JP7679664B2 - Decorative sheets and decorative panels - Google Patents

Description

The present invention relates to a decorative sheet and a decorative board using the decorative sheet.

When decorating building materials, furniture, home appliances, and other components, decorative panels with decorative sheets attached to them are commonly used.

To give the decorative board a visually appealing design, the decorative sheet may be embossed to create an uneven shape and create a three-dimensional visual effect.

For example, Patent Document 1 discloses a decorative sheet that is formed by laminating, in this order, a pattern-printed layer on one side of a base sheet, a transparent thermoplastic resin layer having an uneven pattern that matches the pattern, a surface protection layer that protects the surface of the transparent thermoplastic resin layer, and a gloss adjustment layer having a pattern with a gloss state that matches the pattern, with the resin that constitutes the surface protection layer penetrating the unevenness of the uneven pattern.

In the decorative sheet of Patent Document 1, a rugged pattern is formed on the surface of the transparent thermoplastic resin layer that has the surface protective layer. This synchronizes the pattern of the picture print layer with the rugged pattern of the transparent thermoplastic resin layer, improving the tactile feel and three-dimensional effect, and improving the realism of the pattern.

In recent years, there has been a demand for extremely excellent designs in which the pattern of the design layer is more in tune with the uneven shape formed on the decorative sheet, and the decorative sheet of Patent Document 1 is still not sufficient, leaving room for further improvement.
Furthermore, since decorative sheets are sometimes attached to floor surfaces, they are also required to have sufficient scratch resistance.

JP 2016-182748 A

The present invention aims to solve the above-mentioned problems and provide a decorative sheet in which the pattern of the design layer and the recesses are in sync, providing excellent design and excellent scratch resistance.

The present inventors have conducted intensive research to solve the above-mentioned problems, and have discovered that in a decorative sheet having at least a picture layer, a transparent resin layer, and a surface protective layer, in this order, on one side of a base sheet, the picture layer has a wood grain pattern, the transparent resin layer and the surface protective layer have thicknesses within a predetermined range, and the surface protective layer has recesses (D1) that are in harmony with characteristic portions of the picture layer, and further, the elastic modulus in the machine direction (E _MD ) and the elastic modulus in the width direction (E _CD ) are within a predetermined range and at a specific ratio, so that the picture pattern and the recesses in the picture layer are in harmony, resulting in excellent design properties and excellent scratch resistance, and have completed the present invention.

That is, the decorative sheet of the present invention is a decorative sheet having at least a pattern layer, a transparent resin layer, and a surface protective layer, in this order, on one side of a substrate, the pattern layer being a wood grain pattern having characteristic portions and non-characteristic portions, the transparent resin layer having a thickness of 90 μm or more and 110 μm or less, the surface protective layer having a thickness of 25 μm or more and 35 μm or less, the transparent resin layer having a recess (D1) that is in phase with the characteristic portion of the pattern layer on the side opposite to the side having the pattern layer, and the decorative sheet has an elastic modulus in the machine direction (E _MD ) and an elastic modulus in the width direction (E _CD ) both of which are 750 MPa or more and 1100 MPa or less, and a ratio of the elastic moduli in the machine direction to the width direction (E _MD /E _CD ) of 1.00 or more and 1.20 or less.

In the decorative sheet of the present invention, it is preferable that the base sheet is made of a colored polyolefin film having a thickness of 50 μm or more and 70 μm or less.
In addition, it is preferable that the characteristic portion of the pattern layer is formed from at least one pattern selected from the group consisting of vessels, knots, annual rings, and spots in the wood grain, and that the color difference ΔE between the characteristic portion and the non-characteristic portion of the pattern layer is 1.3 or more.
The decorative board of the present invention is characterized by comprising the decorative sheet of the present invention on an adherend.

The present invention can provide a decorative sheet in which the pattern of the design layer and the recesses are in sync, providing excellent design and excellent scratch resistance.

1(a) and 1(b) are cross-sectional views showing a schematic view of one example of the decorative sheet of the present invention. 1(a) to 1(c) are cross-sectional views showing a schematic example of the decorative sheet of the present invention. FIG. 1A is a perspective view showing a schematic example of a decorative sheet of the present invention; FIG. 1B is a top view showing a schematic example of a decorative sheet of the present invention; and FIG. 1C is a cross-sectional view showing a schematic example of a decorative sheet of the present invention. FIG. 1 is a cross-sectional view showing a schematic diagram of a preferred example of the decorative sheet of the present invention.

<Decorative sheet>
The decorative sheet of the present invention will now be described.
In the following description, the lower and upper limits of a numerical range expressed by "to" means "greater than or equal to, but not greater than, "(for example, if α to β, then α is greater than or equal to, but not greater than, or equal to, β).

The decorative sheet of the present invention has at least a design layer, a transparent resin layer, a transparent thermoplastic resin layer, and a surface protective layer, in this order, on one side of a base sheet.
FIG. 1 is a cross-sectional view showing a schematic example of a decorative sheet.
In one example of the decorative sheet of the present invention shown in Figure 1, the decorative sheet 10 has at least a pattern layer 2, a transparent resin layer 3, and a surface protective layer 4, in that order, on one side of a base sheet 1, and the pattern layer 2 has a characteristic portion 2a and a non-characteristic portion 2b.
In addition, the transparent resin layer 3 has a recess (D ₁ ) that is in phase with a characteristic portion of the pattern layer 2 on the side opposite the side having the pattern layer 2, and in the decorative sheet 10 of the present invention shown in Figure 1, the pattern layer 2 has a recess (D ₂ ) on the side opposite the side having the base sheet 1, which is located in the stacking direction of the recess (D ₁ ).

