JP7707682B2 - Laminated sheet and method for evaluating weather resistance of laminated sheet - Google Patents

Description

The present invention relates to a laminate sheet and a method for evaluating the weather resistance of the laminate sheet.

Conventionally, laminated sheets are known that are laminated to wood boards, inorganic boards, metal sheets, etc., and used as exterior building materials. 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 issue. It is generally known that, in order to improve weather resistance, ultraviolet absorbers and radical scavengers (light stabilizers) are added to the outermost layer of the laminated sheet (e.g., Patent Documents 1 to 4).

JP 2008-238444 A JP 2007-118584 A JP 2005-088481 A JP 2011-16277 A

When an abnormality such as whitening occurs on the surface of a laminate sheet used outdoors, the weather resistance of the abnormal area is reduced by exposure to ultraviolet rays, wind and rain, and deterioration is accelerated. In other words, deterioration of the exterior of a building occurs as the weather resistance of the laminate sheet decreases.
In recent years, long-term warranties for buildings (e.g., houses) have become commonplace, and as part of this, there is an increasing need for quality assurance of laminated sheets used as exterior building materials. Therefore, as a weather resistance evaluation, for example, it is required to evaluate in advance whether the weather resistance of the laminated sheet will be maintained without deterioration during the period corresponding to the warranty period.
In conventional laminated sheets, the weather resistance has been evaluated by visually observing the change over time of the surface due to ultraviolet irradiation. However, this evaluation method has a problem in that it takes an extremely long time (evaluation time) of several thousand hours to derive the evaluation results.

In view of these problems, the present invention aims 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.

In order to solve the above problems, a laminate sheet according to one aspect of the present invention is a laminate sheet having a printed layer provided on a base sheet, and at least a transparent resin layer and a surface protective layer laminated in this order on the printed layer, the laminate sheet being subjected to an ultraviolet irradiation test for 250 hours using a metal halide lamp under conditions of an illuminance of 65 mW/cm ² using an integrating light meter having a sensitivity wavelength range of 310 nm to 390 nm, a black panel temperature of 63° C., and an internal humidity of 50%, and the front side Martens hardness (N/mm ^{2 ) at a front side measurement position set in an area on the surface protective layer side in the thickness direction of the transparent resin layer and a back side Martens hardness (N/mm 2 )} at a back side measurement position set in an area on the base sheet side in the thickness direction of the transparent resin layer are measured before and after the irradiation test. ), the ratio (A1/A2) of the front side Martens hardness (A1) to the back side Martens hardness (A2) has a rate of change of 10% or less 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 Martens hardness and the back side Martens hardness.

In order to solve the above problems, a laminate sheet according to another aspect of the present invention is a laminate sheet comprising a printed layer provided on a base sheet, and at least a transparent resin layer and a surface protective layer laminated in this order on the printed layer, wherein the transparent resin layer has a Martens hardness of 30 N/ ^mm2 or less, and at least one of the transparent resin layer and the surface protective layer contains a hindered amine-based light stabilizer.

In order to solve the above-mentioned problems, a weather resistance evaluation method according to one embodiment of the present invention is a method for evaluating the weather resistance of 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, the method including an ultraviolet irradiation step of performing an ultraviolet irradiation test for 250 hours using a metal halide lamp on the laminate sheet from the surface protective layer side, which is the outermost surface of the laminate sheet, under conditions of an illuminance of 65 mW/cm ² using an integrating light meter having a sensitivity wavelength range of 310 nm to 390 nm, a black panel temperature of 63° C., and an internal humidity of 50%, and measuring a front side Martens hardness (N/mm ² ) at a front side measurement position set in an area on the surface protective layer side in the thickness direction of the transparent resin layer and a back side Martens hardness (N/mm ² ) at a back side measurement position set in an area on the base sheet side in the thickness direction of the transparent resin layer before and after the ultraviolet irradiation test. and an evaluation step of evaluating weather resistance based on whether a rate of change in a ratio (A1/A2) of the front side Martens hardness (A1) to the back side Martens hardness (A2) before and after the irradiation test is 10% or less, 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 the front side Martens hardness and the back side Martens hardness are measured.

The present invention provides 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.

FIG. 1 is a cross-sectional view illustrating an example of a laminate sheet according to a first embodiment of the present invention. 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. 5 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. 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.

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 schematic diagrams of the invention according to the claims, and the dimensions of the width, thickness, etc. of each part differ from the actual dimensions, and the ratios between these dimensions also differ from the actual dimensions.

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 base sheet side that contacts the attachment surface of the laminate sheet may be referred to as "lower", and the opposite side (front surface) of the laminate sheet that contacts the attachment surface may be referred to as "upper".
Hereinafter, each aspect of each embodiment of the present disclosure will be described with reference to the drawings.

1. First embodiment (1.1) Basic configuration of laminate 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, this embodiment) has a base sheet 11, a printing layer 12, an anchor layer 13, a transparent resin layer 14, and a surface protective 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 the present embodiment may be 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. For this reason, in the laminate sheet 10, the formation of the anchor layer 13 may be omitted.

(Base sheet 11)
As the material of the base sheet 11, for example, a thermoplastic resin can be used. There is no particular limitation 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, propylene-α-olefin copolymer, etc., 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), etc., polyethylene terephthalate, polybutylene terephthalate, polytetramethylene terephthalate, polyethylene naphthalate, polyethylene terephthalate-isophthalate copolymer, 1,4-cyclohexanedimethanol copolymerized polyethylene terephthalate, polyarylate, polyca Examples of the resin that can be used include polyester 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; fluorine resins such as polyvinyl fluoride, polyvinylidene fluoride, polytetrafluoroethylene, ethylene-tetrafluoroethylene copolymer, and ethylene-perfluoroalkyl vinyl ether copolymer; and mixtures, copolymers, composites, laminates, and the like of two or more of these resins.

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 undesirable 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 standpoints 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.

The polyolefin resin may be appropriately selected from the many types already listed according to the intended use of the laminate sheet 10. In particular, polypropylene resins, i.e., homopolymers or copolymers mainly composed of propylene, are most suitable for general use. For example, homopolypropylene resins, random polypropylene resins, block polypropylene resins, etc., alone or in appropriate combination, or resins in which atactic polypropylene is further blended, etc., can be used. In addition, copolymers containing olefin monomers other than propylene are also acceptable, such as propylene-α-olefin copolymers having polypropylene crystal parts 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. 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.

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

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 substrate surface, for example, when the laminate sheet 10 and a specified substrate are bonded together to form an exterior building material. In addition, when utilizing the texture of the substrate surface, 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.

(Print layer 12)
The printed layer 12 is a layer that imparts design to the laminated sheet 10, and is a layer on which a picture is printed using ink on the base sheet 11.
The printing layer 12 is formed using a printing ink, a coating agent, or the like. The printing ink, etc., is not particularly limited, and the same printing ink, etc., used for the printing layer of a conventional decorative sheet can be used. For example, an acrylic ink can be used as the printing ink. As the acrylic ink, for example, an ink using a two-liquid curing type urethane resin obtained by blending an isocyanate curing agent with an acrylic polyol vehicle as a binder resin can be used. In addition, other resin components may be added to the printing layer 12 as necessary. As components other than the binder resin of the printing layer 12, for example, various additives such as colorants such as pigments and dyes, extender pigments, solvents, and light stabilizers can be used. As pigments, for example, condensed azo, insoluble azo, quinacridone, isoindoline, anthraquinone, imidazolone, cobalt, phthalocyanine, carbon, titanium oxide, iron oxide, mica, and the like, and the like, can be mentioned.

