KR20150009864A - A retardation film and display device comprising the same - Google Patents

Abstract

The present invention relates to a retardation film and an image display device thereof. More specifically, the retardation film includes a substrate and a liquid crystal layer which are coupled together though chemical bonding. The chemical bond is formed by the reactive groups on the surface of the substrate and the isocyanate groups and (meta-) acrylate groups present on the end of an adhesion enhancing agent included in the liquid crystal layer. Accordingly, the retardation film can significantly increase the adhesion between layers.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a retardation film,

The present invention relates to a phase difference film in which alignment of a liquid crystal layer is performed without an orientation layer, and an interlayer adhesion force is excellent and an image display apparatus having the same.

2. Description of the Related Art [0002] In recent years, an image display device in which a conventional CRT monitor is dominant has been rapidly developed, and a wider, lighter, and even bendable image display device such as an LCD, an OLED,

The most common liquid crystal display device among image display devices is a liquid crystal display device having a liquid crystal cell such as TN (Twisted Nematic) mode, STN (Super Twisted Nematic) mode, VA (Vertical Alignment) mode, A liquid crystal display device of a transverse electric field system in which an electrode is formed only on one side of a pair of oppositely arranged substrates such as an IPS (In-Plane Switching) mode or an FFS (Fringe Field Switching) mode, Are known.

In the liquid crystal display device, light emitted from a back light, which is a light source, passes through a liquid crystal having anisotropy and a pair of polarizing plates disposed vertically to each other, so that a good image can be obtained in front of the liquid crystal display device, , The display performance is deteriorated. In order to improve the black display state (black characteristic), the side contrast ratio (CR), the color shift, and the like of the liquid crystal display device and to reduce the viewing angle dependency, a retardation film is used. Since the retardation film has a function of converting linearly polarized light into elliptically polarized light or circularly polarized light or converting linearly polarized light in a certain direction into another direction, it is possible to improve the viewing angle, brightness, contrast, etc. of the liquid crystal display device .

The retardation film is usually prepared by coating a liquid crystal on the alignment film after forming a thin alignment film by coating the alignment agent, and then curing the alignment film. The liquid crystal is in a rod-type form or a coin-like discotic form and discotic liquid crystal. Among them, the orientation state of the rod-shaped liquid crystal can be broadly divided into the following five types.

First, the planar orientation refers to the orientation in which the optical axis is parallel to the film plane. Second, the homeotropic orientation refers to the orientation in which the optical axis is perpendicular to the film plane, that is, parallel to the film normal. The tilted orientation refers to an orientation in which the optical axis is inclined at a specific angle between 0 [deg.] And 90 [deg.] With respect to the film plane. Fourth, the splay orientation refers to an orientation in which an optical axis continuously changes at an inclination angle of 0 ° to 90 ° or a minimum value within a range of 0 ° to 90 °. Fifth, a cholesteric orientation refers to an orientation in which an optical axis Parallel to the plane direction is an orientation in which the optical axis is rotated clockwise or counterclockwise by a certain angle when observed in the direction perpendicular to the plane as it progresses in the thickness direction.

As described above, the vertically aligned liquid crystal film, which is the second one of the liquid crystal films, can be used alone or in combination with other films to form a twisted nematic (TN) mode, a super twisted nematic ) Mode, an OCB (Optically Compensated Birefringence) mode, and the like, as an optical film such as a retardation film.

In order to attach the vertically aligned liquid crystal film to a polarizing plate for the purpose of improving brightness or viewing angle, it is preferable to use a roll-to-roll method in which the liquid crystal film is pressed while being passed between rollers opposed to each other at regular intervals, -to-roll operation must be performed. For this, it is desirable to use flexible plastic substrate even under pressure and slight impact.

There have been several proposals for forming vertically aligned 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, since aluminum adheres weakly to the surface of the plastic substrate, a part of aluminum may be removed during peeling, which may cause defects.

European Patent No. 1376163 describes coating a liquid crystal solution having a horizontal or twist orientation on a plastic substrate and then using the liquid crystal solution as an alignment film to implement a vertically aligned liquid crystal thereon. However, in this case, the degree of vertical alignment of the upper liquid crystal layer is determined depending on 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 disclose a film in which a coupling agent of a primary amino silane series is added to a vertically aligned liquid crystal solution to increase the adhesive strength. However, such a primary aminosilane-based coupling agent has the disadvantage of deteriorating the transparency by deteriorating the orientation of the liquid crystal.

Korean Patent Laid-Open Publication No. 2006-0066045 discloses that a polymerizable reactive liquid crystal mixture solution containing a predetermined surfactant is coated on a hydrophilic-treated plastic substrate without using an orientation film for inducing vertical alignment of the liquid crystal, A liquid crystal film was produced. However, there is a problem in that the adhesive strength between the liquid crystal and the substrate is large, and the liquid crystal alignment is unstable, resulting in various defects.