The elastic modulus in the machine direction ( _EMD ) and the elastic modulus in the width direction ( _ECD ) of the decorative sheet 10 of the present invention are both 750 MPa or more and 1100 MPa or less. If it is less than 750 MPa, the picture pattern of the picture layer 2 of the decorative sheet 10 of the present invention will not be synchronized with the recesses ( _D1 ), causing a loss of visual three-dimensional effect and poor design, while if it exceeds 1100 MPa, it will be too rigid and easily crack when the decorative sheet 10 of the present invention is used as a flooring material. The preferable lower limit of the elastic modulus in the machine direction ( _EMD ) and the preferable upper limit of the elastic modulus in the width direction ( _ECD ) are 770 MPa, and the preferable upper limit is 1050 MPa, and the more preferable lower limit is 790 MPa, and the more preferable upper limit is 1000 MPa.

Here, the elastic modulus in the machine direction (E _MD ) is the direction horizontal to the flow of the wood grain pattern of the design layer of the decorative sheet 10 of the present invention, and the elastic modulus in the cross direction (E _CD ) is the direction perpendicular to the flow direction of the wood grain pattern, both of which can be easily determined from the wood grain pattern appearing on the decorative sheet 10 of the present invention.
The elastic modulus in the machine direction (E _MD ) and the elastic modulus in the width direction (E _CD ) were calculated, for example, by preparing a decorative sheet punched into a dumbbell-shaped test piece conforming to JIS K6732 for the elastic modulus in the machine direction (E _MD ) and the elastic modulus in the width direction (E _CD ), and measuring the elastic modulus in the machine direction (E MD ) and the elastic modulus in the width direction (E CD ) using a tensile compression tester at a temperature of 20°C, a tensile speed of 50 mm/min, and a chuck distance of 80 mm. The initial linear portion of the tensile stress-strain curve was then used to calculate the elastic modulus in the machine direction (E MD ) and the elastic modulus in the width direction (E CD ).
E = Δρ/Δε
E: Elastic modulus Δρ: Stress difference due to the original average cross-sectional area between two points on a line Δε: Strain difference between the same two points

In addition, the ratio of the elastic modulus in the machine direction to the width direction of the decorative sheet 10 of the present invention (E _MD /E _CD ) is 1.00 or more and 1.20 or less. When the decorative sheet 10 of the present invention is stretched in the machine direction and adjusted so that the shape of the picture layer and the recess (D1) match within the above ratio range, the shape of the picture layer and the recess (D1) is unlikely to misalign in the horizontal direction, and high designability can be maintained. The preferred upper limit of the above ratio is 1.19, and the more preferred upper limit is 1.18.

The elastic modulus in the machine direction ( _EMD ) and the elastic modulus in the width direction ( _ECD ) and their ratio can be adjusted to be within the above-mentioned ranges, for example, by appropriately adjusting the conditions for producing the surface protective layer (the blending ratio of raw materials, the curing conditions, the aging treatment conditions, etc.).
Next, each layer constituting the decorative sheet 10 will be described.

(Base sheet)
The decorative sheet 10 of the present invention has a base sheet 1 .
The base sheet 1 is not particularly limited, but preferably contains a non-halogen-based thermoplastic resin.

Examples of the non-halogenated thermoplastic resin include low-density polyethylene (including linear low-density polyethylene), medium-density polyethylene, high-density polyethylene, ethylene-α-olefin copolymer, homopolypropylene, polymethylpentene, polybutene, ethylene-propylene copolymer, propylene-butene copolymer, ethylene-vinyl acetate copolymer, saponified ethylene-vinyl acetate copolymer, and mixtures thereof. Thermoplastic ester resins include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyethylene naphthalate-isophthalate copolymer, polycarbonate, and polyarylate. Thermoplastic acrylic resins include polymethyl methacrylate, polyethyl methacrylate, polyethyl acrylate, and polybutyl acrylate. Thermoplastic polyamide resins include nylon-6 and nylon-66. Polyimide, polyurethane, polystyrene, and acrylonitrile-butadiene-styrene resins may also be used.
These non-halogen-based thermoplastic resins may be used alone or in combination of two or more.
Among these, olefin-based thermoplastic resins are preferred because they are excellent in printability for the design layer 2 and inexpensive.

The base sheet 1 may be colored. In this case, the non-halogen-based thermoplastic resin can be colored by adding a coloring agent (pigment or dye).
As the colorant, for example, inorganic pigments such as titanium dioxide, carbon black, and iron oxide, organic pigments such as phthalocyanine blue, and various dyes can be used.
These may be selected from known or commercially available materials, and the amount of colorant added may be appropriately determined according to the desired color tone, etc.

The base sheet 1 may contain various additives such as fillers, matting agents, foaming agents, flame retardants, lubricants, antistatic agents, antioxidants, UV absorbers, and light stabilizers, as necessary.

The thickness of the base sheet 1 is not particularly limited, but is preferably 40 μm or more and 200 μm or less.
The base sheet 1 may be constructed as either a single layer or a multilayer.
In particular, in the decorative sheet 10 of the present invention, the base sheet 1 is preferably made of a colored polyolefin film having a thickness of 50 μm or more and 70 μm or less. By providing a base sheet 1 made of a colored polyolefin film of such a thickness, the elastic modulus requirement described above can be easily satisfied in the combination of the thickness ranges of the transparent resin layer 3 and the surface protective layer 4 described below.

(Pattern layer)
The decorative sheet 10 has a pattern layer 2 .
The pattern layer 2 is a layer that imparts decorativeness to the decorative sheet 10 .

The pattern layer 2 may be, for example, a pattern layer formed by printing various patterns using ink and a printing machine, or it may be a layer that combines a concealing layer and a pattern layer.

By providing the concealing layer, when the above-mentioned base sheet 1 is colored or has color unevenness, it is possible to impart an intended color and adjust the color of the surface.
Furthermore, by providing a pattern layer, the pattern layer 2 having a wood grain pattern can be suitably obtained.
These design patterns are formed by multi-color printing using the usual process colors of yellow, red, blue, and black, as well as by multi-color printing using special colors in which the individual colors that make up the pattern are prepared.

The ink composition used for the design layer 2 is a suitable mixture of binder resin, pigment, colorant such as dye, extender pigment, solvent, stabilizer, plasticizer, catalyst, hardener, etc.

