TWI892269B - Liquid crystal alignment agent for photo-alignment, liquid crystal alignment film and liquid crystal display element - Google Patents

Abstract

The present invention provides a liquid crystal alignment agent for photo-alignment which can lower rate of luminace change after operating, a liquid crystal alignment film formed from the liquid crystal alignment agent, and a liquid crystal display element including the liquid crystal alignment film. The liquid crystal alignment agent comprises a polymer (A) having a specific structure and a solvent (C).

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 for photo-alignment method, and in particular to a liquid crystal alignment agent for photo-alignment method capable of reducing the brightness variation rate after driving, a liquid crystal alignment film formed using the liquid crystal alignment agent, and a liquid crystal display device including the liquid crystal alignment film.

Liquid crystal display units are widely used as display components for personal computers, smart phones, portable phones, and television sets. Liquid crystal display units may include, for example, a liquid crystal layer sandwiched between a device substrate and a color filter substrate, pixel electrodes and a common electrode for applying an electric field to the liquid crystal layer, an alignment film for controlling the alignment of the liquid crystal molecules in the liquid crystal layer, and thin-film transistors (TFTs) for switching the electronic signals supplied to the pixel electrodes. As for the driving methods of liquid crystal molecules, there are known longitudinal electric field methods such as the TN (Twisted Nematic) method and the VA (Vertical Alignment) method, and transverse electric field methods such as the IPS (In-Plane Switching) method and the FFS (Fringe Field Switching) method.

Currently, the most popular liquid crystal alignment film in the industry is made by rubbing the surface of a film composed of polyamide and/or polyimide obtained by imidization, which has been formed on an electrode substrate, in one direction using a cloth such as cotton, nylon or polyester. Rubbing treatment is a simple and highly productive industrial method. However, with the increasing performance, precision and size of liquid crystal display devices, the surface of the alignment film is scratched by dust, mechanical force and static electricity generated by the friction treatment, which in turn leads to various problems such as unevenness within the alignment treatment surface. As an alignment treatment method that replaces friction treatment, a photoalignment method is known that imparts alignment ability to liquid crystals by irradiating them with polarized radiation. Regarding the photoalignment method, Japanese Patent Laid-Open No. 9-297313 discloses the use of a photoisomerization reaction, a photocrosslinking reaction, or a photodecomposition reaction.

However, liquid crystal display cells containing conventional liquid crystal alignment films produced using the photo-alignment method still have poor brightness change rates after driving and cannot meet application requirements.

In view of this, one aspect of the present invention is to provide a liquid crystal alignment agent for photo-alignment method, which comprises a polymer (A) and a solvent (C). The liquid crystal alignment film formed by using this liquid crystal alignment agent can reduce the brightness change rate of the liquid crystal display unit after driving.

Another aspect of the present invention is to provide a liquid crystal alignment film formed using the liquid crystal alignment agent used in the above-mentioned photo-alignment method.

Another aspect of the present invention is to provide a liquid crystal display element comprising the aforementioned liquid crystal alignment film and having a low brightness change rate after driving.

According to the aforementioned aspects of the present invention, a liquid crystal alignment agent for photo-alignment methods is provided, comprising a polymer (A) and a solvent (C). In addition to polymer (A), the liquid crystal alignment agent for photo-alignment methods of the present invention may also optionally comprise a polymer (B). This is described below.

Polymer (A)

The polymer (A) of the present invention can be at least one polymer selected from the group consisting of polyimide precursors obtained by reacting a tetracarboxylic dianhydride component (a1) with a diamine component (a2), and imidized polymers of polyimide precursors. For example, polymer (A) can include a polyimide precursor having an imide precursor structure such as polyamic acid and polyamic acid ester, and/or an imidized product of such a polyimide precursor (i.e., a polyimide).

The polyimide precursor of polymer (A) may include structures represented by the following formulas (I) and (II). (I) (II)

In formula (I), _X1 represents a structure shown in formula (I-1) below; _X2 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; _A1 and _A2 represent divalent aromatic ring groups, and the ring moieties may have substituents, wherein _A1 and _A2 are the same; _Y11 represents , and R ₁ represents a group that is thermally dissociated; Y ₁₂ represents a single bond, an oxygen atom, or a sulfur atom; Z ₁ represents a divalent organic group having at least one of a chain hydrocarbon structure and an alicyclic hydrocarbon structure and having a carbon number of 1 to 15, wherein when Y ₁₂ represents a sulfur atom, the carbon number of the divalent organic group represented by Z ₁ is not less than 2. (I-1)

In Formula (I-1), X ₁₁ , X ₁₂ , X ₁₃ , and X ₁₄ each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, a monovalent organic group having 1 to 6 carbon atoms and containing a fluorine atom, or a phenyl group. X ₁₁ to X ₁₄ may be the same or different, and at least one of X ₁₁ , X ₁₂ , X ₁₃ , and X ₁₄ is not a hydrogen atom. In some embodiments, X ₁ represents the structure shown in Formula (I-1-1). (I-1-1)

In some embodiments, _A1 and _A2 in formula (I) may represent a divalent group formed by removing two hydrogen atoms from a ring portion of a benzene ring, a pyridine ring, or a pyrimidine ring, wherein the ring portion may have a substituent, and _A1 and _A2 are the same; and _Z1 represents , and n represents an integer from 1 to 5.

In formula (II), _X1 and _X2 are as defined above; _Y21 represents a single bond, -O-, -S-, -SS-, _-SO2- , -CO-, 、 , -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -(CH ₂ ) _m -, -O-(CH ₂ ) _m -O-, or -S-(CH ₂ ) _m -S-, wherein m represents an integer from 1 to 12; Y ₂₂ represents a single bond, -O-, -S-, -CO-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, or an alkylene group having 1 to 10 carbon atoms.

In some embodiments, Y ₂₁ and Y ₂₂ in formula (II) can each independently represent —O— or —S—.

If the polymer (A) does not contain the structures shown in formula (I) and formula (II), the liquid crystal alignment film formed by the liquid crystal alignment agent has a poor brightness change rate after driving.

Tetracarboxylic dianhydride component (a1)

In the present invention, the tetracarboxylic dianhydride component (a1) that reacts with the diamine component (a2) may be a tetracarboxylic dianhydride compound, or a tetracarboxylic dianhydride derivative such as a tetracarboxylic acid dihalide, a tetracarboxylic acid dialkyl ester, or a tetracarboxylic acid dialkyl ester dihalide. The tetracarboxylic dianhydride component (a1) may be a single tetracarboxylic dianhydride compound or its derivative, or a combination of multiple tetracarboxylic dianhydride compounds may be used.

The tetracarboxylic dianhydride component (a1) may include an alicyclic tetracarboxylic dianhydride (a1-1) represented by formula (A11) and other tetracarboxylic dianhydrides (a1-2).

Alicyclic tetracarboxylic dianhydride (a1-1) represented by formula (A11)

The tetracarboxylic dianhydride component (a1) used in the reaction to obtain the polymer (A) may comprise an alicyclic tetracarboxylic dianhydride (a1-1) or a derivative thereof represented by the following formula (A11). The alicyclic tetracarboxylic dianhydride (a1-1) or a derivative thereof represented by formula (A11) may be composed of a single tetracarboxylic dianhydride or a derivative thereof, or may be composed of a plurality of tetracarboxylic dianhydrides or derivatives thereof. (A11)

In formula (A11), X ₁₁ , X ₁₂ , X ₁₃ and X ₁₄ are as defined above.

When X ₁₁ , X ₁₂ , X ₁₃ , and X ₁₄ in formula (A11) have a sterically hindered structure, this can result in poor liquid crystal alignment properties of the liquid crystal aligner. Therefore, X ₁₁ , X ₁₂ , X ₁₃ , and X ₁₄ are preferably hydrogen atoms, methyl groups, or ethyl groups, and more preferably methyl groups.

In some specific embodiments, the alicyclic tetracarboxylic dianhydride (a1-1) represented by formula (A11) may include, but is not limited to, compounds represented by the following formulas (A11-1) to (A11-8). Based on the post-drive brightness change rate of a liquid crystal display unit formed with a liquid crystal alignment film containing this liquid crystal alignment agent, the alicyclic tetracarboxylic dianhydride (a1-1) represented by formula (A11) is preferably a compound represented by formula (A11-1). Formula (A11-1) Formula (A11-2) Formula (A11-3) Formula (A11-4) Formula (A11-5) Formula (A11-6) Formula (A11-7) Formula (A11-8)

Based on the total usage amount of the tetracarboxylic dianhydride component (a1) being 100 mol, the usage amount of the alicyclic tetracarboxylic dianhydride (a1-1) represented by formula (A11) can be 30 mol to 100 mol, preferably 40 mol to 100 mol, and more preferably 50 mol to 100 mol.

If the tetracarboxylic dianhydride component (a1) does not contain the alicyclic tetracarboxylic dianhydride (a1-1) represented by formula (A11), the liquid crystal alignment film formed with the liquid crystal alignment agent has a poor brightness change rate after driving.

