Liquid crystal alignment agent for photo-alignment, liquid crystal alignment film and liquid crystal display element

Abstract

A liquid crystal alignment agent for photo-alignment comprises a polymer (A), a solvent (B) and a hydroxyalkylamide (C). Said polymer (A) is selected from at least one polymer of a group consisting of a polyimide precursor and an imidized polymer formed from said polyimide precursor, and said polyimide precursor of said polymer (A) comprises a structure represented by formula (I). Hydroxyalkylamide (C) comprises a structure represented by formula (C1). Definitions of said formula (I) and said formula (C1) are as stated in a specification and claims respectively. This invention also provides a liquid crystal alignment film formed using said liquid crystal alignment agent for photo-alignment, and a liquid crystal display element comprises said liquid crystal alignment film. In this invention, through said hydroxyalkylamide (C), said liquid crystal alignment film formed by said liquid crystal alignment agent for photo-alignment can be given to said liquid crystal display element with less bright spot.

Description

[Technical Field]

[0001] This invention relates to a liquid crystal alignment agent, a liquid crystal alignment film, and a liquid crystal display element, and particularly to a liquid crystal alignment agent, a liquid crystal alignment film, and a liquid crystal display element for photoalignment methods that can reduce bright spots. [Previous Technology]

[0002] Conventional liquid crystal display (LCD) elements are widely used as display components in personal computers, smartphones, mobile phones, and television receivers. An LCD element includes a liquid crystal layer sandwiched between an element substrate and a color filter substrate, pixel electrodes and a common electrode for applying an electric field to the liquid crystal layer, an alignment film for controlling the alignment of the liquid crystal molecules in the liquid crystal layer, and a thin-film transistor (TFT) for switching the electronic signals supplied to the pixel electrodes. Regarding the driving method of the liquid crystal molecules, known methods include longitudinal electric field driving methods such as twisted nematic (TN) and vertical alignment (VA), and transverse electric field driving methods such as in-plane switching (IPS) and fringe field switching (FFS).

[0003] Currently, the most common liquid crystal alignment film in industry is made by rubbing the surface of a film formed on an electrode substrate and composed of polyamide and / or polyimide obtained by amide imidization with cotton cloth, nylon cloth, or polyester cloth in one direction. Friction treatment is a simple and highly productive industrial alignment treatment method. However, with the increasing performance, image quality, and size of liquid crystal display elements, the surface of the liquid crystal alignment film is scratched by dust, mechanical force, and static electricity generated by the friction treatment, which will lead to various problems such as alignment inhomogeneity of the liquid crystal alignment film. As an alternative to friction treatment, photoalignment methods are known to impart alignment ability to liquid crystals by irradiating polarized radiation, such as the photoalignment methods disclosed in Japanese Patent Application Publication No. H09-297313 that utilize photoisomerization reaction, photocrosslinking reaction, or photodecomposition reaction.

[0004] However, when the liquid crystal alignment film prepared by photoalignment is applied to liquid crystal display elements, especially to the manufacture of display devices with curved liquid crystal panels, the liquid crystal panel is curved along the outer surface of the display device housing. As a result, the interstitial bodies inside the liquid crystal panel move within the liquid crystal panel and rub against the liquid crystal alignment film. The liquid crystal alignment film, which is subjected to pressure by the interstitial bodies, cannot adjust the alignment of liquid crystal molecules. For example, when the liquid crystal panel is displayed in black, the peripheral part of the interstitial bodies has light transmission and is displayed as broken bright spots, which becomes a problem and cannot meet the application requirements. [Summary of the Invention]

[0005] Therefore, the first object of the present invention is to provide a liquid crystal alignment agent for photoalignment method that can improve the problem of broken bright spots.

[0006] Therefore, the liquid crystal alignment agent used in the photoalignment method of the present invention comprises a polymer (A), a solvent (B) and a hydroxyalkylamide (C).

[0007] The polymer (A) is selected from at least one polymer in the group consisting of a polyimide precursor and a amide polymer formed from the polyimide precursor, wherein the polyimide precursor of the polymer (A) comprises a structure as shown in formula (I), where X1 is selected from at least one of the groups consisting of structures as shown in formulas (I-1) to (I-7), wherein "*" represents a bond position, (I-1), (I-2), (I-3), (I-4), (I-5), (I-6), (I-7); and in formula (I-1), X11, X12, X13 and X... 14 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 organogroup having 1 to 6 carbon atoms and containing a fluorine atom, or a phenyl group; In formula (I-7), X 15 and X 16 independently represent a hydrogen atom or a methyl group, X 2 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and Y is a tetravalent organogroup.

[0008] The hydroxyalkylamide (C) comprises a structure as shown in formula (C1), wherein each of (C1) R1 to R4 independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms that may have substituents, an alkenyl group having 2 to 6 carbon atoms that may have substituents, or an alkynyl group having 2 to 6 carbon atoms that may have substituents, wherein at least one of R1 to R4 represents an alkyl group substituted with a hydroxyl group.

[0009] Furthermore, a second objective of the present invention is to provide a liquid crystal alignment film that can improve the problem of bright spots.

[0010] Therefore, the liquid crystal alignment film of the present invention is formed using a liquid crystal alignment agent used in the photoalignment method as described above.

[0011] Furthermore, a third objective of the present invention is to provide a liquid crystal display element that can improve the problem of bright spots.

[0012] Therefore, the liquid crystal display element of the present invention includes the liquid crystal alignment film as described above.

[0013] The advantage of the present invention is that by using the hydroxyalkylamide (C) containing the structure shown in formula (C1), the liquid crystal alignment film formed by the liquid crystal alignment agent used in the photoalignment method can impart to the liquid crystal display element a small number of bright spots.

Implementation Method

[0014] The present invention provides a liquid crystal alignment agent for photoalignment method, comprising a polymer (A), a solvent (B) and a hydroxyalkylamide (C).

[0015] Polymer (A)

[0016] The polymer (A) is selected from at least one polymer in the group consisting of a polyimide precursor and a amide polymer formed from the polyimide precursor, wherein the polyimide precursor of the polymer (A) comprises a structure as shown in formula (I). (I)

[0017] In formula (I), X1 is selected from at least one of the groups consisting of structures as shown in formulas (I-1) to (I-7), wherein "*" represents a bond position; X2 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; and Y is a tetravalent organogroup. (I-1), (I-2), (I-3), (I-4), (I-5), (I-6), (I-7)

[0018] In formula (I-1), X11, X12, X13 and X14 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 containing a fluorine atom, or a phenyl group.

[0019] In formula (I-7), X15 and X16 independently represent a hydrogen atom or a methyl group, respectively.

[0020] In some embodiments of the present invention, in formula (I), X1 is selected from the structures shown in formulas (I-1-1) to (I-1-6). (I-1-1), (I-1-2), (I-1-3), (I-1-4), (I-1-5), (I-1-6)

[0021] In some embodiments of the present invention, in formula (I), X1 represents the structure shown in formula (I-1-1). (I-1-1)

[0022] In some embodiments of the present invention, the polymer (A) is selected from at least one of the group consisting of a polyimide precursor formed by reacting a reaction composition comprising a tetracarboxylic dianhydride component (a1) and a diamine component (b1) and a amide polymer formed from the polyimide precursor. For example, the polymer (A) is a polyimide precursor having a polyamide and polyamide ester amide precursor structure, or the polymer (A) is an amide polymer (i.e., polyimide) formed from the polyimide precursor, or the polymer (A) comprises the polyimide precursor and the amide polymer.

[0023] 〈Tetracarboxylic acid dianhydride component (a1)〉

[0024] In addition to tetracarboxylic dianhydride compounds, the tetracarboxylic dianhydride component (a1) may also use tetracarboxylic dianhydride derivatives such as tetracarboxylic dihalides, tetracarboxylic dialkyl esters, or tetracarboxylic dialkyl ester dihalides. The tetracarboxylic dianhydride component (a1) may be used alone or in combination with multiple tetracarboxylic dianhydride compounds or their derivatives.