U.S. Patent No. 6,816,218 European Patent No. 1376163 U.S. Patent No. 20060278851 Japanese Patent Application Laid-Open No. 2006-126757 Korean Patent Publication No. 2006-0066045

It is an object of the present invention to provide a retardation film not containing an alignment film.

Another object of the present invention is to provide a retardation film which is excellent in adhesion between layers and in which the liquid crystal layer and the substrate are not peeled off during the manufacturing process.

It is still another object of the present invention to provide an image display apparatus having the above-described retardation film.

1. A retardation film comprising a liquid crystal layer and a substrate bonded by a chemical bond, wherein the chemical bond is formed by a reaction between a reactive group on the surface of the substrate and an isocyanate group and an isocyanate group present at the end of the adhesive strength- Lt; / RTI > film.

2. The retardation film of 1 above, wherein the adhesive strength enhancer is at least one selected from the group consisting of compounds represented by the following formulas (1) to (4):

[Chemical Formula 1]

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

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

R ₄ and R ₆ independently represent an alkylene group having 1 to 10 carbon atoms which is 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 which is substituted or unsubstituted with an alkoxy group having 1 to 8 carbon atoms,

(2)

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

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

또는 (b)

이고, E₁ 및 E₃는 서로 독립적으로 탄소수 1 내지 8의 알콕시기로 치환 또는 비치환된 탄소수 1 내지 10의 알킬기, 또는 탄소수 1 내지 8의 알콕시기이고, E₂는 탄소수 1 내지 8의 알콕시기로 치환 또는 비치환된 탄소수 1 내지 10의 알킬렌기임),R < ₁₀ > is (a)

Or (b)

E ₁ and E ₃ independently represent an alkyl group having 1 to 10 carbon atoms or an alkoxy group having 1 to 8 carbon atoms which is substituted or unsubstituted with an alkoxy group having 1 to 8 carbon atoms and E ₂ is an alkoxy group having 1 to 8 carbon atoms, A substituted or unsubstituted alkylene group having 1 to 10 carbon atoms,

(3)

(Wherein R < ₁₂ > is hydrogen or a methyl group,

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

[Chemical Formula 4]

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

And R ₁₅ is an alkylene group having 1 to 10 carbon atoms, which is substituted or unsubstituted 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 comprises a liquid crystalline compound comprising a reactive group capable of reacting with an isocyanate group or a (meth) acrylate group of an adhesion promoter.

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

5. The retardation film according to 3 above, wherein the curable composition for forming a liquid crystal layer comprises 0.1 to 15 parts by weight of the adhesive force enhancer based on 100 parts by weight of the liquid crystalline compound.

6. The retardation film of claim 3, wherein the liquid crystalline compound is a vertically aligned liquid crystalline compound.

7. The retardation film of 1 above, 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. The retardation film of 1 above, wherein the base material comprises a surface-treated triacetylcellulose-based, cycloolefin-based or PMMA-based polymer.

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

10. The retardation film as set forth in 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 1 above, wherein the chemical bond between the liquid crystal layer and the substrate is at least one of a urethane bond and a thiolene bond.

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

13. The retardation film according to the above 11, wherein the thiolene 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 film with the thiol group of the above-mentioned substrate.

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

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. An image display apparatus comprising the retardation film according to any one of 1 to 15 above.

17. The image display apparatus of 16, wherein the image display apparatus is an IPS mode.

Since the retardation film of the present invention does not include an alignment film, it is possible to realize a thin film structure and it is easy to manufacture.

In addition, in the phase difference 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, so that the interlaminar adhesive force is very high.

Since the retardation film of the present invention has a very high interlaminar adhesive strength, the peeling phenomenon is remarkably reduced in the desorption process using an adhesive layer in the production of an optical film such as a polarizing film by using it, so that the defect rate is low and the productivity can be improved accordingly .

1 is a schematic cross-sectional view of a retardation film according to the present invention.
Fig. 2 is a diagram showing the relationship of the directions (x, y, z) of the refractive indexes (nx, ny, nz).
3 is a view showing a schematic laminated structure of a display panel having a retardation film of the present invention.

The present invention relates to a retardation film comprising a liquid crystal layer and a substrate bonded by a chemical bond, wherein the chemical bond is formed by a reaction between a reactive group on the surface of the substrate and an isocyanate group and a (meth) Acrylate group, and thus has a very high interlaminar adhesive strength.

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. The retardation film (100) of the present invention has a structure in which a liquid crystal layer (120) is formed on a base material (110).

< Liquid crystal layer >

The liquid crystal layer 120 may be prepared by curing a 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-strengthening agent in addition to (b) a liquid crystal compound, (c) a polymerization initiator, and (d) an organic solvent.