Other tetracarboxylic dianhydrides (a1-2)

Other tetracarboxylic dianhydrides (a1-2) may include tetracarboxylic dianhydride compounds represented by the following formula (A12) and derivatives thereof. (A12)

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

In Formula (A12-5) and 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 multiple X ₁₂ ' groups may be the same or different. a1 in Formula (A12-5) represents an integer of 0 or 1; a1 in Formula (A12-6) represents an integer of 0 or 1. In Formula (A12-14), X ₁₃ ' each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, a monovalent organic group having 1 to 6 carbon atoms and containing a fluorine atom, or a phenyl group, and multiple X ₁₃ ' groups may be the same or different. From the viewpoint of liquid crystal alignment, X ₁₃ ′ preferably represents a hydrogen atom, a halogen atom, a methyl group, or an ethyl group, and more preferably represents a hydrogen atom or a methyl group.

In some specific examples, the aforementioned formula (A12-5) and formula (A12-6) may include but are not limited to the structures shown below.

The aforementioned other tetracarboxylic dianhydrides (a1-2) may be used alone or in combination of two or more.

Based on a total usage amount of 100 mol of the tetracarboxylic dianhydride component (a1), the usage amount of the other tetracarboxylic dianhydride (a1-2) is 0 mol to 70 mol, preferably 0 mol to 60 mol, and more preferably 0 mol to 50 mol.

Diamine component (a2)

The diamine component (a2) may include a diamine compound (a2-1) represented by formula (A21) and a diamine compound (a2-2) represented by formula (A22). Furthermore, the diamine component (a2) may optionally include the following diamine compound (a2-3), other diamine compounds (a2-4), or any combination thereof. The diamine component (a2) may be used singly or in combination of multiple types.

Diamine compound (a2-1)

The diamine compound (a2-1) may have a structure represented by the following formula (A21). (A21)

In formula (A21), _A1 and _A2 represent a divalent aromatic cyclic group, and the cyclic portion may have a substituent, wherein _A1 and _A2 are the same; _Y11 represents , and R ₁ represents a group that is thermally dissociated; Y ₁₂ represents a single bond, an oxygen atom, or a sulfur atom; Z ₁ represents a divalent organic group having at least one of a chain hydrocarbon structure and an alicyclic hydrocarbon structure and having a carbon number of 1 to 15, wherein when Y ₁₂ represents a sulfur atom, the carbon number of the divalent organic group represented by Z ₁ is not less than 2.

In formula (A21), _A1 and _A2 are groups formed by removing two hydrogen atoms from an aromatic ring, and the ring portion may also have a substituent. Examples of aromatic rings include aromatic hydrocarbon rings such as a benzene ring, a naphthalene ring, an anthracene ring, and a biphenyl ring; and nitrogen-containing heterocyclic rings such as a pyridine ring, a pyrimidine ring, a pyrazine ring, and a pyridazine ring. Substituents on the aromatic rings may be, for example, alkyl groups having 1 to 6 carbon atoms. When _A1 and _A2 are the same, this facilitates simple synthesis to prepare polymer (A).

Preferably, _A1 and _A2 can be groups formed by removing two hydrogen atoms from a benzene ring, a biphenyl ring, a pyridine ring, or a pyrimidine ring, so as to obtain a liquid crystal alignment agent that can reduce the brightness change rate of a liquid crystal display device after driving.

In formula (A21), Y ₁₁ represents , and R ₁ represents a group that releases upon heating; Y ₁₂ represents a single bond, an oxygen atom, or a sulfur atom. The protecting group represented by R ₁ is preferably a carbamate protecting group, an amide protecting group, an imide protecting group, or a sulfonamide protecting group. The protecting group represented by R ₁ may have the structure shown in the following formula (A21'-1). The aforementioned protecting group is a highly heat-releasing group, thereby effectively reducing the amount of residual deprotected moieties in the liquid crystal alignment film. (A21'-1)

In formula (A21'-1), ^Y1 represents a single bond or a divalent alkyl group having 1 to 4 carbon atoms.

In formula (A21), _Z1 represents a divalent organic group having a chain hydrocarbon structure with a carbon number of 1 to 15 or an alicyclic hydrocarbon structure with a carbon number of 3 to 15. The "chain hydrocarbon structure" refers to a linear hydrocarbon structure and a branched hydrocarbon structure that do not contain a ring structure but only contain a chain structure. The chain hydrocarbon structure may be saturated or unsaturated. The "alicyclic hydrocarbon structure" refers to a hydrocarbon structure that only contains alicyclic hydrocarbon structures as ring structures and does not contain aromatic ring structures. The alicyclic hydrocarbon structure is not limited to a structure containing only alicyclic hydrocarbons, and a portion thereof may also contain a chain structure.

Preferably, in formula (A21), when _A1 and _A2 represent a divalent group formed by removing two hydrogen atoms from a ring portion of a benzene ring, a pyridine ring or a pyrimidine ring, wherein the ring portion may have a substituent, and _A1 and _A2 are the same; and _Z1 represents , and when n represents an integer from 1 to 5, the liquid crystal alignment film prepared using this liquid crystal alignment agent can further reduce the brightness change rate of the liquid crystal display element after driving.

From the perspective of reducing the brightness change rate after driving, the bonding position of the benzene ring, pyridine ring, or pyrimidine ring represented by _A1 and _A2 in formula (A21) is preferably para relative to the nitrogen atom in formula (A21). The diamine compound (a2-1) represented by formula (A21) is preferably a diamine compound represented by the following formula (A21'-2). (A21'-2)

In formula (A21'-2), _Q1 and _Q2 independently represent -CH- or a nitrogen atom; _Y11 and _Y12 are as defined above; and ^m1 represents an integer from 1 to 5.

In some specific examples, the diamine compound (a2-1) of the present invention may include, but is not limited to, compounds represented by the following formulas (A21-1) to (A21-11). The specific compounds of the diamine compound (a2-1) can be synthesized by suitable general methods of combinatorial organic chemistry. The diamine compound (a2-1) may be used alone or in combination of multiple compounds. In the following formulas (A21-1) to (A21-11), _R represents a t-butyloxycarbonyl group. (A21-1) (A21-2) (A21-3) (A21-4) (A21-5) (A21-6) (A21-7) (A21-8) (A21-9) (A21-10) (A21-11)

Based on 100 mol of the diamine component (a2), the total amount of the diamine compound (a2-1) represented by formula (A21) is 1 mol to 20 mol, preferably 2 mol to 15 mol, and more preferably 3 mol to 10 mol.

If the diamine component (a2) of the polymer (A) does not contain the diamine compound (a2-1) represented by formula (A21), the liquid crystal alignment film formed with the liquid crystal alignment agent has a poor brightness change rate after driving.

Diamine compound (a2-2)

The diamine compound (a2-2) may have a structure represented by the following formula (A22). (A22)

In formula (A22), Y ₂₁ represents a single bond, -O-, -S-, -SS-, -SO ₂ -, -CO-, 、 , -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -(CH ₂ ) _m -, -O-(CH ₂ ) _m -O-, or -S-(CH ₂ ) _m -S-, and m represents an integer from 1 to 12; and Y ₂₂ represents a single bond, -O-, -S-, -CO-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, or an alkylene group having 1 to 10 carbon atoms.

In formula (A22), the hydrogen atom of the benzene ring may or may not be substituted with -F, -CH ₃ , -OH, -CF ₃ , or benzyl. A group whose bonding position is not fixed to any carbon atom constituting the benzene ring represents that its bonding position on the benzene ring is arbitrary. The bonding position of -NH ₂ to the benzene ring is any position other than the bonding position of Y ₂₁ or Y ₂₂ . Preferably, Y ₂₁ and Y ₂₂ each independently represent -O- or -S-. When Y ₂₁ and Y ₂₂ each independently represent -O- or -S-, the liquid crystal alignment film produced using this liquid crystal alignment agent can further reduce the brightness change rate of the liquid crystal display device after driving.

In some specific examples, the diamine compound (a2-2) represented by formula (A22) may include but is not limited to compounds represented by the following formulas (A22-1) to (A22-7). (A22-1) (A22-2) (A22-3) (A22-4) (A22-5) (A22-6) (A22-7)

The above-mentioned diamine compound (a2-2) may be used alone or in combination of two or more.

Based on 100 mol of the total usage of the diamine component (a2), the usage of the diamine compound (a2-2) can be 10 mol to 60 mol, preferably 12 mol to 50 mol, and more preferably 15 mol to 40 mol.

If the diamine component (a2) does not contain the diamine compound (a2-2) represented by formula (A22), the liquid crystal alignment film formed by the liquid crystal alignment agent has a poor brightness change rate after driving.

