Decorative sheet, decorative material and material selection method of decorative sheet

Abstract

To provide a decorative sheet which improves a plurality of physical properties (scratch resistance, contamination resistance and bending resistance) and achieves good balance, and can efficiently evaluate the plurality of physical properties, a decorative material and a material selection method of a decorative sheet.SOLUTION: A decorative sheet 10 includes a base material layer 1 formed using a polyolefin or polyester resin, a pattern layer 2 formed on the base material layer 1, an adhesive layer 3 formed on the pattern layer 2, a transparent resin layer 4 formed on the adhesive layer 3, and a surface protective layer 5 formed on the transparent resin layer 4, wherein the transparent resin layer 4 contains polyolefin as a main component, the surface protective layer 5 contains an acrylic resin and a curing agent as main components, and has a nanoindentation hardness of 150 MPa or more and 180 MPa or less, a composite elastic modulus of 2.5 GPa or more and 3.5 GPa or less, a stress relaxation degree of 0.1 or more and 0.2 or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a decorative sheet, a decorative material, and a method for selecting materials for a decorative sheet. [Background technology]

[0002]

[0003] In recent years, the demand for high functionality in decorative sheets used on the interior and exterior surfaces of buildings, fittings, furniture, etc. has been increasing due to the diversification of usage environments. In terms of physical properties, various innovations have been implemented to achieve a balance between physical properties that are sometimes traded off, such as scratch resistance, stain resistance, and weather resistance, and decorative sheets with excellent performance have been developed. For example, Patent Document 1 discloses the addition of a matting agent with a specific particle size to a surface protective layer in order to impart scratch resistance and stain resistance to a decorative sheet. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-187378 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, decorative sheets have been used in a wide variety of applications, and in order to increase the versatility of decorative sheets, it has become necessary to improve and stabilize multiple physical properties such as scratch resistance, stain resistance, and bending resistance. However, in order to evaluate the above-mentioned multiple physical properties of decorative sheets, it is necessary to carry out a wide variety of measurements, which makes the work complicated. Furthermore, when selecting the material formulation and layer structure during the production of decorative sheets, it is necessary to evaluate the physical properties of a considerable number of samples, which takes a lot of time.

[0005] The present disclosure has been made with a focus on the above-mentioned problems, and aims to provide a decorative sheet, a decorative material, and a method for selecting materials for a decorative sheet that improves and balances multiple physical properties (scratch resistance, contamination resistance, and flex resistance) and that can efficiently evaluate the multiple physical properties. [Means for solving the problem]

[0006] In order to solve the above problems, a decorative sheet according to one embodiment of the present disclosure is a decorative sheet comprising a base layer formed using a polyolefin or polyester resin, a pattern layer formed on the base layer, an adhesive layer formed on the pattern layer, a transparent resin layer formed on the adhesive layer, and a surface protective layer formed on the transparent resin layer, wherein the transparent resin layer is primarily composed of polyolefin, the surface protective layer is primarily composed of acrylic resin and a curing agent, and has a nanoindentation hardness in the range of 150 MPa or more and 180 MPa or less, a composite elastic modulus in the range of 2.5 GPa or more and 3.5 GPa or less, and a stress relaxation rate in the range of 0.1 or more and 0.2 or less.

[0007] Furthermore, a decorative material according to one aspect of the present disclosure is characterized by comprising a substrate and the decorative sheet according to any one of claims 1 to 4 attached to at least one surface of the substrate. In addition, in order to solve the above-mentioned problems, a method for selecting materials for a decorative sheet according to one embodiment of the present disclosure is a decorative sheet comprising a base layer formed using polyolefin or polyester resin, a pattern layer formed on the base layer, an adhesive layer formed on the pattern layer, a transparent resin layer formed on the adhesive layer, and a surface protective layer formed on the transparent resin layer, wherein the transparent resin layer is formed primarily from polyolefin, and the surface protective layer is formed primarily from acrylic resin and a curing agent, and the nanoindentation hardness is set in the range of 150 MPa or more and 180 MPa or less, the composite elastic modulus is set in the range of 2.5 GPa or more and 3.5 GPa or less, and the stress relaxation rate is set in the range of 0.1 or more and 0.2 or less. [Effects of the Invention]

[0008] According to one aspect of the present disclosure, it is possible to provide a decorative sheet, a decorative material, and a method for selecting materials for a decorative sheet that can improve multiple physical properties (scratch resistance and stain resistance) and efficiently evaluate the multiple physical properties. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view schematically illustrating an example of a decorative sheet according to an embodiment of the present disclosure. [Figure 2] FIG. 10 is a cross-sectional view schematically illustrating an example of a decorative material according to a modified example of an embodiment of the present disclosure. [Figure 3] 1 is a graph showing a measurement curve obtained by a nanoindentation method. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present disclosure will be described in detail below. Note that FIG. 1 is a schematic diagram, and the size and shape of each part are appropriately exaggerated for ease of understanding. For example, the relationship between the thickness of each layer and the planar dimensions, the thickness ratio of each layer, etc., differ from the actual ones. Furthermore, the embodiments shown below are merely examples of configurations for embodying the technical idea of ​​the present invention, and the technical idea of ​​the present invention is not limited to the materials, shapes, structures, etc. of the components described below. The technical idea of ​​the present invention can be modified in various ways within the technical scope defined by the claims.

[0011] Furthermore, the directions of "left and right" and "up and down" in the following explanation are merely definitions for the convenience of explanation and do not limit the technical idea of ​​the present disclosure. Therefore, for example, if the page is rotated 90 degrees, "left and right" and "up and down" are read interchangeably, and if the page is rotated 180 degrees, "left" becomes "right" and "right" becomes "left."

[0012] After extensive research, the present inventors have found that evaluation using values ​​obtained by nanoindentation measurement of the cross section of a decorative sheet (values ​​measured with a nanoindenter) allows for efficient selection of material formulations and layer configurations capable of improving physical properties such as scratch resistance, stain resistance, and flex resistance in a decorative sheet. Specifically, they have found that excellent scratch resistance, stain resistance, and flex resistance can be easily imparted to a decorative sheet by ensuring that nanoindentation measurement values ​​such as hardness obtained by nanoindentation measurement (nanoindentation hardness), composite elastic modulus, and stress relaxation degree in a surface protective layer satisfy specific conditions (within a certain range). This has led the present inventors to invent a decorative sheet that has an excellent balance of multiple physical properties, namely scratch resistance, stain resistance, and flex resistance, which are necessary for performance, and a decorative material that includes this decorative sheet.

[0013] A decorative sheet 10 according to an embodiment of the present invention will now be described with reference to Fig. 1. Fig. 1 is a cross-sectional view that schematically shows an example of the structure of the decorative sheet 10.

[0014] (Composition of decorative sheet) As shown in Figure 1, decorative sheet 10 comprises a substrate layer (resin substrate) 1, a pattern layer 2 formed on substrate layer 1, an adhesive layer 3 formed on pattern layer 2, a transparent resin layer 4 formed on adhesive layer 3, and a surface protective layer 5 formed on transparent resin layer 4. Decorative sheet 10 may also comprise a primer layer 6 on the surface of substrate layer 1 opposite to the pattern layer 2. Each layer of the decorative sheet 10 will be described below with reference to FIG.

[0015] (Base material layer 1) The substrate layer 1 is made of, for example, a resin substrate. The resin component constituting the substrate layer 1 is preferably polyolefin or polyester. The resin constituting the substrate layer 1 can be arbitrarily selected from existing materials such as polyethylene, polypropylene, polybutylene, polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate. From the viewpoint of versatility, polyolefin is most preferable as the material for the substrate layer 1. Furthermore, examples of materials other than the above-mentioned polyolefin-based resins include α-olefins (e.g., 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicosene, 3-methyl-1-butene, 3-methyl-1-pentene, 3-ethyl-1-pentene, 4-methyl-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-pentene, 4-ethyl-1-hexene, 3-ethyl-1-hexene, 4,4-dimethyl-1-pentene, 4-ethyl-1-hexene, 3-ethyl-1-hexene, 4,4-dimethyl-1-pentene, 4-ethyl-1-hexene, 3-ethyl-1-hexene, 4-ethyl-1-hexene, 4,4-dimethyl-1-pentene, 4-ethyl-1-hex ... Examples include materials obtained by homopolymerizing or copolymerizing two or more types of α-olefins (e.g., 9-methyl-1-decene, 11-methyl-1-dodecene, 12-ethyl-1-tetradecene), as well as copolymers of ethylene or α-olefins with other monomers, such as ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, ethylene-methyl methacrylate copolymer, ethylene-ethyl methacrylate copolymer, ethylene-butyl methacrylate copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, and ethylene-butyl acrylate copolymer.