(a) Adhesion enhancer

The composition for forming a liquid crystal layer according to the present invention includes an adhesion promoter capable of forming a chemical bond between the liquid crystal layer 120 and the substrate 110. The (meth) acrylate group and the isocyanate group of the adhesion promoter react with a reactive group on the surface of the substrate 110 to form a chemical The bonding strength between the liquid crystal layer 120 and the substrate 110 can be remarkably increased.

In the present invention, (meth) acrylate means acrylate or methacrylate, or, in some cases, both acrylate and methacrylate.

In the present invention, the (meth) acrylate group and the isocyanate group of the adhesive strength enhancer may be added to the liquid crystal layer forming composition at the time when the adhesive force enhancer is mixed with the composition for forming the liquid crystal layer, even if the (meth) acrylate group and / (Meth) acrylate group or isocyanate group is produced through additional treatment, for example, post-treatment such as heat treatment, before chemical bonding with the substrate 110 of the substrate 110. For example, as a functional group in which an isocyanate group is produced through heat treatment, there can be mentioned a pyrazole group connected to an end of the adhesion enhancer by an amide bond. The pyrazole group is separated through a heat treatment process and an isocyanate group is formed at the terminal.

The adhesive strength enhancer according to the present invention may be used without any particular limitation as long as it is a compound having at least one isocyanate group at one terminal and at least one (meth) acrylate group at the other terminal. More specific examples thereof include May be used alone or in combination of two or more.

[Chemical Formula 1]

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

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

R ₄ and R ₆ independently represent an alkylene group having 1 to 10 carbon atoms which is 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 which is substituted or unsubstituted with an alkoxy group having 1 to 8 carbon atoms,

(2)

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

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

또는 (b)

이고, E₁ 및 E₃는 서로 독립적으로 탄소수 1 내지 8의 알콕시기로 치환 또는 비치환된 탄소수 1 내지 10의 알킬기, 또는 탄소수 1 내지 8의 알콕시기이고, E₂는 탄소수 1 내지 8의 알콕시기로 치환 또는 비치환된 탄소수 1 내지 10의 알킬렌기임),R &lt; ₁₀ &gt; is (a)

Or (b)

E ₁ and E ₃ independently represent an alkyl group having 1 to 10 carbon atoms or an alkoxy group having 1 to 8 carbon atoms which is substituted or unsubstituted with an alkoxy group having 1 to 8 carbon atoms and E ₂ is an alkoxy group having 1 to 8 carbon atoms, A substituted or unsubstituted alkylene group having 1 to 10 carbon atoms,

(3)

(Wherein R &lt; ₁₂ &gt; is hydrogen or a methyl group,

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

[Chemical Formula 4]

(Wherein R &lt; ₁₄ &gt; is hydrogen or a methyl group,

And R ₁₅ is an alkylene group having 1 to 10 carbon atoms, which is substituted or unsubstituted 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 adhesive strength enhancer represented by the above formulas (1) to (4) preferably has at least one of the compounds represented by Formulas (2) to &Lt; / RTI &gt;

More specific examples of the adhesive strength enhancers represented by the above formulas (1) to (4) include at least one selected from the group consisting of compounds represented by the following formulas (5) to (15)

[Chemical Formula 5]

[Chemical Formula 6]

(7)

[Chemical Formula 8]

[Chemical Formula 9]

[Chemical formula 10]

(11)

[Chemical Formula 12]

[Chemical Formula 13]

[Chemical Formula 14]

[Chemical Formula 15]

In the compounds represented by the above formula (4) and the compounds represented by the above formula (12), (13), (14) and (15), the terminal dimethylpyrazole group is separated through a heat treatment process such as a drying process, To have an isocyanate group.

The content of the adhesive strength enhancer is preferably from 0.1 to 15 parts by weight per 100 parts by weight of the liquid crystal compound, and more preferably from 0.1 to 15 parts by weight per 100 parts by weight of the liquid crystal compound, .

(b) Liquid crystal property  compound

In the present invention, the liquid crystalline compound is an essential material that is oriented in a specific direction and exhibits the desired effect of the retardation film. The liquid crystalline compound according to the present invention is oriented on a base film without a conventional orientation film for inducing orientation, and in this respect, it is preferably a vertically oriented liquid crystalline compound. Among the vertically aligned liquid crystalline compounds, the present invention can be applied without any particular limitation.

The liquid crystalline compound includes a reactive group which performs a curing reaction after alignment, and this reactive group may also react with an isocyanate group or a (meth) acrylate group of the adhesion promoter. Examples of the reactive group of the liquid crystalline compound include a carbon-carbon unsaturated bond, a hydroxyl group, an epoxy group, a cyano group and the like, preferably a carbon-carbon unsaturated bond. More specifically, the above carbon-carbon unsaturated bond may be a carbonyl-carbon unsaturated bond contained in an acryloyloxy group, a cyanoacrylate group, an allyl group, a cinnamate group or an allyloxy group.

