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

Abstract

A liquid crystal alignment agent comprises a polymer component (A) and a solvent (B), and the polymer component (A) comprises a first polymer (A1). The first polymer (A1) is prepared by reacting a first mixture, and the first mixture comprises a tetracarboxylic dianhydride component (a1) and a diamine component (b1). The tetracarboxylic acid dianhydride component (a1) comprises a tetracarboxylic acid dianhydride mixture (a1-1), and the tetracarboxylic acid dianhydride mixture (a1-1) is composed of a tetracarboxylic acid dianhydride compound as shown in a formula (I) and a tetracarboxylic acid dianhydride compound as shown in a formula (II). The invention also provides a liquid crystal alignment film formed by the liquid crystal alignment agent and a liquid crystal display element comprising the liquid crystal alignment film. # imgabs0 #

Description

Technical Field

[0001] The present invention relates to a display device, and in particular to a liquid crystal display element with an image that is not easy to remain, a liquid crystal alignment film used for the liquid crystal display element, and a liquid crystal alignment agent forming the liquid crystal alignment film. Background Art

[0002] Based on the driving method of liquid crystal molecules, there are currently two types of liquid crystal displays: liquid crystal displays driven by a longitudinal electric field and liquid crystal displays driven by a transverse electric field. Examples of liquid crystal displays driven by a longitudinal electric field include twisted nematic (TN) liquid crystal displays and vertical alignment (VA) liquid crystal displays. Examples of liquid crystal displays driven by a transverse electric field include in-plane switching (IPS) liquid crystal displays and fringe field switching (FFS) liquid crystal displays.

[0003] In the above-mentioned liquid crystal displays, the alignment treatment method using friction mode is currently used to make the liquid crystal alignment film have grooves that can make the liquid crystal molecules arranged along a certain direction. At present, the most popular alignment treatment method in industry is to form a liquid crystal alignment film formed by a polyimide polymer obtained by imidization of a polyamic acid polymer and / or a polyamic acid polymer, and rub it in one direction with a cloth such as cotton, nylon or polyester. The alignment treatment method using friction mode is a simple, highly productive and industrially useful method. However, with the improvement of performance requirements for liquid crystal displays, the refinement of image quality and the enlargement of size, in order to avoid the damage to the liquid crystal alignment film caused by dust and static electricity generated by friction treatment and various problems such as alignment non-uniformity, a light alignment method that gives the liquid crystal alignment film a light alignment ability by irradiating polarized radiation has emerged, such as the light alignment method disclosed in Japanese Patent Laid-Open No. H09297313.

[0004] However, although the liquid crystal alignment film used in the optical alignment method can avoid the problems caused by the alignment treatment using the friction method, the liquid crystal display using the liquid crystal alignment film used in the optical alignment method is currently prone to residual ionic charge after driving, resulting in image retention problems, which makes it unable to meet application requirements. Summary of the invention

[0005] The first object of the present invention is to provide a liquid crystal alignment agent.

[0006] The liquid crystal alignment agent of the present invention comprises a polymer component (A) and a solvent (B). The polymer component (A) comprises a first polymer (A1). The first polymer (A1) is prepared by reacting a first mixture, and the first mixture comprises a tetracarboxylic dianhydride component (a1) and a diamine component (b1). The tetracarboxylic dianhydride component (a1) comprises a tetracarboxylic dianhydride mixture (a1-1), and the tetracarboxylic dianhydride mixture (a1-1) is composed of a tetracarboxylic dianhydride compound represented by formula (I) and a tetracarboxylic dianhydride compound represented by formula (II).

[0007]

[0008] In the liquid crystal alignment agent of the present invention, based on the total usage of the tetracarboxylic dianhydride component (a1) being 100 mol, the usage of the tetracarboxylic dianhydride compound represented by formula (I) is 50 mol to 99.5 mol.

[0009] In the liquid crystal alignment agent of the present invention, based on the total usage of the tetracarboxylic dianhydride component (a1) being 100 mol, the usage of the tetracarboxylic dianhydride compound represented by formula (II) is 0.5 mol to 50 mol.

[0010] The liquid crystal alignment agent of the present invention, based on 100 parts by weight of the polymer component (A), the amount of the solvent (B) is 800 to 3000 parts by weight.

[0011] The liquid crystal alignment agent of the present invention, the polymer component (A) further comprises a second polymer (A2), and the second polymer (A2) is selected from at least one of the group consisting of a polyimide precursor and an imidized polymer formed by the polyimide precursor, and the polyimide precursor of the second polymer (A2) does not comprise the tetracarboxylic dianhydride mixture (a1-1) of the first polymer (A1).

[0012] The liquid crystal alignment agent of the present invention, based on 100 parts by weight of the polymer component (A), the usage amount of the first polymer (A1) is 5 to 85 parts by weight, and the usage amount of the second polymer (A2) is 15 to 95 parts by weight.

[0013] The second purpose of the present invention is to provide a liquid crystal alignment film.

[0014] Therefore, the liquid crystal alignment film of the present invention is formed by the above-mentioned liquid crystal alignment agent.

[0015] The third object of the present invention is to provide a liquid crystal display element.

[0016] Therefore, the liquid crystal display element of the present invention includes the above-mentioned liquid crystal alignment film.

[0017] The beneficial effect of the present invention is that by using the tetracarboxylic dianhydride compound represented by formula (I) and the tetracarboxylic dianhydride compound represented by formula (II), the liquid crystal alignment film formed by the liquid crystal alignment agent of the present invention is used in a liquid crystal display element, which can give the liquid crystal display element the advantage of low afterimage and can meet application requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] none. DETAILED DESCRIPTION

[0019] The present invention will be described in detail below.

[0020] <Liquid crystal alignment agent>

[0021] The liquid crystal alignment agent of the present invention comprises a polymer component (A) and a solvent (B). The polymer component (A) comprises a first polymer (A1). The first polymer (A1) is prepared by reacting a first mixture, and the first mixture comprises a tetracarboxylic dianhydride component (a1) and a diamine component (b1). The tetracarboxylic dianhydride component (a1) comprises a tetracarboxylic dianhydride mixture (a1-1), and the tetracarboxylic dianhydride mixture (a1-1) is composed of a tetracarboxylic dianhydride compound represented by formula (I) and a tetracarboxylic dianhydride compound represented by formula (II).

[0022]

[0023] <First Polymer (A1)>

[0024] The first polymer (A1) is at least one selected from 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 an imidized polymer formed by the polyimide precursor. For example, the first polymer (A1) is a polyimide precursor having an imide precursor structure of polyamic acid and polyamic acid ester, or the first polymer (A1) is an imidized polymer (i.e., polyimide) formed by the polyimide precursor, or the first polymer (A1) includes the polyimide precursor and the imidized polymer.

[0025] [Tetracarboxylic dianhydride component (a1)]

[0026] When the tetracarboxylic dianhydride mixture (a1-1) in the tetracarboxylic dianhydride component (a1) is not composed of the tetracarboxylic dianhydride compound shown in formula (I) and the tetracarboxylic dianhydride compound shown in formula (II), the liquid crystal display element including the liquid crystal alignment film formed by the liquid crystal alignment agent has high image sticking.

[0027] In order to make the liquid crystal display element of the liquid crystal alignment film formed by the liquid crystal alignment agent have lower image sticking, preferably, in some embodiments of the present invention, based on the total usage of the tetracarboxylic dianhydride component (a1) being 100 mol, the usage of the tetracarboxylic dianhydride compound represented by formula (I) is 50 mol to 99.5 mol. More preferably, it is 55 mol to 99.5 mol, and even more preferably, it is 60 mol to 99.5 mol.

[0028] In order to make the liquid crystal display element of the liquid crystal alignment film formed by the liquid crystal alignment agent have lower image sticking, preferably, in some embodiments of the present invention, based on the total usage of the tetracarboxylic dianhydride component (a1) being 100 mol, the usage of the tetracarboxylic dianhydride compound represented by formula (II) is 0.5 mol to 50 mol. More preferably, it is 0.5 mol to 45 mol, and even more preferably, it is 0.5 mol to 40 mol.

[0029] <Other tetracarboxylic dianhydride compounds (a1-2)>

[0030] In some embodiments of the present invention, the tetracarboxylic dianhydride component (a1) further includes other tetracarboxylic dianhydride compounds (a1-2).

[0031] In some embodiments of the present invention, the other tetracarboxylic dianhydride (a1-2) comprises a tetracarboxylic dianhydride compound represented by formula (A11) or a derivative thereof.

