JP7826672B2 - Decorative sheet, packaging box, and packaging body - Google Patents

Description

This disclosure relates to decorative sheets, packaging boxes, and packaging bodies.

Plastic packaging bags are known as packaging containers for storing wet tissues, which are made of a fiber material impregnated with a cleansing liquid such as alcohol, or a lotion or the like. For example, Patent Document 1 proposes a package that stores wet tissues and has an opening for removing the wet tissues, and a removably attached label around the opening.

Meanwhile, decorative sheets are known that improve the design of packaging containers by providing a plastic film with a metallic coating that has a metallic sheen on a paper substrate. Patent Document 2 proposes a container that uses such a decorative sheet.

JP 2015-85968 A Japanese Patent Application Laid-Open No. 2019-5940

Replacing even a portion of plastic containers with paper ones would enable waste reduction and the effective use of resources. However, if containers made of liquid-containing materials are made out of paper, as in Patent Document 1, the liquid will penetrate the paper, making it impossible to maintain sufficient strength. While a laminate of resin and a paper base material, as in Patent Document 2, could be used to reinforce the container, the inventors' investigations revealed that the interface between the resin and paper base material is prone to peeling, making it difficult to maintain sufficient durability.

This disclosure provides a decorative sheet that can maintain sufficient durability even when in contact with moisture. This disclosure also provides a packaging box and packaging body that can maintain sufficient durability even when used to package moist items.

In one aspect, the present disclosure provides a decorative sheet comprising, in this order, waterproof paper, a photocurable resin layer, an adhesive layer, a substrate layer, and a metal film. This decorative sheet comprises waterproof paper, which has excellent resistance to moisture, as well as a photocurable resin layer. This photocurable resin layer also has better water resistance than water-soluble resins such as polyvinyl alcohol. Therefore, the decorative sheet can maintain sufficient durability even when in contact with moisture.

In the decorative sheet, the waterproof paper and the photocured resin layer are in direct contact, and it is preferable that the waterproof paper contains the resin component that makes up the photocured resin layer. This sufficiently increases the adhesive strength between the photocured resin layer and the waterproof paper, further increasing durability. This also further improves the water resistance of the waterproof paper, thereby increasing the water resistance of the decorative sheet.

It is preferable that the waterproof paper has a pigment-containing layer, and that the resin components that make up the photocured resin layer permeate into the pigment-containing layer. Pigment-containing layers typically contain particulate pigments, resulting in a smooth surface and making it difficult for adjacent layers to adhere to them. However, by having the resin components that make up the photocured resin layer permeate into the pigment-containing layer, it is possible to sufficiently increase the adhesive strength between the photocured resin layer and the pigment-containing layer, thereby achieving sufficiently high durability. Furthermore, having a pigment-containing layer on the waterproof paper can improve decorativeness.

The photocured resin layer is preferably composed of a UV-cured resin containing a (meth)acrylic resin. Such UV-cured resins have excellent adhesion and water resistance. This allows the decorative sheet to maintain a sufficiently high strength even when it comes into contact with moisture. The waterproof paper preferably contains a (meth)acrylate monomer and/or a polymer thereof. This further increases the water resistance of the waterproof paper.

The decorative sheet preferably has an Edgewick value of 1.5 mg/ ^mm2 or less when immersed in water at 23°C for 24 hours. Such a decorative sheet has even better water resistance.

The decorative sheet preferably has lines including recesses or through-holes on at least one surface. Using such a decorative sheet makes it easy to produce assemblies such as packaging boxes.

The decorative sheet preferably has an ink layer between the waterproof paper and the photocurable resin layer. This allows for improved design.

In one aspect, the present disclosure provides a packaging box having a box body made of any of the decorative sheets described above. This packaging box has a box body made of any of the decorative sheets described above. As a result, it has sufficient durability even when packaging a packaged item containing moisture. For example, even if the lid label that has an adhesive sealing surface and seals the opening of the box is repeatedly opened and closed, peeling of the decorative sheet that makes up the box body can be sufficiently prevented.

In one aspect, the present disclosure provides a package comprising the above-described packaging box and a packaged item housed in the packaging box. Because this package comprises the above-described packaging box, it can maintain sufficient durability even when packaging a packaged item containing moisture.

It is possible to provide a decorative sheet that can maintain sufficient durability even when in contact with moisture. It is also possible to provide a packaging box and package that can maintain sufficient durability even when packaging a moist packaged item.

