Thermal transfer sheet and intermediate transfer medium

Abstract

To provide a thermal transfer sheet which achieves both adhesion between a base material and a transfer layer, and peelability of a peeling layer during transfer, and enables production of a glossy printed matter.SOLUTION: A thermal transfer sheet includes a base material and a transfer layer, wherein the transfer layer has a peeling layer and a protective layer in this order from the base material side, the peeling layer contains a first resin, a second resin and a third resin as resin materials, the first resin is an acrylic resin, the second resin is a cellulose-based resin, the third resin is polyester, a content of the second resin with respect to 100 pts.mass of the first resin is 3 pts.mass or more and 12 pts.mass or less, and a content of the third resin with respect to 100 pts.mass of the first resin is 0.2 pts.mass or more and 0.8 pts.mass or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a thermal transfer sheet and an intermediate transfer medium. [Background technology]

[0002] A thermal transfer method is widely used as a method for producing a print. According to this thermal transfer method, a thermal transfer sheet having a colorant layer on one side of a base layer is combined with a thermal transfer image receiving sheet having a receiving layer on one side of another base layer, and a thermal transfer image is formed on the receiving layer of the thermal transfer image receiving sheet, thereby obtaining a print.

[0003] Known thermal transfer methods include dye-sublimation thermal transfer and melting thermal transfer. The dye-sublimation thermal transfer method is a method in which a sublimable dye contained in a colorant layer of a thermal transfer sheet is transferred to a receiving layer of a thermal transfer image-receiving sheet by a heating means such as a thermal head. The melting thermal transfer method is a method in which a colorant layer of a thermal transfer sheet is melted or softened by a heating means such as a thermal head, and the colorant layer is transferred onto a receiving layer of a thermal transfer image-receiving sheet.

[0004] With the diversification of printed products, there is a demand for decorated products in which a thermally transferred image is formed on a transferee that does not have a receiving layer on its surface, rather than a printed product in which a thermally transferred image is formed on the receiving layer of a thermal transfer image-receiving sheet. To meet this demand, a method using an intermediate transfer medium in which a transfer layer having a receiving layer as a surface layer is provided on one side of a base layer is known. In this method, a thermally transferred image is formed on the receiving layer, which is the surface layer of the intermediate transfer medium, using a thermal transfer sheet, and then the transfer layer having the receiving layer on which the thermally transferred image is formed is transferred onto the transferee, thereby obtaining a decorated product in which the transfer layer is provided on the transferee.

[0005] Thermal transfer images formed using conventional thermal transfer sheets and transfer layers with a receiving layer on which a thermal transfer image is formed using an intermediate transfer medium are vulnerable to rubbing or scratching and may have low abrasion resistance. Furthermore, glossy prints and decorative products may be required. Therefore, a protective layer is provided on the surface of the thermal transfer image or transfer layer to meet these requirements. For example, Patent Document 1 discloses a protective layer transfer sheet that can obtain glossy prints by transferring a protective layer containing a release layer containing a polyester and a resin with a Vicat softening temperature of 75°C to 110°C as measured by the ISO 306 B50 method. Patent Document 2 also discloses an intermediate transfer medium that has a release layer containing a cellulose-based resin and exhibits good transferability of the transfer layer. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2019-001056 [Patent Document 2] Japanese Patent Application Publication No. 2018-058210 Summary of the Invention [Problem to be solved by the invention]

[0007] The release layers disclosed in Patent Documents 1 and 2 achieve release properties by mixing a cellulose-based resin with an acrylic resin or a vinyl chloride-vinyl acetate copolymer, but there is room for improvement in the glossiness of the printed matter and the adhesion between the substrate and the transfer layer.

[0008] The present disclosure has been made in consideration of the above circumstances, and aims to provide a thermal transfer sheet that achieves both good adhesion between the substrate and the transfer layer and good releasability of the release layer during transfer, and that produces glossy printed matter. [Means for solving the problem]

[0009] The thermal transfer sheet of the present disclosure comprises a substrate and a transfer layer, the transfer layer comprising a release layer and a protective layer in that order from the substrate side, the release layer containing a first resin, a second resin and a third resin as resin materials, the first resin being an acrylic resin, the second resin being a cellulose-based resin and the third resin being polyester, the content of the second resin relative to 100 parts by mass of the first resin being 3 parts by mass or more and 12 parts by mass or less, and the content of the third resin relative to 100 parts by mass of the first resin being 0.2 parts by mass or more and 0.8 parts by mass or less. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to provide a thermal transfer sheet that satisfies both the adhesiveness between the substrate and the transfer layer and the releasability of the transfer layer during transfer, and that can produce a glossy printed product. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic cross-sectional view showing one embodiment of the thermal transfer sheet of the present disclosure. [Figure 2] FIG. 2 is a schematic cross-sectional view showing one embodiment of the thermal transfer sheet of the present disclosure. [Figure 3] FIG. 3 is a schematic cross-sectional view showing one embodiment of the thermal transfer sheet of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0012] In this specification, foil retention refers to the degree to which the transfer layer is prevented from falling off from the base layer when bending stress is applied to the thermal transfer sheet, and when foil retention is good, it means that the transfer layer can be prevented from falling off from the base layer when bending stress is applied to the thermal transfer sheet (i.e., the adhesion between the base layer and the transfer layer is excellent).

