JP2024061781A - Decorative sheet and its manufacturing method - Google Patents

Abstract

[Problem] The present invention aims to provide a decorative sheet and a manufacturing method thereof that achieves high concealment, resistance to defects during printing (printing suitability), scratch resistance, smoothness during wrapping (surface uniformity during wrapping), and bending processability. [Solution] The decorative sheet 10 of this embodiment has a base layer 1 having a core layer 1a made of a mixture of inorganic pigment and polypropylene resin, and a skin layer 1b made of polypropylene resin on both sides of the core layer 1a, and a nucleating agent vesicle in which a nano-sized nucleating agent is encapsulated in a vesicle having a single-layer outer membrane is added to the skin layer 1b. The Martens hardness of the skin layer 1b of the base layer 1 is in the range of 50 N/mm2 to 120 N/mm2. The thickness of the base layer 1 is in the range of 40 μm to 200 μm. [Selected Figure] Figure 1

Description

The present invention is a technology related to decorative sheets used for the surface decoration of interior and exterior buildings, fittings, furniture, construction materials, flooring materials, etc., and a method for manufacturing the same.

In recent years, as shown in Patent Document 1, many decorative sheets using olefin resins (e.g., polypropylene sheets) have been proposed as alternatives to decorative sheets made of polyvinyl chloride, which are of concern in terms of environmental protection. By not using vinyl chloride resin, these decorative sheets suppress the generation of toxic gases and the like when incinerated. However, polypropylene sheets generally have issues such as poor scratch resistance due to their low elastic modulus, and being prone to stretching when tension is applied to the sheets when they are created for printing or other purposes.

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

On the other hand, as mentioned above, since the elastic modulus of colored polypropylene film is low, when it is used as a single-layer decorative sheet, it is necessary to make it scratch-resistant and to prevent it from stretching even when tension is applied during processing such as printing. The stretching when tension is applied can be improved in conventional colored polypropylene films by increasing the layer thickness to about 60 μm or more. Furthermore, the scratch resistance can be improved in conventional colored polypropylene films by providing a transparent resin layer made of polypropylene resin or a top coat layer using a urethane-based thermosetting resin made of polyol and isocyanate, as in Patent Documents 2 and 3.

As in Patent Documents 2 and 3, by optimally selecting the polypropylene resin used in the colored polypropylene film, it is possible to improve scratch resistance and elongation during printing. However, while increasing the crystallinity improves the elastic modulus, the breaking stress does not increase commensurately with the elastic modulus, making the film itself more susceptible to tearing, and problems such as breakage during printing. Furthermore, during post-processing as a decorative sheet, particularly bending such as V-cutting, problems such as cracking and whitening at the bent points are more likely to occur.

Furthermore, as mentioned above, the colored polypropylene film is required to have a hiding property, but in the case of an application requiring a high hiding property, the ratio of inorganic pigment to polypropylene resin may need to be increased accordingly. In addition, the hiding property per unit volume of inorganic pigments varies depending on the type, and in particular, in the case of white pigments (titanium dioxide) which have a low hiding property per unit volume, it is difficult to improve the hiding property unless the concentration is made quite high. Thus, in the case of a colored polypropylene film which requires a high hiding property and contains a high concentration of inorganic pigment, the ratio of polypropylene resin is relatively low, so it is difficult to improve the elastic modulus as mentioned above, and the inorganic pigment on the surface of the colored polypropylene film easily peels off, which may cause problems such as surface powdering and reduced interlayer adhesion when a printed layer, a transparent resin layer, and a topcoat layer are laminated.

As mentioned above, decorative sheets are used as decorative boards by attaching them to the surface of a substrate such as a wooden board. For example, when attaching a decorative sheet to a square piece of timber made up of multiple wooden boards by wrapping, the decorative sheet is attached not only to the surface of the wooden boards, but also to their edges. The edges of wooden boards are rougher than the surface, and there are also steps where the boards are joined together, so the decorative sheet is required to be able to follow these irregularities and create an even surface.

Patent No. 3271022 Patent No. 3861472 Japanese Patent No. 3772634

Conventionally, decorative sheets using colored polypropylene film alone or decorative sheets using colored polypropylene film as a base layer are required to achieve both printability (resistance to stretching, etc.) and scratch resistance, bending workability, hiding power, and surface uniformity during wrapping processing.
In order to meet the above requirements, such as printability, scratch resistance, and surface uniformity during wrapping, it is necessary to make the decorative sheet thicker or increase its elastic modulus, but both of these measures result in a deterioration of bending processability, so there is a trade-off.
In addition, in order to achieve high hiding power, it is necessary to increase the concentration of inorganic pigments, but in this case, it is difficult to improve the elastic modulus, which may make it difficult to improve scratch resistance. Furthermore, powdering may occur on the surface of the base layer, and interlayer adhesion may decrease.

The present invention has been made with a focus on the above points, and aims to provide a decorative sheet using a colored polypropylene film alone that combines printability, scratch resistance, concealment, surface uniformity during wrapping, and bending workability, a decorative sheet with a colored polypropylene film as a base layer, or a method for manufacturing such a decorative sheet.

The inventors have found that by encapsulating a nucleating agent that improves the crystallinity of polypropylene in a vesicle with a single-layer outer membrane to form a vesicle and adding the nucleating agent vesicle to a polypropylene resin, and by further examining and experimenting the manufacturing process in various ways and setting the Martens hardness in the optimal range, it is possible to provide a decorative sheet and a manufacturing method thereof that improves on the above-mentioned problems.

In order to achieve the object, a decorative sheet according to one embodiment of the present invention comprises a base layer having a core layer containing an inorganic pigment and a polypropylene resin, and a skin layer containing a polypropylene resin formed on at least one side of the core layer, the skin layer being formed by adding nucleating agent vesicles having a nano-sized nucleating agent encapsulated in a vesicle having a single-layer outer membrane, the Martens hardness of the skin layer being in the range of 50 N/mm2 ^or more and 120 N/ ^mm2 or less, and the thickness of the base layer being in the range of 40 μm or more and 200 μm or less.

When at least one of a transparent resin layer and a top coat layer is laminated on one side of the base layer, for example, the side of the base layer on which the core layer is formed, it is preferable that the total thickness of the decorative sheet is 100 μm or more and 250 μm or less.
Here, the nucleating agent vesicle is a capsule-like vesicle having a single-layer outer membrane and encapsulating a nucleating agent, and can be prepared, for example, by supercritical reverse phase evaporation. The nucleating agent is a substance that serves as a starting point for crystallization in a crystalline polypropylene resin.

According to one aspect of the present invention, a nucleating agent that improves the crystallinity of polypropylene is converted into a vesicle and added as a nucleating agent vesicle, and the Martens hardness, layer structure, and film thickness are optimized to provide a decorative sheet that is suitable for printing (e.g., resistance to stretching), scratch resistance, hiding power, and both surface uniformity and bending processability during wrapping processing.

1 is a cross-sectional view showing a configuration of a decorative sheet according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing the configuration of another decorative sheet according to an embodiment of the present invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
Here, the drawings are schematic, and the relationship between thickness and planar dimensions, the thickness ratio of each layer, etc. differ from the actual ones. Furthermore, the embodiments shown below are merely examples of configurations for embodying the technical idea of the present invention, and the technical idea of the present invention does not specify the materials, shapes, structures, etc. of the components to those described below. The technical idea of the present invention can be modified in various ways within the technical scope defined by the claims.

"composition"
The decorative sheet 10 of the embodiment shown in FIG. 1 is an example of a single-layer structure having only a base layer 1 (base fabric layer).
The base layer 1 of this embodiment is composed of a colored polypropylene film including a skin layer 1b and a core layer 1a, as shown in Fig. 1. The core layer 1a of the base layer 1 is a layer made of polypropylene resin mixed with an inorganic pigment for coloring. The skin layer 1b of the base layer 1 is made of polypropylene resin and contains a nano-sized nucleating agent. In this embodiment, the nucleating agent is added to the polypropylene resin in the state of a nucleating agent vesicle that is encapsulated in an outer membrane and turned into a vesicle.
The skin layer 1b has a Martens hardness in the range of 50 N/mm2 ^or more and 120 N/ ^mm2 or less, and the substrate layer 1 has a thickness in the range of 40 μm or more and 200 μm or less.

