KR20070029100A - Polymer for liquid crystal aligning and liquid crystal display using the same - Google Patents

Abstract

A copolymer for liquid crystal aligning and a liquid crystal display using the same are provided to show excellent optical and thermal stability while maintaining superiority in the alignment state of a liquid crystal, and to exhibit no afterimage. The copolymer for liquid crystal aligning is represented by the formula(2), and comprises a photo-reactive group and a symmetrical mesogen group in which the center of gravity is linked to a back-bone of the polymer. In the formula(2), Z is polyimide, polysiloxane, or a cyclic or non-cyclic polymer back-bone comprised of hydrogen and at least one selected from carbon, oxygen and nitrogen, S3 and S4 are a spacer, P2 is a photo-reactive group, M2 is a symmetrical mesogen group, wherein the center of gravity is linked to the back-bone of the polymer, p and q represent a molar fraction of a monomer, 0<p<1 and 0<q<1, and n is a repeating unit, and 10<n<10,000.

Description

Liquid Crystal Alignment Copolymer and Liquid Crystal Display Device Using the Same {POLYMER FOR LIQUID CRYSTAL ALIGNING AND LIQUID CRYSTAL DISPLAY USING THE SAME}

1 is a view showing an alignment state of a liquid crystal cell manufactured using a liquid crystal alignment copolymer according to the present invention.

2 is a view showing the thermal stability of the liquid crystal cell prepared using the liquid crystal alignment copolymer according to the present invention.

3 is a view showing the arrangement and alignment state of the liquid crystal molecules in the liquid crystal cell prepared using the liquid crystal alignment copolymer according to the present invention.

4 is a view showing the residual characteristics of the liquid crystal cell prepared by using the liquid crystal alignment copolymer according to the present invention.

The present invention relates to a liquid crystal alignment copolymer and a liquid crystal display device using the same.

Liquid crystal display (LCD) uses an alignment film. The alignment layer mainly uses a polymer material, and acts as a director in the arrangement of the liquid crystal molecules, so that the liquid crystal is moved by an electric field to form an appropriate direction when forming an image. In general, in order to obtain uniform brightness and high contrast ratio in the liquid crystal display device, it is essential to orient the liquid crystal uniformly.

Conventionally, the rubbing method which apply | coated a polymer film like polyimide to the board | substrates, such as glass, and rubbed the surface in a fixed direction with the fiber, such as nylon and polyester, was used as a conventional method of orienting a liquid crystal. However, the rubbing method may generate fine dust or electrostatic discharge (ESD) when the fiber and the polymer film are rubbed, and cause serious problems in manufacturing the liquid crystal panel.

In order to solve the problem of the above rubbing method, in recent years, an optical alignment method has been studied to induce anisotropy (anisotropy) in a polymer film by light irradiation instead of friction and to arrange liquid crystals using the same. As materials that can be used in the photoalignment method, polymers containing photofunctional groups such as azobenzene, cumarine, chalcone, and cinnamate have been developed. These polymers are anisotropically reacted by photoisomerization or photocrosslinking by polarized light irradiation, and thus anisotropy is generated on the surface of the polymer to induce molecular alignment of the liquid crystal in one direction. In order to apply such liquid crystal alignment film materials to the liquid crystal display device substantially, optical and thermal stability should be excellent and there should be no afterimage. However, conventionally known photo-orientation materials exhibit many disadvantages in this respect.

On the other hand, Japanese professor Kawatuki et al. Prepared a photocrosslinkable polymer copolymer containing a liquid crystal mesogen group, induces anisotropy by polarized UV irradiation, and then heat-processes the polymer. The results of improving the anisotropy using liquid crystal properties have been published (Macromol. Chem. Phys. 2001, 202, 3087-3098). Mesogenic groups are polymer materials that exhibit liquid crystallinity in a certain temperature range or in a solution state.

As described above, many copolymers containing photoreactors and mesogen groups are known. However, in the liquid crystalline copolymers published to date, the mesogen group (generally, the molecular structure of the mesogen group is represented by a long rod shape) is perpendicular to the polymer back-bone, and is represented by the following Chemical Formula 1.

[Formula 1]

In Chemical Formula 1,

S1 and S2 are connection groups,

P1 is a photoreactor,

M1 is mesogen group,

a and b represent the monomer mole fraction, and in each case 0 <a <1 and 0 <b <1.

