TWI640584B - Protective film and decorative protective film - Google Patents

Abstract

The invention provides a protective film and a decorative protective film. The protective film has a hard coating layer only on one side of a film substrate, and can be suitably decorated by thermal transfer printing and screen printing. By forming a protective film as described below, a decorative protective film excellent in printing adaptability in the thermal transfer printing method and the screen printing method can be obtained. The protective film is used for an image display window of an image display device. It is characterized in that a hard coating layer is provided on one side of the film substrate, and the contact angle of water on the surface of the other side of the film substrate having the hard coating layer is 70 degrees or less.

Description

Protective film and decorative protective film

The present invention relates to a protective film for an image display window of an image display device such as a liquid crystal panel and an EL display, and a decorative protective film in which the protective film is decorated.

An image display window of an image display device such as a liquid crystal display device used in a small electronic terminal such as a mobile personal computer, an electronic notebook, or a mobile phone is provided with a protective film for preventing the image display device from being damaged or broken. This protective film may be provided with a decorative layer on the back side for the purpose of improving designability and the like (see Patent Document 1).

A protective film for a display window of such an image display device, particularly a protective film for a touch panel application, is generally a protective film having a hard coating layer on both sides of a film substrate, but a protective coating having a hard coating layer on both sides. The film is disadvantageous for reduction in thickness. In addition, in the case of decorative printing on a protective film, thermal transfer printing is an advantageous method in terms of cost. However, for a protective film having a hard coat layer on only one side, the adaptability of thermal transfer printing has not been fully studied. (See Patent Document 2).

Patent Document 1: WO2005 / 081210

Patent Document 2: Japanese Patent Application Laid-Open No. 2011-110902

The problem to be solved by the present invention is to provide a method for The coated protective film may be a protective film suitably decorated by thermal transfer printing or screen printing.

In the present invention, by forming a protective film as described below, a decorative protective film having excellent printing adaptability in a thermal transfer printing method and a screen printing method can be obtained. The protective film is used for an image display device. A protective film for an image display window is characterized in that one side of a film substrate has a hard coating layer, and the other side of the surface of the film substrate having the hard coating layer has a contact angle of water on the surface of 70 degrees or less.

The protective film of the present invention has good printing adaptability even if it has a hard coating layer on only one side. Therefore, it can perform good decorative printing by low-cost thermal transfer printing and screen printing. The reduction of the hard coat layer contributes to the reduction in thickness of electronic equipment. In addition, since the decorative layer can be appropriately formed by the thermal transfer printing method and the screen printing method, it is easy to reduce the printing step difference. When the surface area layer having the decorative layer has an adhesive layer, the printing step difference can also be suppressed. The generation of air bubbles can ensure proper visibility.

The protective film of the present invention is a protective film for an image display window of an image display device, and is a kind of water having a hard coating layer on one side of a film substrate and a surface of the film substrate having the hard coating layer on the other side. A protective film with a contact angle of 70 degrees or less.

[Film substrate]

The film substrate used in the present invention preferably has a contact angle of water on the surface of 70 degrees or less. When the contact angle of water on the surface is within this range, good decorative printing can be performed on the surface of the substrate by thermal transfer printing or screen printing, and further, the adhesion between the decorative layer and the film substrate is good. In addition, by adjusting the contact angle of water on the surface of the film substrate to this range, the adhesion between the hard coat layer and the film substrate is changed. Well.

The thickness of the film substrate is 50 to 160 μm, preferably 80 to 150 μm, and more preferably 90 to 130 μm. In the present invention, by setting the thickness of the film base material within this range, curling can be easily suppressed even when a protective film is provided with a hard coat layer on one side.

Further, as the film substrate, a film substrate having an elastic modulus of 3 to 7 GPa is preferably used, and a film substrate of 3 to 5 GPa is particularly preferably used. When the elastic modulus is within this range, deformation of the film base material is less likely to occur when the protective film is formed, and it is suitable to suppress cracking of the hard coat layer, and it becomes easy to suppress a decrease in hardness of the surface of the protective film. In addition, since the flexibility of the film substrate can be ensured, it is easy to follow the curved surface when the protective film is adhered.

As the film substrate used in the present invention, various resin film substrates generally used as a substrate for a protective film can be used, and examples thereof include polyethylene terephthalate, polybutylene terephthalate, and polynaphthalene. Ethylene diformate, polyethylene, polypropylene, celluloid, cellulose diacetate, cellulose triacetate, cellulose acetate butyl, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, ethylene-vinyl acetate Copolymer, polystyrene, polycarbonate, polymethylpentene, polyfluorene, polyetheretherketone, polyetherfluorene, polyetherfluorene imine, polyfluoreneimide, fluororesin, nylon, acrylic resin and other resin films .

The film substrate used in the present invention may be a substrate composed of only the resin film described above, but a thin primer layer may be provided on the resin film in order to improve the adhesion with the hard coat layer and the decorative layer. Film substrate. Examples of the primer layer include polyester-based, urethane-based, and acrylic-based. In addition, in order to improve the adhesion with the hard coat layer and the decorative layer, a surface relief treatment by a sandblasting method, a solvent treatment method, or the like, or a corona discharge treatment, a chromic acid treatment, a flame treatment, and a hot air treatment may be performed. , Ozone, ultraviolet radiation treatment, surface oxidation treatment and other surface treatment.

