JP7497465B2 - Composition for forming easy-adhesion layer and hard coating film using the same - Google Patents

Description

The present invention relates to a composition for forming an easy-adhesion layer and a hard coating film using the same, and more specifically, to a composition for forming an easy-adhesion layer that can improve the adhesion between a cycloolefin polymer substrate and a hard coating layer, thereby improving the flex resistance of the hard coating film, a hard coating film formed using the same, and an image display device equipped with the hard coating film.

Hard coating films are used for purposes such as surface protection in image display devices such as liquid crystal displays, electroluminescence (EL) displays, plasma displays (PD), and field emission displays (FEDs).

In recent years, flexible display devices that use flexible materials such as plastics instead of existing inflexible glass substrates and can maintain their display performance even when bent like paper are rapidly emerging as the next generation of display devices. Accordingly, research is being conducted into hard coating films that not only have high hardness and excellent scratch resistance, but also do not curl at the film edges during the manufacturing process or use, and have appropriate flexibility to prevent cracks.

On the other hand, cycloolefin polymers (COPs) are expected to be used as substrates for hard coating films due to their excellent transparency, heat resistance, dimensional stability, low moisture absorption, low birefringence, and optical isotropy. However, unlike acrylic and polyester films, cycloolefin polymer films have a small number of polar groups on the film surface, resulting in poor adhesion between the substrate film and the hard coating layer.

Korean Patent Publication No. 10-2017-0107995 discloses a hard coating film manufactured by interposing an easy-adhesion layer containing a mixture of polyolefin resin and styrene-acrylic resin.

However, in the hard coating film, the adhesive layer contains a resin component, which results in a poor degree of crosslinking, making it difficult to achieve sufficient adhesion between the cycloolefin polymer substrate and the hard coating layer, and there are problems with poor bending resistance when applied to a hard coating film.

One object of the present invention is to provide a composition for forming an easy-adhesion layer that can improve the adhesion between a cycloolefin polymer substrate and a hard coating layer.

Another object of the present invention is to provide a hard coating film having improved flex resistance by being formed using the composition for forming an easy-adhesion layer.

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

On the other hand, the present invention provides a composition for forming an easy-adhesion layer, which comprises an aromatic (meth)acrylate, a photoinitiator, and a solvent.

In one embodiment of the present invention, the aromatic (meth)acrylate may be contained in an amount of 50 to 99.9 wt % relative to 100 wt % of the total solid content in the composition for forming an easy-adhesion layer.

The composition for forming an easy-adhesion layer according to one embodiment of the present invention may further contain a translucent resin.

The composition for forming an easy-adhesion layer according to one embodiment of the present invention may be used between a cycloolefin polymer substrate and a hard coating layer.

On the other hand, the present invention
Cycloolefin polymer substrate,
A hard coating film comprising an easy-adhesion layer formed on at least one surface of the cycloolefin polymer substrate, and a hard coating layer formed on the easy-adhesion layer,
The present invention provides a hard coating film, in which the easy-adhesion layer is formed using the easy-adhesion layer-forming composition.

The hard coating film according to one embodiment of the present invention may have a total light transmittance of 90% or more, and may be such that the hard coating film does not break or the hard coating layer does not peel off even after the hard coating film is folded repeatedly 200,000 times with a curvature radius of 1 mm so that the hard coating layer surface faces inward.

In one embodiment of the present invention, the hard coating layer may be formed using a hard coating composition including a translucent resin, a photoinitiator, and a solvent.

In one embodiment of the present invention, the translucent resin may include one or more selected from the group consisting of photocurable (meth)acrylate oligomers and monomers having a (meth)acryloyl group.

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

In another aspect, the present invention provides a window for a flexible display device having the hard coating film.

On the other hand, the present invention provides a polarizing plate equipped with the hard coating film.

On the other hand, the present invention provides a touch sensor equipped with the hard coating film.

The composition for forming an easy-adhesion layer according to the present invention contains an aromatic (meth)acrylate, which can improve the adhesion between the cycloolefin polymer substrate and the hard coating layer, thereby improving the flex resistance of the hard coating film.

The present invention will be explained in more detail below.

One embodiment of the present invention relates to a composition for forming an easy-adhesion layer that contains an aromatic (meth)acrylate, a photoinitiator, and a solvent.

In one embodiment of the present invention, the aromatic (meth)acrylate is a component that provides adhesion between the cycloolefin polymer substrate and the hard coating layer, and is a compound that contains an aromatic ring and a (meth)acrylate functional group in the molecule.

The number of (meth)acrylate functional groups in the aromatic (meth)acrylate is not particularly limited, but is preferably trifunctional or more. In the case of a monofunctional or difunctional aromatic (meth)acrylate, it is preferable to use it in combination with a trifunctional or more aromatic (meth)acrylate rather than using it alone.

