Adhesive film

Abstract

To provide an adhesive film that can be adhered to various three-dimensional surfaces, such as rough surfaces, curved surfaces, and corner portions, and that can provide an excellent metallic appearance.SOLUTION: An adhesive film according to an embodiment includes a clear film layer and an acrylic pressure-sensitive adhesive layer and has a metallic appearance. The acrylic pressure-sensitive adhesive layer includes an acrylic adhesive polymer and a resin-coated metal pigment. The glass transition temperature of the acrylic adhesive polymer is -25°C or lower. The acrylic pressure-sensitive adhesive layer contains from 5 pts.mass to 100 pts.mass of the resin-coated metal pigment relative to 100 pts.mass of the acrylic adhesive polymer.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to adhesive films. [Background technology]

[0002] Adhesive films with a metallic appearance are widely used in markings for vehicles, ships, aircraft, etc., interior and exterior decoration of buildings, illuminated signs, etc. Such adhesive films are generally laminates including a film layer and a pressure-sensitive adhesive layer, and the film layer, the pressure-sensitive adhesive layer, or any other intermediate layer includes a metallic pigment, or a metal layer such as a metal plating, a metal vapor deposition film, or a metal foil is disposed on the surface of the film layer or between the layers that constitute the adhesive film.

[0003] Patent Document 1 (JP 2006-88593 A) describes "a decorative metallic adhesive sheet characterized by being formed by laminating in the following order: an acrylic resin layer (A) which contains an ultraviolet absorber and has a total light transmittance for visible light of 85% or more; a metallic adhesive layer (B) which comprises an acrylic adhesive containing aluminum metal powder and a pearl pigment; a colored soft polyvinyl chloride resin layer (C); and an acrylic adhesive layer (D)." [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2006-88593 A Summary of the Invention [Problem to be solved by the invention]

[0005] The surfaces to which the adhesive film is applied, such as the interior or exterior walls of buildings, are often rough surfaces. The adhesive film is applied not only to flat surfaces, but also to curved surfaces or corners.

[0006] The present disclosure provides an adhesive film that can adhere to a variety of three-dimensional surfaces, such as rough surfaces, curved surfaces, and corners, and can provide an excellent metallic appearance. [Means for solving the problem]

[0007] Typical metal pigments used to impart a metallic appearance, such as aluminum pigments, have low compatibility with pressure-sensitive adhesives. The present inventors have discovered that metal pigments having a resin coating have excellent compatibility with pressure-sensitive adhesives and can impart a metallic appearance to a pressure-sensitive adhesive layer while maintaining adhesion and extensibility.

[0008] According to one embodiment, there is provided an adhesive film having a metallic appearance, comprising a clear film layer and an acrylic pressure-sensitive adhesive layer, wherein the acrylic pressure-sensitive adhesive layer comprises an acrylic adhesive polymer and a resin-coated metal pigment, the glass transition temperature of the acrylic adhesive polymer is −25° C. or lower, and the acrylic pressure-sensitive adhesive layer comprises 5 to 100 parts by mass of the resin-coated metal pigment per 100 parts by mass of the acrylic adhesive polymer. Effect of the Invention

[0009] According to the present disclosure, an adhesive film is provided that can adhere to a variety of three-dimensional surfaces, such as rough surfaces, curved surfaces, and corners, and can provide an excellent metallic appearance.

[0010] It should be noted that the above description should not be construed as a disclosure of all embodiments of the present invention and all advantages related to the present invention. [Brief description of the drawings]

[0011] [Figure 1] FIG. 2 is a schematic cross-sectional view of an adhesive film according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, the present invention will be described in more detail with reference to the drawings for the purpose of illustrating typical embodiments of the present invention, but the present invention is not limited to these embodiments.

[0013] In this disclosure, "(meth)acrylic" means acrylic or methacrylic, and "(meth)acrylate" means acrylate or methacrylate.

[0014] In this disclosure, the term "film" also encompasses an article called a "sheet."

[0015] In this disclosure, "pressure sensitive adhesion" refers to the property of a material or composition to adhere to a variety of surfaces with only slight pressure applied for a short period of time within the temperature range of use, e.g., from 0° C. to 50° C., and not to exceed this temperature, and not to exhibit a phase change (liquid to solid). In this disclosure, "tack" is used interchangeably with "pressure sensitive adhesion."

[0016] In one embodiment, the adhesive film includes a clear film layer and an acrylic pressure-sensitive adhesive layer, and has a metallic appearance. The acrylic pressure-sensitive adhesive layer includes an acrylic adhesive polymer and a resin-coated metal pigment. The resin-coated metal pigment imparts a metallic appearance to the acrylic pressure-sensitive adhesive layer that can be seen through the clear film layer of the adhesive film.

[0017] The clear film layer and the acrylic pressure-sensitive adhesive layer may be in direct contact with each other, or other layers, such as a colored layer, a printed layer, a bulk layer, etc., may be interposed between these layers. Other layers, such as a colored layer, a printed layer, a bulk layer, a surface protection layer, etc., may be laminated on the clear film layer. The adhesive film may further have other functional layers, such as a primer layer that enhances the adhesion between the clear film layer and the acrylic pressure-sensitive adhesive layer. The surface of the clear film layer that contacts the acrylic pressure-sensitive adhesive layer may be subjected to a surface treatment, such as a corona treatment or a plasma treatment.

