KR20180043089A - Hard coating composition and hard coating film prepared from the same - Google Patents

Abstract

Provided is a hard coating composition comprising a photocurable compound represented by chemical formula 1, a dendrimer compound having a plurality of (meth)acrylate end groups, a photoinitiator, and a solvent. The hard coating composition can be used to produce hard coating films with improved hardness, abrasion resistance and flexibility.

Description

TECHNICAL FIELD [0001] The present invention relates to a hard coating composition and a hard coating film using the same. BACKGROUND OF THE INVENTION < RTI ID = 0.0 >

The present invention relates to a hardcoat composition and a hardcoat film using the same.

BACKGROUND ART [0002] Recently, image display devices such as a liquid crystal display (LCD) device or an organic light emitting display (OLED) device have been made thin and flexible. Accordingly, the image display device is widely applied not only to smart phones, tablet PCs, but also to various smart devices featuring portability from various wearable devices have. In addition, the image display device is also implemented as a touch screen panel (TSP).

A window film made of tempered glass may be formed on the display panel in order to protect the image display device from an external environment such as scratches, drop impact, external moisture, oil and the like. However, the window film is disadvantageous in weight of the display panel or the image display device due to the characteristics of tempered glass, and is easily broken by an external impact. In addition, there is a limitation in implementing a flexible characteristic through a bendable and foldable function.

Therefore, research on optical plastic covers, which can secure flexibility and impact resistance in recent years and can replace the window film made of the above tempered glass, is being studied. The optical plastic cover may be made of, for example, polyethylene terephthalate (PET), polyethersulfone (PES), polyethylene naphthalate (PEN), polyacrylate (PAR), polycarbonate And may include the same resin material.

However, the optical plastic cover has a sufficient hardness and scratch resistance as compared with the window film made of the tempered glass, and thus the impact resistance against an external impact in the image display device or the display panel may be deteriorated.

Accordingly, development of a composition for forming a hard-coating film having improved impact resistance to flexibilized properties while realizing impact resistance corresponding to tempered glass has been under development.

In the case of the composition for forming a hard coating film, it is necessary to take measures to solve problems such as curl phenomenon due to shrinkage during curing and deterioration of adhesive strength without deteriorating the flexibility because it involves a curing process.

For example, Korean Patent Laid-Open Publication No. 2016-0100121 discloses a hard coating composition containing a (meth) acrylate based monomer mixture, but there is a limit to the formation of a hard coating film having improved flexibility and abrasion resistance.

Korean Patent Publication No. 10-2016-0100121

An object of the present invention is to provide a hard coating composition having improved flexibility and impact resistance.

An object of the present invention is to provide a hard coat film formed from the hard coat composition.

An object of the present invention is to provide an image display device including the hard coating film.

An object of the present invention is to provide a window of a flexible display device including the hard coating film.

1. A photocurable compound represented by the following formula (1): A dendrimer compound having a plurality of (meth) acrylate end groups; Photoinitiators; And a hard coat composition comprising a solvent:

[Chemical Formula 1]

Wherein R ₁ to R ₄ are each independently hydrogen or a linear or branched alkyl group having 1 to 20 carbon atoms, X is a divalent oxy group or a heterohydrocarbon group containing oxygen, and n is an integer of 1 to 50 And A and B are each independently a (meth) acrylate group.

2. The hard coating composition according to 1 above, wherein the photocurable compound is contained in 3 to 15 parts by weight, based on 100 parts by weight of the total composition.

3. The hard coating composition according to item 1 above, wherein the dendrimer compound has a structure of two generations or more.

4. The hard coating composition according to 3 above, wherein the dendrimer compound has a second- or third-generation structure.

5. The hard coating composition according to item 1 above, wherein the dendrimer compound is contained in an amount of 10 to 60 parts by weight based on 100 parts by weight of the total composition.

