Synthetic resin sheet for easily peelable decorative sheet and easily peelable decorative sheet and decorative board using same

Abstract

The present invention provides a synthetic resin sheet for an easily peelable decorative sheet and an easily peelable decorative sheet and a decorative board that use the synthetic resin sheet. The synthetic resin sheet makes it possible to produce a decorative board by sticking a decorative sheet to a decorative board base material at a construction site without lowering the production efficiency of the decorative board and also makes it possible to use a simple process to easily peel the decorative sheet after the decorative board has been used. Specifically, the present invention provides a synthetic resin sheet for an easily peelable decorative sheet, (1) the synthetic resin sheet being more than 80 μm thick, and (2) the synthetic resin sheet being an unfoamed sheet that contains a synthetic resin and a thermal decomposition–type foaming agent, the thermal decomposition–type foaming agent content being 1.0–5.0 parts by mass per 100 parts by mass of the synthetic resin.

Description

Synthetic resin sheet for easily peelable decorative sheet, and easily peelable decorative sheet and decorative board using the same

[0001] The present invention relates to a synthetic resin sheet for an easily peelable decorative sheet, and to an easily peelable decorative sheet and decorative board using the same.

[0002]

[0003] Conventionally, various decorative sheets have been used for the surface decoration of fixtures, floors, walls, etc. used in the interior and exterior of buildings. For example, decorative sheets composed of a laminate including, in order in the thickness direction, a base sheet, a decorative layer (a solid decorative layer and / or a picture pattern layer), and a surface protective layer have been widely used. These decorative sheets are laminated on various decorative board substrates (called adherends, including, for example, wood, metal, plastic, etc.) depending on the application, and are used as decorative boards in various fields.

[0003]

[0003] Conventionally, decorative boards have been discarded together with the decorative board substrate after their useful life has expired. However, from the viewpoint of effective resource utilization, attempts have been made to recycle the decorative board substrate by peeling the decorative sheet from used decorative boards. For example, one method involves blending a thermally decomposable foaming agent into the adhesive layer that bonds the decorative board substrate and the decorative sheet, and then heat-treating the used decorative board to foam the adhesive layer and reduce the cohesive strength of the adhesive, thereby peeling off the decorative sheet. For example, the background art section of Patent Document 1 describes methods of foaming the adhesive layer to reduce the peel force, or irradiating the adhesive layer with ultraviolet light to inactivate the adhesive and reduce the peel force.

[0004]

[0003] Decorative boards are usually produced on-site by laminating a decorative sheet to a decorative board substrate using an adhesive. However, if the adhesive contains a thermally decomposable foaming agent, it is considered desirable to laminate the decorative board substrate and the decorative sheet at a factory rather than at the construction site, from the standpoint of adhesive shelf life. This is because lamination on-site requires different management and processes than usual, such as replacing the adhesive with a regular adhesive, drying conditions tailored to the adhesive composition, and curing time and temperature after lamination to the decorative board substrate, due to the adhesive containing a thermally decomposable foaming agent. Therefore, it is considered difficult to increase the efficiency of decorative board production using a method in which a thermally decomposable foaming agent is contained in the adhesive used to laminate the decorative board substrate and the decorative sheet.

[0005] Japanese Patent Application Publication No. 2009-40849

[0006] The present invention aims to provide a synthetic resin sheet for easily peelable decorative sheets that can be used to produce decorative sheets by bonding a decorative sheet substrate and a decorative sheet at a construction site without reducing the efficiency of producing the decorative sheets, and that can easily peel the decorative sheet after use of the decorative sheet with a simple process, as well as easily peelable decorative sheets and decorative sheets using the same.

[0007] As a result of extensive research, the present inventors have discovered that the above object can be achieved when a specific synthetic resin sheet containing a thermally decomposable foaming agent is used as a synthetic resin layer (so-called backer layer) of a decorative sheet, and have thus completed the present invention.

[0008] That is, the present invention relates to the following synthetic resin sheet for easily peelable decorative sheet, and easily peelable decorative sheet and decorative board using the same. Item 1. A synthetic resin sheet for easily peelable decorative sheet, characterized in that (1) the synthetic resin sheet has a thickness of more than 80 μm, and (2) the synthetic resin sheet is an unfoamed sheet containing a synthetic resin and a thermally decomposable foaming agent, and the content of the thermally decomposable foaming agent per 100 parts by mass of the synthetic resin is 1.0 part by mass or more and 5.0 parts by mass or less. Item 2. The synthetic resin sheet according to Item 1 above, wherein the synthetic resin contains an ethylene-vinyl acetate copolymer resin (EVA). Item 3. The synthetic resin sheet according to Item 1 or 2 above, wherein the thermally decomposable foaming agent is an azodicarbonamide (ADCA)-based thermally decomposable foaming agent. Item 4. The synthetic resin sheet according to any one of Items 1 to 3 above, wherein the thickness of the synthetic resin sheet is 85 μm or more and 240 μm or less. Item 5. An easily peelable decorative sheet comprising a decorative sheet intermediate having at least a picture pattern layer on a base sheet, and the synthetic resin sheet according to any one of Items 1 to 4 above as a synthetic resin layer below the decorative sheet intermediate. Item 6. An easily peelable decorative sheet according to Item 5 above, wherein the decorative sheet intermediate has a surface protective layer made of a cured product of an ionizing radiation curable resin composition. Item 7. An easily peelable decorative sheet according to Item 6 above, wherein the surface protective layer contains at least one selected from the group consisting of an antibacterial agent, an antiviral agent, and an allergen reducing agent. Item 8. An easily peelable decorative sheet according to Item 7 above, wherein the decorative sheet intermediate has, on the base sheet, the picture pattern layer, a transparent resin layer, a primer layer, and the surface protective layer in this order in the thickness direction. Item 9. A decorative board comprising the easily peelable decorative sheet according to any one of Items 5 to 8 above on a decorative board substrate. Item 10. Item 11. The decorative board according to item 9, wherein the front surface of the decorative board has a hardness of F or more as measured by a pencil scratch hardness test in accordance with JIS K 5600-5-4: 1999. Item 12. The decorative board according to item 9 or 10, wherein the decorative board substrate is a metal steel plate.

[0009] According to the synthetic resin sheet for easily peelable decorative sheet of the present invention, by using it as a synthetic resin layer (so-called backer layer) of the decorative sheet, it is possible to produce a decorative sheet by bonding the decorative sheet substrate and the decorative sheet at the construction site without reducing the efficiency of producing the decorative sheet, and after using the decorative sheet, the decorative sheet can be easily peeled off by a simple process, thereby facilitating the recycling of the decorative sheet substrate.

[0010] Fig. 1 is a cross-sectional schematic diagram showing an example of a synthetic resin sheet (A) for an easily peelable decorative sheet of the present invention, and an easily peelable decorative sheet (B) and decorative board (C) using the same. Fig. 2 is a cross-sectional schematic diagram showing an example of foaming the synthetic resin sheet (A) after use of the decorative board (C) of the present invention to form a foamed synthetic resin sheet (AA). Fig. 3 is a cross-sectional schematic diagram showing an example of an embodiment in which the foamed synthetic resin sheet (AA) is torn after use of the decorative board (C) of the present invention to peel off the decorative sheet (B).

