Seal-type thermal transfer receiving sheet

Abstract

To provide a seal-type thermal transfer receiving sheet usable as a seal for application onto human skin and exhibiting superior print quality.SOLUTION: The seal-type thermal transfer receiving sheet of the present disclosure comprises: a release sheet; and a seal portion having an adhesive layer and a base sheet in this order from the release sheet side, the seal portion being provided so as to be peelable from the release sheet. The base sheet or the seal portion shows both an elastic region and a plastic region under conditions of a tensile test in accordance with JIS-K 7127:1999.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a seal-type thermal transfer image-receiving sheet. [Background technology]

[0002] There are stickers for human skin that are applied to the skin to exhibit design features or other functions, such as nail stickers, body paint stickers, skin stickers, etc. Sticker-type thermal transfer image-receiving sheets are used as such stickers for application to the skin (see, for example, Patent Document 1).

[0003] The sticker-type thermal transfer image receiving sheet disclosed in Patent Document 1 comprises, for example, a release sheet portion and a seal portion comprising, from the release sheet side, an adhesive layer, a base layer, a primer layer, and a receptor layer in this order. When the sticker-type thermal transfer image receiving sheet is used as a seal to be attached to human skin, the seal portion, which has a pattern printed on the receptor layer, is peeled off from the release sheet, and then the adhesive layer is attached to the skin, so that the seal portion is attached to the user's skin.

[0004] The sticker-type thermal transfer image receiving sheet disclosed in Patent Document 1 has the advantage that highly designed stickers can be created on demand using a thermal transfer printer, but it feels stiff and tight when applied to human skin, so there is a demand for a natural feel (bare skin feel) when applied to human skin.

[0005] Therefore, efforts have been made to reduce the thickness of the seal that is attached to the user, and Patent Document 2 discloses a decorative seal in which an adhesive layer and a film are laminated in this order from the release sheet side. This achieves a natural feel when the seal with a printed image is attached to the skin. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-136748 [Patent Document 2] Japanese Patent Application Publication No. 2017-097018 Summary of the Invention [Problem to be solved by the invention]

[0007] However, when a thin seal-type thermal transfer image-receiving sheet is printed using a thermal transfer recording method, it has the problem that print voids with a rough texture occur, making it difficult to maintain print quality.

[0008] An object of the present disclosure is to provide a sticker-type thermal transfer image-receiving sheet that can be used as a sticker to be attached to human skin and has excellent print quality. [Means for solving the problem]

[0009] The seal-type thermal transfer image receiving sheet of the present disclosure comprises a release sheet and a seal portion having an adhesive layer and a base sheet in this order from the release sheet side, the seal portion being releasable from the release sheet, and the base sheet exhibiting both an elastic region and a plastic region under the conditions of a tensile test in accordance with JIS-K 7127:1999. [Effects of the Invention]

[0010] According to the present disclosure, a sticker-type thermal transfer image receiving sheet can be provided that can be used as a sticker to be attached to human skin, does not have a rough texture (grainy feeling in the image) and has excellent print quality. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a cross-sectional view of a seal-type thermal transfer image-receiving sheet according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram illustrating a stress-strain curve obtained by a tensile test in accordance with JIS-K 7127:1999 and JIS K7161. [Figure 3]FIG. 3 shows typical patterns (a) to (e) of stress-strain curves (SS curves) of plastics. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present disclosure will be described in detail. The present disclosure can be implemented in many different forms, and should not be construed as being limited to the description of the following exemplary embodiments. For clarity of explanation, the drawings may show the width, thickness, shape, etc. of each layer more schematically than in the embodiments, but these are merely examples and do not limit the interpretation of the present disclosure. In this specification and each drawing, elements similar to those already described with reference to the previous drawings are designated by the same reference numerals, and detailed descriptions may be omitted as appropriate.

[0013] In the present disclosure, when multiple upper limit candidates and multiple lower limit candidates are listed for a certain parameter, the numerical range of the parameter may be constructed by combining any one upper limit candidate with any one lower limit candidate. Examples of such parameters include physical properties, component content, and layer thickness. As an example, the following statement will be explained: "Parameter B is preferably A1 or greater, more preferably A2 or greater, and even more preferably A3 or greater. Parameter B is preferably A4 or less, more preferably A5 or less, and even more preferably A6 or less." In this example, the numerical range of parameter B may be A1 or greater and A4 or less, A1 or greater and A5 or less, A1 or greater and A6 or less, A2 or greater and A4 or less, A2 or greater and A5 or less, A2 or greater and A6 or less, A3 or greater and A4 or less, A3 or greater and A5 or less, or A3 or greater and A6 or less.

[0014] In this specification, each of the components (for example, resin materials and additives such as mold release agents) appearing in the following description may be used alone or in combination of two or more types.

[0015] [Stick-on thermal transfer image receiving sheet] The seal-type thermal transfer image receiving sheet of the present disclosure includes a release sheet and a seal portion, and the seal portion is provided so as to be releasable from the release sheet. The seal portion includes, from the release sheet side, an adhesive layer and a base sheet in this order.

[0016] Specific examples of the seal-type thermal transfer image-receiving sheet of the present disclosure will be described below with reference to the drawings. The seal-type thermal transfer image receiving sheet 1 shown in Fig. 1 comprises a release sheet 10, an adhesive layer 21, and a base sheet 22, in this order in the thickness direction. In this example, the adhesive layer 21 and the base sheet 22 constitute the seal portion 20. An image of a desired color, such as flesh color, may be formed on the base sheet 22 using a coloring agent such as a dye.