However, when using this type of copolymer as a liquid crystal alignment film, polarization occurs in the molecules of mesogen groups when an electric field is applied in actual LCD driving, and thus may move like a liquid crystal according to the electric field. As such, the movement of the mesogenic groups present in the liquid crystal alignment layer may not only interfere with the well-aligned liquid crystal alignment, but also seriously affect the afterimage.

Accordingly, the inventors of the present invention are excellent in optical and thermal stability with respect to the liquid crystal, and while studying a liquid crystal alignment copolymer having no afterimage, the photoreactor and the center of gravity includes a symmetrical mesogen group connected to the polymer backbone It was confirmed that the liquid crystal alignment copolymer was excellent in optical and thermal stability, and no afterimage appeared, thus completing the present invention.

An object of the present invention is to provide a liquid crystal alignment copolymer comprising a photoreactor and a symmetrical mesogen group in which a center of gravity is connected to a polymer backbone.

In addition, the present invention is to provide a liquid crystal alignment composition comprising the liquid crystal alignment copolymer.

In addition, the present invention is to provide a liquid crystal display device using the liquid crystal alignment composition.

The present invention provides a liquid crystal alignment copolymer comprising a photoreactor and a symmetrical mesogen group whose center of gravity is connected to the polymer backbone.

The present invention also provides a liquid crystal alignment composition comprising the liquid crystal alignment copolymer.

In addition, the present invention provides a liquid crystal display device using the liquid crystal alignment composition.

Hereinafter, the present invention will be described in detail.

The present invention provides a liquid crystal aligning copolymer represented by Chemical Formula 2, including a photoreactor and a symmetrical mesogen group having a center of gravity connected to a polymer main chain.

[Formula 2]

In Chemical Formula 2,

Z is a polyimide; Polysiloxanes; Or a cyclic or non-cyclic polymer back-bone consisting of at least one selected from carbon, oxygen or nitrogen and hydrogen,

S3, S4 is a spacer (spacer),

P2 is a photoreactor,

M2 is a mesogenic group having a center of gravity connected to the polymer backbone and symmetrically

p and q represent the monomer mole fraction, in each case 0 <p <1, 0 <q <1,

n is 10 &lt; n &lt; 10,000 in total repeating units.

S3 and S4 are linking sites, each independently, a bond; Alkyl having 1 to 20 carbon atoms having a linking group of an ether, an ester or an amide, wherein 1 to 5 carbons are unsubstituted or substituted with N or S; Cycloalkyl having 3 to 18 carbon atoms having a linking group of ether, ester or amide, wherein 1 to 5 carbons are unsubstituted or substituted with N or S; And an aryl group having 5 to 18 carbon atoms having a linking group of ether, ester or amide, wherein 1 to 3 carbons are unsubstituted or substituted with N or S.

The mesogenic group (M2) is symmetrical left and right, the center of gravity is connected to the polymer backbone, it may be represented by the formula (3).

[Formula 3]

In Chemical Formula 3,

X and Y are, independently from each other, aryl or cycloalkyl having 3 to 6 carbon atoms, which may be directly bonded to each other or connected by a bond of alkyl, ester, ether, amide, etc. having 1 to 6 carbon atoms, respectively,

E is a terminal moiety selected from the group consisting of hydrogen, halogen, cyano (CN), nitro (NO ₂ ), alkyl having 1 to 12 carbon atoms, and alkyl having 1 to 12 carbon atoms having at least one halogen substituent, or E and Y are directly bonded or connected by ether, ester or amide bond.

In Formula 3, aryl may be selected from phenyl, biphenyl, naphthyl, anthryl or phenanthryl.

The liquid crystal aligning copolymer according to the present invention is characterized in that the mesogen group is horizontally attached to the polymer main chain.

Attached horizontally means that the center of gravity (molecular center) of the mesogen group is connected to the polymer back-bone. Since the molecular structure is symmetrical, polarization is minimized by the electric field, and thus the molecules do not move with the electric field. Therefore, the liquid crystal alignment is not affected even when an electric field is applied, and afterimages do not appear.