[0016] To improve adhesion between adjacent layers, the front and back surfaces of the base layer 1 may be subjected to surface treatments such as corona treatment, plasma treatment, ozone treatment, electron beam treatment, ultraviolet treatment, and dichromate treatment. Furthermore, a primer layer may be provided between the base layer 1 and the pattern layer 2 to ensure adhesion. Furthermore, if the base layer 1 is formed from polyolefin or polyester, adhesion to the pattern layer 2 described below will be ensured, and if the base layer 1 is formed from polyolefin, adhesion to the pattern layer 2 will be even more ensured.

[0017] If it is desired to impart opacity to the decorative sheet 10, a concealing colored sheet may be used as the base layer 1, or a concealing layer (not shown) may be provided above the base layer 1 and below the design layer 2 (between the base layer 1 and the design layer 2). When a colored sheet is used as the base layer 1, the resin material constituting the base layer 1 can be colored by adding a colorant. Examples of colorants that can be used include inorganic pigments (titanium oxide, carbon black, etc.) and organic pigments (phthalocyanine blue, etc.), as well as dyes. The colorant used in this embodiment can be one or more types selected from known or commercially available colorants, and the amount added can be adjusted to achieve the desired opacity and design properties. In addition, various additives such as fillers, foaming agents, flame retardants, lubricants, antistatic agents, antioxidants, nucleating agents, ultraviolet absorbers, light stabilizers, heat stabilizers, colorants, and matting agents may be added to the base layer 1 as needed.

[0018] (Picture layer 2) The design layer 2 is, for example, a layer containing a design printed on the base layer 1 using ink. The ink used to form the design layer 2 may contain, for example, a binder resin. The binder resin contained in the ink used to form the design layer 2 may be appropriately selected from, for example, soluble nitrocellulose, cellulose, vinyl chloride-vinyl acetate copolymer, polyvinyl butyral, polyurethane, acrylic, polyester, and the like, either alone or modified from these. The ink may be water-based, solvent-based, or emulsion-type, and may be a one-component type or a two-component type using a curing agent. Examples of methods for curing the ink used to form the design layer 2 include methods for curing the ink by irradiation with ultraviolet light, electron beams, etc. Among these, the most common method is a method using a urethane-based ink and curing it with polyisocyanate.

[0019] In addition to the binder resin described above, the ink used to form the design layer 2 may contain various additives such as pigments, colorants such as dyes, extender pigments, solvents, and light stabilizers that are commonly contained in inks. Examples of versatile pigments include condensed azo, insoluble azo, quinacridone, isoindoline, anthraquinone, imidazolone, cobalt, phthalocyanine, carbon, titanium oxide, iron oxide, and pearl pigments such as mica. The method for providing the design layer 2 is not particularly limited, and for example, a typical printing method such as gravure printing, offset printing, screen printing, flexographic printing, or inkjet printing can be used.

[0020] (adhesive layer 3) The adhesive layer 3 is a layer provided to bond the pattern layer 2 and the transparent resin layer 4. When the pattern layer 2 is provided only on a portion of the base layer 1, the adhesive layer 3 is provided to bond the base layer 1, the side surfaces of the pattern layer 2, the top surface of the pattern layer 2, and the transparent resin layer 4.

[0021] The material constituting the adhesive layer 3 is not particularly limited, and can be an ink made by appropriately selecting a material that has excellent adhesion to the design layer 2 and the transparent resin layer 4 from, for example, urethane-based, acrylic-based, acrylic silicone-based, fluorine-based, epoxy-based, polyester-based, or other resin materials. The resin component preferably has a reactive group such as a hydroxyl group or a carboxyl group, and is preferably crosslinked with a curing agent having an isocyanate group or a glycidyl group, with crosslinking between a hydroxyl group and an isocyanate group being particularly preferred.

[0022] There is no particular limitation on the method for forming the adhesive layer 3. The adhesive layer 3 can be formed using a common coating method such as gravure coating, microgravure coating, comma coating, knife coating, or die coating.

[0023] When laminating the transparent resin layer 4 onto the base material layer 1 provided with the pattern layer 2, the lamination method is not particularly limited as long as lamination is performed via the adhesive layer 3. For example, various lamination methods such as thermal lamination, extrusion lamination, dry lamination, and sand lamination can be used as the lamination method for the transparent resin layer.

[0024] (Transparent resin layer 4) The transparent resin layer 4 is formed of a transparent resin whose main component is polyolefin. Polyolefins such as polypropylene, polyethylene, polybutene, and various α-olefin copolymers (copolymers of propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, etc.) are used as the material for the transparent resin layer 4. Among these resins, polypropylene is the most preferable material for the transparent resin layer 4. The transparent resin layer 4 of the present embodiment may be a sheet-like layer formed by film formation, or may be a layer formed by laminating already formed sheets. The transparent resin layer 4 may be made of, for example, a highly crystalline polypropylene resin.

[0025] The transparent resin layer 4 preferably contains polyolefin as the main component, accounting for 80% by mass or more, and more preferably 90% by mass or more, of the total mass of the transparent resin layer 4. Note that "a transparent resin layer containing polyolefin as the main component" means that polyolefin accounts for 80% by mass or more of the total mass of the transparent resin layer 4.

[0026] A nucleating agent may be added to the transparent resin layer 4 to improve the hardness of the film. The nucleating agent is added to promote the formation of crystal nuclei during resin crystallization. It can be a melt-type nucleating agent that melts into the resin substrate upon addition and re-precipitates to form crystal nuclei, or a non-melt-type nucleating agent that remains unchanged after addition to the substrate and remains as a crystal nucleus. Examples of nucleating agents for polypropylene resin include metal phosphates, metal benzoates, metal pimelates, metal rosin salts, benzylidene sorbitol, chitocridone, cyanine blue, and talc. When a nucleating agent is added, the degree of crystallinity during film formation increases, and the effect of improving the nanoindentation hardness (described later) of the transparent resin layer 4 is obtained. The amount of nucleating agent added to the transparent resin layer 4 is preferably 0.1 mass % or more with respect to the total mass of the transparent resin layer 4. If the amount added is less than 0.1 mass %, crystallization may not proceed.

[0027] If necessary, various additives such as ultraviolet absorbers, weather resistance agents such as light stabilizers, heat stabilizers, flame retardants, antiblocking agents, catalyst scavengers, and, within the scope of not impairing the features of this embodiment, colorants, light scattering agents, and gloss adjusters may also be added to the transparent resin layer 4. Examples of heat stabilizers that can be used include phenol-based, sulfur-based, phosphorus-based, and hydrazine-based additives. Examples of flame retardants that can be used include aluminum hydroxide and magnesium hydroxide. Examples of ultraviolet absorbers that can be used include benzotriazole-based, benzoate-based, benzophenone-based, and triazine-based ultraviolet absorbers. Examples of light stabilizers that can be used include hindered amine-based additives. These additives are generally added in any combination.

[0028] The method for producing the transparent resin layer 4 is not particularly limited, and for example, a common method such as calender film formation or extrusion film formation can be used. The transparent resin layer 4 may be provided with surface irregularities, or so-called embossed portions (not shown), to impart design features. Examples of methods for providing the irregularities include a method of subjecting the transparent resin layer 4 to thermal embossing after extrusion molding, or a method of simultaneously embossing the extrusion using a chill roll with irregularities during extrusion molding. More specifically, the irregular pattern (embossed pattern) is directly applied to the transparent resin layer 4, e.g., a highly crystalline polypropylene sheet. Methods include a method of applying an irregular pattern to a polypropylene sheet after film formation using heat and pressure using an embossing plate with an irregular pattern, or a method of simultaneously embossing the polypropylene sheet during film formation using an extruder using a chill roll with an irregular pattern. In this case, colored ink can be embedded in the recesses of the irregular pattern to further enhance the design. The irregular pattern may be provided if necessary, but need not be provided if unnecessary. Furthermore, one or both surfaces of the transparent resin layer 4 may be activated, as necessary, by, for example, corona treatment, plasma treatment, electron beam treatment, ultraviolet treatment, or dichromate treatment.

