KR20180027317A - Hard Coating Film and Image Display Device Having the Same - Google Patents

Abstract

The present invention relates to a hard coating film having a first hard coating layer and a second hard coating layer laminated on one surface of a base film. Curl values of the first hard coating layer and the second hard coating layers are A and B, respectively and the relation of A and B is AB < 0. According to the present invention, the hard coating film has excellent anti-bending features and excellent anti-scratch features and can minimize curls.

Description

Technical Field [0001] The present invention relates to a hard coating film and an image display device having the same,

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 flexing resistance and scratch resistance and minimized curling, and an image display apparatus having the hard coating film. will be.

The hard coating film is used for surface protection for image display devices such as a liquid crystal display device, an electroluminescence (EL) display device, a plasma display (PD), and a field emission display (FED).

In recent years, a flexible display device capable of maintaining the display performance even if bent like paper by using a flexible material such as plastic instead of a conventional glass substrate has rapidly emerged as a next-generation display device, and hardness High hardness, scratch resistance, and curl of the edge of the film do not occur during the production process or use, and a hard coating film which does not generate cracks with appropriate flexibility is being studied.

Korean Patent Laid-Open Publication No. 10-2016-0057221 discloses a hard hard coating formed using a hard coating composition comprising an epoxy siloxane resin having a weight average molecular weight of 800 to 30,000, a crosslinking agent containing a compound having an epoxy cyclohexane structure and a photopolymerization initiator Coating film.

However, in the case of such a hard hard coating film, there is a problem in that flexing resistance and / or scratch resistance are not sufficient and curling occurs.

Korean Patent Publication No. 10-2016-0057221

It is an object of the present invention to provide a hard coating film excellent in flex resistance and scratch resistance and controlled in curling.

Another object of the present invention is to provide an image display apparatus provided with the hard coating film.

On the other hand, the present invention is a hard coating film in which a first hard coating layer and a second hard coating layer are laminated on one side of a base film, wherein Curl values of the first hard coating layer and the second hard coating layer are A and B , A hard coating film having AB < 0 is provided.

In one embodiment of the present invention, the first hard coat layer is formed from a first hard coat composition comprising a photocurable acrylic resin, a photopolymerization initiator and a solvent, and the second hard coat layer comprises a photocurable epoxy resin, a photopolymerization initiator and a solvent , &Lt; / RTI &gt;

In one embodiment of the present invention, the first hard coat layer is formed from a first hard coat composition comprising a dendrimer compound having a (meth) acrylate end group, a monofunctional (meth) acrylate, a photopolymerization initiator and a solvent, The second hard coat layer may be formed from a second hard coat composition comprising an alkoxysilane compound having an epoxy group or a polysiloxane resin, a photopolymerization initiator, and a solvent.

On the other hand, the present invention provides an image display apparatus provided with the hard coating film.

The hard coating film according to the present invention can be effectively used for a window of a flexible display device because the curling can be minimized while having excellent flexing resistance and scratch resistance.

Hereinafter, the present invention will be described in more detail.

One embodiment of the present invention is a hard coating film in which a first hard coating layer and a second hard coating layer are laminated on one surface of a base film, wherein Curl values of the first hard coating layer and the second hard coating layer are A and B Quot; AB < 0 &quot;.

In one embodiment of the present invention, the curl values of the first hard coating layer and the second hard coating layer are measured after lamination of the first hard coating layer or the second hard coating layer on the base film, respectively.

The curl value was determined by cutting the hard coat film to a size of 10 cm x 10 cm and then leaving it at 25 DEG C and 48% RH for 24 hours, placing the convex side of the hard coat film against the reference plane and then measuring the average height from the reference plane to the four corners (+) Value in the case of an analogical and (-) value in the case of a counterfeit.

When the hard coating film is positioned such that the surface of the base film faces the reference surface, the surface of the hard coating layer located on the opposite side of the base film is a curl having a concave shape, and vice versa, when the surface of the hard coating layer is convex It is a curl.

Therefore, AB < 0 indicates that one of the curl values of the first hard coating layer and the second hard coating layer is (+) and the other is (-) value. That is, either one of the first hard coating layer and the second hard coating layer has a static and the other has a counter-current.

The generation of curl can be suppressed by satisfying the condition that the product of the curl value of the first hard coat layer and the curl value of the second hard coat layer is less than zero (i.e., AB < 0).

