Thermal transfer sheet

Abstract

To provide a thermal transfer sheet excellent in sticking resistance at the time of thermal transfer and blocking resistance at the time of storage and capable of reducing the abrasion of a thermal head at the time of thermal transfer.SOLUTION: The thermal transfer sheet includes a base material having a first surface and a second surface, a back surface layer provided on the first surface, and at least one of a color material layer and a transferable protective layer provided on the second surface. A thermal transfer sheet comprising: SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a thermal transfer sheet. [Background technology]

[0002] Thermal transfer printing has traditionally been used as a simple printing method. In this method, a thermal transfer sheet, which has a colorant layer provided on a substrate, is superimposed on a thermal transfer image-receiving sheet, and the back surface of the thermal transfer sheet is heated in an image-like pattern using a thermal head provided in a thermal transfer printer, thereby forming an image (thermal transfer image) on the thermal transfer image-receiving sheet.

[0003] Thermal transfer methods are mainly divided into melt transfer and sublimation transfer. Images formed by the thermal transfer method have high density and excellent sharpness. Therefore, the thermal transfer method is suitable for recording binary images such as characters. The sublimation transfer method can control the amount of sublimation dye migration depending on the amount of energy applied, so it can form gradation images with controlled image density for each dot of the thermal head. The sublimation transfer method uses a thermal transfer sheet with different colored dye layers, such as yellow, magenta, cyan, and black, and transfers each color dye onto a thermal transfer image-receiving sheet, making it possible to form high-quality, photographic-like full-color images with excellent intermediate color reproducibility.

[0004] In conventional thermal transfer sheets, a back layer (also commonly referred to as a heat-resistant slip layer) is provided on the surface of the substrate opposite to the surface on which the colorant layer is provided in order to prevent the substrate from fusing to the thermal head during printing and to prevent wrinkles from occurring in the resulting print (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-156110 Summary of the Invention [Problem to be solved by the invention]

[0006] When forming an image with a thermal head using a thermal transfer sheet having a back layer, a substrate, and a colorant layer, the thermal head may fuse to the back layer of the thermal transfer sheet, causing a running problem known as sticking. In this case, inorganic or organic fillers are added to the back layer to roughen the surface of the back layer, thereby reducing the contact area between the back layer and the thermal head, thereby stabilizing the slipperiness.

[0007] However, the present inventors have discovered that if the filler has a high hardness, for example, the thermal head will wear out and the printing life of the thermal head will be shortened, and if the filler has a low hardness, for example, blocking between thermal transfer sheets will occur during storage.

[0008] An object of the present disclosure is to provide a thermal transfer sheet that has excellent sticking resistance during thermal transfer and blocking resistance during storage, and that can reduce wear on a thermal head during thermal transfer. [Means for solving the problem]

[0009] The thermal transfer sheet of the present disclosure comprises a substrate having a first surface and a second surface, a back layer provided on the first surface, and at least one of a colorant layer and a transferable protective layer provided on the second surface, and the back layer contains an organic filler (excluding carbon) having a graphite structure. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to provide a thermal transfer sheet that has excellent sticking resistance during thermal transfer and blocking resistance during storage, and that can reduce wear on a thermal head during thermal transfer. [Brief explanation of the drawings]

[0011] [Figure 1]FIG. 1 is a schematic cross-sectional view of one embodiment of the thermal transfer sheet of the present disclosure. [Figure 2] FIG. 2 is a schematic cross-sectional view of one embodiment of the thermal transfer sheet of the present disclosure. 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 embodiments exemplified below. 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] [Thermal transfer sheet] The thermal transfer sheet of the present disclosure comprises: a substrate having a first surface and a second surface; a back surface layer provided on the first surface; At least one of a colorant layer and a transferable protective layer provided on the second surface; Equipped with.

[0014] The term "transferable protective layer" refers to a protective layer that is peeled from the substrate and transferred onto a transfer-receiving material by applying energy such as thermal energy to the back layer of the thermal transfer sheet. In other words, the transferable protective layer constitutes a transfer layer in the thermal transfer sheet that can be peeled off by the application of energy. Hereinafter, the transferable protective layer will also be simply referred to as "protective layer."

[0015] The thermal transfer sheet 1 of the embodiment shown in FIG. 1 includes a substrate 10, a back layer 20 provided on the first surface 12 of the substrate 10, and a colorant layer 30 provided on the second surface 14 of the substrate 10. The thermal transfer sheet 1 of the embodiment shown in FIG. 2 includes a substrate 10, a back layer 20 provided on the first surface 12 of the substrate 10, and a colorant layer 30 and a protective layer 40 provided in face-sequential order on the second surface 14 of the substrate 10. While FIG. 1 shows an embodiment in which the colorant layer 30 is provided on the substrate 10, the protective layer 40 may also be provided on the substrate 10. The thermal transfer sheet 1 of the embodiment shown in FIGS. 1 and 2 may further include a back primer layer (not shown) located between the substrate 10 and the back layer 20. The thermal transfer sheet 1 of the embodiment shown in FIG. 2 may further include a release layer (not shown) located between the substrate 10 and the protective layer 40.

[0016] <Base material> The substrate can be any substrate without particular restrictions as long as it has heat resistance that can withstand the thermal energy applied when transferring the colorant layer and protective layer from the thermal transfer sheet onto the transfer target, and mechanical strength and solvent resistance that can support the colorant layer and protective layer.

[0017] The substrate has a first surface and a second surface opposite to the first surface. In Figures 1 and 2, the first surface is designated by reference numeral 12 and the second surface is designated by reference numeral 14.

