KR100708994B1 - Biaxial compensator film for vertical alignment lcd - Google Patents

Abstract

The present invention is a novel type of compensation film used to increase the viewing angle of a liquid crystal display device, comprising: a polymer base layer having a negative sign in a plane direction retardation value by uniaxially stretching a polymer film produced by a casting or extrusion process; A protective layer formed by coating and curing an organic or organic / inorganic hybrid composition on at least one side of the polymer base layer; And a polymer coating layer having a negative sign of a phase difference value in the thickness direction formed on the polymer substrate layer on which the protective layer is formed. The compensation film for a liquid crystal display device comprising: a phase direction phase difference and a thickness direction It can have the phase difference at the same time and can be adjusted independently, and the optical axis is orthogonal to each other and can be used as the A type and the negative C type compensation film as one film.

Compensation film, birefringence, VA liquid crystal display, retardation, wide viewing angle film, biaxial optical film

Description

Biaxial Compensator Film for Vertical Alignment LCD

1 is a cross-sectional view showing a cross section of a compensation film for a liquid crystal display device manufactured according to an embodiment of the present invention.

Brief description of the main symbols in the drawings

10: stretched polymer substrate layer

20: organic or organic / inorganic hybrid protective layer

30: polymer coating layer

The present invention relates to a compensation film for a liquid crystal display device, and more particularly, to a compensation film used to increase the viewing angle of a liquid crystal display device, wherein the polymer film is uniaxially stretched to impart a surface direction retardation, and the stretched film is organic. By coating and curing the inorganic hybrid composition, coating a polymer solution, and volatilizing a solvent to prepare a film, wherein the compensation film for a liquid crystal display device is characterized by an optically biaxial design in which the phase difference in the thickness direction and the surface direction difference are orthogonal to each other. It is about.

Recently, as liquid crystal displays have become larger, various forms of retardation compensation films are urgently needed to secure wide viewing angles. The thickness retardation of the compensation film is defined as a difference in refractive index between two axes and the thickness of the film as shown in Equation 1 below. In Equation 1, if ( n _x + n _y ) / 2 is greater than n _z , R _th has a negative value, and if ( n _x + n _y ) / 2 is less than n _z , R _th has a positive value. .

In the above formula, R _th is the thickness retardation, n _x and n _y are the in-plane refractive indexes of the film, n _z is the thickness-direction refractive index of the film, and d is the film thickness.

Since the liquid crystal display uses high birefringence characteristics and orientations of liquid crystal molecules, the refractive index changes according to the viewing angle, and thus the color and brightness of the screen change. Since most liquid crystal molecules used in the vertical alignment method have a positive phase difference in the thickness direction of the liquid crystal display surface, a compensation film having a negative phase difference in the thickness direction is required to compensate for this. In addition, the front of the two polarizers orthogonal to each other do not pass light, but when the angle is inclined, the optical axis of the two polarizers is not orthogonal to cause light leakage. In order to compensate for this, a compensation film having a plane retardation is used. A display device using liquid crystal requires both thickness direction compensation and plane direction difference compensation in order to widen the viewing angle. As a requirement for compensation films, birefringence should be easily controlled. The birefringence of the film is achieved not only by the fundamental birefringence of the material but also by the orientation of the polymer chains in the film. The orientation of the polymer chains is mostly caused by external forces, or due to the inherent properties of the material. The method of orienting a molecule by external force is extending | stretching a polymer film uniaxially or biaxially. Currently, most compensation films are manufactured by biaxially stretching a polymer film. However, in the retardation film production by biaxial stretching, it is difficult to control each desired retardation value independently because the two optical axes are difficult to orthogonal to each other, and the change in the plane direction retardation affects the thickness retardation. And when birefringence is difficult to control and stretches, there is a problem that it is very difficult to obtain a uniform phase difference because the thickness of the film is reduced. In addition, various liquid crystal modes require a compensation film having a slightly different phase difference value, but it is difficult to expect an optimized compensation effect because it is difficult to control minute phase change by biaxial stretching. Currently, negative retardation compensation film is manufactured by various methods, but it is difficult to control the retardation and the price competitiveness is low.

Most polymers have an optical axis in the molecular chain direction and exhibit positive intrinsic birefringence. In addition, it is possible to obtain a birefringence of a film that is significantly different from the inherent birefringence of a polymer according to the film production method. When the film is produced by extrusion, the degree of orientation of the polymer chain depends on the force applied from the outside, but the polymer film made by solution casting has little plane direction retardation because the orientation of the polymer chain in the plane direction is small. Thus, the film by solution casting is uniaxially or biaxially stretched to orient the polymer chain in the plane direction of the film to impart a plane direction retardation. In particular, when the thickness of the film is tens of nanometers in length, the size of the polymer chain, because the influence of the film interface is increased, the orientation of the polymer is maximized to obtain a very high birefringence.