[0018] The adhesive film may have a liner on the surface of the acrylic pressure-sensitive adhesive layer opposite to the clear film layer. The liner, which is an optional component, may be, for example, a plastic material such as polyethylene, polypropylene, polyester, or cellulose acetate, paper, or a laminated paper containing the plastic material. These liners may have a surface that has been subjected to a release treatment using silicone or the like. The thickness of the liner may be generally about 10 μm or more, or about 25 μm or more, and about 500 μm or less, or about 200 μm or less.

[0019] A schematic cross-sectional view of an adhesive film according to one embodiment is shown in Figure 1. The adhesive film 10 has a clear film layer 12, an acrylic pressure-sensitive adhesive layer 14, and optionally a liner 16. The acrylic pressure-sensitive adhesive layer 14 includes an acrylic adhesive polymer 142 and a resin-coated metal pigment 144 dispersed in the acrylic adhesive polymer 142.

[0020] As the clear film layer, for example, a plastic film such as a polyethylene film, a polypropylene film, a polyester film, an acrylic resin film, a polycarbonate film, a polyvinyl chloride film, a polyvinylidene chloride film, a polyurethane film, a polystyrene film, or a polyamide film can be used.

[0021] The thickness of the clear film layer can vary, for example, from about 5 μm or more, about 10 μm or more, or about 20 μm or more, to about 500 μm or less, about 300 μm or less, or about 200 μm or less.

[0022] In one embodiment, the visible light transmittance of the clear film layer is about 70% or more, about 80% or more, or about 90% or more. In the present disclosure, "visible light transmittance" refers to the average visible light transmittance at wavelengths of 380 nm to 780 nm measured in accordance with JIS A 5759:2008.

[0023] The acrylic pressure-sensitive adhesive layer contains an acrylic adhesive polymer and a resin-coated metal pigment.

[0024] The acrylic adhesive polymer can be obtained by polymerizing or copolymerizing a polymerizable composition containing a (meth)acrylic monomer and, if necessary, other monomers having a monoethylenically unsaturated group. In the present disclosure, the (meth)acrylic monomer and the other monomers having a monoethylenically unsaturated group are collectively referred to as polymerizable components. The (meth)acrylic monomer and the other monomers having a monoethylenically unsaturated group may be used alone or in combination of two or more.

[0025] The (meth)acrylic monomer generally contains an alkyl (meth)acrylate, the alkyl group of which may have 1 to 12 carbon atoms. Examples of the alkyl (meth)acrylate include linear or branched alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, 2-methylbutyl (meth)acrylate, isoamyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, and n-dodecyl (meth)acrylate; and alicyclic (meth)acrylates such as cyclohexyl (meth)acrylate, 4-t-butylcyclohexyl (meth)acrylate, and isobornyl (meth)acrylate. Preferably, the alkyl (meth)acrylate comprises methyl acrylate, n-butyl acrylate, 2-methylbutyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, or a combination thereof.

[0026] The alkyl (meth)acrylate constitutes the main component of the acrylic adhesive polymer. In one embodiment, the acrylic adhesive polymer is obtained by copolymerizing a polymerizable composition containing the alkyl (meth)acrylate in an amount of about 50 mass % or more, about 70 mass % or more, or about 80 mass % or more, about 99.5 mass % or less, about 99 mass % or less, or about 98 mass % or less, based on the mass of the polymerizable component, and contains the constituent units derived from the alkyl (meth)acrylate in the above mass ratio.

[0027] The (meth)acrylic monomer may include aromatic (meth)acrylates such as phenyl (meth)acrylate, p-tolyl (meth)acrylate, etc.; phenoxyalkyl (meth)acrylates such as phenoxyethyl (meth)acrylate, etc.; alkoxyalkyl (meth)acrylates such as methoxypropyl (meth)acrylate, 2-methoxybutyl (meth)acrylate, etc.; or cyclic ether-containing (meth)acrylates such as glycidyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, etc.

[0028] The (meth)acrylic monomer or other monomer having a monoethylenically unsaturated group may include a polar monomer copolymerizable with the alkyl (meth)acrylate. Examples of the polar monomer include carboxyl group-containing monomers such as (meth)acrylic acid, monohydroxyethyl phthalate (meth)acrylate, β-carboxyethyl (meth)acrylate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl hexahydrophthalate, crotonic acid, itaconic acid, fumaric acid, citraconic acid, and maleic acid; aminoalkyl (meth)acrylates such as aminoethyl (meth)acrylate; monoalkylaminoalkyl (meth)acrylates such as butylaminoethyl (meth)acrylate; dialkylaminoalkyl (meth)acrylates such as N,N-dimethylaminoethyl acrylate (DMAEA) and N,N-dimethylaminoethyl methacrylate (DMAEMA); Examples of the polar monomers include amino group-containing monomers such as acrylate, dialkylaminoalkyl (meth)acrylamides such as N,N-dimethylaminopropyl acrylamide (DMAPAA), N,N-dimethylaminopropyl methacrylamide, dialkylaminoalkyl vinyl ethers such as N,N-dimethylaminoethyl vinyl ether, N,N-diethylaminoethyl vinyl ether, etc.; amide group-containing monomers such as (meth)acrylamide, N-vinylpyrrolidone, N-vinylcaprolactam, etc.; hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, etc.; and unsaturated nitriles such as (meth)acrylonitrile. These polar monomers can increase the cohesive strength of the pressure-sensitive adhesive layer to improve the adhesive strength.