〔Hard Coating〕

As a hard-coat agent which forms the hard-coat layer used by this invention, active energy can be used suitably. Radiocurable resin composition. Among them, even in a structure having a hard coat layer on only one side of the film substrate, suitable hard coat characteristics are easily obtained, and cracks are not likely to occur in the printing step of the decorative layer and the lamination step of the adhesive layer, so that As a hard-coat agent which forms the hard-coat layer used by this invention, the hard-coat agent containing a urethane (meth) acrylate is used suitably. As the urethane (meth) acrylate, various urethane (meth) acrylates used in hard coating agents can be used. Among them, it is preferable to contain a urethane and two or more (meth) acrylic acid. A fluorenyl acrylate (a1) and a polyfunctional urethane (meth) acrylate (A) obtained by reacting with a polyisocyanate (a2) are necessary components.

Examples of the acrylate (a1) having one hydroxyl group and two or more (meth) acrylfluorene groups in one molecule used in the present invention include trimethylolpropane di (meth) acrylate, neopentyl Polyacrylic acid esters of polyhydric hydroxyl-containing compounds such as alcohol tri (meth) acrylate, neopentaerythritol tetra (meth) acrylate, and dipentaerythritol penta (meth) acrylate. Examples of these polyacrylic acid include polyacrylates. Adducts of esters and ε-caprolactone, adducts of these polyacrylates and alkylene oxide, epoxy acrylates, and the like. These acrylates (a1) can be used individually or in combination of 2 or more types.

Among these acrylates (a1), acrylates having one hydroxyl group and 3 to 5 (meth) acrylfluorene groups in one molecule are preferred. Examples of such acrylates include neopentaerythritol triacrylate, neopentaerythritol tetraacrylate, and dipentaerythritol pentaacrylate. These are particularly preferable because they can obtain a hardened film with high hardness.

Examples of the polyisocyanate (a2) used in the present invention include 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 1,3-stilbene diisocyanate, and 4,4'-diphenyl di Aromatic isocyanate compounds such as isocyanate, 1,5-naphthalene diisocyanate, 4,4'-diphenylmethane diisocyanate; dicyclohexylmethane diisocyanate, isophorone diisocyanate, norbornene diisocyanate, hydrogenated stubble Diisocyanate, hydrogenated methylenebisphenylene diisocyanate, 1,4-cyclohexane diisocyanate, etc., which have two isocyanate groups bonded to an alicyclic hydrocarbon Compounds (hereinafter abbreviated as alicyclic diisocyanates); compounds having two isocyanate groups bonded to aliphatic hydrocarbons such as trimethylene diisocyanate and hexamethylene diisocyanate (hereinafter abbreviated as aliphatic diisocyanates.) Wait. These polyisocyanates can be used alone or in combination of two or more.

In addition, in order to impart high toughness to the coating film and prevent cracks and the like from occurring, these polyisocyanates (a2) are preferably aliphatic diisocyanates or alicyclic diisocyanates, and among these, isophorone diisocyanate and norbornene di Isocyanate, hydrogenated stilbene diisocyanate, hydrogenated methylene bisphenylene diisocyanate, and hexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, dicyclohexylmethane-4,4'-diisocyanate .

In addition, in order to further achieve a balance between high surface hardness and low shrinkage, an active energy ray-curable resin composition is preferred. The active energy ray-curable resin composition is characterized by a coating film cured by active energy ray. Contains two or more different cyclic skeletons, at least one of which is a heterocyclic compound. Examples of the polyisocyanate (a2) include a polyisocyanate (a2-1) having a cyclic skeleton and 1 in one molecule. A urethane acrylate containing a cyclic skeleton formed by the addition reaction of hydroxy groups and two or more (meth) acrylfluorenyl acrylates (a1-1). Particularly preferred is a cyclic skeleton-containing amine formic acid containing two or more cyclic skeletons and one of which is a heterocyclic skeleton, and an addition reaction of a polyfunctional acrylate with a polyisocyanate having a cyclic skeleton. Ester acrylate. In this way, it is possible to obtain a coating film with high surface hardness, low curl, and resistance to cracking in a thin film state after active energy ray curing.

As a method of introducing a heterocyclic skeleton, for example, a polyfunctional (meth) acrylate having a cyclic skeleton and a polyfunctional (meth) acrylate containing a heterocyclic skeleton may be blended separately, or may be combined with (a2 -1) Different acrylates (a1-2) having a heterofunctional skeleton having a polyfunctional (meth) acrylfluorenyl group are used for the aforementioned polyisocyanate (a2-1) having a cyclic skeleton and having 1 molecule 1 hydroxy and 2 or more (meth) acrylfluorenyl acrylates (a1) An active energy ray-curable resin composition containing two or more different cyclic skeletons in one molecule and at least one of which is a heterocyclic skeleton is obtained. As a method for introducing two or more kinds of cyclic skeletons into one molecule, for example, the above-mentioned (a1-2) and a trimer of a polyisocyanate (a2-2) having an alicyclic cyclic skeleton may be mentioned. Additions, etc.

Examples of the polyfunctional acrylate (a1-2) containing a heterocyclic skeleton include bis (acryloxyethyl) hydroxyethyltrimeric isocyanate (ARONIX M-215). Examples of the polyfunctional (meth) acrylate having a separate heterocyclic skeleton include, for example, bis (propenyloxyethyl) hydroxyethyltrimeric isocyanate (ARONIX M-215), and tris (2-hydroxyethyl) ) Isocyanate Triacrylate (ARONIX M-315), Caprolactone Modified Tris (propylene ethoxyethyl) trimeric isocyanate (ARONIX M-325), Neopentyl Glycol Modified Trimethylolpropane Diacrylate (KAYARAD R-604), etc.