The amount of the nucleating agent vesicle added is preferably within a range of 0.05 parts by mass or more and 0.5 parts by mass or less, calculated as the nucleating agent in the nucleating agent vesicle, per 100 parts by mass of the polypropylene resin. The nucleating agent vesicle is preferably a nucleating agent liposome having an outer membrane containing a phospholipid.
If necessary, a pattern layer 2 may be formed (laminated) on one surface of the base layer 1 to improve the design.
The decorative sheet 10 may also have at least one of a transparent resin layer 3 and a topcoat layer 4 laminated on one surface of the base layer 1. The decorative sheet 10 illustrated in Fig. 2 is an example in which a pattern layer 2, a transparent resin layer 3, and a topcoat layer 4 are laminated in this order on one surface of the decorative sheet 10. Either the transparent resin layer 3 or the topcoat layer 4 may be omitted. The pattern layer 2 may also be omitted.

However, when the decorative sheet 10 of this embodiment is provided with the transparent resin layer 3 and the topcoat layer 4, it is preferable to design the total thickness to be within the range of 100 μm to 250 μm. If the total thickness of the decorative sheet 10 is less than 100 μm, the strength of the decorative sheet 10 as a whole is insufficient, which may cause problems with smoothness during wrapping. If the total thickness of the decorative sheet 10 is more than 250 μm, the strength of the decorative sheet 10 as a whole is too high, which may cause problems during bending.

When the transparent resin layer 3 and the top coat layer 4 are provided, for example, the thickness of the base material layer 1 may be 140 μm, the thickness of the transparent resin layer 3 may be 95 μm, and the thickness of the top coat layer 4 may be 15 μm. Here, among the base material layer 1, the pattern layer 2, the transparent resin layer 3, and the top coat layer 4, the pattern layer 2 has a thin layer thickness, so the thickness of the pattern layer 2 may be ignored and the total thickness of the entire decorative sheet 10 may be designed to be within the range of 100 μm to 250 μm.
Depending on design requirements, at least one of the transparent resin layer 3 and the top coat layer 4 may be provided with an uneven shape by embossing. Furthermore, depending on requirements such as scratch resistance, at least one of the transparent resin layer 3 and the top coat layer 4 may be laminated in a plurality of layers, and other known layers may be arranged.

1 and 2, the symbol B represents a substrate. The substrate B is a substrate to which the decorative sheet 10 is attached. The substrate B is not particularly limited, but examples thereof include wood boards, inorganic boards, metal plates, and composite boards made of multiple materials. In addition, a primer layer, a concealing layer, or the like may be provided between the decorative sheet 10 and the substrate B as appropriate.
The tensile modulus of the decorative sheet 10 of this embodiment, particularly the tensile modulus of the base material layer 1 alone, is preferably in the range of 700 MPa to 2000 MPa. If the tensile modulus is less than 700 MPa, defects during printing may not be suppressed, or surface smoothness during wrapping may not be maintained. If the tensile modulus exceeds 2000 MPa, the crystallinity is too high, so even if a nucleating agent vesicle is used, defects such as whitening and cracking may occur during bending. The preferred range of the tensile modulus is 1000 MPa to 1800 MPa. By setting the tensile modulus within this range, defects during printing, scratch resistance, surface smoothness during wrapping, and bending can all be achieved in excellent conditions.

Next, each layer constituting the decorative sheet 10 will be described.
<Base layer 1>
The base layer 1 is a three-layer colored polypropylene film with a core layer 1a and skin layers 1b on both sides. The core layer 1a is made mainly of polypropylene resin, which is colored by mixing inorganic pigments into the polypropylene resin. The skin layer 1b is made of polypropylene resin and does not contain inorganic pigments.
Furthermore, in order to increase crystallinity, a nano-sized nucleating agent is added to the skin layer 1b of the base layer 1. In this embodiment, the nano-sized nucleating agent is added in the form of nucleating agent vesicles.

(Polypropylene resin)
The polypropylene resin used for the core layer 1a is preferably a highly flexible random polypropylene resin having an ethylene content, or a mixture of a known amorphous polypropylene resin with a random polypropylene resin or a homopolypropylene resin with high crystallinity, taking into consideration the dispersibility of the inorganic pigment.
The polypropylene resin used for the skin layer 1b is preferably a highly crystalline homopolypropylene because it is not necessary to consider the dispersibility of inorganic pigments, but is not limited to a highly crystalline homopolypropylene. In applications where processability such as bending is more important, for example, a random polypropylene resin having an ethylene content within a certain range or a known amorphous polypropylene resin can be mixed with the highly crystalline homopolypropylene.
The skin layer 1b of the base layer 1 made of a colored polypropylene film has a Martens hardness adjusted to be within the range of 50 N/mm2 or ^more and 120 N/ ^mm2 or less.

If the Martens hardness is ^less than 50 N/mm2, the surface may not be smooth during wrapping, problems during printing may not be suppressed, or it may be difficult to ensure scratch resistance required for practical use. On the other hand, if the Martens hardness is more than 120 N/ ^mm2 , the crystallinity is too high, and even if a nucleating agent vesicle is used, problems such as whitening and cracking may occur during bending.
The Martens hardness of the skin layer 1b of the base layer 1 is preferably in the range of 80 N/ ^mm2 to 100 N/ ^mm2 . By setting the Martens hardness of the skin layer 1b within this range, defects during printing, surface smoothness during wrapping, scratch resistance, and bending can be all excellently achieved.

Here, Martens hardness is a kind of index showing the hardness (hardness) of a substance, and is defined as the quotient of the indentation force calculated from the load and the surface area of the indentation calculated from the indentation depth, which is calculated by applying a load to an indenter and pressing it into the surface of a sample, and measuring the depth (indentation depth) of the indentation (impression) formed at that time. The measurement is performed according to the method specified in ISO14577.
It is also important that the thickness of the base layer 1 made of a colored polypropylene film is within the range of 40 μm or more and 200 μm or less.

If the thickness of the base layer 1 is less than 40 μm, even if the Martens hardness of the skin layer 1b is in the optimal range, the film strength is insufficient, making it difficult to suppress defects during printing and deterioration of scratch resistance, and also difficult to maintain surface smoothness during wrapping. On the other hand, if the thickness of the base layer 1 is more than 200 μm, there is a high possibility that defects such as whitening and cracking will occur during bending, and during wrapping, the ability to follow the edge surface and laminated parts of the wood substrate will be significantly deteriorated, and the adhesive strength will be insufficient, which may cause defects such as peeling over time.
A more preferable range of the thickness of the base layer 1 is 60 μm or more and 150 μm or less. If the thickness of the base layer 1 is within this range, defects during printing processing, surface smoothness during wrapping processing, scratch resistance, and bending processing can be achieved with a sufficient margin.

Regarding the thickness of the skin layer 1b and the core layer 1a of the base layer 1, it is preferable that the thickness of the core layer 1a is in the range of 3 to 50 times the thickness of one of the skin layers 1b, and it is more preferable that the thickness of the core layer 1a is in the range of 3 to 50 times the thickness of both skin layers 1b. If the thickness of the core layer 1a is less than 3 times the thickness of the skin layer 1b, it is difficult to satisfy the minimum required concealment property as a decorative sheet 10. If the thickness of the core layer 1a is more than 50 times the thickness of the skin layer 1b, the thickness of the skin layer 1b becomes relatively small (thin), so the film strength is insufficient, and even if the Martens hardness is in the optimal range, it is difficult to suppress defects during printing processing and deterioration of scratch resistance.
The thickness of the core layer 1a is more preferably in the range of 10 to 40 times the thickness of the skin layer 1b. By setting the thickness of the core layer 1a within this range, it is possible to achieve a sufficient balance between the hiding power, defects during printing processing, surface smoothness during wrapping processing, scratch resistance, and bending processability.

In this embodiment, it is preferable to use a polypropylene resin having high crystallinity as the polypropylene resin used for the skin layer 1b. In particular, it is preferable to use a highly crystalline homopolypropylene resin, which is a propylene homopolymer having an isotactic pentad fraction (mmmm fraction) of 95% or more, in an amount of 30% by mass to 100% by mass based on the mass of the total polypropylene resin.
The crystallization temperature of polypropylene resin is generally within the range of 100 to 130° C., and when a nucleating agent is added, it is within the range of 110 to 140° C. The decorative sheet 10 of this embodiment
In the skin layer 1b of the colored polypropylene film in the above, the cooling time from the crystallization temperature to the curing completion temperature is controlled by a known cooling process, thereby adjusting the Martens hardness to within the range of 50 N/ ^mm2 to 120 N/ ^mm2 . In addition, when the highly crystalline homopolypropylene resin is less than 30% by mass, the crystallinity is insufficient, and the Martens hardness may be lower than the suitable range even if the cooling process is controlled.

