WO2008153286A2

WO2008153286A2 - Aromatic diamines with a photoreactive aromatic side group, polyamic acid photo-alignment layers with them and method for preparing liquid crystal cells

Info

Publication number: WO2008153286A2
Application number: PCT/KR2008/003154
Authority: WO
Inventors: Mi Hye Yi; Taek Ahn; Hee Jin Park
Original assignee: Korea Research Institute Of Chemical Technology
Priority date: 2007-06-13
Filing date: 2008-06-05
Publication date: 2008-12-18
Also published as: KR100837788B1; WO2008153286A3

Abstract

The present invention relates to photo-alignment layers from polyamic acid with a photoreactive aromatic side group. More specifically, the present invention relates to novel polyamic acid photo-alignment layers prepared by the solution polymerization of acid dianhydrides which comprises alicyclic acid dianhydrides at certain ratio or more and aromatic diamines which comprises aromatic diamines with a photoreactive aromatic side group at certain ratio or more and the preparation method thereof, and the preparation method of aromatic diamines with novel aromatic side group. Said polyamic acid photo-alignment layers provide excellent heat- resistance, surface hardness, transparency and liquid crystal alignment property for polarized UV light.

Description

[DESCRIPTION]

[invention Title]

AROMATIC DIAMINES WITH A PHOTOREACTIVE AROMATIC SIDE GROUP, POLYAMIC ACID PHOTO-ALIGNMENT LAYERS WITH THEM AND METHOD FOR PREPARING LIQUID CRYSTAL CELLS

[Technical Field]

The present invention relates to photo-alignment layers from polyamic acid with a photoreactive aromatic side group and a method for producing the same. More specifically, the present invention provides polyamic acid with excellent solubility in a solvent by the solution polymerization of acid dianhydrides which comprises alicyclic acid dianhydrides at certain ratio or more and aromatic diamines which comprises aromatic diamines with a photoreactive aromatic side group at certain ratio or more. Further, the present invention is characterized in that by illuminating polarized UV light to the polyamic acid, liquid crystals can be aligned without a rubbing process .

The polyamic acid photo-alignment layers that are obtained by illumination with polarized UV light have excellent transparency in visible light region, excellent printability, heat-resistance, surface hardness and liquid crystal alignment property. In particular, they are characterized in that even at low luminous quantity an excellent photo-alignment property can be obtained, and pretilt angles and voltage holding ratio (VHR) are also excellent .

[Background Art]

Generally, polyimide resin represents a highly heat- resistant resin which is prepared by polycondensation of aromatic tetracarboxylic acid or derivatives thereof and an aromatic diamine or an aromatic diisocyanate followed by imidation. Polyimide resin may have various molecular structures depending on the kind of monomers used. In general, pyromellitic acid dianhydride (PMDA) or biphthalic anhydride

(BPDA) as an aromatic tetracarboxylic acid and para-phenylene diamine (p-PDA) , meta-phenylene diamine (m-PDA) , 4,4- oxydianiline (ODA), 4 , 4-methylene dianiline (MDA), 2,2- bisaminophenyl hexafluoropropane (HFDA) , meta- bisaminophenoxydiphenyl sulfone (m-BAPS) , para- bisaminophenoxydiphenyl sulfone (p-BAPS) , 1,4- bisaminophenoxybenzene (TPE-Q), 1, 3-bisaminophenoxybenzene

(TPE-R), 2 , 2-bisaminophenoxyphenylpropane (BAPP), 2,2- bisaminophenoxyphenylhexafluoropropane (HFBAPP) and the like as an aromatic diamine are used for the polylcondensation.

Most of the polyimide resin is an insoluble, infusible and highly heat-resistant resin and has characteristics of (1) an excellent heat and oxidation resistance, (2) high use temperature, (3) an excellent heat resistance having long-term use temperature of about 260 ^°C and short-term use temperature of about 480 ^°Q (4) radiation resistance, (5) an excellent property at low temperature, and (6) an excellent chemical resistance, etc.

However, in spite of having the above-mentioned characteristics, the polyimide resin has a problem that, since it has low light transmittance in visible light region due to the formation of a charge transfer complex, it is hardly applied for a field which requires transparency.

As such, various types of polyimide resin having main- skeleton aliphatic groups were produced and used for a field such as liquid crystal alignment layers, etc. which requires good light transmittance. Especially for the photo-alignment layer which does not undergo a rubbing process, as problems associated with dust or occurrence of static electricity can be solved, it definitely is a field which waits for a new development .

However, alicyclic photo-alignment layers which have been developed until now requires huge quantity of UV light or high wavelength for alignment of liquid crystals so that more processing time is needed for producing alignment layers and more energy is consumed therefor.

[Disclosure of Invention] [Technical Subject]

In order to solve the problems described above, inventors of the present application designed and produced aromatic diamines which have an excellent photo-alignment property at long wavelength of 300 nm or more and low luminous quantity of 200 mJ/cm² or less. Further, by illuminating thus-obtained thin film made of the polyamic acid resin comprising said aromatic diamines with polarized UV light, novel photo- alignment layers having excellent liquid crystal alignment property and VHR (voltage holding ratio), high surface hardness of 4H or more and low pretilt angles in the range of 0.01-2.0°were developed, and therefore the present invention was completed.

Specifically, according to the present invention polyamic acid is prepared from a mixture of alicyclic acid dianhydrides such as tricarboxycyclopentyl acetic acid anhydride (TCA-AH) , 5- (2 , 5-dioxotetrahydrofuryl) -3 -methylcyclohexan-1, 2- dicarboxylic acid dianhydride (DOCDA), 4- (2,5- dioxotetrahydrofuryl-3-yl) -tetraline-1 , 2-dicarboxylic acid dianhydride (DOTDA), 1 , 2 , 3 , 4-cyclobutane tetracarboxylic acid dianhydride (CBDA), 1, 3 -dimethyl-1 , 2 , 3 , 4-cyclobutane tetracarboxylic acid dianhydride (DM-CBDA), 1,2,3,4- cyclopentane tetracarboxylic acid dianhydride (CPDA) , bicycloocten-2 , 3 , 5 , 6 -tetracarboxylic acid dianhydride (BODA), pyromellitic acid dianhydride, benzophenonetetracarboxylic acid dianhydride, oxydiphthalic acid dianhydride, biphthalic acid dianhydride and hexafluoroisopropylidene diphthalic acid dianhydride and a mixture of aromatic diamines having a photoreactive aromatic side group and aromatic diamines. After forming a thin film from the polyamic acid resin followed by illumination with polarized UV light, novel liquid crystal photo-alignment layers which have excellent heat resistance and transparency, high surface hardness and VHR, and low pretilt angles are developed, and therefore the present invention was completed.

Thus, the object of the present invention is to provide polyamic acid which comprises as a monomer the novel aromatic diamines with a photoreactive aromatic side group and has an excellent photo-alignment property and electro-optical property by illumination of polarized UV light with low luminous quantity, photo-alignment layers that are produced from said polyamic acid, and a liquid crystal cell which comprises said photo-alignment layers.

The other object of the present invention is to provide a liquid crystal cell which has long wavelength-alignment property of 300 nm or more and low luminous quantity of 200 mJ/cm² or less, high surface hardness of 4H or more, excellent VHR and low pretilt angles, compared to a liquid crystal cell that is prepared from conventional photo-alignment layers which do not comprise an aromatic side group. [Technical Solution]

The present invention relates to polyamic acid represented by the following chemical formula 2, which comprises as a monomer the novel aromatic diamines with an aromatic side group represented by the following chemical formula 1, and the photo-alignment layers prepared therefrom. Further, the present invention relates to novel aromatic diamine compounds that are represented by the following chemical formula 1.

[Chemical formula 1]

[In the above chemical formula 1, a is an integer from 1 to 10; b is an integer from 0 to 10; provided that when b is an integer from 1 to 10, A represents

R₁, R₂, R₃, R₄ and R₅ are independently to each other a halogen substituted or non-substituted (Cl-ClO) alkyl, a cyano, a nitro, a carboxylic acid, or an aminocarbonyl group,- and when b is 0, A represents

[Chemical formula 2]

[In the above chemical formula 2, m is an integer from 1 to 500;

is a one or two kinds of tetravalent group selected

from a group consisting of

XX XX

R₁, R₁₂ ϊ J R₁.! R 13 ,

0

B is a chemical bond or a ( C1 - C2 ) alkylene , ^~ °^~ , ^c"*

alkylene group may be further substituted with a (C1-C5) alkyl group that is either substituted or non- substituted with fluorine ;

R₁₁, R₁₂, Rn and Ri₄ are independently to each other a hydrogen, a (Cl-ClO) alkyl or a phenyl group; and .'>-"-<;. is a one or two kinds of divalent group selected from a

group consisting of O- TT - -o-

always comprises the aromatic divalent group which has an aromatic side group of said structural formula (g) .]

