White sheet, decorative sheet and manufacturing method thereof

Abstract

To provide a white sheet excellent in concealment without increasing an addition amount of an inorganic pigment compared with a conventional technology, a decorative sheet with the white sheet as a substrate layer, or a method for producing the decorative sheet thereof.SOLUTION: A white sheet 2 according to the present embodiment has a reflected chromaticity measured by a D65 light source in the range of 90 or more and 100 or less as L* in the Lab color system, a* is in the range of -1.5 or more and + 1.5 or less, b* is in the range of -1.5 or more and 2.0 or less, and the spectral reflectance has a minimum value in the range of 500 nm or more and 650 nm or less.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a white sheet, a decorative sheet, and a method for producing the same. [Background technology]

[0002] In recent years, many decorative sheets using olefin resins (e.g., polypropylene sheets) have been proposed as alternatives to decorative sheets made of polyvinyl chloride, which are environmentally hazardous. Patent Document 1, for example, describes a technology related to decorative sheets using olefin resins. These decorative sheets do not use vinyl chloride resin, which reduces the generation of toxic gases and the like when incinerated. However, polypropylene sheets generally have issues such as poor scratch resistance due to their low elastic modulus, and being prone to stretching when tension is applied to the sheets during sheet production for printing, etc.

[0003] A decorative sheet is attached to the surface of a substrate, such as a wood substrate, a metal substrate, or a non-flammable substrate, to form a decorative board, which then imparts a design to the decorative board according to its intended purpose. Therefore, the decorative sheet must completely conceal the surface of the substrate as needed. In this case, a decorative sheet that is at least colored with a pigment and has concealing properties must be used. The simplest decorative sheet configuration is one consisting of only a base layer made of a single colored sheet (single layer). With such a decorative sheet consisting of only a base layer, the designs that can be imparted are typically limited to a single color without a pattern. However, by adding a lustrous material such as aluminum flakes or pearl pigments as a pigment, a lustrous feel can be imparted, making it possible to achieve a sufficient design. Furthermore, if a more sophisticated design is desired, it is also effective to decorate the surface of the base layer, for example by printing.

[0004] Among decorative sheets, white sheets are used for door frames, baseboards, various storage compartments, etc. The surface of the substrate is easily visible through white sheets, so a large amount of pigment needs to be added to impart hiding power. However, adding a large amount of pigment makes the entire white sheet hard and prone to breaking, which is a problem. Patent Document 2 proposes a decorative sheet that contains an inorganic pigment in a vesiculated state, and that has excellent hiding power even when the amount of pigment added is increased, but it is not possible to avoid increasing the amount of pigment added, and the problem of easy breaking remains. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3271022 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-155233 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in light of the above-mentioned points, and aims to provide a white sheet with good hiding properties, a decorative sheet using a white sheet as a substrate layer, and a method for manufacturing such a decorative sheet, without increasing the amount of inorganic pigment added compared to conventional techniques. [Means for solving the problem]

[0007] The present inventors have conducted various studies and experiments, and have found that, for example, titanium oxide and at least one blue color It has been found that by adding a pigment to a resin, it is possible to provide a white sheet or decorative sheet with excellent hiding power and a minimum value of spectral reflectance in the range of 500 nm to 650 nm, and a method for producing the same.

[0008] In order to achieve the object, a white sheet according to one aspect of the present invention is a white sheet in which, in the Lab color system, the reflected chromaticity measured with a D65 light source is in the range of L* 90 to 100, a* -1.5 to +1.5, and b* -1.5 to 2.0. The gist is that the spectral reflectance has a minimum value within the range of 500 nm or more and 650 nm or less. [Effects of the Invention]

[0009] According to one aspect of the present invention, it is possible to provide a white sheet, a decorative sheet, and a method for manufacturing the same that have excellent flexibility such as bending workability and excellent hiding power, since there is no need to increase the amount of inorganic pigment added compared to conventional techniques. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view showing the structure of a decorative sheet according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing the structure of another decorative sheet according to an embodiment of the present invention. [Figure 3] FIG. 2 is a cross-sectional view showing the structure of another decorative sheet according to an embodiment of the present invention. [Figure 4] 1 is a graph showing the spectral reflectance of a white sheet containing only titanium oxide. [Figure 5] 1 is a graph showing the spectral reflectance of sheets containing cobalt blue and ultramarine blue as blue pigments. [Figure 6] 1 is a graph showing the spectral reflectance measured on the same white sheet with a white background and a black background. [Figure 7] 1 is a graph showing the spectral reflectances of Examples 1 to 4 and Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The drawings are schematic, and the relationship between thickness and 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 does not specify the materials, shapes, structures, etc. of the components to those described below. The technical idea of ​​the present invention can be modified in various ways within the technical scope defined by the claims.

[0012] "composition" The decorative sheet 1 of the embodiment shown in FIG. 1 is an example of a single-layer structure consisting of only a white sheet 2. Alternatively, as shown in FIG. 2, the white sheet 2 of this embodiment may be composed of a colored layer 3 formed by mixing an inorganic pigment into a polypropylene resin, and a skin layer 4 formed on at least one side of the colored layer 3 and made of polypropylene resin. The skin layer 4 is intended to prevent the inorganic pigment contained in the colored layer 3 from bleeding and adhering to the manufacturing equipment during the manufacturing process, resulting in poor film formation. The skin layer 4 may contain a nano-sized nucleating agent to improve crystallinity. Improving crystallinity improves scratch resistance. In this embodiment, the nucleating agent may be contained in the form of a nucleating agent vesicle, for example, encapsulated in an outer membrane.