The photoreactor (P2) is not particularly limited, but is preferably selected from the group consisting of substituted or unsubstituted azobenzene, stilbenzene, coumarin, chalcone, and cinnamate. Substituents here are preferably halogen, alkyl of 1 to 6 carbons, alkoxy or hydroxy group of 1 to 6 carbons. If the photoreactor is cinnamate or chalcone, the liquid crystal alignment is induced perpendicular to the polarized UV irradiation direction, ie parallel to the polymer backbone, which coincides with the molecular axis of the mesogen group. This further stabilizes the liquid crystal alignment and can achieve even more improved orientation.

Specific examples of the liquid crystal alignment copolymer of the present invention may be a copolymer represented by the following Chemical Formula 2-1 or Chemical Formula 2-2, but are not limited thereto.

<Formula 2-1>

<Formula 2-2>

The present invention also provides a liquid crystal alignment composition comprising the liquid crystal alignment copolymer.

The liquid crystal alignment composition according to the present invention may include, in addition to the liquid crystal alignment copolymer, a conventional solvent or additive known in the art.

A liquid crystal alignment layer may be manufactured using the liquid crystal alignment composition.

The liquid crystal alignment layer may be prepared according to a conventional method known in the art, for example, 1) preparing a liquid crystal alignment solution by dissolving the liquid crystal alignment copolymer in a solvent; And 2) applying the liquid crystal alignment solution on a substrate and removing the solvent, followed by light irradiation.

In step 1), the available solvent is N-methylpyrrolidone (NMP), N-ethylpyrrolidone (NEP), dimethylformamide (DMF), butyl cellosolve, γ-butyrolactone, chlorobenzene , Dimethyl sulfoxide (DMSO), dimethylacetamide, cyclopentanone, cyclohexanone, cyclohexanone, tetrahydrofuran (THF), dichloroethane or mixtures thereof, and the like.

The non-volatile content of the copolymer in the liquid crystal alignment solution is not particularly limited and may be appropriately adjusted according to the coating method to be used. If possible, a range of 2 to 5% by weight per 100% by weight of the total solution is preferred.

In step 2), the liquid crystal alignment solution is applied to a substrate, such as a glass substrate, and then the solvent is removed and then irradiated with light.

As a method of applying the liquid crystal alignment solution on a substrate, a method such as roll coating, curtain coating, spin coating, slot die coating, various printing, deposition, or the like known in the art may be used. Can be used.

A base material is a base material normally used as a photo-alignment film, and a glass substrate is preferable. The thickness of the liquid crystal alignment solution applied on the substrate is not particularly limited, and can be adjusted within a conventional range for aligning the liquid crystal, for example, 50 to 100 nm.

In addition, the method for removing the solvent is also not particularly limited, and may be performed by, for example, heating in the range of 150 to 200 ° C. for about 30 minutes to 1 hour.

By performing light irradiation on the surface to which the liquid crystal aligning solution is applied, the liquid crystal aligning film of this invention is manufactured.

The liquid crystal alignment film is a photopolymerization substituent, such as an acrylic group and / or a methacryl group, present in the molecules of the liquid crystal alignment copolymer by light irradiation to cause a photopolymerization reaction to form a crosslinked polymer film and at the same time in the liquid crystal alignment copolymer molecules. The included photoreactors such as azobenzene, coumarin, chalcone or cinnamate exhibit photoisotropy to express photoalignment function.

Irradiation light is not particularly limited, but ultraviolet (UV) light is preferred. In addition, the light irradiation method is also not particularly limited, but may be inclined irradiation or vertical irradiation of ultraviolet rays linearly polarized using a polarizer or unpolarized ultraviolet rays not using a polarizer.

The inclination angle at the time of vertical irradiation is adjustable within the range conventionally performed in the art, and 0 to 30 degrees is preferable, and the irradiation time depends on the power of the lamp, but preferably 5 to 10 minutes.

In addition, the present invention provides a liquid crystal display (liquid crystal display) comprising a liquid crystal alignment film prepared using the composition for the liquid crystal alignment film.

The liquid crystal display device may be manufactured according to conventional methods known in the art. For example, one of the two glass-induced photoreaction substrates having the liquid crystal alignment film prepared as described above is applied to the end of the glass substrate by applying a photoreactive adhesive containing a ball spacer to the end of the glass substrate. One glass substrate is bonded together, and only the portion to which the adhesive is applied is irradiated with ultraviolet rays to bond the cells. After injecting the liquid crystal into the completed cell and heat treatment, to complete the liquid crystal cell.

