TWI874664B - 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, which is suitable for use in a liquid crystal alignment film with high film strength and a liquid crystal display element with suppressed AC afterimage, and does not precipitate solid components when stored at low temperatures. Furthermore, a liquid crystal alignment film obtained from the liquid crystal alignment agent and a liquid crystal display element having the liquid crystal alignment film are provided. A liquid crystal alignment agent contains the following (A) component and (B) component: (A) component: a polymer (A) having the ability to align liquid crystals, (B) component: a hydroxyalkylamide compound (B) represented by the following formula (1); (R is an alkyl group having 1 to 6 carbon atoms, R ₁ and R ₂ each independently represent a hydrogen atom or a monovalent organic group having 1 to 6 carbon atoms, and A represents a divalent organic group having 1 to 30 carbon atoms.)

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, and a liquid crystal display element.

In the past, liquid crystal display devices were widely used as display parts of personal computers, smart phones, mobile phones, televisions, etc. Liquid crystal display devices have, for example, a liquid crystal layer sandwiched between an element substrate and a color filter substrate, pixel electrodes and common electrodes for applying an electric field to the liquid crystal layer, an alignment film for controlling the alignment of liquid crystal molecules in the liquid crystal layer, and a thin film transistor (TFT) for switching the electrical signal supplied to the pixel electrode. As for the driving method of liquid crystal molecules, longitudinal electric field methods such as TN (Twisted Nematic) method and VA (Vertical Alignment) method, and transverse electric field methods such as IPS (In-Plane Switching) method and FFS (Fringe Field Switching) method are known.

At present, the most popular liquid crystal alignment film in the industry is made by rubbing the surface of a film composed of polymers represented by polyamide and/or polyimide obtained by imidization formed on an electrode substrate in one direction with a cloth such as cotton, nylon, polyester, etc., so-called rubbing. Rubbing is a simple and productive method useful in industry. However, with the high performance, high precision, and large size of liquid crystal display elements, various problems such as scratches, dust, mechanical force or static electricity on the surface of the alignment film produced by rubbing, and unevenness in the alignment process have become apparent. As an alignment treatment method replacing the rubbing treatment, a photo-alignment method is known in which alignment energy is imparted to liquid crystal by irradiating polarized radiation. Some have proposed photo-alignment methods that utilize photoisomerization reaction, photocrosslinking reaction, photodecomposition reaction, etc. (for example, refer to Non-Patent Document 1 and Patent Document 1).

In recent years, large-screen and high-definition LCD TVs have become the mainstream, and small display terminals such as smartphones, tablet PCs, or car navigation have become popular, and the demand for high-quality LCD display components has increased and improved compared to the past. For the reliability test of LCD display components for mobile applications such as smartphones and in-vehicle applications such as car navigation, a panel vibration test is implemented. This vibration test requires that no defects such as bright spots are generated. In order to obtain a LCD display component that does not produce defects after the vibration test, for example, a method of improving the mechanical strength of the liquid crystal alignment film is considered. As for the method of improving the mechanical strength of the liquid crystal alignment film, especially the method of improving the film strength, the method of adding a crosslinking agent to the liquid crystal alignment agent can be cited. In addition, in the IPS method and FFS drive method, the stability of the liquid crystal alignment has also become important. If the stability of the alignment is low, the liquid crystal cannot be restored to its initial state when driven for a long time, which may cause a decrease in contrast or burn-in (hereinafter referred to as AC afterimage). As a means to solve these problems, a liquid crystal alignment agent containing a specific polyimide component and a specific hydroxyalkylamide compound has been proposed (for example, refer to Patent Document 2). [Prior Art Document] [Patent Document]

[Patent document 1] Japanese Patent Publication No. 9-297313 [Patent document 2] WO2018/092811 [Non-patent document]

[Non-patent document 1] "Liquid crystal photo-alignment film" Kidowaki, Ichimura Functional Materials, November 1997, Vol.17, No.11, P.13-22

[Identify the problem you want to solve]

Liquid crystal alignment agents are usually stored in an extremely low temperature environment (e.g., -20°C) to prevent polymer degradation during the period from manufacturing to shipment. On the other hand, in the research of the inventors of this case, it was found that when the hydroxyalkylamide compound described in Patent Document 2 is added to the liquid crystal alignment agent, the film strength of the obtained liquid crystal alignment film is improved, and a liquid crystal display element with suppressed AC afterimage can be obtained, but the solid components contained in the liquid crystal alignment agent will precipitate when stored at low temperatures. Once the solid components are precipitated, they are not easy to dissolve again, and there is a risk of causing problems such as printing defects in the manufacturing process of liquid crystal display elements. Although the reason for the precipitation of such solid components has not been determined, it is speculated that one reason is the high polarity of the hydroxyalkylamide compound used in the liquid crystal alignment agent. Therefore, there is a demand for a liquid crystal alignment agent that does not produce precipitation of solid components even when stored in a refrigerated state.

Considering the above situation, the purpose of the present invention is to provide a liquid crystal alignment agent that can be used in a liquid crystal alignment film with high film strength and a liquid crystal display element with suppressed AC afterimage, and no solid components will be precipitated when stored at low temperature. In addition, the purpose of the present invention is to provide a liquid crystal alignment film obtained from the liquid crystal alignment agent and a liquid crystal display element having the liquid crystal alignment film. [Means for solving the problem]

The inventors of this case conducted in-depth research to achieve the above-mentioned goal and found that a liquid crystal alignment agent containing a specific hydroxyalkylamide compound is extremely effective in achieving the above-mentioned purpose, thereby completing the present invention.

The present invention includes the following aspects. [1] A liquid crystal alignment agent, comprising the following components (A) and (B): Component (A): a polymer (A) having the ability to align liquid crystals; Component (B): a hydroxyalkylamide compound (B) represented by the following formula (1); (R is an alkyl group having 1 to 6 carbon atoms, R ₁ and R ₂ each independently represent a hydrogen atom or a monovalent organic group having 1 to 6 carbon atoms, and A represents a divalent organic group having 1 to 30 carbon atoms.)

Another aspect of the present invention includes the following aspects. [1] A liquid crystal alignment agent, comprising the following (A') component and (B') component: (A') component: a polymer (A') having the ability to align liquid crystals; (B') component: a hydroxyalkylamide compound (B') represented by the following formula (1'); [Chemical 2] (R' represents a monovalent organic group represented by the group "*-C(R _2' ) ₂ -C(R _1' ) ₂ -OH" (* represents a bonding site, R _1' and R _2' each independently represent a hydrogen atom or a monovalent organic group having 1 to 6 carbon atoms), and multiple R's may be the same or different; n is an integer of 1 to 30; L _1' is a divalent organic group having 1 to 10 carbon atoms, and multiple L _1's may be the same or different.) [Effects of the Invention]

According to the present invention, there can be provided a liquid crystal alignment agent which is suitable for use in a liquid crystal alignment film having high film strength and a liquid crystal display element with suppressed AC afterimage and which does not precipitate solid components when stored at low temperatures, a liquid crystal alignment film obtained from the liquid crystal alignment agent, and a liquid crystal display element having the liquid crystal alignment film.

The following describes in detail a liquid crystal alignment agent containing a specific hydroxyalkylamide compound, a liquid crystal alignment film formed using the liquid crystal alignment agent, and a liquid crystal display element having the liquid crystal alignment film. However, the description of the constituent elements described below is an example of an embodiment of the present invention and is not limited to the contents thereof. In the following description, the description of "(meth)acrylic acid" means both acrylic acid and methacrylic acid. In addition, as for "halogen atoms", fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, etc. can be listed.

(Liquid crystal alignment agent) The liquid crystal alignment agent of the present invention contains a polymer (A) (also referred to as component (A) in the present invention) or a polymer (A') (also referred to as component (A') in the present invention) having the ability to align liquid crystals. The polymer (A') includes an ideal specific example, and the same compounds as the polymer (A) can be listed. In addition, one embodiment of the liquid crystal alignment agent of the present invention contains the above-mentioned polymer (A) and a hydroxyalkylamide compound (B) represented by the above-mentioned formula (1) (also referred to as component (B) in the present invention). In addition, another embodiment of the liquid crystal alignment agent of the present invention contains the above-mentioned polymer (A') and a hydroxyalkylamide compound (B') represented by the above-mentioned formula (1') (also referred to as component (B') in the present invention).

<Component (A), component (A')> The liquid crystal alignment agent of the present invention contains a polymer capable of aligning liquid crystals, similar to the known ones. The polymer is not particularly limited as long as it has the ability to align liquid crystals. As for the polymer, for example, polyimide precursors, polyimides which are imide products of polyimide precursors, acrylic polymers, methacrylic polymers, acrylamide polymers, methacrylamide polymers, polystyrene, polysiloxane, polyamide, polyester, polyurethane, polycarbonate, polyurea, polyphenol (novolac resin), maleimide polymers, polymers into which compounds having an isocyanuric acid skeleton or a tris-based skeleton are introduced, etc.

As for the raw materials for producing these polymers, the following can be listed respectively. When the polymer is a polyimide precursor such as polyamic acid, polyamic acid ester, or polyimide, at least one compound selected from tetracarboxylic acid or its derivatives (preferably tetracarboxylic dianhydride) and diamine can be listed. When the polymer is a (meth)acrylic acid polymer, (meth)acrylic acid or its derivatives, (meth)acrylic acid ester or its derivatives can be listed. When the polymer is a (meth)acrylamide polymer, (meth)acrylamide or its derivatives can be listed.

