Decorative sheet and method for manufacturing decorative sheet

Abstract

To provide a decorative sheet capable of reducing the occurrence of delamination.SOLUTION: A decorative sheet 10 comprises a base material 11, a pattern layer 12, an adhesive layer 13, a transparent resin layer 14, and a surface protection layer 15 in this order. The adhesive layer 13 comprises an acrylic resin and an isocyanate curing agent as a cross-linking component. The acrylic resin is composed of (a) at least one monofunctional acrylic ester monomer with a carbon number of 4 or less and a homopolymer glass transition temperature of 0°C or lower, (b) at least one monofunctional acrylic ester monomer with a carbon number of 8 or more, and (c) at least one monofunctional acrylic ester monomer with hydroxyl groups, and has a property ranged in which (a) accounts for half or more of the total mass of the monomer, with a glass transition temperature in the range of -45 to -10°C, and with a hydroxyl group value in the range of 40 mg KOH / g or more and 200 mg KOH / g or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a decorative sheet. and a method for manufacturing a decorative sheet Regarding. [Background technology]

[0002] For interior or exterior building materials such as walls, ceilings, floors, and entrance doors, and for fixtures or fittings such as window frames, doors, handrails, baseboards, moldings, and moldings, decorative sheets are generally applied to adherends made of metal materials such as steel plates, resin materials, or wood materials. Many decorative sheets are laminated, and decorative sheets used for building exteriors, bathrooms, etc., in particular, can have problems such as moisture penetrating from the edges of the decorative sheet into the interior of the decorative sheet, causing interlayer delamination.

[0003] Generally, when manufacturing a decorative sheet, which is a laminate, an adhesive layer may be provided. This adhesive layer is generally made of acrylic resin, polyurethane resin, epoxy resin, or polyester resin (Patent Document 1). In such cases, delamination may occur between the adhesive layer and the transparent resin layer formed on the adhesive layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4737722 Summary of the Invention [Problem to be solved by the invention]

[0005] In order to solve the above problems, the present invention aims to provide a decorative sheet that can reduce the occurrence of delamination (particularly the occurrence of delamination between an adhesive layer and a transparent resin layer). [Means for solving the problem]

[0006] After extensive research, the inventors discovered that the above-mentioned goals can be achieved by using a decorative sheet that uses a resin containing specific elements in the adhesive layer (also called an anchor layer or anchor coat layer), and thus arrived at the present invention. In order to solve the above problems, a decorative sheet according to one aspect of the present invention is a decorative sheet comprising a polyolefin substrate, a design layer, an anchor coat layer, a transparent resin layer containing polypropylene as a main component, and a top coat layer in this order, wherein the anchor coat layer is composed of an acrylic resin and an isocyanate curing agent as a crosslinking component, The acrylic resin is a resin having the properties of a glass transition temperature in the range of -45 to -10°C and a hydroxyl value in the range of 40 mgKOH / g or more and 200 mgKOH / g or less, polymerized using (a) at least one monofunctional acrylic ester monomer having 4 or less carbon atoms and a glass transition temperature of the homopolymer of 0°C or less, (b) at least one monofunctional acrylic ester monomer having 8 or more carbon atoms, and (c) at least one monofunctional acrylic ester monomer having a hydroxyl group, with (a) accounting for half or more of the total mass of the monomers. [Effects of the Invention]

[0007] According to one aspect of the present invention, there is provided a decorative sheet that can reduce the occurrence of delamination (particularly the occurrence of delamination between an adhesive layer and a transparent resin layer). [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram showing the cross-sectional structure of a decorative sheet according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Configuration of decorative sheet] The configuration of a decorative sheet according to one embodiment of the present invention will be described with reference to the drawings. The configuration shown in Fig. 1 is a schematic diagram, and the relationship between thickness and planar dimensions, the thickness ratio of each layer, and the like differ from the actual configuration. Furthermore, the embodiments shown below are merely examples of configurations that embody the technical concept of the present invention, and the technical concept of the present invention is not limited to the materials, shapes, structures, and the like of the components described below. Various modifications can be made to the technical concept of the present invention within the technical scope defined by the claims.

[0010] Fig. 1 is a cross-sectional view showing the configuration of a decorative sheet 10 according to this embodiment. The decorative sheet 10 comprises a substrate (polyolefin substrate) 11, a design layer 12 formed on the substrate 11, an adhesive layer (anchor coat layer) 13 formed on the design layer 12, a transparent resin layer 14 formed on the adhesive layer 13, and a surface protective layer (top coat layer) 15 formed on the transparent resin layer 14. Hereinafter, as this embodiment, a decorative sheet 10 in which the transparent resin layer 14 is bonded via the adhesive layer 13 to the substrate 11 on which the design layer 12 is printed, and further provided with the surface protective layer 15, will be described with reference to Fig. 1.