[0029] In the decorative sheet 10 according to this embodiment, the transparent resin layer 4 preferably satisfies specific conditions for nanoindentation hardness, which are nanoindentation measurement values, composite elastic modulus, and stress relaxation rate. Specifically, it is preferable that the transparent resin layer 4 satisfies the condition (first condition) that the nanoindentation hardness is 30 MPa or less, the composite elastic modulus is 1.0 GPa or less, and the stress relaxation rate is 0.3 or more for the above three types of nanoindentation measurement values.

[0030] When the above three types of nanoindentation measurement values ​​of the transparent resin layer 4 satisfy the above first condition, the interaction with the laminated surface protection layer 5 reliably improves scratch resistance, contamination resistance, and bending resistance (processability), resulting in a better balance of the multiple physical properties (particularly physical properties suitable for bending processing) in the decorative sheet 10.

[0031] On the other hand, if the nanoindentation hardness of the transparent resin layer 4 exceeds 30 MPa, the composite elastic modulus exceeds 1.0 GPa, or the stress relaxation rate is less than 0.3, and the above three types of nanoindentation measurement values ​​do not satisfy the above specific condition (first condition) (are values ​​outside the range), cracks may occur in the resin during bending, resulting in poor processability.

[0032] The nanoindentation hardness of the transparent resin layer 4 can be adjusted by improving the crystallinity by adding a nucleating agent, by adjusting the thermal history during film formation, or by adding a soft component resin. Furthermore, by adjusting the nanoindentation hardness as described above, other nanoindentation measurement values ​​(composite elastic modulus and stress relaxation rate) are also adjusted accordingly. The nanoindentation measurement will be described in detail later.

[0033] (Surface protective layer 5) In this embodiment, the surface protective layer 5 is a layer provided to impart functions such as weather resistance, scratch resistance, stain resistance, and designability to the decorative sheet 10. Suitable materials for forming the surface protective layer 5 include, for example, ionizing radiation curable resins and thermosetting resins.

[0034] The ionizing radiation curable resin may be any known material, such as various monomers or commercially available oligomers. For example, it is preferable to use polyfunctional monomers such as urethane acrylate, pentaerythritol triacrylate (PET3A), pentaerythritol tetraacrylate (PET4A), trimethylolpropane triacrylate (TMPTA), dipentaerythritol hexaacrylate (DPHA), or polyfunctional oligomers, or mixtures thereof. An example of the polyfunctional oligomer is Shiko UV-1700B (manufactured by Mitsubishi Chemical Corporation).

[0035] Furthermore, the thermosetting resin used in the surface protection layer 5 is not particularly limited, and can be selected and combined as appropriate from, for example, various acrylic polymers, various polyesters, various polyethers, various polycarbonates, various polyurethanes, and other polymers having reactive groups such as hydroxyl groups or carboxyl groups, and curing agents having difunctional or higher functional isocyanate groups, epoxy groups, and the like.

[0036] The hardness of the resin can be adjusted by adjusting the monomer composition of the acrylic polymer among the thermosetting resins. Therefore, the surface protection layer 5 in this embodiment mainly comprises an acrylic resin and a curing agent. The main components preferably account for 80% by mass or more, more preferably 90% by mass or more, of the total mass of the surface protection layer 5. More specifically, in terms of versatility of the material, it is preferable that the surface protective layer 5 contains at least methyl methacrylate, 2-hydroxyethyl methacrylate, and butyl acrylate as monomer components. That is, in this embodiment, the acrylic resin, which is one of the main components of the surface protective layer 5, is preferably composed of at least methyl methacrylate, 2-hydroxyethyl methacrylate, and butyl acrylate. This allows the surface protective layer 5 to have the desired hardness and to suitably control the nanoindentation measurement values.

[0037] Furthermore, the curing agent, which is one of the main components of the surface protection layer 5, must be selected taking into consideration its reactivity with the polar groups in the resin, and isocyanate compounds, epoxy compounds, hydrazine compounds, etc. are used. However, the curing agent component used in this embodiment is preferably an isocyanate compound having two or more functional groups (bifunctional or more).

[0038] The hydroxyl value of the acrylic resin constituting the surface protective layer 5 is preferably 10 mgKOH / g or more and 50 mgKOH / g or less. When a resin having hydroxyl groups is used for the surface protective layer 5, if the hydroxyl value is 10 mgKOH / g or more and 50 mgKOH / g or less, the cured surface protective layer 5 exhibits scratch resistance, contamination resistance, and flexibility resistance (processability) suitable for bending applications. This can effectively suppress changes in appearance during processing, for example, when attaching to an adherend. On the other hand, if the hydroxyl value is less than 10 mgKOH / g, the cured film may be soft and have reduced scratch resistance. If the hydroxyl value exceeds 50 mgKOH / g, the cured film may be hard and have reduced processability.

[0039] The blending amount of methyl methacrylate in the entire acrylic resin, which is the main component of the surface protective layer 5, is preferably within a range of 65% by mass to 85% by mass, both inclusive, relative to the mass of the entire acrylic resin. This allows for better scratch resistance, stain resistance, and flex resistance (processability). Furthermore, the blending ratio of 2-hydroxyethyl methacrylate in the acrylic resin, which is the main component of the surface protective layer 5, is preferably such that methyl methacrylate is the most abundant, butyl acrylate is the second most abundant, and 2-hydroxyethyl methacrylate is the least abundant. This allows for improved scratch resistance, stain resistance, and flex resistance, and particularly good flex resistance.

[0040] The glass transition temperature (Tg) of the surface protective layer 5 is preferably in the range of 50°C or higher and 80°C or lower. When the glass transition temperature is within the above range, the cured surface protective layer 5 exhibits scratch resistance, contamination resistance, and processability suitable for bending applications. On the other hand, if the glass transition temperature is lower than 50°C, the cured film will be soft and scratch resistance may be reduced. On the other hand, if the glass transition temperature exceeds 80°C, the cured film will be hard and bending resistance (processability) may be reduced.

[0041] By adjusting the hydroxyl groups and glass transition temperature by the type and amount of thermosetting resin used in the surface protective layer 5, the nanoindentation measurement values ​​of the surface protective layer 5 described below can be suitably controlled, and the decorative sheet 10 can have good physical properties (scratch resistance, contamination resistance, and processability (flexibility)) that are particularly suitable for bending processing.

[0042] Similar to the transparent resin layer 4, the surface protective layer 5 may contain, as needed, various additives such as weathering agents such as ultraviolet absorbers, light stabilizers, and heat stabilizers, flame retardants, antiblocking agents, and catalyst scavengers, as well as colorants, light scattering agents, and gloss adjusters, provided that the features of this embodiment are not impaired. The various additives may be made of the same materials as those used for the transparent resin layer 4.

[0043] In particular, it is preferable to use an ultraviolet absorber having a triazine skeleton or a light stabilizer having a NOR skeleton as a weather resistance agent in the surface protective layer 5. This can improve the weather resistance of the decorative sheet 10. While the various additives mentioned above are generally added in any combination, it is preferable that the surface protective layer 5 contains at least both an ultraviolet absorber having a triazine skeleton and a light stabilizer having a NOR skeleton.

[0044] The method for forming the surface protection layer 5 is not particularly limited, and the surface protection layer 5 may be formed by preparing a coating liquid from the above-mentioned material and applying it by a conventional method such as gravure coating, microgravure coating, comma coating, knife coating, or die coating, and then curing it by a method suitable for the material, such as heat curing or ultraviolet curing. Alternatively, the surface protective layer 5 may be provided after the pattern layer 2 formed on the base layer 1 and the transparent resin layer 4 are bonded together via the adhesive layer 3 .