Accordingly, any liquid crystalline compound having a reactive group among vertically aligned liquid crystalline compounds used in the art can be used in the present invention without limitation, and the liquid crystalline compound ordinarily used in the art is not limited to such a reactive group 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 the following compounds represented by the following formulas (16) to (18).

[Chemical Formula 16]

[Chemical Formula 17]

[Chemical Formula 18]

On the other hand, the chemical bonding between the reactive group of the liquid crystalline compound and the isocyanate group or the (meth) acrylate group of the adhesive strength enhancer is shown in the following Schemes 1 to 6.

(c) Polymerization initiator

In the composition for forming a liquid crystal layer according to the present invention, as the polymerization initiator, photoinitiators or decomposition agents commonly used in the art can be used, and photoinitiators can be preferably used.

More specifically, examples of the photoinitiator include a triazine-based compound, an acetophenone-based compound, a nonimidazole-based compound, an oxime-based compound, a benzoin-based compound, a benzophenone-based compound, a thioxanthone- However, the present invention is not limited thereto.

Examples of the styrenic compound include 2,4-bis (trichloromethyl) -6- (4-methoxyphenyl) -1,3,5-triazine, 2,4-bis (trichloromethyl) (Trichloromethyl) -6-piperonyl-1,3,5-triazine, 2,4-bis (trichloromethyl) Bis (trichloromethyl) -6- [2- (5-methylfuran-2-yl) -Yl) ethenyl] -1,3,5-triazine, 2,4-bis (trichloromethyl) -6- [2- (furan- Azine, 2,4-bis (trichloromethyl) -6- [2- (4-diethylamino-2-methylphenyl) ethenyl] -1,3,5-triazine, 2,4- Methyl) -6- [2- (3,4-dimethoxyphenyl) ethenyl] -1,3,5-triazine.

Examples of the acetophenone compound include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyldimethylketal, 2- 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropane-1- (2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl] propane 1-one, 2-methyl-2-amino (4-morpholinophenyl) ethan- (4-morpholinophenyl) ethan-1-one, 2-methyl-2-amino (4 (4-morpholinophenyl) propane-1-one, 2-methyl-2- 1-one, 2-ethyl-2-amino (4-morpholinophenyl) butan- Propan-1-one, 2-methyl-2-dimethylamino (4-morpholinophenyl) Polynophenyl) propan-1-one, and the like.

Examples of the biimidazole-based compound include 2,2'-bis (2-chlorophenyl) -4,4 ', 5,5'-tetraphenylbiimidazole, 2,2'-bis -Dichlorophenyl) -4,4 ', 5,5'-tetraphenylbiimidazole, 2,2'-bis (2-chlorophenyl) -4,4' Imidazole, 2,2'-bis (2-chlorophenyl) -4,4 ', 5,5'-tetra (trialkoxyphenyl) biimidazole, phenyl group at 4,4' An imidazole compound substituted by a haloalkoxy group, and the like. Among them, 2,2'-bis (2-chlorophenyl) -4,4 ', 5,5'-tetraphenylbiimidazole, 2,2'-bis (2,3- , 5,5'-tetraphenylbiimidazole are preferably used.

As the oxime-based compound, 0-ethoxycarbonyl-α-oximino-1-phenylpropan-1-one and the like can be given.

Examples of the above benzotriene compound include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether and the like.

Examples of the above benzophenone compounds include benzophenone, methyl 0-benzoylbenzoate, 4-phenylbenzophenone, 4-benzoyl-4'-methyldiphenylsulfide, 3,3 ', 4,4'-tetra tert-butylperoxycarbonyl) benzophenone, 2,4,6-trimethylbenzophenone, and the like.

Examples of the thioxanthone compound include 2-isopropylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone, 1-chloro-4-propanedioxanthone, etc. .

Examples of the anthracene compound include 9,10-dimethoxyanthracene, 2-ethyl-9,10-dimethoxyanthracene, 9,10-diethoxyanthracene, 2-ethyl-9,10-diethoxyanthracene, .

In addition to these, it is also possible to use 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 10-butyl-2-chloroacridone, 2-ethyl anthraquinone, benzyl, 9,10-phenanthrenequinone, camphorquinone, phenylclyoxylic acid Methyl, titanocene compounds, and photopolymerization initiators having a group capable of chain transfer described in JP-A No. 2002-544205.

In another aspect of the composition for forming a liquid crystal layer of the present invention, a photoinitiator may not be included. Photoinitiators have the advantage that the photopolymerization reaction facilitates the photopolymerization reaction. However, if the photoinitiator is used in excessive amounts, the photoinitiator may act as an impurity to lower the alignment power, to break the alignment of the liquid crystal, to cause light leakage upon cross polarization, or to sublimate the initiator after photo- If the intensities of the initiator response wavelengths are very high relative to the wavelengths of the reacting wavelengths, the production efficiency may be lowered due to the lowering of the line speed in order to achieve the optical alignment. In this respect, the composition for forming a liquid crystal layer of the present invention may or may not contain a very small amount of a photoinitiator.

