Laminated sheet and method for evaluating weather resistance of laminated sheet

Abstract

To provide a laminated sheet which can shorten weather resistance evaluation time capable of shortening time required for weather resistance evaluation, and a weather resistance evaluation method for the laminated sheet.SOLUTION: In a laminated sheet 10, when an ultraviolet irradiation test is performed on the laminated sheet 10 from the side of a surface protective layer 15 using a metal halide lamp for 250 hours, and surface side indentation hardness (HIT) at a surface side measurement position E1 set in a region on the side of the surface protective layer 15 in a thickness direction of a transparent resin layer 14 and back face side indentation hardness (HIT) at a back face side measurement position E2 set in a region on the side of a base material sheet 11 in the thickness direction of the transparent resin layer 14 are measured before and after the irradiation test, a change rate before and after the irradiation test of a ratio (R1 / R2) of the surface side indentation hardness (R1) to the back face side indentation hardness (R2) is less than 20%.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a laminate sheet and a method for evaluating the weather resistance of the laminate sheet. [Background technology]

[0002] Conventionally, laminated sheets are known that are used as exterior building materials by being attached to wood boards, inorganic boards, metal plates, etc. Since laminated sheets used for the exterior of buildings are exposed to ultraviolet rays, wind and rain outdoors, improving their weather resistance is a major challenge. To improve weather resistance, it is generally known to add an ultraviolet absorber or a radical scavenger (light stabilizer) to the outermost layer of the laminated sheet (e.g., Patent Documents 1 to 4). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-238444 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-118584 [Patent Document 3] Japanese Patent Application Laid-Open No. 2005-088481 [Patent Document 4] Japanese Patent Application Laid-Open No. 2011-16277 Summary of the Invention [Problem to be solved by the invention]

[0004] When a laminate sheet used outdoors develops abnormalities such as whitening on its surface, the area where the abnormality occurred is exposed to ultraviolet rays, wind, and rain, which reduces its weather resistance and accelerates its deterioration. In other words, the deterioration of the weather resistance of the laminate sheet leads to the deterioration of the building exterior. In recent years, long-term warranties for buildings (e.g., houses) have become commonplace, and as part of this, there is a growing need for quality assurance of laminate sheets used as exterior building materials. Therefore, there is a need to evaluate the weather resistance of laminate sheets in advance, for example, to determine whether the weather resistance of the laminate sheets will be maintained without deterioration over a period equivalent to the warranty period. The weather resistance of conventional laminated sheets has been evaluated by visually observing the changes in the surface over time due to ultraviolet light irradiation. However, this evaluation method has the problem that it takes an extremely long time (evaluation time) of several thousand hours to derive the evaluation results.

[0005] In view of the above problems, an object of the present invention is to provide a laminate sheet that can shorten the time required for weather resistance evaluation and a method for evaluating the weather resistance of the laminate sheet.

[0006] In order to solve the above problems, a laminate sheet according to one aspect of the present invention is a laminate sheet in which a printed layer is provided on a base sheet, and at least a transparent resin layer and a surface protective layer are laminated on the printed layer in this order, and the laminate sheet is exposed to an illuminance of 65 mW / cm 2 from the surface protective layer side when measured using an integrating actinometer having a sensitivity wavelength range of 310 nm to 390 nm. 2 A 250-hour ultraviolet irradiation test was performed using a metal halide lamp under conditions of a black panel temperature of 63°C and a humidity inside the chamber of 50%, and the surface indentation hardness (H IT ) and the back surface indentation hardness (H IT ), the ratio (R1 / R2) of the front-side indentation hardness (R1) to the back-side indentation hardness (R2) changes by less than 20% before and after the irradiation test, and the back-side measurement position and the back-side measurement position are set in areas of the transparent resin layer that are not affected by other layers when measuring the front-side indentation hardness and the back-side indentation hardness.

[0007] In order to solve the above problems, another aspect of the present invention provides a laminated sheet in which a printed layer is provided on a base sheet, and at least a transparent resin layer and a surface protective layer are laminated on the printed layer in this order, and the transparent resin layer has an indentation hardness of 45 N / mm 2 and at least one of the transparent resin layer and the surface protective layer contains a hindered amine-based light stabilizer.

[0008] In order to solve the above-mentioned problems, a weather resistance evaluation method according to one aspect of the present invention is a method for evaluating the weather resistance of a laminated sheet in which a printed layer is provided on a base sheet, and at least a transparent resin layer and a surface protective layer are laminated on the printed layer in this order, the method comprising: applying an illuminance of 65 mW / cm to the laminated sheet from the surface protective layer side, which is the outermost surface of the laminated sheet, using an integrating actinometer having a sensitivity wavelength range of 310 nm to 390 nm; 2 an ultraviolet irradiation step of performing an ultraviolet irradiation test for 250 hours using a metal halide lamp under conditions of a black panel temperature of 63°C and a humidity inside the chamber of 50%; and measuring the surface side indentation hardness (H IT ) and the back surface indentation hardness (H IT and an evaluation step of evaluating weather resistance based on whether the rate of change in the ratio (R1 / R2) of the front-side indentation hardness (R1) to the back-side indentation hardness (R2) before and after the irradiation test is less than 20%, wherein the front-side measurement position and the back-side measurement position are set in areas of the transparent resin layer that are not affected by other layers when measuring the front-side indentation hardness and the back-side indentation hardness. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a laminate sheet that can shorten the time required for weather resistance evaluation and a method for evaluating the weather resistance of the laminate sheet. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view illustrating an example of a laminate sheet according to a first embodiment of the present invention. [Figure 2] 1 is a flowchart showing an example of a method for evaluating weather resistance of a laminate sheet according to a first embodiment of the present invention. [Figure 3] 10 is a flowchart showing an example of a method for evaluating weather resistance of a laminate sheet according to a second embodiment of the present invention. [Figure 4] 10 is a flowchart showing an example of a method for evaluating weather resistance of a laminate sheet according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present disclosure will be described below through embodiments, but the following embodiments do not limit the invention according to the claims. Furthermore, not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention. Furthermore, the drawings are merely schematic illustrations of the invention according to the claims, and the dimensions of the width, thickness, etc. of each part may differ from the actual dimensions, and the ratios between these dimensions may also differ from the actual dimensions.

[0012] A laminate sheet according to a first embodiment of the present disclosure will be described. The laminate sheet according to the present disclosure is, for example, a laminate sheet applied to building exterior fittings. In the following description, the side of the base sheet that contacts the adhesive surface of the laminate sheet may be referred to as "bottom," and the side opposite to the side that contacts the adhesive surface of the laminate sheet (front surface) may be referred to as "top." Hereinafter, each aspect of each embodiment of the present disclosure will be described with reference to the drawings.

[0013] 1. First embodiment (1.1) Basic structure of laminated sheet Fig. 1 is a schematic diagram showing a cross section of a laminate sheet 10 according to this embodiment, and is a front view of the cross section. As shown in Fig. 1, the laminate sheet 10 according to the first embodiment of the present invention (hereinafter referred to as this embodiment) has a base sheet 11, a printing layer 12, an anchor layer 13, a transparent resin layer 14, and a surface protection layer 15 laminated in this order. The configuration of each of the above-mentioned layers will be described below. The laminate sheet 10 according to this embodiment may be any laminate sheet in which a printed layer 12 is provided on a base sheet 11, and at least a transparent resin layer 14 and a surface protective layer 15 are laminated in this order on the printed layer 12. Therefore, the formation of the anchor layer 13 may be omitted in the laminate sheet 10.

[0014] (Base sheet 11) The material for the base sheet 11 can be, for example, a thermoplastic resin. There are no particular limitations on the thermoplastic resin, and the same thermoplastic resins as those used for the base material of conventional decorative sheets can be used. For example, polyolefin resins such as polyethylene, polypropylene, polymethylpentene, polybutene, ethylene-propylene copolymer, ethylene-α-olefin copolymer, and propylene-α-olefin copolymer; polyolefin-based resins such as olefin-based copolymer resins such as ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, ethylene-(meth)acrylic acid (ester) copolymer, and ethylene-unsaturated carboxylic acid copolymer metal neutralized product (ionomer); polyethylene terephthalate, polybutylene terephthalate, polytetramethylene terephthalate, polyethylene naphthalate, polyethylene terephthalate-isophthalate copolymer, 1,4-cyclohexanedimethanol copolymerized polyethylene terephthalate, polyarylate, polycarbonate, etc. Examples of resins that can be used include polyester resins such as carbonate, acrylic resins such as poly(meth)acrylonitrile, polymethyl(meth)acrylate, polyethyl(meth)acrylate, polybutyl(meth)acrylate, and polyacrylamide, polyamide resins such as 6-nylon, 6,6-nylon, and 6,10-nylon, styrene resins such as polystyrene, AS resin, and ABS resin, vinyl resins such as polyvinyl chloride, polyvinyl acetate, polyvinyl alcohol, polyvinyl acetal, and polyvinyl butyral, and fluorine-based resins such as polyvinyl fluoride, polyvinylidene fluoride, polytetrafluoroethylene, ethylene-tetrafluoroethylene copolymer, and ethylene-perfluoroalkyl vinyl ether copolymer, as well as mixtures, copolymers, composites, and laminates of two or more of these resins.

[0015] Although many thermoplastic resins have been listed here as thermoplastic resins that can be used for the base sheet 11, in light of the recent growing social interest in environmental issues, it is not desirable to use thermoplastic resins that contain chlorine (halogen), such as polyvinyl chloride resin, and it is preferable to use non-halogen thermoplastic resins. In particular, from the viewpoints of various physical properties, processability, versatility, economic efficiency, etc., it is most desirable to use polyolefin resins or polyester resins (amorphous or biaxially oriented) as non-halogen thermoplastic resins.

[0016] The polyolefin resin may be appropriately selected from the many types already listed, depending on the intended use of the laminate sheet 10. In particular, polypropylene resins, i.e., homopolymers or copolymers containing propylene as the main component, are most suitable for general applications. For example, homopolypropylene resins, random polypropylene resins, block polypropylene resins, etc., may be used alone or in appropriate combinations, or resins in which atactic polypropylene is further blended. Furthermore, copolymers containing olefin monomers other than propylene may also be used. For example, a propylene-α-olefin copolymer having polypropylene crystalline portions and containing 15 mol% or more of one or more comonomers of α-olefins having 2 to 20 carbon atoms other than propylene, preferably ethylene, butene-1, 4-methylpentene-1, hexene-1, or octene-1, may be used. In addition, modifiers such as low-density polyethylene, ethylene-α-olefin copolymer, ethylene-propylene copolymer rubber, ethylene-propylene-non-conjugated diene copolymer rubber, styrene-butadiene copolymer, or hydrogenated products thereof, which are usually used to soften polypropylene resins, can be added as appropriate.

[0017] As the base sheet 11, in addition to the above-mentioned thermoplastic resins, any material selected from paper, rubber, nonwoven fabric, synthetic paper, metal foil, etc. can be used. Examples of paper include tissue paper, titanium paper, and resin-impregnated paper. Examples of rubber include ethylene-propylene copolymer rubber, ethylene-propylene-diene copolymer rubber, styrene-butadiene copolymer rubber, styrene-isoprene-styrene block copolymer rubber, styrene-butadiene-styrene block copolymer rubber, and polyurethane. Examples of nonwoven fabric include organic and inorganic nonwoven fabrics. Examples of metals for the metal foil include aluminum, iron, gold, and silver. To improve adhesion to adjacent layers, the base sheet 11 may be subjected to surface treatment such as corona treatment, plasma treatment, ozone treatment, electron beam treatment, ultraviolet treatment, or dichromate treatment.

[0018] Furthermore, the base sheet 11 in this embodiment may be an opaque colored olefin-based resin layer (colored thermoplastic resin layer) that has concealing properties. This allows the base sheet 11 to conceal color variations and defects on the surface of the substrate, for example, when the laminate sheet 10 is bonded to a predetermined substrate to form an exterior building material. Furthermore, when the texture of the substrate surface is to be utilized, the base sheet 11 may be a colored olefin-based resin layer that is transparent enough to allow the substrate surface to be seen through.

[0019] (Print layer 12) The printed layer 12 is a layer that imparts design to the laminated sheet 10, and is a layer of a picture printed on the base sheet 11 using ink. The printed layer 12 is formed using printing ink, coating agent, or the like. There are no particular limitations on the printing ink, and the same printing ink as used for the printing layer of conventional decorative sheets can be used. For example, an acrylic ink can be used as the printing ink. For example, an acrylic ink can be used, which uses a two-component curing urethane resin as the binder resin, which is formed by blending an acrylic polyol vehicle with an isocyanate curing agent. Other resin components may also be added to the printed layer 12 as needed. Components other than the binder resin of the printed layer 12 include, for example, pigments, colorants such as dyes, extender pigments, solvents, light stabilizers, and various other additives. Examples of pigments include condensed azo, insoluble azo, quinacridone, isoindoline, anthraquinone, imidazolone, cobalt, phthalocyanine, carbon, titanium oxide, iron oxide, mica, and other pearl pigments.