[0013] If necessary, a design layer 5 may be formed (laminated) on one side of the white sheet 2 to improve the design. Furthermore, the decorative sheet 1 may have at least one of a transparent resin layer 6 and a top coat layer 7 laminated on one side of the white sheet 2. The decorative sheet 1 illustrated in FIG. 3 is an example in which a design layer 5, a transparent resin layer 6, and a top coat layer 7 are laminated in this order on one side of the white sheet 2. Furthermore, either the transparent resin layer 6 or the top coat layer 7 may be omitted. Furthermore, the design layer 5 may be omitted.

[0014] At least one of the transparent resin layer 6 and the top coat layer 7 may be provided with an embossed pattern (embossed pattern 6a) depending on design requirements. Ink can be embedded in the pattern 6a to further improve the design. If there are problems with the adhesion between the design layer 5 and the transparent resin layer 6, an adhesive resin layer 6b may be provided as appropriate. When the adhesive resin layer 6b is provided, the transparent resin layer 6 and the adhesive resin layer 6b are formed by co-extrusion. The adhesive resin layer 6b may be formed, for example, from an acid-modified resin such as polypropylene, polyethylene, or acrylic resin. The thickness of the adhesive resin layer 6b is preferably 2 μm or more to improve adhesive strength. Furthermore, if scratch resistance or other requirements are required, it is possible to laminate multiple layers of at least one of the transparent resin layer 6 and the top coat layer 7, and other known layers may also be arranged.

[0015] 1, 2, and 3, the symbol B represents a substrate. The substrate B is a substrate to which the decorative sheet 1 is attached. There are no particular limitations on the substrate B, but examples include wood boards, inorganic boards, metal plates, and composite boards made of multiple materials. A primer layer 8 or a concealing layer (not shown) may be provided between the decorative sheet 1 and the substrate B as appropriate.

[0016] The tensile modulus of the decorative sheet 1 of this embodiment, particularly the tensile modulus of the white sheet 2 alone, is preferably in the range of 1000 MPa or more and 2200 MPa or less. If the tensile modulus is less than 1000 MPa, scratch resistance tends to deteriorate. If the tensile modulus exceeds 2200 MPa, the crystallinity is too high, and even when a nucleating agent (e.g., nucleating agent vesicles) is used, problems such as whitening and cracking may occur during bending.

[0017] Next, each layer that constitutes the decorative sheet 1 will be described.

[0018] <White sheet 2> White sheet 2 has a reflective chromaticity measured with a D65 light source of L* of 90 or more in the Lab color system. The sheet is formed so that the reflectance is within the range of 0 or less, a* is within the range of -1.5 to +1.5, and b* is within the range of -1.5 to 2.0, and the spectral reflectance has a minimum value within the range of 500 nm to 650 nm. The sheet has a colored layer 3, which is formed, for example, by mixing an inorganic pigment into a resin at an appropriate ratio. If the colored layer 3 is the outermost layer, the pigment components contained in the colored layer 3 may bleed and contaminate the T-die of the extruder or the rolls during transport. Therefore, it is desirable to provide a skin layer 4 on both sides of the colored layer 3. If the skin layer 4 is thin, the pigment components contained in the colored layer 3 will bleed, so the thickness of the skin layer 4 is preferably 3 μm or more. It is sufficient that the skin layer 4 is formed on at least one side of the colored layer 3.

[0019] The thickness of the white sheet 2 is preferably in the range of 50 μm to 150 μm. If the thickness of the white sheet 2 is less than 50 μm, the ability to cover the unevenness of the base (unevenness) is poor, which is undesirable. On the other hand, if the thickness of the white sheet 2 exceeds 150 μm, problems such as whitening and cracking may occur during bending.

[0020] (inorganic pigments) The inorganic pigment contains, for example, titanium oxide, to impart hiding properties to the white sheet 2. The white sheet 2 serves to conceal the pattern on the substrate B. In order to obtain the hiding properties required from the standpoint of the design of the decorative sheet 1, a light transmittance of 40% or less is preferable. If the hiding properties are low, the pattern of the picture layer 5 and the substrate B will be mixed together, which is undesirable. By containing an inorganic pigment, a decorative sheet 1 with good hiding properties can be obtained. The total amount of inorganic pigment mixed (added amount) is preferably in the range of 5 to 70 parts by mass, based on 100 parts by mass of the resin material. If the mixed amount is less than 5 parts by mass, the hiding properties will be poor, and if the mixed amount is more than 70 parts by mass, the white sheet 2 will become embrittled, which is undesirable.

[0021] Figure 4 shows a graph of the spectral reflectance of a white sheet containing only titanium oxide. Although it has low light reflectance, it exhibits a reflectance of over 90% in the wavelength range from 450 nm to 700 nm. The white sheet 2 contains at least one type of blue pigment as an inorganic pigment in addition to the above-mentioned titanium oxide.

[0022] In ancient times, powdered lapis lazuli was used as a blue pigment to create a beautiful blue-purple color. This was called ultramarine because it was brought from far across the ocean. Nowadays, it can be synthesized and is known as ultramarine. Ultramarine can be made, for example, by mixing and baking the clay mineral kaolin with sulfur and activated carbon. The three-dimensional aluminosilicate lattice that makes up ultramarine contains three sulfur atoms that are bonded to form an ion. The blue color of the pigment is due to a radical anion with an unpaired electron, and its drawback is that it is vulnerable to acids. Ultramarine can also be made by mixing, for example, a sulfur-containing sodium silicate complex (Na 8-10 Al6Si6O 24 S 2-4 ) is available.

[0023] Prussian blue (Millory blue), also known as Prussian blue, is the first synthetic pigment developed in Germany. Cobalt blue is another bright blue pigment. Other inorganic pigments that can be used include cerulean blue and gosu (underglaze). Prussian blue (Millory blue) is a pigment with the formula Fe4[Fe(CN)6]3, for example. Cobalt blue is a pigment with the formula CoAl2O4 or CoOAl2O3, for example. Cerulean blue is a pigment with the formula CoO·nSnO2·mMgO (n = 1.5-3.5, m = 2-6). Gosu is made of, for example, quartz, halloysite, and lithiopholite.

