194] to [0200] of International Publication WO2011/132751 (published October 27, 2011), as compounds that promote charge transfer in the liquid crystal alignment film and promote charge escape from the element. This amine may be added directly to the liquid crystal alignment agent, but it is preferable to add it after making it into a solution with a concentration of 0.1 to 10% by mass, preferably 1 to 7% by mass. There are no particular limitations on the solvent, so long as it dissolves the specific polymer.

<Liquid crystal alignment film/Liquid crystal display element>
The liquid crystal alignment film of the present invention is a film obtained by applying the above liquid crystal alignment agent to a substrate, drying and baking. The substrate is not particularly limited as long as it has high transparency, and examples thereof include glass substrates, silicon nitride substrates, and plastic substrates such as acrylic substrates and polycarbonate substrates. Substrates on which ITO electrodes for driving liquid crystals are formed are preferred from the viewpoint of process simplification. 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 alignment agent to a substrate and forming a film include screen printing, offset printing, flexographic printing, an inkjet method, a spray method, etc. Among these, the application and film formation method by the inkjet method is preferably used.
After the liquid crystal alignment agent is applied to the substrate, the solvent can be evaporated to form a film (coating) by a heating means such as a hot plate, a heat circulation oven, or an IR (infrared) oven. The drying and baking process after the liquid crystal alignment agent is applied can be performed at any temperature and time. Usually, the film is baked at 50 to 180° C. for 1 to 10 minutes to sufficiently remove the solvent contained therein, or may be baked at 150 to 300° C. for 5 to 120 minutes to further perform thermal imidization. If the film after baking is too thin, the reliability of the liquid crystal display element may decrease, so the thickness is preferably 5 to 300 nm, more preferably 10 to 200 nm.

The alignment treatment method for the liquid crystal alignment film obtained from the liquid crystal alignment agent of the present invention may be a rubbing treatment method, but a photo-alignment treatment method is preferred. As a photo-alignment treatment method, a method is given in which the surface of the above-mentioned film-like material is irradiated with radiation deflected in a certain direction, and in some cases, baked at a temperature of preferably 150 to 250°C to impart liquid crystal alignment properties (also called liquid crystal alignment ability). As the radiation, ultraviolet rays or 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 preferable, and more preferably 200 to 400 nm are more preferable.

In addition, when irradiating with radiation, the substrate having the film-like material may be irradiated while being heated at 50 to 250° C. in order to improve the liquid crystal alignment. The radiation dose is preferably 1 to 10,000 mJ/ ^cm2 . Of these, 100 to 5,000 mJ/ ^cm2 is more preferable. The liquid crystal alignment film thus produced can stably align liquid crystal molecules in a certain direction.
Furthermore, the liquid crystal alignment film irradiated with polarized radiation by the above method can be treated with water or a solvent, or the liquid crystal alignment film irradiated with radiation can be heat-treated.

The solvent used in the contact treatment is not particularly limited as long as it dissolves the decomposition product generated from the film-like material by irradiation with radiation. Specific examples include water, methanol, ethanol, 2-propanol, acetone, methyl ethyl ketone, 1-methoxy-2-propanol, 1-methoxy-2-propanol acetate, butyl cellosolve, ethyl lactate, methyl lactate, diacetone alcohol, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, propyl acetate, butyl acetate, cyclohexyl acetate, and the like. Among these, water, 2-propanol, 1-methoxy-2-propanol, or ethyl lactate is preferred from the viewpoint of versatility and solvent safety. Water, 1-methoxy-2-propanol, or ethyl lactate is more preferred. The solvent may be one type or a combination of two or more types.

Examples of the contact treatment include immersion treatment and spray treatment (also called spray treatment). The treatment time for these treatments is preferably 10 seconds to 1 hour in order to efficiently dissolve the decomposition products generated from the film-like material by irradiation with radiation. Of these, immersion treatment for 1 to 30 minutes is preferable. The solvent used in the contact treatment may be at room temperature or heated, preferably 10 to 80°C. Of these, 20 to 50°C is preferable. In addition, ultrasonic treatment or the like may be performed as necessary in terms of the solubility of the decomposition products.

