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 an optical alignment method, a liquid crystal alignment film and a liquid crystal display element, wherein the liquid crystal alignment agent can improve broken bright spots. The liquid crystal alignment agent for the optical alignment method comprises a polymer (A) and a solvent (B), the surface of a liquid crystal alignment film formed by the liquid crystal alignment agent is subjected to a wear resistance test, and the minimum friction number of scars on the surface of the liquid crystal alignment film is more than 50. The polymer (A) is at least one polymer selected from a 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). # imgabs0 #

Description

Technical Field

[0001] The present invention relates to a liquid crystal aligning agent, a liquid crystal alignment film, and a liquid crystal display element, and particularly to a liquid crystal aligning agent, a liquid crystal alignment film, and a liquid crystal display element for a photo-alignment method. Background Art

[0002] Existing liquid crystal display elements are widely used as display components for personal computers, smart phones, mobile phones, or television receivers. A 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 (Thin-Film Transistors, TFTs) for switching electronic signals supplied to the pixel electrodes. In terms of the driving method of liquid crystal molecules, longitudinal electric field methods such as the twisted nematic (TN) method and the vertical alignment (VA) method, and transverse electric field methods such as the in-plane switching (IPS) method and the fringe field switching (FFS) method are known.

[0003] Currently, the most widely used liquid crystal alignment film in the industry is obtained by rubbing the surface of a film formed on an electrode substrate and composed of polyamic acid and / or polyimide obtained by imidization thereof with a cloth such as cotton, nylon, or polyester in one direction. Rubbing treatment is a simple and highly productive industrial method. However, with the high performance, high fineness, and large size of liquid crystal display elements, various problems such as dust, mechanical force, and static electricity generated by rubbing treatment on the surface of the alignment film form scars, leading to unevenness in the alignment treatment surface. As an alignment treatment method alternative to rubbing treatment, a photo-alignment method that imparts liquid crystal alignment ability by irradiating polarized radiation is known. Regarding the photo-alignment method, Japanese Patent Application 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.

[0004] However, when the liquid crystal alignment film obtained by the photo-alignment method is applied to a liquid crystal display element, especially when manufacturing a display device having a curved shape liquid crystal panel, the liquid crystal panel is bent along the outer surface of the housing. As a result, the spacer existing inside the liquid crystal panel moves within the liquid crystal panel and rubs the liquid crystal alignment film. The liquid crystal alignment film that applies pressure with the spacer cannot adjust the alignment of the liquid crystal. For example, although the liquid crystal panel performs black display, light will transmit through the peripheral part of the spacer, resulting in bright spots and becoming a problem.

[0005] However, in a liquid crystal display device including a conventional liquid crystal alignment film prepared by a photo-alignment method, there are still too many bright spots, and it cannot meet the application requirements. Summary of the Invention

[0006] The present invention provides a liquid crystal aligning agent for photo-alignment method, a liquid crystal alignment film, and a liquid crystal display device. The liquid crystal alignment film formed by the liquid crystal aligning agent for photo-alignment method has a high number of wear-resistant times. Even when physical friction such as friction caused by a spacer occurs, the liquid crystal display device will not generate too many bright spots due to scratches on the liquid crystal alignment film.

[0007] The present invention provides a liquid crystal aligning agent for photo-alignment method, which includes a polymer (A) and a solvent (B). When a wear-resistant test is performed on the surface of the liquid crystal alignment film formed by the liquid crystal aligning agent, the minimum number of friction times when scratches appear on the surface of the liquid crystal alignment film is greater than 50 times.

[0008] The polymer (A) is selected from at least one polymer in the group consisting of a polyimide precursor and an imidized polymer of the polyimide precursor. The polyimide precursor of the polymer (A) includes a structure represented by the following formula (I).

[0009]

[0010] In formula (I), X 1 represents at least one selected from the group consisting of structures represented by the following formula (I-1) to formula (I-7); X 2 each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; Y represents a divalent organic group; * represents a bonding position.

[0011]

[0012] 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; * represents a bonding position.

[0013] In formula (I-2) to formula (I-6), * represents a bonding position.

[0014] In formula (I-7), X 15 and X 16 each independently represents a hydrogen atom or a methyl group; * represents a bonding position.

[0015] In an embodiment of the present invention, the above-mentioned wear resistance test includes the following steps: providing a first unit, where the first unit includes a first substrate and a liquid crystal alignment film formed by a liquid crystal aligning agent, and the liquid crystal alignment film is located on the first substrate; providing a second unit, where the second unit includes a second substrate and a plurality of spacers, and the plurality of spacers are distributed on the second substrate; docking the first unit and the second unit to form a test unit, where the liquid crystal alignment film in the first unit contacts the plurality of spacers in the second unit; and using a wear testing machine to apply a load of 2000 grams to the test unit in a first direction parallel to the stacking direction of the first unit and the second unit, and perform friction on the test unit in a second direction perpendicular to the stacking direction, and observe the minimum number of friction times when scars appear on the surface of the liquid crystal alignment film.

[0016] In an embodiment of the present invention, the minimum number of friction times when scars appear on the surface of the above-mentioned liquid crystal alignment film is greater than 80 times.

[0017] In an embodiment of the present invention, the minimum number of friction times when scars appear on the surface of the above-mentioned liquid crystal alignment film is greater than 100 times.

[0018] In an embodiment of the present invention, the above-mentioned X 1 represents the structures shown by the following formulas (I-1-1) to (I-1-6):

[0019]

[0020] where * represents the bonding position.

[0021] In an embodiment of the present invention, the above-mentioned X 1 represents the structure shown by formula (I-1-1).

[0022] In an embodiment, the liquid crystal aligning agent further includes a compound (C) having at least one group selected from the group consisting of the group shown by the following formula (C1) and the group shown by the following formula (C2):

[0023]

[0024] In formula (C1), G 1 and G 2 each independently represent a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or -CH2-OH, and * represents the bonding position.

[0025]

[0026] In formula (C2), G 3 represents an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or an alkynyl group having 2 to 6 carbon atoms, and G 4represents 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, and * represents the bonding position.

[0027] In one embodiment of the present invention, the molecular structure of the polymer (A) has a group of -N(D)-, where D represents a urethane-based protecting group.

[0028] The present invention provides a liquid crystal alignment film formed using a liquid crystal aligning agent by the above-described photo-alignment method.

[0029] The present invention provides a liquid crystal display element including the liquid crystal alignment film as described above.

[0030] Based on the above, the present invention provides a liquid crystal aligning agent for a photo-alignment method, a liquid crystal alignment film, and a liquid crystal display element. By performing a wear resistance test on the surface of the liquid crystal alignment film formed by the liquid crystal aligning agent, the minimum number of friction times at which scars appear on the surface of the liquid crystal alignment film is limited to be greater than 50 times. Therefore, the liquid crystal display element will not generate excessive bright spots due to scars on the liquid crystal alignment film, thereby improving the situation of excessive bright spots.