The urethane acrylate (A) used in the present invention can be obtained by subjecting the two components of the polyisocyanate (a2) and the acrylate (a1) to an addition reaction. As the hydroxyl equivalent, the ratio of the aforementioned acrylate (a1) to the isocyanate 1 equivalent in the polyisocyanate (a2) is usually preferably 0.1 to 50, more preferably 0.1 to 10, still more preferably 0.9 to 1.3, and particularly preferably It is 1.01 to 1.24. The reaction temperature of the polyisocyanate (a2) and the acrylate (a1) is preferably 30 to 150 ° C, and more preferably 50 to 100 ° C. Here, the end point of the reaction can be confirmed by, for example, disappearance of the infrared absorption spectrum of 2250 cm ^-1 representing an isocyanate group, and determining the content of the isocyanate group by the method described in JIS K 7301-1995. In addition, the number of (meth) acrylfluorenyl groups of the urethane (meth) acrylate (A) is preferably 5 or more on average.

The molecular weight of the urethane acrylate (A) is preferably in the range of 500 to 1,500. As long as the molecular weight is within this range, a sufficiently hardened hardened film can be obtained, and the hardening shrinkage becomes small, and the curl of the film having the hardened film can be easily reduced, which is preferable.

The blending amount of the urethane acrylate (A) in 100 parts by weight of the resin component in the resin composition is preferably 5 to 90 parts by weight, more preferably 10 to 70 parts by weight, It is more preferably 10 to 60 parts by weight. As long as the blending amount of the urethane acrylate (A) is within this range, a sufficiently high hardness hardened film can be obtained without coating film defects, the surface is excellent in antifouling properties, and the hardening shrinkage becomes small, making it easy to make A film having such a cured coating is small, which is preferable.

In addition, in the active energy ray-curable resin composition used in the present invention, in addition to the urethane acrylate (A), urethane acrylic acid other than the urethane acrylate (A) may be added. Ester (B). Examples of the urethane acrylate (B) include an addition reaction of a polyhydric alcohol with the polyisocyanate (a2), and further having one hydroxyl group and two or more (meth) propylenes in one molecule. A fluorenyl acrylate (a1) is obtained by an addition reaction. The blending amount when the urethane acrylate (B) is blended in the resin composition is preferably 10 to 150 parts by weight, and more preferably 100 parts by weight of the urethane acrylate (A). It is 50 to 130 parts by weight.

In addition, in the active energy ray-curable resin composition used in the present invention, in order to obtain high pencil hardness, it is also preferable to blend a polymer (C) having a high (meth) acrylfluorene equivalent. Examples of the polymer (C) include a (meth) acrylate polymer (c1) having a hydroxyl group, a carboxyl group, an epoxy group, or the like as a reactive functional group in a side chain, and a polymer (c1) Polymers having a (meth) acrylfluorene group by reacting α, β-unsaturated compounds (c2) with functional groups such as isocyanate groups, carboxyl groups, fluorenyl halide groups, hydroxyl groups, and epoxy groups that are reactive with functional groups.

Various photoinitiators can be used as the photoinitiator for the active energy ray-curable resin composition used as the above-mentioned hard coating agent. If a particularly representative one is exemplified, benzophenone and diphenylethyl may be mentioned. Dione, Michelin, thioxanthone, anthraquinone and the like generate free radical type compounds by dehydrogenation. These compounds are generally used in combination with tertiary amines such as methylamine, diethanolamine, N-methyldiethanolamine, and tributylamine as dehydrogenating agents.

Examples of other types of photopolymerization initiators include compounds that generate a radical type by intramolecular cleavage. Specific examples include benzoin, dialkoxyacetophenone, fluorenyl oxime ester, diacetophenone ketal, hydroxyalkyl phenone, and haloketone.

In the active energy ray-curable resin composition used as a hard coating agent in the present invention, the amount of the photoinitiator to be mixed with the active energy ray-curable resin composition is relative to the active energy ray-curable resin composition. The total weight of the resin composition is 100 parts by weight, preferably 1 to 10 parts by weight, and even more preferably 3 to 9 parts by weight.

The hard coating agent for forming a hard coat layer used in the present invention is preferably added to the above active energy ray-curable resin composition for the purpose of improving surface properties such as surface sliding properties, stain resistance, and fingerprint adhesion resistance. An additive composed of a composition containing a compound having a fluorocarbon chain, a dimethylsiloxane chain, and a hydrocarbon chain having 12 or more carbon atoms. The addition amount of the additive containing a compound having a fluorocarbon chain, a dimethylsiloxane chain, and a hydrocarbon chain having 12 or more carbon atoms is preferably 0.05 to 5% by weight based on the active energy ray-curable resin composition. And more preferably 0.1 to 2% by weight.

Among them, fluorocarbon-chain-containing compounds are excellent in surface properties such as stain resistance, fingerprint adhesion resistance, and singular pen and ink wiping properties, and thus can be suitably used.

〔Protective film〕

The protective film of the present invention can be produced by applying a hard coating agent to one surface of the film substrate and curing the hard coating agent to laminate a hard coating layer.

