TWI865340B - Liquid crystal alignment agent for photo-alignment, liquid crystal alignment film and liquid crystal display element - Google Patents

Abstract

A present invention relates to a liquid crystal alignment agent for photo-alignment, a liquid crystal alignment film formed from said liquid crystal alignment agent for photo-alignment, and a liquid crystal display element that comprises said liquid crystal alignment film and is not easy to flicker after being driven by high voltage. Said liquid crystal alignment agent for photo-alignment comprises a polymer component (A) and a solvent (B). Said polymer component (A) includes a first polymer (A1) and a second polymer (A2). Wherein, said second polymer (A2) is selected from at least one of a group consisting of a polyimide precursor and an imidized polymer formed from said polyimide precursor, and said polyimide precursor of said second polymer (A2) comprises a structure represented by formula (II), and definitions of V ¹, V ², V ³, and W ¹in said formula (II) are as stated in a specification and claims respectively.

Description

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

The present invention relates to a liquid crystal alignment agent, a liquid crystal alignment film and a liquid crystal display element, and in particular to a liquid crystal alignment agent for a photo-alignment method that is not prone to flickering after being driven by a high voltage, a liquid crystal alignment film formed by the liquid crystal alignment agent for the photo-alignment method, and a liquid crystal display element comprising the liquid crystal alignment film.

In recent years, LCDs are often used in applications such as medical equipment, aerospace, image processing, and industrial control that require high resolution and fast response time. LCDs used in the above applications need to be able to quickly and accurately display high-resolution images and data, and also need to be able to withstand extreme environmental conditions. Driving LCDs with high voltage can give LCDs higher pixel density and faster refresh rates, thereby meeting the needs of the above special applications.

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 such liquid crystal displays driven by longitudinal electric fields are twisted nematic (TN) type liquid crystal displays and vertical alignment (VA) type liquid crystal displays. Examples of such liquid crystal displays driven by transverse electric fields 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 cloth, nylon cloth 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 obtained by the optical alignment method can avoid the problems caused by the alignment treatment method using the friction method, the liquid crystal display using the liquid crystal alignment film obtained by the optical alignment method currently has a problem of excessive flicker after being driven by a high voltage, making it unable to meet application requirements.

Therefore, the first object of the present invention is to provide a liquid crystal alignment agent for use in a photo-alignment method.

Therefore, the liquid crystal alignment agent used in the photo-alignment method of the present invention comprises a polymer component (A) and a solvent (B).

The polymer component (A) includes a first polymer (A1) and a second polymer (A2), wherein the first polymer (A1) is at least one selected from the group consisting of a polyimide precursor and an imidized polymer formed from the polyimide precursor, and the second polymer (A2) is at least one selected from the group consisting of a polyimide precursor and an imidized polymer formed from the polyimide precursor.

The polyimide precursor of the first polymer (A1) comprises a structure represented by formula (I), Formula (I) ^X1 represents at least one of the group consisting of the structures represented by formula (I-1) to formula (I-7), wherein "*" represents a bonding position, Formula (I-1), Formula (I-2), Formula (I-3), Formula (I-4), Formula (I-5), Formula (I-6), In formula (I-7), ^X11 , ^X12 , ^X13 and ^X14 each independently represent 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 having 1 to 6 carbon atoms and containing fluorine, or a phenyl group, ^X15 and ^X16 each independently represent hydrogen or a methyl group, ^X2 represents hydrogen or an alkyl group having 1 to 4 carbon atoms, ^X3 represents hydrogen or an alkyl group having 1 to 4 carbon atoms, and ^Y1 represents a divalent organic group.

The polyimide precursor of the second polymer (A2) comprises a structure represented by formula (II), Formula (II) V ¹ represents the structure shown in formula (II-1), wherein "*" represents the bonding position, Formula (II-1): ^V2 represents hydrogen or an alkyl group having 1 to 4 carbon atoms, ^V3 represents hydrogen or an alkyl group having 1 to 4 carbon atoms, ^W1 represents a structure represented by formula (II-2), Formula (II-2) In the formula (II-2), at least two of R ¹ to R ¹⁰ are "*" representing a bonding position, and the rest are H or a monovalent organic group.

Furthermore, the second object 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 liquid crystal alignment agent used in the photo-alignment method as described above.

Furthermore, 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 liquid crystal alignment film as described above.

The effect of the present invention is that by using the second polymer (A2) prepared by the polyimide precursor having the structure shown in formula (II), the liquid crystal alignment film formed by the liquid crystal alignment agent used in the photoalignment method can give the liquid crystal display element a low flicker degree after high-voltage driving, so the liquid crystal display element is not easy to flicker after being driven by high voltage.

The present invention provides a liquid crystal alignment agent for photo-alignment method, comprising: a polymer component (A) and a solvent (B). The polymer component (A) comprises a first polymer (A1) and a second polymer (A2).

《Polymer component (A)》

<First polymer (A1)>

The first polymer (A1) is at least one selected from the group consisting of a polyimide precursor and an imidized polymer formed by the polyimide precursor. The polyimide precursor of the first polymer (A1) comprises a structure shown in formula (I). Formula (I)

In the formula (I), ^X1 represents at least one of the group consisting of the structures represented by formula (I-1) to formula (I-7), wherein "*" represents a bonding position, ^X2 represents hydrogen or an alkyl group having 1 to 4 carbon atoms, ^X3 represents hydrogen or an alkyl group having 1 to 4 carbon atoms, and ^Y1 represents a divalent organic group. Formula (I-1), Formula (I-2), Formula (I-3), Formula (I-4), Formula (I-5), Formula (I-6), Formula (I-7)

In the formula (I-1), ^X11 , ^X12 , ^X13 and ^X14 independently represent 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 having 1 to 6 carbon atoms and containing fluorine, or a phenyl group.

In the formula (I-7), ^X15 and ^X16 each independently represent hydrogen or methyl.