[0011] (Adhesive layer) The adhesive layer 13 is a layer provided to bond the design layer 12 and the transparent resin layer 14 together. The adhesive layer 13 is made of an acrylic resin and is formed using a common coating method such as gravure coating, microgravure coating, comma coating, knife coating, or die coating. The acrylic resin constituting adhesive layer 13 is a resin having the properties of a glass transition temperature in the range of -45 to -10°C and a hydroxyl value in the range of 40 mgKOH / g or more and 200 mgKOH / g or less, polymerized using (a) at least one monofunctional acrylic ester monomer having 4 or less carbon atoms and a homopolymer glass transition temperature of 0°C or less, (b) at least one monofunctional acrylic ester monomer having 8 or more carbon atoms, and (c) at least one monofunctional acrylic ester monomer having a hydroxyl group, with (a) accounting for more than half of the total monomer mass. By adding an appropriate amount of a curing agent such as isocyanate to this, the adhesive layer 13 can be cured.

[0012] The acrylic acid ester monomer having 4 or less carbon atoms that constitutes the acrylic resin of this embodiment can be, for example, at least one of ethyl acrylate, normal propyl acrylate, normal butyl acrylate, isobutyl acrylate, etc. These acrylic acid ester monomers have a low glass transition temperature and therefore exhibit appropriate tackiness, preventing crosslinking by an isocyanate curing agent from progressing in a state in which the transparent resin layer 14 is floating, and enabling uniform adhesion between the design layer 12 and the transparent resin layer 14.

[0013] The acrylic acid ester monomer having 8 or less carbon atoms that constitutes the acrylic resin of this embodiment can be at least one of octyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, etc. The incorporation of these acrylic acid ester monomers has the effect of reducing polarity, making them compatible with the transparent resin layer 14 and improving adhesion. Improved adhesion between the transparent resin layer 14 and the adhesive layer 13 makes it difficult for water to enter the gap between the layers, and improved moisture resistance can also be expected.

[0014] The acrylic resin of this embodiment may be made of at least one hydroxyl group-containing acrylic ester monomer selected from the group consisting of hydroxyethyl acrylate, hydroxyethyl methacrylate, and the like. The use of these acrylic ester monomers allows the acrylic resin to be provided with hydroxyl groups. The presence of hydroxyl groups allows crosslinking with a curing agent, which is expected to improve adhesion, moisture resistance, and heat resistance.

[0015] The glass transition temperature of the acrylic resin of this embodiment may be -45°C or higher, and preferably -30°C or higher. The glass transition temperature is preferably -10°C or lower, and more preferably -15°C or lower. If the glass transition temperature is lower than -45°C, the cohesive strength of the acrylic resin is low, resulting in no tackiness, insufficient adhesion between the pattern layer and the transparent resin layer before crosslinking, and no uniform adhesion. If the glass transition temperature is higher than -10°C, the cohesive strength of the acrylic resin is high, resulting in no tackiness and poor adhesion.

[0016] The hydroxyl value of the acrylic resin of this embodiment is preferably 40 mgKOH / g or more, more preferably 80 mgKOH / g or more. The hydroxyl value is preferably 200 mgKOH / g or less, more preferably 160 mgKOH / g or less. If the hydroxyl value is less than 40 mgKOH / g, the reaction with the curing agent added to increase the crosslink density of the acrylic resin may not proceed. If the hydroxyl value is more than 200 mgKOH / g, the water resistance may decrease, or the reactivity with the crosslinking agent may be too high, resulting in a short pot life.

[0017] The curing agent used to cure the acrylic resin of the present embodiment is not particularly limited, and can be appropriately selected from commercially available curing agents including, for example, hexamethylene diisocyanate, isophorone diisocyanate, tolylene diisocyanate, xylylene diisocyanate and its hydrogenated products, or diphenylmethane diisocyanate and its hydrogenated products.

[0018] In addition, examples of the ultraviolet absorber (UVA) having a triazine skeleton to be added to the acrylic resin of this embodiment include 2,4-Bis(2,4-dimethylphenyl)-6-(2-hydroxy-4-n-octyloxyphenyl)-1,3,5-triazine, 2-(2-hydroxy-4-methoxyphenyl)-4,6-diphenyl-1,3,5-triazine, and Ethylhexyl Triazone, 2-(2,4-Dihydroxyphenyl)-4,6-diphenyl-1,3,5-triazine, 2,4,6-Tris(4-butoxy-2-hydroxyphenyl)-1,3,5-triazine, N,N',N''-Tri(m-tolyl)-1,3,5-triazine-2,4,6-triamine, 2-(2,4-Dihydroxyphenyl)-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine, 2,4,6-Tris(2,4-dihydroxyphenyl)-1,3,5-triazine, Bemotrizinol, and the like can be appropriately selected and used. UVA with a triazine skeleton is expected to have stronger absorption, long-lasting durability, and excellent heat resistance compared to UVA without a triazine skeleton.