When the polymer is polystyrene, styrene or its derivatives can be listed. When the polymer is polysiloxane, silane compounds having methoxy groups or ethoxy groups can be listed. When the polymer is polyamide, at least one dicarboxylic acid component selected from dicarboxylic acids and their derivatives and a diamine component can be listed. When the polymer is polyester, at least one dicarboxylic acid component selected from dicarboxylic acids and their derivatives and a diol component can be listed.

When the polymer is a polyurethane, examples include isocyanate compounds and compounds having a hydroxyl group. When the polymer is a polycarbonate, examples include bisphenol derivatives and phosgene or phosgene equivalents (such as trichlorophosgene) or diphenyl carbonate. When the polymer is a polyurea, examples include diisocyanate derivatives and diamine components. When the polymer is a maleimide polymer, examples include maleimide derivatives alone or copolymerization with styrene. When the polymer is a polymer into which a compound having an isocyanuric acid skeleton or a tris-indium skeleton is introduced, examples include compounds having an isocyanuric acid skeleton or a tris-indium skeleton.

<<Polyimide polymer>> As for the polymer contained in the liquid crystal alignment agent of the present invention, it is preferable to select one or more polymers selected from the group consisting of polyimide precursors and polyimide compounds which are polyimide precursors (hereinafter also referred to as polyimide polymers) from the viewpoints of the practicality as a liquid crystal alignment agent, the mechanical strength of the coating film, and the liquid crystal alignment. The above-mentioned polyimide polymer can be produced by a known method. For example, polyamide which is a polyimide precursor can be obtained by subjecting a tetracarboxylic acid component composed of tetracarboxylic dianhydride or its derivative to polymerization (polycondensation) reaction with a diamine component, and polyimide can be obtained by subjecting the polyimide precursor to imidization. Examples of the derivative of tetracarboxylic dianhydride include dihalogenated tetracarboxylic acids, tetracarboxylic acid dialkyl esters, and dihalogenated tetracarboxylic acid dialkyl esters.

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

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

[Chemistry 3] (X represents a structure selected from the following formulas (x-1) to (x-13).)

[Chemistry 4] ( ^R1 to ^R4 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; ^R5 and ^R6 each independently represent a hydrogen atom or a methyl group; j and k are integers of 0 or 1; _A1 and _A2 each independently represent a single bond, -O-, -CO-, -COO-, a phenylene group, a sulfonyl group, or an amide group; multiple _A2s may be the same or different; *1 is a bond to the anhydride group on one side, and *2 is a bond to the anhydride group on the other side.)

As a preferred specific example of the tetracarboxylic dianhydride or its derivative represented by the above formula (2), X is selected from the above formulas (x-1) to (x-8) and (x-10) to (x-13).

In the above formula (x-1), it is preferable to be selected from the group consisting of the following formulas (x1-1) to (x1-6).

[Chemistry 5] (*1 is the bonding site of the anhydride group on one side, and *2 is the bonding site of the anhydride group on the other side.)

As specific examples of the above-mentioned formulas (x-12) and (x-13), the following formulas (x-14) to (x-29) can be cited. In addition, the "*" in the formulas represents the bonding position.

[Chemistry 6]

[Chemistry 7]

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

＜＜＜Diamine component＞＞＞ The diamine component used in the production of the polyimide precursor is not particularly limited, but is preferably a diamine component containing at least one diamine selected from the diamines represented by the following formulas (3) and (3i).

[Chemistry 8] (Y ₃ represents a divalent organic group represented by the following formula (O). R represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. Y _3i represents a divalent organic group represented by the following formula (O').

[Chemistry 9] (Ar represents a divalent benzene ring, a biphenyl structure, or a naphthalene ring. Two Ars may be the same or different, and any hydrogen atom of the above ring may be substituted with a monovalent substituent. p is an integer of 0 or 1. _Q3 represents -( _CH2 ) _n- (n is an integer of 2 to 18), or a group obtained by _replacing at least a part of -CH2- of the above -( _CH2 ) _n- with any one of -O-, -C(=O)-, or -O-C(=O)-. * represents a bonding site.)

[Chemistry 10] (Ar' represents a divalent benzene ring or a biphenyl structure. Two Ar' may be the same or different, and any hydrogen atom of the above ring may be substituted with a monovalent substituent. p' is an integer of 0 or 1. _{Q 3'} represents -(CH ₂ ) _n - (n is an integer of 2 to 18), or a group obtained by replacing at least a part of -CH ₂ - of the above -(CH ₂ ) _n - with -O-, -C(=O)- or -O-C(=O)-. * represents a bonding site.)

Examples of the substituent of the above ring include a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a fluoroalkyl group having 1 to 10 carbon atoms, a fluoroalkenyl group having 2 to 10 carbon atoms, a fluoroalkoxy group having 1 to 10 carbon atoms, a carboxyl group, a hydroxyl group, an alkyloxycarbonyl group having 1 to 10 carbon atoms, a cyano group, and a nitro group.

The divalent organic group represented by the above formula (O) is preferably a divalent organic group represented by the following formulas (o-1) to (o-16) from the viewpoint of improving the alignment of liquid crystal.

[Chemistry 11]

[Chemistry 12]

[Chemistry 13] (“*” indicates the bond position.)

The divalent organic group represented by the above formula (O') is preferably a divalent organic group represented by the above formulas (o-7) to (o-16) from the viewpoint of improving the liquid crystal alignment.

Preferred specific examples of the diamine represented by the above formula (3i) include compounds represented by the following formulas (3i-1) to (3i-5).

[Chemistry 14]

The total ratio of the diamine represented by formula (3) and the diamine represented by formula (3i) is preferably 1 to 95 mol %, more preferably 1 to 90 mol %, and further preferably 5 to 90 mol %, based on 1 mol of the diamine component.

The polyimide polymer used in the present invention may have at least one nitrogen-containing structure (hereinafter also referred to as a nitrogen-containing structure) selected from the group consisting of nitrogen-containing heterocyclic rings (however, excluding the imide rings of polyimide), diamine groups, and tertiary amine groups, from the viewpoint of improving the voltage retention rate 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, for example, a diamine having a nitrogen-containing structure in at least a part of the raw materials.

As for the nitrogen-containing heterocyclic ring which the above-mentioned diamine having a nitrogen-containing structure may also have, for example, pyrrole, imidazole, pyrazole, triazole, pyridine, pyrimidine, pyrimidine, pyrimidine, pyrimidine, indole, benzimidazole, purine, quinoline, isoquinoline, isoquinoline, oxadiazole, quinazoline, pyrimidine, tririmidine, carbazole, acridine, piperidine, piperidine, pyrrolidine, hexamethyleneimine, etc. Among them, pyridine, pyrimidine, pyrimidine, piperidine, piperidine, quinoline, carbazole or acridine is preferred.

The diamine having a nitrogen-containing structure may have a secondary amine group and a tertiary amine group, for example, those represented by the following formula (n).

[Chemistry 15] In the above formula (n), R represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. "*" represents a bonding site to the hydrocarbon group.

Examples of the monovalent alkyl group of R in the above formula (n) include alkyl groups such as methyl, ethyl, and propyl; cycloalkyl groups such as cyclohexyl; and aryl 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-diaminophenyl)-piperidinium, 3,6-diaminoacridine, N-ethyl-3,6-diaminocarbazole, N-phenyl-3,6-diaminocarbazole, compounds represented by the following formulas (Dp-1) to (Dp-9), and compounds represented by the following formulas (z-1) to (z-18).

[Chemistry 16]

[Chemistry 17]

[Chemistry 18]

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, from the viewpoint of improving the voltage holding ratio of the liquid crystal display element. In addition, 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 listed below, but the present invention is not limited to them. A diamine having 6 to 30 carbon atoms and having a group "-N(D)- (D represents a carbamate protective group)" in the molecule; 4,4'-diaminoazobenzene and the following formulas (d _T -1) to (d _T -3) diamines having a photo-alignment group; 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminobenzophenone, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenyl)benzene, 1,3-bis(4-aminophenyl)benzene, 1,4-bis(4-aminobenzyl)benzene, 2,4-diaminophenol, 3,5-diaminophenol, 3,5-diaminobenzyl alcohol, 2,4-diaminobenzyl alcohol , 4,6-diaminoresorcinol; diamines having a carboxyl group, such as 2,4-diaminobenzoic acid, 2,5-diaminobenzoic acid, 3,5-diaminobenzoic acid and diamine compounds represented by the following formulas (3b-1) to (3b-4); 4-(2-(methylamino)ethyl)aniline, 4-(2-aminoethyl)aniline, 4,4'-diaminodiphenylmethane, 4,4'-diaminobenzophenone, 4,4'-diaminodiphenyl ether, 4,4'-diaminobenzanilide, 4,4'-diaminoazobenzene, 1-(4-aminophenyl)-1,3,3-trimethyl-1H-dihydroindene-5-amine, 1-(4-aminophenyl)-2 ,3-dihydro-1,3,3-trimethyl-1H-indene-6-amine; diamines having urea bonds such as diamines represented by the following formulas (h-1) to (h-3); diamines having amide bonds represented by the following formulas (h-4) to (h-6); diamines having photopolymerizable groups at the ends such as 2-(2,4-diaminophenoxy)ethyl methacrylate and 2,4-diamino-N,N-diallylaniline; cholestanyloxy-3,5-diaminobenzene, cholestenyloxy-3,5-diaminobenzene, cholestanyloxy-2,4-diaminobenzene, 3,5-diaminobenzoic acid Diamines having a steroid skeleton such as steryl esters, 3,5-diaminobenzoic acid cholesteryl ester, 3,5-diaminobenzoic acid lanostanyl ester and 3,6-bis(4-aminobenzyloxy)cholestane; diamines represented by the following formulas (V-1) to (V-6); diamines having a siloxane bond such as 1,3-bis(3-aminopropyl)-tetramethyldisiloxane; diamines having an oxazoline structure such as the following formulas (Ox-1) to (Ox-2); diamines obtained by bonding two amino groups to a group represented by any one of the formulas (Y-1) to (Y-167) described in International Publication No. 2018/117239, etc.

