Composition for liquid crystal alignment agent, manufacturing method of liquid crystal alignment film, liquid crystal alignment film using the same and liquid crystal display device

Abstract

Provided are a composition for a liquid crystal alignment agent, a manufacturing method of a liquid crystal alignment film, a liquid crystal alignment film using the same, and a liquid crystal display device including the liquid crystal alignment film. More specifically, there are provided the manufacturing method of a liquid crystal alignment film capable of providing the liquid crystal alignment film in which light irradiation energy is able to be reduced, and alignment characteristic and stability are excellent and the voltage holding ratio and electrical characteristics are also excellent through a simple process including applying and drying the composition for a liquid crystal alignment agent on the substrate, directly performing light irradiation to conduct alignment treatment while a high-temperature heat treatment process is omitted, followed by curing by heat treatment, the liquid crystal alignment film, and the liquid crystal display device including the same.

Claims

1. A composition for a liquid crystal alignment agent comprising: a first polymer for the liquid crystal alignment agent including a repeating unit represented by Chemical Formula 1 below, a repeating unit represented by Chemical Formula 2 below and a repeating unit represented by Chemical Formula 3 below, and a second polymer for the liquid crystal alignment agent consisting of a repeating unit represented by Chemical Formula 4 below, wherein the repeating unit represented by Chemical Formula 4 below is different from the repeating unit represented by Chemical Formula 2 below and the repeating unit represented by Chemical Formula 3 below, wherein the first polymer for the liquid crystal alignment agent includes 10 mol % to 74 mol % of the repeating unit represented by Chemical Formula 1 with respect to all of the repeating units represented by Chemical Formulae 1 to 3, and 11.9 mol % to 15.1 mol % of the repeating unit represented by Chemical Formula 2 with respect to all of the repeating units represented by Chemical Formulae 1 to 3, wherein a weight ratio of the first polymer for the liquid crystal alignment agent and the second polymer for the liquid crystal alignment agent is 15:85 to 85:15: ##STR00012## in Chemical Formulae 1 to 4, R.sup.1 and R.sup.2 are each independently hydrogen or a C1-C10 alkyl group, and not both of R.sup.1 and R.sup.2 are hydrogen, R.sup.3 and R.sup.4 are each independently hydrogen or a C1-C10 alkyl group, X.sup.1 is a quadrivalent organic group represented by Chemical Formula 5 below, ##STR00013## R.sup.5 to R.sup.8 are each independently hydrogen or a C1-C6 alkyl group, X2 to X4 are each independently a quadrivalent organic group represented by Chemical Formula 7 below: ##STR00014## in the Chemical Formula 7, R.sup.5 to R.sup.8 are each independently hydrogen or a C1-C6 alkyl group, and L.sup.2 is any one selected from the group consisting of a single bond, —O—, —CO—, —S—, —SO—, —SO.sub.2—, —CR.sup.11R.sup.12—, —CONH—, —COO—, —(CH.sub.2).sub.Z—, —O(CH.sub.2).sub.ZO—, —COO—(CH.sub.2).sub.Z—OCO—, phenylene, and a combination thereof, wherein R.sup.11 and R.sup.12 are each independently hydrogen, a C1-C10 alkyl group or a C1-C10 fluoroalkyl group, and z is an integer of 1 to 10, Y.sup.1 is a bivalent organic group represented by Chemical Formula 6 below: ##STR00015## in the Chemical Formula 6, p and q are each independently an integer of 0, k is an integer of 1, and n is an integer of 0, and Y.sup.2 to Y.sup.4 are each independently a bivalent organic group represented by the Chemical Formula 6, wherein R.sup.9 and R.sup.10 are each independently halogen, a cyano group, a C1-C3 alkyl group, a C2-C3 alkenyl group, a C1-C3 alkoxy group, a C1-C3 fluoroalkyl group or a C1-C3 fluoroalkoxy group, p and q are each independently an integer of 0 to 4, L.sub.1 is a single bond, —O—, —CO—, —S—, —SO.sub.2—, —C(CH.sub.3).sub.2—, —C(CF.sub.3).sub.2—, —CONH—, —COO—, —(CH.sub.2).sub.z—, —O(CH.sub.2).sub.zO—, —O(CH.sub.2).sub.z—, —NH—, —NH(CH.sub.2).sub.Z—NH—, —NH(CH.sub.2).sub.ZO—, —OCH.sub.2—C(CH.sub.3).sub.2—CH.sub.2O—, —OCO—(CH.sub.2).sub.z—OCO— or —OCO—(CH.sub.2).sub.z—COO—, z is an integer of 1 to 10, k and m are each independently an integer of 1 to 3, and n is an integer of 0 to 3.

