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

Abstract

The invention provides a liquid crystal alignment agent for a light alignment method, a liquid crystal alignment film formed by using the liquid crystal alignment agent, and a liquid crystal display element comprising the liquid crystal alignment film, wherein the liquid crystal alignment agent can reduce flicker degree after high-voltage driving. The liquid crystal alignment agent comprises a polymer (A) with a specific structure, a polymer (B) with another specific structure and a solvent (C).

Description

Technical Field

[0001] The present invention relates to a liquid crystal aligning agent for photo-alignment method, and particularly provides a liquid crystal aligning agent for photo-alignment method capable of reducing the flicker degree after high voltage driving, a liquid crystal alignment film formed by using this liquid crystal aligning agent, and a liquid crystal display element including this liquid crystal alignment film. Background Art

[0002] Conventional liquid crystal display elements are widely used as display components for personal computers, smart phones, portable phones, television receivers, etc. The liquid crystal display element may include a liquid crystal layer sandwiched between an element substrate and a color filter substrate, pixel electrodes and common electrodes for applying an electric field to the liquid crystal layer, an alignment film for controlling the alignment of liquid crystal molecules in the liquid crystal layer, and thin film transistors (TFTs) for switching the electronic signals supplied to the pixel electrodes. In terms of the driving method of liquid crystal molecules, longitudinal electric field methods such as TN (Twisted Nematic) method and VA (Vertical Alignment) method are known, as well as transverse electric field methods such as IPS (In-Plane Switching) method and FFS (Fringe Field Switching) method.

[0003] Currently, the most widely used liquid crystal alignment film in the industry is obtained by rubbing the surface of a film composed of polyamic acid and / or polyimide obtained by imidization thereof formed on an electrode substrate with a cloth such as cotton, nylon or polyester in one direction. The rubbing treatment is a commonly used industrial method that is simple and has high productivity. However, with the high performance, high fineness and large size of liquid crystal display elements, various problems such as unevenness in the alignment treatment surface are caused by dust, mechanical force and static electricity generated on the surface of the alignment film due to the rubbing treatment. As an alternative alignment treatment method to the rubbing treatment, a photo-alignment method of imparting liquid crystal alignment ability by irradiating polarized radiation is known. For the photo-alignment method, Japanese Patent Laid-Open No. 9-297313 has disclosed those using a photo-isomerization reaction, those using a photo-crosslinking reaction, or those using a photo-decomposition reaction, etc.

[0004] In recent years, since liquid crystal displays are often used in fields such as medical equipment, aerospace, image processing and industrial control that require high resolution and fast response time, and the aforementioned applications require a display that can quickly and accurately display high-resolution images and data and must be able to withstand extreme environmental conditions. Therefore, driving a liquid crystal display at a high voltage can provide a higher pixel density and a faster update rate, thus meeting the requirements of the above special applications.

[0005] However, after high-voltage driving, a liquid crystal display element containing a conventional liquid crystal alignment film prepared by the photo-alignment method has a problem of excessive flicker, so it cannot meet the application requirements. SUMMARY OF THE INVENTION

[0006] In view of this, one aspect of the present invention is to provide a liquid crystal aligning agent for photo-alignment method, which comprises a polymer (A), a polymer (B) and a solvent (C). The liquid crystal alignment film formed by using this liquid crystal aligning agent can reduce the flicker after high-voltage driving of the liquid crystal display element.

[0007] Another aspect of the present invention is to provide a liquid crystal alignment film formed by using the above liquid crystal aligning agent for photo-alignment method.

[0008] Another aspect of the present invention is to provide a liquid crystal display element which comprises the aforementioned liquid crystal alignment film and has a low brightness change rate after driving.

[0009] According to the above aspects of the present invention, a liquid crystal aligning agent for photo-alignment method is proposed, and this liquid crystal aligning agent comprises a polymer (A), a polymer (B) and a solvent (C).

[0010] Polymer (A)

[0011] The polymer (A) of the present invention can be selected from at least one polymer in the group consisting of a polyimide precursor obtained by reacting a tetracarboxylic dianhydride component (a1) and a diamine component (a2), and an imidized polymer of the polyimide precursor. For example, the polymer (A) may include, for example, a polyimide precursor having a structure of an imide precursor such as polyamic acid and polyamic acid ester, and / or an imidized product (i.e., polyimide) of the polyimide precursor.

[0012] The polyimide precursor of the polymer (A) may include a structure represented by the following formula (I):

[0013]

[0014] In formula (I), X1 is at least one selected from the group consisting of structures represented by the following formula (I-1) to formula (I-7), where "*" represents the bonding position; X2 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; Y1 represents a divalent organic group:

[0015]

[0016] In formula (I-1), X 11 , X 12 , X 13 and X 14Each 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. In formula (I-7), X 15 and X 16 each independently represent a hydrogen atom or a methyl group.

[0017] When the polymer (A) does not contain the structure represented by formula (I), the liquid crystal display element having a liquid crystal alignment film formed by this liquid crystal aligning agent is liable to have a problem of excessive flicker after high-voltage driving.

[0018] Tetracarboxylic dianhydride component (a1)

[0019] In addition to using a tetracarboxylic dianhydride compound, the tetracarboxylic dianhydride component (a1) that reacts with the diamine component (a2) in the present invention can also use tetracarboxylic dihalides, tetraalkyl esters of tetracarboxylic acids, or derivatives of tetracarboxylic dianhydrides such as tetraalkyl ester dihalides of tetracarboxylic acids. The tetracarboxylic dianhydride component (a1) can be used alone with one kind of tetracarboxylic dianhydride compound or its derivative, or can be used in combination by mixing multiple kinds.

[0020] The tetracarboxylic dianhydride component (a1) can include the alicyclic tetracarboxylic dianhydride (a1-1) represented by formula (A11) and other tetracarboxylic dianhydrides (a1-2).

[0021] The alicyclic tetracarboxylic dianhydride (a1-1) represented by formula (A11)

[0022] The tetracarboxylic dianhydride component (a1) used to react to obtain the polymer (A) can include the alicyclic tetracarboxylic dianhydride (a1-1) represented by the following formula (A11) or its derivative:

[0023]

[0024] The alicyclic tetracarboxylic dianhydride (a1-1) represented by formula (A11) or a derivative thereof 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) represented by 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 these four carboxyl groups are bonded to an aromatic ring. Alternatively, it does not have to be composed only of an alicyclic structure, and a part thereof may also have a chain hydrocarbon structure or an aromatic ring structure. The 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 does not have to be composed only of an aromatic ring structure, and a part thereof may also have a chain hydrocarbon structure or an alicyclic structure. The acyclic aliphatic tetracarboxylic dianhydride may be, for example, an acid dianhydride obtained by intramolecular dehydration of four carboxyl groups bonded to a chain hydrocarbon structure. However, it does not have to be composed only of a chain hydrocarbon structure, and a part thereof may also have an alicyclic structure or an aromatic ring structure.

[0025] In formula (A11), X1 may be selected from at least one of the structures represented by the following formulas (I-1) to (I-7), and "*" represents the bonding position:

[0026]

[0027]

[0028] 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.

[0029] In some embodiments, X1 may represent the structures represented by the following formulas (I-1-1) to (I-1-6):

[0030]

[0031]

[0032] Preferably, X1 represents the structure represented by formula (I-1-1). When X1 represents the structure represented by formula (I-1-1), the flicker degree after high-voltage driving of a liquid crystal display element including a liquid crystal alignment film formed therefrom can be further improved.