[0025] 〔Alicyclic tetracarboxylic dianhydride compound (a1-1)〕

[0026] In some embodiments of the present invention, the tetracarboxylic dianhydride component (a1) comprises an alicyclic tetracarboxylic dianhydride compound (a1-1) or a derivative thereof as shown in formula (A11). (A11)

[0027] The alicyclic tetracarboxylic dianhydride compound (a1-1) or its derivatives represented by formula (A11) can be composed of a single tetracarboxylic dianhydride or its derivative, or can be composed of multiple tetracarboxylic dianhydrides or their derivatives. The alicyclic tetracarboxylic dianhydride compound (a1-1) represented by formula (A11) is, for example, an acid dianhydride obtained by intramolecularly dehydrating four carboxyl groups, including at least one carboxyl group bonded to an alicyclic structure. However, none of these four carboxyl groups are bonded to an aromatic ring. Alternatively, it may not be necessary to consist solely of an alicyclic structure; a portion of it may also have a chain hydrocarbon structure or an aromatic ring structure. An aromatic tetracarboxylic dianhydride is, for example, an acid dianhydride obtained by intramolecularly dehydrating four carboxyl groups, including at least one carboxyl group bonded to an aromatic ring. However, an aromatic tetracarboxylic dianhydride may not be necessary to consist solely of an aromatic ring structure; a portion of it may also have a chain hydrocarbon structure or an alicyclic structure. Acyclic aliphatic tetracarboxylic dianhydrides are, for example, acid dianhydrides obtained by intramolecular dehydration of the four carboxyl groups bonded to a chain hydrocarbon structure. However, acyclic aliphatic tetracarboxylic dianhydrides do not necessarily have to be composed solely of a chain hydrocarbon structure; a portion of them may also have an alicyclic or aromatic ring structure.

[0028] In formula (A11), X1 is selected from at least one of the groups consisting of the structures shown in formulas (I-1) to (I-7), and "*" represents the bond position. (I-1), (I-2), (I-3), (I-4), (I-5), (I-6), (I-7)

[0029] In the formula (I-1), X11, X12, X13 and X14 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 containing a fluorine atom, or a phenyl group.

[0030] In this formula (I-7), X15 and X16 independently represent a hydrogen atom or a methyl group, respectively.

[0031] In some embodiments of the present invention, in formula (A11), the structure represented by formula (I-1) of X1 is selected from the structures represented by formulas (I-1-1) to (I-1-6). (I-1-1), (I-1-2), (I-1-3), (I-1-4), (I-1-5), (I-1-6)

[0032] In some embodiments of the present invention, preferably, in formula (A11), the structure of X1 represented by formula (I-1) is the structure represented by formula (I-1-1).

[0033] In some embodiments of the present invention, based on the total amount of the tetracarboxylic dianhydride component (a1) being 100 mol, the amount of the alicyclic tetracarboxylic dianhydride compound (a1-1) represented by formula (A11) used is 30 mol to 100 mol, preferably, the amount of the alicyclic tetracarboxylic dianhydride compound (a1-1) represented by formula (A11) used is 40 mol to 100 mol, and more preferably, the amount of the alicyclic tetracarboxylic dianhydride compound (a1-1) represented by formula (A11) used is 50 mol to 100 mol.

[0034] 〔Other tetracarboxylic dianhydride compounds (a1-2)〕

[0035] In some embodiments of the present invention, the tetracarboxylic dianhydride component (a1) further comprises other tetracarboxylic dianhydride compounds (a1-2).

[0036] In some embodiments of the present invention, the other tetracarboxylic dianhydride compound (a1-2) comprises a tetracarboxylic dianhydride compound or a derivative thereof as shown in formula (A12). (A12)

[0037] In formula (A12), X 1' represents the structure shown in formulas (A12-1) to (A12-32), where "*" represents the bond position. (A12-1), (A12-2), (A12-3), (A12-4), (A12-5), (A12-6), (A12-7), (A12-8), (A12-9), (A12-10), (A12-11), (A12-12), (A12-13), (A12-14), (A12-15), (A12-16), (A12 -17), (A12-18), (A12-19), (A12-20), (A12-21), (A12-22), (A12-23), (A12-24), ( A12-25), (A12-26), (A12-27), (A12-28), (A12-29), (A12-30), (A12-31), (A12-32)

[0038] In formula (A12-1), a1 is 1 to 12. In formula (A12-5), X11' represents a single bond, -O-, -CO-, -COO-, phenyl, sulfonyl, or amide, and a1 represents 0 or 1. In formula (A12-6), X11' and X12' independently represent a single bond, -O-, -CO-, -COO-, phenyl, sulfonyl, or amide, and multiple X12's may be the same or different, and a1 represents 0 or 1. In formula (A12-11), a1 represents 2 to 6. In formula (A12-13), a1 represents 1 to 2. In formulas (A12-14), X 13' independently represents hydrogen, halogen, alkyl with 1 to 6 carbon atoms, alkenyl with 2 to 6 carbon atoms, alkynyl with 2 to 6 carbon atoms, a monovalent organic group containing fluorine and having 1 to 6 carbon atoms, or a phenyl group, and the plurality of X 13' may be the same or different. From the viewpoint of liquid crystal alignment, it is preferable that the X 13' independently represents hydrogen, halogen, methyl or ethyl, and more preferably, the X 13' independently represents hydrogen or methyl.

[0039] In some embodiments of the present invention, formulas (A12-5) and (A12-6) include, but are not limited to, ...

[0040] The other tetracarboxylic dianhydride compound (a1-2) may be used alone or in combination. In some embodiments of the present invention, based on a total amount of 100 mol of the tetracarboxylic dianhydride component (a1), the amount of the other tetracarboxylic dianhydride compound (a1-2) used is 0 to 70 mol, preferably 0 to 60 mol, and more preferably 0 to 50 mol.

[0041] 〈Diamine component (b1)〉

[0042] In some embodiments of the present invention, the diamine component (b1) comprises a diamine compound (b1-1).

[0043] 〔Diamine compound (b1-1)〕

[0044] The diamine compound (b1-1) is a diamine compound as shown in formulas (A22-1) to (A22-2). (A22-1)(A22-2)

[0045] In formula (A22-1), Y 21 represents a divalent organic group as shown in formula (A22-3), and each of the plurality of Y 22 independently represents an alkyl group having 1 to 6 carbon atoms. In formula (A22-2), each of the plurality of Y 23 independently represents a divalent organic group as shown in formula (A22-3'). Formula (A22-3) Formula (A22-3')

[0046] In the divalent organic group shown in formula (A22-3), Ar independently represents a divalent benzene ring, biphenyl structure or naphthalene ring, and the hydrogen atom of the benzene ring, biphenyl structure or naphthalene ring can be replaced by a monovalent substituent or not replaced; Y 21' represents -(CH 2) n-, n represents an integer from 2 to 18, and at least one of -CH 2- in -(CH 2) n- can be replaced by -O-, -C(=O)- or -OC(=O)- or not replaced; p1 represents 0 or 1; "*" represents the bond position.

[0047] In the divalent organic groups shown in the formula (A22-3'), Ar' independently represents a divalent benzene ring or biphenyl structure, and the hydrogen atoms of the benzene ring or biphenyl structure can be substituted by a monovalent substituent or not substituted; Y23' represents -(CH2)n-, n represents an integer from 2 to 18, and at least one of the -CH2- in -(CH2)n- can be substituted by -O-, -C(=O)- or -OC(=O)- or not substituted; p2 represents 0 or 1; "*" represents the bond position.

[0048] Among the divalent organic groups shown in formula (A22-3) and the divalent organic groups shown in formula (A22-3'), the monovalent substituents of the benzene ring, biphenyl structure, or naphthyl ring are, for example, halogens, alkyl groups having 1 to 10 carbon atoms, alkenyl groups having 2 to 10 carbon atoms, alkoxy groups having 1 to 10 carbon atoms, fluoroalkyl groups having 1 to 10 carbon atoms, fluoroalkenyl groups having 2 to 10 carbon atoms, fluoroalkoxy groups having 1 to 10 carbon atoms, carboxyl groups, hydroxyl groups, alkoxycarbonyl groups having 1 to 10 carbon atoms, cyano groups, or nitro groups, etc.