2. A manufacturing method of a liquid crystal alignment film comprising: applying the composition for a liquid crystal alignment agent of claim 1 to a substrate to form a coating film; drying the coating film; performing a light irradiation on the coating film immediately after the drying to conduct alignment treatment; and curing the coating film on which the alignment treatment is performed, by a heat treatment.

3. The manufacturing method of claim 2, wherein: the composition for a liquid crystal alignment agent is obtained by dissolving or dispersing the first polymer for the liquid crystal alignment agent and the second polymer for the liquid crystal alignment agent in an organic solvent.

4. The manufacturing method of claim 2, wherein: the drying of the coating film is performed at 50° C. to 150° C.

5. The manufacturing method of claim 2, wherein: the light irradiation in the alignment treatment is performed with polarized ultraviolet ray having a wavelength of 150 nm to 450 nm.

6. The manufacturing method of claim 2, wherein: the heat treatment temperature in the curing of the coating film is 150° C. to 300° C.

7. A liquid crystal alignment film manufactured by claim 2.

8. A liquid crystal display device comprising the liquid crystal alignment film of claim 7.

Description

MODE FOR INVENTION

(1) The present invention will be described in more detail in the following Examples. However, the following Examples are provided only to illustrate the present invention, and accordingly, the present invention is not limited to the following Examples.

Preparation Example 1: Synthesis of Diamine Da-1

(2) Diamine DA-1 was synthesized according to Reaction Scheme 1 below:

(3) ##STR00006##

(4) 1,3-dimethylcyclobutane-1,2,3,4-tetracarboxylic dianhydride (DMCBDA) and 4-nitroaniline were dissolved in dimethylformamide (DMF) to prepare a mixture. Then, the mixture was reacted at about 80° C. for about 12 hours to prepare an amic aid. Then, the amic acid was dissolved in DMF, and acetic anhydride and sodium acetate were added thereto, thereby preparing a mixture. Then, the amic acid included in the mixture was imidized at about 90° C. for about 4 hours. The thus-obtained imide was dissolved in dimethylacetamide (DMAc), and Pd/C was added thereto, thereby preparing a mixture. The mixture was reduced at 45° C. and under hydrogen pressure of 6 bar for 20 minutes, thereby preparing the diamine DA-1.

Preparation Example 2: Synthesis of Diamine DA-2

(5) ##STR00007##

(6) A diamine DA-2 having the above structure was prepared in the same manner as in Preparation Example 1 except that cyclobutane-1,2,3,4-tetracarboxylic dianhydride (CBDA) was used instead of 1,3-dimethylcyclobutane-1,2,3,4-tetracarboxylic dianhydride.

Preparation Example 3: Synthesis of Diamine Da-3

(7) ##STR00008##

(8) A diamine DA-3 having the above structure was prepared in the same manner as in Preparation Example 1 except that pyromellitic dianhydride (PMDA) was used instead of 1,3-dimethylcyclobutane-1,2,3,4-tetracarboxylic dianhydride.

Preparation Example 4: Synthesis of Diamine DA-4

(9) ##STR00009##

(10) The diamine DA-4 was synthesized according to Reaction Scheme 2 below:

(11) ##STR00010##

(12) 25 g of pyromellitic dianhydride (PMDA) was added to 250 mL of methanol, 1 or 2 drops of hydrochloric acid was added thereto, and the mixture was heated under reflux at 75° C. for 5 hours. The solvent was removed under reduced pressure, and 300 mL of ethyl acetate and normal hexane were added to solidify the mixture. The resulting solid was filtered under reduced pressure and dried under reduced pressure at 40° C. to obtain 32 g of M1.

(13) 100 mL of toluene was added to 34 g of the obtained M1, and 35 g of oxalyl chloride was added dropwise at room temperature. Two or three drops of dimethylformamide (DMF) were added dropwise and the mixture was stirred at 50° C. for 16 hours. The mixture was cooled to room temperature, and the solvent and residual oxalyl chloride were removed under reduced pressure. 300 mL of normal hexane was added to the yellow solid product, and the mixture was heated to 80° C. under reflux. The heated reaction solution was filtered to remove impurity that was not soluble in n-hexane. The resultant solution was slowly cooled up to room temperature to obtain white crystals, the white crystals were filtered and dried in a oven under reduced pressure at 40° C. to obtain 32.6 g of M2.

(14) 29.6 g of 4-nitroaniline and 21.7 g of triethanolamine (TEA) were added to 400 mL of tetrahydrofuran (THF) and 32.6 g of M2 was added at room temperature. The mixture was stirred at room temperature for 16 hours to obtain a precipitate, and the precipitate was filtered. 400 mL of dichloromethane was added to the filtrate, and the mixture was washed with 0.1N hydrochloric acid, and then washed with a saturated aqueous sodium bicarbonate (NaHCO.sub.3) solution again. The washed organic solution was filtered under reduced pressure to obtain a solid product, and the solid product was recrystallized with dichloromethane to obtain 43 g of a solid dinitro compound M3.