[0017] The seal-type thermal transfer image receiving sheet may further include a receiving layer (not shown) on the surface of the base sheet. The seal-type thermal transfer image receiving sheet may include a release sheet, an adhesive layer, a base sheet, and a receiving layer in this order in the thickness direction. The seal-type thermal transfer image receiving sheet may further include an adhesive layer, a masking layer, and a protective layer (not shown). The seal-type thermal transfer image receiving sheet may include a release sheet, a pressure-sensitive adhesive layer, a substrate sheet, an adhesive layer, a masking layer, a receiving layer, and a protective layer in this order in the thickness direction. In these examples, an image of a desired color, such as flesh color, may be formed on the receptor layer using a colorant such as a dye.

[0018] In one embodiment, the seal type thermal transfer image receiving sheet of the present disclosure is in the form of a long strip, and FIG. 1 is a cross-sectional view of, for example, a seal type thermal transfer image receiving sheet 1 taken perpendicular to the longitudinal direction.

[0019] <Base sheet> The seal-type thermal transfer image receiving sheet of the present disclosure includes a substrate sheet, which constitutes a seal portion.

[0020] The base sheet or the seal portion exhibits both an elastic region and a plastic region under the conditions of a tensile test conforming to JIS-K 7127:1999. That is, the base sheet or the seal portion has hard and tenacious mechanical properties. As a result, when a thermal transfer image is formed on the seal portion using, for example, a thermal transfer printer, the seal-type thermal transfer image receiving sheet of the present disclosure is less likely to undergo deformation of the base sheet or the surface of the seal portion, which would adversely affect the print, even if there are changes in external factors caused by the thermal transfer printer, etc. Therefore, the seal-type thermal transfer image receiving sheet of the present disclosure can be used as a seal to be applied to human skin and has excellent print quality.

[0021] As shown in Figure 2, the base sheet or the seal portion preferably has a yield point in a "stress-strain curve" (also called an "SS curve") obtained by a tensile test in accordance with JIS-K 7127:1999 and JIS K7161.

[0022] Here, the yield point is the point on the "stress-strain curve" where the stress exceeds the maximum value and the tensile stress σ decreases. The yield point on the "stress-strain curve" occurs at the boundary between the "elastic region" (the region where the material returns to its original shape like a spring when the applied force is removed) and the "plastic region" (the region where the material does not return to its original shape even when the force is removed).

[0023] When the stress on the vertical axis exceeds the Hooke's elastic limit, it increases nonlinearly and reaches the upper yield point A (usually the upper yield point is considered the yield point), at which point necking occurs. In the necked area, heat is generated due to the sudden orientation of the molecules, causing so-called strain softening, which drops to the lower yield point B, and the necking continues to grow.

[0024] The stretched necked portion is strengthened by molecular orientation, so the stress does not decrease below the lower yield point B but continues to grow toward the unstretched portion, and eventually the entire test piece is stretched and strengthened, causing the stress to rise again and reach the breaking point C.

[0025] Regarding the strain on the horizontal axis, there is first the elastic strain region where stress and strain are proportional. Generally, the elastic strain of plastics is less than 1%, and the region where it can be treated as an elastic body is very narrow. Next is the delayed elastic strain region, where elastic strain and plastic strain occur simultaneously. Furthermore, after passing the upper yield point A, it enters the plastic strain region where necking grows, eventually leading to fracture.

[0026] A material with a wide plastic strain range has a greater ability to absorb impact energy. Figure 3 shows typical patterns (a) to (e) of the SS curve of plastics. The properties of the material can be read from these patterns (a) to (e).

[0027] As shown in Figure 3(e), if the sheet has hard and resilient mechanical properties, deformation of the base sheet or the seal portion that would adversely affect printing can be suppressed even if external factors change due to the thermal transfer printer, resulting in a seal-type thermal transfer image-receiving sheet with excellent print quality.

[0028] The base sheet or the seal portion preferably has a yield point between 1% and 10% strain in the above-mentioned "stress-strain curve." More preferably, the yield point is between 1.5% and 7.5% strain. Even more preferably, the yield point is between 2.0% and 5.0% strain. This gives the base sheet or the seal portion hard and tenacious mechanical properties, so that deformation of the base sheet or the seal portion that would adversely affect printing can be suppressed even if there are changes in external factors caused by the thermal transfer printer, resulting in a seal-type thermal transfer image-receiving sheet with excellent print quality.

[0029] In the above-mentioned "stress-strain curve," the base sheet or the seal portion preferably has a tensile stress σ of 10 MPa or more at a strain of 3.5%. This makes it possible to suppress deformation of the base sheet or the seal portion that would adversely affect printing even if there are changes in external factors caused by the thermal transfer printer, resulting in a seal-type thermal transfer image-receiving sheet with excellent printing quality, if the base sheet or the seal portion has hard and tenacious mechanical properties. Furthermore, in the above-mentioned "stress-strain curve," the tensile stress σ when the strain is 15% is more preferably 10 MPa or more, and the tensile stress σ when the strain is 25% is even more preferably 10 MPa or more. Furthermore, in the above-mentioned "stress-strain curve," the tensile stress σ of the base sheet or the seal portion at a strain of 3.5% is preferably 150 MPa or less, more preferably 100 MPa or less, and even more preferably 75 MPa or less.

[0030] Examples of the substrate sheet include resin films formed from resin materials, such as polyurethane, polyester, polyamide, polyimide, polyolefin, vinyl resin, styrene resin, acrylic resin, and cellulose resin. Among the above resin films, polyvinyl chloride (PVC) film, urethane film, and polyethylene film are preferred.