Indeed, the liquid crystal display device of the present invention having the liquid crystal alignment layer not only exhibits an excellent alignment state, but also maintains an excellent alignment state of the liquid crystal even after a long time thermal stability test, and does not show an afterimage on the afterimage side, which is an electrical property. There is.

Hereinafter, preferred examples are provided to aid in understanding the present invention. However, the following examples are merely provided to more easily understand the present invention, and the contents of the present invention are not limited thereto.

Example 1 :

1. Preparation of Copolymer 1

<Formula 2-1>

1-a. Preparation of 4- (4-fluoro cinnamoyl) hydroxy styrene monomer

To 10 g (0.06 mole) of 4-fluoro cinnamic acid, 10 ml of thionyl chloride and a small amount of dimethylformamide were added, stirred at room temperature for 24 hours, and then the remaining thionyl chloride was removed from the resulting solution under reduced pressure to obtain 4-fluorocinna Moyl chloride was obtained.

7.2 g (0.02 mole) of 4-hydroxy styrene was dissolved in 200 ml of tetrahydrofuran and 8 ml of triethylamine was added thereto. The solution which melt | dissolved said 4-fluorocinnamoyl chloride in 20 ml of tetrahydrofuran was slowly dripped at this solution, and it was made to react. After reacting at room temperature for about 5 hours, the solvent was removed from the obtained reaction solution under reduced pressure and then precipitated in water. The precipitate was washed with water and recrystallized from ethanol to obtain 13 g of 4- (4-fluoro cinnamoyl) hydroxy styrene.

The obtained monomer was confirmed using the nuclear magnetic resonance spectroscopy (1H-NMR).

¹ H NMR (400 MHz, CDCl ₃ ): 7.81-7.51 (m, 3H), 7.35-7.13 (m, 6H), 6.72 (d, J = 16 Hz, 1H), 6.69-6.61 (m, 1H), 5.57 (d, J = 16 Hz, 1H), 5.09 (d, J = 12 Hz, 1H).

1-b. Preparation of 2,5-bis [(4-fluorobenzoyl) oxy] benzyl methacrylate monomer

5 g (0.036 mole) of 2,5-dihydroxy benzaldehyde was dissolved in 100 ml of tetrahydrofuran, 5 ml of triethylamine was added, and then 5.6 g of 4-fluorocinnamoyl chloride was added to this solution. The solution dissolved in ㎖ was slowly added dropwise to react. After reacting at room temperature for about 5 hours, the obtained reaction solution was decompressed to remove a considerable amount of solvent, and then precipitated in water. The obtained precipitate was washed several times with water and ethanol and dried under reduced pressure to obtain 10 g of 2,5-bis [(4-fluorobenzoyl) oxy] benzaldehyde. 10 g (0.026 mole) of 2,5-bis [(4-fluorobenzoyl) oxy] benzaldehyde was dissolved in 200 ml of dimethyl sulfoxide, and then slowly added 3 g (0.078 mole) of sodium borohydride at room temperature. Reaction was carried out for 24 hours. The obtained reaction solution was added to excess water to precipitate. The precipitate obtained was washed several times with water and recrystallized from ethanol to give 6 g of 2,5-bis [(4-fluorobenzoyl) oxy] benzyl alcohol. 6 g (0.016 mole) of 2,5-bis [(4-fluorobenzoyl) oxy] benzyl alcohol obtained was dissolved in 120 ml of tetrahydrofuran, followed by addition of 2 ml of triethylamine, and 1.8 g of methacryloyl chloride at room temperature. (0.017mole) was slowly added dropwise and reacted for 5 hours. A considerable amount of solvent was removed from the obtained reaction solution under reduced pressure and then precipitated in water. The precipitate was washed with water and recrystallized from ethanol to give 6.5 g of 2,5-bis [(4-fluorobenzoyl) oxy] benzyl methacrylate.

The obtained monomer was confirmed using the nuclear magnetic resonance spectroscopy (1H-NMR).