In some embodiments of the present invention, the structure represented by formula (I-1) of X ¹ is selected from the structures represented by formula (I-1-1) to formula (I-1-6). Formula (I-1-1), Formula (I-1-2), Formula (I-1-3), Formula (I-1-4), Formula (I-1-5), Formula (I-1-6)

In some embodiments of the present invention, the structure represented by formula (I-1) of X ¹ is selected from the structure represented by formula (I-1-1). Formula (I-1-1)

In some embodiments of the present invention, the first polymer (A1) is selected from at least one of the group consisting of a polyimide precursor obtained by reacting a tetracarboxylic dianhydride component (a1) and a diamine component (b1), and an imidized polymer formed from the polyimide precursor.

[Tetracarboxylic dianhydride component (a1)]

[Alicyclic tetracarboxylic dianhydride compound (a1-1)]

In some embodiments of the present invention, the tetracarboxylic dianhydride component (a1) comprises an alicyclic tetracarboxylic dianhydride compound (a1-1) represented by formula (A11) or a derivative thereof. Formula (A11)

The alicyclic tetracarboxylic dianhydride compound (a1-1) or its derivative represented by the formula (A11) may be composed of a single tetracarboxylic dianhydride or its derivative, or may be composed of a plurality of tetracarboxylic dianhydrides or their derivatives. The alicyclic tetracarboxylic dianhydride compound (a1-1) represented by the formula (A11) 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 are 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 of only an aromatic ring structure, and a part of it may have a chain hydrocarbon structure or an alicyclic structure. 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 be composed of only a chain hydrocarbon structure, and a part of it may have an alicyclic structure or an aromatic ring structure.

In the formula (A11), ^X1 is at least one selected from the group consisting of the structures shown in formula (I-1) to formula (I-7), and "*" represents a bonding position. Formula (I-1), Formula (I-2), Formula (I-3), Formula (I-4), Formula (I-5), Formula (I-6), Formula (I-7)

In the formula (I-1), ^X11 , ^X12 , ^X13 and ^X14 each independently represent 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 having 1 to 6 carbon atoms and containing a fluorine atom, or a phenyl group. In the formula (I-7), ^X15 and ^X16 each independently represent hydrogen or a methyl group.

In some embodiments of the present invention, in the formula (A11), the structure of the formula (I-1) of X ¹ is selected from the structures shown in formulas (I-1-1) to (I-1-6). Formula (I-1-1), Formula (I-1-2), Formula (I-1-3), Formula (I-1-4), Formula (I-1-5), Formula (I-1-6)

In some embodiments of the present invention, preferably, the structure represented by formula (I-1) of X ¹ is the structure represented by formula (I-1-1).

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

[Other tetracarboxylic dianhydride compounds (a1-2)]

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

In some embodiments of the present invention, the other tetracarboxylic dianhydride compound (a1-2) comprises a tetracarboxylic dianhydride compound represented by formula (A12) or a derivative thereof. Formula (A12)

In the formula (A12), X ^1′ represents a structure as shown in formula (A12-1) to formula (A12-32), wherein “*” represents a bonding position. Formula (A12-1), Formula (A12-2), Formula (A12-3), Formula (A12-4), Formula (A12-5), Formula (A12-6), Formula (A12-7), Formula (A12-8), Formula (A12-9), Formula (A12-10), Formula (A12-11), Formula (A12-12), Formula (A12-13), Formula (A12-14), Formula (A12-15), Formula (A12-16), Formula (A12-17), Formula (A12-18), Formula (A12-19), Formula (A12-20), Formula (A12-21), Formula (A12-22), Formula (A12-23), Formula (A12-24), Formula (A12-25), Formula (A12-26), Formula (A12-27), Formula (A12-28), Formula (A12-29), Formula (A12-30), Formula (A12-31), Formula (A12-32)

In the formula (A12-1), a1 is 1 to 12. In the formula (A12-5), 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 the 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's are the same or different, and a1 represents 0 or 1. In the formula (A12-11), a1 represents 2 to 6. In the formula (A12-13), a1 represents 1 to 2. In the formula (A12-14), 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's are the same or different. From the viewpoint of liquid crystal alignment, preferably, the X ^13' independently represents hydrogen, a halogen, a methyl group or an ethyl group, and more preferably, the X ^13' independently represents hydrogen or a methyl group.

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

The other tetracarboxylic dianhydride compound (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 compound (a1-2) is 0 mol to 70 mol, preferably, the amount of the other tetracarboxylic dianhydride compound (a1-2) is 0 mol to 60 mol, and more preferably, the amount of the other tetracarboxylic dianhydride compound (a1-2) is 0 mol to 50 mol.

[Diamine component (b1)]

[Diamine compound (b1-1)]

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 the formula (A21-1), Y ²¹ represents a divalent organic group as shown in the formula (A21-3), and a plurality of Y ^22s each independently represent hydrogen or an alkyl group having a carbon number of 1 to 6. In the formula (A21-2), a plurality of Y ^23s each independently represent a divalent organic group as shown in the formula (A21-3'). Formula (A21-3) Formula (A21-3')

In the divalent organic group represented by the formula (A21-3), Ar independently represents a divalent benzene ring, a biphenyl structure or a naphthyl ring, and the hydrogen atom of the benzene ring, the biphenyl structure or the naphthyl ring may be substituted by a monovalent substituent group or may not be substituted; Y ^21' 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 the 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 ^23' 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 the formula (A21-3) and the divalent organic group represented by the 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.

In some embodiments of the present invention, from the perspective of improving the alignment of liquid crystals, preferably, the divalent organic group represented by formula (A21-3) is at least one of the groups represented by formula (A21-3-1) to formula (A21-3-16), wherein "*" represents the 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 the formula (A21-3-1), m is 0 to 1, and n is 1 to 6. In the formula (A21-3-2), n is 1 to 6. In the formula (A21-3-3), n is 2 to 6. In the formula (A21-3-4), n is 1 to 6. In the formula (A21-3-5), n is 1 to 6. In the formula (A21-3-6), n is 2 to 6. In the formula (A21-3-7), n is 1 to 6. In the formula (A21-3-8), n is 1 to 6. In the formula (A21-3-9), n is 2 to 6. In the formula (A21-3-10), m is 1 to 3, and n is 1 to 4. In the formula (A21-3-11), n is 1 to 6. In the formula (A21-3-12), n is 1 to 6. In the formula (A21-3-13), m is 0 to 1, and n is 1 to 6. In the formula (A21-3-14), m is 1 to 3, and n is 1 to 4.