Specific examples of monofunctional aromatic (meth)acrylates include phenoxybenzyl (meth)acrylate, o-phenylphenol ethylene oxide (meth)acrylate, benzyl (meth)acrylate, biphenyl methyl (meth)acrylate, phenyl ethylene oxide (meth)acrylate, nonylphenol ethylene oxide (meth)acrylate, and phenoxyethyl (meth)acrylate. Examples of difunctional aromatic acrylates include bisphenol A ethylene oxide di(meth)acrylate, bisphenol F ethylene oxide di(meth)acrylate, and Miramer MU3603. Examples of trifunctional aromatic (meth)acrylates include Miramer PU370. Examples of hexafunctional aromatic (meth)acrylates include Miramer PU640.

The aromatic (meth)acrylate may be contained in an amount of 50 to 99.9% by weight based on 100% by weight of the total solid content in the composition for forming an easy-adhesion layer. If the content of the aromatic (meth)acrylate is less than 50% by weight, sufficient bonds with the cycloolefin polymer substrate cannot be formed, which may result in poor adhesion.

In one embodiment of the present invention, the photoinitiator may be any photoinitiator that can form radicals by irradiation with light and is used in the relevant technical field, without any particular limitations. For example, hydroxyketones, aminoketones, hydrogen abstraction photoinitiators, etc. may be used.

Specific examples of the photoinitiator include 2-methyl-1-[4-(methylthio)phenyl]2-morpholinepropanone-1, diphenyl ketone, benzyl dimethyl ketal, 2-hydroxy-2-methyl-1-phenyl-1-one, 2,2-dimethoxy-2-phenyl-acetophenone, anthraquinone, fluorene, triphenylamine, carbazole, 3-methylacetophenone, 4-chloroacetophenone, 4,4-dimethoxyacetophenone, 4,4-diaminobenzophenone, 1-hydroxycyclohexylphenyl ketone, benzophenone, and diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide. The photoinitiators exemplified above may be used alone or in combination of two or more.

The content of the photoinitiator is not particularly limited, and may be, for example, 0.1 to 10 wt %, preferably 1 to 5 wt %, based on 100 wt % of the solid content in the composition for forming an easy-adhesion layer. If the content of the photoinitiator is less than 0.1 wt %, the curing speed of the composition is slow and uncured portions occur, resulting in poor mechanical properties of the coating layer. If the content of the photoinitiator is more than 10 wt %, cracks may occur in the coating film due to overcuring.

The solvent may be any solvent used in the art without any particular restrictions. Specifically, alcohols (methanol, ethanol, isopropanol, butanol, methyl cellosolve, ethyl cellosolve, etc.), ketones (methyl ethyl ketone, methyl butyl ketone, methyl isobutyl ketone, diethyl ketone, dipropyl ketone, cyclohexanone, etc.), acetates (ethyl acetate, propyl acetate, n-butyl acetate, tert-butyl acetate, methyl cellosolve acetate, ethyl cellosolve acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monopropyl ether acetate, methoxybutyl acetate, methoxypentyl acetate, etc.), hexanes (hexane, heptane, octane, etc.), benzenes (benzene, toluene, xylene, etc.), and ethers (diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dipropyl ether, diethylene glycol dibutyl ether, propylene glycol monomethyl ether, etc.) may be used. The above-listed solvents may be used alone or in combination of two or more.

The solvent may be included in an amount of 10 to 95% by weight based on 100% by weight of the total composition for forming the easy-adhesion layer. If the content of the solvent is less than 10% by weight, the viscosity is high, which not only makes the workability poor, but also makes it difficult to sufficiently promote swelling of the base film. If the content of the solvent is more than 95% by weight, the drying process takes a long time, which is disadvantageous in terms of economy.

The composition for forming an easy-adhesion layer according to one embodiment of the present invention may further contain a translucent resin.

The translucent resin is a photocurable resin, and the photocurable resin may contain a photocurable (meth)acrylate oligomer and/or monomer.