[0031] To make the above features and advantages of the present invention more obvious and understandable, the following specific embodiments are given and described in detail in conjunction with the accompanying drawings as follows. Description of the Drawings

[0032] Figure 1A is a schematic diagram of the first step of the wear resistance test;

[0033] Figure 1B is a schematic diagram of the second step of the wear resistance test;

[0034] Figure 1C is a schematic diagram of the third step of the wear resistance test;

[0035] Figure 1D is a schematic diagram of the fourth step of the wear resistance test.

[0036] Description of the Reference Numerals

[0037] 10: Test unit

[0038] 110: First unit

[0039] 112: First substrate

[0040] 114: Liquid crystal alignment film

[0041] 120: Second unit

[0042] 122: Second substrate

[0043] 124: Spacer

[0044] D1: First direction

[0045] D2: Second direction

[0046] M: Abrasion testing machine

[0047] P: Pressure

[0048] S1: Surface Detailed implementation manner

[0049] <Liquid crystal alignment agent for photo-alignment method>

[0050] This embodiment provides a liquid crystal alignment agent for a photo-alignment method, which includes a polymer (A) and a solvent (B).

[0051] Among them, the surface of the liquid crystal alignment film formed by the liquid crystal alignment agent is subjected to an abrasion resistance test, and the minimum number of friction times when scratches appear on the surface of the liquid crystal alignment film is greater than 50 times, preferably greater than 80 times, and more preferably greater than 100 times. When the minimum number of friction times when scratches appear on the surface of the liquid crystal alignment film is greater than 50 times, the liquid crystal display element will not generate too many bright spots due to the scratches on the liquid crystal alignment film, thereby improving the situation of too many bright spots. When the minimum number of friction times when scratches appear on the surface of the liquid crystal alignment film is equal to or less than 50 times, the liquid crystal display element has a situation of too many bright spots and is not good.

[0052] When the minimum number of friction times when scratches appear on the surface of the liquid crystal alignment film is greater than 80 times, the number of bright spots of the liquid crystal display element can be further reduced, and the effect of improving the bright spots of the liquid crystal display element is better.

[0053] When the minimum number of friction times when scratches appear on the surface of the liquid crystal alignment film is greater than 100 times, the number of bright spots of the liquid crystal display element can be further reduced, and the effect of improving the bright spots of the liquid crystal display element is even better.

[0054] As Figures 1A to 1D shown, the abrasion resistance test includes the following steps:

[0055] Please refer to Figure 1A , the first step is to provide a first unit 110, where the first unit 110 includes a first substrate 112 and a liquid crystal alignment film 114 formed by the liquid crystal alignment agent, and the liquid crystal alignment film 114 is located on the first substrate 112. Further, as Figure 1A shown, the liquid crystal alignment film 114 covers the first substrate 112.

[0056] Please refer to Figure 1B, the second step is to provide a second unit 120, where the second unit 120 includes a second substrate 122 and a plurality of spacer bodies 124, and the plurality of spacer bodies 124 are distributed on the second substrate 122. Further, the plurality of spacer bodies 124 are distributed on the second substrate 122 in such a way that the distance between any one spacer body 124 and an adjacent spacer body 124 is a certain distance, and the said distance is not particularly limited, for example, it is the distance between each existing spacer body in a liquid crystal display element.

[0057] There is no particular limitation on the materials of the first substrate 112 and the second substrate 122. Specifically, they can be the substrates described in the manufacturing methods of the liquid crystal alignment film and the liquid crystal display element to be described later. There is no particular limitation on the material of the spacer body. For example, it can be a photoresist or an alumina ball.

[0058] Please refer to Figure 1C , the third step is to dock the first unit 110 and the second unit 120 to form a test unit 10, where the liquid crystal alignment film 114 in the first unit 110 contacts the plurality of spacer bodies 124 in the second unit 120.

[0059] Please refer to Figure 1D , the fourth step is to use a wear testing machine M to apply a pressure P of 2000 grams on the first unit 110 side of the test unit 10 in a first direction D1 parallel to the stacking direction of the first unit 110 and the second unit 120, and to perform friction on the test unit 10 in a second direction D2 perpendicular to the stacking direction, and observe the minimum number of friction times when scars appear on the surface S1 of the liquid crystal alignment film 114. For example, the wear testing machine M can be a wear testing machine manufactured by Yangyi Technology Co., Ltd. with the model QC-621H. In addition, the test parameters can be a load of 2000 grams (i.e., the pressure P is 2000 grams), the moving distance of the wear testing machine is 4 cm, the moving speed is 2 cm / s, and one round trip of friction is counted as 1 time.

[0060] Polymer (A)

[0061] The polymer (A) of this embodiment is selected from at least one polymer in the group consisting of a polyimide precursor and an imidized polymer of the polyimide precursor. The polyimide precursor of the polymer (A) contains the structure shown by the following formula (I).

[0062]

[0063] In formula (I), X 1 represents at least one selected from the group consisting of the structures shown by the following formula (I-1) to formula (I-7); X 2 each independently represents a hydrogen atom or an alkyl group with 1 to 4 carbon atoms; Y represents a divalent organic group; * represents the bonding position.

[0064]

[0065] 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 * represents the bonding position. In one embodiment, X 11 and X 13 each independently represents an alkyl group having 1 to 3 carbon atoms, and X 12 and X 14 each independently represents a hydrogen atom. In another embodiment, X 11 , X 12 , X 13 , and X 14 each independently represents a hydrogen atom.

[0066] In formulas (I-2) to (I-6), * represents the bonding position;

[0067] In formula (I-7), X 15 and X 16 each independently represents a hydrogen atom or a methyl group, and * represents the bonding position.

[0068] In one embodiment, the above-mentioned X 1 represents a structure represented by the following formulas (I-1-1) to (I-1-6):

[0069]

[0070] where * represents the bonding position.

[0071] In formula (I), X 1 preferably represents a structure represented by formula (I-1), more preferably a structure represented by formula (I-1-1) or (I-1-6), and still more preferably a structure represented by formula (I-1-1).

[0072] In one embodiment, the molecular structure of the above-mentioned polymer (A) has a group of -N(D)-, where D represents a urethane-based protecting group.

[0073] Furthermore, the polymer (A) of the present embodiment may be selected from at least one polymer in the group consisting of polyimide precursors obtained by reacting a tetracarboxylic dianhydride component (a1) and a diamine component (a2), and imidized polymers of the polyimide precursors. For example, the polymer (A) may, for example, include polyimide precursors having imide precursor structures such as polyamic acid and polyamic acid ester, and imidized polymers of these polyimide precursors.

[0074] tetracarboxylic dianhydride component (a1)

[0075] In addition to using tetracarboxylic dianhydride compounds, the tetracarboxylic dianhydride component (a1) that reacts with the diamine component (a2) in the present embodiment may also use tetracarboxylic dihalides, tetraalkyl esters of tetracarboxylic acids, or tetraalkyl ester dihalides of tetracarboxylic acids and other tetracarboxylic dianhydride derivatives. The tetracarboxylic dianhydride component (a1) may be used alone with one tetracarboxylic dianhydride compound or its derivative, or may be used in combination with a variety of combinations.

