WO2015008925A1 - Polarising film and image display apparatus having same - Google Patents

Abstract

The present invention relates to a polarising film and an image display apparatus having the same. More specifically, the present invention relates to a polarising film provided with a liquid crystal layer and a substrate that are coupled together by a chemical bond, wherein the chemical bond is formed by a reactive group provided on a surface of the substrate, and an isocyanate group and a (meth)acrylate group provided on the end of an adhesion promoter included in the liquid crystal layer, which thereby provides a very high adhesion between respective layers.

Description

Retardation film and image display apparatus having same

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a retardation film having an alignment layer without an alignment layer and having excellent interlayer adhesion, and an image display device having the same.

BACKGROUND ART Image display apparatuses, which are mainly dominated by conventional CRT monitors, have recently been rapidly developed, and wider, lighter and even bent image display apparatuses such as LCDs, OLEDs, and electronic papers have been introduced one after another.

Among the image display devices, the most common liquid crystal display device is, in addition to conventionally known liquid crystal display devices having liquid crystal cells such as TN (Twisted? Nematic) mode, STN (Super Twisted Nematic) mode, VA (Vertical Alignment) mode, A transverse electric field type liquid crystal display device in which electrodes are formed only on one side of a pair of opposing substrates, such as IPS (In-Plane® Switching) mode or FFS (Fringe Field Switching) mode, to generate an electric field in parallel with the substrate. It is known to include.

In the liquid crystal display, the light emitted from the back light, which is the light source, passes through the liquid crystal having anisotropy and a pair of polarizing plates disposed perpendicular to each other, so that a good image can be obtained from the front of the liquid crystal display, but viewed from the side. In this case, the viewing angle dependence of deterioration of display performance is shown. In order to improve the black display state (black characteristic), side contrast ratio (CR), color shift, and the like of such a liquid crystal display, and to reduce the viewing angle dependency, a retardation film is used. Since the retardation film converts linearly polarized light into elliptical polarization or circularly polarized light, or converts linearly polarized light in a certain direction to another direction, the retardation film can improve the viewing angle, brightness, contrast, etc. of the liquid crystal display by using the same. .

The retardation film is usually manufactured by coating an alignment agent to form a thin alignment film, then coating the liquid crystal onto the alignment film to orient and curing the liquid crystal, and the liquid crystal is a rod-type or coin-shaped discotic. It can be divided into (discotic) liquid crystal, among which the alignment state of the rod-shaped liquid crystal can be largely divided into five types as follows.

First, planar orientation refers to an orientation in which the optical axis is parallel to the film plane, and second, homeotropic orientation refers to an orientation where the optical axis is perpendicular to the film plane, that is, parallel to the film normal. Tilted orientation refers to an orientation in which the optical axis is inclined at a certain angle between 0 ° and 90 ° with respect to the film plane. And fourth, the splay orientation refers to the orientation in which the optical axis continuously changes at an inclination angle of 0 ° to 90 °, or at a minimum within the range of 0 ° to 90 °. Fifth, the cholesteric orientation indicates that the optical axis is in the film plane. Parallel to is similar to the planar orientation, but refers to an orientation in which the optical axis rotates by a certain angle clockwise or counterclockwise when viewed in the vertical direction with respect to the thickness direction.

Among these, the second vertically aligned liquid crystal film is used alone or in combination with another film, and as described above, TN (Twist Nematic) mode, STN (Super Twist Nematic) mode, IPS (In Plane Switching) mode, VA (Vertical Alignment) It can be used as an optical film, such as a retardation film, in liquid crystal display devices, such as a) mode and an OCB (Optically Compensated Birefringence) mode.

The vertical alignment liquid crystal film is roll-to-roll pressed while passing between rollers facing each other at regular intervals, such as in a polarizing plate fabrication process, in order to adhere to a polarizing plate for the purpose of brightness enhancement or viewing angle compensation. It is desirable to use a plastic substrate that is flexible to pressure and slight impacts.

Several proposals have been made to form vertically oriented liquid crystals on such plastic films.

U. S. Patent No. 6,816, 218 describes the use of an aluminum film deposited on a plastic substrate as a vertical alignment film. In this case, because aluminum is weakly attached to the surface of the plastic substrate, part of the aluminum may be removed during peeling, which may cause a defect.

EP 1 3616 3 describes coating a liquid crystal solution having a horizontal or twisted orientation on a plastic substrate, and then using this as an alignment layer to implement a vertically aligned liquid crystal thereon. However, in this case, there is a problem in that the degree of vertical alignment of the liquid crystal layer is determined according to the degree of curing of the liquid crystal used as the alignment layer.

U.S. Patent No. 20060278851 and Japanese Patent Laid-Open No. 2006-126757 show films having increased adhesion by adding a primary amino silane-based coupling agent to a vertically oriented liquid crystal solution. However, these primary amino silane-based coupling agents show a weakness that degrades the transparency of the liquid crystals as a result.

In Korean Laid-Open Patent Publication No. 2006-0066045, a polymerizable reactive liquid crystal mixture solution containing a predetermined surfactant is coated on a hydrophilic plastic substrate and subjected to vertical alignment without the need to separately use an alignment film for inducing vertical alignment of liquid crystals. A liquid crystal film was made. However, there is a big problem in the adhesion between the liquid crystal and the substrate, there is a problem that the defects occur due to the liquid crystal orientation is unstable fundamentally.

[Preceding technical literature]

[Patent Documents]

(Patent Document 1) US Patent No. 6,816,218

(Patent Document 2) European Patent No. 1377163

(Patent Document 3) US Patent No. 20060278851

(Patent Document 4) Japanese Laid-Open Patent No. 2006-126757

(Patent Document 5) Korean Patent Publication No. 2006-0066045

An object of the present invention is to provide a retardation film containing no alignment film.

Moreover, another object of this invention is to provide the retardation film which is excellent in the adhesive force between each layer, and does not peel a liquid crystal layer and a base material in a manufacturing process.