¹ H NMR (400 MHz, DMSO-d ⁶ ): 7.63-7.51 (m, 4H), 7.50-7.47 (m, 1H), 7.42-7.38 (m, 2H), 7.36-7.25 (m, 4H), 6.09 -6.08 (m, 1H), 5.59-5.58 (m, 2H), 5.57 (dt, J = 1.7, 0.9 Hz, 1H), 1.94 (dd, J = 1.6, 0.9 Hz, 3H).

1-c. Preparation of Copolymer 1

2 g (7.46 mmol) of 4- (4-fluoro cinnamoyl) hydroxy styrene prepared in 1-a, 2,5-bis [(4-fluorobenzoyl) oxy] benzyl meta prepared in 1-b 3.37 g (7.46 mmol) of acrylate and 260 mg of azoisobutyronitrile were dissolved in 35 ml of dimethylformamide, bubbled with nitrogen at room temperature for 30 minutes, and the temperature was raised to 80 ° C. and reacted for 24 hours. After cooling this reaction solution to room temperature, it dripped in excess methanol and precipitated. The obtained precipitate was filtered under reduced pressure, dissolved in 35 ml of dimethylformamide, reprecipitated in excess methanol, filtered under reduced pressure and dried under vacuum to obtain copolymer 1 (12.8 g) of the above <Formula 2-1>.

Molecular weight was measured using GPC, and the number average molecular weight (Mn) was 36,000 and the weight average molecular weight (Mw) was 64,800.

2. Preparation of liquid crystal alignment solution

The copolymer 1 prepared in 1 was dissolved in a mixed solution of N-methylpyrrolidone and butyl cellosolve to make the non-volatile content of the copolymer 1 2%, which was filtered through a 0.2 μm filter to form a liquid crystal alignment solution. Was prepared.

3. Manufacturing of liquid crystal cell

After the liquid crystal alignment solution prepared in 2 was coated with a thickness of 80 nm on a glass substrate coated with an indium tin oxide (ITO) electrode, the glass substrate was dried at 200 ° C. for 1 hour to remove the solvent. The surface coated with the liquid crystal alignment solution was irradiated with ultraviolet light at intervals of 5 seconds, 10 seconds, 30 seconds, 1 minute, 5 minutes, and 10 minutes at an inclination angle of 0 to 30 degrees from the surface of the glass substrate with respect to ultraviolet rays to induce a photoreaction. On one of the two glass substrates inducing photoreaction, a photoreactive adhesive containing a ball spacer is applied to the end of the glass substrate, and then the other glass substrate is bonded to the glass substrate to irradiate ultraviolet rays only at the portion where the adhesive is applied. The cells were joined. After injecting the liquid crystal into the completed cell and heat treatment for 2 minutes at 100 ℃ to complete the liquid crystal cell.

Example 2 :

1. Preparation of Copolymer 2

<Formula 2-2>

1-a. Preparation of 4- (cinnamoyl oxy) phenyl methacrylate monomer

6.5 g (0.059 mole) of hydroquinone was dissolved in 300 ml of tetrahydrofuran, and 13 ml of triethylamine was added thereto. A solution in which 9.8 g (0.059 mole) of cinnamoyl chloride was dissolved in 20 ml of tetrahydrofuran was slowly added dropwise to this solution at 0 ° C to react. After reacting at room temperature for about 5 hours, the solvent was removed from the obtained reaction solution under reduced pressure and then precipitated in water. The precipitate was washed with water and recrystallized from ethanol to obtain 7.8 g of 4- (cinnamoyl oxy) phenol.

7.8 g (0.032 mole) of 4- (cinnamoyl oxy) phenol obtained was dissolved in 300 ml of tetrahydrofuran, and then 6.7 ml of triethylamine was added. A solution obtained by dissolving 3.7 g (0.036 mole) of methacryloyl chloride in 5 ml of tetrahydrofuran was slowly added dropwise at 0 ° C. to the solution. After reacting at room temperature for about 5 hours, the solvent was removed from the obtained reaction solution under reduced pressure and then precipitated in water. The precipitate was washed with water and recrystallized from ethanol to give 8.2 g of 4- (cinnamoyl oxy) phenyl methacrylate.

The obtained monomer was confirmed using the nuclear magnetic resonance spectroscopy (1H-NMR).