The thickness of the hard coat layer is preferably 5 to 15 μm, more preferably 7 to 15 μm, and particularly preferably 8 to 12 μm. In the present invention, by setting the thickness of the hard coat layer within this range, even when a hard coat layer is provided on one side, curling is easily suppressed, and cracks are less likely to occur in the printing step.

The protective film of the present invention has a hard coating layer on only one side, and cracks of the hard coating layer are not easy to occur in printing steps such as thermal transfer printing and screen printing, and has suitable printing adaptability.

Examples of the method for applying a hard coating agent to a film substrate include gravure coating, roll coating, corner wheel coating, air knife coating, kiss coating, spray coating, suspension coating, dip coating, spin coating, wheel coating, and bristles. Coating, full-plate coating using a screen, wire rod coating, flow coating, and the like. In addition, offset Printing methods such as printing and letterpress are also possible. Among them, gravure coating, roll coating, notch wheel coating, air knife coating, kiss coating, wire rod coating, and flow coating are preferable because they can obtain a more stable thickness.

The hard coating agent hardening device may be appropriately used depending on the hard coating agent to be used. When the active energy ray-curable resin composition is used as the hard coating agent, it may be hardened using active energy rays such as light, electron beam, and radiation . Specific energy sources or hardening devices include, for example, sterilization lamps, ultraviolet fluorescent lamps, carbon arcs, xenon lamps, high-pressure mercury lamps for copying, medium- or high-pressure mercury lamps, ultra-high-pressure mercury lamps, electrodeless lamps, metal halide lamps, Ultraviolet light using natural light as a light source, or an electron beam generated by a scanning type or curtain type electron beam accelerator.

Among them, ultraviolet rays are particularly preferred. From the viewpoint of efficiency of polymerization, it is preferable to irradiate in an inert gas environment such as nitrogen. In addition, if necessary, heat may be used in combination as an energy source, and heat treatment may be performed after hardening using active energy rays.

As a device for irradiating active energy rays, when ultraviolet rays are used, examples of the light source include low-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, electrodeless lamps (melt lamps), chemical lamps, black light lamps, mercury-xenon lamps, Short arc lamps, helium and cadmium lasers, argon lasers, sunlight, LEDs, etc. In addition, when the active energy ray-curable resin composition used in the present invention is applied to a film substrate to form a cured film, if a flash-irradiated xenon flash lamp is used, the thermal influence on the film substrate can be reduced, and thus it is relatively small. good.

In addition, during continuous roll-to-roll production, since the protective film is wound into a roll shape, the hard coating layer and the other surface opposite to the surface having the hard coating layer are laminated. When an additive such as a fluorocarbon chain or a dimethylsiloxane chain is used in the hard coating layer as described above, the additive component is transferred to the film substrate surface on the other side of the surface having the hard coating layer. Surface contamination. In the protective film of the present invention, since the contact angle of water on the surface of the film substrate having the hard coating layer on the other side is maintained at 70 degrees or less to avoid the aforementioned contamination, a hard coating agent is applied to the film substrate and In the hardening step, a protective film may be simultaneously laminated on the other side opposite to the side having the hard coat layer.

〔Decorative Protective Film〕

The protective film of the present invention can be a decorative protective film for a portable electronic device or the like by providing a decorative layer. The decorative layer of the decorative protective film of the present invention can be produced by printing a decorative layer on the other surface of the protective film substrate with respect to the surface having a hard coat layer. Examples of a method for printing a decorative layer on a protective film substrate include a screen printing method, a screen printing method, a gravure printing method, and a thermal transfer printing method. Among these, a screen printing method, a screen printing method, and a thermal transfer printing method capable of printing a highly concealable decorative layer are preferred. In particular, the thermal transfer printing method is preferable because it can make the decorative layer thin.

As the ink which can be used for the screen printing method and the screen printing method, a solvent-based or UV-curable system can be used. In particular, the solvent-based ink can be used suitably because it can be printed at a low cost because the solvent is dried only in a drying oven and a special device such as a UV irradiation device is not required.

As the ink that can be used for the thermal transfer method, a resin type or a wax type can be used. Among them, the resin type can be suitably used because it has excellent weather resistance.

The thickness of the decorative layer is preferably 20 μm or less, more preferably 1 to 15 μm, and particularly preferably 2 to 10 μm. The protective film of the present invention can suitably form a decorative layer having the thickness by a screen printing method or a thermal transfer printing method. By forming the decorative layer having the thickness, an adhesive layer can be formed on the side surface of the decorative layer. The generation of air bubbles near the decorative layer is suitably suppressed.

The adhesive layer of the decorative protective film of the present invention can be directly adhered with an adhesive tape on the decorative layer side surface of the decorative protective film substrate, or the adhesive layer can be directly coated on the decorative layer side surface of the decorative protective film substrate. Layers.

As the adhesive used in the adhesive layer used in the present invention, a known acrylic, rubber-based, or silicone-based adhesive resin can be used. Among these, from the viewpoint of adhesion with the decorative layer, an acrylic copolymer containing a (meth) acrylate monomer having an alkyl group having 2 to 14 carbon atoms as a repeating unit as a main monomer component is preferred.

