JP7779011B2 - Decorative sheet and method for manufacturing decorative sheet - Google Patents

Description

The present invention relates to decorative sheets used on the interior and exterior surfaces of buildings, fixtures, furniture, etc., and to a method for manufacturing such decorative sheets.

With the diversification of usage environments in recent years, there has been a growing demand for decorative sheets with higher functionality. Generally, it is difficult to simultaneously achieve high functionality in all physical properties, such as weather resistance, scratch resistance, and stain resistance. For this reason, a top coat layer is often provided on the outermost surface of decorative sheets to impart functionality. To impart weather resistance to this top coat layer, it is common to add weather-resistant agents such as ultraviolet absorbers and light stabilizers. Examples of prior art include decorative sheets described in Patent Document 1.

Japanese Patent Application Laid-Open No. 2019-30998

Decorative sheets are also being used for exterior applications, and improving weather resistance in particular is a challenge. To improve weather resistance, it is common to add weather resistance agents such as ultraviolet absorbers and light stabilizers to the top coat layer. Increasing the amount of these agents added generally improves weather resistance, but this can potentially reduce physical properties such as scratch resistance and stain resistance of the top coat layer. In other words, in conventional decorative sheets, there is a so-called trade-off between improving weather resistance and improving scratch resistance and stain resistance.
The present invention aims to provide a decorative sheet with excellent weather resistance and scratch resistance, and a method for manufacturing such a decorative sheet, by specifying the resin composition of the top coat layer and minimizing the amount of weather resistance agent used in combination, without compromising other performance properties.

The inventors discovered the present invention by studying the composition of the acrylic resin used in the top coat layer with the aim of further improving the weather resistance and scratch resistance of the decorative sheet.
In order to solve the above problems, a decorative sheet according to one embodiment of the present invention comprises a polyolefin substrate, a pattern layer formed on the polyolefin substrate, an anchor coat layer formed on the pattern layer, a transparent resin layer formed on the anchor coat layer, the transparent resin layer having polypropylene as its main component and a film thickness in the range of 70 μm to 100 μm, and a top coat layer formed on the transparent resin layer, the transparent resin layer having acrylic resin as its main component and a film thickness in the range of 3 μm to 15 μm, wherein the top coat layer is composed of an aqueous acrylic resin emulsion having a glass transition temperature of 80°C or higher and an acid value of 50 mgKOH/g or higher, and a carbodiimide curing agent.

Furthermore, one aspect of the present invention relates to a method for manufacturing a decorative sheet, which comprises laminating a design layer, an anchor coat layer, a transparent resin layer, and a top coat layer on a substrate in at least this order, wherein the transparent resin layer is primarily composed of polypropylene and has a thickness in the range of 70 μm to 100 μm, and the top coat layer is primarily composed of acrylic resin and has a thickness in the range of 3 μm to 15 μm, and the top coat layer is formed from an aqueous acrylic resin emulsion having a glass transition temperature of 80°C or higher and an acid value of 50 mg KOH/g or higher, and a carbodiimide curing agent.

According to one aspect of the present invention, by specifying the resin composition of the top coat layer, it is possible to provide a decorative sheet with excellent weather resistance and scratch resistance without compromising other performance properties, as well as a method for manufacturing such a decorative sheet.

1 is a schematic cross-sectional view illustrating the configuration of a decorative sheet according to an embodiment of the present invention.

Next, an embodiment of the present invention will be described with reference to the drawings. The drawings are schematic, and the relationship between thickness and planar dimensions, the thickness ratio of each layer, etc. may differ from the actual ones. Therefore, specific thicknesses and dimensions should be determined by taking the following description into consideration.
Furthermore, the embodiments shown below are merely examples of devices and methods for embodying the technical concept of the present invention, and the technical concept of the present invention does not limit the materials, shapes, structures, arrangements, etc. of the components to those described below. The technical concept of the present invention can be modified in various ways within the technical scope defined by the claims.

[Overall configuration of decorative sheet]
As shown in Figure 1, a decorative sheet 10 according to an embodiment of the present invention (hereinafter referred to as this embodiment) comprises a substrate layer 11, a design layer 12, an anchor layer 13, a transparent resin layer 14, and a top coat layer 15 laminated in this order. The configuration of each of the above-mentioned layers will be described below.

(Base material layer 11)
The substrate layer 11 is a layer composed of a polyolefin substrate, i.e., a substrate containing polyolefin or a substrate containing only polyolefin. Examples of polyolefins that constitute the substrate layer 11 include polyethylene, polypropylene, and polybutylene, with polyethylene being particularly preferred. By using a polyolefin substrate as the substrate layer 11, the generation of harmful gases and the like during disposal can be reduced. Furthermore, by using a substrate containing polyethylene or a substrate containing only polyethylene as the substrate layer 11, the generation of harmful gases and the like during disposal can be further reduced.