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

(Inorganic pigments)
The inorganic pigment may be a known inorganic pigment, typically titanium oxide, for imparting hiding power. Examples of inorganic pigments for coloring include iron-zinc, chromium-antimony, iron-aluminum composite oxides, and iron oxide, and the like, and the blending ratio of these can be freely adjusted according to the desired color. In addition, lustrous materials such as aluminum flakes and pearl pigments can also be added as inorganic pigments. In addition, organic pigments such as carbon black may also be used in combination as inorganic pigments.
Furthermore, additives such as fatty acid metal salts may be added to improve dispersibility and extrudability.

(Nucleating Agent Vesicles)
In addition, the skin layer 1b of the base layer 1 contains a nano-sized nucleating agent. The nano-sized nucleating agent is added to the polypropylene resin in the form of a nucleating agent vesicle encapsulated in a vesicle having an outer membrane of a single layer membrane and used. Since the skin layer 1b of the base layer 1 contains a nucleating agent, the crystallization degree can be improved, and the scratch resistance (scratch resistance) of the base layer 1 can be improved. In this embodiment, the nucleating agent in the resin constituting the skin layer 1b of the base layer 1 may be encapsulated in a vesicle with a part of the nucleating agent exposed.
It is preferable that the average particle size of the nano-sized nucleating agent is 1/2 or less of the wavelength range of visible light. Specifically, since the wavelength range of visible light is within the range of 400 nm or more and 750 nm or less, it is preferable that the average particle size is 375 nm or less.

Nano-sized nucleating agents have extremely small particle sizes, so the number of nucleating agents present per unit volume and their surface area increase inversely proportional to the cube of the particle diameter. As a result, the distance between each nucleating agent particle becomes closer, so that when crystal growth occurs from the surface of one nucleating agent particle added to the polypropylene resin, the end from which the crystal is growing immediately comes into contact with the end of the crystal growing from the surface of another nucleating agent particle adjacent to the one nucleating agent particle, and the ends of the crystals inhibit each other's growth, stopping the growth of each crystal. For this reason, the average particle size of the spherulites in the crystalline part of the crystalline polypropylene resin can be reduced, for example, the spherulite size can be reduced to 1 μm or less. As a result, a colored polypropylene film with high crystallinity and high hardness can be obtained, and the stress concentration between the spherulites that occurs during bending processing can be efficiently dispersed, thereby realizing a colored polypropylene film that suppresses cracking and whitening during bending processing.

Here, when the nucleating agent is simply added, the particle size of the nucleating agent in the polypropylene resin increases due to secondary aggregation, and the number of crystal nuclei relative to the amount of nucleating agent added may be significantly smaller than when the nucleating agent is added as a vesicle. As a result, the average particle size of the spherulites in the crystalline portion of the polypropylene resin becomes large, and cracking and whitening during bending may not be suppressed. Therefore, it may not be possible to improve the elastic modulus and processability by increasing the crystallinity at the same time.

In the skin layer 1b of the base layer 1 made of a colored polypropylene film constituting the decorative sheet 10 of this embodiment, nucleating agent vesicles are preferably added in an amount of 0.05 to 0.5 parts by mass, calculated as the amount of nucleating agent added, per 100 parts by mass of polypropylene resin as the main component, and more preferably in an amount of 0.1 to 0.3 parts by mass. If the amount of nucleating agent vesicles added is less than 0.05 parts by mass, the crystallinity may not be sufficiently improved and the required elastic modulus (hardness) may not be reached. In addition, if the amount of nucleating agent vesicles added is more than 0.5 parts by mass, spherulite growth may be inhibited due to an excess of crystal nuclei, and as a result, the crystallinity may not be sufficiently improved and the required elastic modulus (hardness) may not be reached.

As a method for nano-sizing the nucleating agent, for example, a solid-phase method in which the nucleating agent is mainly mechanically pulverized to obtain nano-sized particles, a liquid-phase method in which nano-sized particles are synthesized or crystallized in a solution in which the nucleating agent or nucleating agent is dissolved, and a gas-phase method in which nano-sized particles are synthesized or crystallized from a nucleating agent or a gas or vapor containing the nucleating agent can be appropriately used. Examples of solid-phase methods include ball mills, bead mills, rod mills, colloid mills, conical mills, disk mills, hammer mills, and jet mills. Examples of liquid-phase methods include crystallization methods, co-precipitation methods, sol-gel methods, liquid-phase reduction methods, and hydrothermal synthesis methods. Examples of gas-phase methods include electric furnace methods, chemical flame methods, laser methods, and thermal plasma methods.

The preferred method for nano-sizing a nucleating agent is supercritical reverse phase evaporation. Supercritical reverse phase evaporation is a method for producing capsules (nano-sized vesicles) encapsulating a target substance using carbon dioxide in a supercritical state or under temperature or pressure conditions above the critical point. Carbon dioxide in a supercritical state refers to carbon dioxide in a supercritical state above the critical temperature (30.98°C) and critical pressure (7.3773±0.0030 MPa), and carbon dioxide under temperature or pressure conditions above the critical point refers to carbon dioxide under conditions where only the temperature or only the pressure exceeds the critical conditions.

In addition, as a specific nano-processing method using the supercritical reverse phase evaporation method, first, an aqueous phase is injected into a mixed fluid of supercritical carbon dioxide, phospholipids as an outer membrane forming substance, and a nucleating agent as an encapsulating substance, and an emulsion of supercritical carbon dioxide and aqueous phase is generated by stirring. Next, the pressure is reduced, and the carbon dioxide expands and evaporates, causing a phase inversion, and nanocapsules (nanovesicles) are generated in which the phospholipids cover the surface of the nucleating agent particles with a single layer membrane. By using this supercritical reverse phase evaporation method, unlike the conventional encapsulation method in which the outer membrane on the surface of the nucleating agent particles becomes multiple membranes, it is possible to easily generate capsules with a single layer membrane, and therefore to prepare capsules with a smaller diameter.
The nucleating agent vesicle can be prepared by, for example, the Bangham method, the extrusion method, the hydration method, the surfactant dialysis method, the reverse phase evaporation method, the freeze-thaw method, the supercritical reverse phase evaporation method, etc. Among these, the supercritical reverse phase evaporation method is particularly preferred.

The outer membrane constituting the nucleating agent vesicle is, for example, composed of a monolayer membrane, and the outer membrane is composed of a substance containing a biological lipid such as a phospholipid.
In this embodiment, a nucleating vesicle whose outer membrane is composed of a material containing a biological lipid such as a phospholipid is referred to as a nucleating liposome.
Examples of phospholipids constituting the outer membrane include glycerophospholipids such as phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, phosphatidic acid, phosphatidylglycerol, phosphatidylinositol, cardiopin, yolk egg lecithin, hydrogenated yolk egg lecithin, soybean lecithin, and hydrogenated soybean lecithin; and sphingophospholipids such as sphingomyelin, ceramide phosphorylethanolamine, and ceramide phosphorylglycerol.

Other substances that form the outer membrane of the vesicle include dispersants such as nonionic surfactants and mixtures of these with cholesterols or triacylglycerol. Among these, examples of nonionic surfactants that can be used include one or more of the following: polyglycerin ether, dialkylglycerin, polyoxyethylene hydrogenated castor oil, polyoxyethylene alkyl ether, polyoxyethylene sorbitan fatty acid ester, sorbitan fatty acid ester, polyoxyethylene polyoxypropylene copolymer, polybutadiene-polyoxyethylene copolymer, polybutadiene-poly 2-vinylpyridine, polystyrene-polyacrylic acid copolymer, polyethylene oxide-polyethylethylene copolymer, polyoxyethylene-polycaprolactam copolymer, etc. Examples of cholesterols that can be used include cholesterol, α-cholestanol, β-cholestanol, cholestane, desmosterol (5,24-cholestadiene-3β-ol), sodium cholate, cholecalciferol, etc.

The outer membrane of the liposome may be formed from a mixture of phospholipids and a dispersant. In the decorative sheet 10 of this embodiment, it is preferable that the nucleating agent vesicle is a radical scavenger liposome having an outer membrane containing phospholipids, and by forming the outer membrane from phospholipids, it is possible to improve the compatibility between the vesicle and the resin material that is the main component of the base layer 1.