[0049] In some embodiments of the present invention, from the viewpoint of improving liquid crystal alignment, it is preferable that the divalent organic group represented by formula (A22-3) is at least one of the groups represented by formulas (A22-3-1) to (A22-3-16), wherein "*" represents a bonding position. (A22-3-1), (A22-3-2), (A22-3-3), (A22-3-4), (A22-3-5), (A22-3-6), (A22-3-7), (A22-3-8), (A22-3-9), (A22-3-10), (A22-3-11), (A22-3-12), (A22-3-13), (A22-3-14), (A22-3-15), (A22-3-16)

[0050] In formula (A22-3-1), m is 0 to 1, and n is 1 to 6. In formula (A22-3-2), n is 1 to 6. In formula (A22-3-3), n is 2 to 6. In formula (A22-3-4), n is 1 to 6. In formula (A22-3-5), n is 1 to 6. In formula (A22-3-6), n is 2 to 6. In formula (A22-3-7), n is 1 to 6. In formula (A22-3-8), n is 1 to 6. In formula (A22-3-9), n is 2 to 6. In formula (A22-3-10), m is 1 to 3, and n is 1 to 4. In equation (A22-3-11), n ​​is 1 to 6. In equation (A22-3-12), n is 1 to 6. In equation (A22-3-13), m is 0 to 1, and n is 1 to 6. In equation (A22-3-14), m is 1 to 3, and n is 1 to 4.

[0051] In some embodiments of the present invention, from the viewpoint of improving liquid crystal alignment, it is preferable that the divalent organic group represented by formula (A22-3') is the group represented by formula (A22-3-7) to formula (A22-3-16).

[0052] In some embodiments of the present invention, when the diamine compound (b1-1) comprises a diamine compound represented by the complex formula (A22-1), preferably, the diamine compound represented by the formula (A22-1) is a combination of diamine compounds of formula (A22-3-1) to (A22-3-14) represented by Y 21 in formula (A22-1) and diamine compounds of formula (A22-3-15) to (A22-3-16) represented by Y 21 in formula (A22-1).

[0053] In some embodiments of the present invention, the diamine compound represented by formula (A22-2) is, for example, but not limited to, the diamine compounds represented by formulas (A22-2-1), (A22-2-2), (A22-2-3), (A22-2-4), and (A22-2-5).

[0054] In formula (A22-2-1), m is 1 to 6 and n is 1 to 6. In formula (A22-2-2), m is 1 to 6 and n is 1 to 6. In formula (A22-2-3), m is 2 to 6 and n is 2 to 6.

[0055] The diamine compound (b1-1) can be used alone or in combination with other compounds. In some embodiments of the present invention, based on a total amount of 100 mol of the diamine component (b1), the amount of the diamine compound (b1-1) used is 20 to 90 mol, preferably 25 to 80 mol, and more preferably 30 to 70 mol.

[0056] 〔Diamine compounds having a -N(D)- group (b1-2)〕

[0057] In some embodiments of the present invention, the diamine component (b1) further comprises a diamine compound (b1-2) having a -N(D)- group.

[0058] From the viewpoint of improving the voltage retention rate of liquid crystal display elements, the polymer (A) may selectively have a -N(D)- group (where D represents a carbamate protecting group). The polymer (A) having the -N(D)- group can be obtained by using a monomer having the -N(D)- group as at least a portion of the reactants, or by using a monomer having the -N(D)- group as a capping agent as described below. In some specific examples, the monomer having the -N(D)- group is, for example, a diamine compound (b1-2) having the -N(D)- group. For example, the carbamate protecting group is, for example, but not limited to, tributoxycarbonyl (Boc) or 9-pyromethoxycarbonyl.

[0059] In some embodiments of the present invention, preferably, the diamine compound (b1-2) having a -N(D)- group comprises a diamine compound having at least one aromatic group (e.g., a benzene ring). More preferably, the diamine compound (b1-2) having a -N(D)- group comprises a diamine compound having at least one aromatic group and having 6 to 30 carbon atoms in residues other than the substituent (D). In some specific examples of the present invention, the diamine compound (b1-2) having a -N(D)- group is, for example, but not limited to, diamine compounds as shown in formulas (A23-1) to (A23-11). (A23-1), (A23-2), (A23-3), (A23-4), (A23-5), (A23-6), (A23-7), (A23-8), (A23-9), (A23-10), (A23-11)

[0060] In equation (A23-1), n ​​is 1 to 6. In equation (A23-2), n is 1 to 6. In equation (A23-4), m is 1 to 6, and n is 1 to 6. In equation (A23-7), m is 1 to 6, and n is 1 to 6. In equation (A23-9), n is 1 to 6. In equation (A23-11), n ​​is 1 to 6.

[0061] The diamine compound (b1-2) having the -N(D)- group can be used alone or in combination with other compounds. In some embodiments of the present invention, based on a total amount of 100 mol of the diamine component (b1), the amount of the diamine compound (b1-2) having the -N(D)- group used is 2 to 60 mol, preferably 10 to 50 mol, and more preferably 15 to 40 mol.

[0062] 〔Other diamine compounds (b1-3)〕

[0063] In some embodiments of the present invention, the diamine component (b1) further comprises other diamine compounds (b1-3).

[0064] The other diamine compounds (b1-3) include, but are not limited to, diamine compounds having photoalignment groups, 4-amino-N-methylphenethylamine, 2,4-diaminophenol, 3,5-diaminophenol, 3,5-diaminobenzyl alcohol, 2,4-diaminobenzyl alcohol, 4,6-diaminoresorcinol, diamine compounds having carboxyl groups, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, etc. Diphenyl ketone, 1,4-bis(4-aminobenzyl)benzene, 4,4'-diaminodiphenyl ether, 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, diamine compounds with urea bonds, diamine compounds with amide bonds, diamine compounds with photopolymerizable groups at the ends, diamine compounds with siloxane bonds, diamine compounds with oxazoline structures, or diamine compounds with nitrogen-containing structures, etc.

[0065] The diamine compound having a photoalignment group is, for example, but not limited to, 4,4'-diaminoazobenzene, or diamine compounds as shown in formulas (A24-1) to (A24-3). (A24-1), (A24-2), (A24-3)

[0066] The diamine compound having a carboxyl group is, for example, but not limited to, 2,4-diaminobenzoic acid, 2,5-diaminobenzoic acid, 3,5-diaminobenzoic acid, or diamine compounds as shown in formulas (A24-4) to (A24-7). (A24-4), (A24-5), (A24-6), (A24-7)

[0067] In formula (A24-4), Y 41 represents a single bond, -CH 2-, -C 2H 4-, -C(CH 3) 2-, -CF 2-, -C(CF 3) 2-, -O-, -CO-, -NH-, -N(CH 3)-, -CONH-, -NHCO-, -CH 2O-, -OCH 2-, -COO-, -OCO-, -CON(CH 3)-, or -N(CH 3)CO-; m1 and m2 each independently represent integers from 0 to 4, and (m1+m2) represents integers from 1 to 4. In formula (A24-5), m3 and m4 each independently represent integers from 1 to 5. In formula (A24-6), Y 42 represents a straight-chain or branched alkyl group with 1 to 5 carbon atoms; m5 represents integers from 1 to 5. In formula (A24-7), Y 43 and Y 44 independently represent single bonds, -CH 2-, -C 2H 4-, -C(CH 3) 2-, -CF 2-, -C(CF 3) 2-, -O-, -CO-, -NH-, -N(CH 3)-, -CONH-, -NHCO-, -CH 2O-, -OCH 2-, -COO-, -OCO-, -CON(CH 3)- or -N(CH 3)CO-; m6 represents an integer from 1 to 4.

[0068] The diamine compound having a urea bond is, for example, but not limited to, diamine compounds shown in formulas (A24-8), (A24-9), and (A24-10).

[0069] In equation (A24-8), n1 is 0 to 6, and n2 is 1 to 6. In equation (A24-9), n1 is 1 to 6, and n2 is 1 to 6. In equation (A24-10), n is 1 to 6.

[0070] The diamine compound having an amide bond is, for example, but not limited to, the diamine compounds having an amide bond as shown in formulas (A24-11), (A24-12), and (A24-13).

[0071] In formula (A24-12), n is 1 to 6. In formula (A24-13), n1 is 1 to 6, and n2 is 1 to 6.