(d) an organic solvent

In the composition for forming a liquid crystal layer according to the present invention, an organic solvent ordinarily used in the art can be used as the organic solvent without any 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, methoxybutyl acetate, and methoxypentyl 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; Butyldiol monoalkyl ethers such as methoxybutyl alcohol, ethoxybutyl alcohol, propoxybutyl alcohol and butoxybutyl alcohol; Butanediol monoalkyl ether acetates such as methoxybutyl acetate, ethoxybutyl acetate, propoxybutyl acetate and butoxybutyl acetate; Butanediol monoalkyl ether propionates such as methoxy butyl propionate, ethoxy butyl propionate, propoxy butyl propionate and butoxy butyl 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 and glycerin; Examples of the solvent include methyl acetate, ethyl acetate, propyl acetate, butyl acetate, ethyl 2-hydroxypropionate, methyl 2-hydroxy-2-methylpropionate, ethyl 2-hydroxypropionate, methylhydroxyacetate, , Hydroxybutyl acetate, methyl lactate, ethyl lactate, propyl lactate, butyl lactate, methyl 3-hydroxypropionate, ethyl 3-hydroxypropionate, propyl 3-hydroxypropionate, butyl 3-hydroxypropionate, Methyl methoxyacetate, methyl methoxyacetate, methyl methoxyacetate, ethyl methoxyacetate, propyl methoxyacetate, butyl methoxyacetate, ethoxyacetate, ethoxyacetate, ethoxyacetate, ethoxyacetate, propoxy Methyl acetate, ethyl propoxyacetate, propoxypropylacetate, butyl propoxyacetate, methyl butoxyacetate, ethyl butoxyacetate, butyl Methoxypropionate, ethyl 2-methoxypropionate, butyl 2-methoxypropionate, methyl 2-ethoxypropionate, ethyl 2-ethoxypropionate, ethyl 2-ethoxypropionate, , Propyl 2-ethoxypropionate, butyl 2-ethoxypropionate, methyl 2-butoxypropionate, ethyl 2-butoxypropionate, propyl 2-butoxypropionate, butyl 2-butoxypropionate, Ethoxypropionate, propyl 3-ethoxypropionate, propyl 3-ethoxypropionate, butyl 3-ethoxypropionate, ethyl 3-methoxypropionate, propyl 3-methoxypropionate, butyl 3-methoxypropionate, Propoxy propionate, methyl 3-butoxypropionate, ethyl 3-butoxypropionate, 3-butoxypropionic acid ethyl, 3-propoxypropionate, Esters such as ropil, 3-butoxy-propionic acid butyl; Cyclic ethers such as tetrahydrofuran and pyran; and cyclic esters such as? -butyrolactone, which may be used alone or in admixture of two or more.

(e) Additive

The composition for forming a liquid crystal layer of the present invention may further contain additives such as a filler, a curing agent, a leveling agent, an adhesion promoter, an antioxidant, an ultraviolet absorber, an aggregation inhibitor and a chain transfer agent.

<Description>

As the substrate 110 according to the present invention, any substrate that has a reactive group capable of forming a chemical bond by reacting with an isocyanate group or a (meth) acrylate group on the surface of the substrate used in the art can be used in the present invention without limitation. Can also be used in the present invention without limitation as long as the substrate commonly used in the art can introduce a reactive group to the surface through a surface treatment process known in the art even if such a reactive group is not itself a pertinent reactive group.

The substrate 110 that can be used is preferably a transparent material, for example, a film including a TAC (triacetyl cellulose) system, a COP (cyclo-olefin polymer) system, a PMMA (poly (methyl methacrylate) TAC, COP and PMMA, on their own, do not have a reactive group capable of reacting with isocyanate or (meth) acrylate on the surface.

Therefore, a reactive group can be introduced to the surface through the surface treatment. When a hydroxy group is taken as an example, a hydroxy group is introduced on the surface when the TAC surface is subjected to a safonification treatment. When the surface of the COP is subjected to plasma treatment, Can be introduced. Other surface treatments include dry treatments such as corona treatment and primer treatment; Chemical treatment such as alkali treatment including a saponification treatment; And a coating treatment for forming an adhesive layer. Preferably, the cellulose-based film is subjected to an alkali treatment comprising a saponification treatment; Acrylic, polyolefin and polyester films are advantageous in dry processing such as corona treatment or plasma treatment. More specific examples of the plasma treatment include at least one of a remote plasma, a direct plasma, and a monomer plasma.

