JP7484122B2 - White sheet, decorative sheet and manufacturing method thereof - Google Patents

Description

The present invention relates to a white sheet, a decorative sheet, and a method for manufacturing the same.

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 of concern in terms of environmental protection. One example of technology related to decorative sheets using olefin resins is the technology described in Patent Document 1. These decorative sheets do not use polyvinyl chloride resin, and therefore the generation of toxic gases and the like during incineration is suppressed. 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.

By the way, a decorative sheet is attached to the surface of a substrate such as a wooden substrate, a metal substrate, or a non-flammable substrate to become a decorative board, and the decorative sheet imparts a design to the decorative board according to the purpose. Therefore, the decorative sheet needs to cover the surface of the substrate completely as necessary. In this case, it is necessary to use a decorative sheet that is at least colored with a pigment and has concealing properties. The simplest configuration of a decorative sheet is a configuration consisting of only a base layer consisting of a single colored sheet (single layer). In the case of such a decorative sheet consisting of only a base layer, the design that can be imparted is usually limited to a single color without a pattern, but it is possible to impart a sense of brilliance by adding a lustrous material such as aluminum flakes or pearl pigments as a pigment, so that a necessary and sufficient design expression is possible. In addition, if you want to impart a more sophisticated design, it is also effective to decorate the surface of the base layer by printing, etc.

Among decorative sheets, white sheets are used for door frames, baseboards, various storage compartments, etc. The surface of the base material is easily visible through the white sheet, and 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 problematic. Patent Document 2 proposes a decorative sheet that contains an inorganic pigment in a vesiculated state and 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 the sheet being prone to breaking has not been resolved.

Patent No. 3271022 JP 2016-155233 A

The present invention has been made with the above points in mind, and aims to provide a white sheet with good hiding power, a decorative sheet with a white sheet as a base layer, or a method for manufacturing such a decorative sheet, without increasing the amount of inorganic pigment added compared to the prior art.

The inventors conducted various studies and experiments and discovered that, for example, by adding titanium oxide and at least one type of blue pigment to a resin, it is possible to provide a white sheet, decorative sheet, and method for producing the same that have excellent concealing properties and a minimum value of spectral reflectance in the range of 500 nm to 650 nm.

In order to achieve this objective, the white sheet according to one embodiment of the present invention is a white sheet whose reflected chromaticity measured with a D65 light source is in the range of L* 90 to 100 in the Lab color system, a* -1.5 to +1.5 in the range, and b* -1.5 to 2.0 in the range, and whose spectral reflectance has a minimum value in the range of 500 nm to 650 nm.

According to one aspect of the present invention, it is possible to provide a white sheet, a decorative sheet, and a manufacturing method thereof that are excellent in flexibility such as bending workability and excellent in hiding power because there is no need to increase the amount of inorganic pigment added compared to the conventional technology.

1 is a cross-sectional view showing a structure of a decorative sheet according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing the structure of another decorative sheet according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing the structure of another decorative sheet according to an embodiment of the present invention. 1 is a graph showing the spectral reflectance of a white sheet containing only titanium oxide. 1 is a graph showing the spectral reflectance of sheets containing cobalt blue and ultramarine blue as blue pigments. 1 is a graph showing the spectral reflectance measured for the same white sheet with a white background and with a black background. 1 is a graph showing the spectral reflectance of Examples 1 to 4 and Comparative Example 1.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
Here, 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.

"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. The white sheet 2 of the present 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, as shown in FIG. 2. 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 the crystallinity. By improving the crystallinity, the scratch resistance is improved. In this embodiment, the nucleating agent may be contained in the form of a nucleating agent vesicle that is encapsulated in an outer membrane and vesiculated.

If necessary, a pattern layer 5 may be formed (laminated) on one side of the white sheet 2 to improve the design. The decorative sheet 1 may also have at least one of a transparent resin layer 6 and a topcoat 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 pattern layer 5, a transparent resin layer 6, and a topcoat layer 7 are laminated in this order on one side of the white sheet 2. Either the transparent resin layer 6 or the topcoat layer 7 may be omitted. The pattern layer 5 may also be omitted.