[0019] Furthermore, the light stabilizer (HALS) having a NOR skeleton to be added to the acrylic resin of this embodiment can be appropriately selected from decanedioic acid, bis(2,2,6,6-tetramethyl-1-(octyloxy)-4-piperidinyl)ester, reaction products with 1,1-dimethylethylhydroperoxide and octane, 2,4-bis[N-Butyl-N-(1-cyclohexyloxy-2,2,6,6-tetramethylpiperidic-4-yl)amino]-6-(2-hydroxyethylamine)-1,3,5-triazine, etc. HALS having a NOR skeleton has low basicity, so there is no risk of reaction even when it is added to a coating material containing an acidic catalyst or resin.

[0020] The method for joining the transparent resin layer 14 to the substrate 11 provided with the pattern layer 12 can be via an adhesive layer 13, and various lamination techniques such as thermal lamination, extrusion lamination, dry lamination, and sand lamination can be used.

[0021] (base material) The resin constituting the substrate 11, i.e., the resin component, is preferably polyolefin or polyester, and polyolefin is most preferred from the viewpoint of versatility. The resin constituting the substrate 11 can be arbitrarily selected from existing materials such as polyethylene, polypropylene, polybutylene, polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate. Furthermore, examples of materials other than the 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- Examples include homopolymers or copolymers of two or more types of α-olefins (e.g., hexene, 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.

[0022] To improve adhesion between the substrate 11 and adjacent layers, the substrate 11 may be subjected to surface treatment such as corona treatment, plasma treatment, ozone treatment, electron beam treatment, ultraviolet treatment, dichromate treatment, etc. Furthermore, a primer layer (not shown) may be provided between the substrate 11 and the pattern layer 12 to ensure adhesion. If the substrate 11 is made of polyolefin or polyester, adhesion to the design layer 12 described below is ensured, and if it is made of polyolefin, adhesion to the design layer 12 is even more ensured.

[0023] If it is desired to impart hiding properties to the decorative sheet 10, a hiding colored sheet may be used for the substrate 11, or a hiding layer (not shown) may be provided on the substrate 11 and below the design layer 12. When a colored sheet is used as the substrate 11, the resin material constituting the substrate 11 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 obtain the desired hiding properties and design properties. In addition, various additives such as fillers, foaming agents, flame retardants, lubricants, antistatic agents, antioxidants, crystal nucleating agents, ultraviolet absorbers, light stabilizers, heat stabilizers, colorants, and matting agents may be added to the substrate 11 as needed.

[0024] (Picture layer) The design layer 12 is, for example, a layer including a design printed on the substrate 11 using ink. The ink used to form the design layer 12 may contain, for example, a binder resin. The binder resin contained in the ink used to form the design layer 12 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. Furthermore, the binder resin may be water-based, solvent-based, or emulsion-type, and may be either a one-component type or a two-component type using a curing agent. In this embodiment, the ink used to form the design layer 12 is preferably a water-based colored ink from the viewpoint of coatability. Examples of methods for curing the ink used to form the design layer 12 include methods for curing the ink by irradiation with ultraviolet light, electron beams, etc. Among these, the most common method is to use a urethane-based ink and to cure it with polyisocyanate.

[0025] In addition to the binder resin described above, the ink used to form the design layer 12 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 12 is not particularly limited, and for example, a typical printing method such as gravure printing, offset printing, screen printing, flexographic printing, or ink jet printing can be used.

[0026] (Transparent resin layer) Polyolefins are preferably used as the material for the transparent resin layer 14, such as polypropylene, polyethylene, polybutene, and various α-olefin copolymers (copolymers of propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, etc.). Of these resins, polypropylene is the most preferred material for the transparent resin layer 14. The transparent resin layer 14 of the present embodiment may be a sheet formed by film formation or may be a laminate of already formed sheets. The transparent resin layer 14 may be made of, for example, a highly crystalline polypropylene resin.

[0027] It is preferable that polypropylene accounts for 80% by mass or more, and more preferably 90% by mass or more, of the total mass of the transparent resin layer 14. Note that "a transparent resin layer containing polypropylene as a main component" means that polypropylene accounts for 80% by mass or more of the total mass of the transparent resin layer 14.

[0028] If necessary, various additives such as a heat stabilizer, a flame retardant, an ultraviolet absorber, a light stabilizer, an antiblocking agent, a catalyst scavenger, and, to the extent that the characteristics of this embodiment are not impaired, a colorant, a light scattering agent, and a gloss adjuster may also be added to the transparent resin layer 14. Generally, any combination of the following is added: heat stabilizers, such as phenol-based, sulfur-based, phosphorus-based, and hydrazine-based; flame retardants, such as aluminum hydroxide and magnesium hydroxide; ultraviolet absorbers, such as benzotriazole-based, benzoate-based, benzophenone-based, and triazine-based; and light stabilizers, such as hindered amine-based.