[0020] The method for providing the printed layer 12 is not particularly limited, and can be, for example, a typical printing method such as gravure printing, offset printing, screen printing, flexographic printing, inkjet printing, etc. In addition, any pattern can be used as the design of the printed layer 12, such as a wood grain pattern, a stone pattern, a fabric pattern, an abstract pattern, a geometric pattern, or a combination of two or more of these.

[0021] (Anchor layer 13) The anchor layer (anchor coat layer) 13 is a layer provided to enhance the adhesiveness between the base sheet 11 (lower base) and the transparent resin layer 14 (upper base). In this embodiment, the substrate sheet 11 provided with the printing layer 12 and the transparent resin layer 14 may be bonded via the anchor layer 13. Various lamination techniques, such as thermal lamination, extrusion lamination, dry lamination, and sand lamination, can be used as the bonding technique. Considering the various performance characteristics of the laminated sheet 10 according to this embodiment, dry lamination is preferred as the bonding technique. Therefore, the anchor layer 13 is preferably a dry lamination adhesive layer using a dry lamination adhesive. The anchor layer 13 is also formed using a conventional coating method, such as gravure coating, microgravure coating, comma coating, knife coating, or die coating. The anchor layer 13 is not essential for the laminated sheet 10, and the anchor layer 13 may not be provided.

[0022] (Transparent resin layer 14) The transparent resin layer 14 is a layer for improving the weather resistance and durability of the laminate sheet 10. The transparent resin layer 14 is formed using, for example, a polyolefin resin. Examples of polyolefin resins include polyolefin resins such as polyethylene, polypropylene, polymethylpentene, polybutene, ethylene-propylene copolymer, ethylene-α-olefin copolymer, and propylene-α-olefin copolymer; polyolefin-based resins such as olefin-based copolymer resins such as ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, ethylene-(meth)acrylic acid (ester) copolymer, and ethylene-unsaturated carboxylic acid copolymer metal neutralized product (ionomer); and mixtures, copolymers, composites, laminates, and the like of two or more of these. The type of polyolefin resin constituting the transparent resin layer 14 may be one type or multiple types. Of these polyolefin resins, polypropylene resin can be suitably used as the polyolefin resin constituting the transparent resin layer 14. That is, in the laminate sheet 10 according to this embodiment, the transparent resin layer 14 may be formed from polypropylene.

[0023] In addition, in the laminate sheet 10 according to this embodiment, the transparent resin layer 14 preferably contains an ultraviolet absorber (UVA) or a light stabilizer as a weather resistance agent in order to improve the weather resistance of the laminate sheet 10.

[0024] The transparent resin layer 14 preferably contains at least a light stabilizer among the weathering agents. Hindered amine light stabilizers (HALS), which are light stabilizers using hindered amine compounds, can be suitably used as the light stabilizer. In other words, the transparent resin layer 14 in the laminate sheet 10 preferably contains HALS. HALS functions as a radical scavenger that captures radicals generated by exposure to ultraviolet light and suppresses decomposition of the coating film. Therefore, by including HALS in the transparent resin layer 14, the weather resistance of the laminate sheet 10 can be improved.

[0025] Furthermore, it is more preferable that the transparent resin layer 14 contains an ultraviolet absorber (UVA) in addition to HALS. The ultraviolet absorber has the effect of suppressing the generation of radicals. By containing HALS and UVA, which have different functions as weather resistance agents, a synergistic effect of the radical control effect and the radical generation suppression effect can be obtained, and the weather resistance of the laminate sheet 10 can be further improved.

[0026] Examples of ultraviolet absorbers include benzotriazole-based, benzoate-based, benzophenone-based, triazine-based, benzoate-based, and cyanoacrylate-based ultraviolet absorbers. One type of ultraviolet absorber among these may be added to the transparent resin layer 14, or a mixture of multiple types of ultraviolet absorbers may be added. In this embodiment, a benzotriazole-based ultraviolet absorber is preferably used as the ultraviolet absorber added to the transparent resin layer 14.

[0027] The transparent resin layer 14 preferably contains 0.2 parts by mass or more of a light stabilizer (HALS) relative to the total mass of the transparent resin layer 14. If the content of the light stabilizer in the transparent resin layer 14 is less than 0.2 parts by mass, sufficient weather resistance may not be obtained. Furthermore, from the viewpoints of reducing costs and maintaining the content of the resin component in the transparent resin layer 14, the content of the light stabilizer in the transparent resin layer 14 is preferably 1 part by mass or less relative to the total mass of the transparent resin layer 14.

[0028] Furthermore, the transparent resin layer 14 preferably contains an ultraviolet absorber (UVA) in an amount of 0.2 parts by mass or more relative to the total mass of the transparent resin layer 14. If the content of the ultraviolet absorber in the transparent resin layer 14 is less than 0.2 parts by mass, sufficient weather resistance may not be obtained. Furthermore, from the viewpoints of preventing bleeding and maintaining the content of the resin component in the transparent resin layer 14, the content of the ultraviolet absorber in the transparent resin layer 14 is preferably in the range of 1 part by mass or less relative to the total mass of the transparent resin layer 14.

[0029] Thus, in this embodiment, the transparent resin layer 14 is preferably a polypropylene resin composition (polyolefin resin composition) containing at least a light stabilizer, and more preferably a polypropylene resin composition containing a light stabilizer and an ultraviolet absorber. This allows the laminate sheet 10 used for exterior applications to have excellent weather resistance.

[0030] The thickness of the transparent resin layer 14 is preferably in the range of 40 μm to 100 μm. If the thickness of the transparent resin layer 14 is less than 40 μm, weather resistance and scratch resistance may be reduced. If the thickness of the transparent resin layer 14 exceeds 100 μm, the manufacturing cost may increase and flexibility may be reduced.

[0031] If necessary, various additives such as a heat stabilizer, an antiblocking agent, a catalyst scavenger, a colorant, a light scattering agent, and a gloss adjuster may be added to the transparent resin layer 14. As the heat stabilizer, phenol-based, sulfur-based, phosphorus-based, hydrazine-based, and other additives are generally added in any combination.

[0032] The method for forming the transparent resin layer 14 is not particularly limited. The transparent resin layer 14 can be formed using a common method such as calendar film formation or extrusion film formation. Among these, extrusion molding is preferred as a method for forming the transparent resin layer 14. Extrusion molding allows the transparent resin layer 14 to be formed uniformly. Furthermore, in order to provide a design, the transparent resin layer 14 may be provided with surface irregularities. Examples of methods for providing the irregularities include a method of subjecting the transparent resin layer 14 to hot embossing after extrusion molding, and a method of subjecting the extrusion layer 14 to embossing simultaneously with extrusion molding using a cooling roll provided with irregularities.

[0033] (Surface protective layer) The surface protective layer 15 is a layer formed on the transparent resin layer 14, and is a layer provided to impart functions such as weather resistance, scratch resistance, stain resistance, and designability to the laminate sheet 10. For example, a reaction product (hereinafter also referred to as an "isocyanate-cured acrylic resin composition") containing an acrylic resin composition as the main component and polyisocyanate as a curing agent can be used as the material for the surface protective layer 15, in consideration of improving the weather resistance of the surface protective layer 15. As the acrylic resin composition, for example, an acrylic polyol can be used. Examples of acrylic polyols that can be used include acrylic polymer compounds having hydroxyl groups in their side chains, which are obtained by blending and copolymerizing ordinary acrylic monomers such as methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, and 2-ethylhexyl methacrylate with hydroxyl group-containing monomers such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl acrylate, and, if necessary, copolymerizable polymerizable monomers such as styrene, α-methylstyrene, vinyltoluene, divinylbenzene, vinyl acetate, vinyl butyrate, vinyl versatate, ethyl vinyl ether, acrylonitrile, and methacrylonitrile.

[0034] Furthermore, for example, a trimer of hexamethylene diisocyanate can be used as the isocyanate prepolymer of polyisocyanate in consideration of the weather resistance of the surface protective layer 15. Furthermore, for example, a urethane bond can be used as the side chain of the isocyanate prepolymer in consideration of imparting flexibility to the surface protective layer 15.

[0035] Furthermore, in consideration of scratch resistance, weather resistance, and durability, the material for the surface protective layer 15 can be, for example, a mixture of an ionizing radiation-curable resin and an isocyanate-curable acrylic resin composition. For scratch resistance, the surface protective layer 15 preferably has a hardness of B or higher in a pencil hardness test according to JIS K 5600. The ionizing radiation-curable resin can be, for example, a composition whose main component is at least one of a prepolymer, oligomer, and monomer having a polymerizable unsaturated bond such as a (meth)acryloyl group, which undergoes a crosslinking reaction upon irradiation with ionizing radiation. Examples of ionizing radiation that can be used include electron beams and ultraviolet rays. Additives such as a polymerization initiator and a sensitizer may be added to the ionizing radiation-curable resin as needed.

[0036] Examples of prepolymers and oligomers having a polymerizable unsaturated bond that can be used include melamine (meth)acrylate, epoxy (meth)acrylate, urethane (meth)acrylate, polyester (meth)acrylate, polyether (meth)acrylate, polyol (meth)acrylate, etc. Examples of monomers that can be used include monofunctional monomers such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, cyclohexyl (meth)acrylate, ethylhexyl (meth)acrylate, hydroxyethyl (meth)acrylate, and glycidyl (meth)acrylate, bifunctional monomers such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, polyethylene glycol diacrylate, propylene glycol diacrylate, butanediol diacrylate, and hexanediol diacrylate, and polyfunctional monomers such as trimethylolpropane triacrylate, pentaerythritol tetraacrylate, and dipentaerythritol hexaacrylate.

[0037] The isocyanate-curable acrylic resin composition may be, for example, a reaction product of an acrylic resin composition as a base component and a polyisocyanate as a curing agent. For example, an acrylic polyol compound may be used as the acrylic resin composition. Examples of the acrylic polyol compound include acrylic polymer compounds having hydroxyl groups in their side chains, which can be obtained by blending and copolymerizing ordinary acrylic monomers such as methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, and 2-ethylhexyl methacrylate with hydroxyl group-containing monomers such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl acrylate, and, if necessary, copolymerizable polymerizable monomers such as styrene, α-methylstyrene, vinyltoluene, divinylbenzene, vinyl acetate, vinyl butyrate, vinyl versatate, ethyl vinyl ether, acrylonitrile, and methacrylonitrile.

[0038] Examples of isocyanate prepolymers of polyisocyanates include tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), naphthalene diisocyanate (NDI), xylylene diisocyanate (XDI), hydrogenated diphenylmethane diisocyanate (hydrogenated MDI), hydrogenated xylylene diisocyanate (hydrogenated XDI), hexamethylene diisocyanate (HDI), and isophorone diisocyanate (IPDI). Considering weather resistance, yellowing, and productivity, a trimer of hexamethylene diisocyanate (HDI) can be used. That is, an isocyanurate type made from HDI, i.e., HDI isocyanurate, a derivative of HDI, can be used. Furthermore, for example, a urethane bond can be used as the side chain of the isocyanate prepolymer to impart flexibility to the surface protective layer 15.

[0039] The surface protection layer 15 may be made of an acrylic resin such as polymethyl (meth)acrylate, polyethyl (meth)acrylate, polybutyl (meth)acrylate, or polyacrylamide.

[0040] As described above, the surface protection layer 15 in this embodiment is preferably a layer containing an acrylic resin as its main component. Here, the term "main component" as used herein refers to a resin material that accounts for 70% by mass or more, preferably 90% by mass or more, of the material constituting the target layer. In other words, the surface protection layer 15 is preferably formed from an acrylic resin.

[0041] The surface protective layer 15 preferably contains at least one of a light stabilizer or an ultraviolet absorber. That is, the surface protective layer 15 is preferably formed of an acrylic resin composition containing at least one of a ultraviolet absorber or a light stabilizer. The surface protective layer 15 may be composed entirely of an acrylic resin, except for the light stabilizer and the ultraviolet absorber. In this embodiment, the surface protective layer 15 may contain a hindered amine light stabilizer (HALS) as a light stabilizer, similar to the transparent resin layer 14. The surface protective layer 15 may contain an ultraviolet absorber such as a benzotriazole, benzoate, benzophenone, triazine, benzoate, or cyanoacrylate, similar to the ultraviolet absorber contained in the transparent resin layer 14.

[0042] Furthermore, it is more preferable that the surface protective layer 15 contains both a light stabilizer and an ultraviolet absorber (UVA), which can provide a synergistic effect of both the radical control effect and the radical generation suppression effect, thereby further improving the weather resistance of the laminate sheet 10.

[0043] The content of the light stabilizer (in this example, HALS) in the surface protective layer 15 is preferably 0.2 parts by mass or more with respect to the total mass of the surface protective layer 15. If the content of the light stabilizer in the surface protective layer 15 is less than 0.2 parts by mass, sufficient weather resistance may not be obtained. Furthermore, from the viewpoints of reducing costs and maintaining the content of the resin component in the surface protective layer 15, the content of the light stabilizer in the transparent resin layer 14 is preferably 1 part by mass or less with respect to the total mass of the surface protective layer 15.