Here, depending on the design requirements, at least one of the transparent resin layer 6 and the topcoat layer 7 may be given an embossed uneven pattern (embossed pattern 6a). Ink can be embedded in the embossed pattern 6a to further improve the design. If there is a problem 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, it is formed by co-extrusion of the transparent resin layer 6 and the adhesive resin layer 6b. The adhesive resin layer 6b may be formed of, for example, polypropylene, polyethylene, acrylic resin, or the like, which has been acid-modified. The thickness of the adhesive resin layer 6b is preferably 2 μm or more for the purpose of improving the adhesive strength. Furthermore, depending on the requirements for scratch resistance, at least one of the transparent resin layer 6 and the topcoat layer 7 may be laminated in multiple layers, and other known layers may be arranged.

In Figures 1, 2 and 3, the symbol B represents a substrate. Substrate B is a substrate to which 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 decorative sheet 1 and substrate B as appropriate.

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 to 2200 MPa. 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 if a nucleating agent (e.g., nucleating agent vesicles) is used, problems such as whitening and cracking may occur during bending.

Next, we will explain each layer that makes up the decorative sheet 1.

<White sheet 2>
The white sheet 2 is formed so that the reflected chromaticity measured with a D65 light source is in the Lab color system, 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 has a minimum value in the range of 500 nm to 650 nm, and has a colored layer 3 formed by mixing an inorganic pigment with a resin in an appropriate ratio, for example. If the colored layer 3 is the outermost layer, the pigment component contained in the colored layer 3 may bleed and contaminate the T-die of the extruder and the roll during transportation, so 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 component 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.

The thickness of the white sheet 2 is preferably within the range of 50 μm to 150 μm. If the thickness of the white sheet 2 is less than 50 μm, the performance of covering the unevenness of the base (unevenness) is poor, which is not preferable. 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.

(Inorganic pigments)
The inorganic pigment contains, for example, titanium oxide in order to impart hiding properties to the white sheet 2. The white sheet 2 plays a role in hiding the pattern of the substrate B. In order to obtain the hiding properties required from the viewpoint of the design of the decorative sheet 1, the light transmittance is preferably 40% or less. If the hiding properties are low, the pattern of the picture layer 5 and the substrate B will be mixed, which is not preferable. By containing the inorganic pigment, a decorative sheet 1 with good hiding properties can be obtained. The total mixed amount (addition amount) of the inorganic pigment is preferably within the range of 5 parts by mass 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 not preferable.

A graph of the spectral reflectance of a white sheet containing only titanium oxide is shown in Figure 4. The spectral reflectance is low on the short wavelength side, but the reflectance is 90% or more 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.

In ancient times, powdered lapis lazuli was used as a beautiful blue-purple pigment. It was called ultramarine because it was brought from far across the sea. It can now be synthesized and is known as ultramarine. Ultramarine can be made, for example, by mixing the clay mineral kaolin with sulfur and activated carbon and baking it. The three-dimensional aluminosilicate lattice that makes up ultramarine contains three sulfur atoms that are bonded together to form ions. The blue color of the pigment is due to a radical anion with an unpaired electron, and its weakness is that it is vulnerable to acids. For example, ultramarine is a complex of sodium silicate containing sulfur (Na _8-10 Al ₆ Si ₆ O ₂₄ S _2-4 ).

Prussian blue (Millory blue) is the first synthetic pigment born in Germany, also known as Prussian blue, and there is also cobalt blue as a bright blue pigment. Other inorganic pigments such as cerulean blue and gosu can also be used. Prussian blue (Millory blue) is, for example, a pigment represented by the composition formula Fe ₄ [Fe(CN) ₆ ] _3. Cobalt blue is, for example, a pigment represented by the composition formula CoAl ₂ O ₄ or CoOAl ₂ O _3. Cerulean blue is, for example, a pigment represented by the composition formula CoO.nSnO _2.mMgO (n=1.5-3.5, m=2-6). Gosu is, for example, quartz, halloysite, and lithiophorite.

5 shows a graph of the spectral reflectance of sheets containing cobalt blue and ultramarine alone as blue pigments. Although the reflectance differs depending on the type of blue pigment, qualitatively, blue pigments exhibit a spectral reflectance with a minimum value in the range of 500 nm to 650 nm.
The amount of blue pigment added is desirably within the range of 1 part by mass 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 color becomes too bluish and cannot be recognized as white.