[0013] [Thermal transfer sheet] The thermal transfer sheet of the present disclosure includes a substrate and a transfer layer. The transfer layer includes, from the substrate side, a release layer and a protective layer in this order. The release layer contains a first resin, a second resin, and a third resin as resin materials, where the first resin is an acrylic resin, the second resin is a cellulose-based resin, and the third resin is polyester. The content of the second resin per 100 parts by mass of the first resin is 3 parts by mass or more and 12 parts by mass or less, and the content of the third resin per 100 parts by mass of the first resin is 0.2 parts by mass or more and 0.8 parts by mass or less. The thermal transfer sheet of the present disclosure will be described in more detail below by way of preferred embodiments.

[0014] Fig. 1 is a cross-sectional view showing one embodiment of a thermal transfer sheet according to the present disclosure. In Fig. 1, the thermal transfer sheet 1 comprises a substrate 10 and a transfer layer 20 provided on the substrate 10. The transfer layer 20 comprises a release layer 21 and a protective layer 22, in this order from the substrate 10 side in the thickness direction of the thermal transfer sheet 1. The protective layer 22 constitutes a surface layer on one side of the transfer layer 20.

[0015] 2 is a cross-sectional view showing another embodiment of the thermal transfer sheet of the present disclosure. In Fig. 2, the transfer layer 20 includes a release layer 21, a protective layer 22, and an adhesive layer 23, in this order from the substrate 10 side in the thickness direction of the thermal transfer sheet 1.

[0016] 3 is a cross-sectional view showing another embodiment of the thermal transfer sheet of the present disclosure. In Fig. 3, the transfer layer 20 includes a release layer 21, a protective layer 22, and a receiving layer 24, in this order from the substrate 10 side in the thickness direction of the thermal transfer sheet 1.

[0017] The thermal transfer sheet of the embodiment shown in FIGS. 1 and 2 includes a release layer 30 between the substrate 10 and the transfer layer 20 . The thermal transfer sheet of the embodiment in FIG. 2 includes a back layer 40 on the surface of the substrate 10 opposite to the surface on which the transfer layer 20 is provided. Each layer of the thermal transfer sheet of the present disclosure will be described below.

[0018] <Base material> The substrate can be any substrate without particular limitations as long as it has heat resistance to the thermal energy applied during thermal transfer and has mechanical strength sufficient to support the transfer layer and the like provided on the substrate.

[0019] The substrate can be, for example, a film made of a resin material (hereinafter also referred to as a "resin film"). Examples of the resin material include polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, 1,4-polycyclohexylene dimethylene terephthalate, and terephthalic acid-cyclohexanedimethanol-ethylene glycol copolymer; polyamide; polyimide; polycarbonate; polyolefins such as polyethylene, polypropylene, and polymethylpentene; polystyrene; vinyl resins such as vinyl chloride resin, vinyl acetate resin, vinyl chloride-vinyl acetate copolymer, polyvinyl alcohol, and polyvinylpyrrolidone; vinyl acetal resins such as polyvinyl acetoacetal and polyvinyl butyral; (meth)acrylic resins such as poly(meth)acrylate; cellulose resins such as cellophane, cellulose acetate, nitrocellulose, cellulose acetate propionate, and cellulose acetate butyrate; and ionomers.

[0020] Among the above resin materials, polyester is preferred from the viewpoint of heat resistance and mechanical strength, polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) are more preferred, and PET is even more preferred.

[0021] In the present disclosure, "(meth)acrylic" encompasses both "acrylic" and "methacrylic," and "(meth)acrylate" encompasses both "acrylate" and "methacrylate."

[0022] A resin film laminate may be used as the substrate, and the resin film laminate can be produced by, for example, dry lamination, wet lamination, or extrusion.

[0023] The resin film may be a stretched film or an unstretched film. From the viewpoint of strength, a stretched film that is uniaxially or biaxially stretched is preferred.

[0024] When an intermediate layer such as a release layer is provided between the substrate layer and the transfer layer, the surface of the substrate layer on the transfer layer side may be subjected to a surface treatment in order to enhance adhesion between the substrate layer and the intermediate layer. Examples of the surface treatment method include corona discharge treatment, flame treatment, ozone treatment, ultraviolet treatment, radiation treatment, roughening treatment, chemical treatment, plasma treatment, low-temperature plasma treatment, primer treatment, and grafting treatment.

[0025] The thickness of the substrate is preferably from 1 μm to 50 μm, more preferably from 3 μm to 25 μm, which can improve, for example, the mechanical strength of the substrate and the transfer of thermal energy during thermal transfer.

[0026] <Transfer layer> The transfer layer comprises a release layer and a protective layer in this order from the substrate side in the thickness direction of the thermal transfer sheet. The transfer layer is a layer that can be peeled off from the substrate by thermal transfer. In one embodiment, the transfer layer further comprises an adhesive layer. The adhesive layer constitutes the surface layer of the transfer layer on the protective layer side. In another embodiment, the transfer layer further comprises a receiving layer. The receiving layer constitutes the surface layer of the transfer layer on the protective layer side.

[0027] (peeling layer) In one embodiment, the transfer layer in the thermal transfer sheet includes a release layer as the layer located closest to the substrate among the layers constituting the transfer layer. The release layer is a layer that is transferred together with the protective layer during thermal transfer. By providing the release layer, the transferability of the transfer layer can be further improved. In other words, the releaseability of the transfer layer from the substrate layer when transferring the transfer layer from the thermal transfer sheet can be improved. The release layer is transferred as part of the transfer layer during thermal transfer. After transfer, the release layer becomes the surface layer of the transfer recipient, such as a print or a thermal transfer image, and has the effect of improving the abrasion resistance of the transfer recipient and imparting a glossy surface layer.