[0032] The dianhydride compound is

[0033] In formula (A11), X 1 ' represents the structures represented by formula (A11-1) to formula (A11-32), wherein "*" represents the bonding position,

[0034]

[0035]

[0036]

[0037] In formula (A11-1), a1 is 1 to 12. In formula (A11-5), X 11 ' represents a single bond, -O-, -CO-, -COO-, phenylene, sulfonyl or amide, and a1 represents 0 or 1. In formula (A12-6), X 11 ' and X 12 'respectively independently represent a single bond, -O-, -CO-, -COO-, phenylene, sulfonyl or amide, and multiple X 12' are the same or different, and a1 represents 0 or 1. In formula (A11-11), a1 represents 2 to 6. In formula (A11-13), a1 represents 1 to 2. In formula (A11-14), X 13 'respectively independently represent hydrogen, halogen, 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 fluorine, or a phenyl group, and a plurality of X 13 ' are the same or different. Based on the viewpoint of liquid crystal alignment, preferably, X 13 ' represents hydrogen, halogen, methyl or ethyl, more preferably, represents hydrogen or methyl.

[0038] In some embodiments of the present invention, formula (A11-5) and formula (A11-6) include but are not limited to

[0039] The other tetracarboxylic dianhydride (a1-2) can be used alone or in combination. In some embodiments of the present invention, based on the total amount of the tetracarboxylic dianhydride component (a1) being 100 mol, the usage amount of the other tetracarboxylic dianhydride (a1-2) is 0 mol to 70 mol, preferably 0 mol to 60 mol, more preferably 0 mol to 50 mol, and even more preferably 0 mol to 10 mol.

[0040] <Diamine component (b1)>

[0041] In order to give the liquid crystal display element including the liquid crystal alignment film formed by the liquid crystal alignment agent lower image sticking and better stability, preferably, in some embodiments of the present invention, the diamine component (b1) includes a diamine compound (b1-1), and the diamine compound (b1-1) is a diamine compound represented by formula (A21-1) to formula (A21-2),

[0042]

[0043] In formula (A21-1), Y 31 represents a divalent organic group represented by formula (A21-3), and a plurality of Y 32 Each independently represents hydrogen or an alkyl group having 1 to 6 carbon atoms. 33 Each independently represents a divalent organic group represented by formula (A21-3'),

[0044]

[0045] In the divalent organic group represented by formula (A21-3), Ar independently represents a divalent benzene ring, biphenyl structure or naphthalene ring, and the hydrogen atoms of the benzene ring, biphenyl structure or naphthalene ring may be substituted by a monovalent substituent or may not be substituted; Y 31 'Representative-(CH 2 ) n -, n represents an integer from 2 to 18, and -(CH 2 ) n -At least one of -CH 2 - may be substituted by -O-, -C(=O)- or -OC(=O)- or may be unsubstituted; p1 represents 0 or 1; "*" represents a bonding position.

[0046] In the divalent organic group represented by formula (A21-3'), Ar' independently represents a divalent benzene ring or a biphenyl structure, and the hydrogen atoms of the benzene ring or the biphenyl structure may be substituted by a monovalent substituent or may not be substituted; Y 33 'Representative-(CH 2 ) n -, n represents an integer from 2 to 18, and -(CH 2 ) n -At least one of -CH 2 - may be substituted by -O-, -C(=O)- or -OC(=O)- or may be unsubstituted; p2 represents 0 or 1; "*" represents the bonding position.

[0047] In the divalent organic group represented by formula (A21-3) and the divalent organic group represented by formula (A21-3'), the monovalent substituent group of the benzene ring, biphenyl structure, or naphthalene ring is, for example, a halogen, 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 alkoxycarbonyl group having 1 to 10 carbon atoms, a cyano group, or a nitro group.

[0048] From the viewpoint of improving the liquid crystal alignment, preferably, the divalent organic group represented by formula (A21-3) is a group represented by formula (A21-3-1) to formula (A21-3-16), wherein "*" represents a bonding position,

[0049]

[0050]

[0051] In formula (A21-3-1), m is 0 to 1, and n is 1 to 6. In formula (A21-3-2), n is 1 to 6. In formula (A21-3-3), n is 2 to 6. In formula (A21-3-4), n is 1 to 6. In formula (A21-3-5), n is 1 to 6. In formula (A21-3-6), n is 2 to 6. In formula (A21-3-7), n is 1 to 6. In formula (A21-3-8), n is 1 to 6. In formula (A21-3-9), n is 2 to 6. In formula (A21-3-10), m is 1 to 3, and n is 1 to 4. In formula (A21-3-11), n ​​is 1 to 6. In formula (A21-3-12), n is 1 to 6. In formula (A21-3-13), m is 0 to 1, and n is 1 to 6. In formula (A21-3-14), m is 1 to 3, and n is 1 to 4.

[0052] From the viewpoint of improving the liquid crystal alignment, preferably, the divalent organic group represented by formula (A21-3') is a group represented by formula (A21-3-7) to formula (A21-3-16).

[0053] When the diamine compound (b1-1) comprises a plurality of diamine compounds represented by formula (A21-1), preferably, Y in formula (A21-1) 31 The diamine compounds of formula (A21-3-1) to formula (A21-3-14) and Y in formula (A21-1) 31 It represents a combination of diamine compounds of formula (A21-3-15) to formula (A21-3-16).

[0054] In some embodiments of the present invention, the diamine compound represented by formula (A21-2) is, for example but not limited to, the diamine compounds represented by formula (A21-2-1) to formula (A21-2-5),

[0055]

[0056] In formula (A21-2-1), m is 1 to 6, and n is 1 to 6. In formula (A21-2-2), m is 1 to 6, and n is 1 to 6. In formula (A21-2-3), m is 2 to 6, and n is 2 to 6.

[0057] The diamine compound (b1-1) can be used alone or in combination. In some embodiments of the present invention, based on 100 mol of the total amount of the diamine component (b1), the amount of the diamine compound (b1-1) used is 20 mol to 90 mol, preferably 25 mol to 80 mol, and more preferably 30 mol to 70 mol.

[0058] In some embodiments of the present invention, the diamine component (b1) further comprises a diamine compound (b1-2) having a -N(D)- group.

[0059] Based on the viewpoint of improving the alignment property of the liquid crystal alignment film, the molecular structure of the first polymer (A1) may selectively have an -N(D)- group (wherein D represents a carbamate-based protecting group). The first polymer (A1) having an -N(D)- group may be obtained by a method in which a monomer having an -N(D)- group is used as at least a part of the reaction raw material, or by a method in which a monomer having an -N(D)- group is used as the following end-capping agent. In some specific examples, the monomer having an -N(D)- group is, for example, a diamine compound (b1-2) having an -N(D)- group. For example, the carbamate-based protecting group is, for example, but not limited to, tert-butyloxycarbonyl (Boc for short) or 9-fluorenylmethoxycarbonyl.

[0060] Preferably, the diamine compound (b1-2) having a -N(D)- group includes 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 includes a diamine compound having at least one aromatic group and a residue other than the substituent (D) having a carbon number of 6 to 30. In some specific examples, the diamine compound (b1-2) having a -N(D)- group is, for example, but not limited to, a diamine compound represented by formula (A22-1) to formula (A22-10),

[0061]

[0062]

[0063] In formula (A22-1), n ​​is 1 to 6. In formula (A22-2), n is 1 to 6. In formula (A22-4), m is 1 to 6, and n is 1 to 6. In formula (A22-7), m is 1 to 6, and n is 1 to 6. In formula (A22-9), n is 1 to 6.

[0064] The diamine compound (b1-2) having a group of -N(D)- can be used alone or in combination. In some embodiments of the present invention, based on the total amount of the diamine component (b1) being 100 moles, the amount of the diamine compound (b1-2) having a group of -N(D)- is 2 to 60 moles, preferably 10 to 50 moles, and more preferably 15 to 40 moles.

[0065] In some embodiments of the present invention, the diamine component (b1) further comprises other diamine compounds (b1-3).

[0066] The other diamine compounds (b1-3) include, but are not limited to, diamine compounds having a photoalignment group, 2,4-diaminophenol, 3,5-diaminophenol, 3,5-diaminobenzyl alcohol, 2,4-diaminobenzyl alcohol, 4,6-diaminoresorcinol, diamine compounds having a carboxyl group, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 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, a diamine compound having a urea bond, a diamine compound having an amide bond, a diamine compound having a photopolymerizable group at the end, a diamine compound having a siloxane bond, or Diamine compounds with oxazoline structure, etc.