The base layer 11 is preferably a layer made of a polyolefin base material as described above, but may be a layer made of other materials. Below, a base layer 11 made of a material other than polyolefin will be described.
The substrate layer 11 can be made of any material selected from, for example, paper, synthetic resin, synthetic resin foam, rubber, nonwoven fabric, synthetic paper, metal foil, etc. Examples of paper include tissue paper, titanium paper, and resin-impregnated paper. Examples of synthetic resins include polystyrene, polycarbonate, polyester, polyamide, ethylene-vinyl acetate copolymer, polyvinyl alcohol, and acrylic. Examples of rubber include ethylene-propylene copolymer rubber, ethylene-propylene-diene copolymer rubber, styrene-butadiene copolymer rubber, styrene-isoprene-styrene block copolymer rubber, styrene-butadiene-styrene block copolymer rubber, and polyurethane. Examples of nonwoven fabrics include organic and inorganic nonwoven fabrics. Examples of metals for the metal foil include aluminum, iron, gold, and silver.
To improve adhesion to adjacent layers, the substrate layer 11 may be subjected to surface treatment such as corona treatment, plasma treatment, ozone treatment, electron beam treatment, ultraviolet treatment, or dichromate treatment.

(Picture layer 12)
The design layer 12 is a layer of a design printed on the base layer 11 using ink.

The ink forming the design layer 12 contains a binder, which can be selected from, for example, soluble nitrocellulose, cellulose, vinyl chloride-vinyl acetate copolymer, polyvinyl butyral, polyurethane, acrylic, polyester, etc., either alone or modified. The binder may be water-based, solvent-based, or emulsion-type, and may be a one-component type or a two-component type that uses a hardener. Furthermore, the design layer 12 may be formed using a curable ink, which is cured by exposure to ultraviolet light or electron beams. A particularly common method is to use a urethane-based ink and harden it with an isocyanate to form the design layer 12.

In addition to the binders mentioned above, the design layer 12 may contain pigments, colorants such as dyes, extender pigments, solvents, and various additives that are commonly found in inks. Examples of versatile pigments include condensed azo, insoluble azo, quinacridone, isoindoline, anthraquinone, imidazolone, cobalt, phthalocyanine, carbon, titanium oxide, iron oxide, and pearl pigments such as mica.

The curing agent used to cure urethane-based inks is not particularly limited, and can be appropriately selected from commercially available curing agents including, for example, hexamethylene diisocyanate, isophorone diisocyanate, tolylene diisocyanate, xylylene diisocyanate and its hydrogenated products, or diphenylmethane diisocyanate and its hydrogenated products.

In addition to applying ink, it is also possible to apply a design to the pattern layer 12 by vapor deposition or sputtering of various metals.
It is also preferable that a light stabilizer be added to the ink described above, which can suppress deterioration of the decorative sheet 10 itself caused by light degradation of the ink, thereby extending the life of the decorative sheet 10. In order to effectively suppress deterioration of the decorative sheet 10 itself caused by light degradation of the ink, it is preferable to set the content of the light stabilizer within the range of 1% by mass or more and 5% by mass or less of the total mass of the ink.

The method for forming the design layer 12 is not particularly limited. The design layer 12 can be formed using conventional printing methods such as gravure printing, offset printing, screen printing, flexographic printing, and inkjet printing.

(Anchor layer 13)
The anchor layer (anchor coat layer) 13 is a layer provided to enhance the adhesion between the design layer 12 and the transparent resin layer 14 .
The material constituting the anchor layer 13 is not particularly limited, and can be selected from resin materials such as urethane, acrylic, acrylic silicone, fluorine, epoxy, and polyester, and can be made into ink by appropriately selecting a material that has excellent adhesion between the pattern layer 12 and the transparent resin layer 14.
There is no particular limitation on the method for forming the anchor layer 13. The anchor layer 13 can be formed using a common coating method such as gravure coating, microgravure coating, comma coating, knife coating, or die coating.

(Transparent resin layer 14)
The transparent resin layer 14 is a layer provided to improve the strength (mechanical strength) of the entire decorative sheet 10 .
The transparent resin layer 14 is a layer containing polypropylene as a main component. Here, the term "main component" refers to the quantitative main component, and the mass of polypropylene accounts for 50 mass% or more of the total mass of the transparent resin layer 14.