[0045] In the decorative sheet 10 according to this embodiment, the surface protective layer 5 satisfies specific conditions for three types of nanoindentation measurement values, namely, nanoindentation hardness, composite elastic modulus, and stress relaxation rate. Specifically, the surface protection layer 5 satisfies the condition (second condition) that, for the above three types of nanoindentation measurement values, the nanoindentation hardness is in the range of 150 MPa or more and 180 MPa or less, the composite elastic modulus is in the range of 2.5 GPa or more and 3.5 GPa or less, and the stress relaxation rate is in the range of 0.1 or more and 0.2 or less.

[0046] When the nanoindentation measurement values ​​(hardness, composite modulus, and stress relaxation) of the surface protective layer 5 satisfy the second condition, physical properties such as scratch resistance, stain resistance, and flex resistance (processability) are improved, and a good balance of these physical properties is achieved in the decorative sheet 10. In other words, a decorative sheet having excellent physical properties can be obtained. On the other hand, if the surface protective layer 5 has a nanoindentation hardness exceeding 180 MPa, a composite modulus exceeding 3.5 GPa, or a stress relaxation rate less than 0.1, and the three types of nanoindentation measurement values ​​do not satisfy the specific condition (second condition) (are outside the range), the processability may be poor. Also, if the nanoindentation hardness is less than 150 MPa, a composite modulus is less than 2.5 GPa, or a stress relaxation rate greater than 0.2, and the second condition is not satisfied, the scratch resistance may be poor.

[0047] In other words, when the three nanoindentation measurement values ​​of the surface protective layer 5 satisfy the second condition, the multiple physical properties required of the decorative sheet 10, particularly scratch resistance, contamination resistance, and processability (flex resistance), which are physical properties suitable for bending applications, are improved. Therefore, the multiple physical properties can be efficiently evaluated using the nanoindentation measurement values ​​of the surface protective layer 5. Furthermore, when the three nanoindentation measurement values ​​of the transparent resin layer 4 satisfy the first condition, the interaction between the surface protective layer 5 and the transparent resin layer 4 further improves the multiple physical properties required of the decorative sheet 10. Therefore, the multiple physical properties can be evaluated more efficiently using the nanoindentation measurement values ​​of the transparent resin layer 4 and the surface protective layer 5.

[0048] The nanoindentation hardness of the surface protective layer can be adjusted by the hydroxyl value and glass transition temperature (Tg) of the resin material (monomer) used, as described above. Furthermore, by adjusting the hardness of the nanoindentation measurement values ​​as described above, other nanoindentation measurement values ​​(composite modulus of elasticity, stress relaxation rate) are also adjusted accordingly.

[0049] (Primer layer 6) The decorative sheet 10 according to this embodiment may further comprise a primer layer 6 on the back surface of the base layer 1, which is the surface opposite to the surface on which the design layer 2 is located. The primer layer 6 may be formed from the same component as the binder resin contained in the colored ink for forming the design layer 2.

[0050] The method for forming the primer layer 6 is not particularly limited, and the primer layer 6 may be formed by preparing a coating liquid from the above-mentioned material and applying it by a conventional method such as gravure coating, microgravure coating, comma coating, knife coating, or die coating, and then curing it by a method suitable for the material, such as heat curing or ultraviolet curing. In addition, the primer layer 6 may be provided after forming a laminate having the base layer 1, the pattern layer 2, the adhesive layer 3, the transparent resin layer 4, and the surface protective layer 5 in this order, or the primer layer 6 may be provided in advance on the back surface of the base layer 1, and then a laminate having the base layer 1 with the primer layer 6 provided thereon, the pattern layer 2, the adhesive layer 3, the transparent resin layer 4, and the surface protective layer 5 in this order may be formed.

[0051] Furthermore, since the primer layer 6 is applied to the back surface of the decorative sheet 10, and in consideration of the fact that it will be wound up into a web, inorganic fillers such as silica, alumina, magnesia, titanium oxide, barium sulfate, etc. may be added to the primer layer 6 to avoid blocking and to improve adhesion with the adhesive.

[0052] (Thickness of each layer) The thickness of each layer constituting the decorative sheet 10 of this embodiment will be described below. The thickness of the base layer 1 is preferably in the range of 20 μm to 150 μm, more preferably in the range of 50 μm to 100 μm, taking into consideration printing workability and cost. The thickness of the design layer 2 is preferably in the range of 0.5 μm to 10 μm, more preferably in the range of 1 μm to 5 μm, taking into consideration printing workability and cost. The thickness of the adhesive layer 3 is preferably in the range of 0.5 μm to 3 μm, more preferably in the range of 1 μm to 2.5 μm, and even more preferably in the range of 1.5 μm to 2 μm, taking into consideration hydrolysis resistance, printing workability, cost, etc. The thickness of the transparent resin layer 4 is preferably in the range of 20 μm to 200 μm, more preferably in the range of 70 μm to 100 μm, taking into consideration printing workability and cost, etc. Considering printing workability, costs, etc., the thickness of the surface protective layer 5 is preferably in the range of 13 μm to 20 μm, and more preferably in the range of 3 μm to 15 μm. If both the transparent resin layer and the surface protective layer are too thin, scratch resistance tends to be poor, and if they are too thick, processability tends to be poor.

[0053] If the thickness of each layer is less than the respective lower limit values, the function (performance) of each layer may not be sufficiently obtained. Also, even if the thickness of each layer exceeds the respective upper limit values, the function (performance) of each layer does not improve significantly, so it is preferable from the viewpoint of production costs to set the thickness of each layer to be equal to or less than the respective upper limit values.

[0054] Furthermore, in consideration of printing workability, cost, etc., the thickness of the primer layer 6 is preferably in the range of 0.5 μm to 10 μm, and more preferably in the range of 1 μm to 5 μm. If the thickness of the primer layer 6 is in the range of 1 μm to 5 μm, the function (performance) of the primer layer 6 can be reliably exhibited. Additionally, it is preferable that the total thickness of the decorative sheet 10 be within the range of 45 μm or more and 250 μm or less. If the total thickness of the decorative sheet 10 is less than 45 μm, the strength of the entire decorative sheet 10 will be insufficient, and if the decorative sheet 10 is manufactured in-line, for example, there is a risk that the decorative sheet 10 will be damaged during manufacturing. If the total thickness of the decorative sheet 10 exceeds 250 μm, the flexibility of the entire decorative sheet 10 will decrease, and there is a risk that cracks or deformation will occur in the decorative sheet 10. If the total thickness of the decorative sheet 10 is within the range of 45 μm or more and 250 μm or less, printing workability can be easily improved and manufacturing costs can be reduced.

[0055] (Variation) A decorative material according to a modified example of this embodiment of the present disclosure will be described with reference to Fig. 2. The decorative sheet 10 according to this embodiment can be suitably used to prepare a decorative material (for example, a decorative material for floors) by laminating it with a substrate for the decorative material (for example, a wood substrate). Fig. 2 is a cross-sectional view illustrating one structural example of a decorative material 100 according to a modified example of this embodiment of the present disclosure.

[0056] 2, the decorative material 100 according to this modification is obtained by laminating the decorative sheet 10 according to this embodiment onto a substrate 12 so that the surface protective layer 5 of the decorative sheet 10 is the outermost layer. That is, the decorative material 100 differs from the decorative sheet 10 in that it includes an adhesive 11 and a substrate 12.

[0057] (decorative materials) 2, decorative material 100 has a design layer 2, adhesive layer 3, transparent resin layer 4, and surface protection layer 5 laminated in this order on one side of base layer 1 of decorative sheet 10, and a primer layer 6, adhesive 11, and base material 12 on the other side of base material layer 1. In other words, decorative material 100 comprises base material 12 and decorative sheet 10, which is a laminate bonded to at least one side of base material 12. This makes it possible for the decorative material 100 to provide a decorative material with excellent scratch resistance and stain resistance.

[0058] (wood base material) The substrate 12 may be a wood substrate. A wood board is used as the substrate 12, which is a wood substrate. More specifically, examples of wood boards include chipboards and wood fiberboards (MDF, HDF, etc.). Furthermore, a combination of these chipboards or wood fiberboards with wood veneers or wood plywood may also be used as the wood substrate (substrate 12).

