LIQUID CRYSTAL ALIGNING AGENT, LIQUID CRYSTAL ALIGNMENT FILM AND LIQUID CRYSTAL DISPLAY ELEMENT

Abstract

The present invention provides: a liquid crystal alignment film which has good liquid crystal alignment properties, while having excellent pretilt angle developability; a liquid crystal display element which is provided with this liquid crystal alignment film; and a liquid crystal aligning agent which enables the achievement of this liquid crystal alignment film. The present invention provides a liquid crystal aligning agent which contains: as a component (A), a compound that has a thermally crosslinkable group and a photo-alignment group represented by formula (pa-1), wherein the thermally crosslinkable group is capable of forming a covalent bond by being reacted with a carboxy group; and as a component (B), a polyamic acid and a solvent. (In formula (pa-1), A represents a phenylene group or the like; R1 represents COO or OCO; R2 represents a cyclohexane-1,4-diyl group; R3 represents a cyclohexane-1,4-diyl group; R4 represents a linear or branched alkyl group having 1 to 40 carbon atoms, and some or all of the hydrogen atoms in this alkyl group may be substituted by fluorine atoms; D represents an oxygen atom, a sulfur atom or NRd-; a represents an integer of 0 to 3; and * denotes a bonding position.)

Claims

1: A liquid crystal aligning agent comprising: a compound having a photo-alignable group represented by the following formula (pa-1) and a thermally crosslinkable group as a component (A), wherein the thermally crosslinkable group reacts with a carboxy group to form a covalent bond; a polyamic acid as a component (B); and a solvent: ##STR00018## wherein A represents a pyrimidine-2,5-diyl group, a pyridine-2,5-diyl group, a thiophene-2,5-diyl group, a furan-2,5-diyl group, a 1,4- or 2,6-naphthylene group or a phenylene group, which may be optionally substituted with a group selected from a fluorine atom, a chlorine atom and a cyano group, an alkoxy group having 1 to 5 carbon atoms, or a linear or branched alkyl residue having 1 to 5 carbon atoms which may be optionally substituted with one cyano group, or one or more halogen atoms, R.sub.1 represents COO or OCO, R.sub.2 represents a cyclohexane-1,4-diyl group, R.sub.3 represents a cyclohexane-1,4-diyl group, R.sub.4 represents a linear or branched alkyl group having 1 to 40 carbon atoms wherein a part of hydrogen atoms or all hydrogen atoms of the alkyl group may be substituted with fluorine atoms, D represents an oxygen atom, a sulfur atom, or NR.sub.d wherein R.sub.d represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, a represents an integer from 0 to 3, * represents a bonding position, and X and Y each independently represents a hydrogen atom, a fluorine atom, a chlorine atom, a cyano group or an alkyl group having 1 to 3 carbon atoms wherein a part of hydrogen atoms or all hydrogen atoms of the alkyl group may be substituted with fluorine atoms.

2: The liquid crystal aligning agent according to claim 1, wherein the thermally crosslinkable group in the component (A) is a group selected from an epoxy site-containing group, an oxetane site-containing group, a thiirane site-containing group, and a cyclocarbonate group.

3: The liquid crystal aligning agent according to claim 1, wherein the thermally crosslinkable group in the component (A) is an epoxy site-containing group.

4: A liquid crystal alignment film formed using the liquid crystal aligning agent according to claim 1.

5: A method for manufacturing a liquid crystal alignment film comprising the steps of: applying the liquid crystal aligning agent according to claim 1 on a substrate, to form a coating film, and irradiating the coating film with light in a state where the coating film is not in contact with the liquid crystal layer or is in contact with the liquid crystal layer.

6: A liquid crystal display element comprising the liquid crystal alignment film according to claim 4.