[0072] The diamine compound with a photopolymerizable group at the end is, for example, but not limited to, 2-(2,4-diaminophenoxy)ethyl methacrylate or 2,4-diamino-N,N-diallyl aniline.

[0073] The diamine compound having a siloxane bond is, for example, but not limited to, 3-bis(3-aminopropyl)-tetramethyldisiloxane.

[0074] The diamine compound having an oxazoline structure includes, but is not limited to, diamine compounds of formulas (A24-14) to (A24-15). (A24-14), (A24-15)

[0075] The nitrogen-containing structure of the diamine compound having a nitrogen-containing structure is selected from at least one of the group consisting of nitrogen-containing heterocycles, secondary amine groups and tertiary amine groups.

[0076] The nitrogen-containing heterocycle of the diamine compound having a nitrogen-containing atom structure is, for example, but not limited to, pyrrole, imidazole, pyrazole, triazole, pyridine, pyrimidine, pyridine, indole, benzimidazole, purine, quinoline, isoquinoline, acetidine, quinoline, pyridine, triazole, carbazole, acridine, piperidine, piperidine, pyrrolidine, or hexamethyleneimine, etc. In some embodiments of the present invention, preferably, the nitrogen-containing heterocycle is pyridine, pyrimidine, pyridine, piperidine, piperidine, quinoline, carbazole, or acridine.

[0077] In some embodiments of the present invention, the nitrogen-containing structure of the diamine compound having a nitrogen-containing atom structure is a secondary amino group and a tertiary amino group as shown in formula (A25). (A25)

[0078] In this formula (A25), Z represents hydrogen, alkyl, cycloalkyl or aryl with 1 to 10 carbon atoms; "*" represents the bond position.

[0079] The alkyl group having 1 to 10 carbon atoms is, for example, but not limited to, methyl, ethyl, or propyl. The cycloalkyl group is, for example, but not limited to, cyclohexyl. The aryl group is, for example, but not limited to, phenyl or tolyl. In some embodiments of the invention, preferably, Z is hydrogen or methyl.

[0080] The diamine compound having a nitrogen-containing atom structure is, for example but not limited to, 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, diamine compounds as shown in formulas (A25-1) to (A25-8), or diamine compounds as shown in formulas (A25-9) to (A25-26). (A25-1), (A25-2), (A25-3), (A25-4), (A25-5), (A25-6), (A25-7), (A25-8), (A25-9), (A25-10), (A25-11), (A25-12), (A25-13), (A25 -14), (A25-15), (A25-16), (A25-17), (A25-18), (A25-19), (A25-20), (A25-21), (A25-22), (A25-23), (A25-24), (A25-25), (A25-26)

[0081] In formula (A25-5), n represents 1 to 4. In formula (A25-6), n represents 1 to 4.

[0082] The other diamine compounds (b1-3) may be used alone or in combination. In some embodiments of the present invention, based on a total amount of 100 mol of the diamine component (b1), the amount of the other diamine compound (b1-3) used is 0 to 65 mol, preferably 0 to 50 mol, and more preferably 0 to 35 mol.

[0083] Solvent (B)

[0084] From the viewpoint of forming a uniform thin film, the liquid crystal alignment agent is taken in the form of a coating liquid to produce a liquid crystal alignment film. In some embodiments of the present invention, preferably, the liquid crystal alignment agent used in the photoalignment method of the present invention is a coating liquid containing a polymer (A) and a solvent (B). The concentration of polymer (A) in the liquid crystal alignment agent used in the photoalignment method can be appropriately varied based on the desired coating thickness. In some embodiments of the present invention, from the viewpoint of forming a uniform and defect-free coating film, preferably, the concentration of polymer (A) in the liquid crystal alignment agent used in the photoalignment method is 1 wt% or more. In some embodiments of the present invention, from the viewpoint of the storage stability of the solution, preferably, the concentration of polymer (A) in the liquid crystal alignment agent used in the photoalignment method is 10 wt% or less. In some embodiments of the present invention, the ideal concentration of polymer (A) is 2 wt% to 8 wt%. The content of polymer (A) in the liquid crystal alignment agent used in the photoalignment method can be appropriately changed by the coating method of the liquid crystal alignment agent and / or the film thickness of the liquid crystal alignment film to be obtained. In some embodiments of the present invention, preferably, the content of polymer (A) is 2wt% to 10wt%, more preferably, the content of polymer (A) is 3wt% to 8wt%.

[0085] The solvent (B) in the liquid crystal alignment agent used in this photoalignment method is, for example, an organic solvent, and there are no particular limitations on the solvent (B), as long as it can uniformly dissolve the polymer (A). The solvent (B) includes, but is not limited to, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethyllactamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, dimethyl sulfoxide, γ-butyrolactone, γ-valerolactone, 1,3-dimethyl-2-imidazolidineone, methyl ethyl ketone, cyclohexanone, cyclopentanone, 3-methoxy-N,N-dimethylpropionic acid, and 3-butoxy-N,N-dimethylpropionic acid. The solvents used are 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, or N-cyclohexyl-2-pyrrolidone, etc., and the solvents mentioned above are also called good solvents. In some embodiments of the present invention, preferably, the solvent (B) is N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, 3-methoxy-N,N-dimethylpropionic acid, 3-butoxy-N,N-dimethylpropionic acid, or γ-butyrolactone. In some embodiments of the present invention, the total amount of solvent (B) in the liquid crystal alignment agent used in the photoalignment method is 100 wt%, and the amount of good solvent used is 20 wt% to 99 wt%. Preferably, the amount of good solvent used is 20 wt% to 90 wt%, and more preferably, the amount of good solvent used is 30 wt% to 80 wt%.

[0086] In some embodiments of the present invention, preferably, the solvent (B) in the liquid crystal alignment agent used in the photoalignment method includes the aforementioned good solvent and a lean solvent that can improve the coatability and surface smoothness of the coating film during liquid crystal alignment agent coating. In some embodiments of the present invention, preferably, based on the total amount of solvent (B) in the liquid crystal alignment agent used in the photoalignment method being 100 wt%, the amount of the lean solvent used is 1 wt% to 80 wt%, more preferably, the amount of the lean solvent used is 10 wt% to 80 wt%, and even more preferably, the amount of the lean solvent used is 20 wt% to 70 wt%. The type and amount of the lean solvent can be appropriately selected according to the coating apparatus, coating conditions, and / or coating environment of the liquid crystal alignment agent.

[0087] The lean solvent includes, but is not limited to, diisopropyl ether, diisobutyl ether, diisobutylmethanol (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, propyl carbonate, ethyl carbonate, ethylene glycol monobutyl ether (butyl ceroxysulfate), ethylene glycol monoisopentyl ether, ethylene glycol monohexyl ether, propylene glycol monobutyl ether, 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 ether 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, or diisobutyl ketone (2,6-dimethyl-4-heptanone), etc.

[0088] In some embodiments of the present invention, preferably, the lean solvent is diisobutyl methanol, 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, etc.

