TWI897382B - 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 flicker rate after high voltage driving, 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, a polymer (B) having another 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 use in photo-alignment methods, and more particularly to a liquid crystal alignment agent for use in photo-alignment methods that can reduce flicker after high-voltage 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 displays (LCDs) are widely used as display components in personal computers, smartphones, portable phones, and televisions. LCDs may include a liquid crystal layer sandwiched between a device substrate and a color filter substrate; pixel electrodes and a common electrode that apply an electric field to the liquid crystal layer; an alignment film that controls the alignment of the liquid crystal molecules in the liquid crystal layer; and thin-film transistors (TFTs) that switch the electronic signals supplied to the pixel electrodes. Known methods for driving the liquid crystal molecules include longitudinal electric field methods such as TN (twisted nematic) and VA (vertical alignment); and transverse electric field methods such as IPS (in-plane switching) and FFS (fringe field switching).

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 Application Laid-Open No. 9-297313 discloses methods utilizing photoisomerization reactions, photocrosslinking reactions, or photodecomposition reactions.

In recent years, LCDs have been frequently used in fields requiring high resolution and fast response times, such as medical equipment, aerospace, image processing, and industrial control. These applications require displays that can quickly and accurately display high-resolution images and data, while also being able to withstand extreme environmental conditions. Therefore, driving LCDs with high voltages offers higher pixel density and faster refresh rates, meeting the demands of these specialized applications.

However, liquid crystal display devices containing conventional liquid crystal alignment films produced using photo-alignment methods suffer from excessively high flicker when driven by high voltages, thus failing to meet application requirements.

In light of this, one aspect of the present invention is to provide a liquid crystal alignment agent for photo-alignment methods, comprising a polymer (A), a polymer (B), and a solvent (C). The liquid crystal alignment film formed using this liquid crystal alignment agent can reduce the flicker of liquid crystal display devices after high-voltage 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 device comprising the aforementioned liquid crystal alignment film and having a low brightness change rate after driving.

According to the above aspects of the present invention, a liquid crystal alignment agent for photo-alignment is provided, and the liquid crystal alignment agent comprises a polymer (A), a polymer (B), and a solvent (C).

Polymer (A)

The polymer (A) of the present invention may be at least one polymer selected from the group consisting of polyimide precursors obtained by reacting a tetracarboxylic dianhydride component (a1) and a diamine component (a2), and imidized polymers of polyimide precursors. For example, polymer (A) may 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 comprise a structure as shown in the following formula (I).

In formula (I), X ₁ is at least one selected from the group consisting of the structures represented by formulae (I-1) to (I-7), wherein "*" represents a bonding position; and X ₂ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

In formula (I-1), X ₁₁ , X ₁₂ , X ₁₃ , and X ₁₄ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, a monovalent organic group having 1 to 6 carbon atoms and containing a fluorine atom, or a phenyl group. In formula (I-7), X ₁₅ and X ₁₆ each independently represent a hydrogen atom or a methyl group.

If polymer (A) does not contain the structure shown in formula (I), the liquid crystal alignment film formed with this liquid crystal alignment agent may have a high flicker after high voltage 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 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 include an alicyclic tetracarboxylic dianhydride (a1-1) or a derivative thereof as shown in the following formula (A11). The alicyclic tetracarboxylic dianhydride (a1-1) or a derivative thereof shown in 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. In the present invention, the alicyclic tetracarboxylic dianhydride (a1-1) shown in formula (A11) may be, for example, an acid dianhydride obtained by intramolecular dehydration of four carboxyl groups, including at least one carboxyl group bonded to an alicyclic structure. However, none of the four carboxyl groups are bonded to an aromatic ring. Alternatively, it is not necessary to be composed solely of an alicyclic structure; a portion thereof may have a chain hydrocarbon structure or an aromatic ring structure. An aromatic tetracarboxylic dianhydride may be, for example, an acid dianhydride obtained by intramolecular dehydration of four carboxyl groups, including at least one carboxyl group bonded to an aromatic ring. However, it is not necessary to be composed solely of an aromatic ring structure; a portion thereof may have a chain hydrocarbon structure or an alicyclic structure. An acyclic aliphatic tetracarboxylic dianhydride may be, for example, an acid dianhydride obtained by intramolecular dehydration of four carboxyl groups bonded to a chain hydrocarbon structure. However, it is not necessary to be composed solely of a chain hydrocarbon structure; a portion thereof may have an alicyclic structure or an aromatic ring structure.