7: A compound having a photo-alignable group represented by the following formula (pa-1) and a thermally crosslinkable group, where the thermally crosslinkable group is a group capable of reacting with a carboxy group to form a covalent bond: ##STR00019## wherein A represents a pyrimidine-2,5-diyl group, a pyridine-2,5-diyl group, a thiophene-2,5-diyl group, a furan-2,5-diyl group, a 1,4- or 2,6-naphthylene group or a phenylene group, which may be optionally substituted with a group selected from a fluorine atom, a chlorine atom and a cyano group, an alkoxy group having 1 to 5 carbon atoms, or a linear or branched alkyl residue having 1 to 5 carbon atoms which may be optionally substituted with one cyano group, or one or more halogen atoms, R.sub.1 represents COO or OCO, R.sub.2 represents a cyclohexane-1,4-diyl group, R.sub.3 represents a cyclohexane-1,4-diyl group, R.sub.4 represents a linear or branched alkyl group having 1 to 40 carbon atoms wherein a part of hydrogen atoms or all hydrogen atoms of the alkyl group may be substituted with a fluorine atom, D represents an oxygen atom, a sulfur atom, or NR.sub.d wherein R.sub.d represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, a represents an integer from 0 to 3, * represents a bonding position, and X and Y each independently represents a hydrogen atom, a fluorine atom, a chlorine atom, a cyano group or an alkyl group having 1 to 3 carbon atoms wherein a part of hydrogen atoms or all hydrogen atoms of the alkyl group may be substituted with fluorine atoms.

8: The compound according to claim 7, wherein the thermally crosslinkable group is a group selected from an epoxy site-containing group, an oxetane site-containing group, a thiirane site-containing group, and a cyclocarbonate group.

9: A compound represented by any one of the following formulas (paa-1-ma1) to (paa-1-ma4): ##STR00020##

10: A liquid crystal display element comprising the liquid crystal alignment film prepared by the method according to claim 5.

Description

EXAMPLES

[0132] The present invention will be described in more detail by, but not limited to, following Examples. The abbreviations of the compounds used are as follows:

(Photoalignable Monomer)

[0133] EP1 to EP5: Compounds represented by the following formulas [EP1] to [EP5], respectively. Furthermore, in the formulas (EP1) to (EP5), t represents trans-type of the cyclohexyl group.

##STR00010##

<Tetracarboxylic Dianhydride>

[0134] A1 and A2: Compounds represented by the following formulas [A1] and [A2], respectively:

##STR00011##

<Side Chain Diamine>

[0135] B1 and B2: Compounds represented by the following formulas [B1] and [B2], respectively:

##STR00012##

<Other Diamines>

[0136] C1 and C2: Compounds represented by the following formulas [C1] and [C2], respectively:

##STR00013##

[0137] In addition, the abbreviations of reagents used in the present example are shown below:

(Solvent)

[0138] CH.sub.2Cl.sub.2: Methylene chloride [0139] THF: Tetrahydrofuran [0140] MeOH: Methanol [0141] EtOH: Ethanol [0142] AcOEt: Ethyl acetate [0143] MeCN: Acetonitrile [0144] CHCl.sub.3: Chloroform [0145] NMP: N-Methyl-2-pyrrolidone [0146] BCS: Butyl cellosolve.

<Synthesis of Monomer>

[0147] EP5 was synthesized by the method described in Japanese Patent Application Publication No. 2011-133825. EP1 to EP4 are new compounds that have not been published in literature, and their synthesis methods will be detailed in Monomer Synthesis Examples 1 to 4 below.

<.SUP.1.H-NMR Measurement>

[0148] Equipment: Fourier transform superconducting nuclear magnetic resonance apparatus (FT-NMR) AVANCE III (manufactured by BRUKER) 500 MHZ. [0149] Solvent: Deuterated dimethyl sulfoxide (DMSO-d.sub.6), deuterated chloroform (CDCl.sub.3). [0150] Standard material: Tetramethylsilane (TMS).

Monomer Synthesis Example 1: Synthesis of [EP1]

##STR00014##

[0151] Into a 300 mL four-neck flask, trans, trans-4-pentylbicyclohexyl-4-carboxylic acid (11.2 g, 40.0 mmol), p-toluenesulfonyl chloride (9.2 g, 48.0 mmol), and CH.sub.2Cl.sub.2 (110 g) was charged, 1-methylimidazole (9.9 g, 120 mmol) was added dropwise in an ice bath, and the mixture was stirred at room temperature (25 C.) for 3 hours. Subsequently, 4-hydroxy-trans-cinnamic acid tert-butyl ester (8.8 g, 40.0 mmol) dissolved in CH.sub.2Cl.sub.2 (56 g) in an ice bath was added dropwise, and stirred at room temperature. After the reaction was completed, the reaction solution was concentrated, THE (30 g) was added to the residue, and the mixture was poured into pure water (90 g) to separate the precipitate by filtration. After adding MeOH (100 g) to the resulting crude material and repulp washing at room temperature, AcOEt (100 g) was further added to the crude material and repulping washing was carried out at 0 C., to obtain [EP1-1] (17.1 g, 35.4 mmol, yield: 89%).

