Composition for forming easy-adhesion layer and hard coat film using the same

Abstract

This invention provides a composition for forming an easy-to-adhesive layer comprising an aromatic (meth)acrylate, a photoinitiator, and a solvent, a hard coating film formed therefrom, and an image display device having the aforementioned hard coating film. The easy-to-adhesive layer forming composition of this invention comprises an aromatic (meth)acrylate, thereby improving the adhesion between the cyclic olefin polymer substrate and the hard coating layer, and consequently improving the flexural strength of the hard coating film.

Description

Technical Field

[0001] The present invention relates to a composition for forming an easy-to-adhesive layer and a hard coating film using the same, and more specifically, to a composition for forming an easy-to-adhesive layer that can improve the adhesion between a cyclic olefin polymer substrate and a hard coating layer, thereby improving the flexural strength of the hard coating film, a hard coating film formed therefrom, and an image display device having the aforementioned hard coating film. Background Technology

[0002] Hard coatings are used in image display devices such as liquid crystal displays, electroluminescent (EL) liquid crystal displays, plasma displays (PDs), and field emission displays (FEDs) for surface protection and other purposes.

[0003] In recent years, flexible display devices, which use flexible materials such as plastics to replace traditional inflexible glass substrates and maintain display performance even when bent like paper, have rapidly become the next generation of display devices. Research is underway on hard coatings that are not only hard and scratch-resistant, but also do not curl at the film edges during manufacturing or use, and have appropriate flexibility without cracking.

[0004] On the other hand, cycloolefin polymers (COPs) exhibit excellent transparency, heat resistance, dimensional stability, low moisture absorption, low birefringence, and optical isotropy, making them promising candidates for use as substrates for hard coatings. However, unlike acrylic or polyester films, cycloolefin polymer films have fewer polar groups on their surface, resulting in poor adhesion between the substrate film and the hard coating.

[0005] For this purpose, Korean Patent Publication No. 10-2017-0107995 disclosed a hard coating film manufactured by means of an easily adhesive layer containing a mixture of polyolefin resin and styrene acrylic resin.

[0006] However, the above-mentioned hard coating has the following problems: because the easy-to-adhesive layer contains resin components and has a low degree of cross-linking, it is difficult to achieve sufficient adhesion between the cyclic olefin polymer substrate and the hard coating layer, resulting in decreased bending resistance when applied to hard coating. Summary of the Invention

[0007] Technical issues

[0008] One object of the present invention is to provide a composition for forming an easy-to-adhesive layer that can improve the adhesion between a cyclic olefin polymer substrate and a hard coating.

[0009] Another object of the present invention is to provide a hard coating film with improved flexural strength formed by using the above-described easy-to-adhesive layer forming composition.

[0010] Another object of the present invention is to provide an image display device having the above-described hard coating.

[0011] Methods for solving problems

[0012] On one hand, the present invention provides a composition for forming an easy-to-adhesive layer comprising an aromatic (meth)acrylate, a photoinitiator, and a solvent.

[0013] In one embodiment of the present invention, the content of the above-mentioned aromatic (meth)acrylate may be 50 to 99.9% by weight relative to 100% by weight of the total solid components in the composition for forming an easy-to-adhere layer.

[0014] The composition for forming an easy-to-adhesive layer according to one embodiment of the present invention may further comprise a light-transmitting resin.

[0015] The easy-to-adhesive layer formation composition of one embodiment of the present invention can be used between a cyclic olefin polymer substrate and a hard coating.

[0016] On the other hand, the present invention provides a hard coating film comprising:

[0017] Cycloolefin polymer substrate;

[0018] An easy-to-adhesive layer formed on at least one side of the aforementioned cyclic olefin polymer substrate; and

[0019] A hard coating layer formed on the aforementioned easily bonded layer,

[0020] The aforementioned easy-to-adhesive layer is formed using the aforementioned easy-to-adhesive layer forming composition.

[0021] The hard coating film of one embodiment of the present invention has a total light transmittance of 90% or more, and after the hard coating film is repeatedly folded and unfolded 200,000 times with the hard coating surface facing inward and the curvature radius of 1 mm, the hard coating film will not break or peel off.

[0022] In one embodiment of the present invention, the above-mentioned hard coating can be formed using a hard coating composition comprising a light-transmitting resin, a photoinitiator, and a solvent.

[0023] In one embodiment of the present invention, the above-mentioned light-transmitting resin may comprise one or more selected from the group consisting of light-curable (meth)acrylate oligomers and monomers having (meth)acryloyl groups.

[0024] On the other hand, the present invention provides an image display device having the above-described hard coating.

[0025] On the other hand, the present invention provides a window for a flexible display device having the above-mentioned hard coating.

[0026] On the other hand, the present invention provides a polarizing plate having the above-mentioned hard coating.