In formula (A11), X ₁ can be selected from at least one of the groups consisting of the structures represented by formulas (I-1) to (I-7) below, and “*” represents a bonding position.

In formula (I-1), X ₁₁ , X ₁₂ , X ₁₃ , and X ₁₄ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, a monovalent organic group having 1 to 6 carbon atoms and containing a fluorine atom, or a phenyl group. In formula (I-7), X ₁₅ and X ₁₆ each independently represent a hydrogen atom or a methyl group.

In some embodiments, X ₁ can represent the structures shown in the following formulas (I-1-1) to (I-1-6).

Preferably, _X1 represents a structure represented by formula (I-1-1). When _X1 represents a structure represented by formula (I-1-1), the flicker after high-voltage driving of a liquid crystal display device containing a liquid crystal alignment film formed therewith can be further improved.

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

When the tetracarboxylic dianhydride component (a1) does not contain the alicyclic tetracarboxylic dianhydride (a1-1) represented by formula (A11), the liquid crystal display device containing the liquid crystal alignment film formed therewith is prone to excessive flicker after high voltage driving.

Other tetracarboxylic dianhydrides (a1-2)

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

In formula (A12), X ₁ ′ may represent the structures shown in the following formulas (A12-1) to (A12-32), wherein “*” represents a bonding position.

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) can be used alone or in combination.

Based on a total usage of 100 mol of the tetracarboxylic dianhydride component (a1), the usage 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). Furthermore, the diamine component (a2) may optionally include a diamine compound (a2-2) and a diamine compound (a2-3).

Diamine compound (a2-1)

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

If the diamine component (a2) does not contain the diamine compound (a2-1) represented by formula (A21), the liquid crystal display device containing the liquid crystal alignment film formed therefrom may have a problem of excessively high flicker after high-voltage driving.

Based on a total usage amount of 100 mol of the diamine component (a2), the usage amount of the diamine compound (a2-1) can be 5 mol to 45 mol, preferably 7 mol to 42 mol, and more preferably 10 mol to 40 mol.

Diamine compound (a2-2)

The diamine compound (a2-2) may include a diamine compound represented by the following formula (A22-1) or formula (A22-2).

In formula (A22-1), Y ₃₁ represents a divalent organic group as shown in formula (A22-3) below. Plural Y ₃₂ groups independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. In formula (A22-2), plural Y ₃₃ groups independently represent a divalent organic group as shown in formula (A22-3') below.

In formula (A22-3), 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 (A22-3'), 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 (A22-3) preferably includes the groups represented by formulas (A22-3-1) to (A22-3-16), where "*" represents the bonding position.

In formula (A22-3-14), 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 (A22-3') preferably includes groups represented by formulas (A22-3-7) to (A22-3-16).

When the diamine compound (a2-2) contains a plurality of diamine compounds as represented by formula (A22-1), it is preferably a combination of a diamine compound in which Y ₃₁ in formula (A22-1) represents a diamine compound of formula (A22-3-1) to formula (A22-3-14) and a diamine compound in which Y ₃₁ in formula (A22-1) represents a diamine compound of formula (A22-3-15) to formula (A22-3-16).

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

The aforementioned diamine compound (a2-2) can 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 diamine compound (a2-2) can be 25 mol to 93 mol, preferably 38 mol to 90 mol, and more preferably 50 mol to 87 mol.

Other diamine compounds (a2-3)

In addition to the aforementioned diamine compounds (a2-1) and (a2-2), the diamine component (a2) used to obtain the polymer (A) may optionally further comprise other diamine compounds (a2-3). For example, the other diamine compounds (a2-3) may include, but are not limited to: 4,4'-diaminoazobenzene or diamine compounds represented by the following formulas (A23-1) to (A23-3), 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 (A23-1) to (A23-3). 4) Diamine compounds having a carboxyl group, such as the diamine compounds represented by formula (A23-7); 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ketone, 1,4-bis(4-aminobenzyl)benzene, 4,4'-diaminodiphenyl ether, 1-(4-aminophenyl)-1,3,3-trimethyl-1H-dihydroindane-5-amine or 1-(4-aminophenyl)-2,3-dihydro-1,3,3-trimethyl-1H- Inden-6-amine; diamine compounds having a urea bond, such as diamine compounds represented by the following formulas (A23-8) to (A23-10); diamine compounds having an amide bond, such as diamine compounds represented by the following formulas (A23-11) to (A23-13); diamine compounds having a photopolymerizable group at the end, such as 2-(2,4-diaminophenoxy)ethyl methacrylate or 2,4-diamino-N,N-diallylaniline; diamine compounds having a photopolymerizable group, such as diamine compounds represented by the following formulas (A23-14) to (A23-15); A diamine compound having an oxazoline structure; and 4-amino-N-methylphenethylamine.