The nucleating agent is not particularly limited as long as it is a substance that serves as a starting point for crystallization when the resin crystallizes. Examples of nucleating agents include metal salts of phosphate esters, metal salts of benzoic acid, metal salts of pimelic acid, metal salts of rosin, benzylidene sorbitol, quinacridone, cyanine blue, and talc. In particular, in order to maximize the effect of the nano-processing, it is preferable to use metal salts of phosphate esters, metal salts of benzoic acid, metal salts of pimelic acid, and metal salts of rosin, which are non-melting types and can be expected to have good transparency, but if the material itself can be made transparent by the nano-processing, colored quinacridone, cyanine blue, talc, etc. can also be used. In addition, melting benzylidene sorbitol may be appropriately mixed with a non-melting nucleating agent.

As described above, one of the features (invention specific matters) of the decorative sheet 10 of this embodiment is that "the skin layer 1b of the base layer 1 contains a nucleating agent encapsulated in a vesicle." By adding the nucleating agent encapsulated in a vesicle to the resin composition, the effect of dramatically improving the dispersibility of the nucleating agent in the resin material, i.e., in the skin layer 1b of the base layer 1 is achieved, but it is assumed that there are cases in which it is difficult to directly specify this feature in the structure or characteristics of the object in the completed decorative sheet 10, depending on the situation, and it can be said to be impractical. The reason is as follows. The nucleating agent added in the form of a vesicle is in a dispersed state with high dispersibility, and the nucleating agent is highly dispersed in the skin layer 1b of the base layer 1 even in the state of the produced decorative sheet 10. However, in the process of producing the decorative sheet 10 after the nucleating agent is added in the form of a vesicle to the resin composition constituting the skin layer 1b of the base layer 1 to produce the base layer 1, various treatments such as compression treatment and hardening treatment are usually performed on the laminate, but such treatments may cause the outer membrane of the vesicle containing the nucleating agent to be crushed or chemically reacted, and the nucleating agent is likely not enclosed (enveloped) by the outer membrane, and the state in which the outer membrane is crushed or chemically reacted varies depending on the treatment process of the decorative sheet 10. In a situation in which the nucleating agent is not enclosed by the outer membrane, it is difficult to specify the physical properties themselves in a numerical range, and it is also assumed that it may be difficult to determine whether the constituent material of the crushed outer membrane is the outer membrane of the vesicle or a material added separately from the nucleating agent. Thus, although this embodiment differs from the prior art in that the nucleating agent is highly dispersed in the base layer 1, it is conceivable that there may be cases in which it is impractical to determine within a numerical range the structure and characteristics of the decorative sheet 10 obtained by analyzing the same based on measurements, whether this is because the nucleating agent is added in the form of vesicles encapsulating the nucleating agent.
Here, the nucleating agent vesicle having the above-mentioned structure may also be contained in the transparent resin layer 3 .

(Pattern layer 2)
A pattern layer 2 can be provided on the surface of the colored polypropylene film (base layer 1) to impart a pattern to the decorative sheet 10. Examples of the pattern that can be used include wood grain, stone grain, sand grain, tiled, brickwork, fabric, leather, and geometric shapes.
Furthermore, a base solid ink layer (not shown) may be provided between the base layer 1 and the pattern layer 2 depending on the level of the desired design. The base solid ink layer is provided so as to cover the entire surface of the base layer 1. The base solid ink layer may be multi-layered, having two or more layers, as necessary for hiding properties, etc. Furthermore, the pattern layer 2 may be formed by laminating as many plates as necessary to express the desired design. In this way, the pattern layer 2 and the base solid ink layer may be combined in various ways depending on the desired design, that is, the design to be expressed, but are not particularly limited.

The materials constituting the base solid ink layer and the pattern layer 2 are not particularly limited. For example, printing inks or coating agents obtained by dissolving or dispersing a matrix and a colorant such as a dye or pigment in a solvent can be used. As the matrix, for example, various synthetic resins such as oil-based nitrocellulose resin, two-liquid type urethane resin, acrylic resin, styrene resin, polyester resin, urethane resin, polyvinyl resin, alkyd resin, epoxy resin, melamine resin, fluorine resin, silicone resin, and rubber resin, or mixtures or copolymers thereof can be used. In addition, as the colorant, for example, inorganic pigments such as carbon black, titanium white, zinc oxide, red oxide, yellow lead, Prussian blue, and cadmium red, organic pigments such as azo pigments, lake pigments, anthraquinone pigments, phthalocyanine pigments, isoindolinone pigments, and dioxazine pigments, or mixtures thereof can be used. Examples of the solvent that can be used include toluene, xylene, ethyl acetate, butyl acetate, methyl alcohol, ethyl alcohol, isopropyl alcohol, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, water, and mixtures thereof.

In addition, functional additives such as extender pigments, plasticizers, dispersants, surfactants, tackifiers, adhesion aids, drying agents, hardeners, hardening accelerators, and hardening retarders may be added to the base solid ink layer and the pattern layer 2 in order to impart various functions.
Here, the base solid ink layer and the design layer 2 can be formed by various printing methods such as gravure printing, offset printing, screen printing, electrostatic printing, inkjet printing, etc. In addition, since the base solid ink layer covers the entire surface of the base layer 1, it can also be formed by various coating methods such as roll coating, knife coating, microgravure coating, die coating, etc. These printing and coating methods may be selected separately depending on the layer to be formed, but it is more efficient to select the same method and process them all at once.

(Transparent resin layer 3)
The resin material used as the main component of the transparent resin layer 3 is preferably made of an olefin-based resin, and in addition to polypropylene, polyethylene, polybutene, etc., α-olefins (e.g., propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicosene, 3-methyl-1-butene, 3-methyl-1-pentene, 3-ethyl-1-pentene, 4-methyl-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-pent ... Examples of such copolymers include those obtained by homopolymerizing or copolymerizing two or more of α-olefins such as ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, ethylene-methyl methacrylate copolymer, ethylene-ethyl methacrylate copolymer, ethylene-butyl methacrylate copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-butyl acrylate copolymer, etc. In addition, when it is intended to improve the surface strength of the decorative sheet 10, it is preferable to use a highly crystalline polypropylene resin as in the skin layer 1b of the base layer 1.
In this embodiment, the term "main component" refers to 90% by mass or more of the target material unless otherwise specified.

When the transparent resin layer 3 is provided, the thickness of the transparent resin layer 3 is preferably within a range of 50 μm to 100 μm. When the thickness of the transparent resin layer 3 is less than 50 μm, the effect of improving the scratch resistance of the surface of the transparent resin layer 3 is low, and there is a possibility that the purpose of providing the transparent resin layer 3 is reduced. When the thickness of the transparent resin layer 3 is more than 100 μm, problems such as whitening and cracking during bending may occur.
However, when the topcoat layer 4 is provided on the transparent resin layer 3, the thickness of the transparent resin layer 3 may be less than 50 μm.
In addition, the resin composition constituting the transparent resin layer 3 may contain various functional additives such as a heat stabilizer, a light stabilizer, an antiblocking agent, a catalyst trap, a colorant, a light scattering agent, and a gloss adjuster, if necessary. These various functional additives can be appropriately selected from well-known additives.

(Topcoat layer 4)
When further improvement in scratch resistance or adjustment of gloss is required, a top coat layer 4 can be provided on the surface of the transparent resin layer 3 .
The resin material as the main component of the topcoat layer 4 can be appropriately selected from polyurethane, acrylic silicone, fluorine, epoxy, vinyl, polyester, melamine, aminoalkyd, urea, and other resin materials. The form of the resin material is not particularly limited, and may be water-based, emulsion, solvent-based, or the like. The curing method may be appropriately selected from one-liquid type, two-liquid type, ultraviolet curing method, or the like.

As the resin material used as the main component of the topcoat layer 4, a urethane-based material using isocyanate is suitable from the viewpoints of workability, cost, cohesive strength of the resin itself, etc. As the isocyanate, for example, a curing agent such as an adduct, a biuret, or an isocyanurate, which is a derivative of tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), hexamethylene diisocyanate (HMDI), diphenylmethane diisocyanate (MDI), lysine diisocyanate (LDI), isophorone diisocyanate (IPDI), bis(isocyanatemethyl)cyclohexane (HXDI), trimethylhexamethylene diisocyanate (TMDI), etc., can be appropriately selected and used, but in consideration of weather resistance, a curing agent based on hexamethylene diisocyanate (HMDI) or isophorone diisocyanate (IPDI) having a linear molecular structure is suitable. In addition, when improving the surface hardness, it is preferable to use a resin that is cured by active energy rays such as ultraviolet rays and electron beams. These resins can be used in combination with each other, and for example, by using a hybrid type of a thermosetting type and a photosetting type, it is possible to improve the surface hardness, suppress the cure shrinkage, and improve the adhesion.