[0059] For example, in the decorative material 100, among these wood substrate materials, when chipboard (ten-point average roughness Rzjis: approximately 80 to 250 μm) or a composite substrate having such chipboard on the surface is used, it is possible to suppress the remaining of air bubbles between the decorative sheet 10 and the substrate 12 (wood substrate) using such chipboard. Furthermore, the decorative material 100 using such chipboard as the substrate 12 can exhibit good impact resistance, abrasion resistance, and walking feel. The ten-point average roughness Rzjis is a value measured using a measurement method in accordance with JIS B0601-2001.

[0060] The shape of the base material 12, which is a wood base material, may be a flat plate, taking into consideration that the decorative material 100 is usually installed as a flooring material (flooring). An adhesive 11 can be used to bond the decorative sheet 10 to the base material 12, which is a wood base material. Examples of adhesives that can be used for the adhesive 11 include known adhesives whose active ingredients include polyvinyl acetate, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ionomer, butadiene-acrylonitrile rubber, neoprene rubber, natural rubber, and urethane-based reactive hot melt adhesive (PUR). When bonding the base material 12 (wood base material) and the decorative sheet 10, bonding devices such as a cold press, hot press, roll press, laminator, wrapping machine, edge banding machine, and vacuum press can be used.

[0061] (Effects of this embodiment) The decorative sheet and decorative material according to this embodiment have the following effects. (1) The decorative sheet 10 of this embodiment is a decorative sheet comprising a base layer 1 formed using polyolefin or polyester resin, a pattern layer 2 formed on the base layer 1, an adhesive layer 3 formed on the pattern layer 2, a transparent resin layer 4 formed on the adhesive layer 3, and a surface protective layer 5 formed on the transparent resin layer 4, wherein the transparent resin layer 4 is primarily composed of polyolefin, and the surface protective layer 5 is primarily composed of acrylic resin and a curing agent, and has a nanoindentation hardness in the range of 150 MPa or more and 180 MPa or less, a composite elastic modulus in the range of 2.5 GPa or more and 3.5 GPa or less, and a stress relaxation rate in the range of 0.1 or more and 0.2 or less. According to this configuration, it is possible to provide a decorative sheet that improves and balances multiple physical properties, namely scratch resistance, contamination resistance, and bending resistance (processability), and that allows these multiple physical properties to be efficiently evaluated. (2) The transparent resin layer 4 of the decorative sheet 10 may have a nanoindentation hardness of 30 MPa or less, a composite elastic modulus of 1.0 GPa or less, and a stress relaxation rate of 0.3 or more. According to this configuration, interaction with the surface protective layer 5 can more reliably improve multiple physical properties, namely scratch resistance, contamination resistance, and flex resistance (processability), and achieve a better balance. (3) The surface protective layer 5 of the decorative sheet 10 may have a glass transition temperature in the range of 50°C or higher and 80°C or lower. According to this configuration, the above three nanoindentation measurement values ​​of the surface protection layer 5 can be more suitably controlled, and the above multiple physical properties can be reliably improved. (4) In the decorative sheet 10, the acrylic resin, which is one of the main components of the surface protective layer 5, is composed of at least methyl methacrylate, 2-hydroxyethyl methacrylate, and butyl acrylate, and the acrylic resin may have a hydroxyl value in the range of 10 mgKOH / g or more and 50 mgKOH / g or less. According to this configuration, the above three nanoindentation measurement values ​​of the surface protection layer 5 can be more suitably controlled, and the above multiple physical properties can be reliably improved. (5) The curing agent, which is one of the main components of the surface protective layer 5 of the decorative sheet 10, may contain an isocyanate compound having two or more functional groups. According to this configuration, the reactivity between the curing agent and the polar group in the resin is good, the adhesion between adjacent layers is improved, and the processability (flexibility) is also improved. (6) The decorative material 100 according to this embodiment includes a substrate 12 and a decorative sheet 10 bonded to at least one surface of the substrate 12. According to this configuration, it is possible to provide a decorative material that improves and balances multiple physical properties, namely scratch resistance, stain resistance, and flex resistance (processability), and that allows these multiple physical properties to be efficiently evaluated.

[0062] (Decorative sheet manufacturing method) A method for producing the decorative sheet 10 according to this embodiment will now be described. The manufacturing method of the decorative sheet 10 in this embodiment is a manufacturing method of a laminate (decorative sheet) in which a pattern layer 2 is formed on a base layer 1, an adhesive layer 3 is formed on the pattern layer 2, a transparent resin layer 4 is formed on the adhesive layer 3, and a surface protection layer 5 is formed on the transparent resin layer 4. First, a polyolefin-containing substrate layer 1 is formed to a thickness of 20 μm to 150 μm, and a design layer 2 is formed on the substrate layer 1 to a thickness of 0.5 μm to 10 μm. When forming a primer layer 6, it is preferable to form the primer layer 6 simultaneously with the design layer 2 to a thickness of 0.5 μm to 10 μm. Next, an adhesive layer 3 is formed on the design layer 2 to a thickness of 0.5 μm to 3 μm. Next, a transparent resin layer 4 is formed on the adhesive layer 3 by extrusion molding to a thickness of 70 μm to 100 μm. Next, a surface protection layer 5 is formed on the transparent resin layer 4 to a thickness of 3 μm to 15 μm. In this way, the decorative sheet 10 according to this embodiment is manufactured.

[0063] In the above manufacturing method, the transparent resin layer 4 is formed using polyolefin as the main component. Furthermore, the surface protective layer 5 is formed primarily from an acrylic resin and a curing agent, and the three nanoindentation measurement values ​​are set to satisfy the second condition. That is, the nanoindentation hardness of the surface protective layer 5 is set to a range of 150 MPa to 180 MPa, the composite elastic modulus is set to a range of 2.5 GPa to 3.5 GPa, and the stress relaxation rate is set to a range of 0.1 to 0.2. The nanoindentation measurement values ​​of the surface protective layer 5 can be controlled by adjusting at least one of the hydroxyl group and the glass transition temperature, for example, by adjusting the type and amount of the thermosetting resin.

[0064] The above-described manufacturing method can produce the decorative sheet 10 according to the present embodiment described above. Therefore, it is possible to obtain a decorative sheet that has improved and well-balanced properties, namely scratch resistance, stain resistance, and flex resistance (processability), and that allows these properties to be efficiently evaluated. Furthermore, in the above manufacturing method, it is preferable to set the nanoindentation hardness to 30 MPa or less, the composite elastic modulus to 1.0 GPa or less, and the stress relaxation rate to 0.3 or more in the transparent resin layer 4. This makes it possible to more reliably improve the above-mentioned multiple physical properties through the interaction between the surface protection layer 5 and the transparent resin layer 4, achieving a better balance.

[0065] (How to select materials for decorative sheets) The following describes a method for selecting materials for the decorative sheet 10 of the present embodiment. The method for selecting materials for the decorative sheet 10 of the present embodiment is a method for selecting materials for a laminate (decorative sheet) in which a pattern layer 2 is formed on a base layer 1, an adhesive layer 3 is formed on the pattern layer 2, a transparent resin layer 4 is formed on the adhesive layer 3, and a surface protective layer 5 is formed on the transparent resin layer 4.

[0066] Specifically, in the above-mentioned material selection method, the transparent resin layer 4 is formed using polyolefin as the main component. Furthermore, the surface protective layer 5 is formed primarily from an acrylic resin and a curing agent, and the three nanoindentation measurement values ​​are set to satisfy the second condition. That is, the nanoindentation hardness of the surface protective layer 5 is set to a range of 150 MPa to 180 MPa, the composite elastic modulus is set to a range of 2.5 GPa to 3.5 GPa, and the stress relaxation rate is set to a range of 0.1 to 0.2. The nanoindentation measurement values ​​of the surface protective layer 5 can be controlled by adjusting at least one of the hydroxyl group and the glass transition temperature, for example, by adjusting the type and amount of the thermosetting resin.