[0076] The tetracarboxylic dianhydride component (a1) may include an alicyclic tetracarboxylic dianhydride (a1-1) represented by formula (A11). The tetracarboxylic dianhydride component (a1) may optionally further include other tetracarboxylic dianhydrides (a1-2).

[0077] alicyclic tetracarboxylic dianhydride (a1-1) represented by formula (A11)

[0078] The tetracarboxylic dianhydride component (a1) used to react to obtain the polymer (A) may include an alicyclic tetracarboxylic dianhydride (a1-1) or its derivative represented by the following formula (A11). The alicyclic tetracarboxylic dianhydride (a1-1) or its derivative represented by formula (A11) may be composed of a single tetracarboxylic dianhydride or its derivative, or may be composed of a variety of tetracarboxylic dianhydrides or their derivatives. In the present embodiment, the alicyclic tetracarboxylic dianhydride (a1-1) represented by formula (A11) may, for example, be an acid dianhydride obtained by intramolecular dehydration of four carboxyl groups including at least one carboxyl group bonded to the 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 of it may also have a chain hydrocarbon structure or an aromatic ring structure. The aromatic tetracarboxylic dianhydride may, for example, be 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 of it may also have a chain hydrocarbon structure or an alicyclic structure. The acyclic aliphatic tetracarboxylic dianhydride may, for example, be 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 of it may also have an alicyclic structure or an aromatic ring structure.

[0079]

[0080] In formula (A11), X 1 At least one may be selected from the group consisting of the structures represented by the following formulae (I-1) to (I-7), where * represents a bonding position.

[0081]

[0082]

[0083] 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 * represents a bonding position. In one embodiment, X 11 and X 13 Each independently represents an alkyl group having 1 to 3 carbon atoms, X 12 and X 14 Each independently represents a hydrogen atom. In another embodiment, X 11 、X 12 、X 13 , and X 14 Each independently represents a hydrogen atom.

[0084] In formula (I-2) to formula (I-6), * represents a bonding position.

[0085] In formula (I-7), X 15 and X 16 Each independently represents a hydrogen atom or a methyl group, and * represents a bonding position.

[0086] In some embodiments, X 1 The structures represented by the following formulae (I-1-1) to (I-1-6) can be represented.

[0087]

[0088] In formula (A11), X 1 The structure represented by formula (I-1) is preferred, the structure represented by formula (I-1-1) or formula (I-1-6) is more preferred, and the structure represented by formula (I-1-1) is even more preferred.

[0089] When X 1 When the group represented by formula (I-1-1) is represented, the alicyclic tetracarboxylic dianhydride (a1-1) is a tetracarboxylic dianhydride represented by formula (I-1-1a).

[0090]

[0091] When X1 When it is a group represented by the formula (I-1-6), the alicyclic tetracarboxylic dianhydride (a1-1) is a tetracarboxylic dianhydride represented by the formula (I-1-6a).

[0092]

[0093] 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 the formula (A11) is 30 moles to 100 moles, preferably 40 moles to 100 moles, and more preferably 50 moles to 100 moles.

[0094] Other tetracarboxylic dianhydrides (a1-2)

[0095] The other tetracarboxylic dianhydrides (a1-2) may include tetracarboxylic dianhydride compounds and their derivatives represented by the following formula (A12).

[0096]

[0097] In the formula (A12), X 1 ' may represent a structure represented by the following formula (A12-1) to formula (A12-32), where * represents the bonding position.

[0098]

[0099]

[0100]

[0101] In the formula (A12-5) and the 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 the formula (A12-5), a1 represents an integer of 0 or 1; in the formula (A12-6), a1 represents an integer of 0 or 1. In the 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, 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.

[0102] In some specific examples, the structure represented by formula (A12-5) and the structure represented by formula (A12-6) may include, but are not limited to, the structures represented by the following formulas (A12-5-1) to (A12-5-9) and formulas (A12-6-1) to (A12-6-7).

[0103]

[0104]

[0105]

[0106] The aforementioned other tetracarboxylic dianhydrides (a1-2) can be used alone or in combination of multiple kinds.

[0107] 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 moles to 70 moles, preferably from 0 moles to 60 moles, and more preferably from 0 moles to 50 moles.

[0108] Based on the total number of moles of the diamine component (a2) described below being 100 moles, the usage amount range of the tetracarboxylic dianhydride component (a1) is preferably from 20 moles to 200 moles, and more preferably from 30 moles to 120 moles.

[0109] Diamine component (a2)

[0110] The diamine component (a2) may include a diamine compound (a***-1). In addition, the diamine component (a2) may further include a diamine compound (a2-2). In addition to the diamine compound (a2-1) and the diamine compound (a2-2), the diamine component (a2) may also selectively further include other diamine compounds (a2-3).

[0111] It should be noted that when the diamine component (a2) includes a diamine compound (a2-2) having a -N(D)- group in addition to the diamine compound (a2-1), the formed liquid crystal alignment film has better hardness, so the minimum number of friction times in the wear resistance test is higher, and the number of bright spots caused by scratches on the liquid crystal alignment film in the liquid crystal display element is also less.

[0112] Diamine compound (a2-1)

[0113] The diamine compound (a2-1) may include at least one of the diamine compounds represented by the following formulas (A21-*** and (A21-2). The diamine compound preferably includes the diamine compound represented by the following formula (A21-1).

[0114]

[0115] In formula (A21-1), Y31 represents a divalent organic group represented by the following formula (A21-3). A plurality of Y 32 each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. In formula (A21-2), a plurality of Y 33 each independently represents a divalent organic group represented by the following formula (A21-3').

[0116]

[0117] In formula (A21-3), each Ar independently represents a divalent benzene ring, biphenyl structure, or naphthalene ring, and the hydrogen atoms of the benzene ring, biphenyl structure, or naphthalene ring may be substituted or unsubstituted 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 be substituted or unsubstituted by -O-, -C(=O)-, or -O-C(=O)-; p1 represents an integer of 0 or 1; * represents the bonding position.

[0118] In formula (A21-3'), each 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.

[0119] 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.

[0120] From the viewpoint of improving the liquid crystal alignment, the divalent organic group represented by formula (A21-3) preferably contains at least one of the groups represented by the following formulas (A21-3-1) to (A21-3-16), where * represents the bonding position.

[0121]

[0122]

[0123]

[0124] From the viewpoint of improving the liquid crystal alignment, the divalent organic group represented by the formula (A21-3') preferably contains at least one of the groups represented by the formula (A21-3-7) to the formula (A21-3-16).

[0125] In one embodiment, the diamine compound represented by the formula (A21-1) is preferably Y 31 represents the group represented by the formula (A21-3-7), the group represented by the formula (A21-3-11), or the group represented by the formula (A21-3-15), more preferably Y 31 represents the group represented by the formula (A21-3-7) or the group represented by the formula (A21-3-11).

[0126] Specifically, when Y 31 represents the group represented by the formula (A21-3-7), the diamine compound is, for example, the diamine compound represented by the formula (A21-3-7a).

