How to prevent information leakage from used thermal transfer sheets

Abstract

To provide a method for more surely preventing information leakage from a used heat transfer sheet.SOLUTION: The method for preventing information leakage from the used heat transfer sheet comprises: heat-transferring a color material layer to a transferred body by using the heat transfer sheet provided with a base material, the color material layer provided on one surface side of the base material, a back layer provided on the other surface side of the base material, and a peel-off layer provided field-sequentially with the color material layer; after a prescribed part of the transferred body is peeled off by the peel-off layer, heating the heat transfer sheet after the peeling-off before winding on a take-up reel or heating the heat transfer sheet after the peeling-off after winding on the take-up reel; and heat-sealing the peel-off layer and the back layer which face each other.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to a method for preventing information leakage from used thermal transfer sheets. [Background technology]

[0002] In the production of prints, an image forming method is widely used in which a thermal transfer sheet having a color material layer is used to form an image on a transferee such as a card or a thermal transfer image receiving sheet. In such an image forming method, energy is applied to the thermal transfer sheet to transfer the dye or the like contained in the color material layer to the transferee, thereby forming an image on the transferee.

[0003] However, the above image forming method has the following inherent problem: A pattern corresponding to the image formed on the transfer recipient remains as a print mark on the color material layer of the thermal transfer sheet after image formation, and the image formed on the transfer recipient can be easily identified from the print mark remaining on the color material layer of the thermal transfer sheet after image formation, resulting in information leakage.

[0004] In order to solve such problems, Patent Document 1 discloses a method of preventing information leakage by thermally fusing a transferable protective layer and a back layer in a used thermal transfer sheet. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2008-49663 A Summary of the Invention [Problem to be solved by the invention]

[0006] Since most of the transferable protective layer is transferred to the transferee, only a small amount of the layer remains after the transfer. Therefore, the adhesion between the transferable protective layer and the back layer is low, and there is room for improvement in preventing information leakage.

[0007] Therefore, an object of the present disclosure is to provide a method for more reliably preventing information leakage from used thermal transfer sheets. [Means for solving the problem]

[0008] The inventors have now discovered that information leakage can be more reliably prevented by using a thermal transfer sheet having a layer (hereinafter also referred to as a "peel-off layer") that removes a specified portion from the recipient, and then heat-fusing this peel-off layer to a back layer.

[0009] Therefore, the present disclosure provides a method for preventing information leakage from a used thermal transfer sheet, comprising: A thermal transfer sheet including a substrate, a color material layer provided on one side of the substrate, a back surface layer provided on the other side of the substrate, and a peel-off layer provided in surface sequence with the color material layer is used to thermally transfer the color material layer onto a transferee, and a predetermined portion of the transferee is peeled off by the peel-off layer, and then This is a method in which the thermal transfer sheet after peel-off is heated before being wound onto a take-up reel, or the thermal transfer sheet after peel-off is wound onto a take-up reel, thereby thermally fusing the opposing peel-off layer and back layer. Effect of the Invention

[0010] According to the present disclosure, a method for more reliably preventing information leakage from used thermal transfer sheets can be provided. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic cross-sectional view showing one embodiment of a thermal transfer sheet used in the present disclosure. [Diagram 2] FIG. 1 is a schematic cross-sectional view showing one embodiment of a thermal transfer sheet used in the present disclosure. [Diagram 3] FIG. 1 is a schematic diagram of a rigid pendulum physical property testing machine. [Figure 4] FIG. 1 is a schematic diagram illustrating an example of a configuration of a main part of a thermal transfer printer according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The method according to the present disclosure is a method for preventing information leakage from a used thermal transfer sheet. Specifically, the method according to the present disclosure is a method for thermally transferring the color material layer to a transferee using a thermal transfer sheet including a substrate, a color material layer provided on one side of the substrate, a back layer provided on the other side of the substrate, and a peel-off layer provided in surface sequence with the color material layer, and peeling off a predetermined portion of the transferee with the peel-off layer, and then heating the thermal transfer sheet after peel-off before winding it on a take-up reel or heating the thermal transfer sheet after peel-off after winding it on a take-up reel to thermally fuse the opposing peel-off layer and back layer.