[0033] Based on the total usage amount of the tetracarboxylic dianhydride component (a1) being 100 moles, the usage amount of the alicyclic tetracarboxylic dianhydride (a1-1) represented by formula (A11) is 30 moles to 100 moles, preferably 40 moles to 100 moles, and more preferably 50 moles to 100 moles.

[0034] When the tetracarboxylic dianhydride component (a1) does not contain the alicyclic tetracarboxylic dianhydride (a1-1) represented by formula (A11), the liquid crystal display element containing the liquid crystal alignment film formed therefrom is likely to have a problem of excessive flicker after high-voltage driving.

[0035] Other tetracarboxylic dianhydrides (a1-2)

[0036] The other tetracarboxylic dianhydrides (a1-2) may include the tetracarboxylic dianhydride compounds and their derivatives represented by the following formula (A12):

[0037]

[0038] In formula (A12), X1′ may represent the structures represented by the following formula (A12-1) to formula (A12-32), where " * " represents the bonding position:

[0039]

[0040]

[0041]

[0042]

[0043] In formula (A12-5) and formula (A12-6), X 11 ′ and X 12 ′ each independently represent a single bond, -O-, -CO-, -COO-, phenylene, sulfonyl, or amide group, and multiple X 12 ′ may be the same as or different from each other. In formula (A12-5), a1 represents an integer of 0 or 1; in formula (A12-6), a1 represents an integer of 0 or 1. In formula (A12-14), X 13 ′ 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 containing a fluorine atom and having 1 to 6 carbon atoms, or a phenyl group, and multiple X 13 ′ may be the same as or different from each other. From the viewpoint of liquid crystal alignment property, 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.

[0044] In some specific examples, the aforementioned formula (A12-5) and formula (A12-6) may include but are not limited to the structures shown below:

[0045]

[0046]

[0047] The aforementioned other tetracarboxylic dianhydrides (a1-2) can be used individually or in combination of multiple kinds.

[0048] Based on the total usage amount of the tetracarboxylic dianhydride component (a1) being 100 moles, the usage amount of the other tetracarboxylic dianhydrides (a1-2) is from 0 mole to 70 moles, preferably from 0 mole to 60 moles, and more preferably from 0 mole to 50 moles.

[0049] Diamine component (a2)

[0050] The diamine component (a2) may include a diamine compound (a2-1), a diamine compound (a2-2), and other diamine compounds (a2-3).

[0051] Diamine compound (a2-1)

[0052] The diamine compound (a2-1) may include a diamine compound represented by the following formula (A21-1) or formula (A21-2):

[0053]

[0054] In formula (A21-1), Y 31 represents a divalent organic group represented by the following formula (A21-3). Multiple Ys 32 each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. In formula (A21-2), multiple Ys 33 each independently represent a divalent organic group represented by the following formula (A21-3′):

[0055]

[0056] In formula (A21-3), Ar each independently represents a divalent benzene ring, a biphenyl structure, or a naphthalene ring, and the hydrogen atoms of the benzene ring, biphenyl structure, or naphthalene ring may or may not be substituted by a monovalent substituent group; Y 31 ′ represents -(CH2) n -, n represents an integer from 2 to 18, and at least one -CH2- in -(CH2) n - may or may not be substituted by -O-, -C(=O)-, or -O-C(=O)-; p1 represents an integer of 0 or 1; 「*」 represents the bonding position.

[0057] In formula (A21-3′), Ar′ independently represents a divalent benzene ring or biphenyl structure, and the hydrogen atoms of the benzene ring or biphenyl structure may be substituted or unsubstituted by a monovalent substituent group; Y 33 ′ represents -(CH2) n -, n represents an integer from 2 to 18, and at least one -CH2- in -(CH2) n - may be substituted or unsubstituted by -O-, -C(=O)- or -O-C(=O)-; p2 represents an integer of 0 or 1; 「*」 represents the bonding position.

[0058] The monovalent substituent group of the aforementioned benzene ring, biphenyl structure, or naphthalene 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, etc.

[0059] From the viewpoint of improving the liquid crystal alignment, the divalent organic group represented by formula (A21-3) preferably includes the groups represented by the following formula (A21-3-1) to formula (A21-3-16), where 「*」 represents the bonding position:

[0060]

[0061]

[0062]

[0063] In formula (A21-3-14), multiple m independently represent an integer from 1 to 3.

[0064] From the viewpoint of improving the liquid crystal alignment, the divalent organic group represented by formula (A21-3′) preferably includes the groups represented by formula (A21-3-7) to formula (A21-3-16).

[0065] When the diamine compound (a2-3) contains multiple diamine compounds represented by formula (A21-1), it is preferably that Y in formula (A21-1) 31 represents a combination of a diamine compound represented by formula (A21-3-1) to formula (A21-3-14) and a diamine compound represented by Y31 in formula (A21-1) being a diamine compound represented by formula (A21-3-15) to formula (A21-3-16).

[0066] In some specific examples, the diamine compound represented by the aforementioned formula (A21-2) may include, but is not limited to, the diamine compounds represented by the following formula (A21-2-1) to formula (A21-2-5):

[0067]

[0068]

[0069] The aforementioned diamine compound (a2-1) can be used alone or in combination of multiple types.

[0070] Based on the total usage amount of the diamine component (a2) being 100 moles, the usage amount of the diamine compound (a2-1) can be 25 moles to 93 moles, preferably 38 moles to 90 moles, and more preferably 50 moles to 87 moles.

[0071] Diamine compound (a2-2)

[0072] From the perspective of improving the voltage holding ratio of the liquid crystal display element, the molecular structure of the polymer (A) can selectively have a group of -N(D)- (where D represents a urethane-based protecting group). The polymer (A) having a group of -N(D)- can be obtained by a method of using at least a part of a monomer having a group of -N(D)- as a reaction raw material, or by a method of using it as a capping agent described later. In some specific examples, the monomer having a group of -N(D)- can be, for example, a diamine compound (a2-2) having a group of -N(D)-. For example, the urethane-based protecting group can include, but is not limited to, tert-butoxycarbonyl and 9-fluorenylmethoxycarbonyl.

[0073] Preferably, the diamine compound (a2-2) having a group of -N(D)- includes a diamine compound having at least one aromatic group such as a benzene ring. More preferably, the diamine compound (a2-2) having a group of -N(D)- includes a diamine compound having at least one aromatic group such as a benzene ring, and the residue other than the substituent (D) has 6 to 30 carbon atoms. In some specific examples, the diamine compound (a2-2) having a group of -N(D)- can include, but is not limited to, the diamine compounds represented by the following formulas (A22-1) to (A22-10):

[0074]

[0075]

[0076] The aforementioned diamine compound (a2-2) can be used alone or in combination of multiple types.

[0077] Based on the total usage amount of the diamine component (a2) being 100 moles, the usage amount of the diamine compound (a2-2) can be 0 moles to 68 moles, preferably 0 moles to 52 moles, and more preferably 0 moles to 37 moles.

