Polymer for liquid crystal alignment agent, liquid crystal alignment agent comprising the same, and liquid crystal alignment film and liquid crystal display device using the same

Abstract

The present invention relates to a polymer having excellent liquid crystal alignment and electrical properties and thus is suitable for use as a liquid crystal alignment agent, a liquid crystal alignment agent containing the same, a liquid crystal aligning film formed from the liquid crystal alignment agent, and a liquid crystal display device containing the liquid crystal aligning film.

Claims

1. A liquid crystal alignment film comprising a liquid crystal alignment agent comprising a copolymer comprising two or more repeating units selected from the group consisting of a repeating unit represented by Chemical Formula 1, a repeating unit represented by Chemical Formula 2 and a repeating unit represented by Chemical Formula 3: ##STR00023## wherein, in Chemical Formulae 1 to 3, at least one of R.sup.1 and R.sup.2 is an alkyl group having 1 to 10 carbon atoms, and the other is hydrogen, X.sup.1 to X.sup.3 are each independently a tetravalent organic group represented by Chemical Formula 5, ##STR00024## wherein, in Chemical Formula 5, R.sub.9 to R.sub.14 are each independently hydrogen or an alkyl group having 1 to 10 carbon atoms, L.sub.2 is any one selected from the group consisting of a direct bond, —O—, —CO—, —S—, —SO—, —SO.sub.2—, —CR.sub.15R.sub.16—, —CONH—, —COO—, —(CH.sub.2).sub.b—, —O(CH.sub.2).sub.bO—, —COO—(CH.sub.2).sub.b—OCO—, phenylene, or a combination thereof, R.sub.15 and R.sub.16 are each independently hydrogen, an alkyl group having 1 to 10 carbon atoms, or a fluoroalkyl group having 1 to 10 carbon atoms, and b is an integer of 1 to 10, and Y.sup.1 to Y.sup.3 are each independently a divalent organic group represented by the following Chemical Formula 4: ##STR00025## wherein, in Chemical Formula 4, A is a Group 16 element selected from oxygen (O), sulfur (S), selenium (Se), tellurium (Te), or polonium (Po), and at least one of Z.sub.1 to Z.sub.4 is nitrogen and the rest are carbon, wherein, Y.sup.1 of the repeating unit represented by Chemical Formula 1 is connected to an adjacent repeating unit as —N—Y.sup.1—N or —HN—Y.sup.1—N—, Y.sup.2 of the repeating unit represented by Chemical Formula 2 is connected to an adjacent repeating unit as —HN—Y.sup.2—NH— or —N—Y.sup.2—NH—, and Y.sup.3 of the repeating unit represented by Chemical Formula 3 is connected to an adjacent repeating unit as —NH—Y.sup.3—NH— or —N—Y.sup.3—NH—, and wherein the liquid crystal alignment film is prepared by an alignment treatment including irradiating with polarized light or rubbing in one direction, without preceding or concurrent curing, prior to a curing heat treatment.

2. The liquid crystal alignment film according to claim 1, wherein in the Chemical Formula 4, one of Z.sub.1 to Z.sub.4 is nitrogen and the rest are carbon.

3. The liquid crystal alignment film according to claim 1, wherein in the Chemical Formula 4, one of Z.sub.1 and Z.sub.3 is nitrogen, the other is carbon, and Z.sub.2 and Z.sub.4 are carbon.

4. The liquid crystal alignment film according to claim 1, wherein the Chemical Formula 4 includes one or more divalent organic groups selected from the group consisting of Chemical Formulae 4-1, 4-2, and 4-3: ##STR00026## wherein, in Chemical Formulae 4-1, 4-2, and 4-3, A, Z.sub.1, Z.sub.2, Z.sub.3, and Z.sub.4 are as defined in the Chemical Formula 4.

5. The liquid crystal alignment film according to claim 1, further comprising one or more repeating units selected from the group consisting of a repeating unit represented by Chemical Formula 11, a repeating unit represented by Chemical Formula 12, and a repeating unit represented by Chemical Formula 13: ##STR00027## wherein, in Chemical Formulae 11 to 13, at least one of R.sup.3 and R.sup.4 is an alkyl group having 1 to 10 carbon atoms and the other is hydrogen, X.sup.4 to X.sup.6 are each independently a tetravalent organic group, and Y.sup.4 to Y.sup.6 are each independently a divalent organic group represented by Chemical Formula 14: ##STR00028## wherein, in Chemical Formula 14, R.sup.5 and R.sup.6 are each independently hydrogen, a halogen, a cyano, a C.sub.1-10 alkyl, a C.sub.2-10 alkenyl, a C.sub.1-10 alkoxy, a C.sub.1-10 fluoroalkyl, or a C.sub.1-10 fluoroalkoxy, p and q are each independently an integer of 0 to 4, L.sup.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—, —COO—(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 0 to 3, and n is an integer of 0 to 3, when n=0, k is 1 to 3, and when k=0, m and n are each independently 1 to 3.

6. The liquid crystal alignment film according to claim 5, wherein the Chemical Formula 14 is represented by Chemical Formula 15 or Chemical Formula 16: ##STR00029## wherein, in Chemical Formula 16, D is a direct bond, O, SO.sub.2, or C(R.sub.7)(R.sub.8), wherein R.sub.7 and R.sub.8 are each independently hydrogen, or an alkyl group having 1 to 10 carbon atoms.

7. A liquid crystal display device comprising the liquid crystal alignment film of claim 5.

8. The liquid crystal alignment film according to claim 1, wherein the copolymer has a weight average molecular weight of 1000 g/mol to 200,000 g/mol.

9. A liquid crystal display device comprising the liquid crystal alignment film of claim 1.

Description

DETAILED DESCRIPTION OF THE EMBODIMENTS

(1) Hereinafter, the present invention will be described in more detail in the following examples. However, these examples are provided for the purpose of illustration only, and are not intended to limit the scope of the present invention thereto in any way.