[0027] On the other hand, the present invention provides a touch sensor having the above-described hard coating.

[0028] Invention Effects

[0029] The easy-to-adhesive layer forming composition of the present invention contains aromatic (meth)acrylate, thereby improving the adhesion between the cyclic olefin polymer substrate and the hard coating, thereby improving the bending resistance of the hard coating film. Detailed Implementation

[0030] The present invention will now be described in more detail.

[0031] One embodiment of the present invention relates to a composition for forming an easy-to-adhesive layer, comprising an aromatic (meth)acrylate, a photoinitiator, and a solvent.

[0032] In one embodiment of the present invention, the aromatic (meth)acrylate, as a component that imparts adhesion between the cyclic olefin polymer substrate and the hard coating, is a compound containing an aromatic ring and (meth)acrylate functional groups within its molecule.

[0033] The number of methacrylate functional groups in the above-mentioned aromatic (meth)acrylates is not particularly limited, but is preferably 3 or more functional. For 1 or 2 functional aromatic (meth)acrylates, it is more preferable to use them in combination with 3 or more functional aromatic (meth)acrylates than to use them alone.

[0034] Specifically, 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.

[0035] The content of the aromatic (meth)acrylate can be from 50 to 99.9% by weight relative to 100% by weight of the total solid components in the composition for forming the easy-to-adhere layer. If the content of the aromatic (meth)acrylate is less than 50% by weight, it will not be able to form a sufficient bond with the cyclic olefin polymer substrate, and poor adhesion may occur.

[0036] In one embodiment of the present invention, the photoinitiator can be used without limitation as long as it is a substance used in this technical field that can form free radicals by light irradiation. For example, hydroxy ketones, amino ketones, hydrogen-abstracting photoinitiators, etc., can be used.

[0037] Specifically, the photoinitiators mentioned above include 2-methyl-1-[4-(methylthio)phenyl]2-morpholinoacetone-1, diphenyl ketone, benzoyladium 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 can be used individually or in combination.

[0038] The content of the aforementioned photoinitiator is not particularly limited. For example, relative to 100% by weight of the solid components in the composition for forming an easy-to-adhere layer, the content can be 0.1% to 10% by weight, preferably 1% to 5% by weight. If the content of the aforementioned photoinitiator is less than 0.1% by weight, the curing speed of the composition may be slow, resulting in incomplete curing and a decrease in the mechanical properties of the coating. If it is greater than 10% by weight, the coating may crack due to over-curing.

[0039] The solvents described above can be used without restriction, as long as they are solvents used in this technical field. Specifically, alcohol-based solvents (methanol, ethanol, isopropanol, butanol, methyl cellosolve, ethyl cellosolve, etc.); ketone-based solvents (methyl ethyl ketone, methyl butyl ketone, methyl isobutyl ketone, diethyl ketone, dipropyl ketone, cyclohexanone, etc.); acetate-based solvents (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.); hexane-based solvents (hexane, heptane, octane, etc.); benzene-based solvents (benzene, toluene, xylene, etc.); ether-based solvents (diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dipropyl ether, diethylene glycol dibutyl ether, propylene glycol monomethyl ether, etc.), etc. The solvents exemplified above can be used individually or in combination of two or more.

[0040] The content of the solvent can be 10 to 95% by weight relative to 100% by weight of the composition for forming the easy-to-adhere layer. When the content of the solvent is less than 10% by weight, not only is the viscosity high and the workability poor, but the substrate film cannot be fully swollen. When it is greater than 95% by weight, it has the problems of requiring a lot of time during the drying process and poor economy.

[0041] The composition for forming an easy-to-adhesive layer according to one embodiment of the present invention may further comprise a light-transmitting resin.

[0042] The aforementioned light-transmitting resin is a light-curing resin, which may contain light-curing (meth)acrylate oligomers and / or monomers.

[0043] As the aforementioned photocurable (meth)acrylate oligomers, epoxy (meth)acrylates, urethane (meth)acrylates, etc., are commonly used, with urethane (meth)acrylates being preferred. Uramate (meth)acrylates can be manufactured by reacting an intramolecularly hydroxyl-containing (meth)acrylate with a compound having an isocyanate group in the presence of a catalyst. Specific examples of the aforementioned intramolecularly hydroxyl-containing (meth)acrylates include 2-hydroxyethyl (meth)acrylate, 2-hydroxyisopropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, caprolactone ring-opening hydroxyacrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, and dipentaerythritol hexa(meth)acrylate. Furthermore, specific examples of the compounds containing isocyanate groups mentioned above 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, and 4,4'-diisocyanate. - Methylene bis(cyclohexyl isocyanate), isophorone diisocyanate, toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, xylene-1,4-diisocyanate, tetramethylxylene-1,3-diisocyanate, 1-chloromethyl-2,4-diisocyanate, 4,4'-methylene bis(2,6-dimethylphenyl isocyanate), 4,4'-oxobis(phenyl isocyanate), trifunctional isocyanates derived from hexamethylene diisocyanate, trimethylpropanol addition to toluene diisocyanate, etc.