[0089] In some embodiments of the present invention, preferably, the solvent combination of the good solvent and the poor solvent is, for example, but not limited to, N-methyl-2-pyrrolidone and ethylene glycol monobutyl ether; N-methyl-2-pyrrolidone, γ-butyrolactone and ethylene glycol monobutyl ether; N-methyl-2-pyrrolidone, γ-butyrolactone and propylene glycol monobutyl ether; N-ethyl-2-pyrrolidone and propylene glycol monobutyl ether; N-ethyl-2-pyrrolidone and 4-hydroxy-4-methyl-2-pentanone; N-ethyl-2-pyrrolidone and propylene glycol diacetate; N,N-dimethyllactamine and diisobutyl ketone; N-methyl-2-pyrrolidone and ethyl 3-ethoxypropionate; N-ethyl-2-pyrrolidone and 3-ethoxypropionate. Ethyl acetate; N-methyl-2-pyrrolidone and ethylene glycol monobutyl ether acetate; N-ethyl-2-pyrrolidone and dipropylene glycol dimethyl ether; N,N-dimethyllactamine and ethylene glycol monobutyl ether; N,N-dimethyllactamine and propylene glycol diacetate; N-ethyl-2-pyrrolidone and diethylene glycol diethyl ether; N,N-dimethyllactamine and diethylene glycol diethyl ether; N-methyl-2-pyrrolidone, γ-butyrolactone, 4-hydroxy-4-methyl-2-pentanone and diethylene glycol diethyl ether; N-ethyl-2-pyrrolidone, N-methyl-2-pyrrolidone and 4-hydroxy-4-methyl-2-pentanone; N-ethyl-2-pyrrolidone, 4-hydroxy-4-methyl-2-pentanone and propylene glycol monobutyl ether; N N-methyl-2-pyrrolidone, 4-hydroxy-4-methyl-2-pentanone and diisobutyl ketone; N-methyl-2-pyrrolidone, 4-hydroxy-4-methyl-2-pentanone and dipropylene glycol monomethyl ether; N-methyl-2-pyrrolidone, 4-hydroxy-4-methyl-2-pentanone and propylene glycol monobutyl ether; N-methyl-2-pyrrolidone, 4-hydroxy-4-methyl-2-pentanone and propylene glycol diacetate; γ-butyrolactone, 4-hydroxy-4-methyl-2-pentanone and diisobutyl ketone; γ-butyrolactone, 4-hydroxy-4-methyl-2-pentanone and propylene glycol diacetate; N-methyl-2-pyrrolidone, γ-butyrolactone, propylene glycol monobutyl ether and diisobutyl ketone; N-methyl-2-pyrrolidone, γ-butyrolactone - Butyrolactone and propylene glycol monobutyl ether and diisopropyl ether; N-methyl-2-pyrrolidone, γ-butyrolactone, propylene glycol monobutyl ether and diisobutylmethanol; N-methyl-2-pyrrolidone, γ-butyrolactone and dipropylene glycol dimethyl ether; N-methyl-2-pyrrolidone, propylene glycol monobutyl ether and dipropylene glycol dimethyl ether; N-ethyl-2-pyrrolidone, propylene glycol monobutyl ether and dipropylene glycol monomethyl ether; N-ethyl-2-pyrrolidone, propylene glycol monobutyl ether and propylene glycol diacetate; N-ethyl-2-pyrrolidone, propylene glycol monobutyl ether and diisobutyl ketone; N-ethyl-2-pyrrolidone, γ-butyrolactone and diisobutyl ketone; or N-ethyl-2-pyrrolidone, N,N-dimethyllactamine and diisobutyl ketone, etc.

[0090] The solvent (B) can be used alone or in combination with other solvents. In some embodiments of the invention, based on a total amount of 100 parts by weight of the polymer (A), the amount of solvent (B) used is 800 to 4000 parts by weight, preferably 900 to 3500 parts by weight, and more preferably 1000 to 3000 parts by weight.

[0091] Hydroxyalkylamide (C)

[0092] The hydroxyalkylamide (C) comprises the structure shown in formula (C1). (C1)

[0093] In the formula (C1), R1 to R4 each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms that may have substituents, an alkenyl group having 2 to 6 carbon atoms that may have substituents, or an alkynyl group having 2 to 6 carbon atoms that may have substituents, wherein at least one of R1 to R4 represents an alkyl group substituted with a hydroxyl group.

[0094] In some embodiments of the present invention, the hydroxyalkylamide (C) is selected from the following compounds: , ...

[0095] In some embodiments of the present invention, based on a total amount of 100 parts by weight of polymer (A), the amount of hydroxyalkylamide (C) used is from 4 parts by weight to 35 parts by weight, preferably from 5 parts by weight to 32 parts by weight, and more preferably from 6 parts by weight to 30 parts by weight.

[0096] When the hydroxyalkylamide (C) is not used in the liquid crystal alignment agent used in the photoalignment method, the liquid crystal display element containing the liquid crystal alignment film made using the liquid crystal alignment agent used in the photoalignment method has a serious problem of broken spots.

[0097] In some embodiments of the present invention, in order to further reduce the number of bright spots in a liquid crystal display element comprising a liquid crystal alignment film made using a liquid crystal alignment agent for photoalignment, at least three of R1 to R4 represent alkyl groups substituted with hydroxyl groups.

[0098] Additives (D)

[0099] In some embodiments of the present invention, the liquid crystal alignment agent used in the photoalignment method of the present invention further comprises an additive (D). This additive (D) includes, but is not limited to, adhesion promoters for improving the adhesion between the liquid crystal alignment film and the substrate or between the liquid crystal alignment film and the sealant, crosslinking compounds for improving the strength of the liquid crystal alignment film, compounds for promoting amide imidization, and dielectric or conductive materials for adjusting the dielectric constant or resistance of the liquid crystal alignment film.

[0100] The sealing aid is, for example, but not limited to, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyldiethoxymethylsilane, 2-aminopropyltrimethoxysilane, 2-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-ureopropyltrimethoxysilane, 3-ureopropyltriethoxysilane, N-ethoxycarbonyl-3-aminopropyltrimethoxysilane, N-ethoxycarbonyl-3-aminopropyltriethoxysilane, N-triethoxysilylpropyltriethyleneethyltriamine, N-trimethoxysilylpropyltriethyleneethyltriamine, vinyl Trimethoxysilane, vinyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-epoxypropoxypropylmethyldimethoxysilane, 3-epoxypropoxypropyltrimethoxysilane, 3-epoxypropoxypropylmethyldiethoxysilane, 3-epoxypropoxypropyltriethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-propenyloxypropyltrimethoxysilane, tris(3-trimethoxysilylpropyl)isocyanurate, or 3-isocyanatepropyltriethoxysilane, etc., are silane coupling agents. When using this bonding agent, based on the viewpoint of exhibiting good resistance to AC image retention, it is preferable that the amount of the bonding agent used is 0.1 to 30 parts by weight relative to 100 parts by weight of the total amount of polymer (A) in the liquid crystal alignment agent used in the photoalignment method, and more preferably, the amount of the bonding agent used is 0.1 to 20 parts by weight.

[0101] Based on the viewpoint of exhibiting good resistance to AC image retention and effectively improving film strength, the crosslinking compound may be a compound having at least one group selected from the group consisting of the group shown in formula (D1) and the group shown in formula (D2), or a compound selected from the compound shown in formula (D3). (D1), (D2), (D3)

[0102] In formula (D1), G1 and G2 each independently represent a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or -CH2-OH. In formula (D2), G3 represents 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. G4 represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or an alkynyl group having 2 to 6 carbon atoms. In formula (D3), G5 represents a (g1+g2) valence organic group containing an aromatic ring. G6 represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. g1 represents an integer from 1 to 6, and g2 represents an integer from 0 to 4.

[0103] In formula (D3), the (g1+g2) valence organic group represented by G5 can be an aromatic hydrocarbon group with 6 to 30 carbon atoms, an aromatic hydrocarbon group with 6 to 30 carbon atoms bonded directly or alternately by a linking group, or an aromatic heterocycle group. The aromatic hydrocarbon can be, for example, benzene or naphthalene. The aromatic heterocycle can be exemplified by the above-described nitrogen-containing heterocycles. The linking group can be an alkyl group with 1 to 10 carbon atoms, or a group from which one hydrogen atom is removed, or a divalent or trivalent cyclohexane, etc. Any hydrogen atom of the alkyl group can also be replaced by a fluorine atom or an organic group such as trifluoromethyl. In formula (D3), the alkyl group represented by G 6 with 1 to 5 carbon atoms can be methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, dibutyl, terbutyl or n-pentyl.

[0104] Specific examples of compounds containing ethylene oxide include N,N,N',N'-tetracyclooxypropylmethylenediamine, 1,3-bis(N,N-dicyclooxypropylaminomethyl)cyclohexane, N,N,N',N'-tetracyclooxypropyl-4,4'-diaminodiphenylmethane, N,N,N',N'-tetracyclooxypropyl-p-phenylenediamine, and compounds containing nitrogen atoms as shown in formulas (D4), (D5), and (D6).

[0105] Specific examples of compounds having an propylene oxide alkyl group can be listed below as compounds represented by formulas (D7) to (D16). (D7), (D8), (D9), (D10), (D11), (D12), (D13), (D14), (D15), (D16)

[0106] In equation (D7), n represents 1 to 3. In equation (D13), n represents 1 to 3. In equation (D14), n represents 1 to 100. In equation (D15), R represents, where "*" represents the bond position. In equation (D16), n represents 1 to 10.