¹ H NMR (400 MHz, CDCl 3): 6.62 (d, J = 16 Hz, 1H), 7.46-7.38 (m, 5H), 7.36-7.26 (m, 4H), 6.72 (d, J = 16 Hz, 1H), 6.09-6.07 (m, 1 H), 5.57 (dt, J = 3.8, 0.9 Hz, 1 H), 1.95 (dd, J = 1.6, 0.9 Hz, 3H).

1-b. Preparation of 2,5-bis [(4-methoxybenzoyl) oxy] benzyl- (3-methacryloyloxy) propionate monomer

Except for using 4-methoxycinnamoyl chloride instead of 4-fluorocinnamoyl chloride in 1-b of Example 1 in the same manner as in Example 1-b 2,5-bis [(4-meth Oxybenzoyl) oxy] benzyl alcohol was prepared.

5 g (0.012 mole) of the 2,5-bis [(4-methoxybenzoyl) oxy] benzyl alcohol was dissolved in 100 ml of tetrahydrofuran, and 3.4 ml of triethylamine was added thereto. A solution obtained by dissolving 4.1 g (0.024 mole) of 3-bromopropionyl chloride in 5 ml of tetrahydrofuran was slowly added dropwise at 0 ° C. to the solution. After reacting at room temperature for 24 hours, the solvent was removed from the reaction solution obtained under reduced pressure and then precipitated in water. The precipitate was washed with water and recrystallized with ethyl acetate and n-hexane to obtain 5.6 g of 2,5-bis [(4-methoxybenzoyl) oxy] benzyl-3-bromo propionate. 5.6 g (0.01 mole) of obtained 2,5-bis [(4-methoxybenzoyl) oxy] benzyl-3-bromo propionate, 2.16 g (0.02 mole) of sodium methacrylate, and 100 mg of hydroquinone were dried with anhydrous dimethyl. After dissolving in 100 ml of formamide, the mixture was reacted at 100 ° C for 24 hours. The obtained reaction solution was added dropwise to excess water to form a precipitate, which was recrystallized from methanol to give 2,5-bis [(4-methoxybenzoyl) oxy] benzyl- (3-methacryloyloxy) propionate 4.2 g was obtained.

The obtained monomer was confirmed using the nuclear magnetic resonance spectroscopy (1H-NMR).

¹ H NMR (400 MHz, DMSO-d ⁶ ): 7.93-7.83 (m, 4H), 7.50-7.47 (m, 1H), 7.42-7.38 (m, 2H), 6.93-6.88 (m, 4H), 6.08 -6.07 (m, 1H), 5.57 (dt, J = 1.7, 0.9 Hz, 1H), 5.53-5.52 (m, 2H), 4.22 (t, J = 4 Hz, 2H), 3.83 (s, 6H), 2.56 (t, J = 4 Hz, 2H), 1.94 (dd, J = 1.6, 0.9 Hz, 3H).

1-c. Preparation of Copolymer 2

2 g (6.49 mmol) of 4- (cinnamoyl oxy) phenyl methacrylate monomer prepared in 1-a, 2,5-bis [(4-methoxybenzoyl) oxy] benzyl- ( 3.56 g (6.49 mmol) of 3-methacryloyloxy) propionate monomer and 160 mg of azoisobutyronitrile were dissolved in 28 ml of dimethylformamide, bubbling with nitrogen for 30 minutes at room temperature, and then the temperature was raised to 80 ° C. and 24 The reaction was time. After cooling this reaction solution to room temperature, it dripped in excess methanol and precipitated. The obtained precipitate was filtered under reduced pressure, dissolved in 30 ml of dimethylformamide, reprecipitated in excess methanol, filtered under reduced pressure and dried under vacuum to obtain copolymer 2 (3.5 g) of the above <Formula 2-2>.

The molecular weight of the obtained polymer was measured using GPC. The number average molecular weight (Mn) was 45,300 and the weight average molecular weight (Mw) was 99,600.

2. Preparation of liquid crystal alignment solution

A liquid crystal alignment solution was prepared in the same manner as in Example 1 2, except that Copolymer 2 was used instead of Copolymer 1 in 2 of Example 1.

3. Manufacturing of liquid crystal cell

A liquid crystal cell was manufactured in the same manner as in Example 3, 3 using the liquid crystal alignment solution prepared in 2 above.

Comparative Example 1 :

A liquid crystal alignment solution and a liquid crystal cell were manufactured in the same manner as in Example 1, except that polyvinyl cinnamate, which is a conventionally well-known polymer type photoalignment agent, was used.