[0067] The above-described material selection method makes it possible to obtain the decorative sheet 10 according to the present embodiment described above. Therefore, it is possible to obtain a decorative sheet that has improved and well-balanced properties, namely scratch resistance, stain resistance, and flex resistance (processability), and that allows these properties to be efficiently evaluated. Furthermore, the above-mentioned material selection method preferably sets the nanoindentation hardness to 30 MPa or less, the composite elastic modulus to 1.0 GPa or less, and the stress relaxation rate to 0.3 or more in the transparent resin layer 4. This makes it possible to more reliably improve the above-mentioned multiple physical properties through the interaction between the surface protection layer 5 and the transparent resin layer 4, achieving a better balance.

[0068] (nanoindentation measurement value) Next, the nanoindentation measurement values ​​(nanoindentation hardness, composite elastic modulus, and stress relaxation rate) will be explained in detail. In the present disclosure, the nanoindentation measurement values ​​represent three measurements calculated by the nanoindentation method: hardness, composite modulus, and stress relaxation rate. The nanoindentation method is a measurement method in which a quasi-static indentation test is performed on a target object to be measured (in this example, the transparent resin layer 4 and the surface protective layer 5) to obtain the mechanical properties of the sample. The indentation test yields the graph shown in FIG. 3. FIG. 3 is a graph showing a load-displacement curve. The vertical axis of the graph represents the load applied to the layer to be measured, and the horizontal axis represents the indentation depth of the indenter, i.e., the displacement.

[0069] The contact depth hc is calculated by analysis using the Oliver-Pharr method. The contact depth hc can be calculated by the following formula (1).

[0070]

number

[0071] Here, ε is a constant related to the indenter shape in the indentation test. For a Berkovich indenter, this constant is 0.75. The maximum load Pmax and maximum displacement hmax of the unloading curve can be determined based on the graph shown in Figure 3. S is contact stiffness. Contact stiffness S is the slope of the approximate curve immediately after removal when the unloading curve in Figure 3 is fitted with the function of the following equation (2) over the range of 60 to 95% of the maximum load. A, hf, and m in equation (2) represent fitting parameters used in the fitting.

[0072]

number

[0073] Next, the contact projected area Ac, which indicates the cross-sectional area of ​​the indenter, is calculated based on the shape of the indenter and the contact depth hc. The contact projected area Ac can be expressed as a function of the contact depth hc, as shown in the following equation (3). This equation corrects for the influence of the roundness of the indenter tip using correction terms C1 to C5. C1 to C5 were calculated by measuring fused quartz as a test specimen with maximum loads of 20 μN to 10 mN, and the measurement results of the composite elastic modulus under each maximum load condition were consistent with the composite elastic modulus Er of fused quartz, which is 69.6 GPa.

[0074]

number

[0075] Next, the composite elastic modulus Er is calculated based on the contact projected area Ac and the contact stiffness S. The composite elastic modulus Er can be calculated by the following formula (4).

[0076]

number

[0077] The composite elastic modulus Er is determined by measuring the composite elastic modulus at multiple locations, for example, 30 locations, per test piece, and averaging the obtained composite elastic moduli to obtain the composite elastic modulus Er.

[0078] Next, the nanoindentation hardness H is calculated based on the contact projected area Ac and the maximum load Pmax of the unloading curve shown in Fig. 3. The nanoindentation hardness H can be determined by the following formula (5).

[0079]

number

[0080] The degree of stress relaxation is a value (parameter) that indicates the degree to which stress changes with respect to a certain strain. The degree of stress relaxation is calculated based on the maximum load (Fmax) of the load curve and the maximum load (Pmax) of the unload curve in the measurement curve (load-displacement curve) shown in Figure 3 obtained by the nanoindentation method. The degree of stress relaxation can be determined by the following formula (6).

[0081]

number

[0082] A specific method for measuring nanoindentation measurements will be described later.

[0083] (Example) The present invention will be described in detail below with reference to examples and comparative examples, but the present disclosure is not limited to the following examples.

[0084] Example 1 [Synthesis of acrylic resin solution for surface protection layer] The acrylic resin (acrylic resin solution A) which is the main component forming the surface protective layer 5 was synthesized as follows. Into a four-neck flask equipped with a stirrer, nitrogen inlet tube, and reflux condenser, 100 g of monomers (methyl methacrylate (84 g), 2-hydroxyethyl methacrylate (13 g), butyl acrylate (3 g)) were introduced, and 150 g of methyl ethyl ketone was added and dissolved, followed by stirring under a nitrogen atmosphere. Polymerization was initiated by adding 0.2 g of α,α'-azobisisobutyronitrile, and the mixture was heated and stirred for 8 hours in a 60°C oil bath. 80 g of ethyl acetate was added to dilute the mixture, yielding a colorless, viscous acrylic resin solution A with a solids content of approximately 30%. [Preparation of coating material for surface protection layer] The surface protective layer coating material was prepared by blending the above-mentioned acrylic resin solution A with the following curing agent, gloss adjuster, ultraviolet absorber, and light stabilizer. Resin: Acrylic resin solution A 120 parts by weight Curing agent: Duranate (registered trademark) TPA-100 (manufactured by Asahi Kasei Corporation) 5 parts by mass Gloss adjuster (inorganic particles): Silohobic (registered trademark) 702 (manufactured by Fuji Silysia Chemical Ltd.) 10 parts by mass Ultraviolet absorber: Tinuvin (registered trademark) 400 (manufactured by BASF) 5.0 parts by mass Light stabilizer: Tinuvin (registered trademark) 123 (manufactured by BASF) 2.0 parts by mass Diluent: ethyl acetate 50 parts by weight [Preparation of polypropylene resin for transparent resin layer] The following materials were blended into the polypropylene resin that is the main component of the transparent resin layer. The added amount is shown as a percentage of the total mass of the transparent resin layer. UV absorber: benzophenone-based UV absorber: 0.5% by mass Light stabilizer: Hindered amine light stabilizer: 0.5% by mass

[0085] [Creating decorative sheets] A 55 μm thick polyethylene sheet with opacity was used as the base layer 1, and a 3 μm thick pattern layer 2 was formed on one side of it using a two-component urethane ink (V180, manufactured by Toyo Ink Co., Ltd.) by gravure printing.In addition, a primer layer 6 composed of the same resin components as the pattern layer 2 was formed on the other side of the base layer 1. On the surface of this pattern layer 2, a dry laminating adhesive (Takelac A540; manufactured by Mitsui Chemicals, Inc.; application amount: 2 g / m) was applied. 2 ) was used to form an adhesive layer 3 with a thickness of 2 μm by gravure printing, and then a transparent resin layer 4 with a thickness of 70 μm was formed on top of this by extrusion lamination using a polypropylene resin containing the above-mentioned ultraviolet absorber and light stabilizer. Furthermore, the above-mentioned surface protective layer coating material was used to provide a surface protective layer 5 with a thickness of 6 μm on this transparent resin layer 4 by gravure coating. In this way, the decorative sheet 10 of Example 1 was produced.

[0086] <Example 2> The decorative sheet of Example 2 was produced in the same manner as Example 1, except that the monomer composition in the synthesis of the acrylic resin solution for the surface protective layer was 65 g of methyl methacrylate, 2 g of 2-hydroxyethyl methacrylate, and 33 g of butyl acrylate per 100 g of monomer, and 0.1 mass % of a nucleating agent was added to the transparent resin layer.

[0087] Example 3 A decorative sheet according to Example 3 was produced in the same manner as in Example 1, except that 20% by mass of soft polypropylene (PP) with an ethylene content of 15% was mixed into the transparent resin layer.

[0088] Example 4 The decorative sheet of Example 4 was produced in the same manner as Example 3, except that the monomer composition in the synthesis of the acrylic resin solution for the surface protective layer was 65 g of methyl methacrylate, 2 g of 2-hydroxyethyl methacrylate, and 33 g of butyl acrylate per 100 g of monomer.

[0089] <Example 5> The decorative sheet of Example 5 was produced in the same manner as Example 3, except that the monomer composition in the synthesis of the acrylic resin solution for the surface protective layer was 74 g of methyl methacrylate, 15 g of 2-hydroxyethyl methacrylate, and 11 g of butyl acrylate per 100 g of monomer.

[0090] Example 6 The decorative sheet of Example 6 was produced in the same manner as Example 3, except that the monomer composition in the synthesis of the acrylic resin solution for the surface protective layer was 85 g of methyl methacrylate, 2 g of 2-hydroxyethyl methacrylate, and 13 g of butyl acrylate per 100 g of monomer.