Diamine compound (a2-3)

The diamine compound (a2-3) may include a diamine compound represented by the following formula (A23-1) or formula (A23-2). (A23-1) (A23-2)

In formula (A23-1), Y ₃₁ represents a divalent organic group as shown in formula (A23-3) below. Plural Y ₃₂ groups independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. In formula (A23-2), plural Y ₃₃ groups independently represent a divalent organic group as shown in formula (A23-3') below. (A23-3) (A23-3')

In formula (A23-3), Ar independently represents a divalent benzene ring, a biphenyl structure, or a naphthyl ring, and the hydrogen atom of the benzene ring, biphenyl structure, or naphthyl ring may or may not be substituted by a monovalent substituent group; Y ₃₁ ' represents -(CH ₂ ) _n -, n represents an integer from 2 to 18, and at least one -CH ₂ - in -(CH ₂ ) _n - may or may not be substituted by -O-, -C(═O)-, or -OC(═O)-; p1 represents an integer of 0 or 1; and "*" represents a bonding position.

In formula (A23-3'), Ar' independently represents a divalent benzene ring or a biphenyl structure, and the hydrogen atom of the benzene ring or biphenyl structure may or may not be substituted by a monovalent substituent group; Y ₃₃ ' represents -(CH ₂ ) _n -, n represents an integer from 2 to 18, and at least one -CH ₂ - in -(CH ₂ ) _n - may or may not be substituted by -O-, -C(=O)-, or -OC(=O)-; p2 represents an integer of 0 or 1; and "*" represents a bonding position.

The monovalent substituent of the aforementioned benzene ring, biphenyl structure, or naphthyl ring may be, for example, a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a fluoroalkyl group having 1 to 10 carbon atoms, a fluoroalkenyl group having 2 to 10 carbon atoms, a fluoroalkoxy group having 1 to 10 carbon atoms, a carboxyl group, a hydroxyl group, an alkoxycarbonyl group having 1 to 10 carbon atoms, a cyano group, or a nitro group.

From the perspective of improving the liquid crystal alignment, the divalent organic group represented by formula (A23-3) preferably includes groups represented by the following formulas (A23-3-1) to (A23-3-16), where "*" represents a bonding position. (A23-3-1) (A23-3-2) (A23-3-3) (A23-3-4) (A23-3-5) (A23-3-6) (A23-3-7) (A23-3-8) (A23-3-9) (A23-3-10) (A23-3-11) (A23-3-12) (A23-3-13) (A23-3-14) (A23-3-15) (A23-3-16)

In formula (A23-3-14), each of the multiple m's independently represents an integer from 1 to 3.

From the perspective of improving the liquid crystal alignment, the divalent organic group represented by formula (A23-3') preferably includes groups represented by formulas (A23-3-7) to (A23-3-16).

When the diamine compound (a2-3) contains a plurality of diamine compounds as represented by formula (A23-1), it is preferably a combination of a diamine compound in which Y ₃₁ in formula (A23-1) represents a diamine compound of formula (A23-3-1) to formula (A23-3-14) and a diamine compound in which Y ₃₁ in formula (A23-1) represents a diamine compound of formula (A23-3-15) to formula (A23-3-16).

In some specific examples, the diamine compound represented by the aforementioned formula (A23-2) may include, but is not limited to, diamine compounds represented by the following formulas (A23-2-1) to (A23-2-5). (A23-2-1) (A23-2-2) (A23-2-3) (A23-2-4) (A23-2-5)

The aforementioned diamine compounds (a2-3) may be used alone or in combination of two or more.

Based on 100 mol of the total usage of the diamine component (a2), the usage of the diamine compound (a2-3) may be 20 mol to 89 mol, preferably 38 mol to 90 mol, and more preferably 50 mol to 87 mol.

Other diamine compounds (a2-4)

In addition to the aforementioned diamine compound (a2-1) represented by formula (A21), the diamine compound (a2-2) represented by formula (A22), and the diamine compound (a2-3), the diamine component (a2) used to obtain the polymer (A) may optionally include another diamine compound (a2-4). For example, other diamine compounds (a2-4) may include, but are not limited to: 4,4'-diaminoazobenzene or diamine compounds represented by the following formulas (A24-1) to (A24-3), such as diamine compounds having a photoalignment group; 2,4-diaminophenol, 3,5-diaminophenol, 3,5-diaminobenzyl alcohol, 2,4-diaminobenzyl alcohol, or 4,6-diaminoresorcinol; 2,4-diaminobenzoic acid, 2,5-diaminobenzoic acid, 3,5-diaminobenzoic acid, or diamine compounds represented by the following formulas (A24-4) to (A24-7), such as diamine compounds having a carboxyl group; 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ketone, 1,4-diaminodiphenyl ketone, (4-aminobenzyl)benzene, 4,4'-diaminodiphenyl ether, 1-(4-aminophenyl)-1,3,3-trimethyl-1H-dihydroindene-5-amine or 1-(4-aminophenyl)-2,3-dihydro-1,3,3-trimethyl-1H-indene-6-amine; diamine compounds having a urea bond, such as diamine compounds represented by the following formulas (A24-8) to (A24-10); Diamine compounds having an amide bond represented by formula (A24-11) to formula (A24-13); diamine compounds having a photopolymerizable group at the end, such as 2-(2,4-diaminophenoxy)ethyl methacrylate or 2,4-diamino-N,N-diallylaniline; and diamine compounds having an oxazoline structure, such as the diamine compounds represented by formula (A24-14) to formula (A24-15). (A24-1) (A24-2) (A24-3) (A24-4) (A24-5) (A24-6) (A24-7) (A24-8) (A24-9) (A24-10) (A24-11) (A24-12) (A24-13) (A24-14) (A24-15)

In formula (A24-4), _Y41 represents a single bond, _-CH2- , -C2H4-, -C(CH3) _2- , _-CF2- , -C( _CF3 ) _2- , -O-, -CO-, -NH-, -N( _CH3 ) _- , -CONH-, -NHCO-, -CH2O-, -OCH2-, -COO-, -OCO- _, -CON( _{CH3 )} -, or -N( _CH3 )CO-; m1 and m2 each independently represent an integer from 0 to 4, and (m1+m2) represents an integer from 1 to 4. _In formula (A24-5), _m3 and m4 each independently represent an integer from 1 to 5. In formula (A24-6), _Y42 represents a linear or branched alkyl group having 1 to 5 carbon atoms; m5 represents an integer from 1 to 5. In formula (A24-7), _Y43 and _Y44 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 aforementioned other diamine compounds (a2-4) may be used alone or in combination of two or more.

Based on a total usage amount of 100 mol of the diamine component (a2), the usage amount of the other diamine compounds (a2-4) may be 0 mol to 80 mol, preferably 0 mol to 60 mol, and more preferably 0 mol to 40 mol.

Polymer (B)

In addition to the aforementioned polymer (A), the liquid crystal alignment agent of the present invention may optionally contain a polymer (B) selected from the group consisting of a polyimide precursor obtained using a tetracarboxylic dianhydride component (b1) and a diamine component (b2), and an imidized polymer of such a polyimide precursor (i.e., a polyimide). For example, polymer (B) may include, but is not limited to, at least one polymer selected from the group consisting of a polyimide precursor obtained using a tetracarboxylic dianhydride component (b1) and a diamine component (b2) that does not contain the aforementioned specific diamine compounds (e.g., diamine compound (a2-1) and diamine compound (a2-2)), and an imidized polymer of such a polyimide precursor (i.e., a polyimide). Specific examples of the polyimide precursor include polyamic acid or polyamic acid ester, etc. The polymer (B) may be used alone or in combination of two or more.

The ratio of polymer (A) to polymer (B) (i.e., the mass ratio of [polymer (A)]/[polymer (B)]) can be 10/90 to 90/10, preferably 20/80 to 90/10, and more preferably 20/80 to 80/20.

Tetracarboxylic dianhydride component (b1)

The tetracarboxylic dianhydride component (b1) used to obtain the polymer (B) may include, but is not limited to, a non-cyclic aliphatic tetracarboxylic dianhydride compound, an alicyclic tetracarboxylic dianhydride compound, an aromatic tetracarboxylic dianhydride compound, or derivatives of these compounds. Specific examples of the non-cyclic aliphatic tetracarboxylic dianhydride compound, the alicyclic tetracarboxylic dianhydride compound, and the aromatic tetracarboxylic dianhydride compound may include, for example, the tetracarboxylic dianhydride compounds exemplified for the polymer (A). Preferably, the tetracarboxylic dianhydride component (b1) may include an alicyclic tetracarboxylic dianhydride or a derivative thereof as represented by the above formula (A11), or a tetracarboxylic dianhydride compound or a derivative thereof as represented by the above formula (A12) where X ₁ ' represents a structure represented by formula (A12-1) to formula (A12-6). The tetracarboxylic dianhydride component (b1) may be used alone or in combination of a plurality of types.

To further reduce the brightness change rate after driving, the tetracarboxylic dianhydride component (b1) preferably includes a tetracarboxylic dianhydride compound represented by formula (A12) above and wherein X ₁ ' represents a structure represented by formula (III) below (hereinafter referred to as tetracarboxylic dianhydride compound (b1-1)). (III)

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

The aforementioned tetracarboxylic dianhydride compound (b1-1) may be used alone or in combination of two or more.