Moreover, another object of this invention is to provide the image display apparatus provided with the retardation film mentioned above.

1. A retardation film having a base material and a liquid crystal layer bonded by a chemical bond, wherein the chemical bond is an isocyanate group and (meth) acryl present at the terminal of the adhesion enhancer included in the reactive group on the surface of the base material and the liquid crystal layer. A retardation film formed by a rate group.

2. The retardation film of claim 1, wherein the adhesion enhancer is one or more selected from the group consisting of compounds of Formulas 1 to 4 below:

[Formula 1]

(Wherein R ₁ and R ₂ are each independently hydrogen or a methyl group,

R ₃ and R ₇ are each independently an alkylene group having 1 to 10 carbon atoms unsubstituted or substituted with a group selected from the group consisting of a ketone group, an ester group and a thiol group,

R ₄ and R ₆ are each independently an alkylene group having 1 to 10 carbon atoms unsubstituted or substituted with a group selected from the group consisting of an amide group, a ketone group, an ester group and a thiol group,

R ₅ is an alkylene group having 1 to 10 carbon atoms unsubstituted or substituted with an alkoxy group having 1 to 8 carbon atoms,

[Formula 2]

(Wherein R ₇ and R ₈ are each independently hydrogen or a methyl group,

R ₉ and R ₁₁ are each independently an alkylene group having 1 to 10 carbon atoms unsubstituted or substituted with a group selected from the group consisting of a ketone group, an ester group and a thiol group,

R ₁₀ is (a)

Or (b)

E ₁ and E ₃ are each independently a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms or an alkoxy group having 1 to 8 carbon atoms, and E ₂ is an alkoxy group having 1 to 8 carbon atoms. Substituted or unsubstituted alkylene group having 1 to 10 carbon atoms,

[Formula 3]

(Wherein R ₁₂ is hydrogen or a methyl group,

R ₁₃ is an alkylene group having 1 to 10 carbon atoms unsubstituted or substituted with a group selected from the group consisting of a ketone group, an ester group and a thiol group; and

[Formula 4]

(Wherein, R ₁₄ is hydrogen or a methyl group,

R ₁₅ is an alkylene group having 1 to 10 carbon atoms unsubstituted or substituted with a group selected from the group consisting of a ketone group, an ester group and a thiol group.

3. The retardation film of claim 1, wherein the liquid crystal layer is formed of a curable composition containing a liquid crystal compound including a reactive group capable of reacting with an isocyanate group or a (meth) acrylate group of an adhesion enhancing agent.

4. The retardation film of the above 3, wherein the reactive group of the liquid crystal compound is a carbon-carbon unsaturated bond, a hydroxyl group, an epoxy group or a cyano group.

5. In the above 3, the curable composition for forming a liquid crystal layer retardation film containing 0.1 to 15 parts by weight of the adhesion strength enhancer based on 100 parts by weight of the liquid crystal compound.

6. In the above 3, wherein the liquid crystal compound is a retardation film is a vertical alignment liquid crystal compound.

7. The retardation film of claim 1, wherein the reactive group on the surface of the substrate is at least one selected from the group consisting of a hydroxyl group, a thiol group, a carboxyl group, and an amine group.

8. according to the above 1, wherein the substrate is a retardation film containing triacetyl cellulose-based, cycloolefin-based or PMMA-based polymer.

9. The retardation film of claim 8, wherein the surface treatment is at least one treatment selected from the group consisting of saponification treatment, primer treatment, corona treatment, plasma treatment, and coating treatment.

10. The retardation film of claim 9, wherein the plasma treatment is at least one selected from the group consisting of a remote plasma treatment, a direct plasma treatment, and a monomer plasma treatment.

11. In the above 1, wherein the chemical bond between the liquid crystal layer and the substrate is at least one of a urethane bond and a thiylene bond retardation film.

12. The retardation film of claim 11, wherein the urethane bond between the liquid crystal layer and the substrate is formed by the reaction of an isocyanate group of the adhesion enhancing agent of the alignment layer with a hydroxyl group, a thiol group, a carboxyl group, or an amine group of the substrate.

13. The retardation film of claim 11, wherein the thiylene bond between the liquid crystal layer and the substrate is formed by the reaction of the (meth) acrylate group of the adhesion enhancing agent of the alignment layer with the thiol group of the substrate.

14. The retardation film of the above 1, wherein the substrate has a water contact angle of 60 to 80 ° of the liquid crystal layer side surface.

15. The retardation film of 1 above, wherein the substrate is a + A plate or a -B plate and the liquid crystal layer is a + C plate.

16. Image display device having a phase difference film of any one of the above 1 to 15.

17. The image display apparatus according to 16 above, wherein the image display apparatus is in an IPS mode.

Since the retardation film of the present invention does not include an alignment film, a thin film structure can be realized and manufacturing is easy.

In addition, in the retardation film of the present invention, a chemical bond is formed between the liquid crystal layer and the base film in the process of forming the liquid crystal layer, and thus the interlayer adhesion is very high.

Since the retardation film of the present invention has a very high interlayer adhesion, the peeling phenomenon is remarkably reduced during the desorption process using the adhesive layer in manufacturing an optical film such as a polarizing film using the same, and thus the defect rate is low, thereby improving productivity. .

1 is a schematic cross-sectional view of a retardation film according to the present invention.

FIG. 2 is a diagram showing the relationship between the directions (x, y, z) of the refractive indices nx, ny, and nz.

3 is a view showing a schematic laminated structure of a display panel having a phase difference film of the present invention.

The present invention provides a retardation film having a liquid crystal layer and a substrate bonded by a chemical bond, wherein the chemical bond is an isocyanate group and (meth) present at the end of the adhesion enhancing agent contained in the reactive group on the surface of the substrate and the liquid crystal layer. By forming with an acrylate group, it is related with the retardation film with very high interlayer adhesion.