Preparation Examples 1 to 3: Preparation of Diamine

Preparation Example 1

(2) ##STR00018##

(3) After 17.1 g (100 mmol) of 2-chloro-5-nitropyridine (compound 1) and 12.5 g (98.6 mmol) of 4-nitrophenol (compound 2) were completely dissolved in 200 mL dimethyl sulfoxide (DMSO), 27.2 g (200 mmol) of potassium carbonate (K.sub.2CO.sub.3) was added thereto and the mixture was stirred at room temperature for 16 hours. When the reaction was completed, the reaction product was charged into a container containing 500 mL of water and stirred for 1 hour. A solid obtained by filtration was washed with 200 mL of water and 200 mL of ethanol to synthesize 16 g (61.3 mmol) of a compound 3 (yield: 57%).

(4) ##STR00019##

(5) The compound 3 was dissolved in 200 mL of a 1:1 mixed solution of ethyl acetate (EA) and THF, 0.8 g of palladium (Pd)/carbon (C) was added thereto, and the mixture was stirred for 12 hours under a hydrogen atmosphere. After completion of the reaction, the reaction mixture was filtered through a pad of Celite and then concentrated to obtain 11 g of a diamine compound 4 (yield: 89%).

(6) 1H NMR (500 MHz, DMSO-d6) δ 7.48 (dd, J=3.0, 0.7 Hz, 1H), 7.01 (dd, J=8.6, 3.0 Hz, 1H), 6.70-6.66 (m, 2H), 6.58 (dd, J=8.6, 0.6 Hz, 1H), 6.55-6.50 (m, 2H), 4.92 (s, 2H), 4.85 (s, 2H).

Preparation Example 2

(7) ##STR00020##

(8) The diamine of Preparation Example 2 was prepared in the same manner as in Preparation Example 1, except that 3-nitrophenol was used instead of 4-nitrophenol (compound 2).

Preparation Example 3

(9) ##STR00021##

(10) The diamine of Preparation Example 3 was prepared in the same manner as in Preparation Example 1, except that 2-chloro-4-nitropyridine was used instead of 2-chloro-5-nitropyridine (compound 1).

Synthesis Examples and Comparative Synthesis Examples: Synthesis of Polymer for Liquid Crystal Alignment Agent

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

(11) 19.840 g (0.099 mmol) of the diamine prepared in Preparation Example 1 was completely dissolved in 225.761 g of anhydrous N-methyl pyrrolidone (NMP).

(12) Then, under an ice bath, 20.0 g (0.092 mmol) of pyromellitic dianhydride (PMDA) was added to the solution and stirred at room temperature for 16 hours to prepare a polymer P-1 for a liquid crystal alignment agent. The molecular weight of the polymer P-1 was confirmed by GPC, and as a result, the weight average molecular weight (Mw) was 25,000 g/mol.

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

(13) 14.708 g (0.073 mmol) of the diamine prepared in Preparation Example 1 was completely dissolved in 196.681 g of anhydrous N-methyl pyrrolidone (NMP).

(14) Then, under an ice bath, 20.0 g (0.068 mmol) of 3,3′,4,4′-biphenyl tetracarboxylic acid dianhydride (BPDA) was added to the solution and stirred at room temperature for 16 hours to prepare a polymer P-2 for a liquid crystal alignment agent. The molecular weight of the polymer P-2 was confirmed by GPC, and as a result, the weight average molecular weight (Mw) was 23,000 g/mol.

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

(15) 19.305 g (0.096 mmol) of the diamine prepared in Preparation Example 1 was completely dissolved in 222.726 g of anhydrous N-methyl pyrrolidone (NMP).

(16) Then, under an ice bath, 20.0 g (0.089 mmol) of 1,2,4,5-cyclohexanetetracarboxylic dianhydride (HPMDA) was added to the solution and stirred at room temperature for 16 hours to prepare a polymer P-3 for a liquid crystal alignment agent. The molecular weight of the polymer P-3 was confirmed by GPC, and as a result, the weight average molecular weight (Mw) was 25,500 g/mol.

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

(17) 1.984 g (0.01 mmol) of the diamine prepared in Preparation Example 1 and 9.596 g (0.089 mmol) of p-phenylenediamine (p-PDA) were completely dissolved in 178.952 g of anhydrous N-methyl pyrrolidone (NMP).

(18) Then, under an ice bath, 20.0 g (0.092 mmol) of pyromellitic dianhydride (PMDA) was added to the solution and stirred at room temperature for 16 hours to prepare a polymer P-4 for a liquid crystal alignment agent. The molecular weight of the polymer P-4 was confirmed by GPC, and as a result, the weight average molecular weight (Mw) was 24,000 g/mol.

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

(19) 9.920 g (0.049 mmol) of the diamine prepared in Preparation Example 1 and 5.331 g (0.049 mmol) of p-phenylenediamine (p-PDA) were completely dissolved in 199.756 g of anhydrous N-methyl pyrrolidone (NMP).

(20) Then, under an ice bath, 20.0 g (0.092 mmol) of pyromellitic dianhydride (PMDA) was added to the solution and stirred at room temperature for 16 hours to prepare a polymer P-5 for a liquid crystal alignment agent. The molecular weight of the polymer P-5 was confirmed by GPC, and as a result, the weight average molecular weight (Mw) was 27,000 g/mol.

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

(21) 1.984 g (0.01 mmol) of the diamine prepared in Preparation Example 1 and 17.768 g (0.089 mmol) of 4,4′-oxydianiline (ODA) were completely dissolved in 225.263 g of anhydrous N-methyl pyrrolidone (NMP).

(22) Then, under an ice bath, 20.0 g (0.092 mmol) of pyromellitic dianhydride (PMDA) was added to the solution and stirred at room temperature for 16 hours to prepare a polymer P-6 for a liquid crystal alignment agent. The molecular weight of the polymer P-6 was confirmed by GPC, and as a result, the weight average molecular weight (Mw) was 27,000 g/mol.

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

(23) 9.920 g (0.049 mmol) of the diamine prepared in Preparation Example 1 and 9.871 g (0.049 mmol) of 4,4′-oxydianiline (ODA) were completely dissolved in 225.484 g of anhydrous N-methyl pyrrolidone (NMP).