As the photocurable (meth)acrylate oligomer, epoxy (meth)acrylate, urethane (meth)acrylate, etc. are usually used, and urethane (meth)acrylate is preferred. Urethane (meth)acrylate may be produced by reacting a (meth)acrylate having a hydroxy group in the molecule with a compound having an isocyanate group in the presence of a catalyst. Specific examples of the (meth)acrylate having a hydroxy group in the molecule include 2-hydroxyethyl (meth)acrylate, 2-hydroxyisopropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, caprolactone ring-opened hydroxyacrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, etc. Specific examples of the compound having an isocyanate group include 1,4-diisocyanatobutane, 1,6-diisocyanatohexane, 1,8-diisocyanatooctane, 1,12-diisocyanatododecane, 1,5-diisocyanato-2-methylpentane, trimethyl-1,6-diisocyanatohexane, 1,3-bis(isocyanatomethyl)cyclohexane, trans-1,4-cyclohexene diisocyanate, 4,4'-methylenebis(cyclohexylisocyanate), isophorone diisocyanate, These include trifunctional isocyanates derived from isocyanate, toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, xylene-1,4-diisocyanate, tetramethylxylene-1,3-diisocyanate, 1-chloromethyl-2,4-diisocyanate, 4,4'-methylenebis(2,6-dimethylphenylisocyanate), 4,4'-oxybis(phenylisocyanate), hexamethylene diisocyanate, and trimethanepropanol adduct toluene diisocyanate.

The monomer may be any commonly used monomer without any particular limitations. Monomers having an unsaturated group such as a (meth)acryloyl group, a vinyl group, a styryl group, or an allyl group as a photocurable functional group in the molecule are preferred, and among these, monomers having a (meth)acryloyl group are preferred.

Specific examples of the monomer having a (meth)acryloyl group include neopentyl glycol acrylate, 1,6-hexanediol di(meth)acrylate, propylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethylolethane tri(meth)acrylate, pentaglycerol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, dipentaerythritol It may be one or more selected from the group consisting of penta(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tripentaerythritol tri(meth)acrylate, tripentaerythritol hexa(meth)acrylate, bis(2-hydroxyethyl)isocyanurate di(meth)acrylate, hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, hydroxybutyl(meth)acrylate, isooctyl(meth)acrylate, isodecyl(meth)acrylate, stearyl(meth)acrylate, tetrahydrofurfuryl(meth)acrylate, phenoxyethyl(meth)acrylate, and isoborneol(meth)acrylate.

The light-curable (meth)acrylate oligomers and monomers that are the light-transmitting resins exemplified above may be used alone or in combination of two or more.

For example, the translucent resin may be a compound that corresponds to an aliphatic (meth)acrylate among the photocurable (meth)acrylate oligomers and/or monomers described above.

The translucent resin is not particularly limited, but may be contained in an amount of 49.9% by weight or less relative to 100% by weight of the total solid content in the composition for forming an easy-adhesion layer. If the translucent resin is contained in an amount exceeding 49.9% by weight, the content of aromatic (meth)acrylate may be relatively insufficient to form a sufficient bond with the cycloolefin polymer substrate, resulting in poor adhesion.

The composition for forming an easy-adhesion layer according to one embodiment of the present invention may further contain a leveling agent to impart smoothness and coatability to the coating film during coating.

The leveling agent may be a commercially available silicone-based leveling agent, a fluorine-based leveling agent, an acrylic polymer-based leveling agent, or the like, such as BYK-306, BYK-307, BYK-310, BYK-313, BYK-323, BYK-331, BYK-333, BYK-337, BYK-371, BYK-373, BYK-375, BYK-377, BYK-378, BYK-3440, BYK-3570, BYK-UV3500, BYK-UV3530, BYK-UV3570 manufactured by BYK Chemie, and TEGO Glide 410, TEGO Glide 411, TEGO Glide manufactured by Degussa. 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, FC-4432 manufactured by 3M, etc. may be used. The leveling agent may be contained in the range of 0.1 to 3 wt % relative to 100 wt % of the total of the composition for forming the easy-adhesion layer.

The composition for forming an easy-adhesion layer according to one embodiment of the present invention may be used between a cycloolefin polymer substrate and a hard coating layer. The composition for forming an easy-adhesion layer according to one embodiment of the present invention contains an aromatic (meth)acrylate, so that the adhesive strength between the CH group and the aromatic group on the surface of the cycloolefin polymer substrate can ensure adhesion to the substrate, and when the hard coating layer is formed, the unreacted acrylate group participates in the UV curing reaction to ensure adhesive strength with the hard coating layer. Accordingly, the composition for forming an easy-adhesion layer according to one embodiment of the present invention can be applied between the cycloolefin polymer substrate and the hard coating layer to provide a hard coating film with excellent flex resistance.

Therefore, one embodiment of the present invention relates to a hard coating film formed using the above-mentioned composition for forming an easy-adhesion layer.

The hard coating film according to one embodiment of the present invention is
Cycloolefin polymer substrate,
A hard coating film comprising an easy-adhesion layer formed on at least one surface of the cycloolefin polymer substrate, and a hard coating layer formed on the easy-adhesion layer,
The easy-adhesion layer is formed using the above-mentioned easy-adhesion layer-forming composition.