As the inorganic pigment contained in the white sheet 2, in addition to the titanium oxide and blue pigment, known inorganic pigments can be mixed and used. The inorganic pigments to be mixed are not particularly limited, but examples thereof include natural inorganic pigments and synthetic inorganic pigments. Examples of natural inorganic pigments include earth pigments, baked 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.

The white sheet 2 contains titanium oxide and at least one type of blue pigment in an appropriate mixing ratio, which gives it a spectral reflectance with a minimum value in the range of 500 nm to 650 nm. The opacity is judged by the color difference when the base is white or black, but as shown in Figure 6, the spectral reflectance shows differences 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.

(resin)
The resin to be mixed with the inorganic pigment is preferably an olefin-based resin from the viewpoint of environmental protection. Examples of the olefin-based resin include olefin homopolymers such as ethylene, propylene, and butene, block copolymers and random copolymers of ethylene-propylene, 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 them, polyethylene and polypropylene are preferred from the viewpoint of obtaining excellent scratch resistance and good bending processability.

[Polyethylene resin]
The polyethylene may be a homopolymer of ethylene, or a copolymer of ethylene and another comonomer copolymerizable with ethylene (e.g., α-olefins such as propylene, 1-butene, 1-hexene, and 1-octene, vinyl acetate, vinyl alcohol, etc.). 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 kinds.

[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 specified 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.

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 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 if the manufacturing process is controlled. Similarly, when highly crystalline homopolypropylene resin is less than 50% by mass, the crystallinity is insufficient, and the tensile modulus may be lower than the preferred range even if the manufacturing process is controlled.

The isotactic pentad fraction (mmmm fraction) is calculated from a numerical value (electromagnetic wave absorption rate) obtained by resonating a resin material at a predetermined resonance frequency using 13C-NMR measurement (nuclear magnetic resonance measurement) using carbon C (nuclear species) with a mass of 13, and specifies the atomic arrangement, electronic structure, and molecular microstructure of the resin material. The pentad fraction of crystalline polypropylene resin is the ratio of five propylene units lined up 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 mainly determine the scratch resistance of the surface, and basically, the higher the pentad fraction, the higher the crystallinity.

When a substrate having 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.

<Pattern layer 5>
A pattern layer 5 for adding a pattern to the decorative sheet 1 can be provided on the surface of the white sheet 2. Examples of the pattern that can be used include wood grain, stone grain, sand grain, tiled pattern, brickwork pattern, fabric grain, leather pattern, and geometric figures.
Furthermore, a base solid ink layer (not shown) may be provided between the white sheet 2 and the pattern 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 be multi-layered, having two or more layers, as necessary for hiding properties, etc. Furthermore, the pattern layer 5 may be formed by laminating as many plates as necessary to express the desired design. In this way, the pattern layer 5 and the base solid ink layer may be combined in various ways depending on the desired design, that is, the design to be expressed, but are not particularly limited.

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

In addition, functional additives such as extender pigments, plasticizers, dispersants, surfactants, tackifiers, adhesion aids, drying agents, hardeners, hardening accelerators, and hardening retarders may be added to the base solid ink layer and the design layer 5 in order 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, inkjet printing, etc. In addition, 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, die coating, etc. 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 them 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 during the production of the decorative sheet 1 can be improved, and the production costs can be reduced.

<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 (e.g., 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, 4,4-dimethyl ... Examples of such copolymers include those obtained by homopolymerizing or copolymerizing two or more of α-olefins (e.g., 4-ethyl-1-hexene, 3-ethyl-1-hexene, 9-methyl-1-decene, 11-methyl-1-dodecene, 12-ethyl-1-tetradecene, etc.) and those obtained by copolymerizing 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.
In this embodiment, the term "main component" refers to 90% by mass or more of the target material unless otherwise specified.

When the 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. In addition, if the thickness of the transparent resin layer 6 exceeds 100 μm, the rigidity of the decorative sheet 1 is too high, and problems such as whitening and cracking may occur during bending.
However, when the topcoat layer 7 is provided on the transparent resin layer 6, the thickness of the transparent resin layer 6 may be less than 50 μm.

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 capture agent, a colorant, a light scattering agent, and a gloss adjuster, as necessary. These various functional additives can be appropriately selected from well-known additives.