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

(Anchor layer 13)
The anchor layer (anchor coat layer) 13 is a layer provided to enhance adhesion between the base sheet 11 (lower base) and the transparent resin layer 14 (upper base).
In this embodiment, the base sheet 11 provided with the printing layer 12 and the transparent resin layer 14 may be bonded via the anchor layer 13, and various lamination methods such as thermal lamination, extrusion lamination, dry lamination, and sand lamination may be used as the bonding method. Considering the various performances of the laminated sheet 10 according to this embodiment, the bonding method is preferably a dry lamination method. For this reason, the anchor layer 13 is preferably a dry lamination adhesive layer using a dry lamination adhesive. The anchor layer 13 is formed using a normal coating method such as gravure coating, microgravure coating, comma coating, knife coating, and die coating.
In addition, the anchor layer 13 is not essential to the laminate sheet 10, and the anchor layer 13 may not be provided.

(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, for example, using a polyolefin resin. Examples of the polyolefin resin include polyolefin resins such as polyethylene, polypropylene, polymethylpentene, polybutene, ethylene-propylene copolymer, ethylene-α-olefin copolymer, and propylene-α-olefin copolymer, and 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), or 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 the present embodiment, the transparent resin layer 14 may be formed of polypropylene.

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.

It is preferable that the transparent resin layer 14 contains at least a light stabilizer among the weathering agents. As the light stabilizer, a hindered amine light stabilizer (Hindered Amine Light Stabilizers: HALS), which is a light stabilizer using a hindered amine compound, can be suitably used. In other words, it is preferable that the transparent resin layer 14 in the laminated sheet 10 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 containing HALS in the transparent resin layer 14, the weather resistance of the laminated sheet 10 can be improved.

Moreover, it is further preferable that the transparent resin layer 14 contains an ultraviolet absorber (UVA) in addition to the 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 effect of suppressing the generation of radicals can be obtained, and the weather resistance of the laminate sheet 10 can be further improved.

Examples of ultraviolet absorbents include benzotriazole-based, benzoate-based, benzophenone-based, triazine-based, benzoate-based, and cyanoacrylate-based ultraviolet absorbents. One type of ultraviolet absorbent among these may be added to the transparent resin layer 14, or a mixture of multiple types of ultraviolet absorbents may be added. In this embodiment, a benzotriazole-based ultraviolet absorbent can be suitably used as the ultraviolet absorbent added to the transparent resin layer 14.

It is preferable that the transparent resin layer 14 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. In addition, from the viewpoint of reducing costs and maintaining the content rate of the resin component in the transparent resin layer 14, it is preferable that the content of the light stabilizer in the transparent resin layer 14 is 1 part by mass or less relative to the total mass of the transparent resin layer 14.

The transparent resin layer 14 preferably contains 0.2 parts by mass or more of an ultraviolet absorbing agent (UVA) relative to the total mass of the transparent resin layer 14. If the content of the ultraviolet absorbing agent in the transparent resin layer 14 is less than 0.2 parts by mass, sufficient weather resistance may not be obtained. From the viewpoint of preventing the occurrence of bleeding and maintaining the content rate of the resin component in the transparent resin layer 14, the content of the ultraviolet absorbing agent 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.

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 makes it possible to impart excellent weather resistance to the laminate sheet 10 used for exterior purposes.

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, the weather resistance and scratch resistance may decrease. If the thickness of the transparent resin layer 14 exceeds 100 μm, the manufacturing cost may increase and the flexibility may decrease.

In addition, various additives such as heat stabilizers, antiblocking agents, catalyst traps, colorants, light scattering agents, and gloss adjusters can be added to the transparent resin layer 14 as necessary. Phenol-based, sulfur-based, phosphorus-based, hydrazine-based, and other additives are generally added in any combination as heat stabilizers.

The method for forming the transparent resin layer 14 is not particularly limited. The transparent resin layer 14 can be formed using a normal 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.
To provide a design, the transparent resin layer 14 may have a surface irregularity. Examples of methods for providing the irregularity include a method of subjecting the transparent resin layer 14 to hot embossing after extrusion molding, and a method of subjecting the layer to embossing simultaneously with extrusion molding using a cooling roll having irregularities formed thereon during extrusion molding.

(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.
As the material for the surface protective layer 15, for example, a reaction product containing an acrylic resin composition as a main component and polyisocyanate as a curing agent (hereinafter also referred to as an "isocyanate-cured acrylic resin composition") can be used 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. As the acrylic polyol, for example, an acrylic polymer compound having a hydroxyl group in a side chain obtained by blending and copolymerizing a monomer containing a hydroxyl group such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, and the like with a normal acrylic monomer such as methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, or 2-ethylhexyl methacrylate, and, if necessary, a copolymerizable polymerizable monomer such as styrene, α-methylstyrene, vinyl toluene, divinylbenzene, vinyl acetate, vinyl butyrate, vinyl versatate, ethyl vinyl ether, acrylonitrile, or methacrylonitrile can be used.

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

In addition, as the material of the surface protective layer 15, for example, a mixture of an ionizing radiation curable resin and an isocyanate curable acrylic resin composition can be used, taking into consideration scratch resistance, weather resistance, and durability. In terms of scratch resistance, the surface protective layer 15 preferably has a hardness of B or more in a pencil hardness test according to JIS K 5600. In addition, as the ionizing radiation curable resin, for example, a composition containing as a main component at least one of a prepolymer, oligomer, and monomer having a polymerizable unsaturated bond such as a (meth)acryloyl group that has the property of undergoing a crosslinking reaction when irradiated with ionizing radiation can be used. As the ionizing radiation, for example, an electron beam or ultraviolet light can be used. To the ionizing radiation curable resin, for example, additives such as a polymerization initiator and a sensitizer may be added as necessary.

Examples of prepolymers and oligomers having a polymerizable unsaturated bond 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.

As an isocyanate-cured acrylic resin composition, for example, a reaction product of an acrylic resin composition as a base material and a polyisocyanate as a curing agent can be used. As an acrylic resin composition, for example, an acrylic polyol compound can be used. Examples of acrylic polyol compounds include acrylic polymer compounds having hydroxyl groups in the side chains 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 monomers containing hydroxyl groups 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, vinyl toluene, divinylbenzene, vinyl acetate, vinyl butyrate, vinyl versatate, ethyl vinyl ether, acrylonitrile, and methacrylonitrile.

As the isocyanate prepolymer of polyisocyanate, for example, 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), isophorone diisocyanate (IPDI), etc. can be used. In particular, in consideration of weather resistance, yellowing, and productivity, a trimer of hexamethylene diisocyanate (HDI) can be used. That is, an isocyanurate type using HDI as a raw material, that is, HDI isocyanurate, which is a derivative of HDI, can be used. In addition, as the side chain of the isocyanate prepolymer, for example, a urethane bond can be used in consideration of imparting flexibility to the surface protective layer 15.

In addition, the material of the surface protection layer 15 may be an acrylic resin such as polymethyl (meth)acrylate, polyethyl (meth)acrylate, polybutyl (meth)acrylate, or polyacrylamide.

In this way, the surface protection layer 15 in this embodiment is preferably a layer whose main component is an acrylic resin. Here, the main component in this specification refers to a resin material that is contained in 70% by mass or more, preferably 90% by mass or more, of the material that constitutes the target layer. In other words, the surface protection layer 15 is preferably formed from an acrylic resin.

In addition, the surface protective layer 15 preferably contains at least one of a light stabilizer or an ultraviolet absorber. In other words, the surface protective layer 15 is preferably formed of an acrylic resin composition containing at least one of an ultraviolet absorber or a light stabilizer. The surface protective layer 15 may be composed of an acrylic resin in all of its resin components 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, as in 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, as in the ultraviolet absorber contained in the transparent resin layer 14.

Moreover, it is further preferable that the surface protective layer 15 contains both a light stabilizer and an ultraviolet absorber (UVA). This provides a synergistic effect between the radical control effect and the effect of suppressing the generation of radicals, thereby further improving the weather resistance of the laminate sheet 10.

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. In addition, from the viewpoint of reducing costs and maintaining the content rate 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.