[0018] Examples of the substrate include resin films made of resin materials, such as polyesters (e.g., polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polyethylene terephthalate-isophthalate copolymer, and terephthalic acid-cyclohexanedimethanol-ethylene glycol copolymer); polyamides (e.g., nylon 6 and nylon 6,6); polyolefins (e.g., polyethylene, polypropylene, and polymethylpentene); vinyl resins (e.g., polyvinyl chloride and vinyl chloride-vinyl acetate copolymer); (meth)acrylic resins (e.g., polymethyl (meth)acrylate); polyimides; polycarbonates; engineering resins (e.g., polyarylate, polysulfone, polyethersulfone, polyphenylene ether, polyphenylene sulfide, polyaramid, polyetherketone, and polyetheretherketone); styrene resins (e.g., polystyrene, high-impact polystyrene, acrylonitrile-styrene copolymer, and acrylonitrile-butadiene-styrene copolymer); and cellulose resins (e.g., cellulose acetate and nitrocellulose). Among resin films, resin films made of polyesters such as PET and PEN are preferred from the viewpoint of excellent heat resistance and mechanical strength. The resin film can contain one or more types of resin materials.

[0019] In the present disclosure, "(meth)acrylate" encompasses both "acrylate" and "methacrylate," and "(meth)acrylic" encompasses both "acrylic" and "methacrylic."

[0020] The substrate may be, for example, a paper substrate such as glassine paper, condenser paper, and paraffin paper.

[0021] The substrate may be a laminate having multiple layers. For example, a resin film laminate may be used as the substrate. The resin film laminate can be produced by, for example, dry lamination, wet lamination, or extrusion. The substrate may be a stretched film or an unstretched film, or may be a film stretched uniaxially or biaxially from the viewpoint of improving strength. In one embodiment, the substrate is elongated.

[0022] The thickness of the substrate is preferably 0.5 μm or more, more preferably 1 μm or more, and preferably 50 μm or less, more preferably 20 μm or less, and even more preferably 10 μm or less. This can further improve the balance between the mechanical strength and the transferability of the colorant layer and the protective layer, for example. The thickness of the substrate is, for example, 0.5 μm or more and 50 μm or less.

[0023] <Back layer> The thermal transfer sheet of the present disclosure includes a backing layer (also referred to as a heat-resistant slipping layer) on the first surface of the substrate. The backing layer contains melamine cyanurate particles. By providing such a backing layer, it is possible to suppress, for example, sticking during thermal transfer, blocking during storage, and wear of the thermal head during thermal transfer. Although melamine cyanurate particles are an organic filler, they have a high heat resistance temperature of, for example, 250°C or higher. Melamine cyanurate particles are presumed to have a graphite structure, and therefore, although they are an organic filler, they have cleavage properties. Melamine cyanurate particles are not as hard as, for example, talc, and have an appropriate hardness. For these reasons, it is presumed that a backing layer has been formed that has excellent heat resistance, slipperiness (running property), and blocking resistance, and can suppress wear of the thermal head.

[0024] The melamine cyanurate particles contain melamine cyanurate. Melamine cyanurate is, for example, a compound represented by the following formula: [ka]

[0025] The average particle size of the melamine cyanurate particles is preferably 1 μm or more, more preferably 1.2 μm or more, even more preferably 1.5 μm or more, and preferably 10 μm or less, more preferably 8 μm or less, and even more preferably 5 μm or less. When the average particle size is equal to or greater than the lower limit, the anti-blocking properties tend to be better. When the average particle size is equal to or less than the upper limit, the lubricity (running properties) tend to be better. The average particle size of the melamine cyanurate particles is, for example, 1 μm or more and 10 μm or less.

[0026] The average particle size of the melamine cyanurate particles means the average value (arithmetic mean diameter) of the major axis length of the particle diameter measured for 100 randomly selected non-agglomerates when the surface of the back layer is observed with a scanning electron microscope (SEM).

[0027] The shape of the melamine cyanurate particles may be, for example, any of spherical, acicular, polygonal and irregular shapes. The back layer may contain one or more types of melamine cyanurate particles.

[0028] The content of melamine cyanurate particles in the back layer is preferably 1% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, and preferably 30% by mass or less, more preferably 28% by mass or less, and even more preferably 20% by mass or less. When the content of melamine cyanurate particles is equal to or greater than the lower limit, for example, the coefficient of friction of the back layer tends to decrease, leading to better anti-sticking properties and better anti-blocking properties. When the content of melamine cyanurate particles is equal to or less than the upper limit, for example, particle detachment can be suppressed, and a decrease in slippage during printing can be suppressed. The content of melamine cyanurate particles in the back layer is, for example, 1% by mass or more and 30% by mass or less.

[0029] The melamine cyanurate particles may be commercially available products, such as MC-4000, MC-4500, and MC-6000 manufactured by Nissan Chemical Industries Co., Ltd., and MC-20S and MC-2010N manufactured by Sakai Chemical Industry Co., Ltd.

[0030] In one embodiment, the back layer contains a resin material, such as styrene resins such as polystyrene and acrylonitrile-styrene copolymer; vinyl resins such as polyvinyl chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, polyvinyl alcohol, polyvinyl butyral, polyvinyl acetal, and polyvinyl pyrrolidone; (meth)acrylic resins such as polymethyl (meth)acrylate; polyolefins such as polyethylene, polypropylene, and polymethylpentene; polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, 1,4-polycyclohexylene dimethylene terephthalate, and terephthalic acid-cyclohexanedimethanol-ethylene glycol copolymer; cellulose resins such as methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, ethylhydroxyethyl cellulose, hydroxypropyl cellulose, cellulose acetate, nitrocellulose, cellulose acetate propionate, and cellulose acetate butyrate; polyamides; polyimides; polycarbonates; and ionomer resins.

[0031] From the viewpoint of heat resistance and the like, the glass transition temperature (Tg) of the resin material is preferably 80°C or higher, more preferably 100°C or higher, even more preferably 120°C or higher, and preferably 200°C or lower, more preferably 180°C or lower, and even more preferably 150°C or lower. Tg is obtained by differential scanning calorimetry (DSC) in accordance with JIS K7121. The Tg of the resin material is, for example, 80°C or higher and 200°C or lower.