[0013] The peel-off layer is a layer that removes (peels off) a predetermined portion from a transferee. After peel-off, the surface of the peel-off layer has an area where a predetermined portion of the transferee is attached (hereinafter also referred to as an "attached area") and an area where the portion is not attached, that is, an area where the peel-off layer is exposed (hereinafter also referred to as an "exposed area"). In the peel-off layer after peel-off, the exposed area occupies most of the peel-off layer. Therefore, the method according to the present disclosure can more reliably prevent information leakage by heat-sealing the exposed area that occupies most of the peel-off layer after peel-off to the back layer. In addition, the peel-off layer has a function of peeling off a predetermined portion from a transfer target, and therefore has excellent adhesiveness to other layers. Therefore, from the viewpoint of the function of the peel-off layer, the method according to the present disclosure can more reliably prevent information leakage.

[0014] In the method according to the present disclosure, heating when heat-sealing the peel-off layer and the back layer may be performed either before the thermal transfer sheet after peel-off is wound onto the take-up reel or after the thermal transfer sheet after peel-off is wound onto the take-up reel. When the peel-off thermal transfer sheet is heated before being wound onto the take-up reel, the peel-off layer is melted by the heating in advance, and the peel-off layer and the back layer are thermally fused together at the same time as the thermal transfer sheet is wound onto the take-up reel. On the other hand, when the thermal transfer sheet after peel-off is heated after being wound up on a take-up reel, the peel-off layer melts due to heating while in contact with the back layer, and the peel-off layer and the back layer are thermally fused together.

[0015] The thermal transfer sheet used in the present disclosure comprises a substrate, a colorant layer provided on one side of the substrate, a back layer provided on the other side of the substrate, and a peel-off layer provided in surface sequence with the colorant layer. In one embodiment, the thermal transfer sheet comprises a primer layer between the substrate and the peel-off layer. The primer layer is adjacent to the substrate and the peel-off layer.

[0016] Hereinafter, one embodiment of the thermal transfer sheet used in the present disclosure will be described with reference to the drawings.

[0017] In one embodiment, the thermal transfer sheet 10 includes a substrate 11, a color material layer 12, a back layer 13, and a peel-off layer 14, as shown in Fig. 1. The color material layer 12 is provided on one surface of the substrate 11. The back layer 13 is provided on the other surface of the substrate 11. The peel-off layer 14 is provided in surface sequence with the color material layer 12.

[0018] In one embodiment, the thermal transfer sheet 10 includes a substrate 11, a color material layer 12, a back layer 13, a peel-off layer 14, and a primer layer 15, as shown in Fig. 1. The color material layer 12 is provided on one surface of the substrate 11. The back layer 13 is provided on the other surface of the substrate 11. The peel-off layer 14 is provided in surface sequence with the color material layer 12. The primer layer 15 is located between the substrate 11 and the peel-off layer 14, and is adjacent to the substrate 11 and the peel-off layer 14.

[0019] In one embodiment, a primer layer 15 may be provided between the substrate 11 and the colorant layer 12 (not shown).

[0020] The layer structure of the thermal transfer sheet 10 can be appropriately combined.

[0021] Each layer that the thermal transfer sheet may have will be described below.