1 is a cross-sectional view showing a decorative sheet according to an embodiment. FIG. 2 is a diagram showing a schematic diagram of the internal structure of a pigment-containing layer of waterproof paper in the decorative sheet of FIG. 1 . 1 shows the results of infrared spectroscopy (IR) measurement of the release surface of the decorative sheet of Example 1. 1 shows the results of infrared spectroscopy (IR) measurement of the peeled surface of the decorative sheet of Example 2. 10 shows the results of infrared spectroscopy (IR) measurement of the peeled surface of the decorative sheet of Comparative Example 3.

One embodiment of the present invention will be described below, with reference to the drawings where appropriate. However, the following embodiment is merely an example for explaining the present invention, and is not intended to limit the present invention to the following content. In the description, the same reference numerals will be used for the same elements or elements having the same functions, and duplicate descriptions will be omitted where appropriate.

The decorative sheet 10 of FIG. 1 comprises, in this order, waterproof paper 11, a photocurable resin layer 12, an adhesive layer 14, a base layer 16, and a metal film 18. The waterproof paper 11 comprises, from the front surface 10A of the decorative sheet 10, a paper layer 11a containing a paper material such as resin and pulp, and a pigment-containing layer 11b containing a pigment, in this order. Examples of pigments contained in the pigment-containing layer 11b include white pigments such as kaolin, clay, engineered kaolin, delaminated clay, heavy calcium carbonate, and light calcium carbonate. However, the types of pigments are not limited to these, and other pigments include various pigments such as purple pigments and blue pigments. The pigment-containing layer may contain a single pigment selected from the above, or a combination of two or more pigments. The pigment-containing layer 11b may contain particulate pigments as well as binders, fillers, fluorescent dyes, etc. that bind the pigments together. The pigment-containing layer 11b may also be a layer known as a clay layer.

The Edgewick value of the waterproof paper 11, measured after immersion in water at 23°C for 24 hours, is preferably less than 4 mg/ ^mm² , more preferably less than 2 mg/ ^mm² , and even more preferably less than 1.6 mg/ ^mm² . This ensures that the decorative sheet 10 has sufficiently high water resistance.

The Edge Wick value in this specification can be measured by the following procedure. A laminate film is attached to the entire front and back surfaces of the waterproof paper to be measured. Then, the film is cut into a rectangle (15 mm x 100 mm) to obtain a test sample. The mass of the test sample is measured before immersion in water. The test sample is immersed in water at 23°C for 1 to 24 hours, and then removed from the water and the mass of the test sample is measured. The Edge Wick value can be calculated from the mass of the test sample before and after immersion in water using the following formula.
Edgewick value = difference in mass of test sample before and after immersion / total area of the four edge faces of waterproof paper after cutting

The basis weight of the waterproof paper 11 may be, for example, 100 to 800 g/ ^m² , or 200 to 600 g/ ^m² . This allows for both sufficient rigidity and good assembly ease. The thickness of the waterproof paper 11 may be 100 to 800 μm, or 200 to 600 μm.

The paper layer 11a of the waterproof paper 11 that forms one surface 10A of the decorative sheet 10 contains resin, which prevents moisture absorption from the surface 10A. In a modified example, a resin coating layer made of, for example, acrylic resin may be provided to cover the surface of the paper layer 11a. The resin contained in the paper layer 11a and the resin that constitutes the resin coating layer may be the same type or different types. An example of a resin contained in the resin coating layer is a (meth)acrylic resin.

The structure of the waterproof paper is not limited to the one described above, and various types can be used that contain resin components to improve water resistance. Waterproof paper can be made using known methods, or commercially available products can be used. Commercially available products include "N Mitsubishi Waterproof" manufactured by Mitsubishi Paper Mills, Ltd., and "Ecovalley V" and "Ecovalley K" manufactured by Nippon Paper Industries Co., Ltd.

The pigment-containing layer 11b of the waterproof paper 11 in the decorative sheet 10 is preferably in direct contact with the photocurable resin layer 12. By providing the waterproof paper 11 with the pigment-containing layer 11b, the aesthetic appeal and design of the decorative sheet 10 can be improved. However, the pigment-containing layer 11b is prone to absorbing moisture, and the inclusion of particulate pigments makes the surface smooth, making adhesion to other layers more likely to be impaired. In this embodiment, the photocurable resin layer 12, which has excellent adhesion to the pigment-containing layer 11b and excellent water resistance, is adhered to the pigment-containing layer 11b, and one entire side of the pigment-containing layer 11b is covered by the photocurable resin layer 12. This prevents moisture from penetrating the interface between the pigment-containing layer 11b and the photocurable resin layer 12. Therefore, the decorative sheet 10 can fully maintain its excellent durability even when exposed to moisture.