[0028] In one embodiment, the release layer contains a first resin, a second resin, and a third resin as resin materials, where the first resin is an acrylic resin, the second resin is a cellulose-based resin, and the third resin is polyester.

[0029] "First Resin" The first resin is an acrylic resin. In the thermal transfer sheet of the present disclosure, the release layer contains an acrylic resin as the first resin, so that both the foil retention of the transfer layer and the releasability (hot releasability) of the transfer layer from the substrate layer when transferring the transfer layer from the thermal transfer sheet can be achieved. Furthermore, after transfer, when the release layer becomes the surface layer of the transfer recipient, it improves the abrasion resistance of the transfer recipient and imparts a glossy surface layer.

[0030] Examples of acrylic resins include polymethyl methacrylate, polyethyl methacrylate, and polybutyl acrylate. Among these, polymethyl methacrylate is preferred from the viewpoint of abrasion resistance. The release layer can contain one or more first resins. The acrylic resin may also be copolymerized with other monomers, such as 2-hydroxyethyl (meth)acrylate, cycloalkyl (meth)acrylate, isobornyl (meth)acrylate, phenyl (meth)acrylate, benzyl (meth)acrylate, methacrylic acid, and styrene.

[0031] The lower limit of the glass transition temperature (Tg) of the acrylic resin is preferably 40°C or higher, more preferably 50°C or higher, and even more preferably 60°C or higher. The upper limit is preferably 120°C or lower, more preferably 110°C or lower, and even more preferably 105°C or lower. When the lower limit of the glass transition temperature of the acrylic resin is 40°C or higher, the foil-cutting properties of the coating film are improved. When the upper limit is 120°C or lower, the hot peelability is improved. In the present disclosure, the glass transition temperature (Tg) is a value obtained by DSC in accordance with JIS K7121:2012.

[0032] The lower limit of the weight-average molecular weight (Mw) of the acrylic resin is preferably 10,000 or more, more preferably 15,000 or more, and even more preferably 20,000 or more. The upper limit is preferably 300,000 or less, more preferably 150,000 or less, and even more preferably 100,000 or less. When the lower limit of the weight-average molecular weight of the acrylic resin is 10,000 or more, the abrasion resistance is improved. When the upper limit is 300,000 or less, the peelability of the coating film is improved. In the present disclosure, the weight average molecular weight (Mw) is a value measured by gel permeation chromatography (GPC) analysis and converted into standard polystyrene.

[0033] The lower limit of the acid value (mgKOH / g) of the acrylic resin is preferably 0 or more, more preferably 2 or more, and even more preferably 10 or more. The upper limit is preferably 30 or less, more preferably 20 or less, and even more preferably 15 or less. In the present disclosure, the acid value (mgKOH / g) is a value obtained in accordance with JIS K0070:1992.

[0034] "Second Resin" The second resin is a cellulose-based resin. In the thermal transfer sheet of the present disclosure, the release layer contains a cellulose-based resin as the second resin, so that the peelability (heat-release property) of the transfer layer from the substrate layer when transferring the transfer layer from the thermal transfer sheet can be adjusted. Specifically, the peel force of the transfer layer from the substrate layer when transferring the transfer layer from the thermal transfer sheet can be reduced. That is, when the release layer contains only the first resin (acrylic resin) as the resin material, the region (process margin) in which the above-mentioned foil retention and heat-release property can be achieved simultaneously is narrow. However, when the release layer contains the second resin (cellulose-based resin) as the resin material, the heat-release property can be adjusted, so that the above-mentioned process margin can be expanded.

[0035] Examples of cellulose-based resins include cellophane, cellulose acetate, nitrocellulose, cellulose acetate propionate, cellulose acetate butyrate, and hydroxypropyl cellulose. Among these, cellulose acetate propionate and cellulose acetate butyrate are preferred from the viewpoint of hot releasability. The release layer can contain one or more second resins.

[0036] The lower limit of the glass transition temperature (Tg) of the cellulose-based resin is preferably 80°C or higher, more preferably 90°C or higher, and even more preferably 100°C or higher. The upper limit is preferably 150°C or lower, more preferably 140°C or lower, and even more preferably 130°C or lower. When the lower limit of the glass transition temperature of the cellulose-based resin is 80°C or higher, hot peelability is improved. When the upper limit is 150°C or lower, gloss is improved.

[0037] The number-average molecular weight (Mn) of the cellulose-based resin has a lower limit of preferably 10,000 or more, more preferably 15,000 or more, and even more preferably 20,000 or more. The upper limit is preferably 60,000 or less, more preferably 50,000 or less, and even more preferably 40,000 or less. When the lower limit of the number-average molecular weight of the cellulose-based resin is 10,000 or more, hot peelability is improved. When the upper limit is 60,000 or less, gloss is improved. In the present disclosure, the number average molecular weight (Mn) is a value obtained by gel permeation chromatography (GPC) in accordance with JIS K7252-1:2016, converted into polystyrene.