[0011] 1. Synthetic resin sheet for easily peelable decorative sheet, and easily peelable decorative sheet The synthetic resin sheet for easily peelable decorative sheet of the present invention is a synthetic resin sheet that can be used as a constituent member of the easily peelable decorative sheet of the present invention (particularly a synthetic resin layer as a so-called backer layer), and is characterized by satisfying the following requirements: (1) the synthetic resin sheet has a thickness of more than 80 μm, (2) the synthetic resin sheet is an unfoamed sheet containing a synthetic resin and a thermally decomposable foaming agent, and the content of the thermally decomposable foaming agent per 100 parts by mass of the synthetic resin is 1.0 part by mass or more and 5.0 parts by mass or less.

[0012] The synthetic resin sheet for the easily peelable decorative sheet of the present invention (hereinafter also referred to as the "synthetic resin sheet of the present invention") having the above-mentioned characteristics can be used as a synthetic resin layer (so-called backer layer; the same applies hereinafter) of the easily peelable decorative sheet of the present invention (hereinafter also referred to as the "decorative sheet of the present invention"), allowing a decorative sheet to be produced at the construction site by laminating the decorative sheet of the present invention to a decorative sheet substrate without reducing the efficiency of decorative sheet production, and after use of the decorative sheet, the decorative sheet can be easily peeled off by a simple process. Specifically, a decorative sheet having the synthetic resin sheet of the present invention as a synthetic resin layer can be produced in a factory, and at the construction site, a decorative sheet can be produced by laminating the decorative sheet of the present invention to a decorative sheet substrate using a conventional adhesive. Furthermore, after use of the decorative sheet, the decorative sheet can be separated from the decorative sheet substrate by heat-treating the decorative sheet to foam the synthetic resin sheet (synthetic resin layer), and the foamed layer can be broken to peel off the decorative sheet. Therefore, by using the synthetic resin sheet of the present invention, the decorative sheet substrate can be easily separated from the decorative sheet, promoting recycling. In a preferred embodiment of the present invention, the synthetic resin sheet (synthetic resin layer) is foamed by heat treatment at about 220°C, and the foamed layer is broken to peel off the decorative sheet, and the synthetic resin sheet is preferably prepared so as to obtain such foaming characteristics. Note that if the synthetic resin sheet itself is heat resistant in a heat resistance test at 180°C (a 180°C heat resistance test using edible oil in accordance with JIS K 6902), it can be used appropriately as an interior or exterior decoration for a building without causing unintended foaming during actual use of the decorative panel.

[0013] The layer structure of the decorative sheet of the present invention is not particularly limited as long as the synthetic resin sheet of the present invention is used as the synthetic resin layer, but examples include a layer structure comprising a decorative sheet intermediate having at least a picture pattern layer on a base sheet, and the synthetic resin sheet of the present invention as a synthetic resin layer below the decorative sheet intermediate. Among these, it is preferable that the decorative sheet intermediate has a surface protective layer made of a cured product of an ionizing radiation curable resin composition, and it is particularly preferable that the decorative sheet intermediate have a layer structure comprising, on a base sheet, a picture pattern layer, a transparent resin layer, a primer layer, and the surface protective layer in this order in the thickness direction.

[0014] Figure 1 is a cross-sectional schematic diagram showing an example of a synthetic resin sheet (A) for an easily peelable decorative sheet of the present invention, and an easily peelable decorative sheet (B) and decorative board (C) using the same. Hereinafter, the synthetic resin sheet (A) of the present invention will be described as the synthetic resin layer (so-called backer layer) of the decorative sheet (B) of the present invention, with reference to Figure 1 as an example. In Figure 1, the direction in which the surface protective layer 6 is located as viewed from the base sheet 1 of the decorative sheet is referred to as the "upper" side, "front" side, "front surface" side, etc., and the direction in which the synthetic resin sheet 8 is located as viewed from the base sheet 1 is referred to as the "lower" side, "back" side, "rear" side, etc.

[0015] The decorative sheet (B) of the present invention shown in Figure 1 has, in order in the thickness direction, a picture pattern layer 2, an adhesive layer 3, a transparent resin layer 4, a primer layer 5, and a surface protective layer 6 laminated on a base sheet 1, and a synthetic resin sheet 8 laminated on the back surface of the base sheet 1 via a back primer layer 7 and an adhesive layer 9. Here, the synthetic resin sheet 8 is the synthetic resin layer (so-called backer layer) of the decorative sheet (B), which exhibits the specified easy peelability of the present application after foaming and also functions as a synthetic resin layer (so-called backer layer) to improve the scratch resistance, impact resistance, etc. of the decorative board (C). In Figure 1, the decorative board (C) is formed by laminating the decorative sheet (B) on a decorative board substrate 11 via an adhesive layer 10.

[0016] After the useful life of the decorative board (C) has elapsed, the decorative board (C) can be heat-treated to foam the synthetic resin sheet (A), and the foamed layer can be broken to peel off the decorative sheet (B), thereby separating it from the decorative board substrate 11. Therefore, by using the synthetic resin sheet 8 of the present invention, the decorative board substrate 11 can be separated from the decorative board (C), facilitating recycling.

[0017] Each layer constituting the decorative sheet of the present invention will be explained below with reference to Figure 1. In the following description, the lower and upper limits of numerical ranges expressed by "to" mean "greater than or equal to" (for example, if α to β, it means greater than or equal to α and less than or equal to β).

[0018] Substrate Sheet 1 As the substrate sheet, a sheet made of a synthetic resin such as a polyolefin resin, a polyester resin, a polyacrylic resin, a polyamide resin, a polyurethane resin, a polystyrene resin, or a polyvinyl chloride resin can be used. The substrate sheet may be a sheet made of a synthetic resin containing only one of the above resins, or a sheet made of a synthetic resin containing a mixture of two or more of the above resins. Among these, a sheet made of a polyolefin resin or a polyester resin is preferred as the substrate sheet.

[0019] Examples of the polyolefin resin include thermoplastic polyolefin resins, such as polyethylene, ethylene-α-olefin copolymer, polypropylene, polymethylpentene, polybutene, ethylene-propylene copolymer, propylene-butene copolymer, ethylene-vinyl acetate copolymer, saponified ethylene-vinyl acetate copolymer, ethylene-(meth)acrylic acid copolymer, and ethylene-(meth)acrylic acid ester copolymer. Of these, polypropylene is preferred.

[0020] Examples of polyester resins include polyethylene terephthalate, highly heat-resistant polyalkylene terephthalate (for example, polyethylene terephthalate in which part of the ethylene glycol has been substituted with 1,4-cyclohexanedimethanol, diethylene glycol, or the like, known as PET-G (manufactured by Eastman Chemical Company)), polybutylene terephthalate, polyethylene naphthalate, polyethylene naphthalate-isophthalate copolymer, etc. Among these, highly heat-resistant polyalkylene terephthalate is preferred.

[0021] The thickness of the substrate sheet is not limited, but is preferably 50 to 90 μm, more preferably 60 to 80 μm. A sheet made of polypropylene is particularly preferred as the substrate sheet.

[0022] The substrate sheet may be colored as necessary. The surface may be subjected to a surface treatment such as corona discharge treatment, plasma treatment, or ozone treatment, or may be coated with a primer layer to improve adhesion to adjacent layers.