Hereinafter, the present invention will be described in detail.

The structure of one embodiment of the retardation film according to the present invention is shown in FIG. 1. The retardation film 100 of the present invention has a structure in which the liquid crystal layer 120 is formed on the substrate 110.

<Liquid crystal layer>

The liquid crystal layer 120 may be manufactured by curing the composition for forming a liquid crystal layer. The composition for forming a liquid crystal layer according to the present invention further comprises (a) an adhesion enhancing agent in addition to (b) a liquid crystal compound, (c) a polymerization initiator, and (d) an organic solvent which are commonly used in the art.

(a) adhesion enhancer

The composition for forming a liquid crystal layer according to the present invention includes an adhesion enhancing agent capable of forming a chemical bond between the liquid crystal layer 120 and the substrate 110. The adhesion enhancer has a structure including an isocyanate group at one end and a (meth) acrylate group at the other end, and the (meth) acrylate group and the isocyanate group of the adhesion enhancer react with a reactive group on the surface of the substrate 110 to chemically Forming a bond, the adhesion between the liquid crystal layer 120 and the substrate 110 can be significantly increased.

In the present invention, (meth) acrylate means either acrylate or methacrylate, or optionally both acrylate and methacrylate.

In the present invention, the (meth) acrylate group and the isocyanate group of the adhesion strength agent are retardation films even when the adhesion strength agent is not mixed with the composition for forming a liquid crystal layer, even if the (meth) acrylate group and / or isocyanate group are not included at the terminal. It is also defined as referring to a functional group where a (meth) acrylate group or an isocyanate group is produced through further treatment, such as heat treatment, prior to chemical bonding with the substrate 110. For example, as a functional group in which an isocyanate group is produced through heat treatment, a pyrazole group connected by an amide bond to the terminal of the adhesion promoter may be mentioned. Gastric pyrazole groups are separated through a heat treatment process, an isocyanate group is formed at the end.

As the adhesion enhancing agent according to the present invention, any compound having a structure including at least one isocyanate group at one end and a (meth) acrylate group at the other end may be used without particular limitation, and more specifically, the following Chemical Formulas 1 to 4 Can be used alone or in combination of two or more of them:

[Formula 1]

(Wherein R ₁ and R ₂ are each independently hydrogen or a methyl group,

R ₃ and R ₇ are each independently an alkylene group having 1 to 10 carbon atoms unsubstituted or substituted with a group selected from the group consisting of a ketone group, an ester group and a thiol group,

R ₄ and R ₆ are each independently an alkylene group having 1 to 10 carbon atoms unsubstituted or substituted with a group selected from the group consisting of an amide group, a ketone group, an ester group and a thiol group,

R ₅ is an alkylene group having 1 to 10 carbon atoms unsubstituted or substituted with an alkoxy group having 1 to 8 carbon atoms,

[Formula 2]

(Wherein R ₇ and R ₈ are each independently hydrogen or a methyl group,

R ₉ and R ₁₁ are each independently an alkylene group having 1 to 10 carbon atoms unsubstituted or substituted with a group selected from the group consisting of a ketone group, an ester group and a thiol group,

R ₁₀ is (a)

Or (b)

E ₁ and E ₃ are each independently a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms or an alkoxy group having 1 to 8 carbon atoms, and E ₂ is an alkoxy group having 1 to 8 carbon atoms. Substituted or unsubstituted alkylene group having 1 to 10 carbon atoms,

[Formula 3]

(Wherein R ₁₂ is hydrogen or a methyl group,

R ₁₃ is an alkylene group having 1 to 10 carbon atoms unsubstituted or substituted with a group selected from the group consisting of a ketone group, an ester group and a thiol group; and

[Formula 4]

(Wherein, R ₁₄ is hydrogen or a methyl group,

R ₁₅ is an alkylene group having 1 to 10 carbon atoms unsubstituted or substituted with a group selected from the group consisting of a ketone group, an ester group and a thiol group.

In the composition for forming a liquid crystal layer according to the present invention, the adhesion enhancer represented by Chemical Formulas 1 to 4 is represented by at least one of the compounds represented by Chemical Formulas 2 to 4 and Chemical Formula 1 to secure superior interlayer adhesion. It can be used as a mixture of the compounds.

More specific examples of the adhesion enhancer of Formula 1 to Formula 4 may include at least one selected from the group consisting of compounds represented by the following Formulas 5 to 15:

[Formula 5]

[Formula 6]

[Formula 7]

[Formula 8]

[Formula 9]

[Formula 10]

[Formula 11]

[Formula 12]

[Formula 13]

[Formula 14]

[Formula 15]

Compounds represented by the above formula (4) and compounds represented by the above formulas (12), (13), (14) and (15), which are examples of the compounds, are separated from the terminal by dimethyl pyrazole group through a heat treatment process such as a drying process, and thus It will have an isocyanate group.

The content of the adhesion enhancing agent is 0.1 to 15 parts by weight of the adhesion enhancing agent with respect to 100 parts by weight of the liquid crystal compound effectively exerts the effect of strengthening the adhesion between the substrate and the liquid crystal layer, while maintaining the liquid crystal orientation and does not reduce the phase difference Preferred at

(b) liquid crystalline compound

In the present invention, the liquid crystal compound is a main raw material which is oriented in a specific direction and exhibits the desired effect of the retardation film. The liquid crystal compound according to the present invention is oriented on the base film without a conventional alignment film for inducing alignment, and in this respect, the liquid crystal compound is preferably a vertical alignment liquid crystal compound. Among the vertically aligned liquid crystal compounds, the present invention can be applied without particular limitation.