[0078] Other diamine compounds (a2-3)

[0079] In addition to the aforementioned diamine compounds (a2-1) and (a2-2), the diamine component (a2) used to obtain the polymer (A) may optionally contain 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 having a photo-alignment group such as the diamine compounds represented by the following formulas (A23-1) to (A23-3); 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 having a carboxyl group such as the diamine compounds represented by the following formulas (A23-4) to (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-indene-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 the diamine compounds represented by the following formulas (A23-8) to (A23-10); diamine compounds having an amide bond such as the 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 an oxazoline structure such as the diamine compounds represented by the following formulas (A23-14) to (A23-15):

[0080]

[0081]

[0082]

[0083] In formula (A23-4), Y 51 represents a single bond, -CH2-, -C2H4-, -C(CH3)2-, -CF2-, -C(CF3)2-, -O-, -CO-, -NH-, -N(CH3)-, -CONH-, -NHCO-, -CH2O-, -OCH2-, -COO-, -OCO-, -CON(CH3)- or -N(CH3)CO-; m1 and m2 each independently represent an integer from 0 to 4, and (m1 + m2) represents an integer from 1 to 4. In formula (A23-5), m3 and m4 each independently represent an integer from 1 to 5. In formula (A23-6), Y 52represents a linear or branched alkyl group having 1 to 5 carbon atoms; m5 represents an integer from 1 to 5. In formula (A23-7), Y 53 and Y 54 each independently 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-; m6 represents an integer from 1 to 4.

[0084] The above-mentioned other diamine compounds (a2-3) can be used alone or in combination of multiple kinds.

[0085] Based on the total usage amount of the diamine component (a2) being 100 moles, the usage amount of the other diamine compounds (a2-3) can be 0 moles to 68 moles, preferably 0 moles to 52 moles, and more preferably 0 moles to 37 moles.

[0086] Polymer (B)

[0087] In addition to the aforementioned polymer (A), the liquid crystal aligning agent of the present invention may optionally contain a polymer (B) selected from the group consisting of a polyimide precursor obtained by using a tetracarboxylic dianhydride component (b1) and a diamine component (b2), and an imidized polymer (i.e., polyimide) of this polyimide precursor. For example, the polymer (B) may include, but is not limited to, at least one polymer selected from the group consisting of a polyimide precursor obtained by using a tetracarboxylic dianhydride component (b1) and a diamine component (b2) that does not contain the above-mentioned specific diamine compound, and an imidized product (i.e., polyimide) of this polyimide precursor. Specific examples of the above polyimide precursor may include polyamic acid or polyamic acid ester, etc. The said polymer (B) can be used alone or in combination of multiple kinds.

[0088] The dosage 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.

[0089] The polyimide precursor of polymer ( B ) contains the structures shown in the following formulas (II) and (III):

[0090]

[0091]

[0092] In Formula (II) and Formula (III), X3 represents a tetravalent organic group; X4 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

[0093] When the polymer (B) does not simultaneously contain the structures of the above Formula (II) and Formula (III), the liquid crystal display element with a liquid crystal alignment film formed by this liquid crystal aligning agent is likely to have a problem of excessive flicker after high-voltage driving.

[0094] Tetracarboxylic dianhydride component (b1)

[0095] The tetracarboxylic dianhydride component (b1) used to obtain the polymer (B) may, for example, include but are not limited to acyclic aliphatic tetracarboxylic dianhydride compounds, alicyclic tetracarboxylic dianhydride compounds, aromatic tetracarboxylic dianhydride compounds, or derivatives of these compounds. Specific examples of the acyclic aliphatic tetracarboxylic dianhydride compounds, alicyclic tetracarboxylic dianhydride compounds, and aromatic tetracarboxylic dianhydride compounds may, for example, include the tetracarboxylic dianhydride compounds exemplified in the aforementioned polymer (A). Preferably, the tetracarboxylic dianhydride component (b1) may include an alicyclic tetracarboxylic dianhydride or a derivative thereof represented by the above formula (A11), or a tetracarboxylic dianhydride compound or a derivative thereof represented by the above formula (A12) in which X1′ 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 multiple kinds.

[0096] From the perspective of further improving the flicker degree after high-voltage driving, the tetracarboxylic dianhydride component (b1) preferably includes a tetracarboxylic dianhydride compound represented by the above formula (A12) in which X1′ represents a structure represented by the following formula (B11) (hereinafter referred to as the tetracarboxylic dianhydride compound (b1-1)):

[0097]

[0098] In the above formula (B11), Z 11 represents a single bond; and "*" represents the bonding position.

[0099] The aforementioned tetracarboxylic dianhydride compound (b1-1) may be used alone or in combination of multiple kinds.

[0100] More preferably, the tetracarboxylic dianhydride component (b1) includes a tetracarboxylic dianhydride compound represented by the following formula (IV):

[0101]

[0102] Based on the total usage amount of the tetracarboxylic dianhydride component (b1) being 100 moles, the usage amount of the tetracarboxylic dianhydride compound (b1-1) may be 30 moles to 100 moles, preferably 40 moles to 100 moles, and more preferably 50 moles to 100 moles.

[0103] When the tetracarboxylic dianhydride component (b1) contains the tetracarboxylic dianhydride compound (b1-1), the flicker degree after high-voltage driving of the liquid crystal display element including the liquid crystal alignment film formed therefrom can be further improved.

[0104] Diamine component (b2)

[0105] The diamine component (b2) used to obtain the polymer (B) may include the diamine compound (b2-1) represented by the following formula (B21) and the diamine compound (b2-2) represented by the following formula (B22):

[0106]

[0107] In addition, the diamine component (b2) may include, but is not limited to, the aforementioned diamine component (a2).

[0108] If the diamine component (b2) does not contain the diamine compound (b2-1) represented by the above formula (B21), the liquid crystal display element including the liquid crystal alignment film formed therefrom is likely to have a problem of excessive flicker degree after high-voltage driving.

[0109] If the diamine component (b2) does not contain the diamine compound (b2-2) represented by the above formula (B22), the liquid crystal display element including the liquid crystal alignment film formed therefrom is likely to have a problem of excessive flicker degree after high-voltage driving.

[0110] The aforementioned diamine component (b2) can be used alone or in combination of multiple types.

[0111] Based on the total usage amount of the diamine component (b2) being 100 moles, the usage amount of the diamine compound (b2-1) can be 3 moles to 97 moles, preferably 5 moles to 95 moles, and more preferably 7 moles to 93 moles.

[0112] Based on the total usage amount of the diamine component (b2) being 100 moles, the usage amount of the diamine compound (b2-2) can be 3 moles to 90 moles, preferably 4 moles to 80 moles, and more preferably 5 moles to 70 moles.

[0113] Method for producing the polymer

[0114] The production of polymer (A) or polymer (B) can be carried out by subjecting the aforementioned diamine component and tetracarboxylic dianhydride component to a (polycondensation) reaction in a solvent. When a part of polymer (A) or polymer (B) has an amic acid structure, for example, by reacting the tetracarboxylic dianhydride component with the diamine component, a polymer having an amic acid structure (i.e., polyamic acid) is obtained. The aforementioned solvent is not particularly limited as long as it can 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, dimethyl sulfoxide, or 1,3-dimethyl-2-imidazolidinone. In some specific examples, when the solvent solubility of the polymer is relatively high, the solvent may include methyl ethyl ketone, cyclohexanone, cyclopentanone, 4-hydroxy-4-methyl-2-pentanone, or solvents represented by the following formulas (D-1) to (D-3):

[0115]

[0116] In formula (D-1), Z1 represents an alkyl group having 1 to 3 carbon atoms. In formula (D-2), Z2 represents an alkyl group having 1 to 3 carbon atoms. In formula (D-3), Z3 represents an alkyl group having 1 to 4 carbon atoms.