The transparent resin layer 14 may contain resin components other than polypropylene. Olefin-based resins are suitable as materials other than polypropylene that can be included in the transparent resin layer 14. In addition to polyethylene and polybutene, alpha-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-pent ... Examples include homopolymers or copolymers of two or more types of α-olefins (such as ethylene, 4-ethyl-1-hexene, 3-ethyl-1-hexene, 9-methyl-1-decene, 11-methyl-1-dodecene, and 12-ethyl-1-tetradecene), as well as copolymers of ethylene or α-olefins with other monomers, such as ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, ethylene-methyl methacrylate copolymer, ethylene-ethyl methacrylate copolymer, ethylene-butyl methacrylate copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, and ethylene-butyl acrylate copolymer.

In addition, in order to improve the surface strength of the decorative sheet 10, it is preferable to use highly crystalline polypropylene as the resin that constitutes the transparent resin layer 14. In other words, it is preferable that the transparent resin layer 14 be a layer whose main component is highly crystalline polypropylene.

The transparent resin layer 14 may also contain, as weather resistance agents, an ultraviolet absorber having a triazine skeleton and a light stabilizer having a NOR skeleton. The transparent resin layer 14 may also contain, for example, a benzophenone-based ultraviolet absorber and a hindered amine-based light stabilizer as weather resistance agents. The benzophenone-based ultraviolet absorber is preferably present in a range of 0.1% by mass or more and 5% by mass or less, relative to the total mass of the transparent resin layer 14. The hindered amine-based light stabilizer is preferably present in a range of 0.1% by mass or more and 5% by mass or less, relative to the total mass of the transparent resin layer 14.

In addition, various additives such as heat stabilizers, light stabilizers, antiblocking agents, catalyst scavengers, colorants, light scattering agents, and gloss adjusters can also be added to the transparent resin layer 14 as needed. Phenol-based, sulfur-based, phosphorus-based, and hydrazine-based heat stabilizers are commonly added, while hindered amine-based and other light stabilizers are commonly added in any combination.

The method for forming the transparent resin layer 14 is not particularly limited. The transparent resin layer 14 can be formed using a common method such as calendar film formation or extrusion film formation. Among these, extrusion molding is preferred as a method for forming the transparent resin layer 14. Extrusion molding allows the transparent resin layer 14 to be formed uniformly.
Furthermore, in order to provide a design, the transparent resin layer 14 may be provided with surface irregularities. Examples of methods for providing the irregularities include a method of subjecting the transparent resin layer 14 to hot embossing after extrusion molding, and a method of subjecting the transparent resin layer 14 to embossing simultaneously with extrusion molding using a cooling roll provided with irregularities during extrusion molding.

(Top coat layer 15)
The topcoat layer 15 is a layer provided to impart functions such as weather resistance, scratch resistance, stain resistance, and designability to the decorative sheet 10 .
The material constituting the topcoat layer 15 is not particularly limited, and for example, an ionizing radiation curable resin or a thermosetting resin is preferably used.
As the ionizing radiation curable resin, known materials such as various monomers and commercially available oligomers can be used. For example, it is preferable to use polyfunctional monomers such as pentaerythritol triacrylate (PET3A), pentaerythritol tetraacrylate (PET4A), trimethylolpropane triacrylate (TMPTA), dipentaerythritol hexaacrylate (DPHA), etc., polyfunctional oligomers such as Shikou UV-1700B (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), or mixtures thereof.

Preferred thermosetting resins are those formed by thermally curing a polymer containing carboxyl groups and a carbodiimide compound, as described below. The polymer containing carboxyl groups is not particularly limited, but may be used to impart mechanical properties, such as by extending the molecular structure. Suitable polymers may be selected from, for example, various acrylic polymers, polyesters, polyethers, polycarbonates, and polyurethanes.

Carbodiimide is a functional group represented by -N=C=N-, possessing excellent reactivity and used in a variety of applications. Carbodiimide compounds also inhibit hydrolysis, a major issue for most general-purpose resins, by capturing the acid in the polymer that catalyzes the decomposition reaction, making them effective in improving weather resistance. As with the above, carbodiimide compounds include, but are not limited to, diisopropylcarbodiimide, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, N-3-dimethylaminopropyl-N'-ethylcarbodiimide, N-tert-butyl-N'-ethylcarbodiimide, N-cyclohexyl-N'-2-morpholinoethylcarbodiimide meso-p-toluenesulfonic acid, and N,N'-di-tert-butylcarbodiimide. A major carbodiimide compound product is "Carbodilite V-02-L2" manufactured by Nisshinbo Chemical Inc.

In addition, the resin constituting the top coat layer 15 in this embodiment is preferably an acrylic copolymer having a glass transition temperature of 80° C. or higher and an acid value of 50 mgKOH/g or higher, which is crosslinked with a curing agent. If the glass transition temperature is 80° C. or lower, the surface hardness of the top coat layer 15 may decrease, and scratch resistance may be reduced. If the acid value is 50 mgKOH/g or lower, the crosslink density after curing is low, and scratch resistance may be reduced.
The acrylic resin contained in the top coat layer 15 is preferably an aqueous emulsion. If the acrylic resin contained in the top coat layer 15 is an aqueous emulsion, a resin coating film with a high molecular weight is obtained, and the surface hardness and contamination resistance of the top coat layer 15 are improved.