6. The hard coating composition of 1 above, further comprising inorganic nanoparticles.

7. The composition of claim 6, wherein the inorganic nanoparticles comprise metal oxide nanoparticles.

8. A hardcoat film formed from any one of the hard coating compositions of any one of claims 1 to 7.

9. An image display device comprising the hard coating film of the above 8.

10. A window of a flexible display device comprising the hard coating film of claim 8.

According to embodiments of the present invention, the hard coating composition may comprise, for example, a PDMS-based photo-curable compound and a dendrimer compound having a (meth) acrylate end group. Therefore, a hard coat film having improved flexibility properties such as flexibility, curling property, and bending property can be obtained while improving the durability such as hardness, abrasion resistance and the like by using the hard coating composition.

The hard coating film can be applied to a window film of an image display device, for example, a flexible display device, so that flexibility and mechanical durability of the flexible display device can be simultaneously enhanced and improved. In addition, the hard coating film can be effectively applied to an optical film such as a polarizing plate of an image display apparatus.

According to embodiments of the present invention, the hard coating composition comprises a photocurable compound having a specific structure, a dendrimer compound having a (meth) acrylate end group, a photoinitiator, and a solvent, and using the hard coating composition, , Scratch resistance and the like can be enhanced and a hard coating film having improved curl characteristics and flexibility can be formed.

Hereinafter, embodiments of the present invention will be described in detail.

<Hard Coating Composition>

Photocurable compound

The photocurable compound contained in the hard coating composition according to the embodiments of the present invention may be added to the hardening process after application of the composition to improve the mechanical properties (e.g., hardness, abrasion resistance, scratch resistance, etc.) ) Can be improved.

According to embodiments of the present invention, the photo-curable compound has a polydimethylsiloxane (PDMS) -based structure, and may include, for example, a compound represented by the following formula (1).

[Chemical Formula 1]

In the general formula (1), R ₁ to R ₄ are each independently hydrogen or a linear or branched alkyl group having 1 to 20 carbon atoms. R ₁ to R ₄ may be the same or different from each other. X may represent a hetero-hydrocarbon group containing a divalent oxy group (oxygen) or oxygen. Examples of the oxygen-containing hetero hydrocarbon group include an oxyalkylene group having 1 to 10 carbon atoms. n is an integer from 1 to 50; A and B each independently may represent a (meth) acrylate group. A and B may be the same or different from each other.

In the present application, the term "(meth) acryl" refers to "methacryl-", "acryl-", or both.

For PDMS-based compounds, a number of Si-O bonds can be included within the molecular structure (e.g., n per molecule). In the case of the Si-O bond, the photo-curing compound has a bonding energy and a bonding angle larger than that of the Si-C bond, so that the photo-curing compound has low shrinkage, durability, abrasion resistance, Flexibility can be imparted.

According to the embodiments of the present invention, for example, A and B including a (meth) acrylate group capable of participating in a polymerization reaction or a curing reaction at both ends of a molecular structure in the formula (1) may be bonded. Therefore, when the curing process is carried out, the photocurable compound may undergo polymerization or curing in the horizontal direction. In this case, the hard coating film or the hard coating layer includes a resin material having a linear structure and improved in polymerization degree or degree of curing, whereby flexible properties such as flexibility and curling characteristics can be further improved.

In some embodiments, the photocurable compound may be included in an amount of about 3 to 15 parts by weight, preferably about 5 to 10 parts by weight, in 100 parts by weight of the hard coating composition. When the content of the photo-curing compound is less than about 3 parts by weight, desired durability (hardness, abrasion resistance, etc.) of the hard coating film or the hard coating layer may not be secured. If the content of the photo-curing compound exceeds about 15 parts by weight, sufficient curing of the dendrimer compound may not be performed due to steric hindrance with a dendrimer compound described later.

In some embodiments, the hard coating composition may further comprise additional photocurable compounds known in the art. For example, the additional photocurable compound may be selected from the group consisting of dipentaerythritol hexa (meth) acrylate, dipentaerythritol penta (meth) acrylate, pentaerythritol tetra (meth) acrylate, ditrimethylolpropane tetra (meth) (Meth) acrylate such as (meth) acrylate, (meth) acrylate, ester (meth) acrylate, ether (meth) acrylate and epoxy (meth) acrylate, melamine Acrylate functional groups.