The photocurable resin layer 12 is composed of a cured resin obtained by irradiating a photosensitive resin composition with light. The cured resin is preferably a UV-cured resin obtained by irradiating a photosensitive resin composition with ultraviolet light. By using a UV-cured resin as the photocurable resin layer 12, water resistance can be further improved. From the same perspective, a photoradical polymerization type UV-cured resin is preferred. From the perspective of further improving water resistance, the cured UV resin preferably contains a (meth)acrylic resin. The (meth)acrylic resin can be obtained, for example, as a polymer of a monomer having an acryloyl group and/or a methacryloyl group. The (meth)acrylic resin may also be obtained by polymerizing such a monomer with an oligomer having an acryloyl group and/or a methacryloyl group. Examples of the monomer include a (meth)acrylate monomer, and examples of the oligomer include a (meth)acrylate oligomer.

The photosensitive resin composition may contain a monomer, an oligomer, an additive including a photopolymerization initiator, and an organic solvent. The photosensitive resin composition may contain 50 to 90 parts by weight, or 60 to 80 parts by weight, of the monomer relative to a total of 100 parts by weight of the monomer and oligomer. This allows the monomer to sufficiently penetrate the waterproof paper 11 while achieving high adhesive strength. The photosensitive resin composition may contain 3 to 20 parts by weight, or 5 to 15 parts by weight, of the additive relative to the total of 100 parts by weight.

Examples of monomers include acrylic monomers, vinyl monomers, and allyl monomers. Acrylic monomers include those having an acryloyl group and/or a methacryloyl group as a functional group involved in the photocuring reaction (photopolymerization reaction). In this disclosure, acryloyl groups and methacryloyl groups may be referred to as (meth)acryloyl groups. Acrylic monomers may be (meth)acrylic acid esters, acid amides of nitrogen-containing compounds and (meth)acrylic acid, (meth)acrylic acid, etc. In this disclosure, acrylic acid and methacrylic acid may be referred to as (meth)acrylic acid. Furthermore, acrylic acid esters (or acrylates) and methacrylic acid esters (or methacrylates) may be referred to as (meth)acrylic acid esters (or (meth)acrylates).

As the (meth)acrylic acid ester, a (meth)acrylic acid alkyl ester can be used. Specific examples include (meth)acrylic acid alkyl esters in which the alkyl group has 1 to 8 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, and 2-hydroxyethyl (meth)acrylate.

Vinyl-based monomers include those having a vinyl group as a functional group involved in the photocuring reaction (photopolymerization reaction). Examples of vinyl-based monomers include vinyl ethers (e.g., vinyl ethers of monohydric alcohols), vinyl esters (divinyl adipate, divinyl maleate, divinyl phthalate, divinyl isophthalate, divinyl itaconate), and alicyclic vinyl monomers. Allyl-based monomers include monomers having an allyl group as a functional group involved in the photocuring reaction (photopolymerization reaction). Examples of allyl-based monomers include allyl ethers (allyl ethers of monohydric alcohols, etc.).

Examples of oligomers include those that cure or polymerize due to the action of radicals, cations, or anions generated by light irradiation. The weight-average molecular weight of the oligomer is, for example, 8,000 or more, and may be 10,000 or more. The weight-average molecular weight of the oligomer is, for example, 40,000 or less, and may be 30,000 or less. The weight-average molecular weight can be measured using gel permeation chromatography (GPC) or pyrolysis (Py)-GC/MS (a gas chromatograph-mass spectrometer equipped with a pyrolyzer).

The oligomer has a functional group that participates in the photocuring reaction (photopolymerization reaction). Examples of such functional groups include (meth)acryloyl groups, vinyl groups, allyl groups, and dienyl groups. Of these, from the perspective of further improving water resistance, it is preferable to include a (meth)acrylate-based oligomer having a (meth)acryloyl group. In this disclosure, acrylate-based oligomers having an acryloyl group and methacrylate-based oligomers having a methacryloyl group may be referred to as (meth)acrylate-based oligomers.

Photopolymerization initiators are activated by the action of light (e.g., ultraviolet light) and initiate the curing (polymerization) of reactive monomers. Examples of photopolymerization initiators include radical polymerization initiators that generate radicals under the action of light (ultraviolet light), and cation generators that generate acids (or cations) under the action of light (ultraviolet light). One type of photopolymerization initiator may be used alone, or two or more types may be used in combination. Examples of radical polymerization initiators include alkylphenone-based photopolymerization initiators and acylphosphine oxide-based photopolymerization initiators.