Specific examples of the (meth) acrylate monomer having 2 to 14 carbon atoms include ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, secondary butyl acrylate, and tertiary butyl acrylate. Ester, n-hexyl acrylate, cyclohexyl acrylate, n-octyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, isodecyl acrylate, lauryl acrylate, methyl methacrylate, Ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, secondary butyl methacrylate, tertiary butyl methacrylate, n-hexyl methacrylate, Cyclohexyl acrylate, n-octyl methacrylate, isooctyl methacrylate, 2-ethylhexyl methacrylate, isononyl methacrylate, isodecyl methacrylate, lauryl methacrylate Wait.

Among them, an alkyl methacrylate having an alkyl side chain having 4 to 9 carbon atoms or an alkyl acrylate having an alkyl side chain having 4 to 9 carbon atoms is more preferable, and an alkyl acrylate having 4 carbon atoms is more preferable. Alkyl acrylate with ~ 9 alkyl side chains. Of these, particularly preferred are n-butyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, and ethyl acrylate. By using an (meth) acrylic acid alkyl ester having an alkyl side chain having a carbon number in this range, it becomes easy to secure an appropriate adhesive force.

The content of the (meth) acrylic acid ester having 2 to 14 carbon atoms in the monomer constituting the acrylic copolymer used in the adhesive layer of the present invention is preferably 90 to 99% by weight, and more preferably 90%. ~ 96% by weight. By setting the content of the (meth) acrylate having 2 to 14 carbon atoms in the carboxyl group-containing (meth) acrylate copolymer within this range, it becomes easy to secure an appropriate adhesive force.

In the acrylic copolymer, a (meth) acrylic acid ester monomer having a polar group such as a hydroxyl group, a carboxyl group, or an amine group in a side chain, and other vinyl-based monomers are further preferable as a monomer component.

As the monomer having a hydroxyl group, for example, 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, Hydroxypropyl (meth) acrylates, caprolactone modified (meth) acrylates, polyethylene glycol mono (meth) acrylates, polypropylene glycol (meth) acrylates, and other (meth) groups containing hydroxyl groups Among the acrylates, 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 6-hydroxyhexyl (meth) acrylate are preferably used as copolymerization components.

As the monomer having a carboxyl group, acrylic acid, methacrylic acid, itaconic acid, maleic acid, crotonic acid, (meth) acrylic acid dimer, ethylene oxide modified succinic acid acrylate, and the like can be used. Preferably, acrylic acid is used as a copolymerization component.

As the monomer having a nitrogen atom, N-vinyl-2-pyrrolidone, N-vinyl caprolactam, acrylmorpholine, acrylamide, N, N-dimethylacrylamide can be used. N-vinylamine-containing vinyl monomers such as amines and 2- (perhydrophthalimide-N-yl) ethyl acrylate, among which N-vinyl-2-pyrrolidone is preferably used , N-vinyl caprolactam, acrylamidomorphine as copolymerization components.

Examples of the vinyl-based monomer having another polar group include vinyl acetate, acrylonitrile, maleic anhydride, and itaconic anhydride.

The content of the monomer having a polar group is preferably 0.1 to 20% by weight, more preferably 1 to 13% by weight, and still more preferably 1.5 to 8% by weight, the monomer component constituting the acrylic copolymer. By including in this range, it is easy to adjust the cohesive force, the holding force, and the adhesiveness of the adhesive to an appropriate range.

The weight average molecular weight Mw of the acrylic copolymer used in the adhesive layer is preferably 400,000 to 1.4 million, and more preferably 600,000 to 1.2 million. When the weight average molecular weight Mw of the acrylic copolymer is within the above range, it is easy to adjust the adhesive force to a specific range.

Here, the weight average molecular weight Mw of the acrylic copolymer can be measured by gel permeation chromatography (GPC). More specifically, “SC8020” manufactured by Tosoh Corporation, which is a GPC measurement device, can be obtained by measuring the polystyrene conversion value under the following GPC measurement conditions.

(GPC measurement conditions)

‧Concentration of sample: 0.5% by weight (tetrahydrofuran solution)

‧Sample injection volume: 100 μL

‧Eluent: Tetrahydrofuran (THF)

‧Flow rate: 1.0mL / min

‧Column temperature (measurement temperature): 40 ℃

‧Pipe: "TSK gel GMHHR-H" manufactured by Tosoh Corporation

‧Detector: Differential Refraction

In order to further improve the cohesive force of the adhesive layer, it is preferable to add a crosslinking agent to the adhesive. Examples of the crosslinking agent include an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, and a chelate-based crosslinking agent. The addition amount of the crosslinking agent is preferably adjusted so that the gel fraction of the adhesive layer is 25 to 80%. More preferably, the gel fraction is 40 to 75%. Among them, the best is 50 ~ 70%. If the gel fraction is less than 25%, the pencil hardness of the surface when the protective adhesive film is adhered to the panel is reduced. On the other hand, when the gel fraction exceeds 80%, the adhesiveness decreases. The gel fraction is expressed by the following percentage: the cured adhesive layer was immersed in toluene, left for 24 hours, and the weight of the remaining insoluble components after drying was measured, and the percentage was relative to the original weight.

In order to further improve the adhesion of the adhesive layer, a tackifier resin may be added. As the addition amount of the tackifier resin, when the adhesive resin is an acrylic copolymer, it is preferable to add 10 to 60 parts by weight based on 100 parts by weight of the acrylic copolymer. In the case where adhesion is important, it is best to add 20 to 50 parts by weight.