Alternatively, the additional photocurable compound may include a compound having a (meth) acryloyl group or a vinyl group as a polymerizable unsaturated group, and examples thereof include a (meth) acrylic acid ester, an N-vinyl compound, a vinyl- Vinyl ethers and vinyl esters, and the like.

Dendrimer compound

According to embodiments of the present invention, a dendrimer compound may be added to the hard coating composition to further improve the flexibility and hardness of the hard coating film or hard coating layer.

In the present application, a dendrimer compound may mean a compound in which the chains of molecules are regularly polymerized outward from the center. On the other hand, the term "generation" of a dendrimer compound means a step in which a dendrimer structure is grown, and it is understood that each time a constant repeating unit structure is added based on the center of a molecule, one generation is increased. For example, when the first-generation branch ends of the formed first polymerization reaction proceed to the second generation, the polymerization reaction proceeds repeatedly.

According to embodiments of the present invention, the dendrimer compound has a plurality of (meth) acrylate end groups and may have a structure of two generations or more.

For example, the terminal group of the dendrimer compound may be represented by the following formula (2).

(2)

In formula (2), for example, R ₅ is a direct bond or an alkylene group having 1 to 6 carbon atoms, and R ₆ may be a hydrogen atom or a methyl group.

As a non-limiting example, the dendrimer compound may be prepared via the following reaction pathway. The following reaction path is provided to illustrate an example of a dendrimer compound having a (meth) acrylate end group of a third generation structure, and the dendrimer compound of the present invention should not be construed as being limited thereto.

[Reaction path]

Referring to the above reaction pathway, a first-generation dendrimer structure in which DMPA is condensed is formed at the center of TMP, and a dendrimer generation can be increased by repeated condensation polymerization of DMPA as a branch structure. For example, condensation polymerization of acrylic acid at a terminal group after the third generation may yield a dendrimer compound having a polyfunctional acrylate group at the terminal.

According to the embodiments of the present invention, a polymerizable functional group is formed at the branched end of the dendrimer compound and may have a structure of two generations or more. Thus, as compared with a general polymerizable compound, more polymerizable functional groups than the polymer unit molecular weight are contained, so that excellent hardness characteristics can be realized.

In some embodiments, the dendrimer compound may have a structure of second or third generation. If the dendrimer compound is more than 4 generations, the number of the polymerizable functional groups may be excessively increased, which may lower the flexibility and curling characteristics.

In addition, in the dendrimer compound, since the polymerizable functional group is contained only at the branch terminals, the center portion of the polymer can ensure appropriate flexibility and bending properties, thereby securing the hardness of the hard coating film or hard coating layer Curl characteristics and flexibility can be improved.

In some embodiments, the dendrimer compound may be included in an amount of about 10 to 60 parts by weight, preferably about 15 to 55 parts by weight, in 100 parts by weight of the hard coating composition. If the content of the dendrimer compound is less than about 10 parts by weight, desired flexibility properties (e.g., flexibility and bending properties) of the hard coat film or the hard coat layer may not be secured. When the content of the dendrimer compound is more than about 60 parts by weight, stiffness with the above-described photo-curing compound may lead to a decrease in hardness due to insufficient hardening.

Photoinitiator

The photoinitiator is included for the photocuring induction of the hard coating composition, and can be used without particular limitation, for example, conventional initiators in the art capable of forming radicals by light irradiation.

Examples of the photoinitiator include a Type 1 initiator that generates a radical by decomposition of a molecule due to a difference in chemical structure or molecular binding energy, and a Type 2 initiator that coexists with a tertiary amine to induce hydrogen recycle.

For example, the Type 1 initiator may be selected from the group consisting of 4-phenoxydichloroacetophenone, 4-t-butyldichloroacetophenone, 4-t-butyl trichloroacetophenone, diethoxyacetophenone, 2-methylpropan-1-one, 1- (4-dodecylphenyl) -2-hydroxy-2- (2-hydroxy-2-propyl) ketone, 1-hydroxycyclohexyl phenyl ketone and the like, benzoin, benzo Benzoin ethers such as methyl ether, benzoin ethyl ether and benzyl dimethyl ketal, acylphosphine oxides, titanocene compounds, and the like.