The binder resin is not particularly limited, and examples of preferred binder resins include urethane resin, acrylic resin, urethane-acrylic resin, urethane-acrylic copolymer resin, vinyl chloride/vinyl acetate copolymer resin, vinyl chloride/vinyl acetate/acrylic copolymer resin, acrylic resin, polyester resin, and nitrocellulose resin. Any of these may be used as the binder resin, either alone or in combination of two or more.

Preferred examples of the colorant include inorganic pigments such as carbon black (ink), iron black, titanium white, antimony white, yellow lead, titanium yellow, red iron oxide, cadmium red, ultramarine blue, and cobalt blue; organic pigments such as quinacridone red, isoindolinone yellow, and phthalocyanine blue; metal pigments consisting of scaly flakes of dyes, aluminum, brass, and the like; and pearlescent (pearl) pigments consisting of scaly flakes of titanium dioxide-coated mica, basic lead carbonate, and the like.
These may be used alone or in combination of two or more.

The pattern layer 2 is a wood grain pattern having a characteristic portion 2a and a non-characteristic portion 2b.
The characteristic portion 2a refers to a portion having characteristics that allow the pattern of the pattern layer 2 to be recognized, such as vessels in the wood grain, knots, annual rings, and spots.
The non-characteristic portion 2b refers to a portion other than the characteristic portion 2a.

In the design layer 2, the color difference ΔE between the characteristic portion 2a and the non-characteristic portion 2b is preferably 1.3 or more.
By setting the color difference ΔE in this range, the design can be made more excellent.
The color difference ΔE is more preferably 1.5 or more, further preferably 1.8 or more, and particularly preferably 2.0 or more.

In this specification, the method for measuring and calculating the color difference ΔE is as follows.
In the decorative sheet 10, the L ^* , a ^* and b ^* in the L ^* a ^* b ^* color system of the characteristic portion 2a and the non-characteristic portion 2b are measured using a spectrophotometer (SE6000 manufactured by Nippon Denshoku Industries Co., Ltd.) by irradiating light (D65 light source) at an incident angle of 10 degrees (the normal direction to the surface on the transparent resin layer 3 side is set to 0 degrees) onto the surface of the side of the decorative sheet 10 having the transparent resin layer 3 (the side having the surface protective layer if the decorative sheet 10 has a surface protective layer 4), and based on the total reflected light (specular reflected light + diffuse reflected light).
Here, L ^* , a ^* and b ^* in the characteristic portion 2a are respectively designated as L ₁ ^* , a ₁ ^* and b ₁ ^* , and L ^* , a ^* and b ^* in the non-characteristic portion 2b are respectively designated as L ₂ ^* , a ₂ ^* and b ₂ ^* .
The term "L ^* a ^* b ^* color system" refers to a color system standardized by the CIE (International Commission on Illumination) and adopted in JIS Z8781-4: 2013. In the L ^* a ^* b ^* color system, lightness is represented by L ^* , and chromaticity indicating hue and saturation is represented by a ^* and b ^* .

The above measured values can be substituted into the following formula to calculate the value.
Color difference ΔE = ((L ₁ ^* - _{L 2} ^* ) ² + (a ₁ ^* - a ₂ ^* ) ² + (b ₁ ^* - b ₂ ^* ) ² ) ^1/2

The thickness of the pattern layer 2 is not particularly limited, but is preferably at least 0.1 μm, and more preferably from 0.5 μm to 600 μm. If the thickness of the pattern layer 2 is within the above range, it can impart an excellent design to the decorative sheet 10 and also provide hiding properties.

Methods for forming the pattern layer 2 include, for example, gravure printing, offset printing, screen printing, flexographic printing, electrostatic printing, inkjet printing, etc. In addition, when forming a concealing layer, various coating methods such as roll coating, knife coating, air knife coating, die coating, lip coating, comma coating, kiss coating, flow coating, and dip coating can also be used.

(Transparent resin layer)
The decorative sheet 10 has a transparent resin layer 3 .
The transparent resin layer 3 is preferably a layer formed from a thermoplastic resin.
The transparent resin layer 3 is not particularly limited as long as it allows the pattern layer 2 to be seen, and may be any of colorless transparent, colored transparent, translucent, and the like.

Examples of the thermoplastic resin include olefin resins such as polyethylene, polypropylene, polybutene, polymethylpentene, and olefin-based thermoplastic elastomers; polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, ethylene glycol-terephthalic acid-isophthalic acid copolymer resin, terephthalic acid-ethylene glycol-1,4 cyclohexane dimethanol copolymer resin, and polyester-based thermoplastic elastomers; acrylic resins such as polymethyl (meth)acrylate, methyl (meth)acrylate-butyl (meth)acrylate copolymer resin, and methyl (meth)acrylate-styrene copolymer resin; polycarbonate resin, polyvinyl chloride, polystyrene, and ionomers.
Among these, polyethylene or polypropylene is more preferred because of its high tensile strength, excellent chemical resistance, and excellent production process.
In this specification, (meth)acrylate means acrylate or methacrylate.

The polyethylene may be a homopolymer of ethylene, or a copolymer of ethylene and another comonomer copolymerizable with ethylene (for example, an α-olefin such as propylene, 1-butene, 1-hexene, or 1-octene, vinyl acetate, or vinyl alcohol).
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), and cross-linked polyethylene (PEX).
These polyethylenes may be used alone or in combination of two or more.

The polypropylene may be a homopolymer of propylene, or a copolymer of propylene and another comonomer copolymerizable with propylene (e.g., α-olefins such as ethylene, 1-butene, 1-hexene, and 1-octene; vinyl acetate, vinyl alcohol, etc.).
These polypropylenes may be used alone or in combination of two or more.
In the present invention, a homopolymer of propylene (homopolypropylene) is particularly preferred from the viewpoint of excellent scratch resistance and bending processability.

The transparent resin layer 3 may be composed of one layer, or two or more layers.

