KR20160114339A - Hard coating film and image display device having the same - Google Patents

Abstract

The present invention relates to a hard coating film and an image display device provided with the same and, more specifically, relates to a hard coating film, which exhibits excellent hardness, has the resistance to the accumulated fatigue fracture, and exhibits excellent bending properties. The hard coating film has a structure on an upper part of a substrate film, wherein a first coating layer and a second coating layer having different values of specific tonic parameters are alternately laminated.

Description

TECHNICAL FIELD [0001] The present invention relates to a hard coating film and an image display device having the hard coating film.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hard coating film and an image display apparatus having the same, and more particularly to a hard coating film having excellent hardness and flexibility.

BACKGROUND ART [0002] Recently, a thin display device using a flat panel display device such as a liquid crystal display or an organic light emitting diode (OLED) display has received great attention. Particularly, these thin display devices are realized in the form of a touch screen panel, and are characterized by being portable not only in a smart phone, a tablet PC, but also in various wearable devices It is widely used in various smart devices.

These portable touch screen panel based display devices have a window cover for display protection on a display panel in order to protect the display panel from scratches or external impacts, and in most cases, the tempered glass for display is used as a window cover. Tempered glass for displays is thinner than ordinary glass, but is characterized by high strength and scratch resistance.

However, since the tempered glass has a disadvantage that it is not suitable for weight reduction of a portable device due to its heavy weight, it is difficult to realize an unbreakable property because it is vulnerable to an external impact, and is not bendable, It is not suitable as a flexible display material having a foldable function.

In recent years, studies on optical plastic covers having strength or scratch resistance corresponding to tempered glass, while ensuring flexibility and impact resistance, have been made variously. Polyethylene terephthalate (PET), polyethersulfone (PES), polyethylene naphthalate (PEN), polyacrylate (PAR), polycarbonate (PC) , Polyimide (PI), and the like. However, these polymer plastic substrates not only lack physical properties in terms of hardness and scratch resistance as compared with tempered glass used as a window cover for display protection, but also have insufficient impact resistance. Therefore, various attempts have been made to complement the physical properties required by coating the composite resin composition on these plastic substrates.

Accordingly, in the case of general hard coating, a composition comprising a resin containing a photo-curable functional group, a curing agent, a curing catalyst, and other additives is used. In particular, a high functional group In the case of a composite resin, it can be coated on an optical plastic substrate film to be used as a display protection window having improved hardness and scratch resistance.

However, in the case of a general photocurable composite resin, it is difficult to realize a high hardness corresponding to tempered glass, curl phenomenon due to shrinkage during curing is largely generated, and flexibility is not sufficient, It is not suitable as a protective window cover.

Korean Patent Laid-Open Publication No. 2013-74167 discloses a plastic substrate.

Korea Patent Publication No. 2013-74167

It is an object of the present invention to provide a hard coating film capable of simultaneously realizing hardness and flexibility.

It is another object of the present invention to provide an image display device having the hard coating film.

1. A hard coating film comprising a first coating layer and a second coating layer alternately stacked on a base film, wherein the first coating layer and the second coating layer have different rigidity values,

[Equation 1]

Rigidity (kPa · mm) = Elastic modulus (GPa) Ⅹ Layer thickness (㎛).

2. The hard coating film according to claim 1, wherein the first coating layer and the second coating layer are provided in plural numbers, respectively, and the first coating layer and the second coating layer satisfy the rigidity limit value expressed by the following formula (2) :

&Quot; (2) "

0.1R? X? 0.5R

(Wherein R is an average stiffness of the first coating layer disposed on both sides of the second coating layer,

And X is the rigidity of the second coating layer).

3. The hard coating film of 1 above, wherein said first coating layer has a rigidity value of 3 to 15 in formula (1).

4. The hard coating film of 2 above, wherein said plurality of first coating layers each have different stiffness values.

5. The hard coating film of 2 above, wherein said plurality of second coating layers each have different stiffness values.

6. The hard coating film of 1 above, wherein the thickness of the first coating layer is 1 to 20 占 퐉.

7. The hard coating film according to item 1, wherein the thickness of the second coating layer is 1 to 10 mu m.

8. The hard coating film of 1 above, wherein the first coating layer is formed by a radical polymerization reaction.

9. The hard coating film of 1 above, wherein the second coating layer is formed by cationic polymerization.

10. The hard coating film of 1 above, wherein the total number of the first coating layer and the second coating layer is 2 to 10.

11. The composition of claim 1, wherein the base film is selected from the group consisting of triacetyl cellulose, acetyl cellulose butyrate, ethylene-vinyl acetate copolymer, propionyl cellulolose, butyryl cellulose, acetyl propionyl cellulose, polyester, polystyrene, Polyetherimide, polyacrylate, polyimide, polyether sulfone, polysulfone, polyethylene, polypropylene, polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl acetal, polyether ketone, polyether ether Wherein the hard coat film is selected from the group consisting of polyethylene terephthalate, polyethylene terephthalate, polyethylene terephthalate, and polycarbonate.