[0029] Other monomers having a monoethylenically unsaturated group include, for example, aromatic vinyl monomers such as styrene, α-methylstyrene, vinyl toluene, and the like; and vinyl esters such as vinyl acetate.

[0030] The acrylic adhesive polymer is preferably a carboxy group-containing (meth)acrylic polymer. The carboxy group-containing (meth)acrylic polymer can be obtained by copolymerizing a polymerizable composition containing a carboxy group-containing monomer as a polymerizable component. The carboxy group-containing (meth)acrylic polymer can increase the cohesive force and improve the adhesive force due to the presence of the carboxy group. The carboxy group-containing (meth)acrylic polymer can sometimes increase the adhesion between the clear film layer and the acrylic pressure-sensitive adhesive layer. The carboxy group-containing monomer is preferably (meth)acrylic acid.

[0031] In one embodiment, the carboxy group-containing (meth)acrylic polymer is obtained by copolymerizing a polymerizable composition containing a carboxy group-containing monomer in an amount of about 0.5 mass % or more, about 1 mass % or more, or about 2 mass % or more, about 15 mass % or less, about 10 mass % or less, or about 8 mass % or less, based on the mass of the polymerizable component, and contains constitutional units derived from the carboxy group-containing monomer in the above-mentioned mass ratio.

[0032] The polymerization or copolymerization of the acrylic adhesive polymer can be carried out by radical polymerization. As the radical polymerization, known polymerization methods such as solution polymerization, suspension polymerization, emulsion polymerization, and bulk polymerization can be used. It is advantageous to use solution polymerization, which can easily synthesize a polymer with a high molecular weight. As the polymerization initiator, for example, organic peroxides such as benzoyl peroxide, lauroyl peroxide, and bis(4-tert-butylcyclohexyl)peroxydicarbonate; or azo polymerization initiators such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), dimethyl-2,2-azobis(2-methylpropionate), 4,4'-azobis(4-cyanovaleric acid), dimethyl 2,2'-azobis(2-methylpropionate), and azobis(2,4-dimethylvaleronitrile) (AVN) can be used. The amount of the polymerization initiator used is generally about 0.01 parts by weight or more, or about 0.05 parts by weight or more, and about 5 parts by weight or less, or about 3 parts by weight or less, based on 100 parts by weight of the polymerizable component.

[0033] The glass transition temperature (Tg) of the acrylic adhesive polymer is about -25°C or lower. By setting the glass transition temperature of the acrylic adhesive polymer to about -25°C or lower, pressure-sensitive adhesive properties can be imparted to the acrylic pressure-sensitive adhesive layer at the use temperature (e.g., 5°C to 35°C) even when combined with a resin-coated metal pigment in an amount sufficient to exhibit a metallic appearance. In one embodiment, the glass transition temperature of the acrylic adhesive polymer is about -30°C or lower, or about -35°C or lower. In one embodiment, the glass transition temperature of the acrylic adhesive polymer is about -70°C or higher, about -65°C or higher, or about -60°C or higher. By setting the glass transition temperature of the acrylic adhesive polymer to about -70°C or higher, adhesive strength and holding strength can be imparted to the pressure-sensitive adhesive layer.

[0034] The glass transition temperature (Tg) of acrylic adhesive polymers is calculated by the following FOX formula (Fox, TG, Bull. Am. Phys. Soc., 1 (1956), p. 123), assuming that each polymer is copolymerized with n kinds of monomers.

number

number

[0035] In one embodiment, the weight average molecular weight (Mw) of the acrylic adhesive polymer is about 150,000 or more, about 200,000 or more, or about 250,000 or more, and about 2,000,000 or less, about 1,500,000 or less, or about 1,000,000 or less. In the present disclosure, the "weight average molecular weight" refers to the molecular weight calculated using standard polystyrene by gel permeation chromatography (GPC).

[0036] The resin-coated metal pigment is a pigment in which at least a part of the surface of the metal pigment is coated with a resin, and has excellent miscibility with acrylic adhesive polymers. By using the resin-coated metal pigment, it is possible to impart a metallic appearance to the acrylic pressure-sensitive adhesive layer while maintaining adhesion and extensibility. The resin-coated metal pigment may be used alone or in combination of two or more kinds.

[0037] The metal contained in the resin-coated metal pigment is not particularly limited, and examples thereof include aluminum, zinc, iron, magnesium, copper, nickel, and alloys thereof. It is preferable that the resin-coated metal pigment contains aluminum, since it can effectively provide metallic luster with a smaller amount of use and is inexpensive.

[0038] The material constituting the resin coating of the resin-coated metal pigment is not particularly limited, and examples thereof include acrylic resins, polyolefins, polybutadienes, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, fluororesins, polyvinyl ethers, polystyrenes, and copolymers and blends thereof. The resin-coated metal pigment preferably has an acrylic resin coating because of its excellent miscibility with acrylic adhesive polymers.