[0127]

[0128] Specifically, when Y 31 represents the group represented by the formula (A21-3-11), the diamine compound is, for example, the diamine compound represented by the formula (A21-3-11a).

[0129]

[0130] When Y 31 represents the group represented by the formula (A21-3-15), the diamine compound is, for example, the diamine compound represented by the formula (A21-3-15a).

[0131]

[0132] When the diamine compound (a2-1) contains a plurality of diamine compounds represented by the formula (A21-1), it is preferably Y in the formula (A21-1) 31 represents at least one of the diamine compounds represented by the formula (A21-3-1) to the formula (A21-3-14) and Y in the formula (A21-1) 31 represents a combination formed by at least one of the diamine compounds represented by the formula (A21-3-15) to the formula (A21-3-16).

[0133] 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 the formula (A21-2-5).

[0134]

[0135]

[0136] The aforementioned diamine compound (a2-1) can be used alone or in combination of multiple types.

[0137] 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 90 moles.

[0138] Diamine compound (a2-2)

[0139] From the perspective of further reducing the number of bright dots in 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). In other words, when the molecular structure of the polymer (A) has a group of -N(D)-, the formed liquid crystal alignment film has better hardness, so the minimum number of friction times in the wear resistance test is higher, and the bright dots generated due to scratches on the liquid crystal alignment film in the liquid crystal display element can be further improved.

[0140] The polymer (A) having a group of -N(D)- can be obtained by a method of using a monomer having a group of -N(D)- as at least a part of the reaction raw materials, or by using it as a capping agent described later. In some specific examples, the above-mentioned 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, 9-fluorenylmethoxycarbonyl. The urethane-based protecting group is preferably tert-butoxycarbonyl.

[0141] 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.

[0142] 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 (A22-11). In formulas (A22-1) to (A22-11), Boc is tert-butoxycarbonyl.

[0143]

[0144]

[0145] In formula (A22-11), Q 1 and Q 2 each independently represents -CH- or a nitrogen atom; Y 4 represents and R 1 represents a carbamate protecting group; Y 5 represents a single bond, an oxygen atom or a sulfur atom group; m 1 represents an integer from 1 to 5.

[0146] In some specific examples, the compound represented by formula (A22-11) of this embodiment may include, but is not limited to, the compounds represented by the following formulas (A22-11-1) to (A22-11-11). There is no particular limitation on the method for producing the compound represented by formula (A22-11), and it can be synthesized by a suitable combination of general methods of organic chemistry. In the following formulas (A22-11-1) to (A22-11-11), Boc is tert-butyloxy carbonyl.

[0147]

[0148]

[0149]

[0150] The aforementioned diamine compound (a2-2) can be used alone or in combination of multiple kinds.

[0151] The diamine compound (a2-2) is preferably the diamine compound represented by formula (A22-4a), formula (A22-7a), and formula (A22-11-2a).

[0152] When the diamine compound (a2-2) is of formula (A22-4), the diamine compound (a2-2) is, for example, the diamine compound represented by formula (A22-4a).

[0153]

[0154] When the diamine compound (a2-2) is of formula (A22-7), the diamine compound (a2-2) is, for example, the diamine compound represented by formula (A22-7a).

[0155]

[0156] When the diamine compound (a2-2) is of formula (A22-11-2), the diamine compound (a2-2) is, for example, the diamine compound represented by formula (A22-11-2a).

[0157]

[0158] 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 from 0 mole to 68 moles, preferably from 0 mole to 52 moles, and more preferably from 0 mole to 37 moles.

[0159] Other diamine compounds (a2-3)

[0160] The diamine component (a2) may also optionally further 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 formula (A23-1) to formula (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 formula (A23-4) to 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-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 formula (A23-8) to formula (A23-10); diamine compounds having an amide bond represented by the following formula (A23-11) to formula (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; diamines having a siloxane bond, such as 3-bis(3-aminopropyl)-tetramethyldisiloxane; diamine compounds having an oxazoline structure such as the diamine compounds represented by the following formula (A23-14) to formula (A23-15). Oxazoline structure diamine compounds.

[0161]

[0162]

[0163]

[0164] In formula (A23-4), Y 51represents 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.

[0165] In formula (A23-5), m3 and m4 each independently represent an integer from 1 to 5.

[0166] In formula (A23-6), Y 52 represents a straight-chain or branched alkyl group having 1 to 5 carbon atoms; m5 represents an integer from 1 to 5.

[0167] In formula (A23-7), Y 53 and Y 54 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.

[0168] The aforementioned other diamine compound (a2-3) can be used alone or in combination of multiple kinds.

[0169] Based on the total usage amount of the diamine component (a2) being 100 moles, the usage amount of the other diamine compound (a2-3) can be from 0 moles to 68 moles, preferably from 0 moles to 52 moles, and more preferably from 0 moles to 37 moles.

[0170] Preparation method of the polymer

[0171] The preparation of the polymer (A) 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 the polymer (A) has an amic acid structure, for example, by reacting the tetracarboxylic dianhydride component with the diamine component to obtain a polymer having an amic acid structure (i.e., polyamic acid). 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. A specific example of the solvent is preferably N-methyl-2-pyrrolidone. In some specific examples, when the solvent solubility of the polymer is high, the solvent may include methyl ethyl ketone, cyclohexanone, cyclopentanone, 4-hydroxy-4-methyl-2-pentanone, or a solvent represented by the following formulas (AS-1) to (AS-3).

[0172]

[0173] In formula (AS-1), Z 1 represents an alkyl group having 1 to 3 carbon atoms.

[0174] In formula (AS-2), Z 2 represents an alkyl group having 1 to 3 carbon atoms.

[0175] In formula (AS-3), Z 3 represents an alkyl group having 1 to 4 carbon atoms.

[0176] 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. When carrying out the reaction, the ratio of the total molar number of the diamine component to the total molar number of the tetracarboxylic dianhydride component is preferably 0.8 to 1.2. Similar to a general polycondensation reaction, the closer this molar ratio is to 1.0, the larger the molecular weight of the formed polymer (A).

[0177] A polymer having an amic acid ester structure can be obtained, for example, by the following existing methods: (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.

[0178] The imidized product in the polymer (A) contained in the liquid crystal aligning agent of this embodiment can be obtained, for example, by subjecting the previously obtained polymer to cyclodehydration. In the above 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.

[0179] As for the method for 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.

[0180] 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 preferably stirring is carried out 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 times to 30 times the molar equivalent of the amic acid group, and more preferably 2 times to 20 times; the addition amount of the acid anhydride is preferably 1 time to 50 times the molar equivalent of the amic acid group, and more preferably 3 times to 30 times. Specific examples of the basic catalyst can include but are not limited to pyridine, triethylamine, trimethylamine, tributylamine, or 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, or 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.

[0181] 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 solvent 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, or 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 solvent used can be, for example, alcohols or ketone hydrocarbons, etc. If three or more solvents selected therefrom are used, the purification efficiency can be further improved, so it is more ideal.