[0152] Into a 500 mL four-neck flask, [EP1-1] (17.1 g, 35.4 mmol) and formic acid (260 g) were charged, and stirred at 0 C. After the reaction was completed, the reaction solution was poured into pure water (1500 g) to separate the precipitate by filtration. To the resulting crude, MeCN (300 g) was added, repulp washing was carried out at the room temperature, to obtain [EP1-2] (14.8 g, 34.7 mmol, yield: 98%).

[0153] Into a 500 mL four-neck flask, [EP1-2] (14.8 g, 34.7 mmol), p-toluenesulfonyl chloride (7.9 g, 42.0 mmol), and CH.sub.2Cl.sub.2 (150 g) were charged. Thereto, 1-methylimidazole (8.5 g, 104 mmol) was added dropwise in an ice bath, and the mixture was stirred at room temperature for 3 hours. Subsequently, glycidol (2.8 g, 38.0 mmol) dissolved in CH.sub.2Cl.sub.2 (74 g) in an ice bath was added dropwise, and stirred at room temperature. After the reaction was completed, the reaction solution was concentrated, THF (50 g) was added to the residue, and the mixture was poured into pure water (500 g) to separate the precipitate by filtration. Subsequently, the resulting crude product was isolated by silica gel column chromatography (AcOEt:Heptane=1:10 (volume ratio)), to obtain the target [EP1] (white solid) (5.1 g, 10.5 mmol, yield: 30%). The results of 1H-NMR of the target product are shown below. The results confirmed that the resulting solid was the desired [EP1].

[0154] .sup.1H-NMR (500 MHZ, CDCl.sub.3): (ppm=) 7.69-7.72 (d, 1H), 7.53-7.55 (d, 2H), 7.09-7.11 (d, 2H), 6.41-6.44 (d, 1H), 4.53-4.56 (m, 1H), 4.04-4.07 (m, 1H), 3.28-3.30 (m, 1H), 2.88-2.90 (t, 1H), 2.70-2.71 (m, 1H), 2.45-2.49 (m, 1H), 2.14-2.16 (d, 2H), 1.85-1.87 (d, 2H), 1.71-1.78 (m, 4H), 1.50-1.57 (m, 2H), 1.22-1.32 (m, 6H), 0.95-1.17 (m, 9H), 0.84-0.90 (m, 5H).

Monomer Synthesis Example 2: Synthesis of [EP2]

##STR00015##

[0155] Into 300 mL four-necked flask, trans, trans-4-propylbicyclohexyl-4-carboxylic acid (10.1 g, 40.0 mmol), p-toluenesulfonyl chloride (9.2 g, 48.0 mmol), and CH.sub.2Cl.sub.2 (101 g) were charged, 1-methylimidazole (9.9 g, 120 mmol) was added dropwise in an ice bath, and the mixture was stirred at room temperature for 3 hours. Subsequently, 4-hydroxy-trans-cinnamic acid tert-butyl ester (8.8 g, 40.0 mmol) dissolved in CH.sub.2Cl.sub.2 (51 g) in an ice bath was added dropwise, and stirred at room temperature. After the reaction was completed, the reaction solution was concentrated, THF (30 g) was added to the residue, and the mixture was poured into pure water (90 g) to separate the precipitate by filtration. After adding MeOH (100 g) to the resulting crude material and performing repulp washing at room temperature, AcOEt (100 g) was further added to the crude material, and repulping washing was carried out at 0 C., to obtain [EP2-1] (16.6 g, 36.6 mmol, yield: 92%).

[0156] Into a 500 mL four-necked flask, [EP2-1] (16.6 g, 36.6 mmol) and formic acid (250 g) were charged, and stirred at 50 C. After the reaction was completed, the reaction solution was poured into pure water (1500 g), to separate the precipitate by filtration. To the resulting crude product, MeCN (150 g) was added, and it was repulped and washed at room temperature, to obtain [EP2-2] (14.4 g, 36.2 mmol, yield: 99%).

