TWI859005B - Liquid crystal alignment agent, liquid crystal alignment film and liquid crystal display element - Google Patents

Abstract

A liquid crystal alignment agent comprises a polymer component (A) and a solvent (B). The polymer component (A) includes a first polymer (A1) obtained from a first mixture by a reaction. The first mixture contains a tetracarboxylic dianhydride component (a1) and a diamine component (b1) wherein the tetracarboxylic dianhydride component (a1) includes a tetracarboxylic dianhydride mixture (a1-1) consisting of a tetracarboxylic dianhydride compound represented by formula (I) and a tetracarboxylic dianhydride compound represented by formula (II). 式(I)

Description

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

The present invention relates to a display device, in particular to a liquid crystal display element with less image residue, a liquid crystal alignment film used for the liquid crystal display element, and a liquid crystal alignment agent for forming the liquid crystal alignment film.

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

In the above-mentioned liquid crystal displays, the alignment treatment method using friction is currently used to make the liquid crystal alignment film have grooves that can align the liquid crystal molecules along a certain direction. The most popular alignment treatment method in the industry is to rub the liquid crystal alignment film formed by polyamide polymer and/or polyimide polymer obtained by imidization of polyamide polymer with cotton, nylon or polyester cloth in one direction. The alignment treatment method using friction is a simple, high-productivity and industrially useful method. However, with the increasing performance requirements for liquid crystal displays, finer picture quality and larger sizes, in order to avoid various problems such as damage to the liquid crystal alignment film caused by dust and static electricity generated by friction processing and alignment non-uniformity, photo-alignment methods have emerged that endow the liquid crystal alignment film with photo-alignment capabilities by irradiating polarized radiation, such as the photo-alignment method disclosed in Japanese Patent Laid-Open No. H09297313.

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 ion charges after being driven, resulting in image residue problems, which makes it impossible to meet application requirements.

Therefore, the first object of the present invention is to provide a liquid crystal alignment agent.

Therefore, 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), wherein 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), Formula (I) Formula (II).

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

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

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

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

The 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 the application requirements.

The present invention is described in detail below.

＜ Liquid crystal alignment agent ＞

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), wherein 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), Formula (I) Formula (II).

＜ First polymer (A1)＞

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.

[ Tetracarboxylic dianhydride component (a1)]

When the tetracarboxylic dianhydride mixture (a1-1) in the tetracarboxylic dianhydride component (a1) is not composed of the tetracarboxylic dianhydride compound represented by formula (I) and the tetracarboxylic dianhydride compound represented by formula (II), the liquid crystal display element including the liquid crystal alignment film formed by the liquid crystal alignment agent has high afterimage properties.

In order to make the liquid crystal display element of the liquid crystal alignment film formed by the liquid crystal alignment agent have lower afterimage property, 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.

In order to make the liquid crystal display device of the liquid crystal alignment film formed by the liquid crystal alignment agent have lower afterimage property, 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.

＜ Other tetracarboxylic dianhydride compounds (a1-2)＞

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

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, wherein the tetracarboxylic dianhydride compound represented by formula (A11) is Formula (A11).

In formula (A11), X ^1' represents a structure represented by formula (A11-1) to formula (A11-32), wherein "*" represents a bonding position, Formula (A11-1), Formula (A11-2), Formula (A11-3), Formula (A11-4), Formula (A11-5), Formula (A11-6), Formula (A11-7), Formula (A11-8), Formula (A11-9), Formula (A11-10), Formula (A11-11), Formula (A11-12), Formula (A11-13), Formula (A11-14), Formula (A11-15), Formula (A11-16), Formula (A11-17), Formula (A11-18), Formula (A11-19), Formula (A11-20), Formula (A11-21), Formula (A11-22), Formula (A11-23), Formula (A11-24), Formula (A11-25), Formula (A11-26), Formula (A11-27), Formula (A11-28), Formula (A11-29), Formula (A11-30), Formula (A11-31), Formula (A11-32).

In formula (A11-1), a1 is 1 to 12. In formula (A11-5), X ^11′ represents a single bond, -O-, -CO-, -COO-, a phenylene group, a sulfonyl group or an amide group, and a1 represents 0 or 1. In formula (A12-6), X ^11′ and X ^12′ each independently represent a single bond, -O-, -CO-, -COO-, a phenylene group, a sulfonyl group or an amide group, and a plurality of 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' independently represents hydrogen, a 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 containing fluorine and having 1 to 6 carbon atoms, or a phenyl group, and a plurality of X ^13' groups are the same or different. From the viewpoint of liquid crystal alignment, preferably, X ^13' represents hydrogen, a halogen, a methyl group or an ethyl group, and more preferably, represents hydrogen or a methyl group.

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

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 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.

＜ Diamine component (b1)＞

In order to provide a liquid crystal display device including a liquid crystal alignment film formed by the liquid crystal alignment agent with lower afterimage and better stability, preferably, in some embodiments of the present invention, the diamine component (b1) comprises a diamine compound (b1-1), and the diamine compound (b1-1) is a diamine compound represented by formula (A21-1) to formula (A21-2), Formula (A21-1), Formula (A21-2).