[0044] The monomers mentioned above can be any commonly used monomers without limitation. As photocurable functional groups, monomers with unsaturated groups such as (meth)acryloyl, vinyl, styrene, and allyl in the molecule are preferred, among which monomers with (meth)acryloyl are preferred.

[0045] Specific examples of monomers having the aforementioned (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 tri(meth)acrylate, dipentaerythritol tetra ... The applicant may select one or more from the group consisting of pentamethacrylate, dipentaerythritol tetramethacrylate, dipentaerythritol hexamethacrylate, tripentaerythritol trimethacrylate, tripentaerythritol hexamethacrylate, bis(2-hydroxyethyl)isocyanurate dimethacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, isooctyl methacrylate, isodecanyl methacrylate, stearyl methacrylate, tetrahydrofurfuryl methacrylate, phenoxyethyl methacrylate, and isobornyl methacrylate.

[0046] The light-curable (meth)acrylate oligomers and monomers exemplified above as light-transmitting resins can be used individually or in combination of two or more.

[0047] For example, in the above-mentioned light-curing (meth)acrylate oligomers and / or monomers, the light-transmitting resin may be a compound belonging to the aliphatic (meth)acrylate group.

[0048] There is no particular limitation on the content of the above-mentioned transparent resin, which can be 49.9% by weight or less relative to 100% by weight of the total solid components in the above-mentioned easy-to-adhere layer forming composition. If the content of the above-mentioned transparent resin is greater than 49.9% by weight, the content of aromatic (meth)acrylate will be relatively insufficient and unable to form a sufficient bond with the cyclic olefin polymer substrate, which may result in poor adhesion.

[0049] The composition for forming an easy-to-adhesive layer according to one embodiment of the present invention may further include a leveling agent to impart smoothness and coatability to the coating film during application.

[0050] The leveling agents mentioned above can be commercially available silicone-based, fluorinated, or acrylic polymer-based leveling agents. For example, 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, and BYK-UV3570 from BYK Chemicals, and TEGO Glide 410, TEGO Glide 411, TEGO Glide 415, TEGO Glide 420, TEGO Glide 432, and TEGO Glide from TIGABYTE can be used. 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, 3M's FC-4430, FC-4432, etc. The content of the leveling agent can be in the range of 0.1% to 3% by weight relative to 100% of the total composition for forming the above-mentioned easy-to-adhere layer.

[0051] An easy-to-adhesion layer forming composition according to one embodiment of the present invention can be used between a cyclic olefin polymer substrate and a hard coating layer. The easy-to-adhesion layer forming composition according to one embodiment of the present invention contains aromatic (meth)acrylates, thereby ensuring adhesion to the substrate due to the bonding force between the CH groups on the surface of the cyclic olefin polymer substrate and the aromatic groups. Simultaneously, unreacted acrylate groups participate in the UV curing reaction during the formation of the hard coating layer, ensuring adhesion to the hard coating layer. Therefore, the easy-to-adhesion layer forming composition according to one embodiment of the present invention can be applied between a cyclic olefin polymer substrate and a hard coating layer to provide a hard coating film with excellent flexural strength.

[0052] Therefore, one embodiment of the present invention relates to a hard coating film formed using the above-described easy-to-adhere layer forming composition.

[0053] A hard coating film according to one embodiment of the present invention comprises:

[0054] Cycloolefin polymer substrate;

[0055] An easy-to-adhesive layer formed on at least one side of the aforementioned cyclic olefin polymer substrate; and

[0056] A hard coating layer formed on the aforementioned easily bonded layer,

[0057] The aforementioned easy-to-adhesive layer is formed using the aforementioned easy-to-adhesive layer forming composition.

[0058] The hard coating film of one embodiment of the present invention has excellent transmittance characteristics and bending resistance. Specifically, the hard coating film of one embodiment of the present invention has a total light transmittance of over 90%, and after being repeatedly folded and unfolded 200,000 times with the hard coating surface facing inward and at a radius of curvature of 1 mm, the hard coating film will not break or peel off.

[0059] The above total light transmittance (Tt, %) is obtained by measuring the incident light intensity (T0) and the total transmitted light intensity (T1) through the hard coating film and calculating it using the following mathematical formula 1.

[0060] [Mathematical Expression 1]

[0061] Total light transmittance (Tt, %) = (T1 / T0) × 100

[0062] The above-mentioned total light transmittance can be measured, for example, using a haze meter (Murakami Corporation) according to the method described in the experimental examples below.