[0044] Furthermore, the content of the ultraviolet absorber (UVA) in the surface protective layer 15 is preferably 0.2 parts by mass or more with respect to the total mass of the surface protective layer 15. If the content of the ultraviolet absorber in the surface protective layer 15 is less than 0.2 parts by mass, sufficient weather resistance may not be obtained. Furthermore, from the viewpoint of preventing bleeding and maintaining the content of the resin component in the surface protective layer 15, the content of the ultraviolet absorber in the transparent resin layer 14 is preferably in the range of 1 part by mass or less with respect to the total mass of the surface protective layer 15.

[0045] The content of the ultraviolet absorber in the surface protective layer 15 may be greater than the content of the ultraviolet absorber in the transparent resin layer 14. The content of the light stabilizer in the surface protective layer 15 may be greater than the content of the light stabilizer in the transparent resin layer 14. The light stabilizer and ultraviolet absorber contained in the surface protective layer 15 may be the same as or different from those contained in the transparent resin layer 14 .

[0046] The surface protective layer 15 may contain various additives, such as a heat stabilizer, an antiblocking agent, a catalyst scavenger, a colorant, a light scattering agent, and a gloss adjuster, as needed. The method for forming the surface protection layer 15 is not particularly limited, and the surface protection layer 15 is formed by applying a coating liquid made from the above-mentioned material using a conventional method such as gravure coating, microgravure coating, comma coating, knife coating, or die coating, and then curing it using a method suitable for the material, such as heat curing or ultraviolet curing.

[0047] Furthermore, the thickness of the surface protective layer 15 is preferably within a range of 3 μm to 15 μm. If the thickness of the surface protective layer 15 is 3 μm or more, scratch resistance is improved. If the thickness of the surface protective layer 15 is 15 μm or less, there is no need to use an unnecessarily large amount of resin material, and costs can be reduced.

[0048] Furthermore, in the laminate sheet 10 according to the first embodiment of the present invention, an embossed pattern (concave and recessed pattern) may be formed on the surface protective layer 15. By forming an embossed pattern (not shown), any desired concave and recessed shape, such as a wood grain vessel shape, can be formed three-dimensionally on the surface protective layer 15. This allows the production of a laminate sheet 10 with excellent texture and weather resistance.

[0049] (Weather Resistance Evaluation of Laminated Sheet 10) Next, a method for evaluating the weather resistance of the laminate sheet 10 according to this embodiment will be described with reference to Figures 1 and 2. Figure 2 is a flowchart showing an example of the flow of the weather resistance evaluation method according to this embodiment.

[0050] The inventors of the present invention have conducted extensive research into evaluating the weather resistance of laminate sheets used for exterior applications and shortening the evaluation time involved, and have found that it is possible to evaluate weather resistance based on changes in Martens hardness in the transparent resin layer 14 due to exposure to ultraviolet light. By evaluating weather resistance based on changes in Martens hardness, they have succeeded in significantly shortening the evaluation time. An example of the weather resistance evaluation method according to this embodiment will be specifically described below. In the following description, an example will be described in which weather resistance evaluation is performed on a laminate sheet 10 using the weather resistance evaluation method according to this embodiment, but the present invention is not limited to this, and weather resistance evaluation may also be performed on a specimen (sample) in which a surface protective layer 15 is formed on a transparent resin layer 14. In either case, equivalent evaluation results can be obtained.

[0051] (Pre-irradiation hardness measurement step S1) As shown in FIG. 2, in the method for evaluating the weather resistance of the laminated sheet 10 according to this example, first, in the pre-irradiation hardness measurement step, the Martens hardness (N / mm 2 ) is measured.

[0052] Here, the measurement of the Martens hardness in the transparent resin layer 14 will be described. In the pre-irradiation hardness measurement step, the Martens hardness is measured in two regions in the transparent resin layer 14. FIG. 1 illustrates two measurement positions in the transparent resin layer 14: a front-side measurement position E1 and a back-side measurement position E2. The front-side measurement position E1 is set in an area on the surface protective layer 15 side (front side) in the thickness direction of the transparent resin layer 14. The back-side measurement position E2 is set in an area on the base sheet 11 side (back side) in the thickness direction of the transparent resin layer 14.

[0053] Here, the Martens hardness at the front-side measurement position E1 is referred to as the front-side Martens hardness, and the Martens hardness at the back-side measurement position E2 is referred to as the back-side Martens hardness. That is, in the pre-irradiation hardness measurement step, the front-side Martens hardness at the front-side measurement position E1 and the back-side Martens hardness at the back-side measurement position E2 are measured.

[0054] 1, the front-side measurement position E1 and the back-side measurement position E2 are located on the cut surface of the transparent resin layer 14 when the laminate sheet 10 is cut in the thickness direction. That is, in the pre-irradiation hardness measurement step S1, when measuring the front-side Martens hardness and the back-side Martens hardness, the sample of the laminate sheet 10 is cut in the thickness direction to expose the cross section.

[0055] Furthermore, the front-side measurement position E1 and the back-side measurement position E2 are set in regions of the transparent resin layer 14 that are not affected by other layers when measuring the front-side Martens hardness and the back-side Martens hardness. Here, the region that is not affected by other layers refers to a region that is not reached by infiltration (bleed, etc.) of components from other layers in contact with the transparent resin layer 14, for example. That is, the front-side measurement position E1 is set in an area of ​​the transparent resin layer 14 that is not affected by infiltration from the surface protective layer 15 when measuring the front-side Martens hardness. The back-side measurement position E2 is set in an area of ​​the transparent resin layer 14 that is not affected by infiltration from the base sheet 11 and the layers (printed layer 12, anchor layer 13) provided on the base sheet 11 when measuring the back-side Martens hardness.

[0056] For example, it is preferable that the front-side measurement position E1 is set in an area 10 μm away in the thickness direction from the interface of the transparent resin layer 14 on the surface protective layer 15 side toward the base sheet 11 side, and the back-side measurement position E2 is set in a position 10 μm away in the thickness direction from the interface of the transparent resin layer 14 on the base sheet 11 side toward the surface protective layer 15 side. This makes it possible to reliably measure the front-side Martens hardness without being affected by the surface protective layer 15, and to reliably measure the back-side Martens hardness without being affected by each layer (printed layer 12 or anchor layer 13) provided on the base sheet 11.

[0057] Note that the front-side measurement position E1 and the back-side measurement position E2 shown in Fig. 1 are just examples, and the front-side measurement position E1 and the back-side measurement position E2 are not limited to the positions shown in Fig. 1. As described above, the front-side measurement position E1 and the back-side measurement position E2 only need to be separated from the boundary surface on the surface protective layer 15 side and the boundary surface on the base sheet 11 side, respectively, to an extent that they are not affected by other layers when measuring the Martens hardness.

[0058] The front-side Martens hardness and the back-side Martens hardness can be measured using a microhardness measuring device. For example, a FischerSCOPE Hm2000 manufactured by Fischer can be used as the microhardness measuring device. The microhardness measuring device measures the front-side Martens hardness and the back-side Martens hardness using load parameters: the load is increased to 5 mN over 10 seconds at the front-side measurement position E1 and the back-side measurement position E2, and then maintained at 5 mN for 5 seconds, and then decreased to 0.1 mN over 10 seconds.

[0059] The Martens hardness on the surface before the irradiation test was 20N / mm 2 It is preferable that the above-mentioned condition is satisfied: This makes it possible to confirm that the laminate sheet 10 has weather resistance suitable for outdoor use before being irradiated with ultraviolet rays.

[0060] (Ultraviolet irradiation process S2) 2, after the pre-irradiation hardness measurement step S1 is performed, an ultraviolet irradiation step is performed. In the ultraviolet irradiation step S2, an ultraviolet irradiation test is performed on the laminated sheet 10.

[0061] Here, the ultraviolet irradiation test in the ultraviolet irradiation step S2 will be specifically described. In this example, the ultraviolet irradiation test is performed using a metal halide lamp as the light source. The ultraviolet irradiation test using a metal halide lamp can be performed using, for example, a "Metal Weather Tester (KW-R7TP-A) manufactured by Daipla Wintes Co., Ltd."

[0062] The conditions for the ultraviolet irradiation test in this example are an illuminance of 65 mW / cm using an integrated actinometer with a sensitivity wavelength range of 310 nm to 390 nm. 2 The black panel temperature is 63°C, and the humidity inside the chamber is 50%. As the integrating actinometer, for example, an "Ultraviolet Illuminance Meter UIT-201: manufactured by Ushio Inc." Under these conditions, a 250-hour ultraviolet irradiation test is performed on the laminate sheet 10 from the surface protection layer 15 side, which is the outermost surface of the laminate sheet 10, using a metal halide lamp. The ultraviolet irradiation test is carried out on a laminate sheet having the same composition as the laminate sheet 10 used in the pre-irradiation hardness measurement step S1, and whose cross section is not exposed.

[0063] (Post-irradiation hardness measurement step S3) As shown in FIG. 2, after the ultraviolet irradiation step S2, a post-irradiation hardness measurement step S3 is performed. In the post-irradiation hardness measurement step S3, the Martens hardness of the transparent resin layer 14 after the ultraviolet irradiation test is measured. In this step, the front-side Martens hardness at the front-side measurement position E1 and the back-side Martens hardness at the back-side measurement position E2 are measured, similar to the pre-irradiation hardness measurement step S1. In this way, in the method for evaluating the weather resistance of the laminate sheet 10 according to this embodiment, the front-side Martens hardness and the back-side Martens hardness are measured before and after the ultraviolet irradiation test. In the post-irradiation hardness measuring step S3, the Martens hardness of the front side and the Martens hardness of the back side are measured for the sample of the laminate sheet 10 after the ultraviolet irradiation test in the ultraviolet irradiation step S2. The pre-irradiation hardness measuring step S1 and the post-irradiation hardness measuring step S3 may be collectively referred to as a "Martens hardness measuring step."

[0064] (Hardness ratio calculation step S4) 2, after the post-irradiation hardness measurement step S3 is performed, the hardness ratio calculation step S4 is performed. In the hardness ratio calculation step S4, the ratio (A1 / A2) of the front-side Martens hardness (A1) to the back-side Martens hardness (A2) of the transparent resin layer 14 of the laminate sheet 10 is calculated.

[0065] Specifically, in the hardness ratio calculation step S4, the ratio between the front-side Martens hardness measured in the pre-irradiation hardness measurement step S1 and the back-side Martens hardness is first calculated as the pre-irradiation hardness ratio. Furthermore, the ratio between the front-side Martens hardness measured in the post-irradiation hardness measurement step S3 and the back-side Martens hardness is calculated as the post-irradiation hardness ratio. By calculating the ratio from the Martens hardness values ​​measured in the pre-irradiation hardness measurement step S1 and the post-irradiation hardness measurement step S3, data variability can be corrected, and the accuracy of evaluation based on Martens hardness can be improved.

[0066] (Hardness ratio change rate calculation step S5) 2, after the hardness ratio calculation step S4 is performed, the hardness ratio change rate calculation step S5 is performed. In this embodiment, the hardness ratio change rate calculation step S5 calculates the change rate (%) of the ratio (A1 / A2) between the front-side Martens hardness and the back-side Martens hardness before and after the ultraviolet light irradiation step S2. Specifically, the above-mentioned rate of change is calculated using the pre-irradiation hardness ratio and the post-irradiation hardness ratio calculated in the hardness ratio calculation step S4. Here, when the rate of change is defined as "C1", the rate of change (C1) is calculated using, for example, the following formula (1). C1=(hardness ratio after irradiation - hardness ratio before irradiation) / hardness ratio before irradiation...(1) The rate of change (rate of increase) in the Martens hardness ratio after ultraviolet irradiation relative to the Martens hardness ratio before ultraviolet irradiation is calculated using the above formula (1).

[0067] (Evaluation step S6) 2, after the hardness ratio change rate calculation step S5 is performed, an evaluation step S6 is then performed. In the evaluation step S6 of this embodiment, the weather resistance of the laminate sheet 10 is evaluated based on the change rate (C1) of the ratio (A1 / A2) of the front-side Martens hardness to the back-side Martens hardness before and after the ultraviolet light irradiation step S2. Specifically, in the evaluation step S6, whether the laminate sheet 10 has sufficient weather resistance is evaluated based on whether the change rate (C1) of the Martens hardness ratio is equal to or less than a predetermined threshold value. Here, sufficient weather resistance means that when the laminate sheet 10 is used outdoors, the weather resistance can be maintained for at least five years without causing abnormalities such as whitening on the surface.