[0031] The substrate sheet may contain a plasticizer, such as phthalic acid plasticizers such as dioctyl phthalate, diisononyl phthalate, octyldecyl phthalate, and diisodecyl phthalate, adipic acid plasticizers such as di-2-ethylhexyl adipate, diisononyl adipate, and diisodecyl adipate, di-2-ethylhexyl azelaate, di-2-ethylhexyl sebacate, tricresyl phosphate, trixylyl phosphate, tributyl phosphate, tri-2-ethylhexyl phosphate, octyldiphenyl phosphate, chlorinated paraffin, chlorinated fatty acid ester, and epoxidized soybean oil. The base sheet may contain one type of plasticizer, or may contain two or more types of lubricants.

[0032] The content of the plasticizer in the base sheet is preferably 1% by mass to 50% by mass, more preferably 3% by mass to 30% by mass, which allows the mechanical properties of the base sheet or the seal portion to be adjusted so that the base sheet or the seal portion has a yield point in a stress-strain curve obtained by a tensile test in accordance with JIS-K 7127:1999.

[0033] The substrate sheet may contain additives other than plasticizers. Examples of other additives include ultraviolet absorbers, light stabilizers, antioxidants, colorants, fillers, and release agents. The substrate sheet may contain a colorant as needed. The substrate sheet may contain a colorant to match the color tone of the seal portion to a desired color, such as skin color. Examples of colorants include pigments and dyes.

[0034] The substrate sheet may contain, in addition to resins other than those exemplified above and plasticizers added as needed, additives such as stabilizers, titanium oxide, silica, and the like.

[0035] The method for forming the substrate sheet is not particularly limited, but the substrate sheet can be formed by mixing the resins exemplified above, the plasticizers added as needed, and any additives in any desired ratios and thermally processing them. Alternatively, instead of thermal processing, the substrate sheet can be formed by dispersing or dissolving the resins exemplified above, the plasticizers added as needed, and any additives in an appropriate solvent, and then applying and drying the resulting coating liquid onto the adhesive layer or any layer provided on the adhesive layer.

[0036] The thickness of the substrate sheet is preferably 30 μm or more, more preferably 45 μm or more. A seal-type thermal transfer image receiving sheet having a substrate sheet with a thickness of 30 μm or more can, for example, suppress the occurrence of wrinkles when the seal is applied. Furthermore, a seal-type thermal transfer image receiving sheet having a substrate sheet with a thickness of 30 μm or more can easily peel off and apply the release sheet from the seal portion without the substrate sheet (seal portion) becoming distorted, thereby improving workability. The thickness of the substrate sheet is preferably 120 μm or less, more preferably 95 μm or less. A sticker-type thermal transfer image receiving sheet including such a substrate sheet can, for example, suppress the discomfort felt by the user after the sticker is applied.

[0037] A thermal transfer image may be provided directly on the surface of the base sheet, which allows the total thickness of the seal portion to be reduced, thereby preventing, for example, discomfort felt by the user after the seal is applied.

[0038] A printed layer may be provided on the surface of the substrate sheet. The printed layer may be a layer for adjusting the color tone of the laminated sheet to a desired color, such as skin color. The printed layer contains a colorant. Examples of the colorant include pigments and dyes.

[0039] <Adhesive layer> The seal-type thermal transfer image receiving sheet of the present disclosure includes an adhesive layer, which constitutes a seal portion.

[0040] The adhesive layer is formed using, for example, a pressure-sensitive adhesive. A pressure-sensitive adhesive is a material that has adhesive properties at room temperature and can be attached to an adherend by applying pressure. For example, even when an adherend attached to the adhesive layer is peeled off, the adhesive layer retains practical adhesive strength.

[0041] The substrate sheet may be transparent. It is sufficient that the substrate sheet is transparent enough to allow light to pass through, and so long as this is the case, the substrate sheet may be translucent or colored and transparent. The substrate sheet may also have opacifying properties. In this specification, the term "transparency" refers to a degree of transparency that allows light irradiated from one side of the substrate sheet through the substrate sheet to be visible from the other side, and means, for example, that the substrate sheet has a visible light transmittance within a measurement wavelength range of 380 nm to 780 nm. Visible light transmittance is determined as the average value of the transmittance at each wavelength measured using a spectrophotometer (Shimadzu Corporation's "UV-3100PC," compliant with JIS K 0115) within a measurement wavelength range of 380 nm to 780 nm.

[0042] Examples of adhesives include acrylic adhesives, urethane adhesives, silicone adhesives, rubber adhesives, vinyl alkyl ether adhesives, polyester adhesives, polyamide adhesives, and fluorine-based adhesives. The adhesive may contain a solvent. For example, either a water-based or solvent-based solvent can be used. For medical use, it is preferable to select an adhesive that causes little skin rash or irritation to the skin, and for example, acrylic adhesives and urethane adhesives are preferred.

[0043] The adhesive layer may contain additives. Examples of additives include ultraviolet absorbers, light stabilizers, antioxidants, colorants, fillers, and release agents. The adhesive layer may contain a colorant, if necessary. The adhesive layer may contain a colorant to match the color tone of the laminated sheet to a desired color, such as skin color. Examples of colorants include pigments and dyes.

[0044] The adhesive strength of the adhesive layer is preferably 5000 gf / 50 mm or less, more preferably 100 gf / 50 mm or more and 5000 gf / 50 mm or less. If the adhesive strength is 5000 gf / 50 mm or less, there is little risk of damaging the adherend (particularly human or animal skin) when the sheet is applied incorrectly or removed during replacement. If the adhesive strength is 100 gf / 50 mm or more, for example, adhesive strength to the adherend (particularly human or animal skin) can be ensured, and peeling of the sheet due to sweating, movement, etc. can be prevented.