[0038] The lower limit of the content of the second resin relative to 100 parts by mass of the first resin is 3 parts by mass or more, preferably 4 parts by mass or more, and more preferably 5 parts by mass or more. The upper limit is 12 parts by mass or less, preferably 11 parts by mass or less, and more preferably 10 parts by mass or less. Specifically, the content of the second resin relative to 100 parts by mass of the first resin in the release layer is 3 parts by mass or more and 12 parts by mass or less. When the content of the second resin relative to 100 parts by mass of the first resin is equal to or greater than the lower limit, the peeling force of the transfer layer from the substrate layer when transferring the transfer layer from the thermal transfer sheet can be reduced. When the content of the second resin relative to 100 parts by mass of the first resin is equal to or less than the upper limit, the glossiness of the surface layer is not impaired when the release layer after transfer becomes the surface layer of the transfer recipient (a glossy surface layer can be obtained).

[0039] "Third Resin" The third resin is polyester. In the thermal transfer sheet of the present disclosure, the release layer contains polyester as the third resin, so that the foil retention of the transfer layer can be adjusted. Specifically, the adhesion between the base layer and the transfer layer in the thermal transfer sheet can be improved. That is, when the release layer contains only the first resin (acrylic resin) as the resin material, the region (process margin) in which the above-mentioned foil retention and hot peelability can be achieved simultaneously is narrow. However, when the release layer contains the third resin (polyester) as the resin material, the foil retention can be adjusted, so that the above-mentioned process margin can be expanded.

[0040] The polyester may be, for example, a copolymer of a monomer component containing a dicarboxylic acid compound and a diol compound.

[0041] Examples of dicarboxylic acid compounds include malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, eicosanedioic acid, pimelic acid, azelaic acid, methylmalonic acid, ethylmalonic acid, adamantanedicarboxylic acid, norbornenedicarboxylic acid, cyclohexanedicarboxylic acid, decalindicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 5-sodiumsulfoisophthalic acid, phenylendanedicarboxylic acid, anthracenedicarboxylic acid, phenanthrenedicarboxylic acid, 9,9'-bis(4-carboxyphenyl)fluorene acid, and ester derivatives thereof.

[0042] Examples of diol compounds include ethylene glycol, 1,2-propanediol, 1,3-propanediol, butanediol, 2-methyl-1,3-propanediol, hexanediol, neopentyl glycol, cyclohexanedimethanol, cyclohexanediethanol, decahydronaphthalenedimethanol, decahydronaphthalenediethanol, norbornanedimethanol, norbornanediethanol, tricyclodecanedimethanol, tricyclodecaneethanol, tetracyclododecanedimethanol, tetracyclododecanediethanol, decalindimethanol, and decalindiethanol. , 5-methylol-5-ethyl-2-(1,1-dimethyl-2-hydroxyethyl)-1,3-dioxane, cyclohexanediol, bicyclohexyl-4,4'-diol, 2,2-bis(4-hydroxycyclohexylpropane), 2,2-bis(4-(2-hydroxyethoxy)cyclohexyl)propane, cyclopentanediol, 3-methyl-1,2-cyclopentadiol, 4-cyclopentene-1,3-diol, adamantanediol, paraxylene glycol, bisphenol A, bisphenol S, styrene glycol, trimethylolpropane, and pentaerythritol.

[0043] The monomer components forming the polyester may contain other compounds as copolymerization components in addition to the dicarboxylic acid compound and the diol compound. The proportion of structural units derived from other compounds in the polyester is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less.

[0044] The release layer can contain one or more third resins.

[0045] The lower limit of the glass transition temperature (Tg) of the polyester is preferably 20°C or higher, more preferably 40°C or higher, and even more preferably 60°C or higher. The upper limit is preferably 90°C or lower, more preferably 80°C or lower, and even more preferably 70°C or lower. When the lower limit of the glass transition temperature of the polyester is 20°C or higher, foil retention is improved. When the upper limit is 90°C or lower, hot peelability is improved.

[0046] The lower limit of the number average molecular weight (Mn) of the polyester is preferably 3000 or more, more preferably 5000 or more, and even more preferably 10,000 or more. The upper limit is preferably 70,000 or less, more preferably 50,000 or less, and even more preferably 30,000 or less. When the lower limit of the number average molecular weight of the polyester is 3000 or more, hot peelability is improved. When the upper limit is 50,000 or less, foil retention is improved.

[0047] The upper limit of the acid value (mgKOH / g) of the polyester is preferably 10 or less, more preferably 5 or less, and even more preferably 3 or less. When the upper limit is 10 or less, the foil retention is improved.

[0048] The lower limit of the content of the third resin relative to 100 parts by mass of the first resin is 0.2 parts by mass or more, preferably 0.3 parts by mass or more, and more preferably 0.4 parts by mass or more. The upper limit is 0.8 parts by mass or less, preferably 0.7 parts by mass or less, and more preferably 0.6 parts by mass or less. Specifically, the content of the third resin relative to 100 parts by mass of the first resin in the release layer is 0.2 parts by mass or more and 0.8 parts by mass or less. When the content of the third resin relative to 100 parts by mass of the first resin is equal to or greater than the lower limit, adhesion between the base layer and the transfer layer in the thermal transfer sheet can be ensured. When the content of the third resin relative to 100 parts by mass of the first resin is equal to or less than the upper limit, the peeling force of the transfer layer from the base layer when transferring the transfer layer from the thermal transfer sheet can be reduced.

[0049] In one embodiment, the content of the resin material in the release layer is preferably 70% by mass or more and 100% by mass or less, more preferably 80% by mass or more and 100% by mass or less, thereby further improving the abrasion resistance of the transfer target, such as a printed matter or a thermally transferred image, while maintaining the thermal transferability of the transfer layer.