Examples of alkylphenone-based photopolymerization initiators include 2,2-dimethoxy-1,2-diphenylethan-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propan-1-one, 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, and 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone.

Examples of acylphosphine oxide photopolymerization initiators include 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide and bis(2,4,6-trimethylbenzoyl)-phenyl-phosphine oxide. These photopolymerization initiators are merely examples and are not limited to these.

Examples of organic solvents include alcohols, ethers, and ketones. These may be used alone or in combination. The photosensitive resin composition may contain optional components in addition to the components described above. Examples of such components include colorants, antioxidants, antifoaming agents, fillers, and stabilizers.

To facilitate penetration of the monomer into the waterproof paper 11, the monomer preferably contains a (meth)acrylate monomer. There is no particular limitation on the number of functional groups of the (meth)acrylate monomer.

When the photocured resin layer 12 and the pigment-containing layer 11b of the waterproof paper 11 are in direct contact, the resin components that make up the photocured resin layer 12 can smoothly penetrate into the waterproof paper 11. Examples of resin components that can penetrate include monomers contained in the photosensitive resin composition before the photocured resin layer is cured. By penetrating such resin components and forming a resin component-impregnated layer in the pigment-containing layer 11b of the waterproof paper 11, the water resistance of the waterproof paper 11 and the adhesive strength between the waterproof paper 11 and the photocured resin layer 12 can be improved. The waterproof paper 11 may contain this monomer, or it may contain a polymer obtained by polymerizing this monomer.

Figure 2 shows a schematic diagram of the internal structure of the pigment-containing layer 11b of the waterproof paper 11 in the decorative sheet 10. The photocured resin layer 12 is formed by applying a photosensitive resin composition to the surface of the pigment-containing layer 11b and then irradiating the layer with light. When the photosensitive resin composition is applied to the surface of the pigment-containing layer 11b, resin components 63, such as monomers contained in the photosensitive resin composition, penetrate into the pigment-containing layer 11b. The monomers contained in this resin component 63 may or may not polymerize upon light irradiation. Thus, the pigment-containing layer 11b of the waterproof paper 11 contains resin components, such as monomers and/or their polymers. The pigment-containing layer 11b may contain only a portion of the resin component, or it may have a concentration gradient in which the concentration of the resin component increases with increasing proximity to the photocured resin layer 12. This ensures sufficient adhesion to the photocured resin layer 12 while also providing sufficient strength at the boundary between the portion containing the resin component derived from the photosensitive resin composition and the portion not containing the resin component.

The permeated resin component 63 is thought to become entangled with, for example, the pigment 61 and other components, forming a network within the pigment-containing layer 11b. This improves the water resistance of the pigment-containing layer 11b. Furthermore, the resin component 63 that permeates the pigment-containing layer 11b also bonds with the resin component contained in the photocured resin layer 12. This improves the adhesive strength between the waterproof paper 11 and the photocured resin layer 12.

The molecular weight of the monomer contained in the photosensitive resin composition is preferably 500 or less, more preferably 400 or less, and even more preferably 300 or less. This allows the monomer to easily penetrate the waterproof paper 11, thereby sufficiently improving water resistance. The molecular weight of the monomer may be, for example, 100 or more.

The thickness of the photocurable resin layer 12 is preferably 2 to 10 μm, and more preferably 3 to 5 μm. This allows for a sufficiently high level of both ease of folding and moisture resistance.

The adhesive layer 14 functions to bond the photocurable resin layer 12 and the base material layer 16 together. Examples of adhesives contained in the adhesive layer 14 include polyvinyl alcohol-based adhesives, urethane-based adhesives, polyester-based adhesives, polyether-based adhesives, epoxy-based adhesives, polyethyleneimine-based adhesives, and polybutadiene-based adhesives. Of these, it is preferable to include an epoxy-based adhesive in order to further improve water resistance. The thickness of the adhesive layer 14 is preferably 2 to 10 μm, and more preferably 4 to 8 μm. This allows for a sufficiently high level of both ease of bending and water resistance.

It is preferable to provide an ink layer partially between the waterproof paper 11 and the photocurable resin layer 12. This improves the design. Even if an ink layer is provided partially between the waterproof paper 11 and the photocurable resin layer 12, the waterproof paper 11 and the photocurable resin layer 12 are still bonded with high adhesive strength in other areas between the waterproof paper 11 and the photocurable resin layer 12. Therefore, even if an ink layer is provided partially between the waterproof paper 11 and the photocurable resin layer 12, good adhesion can be maintained.