Polyamic acid which is represented by chemical formula 2 described above is used for preparing photo-alignment layers and is produced by solvent polymerization between tetracarboxylic acid dianhydride monomer and diamine monomer. For tetracarboxylic acid dianhydride monomer, it is selected from tricarboxycyclopentylacetic acid anhydride (TCA-AH) , 5- (2 , 5-dioxotetrahydrofuryl) -3-methylcyclohexan-l, 2-dicarboxylic acid dianhydride (DOCDA), 4- (2 , 5-dioxotetrahydrofuryl-3 -yl) - tetralin-1, 2-dicarboxylic acid dianhydride (DOTDA), 1,2,3,4- cyclobutane tetracarboxylic acid dianhydride (CBDA), 1,3- dimethyl-1 , 2 , 3 , 4-cyclobutane tetracarboxylic acid dianhydride (DM-CBDA) , 1, 2, 3, 4-cyclopentane tetracarboxylic acid dianhydride (CPDA), bicycloocten-2 , 3 , 5 , 6 -tetracarboxylic acid dianhydride (BODA) , and pyromellitic acid dianhydride (PMDA) , benzophenonetetracarboxylic acid dianhydride, oxydiphthalic acid dianhydride, biphthalic acid dianhydride (BPDA) and hexafluoroisopropylidene diphthalic acid dianhydride, etc., but not limited thereto.

Further, for aromatic diamine monomer, it is selected from para-phenylene diamine (p-PDA) , meta-phenylene diamine (m-PDA) , 4 , 4-oxydianiline (ODA), 4 , 4-methylenedianiline (MDA), 2 , 2-bisaminophenylhexafluoropropane (HFDA), meta- bisaminophenoxydiphenylsulfone (m-BAPS) , para- bisaminophenoxydiphenylsulfone (p-BAPS) , 1,4- bisaminophenoxybenzene (TPE-Q), 1 , 3-bisaminophenoxybenzene (TPE-R), 2 , 2-bisaminophenoxyphenylpropane (BAPP), 2,2- bisaminophenoxyphenylhexafluoropropane (HFBAPP), etc., and although not limited thereto the aromatic diamine compound of chemical formula 1 comprising an aromatic side group should be comprised as a monomer.

In short, for producing polyamic acid represented by chemical formula 2 described above, by using monomers of tetracarboxylic acid dianhydride in an appropriate mixing ratio, polyaraic acid derivatives with improved pπntability and minimized loss m mechanical properties and heat resistance can be obtained.

According to the present invention, tetracarboxylic acid dianhydπde is used m an amount of 1 to 100 mol % compared to the total amount of acid dianhydride . Monomers of tetracarboxylic acid dianhydride are selected from tπcarboxycyclopentylacetic acid anhydride (TCA-AH), 5- (2, 5- dioxotetrahydrofuryl) -3-methylcyclohexane-l, 2-dicarboxylic acid dianhydride (DOCDA), 4- (2 , 5-dioxotetrahydrofuryl-3 -yl) - tetralm-1, 2-dicarboxylic acid dianhydride (DOTDA), 1,2,3,4- cyclobutane tetracarboxylic acid dianhydride (CBDA), 1,3- dimethyl-1, 2, 3 , 4 -cyclobutane tetracarboxylic acid dianhydride

(DM-CBDA), 1, 2, 3 , 4-cyclopentane tetracarboxylic acid dianhydride (CPDA), bicycloocten-2 , 3 , 5 , 6 -tetracarboxylic acid dianhydride (BODA) , pyromellitic acid dianhydride (PMDA) , benzophenonetetracarboxylic acid dianhydride, oxydiphthalic acid dianhydride, biphthalic acid dianhydride (BPDA) and hexafluoroisopropylidene diphthalic acid dianhydride, etc., but not limited thereto. When the aromatic diamine compound

(g) , that is represented by chemical formula 1 described above, is used m an amount of 1 to 100 mol % compared to the total amount of diamine compound, a material which can fully exhibit the physical properties aimed in the present invention can be characteristically obtained

The polyamic acid derivative which is produced by using the aromatic diamine compound (g) of chemical formula 1 described above as an essential monomer is a novel compound that had never been synthesized before. By having a photoreactive aromatic side group, the polyamic acid derivative has high photo-alignment property at long wavelength and low luminous quantity, and improved transparency, pπntability, and mechanical properties. In particular, it is a novel polymer composition which can be used to provide a liquid crystal cell having improved pretilt angles and electro-optical properties.

The polyamic acid derivative according to the present invention has characteristics as follows: weight average molecular weight (Mw) of 10,000 ~ 500,000 g/mol, intrinsic viscosity of 0.3 ~ 2.0 dL/g, glass transition temperature of 200 ~ 400 °C and imidation temperature of 200 - 350 ^°C Moreover, the polyamic acid derivative according to the present invention is characterized m that at room temperature it is easily soluble m a non-protic solvent such as dimethylacetamide (DMAc) , dimethylformamide (DMF) , N-methyl-2- pyrrolidone (NMP) , acetone and ethyl acetate (EA) and an organic solvent such as meta-cresol (m-cresol) , etc. In particular, even for a low absorptive solvent such as tetrahydrofuran (THF) and gamma-butyrolactone (GBL), etc., it has high solubility of 10 weight % or more at room temperature. In addition, it also has high solubility in a mixture of the solvents described above.

Even for a mixture comprising various polyamic acid derivatives having the above-described physical properties, it is possible that the physical properties desired in the present invention can be obtained.

In addition, when the liquid crystal cell comprising the photo-alignment layers that are produced by illumination of the above-described polyamic acid with polarized UV light of 300 ~ 460 nm wavelength and 100 ~ 1000 mJ/cm² intensity was evaluated in terms of electro-optical property, it is found that the pretilt angles are in the range of 0.01 ~ 2.0°and VHR is in the range of 99.0 ~ 99.5% at the voltage of 3V at 25 ^°C

Because the polyamic acid according to the present invention has excellent solubility and liquid crystal alignment property, etc. while maintaining the excellent properties of conventional polyimide resin, it can be used as a core heat-resistant material for a high-tech industry including various electric, electronic, space and aeronautical field.

[Brief Description of Drawings] Figure 1 is a ¹H NMR spectrum of DA-I that is prepared according to Preparation example 1.

Figure 2 is a ¹H NMR spectrum of DA-2 that is prepared according to Preparation example 2.

Figure 3 is a ¹H NMR spectrum of DA- 3 that is prepared according to Preparation example 3.

Figure 4 is a ¹H NMR spectrum of DA-4 that is prepared according to Preparation example 4.

Figure 5 is a ¹H NMR spectrum of CBDA that is prepared according to Preparation example 5.

Figure 6 is a ¹H NMR spectrum of DM-CBDA that is prepared according to Preparation example 6.

Figure 7 is a ¹H NMR spectrum of PAA-I that is prepared according to Example 1.

[Best Mode]

Hereinafter, the present invention is described in more detail based on the preparation examples and the examples. But, these examples are not intended to limit the scope of the present invention.

[Preparation example 1-4] Preparation of aromatic diamines having a photoreactive aromatic side group

[Preparation example 1] Preparation of 3-biphenyl-4-yl-acrylic acid 3 , 5-diamino-benzyl ester (DA-I) (1) To a 25OmL round-bottomed flask equipped with a heating reflux condenser, 2g of biphenyl-4-carbaldehyde was added and dissolved in 100ml benzene, followed by the addition of 4.2g of (carbethoxymethylene) -triphenylphosphorane. The mixture was refluxed with stirring at 80^°Cfor 8 hours. After cooling the reaction mixture to the room temperature, polar solvent within benzene was removed by using an excess amount of saturated brine. The solution which had been finally dehydrated with anhydrous magnesium sulfate was concentrated under reduced pressure to give a reaction product comprising a trace amount of impurities . With subsequent purification by silica-gel column chromatography (EA (ethyl acetate) : Hx (hexane) = 1:4), a white solid was obtained.

(2) To a 25OmL round-bottomed flask, 4.55g of 3-biphenyl- 4-yl-acrylic acid ethyl ester was added and dissolved in 100ml mixture solvent comprising THF/ EtOH/ H₂O (volume ratio; 1/1/1) , followed by the addition of 5g of lithium hydroxide. The mixture was stirred for 2 hours. The reaction mixture was then titrated with hydrogen chloride for neutralization, and the precipitate was filtered and dried to obtain the white compound of 3-biphenyl-4-yl-acrylic acid.

(3) To a 50OmL round-bottomed flask, 2g of 3-biphenyl-4- yl-acrylic acid was added and dissolved in 200ml metacresol, followed by the addition of 2ml of oxalyl chloride and stirring of the mixture. Then, two or three drops of dimethylformamide were added thereto and the mixture was stirred for 2 hours at room temperature. The reaction mixture was concentrated under reduced pressure to remove volatile compounds. As a result, the yellow compound of 3-biphenyl-4- yl-acryloyl chloride was obtained.