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. In formula (A21-2), a plurality of Y ³³ each independently represents a divalent organic group represented by formula (A21-3'), Formula (A21-3), Formula (A21-3').

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

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

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 naphthyl 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.

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, Formula (A21-3-1), Formula (A21-3-2), Formula (A21-3-3), Formula (A21-3-4), Formula (A21-3-5), Formula (A21-3-6), Formula (A21-3-7), Formula (A21-3-8), Formula (A21-3-9), Formula (A21-3-10), Formula (A21-3-11), Formula (A21-3-12), Formula (A21-3-13), Formula (A21-3-14), Formula (A21-3-15), Formula (A21-3-16).

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.

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).

When the diamine compound (b1-1) contains a diamine compound represented by a plurality of formulas (A21-1), preferably, Y ³¹ in formula (A21-1) represents a diamine compound of formula (A21-3-1) to formula (A21-3-14) and Y ³¹ in formula (A21-1) represents a combination of diamine compounds of formula (A21-3-15) to formula (A21-3-16).

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), Formula (A21-2-1), Formula (A21-2-2), Formula (A21-2-3), Formula (A21-2-4), Formula (A21-2-5).

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.

The diamine compound (b1-1) 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 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.

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

From the viewpoint of improving the alignment 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 protective group). The first polymer (A1) having an -N(D)- group can be obtained by using a monomer having an -N(D)- group as at least a part of the reaction raw material, or by using a monomer having an -N(D)- group 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 protective group is, for example, but not limited to, tert-butyloxycarbonyl (Boc for short) or 9-fluorenylmethoxycarbonyl.

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), Formula (A22-1), Formula (A22-2), Formula (A22-3), Formula (A22-4), Formula (A22-5), Formula (A22-6), Formula (A22-7), Formula (A22-8), Formula (A22-9), Formula (A22-10).

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.

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 mol, the amount of the diamine compound (b1-2) having a group of -N(D)- is 2 mol to 60 mol, preferably 10 mol to 50 mol, and more preferably 15 mol to 40 mol.

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

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'-diaminodiphenylketone, 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 a diamine compound having an oxazoline structure, etc.

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), Formula (A23-1), Formula (A23-2), Formula (A23-3).

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), Formula (A23-4), Formula (A23-5), Formula (A23-6), Formula (A23-7).

In formula (A23-4), ^Y51 represents a single bond, _-CH2- , _-C2H4- , -C( _CH3 ) _2- , _-CF2- , -C( _CF3 ) _2- , -O-, -CO-, -NH-, _-N ( _CH3 )-, -CONH-, -NHCO-, -CH2O- _{, -OCH2-} , -COO-, -OCO-, -CON( _CH3 )- or -N( _CH3 )CO-; m1 and m2 each independently represent an integer 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), ^Y52 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) _, ^Y53 and ^Y54 each independently represent a single bond, _-CH2- , _-C2H4- , -C( _CH3 ) _2- , -CF2-, -C( _CF3 ) _2- , -O-, _-CO- , -NH-, -N _{( CH3} )-, -CONH-, -NHCO-, -CH2O-, _-OCH2- , -COO-, -OCO-, -CON( _CH3 )- or -N( _CH3 )CO-; m6 represents an integer from 1 to 4.

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), Formula (A23-8), Formula (A23-9), Formula (A23-10).

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.

The diamine compound having an amide bond is, for example but not limited to, the diamine compound having an amide bond represented by formula (A23-11) to formula (A23-13), Formula (A23-11), Formula (A23-12), Formula (A23-13).

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

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.

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

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), Formula (A23-14), Formula (A23-15).

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) is 0 mol to 65 mol, preferably 0 mol to 50 mol, and more preferably 0 mol to 35 mol.

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 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 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.

＜ Second polymer (A2)＞

In some embodiments of the present invention, the polymer component (A) further comprises a second polymer (A2).

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 a plurality of types.

＜ Tetracarboxylic dianhydride component (a2)＞

The tetracarboxylic dianhydride component (a2) includes, but is not limited to, acyclic aliphatic tetracarboxylic dianhydride compounds, alicyclic tetracarboxylic dianhydride compounds, aromatic tetracarboxylic dianhydride compounds, or derivatives thereof. The tetracarboxylic dianhydride component (a2) may be used alone or in combination of a plurality of types.

The acyclic 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 acyclic aliphatic tetracarboxylic dianhydride does not need to be composed only of a chain hydrocarbon structure, and a portion thereof may have an alicyclic structure or an aromatic ring structure.

The alicyclic tetracarboxylic dianhydride may be, 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 have a chain hydrocarbon structure or an aromatic ring structure.

The aromatic 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 aromatic ring. However, the aromatic tetracarboxylic dianhydride does not need to be composed only of an aromatic ring structure, and a portion thereof may have a chain hydrocarbon structure or an alicyclic structure.