[0022] There are no particular limitations on the substrate, so long as it has heat resistance sufficient to withstand the thermal energy (e.g., heat from a thermal head) applied when peeling off a specified portion of the transfer-receiving body, and mechanical strength and solvent resistance sufficient to support each layer, such as the peel-off layer, can be used. Examples of the substrate include polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), 1,4-polycyclohexylene dimethylene terephthalate, and terephthalic acid-cyclohexanedimethanol-ethylene glycol copolymers; polyamides such as nylon 6 and nylon 6,6; polyolefins such as polyethylene (PE), polypropylene (PP), and polymethylpentene; polyvinyl chloride, polyvinyl alcohol (PVA), polyvinyl acetate, vinyl chloride-vinyl acetate copolymers, polyvinyl butyrate, and the like. Films (hereinafter simply referred to as "resin films") made of resin materials such as vinyl resins such as polyvinylpyrrolidone (PVP) and other vinyl resins; (meth)acrylic resins such as polyacrylate, polymethacrylate, and polymethyl methacrylate; imide resins such as polyimide and polyetherimide; cellulose resins such as cellophane, cellulose acetate, nitrocellulose, cellulose acetate propionate (CAP), and cellulose acetate butyrate (CAB); styrene resins such as polystyrene (PS), polycarbonate, and ionomer resins can be used. Among the above-mentioned resin materials, polyester is preferred, and PET is particularly preferred, from the viewpoints of heat resistance and mechanical strength. In the present disclosure, "(meth)acrylic" refers to both "acrylic" and "methacrylic", and "(meth)acrylate" refers to both "acrylate" and "methacrylate".

[0023] The substrate may be a laminate in which the above-mentioned resin film is laminated. The laminate can be produced by utilizing a dry lamination method, a wet lamination method, an extrusion method, or the like.

[0024] The resin film may be a stretched film or an unstretched film. From the viewpoint of strength, the resin film is preferably a uniaxially or biaxially stretched film.

[0025] The thickness of the substrate is preferably 2 μm or more, more preferably 3 μm or more, while the thickness of the substrate is preferably less than 25 μm, more preferably 10 μm or less.

[0026] The substrate may be subjected to an adhesive treatment on its surface in order to improve adhesion with other layers. That is, a substrate subjected to an adhesive treatment may be used as the substrate of the thermal transfer sheet. Examples of the adhesive treatment include known resin surface modification techniques such as corona discharge treatment, flame treatment, ozone treatment, ultraviolet treatment, radiation treatment, roughening treatment, chemical treatment, plasma treatment, low-temperature plasma treatment, and grafting treatment. Two or more of these adhesive treatments may be used in combination.

[0027] The peel-off layer is a layer for removing (peeling off) a desired portion of a transfer target.

[0028] The peel-off layer may contain one or more thermoplastic resins. The thermoplastic resin contained in the peel-off layer may be selected from conventionally known thermoplastic resins. Examples of the thermoplastic resin contained in the peel-off layer include vinyl chloride resin, vinyl chloride-vinyl acetate copolymer, acrylic resin, polyester, polyamide, styrene acrylic resin, styrene-vinyl chloride-vinyl acetate copolymer, butyral resin, epoxy resin, polyamide, etc. The peel-off layer preferably contains at least one selected from the group consisting of vinyl chloride-vinyl acetate copolymer and polyester, and more preferably contains both vinyl chloride-vinyl acetate copolymer and polyester. The polyester is preferably a crystalline polyester. Such a peel-off layer has significantly improved peel-off properties.

[0029] In the peel-off layer, the mass ratio of the vinyl chloride-vinyl acetate copolymer to the polyester is preferably 0.3 or more, more preferably 0.4 or more, while the mass ratio is preferably 2 or less, more preferably 1.5 or less, and even more preferably 0.8 or less.

[0030] Crystalline polyester refers to a polyester that shows a clear melting peak in one of two heating processes, which are performed using a differential scanning calorimeter: heating from -100°C to 300°C at 20°C / min, then cooling from 300°C to -100°C at 50°C / min, and then heating from -100°C to 300°C at 20°C / min.

[0031] The logarithmic attenuation factor ΔE at 100°C obtained by rigid pendulum measurement of the peel-off layer is preferably 0.25 or more, more preferably 0.30 or more. This allows a part of the transfer material to be peeled off more satisfactorily even when heated with low energy. For example, ΔE can be increased by increasing the content of crystalline polyester in the peel-off layer. There is no particular upper limit for ΔE, and ΔE may be, for example, 0.50 or less, or 0.45 or less.