[0023] The pattern layer 2 provides the decorative sheet with a desired pattern (design), and the type of pattern is not limited. Examples include wood grain, leather, stone, sand, tile, brickwork, fabric, geometric shapes, letters, symbols, and abstract patterns.

[0024] The method for forming the picture pattern layer is not particularly limited, and for example, the picture pattern layer may be formed on the front surface of the substrate sheet by a printing method using an ink obtained by dissolving (or dispersing) a known colorant (dye or pigment) together with a binder resin in a solvent (or dispersion medium). From the viewpoint of reducing VOCs in the decorative sheet, an aqueous composition can also be used as the ink.

[0025] Examples of colorants include inorganic pigments such as carbon black, titanium white, zinc white, red iron oxide, iron blue, and cadmium red; organic pigments such as azo pigments, lake pigments, anthraquinone pigments, quinacridone pigments, phthalocyanine pigments, isoindolinone pigments, and dioxazine pigments; metal powder pigments such as aluminum powder and bronze powder; pearlescent pigments such as titanium oxide-coated mica and bismuth oxide chloride; fluorescent pigments; and luminous pigments. These colorants can be used alone or in combination. These colorants may be used together with fillers such as silica, extender pigments such as organic beads, neutralizers, surfactants, and the like.

[0026] Examples of binder resins that can be used include hydrophilically treated polyester-based urethane resins, polyesters, polyacrylates, polyvinyl acetates, polybutadiene, polyvinyl chloride, chlorinated polypropylene, polyethylene, polystyrene, polystyrene-acrylate copolymers, rosin derivatives, alcohol adducts of styrene-maleic anhydride copolymers, and cellulose-based resins. Specific examples include polyacrylamide-based resins, poly(meth)acrylic acid-based resins, polyethylene oxide-based resins, poly(N-vinylpyrrolidone)-based resins, water-soluble polyester-based resins, water-soluble polyamide-based resins, water-soluble amino-based resins, water-soluble phenol-based resins, and other water-soluble synthetic resins; and water-soluble natural polymers such as polynucleotides, polypeptides, and polysaccharides. Other examples include natural rubber, synthetic rubber, polyvinyl acetate-based resins, (meth)acrylic resins, polyvinyl chloride-based resins, and polyurethane-polyacrylic resins. The above binder resins can be used alone or in combination of two or more.

[0027] Examples of solvents (or dispersion media) include petroleum-based organic solvents such as hexane, heptane, octane, toluene, xylene, ethylbenzene, cyclohexane, and methylcyclohexane; ester-based organic solvents such as ethyl acetate, butyl acetate, 2-methoxyethyl acetate, and 2-ethoxyethyl acetate; alcohol-based organic solvents such as methyl alcohol, ethyl alcohol, normal propyl alcohol, isopropyl alcohol, isobutyl alcohol, ethylene glycol, and propylene glycol; ketone-based organic solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ether-based organic solvents such as diethyl ether, dioxane, and tetrahydrofuran; chlorine-based organic solvents such as dichloromethane, carbon tetrachloride, trichloroethylene, and tetrachloroethylene; and inorganic solvents such as water. These solvents (or dispersion media) can be used alone or in combination of two or more.

[0028] Examples of printing methods used to form the picture pattern layer include gravure printing, offset printing, screen printing, flexographic printing, electrostatic printing, and inkjet printing. Furthermore, when forming a colored concealing layer (a fully solid picture pattern layer) described below, examples of coating methods include roll coating, knife coating, air knife coating, die coating, lip coating, comma coating, kiss coating, flow coating, and dip coating. Other methods include hand-drawing, ink-flowing, photography, transfer printing, laser beam writing, electron beam writing, partial vapor deposition of metals or the like, and etching, and may be combined with other forming methods.

[0029] The thickness of the picture pattern layer is not limited and can be set appropriately depending on the product characteristics, but is preferably about 0.1 to 10 μm.

[0030] Colored Concealing Layer In the decorative sheet of the present invention, a colored concealing layer may be further formed between the substrate sheet and the picture pattern layer.

[0031] The colored concealing layer is only required to be able to conceal the base color of the adherend when the decorative sheet and the adherend are joined together, and is usually formed so as to cover the base sheet.

[0032] The colored concealing layer can be formed by the above-mentioned known printing methods, and the ink used to form the picture pattern layer can be used as it is.

[0033] The coating amount (dry mass) of the colored hiding layer is 2 to 30 g / m ２ The thickness of the colored concealing layer is usually about 0.1 to 20 μm, preferably about 1 to 10 μm.

[0034] Adhesive Layer 3 In order to improve adhesion between the transparent resin layer and the picture pattern layer described below, an adhesive layer is formed on the picture pattern layer. The adhesive layer is preferably a transparent adhesive layer. The transparency of the transparent adhesive layer includes, for example, colorless transparency, colored transparency, translucency, etc.

[0035] The adhesive is not particularly limited, and any adhesive known in the field of decorative sheets can be used.

[0036] Adhesives known in the field of decorative sheets include, for example, thermoplastic resins such as polyamide resins, acrylic resins, and vinyl acetate resins; and thermosetting resins such as urethane resins. These adhesives can be used alone or in combination of two or more. Two-component curing polyurethane resins or polyester resins using isocyanate as a curing agent can also be used.

[0037] The adhesive layer can be formed by the above-mentioned known printing method.

[0038] The thickness (dry thickness) of the adhesive layer is not limited, but is preferably about 0.1 to 30 μm, more preferably about 1 to 20 μm, and even more preferably about 5 to 15 μm.

[0039] Transparent Resin Layer 4 A transparent resin layer is formed on the picture pattern layer.

[0040] The transparent resin layer is not particularly limited as long as it is transparent, and may be colorless and transparent, colored and transparent, translucent, etc. Examples of resins constituting the transparent resin layer include polyethylene, ethylene-α-olefin copolymer, polypropylene such as homopolypropylene and random polypropylene, polymethylpentene, polybutene, ethylene-propylene copolymer, propylene-butene copolymer, ethylene-vinyl acetate copolymer, saponified ethylene-vinyl acetate copolymer, ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylic acid ester copolymer, olefin-based resins such as olefin-based elastomers, polyethylene terephthalate, polybutylene terephthalate, polyamide, ionomer, acrylic acid ester-based polymer, methacrylic acid ester-based polymer, polycarbonate, cellulose triacetate, etc. These resins may be used alone or in combination of two or more.

[0041] The transparent resin layer is preferably a transparent thermoplastic resin layer, and more preferably contains a polyolefin-based resin such as a polypropylene resin or a polyethylene resin. The transparent resin layer is even more preferably a polyolefin-based resin layer. Furthermore, the resin constituting the transparent resin layer is even more preferably the above-mentioned olefin-based resin or ionomer-based resin. The transparent resin layer is particularly preferably a polypropylene resin layer.

[0042] The transparent resin layer may be colored as long as it has transparency, but it is preferable not to blend a colorant therein.

[0043] The thickness of the transparent resin layer is not limited, but is preferably 40 to 120 μm, more preferably 50 to 110 μm, and even more preferably 60 to 100 μm.

[0044] Primer Layer 5 A primer layer is formed on the transparent resin layer.

[0045] The primer layer can be formed by applying a known primer agent to the front surface of the transparent resin layer. Examples of the primer agent include a urethane resin-based primer agent made of an acrylic-modified urethane resin (acrylic urethane-based resin), a primer agent made of a urethane-cellulose-based resin (e.g., a resin obtained by adding hexamethylene diisocyanate to a mixture of urethane and soluble nitrocellulose), and a resin-based primer agent made of an acrylic-urethane block copolymer.