After the contact treatment, it is preferable to perform rinsing (also called rinsing) with a low boiling point solvent such as water, methanol, ethanol, 2-propanol, acetone, methyl ethyl ketone, etc., and to perform baking. In this case, either rinsing or baking may be performed, or both may be performed. The baking temperature is preferably 150 to 300°C. Of these, 180 to 250°C is preferable, and 200 to 230°C is more preferable. The baking time is preferably 10 seconds to 30 minutes, and of these, 1 to 10 minutes is preferable.
The heat treatment of the coating film irradiated with the above radiation is more preferably carried out at 50 to 300° C. for 1 to 30 minutes, and even more preferably at 120 to 250° C. for 1 to 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 horizontal electric field type such as an IPS type or an FFS type from the viewpoint of obtaining high liquid crystal alignment properties, and is particularly useful as a liquid crystal alignment film for a liquid crystal display element of an FFS type. The liquid crystal display element is obtained by obtaining a substrate with a liquid crystal alignment film obtained from the liquid crystal alignment agent of the present invention, and then producing a liquid crystal cell by a known method, and using the liquid crystal cell.
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. 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.

Specifically, 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 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 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 placed on the other substrate so that the liquid crystal alignment film faces each other, and the periphery is bonded with a sealant. In order to control the gap between the substrates, spacers are usually mixed into the sealant, and it is also preferable to disperse spacers for controlling the gap between the substrates in the in-plane portion where the sealant is not provided. An opening is provided in a part of the sealant so that liquid crystal material can be filled from the outside. Next, 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 this opening is sealed with an adhesive. For injection, a vacuum injection method or a method utilizing capillary action in the atmosphere may be used. The liquid crystal material may be either a positive type liquid crystal material or a negative type liquid crystal material, but a negative type liquid crystal material is preferable. Next, a polarizing plate is installed. Specifically, a pair of polarizing plates are attached to the surface opposite to the liquid crystal layer of the two substrates.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto. The abbreviations of compounds and the methods for measuring the properties are as follows.
<Solvent>
DMF: N,N-dimethylformamide, NMP: N-methyl-2-pyrrolidone, GBL: γ-butyrolactone, BCS: butyl cellosolve <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: See formula (DA-4) below DA-5: 4,4'-diaminodiphenylamine DA-6: 4,4'-diaminodiphenylmethane

<Tetracarboxylic acid dianhydride>

<Additives>

T-1 to T-4 are new compounds that have not been published in the literature, and their synthesis methods are described in detail in Synthesis Examples 1 to 4 below.

< ^1H -NMR Measurement>
Apparatus: Fourier transform type superconducting nuclear magnetic resonance apparatus (FT-NMR) "AVANCE III" (manufactured by BRUKER) 500 MHz.
Solvent: deuterated chloroform (CDCl ₃ ) or deuterated N,N-dimethylsulfoxide ([D ₆ ]-DMSO) Standard: tetramethylsilane (TMS).

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

In a 1L four-neck 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 charged and stirred at 130°C. After completion of the reaction, the reaction solution was poured into ethyl acetate (1000 g), neutralized with 1N-hydrochloric acid aqueous solution (1000 g), and washed with pure water (1000 g). The obtained organic layer was concentrated, and the obtained crude product was isolated by silica gel column chromatography (eluent: hexane only) to obtain 4.7 g of a white solid. From the results of ¹ H-NMR shown below, it was confirmed that this solid was [T-1].
¹ H-NMR (500MHz, [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]:

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) were charged into a 1 L four-neck flask and stirred at 80°C. After completion of the reaction, the reaction system was poured into ethyl acetate (500 g) and the organic layer was washed with pure water (1500 g). The resulting organic layer was concentrated, and the resulting crude product was isolated by silica gel column chromatography (eluent: hexane only) to obtain 66.6 g of [T-2-1].