(24) Then, under an ice bath, 20.0 g (0.092 mmol) of pyromellitic dianhydride (PMDA) was added to the solution and stirred at room temperature for 16 hours to prepare a polymer P-7 for a liquid crystal alignment agent. The molecular weight of the polymer P-7 was confirmed by GPC, and as a result, the weight average molecular weight (Mw) was 27,500 g/mol.

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

(25) 1.984 g (0.01 mmol) of the diamine prepared in Preparation Example 1 and 17.593 g (0.089 mmol) of 4,4′-methylenedianiline (MDA) were completely dissolved in 224.272 g of anhydrous N-methyl pyrrolidone (NMP).

(26) Then, under an ice bath, 20.0 g (0.092 mmol) of pyromellitic dianhydride (PMDA) was added to the solution and stirred at room temperature for 16 hours to prepare a polymer P-8 for a liquid crystal alignment agent. The molecular weight of the polymer P-8 was confirmed by GPC, and as a result, the weight average molecular weight (Mw) was 28,500 g/mol.

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

(27) 9.920 g (0.049 mmol) of the diamine prepared in Preparation Example 1 and 9.774 g (0.049 mmol) of 4,4′-methylenedianiline (MDA) were completely dissolved in 224.934 g of anhydrous N-methyl pyrrolidone (NMP).

(28) Then, under an ice bath, 20.0 g (0.092 mmol) of pyromellitic dianhydride (PMDA) was added to the solution and stirred at room temperature for 16 hours to prepare a polymer P-9 for a liquid crystal alignment agent. The molecular weight of the polymer P-9 was confirmed by GPC, and as a result, the weight average molecular weight (Mw) was 28,500 g/mol.

Synthesis Example 10: Polymer P-10 for Liquid Crystal Alignment Agent

(29) 1.471 g (0.007 mmol) of the diamine prepared in Preparation Example 1 and 7.114 g (0.066 mmol) of p-phenylenediamine (p-PDA) were completely dissolved in 161.980 g of anhydrous N-methyl pyrrolidone (NMP).

(30) Then, under an ice bath, 20.0 g (0.068 mmol) of 3,3′,4,4′-biphenyl tetracarboxylic acid dianhydride (BPDA) was added to the solution and stirred at room temperature for 16 hours to prepare a polymer P-10 for a liquid crystal alignment agent. The molecular weight of the polymer P-10 was confirmed by GPC, and as a result, the weight average molecular weight (Mw) was 25,500 g/mol.

Synthesis Example 11: Polymer P-11 for Liquid Crystal Alignment Agent

(31) 1.471 g (0.007 mmol) of the diamine prepared in Preparation Example 1 and 13.172 g (0.066 mmol) of 4,4′-oxydianiline (ODA) were completely dissolved in 196.312 g of anhydrous N-methyl pyrrolidone (NMP).

(32) Then, under an ice bath, 20.0 g (0.068 mmol) of 3,3′,4,4′-biphenyl tetracarboxylic acid dianhydride (BPDA) was added to the solution and stirred at room temperature for 16 hours to prepare a polymer P-11 for a liquid crystal alignment agent. The molecular weight of the polymer P-11 was confirmed by GPC, and as a result, the weight average molecular weight (Mw) was 25,000 g/mol.

Synthesis Example 12: Polymer P-12 for Liquid Crystal Alignment Agent

(33) 1.471 g (0.007 mmol) of the diamine prepared in Preparation Example 1 and 13.043 g (0.066 mmol) of 4,4′-methylenedianiline (MDA) were completely dissolved in 195.578 g of anhydrous N-methyl pyrrolidone (NMP).

(34) Then, under an ice bath, 20.0 g (0.068 mmol) of 3,3′,4,4′-biphenyl tetracarboxylic acid dianhydride (BPDA) was added to the solution and stirred at room temperature for 16 hours to prepare a polymer P-12 for a liquid crystal alignment agent. The molecular weight of the polymer P-12 was confirmed by GPC, and as a result, the weight average molecular weight (Mw) was 26,000 g/mol.

Synthesis Example 13: Polymer P-13 for Liquid Crystal Alignment Agent

(35) 1.930 g (0.01 mmol) of the diamine prepared in Preparation Example 1 and 9.337 g (0.086 mmol) of p-phenylenediamine (p-PDA) were completely dissolved in 177.181 g of anhydrous N-methyl pyrrolidone (NMP).

(36) Then, under an ice bath, 20.0 g (0.089 mmol) of 1,2,4,5-cyclohexanetetracarboxylic dianhydride (HPMDA) was added to the solution and stirred at room temperature for 16 hours to prepare a polymer P-13 for a liquid crystal alignment agent. The molecular weight of the polymer P-13 was confirmed by GPC, and as a result, the weight average molecular weight (Mw) was 25,500 g/mol.

Synthesis Example 14: Polymer P-14 for Liquid Crystal Alignment Agent

(37) 1.930 g (0.01 mmol) of the diamine prepared in Preparation Example 1 and 17.289 g (0.086 mmol) of 4,4′-oxydianiline (ODA) were completely dissolved in 222.242 g of anhydrous N-methyl pyrrolidone (NMP).

(38) Then, under an ice bath, 20.0 g (0.089 mmol) of 1,2,4,5-cyclohexanetetracarboxylic dianhydride (HPMDA) was added to the solution and stirred at room temperature for 16 hours to prepare a polymer P-14 for a liquid crystal alignment agent. The molecular weight of the polymer P-14 was confirmed by GPC, and as a result, the weight average molecular weight (Mw) was 26,500 g/mol.

Synthesis Example 15: Polymer P-15 for Liquid Crystal Alignment Agent

(39) 1.930 g (0.01 mmol) of the diamine prepared in Preparation Example 1 and 17.119 g (0.086 mmol) of 4,4′-methylenedianiline (MDA) were completely dissolved in 221.278 g of anhydrous N-methyl pyrrolidone (NMP).

(40) Then, under an ice bath, 20.0 g (0.089 mmol) of 1,2,4,5-cyclohexanetetracarboxylic dianhydride (HPMDA) was added to the solution and stirred at room temperature for 16 hours to prepare a polymer P-15 for a liquid crystal alignment agent. The molecular weight of the polymer P-15 was confirmed by GPC, and as a result, the weight average molecular weight (Mw) was 25,500 g/mol.