[0067] The diamine compound having a photo-alignment group is, for example but not limited to, 4,4'-diaminoazobenzene, or diamine compounds represented by formula (A23-1) to formula (A23-3),

[0068]

[0069] 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 represented by formula (A23-4) to formula (A23-7),

[0070]

[0071] In formula (A23-4), Y 51 Represents a single bond, -CH 2 -、-C 2 H 4 -、-C(CH 3 ) 2 -、-CF 2 -、-C(CF 3 ) 2 -、-O-、-CO-、-NH-、-N(CH 3 )-、-CONH-、-NHCO-、-CH 2 O-、-OCH 2 -、-COO-、-OCO-、-CON(CH 3 )-or-N(CH 3)CO-; m1 and m2 each independently represent an integer from 0 to 4, and (m1+m2) represents an integer from 1 to 4. In formula (A23-5), m3 and m4 each independently represent an integer from 1 to 5. In formula (A23-6), Y 52 represents a linear or branched alkyl group having 1 to 5 carbon atoms; m5 represents an integer from 1 to 5. In formula (A24-7), Y 53 and Y 54 Each independently represents a single bond, -CH 2 -、-C 2 H 4 -、-C(CH 3 ) 2 -、-CF 2 -、-C(CF 3 ) 2 -、-O-、-CO-、-NH-、-N(CH 3 )-、-CONH-、-NHCO-、-CH 2 O-、-OCH 2 -、-COO-、-OCO-、-CON(CH 3 )-or-N(CH 3 )CO-; m6 represents an integer from 1 to 4.

[0072] The diamine compound having a urea bond is, for example, but not limited to, the diamine compounds represented by formula (A23-8) to formula (A23-10),

[0073]

[0074] In formula (A23-8), n1 is 0 to 6, and n2 is 1 to 6. In formula (A23-9), n1 is 1 to 6, and n2 is 1 to 6. In formula (A23-10), n is 1 to 6.

[0075] The diamine compound having an amide bond is, for example but not limited to, a diamine compound having an amide bond represented by formula (A23-11) to formula (A23-13),

[0076]

[0077] In formula (A23-12), n is 1 to 6. In formula (A23-13), n1 is 1 to 6, and n2 is 1 to 6.

[0078] The diamine compound having a photopolymerizable group at the end thereof may be, for example but not limited to, 2-(2,4-diaminophenoxy)ethyl methacrylate or 2,4-diamino-N,N-diallylaniline.

[0079] The diamine compound having a siloxane bond is, for example, but not limited to, 3-bis(3-aminopropyl)-tetramethyldisiloxane.

[0080] The tool The diamine compound having an oxazoline structure is for example, but not limited to, the diamine compounds represented by formula (A23-14) to formula (A23-15),

[0081]

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

[0083] In order to make the liquid crystal display device including the liquid crystal alignment film formed by the liquid crystal alignment agent of the present invention have the advantage of being less prone to flickering, preferably, in some embodiments of the present invention, based on the total usage of the polymer component (A) being 100 parts by weight, the usage of the first polymer (A1) is 5 parts by weight to 85 parts by weight. More preferably, it is 10 parts by weight to 80 parts by weight, and even more preferably, it is 10 parts by weight to 75 parts by weight.

[0084] <Second Polymer (A2)>

[0085] In some embodiments of the present invention, the polymer component (A) further includes a second polymer (A2).

[0086] The second polymer (A2) 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 (a2) and a diamine component (b2) and an imidized polymer formed by the polyimide precursor, wherein the tetracarboxylic dianhydride component (a2) of the second polymer (A2) does not contain the tetracarboxylic dianhydride mixture (a1-1) in the tetracarboxylic dianhydride component (a1) of the first polymer (A1). For example, the second polymer (A2) is a polyimide precursor having an imide precursor structure of polyamic acid and polyamic acid ester, or the second polymer (A2) is an imidized polymer (i.e., polyimide) formed by the polyimide precursor, or the second polymer (A2) includes the polyimide precursor and the imidized polymer. The second polymer (A2) can be used alone or in combination of multiple types.

[0087] <Tetracarboxylic dianhydride component (a2)>

[0088] The tetracarboxylic dianhydride component (a2) includes, but is not limited to, a non-cyclic aliphatic tetracarboxylic dianhydride compound, an alicyclic tetracarboxylic dianhydride compound, an aromatic tetracarboxylic dianhydride compound, or derivatives thereof. The tetracarboxylic dianhydride component (a2) can be used alone or in combination of multiple types.

[0089] The non-cyclic aliphatic tetracarboxylic dianhydride may be, for example, an acid dianhydride obtained by intramolecular dehydration of four carboxyl groups bonded to a chain hydrocarbon structure. However, the non-cyclic aliphatic tetracarboxylic dianhydride does not need to consist only of a chain hydrocarbon structure, and a portion thereof may also have an alicyclic structure or an aromatic ring structure.

[0090] The alicyclic tetracarboxylic dianhydride is, for example, an acid dianhydride obtained by intramolecular dehydration of four carboxyl groups including at least one carboxyl group bonded to an alicyclic structure. However, none of the four carboxyl groups is bonded to an aromatic ring. Alternatively, 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.

[0091] The aromatic tetracarboxylic dianhydride is obtained by, for example, intramolecularly dehydrating four carboxyl groups including at least one carboxyl group bonded to an aromatic ring. However, the aromatic tetracarboxylic dianhydride does not need to consist of only an aromatic ring structure, and a portion thereof may have a chain hydrocarbon structure or an alicyclic structure.

[0092] Preferably, the tetracarboxylic dianhydride component (a2) comprises the above formula (A11) and X 1 ' represents a tetracarboxylic dianhydride compound or a derivative thereof having a structure represented by formula (A11-1) to formula (A11-6).

[0093] Preferably, the tetracarboxylic dianhydride component (a2) comprises a tetracarboxylic dianhydride having a formula (A11) and X 1 ' is a tetracarboxylic dianhydride compound (a2-1) having a structure represented by formula (III),

[0094] In formula (III), Z 11 represents a single bond, and “*” represents the bond position.

[0095] The tetracarboxylic dianhydride compound (a2-1) can be used alone or in combination. More preferably, the tetracarboxylic dianhydride component (a2) comprises a tetracarboxylic dianhydride compound represented by formula (IV),

[0096] In some embodiments of the present invention, based on the total amount of the tetracarboxylic dianhydride component (a2) being 100 mol, the usage amount of the tetracarboxylic dianhydride compound (a2-1) is 30 mol to 100 mol, preferably, 40 mol to 100 mol, and more preferably, 50 mol to 100 mol.

[0097] <Diamine component (b2)>

[0098] The diamine component (b2) is, for example but not limited to, the diamine component (b1) of the first polymer (A1), or a diamine compound (b2-1) having a nitrogen-containing atom structure. The diamine component (b2) can be used alone or in combination of multiple types.

[0099] <Diamine compound (b2-1) having a nitrogen atom-containing structure>

[0100] The nitrogen-containing atom structure in the diamine compound (b2-1) having a nitrogen-containing atom structure is at least one selected from the group consisting of a nitrogen-containing heterocyclic ring, a secondary amine group, and a tertiary amine group.

[0101] The nitrogen-containing heterocyclic ring of the diamine compound (b2-1) having a nitrogen-containing structure is, for example but not limited to, pyrrole, imidazole, pyrazole, triazole, pyridine, pyrimidine, tantalum, etc. , pyridine , indole, benzimidazole, purine, quinoline, isoquinoline, Pyridine, quinone Linole ,three , carbazole, acridine, piperidine, piperidine Preferably, the nitrogen-containing heterocyclic ring is pyridine, pyrimidine, pyrrolidine or hexamethyleneimine. , piperidine, piperidine , quinoline, carbazole or acridine.

[0102] The nitrogen-containing atom structure in the diamine compound (b2-1) having a nitrogen-containing atom structure is a secondary amine group and a tertiary amine group represented by formula (B21),

[0103]

[0104] In formula (B21), Z represents hydrogen, an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group, or an aryl group; "*" represents a bonding position.

[0105] The alkyl group with a carbon number of 1 to 10 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. Preferably, Z is hydrogen or methyl.

[0106] The diamine compound (b2-1) 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)-piperidin , 3,6-diaminoacridine, N-ethyl-3,6-diaminocarbazole, N-phenyl-3,6-diaminocarbazole, diamine compounds represented by formula (B21-1) to (B21-8), or diamine compounds represented by formula (B21-9) to (B21-26),

[0107]

[0108]

[0109] In formula (B21-5), n represents 1 to 4. In formula (B21-6), n represents 1 to 4. The diamine compound (b2-1) having a nitrogen atom-containing structure may be used alone or in combination of two or more.