[0024] Figure 5 shows a graph of the spectral reflectance of sheets containing cobalt blue and ultramarine alone as blue pigments. Although reflectance varies depending on the type of blue pigment, qualitatively, blue pigments exhibit spectral reflectance with a minimum value in the range of 500 nm to 650 nm. The amount of blue pigment added is preferably within the range of 1 to 2 parts by mass, based on 100 parts by mass of titanium oxide. If the amount of blue pigment added is less than 1 part by mass, it is difficult to obtain the effect of improving hiding power, and if the amount added is more than 2 parts by mass, the result will have a strong blue tinge and will not be recognized as white.

[0025] In addition to the titanium oxide and blue pigments, other known inorganic pigments may be mixed and used as the inorganic pigment contained in the white sheet 2. The inorganic pigments to be mixed are not particularly limited, but examples include natural inorganic pigments and synthetic inorganic pigments. Examples of natural inorganic pigments include earth pigments, calcined earth, and mineral pigments. Examples of synthetic inorganic pigments include oxide pigments, hydroxide pigments, sulfide pigments, silicate pigments, phosphate pigments, carbonate pigments, metal powder pigments, and carbon pigments. Organic pigments such as phthalocyanine and carbon black may also be used in combination.

[0026] The white sheet 2 contains titanium oxide and at least one kind of blue pigment in an appropriate blending ratio. By doing so, a spectral reflectance with a minimum value in the range of 500 nm to 650 nm can be obtained. The opacity is judged by the color difference when the base is white or black, but as shown in Figure 6, differences in spectral reflectance appear on the long wavelength side of 500 nm or more. Therefore, if the spectral reflectance on the long wavelength side is reduced in advance with a blue pigment, a sheet with good opacity can be obtained.

[0027] (resin) The resin to be mixed with the inorganic pigment is preferably an olefin resin from the viewpoint of environmental protection. Examples of the olefin resin include olefin homopolymers such as ethylene, propylene, and butene, block copolymers and random copolymers of ethylene and propylene, and copolymers of ethylene and propylene. Examples of suitable copolymers include copolymers of at least one of ethylene and propylene with at least one other olefin such as butene, pentene, and hexene, and copolymers of at least one of ethylene and propylene with at least one other monomer such as vinyl acetate and vinyl alcohol. Among these, polyethylene and polypropylene are preferred from the viewpoint of obtaining excellent scratch resistance and good bending processability.

[0028] [Polyethylene resin] Polyethylene may be a homopolymer of ethylene or a copolymer of ethylene and other comonomers copolymerizable with ethylene (e.g., propylene, 1-butene, 1-hexene, 1-octene, etc.). The copolymer may be a copolymer with an α-olefin such as vinyl acetate, vinyl alcohol, or the like. Examples of polyethylene resins include high-density polyethylene (HDPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), very low-density polyethylene (VLDPE), ultra-high molecular weight polyethylene (UHMWPE), cross-linked polyethylene (PEX), etc. These polyethylenes may be used alone or in combination of two or more.

[0029] [Polypropylene resin] It is preferable to use a highly crystalline polypropylene as the polypropylene resin, as described below. However, the highly crystalline homopolypropylene can be mixed with, for example, a random polypropylene resin having an ethylene content within a predetermined range or a known amorphous polypropylene resin. In this embodiment, it is preferable to use a polypropylene resin having high crystallinity as the polypropylene resin. In particular, it is preferable to use a highly crystalline homopolypropylene resin, which is a propylene homopolymer having an isotactic pentad fraction (mmmm fraction) of 95% or more, in an amount of 50% by mass to 100% by mass based on the mass of the total polypropylene resin.

[0030] The crystallization temperature of polypropylene resin is generally within the range of 100°C to 130°C, and when a nucleating agent is added, it is within the range of 110°C to 140°C. Furthermore, when a polypropylene resin with an isotactic pentad fraction (mmmm fraction) of less than 95% is used, the crystallinity is insufficient, and the tensile modulus may be lower than the preferred range even when the manufacturing process is controlled. Similarly, when a highly crystalline homopolypropylene resin is used in an amount of less than 50% by mass, the crystallinity is insufficient, and the tensile modulus may be lower than the preferred range even when the manufacturing process is controlled.

[0031] Here, the isotactic pentad fraction (mmmm fraction) is calculated from the numerical value (electromagnetic wave absorption rate) obtained by resonating a resin material at a predetermined resonance frequency using 13C-NMR (nuclear magnetic resonance) measurement using carbon (C) with a mass of 13. This value defines the atomic arrangement, electronic structure, and molecular microstructure of the resin material. The pentad fraction of a crystalline polypropylene resin is the ratio of five propylene units arranged in a row as determined by 13C-NMR and is used as a measure of crystallinity or stereoregularity. The pentad fraction is one of the important factors that primarily determine the scratch resistance of a surface; generally, a higher pentad fraction indicates a higher degree of crystallinity.

[0032] When a substrate with an inactive surface formed from a resin such as an olefin-based resin is used for the decorative sheet 1, it is desirable to subject the front and back of the white sheet 2 to, for example, corona treatment, plasma treatment, ozone treatment, electron beam treatment, ultraviolet treatment, dichromate treatment, etc. Furthermore, additives such as fatty acid metal salts may be added to resins such as polypropylene resins in order to improve dispersibility and extrudability.