More preferably, the tetracarboxylic dianhydride component (b1) comprises a tetracarboxylic dianhydride compound represented by the following formula (IV). (IV)

Based on the total usage of the tetracarboxylic dianhydride component (b1) being 100 mol, the usage of the tetracarboxylic dianhydride compound (b1-1) can be 30 mol to 100 mol, preferably 40 mol to 100 mol, and more preferably 50 mol to 100 mol.

If the tetracarboxylic dianhydride component (b1) includes the tetracarboxylic dianhydride compound (b1-1), the liquid crystal alignment film formed with the liquid crystal alignment agent can have a better brightness change rate after driving.

Diamine component (b2)

The diamine component (b2) used to obtain the polymer (B) may include, but is not limited to, the aforementioned diamine component (a2), or a diamine compound having at least one nitrogen-containing structure selected from the group consisting of a nitrogen-containing heterocyclic ring, a diamine group, and a tertiary amine group (hereinafter referred to as the diamine compound (b2-1)). However, the diamine component (b2) does not include the aforementioned diamine compound (a2-1) and diamine compound (a2-2).

The diamine component (b2) may be used alone or in combination of two or more.

Diamine compound (b2-1)

The diamine compound (b2-1) having the above-mentioned specific nitrogen-containing atom structure may have a nitrogen-containing heterocyclic ring, such as pyrrole, imidazole, pyrazole, triazole, pyridine, pyrimidine, pyrimidine, pyr ... pyridine , indole, benzimidazole, purine, quinoline, isoquinoline, oxadiazole, quinoline, pyridine ,three , carbazole, acridine, piperidine, piperidine , pyrrolidine or hexamethyleneimine, etc. Among them, pyridine, pyrimidine, pyrrolidine, , piperidine, piperidine , quinoline, carbazole or acridine is preferred.

The diamine compound (b2-1) having the above-mentioned specific nitrogen-containing structure may include a diamine group and a tertiary amine group as represented by the following formula (B21). (B21)

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

The alkyl group represented by Z may include, but is not limited to, methyl, ethyl, or propyl; the cycloalkyl group represented by Z may include, but is not limited to, cyclohexyl; and the aryl group represented by Z may include, but is not limited to, phenyl or tolyl. Z is preferably a hydrogen atom or a methyl group.

Specific examples of the diamine compound (b2-1) having the above-mentioned specific nitrogen-containing atom structure include: 2,6-diaminopyridine, 3,4-diaminopyridine, 2,4-diaminopyrimidine, 3,6-diaminocarbazole, N-methyl-3,6-diaminocarbazole, 1,4-bis-(4-aminophenyl)-piperidin , 3,6-diaminoacridine, N-ethyl-3,6-diaminocarbazole, N-phenyl-3,6-diaminocarbazole, diamine compounds represented by the following formulas (B21-1) to (B21-8), or diamine compounds represented by the following formulas (B21-9) to (B21-26). (B21-1) (B21-2) (B21-3) (B21-4) (B21-5) (B21-6) (B21-7) (B21-8) (B21-9) (B21-10) (B21-11) (B21-12) (B21-13) (B21-14) (B21-15) (B21-16) (B21-17) (B21-18) (B21-19) (B21-20) (B21-21) (B21-22) (B21-23) (B21-24) (B21-25) (B21-26)

The diamine compound (b2-1) may be used alone or in combination of two or more.

Based on 100 mol of the total usage of the diamine component (b2), the usage of the diamine compound (b2-1) can be 15 mol to 100 mol, preferably 20 mol to 90 mol, and more preferably 25 mol to 80 mol.

If the diamine component (b2) includes the diamine compound (b2-1), the liquid crystal alignment film prepared using this liquid crystal alignment agent can further reduce the brightness change rate of the liquid crystal display device after driving.

Polymer production method

The production of polymer (A) or polymer (B) can be carried out by reacting the aforementioned diamine component and tetracarboxylic dianhydride component in a solvent (polycondensation). When a portion of polymer (A) or polymer (B) has an acylamidic acid structure, for example, by reacting the tetracarboxylic dianhydride component with the diamine component, a polymer having an acylamidic acid structure (i.e., polyacylamidic acid) can be obtained. The aforementioned solvent is not particularly limited; it only needs to be able to dissolve the formed polymer. For example, specific examples of the solvent may include, but are not limited to, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, γ-butyrolactone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide, or 1,3-dimethyl-2-imidazolidinone. In some embodiments, when the polymer has high solvent solubility, the solvent may include methyl ethyl ketone, cyclohexanone, cyclopentanone, 4-hydroxy-4-methyl-2-pentanone, or solvents represented by Formulas (D-1) to (D-3) below. In Formula (D-1), Z ₁ represents an alkyl group having 1 to 3 carbon atoms. In Formula (D-2), Z ₂ represents an alkyl group having 1 to 3 carbon atoms. In Formula (D-3), Z ₃ represents an alkyl group having 1 to 4 carbon atoms. (D-1) (D-2) (D-3)

The aforementioned solvents can be used alone or in combination. Secondly, even if the solvent cannot dissolve the polymer, it can still be mixed with the above-mentioned solvents 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, but preferably 1 wt% to 50 wt%, and more preferably 5 wt% to 30 wt%. The reaction can also be carried out at a high concentration initially, and then additional solvent is added. During the reaction, the ratio of the total molar number of the diamine component to the total molar number of the tetracarboxylic dianhydride component is preferably 0.8 to 1.2. Similar to a general polycondensation reaction, the closer this molar ratio is to 1.0, the greater the molecular weight of the polymer (A) or polymer (B) formed.

Polymers having an acylamidoester structure can be obtained, for example, by the following known methods: (1) a method of further 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 imide compound in polymer (A) or polymer (B) contained in the liquid crystal alignment agent of the present invention can be obtained, for example, by ring-closing the polymer obtained above. In the imide compound, the ring-closure ratio (also known as the imidization ratio) of the functional groups possessed by the amino acid group or its derivatives does not necessarily need to be 100%; the imidization ratio can be arbitrarily adjusted according to the application and/or purpose.

The imidization product can be obtained by, for example, directly heating the polymer solution obtained from the above reaction for thermal imidization, or by catalytic imidization in which a catalyst is added to the polymer solution. When thermal imidization is performed in solution, the temperature is preferably 100°C to 400°C, more preferably 120°C to 250°C. During thermal imidization, water generated during the imidization reaction is preferably removed from the system.

The aforementioned catalytic imidization can be carried out, for example, by adding an alkaline catalyst and an acid anhydride to the polymer solution obtained from the reaction, preferably with stirring at -20°C to 250°C, and more preferably at 0°C to 180°C. The amount of alkaline catalyst added is preferably 0.5 to 30 mol times, and more preferably 2 to 20 mol times, based on the amount of amide groups; the amount of acid anhydride added is preferably 1 to 50 mol times, and more preferably 3 to 30 mol times, based on the amount of amide groups. Specific examples of alkaline catalysts include, but are not limited to, pyridine, triethylamine, trimethylamine, tributylamine, or trioctylamine. Pyridine is particularly suitable because it has a moderate alkalinity that facilitates the reaction. Specific examples of acid anhydrides include, but are not limited to, acetic anhydride, trimellitic anhydride, or pyromellitic anhydride. Acetic anhydride is preferred because it facilitates purification after the reaction. The imidization rate in the catalytic imidization reaction can be controlled by adjusting the catalyst amount, reaction temperature, and/or reaction time.

When the imide formed is recovered from the above-mentioned imidization reaction solution, the reaction solution is added to a solvent and precipitated. The solvent used for precipitation may include, but is 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 room temperature or under normal pressure or reduced pressure. Alternatively, the polymer recovered by precipitation can be dissolved in a solvent again and recovered by reprecipitation. This operation can be repeated 2 to 10 times to reduce impurities in the polymer. The solvent used can be, for example, an alcohol or a ketone. If more than three of the selected solvents are used, the refining efficiency can be further improved, which is more ideal.

Solution viscosity and molecular weight of polymers

When prepared into a solution with a concentration of 10 wt% to 15 wt%, the concentration of the polymer (A) or polymer (B) of the present invention is not particularly limited. For ease of operation, the solution concentration can be, for example, 10 mPa·s to 1000 mPa·s. The viscosity (mPa·s) of the polymer solution is the value measured at 25°C using an E-type rotational viscometer using a good solvent for the polymer (e.g., γ-butyrolactone or N-methyl-2-pyrrolidone) to prepare a polymer solution with a concentration of 10 wt% to 15 wt%.

The polymer (A) or polymer (B) of the present invention preferably has a weight average molecular weight ( _Mw ) in terms of polystyrene, as measured by gel permeation chromatography ( _GPC ), of 1,000 to 500,000, and more preferably 2,000 to 500,000. Furthermore, the molecular weight distribution ( _Mw / _Mn ), represented by the ratio of Mw to the number average molecular weight ( _Mn ) in terms of polystyrene, as measured by GPC, is preferably 15 or less, and more preferably 10 or less. When the molecular weight of the polymer is within the aforementioned range, it can ensure good alignment and stability of the liquid crystal display device.