[0046] The primer agent may contain additives as needed. Examples of additives include fillers such as calcium carbonate and clay, flame retardants such as magnesium hydroxide, antioxidants, lubricants, foaming agents, ultraviolet absorbers, and light stabilizers. The amount of additives added can be appropriately determined depending on the product characteristics.

[0047] The amount of primer applied (dry mass) is not particularly limited, but is usually 0.1 to 100 g / m ２ , preferably 0.1 to 50 g / m ２ That's about it.

[0048] The thickness of the primer layer is not limited, but is preferably about 0.01 to 10 μm, and more preferably about 0.1 to 1 μm.

[0049] Surface Protective Layer 6 A surface protective layer is formed as the outermost layer of the decorative sheet.

[0050] The resin forming the surface protective layer is preferably a curable resin. The resin forming the surface protective layer is more preferably at least one resin selected from the group consisting of thermoplastic resins, thermosetting resins, and ionizing radiation curable resins. From the viewpoints of high surface hardness, productivity, etc., the resin forming the surface protective layer is particularly preferably an ionizing radiation curable resin. Furthermore, from the viewpoint of further improving weather resistance, the ionizing radiation curable resin is most preferably an electron beam curable resin. The surface protective layer is not particularly limited as long as it is transparent, and may be colorless and transparent, colored and transparent, translucent, etc.

[0051] Examples of thermoplastic resins include vinyl chloride resin, polypropylene resin, polyethylene resin, and polyester resin.

[0052] Examples of thermosetting resins include unsaturated polyester resins, polyurethane resins (including two-component curing polyurethanes), epoxy resins, aminoalkyd resins, phenolic resins, urea resins, diallyl phthalate resins, melamine resins, guanamine resins, melamine-urea co-condensation resins, silicon resins, and polysiloxane resins.

[0053] The surface protective layer preferably contains an ionizing radiation curable resin or a two-component curable urethane resin. When the surface protective layer contains these resins, it is easy to further improve the abrasion resistance, impact resistance, contamination resistance, scratch resistance, weather resistance, etc. of the decorative sheet. The surface protective layer is more preferably made of a cured product of an ionizing radiation curable resin composition. The surface protective layer is particularly preferably made of a cured product of an electron beam curable resin composition.

[0054] The resins may contain crosslinking agents, polymerization initiators, curing agents, polymerization accelerators, etc. For example, curing agents such as isocyanates and organic sulfonates may be added to unsaturated polyester resins and polyurethane resins, organic amines may be added to epoxy resins, and peroxides such as methyl ethyl ketone peroxide and radical initiators such as azoisobutylnitrile may be added to unsaturated polyester resins.

[0055] Examples of methods for forming a surface protective layer using a thermosetting resin include applying a solution of the thermosetting resin by a coating method such as roll coating or gravure coating, followed by drying and curing. The amount of the solution applied (dry thickness) is preferably about 5 to 50 μm, and more preferably about 5 to 40 μm.

[0056] The ionizing radiation curable resin is not limited as long as it undergoes a crosslinking polymerization reaction upon irradiation with ionizing radiation and changes into a three-dimensional polymer structure. For example, one or more prepolymers, oligomers, and monomers having a polymerizable unsaturated bond or an epoxy group in the molecule that can be crosslinked upon irradiation with ionizing radiation can be used. Examples include acrylate resins such as urethane acrylate, polyester acrylate, and epoxy acrylate; silicon resins such as siloxane; polyester resins; and epoxy resins. As the ionizing radiation curable resin, urethane acrylate oligomers are preferred.

[0057] Ionizing radiation includes ultraviolet rays (near ultraviolet rays, vacuum ultraviolet rays, etc.), X-rays, electron beams, ion beams, etc., and among these, ultraviolet rays or electron beams are preferred, with electron beams being more preferred.

[0058] The ultraviolet light source may be an ultra-high pressure mercury lamp, a high pressure mercury lamp, a low pressure mercury lamp, a carbon arc lamp, a black light fluorescent lamp, or a metal halide lamp. The wavelength of the ultraviolet light is about 190 to 380 nm.

[0059] As the electron beam source, for example, an electron beam accelerator such as a Cockcroft-Waldt type, Van de Graaf type, resonant transformer type, insulating core transformer type, linear type, dynamitron type, or high frequency type can be used. The energy of the electron beam is preferably about 100 to 1000 keV, more preferably about 100 to 300 keV. The dose of the electron beam is preferably about 2 to 15 Mrad.

[0060] Ionizing radiation curable resins are sufficiently cured by irradiation with electron beams, but when curing is performed by irradiation with ultraviolet rays, it is preferable to add a photopolymerization initiator (sensitizer).

[0061] In the case of a resin system having a radically polymerizable unsaturated group, the photopolymerization initiator may be, for example, at least one of acetophenones, benzophenones, thioxanthones, benzoin, benzoin methyl ether, Michler's benzoyl benzoate, Michler's ketone, diphenyl sulfide, dibenzyl disulfide, diethyl oxide, triphenylbiimidazole, isopropyl-N,N-dimethylaminobenzoate, etc. In the case of a resin system having a cationically polymerizable functional group, the photopolymerization initiator may be, for example, at least one of aromatic diazonium salts, aromatic sulfonium salts, metallocene compounds, benzoin sulfonate esters, furyloxysulfoxonium diallyliodosyl salts, etc.

[0062] The amount of the photopolymerization initiator to be added is not particularly limited, but is generally 0.1 to 10 parts by mass per 100 parts by mass of the ionizing radiation curable resin.

[0063] When forming a surface protective layer using an ionizing radiation curable resin, the layer can be formed, for example, by applying a solution of the ionizing radiation curable resin by a coating method such as gravure coating or roll coating, and then irradiating the coating film with ionizing radiation.

[0064] The thickness of the surface protective layer is not limited depending on the desired surface performance, but is preferably 3 to 45 μm, more preferably 5 to 35 μm, and even more preferably 10 to 25 μm. When the surface protective layer is 3 μm or more, the abrasion resistance of the decorative sheet is further improved. Furthermore, when the surface protective layer is 45 μm or less, warping and whitening of the decorative sheet are further suppressed.

[0065] To further impart scratch resistance and abrasion resistance to a surface protective layer formed from an ionizing radiation curable resin, an inorganic filler may be blended in. Examples of inorganic fillers include powdered aluminum oxide, silicon carbide, silicon dioxide, calcium titanate, barium titanate, magnesium pyroborate, zinc oxide, silicon nitride, zirconium oxide, chromium oxide, iron oxide, boron nitride, diamond, emery sand, and glass fiber.

[0066] The surface protective layer may contain various additives, such as a solvent, a colorant such as a dye or a pigment, an inorganic filler such as an inorganic filler, an antifoaming agent, a leveling agent, a thixotropy-imparting agent, a flame retardant, an antibacterial agent, an antiviral agent, or an allergen-reducing agent, as needed.

[0067] The surface protective layer preferably contains at least one selected from the group consisting of an antibacterial agent, an antiviral agent, and an allergen reducing agent.