In some embodiments of the present invention, from the perspective of improving the alignment of liquid crystals, preferably, the divalent organic group represented by formula (A21-3') is at least one of the groups represented by formulas (A21-3-7) to (A21-3-16).

When the diamine compound (b1-1) contains a diamine compound represented by a plurality of formulas (A21-1), preferably, the diamine compound represented by formula (A21-1) is a combination of a diamine compound represented by formula (A21-3-1) to formula (A21-3-14) in ^{which Y 21 in} formula (A21-1) represents a diamine compound represented by 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 the formula (A21-2-1), m is 1 to 6, and n is 1 to 6. In the formula (A21-2-2), m is 1 to 6, and n is 1 to 6. In the 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, the amount of the diamine compound (b1-1) used is 25 mol to 80 mol, and more preferably, the amount of the diamine compound (b1-1) used is 30 mol to 70 mol.

﹝Diamine compound (b1-2)﹞

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 voltage retention rate of the liquid crystal display element, 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 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 of the present invention, 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.

In some embodiments of the present invention, preferably, the diamine compound (b1-2) having a -N(D)- group comprises a diamine compound having at least one aromatic group (e.g., a benzene ring). More preferably, the diamine compound (b1-2) having a -N(D)- group comprises a diamine compound having at least one aromatic group and a carbon number of 6 to 30 in the residue other than the substituent (D). In some specific examples of the present invention, the diamine compound (b1-2) having a -N(D)- group is, for example but not limited to, a diamine compound as shown in 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 the formula (A22-1), n is 1 to 6. In the formula (A22-2), n is 1 to 6. In the formula (A22-4), m is 1 to 6, and n is 1 to 6. In the formula (A22-7), m is 1 to 6, and n is 1 to 6. In the 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 diamine compound (b1-2) having a group of -N(D)- is used in an amount of 2 to 60 mol, preferably, the diamine compound (b1-2) having a group of -N(D)- is used in an amount of 10 to 50 mol, and more preferably, the diamine compound (b1-2) having a group of -N(D)- is used in an amount of 15 to 40 mol.

﹝Other diamine compounds (b1-3)﹞

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

The diamine compound having a carboxyl group may be, 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 (A23-7). Formula (A23-4), Formula (A23-5), Formula (A23-6), Formula (A23-7)

In the formula (A23-4), ^Y31 represents a single bond, _-CH2- , _-C2H4- , -C( _CH3 ) _2- , _-CF2- , -C( _CF3 ) _2- , -O-, -CO-, -NH-, -N(CH3)-, -CONH-, -NHCO-, -CH2O- _{, -OCH2- ,} -COO-, -OCO-, -CON( _CH3 )- or -N( _CH3 )CO-; m1 and m2 each independently represent an integer _of 0 to 4, and (m1+m2) represents an integer of 1 to 4. In the formula (A23-5), m3 and m4 each independently represent an integer of 1 to 5. In the formula (A23-6), ^Y32 represents a linear or branched alkyl group having 1 to 5 carbon atoms; m5 represents an integer from 1 to 5. In the formula (A23-7), ^Y33 and ^Y34 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 includes, but is not limited to, diamine compounds represented by formula (A23-8) to formula (A23-10). Formula (A23-8), Formula (A23-9), Formula (A23-10)

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

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

In the formula (A23-12), n is 1 to 6. In the 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 includes, but is not limited to, 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, the amount of the other diamine compound (b1-3) is 0 mol to 50 mol, and more preferably, the amount of the other diamine compound (b1-3) is 0 mol to 35 mol.

<Second polymer (A2)>

The second polymer (A2) is at least one selected from the group consisting of a polyimide precursor and an imidized polymer formed from the polyimide precursor. The polyimide precursor of the second polymer (A2) comprises a structure represented by formula (II). Formula (II)

In the formula (II), ^V1 represents the structure represented by the formula (II-1), wherein "*" represents the bonding position, ^V2 represents hydrogen or an alkyl group having 1 to 4 carbon atoms, ^V3 represents hydrogen or an alkyl group having 1 to 4 carbon atoms, and ^W1 represents the structure represented by the formula (II-2). Formula (II-1) Formula (II-2)

In the formula (II-2), at least two of ^R1 to ^R10 are "*" representing a bonding position, and the rest are H or a monovalent organic group.

In some embodiments of the present invention, the polyimide precursor of the second polymer (A2) is formed by reacting a reaction composition comprising a tetracarboxylic dianhydride component (a2) and a diamine component (b2), wherein the tetracarboxylic dianhydride component (a2) comprises V ¹ in the structure represented by formula (II), and the diamine component (b2) comprises W ¹ in the structure represented by formula (II).

[Tetracarboxylic dianhydride component (a2)]

[Tetracarboxylic dianhydride compound (a2-1)]

In some embodiments of the present invention, the tetracarboxylic dianhydride component (a2) comprises a tetracarboxylic dianhydride compound (a2-1) having a structure represented by formula (A12) and X ^1′ having a structure represented by formula (II-1). Formula (A12) Formula (II-1)

In the formula (II-1), "*" represents a bonding position.

In some embodiments of the present invention, based on the total usage of the tetracarboxylic dianhydride component (a2) being 100 mol, the usage of the tetracarboxylic dianhydride compound (a2-1) is 50 mol to 100 mol, preferably, the usage of the tetracarboxylic dianhydride compound (a2-1) is 60 mol to 100 mol, and more preferably, the usage of the tetracarboxylic dianhydride compound (a2-1) is 70 mol to 100 mol.

When the tetracarboxylic dianhydride component (a2) does not contain the tetracarboxylic dianhydride compound (a2-1), the liquid crystal display element including the liquid crystal alignment film formed by the liquid crystal alignment agent used in the photo-alignment method has a high flicker after being driven by a high voltage.