[0032] The resin material may be a cured resin formed by curing a hydroxyl group-containing resin with an isocyanate curing agent. This can further suppress sticking during thermal transfer, for example. Examples of hydroxyl group-containing resins include polyvinyl alcohol, polyvinyl butyral, polyvinyl acetal, and (meth)acrylic polyol. One or more types of hydroxyl group-containing resins can be used. Examples of isocyanate curing agents include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,5-naphthalene diisocyanate, tolidine diisocyanate, p-phenylene diisocyanate, cyclohexane-1,4-diisocyanate, xylylene diisocyanate, triphenylmethane triisocyanate, and tris(isocyanatophenyl)thiophosphate. One or more types of isocyanate curing agents can be used.

[0033] The molar equivalent ratio (-NCO / -OH) of the isocyanate group (-NCO) of the isocyanate curing agent to the hydroxyl group (-OH) of the hydroxyl group-containing resin is preferably 1.5 or more, which can improve the heat resistance of the back layer and reduce the thermal energy transmitted to the substrate, thereby further improving the printability.

[0034] The back layer can contain one or more types of resin materials. The content of the resin material in the back layer is preferably 30% by mass or more, more preferably 35% by mass or more, and preferably 90% by mass or less, more preferably 80% by mass or less. This can, for example, further improve printability. The content of the resin material is, for example, 30% by mass or more and 90% by mass or less.

[0035] The back layer may further contain a lubricant. This can improve the slipperiness of the thermal transfer sheet during printing, and further suppress the occurrence of sticking and printing wrinkles. Examples of lubricants include waxes such as polyethylene wax, polypropylene wax, Fischer-Tropsch wax, carnauba wax, paraffin wax, alkoxylated alcohol-modified wax, and acid-modified wax; metal soaps such as zinc stearate, zinc stearyl phosphate, calcium stearate, and magnesium stearate; sucrose fatty acid esters, glycerin fatty acid esters, stearyl alcohol, fatty acid amides, phosphate esters, and silicone oils. Among these, waxes are preferred, and hydrocarbon waxes are more preferred. For example, alkoxylated alcohol-modified waxes such as ethoxylated alcohol-modified waxes and acid-modified waxes such as maleic anhydride-modified waxes are preferred, with ethoxylated alcohol-modified hydrocarbon waxes and maleic anhydride-modified hydrocarbon waxes being more preferred. Carnauba wax is also preferred.

[0036] Other examples of lubricants include polytetrafluoroethylene, melamine-formaldehyde condensates, carbon black, graphite, molybdenum disulfide, organic molybdenum, boron nitride, silane nitride, talc, and kaolin.

[0037] From the viewpoints of lubricating properties, anti-sticking properties, heat resistance, etc., the lubricant is preferably a lubricant having a melting point of 70° C. or more and 150° C. or less, and more preferably a hydrocarbon wax having a melting point of 70° C. or more and 150° C. or less. The melting point is preferably 75° C. or more, more preferably 80° C. or more, even more preferably 90° C. or more, and preferably 140° C. or less, more preferably 130° C. or less, and even more preferably 120° C. or less. The melting point is obtained by differential scanning calorimetry (DSC) in accordance with JIS K7121.

[0038] The molecular weight of the hydrocarbon wax is preferably 500 or more and 10,000 or less, more preferably 800 or more and 5,000 or less, from the viewpoints of mechanical strength, hardness, sticking resistance, and the like.

[0039] The back layer may contain one or more types of lubricants. The content of the lubricant in the back layer is preferably 1% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, and preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 35% by mass or less. This can, for example, further improve the slipperiness of the thermal transfer sheet. The content of the lubricant is, for example, 1% by mass or more and 50% by mass or less.

[0040] The back layer may contain additives such as a plasticizer, an antistatic agent, an ultraviolet absorber, a release agent, a dispersant, etc. The back layer can contain one or more of the above additives.

[0041] The thickness of the back layer is preferably 0.1 μm or more, more preferably 0.3 μm or more, and preferably 5 μm or less, more preferably 2 μm or less, from the viewpoint of improving heat resistance, slipperiness, etc. The thickness of the back layer is, for example, 0.1 μm or more and 5 μm or less.

[0042] The back layer can be formed, for example, by applying a coating liquid containing the above-mentioned materials to a substrate by known means such as roll coating, reverse roll coating, gravure coating, reverse gravure coating, bar coating, or rod coating, and then drying the applied coating.

[0043] The static friction coefficient of the surface of the back layer in the thermal transfer sheet of the present disclosure is preferably 0.45 or less, more preferably 0.38 or less, and even more preferably 0.37 or less. The lower limit of the static friction coefficient is not particularly limited and may be, for example, 0.10 or 0.20. When the static friction coefficient is equal to or less than the upper limit, for example, sticking during printing tends to be more effectively suppressed.

[0044] The coefficient of dynamic friction of the surface of the back layer in the thermal transfer sheet of the present disclosure is preferably 0.25 or less, more preferably 0.17 or less, and even more preferably 0.15 or less. The lower limit of the coefficient of dynamic friction is not particularly limited and may be, for example, 0.01 or 0.05. When the coefficient of dynamic friction is equal to or less than the upper limit, for example, sticking during printing tends to be more effectively suppressed.

[0045] In the thermal transfer sheet of the present disclosure, the difference between the static and dynamic friction coefficients of the surface of the back layer (static friction coefficient - dynamic friction coefficient) is preferably less than 0.28, more preferably less than 0.24, and even more preferably 0.23 or less.