(4) To a 50OmL round-bottomed flask equipped with an ice bath, 3.02g of di- tert-butyl 5- (hydroxy methyl) -1,3- phenylenedicarbamate was added and dissolved in 250ml metacresol, followed by the addition of 2.Og of 3-biphenyl-4- yl-acryloyl chloride and stirring. Then, 1. Ig of triethylamme was slowly added to the mixture at 0 ^°C the temperature was gradually increased to room temperature, and the mixture was continuously stirred for 12 hours. Polar solvent within benzene was removed by treating the reaction mixture with an excess amount of saturated brine. The solution which had been finally dehydrated with anhydrous magnesium sulfate was concentrated under reduced pressure to give a reaction product comprising a trace amount of impurities. With subsequent purification by silica-gel column chromatography (EA:Hx=l:4), a white solid was obtained.

(5) To a 50OmL round-bottomed flask, 4.5g of 3-biphenyl- 4-yl-acrylic acid 3 , 5-bis- tert-butoxycarbonylamino-benzyl ester was added and dissolved in 200ml metacresol, followed by the addition of lOOral of trifluoroacetic acid and stirring at room temperature for 4 hours . The reaction mixture was concentrated under reduced pressure to remove volatile compounds and then diluted with 250ml metacresol. Thus- obtained diluted reaction mixture was neutralized with sodium hydrogen carbonate and polar solvent within metacresol was removed by using an excess amount of saturated brine. The solution which had been finally dehydrated with anhydrous magnesium sulfate was concentrated under reduced pressure to give a reaction product comprising a trace amount of impurities. With subsequent purification by silica-gel column chromatography (EA:Hx=3:2), the yellow compound of 3-biphenyl- 4-yl-acrylic acid 3 , 5-diamino-benzyl ester (DA-I) was obtained. Figure 1 is a NMR spectrum of DA-I.

[Preparation example 2] Preparation of 3-naphthalen-l-yl- acrylic acid 3 , 5-diamino-benzyl ester (DA-2)

(1) To a 50OmL round-bottomed flask, 2g of 3 -naphthalene- 1-yl acrylic acid was added and dissolved in 200ml metacresol, followed by the addition of 2ml of oxalyl chloride and stirring of the mixture. Then, two or three drops of N, N- dimethylformamide (DMF) were added thereto and the mixture was stirred for 2 hours at room temperature. The reaction mixture was concentrated under reduced pressure to remove volatile compounds. As a result, the yellow compound of 3-naphthalen-l- yl-acryloyl chloride was obtained.

(2) To a 50OmL round-bottomed flask equipped with an ice bath, 6g of di-tert-butyl 5- (hydroxy methyl) -1, 3 -phenylene dicarbamate was added and dissolved in 250ml metacresol, followed by the addition of 2.01g of 3-naphthalen-l-yl- acryloyl chloride and stirring. Then, 1.51g of triethylamine was slowly added to the mixture at 0 ^°Q the temperature was gradually increased to room temperature and the mixture was continuously stirred for 12 hours. Polar solvent within metacresol was removed by treating the reaction mixture with an excess amount of saturated brine. The solution which had been finally dehydrated with anhydrous magnesium sulfate was concentrated under reduced pressure to give a reaction product comprising a trace amount of impurities. With subsequent purification by silica-gel column chromatography (EA: Hx=I : 4) , a white solid was obtained.

(3) To a 50OmL round-bottomed flask, 6g of 3-naphthalen- 1-yl-acrylic acid 3 , 5-bis-tert-butoxycarbonyl amino benzyl ester was added and dissolved m 200ml metacresol, followed by the addition of 100ml of trifluoroacetic acid and stirring at room temperature for 4 hours . The reaction mixture was concentrated under reduced pressure to remove volatile compounds and then diluted with 250ml metacresol. Thus- obtained diluted reaction mixture was neutralized with sodium hydrogen carbonate and polar solvent within metacroesol was removed by using an excess amount of saturated brine. The solution which had been finally dehydrated with anhydrous magnesium sulfate was concentrated under reduced pressure to give a reaction product comprising a trace amount of impurities. With subsequent purification by silica-gel column chromatography (EA:Hx=3:2), the yellow compound of 3- naphthalen-2-yl-acrylic acid 3 , 5-diamino-benzyl ester (DA-2) was obtained. Figure 2 is a NMR spectrum of DA-2.

[Preparation example 3] Preparation of 3-naphthalen-l-yl- acrylic acid 3 - (3 , 5 -diamino-phenyl) -propyl ester (DA-3)

(1) To a 10OmL round-bottomed flask equipped with a heating reflux condenser, 2g of di-tert-butyl 5- (hydroxymethyl) -1 , 3-phenylenedicarbamate was added and dissolved in 20ml benzene, followed by the addition of 1.23g of MnO₂ as a catalyst. The mixture was refluxed with stirring at 80 ^"C for 6 hours. After cooling to the room temperature, the mixture was filtered through celite filter and concentrated. A white solid was obtained by subsequent solidification using ether . (2) To a 10OmL round-bottomed flask equipped wxth a heating reflux condenser, 1.8g of (3-tert-butoxy carbonylammo- 5 - formyl-phenyl) -carbamic acid tert-butyl ester was added and dissolved in 30ml benzene, followed by the addition of 2.16 g of (carbethoxymethylene) - triphenylphosphorane . The mixture was refluxed under stirring for 24 hours at 90 ^°C After cooling to room temperature, the reaction mixture was concentrated under reduced pressure to remove volatile compounds. With subsequent purification by silica-gel column chromatography (EA:Hx=l:2), a white solid compound was obtained.

(3) To a hydrogenation reactor, 40ml of ethanol was added, 2.12 g of 3- (3 , 5-bis-tert-butoxycarbonyl amino-phenyl) -acrylic acid ethyl ester was dissolved therein, and 0.5g of Pd/C as a catalyst (10%) was added. The reduction was carried out at the pressure of 3.5 atm for 5 to 6 hours. After removing Pd/C using a membrane filter, the reaction mixture was concentrated under reduced pressure to obtain a white solid.

(4) To a 10OmL round-bottomed flask equipped with an ice bath, 2g of 3 - (3 , 5-bis-tert-butoxy carbonylamino-phenyl) - acrylic acid ethyl ester was added and dissolved in 30ml THF, followed by the slow addition of 0.39g of lithium aluminum hydroxide at 0 ^°C The mixture was stirred at for 5 hours. After cooling the reaction mixture by slowly adding methanol until no gas is generated, the mixture was added to 30ml of ethyl ether. Then a small amount of brine (i.e., ImI) was added thereto and the mixture was stirred for 1 hour. The solution which had been finally dehydrated with anhydrous magnesium sulfate was concentrated under reduced pressure. With subsequent purification by silica-gel column chromatography (EA:Hx=l : 4) , a white solid was obtained.

(5) To a 10OmL round-bottomed flask equipped with an ice bath, 0.51g of [3 -tert-butoxycarbonyl amino-5- (3 -hydroxy- propyl) -phenyl] -carbamic acid tert-butyl ester was added and dissolved in 30ml metacresol, followed by the addition of 0.78g of 3 -naphthalen-1-yl-acryloyl chloride and stirring. Then, 0.477g of triethylamine was slowly added to the mixture at 0 ^°Q the temperature was gradually increased to room temperature and the mixture was continuously stirred for 12 hours. Polar solvent within metacresol was removed by treating the reaction mixture with an excess amount of saturated brine. The solution which had been finally dehydrated with anhydrous magnesium sulfate was concentrated under reduced pressure to give a reaction product comprising a trace amount of impurities. With subsequent purification by silica-gel column chromatography (EA: Hx=I : 4 ) , a white solid was obtained. (6) To a 10OmL round-bottomed flask, 0.65g of 3- naphthalen-1-yl-acrylic acid 3- (3 , 5-bis- tert-butoxycarbonyl amino-phenyl) -propyl ester was added and dissolved in 50ml metacresol, followed by the addition of 20ml of trifluoroacetic acid and stirring at room temperature for 4 hours . The reaction mixture was concentrated under reduced pressure to remove volatile compounds and then diluted with 50ml metacresol. Thus-obtained diluted reaction mixture was neutralized with sodium hydrogen carbonate and polar solvent within metacroesol was removed by using an excess amount of saturated brine. The solution which had been finally dehydrated with anhydrous magnesium sulfate was concentrated under reduced pressure to give a reaction product comprising a trace amount of impurities. With subsequent purification by silica-gel column chromatography (EA:Hx=3:2), liquid-phase yellow compound of 3 -naphthalen-1-yl-acrylic acid 3- (3,5- diamino-phenyl) -propyl ester (DA-3) was obtained. Figure 3 is a NMR spectrum of DA-3.

[Preparation example 4] Preparation of 3-naphthalen-l-yl- acrylic acid 5- (3 , 5 -diamino-phenyl) -pentyl ester (DA-4)

(1) To a 25OmL round-bottomed flask equipped with a heating reflux condenser, 11.63g of (3-tert-butoxy carbonylamino-5-formyl-phenyl) -carbamic acid tert-butyl ester was added and dissolved in 100ml dried THF, followed by the addxtion of 9.4ml of triethyl 4-phosphonocrotonate and 1.6g of lithium hydroxide. The mixture was refluxed with stirring at 70 "C for 9 hours. After cooling to the room temperature, the reaction mixture was filtered through celite and the filtrate was concentrated under reduced pressure. With subsequent purification by silica-gel column chromatography (EA:Hx=l:4) of the concentrated mixture, a yellow solid compound was obtained.