[0117] The aforementioned solvent can be used alone or in combination of multiple solvents. Secondly, even a solvent that cannot dissolve the polymer can still be used in combination with the above solvents within the range where the formed polymer does not precipitate. When the diamine component and the tetracarboxylic dianhydride component react in a 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 initially carried out at a high concentration and then additional solvent can be added later. When carrying out the reaction, the molar ratio of the total molar amount of the diamine component to the total molar amount 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 larger the molecular weight of the formed polymer (A) or polymer (B).

[0118] A polymer having an amic acid ester structure can be obtained, for example, by known methods such as the following: (1) a method of further reacting the polyamic acid obtained by the above method with an esterifying agent, (2) a method of reacting a tetracarboxylic diester compound with a diamine compound, or (3) a method of reacting a tetracarboxylic diester dihalide with a diamine compound.

[0119] The imidized product in the polymer (A) or polymer (B) contained in the liquid crystal aligning agent of the present invention can be obtained, for example, by subjecting the aforementioned obtained polymer to a cyclodehydration reaction. In this imidized product, the cyclodehydration rate (also referred to as the imidization rate) of the functional group possessed by the amic acid group or its derivative does not necessarily have to be 100%, and the imidization rate can be arbitrarily adjusted according to the use and / or purpose.

[0120] For the method of obtaining the imidized product, it can be, for example, thermal imidization by directly heating the polymer solution obtained from the above reaction, or catalytic imidization by adding a catalyst to the polymer solution. When performing thermal imidization in a solution, the temperature is preferably 100°C to 400°C, and more preferably 120°C to 250°C. When performing thermal imidization, it is preferable to discharge the water generated by the imidization reaction out of the system together.

[0121] The aforementioned catalytic imidization can be carried out, for example, by adding a basic catalyst and an acid anhydride to the polymer solution obtained from the reaction, and it is preferably stirred at -20°C to 250°C, and more preferably at 0°C to 180°C. The addition amount of the basic catalyst is preferably 0.5 to 30 molar times, and more preferably 2 to 20 molar times, based on the amic acid group; the addition amount of the acid anhydride is preferably 1 to 50 molar times, and more preferably 3 to 30 molar times, based on the amic acid group. Specific examples of the basic catalyst can include, but are not limited to, pyridine, triethylamine, trimethylamine, tributylamine, trioctylamine, etc. Among them, pyridine is more ideal because it has an appropriate basicity to promote the reaction. Specific examples of the acid anhydride can include, but are not limited to, acetic anhydride, trimellitic anhydride, pyromellitic dianhydride, etc. Among them, if acetic anhydride is used, purification after the reaction is easier, so it is more ideal. The imidization rate of catalytic imidization can be controlled by adjusting the catalyst amount, reaction temperature, and / or reaction time.

[0122] When recovering the formed imidized product from the reaction solution of the above imidization, the reaction solution can be poured into a solvent to precipitate it. The solvents used for precipitation can include, but are not limited to, methanol, ethanol, isopropanol, acetone, hexane, butyl cellosolve, heptane, methyl ethyl ketone, methyl isobutyl ketone, toluene, benzene, water, etc. After filtering and recovering the polymer precipitated in the solvent, it can be dried at normal pressure or reduced pressure, at room temperature or by heating. Or, the precipitated and recovered polymer is dissolved in a solvent again and subjected to reprecipitation and recovery, and this operation is repeated 2 to 10 times to reduce the impurities in the polymer. The solvents used can be, for example, alcohols or ketone hydrocarbons. If three or more solvents selected therefrom are used, the purification efficiency can be further improved, so it is more ideal.

[0123] Solution Viscosity and Molecular Weight of Polymer

[0124] When configured as a solution with a concentration of 10 wt% to 15 wt%, the solution concentration of the polymer (A) or polymer (B) of the present invention is not particularly limited. From the perspective of easier operation, its solution concentration can be, for example, 10 mPa·s to 1000 mPa·s. The solution viscosity (mPa·s) of the polymer is the value measured at 25 °C using an E-type rotational viscometer for a polymer solution prepared with a good solvent for the polymer (such as γ-butyrolactone or N-methyl-2-pyrrolidone, etc.) at a concentration of 10 wt% to 15 wt%.

[0125] The weight average molecular weight (M w ) of the polymer (A) or polymer (B) of the present invention measured by gel permeation chromatography (GPC) in terms of polystyrene conversion is preferably 1,000 to 500,000, and more preferably 2,000 to 500,000. Secondly, the ratio of M w to the number average molecular weight (M n ) measured by GPC in terms of polystyrene conversion, which represents the molecular weight distribution (M w / M n ), is preferably 15 or less, and more preferably 10 or less. When the molecular weight of the polymer is within the aforementioned molecular weight range, it can ensure good alignment and stability of the liquid crystal display element.

[0126] End-capping agent

[0127] When synthesizing the polymer (A) or polymer (B) of the present invention, the aforementioned tetracarboxylic dianhydride component and diamine component can be used, and an appropriate end-capping agent is used to synthesize a terminal-sealed polymer. The terminal-sealed polymer has the effect of improving the film hardness of the liquid crystal alignment film obtained by coating and improving the adhesion characteristics of the sealant and the liquid crystal alignment film. The terminals of the polymer (A) or polymer (B) of the present invention can, 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 general condensation reactions, or by sealing the terminals using the end-capping agents described below. Similarly, the aforementioned derivatives can be obtained, for example, using the following end-capping agents.

[0128] For example, the capping agent may include, but is not limited to, acid anhydrides such as acetic anhydride, maleic anhydride, nadic 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; dicarbonate diester compounds such as di-tert-butyl dicarbonate or diallyl dicarbonate; chlorocarbonyl compounds such as acryloyl chloride, methacryloyl chloride or nicotinoyl 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.

[0129] The capping agent can be used alone or in combination of multiple kinds.

[0130] Based on the total usage amount of the diamine component being 100 mole parts, the usage amount of the capping agent is preferably 0.01 to 20 mole parts, and more preferably 0.01 to 10 mole parts.

[0131] Other polymers

[0132] The liquid crystal aligning agent of the present invention contains polymer (A), polymer (B) and solvent (C). In addition to polymer (A) and polymer (B), the liquid crystal aligning agent of the present invention may selectively contain other polymers. The types of other polymers may include, but are not limited to, polyester, polyamide, polyurea, polyorganosiloxane, cellulose derivatives, polyacetal, polystyrene or its derivatives, poly(styrene-phenylmaleimide) derivatives, or poly(meth)acrylate, etc.

[0133] Solvent (C)

[0134] From the perspective of forming a uniform thin film, the liquid crystal aligning agent is in the form of a coating solution to fabricate a liquid crystal alignment film. The liquid crystal aligning agent of the present invention is preferably a coating solution containing the above polymer component and an organic solvent (i.e., the aforementioned solvent (C)). Among them, based on the set thickness of the coating film to be formed, the polymer concentration in the liquid crystal aligning agent can be appropriately changed. From the perspective of forming a uniform and defect-free coating film, the polymer concentration in the liquid crystal aligning agent is preferably 1 wt% or more. From the perspective of the storage stability of the solution, the polymer concentration in the liquid crystal aligning agent is preferably 10 wt% or less. The ideal polymer concentration can be 2 wt% to 8 wt%. The content of the polymer (A) in the liquid crystal aligning agent can be appropriately changed by the coating method of the liquid crystal aligning agent and / or the film thickness of the desired liquid crystal alignment film, and it is preferably 2 wt% to 10 wt%, and more preferably 3 wt% to 7 wt%.