The substrate layer 16 may be a resin film. Examples of resin films include polyester films such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN); polyolefin films such as polyethylene and polypropylene; polystyrene films; polyamide films such as nylon 66; polycarbonate films; and engineering plastic films such as polyacrylonitrile and polyimide films. The surface of the substrate layer 16 facing the adhesive layer 14 may be subjected to at least one treatment selected from chemical treatment, solvent treatment, corona treatment, plasma treatment, and ozone treatment. The thickness of the substrate layer 16 is not particularly limited and may be, for example, 3 to 50 μm or 6 to 30 μm.

The metal film 18 may contain aluminum, tin, indium, nickel, copper, silver, gold, platinum, brass, chromium, or zinc, or an alloy of these metals. It may contain one of these metals alone, or two or more of them in combination. The metal film 18 can be produced by, for example, vacuum deposition, sputtering, or ion plating. The thickness of the metal film 18 is, for example, 10 to 2000 nm, and preferably 10 to 100 nm. This allows for the low-cost production of a decorative sheet 10 with excellent decorative properties due to its metallic luster.

A metallized film or metal foil laminated film in which the base layer 16 and metal film 18 are integrated may also be used. An ink layer may be provided on the surface 10B of the decorative sheet 10 on the metal film 18 side. This allows decorative sheets with a variety of designs to be obtained. Because the decorative sheet 10 has an excellent aesthetic appearance, it can be suitably used as an exterior material for packaging containers and as a board material for packaging boxes.

An example of a manufacturing method for the decorative sheet 10 is described below. A photosensitive resin composition is applied to the surface of the waterproof paper 11 on the side of the pigment-containing layer 11b. The surface of the coating layer of the photosensitive resin composition is then irradiated with light (ultraviolet rays) to photopolymerize the reactive monomers and reactive oligomers. The light (ultraviolet rays) is irradiated with an intensity and duration sufficient to form a photocured resin layer. This forms a photocured resin layer 12 on one side of the waterproof paper 11.

An adhesive is applied to one side of the photocurable resin layer 12, and the photocurable resin layer 12 is then bonded to a metal vapor deposition film or metal foil laminated film via the adhesive. This completes the production of the decorative sheet 10.

The decorative sheet 10 maintains sufficient durability even when in contact with moisture. For this reason, it can be suitably used, for example, as a sheet material for packaging boxes that package impregnated objects impregnated with moisture, aqueous solutions, emulsions, etc. The decorative sheet 10 may be a paper pattern (backing) with ruled lines on at least one of the surfaces 10A and 10B that serve as starting points for folding. The ruled lines may be grooves (recesses), or perforated through-holes may be formed.

To ensure smooth folding and high rigidity when the packaging box is formed, the thickness of the decorative sheet 10 is preferably 0.3 to 0.5 mm, and more preferably 0.40 to 0.45 mm. The decorative sheet 10 is folded so that the waterproof paper 11 is on the inside and the metal film 18 is on the outside. This makes it possible to obtain a packaging container and package that can maintain excellent durability even when packaging a moist packaged item. Such a packaging container and package has excellent aesthetic appeal, as it has the metal film 18 on the outer surface. Furthermore, the inclusion of waterproof paper 11 reduces the amount of plastic waste, thereby helping to conserve resources.

The Edge Wick value of the decorative sheet 10 when immersed in water at 23°C for 24 hours is preferably 1.5 mg/ ^mm2 or less. The Edge Wick value of the decorative sheet 10 can be measured using the same method as that for measuring the Edge Wick value of the waterproof paper 11. The durability of the decorative sheet 10 tends to depend on the adhesive strength (peel strength) between the waterproof paper 11 and the photocured resin layer 12. This adhesive strength (peel strength) tends to decrease as the amount of water absorbed by the decorative sheet 10 increases. Because the Edge Wick value of the decorative sheet 10 tends to depend on the amount of water absorbed by the waterproof paper 11, the durability of the decorative sheet 10 can be maintained at a high level by reducing the Edge Wick value of the decorative sheet 10.

The peel strength of the decorative sheet 10 after immersion in water at 20°C for 1 hour is preferably 0.4 [N/15 mm] or more, more preferably 0.5 [N/15 mm] or more, and even more preferably 0.6 [N/15 mm] or more. This peel strength is measured using the "Peel Adhesion Strength (2)" measurement method described in the Examples.

The decorative sheet 10 may be assembled into a packaging box. A packaging box made of the decorative sheet 10, which has excellent durability and water resistance, may be used to package an impregnated product (such as wet tissues) made of a fiber material impregnated with a cleaning solution such as alcohol or a lotion. In other words, the decorative sheet 10 may be used as a packaging box for such an impregnated product. The decorative sheet 10 maintains sufficient durability even when in contact with liquids such as water or alcohol. However, the uses of the decorative sheet 10 are not limited to this.