[0029] The method for producing the transparent resin layer 14 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 14 may be provided with surface irregularities, or so-called embossing, to impart design. Examples of methods for providing the irregularities include a method of subjecting the transparent resin layer 14 to thermal embossing after extrusion molding, or a method of embossing simultaneously with extrusion molding using a chill roll with irregularities during extrusion molding. More specifically, the irregular pattern (embossed pattern) is directly applied to the transparent resin layer 14, for example, a highly crystalline polypropylene sheet. Examples of such methods include a method of applying an irregular pattern to a polypropylene sheet after film formation using an embossing plate with an irregular pattern under heat and pressure, or a method of embossing simultaneously with cooling using a chill roll with an irregular pattern during film formation using an extruder. Here, colored ink can be embedded in the recesses of the irregular pattern to further enhance the design.

[0030] The uneven pattern may be provided if necessary, but may not be provided if unnecessary. Furthermore, one or both surfaces of the transparent resin layer 14 may be activated, as necessary, by, for example, corona treatment, plasma treatment, electron beam treatment, ultraviolet treatment, dichromate treatment, or the like.

[0031] (Surface protective layer) The surface protective layer 15 according to this embodiment is a layer provided to impart functions such as weather resistance, scratch resistance, stain resistance, and designability to the decorative sheet 10. The material constituting the surface protective layer 15 is not particularly limited, and can be appropriately selected from, for example, urethane-based, acrylic-based, acrylic silicone-based, fluorine-based, and epoxy-based resin materials.

[0032] From the viewpoint of coatability, an ink containing a urethane polymer as a main component is suitable as the material for the surface protective layer 15. Here, "an ink containing a urethane polymer as a main component" means that the urethane polymer accounts for 80% by mass or more of the total mass of the ink. In this embodiment, a urethane-based surface protection layer 15 utilizing an isocyanate reaction is desirable from the viewpoints of workability, cost, and the cohesive strength of the resin itself.

[0033] In forming the surface protective layer 15, the isocyanate may be appropriately selected from curing agents such as adducts, biurets, and isocyanurates, which are derivatives of tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), hexamethylene diisocyanate (HMDI), diphenylmethane diisocyanate (MDI), lysine diisocyanate (LDI), isophorone diisocyanate (IPDI), bis(isocyanatomethyl)cyclohexane (HXDI), trimethylhexamethylene diisocyanate (TMDI), and the like, as well as various prepolymers.

[0034] If necessary, the surface protective layer 15 may contain various additives such as an ultraviolet absorber, a heat stabilizer, a light stabilizer, an antiblocking agent, a catalyst scavenger, a colorant, a light scattering agent, and a gloss adjuster. Among these, it is preferable that at least one of an ultraviolet absorber and a light stabilizer is contained.

[0035] The method for forming the surface protection layer 15 is not particularly limited, and the surface protection layer 15 may be formed by applying a coating liquid of the above-mentioned material using a conventional method such as gravure coating, microgravure coating, comma coating, knife coating, or die coating, and then curing the liquid using a method suitable for the material, such as heat curing or ultraviolet curing. Alternatively, the surface protection layer 15 may be provided after the pattern layer 12 formed on the substrate 11 and the transparent resin layer 14 are bonded together via the adhesive layer 13 .

[0036] (Primer layer) The decorative sheet 10 according to this embodiment may further comprise a primer layer 16 on the back surface, which is the surface of the substrate 11 opposite to the surface on which the design layer 12 is located. The primer layer 16 may be formed from the same component as the binder resin contained in the colored ink for forming the design layer 12 .

[0037] The method for forming the primer layer 16 is not particularly limited, and the primer layer 16 may be formed by applying a coating liquid made from the above-mentioned material by a conventional method such as gravure coating, microgravure coating, comma coating, knife coating, or die coating, and then curing the coating by a method suitable for the material, such as thermal curing or ultraviolet curing.

[0038] In addition, the primer layer 16 may be provided after forming a laminate having the base material 11, the pattern layer 12, the adhesive layer 13, the transparent resin layer 14, and the surface protective layer 15 in this order, or after providing the primer layer 16 on the back surface of the base material 11, a laminate may be formed having the base material 11 with the primer layer 16 provided thereon, the pattern layer 12, the adhesive layer 13, the transparent resin layer 14, and the surface protective layer 15 in this order.

[0039] Furthermore, considering that the primer layer 16 will be applied to the back surface of the decorative sheet and will be wound up in web form, inorganic fillers such as silica, alumina, magnesia, titanium oxide, barium sulfate, etc. may be added to the primer layer 16 to avoid blocking and improve adhesion with the adhesive.