The thickness of the transparent resin layer 3 is 90 μm or more and 110 μm or less. By having a transparent resin layer 3 with a thickness in this range, the decorative sheet 10 of the present invention can obtain excellent scratch resistance and bending processability. The thickness of the transparent resin layer 3 is preferably 95 μm or more and 105 μm or less.

When the transparent resin layer 3 is composed of two or more layers, the total thickness of the transparent resin layer 3 must be within the above range.

When the transparent resin layer 3 is composed of a plurality of layers, the resins may be the same or different in type, and the thicknesses of the base material made of a plurality of resins may be the same or different.
The method for laminating two or more transparent resin layers 3 is not limited as long as it is a common method, and examples thereof include dry lamination and extrusion heat lamination.

The transparent resin layer 3 may be subjected to surface treatments such as saponification treatment, glow discharge treatment, corona discharge treatment, plasma discharge treatment, ultraviolet (UV) treatment, and flame treatment, without departing from the spirit of the present invention.

(Surface protective layer)
The decorative sheet 10 preferably has a surface protective layer on the side of the transparent resin layer 3 opposite to the side on which the pattern layer 2 is provided.
The surface protective layer 4 may have a recess as shown in FIG. 1( a ), or may not have a recess as shown in FIG. 1( b ).

The surface protective layer 4 is a layer that imparts durability (scratch resistance, contamination resistance, weather resistance, etc.) to the decorative sheet 10, and by having the surface protective layer 4, it is possible to more effectively protect the pattern layer 2, and it is possible to effectively prevent a decrease in the design due to scratches on the decorative sheet 10 itself.
The surface protective layer 4 may have a single layer structure, or may have a multiple layer structure made of the same or different materials, or may be a suitable mixture of the materials shown below.

The surface protection layer 4 is not particularly limited, but may be made of, for example, a two-component curable resin or a crosslinked cured product of an ionizing radiation curable resin composition.
The crosslinked and cured product is preferably transparent, and may be translucent or colored so long as it is transparent and the design layer 2 can be visually recognized.

The two-component curing resin is not particularly limited as long as it is a resin that is cured by adding a curing agent to a base material. A two-component curing urethane resin in which the base material is a polyol (polyhydric alcohol) and the curing agent is an isocyanate curing agent is preferred.
As the ionizing radiation curable resin, for example, an oligomer (hereinafter, so-called prepolymer, macromonomer, etc. are also included) having a radical polymerizable unsaturated bond or a cationic polymerizable functional group in the molecule and/or a monomer having a radical polymerizable unsaturated bond or a cationic polymerizable functional group in the molecule is preferably used. Here, ionizing radiation means electromagnetic waves or charged particles having energy capable of polymerizing or crosslinking molecules, and generally includes electron beams (EB) or ultraviolet rays (UV).

The above oligomers or monomers include, for example, compounds having radically polymerizable unsaturated groups such as (meth)acryloyl groups and (meth)acryloyloxy groups, and cationic polymerizable functional groups such as epoxy groups in the molecule. These oligomers and monomers can be used alone or in combination. In this specification, the above (meth)acryloyl group means an acryloyl group or a methacryloyl group.

As the oligomer having a radically polymerizable unsaturated group in the molecule, for example, oligomers such as urethane (meth)acrylate, polyester (meth)acrylate, epoxy (meth)acrylate, melamine (meth)acrylate, and triazine (meth)acrylate can be preferably used, and urethane (meth)acrylate oligomers are more preferable. As for the molecular weight, those having a molecular weight of about 250 to 100,000 are usually used.

The monomer having a radically polymerizable unsaturated group in the molecule is preferably, for example, a polyfunctional monomer, and more preferably a polyfunctional (meth)acrylate.
Examples of the polyfunctional (meth)acrylate include diethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, bisphenol A ethylene oxide modified di(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethylolpropane ethylene oxide tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate {pentafunctional (meth)acrylate}, dipentaerythritol hexa(meth)acrylate {hexafunctional (meth)acrylate}, etc. Here, the polyfunctional monomer refers to a monomer having a plurality of radically polymerizable unsaturated groups.

It is more preferable that the ionizing radiation curable resin composition contains an ionizing radiation curable resin component consisting of a urethane acrylate oligomer and a polyfunctional monomer, and it is particularly preferable that the ionizing radiation curable resin component has a urethane acrylate oligomer/polyfunctional monomer (mass ratio) of 6/4 to 9/1. This mass ratio range allows the composition to have better scratch resistance.
If necessary, a monofunctional monomer may be appropriately used in addition to the ionizing radiation curable resin component.
Examples of the monofunctional monomer include methyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and phenoxyethyl (meth)acrylate.

When the ionizing radiation curable resin composition is crosslinked by ultraviolet light, it is preferable to add a photopolymerization initiator to the ionizing radiation curable resin composition.
When the ionizing radiation curable resin composition is a resin system having a radical polymerizable unsaturated group, acetophenones, benzophenones, thioxanthones, benzoins, and benzoin methyl ethers can be used alone or in combination as the photopolymerization initiator.
When the ionizing radiation curable resin composition is a resin system having a cationically polymerizable unsaturated group, the photopolymerization initiator may be an aromatic diazonium salt, an aromatic sulfonium salt, an aromatic iodonium salt, a methacerone compound, a benzoin sulfonate ester, or the like, either alone or in combination. The amount of these photopolymerization initiators to be added is about 0.1 to 10 parts by mass per 100 parts by mass of the ionizing radiation curable resin component.

In addition, various additives may be further added to the ionizing radiation curable resin composition as necessary. Examples of these additives include thermoplastic resins such as urethane resin, polyvinyl acetal resin, polyester resin, polyolefin resin, styrene resin, polyamide resin, polycarbonate resin, acetal resin, vinyl chloride-vinyl acetate copolymer resin, vinyl acetate resin, acrylic resin, and cellulose resin; lubricants such as silicone resin, wax, and fluorine resin; ultraviolet absorbers such as benzotriazole, benzophenone, and triazine; light stabilizers such as hindered amine radical scavengers; and colorants such as dyes and pigments.