[0050] The release layer, in one embodiment, may contain a wax. Examples of waxes include natural waxes such as beeswax, spermaceti, Japan wax, rice bran wax, carnauba wax, candelilla wax, and montan wax; synthetic waxes such as paraffin wax, microcrystalline wax, oxidized wax, ozokerite, ceresin, ester wax, and polyethylene wax; higher saturated fatty acids such as margaric acid, lauric acid, myristic acid, palmitic acid, stearic acid, furoic acid, and behenic acid; higher saturated monohydric alcohols such as stearyl alcohol and behenyl alcohol; higher esters such as fatty acid esters of sorbitan; and higher fatty acid amides such as stearic acid amide and oleic acid amide. Among these, polyethylene wax is preferred from the viewpoint of the thermal transferability of the transfer layer. The release layer can contain one or more waxes.

[0051] In one embodiment, the wax content in the release layer is preferably 0.1% by mass to 15% by mass, more preferably 1% by mass to 10% by mass, relative to the solid mass of the binder resin, which can further improve the thermal transferability of the transfer layer.

[0052] The release layer may contain additives. Examples of additives include metal soaps, plasticizers, antistatic agents, ultraviolet absorbers, inorganic particles, organic particles, release agents, and dispersants. The release layer may contain one or more additives. To further improve the abrasion resistance, the resin contained in the release layer may be hardened by an isocyanate hardener, a titanium chelating agent, an epoxy hardener, or the like.

[0053] The thickness of the release layer is preferably 0.1 μm or more and 3.0 μm or less, and more preferably 0.2 μm or more and 2.0 μm or less, which can, for example, further improve the transferability of the transfer layer.

[0054] (protective layer) The protective layer is a layer for protecting a transfer object such as a print or a thermal transfer image, or the receiving layer if the transfer layer includes a receiving layer. In one embodiment, the thermal transfer sheet of the present disclosure includes a protective layer on the surface of the release layer of the transfer layer, between the release layer and the adhesive layer, or between the release layer and the receiving layer.

[0055] In one embodiment, the protective layer contains one or more resin materials, such as polyester, polyurethane, polystyrene, (meth)acrylic resin, and (meth)acrylic polyol resin. The protective layer may contain one or more of the above additives.

[0056] The thickness of the protective layer is preferably 0.5 μm or more and 7 μm or less, and more preferably 1 μm or more and 5 μm or less, which can, for example, further improve the durability of the protective layer.

[0057] The release layer can be formed, for example, by dispersing or dissolving the components described above in water or an appropriate organic solvent to prepare a coating liquid, and then applying and drying the coating liquid onto a substrate or any layer (e.g., a release layer) provided on the substrate by the coating method described above. In one embodiment, an organic solvent-based coating liquid is used as the release layer coating liquid to form the release layer, and an organic solvent-based coating liquid is used as the protective layer coating liquid to form the protective layer. Examples of organic solvents include ketone-based solvents such as methyl ethyl ketone, aromatic solvents such as toluene, ester-based solvents such as ethyl acetate, and mixed solvents thereof.

[0058] (adhesive layer) In one embodiment, the thermal transfer sheet of the present disclosure may include an adhesive layer on the surface of the protective layer of the transfer layer, which can improve adhesion between the transfer recipient and the transfer layer (protective layer) when the transfer layer is transferred to the transfer recipient.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] The thickness of the adhesive layer is preferably 0.1 μm or more and 10 μm or less, and more preferably 0.5 μm or more and 2 μm or less.

[0063] 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 protective layer by the known coating method described above, and then dried.

[0064] (receptor layer) In one embodiment, the thermal transfer sheet of the present disclosure may include a receiving layer on the surface of the protective layer of the transfer layer. The thermal transfer sheet of the present disclosure may be used as an intermediate transfer medium. In this case, the receiving layer constitutes a surface layer on one side of the intermediate transfer medium.

[0065] In one embodiment, the receiving layer contains a resin material, for example, polyolefins such as polyethylene and polypropylene, vinyl resins such as polyvinyl chloride, polyvinyl acetate, and vinyl chloride-vinyl acetate copolymers, polyesters such as polyethylene terephthalate and polyethylene naphthalate, polystyrene, (meth)acrylic resins, polyamides, polyimides, polycarbonates, polyurethanes, cellulose resins, and ionomer resins. The receiving layer can contain one or more types of resin materials.

[0066] The content of the resin material in the receiving layer is preferably 80% by mass to 99% by mass, more preferably 85% by mass to 98% by mass, which can further improve the receptivity of, for example, sublimation dyes.

[0067] In one embodiment, the receptor layer contains a release agent, which can improve the releasability between the receptor layer and the thermal transfer sheet including the sublimation transfer colorant layer when the thermal transfer sheet of the present disclosure is used as an intermediate transfer medium, for example.

[0068] Examples of the release agent include fluorine compounds, phosphate ester compounds, higher fatty acid amide compounds, metal soaps, silicone oils, and waxes such as polyethylene wax and paraffin wax. Among these, silicone oils are preferred from the viewpoint of the above-mentioned release properties.

[0069] Examples of silicone oils include straight silicone oils such as dimethyl silicone oil and methylphenyl silicone oil, as well as modified silicone oils such as amino-modified silicone oil, epoxy-modified silicone oil, carboxy-modified silicone oil, (meth)acrylic-modified silicone oil, mercapto-modified silicone oil, carbinol-modified silicone oil, fluorine-modified silicone oil, methylstyryl-modified silicone oil, and polyether-modified silicone oil. Modified silicone oils include single-end type, double-end type, and side-chain single-end type. The receiving layer may contain one or more types of release agents.