[0046] The static and dynamic friction coefficients are measured in accordance with JIS K7125:1999 "Plastics - Films and Sheets - Friction Coefficient Test Method." The friction coefficient measurement conditions are: sliding piece load: 1.96 N, sliding piece contact area: 40 cm 2 Test speed: 100 mm / min. Details are given in the Examples section.

[0047] <Rear primer layer> The thermal transfer sheet of the present disclosure may include a rear primer layer between the substrate and the rear layer. This can improve adhesion between the substrate and the rear layer, for example. The rear primer layer contains, for example, a thermoplastic resin. As the thermoplastic resin, for example, a conventionally known resin exhibiting adhesive properties, such as polyester or (meth)acrylic resin, can be appropriately selected and used.

[0048] <Color layer> In one embodiment, the thermal transfer sheet of the present disclosure comprises a colorant layer on the second surface of the substrate.

[0049] In the thermal transfer sheet 1 of the embodiment shown in Fig. 1, a single colorant layer 30 is provided on the second surface 14 of the substrate 10. Multiple colorant layers, for example, a yellow layer, a magenta layer, a cyan layer, and optionally a black layer, may be provided on the second surface of the substrate in face-sequential order, for example, in the longitudinal direction of the substrate.

[0050] The thermal transfer sheet may include a colorant layer and a protective layer provided in surface order on the second surface of the substrate. By using the thermal transfer sheet of this embodiment, the colorant layer of the thermal transfer sheet is thermally transferred to a transfer receiving material to form an image, and then the protective layer from the thermal transfer sheet is thermally transferred onto the image so as to cover at least the printed portion, thereby producing a printed product with excellent durability.

[0051] A combination of at least one colorant layer and a protective layer provided face-sequentially to the colorant layer is referred to as a "unit" (U). The thermal transfer sheet of the present disclosure may have one unit repeated on the second surface of a long substrate, i.e., multiple units provided face-sequentially in the longitudinal direction of the substrate.

[0052] One unit may contain a single colorant layer or multiple colorant layers. When one unit contains multiple colorant layers, i.e., when it is a group of colorant layers, the colorant layers are provided in frame sequence. In one embodiment, one unit consists of a yellow layer (Y), a magenta layer (M), a cyan layer (C), a black layer (BK), and a protective layer (OP). In one embodiment, one unit consists of a black layer (BK) and a protective layer (OP).

[0053] The colorant layer may be, for example, a sublimation transfer colorant layer in which a sublimation dye is dissolved or dispersed in a binder, or a melt transfer colorant layer in which a colorant such as a pigment or dye is dispersed in a heat-melt binder. The thermal transfer sheet may include both a sublimation transfer colorant layer and a melt transfer colorant layer. For example, the yellow, magenta, and cyan colorant layers may be sublimation transfer colorant layers, and the black colorant layer may be a melt transfer colorant layer, and these colorant layers may be provided in surface order on the second surface of the substrate. For example, the gradation image portion may be formed by a sublimation transfer recording method, and the character portion may be formed by a melt transfer recording method.

[0054] In one embodiment, the colorant layer contains a binder and a colorant. Examples of binders include resin materials such as polyester, polyurethane, polyamide, polyimide, polycarbonate, polyolefin, (meth)acrylic resin, vinyl resin, styrene resin, cellulose resin, phenoxy resin, and ionomer resin. In addition to the above-mentioned resin materials, waxes such as microcrystalline wax, carnauba wax, paraffin wax, Fischer-Tropsch wax, polyethylene wax, Japan wax, beeswax, whale wax, Ibota wax, wool wax, shellac wax, candelilla wax, petrolactam, polyester wax, partially modified wax, fatty acid ester, and fatty acid amide may also be used as binders in the melt-transfer colorant layer. The melt-transfer colorant layer may contain both a resin material and a wax. The colorant layer may contain one or more types of binder.

[0055] The coloring material may be a pigment such as an organic pigment or an inorganic pigment, or may be a dye. The dye may be a sublimation dye. Specific examples of the coloring material include carbon black, acetylene black, lamp black, black smoke, iron black, aniline black, silica, calcium carbonate, titanium oxide, cadmium red, cadmium phosphate red, chrome red, vermilion, red iron oxide, azo pigments, alizarin lake, quinacridone, cochineal lake perylene, yellow ochre, aureolin, cadmium yellow, cadmium orange, chrome yellow, zinc yellow, Naples yellow, nickel yellow, greenish yellow, ultramarine, rock ultramarine, cobalt, phthalocyanine, anthraquinone, and indicoid. , cinnabar green, cadmium green, chrome green, phthalocyanine, azomethine, perylene, aluminum pigments; and sublimable dyes such as diarylmethane dyes, triarylmethane dyes, thiazole dyes, merocyanine dyes, pyrazolone dyes, methine dyes, indoaniline dyes, acetophenoneazomethine dyes, pyrazoloazomethine dyes, xanthene dyes, oxazine dyes, thiazine dyes, azine dyes, acridine dyes, azo dyes, spiropyran dyes, indolinospiropyran dyes, fluoran dyes, naphthoquinone dyes, anthraquinone dyes, and quinophthalone dyes. Examples of the hues of the coloring materials include magenta, yellow, cyan, and black. The colorant layer can contain one or more types of colorants.

[0056] The colorant layer may contain one or more of the above additives.

[0057] In one embodiment, the colorant layer is a sublimation transfer colorant layer. The content of the binder in the sublimation transfer colorant layer is preferably 20% by mass or more, more preferably 30% by mass or more, and preferably 95% by mass or less, more preferably 90% by mass or less. The content of the binder is, for example, 20% by mass or more and 95% by mass or less.

[0058] The content of the sublimation dye in the sublimation transfer colorant layer is preferably 5% by mass or more, more preferably 10% by mass or more, and preferably 80% by mass or less, more preferably 70% by mass or less. This can improve, for example, the print density and storage stability. The content of the sublimation dye is, for example, 5% by mass or more and 80% by mass or less.