(2) To a hydrogenation reactor, 100ml of ethanol was added, 14.6 g of 5- (3 , 5-bis- tert-butoxycarbonyl amino-phenyl) - penta-2 , 4 -dienoic acid ethyl ester was dissolved therein, and Ig of Pd/C as a catalyst (10%) was added. The reduction was carried out at the pressure of 3.5 atm for 5 to 6 hours. After removing Pd/C using a membrane filter, the reaction mixture was concentrated under reduced pressure to obtain a white solid .

(3) To a 50OmL round-bottomed flask equipped with an ice bath, 14.9g of 5- (3 , 5-bis- tert-butoxy carbonylammo-phenyl) 1- acrylic acid ethyl ester was added and dissolved in 200ml THF, followed by the slow addition of 3.4g of lithium aluminum hydride 0 ^°C The mixture was stirred at for 5 hours. After cooling the reaction mixture by slowly adding methanol until no gas is generated, the mixture was added to 150ml of ethyl ether. Then a small amount of brine (i.e., 2ml) was added thereto and the mixture was stirred for 1 hour. The solution which had been finally dehydrated with anhydrous magnesium sulfate was concentrated under reduced pressure. With subsequent purification by silica-gel column chromatography (EA:Hx=l:4), a white solid was obtained.

(4) To a 50OmL round-bottomed flask equipped with an ice bath, 11.58g of [3 - tert-Butoxycarboylamino-5- (5-hydroxy- propyl) -phenyl] -carbamic acid tert-butyl ester was added and dissolved in 250ml metacresol, followed by the addition of 10.81g of 3-naphthalen-l-yl-acryloyl chloride and stirring. Then, 8.2ml of triethylamine was slowly added to the mixture at 0 ^"C , the temperature was gradually increased to room temperature and the mixture was continuously stirred for 12 hours . Polar solvent within metacresol was removed by treating the reaction mixture with an excess amount of saturated brine. The solution which had been finally dehydrated with anhydrous magnesium sulfate was concentrated under reduced pressure to give a reaction product comprising a trace amount of impurities. With subsequent purification by silica-gel column chromatography (EA:Hx=l:4), a white solid was obtained.

(5) To a 50OmL round-bottomed flask, 14.6g of 3- naphthalen-1-yl-acrylic acid 5- (3 , 5-bis- tert-butoxycarbonyl amino-phenyl) -propyl ester was added and dissolved in 200ml metacresol, followed by the addition of 100ml of trifluoroacetic acid and stirring at room temperature for 4 hours. The reaction mixture was concentrated under reduced pressure to remove volatile compounds and then diluted with 200ml metacresol. Thus-obtained diluted reaction mixture was neutralized with sodium hydrogen carbonate and polar solvent within metacroesol was removed by using an excess amount of saturated brine. The solution which had been finally dehydrated with anhydrous magnesium sulfate was concentrated under reduced pressure to give a reaction product comprising a trace amount of impurities. With subsequent purification by silica-gel column chromatography (EA:Hx=3:2), liquid-phase yellow compound of 3 -naphthalen-1-yl-acrylic acid 5- (3,5- diamino-phenyl) -pentyl ester (DA-4) was obtained. Figure 4 is a NMR spectrum of DA-4.

[Comparative preparation example 1] Preparation of 3,5-diamino benzyl cinnamate (DA-5)

(1) To a hydrogenation reactor, 100ml of ethanol was added, 10 g of 3,5-dinitro benzyl alcohol was dissolved therein, and Ig of Pd/C as a catalyst (5%) was added. The reduction was carried out at the pressure of 3.5 atm for 6 hours. After removing Pd/C using a membrane filter, the reaction mixture was concentrated under reduced pressure to obtain a solid, which was then recrystallized with ethanol to give the product.

(2) To a 50OmL round-bottomed flask equipped with an ice bath, 6g of 3,5-diamino benzyl alcohol was added and dissolved in 240ml of a solvent mixture comprising 1 , 4-dioxane/water (H₂O) (volume ratio,- 4/1), followed by the addition of 13.8g of sodium carbonate (Na₂CO₃) and 23.22g of di-tert-butyl dicarbonate (t-BOC) as a catalyst and stirring at 0^°Cfor 5 min. Then, the temperature was gradually increased to room temperature and the mixture was continuously stirred for 7 hours . The reaction mixture was filtered to remove sodium carbonate and to the resultant after the concentration under reduced pressure 200ml of ethyl acetate was added for dilution. Polar solvent within ethyl acetate was removed by treating the reaction mixture with an excess amount of saturated brine. The solution which had been finally dehydrated with anhydrous magnesium sulfate (MgSO₄) was concentrated under reduced pressure to give a reaction product comprising a trace amount of impurities. With subsequent recrystallization in ethyl acetate, a white solid was obtained.

(3) To a 50OmL round-bottomed flask equipped with an ice bath, 6g of di-tert-butyl 5- (hydroxymethyl) -1, 3-phenylene dicarbamate was added and dissolved in 250ml metacresol, followed by the addition of 3.5g of cinnamoyl chloride and stirring. Then, 4g of triethylamine was slowly added to the mixture at 0 ^°C , the temperature was gradually increased to room temperature and the mixture was continuously stirred for 12 hours . Polar solvent within metacresol was removed by treating the reaction mixture with an excess amount of saturated brine. The solution which had been finally dehydrated with anhydrous magnesium sulfate was concentrated under reduced pressure to give a reaction product comprising a trace amount of impurities. With subsequent purification by silica-gel column chromatography (EA:Hx=l:4), a white solid was obtained.

(4) To a 50OmL round-bottomed flask, 6g of 3 , 5-bis ( tert- butoxycarbonylamino) benzyl cinnamate was added and dissolved in 200ml metacresol, followed by the addition of 100ml of trifluoroacetic acid (CF₃COOH) and stirring at room temperature for 4 hours. The reaction mixture was concentrated under reduced pressure to remove volatile compounds and then diluted with 250ml metacresol. Thus-obtained diluted reaction mixture was neutralized with sodium hydrogen carbonate and polar solvent within metacroesol was removed by using an excess amount of saturated brine. The solution which had been finally dehydrated with anhydrous magnesium sulfate was concentrated under reduced pressure to give a reaction product comprising a trace amount of impurities. With subsequent purification by silica-gel column chromatography (EA:Hx=3:2), yellow colored compound in liquid phase was obtained.

[Preparation example 5-6] Preparation of aliphatic acid dianhydride having an alkyl group (chemical formula 3)

[Chemical formula 3]

[Preparation example 5] Preparation of 1,2,3,4- cyclobutanetetracarboxylic acid dianhydride (CBDA)

To a 2L quartz glass photoreactor equipped with sixteen UV lamps (300nm) , a stirrer and a cooler were attached and 250ml of ethyl acetate and lOOg of maleic anhydride were added thereto followed by stirring for complete mixing. To avoid an excessive temperature increase, an air-cooling type cooler was first run and then UV light was illuminated for a photoreaction for 240 hours with stirring so as not to have the reactants adhered to the reactor walls. As a result, 71 g of white solid was obtained. After the filtration, the white solid was dried for 24 hrs in a vacuum dryer at 60 ^°C Thus- obtained solid was then added to acetic anhydride, dissolved therein and slowly heated to 150 ^°C followed by the reaction for 24 hrs . Hot reaction solution was filtered through a filter paper to remove impurities and kept in a freezer at the temperature of 0 ^°C or less for recrystallization for 24 hours to obtain a yellow solid. Thus-obtained solid was filtered and washed three times with 1,4-dioxane to remove acetic anhydride, and then dried in a vacuum oven at 60^°Cfor 48 hours to obtain 64 g of 1 , 2 , 3 , 4 -cyclobutane tetracarboxylic acid dianhydride (CBDA) . Figure 5 is a ¹H NMR spectrum of said CBDA compound.

[Preparation example 6] Preparation of 1, 3-dimethyl-l, 2 , 3 , 4- cyclobutanetetracarboxylic acid dianhydride (DM-CBDA)

To a 2L quartz glass photoreactor equipped with sixteen UV lamps (300nm) , a stirrer and a cooler were attached and 250ml of ethyl acetate and lOOg of citraconic anhydride were added thereto followed by stirring for complete mixing. To avoid an excessive temperature increase, an air-cooling type cooler was first run and then UV light was illuminated for a photoreaction for 150 hours with stirring so as not to have the reactants adhered to the reactor walls. As a result, 40 g of white solid was obtained. After the filtration, the white solid was dried for 24 hrs in a vacuum dryer at 60 ^°C Thus- obtained solid was then added to acetic anhydride, dissolved therein and slowly heated to 150 °C followed by the reaction for 24 hrs. Hot reaction solution was filtered through a filter paper to remove impurities and kept in a freezer at the temperature of 0 ^°C or less for recrystallization for 24 hours to obtain a yellow solid. Thus-obtained solid was filtered and washed three times with 1,4-dioxane to remove acetic anhydride, and then dried in a vacuum oven at 60^°Cfor 48 hours to obtain 35 g of yellow 1 , 3-dimethyl-1 , 2 , 3 , 4-cyclobutane tetracarboxylic acid dianhydride (DM-CBDA) . Figure 6 is a ¹H NMR spectrum of said DM-CBDA compound.