The liquid crystalline compound includes a reactive group that performs a curing reaction after orientation, and the reactive group may also react with an isocyanate group or a (meth) acrylate group of the adhesion enhancer. Examples of the reactive group of the liquid crystal compound include a carbon-carbon unsaturated bond, a hydroxy group, an epoxy group, a cyano group, and the like, and preferably a carbon-carbon unsaturated bond. More specifically, the carbon-carbon unsaturated bond may be a carbon-carbon unsaturated bond included in an acryloyloxy group, cyanoacrylate group, allyl group, cinnamate group, or allyloxy group.

Therefore, any liquid crystalline compound having a reactive group among the vertically oriented liquid crystalline compounds used in the art may be used in the present invention without limitation, and the liquid crystalline compound commonly used in the art is such a reactive group as such. If not present, it can be used in the present invention without limitation as long as a reactive group can be introduced at the terminal through a pretreatment process known in the art. More specific examples of such a liquid crystalline compound include compounds represented by the following formulas (16) to (18).

[Formula 16]

[Formula 17]

[Formula 18]

On the other hand, the chemical bond of the reactive group of the liquid crystal compound and the isocyanate group or (meth) acrylate group of the adhesion enhancing agent, see Schemes 1 to 6 described later.

(c) polymerization initiator

In the composition for forming a liquid crystal layer according to the present invention, a photoinitiator or a thermal initiator commonly used in the art may be used as the polymerization initiator, and preferably a photoinitiator may be used.

More specifically, examples of the photoinitiator include triazine compounds, acetophenone compounds, biimidazole compounds, oxime compounds, benzoin compounds, benzophenone compounds, thioxanthone compounds, anthracene compounds, and the like. However, the present invention is not limited thereto.

As the above triazine-based compound, for example, 2,4-bis (trichloromethyl) -6- (4-methoxyphenyl) -1,3,5-triazine, 2,4-bis (trichloromethyl)- 6- (4-methoxynaphthyl) -1,3,5-triazine, 2,4-bis (trichloromethyl) -6-piperonyl-1,3,5-triazine, 2,4- Bis (trichloromethyl) -6- (4-methoxystyryl) -1,3,5-triazine, 2,4-bis (trichloromethyl) -6- [2- (5-methylfuran-2 -Yl) ethenyl] -1,3,5-triazine, 2,4-bis (trichloromethyl) -6- [2- (furan-2-yl) ethenyl] -1,3,5-tri Azine, 2,4-bis (trichloromethyl) -6- [2- (4-diethylamino-2-methylphenyl) ethenyl] -1,3,5-triazine, 2,4-bis (trichloro Methyl) -6- [2- (3,4-dimethoxyphenyl) ethenyl] -1,3,5-triazine and the like.

As the acetophenone-based compound, for example, diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyl dimethyl ketal, 2-hydroxy-1- [4- (2 -Hydroxyethoxy) phenyl] -2-methylpropane-1-one, 1-hydroxycyclohexylphenyl ketone, 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropane-1- On, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butan-1-one, 2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl] propane Oligomer of -1-one, 2-methyl-2-amino (4-morpholinophenyl) ethan-1-one, 2-ethyl-2-amino (4-morpholinophenyl) ethan-1-one, 2 -Propyl-2-amino (4-morpholinophenyl) ethan-1-one, 2-butyl-2-amino (4-morpholinophenyl) ethan-1-one, 2-methyl-2-amino (4 -Morpholinophenyl) propane-1-one, 2-methyl-2-amino (4-morpholinophenyl) butan-1-one, 2-ethyl-2-amino (4-morpholinophenyl) propane- 1-one, 2-ethyl-2-amino (4-morpholinophenyl) butan-1-one, 2-methyl-2-meth Amino (4-morpholinophenyl) propane-1-one, 2-methyl-2-dimethylamino (4-morpholinophenyl) propane-1-one, 2-methyl-2-diethylamino (4-mor Polynophenyl) propan-1-one etc. are mentioned.

As the biimidazole-based compound, for example, 2,2'-bis (2-chlorophenyl) -4,4 ', 5,5'-tetraphenylbiimidazole, 2,2'-bis (2,3 -Dichlorophenyl) -4,4 ', 5,5'-tetraphenylbiimidazole, 2,2'-bis (2-chlorophenyl) -4,4', 5,5'-tetra (alkoxyphenyl) ratio Imidazole, 2,2'-bis (2-chlorophenyl) -4,4 ', 5,5'-tetra (trialkoxyphenyl) biimidazole, phenyl group at 4,4', 5,5 'position And imidazole compounds substituted with a boalkoxy group. Among them, 2,2'-bis (2-chlorophenyl) -4,4 ', 5,5'-tetra phenylbiimidazole, 2,2'-bis (2,3-dichlorophenyl) -4,4' , 5,5'-tetraphenylbiimidazole is preferably used.

Examples of the above oxime compounds include 0-ethoxycarbonyl-α-oxyimino-1-phenylpropan-1-one and the like.

As said benzoin type compound, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, etc. are mentioned, for example.

As the above benzophenone-based compound, for example, benzophenone, methyl 0-benzoylbenzoate, 4-phenylbenzophenone, 4-benzoyl-4'-methyldiphenyl sulfide, 3,3 ', 4,4'-tetra ( tert-butylperoxycarbonyl) benzophenone, 2,4,6-trimethylbenzophenone, etc. are mentioned.

Examples of the thioxanthone-based compound include 2-isopropyl thioxanthone, 2,4-diethyl thioxanthone, 2,4-dichloro thioxanthone, 1-chloro-4-propoxy thioxanthone, and the like. Can be mentioned.

Examples of the anthracene-based compound include 9,10-dimethoxyanthracene, 2-ethyl-9,10-dimethoxyanthracene, 9,10-diethoxyanthracene, 2-ethyl-9,10-diethoxyanthracene, and the like. Can be mentioned.

In addition, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 10-butyl-2-chloroacridone, 2-ethylanthraquinone, benzyl, 9,10-phenanthrenequinone, camphorquinone, phenylclioxylic acid Methyl, a titanocene compound, the photoinitiator which has group which can cause the chain transfer described in Unexamined-Japanese-Patent No. 2002-544205, etc. are mentioned.