The hard coating film according to one embodiment of the present invention has excellent transmittance characteristics and bending resistance. Specifically, the hard coating film according to one embodiment of the present invention may have a total light transmittance of 90% or more, and may be such that the hard coating film does not break or the hard coating layer does not peel off even after the hard coating film is repeatedly folded 200,000 times with a curvature radius of 1 mm with the hard coating layer surface facing inward.

The total light transmittance (Tt, %) is calculated by measuring the intensity of light incident on the hard coating film (T ₀ ) and the intensity of the total light transmitted through the hard coating film (T ₁ ) according to the following Equation 1.
[Mathematical Formula 1]
Total light transmittance (Tt, %)=(T ₁ /T ₀ )×100
The total light transmittance may be measured, for example, using a haze meter (manufactured by Murakami Color Research Institute) according to the method described in the Experimental Examples below.

In one embodiment of the present invention, the cycloolefin polymer substrate serves as a base substrate for the hard coating film and contains a cycloolefin polymer (COP) and has excellent transparency.

The COP is a general term referring to resins produced by polymerization of cyclic olefins as monomers, and specific examples thereof include ring-opening (co)polymers of cyclic olefins; addition polymers of cyclic olefins; copolymers (usually random copolymers) of cyclic olefins and α-olefins such as ethylene or propylene; graft modified products modified with unsaturated carboxylic acids or derivatives thereof; and hydrogenated products thereof. Specific examples of cyclic olefins include norbornene-based monomers.

Specifically, the COP may be a polymer obtained by selectively hydrogenating one or more of the monomers represented by the following chemical formulas 1 to 3 through ring-opening metathesis polymerization.

The process for producing a COP from the ring-opening metathesis polymerization reaction of one or more of the monomers represented by the chemical formulas 1 to 3 can be easily carried out according to a conventional method.

For example, the polymerization step may be carried out using palladium(II) acetylacetonate [Pd(acac) ₂ ] and tricyclohexylphosphine as the polymerization catalyst and dimethylanilinium tetrakis(pentafluorophenyl)borate as the cocatalyst.

In one embodiment of the present invention, the COP may be prepared by mixing a ring-opening polymerizable cyclic olefin other than a norbornene-based monomer without compromising the object of the present invention. Specific examples of such cyclic olefins include compounds having one reactive double bond, such as cyclopentene, cyclooctene, and 5,6-dihydrodicyclopentadiene.

The COP may be further hydrogenated after the ring-opening metathesis polymerization reaction. The hydrogenation may be carried out by reacting with hydrogen gas in the presence of a hydrogenation catalyst according to a method known in the art. The hydrogenation rate is preferably 90% or more, more preferably 95% or more, and even more preferably 99% or more. A hydrogenation rate within the above range can provide excellent heat degradation resistance, light degradation resistance, etc.

Regarding the COP, various products are commercially available. Specific examples of the COP include products manufactured by Zeon Corporation under the trade names "ZF-16", "ZEONEX" and "ZEONOR", products manufactured by JSR Corporation under the trade name "Arton", products manufactured by TICONA Corporation under the trade name "TOPAS", and products manufactured by Mitsui Chemicals, Inc. under the trade name "APEL".

Any suitable molding method may be used to form a substrate film from the COP. Specific examples include compression molding, transfer molding, injection molding, extrusion molding, blow molding, powder molding, FRP molding, and casting. Extrusion molding and casting are preferred because the resulting film can have improved smoothness and good optical uniformity. Molding conditions may be set appropriately depending on the composition or type of resin used, the desired properties for the optical film, and the like.

The thickness of the cycloolefin polymer substrate is not particularly limited, but may be 10 to 1000 μm, specifically 20 to 150 μm. If the thickness of the transparent substrate is less than 10 μm, the strength of the film will decrease and the processability will be poor, and if it exceeds 1000 μm, problems will arise such as reduced transparency and an increased weight of the hard coating film.

In one embodiment of the present invention, the above-mentioned composition for forming an easy-adhesion layer is applied to at least one surface of the cycloolefin polymer substrate and cured to form an easy-adhesion layer.

The composition for forming an easy-adhesion layer according to one embodiment of the present invention may be applied to a substrate (coating process) using a known method such as a die coater, air knife, reverse roll, spray, blade, casting, gravure, microgravure, or spin coating.

After the composition for forming an easy-adhesion layer is applied to the substrate, the composition is dried by evaporating the solvent, and then cured by irradiating UV light. The irradiation amount of the UV light may be specifically about 10 to 500 mJ/ ^cm2 , more specifically 50 to 400 mJ/ ^cm2 .