[0045] The thickness of the adhesive layer is preferably 3 μm or more, more preferably 5 μm or more, and preferably 40 μm or less, more preferably 30 μm or less. The thickness of the adhesive layer is, for example, 3 μm or more and 40 μm or less.

[0046] <Release sheet> The seal-type thermal transfer image-receiving sheet of the present disclosure includes a release sheet.

[0047] Examples of release sheets include release paper with at least one release-treated surface of a paper substrate and resin films with at least one release-treated surface of a resin film. Examples of release treatments include treatments using release agents such as silicone resin-based release agents, alkyd resin-based release agents, long-chain alkyl compound-based release agents, and fluororesin-based release agents. Examples of resin films include resin films formed from resin materials such as polyolefin, vinyl resin, styrene resin, acrylic resin, fluororesin, polyester, and polyamide.

[0048] The thickness of the release sheet is preferably 50 μm or more, more preferably 100 μm or more, and preferably 300 μm or less, more preferably 200 μm or less. The thickness of the release sheet is, for example, 50 μm or more and 300 μm or less.

[0049] (Concealment layer) The seal type thermal transfer image receiving sheet of the present disclosure may be provided with a hiding layer. The hiding layer may be a white primer layer containing a white pigment and a resin material. Examples of white pigments include titanium oxide, zinc oxide, zinc sulfide, barium sulfate, and calcium carbonate. Among these, titanium oxide is preferred from the viewpoint of whiteness. The hiding layer may contain one or more white pigments.

[0050] The content of the white pigment in the hiding layer is preferably 40% by mass or more and 85% by mass or less, more preferably 50% by mass or more and 80% by mass or less. By increasing or decreasing the content of the white pigment in the hiding layer, the hiding ratio of the hiding layer can be adjusted to a desired value.

[0051] Examples of resin materials include (meth)acrylic resins, polyolefins, styrene resins, vinyl resins such as ethylene-vinyl acetate copolymers and vinyl chloride-vinyl acetate copolymers, polyesters, polyamides, imide resins, cellulose resins, polyol resins, polycarbonates, and ionomer resins. The hiding layer can contain one or more resin materials.

[0052] The content of the resin material in the hiding layer is preferably 10% by mass to 70% by mass, more preferably 10% by mass to 50% by mass, which can prevent re-aggregation of the white pigment and provide high hiding power.

[0053] The hiding layer may contain additives. Examples of additives include fillers, plasticizers, antistatic agents, UV absorbers, release agents, and dispersants. The hiding layer can contain one or more additives.

[0054] The thickness of the hiding layer is preferably 0.6 μm or more, more preferably 0.8 μm or more, and even more preferably 1.0 μm or more. The thickness of the hiding layer is preferably 6 μm or less, more preferably 5 μm or less, and even more preferably 4 μm or less. Here, increasing the thickness of the hiding layer can hide the color of the base. On the other hand, decreasing the thickness of the hiding layer can reduce the hiding rate of the hiding layer.

[0055] The concealing layer can be formed, for example, by dispersing or dissolving the components described above in a suitable solvent to prepare a coating liquid, which is then applied to any layer to be provided on the base sheet of the sealing portion using the known coating method described above, and then dried.

[0056] (adhesive layer) The seal type thermal transfer image receiving sheet of the present disclosure may have an adhesive layer. In one embodiment, the seal-type thermal transfer image-receiving sheet may have an adhesive layer between the substrate sheet and the concealing layer, thereby improving the adhesion between the substrate layer and the concealing layer.

[0057] The adhesive layer preferably contains a resin material. Examples of the resin material include (meth)acrylic resin, vinyl resin, polyolefin, polyester, polyurethane, epoxy resin, urea resin, melamine resin, and phenol resin. The adhesive layer can contain one or more resin materials.

[0058] The content of the resin material in the adhesive layer is preferably 70% by mass or more and 100% by mass or less, and more preferably 80% by mass or more and 100% by mass or less.

[0059] The adhesive layer may be a layer obtained by curing a resin material with a curing agent, such as an isocyanate compound, an aliphatic amine, a cyclic aliphatic amine, an aromatic amine, or an acid anhydride.

[0060] The thickness of the adhesive layer is preferably 0.1 μm or more, more preferably 0.5 μm or more, and preferably 10 μm or less, more preferably 2 μm or less. The thickness of the adhesive layer is, for example, 0.1 μm or more and 10 μm or less.

[0061] The adhesive layer can be formed, for example, by dispersing or dissolving the components described above in a suitable solvent to prepare a coating liquid, which is then applied onto the hiding layer by the known coating method described above and dried.

[0062] (receptor layer) The seal-type thermal transfer image-receiving sheet of the present disclosure may include a receptor layer, which is located on the surface of the substrate sheet opposite the adhesive layer in the seal portion. The receiving layer is a layer for receiving dyes and the like transferred from the thermal transfer sheet. For example, when forming an image (thermal transfer image) using a printer, the image may be formed on a receiving layer previously provided on a substrate sheet, or a concealing layer may be formed on a transfer sheet, and the receiving layer may be provided on the concealing layer. The image may be, for example, an image for adjusting the color tone of the seal portion to a desired color, such as skin color.