[Chemistry 19]

[Chemistry 20] (In formula (3b-1), ^A1 represents a single bond, -CH2-, -C2H4-, -C(CH3) _2- , _-CF2- , -C(CF3) _2- , -O-, -CO-, -NH-, -N(CH3)-, -CONH-, _-NHCO- , -CH2O-, _-OCH2- , -COO-, -OCO-, -CON(CH3)- or -N(CH3)CO-, _m1 and m2 each independently represent an integer of 0 to 4, and m1+m2 is an integer of 1 to 4. In formula ( _{3b- 2} ), m3 and m4 each independently represent an integer of 1 to 5. In formula (3b- ₃ ), A1 represents a single bond, -CH2-, -C2H4-, -C(CH3)2-, -CF2-, -C(CF3) _2- , -O-, -NH-, -N _(CH3 )-, -CONH-, -NHCO-, -CH2O-, -OCH2-, -COO-, -OCO-, -CON( _CH3 )- or -N(CH3)CO-, m1 and m2 each independently represent an integer of 0 to 4, and m1+m2 is an integer of 1 to 4. In formula (3b-2), m3 and m4 each independently represent an integer of 1 to 5. In formula (3b-3), A1 represents a single bond, -CH2-, -C2H4-, -C( _CH3 )2-, -C(CF3)2-, -O-, -NHCO-, -CH2O-, -OCH2-, -COO-, -OCO-, -CON(CH3)- or -N(CH3)CO-, m1 and m2 each independently represent an integer of 0 to 4, and m1+m2 is an integer of 1 to 4. ² represents a linear or branched alkyl group having 1 to 5 carbon atoms, and m5 represents an integer from 1 to 5. In formula (3b-4), ^A3 and ^A4 each independently represent a single bond, _-CH2- , _-C2H4- , -C(CH3) _2- , _-CF2- , -C( _CF3 ) _2- , -O-, -CO-, -NH-, -N _{( CH3} )-, -CONH-, -NHCO-, _-CH2O- , _-OCH2- , -COO-, -OCO-, -CON( _CH3 )- or -N( _CH3 )CO- _, and m6 represents an integer from 1 to 4.)

[Chemistry 21]

[Chemistry 22] ( ^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- , or -O-( _{CH2 ) m} -O- ( _m is an integer of 1 to 6); ^Rv1 to ^Rv4 and ^R1a to ^R1b each independently represent 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.)

[Chemistry 23]

As the diamine having 6 to 30 carbon atoms and having the above-mentioned group "-N(D)- (D represents a carbamate protective group)" in the molecule, the compounds represented by the following formulas (5-1) to (5-10) can be cited.

[Chemistry 24] (Boc represents tert-butoxycarbonyl.)

<Component (B)> One aspect of the liquid crystal alignment agent of the present invention is characterized by containing a hydroxyalkylamide compound (B) represented by the following formula (1).

[Chemistry 25] (R is an alkyl group having 1 to 6 carbon atoms, R ₁ and R ₂ each independently represent a hydrogen atom or a monovalent organic group having 1 to 6 carbon atoms, and A represents a divalent organic group having 1 to 30 carbon atoms.)

Examples of the alkyl group having 1 to 6 carbon atoms in R in the above formula (1) include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, t-butyl, n-pentyl, n-hexyl, cyclopentyl and cyclohexyl.

Examples of the monovalent organic group having 1 to 6 carbon atoms for R ₁ and R ₂ in the above formula (1) include alkyl groups having 1 to 6 carbon atoms, alkenyl groups having 2 to 6 carbon atoms, alkynyl groups having 2 to 6 carbon atoms, heteroatom-containing groups containing groups having heteroatom atoms between carbon atoms of these groups, and groups obtained by replacing some or all of the hydrogen atoms in the above alkyl groups, alkenyl groups, alkynyl groups and heteroatom-containing groups with substituents.

Examples of the group having a heteroatom include 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, and include -O-, -NR- (R represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms), -CO-, -S-, -CO-, and groups obtained by combining these. Among them, -O- is preferred.

Examples of the substituent include halogen atoms such as fluorine, chlorine, bromine and iodine atoms; alkoxy groups such as methoxy, ethoxy and propoxy; alkoxycarbonyl groups such as methoxycarbonyl and ethoxycarbonyl; alkoxycarbonyloxy groups such as methoxycarbonyloxy and ethoxycarbonyloxy; cyano, nitro and hydroxyl groups.

From the viewpoint of improving the alignment of liquid crystal, _R1 in the above formula (1) is preferably a hydrogen atom or a methyl group, and _R2 is preferably a hydrogen atom.

Examples of the divalent organic group having 1 to 30 carbon atoms in A of the above formula (1) include a divalent alkyl group, a divalent heteroatom-containing group containing the above-mentioned heteroatom-containing group between carbon atoms of the alkyl group, and a divalent organic group obtained by replacing a part or all of the hydrogen atoms in the above-mentioned divalent alkyl group and the divalent heteroatom-containing group with the substituents exemplified above for R ₁ and R ₂ .

Examples of the above-mentioned divalent alkyl group include divalent alkyl groups obtained by removing two hydrogen atoms from alkanes such as methane, ethane, propane and butane; alkenes such as ethylene, propylene, butene and pentene; chain hydrocarbons having 1 to 30 carbon atoms such as acetylene, propyne, butyne and pentyne; cycloalkanes such as cyclopropane, cyclobutane, cyclopentane, cyclohexane, norbornane and adamantane; alicyclic hydrocarbons having 3 to 30 carbon atoms such as cycloalkenes such as cyclopropene, cyclobutene, cyclopentene, cyclohexene and norbornene; and aromatic hydrocarbons having 6 to 30 carbon atoms such as benzene, toluene, xylene, mesitylene, naphthalene, methylnaphthalene, dimethylnaphthalene and anthracene.

A in the above formula (1) is preferably a divalent alkyl group having 1 to 30 carbon atoms, more preferably a divalent chain alkyl group having 1 to 30 carbon atoms, or a divalent alkyl group obtained by excluding two hydrogen atoms from an aromatic alkyl group having 6 to 30 carbon atoms. The divalent chain alkyl group having 1 to 30 carbon atoms is preferably a divalent chain alkyl group having 2 to 30 carbon atoms, more preferably a divalent chain alkyl group having 2 to 16 carbon atoms.

The hydroxyalkylamide compound represented by the above formula (1) is preferably any one of the compounds represented by the following formulas (b-1) to (b-3).

[Chemistry 26]

The ideal content of the hydroxyalkylamide compound represented by the above formula (1) in the liquid crystal alignment agent of the present invention is preferably 0.1 to 50 parts by mass, more preferably 0.1 to 30 parts by mass, relative to 100 parts by mass of the component (A).

<(B’) component> Another aspect of the liquid crystal alignment agent of the present invention is characterized by containing a hydroxyalkylamide compound (B’) represented by the following formula (1’).

[Chemistry 27] (R' represents a monovalent organic group represented by the group "*-C(R _2' ) ₂ -C(R _1' ) ₂ -OH" (* represents a bonding site. _{R 1'} and R _2' each independently represent a hydrogen atom or a monovalent organic group having 1 to 6 carbon atoms.) Multiple R's may be the same or different. n is an integer of 1 to 30. _{L 1'} is a divalent organic group having 1 to 10 carbon atoms. Multiple L _1's may be the same or different.)

Examples of the monovalent organic group having 1 to 6 carbon atoms for R _1' and R _2' in the above formula (1') include the structures exemplified for R ₁ and R ₂ in the above formula (1), and the structures including preferred specific examples are the same as those for R ₁ and R ₂ , respectively.

Examples of the divalent organic group having 1 to 10 carbon atoms in L _1' in the above formula (1') include a divalent alkyl group having 1 to 10 carbon atoms, a divalent heteroatom-containing group containing the above heteroatom-containing group between carbon atoms of the alkyl group, and a divalent organic group obtained by replacing a part or all of the hydrogen atoms in the above divalent alkyl group and the divalent heteroatom-containing group with the substituents exemplified for R ₁ and R ₂ in the above formula (1). Specific examples of the divalent alkyl group include the alkyl groups exemplified for A in the above formula (1). L _1' in the above formula (1') is preferably a divalent alkyl group having 1 to 10 carbon atoms, more preferably a divalent chain alkyl group having 1 to 10 carbon atoms, or a divalent alkyl group obtained by excluding two hydrogen atoms from an aromatic alkyl group having 6 to 10 carbon atoms. The divalent chain alkyl group having 1 to 10 carbon atoms is preferably a divalent chain alkyl group having 2 to 10 carbon atoms, more preferably a divalent chain alkyl group having 2 to 8 carbon atoms.