As the electron beam source of the ionizing radiation, for example, various electron beam accelerators such as Cockcroft-Walton type, Van de Graff type, resonant transformer type, insulating core transformer type, or linear type, dynamitron type, high frequency type, etc. can be used, which irradiate electrons having an energy of 70 to 1000 keV. The exposure dose of the ionizing radiation is preferably, for example, about 1 to 10 Mrad.
As the ultraviolet ray source of the ionizing radiation, for example, a light source such as an extra-high pressure mercury lamp, a high pressure mercury lamp, a low pressure mercury lamp, a carbon arc lamp, a black light, a metal halide lamp, etc. can be used, and the wavelength of the ultraviolet ray is usually in the wavelength range of 190 to 380 nm.

In the decorative sheet 1 of the present invention, the thickness of the surface protective layer 4 is 25 μm or more and 35 μm or less. If the thickness of the surface protective layer 4 is less than 25 μm, sufficient durability (scratch resistance, stain resistance, weather resistance, etc.) cannot be imparted, and if it exceeds 35 μm, the transmittance decreases and the visibility of the pattern of the pattern layer decreases.
The preferred lower limit of the thickness of the surface protective layer 4 is 28 μm, and the preferred upper limit is 33 μm.

The surface protective layer 4 may be composed of a single layer or two or more layers. If it is composed of multiple layers, the materials constituting each layer may be the same or different, but the total film thickness is 25 μm or more and 35 μm or less.
In addition, it is preferable that the surface protective layer 4 contains inorganic fine particles such as silica fine particles because they can impart excellent scratch resistance. Known silica fine particles can be used, but it is preferable that the average particle size of the silica fine particles is equal to or smaller than the thickness of the surface protective layer 4 in which they are contained.

(Other layers)
The decorative sheet 10 may have a primer layer, an adhesive layer, a backer layer, and the like, as necessary.

The primer layer can be formed by applying a known primer agent. Examples of primer agents include urethane resin-based primer agents made of acrylic-modified urethane resin (acrylic urethane-based resin), urethane-cellulose-based resin (for example, a resin obtained by adding hexamethylene diisocyanate to a mixture of urethane and soluble cellulose), and resin-based primer agents made of acrylic and urethane block copolymers. Additives may be blended into the primer agent as necessary. Examples of additives include fillers such as calcium carbonate and clay, flame retardants such as magnesium hydroxide, antioxidants, lubricants, foaming agents, ultraviolet absorbers, and light stabilizers. The amount of additives blended can be set appropriately depending on the product characteristics.

The primer layer may contain an ultraviolet absorbing agent, if necessary.
As the ultraviolet absorbing agent, any known ultraviolet absorbing agent can be appropriately selected and used.

The thickness of the primer layer is not particularly limited, but is preferably 0.01 to 10 μm, and more preferably 0.1 to 1 μm.

The adhesive layer is not particularly limited, and any known adhesive may be used. Examples include polyurethane, acrylic, polyolefin, polyvinyl acetate, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ionomer, butadiene-acrylonitrile rubber, neoprene rubber, natural rubber, etc. These adhesives may be used alone or in combination of two or more.

The thickness of the adhesive layer after drying is preferably about 0.1 to 30 μm, and more preferably about 1 to 5 μm.

The decorative sheet 10 may have a backer layer as the bottom layer of the substrate 1 (the side opposite to the side on which the design layer 2 is laminated) in order to impart scratch resistance and impact resistance.
As the backer layer, a known backer layer disclosed in JP-A-2014-188941 or the like can be appropriately selected and used.

(Recesses (D1) and (D2))
1, the decorative sheet of the present invention has a transparent resin layer 3, on the side opposite to the side having the pattern layer 2, having a recess (D1) that is in phase with the characteristic portion 2a of the pattern layer 2. In addition, it is preferable that this pattern layer 2 has a recess (D2) on the side opposite to the side having the substrate 1, which is located in the lamination direction of the recess (D1).

The recess (D1) has a shape that matches the characteristic portion 2a of the design layer 2.
The recess (D1) may have a shape that is modeled after the outline of the characteristic portion 2a of the pattern of the pattern layer 2, or may have a simplified shape of the outline of the characteristic portion 2a of the pattern of the pattern layer 2, or may have a similar shape that is a reduced or enlarged version of the outline of the characteristic portion 2a.

The recess (D1) is positioned so as to coincide with the characteristic portion 2a of the pattern layer 2.
2(a) to (c) are cross-sectional views that typically show one example of the decorative sheet of the present invention.
The positional relationship between the recess (D1) and the characteristic portion 2a of the design layer 2 may be any one of those shown in Figures 2(a) to 2(c).
That is, as shown in Figure 2(a), in the stacking direction, the characteristic portion 2a of the pattern layer 2 and the recess (D1) may be positioned so as to overlap, as shown in Figure 2(b), the characteristic portion 2a of the pattern layer 2 and the recess (D1) may be positioned so as to partially overlap, or as shown in Figure 2(c), the characteristic portion 2a of the pattern layer 2 and the recess (D1) may be positioned so as not to overlap.
2(c), in plan view, the recess (D1) is located in the vicinity of the characteristic portion 2a of the pattern layer 2. The above-mentioned vicinity means that in plan view, the distance between the position of the characteristic portion 2a and the position of the recess (D1) having a shape corresponding to the characteristic portion 2a is 70 mm or less.
These can be appropriately set depending on the design of the pattern layer 2.
In addition, the harmonious relationship between the recess (D1) and the characteristic portion 2a does not necessarily have to be established over the entire surface of the design, and there may be some areas that are not harmonious as long as it does not impair the overall design feel.
The width of the recess (D1) will be described later.

The recess (D2) is located in the stacking direction of the recess (D1).
As shown in FIGS. 2(a) to 2(c), the recess (D2) is located at a position overlapping the recess (D1) in the stacking direction.
In addition, the recess (D2) may be formed in the characteristic portion 2a of the pattern layer 2 as shown in Figure 2(a), or may be formed across from the characteristic portion 2a to the non-characteristic portion 2b of the pattern layer 2 as shown in Figure 2(b), or may not be formed in the characteristic portion 2a of the pattern layer 2 as shown in Figure 2(c) (the recess (D2) is formed in the non-characteristic portion 2b).