Comparative Example 2 :

1. Preparation of Copolymer with Mesogen Group Attached to Polymer Vertically

1-a. Preparation of 4- (cinnamoyl oxy) phenyl methacrylate monomer

What was prepared in Example 1-a of Example 2 was used.

1-b. Preparation of 6- (4'-methoxy-4-biphenyloxy) hexyl methacrylate monomer

5 '(0.02 mole) of 4'-methoxy-4-hydroxybiphenyl, 4.34 g (0.024 mole) of 6-bromohexanol and 4.14 g of potassium carbonate were dissolved in 200 ml of methyl ethyl ketone, followed by stirring under reflux for 24 hours. I was. The reaction was then washed with water and the remaining organic solution was distilled under reduced pressure. The remaining organic substance was purified by column chromatography using a 1: 1 solvent of ethyl acetate, n-hexane, and silica gel to obtain 4.6 g of pure 6- (4'-methoxy-4-biphenyloxy) hexanol. 4.6 g (0.015 mole) of 6- (4'-methoxy-4-biphenyloxy) hexanol obtained was dissolved in 200 ml of tetrahydrofuran, followed by addition of 3.13 ml of triethylamine. A solution in which 1.9 g (0.018 mole) of methacryloyl chloride was dissolved in 3 ml of tetrahydrofuran was slowly added dropwise at 0 ° C. to the solution. After reacting at room temperature for about 5 hours, the solvent was removed from the obtained reaction solution under reduced pressure and then precipitated in water. The precipitate was washed with water and recrystallized from methanol to obtain 4.5 g of 6- (4'-methoxy-4-biphenyloxy) hexyl methacrylate.

1-c. Preparation of Copolymer with Mesogen Group Attached to Polymer Vertically

2 g (6.49 mmol) of 4- (cinnamoyl oxy) phenyl methacrylate monomer prepared in 1-a of Example 2, 6- (4′-methoxy-4-biphenyloxy prepared in 1-b ) Hexyl methacrylate 2.39g (6.46mmol) was prepared in the same manner as in Example 2 1-c to obtain a copolymer 3g mesogenic groups are attached vertically to the polymer.

The molecular weight of the obtained polymer was measured using GPC. The number average molecular weight (Mn) was 23,50000 and the weight average molecular weight (Mw) was 52,300.

2. Preparation of liquid crystal alignment solution

A liquid crystal alignment solution was prepared in the same manner as in Example 1 2, except that the copolymer in which the mesogen group was vertically attached to the polymer instead of the copolymer 1 was used in Example 1 2.

3. Manufacturing of liquid crystal cell

A liquid crystal cell was manufactured in the same manner as in Example 3, 3 using the liquid crystal alignment solution prepared in 2 above.

Experimental Example 1  : Evaluation of the alignment state of the liquid crystal cell according to the present invention

In order to evaluate the alignment state of the liquid crystal cell manufactured using the liquid crystal alignment copolymer according to the present invention, the following experiment was performed.

Using the liquid crystal cells manufactured in Examples 1 and 2 and Comparative Examples 1 and 2, the alignment states of the liquid crystal cells were determined by dividing the light and dark states between two polarizing plates having perpendicular polarization directions.

The results are shown in FIG.

As shown in Figure 1, in the case of the liquid crystal cell prepared by using the liquid crystal alignment copolymer according to the present invention (Examples 1 and 2), there was no defect at all when visual observation showed excellent alignment. In addition, in the case of Comparative Examples 1 and 2, the initial culture state was good.

Experimental Example 2  : Evaluation of Thermal Stability of Liquid Crystal Cell According to the Present Invention

In order to confirm the thermal stability of the liquid crystal cell prepared using the liquid crystal alignment copolymer according to the present invention, the following experiment was performed.

In the manufacturing process of the liquid crystal cell according to Examples 1 and 2 and Comparative Examples 1 and 2, after bonding the two glass substrates and left for 30 minutes at 150 ℃ before injecting the liquid crystal, it is cooled to room temperature and the liquid crystal is injected. After that, their orientation was confirmed.

The results are shown in FIGS. 2 and 3.