[0110] When the diamine component (b2) includes the diamine compound (b2-1) having a nitrogen atom-containing structure, a liquid crystal display element including a liquid crystal alignment film formed by the liquid crystal alignment agent has a lower brightness change rate after driving.

[0111] In some embodiments of the present invention, based on the total amount of the diamine component (b2) being 100 mol, the usage amount of the diamine compound having a nitrogen atom structure (b2-1) is 15 mol to 100 mol, preferably, 20 mol to 90 mol, and more preferably, 25 mol to 80 mol.

[0112] In order to make the liquid crystal display element including the liquid crystal alignment film formed by the liquid crystal alignment agent of the present invention have the advantage of being less prone to flicker, preferably, in some embodiments of the present invention, based on the total usage of the polymer component (A) being 100 parts by weight, the usage of the second polymer (A2) is 15 to 95 parts by weight, more preferably, 20 to 90 parts by weight, and even more preferably, 25 to 90 parts by weight.

[0113] In some embodiments of the present invention, based on 100 parts by weight of the total usage of the polymer component (A), the usage of the first polymer (A1) is 5 to 90 parts by weight, and the usage of the second polymer (A2) is 10 to 95 parts by weight.

[0114] <Method for preparing the first polymer (A1) and the second polymer (A2)>

[0115] The manufacture of the first polymer (A1) and the second polymer (A2) can be carried out by reacting the above-mentioned diamine component and tetracarboxylic dianhydride component in a solvent (condensation polymerization). When a portion of the first polymer (A1) and the second polymer (A2) has an amic acid structure, for example, by reacting the tetracarboxylic dianhydride component with the diamine component to obtain a polymer having an amic acid structure (i.e., polyamic acid). The solvent is not particularly limited, and only needs to be able to dissolve the formed polymer. For example, the solvent is, for example, but not limited to, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, γ-butyrolactone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide or 1,3-dimethyl-2-imidazolidinone, etc. In some embodiments of the present invention, when the solvent solubility of the polymer is high, the solvent is, for example, methyl ethyl ketone, cyclohexanone, cyclopentanone, 4-hydroxy-4-methyl-2-pentanone, or a solvent as shown in formula (D-1) to formula (D-3), HO-CH 2 -CH 2 -OZ 2 Formula (D-2), HO-CH 2 -CH 2 -O-CH 2 -CH 2 -OZ 3 Formula (D-3).

[0116] In formula (D-1), Z 1 represents an alkyl group having 1 to 3 carbon atoms. In formula (D-2), Z 2 represents an alkyl group having 1 to 3 carbon atoms. In formula (D-3), Z 3 It represents an alkyl group having 1 to 4 carbon atoms.

[0117] The solvent can be used alone or in combination. Secondly, even if it is a solvent that cannot dissolve the polymer, the solvent that cannot dissolve the polymer can still be mixed with the above-mentioned solvent within the range that the generated polymer will not precipitate. When the diamine component and the tetracarboxylic dianhydride component react in a solvent, the reaction can be carried out at any concentration, preferably, the concentration of the reaction is 1wt% to 50wt%, more preferably, 5wt% to 30wt%. The reaction can also be carried out at a high concentration initially, and then, additional solvent is added. When reacting, preferably, the ratio of the total mole number of the diamine component to the total mole number of the tetracarboxylic dianhydride component is 0.8 to 1.2. Similar to the general polycondensation reaction, the closer the ratio of the total mole number of the diamine component to the total mole number of the tetracarboxylic dianhydride component is to 1.0, the greater the molecular weight of the first polymer (A1) or the second polymer (A2) formed.

[0118] The polymer having an amic acid ester structure can be obtained, for example, by a conventional method, and the conventional method is (1) a method of reacting the polyamic acid obtained by the above method with an esterifying agent, (2) a method of reacting a tetracarboxylic acid diester compound with a diamine compound, or (3) a method of reacting a tetracarboxylic acid diester dihalide with a diamine compound.

[0119] The imidized polymer in the first polymer (A1) or the second polymer (A2) of the liquid crystal alignment agent of the present invention can be obtained, for example, by ring-closing the polymer having an amic acid ester structure. In the imidized polymer, the ring-closing rate (also called the imidization rate) of the functional group possessed by the amic acid group or its derivative does not necessarily need to be 100%, and the imidization rate of the imidized polymer can be arbitrarily adjusted according to the use and / or purpose.

[0120] The method for obtaining the imidized polymer is, for example, thermal imidization in which a solution containing a polymer having an amic acid ester structure is directly heated, or catalytic imidization in which a catalyst is added to the solution. When thermal imidization is performed in the solution, preferably, the temperature is 100° C. to 400° C., more preferably, 120° C. to 250° C. When thermal imidization is performed, preferably, water generated by the imidization reaction is also discharged out of the system.

[0121] The catalytic imidization is carried out, for example, by adding an alkaline catalyst and anhydride to the solution, preferably, stirring is carried out at -20°C to 250°C, more preferably, at 0°C to 180°C. Preferably, the amount of the alkaline catalyst added is 0.5 to 30 times the molar equivalent of the amide acid group, more preferably, 2 to 20 times. Preferably, the amount of the anhydride added is 1 to 50 times the molar equivalent of the amide acid group, more preferably, 3 to 30 times. The alkaline catalyst is, for example, but not limited to, pyridine, triethylamine, trimethylamine, tributylamine or trioctylamine. Since pyridine has a moderate alkalinity for the reaction, it is more ideal. The anhydride is, for example, but not limited to, acetic anhydride, trimellitic anhydride or pyromellitic anhydride. When acetic anhydride is used, purification after the reaction is easier, so it is more ideal. The imidization rate of the catalytic imidization can be controlled by adjusting the amount of catalyst, reaction temperature and / or reaction time.

[0122] When the imidized polymer formed is recovered from the above-mentioned imidized reaction solution, the reaction solution is put into a solvent and precipitated. The solvent used for precipitation is, for example, but not limited to, methanol, ethanol, isopropanol, acetone, hexane, butyl cellosolve, heptane, methyl ethyl ketone, methyl isobutyl ketone, toluene, benzene or water. After filtering and recovering the polymer precipitated by the solvent, it can be dried at normal temperature or under reduced pressure. Alternatively, the polymer recovered by precipitation is dissolved in a solvent and reprecipitated and recovered. This operation is repeated 2 to 10 times to reduce impurities in the polymer. The solvent used can be, for example, alcohols or ketone hydrocarbons. If used in the three or more solvents selected therein, the efficiency of refining can be further improved, so it is more ideal.

[0123] When the first polymer (A1) or the second polymer (A2) of the present invention is configured to have a concentration of 10 wt% to 15 wt%, the solution viscosity is not particularly limited. Based on the viewpoint of easier operation, the solution viscosity may be, for example, 10 mPa·s to 1000 mPa·s. The solution viscosity (mPa·s) of the polymer is a value measured at 25°C using a good solvent for the polymer (e.g., γ-butyrolactone or N-methyl-2-pyrrolidone, etc.) to prepare a polymer solution having a concentration of 10 wt% to 15 wt%.

[0124] Preferably, the weight average molecular weight (Mw) of the first polymer (A1) or the second polymer (A2) of the present invention measured by gel permeation chromatography (GPC) in terms of polystyrene is 1,000 to 500,000, more preferably, 2,000 to 500,000. Secondly, preferably, 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 15 or less, more preferably, 10 or less. When the molecular weight of the polymer is within the above molecular weight range, good orientation and stability of the liquid crystal display element can be ensured.

[0125] When synthesizing the first polymer (A1) or the second polymer (A2) of the present invention, the tetracarboxylic dianhydride component and the diamine component as described above can be used, and an appropriate end-capping agent can be used to synthesize an end-sealed polymer. The end-sealed polymer has the effect of improving the film hardness of the liquid crystal alignment film obtained by coating, and improving the sealing properties of the sealant and the liquid crystal alignment film. The end of the first polymer (A1) or the second polymer (A2) of the present invention can be, for example, an amine group, a carboxyl group, an anhydride group or a derivative thereof. The amine group, the carboxyl group, the anhydride group or a derivative thereof can be obtained by a general condensation reaction, or by using the following end-capping agent to seal the end. Similarly, the above-mentioned derivatives can be obtained, for example, using the following end-capping agent.