The content of the ultraviolet absorbing agent (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 absorbing agent in the surface protective layer 15 is less than 0.2 parts by mass, sufficient weather resistance may not be obtained. From the viewpoint of preventing the occurrence of bleeding and maintaining the content rate of the resin component in the surface protective layer 15, the content of the ultraviolet absorbing agent 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.

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 absorbing agent contained in the surface protective layer 15 may be of the same type as those contained in the transparent resin layer 14, or may be of different types.

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 required.
The method for forming the surface protective layer 15 is not particularly limited, and the above-mentioned material is made into a coating liquid and applied by a conventional method such as gravure coating, microgravure coating, comma coating, knife coating, or die coating, and then cured by a method suitable for the material, such as thermal curing or ultraviolet curing, to form the surface protective layer 15.

The thickness of the surface protective layer 15 is preferably in the 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 a larger amount of resin material than necessary, and costs can be reduced.

In addition, in the laminate sheet 10 according to the first embodiment of the present invention, an embossed pattern (uneven pattern) may be formed on the surface protective layer 15. By forming an embossed pattern (not shown), any desired uneven shape, such as a 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 excellent weather resistance.

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

The inventors of the present invention have conducted extensive research into weather resistance evaluation of laminated sheets used for exterior applications and the shortening of the evaluation time involved, and have found that it is possible to evaluate weather resistance based on the change in Martens hardness of the transparent resin layer 14 due to exposure to ultraviolet light. By performing weather resistance evaluation based on the change in Martens hardness, the inventors have succeeded in significantly shortening the time involved in the evaluation.
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 the weather resistance evaluation method according to the present embodiment is performed on the laminate sheet 10, but the present invention is not limited to this, and weather resistance evaluation may be performed on a specimen (sample) in which the surface protective layer 15 is formed on the transparent resin layer 14. In either case, the same evaluation results can be obtained.

(Pre-irradiation hardness measurement step S1)
As shown in FIG. 2, in the method for evaluating the weather resistance of the laminate sheet 10 according to this embodiment, first, the Martens hardness (N/mm ² ) of the transparent resin layer 14 is measured in a pre-irradiation hardness measuring step.

Here, the measurement of Martens hardness in the transparent resin layer 14 will be described. In the pre-irradiation hardness measurement process, the Martens hardness is measured in two regions in the transparent resin layer 14. In FIG. 1, the front side measurement position E1 and the back side measurement position E2 are illustrated as two measurement positions in the transparent resin layer 14. The front side measurement position E1 is set in the region 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 the region on the base sheet 11 side (back side) in the thickness direction of the transparent resin layer 14.

Here, the Martens hardness at the front side measurement position E1 is the front side Martens hardness, and the Martens hardness at the back side measurement position E2 is the back side Martens hardness. In other words, in the pre-irradiation hardness measurement process, 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.

As shown in FIG. 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 laminated sheet 10 is cut in the thickness direction. In other words, in the pre-irradiation hardness measurement process S1, when measuring the front side Martens hardness and the back side Martens hardness, the sample of the laminated sheet 10 is cut in the thickness direction to expose the cross section.

Moreover, 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 influenced by other layers when measuring the front side Martens hardness and the back side Martens hardness. Here, the region that is not influenced by other layers refers to a region that is not reached by infiltration (bleed, etc.) of a component from another layer 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.

For example, 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 side, 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 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 (printing layer 12 or anchor layer 13) provided on the base sheet 11.

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 to an extent that they are not affected by other layers when measuring the Martens hardness.

The front side Martens hardness and the back side Martens hardness can be measured using a microhardness measuring device. For example, a "Fischer FISCHERSCOPE Hm2000" can be used as the microhardness measuring device. The microhardness measuring device measures the front side Martens hardness and the back side Martens hardness by using load parameters that increase the load to 5 mN over 10 seconds at the front side measurement position E1 and the back side measurement position E2, respectively, and then hold this load for 5 seconds and decrease the load to 0.1 mN over 10 seconds.

The Martens hardness of the front surface side before the irradiation test is preferably 20 N/ ^mm2 or less. This makes it possible to confirm that the laminate sheet 10 has weather resistance suitable for outdoor use before the ultraviolet irradiation is performed.

(Ultraviolet irradiation step 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.

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.".

The conditions for the ultraviolet irradiation test in this example are an illuminance of 65 mW/ ^cm2 on an integrating light meter with a sensitivity wavelength range of 310 nm to 390 nm, a black panel temperature of 63° C., and a humidity inside the chamber of 50%. As the integrating light meter, for example, an "Ultraviolet Illuminance Meter UIT-201: manufactured by Ushio Inc." is used. Under these conditions, an ultraviolet irradiation test is performed for 250 hours on the laminate sheet 10 from the surface protective 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.

(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 in the same manner as in the pre-irradiation hardness measurement step S1. In this manner, 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 is carried out 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."

(Hardness ratio calculation step S4)
2, after the post-irradiation hardness measurement step S3 is performed, a hardness ratio calculation step S4 is performed in which 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.

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, the variability in the data can be corrected and the evaluation accuracy based on the Martens hardness can be improved.

(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 the present embodiment, the hardness ratio change rate calculation step S5 calculates the change rate (%) of the ratio (A1/A2) of the front side Martens hardness to the back side Martens hardness before and after the ultraviolet ray 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 "C1", the rate of change (C1) is calculated, for example, using 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) of the Martens hardness ratio after ultraviolet irradiation relative to the Martens hardness ratio before ultraviolet irradiation is calculated using the above formula (1).

(Evaluation process S6)
As shown in Fig. 2, after the hardness ratio change rate calculation step S5 is performed, the evaluation step S6 is performed. In the evaluation step S6 in this embodiment, the weather resistance of the laminated 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 ray irradiation step S2. Specifically, in the evaluation step S6, it is evaluated whether the laminated sheet 10 has sufficient weather resistance 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.

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 during 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 when the ultraviolet irradiation time is 250 hours, the threshold value for the rate of change in the Martens hardness ratio is set to "10%" and the initial change in the weather resistance of the laminated sheet is captured by determining whether the rate of change is 10% or less, thereby making it possible to evaluate whether the weather resistance can be maintained for at least 5 years. Therefore, in this embodiment, the ultraviolet irradiation time is set to 250 hours and the threshold value for evaluating the weather resistance based on the rate of change in the Martens hardness ratio is set to 10%.

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 hardening (deterioration) of the laminated sheet 10 due to exposure to ultraviolet rays 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%.

In this way, in the evaluation step S6, the laminate sheet 10 is evaluated for sufficient weather resistance 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.

In other words, in this embodiment, in the evaluation step S6, 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 by being configured so that the rate of change (C1) is equal to or less than 10%.

In addition, the smaller the value of the rate of change (C1), i.e., the closer to 0%, the less deterioration occurs and the longer the period during which weather resistance is maintained. Therefore, when the rate of change (C1) of the Martens hardness ratio before and after the ultraviolet irradiation test in the ultraviolet irradiation step S2 is less than 5%, it may be evaluated that the weather resistance of the laminated sheet 10 can be maintained for a period of 5 to 10 years when used outdoors.
In addition, the above-mentioned 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.

In the evaluation method of the laminate sheet 10 according to the present embodiment, the measurement of the Martens hardness in the hardness measurement steps (pre-irradiation hardness measurement step S1, post-irradiation hardness measurement step S3), the calculation process and the judgment process in the hardness ratio calculation step S4, the hardness ratio change rate calculation step S5, and the evaluation step S6 may be performed by a predetermined electronic calculator (computer, etc.). Therefore, the time related to the weather resistance evaluation of the laminate sheet 10 according to the present embodiment is mainly the ultraviolet ray irradiation time in the ultraviolet ray irradiation step S2.
Conventionally, in a method for visually evaluating the weather resistance of a laminate sheet, the time required for evaluation was several thousand hours (for example, about 1000 to 3000 hours). In contrast, in the method for evaluating the weather resistance of the laminate sheet 10 according to the present embodiment, the time required for the weather resistance evaluation is about 250 hours. In other words, according to the method for evaluating the weather resistance according to the present embodiment, the time required for the weather resistance evaluation can be reduced by 70% or more.