In the hard coating film according to an embodiment of the present invention, the curl value of the first hard coat layer may be (+) and the curl value of the second hard coat layer may be (-). At this time, curl generation can be minimized.

A hard coating film according to an embodiment of the present invention can be produced by applying a hard coating composition on one side of a substrate film and curing the sequentially formed first hard coating layer and second hard coating layer.

The hard coating film according to one embodiment of the present invention is characterized in that any one of the first hard coating composition or the second hard coating composition described below is used to form the first hard coating layer and the other hard coating composition is used as the second hard coating composition, Can be used to form a coating layer. For example, a first hard coat layer may be formed from the first hard coat composition, and a second hard coat layer may be formed from the second hard coat composition.

As the base film, any transparent polymer film can be used. The polymer film can be produced by a film-forming method or an extrusion method according to the molecular weight and the film production method, and can be used regardless of the commercially available transparent polymer film. Examples thereof include triacetyl cellulose, acetyl cellulose butyrate, ethylene- But are not limited to, vinyl acetate copolymer, propionyl cellulolose, butyryl cellulose, acetyl propionyl cellulose, polyester, polystyrene, polyamide, polyether imide, polyacryl, polyimide, polyether sulfone, polysulfone, Polyolefins such as polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl acetal, polyether ketone, polyether ether ketone, polyethersulfone, polymethylmethacrylate, polyethylene terephthalate, polybutylene terephthalate, Polyethylene naphthalate, poly And various transparent polymeric substrates such as polycarbonate and polycarbonate.

The thickness of the base film is not particularly limited, but may be 10 to 1000 탆, specifically 20 to 150 탆. When the thickness of the base film is less than 10 mu m, the strength of the film is lowered and the workability is lowered. When the thickness is more than 1000 mu m, the transparency is decreased or the weight of the hard coating film is increased.

The thicknesses of the first hard coating layer and the second hard coating layer may each be 1 to 10 탆. When the thicknesses of the first hard coating layer and the second hard coating layer are less than 1 탆, it may be difficult to ensure hardness. If the thickness of the first hard coating layer and the second hard coating layer is more than 10 탆, the flexing resistance may be decreased or the curl may be increased.

<First Hard coating  Composition>

In one embodiment of the present invention, the first hard coating composition may comprise a photocurable acrylic resin, a photopolymerization initiator, and a solvent.

The photocurable acrylic resin may include at least one selected from the group consisting of a dendrimer compound having a (meth) acrylate terminal group and a monofunctional (meth) acrylate.

In one embodiment of the present invention, the dendrimer compound having a (meth) acrylate terminal group can be used for ultraviolet curing by replacing the terminal of the branch structure with a (meth) acrylate group, and the center thereof is completely aliphatic, Ester linkage. Therefore, the dendrimer compound having a (meth) acrylate terminal group has a structural characteristic that it has a functional group with respect to the molecular weight as the generation increases, as compared with the general multifunctional acrylate monomer, and the functional group is distributed at the terminal, Can contribute to the improvement of the bending property. As a result, it is possible to obtain a curl and a hard hard coating film having improved flexibility.

The dendrimer compound having the (meth) acrylate terminal group may be represented by the following formula (1)

[Chemical Formula 1]

[R ₁ ] _4-n -C- [R ₂ -OR ₃ ] _n

In this formula,

R ₁ is a C ₁ -C ₆ alkyl group,

R ₂ is a C ₁ -C ₆ alkylene group,

로서, 적어도 하나의 R₃는

이고,R ₃ is a (meth) acryloyl group or

, At least one R &lt; ₃ &gt;

ego,

로서, 적어도 하나의 R₄는

이며, R ₄ is a (meth) acryloyl group or

, At least one R &lt; ₄ &gt;

Lt;

이고,R ₅ is a (meth) acryloyl group or

ego,

R ₆ is a (meth) acryloyl group,

n is an integer of 2 to 4,

m, x and y are integers of 2 or 3;

As used herein, the C ₁ -C ₆ alkyl group means a linear or branched monovalent hydrocarbon having 1 to 6 carbon atoms, for example, methyl, ethyl, n-propyl, i-propyl, , i-butyl, t-butyl, n-pentyl, n-hexyl, and the like.