[0126] The end-capping agent is, for example, but not limited to, anhydride, dicarbonic acid diester compound, chlorocarbonyl compound, monoamine compound or monoisocyanate compound. The anhydride is, for example, but not limited to, acetic anhydride, maleic anhydride, neddic anhydride, phthalic anhydride, itaconic anhydride, cyclohexanedicarboxylic anhydride, 3-hydroxyphthalic anhydride, trimellitic anhydride, 3-((3-trimethoxysilyl)propyl)-3,4-dihydrofuran-2,5-dione, 4,5,6,7-tetrafluoroisobenzofuran-1,3-dione or 4-ethynylphthalic anhydride. The dicarbonic acid diester compound is, for example, but not limited to, di-tert-butyl dicarbonate or diallyl dicarbonate. The chlorocarbonyl compound is, for example, but not limited to, acryloyl chloride, methacryloyl chloride or nicotinyl chloride. The monoamine compound includes, but is not limited to, aniline, 2-aminophenol, 3-aminophenol, 4-aminosalicylic acid, 5-aminosalicylic acid, 6-aminosalicylic acid, 2-aminobenzoic acid, 3-aminobenzoic acid, 4-aminobenzoic acid, cyclohexylamine, n-butylamine, n-pentylamine, n-hexylamine, n-heptylamine or n-octylamine, etc. The monoisocyanate compound includes, but is not limited to, ethyl isocyanate, phenyl isocyanate or naphthyl isocyanate, etc.

[0127] The end-capping agent can be used alone or in combination. In some embodiments of the present invention, preferably, based on 100 molar parts of the total amount of the diamine component, the amount of the end-capping agent used is 0.01 molar parts to 20 molar parts, more preferably, 0.01 molar parts to 10 molar parts.

[0128] The polymer component (A) of the liquid crystal alignment agent of the present invention may optionally further comprise other polymers, such as, but not limited to, polyester, polyamide, polyurea, polyorganosiloxane, cellulose derivative, polyacetal, polystyrene or its derivatives, poly(styrene-phenylmaleimide) derivatives, or poly(meth)acrylate.

[0129] [Solvent (B)]

[0130] Based on the viewpoint of forming a uniform film, the liquid crystal alignment agent takes the form of a coating liquid to produce a liquid crystal alignment film. Preferably, the liquid crystal alignment agent of the present invention is a coating liquid containing a polymer component (A) and a solvent (B). Based on the set thickness of the coating film to be formed, the concentration of the polymer component (A) in the liquid crystal alignment agent can be appropriately changed. Based on the viewpoint of forming a uniform and defect-free coating film, preferably, the concentration of the polymer component (A) in the liquid crystal alignment agent is 1wt% or more. Based on the viewpoint of the storage stability of the solution, preferably, the concentration of the polymer component (A) in the liquid crystal alignment agent is 10wt% or less. The ideal concentration of the polymer component (A) is 2wt% to 8wt%. The content of the polymer component (A) in the liquid crystal alignment agent can be appropriately changed by the coating method of the liquid crystal alignment agent and / or the film thickness of the desired liquid crystal alignment film, preferably, 2wt% to 10wt%, more preferably, 3wt% to 8wt%.

[0131] The solvent (B) in the liquid crystal alignment agent is, for example, an organic solvent, and the solvent (B) is not particularly limited, and only needs to be able to uniformly dissolve the polymer component (A). The solvent (B) is, for example, but 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-imidazolidinone, methyl ethyl ketone, cyclohexanone, cyclopentanone, 3-methoxy-N,N-dimethylpropionamide, 3-butoxy-N,N-dimethylpropionamide , 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 above solvents are also called good solvents. N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, 3-methoxy-N,N-dimethylpropionamide, 3-butoxy-N,N-dimethylpropionamide or γ-butyrolactone is preferred. In some embodiments of the present invention, based on the total amount of solvent (B) in the liquid crystal alignment agent being 100 wt %, the amount of good solvent used is 20 wt % to 99 wt %, preferably 20 wt % to 90 wt %, and more preferably 30 wt % to 80 wt %.

[0132] Secondly, preferably, the solvent (B) in the liquid crystal alignment agent comprises the above-mentioned good solvent and a poor solvent that can improve the coating property of the liquid crystal alignment agent and the surface smoothness of the coating film when the liquid crystal alignment agent is coated. Preferably, based on the total amount of the solvent (B) in the liquid crystal alignment agent being 100wt%, the amount of the poor solvent used is 1wt% to 80wt%, more preferably, 10wt% to 80wt%, and even more preferably, 20wt% to 70wt%. The type and amount of the poor solvent used can be appropriately selected according to the coating device, coating conditions and / or coating environment of the liquid crystal alignment agent.

[0133] The poor solvent is, for example, but not limited to, 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, ethyl carbonate, ethylene glycol monobutyl ether (butyl cellulose), 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 acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, ethyl 3-methoxypropionate, propyl 3-methoxypropionate, butyl 3-methoxypropionate, n-butyl lactate, isopentyl lactate, diethylene glycol monoethyl ether, or diisobutyl ketone (2,6-dimethyl-4-heptanone), etc.

[0134] Preferably, the poor solvent is 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.

[0135] 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-dimethyl lactamide and diisobutyl ketone; N-methyl-2-pyrrolidone and ethyl 3-ethoxypropionate; N-ethyl-2-pyrrolidone and ethyl 3-ethoxypropionate; N-methyl-2-pyrrolidone and ethyl Glycol monobutyl ether acetate; N-ethyl-2-pyrrolidone and dipropylene glycol dimethyl ether; N,N-dimethyl lactamide and ethylene glycol monobutyl ether; N,N-dimethyl lactamide and propylene glycol diacetate; N-ethyl-2-pyrrolidone and diethylene glycol diethyl ether; N,N-dimethyl lactamide 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-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 and propylene glycol diacetate Glycol monobutyl ether and diisopropyl ether; N-methyl-2-pyrrolidone, γ-butyrolactone, propylene glycol monobutyl ether and diisobutyl carbinol; 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-dimethyl lactamide and diisobutyl ketone, etc.

[0136] The solvent (B) can be used alone or in combination. In some embodiments of the present invention, based on 100 parts by weight of the total amount of the polymer component (A), the amount of the solvent (B) used is 800 to 3000 parts by weight, preferably 900 to 2800 parts by weight, and more preferably 1000 to 2500 parts by weight.

[0137] The liquid crystal alignment agent of the present invention further comprises additives, such as but not limited to adhesion aids 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 imidization, dielectrics or conductive substances for adjusting the dielectric constant or resistance of the liquid crystal alignment film, etc.

[0138] The adhesion 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-ureidopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, N-ethoxycarbonyl-3-aminopropyltrimethoxysilane, N-ethoxycarbonyl-3-aminopropyltriethoxysilane, N-triethoxysilylpropyltriethyltriamine, N-trimethoxysilylpropyltriethyltriamine, vinyltrimethoxysilane, Silane coupling agents include silane, vinyl triethoxysilane, 2-(3,4-epoxycyclohexyl)ethyl trimethoxysilane, 3-glycidoxypropyl methyl dimethoxysilane, 3-glycidoxypropyl trimethoxysilane, 3-glycidoxypropyl methyl diethoxysilane, 3-glycidoxypropyl triethoxysilane, 3-methacryloxypropyl methyl dimethoxysilane, 3-methacryloxypropyl trimethoxysilane, 3-methacryloxypropyl methyl diethoxysilane, 3-methacryloxypropyl triethoxysilane, 3-acryloxypropyl trimethoxysilane, tris(3-trimethoxysilylpropyl) isocyanurate, or 3-isocyanate propyl triethoxysilane. When using a bonding aid, based on the viewpoint of exhibiting good resistance to AC image sticking, preferably, the amount of the bonding aid used is 0.1 to 30 parts by weight, more preferably, 0.1 to 20 parts by weight, relative to the total amount of 100 parts by weight of the polymer component (A) in the liquid crystal alignment agent.

[0139] Based on the viewpoint of exhibiting good resistance to AC image sticking and effectively improving film strength, the crosslinking compound is a compound having an ethylene oxide group, a propylene oxide group, at least one group selected from the group consisting of a group represented by formula (E1) and a group represented by formula (E2), or a compound selected from the compound represented by formula (E3),

[0140] In formula (E1), G 1 and G 2 Each independently represents hydrogen, an alkyl group having 1 to 3 carbon atoms, or -CH 2 -OH. In formula (E2), G 3 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. 4 represents hydrogen, 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. 5 It represents a (g1+g2)-valent organic group containing an aromatic ring. 6 represents hydrogen or an alkyl group having a carbon number of 1 to 5. g1 represents an integer of 1 to 6, and g2 represents an integer of 0 to 4.