In the above formula (1'), n is preferably an integer of 1 to 20, and further preferably an integer of 2 to 20.

The hydroxyalkylamide compound represented by the above formula (1') is preferably any one of the compounds represented by the following formulas (b'-1) to (b'-5). [Chemistry 28]

The ideal content of the hydroxyalkylamide compound represented by the above formula (1') in the liquid crystal alignment agent of the present invention is preferably 0.1 to 50 parts by mass, more preferably 0.1 to 30 parts by mass, relative to 100 parts by mass of the component (A').

<Production method of polyamide> The polyamide used as a precursor of polyimide in the present invention can be produced by the following method. Specifically, the above-mentioned tetracarboxylic acid component and the above-mentioned diamine component are reacted (condensation polymerization) 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. Specific examples of the organic solvent used in the above reaction include N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, γ-butyrolactone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide, and 1,3-dimethyl-2-imidazolidinone. In addition, when the polymer has high solvent solubility, methyl ethyl ketone, cyclohexanone, cyclopentanone, 4-hydroxy-4-methyl-2-pentanone, or solvents represented by the following formulas [D-1] to [D-3] can be used. These solvents can also be used in combination of two or more.

[Chemistry 29] (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 reaction can be carried out at any concentration, preferably 1 to 50% by mass, more preferably 5 to 30% by mass. It can also be carried out at a high concentration at the beginning of the reaction, and then the solvent can be added. In the reaction, the ratio of the total molar number of the diamine component to the total molar number of the tetracarboxylic acid component is preferably 0.8 to 1.2. As in the usual polycondensation reaction, the closer the molar ratio is to 1.0, the larger the molecular weight of the generated polyamide becomes.

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

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

When preparing the above-mentioned polyimide precursor, a terminal-modified polymer can be obtained by using a suitable end-capping agent, similar to the above-mentioned tetracarboxylic acid derivatives and diamines. As for the terminal modifier, for example, anhydrides such as acetic anhydride, maleic anhydride, nedic anhydride, phthalic anhydride, itaconic anhydride, cyclohexanedicarboxylic anhydride, 3-hydroxyphthalic anhydride, 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, 4-aminobenzoic acid; monoisocyanate compounds such as ethyl isocyanate, phenyl isocyanate, naphthyl isocyanate, etc. can be cited. The usage ratio of the terminal modifier is preferably 40 mol parts or less, more preferably 30 mol parts or less, based on 100 mol parts of the total diamine components used.

<Production method of polyimide> The polyimide used in the present invention can be produced by imidizing polyamic acid or polyamic acid ester, which is a precursor of polyimide, by a known method. In polyimide, the ring closure rate (also called imidization rate) of the functional group possessed by polyamic acid or polyamic acid ester does not necessarily have to be 100%, and can be arbitrarily adjusted according to the application and purpose.

As for the method of obtaining polyimide by imidizing the polyamic acid or polyamic acid ester, there are two methods, namely, directly heating the solution of the polyamic acid or polyamic acid ester to perform thermal imidization, or adding a catalyst to the solution of the polyamic acid or polyamic acid ester to perform catalytic imidization. It is ideal to perform the thermal imidization at a temperature of 100 to 400°C, preferably 120 to 250°C, while discharging the water generated by the imidization reaction to the outside of the system.

Catalytic imidization can be carried out by adding an alkaline catalyst and an acid anhydride to a polymer solution and stirring at -20 to 250°C, preferably 0 to 180°C. The amount of the alkaline catalyst is 0.5 to 30 mole times of the amide group or amide ester group, preferably 2 to 20 mole times, and the amount of the acid anhydride is 1 to 50 mole times of the amide group or amide ester group, preferably 3 to 30 mole times. As for the alkaline catalyst, pyridine, triethylamine, trimethylamine, tributylamine, trioctylamine, etc. can be listed, among which pyridine has a suitable alkalinity for the reaction to proceed and is more ideal. As for the acid anhydride, acetic anhydride, trimellitic anhydride, pyromellitic anhydride, etc. can be listed. Among them, if acetic anhydride is used, purification after the reaction is easy and more ideal. The imidization rate of catalytic imidization can be controlled by adjusting the amount of catalyst, reaction temperature, and reaction time.

When recovering the generated polyimide from the reaction solution of catalytic imidization, the reaction solution is put into a solvent for precipitation. As for the solvent used for precipitation, methanol, ethanol, isopropanol, acetone, hexane, butyl cellulose, heptane, methyl ethyl ketone, methyl isobutyl ketone, toluene, benzene, water, etc. can be listed. The polymer put into the solvent and precipitated is filtered and recovered, and can be dried at normal pressure or reduced pressure, at room temperature or by heating. In addition, if the polymer recovered by precipitation is repeatedly dissolved in a solvent again and precipitated and recovered again for 2 to 10 times, the impurities in the polymer can be reduced. Examples of the solvent at this time include alcohols, ketones, hydrocarbons, and the like. It is more preferable to use three or more solvents selected from these solvents because the efficiency of purification can be further improved.

<Polymer solution viscosity and molecular weight> When the polyamine, polyamine ester and polyimide used in the present invention are prepared into a solution with a concentration of 10 to 15% by mass, it is ideal to have a solution viscosity of 10 to 1000 mPa･s, for example, from the perspective of workability, but there is no particular limitation. In addition, the solution viscosity (mPa･s) of the above polymer is a value measured at 25°C using an E-type rotational viscometer for a polymer solution with a concentration of 10 to 15% by mass prepared using a good solvent for the polymer (e.g., γ-butyrolactone, N-methyl-2-pyrrolidone, etc.).

The weight average molecular weight (Mw) of the polyamine, polyamic acid ester and polyimide measured by gel permeation chromatography (GPC) in terms of polystyrene is preferably 1,000 to 500,000, more preferably 2,000 to 500,000. In addition, the molecular weight distribution (Mw/Mn) represented by the ratio of Mw to the number average molecular weight (Mn) in terms of polystyrene measured by GPC is preferably 15 or less, more preferably 10 or less. By having such a molecular weight range, good liquid crystal alignment of the liquid crystal display element can be ensured.

<Ideal state of liquid crystal alignment agent> As for the ideal state of the liquid crystal alignment agent of the present invention, for example, a solution obtained by dissolving a polymer having the ability to align liquid crystals in a solvent, to which a hydroxyalkylamide compound of the above formula (1) or (1') is added can be cited. The content (concentration) of the polymer contained in the liquid crystal alignment agent of the present invention can be appropriately changed depending on the setting of the thickness of the coating to be formed. Considering the viewpoint of forming a uniform and defect-free coating, it is preferably 1% by mass or more, and considering the viewpoint of the storage stability of the solution, it is preferably 10% by mass or less. The content of the hydroxyalkylamide compound of the formula (1) or (1') is preferably 1 to 15% by mass, more preferably 2 to 10% by mass, and particularly preferably 2 to 8% by mass, relative to the total content of the polymer and the hydroxyalkylamide compound of the formula (1) or (1') contained in the liquid crystal alignment agent.

The solvent contained in the liquid crystal alignment agent is not particularly limited as long as it can uniformly dissolve the polymer component. Specific examples thereof include N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethyllactamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, dimethylsulfoxide, γ-butyrolactone, γ-valerolactone, 1,3-dimethyl-2-imidazolidinone, methyl ethyl ketone, cyclohexanone, cyclopentanone, 3-methoxy-N,N-dimethylpropaneamide, 3-butoxy-N,N-dimethylpropaneamide, Amine, N-(n-propyl)-2-pyrrolidone, N-isopropyl-2-pyrrolidone, N-(n-butyl)-2-pyrrolidone, N-(tert-butyl)-2-pyrrolidone, N-(n-pentyl)-2-pyrrolidone, N-methoxypropyl-2-pyrrolidone, N-ethoxyethyl-2-pyrrolidone, N-methoxybutyl-2-pyrrolidone, N-cyclohexyl-2-pyrrolidone (these are also collectively referred to as "good solvents"), etc. Among them, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, 3-methoxy-N,N-dimethylpropaneamide, 3-butoxy-N,N-dimethylpropaneamide or γ-butyrolactone is preferred. The content of the good solvent is preferably 20-99 mass % of the total solvent contained in the liquid crystal alignment agent, more preferably 20-90 mass %, and particularly preferably 30-80 mass %.

In addition, the solvent contained in the liquid crystal alignment agent is preferably a mixed solvent containing a solvent (also called a poor solvent) that improves the coating property and surface smoothness of the coating film when the liquid crystal alignment agent is applied in addition to the above-mentioned solvents. Specific examples of the solvents used in combination are as follows, but are not limited to these.