In formula (A23-4), Y ₅₁ represents a single bond, -CH ₂ -, -C ₂ H ₄ -, -C(CH ₃ ) ₂ -, -CF ₂ -, -C(CF ₃ ) ₂ -, -O-, -CO-, -NH-, -N(CH ₃ )-, -CONH-, -NHCO-, -CH ₂ O-, -OCH ₂ -, -COO-, -OCO-, -CON(CH ₃ )-, or -N(CH ₃ )CO-; m1 and m2 each independently represent an integer from 0 to 4, and (m1 + m2) represents an integer from 1 to 4. In formula (A23-5), m3 and m4 each independently represent an integer from 1 to 5. In formula (A23-6), _Y52 represents a linear or branched alkyl group having 1 to 5 carbon atoms; m5 represents an integer from 1 to 5. In formula (A23-7), _Y53 and _Y54 each independently represent a single bond, _-CH2- , _-C2H4- , -C( _CH3 ) _2- , _-CF2- , -C( _CF3 ) _2- , -O-, _-CO- , -NH-, -N( _CH3 )-, -CONH-, -NHCO-, _-CH2O- , _-OCH2- , -COO-, -OCO-, -CON( _CH3 )-, or -N( _CH3 )CO-; m6 represents an integer from 1 to 4.

The aforementioned other diamine compounds (a2-3) can be used alone or in combination.

Based on a total usage amount of 100 mol of the diamine component (a2), the usage amount of the other diamine compounds (a2-3) can be 0 mol to 68 mol, preferably 0 mol to 52 mol, and more preferably 0 mol to 37 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 compound, 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. 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.

The polyimide precursor of polymer (B) comprises the structure shown in the following formula (II).

In formula (II), X ₃ represents a tetravalent organic group; X ₄ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

If polymer (B) does not contain the structure of formula (II), the liquid crystal alignment film formed by this liquid crystal alignment agent is prone to excessive flicker after high voltage driving.

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 improve the flash after high voltage driving, the tetracarboxylic dianhydride component (b1) preferably comprises a tetracarboxylic dianhydride compound represented by the above formula (A12) and wherein X ₁ ' represents a structure represented by the following formula (III) (hereinafter referred to as tetracarboxylic dianhydride compound (b1-1)).

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

The aforementioned tetracarboxylic dianhydride compound (b1-1) can 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).

Based on a total usage amount of 100 mol of the tetracarboxylic dianhydride component (b1), the usage amount 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 a tetracarboxylic dianhydride compound (b1-1) represented by formula (III), the flicker after high-voltage driving of a liquid crystal display device containing a liquid crystal alignment film formed therewith can be further improved.

Diamine component (b2)

The diamine component (b2) used to obtain the polymer (B) may include a diamine compound (b2-1) represented by the following formula (B21).

If the diamine component (b2) does not contain the diamine compound (b2-1) represented by formula (B21), the liquid crystal display device containing the liquid crystal alignment film formed therewith may have a problem of excessively high flicker after high-voltage driving.

Based on a total usage amount of 100 mol of the diamine component (b2), the usage amount of the diamine compound (b2-1) can be 3 mol to 100 mol, preferably 5 mol to 100 mol, and more preferably 7 mol to 100 mol.

Additionally, the diamine component (b2) 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 diamine compound (b2-2)). However, the diamine component (b2) does not include the aforementioned diamine compound (a2-1).

Diamine component (b2-2)

The diamine compound (b2-2) 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, Pyridine, quinone phenanthene, tie ,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 (b2-2) having the above-mentioned specific nitrogen-containing structure may contain a diamine group and a tertiary amine group as shown in the following formula (B22).