To the adhesive, well-known and commonly used additives other than the above can be added. For example, in order to improve the adhesion to glass, a silane coupling agent may be added in the range of 0.001 to 0.005. In addition, plasticizers, softeners, fillers, pigments, flame retardants, and the like can be added.

[Image display device]

The protective film of the present invention can be applied to image display devices such as liquid crystal display devices and organic EL display devices. Display device's image display window. Particularly suitable for images of portable electronic devices such as thin electronic notebooks, mobile phones, PHS, digital cameras, music players, televisions, notebook personal computers, smartphones, tablets, game consoles, e-books, etc. Display window.

As a preferred embodiment of the protective film of the present invention, for example, in the protective film configured as described above, the adhesive layer provided on the protective film can be peeled off at a position suitable for various terminals such as a portable electronic terminal to be applied. A method for forming an image display device by peeling off a film and laminating it with a glass substrate touch panel, a glass cover plate for protecting an image display panel, an organic EL panel, and a liquid crystal panel. Since the image display device can be easily decorated, it is extremely useful as a display application of various portable electronic terminals having the image display device.

Examples

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited thereto.

(Synthesis example 1)

<Synthesis of Urethane Acrylate (A1)>

In a flask equipped with a stirrer, a gas duct, a cooling pipe, and a thermometer, 250 parts by mass of butyl acetate, 206 parts by mass of norbornene diisocyanate (hereinafter referred to as NBDI), 0.5 parts by mass of p-methoxyphenol, and After 0.5 parts by mass of dibutyltin acetate, the temperature was raised to 70 ° C while blowing in air, and neopentaerythritol triacrylate (hereinafter referred to as PE3A) / nepentaerythritol tetraacrylate (hereinafter referred to as PE4A) was added dropwise over 1 hour. ) 795 parts by mass of a mixture (mixture with a mass ratio of 75/25). After the dropwise addition, the reaction was performed at 70 ° C for 3 hours, and the reaction was further performed until the infrared absorption spectrum of 2250 cm ^-1 representing an isocyanate group disappeared, and a polyfunctional urethane acrylate (A1) / PE4A mixture containing an alicyclic compound was obtained. (A mixture with a mass ratio of 80/20, a 80% by mass butyl acetate solution of nonvolatile matter). Here, the molecular weight (calculated value) of the urethane acrylate (A1) was 802.

(Synthesis example 2)

<Synthesis of Urethane Acrylate (A2)>

In a flask equipped with a stirrer, a gas duct, a cooling pipe, and a thermometer, 254 parts by mass of butyl acetate, 222 parts by mass of isophorone diisocyanate (hereinafter referred to as IPDI), 0.5 parts by mass of p-methoxyphenol, and 0.5 parts by mass of dibutyltin acetate was heated to 70 ° C, and then 795 parts by mass of a PE3A / PE4A mixture (mixture with a mass ratio of 75/25) was added dropwise over 1 hour. After the dropwise addition, the reaction was carried out at 70 ° C for 3 hours, and the reaction was further performed until the infrared absorption spectrum of 2250 cm ^-1 representing an isocyanate group disappeared to obtain a polyfunctional urethane acrylate (A2) / PE4A mixture containing an alicyclic compound. (A mixture with a mass ratio of 80/20, a 80% by mass butyl acetate solution of nonvolatile matter). Here, the molecular weight (calculated value) of the urethane acrylate (A2) was 818.

(Synthesis example 3)

<Synthesis of Urethane Acrylate (A3)>

In a flask equipped with a stirrer, a gas duct, a cooling pipe, and a thermometer, 254 parts by mass of butyl acetate, 222 parts by mass of isophorone diisocyanate (hereinafter referred to as IPDI), 0.5 parts by mass of p-methoxyphenol, and 0.5 parts by mass of dibutyltin acetate, and after heating up to 70 ° C, 369 parts by mass of bis (propenyloxyethyl) hydroxyethyltrimeric isocyanate and a mixture of PE3A / PE4A (mixture of 75/25 by mass) were added dropwise over 1 hour. 398 parts by mass. After the dropwise addition, the reaction was performed at 70 ° C for 3 hours, and the reaction was further performed until the infrared absorption spectrum of 2250 cm ^-1 representing the isocyanate group disappeared, and a polyfunctional urethane acrylic acid containing an alicyclic compound and a heterocyclic compound in one molecule was obtained. Ester (A3) / PE4A mixture (a mixture with a mass ratio of 91/9, a non-volatile content 80% by mass butyl acetate solution). Here, the molecular weight (calculated value) of the urethane acrylate (A3) was 889.

(Synthesis example 4)

In a flask equipped with a stirrer, a gas duct, a condenser, and a thermometer, add ARONIX M-305 [neopentaerythritol triacrylate / neopentaerythritol tetraacrylate manufactured by Toa Kosei Co., Ltd./60 / 40 (weight ratio) mixture, hydroxyl value of 116 mg KOH / g] 549.1 parts, 0.1 part of dibutyltin diacetate, SUMILIZER BHT [antioxidant manufactured by Sumitomo Chemical Industry Co., Ltd.] 0.6 parts, Methoquinone [made by Seiko Chemical Industry Co., Ltd.] Polymerization inhibitor] 0.1 parts, and 160.0 parts of butyl acetate, and the temperature was gradually raised while mixing uniformly. When it reached 60 ° C, 90.9 parts of Desmodur H [hexamethylene diisocyanate made by Sumitomo Bayer Polyurethane Co., Ltd., NCO% = 50%] was added, and then reacted at 80 ° C for 5 hours to obtain urethane acrylate (A4) 800. Serving.