Thus, according to the method for evaluating the weather resistance of the laminate sheet 10 of this embodiment, the time required for evaluating the laminate sheet can be significantly reduced. This makes it possible to reduce costs and the burden on personnel involved in the evaluation, and to obtain evaluation results quickly for commercial materials. In addition, in the method for evaluating the weather resistance of the laminate sheet 10 of this embodiment, the weather resistance is evaluated based on numerical data (the rate of change in the Martens hardness ratio (C1) and the threshold value (10%)). This makes it possible to improve the evaluation accuracy compared to visual evaluation.
In addition, the laminate sheet 10 of this embodiment is configured so that the rate of change in 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, thereby providing excellent weather resistance and shortening the time required for weather resistance evaluation.

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 protective layer 15 side, which is the outermost surface of the laminate sheet 10, at 65 mW/ ^cm2 using an integrated actinometer with a sensitivity wavelength range of 310 nm to 390 nm. 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 an internal humidity of 50%, a Martens hardness measurement step (pre-irradiation hardness measurement step S1, post-irradiation hardness measurement step S3) in which a 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 a 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 are measured before and after the ultraviolet irradiation test in the ultraviolet irradiation step S2, and an evaluation step S6 in which weather resistance is evaluated based on whether a 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 (the surface protective layer 15 and each layer on the base sheet 11) when measuring the front side Martens hardness and the back side Martens hardness.

As a result, the weather resistance evaluation method for the laminate sheet 10 according to this embodiment can shorten the time required for the weather resistance evaluation.

Moreover, 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. Furthermore, when a 250-hour ultraviolet irradiation test (ultraviolet irradiation step S2) is performed on the laminate sheet 10 from the surface protective layer 15 side under conditions of an illuminance of 65 mW/ ^cm2 using an integrating light meter with a sensitivity wavelength range of 310 nm to 390 nm, a black panel temperature of 63°C, and a chamber humidity of 50%, and when a 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 a 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 of the transparent resin layer 14 are measured before and after the ultraviolet irradiation test (when a Martens hardness measurement step is performed), the ratio (A1/A2) of the front-side Martens hardness to the back-side Martens hardness changes by 10% or less 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 influenced by other layers (the surface protective layer 15 and each layer on the base sheet 11) when measuring the front side Martens hardness and the back side Martens hardness.

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.

(Modification)
Furthermore, 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, and the transparent resin layer 14 has a Martens hardness of 30 N/mm2 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 such a configuration, the laminate sheet 10 has excellent weather resistance, and the time required for weather resistance evaluation can be shortened.

Here, the Martens hardness (N/ ^mm2 ) of the transparent resin layer 14 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 a 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 preferably in the range of 1 N/mm2 or ^more and 30 N/ ^mm2 or less, and more preferably 20 N/ ^mm2 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.

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 Fig. 1 and Fig. 3. Fig. 3 is a flow chart for explaining an example of the flow of a method for evaluating a laminated sheet 10 according to this embodiment.
The weather resistance evaluation method according to this embodiment differs from the weather resistance evaluation method of 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.

The inventors of the present invention have conducted extensive research into weather resistance evaluation of laminated sheets used for exterior applications and the shortening of the evaluation time involved, and have found that it is possible to evaluate weather resistance based on the change in indentation modulus of the transparent resin layer 14 due to exposure to ultraviolet light. By performing weather resistance evaluation based on the change in indentation modulus of elasticity, the inventors have succeeded in significantly shortening the time involved in the evaluation.
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 similarities will be omitted as appropriate.

(Pre-irradiation elastic modulus measurement step S21)
3, in the method for evaluating the weather resistance of the laminate sheet 10 according to this embodiment, first, in a pre-irradiation elastic modulus measurement step, the indentation elastic modulus (E _IT /1-V _S ^2) of the transparent resin layer 14 is measured. The unit of the indentation elastic modulus is 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.

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 Fig. 1. Here, the indentation elastic modulus at the front side measurement position E1 is the front side indentation elastic modulus, and the indentation elastic modulus at the back side measurement position E2 is 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, when measuring the front-side indentation elastic modulus and the back-side indentation elastic modulus, the sample of the laminate sheet 10 is cut in the thickness direction to expose the cross section. In addition, 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 even when measuring the front-side indentation elastic modulus and the back-side indentation elastic modulus.
In this embodiment, similarly to 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 side, 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 side. 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 (printed layer 12 or anchor layer 13) provided on the base sheet 11.

The front side indentation elastic modulus and the back side indentation elastic modulus can be measured using a microhardness measuring device. For example, a "Fischer FISCHERSCOPE Hm2000" can be used as the microhardness measuring device. The microhardness measuring device measures the front side indentation elastic modulus (E IT /1-v s ^2) and the back side indentation elastic modulus (E _IT /1-v _s ^2) by using a load parameter that increases the load to 5 mN over 10 seconds for each of the front side measurement position E1 and the back side measurement position _E2 , and then holds the load for 5 seconds and decreases the load to 0.1 mN over 10 _seconds .
Note that elastic modulus measurement using an indentation tester (the microhardness measuring device described above) does not measure the true indentation elastic modulus (E _IT ), but rather measures the coefficient of indentation elastic modulus (E _IT /1-v _s ^2) including the Poisson's ratio of the measurement sample. For this reason, in this example, the coefficient of indentation elastic modulus (E _IT /1-v _s ^2) that can be measured using an indentation tester will be referred to as the indentation elastic modulus.

(Ultraviolet irradiation step S22)
3, after the pre-irradiation elastic modulus measurement step S21 is performed, an ultraviolet irradiation step S22 is performed. In the ultraviolet irradiation step S22, an ultraviolet irradiation test is performed on the laminated sheet 10. The ultraviolet irradiation test in the ultraviolet irradiation step S22 is similar to the ultraviolet irradiation test in the ultraviolet irradiation step S2 in the first embodiment, and therefore a description thereof will be omitted.

(Post-irradiation elastic modulus measurement step S23)
As shown in Fig. 3, after the ultraviolet irradiation step S22, a post-irradiation elastic modulus measurement step S23 is then performed. 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 in the same manner as in the pre-irradiation elastic modulus measurement step S21. In this manner, 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.

In the post-irradiation elastic modulus measurement step S23, the front side indentation elastic modulus and the back side indentation elastic modulus are measured for the sample of the laminated sheet 10 after the ultraviolet irradiation test is performed in the ultraviolet irradiation step S22. In addition, the pre-irradiation elastic modulus measurement step S21 and the post-irradiation elastic modulus measurement step S23 may be collectively referred to as the "elastic modulus measurement step."

(Elasticity ratio calculation step S24)
3, after the post-irradiation elastic modulus measuring step S23 is performed, an elastic modulus ratio calculating step S24 is performed in which the ratio (P1/P2) of the front side indentation elastic modulus (P1) to the back side indentation elastic modulus (P2) in 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, the variation in the data can be corrected and the evaluation accuracy based on the indentation elastic modulus can be improved.

(Elasticity 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 ray irradiation step S22.
Specifically, the above-mentioned rate of change is calculated using the pre-irradiation elastic modulus ratio and the post-irradiation elastic modulus ratio calculated in the elastic modulus ratio calculation step S24. Here, when the rate of change is "C2", the rate of change (C2) is calculated, for example, using 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).