Specific examples of the reactive group that the base material 110 can have on its surface through such a surface treatment include a hydroxyl group, a thiol group, a carboxyl group, and an amine group.

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 easy surface energy for vertical alignment of the liquid crystalline compound in the liquid crystal layer. Such hydrophilicity is not particularly limited as long as the liquid crystalline compound is suitable for vertical orientation, and for example, the water contact angle may be 60 to 80 °, but is not limited thereto.

Further, in the present invention, the base material 110 may not have a retardation value, and may have a retardation value as required. When the substrate 110 has a retardation value, it can be combined with the retardation value of the liquid crystal layer 120 to exhibit a desired effect. A method of imparting a retardation value to the base material 110 may be a method of using a material having a desired retardation value of the base material 110 or a method of performing a stretching process in the production process of the base material 110.

< Phase difference  Film>

The present invention provides a phase difference film (100) comprising a liquid crystal layer (120) and a substrate (110) bonded by chemical bonding. The chemical bonding is a bond formed between an adhesive strength enhancer containing an isocyanate group and a (meth) acrylate group contained in the liquid crystal layer 120 at the terminal thereof and a reactive group on the surface of the substrate 110. More specifically, the chemical bonding is performed by a reaction between an isocyanate group or (meth) acrylate group of the adhesion promoter exposed on the substrate side surface of the liquid crystal layer 120 and a reactive group present on the liquid crystal layer side surface of the substrate 110 Lt; / RTI &gt; Accordingly, the retardation film of the present invention can remarkably improve the interlayer adhesion force between the liquid crystal layer 120 and the substrate 110.

The chemical bonding that can be formed by the reaction between the isocyanate or the (meth) acrylate of the liquid crystal layer 120 and the reactive group of the substrate 110 can be performed by, for example, mixing the isocyanate group of the adhesive strength enhancer of the liquid crystal layer 120, A urethane bond formed by the reaction of a hydroxyl group, a thiol group, a carboxyl group, or an amine group; And a thiolene bond formed by the reaction of the (meth) acrylate group of the adhesion promoter of the liquid crystal layer 120 and the thiol group of the base material 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 of the substrate surface with an isocyanate group of an adhesion promoter, Reaction formula 4 is as follows.

For reference, the chemical bonding between the reactive group of the liquid crystalline compound in the liquid crystal layer 120 and the adhesive strength enhancer is the same as the above reaction mechanism. In addition, the reaction formula of the epoxy group and the cyano group in the reactive group of the liquid crystalline compound and the adhesion- 5 and Scheme 6. The cyano group can be pre-treated with H ₂ O under heating to react with an isocyanate group by modification with an amine group or a carboxylic acid.

[Reaction Scheme 1]

[Reaction Scheme 2]

[Reaction Scheme 3]

[Reaction Scheme 4]

[Reaction Scheme 5]

[Reaction Scheme 6]

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

Where nx and ny are plane refractive indexes of the film and x is a vibration direction in which the plane refractive index becomes the maximum, the refractive index due to light oscillating in this direction is nx, nx and ny are perpendicular to each other, ny, and nz represents a refractive index perpendicular to the plane defined by nx and ny (film thickness direction). The directional relationships of nx, ny, and nz are schematically shown in Fig.

In the above Equation (1), R _th is a thickness retardation value indicating a difference in refractive index in the thickness direction with respect to the in-plane averaged refractive index, and R _o is a thickness direction retardation value Is defined as a front retardation value which is a substantial retardation when passed.

Where nx and ny are plane refractive indexes of the film and x is a vibration direction in which the plane refractive index becomes the maximum, the refractive index due to light oscillating in this direction is nx, nx and ny are perpendicular to each other, ny, nz represents the refractive index perpendicular to the plane defined by nx and ny (thickness direction of the film), and d represents the thickness of the film.

Where nx and ny are plane refractive indexes of the film and x is a vibration direction in which the plane refractive index becomes the maximum, the refractive index due to light oscillating in this direction is nx, nx and ny are perpendicular to each other, ny, and d represents the thickness of the film.

Typically, the plate type of the retardation is 1) when the light travels in a specific direction, the refractive indexes of all the vibration directions on the traveling direction are all the same, and the traveling direction of light in which the phase difference of light traveling in the traveling direction does not exist An A plate in the case where the optical axis in the in-plane direction exists; 2) C plate when the optical axis exists in the vertical direction of the plane; And 3) when there are two optical axes, it is called a 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, the above definition is theoretical and it is practically very difficult to make A plates, B plates and C plates that perfectly match the above definition. Accordingly, the refractive index ratio, the frontal retardation, and the like are usually set within a predetermined range within a range that does not largely deviate from the above definition, if necessary.