(15) 43 g of the obtained dinitro compound M3 was placed in a high-pressure reactor and dissolved in 500 mL of THF. 2.2 g of 10 wt % Pd—C was added thereto and stirred at room temperature for 16 hours under hydrogen gas (H.sub.2) at 3 atm. After the reaction, Pd—C was removed by filtration through celite filter, and the filtrate was concentrated under reduced pressure to obtain 37 g of esterified diamine DA-4.

Preparation Example 5: Synthesis of Diamine DA-5

(16) ##STR00011##

(17) DA-5 having the above-described structure was prepared in the same manner as in Preparation Example 4 except that cyclobutane-1,2,3,4-tetracarboxylic dianhydride (CBDA) was used instead of pyromellitic dianhydride (PMDA).

(18) [Preparation of First Polymer for Liquid Crystal Alignment Agent]

Synthesis Example 1: Preparation of Polymer for Liquid Crystal Alignment Agent P-1

(19) 5.0 g (13.3 mmol) of DA-2 prepared in Preparation Example 2 was completely dissolved in 71.27 g of anhydrous N-methyl pyrrolidone (NMP). In addition, 2.92 g (13.03 mmol) of 1,3-dimethyl-cyclobutane-1,2,3,4-tetracarboxylic dianhydride (DMCBDA) was added to the solution under an ice bath, and the mixture was stirred at room temperature for 16 hours. Further, the obtained solution was injected into an excessive amount of distilled water to form a precipitate. Subsequently, the resulting precipitate was filtered, washed twice with distilled water, and washed again with methanol three times. The thus-obtained solid product was dried in an oven under reduced pressure at 40° C. for 24 hours to obtain 6.9 g of a polymer for a liquid crystal alignment agent P-1.

(20) As a result of confirming molecular weights of P-1 through GPC, the number average molecular weight (Mn) was 15,500 g/mol and the weight average molecular weight (Mw) was 31,000 g/mol. The monomer structure of the polymer P-1 was determined by the equivalence ratio of the used monomers, and the polymer P-1 had an imide structure ratio of 50.5% and an amic acid structure ratio of 49.5% in the molecule.

Synthesis Example 2: Preparation of Polymer for Liquid Crystal Alignment Agent P-2

(21) A polymer for a liquid crystal alignment agent P-2 was prepared in the same manner as in Synthesis Example 1 except that 5.0 g of DA-1 and 1.07 g of p-phenylenediamine (PDA) were first dissolved in 103.8 g of NMP, and then, 2.12 g of cyclobutane-1,2,3,4-tetracarboxylic dianhydride (CBDA) and 3.35 g of 4,4′-oxydiphthalic dianhydride (OPDA) were added thereto. As a result of confirming molecular weights of P-2 through GPC, the number average molecular weight (Mn) was 18,000 g/mol and the weight average molecular weight (Mw) was 35,000 g/mol. In addition, the polymer P-2 had an imide structure ratio of 36.4% and an amic acid structure ratio of 63.6% in the molecule.

Synthesis Example 3: Preparation of Polymer for Liquid Crystal Alignment Agent P-3

(22) A polymer for a liquid crystal alignment agent P-3 was prepared in the same manner as in Synthesis Example 1 except that 6.0 g of DA-2 and 1.37 g of 4,4′-oxydianiline (ODA) were first dissolved in 110.5 g of NMP, and then, 3.47 g of DMCBDA and 1.44 g of pyromellitic dianhydride (PMDA) were added thereto. As a result of confirming molecular weights of P-3 through GPC, the number average molecular weight (Mn) was 14,500 g/mol and the weight average molecular weight (Mw) was 29,000 g/mol. In addition, the polymer P-3 had an imide structure ratio of 41.9% and an amic acid structure ratio of 58.1% in the molecule.

Synthesis Example 4: Preparation of Polymer for Liquid Crystal Alignment Agent P-4

(23) A polymer for a liquid crystal alignment agent P-4 was prepared in the same manner as in Synthesis Example 1 except that 5.0 g of DA-1 and 2.8 g of DA-5 were first dissolved in 115.9 g of NMP, and then, 4.08 g of cyclobutane-1,2,3,4-tetracarboxylic dianhydride (CBDA) was added thereto. As a result of confirming molecular weights of P-4 through GPC, the number average molecular weight (Mn) was 17,000 g/mol and the weight average molecular weight (Mw) was 35,000 g/mol. In addition, the polymer P-4 had an imide structure ratio of 35.3%, an amic acid ester structure ratio of 15.1%, and an amic acid structure ratio of 49.5% in the molecule.