[0157] Into a 500 mL four-neck flask, [EP2-2] (14.1 g, 35.3 mmol), p-toluenesulfonyl chloride (8.1 g, 42.0 mmol), and CH.sub.2C12 (140 g) were charged. Thereto, 1-methylimidazole (8.7 g, 106.0 mmol) was added dropwise in an ice bath, and the mixture was stirred at room temperature for 3 hours. Subsequently, glycidol (2.9 g, 39.0 mmol) dissolved in CH.sub.2C12 (70 g) in an ice bath was added dropwise, and stirred at room temperature. After the reaction was completed, the reaction solution was concentrated, THF (50 g) was added to the residue, and the mixture was poured into pure water (500 g) to separate the precipitate by filtration. Subsequently, the resulting crude product was isolated by silica gel column chromatography (AcOEt:Heptane=1:10 (volume ratio)) to obtain the target [EP2] (white solid) (8.5 g, 18.6 mmol, yield: 53%). The results of 1H-NMR of the target product are shown below. The results confirmed that the resulting solid was the target [EP2].

[0158] .sup.1H-NMR (500 MHz, CDCl.sub.3): (ppm=) 7.69-7.72 (d, 1H), 7.53-7.55 (d, 2H), 7.09-7.11 (d, 2H), 6.41-6.44 (d, 1H), 4.53-4.56 (m, 1H), 4.04-4.07 (m, 1H), 3.29-3.29 (m, 1H), 2.88-2.90 (t, 1H), 2.69-2.71 (m, 1H), 2.44-2.48 (m, 1H), 2.14-2.16 (d, 2H), 1.85-1.87 (d, 2H), 1.71-1.78 (m, 4H), 1.50-1.56 (m, 2H), 1.27-1.33 (m, 2H), 0.95-1.16 (m, 9H), 0.84-0.89 (m, 5H).

Monomer Synthesis Example 3: Synthesis of [EP3]

##STR00016##

[0159] Into a 1 L four-necked flask, trans, trans-4-(4,4,4-trifluorobutyl) [1,1-bicyclohexyl]-4-carboxylic acid (30.0 g, 94.0 mmol), p-toluenesulfonyl chloride (21.4 g, 112 mmol) and CH.sub.2Cl.sub.2 (300 g) were charged, and 1-methylimidazole (23.1 g, 281.0 mmol) was added dropwise in an ice bath, followed by stirring at room temperature for 3 hours. Subsequently, 4-hydroxy-trans-cinnamic acid tert-butyl ester (22.7 g, 103 mmol) dissolved in CH.sub.2Cl.sub.2 (150 g) in an ice bath was added dropwise thereto, and stirred at room temperature. After the reaction was completed, the reaction solution was concentrated, THF (150 g) was added to the residue, and the mixture was poured into pure water (1000 g) to separate the precipitate by filtration. To the resulting crude material, AcOEt (200 g) was added, and repulp washing was carried out at 0 C., to obtain [EP3-1] (46.5 g, 88.9 mmol, yield: 95%).

[0160] Into a 2 L four-necked flask, [EP3-1] (46.5 g, 88.9 mmol) and formic acid (700 g) were charged, and stirred at 50 C. After the reaction was completed, the reaction solution was poured into pure water (2000 g), to separate the precipitate by filtration. To the resulting crude product, MeCN (300 g) was added, and repulped and washed at room temperature, to obtain [EP3-2] (41.3 g, 88.6 mmol, yield: 99%).

[0161] Into a 300 mL four-necked flask, [EP3-2] (10.0 g, 21.4 mmol), (2S)-(+)-glycidyl tosylate (5.4 g, 23.6 mmol), cesium carbonate (8.4 g, 25.7 mmol) and NMP (100 g) were charged, and stirred at 40 C. After the reaction was completed, the reaction solution was poured into pure water (600 g), made weakly acidic using a 1N aqueous hydrochloric acid solution, to separate the precipitate by filtration. To the resulting crude material, MeOH (300 g) was added, and repulp washing was carried out at room temperature. Subsequently, the resulting crude product was isolated by silica gel column chromatography (CHCl.sub.3:MeCN=100:1 (volume ratio)), to obtain the target [EP3] (white solid) (5.3 g, 10.1 mmol, yield: 48%). The results of 1H-NMR of the target product are shown below. The results confirmed that the resulting solid was the target [EP3].