[0068] The inorganic filler can be used as a means for imparting predetermined surface properties to the surface protective layer by incorporating an inorganic filler having a thickness greater than that of the surface protective layer. The inorganic filler can also be used as a matting agent, and incorporating the inorganic filler in the surface protective layer is expected to have the effect of suppressing cure shrinkage of the surface protective layer. Therefore, in the present invention, it is preferable that the inorganic filler has been surface-treated (hydrophobized). Furthermore, among these additives, it is preferable that at least one selected from the group consisting of antibacterial agents, antiviral agents, and allergen-reducing agents be incorporated into the surface protective layer, which is the outermost layer, in order to facilitate the attainment of the desired effect.

[0069] When an inorganic filler is added to the surface protective layer, the amount of the inorganic filler added is about 1 to 80 parts by mass per 100 parts by mass of the ionizing radiation curable resin.

[0070] The antibacterial agent includes inorganic antibacterial agents and organic antibacterial agents. In particular, inorganic antibacterial agents are desirable because they are generally safer than organic antibacterial agents and have excellent durability and heat resistance. Inorganic antibacterial agents are antibacterial metals such as silver, copper, and zinc supported on various inorganic carriers. When the surface protective layer contains an antibacterial agent, the content of the antibacterial agent is preferably 0.1 to 10 parts by mass per 100 parts by mass of the resin component of the surface protective layer, but the details can be adjusted appropriately depending on the type of antibacterial agent.

[0071] The antiviral agents can generally be broadly divided into organic and inorganic types. Organic antiviral agents include quaternary ammonium salts, quaternary phosphonium salts, pyridines, pyrithiones, benzimidazoles, organic iodines, isothiazolinones, anions, and ethers. Inorganic antiviral agents include those in which metal ions such as silver, copper, and zinc are supported on a carrier such as zeolite, apatite, zirconia, glass, or molybdenum oxide. When the surface protective layer contains an antiviral agent, the content of the antiviral agent is preferably 0.1 to 10 parts by mass per 100 parts by mass of the resin component of the surface protective layer, but the details can be adjusted appropriately depending on the type of antiviral agent.

[0072] Among the organic antiviral agents, benzimidazole-based antiviral agents, anionic-based antiviral agents, or ether-based antiviral agents that maintain a particle shape are particularly preferred. "Maintaining a particle shape" here means that the agent exists in a particle state without dissolving in the composition (the ink before curing) that becomes the curable resin of the surface protective layer. Therefore, during the process of forming the surface protective layer, particles of imidazole-based compounds, particles of anionic compounds, or particles of ether-based compounds tend to float up, making it easier to unevenly distribute the particles of imidazole-based compounds, anionic compounds, or particles of ether-based compounds on the outermost surface side of the surface protective layer. Furthermore, unevenly distributing the particles of imidazole-based compounds, anionic compounds, or particles of ether-based compounds on the outermost surface side of the surface protective layer can reduce the amount of antiviral agent added necessary to achieve a predetermined antiviral property, thereby making it easier to prevent a decrease in the scratch resistance of the surface protective layer.

[0073] The anionic antiviral agent preferably contains, for example, a styrene resin, a styrene polymer derivative compound, and an unsaturated carboxylic acid derivative compound. Furthermore, the styrene polymer derivative compound and the unsaturated carboxylic acid derivative compound preferably contain at least one structure selected from the groups consisting of styrene, sodium sulfonate, acrylic acid, maleic acid, and fumaric acid, and more preferably contain all of these structures. This is because viruses are broadly classified into two types, those with and without envelopes, and it is believed that the structures of antiviral agents that can effectively inhibit the activity of each type differ. Therefore, for example, if effectiveness against only influenza viruses, which are non-enveloped viruses, is desired, it is sufficient to contain only a styrene polymer derivative compound, and in some cases, sufficient effectiveness can be obtained by containing only a simple styrene resin.

[0074] As the inorganic antiviral agent, a silver-based antiviral agent is preferable from the viewpoint of being non-toxic to living organisms and excellent in safety, and among these, a phosphate glass-supported silver compound, a silver zeolite compound, and a molybdenum oxide-silver double salt compound are more preferable because they exhibit antiviral activity even in small amounts and therefore the amount added can be reduced.

[0075] As antiviral agents, phosphate-based glass silver-supported compounds are particularly preferred.

[0076] When the silver-based antiviral agent is contained in the surface protective layer, discoloration may occur depending on the surface protective layer (the discoloration may occur due to heat or light in the paint state to which the agent is added, or may occur due to heat or light after the surface protective layer is formed), but in this case, it is possible to improve the situation by appropriately adding an ultraviolet inhibitor, a light stabilizer, etc. For example, the use of a benzotriazole-based compound for the molybdenum oxide silver double salt compound can be expected to have an effect of improving discoloration.

[0077] The allergen reducing agent contains either an inorganic compound or an organic compound, and may be used alone or in combination of two or more different compounds. The inorganic compound is preferably a metal-supported material. When the surface protective layer contains an allergen reducing agent, the amount of the allergen reducing agent added is preferably 0.1 to 10 parts by mass per 100 parts by mass of the resin component of the surface protective layer, but the amount can be adjusted appropriately depending on the type of allergen reducing agent.

[0078] Back primer layer 7 A back primer layer is formed under (on the back side of) the base sheet. The provision of the back primer layer is advantageous for adhesion between the base sheet and the synthetic resin sheet.

[0079] The back primer layer can be formed by applying a known primer agent to the front surface of the transparent resin layer. Examples of primer agents include urethane resin-based primer agents made from acrylic-modified urethane resin (acrylic urethane-based resin), urethane-cellulose-based resin (e.g., a resin obtained by adding hexamethylene diisocyanate to a mixture of urethane and soluble nitrocellulose), and resin-based primer agents made from a block copolymer of acrylic and urethane.

[0080] The primer agent may contain additives as needed. Examples of additives include fillers such as calcium carbonate and clay, flame retardants such as magnesium hydroxide, antioxidants, lubricants, foaming agents, ultraviolet absorbers, and light stabilizers. The amount of additives added can be appropriately determined depending on the product characteristics.

[0081] The amount of primer applied (dry mass) is not particularly limited, but is usually 0.1 to 100 g / m ２ about 0.1 to 50 g / m ２ That's about it.

[0082] The thickness of the back primer layer is not limited, but is preferably about 0.01 to 10 μm, and more preferably about 0.1 to 1 μm.

[0083] Adhesive Layer 9 In order to obtain adhesion between the synthetic resin sheet (synthetic resin layer serving as a backer layer) described later and the back primer layer, an adhesive layer is formed under the back primer layer. The adhesive layer may or may not be transparent. The definition of transparency is as described above.

[0084] The adhesive is not particularly limited, and any adhesive known in the field of decorative sheets can be used.

[0085] Adhesives known in the field of decorative sheets include, for example, thermoplastic resins such as polyamide resins, acrylic resins, and vinyl acetate resins; and thermosetting resins such as urethane resins. These adhesives can be used alone or in combination of two or more. Two-component curing polyurethane resins or polyester resins using isocyanate as a curing agent can also be used.

[0086] The adhesive layer can be formed by the above-mentioned known printing method.

[0087] The thickness (dry thickness) of the adhesive layer is not limited, but is preferably about 0.1 to 30 μm, more preferably about 1 to 20 μm, and even more preferably about 5 to 15 μm.