In this case, the thickness of the easy-adhesion layer formed may be specifically 0.1 to 5 μm, more specifically 0.3 to 3 μm. When the thickness of the easy-adhesion layer is within the above range, excellent adhesion and bending resistance can be obtained.

In one embodiment of the present invention, the hard coating layer may be formed using a hard coating composition including a light-transmitting resin, a photoinitiator, and a solvent.

The light-transmitting resin is a photocurable resin, and the light-transmitting resin may contain a light-curable (meth)acrylate oligomer and/or monomer. In terms of adhesion to the easy-adhesion layer, it is preferable that the light-transmitting resin contains one or more selected from the group consisting of a light-curable (meth)acrylate oligomer and a monomer having a (meth)acryloyl group.

The specific types of the photocurable (meth)acrylate oligomer and the monomer having a (meth)acryloyl group may be the same as those used in the composition for forming the easy-adhesion layer described above.

The monomer having a (meth)acryloyl group may be a dendrimer compound having a (meth)acrylate terminal group.

The dendrimer compound having a (meth)acrylate end group may be used for UV curing by replacing the end of the branched structure with a (meth)acrylate group, and has a structural characteristic that the center is completely aliphatic and consists of a tertiary ester bond. Therefore, compared to general multifunctional acrylate monomers, the dendrimer compound having a (meth)acrylate end group has a structural characteristic that it has a large number of functional groups relative to the molecular weight as the generation increases, and the distribution of functional groups at the end allows the core portion to contribute to improving the bending properties during curing. As a result, a hard coating film with high hardness and improved curl and flexibility can be obtained.

The dendrimer compound having the (meth)acrylate end group may be commercially available or may be produced according to a method known in the art. For example, a specific polyhydric alcohol is used as the central skeleton and condensed with dimethylolpropionic acid to form a first generation dendrimer structure, and then the dimethylolpropionic acid is repeatedly condensed as a branched structure to grow into a second generation or higher structure. The end group is then condensed with acrylic acid to obtain a highly branched dendrimer compound whose ends are substituted with a large number of (meth)acrylate groups.

The amount of the light-transmitting resin is not particularly limited, but may be 1 to 80% by weight relative to 100% by weight of the total hard coating composition. If it is less than 1% by weight, it is difficult to achieve a sufficient improvement in hardness, and if it exceeds 80% by weight, there is a problem of severe curling.

The photoinitiator may be the same as that used in the composition for forming the easy-adhesion layer described above.

The photoinitiator may be included in an amount of 0.1 to 10 wt %, preferably 1 to 5 wt %, based on 100 wt % of the total hard coating composition. If the content of the photoinitiator is less than 0.1 wt %, the curing speed of the composition is slow and uncured, resulting in poor mechanical properties, while if it exceeds 10 wt %, cracks may occur in the coating film due to overcuring.

The solvent may be the same as that used in the composition for forming the easy-adhesion layer described above.

The solvent may include a fluorine-based solvent. The fluorine-based solvent increases the solubility of the fluorine-based UV-curable functional group-containing compound described below, thereby maintaining the wettability and coating state of the hard coating film produced excellently, and also plays a role in forming a high-concentration fluorine component layer on the surface of the hard coating layer produced by orienting the fluorine-based UV-curable functional groups on the surface of the hard coating layer during the coating and drying process.

The fluorine-based solvent may be perfluorohexylethyl alcohol, perfluoroether, perfluorohexane, etc., and examples of commercially available products include HFE-7100, HFE-7300, HFE-7500, FC-3283, FC-40, FC-770 manufactured by 3M, and C6FOH-BF manufactured by Nikka Corporation, but are not limited to these.

The solvent may be included in an amount of 5 to 90% by weight, preferably 7 to 85% by weight, based on 100% by weight of the total hard coating composition. If it is less than 5% by weight, the viscosity is high and workability is poor, and if it exceeds 90% by weight, it is difficult to control the coating thickness, and uneven drying occurs, resulting in poor appearance.

In one embodiment of the present invention, the hard coating composition may further include a fluorine-based UV-curable functional group-containing compound.

The fluorine-based UV-curable functional group-containing compound is a component that provides antifouling and abrasion resistance, and is not particularly limited as long as it contains fluorine and also has a UV-curable functional group.

The fluorine-based UV-curable functional group-containing compound may be one or more selected from the group consisting of (meth)acrylates containing perfluoroalkyl groups, (meth)acrylates containing perfluoropolyether groups, (meth)acrylates containing perfluoroaliphatic cyclic groups, and (meth)acrylates containing perfluoroaromatic groups. In this case, it is preferable because it has the advantage of exhibiting excellent antifouling performance and forming a chemical bond with the hard coating layer, thereby maintaining the antifouling performance for a long period of time even after repeated use.