Japanese Patent Application Laid-Open No. 2001-194668 discloses a thickness retardation compensation film produced by uniaxially stretching a polycarbonate film having a retardation in a plane direction and laminating them perpendicularly to each other. This manufacturing method requires a complicated lamination process, and requires the optical axes to be perpendicular to each other when laminating two films. In addition, U.S. Patent Application No. 5,043,413 introduces a process for preparing polyarylates having low plane birefringence. The polyarylate was prepared by the solution casting method, and then the film was stretched to compare the birefringence. The low birefringence polyarylate having the birefringence of the stretched polyarylate film of 25.7 × 10 ⁻⁵ or less was polymerized. As such, birefringence by stretching mainly gives birefringence in the plane direction, and the compensation film for vertical alignment liquid crystal requires two axes of birefringence at the same time. US Patent Application No. 5,285,303 discloses a method for obtaining a phase difference in the thickness direction by uniaxial stretching of a polyarylate film and shrinkage in a direction perpendicular to the stretching direction for a compensation film for a wide viewing angle. In general, the phase difference of the liquid crystal is 100 to 400 nm, and in order to compensate for this, the compensation film needs a phase difference of -100 to -400 nm having the opposite sign. However, since the orientation of the polymer chain is small, there is a limit in obtaining a desired phase difference. Japanese Patent Application Laid-Open No. 1999-95208 proposes a method for producing a phase difference compensation film by stretching various polymer films. Films which can be used here are polycarbonates, polyarylates, polysulfones. The biaxial stretching process of the polymer film to obtain a phase difference in the thickness direction necessarily affects the phase difference in the plane direction, so that there is a disadvantage in that the phase difference in the thickness direction and the plane direction must be simultaneously controlled. In fact, it is very difficult and impossible to obtain a desired value at the same time by stretching the phase difference between the surface direction and the thickness direction with one film.

In order to solve the above problems, the present invention is easier than the conventional biaxial stretching method, and can be adjusted independently of the surface direction phase difference and thickness direction phase difference, and the optical film is perpendicular to each other compensation film for the liquid crystal display device and its manufacture To provide a method.

The above object of the present invention can be achieved by the present invention described below.

In order to achieve the above object, the present invention is a compensation film for a liquid crystal display device, a polymer substrate layer having a surface direction retardation value defined by Equation 2 by uniaxially stretching the polymer film produced by the casting or extrusion process; A protective layer formed by coating and curing an organic or organic / inorganic hybrid composition on at least one side of the polymer base layer; It provides a compensation film for a liquid crystal display device comprising a; a polymer coating layer having a phase difference value in the thickness direction defined by the following Equation 1, formed on the protective substrate formed polymer base layer.

[Equation 1]

R _in = (n _x -n _y ) × d

In the above formula, n _z is the thickness direction refractive index of the film, n _x and n _y is the surface direction refractive index of the film, d is the thickness of the film, R _th is the thickness direction phase difference, R _in is the surface direction phase difference.

In addition, the present invention comprises the steps of uniaxially stretching the polymer film; Coating and curing the organic / inorganic hybrid composition on the stretched film; And coating a polymer solution selected from the group consisting of polyarylate, cycloolefin polymer, and polyimide on the cured film of the organic / inorganic hybrid composition, and volatilizing a solvent to prepare a polymer film. Provided is a method of manufacturing a compensation film for a liquid crystal display device.

It is preferable that the thickness direction retardation value defined by Equation 1 of the entire compensation film is 30 nm or more while having a negative sign, and the plane retardation value defined by Equation 2 is 20 nm or more.

The polymer substrate layer has a structure in which a phase difference defined by Equation 1 has a negative sign of 20 nm or more, at least one film is laminated, and a thickness of the polymer substrate layer is 10 μm to 200 μm, polycarbonate, Optically uniform and transparent polymer films drawn and selected from the group consisting of triacetylcellulose, cycloolefin (co) polymers and (meth) acrylate polymers can be used.

The film used as the polymer base layer may be subjected to a surface treatment selected from the group consisting of corona treatment, ion beam treatment, acid / base treatment, and ultraviolet treatment to improve adhesion to the protective layer coated on the film.

The organic / inorganic hybrid composition may be a mixture comprising an organosilane, a metal alkoxide and a filler.