In another aspect of the composition for forming a liquid crystal layer of the present invention, the photoinitiator may not be included. Photoinitiators have the advantage that the photo-alignment agent facilitates the photopolymerization reaction. However, when the photoinitiator is used in an excessive amount, it acts as an impurity, lowers the orientation force, breaks down the liquid crystal orientation, and may cause light leakage phenomenon during cross polarization, or the photoinitiator may be sublimated after photocuring to contaminate the mask. When the intensity of the initiator reaction wavelength is very high compared to the wavelength at which the reaction occurs, side effects may be reduced such as lowering the line speed for the optical alignment. In this aspect, the composition for forming a liquid crystal layer of the present invention may or may not contain a very small amount of photoinitiator.

(d) organic solvent

In the composition for forming a liquid crystal layer according to the present invention, as the organic solvent, an organic solvent commonly used in the art may be used without particular limitation. Ethylene glycol monoalkyl ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether and ethylene glycol monobutyl ether; Diethylene glycol dialkyl ethers such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol ethyl methyl ether, diethylene glycol dipropyl ether and diethylene glycol dibutyl ether; Ethylene glycol alkyl ether acetates such as methyl cellosolve acetate, ethyl cellosolve acetate, ethylene glycol monobutyl ether acetate, and ethylene glycol monoethyl ether acetate; Alkylene glycol alkyl ether acetates such as propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monopropyl ether acetate, methoxy butyl acetate, and methoxy pentyl acetate; Propylene glycol monoalkyl ethers such as propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, and propylene glycol monobutyl ether; Propylene glycol dialkyl ethers such as propylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol ethyl methyl ether, propylene glycol dipropyl ether propylene glycol propyl methyl ether and propylene glycol ethyl propyl ether; Propylene glycol alkyl ether propionates such as propylene glycol methyl ether propionate, propylene glycol ethyl ether propionate, propylene glycol propyl ether propionate and propylene glycol butyl ether propionate; Butyl diol monoalkyl ethers such as methoxy butyl alcohol, ethoxy butyl alcohol, propoxy butyl alcohol and butoxy butyl alcohol; Butanediol monoalkyl ether acetates such as methoxy butyl acetate, ethoxy butyl acetate, propoxy butyl acetate and butoxy butyl acetate; Butanediol monoalkyl ether propionates such as methoxybutyl propionate, ethoxybutyl propionate, propoxybutyl propionate and butoxybutyl propionate; Dipropylene glycol dialkyl ethers such as dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, and dipropylene glycol methyl ethyl ether; Aromatic hydrocarbons such as benzene, toluene, xylene and mesitylene; Ketones such as methyl ethyl ketone, acetone, methyl amyl ketone, methyl isobutyl ketone and cyclohexanone; Alcohols such as ethanol, propanol, butanol, hexanol, cyclohexanol, ethylene glycol, glycerin; Methyl acetate, ethyl acetate, propyl acetate, butyl acetate, 2-hydroxypropionate, methyl 2-hydroxy-2-methylpropionate, 2-hydroxy-2-methylpropionate, methyl hydroxyacetate, ethyl hydroxyacetate , Butyl hydroxy acetate, methyl lactate, ethyl lactate, propyl lactate, butyl lactate, 3-hydroxypropionate methyl, 3-hydroxypropionate ethyl, 3-hydroxypropionate propyl, 3-hydroxypropionate butyl, 2-hydroxy 3-Methyl methyl butyrate, methyl methoxy acetate, ethyl methoxy acetate, methoxy acetate propyl, butyl acetate, ethoxy acetate methyl, ethoxy acetate, ethoxy acetate propyl, butyl ethoxy acetate, propoxy Methyl acetate, ethyl propoxy acetate, propyl propoxy acetate, butyl propoxy acetate, methyl butoxy acetate, ethyl butoxy acetate, Propyl acetate, butyl butoxy acetate, methyl 2-methoxypropionate, 2-methoxy ethylpropionate, propyl 2-methoxypropionate, butyl 2-methoxypropionate, methyl 2-ethoxypropionate, ethyl 2-ethoxypropionate Propyl 2-ethoxypropionate, butyl 2-ethoxypropionate, methyl 2-butoxypropionate, ethyl 2-butoxypropionate, propyl 2-butoxypropionate, butyl 2-butoxypropionate, methyl 3-methoxypropionate, 3-methoxy ethylpropionate, 3-methoxy propylpropionate, 3-methoxy propylpropionate, 3-ethoxy propylpropionate, 3-ethoxy propylpropionate, 3-ethoxy propylpropionate, 3-ethoxy propylpropionate, 3 Methyl propoxypropionate, 3-propoxy propionate, 3-propoxypropionate, butyl 3-propoxypropionate, methyl 3-butoxypropionate, ethyl 3-butoxypropionate, 3-butoxypropionic acid Esters such as ropil, 3-butoxy-propionic acid butyl; Cyclic ethers such as tetrahydrofuran and pyran; Cyclic esters, such as (gamma) -butyrolactone, etc. can be used individually or in mixture of 2 or more types, respectively.

(e) additives

The composition for forming a liquid crystal layer of the present invention may further include additives such as a filler, a curing agent, a leveling agent, an adhesion promoter, an antioxidant, an ultraviolet absorber, an anti-agglomerating agent, and a chain transfer agent, respectively, as necessary.

<Base material>

The substrate 110 according to the present invention can be used in the present invention without limitation as long as the substrate has a reactive group capable of reacting with an isocyanate group or a (meth) acrylate group to form a chemical bond among the substrates used in the art. In addition, the substrate commonly used in the art may be used in the present invention without limitation as long as the reactive group may be introduced to the surface through a surface treatment process known in the art, even if such substrate is not used as such.