12. An image display device comprising a hard coating film according to any one of the above 1 to 11.

The hard coating film of the present invention can simultaneously achieve excellent hardness and flexibility by alternately laminating coating layers having different rigidity parameter values.

In addition, the hard coating film of the present invention satisfies a specific rigidity threshold value parameter between alternately laminated layers, and is thus suitable for application to flexible displays by significantly improving resistance to fatigue failure accumulated through interaction between layers .

1 is a cross-sectional view of a hard coating film according to an embodiment of the present invention.
2 schematically shows an apparatus for measuring bending properties in the present invention.

The present invention relates to a hard coating film and an image display apparatus having the same, and more particularly to a hard coating film having a structure in which a first coating layer and a second coating layer having different stiffness parameter values are alternately stacked on a base film , An excellent hardness and at the same time resistance to accumulated fatigue failure and exhibiting excellent bending properties, and an image display apparatus having the same.

FIG. 1 is a vertical sectional view of a hard coating film according to an embodiment of the present invention. Hereinafter, the present invention will be described in detail with reference to the drawings.

The present invention includes a first coating layer 200 (210, 220, 230) and a second coating layer 300 (310, 320) alternately stacked on a base film (100) and a base film (100).

The first coating layer 200 and the second coating layer 300 have different values of stiffness parameters expressed by Equation (1).

[Equation 1]

Rigidity (kPa · mm) = Elastic modulus (GPa) Ⅹ Layer thickness (㎛).

The stiffness parameter represented by the formula (1) is a result of deriving a specific relationship between the modulus of elasticity and the thickness, which affects the hardness and bending characteristics of the film. The present invention is characterized in that two layers having different rigidity are alternately laminated, The hardness and bending characteristics of the opposite relationship can be improved at the same time. In particular, the resistance to fatigue failure is significantly improved and the application to the flexible display is facilitated.

For reference, when a continuous stress is applied to a solid material, the material is broken at a stress much lower than the tensile strength. The continuous fatigue of the material is the repetitive stress applied to the material, and fatigue failure is called fatigue failure.

The rigidity values of the first coating layer 200 and the second coating layer 300 according to the present invention are not particularly limited as long as they are laminated and have different values. For example, the rigidity values may be 0.1 to 15 kPa · mm have. In addition, when the rigidity of the first coating layer 200 is greater than the rigidity of the second coating layer 300, the rigidity of the first coating layer 200 may be 3 to 15 kPa · mm, preferably 5 to 10 kPa · mm, and the rigidity value of the second coating layer 300 may be 0.1 to 5 kPa · mm, preferably 0.4 to 3 kPa · mm. If the above range is satisfied, the hardness and bending property of the hard coating film can be further improved upon continuous folding by eliminating fatigue accumulation.

The thicknesses of the first coating layer 200 and the second coating layer 300 according to the present invention are not particularly limited as long as the thickness satisfies the stiffness relationship of Equation 1, Lt; / RTI > If the rigidity of the first coating layer 200 is greater than the rigidity of the second coating layer 300, the thickness of the first coating layer 200 may be greater than the thickness of the second coating layer 300, 1 to 20 탆, preferably 3 to 10 탆, and the thickness of the second coating layer 300 may be 1 to 10 탆, preferably 1 to 5 탆. When the thickness of the single layer is more than the above range, it is difficult to ensure transparency of the coating film, the uniform film can not be secured and the appearance may be poor. When the thickness is less than the above range, the curing is poor and it is difficult to secure desirable mechanical properties. The thickness of the coating layer can be appropriately adjusted to suit the viscosity of the coating liquid and the apparatus (e.g., a coater) used in the coating process.

The modulus of elasticity of the first coating layer 200 and the second coating layer 300 according to the present invention is not particularly limited as long as it satisfies the stiffness relationship of Equation 1, . If the rigidity of the first coating layer 200 is greater than the rigidity of the second coating layer 300, the modulus of elasticity of the first coating layer 200 may be greater than the modulus of elasticity of the second coating layer 300, 4 to 9 Gpa, preferably 6 to 9 Gpa, and the elastic modulus of the second coating layer 300 may be 1 to 5 GPa, preferably 1 to 3 GPa. When the elastic modulus of each coating layer is lower than the above range, it is difficult to ensure hardness. If the elastic modulus is above the above range, durability may be lowered at the time of folding. By adjusting the elastic modulus to an appropriate range simultaneously with the thickness, the rigidity value of Equation (1) can be satisfied.

In the present invention, the plurality of first coating layers 200, 210, 220, and 230 and the second coating layers 300 and 310 and 320 may be alternately provided. In this case, (See FIG. 1).

When a plurality of the first coating layers 200, 210, 220 and 230 and the second coating layers 300 and 310 and 320 are alternately provided, the first coating layer 200 (210, 220, 230) and the second coating layer 300, 310, and 320 may satisfy the rigidity limit value expressed by the following equation (2).