[0032] In the present disclosure, the logarithmic decrement ΔE is measured as follows. First, the thermal transfer sheet is cut into a size of 15 mm width × 50 mm length to prepare a test sample S.

[0033] A rigid pendulum physical property tester A is prepared, which is equipped with a test sample temperature adjustment table B, a cylindrical cylinder C, a pendulum frame D, and a vibration displacement detector E (see FIG. 3). The arrow in FIG. 3 indicates the swing direction of the pendulum frame D, which is parallel to the longitudinal direction of the fixed test sample S. The test sample S is fixed on this test sample temperature adjustment table B with Kapton tape affixed to a location that does not affect the measurement results, with the peel-off layer facing upward, and a temperature sensor is placed on the test sample S.

[0034] The test sample S is fixed so that its length direction is perpendicular to the central axis of the cylindrical cylinder C. In addition, the cylindrical cylinder C is disposed so as to be in contact with the surface of the peel-off layer.

[0035] Next, the test sample temperature adjustment stand B is heated from 25° C. to 130° C. at a heating rate of 3° C. / min, and the logarithmic decrement ΔE of the peel-off layer at this time is measured.

[0036] Specifically, the logarithmic attenuation rate ΔE is used when the temperature of the peel-off layer of test sample S becomes 100°C. Note that the test sample that has already been measured is not used again, but a different test sample is used to measure three times, and the average value is taken as the logarithmic attenuation rate ΔE (ΔE=[ln(A1 / A2)+ln(A2 / A3)+···ln(An / An+1)] / n, A: amplitude, n: wave number, initial amplitude A1: approximately 0.3 degrees). ln represents the natural logarithm.

[0037] As the rigid pendulum physical property tester A, an RPT-3000W manufactured by A&D Co., Ltd. or an equivalent device can be used.

[0038] As the test sample temperature adjustment stand B, a cold block CHB-100 or a device of a similar level can be used. As the cylindrical cylinder C, a cylindrical cylinder edge RBP-060 or a device of a similar order can be used. As the pendulum frame D, an FRB-100 or a similar device can be used. The above CHB-100, RBP-060 and FRB-100 are devices or components that the RPT-3000W includes.

[0039] The peel-off layer may contain one or more additives such as a filler, a plasticizer, an ultraviolet absorbing agent, and a dispersing agent.

[0040] The thickness of the peel-off layer is preferably 0.2 μm or more, more preferably 0.4 μm or more, while the thickness of the peel-off layer is preferably 10 μm or less, more preferably 5 μm or less, and even more preferably 1 μm or less.

[0041] The peel-off layer can be formed, for example, by dispersing or dissolving the above-mentioned materials in water or an appropriate organic solvent to prepare a coating liquid, applying the coating liquid onto a substrate or a primer layer or the like by a known means to form a coating film, and drying the coating film. Examples of the known means include roll coating, reverse roll coating, gravure coating, reverse gravure coating, bar coating, and rod coating.

[0042] The color material layer is a layer for forming an image on the surface of a transfer medium. The color material layer may be a sublimation transfer type color material layer in which only the sublimation dye contained in the color material layer is transferred, or a melt transfer type color material layer in which the color material layer itself is transferred. The thermal transfer sheet may include both a sublimation transfer type color material layer and a melt transfer type color material layer as the color material layer.

[0043] The colorant layer contains one or more colorants. The colorant may be a pigment or a dye. The dye may be a sublimable dye. Examples of the coloring material contained in the coloring material layer 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 ocher, aureolin, cadmium yellow, cadmium orange, chrome yellow, zinc yellow, Naples yellow, nickel yellow, azo pigments, greenish yellow, ultramarine, rock ultramarine, cobalt, phthalocyanine, anthraquinone, and iridium. pigments such as cadmium green, cinnabar green, cadmium green, chrome green, phthalocyanine, azomethine, perylene and aluminum pigments; and dyes such as diarylmethane dyes, triarylmethane dyes, thiazole dyes, merocyanine dyes, pyrazolone dyes, methine dyes, indoaniline dyes, acetophenone azomethine 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.