For example, the Type 2 initiator may be benzophenone, benzoyl benzoic acid, benzoyl benzoic acid methyl ether, 4-phenylbenzophenone, hydroxybenzophenone, 4-benzoyl- Methyl-4-methoxybenzophenone, benzophenones such as thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone and isopropylthioxanthone, Tone and the like.

The above-mentioned photoinitiators may be used alone or in combination of two or more. The above-mentioned Type 1 and Type 2 initiators may be used singly or in combination.

The content of the photoinitiator is not particularly limited as long as it is a content capable of sufficiently promoting photopolymerization or photo-curing. For example, about 0.1 to 5 parts by weight, preferably about 0.5 to 3 parts by weight Can be. If the amount of the photoinitiator is less than about 0.1 part by weight, the curing may not be sufficiently performed so that the mechanical properties and adhesiveness of the hard coating film or the hard coating layer may not be secured. If the amount of the photoinitiator exceeds about 5 parts by weight, adhesion failure, cracking, and curling due to curing shrinkage may result.

solvent

In hard coating compositions according to embodiments of the present invention, solvents commonly used in the art can be used without any particular limitation.

(Methyl ethyl ketone, methyl butyl ketone, methyl isobutyl ketone, diethyl ketone, dipropyl ketone, etc.), acetate (methyl ethyl ketone, (N-hexane, n-heptane, benzene, toluene, and the like) such as methyl acetate, ethyl acetate, butyl acetate, propyleneglycol methoxyacetate, cellosolve system (methyl cellosolve, ethyl cellosolve, Xylene, etc.) may be used. These solvents may be used alone or in combination of two or more.

The content of the solvent is not particularly limited as long as it is an amount capable of dissolving the components of the composition described above, but about 20 to 70 parts by weight of the solvent may be included in 100 parts by weight of the hard coating composition. If the content of the solvent is less than about 20 parts by weight, the viscosity of the composition may be excessively increased, resulting in deterioration of coatability and workability. When the content of the solvent is more than about 70 parts by weight, it is difficult to form a hard coating film or a hard coating layer having a uniform thickness, which may cause stains during drying and deteriorate optical properties.

Inorganic nanoparticle

In some embodiments, the hard coating composition may further comprise inorganic nanoparticles. As the inorganic nanoparticles are included, the mechanical properties such as abrasion resistance, scratch resistance, and pencil hardness of the hard coating film or the hard coating layer can be further improved.

The kind of the inorganic nanoparticles is not particularly limited, and examples thereof include Al ₂ O ₃ , SiO ₂ , ZnO, ZrO ₂ , BaTiO ₃ , TiO ₂ , Ta ₂ O ₅ , Ti ₃ O ₅ , indium- (ITO), indium-zinc-oxide can be a (ATO), ZnO-Al, Nb 2 O 3, SnO, MgO , or metal oxide-based combinations thereof-oxide (IZO), antimony-tin. In one embodiment, Al ₂ O ₃ , SiO ₂ and / or ZrO ₂ may be used as the inorganic nanoparticles.

In one embodiment, the average particle size of the inorganic nanoparticles may be about 1 to 100 nm, and preferably about 5 to 50 nm. When the average particle diameter of the inorganic nanoparticles is less than about 1 nm, the aggregation of particles may occur and the film uniformity may be lowered. When the average particle diameter of the inorganic nanoparticles exceeds about 100 nm, not only the optical properties of the hard coating film or the hard coating layer may deteriorate, but also the mechanical properties may be impaired.

In one embodiment, the inorganic nanoparticles may be included in an amount of about 5 to 40 parts by weight, based on 100 parts by weight of the hard coating composition. When the content of the inorganic nanoparticles is less than about 5 parts by weight, mechanical properties such as sufficient abrasion resistance, scratch resistance and pencil hardness may not be realized. If the content of the inorganic nanoparticles exceeds about 40 parts by weight, the polymerization or curing of the dendrimer compound and / or the photo-curable compound may be hindered and the mechanical properties may be weakened.