[0182] Solution Viscosity and Molecular Weight of Polymer

[0183] When configured as a solution with a concentration of 10 wt% to 15 wt%, the solution viscosity of the polymer (A) in this example is not particularly limited. From the perspective of easy operation, its solution viscosity can be, for example, 10 mPa·s to 1000 mPa·s. The solution viscosity (mPa·s) of the polymer is a value measured at 25 °C using an E-type rotational viscometer for a polymer solution prepared with a good solvent (such as γ-butyrolactone or N-methyl-2-pyrrolidone, etc.) of the above polymer at a concentration of 10 wt% to 15 wt%.

[0184] The weight-average molecular weight (M w ) of the polymer (A) in this example 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.

[0185] End-capping agent

[0186] When synthesizing the polymer (A) in this example, the aforementioned tetracarboxylic dianhydride component and diamine component can be used, and an appropriate end-capping agent can be used to synthesize a terminally-sealed polymer. The terminally-sealed polymer has the effects 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 terminal of the polymer (A) in this example may, for example, contain an amino group, a carboxyl group, an acid anhydride group, or derivatives thereof. The amino group, carboxyl group, acid anhydride group, or derivatives thereof can be obtained through general condensation reactions or by sealing the terminal using the end-capping agent described below. Similarly, the aforementioned derivatives can be obtained, for example, using the following end-capping agent.

[0187] 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.

[0188] The capping agent may be used alone or in combination of multiple kinds.

[0189] 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.

[0190] Other polymers

[0191] The liquid crystal aligning agent of this embodiment contains polymer (A). In addition to polymer (A), the liquid crystal aligning agent of this embodiment may selectively further 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.

[0192] Solvent (B)

[0193] From the perspective of forming a uniform thin film, the liquid crystal aligning agent takes the form of a coating solution to fabricate a liquid crystal alignment film. The liquid crystal aligning agent of this embodiment is preferably a coating solution containing the above polymer components and an organic solvent (hereinafter referred to as solvent (B)). Among them, based on the set film thickness 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 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%.

[0194] There is no particular limitation on the organic solvent contained in the liquid crystal aligning agent, and it only needs to be able to uniformly dissolve the aforementioned polymer. Specific examples thereof may include, but are not limited to, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethyl lactamide, 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-dimethyl propionamide, 3-butoxy-N,N-dimethyl propionamide, 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-dimethyl propionamide, 3-butoxy-N,N-dimethyl propionamide or γ-butyrolactone are preferred. Based on the total amount of the solvent used in the liquid crystal aligning agent being 100 wt%, the amount of the good solvent used can be 20 wt% to 99 wt%, preferably 20 wt% to 90 wt%, and more preferably 30 wt% to 80 wt%.

[0195] 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 coating of the liquid crystal aligning agent and the surface smoothness of the coating film. Specific examples of the poor solvent to be used may include, but are not limited to, the solvents described below. Based on the total amount of the solvent used in the liquid crystal aligning agent being 100 wt%, the amount of the poor solvent used 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 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, etc.

[0196] For example, the lean 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 n-butyl ether), 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.

[0197] 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.

[0198] Preferred solvent combinations of good solvents and poor solvents can 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-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, γ-butyrolactone, propylene glycol monobutyl ether and diisobutyl methanol; 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-dimethyl lactamide and diisobutyl ketone, etc.

[0199] Specific examples of the solvent (B) are preferably N-methyl-2-pyrrolidone (NMP), ethylene glycol n-butyl ether, N,N-dimethylacetamide, or a combination thereof.

[0200] The aforementioned solvent (B) can be used alone or in combination of multiple types.

[0201] Based on 100 parts by weight of the polymer (A), the solvent (B) is 800 to 4000 parts by weight, preferably 900 to 3500 parts by weight, and more preferably 1000 to 3000 parts by weight.

[0202] Compound (C)

[0203] In one embodiment, the liquid crystal alignment agent further includes a compound (C) having at least one group selected from the group consisting of the group represented by the following formula (C1) and the group represented by the following formula (C2). When the liquid crystal alignment agent further includes the compound (C), the number of bright dots in the liquid crystal display element can be further reduced, and the effect of improving the bright dots in the liquid crystal display element is better.

[0204]

[0205] In formula (C1), G 1 and G 2 each independently represent a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or -CH2-OH, and * represents the bonding position.

[0206]

[0207] In formula (C2), G 3 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, G 4 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, and * represents the bonding position.

[0208] Compound having the group represented by formula (C1)

[0209] Specific examples of the compound having the group represented by formula (C1) can include compounds represented by the following formulas (C1-1) to (C1-12).

[0210]

[0211]

[0212]

[0213] A compound having a group represented by formula (C2)

[0214] Specific examples of the compound having a group represented by formula (C2) include compounds represented by the following formulas (C2-1) to (C2-4).

[0215]

[0216]

[0217] Specific examples of compound (C) preferably include a compound represented by formula (C1-1), a compound represented by formula (C1-2), a compound represented by formula (C1-3), a compound represented by formula (C1-4), a compound represented by formula (C2-1) (n = 4), or a combination thereof.

[0218] The aforementioned compound (C) can be used alone or in combination of multiple types.

[0219] Based on 100 parts by weight of polymer (A), compound (C) is 0.5 to 20 parts by weight, preferably 0.8 to 18 parts by weight, more preferably 1 to 15 parts by weight.

[0220] Additive (D)

[0221] The liquid crystal alignment agent of this example can also selectively add components other than the polymer component and the organic solvent (hereinafter referred to as additive (D)). These additives (D) can include, for example, but are not limited to: an adhesion aid (D-1) for improving the adhesion between the liquid crystal alignment film and the substrate or the adhesion between the liquid crystal alignment film and the sealant, a compound for improving the strength of the liquid crystal alignment film (hereinafter referred to as a crosslinkable compound (D-2)), a compound for promoting imidization (D-3), a dielectric or conductive substance for adjusting the dielectric constant or resistance of the liquid crystal alignment film, etc.

[0222] Adhesion aid (D-1)

[0223] The aforementioned adhesion promoter (D-1) can 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, etc., which are silane coupling agents.

[0224] The aforementioned adhesion promoter (D-1) can be used alone or in combination of two or more.

[0225] Relative to 100 parts by weight of the total amount of the polymer (A) used in the liquid crystal alignment agent, the amount of the adhesion promoter (D-1) used is preferably 0.1 part by weight to 30 parts by weight, and more preferably 0.1 part by weight to 20 parts by weight.

[0226] Crosslinkable compound (D-2)

[0227] The aforementioned crosslinkable compound (D-2) includes at least one of a compound having an oxiranyl group, a compound having an oxetanyl group, and a compound represented by the following formula (d2-1).

[0228]

[0229] In formula (d2-1), G 5 represents a (g1 + g2)-valent organic group containing an aromatic ring. G 6 represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. g1 represents an integer of 1 to 6, and g2 represents an integer of 0 to 4.