The adhesive used to bond the pattern layer 5 and the transparent resin layer 6 can be any material, and can be any lamination method, such as thermal lamination, extrusion lamination, or dry lamination. The adhesive can be selected from acrylic, polyester, or polyurethane materials. In general, due to its cohesive strength, a two-liquid curing urethane material that utilizes the reaction between isocyanate and polyol is desirable. There are no particular restrictions on the lamination method, but methods that apply heat and pressure, extrusion lamination, and dry lamination are common. In addition, when applying an embossed pattern 6a, there is a method in which a sheet that has been laminated by various methods is embossed by heat and pressure, or a method in which a concave-convex pattern is provided on a cooling roll and embossed at the same time as extrusion lamination.

Also, a method can 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.
In addition, when further lamination strength is required by 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, lamination is performed by co-extrusion of the transparent resin layer 6 and the adhesive resin layer 6b. The adhesive resin layer 6b may be formed of, for example, polypropylene, polyethylene, acrylic resin, or other resin that has been acid-modified. The thickness of the adhesive resin layer 6b is desirably 2 μm or more for the purpose of improving adhesive strength.

<Top coat layer 7>
When 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 topcoat layer 7 can be appropriately selected from polyurethane, acrylic silicone, fluorine, epoxy, vinyl, polyester, melamine, aminoalkyd, urea, and other resin materials. The form of the resin material is not particularly limited, and may be water-based, emulsion, solvent-based, or the like. The curing method may also be appropriately selected from one-liquid type, two-liquid type, ultraviolet curing method, and the like.

As the resin material used as the main component of the topcoat layer 7, a urethane-based resin using isocyanate is suitable from the viewpoints of workability, cost, cohesive strength of the resin itself, etc. As the isocyanate, for example, a curing agent such as an adduct, biuret, or isocyanurate, which is a derivative of tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), hexamethylene diisocyanate (HMDI), diphenylmethane diisocyanate (MDI), lysine diisocyanate (LDI), isophorone diisocyanate (IPDI), bis(isocyanatemethyl)cyclohexane (HXDI), trimethylhexamethylene diisocyanate (TMDI), etc., can be appropriately selected and used. However, in consideration of weather resistance, a curing agent based on hexamethylene diisocyanate (HMDI) or isophorone diisocyanate (IPDI) having a linear molecular structure is suitable. In addition, when trying to improve 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. For example, by using a hybrid type of thermosetting and photocuring, it is possible to improve the surface hardness, suppress the cure shrinkage, and improve the adhesion.

A gloss regulator can be added to the topcoat layer 7 to adjust the gloss. Any known gloss regulator available on the market may be used. For example, fine particles made of inorganic materials such as silica, glass, alumina, calcium carbonate, barium sulfate, etc. may be used as the gloss regulator. Alternatively, fine particles made of organic materials such as acrylic may be used. However, when high transparency is required, it is desirable to use fine particles of highly transparent silica, glass, acrylic, etc. In particular, among fine particles such as silica and glass, gloss regulators that are not solid spherical particles but have low bulk density formed by secondary aggregation of fine primary particles have a high matting effect relative to the amount added. Therefore, by using such gloss regulators, the amount of gloss regulator added can be reduced.

In order to impart various functions to the topcoat layer 7, functional additives such as antibacterial agents and antifungal agents may be added. Also, an ultraviolet absorber and a light stabilizer may be added as necessary. As the ultraviolet absorber, for example, a benzotriazole-based, benzoate-based, benzophenone-based, triazine-based, or cyanoacrylate-based agent may be used. As the light stabilizer, a hindered amine-based agent may be used.
The thickness of the topcoat layer 7 is preferably in the range of 3 μm to 15 μm. If the thickness of the topcoat layer 7 is less than 3 μm, the effect of improving scratch resistance is low, and there is little point in providing the topcoat layer 7. If the thickness of the topcoat layer 7 is more than 15 μm, cracks or breaks will occur during bending, causing problems in terms of design and deterioration of weather resistance.

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

"Production 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 having high crystallinity. The polypropylene resin may be used alone or in combination.
The above-mentioned 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.

<Actions and other details>
(1) The white sheet 2 of this embodiment has a reflected chromaticity measured with a D65 light source in the Lab color system, where 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, and the spectral reflectance has a minimum value in the range of 500 nm or more and 650 nm or less.
With this configuration, there is no need to increase the amount of inorganic pigment added compared to the 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.