[Diamine component (b2)]

The diamine component (b2) is, for example but not limited to, the diamine component (b1) of the first polymer (A1), a diamine compound (b2-1) or a diamine compound (b2-2) having a nitrogen atom-containing structure. The diamine component (b2) can be used alone or in combination of two or more.

[Diamine compound (b2-1)]

In some embodiments of the present invention, the diamine component (b2) comprises a diamine compound (b2-1) having a structure as shown in formula (II-2). Formula (II-2)

In the formula (II-2), two of R ¹ to R ¹⁰ are -NH ₂ , and the rest are hydrogen or a monovalent organic group other than -NH ₂ , and they are the same or different.

In some embodiments of the present invention, the diamine compound (b2-1) is, for example but not limited to, a diamine compound having a structure as shown in formula (III) or a diamine compound having a structure as shown in formula (IV). Formula (III) Formula (IV)

In some embodiments of the present invention, in the formula (III) and the formula (IV), the hydrogen on the benzene ring may also be replaced by a monovalent organic group other than -NH _2. The monovalent organic group other than -NH ₂ is, for example but not limited to, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, a cycloalkyl group, a phenyl group, a biphenyl group, a terphenyl group, a fluorine group, or an organic group formed by any combination thereof.

In some embodiments of the present invention, based on the viewpoint of improving the alignment of liquid crystal, preferably, the diamine compound (b2-1) is selected from 4,4'-diaminodiphenylamine and 2,4-diaminodiphenylamine, and more preferably, the diamine compound (b2-1) is 4,4'-diaminodiphenylamine.

In some embodiments of the present invention, based on the total usage of the diamine component (b2) being 100 mol, the usage of the diamine compound (b2-1) is 50 mol to 100 mol, preferably, the usage of the diamine compound (b2-1) is 60 mol to 100 mol, and more preferably, the usage of the diamine compound (b2-1) is 70 mol to 100 mol.

When the diamine component (b2) does not contain the diamine compound (b2-1), the liquid crystal display element including the liquid crystal alignment film formed by the liquid crystal alignment agent for the photo-alignment method has a high flicker after being driven by a high voltage.

[Diamine compound having a nitrogen atom-containing structure (b2-2)]

The nitrogen-containing atom structure in the diamine compound (b2-2) having a nitrogen-containing atom structure is at least one selected from the group consisting of a nitrogen-containing heterocyclic ring, a diamine group, and a tertiary amine group, and the diamine component (b2-2) does not contain the diamine compound (b2-1).

The nitrogen-containing heterocyclic ring of the diamine compound (b2-2) 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.

In some embodiments of the present invention, the nitrogen-containing atom structure in the diamine compound (b2-2) having a nitrogen-containing atom structure is a diamine group and a tertiary amine group represented by formula (B21). Formula (B21)

In the 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.

In some embodiments of the present invention, the diamine compound (b2-2) 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 (B21-7), or diamine compounds represented by formula (B21-8) to (B21-25). 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)

In the formula (B21-4), n represents 1 to 4. In the formula (B21-5), n represents 1 to 4. The diamine compound (b2-2) having a nitrogen atom-containing structure may be used alone or in combination of two or more.

In some embodiments of the present invention, based on the total amount of the diamine component (b2) being 100 mols, the usage amount of the diamine compound having a nitrogen atom structure (b2-2) is 0 mol to 90 mols, preferably, the usage amount of the diamine compound having a nitrogen atom structure (b2-2) is 10 mol to 85 mols, and more preferably, the usage amount of the diamine compound having a nitrogen atom structure (b2-2) is 20 mol to 80 mols.

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 first polymer (A1) used is 5 parts by weight to 85 parts by weight, preferably, the amount of the first polymer (A1) used is 10 parts by weight to 80 parts by weight, and more preferably, the amount of the first polymer (A1) used is 10 parts by weight to 75 parts by weight; the amount of the second polymer (A2) used is 15 parts by weight to 95 parts by weight, preferably, the amount of the second polymer (A2) used is 20 parts by weight to 90 parts by weight, and more preferably, the amount of the second polymer (A2) used is 25 parts by weight to 90 parts by weight. When the amounts of the first polymer (A1) and the second polymer (A2) used are both within the above range, the liquid crystal display element comprising the liquid crystal alignment film formed by the liquid crystal alignment agent used in the photoalignment method has a lower flicker after high voltage driving.

<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 tetracarboxylic dianhydride component and diamine 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 and the diamine component are reacted 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 represented by formula (D-1) to formula (D-3). Formula (D-1), Formula (D-2), Formula (D-3)

In the formula (D-1), Z ¹ represents an alkyl group having 1 to 3 carbon atoms. In the formula (D-2), Z ² represents an alkyl group having 1 to 3 carbon atoms. In the 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 total concentration of the diamine component and the tetracarboxylic dianhydride component is 1wt% to 50wt%, and more preferably, the total concentration of the diamine component and the tetracarboxylic dianhydride component is 5wt% to 30wt%. The reaction can also be carried out at a high concentration at the beginning, 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 for the photo-alignment method 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 rate (also called the imidization rate) of the functional group possessed by the acylamidate group or its derivative is not necessarily 100%, and the imidization rate 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, direct heating of a solution containing a polymer having an amide structure by thermal imidization, or catalytic imidization by adding a catalyst to the solution containing a polymer having an amide structure. When thermal imidization is performed in the solution containing a polymer having an amide structure, the temperature is preferably 100° C. to 400° C., more preferably 120° C. to 250° C. When thermal imidization is performed, water generated by the imidization reaction is preferably discharged out of the system.