[Examples 1-16 and Comparative examples 1-6] Production of polyamic acid photo- alignment layers

Polyamic acid photo-alignment layers of Example 1 to 16 and Comparative examples 1 to 6 were produced with the components and mol % described in Table 1 described below. Detailed process for the production is as follows.

[Table 1] Constitution of the polyamic acid monomers

50

[Example 1] Production of polyamic acid photo-alignment layers (PAA-I)

In a 500ml reactor equipped with a stirrer and a nitrogen gas injector, 3.44g (0.01 mole) of DA-I which had been produced in Preparation example 1 was dissolved in N-methyl-2- pyrrolidone under slow nitrogen flushing. Then, 1.96 g (0.01 mole) of solid CBDA, which had been prepared in Preparation example 5, was slowly added thereto under nitrogen flushing. In this case, the solid content was fixed at 15 weight %, and by maintaining the reaction temperature at 0 ^°C or less, the mixture was stirred for 36 hours to obtain a solution of polyamic acid. After having the solution viscosity of thus- obtained polyamic acid solution maintained at 30cp at room temperature, the solution was spin-coated on a ITO glass plate to 0.11 μm thickness. The plate was subjected to thermosetting at the temperatures of 90 ^°C for 2 min and 230 ^°C for 30 min, followed by illumination with polarized UV light having wavelengths of 300-400nm (intensity 200mJ/cm²) to obtain a photo-aligned polyamic acid thin film (PAA-I) . Physical properties of the resulting polyamic acid thin film are summarized in Table 2 described below. Figure 7 is NMR data thereof .

Alternatively, after having the solution viscosity of thus-obtained polyamic acid solution maintained at 30cp at room temperature, it was spin-coated on a ITO glass plate to 0.14μm thickness. The plate was subjected to thermosetting at the temperatures of 230 ^°C for 30 min, followed by illumination with polarized UV light to obtain a liquid crystal cell. Measurement results of pretilt angles and voltage holding ratio (VHR) for the liquid crystal cell are described in Table 3 below. For the illumination, the wavelength of UV light was controlled to be m the range of 300~460nm and in accordance with the illumination amount of 200 ~ 1,000 mJ/cm², homogeneous alignment of the liquid crystals was observed. The liquid crystal used for the test was E-7 by Merck. By inserting a polarization plate between the thin film and the UV lamp, polarized UV light was generated. The polarization plate used has a degree of polarization of 99 % or more and light transparency of 30 + 2%. The alignment state of the liquid crystal was visually observed by using a polarization microscope, and pretilt angles of each liquid crystal cell were determined based on a crystal rotation method. VHR was measured at 25 ^°C at the voltage of 3V.

[Example 2] Production of polyamic acid photo-alignment layers (PAA-2)

In a 500ml reactor equipped with a stirrer and a nitrogen gas injector, 3.18g (0.01 mole) of DA-2 which had been produced m Preparation example 2 was dissolved in N-methyl-2- pyrrolidone under slow nitrogen flushing. Then, 1.96 g (0.01 mole) of solid CBDA, which had been prepared in Preparation example 5, was slowly added thereto under nitrogen flushing. In this case, the solid content was fixed at 15 weight %, and by maintaining the reaction temperature at 0 ^°C or less, the mixture was stirred for 36 hours to obtain a solution of polyamic acid. After having the solution viscosity of thus- obtained polyamic acid solution maintained at 30cp at room temperature, it was spin-coated on a ITO glass plate to 0.11 μm thickness. The plate was subjected to thermosetting at the temperatures of 90 ^°C for 2 min and 230 ^°C for 30 min, followed by an irradiation with polarized UV light having wavelengths of 300-400nm (intensity 200mJ/cm²) to obtain a photo-aligned polyamic acid thin film (PAA-2) . Physical properties of the resulting polyamic acid thin film are summarized in Table 2 described below. Moreover, pretilt angles and VHR data that had been measured under the same condition as Example 1 are respectively summarized in Table 3 described below.

[Example 3] Production of polyamic acid photo-alignment layers (PAA-3)

In a 500ml reactor equipped with a stirrer and a nitrogen gas injector, 3.48g (0.01 mole) of DA-3 which had been produced in Preparation example 3 was dissolved in N-methyl-2- pyrrolidone under slow nitrogen flushing. Then, 1.96 g (0.01 mole) of solid CBDA, which had been prepared in Preparation example 5, was slowly added thereto under nitrogen flushing. In this case, the solid content was fixed at 15 weight %, and by maintaining the reaction temperature at 0 ^°C or less, the mixture was stirred for 36 hours to obtain a solution of polyamic acid. After having the solution viscosity of thus- obtained polyamic acid solution maintained at 30cp at room temperature, it was spin-coated on a ITO glass plate to 0.11 μm thickness. The plate was subjected to thermosetting at the temperatures of 90 ^°C for 2 mm and 230 ^°C for 30 mm, followed by illumination with polarized UV light having wavelengths of 300-400nm (intensity 200mJ/cm²) to obtain a photo-aligned polyamic acid thin film (PAA- 3) Physical properties of the resulting polyamic acid thin film are summarized in Table 2 described below. Moreover, pretilt angles and VHR data that had been measured under the same condition as Example 1 are respectively summarized m Table 3 described below.

[Example 4] Production of polyamic acid photo-alignment layers (PAA-4)

In a 500ml reactor equipped with a stirrer and a nitrogen gas injector, 3.76 g (0.01 mole) of DA-4 which had been produced m Preparation example 4 was dissolved in N-methyl-2- pyrrolidone under slow nitrogen flushing. Then, 1.96 g (0.01 mole) of solid CBDA, which had been prepared m Preparation example 5, was slowly added thereto under nitrogen flushing. In this case, the solid content was fixed at 15 weight %, and by maintaining the reaction temperature at 0 tor less, the mixture was stirred for 36 hours to obtain a solution of polyamic acid. After having the solution viscosity of thus- obtained polyamic acid solution maintained at 30cp at room temperature, it was spin-coated on a ITO glass plate to 0.11 μm thickness. The plate was subjected to thermosetting at the temperatures of 90 ^"C for 2 min and 230 ^°C for 30 min, followed by an irradiation with polarized UV light having wavelengths of 300-400nm (intensity 200mJ/cm²) to obtain a photo-aligned polyamic acid thin film (PAA-4) . Physical properties of the resulting polyamic acid thin film are summarized in Table 2 described below. Moreover, pretilt angles and VHR data that had been measured under the same condition as Example 1 are respectively summarized in Table 3 described below.

[Example 5] Production of polyamic acid photo-alignment layers (PAA-5)

In a 500ml reactor equipped with a stirrer and a nitrogen gas injector, 3.44 g (0.01 mole) of DA-I which had been produced in Preparation example 1 and 1.98 g (0.01 mole) of 4- (4 -aminobenzyl) benzenamine were dissolved in N-methyl-2- pyrrolidone under slow nitrogen flushing. Then, 3.92 g (0.02 mole) of solid CBDA, which had been prepared in Preparation example 5, was slowly added thereto under nitrogen flushing. In this case, the solid content was fixed at 15 weight %, and by maintaining the reaction temperature at 0 ^°C or less, the mixture was stirred for 36 hours to obtain a solution of polyamic acid. After having the solution viscosity of thus- obtained polyamic acid solution maintained at 30cp at room temperature, it was spin-coated on a ITO glass plate to 0.11 μm thickness. The plate was subjected to thermosetting at the temperatures of 90 ^"C for 2 min and 230 ^°C for 30 min, followed by an irradiation with polarized UV light having wavelengths of 300-400nm (intensity 200mJ/cm²) to obtain a photo-aligned polyamic acid thin film (PAA-5) . Physical properties of the resulting polyamic acid thin film are summarized in Table 2 described below. Moreover, pretilt angles and VHR data that had been measured under the same condition as Example 1 are respectively summarized in Table 3 described below.

[Example 6] Production of polyamic acid photo-alignment layers (PAA-6)

In a 500ml reactor equipped with a stirrer and a nitrogen gas injector, 3.18 g (0.01 mole) of DA-2 which had been produced in Preparation example 2 and 1.98 g (0.01 mole) of 4- (4 -aminobenzyl) benzene amine were dissolved in N-methyl-2- pyrrolidone under slow nitrogen flushing. Then, 3.92 g (0.02 mole) of solid CBDA, which had been prepared in Preparation example 5, was slowly added thereto under nitrogen flushing. In this case, the solid content was fixed at 15 weight %, and by maintaining the reaction temperature at 0 ^°C or less, the mixture was stirred for 36 hours to obtain a solution of polyamic acid. After having the solution viscosity of thus- obtained polyamic acid solution maintained at 30cp at room temperature, it was spin-coated on a ITO glass plate to 0.11 μm thickness. The plate was subjected to thermosetting at the temperatures of 90 ^°C for 2 min and 230 ^°C for 30 min, followed by an irradiation with polarized UV light having wavelengths of 300-400nm (intensity 200mJ/cm²) to obtain a photo-aligned polyamic acid thin film (PAA- 6) . Physical properties of the resulting polyamic acid thin film are summarized in Table 2 described below. Moreover, pretilt angles and VHR data that had been measured under the same condition as Example 1 are respectively summarized in Table 3 described below.