Synthesis Example 16: Polymer P-16 for Liquid Crystal Alignment Agent

(41) 1.984 g (0.01 mmol) of the diamine prepared in Preparation Example 2 and 9.596 g (0.089 mmol) of p-phenylenediamine (p-PDA) were completely dissolved in 178.952 g of anhydrous N-methyl pyrrolidone (NMP).

(42) Then, under an ice bath, 20.0 g (0.092 mmol) of pyromellitic dianhydride (PMDA) was added to the solution and stirred at room temperature for 16 hours to prepare a polymer P-16 for a liquid crystal alignment agent. The molecular weight of the polymer P-16 was confirmed by GPC, and as a result, the weight average molecular weight (Mw) was 22,000 g/mol.

Synthesis Example 17: Polymer P-17 for Liquid Crystal Alignment Agent

(43) 1.984 g (0.01 mmol) of the diamine prepared in Preparation Example 2 and 17.768 g (0.089 mmol) of 4,4′-oxydianiline (ODA) were completely dissolved in 225.263 g of anhydrous N-methyl pyrrolidone (NMP).

(44) Then, under an ice bath, 20.0 g (0.092 mmol) of pyromellitic dianhydride (PMDA) was added to the solution and stirred at room temperature for 16 hours to prepare a polymer P-17 for a liquid crystal alignment agent. The molecular weight of the polymer P-17 was confirmed by GPC, and as a result, the weight average molecular weight (Mw) was 26,500 g/mol.

Synthesis Example 18: Polymer P-18 for Liquid Crystal Alignment Agent

(45) 1.984 g (0.01 mmol) of the diamine prepared in Preparation Example 2 and 17.593 g (0.089 mmol) of 4,4′-methylenedianiline (MDA) were completely dissolved in 224.272 g of anhydrous N-methyl pyrrolidone (NMP).

(46) Then, under an ice bath, 20.0 g (0.092 mmol) of pyromellitic dianhydride (PMDA) was added to the solution and stirred at room temperature for 16 hours to prepare a polymer P-18 for a liquid crystal alignment agent. The molecular weight of the polymer P-18 was confirmed by GPC, and as a result, the weight average molecular weight (Mw) was 24,500 g/mol.

Synthesis Example 19: Polymer P-19 for Liquid Crystal Alignment Agent

(47) 1.984 g (0.01 mmol) of the diamine prepared in Preparation Example 3 and 9.596 g (0.089 mmol) of p-phenylenediamine (p-PDA) were completely dissolved in 178.952 g of anhydrous N-methyl pyrrolidone (NMP).

(48) Then, under an ice bath, 20.0 g (0.092 mmol) of pyromellitic dianhydride (PMDA) was added to the solution and stirred at room temperature for 16 hours to prepare a polymer P-19 for a liquid crystal alignment agent. The molecular weight of the polymer P-19 was confirmed by GPC, and as a result, the weight average molecular weight (Mw) was 22,500 g/mol.

Synthesis Example 20: Polymer P-20 for Liquid Crystal Alignment Agent

(49) 1.984 g (0.01 mmol) of the diamine prepared in Preparation Example 3 and 17.768 g (0.089 mmol) of 4,4′-oxydianiline (ODA) were completely dissolved in 225.263 g of anhydrous N-methyl pyrrolidone (NMP).

(50) Then, under an ice bath, 20.0 g (0.092 mmol) of pyromellitic dianhydride (PMDA) was added to the solution and stirred at room temperature for 16 hours to prepare a polymer P-20 for a liquid crystal alignment agent. The molecular weight of the polymer P-20 was confirmed by GPC, and as a result, the weight average molecular weight (Mw) was 24,500 g/mol.

Synthesis Example 21: Polymer P-21 for Liquid Crystal Alignment Agent

(51) 1.984 g (0.01 mmol) of the diamine prepared in Preparation Example 3 and 17.593 g (0.089 mmol) of 4,4′-methylenedianiline (MDA) were completely dissolved in 224.272 g of anhydrous N-methyl pyrrolidone (NMP).

(52) Then, under an ice bath, 20.0 g (0.092 mmol) of pyromellitic dianhydride (PMDA) was added to the solution and stirred at room temperature for 16 hours to prepare a polymer P-21 for a liquid crystal alignment agent. The molecular weight of the polymer P-21 was confirmed by GPC, and as a result, the weight average molecular weight (Mw) was 26,000 g/mol.

Synthesis Example 22: Polymer P-22 for Liquid Crystal Alignment Agent

(53) 1.93 g (0.01 mmol) of the diamine prepared in Preparation Example 1 and 9.337 g (0.086 mmol) of p-phenylenediamine (p-PDA) were completely dissolved in 177.181 g of anhydrous N-methyl pyrrolidone (NMP).

(54) Then, under an ice bath, 20.0 g (0.089 mmol) of 1,3-dimethyl-cyclobutane-1,2,3,4-tetracarboxylic dianhydride (DMCBDA) was added to the solution and stirred at room temperature for 16 hours to prepare a polymer P-22 for a liquid crystal alignment agent. The molecular weight of the polymer P-22 was confirmed by GPC, and as a result, the weight average molecular weight (Mw) was 21,000 g/mol.

Synthesis Example 23: Polymer P-23 for Liquid Crystal Alignment Agent

(55) 19.305 g (0.096 mmol) of the diamine prepared in Preparation Example 1 was completely dissolved in 222.726 g of anhydrous N-methyl pyrrolidone (NMP).

(56) Then, under an ice bath, 20.0 g (0.089 mmol) of 1,3-dimethyl-cyclobutane-1,2,3,4-tetracarboxylic dianhydride (DMCBDA) was added to the solution and stirred at room temperature for 16 hours to prepare a polymer P-23 for a liquid crystal alignment agent. The molecular weight of the polymer P-23 was confirmed by GPC, and as a result, the weight average molecular weight (Mw) was 23,500 g/mol.

Synthesis Example 24: Polymer P-24 for Liquid Crystal Alignment Agent

(57) 1.93 g (0.01 mmol) of the diamine prepared in Preparation Example 1 and 17.119 g (0.086 mmol) of 4,4′-methylenedianiline (MDA) were completely dissolved in 221.278 g of anhydrous N-methyl pyrrolidone (NMP).