[0135] There is no particular limitation on the organic solvent contained in the liquid crystal aligning agent, as long as it can uniformly dissolve the aforementioned polymer. Specific examples thereof may include, but are not limited to, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethyllactamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, dimethyl sulfoxide, γ-butyrolactone, γ-valerolactone, 1,3-dimethyl-2-imidazolidinone, methyl ethyl ketone, cyclohexanone, cyclopentanone, 3-methoxy-N,N-dimethylpropanamide, 3-butoxy-N,N-dimethylpropanamide, 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 solvent is also called a good solvent. Among them, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, 3-methoxy-N,N-dimethylpropanamide, 3-butoxy-N,N-dimethylpropanamide or γ-butyrolactone are preferred. Based on the total usage amount of the solvent in the liquid crystal aligning agent being 100 wt%, the usage amount of the good solvent can be 20 wt% to 99 wt%, preferably 20 wt% to 90 wt%, and more preferably 30 wt% to 80 wt%.

[0136] Secondly, the organic solvent in the liquid crystal aligning agent is preferably a mixed solvent of the aforementioned solvent and a solvent (also called a poor solvent) that can improve the coatability during the coating of the liquid crystal aligning agent and the surface smoothness of the coating film. Specific examples of the poor solvent to be used in combination include, but are not limited to, the solvents described below. Based on the total usage amount of the solvent in the liquid crystal aligning agent being 100 wt%, the usage amount of the poor solvent is preferably 1 wt% to 80 wt%, more preferably 10 wt% to 80 wt%, and particularly preferably 20 wt% to 70 wt%. The type and usage amount of the poor solvent can be appropriately selected according to the coating device, coating conditions, and / or coating environment of the liquid crystal aligning agent.

[0137] For example, the poor solvent can be, for example: 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 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, ethylene carbonate, ethylene glycol monobutyl ether (butyl cellosolve), ethylene glycol monoisoamyl 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.

[0138] 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 are preferred.

[0139] The solvent combination of a good solvent and a 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-dimethyl lactamide and diisobutyl ketone; N-methyl-2-pyrrolidone and ethyl 3-ethoxypropionate; N-ethyl-2-pyrrolidone and ethyl 3-ethoxypropionate; N-methyl-2-pyrrolidone and ethylene glycol monobutyl ether acetate; N-ethyl-2-pyrrolidone and dipropylene glycol dimethyl ether; N,N-dimethyl lactamide and ethylene glycol monobutyl ether; N,N-dimethyl lactamide and propylene glycol diacetate; N-ethyl-2-pyrrolidone and diethylene glycol diethyl ether; N,N-dimethyl lactamide and diethylene glycol diethyl ether; N-methyl-2-pyrrolidone, γ-butyrolactone, 4-hydroxy-4-methyl-2-pentanone and diethylene glycol diethyl ether; N-ethyl-2-pyrrolidone, N-methyl-2-pyrrolidone and 4-hydroxy-4-methyl-2-pentanone; N-ethyl-2-pyrrolidone, 4-hydroxy-4-methyl-2-pentanone and propylene glycol monobutyl ether; N-methyl-2-pyrrolidone, 4-hydroxy-4-methyl-2-pentanone and diisobutyl ketone; N-methyl-2-pyrrolidone, 4-hydroxy-4-methyl-2-pentanone and dipropylene glycol monomethyl ether; N-methyl-2-pyrrolidone, 4-hydroxy-4-methyl-2-pentanone and propylene glycol monobutyl ether; N-methyl-2-pyrrolidone, 4-hydroxy-4-methyl-2-pentanone and propylene glycol diacetate; γ-butyrolactone, 4-hydroxy-4-methyl-2-pentanone and diisobutyl ketone; γ-butyrolactone, 4-hydroxy-4-methyl-2-pentanone and propylene glycol diacetate; N-methyl-2-pyrrolidone, γ-butyrolactone, propylene glycol monobutyl ether and diisobutyl ketone; N-methyl-2-pyrrolidone, γ-butyrolactone and propylene glycol monobutyl ether and diisopropyl ether; N-methyl-2-pyrrolidone, v-butyrolactone, propylene glycol monobutyl ether and diisobutyl methanol; N-methyl-2-pyrrolidone, v-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, v-butyrolactone and diisobutyl ketone; or N-ethyl-2-pyrrolidone, N,N-dimethyl lactamide and diisobutyl ketone, etc.

[0140] The aforementioned solvent (C) can be used alone or in combination of multiple solvents.

[0141] Based on the total usage amount of polymer (A) and polymer (B) being 100 parts by weight, the usage amount of solvent (C) is from 800 parts by weight to 4000 parts by weight, preferably from 900 parts by weight to 3500 parts by weight, and more preferably from 1000 to 3000 parts by weight.

[0142] Additive components

[0143] The liquid crystal aligning agent of the present invention may also selectively add components other than the polymer component and the organic solvent (hereinafter referred to as additive components). These additive components may include, for example, but are not limited to: adhesion aids for improving the adhesion between the liquid crystal alignment film and the substrate or between the liquid crystal alignment film and the sealant, compounds for improving the strength of the liquid crystal alignment film (hereinafter referred to as crosslinking compounds), compounds for promoting imidization, dielectrics or conductive substances for adjusting the dielectric constant or resistance of the liquid crystal alignment film, etc.

[0144] Adhesion aid

[0145] The aforementioned adhesion aid 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, vinyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, tris(3-trimethoxysilylpropyl)isocyanurate, or 3-isocyanatopropyltriethoxysilane and other silane coupling agents. When using an adhesion aid, from the perspective of showing good resistance to AC smear, based on the total usage amount of the polymer in the liquid crystal aligning agent being 100 parts by weight, the usage amount of the adhesion aid is preferably from 0.1 part by weight to 30 parts by weight, and more preferably from 0.1 part by weight to 20 parts by weight.

[0146] Crosslinking compound

[0147] Regarding the aforementioned crosslinkable compound, from the perspective of exhibiting good resistance to AC residues and effectively improving the film strength, it may be a compound having an oxiranyl group, an oxetanyl group, at least one group selected from the group consisting of the group represented by the following formula (E1) and the group represented by the following formula (E2), or a compound selected from the compounds represented by the following formula (E3):

[0148]

[0149] 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.

[0150] In formula (E3), examples of the (g1 + g2)-valent organic group containing an aromatic ring represented by G5 include a (g1 + g2)-valent aromatic hydrocarbon group having 6 to 30 carbon atoms, a (g1 + g2)-valent organic group formed by directly or indirectly bonding a (g1 + g2)-valent aromatic hydrocarbon group having 6 to 30 carbon atoms through a linking group, or a (g1 + g2)-valent group having an aromatic heterocycle. The aromatic hydrocarbon may be, for example, benzene or naphthalene. Examples of the aromatic heterocycle include the exemplified aromatic heterocycles having a specific nitrogen atom-containing structure as described above. Examples of the linking group include an alkylene group having 1 to 10 carbon atoms or a group obtained by removing one hydrogen atom from the alkylene group, or a divalent or trivalent cyclohexane. Among them, any hydrogen atom of the alkylene group may also be substituted with an organic group such as a fluorine atom or a trifluoromethyl group. In formula (E3), examples of the alkyl group having 1 to 5 carbon atoms represented by G6 include methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, or n-pentyl.