[0068] In this embodiment, the threshold value for the weather resistance evaluation is set according to the change in Martens hardness due to ultraviolet irradiation, the ultraviolet irradiation time in the ultraviolet irradiation step S2, and the period for which weather resistance is required to be maintained (e.g., warranty period). Generally, the warranty period for a building (such as a house) is about 5 to 10 years. The inventors have discovered that by setting the threshold for the rate of change in the Martens hardness ratio to "10%" when the ultraviolet irradiation time is 250 hours and determining whether the rate of change is 10% or less to capture the initial change in the weather resistance of the laminate sheet, it is possible to evaluate whether the weather resistance will be maintained for at least 5 years. Therefore, in this embodiment, the ultraviolet irradiation time is set to 250 hours, and the threshold for evaluating weather resistance based on the rate of change in the Martens hardness ratio is set to 10%.

[0069] The change rate (C1) of the ratio (A1 / A2) of the front-side Martens hardness to the back-side Martens hardness before and after the ultraviolet irradiation step S2 is 10% or less, which indicates that the flexibility of the laminated sheet 10 is maintained and that hardening (deterioration) of the laminated sheet 10 due to ultraviolet exposure is suppressed. Therefore, weather resistance is maintained for a longer period of time compared to when the change rate (C1) of the Martens hardness ratio exceeds 10%.

[0070] In this way, in the evaluation step S6, whether the laminate sheet 10 has sufficient weather resistance is evaluated based on whether the rate of change (C1) of the ratio (A1 / A2) of the front-side Martens hardness to the back-side Martens hardness before and after the ultraviolet irradiation test in the ultraviolet irradiation step S2 is 10% or less. This makes it possible to evaluate whether the laminate sheet 10 can maintain its weather resistance for at least five years.

[0071] That is, in the evaluation step S6 of this embodiment, if the rate of change (C1) is equal to or less than the threshold value of 10%, the laminate sheet 10 is evaluated as having sufficient weather resistance, and if the rate of change (C1) is not equal to or less than 10%, i.e., if the rate of change (C1) exceeds 10%, the laminate sheet 10 is evaluated as not having sufficient weather resistance. In other words, the laminate sheet 10 has sufficient weather resistance when configured so that the rate of change (C1) is equal to or less than 10%.

[0072] Furthermore, the smaller the value of the change rate (C1), i.e., the closer to 0%, the less deterioration there is and the longer the period for which weather resistance is maintained. Therefore, if the change rate (C1) of the Martens hardness ratio before and after the ultraviolet irradiation test in the ultraviolet irradiation step S2 is less than 5%, it can be evaluated that the weather resistance of the laminate sheet 10 can be maintained for a period of 5 to 10 years when used outdoors. Furthermore, the above rate of change (C1) may be a negative value, but this indicates that there is almost no change in the Martens hardness ratio before and after the ultraviolet irradiation test in the ultraviolet irradiation step S2, and does not indicate softening of the laminated sheet 10.

[0073] In the evaluation method for the laminate sheet 10 according to this embodiment, the measurement of the Martens hardness in the hardness measurement steps (pre-irradiation hardness measurement step S1, post-irradiation hardness measurement step S3), and the calculation and determination processes in the hardness ratio calculation step S4, hardness ratio change rate calculation step S5, and evaluation step S6 may be performed by a predetermined electronic calculator (such as a computer). Therefore, the time required for evaluating the weather resistance of the laminate sheet 10 according to this embodiment is mainly the ultraviolet irradiation time in the ultraviolet irradiation step S2. In conventional methods for visually evaluating the weather resistance of laminate sheets, the time required for evaluation is several thousand hours (for example, approximately 1,000 to 3,000 hours). In contrast, in the method for evaluating the weather resistance of laminate sheets 10 according to this embodiment, the time required for the weather resistance evaluation is approximately 250 hours. In other words, the weather resistance evaluation method according to this embodiment can reduce the time required for the weather resistance evaluation by 70% or more.

[0074] As described above, the weather resistance evaluation method for the laminate sheet 10 according to this embodiment can significantly reduce the time required to evaluate the laminate sheet. This reduces costs, reduces the burden on personnel involved in the evaluation, and enables the rapid acquisition of evaluation results for commercial products. Furthermore, the weather resistance evaluation method for the laminate sheet 10 according to this embodiment evaluates weather resistance based on numerical data (the rate of change in the Martens hardness ratio (C1) and the threshold value (10%)). This improves the evaluation accuracy compared to visual evaluation. Furthermore, the laminated sheet 10 of this embodiment is configured so that the ratio of the Martens hardness on the front side to the Martens hardness on the back side (A1 / A2) changes by 10% or less before and after the irradiation test, thereby providing excellent weather resistance and shortening the time required for weather resistance evaluation.

[0075] As described above, the method for evaluating the weather resistance of the laminate sheet 10 according to this embodiment is a method for evaluating the weather resistance of the laminate sheet 10 by measuring the illuminance of the laminate sheet 10 from the surface protection layer 15 side, which is the outermost surface of the laminate sheet 10, at 65 mW / cm using an integrating actinometer having a sensitivity wavelength range of 310 nm to 390 nm. 2 The method includes an ultraviolet irradiation step S2 in which an ultraviolet irradiation test is performed for 250 hours using a metal halide lamp under conditions of a black panel temperature of 63°C and a humidity inside the chamber of 50%; a Martens hardness measurement step (pre-irradiation hardness measurement step S1, post-irradiation hardness measurement step S3) in which, before and after the ultraviolet irradiation test in the ultraviolet irradiation step S2, the front-side Martens hardness (A1) at a front-side measurement position E1 set in an area on the surface protective layer 15 side in the thickness direction of the transparent resin layer 14 and the back-side Martens hardness (A2) at a back-side measurement position E2 set in an area on the base sheet 11 side in the thickness direction within the transparent resin layer 14; and an evaluation step S6 in which the weather resistance is evaluated based on whether the rate of change (C1) of the ratio (A1 / A2) of the front-side Martens hardness to the back-side Martens hardness before and after the irradiation test is 10% or less. Furthermore, the front side measurement position E1 and the back side measurement position E2 are set in areas of the transparent resin layer 14 that are not affected by other layers (surface protective layer 15, each layer on the base sheet 11) when measuring the front side Martens hardness and the back side Martens hardness.

[0076] As a result, the method for evaluating the weather resistance of the laminate sheet 10 according to this embodiment can shorten the time required for evaluating the weather resistance.

[0077] Furthermore, the laminate sheet 10 according to this embodiment is configured so that the weather resistance evaluation method shown in FIG. 2 can be applied. Specifically, the laminate sheet 10 according to this embodiment is a laminate sheet in which a printed layer 12 is provided on a base sheet 11, and at least a transparent resin layer 14 and a surface protective layer 15 are laminated in this order on the printed layer 12. The laminate sheet 10 is also configured such that the illuminance of the laminate sheet 10 is 65 mW / cm when measured from the surface protective layer 15 side using an integrating actinometer having a sensitivity wavelength range of 310 nm to 390 nm. 2 A 250-hour ultraviolet irradiation test (ultraviolet irradiation step S2) was conducted using a metal halide lamp under conditions of a black panel temperature of 63°C and a humidity inside the chamber of 50%, and when the front-side Martens hardness (A1) at the front-side measurement position E1 set in the area on the surface protective layer 15 side in the thickness direction of the transparent resin layer 14 and the back-side Martens hardness (A2) at the back-side measurement position E2 set in the area on the base sheet 11 side in the thickness direction of the transparent resin layer 14 were measured before and after the ultraviolet irradiation test (when the Martens hardness measurement step was conducted), the ratio (A1 / A2) of the front-side Martens hardness to the back-side Martens hardness showed a change of 10% or less before and after the irradiation test. Furthermore, in the laminated sheet 10, the front side measurement position E1 and the back side measurement position E2 are set in areas of the transparent resin layer 14 that are not affected by other layers (surface protective layer 15, each layer on the base sheet 11) when measuring the front side Martens hardness and the back side Martens hardness.

[0078] As a result, the laminate sheet 10 according to this embodiment has excellent weather resistance and can shorten the time required for weather resistance evaluation.

[0079] (Variation) The laminated sheet 10 according to this embodiment is a laminated sheet in which a printed layer 12 is provided on a base sheet 11, and at least a transparent resin layer 14 and a surface protective layer 15 are laminated in this order on the printed layer 12. The transparent resin layer 14 has a Martens hardness of 30 N / mm 2 The transparent resin layer 14 and the surface protective layer 15 may each contain a hindered amine-based light stabilizer. Even with this configuration, the laminate sheet 10 has excellent weather resistance, and the time required for weather resistance evaluation can be shortened.

[0080] Here, the Martens hardness (N / mm 2 ) may be the front-side Martens hardness at the front-side measurement position E1, the back-side Martens hardness at the back-side measurement position E2, or the Martens hardness in the region between the front-side measurement position E1 and the back-side measurement position E2 in the thickness direction of the transparent resin layer 14. The Martens hardness of the transparent resin layer 14 is 1 N / mm 2 More than 30N / mm 2 The following range is preferable: 20N / mm 2 The following is more preferred: In addition, the hindered amine-based light stabilizer may be contained in both the transparent resin layer 14 and the surface protective layer 15, or may be contained only in the transparent resin layer 14, or may be contained only in the surface protective layer 15.

[0081] Second Embodiment (Weather resistance evaluation) A method for evaluating the weather resistance of a decorative sheet according to a second embodiment of the present invention (hereinafter referred to as this embodiment) will be described with reference to Figures 1 and 3. Figure 3 is a flowchart for explaining an example of the flow of a method for evaluating a laminate sheet 10 according to this embodiment. The weather resistance evaluation method according to this embodiment differs from the weather resistance evaluation method for the laminate sheet 10 according to the first embodiment in that the weather resistance of the laminate sheet 10 is evaluated based on the indentation elastic modulus.

[0082] The inventors of the present invention have conducted extensive research into evaluating the weather resistance of laminate sheets used for exterior applications and shortening the evaluation time involved, and have found that it is possible to evaluate weather resistance based on changes in the indentation modulus of the transparent resin layer 14 due to exposure to ultraviolet light. By evaluating weather resistance based on changes in the indentation modulus, they have succeeded in significantly shortening the evaluation time. An example of the weather resistance evaluation method according to this embodiment will be specifically described below. In the following explanation, differences from the method for evaluating the weather resistance of the laminate sheet 10 according to the first embodiment (see FIG. 2) will be mainly explained, and detailed explanation of similar points will be omitted as appropriate.

[0083] (Pre-irradiation elastic modulus measurement step S21) As shown in FIG. 3, in the method for evaluating the weather resistance of the laminated sheet 10 according to this example, first, in the pre-irradiation elastic modulus measurement step, the indentation elastic modulus (E IT / 1-V S The indentation elastic modulus is measured in units of MPa. The pre-irradiation elastic modulus measurement step S21 differs from the pre-irradiation hardness measurement step S1 in the first embodiment in that the indentation elastic modulus is measured at a front-side measurement position E1 and a back-side measurement position E2.

[0084] In the pre-irradiation elastic modulus measurement step S21, the indentation elastic modulus is measured at the front-side measurement position E1 and the back-side measurement position E2 shown in Figure 1. Here, the indentation elastic modulus at the front-side measurement position E1 is referred to as the front-side indentation elastic modulus, and the indentation elastic modulus at the back-side measurement position E2 is referred to as the back-side indentation elastic modulus. In other words, in the pre-irradiation elastic modulus measurement step, the front-side indentation elastic modulus at the front-side measurement position E1 and the back-side indentation elastic modulus at the back-side measurement position E2 are measured. In the pre-irradiation elastic modulus measuring step S21, similarly to the pre-irradiation hardness measuring step S1, the sample of laminate sheet 10 is cut in the thickness direction to expose the cross section when measuring the front-side indentation elastic modulus and the back-side indentation elastic modulus. The front-side measurement position E1 and the back-side measurement position E2 are set in areas of transparent resin layer 14 that are not affected by other layers when measuring the front-side indentation elastic modulus and the back-side indentation elastic modulus. In this embodiment, as in the first embodiment, the front-side measurement position E1 is preferably set in an area 10 μm away in the thickness direction from the interface of the transparent resin layer 14 on the surface protective layer 15 side toward the base sheet 11, and the back-side measurement position E2 is preferably set in a position 10 μm away in the thickness direction from the interface of the transparent resin layer 14 on the base sheet 11 side toward the surface protective layer 15. This makes it possible to reliably measure the front-side indentation elastic modulus without being affected by the surface protective layer 15, and to reliably measure the back-side indentation elastic modulus without being affected by each layer (printing layer 12 or anchor layer 13) provided on the base sheet 11.

[0085] The front-side indentation elastic modulus and the back-side indentation elastic modulus can be measured using a microhardness measurement device. For example, a FischerSCOPE Hm2000 manufactured by Fischer can be used as the microhardness measurement device. The microhardness measurement device measures the front-side indentation elastic modulus (E IT / 1-v s ^2) and backside indentation elastic modulus (E IT / 1-v s ^2) is measured. In addition, the true indentation elastic modulus (E IT ) but the modulus of indentation elasticity (E IT / 1-v s Therefore, in this example, the coefficient of indentation elasticity (E IT / 1-v s ^2) will be called the indentation elastic modulus.