Capping agent

When synthesizing the polymer (A) or polymer (B) of the present invention, the tetracarboxylic dianhydride component and the diamine component as described above can be used, and an appropriate end-capping agent can be used to synthesize an end-sealed polymer. The end-sealed polymer has the effect of improving the film hardness of the liquid crystal alignment film obtained by coating, and improving the adhesion properties of the sealant and the liquid crystal alignment film. The end of the polymer (A) or polymer (B) of the present invention may, for example, contain an amino group, a carboxyl group, an acid anhydride group or a derivative thereof. The amino group, carboxyl group, acid anhydride group or a derivative thereof can be obtained by a general condensation reaction, or by sealing the end using the end-capping agent described later. Similarly, the aforementioned derivatives can be obtained, for example, using the following end-capping agent.

For example, the end-capping agent may include, but is not limited to, anhydrides such as acetic anhydride, maleic anhydride, nedic 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; dibutyl dicarbonate or diallyl dicarbonate; Carbonic acid diester compounds; chlorocarbonyl compounds such as acryloyl chloride, methacryloyl chloride, or nicotinyl chloride; monoamine compounds such as aniline, 2-aminophenol, 3-aminophenol, 4-aminosalicylic acid, 5-aminosalicylic acid, 6-aminosalicylic acid, 2-aminobenzoic acid, 3-aminobenzoic acid, 4-aminobenzoic acid, cyclohexylamine, n-butylamine, n-pentylamine, n-hexylamine, n-heptylamine, or n-octylamine; monoisocyanate compounds such as ethyl isocyanate, phenyl isocyanate, or naphthyl isocyanate, etc.

The blocking agents may be used alone or in combination.

Based on 100 mol parts of the total diamine component used, the amount of the end-capping agent used is preferably 0.01 mol parts to 20 mol parts, and more preferably 0.01 mol parts to 10 mol parts.

Other ingredients in liquid crystal alignment agents

The liquid crystal alignment agent of the present invention may include a polymer (A) and, if necessary, a polymer (B). In addition to polymers (A) and (B), the liquid crystal alignment agent of the present invention may optionally include other polymers. Examples of such other polymers include, but are not limited to, polyesters, polyamides, polyureas, polyorganosiloxanes, cellulose derivatives, polyacetals, polystyrene or its derivatives, poly(styrene-phenylmaleimide) derivatives, or poly(meth)acrylates.

Solvent (C)

From the perspective of forming a uniform thin film, the liquid crystal alignment agent is in the form of a coating liquid to produce a liquid crystal alignment film. The liquid crystal alignment agent of the present invention is preferably a coating liquid containing the above-mentioned polymer component and an organic solvent (hereinafter referred to as solvent (C)). Among them, based on the set coating thickness to be formed, the polymer concentration in the liquid crystal alignment agent can be appropriately changed. From the perspective of forming a uniform and defect-free coating, the polymer concentration in the liquid crystal alignment agent is preferably above 1 wt%. From the perspective of the storage stability of the solution, the polymer concentration in the liquid crystal alignment agent is preferably below 10 wt%. The ideal polymer concentration can be 2 wt% to 8 wt%. The content of polymer (A) in the liquid crystal alignment agent can be appropriately changed by the liquid crystal alignment agent coating method and/or the desired liquid crystal alignment film thickness, and is preferably 2 wt % to 10 wt %, and more preferably 3 wt % to 7 wt %.

There is no particular limitation on the organic solvent contained in the liquid crystal alignment agent, as long as it can uniformly dissolve the aforementioned polymer. Specific examples include, but are 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 aforementioned organic solvents are also referred to as 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 are preferred. Based on 100 wt% of the total amount of solvent used in the liquid crystal alignment agent, the amount of good solvent used may be 20 wt% to 99 wt%, preferably 20 wt% to 90 wt%, and more preferably 30 wt% to 80 wt%.

Secondly, the organic solvent in the liquid crystal alignment agent is preferably a mixed solvent comprising the aforementioned solvents and a solvent that improves the coating properties and surface smoothness of the coating film during coating (also known as a poor solvent). Specific examples of the poor solvent used include, but are not limited to, the solvents described below. Based on a total solvent usage of 100 wt% in the liquid crystal alignment agent, the usage of the poor solvent is preferably 1 wt% to 80 wt%, more preferably 10 wt% to 80 wt%, and even more preferably 20 wt% to 70 wt%. The type and amount of solvent used can be appropriately selected based on the liquid crystal alignment agent coating equipment, coating conditions, and/or coating environment.

For example, the anisotropic solvent may be diisopropyl ether, diisobutyl ether, diisobutyl carbinol (2,6-dimethyl-4-heptanol), ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, 1,2-butoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, 4-hydroxy-4-methyl-2-pentanone, diethylene glycol methyl ethyl ether, diethylene glycol dibutyl ether, 3-ethoxybutyl acetate, 1-methylpentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, ethylene glycol monoacetate, ethylene glycol diacetate, propylene carbonate, ethyl carbonate, ethylene glycol monobutyl ether (butyl cellulose), ethylene glycol monoisopentyl ether, ethylene glycol monohexyl ether, propylene glycol monobutyl ether, 1-(2-butoxyethoxy) )-2-propanol, 2-(2-butoxyethoxy)-1-propanol, propylene glycol monomethyl ether acetate, propylene glycol diacetate, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol dimethyl ether, ethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, 2-(2-ethoxyethoxy)ethyl acetate, diethylene glycol acetate, propylene glycol diacetate, n-butyl acetate, propylene glycol monoethyl ether acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, ethyl 3-methoxypropionate, propyl 3-methoxypropionate, butyl 3-methoxypropionate, n-butyl lactate, isoamyl lactate, diethylene glycol monoethyl ether, or diisobutyl ketone (2,6-dimethyl-4-heptanone), etc.

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

The solvent combination of good solvent and poor solvent is preferably, 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-dimethyllactamide and diisobutyl ketone; N-methyl-2-pyrrolidone and ethyl 3-ethoxypropionate; N-ethyl-2-pyrrolidone and ethyl 3-ethoxypropionate; N-methyl-2-pyrrolidone and ethyl Glycol monobutyl ether acetate; N-ethyl-2-pyrrolidone and dipropylene glycol dimethyl ether; N,N-dimethyl lactamide and ethylene glycol monobutyl ether; N,N-dimethyl lactamide and propylene glycol diacetate; N-ethyl-2-pyrrolidone and diethylene glycol diethyl ether; N,N-dimethyl lactamide and diethylene glycol diethyl ether; N-methyl-2-pyrrolidone, γ-butyrolactone, 4-hydroxy-4-methyl-2-pentanone and diethylene glycol diethyl ether; N-ethyl-2-pyrrolidone, N-methyl-2-pyrrolidone and 4-hydroxy-4-methyl-2-pentanone; N-ethyl-2-pyrrolidone, 4-hydroxy-4-methyl-2-pentanone and propylene glycol monobutyl ether; N-methyl-2-pyrrolidone, 4-Hydroxy-4-methyl-2-pentanone and diisobutyl ketone; N-methyl-2-pyrrolidone, 4-hydroxy-4-methyl-2-pentanone and dipropylene glycol monomethyl ether; N-methyl-2-pyrrolidone, 4-hydroxy-4-methyl-2-pentanone and propylene glycol monobutyl ether; N-methyl-2-pyrrolidone, 4-hydroxy-4-methyl-2-pentanone and propylene glycol diacetate; γ-butyrolactone, 4-hydroxy-4-methyl-2-pentanone and diisobutyl ketone; γ-butyrolactone, 4-hydroxy-4-methyl-2-pentanone and propylene glycol diacetate; N-methyl-2-pyrrolidone, γ-butyrolactone, propylene glycol monobutyl ether and diisobutyl ketone; N-methyl-2-pyrrolidone, γ-butyrolactone and propylene glycol diacetate. Glycol monobutyl ether and diisopropyl ether; N-methyl-2-pyrrolidone, γ-butyrolactone, propylene glycol monobutyl ether, and diisobutyl carbinol; N-methyl-2-pyrrolidone, γ-butyrolactone, and dipropylene glycol dimethyl ether; N-methyl-2-pyrrolidone, propylene glycol monobutyl ether, and dipropylene glycol dimethyl ether; N-ethyl-2-pyrrolidone, propylene glycol monobutyl ether, and dipropylene glycol monomethyl ether; N-ethyl-2-pyrrolidone, propylene glycol monobutyl ether, and propylene glycol diacetate; N-ethyl-2-pyrrolidone, propylene glycol monobutyl ether, and diisobutyl ketone; N-ethyl-2-pyrrolidone, γ-butyrolactone, and diisobutyl ketone; or N-ethyl-2-pyrrolidone, N,N-dimethyllactamide, and diisobutyl ketone, etc.