Preferably, the tetracarboxylic dianhydride component (a2) comprises a tetracarboxylic dianhydride compound or a derivative thereof as shown in the above formula (A11) and X ^1′ represents a structure shown in formula (A11-1) to formula (A11-6).

Preferably, the tetracarboxylic dianhydride component (a2) comprises a tetracarboxylic dianhydride compound (a2-1) having a structure represented by formula (A11) and X ^1' having a structure represented by formula (III). Formula (III).

In formula (III), Z ¹¹ represents a single bond, and “*” represents a bonding position.

The tetracarboxylic dianhydride compound (a2-1) may be used alone or in combination of two or more.

More preferably, the tetracarboxylic dianhydride component (a2) comprises a tetracarboxylic dianhydride compound represented by formula (IV), Formula (IV).

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

＜ Diamine component (b2)＞

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 atom-containing structure. The diamine component (b2) can be used alone or in combination of two or more.

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

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

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, pyrimidine, pyrimidine, pyrimidine, indole, benzimidazole, purine, quinoline, isoquinoline, oxadiazole, quinoline, pyrimidine, tririmidine, carbazole, acridine, piperidine, piperidine, pyrrolidine or hexamethyleneimine, etc. Preferably, the nitrogen-containing heterocyclic ring is pyridine, pyrimidine, pyrimidine, piperidine, piperidine, quinoline, carbazole or acridine.

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

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.

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.

The diamine compound (b2-1) having a nitrogen atom-containing 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)-piperidinium, 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), Formula (B21-1), Formula (B21-2), Formula (B21-3), Formula (B21-4), Formula (B21-5), Formula (B21-6), Formula (B21-7), Formula (B21-8), Formula (B21-9), Formula (B21-10), Formula (B21-11), Formula (B21-12), Formula (B21-13), Formula (B21-14), Formula (B21-15), Formula (B21-16), Formula (B21-17), Formula (B21-18), Formula (B21-19), Formula (B21-20), Formula (B21-21), Formula (B21-22), Formula (B21-23), Formula (B21-24), Formula (B21-25), Formula (B21-26).

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.

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

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 (b2-1) having a nitrogen atom-containing structure is 15 mol to 100 mol, preferably 20 mol to 90 mol, and more preferably 25 mol to 80 mol.

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.

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.

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

The first polymer (A1) and the second polymer (A2) can be produced by reacting the above-mentioned diamine component and tetracarboxylic dianhydride component in a solvent (polycondensation). When a portion of the first polymer (A1) and the second polymer (A2) has an acylamidic acid structure, for example, the tetracarboxylic dianhydride component is reacted with the diamine component to obtain a polymer having an acylamidic acid structure (i.e., polyacylamidic 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. 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), Formula (D-1), Formula (D-2), Formula (D-3).

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 represents an alkyl group having 1 to 4 carbon atoms.

The solvent can be used alone or in combination. Secondly, even if the solvent is insoluble in the polymer, the solvent can 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 the solvent, the reaction can be carried out at any concentration. Preferably, the concentration of the reaction is 1wt% to 50wt%, and more preferably, 5wt% to 30wt%. The reaction can also be carried out at a high concentration initially, and then the solvent is added additionally. When the reaction is carried out, preferably, the ratio of the total molar number of the diamine component to the total molar number of the tetracarboxylic dianhydride component is 0.8 to 1.2. Similar to a general polycondensation reaction, the closer the ratio of the total molar number of the diamine component to the total molar number of the tetracarboxylic dianhydride component is to 1.0, the larger the molecular weight of the first polymer (A1) or the second polymer (A2) formed.

The polymer having an acylamidoester structure can be obtained, for example, by a known method, and the known method is (1) a method of reacting the polyacylamidoester 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.

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 acylamidate structure. In the imidized polymer, the ring-closing ratio (also called the imidization ratio) of the functional group possessed by the acylamidate group or its derivative is not necessarily 100%, and the imidization ratio of the imidized polymer can be arbitrarily adjusted according to the use and/or purpose.

The method for obtaining the imidized polymer includes, for example, directly heating a solution containing a polymer having an amide structure for thermal imidization, or adding a catalyst to the solution for catalytic imidization. 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 discharged out of the system.

The catalytic imidization is carried out, for example, by adding an alkaline catalyst and an acid 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 group, more preferably, 2 to 20 times. Preferably, the amount of the acid anhydride added is 1 to 50 times the molar equivalent of the amide group, more preferably, 3 to 30 times. The alkaline catalyst is, for example, but not limited to, pyridine, triethylamine, trimethylamine, tributylamine or trioctylamine. Among them, pyridine is ideal because it has a moderate alkalinity that allows the reaction to proceed. The acid anhydride is, for example, but not limited to, acetic anhydride, trimellitic anhydride, or pyromellitic anhydride. Among them, 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.

When the imidized polymer is recovered from the 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 in the solvent, it can be dried at normal pressure or reduced pressure, at room temperature or by heating. 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 ketones. If more than three selected solvents are used, the efficiency of purification can be further improved, which is more ideal.