[0088] Synthetic Resin Sheet 8 The synthetic resin sheet of the present invention is a member that forms the synthetic resin layer (so-called backer layer) of the decorative sheet of the present invention, and is characterized by satisfying the following requirements: (1) the synthetic resin sheet has a thickness of more than 80 μm, and (2) the synthetic resin sheet is an unfoamed sheet containing a synthetic resin and a thermally decomposable foaming agent, and the content of the thermally decomposable foaming agent per 100 parts by mass of the synthetic resin is 1.0 part by mass or more and 5.0 parts by mass or less.

[0089] The synthetic resin sheet of the present invention is an unfoamed sheet containing a synthetic resin and a thermally decomposable foaming agent, and functions as the synthetic resin layer of the decorative sheet when the decorative board is in use. After use, the decorative board can be separated from the decorative board substrate by heat treating the decorative board to foam the synthetic resin sheet (synthetic resin layer), breaking down the foamed layer, and peeling off the decorative sheet. This facilitates recycling of the decorative board substrate.

[0090] The resin component constituting the synthetic resin sheet may be any thermoplastic resin conventionally used to form the foamed resin layer of foam wallpaper, with ethylene-vinyl acetate copolymer resin (EVA) being preferred. The vinyl acetate (VA) content in EVA is preferably 10 to 19% by mass, more preferably 10 to 15% by mass.

[0091] The melt flow rate (hereinafter also referred to as "MFR") of the EVA is not limited, but is preferably about 40 to 75 g / 10 min, and more preferably about 50 to 60 g / 10 min. If the MFR of the EVA is in the above range, it becomes easy to form a synthetic resin sheet-forming composition containing the EVA and the thermally decomposable foaming agent by extrusion molding.

[0092] The MFR is a value measured by the test method described in JIS K 7210 (flow test method for thermoplastics). The test conditions adopted were "190°C, 21.18N (2.16 kgf)" described in JIS K 6760.

[0093] Examples of thermally decomposable foaming agents include azo-based foaming agents such as azodicarbonamide (ADCA) and azobisformamide; and hydrazide-based foaming agents such as oxybenzenesulfonylhydrazide (OBSH) and paratoluenesulfonylhydrazide. The content of the thermally decomposable foaming agent can be appropriately set depending on the type of foaming agent, the expansion ratio, etc. The expansion ratio of the synthetic resin layer when the decorative sheet is peeled off is usually 1.5 times or more, preferably about 3 to 7 times. In the present invention, the content of the thermally decomposable foaming agent is 1.0 parts by mass or more and 5.0 parts by mass or less per 100 parts by mass of the synthetic resin contained in the synthetic resin sheet. The content of the thermally decomposable foaming agent is preferably 3.0 parts by mass or more and 5.0 parts by mass or less per 100 parts by mass of the synthetic resin. EVA is particularly preferred as the synthetic resin contained in the synthetic resin sheet. The thermally decomposable foaming agent contained in the synthetic resin sheet is preferably an azodicarbonamide (ADCA)-based thermally decomposable foaming agent.

[0094] The synthetic resin sheet of the present invention may contain, in addition to the synthetic resin and the thermally decomposable foaming agent, known additives as necessary. Examples of additives include inorganic fillers, foam cell regulators, heat stabilizers, and flame retardants. The content of the additives can be appropriately set depending on the desired properties.

[0095] Among the additives, examples of inorganic fillers include calcium carbonate, aluminum hydroxide, magnesium hydroxide, antimony trioxide, zinc borate, and molybdenum compounds. The inclusion of an inorganic filler can provide effects such as suppressing transparency and improving surface properties. The content of the inorganic filler is preferably 1 to 100 parts by mass, and more preferably 20 to 70 parts by mass, per 100 parts by mass of the resin component (particularly EVA) of the synthetic resin sheet.

[0096] The synthetic resin sheet of the present invention can be formed by extrusion molding a synthetic resin sheet-forming composition containing a synthetic resin and a thermally decomposable foaming agent, for example, at 90 to 120° C. Since the decomposition temperature of thermally decomposable foaming agents such as ADCA is about 220° C., they do not foam at the above temperature, and an unfoamed synthetic resin sheet can be produced.

[0097] The synthetic resin sheet may be irradiated with electron beams. If the synthetic resin is EVA, it can be crosslinked by electron beam irradiation, allowing the expansion ratio to be adjusted. When the synthetic resin is EVA, the energy of the electron beam is preferably 150 to 250 kV. The irradiation dose is preferably 1 to 7 Mrad. A known electron beam irradiation device can be used as the electron beam source.

[0098] When electron beam irradiation is performed, the composition for forming a synthetic resin sheet may contain a cross-linking aid. The cross-linking aid may be any agent that promotes cross-linking by electron beam irradiation, and examples thereof include polyfunctional monomers and oligomers such as neopentyl glycol dimethacrylate and trimethylolpropane trimethacrylate. The amount of the cross-linking aid is preferably 1 to 10 parts by mass, more preferably 1 to 4 parts by mass, per 100 parts by mass of the synthetic resin (particularly EVA).

[0099] The thickness of the synthetic resin sheet of the present invention is greater than 80 μm. The thickness of the synthetic resin sheet is preferably 81 μm or more and 500 μm or less, and more preferably 85 μm or more and 240 μm or less. When the thickness of the synthetic resin sheet is within this range, it can contribute to improving the surface performance of the decorative sheet as a synthetic resin layer (so-called backer layer), and can ensure good adhesion of the synthetic resin sheet when the decorative board of the present invention described below is used.

[0100] Embossed Textured Pattern The decorative sheet may be embossed from the surface protective layer side (upper side of the decorative sheet) to form a textured pattern. The textured pattern can be formed by hot pressing, hairline processing, etc. Examples of textured patterns include vessel grooves, stone slab surface textures, cloth surface textures, matte finish, sand grain, hairline, and linear grooves.

[0101] In this specification, the thickness of each layer of the decorative sheet is a value measured at a location where the above-mentioned uneven pattern is not formed (a flat location).

[0102] 2. Decorative Board Using Easily Peelable Decorative Sheet The decorative board of the present invention comprises the easily peelable decorative sheet of the present invention on a decorative board substrate. The decorative board is produced by bonding the decorative sheet to the decorative board substrate via an adhesive.

[0103] Decorative Board Substrate (Adherend) 11 The material of the decorative board substrate (adherend) is not limited, and examples thereof include inorganic non-metallic, metallic, wood-based, and plastic-based materials. Specific examples of inorganic non-metallic materials include non-ceramic ceramic materials such as paper cement, extruded cement, slag cement, ALC (lightweight aerated concrete), GRC (glass fiber reinforced concrete), pulp cement, wood chip cement, asbestos cement, calcium silicate, gypsum, and gypsum slag, as well as ceramic materials such as earthenware, pottery, porcelain, stoneware, glass, and enamel. Metallic materials include metal materials (metal steel plates) such as iron, aluminum, and copper. Wood-based materials include veneers, plywood, particle board, fiberboard, and laminated lumber made of cedar, cypress, oak, lauan, teak, and the like. Plastic-based materials include resin materials such as polypropylene, ABS resin, and phenolic resin. Among these, metal materials (metal steel sheets) are preferred from the viewpoint of promoting recycling of the decorative sheet substrate after use of the decorative sheet.