Synthesis Example 5: Preparation of Polymer for Liquid Crystal Alignment Agent P-5

(24) A polymer for a liquid crystal alignment agent P-5 was prepared in the same manner as in Synthesis Example 1 except that 5.0 g of DA-1 and 1.89 g of 4,4′-(1,3-propyldiyl)dioxydianiline, and 2.29 g of DA-4 were first dissolved in 131.00 g of NMP, and then, 5.43 g of DMCBDA was added thereto. As a result of confirming molecular weights of P-5 through GPC, the number average molecular weight (Mn) was 19,500 g/mol and the weight average molecular weight (Mw) was 36,000 g/mol. In addition, the polymer P-5 had an imide structure ratio of 29.8%, an amic acid ester structure ratio of 11.9%, and an amic acid structure ratio of 49.5% in the molecule.

Synthesis Example 6: Preparation of Polymer for Liquid Crystal Alignment Agent P-6

(25) 3.7 g of 4,4′-oxydianiline (ODA) and 2.0 g of p-phenylene diamine (PDA) were completely dissolved in 124.5 g of anhydrous N-methyl pyrrolidone (NMP). In addition, 8.13 g of 1,3-dimethyl-cyclobutane-1,2,3,4-tetracarboxylic dianhydride (DMCBDA) was added to the mixture under an ice bath, and the mixture was stirred at room temperature for 16 hours, thereby preparing a 100% polyamic acid polymer solution PA-6.

(26) 7.4 g of acetic anhydride and 5.7 g of pyridine were added to the thus-prepared PA-6 solution, and the mixture was stirred at 50° C. for 3 hours to perform chemical imidization. Further, the obtained product was injected into an excessive amount of distilled water to form a precipitate. Subsequently, the resulting precipitate was filtered, washed twice with distilled water, and washed again with methanol three times. The thus-obtained solid product was dried in an oven under reduced pressure at 40° C. for 24 hours to obtain a polymer for a liquid crystal alignment agent P-6. As a result of confirming molecular weights of P-6 through GPC, the number average molecular weight (Mn) was 14,500 g/mol and the weight average molecular weight (Mw) was 28,000 g/mol.

(27) Meanwhile, the composition of P-6 was quantitatively analyzed as follows.

(28) The PA-6 solution obtained before the chemical imidization was coated on the glass substrate and was subjected to heat treatment in an oven at 300° C. for 2 hours to perform imidization. The imidization rate of the material obtained through this process was defined as 100%, and C-N peak (1380 cm.sup.−1) of the P-6 obtained through the chemical imidization process and the imide shown in the IR spectroscope were analyzed by comparison. Specifically, the aromatic peak at 1520 cm.sup.−1 was set as a reference for normalization, and a magnitude I of the C-N peak at 1380 cm.sup.−1 of each of PA-6 and P-6 was integrated and substituted into Equation 1 below to quantify the imidization rate.
Imidization rate (%)=[(I.sub.1380,P-6−I.sub.1520,P-6)/(I.sub.1380,PA-6@300−I.sub.1520,PA-6@300)]*100  [Equation 1]

(29) In Equation 1, I.sub.1380,P-6 indicates a magnitude of C-N peak shown at 1380 cm.sup.−1 of P-6, I.sub.1520,P-6 indicates a magnitude of aromatic peak shown at 1520 cm.sup.−1 of P-6, I.sub.1380,PA-6@300 indicates a magnitude of C-N peak shown at 1380 cm.sup.−1 of a material in which PA-6 is heat-treated at 300° C., and I.sub.1520,PA-6@300 indicates a magnitude of an aromatic peak shown at 1520 cm.sup.−1 of a material in which PA-6 is heat-treated at 300° C.

(30) As a result of analyzing the composition of P-6 through the above-described method, the polymer P-6 had an amic acid structure ratio of 35% and an imide structure ratio of 65%.

Synthesis Example 7: Preparation of Polymer for Liquid Crystal Alignment Agent P-7

(31) PA-6 was prepared in the same manner as in Synthesis Example 6, except that 13.0 g of acetic anhydride and 11.5 g of pyridine were used.

(32) However, gelation of the reaction solution proceeded during the reaction for 5 hours. The gelled reaction product was stirred in an excessive amount of distilled water to obtain a solid content. The resulting solid was washed twice with an excessive amount of distilled water, three times with methanol, and then dried at 40° C. in an oven under reduced pressure for 24 hours to prepare a polymer P-7. However, the prepared P-7 was inferior in solubility, and thus, a molecular weight thereof could not be measured. As a result of analyzing the composition through the analysis method of Synthesis Example 6, the polymer P-7 had an imide structure ratio of 75.0% and an amic acid structure ratio of 25.0%.