[0040] Regarding the thickness of each layer constituting the decorative sheet 10 according to this embodiment, the substrate 11 is preferably in the range of 50 μm to 100 μm inclusive, taking into consideration printing workability, cost, etc., the design layer 12 is preferably in the range of 1 μm to 5 μm inclusive, the adhesive layer 13 is preferably in the range of 1 μm to 3 μm inclusive, the transparent resin layer 14 is preferably in the range of 70 μm to 100 μm inclusive, and the surface protective layer 15 is preferably in the range of 3 μm to 15 μm inclusive. Furthermore, taking into consideration hydrolysis resistance, printing workability, cost, etc., the thickness of the adhesive layer 13 is more preferably in the range of 1 μm to 2.5 μm inclusive, and even more preferably in the range of 1.5 μm to 2 μm inclusive.

[0041] If the thickness of each layer is less than the respective lower limit values, the function (performance) of each layer may not be obtained. On the other hand, if the thickness of each layer exceeds the respective upper limit values, the function (performance) of each layer will not be significantly improved. Therefore, from the viewpoint of production costs, it is preferable to set the thickness of each layer to be equal to or less than the respective upper limit values.

[0042] Furthermore, when a primer layer 16 is provided, the thickness of the primer layer 16 is preferably in the range of 1 μm to 5 μm. If the thickness of the primer layer 16 is within the above numerical range, the function (performance) of the primer layer 16 can be reliably exhibited. The total thickness of the decorative sheet 10 is preferably within the range of 125 μm to 240 μm. Within the above range, the printing workability can be easily improved and the manufacturing cost can be reduced.

[0043] The peel strength between the adhesive layer 13 and the transparent resin layer 14 in the decorative sheet 10 according to this embodiment is preferably 15 N / inch or more. If the peel strength between the adhesive layer 13 and the transparent resin layer 14 is 15 N / inch or more, when the decorative sheet 10 is produced in roll form, slippage of the roll can be reliably prevented. Furthermore, it is preferable that the peel strength between the adhesive layer 13 and the transparent resin layer 14 is 10 N / inch or more after the decorative sheet 10 is exposed to an environment of 40°C and 90% RH for 500 hours. If the peel strength between the adhesive layer 13 and the transparent resin layer 14 is 10 N / inch or more after the decorative sheet 10 is exposed to an environment of 40°C and 90% RH for 500 hours, the decorative sheet 10 can be endowed with excellent durability.

[0044] Furthermore, if the decorative sheet 10 is tested in a super xenon testing machine (Toyo Seiki Atlas Weatherometer Ci4000) under test conditions of 180W light irradiation, 12 minutes of rain / 120 minutes cycle, and for 24 hours, and the peel strength between the adhesive layer 13 and the transparent resin layer 14 is 10 N / inch or more, the decorative sheet will have excellent weather resistance and can be used outdoors.

[0045] The peel strength in this embodiment can be determined, for example, by the interlayer peel test described below.

[0046] <Delamination test> In a decorative sheet 10 in which the adhesive layer 13 has a thickness of 10 μm, a test (interlayer peeling test) is carried out to determine whether peeling occurs between the adhesive layer 13 and the transparent resin layer 14. After Nichiban cellophane tape is pressed onto the surface of the decorative sheet 10, it is strongly peeled off with a certain force (for example, 5 N / inch, 10 N / inch, 15 N / inch, or 20 N / inch), and the presence or absence of peeling between the adhesive layer 13 and the transparent resin layer 14 is evaluated under a microscope. In this embodiment, the maximum force at which peeling does not occur between the adhesive layer 13 and the transparent resin layer 14 is defined as the "peel strength."

[0047] It should be noted that the measurement of peel strength in this embodiment is not limited to the above method, and for example, a T-peel test may be performed between the adhesive layer 13 and the transparent resin layer 14 in accordance with JIS K6854-3:1999 to measure (determine) the peel strength between the adhesive layer 13 and the transparent resin layer 14.

[0048] [Method for manufacturing decorative sheet] A method for producing a decorative sheet 10 according to one embodiment of the present invention will now be briefly described. First, on the substrate 11, which is a polyolefin substrate with a thickness in the range of 50 μm to 100 μm, the design layer 12 is formed with a colored ink containing a urethane polymer as a binder to a thickness of 1 μm to 5 μm. Next, on the pattern layer 12, an adhesive layer 13 is formed with a thickness of 1 μm or more and 3 μm or less. The adhesive layer 13 is composed of at least an acrylic resin as a resin component and an isocyanate curing agent as a cross-linking component, and the acrylic resin is polymerized using at least one acrylic ester monomer having 4 or less carbon atoms, at least one acrylic ester monomer having 8 or more carbon atoms, and at least one acrylic ester monomer having a hydroxyl group, and has a glass transition temperature in the range of -45 to -10°C and a hydroxyl value in the range of 40 mgKOH / g or more and 200 mgKOH / g or less.