[0086] (Ultraviolet irradiation process S22) 3, after the pre-irradiation elastic modulus measurement step S21 is performed, an ultraviolet irradiation step S22 is then performed. In the ultraviolet irradiation step S22, an ultraviolet irradiation test is performed on the laminate sheet 10. The ultraviolet irradiation test in the ultraviolet irradiation step S22 is the same as the ultraviolet irradiation test in the ultraviolet irradiation step S2 in the first embodiment, and therefore a description thereof will be omitted.

[0087] (Post-irradiation elastic modulus measurement step S23) 3, after the ultraviolet irradiation step S22, a post-irradiation elastic modulus measurement step S23 is carried out. In the post-irradiation elastic modulus measurement step S23, the indentation elastic modulus of the transparent resin layer 14 after the ultraviolet irradiation test is measured. In this step, the front-side indentation elastic modulus at the front-side measurement position E1 and the back-side indentation elastic modulus at the back-side measurement position E2 are measured, similar to the pre-irradiation elastic modulus measurement step S21. In this way, in the method for evaluating the weather resistance of the laminate sheet 10 according to this embodiment, the front-side indentation elastic modulus and the back-side indentation elastic modulus are measured before and after the ultraviolet irradiation test.

[0088] In the post-irradiation elastic modulus measuring step S23, the front-side indentation elastic modulus and the back-side indentation elastic modulus are measured for the sample of laminate sheet 10 after the ultraviolet irradiation test in the ultraviolet irradiation step S22. The pre-irradiation elastic modulus measuring step S21 and the post-irradiation elastic modulus measuring step S23 may be collectively referred to as the "elastic modulus measuring step."

[0089] (Elastic modulus ratio calculation step S24) 3, after the post-irradiation elastic modulus measuring step S23 is performed, the elastic modulus ratio calculating step S24 is performed. In the elastic modulus ratio calculating step S24, the ratio (P1 / P2) of the front-side indentation elastic modulus (P1) to the back-side indentation elastic modulus (P2) of the transparent resin layer 14 of the laminate sheet 10 is calculated. Specifically, in the elastic modulus ratio calculation step S24, the ratio between the front-side indentation elastic modulus and the back-side indentation elastic modulus measured in the pre-irradiation elastic modulus measurement step S21 is first calculated as the pre-irradiation elastic modulus ratio. Furthermore, the ratio between the front-side indentation elastic modulus and the back-side indentation elastic modulus measured in the post-irradiation elastic modulus measurement step S23 is calculated as the post-irradiation elastic modulus ratio. By calculating the ratio from the indentation elastic modulus values ​​measured in the pre-irradiation elastic modulus measurement step S21 and the post-irradiation elastic modulus measurement step S23, data variability can be corrected, improving the accuracy of the evaluation based on the indentation elastic modulus.

[0090] (Elastic modulus ratio change rate calculation step S25) 3, after the elastic modulus ratio calculation step S24 is performed, the elastic modulus ratio change rate calculation step S25 is performed. In this embodiment, the elastic modulus ratio change rate calculation step S25 calculates the change rate (%) of the ratio (P1 / P2) of the front-side indentation elastic modulus to the back-side indentation elastic modulus before and after the ultraviolet light irradiation step S22. Specifically, the above-mentioned rate of change is calculated using the pre-irradiation elastic modulus ratio and post-irradiation elastic modulus ratio calculated in the elastic modulus ratio calculation step S24. Here, when the rate of change is defined as "C2", the rate of change (C2) is calculated using, for example, the following formula (2). C2 = (elastic modulus ratio after irradiation - elastic modulus ratio before irradiation) / elastic modulus ratio before irradiation (2) The rate of change (rate of increase) of the indentation elastic modulus ratio after ultraviolet irradiation relative to the indentation elastic modulus ratio before ultraviolet irradiation is calculated using the above formula (2).

[0091] (Evaluation step S26) 3, after the elastic modulus ratio change rate calculation step S25 is performed, the evaluation step S26 is then performed. In the evaluation step S26 of this embodiment, the weather resistance of the laminate sheet 10 is evaluated based on the change rate (C2) of the ratio (P1 / P2) of the front-side indentation elastic modulus to the back-side indentation elastic modulus before and after the ultraviolet light irradiation step S22. Specifically, in the evaluation step S26, whether the laminate sheet 10 has sufficient weather resistance is evaluated based on whether the change rate (C2) of the indentation elastic modulus ratio is less than a predetermined threshold value. Here, sufficient weather resistance means that when the laminated sheet 10 is used outdoors, its weather resistance can be maintained for at least five years without any abnormalities such as whitening on the surface, as in the weather resistance evaluation in the first embodiment described above.

[0092] In this embodiment, the threshold value for the weather resistance evaluation is set according to the change in indentation modulus due to ultraviolet irradiation, the ultraviolet irradiation time in the ultraviolet irradiation step S22, and the period for which weather resistance is required to be maintained (e.g., warranty period). Generally, the warranty period for a building (such as a house) is about 5 to 10 years. The inventors have discovered that by setting the threshold for the rate of change in the indentation elastic modulus ratio to "25%" when the ultraviolet irradiation time is 250 hours and determining whether the rate of change is less than 25% to capture the initial change in the weather resistance of the laminate sheet, it is possible to evaluate whether or not the weather resistance will be maintained for at least 5 years. Therefore, in this embodiment, the ultraviolet irradiation time is set to 250 hours, and the threshold for evaluating weather resistance based on the rate of change in the indentation elastic modulus ratio is set to 25%.

[0093] The change rate (C2) of the ratio (P1 / P2) of the front-side indentation elastic modulus to the back-side indentation elastic modulus before and after the ultraviolet irradiation step S22 is less than 25%, which indicates that the flexibility of the laminate sheet 10 is maintained and that hardening (deterioration) of the laminate sheet 10 due to ultraviolet exposure is suppressed. Therefore, weather resistance is maintained for a longer period of time than when the change rate (C2) of the indentation elastic modulus is 25% or more.

[0094] Thus, in the evaluation step S26, whether the laminate sheet 10 has sufficient weather resistance is evaluated based on whether the rate of change (C2) of the ratio (P1 / P2) of the front-side indentation elastic modulus to the back-side indentation elastic modulus before and after the ultraviolet irradiation test in the ultraviolet irradiation step S22 is less than 25%. This makes it possible to evaluate whether the laminate sheet 10 can maintain its weather resistance for at least five years.

[0095] That is, in the present embodiment, in the evaluation step S26, if the rate of change (C2) is less than the threshold value "25%," the laminate sheet 10 is evaluated as having sufficient weather resistance, and if the rate of change (C2) is not less than 25%, that is, if the rate of change (C2) is 25% or more, the laminate sheet 10 is evaluated as not having sufficient weather resistance. In other words, the laminate sheet 10 has sufficient weather resistance when configured so that the rate of change (C2) is less than 25%.

[0096] Furthermore, the smaller the value of the rate of change (C2), i.e., the closer to 0%, the less deterioration there is, and the longer the weather resistance tends to be maintained. Therefore, for example, if the rate of change (C2) of the indentation elastic modulus before and after the ultraviolet irradiation test in the ultraviolet irradiation step S22 is less than 5%, there is a high probability that the weather resistance of the laminate sheet 10 will be maintained for a period of 5 to 10 years when used outdoors. Furthermore, the above rate of change (C2) may be a negative value, but this indicates that there is almost no change in the indentation elastic modulus ratio before and after the ultraviolet irradiation test in the ultraviolet irradiation step S22, and does not indicate softening of the laminated sheet 10.

[0097] Furthermore, in the evaluation method for the laminate sheet 10 according to this embodiment, the measurement of the indentation elastic modulus in the elastic modulus measurement steps (pre-irradiation elastic modulus measurement step S21, post-irradiation elastic modulus measurement step S23), and the calculation and determination processes in the elastic modulus ratio calculation step S24, elastic modulus ratio change rate calculation step S25, and evaluation step S26 may be performed by a predetermined electronic calculator (such as a computer), as in the weather resistance evaluation method according to the first embodiment. As in the weather resistance evaluation method according to the first embodiment, the weather resistance evaluation method according to this embodiment can reduce the time required for weather resistance evaluation by 70% or more.

[0098] As described above, the weather resistance evaluation method for laminate sheet 10 according to this embodiment can significantly reduce the time required for evaluating the laminate sheet, thereby reducing costs and the burden on personnel involved in the evaluation, and enabling rapid evaluation results for commercial materials. Furthermore, the weather resistance evaluation method for laminate sheet 10 according to this embodiment evaluates weather resistance based on numerical data (the rate of change in the indentation elastic modulus ratio (C2) and the threshold value (25%)). This improves the evaluation accuracy compared to visual evaluation. Furthermore, the laminated sheet 10 of this embodiment is configured so that the ratio of the front side indentation elastic modulus to the back side indentation elastic modulus (P1 / P2) changes by less than 25% before and after the irradiation test, thereby providing excellent weather resistance and shortening the time required for weather resistance evaluation.

[0099] As described above, the method for evaluating the weather resistance of the laminate sheet 10 according to this embodiment is a method for evaluating the weather resistance of the laminate sheet 10 by measuring the illuminance of the laminate sheet 10 from the surface protection layer 15 side, which is the outermost surface of the laminate sheet 10, at 65 mW / cm using an integrating actinometer having a sensitivity wavelength range of 310 nm to 390 nm. 2 An ultraviolet irradiation test is performed for 250 hours using a metal halide lamp under the conditions of a black panel temperature of 63°C and a humidity inside the chamber of 50% in an ultraviolet irradiation step S22. Before and after the ultraviolet irradiation test in the ultraviolet irradiation step S22, the surface side indentation elastic modulus (E IT / 1-V S ^2), and the back surface side indentation elastic modulus (E IT / 1-V SThe method includes an indentation modulus measurement process (pre-irradiation elastic modulus measurement process S21, post-irradiation elastic modulus measurement process S23) for measuring the indentation modulus (P1) and the indentation modulus (P2) of the front-side indentation elastic modulus (P1) and the back-side indentation elastic modulus (P2) before and after the irradiation test (pre-irradiation elastic modulus measurement process S26), and an evaluation process S26 for evaluating weather resistance based on whether the rate of change (C2) of the ratio (P1 / P2) of the front-side indentation elastic modulus (P1) to the back-side indentation elastic modulus (P2) before and after the irradiation test is less than 25%. Furthermore, the front-side measurement position E1 and the back-side measurement position E2 are set in areas of the transparent resin layer 14 that are not affected by other layers (surface protective layer 15, each layer on the base sheet 11) when measuring the front-side indentation elastic modulus and the back-side indentation elastic modulus.

[0100] As a result, the method for evaluating the weather resistance of the laminate sheet 10 according to this embodiment can shorten the time required for evaluating the weather resistance.

[0101] Furthermore, the laminate sheet 10 according to this embodiment is configured so that the weather resistance evaluation method shown in FIG. 3 can be applied. Specifically, the laminate sheet 10 according to this embodiment is a laminate sheet in which a printed layer 12 is provided on a base sheet 11, and at least a transparent resin layer 14 and a surface protective layer 15 are laminated in this order on the printed layer 12. The laminate sheet 10 is also configured such that the illuminance of the laminate sheet 10 is 65 mW / cm when measured from the surface protective layer 15 side using an integrating actinometer having a sensitivity wavelength range of 310 nm to 390 nm. 2 Under the conditions of a black panel temperature of 63°C and a humidity inside the chamber of 50%, a 250-hour ultraviolet irradiation test was performed using a metal halide lamp, and the surface-side indentation elastic modulus (E IT / 1-V S ^2), and the back surface side indentation elastic modulus (E IT / 1-V SWhen the indentation modulus (P1) and the backside indentation modulus (P2) are measured (when the indentation modulus measurement step is performed), the ratio (P1 / P2) of the front-side indentation modulus (P1) to the backside indentation modulus (P2) changes by less than 25% before and after the irradiation test. Furthermore, in the laminate sheet 10, the front-side measurement position E1 and the backside measurement position E2 are set in areas of the transparent resin layer 14 that are not affected by other layers (the surface protective layer 15 and each layer on the base sheet 11) when the front-side indentation modulus and the backside indentation modulus are measured.

[0102] As a result, the laminate sheet 10 according to this embodiment has excellent weather resistance and can shorten the time required for weather resistance evaluation.

[0103] (Variation) The laminated sheet 10 according to the present embodiment is a laminated sheet in which a printed layer 12 is provided on a base sheet 11, and at least a transparent resin layer 14 and a surface protective layer 15 are laminated in this order on the printed layer 12. The transparent resin layer 14 has an indentation modulus of elasticity (E IT / 1-V S ^2) may be 600 MPa or less, and at least one of the transparent resin layer 14 and the surface protective layer 15 may contain a hindered amine-based light stabilizer. Even with this configuration, the laminate sheet 10 has excellent weather resistance, and the time required for weather resistance evaluation can be shortened.