[Example 7] Production of polyamic acid photo-alignment layers (PAA-7)

In a 500ml reactor equipped with a stirrer and a nitrogen gas injector, 3.48 g (0.01 mole) of DA-3 which had been produced in Preparation example 3 and 1.98 g (0.01 mole) of 4- (4-aminobenzyl) benzene amine were dissolved in N-methyl-2- pyrrolidone under slow nitrogen flushing. Then, 3.92 g (0.02 mole) of solid CBDA, which had been prepared in Preparation example 5, was slowly added thereto under nitrogen flushing. In this case, the solid content was fixed at 15 weight %, and by maintaining the reaction temperature at 0 ^°C or less, the mixture was stirred for 36 hours to obtain a solution of polyamic acid. After having the solution viscosity of thus- obtained polyamic acid solution maintained at 30cp at room temperature, it was spin-coated on a ITO glass plate to 0.11 /m thickness. The plate was subjected to thermosetting at the temperatures of 90 ^°C for 2 mm and 230 ^°C for 30 min, followed by an irradiation with polarized UV light having wavelengths of 300-400nm (intensity 200mJ/cm²) to obtain a photo-aligned polyamic acid thin film (PAA- 7) . Physical properties of the resulting polyamic acid thin film are summarized in Table 2 described below. Moreover, pretilt angles and VHR data that had been measured under the same condition as Example 1 are respectively summarized m Table 3 described below.

[Example 8] Production of polyamic acid photo-alignment layers (PAA- 8)

In a 500ml reactor equipped with a stirrer and a nitrogen gas injector, 3.76 g (0.01 mole) of DA-4 which had been produced m Preparation example 4 and 1.98 g (0.01 mole) of 4- (4-ammobenzyl) benzenamme were dissolved in N-methyl-2- pyrrolidone under slow nitrogen flushing. Then, 3.92 g (0.02 mole) of solid CBDA, which had been prepared in Preparation example 5, was slowly added thereto under nitrogen flushing. In this case, the solid content was fixed at 15 weight %, and by maintaining the reaction temperature at 0 ^°C or less, the mixture was stirred for 36 hours to obtain a solution of polyamic acid. After having the solution viscosity of thus- obtained polyamic acid solution maintained at 30cp at room temperature, it was spin-coated on a ITO glass plate to 0.11 [M thickness. The plate was subjected to thermosetting at the temperatures of 90 ^°C for 2 min and 230 ^°C for 30 mm, followed by illumination with polarized UV light having wavelengths of 300-400nm (intensity 200mJ/cm²) to obtain a photo-aligned polyamic acid thin film (PAA- 8) . Physical properties of the resulting polyamic acid thin film are summarized in Table 2 described below. Moreover, pretilt angles and VHR data that had been measured under the same condition as Example 1 are respectively summarized in Table 3 described below.

[Example 9] Production of polyamic acid photo-alignment layers (PAA-9)

In a 500ml reactor equipped with a stirrer and a nitrogen gas injector, 3.44 g (0.01 mole) of DA-I which had been produced m Preparation example 1 was dissolved m N-methyl-2- pyrrolidone under slow nitrogen flushing. Then, 2.24 g (0.01 mole) of solid DM-CBDA, which had been prepared in Preparation example 6, was slowly added thereto under nitrogen flushing. In this case, the solid content was fixed at 15 weight %, and by maintaining the reaction temperature at 0 ^°C or less, the mixture was stirred for 36 hours to obtain a solution of polyamic acid. After having the solution viscosity of thus- obtained polyamic acid solution maintained at 30cp at room temperature, it was spin-coated on a ITO glass plate to 0.11 μm thickness. The plate was subjected to thermosetting at the temperatures of 90 ^°Cfor 2 min and 230 ^°C for 30 min, followed by an irradiation with polarized UV light having wavelengths of 300-400nm (intensity 200mJ/cm²) to obtain a photo-aligned polyamic acid thin film (PAA-9) . Physical properties of the resulting polyamic acid thin film are summarized in Table 2 described below. Moreover, pretilt angles and VHR data that had been measured under the same condition as Example 1 are respectively summarized in Table 3 described below.

[Example 103 Production of polyamic acid photo-alignment layers (PAA-10)

In a 500ml reactor equipped with a stirrer and a nitrogen gas injector, 3.18 g (0.01 mole) of DA-2 which had been produced in Preparation example 2 was dissolved in N-methyl-2- pyrrolidone under slow nitrogen flushing. Then, 2.24 g (0.01 mole) of solid DM-CBDA, which had been prepared in Preparation example 6, was slowly added thereto under nitrogen flushing. In this case, the solid content was fixed at 15 weight %, and by maintaining the reaction temperature at 0 ^°C or less, the mixture was stirred for 36 hours to obtain a solution of polyamic acid. After having the solution viscosity of thus- obtained polyamic acid solution maintained at 30cp at room temperature, it was spin-coated on a ITO glass plate to 0.11 μm thickness. The plate was subjected to thermosetting at the temperatures of 90 ^°C for 2 min and 230 ^°C for 30 min, followed by an irradiation with polarized UV light having wavelengths of 300-400nm (intensity 200mJ/cm²) to obtain a photo-aligned polyamic acid thin film (PAA-10) . Physical properties of the resulting polyamic acid thin film are summarized in Table 2 described below. Moreover, pretilt angles and VHR data that had been measured under the same condition as Example 1 are respectively summarized in Table 3 described below.

[Example 11] Production of polyamic acid photo-alignment layers (PAA-Il)

In a 500ml reactor equipped with a stirrer and a nitrogen gas injector, 3.44 g (0.01 mole) of DA-I which had been produced in Preparation example 1 and 1.98 g (0.01 mole) of 4- (4 -aminobenzyl) benzenamine were dissolved in N-methyl-2- pyrrolidone under slow nitrogen flushing. Then, 4.48 g (0.02 mole) of solid DM-CBDA, which had been prepared in Preparation example 6, was slowly added thereto under nitrogen flushing. In this case, the solid content was fixed at 15 weight %, and by maintaining the reaction temperature at 0 °C or less, the mixture was stirred for 36 hours to obtain a solution of polyamic acid. After having the solution viscosity of thus- obtained polyamic acid solution maintained at 30cp at room temperature, it was spin-coated on a ITO glass plate to 0.11 μm thickness. The plate was subjected to thermosetting at the temperatures of 90 "C for 2 mm and 230 ^°C for 30 min, followed by an irradiation with polarized UV light having wavelengths of 300-400nm (intensity 200mJ/cm²) to obtain a photo-aligned polyamic acid thin film (PAA-Il) . Physical properties of the resulting polyamic acid thin film are summarized in Table 2 described below. Moreover, pretilt angles and VHR data that had been measured under the same condition as Example 1 are respectively summarized m Table 3 described below.

[Example 12] Production of polyamic acid photo-alignment layers (PAA- 12)

In a 500ml reactor equipped with a stirrer and a nitrogen gas injector, 3.18 g (0.01 mole) of DA-2 which had been produced m Preparation example 2 and 1.98 g (0.01 mole) of 4- (4-ammobenzyl) benzenamme were dissolved m N-methyl-2- pyrrolidone under slow nitrogen flushing. Then, 4.48 g (0.02 mole) of solid DM-CBDA, which had been prepared in Preparation example 6, was slowly added thereto under nitrogen flushing. In this case, the solid content was fixed at 15 weight %, and by maintaining the reaction temperature at 0 ^°C or less, the mixture was stirred for 36 hours to obtain a solution of polyamic acid. After having the solution viscosity of thus- obtained polyamic acid solution maintained at 30cp at room temperature, it was spin-coated on a ITO glass plate to 0.11 μm thickness. The plate was subjected to thermosetting at the temperatures of 90^°Cfor 2 min and 230 ^°C for 30 min, followed by an irradiation with polarized UV light having wavelengths of 300-400nm (intensity 200mJ/cm²) to obtain a photo-aligned polyamic acid thin film (PAA-12) . Physical properties of the resulting polyamic acid thin film are summarized in Table 2 described below. Moreover, pretilt angles and VHR data that had been measured under the same condition as Example 1 are respectively summarized in Table 3 described below.