[0049] Next, a transparent resin layer 14 containing polypropylene as a main component is formed on the adhesive layer 13 by extrusion molding to a thickness of 70 μm or more and 100 μm or less. Finally, the surface protection layer 15 is formed on the transparent resin layer 14 with an ink containing a urethane polymer as a main component, to a thickness of 3 μm to 15 μm. In this way, the decorative sheet 10 according to this embodiment is manufactured.

[0050] Furthermore, after forming the design layer 12 and before forming the adhesive layer 13, the surface of the design layer 12 on the adhesive layer 13 side may be subjected to a surface treatment so that the wetting index is 60 dyne or more. In addition, the colored ink used in the process of forming the pattern layer 12 may contain a binder resin, and a primer layer 16 consisting of the same components as the binder resin contained in the colored ink and having a film thickness in the range of 1 μm to 5 μm may be formed on the back surface, which is the surface opposite to the surface of the substrate 11 on which the pattern layer 12 is formed.

[0051] EXAMPLES The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0052] Example 1 As shown in Table 1, a side-arm reaction vessel for a personal synthesis system (Tokyo Rikakikai) was charged with 85 parts of EA (Kanto Chemical Co., Ltd.) as an acrylic ester monomer with 4 or fewer carbon atoms, 10 parts of HEA (Kanto Chemical Co., Ltd.) as an acrylic ester monomer with a hydroxyl group, and 5 parts of LA (Kanto Chemical Co., Ltd.) as an acrylic ester monomer with 8 or more carbon atoms. AIBN (polymerization initiator) was added at a monomer-to-monomer ratio of 1 mol%, and solvent was added to the mixture to a monomer mass of 30 wt%. After argon was bubbled through the mixture at room temperature for 15 minutes, the mixture was heated and stirred at 70°C in a closed system for 8 hours to produce an acrylic resin with a glass transition temperature of -19°C and a hydroxyl value of 48 mgKOH / g. The glass transition temperature of "EA" is -20°C.

[0053] A wood grain pattern was gravure printed onto a 70 μm thick polyethylene substrate with opacity using a two-component urethane ink (V180; manufactured by Toyo Ink Co., Ltd.) to form a pattern layer (3 μm thick). This two-component urethane ink contains a binder resin. A mixture of the above acrylic resin and 1.2 equivalents of an isocyanate curing agent, Duranate TSE-100 (Asahi Kasei), was applied to the substrate thus obtained to form an adhesive layer (anchor coat layer: thickness 2 μm). The substrate and a transparent polyolefin resin forming a transparent resin layer were dry laminated via this adhesive layer, with the thickness of the transparent resin layer being 80 μm.

[0054] Furthermore, as a surface protective layer, a two-component cured polyurethane resin layer consisting of an acrylic polyol (a copolymer of methyl methacrylate and 2-hydroxy methacrylate) and a curing agent (a nurate form of hexamethylene diisocyanate) was applied onto the transparent polyolefin resin (layer thickness: 8 μm), thereby obtaining the decorative sheet of Example 1.

[0055] <Example 2> The decorative sheet of Example 2 was obtained in the same manner as in Example 1, except that the amount of EA (manufactured by Kanto Chemical Co., Ltd.) used in Example 1 was changed to 75 parts and the amount of HEA (manufactured by Kanto Chemical Co., Ltd.) to 20 parts, and an acrylic resin with a glass transition temperature of -18°C and a hydroxyl value of 97 mgKOH / g was used.

[0056] Example 3 The decorative sheet of Example 3 was obtained in the same manner as in Example 1, except that the amount of EA (manufactured by Kanto Chemical Co., Ltd.) used in Example 1 was changed to 65 parts and the amount of HEA (manufactured by Kanto Chemical Co., Ltd.) to 30 parts, and an acrylic resin with a glass transition temperature of -18°C and a hydroxyl value of 145 mgKOH / g was used.

[0057] Example 4 The decorative sheet of Example 4 was obtained in the same manner as in Example 1, except that the amount of EA (manufactured by Kanto Chemical Co., Ltd.) used in Example 1 was changed to 55 parts and the amount of HEA (manufactured by Kanto Chemical) to 40 parts, and an acrylic resin with a glass transition temperature of -17°C and a hydroxyl value of 193 mgKOH / g was used.

[0058] <Example 5> A decorative sheet of Example 5 was obtained in the same manner as in Example 1, except that Tinvin 479 was added as a triazine-based ultraviolet absorber to the acrylic resin prepared in Example 3.

[0059] Example 6 The decorative sheet of Example 6 was obtained in the same manner as in Example 1, except that Tinvin 479 was added as a triazine-based ultraviolet absorber and Tin 123 as a NOR-type light stabilizer to the acrylic resin produced in Example 3.