[T-2-1] (66.6 g, 378 mmol) and N,N-dimethylaniline (300 g) were charged into a 1 L four-neck 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), and 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(tosyloxy)ethane (18.5 g, 50 mmol), potassium carbonate (20.7 g, 150 mmol), and DMF (170 g) were charged into a 500 mL four-neck flask and stirred at 80° C. After completion of the reaction, 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 isolated 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]:

4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenol (18.9 g, 86 mmol), 1,2-bis(tosyloxy)ethane (15.9 g, 43 mmol), potassium carbonate (17.8 g, 129 mmol), and DMF (190 g) were charged into a 500 mL four-neck flask and stirred at 80°C. After the reaction was completed, the reaction system was filtered to remove the potassium carbonate, 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, which was then repulped and washed at room temperature to obtain 14.0 g of [T-3-1].

A 500 mL four-neck flask was charged with [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) 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 isolated 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].
^1H -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]:

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 charged into a 500 mL four-neck flask and stirred at 80°C. After completion of the reaction, 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].

[T-4-1] (30.8 g, 190 mmol) and N,N-dimethylaniline (200 g) were charged into a 500 mL four-neck flask 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 1N 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].

[T-4-2] (30.3 g, 187 mmol), 1,2-bis(tosyloxy)ethane (34.4 g, 93 mmol), potassium carbonate (38.6 g, 279 mmol), and DMF (360 g) were charged into a 500 mL four-neck flask and stirred at 80° C. After completion of the reaction, 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 isolated by silica gel column chromatography (eluent: ethyl acetate/hexane = 1/80 (volume ratio)), to obtain 18.7 g of a transparent liquid. From the ¹ H-NMR results shown below, it was confirmed that this liquid was the target [T-4].
^1H -NMR (500MHz, [ _D6 ]-DMSO): δ7.02 (s, 4H), 5.87-5.96 (m, 2H), 5.05-5.09 (m, 2H), 5.00-5.03 (m, 2H), 4.04 (s, 4H), 3.24-3.25 (d, 4H), 2.22 ( s, 12H)

<Method of measuring viscosity>
The measurements were performed using an E-type viscometer TVE-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.

<Method of measuring molecular weight>
Measurement was carried out using a GPC (room temperature gel permeation chromatography) device, and the number average molecular weight (Mn) and weight average molecular weight (Mw) were calculated as values calculated in terms of polyethylene glycol and polyethylene oxide.
GPC apparatus: Shodex (GPC-101), column: Shodex (KD803, KD805 in series), column temperature: 50°C, eluent: N,N-dimethylformamide (additives: lithium bromide hydrate (LiBr.H ₂ O) 30 mmol/L, phosphoric acid anhydrous crystal (o-phosphoric acid) 30 mmol/L, tetrahydrofuran (THF) 10 ml/L), flow rate: 1.0 ml/min. Standard samples for creating calibration curves: TSK standard polyethylene oxide (weight average molecular weight (Mw) about 900,000, 150,000, 100,000, 30,000) manufactured by Tosoh Corporation, and polyethylene glycol (peak top molecular weight (Mp) about 12,000, 4,000, 1,000) manufactured by Polymer Laboratory. In order to avoid overlapping peaks, two samples, a mixture of four types of 900,000, 100,000, 12,000, and 1,000, and a mixture of three types of 150,000, 30,000, and 4,000, were measured separately.