The catalytic imidization is performed, for example, by adding an alkaline catalyst and an acid anhydride to the solution containing the polymer having an acylamidate structure, preferably stirring at -20°C to 250°C, more preferably stirring 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 acylamidate group, more preferably, the amount of the alkaline catalyst added is 2 to 20 times the molar equivalent of the acylamidate group. Preferably, the amount of the acid anhydride added is 1 to 50 times the molar equivalent of the acylamidate group, more preferably, the amount of the acid anhydride added is 3 to 30 times the molar equivalent of the acylamidate group. The alkaline catalyst includes, but is not limited to, pyridine, triethylamine, trimethylamine, tributylamine, or trioctylamine. Pyridine is preferred because it has a moderate alkalinity that allows the reaction to proceed. The acid anhydride includes, but is not limited to, acetic anhydride, trimellitic anhydride, or pyromellitic anhydride. When acetic anhydride is used, purification after the reaction is easier, so it is preferred. The imidization rate of the catalytic imidization can be controlled by adjusting the amount of the catalyst, the reaction temperature, and/or the 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 a solution containing the first polymer (A1) or the second polymer (A2) at a concentration of 10 wt% to 15 wt% is prepared, 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, 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 containing the polymer at a concentration of 10 wt% to 15 wt%, and using an E-type rotational viscometer.

In some embodiments of the present invention, 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 weight average molecular weight and the number average molecular weight of the polymer are within the above molecular weight range, good orientation and stability of the liquid crystal display element can be ensured.

In some embodiments of the present invention, 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, the end-capping agent is used in an amount of 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 thin 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 used in the optical alignment method 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 used in the optical alignment method 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 used in the optical alignment method 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 used in the optical alignment method 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 used in the photo-alignment method 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, the content of the polymer component (A) is 2wt% to 10wt%, and more preferably, the content of the polymer component (A) is 3wt% to 8wt%.

The solvent (B) is, for example, an organic solvent, and there is no particular limitation on the solvent (B), as long as it can 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, 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, the total amount of the solvent (B) in the liquid crystal alignment agent used in the photo-alignment method is 100wt%, the usage amount of the good solvent is 20wt% to 99wt%, preferably, the usage amount of the good solvent is 20wt% to 90wt%, and more preferably, the usage amount of the good solvent is 30wt% to 80wt%.

In some embodiments of the present invention, preferably, the solvent (B) 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. Preferably, based on the total amount of the solvent (B) being 100wt%, the usage amount of the poor solvent is 1wt% to 80wt%, more preferably, the usage amount of the poor solvent is 10wt% to 80wt%, and particularly preferably, the usage amount of the poor solvent is 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.

In some embodiments of the present invention, preferably, the solvent combination of the good solvent and the poor solvent is, for example but not limited to, N-methyl-2-pyrrolidone and ethylene glycol monobutyl ether; N-methyl-2-pyrrolidone, γ-butyrolactone and ethylene glycol monobutyl ether; N-methyl-2-pyrrolidone, γ-butyrolactone and propylene glycol monobutyl ether; N-ethyl-2-pyrrolidone and propylene glycol monobutyl ether; N-ethyl-2-pyrrolidone and 4-hydroxy-4-methyl-2-pentanone; N-ethyl-2-pyrrolidone and propylene glycol diacetate; N,N-dimethyl lactamide and diisobutyl ketone; N-methyl-2-pyrrolidone and ethyl 3-ethoxypropionate; N-ethyl-2-pyrrolidone and ethyl 3-ethoxypropionate; -Methyl-2-pyrrolidone and ethylene 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 Lactone and propylene 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 100 parts by weight of the total amount of the polymer component (A), the amount of the solvent (B) used is 800 to 4000 parts by weight, preferably 900 to 3500 parts by weight, and more preferably 1000 to 3000 parts by weight.

《Additives (C)》

In some embodiments of the present invention, the liquid crystal alignment agent used in the photo-alignment method of the present invention further comprises an additive (C). The additive (C) includes, but is not limited to, a bonding aid for improving the adhesion between the liquid crystal alignment film and the substrate or the adhesion between the liquid crystal alignment film and the sealant, a cross-linking compound for improving the strength of the liquid crystal alignment film, a compound for promoting imidization, a dielectric or conductive substance for adjusting the dielectric constant or resistance of the liquid crystal alignment film, and the like.

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 the adhesion aid is used, from the viewpoint of exhibiting good resistance to AC afterimage, preferably, the adhesion aid is used in an amount of 0.1 to 30 parts by weight relative to 100 parts by weight of the total amount of the polymer component (A), and more preferably, the adhesion aid is used in an amount of 0.1 to 20 parts by weight.

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 the formula (E1), ^G1 and ^G2 each independently represent hydrogen, an alkyl group having 1 to 3 carbon atoms, or -CH2 _- OH. In the 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, and ^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 the formula (E3), ^G5 represents an (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 the 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 in which an aromatic hydrocarbon group having 6 to 30 carbon atoms is directly or indirectly bonded to 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 the 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 may be, 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 as shown in Formula (E4) to Formula (E6), etc. Formula (E4), Formula (E5), Formula (E6)

The compound having an propylene oxide group includes, but is not limited to, 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 the formula (E7), n represents 1 to 3. In the formula (E13), n represents 1 to 3. In the formula (E14), n represents 1 to 100. In the formula (E15), R represents , wherein "*" represents a bonding position. In the 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) includes, but is not limited to, compounds represented by formula (E2-1) to formula (E2-4). Formula (E2-1), Formula (E2-2), Formula (E2-3), Formula (E2-4)

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

The compound having the group represented by formula (E3) includes, but is not limited to, 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 some embodiments of the present invention, preferably, based on the total amount of the polymer component (A) 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.

In some embodiments of the present invention, the compound used to promote 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 above-mentioned cross-linking compound and adhesion promoter), or a compound that generates the basic site when calcined. More preferably, the compound used to promote 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 is a protected amino acid. 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 formation of an imidized compound, more preferably, a specific example of the compound for promoting imidization can be exemplified by 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 liquid crystal alignment agent used in the above-mentioned photo-alignment method. The liquid crystal alignment film of the present invention can be used as a liquid crystal alignment film of a horizontal alignment type or a vertical alignment type (VA type), and is suitable for a liquid crystal alignment film of a horizontal alignment type liquid crystal display element such as an IPS mode or a FFS mode. 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 for the optical alignment method 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, and it only needs to be a highly transparent substrate. A glass substrate or a silicon nitride substrate can also 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 it is only a single-sided substrate, 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 or FFS type liquid crystal display element, the comb-tooth type uses an electrode substrate composed of a patterned transparent conductive film or metal film and an opposing substrate without an electrode.