[0033] <Picture layer 5> A pattern layer 5 can be provided on the surface of the white sheet 2 to add a pattern to the decorative sheet 1. Examples of patterns that can be used include wood grain, stone grain, sand grain, tiled, brickwork, fabric grain, leather-striped patterns, and geometric shapes. Furthermore, a base solid ink layer (not shown) may be provided between the white sheet 2 and the picture layer 5 depending on the level of the desired design. The base solid ink layer is provided, for example, so as to cover the entire surface of the white sheet 2. The base solid ink layer may also be multi-layered, consisting of two or more layers, as needed for hiding properties, etc. Furthermore, the picture layer 5 may be formed by laminating the same number of plates as necessary to express the desired design. In this way, the picture layer 5 and the base solid ink layer can be combined in various ways depending on the desired design, i.e., the design to be expressed, but there are no particular limitations.

[0034] The materials constituting the base solid ink layer and the design layer 5 are not particularly limited. Examples of materials that can be used for the base solid ink layer and the design layer 5 include printing inks and coating agents prepared by dissolving or dispersing a matrix and a colorant such as a dye or pigment in a solvent. Examples of matrices that can be used include various synthetic resins, such as oil-based nitrocellulose resins, two-component urethane resins, acrylic resins, styrene resins, polyester resins, urethane resins, polyvinyl resins, alkyd resins, epoxy resins, melamine resins, fluorine-containing resins, silicone resins, and rubber resins, as well as mixtures and copolymers thereof. Examples of colorants that can be used include inorganic pigments such as carbon black, titanium white, zinc white, red iron oxide, yellow lead, iron blue, and cadmium red; organic pigments such as azo pigments, lake pigments, anthraquinone pigments, phthalocyanine pigments, isoindolinone pigments, and dioxazine pigments; and mixtures thereof. As the solvent, for example, toluene, xylene, ethyl acetate, butyl acetate, methyl alcohol, ethyl alcohol, isopropyl alcohol, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, water, or a mixture thereof can be used.

[0035] In addition, functional additives such as extender pigments, plasticizers, dispersants, surfactants, tackifiers, adhesion aids, drying agents, curing agents, curing accelerators, and curing retarders may be added to the base solid ink layer and the pattern layer 5 to impart various functions. Here, the base solid ink layer and the design layer 5 can be formed by various printing methods, such as gravure printing, offset printing, screen printing, electrostatic printing, and inkjet printing. Furthermore, since the base solid ink layer covers the entire surface of the white sheet 2, it can also be formed by various coating methods, such as roll coating, knife coating, microgravure coating, and die coating. These printing and coating methods may be selected separately depending on the layer to be formed, but it is more efficient to select the same method and process all at once. The thickness of the design layer 5 is preferably within the range of 3 μm to 20 μm. When the thickness of the design layer 5 is within this range, the printing can be made clear, the printing workability when producing the decorative sheet 1 is improved, and production costs can be reduced.

[0036] <Transparent resin layer 6> The resin material used as the main component of the transparent resin layer 6 is preferably made of an olefin-based resin, and in addition to polypropylene, polyethylene, polybutene, etc., α-olefins (for example, propylene, 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, Examples of such copolymers include homopolymers or copolymers of 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, ethylene-butyl acrylate copolymer, etc. Furthermore, when it is intended to improve the surface strength of the decorative sheet 1, it is preferable to use highly crystalline polypropylene. Here, in this embodiment, the term "main component" refers to 90% by mass or more of the target material unless otherwise specified.

[0037] When a transparent resin layer 6 is provided, the thickness of the transparent resin layer 6 is preferably within a range of 50 μm to 100 μm. If the thickness of the transparent resin layer 6 is less than 50 μm, the effect of improving the scratch resistance of the surface of the transparent resin layer 6 is low, and there is little point in providing the transparent resin layer 6. Furthermore, if the thickness of the transparent resin layer 6 exceeds 100 μm, the decorative sheet 1 may have too high rigidity, which may cause defects such as whitening and cracking during bending. However, when the top coat layer 7 is provided on the transparent resin layer 6, the thickness of the transparent resin layer 6 may be less than 50 μm.

[0038] The resin composition constituting the transparent resin layer 6 may contain various functional additives, such as a heat stabilizer, a light stabilizer, an antiblocking agent, a catalyst scavenger, a colorant, a light scattering agent, and a gloss adjuster, as needed. These various functional additives can be appropriately selected from well-known additives.

[0039] The adhesive used to bond the design layer 5 and the transparent resin layer 6 can be any material, and lamination methods such as thermal lamination, extrusion lamination, and dry lamination are available. The adhesive can be selected from acrylic, polyester, polyurethane, and other materials. Due to their cohesive strength, two-component curing urethane materials that utilize the reaction between isocyanate and polyol are typically preferred. While there are no particular restrictions on the lamination method, methods that apply heat and pressure, extrusion lamination, and dry lamination are common. To apply an embossed pattern 6a, a sheet may be laminated using various methods and then embossed by heat and pressure, or a cooling roll may be provided with a concave-convex pattern and embossed simultaneously with extrusion lamination.

[0040] Alternatively, a method may be used in which the pattern layer 5, which has been embossed simultaneously with extrusion, and the transparent resin layer 6 are bonded together by heat or dry lamination. Furthermore, when further lamination strength is required in the extrusion lamination method, an adhesive resin layer 6b may be provided between the transparent resin layer 6 and the adhesive. When the adhesive resin layer 6b is provided, the transparent resin layer 6 and the adhesive resin layer 6b are laminated by co-extrusion. The adhesive resin layer 6b may be formed from, for example, an acid-modified resin such as polypropylene, polyethylene, or acrylic resin. The thickness of the adhesive resin layer 6b is preferably 2 μm or more to improve adhesive strength.