<Method for measuring imidization rate>
20 mg of polyimide powder was placed in an NMR sample tube (NMR sampling tube standard, φ5 (Kusano Scientific Co., Ltd.)), deuterated dimethyl sulfoxide (DMSO-d ₆ , 0.05% TMS (tetramethylsilane) mixture) (0.53 mL) was added, and the solution was completely dissolved by applying ultrasonic waves. Proton NMR at 500 MHz was measured using a Fourier transform superconducting nuclear magnetic resonance device (FT-NMR) "AVANCE III" (BRUKER Co., Ltd.). The imidization rate was determined by the following formula using the proton peak integrated value of this proton and the proton peak integrated value of the proton peak derived from the NH group of the amic acid that appears around 9.5 ppm to 10.0 ppm.
Imidization rate (%)=(1−α·x/y)×100
In the above formula, x is the integrated value of the proton peak derived from the NH group of the amic acid, y is the integrated value of the peak of the reference proton, and α is the ratio of the number of the reference protons to one NH group proton of the amic acid in the case of polyamic acid (imidization rate 0%).

(Synthesis Example 5)
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) were weighed out into a 100 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and NMP (46.2 g) was added, and the mixture was stirred and dissolved while feeding nitrogen. CA-1 (5.70 g, 25.4 mmol) and CA-2 (1.20 g, 4.80 mmol) were added while stirring this diamine solution, and NMP (39.1 g) was added so that the solid content concentration became 15% by mass, and the mixture was stirred at 40 ° C. for 24 hours to obtain a polyamic acid solution (A) (viscosity: 450 mPa s). The molecular weight of the polyamic acid was Mn = 11,200, Mw = 26,900.

(Synthesis Example 6)
DA-5 (5.10 g, 25.6 mmol) and DA-6 (1.27 g, 6.41 mmol) were placed in a 100 m L four-neck flask equipped with a stirrer and a nitrogen inlet tube, and NMP (36.1 g) was added, followed by stirring and dissolving while feeding nitrogen. CA-2 (4.00 g, 16.0 mmol) and CA-3 (4.42 g, 15.0 mmol) were added while stirring this diamine solution, and NMP (47.7 g) was added so that the solids concentration became 15% by mass, and the mixture was stirred at 50° C. for 24 hours to obtain a polyamic acid solution (B) (viscosity: 904 mPa·s). The molecular weight of the polyamic acid was Mn=14,600, Mw=37,500.

(Synthesis Example 7)
The obtained polyamic acid solution (A) (30 g) was weighed out into a 100 ml four-neck flask equipped with a stirrer and a nitrogen inlet tube, and NMP (15.0 g) was added and stirred for 30 minutes. Acetic anhydride (4.89 g) and pyridine (1.51 g) were added to the obtained polyamic acid solution, and the mixture was heated at 50 ° C for 2 hours and 30 minutes to perform chemical imidization. The obtained reaction solution was poured into methanol (154 mL) while stirring, and the precipitate was filtered out, and then washed three times with methanol (154 mL). The obtained resin powder was dried at 60 ° C for 12 hours to obtain polyimide resin powder (A). The imidization rate of this polyimide resin powder was 64%, Mn = 9,900, and Mw = 20,000.

(Synthesis Example 8)
The polyimide resin powder (A) (3.00 g) obtained in Synthesis Example 7 was weighed out into a 100 mL Erlenmeyer flask, and NMP (22.0 g) was added thereto so that the solid content concentration became 12%, and the mixture was stirred at 70° C. for 24 hours to dissolve the polyimide resin powder (A), thereby obtaining a polyimide solution (A).

Example 1
The polyimide solution (A) (3.80 g) obtained in Synthesis Example 8 and the polyamic acid solution (B) (4.56 g) obtained in Synthesis Example 6 were weighed into a 100 mL Erlenmeyer flask, T-1 (0.114 g), NMP (1.64 g), GBL (6.00 g), and BCS (4.00 g) were added, and the mixture was stirred at room temperature for 3 hours to obtain a liquid crystal alignment agent (1). No abnormalities such as turbidity or precipitation were observed in this liquid crystal alignment agent, and it was confirmed that the solution was homogeneous.

(Examples 2 to 5)
The liquid crystal alignment agents (2) to (5) of Examples 2 to 5 were obtained in the same manner as in Example 1, except that T-2, T-3, T-4, or T-5 was used instead of T-1. It was confirmed that the liquid crystal alignment agents (2) to (5) were homogeneous solutions without any abnormality such as turbidity or precipitation.