When the solution is prepared into a concentration of 10wt% to 15wt%, the solution viscosity of the first polymer (A1) or the second polymer (A2) of the present invention is not particularly limited. Based on the viewpoint of easier operation, the solution viscosity can be, for example, 10mPa·s to 1000mPa·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 with a concentration of 10wt% to 15wt%.

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) measured by GPC in terms of polystyrene 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.

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 a suitable 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.

The end-capping agent may be, for example, but not limited to, an acid anhydride, a dicarbonic acid diester compound, a chlorocarbonyl compound, a monoamine compound, or a monoisocyanate compound. The acid anhydride may be, 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 may be, for example, but not limited to, di-tert-butyl dicarbonate or diallyl dicarbonate. The chlorocarbonyl compound may be, 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. The monoisocyanate compound includes, but is not limited to, ethyl isocyanate, phenyl isocyanate, or naphthyl isocyanate.

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

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

[ Solvent (B)]

From the perspective 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). Among them, based on the set coating thickness to be formed, the concentration of the polymer component (A) in the liquid crystal alignment agent can be appropriately changed. From the perspective of forming a uniform and defect-free coating, preferably, the concentration of the polymer component (A) in the liquid crystal alignment agent is greater than 1wt%. From the perspective of the storage stability of the solution, preferably, the concentration of the polymer component (A) in the liquid crystal alignment agent is less than 10wt%. 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, it is 2wt% to 10wt%, more preferably, it is 3wt% to 8wt%.

The solvent (B) in the liquid crystal alignment agent is, for example, an organic solvent, and the solvent (B) is not particularly limited, as long as it can evenly 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, dimethylsulfoxide, 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. Among them, 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 the solvent (B) in the liquid crystal alignment agent being 100 wt %, the amount of the good solvent used is 20 wt % to 99 wt %, preferably 20 wt % to 90 wt %, and more preferably 30 wt % to 80 wt %.

Secondly, preferably, the solvent (B) in the liquid crystal alignment agent includes 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. Preferably, based on the total amount of the solvent (B) in the liquid crystal alignment agent being 100wt%, the usage amount of the poor solvent is 1wt% to 80wt%, more preferably, 10wt% to 80wt%, and even more preferably, 20wt% to 70wt%. The type and usage amount of the poor solvent can be appropriately selected according to the coating device, coating conditions and/or coating environment of the liquid crystal alignment agent.

The poor solvent includes, but is 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 celoxylate), 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, isoamyl lactate, diethylene glycol monoethyl ether, or diisobutyl ketone (2,6-dimethyl-4-heptanone), etc.

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.

Preferably, the solvent combination of good solvent and 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-dimethyllactamide and diisobutyl ketone, etc.

The solvent (B) can be used alone or in combination. In some embodiments of the present invention, based on the total amount of the polymer component (A) being 100 parts by weight, 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.

The liquid crystal alignment agent of the present invention further includes 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, cross-linking 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.

The adhesion promoter is, for example but not limited to, 3-aminopropyl trimethoxysilane, 3-aminopropyl triethoxysilane, 3-aminopropyl diethoxymethyl silane, 2-aminopropyl trimethoxysilane, 2-aminopropyl triethoxysilane, N-(2-aminoethyl)-3-aminopropyl trimethoxysilane, N-(2-aminoethyl)-3-aminopropyl methyl dimethoxysilane, 3-ureidopropyl trimethoxysilane, 3-ureidopropyl triethoxysilane, N-ethoxycarbonyl-3-aminopropyl trimethoxysilane, N-ethoxycarbonyl-3-aminopropyl triethoxysilane, N-triethoxysilylpropyl triethyl triamine, N-trimethoxysilylpropyl triethyl triamine, vinyl trimethoxysilane, Silane, vinyl triethoxysilane, 2-(3,4-epoxyhexyl)ethyl trimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-methacryloyloxypropylmethyldimethoxysilane Silane coupling agents such as methoxysilane, 3-methacryloxypropyl trimethoxysilane, 3-methacryloxypropyl methyldiethoxysilane, 3-methacryloxypropyl triethoxysilane, 3-acryloxypropyl trimethoxysilane, tris(3-trimethoxysilylpropyl) isocyanurate, or 3-isocyanatepropyl triethoxysilane. When a bonding aid is used, based on the viewpoint of exhibiting good resistance to AC afterimage, 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 100 parts by weight of the total amount of the polymer component (A) in the liquid crystal alignment agent.

From the viewpoint of exhibiting good resistance to AC afterimage 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), Formula (E1), Formula (E2), Formula (E3).

In formula (E1), ^G1 and ^G2 each independently represent hydrogen, an alkyl group having 1 to 3 carbon atoms, or -CH2 _- OH. In formula (E2), ^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 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. In formula (E3), ^G5 represents a (g1+g2)-valent organic group containing an aromatic ring. ^G6 represents hydrogen 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.