[0039] The shape of the resin-coated metal pigment is not particularly limited, and examples thereof include flake, sphere, needle, and lump shapes. Since a smaller amount of the resin-coated metal pigment can effectively provide metallic luster, the resin-coated metal pigment is preferably flake-shaped.

[0040] In one embodiment, the average particle size of the resin-coated metal pigment is about 5 μm or more, about 7 μm or more, or about 10 μm or more, and about 70 μm or less, about 50 μm or less, or about 40 μm or less. By setting the average particle size of the resin-coated metal pigment to be within the above range, the resin-coated metal pigment can be more uniformly dispersed in the acrylic pressure-sensitive adhesive layer. The average particle size of the resin-coated metal pigment can be determined by a volume cumulative particle size D that can be determined using a laser diffraction / scattering particle size distribution measurement. 50 It is.

[0041] The acrylic pressure-sensitive adhesive layer contains about 5 parts by mass or more and about 100 parts by mass or less of the resin-coated metal pigment based on 100 parts by mass of the acrylic adhesive polymer. By making the content of the resin-coated metal pigment about 5 parts by mass or more, it is possible to impart a metallic appearance to the entire acrylic pressure-sensitive adhesive layer. By making the content of the resin-coated metal pigment about 100 parts by mass or less, it is possible to maintain the adhesiveness and extensibility of the acrylic pressure-sensitive adhesive layer. In one embodiment, the acrylic pressure-sensitive adhesive layer contains about 6 parts by mass or more, or about 8 parts by mass or more, and about 50 parts by mass or less, or about 30 parts by mass or less of the resin-coated metal pigment based on 100 parts by mass of the acrylic adhesive polymer.

[0042] In one embodiment, the content of the pigment other than the resin-coated metal pigment in the acrylic pressure-sensitive adhesive layer is less than about 5 parts by weight, less than about 3 parts by weight, or less than about 1 part by weight based on 100 parts by weight of the acrylic adhesive polymer. By making the content of the pigment other than the resin-coated metal pigment in the acrylic pressure-sensitive adhesive layer less than about 5 parts by weight, the quality of the metallic appearance of the acrylic pressure-sensitive adhesive layer can be improved.

[0043] The acrylic pressure-sensitive adhesive layer may further contain a dispersant that enhances the dispersibility of the resin-coated metal pigment in the acrylic adhesive polymer. Examples of the dispersant include low molecular weight dispersants including anionic compounds, cationic compounds, and nonionic compounds, and polymer dispersants having anionic, cationic, or nonionic polar groups. The dispersants may be used alone or in combination of two or more.

[0044] The dispersant preferably has a basic group. The dispersant having a basic group can disperse the resin-coated metal pigment more effectively in the acrylic adhesive polymer. In an embodiment in which the acrylic adhesive polymer includes a carboxyl group-containing (meth)acrylic polymer, the dispersant having a basic group can also interact with the carboxyl group-containing (meth)acrylic polymer to increase the cohesive strength of the acrylic pressure-sensitive adhesive layer, thereby increasing the adhesive strength and holding strength of the acrylic pressure-sensitive adhesive layer.

[0045] In one embodiment, the low molecular weight dispersant comprises at least one selected from the group consisting of piperidyl compounds and benzotriazole compounds. The piperidyl compounds and benzotriazole compounds can further enhance the dispersibility of the resin-coated metal pigment. In an embodiment in which the acrylic adhesive polymer comprises a carboxyl group-containing (meth)acrylic polymer, the triazole ring or piperidine ring of the piperidyl compounds and benzotriazole compounds interacts with the carbonyl group of the carboxyl group-containing (meth)acrylic polymer to enhance the cohesive strength of the acrylic pressure-sensitive adhesive layer, thereby enhancing the adhesive strength and holding strength of the acrylic pressure-sensitive adhesive layer.

[0046] The piperidyl compound preferably has at least two piperidyl groups, and these piperidyl groups are bonded via a divalent linking group having 4 or more, 6 or more, or 8 or more carbon atoms. The piperidyl compound having the piperidyl groups bonded via a divalent linking group having 4 or more, 6 or more, or 8 or more carbon atoms has excellent compatibility with acrylic adhesive polymers.

[0047] The piperidyl compound may be one that can be used as a hindered amine light stabilizer (HALS). By using a hindered amine light stabilizer as the piperidyl compound, it is possible to impart ultraviolet resistance to the acrylic pressure-sensitive adhesive layer.

[0048] Examples of the piperidyl compound include bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate, bis(2,2,6,6-tetramethyl-1-(octyloxy)-4-piperidyl)sebacate, bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)-[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl [1,2,2,6,6-pentamethyl-4-piperidyl)butane-1,2,3,4-tetracarboxylate, and tetrakis(2,2,6,6-tetramethyl-4-piperidyl)butane-1,2,3,4-tetracarboxylate.

[0049] The benzotriazole compound is preferably a 2H-benzotriazole compound, more preferably having a substituted or unsubstituted hydroxyphenyl group at position 2. The 2H-benzotriazole compound, particularly the 2H-benzotriazole compound having a substituted or unsubstituted hydroxyphenyl group at position 2, has excellent compatibility with acrylic adhesive polymers.