[0059] 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.

[0060] A dye primer layer may be provided between the substrate and the sublimation transfer colorant layer.

[0061] In one embodiment, the colorant layer is a melt transfer type colorant layer. The binder content in the melt transfer colorant layer is preferably 20% by mass or more, more preferably 30% by mass or more, and is preferably 90% by mass or less, more preferably 80% by mass or less. The binder content is, for example, 20% by mass or more and 90% by mass or less.

[0062] The content of the colorant in the melt-transfer colorant layer is preferably 10% by mass or more, more preferably 20% by mass or more, and preferably 60% by mass or less, more preferably 50% by mass or less. The content of the colorant is, for example, 10% by mass or more and 60% by mass or less.

[0063] A release layer may be provided between the substrate and the melt-transfer colorant layer.

[0064] The thickness of the colorant layer is preferably 0.1 μm or more, more preferably 0.5 μm or more, and preferably 20 μm or less, more preferably 10 μm or less, and even more preferably 5 μm or less. The thickness of the colorant layer is, for example, 0.1 μm or more and 20 μm or less.

[0065] The colorant layer can be formed, for example, by applying a coating liquid containing the above-mentioned materials to a substrate 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 applied coating.

[0066] <Transferable Protective Layer> In one embodiment, the thermal transfer sheet of the present disclosure includes a protective layer on the second surface of the substrate. The protective layer is a layer that protects the surface of the transfer recipient after the transfer from the thermal transfer sheet to the transfer recipient.

[0067] In one embodiment, the protective layer comprises a release layer and an adhesive layer from the substrate side. That is, in one embodiment, the protective layer comprises a release layer and an adhesive layer provided on the surface of the release layer opposite the substrate. In one embodiment, the adhesive layer comes into contact with the transfer recipient when the protective layer is transferred onto the transfer recipient. In one embodiment, the release layer constitutes the surface layer of the print obtained when the protective layer is transferred onto the transfer recipient.

[0068] In one embodiment, the thermal transfer sheet of the present disclosure includes a colorant layer and a protective layer on the second surface of the substrate, the colorant layer and the protective layer being provided in face order on the second surface of the substrate. The colorant layer and the protective layer are provided in face order, for example, in the longitudinal direction of the substrate. By providing the colorant layer and the protective layer on the substrate, for example, it is possible to form a thermal transfer image on a transfer recipient and transfer the protective layer onto the formed thermal transfer image using the same thermal transfer sheet.

[0069] (peeling layer) In one embodiment, the protective layer includes a release layer, which is the layer that is located closest to the substrate among the layers that make up the protective layer. The provision of the release layer can further improve the transferability of the protective layer. The release layer is transferred as part of the protective layer during thermal transfer, and after the final transfer of the protective layer, the release layer becomes the surface layer of the thermally transferred image, improving the abrasion resistance of the thermally transferred image.

[0070] The release layer, in one embodiment, contains a binder. Examples of binders include resin materials, such as (meth)acrylic resins, styrene resins, vinyl resins such as polyvinyl alcohol, polyvinyl acetate, polyvinyl chloride, vinyl chloride-vinyl acetate copolymers, polyvinyl butyral, polyvinyl acetal, and polyvinyl pyrrolidone, polyesters such as polyethylene terephthalate and polyethylene naphthalate, cellulose resins such as ethyl cellulose, hydroxyethyl cellulose, ethylhydroxycellulose, methyl cellulose, and cellulose acetate, polyamides, polyurethanes, polycarbonates, phenoxy resins, epoxy resins, silicone-modified versions of these resins, ultraviolet-absorbing resins, and ionizing radiation-curable resins.

[0071] 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.

[0072] The release layer may contain one or more binders. The content of the binder in the release layer is preferably 80% by mass or more, and more preferably 85% by mass or more, which can impart sufficient durability to the release layer, for example.

[0073] The release layer may contain a lubricant, which, for example, allows the dynamic friction coefficient to be set lower, the running properties of the thermal transfer sheet to be maintained good, and the occurrence of wrinkles in the resulting print can be suppressed.

[0074] Examples of lubricants include waxes; metal salts of higher fatty acids; organic particles such as (meth)acrylic resins, crosslinked polystyrene, and fluororesins (e.g., polytetrafluoroethylene); and inorganic particles such as silica, clay, talc, titanium oxide, calcium carbonate, and barium sulfate.

[0075] Examples of waxes include synthetic waxes such as paraffin wax, microcrystalline wax, silicone wax, oxidized wax, ozokerite, ceresin, polyester wax, and polyethylene wax; natural waxes such as beeswax, spermaceti, Japan wax, rice bran wax, carnauba wax, candelilla wax, and montan 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 fatty acid esters such as sorbitan fatty acid esters; and higher fatty acid amides such as stearic acid amide and oleic acid amide. Examples of metal salts of higher fatty acids include zinc stearate, zinc stearyl phosphate, calcium stearate, and magnesium stearate.

[0076] The release layer may contain one or more lubricants. The content of the lubricant in the release 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. This allows, for example, the effect of the lubricant to be exerted while ensuring transparency. The content of the lubricant is, for example, 1% by mass or more and 20% by mass or less.

[0077] The release layer may contain an additive, such as a benzophenone-based ultraviolet absorber, a benzotriazole-based ultraviolet absorber, a benzoate-based ultraviolet absorber, a triazine-based ultraviolet absorber, titanium oxide, or zinc oxide; a light stabilizer such as a hindered amine-based light stabilizer or a Ni chelate-based light stabilizer; or an antioxidant such as a hindered phenol-based antioxidant, a sulfur-based antioxidant, a phosphorus-based antioxidant, or a lactone-based antioxidant.

[0078] The release layer may contain one or more additives. The content of the additive in the release layer may be, for example, 20% by mass or less, or 15% by mass or less.