In formula (E3), the (g1+g2)-valent organic group having an aromatic ring of ^G5 is, for example, a (g1+g2)-valent aromatic hydrocarbon group having 6 to 30 carbon atoms, a (g1+g2)-valent organic group to which an aromatic hydrocarbon group having 6 to 30 carbon atoms is directly or via a linking group, or a (g1+g2)-valent group having an aromatic heterocyclic ring. The aromatic hydrocarbon is, for example, benzene or naphthalene. The aromatic heterocyclic ring is, for example, the exemplified aromatic heterocyclic ring of the nitrogen atom-containing structure described above. The linking group is, for example, an alkylene group having 1 to 10 carbon atoms or a group from which a hydrogen atom is removed, or a divalent or trivalent cyclohexane. Any hydrogen of the alkylene group may also be substituted with an organic group such as a fluorine atom or a trifluoromethyl group. In formula (E3), ^G6 represents an alkyl group having 1 to 5 carbon atoms, such as methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, t-butyl or n-pentyl.

The compound having an ethylene oxide group is, for example but not limited to, N,N,N',N'-tetraethylene oxide propyl meta-xylene diamine, 1,3-bis(N,N-diethylene oxide propylaminomethyl)cyclohexane, N,N,N',N'-tetraethylene oxide propyl-4,4'-diaminodiphenylmethane, N,N,N',N'-tetraethylene oxide propyl-p-phenylenediamine, or nitrogen-containing compounds represented by formula (E4) to formula (E6), Formula (E4), Formula (E5), Formula (E6).

The compound having an propylene oxide group is, for example but not limited to, the compounds represented by formula (E7) to formula (E16), Formula (E7), Formula (E8), Formula (E9), Formula (E10), Formula (E11), Formula (E12), Formula (E13), Formula (E14), Formula (E15), Formula (E16).

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.

The compound having the group represented by formula (E1) includes, but is not limited to, compounds represented by formula (E1-1) to formula (E1-12), Formula (E1-1), Formula (E1-2), Formula (E1-3), Formula (E1-4), Formula (E1-5), Formula (E1-6), Formula (E1-7), Formula (E1-8), Formula (E1-9), Formula (E1-10), Formula (E1-11), Formula (E1-12).

The compound having the group represented by formula (E2) is, for example but not limited to, the compounds represented by formula (E2-1) to formula (E2-4), Formula (E2-1), Formula (E2-2), Formula (E2-3), Formula (E2-4).

In formula (E2-1), n represents 2 to 16. In formula (E2-2), n represents 2 to 16.

The compound having the group represented by formula (E3) is, for example but not limited to, the compounds represented by formula (E3-1) to formula (E3-10), Formula (E3-1), Formula (E3-2), Formula (E3-3), Formula (E3-4), Formula (E3-5), Formula (E3-6), Formula (E3-7), Formula (E3-8), Formula (E3-9), Formula (E3-10).

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 crosslinking compound used is 0.5 to 20 parts by weight. In particular, based on the viewpoint of the crosslinking reaction and the good resistance to AC afterimage, more preferably, the amount of the crosslinking compound used is 1 to 15 parts by weight.

Preferably, the compound for promoting imidization is a compound having a basic site (e.g., a primary amine group, an aliphatic heterocycle (e.g., a pyrrolidine skeleton), an aromatic heterocycle (e.g., an imidazole ring or an indole ring), or a guanidine group, etc.) (excluding the crosslinking compound and the adhesion promoter), or a compound that generates the basic site when calcined. More preferably, the compound for promoting imidization is a compound that generates the basic site when calcined, for example, an amino acid having a part or all of the basic site of the amino acid being protected. The amino acid is, for example, glycine, alanine, cysteine, methionine, asparagine, glutamine, valine, leucine, phenylalanine, tyrosine, tryptophan, proline, hydroxyproline, arginine, histidine, lysine, or ornithine. For the purpose of promoting the amidation compound, more preferably, a specific example can be N-α-(9-fluorenylmethoxycarbonyl)-N-τ-(tert-butyloxycarbonyl)-L-histidine.

＜Liquid crystal alignment film and liquid crystal display element＞

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 manufactured, for example, by the method of steps (1) to (4), or by the method of steps (1) to (2) and step (4).

Step (1): Apply liquid crystal alignment agent on the substrate

The liquid crystal alignment agent of the present invention is applied on one side of a substrate having 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 may be used together 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 may be used, and the electrode used may be a light-reflecting material such as aluminum. Furthermore, when manufacturing an IPS-type liquid crystal display element, a comb-tooth type uses an electrode substrate having a patterned transparent conductive film or metal film and an opposing substrate having no electrode.

The method of coating the liquid crystal alignment agent on the substrate and forming a film can be screen printing, lithography, flexographic printing, inkjet method or inkjet coating method, etc. Preferably, the film forming method is coating using the inkjet method.

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

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 is coated 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 polyamine or polyamine ester can be performed. The drying and calcining steps after the liquid crystal alignment agent of the present invention has been coated can be selected at 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 carried out at 40°C to 150°C. There is no particular limitation on the drying time, and it may be, for example, 1 minute to 10 minutes or 1 minute to 5 minutes. When thermal imidization of polyamine acid or polyamine ester is performed, after the above-mentioned drying step, a calcination step may be further performed at a temperature of, for example, 150°C to 300°C or 150°C to 250°C. There is no particular limitation on the calcination time, and it may be, 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 film thickness is 5nm to 300nm, and more preferably, 10nm to 200nm.