[Example 13] Production of polyamic acid photo-alignment layers (PAA- 13)

In a 500ml reactor equipped with a stirrer and a nitrogen gas injector, 3.48 g (0.01 mole) of DA-3 which had been produced in Preparation example 3 was dissolved in N-methyl-2- pyrrolidone under slow nitrogen flushing. Then, 2.24 g (0.01 mole) of solid DM-CBDA, which had been prepared in Preparation example 6, was slowly added thereto under nitrogen flushing. In this case, the solid content was fixed at 15 weight %, and by maintaining the reaction temperature at 0 ^°C or less, the mixture was stirred for 36 hours to obtain a solution of polyamic acid. After having the solution viscosity of thus- obtained polyamic acid solution maintained at 30cp at room temperature, it was spin-coated on a ITO glass plate to 0.11 /m thickness. The plate was subjected to thermosetting at the temperatures of 90 ^°C for 2 min and 230 ^°C for 30 min, followed by an irradiation with polarized UV light having wavelengths of 300-400nm (intensity 200mJ/cm²) to obtain a photo-aligned polyamic acid thin film (PAA-13) . Physical properties of the resulting polyamic acid thin film are summarized in Table 2 described below. Moreover, pretilt angles and VHR data that had been measured under the same condition as Example 1 are respectively summarized in Table 3 described below.

[Example 14] Production of polyamic acid photo-alignment layers (PAA-14)

In a 500ml reactor equipped with a stirrer and a nitrogen gas injector, 3.76 g (0.01 mole) of DA-4 which had been produced in Preparation example 4 was dissolved in N-methyl-2- pyrrolidone under slow nitrogen flushing. Then, 2.24 g (0.01 mole) of solid DM-CBDA, which had been prepared in Preparation example 6, was slowly added thereto under nitrogen flushing. In this case, the solid content was fixed at 15 weight %, and by maintaining the reaction temperature at 0 ^°C or less, the mixture was stirred for 36 hours to obtain a solution of polyamic acid. After having the solution viscosity of thus- obtained polyamic acid solution maintained at 30cp at room temperature, it was spin-coated on a ITO glass plate to 0.11 μm thickness. The plate was subjected to thermosetting at the temperatures of 90^°Cfor 2 min and 230 ^°C for 30 min, followed by an irradiation with polarized UV light having wavelengths of 300-400nm (intensity 200mJ/cm²) to obtain a photo-aligned polyamic acid thin film (PAA- 14) . Physical properties of the resulting polyamic acid thin film are summarized in Table 2 described below. Moreover, pretilt angles and VHR data that had been measured under the same condition as Example 1 are respectively summarized in Table 3 described below.

[Example 15] Production of polyamic acid photo-alignment layers (PAA-15)

In a 500ml reactor equipped with a stirrer and a nitrogen gas injector, 3.48 g (0.01 mole) of DA-3 which had been produced in Preparation example 3 and 1.98 g (0.01 mole) of 4- (4-aminobenzyl) benzenamine were dissolved in N-methyl-2- pyrrolidone under slow nitrogen flushing. Then, 4.48 g (0.02 mole) of solid DM-CBDA, which had been prepared in Preparation example 6, was slowly added thereto under nitrogen flushing. In this case, the solid content was fixed at 15 weight %, and by maintaining the reaction temperature at 0 °C or less, the mixture was stirred for 36 hours to obtain a solution of polyamic acid. After having the solution viscosity of thus- obtained polyamic acid solution maintained at 30cp at room temperature, it was spin-coated on a ITO glass plate to 0.11 μm thickness. The plate was subjected to thermosetting at the temperatures of 90 ^°C for 2 min and 230 ^°C for 30 tnin, followed by an irradiation with polarized UV light having wavelengths of 300-400nm (intensity 200mJ/cm²) to obtain a photo-aligned polyamic acid thin film (PAA- 15) . Physical properties of the resulting polyamic acid thin film are summarized in Table 2 described below. Moreover, pretilt angles and VHR data that had been measured under the same condition as Example 1 are respectively summarized in Table 3 described below.

[Example 16] Production of polyamic acid photo-alignment layers (PAA-16)

In a 500ml reactor equipped with a stirrer and a nitrogen gas injector, 3.76 g (0.01 mole) of DA-4 which had been produced in Preparation example 4 and 1.98 g (0.01 mole) of 4- (4-aminobenzyl) benzenamine were dissolved in N-methyl-2- pyrrolidone under slow nitrogen flushing. Then, 4.48 g (0.02 mole) of solid DM-CBDA, which had been prepared in Preparation example 6, was slowly added thereto under nitrogen flushing. In this case, the solid content was fixed at 15 weight %, and by maintaining the reaction temperature at 0 ^°C or less, the mixture was stirred for 36 hours to obtain a solution of polyamic acid. After having the solution viscosity of thus- obtained polyamic acid solution maintained at 30cp at room temperature, it was spin-coated on a ITO glass plate to 0.11 μni thickness. The plate was subjected to thermosetting at the temperatures of 90^°Cfor 2 min and 230 ^°C for 30 min, followed by an irradiation with polarized UV light having wavelengths of 300-400nm (intensity 200mJ/cm²) to obtain a photo-aligned polyamic acid thin film (PAA- 16) . Physical properties of the resulting polyamic acid thin film are summarized in Table 2 described below. Moreover, pretilt angles and VHR data that had been measured under the same condition as Example 1 are respectively summarized in Table 3 described below.

[Comparative example 1] Production of polyamic acid photo- alignment layers (PAA- 17)

In a 500ml reactor equipped with a stirrer and a nitrogen gas injector, 2.68 g (0.01 mole) of DA-5 which had been produced in Comparative preparation example 1 was dissolved in N-methyl-2 -pyrrolidone under slow nitrogen flushing. Then, 1.96 g (0.01 mole) of solid CBDA, which had been prepared in Preparation example 5, was slowly added thereto under nitrogen flushing. In this case, the solid content was fixed at 15 weight %, and by maintaining the reaction temperature at 0 ^°C or less, the mixture was stirred for 36 hours to obtain a solution of polyamic acid. After having the solution viscosity of thus-obtained polyamic acid solution maintained at 30cp at room temperature, it was spin-coated on a ITO glass plate to 0.11 μm thickness. The plate was subjected to thermosetting at the temperatures of 90 ^°C for 2 min and 230 ^°C for 30 min, followed by illumination with polarized UV light having wavelengths of 300-400nm (intensity 600mJ/cm²) to obtain a photo-aligned polyamic acid thin film (PAA- 17) . Physical properties of the resulting polyamic acid thin film are summarized in Table 2 described below. Moreover, pretilt angles and VHR data that had been measured under the same condition as Example 1 are respectively summarized in Table 3 described below.

[Comparative example 2] Production of polyamic acid photo- alignment layers (PAA-18)

In a 500ml reactor equipped with a stirrer and a nitrogen gas injector, 2.68 g (0.01 mole) of DA-5 which had been produced in Comparative preparation example 1 and 1.98 g (0.01 mole) of 4 - (4 -aminobenzyl) benzenamine were dissolved in N- methyl-2-pyrrolidone under slow nitrogen flushing. Then, 3.92 g (0.02 mole) of solid CBDA, which had been prepared in Preparation example 5, was slowly added thereto under nitrogen flushing. In this case, the solid content was fixed at 15 weight %, and by maintaining the reaction temperature at 0 ^°C or less, the mixture was stirred for 36 hours to obtain a solution of polyamic acid. After having the solution viscosity of thus-obtained polyamic acid solution maintained at 30cp at room temperature, it was spin-coated on a ITO glass plate to 0.11 μm thickness. The plate was subjected to thermosetting at the temperatures of 90 ^°C for 2 min and 230 ^°C for 30 min, followed by an irradiation with polarized UV light having wavelengths of 300-400nm (intensity 600mJ/cm²) to obtain a photo-aligned polyamic acid thin film (PAA-18) . Physical properties of the resulting polyamic acid thin film are summarized in Table 2 described below. Moreover, pretilt angles and VHR data that had been measured under the same condition as Example 1 are respectively summarized in Table 3 described below.

[Comparative example 3] Production of polyamic acid photo- alignment layers (PAA-19)

In a 500ml reactor equipped with a stirrer and a nitrogen gas injector, 1.08 g (0.01 mole) of benzene-1, 4 -diamine was dissolved in N-methyl-2-pyrrolidone under slow nitrogen flushing. Then, 1.96 g (0.01 mole) of CBDA, which had been prepared in Preparation example 5, was slowly added thereto under nitrogen flushing. In this case, the solid content was fixed at 15 weight %, and by maintaining the reaction temperature at 0 ^°C or less, the mixture was stirred for 36 hours to obtain a solution of polyamic acid. After having the solution viscosity of thus-obtained polyamic acid solution maintained at 30cp at room temperature, it was spin-coated on a ITO glass plate to 0.11 μm thickness. The plate was subjected to thermosetting at the temperatures of 90 ^°C for 2 mm and 230 ^°C for 30 mm, followed by an irradiation with polarized UV light having wavelengths of 300-400nm (intensity l,500mJ/cm²) to obtain a photo-aligned polyamic acid thin film (PAA- 19) . Physical properties of the resulting polyamic acid thin film are summarized m Table 2 described below. Moreover, pretilt angles and VHR data that had been measured under the same condition as Example 1 are respectively summarized in Table 3 described below.