The aforementioned solvent (C) may be used alone or in combination of two or more.

Based on 100 parts by weight of the total amount of polymer (A) and polymer (B), the amount of solvent (C) 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

The liquid crystal alignment agent of the present invention may also optionally contain ingredients other than the polymer component and the organic solvent (hereinafter referred to as additives). These additives may include, but are not limited to: adhesion promoters for improving the adhesion between the liquid crystal alignment film and the substrate or between the liquid crystal alignment film and the sealant, compounds for increasing the strength of the liquid crystal alignment film (hereinafter referred to as crosslinking compounds), compounds for promoting imidization, and dielectrics or conductive substances for adjusting the dielectric constant or resistance of the liquid crystal alignment film.

Sealing agent

The aforementioned adhesion promoter may be, for example, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyldiethoxymethylsilane, 2-aminopropyltrimethoxysilane, 2-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-ureidopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, N-ethoxycarbonyl-3-aminopropyltrimethoxysilane, N-ethoxycarbonyl-3-aminopropyltriethoxysilane, N-triethoxysilylpropyltriethylenetriamine, N-trimethoxysilylpropyltriethylenetriamine, vinyltrimethoxysilane, Silane, vinyl triethoxysilane, 2-(3,4-epoxycyclohexyl)ethyl trimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-methacryloyloxypropylmethyldimethoxysilane Silane coupling agents such as methoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, tris(3-trimethoxysilylpropyl)isocyanurate, or 3-isocyanatepropyltriethoxysilane are also used. When a bonding agent is used, the amount of the bonding agent used is preferably 0.1 to 30 parts by weight, and more preferably 0.1 to 20 parts by weight, relative to 100 parts by weight of the total amount of the polymer in the liquid crystal alignment agent, in order to exhibit good resistance to AC residual image.

Cross-linked compounds

The crosslinking compound described above may be a compound having an ethylene oxide group, an propylene oxide group, at least one group selected from the group consisting of a group represented by the following formula (E1) and a group represented by the following formula (E2), or a compound selected from the compound represented by the following formula (E3), from the viewpoint of exhibiting good resistance to AC afterimages and effectively improving film strength. (E1) (E2) (E3)

In formula (E1), _G1 and _G2 each independently represent a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or -CH2 _- OH. In formula (E2), _G3 represents an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or an alkynyl group having 2 to 6 carbon atoms. _G4 represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or an alkynyl group having 2 to 6 carbon atoms. In formula (E3), _G5 represents a (g1+g2)-valent organic group containing an aromatic ring. _G6 represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. g1 represents an integer from 1 to 6, and g2 represents an integer from 0 to 4.

In formula (E3), the (g1+g2)-valent organic group having an aromatic ring represented by _G5 can be a (g1+g2)-valent aromatic alkyl group having 6 to 30 carbon atoms, a (g1+g2)-valent organic group formed by directly or via a linking group bonding an aromatic alkyl group having 6 to 30 carbon atoms, or a (g1+g2)-valent group having an aromatic heterocyclic ring. The aromatic alkyl group can be, for example, benzene or naphthalene. The aromatic heterocyclic ring can be exemplified by the aromatic heterocyclic rings of the aforementioned specific nitrogen-containing structures. The linking group can be an alkylene group having 1 to 10 carbon atoms, a group obtained by removing a hydrogen atom from the alkylene group, or a divalent or trivalent cyclohexane. Any hydrogen atom of the alkylene group may be substituted with a fluorine atom or an organic group such as a trifluoromethyl group. In formula (E3), the alkyl group having 1 to 5 carbon atoms represented by _G6 can be methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, or n-pentyl.

Compounds with ethylene oxide groups

Specific examples of the compound having an oxirane group include N,N,N',N'-tetraoxopropyl-m-xylenediamine, 1,3-bis(N,N-dioxopropylaminomethyl)cyclohexane, N,N,N',N'-tetraoxopropyl-4,4'-diaminodiphenylmethane, N,N,N',N'-tetraoxopropyl-p-phenylenediamine, and nitrogen-containing compounds such as those represented by the following formulas (E4) to (E6). (E4) (E5) (E6)

Compounds with propylene oxide groups

Specific examples of the compound having an propylene oxide group include compounds represented by the following formulas (E7) to (E16). (E7) (E8) (E9) (E10) (E11) (E12) (E13) (E14) (E15) (E16)

In formula (E15), R represents , where "*" represents the key position.

Compounds having a group represented by formula (E1)

Specific examples of the compound having the group represented by formula (E1) include compounds represented by the following formulas (E1-1) to (E1-12). (E1-1) (E1-2) (E1-3) (E1-4) (E1-5) (E1-6) (E1-7) (E1-8) (E1-9) (E1-10) (E1-11) (E1-12)

Compounds having a group represented by formula (E2)

Specific examples of the compound having the group represented by formula (E2) include the compounds represented by the following formulas (E2-1) to (E2-4). (E2-1) (E2-2) (E2-3) (E2-4)

Compounds having a group represented by formula (E3)

Specific examples of the compound having the group represented by formula (E3) include compounds represented by the following formulas (E3-1) to (E3-10). (E3-1) (E3-2) (E3-3) (E3-4) (E3-5) (E3-6) (E3-7) (E3-8) (E3-9) (E3-10)

In the liquid crystal alignment agent of the present invention, the amount of the crosslinking compound used is preferably 0.5 to 20 parts by weight based on 100 parts by weight of the total polymer used in the liquid crystal alignment agent. Furthermore, based on the perspectives of crosslinking reaction progress and good resistance to AC afterimages, the amount of the crosslinking compound used is more preferably 1 to 15 parts by weight.

Compounds that promote imidization

The compound used to promote imidization is preferably a compound (excluding the crosslinking compound and bonding aid) 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), or a compound that generates such a basic site upon calcination. More preferably, the compound promoting imidization is a compound that generates such a basic site upon calcination, and a specific example thereof is an amino acid in which the basic site is partially or entirely protected. Specific examples of the aforementioned amino acids include glycine, alanine, cysteine, methionine, asparagine, glutamine, valine, leucine, phenylalanine, tyrosine, tryptophan, proline, hydroxyproline, arginine, histidine, lysine, or guanine. For the purpose of promoting the amidation of a compound, a more preferred example is N-α-(9-fluorenylmethoxycarbonyl)-N-τ-(tert-butoxycarbonyl)-L-histidine.

Liquid crystal alignment film and method for manufacturing liquid crystal display element

The liquid crystal alignment film of the present invention is obtained from the aforementioned liquid crystal alignment agent. The liquid crystal alignment film of the present invention can be used as a horizontal alignment type or vertical alignment type (VA type) liquid crystal alignment film, and is suitable for a liquid crystal alignment film of a horizontal alignment type liquid crystal display element such as an IPS mode or an FFS mode. The liquid crystal display element of the present invention has the aforementioned liquid crystal alignment film. The liquid crystal display element of the present invention can be produced, for example, by the following method of steps (1) to (4) or steps (1) to (2) and step (4).

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

The liquid crystal alignment agent of the present invention is applied to one side of a substrate having a patterned transparent conductive film using an appropriate coating method such as roll coating, spin coating, printing, or inkjet. The substrate is not particularly limited; it only needs to be highly transparent. Glass or silicon nitride substrates can also be used in conjunction with plastic substrates such as acrylic or polycarbonate substrates. Furthermore, in reflective liquid crystal display devices, if only a single-sided substrate is used, opaque materials such as silicon wafers can be used, and the electrodes used can also be made of light-reflective materials such as aluminum. Furthermore, when manufacturing IPS or FFS liquid crystal elements, the comb-tooth type uses an electrode substrate composed of a patterned transparent conductive film or metal film and an opposite substrate without an electrode.

The liquid crystal alignment agent can be applied to the substrate to form a film by screen printing, offset printing, flexographic printing, inkjet printing, or spray coating. Among them, the preferred method for forming the film is inkjet coating.

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 IR (infrared) oven, or thermal imidization of polyamine or polyamine ester can be performed. The drying and calcining steps performed after the liquid crystal alignment agent of the present invention has been coated can be selected at any temperature and time, and multiple drying or calcining steps can be performed. The drying temperature can be, for example, 40°C to 180°C. Based on the viewpoint of shortening the process, it can be carried out at 40°C to 150°C. The drying time is not particularly limited and may be, for example, 1 to 10 minutes or 1 to 5 minutes. When thermal imidization of polyamic acid or polyamic ester is performed, after the aforementioned drying step, a calcination step may be further performed at a temperature of, for example, 150°C to 300°C or 150°C to 250°C. The calcination time is not particularly limited and may be, for example, 5 to 40 minutes or 5 to 30 minutes. If the calcined film is too thin, the reliability of the liquid crystal display device will be reduced. Therefore, the film thickness is preferably 5 nm to 300 nm, and more preferably 10 nm to 200 nm.