The inorganic nanoparticles may be manufactured directly or commercially available. In the case of a commercially available product, for example, a product in which the inorganic nanoparticles are dispersed in an organic solvent at a concentration of about 10 to 80% by weight can be used

additive

The hard coating composition according to the embodiments of the present invention may further include an additive for improving physical properties such as film uniformity within a range that does not inhibit the mechanical properties of the hard coat film or the hard coat layer. For example, the additive may include a leveling agent, a UV stabilizer, a heat stabilizer, and the like.

For example, the leveling agent may be added to improve the smoothness and coatability of the hard coating film formed from the composition or the hard coating layer. The leveling agent may include a silicone-based, fluorine-based, or acrylic polymer-based agent. Examples of commercially available leveling agents include BYK-323, BYK-331, BYK-333, BYK-337, BYK-373, BYK-375, BYK-377 and BYK-378; TEGO Glide 411, TEGO Glide 415, TEGO Glide 420, TEGO Glide 432, TEGO Glide 435, TEGO Glide 440, TEGO Glide 450, TEGO Glide 455, TEGO Rad 2100, TEGO Rad 2200N, TEGO Rad 2250, TEGO Rad 2300, TEGO Rad 2500; FC-4430 and FC-4432 manufactured by 3M Company. For example, the leveling agent may be used in an amount ranging from about 0.1 to 1 part by weight based on the total weight of the hard coating composition, taking into account film uniformity and hardness improvement aspects.

In some embodiments, the hard coating composition may further comprise a UV stabilizer and / or a heat stabilizer. The ultraviolet stabilizer may be added in order to prevent the surface of the coating film formed from the composition from being discolored or broken by exposure to ultraviolet rays by blocking or absorbing ultraviolet rays. UV stabilizers can be classified into absorbents, quenchers and hindered amine light stabilizers (HALS) according to their action mechanisms, and examples thereof include phenyl salicylates (absorbents), benzo Benzophenone, benzotriazole, a nickel derivative (quencher), a radical scavenger, and the like can be used. As the thermal stabilizer, polyphenol-based, phosphite-based and lactone-based thermal stabilizers can be used.

The ultraviolet stabilizer and the heat stabilizer may be appropriately mixed and used at a level that does not hinder the ultraviolet curing process. For example, the additive may be included in the range of about 0.1 to 3 parts by weight, based on 100 parts by weight of the hard coating composition.

<Hard Coating Film>

Embodiments of the present invention provide a hardcoat film formed from the hardcoat composition described above. The hard coating film may be separately manufactured and applied to an optical device or an electronic device, but may alternatively be provided as a hard coating layer formed by being directly applied on a structure of at least a part of the optical device or the electronic device.

For example, the hard coating composition may be applied to a substrate film to form a hard coating film through a curing process such as an ultraviolet curing process.

A transparent polymer film may be used as the base film. For example, the substrate film may be formed of a material selected from the group consisting of triacetylcellulose, acetylcellulose butyrate, ethylene-vinyl acetate copolymer, propionylcellulose, butyrylcellulose, acetylpropionylcellulose, polyester, polystyrene, polyamide, polyetherimide , Polyacrylic, polyimide, polyethersulfone, polysulfone, polyethylene, polypropylene, polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl acetal, polyether ketone, polyetheretherketone, poly And polymer films such as polyether sulfone, polymethyl methacrylate, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and polycarbonate. The base film may contain either of these alone or two or more of them.

In the case of a polymer base film in which the surface is changed to a hydrophilic surface by hydrolysis or saponification, it is difficult to secure adhesion in the case of using a conventional hard coating layer composition, or the mechanical properties of the hard coating layer may be deteriorated have. However, the hard coating composition according to the above-described embodiments of the present invention can secure excellent adhesion even for the base film without deteriorating the mechanical properties.

A surface treatment such as a plasma treatment or a corona treatment may be performed on the base film in order to improve adhesion with the hard coating film.