A gloss regulator can be added to the topcoat layer 4 to adjust the gloss. The gloss regulator may be a known, commercially available product. For example, fine particles made of inorganic materials such as silica, glass, alumina, calcium carbonate, barium sulfate, etc. may be used. Alternatively, fine particles made of organic materials such as acrylic may be used. However, when high transparency is required, it is desirable to use fine particles of highly transparent silica, glass, acrylic, etc. In particular, among fine particles such as silica and glass, gloss regulators that are not solid spherical particles but have a low bulk density formed by secondary aggregation of fine primary particles have a high matting effect relative to the amount added. Therefore, by using such gloss regulators, the amount of gloss regulator added can be reduced.

In order to impart various functions to the topcoat layer 4, functional additives such as antibacterial agents and antifungal agents may be added. Also, an ultraviolet absorber and a light stabilizer may be added as necessary. As the ultraviolet absorber, for example, a benzotriazole-based, benzoate-based, benzophenone-based, triazine-based, or cyanoacrylate-based agent may be used. As the light stabilizer, a hindered amine-based agent may be used.
The thickness of the topcoat layer 4 is preferably in the range of 3 μm to 15 μm. If the thickness of the topcoat layer 4 is less than 3 μm, the effect of improving scratch resistance is low, and there is a possibility that the purpose of providing the topcoat layer 4 is reduced. If the thickness of the topcoat layer 4 exceeds 15 μm, cracks or breaks may occur during bending, which may cause design problems or problems of deteriorated weather resistance.

<Production Method>
A manufacturing example of the decorative sheet 10 will be described.
A nucleating agent vesicle is prepared by encapsulating a nucleating agent in a vesicle, and the prepared nucleating agent vesicle is added to a polypropylene resin to prepare a resin material for a skin layer. Also, an inorganic pigment is added to the polypropylene resin to prepare a resin material for a core layer.
The nucleating agent vesicle is prepared, for example, by encapsulating the nucleating agent in a vesicle having a monolayer membrane by supercritical reverse phase evaporation to form a vesicle.

The polypropylene resin used for the skin layer 1b is preferably a highly crystalline homopolypropylene resin having an isotactic pentad fraction (mmmm fraction) of 95% or more in the range of 30% by mass to 100% by mass.
The above-mentioned resin materials for the base layer are individually heated and melted, and then molded into a sheet having a thickness in the range of 40 μm to 200 μm by extrusion molding or the like to form the base layer 1 .
The skin layer 1b and the core layer 1a can be molded separately and then bonded together, for example, using dry lamination to produce the base layer 1. However, it is simpler and more productive to merge the molten resins in a T-die or a feed block before the T-die during extrusion molding and produce the base layer 1 by co-extrusion molding.

At this time, the Martens hardness of the skin layer 1b of the base layer 1 is controlled within the range of 50 N/ ^mm2 or more and 120 N/ ^mm2 or less by adjusting the cooling time from the crystallization temperature to the hardening completion temperature using a known adjustment method.
Furthermore, if necessary, a design layer 2 is formed on the upper surface of the base layer 1 by printing, and at least one of a transparent resin layer 3 and a top coat layer 4 is formed thereon by printing.
In this case, it is preferable that the thickness of the transparent resin layer 3 is within the range of 50 μm or more and 100 μm or less, the thickness of the topcoat layer 4 is within the range of 3 μm or more and 15 μm or less, and the total thickness of the decorative sheet 10 is within the range of 100 μm or more and 250 μm or less.

<Actions and other details>
(1) The decorative sheet 10 of this embodiment has a base layer 1 made of a colored polypropylene film having a core layer 1a formed by mixing an inorganic pigment into polypropylene resin, and skin layers 1b made of polypropylene resin on both sides of the core layer 1a, and the skin layer 1b of the base layer 1 is formed by incorporating a nano-sized nucleating agent into polypropylene resin, and the nucleating agent is added in the form of nucleating agent vesicles that are encapsulated in an outer membrane, the skin layer 1b of the base layer 1 has a Martens hardness in the range of 50 N/ ^mm2 or more and 120 N/ ^mm2 or less, and the thickness of the base layer 1 is in the range of 40 μm or more and 200 μm or less.
According to this configuration, a nucleating agent that improves the crystallinity of polypropylene is vesiculated and added as a nucleating agent vesicle, and the Martens hardness and film thickness are further optimized to provide a decorative sheet 10 that has both printability (resistance to stretching, etc.), surface smoothness during wrapping processing, and scratch resistance and bending processability.

(2) In the decorative sheet 10 of this embodiment, the thickness of the core layer 1a is preferably in the range of 3 to 50 times the thickness of at least one of the skin layers 1b of the base layer 1.
According to this configuration, it is possible to achieve a sufficient balance between printability (resistance to stretching, etc.), surface smoothness during wrapping, scratch resistance, high hiding power and bending processability.
(3) In the decorative sheet 10 of this embodiment, it is preferable that the amount of nucleating agent vesicle added to the skin layer 1b of the base material layer 1 is within the range of 0.05 parts by mass or more and 0.5 parts by mass or less, calculated as the nucleating agent in the nucleating agent vesicle, per 100 parts by mass of polypropylene resin.
According to this configuration, the degree of crystallinity of the polypropylene resin constituting the skin layer 1b of the base material layer 1 is sufficiently improved, and the necessary elastic modulus (hardness) can be reliably ensured.

(4) In the decorative sheet 10 of this embodiment, the nucleating agent vesicle is preferably a nucleating agent liposome having an outer membrane containing phospholipids.
This configuration can improve the compatibility between the resin material, which is the main component of the base layer 1, and the vesicles.
(5) In the decorative sheet 10 of this embodiment, it is preferable that the design layer 2 is laminated on one surface of the base layer 1, for example, on the surface of the base layer 1 on which the skin layer 1b is formed.
According to this configuration, the design of the decorative sheet 10 can be improved.

(6) In the decorative sheet 10 of this embodiment, at least one of a transparent resin layer 3 and a top coat layer 4 is laminated on one side of the base layer 1, for example, the side of the base layer 1 on which the skin layer 1b is formed, and it is preferable that the total thickness of the decorative sheet 10 is in the range of 100 μm or more and 250 μm or less.
With this configuration, the ability to conform to the edge faces and layered portions of the wood substrate during wrapping processing becomes significantly poor, resulting in insufficient adhesive strength, which can prevent problems such as peeling over time.

"Variations"
In this embodiment, as shown in Fig. 1, the case where the skin layer 1b is formed on both sides of the core layer 1a has been described, but the present invention is not limited to this. For example, the skin layer 1b formed on the surface of the base layer 1 on the base slope B side does not have to be formed. Even in a form that does not include the skin layer 1b formed on the surface of the base layer 1 on the base slope B side, the above-mentioned effects can be obtained.
In addition, the thickness of the skin layer 1b formed on both sides of the substrate layer 1 (core layer 1a) may be different from each other. Specifically, the thickness of the skin layer 1b formed on the surface of the substrate layer 1 may be thicker than the thickness of the skin layer 1b formed on the surface of the substrate layer 1 on the substrate B side. More preferably, the thickness of the skin layer 1b formed on the surface of the substrate layer 1 is in the range of 1.1 times or more and 3.0 times or less of the thickness of the skin layer 1b formed on the surface of the substrate B side of the substrate layer 1. If the thickness of the skin layer 1b formed on the surface of the substrate layer 1 on the substrate B side is within the above numerical range, it is possible to achieve a balance between printability (e.g., stretch resistance), surface smoothness during wrapping, scratch resistance, high concealment and bending processability with even more leeway.

The thickness of the skin layer 1b is preferably in the range of 0.1 to 1.0 times the thickness of the core layer 1a, more preferably in the range of 0.2 to 0.5 times. If the thickness of the skin layer 1b is within the above numerical range, it is possible to more easily achieve compatibility between printability (e.g., stretch resistance), surface smoothness during wrapping, scratch resistance, high hiding power and bending processability.
In addition, the skin layer 1b is formed by adding nucleating agent vesicles to the polypropylene resin, and the amount of the nano-sized nucleating agent added may be different between the skin layer 1b formed on the surface of the substrate layer 1 and the skin layer 1b formed on the surface of the substrate layer 1 on the substrate B side. For example, the amount of the nano-sized nucleating agent added may be greater in the skin layer 1b formed on the surface of the substrate layer 1 than in the skin layer 1b formed on the surface of the substrate B side of the substrate layer 1. Specifically, the amount of the nano-sized nucleating agent added may be in the range of 1.1 times or more and 3.0 times or less in the skin layer 1b formed on the surface of the substrate layer 1 on the substrate B side. If the amount of the nano-sized nucleating agent added is within the above numerical range, it is possible to achieve both printability (e.g., stretch resistance), surface smoothness during wrapping, scratch resistance, high concealment and bending workability with even more leeway.