The organosilane may be 20 to 99.99% by weight, and the metal alkoxide may be used at 20 to 70% by weight.

The organic / inorganic hybrid layer may be selected from the group consisting of UV cured or thermoset acrylate polymers, methacrylate polymers and acrylate / methacrylate copolymers.

The composition for preparing such an organic / inorganic hybrid layer is a resin composition capable of room temperature curing and heat curing, and is prepared by partially hydrolyzing a hydrolyzable organosilane in colloidal silica dispersed in an organic solvent, water, or a mixture thereof. An acrylic resin selected from the group consisting of a silica-dispersed oligomer solution of silane, an acrylate oligomer, a methacrylate oligomer and an oligomer of acrylate / methacrylate, and a curing catalyst.

Another type of organic / inorganic hybrid composition is a silicone oligomer solution, an acrylate oligomer solution, an acrylate monomer having two or more acrylate functional groups by hydrolyzing a UV-curable or thermosetting silicone coupling agent and an oily colloidal silica. Solutions, and photoinitiators and / or thermal initiators.

Preferably, the organic or organic / inorganic hybrid protective layer has a thickness of 0.01 μm to 10 μm. Hereinafter, an organic or organic / inorganic hybrid protective layer is called a protective layer.

In addition, the polymer coating layer may be prepared by coating a polyarylate solution with a phase difference defined by Equation 1 having a negative sign of 30 nm or more and a layer thickness of 10 μm or less and evaporating a solvent.

The polyarylate may be a polymer composed of A and B components represented by the following Chemical Formula 1.

Wherein R1, R2, R3 and R4 are each independently hydrogen, alkyl having C ₁ to C ₁₂ carbon atoms, arylalkyl having C ₆ to C ₁₂ carbon atoms, C ₆ to C ₁₂ acyl having aryl (aryl), alkoxy (alkoxy), the number of carbon atoms of the C ₁ ~ C ₁₂ having a nitrile (nitrile), C having a carbon number of ₁ ~ C ₁₂ having the carbon number of alkyl group of C ₁ ~ C ₁₂ having a number of carbon atoms ( acyl) or halogen, W is alkylidene having from ₁ to ₃₀ carbon atoms, alkylene having from ₂ to ₃₀ carbon atoms, cycloalkyl having from ₃ to ₃₀ carbon atoms Cycloalkylidene, cycloalkene having ₃ to ₃₀ carbon atoms or phenyl-substituted alkylene having ₁ to ₃₀ carbon atoms substituted with phenyl, oxygen, sulfur, sulfoxide, sulfone or may be a single bond, Y is an aromatic group groups C ₁ -C ₂ alkyl or halogen substituted or unsubstituted terephthalic acid, isophthalic acid, diben Acid or naphthalene dicarboxylic acid, or means a mixture thereof.

The polyarylate is an aromatic polymer prepared by condensation polymerization of an aromatic diol and an aromatic dicarboxylic acid, and preferably an entanglement molecular weight of 20,000 g / mol or more.

Hereinafter, the present invention will be described in detail.

In the compensation film used to increase the wide viewing angle of the liquid crystal display device, the polyarylate solution having a high thickness retardation is coated on the uniaxially stretched film to have the retardation in the polymer film regardless of the retardation in the thickness direction. And a compensation film having a thickness direction retardation at the same time. An organic / inorganic hybrid layer is used between the two polymers to solve problems such as adhesion, solvent penetration, warpage, and low orientation of the polymer.

The multifunctional compensation film is a retardation compensation film laminated on the uniaxially stretched polymer base layer 10 as the protective layer 20 and the coating layer 30 as shown in FIG. 1, and is protected on at least one side of the polymer base layer 10. A layer 20 and a polymer coating layer 30 are sequentially coated with a predetermined thickness to show a structure of manufacturing a film.

Compared with the conventional compensation film, the biaxial compensation film proposed in the present invention can independently adjust the phase difference in each direction, and by implementing a multilayer structure, it is characterized by maximizing efficiency by separating the functions of each layer. That is, as shown in FIG. 1, in the multilayer compensation film having three layers, the polymer base layer 10, which is the first layer, mainly gives a plane retardation, and the protective layer 20, which is the second layer, has a mechanical property such as curl prevention and polymer orientation of the coating layer. Mainly to improve the Finally, the polymer coating layer 30 provides a phase difference in the thickness direction. By doing so, it is possible to obtain a biaxial compensation film having a desired phase difference and having two optical axes perpendicular to each layer.