[0104] Adhesive layer 10: In order to obtain adhesion between the decorative board substrate and the easily peelable decorative sheet of the present invention, an adhesive layer is formed between the synthetic resin sheet and the decorative board substrate. The adhesive used for this purpose is also specifically called an adhesive for adherends.

[0105] Known adhesives can be used as the adhesive for adherends, including, for example, heat-sensitive adhesives and pressure-sensitive adhesives. Resins used in adhesives for adherends include, for example, acrylic resins, polyurethane resins, vinyl chloride resins, vinyl acetate resins, vinyl chloride-vinyl acetate copolymer resins, styrene-acrylic copolymer resins, polyester resins, and polyamide resins, and these can be used alone or in combination. Two-component curing polyurethane adhesives and polyester adhesives that use an isocyanate compound as a curing agent can also be used as adhesives for adherends. Furthermore, acrylic, urethane, silicone, rubber, and other pressure-sensitive adhesives can also be used as adhesives for adherends.

[0106] From the viewpoint of obtaining excellent adhesiveness, the thickness of the adhesive layer is preferably from 1 μm to 100 μm, more preferably from 5 μm to 50 μm, and even more preferably from 10 μm to 30 μm.

[0107]

[0033] A decorative sheet is produced by bonding a decorative sheet to a decorative sheet substrate via an adhesive for an adherend. For example, a lamination method is used in which the adhesive for an adherend is applied to the decorative sheet substrate, the decorative sheet of the present invention is laminated, and pressure is applied using a pressure roller or the like.

[0108] When a heat-sensitive adhesive (hot-melt adhesive) is used, the heating temperature is preferably 160° C. or higher and 200° C. or lower, although this depends on the type of adhesive, and for reactive hot-melt adhesives, the heating temperature is preferably 100° C. or higher and 130° C. or lower. Heating is also common in vacuum forming, and the temperature is preferably 80° C. or higher and 130° C. or lower, and more preferably 90° C. or higher and 120° C. or lower.

[0109] After laminating the decorative board base material and decorative sheet, the laminate can be cut to any size, and the surface and end grain can be grooved, chamfered, etc. using a cutting machine such as a router or cutter, and then used for various purposes, such as exterior and interior components of buildings such as walls, window frames, and doors.

[0110] 3. Recycling of the decorative board substrate (adherend) After use, such as after the end of its useful life, the decorative board of the present invention can be recycled by peeling the decorative sheet from the decorative board and recycling the decorative board substrate (adherend). Specifically, the decorative board of the present invention has a synthetic resin layer (so-called backer layer) made of the synthetic resin sheet of the present invention on the back side of the decorative sheet, and this synthetic resin layer contains a thermally decomposable foaming agent. Therefore, after use, the decorative board can be separated from the decorative board substrate by heat-treating the decorative board to foam the synthetic resin sheet (synthetic resin layer), and then tearing the foamed layer and peeling off the decorative sheet. In Figure 2, AA represents the foamed synthetic resin sheet, and Figure 3 illustrates one embodiment in which the foamed synthetic resin sheet AA is torn and the decorative sheet B is peeled off.

[0111] In a preferred embodiment of the present invention, the synthetic resin sheet (synthetic resin layer) is foamed by heat treatment at approximately 220°C, and the foamed layer is then broken to remove the decorative sheet. It is preferable to prepare the synthetic resin sheet so that such foaming characteristics can be obtained. Such foaming characteristics are easily obtained, for example, by using EVA as the synthetic resin of the synthetic resin sheet and an ADCA-based thermal decomposition foaming agent. Furthermore, if the synthetic resin sheet itself is heat resistant in a 180°C heat resistance test (180°C heat resistance test using edible oil in accordance with JIS K 6902), it can be used appropriately as an interior or exterior decoration for a building without causing unintended foaming during actual use of the decorative panel.

[0112] The present invention will be specifically explained below with reference to examples, comparative examples and test examples, but the present invention is not limited to the contents shown in the examples.

[0113] Example 1 [Preparation of decorative sheet intermediate] A back primer layer (2 μm thick) made of a urethane-cellulose resin was formed on the back surface of a substrate sheet made of a 60 μm thick colored polypropylene film. Next, a picture pattern layer (2 μm thick) was formed on the front surface of the substrate sheet by gravure printing with an acrylic-urethane ink. A transparent adhesive layer (3 μm thick) was formed on the picture pattern layer using a urethane adhesive, and then a transparent polypropylene resin was laminated on top of it using a hot-melt extrusion method to form a transparent resin layer (80 μm thick) made of polypropylene. After corona treatment was performed on the front surface of the transparent resin layer (the surface of the transparent resin layer opposite the transparent adhesive layer side), a primer layer (2 μm thick) made of a urethane resin was applied to form the primer layer. Furthermore, an electron beam-curable resin made of an acrylic-urethane copolymer resin was coated on the front surface of the primer layer (the surface of the primer layer opposite the transparent resin layer), and then cured by electron beam irradiation (125 KeV, 60 Mrad) using an electron beam irradiation device to form a surface protective layer (thickness 15 μm). To impart design, an embossing process was performed on the surface protective layer to create a textured pattern. [Preparation of Synthetic Resin Sheet] Ethylene-vinyl acetate copolymer resin (EVA, VA content 10% by mass, MFR 75 g / 10 min) was prepared, and 4.7 parts by mass of an azodicarbonamide (ADCA)-based thermal decomposition type blowing agent was added to 100 parts by mass of EVA. The mixture was extruded using a T-die extruder to form a film with a thickness of 85 μm. This resulted in a synthetic resin sheet (synthetic resin layer as a backer layer). [Preparation of decorative sheet] A two-component curing polyurethane adhesive using isocyanate as a curing agent was applied to a synthetic resin sheet at a rate of 10 g / m. ２After coating to form an adhesive layer (10 μm thick), the adhesive layer was bonded to the back primer layer side of the decorative sheet intermediate to obtain a decorative sheet. [Fabrication of Decorative Board] A 100 μm thick polyethylene terephthalate sheet was prepared as the decorative board substrate (adherend), and the decorative board substrate was bonded to the synthetic resin sheet side of the decorative sheet using the following adhesive for adherend to obtain a decorative board. Adhesive for Adherend: Main agent... saturated copolymer polyester resin ("Aronmelt PES-320SAM40" manufactured by Toa Gosei Chemical Industry Co., Ltd.) Curing agent... modified polyisocyanate-based curing agent ("Coronate L" manufactured by Nippon Polyurethane Industry Co., Ltd.).

[0114] Example 2 A decorative board was produced in the same manner as in Example 1, except that the thickness of the synthetic resin sheet was 120 μm and the content of the thermal decomposition type foaming agent was 3.0 parts by mass per 100 parts by mass of EVA.

[0115] Example 3 A decorative board was produced in the same manner as in Example 1, except that the thickness of the synthetic resin sheet was 200 μm and the content of the thermal decomposition type foaming agent was 3.8 parts by mass per 100 parts by mass of EVA.

[0116] Example 4 A decorative board was produced in the same manner as in Example 1, except that the thickness of the synthetic resin sheet was 240 μm and the content of the thermally decomposable foaming agent was 3.0 parts by mass per 100 parts by mass of EVA.

[0117] Comparative Example 1 A decorative board was produced in the same manner as in Example 1, except that no synthetic resin sheet was used.