[0050] The benzotriazole compound may be one that can be used as an ultraviolet absorbing agent (UVA). By using a benzotriazole compound having ultraviolet absorbing properties, ultraviolet resistance can be imparted to the acrylic pressure-sensitive adhesive layer.

[0051] Examples of the benzotriazole compound include 2-(2H-benzotriazole-2-yl)-p-cresol, 2-(2H-benzotriazole-2-yl)-4-methylphenol, 2-(2H-benzotriazole-2-yl)-4-methyl-6-(linear or branched)dodecylphenol, 2-(2H-benzotriazole-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol, 2-(5-chloro-2H-benzotriazole-2-yl)-6-(1, 1-dimethylethyl)-4-methylphenol, 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol, 2,2'-methylene-bis[6-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol], and C7-9 branched and straight chain alkyl esters of 3-(2H-benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxy-benzenepropanoic acid.

[0052] In one embodiment, the polymer dispersant comprises an amino group-containing (meth)acrylic polymer. The amino group-containing (meth)acrylic polymer not only enhances the dispersibility of the resin-coated metal pigment, but also has excellent compatibility with (meth)acrylic polymers having acidic groups such as carboxy groups. The amino group-containing (meth)acrylic polymer can be obtained by copolymerizing a polymerizable composition containing an amino group-containing monomer as a polymerizable component among the polymerizable compositions described in relation to the acrylic adhesive polymer. As the amino group-containing monomer, a dialkylaminoalkyl (meth)acrylate such as N,N-dimethylaminoethyl acrylate (DMAEA) or N,N-dimethylaminoethyl methacrylate (DMAEMA) is preferred.

[0053] In one embodiment, the amino group-containing (meth)acrylic polymer is obtained by copolymerizing a polymerizable composition containing an amino group-containing monomer in an amount of about 0.5% by mass or more, about 1% by mass or more, or about 3% by mass or more, about 20% by mass or less, about 15% by mass or less, or about 10% by mass or less, based on the mass of the polymerizable component, and contains constitutional units derived from the amino group-containing monomer in the above-mentioned mass ratio.

[0054] In one embodiment, the glass transition temperature (Tg) of the amino group-containing (meth)acrylic polymer is about 0° C. or more, about 20° C. or more, or about 40° C. or more, and about 150° C. or less, about 135° C. or less, or about 120° C. or less. The glass transition temperature of the amino group-containing (meth)acrylic polymer can be determined using the FOX equation, similarly to the acrylic adhesive polymer.

[0055] The weight average molecular weight of the amino group-containing (meth)acrylic polymer is not particularly limited, and can be, for example, about 1,000 or more, about 5,000 or more, about 10,000 or more, about 200,000 or less, about 100,000 or less, or about 80,000 or less.

[0056] The content of the dispersant in the acrylic pressure-sensitive adhesive layer can be about 10 parts by weight or more, about 20 parts by weight or more, or about 40 parts by weight or more, and about 500 parts by weight or less, about 300 parts by weight or less, or about 250 parts by weight or less, relative to 100 parts by weight of the resin-coated metal pigment.

[0057] The acrylic pressure-sensitive adhesive layer can be formed on the clear film layer, on other layers constituting the laminate including the clear film layer, or on the liner using a pressure-sensitive adhesive composition containing an acrylic adhesive polymer and a resin-coated metal pigment, and optionally a dispersant, a crosslinker, a solvent, and / or other additives.

[0058] The crosslinking agent is not particularly limited as long as it can form a crosslink between the polymer chains of the acrylic adhesive polymer. By using the crosslinking agent, the cohesive force of the acrylic pressure-sensitive adhesive layer can be increased, and thus the adhesive force and holding force of the acrylic pressure-sensitive adhesive layer can be increased. For example, when the acrylic adhesive polymer is a carboxyl group-containing (meth)acrylic polymer, the crosslinking agent can be an epoxy crosslinking agent, a bisamide crosslinking agent, an aziridine crosslinking agent, a carbodiimide crosslinking agent, an isocyanate crosslinking agent, or the like. The crosslinking agent may be used alone or in combination of two or more kinds.

[0059] Examples of epoxy crosslinking agents include N,N,N',N'-tetraglycidyl-1,3-benzenedi(methaneamine) (trade names include TETRAD-X (Mitsubishi Gas Chemical Company, Inc., Chiyoda-ku, Tokyo, Japan), E-AX, and E-5XM (all of which are manufactured by Soken Chemical & Engineering Co., Ltd., Toshima-ku, Tokyo, Japan)), and N,N'-(cyclohexane-1,3-diylbismethylene)bis(diglycidylamine) (trade names include TETRAD-C (Mitsubishi Gas Chemical Company, Inc., Chiyoda-ku, Tokyo, Japan), and E-5C (Soken Chemical & Engineering Co., Ltd., Toshima-ku, Tokyo, Japan)).

[0060] Examples of bisamide crosslinking agents include 1,1'-(1,3-phenylenedicarbonyl)bis(2-methylaziridine), 1,4-bis(ethyleneiminocarbonylamino)benzene, 4,4'-bis(ethyleneiminocarbonylamino)diphenylmethane, and 1,8-bis(ethyleneiminocarbonylamino)octane.