In the decorative sheet 10, the depth H of the recess (D1) is preferably greater than the depth h of the recess (D2).
By providing such recesses (D1) and recesses (D2), the picture pattern of the picture layer and the recesses are in harmony with each other, and it is possible to provide an extremely excellent design having a visually three-dimensional effect.
The relationship between the depth H of the recess (D1) and the depth h of the recess (D2) applies between the recess (D1) and the recess (D2) which are located in the stacking direction (overlapping when viewed in a plane).

In terms of imparting a three-dimensional effect to the decorative sheet 10, the ratio (h/H) of the depth h of the recess (D2) to the depth H of the recess (D1) is preferably 0.25 or more and 0.60 or less, more preferably 0.26 or more and 0.55 or less, even more preferably 0.28 or more and 0.50 or less, and particularly preferably 0.30 or more and 0.48 or less.

The depth H of the recess (D1) may be any size that can favorably impart a three-dimensional effect, and is, for example, preferably 50 μm or more and 200 μm or less, and more preferably 55 μm or more and 190 μm or less.
The depth h of the recess (D2) is, for example, preferably 13 μm or more and 100 μm or less, and more preferably 17 μm or more and 92 μm or less.
In addition, the numerical ranges of the depth H and the depth h do not necessarily have to be established for all recesses (D1) and recesses (D2), and there may be recesses (D1) and recesses (D2) that do not satisfy the above numerical ranges as long as the overall design is not impaired.
For example, as long as the overall design is not impaired, some of the harmonious recesses (D1) and recesses (D2) may not satisfy the magnitude relationship of depth H>depth h.
However, from the viewpoint of providing a suitable design, when the decorative sheet 10 is viewed in plan and the recesses (D1) and (D2) located in the lamination direction of any 10 cm x 10 cm area are checked, it is preferable that less than 30% of the recesses do not satisfy the relationship of depth H > depth h. Such checking can be performed using an electron microscope and its measurement conditions described below.

The width W of the recess (D1) depends on the pattern formed on the pattern layer 2, but is preferably, for example, from 400 μm to 2000 μm, and more preferably from 500 μm to 1500 μm.
The width w of the recess (D2) is, for example, preferably 5 μm or more and 400 μm or less, and more preferably 10 μm or more and 100 μm or less.

It is preferable that the decorative sheet 10 has a recess (D3) on the side of the pattern layer 2 of the substrate 1 and a recess (D4) on the side opposite the pattern layer 2 of the substrate 1, which are located in the stacking direction of the recess (D1) and the recess (D2).
In this case, it is preferable that the depths of the recesses decrease in the order of recess (D1), recess (D2), recess (D3), and recess (D4).
Furthermore, when the decorative sheet 10 has a surface protective layer 4 and has a recess (referred to as D5) on the opposite side of the surface protective layer 4 from the transparent resin layer 3, which is located in the stacking direction of the recess (D1) and the recess (D2), it is preferable that the depth of the recess decreases in the order of recess (D5), recess (D1), recess (D2), recess (D3), and recess (D4).
By having such recesses (D1 to D5), it is possible to favorably achieve a design in which the picture pattern of the picture layer and the recesses are in harmony with each other.
Such recesses (D1 to D5) can be suitably formed by the manufacturing method of the decorative sheet of the present invention described below.
The depth relationships of the recesses (D1 to D5) are established among the recesses (D1 to D5) located in the stacking direction (overlapping when viewed from above).

A method for measuring the width W and depth H of the recess (D1) and the width w and depth h of the recess (D2) will be described.
FIG. 3(a) is a perspective view showing a schematic example of a decorative sheet of the present invention, (b) is a top view showing a schematic example of a decorative sheet of the present invention, and (c) is a cross-sectional view showing a schematic example of a decorative sheet of the present invention.
As shown in Fig. 3(a), a recess formed on the surface of the decorative sheet 10 is selected. As shown in Fig. 3(b), the long axis and short axis of the selected recess are determined. Then, as shown in Fig. 3(c), the sheet is cut along the short axis, and the cut surface is observed under an electron microscope to measure the widths (W and w) and depths (H and h) of the recesses (D1) and (D2).
As shown in Figure 3 (c), the depth H of the recess (D1) means the vertical distance from the surface of the transparent resin layer 3 to the deepest part of the recess (D1), and the depth h of the recess (D2) means the vertical distance from the surface of the pattern layer 2 to the deepest part of the recess (D2).
The long axis of a recess refers to the point where the length of a straight line connecting two points on the periphery of the recess is at its maximum, and the short axis of a recess refers to the point where the length is at its maximum in the perpendicular direction to the long axis.

When the transparent resin layer 3 is the outermost layer, the minor axis of the recess formed on the surface of the decorative sheet 10 coincides with the width W of the recess (D1).
4, the decorative sheet 10 has at least the pattern layer 2, the transparent resin layer 3, and the surface protective layer 4, in this order, on one side of the base sheet 1, so the width W of the recess (D1) is smaller than the minor axis of the recess formed on the surface of the decorative sheet 10. In this case, the cross section cut along the minor axis of the recess can be observed and measured with an electron microscope.

In addition, the width W and depth H of the recess (D1), and the width w and depth h of the recess (D2) refer to the average values calculated by randomly selecting 10 recesses formed on the surface of the decorative sheet 10 and measuring them using the method described above.
The measurement conditions using an electron microscope include, for example, a shape analysis laser microscope (measuring unit "VK-X1050", base "VK-D1", controller "VK-X1000" (manufactured by KEYENCE Corporation)) and measurement can be performed by observing at a magnification of 300 times.

Examples of resin paints that can be used to form a colored surface protective layer include organic solvent-based paints that are quick-drying and made of urethane resin, acrylic urethane resin, epoxy resin, polyester resin, etc., and water-based paints that are friendly to the natural and working environments. Among these, water-based paints containing urethane resins are preferred.
As the colorant, those described above for the design layer can be used.
As a method for coloring with the resin coating material, for example, the method described in Japanese Patent No. 4,569,720 can be applied.