[0230] In formula (d2-1), G 5Examples of the (g1 + g2)-valent organic group having an aromatic ring represented include a (g1 + g2)-valent aromatic hydrocarbon group having 6 to 30 carbon atoms, a (g1 + g2)-valent organic group formed by directly bonding or bonding through a linking group an aromatic hydrocarbon group having 6 to 30 carbon atoms, 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 the specific nitrogen atom-containing structures 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 these alkylene groups, or a divalent or trivalent cyclohexane. Among them, any hydrogen atom of these alkylene groups may also be substituted with an organic group such as a fluorine atom or a trifluoromethyl group. In formula (d2-1), G 6 Examples of the alkyl group having 1 to 5 carbon atoms represented include methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, or n-pentyl.

[0231] Compound having an oxiranyl group

[0232] Specific examples of the compound having an oxiranyl group 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 represented by the following formulas (d2-2) to (d2-4).

[0233]

[0234]

[0235] Compound having an epoxypropyl group

[0236] Specific examples of the compound having an epoxypropyl group include compounds represented by the following formulas (d2-5) to (d2-14).

[0237]

[0238]

[0239] Formula (d2-11)

[0240]

[0241]

[0242] In formula (d2-13), R represents a group represented by formula (d2-13-1), where * represents the bonding position.

[0243]

[0244] A compound having a group represented by formula (d2-1)

[0245] Specific examples of the compound having a group represented by formula (d2-1) may be compounds represented by the following formulas (d2-1-1) to (d2-1-10).

[0246]

[0247]

[0248] The aforementioned crosslinkable compound (D-2) can be used alone or in combination of multiple kinds.

[0249] In the liquid crystal alignment agent of this example, based on the total amount of the polymer in the liquid crystal alignment agent being 100 parts by weight, the amount of the crosslinkable compound (D-2) 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 (D-2) used is more preferably 1 to 15 parts by weight.

[0250] Compound (D-3) for promoting imidization

[0251] The aforementioned compound (D-3) for promoting imidization is preferably a compound having a basic site (for example: primary amino group, aliphatic heterocycle (such as pyrrolidine skeleton), aromatic heterocycle (such as imidazole ring or indole ring), or guanidine group, etc.) (except for the aforementioned crosslinkable compound (D-2) and adhesion promoter (D-1)), or a compound that generates the basic site when heated. More preferably, the compound (D-3) for promoting imidization is a compound that generates the basic site when heated, and specific examples thereof may be, for example, amino acids in which part or all of the basic sites are protected amino acids. Specific examples of the above 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 (D-3) for promoting imidization, more preferred specific examples may include N-α-(9-fluorenylmethoxycarbonyl)-N-τ-(tert-butoxycarbonyl)-L-histidine.

[0252] The aforementioned compound (D-3) for promoting imidization can be used alone or in combination of multiple kinds.

[0253] <Method for manufacturing a liquid crystal alignment film and a liquid crystal display element>

[0254] This example provides a liquid crystal alignment film formed using the liquid crystal alignment agent by the above-mentioned photo-alignment method.

[0255] This embodiment provides a liquid crystal display element including the liquid crystal alignment film as described above.

[0256] The liquid crystal alignment film of this embodiment is obtained from the aforementioned liquid crystal aligning agent. The liquid crystal alignment film of this embodiment can be used as a horizontally aligned type or 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 FFS mode. The liquid crystal display element of this embodiment includes the aforementioned liquid crystal alignment film. The liquid crystal display element of this embodiment can be manufactured, for example, by the following steps (1) to (4) or the method of steps (1) to (2) and step (4).

[0257] Step (1): Coating the liquid crystal aligning agent on a substrate

[0258] Using an appropriate coating method such as roll coating, spin coating, printing, or inkjet printing, coat the liquid crystal aligning agent of this embodiment on one side of a substrate provided with a patterned transparent conductive film. Among them, the substrate has no particular limitation, and it only needs to be a highly transparent substrate. A glass substrate or a silicon nitride substrate can also be used in combination with a plastic substrate such as an acrylic substrate or a polycarbonate substrate. Secondly, in a reflective liquid crystal display element, if only one-sided substrate is used, an opaque material such as a silicon wafer can also be used, and the electrode used can also be a light-reflective material such as aluminum. Furthermore, when manufacturing an IPS type or FFS type liquid crystal element, a comb-shaped type uses an electrode substrate composed of a patterned transparent conductive film or a metal film that has been provided and a counter substrate without an electrode.

[0259] Examples of the method of coating the liquid crystal aligning agent on the substrate and forming a film include screen printing, lithography, flexography, inkjet printing, or spraying. Among them, the method of forming a film is preferably coating by inkjet printing.

[0260] Step (2): Heating the coated liquid crystal aligning agent

[0261] Step (2) is a step of heating the liquid crystal aligning agent coated on the substrate to form a film. After the liquid crystal aligning agent is coated on the substrate, heating means such as a hot plate, a thermal cycle type oven, or an infrared (IR) type oven can be used to evaporate the solvent, or to perform thermal imidization of polyamic acid or polyamic acid ester. The drying and heating steps performed after coating the liquid crystal aligning agent of this embodiment can be carried out at any temperature and time, and the drying or heating steps can be carried out multiple times. The drying temperature can be, for example, 40°C to 180°C. From the perspective of shortening the treatment, it can be carried out 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, a heating step can be further carried out at a temperature of, for example, 150°C to 300°C or 150°C to 250°C. The heating time is not particularly limited, and examples thereof include 5 minutes to 40 minutes or 5 minutes to 30 minutes. If the film-like material after heating 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.

[0262] Step (3): Perform an alignment treatment on the film obtained in step (2)

[0263] 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 above-mentioned 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 Polymer Stabilized Alignment (PSA) mode, the formed coated film can be directly used as a liquid crystal alignment film, but an alignment treatment can also be performed on these coated films to impart alignment ability. Examples of the alignment treatment of the liquid crystal alignment film include the rubbing treatment method or the photo-alignment treatment method (also referred to as the "photo-alignment method"), and the photo-alignment treatment method is preferably used. The photo-alignment treatment method can be a method of 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.

[0264] The irradiation amount of the aforementioned radiation can be 1 mJ / cm 2 to 10,000 mJ / cm 2 and is preferably 100 mJ / cm 2 to 5,000 mJ / cm 2 and 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 amount for the alignment treatment is 100 mJ / cm 2 to 5000 mJ / cm 2 . When irradiating with radiation, in order to improve the liquid crystal alignment property, the substrate of the aforementioned 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 aforementioned method can be subjected to contact treatment with a solvent, or the liquid crystal alignment film irradiated with radiation can be heat-treated.

[0265] The solvent used for the aforementioned contact treatment is not particularly limited, and it only needs to be able to dissolve the decomposition products generated from the film-like material after radiation irradiation. Specific examples can 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 kinds.

[0266] The temperature for heat-treating the aforementioned radiation-irradiated coating film 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.

[0267] Step (4): Fabricate a liquid crystal cell

[0268] Prepare two of the aforementioned liquid crystal alignment film substrates formed, and dispose 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) between them with the liquid crystal alignment films facing 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 separated by the substrate surfaces and the sealant. After it contacts the film surface, seal the injection hole.