[0079] The thickness of the release layer is preferably 0.1 μm or more, more preferably 0.3 μm or more, and even more preferably 0.5 μm or more, and is preferably 20 μm or less, more preferably 10 μm or less, and even more preferably 3 μm or less. This can, for example, prevent transfer defects of the protective layer and provide sufficient protective function to the transfer target. The thickness of the release layer is, for example, 0.1 μm or more and 20 μm or less.

[0080] The release layer can be formed, for example, by applying a coating liquid containing the above-mentioned materials to the substrate or the release layer by known means such as roll coating, reverse roll coating, gravure coating, reverse gravure coating, bar coating, and rod coating, and then drying the coating.

[0081] (Adhesive layer) In one embodiment, the protective layer includes an adhesive layer provided on the surface of the release layer opposite the substrate. The adhesive layer is a layer that improves adhesion between the protective layer and the transfer target. The adhesive layer can be formed, for example, from a conventionally known pressure-sensitive adhesive or heat-sensitive adhesive.

[0082] In one embodiment, the adhesive layer contains a resin material. Examples of resin materials include vinyl resins such as polyvinyl chloride, polyvinyl acetate, and vinyl chloride-vinyl acetate copolymers, (meth)acrylic resins, acid-modified polyolefins such as α-olefin-maleic anhydride copolymers, polyesters, polyurethanes, cellulose resins, silicone resins, fluororesins, and various resins modified with silicone or fluorine. Among these, vinyl chloride-vinyl acetate copolymers, polyesters, and (meth)acrylic resins are more preferred.

[0083] The glass transition temperature (Tg) of the resin material contained in the adhesive layer is preferably 40°C or higher, more preferably 50°C or higher, even more preferably 55°C or higher, and preferably 90°C or lower, more preferably 80°C or lower, even more preferably 75°C or lower. This can further improve, for example, printing performance. Tg is, for example, 40°C or higher and 90°C or lower.

[0084] The adhesive layer can contain one or more types of resin materials. The content of the resin material in the adhesive layer is preferably 80% by mass or more, and more preferably 85% by mass or more.

[0085] The adhesive layer may contain a lubricant, which, for example, can maintain good running properties of the thermal transfer sheet and prevent wrinkles from occurring in the resulting print. The details of the lubricant are as described above, and will not be described here.

[0086] The adhesive layer may contain one or more types of lubricants. The content of the lubricant in the adhesive 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. This allows, for example, the effect of the lubricant to be exerted while ensuring transparency. The content of the lubricant is, for example, 1% by mass or more and 20% by mass or less.

[0087] The adhesive layer may contain one or more of the above additives.

[0088] The thickness of the adhesive layer is preferably 0.5 μm or more, and preferably 10 μm or less, more preferably 8 μm or less, and even more preferably 5 μm or less. The thickness of the adhesive layer is, for example, 0.5 μm or more and 10 μm or less.

[0089] The adhesive layer can be formed, for example, by applying a coating liquid containing the above-mentioned materials to the release layer by known means such as roll coating, reverse roll coating, gravure coating, reverse gravure coating, bar coating, or rod coating, and then drying the coating.

[0090] <Release layer> In one embodiment, the thermal transfer sheet of the present disclosure includes a release layer located between the substrate and the protective layer. The release layer is an optional layer that allows the protective layer to be easily peeled from the substrate during thermal transfer, and remains on the substrate side during thermal transfer.

[0091] In one embodiment, the release layer contains a binder and a release agent. Examples of binders include resin materials such as (meth)acrylic resin, vinyl resin, polyurethane, polyamide, polyimide, melamine resin, polyol resin, silicone resin, silicone-modified (meth)acrylic resin, fluororesin, fluororesin-modified resin, and cellulose resin. The release layer may contain one or more binders.

[0092] Examples of the release agent include metal soaps such as zinc stearate, zinc stearyl phosphate, calcium stearate, and magnesium stearate, silicone oil, fluorine compounds, phosphate esters, fatty acid amides, polyethylene wax, carnauba wax, and paraffin wax. The release layer may contain one or more types of release agents.

[0093] The release layer may contain one or more of the above additives.

[0094] The thickness of the release layer is preferably 0.5 μm or more, more preferably 1 μm or more, and preferably 3 μm or less, more preferably 1.5 μm or less. This can improve the transferability of the protective layer in the thermal transfer sheet, for example. The thickness of the release layer is, for example, 0.5 μm or more and 3 μm or less.

[0095] The release layer can be formed, for example, by applying a coating liquid containing the above-mentioned materials to a substrate by known means such as roll coating, reverse roll coating, gravure coating, reverse gravure coating, bar coating, or rod coating, and then drying the coating.

[0096] [Manufacturing method for prints] The method for producing a printed matter of the present disclosure includes a step of preparing the thermal transfer sheet of the present disclosure and a transfer object (preparation step), and at least one of an image forming step and a transfer step. In one embodiment, the production method of the present disclosure produces a printed matter having an image composed of characters, line drawings, patterns, symbols, and combinations thereof, and a protective layer provided on the image.

[0097] <Preparation process> In the preparation step, the thermal transfer sheet of the present disclosure and a transfer-receiving object are prepared.

[0098] Examples of the transfer substrate include the resin films, glass substrates, metal substrates, ceramic substrates, cloth substrates, and paper substrates described above as substrates for thermal transfer sheets, as well as laminated substrates thereof. The transfer substrate may also be a card substrate primarily composed of polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, or polycarbonate. Examples of the cloth substrate include substrates formed from fibers such as nylon fibers, polyester fibers, rayon fibers, acetate fibers, acrylic fibers, vinylon fibers, polypropylene fibers, and polyvinylidene chloride fibers; and natural fibers such as cotton, silk, linen, and wool. Examples of the paper substrate include fine paper, plain paper, art paper, coated paper, resin-coated paper, cast-coated paper, cardboard, synthetic paper, and impregnated paper. The transfer substrate may also be, for example, a thermal transfer image-receiving sheet comprising a substrate and a receiving layer provided on one side of the substrate. The transfer substrate may bear an image, may be colored, and may be transparent.