The hard coating film is formed by coating and hardening the above-mentioned hard coating composition on the base film. As the coating method, a slit coating method, a knife coating method, a spin coating method, a casting method, a micro gravure coating method, Coating methods such as spray coating, bar coating, roll coating, wire bar coating, dip coating, spray coating, screen printing, gravure printing, flexographic printing, A capillary coating method and the like can be used.

The thickness of the hard coating film is not particularly limited, and may be, for example, 5 to 100 占 퐉. The thickness exhibits excellent hardness, abrasion resistance and flexibility within the above range, and it is possible to prevent shrinkage phenomenon or curling phenomenon after curing.

The laminate of the base film and the hard coating film may be utilized as an optical film of an image display device. For example, the optical film can be applied as, for example, a window film or a protective film of an image display apparatus, and can realize excellent visibility and optical characteristics while protecting the image display apparatus against external impact.

In some embodiments, the base film includes a polarizing layer, and the optical film may be provided as a polarizing plate having a hard coating film.

<Image Display Device>

Embodiments of the present invention provide a hard coating film formed of the hard coating composition described above, or an image display device including the above optical film.

For example, the hard coating film or the optical film has excellent hardness, abrasion resistance, flexibility, and can be applied as a window film formed on the outermost surface of an image display device. Alternatively, the hard coating film or the optical film may be inserted into the image display device, for example, in the form of a polarizing plate.

The image display device may be a flexible display device including various image display devices such as a liquid crystal display device, an electroluminescent display device, a plasma display device, and a field emission display device and having flexibility and bending property.

In this case, the hard coating film according to the embodiments of the present invention can be more effectively applied to the window of the flexible display device. The flexibility and durability of the window can be improved by the interaction of the photo-curing compound and the dendrimer compound included in the hard coating composition according to the embodiments of the present invention. Thus, for example, the impact resistance and wear resistance of the flexible display device are improved, and damage such as cracking and peeling can be prevented even when bending or bending.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited by the scope of the appended claims, It will be apparent to those skilled in the art that various changes and modifications can be made in the embodiments within the scope of the claims, and such variations and modifications are within the scope of the appended claims.

Examples and Comparative Examples

Hard coating compositions of Examples and Comparative Examples were prepared with the components and the contents (parts by weight) shown in Table 1 below.

Photocurable
compound
(A) Dendrimer compound
(B) Photoinitiator
(C) Inorganic nano
particle
(D) solvent
(E) Example 1 5 50 0.5 20 24.5 Example 2 8 40 0.5 30 21.5 Example 3 12 50 0.5 10 27.5 Example 4 16 50 0.5 10 23.5 Example 5 25 30 0.5 10 34.5 Comparative Example 1 - 45 0.5 30 24.5 Comparative Example 2 40 - 0.5 25 34.5

Specific compounds used as the respective components are as follows.

(A) Photo-curing compound (see Chemical Formula 1): Product name X-22-164 (Shin-Etsu)

(B) (meth) acrylate terminal dendrimer compound:

    SP-1106 (18-functional 3rd generation dendrimer manufactured by Miwon Specialty Chemicals)

(C) Photoinitiator: Product name CP-4 (manufactured by Miwon Specialty Chemicals)

(D) Inorganic nanoparticles: Product name PGME-AC-2140Y (manufactured by Nissan Chemical Industries, Ltd.)

(E) Solvent: methyletone ketone

Experimental Example

The hard coating compositions of Examples and Comparative Examples were coated on one side of an 80 μm optical polyimide film (L-3430, Mitsubishi Gas Chemical Co., Ltd.) using a bar coater and dried to form a coating film having a thickness of 10 μm, Lt; 0 &gt; C for 3 minutes. Thereafter, using a high-pressure mercury lamp, the hard coating film was prepared by curing at a light amount of 0.5J.

(1) 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 tested five times per pencil hardness using a Mitsubishi product and the maximum pencil hardness at which the scratch was less than or equal to one time was expressed as the pencil hardness of the hard coating film.

(2) 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: 11-20 scratches

C: 21 ~ 30 scratches

D: More than 31 scratches

(3) Adhesion

11 straight lines were drawn on the coated surface of each hard coating film at intervals of 1 mm to form 100 squares, and then peel test was performed three times using a tape (CT-24, Nichii Co., Ltd.). Three sets of 100 squares were tested and the average was recorded.