[0063] In one embodiment of the present invention, the above-mentioned cyclic olefin polymer substrate serves as the base substrate for the hard coating film, and contains cyclic olefin polymer (COP) with excellent transparency.

[0064] The term COP is a general term for resins manufactured by the polymerization of cyclic olefins as monomers. Specific examples include: ring-opening (co)polymers of cyclic olefins; addition polymers of cyclic olefins; copolymers (usually random copolymers) of cyclic olefins with α-olefins such as ethylene or propylene; graft-modified products derived from unsaturated carboxylic acids or their derivatives; and their hydrides. Specific examples of cyclic olefins include norbornene monomers.

[0065] Specifically, the aforementioned COP can be a polymer obtained by performing ring-opening metathesis polymerization on one or more of the monomers represented by the following chemical formulas 1 to 3 and selectively hydrogenating them.

[0066] [Chemical Formula 1]

[0067]

[0068] [Chemical Formula 2]

[0069]

[0070] [Chemical Formula 3]

[0071]

[0072] The process of producing COP by ring-opening polymerization of one or more of the monomers represented by the above chemical formulas 1 to 3 can be easily carried out according to conventional methods.

[0073] For example, the polymerization process can be carried out using palladium(II) acetylacetone [Pd(acac)2] and tricyclohexylphosphine as polymerization catalysts and dimethylanilinium tetrakiss(pentafluorophenyl)borate as a co-catalyst.

[0074] In one embodiment of the present invention, the aforementioned COP can be manufactured by mixing other ring-opening polymerizable cyclic olefins other than norbornene monomers without hindering the objectives of the present invention. Specific examples of such cyclic olefins include compounds having a reactive double bond, such as cyclopentene, cyclooctene, and 5,6-dihydrodicyclopentadiene.

[0075] The aforementioned COP can be further hydrogenated after the ring-opening polymerization reaction. This hydrogenation can be carried out by reacting hydrogen with a hydrogenation catalyst in the presence of 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. Hydrogenation rates within the above range provide excellent heat degradation resistance, light degradation resistance, etc.

[0076] Various commercially available products are available for the aforementioned COP. Specific examples of the aforementioned COP include those manufactured by ZEONCORPORATION under the brand names "ZF-16", "ZEONEX", and "ZEONOR", those manufactured by JSR Corporation under the brand name "Arton", those manufactured by TICONA Corporation under the brand name "TOPAS", and those manufactured by Mitsui Chemicals Co., Ltd. under the brand name "APEL".

[0077] As a method for forming a substrate film from the aforementioned COP, any suitable molding method can be used. Specific examples include compression molding, transfer molding, injection molding, extrusion molding, blow molding, powder molding, FRP molding, and leveling. Extrusion molding and leveling are preferred because the resulting films can possess improved smoothness and good optical uniformity. Molding conditions can be appropriately selected based on the composition or type of resin used, the desired characteristics of the optical film, etc.

[0078] There is no particular limitation on the thickness of the aforementioned cyclic olefin polymer substrate, which can be from 10 to 1000 μm, specifically from 20 to 150 μm. If the thickness of the aforementioned transparent substrate is less than 10 μm, the film strength decreases and the processability deteriorates; if it is greater than 1000 μm, the transparency decreases and the weight of the hard coating increases.

[0079] In one embodiment of the present invention, the above-mentioned easy-to-adhesive layer forming composition is coated on at least one side of the above-mentioned cyclic olefin polymer substrate and cured thereon to form an easy-to-adhesive layer.

[0080] The composition for forming an easy-to-adhere layer according to one embodiment of the present invention can be coated onto a substrate by appropriately using known methods such as a die coater, air knife, reverse roller, spraying, doctor blade, casting, gravure printing, microgravure printing, spin coating, etc.

[0081] After the above-mentioned easy-to-adhere layer forming composition is applied to the substrate, the solvent is evaporated and dried, and then cured by UV light. The specific UV light irradiation dose can be approximately 10 to 500 mJ / cm². 2 More specifically, it can be 50 to 400 mJ / cm 2 .

[0082] At this point, the thickness of the formed easy-to-adhere layer can be specifically 0.1 to 5 μm, more specifically 0.3 to 3 μm. When the thickness of the easy-to-adhere layer is within the above range, excellent adhesion and bending resistance can be obtained.

[0083] In one embodiment of the present invention, the above-mentioned hard coating can be formed using a hard coating composition comprising a light-transmitting resin, a photoinitiator, and a solvent.

[0084] The aforementioned translucent resin is a photocurable resin, which may contain photocurable (meth)acrylate oligomers and / or monomers. From the perspective of adhesion to easily bonded layers, the aforementioned translucent resin preferably contains one or more components selected from the group consisting of photocurable (meth)acrylate oligomers and monomers having (meth)acryloyl groups.