The polymer base layer 10 may be manufactured by extrusion or solution casting method with a film having little or no phase difference in thickness direction, and then uniaxially stretched at a temperature about 10 ° C. higher or lower than the glass transition temperature of the polymer. . The polymer base layer 10 may be made of a single polymer or a polymer composite material containing a blend of two or more polymers or an organic or inorganic additive. As the polymer that can be used as the substrate layer, polycarbonate, triacetyl cellulose, cycloolefin polymer, cycloolefin copolymer, (meth) acrylate resin, etc. may be used regardless of the glass transition temperature. Such a polymer film is a film having a thickness of about 50 to 300 microns (µm) and manufactured by a solution casting or melt extrusion process. The type and thickness of the film is determined by the retardation value. The film is uniaxially stretched to have a plane retardation. Annealing in the vicinity of the glass transition temperature is recommended to minimize temperature-deformation after film production. After annealing, primer coating may be performed on the surface of the polymer base film to improve the coating property and adhesion, or surface treatment may be performed by corona, oxygen or carbon dioxide plasma, ultraviolet-ozone, reaction gas inflow, or ion beam.

The protective layer is an organic or inorganic / organic hybrid protective layer 20 which not only improves the mechanical strength of the film and the adhesion of the substrate layer and the coating layer, but also the orientation of the polymer coated thereon by the surface properties depending on the degree of curing of the layer. It affects and plays an important role in determining the phase difference of the upper polymer coating layer. The protective layer is coated with a polymer base layer by a method such as spin coating, roll coating, bar coating, dip coating, gravure coating, comma coating, slot coating or spray coating, and the like, followed by thermosetting, UV curing, and infrared rays. It can harden | cure and manufacture by a high frequency heat processing method. After curing, the protective layer has a thickness of 0.5 to 5 microns (µm). In the above, the organic protective layer may be selected from the group consisting of UV-cured or thermoset acrylate polymer, methacrylate polymer and acrylate / methacrylate copolymer.

The organic / inorganic hybrid composition is composed of a mixture of an organosilane, a metal alkoxide, and a filler, and in some cases, an appropriate solvent, a polymerization catalyst, and an additive may be used.

In addition, the above-mentioned protective layer 20 has a variety of cross-linked forms in addition to the above-mentioned sol gel for the purpose of preventing the organic solvent of the polymer coating layer 30 penetrates into the polymer base layer 10. The compound of can be used. Firstly an acrylate represented by the formula (CH ₂ = CRCOO) _n R ¹ (wherein R is a hydrogen atom or a methyl group, R ¹ represents an organic matter, n is at least 2) and is UV curable and thermoset. Methacrylate polymers (US Pat. No. 4,605,465) can be used. Secondly, R ² _n SiX _4-n , a coating resin composition capable of both room temperature curing and heat curing and having excellent storage stability (wherein R ² is a homo or hetero substituted or unsubstituted C _1-9 monovalent hydrocarbon group or Organosilanes prepared by partially hydrolyzing a hydrolyzable organosilane represented by phenyl group, n is an integer of 0 to 3 and X is a hydrolysable functional group) in colloidal silica dispersed in an organic solvent, water or a mixture thereof. Silica-dispersed oligomer solution; Acrylic resins which are copolymers of acrylates and / or methacrylates represented by CH ₂ = CR ³ (COOR ⁴ ) (wherein R ³ represents a hydrogen atom or a methyl group and R ⁴ represents an organic substance); And a composition (Korea Patent Publication No. 1997-707487) composed of a curing catalyst. Finally, a silicone oligomer solution having two or more acrylate functional groups by hydrolyzing a UV-curable and / or thermosetting silicone coupling agent and an oily colloidal silica; Acrylate oligomer solution; Acrylate monomer solution; And compositions (photo Korean Patent No. 2002-0020599) composed of photoinitiators and / or thermal initiators.

The polymer coating layer 30 for imparting a thickness direction refractive index is coated with a solution made by dissolving a polymer having high birefringence in an organic solvent at a concentration of 10% by weight or less to prepare a film by volatilizing the solvent. The polymer that can be used in the layer should be a polymer having a high negative birefringence such as polyarylate, cycloolefin polymer, polyimide and the like. When these polymers are prepared into a film having a thickness of 50 to 100 µm by solvent casting, the phase difference of the film is excessively high, so that the film alone is not suitable for use as a compensation film. Therefore, it is necessary to use additives or to change the film manufacturing process to control their retardation. However, in the present invention, by coating a high birefringence polymer with a thin film of 0.1 ~ 5㎛ thickness it can be seen that the thickness direction retardation can be obtained without stretching. The phase difference of the entire laminated film can be obtained by adjusting the coating thickness of the layer and the composition of the protective layer. Retardation may also be affected by volatilization conditions of the solvent.