As used herein, a C ₁ -C ₆ alkylene group means a linear or branched divalent hydrocarbon having 1 to 6 carbon atoms, and includes, for example, methylene, ethylene, propylene, and butylene. It is not.

In one embodiment of the present invention, the dendrimer compound having the (meth) acrylate terminal group may have a structure represented by the following general formula (2): &lt; EMI ID =

(2)

Dendrimer compounds having (meth) acrylate end groups are commercially available or can be prepared according to methods known in the art. For example, a first-generation dendrimer structure is formed by condensing a specific polyhydric alcohol with dimethylol propionic acid as a central skeleton, and then dimethylol propionic acid is repeatedly condensed as a branched structure to grow a structure of second generation or more , And a condensation reaction of acrylic acid at the terminal end makes it possible to obtain a dendrimer compound which is highly branched and whose terminals are substituted with a plurality of (meth) acrylate groups.

The dendrimer compound may be contained in an amount of 30 to 60% by weight, preferably 35 to 55% by weight based on 100% by weight of the entire first hard coating composition. If it is less than 30% by weight, it may be difficult to exhibit the bending property, and if it is more than 60% by weight, it may be difficult to impart hardness characteristics to the coating layer due to the presence of unreacted functional groups due to the steric hindrance effect.

In one embodiment of the present invention, the monofunctional (meth) acrylate may be used for ultraviolet curing and may improve flexibility and minimize curl by improving the bending properties of the hardcoat film.

Specific examples of the monofunctional (meth) acrylate include ethyl (meth) acrylate, methyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, butyl (meth) acrylate, isobutyl (Meth) acrylate, 2-methoxyethyl (meth) acrylate, isodecyl (meth) acrylate, octyl (meth) acrylate, isooctyl ) Acrylate and the like can be used.

The monofunctional (meth) acrylate may be included in an amount of 5 to 10% by weight based on 100% by weight of the entire first hard coating composition. If it is less than 5% by weight, it may be difficult to impart flexibility, and if it is more than 10% by weight, the hardness characteristics may be deteriorated.

In one embodiment of the present invention, the photopolymerization initiator is used for the photocuring of the first hard coating composition, and any initiator that can be used in the art can be used without limitation.

As the photopolymerization initiator, a Type 1 type photopolymerization initiator in which a radical is generated by decomposition of a molecule due to a difference in chemical structure or molecular binding energy, and a hydrogen recycling type Type 2 photopolymerization initiator coexist with a tertiary amine. Specific examples of the Type 1 type photopolymerization initiator include 4-phenoxydichloroacetophenone, 4-t-butyldichloroacetophenone, 4-t-butyl trichloroacetophenone, diethoxyacetophenone, 2- 1- (4-dodecylphenyl) -2-hydroxy-2-methylpropan-1- Acetophenones such as methylpropane-1-one, 4- (2-hydroxyethoxy) -phenyl (2-hydroxy-2-propyl) ketone and 1-hydroxycyclohexylphenylketone, benzoin, Benzoin such as methyl ether, benzoin ethyl ether and benzyl dimethyl ketal, acylphosphine oxides and titanocene compounds. Specific examples of the Type 2 type photopolymerization initiator include benzophenone, benzoylbenzoic acid, benzoylbenzoic acid methyl ether, 4-phenylbenzophenone, hydroxybenzophenone, 4-benzyl-4'-methyldiphenylsulfide, 3,3 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, and isopropylthioxanthone, and the like; Thioxanthone and the like. These may be used alone or in combination of two or more. The Type 1 type photopolymerization initiator and the Type 2 type photopolymerization initiator may be used alone or in combination.

The photopolymerization initiator may be contained in an amount of 0.1 to 5% by weight, preferably 1 to 3% by weight based on 100% by weight of the entire first hard coating composition. If it is less than 0.1% by weight, hardening does not proceed sufficiently and it is difficult to realize the mechanical properties and adhesion of the finally obtained coating film. If it exceeds 5% by weight, poor adhesion or cracking and curling due to hardening shrinkage may occur.