(Evaluation step S26)
3, after the elastic modulus ratio change rate calculation step S25 is performed, the evaluation step S26 is performed. In the evaluation step S26 in this embodiment, the weather resistance of the laminated 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 ray irradiation step S22. Specifically, in the evaluation step S26, it is evaluated whether the laminated sheet 10 has sufficient weather resistance 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, similar to the weather resistance evaluation in the first embodiment described above, when the laminate sheet 10 is used outdoors, the weather resistance can be maintained for at least five years without abnormalities such as whitening on the surface.

In this embodiment, the above threshold value for the weather resistance evaluation is set according to the change in indentation elastic modulus due to ultraviolet irradiation, the ultraviolet irradiation time in the ultraviolet irradiation step S22, and the period during 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 value for the rate of change in the indentation elastic modulus ratio to "25%" when the ultraviolet irradiation time is 250 hours, and capturing the initial change in weather resistance of the laminated sheet by determining whether the rate of change is less than 25%, it is possible to evaluate whether the weather resistance can be maintained for at least 5 years. Therefore, in this embodiment, the ultraviolet irradiation time is 250 hours, and the threshold value for evaluating weather resistance based on the rate of change in the indentation elastic modulus ratio is set to 25%.

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 laminated sheet 10 is maintained and hardening (deterioration) of the laminated sheet 10 due to exposure to ultraviolet light is suppressed. Therefore, weather resistance is maintained for a longer period of time compared to when the change rate (C2) of the indentation elastic modulus is 25% or more.

In this way, in the evaluation step S26, the laminate sheet 10 is evaluated for sufficient weather resistance 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.

In other words, in this 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%, i.e., 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 by being configured so that the rate of change (C2) is less than 25%.

In addition, 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 period during which weather resistance is maintained tends to be. Therefore, for example, when 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 will be maintained for a period of 5 to 10 years when the laminate sheet 10 is used outdoors.
In addition, the above-mentioned 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.

In addition, in the evaluation method of the laminated sheet 10 according to this embodiment, the measurement of the indentation elastic modulus in the elastic modulus measurement process (pre-irradiation elastic modulus measurement process S21, post-irradiation elastic modulus measurement process S23), the calculation process and judgment process in the elastic modulus ratio calculation process S24, the elastic modulus ratio change rate calculation process S25, and the evaluation process S26 may be performed by a predetermined electronic calculator (computer, etc.) in the same manner as in the weather resistance evaluation method according to the first embodiment. In the weather resistance evaluation method according to this embodiment, the time required for weather resistance evaluation can be reduced by 70% or more, as in the weather resistance evaluation method according to the first embodiment.

Thus, according to the method for evaluating the weather resistance of the laminated sheet 10 of this embodiment, the time required for evaluating the laminated sheet can be significantly shortened, which reduces costs and the burden on personnel involved in the evaluation, and enables rapid evaluation results to be obtained for commercial materials. In addition, in the method for evaluating the weather resistance of the laminated sheet 10 of this embodiment, the weather resistance is evaluated 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 laminate sheet 10 of this embodiment is configured so that the rate of change in the ratio of the front side indentation elastic modulus to the back side indentation elastic modulus (P1/P2) before and after the irradiation test is less than 25%, thereby providing excellent weather resistance and shortening the time required for weather resistance evaluation.

As described above, the weather resistance evaluation method of the laminate sheet 10 according to this embodiment includes an ultraviolet irradiation step S22 in which an ultraviolet irradiation test is performed for 250 hours using a metal halide lamp under conditions of an illuminance of 65 mW/cm ² using an integrating light meter having a sensitivity wavelength range of 310 nm to 390 nm from the surface protective layer 15 side, a black panel temperature of 63° C., and an internal humidity of 50%, and measuring a front side indentation elastic modulus (E IT /1-V S ^2) at a front side measurement position E1 set in a region on the surface protective layer 15 side in the thickness direction of the transparent resin layer 14 and a back side indentation elastic modulus (E _IT /1-V _S ^2) at a back side measurement position E2 set in a region on the base sheet 11 side in the thickness direction of the transparent resin layer 14 before and after the ultraviolet irradiation test in the ultraviolet irradiation step _{S22 .} The method includes an indentation modulus measurement step (pre-irradiation elastic modulus measurement step S21, post-irradiation elastic modulus measurement step S23) for measuring the indentation modulus of the surface side (P1) and the indentation modulus of the back side (P2) before and after the irradiation test, and an evaluation step S26 for evaluating the weather resistance based on whether the change rate (C2) of the ratio (P1/P2) of the surface 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 surface 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 (the surface protective layer 15, each layer on the base sheet 11) when measuring the surface side indentation elastic modulus and the back side indentation elastic modulus.

As a result, the weather resistance evaluation method for the laminate sheet 10 according to this embodiment can shorten the time required for the weather resistance evaluation.

Moreover, 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 subjected to an ultraviolet irradiation test for 250 hours using a metal halide lamp under conditions of an illuminance of 65 mW/cm ² measured with an integrating light meter having a sensitivity wavelength range of 310 nm to 390 nm, a black panel temperature of 63° C., and an internal humidity of 50%, and the front side indentation elastic modulus (E _IT /1-V _S ^2) 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 a back side indentation elastic modulus (E _IT /1-V _S ^2) at a back side measurement position E2 set in an area on the base sheet 11 side in the thickness direction of the transparent resin layer 14 are measured before and after the ultraviolet irradiation test. ^2) is measured (when the indentation elastic modulus measurement step is performed), the ratio (P1/P2) of the front side indentation elastic modulus (P1) to the back side indentation elastic 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 back side 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 elastic modulus and the back side indentation elastic modulus are measured.

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.

(Modification)
Moreover, 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, and the transparent resin layer 14 has an indentation elastic modulus (E _IT /1-V _S ^2) of 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 such a configuration, the laminate sheet 10 has excellent weather resistance, and the time required for weather resistance evaluation can be shortened.

Here, the indentation elastic modulus of the transparent resin layer 14 may be the front side indentation elastic modulus at the front side measurement position E1, the back side indentation elastic modulus at the back side measurement position E2, or the indentation elastic modulus in a 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 elastic modulus of the transparent resin layer 14 is preferably in the range of 300 Ma or more and 600 MPa or less, 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.

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 Fig. 1 and Fig. 4. Fig. 4 is a flow chart for explaining an example of the flow of a method for evaluating a laminated sheet 10 according to this embodiment.
The weather resistance evaluation method according to this embodiment differs from the weather resistance evaluation methods according to the first and second embodiments in that the weather resistance of the laminate sheet 10 is evaluated based on the indentation hardness.

The inventors of the present invention have conducted extensive research into weather resistance evaluation of laminated sheets used for exterior applications and the shortening of the evaluation time involved, and as a result have found that it is possible to evaluate weather resistance based on the change in indentation hardness (H _IT ) of the transparent resin layer 14 due to exposure to ultraviolet light. By performing weather resistance evaluation based on the change in indentation hardness, the inventors have succeeded in significantly shortening the time involved in the evaluation.
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 similarities will be omitted as appropriate.

(Pre-irradiation indentation hardness measurement step S31)
4, in the method for evaluating the weather resistance of the laminate sheet 10 according to this embodiment, first, in a pre-irradiation indentation hardness measurement step S31, the indentation hardness (H _IT ) of the transparent resin layer 14 is measured. The unit of indentation hardness is N/mm ^2. The pre-irradiation indentation hardness measurement step S31 differs from the pre-irradiation hardness measurement step S1 in the first embodiment in that the indentation hardness is measured at a front side measurement position E1 and a back side measurement position E2.

In the pre-irradiation indentation hardness measurement step 31, the indentation hardness is measured at the front side measurement position E1 and the back side measurement position E2 shown in Fig. 1. Here, the indentation hardness at the front side measurement position E1 is the front side indentation hardness, and the indentation hardness at the back side measurement position E2 is 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 hardness measurement step S31, similarly to the pre-irradiation hardness measurement step S1, the sample of the 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. 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 even when measuring the front side indentation hardness and the back side indentation hardness.
In this embodiment, similarly to the first embodiment, it is preferable that the front side measurement position E1 is 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 side, and the back side measurement position E2 is 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 side. 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 (printed layer 12 or anchor layer 13) provided on the base sheet 11.