[0041] <Top coat layer 7> If further improvement in scratch resistance or adjustment of gloss is required, a top coat layer 7 can be provided on the surface of the transparent resin layer 6. The resin material as the main component of the top coat layer 7 can be appropriately selected from polyurethane-based, acrylic silicone-based, fluorine-based, epoxy-based, vinyl-based, polyester-based, melamine-based, aminoalkyd-based, urea-based, and other resin materials. The form of the resin material is not particularly limited, and may be aqueous, emulsion-based, solvent-based, or the like. The curing method may also be a one-component type. The method can be selected appropriately from a type, a two-component type, an ultraviolet curing method, etc.

[0042] As the resin material used as the main component of the top coat layer 7, a urethane-based resin using isocyanate is preferred from the viewpoints of workability, cost, the cohesive strength of the resin itself, etc. The isocyanate can 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), etc., but in consideration of weather resistance, curing agents based on hexamethylene diisocyanate (HMDI) or isophorone diisocyanate (IPDI), which have a linear molecular structure, are preferred. In addition, when improving the surface hardness, it is preferable to use a resin that is cured by active energy rays such as ultraviolet rays or electron beams. These resins can be used in combination with each other, and for example, by using a hybrid type of thermosetting and photocuring resins, it is possible to improve the surface hardness, suppress shrinkage on curing, and improve adhesion.

[0043] A gloss adjuster can be added to the top coat layer 7 to adjust the gloss. Commercially available gloss adjusters may be used. Examples of gloss adjusters include fine particles made of inorganic materials such as silica, glass, alumina, calcium carbonate, and barium sulfate. Alternatively, fine particles made of organic materials such as acrylic may also be used. However, when high transparency is required, it is desirable to use highly transparent fine particles such as silica, glass, and acrylic. In particular, among fine particles such as silica and glass, gloss adjusters with low bulk density, which are formed by secondary aggregation of fine primary particles rather than solid spherical particles, have a high matting effect relative to the amount added. Therefore, by using such gloss adjusters, the amount of gloss adjuster added can be reduced.

[0044] Furthermore, functional additives such as antibacterial agents and antifungal agents may be added to impart various functions to the top coat layer 7. Furthermore, ultraviolet absorbers and light stabilizers may be added as needed. Examples of ultraviolet absorbers that can be used include benzotriazoles, benzoates, benzophenones, triazines, and cyanoacrylates. Furthermore, hindered amines can be used as light stabilizers. The thickness of the top coat layer 7 is preferably in the range of 3 μm to 15 μm. If the thickness of the top coat layer 7 is less than 3 μm, the effect of improving scratch resistance is low, and there is little point in providing the top coat layer 7. If the thickness of the top coat layer 7 exceeds 15 μm, cracks and breaks may occur during bending, causing problems in terms of design and deterioration of weather resistance.

[0045] <Primer layer 8> The material for primer layer 8 can basically be the same as that for pattern layer 5. Considering that it is applied to the back surface of decorative sheet 1 and wound up in web form, inorganic fillers such as silica, alumina, magnesia, titanium oxide, and barium sulfate may be added to primer layer 8 to avoid blocking and improve adhesion with the adhesive. The coating thickness of primer layer 8 is preferably within the range of 0.1 μm to 3.0 μm, as its purpose is to ensure adhesion with substrate B. Note that primer layer 8 is necessary when the surface of white sheet 2 is inactive, such as an olefin-based material, but is not particularly necessary when the surface is active.

[0046] "Manufacturing method" A manufacturing example of the decorative sheet 1 will now be described. The polypropylene resin used in the colored layer 3 is preferably a mixture of a random polypropylene resin having an ethylene content within a predetermined range or a known amorphous polypropylene resin, in order to facilitate dispersion of the inorganic pigment described below. The polypropylene resin used in the skin layer 4 is preferably a homopolypropylene resin with high crystallinity. The polypropylene resins may be used alone or in combination. The resin material for the white sheet is heated and melted, and formed into a sheet having a thickness in the range of 50 μm to 150 μm by extrusion molding or the like, to form the white sheet 2. Furthermore, if necessary, a design layer 5 is formed on the upper surface of the white sheet 2 by printing, and at least one of a transparent resin layer 6 and a top coat layer 7 is formed thereon.

[0047] <Other effects> (1) The white sheet 2 of this embodiment has a reflection chromaticity measured with a D65 light source in the Lab color system, where L* is in the range of 90 to 100, a* is in the range of -1.5 to +1.5, and b* is in the range of -1.5 to 2.0, and the spectral reflectance is 500 nm to 65 It has a minimum value within the range of 0 nm or less. With this configuration, it is not necessary to increase the amount of inorganic pigment added compared to conventional technology, so it is possible to provide a white sheet 2 that is excellent in flexibility and hiding power, and a decorative sheet 1 that includes this white sheet 2.

[0048] (2) The white sheet 2 of this embodiment has a colored layer 3 containing an inorganic pigment and a resin, and the inorganic pigment may contain titanium oxide and at least one type of blue pigment. With this configuration, it is possible to reliably provide a white sheet 2 with excellent whiteness, and a decorative sheet 1 including this white sheet 2.

[0049] (3) The white sheet 2 of this embodiment contains ultramarine, Prussian blue, and other blue pigments. At least one of the following colors may be selected: Lory Blue, Cobalt Blue, Cerulean Blue, and Gosu. The compound may contain one of both. With this configuration, it is possible to reliably provide a white sheet 2 with even more excellent whiteness, and a decorative sheet 1 including this white sheet 2.

[0050] (4) In the white sheet 2 of the present embodiment, the content of the blue pigment may be in the range of 1 part by mass to 2 parts by mass, based on 100 parts by mass of titanium oxide. With this configuration, it is possible to reliably provide a white sheet 2 with even more excellent whiteness, and a decorative sheet 1 including this white sheet 2.