[0107] Specific examples of compounds having the group shown in formula (D1) can be listed as compounds shown in formulas (D1-1) to (D1-12). (D1-1), (D1-2), (D1-3), (D1-4), (D1-5), (D1-6), (D1-7), (D1-8), (D1-9), (D1-10), (D1-11), (D1-12)

[0108] Specific examples of compounds having the group shown in formula (D2) can be listed as compounds shown in formulas (D2-1) to (D2-4). (D2-1), (D2-2), (D2-3), (D2-4)

[0109] In formula (D2-1), n ​​represents 2 to 16. In formula (D2-2), n represents 2 to 16.

[0110] Specific examples of compounds having the group shown in formula (D3) can be the compounds shown in formulas (D3-1) to (D3-10). (D3-1), (D3-2), (D3-3), (D3-4), (D3-5), (D3-6), (D3-7), (D3-8), (D3-9), (D3-10)

[0111] In some embodiments of the present invention, the total amount of polymer (A) used in the liquid crystal alignment agent for the photoalignment method is 100 parts by weight. Preferably, the amount of the crosslinking compound used is 0.5 parts by weight to 20 parts by weight. More preferably, based on the view that the crosslinking reaction proceeds and exhibits good resistance to AC image retention, the amount of the crosslinking compound used is 1 part by weight to 15 parts by weight.

[0112] In some embodiments of the present invention, preferably, the compound used to promote aceimination is a compound having a basic site [e.g., a primary amino group, an aliphatic heterocycle (such as a pyrrolidine skeleton), an aromatic heterocycle (such as an imidazole ring or an indole ring), or a guanidine group, etc.] (except for the aforementioned crosslinking compounds and binding aids), or a compound that produces the basic site upon calcination. More preferably, the compound promoting aceimination is a compound that produces the basic site upon calcination, and specific examples may be, for example, amino acids in which part or all of the basic site is protected. Specific examples of the aforementioned amino acids include glycine, alanine, cysteine, methionine, aspartic acid, glutamine, valine, leucine, phenylalanine, tyrosine, tryptophan, proline, hydroxyproline, arginine, histamine, lysine, or ornithine. For the purpose of promoting aceiminization, more preferably, specific examples of compounds for promoting aceiminization can be listed as N-α-(9-enylmethoxycarbonyl)-N-τ-(tert-butoxycarbonyl)-L-histidine.

[0113] Preparation method of liquid crystal alignment film and liquid crystal display element

[0114] The liquid crystal alignment film of the present invention is obtained from the liquid crystal alignment agent used in the aforementioned photoalignment method. The liquid crystal alignment film of the present invention can be used as a horizontally aligned or vertically aligned (VA type) liquid crystal alignment film, and is suitable as a liquid crystal alignment film for horizontally aligned liquid crystal display elements such as IPS or FFS types. The liquid crystal display element of the present invention includes the liquid crystal alignment film. The liquid crystal display element of the present invention can be manufactured, for example, by the method described in steps (1) to (4) or steps (1) to (2) and (4).

[0115] Step (1): Apply liquid crystal alignment agent onto the substrate

[0116] Using a suitable coating method such as roll coating, spin coating, printing, or inkjet coating, the liquid crystal alignment agent for the photoalignment method of the present invention is coated on one side of a substrate having a patterned transparent conductive film. The substrate is not particularly limited; it only needs to be a highly transparent substrate, and glass substrates or silicon nitride substrates can be used in combination with plastic substrates such as acrylic substrates or polycarbonate substrates. Furthermore, in reflective liquid crystal display elements, if only a single-sided substrate is used, opaque materials such as silicon wafers can be used, and the electrodes used can be made of light-reflective materials such as aluminum. Moreover, when manufacturing IPS or FFS type liquid crystal display elements, the comb-type uses an electrode substrate composed of a patterned transparent conductive film or metal film and an opposing substrate without electrodes.

[0117] Methods for coating the liquid crystal alignment agent used in the photoalignment method onto a substrate and forming a film include screen printing, offset printing, flexographic printing, inkjet printing, or spraying. Preferably, the film forming method utilizes inkjet coating.

[0118] Step (2): Calcine the coated liquid crystal alignment agent

[0119] Step (2) is a step of calcining the liquid crystal alignment agent coated on the substrate to form a film. After the liquid crystal alignment agent for photoalignment is coated on the substrate, the solvent can be evaporated by heating means such as a hot plate, a thermal cycling oven, or an IR (infrared) oven, or the polyamide or polyamide ester can be thermally amided. The drying and calcination steps performed after coating the liquid crystal alignment agent for photoalignment can be performed at any temperature and time, and multiple drying or calcination steps can be performed. The temperature of the drying step can be, for example, from 40°C to 180°C. From the viewpoint of shortening the processing time, the drying step can be performed at 40°C to 150°C. The time of the drying step is not particularly limited, and it can be, for example, from 1 minute to 10 minutes or from 1 minute to 5 minutes. During the thermal amide formation of polyamide or polyamide ester, after the drying step, a calcination step can be further performed at a temperature of, for example, 150°C to 300°C or 150°C to 250°C. The duration of this calcination step is not particularly limited, and examples include 5 to 40 minutes or 5 to 30 minutes. If the film obtained after this calcination step is too thin, the reliability of the liquid crystal display element will decrease; therefore, preferably, the thickness of the film is 5 nm to 300 nm, and more preferably, the thickness of the film is 10 nm to 200 nm.

[0120] Step (3): Perform alignment treatment on the membrane obtained in step (2).

[0121] Step (3) involves performing alignment treatment on the film obtained in step (2), depending on the circumstances. In other words, in horizontally aligned liquid crystal display elements such as IPS or FFS, alignment treatment is performed on the film to impart alignment capability. On the other hand, in vertically aligned liquid crystal display elements such as VA or PSA, the formed film can be used directly as a liquid crystal alignment film, but alignment treatment can also be performed on the film to impart alignment capability. Alignment treatment of the liquid crystal alignment film can include rubbing treatment or photoalignment treatment, preferably photoalignment treatment. Photoalignment treatment can include irradiating the surface of the film with radiation that has been deflected in a certain direction, and, depending on the circumstances, heating it at a temperature of 150°C to 250°C to impart liquid crystal alignment property (also known as liquid crystal alignment capability). The radiation can be ultraviolet light or visible light with a wavelength of 100nm to 800nm. Preferably, the radiation is ultraviolet light with a wavelength of 100 nm to 400 nm, and more preferably, the radiation is ultraviolet light with a wavelength of 200 nm to 400 nm.

[0122] The radiation dose can be from 1 mJ / cm² to 10,000 mJ / cm², preferably from 100 mJ / cm² to 5,000 mJ / cm², more preferably from 100 mJ / cm² to 1500 mJ / cm², and even more preferably from 100 mJ / cm² to 1000 mJ / cm². When using a conventional liquid crystal alignment agent, the light irradiation dose for the alignment process is from 100 mJ / cm² to 5000 mJ / cm². However, the liquid crystal alignment agent used in the photoalignment method of the present invention can still obtain a liquid crystal alignment film in which the variation (non-uniformity) of liquid crystal alignment within the film surface is effectively suppressed, even if the light irradiation dose for the alignment process is reduced. To improve liquid crystal alignment during irradiation, the substrate having the film can be heated to 50°C to 250°C simultaneously with the irradiation. Liquid crystal alignment films produced in this manner allow liquid crystal molecules to be stably aligned in a specific direction. Furthermore, the liquid crystal alignment film irradiated with polarized radiation in the aforementioned method can be contact-treated with a solvent, or the irradiated liquid crystal alignment film can be heat-treated.

[0123] There are no particular limitations on the solvent used in this contact treatment, as long as it can dissolve the decomposition products generated from the film after radiation irradiation. Specific examples of solvents used in this contact treatment include water, methanol, ethanol, 2-propanol, acetone, methyl ethyl ketone, 1-methoxy-2-propanol, 1-methoxy-2-propanol acetate, butyl ceroxysulfate, ethyl lactate, methyl lactate, diacetone alcohol, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, propyl acetate, butyl acetate, or cyclohexyl acetate, etc. In some embodiments of the present invention, from the viewpoint of versatility and safety, it is preferable that the solvent used in this contact treatment is water, 2-propanol, 1-methoxy-2-propanol, or ethyl lactate; more preferably, it is water, 1-methoxy-2-propanol, or ethyl lactate. The solvent used in this contact treatment can be used alone or in combination of several solvents.