The front side indentation hardness and the back side indentation hardness can be measured using a microhardness measuring device. For example, a "Fischer FISCHERSCOPE Hm2000" can be used as the microhardness measuring device. The microhardness measuring device measures the front side indentation hardness (H IT ) and the back side indentation hardness (H IT ) by using a load parameter that increases the load to 5 mN over 10 seconds at each of the front side measurement position _E1 and the back side measurement position E2, and then holds the load for 5 seconds and decreases the load to 0.1 _mN over 10 seconds.

(Ultraviolet irradiation step S32)
4, after the pre-irradiation indentation hardness measurement step S31 is performed, an ultraviolet irradiation step S32 is 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 similar to the ultraviolet irradiation test in the ultraviolet irradiation step S2 in the first embodiment, and therefore a description thereof will be omitted.

(Post-irradiation indentation hardness measurement step S33)
As shown in Fig. 4, after the ultraviolet irradiation step S32, 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, 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 same manner as in the pre-irradiation indentation hardness measurement step S31. In this manner, 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.

In the post-irradiation indentation hardness measurement process S33, the front side indentation hardness and back side indentation hardness are measured for the laminated sheet 10 sample after the ultraviolet light irradiation test in the ultraviolet light irradiation process S22. In addition, the pre-irradiation indentation hardness measurement process S31 and the post-irradiation indentation hardness measurement process S33 may be collectively referred to as the "indentation hardness measurement process."

(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 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 and the back side indentation hardness measured in the pre-irradiation indentation hardness measurement step S31 is first calculated as the pre-irradiation indentation hardness ratio. Furthermore, the ratio between the front side indentation hardness and the back side indentation hardness measured in the post-irradiation indentation hardness measurement step S33 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, the variation in the data can be corrected and the evaluation accuracy based on the indentation hardness can be improved.

(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 ray 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 "C3", the rate of change (C3) is calculated, for example, using 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) of the indentation hardness ratio after ultraviolet irradiation relative to the indentation hardness ratio before ultraviolet irradiation is calculated using the above formula (3).

(Evaluation step S36)
As shown in Fig. 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 in this embodiment, the weather resistance of the laminated 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 ray irradiation step S32. Specifically, in the evaluation step S36, it is evaluated whether the laminated sheet 10 has sufficient weather resistance 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, similar to the weather resistance evaluation in the first embodiment described above, when the laminate sheet 10 is used outdoors, the weather resistance can be maintained for at least five years without abnormalities such as whitening on the surface.

In this embodiment, the above 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 during 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 value for the rate of change in the indentation hardness ratio to "20%" when the ultraviolet irradiation time is 250 hours, and capturing the initial change in the weather resistance of the laminated sheet by determining whether the rate of change is less than 20%, it is possible to evaluate whether the weather resistance can be maintained for at least 5 years. Therefore, in this embodiment, the ultraviolet irradiation time is 250 hours, and the threshold value for evaluating weather resistance based on the rate of change in the indentation hardness ratio is set to 20%.

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 laminated sheet 10 is maintained and hardening (deterioration) of the laminated sheet 10 due to exposure to ultraviolet light is suppressed. Therefore, weather resistance is maintained for a longer period of time compared to when the change rate (C3) of the indentation hardness is 20% or more.

In this way, in the evaluation step S36, the laminate sheet 10 is evaluated for sufficient weather resistance 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.

In other words, in this 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 by being configured so that the rate of change (C3) is less than 20%.

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.
In addition, the above-mentioned 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.

In the evaluation method for the laminated sheet 10 according to this embodiment, the measurement of the indentation hardness in the indentation hardness measurement process (pre-irradiation indentation hardness measurement process S31, post-irradiation indentation hardness measurement process S33), the calculation process and the judgment process in the indentation hardness ratio calculation process S34, the indentation hardness ratio change rate calculation process S35, and the evaluation process S36 may be performed by a predetermined electronic calculator (computer, etc.) in the same manner as in the weather resistance evaluation method according to the first embodiment. In the weather resistance evaluation method according to this embodiment, the time required for the weather resistance evaluation can be reduced by 70% or more, as in the weather resistance evaluation method according to the first embodiment.

Thus, according to the method for evaluating the weather resistance of the laminated sheet 10 of this embodiment, the time required for evaluating the laminated sheet can be significantly shortened, which reduces costs and the burden on personnel involved in the evaluation, and enables rapid evaluation results to be obtained for commercial materials. In addition, in the method for evaluating the weather resistance of the laminated sheet 10 of this embodiment, the weather resistance is evaluated based on numerical data (the rate of change in the indentation hardness ratio (C3) and the threshold value (20%)). This improves the evaluation accuracy compared to visual evaluation.
Furthermore, the laminate sheet 10 of this embodiment is configured so that the rate of change in the ratio (R1/R2) of the front side indentation hardness to the back side indentation hardness before and after the irradiation test is less than 20%, thereby providing excellent weather resistance and shortening the time required for weather resistance evaluation.

As described above, the weather resistance evaluation method of the laminate sheet 10 according to this embodiment includes an ultraviolet irradiation step S32 of performing an ultraviolet irradiation test for 250 hours using a metal halide lamp on the laminate sheet 10 from the surface protective layer 15 side, which is the outermost surface of the laminate sheet 10, under conditions of an illuminance of 65 mW/cm ² using an integrating light meter with a sensitivity wavelength range of 310 nm to 390 nm, a black panel temperature of 63° C., and an internal humidity of 50%, and measuring a front side indentation hardness (H IT ) 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 a back side indentation hardness (H _IT ) at a back side measurement position E2 set in an area on the base sheet 11 side in the thickness direction of the transparent resin layer before and after the ultraviolet irradiation test in the ultraviolet irradiation step _S32. The method includes an indentation hardness measurement step (pre-irradiation indentation hardness measurement step S31, post-irradiation indentation hardness measurement step S33) for measuring the surface hardness R1 and the back surface hardness R2, and an evaluation step for evaluating the weather resistance based on whether the rate of change in the ratio (R1/R2) of the surface hardness (R1) to the back surface hardness (R2) before and after the irradiation test is less than 20%. Furthermore, the surface measurement position E1 and the back surface measurement position E2 are set in areas of the transparent resin layer 14 that are not affected by other layers when the surface hardness and the back surface hardness are measured.

As a result, the weather resistance evaluation method for the laminate sheet 10 according to this embodiment can shorten the time required for the weather resistance evaluation.

Moreover, 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. Furthermore, when an ultraviolet irradiation test is performed for 250 hours using a metal halide lamp under conditions of an illuminance of 65 mW/ ^cm2 using an integrating light meter with a sensitivity wavelength range of 310 nm to 390 nm, a black panel temperature of 63°C, and a humidity inside the chamber of 50%, and when the front side indentation hardness (H IT ) 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 indentation hardness (H _IT ) 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 are measured before and after the ultraviolet irradiation test (when an indentation hardness measurement process 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 influenced by other layers when measuring the front side indentation hardness and the back side indentation hardness.

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.

(Modification)
Furthermore, 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, and the transparent resin layer 14 has an indentation hardness (H _IT ) of 45 N/ ^mm2 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 such a configuration, the laminate sheet 10 has excellent weather resistance, and the time required for weather resistance evaluation can be shortened.

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 a 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 preferably in the range of 10 N/ ^mm2 to 45 N/ ^mm2 , and more preferably 30 N/ ^mm2 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.