Using the various urethane acrylates and / or polymers synthesized as described above, an active energy ray-curable resin composition to be a hard coating material is prepared.

(Preparation Example 1)

The following materials were mixed uniformly: 23.01 parts by mass of ethyl acetate, a polyfunctional urethane acrylate (A1) / PE4A mixture containing an alicyclic compound (mixture of 80/20 by mass, 80% by mass of acetic acid with a nonvolatile content) Butyl ester solution) 19.64 parts by mass, alicyclic compound-containing polyfunctional urethane acrylate (A2) / PE4A mixture (mixture of mass ratio 80/20, non-volatile content 80% by mass of butyl acetate solution) 19.64 A polyfunctional urethane acrylate (A3) / PE4A mixture (a mixture having a mass ratio of 91/9 and a non-volatile content of 80% by mass of butyl acetate solution in one part by mass containing an alicyclic compound and a heterocyclic compound) ) 15.71 parts by mass, bis neopentaerythritol hexaacrylate (hereinafter referred to as DPHA) 18.86 parts by mass, photoinitiator 1-hydroxycyclohexylphenyl ketone (hereinafter referred to as HCPK.) 2.51 parts by mass, photoinitiator Diphenyl 2,4,6-trimethylbenzylidenephosphine oxide (hereinafter referred to as TPO) 0.63 parts by mass of a reactive fluorine antifouling agent (OPTOOL DAC-HP, manufactured by Daikin Industry Co., Ltd. , 20% by mass of non-volatile content) 2.0 parts by mass, and then 40 masses based on non-volatile content % Manner diluted with propylene glycol monomethyl ether (hereinafter referred to as PGME.), To prepare a hard coat agent (1).

(Preparation Example 2)

Butyl acetate was added to the urethane acrylate (A4) to dilute it so that the non-volatile content concentration was 35%, and then Irgacure # 184 [a photopolymerization initiator made by Ciba Fine Chemicals Co., Ltd., 1-hydroxy-cyclohexyl-phenyl-one] 3.2 parts to prepare a hard coating agent (2).

(Preparation Example 3)

20 parts by mass of LIGHT ESTER TMP (acrylate monomer, manufactured by Kyoei Corporation), 18.5 parts by mass of NK OLIGO U-4HA (urethane acrylate, manufactured by Shin Nakamura Chemical Co., Ltd.), and Irgacure 184 (light starter, gasoline 1.5 parts by mass of Bajing Chemical Co., Ltd. were uniformly mixed, and then diluted with methyl ethyl ketone (MEK) so that the non-volatile content became 40% by mass, thereby preparing a hard coating agent (3).

(Example 1)

A 100 μm-thick polyethylene terephthalate film (COSMO SHINE A4300 manufactured by Toyobo Co., Ltd.) was used as a film substrate, and the hard coating agent (1) prepared above was coated on one side of the substrate, and dried at 60 ° C for 90 minutes. Seconds later, an ultraviolet irradiation device ("F450" manufactured by Fusion UV Systems Japan Co., Ltd., lamp: 120 W / cm, H bulb) was irradiated with ultraviolet light in an amount of 0.5 J / cm2 in an air atmosphere to form a 10 μm-thick A hard coat layer was obtained to obtain a protective film with a total thickness of 110 μm.

(Example 2)

A protective film having a total thickness of 110 μm was obtained in the same manner as in Example (1), except that a polyethylene film having a thickness of 100 μm (untreated surface of COSMO SHINE A4100 manufactured by Toyobo Co., Ltd.) was used as a film substrate. .

(Example 3)

A protective film having a total thickness of 110 μm was obtained in the same manner as in Example (1), except that a film made of polyethylene terephthalate (COSMO SHINE TA017 manufactured by Toyobo Co., Ltd.) was used as a film substrate with a thickness of 100 μm.

(Example 4)

A protective film having a total thickness of 110 μm was obtained in the same manner as in Example (1), except that a film made of polyethylene terephthalate (DIAFOIL φ 300E manufactured by Mitsubishi Polyester Corporation) was used as a film substrate with a thickness of 100 μm.

(Example 5)

A protective film having a total thickness of 110 μm was obtained in the same manner as in Example (1), except that a polyethylene terephthalate film (LUMIRROR U46, manufactured by Toray Industries, Inc.) was used as a film substrate with a thickness of 100 μm.

(Comparative example 1)

The opposite side of the hard coat layer of the protective film described in Example (1) was bonded to the hard coat side of the protective film described in Example (1), and a load of 40 kg / 10 mm square was applied at 40 ° C. Leave in the environment for 1 week. After that, the protective film was removed and left at 23 ° C and 50% for 1 day as a test piece.

(Comparative example 2)

The hard coat agent (2) was coated on the opposite side of the hard coat layer of the protective film described in Example (1), dried at 60 ° C for 90 seconds, and then irradiated with ultraviolet rays in an air atmosphere (Fusion UV Systems Japan "F450" (manufactured by Co., Ltd., lamp: 120 W / cm, H bulb) was irradiated with ultraviolet rays in an amount of 0.5 J / cm2 to form a hard coat layer having a thickness of 5 μm, thereby obtaining a double-sided protective film having a total thickness of 115 μm.