In the present invention, polyarylate is used as the polymer coating layer. Applicable polyarylate may be represented by the following Chemical Formula 1.

[Formula 1]

Wherein R1, R2, R3 and R4 are each independently hydrogen, alkyl having C ₁ to C ₁₂ carbon atoms, arylalkyl having C ₆ to C ₁₂ carbon atoms, C ₆ to C ₁₂ aryl group having a number of C _{(aryl), C 1 ~ C} 12 nitriles having a carbon number of (nitrile), acylamino (acyl having alkoxy (alkoxy), C having a carbon number of ₁ ~ C ₁₂ having a number of carbon atoms of the C ₁ ~ C ₁₂ ) Or halogen, and W is alkylidene having a carbon number of C ₁ to C ₃₀ , alkylene having a carbon number of C ₂ to C ₃₀ , cycloalkylidene having a carbon number of C ₃ to C ₃₀ ( cycloalkylidene), cycloalkene having ₃ to ₃₀ carbon atoms or phenyl-substituted alkylene having ₁ to ₃₀ carbon atoms substituted with phenyl, oxygen, sulfur, sulfoxide, sulfone or single It can be a combination. Specifically applicable aromatic dihydroxy compounds are bis (4-hydroxyaryl) alkane, for example bis (4-hydroxyphenyl) methane (bis (4-hydroxyphenyl) methane), 2,2-bis (4-hydroxyphenyl) propane (2,2-bis (4-hydroxyphenyl) propane, BPA), 2,2-bis (4-hydroxyphenyl) ethane (2,2- bis (4-hydroxyphenyl) ethane), 2,2-bis (4-hydroxy-3-methylphenyl) propane (2,2-bis (4-hydroxy-3-methylphenyl) propane), 2,2-bis (4 -Hydroxyphenyl) heptane (2,2-bis (4-hydroxyphenyl) heptane), 2,2-bis (4-hydroxy-3,5-dichlorophenyl) propane (2,2-bis (4-hydroxy- 3,5-dichlorophenyl) propane), 2,2-bis (4-hydroxy-3,5-dibromophenyl) propane (2,2-bis (4-hydroxy-3,5-dibromophenyl) propane), Bis (4-hydroxyphenyl) phenylmethane, 4,4-dihydroxyphenyl-1,1-m-diisopropylbenzene (4,4-dihydroxyphenyl-1,1- m-diisopropylbenzene), 4,4-dihydroxyfe -9,9-fluorene (4,4-dihydroxyphenyl-9,9-fluorene), 2,2-bis (4-hydroxyphenyl) fluorene (2,2-bis (4-hydroxyphenyl) fluorine, BHPF) , 9,9-bis (3,5-dimethyl-4-hydroxyphenyl) fluorene (9,9-bis (3,5-dimethyl-4-hydroxyphenyl) fluorene, BDMPF) or 9,9-bis (3 , 5-dibromo-4-hydroxyphenyl) fluorene (9,9-bis (3,5-dibromo-4-hydroxyphenyl) fluorine, BFBPF) etc., and can mix and use 1 or more types.

In addition, bis (hydroxyaryl) cycloalkanes (bis (hydroxyaryl) cyclo alkanes), for example, 1,1-bis (4,4-dihydroxyphenyl) cyclopentane (1,1-bis ( 4,4-hydroxyphenyl) cyclopentane), 1,1-bis (4,4-dihydroxyphenyl) cyclohexane (1,1-bis (4,4-hydroxyphenyl) cyclohexane), 1-methyl-1- (4 -Hydroxyphenyl) -4- (dimethyl-4-hydroxyphenyl) cyclohexane (1-methyl-1- (4-hydroxyphenyl) -4- (dimethyl-4-hydroxyphenyl) cyclohexane), 4- {1- [ 3- (4-hydroxyphenyl) -4-methylcyclohexyl] -1-methylethyl} phenol (4- {1- [3- (4-hydroxyphenyl) -4-methylcyclohexyl] -1-methylethyl} phenol), 4,4- [1-methyl-4- (1-methylethyl) -1,3-cyclohexylidyl] bisphenol (4,4- [1-methyl-4- (1-methylethyl) -1,3- cyclohexylidyl] bisphenol), 2,2,2,2-tetrahydro-3,3,3,3-tetramethyl-1,1-spirobis- [1H] -indene-6,6-diol (2,2, 2,2-tetrahydro-3,3,3,3-tetramethyl-1,1-spirobis- [1H] -indene-6,6-diol), etc. There is also.