[0099] <Image forming process> When the thermal transfer sheet of the present disclosure includes a colorant layer, an image is formed on a transferee by the colorant layer of the thermal transfer sheet in the image forming step. For example, the colorant layer of the thermal transfer sheet is brought into contact with the surface of the transferee, and then heat is applied to a desired area of ​​the thermal transfer sheet to form an image on the transferee.

[0100] For example, an image can be formed using a thermal transfer printer having a thermal head. In one embodiment, an image is formed by overlapping a thermal transfer sheet and a transfer-receiving material, passing them between a thermal head and a platen roll provided in the thermal transfer printer, and heating the thermal transfer sheet using the thermal head. The thermal transfer recording method for forming an image on a transfer-receiving material may be a sublimation transfer type, a melt transfer type, or a combination of these. For example, a sublimation transfer type and a melt transfer type may be combined, and a gradation image portion may be formed by a sublimation transfer type recording method, and a character portion may be formed by a melt transfer type recording method.

[0101] <Transfer process> When the thermal transfer sheet of the present disclosure has a protective layer, in the transfer step, at least a portion of the protective layer of the thermal transfer sheet is transferred so as to cover at least the image formed on the transfer recipient. Note that the image may be an image formed using the thermal transfer sheet of the present disclosure having a colorant layer and a transfer layer, or an image formed using a conventionally known thermal transfer sheet.

[0102] For example, the protective layer can be transferred using a thermal transfer printer having a thermal head. In one embodiment, the thermal transfer sheet and the image-formed object are superimposed on each other and passed between a thermal head and a platen roll of the thermal transfer printer, and the thermal transfer sheet is heated using the thermal head, thereby transferring the protective layer so as to cover the image formed on the object. The protective layer may be transferred using a heat roll method. The protective layer may be transferred by sandwiching the thermal transfer sheet and the image-formed object between heated flat plates, or between heated flat plates and rolls, and then hot pressing.

[0103] When a thermal head is used as the thermal transfer means for the protective layer, the same thermal head as that used for image formation may be used, or a different thermal head may be used. In the present disclosure, the thermal transfer means for image formation and the thermal transfer means for the protective layer may be performed in-line using a single thermal transfer printer.

[0104] The present disclosure relates to, for example, the following [1] to [6]. [1] A thermal transfer sheet comprising a substrate having a first surface and a second surface, a back layer provided on the first surface, and at least one of a colorant layer and a transferable protective layer provided on the second surface, wherein the back layer contains melamine cyanurate particles. [2] The thermal transfer sheet according to [1] above, wherein the average particle size of the melamine cyanurate particles is 1 μm or more and 10 μm or less. [3] The thermal transfer sheet according to [1] or [2] above, wherein the content of melamine cyanurate particles in the back layer is 1% by mass or more and 30% by mass or less. [4] The thermal transfer sheet according to any one of the above [1] to [3], wherein the back layer further contains, as a lubricant, a hydrocarbon wax having a melting point of 70°C or higher and 150°C or lower. [5] A thermal transfer sheet according to any one of [1] to [3] above, wherein the back layer further contains at least one lubricant selected from the group consisting of maleic anhydride modified wax, ethoxylated alcohol modified wax, and carnauba wax. [6] The thermal transfer sheet according to any one of the above [1] to [5], wherein the static friction coefficient of the surface of the back layer is 0.45 or less. [Example]

[0105] The thermal transfer sheet of the present disclosure will be described below based on examples, but the thermal transfer sheet of the present disclosure is not limited to these examples. In the following description, "parts by mass" will be simply referred to as "parts." The amounts of components contained in the coating liquid described below are solid content amounts.

[0106] [Example 1] A PET film (Lumirror (registered trademark) #5A-F53, Toray Industries, Inc.) with a thickness of 5 μm or less was prepared as a substrate. The following back layer coating liquid was applied to one side of the PET film and dried at 100°C for 2 minutes to form a 1.2 μm thick back layer. The following yellow dye layer coating liquid, the following magenta dye layer coating liquid, and the following cyan dye layer coating liquid were applied in face order to the side of the PET film opposite the back layer and dried at 80°C for 1 minute to form a 1 μm thick yellow dye layer, a 1 μm thick magenta dye layer, and a 1 μm thick cyan dye layer in face order on the PET film. In this manner, a thermal transfer sheet was obtained.

[0107] <Coating liquid for back layer> Resin materials 58 parts (Acrylonitrile-styrene copolymer, Product name: Cevian (registered trademark) NA, Daicel Corporation Lubricant A 14 parts (Ethoxylated alcohol modified wax, melting point: 106°C, Product name: Unitox 750, Toyochem Co., Ltd. Lubricant B 14 parts (Maleic anhydride modified wax, melting point: 96°C, Product name: Ceramer 67, Toyochem Co., Ltd. Filler 14 parts (Melamine cyanurate particles, average particle size: 3 μm, Product name: MC-2010N, Sakai Chemical Industry Co., Ltd. 200 parts methyl ethyl ketone (MEK) 100 parts toluene

[0108] <Coating liquid for yellow dye layer> 6 parts Solvent Yellow 93 Polyvinyl acetal 5 parts (Product name: S-LEC (registered trademark) KS-5, Sekisui Chemical Co., Ltd.) ·MEK 50 copies 50 parts toluene

[0109] <Coating liquid for magenta dye layer> 3 parts Disperse Red 60 4 parts Disperse Violet 26 Polyvinyl acetal 5 parts (Product name: S-LEC (registered trademark) KS-5, Sekisui Chemical Co., Ltd.) ·MEK 50 copies 50 parts toluene