(2) The white sheet 2 of the present embodiment has a colored layer 3 containing an inorganic pigment and a resin. 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 having excellent whiteness, and a decorative sheet 1 including the white sheet 2.

(3) The white sheet 2 of the present embodiment may contain at least one blue pigment selected from ultramarine, Prussian blue (milory blue), cobalt blue, cerulean blue, and gosu.
With this configuration, it is possible to reliably provide a white sheet 2 having even more excellent whiteness, and a decorative sheet 1 including the white sheet 2.

(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 or more and 2 parts by mass or less, based on 100 parts by mass of titanium oxide.
With this configuration, it is possible to reliably provide a white sheet 2 having even more excellent whiteness, and a decorative sheet 1 including the white sheet 2.

(5) In the white sheet 2 of the present embodiment, the resin contained in the colored layer 3 may be polypropylene.
With this configuration, there is no need to increase the amount of inorganic pigment added compared to the 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.

(6) The white sheet 2 of the present 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.

(7) The white sheet 2 of the present embodiment may have a thickness in the range of 50 μm or more and 150 μm or less.
With this configuration, it is possible to impart both unevenness and bending workability to the white sheet 2.

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

Example 1
As the raw material of the colored layer 3, 40 parts by mass of titanium oxide pigment and 0.4 parts by mass of cobalt blue pigment were added and mixed with 59.6 parts by mass of polypropylene resin as inorganic pigment. As the raw material of the skin layer 4, 0.5 parts by mass of a hindered amine-based light stabilizer ("Chimasorb 944" manufactured by BASF) and 0.5 parts by mass of a benzotriazole-based ultraviolet absorber ("Tinuvin 328" manufactured by BASF) were added and mixed with 100 parts by mass of polypropylene resin. The mixture of the colored layer 3 and the mixture of the skin layer 4 were co-extruded using a melt extruder in the order of the skin layer 4, the colored layer 3, and the skin layer 4 to a thickness of 10 μm: 120 μm: 10 μm to form a white sheet 2.

Example 2
A white sheet 2 was produced 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 0.8 parts by mass.
Example 3
Regarding the blue pigment added to the colored layer 3 described above, 0.4 parts by mass of ultramarine blue pigment was added, but in the same manner as in Example 1, co-extrusion was performed using a melt extruder to form a white sheet 2.

Example 4
A white sheet 2 was produced 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
A white sheet 2 was produced by co-extruding the skin layer 4, colored layer 3, and skin layer 4 in the order of 3 μm:44 μm:3 μm using a melt extruder, using the same mixture for the colored layer 3 and the mixture for the skin layer 4 as in Example 1.

Example 6
A white sheet 2 was produced by co-extruding the skin layer 4, colored layer 3, and skin layer 4 in the order of 3 μm:94 μm:3 μm using a melt extruder, using the same mixture for the colored layer 3 and the mixture for the skin layer 4 as in Example 1.
(Example 7)
A white sheet 2 was produced by co-extruding a mixture of the colored layer 3 and the skin layer 4 similar to those in Example 1 in the order of skin layer 4, colored layer 3, and skin layer 4 in thicknesses of 3 μm: 34 μm: 3 μm using a melt extruder.

(Example 8)
A white sheet 2 was produced by co-extruding a mixture of the colored layer 3 and the skin layer 4 similar to those in Example 1 in the order of skin layer 4, colored layer 3, and skin layer 4 in thicknesses of 10 μm: 160 μm: 10 μm using a melt extruder.
(Example 9)
A pattern was printed on the surface of a 140 μm-thick white sheet 2 produced in the same manner as in Example 1 to form a pattern layer 5. The pattern 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-based 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 the pattern layer 5. Furthermore, a two-component curing urethane top coat ("W184" manufactured by DIC Graphics Co., Ltd.) was applied in an amount of 3 g/m ² to form a top coat layer 7. In this way, a decorative sheet 1 having a thickness of 145 μm was obtained as shown in FIG. 3.

Example 10
A topcoat 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 topcoat 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.