As dihydroxy diaryl ether, for example, bis (4-hydroxyphenyl) ether, bis (4-hydroxy-3, 5- dichlorophenyl) ether, 4, 4- dihydroxy-3, 3-dimethylphenyl ether; As dihydroxydiaryl sulfide, for example, 4, 4- dihydroxy diphenyl sulfide, 4, 4- dihydroxy-3, 3- dimethyl diphenyl sulfide; As the dihydroxydiaryl sulfoxide, for example, 4,4-dihydroxydiphenyl sulfoxide, 4,4-dihydroxy-3,3-dimethyldiphenyl sulfoxide; As dihydroxy diaryl sulfone, 4, 4- dihydroxy diphenyl sulfone, 4, 4- dihydroxy-3, 3- dimethyl diphenyl sulfone, etc. are mentioned, for example, 2 or more types of these are mixed. It may be used.

In Chemical Formula 1, Y may include terephthalic acid, isophthalic acid, dibenzoic acid, naphthalenedicarboxylic acid, or aromatic dicarboxylic acid substituted with C ₁ -C ₂ alkyl or a halogen group thereof in an aromatic group. You may mix and use species or more.

In particular, the present invention used a polyarylate containing the following repeating unit, and is not limited to the following structure.

Hereinafter, the present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited to the examples. In addition, the polyarylate mentioned above is not limited to the following synthesis examples.

Synthesis Example

9.93 g of 2,2-bis (4-hydroxyphenyl) propane, 0.066 g of t-butylphenol, 3.85 g of NaOH, and 92 g of distilled water were mixed in a reactor equipped with a stirrer, followed by stirring and melting. Thereafter, 0.48 g of benzyltriethylammonium bromide and 6.5 g of methylene chloride were added while maintaining the temperature of the reactor at 20 °, followed by vigorous stirring. Separately, 8.84 g of aromatic carboxylic acid mixture in which isophthalic acid and terephthalic acid were mixed in the same mole number was dissolved in 106 g of methylene chloride. This solution was added to the previously prepared aqueous alkali solution. After polymerization for 1 hour, the reaction was terminated by adding acetic acid, and then washed several times by adding 1 volume of methylene chloride and 2 volumes of distilled water. Washing was repeated until the filtrate had a conductivity of 50 μs / cm or less and the solution was added to methanol to precipitate the polymer. The composition of the dihydroxy monomer of the synthesized polyarylate was 100 mol% of 2,2-bis (4-hydroxyphenyl) propane (BPA), the glass transition temperature was 200 ° C, and the molecular weight was 98,000 g / mol.

Example 1

The polycarbonate film prepared by the organic solvent casting process having a thickness direction of 100 μm and having a thickness direction of −59 nm and no surface direction retardation was heat-treated in a convection oven at 150 ° C. for 2 minutes, followed by stretching by 10% in one axis and cooling to the surface direction. Phase difference was given. Thermal curing was performed by coating a silica-dispersed acrylate oligomer solution of an organosilane, which is an organic / inorganic hybrid composition, as a protective layer on the polycarbonate film having a plane retardation and a thickness retardation. The coating thickness of the protective layer measured by alpha stepper was 1.5 micrometers.

In the above synthesis example, 5 wt% of polyarylate polymerized with 100 mol% of bisphenol A was added to a dichloroethane solvent to prepare a solution. 5 wt% polyarylate solution was coated on the protective layer coated polycarbonate prepared above with a thickness control bar coater to a thickness as shown in Table 1, and the solvent was dried at room temperature for 1 hour and dried at 90 ° C. The residual solvent was dried again for 5 minutes in an oven to obtain a compensation film. The thickness of the coating layer was measured by alpha stepper. The optical characteristics of the base material layer and the laminated film were confirmed by the surface direction phase difference and the thickness direction phase difference. The thickness direction retardation of the film was measured by retardation at the 50 degree angle and -50 degree angle of the film surface and the light beam, and the thickness direction retardation was calculated by the following equation.

Where R _th is the thickness retardation, R _?? Is the phase difference at the angle θ , R _in is the plane retardation of the film measured when θ is 0, and θ is the angle between the film surface and incident light.

Equation (1) it is defined by the R _th by the relation of different refractive index in each direction in such a manner as to define the R _th. On the other hand, Equation 3 represents a relational expression for measuring R _th and the phase difference value is calculated by Equation 3 from the transmittance data, and all phase difference results according to the present embodiment are calculated by Equation 3.

Example 2

A compensation film was prepared in the same manner as in Example 1 except that the triacetyl cellulose substrate biaxially stretched instead of the polycarbonate substrate stretched in Example 1 was used. Optical properties of the compensation film of Example 2 are shown in Table 1.