[0085] Regarding the specific types of the above-mentioned photocurable (meth)acrylate oligomers and monomers having (meth)acryloyl groups, the same types used in the above-mentioned compositions for forming easy-to-adhere layers can be used.

[0086] Furthermore, as the monomer having (meth)acryloyl groups mentioned above, dendritic compounds having (meth)acrylate terminal groups can be used.

[0087] The aforementioned dendritic compounds with (meth)acrylate terminal groups have the following structural features: the ends of the branched structure are replaced by (meth)acrylate groups for UV curing, and their core is entirely aliphatic and composed of three-dimensional ester bonds. Therefore, compared to general multifunctional acrylate monomers, these dendritic compounds with (meth)acrylate terminal groups exhibit a structural feature where, with increasing generation, they possess more functional groups relative to molecular weight, and these functional groups are distributed at the ends, thus the core portion contributes to improved bending properties during curing. Consequently, a high-hardness hard coating film with improved curl and flexibility can be obtained.

[0088] The aforementioned dendritic compounds with (meth)acrylate terminal groups can be commercially available or manufactured using methods known in the art. For example, using a specific polyol as the central backbone, a first-generation dendritic structure is formed by condensing it with dimethylolpropionic acid. Then, as the molecular structure, the dimethylolpropionic acid is repeatedly condensed to grow a second-generation or higher structure. Finally, acrylic acid is condensed with the terminal groups to obtain a highly branched dendritic compound with a large number of (meth)acrylate groups at the ends.

[0089] There is no particular limitation on the content of the above-mentioned translucent resin, which can be 1 to 80% by weight relative to 100% of the total hard coating composition. If it is less than 1% by weight, it is difficult to achieve a sufficient increase in hardness, and if it is greater than 80% by weight, there is a problem of increased curling.

[0090] As the above-mentioned photoinitiator, the same photoinitiator used in the above-mentioned composition for forming an easy-to-adhere layer can be used.

[0091] Relative to 100% by weight of the above-mentioned hard coating composition, the content of the above-mentioned photoinitiator can be from 0.1% to 10% by weight, preferably from 1% to 5% by weight. When the content of the above-mentioned photoinitiator is less than 0.1% by weight, the curing speed of the composition may be slow, uncured coating may occur, and the mechanical properties of the coating may be reduced. When it is greater than 10% by weight, the coating may crack due to over-curing.

[0092] As the solvent described above, the same solvent used in the composition for forming the easy-to-adhere layer described above can be used.

[0093] Furthermore, the solvent mentioned above may include fluorinated solvents. These fluorinated solvents can increase the solubility of the fluorinated UV-curable functional compounds described later, thereby not only maintaining excellent wettability and coating condition of the manufactured hard coating film, but also causing the fluorinated UV-curable functional groups to be oriented and formed on the surface of the hard coating during coating and drying processes, thus forming a high-concentration fluorine layer on the surface of the manufactured hard coating.

[0094] As the aforementioned fluorinated solvents, perfluorohexyl ethyl alcohol, perfluoroether, perfluorohexane, etc., can be used. Commercially available products include 3M's HFE-7100, HFE-7300, HFE-7500, FC-3283, FC-40, FC-770, and Nichih Corporation's C6FOH-BF, but are not limited to these.

[0095] The solvent content can be 5 to 90% by weight relative to 100% of the total hard coating composition, preferably 7 to 85% by weight. When it is less than 5% by weight, the viscosity is high and the workability is poor. When it is greater than 90% by weight, it is difficult to adjust the coating thickness and drying lines occur, resulting in poor appearance.

[0096] In one embodiment of the present invention, the above-mentioned hard coating composition may further include a compound containing a fluorine-based UV-curable functional group.

[0097] The aforementioned fluorine-containing UV-curable functional group compounds are components that impart antifouling and abrasion resistance. There are no particular limitations as long as they contain fluorine and also have UV-curable functional groups.

[0098] The aforementioned fluorine-containing UV-curable functional group compound can be selected from one or more of the group consisting of (meth)acrylates containing perfluoroalkyl groups, (meth)acrylates containing perfluoropolyether groups, (meth)acrylates containing perfluorocycloaliphatic groups, and (meth)acrylates containing perfluoroaromatic groups. In this case, it has the advantage of exhibiting excellent antifouling performance while maintaining excellent durability of antifouling performance for a long time after repeated use due to the formation of chemical bonds with the hard coating. Therefore, it is preferred.

[0099] Relative to 100% by weight of the total solid components in the above-described hard coating composition, the content of the fluorine-containing UV-curable functional group compound can be from 0.01 to 30% by weight, preferably from 0.01 to 20% by weight, and more preferably from 0.01 to 10% by weight. When the content of the fluorine-containing UV-curable functional group compound is within the above range, excellent abrasion resistance and stain resistance can be imparted, and therefore it is preferred. When the content of the UV-curable functional group compound is less than the above range, it may be difficult to achieve sufficient abrasion resistance or stain resistance; when it is greater than the above range, the film hardness or scratch resistance may decrease.