[0104] Here, the indentation modulus of the transparent resin layer 14 may be the front-side indentation modulus at the front-side measurement position E1, the back-side indentation modulus at the back-side measurement position E2, or the indentation modulus in the region between the front-side measurement position E1 and the back-side measurement position E2 in the thickness direction of the transparent resin layer 14. The indentation modulus of the transparent resin layer 14 is preferably in the range of 300 MPa to 600 MPa, and more preferably 450 MPa or less. In addition, the hindered amine-based light stabilizer may be contained in both the transparent resin layer 14 and the surface protective layer 15, or may be contained only in the transparent resin layer 14, or may be contained only in the surface protective layer 15.

[0105] Third Embodiment (Weather resistance evaluation) A method for evaluating the weather resistance of a decorative sheet according to a third embodiment of the present invention (hereinafter referred to as this embodiment) will be described with reference to Figures 1 and 4. Figure 4 is a flowchart for explaining an example of the flow of a method for evaluating a laminate sheet 10 according to this embodiment. The weather resistance evaluation method according to this embodiment differs from the weather resistance evaluation methods for the laminate sheet 10 according to the first and second embodiments in that the weather resistance of the laminate sheet 10 is evaluated based on the indentation hardness.

[0106] The inventors of the present invention have conducted extensive research into weather resistance evaluation of laminated sheets used for exterior applications and shortening the evaluation time. As a result, they have found that the indentation hardness (H IT We found that it is possible to evaluate weather resistance based on changes in the indentation hardness. We also succeeded in significantly reducing the time required for the evaluation by evaluating weather resistance based on changes in the indentation hardness. An example of the weather resistance evaluation method according to this embodiment will be specifically described below. In the following explanation, differences from the method for evaluating the weather resistance of the laminate sheet 10 according to the first embodiment (FIG. 2) will be mainly explained, and detailed explanation of similar points will be omitted as appropriate.

[0107] (Pre-irradiation indentation hardness measurement step S31) As shown in FIG. 4, in the method for evaluating the weather resistance of the laminated sheet 10 according to this example, first, in a pre-irradiation indentation hardness measurement step S31, the indentation hardness (H IT The unit of indentation hardness is N / mm 2 The pre-irradiation indentation hardness measuring step S31 differs from the pre-irradiation hardness measuring step S1 in the first embodiment in that the indentation hardness is measured at the front-side measurement position E1 and the back-side measurement position E2.

[0108] In the pre-irradiation indentation hardness measurement step 31, indentation hardness is measured at the front-side measurement position E1 and the back-side measurement position E2 shown in Figure 1. Here, the indentation hardness at the front-side measurement position E1 is referred to as the front-side indentation hardness, and the indentation hardness at the back-side measurement position E2 is referred to as the back-side indentation hardness. In other words, in the pre-irradiation indentation hardness measurement step, the front-side indentation hardness at the front-side measurement position E1 and the back-side indentation hardness at the back-side measurement position E2 are measured. In the pre-irradiation indentation hardness measurement step S31, similarly to the pre-irradiation hardness measurement step S1, the sample of laminate sheet 10 is cut in the thickness direction to expose the cross section when measuring the front-side indentation hardness and the back-side indentation hardness. Furthermore, the front-side measurement position E1 and the back-side measurement position E2 are set in areas of transparent resin layer 14 that are not affected by other layers when measuring the front-side indentation hardness and the back-side indentation hardness. In this embodiment, as in the first embodiment, the front-side measurement position E1 is preferably set in an area 10 μm away in the thickness direction from the boundary surface of the transparent resin layer 14 on the surface protective layer 15 side toward the base sheet 11, and the back-side measurement position E2 is preferably set in a position 10 μm away in the thickness direction from the boundary surface of the transparent resin layer 14 on the base sheet 11 side toward the surface protective layer 15. This makes it possible to reliably measure the front-side indentation hardness without being affected by the surface protective layer 15, and to reliably measure the back-side indentation hardness without being affected by each layer (printing layer 12 or anchor layer 13) provided on the base sheet 11.

[0109] The front-side indentation hardness and the back-side indentation hardness can be measured using a microhardness measuring device. For example, a FischerSCOPE Hm2000 manufactured by Fischer can be used as the microhardness measuring device. The microhardness measuring device measures the front-side indentation hardness (H IT ) and backside indentation hardness (H IT ) is measured.

[0110] (Ultraviolet irradiation process S32) 4, after the pre-irradiation indentation hardness measurement step S31 is performed, an ultraviolet irradiation step S32 is then performed. In the ultraviolet irradiation step S32, an ultraviolet irradiation test is performed on the laminated sheet 10. The ultraviolet irradiation test in the ultraviolet irradiation step S32 is the same as the ultraviolet irradiation test in the ultraviolet irradiation step S2 in the first embodiment, and therefore a description thereof will be omitted.

[0111] (Post-irradiation indentation hardness measurement step S33) As shown in Figure 4, after the ultraviolet irradiation step S32 is performed, a post-irradiation indentation hardness measurement step S33 is then performed. In the post-irradiation indentation hardness measurement step S33, the indentation hardness of the transparent resin layer 14 after the ultraviolet irradiation test is measured. In this step, similar to the pre-irradiation indentation hardness measurement step S31, the front-side indentation hardness at the front-side measurement position E1 and the back-side indentation hardness at the back-side measurement position E2 are measured. In this way, in the method for evaluating the weather resistance of the laminate sheet 10 according to this embodiment, the front-side indentation hardness and the back-side indentation hardness are measured before and after the ultraviolet irradiation test.

[0112] In the post-irradiation indentation hardness measurement step S33, the front-side indentation hardness and back-side indentation hardness are measured for the sample of laminate sheet 10 after the ultraviolet light irradiation test in the ultraviolet light irradiation step S22. The pre-irradiation indentation hardness measurement step S31 and the post-irradiation indentation hardness measurement step S33 may be collectively referred to as the "indentation hardness measurement step."

[0113] (Indentation hardness ratio calculation step S34) 4, after the post-irradiation indentation hardness measurement step S33 is performed, the indentation hardness ratio calculation step S34 is then performed. In the indentation hardness ratio calculation step S34, the ratio (R1 / R2) of the front-side indentation hardness (R1) to the back-side indentation hardness (R2) of the transparent resin layer 14 of the laminate sheet 10 is calculated. Specifically, in the indentation hardness ratio calculation step S34, the ratio between the front-side indentation hardness measured in the pre-irradiation indentation hardness measurement step S31 and the back-side indentation hardness is first calculated as the pre-irradiation indentation hardness ratio. Furthermore, the ratio between the front-side indentation hardness measured in the post-irradiation indentation hardness measurement step S33 and the back-side indentation hardness is calculated as the post-irradiation indentation hardness ratio. By calculating the ratio from the indentation hardness values ​​measured in the pre-irradiation indentation hardness measurement step S31 and the post-irradiation indentation hardness measurement step S33, data variability can be corrected, improving the accuracy of evaluation based on indentation hardness.

[0114] (Indentation hardness ratio change rate calculation step S35) 4, after the indentation hardness ratio calculation step S34 is performed, the indentation hardness ratio change rate calculation step S35 is performed. In this embodiment, the indentation hardness ratio change rate calculation step S35 calculates the change rate (%) of the ratio (R1 / R2) between the front-side indentation hardness and the back-side indentation hardness before and after the ultraviolet light irradiation step S32. Specifically, the above-mentioned rate of change is calculated using the pre-irradiation indentation hardness ratio and the post-irradiation indentation hardness ratio calculated in the indentation hardness ratio calculation step S34. Here, when the rate of change is designated as "C3", the rate of change (C3) is calculated using, for example, the following formula (3). C3=(Indentation hardness ratio after irradiation - Indentation hardness ratio before irradiation) / Indentation hardness ratio before irradiation...(3) The rate of change (rate of increase) in the indentation hardness ratio after ultraviolet irradiation relative to the indentation hardness ratio before ultraviolet irradiation is calculated using the above formula (3).

[0115] (Evaluation step S36) 4, after the indentation hardness ratio change rate calculation step S35 is performed, the evaluation step S36 is then performed. In the evaluation step S36 of this embodiment, the weather resistance of the laminate sheet 10 is evaluated based on the change rate (C3) of the ratio (R1 / R2) of the front-side indentation hardness to the back-side indentation hardness before and after the ultraviolet light irradiation step S32. Specifically, in the evaluation step S36, whether the laminate sheet 10 has sufficient weather resistance is evaluated based on whether the change rate (C3) of the indentation hardness ratio is less than a predetermined threshold value. Here, sufficient weather resistance means that when the laminated sheet 10 is used outdoors, its weather resistance can be maintained for at least five years without any abnormalities such as whitening on the surface, as in the weather resistance evaluation in the first embodiment described above.

[0116] In this embodiment, the threshold value for the weather resistance evaluation is set according to the change in indentation hardness due to ultraviolet irradiation, the ultraviolet irradiation time in the ultraviolet irradiation step S32, and the period for which weather resistance is required to be maintained (e.g., warranty period). Generally, the warranty period for a building (such as a house) is about 5 to 10 years. The inventors discovered that by setting the threshold for the rate of change in the indentation hardness ratio to "20%" when the ultraviolet irradiation time is 250 hours and determining whether the rate of change is less than 20% to capture the initial change in the weather resistance of the laminate sheet, it is possible to evaluate whether or not the weather resistance will be maintained for at least 5 years. Therefore, in this embodiment, the ultraviolet irradiation time is set to 250 hours, and the threshold for evaluating weather resistance based on the rate of change in the indentation hardness ratio is set to 20%.

[0117] The change rate (C3) of the ratio (R1 / R2) of the front-side indentation hardness to the back-side indentation hardness before and after the ultraviolet irradiation step S32 is less than 20%, which indicates that the flexibility of the laminate sheet 10 is maintained and hardening (deterioration) of the laminate sheet 10 due to exposure to ultraviolet light is suppressed. Therefore, weather resistance is maintained for a longer period of time than when the change rate (C3) of the indentation hardness is 20% or more.

[0118] Thus, in the evaluation step S36, whether the laminate sheet 10 has sufficient weather resistance is evaluated based on whether the rate of change (C3) of the ratio (R1 / R2) of the front-side indentation hardness to the back-side indentation hardness before and after the ultraviolet irradiation test in the ultraviolet irradiation step S32 is less than 20%. This makes it possible to evaluate whether the laminate sheet 10 can maintain its weather resistance for at least five years.

[0119] That is, in the present embodiment, in the evaluation step S26, if the rate of change (C3) is less than the threshold value "20%," the laminate sheet 10 is evaluated as having sufficient weather resistance, and if the rate of change (C3) is not less than 20%, i.e., if the rate of change (C3) is 20% or more, the laminate sheet 10 is evaluated as not having sufficient weather resistance. In other words, the laminate sheet 10 has sufficient weather resistance when configured so that the rate of change (C3) is less than 20%.

[0120] Furthermore, the smaller the value of the rate of change (C3), that is, the closer to 0%, the less deterioration there is, and the longer the period during which weather resistance is maintained tends to be. Furthermore, the above rate of change (C3) may be a negative value, but this indicates that there is almost no change in the indentation hardness ratio before and after the ultraviolet irradiation test in the ultraviolet irradiation step S32, and does not indicate softening of the laminated sheet 10.

[0121] Furthermore, in the evaluation method for the laminate sheet 10 according to this embodiment, the indentation hardness measurements in the indentation hardness measurement steps (pre-irradiation indentation hardness measurement step S31, post-irradiation indentation hardness measurement step S33), and the calculation and determination processes in the indentation hardness ratio calculation step S34, indentation hardness ratio change rate calculation step S35, and evaluation step S36 may be performed by a predetermined electronic calculator (such as a computer), as in the weather resistance evaluation method according to the first embodiment. As in the weather resistance evaluation method according to the first embodiment, the weather resistance evaluation method according to this embodiment can reduce the time required for weather resistance evaluation by 70% or more.

[0122] As described above, the weather resistance evaluation method for laminate sheet 10 according to this embodiment can significantly reduce the time required for evaluating the laminate sheet, thereby reducing costs and the burden on personnel involved in the evaluation, and enabling rapid evaluation results for commercial products. Furthermore, the weather resistance evaluation method for laminate sheet 10 according to this embodiment evaluates weather resistance based on numerical data (the rate of change in indentation hardness ratio (C3) and the threshold value (20%)). This improves evaluation accuracy compared to visual evaluation. Furthermore, the laminated sheet 10 of this embodiment is configured so that the ratio of the front side indentation hardness to the back side indentation hardness (R1 / R2) changes by less than 20% before and after the irradiation test, thereby providing excellent weather resistance and shortening the time required for weather resistance evaluation.