[0269] The second method, called the ODF (One Drop Fill) method. A sealant such as an ultraviolet curable one is coated at a predetermined position on one of the two substrates on which the liquid crystal alignment film has been formed, and a liquid crystal composition is dropped at a plurality of predetermined positions on the surface of the liquid crystal alignment film. Then, the other substrate is bonded in a manner facing the liquid crystal alignment film, and the liquid crystal composition is pressed over the entire surface of the substrate to bring it into contact with the film surface. Next, ultraviolet light is irradiated over the entire surface of the substrate to harden the sealant. When any of the above methods is carried out, it is preferably further to heat the liquid crystal composition used to the temperature at which it becomes the isotropic phase and then slowly cool it to room temperature to remove the flow alignment during liquid crystal filling. Next, when the coating film is subjected to a rubbing treatment, the two substrates are arranged 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 hardening agent and alumina balls as a spacer. As for the liquid crystal used above, that is, the liquid crystal compound or liquid crystal composition, it is not particularly limited here. Examples of the liquid crystal composition include nematic liquid crystals and smectic liquid crystals, and preferably nematic liquid crystals.

[0270] If necessary, a polarizing plate may be bonded to the outer surface of the liquid crystal cell to obtain a liquid crystal display element. Examples of the polarizing plate bonded to the outer surface of the liquid crystal cell include a polarizing film obtained by stretching and aligning polyvinyl alcohol and simultaneously absorbing iodine, and called an "H film". It can be a polarizing plate sandwiched by a cellulose acetate protective film, or a polarizing plate composed of the H film itself.

[0271] The present invention will be further described with the following experimental examples, but it should be understood that these experimental examples are only for illustrative purposes and should not be construed as a limitation on the implementation of the present invention.

[0272] Synthesis Example of Polymer (A)

[0273] Synthesis Example A-1

[0274] A nitrogen inlet, a stirrer, a condenser, and a thermometer were set on a four-necked conical flask with a volume of 500 mL, and nitrogen was introduced. Then, 0.0225 mol (45 mol%) of a2-1-1, 0.175 mol (35 mol%) of a2-1-2, 0.005 mol (10 mol%) of a2-1-3, 0.005 mol (10 mol%) of a2-2-1, and 80 g of N-methyl-2-pyrrolidone (hereinafter referred to as NMP) as the diamine component were added, and the mixture was stirred at room temperature until dissolved. Subsequently, 0.05 mol (100 mol%) of a1-1-1 and 20 g of NMP as the tetracarboxylic dianhydride component 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. Thereafter, the product was placed in a vacuum oven and dried at a temperature of 60 °C to obtain the polymer (A-1).

[0275] Synthesis Examples A-2 to A-6

[0276] The polymers (A-1) to (A-6) of Synthesis Examples A-2 to A-6 were prepared by the same procedure as Synthesis Example A-1, and the differences were as follows: the types and amounts used of the diamine component and the tetracarboxylic dianhydride component in Synthesis Example A-1 were changed (as shown in Table 1). In Table 1, the amounts of each component are expressed in "mol%", and the actual number of moles used was calculated by setting 0.05 mol as 100 mol%. The detailed proportion of the amounts used can be referred to Synthesis Example A-1. The compounds corresponding to the abbreviations in Table 1 are shown in Table 2.

[0277] Table 1

[0278]

[0279] Table 2

[0280]

[0281]

[0282] Synthesis Example A’

[0283] A nitrogen inlet, a stirrer, a condenser and a thermometer were set on a four-necked conical flask with a volume of 500 ml, and nitrogen was introduced. Then, 0.05 mol of 4,4'-diaminodiphenylamine and 80 g of N-methyl-2-pyrrolidone were added, and the mixture was stirred at room temperature until dissolved. Then, 0.05 mol of biphenyltetracarboxylic dianhydride and 20 g of N-methyl-2-pyrrolidone were added, and the reaction was carried out at room temperature for 2 hours to obtain a reaction solution. The reaction solution was poured into 1500 ml of water to precipitate the polymer, and then, filtration treatment was carried out to obtain a filter cake. Then, the filter cake was washed with methanol, and then, filtration was carried out. Among them, washing with methanol and filtration were carried out three times in total. Then, it was placed in a vacuum oven and dried at 60 °C to obtain the polymer (A').

[0284] Examples and Comparative Examples of Liquid Crystal Alignment Agents

[0285] The following describes Experimental Examples 1 to 8 and Comparative Example 1 of the liquid crystal alignment agent:

[0286] 100 parts by weight of the polymer (A-1-1), 600 parts by weight of N-methyl-2-pyrrolidone (abbreviated as B-1) and 2 parts by weight of the compound C-1 (abbreviated as C-1) were weighed, and the mixture was stirred and mixed at room temperature to form the liquid crystal alignment agent of Experimental Example 1. The liquid crystal alignment agent of Experimental Example 1 was evaluated by the following evaluation methods, and the results are shown in Table 3.

[0287] Experimental Examples 2 to 8 and Comparative Example 1

[0288] The liquid crystal alignment agents of Experimental Examples 2 to 8 and Comparative Example 1 were prepared by the same steps as in Experimental Example 1, and the differences were as follows: the types and amounts of the components were changed, as shown in Table 3. The liquid crystal alignment agents prepared in Experimental Examples 2 to 8 and Comparative Example 1 were evaluated by the following evaluation methods, and the results are shown in Table 3. The compounds corresponding to the abbreviations in Table 1 are shown in Table 4.

[0289]

[0290] [[ID=2i]]Table 4

[0291]

[0292]

[0293] [Evaluation Method]

[0294] a. Abrasion Resistance Test

[0295] The liquid crystal aligning agent was spin-coated onto a 100 mm × 100 mm glass substrate with an ITO conductive film. Then, the glass substrate coated with the liquid crystal aligning agent was dried on a hot plate at 80 °C for 3 minutes. Subsequently, it was baked in a hot air circulation oven at 230 °C for 30 minutes to obtain a coating film with a film thickness of 100 nm formed on the glass substrate. The coating film was irradiated with ultraviolet light with a wavelength of 254 nm through a polarizing plate, and then baked in a hot air circulation oven at 230 °C for 30 minutes to obtain the first unit containing the liquid crystal alignment film.

[0296] Subsequently, the spacer was spin-coated onto a 100 mm × 100 mm plain glass substrate with a photosensitive resin composition. Then, it was pre-baked at 90 °C for 150 seconds to form a pre-baked coating film. Then, using a photomask with a specific pattern, the obtained pre-baked coating film was exposed with an exposure machine (energy: 60 mJ / cm 2 ), and then immersed in a 0.0438 wt% aqueous potassium hydroxide (KOH) solution for 70 seconds for development to remove the unexposed part. Then, it was washed with pure water and post-baked at 235 °C for 30 minutes to obtain the second unit containing the spacer.

[0297] Subsequently, the first unit containing the liquid crystal alignment film and the second unit containing the spacer were docked with the liquid crystal alignment film in contact with the spacer to form a test unit.