[0151] Compound having an oxiranyl group

[0152] Specific examples of the compound having an oxiranyl group may include N,N,N′,N′-tetraglycidyl-m-xylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, N,N,N′,N′-tetraglycidyl-4,4′-diaminodiphenylmethane, N,N,N′,N′-tetraglycidyl-p-phenylenediamine, and nitrogen atom-containing compounds such as those represented by the following formulas (E4) to (E6):

[0153]

[0154]

[0155] Compound having an epichlorohydrin group

[0156] Specific examples of the compound having an epichlorohydrin group may include compounds represented by the following formulas (E7) to (E16):

[0157]

[0158]

[0159]

[0160] In formula (E15), R represents wherein " * " represents the bonding position.

[0161] Compound having a group represented by formula (E1)

[0162] Specific examples of the compound having a group represented by formula (E1) may include compounds represented by the following formulas (E1-1) to (E1-12):

[0163]

[0164]

[0165]

[0166] Compound having a group represented by formula (E2)

[0167] Specific examples of the compound having a group represented by formula (E2) may include compounds represented by the following formulas (E2-1) to (E2-4):

[0168]

[0169]

[0170] Compound having a group represented by formula (E3)

[0171] Specific examples of the compound having a group represented by formula (E3) may include compounds represented by the following formulas (E3-1) to (E3-10):

[0172]

[0173]

[0174]

[0175] In the liquid crystal aligning agent of the present invention, based on 100 parts by weight of the total amount of the polymer in the liquid crystal aligning agent, the amount of the crosslinkable compound used is preferably 0.5 to 20 parts by weight. Among them, from the viewpoints of the progress of the crosslinking reaction and good resistance to AC afterimages, the amount of the crosslinkable compound used is more preferably 1 to 15 parts by weight.

[0176] Compound for promoting imidization

[0177] The aforementioned compound for promoting imidization is preferably a compound having a basic site (for example, a primary amino group, an aliphatic heterocycle (such as a pyrrolidine skeleton), an aromatic heterocycle (such as an imidazole ring or an indole ring), or a guanidine group, etc.) (except for the above-mentioned crosslinkable compound and adhesion promoter), or a compound that generates the basic site during calcination. More preferably, the compound for promoting imidization is a compound that generates the basic site during calcination, and specific examples thereof may be, for example, an amino acid in which part or all of the basic site of the amino acid is protected. Specific examples of the above-mentioned amino acids may include glycine, alanine, cysteine, methionine, asparagine, glutamic acid, valine, leucine, phenylalanine, tyrosine, tryptophan, proline, hydroxyproline, arginine, histidine, lysine, or ornithine. For the purpose of the compound for promoting imidization, more preferred specific examples may include N-α-(9-fluorenylmethoxycarbonyl)-N-τ-(tert-butoxycarbonyl)-L-histidine.

[0178] Method for manufacturing a liquid crystal alignment film and a liquid crystal display element

[0179] The liquid crystal alignment film of the present invention is obtained from the aforementioned liquid crystal aligning agent. The liquid crystal alignment film of the present invention can be used as a horizontally aligned type or a vertically aligned type (VA type) liquid crystal alignment film, and it is a liquid crystal alignment film suitable for horizontally aligned type liquid crystal display elements such as the IPS mode or the FFS mode. The liquid crystal display element of the present invention includes the aforementioned liquid crystal alignment film. The liquid crystal display element of the present invention can be manufactured, for example, by the following steps (1) to (4) or the method of steps (1) to (2) and step (4).

[0180] Step (1): Coating the liquid crystal aligning agent on a substrate

[0181] The liquid crystal aligning agent of the present invention is coated on one surface of a substrate provided with a patterned transparent conductive film by an appropriate coating method such as a roll coating method, a spin coating method, a printing method, or an inkjet method. Herein, the substrate is not particularly limited as long as it is a highly transparent substrate, and a glass substrate or a silicon nitride substrate may be used in combination with a plastic substrate such as an acrylic substrate or a polycarbonate substrate. Further, in a reflective liquid crystal display element, an opaque material such as a silicon wafer can be used even for only one side of the substrate, and the electrode used can also be a light-reflective material such as aluminum. Moreover, when manufacturing an IPS type or FFS type liquid crystal element, a comb-shaped electrode substrate formed by disposing a patterned transparent conductive film or a metal film and a counter substrate without an electrode are used.

[0182] Examples of the method for coating the liquid crystal aligning agent on the substrate and forming a film include screen printing, lithography, flexography, inkjet method, or spraying method. Among them, the method for forming a film is preferably coating by the inkjet method.

[0183] Step (2): Calcining the coated liquid crystal aligning agent

[0184] Step (2) is a step of calcining the liquid crystal aligning agent coated on the substrate to form a film. After coating the liquid crystal aligning agent on the substrate, heating means such as a hot plate, a heat cycle type oven, or an IR (infrared) type oven can be used to evaporate the solvent, or thermal imidization of polyamic acid or polyamic acid ester can be performed. The drying and calcining steps performed after coating the liquid crystal aligning agent of the present invention can be selected at any temperature and time, and multiple drying or calcining steps can be performed. The drying temperature can be, for example, 40°C to 180°C. From the viewpoint of shortening the treatment, it can be performed at 40°C to 150°C. The drying time is not particularly limited, and it can be, for example, 1 minute to 10 minutes or 1 minute to 5 minutes. When performing thermal imidization of polyamic acid or polyamic acid ester, after the aforementioned drying step, the calcining step can be further performed at a temperature of, for example, 150°C to 300°C or 150°C to 250°C. The calcining time is not particularly limited, and examples thereof include 5 minutes to 40 minutes or 5 minutes to 30 minutes. If the thickness of the calcined film-like material is too thin, the reliability of the liquid crystal display element will be reduced. Therefore, the thickness of the film-like material is preferably 5 nm to 300 nm, and more preferably 10 nm to 200 nm.

[0185] Step (3): Performing an alignment treatment on the film obtained in step (2)

[0186] Step (3) is to perform an alignment treatment on the film obtained in step (2) as appropriate. In other words, in a horizontally aligned liquid crystal display element such as the IPS mode or the FFS mode, the coated film is subjected to an alignment treatment to impart alignment ability. On the other hand, in a vertically aligned liquid crystal display element such as the VA mode or the PSA mode, the formed coated film can be directly used as a liquid crystal alignment film, but the coated film can also be subjected to an alignment treatment to impart alignment ability. Examples of the alignment treatment of the liquid crystal alignment film include a rubbing treatment method or a photo-alignment treatment method, and preferably a photo-alignment treatment method. The photo-alignment treatment method can be exemplified by irradiating the surface of the above-mentioned film-like material with radiation that has been deflected in a certain direction, and as appropriate, preferably heating at a temperature of 150 °C to 250 °C to impart liquid crystal alignment (also referred to as liquid crystal alignment ability). The radiation can be ultraviolet light or visible light with a wavelength of 100 nm to 800 nm. Among them, the radiation is preferably ultraviolet light with a wavelength of 100 nm to 400 nm, and more preferably ultraviolet light with a wavelength of 200 nm to 400 nm.