[0162] .sup.1H-NMR (500 MHZ, CDCl.sub.3): (ppm=) 7.69-7.72 (d, 1H), 7.53-7.55 (d, 2H), 7.09-7.11 (d, 2H), 6.41-6.44 (d, 1H), 4.54-4.57 (m, 1H), 4.03-4.07 (m, 1H), 3.28-3.30 (m, 1H), 2.88-2.90 (t, 1H), 2.70-2.71 (m, 1H), 2.44-2.49 (m, 1H), 2.14-2.17 (d, 2H), 2.01-2.07 (m, 2H), 1.85-1.87 (d, 2H), 1.73-1.79 (m, 4H), 1.52-1.58 (m, 4H), 1.22-1.26 (m, 2H), 0.96-1.18 (m, 7H), 0.85-0.92 (m, 2H).

Monomer Synthesis Example 4: Synthesis of [EP4]

##STR00017##

[0163] Into a 200 mL four-necked flask, trans, trans-4-(4,4,4-trifluoropropyl) [1,1-bicyclohexyl]-4-carboxylic acid (9.2 g, 30.0 mmol), 4-hydroxy-trans-cinnamic acid tert-butyl ester (6.6 g, 30.0 mmol), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (8.6 g, 45.0 mmol), 4-dimethylaminopyridine (0.4 g, 3.0 mmol) and THF (92 g) were charged, and stirred at room temperature. After the reaction was completed, the reaction solution was poured into pure water (1500 g), to separate the precipitate by filtration. To the resulting crude product, MeOH (300 g) was added, and repulp washing was carried out at room temperature, to obtain [EP4-1] (13.7 g, 26.9 mmol, yield: 90%).

[0164] Into a 1 L four-necked flask, [EP4-1] (13.7 g, 26.9 mmol) and formic acid (205 g) were charged, and stirred at 50 C. After the reaction was completed, the reaction solution was poured into pure water (1000 g), to separate the precipitate by filtration. To the resulting crude product, MeCN (300 g) was added, and it was repulped and washed at room temperature, to obtain [EP4-2] (11.9 g, 26.2 mmol, yield: 98%).

[0165] Into a 200 mL four-neck flask, [EP4-2] (6.0 g, 13.3 mmol), p-toluenesulfonyl chloride (3.0 g, 15.9 mmol), and CH.sub.2Cl.sub.2 (60 g) were charged. Thereto, 1-methylimidazole (3.3 g, 40.0 mmol) was added dropwise in an ice bath, and the mixture was stirred at room temperature for 3 hours. Subsequently, glycidol (1.1 g, 14.6 mmol) dissolved in CH.sub.2Cl.sub.2 (30 g) in an ice bath was added dropwise, and stirred at room temperature. After the reaction was completed, the reaction solution was concentrated, AcOEt (600 g) was added to the residue, and the organic layer was washed with pure water (1200 g) and concentrated. Subsequently, AcOEt (30 g) and EtOH (150) were added to the resulting crude product, followed by repulping and washing at 0 C., to obtain the target [EP4] (white solid) (3.1 g, 6.0 mmol, yield: 45%). The results of 1H-NMR of the target product are shown below. The results confirmed that the resulting solid was the target [EP4].

[0166] .sup.1H-NMR (500 MHZ, CDCl.sub.3): (ppm=) 7.69-7.72 (d, 1H), 7.53-7.55 (d, 2H), 7.09-7.11 (d, 2H), 6.41-6.44 (d, 1H), 4.54-4.57 (m, 1H), 4.03-4.07 (m, 1H), 3.28-3.30 (m, 1H), 2.88-2.90 (t, 1H), 2.70-2.71 (m, 1H), 2.44-2.49 (m, 1H), 2.15-2.17 (d, 2H), 2.05-2.10 (m, 2H), 1.85-1.87 (d, 2H), 1.75-1.79 (m, 4H), 1.52-1.57 (m, 2H), 1.42-1.50 (m, 2H), 1.20-1.22 (m, 1H), 0.88-1.14 (m, 8H)

Synthesis of Polyamic Acid

Synthesis Example 1

[0167] C1 (2.16 g, 20.00 mmol) and A1 (4.35 g, 19.4 mmol) were dissolved in NMP (26.2 g), and reacted at 60 C. for 10 hours, to give a polyamic acid solution (PAA-1A) having a solid concentration of 20% by mass.