[0063] The material constituting the receiving layer may be, for example, a resin material. Examples of the resin material include polyolefin, vinyl resin, styrene resin, acrylic resin, polyester, polyamide, polyimide, polyurethane, polycarbonate, cellulose resin, and ionomer resin. Examples of the polyolefin include polyethylene and polypropylene. Examples of the vinyl resin include polyvinyl chloride, polyvinyl acetate, and vinyl chloride-vinyl acetate copolymer. Examples of the polyester include polyethylene terephthalate and polyethylene naphthalate. The resin material constituting the receiving layer is preferably a vinyl resin, and more preferably a vinyl chloride-vinyl acetate copolymer.

[0064] The content of the resin material in the receiving layer is preferably 70% by mass or more, and more preferably 80% by mass or more, relative to the total mass of the receiving layer, which can provide the receiving layer with sufficient durability, for example.

[0065] The receiving layer may contain additives such as ultraviolet absorbers, light stabilizers, antioxidants, colorants, fillers, and release agents.

[0066] The content of the additive in the receiving layer is preferably 1% by mass or more, more preferably 2% by mass or more, and preferably 30% by mass or less, more preferably 20% by mass or less, based on the total mass of the receiving layer. The content of the additive in the receiving layer is, for example, 1% by mass or more and 30% by mass or less.

[0067] The thickness of the receptor layer is preferably 0.3 μm or more, more preferably 0.5 μm or more, and even more preferably 0.8 μm or more. The thickness of the receptor layer is preferably 5.0 μm or less, more preferably 3.0 μm or less, and even more preferably 2.0 μm or less. Here, if the thickness of the receptor layer is greater than the lower limit, sufficient print density cannot be obtained. On the other hand, if the thickness of the receptor layer is less than the upper limit, the conformability when applied to the skin is insufficient, and a sense of unity with the skin cannot be obtained.

[0068] When a receiving layer is provided on a substrate sheet in advance, the solvent contained in the coating liquid may melt and damage the substrate sheet, or cause denaturation or deformation during the process of applying and drying a coating liquid for the receiving layer on the hiding layer. In this case, it is preferable to transfer the receiving layer onto the substrate sheet by thermal transfer. The receiving layer may be provided on the substrate sheet in advance, or may be provided by thermal transfer onto the substrate sheet during image formation.

[0069] (protective layer) The seal type thermal transfer image receiving sheet of the present disclosure may be provided with a protective layer. The seal-type thermal transfer image receiving sheet of the present disclosure may have a seal portion that includes, for example, an adhesive layer, a base sheet, a concealing layer, a receiving layer, and a protective layer in this order, or may have an adhesive layer, a base sheet, a concealing layer, a receiving layer on which an image is formed, and a protective layer in this order.

[0070] The protective layer may be made of a resin material, such as polyester, polyamide, polyurethane, polycarbonate, vinyl resin, styrene resin, acrylic resin, acrylic polyol resin, cellulose resin, phenoxy resin, epoxy resin, silicone-modified versions of these resins, ultraviolet-absorbing resins, and ionizing radiation-curable resins.

[0071] Examples of polyesters include polyethylene terephthalate and polyethylene naphthalate. Examples of vinyl resins include vinyl chloride-vinyl acetate copolymer, polyvinyl chloride, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl acetal, and polyvinyl pyrrolidone. Examples of cellulose resins include ethyl cellulose, hydroxyethyl cellulose, ethylhydroxycellulose, methyl cellulose, and cellulose acetate.

[0072] Examples of ionizing radiation curable resins include resins obtained by crosslinking and curing a radical polymerizable polymer or a radical polymerizable oligomer by irradiating it with ionizing radiation. Specific examples include resins obtained by adding a photopolymerization initiator to a radical polymerizable polymer or a radical polymerizable oligomer as needed, and polymerizing and crosslinking the resulting polymer or oligomer by irradiating it with an electron beam or ultraviolet light.

[0073] The content of the resin material in the protective layer is preferably 80% by mass or more, and more preferably 85% by mass or more, relative to the total mass of the protective layer, which can provide, for example, sufficient durability to the protective layer.

[0074] The protective layer may contain additives. Examples of additives include ultraviolet absorbers, light stabilizers, antioxidants, colorants, fillers, and release agents. The protective layer may contain a colorant, if necessary. The protective layer may contain a colorant to match the color tone of the laminated sheet to a desired color, such as skin color. Examples of colorants include pigments and dyes.

[0075] The content of the additive in the protective layer is preferably 1% by mass or more, more preferably 2% by mass or more, and preferably 20% by mass or less, more preferably 15% by mass or less, relative to the total mass of the protective layer. The content of the additive in the protective layer is, for example, 1% by mass or more and 20% by mass or less.

[0076] The thickness of the protective layer is preferably 0.1 μm or more, more preferably 0.5 μm or more, even more preferably 1 μm or more, and preferably 20 μm or less, more preferably 10 μm or less, even more preferably 5 μm or less. Such a protective layer can, for example, impart sufficient protective function to the seal-type thermal transfer image-receiving sheet. The thickness of the protective layer is, for example, 0.1 μm or more and 20 μm or less.

[0077] The protective layer can be formed, for example, by applying a coating liquid containing the above-mentioned materials to a receiving layer or the like by a known means such as roll coating, reverse roll coating, gravure coating, reverse gravure coating, bar coating, or rod coating, and then drying the coating.

[0078] The protective layer can be formed, for example, by preparing a thermal transfer sheet having a protective layer, superimposing the thermal transfer sheet on a substrate film or the like corresponding to the substrate sheet, and transferring the protective layer onto the receiving layer or the receiving layer on which an image is formed by a thermal transfer process.