<Method of manufacturing decorative sheet>
A manufacturing method for the decorative sheet of the present invention, for example in the case of the configuration shown in Figure 1 (a), can include a lamination step of laminating, at least in this order, a pattern layer having characteristic and non-characteristic portions, a transparent resin layer, and a surface protective layer on one side of a base sheet, and a shaping step of embossing the surface protective layer from the side opposite to the side having the pattern layer, thereby forming a recess (D1) in sync with the characteristic portion of the pattern layer on the side opposite to the side having the pattern layer of the transparent resin layer.
In the shaping step, a recess (D2) located in the stacking direction of the recess (D1) on the opposite side of the pattern layer from the side having the substrate can also be formed. In this case, it is preferable that the depth H of the recess (D1) is greater than the depth h of the recess (D2).

The lamination process is a process of laminating a pattern layer, a transparent resin layer, and a surface protection layer at least in this order on one side of the base sheet.

In the lamination process, the above-mentioned base sheet 1, pattern layer 2, transparent resin layer 3 and surface protective layer 4 can be used, and the pattern layer 2, transparent resin layer 3 and surface protective layer 4 may be laminated at least in this order on one side of the base sheet 1.
The above-mentioned adhesive layer or primer layer may be provided on one surface of each of the above-mentioned layers or between the layers.
At this time, the thicknesses of the transparent resin layer and the surface protective layer are adjusted to be within the above-mentioned ranges, and further, the compounding ratio of the raw materials of the surface protective layer, the curing treatment conditions, the aging treatment conditions, etc. are adjusted so that the elastic modulus in the machine direction ( _EMD ) and the elastic modulus in the width direction ( _ECD ) and the ratio thereof are adjusted to be within the above-mentioned ranges.

The shaping step is a step of embossing the surface protective layer from the side opposite to the side having the design layer, to form recesses that correspond to the characteristic portions of the design layer.
By having the above-mentioned shaping process, a recess (D1) that is in sync with the characteristic portion of the pattern layer and a recess (D2) that is smaller than the recess (D1) are formed at a position in the stacking direction of the recess (D1) so as to follow the recess (D1).

The embossing may be carried out, for example, by a known sheet-type or rotary embossing machine.
As the pattern used in the embossing process, a design that matches with the above-mentioned design layer 2 can be appropriately selected and used.

The temperature for the embossing process is not particularly limited, but a temperature that reduces the loss of recesses during hot-press molding, known as embossing return, is preferred.

In the case of the configuration shown in FIG. 1(b), a method can be used in which the surface protection layer is not laminated in the lamination step, and the embossing process is performed in the shaping step from the side opposite to the side having the pattern layer of the transparent resin layer, and then the surface protection layer is laminated.

The decorative sheet produced by the decorative sheet manufacturing method of the present invention has, on one side of the substrate, at least a pattern layer, a transparent resin layer, and a surface protective layer, in that order, the transparent resin layer has a recess (D1) that is in harmony with the characteristic portion of the pattern layer, and further, the elastic modulus in the machine direction (E _MD ) and the elastic modulus in the width direction (E _CD ) and the ratio between these are within specified ranges, so that the pattern of the pattern layer and the recess are in harmony, providing extremely excellent design, and also excellent scratch resistance.

<Decorative board>
The decorative board of the present invention is characterized by comprising the decorative sheet of the present invention on an adherend.

Examples of the adherend include wood boards such as wood veneer, wood plywood, particle board, and MDF (medium density fiberboard); gypsum-based boards such as gypsum boards and gypsum slag boards; cement boards such as calcium silicate boards, asbestos slate boards, lightweight foamed concrete boards, and hollow extruded cement boards; fiber cement boards such as pulp cement boards, asbestos cement boards, and wood chip cement boards; ceramic boards such as pottery, porcelain, earthenware, glass, and enamel; metal boards such as iron boards, galvanized steel boards, polyvinyl chloride sol-coated steel boards, aluminum boards, and copper boards; polyolefin resin boards, polyvinyl chloride resin boards, acrylic resin boards, A Examples of such resins include thermoplastic resin plates such as BS plates and polycarbonate plates; thermosetting resin plates such as phenolic resin plates, urea resin plates, unsaturated polyester resin plates, polyurethane resin plates, epoxy resin plates and melamine resin plates; and so-called FRP plates obtained by impregnating and curing a resin such as phenolic resin, urea resin, unsaturated polyester resin, polyurethane resin, epoxy resin, melamine resin, diallyl phthalate resin, into a glass fiber nonwoven fabric, cloth, paper, or other various fibrous base material. These may be used alone, or two or more of these may be laminated to form a composite substrate.
In addition, the thermoplastic resin board or thermosetting resin board may contain various additives, such as coloring materials (pigments or dyes), fillers such as wood powder or calcium carbonate, matting agents such as silica, foaming agents, flame retardants, lubricants such as talc, antistatic agents, antioxidants, ultraviolet absorbers, and light stabilizers, as necessary.
The thickness of the adherend is not particularly limited.

The method for laminating the decorative sheet of the present invention to the above-mentioned adherend is not particularly limited, and examples include laminating via the above-mentioned primer layer or via the above-mentioned adhesive layer.

Next, the present invention will be described in more detail using examples, but the present invention is not limited to these examples.