[0110] <Coating liquid for cyan dye layer> 4 parts Solvent Blue 63 Disperse Blue 354 4 parts Polyvinyl acetal 5 parts (Product name: S-LEC (registered trademark) KS-5, Sekisui Chemical Co., Ltd.) ·MEK 50 copies 50 parts toluene

[0111] [Examples 2 to 5 and Comparative Examples 1 to 3] A thermal transfer sheet was obtained in the same manner as in Example 1, except that the solid components in the back layer were changed to those shown in Table 1. Details of the resin materials and fillers shown in Table 1 are as follows. Acrylic resin (Product name: Dianale (registered trademark) BR-85, Mitsubishi Chemical Corporation) Cellulose acetate butyrate resin (Product name: CAB-551-0.2, Eastman Chemical Japan Co., Ltd.) Melamine-formaldehyde condensate particles (Average particle size: 0.2 μm, product name: Eposter (registered trademark) S, Nippon Shokubai Co., Ltd.) Polytetrafluoroethylene particles (Average particle size: 5 to 7 μm, Product name: Polyflon (registered trademark) PTFE L-5F, Daikin Industries, Ltd. ·talc (Average particle size: 5.1 μm, Product name: MicroAce (registered trademark) P-3, Nippon Talc Co., Ltd.

[0112] [Coefficient of friction] In accordance with JIS K7125:1999 "Plastics - Films and Sheets - Test Method for Coefficient of Friction," the static and dynamic friction coefficients were measured between the back surface of the thermal transfer sheet and a polycarbonate plate (thickness 2 mm, product name: PC-1600 Polycarbonate Plate / Transparent, Takiron C.I. Co., Ltd.). The measurement conditions were: load of sliding piece: 1.96 N, contact area of ​​sliding piece: 40 cm 2 The test speed was 100 mm / min. The measurement was carried out five times, and the average value of the obtained measurements was taken as the coefficient of friction for each test piece.

[0113] [Blocking resistance] The thermal transfer sheets obtained in the Examples and Comparative Examples were prepared and cut to two 5 cm x 5 cm test pieces. These test pieces were stacked so that the dye layer (colorant layer) of one test piece was in contact with the back layer of the other test piece, and then stored in an oven at 50°C for 24 hours while applying a load of 1.57 MPa. After storage, the test pieces were peeled apart by hand and evaluated based on the following evaluation criteria. The evaluation results are shown in Table 1. A: No blocking occurred at all. B: Slight blocking has occurred. C: Blocking occurs partially. D: Blocking occurs all over the surface.

[0114] [Thermal head wear] The thermal transfer sheets obtained in the examples and comparative examples were left to stand for two weeks in an environment of 23°C temperature and 50% relative humidity. Using the thermal transfer sheets after standing and a thermal transfer printer (DS620, manufactured by Dai Nippon Printing Co., Ltd.), 2000 prints were produced by forming a black solid image (0 / 255 image gradation) on the original image receiving paper of the thermal transfer printer under the following conditions. (Printing conditions) Resolution: 300 x 300 dpi (high speed mode) Print size: PC size

[0115] The thermal head of the thermal transfer printer after use was observed using an electron microscope (Keyence Corporation, Digital Microscope VHX-6000) and evaluated based on the following evaluation criteria. The evaluation results are shown in Table 1. A: There is almost no wear on the thermal head. B: The thermal head is slightly worn. C: The thermal head is severely worn.

[0116] [Sticking resistance] The prints obtained in the above evaluation of [thermal head wear] and the thermal transfer sheet after printing were visually observed and evaluated based on the following evaluation criteria. The evaluation results are shown in Table 1. A: No sticking occurred at all. B: Slight sticking has occurred. C: Sticking has occurred in some areas. D: Sticking occurs over the entire surface.

[0117] [Table 1]

[0118] In Comparative Example 1, melamine-formaldehyde particles were used as the filler. However, because melamine-formaldehyde particles have a high static friction coefficient, the anti-sticking properties were insufficient. In Comparative Example 2, polytetrafluoroethylene particles were used as the filler. However, because polytetrafluoroethylene particles are soft, the anti-blocking properties were insufficient. In Comparative Example 3, talc was used as the filler. However, because talc is hard, wear of the thermal head was observed.

[0119] In the examples, melamine cyanurate particles are used as the filler, which results in a thermal transfer sheet that is excellent in anti-sticking and anti-blocking properties and can reduce abrasion of the thermal head. [Explanation of symbols]

[0120] 1...Thermal transfer sheet 10...Base material 12...First surface of substrate 14...Second surface of substrate 20…Back layer 30...color material layer 40...Transferable protective layer

Claims

1. a substrate having a first surface and a second surface; a back surface layer disposed on the first surface; At least one of a colorant layer and a transferable protective layer provided on the second surface; A thermal transfer sheet comprising: The back surface layer contains an organic filler having a graphite structure (excluding carbon). Thermal transfer sheet.

2. 2. The thermal transfer sheet according to claim 1, wherein the organic filler has an average particle size of 1 μm or more and 10 μm or less.

3. The thermal transfer sheet according to claim 1 or 2, wherein the content of the organic filler in the back layer is 1% by mass or more and 30% by mass or less.

4. 4. The thermal transfer sheet according to claim 1, wherein the back layer further contains a hydrocarbon wax having a melting point of 70° C. or higher and 150° C. or lower as a lubricant.

5. The thermal transfer sheet according to any one of claims 1 to 3, wherein the back layer further contains at least one lubricant selected from the group consisting of maleic anhydride-modified wax, ethoxylated alcohol-modified wax, and carnauba wax.

6. 6. The thermal transfer sheet according to claim 1, wherein the surface of the back layer has a static friction coefficient of 0.45 or less.

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