[0298] Subsequently, using an abrasion tester (manufactured by Yangyi Technology Co., Ltd., model: QC-621H), a pressure of 2000 g was applied to the first unit side of the test unit in the first direction parallel to the lamination direction of the first unit and the second unit 120, and the test unit was rubbed in the second direction perpendicular to the lamination direction. The minimum number of friction times when scratches appeared on the surface of the liquid crystal alignment film was observed and recorded. The moving distance of the abrasion tester was 4 cm, the moving speed was 2 cm / s, and one round trip of friction was counted as 1 time. The larger the minimum number of friction times, the better the wear resistance.

[0299] b. Bright spot fragmentation test

[0300] Prepare two first units with a liquid crystal alignment film obtained in the wear resistance test. Install one of the first units on a device manufactured by Bruker AXS, model UMT-2 (the sensor is FVL, and a sapphire ball with a size of 1.6 mm is installed at the tip of the device). After 100 seconds, perform a scratch test from 1 mN to 20 mN at 0.5 mm on the horizontal axis (5 mm / second) and 2 mm in the moving direction, and then drop liquid crystal MLC-2041 (manufactured by Merck). Disperse a spacer with a size of 4 μm on the other first unit and clamp it toward the side where MLC-2041 is dropped. Observe the scratched part with a polarizing microscope (model ECLIPSEE600WPOL, manufactured by Nikon) in a state where the polarizing plate is at 90 degrees to observe whether light passes through, and evaluate according to the number of bright spots and the following criteria.

[0301] ※: The number of tiny bright spots ≤ 5.

[0302] ◎: 6 ≤ the number of tiny bright spots ≤ 9.

[0303] ○: 10 ≤ the number of tiny bright spots ≤ 12.

[0304] △: 13 ≤ the number of tiny bright spots ≤ 15.

[0305] ╳: The number of tiny bright spots ≥ 16.

[0306] [Evaluation Results]

[0307] As can be seen from Table 3, compared with the liquid crystal aligning agent with a minimum number of friction times equal to or less than 50 times in the wear resistance test (Comparative Example 1), the liquid crystal aligning agents with a minimum number of friction times greater than 50 times (Examples 1 to 8) have excellent results in the broken bright spot test. Further, when the minimum number of friction times when scratches appear on the surface of the liquid crystal alignment film is greater than 50 times (Examples 1 to 8), the liquid crystal display element will not generate too many broken bright spots due to the scratches on the liquid crystal alignment film, thus improving the situation of excessive broken bright spots. When the minimum number of friction times when scratches appear on the surface of the liquid crystal alignment film is equal to or less than 50 times (Comparative Example 1), there is a situation of excessive broken bright spots in the liquid crystal display element.

[0308] When the minimum number of friction times when scratches appear on the surface of the liquid crystal alignment film is greater than 80 times (Examples 1 to 7), the number of broken bright spots in the liquid crystal display element can be further reduced, and the effect of improving the broken bright spots in the liquid crystal display element is better.

[0309] When the minimum number of friction times when scratches appear on the surface of the liquid crystal alignment film is greater than 100 times (Examples 1 to 5), the number of broken bright spots in the liquid crystal display element can be further reduced, and the effect of improving the broken bright spots in the liquid crystal display element is even better.

[0310] In summary, the present embodiment provides a liquid crystal aligning agent for photo-alignment method, a liquid crystal alignment film, and a liquid crystal display element. By performing a wear resistance test on the surface of the liquid crystal alignment film formed by the liquid crystal aligning agent, the minimum number of friction times when scars appear on the surface of the liquid crystal alignment film is limited to be greater than 50 times. Therefore, excessive bright dots will not be generated in the liquid crystal display element due to scars on the liquid crystal alignment film, thereby improving the situation of excessive bright dots.

[0311] Although the present invention has been disclosed as above by way of embodiments, it is not intended to limit the present invention. Any person skilled in the art within the technical field to which the present invention pertains can make some modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the scope defined by the claims.

Claims

1. A liquid crystal alignment agent for photo-alignment method, comprising: Polymer (A); and Solvent (B), wherein a wear resistance test is performed on the surface of the liquid crystal alignment film formed by the liquid crystal alignment agent, and the minimum number of friction times at which scars appear on the surface of the liquid crystal alignment film is greater than 50 times, The polymer (A) is 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) contains a structure represented by the following formula (I), In formula (I), X 1 represents at least one selected from the group consisting of the structures represented by the following formulas (I-1) to (I-7); X 2 each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; Y represents a divalent organic group; * represents the bonding position; 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 * represents the bonding position; In formula (I-2) to formula (I-6), * represents the bonding position; In formula (I-7), X 15 and X 16 each independently represent a hydrogen atom or a methyl group, and * represents the bonding position.

2. The liquid crystal alignment agent for photo-alignment method according to claim 1, wherein the wear resistance test comprises the following steps: Providing a first unit, wherein the first unit comprises the liquid crystal alignment film formed by a first substrate and the liquid crystal alignment agent, and the liquid crystal alignment film is located on the first substrate; Providing a second unit, wherein the second unit comprises a second substrate and a plurality of spacers, and the plurality of spacers are distributed on the second substrate; Docking the first unit and the second unit to form a test unit, wherein the liquid crystal alignment film in the first unit contacts the plurality of spacers in the second unit; And Using a wear testing machine, applying a pressure of 2000 grams in a first direction parallel to the stacking direction of the first unit and the second unit to the test unit, and rubbing the test unit in a second direction perpendicular to the stacking direction, and observing the minimum number of friction times at which scars appear on the surface of the liquid crystal alignment film.

3. The liquid crystal alignment agent for photo-alignment method according to claim 1, wherein the minimum number of friction times at which scars appear on the surface of the liquid crystal alignment film is greater than 80 times.

4. The liquid crystal alignment agent for photo-alignment method according to claim 1, wherein the minimum number of friction times at which scars appear on the surface of the liquid crystal alignment film is greater than 100 times.

5. The liquid crystal aligning agent for photo-alignment method according to claim 1, wherein X 1 represents a structure represented by the following formulas (I-1-1) to (I-1-6): wherein * represents the bonding position.

6. The liquid crystal aligning agent for photo-alignment method according to claim 5, wherein X 1 represents a structure represented by the formula (I-1-1).

7. The liquid crystal alignment agent for photo-alignment method according to claim 1, wherein the liquid crystal alignment agent further comprises a compound (C) having at least one group selected from the group consisting of a group represented by the following formula (C1) and a group represented by the following formula (C2): In formula (C1), G 1 and G 2 each independently represents a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or -CH2-OH, and * represents the bonding position. In formula (C2), G 3 represents an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or an alkynyl group having 2 to 6 carbon atoms, and G 4 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, and * represents a bonding position.

8. The liquid crystal alignment agent for photo-alignment method according to claim 1, wherein the molecular structure of the polymer (A) has a group of -N(D)-, wherein D represents a urethane-based protecting group.

9. A liquid crystal alignment film formed by using the liquid crystal alignment agent for photo-alignment method according to any one of claims 1 to 8.

10. A liquid crystal display element, comprising: the liquid crystal alignment film according to claim 9.

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