[0100] In addition to the above-mentioned components, the above-mentioned hard coating composition may further include components commonly used in the art, such as leveling agents, UV stabilizers, heat stabilizers, antioxidants, surfactants, lubricants, antifouling agents, etc.

[0101] The hard coating film of one embodiment of the present invention can be manufactured by applying the above-described hard coating composition onto an easy-to-adhere layer formed on at least one side of a cyclic olefin polymer substrate and curing it to form a hard coating layer.

[0102] The above-mentioned hard coating composition can be applied to the easy-to-adhere layer by appropriate use of known methods such as die coating machine, air knife, reverse roller, spraying, doctor blade, casting, gravure printing, microgravure printing, spin coating, etc.

[0103] After applying the above-described hard coating composition to an easy-to-adhere layer, it is dried at a temperature of 30 to 150°C for 10 seconds to 1 hour, more specifically 30 seconds to 30 minutes, to allow the volatiles to evaporate. Then, it is cured by irradiation with UV light. The specific UV light irradiation dose can be approximately 0.01 to 10 J / cm². 2 More specifically, it can be 0.1 to 2 J / cm 2 .

[0104] At this point, the thickness of the hard coating can be specifically 2 to 30 μm, more specifically 3 to 20 μm. When the thickness of the hard coating is within the above range, excellent hardness and bending resistance can be obtained.

[0105] One embodiment of the present invention relates to an image display device having the above-described hard coating. For example, the hard coating of the present invention can be used as a window in an image display device, particularly a flexible display device or a foldable display device. Furthermore, the hard coating of the present invention can also be attached to polarizing plates, touch sensors, etc.

[0106] The hard coating of one embodiment of the present invention can be used in reflective, transmissive, and semi-transmissive LCDs, or LCDs with various driving methods such as TN, STN, OCB, HAN, VA, and IPS. Furthermore, the hard coating of one embodiment of the present invention can also be used in various image display devices such as plasma displays, field emission displays, organic EL displays, inorganic EL displays, and electronic paper.

[0107] The present invention will be described in more detail below through examples, comparative examples, and experimental examples. It will be apparent to those skilled in the art that these examples, comparative examples, and experimental examples are merely illustrative of the invention, and the scope of the invention is not limited thereto.

[0108] Manufacturing Example 1: Manufacturing of a Composition for Forming an Easy-to-Adhesive Layer

[0109] A composition for forming an easy-to-adhesive layer was prepared by mixing 19.2 parts by weight of a hexafunctional aromatic acrylate (Miramer PU640), 80 parts by weight of methyl ethyl ketone, 0.5 parts by weight of 1-hydroxycyclohexylphenyl ketone, and 0.3 parts by weight of a leveling agent (BYK UV-3530) using a mixer and filtering the mixture using a PP filter.

[0110] Manufacturing Example 2: Manufacturing of a Composition for Forming an Easy-to-Adhesive Layer

[0111] 14.2 parts by weight of a hexafunctional aromatic acrylate (Miramer PU640), 5 parts by weight of a hexafunctional aliphatic acrylate (Miramer PU620), 80 parts by weight of methyl ethyl ketone, 0.5 parts by weight of 1-hydroxycyclohexylphenyl ketone, and 0.3 parts by weight of a leveling agent (BYK UV-3530) were mixed using a mixer and filtered using a PP filter to prepare a composition for forming an easy-to-adhere layer.

[0112] Manufacturing Example 3: Manufacturing of a Composition for Forming an Easy-to-Adhesive Layer

[0113] Five parts by weight of a hexafunctional aromatic acrylate (Miramer PU640), 14.2 parts by weight of a hexafunctional aliphatic acrylate (Miramer PU620), 80 parts by weight of methyl ethyl ketone, 0.5 parts by weight of 1-hydroxycyclohexylphenyl ketone, and 0.3 parts by weight of a leveling agent (BYK UV-3530) were mixed using a mixer and filtered through a PP filter to prepare a composition for forming an easy-to-adhere layer.

[0114] Manufacturing Example 4: Manufacturing of a Composition for Forming an Easy-to-Adhesive Layer

[0115] 19.2 parts by weight of a hexafunctional aliphatic acrylate (Miramer PU620), 80 parts by weight of methyl ethyl ketone, 0.5 parts by weight of 1-hydroxycyclohexylphenyl ketone and 0.3 parts by weight of a leveling agent (BYK UV-3530) were mixed using a mixer and filtered using a PP filter to prepare a composition for forming an easy-to-adhere layer.