&Quot; (2) "

0.1R? X? 0.5R

(Wherein R is the average stiffness of the first coating layer disposed on both sides of the second coating layer, and X is the rigidity of the second coating layer).

1, the first hard coating layer 210 and the second hard coating layer 220 are formed on the first coating layer 220 and the second hard coating layer 220, respectively. And the second coating layer 230 between the first coating layer 230 and the second coating layer 230.

According to the above formula (2), the hard coating film according to the present invention can be formed by laminating a layer having a relatively small rigidity between the layers having a large rigidity, thereby enabling the layer having a small rigidity to absorb the accumulated fatigue caused by the repeated stress, So that the characteristics can be further improved.

In the present invention, when the first coating layer 210 and the second coating layer 310 are stacked one by one, the rigidity limit value of Equation (2) is obtained by using the middle layer as the first coating layer 210, Lt; RTI ID = 0.0 > 100 < / RTI > In this case, R is the mean stiffness of the base film 100 and the second coating layer 310 disposed on both sides of the first coating layer 210, and X is the rigidity of the first coating layer 210 .

In the present invention, when a plurality of the first coating layers 200, 210, 220, 230 and the second coating layers 300, 310, 320 are alternately provided, the first coating layer 200 (210, 220, 230) And the second coating layer 300 (310, 320) may have different stiffness values, respectively.

Also, the first coating layers 200, 210, 220, and 230 may have different thicknesses and elastic moduli, and the second coating layers 300 and 310 and 320 may have different thicknesses and elastic moduli.

In the present invention, the total number of the coating layers to be laminated is not particularly limited, but it is preferably 2 to 10 in terms of securing flexibility. In the lamination, the uppermost layer opposed to the base film is more rigid It is preferable that these large layers are laminated.

Further, in the present invention, the thickness range of the total coating layer excluding the base film may be 10 to 80 탆, preferably 15 to 60 탆.

The base film according to the present invention can be used without particular limitation as long as it is a transparent material having an appropriate flexibility, and examples thereof include triacetylcellulose, acetylcellulose butyrate, ethylene-vinyl acetate copolymer, propionylcellulose, Polypropylene, polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinylidene chloride, polyvinylidene chloride, polyvinylidene chloride, polyvinylidene chloride, polyvinylidene chloride, polyvinylidene chloride, polyvinylidene chloride, Vinyl alcohol, polyvinyl acetal, polyether ketone, polyether ether ketone, polyether sulfone, polymethyl methacrylate, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and polycarbonate.

According to an embodiment of the present invention, the rigidity of the first coating layer 200 among the first coating layer 200 and the second coating layer 300, which are alternately stacked on the base film 100, May be greater than the rigidity of the coating layer (300).

The first coating layer

In this case, the rigidity value of the first coating layer 200 may be 3 to 15 kPa · mm, and the rigidity value of the second coating layer 300 may be 0.1 to 5 kPa · mm.

In order to realize the rigidity value of the first coating layer 200, the first coating layer may be formed in the range of the elastic modulus and the thickness within the above-mentioned range. The first coating layer may be cured by radical polymerization, , And incorporating inorganic particles in the coating layer.

The first coating layer 200 according to the present invention may be formed of a composition for forming a first hard coating including a photo-radical polymerizable compound, a photo-radical polymerization initiator, inorganic particles and a solvent.

The photo-radical polymerizable compound according to the present invention includes a radically polymerizable functional group and may be a photo-radical polymerizable monomer, a photo-radical polymerizable oligomer, or the like.

The photo-radical polymerizable oligomer may be a urethane (meth) acrylate oligomer for improving the scratch resistance and hardness of the cured product and for increasing the modulus of the coating layer.

The urethane (meth) acrylate oligomer may be a compound having two or more substituents each represented by the following formula (1) and (meth) acroyl group in the molecule.

[Chemical Formula 1]

* -OC (= O) NH- *

The urethane (meth) acrylate oligomer may be one produced by reacting 1 mole of a diisocyanate represented by the following formula (2) with 2 moles of an active hydrogen-containing polymerizable unsaturated compound.

(2)

R1-OC (= O) NH-R3-NHC (= O) O-R2

In the formulas, R 1 and R 2 are each independently a substituent group containing a (meth) acryloyl group derived from an active hydrogen-containing polymerizable unsaturated compound, and R 3 is a divalent substituent derived from a diisocyanate.

Specific examples of the urethane (meth) acrylate oligomer include the reaction of 2-hydroxyethyl (meth) acrylate and 2,4-tolylene diisocyanate, the reaction of 2-hydroxyethyl (meth) Reaction of isocyanate, reaction of 2-hydroxybutyl (meth) acrylate and 2,4-tolylene diisocyanate, reaction of 2-hydroxybutyl (meth) acrylate and isophorone diisocyanate, reaction of pentaerythritol tri ) Acrylate and 2,4-toluene diisocyanate, the reaction of pentaerythritol tri (meth) acrylate and isophorone diisocyanate, the reaction of pentaerythritol tri (meth) acrylate and dicyclohexylmethane diisocyanate, The reaction of dipentaerythritol penta (meth) acrylate and isophorone diisocyanate, the reaction of dipentaerythritol penta (meth) acrylate It may be a bit and the reaction product of dicyclohexyl diisocyanate.