[0051] (5) In the white sheet 2 of this embodiment, the resin contained in the colored layer 3 may be polypropylene. With this configuration, it is not necessary to increase the amount of inorganic pigment added compared to conventional technology, so it is possible to provide a white sheet 2 that is excellent in flexibility and hiding power, and a decorative sheet 1 that includes this white sheet 2.

[0052] (6) The white sheet 2 of this embodiment further has a skin layer 4 formed on at least one surface of the colored layer 3, and the skin layer 4 may contain a polypropylene resin. With this configuration, bleeding of the inorganic pigment can be reduced.

[0053] (7) The white sheet 2 of this embodiment may have a thickness in the range of 50 μm to 150 μm. With this configuration, the white sheet 2 can be given both unevenness and bendability.

[0054] [Example] Specific examples of the decorative sheet 1 of this embodiment will be described below.

[0055] Example 1 The raw materials for the colored layer 3 were 59.6 parts by mass of polypropylene resin, to which 40 parts by mass of titanium oxide pigment and 0.4 parts by mass of cobalt blue pigment were added and mixed. The raw materials for the skin layer 4 were 100 parts by mass of polypropylene resin, to which 0.5 parts by mass of a hindered amine light stabilizer (BASF's "Chimassorb 944") and 0.5 parts by mass of a benzotriazole UV absorber (BASF's "Tinuvin 328") were added and mixed. The mixture for the colored layer 3 and the mixture for the skin layer 4 were co-extruded using a melt extruder in the order of skin layer 4, colored layer 3, and skin layer 4 to a thickness of 10 μm:120 μm:10 μm, to form a white sheet 2.

[0056] Example 2 A white sheet 2 was formed by co-extrusion using a melt extruder in the same manner as in Example 1, except that the cobalt blue pigment added to the colored layer 3 was added so as to be 0.8 parts by mass. Example 3 Regarding the blue pigment added to the colored layer 3, a white sheet 2 was produced by co-extrusion using a melt extruder in the same manner as in Example 1, except that 0.4 parts by mass of ultramarine blue pigment was added.

[0057] Example 4 A white sheet 2 was formed by co-extrusion using a melt extruder in the same manner as in Example 1, except that the cobalt blue pigment added to the colored layer 3 was added in an amount of 0.2 parts by mass. Example 5 Using the same mixture of colored layer 3 and skin layer 4 as in Example 1, a white sheet 2 was produced by co-extrusion using a melt extruder in the order of skin layer 4, colored layer 3, and skin layer 4 to a thickness of 3 μm:44 μm:3 μm.

[0058] Example 6 Using the same mixture of colored layer 3 and skin layer 4 as in Example 1, a white sheet 2 was produced by co-extrusion using a melt extruder in the order of skin layer 4, colored layer 3, and skin layer 4 to a thickness of 3 μm:94 μm:3 μm. Example 7 Using the same mixture of colored layer 3 and skin layer 4 as in Example 1, a white sheet 2 was produced by co-extrusion using a melt extruder in the order of skin layer 4, colored layer 3, and skin layer 4 to a thickness of 3 μm:34 μm:3 μm.

[0059] Example 8 Using the same mixture of colored layer 3 and mixture of skin layer 4 as in Example 1, a white sheet 2 was produced by co-extrusion using a melt extruder in the order of skin layer 4, colored layer 3, and skin layer 4 to a thickness of 10 μm: 160 μm: 10 μm. Example 9 A design layer 5 was formed by printing a design on the surface of a 140 μm thick white sheet 2 produced in the same manner as in Example 1. The design layer 5 was formed using a two-component urethane ink (V180; manufactured by Toyo Ink Co., Ltd.) to which 0.5 parts by mass of a hindered amine light stabilizer (Chimasorb 944; manufactured by BASF) was added relative to the binder resin content of the ink. A primer layer 8 was also formed on the back surface of the white sheet 2. The primer layer 8 was formed by printing the same two-component urethane ink as used for the design layer 5. Furthermore, a two-component curing urethane top coat ("W184" manufactured by DIC Graphics Corporation) was applied in an amount of 3 g / m. 2 Apply with A backcoat layer 7 was formed. In this way, a decorative sheet 1 having a thickness of 145 μm was obtained, as shown in FIG.

[0060] Example 10 A top coat layer 7 was formed in the same manner as in Example 9 on a white sheet 2 having a thickness of 140 μm, which was produced in the same manner as in Example 2, to obtain a decorative sheet 1 having a thickness of 145 μm. Example 11 A top coat layer 7 was formed in the same manner as in Example 9 on a white sheet 2 having a thickness of 140 μm, which was produced in the same manner as in Example 3, to obtain a decorative sheet 1 having a thickness of 145 μm.

[0061] Example 12 A top coat layer 7 was formed in the same manner as in Example 9 on a white sheet 2 having a thickness of 140 μm, which was produced in the same manner as in Example 4, to obtain a decorative sheet 1 having a thickness of 145 μm. Example 13 A top coat layer 7 was formed in the same manner as in Example 9 on a white sheet 2 having a thickness of 50 μm, which was produced in the same manner as in Example 5, to obtain a decorative sheet 1 having a thickness of 55 μm.

[0062] Example 14 A top coat layer 7 was formed in the same manner as in Example 9 on a white sheet 2 having a thickness of 100 μm, which was produced in the same manner as in Example 6, to obtain a decorative sheet 1 having a thickness of 105 μm. Example 15 A top coat layer 7 was formed in the same manner as in Example 9 on a white sheet 2 having a thickness of 40 μm, which was produced in the same manner as in Example 7, to obtain a decorative sheet 1 having a thickness of 45 μm.

[0063] Example 16 A top coat layer 7 was formed in the same manner as in Example 9 on a white sheet 2 having a thickness of 180 μm, which was produced in the same manner as in Example 8, to obtain a decorative sheet 1 having a thickness of 185 μm. Example 17 A white sheet 2 was formed by co-extrusion using a melt extruder in the same manner as in Example 1, except that the cobalt blue pigment added to the colored layer 3 was added so as to be 1.0 part by mass.