The method of coating the liquid crystal alignment agent for the photo-alignment method 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 step and calcining step performed after the liquid crystal alignment agent for the photoalignment method of the present invention has been coated can be selected at any temperature and time, and multiple drying steps or calcining steps can be performed. The temperature of the drying step can be, for example, 40°C to 180°C. Based on the viewpoint of shortening the process, the drying step can be performed at 40°C to 150°C. The time of the drying step is not particularly limited, and it can be, for example, 1 minute to 10 minutes or 1 minute to 5 minutes. When thermal imidization of polyamine acid or polyamine ester is performed, after the drying step, a calcination step can be further performed at a temperature of, for example, 150°C to 300°C or 150°C to 250°C. The time of the calcination step is not particularly limited, and it can be, for example, 5 minutes to 40 minutes or 5 minutes to 30 minutes. When the thickness of 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, and more preferably, the thickness of the film is 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 a horizontal alignment type liquid crystal display element such as the IPS mode or the FFS mode, the film is subjected to an alignment treatment to give it an alignment capability. On the other hand, in a vertical alignment type liquid crystal display element such as the VA mode or the PSA mode, the formed film can be directly used as a liquid crystal alignment film, but the film can also be subjected to an alignment treatment to give it an alignment capability. The alignment treatment of the liquid crystal alignment film can be a friction treatment method or a photo alignment treatment method. Preferably, the alignment treatment of the liquid crystal alignment film is a photo alignment treatment method. The photo-alignment treatment method can be listed as a method of irradiating the surface of the film-like object with radiation that has been deflected in a certain direction, and preferably heating it at a temperature of 150° C. to 250° C. to give liquid crystal alignment (also called 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, the radiation is ultraviolet light with a wavelength of 200nm to 400nm.

The radiation dose 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 irradiation dose for the alignment treatment is 100mJ/ ^cm2 to 5000mJ/ ^cm2 , but the liquid crystal alignment agent used in the photo-alignment method of the present invention can 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 irradiation dose for the alignment treatment is reduced. When irradiating the 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 made 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 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, the solvent is preferably water, 2-propanol, 1-methoxy-2-propanol or ethyl lactate, and more preferably, water, 1-methoxy-2-propanol or ethyl lactate. The solvent can be used alone or in combination.

In some embodiments of the present invention, preferably, the temperature of the heat treatment on the film irradiated with radiation is 50° C. to 300° C., more preferably, the temperature of the heat treatment is 120° C. to 250° C. Preferably, the heat treatment time is 1 minute to 30 minutes.

Step (4): Making liquid crystal cells

Two substrates with liquid crystal alignment films formed on the surfaces are prepared, and liquid crystal is arranged between the two substrates facing each other. For example, the following two methods can be listed. The first method is to first arrange the two substrates 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 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 having a liquid crystal alignment film formed on the surface, and then a liquid crystal composition is dropped 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 onto the entire surface of the liquid crystal alignment film so that it contacts the film surface of the other liquid crystal alignment film. Then, ultraviolet light is irradiated onto the entire surface of the substrate to cure the sealant. When performing any of the above methods, 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 film is subjected to rubbing treatment, the two substrates are arranged to face each other at a predetermined angle with respect to the rubbing directions of the films, for example, 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 may be, for example, a nematic liquid crystal or a lamellar liquid crystal. Preferably, the liquid crystal composition is a 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)

A nitrogen inlet, a stirrer, a condenser and a thermometer were installed on a 500 ml four-necked conical flask, and nitrogen was introduced. Then, 0.035 mol (70 mol%) of compound b1-1-1, 0.01 mol (20 mol%) of compound b1-2-1, 0.005 mol (10 mol%) of compound b1-3-1 and 80 g of N-methyl-2-pyrrolidone were added, and stirred at room temperature until dissolved. Then, 0.05 mol (100 mol%) of compound a1-1-1 and 20 g of N-methyl-2-pyrrolidone were added, and reacted at room temperature for 2 hours to obtain a reaction solution. The reaction solution was poured into 1500 ml of water to precipitate a polymer, and then filtered to obtain a filter cake. The filter cake was then washed with methanol and filtered again. The filter cake was washed with methanol and filtered three times to obtain a crude product. The crude product was then placed in a vacuum oven and dried at 60° C. to obtain a first polymer (A1).

[Preparation Examples 2 to 6] First polymer (A1)

Preparation Examples 2 to 6 are used to prepare the first polymer (A1) in a similar manner to Preparation Example 1, except that the types and amounts of the tetracarboxylic dianhydride component (a1) and the diamine component (b1) are changed in Preparation Examples 2 to 6, as shown in Table 1.

Table 1 Unit: mole% Preparation example 1 2 3 4 5 6 Tetracarboxylic dianhydride component (a1) a1-1-1 100 100 100 95 90 90 a1-2-1 -- -- -- 5 -- -- a1-2-2 -- -- -- -- 10 -- a1-2-3 -- -- -- -- -- 10 Diamine component (b1) b1-1-1 70 -- -- 70 -- 70 b1-1-2 -- 70 60 -- 70 -- b1-2-1 20 -- -- 20 -- 20 b1-2-2 -- 20 20 -- 20 -- b1-3-1 10 10 10 10 10 10 b1-3-2 -- -- 10 -- -- -- Note: "--" means not added. a1-1-1: a1-2-1: a1-2-2: a1-2-3: b1-1-1: b1-1-2: b1-2-1: b1-2-2: b1-3-1: b1-3-2:

[Preparation Example 7] Second polymer (A2)

A nitrogen inlet, a stirrer, a condenser and a thermometer were installed on a 500 ml four-necked conical flask, and nitrogen was introduced. Then, 0.05 mol (100 mol%) of compound b2-1-1 and 80 g of N-methyl-2-pyrrolidone were added, and stirred at room temperature until dissolved. Next, 0.05 mol (100 mol%) of compound a2-1-1 and 20 g of N-methyl-2-pyrrolidone were added, and the mixture was reacted at room temperature for 2 hours to obtain a reaction solution. The reaction solution was poured into 1500 ml of water to precipitate a polymer, and then filtered to obtain a filter cake. The filter cake was then washed with methanol and filtered again. The filter cake was washed with methanol and filtered three times to obtain a crude product. The crude product was then placed in a vacuum oven and dried at 60° C. to obtain a second polymer (A2).