In one embodiment of the present invention, the solvent can be used without limitation as long as it is used in the technical field. Specifically, alcohol-based solvents such as methanol, ethanol, isopropanol, butanol, and propylene glycol methoxy alcohol; Ketones such as methyl ethyl ketone, methyl butyl ketone, methyl isobutyl ketone, diethyl ketone and dipropyl ketone; Acetate-based solvents such as methyl acetate, ethyl acetate, butyl acetate and propylene glycol methoxyacetate; Cellosolves such as methyl cellosolve, ethyl cellosolve and propyl cellosolve; And hydrocarbons such as normal hexane, normal heptane, benzene, toluene and xylene. These solvents may be used alone or in combination of two or more.

The solvent may be included in an amount of 5 to 90% by weight, preferably 10 to 85% by weight, based on 100% by weight of the total amount of the first hard coating composition. When the amount is less than 5% by weight, the viscosity is high and workability is poor. When the amount is more than 90% by weight, it is difficult to adjust the thickness of the coating film and drying unevenness may occur.

In one embodiment of the present invention, the first hard coating composition may further comprise inorganic particles to further improve the mechanical properties.

The inorganic particles may have an average particle diameter of 1 to 100 nm, preferably 5 to 50 nm. Such inorganic particles are uniformly formed in the coating film, and mechanical properties such as abrasion resistance, scratch resistance and pencil hardness can be improved. If the particle size is less than the above range, agglomeration occurs in the composition and a uniform coating film can not be formed. As a result, the above effect can not be expected. On the other hand, if the particle size exceeds the above range, The mechanical properties may be deteriorated.

The inorganic particles may be metal oxides and may be selected from the group consisting of 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- ₂ O ₃ , SnO, and MgO. In particular, Al ₂ O ₃ , SiO ₂ , ZrO ₂ and the like can be used.

The inorganic particles can be produced directly or commercially available. In the case of commercially available products, those dispersed in an organic solvent at a concentration of 10 to 80% by weight can be used.

The inorganic particles may be included in an amount of 5 to 50 wt% based on the total 100 wt% of the first hard coating composition. If it is less than 5% by weight, mechanical properties such as abrasion resistance, scratch resistance and pencil hardness may not be sufficient. If it exceeds 50% by weight, mechanical properties may be deteriorated and appearance may be deteriorated.

In one embodiment of the present invention, the first hard coating composition may further include components commonly used in the art, for example, a leveling agent, a UV stabilizer, a heat stabilizer, etc., in addition to the above components.

The leveling agent can be used to impart smoothness and coatability of a coating film when the composition is coated. Examples of the leveling agent include BYK-323, BYK-331, BYK-333, and BYK-333 manufactured by BYK Corporation, TEGO Glide 411, TEGO Glide 415, TEGO Glide 420, TEGO Glide 432, TEGO Glide 435, TEGO Glide 440, TEGO Glide 440, TEGO Glide 412, BYK- Glide 450, TEGO Glide 455, TEGO Rad 2100, TEGO Rad 2200N, TEGO Rad 2250, TEGO Rad 2300, TEGO Rad 2500, 3M FC-4430 and FC-4432. The leveling agent may be used in an amount of 0.1 to 1% by weight based on 100% by weight of the total amount of the first hard coating composition.

The ultraviolet stabilizer may be added for the purpose of protecting the coating film by blocking or absorbing ultraviolet rays, since the surface of the cured coating film is decomposed by continuous ultraviolet ray exposure to be discolored and crumbled. The ultraviolet stabilizer is classified into an absorbent, a quencher, and a hindered amine light stabilizer (HALS) according to the action mechanism. Depending on the chemical structure, it can be divided into Phenyl Salicylates, Benzophenone, Benzotriazole, Nickel Derivatives and Radical Scavenger. . In the present invention, there is no particular limitation as long as it is an ultraviolet stabilizer that does not significantly change the initial color of the coating film.

The heat stabilizer is a commercially applicable product, and it can be used either alone or in combination with a polyphenol as a primary heat stabilizer, a phosphite as a secondary heat stabilizer, and a lactone system.

The ultraviolet stabilizer and the heat stabilizer can be appropriately used at a level at which the ultraviolet curing property is not affected.

The first hard coating composition can be coated on a substrate film by appropriately using a known method such as die coater, air knife, reverse roll, spray, blade, casting, gravure, microgravure, spin coating and the like.