[0141] In formula (E3), G 5 A (g1+g2)-valent organic group having an aromatic ring, such as a (g1+g2)-valent aromatic hydrocarbon group having 6 to 30 carbon atoms, an aromatic hydrocarbon group having 6 to 30 carbon atoms directly or through a linking group, or a (g1+g2)-valent organic group having an aromatic heterocycle. The aromatic hydrocarbon is, for example, benzene or naphthalene. The aromatic heterocycle is, for example, the aromatic heterocycle exemplified by the above-mentioned nitrogen-containing atom structure. The linking group is, for example, an alkylene group having 1 to 10 carbon atoms or a group removing a hydrogen atom from the alkylene group, or a divalent or trivalent cyclohexane. Any hydrogen of the alkylene group may also be replaced by an organic group such as a fluorine atom or a trifluoromethyl group. In formula (E3), G 6 The represented alkyl group having a carbon number of 1 to 5 is, for example, methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, t-butyl or n-pentyl.

[0142] The compound having an oxirane group is, for example but not limited to, N,N,N',N'-tetracyclyl-m-xylene diamine, 1,3-bis(N,N-dicyclylaminomethyl)cyclohexane, N,N,N',N'-tetracyclyl-4,4'-diaminodiphenylmethane, N,N,N',N'-tetracyclyl-p-phenylenediamine, or nitrogen-containing compounds represented by formula (E4) to formula (E6),

[0143] The compound having an propylene oxide group is for example, but not limited to, the compounds represented by formula (E7) to formula (E16),

[0144]

[0145] In formula (E1), n ​​represents 1 to 3. In formula (E13), n represents 1 to 3. In formula (E14), n represents 1 to 100. In formula (E15), R represents Wherein, "*" represents a bonding position. In formula (E16), n represents 1 to 10.

[0146] The compound having the group represented by formula (E1) is for example, but not limited to, the compounds represented by formula (E1-1) to formula (E1-12),

[0147]

[0148] The compound having a group represented by formula (E2) is, for example but not limited to, compounds represented by formula (E2-1) to formula (E2-4),

[0149] In formula (E2-1), n ​​represents 2 to 16. In formula (E2-2), n represents 2 to 16.

[0150] The compound having a group represented by formula (E3) is, for example but not limited to, compounds represented by formula (E3-1) to formula (E3-10),

[0151]

[0152] In the liquid crystal alignment agent of the present invention, preferably, based on the total amount of the polymer component (A) of the liquid crystal alignment agent being 100 parts by weight, the amount of the cross-linking compound used is 0.5 to 20 parts by weight. Based on the viewpoint of the cross-linking reaction and the good resistance to AC image sticking, more preferably, the amount of the cross-linking compound used is 1 to 15 parts by weight.

[0153] Preferably, the compound for promoting imidization is a compound having a basic site (for example, a primary amine 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 cross-linking compound and the close-fitting aid), or a compound that produces the basic site when calcined. More preferably, the compound for promoting imidization is a compound that produces the basic site when calcined, for example, a part or all of the basic site of an amino acid is a protected amino acid. The amino acid is, for example, glycine, alanine, cysteine, methionine, asparagine, glutamic acid, valine, leucine, phenylalanine, tyrosine, tryptophan, proline, hydroxyproline, arginine, histidine, lysine, or ornithine. For the purpose of promoting the imidization compound, more preferably, N-α-(9-fluorenylmethoxycarbonyl)-N-τ-(tert-butoxycarbonyl)-L-histidine can be cited as a specific example.

[0154] <Liquid crystal alignment film and liquid crystal display element>

[0155] The liquid crystal alignment film of the present invention is formed by the above-mentioned liquid crystal alignment agent. The liquid crystal alignment film of the present invention can be used as a liquid crystal alignment film of a horizontal alignment type liquid crystal display element of IPS. 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 produced, for example, by the method of steps (1) to (4), or by the method of steps (1) to (2) and step (4).

[0156] Step (1): Applying a liquid crystal alignment agent onto a substrate

[0157] The liquid crystal alignment agent of the present invention is applied to one side of a substrate provided with a patterned transparent conductive film by using an appropriate coating method such as roller coating, spin coating, printing or inkjet. There is no particular limitation on the substrate, as long as it is a highly transparent substrate. A glass substrate or a silicon nitride substrate can also be used in combination with a plastic substrate such as an acrylic substrate or a polycarbonate substrate. Secondly, in a reflective liquid crystal display element, when only a single-sided substrate is used, an opaque material such as a silicon wafer can also be used, and the electrode used can also be a light-reflecting material such as aluminum. Furthermore, when making an IPS-type liquid crystal display element, a comb-tooth type uses an electrode substrate composed of a patterned transparent conductive film or metal film and an opposing substrate without an electrode.

[0158] The method of coating the liquid crystal alignment agent on the substrate to form a film may include screen printing, lithography, flexographic printing, inkjet method or spray coating method, etc. Preferably, the film forming method is coating using an inkjet method.

[0159] Step (2): calcining the coated liquid crystal alignment agent

[0160] 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 by heating means such as a hot plate, a heat circulation oven or an infrared oven, or thermal imidization of polyamic acid or polyamic acid ester can be performed. The drying and calcining steps performed after the liquid crystal alignment agent of the present invention has been applied can select any temperature and time, and multiple drying or calcining steps can be performed. The drying temperature can be, for example, 40°C to 180°C. From the perspective of shortening the process, it can be performed at 40°C to 150°C. The drying time is not particularly limited, and it can be, for example, 1 minute to 10 minutes or 1 minute to 5 minutes. When thermal imidization of polyamic acid or polyamic acid ester is performed, after the above-mentioned 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 calcination time is not particularly limited, for example, 5 minutes to 40 minutes or 5 minutes to 30 minutes. When the film after calcination is too thin, the reliability of the liquid crystal display element will be reduced. Therefore, preferably, the thickness of the film is 5nm to 300nm, more preferably, 10nm to 200nm.

[0161] Step (3): Align the film obtained in step (2)

[0162] Step (3) is to perform an alignment treatment on the film obtained in step (2) as appropriate. That is, in a horizontal alignment type liquid crystal display element of IPS, the coating film is subjected to an alignment treatment to impart alignment capability. The alignment treatment is a photo-alignment treatment. The photo-alignment treatment can be listed as a method of irradiating the surface of the above-mentioned film-like object with radiation that has been deflected in a certain direction, and, as appropriate, preferably heating at a temperature of 150°C to 250°C to impart liquid crystal alignment (also referred to as liquid crystal alignment capability). The radiation can use ultraviolet light or visible light with a wavelength of 100nm to 800nm. Preferably, the radiation is ultraviolet light with a wavelength of 100nm to 400nm, more preferably, ultraviolet light with a wavelength of 200nm to 400nm.

[0163] The radiation dose can be 1mJ / cm 2 Up to 10,000mJ / cm 2 , preferably, 100 mJ / cm 2 Up to 5,000mJ / cm 2 , more preferably, 100 mJ / cm 2 Up to 1500mJ / cm 2 , preferably, 100 mJ / cm 2 Up to 1000mJ / cm 2 When using a general liquid crystal alignment agent, the light exposure for the alignment treatment is 100mJ / cm 2 Up to 5000mJ / cm 2However, the liquid crystal alignment agent of the present invention can still form a liquid crystal alignment film in which the variation (non-uniformity) of the liquid crystal alignment within the film surface is effectively suppressed even if the amount of light irradiation in the alignment treatment is reduced. When irradiating radiation, in order to improve the liquid crystal alignment, the substrate having the film-like object can be heated at 50°C to 250°C while irradiating. The liquid crystal alignment film produced in this way can stably align the liquid crystal molecules in a certain direction. Secondly, the liquid crystal alignment film that has been irradiated with polarized radiation in the above method can be contact-treated with a solvent, or the liquid crystal alignment film that has been irradiated with radiation can be heated.

[0164] The solvent used in the above-mentioned contact treatment is not particularly limited, and it only needs to be able to dissolve the decomposition products generated from the film after being irradiated with radiation. The solvent can be water, methanol, ethanol, 2-propanol, acetone, methyl ethyl ketone, 1-methoxy-2-propanol, 1-methoxy-2-propanol acetate, butyl cellulose, ethyl lactate, methyl lactate, diacetone alcohol, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, propyl acetate, butyl acetate, or cyclohexyl acetate. Based on the viewpoints of versatility and safety, preferably, the solvent is water, 2-propanol, 1-methoxy-2-propanol or ethyl lactate, and more preferably, it is water, 1-methoxy-2-propanol or ethyl lactate. The solvent can be used alone or in combination.