[0187] The irradiation dose of the aforementioned radiation can be 1 mJ / cm2 to 10,000 mJ / cm 2 , preferably 100 mJ / cm 2 to 5,000 mJ / cm 2 , more preferably 100 mJ / cm2 to 1500 mJ / cm 2 , and particularly preferably 100 mJ / cm 2 to 1000 mJ / cm 2 . When using a general liquid crystal aligning agent, the light irradiation dose for the alignment treatment is 100 mJ / cm 2 to 5000 mJ / cm 2 , but for the liquid crystal aligning agent of the present invention, even if the light irradiation dose for the alignment treatment is reduced, a liquid crystal alignment film can still be obtained in which the variation (non-uniformity) of the liquid crystal alignment within the film surface is effectively suppressed. When irradiating the radiation, in order to improve the liquid crystal alignment, the substrate of the above-mentioned film-like material can be heated at 50 °C to 250 °C while irradiating. The liquid crystal alignment film produced in this way can make the liquid crystal molecules align stably in a certain direction. Next, the liquid crystal alignment film irradiated with polarized radiation in the above-mentioned method can be subjected to a contact treatment with a solvent, or the liquid crystal alignment film irradiated with radiation can be subjected to a heat treatment.

[0188] The solvent used in the foregoing contact treatment is not particularly limited, as long as it can dissolve the decomposition products generated from the film-like material after irradiation with radiation. Specific examples include water, methanol, ethanol, 2-propanol, acetone, methyl ethyl ketone, 1-methoxy-2-propanol, 1-methoxy-2-propyl acetate, butyl cellosolve, ethyl lactate, methyl lactate, diacetone alcohol, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, propyl acetate, butyl acetate, or cyclohexyl acetate, etc. Among them, from the viewpoints of versatility and safety, water, 2-propanol, 1-methoxy-2-propanol or ethyl lactate is preferred, and water, 1-methoxy-2-propanol or ethyl lactate is more preferred. The solvent can be used alone or in combination of multiple solvents.

[0189] The temperature for heat-treating the foregoing radiation-irradiated coating film is preferably 50°C to 300°C, and more preferably 120°C to 250°C. The time for heat treatment is preferably 1 minute to 30 minutes.

[0190] Step (4): Fabricate a liquid crystal cell

[0191] Prepare two pieces of the foregoing liquid crystal alignment film substrates formed, and dispose a liquid crystal between the two substrates facing each other. For example, the following two methods can be cited. The first method is to first dispose the two substrates facing each other with a gap (cell gap) therebetween in such a manner that the liquid crystal alignment films face each other. Then, bond the peripheral portions of the two substrates with a sealant, and then inject and fill the liquid crystal composition into the cell gap partitioned by the substrate surfaces and the sealant. After the liquid crystal composition contacts the film surface, seal the injection hole.

[0192] The second method is a method called ODF (One Drop Fill). Apply a sealant such as an ultraviolet curable sealant at a predetermined position on one of the two substrates on which the liquid crystal alignment film has been formed, and then drop the liquid crystal composition at a plurality of predetermined positions on the liquid crystal alignment film surface. Then, bond the other substrate in such a manner that the liquid crystal alignment films face each other, and press the liquid crystal composition over the entire surface of the substrate so that it contacts the film surface. Next, irradiate ultraviolet light over the entire surface of the substrate to cure the sealant. When either of the foregoing methods is carried out, it is preferably to further heat the liquid crystal composition used to an isotropic phase temperature and then slowly cool it to room temperature to remove the flow alignment during liquid crystal filling. Secondly, when performing a rubbing treatment on the coating film, the two substrates are disposed facing each other with the rubbing directions of the respective coating films forming a predetermined angle, for example, in an orthogonal or antiparallel manner. The sealant can be, for example, an epoxy resin containing a curing agent and alumina balls as spacers. The liquid crystal composition can include nematic liquid crystals and smectic liquid crystals, and nematic liquid crystals are preferred.

[0193] A polarizing plate may be attached to the outer surface of the liquid crystal cell as needed to obtain a liquid crystal display element. Examples of the polarizing plate attached to the outer surface of the liquid crystal cell include a polarizing film obtained by stretching and aligning polyvinyl alcohol and simultaneously absorbing iodine, which is called an "H film". It may be a polarizing plate sandwiched between cellulose acetate protective films, or a polarizing plate composed of the H film itself.

[0194] The following uses examples to illustrate the application of the present invention, but it is not intended to limit the present invention. Any person skilled in this art can make various modifications and refinements without departing from the spirit and scope of the present invention. Detailed implementation manners

[0195] Preparation of polymer (A)

[0196] Synthesis example A-1

[0197] A nitrogen inlet, a stirrer, a condenser, and a thermometer were installed on a 500-ml four-necked conical flask, and nitrogen was introduced. Then, 0.80 g (0.0025 mol) of diamine compound (a2-1-1), 7.15 g (0.025 mol) of diamine compound (a2-1-2), 7.74 g (0.0175 mol) of diamine compound (a2-2-1), 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 the mixture was 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 the reaction was carried out at room temperature for 2 hours. After the reaction was completed, the reaction solution was poured into 1500 ml of water to precipitate the polymer. The obtained polymer was filtered, and the steps of washing and filtering with methanol were repeated three times. Then, the product was placed in a vacuum oven and dried at a temperature of 60 °C to obtain the polymer (A-1) of Synthesis example A-1, and its formulation is shown in Table 1.

[0198] Synthesis examples A-2 to A-6

[0199] Synthesis examples A-2 to A-6 used the same preparation method as that for preparing the polymer (A-1) of Synthesis example A-1, except that the types and amounts of raw materials in the polymer were changed in Synthesis examples A-2 to A-6. Its formulation is shown in Table 1, and will not be elaborated here.

[0200] Preparation of polymer (B)

[0201] Synthesis examples B-1 to B-6 and Comparative synthesis examples B'-1 to B'-3

[0202] Synthesis Examples B-1 to B-6 and Comparative Synthesis Examples B'-1 to B'-3 used the same preparation method as the method for preparing the polymer (A-1) in Synthesis Example A-1, except that Synthesis Examples B-1 to B-6 and Comparative Synthesis Examples B'-1 to B'-3 changed the types and usage amounts of the raw materials in the polymer. Their formulations are shown in Table 2 respectively, and will not be elaborated here.

[0203] Preparation of Liquid Crystal Alignment Agent, Liquid Crystal Alignment Film and Liquid Crystal Display Element

[0204] Example 1

[0205] 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 obtain the liquid crystal alignment agent of Example 1.

[0206] The above-prepared liquid crystal alignment agent was spin-coated on a glass substrate on which a pixel electrode was formed. The pixel electrode was an IPS driving electrode having a pair of ITO electrodes (electrode width: 10 μm, electrode spacing: 10 μm, and electrode height: 50 nm). The pair of ITO electrodes had a comb-like shape respectively, and the comb-like portions of each other were arranged in a separated and meshed manner. Then, the glass substrate coated with the liquid crystal alignment agent was dried on a hot plate at 80 °C for 3 minutes and then baked in a hot air circulation oven at 250 °C for 30 minutes to form a coating film with a film thickness of 100 nm.

[0207] After irradiating the coating film surface with ultraviolet light having a wavelength of 254 nm through a polarizing plate, it was baked in a hot air circulation oven at 250 °C for 30 minutes to obtain a substrate with a liquid crystal alignment film. Similarly, a coating film was formed on the counter substrate and alignment treatment was applied. The counter substrate was a glass substrate without an electrode formed thereon but having columnar spacers with a height of 4 μm.