Synthesis Example 8: Preparation of Polymer for Liquid Crystal Alignment Agent P-8

(33) A polymer for a liquid crystal alignment agent P-8 was prepared in the same manner as in Synthesis Example 1 except that 10.0 g of DA-3 was first dissolved in 140.0 g of NMP, and then, 5.52 g of DMCBDA was added thereto. As a result of confirming molecular weights of P-8 through GPC, the number average molecular weight (Mn) was 22,000 g/mol and the weight average molecular weight (Mw) was 39,000 g/mol. In addition, as a result of analyzing the monomer structure of P-8, the polymer P-8 had an imide structure ratio of 50.5% and an amic acid structure ratio of 49.5% in the molecule.

Synthesis Example 9: Preparation of Polymer for Liquid Crystal Alignment Agent P-9

(34) A polymer for a liquid crystal alignment agent P-9 was prepared in the same manner as in Synthesis Example 1 except that 2.0 g of DA-2 and 5.2 g of p-phenylenediamine (PDA) were first dissolved in 170.0 g of NMP, and 11.68 g of 1,3-dimethyl-cyclobutane-1,2,3,4-tetracarboxylic acid dianhydride (DMCBDA) was added thereto. As a result of confirming molecular weights of P-9 through GPC, the number average molecular weight (Mn) was 16,000 g/mol and the weight average molecular weight (Mw) was 28,000 g/mol. In addition, as a result of analyzing the monomer structure of P-9, the polymer P-9 had an imide structure ratio of 9.3% and an amic acid structure ratio of 90.2% in the molecule.

(35) [Preparation of Second Polymer for Liquid Crystal Alignment Agent]

Synthesis Example 10: Preparation of Polymer for Liquid Crystal Alignment Agent Q-1

(36) A polymer for a liquid crystal alignment agent Q-1 was prepared in the same manner as in Synthesis Example 1 except that 5.00 g of 4,4′-methylenedianiline and 5.05 g of 4,4′-oxydianiline were first dissolved in 221.4 g of NMP, and 14.55 g of 4,4′-biphthalic anhydride was added thereto. As a result of confirming molecular weights of Q-1 through GPC, the number average molecular weight (Mn) was 25,000 g/mol and the weight average molecular weight (Mw) was 40,000 g/mol.

Synthesis Example 11: Preparation of Polymer for Liquid Crystal Alignment Agent Q-2

(37) A polymer for a liquid crystal alignment agent Q-2 was prepared in the same manner as in Synthesis Example 1 except that 7.0 g of 4,4′-(1,4-butanediyl)dioxydianiline and 2.19 g of 4,4′-iminodianiline were first dissolved in 178.1 g of NMP, and 10.59 g of 4,4′-biphthalic anhydride was added thereto. As a result of confirming molecular weights of Q-2 through GPC, the number average molecular weight (Mn) was 28,000 g/mol and the weight average molecular weight (Mw) was 45,000 g/mol.

Synthesis Example 12: Preparation of Polymer for Liquid Crystal Alignment Agent Q-3

(38) A polymer for a liquid crystal alignment agent Q-3 was prepared in the same manner as in Synthesis Example 1 except that 10.0 g of 4,4′-(1,3-propyldiy)dioxydianiline was first dissolved in 180.7 g of NMP, and 4.16 g of pyromellitic dianhydride (PMDA) and 5.92 g of 4,4′-oxydiphthalic anhydride were added thereto. As a result of confirming molecular weights of Q-3 through GPC, the number average molecular weight (Mn) was 26,500 g/mol and the weight average molecular weight (Mw) was 43,000 g/mol.

Experimental Example: Evaluation of Characteristics of Liquid Crystal Alignment Film

Preparation of Liquid Crystal Alignment Agent and Manufacture of Liquid Crystal Cell

(39) (1) Preparation of Liquid Crystal Alignment Agent

Example 1

(40) 1.0 g of the polymer P-1 obtained in Synthesis Example 1 and 1.0 g of the polymer Q-1 obtained in Synthesis Example 10 were dissolved in a mixed solvent in which 30 g of NMP and 8 g of n-butoxyethanol were mixed, thereby obtaining a 5 wt % solution. Then, the obtained solution was pressure-filtered through a filter made of poly(tetrafluorene ethylene) and having a pore size of 0.2 μm, thereby preparing a liquid crystal alignment agent A-1.

Example 2

(41) 1.0 g of the polymer P-1 obtained in Synthesis Example 1 and 1.0 g of the polymer Q-2 obtained in Synthesis Example 11 were dissolved in a mixed solvent in which 30 g of NMP and 8 g of n-butoxyethanol were mixed, thereby obtaining a 5 wt % solution. Then, the obtained solution was pressure-filtered through a filter made of poly(tetrafluorene ethylene) and having a pore size of 0.2 μm, thereby preparing a liquid crystal alignment agent A-2.