[0124] In some embodiments of the present invention, preferably, the temperature for heating the irradiated film is 50°C to 300°C, more preferably, the temperature for heating is 120°C to 250°C. Preferably, the heating time is 1 minute to 30 minutes.

[0125] Step (4): Fabrication of liquid crystal cells

[0126] Prepare two substrates with liquid crystal alignment films formed on their surfaces, and place liquid crystal between the two substrates facing each other. For example, the following two methods can be used. In the first method, firstly, place the two substrates facing each other with their liquid crystal alignment films facing each other, separated by a gap (intercellular space). Then, bond the peripheral portions of the two substrates together with a sealant, and then inject the liquid crystal composition to fill the intercellular space separated by the substrate surface and the sealant. After it contacts the film surface, seal the injection hole.

[0127] The second method is called ODF (One Drop Fill). A UV-curable sealant is applied to predetermined positions on one of two substrates on which a liquid crystal alignment film is formed. Then, a liquid crystal composition is dropped onto multiple predetermined positions on the surface of the liquid crystal alignment film. Next, the other substrate is bonded with the liquid crystal alignment films facing each other, and the liquid crystal composition is pressed against the entire surface of the liquid crystal alignment film, making it contact the surface of the other liquid crystal alignment film. Then, the entire surface of the substrate is irradiated with UV light to harden the sealant. Preferably, when performing any of the aforementioned methods, the liquid crystal composition used is further heated to a temperature at which it becomes isotropic, and then slowly cooled to room temperature to remove the flow alignment during liquid crystal filling. Next, when performing a rubbing treatment on the film, the two substrates are arranged facing each other at a predetermined angle to the rubbing direction of each film, for example, in an orthogonal or antiparallel manner. The sealant can be, for example, an epoxy resin containing a hardener and alumina balls as spacers. The liquid crystal composition may include nematic liquid crystals and lamellar liquid crystals, and preferably, the liquid crystal composition is a nematic liquid crystal.

[0128] A polarizing plate may be attached to the outer surface of the liquid crystal cell as needed to obtain a liquid crystal display element. The polarizing plate attached to the outer surface of the liquid crystal cell may be a polarizing film that extends and aligns with polyvinyl alcohol and simultaneously absorbs iodine, and is called an "H film". The polarizing plate may be a polarizing plate sandwiched with a cellulose acetate protective film, or a polarizing plate composed of the H film itself.

[0129] The present invention will be further described with reference to the following embodiments, but it should be understood that the embodiments are only for illustrative purposes and should not be construed as limiting the implementation of the present invention.

[0130] [Synthesis Example A-1] Polymer (A)

[0131] A nitrogen inlet, stirrer, condenser, and thermometer were installed on a 500 mL four-necked conical flask, and nitrogen gas was introduced. Then, 0.005 mol (10 mol%) of compound (b1-a), 0.0165 mol (33 mol%) of compound (b1-b), 0.005 mol (10 mol%) of compound (b1-c), and 0.0235 mol (47 mol%) of compound (b1-d) and 80 g of N-methyl-2-pyrrolidone (hereinafter referred to as NMP) were added, and stirred at 25 °C until dissolved. Next, 0.05 mol (100 mol%) of compound (a1-a) and 20 g of NMP were added, and the reaction was carried out at 25 °C for 2 hours to obtain a reaction solution. The reaction solution was poured into 1500 mL of water to precipitate the polymer. The precipitate was then filtered to obtain a filter cake. The filter cake was then washed with methanol and filtered again. This washing and filtration process with methanol was repeated three times to obtain a crude product. The crude product was then placed in a vacuum oven and dried at 60°C to obtain polymer (A).

[0132] [Synthesis Examples A-2 to A-4] Polymer (A)

[0133] Synthetic Examples A-2 to A-4 were prepared by a method similar to that of Synthetic Example A-1, except that the types and amounts of tetracarboxylic acid dianhydride component (a1) and diamine component (b1) were changed in Synthetic Examples A-2 to A-4, as shown in Table 1.

[0134] Table 1 Unit: mol% Synthesis example A-1 A-2 A-3 A-4 Tetracarboxylic dianhydride component (a1) a1-a 100 100 100 -- a1-b -- -- -- 100 Diamine component (b1) b1-a 10 20 15 10 b1-b 33 -- 45 -- b1-c 10 15 20 -- b1-d 47 -- 10 -- b1-e -- 38 10 70 b1-f -- 27 -- 20 Note: "--" indicates that it has not been added. a1-a: a1-b: b1-a: b1-b: b1-c: b1-d: b1-e: b1-f:

[0135] [Example 1] Liquid crystal alignment agent, liquid crystal alignment film and liquid crystal display element for photoalignment method

[0136] 100 parts by weight of polymer (A) of synthesis example A-1, 800 parts by weight of solvent B-1 (of type N-methyl-2-pyrrolidone) and 13 parts by weight of hydroxyalkylamide C-1 were stirred and mixed at 25°C to obtain a liquid crystal alignment agent for photoalignment.

[0137] The liquid crystal alignment agent for photoalignment was spin-coated onto the pixel electrode of a glass substrate containing a pixel electrode. The pixel electrode is an IPS driving electrode having a pair of indium tin oxide (ITO) electrodes (electrode width 10 μm, electrode spacing 10 μm, and electrode height 50 nm). The pair of ITO electrodes are serrated, and the serrated portions are arranged in a separated and interlocking manner. Then, the glass substrate coated with the liquid crystal alignment agent for photoalignment was placed on a heating plate at 80°C and dried for 3 minutes. Next, it was baked in a hot air circulating oven at 250°C for 30 minutes to form a film with a thickness of 100 nm on the glass substrate. The film is irradiated with ultraviolet light at a wavelength of 254nm through a polarizing plate, and then baked in a hot air circulating oven at 250°C for 30 minutes to form a liquid crystal alignment film, thereby obtaining a first laminate containing the liquid crystal alignment film.

[0138] The liquid crystal alignment agent for photoalignment was spin-coated onto a glass substrate without pixel electrodes and having columnar spacers with a height of 4 μm. The glass substrate coated with the liquid crystal alignment agent was then placed on a heating plate at 80°C and dried for 3 minutes. Next, it was baked in a hot air circulating oven at 250°C for 30 minutes to form a 100 nm thick film of the liquid crystal alignment agent on the glass substrate. The film was then irradiated with ultraviolet light at a wavelength of 254 nm through a polarizing plate and baked in a hot air circulating oven at 250°C for 30 minutes to form a liquid crystal alignment film, thus obtaining a second laminate containing the liquid crystal alignment film.

[0139] A sealant is printed on one of the first and second laminates. Then, the liquid crystal alignment films of the first and second laminates are bonded together with their alignment directions at 0°. The sealant is then hardened to obtain a laminate containing an injection port and liquid crystal cell holes communicating with the injection port. Next, liquid crystal MLC-2041 (manufactured by Merck) is injected into the liquid crystal cell holes using a depressurized injection method, and the injection port is sealed. Then, two polarizing plates are respectively disposed on the top and bottom surfaces defined by the glass substrates in the laminate to obtain a liquid crystal display element.

[0140] [Examples 2 to 5 and Comparative Examples 1 to 2] Liquid crystal alignment agent, liquid crystal alignment film and liquid crystal display element for photoalignment method

[0141] Examples 2 to 5 and Comparative Examples 1 to 2 were obtained using a method similar to that of Example 1 to obtain liquid crystal alignment agents, liquid crystal alignment films, and liquid crystal display elements for photoalignment. The difference was that Examples 2 to 5 and Comparative Examples 1 to 2 changed the types and / or amounts of polymer (A), solvent (B), hydroxyalkylamide (C), and additive (D) in the liquid crystal alignment agent for photoalignment, as shown in Table 2. In Comparative Examples 1 to 2, the liquid crystal alignment agent for photoalignment did not use solvent (B) and hydroxyalkylamide (C).