(58) Then, under an ice bath, 20.0 g (0.089 mmol) of 1,3-dimethyl-cyclobutane-1,2,3,4-tetracarboxylic dianhydride (DMCBDA) was added to the solution and stirred at room temperature for 16 hours to prepare a polymer P-24 for a liquid crystal alignment agent. The molecular weight of the polymer P-24 was confirmed by GPC, and as a result, the weight average molecular weight (Mw) was 22,500 g/mol.

Synthesis Example 25: Polymer P-25 for Liquid Crystal Alignment Agent

(59) 1.93 g (0.01 mmol) of the diamine prepared in Preparation Example 1 and 17.119 g (0.086 mmol) of 4,4′-methylenedianiline (MDA) were completely dissolved in 219.749 g of anhydrous N-methyl pyrrolidone (NMP).

(60) Then, under an ice bath, 10.0 g (0.045 mmol) of 1,3-dimethyl-cyclobutane-1,2,3,4-tetracarboxylic dianhydride (DMCBDA) and 9.73 g (0.045 mmol) of pyromellitic dianhydride (PMDA) were added to the solution and stirred at room temperature for 16 hours to prepare a polymer P-25 for a liquid crystal alignment agent. The molecular weight of the polymer P-25 was confirmed by GPC, and as a result, the weight average molecular weight (Mw) was 22,000 g/mol.

Comparative Synthesis Example 1: Polymer R-1 for Liquid Crystal Alignment Agent

(61) 26.852 g (0.099 mmol) of p-phenylenediamine (p-PDA) was completely dissolved in 265.496 g of anhydrous N-methyl pyrrolidone (NMP).

(62) Then, under an ice bath, 20.0 g (0.092 mmol) of pyromellitic dianhydride (PMDA) was added to the solution and stirred at room temperature for 16 hours to prepare a polymer R-1 for a liquid crystal alignment agent. The molecular weight of the polymer R-1 was confirmed by GPC, and as a result, the weight average molecular weight (Mw) was 26,000 g/mol.

Comparative Synthesis Example 2: Polymer R-2 for Liquid Crystal Alignment Agent

(63) 19.743 g (0.099 mmol) of 4,4′-oxydianiline (ODA) was completely dissolved in 225.208 g of anhydrous N-methyl pyrrolidone (NMP).

(64) Then, under an ice bath, 20.0 g (0.092 mmol) of pyromellitic dianhydride (PMDA) was added to the solution and stirred at room temperature for 16 hours to prepare a polymer R-2 for a liquid crystal alignment agent. The molecular weight of the polymer R-2 was confirmed by GPC, and as a result, the weight average molecular weight (Mw) was 21,000 g/mol.

Comparative Synthesis Example 3: Polymer R-3 for Liquid Crystal Alignment Agent

(65) 19.548 g (0.089 mmol) of 4,4′-methylenedianiline (MDA) was completely dissolved in 224.218 g of anhydrous N-methyl pyrrolidone (NMP).

(66) Then, under an ice bath, 20.0 g (0.092 mmol) of pyromellitic dianhydride (PMDA) was added to the solution and stirred at room temperature for 16 hours to prepare a polymer R-3 for a liquid crystal alignment agent. The molecular weight of the polymer R-3 was confirmed by GPC, and as a result, the weight average molecular weight (Mw) was 23,000 g/mol.

Comparative Synthesis Example 4: Polymer R-4 for Liquid Crystal Alignment Agent

(67) A polymer R-4 for liquid crystal alignment agent was prepared in the same manner as in Synthesis Example 1, except that a compound represented by Chemical Formula A was used instead of the diamine prepared in Preparation Example 1.

(68) ##STR00022##

Examples and Comparative Examples: Preparation of Liquid Crystal Alignment Agent

Example 1

(69) 20 g of the polymer P-1 for a liquid crystal alignment agent of Synthesis Example 1 was dissolved in a mixed solvent of 8.65 g of NMP, 19.95 g of GBL, and 11.4 g of 2-butoxyethanol to obtain a 5 wt % solution. Then, the solution thus obtained was subjected to pressure filtration using a filter having a pore size of 0.1 μm and made of poly(tetrafluoroethylene) to prepare a liquid crystal alignment agent A-1.

Example 2

(70) 20 g of the polymer P-2 for a liquid crystal alignment agent of Synthesis Example 2 was dissolved in a mixed solvent of 8.65 g of NMP, 19.95 g of GBL, and 11.4 g of 2-butoxyethanol to obtain a 5 wt % solution. Then, the solution thus obtained was subjected to pressure filtration using a filter having a pore size of 0.1 μm and made of poly(tetrafluoroethylene) to prepare a liquid crystal alignment agent A-2.

Example 3

(71) 20 g of the polymer P-3 for a liquid crystal alignment agent of Synthesis Example 3 was dissolved in a mixed solvent of 8.65 g of NMP, 19.95 g of GBL, and 11.4 g of 2-butoxyethanol to obtain a 5 wt % solution. Then, the solution thus obtained was subjected to pressure filtration using a filter having a pore size of 0.1 m and made of poly(tetrafluoroethylene) to prepare a liquid crystal alignment agent A-3.

Example 4

(72) 20 g of the polymer P-4 for a liquid crystal alignment agent of Synthesis Example 4 was dissolved in a mixed solvent of 8.65 g of NMP, 19.95 g of GBL, and 11.4 g of 2-butoxyethanol to obtain a 5 wt % solution. Then, the solution thus obtained was subjected to pressure filtration using a filter having a pore size of 0.1 m and made of poly(tetrafluoroethylene) to prepare a liquid crystal alignment agent B-1.

Example 5

(73) 20 g of the polymer P-5 for a liquid crystal alignment agent of Synthesis Example 5 was dissolved in a mixed solvent of 8.65 g of NMP, 19.95 g of GBL, and 11.4 g of 2-butoxyethanol to obtain a 5 wt % solution. Then, the solution thus obtained was subjected to pressure filtration using a filter having a pore size of 0.1 m and made of poly(tetrafluoroethylene) to prepare a liquid crystal alignment agent B-2.