The substrate 110 that can be used is preferably a transparent material, for example, a film including a triacetyl cellulose (TAC) -based, cyclo-olefin polymer (COP) -based, poly (methyl methacrylate) -based polymer, or the like. TAC, COP and PMMA by themselves do not have reactive groups on the surface that can react with isocyanates or (meth) acrylates.

Therefore, reactive groups may be introduced to the surface through surface treatment. When the hydroxyl group is described as an example, a hydroxy group is introduced to the surface when the saponification treatment is performed on the TAC surface, and a hydroxy group is formed on the surface when the plasma treatment is performed on the surface of the COP. Can be introduced. Other surface treatments include dry treatments such as corona treatment and primer treatment; Chemical treatment such as alkali treatment including saponification treatment; The coating process which forms an adhesive bond layer, etc. are mentioned. Preferably, the cellulose-based film is alkali treatment including saponification treatment; Acrylic, polyolefin and polyester films are advantageous for dry treatment such as corona treatment or plasma treatment. As a more specific example of the plasma treatment, at least one process may be performed among a remote plasma, a direct plasma, and a monomer plasma.

Specific examples of the reactive group that the substrate 110 may have on the surface through the surface treatment as described above include a hydroxy group, a thiol group, a carboxyl group, an amine group, and the like.

On the other hand, such a reactive group on the surface of the substrate 110 is a hydrophilic group. The hydrophilic group on the surface of the substrate 110 provides surface energy that is easy for the liquid crystal compound of the liquid crystal layer to vertically align. Such hydrophilicity is not particularly limited as long as it is suitable to vertically align the liquid crystal compound, and for example, the water contact angle may be 60 to 80 °, but is not limited thereto.

In addition, in the present invention, the substrate 110 may not have a phase difference value, and may have a phase difference value as necessary. When the substrate 110 has a retardation value, the substrate 110 may be combined with the retardation value of the liquid crystal layer 120 to achieve the desired effect. The method of providing the retardation value to the substrate 110 may include a material having a required retardation value of the substrate 110, a method of performing a stretching process in the manufacturing process of the substrate 110, and the like.

<Phase difference film>

The present invention provides a retardation film 100 having a liquid crystal layer 120 and a substrate 110 bonded by a chemical bond. The chemical bond is a bond formed between an adhesion enhancer including an isocyanate group and a (meth) acrylate group included in the liquid crystal layer 120 and a reactive group on the surface of the substrate 110. More specifically, the chemical bonding is caused by the reaction of an isocyanate group or (meth) acrylate of an adhesion enhancing agent exposed on the substrate side surface of the liquid crystal layer 120 with a reactive group present on the liquid crystal layer side surface of the substrate 110. Is a chemical bond formed. Through this, the retardation film of the present invention can significantly improve the interlayer adhesion between the liquid crystal layer 120 and the substrate 110.

The chemical bond that can be formed by reacting the isocyanate or (meth) acrylate of the liquid crystal layer 120 with the reactive group of the substrate 110 may be, for example, an isocyanate group of the adhesion enhancing agent of the liquid crystal layer 120 and the substrate 110. Urethane bonds formed by reaction of a hydroxyl group, a thiol group, a carboxyl group, or an amine group; And a thiylene bond formed by the reaction of the (meth) acrylate group of the adhesive strength enhancer of the liquid crystal layer 120 with the thiol group of the substrate 110.

As a specific example, the urethane bond between the liquid crystal layer 120 and the substrate 110 is formed by reacting a hydroxyl group, a thiol group, a carboxyl group or an amine group on the surface of the substrate with an isocyanate group of an adhesion enhancing agent. Same as Scheme 4.

For reference, the chemical bond between the reactive group and the reinforcing agent of the liquid crystal compound inside the liquid crystal layer 120 is the same as the reaction mechanism. 5 and Scheme 6. The cyano group can be pretreated with H ₂ O with heating and transformed into amine groups or carboxylic acids to react with isocyanate groups.

Scheme 1

Scheme 2

Scheme 3

Scheme 4

Scheme 5

Scheme 6

The retardation film of the present invention may have various retardation functions depending on the type of liquid crystal used. The retardation function of the retardation film may be classified according to the refractive index ratio Nz, and in the present invention, the refractive index ratio Nz is defined by Equation 1 below:

Equation 1

In the formula, when nx and ny are the plane refractive indices of the film and x is the vibration direction in which the plane refractive index becomes the largest, the refractive index due to the light vibrating in this direction is nx, and nx and ny are perpendicular to each other and nx ≥ ny, and nz represents a refractive index perpendicular to the plane defined by nx and ny (thickness direction of the film). Directional relations of nx, ny, and nz are schematically illustrated in FIG. 2.

In Equation 1, R _th is a thickness direction retardation value representing the difference in refractive index in the thickness direction with respect to the in-plane average refractive index, and is defined by Equation 2 below, and R _o represents the normal direction of the film (vertical direction). When it passes, it is defined by following formula (3) as a front phase difference value which is a substantial phase difference.

Equation 2

In the formula, when nx and ny are the plane refractive indices of the film and x is the vibration direction in which the plane refractive index becomes the largest, the refractive index due to the light vibrating in this direction is nx, and nx and ny are perpendicular to each other and nx ≥ ny, nz represents a refractive index perpendicular to the plane defined by nx and ny (thickness direction of the film), and d represents the thickness of the film.

Equation 3

In the formula, when nx and ny are the plane refractive indices of the film and x is the vibration direction in which the plane refractive index becomes the largest, the refractive index due to the light vibrating in this direction is nx, and nx and ny are perpendicular to each other and nx ≥ ny and d represents the thickness of the film.

In general, the type of plate of the phase difference is 1) when the light travels in a specific direction, the refractive indices of all vibration directions on the traveling direction are all the same, and thus the traveling direction of the light in which there is no phase difference of the light traveling in the traveling direction is present. An phosphorus optical axis in the in-plane direction, A plate; 2) a C plate if the optical axis is present in the vertical direction of the plane; And 3) when there are two optical axes, it is called B plate. More specifically, it is as follows.