[0061] Examples of aziridine-based crosslinking agents include 2,2-bishydroxymethylbutanol-tris[3-(1-aziridinyl)propionate (trade names are Chemitite (registered trademark) PZ-33 (Nippon Shokubai Co., Ltd., Osaka City, Osaka Prefecture, Japan) and Crosslinker CX-100 (DSM Coating Resins BV, Zwolle, Kingdom of the Netherlands).

[0062] Examples of carbodiimide crosslinking agents include Carbodilite V-03, V-05, and V-07 (all from Nisshinbo Chemical Inc., Chuo-ku, Tokyo, Japan).

[0063] Examples of isocyanate crosslinking agents include Coronate L and Coronate HK (both manufactured by Tosoh Corporation, Minato-ku, Tokyo, Japan).

[0064] The crosslinking agent can be used in an amount of about 0.01 parts by weight or more, about 0.02 parts by weight or more, or about 0.05 parts by weight or more, about 0.5 parts by weight or less, about 0.4 parts by weight or less, or about 0.3 parts by weight or less, based on 100 parts by weight of the acrylic adhesive polymer.

[0065] Examples of the solvent include methanol, ethanol, hexane, heptane, toluene, acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, butyl acetate, and the like, or mixtures of these solvents.

[0066] Examples of other additives include ultraviolet absorbers, antioxidants, heat stabilizers, fillers, and tackifiers.

[0067] The thickness of the acrylic pressure-sensitive adhesive layer is not particularly limited, and can be, for example, about 5 μm or more, about 10 μm or more, or about 20 μm or more, and about 200 μm or less, about 100 μm or less, or about 80 μm or less.

[0068] The adhesive film can be produced by a known method. For example, the pressure-sensitive adhesive composition is applied onto a liner by knife coating, bar coating, or the like, and dried to form an acrylic pressure-sensitive adhesive layer. In order to react with the optional crosslinking agent, the acrylic pressure-sensitive adhesive layer may be heated using hot air, an oven, or the like during drying. A clear film layer or a laminate including a clear film layer can be laminated onto the obtained acrylic pressure-sensitive adhesive layer by a method such as dry lamination to produce an adhesive film. The pressure-sensitive adhesive composition can also be applied directly onto the clear film layer or onto another layer constituting the laminate including the clear film layer, and dried to produce an adhesive film.

[0069] The acrylic pressure-sensitive adhesive layer may be solid, porous or foamed. The adhesive surface of the acrylic pressure-sensitive adhesive layer may be flat or uneven. The uneven adhesive surface includes an adhesive surface in which a convex portion containing a solid content or a reactant of the pressure-sensitive adhesive composition and a concave portion surrounding the convex portion are formed on the adhesive surface of the acrylic pressure-sensitive adhesive layer, and a communication path that communicates with the outside and is defined by the concave portion between the adherend surface and the adhesive surface when the adhesive layer is adhered to the adherend is formed. An example of a method for forming an uneven adhesive surface will be described below.

[0070] A liner having a release surface with a predetermined uneven structure is prepared. A pressure-sensitive adhesive composition is applied to the release surface of the liner, and heated as necessary to form an acrylic pressure-sensitive adhesive layer. This transfers the uneven structure (negative structure) of the liner to the surface of the acrylic pressure-sensitive adhesive layer that contacts the liner (this becomes the adhesive surface of the adhesive film), forming an uneven adhesive surface with a predetermined structure (positive structure) on the adhesive surface. As described above, the unevenness of the adhesive surface is designed in advance to include grooves that can form communication paths when the convex parts are adhered to the adherend.

[0071] The grooves of the acrylic pressure-sensitive adhesive layer may be formed by arranging grooves of a certain shape on the adhesive surface along a regular pattern as long as air bubbles are prevented from remaining when the adhesive film is applied, or may be formed by arranging grooves of an indefinite shape to form an irregular pattern. When a plurality of grooves are formed so as to be arranged substantially parallel to each other, the arrangement interval of the grooves is preferably about 10 μm or more and about 2000 μm or less. The depth of the groove (the distance from the adhesive surface to the bottom of the groove measured in the direction of the base layer) is usually about 10 μm or more and about 100 μm or less. The shape of the groove is also not particularly limited as long as it does not impair the effects of the present invention. For example, the shape of the groove can be substantially rectangular (including trapezoidal), substantially semicircular, or substantially semielliptical in the cross section of the groove in the direction perpendicular to the adhesive surface.

[0072] The adhesive strength of the adhesive film in one embodiment is about 2.5 N / 25 mm or more, about 3 N / 25 mm or more, or about 4 N / 25 mm or more when measured using a SUS304 plate as an adherend in accordance with JIS Z 0237:2009. The adhesive strength of the adhesive film is generally about 50 N / 25 mm or less, about 45 N / 25 mm or less, or about 40 N / 25 mm or less. In the present disclosure, the measurement procedure and conditions for the adhesive strength of the adhesive film refer to "2-3. Adhesive Strength C" described in the Examples.

[0073] The adhesive film of the present disclosure can be used for markings on vehicles, ships, aircraft, etc., the interior and exterior of buildings, illuminated signs, etc., and is particularly suitable for applications in which a metallic appearance is imparted to three-dimensional surfaces such as rough surfaces, curved surfaces, and corners. EXAMPLES

[0074] The following examples illustrate specific embodiments of the disclosure, but do not limit the invention. All parts and percentages are by weight unless otherwise specified.