The retardation film of the present invention may have various retardation functions depending on the orientation direction of the liquid crystal described above, and when the vertically aligned liquid crystal is used, the liquid crystal layer 120 may be a + C plate retardation film . Theoretically, a + C plate means a case where the refractive index ratio (Nz) is -∞, and in the present invention, a case of -6 or less is defined as a + C plate. In this respect, in the present invention, the + C plate is also determined when the refractive index ratio (Nz) is -6 or less.

In another embodiment of the present invention, the retardation film 100 may be formed by using a + A plate or a substrate 110, which is a -B plate, when the liquid crystal layer 120 is a + C plate, 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, a case of 0.9 to 1.1 is defined as a + A plate in consideration of a practical situation. In this respect, in the present invention, when the refractive index ratio (Nz) is 0.9 to 1.1, it is also judged as + A plate. Therefore, when the substrate 110 of the present invention is a + A plate or a -B plate, it means that the refractive index ratio Nz is 0.9 or more, 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 a -B plate, R _o may be 115 to 125 nm.

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

<Image Display Device>

The present invention provides an image display apparatus having the above-described retardation film of the present invention. The retardation film of the present invention may be bonded to a polarizing film using an adhesive or the like, or may be directly bonded to one side of a PVA polarizer instead of a protective film to be used for a display panel. Such a display panel can be typically applied to a liquid crystal display device or the like.

FIG. 3 shows a schematic laminated structure of a display panel having the retardation film 100 of the present invention. FIG. 3 shows a structure in which the retardation film of the present invention is directly bonded to one surface of the upper polarizer 300. The liquid crystal layer 120 of the retardation film of the present invention is directly bonded to one surface of the upper polarizer 300 and the base 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 top plate polarizer 300 and the liquid crystal layer 120, which is a + C plate, can be bonded using an adhesive known in the art, and can be bonded by, for example, an aqueous or UV-based adhesive. The liquid crystal cell 400 and the substrate 110 may be bonded together using a pressure-sensitive adhesive or an adhesive known in the art.

A lower plate polarizer 300 'may be disposed on the 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 plate polarizer 300'. The protective film 500 is formed of R &lt; ₀ &gt; And _Rth may be zero.

However, the above-described display panel is merely an example according to the present invention, and can include configurations known to those skilled in the art, except for the retardation film of the present invention, I never do that.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to examples. However, the embodiments according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to enable those skilled in the art to more fully understand the present invention.

Example  1-7 and Comparative Example  1-2

A composition for forming a liquid crystal layer was prepared with the composition shown in Table 1 below. In Table 1, the liquid crystalline compound is a vertically aligned liquid crystalline compound in which the compound of Formula 16 (BASF), the compound of Formula 17 (Aekyung Chemical Co.) and the compound of Formula 18 (Aekyoung Chemical Co.) are mixed at a weight ratio of 28:38:28 Were used.

On the other hand, a composition for forming a liquid crystal layer of Example 1-7 and Comparative Example 1-2 was applied to a stretched COP film through which a hydroxy group was introduced (except for Examples 5 and 6) through a Plasma surface treatment, Dried for 1 minute, and exposed to a curing reaction to prepare a retardation film.

ingredient Example Comparative Example One 2 3 4 5 6 7 One 2 Liquid crystal layer composition Liquid crystal compound 29.526 27.992 27.992 27.992 27.992 27.992 27.992 29.97 29.673 Adhesion enhancer Formula 5 0.148 1.682 Formula 7 1.682 Formula 9 1.682 Formula 11 1.682 Formula 13 1.682 Formula 15 1.682 Photoinitiator 0.296 0.296 0.296 0.296 0.296 0.296 0.296 0.297 Leveling agent 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 Organic solvent 70 70 70 70 70 70 70 70 70 materials material Stretched COP Stretched COP Stretched COP Stretched COP Stretched COP Stretched COP Stretched COP Stretched COP Stretched COP Surface treatment Plasma Plasma Plasma Plasma invisible Plasma Plasma invisible Plasma Plasma Plasma Photoinitiator: 2-methyl-1- [4- (methylthio) phenyl] -2- (4-morpholinyl)
Leveling agent: Acrylic copolymer (BYK-361N, BYK)
Organic solvent: propylene glycol-1-monomethyl ether-2-acetate

Test Example

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

< Phase difference 1 >

R0; The retardation of the retardation film measured at a viewing angle of 0 °

R50, R-50; The 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

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

< Phase difference 2 >

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

R5; The 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

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

&Lt; Interlayer adhesion force &

The grooves were formed on the surface of the liquid crystal layer using a cross hatch to form 100 squares. The Nichiban tape was attached and the tape was separated in the vertical direction. When the liquid crystal layer was evaluated through an optical microscope, the degree of peeling was evaluated on the following pattern.