[0123] As described above, the method for evaluating the weather resistance of the laminate sheet 10 according to this embodiment is a method for evaluating the weather resistance of the laminate sheet 10 by measuring the illuminance of the laminate sheet 10 from the surface protection layer 15 side, which is the outermost surface of the laminate sheet 10, at 65 mW / cm using an integrating actinometer having a sensitivity wavelength range of 310 nm to 390 nm. 2 An ultraviolet irradiation test is performed for 250 hours using a metal halide lamp under the conditions of a black panel temperature of 63°C and a humidity inside the chamber of 50% in an ultraviolet irradiation step S32. Before and after the ultraviolet irradiation test in the ultraviolet irradiation step S32, the surface hardness (H IT ) and the back surface indentation hardness (H IT and an evaluation step of evaluating weather resistance based on whether the rate of change in the ratio (R1 / R2) of the front-side indentation hardness (R1) to the back-side indentation hardness (R2) before and after the irradiation test is less than 20%. Furthermore, the front-side measurement position E1 and the back-side measurement position E2 are set in areas of the transparent resin layer 14 that are not affected by other layers when measuring the front-side indentation hardness and the back-side indentation hardness.

[0124] As a result, the method for evaluating the weather resistance of the laminate sheet 10 according to this embodiment can shorten the time required for evaluating the weather resistance.

[0125] Furthermore, the laminate sheet 10 according to this embodiment is configured so that the weather resistance evaluation method shown in FIG. 4 can be applied. Specifically, the laminate sheet 10 according to this embodiment is a laminate sheet in which a printed layer 12 is provided on a base sheet 11, and at least a transparent resin layer 14 and a surface protective layer 15 are laminated in this order on the printed layer 12. The laminate sheet 10 is also configured such that the illuminance of the laminate sheet 10 is 65 mW / cm when measured from the surface protective layer 15 side using an integrating actinometer having a sensitivity wavelength range of 310 nm to 390 nm. 2 Under the conditions of a black panel temperature of 63°C and a humidity inside the chamber of 50%, a 250-hour ultraviolet irradiation test was performed using a metal halide lamp, and the surface-side indentation hardness (H IT ) and the back surface indentation hardness (H IT When the indentation hardness measurement step is performed, the ratio (R1 / R2) of the front-side indentation hardness (R1) to the back-side indentation hardness (R2) changes by less than 20% before and after the irradiation test. Furthermore, in the laminate sheet 10, the front-side measurement position E1 and the back-side measurement position E2 are set in areas of the transparent resin layer 14 that are not affected by other layers when measuring the front-side indentation hardness and the back-side indentation hardness.

[0126] As a result, the laminate sheet 10 according to this embodiment has excellent weather resistance and can shorten the time required for weather resistance evaluation.

[0127] (Variation) The laminated sheet 10 according to the present embodiment is a laminated sheet in which a printed layer 12 is provided on a base sheet 11, and at least a transparent resin layer 14 and a surface protective layer 15 are laminated in this order on the printed layer 12. The transparent resin layer 14 has an indentation hardness (H IT ) is 45N / mm 2 The transparent resin layer 14 and the surface protective layer 15 may each contain a hindered amine-based light stabilizer. Even with this configuration, the laminate sheet 10 has excellent weather resistance, and the time required for weather resistance evaluation can be shortened.

[0128] Here, the indentation hardness of the transparent resin layer 14 may be the front-side indentation hardness at the front-side measurement position E1, the back-side indentation hardness at the back-side measurement position E2, or the indentation hardness in the region between the front-side measurement position E1 and the back-side measurement position E2 in the thickness direction of the transparent resin layer 14. The indentation hardness of the transparent resin layer 14 is 10 N / mm or more. 2 Over 45N / mm 2 The following range is preferable: 30N / mm 2 The following is more preferred: In addition, the hindered amine-based light stabilizer may be contained in both the transparent resin layer 14 and the surface protective layer 15, or may be contained only in the transparent resin layer 14, or may be contained only in the surface protective layer 15.

[0129] (Example) The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples in any way. Example 1 (Step of forming resin sheet for transparent resin layer) First, a benzotriazole-based UV absorber and a hindered amine-based light stabilizer were added to a homopolypropylene resin to prepare a resin material for the transparent resin layer. The homopolypropylene resin used had a mesopentad fraction of 95% or more and a melt flow rate (MFR) of 4.5 g / 10 min (JIS K 7210:99). The resin material for the transparent resin layer also contained a benzotriazole-based UV absorber and a hindered amine-based light stabilizer. The benzotriazole-based UV absorber, "Tinuvin 328 (manufactured by BASF)," was used, and 2000 ppm (0.2 parts by mass) of the homopolypropylene resin was added. The hindered amine-based light stabilizer, "Chimasorb 944 (manufactured by BASF)," was used, and 2000 ppm (0.2 parts by mass) of the homopolypropylene resin was added. The resin material for the transparent resin layer was extruded using a melt extruder to produce an 80 μm-thick polypropylene transparent resin sheet for use as the transparent resin layer. (Surface protection layer formation process) A benzotriazole-based UV absorber and a hindered amine-based light stabilizer were added to an acrylic urethane resin on the surface of the transparent resin layer to form a resin material for a surface protective layer. A two-component curing urethane top coat (W184; manufactured by DIC Graphics Corporation) was used as the acrylic urethane resin. A benzotriazole-based UV absorber and a hindered amine-based light stabilizer were also added to the resin material for the surface protective layer. The benzotriazole-based UV absorber used was "Tinuvin 328; manufactured by BASF," and 2000 ppm (0.2 parts by mass) was added to the urethane top coat. The hindered amine-based light stabilizer used was "Chimasorb 944; manufactured by BASF," and 2000 ppm (0.2 parts by mass) was added to the urethane top coat. This resin material for a surface protective layer was applied to the transparent resin layer to a thickness of 6 g / m. 2 and dried to form a surface protective layer.

[0130] <Example 2> A transparent resin layer and a surface protective layer according to Example 2 were produced in the same manner as in Example 1, except that no ultraviolet absorber was added to the resin material for the transparent resin layer.

[0131] Example 3 A transparent resin layer and a surface protective layer according to Example 3 were produced in the same manner as in Example 1, except that no ultraviolet absorber was added to the resin material for the surface protective layer.

[0132] Example 4 A transparent resin layer and a surface protective layer according to Example 4 were prepared in the same manner as in Example 1, except that no hindered amine-based light stabilizer was added to the urethane top coat, which was the resin material for the surface protective layer.

[0133] <Example 5> A transparent resin layer and a surface protective layer according to Example 5 were produced in the same manner as in Example 1, except that neither an ultraviolet absorber nor a hindered amine-based light stabilizer was added to the resin material for the surface protective layer, and only a urethane top coat was used.

[0134] Example 6 The homopolypropylene resin in the resin material for the transparent resin layer had a mesopentad fraction of 95% or more and an MFR (melt flow rate) of 6.2 g / 10 min (JIS K 7210:99). Otherwise, the transparent resin layer and surface protective layer of Example 6 were produced in the same manner as in Example 1.

[0135] <Comparative Example 1> A transparent resin layer and a surface protective layer according to Comparative Example 1 were produced in the same manner as in Example 1, except that the resin material for the transparent resin layer was a homopolypropylene resin only.

[0136] <Comparative Example 2> A transparent resin layer and a surface protective layer according to Comparative Example 2 were prepared in the same manner as in Example 1, except that no hindered amine-based light stabilizer was added to the resin material for the transparent resin layer.

[0137] <Comparative Example 3> The homopolypropylene resin in the resin material for the transparent resin layer had a mesopentad fraction of 95% or more and an MFR (melt flow rate) of 15 g / 10 min (JIS K 7210:99).Other than that, the transparent resin layer and surface protective layer according to Comparative Example 3 were prepared in the same manner as in Example 1.

[0138] <Evaluation> Each sample (transparent resin layer and surface protective layer) obtained in Examples 1 to 5 and Comparative Examples 1 to 3 was subjected to (1) weather resistance evaluation based on Martens hardness, (2) weather resistance evaluation based on indentation modulus, and (3) weather resistance evaluation based on indentation hardness. The results of evaluation (1) above are shown in Table 1 below, the results of evaluation (2) above are shown in Table 2 below, and the results of evaluation (3) above are shown in Table 3 below.

[0139] [Table 1]

[0140] [Table 2]

[0141] [Table 3]

[0142] The evaluation contents of each weather resistance evaluation are explained below. <Weather resistance evaluation based on Martens hardness> (1-1) Martens hardness measurement before UV irradiation Using a Fischer FISCHERSCOPE Hm2000 microhardness measuring device, the Martens hardness was measured at two locations (front surface side measurement location and back surface side measurement location) on the transparent resin layer for each sample of Examples 1 to 6 and Comparative Examples 1 to 3 before the ultraviolet irradiation test described below in (1-2). The front surface side measurement location was a location 10 μm away from the boundary surface of the transparent resin layer with the surface protective layer in the thickness direction (the direction opposite to the surface protective layer). The back surface side measurement location was a location 10 μm away from the surface (back surface) on the opposite side of the surface protective layer in the thickness direction (toward the surface protective layer). The Martens hardness at the measurement position on the front side (front side Martens hardness) and the Martens hardness at the measurement position on the back side (back side Martens hardness) were measured using a microhardness measuring device with load parameters that increased the load to 5 mN over 10 seconds for each of the measurement positions on the front side and the back side, held this load for 5 seconds, and then decreased the load to 0.1 mN over 10 seconds. The "Before irradiation test" column in Table 1 shows the Martens hardness (front side Martens hardness, back side Martens hardness) before the ultraviolet irradiation test for each sample of Examples 1 to 6 and Comparative Examples 1 to 3, along with the Martens hardness ratio (front side Martens hardness before irradiation test / back side Martens hardness before irradiation test).

[0143] (1-2) UV irradiation test Using a "Daipla Wintes Metal Weather Tester (KW-R7TP-A)," an ultraviolet irradiation test was carried out on each sample of Examples 1 to 6 and Comparative Examples 1 to 3. The test conditions were an illuminance of 65 mW / cm2 measured using an integrating actinometer with a sensitivity wavelength range of 310 nm to 390 nm. 2 The black panel temperature was 63°C, and the humidity inside the chamber was 50%. An ultraviolet illuminance meter UIT-201, manufactured by Ushio Inc., was used as the integrating light actinometer. Using this, samples for measuring Martens hardness after ultraviolet irradiation, which will be described later, were prepared.

[0144] (1-3) Martens hardness measurement after ultraviolet irradiation After the ultraviolet irradiation test in (1-2) above was performed, the front-side Martens hardness and back-side Martens hardness of each sample of Examples 1 to 6 and Comparative Examples 1 to 3 were measured in the same manner as the pre-irradiation Martens hardness measurement in (1-1) above. The "After irradiation test" column in Table 1 shows the Martens hardness (front side Martens hardness, back side Martens hardness) after the ultraviolet irradiation test for each sample of Examples 1 to 6 and Comparative Examples 1 to 3, along with the Martens hardness ratio (front side Martens hardness after irradiation test / back side Martens hardness after irradiation test).

[0145] (1-4) Life test Each sample of Examples 1 to 6 and Comparative Examples 1 to 3 was subjected to a test using a metal weather tester (KW-R7TP-A) manufactured by Daipla Wintes Co., Ltd., at an illuminance of 65 mW / cm. 2 Light irradiation was carried out under conditions of a black panel temperature of 63°C and a chamber humidity of 50% (Ushio Inc. UV illuminance meter UIT-201, calibrated), and each sample was visually inspected every 24 hours. In the lifespan test, the time (h) until whitening was confirmed on the outermost surface (surface protection layer) was taken as the lifespan (weather resistance retention period) of each sample, and weather resistance was evaluated. [Evaluation criteria] ◎: 2800 hours or more 〇: Over 2500 hours ×: Less than 2500 hours In this evaluation, if the time (lifetime) until whitening was confirmed on the outermost surface (surface protective layer) was 2,500 hours or more, the weather resistance of the laminated sheet could be maintained for 5 years (excellent weather resistance), and it was rated as passing "○". In addition, if the evaluation result is "◎", it indicates that the weather resistance of the laminated sheet can be maintained for a period of 5 years or more and 10 years or less.

[0146] (Weather resistance evaluation results based on Martens hardness) As shown in Table 1, the evaluation results of Examples 1 to 6 showed that when the rate of change in the Martens hardness ratio (front side Martens hardness / back side Martens hardness) before and after the ultraviolet irradiation test was 10% or less, the life evaluation results were good (all passing "O" or above) and the sample had excellent weather resistance. Furthermore, the evaluation results of Examples 1 and 2 showed that when the rate of change in the Martens hardness ratio was less than 5%, the life evaluation results were extremely good (A).

[0147] In contrast, the evaluation results of Comparative Examples 1 to 3 showed that when the rate of change in the Martens hardness ratio before and after the ultraviolet irradiation test exceeded 10%, the life evaluation result was unsuccessful (×), indicating insufficient weather resistance. From the above, it was found that weather resistance can be evaluated by whether the rate of change in the Martens hardness ratio is 10% or less. Furthermore, by evaluating weather resistance based on Martens hardness, it was found that the weather resistance evaluation of a laminated sheet can be completed in 250 hours (ultraviolet light irradiation time in the ultraviolet light irradiation test), which would require several thousand hours (more than 2,000 hours in this example) if evaluated visually, and that the evaluation time can be significantly reduced compared to visual evaluation.