(1) Nz = -∞: + C plate (POSITIVE C PLATE), nz> nx = ny

(2) Nz <0: + B plate (POSITIVE B PLATE), nz> nx> ny

(3) Nz = 0: -A plate (NEGATIVE A PLATE), nx = nz> ny

(4) 0 <Nz <1: Z-axis oriented film, nx> nz> ny

(5) Nz = 1: + A plate (POSITIVE A PLATE), nx> ny = nz

(6) 1 <Nz: -B plate (NEGATIVE B PLATE), nx> ny> nz

(7) Nz = ∞: -C plate (NEGATIVE C PLATE), nx = ny> nz

However, such a definition is theoretical, and it is practically very difficult to make A plate, B plate and C plate which perfectly match the definition. Therefore, as necessary, values such as the refractive index ratio, the front phase difference, and the like are set within a range that does not deviate greatly from the above definition in a predetermined range.

The retardation film of the present invention may have various retardation functions according to the alignment direction of the liquid crystal described above, and when the vertical alignment liquid crystal is used, the liquid crystal layer 120 may be a retardation film having a + C plate. . Theoretically, the + C plate means a case where the refractive index ratio Nz is -∞, but in the present invention, a case where the refractive index ratio Nz is -6 or less is defined as + C plate. In this aspect, in the present invention, even when the refractive index ratio Nz is -6 or less, the + C plate is determined.

In addition, in another embodiment of the present invention, when the liquid crystal layer 120 is a + C plate, the retardation film 100 uses a substrate 110 that is a + A plate or a -B plate to provide viewing angle compensation characteristics. It may be a retardation film having. Theoretically, the + A plate means a case where the refractive index ratio Nz is 1, but in the present invention, the case of 0.9 to 1.1 is defined as a + A plate in consideration of a realistic situation. In this aspect, in the present invention, the case where the refractive index ratio Nz is 0.9 to 1.1 is also determined as + A plate. Therefore, when the substrate 110 of the present invention is a + A plate or a -B plate, when the refractive index ratio Nz is 0.9 or more, it means a case where it is preferably 1 or more. In addition, when the substrate 110 is a + A plate, R _o may be 120 to 140 nm, and in the case of -B plate, R _o may be 115 to 125 nm.

The retardation film having such viewing angle compensation characteristics can be usefully used in an image display device having a liquid crystal cell of IPS mode.

<Image display device>

This invention provides the image display apparatus provided with the retardation film of this invention mentioned above. The retardation film of the present invention may be used in a display panel by being bonded to the polarizing film using an adhesive or the like directly bonded to one surface of the PVA polarizer instead of the protective film. Such a display panel may be typically applied to a liquid crystal display or the like.

3 shows a schematic laminated structure of a display panel having a phase difference film 100 of the present invention. 3 illustrates a structure in which the phase difference film of the present invention is directly bonded to one surface of the upper polarizer 300. The liquid crystal layer 120 of the phase difference film of the present invention is directly bonded to one surface of the upper polarizer 300, and the substrate 110 having an optical axis of 0 ° is bonded to the liquid crystal cell 400 side of the liquid crystal layer 120. In this case, the liquid crystal layer 120 may be a + C plate, and the substrate 110 may be a + A plate or a -B plate. In addition, the liquid crystal cell 400 may be an IPS mode liquid crystal cell.

The PVA-based upper polarizer 300 and the + C plate liquid crystal layer 120 may be bonded using an adhesive known in the art, for example, may be bonded with an aqueous or UV-based adhesive. The liquid crystal cell 400 and the substrate 110 may be bonded using an adhesive or an adhesive known in the art.

A lower polarizer 300 ′ is disposed on a lower surface of the liquid crystal cell 400, and a protective film 500 may be inserted between the liquid crystal cell 400 and the lower polarizer 300 ′. The protective film 500 may be R _o and R _th zero.

However, the above-described display panel is only one example according to the present invention, and may include a configuration known to those skilled in the art, except for having the retardation film of the present invention, and is particularly limited in the present invention. I never do that.

Hereinafter, the present invention will be described in detail with reference to Examples. However, embodiments according to the present invention can be modified in many different forms, the scope of the present invention should not be construed as limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art.

Example 1-7 and Comparative Example 1-2

To prepare a composition for forming a liquid crystal layer in the composition shown in Table 1. In Table 1, the liquid crystal compound is a vertically oriented liquid crystal compound, and the compound of Formula 16 (BASF), the compound of Formula 17 (Aekyung Chem) and the compound of Formula 18 (Aekyung Chem) are used in a weight ratio of 28:38:28. A mixture was used.

Meanwhile, the liquid crystal layer forming compositions of Examples 1-7 and Comparative Examples 1-2 were applied to a stretched COP film having a hydroxyl group introduced (except Examples 5 and 6) through plasma surface treatment, and at a temperature of 60 ° C. After drying for 1 minute, it was exposed to induce a curing reaction to prepare a retardation film.

Table 1

Test Example

The retardation film thus prepared was subjected to the following test, and the results are shown in Table 2 below.