Step (3): Performing an alignment treatment on the film obtained in step (2)

Step (3) is to perform an alignment treatment on the film obtained in step (2) as appropriate. That is, in the horizontal alignment type liquid crystal display element of IPS, the coating film is subjected to an alignment treatment to impart alignment ability. The alignment treatment is a photo-alignment treatment. The photo-alignment treatment can be exemplified by 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 ability). 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, and more preferably, ultraviolet light with a wavelength of 200nm to 400nm.

The radiation exposure amount may be 1mJ/ ^cm2 to 10,000mJ/ ^cm2 , preferably 100mJ/ ^cm2 to 5,000mJ/ ^cm2 , more preferably 100mJ/ ^cm2 to 1500mJ/ ^cm2 , and particularly preferably 100mJ/ ^cm2 to 1000mJ/ ^cm2 . When a general liquid crystal alignment agent is used, the light exposure amount for the alignment treatment is 100mJ/ ^cm2 to 5000mJ/ ^cm2 , but the liquid crystal alignment agent of the present invention can still form a liquid crystal alignment film in which the variation (unevenness) of the liquid crystal alignment in the film surface is effectively suppressed even if the light exposure amount for the alignment treatment is reduced. When irradiating radiation, in order to improve the liquid crystal alignment, the substrate with 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 make the liquid crystal molecules stably align in a certain direction. Secondly, the liquid crystal alignment film irradiated with polarized radiation in the above method can be contact-treated with a solvent, or the liquid crystal alignment film irradiated with radiation can be heated.

The solvent used in the above-mentioned contact treatment is not particularly limited, and it only needs to be able to dissolve the decomposition products generated from the film after irradiation. The solvent is, for example, water, methanol, ethanol, 2-propanol, acetone, methyl ethyl ketone, 1-methoxy-2-propanol, 1-methoxy-2-propanol acetate, butyl celoxylate, ethyl lactate, methyl lactate, diacetone alcohol, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, propyl acetate, butyl acetate, or cyclohexyl acetate. Among them, based on the viewpoint of versatility and safety, it is preferred that 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.

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.

Step (4): Making liquid crystal cells

Prepare two substrates with the liquid crystal alignment films formed above, and arrange the liquid crystal between the two substrates facing each other. For example, the following two methods can be listed. The first method is to arrange the two substrates facing each other with a gap (cell gap) between them in a way that the liquid crystal alignment films face each other. Then, the periphery of the two substrates is bonded with a sealant, and then the liquid crystal composition is injected into the cell gap separated by the substrate surface and the sealant, and after it contacts the film surface, the injection hole is sealed.

The second method is called ODF (One Drop Fill) method. A sealant such as a 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 onto a plurality of predetermined positions on the surface of the liquid crystal alignment film. Then, the other substrate is bonded with the liquid crystal alignment films facing each other, and the liquid crystal composition is pushed onto the entire surface of the substrate so that it contacts the film surface. Then, ultraviolet light is irradiated onto the entire surface of the substrate to cure 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 is subjected to friction treatment, the two substrates are arranged to face each other with the friction directions of each coating forming a predetermined angle with each other, such as being orthogonal or antiparallel. The sealant may be, for example, epoxy resin containing a hardener and aluminum oxide balls as spacers. The liquid crystal composition may be, for example, nematic liquid crystal or lamellar liquid crystal, preferably, nematic liquid crystal.

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 extends and aligns 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.

The present invention will be further described with respect to the following embodiments, but it should be understood that the embodiments are only for illustrative purposes and should not be interpreted as limitations on the implementation of the present invention.

Preparation Example 1     First polymer (A1)--polyimide precursor

A 500 ml four-necked conical flask was equipped with a nitrogen inlet, a stirrer, a condenser and a thermometer, 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. Then, the filter cake is 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).

Preparation Examples 2 to 5, Preparation Example 7 and Comparative Preparation Examples 1 to 2

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.

Preparation Example 6 - Imidization Polymer

A 500 ml four-necked conical flask was equipped with a nitrogen inlet, a stirrer, a condenser and a thermometer, 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 an imidization reaction to obtain a reaction solution. The reaction solution is poured into 1500 milliliters of water to precipitate a polymer. Then, it is filtered 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).