[0070] The content of the release agent in the receiving layer is preferably 0.5% by mass to 20% by mass, more preferably 0.5% by mass to 10% by mass, which can improve the releasability, for example.

[0071] The receiving layer may contain an additive. Examples of additives include plasticizers, UV absorbers, inorganic particles, organic particles, and dispersants. The receiving layer may contain one or more additives. The content of the additive per 100 parts by mass of the resin material contained in the receiving layer is preferably 0.1 parts by mass or more and 20 parts by mass or less, more preferably 0.5 parts by mass or more and 10 parts by mass or less.

[0072] The thickness of the receiving layer is preferably 0.5 μm to 20 μm, more preferably 1 μm to 10 μm, which can improve the density of the image formed on the receiving layer and the transferability of the transfer layer.

[0073] The receiving layer can be formed, for example, by dispersing or dissolving the components described above in an appropriate solvent to prepare a coating liquid, which is then applied onto the protective layer by the known coating method described above, and then dried.

[0074] <Release layer> In one embodiment, the thermal transfer sheet of the present disclosure may include a release layer between the substrate and the transfer layer. The release layer is a layer that improves the releasability of the transfer layer provided on the substrate. The release layer is a layer that does not constitute the transfer layer and remains on the substrate side when the transfer layer is transferred onto a transfer-receiving body.

[0075] The resin material constituting the release layer is not particularly limited as long as it has high adhesion to the substrate and appropriate releasability that allows the transfer layer to be easily peeled off. Examples of such resin materials include silicone resins, fluororesins, polyvinyl alcohol, (meth)acrylic resins, thermally crosslinkable epoxy-amino resins, thermally crosslinkable alkyd-amino resins, melamine resins, urea resins, and cellulose resins. Among these, silicone resins are preferred because they can improve the transferability of the transfer layer. The release layer can contain one or more of the above resin materials.

[0076] The release layer may contain additives. Examples of additives include fillers, plasticizers, antistatic agents, UV absorbers, organic particles, inorganic particles, release agents, and dispersants. The release layer may contain one or more additives.

[0077] The thickness of the release layer is preferably 0.1 μm or more and 3 μm or less, more preferably 0.3 μm or more and 2 μm or less, which can, for example, further improve the transferability of the transfer layer.

[0078] The release layer can be formed, for example, by dispersing or dissolving the above-described components in water or an appropriate organic solvent to prepare a coating liquid, and then applying the coating liquid to a substrate by the above-described coating method and drying it. By heating the coating film after drying, for example, the curing of the silicone resin can be effectively promoted, and the transferability of the transfer layer can be further improved.

[0079] <Back layer> In one embodiment, the thermal transfer sheet of the present disclosure may include a backing layer on the surface of the substrate opposite to the transfer layer, which can, for example, prevent sticking and wrinkles caused by heat during thermal transfer.

[0080] In one embodiment, the back layer contains a resin material. Examples of the resin material include silicone resin, (meth)acrylic-modified silicone resin, vinyl resin, vinyl acetal resin, polyester, polyamide, polyurethane, polyolefin, polystyrene, (meth)acrylic resin, cellulose resin, and phenol resin. The back layer can contain one or more types of resin materials.

[0081] In one embodiment, the back layer may be a layer formed by crosslinking a resin material having a reactive group such as a hydroxyl group using a crosslinking agent such as a polyisocyanate compound. Examples of polyisocyanate compounds include xylene diisocyanate, toluene diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate. One or more crosslinking agents can be used.

[0082] The back layer may contain additives. Examples of additives include plasticizers, antistatic agents, ultraviolet absorbers, organic particles, inorganic particles, release agents, and dispersants. The back layer may contain one or more additives. The thickness of the back layer is preferably 0.05 μm or more and 3 μm or less.

[0083] The back layer can be formed, for example, by dispersing or dissolving the components described above in water or an appropriate organic solvent to prepare a coating liquid, applying the coating liquid onto a substrate using the coating means described above to form a coating film, and drying.

[0084] [How to use the thermal transfer sheet] <Thermal transfer sheet> In one embodiment, the thermal transfer sheet of the present disclosure may further include a colorant layer on one side of the substrate layer, in frame sequence with the transfer layer. In this embodiment, the colorant layer and the transfer layer are provided in frame sequence on one side of the substrate layer. By using the thermal transfer sheet of this embodiment, a thermal transfer image can be formed on the receiving layer of a transfer recipient or the receiving layer of an intermediate transfer medium. Therefore, by using the thermal transfer sheet of the present disclosure, it is possible to simultaneously form a thermal transfer image on the receiving layer of a transfer recipient or an intermediate transfer medium and transfer a transfer layer (protective layer) onto the thermal transfer image, without using a separate thermal transfer sheet including a colorant layer.

[0085] For example, when a thermal transfer image is formed by a sublimation thermal transfer method, the colorant layer is a sublimation transfer type colorant layer containing a sublimation dye and a binder resin.

[0086] The sublimation dye preferably has sufficient color density and does not discolor or fade due to light, heat, etc. Examples of such sublimation dyes include red dyes, yellow dyes, and blue dyes. The sublimation transfer colorant layer can contain one or more sublimation dyes. The content of the sublimation dye in the sublimation transfer colorant layer is preferably 5% by mass or more and 80% by mass or less, more preferably 10% by mass or more and 70% by mass or less.