In formula (B22), 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 may include, but is not limited to, cyclohexyl; and the aryl group 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 (b2-2) 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 (B22-1) to (B22-8), or diamine compounds represented by the following formulas (B22-9) to (B22-26).

The diamine component (b2) can be used alone or in combination.

Based on a total usage amount of 100 mol of the diamine component (b2), the usage amount of the diamine compound (b2-2) can be 3 mol to 90 mol, preferably 5 mol to 80 mol, and more preferably 7 mol to 70 mol.

If the diamine component (b2) includes at least one nitrogen-containing diamine compound (b2-2) selected from the group consisting of nitrogen-containing heterocyclic rings, diamine groups, and tertiary amine groups, the flicker after high-voltage driving of a liquid crystal display device containing a liquid crystal alignment film formed therewith can be further improved.

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.

The aforementioned solvents can be used singly or as a mixture of multiples. Furthermore, even if a solvent cannot dissolve the polymer, it can still be mixed with the aforementioned solvents, as long as the resulting polymer does 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, it is 1 wt% to 50 wt%, and more preferably, 5 wt% to 30 wt%. The reaction can also be carried out initially at a high concentration, with additional solvent added later. 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 conventional polycondensation reaction, the closer this molar ratio is to 1.0, the greater the molecular weight of the resulting polymer (A) or polymer (B).

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 the 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 amide group or its derivative 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 by adding a catalyst to the polymer solution. When thermal imidization is performed in solution, the temperature is preferably 100°C to 400°C, and more preferably 120°C to 250°C. During thermal imidization, it is preferred to remove water generated during the imidization reaction 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 of the catalytic imidization 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 three or more 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 10wt% to 15wt% solution, the concentration of polymer (A) or polymer (B) of the present invention is not particularly limited. For ease of handling, the solution concentration can be, for example, 10mPa‧s to 1000mPa‧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 10wt% to 15wt% polymer solution.

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 diamine component described above can be used in combination with an appropriate end-capping agent to synthesize an end-sealed polymer. End-sealed polymers can improve the film hardness of the liquid crystal alignment film obtained by coating, as well as enhance the adhesion between the sealant and the liquid crystal alignment film. The ends of the polymer (A) or polymer (B) of the present invention may, for example, contain amino groups, carboxyl groups, acid anhydride groups, or derivatives thereof. Amino groups, carboxyl groups, acid anhydride groups, or derivatives thereof can be obtained through a conventional condensation reaction or by capping the ends using an end-capping agent described below. Similarly, the aforementioned derivatives can be obtained, for example, using the end-capping agent described below.

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 agent can 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 polymers

The liquid crystal alignment agent of the present invention comprises a polymer (A), a polymer (B), and a solvent (C). In addition to polymers (A) and (B), the liquid crystal alignment agent of the present invention may optionally comprise 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 (i.e., the aforementioned 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 1wt%. From the perspective of the storage stability of the solution, the polymer concentration in the liquid crystal alignment agent is preferably below 10wt%. The ideal polymer concentration can be 2wt% to 8wt%. The content of polymer (A) in the liquid crystal alignment agent can be appropriately varied by the liquid crystal alignment agent coating method and/or the desired liquid crystal alignment film thickness. It 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 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 the total amount of solvent used in the liquid crystal alignment agent being 100 wt%, the amount of good solvent used can 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 mixture of the aforementioned solvents and a solvent that improves the coating properties and surface smoothness of the coating film during application (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 the total amount of solvents used in the liquid crystal alignment agent being 100wt%, the amount of the poor solvent used is preferably 1wt% to 80wt%, more preferably 10wt% to 80wt%, and even more preferably 20wt% to 70wt%. 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 preferred solvent combination of a good solvent and a poor solvent may be, 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 ethylene glycol monobutyl ether. 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) can be used alone or in combination.

Based on a total amount of 100 parts by weight 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.

Additive ingredients

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)ethyltrimethoxysilane, 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. When using a bonding agent, 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 can 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), in order to exhibit good resistance to AC afterimages and effectively improve film strength.

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 containing ethylene oxide

Specific examples of compounds containing an ethylene oxide group include N,N,N',N'-tetraethylene oxide propyl-m-xylenediamine, 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, and compounds containing nitrogen atoms such as those shown in the following formulas (E4) to (E6).