Examples thereof include diisopropyl ether, diisobutyl ether, diisobutyl carbinol (2,6-dimethyl-4-heptanol), ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, 1,2-butoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, 4-hydroxy-4-methyl-2-pentanone, diethylene glycol methyl ethyl ether, diethylene glycol dibutyl ether, 3-ethoxybutyl acetate, 1-methylpentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, ethylene glycol monoacetate, ethylene glycol diacetate, propylene carbonate, ethylene carbonate, ethylene glycol monobutyl ether, ethylene glycol monoisopentyl ether, ethylene glycol monohexyl ether, propylene glycol monobutyl ether, and 1-(2-butoxyethoxy)-2-propanol. , 2-(2-butoxyethoxy)-1-propanol, propylene glycol monomethyl ether acetate, propylene glycol diacetate, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol dimethyl ether, ethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, 2-(2-ethoxyethoxy) ethyl acetate, diethylene glycol acetate, propylene glycol diacetate, n-butyl acetate, propylene glycol monoethyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, ethyl 3-methoxypropionate, propyl 3-methoxypropionate, butyl 3-methoxypropionate, n-butyl lactate, isoamyl lactate, diethylene glycol monoethyl ether, diisobutyl ketone (2,6-dimethyl-4-heptanone), etc. The content of the bad solvent is preferably 1-80% by mass of the total solvent contained in the liquid crystal alignment agent, more preferably 10-80% by mass, and particularly preferably 20-70% by mass. The type and content of the bad solvent can be appropriately selected according to the coating device, coating conditions, coating environment, etc. of the liquid crystal alignment agent.

Among them, diisobutyl carbinol, propylene glycol monobutyl ether, propylene glycol diacetate, diethylene glycol diethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, 4-hydroxy-4-methyl-2-pentanone, ethylene glycol monobutyl ether, ethylene glycol monobutyl ether acetate, or diisobutyl ketone is preferred.

As for the ideal solvent combination of good solvent and poor solvent, N-methyl-2-pyrrolidone and ethylene glycol monobutyl ether, N-methyl-2-pyrrolidone and γ-butyrolactone and ethylene glycol monobutyl ether, N-methyl-2-pyrrolidone and γ-butyrolactone and propylene glycol monobutyl ether, N-ethyl-2-pyrrolidone and propylene glycol monobutyl ether, N-methyl-2-pyrrolidone and γ-butyrolactone and 4-hydroxy-4-methyl-2-pentanone and diethylene glycol diethyl Ether, N-methyl-2-pyrrolidone and γ-butyrolactone and propylene glycol monobutyl ether and diisobutyl ketone, N-methyl-2-pyrrolidone and γ-butyrolactone and propylene glycol monobutyl ether and diisopropyl ether, N-methyl-2-pyrrolidone and γ-butyrolactone and propylene glycol monobutyl ether and diisobutyl carbinol, N-methyl-2-pyrrolidone and γ-butyrolactone and dipropylene glycol dimethyl ether, N-methyl-2-pyrrolidone and propylene glycol monobutyl ether and dipropylene glycol dimethyl ether, etc.

The liquid crystal alignment agent of the present invention may additionally contain components other than the polymer component and the solvent (hereinafter also referred to as additive components). As for such additive components, there can be listed adhesion aids for improving the adhesion between the liquid crystal alignment film and the substrate or the adhesion between the liquid crystal alignment film and the sheet material, compounds for improving the strength of the liquid crystal alignment film (hereinafter also referred to as cross-linking compounds), and dielectrics or conductive substances for adjusting the dielectric constant or resistance of the liquid crystal alignment film.

As the crosslinking compound, for example, from the viewpoint of exhibiting good resistance to AC afterimage and highly improving film strength, there can be cited compounds having at least one group selected from the group consisting of an ethylene oxide group, an oxycyclobutane group, a protected isocyanate group, a protected isothiocyanate group, a group containing an oxazoline ring structure, a group containing a Meldrum's acid structure, and a cyclic carbonate group, a hydroxyalkylamide compound other than the compounds represented by the above formula (1) and formula (1'), or a compound selected from the compounds represented by the following formula (e).

[Chemistry 30] (A represents an (m+n)-valent organic group having an aromatic ring. m represents an integer of 1 to 6, and n represents an integer of 0 to 4. _Re and _Rf each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or an alkynyl group having 2 to 6 carbon atoms. The aromatic ring of A may also be substituted with a monovalent group. Specific examples of the monovalent group include the monovalent organic groups represented by the substituents of Ar in the above formula (O) (except for alkoxy groups having 1 to 10 carbon atoms).)

Specific examples of compounds having an ethylene oxide group include compounds described in paragraph [0037] of Japanese Patent Application Laid-Open No. 10-338880 and compounds having a tricyclic ring in the skeleton described in International Publication No. 2017/170483. Among these, compounds containing nitrogen atoms such as N,N,N',N'-tetraethylene oxide propyl-m-xylene diamine, 1,3-bis(N,N-diethylene oxide propylaminomethyl)cyclohexane, N,N,N',N'-tetraethylene oxide propyl-4,4'-diaminodiphenylmethane, N,N,N',N'-tetraethylene oxide propyl-p-phenylenediamine, and compounds represented by the following formulas (r-1) to (r-3) may be mentioned.

[Chemistry 31]

Specific examples of the compound having an oxacyclobutane group include compounds having two or more oxacyclobutane groups described in paragraphs [0170] to [0175] of International Publication No. 2011/132751.

Specific examples of the compound having a protected isocyanate group include compounds having two or more protected isocyanate groups described in paragraphs [0046] to [0047] of JP-A-2014-224978, compounds having three or more protected isocyanate groups described in paragraphs [0119] to [0120] of WO-2015/141598, and compounds represented by the following formulae (bi-1) to (bi-3).

[Chemistry 32]

Specific examples of the compound having a protected isothiocyanate group include compounds having two or more protected isothiocyanate groups described in Japanese Patent Application Laid-Open No. 2016-200798.

Specific examples of the compound having a group containing an oxazoline ring structure include compounds containing two or more oxazoline ring structures described in paragraph [0115] of JP-A-2007-286597.

Specific examples of the compound having a group containing a Michaelis acid structure include compounds having two or more Michaelis acid structures described in International Publication No. 2012/091088.

Specific examples of the compound having a cyclocarbonate group include compounds described in International Publication No. 2011/155577.

Specific examples of hydroxyalkylamide compounds other than the compounds represented by the above formula (1) and formula (1') include compounds described in International Publication No. 2015/072554, paragraph [0058] of Japanese Patent Publication No. 2016-118753, compounds described in Japanese Patent Publication No. 2016-200798, and compounds described in International Publication No. 2019/142927. Compounds represented by the following formulas (hd-1) to (hd-8) and compounds represented by the following formulas (hd1-1) to (hd1-4) are also exemplified.

[Chemistry 33]

[Chemistry 34]

As the (m+n)-valent organic group having an aromatic ring in A of the above formula (e), there can be mentioned an (m+n)-valent aromatic hydrocarbon group having 6 to 30 carbon atoms, an (m+n)-valent organic group obtained by directly or via a linking group bonding an aromatic hydrocarbon group having 6 to 30 carbon atoms, and an (m+n)-valent group having an aromatic heterocyclic ring. As the above aromatic hydrocarbon, there can be mentioned benzene, naphthalene, etc. Examples of the aromatic heterocyclic ring include pyrrole ring, imidazole ring, pyrazole ring, pyridine ring, pyrimidine ring, quinoline ring, isoquinoline ring, carbazole ring, pyridine ring, pyridine ring, benzimidazole ring, indole ring, quinoline ring, acridine ring, etc. Examples of the above-mentioned linking group include alkylene groups having 1 to 10 carbon atoms, -NR- (R is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms), alkylene groups having 1 to 10 carbon atoms having a fluorine atom, or groups obtained by removing a hydrogen atom from the above-mentioned alkylene groups, and divalent or trivalent cyclohexane rings. In addition, any hydrogen atom of the above-mentioned alkylene groups may be substituted with an organic group such as a fluorine atom or a trifluoromethyl group. Specific examples include compounds described in International Publication No. 2010/074269 and compounds represented by the following formulae (e-1) to (e-10).

[Chemistry 35]

The above compounds are examples of crosslinking compounds, but are not limited thereto. For example, components other than the above disclosed in International Publication No. 2015/060357, pages 53 [0105] to 55 [0116] can be cited. In addition, the crosslinking compound may be a combination of two or more.

In the liquid crystal alignment agent of the present invention, the content of the crosslinking compound is preferably 0.5 to 20 parts by weight relative to 100 parts by weight of the polymer component contained in the liquid crystal alignment agent. In view of the crosslinking reaction and good resistance to AC afterimage, it is more preferably 1 to 15 parts by weight.

Examples of the adhesion promoter include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyldiethoxymethylsilane, 2-aminopropyltrimethoxysilane, 2-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-ureidopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, N-ethoxycarbonyl-3-aminopropyltrimethoxysilane, and N- Ethoxycarbonyl-3-aminopropyl triethoxysilane, N-triethoxysilylpropyl triethylene triamine, N-trimethoxysilylpropyl triethylene triamine, 10-trimethoxysilyl-1,4,7-triazadecane, 10-triethoxysilyl-1,4,7-triazadecane, 9-trimethoxysilyl-3,6-diazanonyl acetate, 9-triethoxysilyl-3,6-diazanonyl acetate, N-benzyl-3-aminopropyl trimethoxysilane, N-benzyl-3-aminopropyl triethoxysilane, N-phenyl -3-aminopropyl trimethoxysilane, N-phenyl-3-aminopropyl triethoxysilane, N-bis(oxyethyl)-3-aminopropyl trimethoxysilane, N-bis(oxyethyl)-3-aminopropyl triethoxysilane, vinyl trimethoxysilane, vinyl triethoxysilane, 2-(3,4-epoxyhexyl)ethyl trimethoxysilane, 3-glycidoxypropyl methyl dimethoxysilane, 3-glycidoxypropyl trimethoxysilane, 3-glycidoxypropyl methyl diethoxysilane, 3-glycidoxy Silane coupling agents include propyl triethoxysilane, p-phenylene trimethoxysilane, 3-methacryloxypropyl methyl dimethoxysilane, 3-methacryloxypropyl trimethoxysilane, 3-methacryloxypropyl methyl diethoxysilane, 3-methacryloxypropyl triethoxysilane, 3-acrylpropyl trimethoxysilane, tris-(trimethoxysilylpropyl) isocyanurate, 3-butylene propyl methyl dimethoxysilane, 3-butylene propyl trimethoxysilane, and 3-isocyanate propyl triethoxysilane. When a silane coupling agent is used, the amount thereof is preferably 0.1 to 30 parts by mass, more preferably 0.1 to 20 parts by mass, based on 100 parts by mass of the polymer component contained in the liquid crystal alignment agent, from the viewpoint of exhibiting good resistance to AC afterimage.