Example 12
A topcoat 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 topcoat layer 7 was formed in the same manner as in Example 9 on a white sheet 2 having a thickness of 50 μm produced in the same manner as in Example 5, to obtain a decorative sheet 1 having a thickness of 55 μm.

(Example 14)
A topcoat layer 7 was formed in the same manner as in Example 9 on a white sheet 2 having a thickness of 100 μm produced in the same manner as in Example 6, to obtain a decorative sheet 1 having a thickness of 105 μm.
(Example 15)
A topcoat 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.

(Example 16)
A topcoat layer 7 was formed in the same manner as in Example 9 on a white sheet 2 having a thickness of 180 μm 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 produced 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 1.0 part by mass.

(Example 18)
A topcoat layer 7 was formed in the same manner as in Example 9 on a white sheet 2 having a thickness of 140 μm 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 a polyethylene resin was used instead of a polypropylene resin as the raw material for the colored layer 3 described above.

(Example 20)
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, and were co-extruded using a melt extruder in the same manner as in Example 1 to produce a white sheet 2.
(Example 21)
A white sheet 2 was produced by coextrusion using a melt extruder in the same manner as in Example 1, except that the skin layer 4 was not formed.
(Example 22)
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, and were co-extruded using a melt extruder in the same manner as in Example 1 to produce a white sheet 2.

(Comparative Example 1)
A 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 pattern was printed on the surface of a 50 μm-thick white sheet 2 produced in the same manner as in Comparative Example 1 to form a pattern layer 5. The pattern 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-based 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 the pattern layer 5. Furthermore, a two-component curing urethane top coat ("W184" manufactured by DIC Graphics Co., Ltd.) was applied in an 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. 3.
(Comparative Example 3)
A white sheet 2 was produced 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.

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

<Spectral reflectance>
The spectral reflectance was measured from 400 to 700 nm using a fluorescent spectrodensitometer (FD-7) manufactured by Konica Minolta, Inc. Since white sheets with low hiding power are affected by the color of the base, all sheets were measured on a white base of hiding test paper (byko-chart high brightness 2A) manufactured by BYK-GARDNER.
7 shows the spectral reflectances of Examples 1 to 4 and Comparative Example 1. Examples 1 to 4 contain a blue pigment, and therefore have a minimum value between 500 nm and 650 nm, whereas Comparative Example 1 does not contain a blue pigment, and therefore shows a monotonically decreasing spectral reflectance.

<Hue>
The hue was evaluated by measuring the chromaticity using an X-rite spectrophotometer (530JP/LP) under a D65 light source and a BYK-GARDNER hiding test paper (byko-chart high lightness 2A) on a white background.

<Concealment>
The hiding power was evaluated by measuring the color difference between a white and black background using a spectrophotometer (530JP/LP) manufactured by X-rite and a hiding test paper (byko-chart high brightness 2A) manufactured by BYK-GARDNER. The smaller the color difference, the better the hiding power. A value of 0.5 or less was evaluated as "◎", a value of more than 0.5 and 0.7 or less was evaluated as "○", a value of more than 0.7 and 1.0 or less was evaluated as "△", and a value of more than 1.0 was evaluated as "×". Note that an evaluation of "△" or higher does not pose any practical problem.

<Bending suitability>
In the bending workability test, first, each sheet 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) 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 see if whitening or cracks occurred, and the state of bending workability was evaluated.
When no whitening or cracks were observed, the rating was "◎", when only slight whitening was observed in some areas, the rating was "○", when whitening was observed in some areas, the rating was "△", and when whitening was observed over the entire surface or when cracks were observed in some areas, the rating was "×". Note that a rating of "△" or higher is acceptable for practical use.

The evaluation results are shown in Table 1.

As can be seen from Table 1, the decorative sheets of Examples 1 to 3 and Examples 9 to 11 had very good concealing properties and could be finished without any problems when bent. Furthermore, it can be seen that the decorative sheets of Examples 9 to 11 were each formed by laminating a pattern layer 5 and a topcoat layer 7 onto the decorative sheets of Examples 1 to 3, imparting a high level of design while also achieving both concealing properties and bending properties.
The decorative sheets of Examples 4 and 12 were produced with a low blue pigment addition amount of 0.2, so the hiding power was slightly poor, but was at a level that would not cause any problems 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 somewhat poor, but at a level that would not cause any practical problems.