Examples of the photo-radical polymerizable monomer include monofunctional and / or polyfunctional (meth) acrylates, which may be used alone or in combination of two or more thereof

Specific examples thereof include trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, glycerol tri (meth) acrylate, tris (2-hydroxyethyl) isocyanurate Butanediol di (meth) acrylate, 1-butanediol di (meth) acrylate, 1-butanediol di (meth) acrylate, ethylene glycol di (meth) acrylate, propylene glycol Acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, neopentyl glycol di (Meth) acrylate, ethylene oxide or propylene oxide-added poly (meth) acrylate in the (meth) acrylic acid ester, bis (2-hydroxyethyl) isocyanurate di .; Oligoester (meth) acrylate, oligoether (meth) acrylate, oligourethane (meth) acrylate and oligoepoxy (meth) acrylate having 1 to 3 (meth) acryloyl groups in the molecule; Hydroxypropyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, and ethylene oxide or propylene oxide addition products to the (meth) acrylic acid ester; And mono (meth) acrylic acid esters such as iso-octyl (meth) acrylate, iso-decyl (meth) acrylate, stearyl (meth) acrylate, tetrahydrofurfuryl (Meth) acrylate and dipentaerythritol hexa (meth) acrylate, dipentaerythritol hydroxypenta (meth) acrylate, pentaerythritol tetra (meth) acrylate, Acrylate, ditrimethylolpropane tetra (meth) acrylate, and the like.

The content ratio of the photo-radical polymerizable monomer to the oligomer is not particularly limited and may be suitably selected in consideration of workability and the like, and may be included in a ratio of 0:10 to 10: 0, for example.

The content of the photo-radical polymerizable compound is not particularly limited and may be, for example, 5 to 50 parts by weight, preferably 10 to 40 parts by weight, based on 100 parts by weight of the total composition. When the amount of the polymerizable compound is less than 5 parts by weight, the elastic modulus of the coating layer is decreased and cracks can easily occur in the coating layer at the time of bending. When the amount exceeds 50 parts by weight, the coating property is decreased due to high viscosity, A problem may arise.

The inorganic particles according to the present invention are added to improve the mechanical properties such as abrasion resistance scratch resistance and the like in the coating layer and to improve the elastic modulus of the coating layer and have an average particle diameter of 1 to 800 nm and preferably 5 to 100 nm .

When the particle size of the inorganic particles is less than 1 nm, it is impossible to form a uniform coating layer by coagulating in the composition, and thus the above-mentioned effect can not be expected. When the particle diameter of the inorganic particles exceeds 800 nm, the optical properties of the finally obtained coating layer may be deteriorated, and the mechanical properties may be deteriorated.

The type of the inorganic particles may be a metal oxide, for _{example, Al 2 O 3, SiO 2} , ZnO, ZrO 2, BaTiO 3, TiO 2, Ta 2 O 5, Ti 3 O 5, ITO, IZO, ATO , ZnO-Al, Nb ₂ O _3, there may be mentioned SnO, MgO, etc., preferably Al ₂ O _3, SiO _2, ZrO ₂ is good. These may be used alone or in combination of two or more.

The content of the inorganic particles is not particularly limited, but may be 10 to 80 parts by weight, preferably 10 to 60 parts by weight, based on 100 parts by weight of the total composition. When the amount of the photopolymerizable compound is less than 10 parts by weight, it is difficult to realize the above-mentioned effect in a small amount. When the amount of the photopolymerizable compound is more than 80 parts by weight, both the optical properties and mechanical properties of the coating layer may be lowered and cracks may easily occur.

The photo radical polymerization initiator according to the present invention is not particularly limited as long as it can form a radical by light irradiation.

The photo radical polymerization initiator includes a first type initiator that generates radicals by decomposition of a molecule due to a chemical structure or molecular binding energy difference, and a second type initiator that generates radicals by hydrogen reclamation. The first type initiator and the second type initiator may be used alone or in combination.

Specific examples of usable type 1 initiators include 4-phenoxydichloroacetophenone, 4-t-butyldichloroacetophenone, 4-t-butyl trichloroacetophenone, diethoxyacetophenone, 2- 2-methylpropan-1-one, 1- (4-dodecylphenyl) -2-hydroxy-2- Acetophenones such as methylpropane-1-one, 4- (2-hydroxyethoxy) -phenyl (2-hydroxy-2-propyl) ketone and 1-hydroxycyclohexyl phenyl ketone; Benzoins such as benzoin, benzoin methyl ether, benzoin ethyl ether and benzyl dimethyl ketal; Acylphosphine oxides; Titanocene compounds; And the like. These may be used alone or in combination of two or more.