(Liquid crystal alignment film) The liquid crystal alignment film of the present invention is formed using the liquid crystal alignment agent of the present invention. As for the ideal embodiment of the method for manufacturing the liquid crystal alignment film of the present invention, for example, there can be cited a method for manufacturing the liquid crystal alignment film comprising a step of applying the liquid crystal alignment agent to a substrate (step (1)), a step of calcining the applied liquid crystal alignment agent (step (2)), and, if necessary, a step of performing an alignment treatment on the film obtained in step (2) (step (3)).

<Step (1)> As for the substrate used for coating the liquid crystal alignment agent in the present invention, there is no particular limitation as long as it is a highly transparent substrate. A glass substrate, a silicon nitride substrate, an acrylic substrate, a plastic substrate such as a polycarbonate substrate, etc. can also be used. In this case, it is more ideal to use a substrate formed with an ITO electrode, etc. for driving the liquid crystal, from the perspective of simplifying the process. In addition, if the reflective liquid crystal display element is only on one side of the substrate, an opaque material such as a silicon wafer can also be used. In this case, the electrode can also be made of a light-reflecting material such as aluminum.

As for the method of coating the liquid crystal alignment agent on the substrate to form a film, screen printing, offset printing, flexographic printing, ink jetting, or spraying can be listed. Among them, the coating and film forming method by ink jetting can be appropriately used.

<Step (2)> Step (2) is a step of calcining the liquid crystal alignment agent applied on the substrate to form a film. After the liquid crystal alignment agent is applied on the substrate, the solvent can be evaporated or the thermal imidization of the amide acid or amide ester in the polymer can be performed by heating means such as a hot plate, a heat circulation oven or an IR (infrared) oven. The drying and calcining steps after applying the liquid crystal alignment agent of the present invention can be selected at any temperature and time, and can also be performed several times. As for the temperature for evaporating the solvent of the liquid crystal alignment agent, for example, it can be carried out at 40 to 180°C. From the perspective of shortening the process, it can also be carried out at 40 to 150°C. There is no particular limitation on the calcination time, and it can be 1 to 10 minutes or 1 to 5 minutes. In the case of thermal imidization of amide or amide ester in the polymer, after the step of evaporating the above-mentioned organic solvent, there can be a step of calcination at a temperature range of 150 to 300°C or 150 to 250°C. There is no particular limitation on the calcination time, and it can be 5 to 40 minutes or 5 to 30 minutes. If the film after calcination is too thin, the reliability of the liquid crystal display element may be reduced, so it is preferably 5 to 300nm, and more preferably 10 to 200nm.

<Step (3)> Step (3) is a step of performing an alignment treatment on the film obtained in step (2) as appropriate. That is, in a vertical alignment type liquid crystal display element such as a VA mode or a PSA mode, the formed coating film can be used directly as a liquid crystal alignment film, or the coating film can be subjected to a treatment for imparting alignment energy. As for the alignment treatment method of the liquid crystal alignment film, it can be a friction treatment method, preferably a photo-alignment treatment method. As for the photo-alignment treatment method, a method can be cited in which the surface of the above-mentioned film-like object is irradiated with radiation biased in a certain direction, and a heating treatment is preferably performed at a temperature of 150 to 250°C as appropriate to impart liquid crystal alignment (also called liquid crystal alignment energy). As the radiation, ultraviolet light or visible light having a wavelength of 100 to 800 nm can be used, and ultraviolet light having a wavelength of 100 to 400 nm is preferred, and ultraviolet light having a wavelength of 200 to 400 nm is more preferred.

The irradiation dose of the above radiation is preferably 1 to 10,000 mJ/cm ² . Among them, it is preferably 100 to 5,000 mJ/cm ² . In addition, in the case of irradiation with radiation, in order to improve the liquid crystal alignment, the substrate having the above film-like object can also be irradiated while being heated at 50 to 250°C. The above liquid crystal alignment film prepared in this way can make the liquid crystal molecules stably align in a certain direction. In addition, in the above method, water or a solvent can be used to contact the liquid crystal alignment film irradiated with polarized radiation, or the liquid crystal alignment film irradiated with radiation can be heated.

The solvent used in the above-mentioned contact treatment is not particularly limited as long as it is a solvent that dissolves the decomposition products generated from the film-like material due to the irradiation of radiation. As specific examples, water, methanol, ethanol, 2-propanol, acetone, methyl ethyl ketone, 1-methoxy-2-propanol, 1-methoxy-2-propanol acetate, butyl celoxylate, ethyl lactate, methyl lactate, diacetone alcohol, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, propyl acetate, butyl acetate, cyclohexyl acetate, etc. can be cited. Among them, considering the general applicability and safety of the solvent, water, 2-propanol, 1-methoxy-2-propanol or ethyl lactate is preferred. More preferably, water, 1-methoxy-2-propanol or ethyl lactate is preferred. The solvent may be one kind or a combination of two or more kinds.

As for the above-mentioned contact treatment, immersion treatment and spray treatment (also called spray treatment) can be listed. The treatment time in these treatments is preferably 10 seconds to 1 hour, considering the viewpoint of efficiently dissolving the decomposition products generated from the film due to the irradiation of radiation. Among them, it is suitable to carry out immersion treatment for 1 to 30 minutes. In addition, the solvent during the above-mentioned contact treatment can be at room temperature or heated, preferably 10 to 80°C. Among them, it is preferably 20 to 50°C. In addition, considering the viewpoint of the solubility of the decomposition products, ultrasonic treatment can also be carried out according to needs.

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

(Liquid crystal display element) The liquid crystal display element of the present invention has the liquid crystal alignment film of the present invention. The liquid crystal alignment film of the present invention is suitable as a liquid crystal alignment film for liquid crystal display elements of transverse electric field modes such as IPS mode and FFS mode from the viewpoint of obtaining high liquid crystal alignment, and is particularly useful as a liquid crystal alignment film for liquid crystal display elements of FFS mode. After obtaining a substrate with a liquid crystal alignment film obtained by the liquid crystal alignment agent of the present invention, a liquid crystal unit is prepared by a known method, and liquid crystal is arranged in the liquid crystal unit, thereby manufacturing a liquid crystal display element. Specifically, the following two methods can be listed. The first method is to first arrange two substrates opposite to each other with a gap (liquid crystal gap, cell gap) in between in a manner that the respective liquid crystal alignment films face each other. Then, the peripheries of the two substrates are bonded together using a sealant, and after the liquid crystal composition is injected into the liquid crystal gap separated by the substrate surface and the sealant and contacts the film surface, the injection hole is sealed.

The second method is called ODF (One Drop Fill). For example, a UV-curable sealant is applied at a predetermined location on one of the two substrates on which the liquid crystal alignment film is formed, and a liquid crystal composition is further dripped at a predetermined number of locations on the surface of the liquid crystal alignment film. Afterwards, the other substrate is bonded with the liquid crystal alignment films facing each other to squeeze and diffuse the liquid crystal composition on the entire surface of the substrate to contact the film surface. Then, the entire surface of the substrate is irradiated with ultraviolet light to cure the sealant. Regardless of which method is used, it is more desirable to heat the liquid crystal composition used to a temperature at which it becomes isotropic and then slowly cool it to room temperature to remove the flow alignment during liquid crystal filling. In addition, when the coating is subjected to friction treatment, the two substrates are arranged to face each other in such a way that the friction directions in each coating are at a predetermined angle to each other, such as perpendicular or anti-parallel. The same is true when the photo-alignment treatment is performed, and the alignment directions are arranged to face each other in such a way that they are at a predetermined angle to each other, such as perpendicular or anti-parallel. As a sealant, for example, an epoxy resin containing a hardener and aluminum oxide balls as spacers can be used. As liquid crystals, nematic liquid crystals and lamellar liquid crystals can be listed, among which nematic liquid crystals are preferred.

Liquid crystal material can use either positive liquid crystal material or negative liquid crystal material, preferably negative liquid crystal material. Then, a polarizing plate is set. Specifically, a pair of polarizing plates are attached to the surface of the two substrates opposite to the liquid crystal layer. As a polarizing plate, a polarizing film called "H film" obtained by stretching and aligning polyvinyl alcohol while absorbing iodine is sandwiched by a cellulose acetate protective film, or a polarizing plate composed of the H film itself can be cited. [Example]

The present invention is described in more detail with reference to the following examples, but the present invention is not limited thereto. The abbreviations of the following compounds and the methods for measuring the properties are as follows. In addition, "Boc" represents tert-butyloxycarbonyl.