[0060] Example 7 A decorative sheet of Example 7 was obtained in the same manner as in Example 1, except that the thickness of the adhesive layer (anchor coat layer) in Example 1 was changed to 5 μm.

[0061] Example 8 A decorative sheet of Example 8 was obtained in the same manner as in Example 1, except that the material for the surface protective layer (top coat layer) in Example 1 was Acrydic FL-638-BE (acrylic resin manufactured by DIC Corporation).

[0062] <Comparative Example 1> The decorative sheet of Comparative Example 1 was obtained in the same manner as in Example 1, except that the LA (manufactured by Kanto Chemical Co., Ltd.) used in Example 1 was not added and an acrylic resin with a glass transition temperature of -18°C and a hydroxyl value of 169 mgKOH / g was used instead.

[0063] <Comparative Example 2> The decorative sheet of Comparative Example 2 was obtained in the same manner as in Example 1, except that the EA (manufactured by Kanto Chemical Co., Ltd.) used in Example 1 was changed to n-BA (Kanto Chemical), and an acrylic resin with a glass transition temperature of -49°C and a hydroxyl value of 48 mgKOH / g was used.

[0064] <Comparative Example 3> The decorative sheet of Comparative Example 3 was obtained in the same manner as in Example 1, except that the EA (manufactured by Kanto Chemical Co., Ltd.) used in Example 3 was changed to t-BA (manufactured by Kanto Chemical Co., Ltd.) and an acrylic resin with a glass transition temperature of -9°C and a hydroxyl value of 145 mgKOH / g was used.

[0065] <Comparative Example 4> The decorative sheet of Comparative Example 4 was obtained in the same manner as in Example 1, except that the amount of EA (manufactured by Kanto Chemical Co., Ltd.) used in Example 1 was changed to 90 parts and the amount of HEA (manufactured by Kanto Chemical Co., Ltd.) to 5 parts, and an acrylic resin with a glass transition temperature of -18°C and a hydroxyl value of 24 mgKOH / g was used.

[0066] <Comparative Example 5> The decorative sheet of Comparative Example 5 was obtained in the same manner as in Example 1, except that the amount of EA (manufactured by Kanto Chemical Co., Ltd.) used in Example 1 was changed to 50 parts and the amount of HEA (manufactured by Kanto Chemical Co., Ltd.) to 45 parts, and an acrylic resin with a glass transition temperature of -17°C and a hydroxyl value of 217 mgKOH / g was used.

[0067] <Comparative Example 6> A decorative sheet of Comparative Example 6 was obtained in the same manner as in Example 1, except that the isocyanate curing agent used in Example 1 was replaced with the epoxy curing agent Denacol EX-830 (Nagase Chemtec).

[0068] <Evaluation> The decorative sheets obtained in the above Examples and Comparative Examples were each measured and evaluated for peel strength (N / inch) and peel strength (N / inch) after 500 hours of exposure in a 90% RH environment using the following method. The evaluation results are shown in Table 1. In Table 1, "EA" stands for "ethyl acrylate," "LA" stands for "lauryl acrylate," "HEA" stands for "hydroxyethyl acrylate," "n-BA" stands for "normal butyl acrylate," and "i-BA" stands for "isobutyl acrylate."

[0069] <Delamination test> For the decorative sheets of each example and comparative example in which the adhesive layer was made 10 μm thick, a test (interlayer peeling test) was carried out to determine whether peeling occurred between the adhesive layer and the transparent resin layer. After pressing Nichiban cellophane tape onto the surface of the decorative sheet, it was strongly peeled off with a constant force (increasing in 1 N / inch increments from 1 N / inch to 20 N / inch), and the presence or absence of peeling between the adhesive layer and the transparent resin layer was evaluated under a microscope. In this example, the maximum force at which peeling did not occur between the adhesive layer and the transparent resin layer was defined as "peel strength (N / inch)."

[0070] The "peel strength (N / inch) after moisture resistance test" was defined as the peel strength (N / inch) obtained by placing the decorative sheets of each example and each comparative example in a HAST chamber (highly accelerated life test apparatus), exposing them to an environment of 40°C and 90% RH for 500 hours, and then conducting the above-mentioned interlayer peel test. In addition, the "peel strength after weather resistance test (N / inch)" was the peel strength obtained by conducting the above-mentioned interlayer peel test after testing for 24 hours using a super xenon testing machine (Toyo Seiki Atlas Weather-O-Meter Ci4000) under test conditions of 180W light irradiation, 12 minutes of rainfall / 120 minutes cycle.