Example 3

(42) 1.0 g of the polymer P-2 obtained in Synthesis Example 2 and 1.0 g of the polymer Q-2 obtained in Synthesis Example 11 were dissolved in a mixed solvent in which 30 g of NMP and 8 g of n-butoxyethanol were mixed, thereby obtaining a 5 wt % solution. Then, the obtained solution was pressure-filtered through a filter made of poly(tetrafluorene ethylene) and having a pore size of 0.2 μm, thereby preparing a liquid crystal alignment agent A-3.

Example 4

(43) 1.2 g of the polymer P-3 obtained in Synthesis Example 3 and 0.8 g of the polymer Q-1 obtained in Synthesis Example 10 were dissolved in a mixed solvent in which 30 g of NMP and 8 g of n-butoxyethanol were mixed, thereby obtaining a 5 wt % solution. Then, the obtained solution was pressure-filtered through a filter made of poly(tetrafluorene ethylene) and having a pore size of 0.2 μm, thereby preparing a liquid crystal alignment agent A-4.

Example 5

(44) 1.4 g of the polymer P-4 obtained in Synthesis Example 4 and 0.6 g of the polymer Q-3 obtained in Synthesis Example 12 were dissolved in a mixed solvent in which 30 g of NMP and 8 g of n-butoxyethanol were mixed, thereby obtaining a 5 wt % solution. Then, the obtained solution was pressure-filtered through a filter made of poly(tetrafluorene ethylene) and having a pore size of 0.2 μm, thereby preparing a liquid crystal alignment agent A-5.

Example 6

(45) 1.0 g of the polymer P-5 obtained in Synthesis Example 5 and 1.0 g of the polymer Q-3 obtained in Synthesis Example 12 were dissolved in a mixed solvent in which 30 g of NMP and 8 g of n-butoxyethanol were mixed, thereby obtaining a 5 wt % solution. Then, the obtained solution was pressure-filtered through a filter made of poly(tetrafluorene ethylene) and having a pore size of 0.2 μm, thereby preparing a liquid crystal alignment agent A-6.

Example 7

(46) 0.4 g of the polymer P-6 obtained in Synthesis Example 6 and 1.6 g of the polymer Q-2 obtained in Synthesis Example 11 were dissolved in a mixed solvent in which 30 g of NMP and 8 g of n-butoxyethanol were mixed, thereby obtaining a 5 wt % solution. Then, the obtained solution was pressure-filtered through a filter made of poly(tetrafluorene ethylene) and having a pore size of 0.2 μm, thereby preparing a liquid crystal alignment agent A-7.

Comparative Example 1

(47) 1.0 g of the polymer P-8 obtained in Synthesis Example 8 and 1.0 g of the polymer Q-1 obtained in Synthesis Example 10 were dissolved in a mixed solvent in which 30 g of NMP and 8 g of n-butoxyethanol were mixed, thereby obtaining a 5 wt % solution. Then, the obtained solution was pressure-filtered through a filter made of poly(tetrafluorene ethylene) and having a pore size of 0.2 μm, thereby preparing a liquid crystal alignment agent B-1.

Comparative Example 2

(48) 2.0 g of the polymer P-2 obtained in Synthesis Example 2 was dissolved in a mixed solvent in which 30 g of NMP and 8 g of n-butoxyethanol were mixed, thereby obtaining a 5 wt % solution. Then, the obtained solution was pressure-filtered through a filter made of poly(tetrafluorene ethylene) and having a pore size of 0.2 μm, thereby preparing a liquid crystal alignment agent B-2.

Comparative Example 3

(49) 2.0 g of the polymer Q-1 obtained in Synthesis Example 10 was dissolved in a mixed solvent in which 30 g of NMP and 8 g of n-butoxyethanol were mixed, thereby obtaining a 5 wt % solution. Then, the obtained solution was pressure-filtered through a filter made of poly(tetrafluorene ethylene) and having a pore size of 0.2 μm, thereby preparing a liquid crystal alignment agent B-3.

Reference Example 1

(50) 1.0 g of the polymer P-7 obtained in Synthesis Example 7 and 1.0 g of the polymer Q-1 obtained in Synthesis Example 10 were attempted to be dissolved in a mixed solvent in which 30 g of NMP and 8 g of n-butoxyethanol were mixed, but the P-7 was not dissolved, and thus, a completely dissolved alignment agent could not be obtained.