Step (3): Perform 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. In other words, in a horizontal alignment type liquid crystal display element such as the IPS mode or the FFS mode, the coating film is subjected to an alignment treatment to impart 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 coating film can be used directly as a liquid crystal alignment film, but the coating film can also be subjected to an alignment treatment to impart alignment capability. The alignment treatment of the liquid crystal alignment film can be exemplified by a friction treatment method or a photo-alignment treatment method, with the photo-alignment treatment method being preferred. Photo-alignment treatment methods include irradiating the surface of the aforementioned film with radiation that has been deflected in a specific direction, and optionally heating the film at a temperature of 150°C to 250°C to impart alignment properties (also known as liquid crystal alignment capability) to the liquid crystal. The radiation can be ultraviolet light or visible light with a wavelength of 100 nm to 800 nm. Ultraviolet light with a wavelength of 100 nm to 400 nm is preferred, and ultraviolet light with a wavelength of 200 nm to 400 nm is more preferred.

The radiation dose can be 1 mJ/ ^cm² to 10,000 mJ/ ^cm² , preferably 100 mJ/ ^cm² to 5,000 mJ/ ^cm² , more preferably 100 mJ/ ^cm² to 1500 mJ/ ^cm² , and even more preferably 100 mJ/ ^cm² to 1000 mJ/ ^cm² . When conventional liquid crystal alignment agents are used, the light dose for alignment treatment is 100 mJ/ ^cm² to 5000 mJ/ ^cm² . However, the liquid crystal alignment agent of the present invention can still produce a liquid crystal alignment film in which variations (non-uniformity) in the liquid crystal alignment property within the film surface are effectively suppressed, even when the light dose for alignment treatment is reduced. During the radiation exposure, the film substrate may be heated to a temperature of 50°C to 250°C to improve the liquid crystal alignment. The liquid crystal alignment film produced in this manner can stably align the liquid crystal molecules in a specific direction. Furthermore, the liquid crystal alignment film irradiated with polarized radiation in the aforementioned method may be contact-treated with a solvent or heated.

There are no particular restrictions on the solvent used in the aforementioned contact treatment; it only needs to be able to dissolve the decomposition products generated from the film after irradiation. Specific examples include water, methanol, ethanol, 2-propanol, acetone, methyl ethyl ketone, 1-methoxy-2-propanol, 1-methoxy-2-propanol acetate, butyl celecoxib, ethyl lactate, methyl lactate, diacetone alcohol, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, propyl acetate, butyl acetate, or cyclohexyl acetate. Among these, water, 2-propanol, 1-methoxy-2-propanol, or ethyl lactate are preferred from the perspectives of versatility and safety, and water, 1-methoxy-2-propanol, or ethyl lactate are more preferred. Solvents may be used alone or in combination.

The temperature for heat treatment of the radiation-irradiated coating is preferably 50° C. to 300° C., more preferably 120° C. to 250° C. The heat treatment time is preferably 1 minute to 30 minutes.

Step (4): Making liquid crystal cells

Prepare two substrates with the aforementioned liquid crystal alignment films and arrange the liquid crystal between the two facing substrates. For example, the following two methods can be used. The first method involves placing the two substrates face-to-face, with the liquid crystal alignment films facing each other, separated by a gap (cell gap). Next, the two substrates are bonded together with a sealant around their perimeters. The liquid crystal composition is then injected into the cell gap defined by the substrate surfaces and the sealant. Once the liquid crystal composition 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 on one of the two substrates on which a liquid crystal alignment film has been formed, and then a liquid crystal composition is added to a plurality of predetermined positions on the surface of the liquid crystal alignment film. Then, the other substrate is attached with the liquid crystal alignment films facing each other, and the liquid crystal composition is pushed onto the entire surface of the substrate so that it contacts the film surface. Then, the entire surface of the substrate is irradiated with ultraviolet light to cure the sealant. When performing any of the aforementioned methods, it is preferred to further heat the liquid crystal composition used to a temperature at which it becomes an isotropic phase, and then slowly cool it to room temperature to remove the flow alignment during liquid crystal filling. Next, when rubbing the coating, the two substrates are positioned so that the rubbing directions of the coatings are at a predetermined angle to each other, such as perpendicular 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 nematic or lamellar, with nematic liquid crystal being preferred.

Optionally, a polarizing plate can be attached to the outer surface of the liquid crystal cell to produce a liquid crystal display. The polarizing plate attached to the outer surface of the liquid crystal cell can be made of a polarizing film called "H-film" that is made of elongated polyvinyl alcohol and absorbs iodine. This can be a polarizing plate sandwiched between cellulose acetate protective films or composed solely of H-film.

The following embodiments are used to illustrate the application of the present invention, but they are not used to limit the present invention. Anyone skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention.

Preparation of polymer (A)

Synthesis Example A-1-1

A 500 ml four-necked Erlenmeyer flask was equipped with a nitrogen inlet, a stirrer, a condenser, and a thermometer, and nitrogen was introduced. Then, 1.215 g (0.0035 mol) of the compound (a2-1-1) represented by formula (A21-1), 6.57 g (0.0225 mol) of the diamine compound (a2-2-3) represented by formula (A22-2), 3.66 g (0.015 mol) of the diamine compound (a2-3-2) represented by formula (A23-2), 1.784 g (0.009 mol) of 4,4'-diaminodiphenylmethane (a2-4-1), and 80 g of N-methyl-2-pyrrolidone (hereinafter referred to as NMP) were added and stirred at room temperature until dissolved. Next, 11.1 g (0.05 mol) of the diamine compound (a1-1-1) represented by formula (A11-1) and 20 g of NMP were added, and the mixture was reacted at room temperature for 2 hours. After the reaction, the reaction solution was poured into 1500 ml of water to precipitate the polymer. The resulting polymer was filtered and then washed and filtered with methanol three times. The product was then placed in a vacuum oven and dried at 60°C to obtain the polymer (A-1-1) of Synthesis Example A-1-1, the formula of which is shown in Table 1.

Synthesis Examples A-1-2 to A-1-6 and Comparative Synthesis Examples A'-1-1 to A'-1-7

Synthesis Examples A-1-2 to A-1-6 and Comparative Synthesis Examples A'-1-1 to Comparative Synthesis Examples A'-1-7 use the same preparation method as the preparation method of the polymer (A-1-1) in Synthesis Example A-1-1. The difference is that Synthesis Examples A-1-2 to A-1-6 and Comparative Synthesis Examples A'-1-1 to Comparative Synthesis Examples A'-1-7 change the types and usage amounts of raw materials in the polymers. The formulas are shown in Table 1 and are not described further here.

Synthesis Example A-2-1

A 500 ml four-necked Erlenmeyer flask was equipped with a nitrogen inlet, a stirrer, a condenser, and a thermometer, and nitrogen was introduced. Then, 1.215 g (0.0035 mol) of the compound (a2-1-1) represented by formula (A21-1), 6.57 g (0.0225 mol) of the diamine compound (a2-2-3) represented by formula (A22-2), 3.66 g (0.015 mol) of the diamine compound (a2-3-2) represented by formula (A23-2), 1.784 g (0.009 mol) of 4,4'-diaminodiphenylmethane (a2-4-1), and 80 g of NMP were added and stirred at room temperature until dissolved. Next, add 11.1 g (0.05 mol) of the diamine compound (a1-1-1) represented by formula (A11-1) and 20 g of NMP. After reacting at room temperature for 6 hours, add 97 g of NMP, 2.55 g of acetic anhydride and 19.75 g of pyridine, raise the temperature to 60°C, and continue stirring for 2 hours to carry out the imidization reaction. After the reaction is completed, pour the reaction solution into 1500 ml of water to precipitate the polymer. Then, filter the obtained polymer, repeat washing and filtering with methanol three times, place it in a vacuum oven, and dry it at a temperature of 60°C to obtain the polymer (A-2-1) of Synthesis Example A-2-1, whose formula is shown in Table 1.

Synthesis Example A-2-2

Synthesis Example A-2-2 uses the same preparation method as the preparation method of the polymer (A-2-1) in Synthesis Example A-2-1. The difference is that Synthesis Example A-2-2 changes the type and amount of raw materials in the polymer. Its formula is shown in Table 1 and is not further described here.

Preparation of polymer (B)

Synthesis Example B-1-1 to Synthesis Example B-1-7

Synthesis Examples B-1-1 through B-1-7 utilize the same preparation method as the polymer (A-1-1) from Synthesis Example A-1-1. The differences between Examples B-1-1 through B-1-7 are the type and amount of raw materials used in the polymers. Their respective formulations are shown in Table 2 and are not further detailed here.

Synthesis Example B-2-1 to Synthesis Example B-2-2

Synthesis Examples B-2-1 and B-2-2 utilize the same preparation method as the polymer (A-2-1) from Synthesis Example A-2-1. The difference lies in the changes in the types and amounts of raw materials used in the polymers. Their respective formulations are shown in Table 2 and are not further detailed here.