[Example]
Specific examples of the decorative sheet 10 of this embodiment will be described below.
(Method of producing nucleating agent vesicles)
First, the method for producing the nucleating agent liposome used in this example will be described.
Nucleating agent liposomes were prepared by the above-mentioned supercritical reverse phase evaporation method, by placing 100 parts by mass of methanol, 70 parts by mass of a phosphate metal salt nucleating agent (Adeka STAB NA-21; manufactured by ADEKA) as a nucleating agent, and 5 parts by mass of phosphatidylcholine as a phospholipid constituting the outer membrane of the vesicle in a high-pressure stainless steel container maintained at 60°C and sealing the container, and injecting carbon dioxide into the container so that the pressure becomes 20 MPa to create a supercritical state. Thereafter, the container was vigorously stirred and 100 parts by mass of ion-exchanged water was injected. After stirring and mixing for another 15 minutes while maintaining the temperature and pressure in a supercritical state, carbon dioxide was discharged from the container and the pressure was returned to atmospheric pressure, thereby obtaining a nucleating agent vesicle in which a nucleating agent is encapsulated in a vesicle having a monolayer outer membrane made of phospholipid.

Example 1
As a raw material for the core layer 1a of the colored polypropylene film, 60 parts by mass of a random polypropylene resin containing 4% ethylene and having a melt flow rate (MFR) of 12 g/10 min (230°C) was blended with 40 parts by mass of titanium oxide pigment as an inorganic pigment, and as a raw material for the skin layer 1b, 50 parts by mass of a highly crystalline homopolypropylene resin containing 4% ethylene and having a melt flow rate (MFR) of 12 g/10 min (230°C) and a pentad fraction of 97.8%, a melt flow rate (MFR) of 15 g/10 min (230°C), and a molecular weight distribution MWD (Mw/Mn) of 2.3 was blended with 50 parts by mass of a random polypropylene resin containing 4% ethylene and having a melt flow rate (MFR) of 12 g/10 min (230°C), and 0.1 part by mass of the above-mentioned nucleating agent vesicle was added as a nucleating agent. These were co-extruded using a melt extruder to produce a base layer 1 made of a colored polypropylene film having a core layer thickness of 30 μm and a skin layer thickness of 5 μm. The substrate layer 1 thus formed has a laminated structure of skin layer 1b/core layer 1a/skin layer 1b.

Example 2
A substrate layer 1 having a thickness of 140 μm was produced by coextrusion molding using a melt extruder in the same manner as in Example 1, except that the above-mentioned core layer thickness was 120 μm and the skin layer thickness was 10 μm.
Example 3
A substrate layer 1 having a thickness of 190 μm was produced by coextrusion molding using a melt extruder in the same manner as in Example 1, except that the above-mentioned core layer thickness was 170 μm and the skin layer thickness was 10 μm.
Example 4
A substrate layer 1 having a thickness of 150 μm was formed by coextrusion molding using a melt extruder in the same manner as in Example 1, except that the above-mentioned core layer thickness was 90 μm and the skin layer thickness was 30 μm.

Example 5
A substrate layer 1 having a thickness of 154 μm was formed by coextrusion molding using a melt extruder in the same manner as in Example 1, except that the above-mentioned core layer thickness was 140 μm and the skin layer thickness was 7 μm.
Example 6
A substrate layer 1 having a thickness of 156 μm was formed by coextrusion molding using a melt extruder in the same manner as in Example 1, except that the above-mentioned core layer thickness was 150 μm and the skin layer thickness was 3 μm.
(Example 7)
A 160 μm-thick substrate layer 1 was produced by co-extrusion molding using a melt extruder in the same manner as in Example 1, except that the nucleating agent vesicle added to the above-mentioned skin layer 1b was 0.05 parts by mass as a nucleating agent, the core layer thickness was 140 μm, and the skin layer thickness was 10 μm.

(Example 8)
A substrate layer 1 having a thickness of 160 μm was formed by coextrusion molding using a melt extruder in the same manner as in Example 7, except that the nucleating agent vesicle added to the above-mentioned skin layer 1b was 0.5 parts by mass as the nucleating agent.
Example 9
Both sides of a 40 μm-thick substrate layer 1 prepared in the same manner as in Example 1 were subjected to corona treatment, and one side was subjected to pattern printing using a two-component curing urethane ink (V180; manufactured by Toyo Ink Mfg. Co., Ltd.) to form a pattern layer 2. Furthermore, a two-component curing urethane top coat (W184; manufactured by DIC Graphics, application amount 10 g/ ^m2 ) was applied to the surface of the pattern layer 2 to form a top coat layer 4, thereby obtaining a decorative sheet 10.

Example 10
A top coat layer 4 was formed in the same manner as in Example 9 on a substrate layer 1 having a thickness of 140 μm, which was prepared in the same manner as in Example 2, to obtain a decorative sheet 10 .
(Example 11)
A top coat layer 4 was formed in the same manner as in Example 9 on a substrate layer 1 having a thickness of 190 μm, which was prepared in the same manner as in Example 3, to obtain a decorative sheet 10 .
Example 12
A top coat layer 4 was formed in the same manner as in Example 9 on a substrate layer 1 having a thickness of 150 μm, which was prepared in the same manner as in Example 4, to obtain a decorative sheet 10 .

(Example 13)
A top coat layer 4 was formed in the same manner as in Example 9 on a substrate layer 1 having a thickness of 154 μm, which was prepared in the same manner as in Example 5, to obtain a decorative sheet 10 .
(Example 14)
A top coat layer 4 was formed in the same manner as in Example 9 on a substrate layer 1 having a thickness of 156 μm, which was prepared in the same manner as in Example 6, to obtain a decorative sheet 10 .

(Example 15)
A top coat layer 4 was formed in the same manner as in Example 9 on a substrate layer 1 having a thickness of 160 μm, which was prepared in the same manner as in Example 7, to obtain a decorative sheet 10 .
(Example 16)
A top coat layer 4 was formed in the same manner as in Example 9 on a substrate layer 1 having a thickness of 160 μm, which was prepared in the same manner as in Example 8, to obtain a decorative sheet 10 .

(Example 17)
A 48 μm thick substrate layer 1 was prepared in the same manner as in Example 1 except that the above-mentioned core layer thickness was 40 μm and the skin layer thickness was 4 μm. One side of the substrate layer 1 was subjected to a corona treatment to set the surface wet tension to 40 dyn/cm or more. A highly crystalline homopolypropylene resin having a pentad fraction of 97.8%, a melt flow rate (MFR) of 15 g/10 min (230° C.) and a molecular weight distribution MWD (Mw/Mn) of 2.3 was extruded using a melt extruder to prepare a 50 μm thick transparent resin layer 3, and both sides of the layer were subjected to a corona treatment to set the surface wet tension to 40 dyn/cm or more.
Next, a pattern was printed on the corona-treated surface of the base layer 1 using a two-component curing urethane ink (V180; manufactured by Toyo Ink Mfg. Co., Ltd.) to form a pattern layer 2. Furthermore, a transparent resin layer 3 was attached to the surface of the pattern layer 2 by a dry lamination method via an adhesive layer made of a dry lamination adhesive (Takelac A540; manufactured by Mitsui Chemicals, Inc., application amount 2 g/ ^m2 ). Next, an embossed pattern was formed on the surface of the transparent resin layer 3 using an embossing mold roll, and then a two-component curing urethane top coat (W184; manufactured by DIC Graphics, application amount 3 g/ ^m2 ) was applied so as to cover the embossed pattern to form a top coat layer 4, thereby obtaining a decorative sheet 10.