[0075] The materials used to prepare the adhesive film are shown in Table 1.

[0076] [Table 1]

[0077] Example 1 A pressure-sensitive adhesive composition was prepared containing adhesive polymer 1 (ADH1), dispersant 1 (DPT1), aluminum paste 1 (AP1) and crosslinker 1 (CL1). The mass ratio of ADH1:DPT1:AP1:CL1 was 100:10:5:0.10 based on the non-volatile content. The pressure-sensitive adhesive composition was applied onto release liner 1 (L1) with a knife coater. The applied layer was dried at 95°C for 5 minutes. After drying, an acrylic pressure-sensitive adhesive layer with a thickness of 30 μm was obtained. The acrylic pressure-sensitive adhesive layer was transferred to film 1 (FL1) by laminating them together to obtain the adhesive film of Example 1.

[0078] Example 2 to Example 27 Adhesive films of Examples 2 to 27 were obtained in the same manner as in Example 1, except that the composition of the pressure-sensitive adhesive composition, the thickness of the acrylic pressure-sensitive adhesive layer, and the film were changed as shown in Table 2.

[0079] Comparative Example 1 and Comparative Example 2 Acrylic pressure-sensitive adhesive layers of Comparative Example 1 and Comparative Example 2 were formed in the same manner as in Example 1, except that the composition of the pressure-sensitive adhesive composition was changed as shown in Table 2. For Comparative Example 1 and Comparative Example 2, the appearance of the acrylic pressure-sensitive adhesive layer was unacceptable as described below, so no adhesive film was produced.

[0080] Comparative Example 3 and Comparative Example 4 Adhesive films of Comparative Example 3 and Comparative Example 4 were obtained in the same manner as in Example 1, except that the composition of the pressure-sensitive adhesive composition and the thickness of the acrylic pressure-sensitive adhesive layer were changed as shown in Table 2. The acrylic pressure-sensitive adhesive layer of the adhesive film of Comparative Example 4 did not contain aluminum paste.

[0081] [Table 2]

[0082] The adhesive films were evaluated for the following items.

[0083] 1.Appearance of acrylic pressure-sensitive adhesive layer The appearance of the acrylic pressure-sensitive adhesive layer was visually observed. An acrylic pressure-sensitive adhesive layer in which the aluminum pigment was well dispersed and the surface was smooth was rated as A. An acrylic pressure-sensitive adhesive layer in which the aluminum pigment was aggregated and the surface was rough was rated as B. An acrylic pressure-sensitive adhesive layer in which the aluminum pigment was not dispersed and the color density was low was rated as C. A rating of A was deemed to be acceptable.

[0084] 2-1. Adhesive strength A The adhesive film was cut into a rectangle of 150 mm in length and 25 mm in width to prepare a test specimen. The test specimen was attached to a melamine-coated board (Partec Co., Ltd., Hiratsuka City, Kanagawa Prefecture, Japan) at 20°C. The attachment method was in accordance with JIS Z 0237:2009. The test specimen was left at 20°C for 48 hours. The adhesive strength (N / 25mm) was measured using a tensile tester (Tensilon (registered trademark) universal testing machine, model number: RTC-1210A, A&D Co., Ltd., Toshima-ku, Tokyo, Japan) at a temperature of 20°C, a peeling speed of 300 mm / min, and a 180° peeling angle.

[0085] 2-2. Adhesive strength B The adhesive film was cut into a rectangle of 150 mm in length and 25 mm in width to prepare a test specimen. The test specimen was attached to a melamine-coated board (Partec Co., Ltd., Hiratsuka City, Kanagawa Prefecture, Japan) at 20°C. The attachment method was in accordance with JIS Z 0237:2009. The test specimen was subjected to a thermal cycle condition of 80°C to -30°C seven times. The adhesive strength (N / 25mm) was measured using a tensile tester (Tensilon (registered trademark) universal testing machine, model number: RTC-1210A, A&D Co., Ltd., Toshima-ku, Tokyo, Japan) at a temperature of 20°C, a peeling speed of 300 mm / min, and a 180° peeling angle.

[0086] 2-3. Adhesive strength C The adhesive film was cut into a rectangle of 150 mm in length and 25 mm in width to prepare a test specimen. The test specimen was attached to a SUS304BA panel (Partec Co., Ltd., Hiratsuka City, Kanagawa Prefecture, Japan) at 20°C. The attachment method was in accordance with JIS Z 0237:2009. The test specimen was left at 20°C for 1 minute. The adhesive strength (N / 25mm) was measured using a tensile tester (Tensilon (registered trademark) universal testing machine, model number: RTC-1210A, A&D Co., Ltd., Toshima-ku, Tokyo, Japan) at a temperature of 20°C, a peeling speed of 300 mm / min, and a 180° peeling angle.

[0087] 3.Heat shrinkability The adhesive film was cut into a rectangle 100 mm long and 50 mm wide to prepare a test specimen. The test specimen was attached to an aluminum panel with a roller in a 23°C environment and left for 24 hours in a 23°C environment. A cross cut was made in the test specimen with a cutter. The test specimen was then heated at 65°C for 48 hours. After heat aging, the shrinkage (mm) of the film was measured under a microscope and the maximum value was recorded.