[Comparative example 4] Production of polyamic acid photo- alignment layers (PAA-20)

In a 500ml reactor equipped with a stirrer and a nitrogen gas injector, 1.08 g (0.01 mole) of benzene-1 , 3 -diamine was dissolved m N-methyl-2-pyrrolidone under slow nitrogen flushing. Then, 1.96 g (0.01 mole) of solid CBDA, which had been prepared m Preparation example 5, was slowly added thereto under nitrogen flushing. In this case, the solid content was fixed at 15 weight %, and by maintaining the reaction temperature at 0 ^°C or less, the mixture was stirred for 36 hours to obtain a solution of polyamic acid. After having the solution viscosity of thus-obtained polyamic acid solution maintained at 30cp at room temperature, it was spin- coated on a ITO glass plate to 0.11 fm thickness. The plate was subjected to thermosetting at the temperatures of 90^°Cfor 2 min and 230 ^°C for 30 min, followed by illumination with polarized UV light having wavelengths of 300-400nm (intensity l,500mJ/cm²) to obtain a photo-aligned polyamic acid thin film (PAA-20) . Physical properties of the resulting polyamic acid thin film are summarized in Table 2 described below. Moreover, pretilt angles and VHR data that had been measured under the same condition as Example 1 are respectively summarized in Table 3 described below.

[Comparative example 5] Production of polyamic acid photo- alignment layers (PAA-21)

In a 500ml reactor equipped with a stirrer and a nitrogen gas injector, 2.00 g (0.01 mole) of 4- (4- aminophenoxy) benzenamine was dissolved in N-methyl-2- pyrrolidone under slow nitrogen flushing. Then, 1.96 g (0.01 mole) of solid CBDA, which had been prepared in Preparation example 5, was slowly added thereto under nitrogen flushing. In this case, the solid content was fixed at 15 weight %, and by maintaining the reaction temperature at 0 ^°C or less, the mixture was stirred for 36 hours to obtain a solution of polyamic acid. After having the solution viscosity of thus- obtained polyamic acid solution maintained at 30cp at room temperature, it was spin-coated on a ITO glass plate to 0.11 μ.m thickness. The plate was subjected to thermosetting at the temperatures of 90 ^"C for 2 min and 230^°Cfor 30 min, followed by an irradiation with polarized UV light having wavelengths of 300-400nm (intensity l,500mJ/cm²) to obtain a photo-aligned polyamic acid thin film (PAA-21) . Physical properties of the resulting polyamic acid thin film are summarized in Table 2 described below. Moreover, pretilt angles and VHR data that had been measured under the same condition as Example 1 are respectively summarized in Table 3 described below.

[Comparative example 6] Production of polyamic acid photo- alignment layers (PAA-22)

In a 500ml reactor equipped with a stirrer and a nitrogen gas injector, 3.34 g (0.01 mole) of 4- (2- (4-aminophenyl) - 1, 1, 1, 3 , 3 , 3-hexafluoropropan-2-yl) benzenamine was dissolved in N-methyl- 2 -pyrrolidone under slow nitrogen flushing. Then, 1.96 g (0.01 mole) of solid CBDA, which had been prepared in Preparation example 5, was slowly added thereto under nitrogen flushing. In this case, the solid content was fixed at 15 weight %, and by maintaining the reaction temperature at 0 ^°C or less, the mixture was stirred for 36 hours to obtain a solution of polyamic acid. After having the solution viscosity of thus-obtained polyamic acid solution maintained at 30cp at room temperature, it was spin-coated on a ITO glass plate to 0.11 /ini thickness. The plate was subjected to thermosetting at the temperatures of 90 ^°C for 2 min and 230 °C for 30 min, followed by an irradiation with polarized UV light having wavelengths of 300-400nm (intensity 1 , 500mJ/cm²) to obtain a photo-aligned polyamic acid thin film (PAA-22) . Physical properties of the resulting polyamic acid thin film are summarized in Table 2 described below. Moreover, pretilt angles and VHR data that had been measured under the same condition as Example 1 are respectively summarized in Table 3 described below.

[Table 2] Characteristic of the photo-alignment layers that are produced from polyamic acid resin

As it is shown in Table 2 above, it was confirmed that the polyamic acid resins according to the present invention have intrinsic viscosity of 0.3 dL/g or more. In addition, it was found that the resins of the present invention have excellent mechanical properties and film formability under solvent casting. As it is shown in the above Table 2, pencil hardness of the polyamic acid thin films comprising a photoreactive aromatic side group, that had been prepared according to Examples 1 to 16, was 4H or more, indicating a significant improvement over the pencil hardness of the thin film produced in Comparative examples 1 to 6 that are related to the polyamic acids without said photoreactive aromatic group.

[Table 3] Characteristic of the liquid crystal cells that are produced from polyamic acid resin

As it is shown in Table 3 above, the liquid crystal cells that had been prepared by using the polyamic acid of the present invention according to Examples 1 to 16 all show an excellent alignment property at low exposure energy of 200 mJ/cm². That is, compared to Comparative examples 3 to 6 wherein aromatic diamines comprising a novel aromatic side group of the present invention are not used, they show an excellent alignment property at low luminous quantity, consequently resulting in excellent VHR and low pretilt angles. Specifically, the pretilt angles were 0.05 - 0.25°or so for Examples 1 to 16, that are lower than those of Comparative examples 1 to 6. In addition, the results indicate that VHR at room temperature is 99% or more.

Taken together, it was confirmed that the liquid crystal cells that had been prepared by using the polyamic acid of the present invention according to Examples 1 to 16 can be suitably used as liquid crystal alignment layers for IPS (in plane switching) -type TFT-TN and STN LCD, which require low pretilt angles and high VHR.

[industrial Applicability]

According to the present invention, liquid crystal alignment layers having a new structure, which have an excellent liquid crystal alignment property, low pretilt angles and an excellent VHR as well as excellent light transmittance, heat-resistance, and mechanical properties, are provided. Thus, they can be suitably used for preparing liquid crystal alignment layers for LCDs of TFT-TN and STN LCD, which require fine electro-optical properties, and as a various high-tech, heat-resistant structured material.

Claims

[CLAIMS]

[Claim l]

Novel aromatic diamine compounds that are represented by the following chemical formula 1. [Chemical formula 1]

R₁, R₇, R₁, R₄ and R₅ are independently to each other a halogen substituted or non-substituted (Cl-ClO) alkyl, a cyano, a nitro, a carboxylic acid, or an aminocarbonyl group; and

when b is 0, A represents

[Claim 2]

A polyamic acid represented by the following chemical formula 2, which comprises as a monomer the aromatic diamines with an aromatic side group represented by the following chemical formula 1. [Chemical formula 1]

[Chemical formula 2]

[In the above chemical formula 1 and 2, a, b, A, R₁, R₂, R_.3 , R₄ and R₅ are identical as those of said claim 1 ; m is an integer from 1 to 500;

βC is a one or two kinds of tetravalent group selected

from a group consisting of

is a chemical bond or a (C1-C2 ) alkylene, -o-

or -°-o-* °- and said alkylene group may be further substituted with a (C1-C5) alkyl group that is either substituted or non- substituted with fluorine ;

Rn, R-_{12 /} Ri₃ and Ri₄ are independently to each other a hydrogen, a (Cl-ClO) alkyl or a phenyl group; and

v-v j__{s a one or two} jζi_ncj_s of divalent group selected from a

group consisting of

[Claim 3]

The polyamic acid of claim 2, wherein said polyamic acid is used for photo-alignment layers. [Claim 4]

The polyamic acid of claim 2, wherein said polyamic acid has intrinsic viscosity of 0.3 ~ 2.0 dL/g and weight average molecular weight (Mw) of 10,000 ~ 500,000 g/mol .

[Claim 5]

The polyamic acid of claim 2, wherein the imidation temperature range of said polyamic acid is 200 ~ 350 ^°C

[Claim β]

The polyamic acid of claim 2, wherein said polyamic acid is soluble in a solvent selected from a group consisting of dimethylacetamide, dimethylformamide, N-methyl-2-pyrrolidone, acetone, ethyl acetate, meta-cresol, tetrahydrofuran and gamma-butyrolactone at room temperature.

[Claim 7]

Photo-alignment layers produced by coating and thermosetting the polyamic acid solution of any one of claims 2 to 6 followed by an irradiation with polarized UV light.

[Claim 8]

The photo-alignment layers of claim 7, wherein the irradiation wavelength of said polarized UV light is 300 ~ 460 nm. [Claim 9]

The photo-alignment layers of claim 8, wherein the the irradiation intensity of said polarized UV light is 100 ~ 1000 mJ/cm². [Claim lθ]

The photo-alignment layers of claim 9, wherein the an irradiation intensity of said polarized UV light is 200 raj/cm². [Claim ll]

The liquid crystal cell comprising the photo-alignment layers according to claim 7.

[Claim 12]

The liquid crystal cell of claim 11, wherein the pretilt angles of said liquid crystal cell are in the range of 0.01 ~ 1.0°.

[Claim 13]

The liquid crystal cell of claim 11, wherein said liquid crystal cell has VHR (voltage holding ratio) of 99.0 ~ 99.5% at the voltage of 3V at 25 ^°C .