◎; No pattern tearing

○: 1 to 3 pattern peeling

△: 4 to 8 on the pattern

X: Pattern peeling exceeded 8

Evaluation items Example Comparative Example One 2 3 4 5 6 7 One 2 Phase difference 1 ◎ ○ ○ ○ ○ ○ ○ ◎ ◎ Phase difference 2 ◎ ○ ○ ○ ○ ○ ○ ◎ ◎ Interlayer adhesion △ ◎ ○ △ ○ △ △ × ×

As shown in Table 2 above, the retardation film of the examples according to the present invention exhibits the same or similar optical performance as the retardation film of the comparative examples, but the interlayer adhesion is superior to the comparative examples.

Claims (17)

Wherein the chemical bond is a bond between a reactive group on the surface of the substrate and an isocyanate group and a (meth) acrylate group present at the end of the adhesive strength enhancer contained in the liquid crystal layer, Wherein the retardation film is formed by a method comprising the steps of:
The retardation film according to claim 1, wherein the adhesive strength enhancer is at least one selected from the group consisting of compounds represented by the following formulas (1) to (4):
[Chemical Formula 1]

(Wherein R ₁ and R ₂ are each independently hydrogen or a methyl group,
R ₃ and R ₇ independently represent an alkylene group having 1 to 10 carbon atoms which is substituted or unsubstituted with a group selected from the group consisting of a ketone group, an ester group and a thiol group,
R ₄ and R ₆ independently represent an alkylene group having 1 to 10 carbon atoms which is 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 which is substituted or unsubstituted with an alkoxy group having 1 to 8 carbon atoms,
(2)

(Wherein R ₇ and R ₈ are independently of each other hydrogen or a methyl group,
R ₉ and R ₁₁ independently represent an alkylene group having 1 to 10 carbon atoms which is substituted or unsubstituted with a group selected from the group consisting of a ketone group, an ester group and a thiol group,
R &lt; ₁₀ &gt; is (a)

Or (b)

E ₁ and E ₃ independently represent an alkyl group having 1 to 10 carbon atoms or an alkoxy group having 1 to 8 carbon atoms which is substituted or unsubstituted with an alkoxy group having 1 to 8 carbon atoms and E ₂ is an alkoxy group having 1 to 8 carbon atoms, A substituted or unsubstituted alkylene group having 1 to 10 carbon atoms,
(3)

(Wherein R &lt; ₁₂ &gt; is hydrogen or a methyl group,
R &lt; ₁₃ &gt; is an alkylene group having 1 to 10 carbon atoms which is substituted or unsubstituted with a group selected from the group consisting of a ketone group, an ester group and a thiol group; and
[Chemical Formula 4]

(Wherein R &lt; ₁₄ &gt; is hydrogen or a methyl group,
And R ₁₅ is an alkylene group having 1 to 10 carbon atoms, which is substituted or unsubstituted with a group selected from the group consisting of a ketone group, an ester group and a thiol group.
The retardation film of claim 1, wherein the liquid crystal layer is formed of a curable composition comprising a liquid crystalline compound comprising a reactive group capable of reacting with an isocyanate group or a (meth) acrylate group of an adhesion promoter.
The retardation film according to claim 3, wherein the reactive group of the liquid crystalline compound is a carbon-carbon unsaturated bond, a hydroxyl group, an epoxy group or a cyano group.
4. 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 adhesive strength enhancer based on 100 parts by weight of the liquid crystalline compound.
4. The retardation film of claim 3, wherein the liquid crystalline compound is a vertically aligned liquid crystalline compound.
The retardation film according to claim 1, wherein the reactive group on the substrate surface is at least one selected from the group consisting of a hydroxyl group, a thiol group, a carboxyl group and an amine group.
The retardation film according to claim 1, wherein the substrate comprises a surface-treated triacetylcellulose-based, cycloolefin-based or PMMA-based polymer.
9. The phase difference film according to claim 8, wherein the surface treatment is at least one treatment selected from the group consisting of a saponification treatment, a primer treatment, a corona treatment, a plasma treatment and a coating treatment.
[Claim 12] The phase difference film of claim 9, wherein the plasma treatment is selected from the group consisting of a remote plasma treatment, a direct plasma treatment, and a monomer plasma treatment.
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 thiolene bond.
The retardation film according to claim 11, wherein the urethane bond between the liquid crystal layer and the substrate is formed by a reaction of an isocyanate group of the adhesive strength enhancer of the alignment layer with a hydroxyl group, a thiol group, a carboxyl group, or an amine group.
[Claim 12] The retardation film of claim 11, wherein the thiolene bond between the liquid crystal layer and the substrate is formed by a reaction between a (meth) acrylate group of the adhesive strength enhancer of the alignment layer and a thiol group of the substrate.
The retardation film according to claim 1, wherein the substrate has a water contact angle of 60 to 80 DEG on the liquid crystal layer side surface.
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.
An image display apparatus comprising the retardation film according to any one of claims 1 to 15.
17. The image display apparatus according to claim 16, wherein the image display apparatus is an IPS mode.

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