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 somewhat poor, but at a level that would not cause any practical problems.
The decorative sheets of Examples 7 and 15 were each produced so that the thickness of the colored layer was as thin as 34 μm, and therefore the hiding power was very poor, but at a level that would not cause any problems in practical use.
The decorative sheets of Examples 8 and 16 were each produced so that the colored layer had a relatively large thickness of 160 μm, and therefore the hiding power was very good, but the bending processability was deteriorated. However, this was at a level that did not pose any practical problems.

The decorative sheets of Examples 17 and 18 were produced with a high blue pigment addition amount of 1.0, so the hue leaned toward 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, and therefore the hiding power was slightly deteriorated, but this was at a level that did not pose any practical problems.
The decorative sheet of Example 21, which does not have a skin layer, exhibits slightly worse hiding power, but this is at a level that does not pose a problem in practical use.
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, and therefore the hiding power was slightly deteriorated, but this was at a level that did not pose any practical problems.

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 at 500 nm to 650 nm, resulting in decorative sheets with inferior hiding power.
The decorative sheet of Comparative Example 3 was produced with a very high blue pigment addition amount of 1.2, so the hue was blue (b* value was -1.75), and was at a level that could not be called a white sheet.

As explained above, the present invention is a technology particularly suited to decorative sheets used for building materials for the exterior and interior of buildings, surfaces of building fixtures, surface materials for home appliances, etc.

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...topcoat layer, 8...primer layer, B...base material

Claims (14)

The reflected chromaticity measured with a D65 light source has an L* in the range of 90 or more and 100 or less, an a* in the range of -1.5 or more and +1.5 or less, and a b* in the range of -1.5 or more and 2.0 or less in the Lab color system.
A white sheet having a spectral reflectance having a minimum value in the range of 500 nm to 650 nm,
The white sheet has a colored layer containing an inorganic pigment and a resin,
the resin contained in the colored layer is polypropylene,
The inorganic pigment contains titanium oxide and at least one type of blue pigment,
The white sheet is characterized in that the blue pigment contains at least one selected from the group consisting of cerulean blue and gosu . The reflected chromaticity measured with a D65 light source has an L* in the range of 90 or more and 100 or less, an a* in the range of -1.5 or more and +1.5 or less, and a b* in the range of -1.5 or more and 2.0 or less in the Lab color system.
A white sheet having a spectral reflectance having a minimum value in the range of 500 nm to 650 nm,
The white sheet has a colored layer containing an inorganic pigment and a resin,
the resin contained in the colored layer is polypropylene,
The white sheet is characterized in that the colored layer does not contain zinc stearate . 3. The white sheet according to claim 2 , wherein the inorganic pigment comprises titanium oxide and at least one type of blue pigment. 4. The white sheet according to claim 3 , characterized in that the blue pigment contains at least one selected from the group consisting of ultramarine, Prussian blue, cobalt blue, cerulean blue, and gosu. 4. The white sheet according to claim 3 , wherein the blue pigment contains at least one selected from the group consisting of cerulean blue and gosu. 6. The white sheet according to claim 3 , wherein the content of the blue pigment is in the range of 1 part by mass to 2 parts by mass, based on 100 parts by mass of titanium oxide. The white sheet further has a skin layer formed on at least one surface of the colored layer,
7. The white sheet according to claim 1, wherein the skin layer contains a polypropylene resin. 8. The white sheet according to claim 1, wherein the thickness of the white sheet is within a range of 50 μm to 150 μm. 9. The white sheet according to claim 1, wherein the polypropylene contained in the colored layer is a propylene homopolymer having an isotactic pentad fraction (mmmm fraction) of 95% or more. 9. The white sheet according to claim 1, wherein the polypropylene contained in the colored layer includes a random polypropylene resin having an ethylene content, or an amorphous polypropylene resin. 2. The white sheet according to claim 1 , wherein the colored layer does not contain zinc stearate. A decorative sheet comprising at least the white sheet according to any one of claims 1 to 11 and a top coat layer. 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. A method for producing a decorative sheet according to claim 1 , 2 or 1 , comprising the steps of:
A method for producing a decorative sheet, comprising the steps of: mixing an inorganic pigment with a resin so that the spectral reflectance has a minimum value within the range of 500 nm to 650 nm to produce a white sheet.

Images