<Phase difference 1>

R0; Phase difference of retardation film measured at 0 ° viewing angle

R50, R-50; Retardation of the retardation film measured at a viewing angle of 50 ° and a viewing angle of -50 °

◎; 0.97 <R0 / R50 or R0 / R-50 <1.03

○: 0.95 <R0 / R50 or R0 / R-50 <0.97 or 1.03 <R0 / R50 or R0 / R-50 <1.05

△: 0.90 <R0 / R50 or R0 / R-50 <0.95 or 1.05 <R0 / R50 or R0 / R-50 <1.1

×: R0 / R50 or R0 / R-50 is 1.1 or more or 0.90 or less

<Phase difference 2>

Rr; Retardation of the retardation film prepared in Comparative Example 1

Rs; Retardation of the retardation film

◎; 0.97 <Rs / Rr <1.03

○: 0.95 <Rs / Rr <0.97 or 1.03 <Rs / Rr <1.05

△: 0.90 <Rs / Rr <0.95 or 1.05 <Rs / Rr <1.1

×: Rs / Rr 1.1 or more or Rs / Rr 0.90 or less

<Layer adhesion>

After forming grooves to form 100 squares on the surface of the liquid crystal layer by using a cross hatch, Nichiban tape was attached and the tape was floated in the vertical direction, and the number of tears was counted to check the interlayer adhesion between the liquid crystal substrates. When the liquid crystal layer was evaluated through an optical microscope, the degree of tearing was evaluated on the following pattern.

◎; No tearing on the pattern

○: 1 to 3 tearing patterns

△: 4 to 8 tears on the pattern

×: more than 8 tears in pattern

TABLE 2

As described in Table 2, the retardation film of the embodiments according to the present invention exhibits the same or similar optical performance as the retardation film of the comparative examples, it can be seen that the interlayer adhesion is superior to the comparative examples.

Claims (17)

1. A retardation film having a liquid crystal layer and a substrate bonded by a chemical bond, wherein the chemical bond is an isocyanate group and a (meth) acrylate group present at a terminal of an adhesion enhancer included in the reactive group on the surface of the substrate and the liquid crystal layer. Retardation film formed by.
2. The retardation film of claim 1, wherein the adhesion enhancer is at least one selected from the group consisting of compounds of Formulas 1 to 4:

   [Formula 1]

   

   (Wherein R ₁ and R ₂ are each independently hydrogen or a methyl group,

   R ₃ and R ₇ are each independently an alkylene group having 1 to 10 carbon atoms unsubstituted or substituted with a group selected from the group consisting of a ketone group, an ester group and a thiol group,

   R ₄ and R ₆ are each independently an alkylene group having 1 to 10 carbon atoms unsubstituted or substituted with a group selected from the group consisting of an amide group, a ketone group, an ester group and a thiol group,

   R ₅ is an alkylene group having 1 to 10 carbon atoms unsubstituted or substituted with an alkoxy group having 1 to 8 carbon atoms,

   [Formula 2]

   

   (Wherein R ₇ and R ₈ are each independently hydrogen or a methyl group,

   R ₉ and R ₁₁ are each independently an alkylene group having 1 to 10 carbon atoms unsubstituted or substituted with a group selected from the group consisting of a ketone group, an ester group and a thiol group,

   R ₁₀ is (a)

   

   Or (b)

   

   E ₁ and E ₃ are each independently a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms or an alkoxy group having 1 to 8 carbon atoms, and E ₂ is an alkoxy group having 1 to 8 carbon atoms. Substituted or unsubstituted alkylene group having 1 to 10 carbon atoms,

   [Formula 3]

   

   (Wherein R ₁₂ is hydrogen or a methyl group,

   R ₁₃ is an alkylene group having 1 to 10 carbon atoms unsubstituted or substituted with a group selected from the group consisting of a ketone group, an ester group and a thiol group; and

   [Formula 4]

   

   (Wherein, R ₁₄ is hydrogen or a methyl group,

   R ₁₅ is an alkylene group having 1 to 10 carbon atoms unsubstituted or substituted with a group selected from the group consisting of a ketone group, an ester group and a thiol group.
3. The retardation film of claim 1, wherein the liquid crystal layer is formed of a curable composition containing a liquid crystal compound containing a reactive group capable of reacting with an isocyanate group or a (meth) acrylate group of an adhesion enhancing agent.
4. The retardation film according to claim 3, wherein the reactive group of the liquid crystal compound is a carbon-carbon unsaturated bond, a hydroxyl group, an epoxy group, or a cyano group.
5. The retardation film according to claim 3, wherein the curable composition for forming a liquid crystal layer comprises 0.1 to 15 parts by weight of the adhesion strength enhancer based on 100 parts by weight of the liquid crystal compound.
6. The retardation film of claim 3, wherein the liquid crystal compound is a vertical alignment liquid crystal compound.
7. The retardation film of claim 1, wherein the reactive group on the surface of the substrate is at least one selected from the group consisting of a hydroxy group, a thiol group, a carboxyl group, and an amine group.
8. The retardation film of claim 1, wherein the substrate comprises a triacetylcellulose-based, cycloolefin-based, or PMMA-based polymer.
9. The retardation film of claim 8, wherein the surface treatment is at least one treatment selected from the group consisting of saponification treatment, primer treatment, corona treatment, plasma treatment, and coating treatment.
10. The retardation film of claim 9, wherein the plasma treatment is at least one selected from the group consisting of a remote plasma treatment, a direct plasma treatment, and a monomer plasma treatment.
11. The retardation film of claim 1, wherein the chemical bond between the liquid crystal layer and the substrate is at least one of a urethane bond and a thiylene bond.
12. The retardation film according to claim 11, wherein the urethane bond between the liquid crystal layer and the substrate is formed by the reaction of an isocyanate group of the adhesion enhancing agent of the alignment layer with a hydroxyl group, thiol group, carboxyl group, or amine group of the substrate.
13. The retardation film of Claim 11 in which the thiylene bond between a liquid crystal layer and a base material is formed by reaction of the (meth) acrylate group of the adhesive strength enhancing agent of the said oriented film, and the thiol group of the said base material.
14. The retardation film according to claim 1, wherein the substrate has a water contact angle of 60 to 80 degrees on the liquid crystal layer side surface.
15. The retardation film of claim 1, wherein the substrate is a + A plate or a -B plate, and the liquid crystal layer is a + C plate.
16. The image display apparatus provided with the retardation film of any one of Claims 1-15.
17. The image display device according to claim 16, wherein the image display device is in an IPS mode.

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