Specific examples of usable type 2 initiators include benzophenone, benzoylbenzoic acid, benzoylbenzoic acid methyl ether, 4-phenylbenzophenone, hydroxybenzophenone, 4-benzoyl-4'-methyldiphenylsulfide, Benzophenones such as 3'-methyl-4-methoxybenzophenone, thioxanthone, 2-chromothioxanone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, Thioxanthone and the like. These may be used alone or in combination of two or more.

The content of the photo-radical polymerization initiator is not particularly limited and may be, for example, 0.1 to 20 parts by weight, preferably 1 to 10 parts by weight, based on 100 parts by weight of the photo-radical polymerizable compound. When the content is less than 0.1 part by weight, hardening does not proceed sufficiently and it may be difficult to realize the mechanical properties and adhesion of the coating layer. If the content is more than 20 parts by weight, problems such as poor adhesion, cracks and curl may occur due to curing shrinkage.

The solvent according to the present invention can be used without limitation as long as it can sufficiently dissolve or disperse the above composition. (Methyl ethyl ketone, methyl butyl ketone, methyl isobutyl ketone, diethyl ketone, dipropyl ketone, etc.) acetate type solvents (e.g., methanol, ethanol, isopropanol, butanol, propylene glycol methoxy alcohol and the like) (Methyl cellosolve, ethyl cellosolve, propyl cellosolve and the like), hydrocarbon type (normal hexane, normal heptane, benzene, toluene, xylene), and the like (methyl acetate, ethyl acetate, butyl acetate, propylene glycol methoxyacetate etc.) , Etc.), or one or more of these solvents may be used in combination.

Since the viscosity of the solvent may vary depending on the coating method and apparatus, the content of the solvent may be adjusted so that the concentration of the composition for forming the first coating layer having the composition mentioned above may be 10 to 90% by weight, preferably 30 to 80% It can be adjusted appropriately.

The second coating layer

When the second coating layer 300 is smaller than the rigidity of the first coating layer 200, the rigidity value of the first coating layer 200 may be 3 to 15 kPa · mm and the rigidity value of the second coating layer 300 may be 0.1 To 5 kPa · mm.

In order to realize the rigidity value of the second coating layer 300, the second coating layer may be formed in the range of the elastic modulus and the thickness within the above-mentioned range. This is because the curing proceeds by the cationic polymerization reaction and the alcoholic resin is used, And the density can be adjusted. When the second coating layer 300 proceeds to a cationic polymerization reaction, an oxygen inhibition reaction does not occur unlike the radical polymerization reaction, which is advantageous for coating a thin film, and the interlayer adhesion can be improved by hydroxyl groups generated during the reaction, More preferable.

According to the present invention, the second coating layer 300 may be formed of a composition for forming a second hard coat layer comprising a photo cationic polymerizable compound, a photo cationic polymerization initiator, and a solvent.

The photo cationic polymerizable compound according to the present invention is a compound containing a cationic polymerizable functional group and not containing a (meth) acryloyl group.

As the photo cationic polymerizable compound, an epoxy-based polymerizable compound is used. As the epoxy-based polymerizable compound, a monomer or a resin containing an epoxy group (oxiranyl group) or an oxetanyl group can be used.

Examples of the monomer include 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 2- (3,4-epoxycyclohexyl-5,5-spiro-3,4- Bis (3,4-epoxycyclohexylmethyl) adipate, bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate, vinylcyclohexene monoxide 1,2- Vinylcyclohexane and the like. These may be used alone or in combination of two or more.

Examples of the resin include, for example, bisphenol A epoxy resin, hydrogenated bisphenol A epoxy resin, bisphenol F epoxy resin, novolac epoxy resin, aliphatic cyclic epoxy resin, brominated epoxy resin, rubber modified epoxy resin, urethane modified epoxy resin, glycidyl An esterified compound, an epoxidized polybutadiene, an epoxidized SBS (SBS is a styrene-butadiene-styrene copolymer), and the like. These may be used alone or in combination of two or more.

The polyol compound is used together with the photo cationic polymerizable compound to further improve the flexibility and hardenability of the hard coat layer.

The polyol according to the present invention is an oligomer having 1 to 6, preferably 2 to 4, hydroxyl groups per molecule, for example, a number average molecular weight of 500 to 5,000.

The structure of the alcohol is not particularly limited and may be a primary, secondary or tertiary alcohol, but a primary alcohol is preferable in terms of reaction yield and rate.

Specific examples of the polyol according to the present invention include polyester polyol; Polycarbonate polyol; Polyethylene glycol; Polypropylene glycol; Polycaprolactone polyol; Polytetramethylene glycol; Tetramethyl trimethylol and polyols derived therefrom; Glycerin and polyols derived therefrom; Pentaerythritol tetra alcohol and polyols derived therefrom; Dipentaerythritol hexa alcohols and polyols derived therefrom; A polyacrylate polyol which is an alcohol (macromer type) contained in a polymer side chain; Polyvinyl alcohol; And the like. These may be used alone or in combination of two or more.