Preparation of liquid crystal alignment agent, liquid crystal alignment film and liquid crystal display element

Example 1

Weigh 50 parts by weight of the polymer (A-1-1) prepared in Synthesis Example A-1-1, 50 parts by weight of the polymer (B-1-1) prepared in Synthesis Example B-1-1, and 2000 parts by weight of NMP (C-1), and stir and mix them at room temperature to prepare the liquid crystal alignment agent of Example 1.

The prepared liquid crystal alignment agent was spin-coated onto a glass substrate, where pixel electrodes were formed. These were IPS driver electrodes consisting of a pair of ITO electrodes (10 μm in width, 10 μm in spacing, and 50 nm in height). The ITO electrodes each had a serrated shape, with the serrated portions arranged in a spaced-apart, interlocking configuration. The glass substrate coated with the liquid crystal alignment agent was then dried on an 80°C hot plate for 3 minutes and then baked in a 250°C hot air circulation oven for 30 minutes to form a 100 nm thick film.

The coated surface was irradiated with 254 nm UV light through a polarizing plate and then baked in a 250°C hot air circulating oven for 30 minutes to produce a substrate with a liquid crystal alignment film. Similarly, a coating was formed and then aligned on a counter substrate, a glass substrate without electrodes but with 4 μm-high columnar spacers.

The two substrates were assembled into a set. A sealant was printed on one of the substrates, and the other substrate was bonded together with the liquid crystal alignment film facing each other and aligned at 0°. The sealant was then cured to create an empty cell. This empty cell was then injected with liquid crystal MLC-2041 (Merck) using a reduced-pressure injection method, and the injection port was sealed to produce the liquid crystal display device of Example 1. The resulting liquid crystal display device was evaluated using the following evaluation method, and the results are shown in Table 3. The method for measuring the brightness change rate after driving is described later.

Examples 2 to 10 and Comparative Examples 1 to 7

Examples 2 to 10 and Comparative Examples 1 to 7 use the same preparation method for the liquid crystal alignment agent, liquid crystal alignment film, and liquid crystal display element as that of Example 1. The difference is that Examples 2 to 10 and Comparative Examples 1 to 7 change the type and usage of the raw materials in the liquid crystal alignment agent. Their formulas and evaluation results are shown in Table 3, respectively, and are not further described here.

Evaluation method

Brightness change rate after driving

Polarizing plates were attached perpendicularly to each other on the top and bottom surfaces of the liquid crystal display elements prepared in Examples 1 to 32 and Comparative Examples 1 to 5. The liquid crystal display unit with the polarizing plates attached was placed on a 10,000 cd/ ^m2 backlight, and the brightness (L0) in the dark state was observed using a luminance meter PR-788. The liquid crystal was then driven at room temperature and an AC voltage of 5 V for 1 hour, and when the voltage of the liquid crystal display unit was disconnected, the brightness (L1) in the dark state was observed using the aforementioned method. The brightness change rate was calculated using the following formula, and the brightness change rate of the liquid crystal display unit after driving was evaluated based on the following criteria. ※: Brightness change rate after driving <1%. ◎: 1% ≤ Brightness change rate after driving <2%. ○: 2% ≤ Brightness change rate after driving <3%. △: 3% ≤ Brightness change rate after driving <5%. ╳: Brightness change rate after driving ≥5%.

From the results in Table 3, it can be seen that if the polymer (A) of the liquid crystal alignment agent of the present invention does not contain the structure shown in formula (I) and formula (II), the liquid crystal alignment film formed by the liquid crystal display unit containing the liquid crystal alignment agent has a poor brightness change rate after driving. Wherein, in formula (I), when _A1 and _A2 represent a divalent group formed by removing two hydrogen atoms from the ring portion of a benzene ring, a pyridine ring or a pyrimidine ring, wherein the ring portion may have a substituent, and _A1 and _A2 are the same, and _Z1 represents When n represents an integer from 1 to 5, a liquid crystal alignment film produced using this liquid crystal alignment agent can further reduce the brightness variation rate of a liquid crystal display device after actuation. In formula (II), when Y ₂₁ and Y ₂₂ independently represent -O- or -S-, a liquid crystal alignment film produced using this liquid crystal alignment agent can further reduce the brightness variation rate of a liquid crystal display device after actuation.

In addition, when the liquid crystal alignment agent of the present invention contains a polymer (B), if the tetracarboxylic dianhydride component (b1) contains a tetracarboxylic dianhydride compound (b1-1), the liquid crystal alignment film prepared using this liquid crystal alignment agent can further reduce the brightness change rate of the liquid crystal display element after driving; if the diamine component (b2) contains a diamine compound (b2-1), the liquid crystal alignment film prepared using this liquid crystal alignment agent can further reduce the brightness change rate of the liquid crystal display element after driving.

It should be noted that although the present invention uses specific compounds, compositions, reaction conditions, processes, analytical methods or specific instruments as examples to illustrate the liquid crystal alignment agent, liquid crystal alignment film and liquid crystal display element used in the photo-alignment method of the present invention, anyone with ordinary knowledge in the technical field to which the present invention belongs will understand that the present invention is not limited thereto. Without departing from the spirit and scope of the present invention, the liquid crystal alignment agent, liquid crystal alignment film and liquid crystal display element used in the photo-alignment method of the present invention may also be carried out using other compounds, compositions, reaction conditions, processes, analytical methods or instruments.

Although the present invention has been disclosed above in the form of embodiments, it is not intended to limit the present invention. Anyone with ordinary knowledge in the technical field to which the present invention belongs may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the scope of the attached patent application.

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Claims (9)

A liquid crystal alignment agent for photo-alignment comprises: a polymer (A) selected from at least one polymer selected from the group consisting of a polyimide precursor and an imidized polymer of the polyimide precursor, wherein the polyimide precursor comprises a structure represented by the following formula (I) and formula (II): (I) In the formula (I), _X1 represents a structure represented by the following formula (I-1); _X2 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; _A1 and _A2 represent a divalent aromatic ring group, and the ring portion may have a substituent, wherein _A1 and _A2 are the same; _Y11 represents , and R ₁ represents a group that is detached by heat; Y ₁₂ represents a single bond, an oxygen atom, or a sulfur atom; Z ₁ represents a divalent organic group having at least one of a chain hydrocarbon structure and an alicyclic hydrocarbon structure and having a carbon number of 1 to 15: (I-1) In formula (I-1), X ₁₁ , X ₁₂ , X ₁₃ , and X ₁₄ each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, a monovalent organic group having 1 to 6 carbon atoms and containing a fluorine atom, or a phenyl group; X ₁₁ to X ₁₄ may be the same or different, and at least one of X ₁₁ , X ₁₂ , X ₁₃ , and X ₁₄ is not a hydrogen atom; (II) In the formula (II), X ₁ and X ₂ are as defined above; Y ₂₁ represents a single bond, -O-, -S-, -SS-, -SO ₂ -, -CO-, 、 , -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -(CH ₂ ) _m -, -O-(CH ₂ ) _m -O-, or -S-(CH ₂ ) _m -S-, wherein m represents an integer from 1 to 12; and Y ₂₂ represents a single bond, -O-, -S-, -CO-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, or an alkylene group having 1 to 10 carbon atoms; and a solvent (C). A liquid crystal alignment agent for photoalignment as described in claim 1, wherein _X1 represents a structure as shown in formula (I-1-1). (I-1-1) The liquid crystal aligner for photoalignment as claimed in claim 1, wherein _A1 and _A2 represent a divalent group formed by removing two hydrogen atoms from a ring portion of a benzene ring, a pyridine ring, or a pyrimidine ring, the ring portion may have a substituent, and _A1 and _A2 are the same; _Z1 represents , and n represents an integer from 1 to 5. The liquid crystal aligner for photoalignment as claimed in claim 1, wherein Y ₂₁ and Y ₂₂ independently represent -O- or -S-. The liquid crystal alignment agent for photoalignment as described in claim 1 further comprises: A polymer (B), at least one polymer selected from the group consisting of a polyimide precursor and an imidized polymer of the polyimide precursor, wherein the polyimide precursor of polymer (B) does not comprise the structure represented by formula (I) or formula (II). The liquid crystal alignment agent for photoalignment as described in claim 5, wherein the polyimide precursor of the polymer (B) is obtained by reacting a tetracarboxylic dianhydride component (b1) and a diamine component (b2), and the tetracarboxylic dianhydride component (b1) comprises a structure represented by the following formula (III): (III) In the formula (III), Z ₁₁ represents a single bond; and “*” represents a bonding position. A liquid crystal alignment agent for photoalignment as described in claim 5, wherein the polyimide precursor of the polymer (B) is obtained by reacting a tetracarboxylic dianhydride component (b1) and a diamine component (b2), and the diamine component (b2) comprises a diamine compound having at least one nitrogen-containing atom structure selected from the group consisting of a nitrogen-containing heterocyclic ring, a diamine group, and a tertiary amino group. A liquid crystal alignment film is formed using a liquid crystal alignment agent for photo-alignment method as described in any one of claims 1 to 7. A liquid crystal display element comprises the liquid crystal alignment film as described in claim 8.