[0168] To the resulting polyamic acid solution (PAA-1A) (10.0 g), NMP (20.0 g) and BCS (20.0 g) were added, and stirred at room temperature for 2 hours, to obtain a polyamic acid solution (PAA-1) having 4% by mass of the solid content concentration.

Synthesis Examples 2 to 3

[0169] Polyamic acid solutions (PAA-2)) to (PAA-3) were synthesized with the compositions shown in Table 1 in a manner similar to the process described in Synthesis Example 1.

TABLE-US-00001 TABLE 1 Acid Other Polymer dianhydride diamine No. Component (19.40 mmol) (20.00 mmol) Synthesis Ex 1 PAA-1 A1 C1 Synthesis Ex 2 PAA-2 A1 C2 Synthesis Ex 3 PAA-3 A2 C1

Synthesis Example 4

[0170] B1 (0.76 g, 2.00 mmol), C1 (1.95 g, 18.00 mmol), and A1 (4.35 g, 19.4 mmol) were dissolved in NMP (28.2 g), and the reaction was carried out at 60 C. for 10 hours, to obtain a polyamic acid solution (PAA-4A) having a solid content concentration of 20% by mass.

[0171] To the resulting polyamic acid solution (PAA-4A) (10.0 g), NMP (20.0 g) and BCS (20.0 g) were added, and stirred at room temperature for 2 hours, to obtain a polyamic acid solution (PAA-4) having 4% by mass of the solid content concentration.

Synthesis Example 5

[0172] A polyamic acid solution (PAA-5) was synthesized with the composition shown in Table 2 in a manner similar to the method described in Synthesis Example 4.

TABLE-US-00002 TABLE 2 Acid Side-chain Other Polymer dianhydride diamine diamine No. Component (19.40 mmol) (2.00 mmol) (18.00 mmol) Synthesis PAA-4 A1 B1 C1 Ex 4 Synthesis PAA-5 A1 B2 C1 Ex 5

Preparation of Liquid Crystal Alignment Agent

Example 1

[0173] To the polyamic acid solution (PAA-1) (50.0 g) obtained in Synthesis Example 1A, EP1 (0.03 g) was added, and stirred at room temperature, to obtain a liquid crystal aligning agent (AL-1).

Examples 2 to 5

[0174] As shown in Table 3, liquid crystal alignment agents (AL-2) to (AL-5) were obtained by carrying out the procedures similar to Example 1, except that polyamic acid solutions (PAA-2) to (PAA-5) were used instead of polyamic acid solution (PAA-1).

Examples 6 to 8

[0175] As shown in Table 3, liquid crystal alignment agents (AL-6) to (AL-8) were obtained by carrying out the procedures similar to Example 1, except that the photo-alignable monomers (EP2) to (EP4) were used instead of the photo-alignable monomer (EP1).

TABLE-US-00003 TABLE 3 Photo- Polyamic acid alignable Liquid crystal solution monomer No. alignment agent (50.00 g) (0.03 g) Ex. 1 AL-1 PAA-1 EP1 Ex. 2 AL-2 PAA-2 EP1 Ex. 3 AL-3 PAA-3 EP1 Ex. 4 AL-4 PAA-4 EP1 Ex. 5 AL-5 PAA-5 EP1 Ex. 6 AL-6 PAA-1 EP2 Ex. 7 AL-7 PAA-1 EP3 Ex. 8 AL-8 PAA-1 EP4

Comparative Example 1

[0176] To the polyamic acid solution (PAA-1) (10.0 g) obtained in Synthesis Example 1A, EP5 (0.06 g) was added, and stirred at room temperature, to obtain a liquid crystal aligning agent (AL-R1).

Comparative Examples 2 to 5

[0177] As shown in Table 4, the procedure was carried out in a manner similar to that in Comparative Example 1, except that (PAA-2) to (PAA-5) were used instead of polyamic acid solution (PAA-1), to obtain liquid crystal alignment agents (AL-R2) to (AL-R5).

TABLE-US-00004 TABLE 4 Photo- Polyamic acid alignable Liquid crystal solution monomer No. alignment agent (10.00 g) (0.06 g) Comp. AL-R1 PAA-1 EP5 Ex. 1 Comp. AL-R2 PAA-2 EP5 Ex. 2 Comp. AL-R3 PAA-3 EP5 Ex. 3 Comp. AL-R4 PAA-4 EP5 Ex. 4 Comp. AL-R5 PAA-5 EP5 Ex. 5

<Production of Liquid Crystal Display Element>

[0178] The liquid crystal aligning agents (AL-1) to (AL-8) obtained in the examples and the liquid crystal aligning agents (AL-R1) to (AL-R5) obtained in the comparative examples were filtered under pressure using a membrane filter having a pore diameter of 1 m.