After the first hard coating composition is applied to the substrate film, the volatiles are evaporated to dryness at a temperature of 30 to 150 DEG C for 10 seconds to 1 hour, more specifically 30 seconds to 30 minutes, And then cured. The irradiation amount of the UV light may be about 0.01 to 10 J / cm 2, and more specifically, about 0.1 to 2 J / cm 2.

<2nd Hard coating  Composition>

In one embodiment of the present invention, the second hard coat composition may comprise a photocurable epoxy resin, a photopolymerization initiator and a solvent.

In addition, the second hard coating composition may further include inorganic particles, and may further include additives such as leveling agents, ultraviolet stabilizers, heat stabilizers and the like, if necessary.

The photocurable epoxy resin may include an alkoxysilane compound having an epoxy group or a polysiloxane resin.

In one embodiment of the present invention, the alkoxysilane compound having an epoxy group may include a compound of the following formula:

(3)

R ⁷ _n Si (OR ⁸ ) _4-n

In the above formula, R ⁷ is an epoxy group, R ⁸ is a C ₁ -C ₂₀ alkyl group, and n is an integer of 1 to 3.

As used herein, a C ₁ -C ₂₀ alkyl group means a linear or branched hydrocarbon group having 1 to 20 carbon atoms, and examples thereof include methyl, ethyl, n-propyl, i-propyl, -Butyl, t-butyl, n-pentyl, n-hexyl, and the like.

The alkoxysilane compound having an epoxy group undergoes a cationic photopolymerization reaction with an epoxy group. The cationic photopolymerization reaction has a relatively low shrinkage ratio, and since there is no oxygen inhibition reaction on the surface, stable curing is possible, and the curing rate is excellent. In addition, the polysiloxane resin produced by the sol-gel reaction of the alkoxysilane compound has high cationic photopolymerization and excellent curing rate due to the presence of a siloxane network. Such an epoxy group-containing alkoxysilane compound and a polysiloxane resin not only provide an excellent hardness to the hard coating composition, but also provide excellent flexibility at the same time.

The alkoxysilane compound having an epoxy group of the above-mentioned formula (3) is preferably at least one selected from the group consisting of 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltriethoxysilane, Propyl trimethoxysilane, and 3-glycidoxypropyl triethoxysilane.

The polysiloxane resin having an epoxy group can be prepared by the hydrolysis-gel reaction of the alkoxysilane compound.

Specifically, the alkoxy group of the alkoxysilane as a starting material is hydrolyzed together with water to form a hydroxyl group, and a siloxane bond is formed by a condensation reaction with an alkoxy group or a hydroxyl group of another alkoxysilane compound to form a polysiloxane.

Catalysts may be preferably introduced to facilitate the hydro-sol-gel reaction. Usable catalysts include acid catalysts such as acetic acid, phosphoric acid, sulfuric acid, hydrochloric acid, nitric acid, chlorosulfonic acid, para-toluic acid, trichloroacetic acid, polyphosphoric acid, pyrophosphoric acid, iodic acid, tartaric acid, perchloric acid or ammonia, sodium hydroxide, Base catalysts such as butylamine, di-n-butylamine, tri-n-butylamine, imidazole, ammonium perchlorate, potassium hydroxide and barium hydroxide, ion exchange resins such as Amberite IPA- ). The amount of the catalyst to be used is not particularly limited, and 0.0001 to 10 parts by weight may be added to 100 parts by weight of the alkoxysilane.

The hydrosol-gel reaction can be carried out by stirring at room temperature for 6 to 144 hours, and may be carried out at 60 to 80 ° C for 12 to 36 hours for accelerating the reaction rate and proceeding the complete condensation reaction.

The alkoxysilane compound or polysiloxane resin may be contained in an amount of 30 to 60% by weight, preferably 35 to 55% by weight based on 100% by weight of the total amount of the second hard coating composition. If it is less than 30% by weight, it is difficult to secure hardness. If it is more than 60% by weight, the coating film is broken and it may be difficult to impart bending properties.

In one embodiment of the present invention, the photopolymerization initiator is used for the photocuring of the second hard coating composition, and any initiator that can be used in the art can be used without limitation.

As the photopolymerization initiator, a cationic photopolymerization initiator capable of generating a cationic species or a Lewis acid by irradiation of active energy rays such as visible light, ultraviolet light, X-ray, or electron beam to initiate polymerization reaction of cationic photo- have.