The top coat layer 15 generally contains a filler as a gloss adjuster. For example, organic materials such as acrylic beads or silicone beads, or inorganic materials such as alumina or silica can be used. However, inorganic silica (silica filler) is preferred in terms of scratch resistance. Silica exhibits better scratch resistance than other materials, which is thought to be due to its moderate hardness.

The silica preferably has a spherical shape and a pore volume of 1 mL/g or more. Silica with a large pore volume (specifically, 1 mL/g or more) tends to have excellent scratch resistance, which is thought to be due to the influence of the binder resin component impregnating the silica pores. Furthermore, silica with a large pore volume has a significant effect of reducing gloss and the required amount of gloss adjuster. The content of the gloss adjuster is preferably in the range of 1% to 30% by mass, and more preferably in the range of 2% to 20% by mass, relative to the total mass of the top coat layer 5. In other words, in this embodiment, when silica (silica filler) with a pore volume of 1 mL/g or more is added as a gloss adjuster, the content of the silica is preferably in the range of 1% to 30% by mass, and more preferably in the range of 2% to 20% by mass, relative to the total mass of the top coat layer 5.

Furthermore, it is preferable that the silica be spherical in shape and have an oil content of, for example, 100 mL to 200 mL/100 g. Silica tends to exhibit excellent scratch resistance when the oil content is large (specifically, 100 mL to 200 mL/100 g), which is thought to be due to the increased affinity between the binder resin component and the silica surface. Furthermore, silica with a large oil content has a significant effect of reducing gloss and the required amount of gloss adjuster. Therefore, in this embodiment, when silica (silica filler) with an oil content of 100 mL to 200 mL/100 g is added as a gloss adjuster, the silica content is preferably in the range of 1% by mass to 30% by mass, and more preferably in the range of 2% by mass to 20% by mass, relative to the total mass of the top coat layer 5.

In order to impart various functions to the top coat layer 15 constituting the decorative sheet 10 of this embodiment, various additives such as heat stabilizers, antiblocking agents, catalyst scavengers, colorants, light scattering agents, antibacterial agents, and antifungal agents may be blended therein.
If necessary, an ultraviolet absorber or a light stabilizer can be added to the top coat layer 15 as a weathering agent. Examples of ultraviolet absorbers include benzotriazoles, benzoates, benzophenones, and triazines. Light stabilizers include hindered amines, and these are typically added in any combination. That is, the top coat layer 15 may contain, as weathering agents, an ultraviolet absorber having a triazine skeleton and a light stabilizer having a NOR skeleton. The content of the ultraviolet absorber having a triazine skeleton in the top coat layer 15 is preferably in the range of 1% by mass to 15% by mass, and more preferably in the range of 3% by mass to 6% by mass, relative to the total mass of the top coat layer 15. The content of the light stabilizer having a NOR skeleton in the top coat layer 15 is preferably in the range of 1% by mass to 10% by mass, and more preferably in the range of 3% by mass to 6% by mass, relative to the total mass of the top coat layer 15. When the content of the ultraviolet absorber having a triazine skeleton and the content of the light stabilizer having a NOR skeleton are within the above-mentioned numerical ranges, the weather resistance can be further improved while maintaining the basic functions of the top coat layer 5, such as scratch resistance and contamination resistance.

In addition, the content of the UV absorber having a triazine skeleton in the top coat layer 15 is preferably greater than the content of the light stabilizer having a NOR skeleton, preferably within the range of 1.5 to 3 times. If the content of the UV absorber having a triazine skeleton is within the above numerical range, it is possible to further improve weather resistance while maintaining the basic functions of the top coat layer 5, such as scratch resistance and contamination resistance.

If necessary, a polyethylene wax may be added as a lubricant to the top coat layer 15. Here, "polyethylene wax" refers to low-molecular-weight polyethylene having a molecular weight of tens of thousands or less. Also, "wax" refers to "(1) a substance that is solid or semi-solid at room temperature and has a melting point of 40°C or higher, and (2) a substance that melts without decomposition when heated and has low viscosity."
Examples of polyethylene waxes that can be used include the "Sun Wax" series manufactured by Sanyo Chemical Industries, Ltd. and the "Hi Wax" series manufactured by Mitsui Chemicals, Inc. The content of the polyethylene wax in the top coat layer 15 is preferably in the range of 1% by mass to 10% by mass, and more preferably in the range of 3% by mass to 6% by mass, relative to the total mass of the top coat layer 15. If the content of the polyethylene wax is within the above numerical range, it is possible to further improve contamination resistance while maintaining the basic functions of the top coat layer 5, such as scratch resistance.