Reference Example 2

(51) 1.8 g of the polymer P-2 obtained in Synthesis Example 2 and 0.2 g of the polymer Q-3 obtained in Synthesis Example 12 were dissolved in a mixed solvent in which 30 g of NMP and 8 g of n-butoxyethanol were mixed, thereby obtaining a 5 wt % solution. Then, the obtained solution was pressure-filtered through a filter made of poly(tetrafluorene ethylene) and having a pore size of 0.2 μm, thereby preparing a liquid crystal alignment agent C-2.

Reference Example 3

(52) 0.2 g of the polymer P-1 obtained in Synthesis Example 1 and 1.8 g of the polymer Q-2 obtained in Synthesis Example 11 were dissolved in a mixed solvent in which 30 g of NMP and 8 g of n-butoxyethanol were mixed, thereby obtaining a 5 wt % solution. Then, the obtained solution was pressure-filtered through a filter made of poly(tetrafluorene ethylene) and having a pore size of 0.2 μm, thereby preparing a liquid crystal alignment agent C-3.

Reference Example 4

(53) 1.0 g of the polymer P-9 obtained in Synthesis Example 9 and 1.0 g of the polymer Q-3 obtained in Synthesis Example 12 were dissolved in a mixed solvent in which 30 g of NMP and 8 g of n-butoxyethanol were mixed, thereby obtaining a 5 wt % solution. Then, the obtained solution was pressure-filtered through a filter made of poly(tetrafluorene ethylene) and having a pore size of 0.2 μm, thereby preparing a liquid crystal alignment agent C-4.

(54) (2) Manufacture of Liquid Crystal Cell

(55) A liquid crystal cell was manufactured in the following method using the liquid crystal alignment agents manufactured by Examples 1 to 7, Comparative Examples 1 to 3, and Reference Examples 1 to 4.

(56) The liquid crystal alignment agent was applied onto a substrate (lower plate) in which comb-shaped IPS (in-plane switching) mode typed ITO electrode patterns having a thickness of 60 nm, an electrode width of 3 μm, and an interval between electrodes of 6 μm were formed on a rectangular glass substrate having a size of 2.5 cm×2.7 cm and a glass substrate (upper plate) in which the electrode patterns were not formed, respectively, by using a spin coating method.

(57) Subsequently, the substrates applied with the liquid crystal alignment agent were placed and dried on a hot plate at about 70° C. for 3 minutes to evaporate the solvent. In order to align the thus-obtained coating films, the respective coating films of the upper and lower plates were irradiated with 254 nm ultraviolet rays in an exposure amount of 1.0 J/cm.sup.2 using an exposure machine to which a linear polarizer was attached.

(58) Then, the aligned upper and lower plates were fired (cured) in an oven at about 230° C. for 30 minutes to obtain a coating film having a film thickness of 0.1 μm. Then, a sealing agent impregnated with a ball spacer having a size of 3 μm was applied to the edge of the upper plate except for a liquid crystal injection hole. Further, the alignment films formed on the upper plate and the lower plate were arranged so that they opposite each other and alignment directions thereof were parallel to each other, and then the upper and lower plates were bonded together and the sealing agent was cured, thereby manufacturing an empty cell. In addition, the liquid crystal was injected into the empty cell, thereby manufacturing an IPS mode liquid crystal cell.

(59) <Evaluation of Characteristics of Liquid Crystal Alignment Film>

(60) (1) Evaluation of Liquid Crystal Alignment Characteristic

(61) Polarizing plates were attached on the upper and lower plates of the above-manufactured liquid crystal cell to be vertical to each other. Here, a polarizing axis of the polarizing plate attached to the lower plate was parallel to an alignment axis of the liquid crystal cell. Further, the liquid crystal cell to which the polarizing plates were attached was placed on a backlight having a brightness of 7,000 cd/m.sup.2, and light leakage was observed with the naked eye. Here, when the liquid crystal alignment film had excellent alignment characteristic to excellently arrange liquid crystals, the light was not passed by the upper and lower polarizing plates that were vertically attached to each other, and the liquid crystal alignment film was observed in dark without defects. A case where the above-described alignment characteristic was observed was marked with as ‘good’, and a case where a liquid crystal flow mark or light leakage such as a bright spot was observed was marked with ‘defective’, and these results were shown in Table 1.

(62) (2) Evaluation of Liquid Crystal Alignment Stability

(63) Liquid crystal alignment stability was evaluated by using the liquid crystal cell to which the polarizing plate was attached which was manufactured for the evaluation of the liquid crystal alignment characteristic (1).

(64) Specifically, the liquid crystal cell to which the polarizing plate was attached was attached on a backlight of 7,000 cd/m.sup.2, and the luminance in the black state was measured using PR-880 which is an equipment for measuring luminance. In addition, the liquid crystal cell was driven at room temperature for 24 hours at an AC voltage of 5V. Then, in a state where the voltage of the liquid crystal cell was turned off, the luminance in the black state was measured in the same manner as described above.