Since the cationic photopolymerization initiator acts catalytically by light, it is excellent in storage stability and workability even when mixed with a cationic photocurable component. Examples of the compound capable of generating a cationic species or a Lewis acid by irradiation with an active energy ray include an onium salt such as an aromatic diazonium salt, an aromatic iodonium salt or an aromatic sulfonium salt; Iron-allene complex and the like. Among them, the aromatic sulfonium salt is preferable because it has ultraviolet ray absorption property even in the wavelength range near 300 nm, and is excellent in curability and can give excellent coating film characteristics. The cationic photopolymerization initiator may be used alone or in combination of two or more.

The photopolymerization initiator may be included in an amount of 0.1 to 5% by weight based on the total 100% by weight of the second hard coating composition. When the content of the photopolymerization initiator is less than 0.1% by weight, the curing rate is slow. When the content of the photopolymerization initiator is more than 5% by weight, excessive cracking may occur in the hard coating layer.

The other components contained in the second hard coating composition and the method of applying, drying and curing thereof are the same as those described in the first hard coating composition, and thus the substrate is omitted in order to avoid duplication.

One embodiment of the present invention relates to an image display apparatus provided with the above-mentioned hard coating film. For example, the hard coating film of the present invention can be used as an image display device, particularly as a window of a flexible display device. Further, the hard coating film of the present invention may be used by being attached to a polarizing plate, a touch sensor, or the like.

The hard coating film according to one embodiment of the present invention can be used in reflective, transmissive, semi-transmissive LCD or various driving LCDs such as TN type, STN type, OCB type, HAN type, VA type and IPS type. The hard coating film according to one embodiment of the present invention can also be used in various image display devices such as a plasma display, a field emission display, an organic EL display, an inorganic EL display, and an electronic paper.

Hereinafter, the present invention will be described more specifically with reference to Examples, Comparative Examples and Experimental Examples. It should be apparent to those skilled in the art that these examples, comparative examples and experimental examples are only for illustrating the present invention, and the scope of the present invention is not limited thereto.

Manufacturing example  1: 1st Hard coating  Preparation of composition

A dendrimer compound (SP-1106, available from Mitsubishi Chemical Corp.) having a (meth) acrylate end group of 40 wt% relative to 100 wt% of the entire first hard coating composition, 5 wt% of monofunctional acrylate (butyl acrylate) (1-hydroxycyclohexyl phenyl ketone), 0.5% by weight of a leveling agent (BYK-3570, BYK KEMISA), and 13% by weight of an inorganic filler % By weight of a solvent (methyl ethyl ketone) was compounded using a stirrer and filtered with a filter made of polypropylene (PP) to prepare a first hard coating composition.

Manufacturing example  2: 2nd Hard coating  Preparation of composition

(SP-3T, manufactured by Shin-A & T C Co., Ltd.), 5 wt% of inorganic silica particles (particle diameter of 10-15 nm), 2.5 wt% of a photopolymerization initiator (bis (BYK-3570, BYK-KEMISA), and 52 wt% of a solvent (methyl ethyl ketone) were mixed using a stirrer and polypropylene (PP ) &Lt; / RTI &gt; filter to prepare a second hard coating composition.

Example  1 to 3 and Comparative Example  1 to 2: Hard coating  Production of film

Example  One:

The first hard coating composition prepared in Preparation Example 1 was dried and coated on one side of an optical polyimide film (100 탆) as a substrate having a thickness of 5 탆 and dried in an oven at 80 캜 for 5 minutes. Then, a UV accumulation amount of 0.5 J / cm &lt; 2 &gt; to form a first hard coat layer. Then, the second hard coating composition prepared in Preparation Example 2 was dried and coated on the first hard coating layer with a thickness of 5 탆, dried in an oven at 80 캜 for 5 minutes, irradiated with a UV cumulative amount of 0.5 J / A hard coat film was prepared by forming a hard coat layer.

Example  2:

The first hard coating composition prepared in Preparation Example 1 was dried and then coated on one side of the substrate to a thickness of 7 μm and the second hard coating composition prepared in Preparation Example 2 was dried and coated on the first hard coating layer with a thickness of 3 μm A hard coat film was prepared in the same manner as in Example 1 except that the second hard coat layer was formed.