Table 1 Unit: mole% Preparation example Comparison of preparation examples 1 2 3 4 5 6 7 1 2 Tetracarboxylic dianhydride component (a1) a1-1-a 99.5 95 80 50 90 80 40 90 0 a1-1-b 0.5 5 20 50 5 10 50 0 0 a1-2-a 0 0 0 0 5 0 10 10 0 a1-2-b 0 0 0 0 0 10 0 0 0 a1-2-c 0 0 0 0 0 0 0 0 100 Diamine component (b1) b1-1-a 70 0 60 10 70 0 0 70 70 b1-1-b 0 70 0 50 0 70 70 0 0 b1-2-a 20 0 20 0 20 0 20 20 20 b1-2-b 0 20 0 20 0 20 0 0 0 b1-3-a 10 10 20 10 10 10 10 10 10 b1-3-b 0 0 0 10 0 0 0 0 0 a1-1-a: ; a1-1-b: ; a1-2-a: ; a1-2-b: ; a1-2-c: ; b1-1-a: ; b1-1-b: ; b1-2-a: ; b1-2-b: ; b1-3-a: ; b1-3-b:

Preparation Example 8 Second polymer (A2) - polyimide precursor

A 500 ml four-necked conical flask was equipped with a nitrogen inlet, a stirrer, a condenser and a thermometer, 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. Then, the filter cake is 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 second polymer (A2).

Preparation Examples 9 to 10

The preparation methods of Preparation Examples 9 to 10 are generally similar to 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.

Table 2 Unit: mole% Preparation example 8 9 10 Tetracarboxylic dianhydride component (a2) a2-a 100 100 0 a2-b 0 0 100 Diamine component (b2) b2-a 80 20 100 b2-b 20 0 0 b2-c 0 80 0 a2-a: ; a2-b: ; b2-a: ; b2-b: ; b2-c:

Embodiment 1

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.

Examples 2 to 14 and Comparative Examples 1 to 2

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 solvents, are changed, as shown in Table 3.

Application Example 1: Liquid Crystal Display Components

The liquid crystal alignment agent of Example 1 is applied on a pixel electrode of a glass substrate including a pixel electrode by rotational coating, wherein the pixel electrode is an IPS driving electrode having a pair of indium tin oxide (ITO) electrodes (electrode width is 10 μm, electrode spacing is 10 μm, and electrode height is 50 nm), and the pair of ITO electrodes are in a comb-tooth shape, and the comb-tooth portions of each other are configured in a separated and interlocking manner. Then, the glass substrate coated with the liquid crystal alignment agent was 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 with a thickness of 100 nm formed on the glass substrate. The coating was irradiated with ultraviolet light 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.

The liquid crystal alignment agent of Example 1 was applied by rotational coating on a glass substrate having no pixel electrodes and columnar spacers with a height of 4 μm, and then the glass substrate coated with the liquid crystal alignment agent was 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 with a thickness of 100 nm formed on the glass substrate. The coating film was irradiated with ultraviolet light 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.

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 being 0°, and then the sealant is cured to obtain a laminate including an injection port and a liquid crystal cell cavity connected to the injection port. Then, liquid crystal MLC-2041 (manufactured by 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 unit 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 unit to form a liquid crystal display element.

Application Examples 2 to 14 and Comparative Application Examples 1 to 2

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.

Table 3 Unit: Weight Embodiment 1 2 3 4 5 6 7 8 Polymer component (A) First polymer (A1) Preparation example 1 0 100 0 0 0 0 0 0 2 0 0 100 0 0 0 0 0 3 0 0 0 100 0 0 0 0 4 0 0 0 0 100 0 0 0 5 0 0 0 0 0 100 0 0 6 0 0 0 0 0 0 100 0 7 100 0 0 0 0 0 0 90 Comparison of preparation examples 1 0 0 0 0 0 0 0 0 2 0 0 0 0 0 0 0 0 Second polymer (A2) Preparation example 8 0 0 0 0 0 0 0 10 9 0 0 0 0 0 0 0 0 10 0 0 0 0 0 0 0 0 Solvent (B) N-Methyl-2-pyrrolidone 1200 0 1200 N-Ethyl-2-pyrrolidone 0 1200 0

Table 4 Embodiment Comparison Example 9 10 11 12 13 14 1 2 Polymer component (A) First polymer (A1) Preparation example 1 0 20 0 0 0 0 0 0 2 0 0 30 0 0 0 0 0 3 0 0 0 40 0 0 0 0 4 0 0 0 0 50 0 0 0 5 0 0 0 0 0 60 0 0 6 0 0 0 0 0 0 0 0 7 30 0 0 0 0 0 0 0 Comparison of preparation examples 1 0 0 0 0 0 0 0 100 2 0 0 0 0 0 0 100 0 Second polymer (A2) Preparation example 8 70 0 70 0 0 30 0 0 9 0 0 0 60 0 0 0 0 10 0 80 0 0 50 0 0 0 Solvent (B) N-Methyl-2-pyrrolidone 1200 N-Ethyl-2-pyrrolidone 0

Evaluation items

Afterimage test: The liquid crystal units of application examples 1 to 14 and comparison application examples 1 to 2 are driven with an AC voltage of 10V for 30 hours, and then the liquid crystal unit is sandwiched between a polarizer and an analyzer of an optical device. Then, the light transmittance of the liquid crystal unit is measured using the optical device, and the minimum relative transmittance (%) is calculated. The optical device includes a light source, a light detector, and a polarizing device arranged between the light source and the light detector, and the polarizing device includes the polarizer and the analyzer. Minimum relative transmittance (%) = [(β-B0)/(B100-B0)] × 100% B0 is blank and is the light transmittance under crossed nicols, i.e., the light transmittance in the dark state; B100 is blank and is the light transmittance under parallel nicols, i.e., the light transmittance in the bright state; β is the minimum light transmittance of the liquid crystal unit under crossed nicols. The degree of the dark 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: ◎ indicates minimum relative transmittance ≤ 0.5%; O indicates 0.5% < minimum relative transmittance ≤ 1.0%; △ indicates 1.0% < minimum relative transmittance ≤ 1.5%; X indicates minimum relative transmittance > 1.5%.