Compounds with propylene oxide groups

Specific examples of compounds having an propylene oxide group include compounds represented by the following formulas (E7) to (E16).

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

Compounds having a group represented by formula (E1) Specific examples of compounds having a group represented by formula (E1) include compounds represented by formulas (E1-1) to (E1-12) below.

A compound having a group represented by formula (E2)

Specific examples of compounds having a group represented by formula (E2) include compounds represented by formulas (E2-1) to (E2-4) below.

A compound having a group represented by formula (E3)

Specific examples of compounds having a group represented by formula (E3) include compounds represented by formulas (E3-1) to (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. To ensure a smooth crosslinking reaction 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 above-mentioned amino acids include glycine, alanine, cysteine, methionine, asparagine, glutamine, valine, leucine, phenylalanine, tyrosine, tryptophan, proline, hydroxyproline, arginine, histidine, lysine, or ornithine. For the purpose of promoting the amidation of a compound, a more preferred example is N-α-(9-fluorenylmethoxycarbonyl)-N-τ-(tert-butyloxycarbonyl)-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 method or an FFS method. 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 steps (1) to (4) or steps (1) to (2) and step (4).

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

The liquid crystal alignment agent of the present invention is applied to one side of a substrate provided with a patterned transparent conductive film using an appropriate coating method such as roll coating, spin coating, printing or inkjet coating. There are no special restrictions on the substrate, as long as it is a highly transparent substrate. A glass substrate or a silicon nitride substrate can also be used in conjunction with a plastic substrate such as an acrylic substrate or a polycarbonate substrate. Secondly, in a reflective liquid crystal display element, if 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 element, 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.

Methods for applying the liquid crystal alignment agent to a substrate to form a film include screen printing, lithographic printing, flexographic printing, inkjet printing, or spray coating. Among them, inkjet coating is the most preferred method for forming a film.

Step (2): Calcination of 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 film after calcination 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 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 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 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 rubbing 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, depending on the circumstances, heating the film at a temperature of 150°C to 250°C to impart liquid crystal alignment properties (also known as liquid crystal alignment ability). The radiation can be ultraviolet light or visible light with a wavelength of 100nm to 800nm. Ultraviolet light with a wavelength of 100nm to 400nm is preferred, and ultraviolet light with a wavelength of 200nm to 400nm 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 achieve a liquid crystal alignment film in which variations (non-uniformity) in the liquid crystal alignment within the film surface are effectively suppressed, even with a reduced light dose for alignment treatment. 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 irradiated coating is preferably 50°C to 300°C, and 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 their respective liquid crystal alignment films separated by a gap (cell gap). Next, the edges of the two substrates are bonded together with a sealant. 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). A UV-curable sealant, such as one, is applied to predetermined locations on one of the two substrates, which already have a liquid crystal alignment film. A liquid crystal composition is then added to the surface of the liquid crystal alignment film at predetermined locations. The other substrate is then attached with the liquid crystal alignment films facing each other, and the liquid crystal composition is pressed against the entire surface of the substrate, contacting the film. The entire surface of the substrate is then irradiated with UV light to cure the sealant. When using any of the aforementioned methods, it is preferred to further heat the liquid crystal composition to a temperature at which it reaches an isotropic phase and then slowly cool it to room temperature to eliminate the flow alignment caused by the liquid crystal filling process. Next, when the coating is rubbed, 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.

If necessary, a polarizing plate can be attached to the outer surface of the liquid crystal cell to produce a liquid crystal display device. The polarizing plate attached to the outer surface of the liquid crystal cell can be a polarizing film made of elongated polyvinyl alcohol that also absorbs iodine, known as an "H-film." This polarizing plate can be sandwiched between cellulose acetate protective films or comprised solely of the H-film.

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

Preparation of polymer (A)

Synthesis Example A-1

A 500 ml four-necked Erlenmeyer flask equipped with a nitrogen inlet, a stirrer, a condenser, and a thermometer was introduced with nitrogen. Then, 0.996 g (0.0025 mol) of diamine compound (a2-1), 8.0 g (0.025 mol) of diamine compound (a2-2-1), 5.05 g (0.0175 mol) of diamine compound (a2-2-4), 1.00 g (0.005 mol) of 4,4-diaminodiphenyl ether (i.e., diamine compound (a2-3-2)), and 80 g of N-methyl-2-pyrrolidone (hereinafter referred to as NMP) were added and stirred at room temperature until dissolved. Next, 3.36 g (0.015 mol) of compound (a1-1-1), 7.56 g (0.035 mol) of compound (a1-2-1), and 20 g of NMP were added and 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 washed with methanol and filtered three times. The product was then dried in a vacuum oven at 60°C to obtain polymer (A-1) of Synthesis Example A-1, the formula of which is shown in Table 1.