Example  3:

The first hard coating composition prepared in Preparation Example 1 was dried and coated on one side of the substrate to a thickness of 3 탆 and the second hard coating composition prepared in Preparation Example 2 was dried and coated on the first hard coating layer with a thickness of 7 탆 A hard coat film was prepared in the same manner as in Example 1 except that the second hard coat layer was formed.

Comparative Example  One:

The first hard coating composition prepared in Preparation Example 1 was dried and then coated on one side of the substrate to a thickness of 5 탆. The first hard coating composition prepared in Preparation Example 1 was dried and coated on the first hard coating layer with a thickness of 5 탆 A hard coat film was prepared in the same manner as in Example 1 except that the second hard coat layer was formed.

Comparative Example  2:

The second hard coating composition prepared in Preparation Example 2 was dried and then coated on one surface of the substrate to a thickness of 5 탆. The second hard coating composition prepared in Preparation Example 2 was dried and coated on the first hard coating layer with a thickness of 5 탆 A hard coat film was prepared in the same manner as in Example 1 except that the second hard coat layer was formed.

Experimental Example  One:

Experimental Example  1-1:

The first hard coating composition prepared in Preparation Example 1 was dried and coated on one side of an optical polyimide film (100 탆) as a substrate having a thickness of 3 탆, dried in an oven at 80 캜 for 5 minutes, J / cm &lt; 2 &gt; to obtain a first hard coating film on which only the first hard coating layer was formed on the base film.

The hard coating film was cut into a size of 10 cm x 10 cm and then left for 24 hours at 25 DEG C and 48% RH. Thereafter, the convex surface of the film was brought into contact with the glass plate on a flat glass plate and the average height of four corners And the curl value was obtained. At this time, the positive (+) value and the negative (-) value were used.

The measured curl value was 3 mm.

Experimental Example  1-2:

A hard coat film was prepared and curl value was measured in the same manner as in Experimental Example 1-1, except that the first hard coat composition was coated after drying to a thickness of 5 탆.

The measured curl value was 5 mm.

Experimental Example  1-3:

A hard coat film was prepared and curl value was measured in the same manner as in Experimental Example 1-1 except that the first hard coat composition was coated after drying to a thickness of 7 mu m.

The measured curl value was 7 mm.

Experimental Example  1-4:

A hard coat film was prepared and the curl value was measured in the same manner as in Experimental Example 1-1, except that the second hard coat composition was used in place of the first hard coat composition.

The measured curl value was -10 mm.

Experimental Example  1-5:

A hard coat film was prepared in the same manner as in Experimental Example 1-2 except that the second hard coat composition was used instead of the first hard coat composition, and the curl value was measured.

The measured curl value was -15 mm.

Experimental Example  1-6:

A hard coat film was prepared and curl value was measured in the same manner as in Experimental Example 1-3, except that the second hard coat composition was used in place of the first hard coat composition.

The measured curl value was -20 mm.

Experimental Example  2:

The physical properties of the hard coating films prepared in the above Examples and Comparative Examples were measured by the following methods, and the results are shown in Table 1 below.

(1) Flexibility at room temperature

After folding in half so that the gap between the faces of the hard coating film (width x length = 10 mm x 100 mm) was 6 mm, it was visually confirmed whether a crack occurred in the folded portion when it was spread again.

<Evaluation Criteria>

◎: No crease occurred in the folded part

○ -A: Creation of crack in folded part (length is 5mm or less, the number is 5 or less)

○ -B: Creation of crack in the folded part (length less than 5mm, number more than 5 but less than 10)

○ -C: Creation of crack in folded part (length less than 5mm, number more than 10)

△ -A: Creation of crack in folded part (length is more than 5mm but less than 10mm, number is not more than 5)

△ -B: Creation of crack in folded part (length is more than 5mm but less than 10mm, number is more than 5 but less than 10)

C: Creation of a folded part (length is more than 5mm but less than 10mm, number is more than 10)

X: Folded portion break

(2) High temperature and high humidity  Flexibility

The film was folded in half so that the gap between the faces of the hard coating film (width × length = 10 mm × 100 mm) was 6 mm, and then the film was left for 24 hours at 85 ° C. and 85% relative humidity. And examined with naked eyes.