[0148] <Weather resistance evaluation based on indentation elastic modulus> (2-1) Measurement of indentation elastic modulus before UV irradiation Using a Fischer FISCHERSCOPE Hm2000 microhardness measuring device, the indentation elastic modulus (E) was measured at two locations (measurement position on the front side and measurement position on the back side) of the transparent resin layer for each sample of Examples 1 to 5 and Comparative Examples 1 to 3 before the ultraviolet irradiation test described below in (2-2).IT / 1-v s The measurement positions on the front side and the back side were the same as those used in measuring the Martens hardness in (1-1) above. The indentation modulus at the measurement position on the front side (front side indentation modulus) and the indentation modulus at the measurement position on the back side (back side indentation modulus) were measured using a microhardness measurement device with load parameters that increased the load to 5 mN over 10 seconds for each of the measurement positions on the front side and the back side, held this load for 5 seconds, and then decreased the load to 0.1 mN over 10 seconds. The "Before irradiation test" column in Table 2 shows the indentation elastic modulus (front side indentation elastic modulus, back side indentation elastic modulus) before the ultraviolet irradiation test for each sample of Examples 1 to 5 and Comparative Examples 1 to 3, along with the indentation elastic modulus ratio (front side indentation elastic modulus before irradiation test / back side indentation elastic modulus before irradiation test).

[0149] (2-2) UV irradiation test An ultraviolet irradiation test was carried out using the same equipment and conditions as in (1-2) above, thereby preparing a sample for measuring the indentation elastic modulus after ultraviolet irradiation, which will be described later.

[0150] (2-3) Measurement of indentation modulus after UV irradiation After the ultraviolet irradiation test in 2-2 above was performed, the front-side indentation elastic modulus and back-side indentation elastic modulus were measured for each sample of Examples 1 to 5 and Comparative Examples 1 to 3 in the same manner as the indentation elastic modulus measurement before irradiation in (2-1) above. The "After irradiation test" column in Table 2 shows the indentation elastic modulus (front side indentation elastic modulus, back side indentation elastic modulus) after the ultraviolet irradiation test for each sample of Examples 1 to 5 and Comparative Examples 1 to 3, along with the indentation elastic modulus ratio (front side indentation elastic modulus after irradiation test / back side indentation elastic modulus after irradiation test).

[0151] (2-4) Life test Weather resistance evaluation was performed using the same equipment and conditions as in (1-4) above for each sample of Examples 1 to 5 and Comparative Examples 1 to 3. As in (1-4) above, the time (h) until whitening was confirmed on the outermost surface (surface protective layer) was defined as the lifespan (weather resistance retention period) of each sample, and weather resistance evaluation was performed. [Evaluation criteria] ◎: 2800 hours or more 〇: Over 2500 hours ×: Less than 2500 hours In this evaluation, as in (1-4) above, if the time (lifetime) until whitening was confirmed on the outermost surface (surface protective layer) was 2,500 hours or more, the weather resistance of the laminate sheet could be maintained for 5 years (excellent weather resistance), and the sheet was rated as passing "○". In addition, if the evaluation result is "◎", it indicates that the weather resistance of the laminate sheet can be maintained for a period of 5 years or more and 10 years or less.

[0152] (Evaluation results based on indentation elastic modulus) As shown in Table 2, the evaluation results of Examples 1 to 5 showed that when the change in the ratio of the indentation elastic modulus (front side indentation elastic modulus / back side indentation elastic modulus) before and after the ultraviolet irradiation test was less than 25%, the life evaluation results were good (all passing "O" or above) and the sample had excellent weather resistance. Furthermore, the evaluation results of Examples 1 and 2 showed that when the rate of change in the ratio of indentation elastic modulus was less than 5%, there was a high probability that the life evaluation result would be extremely good (◎).

[0153] In contrast, the evaluation results of Comparative Examples 1 to 3 showed that when the change rate of the ratio of the indentation elastic modulus before and after the ultraviolet irradiation test was 25% or more, the life evaluation result was failed (×), indicating insufficient weather resistance. From the above, it was found that weather resistance can be evaluated by whether the rate of change in the ratio of indentation elastic modulus is less than 25%. Furthermore, by evaluating weather resistance based on indentation elastic modulus, it was found that the weather resistance evaluation of a laminated sheet can be completed in 250 hours (UV irradiation time in the UV irradiation test), which would require several thousand hours (more than 2000 hours in this example) if evaluated visually, and that the evaluation time can be significantly reduced compared to visual evaluation.

[0154] <Weather resistance evaluation based on indentation hardness> (3-1) Indentation hardness measurement before UV irradiation Using a Fischer FISCHERSCOPE Hm2000 as a microhardness measuring device, the indentation hardness (H ) was measured at two locations (measurement position on the front side and measurement position on the back side) of the transparent resin layer for each sample of Examples 1 to 5 and Comparative Examples 1 to 3 before the ultraviolet irradiation test described below in (3-2). IT The measurement positions on the front side and the back side were the same as those used in measuring the Martens hardness in (1-1) above. The indentation hardness at the measurement position on the front side (front side indentation hardness) and the indentation hardness at the measurement position on the back side (back side indentation hardness) were measured using a microhardness measuring device with load parameters that increased the load to 5 mN over 10 seconds for each of the measurement positions on the front side and back side, held this load for 5 seconds, and then decreased the load to 0.1 mN over 10 seconds. The "Before irradiation test" column in Table 3 shows the indentation hardness (front side indentation hardness, back side indentation hardness) before the ultraviolet irradiation test for each sample of Examples 1 to 5 and Comparative Examples 1 to 3, along with the indentation hardness ratio (front side indentation hardness before irradiation test / back side indentation hardness before irradiation test).

[0155] (3-2) UV irradiation test An ultraviolet irradiation test was carried out using the same equipment and conditions as in (1-2) above, thereby preparing a sample for measuring the indentation hardness after ultraviolet irradiation, which will be described later.

[0156] (3-3) Indentation hardness measurement after ultraviolet irradiation After the ultraviolet irradiation test in 3-2 above was performed, the front side indentation hardness and back side indentation hardness of each sample of Examples 1 to 5 and Comparative Examples 1 to 3 were measured in the same manner as the pre-irradiation indentation hardness measurement in (3-1) above. The "After irradiation test" column in Table 3 shows the indentation hardness (front side indentation hardness, back side indentation hardness) after the ultraviolet irradiation test for each sample of Examples 1 to 5 and Comparative Examples 1 to 3, along with the indentation hardness ratio (front side indentation hardness after irradiation test / back side indentation hardness after irradiation test).

[0157] (3-4) Life test Weather resistance evaluation was performed using the same equipment and conditions as in (1-4) above for each sample of Examples 1 to 5 and Comparative Examples 1 to 3. As in (1-4) above, the time (h) until whitening was confirmed on the outermost surface (surface protective layer) was defined as the lifespan (weather resistance retention period) of each sample, and weather resistance evaluation was performed. [Evaluation criteria] ◎: 2800 hours or more 〇: Over 2500 hours ×: Less than 2500 hours In this evaluation, as in (1-4) above, if the time (lifetime) until whitening was confirmed on the outermost surface (surface protective layer) was 2,500 hours or more, the weather resistance of the laminate sheet could be maintained for 5 years (excellent weather resistance), and the sheet was rated as passing "○". In addition, if the evaluation result is "◎", it indicates that the weather resistance of the laminate sheet can be maintained for a period of 5 years or more and 10 years or less.

[0158] (Evaluation results based on indentation hardness) As shown in Table 3, the evaluation results of Examples 1 to 5 showed that when the change rate of the indentation hardness ratio (front side indentation hardness / back side indentation hardness) before and after the ultraviolet irradiation test was less than 20%, the life evaluation results were good (all passing "O" or above) and the samples had excellent weather resistance.

[0159] In contrast, the evaluation results of Comparative Examples 1 to 3 showed that when the change rate of the indentation hardness ratio before and after the ultraviolet irradiation test was 20% or more, the life evaluation result was failed (×), indicating insufficient weather resistance. From the above, it was found that weather resistance can be evaluated by whether the rate of change in the indentation hardness ratio is less than 20%. Furthermore, by evaluating weather resistance based on indentation hardness, it was found that the weather resistance evaluation of a laminated sheet can be completed in 250 hours (ultraviolet light exposure time in the ultraviolet light exposure test), which would require several thousand hours (more than 2,000 hours in this example) if evaluated visually, and that the evaluation time can be significantly reduced compared to visual evaluation.

[0160] The laminate sheet and the method for evaluating the weather resistance of the laminate sheet of the present invention are not limited to the above-described embodiments and examples, and various modifications are possible within the scope of the invention without impairing its features. [Explanation of symbols]

[0161] 10 Decorative Sheet 11 Base sheet 12 printing layer 13 Anchor Layer 14 Transparent resin layer 15 Surface protective layer E1 Surface side measurement position E2 Back side measurement position

Claims

1. A laminated sheet in which a printed layer is provided on a base sheet, and at least a transparent resin layer and a surface protective layer are laminated in this order on the printed layer, The illuminance of the laminated sheet from the surface protective layer side is 65 mW / cm using an integrating actinometer having a sensitivity wavelength range of 310 nm to 390 nm. ２ A 250-hour ultraviolet irradiation test was conducted using a metal halide lamp under the conditions of a black panel temperature of 63°C and a chamber humidity of 50%. Before and after the irradiation test, the surface-side indentation hardness (H ＩＴ ) and a back surface indentation hardness (H ＩＴ ) and when measured, the ratio (R1 / R2) of the front surface indentation hardness (R1) to the back surface indentation hardness (R2) has a change rate before and after the irradiation test in the range of −3.5% or more and 0.6% or less; the surface protective layer contains a benzotriazole-based ultraviolet absorber as an ultraviolet absorber, the thickness of the transparent resin layer is in the range of 40 μm or more and 100 μm or less; the surface-side measurement position is set in a region spaced 10 μm in a thickness direction from the boundary surface of the transparent resin layer on the surface protective layer side toward the base sheet side, A laminate sheet, wherein the measurement position on the back surface side is set in an area 10 μm away in the thickness direction from the boundary surface of the transparent resin layer on the substrate sheet side toward the surface protective layer side.

2. A laminated sheet as described in Claim 1, wherein the benzotriazole-based ultraviolet absorber contained in the surface protective layer has a structure represented by the following formula (1): 【Chemical 1】

3. The transparent resin layer contains only polypropylene resin as a resin. The laminate sheet according to claim 1 or 2.

4. The transparent resin layer contains a hindered amine light stabilizer. The laminate sheet according to any one of claims 1 to 3.

5. The transparent resin layer contains 0.2 parts by mass or more of a hindered amine light stabilizer relative to the total mass of the transparent resin layer. The laminate sheet according to claim 4.

6. The transparent resin layer contains an ultraviolet absorber. The laminate sheet according to claim 4 or 5.

7. The transparent resin layer contains an ultraviolet absorber in an amount of 0.2 parts by mass or more relative to the total mass of the transparent resin layer. The laminate sheet according to claim 6.

8. The surface protective layer is formed of an acrylic resin. The laminate sheet according to any one of claims 1 to 7.

9. the surface protective layer contains a hindered amine-based light stabilizer, The content of the hindered amine light stabilizer in the surface protective layer is 0.2 parts by mass or more with respect to the total mass of the surface protective layer. The laminate sheet according to any one of claims 1 to 8.

10. The content of the ultraviolet absorber in the surface protective layer is 0.2 parts by mass or more relative to the total mass of the surface protective layer. The laminate sheet according to any one of claims 1 to 9.

11. A method for evaluating weather resistance of a laminated sheet in which a printed layer is provided on a base sheet, and at least a transparent resin layer and a surface protective layer are laminated in this order on the printed layer, comprising: The illuminance of the laminated sheet from the surface protective layer side, which is the outermost surface of the laminated sheet, is 65 mW / cm using an integrating actinometer having a sensitivity wavelength range of 310 nm to 390 nm. ２ an ultraviolet irradiation step of performing an ultraviolet irradiation test for 250 hours using a metal halide lamp under conditions of a black panel temperature of 63°C and a chamber humidity of 50%; Before and after the ultraviolet irradiation test, the surface side indentation hardness (H ＩＴ ) and a back surface indentation hardness (H ＩＴ ) an indentation hardness measurement step of measuring an evaluation step of evaluating weather resistance based on whether a rate of change in the ratio (R1 / R2) of the front-side indentation hardness (R1) to the back-side indentation hardness (R2) before and after the irradiation test is within a range of −3.5% to 0.6%; Including, the thickness of the transparent resin layer is in the range of 40 μm or more and 100 μm or less; the surface-side measurement position is set in a region spaced 10 μm in a thickness direction from the boundary surface of the transparent resin layer on the surface protective layer side toward the base sheet side, The measurement position on the back surface side is set in a region 10 μm away in the thickness direction from the boundary surface of the transparent resin layer on the substrate sheet side toward the surface protective layer side. Method for evaluating weather resistance of laminated sheets.

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