Example 3

A compensation film was prepared in the same manner as in Example 1 except that the biaxially stretched cycloolefin polymer substrate was used instead of the polycarbonate substrate stretched in Example 1. Optical properties of the compensation film of Example 3 are shown in Table 1. The glass transition temperature and molecular weight of the coating layer polymers of Examples 1 to 3 were measured by RSA III of Leometrics and GPC of Agilent, and the glass transition temperature was 200 ° C., and the weight average molecular weight was 98,000 g / mol.

Example 4

Compensation was carried out in the same manner as in Example 1 except that the polyarylate used in Example 1 contained 10 mol% of bisphenol A, a molecular weight of 40,000 g / mol, and a glass transition temperature of 300 ° C. A film was prepared. Optical properties of the compensation film of Example 4 are shown in Table 1.

Comparative Example 1

The same process as in Example 1 was carried out except that the film was prepared using only the polycarbonate substrate not stretched in Example 1.

Comparative Example 2

In Example 1, the same procedure as in Example 1 was performed except that the polyarylate solution was directly coated without using a protective layer on the stretched polycarbonate substrate.

Comparative Example 3

Except for coating only the protective layer on the stretched polycarbonate substrate in Example 1 and prepared without coating the polyarylate it was carried out in the same manner as in Example 1. Optical properties of the compensation films of Comparative Examples 1 to 3 are shown in Table 1.

Organic-Inorganic Hybrid Protective Layer Thickness (μm) Polymer coating layer thickness (㎛) R _in (nm) Total R _th (nm) Comparative Example 1 1.5 2.2 5 -123 Comparative Example 2 0 2 5 -65 Comparative Example 3 1.5 0 5 -59 Example 1 1.5 1.5 43 -165 Example 2 1.5 1.6 75 -207 Example 3 1.5 1.3 110 -240 Example 4 1.5 1.5 43 -165

Since the polymer of the base material layer used in Examples 1 to 4 is biaxially stretched, the surface direction retardation ( R _in ) is present, and the phase difference in the thickness direction is given by the coating of the organic / inorganic hybrid composition and the coating of the polyarylate. A biaxial compensation film was obtained. Since the compensation film has a phase retardation and a thickness retardation at the same time and can control each independently, it can be used as a plane and thickness compensation film as one film. When the solvent evaporated from the polymer solution using THF as a solvent, the orientation of the polymer was different according to the characteristics of the substrate, and thus the thickness direction retardation was different. The higher the affinity with the polymer and the higher the inorganic content, the greater the phase difference.

The multilayer compensation films prepared by Examples 1 to 4 have no bending after drying, and as shown in Table 1, it can be seen that the retardation in the thickness direction is increased than that of the film made of the polycarbonate substrate of Comparative Example 1 only. . And as in Comparative Example 2, the film produced without using the organic / inorganic hybrid protective layer caused the film to bend as the solvent evaporated from the polymer coating layer, and the warping phenomenon occurred due to the attack on the substrate of the solvent. In the case of the absence of the organic-inorganic hybrid protective layer, the phase difference was remarkably reduced, and thus, sufficient phase difference could not be obtained. In addition, the phase difference was remarkably reduced even when there is no polymer coating layer as in Comparative Example 3.

The biaxial compensating film of the present invention provides a retardation in a plane direction and a thickness direction by a new method, and can replace a retardation film by existing stretching. It can be used more suitably for securing. In addition, fine phase difference can be controlled by coating the organic / inorganic hybrid composition with a protective layer and coating a polyarylate solution to control the coating thickness. In addition, there is an advantage in that the plane direction phase difference and the thickness direction phase difference are obtained by independent methods, and each optical axis is perpendicular to each other. As a result, one film can be used as A type and negative (negative birefringence) C type compensation film.

Claims (14)

In the compensation film for a liquid crystal display device, A polymer substrate layer having a plane retardation value defined by Equation 2 by uniaxially stretching a polymer film prepared by a casting or extrusion process; A protective layer formed by coating and curing an organic or organic / inorganic hybrid composition on at least one side of the polymer base layer; And A polymer coating layer formed on the polymer substrate layer on which the protective layer is formed, and having a phase difference value in a thickness direction defined by Equation 1 below; Compensation film for a liquid crystal display device comprising a. [Equation 1]