[0087] Examples of binder resins in the sublimation transfer colorant layer include cellulose resins, vinyl resins, vinyl acetal resins, (meth)acrylic resins, polyurethanes, polyamides, polyimides, and polyesters. The sublimation transfer colorant layer can contain one or more binder resins. The content of the binder resin in the sublimation transfer colorant layer is preferably 20% by mass or more and 75% by mass or less, more preferably 30% by mass or more and 60% by mass or less.

[0088] The sublimation transfer colorant layer may be cured with a curing agent. Examples of the curing agent include epoxy resin, isocyanate, and carbodiimide. One or more types of curing agents may be used.

[0089] The sublimation transfer colorant layer may contain one or more types of inorganic particles and organic particles. Examples of inorganic particles include carbon black, silica, alumina, titanium dioxide, and molybdenum disulfide. Examples of organic particles include polyethylene particles.

[0090] The sublimation transfer colorant layer may contain one or more release agents. Examples of release agents include fluorine compounds, phosphate ester compounds, higher fatty acid amide compounds, metal soaps, silicone oils, and waxes such as polyethylene wax and paraffin wax. The content of the release agent in the sublimation transfer colorant layer is preferably 0.01% by mass or more and 3% by mass or less, more preferably 0.01% by mass or more and 1% by mass or less.

[0091] For example, when a thermal transfer image is formed by a melting type thermal transfer method, the color material layer is a melting type color material layer containing a colorant and a binder resin.

[0092] The colorant preferably has sufficient color density and does not discolor or fade due to light, heat, or the like. Examples include organic pigments, inorganic pigments, and dyes. The colorant color is not limited to cyan, magenta, yellow, or black, but may be any of a variety of colors. The melt-transfer colorant layer may contain one or more colorants. The content of the colorant in the melt-transfer colorant layer is preferably 10% by mass or more and 60% by mass or less, more preferably 20% by mass or more and 50% by mass or less.

[0093] Examples of binder resins in the melt-transfer colorant layer include polyolefins, vinyl resins, vinyl acetal resins, (meth)acrylic resins, polystyrene, polycarbonate, cellulose resins, and petroleum resins. The melt-transfer colorant layer can contain one or more binder resins. The content of the binder resin in the melt-transfer colorant layer is preferably 20% by mass or more and 75% by mass or less, more preferably 30% by mass or more and 60% by mass or less.

[0094] The melt transfer colorant layer may further contain a conventionally known wax. The colorant layer may contain one or more of the above additives.

[0095] The thermal transfer sheet of the present disclosure may have one colorant layer on one side of the base layer, or may have multiple colorant layers of different hues, for example, a yellow colorant layer, a magenta colorant layer, a cyan colorant layer, and a black colorant layer, arranged in face sequence. The thickness of the colorant layer is preferably 0.1 μm or more and 5 μm or less.

[0096] <Intermediate transfer medium> In one embodiment, the thermal transfer sheet of the present disclosure includes a receiving layer on the surface of the protective layer in the transfer layer (see FIG. 3). The thermal transfer sheet of this embodiment can be used as an intermediate transfer medium. This allows a thermal transfer image to be formed on the receiving layer of the intermediate transfer medium of the present disclosure using a thermal transfer sheet including the above-described colorant layer. Therefore, a transfer layer including a thermal transfer image and a protective layer can be transferred onto a desired transfer target.

[0097] <Protective layer transfer sheet> In one embodiment, the thermal transfer sheet of the present disclosure can be used as a protective layer transfer sheet (see Figures 1 and 2). The protective layer transfer sheet of this embodiment can transfer a transfer layer that serves as a protective layer to the surface layer of a transfer recipient, such as a print or a thermally transferred image, thereby improving the abrasion resistance of the transfer recipient and imparting a glossy surface layer.

[0098] The present disclosure relates to, for example, the following [1] to [4]. [1] A thermal transfer sheet comprising a substrate and a transfer layer, the transfer layer includes a release layer and a protective layer in this order from the substrate side, the release layer contains a first resin, a second resin, and a third resin as resin materials; the first resin is an acrylic resin, the second resin is a cellulose-based resin, the third resin is polyester, the content of the second resin relative to 100 parts by mass of the first resin is 3 parts by mass or more and 12 parts by mass or less, A thermal transfer sheet, wherein the content of the third resin relative to 100 parts by mass of the first resin is 0.2 parts by mass or more and 0.8 parts by mass or less. [2] The transfer layer further comprises an adhesive layer; The thermal transfer sheet according to [1] above, wherein the adhesive layer is provided on the surface of the protective layer. [3] The transfer layer further comprises a receiving layer; The thermal transfer sheet according to [1] above, wherein the receiving layer is provided on the surface of the protective layer. [4] The thermal transfer sheet according to any one of the above [1] to [3], further comprising a release layer between the substrate and the transfer layer. [Example]

[0099] The thermal transfer sheet of the present disclosure will be described in more detail below using examples, but the thermal transfer sheet of the present disclosure is not limited to these examples. In the following description, "parts" means "parts by mass." The blending amounts shown in the following description and Table 1 are values ​​converted into solids, excluding water and organic solvents.

[0100] [Preparation example] A coating liquid for a release layer and a coating liquid for a protective layer each having the following formulation were prepared.