[0116] Manufacturing Example 5: Manufacturing of Hard Coating Composition

[0117] A hard coating composition was prepared by mixing 23 parts by weight of a hexafunctional urethane acrylate (Ninakamura Chemical, U-6LPA), 23 parts by weight of a 14-functional acrylate (Osaka Organic Chemical, VISCOAT#1000), 5 parts by weight of a fluorinated solvent (Nippon Hua, C6FOH-BF), 45 parts by weight of methyl ethyl ketone, 3.5 parts by weight of 1-hydroxycyclohexylphenyl ketone, and 0.5 parts by weight of a fluorinated UV-curable functional group compound (Shin-Etsu Chemical, KY-1203) using a mixer and filtering the mixture through a PP filter.

[0118] Example 1: Manufacturing of an easy-to-adhere film

[0119] On a cyclic olefin membrane (Ryon COP, ZF-16, 40 μm) whose surface water contact angle was adjusted to 65 degrees by corona treatment, the easy-to-adhere layer forming composition of Manufacturing Example 1 was coated with a cured thickness of 0.5 μm. After the solvent was dried, the membrane was irradiated with UV cumulative light intensity of 300 mJ / cm under a nitrogen atmosphere. 2 To manufacture easy-to-adhere films.

[0120] Example 2: Manufacturing of an easy-to-adhere film

[0121] The easy-adhesive layer forming composition of Manufacturing Example 2 was used instead of the easy-adhesive layer forming composition of Manufacturing Example 1. Otherwise, the easy-adhesive film was manufactured by the same method as in Example 1.

[0122] Example 3: Manufacturing of Hard Coating Film

[0123] The hard coating composition of Manufacturing Example 5 was applied to the easy-adhesive layer of the easy-adhesive film manufactured in Example 1 above, with a cured thickness of 5 μm. After the solvent was dried, the mixture was irradiated with UV cumulative light intensity of 600 mJ / cm under a nitrogen atmosphere. 2 To manufacture hard coatings.

[0124] Example 4: Manufacturing of Hard Coating Film

[0125] The easy-adhesive film manufactured in Example 2 was used instead of the easy-adhesive film manufactured in Example 1 above. Otherwise, the hard coating film was manufactured by the same method as in Example 3 above.

[0126] Comparative Example 1: Manufacturing of Easy-to-Adhesive Films

[0127] The easy-adhesive layer forming composition of Manufacturing Example 3 was used instead of the easy-adhesive layer forming composition of Manufacturing Example 1. Otherwise, the easy-adhesive film was manufactured by the same method as in Example 1.

[0128] Comparative Example 2: Manufacturing of Easy-to-Adhesive Films

[0129] The easy-adhesive layer forming composition of Manufacturing Example 4 was used instead of the easy-adhesive layer forming composition of Manufacturing Example 1. Otherwise, the easy-adhesive film was manufactured by the same method as in Example 1.

[0130] Comparative Example 3: Manufacturing of Hard Coating Film

[0131] The easy-adhesive film manufactured in Comparative Example 1 was used instead of the easy-adhesive film manufactured in Example 1 above. Otherwise, the hard coating film was manufactured by the same method as in Example 3 above.

[0132] Comparative Example 4: Manufacturing of Hard Coating Film

[0133] The easy-adhesive film manufactured in Comparative Example 2 was used instead of the easy-adhesive film manufactured in Example 1 above. Otherwise, the hard coating film was manufactured by the same method as in Example 3 above.

[0134] Experimental Example 1:

[0135] The physical properties of the membranes manufactured in the above examples and comparative examples were determined using the methods described later, and the results are shown in Table 1 below.

[0136] (1) Fit

[0137] After bonding the substrate film to the glass with the coated surface as the top, the coated surface is then scored with a cutting knife at 1mm intervals in the horizontal and vertical directions in the shape of 100 regular quadrilaterals. Finally, three adhesion tests are performed using Nichiban tape.

[0138] The evaluation result is expressed as "the number of quadrilaterals remaining (OK) after the tightness test / 100".

[0139] (2) Total light transmittance (Tt) and haze

[0140] The total light transmittance (%) and haze (%) of the coating were measured using a Murakami HM-150 haze meter.

[0141] (3) Water contact angle

[0142] The contact angle of water was measured using a KRUSS DSA100 contact angle meter. The droplet volume was set to 3 μl at room temperature.

[0143] (4) Abrasion resistance

[0144] The abrasion resistance was measured using abrasion testing equipment from Taisei Precision Machinery Co., Ltd. The coating surface was rubbed 3000 times with an abrasion test eraser and a 500g hammer, and the contact angle was measured. At this point, a water contact angle of 100° or higher was selected as the acceptable abrasion resistance standard.