The fluorine-based UV-curable functional group-containing compound may be included in an amount of 0.01 to 30% by weight, preferably 0.01 to 20% by weight, and more preferably 0.01 to 10% by weight, based on 100% by weight of the total solid content in the hard coating composition. When the content of the fluorine-based UV-curable functional group-containing compound is within the above range, it is preferable because excellent abrasion resistance and antifouling effects can be imparted. If the content of the UV-curable functional group-containing compound is less than the above range, it may be difficult to achieve the desired abrasion resistance or antifouling properties, and if the content exceeds the above range, the hardness or scratch resistance of the film may be slightly reduced.

In addition to the components described above, the hard coating composition may further contain components commonly used in the art, such as leveling agents, UV stabilizers, heat stabilizers, antioxidants, surfactants, lubricants, and antifouling agents.

The hard coating film according to one embodiment of the present invention can be produced by applying the hard coating composition onto an easy-adhesion layer formed on at least one surface of a cycloolefin polymer substrate and curing the composition to form a hard coating layer.

The hard coating composition may be applied to the easy-adhesion layer (coating process) using any of the known methods, such as die coater, air knife, reverse roll, spray, blade, casting, gravure, microgravure, and spin coating.

After the hard coating composition is applied to the easy-adhesion layer, it is dried by evaporating volatiles at a temperature of 30 to 150° C. for 10 seconds to 1 hour, more specifically, for 30 seconds to 30 minutes, and then cured by irradiating UV light. The irradiation dose of the UV light may be about 0.01 to 10 J/cm ² , more specifically, 0.1 to 2 J/cm ² .

In this case, the thickness of the hard coating layer formed may be specifically 2 to 30 μm, more specifically 3 to 20 μm. When the thickness of the hard coating layer is within the above range, excellent hardness and flex resistance can be obtained.

One embodiment of the present invention relates to an image display device having the above-mentioned hard coating film. As an example, the hard coating film of the present invention may be used as a window of an image display device, particularly a flexible display device or a foldable display device. In addition, the hard coating film of the present invention may be attached to a polarizing plate, a touch sensor, etc.

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

Hereinafter, the present invention will be described in more detail with reference to examples, comparative examples, and experimental examples. Note that these examples, comparative examples, and experimental examples are merely intended to explain the present invention, and it will be obvious to those skilled in the art that the scope of the present invention is not limited to these examples, comparative examples, and experimental examples.

Preparation Example 1: Preparation of a composition for forming an easy-adhesion layer 19.2 parts by weight of a hexafunctional aromatic acrylate (Miramer PU640, manufactured by Miwon), 80 parts by weight of methyl ethyl ketone, 0.5 parts by weight of 1-hydroxycyclohexyl phenyl ketone, and 0.3 parts by weight of a leveling agent (BYK UV-3530, manufactured by BYK) were mixed in a stirrer and filtered using a PP filter to prepare a composition for forming an easy-adhesion layer.

Preparation Example 2: Preparation of a composition for forming an easy-adhesion layer 14.2 parts by weight of a hexafunctional aromatic acrylate (Miramer PU640, manufactured by Miwon), 5 parts by weight of a hexafunctional aliphatic acrylate (Miramer PU620, manufactured by Miwon), 80 parts by weight of methyl ethyl ketone, 0.5 parts by weight of 1-hydroxycyclohexyl phenyl ketone, and 0.3 parts by weight of a leveling agent (BYK UV-3530, manufactured by BYK) were mixed in a stirrer and filtered using a PP filter to prepare a composition for forming an easy-adhesion layer.

Preparation Example 3: Preparation of a composition for forming an easy-adhesion layer 5 parts by weight of a hexafunctional aromatic acrylate (Miramer PU640, manufactured by Miwon), 14.2 parts by weight of a hexafunctional aliphatic acrylate (Miramer PU620, manufactured by Miwon), 80 parts by weight of methyl ethyl ketone, 0.5 parts by weight of 1-hydroxycyclohexyl phenyl ketone, and 0.3 parts by weight of a leveling agent (BYK UV-3530, manufactured by BYK) were mixed in a stirrer and filtered using a PP filter to prepare a composition for forming an easy-adhesion layer.

Preparation Example 4: Preparation of a composition for forming an easy-adhesion layer 19.2 parts by weight of a hexafunctional aliphatic acrylate (Miwon, Miramer PU620), 80 parts by weight of methyl ethyl ketone, 0.5 parts by weight of 1-hydroxycyclohexyl phenyl ketone, and 0.3 parts by weight of a leveling agent (BYK, BYK UV-3530) were mixed in a stirrer and filtered using a PP filter to prepare a composition for forming an easy-adhesion layer.