[0064] Example 18 A top coat layer 7 was formed in the same manner as in Example 9 on a white sheet 2 having a thickness of 140 μm, which was produced in the same manner as in Example 17, to obtain a decorative sheet 1. Example 19 A white sheet 2 was produced by co-extrusion using a melt extruder in the same manner as in Example 1, except that the raw material for the colored layer 3 was changed from polypropylene resin to polyethylene resin.

[0065] Example 20 A white sheet 2 was produced by co-extrusion using a melt extruder in the same manner as in Example 1, except that the raw materials for the above-mentioned colored layer 3 were 69.7 parts by mass of polypropylene resin, 30 parts by mass of titanium oxide pigment, and 0.3 parts by mass of cobalt blue pigment. Example 21 A white sheet 2 was produced by co-extrusion using a melt extruder in the same manner as in Example 1, except that the skin layer 4 was not formed. Example 22 A white sheet 2 was produced by co-extrusion using a melt extruder in the same manner as in Example 1, except that the raw materials for the above-mentioned colored layer 3 were 79.8 parts by mass of polypropylene resin, 20 parts by mass of titanium oxide pigment, and 0.2 parts by mass of cobalt blue pigment.

[0066] (Comparative Example 1) White sheet 2 was produced by co-extrusion using a melt extruder in the same manner as in Example 5, except that the above-mentioned blue pigment was not added. (Comparative Example 2) A design layer 5 was formed by printing a design on the surface of a 50 μm-thick white sheet 2 produced in the same manner as in Comparative Example 1. The design layer 5 was formed using a two-component urethane ink (V180; manufactured by Toyo Ink Co., Ltd.) to which 0.5 parts by mass of a hindered amine light stabilizer (Chimasorb 944; manufactured by BASF) had been added relative to the binder resin content of the ink. A primer layer 8 was also formed on the back surface of the white sheet 2. The primer layer 8 was formed by printing the same two-component urethane ink as used for the design layer 5. Furthermore, a two-component curing urethane top coat ("W184" manufactured by DIC Graphics Corporation) was applied at a coating amount of 3 g / m 2 to form a top coat layer 7. In this way, a decorative sheet 1 having a thickness of 55 μm was obtained, as shown in FIG. (Comparative Example 3) A white sheet 2 was formed by co-extrusion using a melt extruder in the same manner as in Example 1, except that the cobalt blue pigment added to the colored layer 3 was added in an amount of 1.2 parts by mass.

[0067] [evaluation] For the above Examples 1 to 22 and Comparative Examples 1 to 3, the spectral reflectance, hue, hiding power and bending processability were evaluated.

[0068] <Spectral reflectance> The spectral reflectance was measured using a Konica Minolta fluorescent spectrodensitometer (FD-7) from 400 to 700 nm. Since white sheets with low opacity are affected by the color of the base, all sheets were measured using opacity test paper (byk Measurements were taken on a white background (o-chart high brightness 2A). 7 shows the spectral reflectances of Examples 1 to 4 and Comparative Example 1. Since blue pigments were added in Examples 1 to 4, there was a minimum value between 500 nm and 650 nm, but since no blue pigment was added in Comparative Example 1, the spectral reflectance decreased monotonically.

[0069] <Hue> The hue was evaluated using an X-rite spectrophotometer (530JP / LP) under a D65 light source, and the chromaticity was measured on a white background using BYK-GARDNER's opacity test paper (byko-chart high brightness 2A).

[0070] <Concealment> The hiding power was evaluated using an X-rite spectrophotometer (530JP / LP) and judged by the color difference measured on a BYK-GARDNER hiding test paper (byko-chart high brightness 2A) with a white background and a black background. The smaller the color difference, the better the hiding power, with a rating of 0.5 or less being "◎", a rating of more than 0.5 and less than 0.7 being "○", a rating of more than 0.7 and less than 1.0 being "△", and a rating of more than 1.0 being "×". Note that a rating of "△" or higher indicates no practical problems.

[0071] <Bending process suitability> In the bending processability test, first, each of the sheets of Examples 1 to 22 and Comparative Examples 1 to 3 obtained by the above method was attached to one side of a medium-density fiberboard (MDF) serving as substrate B using a urethane adhesive. A V-shaped groove was made on the other side of substrate B up to the boundary where substrate B and decorative sheet 1 were attached, so as not to scratch the decorative sheet 1 on the opposite side. Next, substrate B was bent 90 degrees along the V-shaped groove so that the surface of decorative sheet 1 formed a mountain fold, and the bent portion of the surface of decorative sheet 1 was observed using an optical microscope to determine whether whitening or cracks had occurred, and the state of bending processability was evaluated. If no whitening or cracks are observed, the mark is "◎", and if only a small amount of whitening is observed in some areas, the mark is "○". When whitening was observed on a part of the surface, it was rated as "△", and when whitening was observed on the entire surface or cracks were observed on a part of the surface, it was rated as "×". Note that evaluations of "△" or higher are acceptable for practical use.

[0072] The evaluation results are shown in Table 1. [Table 1]

[0073] As can be seen from Table 1, the decorative sheets of Examples 1 to 3 and Examples 9 to 11 had very good hiding power and presented no problems with bending. Furthermore, the decorative sheets of Examples 9 to 11 were each formed by laminating a pattern layer 5 and a top coat layer 7 onto the decorative sheets of Examples 1 to 3, imparting a sophisticated design while achieving both hiding power and bending processability. The decorative sheets of Examples 4 and 12 were produced with a low blending ratio of blue pigment, 0.2, so the hiding power was slightly poor, but was at a level that would not pose a problem in practical use. The decorative sheets of Examples 5 and 13 were each produced so that the colored layer had a thin thickness of 44 μm, and therefore the hiding power was slightly poor, but at a level that was not problematic in practical use.