[0118] Comparative Example 2 Ethylene-vinyl acetate copolymer resin (EVA, VA content 10% by mass, MFR 75 g / 10 min) was prepared as a synthetic resin sheet, and 4.7 parts by mass of azodicarbonamide (ADCA)-based thermal decomposition type foaming agent was added to 100 parts by mass of EVA. The mixture was extruded into a film with a thickness of 80 μm using a T-die extruder. The film was then heated in a 220 ° C environment for 35 seconds to obtain an EVA foamed resin layer with a thickness of 550 μm. A decorative board was produced in the same manner as in Example 1, except that the EVA foamed resin layer was used as the synthetic resin sheet.

[0119] Comparative Example 3 A decorative board was produced in the same manner as in Example 1, except that the thickness of the synthetic resin sheet was 60 μm and the content of the thermally decomposable foaming agent was 3.0 parts by mass per 100 parts by mass of EVA.

[0120] Comparative Example 4 A decorative board was produced in the same manner as in Example 1, except that the thickness of the synthetic resin sheet was 80 μm and the content of the thermally decomposable foaming agent was 5.2 parts by mass per 100 parts by mass of EVA.

[0121] Comparative Example 5 A decorative board was produced in the same manner as in Example 1, except that the thickness of the synthetic resin sheet was 300 μm and the content of the thermally decomposable foaming agent was 5.2 parts by mass per 100 parts by mass of EVA.

[0122] Test Example 1 [Pencil Hardness of Decorative Laminate] The front surface of the decorative laminate produced in each of the Examples and Comparative Examples was subjected to a pencil scratch hardness test in accordance with JIS K 5600-5-4:1999 to measure the pencil hardness.

[0123] The results are shown in Table 1. Pencil hardness of F or more was evaluated as +, and that of less than F was evaluated as -.

[0124] [Adhesive strength of synthetic resin sheet before and after heat treatment] For the decorative boards produced in each example and comparative example, the adhesiveness of the synthetic resin sheet was measured before and after heat treatment (i.e., before and after foaming; however, in Comparative Example 2, foaming had occurred before the heat treatment).

[0125] Specifically, test pieces measuring 24 mm wide x 150 mm long were prepared both immediately after the decorative board was produced (initial stage) and after heat treatment (heating at 220°C for 2 minutes), and the maximum point load (N / inch) was measured using a T-peel test in accordance with JIS K-6854-3:1999 to measure the adhesive strength of the synthetic resin sheet.

[0126] The adhesive strength of the synthetic resin sheet is good if the initial adhesion is 20 N / inch or more, and if the peelability after heat treatment is 10 N / inch or less, it is easy to tear the synthetic resin sheet after foaming and peel off the decorative sheet.

[0127] Based on the results of the adhesive strength of the synthetic resin sheet, the adhesiveness was evaluated according to the following evaluation criteria. Specifically, if the initial adhesion was 20 N / inch or more and the peelability after heat treatment was 10 N / inch or less, the adhesiveness was evaluated as +. On the other hand, if the initial adhesion was 20 N / inch or less or the peelability after heat treatment was 10 N / inch or more, the adhesiveness was evaluated as -.

[0128] The results are shown in Table 1 below.

[0129] [Heat resistance at 180°C] The decorative boards produced in each example and comparative example were subjected to a 180°C heat resistance test using edible oil in accordance with JIS K 6902. The heat resistance evaluation results are as follows: +: No foaming occurred in the synthetic resin sheet, or even if foaming occurred, the adhesive strength did not decrease to less than 20 N / inch. -: Foaming occurred in the synthetic resin sheet, and the adhesive strength decreased to less than 20 N / inch.

[0130]

[0131] Example 5 A decorative sheet and a decorative board were produced in the same manner as in Example 1, except that 3 parts by mass of a phosphate glass silver-supported compound (PG-711 manufactured by Koa Glass Co., Ltd.) was added as an antiviral agent to 100 parts by mass of the ionizing radiation-curable resin forming the surface protective layer. The process was the same as in Example 1, except that the antiviral agent was added to the surface protective layer.

[0132] The decorative sheets produced in Examples 1 and 5 were used to carry out the following evaluations.

[0133] [Antiviral Properties] <Evaluation Method> The decorative sheets produced in Examples 1 and 5 were subjected to an antiviral performance test in accordance with the antiviral test method (ISO 21702), and the antiviral activity value against influenza virus was calculated and evaluated based on the following evaluation criteria. The results are shown in Table 2. A + rating indicates that there is no problem in practical use. In addition, the antiviral agent (parts by mass) in Table 2 refers to the amount (parts by mass) of antiviral agent used per 100 parts by mass of ionizing radiation curable resin. <Evaluation Criteria> +: Antiviral activity value was 2.0 or more -: Antiviral activity value was less than 2.0

[0134] The results are shown in Table 2.

[0135]

[0136] 1. Base sheet 2. Picture pattern layer 3. Adhesive layer 4. Transparent resin layer 5. Primer layer 6. Surface protective layer 7. Back primer layer 8. Synthetic resin sheet for easily peelable decorative sheet 9. Adhesive layer 10. Adhesive layer 11. Decorative board base material A. Synthetic resin sheet for easily peelable decorative sheet AA. Synthetic resin sheet after foaming B. Easily peelable decorative sheet C. Decorative board

Claims

1. A synthetic resin sheet for an easily peelable decorative sheet, characterized in that: (1) the synthetic resin sheet has a thickness exceeding 80 μm; and (2) the synthetic resin sheet is an unfoamed sheet containing a synthetic resin and a thermally decomposable foaming agent, and the content of the thermally decomposable foaming agent per 100 parts by mass of the synthetic resin is 1.0 part by mass or more and 5.0 parts by mass or less.

2. The synthetic resin sheet according to claim 1, wherein the synthetic resin contains ethylene-vinyl acetate copolymer resin (EVA).

3. The synthetic resin sheet according to claim 1 or 2, wherein the thermally decomposable foaming agent is an azodicarbonamide (ADCA)-based thermally decomposable foaming agent.

4. The synthetic resin sheet according to claim 1 or 2, wherein the thickness of the synthetic resin sheet is 85 μm or more and 240 μm or less.

5. An easily peelable decorative sheet comprising a decorative sheet intermediate having at least a picture pattern layer on a base sheet, and a synthetic resin sheet as defined in claim 1 or 2 as a synthetic resin layer underneath the decorative sheet intermediate.

6. The easily peelable decorative sheet according to claim 5, wherein the decorative sheet intermediate comprises a surface protective layer made of a cured product of an ionizing radiation curable resin composition.

7. The easily peelable decorative sheet according to claim 6, wherein the surface protective layer contains at least one selected from the group consisting of antibacterial agents, antiviral agents, and allergen reducing agents.

8. The easily peelable decorative sheet according to claim 7, wherein the decorative sheet intermediate comprises, on the base sheet, in the thickness direction, the picture pattern layer, a transparent resin layer, a primer layer and the surface protection layer, in that order.

9. A decorative board comprising the easily peelable decorative sheet according to claim 5 on a decorative board substrate.

10. The decorative board according to claim 8, wherein the hardness of the front surface of the decorative board measured by a pencil scratch hardness test in accordance with JIS K 5600-5-4:1999 is F or higher.

11. The decorative board according to claim 8, wherein the decorative board substrate is a metal steel plate.

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