Preparation Example 5: Preparation of hard coating composition 23 parts by weight of a hexafunctional urethane acrylate (U-6LPA, manufactured by Shin-Nakamura Chemical Co., Ltd.), 23 parts by weight of a tetrafunctional acrylate (VISCOAT #1000, manufactured by Osaka Organic Chemical Industry Co., Ltd.), 5 parts by weight of a fluorine-based solvent (C6FOH-BF, manufactured by Nikka Chemical Co., Ltd.), 45 parts by weight of methyl ethyl ketone, 3.5 parts by weight of 1-hydroxycyclohexyl phenyl ketone, and 0.5 parts by weight of a fluorine-based UV-curable functional group-containing compound (KY-1203, manufactured by Shin-Etsu Chemical Co., Ltd.) were mixed in a stirrer and filtered using a PP filter to prepare a hard coating composition.

Example 1: Preparation of easy-adhesion film A cycloolefin film (ZEON Corporation's COP, ZF-16, 40 μm) was corona-treated to adjust the surface water contact angle to a level of 65 degrees, and the composition for forming an easy-adhesion layer of Preparation Example 1 was coated on the film so that the thickness after curing was 0.5 μm. After drying the solvent, an easy-adhesion film was prepared by irradiating the film with an integrated UV dose of 300 mJ/ ^cm2 under a nitrogen atmosphere.

Example 2: Preparation of an easily adhesive film An easily adhesive film was prepared in the same manner as in Example 1, except that the composition for forming an easily adhesive layer in Preparation Example 2 was used instead of the composition for forming an easily adhesive layer in Preparation Example 1.

Example 3: Preparation of hard coating film The hard coating composition of Preparation Example 5 was coated on the adhesive layer of the adhesive film prepared in Example 1 so that the thickness after curing would be 5 μm. After drying the solvent, the hard coating film was irradiated with an integrated UV dose of 600 mJ/ ^cm2 under a nitrogen atmosphere to prepare a hard coating film.

Example 4: Preparation of hard coating film A hard coating film was prepared in the same manner as in Example 3, except that the adhesive film prepared in Example 2 was used instead of the adhesive film prepared in Example 1.

Comparative Example 1: Preparation of an easily adhesive film An easily adhesive film was prepared in the same manner as in Example 1, except that the composition for forming an easily adhesive layer of Preparation Example 3 was used instead of the composition for forming an easily adhesive layer of Preparation Example 1.

Comparative Example 2: Preparation of an easily adhesive film An easily adhesive film was prepared in the same manner as in Example 1, except that the composition for forming an easily adhesive layer of Preparation Example 4 was used instead of the composition for forming an easily adhesive layer of Preparation Example 1.

Comparative Example 3: Preparation of hard coating film A hard coating film was prepared in the same manner as in Example 3, except that the adhesive film prepared in Comparative Example 1 was used instead of the adhesive film prepared in Example 1.

Comparative Example 4: Preparation of hard coating film A hard coating film was prepared in the same manner as in Example 3, except that the adhesive film prepared in Comparative Example 2 was used instead of the adhesive film prepared in Example 1.

Experimental Example 1:
The physical properties of the films prepared in the above examples and comparative examples were measured by the methods described below, and the results are shown in Table 1 below.

(1) Adhesion The substrate film was attached to glass using a transparent adhesive with the coated side facing outward, and then the coating side was cut with a cutter into a grid pattern of 100 pieces spaced 1 mm apart horizontally and vertically. Nichiban tape was then applied, and three adhesion tests were performed.

The evaluation results were expressed as "number of squares that were OK after the adhesion test/100."

(2) Total Light Transmittance (Tt) and Haze The total light transmittance (%) and haze (%) of the coating film were measured using a haze meter HM-150 manufactured by Murakami Color Research Laboratory.

(3) Water Contact Angle The water contact angle was measured using a contact angle measuring instrument DSA100 manufactured by KRUSS Co., Ltd. The droplet volume was 3 μl at room temperature.

(4) Abrasion resistance: The abrasion resistance was measured using an abrasion resistance measuring device manufactured by Daesung Precision Co., Ltd. The coating surface was rubbed 3,000 times with an eraser for abrasion resistance testing and a weight of 500 g, and then the contact angle was measured. At this time, a contact angle of 100° or more was selected as the evaluation standard for pass-level abrasion resistance.

<Evaluation criteria>
○: Contact angle is 100° or more ×: Contact angle is less than 100° (5) Chemical resistance Measurement was performed using an abrasion resistance measuring device manufactured by DAESUNG PRECISION. After dropping 99.9% ethanol onto the coating surface, the area where the ethanol was dropped was rubbed 3000 times with an eraser for abrasion resistance test and a weight of 500g, and then the contact angle was measured. The evaluation was performed while continuously dropping ethanol so that the ethanol would not volatilize during the evaluation. After the evaluation was completed, the ethanol was removed and the water contact angle was measured. At this time, a water contact angle of 95° or more was selected as the evaluation standard for passing chemical resistance.