[0079] <Sticker-type thermal transfer image receiving sheet> The total thickness of the seal-type thermal transfer image receiving sheet of the present disclosure, which is composed of a release sheet, an adhesive layer, and a substrate sheet, is preferably 30 μm or more, more preferably 45 μm or more, and preferably 120 μm or less, more preferably 95 μm or less. The total thickness of the seal-type thermal transfer image receiving sheet is, for example, 30 μm or more and 120 μm or less. If the total thickness of the seal-type thermal transfer image receiving sheet is within the above range, when used as a seal to be applied to human skin, discomfort felt by the user after application of the seal can be reduced, and excellent print quality can be achieved when a thermal transfer image is formed directly on the surface of the substrate sheet in the seal portion or on the receiving layer.

[0080] (Mechanism of action) When printing a thermal transfer sheet using a thermal transfer printer, the thermal transfer sheet receives the dye while being affected by external factors such as heat, pressure, and tensile stress. For example, sticker-type thermal transfer image receiving sheets used for applications that are attached to human skin, such as nail stickers, body paint stickers, and skin stickers, are becoming thinner in the seal area, making them more susceptible to changes in external factors such as the thermal transfer printer. Deformation of the surface of the base sheet can have a negative impact on the print. In particular, sticker-type thermal transfer image receiving sheets that do not have a receptor layer are thermally transferred (sublimation transferred) directly onto the base sheet, and therefore may be more directly affected than regular image receiving sheets.

[0081] Therefore, as a result of intensive research, the inventors have found that the mechanical properties of the seal portion or the base sheet constituting the seal portion affect print quality. Specifically, they have found that when a base sheet or seal portion with hard and brittle or soft but brittle mechanical properties is used, it is easily affected by changes in external factors caused by the thermal transfer printer, causing deformation of the surface of the base sheet or seal portion, which has an adverse effect on print. In contrast, they have found that when a base sheet or seal portion with hard and tenacious mechanical properties is used, deformation of the base sheet or seal portion that would have an adverse effect on print can be suppressed even when changes in external factors caused by the thermal transfer printer are caused.

[0082] The inventors then discovered that a seal-type thermal transfer image receiving sheet with excellent printing quality can be obtained if the base sheet or seal portion has a yield point in a stress-strain curve obtained by a tensile test in accordance with JIS-K 7127:1999 (and JIS K7161), which is an indicator of the hard and tough mechanical properties of the base sheet or seal portion.

[0083] (Application) An example of the use of the seal-type thermal transfer image-receiving sheet of the present disclosure will be described below. In one embodiment, the sticker-type thermal transfer image receiving sheet can be used as a skin design sheet (a sticker for application to human skin; a skin sheet) by forming an image (thermal transfer image) on the surface of the base sheet, or by forming an image on the receiving layer if the sheet has one. Examples of skin design sheets include nail stickers, body paint stickers, and tattoo stickers.

[0084] In one embodiment, a skin design sheet can be produced from a seal-type thermal transfer image receiving sheet. For example, a plurality of skin design sheets may be produced from a seal-type thermal transfer image receiving sheet. For example, a roll of seal-type thermal transfer image receiving sheet may be cut to produce individual seal-type thermal transfer image receiving sheets in the product form.

[0085] By sticking the skin design sheet to the user's skin so that the adhesive layer is in contact with the skin, the user can easily enjoy body painting or the like.

[0086] In addition, by producing a skin design sheet by on-demand printing from a photographed image of the user onto a sticker-type thermal transfer image receiving sheet, the color of the skin design sheet can be matched to the natural skin color of the user, thereby reducing the discomfort felt when the skin design sheet is applied to the user's skin.

[0087] [Manufacturing method of skin design sheet] According to the seal-type thermal transfer image-receiving sheet of the present disclosure, for example, a skin-design sheet can be produced by a thermal transfer process. A long substrate sheet corresponding to the seal-type thermal transfer image receiving sheet of the present disclosure is prepared. The substrate sheet may be provided with an adhesive layer and a release sheet. This substrate sheet and thermal transfer sheet are set in a thermal transfer printer.

[0088] The thermal transfer sheet comprises a substrate and a transferable receiving layer, a dye layer, and optionally a protective layer, which are provided in surface order on one side of the substrate. The receiving layer is a transparent layer that receives the dye transferred from the thermal transfer sheet. Examples of the dye layer include a yellow dye layer, a magenta dye layer, and a cyan dye layer. The dye layer contains a binder resin and a sublimable dye. Known materials can be used for the yellow dye layer, the magenta dye layer, and the cyan dye layer. Details of the receiving layer and the protective layer are as described above. When printing directly on the surface of the substrate sheet or when a receiving layer is previously provided on the substrate sheet, it is not necessary for the thermal transfer sheet to have a receiving layer, or for the receiving layer to be transferred as described below.

[0089] The thermal transfer printer includes a thermal head and a platen roll that sandwich the substrate sheet and heat the thermal transfer sheet. The thermal head heats the receptor layer of the transfer mold, transferring the receptor layer onto the substrate sheet. Next, the thermal head sequentially heats the yellow dye layer, magenta dye layer, and cyan dye layer, for example, based on the data of the skin design sheet, transferring the dyes to the receptor layer transferred onto the substrate sheet to form an image. If necessary, the protective layer of the thermal transfer sheet is then heated, transferring the protective layer onto the receptor layer on which the image has been formed.

[0090] If necessary, the surface of the base sheet may be subjected to a shaping process such as embossing to form a concave-convex shape. For example, an embossing plate or a shaping sheet may be used in the embossing process. The embossing plate and the shaping sheet may be used without any particular restrictions. The surface shapes of the embossing plate and the shaping sheet and the surface shapes shaped by them are almost the inverse of each other.