[0044] The color material layer may contain one or more resin materials, such as polyester, polyamide, polyolefin, vinyl resin, vinyl acetal resin, (meth)acrylic resin, cellulose resin, styrene resin, polycarbonate, butyral resin, phenoxy resin, and ionomer resin.

[0045] The color material layer may contain the above-mentioned additive.

[0046] The thickness of the color material layer is, for example, 0.1 μm or more and 3 μm or less.

[0047] The colorant layer can be formed by dispersing or dissolving the above-mentioned materials in an appropriate solvent to prepare a coating liquid, applying the liquid onto a substrate or a primer layer or the like using the above-mentioned coating means to form a coating film, and drying the coating film.

[0048] The back layer is a layer provided to prevent sticking and wrinkling caused by heating during thermal transfer.

[0049] The back layer contains one or more resin materials. Examples of the resin materials contained in the back layer include silicone resin, vinyl resin, polyester, polyamide, polyolefin, (meth)acrylic resin, polyolefin, polyurethane, acetal resin, cellulose resin, and phenol resin. Among these, the resin material is preferably silicone resin.

[0050] The back layer may contain at least one isocyanate compound. Examples of the isocyanate composition contained in the back layer include silicone isocyanate, xylylene diisocyanate, toluene diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate.

[0051] The back layer may contain at least one solid or liquid lubricant. Examples of the lubricant include various waxes such as polyethylene wax and paraffin wax, higher aliphatic alcohols, organopolysiloxanes, anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, fluorine-based surfactants, organic carboxylic acids and their derivatives, metal soaps, fluorine-based resins, talc, fine particles of inorganic compounds such as silica, etc. Among these, the lubricant is preferably a surfactant, more preferably an anionic surfactant, and particularly preferably a phosphate ester surfactant.

[0052] The ten-point average roughness Rz of the surface of the back layer is preferably 5.0 μm or less. By making the ten-point average roughness Rz 5.0 μm or less, the adhesion to the peel-off layer can be improved. The surface of the back layer means the surface opposite to the substrate. The ten-point average roughness Rz of the surface of the back layer is more preferably 4.0 μm or less, further preferably 3.0 μm or less, and particularly preferably 2.0 μm or less. On the other hand, the ten-point average roughness Rz of the surface of the back layer is, for example, 0.1 μm or more, may be 0.5 μm or more, or may be 1.0 μm or more.

[0053] In this specification, the ten-point average roughness Rz is measured in accordance with JIS B0601:2013. Specifically, the ten-point average roughness Rz is measured using a surface roughness measuring instrument under the following conditions. The surface roughness measuring instrument that can be used is Surfcom 1400 manufactured by Tokyo Seimitsu Co., Ltd. (Measurement conditions) Measurement method: 2D Measurement range: 4mm Measurement pitch: 20μm ·Measurement magnification: 20K λs filter: None Cutoff type: Gaussian Cutoff wavelength: 0.8mm Tilt correction: least squares straight line ·Measurement speed: 0.6mm / s Pickup Type: Standard Pickup

[0054] The back layer may contain the additive material.

[0055] The thickness of the back layer is, for example, not less than 0.01 μm and not more than 3.0 μm.

[0056] The back layer can be formed by dispersing or dissolving the above-mentioned materials in an appropriate solvent to prepare a coating liquid, applying the coating liquid onto a substrate or the like by the above-mentioned coating means to form a coating film, and drying the coating film.

[0057] The primer layer can improve the adhesion between the substrate and the peel-off layer, and can suppress the phenomenon in which the peel-off layer that should remain moves to the transferee side, i.e., the so-called reverse transfer phenomenon of the peel-off layer. In particular, when the printing energy is high, the reverse transfer of the peel-off layer tends to occur easily, so a thermal transfer sheet having a primer layer is suitable.