(Example 18)
A 120 μm thick substrate layer 1 was prepared in the same manner as in Example 1, except that the above-mentioned core layer thickness was 100 μm and the skin layer thickness was 10 μm. One side of the substrate layer 1 was subjected to corona treatment to set the surface wet tension to 40 dyn/cm or more. Next, a highly crystalline homopolypropylene resin having a pentad fraction of 97.8%, a melt flow rate (MFR) of 15 g/10 min (230° C.), and a molecular weight distribution MWD (Mw/Mn) of 2.3 was extruded using a melt extruder to prepare a 70 μm thick transparent resin layer 3, and both sides of the layer were subjected to corona treatment to set the surface wet tension to 40 dyn/cm or more.
Next, a pattern was printed on the corona-treated surface of the base layer 1 using a two-component curing urethane ink (V180; manufactured by Toyo Ink Mfg. Co., Ltd.) to form a pattern layer 2. Furthermore, a transparent resin layer 3 was attached to the surface of the pattern layer 2 by a dry lamination method via an adhesive layer made of a dry lamination adhesive (Takelac A540; manufactured by Mitsui Chemicals, Inc., application amount 2 g/ ^m2 ). Next, an embossed pattern was formed on the surface of the transparent resin layer 3 using an embossing mold roll, and then a two-component curing urethane top coat (W184; manufactured by DIC Graphics, application amount 10 g/ ^m2 ) was applied so as to cover the embossed pattern to form a top coat layer 4, thereby obtaining a decorative sheet 10.

(Example 19)
A 135 μm thick substrate layer 1 was prepared in the same manner as in Example 1, except that the above-mentioned core layer thickness was 115 μm and the skin layer thickness was 10 μm. One side of the substrate layer 1 was subjected to a corona treatment to set the surface wet tension to 40 dyn/cm or more. A highly crystalline homopolypropylene resin having a pentad fraction of 97.8%, a melt flow rate (MFR) of 15 g/10 min (230° C.), and a molecular weight distribution MWD (Mw/Mn) of 2.3 was extruded using a melt extruder to prepare a 100 μm thick transparent resin layer 3, and both sides of the layer were subjected to a corona treatment to set the surface wet tension to 40 dyn/cm or more.
Next, a pattern was printed on the corona-treated surface of the base layer 1 using a two-component curing urethane ink (V180; manufactured by Toyo Ink Mfg. Co., Ltd.) to form a pattern layer 2. Furthermore, a transparent resin layer 3 was attached to the surface of the pattern layer 2 by a dry lamination method via an adhesive layer made of a dry lamination adhesive (Takelac A540; manufactured by Mitsui Chemicals, Inc., application amount 2 g/ ^m2 ). Next, an embossed pattern was formed on the surface of the transparent resin layer 3 using an embossing mold roll, and then a two-component curing urethane top coat (W184; manufactured by DIC Graphics, application amount 15 g/ ^m2 ) was applied so as to cover the embossed pattern to form a top coat layer 4, thereby obtaining a decorative sheet 10.

(Example 20)
A substrate layer 1 having a thickness of 135 μm was formed by coextrusion molding using a melt extruder in the same manner as in Example 1, except that the above-mentioned core layer thickness was 75 μm and the skin layer thickness was 30 μm.
(Example 21)
A substrate layer 1 having a thickness of 171 μm was produced by coextrusion molding using a melt extruder in the same manner as in Example 1, except that the above-mentioned core layer thickness was 165 μm and the skin layer thickness was 3 μm.

(Comparative Example 1)
The same procedure as in Example 1 was carried out, except that the conditions during extrusion were adjusted so that the Martens hardness was 45 N/ ^mm2 , and a substrate layer 1 having a thickness of 140 μm was formed.
(Comparative Example 2)
The same procedure as in Example 1 was carried out, except that the conditions during extrusion molding were adjusted so that the Martens hardness was 130 N/ ^mm2 , and a substrate layer 1 having a thickness of 140 μm was formed.
(Comparative Example 3)
A substrate layer 1 having a thickness of 36 μm was formed by coextrusion molding using a melt extruder in the same manner as in Example 1, except that the above-mentioned core layer thickness was 30 μm and the skin layer thickness was 3 μm.

(Comparative Example 4)
A substrate layer 1 having a thickness of 220 μm was formed by coextrusion molding using a melt extruder in the same manner as in Example 1, except that the above-mentioned core layer thickness was 200 μm and the skin layer thickness was 10 μm.
(Comparative Example 5)
A substrate layer 1 having a thickness of 140 μm was formed by extrusion molding using a melt extruder in the same manner as in Example 2, except that an untreated nucleating agent was used instead of the above-mentioned nucleating agent vesicle.
(Comparative Example 6)
A substrate layer 1 having a thickness of 140 μm was formed by coextrusion molding using a melt extruder in the same manner as in Example 2, except that the above-mentioned nucleating agent vesicle was added as a nucleating agent in an amount of 0.02 parts by mass.

(Comparative Example 7)
A substrate layer 1 having a thickness of 140 μm was produced by co-extrusion molding using a melt extruder in the same manner as in Example 2, except that the above-mentioned nucleating agent vesicle was added as a nucleating agent in an amount of 0.6 parts by mass. (Comparative Example 8)
As a raw material for the colored polypropylene film, 60 parts by mass of a random polypropylene resin containing 4% ethylene and having a melt flow rate (MFR) of 12 g/10 min (230°C) was blended with 40 parts by mass of titanium oxide pigment as an inorganic pigment, and the blend was extruded using a melt extruder to produce a base layer 1 made of a colored polypropylene film having a thickness of 120 μm.

(Comparative Example 9)
As a raw material for the colored polypropylene film, 80 parts by mass of a random polypropylene resin containing 4% ethylene and having a melt flow rate (MFR) of 12 g/10 min (230°C) was blended with 20 parts by mass of titanium oxide pigment as an inorganic pigment, and the blend was extruded using a melt extruder to form a base layer 1 made of a colored polypropylene film having a thickness of 120 μm.

(evaluation)
For the above-mentioned Examples 1 to 21 and Comparative Examples 1 to 9, the state of the base material layer 1 was confirmed, the Martens hardness was measured, and defects during printing (suitability for printing), scratch resistance, smoothness during wrapping (surface uniformity during wrapping), hiding power, and suitability for bending were evaluated.

<Martens hardness>
The measurement was performed using a Martens hardness measuring device (Fisherscope HM2000; Fisher Instruments, Inc.) conforming to ISO14577. The sample was measured from the cross section of the decorative sheet 10 to avoid the influence of the laminated resin layers other than the base layer 1 during measurement. Specifically, the decorative sheet 10 was embedded in a resin such as a cold-curing epoxy resin or a UV-curing resin and sufficiently cured, and then cut so that the cross section of the decorative sheet 10 appeared and mechanically polished to obtain a measurement surface. The specific measurement method is to press an indenter into the base layer 1 on the measurement surface of each sample, and calculate the Martens hardness from the indentation depth and the load. The measurement was performed under the following measurement conditions: test force 10 mN, test force load time 10 seconds, and test force holding time 5 seconds. The calculated Martens hardness of each sample is as shown in Table 1.

<Problems during printing (suitability for printing)>
The picture layer 2 was formed by gravure printing using a gravure printing machine, and the defects in which the base layer 1 was stretched by tension during the printing and the registration was shifted when the colors were laminated were evaluated as printing defects.
The results were rated as "◎" when no register adjustment was required at all, "○" when it was possible to easily adjust the register with automatic register adjustment, "△" when careful register adjustment was required, and "×" when register adjustment was impossible and printing could not continue. Also, the results were rated as "×" when the film broke frequently during printing, causing problems with mass production. A rating of "△" or above was acceptable as a printing process.

<Scratch resistance>
The scratch resistance was evaluated by conducting a pencil hardness test. In the pencil hardness test, a 3B pencil was used, the angle of the pencil was fixed at 45±1° with respect to the decorative sheet 10, and the pencil was slid with a load of 750 kg applied to it to observe the surface condition of the decorative sheet 10 (based on the former JIS standard JIS K5400). The test was conducted five times, and the pencil scratches and marks were evaluated.
The case where no scratches or marks were found was rated as "◎", the case where slight pencil marks were found was rated as "◯", the case where pencil marks were found was rated as "△", and the case where pencil scratches or tears in the colored polypropylene film were found was rated as "×".
If the evaluation is "○" or higher, there is no practical problem. If the evaluation is "△" or higher, there is no problem, although the use is limited to furniture and high vertical surfaces that people cannot touch. Evaluation of "○" or higher is preferable.

<Bending suitability>
In the bending workability test, the decorative sheets 10 of Examples 1 to 21 and Comparative Examples 1 to 9 obtained by the above method were attached to one side of a medium density fiberboard (MDF) as the base material layer 1 using a urethane adhesive, and a V-shaped groove was made in the other side of the base material layer 1 up to the boundary where the base material layer 1 and the decorative sheet 10 were attached so as not to scratch the decorative sheet 10 on the opposite side. Next, the base material layer 1 was bent 90 degrees along the V-shaped groove so that the surface of the decorative sheet 10 was folded in a mountain fold, and the bent portion of the surface of the decorative sheet 10 was observed using an optical microscope to see if there was any whitening or cracking, and the state of bending workability was evaluated.
When no whitening or cracks were observed, the rating was "◎", when slight whitening was observed in some areas, the rating was "○", when whitening was observed in some areas, the rating was "△", and when whitening was observed over the entire surface or when cracks were observed in some areas, the rating was "×". Note that a rating of "△" or higher is acceptable for practical use, but a rating of "○" or higher is preferable.