[0101] <Release layer coating solution (1)> 100 parts of No. 1 resin (acrylic resin) (Dianal (registered trademark) MB-7333, Mitsubishi Chemical Corporation) Second resin (cellulose-based resin) 3.5 parts (Cellulose acetate butyrate, CAB-381-0.5, Eastman) Third resin (polyester) 0.5 parts (Vylon (registered trademark) 200, Toyobo Co., Ltd.) 15 parts polyethylene wax (Slip Agent C, Showa Ink Industrial Co., Ltd.) 125 parts methyl ethyl ketone (MEK) Toluene 125 parts

[0102] <Release layer coating liquid (2) to (13)> Coating solutions (2) to (13) for release layer were prepared in the same manner as coating solution (1) for release layer, except that the ratio of the amounts of the second resin and the third resin was changed as shown in Table 1.

[0103] <Coating liquid for protective layer> Acid-modified polyethylene 8 parts (Arrowbase (registered trademark) SA-1200, Unitika Ltd.) 2 parts polyester (Elite® KA-5034, Tg: 67°C, Mn: 9,000, Unitika Ltd. ·Wednesday 22 parts IPA 68 copies

[0104] [Example 1] A release layer coating solution (1) was applied to one side of a 4.5 μm thick PET film and dried to form a release layer with a thickness of 0.8 μm. A protective layer coating solution was applied to the release layer and dried to form a protective layer with a thickness of 1.2 μm. In this way, a thermal transfer sheet was obtained. In Example 1, the transfer layer was composed of a release layer and a protective layer.

[0105] [Examples 2 to 9 and Comparative Examples 1 to 4] A thermal transfer sheet was produced in the same manner as in Example 1, except that the coating liquid for the release layer was changed as shown in Table 1. In Table 1, the release layer column lists only the relative amounts of the cellulose-based resin and polyester, assuming that the acrylic resin is 1.

[0106] [evaluation] <Foil retention> The area of ​​the thermal transfer sheets obtained in the examples and comparative examples was 100 cm 2The area where the transfer layer was formed was folded once in the longitudinal direction and once in the lateral direction and left to stand. After standing, the sheet was unfolded, visually observed, and evaluated based on the following evaluation criteria. The evaluation results are summarized in Table 1. (Evaluation criteria) ◎: The foil peeling of the transfer layer is 3mm 2 It was less than. ○: The foil peeling of the transfer layer is 3 mm 2 More than 7mm 2 It was less than. △: The foil drop of the transfer layer is 7 mm 2 More than 10mm 2 It was less than. ×: The foil peeling of the transfer layer is 10 mm 2 That was all.

[0107] <Removability> Using genuine receiver paper for a dye-sublimation thermal transfer printer (DS-40, Dai Nippon Printing Co., Ltd.), the protective layer of the thermal transfer sheet of each Example and Comparative Example was transferred onto the genuine receiver paper under the following test printer conditions, thereby obtaining transfers of each Example and Comparative Example. (Test printer conditions) Heating element average resistance: 5545 (Ω) Print density in the main scanning direction: 300 (dpi) Sub-scanning direction print density: 300 (dpi) Line cycle: 4 (msec. / line) Printing pattern (energy gradation): 180 / 255 gradations

[0108] When the above transfer product was formed, the peelability of the protective layer of the thermal transfer sheet of each Example and Comparative Example was evaluated based on the following evaluation criteria. (Evaluation criteria) ⊚: When transferring the transfer layer onto the genuine image receiving paper, no peeling noise is generated, and there is no transfer failure of the transfer layer or peeling marks on the printed matter. ◯: When the transfer layer is transferred onto the genuine image receiving paper, a peeling sound is generated, but there is no transfer failure of the transfer layer and no peeling marks on the printed matter. △: When the transfer layer is transferred onto the genuine image receiving paper, a peeling sound is generated and peeling marks appear on the print. ×: NG: When peeling off the thermal transfer sheet after transferring the transfer layer onto the genuine image receiving paper, the peeling was difficult and part of the thermal transfer sheet was torn.

[0109] <Glossy feel> The prints obtained in the peelability evaluation were visually observed and evaluated based on the following evaluation criteria. (Evaluation criteria) ⊚: It was confirmed that the printed matter had an extremely high specular gloss. ○: It was confirmed that the printed matter had a high specular gloss. △: Cloudy areas were observed in some parts of the print. ×: The entire surface of the printed matter was cloudy and frosted.

[0110] [Table 1] [Explanation of symbols]

[0111] 1: Thermal transfer sheet 10: Base material 20: Transfer layer 21: Peel layer 22:Protective layer 23: Adhesive layer 24: Receptor 30: Release layer 40: Back layer

Claims

1. A thermal transfer sheet comprising a substrate and a transfer layer, the transfer layer includes a release layer and a protective layer in this order from the substrate side, the release layer contains a first resin, a second resin, and a third resin as resin materials; the first resin is an acrylic resin, the second resin is a cellulose-based resin, the third resin is polyester, the content of the second resin relative to 100 parts by mass of the first resin is 3 parts by mass or more and 12 parts by mass or less, A thermal transfer sheet, wherein the content of the third resin relative to 100 parts by mass of the first resin is 0.2 parts by mass or more and 0.8 parts by mass or less.

2. the transfer layer further comprises an adhesive layer; The thermal transfer sheet according to claim 1 , wherein the adhesive layer is provided on the surface of the protective layer.

3. the transfer layer further comprises a receiving layer; The thermal transfer sheet according to claim 1 , wherein the receiving layer is provided on the surface of the protective layer.

4. The thermal transfer sheet according to claim 1 , further comprising a release layer between the substrate and the transfer layer.

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