(Comparative Example 1)
The polyimide solution (A) (3.80 g) obtained in Synthesis Example 8 and the polyamic acid solution (B) (4.56 g) obtained in Synthesis Example 6 were weighed into a 100 mL Erlenmeyer flask, and NMP (1.64 g), GBL (6.00 g), and BCS (4.00 g) were added thereto and stirred at room temperature for 3 hours to obtain a liquid crystal alignment agent (6).

(Comparative Example 2)
A liquid crystal aligning agent (7) was obtained in the same manner as in Example 1, except that T-6 was used instead of T-1.
In addition, the liquid crystal alignment agents (6) and (7) obtained in the above Comparative Examples 1 and 2 were confirmed to be homogeneous solutions without any abnormality such as turbidity or precipitation.

Example 6
The liquid crystal alignment agent (1) obtained in Example 1 was filtered through a filter with a pore size of 1.0 μm, and then coated on a glass substrate with a transparent electrode by spin coating. The coating surface was dried on a hot plate at 80° C. for 2 minutes, and irradiated with 0.25 J/cm ² of linearly polarized ultraviolet light with a wavelength of 254 nm and an extinction ratio of 26:1 through a polarizing plate, and then baked in a hot air circulation oven at 230° C. for 20 minutes to obtain a substrate with a liquid crystal alignment film with a thickness of 100 nm.
The two substrates obtained were combined into a set, and spacers with a diameter of 6 μm were sprayed on the liquid crystal alignment film surface of one of the substrates. A sealant was printed on this substrate, and the other substrate was attached so that the liquid crystal alignment film surfaces faced each other and the alignment direction was 0°, and then the sealant was cured to prepare an empty cell. Liquid crystal MLC-7026-100 (manufactured by Merck) was injected into this empty cell by a reduced pressure injection method, and the injection port was sealed to obtain a liquid crystal cell. When the initial alignment of the liquid crystal cell was confirmed, no flow alignment was confirmed, and the alignment was good. This cell was heat-treated at 120° C. for 60 minutes to prepare a liquid crystal cell.

[Method of evaluating liquid crystal alignment]
The liquid crystal alignment state in the liquid crystal cell prepared by the above procedure was observed using a polarizing microscope (Nikon Corporation, ECLIPSE E600 POL). The liquid crystal alignment was confirmed and there was no flow alignment, and it was judged as "good", and the liquid crystal alignment was not confirmed and there was flow alignment, and it was judged as "bad".

[Measurement of voltage holding ratio]
The liquid crystal cell was aged by placing it on a backlight for 5 days, and then a voltage of 1 V was applied for 60 μs at a temperature of 60° C., and the voltage was measured after 500 ms, and the voltage retention rate was calculated as the voltage retention rate. To measure the voltage retention rate, VHR-1 manufactured by Toyo Corporation was used.
As a result, the voltage holding ratio at 60° C. of the alignment film made of the liquid crystal alignment agent (1) was 61.7%.

(Examples 7 to 10, Comparative Examples 3 to 4)
Liquid crystal cells were prepared in the same manner as in Example 6, except that the liquid crystal alignment agent shown in Table 1 was used instead of the liquid crystal alignment agent (1), and the liquid crystal alignment property and the voltage holding ratio were evaluated. The liquid crystal alignment property and the voltage holding ratio of each of the obtained liquid crystal cells are shown in Table 1.

As shown in Table 1, it was confirmed that in Examples 6 to 10, in which additives (T-1) to (T-5) were added, the voltage retention rate was improved without a decrease in liquid crystal alignment, compared to Comparison Example 3, in which no additives were added, and Comparison Example 4, in which an additive (T-6) different from the aromatic compound of the present invention was added.