Example 6

(74) 20 g of the polymer P-6 for a liquid crystal alignment agent of Synthesis Example 6 was dissolved in a mixed solvent of 8.65 g of NMP, 19.95 g of GBL, and 11.4 g of 2-butoxyethanol to obtain a 5 wt % solution. Then, the solution thus obtained was subjected to pressure filtration using a filter having a pore size of 0.1 m and made of poly(tetrafluoroethylene) to prepare a liquid crystal alignment agent B-3.

Example 7

(75) 20 g of the polymer P-7 for a liquid crystal alignment agent of Synthesis Example 7 was dissolved in a mixed solvent of 8.65 g of NMP, 19.95 g of GBL, and 11.4 g of 2-butoxyethanol to obtain a 5 wt % solution. Then, the solution thus obtained was subjected to pressure filtration using a filter having a pore size of 0.1 m and made of poly(tetrafluoroethylene) to prepare a liquid crystal alignment agent B-4.

Example 8

(76) 20 g of the polymer P-8 for a liquid crystal alignment agent of Synthesis Example 8 was dissolved in a mixed solvent of 8.65 g of NMP, 19.95 g of GBL, and 11.4 g of 2-butoxyethanol to obtain a 5 wt % solution. Then, the solution thus obtained was subjected to pressure filtration using a filter having a pore size of 0.1 m and made of poly(tetrafluoroethylene) to prepare a liquid crystal alignment agent B-5.

Example 9

(77) 20 g of the polymer P-9 for a liquid crystal alignment agent of Synthesis Example 9 was dissolved in a mixed solvent of 8.65 g of NMP, 19.95 g of GBL, and 11.4 g of 2-butoxyethanol to obtain a 5 wt % solution. Then, the solution thus obtained was subjected to pressure filtration using a filter having a pore size of 0.1 m and made of poly(tetrafluoroethylene) to prepare a liquid crystal alignment agent B-6.

Example 10

(78) 20 g of the polymer P-10 for a liquid crystal alignment agent of Synthesis Example 10 was dissolved in a mixed solvent of 8.65 g of NMP, 19.95 g of GBL, and 11.4 g of 2-butoxyethanol to obtain a 5 wt % solution. Then, the solution thus obtained was subjected to pressure filtration using a filter having a pore size of 0.1 m and made of poly(tetrafluoroethylene) to prepare a liquid crystal alignment agent C-1.

Example 11

(79) 20 g of the polymer P-11 for a liquid crystal alignment agent of Synthesis Example 11 was dissolved in a mixed solvent of 8.65 g of NMP, 19.95 g of GBL, and 11.4 g of 2-butoxyethanol to obtain a 5 wt % solution. Then, the solution thus obtained was subjected to pressure filtration using a filter having a pore size of 0.1 μm and made of poly(tetrafluoroethylene) to prepare a liquid crystal alignment agent C-2.

Example 12

(80) 20 g of the polymer P-12 for a liquid crystal alignment agent of Synthesis Example 12 was dissolved in a mixed solvent of 8.65 g of NMP, 19.95 g of GBL, and 11.4 g of 2-butoxyethanol to obtain a 5 wt % solution. Then, the solution thus obtained was subjected to pressure filtration using a filter having a pore size of 0.1 m and made of poly(tetrafluoroethylene) to prepare a liquid crystal alignment agent C-3.

Example 13

(81) 20 g of the polymer P-13 for a liquid crystal alignment agent of Synthesis Example 13 was dissolved in a mixed solvent of 8.65 g of NMP, 19.95 g of GBL, and 11.4 g of 2-butoxyethanol to obtain a 5 wt % solution. Then, the solution thus obtained was subjected to pressure filtration using a filter having a pore size of 0.1 m and made of poly(tetrafluoroethylene) to prepare a liquid crystal alignment agent D-1.

Example 14

(82) 20 g of the polymer P-14 for a liquid crystal alignment agent of Synthesis Example 14 was dissolved in a mixed solvent of 8.65 g of NMP, 19.95 g of GBL, and 11.4 g of 2-butoxyethanol to obtain a 5 wt % solution. Then, the solution thus obtained was subjected to pressure filtration using a filter having a pore size of 0.1 m and made of poly(tetrafluoroethylene) to prepare a liquid crystal alignment agent D-2.

Example 15

(83) 20 g of the polymer P-15 for a liquid crystal alignment agent of Synthesis Example 15 was dissolved in a mixed solvent of 8.65 g of NMP, 19.95 g of GBL, and 11.4 g of 2-butoxyethanol to obtain a 5 wt % solution. Then, the solution thus obtained was subjected to pressure filtration using a filter having a pore size of 0.1 m and made of poly(tetrafluoroethylene) to prepare a liquid crystal alignment agent D-3.

Example 16

(84) 20 g of the polymer P-16 for a liquid crystal alignment agent of Synthesis Example 16 was dissolved in a mixed solvent of 8.65 g of NMP, 19.95 g of GBL, and 11.4 g of 2-butoxyethanol to obtain a 5 wt % solution. Then, the solution thus obtained was subjected to pressure filtration using a filter having a pore size of 0.1 m and made of poly(tetrafluoroethylene) to prepare a liquid crystal alignment agent E-1.

Example 17

(85) 20 g of the polymer P-17 for a liquid crystal alignment agent of Synthesis Example 17 was dissolved in a mixed solvent of 8.65 g of NMP, 19.95 g of GBL, and 11.4 g of 2-butoxyethanol to obtain a 5 wt % solution. Then, the solution thus obtained was subjected to pressure filtration using a filter having a pore size of 0.1 m and made of poly(tetrafluoroethylene) to prepare a liquid crystal alignment agent E-2.

Example 18

(86) 20 g of the polymer P-18 for a liquid crystal alignment agent of Synthesis Example 18 was dissolved in a mixed solvent of 8.65 g of NMP, 19.95 g of GBL, and 11.4 g of 2-butoxyethanol to obtain a 5 wt % solution. Then, the solution thus obtained was subjected to pressure filtration using a filter having a pore size of 0.1 m and made of poly(tetrafluoroethylene) to prepare a liquid crystal alignment agent E-3.