[Preparation Examples 8 to 11 and Comparative Preparation Examples 1 to 3] Second polymer (A2)

Preparation Examples 8 to 11 and Comparative Preparation Examples 1 to 3 are used to prepare the second polymer (A2) by a method similar to that of Preparation Example 7, except that the types and amounts of the tetracarboxylic dianhydride component (a2) and the diamine component (b2) are changed in Preparation Examples 8 to 11 and Comparative Preparation Examples 1 to 3, as shown in Table 2.

Table 2 Unit: mole% Preparation example Comparison of preparation examples 7 8 9 10 11 1 2 3 Tetracarboxylic dianhydride component (a2) a2-1-1 100 100 100 100 80 -- 100 -- a2-a -- -- -- -- -- 100 -- -- a2-b -- -- -- -- 20 -- -- 100 Diamine component (b2) b2-1-1 100 70 -- 80 100 100 -- -- b2-1-2 -- -- 100 -- -- -- -- -- b2-a -- -- -- 20 -- -- -- 100 b2-b -- 30 -- -- -- -- 100 -- b2-c -- -- -- -- -- -- -- -- Note: "--" means not added. a2-1-1: a2-a: a2-b: b2-1-1: b2-1-2: b2-a: b2-b: b2-c:

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

90 parts by weight of the first polymer (A1) of Preparation Example 1, 10 parts by weight of the second polymer (A2) of Preparation Example 7 and 1200 parts by weight of N-methyl-2-pyrrolidone [as a solvent (B)] were stirred and mixed at room temperature to obtain a liquid crystal alignment agent for photoalignment method.

The liquid crystal alignment agent used in the photo-alignment method is applied on the pixel electrode of a glass substrate including the 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 for the photo-alignment method was placed on a heating plate at 80°C for 3 minutes to dry, and then baked in a hot air circulation oven at 250°C for 30 minutes, so that the liquid crystal alignment agent for the photo-alignment method formed a film with a thickness of 100 nm on the glass substrate. The 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, so that the film formed a liquid crystal alignment film, and a first laminate including the liquid crystal alignment film was obtained.

The liquid crystal alignment agent for the photo-alignment method is applied by rotational 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 for the photo-alignment method is placed on a heating plate at 80° C. for drying for 3 minutes, and then baked in a hot air circulation oven at 250° C. for 30 minutes, so that the liquid crystal alignment agent for the photo-alignment method forms a film with a thickness of 100 nm on the glass substrate. The film is 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, so that the film forms a liquid crystal alignment film, and a second laminate including the liquid crystal alignment film is obtained.

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 display element.

[Examples 2 to 6 and Comparative Examples 1 to 3] Liquid crystal alignment agent, liquid crystal alignment film and liquid crystal display element for optical alignment method

Examples 2 to 6 and Comparative Examples 1 to 3 are used to obtain a liquid crystal alignment agent, a liquid crystal alignment film and a liquid crystal display element for the photo-alignment method by a method similar to that of Example 1, with the difference being that Examples 2 to 6 and Comparative Examples 1 to 3 change the type and/or amount of the first polymer (A1), the second polymer (A2) and the solvent (B) in the liquid crystal alignment agent for the photo-alignment method, as shown in Table 3.

[Evaluation Items]

The following description takes the liquid crystal display element of Example 1 as an example, and the liquid crystal display elements of other Examples 2 to 6 and Comparative Examples 1 to 3 are carried out in the same manner.

Flicker after high voltage driving: The liquid crystal display element of Example 1 is placed between two polarizing plates whose polarization axes are arranged in a vertically crossed manner, and the LED backlight source is lit without applying voltage. The configuration angle of the liquid crystal display element of Example 1 is adjusted so that the brightness of the light penetrating the liquid crystal display element of Example 1 reaches the minimum state. Then, an alternating voltage with a frequency of 30 Hz is applied to the liquid crystal display element of Example 1, and the V-T curve (voltage-transmittance curve) is measured at the same time, and then an alternating voltage with a relative transmittance of 23% is calculated as the driving voltage.

Then, under the temperature condition that the temperature of the liquid crystal display element of the embodiment 1 is 23°C, the LED backlight source that has been turned on is turned off, and after being placed in a light-shielded state for 72 hours, the LED backlight source is turned on again, and at the same time when the LED backlight source is turned on, an AC voltage with a relative transmittance of 100% and a frequency of 30 Hz is applied to the liquid crystal display element of the embodiment 1, and after the liquid crystal display element of the embodiment 1 is driven for 24 hours, an AC voltage with a relative transmittance of 23% and a frequency of 30 Hz is applied to the liquid crystal display element of the embodiment 1, and a data acquisition/data recording switching device 34970A (Agilent) connected to a photodiode and an I-V conversion amplifier is used. technologies) tracks the flicker amplitude of the liquid crystal display element of Example 1 and reads the brightness value of the liquid crystal display element of Example 1 through two polarizing plates. The flicker degree of the liquid crystal display element of Example 1 is calculated according to the following formula using the flicker amplitude and the brightness value. Flicker degree (%) = [flicker amplitude/(2×brightness value)]×100%

The lower the flicker, the better the quality of the LCD. The flicker criteria are as follows: ◎ means flicker < 3%, ○ means 4% > flicker ≧ 3%, △ means 5% > flicker ≧ 4%, ╳: flicker ≧ 5%.