[0179] The resulting solution was spin coated on the ITO surface of a glass substrate with a transparent electrode made of an ITO film, dried on a hot plate at 70 C. for 90 seconds, and then baked on a hot plate at 200 C. for 30 minutes, to form a liquid crystal alignment film with a thickness of 100 nm.

[0180] Then, the coating surface was irradiated with 50 mJ/cm.sup.2 of linearly polarized ultraviolet light with a wavelength of 313 nm and an irradiation intensity of 4.3 mW/cm.sup.2 through a polarizing plate from an angle inclined at 40 from the normal direction of the substrate, to form a substrate having a liquid crystal alignment film. Linearly polarized ultraviolet light was prepared by passing ultraviolet light from a high-pressure mercury lamp through a bandpass filter with a wavelength of 313 nm, and then passing it through a polarizing plate with a wavelength of 313 nm.

[0181] Two of the above substrates were prepared, and after 4 m bead spacers were sprinkled on the liquid crystal alignment film of one substrate, a sealant (manufactured by Mitsui Chemicals, Inc., XN-1500T) was applied. Then, the other substrate was attached so that the liquid crystal alignment film surfaces faced each other and the orientation direction was 180, and then the sealant was thermally cured at 120 C. for 90 minutes, to prepare an empty cell. A liquid crystal (MLC-3022, manufactured by Merck & Co., Ltd.) was injected into the empty cell by a reduced pressure injection method to obtain a liquid crystal display element.

Evaluation

(Liquid Crystal Orientation)

[0182] The liquid crystal display element obtained above was subjected to isotropic phase treatment at 120 C. for 1 hour, and then the cell was observed using a polarizing microscope. As an evaluation criterion, a case where there was no alignment defect such as light leakage or domain generation, and uniform liquid crystal driving was obtained when a voltage was applied to the liquid crystal cell, was evaluated as good. The evaluation results are shown in Table 5.

(Pretilt Angle)

[0183] The pretilt angle of the liquid crystal cell was measured by the Mueller matrix method using AxoScan manufactured by Axometrics. The evaluation results are shown in Table 5.

(Evaluation of Pretilt Angle Change)

[0184] A DC voltage of 15 V was applied to the liquid crystal display element whose pretilt angle was measured above, and the pretilt angle was measured again 24 hours later. The amount of change in pretilt angle (.sub.pretilt) was determined from the pretilt angle before and after applying the DC voltage. The evaluation results are shown in Table 5.

TABLE-US-00005 TABLE 5 Liquid crystal Liquid Tilt alignment crystal angle .sub.pretilt No. agent orientation () () Ex. 1 AL-1 Good 88 0.02 Ex. 2 AL-2 Good 88 0.02 Ex. 3 AL-3 Good 87.9 0.02 Ex. 4 AL-4 Good 89 0.01 Ex. 5 AL-5 Good 89.1 0.01 Ex. 7 AL-7 Good 87.9 0.02 Comp. AL-R1 Good 88 0.06 Ex. 1 Comp. AL-R2 Good 88 0.07 Ex. 2 Comp. AL-R3 Good 87.9 0.07 Ex. 3 Comp. AL-R4 Good 89 0.04 Ex. 4 Comp. AL-R5 Good 89.1 0.04 Ex. 5

[0185] Table 5 shows that the liquid crystal alignment film obtained from the liquid crystal alignment agent in which specific compounds EP1 to EP4 were added to polyamic acid had higher tilt stability than the liquid crystal alignment film of the comparative example, specifically, in comparison of Examples 1 and 7 with Comparative Example 1, in comparison of Example 2 with Comparative Example 2, in comparison of Example 3 with Comparative Example 3, in comparison of Example 4 with Comparative Example 4, and in comparison of Example 5 with Comparative Example 5.

INDUSTRIAL APPLICABILITY

[0186] A liquid crystal display element using the liquid crystal alignment agent according to the present invention and a liquid crystal alignment film obtained therefrom can be suitably used for a liquid crystal display element that requires durability, such as for use in a vehicle.