<Surface uniformity (smoothness) during lapping>
In the surface uniformity test during wrapping, a square timber consisting of two sheets of medium density fiberboard (MDF) and three to five sheets of board material or particle board bonded between them was used as the base layer 1, and the decorative sheets 10 of Examples 1 to 21 and Comparative Examples 1 to 9 obtained by the above method were attached to the square timber by wrapping using a hot melt adhesive to obtain a decorative board. Next, the surface where the decorative sheet 10 was bonded to the end of the board material was observed, and the presence of surface irregularities due to unevenness of the board material or steps at the bonding portion of the board material was visually observed. Furthermore, the obtained decorative board was left in an environment of a temperature of 80°C and a humidity of 85% for 1000 hours, and the surface irregularities at the same location and peeling of the decorative sheet 10 were confirmed.
A smooth surface with no visible irregularities or steps at the beginning or after 1000 hours was marked with "◎", a surface that looked slightly rough was marked with "○", unevenness or steps were visible in some areas was marked with "△", unevenness or steps were visible over the entire surface was marked with "X", and peeling of the decorative sheet 10 was observed after 1000 hours was marked with "XX". A rating of "△" or better is acceptable for practical use, but a rating of "○" or better is preferable.

<Concealment>
The evaluation of the hiding power was judged by the color difference measured with a spectrophotometer (530JP/LP) manufactured by X-rite and a hiding test paper (byco-chart high brightness 2A) manufactured by BYK-GARDNER on a white background and a black background. The smaller the color difference value, the better the hiding power. When the hiding power is less than 0.3, it is marked as "◎", when it is 0.3 or more and less than 0.5, it is marked as "〇", when it is 0.5 or more and less than 1.0, it is marked as "△", and when it is 1.0 or more, it is marked as "×". In addition, if it is rated as "〇" or more, there is no practical problem for generally used substrates in general, but when it is rated as "△", it is not suitable for some substrates, but there is no practical problem for the majority of substrates. It is preferable to be rated as "〇" or more.

<Surface condition of substrate layer 1 (surface defects)>
The surface of the base layer 1 was rubbed back and forth 10 times with a cloth, and it was observed whether there was any adhesion on the cloth or any change was observed on the surface of the base layer 1. When there was no adhesion on the cloth and there was no problem on the surface of the base layer 1, it was rated as "Good", and when there was adhesion on the cloth and a change in gloss was observed on the surface of the base layer 1, it was rated as "Poor". In the case of "Poor", it means that the inorganic pigment contained in the base layer 1 was not fixed and peeled off, and therefore it is not suitable for practical use as a decorative sheet by itself or as a decorative sheet 10 laminated with the transparent resin layer 3 or the top coat layer 4. It must be rated as "Good".
The evaluation results are shown in Table 1.

As can be seen from Table 1, the decorative sheets 10 of Examples 1 to 8, 20, and 21, despite their high inorganic pigment loading, do not cause any defects in the base layer 1, and are able to withstand practical use in terms of defects during printing and strength, while also being able to withstand defects during wrapping and bending. Also, the decorative sheets 10 of Examples 9 to 16 have improved scratch resistance by laminating a topcoat layer 4 to Examples 1 to 8, and are able to achieve the required performance with a sufficient margin.

On the other hand, in the decorative sheets 10 of Comparative Examples 1 to 4, the Martens hardness and thickness were not in the optimal range, and therefore defects occurred in either evaluation. In addition, in the decorative sheet 10 of Comparative Example 5, a non-vesiculated nucleating agent was used, and thus defects occurred during bending, even though the crystallization was improved to bring the Martens hardness into the optimal range. This is thought to be due to the fact that the spherulite size was larger than when a vesiculated nucleating agent was used.

Also, in the decorative sheets 10 of Comparative Examples 6 and 7, the Martens hardness was not in the optimum range, and therefore, it was found that either of the evaluation results was problematic.
In Comparative Example 8, the core layer 1a is a single layer to form the decorative sheet 10. The inorganic pigment compounding ratio is set according to the required hiding power, but the absence of the skin layer 1b causes problems on the surface of the base layer 1. Therefore, in Comparative Example 9, the inorganic pigment compounding ratio is lowered in the configuration of Comparative Example 8 so as to prevent problems on the surface of the base layer 1, but the required hiding power cannot be satisfied.

From the above, it became clear that the decorative sheets 10 of Examples 1 to 21 are decorative sheets 10 that do not cause any defects on the surface of the base layer 1, and that combine high concealing properties, defects during printing processing (suitability for printing processing), scratch resistance, smoothness during wrapping processing (surface uniformity during wrapping processing), and suitability for bending processing.
The decorative sheet of the present invention is not limited to the above-mentioned embodiments and examples, and various modifications are possible without departing from the characteristics of the invention.

Reference Signs List 10: Decorative sheet 1: Base material layer 1a: Core layer 1b: Skin layer 2: Design layer 3: Transparent resin layer 4: Topcoat layer B: Substrate

Claims (11)

A substrate layer having a core layer containing an inorganic pigment and a polypropylene resin, and a skin layer formed on at least one surface of the core layer and containing a polypropylene resin,
The skin layer is formed by adding a nucleating agent vesicle having a nano-sized nucleating agent encapsulated therein to a vesicle having a single-layer outer membrane,
The Martens hardness of the skin layer is in the range of 50 N/mm2 ^or more and 120 N/ ^mm2 or less,
The thickness of the base layer is in the range of 40 μm or more and 200 μm or less,
The core layer contains a titanium oxide pigment as the inorganic pigment,
A decorative sheet, wherein the core layer contains only a random polypropylene resin having an ethylene content as the polypropylene resin. The decorative sheet according to claim 1, characterized in that the thickness of the core layer is in the range of 3 to 50 times the thickness of at least one of the skin layers. The decorative sheet according to claim 1 or 2, characterized in that the amount of the nucleating agent vesicle added is in the range of 0.05 parts by mass or more and 0.5 parts by mass or less, calculated as the nucleating agent in the nucleating agent vesicle, per 100 parts by mass of the polypropylene resin. The decorative sheet according to any one of claims 1 to 3, characterized in that the nucleating agent vesicle is a nucleating agent liposome having an outer membrane containing a phospholipid. The decorative sheet according to any one of claims 1 to 4, characterized in that a pattern layer is laminated on one surface of the base layer. At least one of a transparent resin layer and a top coat layer is laminated on one surface of the base layer,
6. The decorative sheet according to claim 1, wherein the total thickness of the decorative sheet is within the range of 100 μm or more and 250 μm or less. The decorative sheet according to any one of claims 1 to 6, characterized in that the nucleating agent vesicle is formed by encapsulating the nucleating agent in a vesicle having a monolayer membrane by supercritical reverse phase evaporation. The decorative sheet according to any one of claims 1 to 7, characterized in that the skin layer contains a random polypropylene resin having an ethylene content as the polypropylene resin. The skin layer contains only two types of polypropylene resin, namely, a random polypropylene resin having an ethylene content and a homopolypropylene resin,
8. The decorative sheet according to claim 1, wherein the content of the random polypropylene resin having the ethylene content and the content of the homopolypropylene resin in the skin layer are the same. A method for producing a decorative sheet according to any one of claims 1 to 9,
A method for producing a decorative sheet, comprising the steps of: preparing a nucleating agent vesicle by encapsulating a nucleating agent in a vesicle to convert the nucleating agent into a vesicle; forming the skin layer on at least ^one side of the core layer using a resin material obtained by adding the prepared nucleating agent vesicle to a polypropylene resin so that the Martens hardness is in the range of 50 N/mm2 or more and 120 N/ ^mm2 or less; and preparing the base material layer having a thickness in the range of 40 μm or more and 200 μm or less. The method for manufacturing a decorative sheet according to claim 10, characterized in that at least one of a transparent resin layer and a topcoat layer is laminated on one side of the base layer, and when the transparent resin layer and the topcoat layer are provided, the thickness of the transparent resin layer is within a range of 50 μm to 100 μm, the thickness of the topcoat layer is within a range of 3 μm to 15 μm, and the total thickness of the decorative sheet is within a range of 100 μm to 250 μm.

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