Table 3 Unit: Weight Embodiment Comparison Example 1 2 3 4 5 6 1 2 3 First polymer (A1) Preparation example 1 90 -- -- -- -- -- 80 -- -- 2 -- 30 -- -- -- -- -- 80 -- 3 -- -- 50 -- -- -- -- -- 80 4 -- -- -- 30 -- -- -- -- -- 5 -- -- -- -- -- 85 -- -- -- 6 -- -- -- -- 80 -- -- -- -- Second polymer (A2) Preparation example 7 10 -- -- -- 20 -- -- -- -- 8 -- 70 -- -- -- -- -- -- -- 9 -- -- 50 -- -- -- -- -- -- 10 -- -- -- 70 -- -- -- -- -- 11 -- -- -- -- -- 15 -- -- -- Comparison of preparation examples 1 -- -- -- -- -- -- 20 -- -- 2 -- -- -- -- -- -- -- 20 -- 3 -- -- -- -- -- -- -- -- 20 Solvent (B) B-1 1200 -- 1200 1200 1200 1200 1200 -- 1200 B-2 -- 1200 -- -- -- -- -- 1200 -- Flicker after high voltage drive ○ ◎ ◎ ◎ ◎ ◎ ╳ ╳ ╳ Note: "--" means no addition. B-1: N-methyl-2-pyrrolidone B-2: N-ethyl-2-pyrrolidone

Referring to Table 3, the liquid crystal alignment agent used in the photo-alignment method of Examples 1 to 6 is prepared using the first polymer (A1) of Preparation Examples 1 to 6 and the second polymer (A2) of Preparation Examples 7 to 11, and in particular, the second polymer (A2) of Preparation Examples 7 to 11 is prepared by the tetracarboxylic dianhydride component (a2) containing the tetracarboxylic dianhydride compound (a2-1) and the diamine component (b2) containing the diamine compound (b2-1). Therefore, the liquid crystal alignment film formed by the liquid crystal alignment agent used in the photo-alignment method of Examples 1 to 6 can give the liquid crystal display element a flicker degree after high-voltage driving of less than 4%, indicating that the liquid crystal display element of Examples 1 to 6 is not prone to flicker after high-voltage driving.

In contrast, in Comparative Examples 1 to 3, the liquid crystal alignment agents for the photo-alignment method of Comparative Examples 1 to 3 are prepared using the first polymers (A1) of Preparation Examples 1 to 6 and the second polymers (A2) of Comparative Examples 1 to 3, wherein the tetracarboxylic dianhydride component (a2) used in the second polymer (A2) of Comparative Example 1 does not contain the tetracarboxylic dianhydride compound (a2-1); the diamine component (b2) used in the second polymer (A2) of Comparative Example 2 does not contain the diamine compound (b2-1); the tetracarboxylic dianhydride component (a2) used in the second polymer (A2) of Comparative Example 3 does not contain the tetracarboxylic dianhydride compound (a2-1), and the diamine component (b2) does not contain the diamine compound (b2-1), so the flicker degree of the liquid crystal display elements of Comparative Examples 1 to 3 after high-voltage driving is greater than 5%, indicating that the liquid crystal display elements of Comparative Examples 1 to 3 are prone to flicker after high-voltage driving.

In summary, by using the second polymer (A2) prepared by the polyimide precursor having the structure shown in formula (II), the liquid crystal alignment film formed by the liquid crystal alignment agent used in the optical alignment method of the present invention can give the liquid crystal display element a low flicker degree after high-voltage driving. Therefore, the liquid crystal display element including the liquid crystal alignment film is not prone to flicker after high-voltage driving, so the purpose of the present invention can be achieved.

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 for photo-alignment method, comprising: a polymer component (A), including a first polymer (A1) and a second polymer (A2), wherein the first polymer (A1) 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 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. Based on the total amount of the polymer component (A) being 100 parts by weight, the usage amount of the first polymer (A1) is 5 parts by weight to 90 parts by weight, and the usage amount of the second polymer (A2) is 10 parts by weight to 95 parts by weight; and a solvent (B); wherein the polyimide precursor of the first polymer (A1) comprises a structure represented by formula (I),

^X1 represents at least one of the group consisting of the structures represented by formula (I-1) to formula (I-7), wherein "*" represents a bonding position,

^X11 , ^X12 , ^X13 and ^X14 independently represent 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 having 1 to 6 carbon atoms and containing fluorine, or a phenyl group; ^X15 and ^X16 independently represent hydrogen or a methyl group; ^X2 represents hydrogen or an alkyl group having 1 to 4 carbon atoms; ^X3 represents hydrogen or an alkyl group having 1 to 4 carbon atoms; and ^Y1 represents a divalent organic group; the polyimide precursor of the second polymer (A2) comprises a structure represented by formula (II),

V ¹ represents the structure represented by formula (II-1), wherein "*" represents the bonding position,

^V2 represents hydrogen or an alkyl group having 1 to 4 carbon atoms, ^V3 represents hydrogen or an alkyl group having 1 to 4 carbon atoms, ^W1 represents a structure represented by formula (II-2),

In the formula (II-2), at least two of ^R1 to ^R10 are "*" representing a bonding position, and the rest are H or a monovalent organic group. The liquid crystal alignment agent for photo-alignment method as described in claim 1, wherein the structure represented by formula (I-1) of ^X1 is selected from the structures represented by formula (I-1-1) to formula (I-1-6),

The liquid crystal alignment agent for photo-alignment method as claimed in claim 1, wherein the structure represented by formula (I-1) of ^X1 is selected from the structure represented by formula (I-1-1),

The liquid crystal alignment agent for photo-alignment method as described in claim 1, wherein the polyimide precursor of the second polymer (A2) is formed by reacting a reaction composition comprising a tetracarboxylic dianhydride component (a2) and a diamine component (b2), and the tetracarboxylic dianhydride component (a2) comprises V ¹ in the structure represented by formula (II), and the diamine component (b2) comprises W ¹ in the structure represented by formula (II). A liquid crystal alignment film is formed by a liquid crystal alignment agent used in a photoalignment method 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.