(Comparative example 3)

A hard coat agent (3) was used as a hard coat agent, and a hard coat layer having a thickness of 10 μm was formed in the same manner as in Example (1) to obtain a protective film having a total thickness of 110 μm.

The protective films obtained in the above examples and comparative examples were evaluated as follows. The results obtained are shown in Table 1.

(Water contact angle)

An automatic contact angle meter DM-501Hi manufactured by Kyowa Interface Science Co., Ltd. was used to measure the contact angle of water under the condition of a droplet volume of 4 microliters.

(Printing adaptability)

<Thermal transfer printing>

The thermal transfer printer F102-TBP, thermal transfer ribbon, and Ricoh B-110C (polyester) made by Fuji label were used to print on the printing side of the protective film, and the ink transfer was visually observed. Then, a celluloid tape (CT-18 manufactured by Nichiban Co., Ltd.) was affixed to the printed layer, and the celluloid tape was quickly peeled off to evaluate the adhesion of the printed layer. The evaluation criteria are set as follows.

：: The ink was firmly transferred, and there was no peeling even after the adhesion test.

○: The ink was transferred, and there was almost no peeling of the ink even after the adhesion test.

×: The ink was not transferred at all.

Or, although the ink has been transferred, the ink is almost completely peeled off after the adhesion test.

(Printing adaptability)

<Screen printing>

Ink SG740 and 700EX manufactured by Seiko Advance were screen-printed on the printed side of the protective film so that the thickness after drying was 5 μm, and dried at 85 ° C. for 30 minutes. After that, the ink transfer was visually observed. Then, a celluloid tape (CT-18 manufactured by Nichiban Corporation) was affixed to the printed layer, and the celluloid tape was quickly peeled off to evaluate the adhesion of the printed layer. The evaluation criteria are set as follows.

：: The ink was firmly transferred, and there was no peeling even after the adhesion test.

○: The ink was transferred, and there was almost no peeling of the ink even after the adhesion test.

×: The ink was not transferred at all.

Or, although the ink has been transferred, the ink is almost completely peeled off after the adhesion test.

(Visibility when the adhesive is laminated)

<Thermal transfer printing>

Using Fuji label's thermal transfer printer F102-TBP, thermal transfer ribbon, and Ricoh's B-110C (polyester), bar codes with a thickness of 0.3 mm and a pitch of 1 mm were printed on the printed side of the protective film. The thickness of the printed layer was 2 μm.

<Screen printing>

The ink SG740 manufactured by Seiko Ink Co., Ltd. was dried on the printing side of the protective film to a thickness of 5 Bar codes were printed in μm, 0.3 mm thick, and 1 mm pitch, and dried at 85 ° C for 30 minutes.

On the printed side of each protective film, a highly transparent substrate-free double-sided adhesive tape ZB150P (adhesive thickness: 15 μm) manufactured by DIC Corporation was affixed. After that, the release film on the other side of the adhesive tape was peeled off and bonded to a glass panel having a thickness of 1.1 mm with a roller. The obtained glass panel with a decorative protective film was subjected to heat, pressure, and defoaming treatment at 50 ° C, 5 atmospheres, and 20 minutes. Then, under a 3-wavelength fluorescent lamp, visual inspection and a microscope (100 times) were used as follows The judgment criterion evaluates the presence or absence of bubbles.

：: No bubbles were observed near the protective film / adhesive layer interface and near the printed layer even when observed under a microscope.

○: No bubbles were observed by visual inspection in the vicinity of the protective film / adhesive layer interface and the printed layer.

×: Bubbles were observed near the protective film / adhesive layer interface and the printed layer.

As can be seen from the above table, as a result of the protective film of the present invention, both the thermal transfer printing method and the screen printing method have excellent printability. On the other hand, the protective film printability of Comparative Examples 1, 2, and 3 was insufficient. In addition, in the protective film of Comparative Example 2, some cracks occurred in a part of the hard coat layer on the printing side during thermal transfer printing.

Claims (3)

A protective film for an image display window of an image display device, characterized in that: one side of a film substrate has a hard coating layer; the other side of the surface of the film substrate with the hard coating layer has a contact angle of water on the surface of 70 degrees or less; a decorative layer is provided on the surface of the other side of the film substrate having the hard coating layer; the thickness of the decorative layer is 20 μm or less; the thickness of the film substrate is 50 to 160 μm, and the elastic modulus is 3 to 7 GPa; the thickness of the hard coating layer is 5 to 15 μm; the hard coating layer is a layer composed of a hardened product of an active energy ray hardening resin composition, and the active energy ray hardening resin composition is composed of two or more kinds A hard coating material obtained by blending a polyfunctional (meth) acrylate oligomer having a cyclic skeleton and a urethane acrylate. The urethane acrylate polyisocyanate and one Addition reactant of an acrylate having one hydroxyl group and two or more (meth) acrylfluorenyl groups in the molecule, and at least one of the two or more polyfunctional (meth) acrylate oligomers having a cyclic skeleton A polyfunctional (meth) acrylate having a heterocyclic ring; the resin group The total amount blended was 100 parts by weight of the acrylate resin component of the carbamate 5 to 90 parts by weight, the molecular weight of the urethane acrylate of 500 to 1,500. For example, the protection film of the first patent application scope, wherein the surface of the protection film is provided with a decorative layer, and an adhesive layer is provided. For example, if the protection film of the first or second patent scope is applied, the decorative layer is printed by thermal transfer printing.