The epoxy-based photo cationic polymerizable compound and the polyol compound may be included so as to satisfy the following formula (3).

&Quot; (3) "

1 < R < 15

(Wherein R 'is the total epoxy equivalent weight of the epoxy-based photo cationic polymerizable compound / the total hydroxyl equivalent weight of the polyol compound).

The total epoxy equivalent of the epoxy-based photo cationic polymerizable compound can be represented by the following formula (4).

&Quot; (4) &quot;

(G) / (epoxy group equivalent (g / eq)) of the epoxy-based photo cationic polymerizable compound.

The total hydroxyl equivalent weight of the polyol compound can be expressed by the following equation (5).

&Quot; (5) &quot;

? (Content of polyol compound (g) / hydroxyl group equivalent (g / eq) of polyol compound).

Equation (4) is obtained by adding the epoxy equivalent of each kind of epoxy-based photo cationic polymerizable compound, and Equation (5) is obtained by adding the hydroxyl group equivalent of each polyol compound.

The epoxy equivalent of the epoxy-based photo cationic polymerizable compound and the equivalent of the hydroxyl group of the polyol compound are not particularly limited and may be appropriately selected within a range satisfying the above-mentioned formulas.

Specifically, for example, when Formula (4) contains 80 g of a polymerizable compound having an epoxy equivalent of 160 g / eq alone, the total epoxy equivalent of the epoxy-based photo cationic polymerizable compound is 0.5. When 40 g of the polymerizable compound having an epoxy equivalent of 160 g / eq and 60 g of a polymerizable compound having an epoxy equivalent of 120 g / eq are contained, the total epoxy equivalent of the epoxy-based photo cationic polymerizable compound is 0.75, which is the sum of 0.25 and 0.5 . This calculation is also applied to Equation (5) in the same manner.

If R 'represented by the above-mentioned formula (3) is less than 10, hardness and reliability of the coating layer are lowered. If it is more than 15, the curing rate is slowed to lower the process yield and the flexibility of the hard coating layer. From the standpoint of simultaneously exhibiting excellent hardness and flexibility, R 'may preferably be 1.5 to 10.

The photo cationic polymerization initiator according to the present invention is not particularly limited as long as it can form a cation by light irradiation, and examples thereof include iron-arene complex compound, aromatic diazonium salt, aromatic iodonium salt, aromatic sulfonium salt, Aluminum complex / silyl ether, and the like. These may be used alone or in combination of two or more.

Specific examples of commercially available photo cationic polymerization initiators include IRGACURE 250 (manufactured by BASF), OPTOMER SP-150 (manufactured by Asahi Denka Kogyo), OPTOMER SP-151 (manufactured by Asahi Denka Kogyo), OPTOMER SP-170 (Manufactured by Nippon Soda Co., Ltd.), SANAID SI-100L (manufactured by Sanshin Chemical Industry Co., Ltd.), CI-2064 (manufactured by Nippon Soda Co., Ltd.), UVE-1014 (manufactured by Asahi Denka Kogyo Co., (Produced by Nippon Soda), CI-2481 (manufactured by Nippon Soda), RHODORSIL Photoinitiator 2074 (manufactured by Rhone Poulenc GmbH), UVI-6990 (manufactured by Union Carbide), BBI-103 (Manufactured by Midori Kagaku), DPS-103 (manufactured by Midori Kagaku), NAT-103 (manufactured by Midori Kagaku), TPS-103 (manufactured by Midori Kagaku) , NDS-103 (manufactured by Midori Kagaku), and the like.

As for the solvent, the components used in the composition for forming the first coating layer can be applied equally.

In the present invention, a plurality of first coating layers 200, 210, 220, and 230 and second coating layers 300 and 310 and 320 may be alternately provided. In this case, May be subjected to a surface treatment such as a plasma treatment, a corona treatment or the like before the upper layer is laminated.

<Image Display Device>

The present invention relates to an image display apparatus capable of simultaneously securing high hardness and flexibility by having the hard coating film, and the image display apparatus of the present invention can further include a configuration known in the art in addition to the above configuration . The hard coating film is excellent in hardness and flexibility, and can be used as an outermost window cover of an image display apparatus, and can be suitably applied to a flexible display in particular.

The image display device may be any of various image display devices such as a liquid crystal display device, an electroluminescence display device, a plasma display device, a field emission display device, and the like.

Manufacturing example  One

&Lt; Composition (A1) for forming first coating layer - Radical  Polymerization>

15 parts by weight of UV-1700B (10-functional urethane acrylate) manufactured by Nippon Synthetic Chemical Industry Co., Ltd., 15 parts by weight of M340 (pentaerythritol trie / tetraacrylate) from Miwon Specialty Chemicals, 20 parts by weight of Ebonic Nanopol C784 (20 nm nano silica, ), 2 parts by weight of Igacure 184 (1-hydroxy-cyclohexyl-phenyl-ketone) as a photoinitiator and 28 parts by weight of methyl ethyl ketone as a solvent were mixed to prepare a composition for forming a first coating layer.