There are no particular limitations on the method for forming the top coat layer 15. The top coat layer 15 may be formed by applying a coating liquid made from the above-mentioned material by a common method such as gravure coating, microgravure coating, comma coating, knife coating, or die coating, and then curing the coating liquid by a method suited to the material, such as thermal curing or ultraviolet curing.
The top coat layer 15 may also be provided after the pattern layer 12 provided on the substrate layer 11 is bonded to the transparent resin layer 14 via the anchor layer 13 .

The following describes the thickness of each layer constituting the decorative sheet 10 of this embodiment. Considering printing workability, cost, and the like, the thickness of the base layer 11 is preferably in the range of 20 μm to 150 μm, and more preferably in the range of 50 μm to 100 μm.
Similarly, in consideration of printing workability, cost, etc., the thickness of the design layer 12 is preferably in the range of 0.5 μm to 10 μm, more preferably in the range of 1 μm to 5 μm.
Similarly, in consideration of printing workability, cost, and the like, the thickness of the anchor layer 13 is preferably in the range of 1 μm to 20 μm, and more preferably in the range of 1 μm to 3 μm.
Similarly, in consideration of printing workability, cost, and the like, the thickness of the transparent resin layer 14 is preferably in the range of 20 μm to 200 μm, and more preferably in the range of 70 μm to 100 μm.

Similarly, in consideration of printing workability, cost, and the like, the thickness of the top coat layer 15 is preferably in the range of 3 μm to 20 μm, and more preferably in the range of 3 μm to 15 μm.
Furthermore, it is preferable that the total thickness of the decorative sheet 10 be in the range of 45 μm or more and 250 μm or less. If the total thickness of the decorative sheet 10 is less than 45 μm, the strength of the entire decorative sheet 10 will be insufficient, and if the decorative sheet 10 is manufactured in-line, for example, there is a risk that the decorative sheet 10 will be damaged during manufacturing. If the total thickness of the decorative sheet 10 exceeds 250 μm, there is a risk that the flexibility of the entire decorative sheet 10 will decrease, and cracks and whitening will occur in the decorative sheet 10.

[Method of manufacturing decorative sheet]
A method for producing the decorative sheet 10 according to this embodiment will now be briefly described.
First, the design layer 12 is formed on the base layer 11 containing polyolefin.
Next, the anchor layer 13 is formed on the pattern layer 12 .
Next, a transparent resin layer 14 containing polypropylene as a main component is formed on the anchor layer 13 by extrusion molding to a thickness of 70 μm or more and 100 μm or less.
Next, a top coat layer 15 containing an acrylic resin as a main component is formed on the transparent resin layer 14 to a thickness of 3 μm to 15 μm.
The top coat layer 15 contains cyclohexyl methacrylate in an acrylic resin in an amount of 20% by mass or more and 70% by mass or less relative to the mass of the acrylic resin.

In the step of forming the transparent resin layer 14, the surface of the transparent resin layer 14 may be treated so that the wettability index of the surface is 60 dyne or more. The wettability index of the surface of the transparent resin layer 14 can be confirmed using a so-called "wetability reagent."
In addition, in at least one of the steps of forming the anchor layer 13 and forming the topcoat layer 15, each layer may be formed using any one of gravure printing, flexographic printing, and inkjet printing.

Examples based on the present invention will be described below.
Example 1
~Synthesis of acrylic resin emulsion~
In a four-neck flask equipped with a stirrer, a nitrogen inlet tube, and a reflux condenser, 75 g of methyl methacrylate, 10 g of ethyl acrylate, and 15 g of methacrylic acid were used as acrylic monomers, 4 g of a copolymer emulsifier (Aqualon AR-10, manufactured by Dai-ichi Kogyo Seiyaku) as an emulsifier, and 0.25 g of potassium persulfate (manufactured by Kokusan Chemical) as an initiator, and emulsion polymerization was carried out in 350 g of water to obtain a milky-white, translucent, viscous acrylic resin emulsion A with a solids content of approximately 30%.