[0145] <Evaluation Criteria>

[0146] ○: Contact angle of 100° or more

[0147] ×: Contact angle less than 100°

[0148] (5) Reagent resistance

[0149] The abrasion resistance was tested using abrasion testing equipment from Taisei Precision Machinery Co., Ltd. After adding 99.9% ethanol to the coating surface, the area with the ethanol was rubbed 3000 times using an abrasion test eraser and a 500g hammer, and the contact angle was measured. Ethanol was continuously added during the evaluation to prevent evaporation. After the evaluation, the ethanol was removed, and the water contact angle was measured. At this point, a water contact angle of 95° or higher was selected as the acceptable standard for reagent resistance.

[0150] <Evaluation Criteria>

[0151] ○: Contact angle is 95° or higher

[0152] ×: Contact angle less than 95°

[0153] (6) Scratch resistance

[0154] After bonding the substrate film to the glass using a transparent adhesive with the coated side as the top, use a steel wool pad (#0000) at 500g / cm² to apply the adhesive. 2 After 10 cycles of rubbing under load, the scratches were observed using a three-wavelength lamp transmission and reflection measurement unit. Scratch resistance was evaluated according to the following evaluation criteria.

[0155] <Evaluation Criteria>

[0156] ○: No scratches seen or fewer than 10 scratches seen

[0157] ×: Seeing more than 10 scratches

[0158] (7) Bending resistance

[0159] The film was repeatedly folded and unfolded 200,000 times with the hard coating facing inwards and a radius of curvature of 1 mm. The occurrence of film breakage and hard coating peeling was observed. Bending resistance was evaluated according to the following criteria.

[0160] <Evaluation Criteria>

[0161] ○: No film rupture or hard coating peeling occurred.

[0162] ×: Membrane rupture or hard coating peeling has occurred.

[0163] [Table 1]

[0164]

[0165] As shown in Table 1 above, it can be seen that the easy-to-adhesive films of Examples 1 and 2, manufactured using the easy-to-adhesive layer forming compositions of Examples 1 and 2 containing the aromatic (meth)acrylates of the present invention, exhibit excellent adhesion of the coated surface, as well as good total light transmittance (Tt) and haze. Furthermore, it can be confirmed that the hard coating films of Examples 3 and 4, on which a hard coating layer is formed on the easy-to-adhesive films of Examples 1 and 2, not only exhibit excellent adhesion, but also excellent water contact angle, abrasion resistance, reagent resistance, scratch resistance, and flexural strength.

[0166] On the other hand, it can be seen that the adhesion of the coating surface of the easy-to-adhesive films of Comparative Examples 1 to 2, which are manufactured using the easy-to-adhesive layer forming compositions of Manufacturing Examples 3 to 4 that do not contain aromatic (meth)acrylates, is poor. In addition, it can be confirmed that the hard coating films of Comparative Examples 3 to 4, on which a hard coating layer is formed on the easy-to-adhesive films of Comparative Examples 1 to 2, not only have reduced adhesion of the coating surface, but also reduced bending resistance.

[0167] The foregoing has described specific aspects of the present invention in detail. It will be apparent to those skilled in the art that such detailed description is merely a preferred embodiment, and the scope of the invention is not limited thereto. Those skilled in the art should be able to make various applications and modifications within the scope of the present invention based on the above description.

[0168] Therefore, the actual scope of the invention will be defined by the appended claims and their equivalents.

Claims

1. A hard coat film comprising: a cyclic olefin polymer substrate; an easy-adhesion layer formed on at least one surface of the cyclic olefin polymer substrate; and a hard coat layer formed on the easy-adhesion layer, the easy-adhesion layer is formed using an easy-adhesion layer forming composition, the easy-adhesion layer forming composition comprises an aromatic (meth)acrylate, a photoinitiator, and a solvent, the hard coat layer is formed using a hard coat composition comprising a light-transmissive resin, a photoinitiator, and a solvent, the light-transmissive resin comprises one or more selected from the group consisting of a photocurable (meth)acrylate oligomer and a monomer having a (meth)acryloyl group, the content of the aromatic (meth)acrylate is 50 to 99.9% by weight, relative to 100% by weight of the total solid content of the easy-adhesion layer forming composition, the content of the light-transmissive resin is 1 to 80% by weight, relative to 100% by weight of the total hard coat composition.

2. The hard coat film according to claim 1, having a total light transmittance of 90% or more, does not cause breakage of the hard coat film or peeling of the hard coat layer after being repeatedly folded and unfolded 200,000 times in a manner such that the hard coat layer faces the inside, with a radius of curvature of 1 mm.

3. The hard coat film according to claim 1 or 2, wherein the easy-adhesion layer forming composition further comprises a light-transmissive resin.

4. An image display device comprising the hard coat film according to any one of claims 1 to 3.

5. A window of a flexible display device comprising the hard coat film according to any one of claims 1 to 3.

6. A polarizing plate comprising the hard coat film according to any one of claims 1 to 3.

7. A touch sensor comprising the hard coat film according to any one of claims 1 to 3.

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