[0091] Example 7 The decorative sheet of Example 7 was produced in the same manner as Example 3, except that the monomer composition in the synthesis of the acrylic resin solution for the surface protective layer was 80 g of methyl methacrylate, 7 g of 2-hydroxyethyl methacrylate, and 13 g of butyl acrylate per 100 g of monomer.

[0092] Example 8 The decorative sheet of Example 8 was produced in the same manner as Example 3, except that the monomer composition in the synthesis of the acrylic resin solution for the surface protective layer was 76 g of methyl methacrylate, 7 g of 2-hydroxyethyl methacrylate, and 17 g of butyl acrylate per 100 g of monomer.

[0093] Example 9 The decorative sheet of Example 9 was produced in the same manner as in Example 3, except that the monomer composition in the synthesis of the acrylic resin solution for the surface protective layer was 83 g of methyl methacrylate, 4 g of 2-hydroxyethyl methacrylate, and 10 g of butyl acrylate per 100 g of monomer.

[0094] <Comparative Example 1> The decorative sheet according to Comparative Example 1 was produced in the same manner as in Example 3, except that the monomer composition in the synthesis of the acrylic resin solution for the surface protective layer was 89 g of methyl methacrylate, 7 g of 2-hydroxyethyl methacrylate, and 4 g of butyl acrylate per 100 g of monomer.

[0095] <Comparative Example 2> The decorative sheet according to Comparative Example 2 was produced in the same manner as in Example 3, except that the monomer composition in the synthesis of the acrylic resin solution for the surface protective layer was 60 g of methyl methacrylate, 7 g of 2-hydroxyethyl methacrylate, and 33 g of butyl acrylate per 100 g of monomer.

[0096] (Measurement of nanoindentation measurements) The nanoindentation measurement values ​​(nanoindentation hardness, composite elastic modulus, and stress relaxation rate) were measured as follows. <Cross-sectional sample creation> The decorative sheets prepared in each Example and Comparative Example were used as samples. First, the front and back surfaces of each decorative sheet were corona-treated, and the film was cut with a razor into 2 x 3 mm strips and embedded in resin. A visible light-curing resin, "Aronix LCR D-800" manufactured by Toa Gosei Co., Ltd., was used as the embedding resin, and after embedding, it was cured by light irradiation. After curing, the embedding resin containing the film pieces was fixed in an insert for an SPM sample holder. Trimming and cross-section cutting of the film were performed with a glass knife at room temperature (25°C). Subsequently, cross-section cutting was performed with a diamond knife at a cutting speed of 3 mm / s and a cutting film thickness of 500 nm until a mirror finish was obtained. A "Leica Microsystems EM UC7 Ultramicrotome" was used as the cross-section cutting device. The cutting direction was horizontal to the layer interface. The cross-sectioned sample (cross-section sample) was fixed in place with an insert for an AFM sample holder and used to measure nanoindentation hardness, composite elastic modulus, and stress relaxation.

[0097] <Measurement> The measurement device used was a Hysitron TI-Premier (product name) manufactured by Bruker Japan Co., Ltd. The indenter used was a Berkovich type diamond indenter manufactured by Bruker Japan Co., Ltd. Nanoindentation measurements were performed by first scanning the surface of the sample in imaging mode with an indenter to obtain height and gradient images, and then positioning the target layers (surface protection layer, transparent resin layer). Then, in displacement control mode, the indenter was indented to a depth of 200 nm at a rate of 100 nm / s, held at the maximum depth for 2 seconds, and then unloaded at a rate of 100 nm / s. Thirty points were designated on the target layer at intervals of 1 μm or more, and an indentation test (indentation and unloading) was performed on each target layer, followed by measurements using the nanoindentation method. To calculate the hardness and composite modulus, we first tested a standard sample of fused quartz and calibrated the relationship between the contact depth and the projected contact area between the indenter and the sample. We then analyzed the unloading curve in the 60-95% range of the maximum load at unloading using the Oliver-Pharr method to calculate the nanoindentation hardness and composite modulus. The stress relaxation was then calculated from the measurement curve (see Figure 3) obtained from the indentation test.

[0098] (Calculation method of hydroxyl value) The hydroxyl value of the acrylic resin for the surface protective layer was measured by potentiometric titration in accordance with JIS K0070 as follows. (1) The reagents are as follows (a) to (c). (a) Acetylation reagent: 25 g of acetic anhydride as specified in JIS K 8886 is placed in a 100 ml volumetric flask, and pyridine as specified in JIS K 8777 is added to bring the total volume to 100 ml, followed by thorough stirring. (b) Phenolphthalein solution: according to "4.3 (Indicators)" of JIS K 8001. (c) 0.5 mol / l potassium hydroxide ethanol solution: Dissolve 35 g of potassium hydroxide specified in JIS K 8574 in 20 ml of water, and add ethanol specified in JIS K 8102 to make 1 liter.

[0099] (2) Equipment and instruments The equipment and instruments shall be as follows (a) to (e). (a) Potentiometric titrator: According to "3.2(3)(a)" of JIS K0070. (b) 5 ml volumetric pipette (c) 100ml measuring cylinder (d) 200ml flat-bottom flask (e) Glycerin bath (suitable for heating to 90-100°C) (3) Measurements shall be performed as follows: (a) to (d). (a) Weigh 2.0 g of sample into a 200 ml flat-bottom flask and add 5 ml of acetylation reagent using a volumetric pipette. (b) Attach an air condenser to the neck of the flat-bottomed flask, and immerse approximately 1 cm of the bottom in a glycerin bath at 95-100°C and heat. After 1 hour, remove the flat-bottomed flask from the bath and allow it to cool. Then, add 1 ml of water from the top of the air condenser and shake to decompose the acetic anhydride. To further complete the decomposition, heat it again in the glycerin bath for 10 minutes, allow it to cool, and then wash the air condenser with 5 ml of ethanol. (c) Add 100 ml of ethanol to a flat-bottom flask as a solvent. Using a potentiometric titrator, perform potentiometric titration with a 0.5 mol / l ethanolic solution of potassium hydroxide, and mark the inflection point of the resulting titration curve as the endpoint. (d) For the blank test, perform (a) to (c) without adding any sample.

[0100] (4) The hydroxyl value is calculated using the following formula. Hydroxyl value = {(V1 - V0) x F x 56.1 (molecular weight of potassium hydroxide)} / S + D V0: Volume (ml) of 0.5 mol / l potassium hydroxide ethanol solution used in the blank test V1: Amount (ml) of 0.5 mol / l potassium hydroxide ethanol solution used in titration F: Factor of 0.5 mol / l potassium hydroxide ethanol solution (mol / l) S: mass of sample (g) D; Acid value (mgKOH / g)

[0101] (evaluation) The decorative sheets of Examples 1 to 9 and Comparative Examples 1 and 2 obtained by the above-mentioned methods were evaluated for scratch resistance, stain resistance, and bending resistance as follows. <Scratch resistance evaluation> A pencil hardness test was carried out on the decorative sheets 10 of each example and each comparative example using a "Tester Sangyo HA-301" under a load of 750 g or 300 g. After the test, the condition of the sample (occurrence of scratches) was evaluated visually. The evaluation criteria were as follows: <Evaluation criteria> ◎: Scratches occur when the hardness is 6B or more (under a load of 750g) 〇: Scratches occur when the hardness is 6B or more (under a load of 300g) ×: Hardness is less than 6B (under a load of 300g) and scratches occur In this evaluation, a score of "〇" or higher was considered a pass.

[0102] <Evaluation of contamination resistance> A 1% aqueous solution of sodium hydroxide was dropped onto the surface of the decorative sheet 10 described above, and after leaving it for 24 hours, the surface was wiped off and the surface condition was visually evaluated according to the following criteria. <Evaluation criteria> 〇: No trace △: Slight traces ×: Clear traces present In this evaluation, "〇" was considered a pass.