- Preparation of coating material for top coat layer -
A coating material for the top coat layer was prepared according to the following formulation.
Resin: Acrylic resin emulsion A, 100 parts by mass Hardener: Carbodilite V-02-L2 (manufactured by Nisshinbo Chemical), 5.0 parts by mass

~Creating decorative sheets~
A 55 μm thick polyethylene sheet with opacity was used as the base layer 11, and a 3 μm thick pattern layer 12 was formed on one side of it using a two-component urethane ink (V180, manufactured by Toyo Ink) by gravure printing, and a primer coat composed of the same resin components as the pattern layer 12 was formed on the other side of the base layer 11.
On the surface of this pattern layer 12, a 2 μm thick anchor layer 13 was formed by gravure printing using a dry laminating adhesive (Takelac A540, manufactured by Mitsui Chemicals, Inc.), and on top of this, a 70 μm thick transparent resin layer 14 was formed by extrusion lamination using a polypropylene resin containing 0.5 mass % of a benzophenone-based ultraviolet absorber and 0.5 mass % of a hindered amine-based light stabilizer.
Furthermore, the above-mentioned coating material for the top coat layer was used to form a top coat layer 15 on the transparent resin layer 14 by gravure coating to a thickness of 7 μm, thereby producing the decorative sheet 10 of Example 1.

~Scratch resistance evaluation~
The scratch resistance of the decorative sheet 10 described above was evaluated under the following conditions, and the state of the sample after the test was visually evaluated.
<Test conditions>
- Hoffman scratch test: BYK Hoffman scratch hardness tester - Test conditions: 100 to 1000 g load, in 100 g increments
<Evaluation criteria>
◯: No damage when scratched with a load of 500 g or more Δ: No damage when scratched with a load of 200 to 400 g ×: Damage occurred even when scratched with a load of 100 g In this evaluation, "◯" was considered to be acceptable.

~Weather resistance evaluation~
The weather resistance of the decorative sheet 10 described above was evaluated under the following conditions, and the state of the sample after the test was visually evaluated.
<Test conditions>
・Super xenon test equipment: Toyo Seiki Atlas Weather-O-Meter Ci4000
Test conditions: 180W light irradiation, 12min rainfall/120min cycle Test method: Visually check for changes in appearance of the decorative sheet surface every 50 hours
<Evaluation criteria>
◎: No change in appearance up to 1000 hours. ○: No change in appearance up to 750 hours, then whitening occurred. △: No change in appearance up to 500 hours, then whitening occurred. ×: Whitening occurred within 500 hours. In this evaluation, a rating of "○" or higher was considered to be a pass.

Example 2
The evaluation was carried out in the same manner as in Example 1, except that the coating material for the top coat layer was formulated as follows.
- Preparation of coating material for top coat layer -
A coating material for the top coat layer was prepared according to the following formulation.
Resin: Acrylic resin emulsion A, 100 parts by weight; Hardener: Carbodilite SV-02 (manufactured by Nisshinbo Chemical Co., Ltd.), 10 parts by weight; Gloss adjuster (inorganic particles): Silo Hobic 702 (manufactured by Fuji Silysia Chemical Co., Ltd.), 7 parts by weight

Example 3
The evaluation was carried out in the same manner as in Example 1, except that the coating material for the top coat layer was formulated as follows.
- Preparation of coating material for top coat layer -
A coating material for the top coat layer was prepared according to the following formulation.
Resin: Acrylic resin emulsion A, 100 parts by weight; Curing agent: Carbodilite SV-02 (manufactured by Nisshinbo Chemical), 10 parts by weight; Ultraviolet absorber: Tinuvin 400DW (manufactured by BASF), 5 parts by weight; Light stabilizer: Tinuvin 123DW (manufactured by BASF), 2 parts by weight

Example 4
The evaluation was carried out in the same manner as in Example 1, except that the coating material for the top coat layer was formulated as follows.
- Preparation of coating material for top coat layer -
A coating material for the top coat layer was prepared according to the following formulation.
Resin: Acrylic resin emulsion A, 100 parts by weight; Hardener: Carbodilite SV-02 (manufactured by Nisshinbo Chemical), 10 parts by weight; Lubricant: AQUAMAT 263 (manufactured by BYK-Chemie), 4 parts by weight

Example 5
The evaluation was carried out in the same manner as in Example 1, except that the decorative sheet was prepared according to the following steps.
~Creating decorative sheets~
A 70 μm thick polyethylene sheet with opacity was used as the base layer 11, and a 2 μm thick pattern layer 12 was formed on one side of it using a two-component urethane ink (V180, manufactured by Toyo Ink) by gravure printing, and a primer coat composed of the same resin components as the pattern layer 12 was formed on the other side of the base layer 11.
On the surface of this pattern layer 12, a 3 μm anchor layer 13 was formed by gravure printing using a dry laminating adhesive (Takelac A540, manufactured by Mitsui Chemicals, Inc.), and on top of this, a 70 μm thick transparent resin layer 14 was formed by extrusion lamination using a polypropylene resin containing 0.5 mass % of a benzophenone-based ultraviolet absorber and 0.5 mass % of a hindered amine-based light stabilizer.
Furthermore, the above-mentioned coating material for the top coat layer was used to form a top coat layer 15 on the transparent resin layer 14 by gravure coating to a thickness of 7 μm, thereby producing the decorative sheet 10 of Example 1.