(Example)
The present invention will be described 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 ultraviolet absorber and a hindered amine-based light stabilizer were added to the homopolypropylene resin to prepare a resin material for the transparent resin layer. Here, a material with a mesopentad fraction of 95% or more and a melt flow rate (MFR) of 4.5 g/10 min (JIS K 7210: 99) was used as the homopolypropylene resin. A benzotriazole-based ultraviolet absorber and a hindered amine-based light stabilizer were added to the resin material for the transparent resin layer. As the benzotriazole-based ultraviolet absorber, "Tinuvin 328: manufactured by BASF Co., Ltd." was used, and 2000 PPM (0.2 parts by mass) was added to the homopolypropylene resin. In addition, as the hindered amine-based light stabilizer, "Chimasorb 944: manufactured by BASF Co., Ltd." was used, and 2000 PPM (0.2 parts by mass) was added to the homopolypropylene resin. Such a resin material for the transparent resin layer was extruded using a melt extruder to form a transparent resin sheet made of polypropylene and having a thickness of 80 μm to be used as the transparent resin layer.
(Surface protection layer forming process)
A benzotriazole-based ultraviolet absorber and a hindered amine-based light stabilizer were added to the acrylic urethane resin on the surface of the above-mentioned transparent resin layer to form a resin material for the surface protective layer. As the acrylic urethane resin, a two-liquid curing urethane top coat (W184; manufactured by DIC Graphics Corporation) was used. In addition, a benzotriazole-based ultraviolet absorber and a hindered amine-based light stabilizer were added to the resin material for the surface protective layer. As the benzotriazole-based ultraviolet absorber, "Tinuvin 328: manufactured by BASF Corporation" was used, and 2000 PPM (0.2 parts by mass) was added to the urethane top coat. As the hindered amine-based light stabilizer, "Chimasorb 944: manufactured by BASF Corporation" was used, and 2000 PPM (0.2 parts by mass) was added to the urethane top coat. Such a resin material for the surface protective layer was applied to the transparent resin layer at a coating thickness of 6 g/m ² and dried to form a surface protective layer.

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 absorbing agent was added to the resin material for the transparent resin layer.

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 absorbing agent was added to the resin material for the surface protective layer.

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.

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 absorbing agent 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.

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

<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 only a homopolypropylene resin.

<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.

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

<Evaluation>
For each sample (transparent resin layer and surface protective layer) obtained in the above Examples 1 to 5 and Comparative Examples 1 to 3, (1) weather resistance evaluation based on Martens hardness, (2) weather resistance evaluation based on indentation elastic modulus, and (3) weather resistance evaluation based on indentation hardness were respectively performed. The evaluation results of (1) above are shown in the following Table 1, the evaluation results of (2) above are shown in the following Table 2, and the evaluation results of (3) above are shown in the following Table 3.

The evaluation contents of each weather resistance evaluation are explained below.
<Weather resistance evaluation based on Martens hardness>
(1-1) Martens hardness measurement before ultraviolet irradiation Using a "Fischer FISCHERSCOPE Hm2000" microhardness measuring device, the Martens hardness was measured at two locations (front side measurement position, back side measurement position) of 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 side measurement position was a position 10 μm away from the boundary surface with the surface protective layer side in the transparent resin layer in the thickness direction (opposite direction to the surface protective layer). The back side measurement position was a position 10 μm away from the surface (back side) on the opposite side of the surface protective layer in the thickness direction (direction of 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 of increasing the load to 5 mN over 10 seconds for each of the measurement positions on the front side and back side, holding this load for 5 seconds, and then decreasing 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).

(1-2) Ultraviolet Irradiation Test Using a "Daipla Wintes Metal Weather Tester (KW-R7TP-A)", an ultraviolet irradiation test was performed on each sample of Examples 1 to 6 and Comparative Examples 1 to 3. The test conditions were an illuminance of 65 mW/cm ² in an integrating light meter with a sensitivity wavelength range of 310 nm to 390 nm, a black panel temperature of 63° C., and a humidity inside the chamber of 50%. As the integrating light meter, an "Ultraviolet Illuminance Meter UIT-201: manufactured by Ushio Inc." was used. In this way, samples for measuring Martens hardness after ultraviolet irradiation, which will be described later, were prepared.

(1-3) Measurement of Martens hardness after ultraviolet irradiation For each sample of Examples 1 to 6 and Comparative Examples 1 to 3 after carrying out the ultraviolet irradiation test of (1-2) above, the Martens hardness of the front side and the Martens hardness of the back side were measured in the same manner as the Martens hardness measurement before irradiation of (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, together with the Martens hardness ratio (front side Martens hardness after irradiation test/back side Martens hardness after irradiation test).

(1-4) Life Test For each sample of Examples 1 to 6 and Comparative Examples 1 to 3, light irradiation was performed using a "Daipla Wintes Metal Weather Tester (KW-R7TP-A)" under conditions of illuminance of 65 mW/ ^cm2 (calibrated with an ultraviolet illuminance meter UIT-201, manufactured by Ushio Inc.), black panel temperature of 63°C, and humidity inside the chamber of 50%, and each sample was visually inspected every 24 hours. In the life test, the time (h) until whitening was confirmed on the outermost surface (surface protective layer) was regarded as the life (weather resistance retention period) of each sample, and weather resistance was evaluated.
[Evaluation Criteria]
◎: 2800 hours or more 〇: 2500 hours or more ×: Less than 2500 hours In this evaluation, if the time (lifetime) until whitening is confirmed on the outermost surface (surface protective layer) is 2500 hours or more, the weather resistance of the laminated sheet can be maintained for 5 years (excellent weather resistance), and it is evaluated 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.

(Weather resistance evaluation results based on Martens hardness)
As shown in Table 1, the evaluation results of Examples 1 to 6 show that when the rate of change in the Martens hardness ratio (front side Martens hardness/rear side Martens hardness) before and after the ultraviolet irradiation test is 10% or less, the life evaluation results are good (all pass "O" or higher) and the sample has excellent weather resistance.
Moreover, from the evaluation results of Examples 1 and 2, it was found that when the rate of change in the Martens hardness ratio was less than 5%, the life evaluation result was extremely good (A).

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 a failure (×) and the weather resistance was insufficient.
From the above, it was found that weather resistance can be evaluated based on whether the rate of change in the Martens hardness ratio is 10% or less. Furthermore, it was found that by using the weather resistance evaluation based on the Martens hardness, the weather resistance evaluation of the laminated sheet, which requires several thousand hours (in this example, more than 2000 hours) by visual observation, can be performed in 250 hours (ultraviolet light irradiation time in the ultraviolet light irradiation test), and the evaluation time can be significantly reduced compared to the visual observation.

<Weather resistance evaluation based on indentation elastic modulus>
(2-1) Measurement of indentation elastic modulus before ultraviolet irradiation Using a "Fischer FISCHERSCOPE Hm2000" microhardness measuring device, the indentation elastic modulus (E IT /1-v s ^2) was measured at two locations (front side measurement location, back side measurement location) 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 ). The front side measurement location and back side measurement location were the same as the locations used for the Martens hardness measurement in (1-1) above.
The indentation elastic modulus at the measurement position on the front side (front side indentation elastic modulus) and the indentation elastic modulus at the measurement position on the back side (back side indentation elastic modulus) were measured using a microhardness measuring device with load parameters of increasing the load to 5 mN over 10 seconds for each of the measurement positions on the front side and back side, holding this load for 5 seconds, and then decreasing 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).

(2-2) Ultraviolet Irradiation Test An ultraviolet irradiation test was carried out using the same equipment and conditions as in (1-2) above, to prepare a sample for measuring the indentation elastic modulus after ultraviolet irradiation, which will be described later.

(2-3) Measurement of indentation elastic modulus after ultraviolet irradiation For each sample of Examples 1 to 5 and Comparative Examples 1 to 3 after carrying out the ultraviolet irradiation test of 2-2 above, the front side indentation elastic modulus and the back side indentation elastic modulus were measured in the same manner as the indentation elastic modulus measurement before irradiation of (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).