[0142] [Evaluation Items]

[0143] The following description uses Example 1 as an example. The other examples and comparative examples are carried out in the same manner.

[0144] Bright Spot Test: The liquid crystal alignment agent used in the photoalignment method of Example 1 was spin-coated onto a glass substrate with an ITO conductive film and a size of 100 mm × 100 mm. The glass substrate coated with the liquid crystal alignment agent was then placed on a heating plate at 80°C and dried for 3 minutes. Next, it was baked in a hot air circulating oven at 230°C for 30 minutes to form a 100 nm thick film of the liquid crystal alignment agent on the glass substrate. The film was then irradiated with ultraviolet light at a wavelength of 254 nm through a polarizing plate, and then baked in a hot air circulating oven at 230°C for 30 minutes to form a liquid crystal alignment film, thus obtaining a test sample containing the liquid crystal alignment film.

[0145] Two test samples containing the liquid crystal alignment film were prepared, and one of the test samples was mounted on a scratch testing device (model UMT-2) manufactured by Bruker AXS (the sensor is FVL, and the scratch testing device includes a pressure head with a 1.6 mm sapphire ball at the tip) for 100 seconds. The pressure head applied a force of 1 mN to 20 mN to the liquid crystal alignment film of the test sample and performed a 2 mm scratch test in the direction of movement of the pressure head. While the pressure head was moving, the pressure head moved synchronously at a speed of 5 mm / s along the horizontal axis relative to the direction of movement for 0.5 mm. After the scratch test was completed, liquid crystal MLC-2041 (manufactured by Merck) was dropped onto the surface of the scratched liquid crystal alignment film.

[0146] Next, 4 μm spacers were dispersed on the surface of the liquid crystal alignment film of another test sample, with the side of the other test sample containing the spacers facing the dropped liquid crystal MLC-2041, thereby sandwiching the liquid crystal MLC-2041 between the test samples to obtain the substrate under test. The scratch-tested area of ​​the substrate under test was observed using a polarizing microscope (ECLIPSE E600WPOL, Nikon) at a 90-degree polarizing plate to observe whether there were any translucent bright spots, and the number of bright spots was evaluated according to the following criteria: ◎: Number of bright spots ≤ 5. ○: 6 bright spots ≤ 9 bright spots. △: 10 bright spots ≤ 12 bright spots. ╳: Number of bright spots ≥ 13 bright spots.

[0147] Table 2 Unit: parts by weight Example Comparative example 1 2 3 4 5 1 2 Polymer (A) Synthesis example A-1 100 -- -- 50 -- 100 -- A-2 -- 100 -- -- 75 -- 100 A-3 -- -- 100 -- -- -- -- A-4 -- -- -- 50 25 -- -- Solvent (B) B-1 800 -- -- 1900 -- -- -- B-2 -- 1300 -- -- 3000 -- -- B-3 -- -- 2400 -- -- -- -- Hydroxyalkylamide (C) C-1 13 -- -- -- -- -- -- C-2 -- twenty four -- -- -- -- -- C-3 -- -- 6 -- -- -- -- C-4 -- -- -- 10 -- -- -- C-5 -- -- -- -- 30 -- -- Additive (D) D-1 -- -- -- -- -- -- 10 Broken highlights ◎ ◎ ◎ ○ ○ ╳ ╳ Note: "--" indicates that it has not been added. B-1: N-methyl-2-pyrrolidone (NMP) B-2: Ethylene glycol n-butyl ether B-3: N,N-dimethylacetamide C-1: C-2: C-3: C-4: C-5: D-1:

[0148] Referring to Table 2, the liquid crystal alignment agents used in the photoalignment method of Examples 1 to 5 were prepared by using hydroxyalkylamides C-1 to C-5. Therefore, the liquid crystal alignment films formed by the liquid crystal alignment agents used in the photoalignment method of Examples 1 to 5 can make the substrate under test have fewer than 9 broken spots. In other words, by using hydroxyalkylamides (C) containing the structure shown in Formula (C1), the liquid crystal alignment agents used in the photoalignment method of Examples 1 to 5 can make the liquid crystal alignment films formed by these liquid crystal alignment agents impart fewer broken spots to the liquid crystal display element.

[0149] Referring to Table 2, in contrast to Comparative Examples 1 and 2, the liquid crystal alignment agent used in the photoalignment method of Comparative Examples 1 and 2 does not contain hydroxyalkylamide (C). Therefore, the test substrates of Comparative Examples 1 and 2 have more than 13 broken spots, indicating that the liquid crystal alignment film formed by the liquid crystal alignment agent used in the photoalignment method of Comparative Examples 1 and 2 will cause too many broken spots in the liquid crystal display element.

[0150] Referring to Table 2, the liquid crystal alignment agents used in the photoalignment method of Examples 1 to 3 were prepared by using hydroxyalkylamides C-1 to C-3, which contain at least three alkyl groups that are substituted with hydroxyl groups. Therefore, the liquid crystal alignment films formed by the liquid crystal alignment agents used in the photoalignment method of Examples 1 to 3 can make the substrate under test have fewer than 5 broken spots. In other words, by using hydroxyalkylamides (C) containing at least three alkyl groups that are substituted with hydroxyl groups, the liquid crystal alignment films formed by the liquid crystal alignment agents used in the photoalignment method can further give the liquid crystal display element fewer broken spots.

[0151] In summary, the liquid crystal alignment agent used in the photoalignment method of the present invention, by using the hydroxyalkylamide (C) containing the structure shown in formula (C1), enables the liquid crystal alignment film formed by the liquid crystal alignment agent used in the photoalignment method to impart fewer speckles to the liquid crystal display element, thus effectively achieving the purpose of the present invention.

[0152] However, the above description is only an embodiment of the present invention and should not be construed as limiting the scope of the present invention. Any simple equivalent changes and modifications made in accordance with the scope of the patent application and the contents of the patent specification of the present invention shall still fall within the scope of the patent of the present invention.

Claims

1. A liquid crystal alignment agent for photoalignment, comprising: a polymer (A); a solvent (B); and a hydroxyalkylamide (C); wherein, The polymer (A) is selected from at least one polymer in the group consisting of a polyimide precursor and a amide polymer formed from the polyimide precursor, wherein the polyimide precursor of the polymer (A) comprises a structure as shown in formula (I), where X1 is selected from at least one of the group consisting of structures as shown in formulas (I-1) to (I-7), wherein "*" represents a bond position, (I-1), (I-2), (I-3), (I-4), (I-5), (I-6), (I-7), and in formula (I-1), X11, X12, X13, and X14 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 organogroup having 1 to 6 carbon atoms and containing a fluorine atom, or a phenyl group. In formula (I-7), X15 and X16 independently represent a hydrogen atom or a methyl group, X2 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, Y is a tetravalent organic group, the hydroxyalkylamide (C) comprises the structure shown in formula (C1), (C1) R1 to R4 each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms that may have substituents, an alkenyl group having 2 to 6 carbon atoms that may have substituents, or an alkynyl group having 2 to 6 carbon atoms that may have substituents, wherein at least one of R1 to R4 represents an alkyl group substituted with a hydroxyl group, and the amount of the hydroxyalkylamide (C) used is 6 to 30 parts by weight based on the total amount of the polymer (A) being 100 parts by weight.

2. The liquid crystal alignment agent for the photoalignment method as described in claim 1, wherein, X1 is selected from the structures shown in equations (I-1-1) to (I-1-6), (I-1-1), (I-1-2), (I-1-3), (I-1-4), (I-1-5), (I-1-6).

3. The liquid crystal alignment agent for the photoalignment method as described in claim 2, wherein, X1 represents the structure shown in equation (I-1-1), (I-1-1).

4. The liquid crystal alignment agent for the photoalignment method as described in claim 1, wherein, At least three of R1 to R4 represent alkyl groups substituted with hydroxyl groups.

5. The liquid crystal alignment agent for the photoalignment method as described in claim 1, wherein, The hydroxyalkylamide (C) is selected from the following compounds: , ...

6. A liquid crystal alignment film formed using a liquid crystal alignment agent for photoalignment as described in any one of claims 1 to 5.

7. A liquid crystal display element comprising a liquid crystal alignment film as described in claim 6.