The adhesion was measured as follows.

i) Adhesion = n / 100

ii) n: the number of rectangles that are not to be peeled out of the whole rectangle, 100: the number of all rectangles

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

(4) curl

The hard coating film was cut into a size of 10 cm × 10 cm and left for 24 hours at 25 ^° C. and 48 RH%, and the height average of four corners from the bottom was measured.

<Evaluation Criteria>

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

○: The average height of four corners is 50 mm or less

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

X: Four corners are completely lifted and the film curls in a cylindrical form

(5) Flexibility at room temperature

The hard coating film was folded in half so that the gap between the faces of the hard coating film was 6 mm and then visually confirmed whether or not cracks occurred in the folded portion when the film was spread again. "Good" when no crack occurred in the folded portion, and "Bad" when the folded portion was cracked.

(6) High temperature and high humidity  Flexibility

The film was folded in half so that the gap between the hard coating film surfaces was 6 mm, and then the film was allowed to stand for 24 hours at 85 ^° C and 85% relative humidity. "Good" when no crack occurred in the folded portion, and "Bad" when the folded portion was cracked.

(7) Crack resistance ( Mandrell )

In order to evaluate the bending property and the cracking property of the hard coating film, a coating film sample cut into a size of 1 cm × 10 cm was placed on a steel bar having a diameter of 2φ to 20φ, the hard coating film was folded by hand, The smallest diameter that does not cause cracking is indicated.

The evaluation results measured as described above are shown in Table 2 below.

Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Pencil hardness 3H 3H 3H 2H 2H H H Abrasion resistance A A A B C C C Adhesiveness 100/100 100/100 100/100 100/100 90/100 80/100 80/100 curl ◎ ◎ ◎ ◎ ○ △ △ Flexibility at room temperature Good Good Good Good Good Bad Bad High temperature and high humidity
Flexibility Good Good Good Good Good Bad Bad Crack resistance
(Mandorele) 2φ 3φ 2φ 3φ 3φ 14φ 16φ

Referring to Table 2, in the case of Examples 1 to 5 including the photo-curing compound and the dendrimer compound according to the embodiments of the present invention, the pencil hardness, Scratch resistance, adhesion, curl characteristic, flexural resistance and crack resistance were obtained.

However, in the case of Example 4 in which the photo-curable compound was more than 15 parts by weight (16 parts by weight), the pencil hardness and scratch resistance were slightly lower than Examples 1 to 3. In the case of Example 5 (25 parts by weight) in which the content of the photo-curable compound was excessively increased, it was confirmed that the scratch resistance, adhesion and curl properties were further deteriorated.

Claims (10)

A photo-curable compound represented by the following formula (1); A dendrimer compound having a plurality of (meth) acrylate end groups; Photoinitiators; And a hard coat composition comprising a solvent:
[Chemical Formula 1]

(Wherein R ₁ to R ₄ are each independently hydrogen or a linear or branched alkyl group having 1 to 20 carbon atoms,
X is a bivalent oxy group or a hetero hydrocarbon group containing oxygen,
n is an integer from 1 to 50, and A and B are each independently a (meth) acrylate group. The hard coating composition according to claim 1, wherein the photocurable compound is contained in 3 to 15 parts by weight of 100 parts by weight of the total composition. The hard coating composition according to claim 1, wherein the dendrimer compound has a structure of two generations or more. 4. The hard coating composition of claim 3, wherein the dendrimer compound has a second or third generation structure. The hard coating composition according to claim 1, wherein the dendrimer compound is contained in an amount of 10 to 60 parts by weight based on 100 parts by weight of the total composition. The hard coating composition of claim 1, further comprising inorganic nanoparticles. 7. The method of claim 6, wherein the inorganic nanoparticles comprise metal oxide nanoparticles, A hardcoat film formed from the hardcoat composition of any one of claims 1 to 7. An image display device comprising the hard coating film of claim 8. A window of a flexible display device comprising the hard coating film of claim 8.