Example 19

(87) 20 g of the polymer P-19 for a liquid crystal alignment agent of Synthesis Example 19 was dissolved in a mixed solvent of 8.65 g of NMP, 19.95 g of GBL, and 11.4 g of 2-butoxyethanol to obtain a 5 wt % solution. Then, the solution thus obtained was subjected to pressure filtration using a filter having a pore size of 0.1 m and made of poly(tetrafluoroethylene) to prepare a liquid crystal alignment agent F-1.

Example 20

(88) 20 g of the polymer P-20 for a liquid crystal alignment agent of Synthesis Example 20 was dissolved in a mixed solvent of 8.65 g of NMP, 19.95 g of GBL, and 11.4 g of 2-butoxyethanol to obtain a 5 wt % solution. Then, the solution thus obtained was subjected to pressure filtration using a filter having a pore size of 0.1 m and made of poly(tetrafluoroethylene) to prepare a liquid crystal alignment agent F-2.

Example 21

(89) 20 g of the polymer P-21 for a liquid crystal alignment agent of Synthesis Example 21 was dissolved in a mixed solvent of 8.65 g of NMP, 19.95 g of GBL, and 11.4 g of 2-butoxyethanol to obtain a 5 wt % solution. Then, the solution thus obtained was subjected to pressure filtration using a filter having a pore size of 0.1 m and made of poly(tetrafluoroethylene) to prepare a liquid crystal alignment agent F-3.

Example 22

(90) 20 g of the polymer P-22 for a liquid crystal alignment agent of Synthesis Example 22 was dissolved in a mixed solvent of 8.65 g of NMP, 19.95 g of GBL, and 11.4 g of 2-butoxyethanol to obtain a 5 wt % solution. Then, the solution thus obtained was subjected to pressure filtration using a filter having a pore size of 0.1 m and made of poly(tetrafluoroethylene) to prepare a liquid crystal alignment agent G-1.

Example 23

(91) 20 g of the polymer P-23 for a liquid crystal alignment agent of Synthesis Example 23 was dissolved in a mixed solvent of 8.65 g of NMP, 19.95 g of GBL, and 11.4 g of 2-butoxyethanol to obtain a 5 wt % solution. Then, the solution thus obtained was subjected to pressure filtration using a filter having a pore size of 0.1 μm and made of poly(tetrafluoroethylene) to prepare a liquid crystal alignment agent G-2.

Example 24

(92) 20 g of the polymer P-24 for a liquid crystal alignment agent of Synthesis Example 24 was dissolved in a mixed solvent of 8.65 g of NMP, 19.95 g of GBL, and 11.4 g of 2-butoxyethanol to obtain a 5 wt % solution. Then, the solution thus obtained was subjected to pressure filtration using a filter having a pore size of 0.1 μm and made of poly(tetrafluoroethylene) to prepare a liquid crystal alignment agent G-3.

Example 25

(93) 20 g of the polymer P-25 for a liquid crystal alignment agent of Synthesis Example 25 was dissolved in a mixed solvent of 8.65 g of NMP, 19.95 g of GBL, and 11.4 g of 2-butoxyethanol to obtain a 5 wt % solution. Then, the solution thus obtained was subjected to pressure filtration using a filter having a pore size of 0.1 m and made of poly(tetrafluoroethylene) to prepare a liquid crystal alignment agent G-4.

Comparative Example 1

(94) 20 g of the polymer R-1 for a liquid crystal alignment agent of Comparative Synthesis Example 1 was dissolved in a mixed solvent of 8.65 g of NMP, 19.95 g of GBL, and 11.4 g of 2-butoxyethanol to obtain a 5 wt % solution. Then, the solution thus obtained was subjected to pressure filtration using a filter having a pore size of 0.1 μm and made of poly(tetrafluoroethylene) to prepare a liquid crystal alignment agent R′-1.

Comparative Example 2

(95) 20 g of the polymer R-2 for a liquid crystal alignment agent of Comparative Synthesis Example 2 was dissolved in a mixed solvent of 8.65 g of NMP, 19.95 g of GBL, and 11.4 g of 2-butoxyethanol to obtain a 5 wt % solution. Then, the solution thus obtained was subjected to pressure filtration using a filter having a pore size of 0.1 μm and made of poly(tetrafluoroethylene) to prepare a liquid crystal alignment agent R′-2.

Comparative Example 3

(96) 20 g of the polymer R-3 for a liquid crystal alignment agent of Comparative Synthesis Example 3 was dissolved in a mixed solvent of 8.65 g of NMP, 19.95 g of GBL, and 11.4 g of 2-butoxyethanol to obtain a 5 wt % solution. Then, the solution thus obtained was subjected to pressure filtration using a filter having a pore size of 0.1 μm and made of poly(tetrafluoroethylene) to prepare a liquid crystal alignment agent R′-3.

Comparative Example 4

(97) 20 g of the polymer R-4 for a liquid crystal alignment agent of Comparative Synthesis Example 4 was dissolved in a mixed solvent of 8.65 g of NMP, 19.95 g of GBL, and 11.4 g of 2-butoxyethanol to obtain a 5 wt % solution. Then, the solution thus obtained was subjected to pressure filtration using a filter having a pore size of 0.1 m and made of poly(tetrafluoroethylene) to prepare a liquid crystal alignment agent R′-4.

Experimental Examples: Measurement of Physical Properties of Liquid Crystal Alignment Agent Obtained in Examples and Comparative Examples

(98) The liquid crystal alignment agent obtained in the example and comparative examples was used to prepare a liquid crystal cell, and the respective physical properties were measured from the liquid crystal cell by the following method. The results are shown in Table 1 below.

(99) Specifically, the liquid crystal alignment agent obtained in the examples and comparative examples was coated onto the upper and lower substrates for a voltage holding ratio (VHR) in which ITO electrodes with a thickness of 60 nm and an area of 1 cm×1 cm were patterned on a square glass substrate with a size of 2.5 cm×2.7 cm by a spin coating method, respectively. Then, the substrates coated with the liquid crystal alignment agent were placed on a hot plate at about 80° C. and dried for 2 minutes to evaporate the solvent.