A packaging body according to one embodiment comprises a packaging box and an item to be packaged within the packaging box. If the packaging box is constructed from decorative sheet 10, at least a portion of the box can be recycled. The packaging box and the packaging body comprising it may be of a type that has an adhesive sealing surface and a lid label that seals the opening of the box, which can be repeatedly opened and closed. The decorative sheet 10 may also be assembled to form a packaging box. Because it has excellent durability and water resistance, peeling of the decorative sheet 10 and damage to the packaging box can be sufficiently prevented, even when the impregnated material described above is contained within it.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. For example, the decorative sheet may include any layer.

The contents of this disclosure will be explained in more detail with reference to examples and comparative examples, but the present disclosure is not limited to the examples below.

[Decorative sheet production 1]
Example 1
Commercially available waterproof paper ("N Mitsubishi Waterproof" manufactured by Mitsubishi Paper Mills, Ltd., basis weight 350 g/m ² ) was prepared. As shown in Figure 1 , this waterproof paper had a laminated structure consisting of a paper layer 11a containing paper materials such as resin and pulp, and a pigment-containing layer 11b containing a pigment (clay). A photosensitive resin composition was applied onto the pigment-containing layer 11b, and ultraviolet light was irradiated from the coated film side to form a photocured resin layer 12, thereby obtaining a laminate. The photosensitive resin composition used contained 62.2 mass% acrylate monomer, 28.8 mass% acrylate oligomer, 0.5 mass% isopropyl alcohol, 0.2 mass% ethylene glycol monobutyl ether, and 8.3 mass% additives including a photopolymerization initiator. A metal halide lamp (wavelength: 250 nm to 450 nm) was used as the ultraviolet light source.

A metallized film consisting of a PET film (thickness: 12 μm) on which an aluminum vapor-deposited layer (thickness: 10-100 nm) was formed, and an epoxy adhesive (main agent: AD391-A (trade name), curing agent: AD391-B (trade name), both manufactured by Toyo-Morton Co., Ltd.) were prepared. The laminate and the metallized film were bonded by dry lamination, with the PET film and the photocurable resin layer facing each other via the epoxy adhesive (application amount: 4.3 g/m ² ). The curing time (aging) was one day at room temperature. In this way, a decorative sheet with the laminate structure shown in Figure 1 was obtained. The thickness of the decorative sheet was measured using a dial gauge and found to be 440 μm.

Example 2
Commercially available waterproof paper ("Ecovalley K" manufactured by Nippon Paper Industries Co., Ltd., basis weight: 350 g/ ^m2 ) was prepared. This waterproof paper had a laminated structure with a resin coating layer made of resin, a paper layer containing paper material such as resin and pulp, and a pigment-containing layer containing a pigment (clay). Except for using this waterproof paper, a decorative sheet was produced in the same manner as in Example 1. The photosensitive resin composition was coated on top of the pigment-containing layer in the same manner as in Example 1. The thickness of the decorative sheet was measured using a dial gauge and found to be 440 μm.

(Comparative Example 1)
The waterproof paper used in Example 1 was used as Comparative Example 1.

(Comparative Example 2)
A sheet of ordinary paper (weighing 310 g/m ² , OK Frace PRO (product name), manufactured by Oji Paper Co., Ltd.) that was not waterproof was prepared. The ordinary paper and the metallized film were bonded together by dry lamination, with the PET film and the ordinary paper facing each other via an epoxy adhesive (application amount: 4.3 g/m ² ). The curing time (aging) was one day at room temperature. In this way, a decorative sheet was obtained with a laminated structure consisting of ordinary paper, an adhesive layer, a base layer (PET film), and a metal film (aluminum vapor-deposited film).

(Comparative Example 3)
Except for not providing a photocurable resin layer, a decorative sheet was produced in the same manner as in Example 1. This decorative sheet had a layered structure consisting of waterproof paper, an adhesive layer, a substrate layer (PET film), and a metal film (aluminum vapor deposition film).

(Comparative Example 4)
The waterproof paper used in Example 2 was used as Comparative Example 4.