(65) A luminance variation was calculated by dividing a difference between the initial luminance (L0) measured before driving the liquid crystal cell and the latter luminance (L1) measured after driving the liquid crystal cell by the initial luminance (L0), and multiplying the obtained value by 100. It means that as the calculated luminance variation is closer to 0%, the liquid crystal alignment stability is more excellent. A case where the luminance variation was less than 10% was marked with ‘excellent’, a case where the luminance variation was 10% or more to less than 20% was marked with ‘normal’, and a case where the luminance variation was 20% or more was marked with ‘defective’, and these results were shown in Table 1.

(66) (3) Evaluation of Voltage Holding Ratio (VHR)

(67) Liquid crystal cells for voltage holding ratio were manufactured by the following methods using the liquid crystal alignment agents prepared in Examples 1 to 7, Comparative Examples 1 to 3, and Reference Examples 1 to 4.

(68) The liquid crystal alignment agent was applied onto each of upper and lower substrates for voltage holding ratio (VHR) in which the ITO electrode having a thickness of 60 nm and an area of 1×1 cm were patterned on a rectangular glass substrate having a size of 2.5 cm×2.7 cm, by using a spin coating method.

(69) Subsequently, the substrates applied with the liquid crystal alignment agent were placed and dried on a hot plate at about 70° C. for 3 minutes to evaporate the solvent. In order to align the thus-obtained coating films, the respective coating films of the upper and lower plates were irradiated with 254 nm ultraviolet rays in an exposure amount of 1.0 J/cm.sup.2 using an exposure machine to which a linear polarizer was attached. Then, the aligned upper and lower plates were fired and cured in an oven at 230° C. for 30 minutes to obtain a coating film having a film thickness of 0.1 μm. Then, a sealing agent impregnated with a ball spacer having a size of 4.5 μm was applied to the edges of the upper and lower plates except for a liquid crystal injection hole. Further, the alignment films were arranged so that alignment treatment directions of the upper and lower plates were parallel to each other while opposing each other, and then the upper and lower plates were bonded together and the sealing agent was UV and thermally cured, thereby manufacturing an empty cell. In addition, the liquid crystal was injected into the empty cell, and the injection hole was sealed with the sealing agent, thereby manufacturing a liquid crystal cell.

(70) The voltage holding ratio (VHR), which is the electrical characteristic of the liquid crystal cell manufactured as described above, was measured by using TOYO 6254 equipment. The voltage holding ratio was measured under severe conditions of 5V, 60 Hz and 60° C. An ideal value of the voltage holding ratio is 100%. As a result of the measurement, a case where the voltage holding ratio was 85% or more was marked with ‘good’ and a case where the voltage holding ratio was less than 85% was marked with ‘defective’, and these results were shown in Table 1 below.

(71) TABLE-US-00001 TABLE 1 Mixed Evaluation of Evaluation Evaluation First Second weight liquid crystal of of voltage polymer polymer ratio alignment alignment holding (P) (Q) (P:Q) characteristics stability ratio Example 1 P-1 Q-1 50:50 Good Good Good Example 2 P-1 Q-2 50:50 Good Good Good Example 3 P-2 Q-2 50:50 Good Good Good Example 4 P-3 Q-1 60:40 Good Good Good Example 5 P-4 Q-3 70:30 Good Good Good Example 6 P-5 Q-3 50:50 Good Good Good Example 7 P-6 Q-2 20:80 Good Good Good Comparative Example 1 P-8 Q-1 50:50 Defective Defective Good Comparative Example 2 P-2 — 100:0  Good Good Defective Comparative Example 3 — Q-1  0:100 Defective Defective Defective Reference Example 1 P-7 Q-1 50:50 — — — Reference Example 2 P-2 Q-3 90:10 Good Good Defective Reference Example 3 P-1 Q-2 10:90 Defective Defective Good Reference Example 4 P-9 Q-3 50:50 Defective Defective Good

(72) As shown in Table 1, the liquid crystal alignment films of Examples 1 to 7 in which the compositions for a liquid crystal alignment agent each including both the first polymer for a liquid crystal alignment agent and the second polymer for a liquid crystal alignment agent of the present invention were used were excellent in all of the liquid crystal alignment characteristic, the stability, and the voltage holding ratio. However, the liquid crystal alignment films of Comparative Examples 1 to 3 in which only one of the first polymer for a liquid crystal alignment agent and the second polymer for a liquid crystal alignment agent was used, or in which a polymer different from the first polymer for a liquid crystal alignment agent was used were defective in some or all of the above-described evaluation factors.