Example 6
The evaluation was carried out in the same manner as in Example 1, except that the coating material for the top coat layer was prepared according to the following formulation and the decorative sheet was prepared according to the following process.
- Preparation of coating material for top coat layer -
A coating material for the top coat layer was prepared according to the following formulation.
Resin: Acrylic resin emulsion A, 100 parts by weight; Curing agent: Carbodilite V-02-L2 (manufactured by Nisshinbo Chemical), 10 parts by weight; Gloss adjuster (inorganic particles): Silohobic 702 (manufactured by Fuji Silysia Chemical), 7 parts by weight; UV absorber: Tinuvin 400DW (manufactured by BASF), 5 parts by weight; Light stabilizer: Tinuvin 123DW (manufactured by BASF), 2 parts by weight; Lubricant: AQUAMAT 263 (manufactured by BYK-Chemie), 4 parts by weight

Example 7
The evaluation was carried out in the same manner as in Example 1, except that the coating material for the top coat layer was formulated as follows.
- Preparation of coating material for top coat layer -
A coating material for the top coat layer was prepared according to the following formulation.
Resin: Acrylic resin emulsion A, 100 parts by weight; Curing agent: Carbodilite SV-02 (manufactured by Nisshinbo Chemical), 10 parts by weight; UV absorber: Tinuvin 400DW (manufactured by BASF), 5 parts by weight; Light stabilizer: Tinuvin 123DW (manufactured by BASF), 2 parts by weight; Gloss adjuster (inorganic particles): Silohobic 702 (manufactured by Fuji Silysia Chemical), 7 parts by weight

~Creating decorative sheets~
A 70 μm thick polyethylene sheet with opacity was used as the base layer 11, and a 2 μm thick pattern layer 12 was formed on one side of it using a two-component urethane ink (V180, manufactured by Toyo Ink) by gravure printing, and a primer coat composed of the same resin components as the pattern layer 12 was formed on the other side of the base layer 11.
On the surface of this pattern layer 12, a 3 μm anchor layer 13 was formed by gravure printing using a dry laminating adhesive (Takelac A540, manufactured by Mitsui Chemicals, Inc.), and on top of this, a 70 μm thick transparent resin layer 14 was formed by extrusion lamination using a polypropylene resin containing 0.5 mass % of a benzophenone-based ultraviolet absorber and 0.5 mass % of a hindered amine-based light stabilizer.
Furthermore, the above-mentioned coating material for the top coat layer was used to form a top coat layer 15 on the transparent resin layer 14 by gravure coating to a thickness of 7 μm, thereby producing the decorative sheet 10 of Example 1.

<Comparative Example 1>
Synthesis of acrylic resin emulsion Evaluation was carried out in the same manner as in Example 1, except that the following formulation was used.
~Synthesis of acrylic resin emulsion~
In a four-neck flask equipped with a stirrer, a nitrogen inlet tube, and a reflux condenser, 50 g of methyl methacrylate, 35 g of ethyl acrylate, and 15 g of methacrylic acid were placed in 350 g of water and emulsion polymerized using 4 g of a copolymer emulsifier (Aqualon AR-10, manufactured by Dai-ichi Kogyo Seiyaku) as an emulsifier, and 0.25 g of potassium persulfate (manufactured by Kokusan Chemical) as an initiator, to obtain a milky-white, translucent, viscous acrylic resin emulsion A with a solids content of approximately 30%.

<Comparative Example 2>
Synthesis of acrylic resin emulsion Evaluation was carried out in the same manner as in Example 1, except that the following formulation was used.
~Synthesis of acrylic resin emulsion~
In a four-neck flask equipped with a stirrer, a nitrogen inlet tube, and a reflux condenser, 85 g of methyl methacrylate, 8 g of ethyl acrylate, and 7 g of methacrylic acid were placed in 350 g of water and emulsion polymerized using 4 g of a copolymer emulsifier (Aqualon AR-10, manufactured by Dai-ichi Kogyo Seiyaku) as an emulsifier, and 0.25 g of potassium persulfate (manufactured by Kokusan Chemical) as an initiator, to obtain a milky-white, translucent, viscous acrylic resin emulsion A with a solids content of approximately 30%.

<Comparative Example 3>
The evaluation was carried out in the same manner as in Example 1, except that an isocyanate-based curing agent (WT30-100, manufactured by Asahi Kasei) was used as the curing agent in the formulation of the coating material for the top coat layer.
<Comparative Example 4>
The evaluation was carried out in the same manner as in Example 1, except that an epoxy-based curing agent (EX-614B, manufactured by Nagase ChemteX) was used as the curing agent in the formulation of the coating material for the top coat layer.