(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. Similarly to (1-4) above, the time (h) until whitening was confirmed on the outermost surface (surface protective layer) was defined as the life (weather resistance retention period) of each sample, and weather resistance evaluation was performed.
[Evaluation Criteria]
◎: 2800 hours or more 〇: 2500 hours or more ×: 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 2500 hours or more, the weather resistance of the laminated sheet could be maintained for 5 years (excellent weather resistance), and it was evaluated 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.

(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 UV irradiation test was less than 25%, the life evaluation results were good (all passing "O" or above) and the samples had excellent weather resistance.
Moreover, from the evaluation results of Examples 1 and 2, it was found that when the rate of change in the ratio of the indentation elastic modulus was less than 5%, there was a high probability that the life evaluation result would be extremely good (A).

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

<Weather resistance evaluation based on indentation hardness>
(3-1) Indentation hardness measurement before ultraviolet irradiation Using a "Fischer FISCHERSCOPE Hm2000" microhardness measuring device, the indentation hardness (H IT ) was measured at two locations (front side measurement location and back side measurement location) 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 ). The front side measurement location and back side measurement location were the same as the locations used for the Martens hardness measurement 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 of increasing the load to 5 mN over 10 seconds for each of the measurement positions on the front side and back side, holding this load for 5 seconds, and then decreasing 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).

(3-2) Ultraviolet Irradiation Test An ultraviolet irradiation test was carried out using the same equipment and conditions as in (1-2) above, to prepare samples for measuring the indentation hardness after ultraviolet irradiation, which will be described later.

(3-3) Indentation Hardness Measurement After UV Irradiation After the UV irradiation test described above in 3-2, the front side indentation hardness and back side indentation hardness were measured for each sample of Examples 1 to 5 and Comparative Examples 1 to 3 in the same manner as the indentation hardness measurement before irradiation described above in (3-1).
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).

(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. Similarly to (1-4) above, the time (h) until whitening was confirmed on the outermost surface (surface protective layer) was defined as the life (weather resistance retention period) of each sample, and weather resistance evaluation was performed.
[Evaluation Criteria]
◎: 2800 hours or more 〇: 2500 hours or more ×: 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 2500 hours or more, the weather resistance of the laminated sheet could be maintained for 5 years (excellent weather resistance), and it was evaluated 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.

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

In contrast, the evaluation results of Comparative Examples 1 to 3 showed that when the rate of change in the ratio of indentation hardness before and after the ultraviolet irradiation test was 20% or more, the life evaluation result was a failure (×) and the weather resistance was insufficient.
From the above, it was found that weather resistance can be evaluated based on 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 the laminated sheet, which requires several thousand hours (2000 hours or more in this example) by visual observation, can be performed in 250 hours (ultraviolet light irradiation time in the ultraviolet light irradiation test), and the evaluation time can be significantly reduced compared to visual observation.

The laminate sheet and the weather resistance evaluation method for the laminate sheet of the present invention are not limited to the above-mentioned embodiments and examples, and various modifications are possible without impairing the characteristics of the invention.

REFERENCE SIGNS LIST 10: decorative sheet 11: base sheet 12: printed layer 13: anchor layer 14: transparent resin layer 15: surface protective layer E1: surface side measurement position E2: back side measurement position

Claims (5)

A laminated sheet including a printed layer provided on a base sheet, and at least a transparent resin layer and a surface protective layer laminated in this order on the printed layer,
The transparent resin layer is
The film is made of polypropylene having a thickness of 80 μm and an MFR in the range of 4.5 g/10 min to 6.2 g/10 min, and contains a benzotriazole-based ultraviolet absorber and a hindered amine-based light stabilizer.
the content of the hindered amine-based light stabilizer in the transparent resin layer is 0.2 parts by mass or more based on the total mass of the transparent resin layer;
the surface protective layer is formed of an acrylic urethane resin and contains at least one of a hindered amine-based light stabilizer and an ultraviolet absorbing agent;
The coating thickness of the acrylic urethane resin forming the surface protective layer on the transparent resin layer is 6 g/ ^m2 ;
A 250-hour ultraviolet irradiation test was performed on the laminate sheet from the surface protective layer side using a metal halide lamp under conditions of an illuminance of 65 mW/ ^cm2 using an integrating light meter with a sensitivity wavelength range of 310 nm to 390 nm, a black panel temperature of 63°C, and a chamber humidity of 50%, and when the front side Martens hardness (N/ ^mm2 ) at a front side measurement position set in the area on the surface protective layer side in the thickness direction of the transparent resin layer and the back side Martens hardness (N/ ^mm2 ) at a back side measurement position set in the area on the base sheet side in the thickness direction of the transparent resin layer were measured before and after the irradiation test,
the ratio (A1/A2) of the front side Martens hardness (A1) to the back side Martens hardness (A2) has a change rate of 10% or less before and after the irradiation test;
The front side Martens hardness (A1) and the back side Martens hardness (A2) measured before the irradiation test are 30 N/mm2 ^or less,
the surface side measurement position is set in a region spaced 10 μm from the boundary surface of the transparent resin layer on the surface protective layer side toward the base sheet side in a thickness direction,
A laminate sheet , wherein the back surface side measurement position is set in an area 10 μm away in the thickness direction from the boundary surface of the transparent resin layer on the base sheet side toward the surface protective layer side . The laminate sheet according to claim 1 , wherein the Martens hardness of the front surface side before the irradiation test is 20 N/mm ² or less. the surface protective layer contains a hindered amine-based light stabilizer,
The laminate sheet according to claim 1 or 2 , wherein the content of the hindered amine-based 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 surface protective layer contains an ultraviolet absorbing agent,
The laminate sheet according to claim 1 , wherein the content of the ultraviolet absorbing agent in the surface protective layer is 0.2 parts by mass or more with respect to the total mass of the surface protective layer. 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 on the printed layer in this order, comprising:
an ultraviolet irradiation step of irradiating the laminated sheet from the surface protective layer side, which is the outermost surface of the laminated sheet, with ultraviolet irradiation for 250 hours using a metal halide lamp under the conditions of an illuminance of 65 mW/ ^cm2 as measured by an integrating light meter having a sensitivity wavelength range of 310 nm to 390 nm, a black panel temperature of 63°C, and a chamber humidity of 50%;
a Martens hardness measurement step of measuring a front side Martens hardness (N/ ^mm2 ) at a front side measurement position set in a region on the surface protective layer side in the thickness direction of the transparent resin layer and a back side Martens hardness (N/ ^mm2 ) at a back side measurement position set in a region on the base sheet side in the thickness direction of the transparent resin layer before and after the ultraviolet irradiation test;
an evaluation step of evaluating weather resistance based on whether a rate of change (A1/A2) between the front side Martens hardness (A1) and the back side Martens hardness (A2) before and after the irradiation test is 10% or less;
Including,
The transparent resin layer is
The sheet is made of polypropylene having a thickness of 80 μm and an MFR in the range of 4.5 g/10 min to 6.2 g/10 min, and contains a hindered amine light stabilizer.
The content of the hindered amine-based light stabilizer in the transparent resin layer is 0.2 parts by mass or more based on the total mass of the transparent resin layer,
the surface protective layer is formed of an acrylic urethane resin and contains at least one of a hindered amine-based light stabilizer and an ultraviolet absorbing agent;
The coating thickness of the acrylic urethane resin forming the surface protective layer on the transparent resin layer is 6 g/ ^m2 ;
The front side Martens hardness (A1) and the back side Martens hardness (A2) measured before the irradiation test are 30 N/mm2 ^or less,
the surface side measurement position is set in a region spaced 10 μm from the boundary surface of the transparent resin layer on the surface protective layer side toward the base sheet side in a thickness direction,
The back surface side measurement position is set in a region 10 μm away in a thickness direction from the boundary surface of the transparent resin layer on the base sheet side toward the surface protective layer side.
A method for evaluating the weather resistance of laminated sheets.