<Evaluation Criteria>

◎: No crease occurred in the folded part

○ -A: Creation of crack in folded part (length is 5mm or less, the number is 5 or less)

○ -B: Creation of crack in the folded part (length less than 5mm, number more than 5 but less than 10)

○ -C: Creation of crack in folded part (length less than 5mm, number more than 10)

△ -A: Creation of crack in folded part (length is more than 5mm but less than 10mm, number is not more than 5)

△ -B: Creation of crack in folded part (length is more than 5mm but less than 10mm, number is more than 5 but less than 10)

C: Creation of a folded part (length is more than 5mm but less than 10mm, number is more than 10)

X: Folded portion break

(3) Pencil Hardness

The pencil hardness was measured by applying a load of 500 g using a pencil hardness tester (PHT, Korea Science and Engineering Corp.). The pencil was made using Mitsubishi products and was performed five times per pencil hardness. If it is more than 2 pieces, it is judged to be defective and it is described as the maximum hardness judged as OK.

(4) Curl ( Curl )

The hard coating film obtained in the above Examples and Comparative Examples was cut into a size of 10 cm x 10 cm and then left for 24 hours at 25 DEG C and 48% RH. Thereafter, the convex surface of the film was brought into contact with the glass plate on a flat glass plate, ), And the curl value was obtained by measuring the height average of the four corners. The results are described in accordance with the following evaluation criteria.

<Evaluation Criteria>

◎: Average height of four corners is 20 mm or less

○: The average height of four corners is more than 20 mm and less than 50 mm

△: The height average of the four corners exceeds 50 mm

X: Four corners were completely lifted and the film curled in a cylindrical shape

(5) Abrasion resistance

And scratch resistance was tested by reciprocating ten times under 1 kg / (2 cm x 2 cm) using a steel wool tester (WT-LCM100, Korea Protec Co.). Steel wool used # 0000.

<Evaluation Criteria>

S: 0 scratches

A: 1 to 10 scratches

B: 11 to 20 scratches

C: 21 to 30 scratches

D: More than 31 scratches

Flexibility at room temperature Flexibility in high temperature and high humidity Pencil hardness curl Abrasion resistance Example 1 ◎ ◎ 3H AB <0 ◎ A Example 2 ◎ ◎ 3H AB <0 ◎ A Example 3 ○ -A ○ -A 3H AB <0 ◎ A Comparative Example 1 Δ-B ? -C 3H AB> 0 × C Comparative Example 2 Δ-B × 3H AB> 0 × C

As shown in Table 1, the hard coating films of Examples 1 to 3 according to the present invention were not only excellent in flex resistance and scratch resistance, but also curl generation was controlled. On the other hand, the hard coating films of Comparative Examples 1 and 2 were confirmed to have poor flexural resistance, scratch resistance and curl characteristics.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Do. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Accordingly, the actual scope of the invention is defined by the appended claims and their equivalents.

Claims (10)

A hard coating film comprising a first hard coating layer and a second hard coating layer laminated on one surface of a base film,
And a Curl value of the first hard coating layer and a curl value of the second hard coating layer are A and B, respectively. The hard coating film according to claim 1, wherein the first hard coating layer and the second hard coating layer each have a thickness of 1 to 10 탆. The method of claim 1, wherein the first hard coat layer is formed from a first hard coat composition comprising a photocurable acrylic resin, a photopolymerization initiator and a solvent,
Wherein the second hard coat layer is formed from a second hard coat composition comprising a photocurable epoxy resin, a photopolymerization initiator, and a solvent. 4. The composition of claim 3, wherein the first hard coat layer is formed from a first hard coat composition comprising a dendritic compound having a (meth) acrylate end group, a monofunctional (meth) acrylate, a photopolymerization initiator and a solvent,
Wherein the second hard coat layer is formed from a second hard coat composition comprising an alkoxysilane compound or polysiloxane resin having an epoxy group, a photopolymerization initiator, and a solvent. 4. The hard coating film of claim 3, wherein the first hard coating composition and the second hard coating composition further comprise inorganic particles. The hard coating film according to claim 1, wherein the curl value of the first hard coat layer is (+) and the curl value of the second hard coat layer is (-). An image display device comprising the hard coating film according to any one of claims 1 to 6. A window of a flexible display device provided with a hard coating film according to any one of claims 1 to 6. A polarizing plate comprising the hard coating film according to any one of claims 1 to 6. A touch sensor comprising the hard coating film according to any one of claims 1 to 6.