<Evaluation criteria>
A: Contact angle is 95° or more. B: Contact angle is less than 95°. (6) Scratch Resistance: The substrate film was attached to glass using a transparent adhesive so that the coated surface was on the front side, and then rubbed 10 times back and forth with steel wool (#0000) at a load of 500 g/ ^cm2 . The measurement area was then illuminated with and reflected light from a three-wavelength lamp to observe scratches. The scratch resistance was evaluated according to the following evaluation criteria.

<Evaluation criteria>
A: No scratches or 10 or less scratches are visible. B: More than 10 scratches are visible. (7) Bending resistance A test was conducted in which the film was repeatedly folded 200,000 times with a curvature radius of 1 mm so that the hard coating layer surface was on the inside, and the film was observed for breakage and peeling of the hard coating layer. The bending resistance was evaluated according to the following evaluation criteria.

<Evaluation criteria>
○: No break in the film or peeling of the hard coating layer occurred. ×: Break in the film or peeling of the hard coating layer occurred.

As seen in Table 1, the adhesive films of Examples 1 and 2 manufactured using the adhesive layer forming compositions of Preparation Examples 1 and 2 containing the aromatic (meth)acrylate according to the present invention have excellent adhesion of the coating surface, and also have good total light transmittance (Tt) and haze. In addition, it was confirmed that the hard coating films of Examples 3 and 4, in which a hard coating layer is formed on the adhesive films of Examples 1 and 2, have excellent adhesion as well as water contact angle, abrasion resistance, chemical resistance, scratch resistance, and bending resistance.

In contrast, the adhesive films of Comparative Examples 1 and 2, which were produced using the adhesive layer-forming compositions of Preparation Examples 3 and 4 that did not contain aromatic (meth)acrylate, were found to have poor adhesion of the coating surface. Furthermore, it was confirmed that the hard coating films of Comparative Examples 3 and 4, in which a hard coating layer was formed on the adhesive films of Comparative Examples 1 and 2, were inferior not only in adhesion of the coating surface but also in bending resistance.

Although specific aspects of the present invention have been described in detail above, it will be clear to anyone with ordinary knowledge in the technical field to which the present invention pertains that these specific descriptions are merely preferred examples and do not limit the scope of the present invention. Anyone with ordinary knowledge in the technical field to which the present invention pertains will be able to make various applications and modifications within the scope of the present invention based on the above content.

Therefore, the true scope of the present invention is defined by the claims and their equivalents.

Claims (11)

A composition for forming an easy-adhesion layer , comprising an aromatic (meth)acrylate, a photoinitiator, and a solvent,
The composition for forming an easy-adhesion layer is used between a cycloolefin polymer substrate and a hard coating layer,
The adhesive layer formed by the adhesive layer-forming composition has one surface in direct contact with the cycloolefin polymer substrate and the other surface in direct contact with the hard coating layer. The composition for forming an easy-adhesion layer according to claim 1, wherein the aromatic (meth)acrylate is contained in an amount of 50 to 99.9% by weight relative to 100% by weight of the total solid content in the composition for forming an easy-adhesion layer. The composition for forming an easy-adhesion layer according to claim 1, further comprising a light-transmitting resin. Cycloolefin polymer substrate,
A hard coating film comprising an easy-adhesion layer formed on at least one surface of the cycloolefin polymer substrate, and a hard coating layer formed on the easy-adhesion layer,
A hard coating film, wherein the easy-adhesion layer is formed using the composition for forming an easy-adhesion layer according to any one of claims 1 to 3 . The total light transmittance is 90% or more,
5. The hard-coating film according to claim 4, wherein the hard-coating film does not break or the hard-coating layer does not peel off even after the hard-coating film is repeatedly folded 200,000 times with a curvature radius of 1 mm so that the hard-coating layer surface faces inward. The hard coating film according to claim 4 , wherein the hard coating layer is formed using a hard coating composition comprising a light-transmitting resin, a photoinitiator, and a solvent. The hard coating film according to claim 6 , wherein the light-transmitting resin comprises at least one selected from the group consisting of a photocurable (meth)acrylate oligomer and a monomer having a (meth)acryloyl group. An image display device comprising the hard coating film according to claim 4 . A window of a flexible display device provided with the hard coating film according to claim 4 . A polarizing plate provided with the hard coating film according to claim 4 . A touch sensor comprising the hard coating film according to claim 4 .