Example 1
A 60 μm thick colored polypropylene film was prepared as a base sheet, a back primer layer (thickness 2 μm) was formed on the back surface of the base sheet, and a wood grain pattern layer was formed on the front surface of the base sheet by gravure printing to a thickness of 2 μm.
A transparent adhesive layer was formed on the pattern layer using a urethane resin to a thickness of 2 μm. A transparent polypropylene resin sheet was laminated on the formed transparent adhesive layer by extrusion lamination to a thickness of 100 μm to form a transparent resin layer.
Next, the surface of the transparent resin layer was subjected to a corona discharge treatment, and then a two-component curing urethane resin was applied thereon to form a primer layer (primer layer for forming a surface protective layer, thickness 2 μm).
A urethane acrylate-based electron beam curable resin (EB resin) was applied in multiple layers by gravure coating on the surface of the primer layer so that the thickness after curing would be 30 μm (lower layer 15 μm, upper layer 15 μm), and then the electron beam was irradiated using an electron beam irradiation device under conditions of an oxygen concentration of 200 ppm or less and an acceleration voltage of 175 KeV and 5 Mrad to cure the electron beam curable resin, thereby forming a surface protective layer.

The materials constituting the lower and upper layers were as follows:
The electron beam curable resin used to form the lower layer contained 30 parts by mass of silica fine particles (particle diameter 6 μm) having a particle diameter equal to or smaller than the coating thickness relative to 100 parts by mass of the electron beam curable resin. The electron beam curable resin used to form the upper layer contained 10 parts by mass of silica fine particles (particle diameter 12 μm) having a particle diameter equal to or smaller than the coating thickness relative to 100 parts by mass of the electron beam curable resin, and 10 parts by mass of silica fine particles (particle diameter 20 μm) having a particle diameter larger than the coating thickness relative to 100 parts by mass of the electron beam curable resin.

The surface protection layer formed as described above was heated with a non-contact infrared heater to soften the base sheet and transparent resin layer, and immediately embossed with heat and pressure to form wood grain pattern recesses on the surface protection layer, producing a decorative sheet.

(Examples 2 to 4, Comparative Examples 1 to 3)
A decorative sheet was prepared in the same manner as in Example 1, except that the thicknesses of the transparent resin layer and the surface protective layer, and the elastic modulus in the machine direction ( _EMD ) and the elastic modulus in the width direction ( _ECD ) were adjusted to the values shown in the table below.
In Comparative Examples 2 and 3, only the upper layer of the surface protective layer was formed.

<Design>
The prepared decorative sheet was visually observed from above, and whether or not the picture pattern of the picture layer was in harmony with the recesses was evaluated based on human sensibility in accordance with the following criteria.
The evaluation results are shown in Table 1.
++: It feels like they are in harmony and has a more three-dimensional design.
+: I feel like we're in sync.
-: The misalignment is visible and it doesn't feel like they are in sync.

<Elastic modulus>
The decorative sheets of the examples and comparative examples were punched out in the machine direction and width direction to form dumbbell-shaped test pieces conforming to JIS-K6732. The test pieces thus prepared were subjected to a tensile test (machine used: ORIENTEC Tensilon universal material testing machine RTC-1250A) at a temperature of 20°C, a tensile speed of 50 mm/min, and a chuck distance of 80 mm. The elastic modulus in the machine direction (E _MD ) and the elastic modulus in the width direction (E _CD ) were calculated from the initial linear portion of the obtained tensile stress-strain curve using the following formula.
E = Δρ/Δε
E: Elastic modulus Δρ: Stress difference due to the original average cross-sectional area between two points on a line Δε: Strain difference between the same two points

<Scratch resistance>
The prepared decorative sheets according to the examples and comparative examples were laminated onto an MDF substrate, and then an abrasion test was carried out based on the JAS Flooring Abrasion Test A to evaluate scratch resistance.
Using a Taber abrasion tester, a test was carried out for 1200 revolutions under the conditions of abrasive paper: S-42, a load of 1000 g (single wheel load of 500 g x 2 pieces, including the load of a rubber disk), and evaluation was carried out according to the following criteria.
+: The remaining area of the design layer in the test portion is 50% or more.
-: The remaining area of the design layer in the test portion is 50% or less.

As shown in Table 1, the transparent resin layer has a recess (D1) that is in harmony with the characteristic portion of the pattern layer, and the thickness of the transparent resin layer and the surface protective layer, as well as the elastic modulus in the flow direction ( _EMD ) and the elastic modulus in the width direction ( _ECD ) are within specified ranges, thereby providing an extremely excellent design in which the wood grain pattern and the recess are in harmony with each other in the pattern layer, and it has also been confirmed that the scratch resistance is also excellent.

The present invention makes it possible to provide a decorative sheet that has an extremely excellent design with the pattern of the pattern layer and the recesses in sync, as well as excellent scratch resistance.

REFERENCE SIGNS LIST 1 Substrate 2 Design layer 2a Characteristic portion 2b Non-characteristic portion 3 Transparent resin layer 4 Surface protective layer 10 Decorative sheet

Claims (4)

A decorative sheet having at least a design layer, a transparent resin layer, and a surface protective layer in this order on one side of a base sheet,
The pattern layer is a wood grain pattern having a characteristic portion and a non-characteristic portion,
the characteristic portion is formed of at least one pattern selected from the group consisting of vessels in wood grain, knots, annual rings, and spots, and the non-characteristic portion is a portion other than the characteristic portion,
The transparent resin layer has a thickness of 90 μm or more and 110 μm or less,
The surface protective layer has a thickness of 25 μm or more and 35 μm or less,
The transparent resin layer has a recess (D1) on the side opposite to the side having the pattern layer, the recess (D1) being in sync with a characteristic portion of the pattern layer,
The decorative sheet is characterized in that the elastic modulus in the machine direction (EMD) and the elastic modulus in the cross direction (ECD) are both 750 MPa or more and 1100 MPa or less, and the ratio of the elastic modulus in the machine direction to the cross direction (EMD/ECD) is 1.00 or more and 1.20 or less. The decorative sheet according to claim 1, wherein the base sheet is a colored polyolefin film having a thickness of 50 μm or more and 70 μm or less. The decorative sheet according to claim 1 or 2, wherein the characteristic portion of the pattern layer is formed from at least one pattern selected from the group consisting of vessels, knots, annual rings, and spots in the wood grain, and the color difference ΔE between the characteristic portion and the non-characteristic portion of the pattern layer is 1.3 or more. A decorative board comprising the decorative sheet according to any one of claims 1 to 3 on an adherend.

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