[Measurement of Edgewick Value]
A laminate film was attached to the entire front and back surfaces of the decorative sheets obtained in each Example and Comparative Example. Test samples were then cut into rectangles (15 mm x 100 mm). The mass of the test samples before immersion in water was then measured. The test samples were then immersed in water at 23°C for 1 to 24 hours, removed from the water, and the mass of the test samples was measured. The Edge Wick value was calculated using the following formula from the mass of the test samples before and after immersion in water. The results are shown in Table 1. The Edge Wick value values in Table 1 are in mg/ ^mm2 .
Edgewick value = difference in mass of test sample before and after immersion / (total area of the four edge faces of the decorative sheet after cutting)

[Measurement of peel adhesive strength (1)]
After measuring the Edge Wick value as described above, the decorative sheets were removed from the test samples, and the peel bond strength of each decorative sheet was measured in accordance with JIS K 6854-1:1999. The peel bond strength of decorative sheets that had not been subjected to the Edge Wick test was measured in the same manner (without immersion). The specific procedure for measuring peel bond strength was as follows. After peeling between the layers at the edge (between the waterproof paper and the photocurable resin layer or adhesive layer), the peel bond strength between the layers was measured using a tensile tester under conditions of an angle of 180°, a pulling rate of 300 mm/min, and a temperature of 20°C. This peel bond strength was defined as the peel bond strength after the Edge Wick test. The measurement results are shown in Table 1. The numerical values for peel bond strength (1) in Table 1 are in "N/15 mm."

[Measurement of peel adhesive strength (2)]
The decorative sheets obtained in each example and comparative example were cut to obtain rectangular samples (15 mm x 100 mm). The samples were immersed in 300 ml of water for 1 hour. After the samples were removed from the water and approximately 10 minutes had passed, the peel bond strength (2) of each sample was measured using the same procedure as in "Measurement of peel bond strength (1)." This peel bond strength was defined as the peel bond strength after the hot water immersion test. The measurement results are shown in Table 1. The numerical values for peel bond strength (2) in Table 1 are in "N/15 mm."

[Measurement of peel adhesive strength (3)]
The decorative sheets obtained in each Example and Comparative Example 3 were cut to obtain rectangular samples (15 mm x 100 mm). The samples were immersed in 300 ml of lotion for 6 hours. The lotion contained ingredients such as water, glycerin, citric acid, propanediol, BG, phenoxyethanol, and methylparaben. Approximately 10 minutes after the samples were removed from the lotion, the peel bond strength (3) of each sample was measured using the same procedure as in "Measurement of Peel Bond Strength (1)." The measurement results are shown in Table 1. The numerical values for peel bond strength (3) in Table 1 are in "N/15 mm."

When comparing the Edgewick values of Example 1 and Comparative Examples 1, 2, and 3, which all use the same waterproof paper, Example 1, which has a photocured resin layer, had the lowest Edgewick value. A similar trend was observed when comparing Example 2 and Comparative Example 4, which also use the same waterproof paper. This confirms that the amount of water absorption can be reduced by providing a photocured resin layer.

The results of peel adhesive strength (1), (2), and (3) confirmed that Examples 1 and 2 maintained sufficient durability even when in contact with moisture. This is thought to be due to improved adhesive strength between the waterproof paper and the photocured resin layer, as well as improved water resistance of the waterproof paper. Furthermore, in the case of lotion, Examples 1 and 2 also exhibited high durability, just as in the case of water.

After measuring the peel adhesive strength (1) for Examples 1 and 2 and Comparative Example 3, IR measurements were performed on the peeled surfaces. Figure 3 shows the IR measurement results for the peeled surface of the decorative sheet in Example 1 that was not subjected to the Edgewick test (absorption spectrum "1" for the peeled surface on the waterproof paper side, and absorption spectrum "2" for the peeled surface on the metal film side). Figure 3 also shows the absorption spectrum for the pigment-containing layer side of the waterproof paper used in Example 1 as control "3." According to these results, the waterproof paper itself (absorption spectrum 3) did not have an absorption peak near 1700 cm- ¹ , whereas both the waterproof paper peeled surface (absorption spectrum 1) and the metal film peeled surface (absorption spectrum 2) had absorption peaks near 1700 cm ^-1 . This absorption peak is thought to be due to the stretching vibration of the carbon-oxygen double bond of resin components such as acrylate monomers. From absorption spectra 1 to 3 in FIG. 3, it was found that the decorative sheet of Example 1 was peeled off at the interface between the waterproof paper and the photocurable resin.