Synthesis Examples A-2 to A-6 and Comparative Synthesis Examples A’-1 to A’-2

Synthesis Examples A-2 through A-6 and Comparative Synthesis Examples A'-1 through A'-2 were prepared using the same method as the polymer (A-1) in Synthesis Example A-1. The differences were that the types and amounts of raw materials used in the polymers were modified in Synthesis Examples A-2 through A-6 and Comparative Synthesis Examples A'-1 through A'-2. The formulations are shown in Table 1 and are not further described here.

Preparation of polymer (B)

Synthesis Examples B-1 to B-4 and Comparative Synthesis Examples B’-1 to B’-2

Synthesis Examples B-1 through B-4 and Comparative Synthesis Examples B'-1 through B'-2 were prepared using the same method as the polymer (A-1) in Synthesis Example A-1. The differences between Synthesis Examples B-1 through B-4 and Comparative Synthesis Examples B'-1 through B'-2 are in the types and amounts of raw materials used in the polymers. Their formulations are shown in Table 2 and are not further detailed here.

Preparation of liquid crystal alignment agents, liquid crystal alignment films, and liquid crystal display devices

Example 1

Weigh 50 parts by weight of the polymer (A-4) prepared in Synthesis Example A-4, 50 parts by weight of the polymer (B-4) prepared in Synthesis Example B-4, and 1500 parts by weight of NMP, and stir and mix 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 (electrode width: 10μm, electrode spacing: 10μm, and electrode height: 50nm). The ITO electrodes each had a serrated shape, with the serrated portions arranged in a spaced-apart, interlocking pattern. 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 circulating oven for 30 minutes, resulting in a 100nm thick coating.

The coated surface was irradiated with 254nm 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 4μm-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 testing the flicker degree after high-voltage driving is described later.

Examples 2 to 12 and Comparative Examples 1 to 4

Examples 2 through 12 and Comparative Examples 1 through 4 utilize the same preparation methods for the liquid crystal alignment agent, liquid crystal alignment film, and liquid crystal display device as Example 1. The difference between Examples 2 through 12 and Comparative Examples 1 through 4 is that the types and amounts of raw materials in the liquid crystal alignment agent are varied. The formulations and evaluation results are shown in Tables 3 and 4, respectively, and are not further described here.

Evaluation method

Flicker intensity after high voltage drive

The fabricated liquid crystal display (LCD) device was placed between two polarizers with their polarization axes perpendicular to each other. The LED backlight was illuminated with no voltage applied, and the LCD device's angle was adjusted to minimize the amount of light passing through. An AC voltage with a frequency of 30 Hz was then applied to the LCD device, and the V-T curve (voltage-transmittance curve) was measured. The AC voltages that produced relative transmittances of 23% and 100% were calculated as the driving voltages.

The flicker measurement method after driving is to turn off the illuminated LED backlight with the LCD device at 23°C. After 72 hours of light shielding, the device is then turned on again. Simultaneously with the backlight onset, an AC voltage with a relative transmittance of 100% and a frequency of 30Hz is applied. The device is then driven for 24 hours. A 30Hz AC voltage with a relative transmittance of 23% is then applied, and the flicker amplitude is tracked. The flicker amplitude is measured using a data acquisition/data recording switching device (Agilent Technologies) connected to a photodiode and an I-V converter amplifier. The luminance of the LCD device located between the two polarizing plates is read. Flicker (FL) is calculated using the following formula (i). The lower the FL, the better the quality of the liquid crystal display device produced using the liquid crystal alignment agent.

In the above formula (i), z is the brightness value read when the device 34970A is driven by an AC voltage with a relative transmittance of 23% and a frequency of 30Hz.

※: FL<3%.

◎: 3% ≤ FL < 3.5%.

○: 3.5% ≤ FL < 4%.

△: 4% ≤ FL < 5%.

×: FL ≥ 5%.