Flicker test: Place the liquid crystal unit of application examples 1 to 14 and comparison application examples 1 to 2 between two polarizers whose polarization axes are arranged in a vertically crossed manner. Then, without applying voltage to the liquid crystal unit, light up the LED backlight source, and adjust the configuration angle of the liquid crystal unit so that the brightness of the light passing through the liquid crystal unit is minimized. Then, apply an AC voltage with a frequency of 30Hz to the liquid crystal unit, and use the detection equipment to measure the voltage and light transmittance, and obtain a curve of voltage-light transmittance. Then, use the curve to calculate the AC voltage with a relative light transmittance of 23% as the driving voltage. Then, the temperature of the liquid crystal unit was controlled at 23°C, and the LED backlight that was turned on was turned off. Then, it was placed in a non-illuminated state for 72 hours. Then, the LED backlight was turned on, and at the same time as the lighting started, the liquid crystal unit was driven for 60 minutes with an AC voltage of 30Hz with a relative light transmittance of 23%. Then, a data acquisition/data recording switching device (made by Agilent technologies; model 34970A) connected to the LED backlight and the I-V 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. Flicker (%) = [Flicker amplitude/(2×brightness value)]×100% The lower the flicker, the better the quality of the LCD display element. The evaluation criteria are: ◎ means flicker <3%; O means 4%> flicker ≧3%; △ means 5%> flicker ≧4%; X means flicker ≧5%.

Table 5 Minimum relative transmittance (%) Flicker(%) Application Examples 1 O O 2 ◎ O 3 ◎ O 4 ◎ O 5 ◎ O 6 ◎ O 7 ◎ O 8 O O 9 O ◎ 10 ◎ ◎ 11 ◎ ◎ 12 ◎ ◎ 13 ◎ ◎ 14 ◎ ◎ Comparison Applications 1 X O 2 X O

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 minimum relative transmittance of the liquid crystal display element after driving, which includes the liquid crystal alignment agents of Examples 1 to 7 using the first polymers, is 0 to ◎. 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) The problem of image residue is not easy to occur. In Comparative Examples 1 to 2, the polymers of Comparative Synthesis Examples 1 to 2 used do not use the tetracarboxylic dianhydride compound represented by formula (I) and the tetracarboxylic dianhydride compound represented by formula (II), so that the minimum relative transmittance of the liquid crystal display element containing the liquid crystal alignment agent using the polymers of Comparative Synthesis Examples 1 to 2 after driving is X. Therefore, 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 represented by formula (I) and the tetracarboxylic dianhydride compound represented by formula (II) is prone to image residue. From the above, it can be seen that the liquid crystal alignment agent of the present invention using the first polymer of the tetracarboxylic dianhydride compound represented by formula (I) and the tetracarboxylic dianhydride compound represented by formula (II) can indeed effectively reduce the image residue.

Furthermore, compared to 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 being driven. As can be seen from the above, the liquid crystal alignment agent of the present invention not only has low afterimage, but also has the advantage of low screen flicker.

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, thereby truly achieving the purpose of the present invention.

However, the above is only an embodiment of the present invention and should not be used to limit the scope of implementation of the present invention. All simple equivalent changes and modifications made according to the scope of the patent application of the present invention and the content of the patent specification are still within the scope of the present patent.

Claims (6)

A liquid crystal alignment agent comprises: a polymer component (A) comprising a first polymer (A1), wherein the first polymer (A1) is prepared by reacting a first mixture, wherein the first mixture comprises a tetracarboxylic dianhydride component (a1) and a diamine component (b1); and a solvent (B), wherein the tetracarboxylic dianhydride component (a1) comprises 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),

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, and the usage of the tetracarboxylic dianhydride compound represented by formula (II) is 0.5 mol to 50 mol. The liquid crystal alignment agent as described in claim 1, wherein the amount of the polymer component (A) used is 100 parts by weight, and the amount of the solvent (B) used is 800 parts by weight to 3000 parts by weight. The liquid crystal alignment agent as described in claim 1, wherein 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). The liquid crystal alignment agent as described in claim 3, wherein, based on 100 parts by weight of the polymer component (A), the amount of the first polymer (A1) used is 5 to 85 parts by weight, and the amount of the second polymer (A2) used is 15 to 95 parts by weight. A liquid crystal alignment film is formed by a liquid crystal alignment agent as described in any one of claims 1 to 4. A liquid crystal display element, comprising a liquid crystal alignment film as described in claim 5.