Figure 4 shows the results of IR measurement of the peeled surfaces (the peeled surface on the waterproof paper side and the peeled surface on the metal film side) of the decorative sheet of Example 2 that was not subjected to the Edgewick test. The symbols 1, 2, and 3 in Figure 4 have the same meanings as in Figure 3. Absorption spectra 1 to 3 in Figure 4 show that the decorative sheet of Example 2 also peeled at the interface between the waterproof paper and the photocurable resin. Furthermore, as in Example 1, an absorption peak was detected near 1700 cm ^-1 on both the peeled surface on the waterproof paper side (absorption spectrum 1) and the peeled surface on the metal film side (absorption spectrum 2).

Figure 5 shows the results of IR measurement of the peeled surfaces (the peeled surfaces on the waterproof paper side and the metallic film side) of the decorative sheet of Comparative Example 3, which was not subjected to the Edgewick test. As a control, Figure 5 also shows the results of IR measurement of the pigment-containing layer side of the waterproof paper used in Example 1. The symbols 1, 2, and 3 in Figure 5 have the same meanings as in Figure 3. In Figure 5, the peeled surfaces on the waterproof paper side and the metallic film side showed spectra similar to those of the waterproof paper itself. This indicates that the waterproof paper itself (the pigment-containing layer itself) had torn and peeled off in the decorative sheet of Comparative Example 1. In the decorative sheet of Comparative Example 3, no peaks derived from the resin components of the photocured resin layer were detected on the peeled surfaces of either the waterproof paper side or the metallic film side.

According to the IR measurement results described above, peaks derived from the resin components of the photocured resin layer were detected on the peel surface of the waterproof paper side of the decorative sheets of Examples 1 and 2, confirming that resin components such as acrylate monomers had permeated the waterproof paper (pigment-containing layer). It is believed that the inclusion of resin components derived from the photosensitive resin composition in the waterproof paper improved the adhesive strength between the waterproof paper and the photocured resin layer and inhibited the penetration of water (lotion), thereby improving the water resistance of the waterproof paper (pigment-containing layer). On the other hand, in the decorative sheet of Comparative Example 3, resin components such as acrylate monomers had not permeated the waterproof paper, which is believed to have resulted in low adhesive strength between the waterproof paper and the photocured resin layer and easy penetration of water (lotion) into the waterproof paper.

After immersion in water for 6 hours, the decorative sheet of Example 1, which had been measured for peel adhesive strength (1), was subjected to IR measurement of the peel surface on the waterproof paper side and the peel surface on the metal film side. No absorption peak was detected near 1700 cm ^-1 on either side. This confirms that it is not the entire pigment-containing layer that is impregnated with resin components such as acrylate monomers, but only a portion of the photocured resin layer side, that the portion containing the resin components maintains high water resistance even after immersion in water for 6 hours, and that the adhesive strength between the pigment-containing layer and the photocured resin layer remains sufficiently high even after immersion in water for 6 hours.

This disclosure makes it possible to provide a decorative sheet that can maintain sufficient durability even when in contact with moisture. It also makes it possible to provide a packaging box and package that can maintain sufficient durability even when packaging a packaged item that contains moisture.

10...decorative sheet, 10A, 10B...surface, 11...water-resistant paper, 11a...paper layer, 11b...pigment-containing layer, 12...photocurable resin layer, 14...adhesive layer, 16...substrate layer, 18...metal film, 61...pigment, 63...resin component.

Claims (10)

A waterproof sheet, a photocurable resin layer, an adhesive layer, a substrate layer, and a metal film are provided in this order ;
The decorative sheet has the waterproof paper and the photocured resin layer in direct contact with each other . 2. The decorative sheet according to claim 1, wherein the waterproof paper contains a resin component that constitutes the photocured resin layer. A decorative sheet according to claim 1 or 2, wherein the waterproof paper has a pigment-containing layer, and the resin component constituting the photocured resin layer permeates the pigment-containing layer. The decorative sheet according to any one of claims 1 to 3, wherein the photocurable resin layer is composed of a UV-cured resin material containing a (meth)acrylic resin. The decorative sheet according to claim 4, wherein the waterproof paper contains a (meth)acrylate monomer and/or a polymer thereof. 6. The decorative sheet according to claim 1, which has an Edgewick value of 1.5 mg/ ^mm2 or less when immersed in water at 23°C for 24 hours. The decorative sheet according to any one of claims 1 to 6, having lines including recesses or through-holes on at least one surface. The decorative sheet according to any one of claims 1 to 7, wherein an ink layer is provided in a portion between the waterproof paper and the photocured resin layer, and the waterproof paper and the photocured resin layer are in direct contact with each other in another portion between the waterproof paper and the photocured resin layer. A packaging box having a box body made from the decorative sheet of any one of claims 1 to 8. A package comprising the packaging box according to claim 9 and an item to be packaged housed in the packaging box.