As shown in Table 1, this example produces a decorative sheet with excellent physical properties, including weather resistance and scratch resistance.

10 decorative sheet 11 substrate layer 12 pattern layer 13 anchor layer 14 transparent resin layer 15 top coat layer

Claims (19)

A substrate;
A design layer formed on the substrate;
An anchor coat layer formed on the design layer;
a transparent resin layer formed on the anchor coat layer, the transparent resin layer containing polypropylene as a main component and having a film thickness in the range of 70 μm to 100 μm;
a top coat layer formed on the transparent resin layer, the top coat layer containing, as a main component, an acrylic resin that is a cured product of a composition comprising an acrylic copolymer having a glass transition temperature of 80°C or higher and an acid value of 50 mgKOH/g or higher and a carbodiimide curing agent , and a film thickness in the range of 3 μm to 15 μm;
The decorative sheet is characterized in that the acrylic copolymer is an acrylic copolymer containing only methyl methacrylate, ethyl acrylate, and methacrylic acid as acrylic monomers. The decorative sheet according to claim 1, characterized in that the top coat layer contains silica filler as a gloss adjuster. The decorative sheet according to claim 1 or 2, characterized in that the top coat layer contains, as weather resistance agents, an ultraviolet absorber having a triazine skeleton and a light stabilizer having a NOR skeleton. The decorative sheet according to any one of claims 1 to 3, characterized in that the top coat layer contains a polyethylene wax as a lubricant. The film thickness of the substrate is in the range of 50 μm or more and 100 μm or less,
The film thickness of the pattern layer is in the range of 1 μm or more and 5 μm or less,
5. The decorative sheet according to claim 1, wherein the thickness of the anchor coat layer is in the range of 1 μm or more and 3 μm or less. the acrylic copolymer is crosslinked with a carbodiimide curing agent;
The decorative sheet according to any one of claims 1 to 5, wherein the carbodiimide curing agent has a pH in the range of 8 to 11. the acrylic copolymer is crosslinked with a carbodiimide curing agent;
The decorative sheet according to any one of claims 1 to 6, wherein the carbodiimide curing agent has an NCN equivalent of 385 or 430. The decorative sheet according to claim 2, characterized in that the silica filler has a pore volume of 1 mL/g or more. The decorative sheet according to claim 2, characterized in that the silica filler has an oil absorption capacity of 100 mL to 200 mL/100 g. A method for producing a decorative sheet, comprising laminating a design layer, an anchor coat layer, a transparent resin layer, and a top coat layer on a substrate in at least this order,
the transparent resin layer is formed with polypropylene as a main component and has a film thickness in the range of 70 μm to 100 μm,
The top coat layer is formed of an acrylic resin as a main component and has a film thickness in the range of 3 μm to 15 μm,
the top coat layer is formed from an acrylic copolymer having a glass transition temperature of 80° C. or higher and an acid value of 50 mg KOH/g or higher and a carbodiimide curing agent;
A method for producing a decorative sheet, wherein the acrylic copolymer is an acrylic copolymer containing only methyl methacrylate, ethyl acrylate, and methacrylic acid as acrylic monomers. The method for manufacturing a decorative sheet according to claim 10, characterized in that the top coat layer contains a silica filler as a gloss adjuster. The method for manufacturing a decorative sheet according to either claim 10 or claim 11, characterized in that the top coat layer contains, as weather resistance agents, an ultraviolet absorber having a triazine skeleton and a light stabilizer having a NOR skeleton. The method for manufacturing a decorative sheet according to any one of claims 10 to 12, characterized in that the top coat layer contains a polyethylene wax as a lubricant. The method for manufacturing a decorative sheet according to any one of claims 10 to 13, characterized in that each coating layer is formed by one of gravure printing, flexographic printing, and inkjet printing. The film thickness of the substrate is in the range of 50 μm or more and 100 μm or less,
The film thickness of the pattern layer is in the range of 1 μm or more and 5 μm or less,
The method for producing a decorative sheet according to any one of claims 10 to 14, wherein the film thickness of the anchor coat layer is in the range of 1 µm or more and 3 µm or less. the acrylic copolymer is crosslinked with the carbodiimide curing agent;
The method for producing a decorative sheet according to any one of claims 10 to 15, characterized in that the carbodiimide curing agent has a pH in the range of 8 to 11. the acrylic copolymer is crosslinked with the carbodiimide curing agent;
The method for producing a decorative sheet according to any one of claims 10 to 16, wherein the carbodiimide curing agent has an NCN equivalent of 385 or 430. The method for manufacturing a decorative sheet according to claim 11, characterized in that the silica filler has a pore volume of 1 mL/g or more. The method for manufacturing a decorative sheet according to claim 11, characterized in that the silica filler has an oil absorption capacity of 100 mL to 200 mL/100 g.