The entire contents of the specification, claims and abstract of Japanese Patent Application No. 2019-184619, filed on October 7, 2019, are hereby incorporated by reference as the disclosure of the specification of the present invention.

Claims (19)

A liquid crystal aligning agent comprising an aromatic compound having two or more structures represented by the following formula (1):

(R is a hydrogen atom or a methyl group. Any hydrogen atom on the benzene ring may be substituted with 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.) The liquid crystal aligning agent according to claim 1 , wherein the aromatic compound is a compound represented by the following formula (b1):

(R has the same meaning 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.) The liquid crystal aligning agent according to claim 2, wherein n in formula (b1) is 2 and A represents a single bond or a divalent linking group. The liquid crystal aligning agent according to claim 2 or 3, wherein in the formula (b1), when n is 2, the divalent linking group 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 represents an integer of 1 to 6, and "*" represents a bond.) The liquid crystal aligning agent according to any one of claims 1 to 4, wherein the aromatic compound is a compound having a molecular weight of 2000 or less. The liquid crystal aligning agent according to any one of claims 1 to 5, wherein the aromatic compound is a compound selected from the group consisting of the following formulas (b-1) to (b-4) and (b-6) :

The liquid crystal alignment agent according to any one of claims 1 to 6, wherein the content of the aromatic compound is 0.1 to 5 mass% based on the total amount of the liquid crystal alignment agent. The liquid crystal alignment agent according to any one of claims 1 to 7, further comprising a polymer capable of aligning liquid crystals. The liquid crystal alignment agent according to any one of claims 1 to 8, which contains at least one polymer selected from the group consisting of polyimide precursors and polyimides which are imidized products of the polyimide precursors. The liquid crystal aligning agent according to claim 9, wherein the polyimide precursor is obtained by using a tetracarboxylic acid component containing a 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 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 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, -COO-, -SO ₂ - or -CONH-. The two A _2s may be the same or different. *1 represents a bond bonded to one acid anhydride group, and *2 represents a bond bonded to the other acid anhydride group.) The liquid crystal aligning agent according to claim 10, wherein the (x-1) is selected from the group consisting of the following formulas (x1-1) to (x1-6):

(*1 is a bond bonded to one acid anhydride group, and *2 is a bond bonded to the other acid anhydride group.) The liquid crystal aligning agent according to any one of claims 9 to 11, wherein the polyimide precursor is obtained using a diamine component containing a diamine represented by the following formula (3):

(A ₁ represents an alkylene group having 2 to 14 carbon atoms, or a group in which at least one of the -CH ₂ - groups in the alkylene is replaced with -O-, -CO-, -OCO-, or -COO-, provided that they are not consecutive. _{A 2} represents a halogen atom, a hydroxy group, an amino group, a thiol group, a nitro group, a phosphate group, or a monovalent organic group having 1 to 20 carbon atoms. When there are multiple A ₂ 's, they may be the same or different. a is an integer of 0 to 4. When there are multiple a's, they 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 aligning agent according to claim 12, wherein the diamine represented by the formula (3) is selected from the group consisting of the following formulas (3-1) to (3-12):

The liquid crystal alignment agent according to any one of claims 9 to 13, wherein the polyimide precursor is obtained using a diamine component containing a diamine having at least one nitrogen-containing structure selected from the group consisting of a nitrogen-containing heterocycle (excluding imide rings contained in polyimide), a secondary amino group, and a tertiary amino group. A method for producing a liquid crystal alignment film, comprising applying the liquid crystal alignment agent according to any one of claims 1 to 14 to a substrate, baking the substrate, and irradiating the resulting film with polarized radiation. The method for producing a liquid crystal alignment film according to claim 15, wherein the film is baked at a temperature of 150 to 250°C. A liquid crystal alignment film formed from the liquid crystal alignment agent according to any one of claims 1 to 14. A liquid crystal display element comprising the liquid crystal alignment film according to claim 17. The liquid crystal display element according to claim 18, which is an IPS driving system or an FFS driving system.