[0071] <Evaluation criteria> The evaluation criteria for each example and each comparative example are as follows. In each example, if the peel strength (N / inch) in both the "initial adhesion test" and the "moisture resistance test" was evaluated as "good," the test was deemed to have passed. For example, an evaluation of "good" in the "initial adhesion test" means that the test is suitable for use in a non-harsh environment, such as for fittings or floors. Furthermore, for example, an evaluation of "good" in the "moisture resistance test" means that the test is suitable for use in wet areas, such as near window sashes, in kitchens, bathrooms, etc. In addition, in Table 1, the comparative examples in which the "initial adhesion test" was not "good" were not subjected to the "moisture resistance test" and the "weather resistance test", and are indicated by "-".

[0072] [Initial adhesion test] ○: Peel strength is 15N / inch or more △: Peel strength is 10N / inch or more and less than 15N / inch ×: Peel strength is less than 10 N / inch

[0073] [Moisture resistance test] ○: Peel strength decreased by 0% to 20% from the initial adhesion △: Peel strength decreased by 20% to 40% from the initial adhesion ×: Peel strength decreased by 40% or more from the initial adhesion

[0074] [Table 1]

[0075] As shown in Table 1, the decorative sheets of Examples 1 to 8 were shown to be decorative sheets in which the occurrence of interlayer delamination between the adhesive layer and the transparent resin layer was reduced. In particular, the decorative sheets of Examples 5 and 6 were shown to have excellent weather resistance. [Industrial Applicability]

[0076] The present invention can be used as a decorative sheet that must be durable against high temperatures and humidity, such as for building exteriors and bathrooms, and also as an indoor sheet for use as a surface material for building fixtures or flooring. [Explanation of symbols]

[0077] 10 Decorative Sheet 11 Base material (polyolefin base material) 12 Picture layer 13 Adhesive layer (anchor coat layer) 14 Transparent resin layer 15 Surface protection layer (top coat layer) 16 Primer layer

Claims

1. A decorative sheet comprising, in this order, a polyolefin substrate, a pattern layer, an anchor coat layer, a transparent resin layer containing polypropylene as a main component, and a top coat layer, the anchor coat layer is made of a cured product of a composition comprising an acrylic resin and an isocyanate curing agent as a cross-linking component, The acrylic resin is a resin having the properties of a glass transition temperature in the range of -45 to -10°C and a hydroxyl value in the range of 40 mgKOH / g or more and 200 mgKOH / g or less, polymerized using (a) at least one monofunctional acrylic ester monomer whose alkyl group has 4 or less carbon atoms and whose homopolymer has a glass transition temperature of 0°C or less, (b) at least one monofunctional acrylic ester monomer whose alkyl group has 8 or more carbon atoms, and (c) at least one monofunctional acrylic ester monomer having a hydroxyl group, with (a) accounting for half or more of the total mass of the monomers.

2. 2. The decorative sheet according to claim 1, wherein the anchor coat layer contains at least one of an ultraviolet absorber having a triazine skeleton and a light stabilizer having a NOR skeleton as a weather resistance agent.

3. The thickness of the polyolefin substrate is in the range of 50 μm or more and 100 μm or less, The film thickness of the pattern layer is in the range of 1 μm or more and 5 μm or less, The thickness of the anchor coat layer is in the range of 1 μm or more and 3 μm or less, the transparent resin layer has a thickness of 70 μm or more and 100 μm or less; 3. The decorative sheet according to claim 1, wherein the thickness of the top coat layer is in the range of 3 μm to 15 μm.

4. 4. The decorative sheet according to claim 1, wherein the top coat layer is formed from a resin containing a urethane polymer as a main component.

5. The polyolefin substrate further includes a primer layer formed on a back surface thereof opposite to the surface on which the design layer is formed, the design layer is formed of a colored ink containing a binder resin, 5. The decorative sheet according to claim 1, wherein the primer layer is formed from the same component as the binder resin contained in the colored ink for forming the design layer.

6. A method for producing a decorative sheet comprising, in this order, a polyolefin substrate, a pattern layer, an anchor coat layer, a transparent resin layer containing polypropylene as a main component, and a top coat layer, In the step of forming the anchor coat layer, the anchor coat layer is formed by curing a composition comprising an acrylic resin and an isocyanate curing agent as a cross-linking component, A method for producing a decorative sheet, characterized in that the step of obtaining the acrylic resin comprises polymerizing a composition comprising (a) at least one monofunctional acrylic ester monomer whose alkyl group has 4 or less carbon atoms and whose homopolymer has a glass transition temperature of 0°C or less, (b) at least one monofunctional acrylic ester monomer whose alkyl group has 8 or more carbon atoms, and (c) at least one monofunctional acrylic ester monomer having a hydroxyl group, wherein (a) accounts for more than half of the total mass of the monomers, to form the acrylic resin so that the glass transition temperature is in the range of -45 to -10°C and the hydroxyl value is in the range of 40 mgKOH / g or more and 200 mgKOH / g or less.

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