As shown in FIG. 2, in the case of the liquid crystal cells manufactured using the liquid crystal alignment copolymer according to the present invention (Examples 1 and 2), even after performing the thermal stability evaluation, there was no change in the alignment state. On the other hand, in the case of Comparative Example 1, the initial alignment state almost disappeared after performing the thermal stability evaluation, and in Comparative Example 2, after performing the thermal stability evaluation, a number of orientation defects were generated.

As shown in Figure 3, in the liquid crystal cell (Example 2) prepared by using the liquid crystal beating copolymer according to the present invention, the liquid crystal molecules were evenly arranged regularly and well aligned. On the other hand, in Comparative Example 1, the arrangement of the liquid crystal molecules was irregular and irregular, and the alignment was also poor.

Experimental Example 3  : Afterimage evaluation of liquid crystal cell according to the present invention

In order to confirm the residual characteristics of the liquid crystal cell prepared using the liquid crystal alignment copolymer according to the present invention, the following experiment was performed.

After applying a voltage of 7V to the liquid crystal cells according to Examples 1 and 2 and Comparative Examples 1 and 2, the residual characteristics were evaluated by turning off the voltage and observing the brightness fluctuations as before.

The results are shown in FIG.

As shown in FIG. 4, in the case of Comparative Examples 1 and 2, the initial luminance change rate is large after turning off the voltage, and it takes a long time to return to the initial luminance value. And 2) not only the initial luminance fluctuation rate was small, but also the time taken to restore the initial luminance value was much shorter.

The liquid crystal alignment copolymer according to the present invention not only exhibits an excellent alignment state but also maintains an excellent alignment state of the liquid crystal even after a long time thermal stability test, and there is an effect that afterimages do not appear in the afterimage as an electrical property.

Claims (7)

A liquid crystal aligning copolymer represented by Chemical Formula 2, comprising a photoreactor and a symmetric mesogen group in which a center of gravity is connected to a polymer main chain. <Formula 2>

In Chemical Formula 2, Z is a polyimide; Polysiloxanes; Or a cyclic or non-cyclic polymer back-bone consisting of at least one selected from carbon, oxygen or nitrogen and hydrogen, S3, S4 is a spacer (spacer), P2 is a photoreactor, M2 is a mesogenic group having a center of gravity connected to the polymer backbone and symmetrically p and q represent the monomer mole fraction, in each case 0 <p <1, 0 <q <1, n is 10 &lt; n &lt; 10,000 in total repeating units. The method according to claim 1, wherein S3 and S4 are each a linking site, each independently, alkyl having 1 to 20 carbon atoms having a linking group of ether, ester or amide unsubstituted or substituted with 1 to 5 carbons; Cycloalkyl having 3 to 18 carbon atoms having a bond, a linking group of ether, ester or amide, wherein 1 to 5 carbons are unsubstituted or substituted with N or S; And 1 to 3 carbons selected from the group consisting of aryl groups having 5 to 18 carbon atoms having a linking group of ether, ester or amide, unsubstituted or substituted with N or S. The liquid crystal aligning copolymer according to claim 1, wherein the mesogen group (M2) is represented by the following Chemical Formula 3. <Formula 3>

In Chemical Formula 3, X and Y are independently of each other, aryl or cycloalkyl having 3 to 6 carbon atoms, which may be directly bonded to each other or connected by a bond of alkyl, ester, ether, amide, etc. having 1 to 6 carbon atoms, respectively, E is a terminal moiety selected from the group consisting of hydrogen, halogen, cyano (CN), nitro (NO ₂ ), alkyl having 1 to 12 carbon atoms, and alkyl having 1 to 12 carbon atoms having at least one halogen substituent, or E and Y are directly bonded or connected by ether, ester or amide bond. The liquid crystal alignment copolymer according to claim 1, wherein the photoreactor (P2) is one selected from the group consisting of substituted or unsubstituted azobenzene, stilbenzene, coumarin, chalcone, and cinnamate. The liquid crystal alignment copolymer according to claim 1, wherein the liquid crystal alignment copolymer is a copolymer represented by the following Chemical Formula 2-1 or Chemical Formula 2-2. <Formula 2-1>

<Formula 2-2>

The liquid crystal aligning composition containing the liquid crystal aligning copolymer of any one of Claims 1-5. Liquid crystal display device comprising a liquid crystal alignment film prepared using the liquid crystal alignment composition of claim 6.

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