(Organic solvent) NMP: N-methyl-2-pyrrolidone GBL: γ-butyl lactone BCS: butyl cylosurfactone DMF: N,N-dimethylformamide

(Diamine) DA-1~DA-6: Compounds represented by the following formulas (DA-1)~(DA-6) respectively

(Tetracarboxylic dianhydride) DAH-1~DAH-2: compounds represented by the following formulas (DAH-1)~(DAH-2) respectively

(Crosslinking agent) AD-1: Compound represented by the following formula (AD-1) AD-2: Compound represented by the following formula (AD-2). The compound is synthesized by the synthesis method described in Japanese Patent Application No. 2018-537481 (paragraphs [0079] to [0080], Figure 5). AD-3: Compound represented by the following formula (AD-3).

[Chemistry 36]

[Chemistry 37]

[Chemistry 38]

[Viscosity] The viscosity of the polyamide solution was measured using an E-type viscometer (made by Toki Sangyo Co., Ltd., TVE-22H), with a sample volume of 1.1 mL, a conical rotor TE-1 (1°34’, R24), and a temperature of 25°C.

[Synthesis of Monomer] The synthesis method of AD-3, a novel compound, is described in detail below.

The product described in the following Synthesis Example 1 was identified by ¹ H-NMR analysis (analysis conditions are as follows). Apparatus: BRUKER ADVANCE III-500MHz Measurement solvent: deuterated dimethyl sulfoxide (DMSO-d ₆ ) Standard substance: tetramethylsilane (TMS) (δ0.0 ppm for ¹ H)

(Synthesis Example 1 Synthesis of AD-3) AD-3 was synthesized according to the following process.

[Chemistry 39]

<Synthesis of AD-3-1> To tetraethylene glycol (10.0 g, 51.5 mmol), succinic anhydride (13.0 g, 130 mmol), dichloromethane (60 g), and 4-dimethylaminopyridine (3.14 g, 25.7 mmol) were added, and the mixture was heated to reflux at 50°C for 6 hours. After the reaction was completed, the mixture was cooled at room temperature (25°C), washed twice with 2 equivalents of hydrochloric acid (60 g), concentrated, and dried to obtain AD-3-1 (yield: 15.6 g, 39.6 mmol, yield 77%). ¹ H-NMR (500MHz) in DMSO-d ₆ : 12.20 (br, 2H), 4.12 (t, 4H), 3.59 (t, 4H), 3.53 (s, 8H), 2.51 (t, 4H), 2.47 (t, 4H).

<Synthesis of AD-3-2> For AD-3-1 (15.6 g, 39.6 mmol), dichloromethane (94 g), oxalyl chloride (10.4 g, 81.9 mmol), and DMF (0.16 g) were added and stirred at room temperature 25°C for 5 hours. After the reaction was completed, the solution was concentrated to obtain a crude product of AD-3-2 (yield: 18 g). The crude product of AD-3-2 obtained was used in the subsequent step.

<Synthesis of AD-3> Dichloromethane (86 g) and triethylamine (8.82 g, 87.2 mmol) were added to bis(2-((trimethylsilyl)oxy)ethyl)amine (20.8 g, 83.3 mmol) and cooled to 0°C in an ice bath. The crude product (18 g) of AD-3-2 diluted with dichloromethane (34 g) was added dropwise. After the addition was completed, the mixture was stirred at room temperature (25°C) for 17 hours. The precipitated triethylamine hydrochloride was removed by filtration. When water was added, the mixture was emulsified and the liquid separation property was greatly deteriorated. Therefore, the entire mixture including the aqueous phase was concentrated. When methanol was added to the crude product, the target product was dissolved and the salt was precipitated. Therefore, the mixture was filtered and concentrated. This was repeated 3 times and the salt was removed by filtration. Methanol (108 g) and acetic acid (0.030 g) were added to the crude product, and the mixture was stirred at 80°C for 2 hours. After the removal of the trimethylsilyl group was confirmed, the reaction solution was concentrated. Methanol was added and azeotropy was repeated. After the acetic acid was removed, acetonitrile and specially made egret activated carbon were added and stirred at 80°C, followed by filtration and concentration. This was repeated twice and dried to obtain AD-3 (yield: 13.1 g, 23.0 mmol, 2-stage yield 58%). ¹ H－NMR（500MHz）in DMSO－d ₆ : 4.98 (br, 4H), 4.12 (t, 4H), 3.59 (t, 4H), 3.57-3.43 (m, 12H), 3.41-3.38 (m, 8H), 3.32 (t, 4H), 2.69-2.61 (m, 4H), 2.53-2.49 (m, 4H).

[Synthesis of polymer] (Production Example 1) DA-1 (1.08 g, 10 mmol), DA-2 (3.66 g, 15 mmol), DA-3 (4.81 g, 15 mmol) and DA-4 (3.98 g, 10 mmol) were added to a 200 mL four-necked flask equipped with a stirring device and a nitrogen inlet tube, and then NMP (132 g) was added and stirred to dissolve while nitrogen was supplied. DAH-1 (10.54 g, 47 mmol) and NMP (40.3 g) were added to the diamine solution while stirring, and then further stirred at 40°C for 12 hours to obtain a polyamide solution (PAA-1) with a solid content concentration of 12 mass %. The viscosity of the polyamide solution was 430 mPa･s.

(Production Example 2) In a 100 mL four-necked flask equipped with a stirring device and a nitrogen inlet tube, DA-5 (3.99 g, 20 mmol) and DA-6 (1.49 g, 5.0 mmol) were weighed and added, and then 49 g of NMP was added and stirred while nitrogen was supplied to dissolve. DAH-2 (4.71 g, 24 mmol) was added to the diamine solution while stirring, and NMP was further added to make the solid content concentration 10% by mass. The mixture was stirred at room temperature for 20 hours to obtain a polyamide solution (PAA-2) (viscosity: 150 mPa･s).

[Preparation of sample solution] (Comparative Example 1) In a 50 mL Erlenmeyer flask with a stirrer, the polyamine solution (PAA-1) (1.33 g) obtained in Preparation Example 1 and the polyamine solution (PAA-2) (2.40 g) obtained in Preparation Example 2 were measured and added. NMP (0.27 g), GBL (2.20 g), BCS (3.00 g), and a 10% NMP solution of AD-1 (0.80 g) were further added, and stirred overnight with a magnetic stirrer to obtain a liquid crystal alignment agent (AL-1).

(Examples 1 to 2) AD-2 to AD-3 were used instead of AD-1. Except for this point, the same operation as in Comparative Example 1 was performed to obtain liquid crystal alignment agents (AL-2) to (AL-3).

(Comparative Example 2) In a 50 mL Erlenmeyer flask with a stirrer, a 10% NMP solution of AD-1 (1.20 g) was added, and NMP (2.80 g), GBL (3.00 g) and BCS (3.00 g) were added, and the mixture was stirred overnight with a magnetic stirrer to obtain a solution (Sol-1).

(Examples 3 to 4) AD-2 to AD-3 were used instead of AD-1. The same operation as in Comparative Example 2 was performed except for this point to obtain solutions (Sol-2) to (Sol-3).

[Evaluation of Liquid Crystal Alignment Agent] The liquid crystal alignment films formed using the liquid crystal alignment agents of Comparative Example 1 and Examples 1-2 and the liquid crystal elements having the liquid crystal alignment films were subjected to the afterimage evaluation and friction resistance test described below.

<Production of Liquid Crystal Cell> Production of a liquid crystal cell having the structure of an FFS type liquid crystal display element. First, prepare a substrate with electrodes. The substrate is a glass substrate with a rectangular shape of 30mm×35mm and a thickness of 0.7mm. An ITO electrode with a flat pattern constituting a counter electrode is formed on the substrate as the first layer, and a SiN (silicon nitride) film formed by CVD is formed on the counter electrode of the first layer as the second layer. The second layer of SiN film functions as an interlayer insulating film and has a film thickness of 500nm. On the second layer of SiN film, a pixel electrode formed by patterning the ITO film to form a comb shape is arranged as the third layer, forming two pixels, the first pixel and the second pixel. The size of each pixel is 10 mm long and about 5 mm wide. At this time, the counter electrode of the first layer and the pixel electrode of the third layer are electrically insulated by the action of the SiN film of the second layer.

The pixel electrode of the third layer has a comb-like shape in which a plurality of electrode elements with a width of 3 μm and bent at an inner angle of 160° are arranged in parallel at intervals of 6 μm in the center. One pixel has a first region and a second region with a line connecting the bent portions of the plurality of electrode elements as a boundary.

Then, the liquid crystal alignment agents (AL-1) to (AL-3) obtained in Comparative Example 1 and Examples 1 to 2 were filtered with a filter having an aperture of 1.0 μm, and then applied by spin coating on the prepared substrate with electrodes and a glass substrate with a columnar spacer having a height of 4 μm and an ITO film formed on the back. After drying on a hot plate at 80°C for 2 minutes, an IR oven was used to calcine at 230°C for 30 minutes to form a coating with a thickness of 100 nm. The coating surface was irradiated with polarized ultraviolet light at 300 mJ/ ^cm2 for alignment treatment. The IR oven was used again to calcine at 230°C for 30 minutes to obtain a substrate with a liquid crystal alignment film. The above two substrates were used as a set, and a sealant (XN-1500T manufactured by Mitsui Chemicals Co., Ltd.) was printed around the liquid crystal injection port. Another substrate was bonded with the liquid crystal alignment films facing each other and the alignment direction was 0°, and the sealant was cured to make an empty cell. Liquid crystal MLC-3019 (manufactured by Merck) was injected into the empty cell by the reduced pressure injection method, and the injection port was sealed to obtain an FFS-driven liquid crystal cell. The FFS-driven liquid crystal cell obtained in the above manner was heated at 110°C for 1 hour, left overnight, and then the following afterimage evaluation was performed.