[0074] The decorative sheets of Examples 6 and 14 were each produced so that the colored layer had a thin thickness of 94 μm, and therefore the hiding power was slightly poor, but at a level that would not pose a problem in practical use. The decorative sheets of Examples 7 and 15 were each produced so that the colored layer had a fairly thin thickness of 34 μm, and therefore the hiding power was very poor, but at a level that would not pose a problem in practical use. The decorative sheets of Examples 8 and 16 were each produced so that the colored layer was quite thick at 160 μm, so the hiding power was very good but the bending processability was poor, although this was at a level that did not pose any practical problems.

[0075] The decorative sheets of Examples 17 and 18 were produced with a formulation in which the amount of blue pigment added was as high as 1.0, so the hue leaned towards blue (b* was on the negative side), but this was at a level that would not cause any problems in practical use. The decorative sheet of Example 19 used polyethylene resin instead of polypropylene resin, but the finish was satisfactory. The decorative sheet of Example 20 had a titanium oxide concentration of 30 parts by mass, which was lower than that of Example 1, so the hiding power was slightly worse, but this was at a level that did not pose any practical problems. The decorative sheet of Example 21 did not have a skin layer, and therefore the hiding power was slightly worse, but it was at a level that did not pose any practical problems. The decorative sheet of Example 22 had a titanium oxide concentration of 20 parts by mass, which was considerably lower than that of Example 1, so the hiding power was slightly worse, but this was at a level that did not pose any practical problems.

[0076] The decorative sheets of Comparative Examples 1 and 2 did not contain a blue pigment and therefore did not have a minimum value in the spectral reflectance between 500 nm and 650 nm, resulting in decorative sheets with poor hiding power. The decorative sheet of Comparative Example 3 was produced with a formulation in which the amount of blue pigment added was extremely high at 1.2, so the hue was blue (b* value was -1.75), and it was at a level that could not be called a white sheet. [Industrial Applicability]

[0077] As explained above, the present invention is a technology particularly suitable for decorative sheets used as building materials for the exterior and interior of buildings, surfaces of building fixtures, surface materials for home appliances, and the like. [Explanation of symbols]

[0078] 1...decorative sheet, 2...white sheet, 3...colored layer, 4...skin layer, 5...pattern layer, 6...transparent resin layer, 6a...embossed pattern, 6b...adhesive resin layer, 7...top coat layer, 8...primer layer, B...substrate

Claims

1. The reflected chromaticity measured with a D65 light source is such that, in the Lab color system, L* is in the range of 90 or more and 100 or less, a* is in the range of -1.5 or more and +1.5 or less, and b* is in the range of -1.5 or more and 2.0 or less, A white sheet having a spectral reflectance with a minimum value in the range of 500 nm or more and 650 nm or less, the white sheet has a colored layer containing an inorganic pigment and a resin, the resin contained in the colored layer is polypropylene, the polypropylene contained in the colored layer contains an amorphous polypropylene resin, The inorganic pigment contains titanium oxide and at least one blue pigment, A white sheet characterized in that the content of the titanium oxide is in the range of 20% by mass or more and 40% by mass or less, based on the mass of the entire white sheet.

2. 2. The white sheet according to claim 1, wherein the blue pigment contains at least one selected from ultramarine, Prussian blue (milory blue), cobalt blue, cerulean blue, and gosu.

3. 2. The white sheet according to claim 1, wherein the blue pigment contains at least one selected from the group consisting of cerulean blue and gosu.

4. 4. The white sheet according to claim 1, wherein the content of the blue pigment is in the range of 1 part by mass or more and 2 parts by mass or less, based on 100 parts by mass of titanium oxide.

5. A white sheet described in any one of claims 1 to 3, characterized in that the content of the blue pigment is in the range of 0.5 parts by mass or more and 1.0 parts by mass or less, or in the range of 2.0 parts by mass or more and 2.5 parts by mass or less, when titanium oxide is taken as 100 parts by mass.

6. The content of the titanium oxide is in the range of 20% by mass or more and 40% by mass or less relative to the mass of the entire white sheet, 4. The white sheet according to claim 1, wherein the content of the blue pigment is in the range of 0.2% by mass or more and 1.0% by mass or less with respect to the total mass of the white sheet.

7. A white sheet described in any one of claims 1 to 3, characterized in that the content of the inorganic pigment is in the range of 20.2 mass% or more and 41.0 mass% or less relative to the mass of the entire white sheet.

8. A white sheet described in any one of claims 1 to 7, characterized in that the inorganic pigment does not contain cobalt borate pigment.

9. the white sheet further has a skin layer formed on at least one surface of the colored layer, 9. The white sheet according to claim 1, wherein the skin layer contains a polypropylene resin.

10. 10. The white sheet according to claim 1, wherein the thickness of the white sheet is in the range of 50 μm to 150 μm.

11. 11. The white sheet according to claim 1, wherein the colored layer does not contain zinc stearate.

12. A decorative sheet comprising at least the white sheet according to any one of claims 1 to 11 and a top coat layer.

13. the top coat layer contains a hindered amine-based light stabilizer and a benzotriazole-based ultraviolet absorber, 13. The decorative sheet according to claim 12, wherein the content of said hindered amine-based light stabilizer is the same as the content of said benzotriazole-based ultraviolet absorber.

14. A method for producing a decorative sheet according to claim 12 or 13, A method for producing a decorative sheet, comprising mixing an inorganic pigment with a resin to produce a white sheet so that the spectral reflectance has a minimum value within the range of 500 nm to 650 nm.

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