[0208] The above two substrates were taken as a group. A sealant was printed on one of them, and the other was bonded to it with the liquid crystal alignment film facing and the alignment direction being 0°, and then the sealant was cured to obtain an empty cell. This empty cell was injected with liquid crystal MLC-2041 (manufactured by Merck) by a reduced-pressure injection method, and the injection port was sealed to obtain the liquid crystal display element of Example 1. The obtained liquid crystal display element was evaluated by the following evaluation method, and the results are shown in Table 3. The detection method for the flicker degree after high-voltage driving will be described later.

[0209] Examples 2 to 12 and Comparative Examples 1 to 3

[0210] Examples 2 to 12 and Comparative Examples 1 to 3 were prepared using the same preparation methods as the liquid crystal aligning agent, liquid crystal alignment film, and liquid crystal display element of Example 1, except that in Examples 2 to 12 and Comparative Examples 1 to 3, the types and usage amounts of raw materials in the liquid crystal aligning agent were changed. Their formulations and evaluation results are shown in Tables 3 and 4 respectively, and will not be elaborated here.

[0211] Table 1

[0212]

[0213]

[0214] Table 2

[0215]

[0216]

[0217] Table 3

[0218]

[0219]

[0220] C-1 N-methyl-2-pyrrolidone (NMP)

[0221] C-2 Ethylene glycol n-butyl ether

[0222] Table 4

[0223]

[0224] Evaluation method

[0225] Flicker after high-voltage driving

[0226] The prepared liquid crystal display element was placed between two polarizing plates with their polarization axes arranged in a perpendicular cross configuration. The LED backlight was lit in a state without applying voltage, and the configuration angle of the liquid crystal display element was adjusted to make the transmitted light brightness reach the minimum state. Then, an alternating voltage with a frequency of 30 Hz was applied to this liquid crystal display element, and at the same time, the V-T curve (voltage-transmittance curve) was measured, and the alternating voltages corresponding to relative transmittances of 23% and 100% were calculated as the driving voltages.

[0227] The method for measuring the after-driving flicker is as follows: Under the temperature condition where the temperature of the liquid crystal display element is 23°C, turn off the lit LED backlight, place it in the dark for 72 hours, then light it up again. At the same time when the backlight is lit, apply an AC voltage with a relative transmittance of 100% and a frequency of 30 Hz and drive it for 24 hours. Then apply an AC voltage with a relative transmittance of 23% and a frequency of 30 Hz and track the amplitude of the flicker. The amplitude of the flicker is measured by using a data acquisition / data recording switching device 34970A (manufactured by Agilent technologies) connected to a photodiode and an I-V conversion amplifier to read the brightness value of the liquid crystal display element passing through two polarizing plates and in the middle. The flicker (FL) is calculated by the following formula (i). The lower the flicker, the better the quality of the liquid crystal display element made of the liquid crystal aligning agent:

[0228]

[0229] In the above formula (i), z is the brightness value read when driving with an AC voltage with a relative transmittance of 23% and a frequency of 30 Hz using the above device 34970A.

[0230] ※: FL < 3%.

[0231] ◎: 3% ≤ FL < 3.5%.

[0232] o: 3.5% ≤ FL < 4%.

[0233] △: 4% ≤ FL < 5%.

[0234] ×: FL ≥ 5%.

[0235] From the results of Table 3 and Table 4, it can be seen that when the diamine component (b2) used to react to form the polymer (B) does not contain the diamine compound (b2-1) shown in the above formula (B21) and the diamine compound (b2-2) shown in the above formula (B22), the liquid crystal display element containing the liquid crystal alignment film formed thereby has a problem of excessive flicker after high-voltage driving. Secondly, when the diamine component (b2) only contains one of the diamine compound (b2-1) shown in the above formula (B21) and the diamine compound (b2-2) shown in the above formula (B22), the resulting liquid crystal display element has a problem of excessive flicker after high-voltage driving.

[0236] In addition, if the tetracarboxylic dianhydride component (a1) used to react to form the polymer (A) contains the structure represented by the formula (I-1-1) (i.e., contains the tetracarboxylic dianhydride compound (a1-1-1)), the afterglow degree of the fabricated liquid crystal display device after high-voltage driving can be further reduced. When the tetracarboxylic dianhydride component (b1) used to react to form the polymer (B) contains the structure represented by the formula (B11) (for example, the tetracarboxylic dianhydride compounds (b1-1-1) to (b1-1-3)), the afterglow degree of the fabricated liquid crystal display device after high-voltage driving can be further reduced.

[0237] It should be added that although the present invention illustrates the liquid crystal aligning agent, liquid crystal alignment film and liquid crystal display device for the photo-alignment method of the present invention with specific compounds, compositions, reaction conditions, processes, analysis methods or specific instruments, it is known to any person with common general knowledge in the technical field to which the present invention pertains that the present invention is not limited thereto. Without departing from the spirit and scope of the present invention, other compounds, compositions, reaction conditions, processes, analysis methods or instruments can also be used for the liquid crystal aligning agent, liquid crystal alignment film and liquid crystal display device for the photo-alignment method of the present invention.

[0238] Although the present invention has been disclosed as above in the embodiments, it is not intended to limit the present invention. Any person with common general knowledge in the technical field to which the present invention pertains can make various modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the appended claims.

Claims

1. A liquid crystal alignment agent for photo-alignment method, characterized in that Comprising: A polymer (A), selected from at least one polymer in the group consisting of a polyimide precursor and an imidized polymer of the polyimide precursor, wherein the polyimide precursor of the polymer (A) has a structure represented by the following formula (I): In the formula (I), X1 is at least one selected from the group consisting of structures represented by the following formulae (I-1) to (I-7), where "*" represents the bonding position; X2 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; Y1 represents a divalent organic group; 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; and In formula (I-7), X 15 and X 16 each independently represent a hydrogen atom or a methyl group; A polymer (B), selected from at least one polymer in the group consisting of a polyimide precursor and an imidized polymer of the polyimide precursor, wherein the polyimide precursor of the polymer (B) has structures represented by the following formula (II) and formula (III): In the formula (II) and the formula (III), X3 represents a tetravalent organic group; X4 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; and A solvent (C).

2. The liquid crystal aligning agent for photo-alignment method according to 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) includes a diamine compound (b2-1) represented by the following formula (B21):

3. The liquid crystal aligning agent for photo-alignment method according to claim 1, characterized in that, The polymer (B) is obtained by reacting a tetracarboxylic dianhydride component (b1) and a diamine component (b2), and the diamine component (b2) includes a diamine compound (b2-2) represented by the following formula (B22):

4. The liquid crystal aligning agent for photo-alignment method according to claim 1, characterized in that, X1 represents structures represented by the following formulae (I-1-1) to (I-1-6):

5. The liquid crystal aligning agent for photo-alignment method according to claim 4, characterized in that X1 represents the structure represented by the formula (I-1-1).

6. The liquid crystal aligning agent for photo-alignment method according to claim 1, characterized in that, The polymer (B) is obtained by reacting a tetracarboxylic dianhydride component (b1) and a diamine component (b2), and the tetracarboxylic dianhydride component (b1) includes a structure represented by the following formula (B11): In formula (B11), Z 11 represents a single bond; and " * " represents the bonding position.

7. A liquid crystal alignment film, characterized in that, Formed by using the liquid crystal aligning agent for the photo-alignment method according to any one of claims 1 to 6.

8. A liquid crystal display element, characterized in that, Comprising the liquid crystal alignment film according to claim 7.

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