[0165] Preferably, the temperature of the heat treatment of the coating film irradiated with radiation is 50° C. to 300° C., more preferably, 120° C. to 250° C. Preferably, the heat treatment time is 1 minute to 30 minutes.

[0166] Step (4): Making liquid crystal cells

[0167] Two liquid crystal alignment film substrates formed as described above are prepared, and liquid crystal is arranged between the two substrates arranged facing each other. For example, the following two methods can be cited. In the first method, the two substrates are arranged facing each other with a gap (cell gap) between them in a manner that the liquid crystal alignment films face each other. Then, the peripheral portions of the two substrates are bonded together with a sealant, and then the liquid crystal composition is injected and filled into the cell gap separated by the substrate surface and the sealant, and after it contacts the film surface, the injection hole is sealed.

[0168] The second method is called ODF (One Drop Fill) method. A sealant such as UV-curable sealant is applied to a predetermined position of one of the two substrates on which a liquid crystal alignment film has been formed, and then a liquid crystal composition is dripped at a plurality of predetermined positions on the surface of the liquid crystal alignment film. Then, the other substrate is attached in a manner that the liquid crystal alignment films face each other, and the liquid crystal composition is pushed on the entire surface of the substrate so that it contacts the film surface. Next, ultraviolet light is irradiated on the entire surface of the substrate to harden the sealant. When any of the above methods is performed, it is preferred that the liquid crystal composition used is further heated to a temperature at which it becomes an isotropic phase, and then slowly cooled to room temperature to remove the flow alignment during liquid crystal filling. Secondly, when the coating film is subjected to friction treatment, the two substrates are arranged to face each other at a predetermined angle with the friction directions of each coating film, for example, in a manner of orthogonal or antiparallel. The sealant may be, for example, an epoxy resin containing a hardener and aluminum oxide balls as spacers. The liquid crystal composition is, for example, a nematic liquid crystal or a smectic liquid crystal, preferably, a nematic liquid crystal.

[0169] If necessary, a polarizing plate can be attached to the outer surface of the liquid crystal cell to obtain a liquid crystal display element. The polarizing plate attached to the outer surface of the liquid crystal cell is, for example, a polarizing film called "H film" that stretches polyvinyl alcohol and absorbs iodine at the same time. The polarizing plate can be a polarizing plate sandwiched by a cellulose acetate protective film, or a polarizing plate composed of the H film itself.

[0170] The present invention will be further described with reference to the following examples, but it should be understood that the examples are only for illustration and should not be construed as limitations on the implementation of the present invention.

[0171] Preparation Example 1: First polymer (A1) - polyimide precursor

[0172] A nitrogen inlet, a stirrer, a condenser and a thermometer were set up on a 500 ml four-necked conical flask, and nitrogen was introduced. Then, 0.035 mol of 0.01 mol 0.005 mol and 80 g of N-methyl-2-pyrrolidone, and stirred at room temperature until dissolved. Then, 0.04975 mol of 0.00025 mol and 20 g of N-methyl-2-pyrrolidone, and react at room temperature for 2 hours to obtain a reaction solution. The reaction solution is poured into 1500 ml of water to precipitate a polymer, and then filtered to obtain a filter cake. The filter cake is then washed with methanol and then filtered, wherein the washing and filtering with methanol are performed three times in total. Then, it is placed in a vacuum oven and dried at 60° C. to obtain a first polymer (A1).

[0173] Preparation Examples 2 to 5, Preparation Example 7 and Comparative Preparation Examples 1 to 2

[0174] The preparation methods of Preparation Examples 2 to 5, Preparation Example 7 and Comparative Preparation Examples 1 to 2 are generally similar to Preparation Example 1, except that the types or amounts of the tetracarboxylic dianhydride component (a1) and the diamine component (b1) are changed, as shown in Table 1.

[0175] Preparation Example 6 - Imidization Polymer

[0176] A nitrogen inlet, a stirrer, a condenser and a thermometer were set up on a 500 ml four-necked conical flask, and nitrogen was introduced. Then, 0.035 mol of 0.01 mol 0.005 mol and 80 g of N-methyl-2-pyrrolidone, and stirred at room temperature until dissolved. Then, 0.04 mol of 0.005 mol 0.005 mol and 20 grams of N-methyl-2-pyrrolidone, and react at room temperature for 6 hours, then add 97 grams of N-methyl-2-pyrrolidone, 2.55 grams of acetic anhydride and 19.75 grams of pyridine, raise the temperature to 60°C, and continue stirring for 2 hours to carry out imidization reaction to obtain a reaction solution. The reaction solution is poured into 1500 ml of water to precipitate the polymer. Then, filter treatment is carried out to obtain a filter cake, and then the filter cake is washed with methanol, and then filtered, wherein the washing and filtering with methanol are carried out three times. Then, it is placed in a vacuum oven and dried at 60°C to obtain the first polymer (A1).

[0177] Table 1

[0178]

[0179]

[0180] Preparation Example 8 Second Polymer (A2) - Polyimide Precursor

[0181] A nitrogen inlet, a stirrer, a condenser and a thermometer were set up on a 500 ml four-necked conical flask, and nitrogen was introduced. Then, 0.04 mol of 0.01 mol and 80 g of N-methyl-2-pyrrolidone, and stirred at room temperature until dissolved. Then, 0.05 mol of and 20 g of N-methyl-2-pyrrolidone, and react at room temperature for 2 hours to obtain a reaction solution. The reaction solution is poured into 1500 ml of water to precipitate a polymer, and then filtered to obtain a filter cake. The filter cake is then washed with methanol and then filtered, wherein the washing with methanol and filtering are performed three times in total. Then, it is placed in a vacuum oven and dried at 60° C. to obtain a second polymer (A2).

[0182] Preparation Examples 9 to 10

[0183] The preparation methods of Preparation Examples 9 to 10 are roughly similar to those of Preparation Example 8, except that the types or amounts of the tetracarboxylic dianhydride component (a2) and the diamine component (b2) are changed, as shown in Table 2.

[0184] Table 2

[0185]

[0186]

[0187] Example 1

[0188] 100 parts by weight of the first polymer of Preparation Example 7 and 1200 parts by weight of N-methyl-2-pyrrolidone were stirred and mixed at room temperature to obtain a liquid crystal alignment agent.

[0189] Examples 2 to 14 and Comparative Examples 1 to 2

[0190] The preparation methods of Examples 2 to 14 and Comparative Examples 1 to 2 are substantially similar to those of Example 1, except that the types or amounts of the first polymer and the second polymer, or the types of the solvents are changed, as shown in Table 3.

[0191] Application Example 1 Liquid Crystal Display Components

[0192] The liquid crystal alignment agent of Example 1 is applied to the pixel electrode of the glass substrate including the pixel electrode by spin coating. The pixel electrode is an IPS driving electrode having a pair of indium tin oxide (ITO) electrodes (electrode width of 10 μm, electrode spacing of 10 μm, and electrode height of 50 nm), the shape of the pair of ITO electrodes is comb-shaped, and the comb-shaped parts of each other are configured in a separated and interlocking manner. Then, the glass substrate coated with the liquid crystal alignment agent is dried on a heating plate at 80°C for 3 minutes, and then baked in a hot air circulation oven at 250°C for 30 minutes to obtain a coating film formed on the glass substrate with a film thickness of 100 nm. The coating film is irradiated with ultraviolet rays with a wavelength of 254 nm through a polarizing plate, and then baked in a hot air circulation oven at 250°C for 30 minutes to obtain a first laminate including a liquid crystal alignment film.

[0193] The liquid crystal alignment agent of Example 1 was applied by spin coating on a glass substrate having no pixel electrode and a columnar spacer with a height of 4 μm, and then the glass substrate coated with the liquid crystal alignment agent was dried on a hot plate at 80° C. for 3 minutes, and then baked in a hot air circulation oven at 250° C. for 30 minutes to obtain a coating film with a thickness of 100 nm formed on the glass substrate. The coating film was irradiated with ultraviolet rays with a wavelength of 254 nm through a polarizing plate, and then baked in a hot air circulation oven at 250° C. for 30 minutes to obtain a second laminate including a liquid crystal alignment film.

[0194] A sealant is printed on one of the first laminate and the second laminate, and then the liquid crystal alignment film of the first laminate is bonded together with the liquid crystal alignment film of the second laminate facing each other and with the alignment direction at 0°. Then, the sealant is cured to obtain a laminate including an injection port and a liquid crystal cell cavity connected to the injection port. Next, liquid crystal MLC-2041 (Merck) is injected into the liquid crystal cell cavity by a reduced pressure injection method, and the injection port is sealed to obtain a liquid crystal cell including the laminate and liquid crystal. Then, polarizing plates are attached perpendicularly to the top and bottom surfaces of the laminate of the liquid crystal cell to form a liquid crystal display element.