[0103] <Evaluation of bending resistance> The decorative sheets 10 of each example and comparative example were subjected to a mandrel test (indicators of crack resistance and fold resistance) in accordance with JIS K5600-5-1:1999. Specifically, a sample of 100 mm in the machine direction and 50 mm in the transverse direction was taken from each decorative sheet, and a bending resistance test was performed using the cylindrical mandrel method. Of the mandrels that did not crack, the diameter of the smallest mandrel was visually evaluated according to the following criteria. <Evaluation criteria> ◎: No cracks at 1mm diameter 〇: Slight cracking at 1mm diameter ×: Clear cracks occur at 1mm diameter In this evaluation, a score of "〇" or higher was considered a pass.

[0104] [Evaluation results] The evaluation results of Examples 1 to 9 and Comparative Examples 1 and 2, along with the compositions of the decorative sheets (surface protective layers) and nanoindentation measurement values, are shown in Table 1. In the sheet compositions shown in Table 1, methyl methacrylate is abbreviated as "MMA," hydroxyethyl methacrylate as "HEMA," and butyl acrylate as "BA." Glass transition temperatures are also abbreviated as "Tg."

[0105] [Table 1]

[0106] As can be seen from Table 1, all of the decorative sheets of Examples 1 to 9 passed the evaluation for all physical properties of scratch resistance, stain resistance, and flex resistance (processability), demonstrating excellent performance. Specifically, the decorative sheets of Examples 1 to 9 were all evaluated as "good" or "good" (pass) for scratch resistance, stain resistance, and flex resistance, resulting in an overall evaluation of "good" or "good." This confirmed that the scratch resistance, stain resistance, and flex resistance were improved and well-balanced. This is thought to be because the surface protective layer of the decorative sheet of each Example had all of the three nanoindentation measurement values ​​that satisfied the second condition above. Furthermore, in Examples 7 to 9, the evaluation results for scratch resistance, contamination resistance, and flex resistance were all rated as "Excellent," confirming that scratch resistance, contamination resistance, and flex resistance were further improved. This is thought to be because, in addition to satisfying the second condition above, all of the nanoindentation measurement values ​​of the transparent resin layer satisfied the first condition above, and the surface protective layer had a glass transition temperature (Tg) of 50°C or higher and 80°C or lower, and a hydroxyl value of the acrylic resin of 10 mgKOH / g or higher and 50 mgKOH / g or lower.

[0107] On the other hand, in Comparative Examples 1 and 2, the nanoindentation measurement values ​​of the surface protective layer did not satisfy the second condition above, and therefore the scratch resistance, contamination resistance, and flex resistance were not sufficiently improved, and the balance of these physical properties was not good, resulting in an overall evaluation of "X."

[0108] From the above, it was found that when the nanoindentation measurement values ​​(hardness, composite modulus, and stress relaxation rate) of the transparent resin layer and the surface protective layer satisfy the above specific condition (second condition), it is possible to improve the multiple physical properties required of the decorative sheet (scratch resistance, stain resistance, and flex resistance), that is, the multiple physical properties are well balanced. In other words, it was found that the multiple physical properties (scratch resistance, stain resistance, and flex resistance) can be efficiently evaluated by the nanoindentation measurement values ​​of the transparent resin layer and the surface protective layer.

[0109] Furthermore, for example, this embodiment can have the following configuration. (1) A decorative sheet comprising a base layer formed using a polyolefin or polyester resin, a pattern layer formed on the base layer, an adhesive layer formed on the pattern layer, a transparent resin layer formed on the adhesive layer, and a surface protective layer formed on the transparent resin layer, the transparent resin layer is mainly composed of polyolefin, The surface protective layer is The main components are acrylic resin and hardener. The nanoindentation hardness is in the range of 150 MPa or more and 180 MPa or less, the composite elastic modulus is in the range of 2.5 GPa or more and 3.5 GPa or less, and the stress relaxation rate is in the range of 0.1 or more and 0.2 or less. A decorative sheet characterized by: (2) The transparent resin layer is The nanoindentation hardness is 30 MPa or less, the composite elastic modulus is 1.0 GPa or less, and the stress relaxation rate is 0.3 or more. The decorative sheet according to (1) above, characterized in that: (3) The surface protective layer has a glass transition temperature in the range of 50°C or higher and 80°C or lower. The decorative sheet according to (1) or (2) above, characterized in that: (4) the acrylic resin among the main components of the surface protective layer contains at least methyl methacrylate, 2-hydroxyethyl methacrylate, and butyl acrylate; The acrylic resin is The hydroxyl value is in the range of 10 mg KOH / g or more and 50 mg KOH / g or less. The decorative sheet according to any one of (1) to (3) above, characterized in that: (5) the curing agent among the main components of the surface protective layer contains an isocyanate compound having two or more functional groups; The decorative sheet according to any one of (1) to (3) above, characterized in that: (6) A substrate; A decorative material comprising the decorative sheet according to any one of (1) to (5) above, attached to at least one surface of the substrate. (7) A decorative sheet comprising a substrate layer formed using a polyolefin or polyester resin, a pattern layer formed on the substrate layer, an adhesive layer formed on the pattern layer, a transparent resin layer formed on the adhesive layer, and a surface protective layer formed on the transparent resin layer, The transparent resin layer is formed using polyolefin as a main component, The surface protection layer is formed using an acrylic resin and a curing agent as main components, and has a nanoindentation hardness set to a range of 150 MPa or more and 180 MPa or less, a composite elastic modulus set to a range of 2.5 GPa or more and 3.5 GPa or less, and a stress relaxation rate set to a range of 0.1 or more and 0.2 or less. A method for selecting materials for decorative sheets. [Industrial Applicability]

[0110] The decorative sheet according to the present disclosure can achieve scratch resistance, stain resistance, and bending resistance all at once, and can therefore be used extremely advantageously in a variety of industries, including the construction industry. [Explanation of symbols]

[0111] 1 Base material layer 2. Picture layer 3 Adhesive layer 4 Transparent resin layer 5 Surface protective layer 6 Primer layer 10 Decorative Sheet 11. Adhesive 12 Base material 100 Cosmetic Materials

Claims

1. A decorative sheet comprising a base layer formed using a polyolefin or polyester resin, a pattern layer formed on the base layer, an adhesive layer formed on the pattern layer, a transparent resin layer formed on the adhesive layer, and a surface protective layer formed on the transparent resin layer, the transparent resin layer is mainly composed of polyolefin, The surface protective layer is The main components are acrylic resin and hardener. The nanoindentation hardness is in the range of 150 MPa or more and 180 MPa or less, the composite elastic modulus is in the range of 2.5 GPa or more and 3.5 GPa or less, and the stress relaxation rate is in the range of 0.1 or more and 0.2 or less. A decorative sheet characterized by:

2. The transparent resin layer is The nanoindentation hardness is 30 MPa or less, the composite elastic modulus is 1.0 GPa or less, and the stress relaxation rate is 0.3 or more. The decorative sheet according to claim 1 .

3. the surface protective layer has a glass transition temperature in the range of 50°C or higher and 80°C or lower; The decorative sheet according to claim 1 .

4. the acrylic resin among the main components of the surface protective layer contains at least methyl methacrylate, 2-hydroxyethyl methacrylate, and butyl acrylate; The acrylic resin is The hydroxyl value is in the range of 10 mg KOH / g or more and 50 mg KOH / g or less. The decorative sheet according to claim 1 .

5. the curing agent among the main components of the surface protective layer contains an isocyanate compound having two or more functional groups; The decorative sheet according to claim 4 .

6. A substrate; and the decorative sheet according to any one of claims 1 to 5 bonded to at least one surface of the substrate. A decorative material characterized by:

7. A decorative sheet comprising a substrate layer formed using a polyolefin or polyester resin, a pattern layer formed on the substrate layer, an adhesive layer formed on the pattern layer, a transparent resin layer formed on the adhesive layer, and a surface protective layer formed on the transparent resin layer, The transparent resin layer is formed using polyolefin as a main component, The surface protection layer is formed mainly from an acrylic resin and a curing agent, and has a nanoindentation hardness in the range of 150 MPa or more and 180 MPa or less, a composite elastic modulus in the range of 2.5 GPa or more and 3.5 GPa or less, and a stress relaxation rate in the range of 0.1 or more and 0.2 or less. A method for selecting materials for decorative sheets.

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