(100) Subsequently, the dried upper and lower substrates were baked (cured) in an oven at about 230° C. for 2000 seconds. Thereafter, in order to align the coating film thus obtained, the surface of the coating film was rubbed in one direction while rotating a rubbing roller of which a rubbing cloth was attached to a metal roller.

(101) Then, the alignment-treated upper and lower substrates were baked (cured) in an oven at about 230° C. for 15 minutes to obtain a coating film with a thickness of 0.1 μm. Thereafter, a sealing agent impregnated with ball spacers with a size of 4.5 μm was coated onto the edges of the upper substrate excluding a liquid crystal inlet. The alignment films formed on the upper and lower substrates were then aligned such that they faced each other and the alignment directions were aligned with each other, and the upper and lower substrates were bonded together and the sealing agent was cured with UV and heat to prepare an empty cell. Then, a liquid crystal was injected into the empty cells, and the inlet was sealed with a sealing agent to prepare a liquid crystal alignment cell.

(102) 1. Voltage Holding Ratio (VHR)

(103) The voltage holding ratio of the liquid crystal alignment cell was measured at 1 Hz and 60° C. using 6254C equipment manufactured by TOYO Corporation as a measuring instrument.

(104) 2. AC Afterimage

(105) Polarizing plates were attached to the upper and lower substrate plates of the liquid crystal alignment cell so as to be perpendicular to each other. The polarizing plate-attached liquid crystal alignment cell was attached on a backlight having luminance of 7000 cd/cm.sup.2, and the luminance in a black state was measured using a luminance or brightness measuring instrument PR-880. Then, the liquid crystal cell was operated at room temperature with an alternating voltage of 5 V for 24 hours. Thereafter, in the voltage-off state of the liquid crystal cell, luminance in the black state was measured as described above. A difference between the initial luminance (L0) measured before operation of the liquid crystal cell and the later luminance (L1) measured after operation was divided by the initial luminance (L0), and then multiplied by 100 to calculate a luminance fluctuation rate. When the calculated luminance fluctuation rate is close to 0%, it means that the alignment stability is excellent. Through the measurement results of the luminance fluctuation rate, the afterimage level was evaluated under the following criteria.

(106) Excellent: when luminance fluctuation rate is less than 10%

(107) Ordinary: when luminance fluctuation rate is between 10% and 20%.

(108) TABLE-US-00001 TABLE 1 Measurement results of Experimental Examples of Examples and Comparative Examples AC Diamine Dicarboxylic VHR afterimage Class Polymer (molar ratio) acid (%) (%) Example 1 P-1 Preparation PMDA 86 Excellent Example 1 Example 2 P-2 Preparation BPDA 87 Excellent Example 1 Example 3 P-3 Preparation HPMDA 90 Excellent Example 1 Example 4 P-4 Preparation PMDA 84 Excellent Example 1, p- PDA (10:89) Example 5 P-5 Preparation PMDA 85 Ordinary Example 1, p- PDA (1:1) Example 6 P-6 Preparation PMDA 87 Excellent Example 1, ODA (10:89) Example 7 P-7 Preparation PMDA 87 Ordinary Example 1, ODA (1:1) Example 8 P-8 Preparation PMDA 87 Excellent Example 1, MDA (10:89) Example 9 P-9 Preparation PMDA 86 Ordinary Example 1, MDA (1:1) Example 10 P-10 Preparation BPDA 85 Excellent Example 1, p- PDA (7:66) Example 11 P-11 Preparation BPDA 87 Excellent Example 1, ODA (7:66) Example 12 P-12 Preparation BPDA 86 Excellent Example 1, MDA (7:66) Example 13 P-13 Preparation HPMDA 88 Ordinary Example 1, p- PDA (10:86) Example 14 P-14 Preparation HPMDA 89 Ordinary Example 1, ODA (10:86) Example 15 P-14 Preparation HPMDA 89 Ordinary Example 1, MDA (10:86) Example 16 P-16 Preparation PMDA 82 Ordinary Example 2, p- PDA (10:89) Example 17 P-17 Preparation PMDA 85 Ordinary Example 2, ODA (10:89) Example 18 P-18 Preparation PMDA 85 Ordinary Example 2, MDA (10:89) Example 19 P-19 Preparation PMDA 84 Ordinary Example 3, p- PDA (10:89) Example 20 P-20 Preparation PMDA 86 Ordinary Example 3, ODA (10:89) Example 21 P-21 Preparation PMDA 85 Ordinary Example 3, MDA (10:89) Example 22 P-22 Preparation DMCBDA 57 Excellent Example 1, p- PDA (10:86) Example 23 P-23 Preparation DMCBDA 65 Excellent Example 1 Example 24 P-24 Preparation DMCBDA 70 Excellent Example 1, MDA (10:86) Example 25 P-25 Preparation DMCBDA, 68 Excellent Example 1, PMDA MDA (10:86) (45:45) Comparative R-1 p-PDA PMDA 55 Ordinary Example 1 Comparative R-2 ODA PMDA 63 Ordinary Example 2 Comparative R-3 MDA PMDA 64 Ordinary Example 3 Comparative R-4 Formula A PMDA 55 Ordinary Example 4

(109) As shown in Table 1, as the liquid crystal alignment agent of the examples contains a polymer produced from a reaction product containing a diamine having an asymmetric structure as in Preparation Examples 1 to 3, the voltage holding ratio (VHR) is improved to as high as 82% to 90%, and the AC afterimage can be maintained at the equivalent level or more.

(110) Particularly, in the case of the liquid crystal alignment agents of Examples 22 to 25, the voltage holding ratio (VHR) is shown as 60% to 70%, but the luminance fluctuation rate is measured to be less than 10%, which confirms that the AC afterimage is remarkably improved.

(111) On the other hand, in the case of the liquid crystal alignment agents of the comparative examples, since the diamine having an asymmetric structure as in Preparation Examples 1 to 3 are not contained in the reaction product during the production of the polymer, it is confirmed that it exhibits a voltage holding ratio (VHR) of 54% to 64% which is significantly lower than that of the examples, and the luminance fluctuation rate increases from 10% to 20%, and thus AC afterimage properties are poor.