The results in Tables 3 and 4 show that when the diamine component (b2) used to react to form polymer (B) does not contain the diamine compound (b2-1) represented by formula (B21), the liquid crystal display device containing the resulting liquid crystal alignment film exhibits excessively high flicker after high-voltage driving. Furthermore, when the diamine component (a2) used to react to form polymer (A) does not contain the diamine compound (a2-1) represented by formula (A21), the liquid crystal display device containing the resulting liquid crystal alignment film exhibits excessively high flicker after high-voltage driving.

Furthermore, if the tetracarboxylic dianhydride component (a1) used to react to form polymer (A) comprises a structure represented by formula (I-1-1) (i.e., comprises tetracarboxylic dianhydride compound (a1-1-1)), the flicker intensity of the resulting liquid crystal display device after high-voltage driving can be further reduced. When the tetracarboxylic dianhydride component (b1) used to react to form polymer (B) comprises a structure represented by formula (III) (e.g., tetracarboxylic dianhydride compounds (b1-1-1) to (b1-1-3)), the flicker intensity of the resulting liquid crystal display device after high-voltage driving can be further reduced. Furthermore, when the diamine component (b2) used to react to form the polymer (B) comprises a diamine compound having at least one nitrogen-containing structure selected from the group consisting of nitrogen-containing heterocyclic rings, diamine groups, and tertiary amine groups (e.g., diamine compounds (b2-2-1) to (b2-2-4)), the flicker of the resulting liquid crystal display device after high-voltage driving can be further reduced.

It should be noted that while 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 device used in the photo-alignment method of the present invention, anyone with ordinary skill in the art to which the present invention pertains will recognize that the present invention is not limited thereto. The liquid crystal alignment agent, liquid crystal alignment film, and liquid crystal display device used in the photo-alignment method of the present invention may also be implemented using other compounds, compositions, reaction conditions, processes, analytical methods, or instruments without departing from the spirit and scope of the present invention.

Although the present invention has been disclosed above in terms of embodiments, this is not intended to limit the present invention. Anyone with ordinary skill in the art to which the present invention pertains may make various modifications and improvements 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 patent application attached hereto.

(without)

Claims (8)

A liquid crystal alignment agent for photo-alignment method comprises: a polymer (A), 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 the polymer (A) comprises a structure represented by the following formula (I): (I) In the formula (I), X ₁ is one selected from the group consisting of the structures represented by the following formulae (I-1) to (I-7), wherein "*" represents a bonding position; X ₂ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; (I-1) (I-2) (I-3) (I-4) (I-5) (I-6) (I-7) In formula (I-1), X ₁₁ , X ₁₂ , X ₁₃ , and X ₁₄ independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, or a monovalent organic group having 1 to 6 carbon atoms and containing a fluorine atom; and in formula (I-7), X ₁₅ and X ₁₆ independently represent a hydrogen atom or a methyl group; a polymer (B) comprising 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) comprises a structure represented by formula (II) below: (II) In formula (II), X ₃ represents a tetravalent organic group; X ₄ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, 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 structure selected from the group consisting of a nitrogen-containing heterocyclic ring, a diamine group, and a tertiary amine group; and a solvent (C). The liquid crystal alignment agent for photoalignment as claimed in claim 1, wherein the polymer (A) is obtained by reacting a tetracarboxylic dianhydride component (a1) and a diamine component (a2), and the diamine component (a2) comprises a compound represented by the following formula (A21): (A21). The liquid crystal alignment agent for photoalignment as claimed in claim 1, wherein the polymer (B) is obtained by reacting a tetracarboxylic dianhydride component (b1) and a diamine component (b2), and the diamine component (b2) comprises a compound represented by the following formula (B21): (B21). The liquid crystal alignment agent for photoalignment as described in claim 1, wherein _X1 represents a structure represented by the following formula (I-1-1) to formula (I-1-6): (I-1-1) (I-1-2) (I-1-3) (I-1-4) (I-1-5) (I-1-6). A liquid crystal alignment agent for photoalignment as described in claim 4, wherein _X1 represents a structure as shown in formula (I-1-1). The liquid crystal alignment agent for photoalignment as described in claim 1, wherein 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 film is formed using a liquid crystal alignment agent for photo-alignment method as described in any one of claims 1 to 6. A liquid crystal display element comprises the liquid crystal alignment film as described in claim 7.