[0195] Application Examples 2 to 14 and Comparative Application Examples 1 to 2

[0196] The preparation methods of Application Examples 2 to 14 and Comparative Application Examples 1 to 2 are substantially similar to that of Application Example 1, except that the liquid crystal alignment agents of Application Examples 2 to 12 and Comparative Application Examples 1 to 2 are the liquid crystal alignment agents of Embodiments 2 to 14 and Comparative Examples 1 to 2, respectively.

[0197] Table 3

[0198]

[0199] Table 4

[0200]

[0201]

[0202] Evaluation Project

[0203] Image sticking test: The liquid crystal units of application examples 1 to 14 and comparative application examples 1 to 2 were driven with an AC voltage of 10V for 30 hours, and then the liquid crystal units were sandwiched between a polarizer and an analyzer of an optical device, and then the light transmittance of the liquid crystal unit was measured using the optical device, and the minimum relative transmittance (%) was calculated. The optical device includes a light source, a light detector, and a polarizing device disposed between the light source and the light detector, and the polarizing device includes the polarizer and the analyzer.

[0204] Minimum relative transmittance (%) = [(β-B0) / (B100-B0)] × 100%

[0205] B0 is blank and is the light transmittance under crossed nicols, i.e. the light transmittance in dark state;

[0206] B100 is blank and is the light transmittance under parallel nicols, i.e. the light transmittance in bright state;

[0207] β is the minimum light transmittance of the liquid crystal unit under crossed Nicols.

[0208] The degree of the dark state black level of the liquid crystal display element is expressed by the minimum relative transmittance of the liquid crystal display element. The smaller the minimum relative transmittance, the lower the afterimage. The evaluation criteria are:

[0209] ◎Indicates minimum relative transmittance ≤ 0.5%;

[0210] O means 0.5%<minimum relative transmittance ≤1.0%;

[0211] △ means 1.0%<minimum relative transmittance ≦1.5%;

[0212] X indicates that the minimum relative transmittance is greater than 1.5%.

[0213] Flicker test: The liquid crystal unit of application examples 1 to 14 and comparative application examples 1 to 2 is placed between two polarizing plates whose polarization axes are arranged in a vertically crossed manner. Then, the LED backlight source is turned on without applying voltage to the liquid crystal unit, and the configuration angle of the liquid crystal unit is adjusted to minimize the brightness of the light passing through the liquid crystal unit. Then, an AC voltage with a frequency of 30 Hz is applied to the liquid crystal unit, and the voltage and light transmittance are measured using a detection device to obtain a voltage-light transmittance curve. Then, using the curve, an AC voltage with a relative light transmittance of 23% is calculated as the driving voltage. Then, the temperature of the liquid crystal unit was controlled at 23°C, and the lit LED backlight was turned off. Then, it was placed in a non-illuminated state for 72 hours, and then the LED backlight was turned on. At the beginning of the lighting, the liquid crystal unit was driven for 60 minutes with an AC voltage of 30 Hz and a relative light transmittance of 23%. Then, a data acquisition / data recording switching device (manufactured by Agilent technologies; model 34970A) connected to the LED backlight and the IV conversion amplifier was used to track the flicker amplitude of the liquid crystal unit and read the brightness value passing through the two polarizing plates and the liquid crystal unit. Then, the flicker degree was calculated using the flicker amplitude and the brightness value.

[0214] Flicker degree (%) = [flicker amplitude / (2×brightness value)]×100%

[0215] The lower the flicker, the better the quality of the liquid crystal display element. The evaluation criteria are: ◎ means flicker < 3%; O means 4%> flicker ≧ 3%; △ means 5%> flicker ≧ 4%; X means flicker ≧ 5%.

[0216] Table 5

[0217]

[0218]

[0219] From the experiments in Tables 3 to 5, it can be seen that in the liquid crystal alignment agents of Examples 1 to 7, the first polymers used in Preparation Examples 1 to 7 adopt the tetracarboxylic dianhydride compound represented by formula (I) and the tetracarboxylic dianhydride compound represented by formula (II), so that the liquid crystal display element comprising the liquid crystal alignment agents of Examples 1 to 7 using the first polymers has a minimum relative transmittance of 0 to ◎ after driving. Therefore, it can be seen that the liquid crystal display element formed by the liquid crystal alignment agent of the present invention using the polymer of the tetracarboxylic dianhydride compound represented by formula (I) and the tetracarboxylic dianhydride compound represented by formula (II) is The components are not prone to image sticking, while in Comparative Examples 1 to 2, the polymers of Comparative Synthesis Examples 1 to 2 used do not use the tetracarboxylic dianhydride compound shown in formula (I) and the tetracarboxylic dianhydride compound shown in formula (II), resulting in the liquid crystal display element containing the liquid crystal alignment agent using the polymers of Comparative Synthesis Examples 1 to 2 having a minimum relative transmittance of X after driving. It can be seen that the liquid crystal display element formed by the liquid crystal alignment agent that does not use the polymer having the tetracarboxylic dianhydride compound shown in formula (I) and the tetracarboxylic dianhydride compound shown in formula (II) is prone to image sticking. As can be seen from the above, the liquid crystal alignment agent of the present invention using the first polymer of the tetracarboxylic dianhydride compound shown in formula (I) and the tetracarboxylic dianhydride compound shown in formula (II) can indeed effectively reduce the image sticking.

[0220] Furthermore, compared with the liquid crystal alignment agents of Examples 1 to 7, the liquid crystal alignment agents of Examples 9 to 14 further include a second polymer (A2), and with the participation of the second polymer, the liquid crystal display element including the liquid crystal alignment film formed by the liquid crystal alignment agents of Examples 9 to 14 has significantly reduced flicker after driving. As can be seen from the above, the liquid crystal alignment agent of the present invention not only has low image sticking, but also has the advantage of low flickering of the screen.

[0221] In summary, by using the tetracarboxylic dianhydride compound represented by formula (I) and the tetracarboxylic dianhydride compound represented by formula (II), the liquid crystal alignment film formed by the liquid crystal alignment agent of the present invention is used in a liquid crystal display element, which can give the liquid crystal display element the advantage of low afterimage and can meet application requirements, so the purpose of the present invention can be achieved.

Claims

1. A liquid crystal alignment agent, characterized in that Include: The polymer component (A) comprises a first polymer (A1), and the first polymer (A1) is prepared by reacting a first mixture, and the first mixture comprises a tetracarboxylic dianhydride component (a1) and a diamine component (b1); and Solvent (B), The tetracarboxylic dianhydride component (a1) includes a tetracarboxylic dianhydride compound mixture (a1-1), and the tetracarboxylic dianhydride mixture (a1-1) is composed of a tetracarboxylic dianhydride compound represented by formula (I) and a tetracarboxylic dianhydride compound represented by formula (II).

2. The liquid crystal alignment agent according to claim 1, characterized in that: Based on 100 mol of the total usage of the tetracarboxylic dianhydride component (a1), the usage of the tetracarboxylic dianhydride compound represented by formula (I) is 50 mol to 99.5 mol.

3. The liquid crystal alignment agent according to claim 1, characterized in that: Based on 100 mol of the total usage of the tetracarboxylic dianhydride component (a1), the usage of the tetracarboxylic dianhydride compound represented by formula (II) is 0.5 mol to 50 mol.

4. The liquid crystal alignment agent according to claim 1, characterized in that: Based on 100 parts by weight of the polymer component (A), the amount of the solvent (B) is 800 parts by weight to 3000 parts by weight.

5. The liquid crystal alignment agent according to claim 1, characterized in that: The polymer component (A) further comprises a second polymer (A2), and the second polymer (A2) is selected from at least one of the group consisting of a polyimide precursor and an imidized polymer formed by the polyimide precursor, and the polyimide precursor of the second polymer (A2) does not comprise the tetracarboxylic dianhydride mixture (a1-1) of the first polymer (A1).

6. The liquid crystal alignment agent according to claim 5, characterized in that: Based on 100 parts by weight of the polymer component (A), the first polymer (A1) is used in an amount of 5 to 85 parts by weight, and the second polymer (A2) is used in an amount of 15 to 95 parts by weight. 7 . A liquid crystal alignment film, formed by the liquid crystal alignment agent according to claim 1 .

8. A liquid crystal display element, characterized in that Comprising: the liquid crystal alignment film as claimed in claim 7.

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