[0088] 4.Appearance when stretched The adhesive film was cut into a square of 50 mm on each side to prepare a test specimen. The test specimen was attached to a stucco-finished board (Test Materials Co., Ltd., Chiyoda-ku, Tokyo, Japan) in an environment of 23°C. The maximum surface roughness (height from top to bottom) of the stucco-finished board was approximately 1.5 mm. The test specimen was pressed without heating using a PFA-1 rivet brush (3M Japan Co., Ltd., Shinagawa-ku, Tokyo, Japan). This caused the test specimen to partially elongate. The appearance of the adhesive film was then visually observed. Test specimens that did not change in appearance were rated A. Test specimens that changed in appearance were rated B. A rating of A was considered a pass.

[0089] 5.Surface gloss The adhesive film was cut into a 50 mm square to prepare a test specimen. The test specimen was attached to an aluminum panel in an environment of 23°C. The 60 degree gloss of the test specimen surface was measured using a portable gloss meter GMX-202 (Murakami Color Research Institute Co., Ltd., Chuo-ku, Tokyo, Japan).

[0090] 6.Weather resistance The adhesive film was cut into a rectangle of 50 mm in length and 30 mm in width to prepare a test specimen. The test specimen was attached to an aluminum panel of 1 mm thickness at room temperature using a squeegee. The test specimen was exposed to xenon light using a xenon weather resistance test device, Ci5000 Weather-Ometer (Toyo Seiki Seisakusho Co., Ltd., Kita-ku, Tokyo, Japan). The test conditions were in accordance with JIS K 5600-7-7:2008. Test specimens that did not change in appearance were rated A. Test specimens that yellowed were rated B. Test specimens that peeled off from the aluminum panel were rated C. A rating of A was considered a pass.

[0091] 7.Removability The adhesive film was cut into a rectangle of 150 mm in length and 25 mm in width to prepare a test specimen. The test specimen was attached to an aluminum panel at 20°C. The test specimen was subjected to a thermal cycle condition of 80°C to -30°C seven times. A tensile tester (Tensilon (registered trademark) universal testing machine, model number: RTC-1210A, A&D Co., Ltd., Toshima-ku, Tokyo, Japan) was used to perform 180° peeling at a temperature of 20°C and a peeling speed of 300 mm / min. The specimens in which no residue of the acrylic pressure-sensitive adhesive layer was observed on the aluminum panel were evaluated as A. The specimens in which separation was observed between the acrylic pressure-sensitive adhesive layer and the film were evaluated as B. The specimens in which residue of the acrylic pressure-sensitive adhesive layer was observed on the aluminum panel were evaluated as C.

[0092] 8. Corrosion resistance The adhesive film was cut into a rectangle of 50 mm in length and 30 mm in width to prepare a test specimen. The test specimen was attached to an aluminum panel of 1 mm thickness at room temperature using a squeegee. The test specimen was exposed to xenon light using a xenon weather resistance test device, Ci5000 Weather-Ometer (Toyo Seiki Seisakusho Co., Ltd., Kita-ku, Tokyo, Japan). The test conditions were in accordance with JIS K 5600-7-7:2008. The adhesive film surface was exposed to xenon light for 500 hours. Test specimens that showed no corrosion were rated A. Test specimens that showed corrosion were rated B. A rating of A was considered a pass.

[0093] Table 3 shows the evaluation results of the adhesive films of Examples 1 to 27 and Comparative Examples 1 to 4.

[0094] [Table 3]

[0095] It will be apparent to those skilled in the art that the above-described embodiments and examples can be modified in various ways without departing from the basic principles of the present invention. It will also be apparent to those skilled in the art that various improvements and modifications of the present invention can be made without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0096] 10 Adhesive film 12 Clear film layer 14 Acrylic pressure-sensitive adhesive layer 142 Acrylic adhesive polymer 144 Resin-coated metal pigments 16 Liner

Claims

1. An adhesive film having a metallic appearance, comprising a clear film layer and an acrylic pressure-sensitive adhesive layer, the acrylic pressure-sensitive adhesive layer contains an acrylic adhesive polymer and a resin-coated metal pigment; The glass transition temperature of the acrylic adhesive polymer is −25° C. or lower, The acrylic pressure-sensitive adhesive layer contains 5 to 100 parts by mass of the resin-coated metal pigment based on 100 parts by mass of the acrylic adhesive polymer.

2. The adhesive film of claim 1 , wherein the resin-coated metal pigment has an acrylic resin coating.

3. 3. The adhesive film according to claim 1, wherein the resin-coated metal pigment comprises aluminum.

4. 3. An adhesive film according to claim 1, wherein the resin-coated metal pigment is scaly.

5. 3. The adhesive film according to claim 1, wherein the clear film layer has a visible light transmittance of 70% or more.

6. The adhesive film according to claim 1 or 2, wherein the adhesive film has an adhesive strength of 2.5 N / 25 mm or more when measured using a SUS304 plate as an adherend in accordance with JIS Z 0237:2009.

7. 3. The adhesive film according to claim 1, wherein the content of the pigment other than the resin-coated metal pigment in the acrylic pressure-sensitive adhesive layer is less than 5 parts by mass based on 100 parts by mass of the acrylic adhesive polymer.

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