[0091] The long seal-type thermal transfer image-receiving sheet is cut parallel to the width direction of the sheet using a cutter in a thermal transfer printer to obtain a sheet-like seal-type thermal transfer image-receiving sheet. If necessary, a protective sheet may be attached to the seal surface of the sheet-like seal-type thermal transfer image-receiving sheet.

[0092] Next, the seal-type thermal transfer image receiving sheet is cut into the shape of the product form of the skin design sheet using a known cutting device. For example, when the seal-type thermal transfer image receiving sheet is viewed from above, the seal-type thermal transfer image receiving sheet is punched into a circular shape. The shape is not particularly limited.

[0093] In this manner, a skin design sheet having a desired shape can be produced. In the above method, the adhesive layer may be provided on the substrate sheet after the thermal transfer process. In this case, it is preferable to provide a release sheet after the adhesive layer is formed.

[0094] In one embodiment of the seal-type thermal transfer image-receiving sheet of the present disclosure, a method for producing a skin design sheet by a thermal transfer process has been described, but the method for producing a skin design sheet is not limited to the above method.

[0095] Furthermore, in one embodiment of the seal-type thermal transfer image-receiving sheet of the present disclosure, a mode in which a thermal transfer printer (thermal printer) is used in the method for producing a skin-design sheet has been described, but the present invention is not limited to this. The printer may be a thermal transfer printer, an inkjet printer, etc. Among these, a thermal transfer printer is preferable. As a thermal transfer printer for use with the seal-type thermal transfer image-receiving sheet of the present disclosure, a dye-sublimation thermal transfer printer, which has excellent color reproducibility and gradation, is suitable.

[0096] The present disclosure relates to, for example, the following [1] to

[10] . [1] A seal-type thermal transfer image receiving sheet comprising a release sheet and a seal portion having an adhesive layer and a base sheet in this order from the release sheet side, the seal portion being provided so as to be releasable from the release sheet, The seal-type thermal transfer image-receiving sheet, wherein the base sheet or the seal portion exhibits both an elastic region and a plastic region under the conditions of a tensile test in accordance with JIS-K 7127:1999. [2] The seal-type thermal transfer image receiving sheet according to [1] above, wherein the base sheet or the seal portion has a yield point in a stress-strain curve obtained by a tensile test in accordance with JIS-K 7127:1999. [3] The seal-type thermal transfer image-receiving sheet according to [2] above, which has a yield point in the stress-strain curve where the strain is between 1% and 10%. [4] The seal-type thermal transfer image-receiving sheet according to [2] above, wherein the tensile stress at a strain of 3.5% in the stress-strain curve is 10 MPa or more. [5] A seal-type thermal transfer image receiving sheet according to any one of [1] to [4] above, wherein the base sheet contains one or more resin materials selected from the group consisting of polyvinyl chloride (PVC) film, urethane film, and polyethylene film. [6] The seal-type thermal transfer image-receiving sheet according to any one of the above [1] to [5], wherein the thickness of the substrate sheet is 30 μm or more and 120 μm or less. [7] The seal-type thermal transfer image receiving sheet according to any one of the above [1] to [6], wherein a thermal transfer image is provided directly on the surface of the base sheet opposite to the adhesive layer. [8] The sealing portion further comprises a receiving layer, The seal-type thermal transfer image-receiving sheet according to any one of the above [1] to [7], wherein the receiving layer is located on the surface of the base sheet opposite to the adhesive layer. [9] The seal-type thermal transfer image-receiving sheet according to [8] above, wherein a thermal transfer image is provided on the receiving layer.

[10] The seal type thermal transfer image receiving sheet according to any one of the above [1] to [9], which is for sublimation transfer type thermal transfer. [Example]

[0097] The seal-type thermal transfer image-receiving sheet of the present disclosure will be described in more detail with reference to examples, but the seal-type thermal transfer image-receiving sheet of the present disclosure is not limited to these examples. In the following description, "parts" means "parts by mass."

[0098] The substrate sheets shown in Table 1 below were prepared. The yield points in the table were determined by checking the presence or absence of a yield point from a "stress-strain curve (SS curve)" obtained using a test method in accordance with JIS-K-7127:1999. The substrate sheets were prepared with a thickness of 50 μm.

[0099] Stress-strain curve The "stress-strain curve" was obtained by a tensile test in accordance with JIS-K 7127:1999 and JIS K7161. The tensile test was carried out using a small tabletop tester (EZ Test series, manufactured by Shimadzu Corporation) as a measuring instrument, and the above-mentioned substrates 1 to 3 were measured under the following measurement conditions. (Measurement conditions) Test piece: Type 2, width 10 mm Initial chuck spacing: 50mm Test speed: 100mm / min Uses a 500N load cell

[0100] <Rating 1> The presence or absence of a yield point was evaluated from the obtained stress-strain curves for the above-mentioned substrates 1 to 3. The results are shown in Table 1. The yield point was determined as the point on the stress-strain curve where the slope first became negative (the first part where the strain increases without increasing the stress: the convex part of the curve). (Evaluation criteria) ○: Yield point ×: No yield point

[0101] <Rating 2> The tensile stress σ at a strain of 3.5% was evaluated from the obtained stress-strain curves for the above-mentioned substrates 1 to 3. The results are shown in Table 1. (Evaluation criteria) ○: Tensile stress is 10MPa or more ×: Tensile stress is less than 10MPa

[0102] [Table 1]

[0103] Example 1 Substrate 1 was prepared as a substrate sheet. An adhesive layer having a thickness of 10 μm was formed on the surface of the substrate sheet using an acrylic adhesive (SK Dyne MD-1, manufactured by Soken Chemical & Engineering Co., Ltd.), and a 100 μm PET film (T60, manufactured by Toray Industries, Inc., thickness: 100 μm) was attached to the release sheet, thereby obtaining a seal-type thermal transfer image-receiving sheet of Example 1.