[Equation 2] R _in = (n _x -n _y ) × d In the above formula, n _z is the thickness direction refractive index of the film, n _x and n _y is the surface direction refractive index of the film, d is the thickness of the film, R _th is the thickness direction phase difference, R _in is the surface direction phase difference. The method of claim 1, The liquid crystal display of the entire compensation film, wherein the thickness retardation value defined by Equation 1 is 30 nm or more while having a negative sign, and the plane retardation value defined by Equation 2 is 20 nm or more. Compensation film for the device. The method of claim 1, The polymer substrate layer has a plane direction retardation of 20 nm or more defined by Equation 2, and has a structure in which one or more films are laminated, and a thickness of the polymer substrate layer is 10 μm to 200 μm, and polycarbonate, triacetyl cellulose, and cyclo A compensation film for a liquid crystal display device, characterized in that the film is an optically uniform and transparent polymer film selected from the group consisting of an olefin (co) polymer and a (meth) acrylate. The method of claim 1, The organic / inorganic hybrid composition is a compensation film for a liquid crystal display device, characterized in that a mixture containing an organosilane, a metal alkoxide and a filler. The method of claim 4, wherein The organosilane is a compensation film for a liquid crystal display device, characterized in that 20 to 99.99% by weight. The method of claim 4, wherein The metal alkoxide is a compensation film for a liquid crystal display device, characterized in that 20 to 70% by weight. The method of claim 1, The protective layer is a compensation film for a liquid crystal display device, characterized in that selected from the group consisting of UV-cured or thermoset acrylate polymer, methacrylate polymer and acrylate / methacrylate copolymer. The method of claim 1, The organic / inorganic hybrid composition is a resin composition capable of room temperature curing and heat curing, and silica-dispersion of an organosilane prepared by partial hydrolysis of a hydrolyzable organosilane in colloidal silica dispersed in an organic solvent, water, or a mixture thereof. Compensation film for a liquid crystal display device comprising an acrylic resin selected from the group consisting of oligomer solution, acrylate oligomer, methacrylate oligomer and oligomer of acrylate / methacrylate, and a curing catalyst. The method of claim 1, The organic / inorganic hybrid composition is a silicone oligomer solution having two or more acrylate functional groups, an acrylate oligomer solution, an acrylate monomer solution, and a photoinitiator by hydrolyzing a UV-curable or thermosetting silicone coupling agent and an oily colloidal silica. And / or a compensation film for a liquid crystal display device comprising a thermal initiator. The method of claim 1, The organic / inorganic hybrid protective layer has a thickness of 0.01 μm to 10 μm. The method of claim 1, The polymer coating layer is a compensation for a liquid crystal display device, characterized in that the phase difference defined by the formula (1) has a negative sign of 30nm or more, the thickness of the layer is manufactured by coating a polyarylate solution of 10㎛ or less film. The method of claim 10, The polyarylate is a compensation film for a liquid crystal display device, characterized in that the polymer is composed of A, B components represented by the following formula (1). [Formula 1]

Wherein R1, R2, R3 and R4 are independently from each other hydrogen, C ₁ ~ C ₁₂ alkyl having a number of carbon atoms, C ₆ ~ C ₁₂ aryl alkyl having a carbon number of, C ₆ ~ C aryl, C having ₁₂ carbon atoms in the ₁ to an acyl group or a halogen with a nitrile, the carbon number of the alkoxy, C ₁ to C ₁₂ having a number of carbon atoms of the C ₁ to C ₁₂ having the carbon number of alkyl group of C _12, W is an alkyl having a carbon number of the C ₁ to C ₃₀ the number of carbon atoms of the alkylidene, C ₂ ~ cycloalkyl alkylidene, C ₃ ~ C with ₃₀ cycles alkene, or having a carbon number of phenyl-substituted C ₁ ~ C ₃₀ having a number of carbon atoms of the C ₃₀ carbon atoms, an alkylene, C ₃ ~ C ₃₀ having a May be alkylene, oxygen, sulfur, sulfoxide, sulfone or a single bond, and Y is terephthalic acid, isophthalic acid, dibenzoic acid or naphthalenedicarboxylic acid substituted or unsubstituted with a C ₁ -C ₂ alkyl or halogen group in an aromatic group. Or a mixture thereof. The method of claim 11, The polyarylate is a compensation film for a liquid crystal display device, characterized in that the entanglement molecular weight is 20,000g / mol or more. Uniaxially stretching the polymer film; Coating and curing the organic / inorganic hybrid composition on the stretched film; And Preparing a polymer film by coating a polymer solution selected from the group consisting of polyarylate, cycloolefin polymer, and polyimide on the cured film of the organic / inorganic hybrid composition, and volatilizing a solvent; Method for producing a compensation film for a liquid crystal display device according to claim 1 comprising a.

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