The composition was spin-coated on a 10 x 10 cm glass to a thickness of the following Table 1, dried at 80 캜 and dried at 500 mJ in a high-pressure mercury lamp. The elastic modulus of the specimen was 8.5 GPa.

&Lt; Composition (B1) for Second Coating Layer - Cationic Polymerization >

69.8 parts by weight of hydrogenated epoxy CEL-2021 (Daicel, epoxy equivalent 130), 24.8 parts by weight of caprolactone polyol Placcel-303 (Daicel, hydroxyl equivalent 100) Cationic photoinitiator Igacure-250 (BASF Corp.) The uncompressed composition was diluted with methyl ethyl ketone to a solid content of 20%. The R 'value of the composition was 2.2, and the composition was spin-coated on a 10 x 10 cm glass to a thickness of the following Table 1, dried at 80 캜 for 1 minute, and cured by a high pressure mercury lamp for 500 mJ. The elastic modulus was 2.1 GPa.

Manufacturing example  2

&Lt; Composition (A2) for forming first coating layer - Radical  Polymerization>

20 parts by weight of EB-1290 (6-functional urethane acrylate) manufactured by SK Chemicals Co., Ltd., 20 parts by weight of M4004 (pentaerythritol ethylene glycol addition tetraacrylate) from Miwon Specialty Chemicals, 20 parts by weight of Ebonics Nanopol C784 (20 nm nano silica, , 2 parts by weight of Igacure 184 (1-hydroxy-cyclohexyl-phenyl-ketone) manufactured by BASF Corporation as a photoinitiator and 38 parts by weight of methyl ethyl ketone as a solvent were mixed to prepare a composition (A2) Respectively.

The composition was spin-coated on a 10 x 10 cm glass to a thickness of the following Table 1, dried at 80 캜 and dried at a pressure of 500 mJ in a high-pressure mercury lamp, and the elastic modulus of the specimen was measured to be 4.2 GPa.

&Lt; Composition (B2) for forming second coating layer - Cationic polymerization >

70.7 parts by weight of hydrogenated epoxy CEL-2021 (Daicel, epoxy equivalent 130), 23.3 parts by weight of caprolactone polyol Placcel-305 (Daicel, hydroxyl equivalent 100) 6 parts by weight of cationic photoinitiator Igacure-250 (BASF Corp.) The uncompressed composition was diluted with methyl ethyl ketone to a solid content of 20%. The R 'value of the above composition was 4.3. The solvent was spin-coated on a 10x10 cm glass to a thickness of the following Table 1, and the solvent was dried at a temperature of 80 캜 and cured at 500 mJ in a high pressure mercury lamp. The elastic modulus of the specimen was 1.4 GPa .

Example  And Comparative Example

Coated on the optical polyimide (Mitsubishi Gas Chemical Company, L-3430, 100 탆, elastic modulus 5 GPa, rigidity 50 kPa kPa mm m) with the components and thickness shown in Table 1 (after drying) and dried at 80 캜 for 1 minute Dried and cured by a high-pressure mercury lamp at 500 mJ to form respective layers, thereby producing a hardcoat film.

In Table 1, the layer formed on the upper surface of the base film is the first coating layer, and the remaining layers are the layers sequentially laminated on the first coating layer.

division Composition Modulus of elasticity (GPa) Film thickness (占 퐉) Rigidity (kPa · mm) Example 1 The first coating layer A1 8.5 4 3.4 The second coating layer B1 2.1 2 0.42 Third coating layer A1 8.5 4 3.4 The fourth coating layer B1 2.1 2 0.42 The fifth coating layer A1 8.5 4 3.4 Example 2 The first coating layer A1 8.5 4 3.4 The second coating layer B1 2.1 2 0.42 Third coating layer A1 8.5 5 4.25 The fourth coating layer B1 2.1 3 0.63 The fifth coating layer A1 8.5 4 3.4 Example 3 The first coating layer A1 8.5 5 4.25 The second coating layer B1 2.1 3 0.63 Third coating layer A1 8.5 6 5.1 The fourth coating layer B1 2.1 4 0.84 The fifth coating layer A1 8.5 7 5.95 Example 4 The first coating layer A1 8.5 6 5.1 The second coating layer B1 2.1 4 0.84 Third coating layer A1 8.5 7 5.95 The fourth coating layer B1 2.1 5 1.05 The fifth coating layer A1 8.5 8 6.8 Example 5 The first coating layer A1 8.5 7 5.95 The second coating layer B1 2.1 4 0.84 Third coating layer A1 8.5 8 6.8 Example 6 The first coating layer A1 8.5 4 3.4 The second coating layer B1 2.1 10 2.1 Third coating layer A1 8.5 4 3.4 Example 7 The first coating layer A1 8.5 5 4.25 The second coating layer B1 2.1 One 0.02 Third coating layer A1 8.5 5 4.25 The fourth coating layer B1 2.1 One 0.02 The fifth coating layer A1 8.5 5 4.25 Example 8
The first coating layer A2 4.2 4 1.68 The second coating layer B2 1.4 2 0.28 Third coating layer A2 4.2 4 2.69 The fourth coating layer B2 1.4 2 0.28 The fifth coating layer A2 4.2 4 1.68 Comparative Example 1 The first coating layer A1 8.5 20 17 Comparative Example 2 The first coating layer B1 2.1 20 4.2 Comparative Example 3 The first coating layer A2 4.2 20 8.4 Comparative Example 4 The first coating layer B2 1.4 20 2.8