<Evaluation of afterimages caused by long-term AC drive> For the above-mentioned FFS-driven liquid crystal unit, an AC voltage of ±5V was applied at a frequency of 30Hz for 120 hours in a constant temperature environment of 60℃ (hereinafter, "FFS-driven liquid crystal unit" is also referred to as "liquid crystal unit"). After that, the pixel electrode and the opposite electrode of the liquid crystal unit were short-circuited and left at room temperature for one day. After leaving, the liquid crystal unit was set between two polarizing plates arranged in a vertical manner with the polarization axis, and the backlight was turned on without applying voltage. The configuration angle of the liquid crystal unit was adjusted to minimize the brightness of the penetrating light. Then, the angle Δ is calculated as the rotation angle from the angle at which the second area of the first pixel is the darkest to the angle at which the first area is the darkest when the liquid crystal unit is rotated. Similarly, the second area is compared with the first area and the same angle Δ is calculated for the second pixel. The average value of the angle Δ of the first pixel and the second pixel is calculated as the angle Δ of the liquid crystal unit. If the angle Δ of the liquid crystal unit obtained above is 0.10° or more, it is evaluated as "×", and if it is less than 0.10°, it is evaluated as "0".

<Friction resistance test> Then, in order to confirm the strength of the liquid crystal alignment film formed using the liquid crystal alignment agents obtained in Examples 1 to 2 and Comparative Example 1, a friction resistance test was performed. The liquid crystal alignment agents (AL-1) to (AL-3) obtained in Comparative Example 1 and Examples 1 to 2 were applied by spin coating to the entire ITO surface of a glass substrate with an ITO electrode. After drying on a hot plate at 80°C for 2 minutes, an IR oven was used to calcine at 230°C for 30 minutes to form a coating with a thickness of 100 nm. The coating surface was irradiated with polarized ultraviolet light at 300 mJ/ ^cm2 to perform an alignment treatment. The substrate with the liquid crystal alignment film was calcined again in an IR oven at 230°C for 30 minutes. The substrate with the liquid crystal alignment film obtained in the above manner was rubbed with a rayon cloth (roller diameter: 120 mm, roller speed: 1000 rpm, moving speed: 20 mm/sec, pushing length: 0.6 mm) and then observed under a microscope to evaluate the friction resistance of the liquid crystal alignment film. The film surface was evaluated as "0" if wrinkles were not observed due to friction, and "×" if wrinkles were observed.

In Comparative Example 1 and Examples 1-2, the evaluation results of the afterimage evaluation of the FFS-driven liquid crystal cell and the evaluation results of the friction resistance test of the liquid crystal alignment film are shown in Table 1 below.

[Table 1] Type of crosslinking agent Liquid crystal alignment agent Afterimage Review Friction resistance Comparison Example 1 AD-1 AL-1 ○ ○ Embodiment 1 AD-2 AL-2 ○ ○ Embodiment 2 AD-3 AL-3 ○ ○

In order to confirm whether the liquid crystal alignment agent is a liquid crystal alignment agent that does not precipitate solid components when stored at low temperatures, the following low-temperature storage stability test was performed using the crosslinking agent solutions (Sol-1) to (Sol-3) of Comparative Example 2 and Examples 3 to 4.

<Low-temperature storage stability test> The crosslinking agent solutions (Sol-1) to (Sol-3) obtained in Comparative Example 2 and Examples 3 to 4 were placed at -20°C for 2 days to evaluate the low-temperature storage stability. The precipitation state of the solution after 2 days was observed. If no precipitation was observed, the low-temperature storage stability was judged to be good for practical use and the evaluation was "0". On the other hand, if precipitation was observed, the low-temperature storage stability was judged to be poor and the evaluation was "×". The results are shown in Table 2 below.

[Table 2] Type of crosslinking agent Liquid crystal alignment agent Low temperature storage stability Comparison Example 2 AD-1 AL-1 × Embodiment 3 AD-2 AL-2 ○ Embodiment 4 AD-3 AL-3 ○ As shown in Tables 1 and 2, AD-2 having an alkylamide moiety and an alkyl group on the N of the amide group, or AD-3 having an alkylamide moiety and an ethylene glycol chain, when used in an alignment agent, can impart good liquid crystal alignment and high friction resistance, and can form an alignment agent with excellent low-temperature storage stability. [Industrial Applicability]

The liquid crystal alignment film obtained by the liquid crystal alignment agent of the present invention can be used in various liquid crystal display elements represented by IPS drive mode or FFS drive mode liquid crystal display elements. However, these display elements are not limited to liquid crystal displays for display purposes, but are also useful in dimming windows and light gates that control the penetration and blocking of light.

Claims (15)

A liquid crystal alignment agent comprises the following components (A) and (B): component (A): a polymer (A) having the ability to align liquid crystals; component (B): a hydroxyalkylamide compound (B) represented by the following formula (1);

R is an alkyl group having 1 to 6 carbon atoms, R ₁ and R ₂ each independently represent a hydrogen atom or a monovalent organic group having 1 to 6 carbon atoms, and A represents a divalent organic group having 1 to 30 carbon atoms. The liquid crystal alignment agent of claim 1, wherein in the formula (1), R ₂ is a hydrogen atom. As in claim 1, the liquid crystal alignment agent, wherein in the formula (1), A is a divalent alkyl group having 1 to 30 carbon atoms. The liquid crystal alignment agent of claim 1, wherein the hydroxyalkylamide compound (B) is any one of the compounds represented by the following formulas (b-1) to (b-3);

The liquid crystal alignment agent of claim 1, wherein the polymer (A) or the polymer (A') is at least one polymer selected from the group consisting of a polyimide precursor and a polyimide which is an imide compound of the polyimide precursor. The liquid crystal alignment agent of claim 5, wherein the polyimide precursor is obtained by using a tetracarboxylic acid component containing tetracarboxylic dianhydride represented by the following formula (2);

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

^R1 to ^R4 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; ^R5 and ^R6 each independently represent a hydrogen atom or a methyl group; j and k are integers of 0 or 1; _A1 and _A2 each independently represent a single bond, -O-, -CO-, -COO-, a phenylene group, a sulfonyl group, or an amide group; multiple _A2s may be the same or different; *1 is bonded to the bonding site of the anhydride group on one side, and *2 is bonded to the bonding site of the anhydride group on the other side. The liquid crystal alignment agent of claim 6, wherein the formula (x-1) is selected from the group consisting of the following formulas (x1-1) to (x1-6);

*1 is bonded to the anhydride group on one side, and *2 is bonded to the anhydride group on the other side. The liquid crystal alignment agent of claim 5, wherein the polyimide precursor is obtained using a diamine component, and the diamine component comprises at least one diamine selected from the diamines represented by the following formulas (3) and (3i);

Y ₃ is a divalent organic group represented by the following formula (O); R is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms; Y _3i is a divalent organic group represented by the following formula (O');

Ar represents a divalent benzene ring, biphenyl structure, or naphthyl ring; two Ars may be the same or different, and any hydrogen atom of the above ring may be substituted with a monovalent substituent; p is an integer of 0 or 1; Q ₃ represents -(CH ₂ ) _n -, n is an integer of 2 to 18, or a group obtained by replacing at least a part of -CH ₂ - of the -(CH ₂ ) _n - with any one of -O-, -C(=O)-, or -OC(=O)-; * represents a bonding site;

Ar' represents a divalent benzene ring or a biphenyl structure; two Ar' may be the same or different, and any hydrogen atom of the ring may be substituted with a monovalent substituent; p' is an integer of 0 or 1; Q _3' represents -(CH ₂ ) _n -, n is an integer of 2 to 18, or a group obtained by replacing at least a part of -CH ₂ - of the -(CH ₂ ) _n - with any one of -O-, -C(=O)- or -OC(=O)-; * represents a bonding site. The liquid crystal alignment agent of claim 8, wherein the divalent organic group represented by the formula (O) is any one of the following formulas (o-1) to (o-16):

The “*” in the formula represents the bond position. As in claim 5, the liquid crystal alignment agent, wherein the polyimide precursor can be obtained using a diamine component, the diamine component contains a diamine having a nitrogen-containing structure selected from at least one of the groups consisting of a nitrogen-containing heterocyclic ring, a diamine group, and a tertiary amine group, but the nitrogen-containing heterocyclic ring excludes the imide ring of the polyimide. A method for manufacturing a liquid crystal alignment film comprises applying a liquid crystal alignment agent as described in any one of claims 1 to 10 on a substrate and calcining the substrate, and irradiating the obtained film with polarized radiation. A method for manufacturing a liquid crystal alignment film as claimed in claim 11, wherein calcination is performed at a temperature of 150-250°C. A liquid crystal alignment film is formed from a liquid crystal alignment agent as described in any one of claims 1 to 10. A liquid crystal display element having a liquid crystal alignment film as claimed in claim 13. The liquid crystal display element of claim 14 is an IPS drive method or a FFS drive method.