[0104] <Example 2> A seal type thermal transfer image receiving sheet of Example 2 was obtained in the same manner as in Example 1, except that Substrate 2 was used instead of Substrate 1 as the substrate sheet.

[0105] <Comparative Example 1> A seal type thermal transfer image receiving sheet of Comparative Example 1 was obtained in the same manner as in Example 1, except that Substrate 3 was used instead of Substrate 1 as the substrate sheet.

[0106] [Print quality] First, on the seal type thermal transfer image receiving sheets of Examples 1 and 2 and Comparative Example 1, a gray image of 11 steps (0 to 255 gradations) of mixed colors of yellow, magenta and cyan was printed using a test printer under the following conditions. (Test printer conditions) Thermal head: F3598 (Toshiba Hokuto Electronics Co., Ltd.) Heating element average resistance: 5300 (Ω) Resolution: 301 (dpi) Head power: 22 (W / dot) Line speed: 2.00msec / line Conveying speed: 2.00msec / line Printing start temperature: 23°C

[0107] Next, the roughness of the images formed on the surface of the substrate sheet was evaluated by the following procedure for the seal type thermal transfer image receiving sheets of Examples 1 and 2 and Comparative Example 1. The evaluation results are shown in Table 2.

[0108] <Image roughness evaluation 1> (Evaluation Procedure) The prints created using the above method were visually evaluated by five subjects. The subjects were selected after confirming in advance that their evaluations using a standard sample were consistent. (Evaluation criteria) ◎: All five people rated it as having no roughness and excellent print quality. ○: All five people evaluated that there was a rough feeling, but that there was no problem in actual use. ×: All five people rated it as having a rough texture.

[0109] <Image roughness evaluation 2> (Evaluation Procedure) The print density (Bk OD value around 0.4) of the prints made by the above method was measured using a scanner under the following conditions for the printed area (N number: 3), and the print quality (graininess) was quantified using image analysis software. The evaluation results are shown in Table 2. (Device) The printed material was scanned using a scanner (CanoScan 9000F Mark II, manufactured by Canon Inc.) under the following conditions: (Scan conditions) Input settings: Paper type: Paper / Photo Color mode: Grayscale Output resolution: 600dpi Image settings: Edge emphasis: OFF, Moire reduction: OFF, Dust and scratch reduction: OFF, Grain reduction: OFF Color Correction: None (Image Processing) Using the image processing software ImageJ (Ver. 1.45s), a histogram was created, the standard deviation was calculated, and the degree of variation was quantified as image quality (graininess). When using the image processing software ImageJ, select "Histogram" from the "Analyze" tab to display a histogram of the selected image. The standard deviation can be calculated from the numerical data used to draw the resulting histogram, and when using ImageJ, the standard deviation is displayed as "StdDev" below the histogram display. The total bit depth of the selected range was set to 8100. (Evaluation criteria) ⊚: The average standard deviation is 3.0 or less, there is no roughness, and the print quality is excellent. ◯: The average standard deviation is 5.0 or less, and there is a rough feeling, but there is no problem in practical use. ×: The average standard deviation is greater than 5.0, and there is a rough feeling.

[0110] [Table 2] [Explanation of symbols]

[0111] 1. Sticker-type thermal transfer image receiving sheet 10 Release sheet 20 Seal part 21 Adhesive layer 22 Base sheet

Claims

1. A seal-type thermal transfer image receiving sheet comprising a release sheet and a seal portion having an adhesive layer and a base sheet in this order from the release sheet side, the seal portion being provided so as to be releasable from the release sheet, The seal-type thermal transfer image-receiving sheet, wherein the base sheet or the seal portion exhibits both an elastic region and a plastic region under the conditions of a tensile test in accordance with JIS-K 7127:1999.

2. 2. The seal-type thermal transfer image-receiving sheet according to claim 1, wherein the base sheet or the seal portion has a yield point in a stress-strain curve obtained by a tensile test in accordance with JIS-K 7127:1999.

3. 3. The seal type thermal transfer image receiving sheet according to claim 2, wherein the stress-strain curve has a yield point where the strain is between 1% and 10%.

4. 3. The seal type thermal transfer image receiving sheet according to claim 2, wherein the tensile stress at a strain of 3.5% in the stress-strain curve is 10 MPa or more.

5. 2. The seal-type thermal transfer image-receiving sheet according to claim 1, wherein the substrate sheet comprises one or more resin materials selected from the group consisting of polyvinyl chloride (PVC) film, urethane film, and polyethylene film.

6. 2. The seal-type thermal transfer image-receiving sheet according to claim 1, wherein the thickness of the substrate sheet is 30 [mu]m or more and 120 [mu]m or less.

7. 2. The seal-type thermal transfer image-receiving sheet according to claim 1, wherein a thermal transfer image is provided directly on the surface of the base sheet opposite to the adhesive layer.

8. The seal portion further comprises a receiving layer, The seal-type thermal transfer image receiving sheet according to claim 1 , wherein the receiving layer is located on the surface of the base sheet opposite to the adhesive layer.

9. 9. The seal type thermal transfer image receiving sheet according to claim 8, wherein the receiving layer is provided with a thermal transfer image.

10. 2. The seal type thermal transfer image receiving sheet according to claim 1, which is for sublimation transfer type thermal transfer.

Images