Test Methods

(1) Evaluation of pencil hardness

The hard coating films according to Examples and Comparative Examples were measured for pencil hardness 5 times under a load of 1000 g using a pencil hardness tester (PHT, Korea Science and Engineering Co., Ltd.). The pencil was used in a Mitsubishi product, The maximum pencil hardness at which the cissing occurred less than once was expressed as the pencil hardness of the hard coat layer.

(2) Evaluation of bending characteristics

The hard coating film according to Examples and Comparative Examples was cut into a size of 10 x 100 mm to prepare a test piece. The coated layer was inserted into a machine repeatedly folding the prepared specimen (Fig. 2, Cobotec CFT-120), and both ends of the sample were fixed with double-sided tape. Thereafter, the radius of curvature of the machine was fixed at 3R, folded 10,000 times at a rate of 540 degrees / min, and the number of times the fracture was started with the naked eye was confirmed.

(3) Evaluation of adhesion

100 squares were formed by grinding 11 straight lines at intervals of 1 mm on the coated surface of the hard coating film according to the examples and the comparative example, and then peeled three times using a tape (CT-24, Nichii Co., Ltd.) Respectively. Three 100 squares were tested and the average was recorded.

The adhesion was recorded as follows.

Adhesion = n / 100

n: the number of rectangles that are not to be peeled out of the entire rectangle

100: total number of squares

Therefore, when one of them was not peeled off, it was recorded as 100/100.

division Pencil hardness Bending property Adhesiveness Example 1 7H 350,000 times 100/100 Example 2 8H 290,000 times 100/100 Example 3 8H 270,000 times 100/100 Example 4 9H 230,000 times 100/100 Example 5 9H 250,000 times 100/100 Example 6 6H 200,000 times 100/100 Example 7 8H 160,000 times 80/100 Example 8 6H 390,000 times 100/100 Comparative Example 1 8H 10,000 times 15/100 Comparative Example 2 3H 380,000 times 100/100 Comparative Example 3 6H 2,000 times 40/100 Comparative Example 4 2H 400,000 times 100/100

Referring to Table 2, in the embodiments satisfying the stiffness relationship according to the present invention, pencil hardness and bending property (flexibility) can be simultaneously realized in an excellent range.

In the case of the comparative examples formed of a single layer having a thickness and an elastic modulus similar to those of the embodiments, the rigidity parameter of the present invention could not be satisfied, and it was impossible to secure a configuration satisfying both hardness and flexibility.

Claims (12)

A hard coating film comprising a first coating layer and a second coating layer alternately stacked on a base film and having different stiffness values,
[Equation 1]
Rigidity (kPa · mm) = Elastic modulus (GPa) Ⅹ Layer thickness (㎛).
The hard coating film according to claim 1, wherein the first coating layer and the second coating layer are provided in plural numbers, respectively, and the first coating layer and the second coating layer satisfy the rigidity limit value represented by the following formula (2)
&Quot; (2) &quot;
0.1R? X? 0.5R
(Wherein R is an average stiffness of the first coating layer disposed on both sides of the second coating layer,
And X is the rigidity of the second coating layer).
The hard coating film of claim 1, wherein the first coating layer has a rigidity value of 3 to 15 in formula (1).
The hard coating film of claim 2, wherein the plurality of first coating layers each have different stiffness values.
The hard coating film of claim 2, wherein the plurality of second coating layers each have different stiffness values.
The hard coating film according to claim 1, wherein the thickness of the first coating layer is 1 to 20 占 퐉.
The hard coating film of claim 1, wherein the thickness of the second coating layer is 1 to 10 mu m.
The hard coating film of claim 1, wherein the first coating layer is formed by a radical polymerization reaction.
The hard coating film of claim 1, wherein the second coating layer is formed by a cationic polymerization reaction.
The hard coating film of claim 1, wherein the total number of the first coating layer and the second coating layer is 2 to 10.
[4] The method according to claim 1, wherein the base film is formed of at least one selected from the group consisting of triacetylcellulose, acetylcellulose butyrate, ethylene-vinyl acetate copolymer, propionylcellulose, butyrylcellulose, acetylpropionylcellulose, polyester, polystyrene, polyamide, Polyethersulfone, polyethylene, polypropylene, polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl acetal, polyether ketone, polyether ether ketone, Wherein the hard coat film is selected from the group consisting of polyether sulfone, polymethyl methacrylate, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate and polycarbonate.
An image display device comprising the hard coating film according to any one of claims 1 to 11.

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