[0058] The primer layer may contain one or more resin materials. Examples of the resin materials contained in the primer layer include polyester, vinyl resin, polyurethane, (meth)acrylic resin, polyamide, polyether, styrene resin, and cellulose resin. Among these, the resin material is preferably polyester from the viewpoint of adhesion between the substrate and the peel-off layer.

[0059] The primer layer is preferably a layer that foams when heated. When the primer layer foams when heated, the primer layer can be pressed against the back layer when the thermal transfer sheet is wound around a take-up reel, thereby improving the adhesion between the primer layer and the back layer.

[0060] In one embodiment, the primer layer may include at least one type of expanding particle in order to expand the primer layer by heating. As the foamed particles, for example, a thermally expandable microcapsule containing a volatile substance can be used. Examples of materials constituting the outer shell of the thermally expandable microcapsule include polyolefins such as ethylene, styrene resins, vinyl acetate, vinyl chloride, vinylidene chloride, and other vinyl resins, polyamides, polyesters, etc. Examples of the volatile substances to be contained include propane, butene, isobutane, isopentene, neopentene, hexane, heptane, methyl chloride, and tetramethylsilane, etc.

[0061] The primer layer may contain the above-mentioned additive.

[0062] The thickness of the primer layer is, for example, not less than 0.05 μm and not more than 2.0 μm.

[0063] The primer layer can be formed by dispersing or dissolving the above-mentioned materials in an appropriate solvent to prepare a coating liquid, applying the coating liquid onto a substrate or the like by the above-mentioned coating means to form a coating film, and drying the coating film.

[0064] The transfer-receiving material used in the present disclosure is not particularly limited as long as it has a layer that is peeled off by a peel-off layer on the side on which an image is formed. Examples of the transfer-receiving material include paper substrates such as fine paper, art paper, coated paper, resin-coated paper, cast-coated paper, paperboard, synthetic paper, and impregnated paper, the following resin films, and laminates thereof, as well as cards.

[0065] In one embodiment, the transferee may be an intermediate transfer medium having a transfer layer including a receiving layer on which an image is formed. The intermediate transfer medium is a medium in which a transfer layer including a receiving layer is provided releasably on a substrate. With such an intermediate transfer medium, a thermal transfer image is formed on the receiving layer of the intermediate transfer medium using a thermal transfer sheet having a colorant layer, and then the transfer layer including the receiving layer is transferred onto any transferee (for example, only a paper substrate), thereby obtaining a printed matter on which a thermal transfer image is formed on any transferee.

[0066] Fig. 4 is a schematic diagram showing an example of the configuration of the main parts of a thermal transfer printer. In Fig. 4, a thermal transfer sheet supply reel 21 around which a thermal transfer sheet 10 is wound, and a transferee supply reel 22 around which a transferee 30 is wound are disposed in the thermal transfer printer. A platen roll 24 and a thermal head 23 are disposed in the middle of the transport path of the thermal transfer sheet 10 and the transferee 30. The thermal transfer sheet 10 and the transferee 30 pass between the platen roll 24 and the thermal head 23 in a pressed state. The used thermal transfer sheet 40 that has passed through the thermal head 23 is transported by a transport roller 25 and taken up by a take-up reel 26. A heating means 27 for heating the taken-up used thermal transfer sheet 40 is disposed on the outside of the take-up reel 26. Here, the thermal transfer sheet 10 comprises a colorant layer 12 provided on one side of a substrate 11, a back layer 13 provided on the other side of the substrate 11, and a peel-off layer 14 provided in surface sequence with the colorant layer 12.

[0067] Next, the operation of the thermal transfer printer will be described. In the initial state, which is a printing standby state, the thermal head 23 is in a head-up state and separated from the platen roll 24. When the thermal transfer sheet supply reel 21 is attached, the leading end of the thermal transfer sheet 10 is passed through the gap between the transport rollers 25, and the leading end is fixed to the take-up reel 26. Meanwhile, the leading end of the transfer recipient 30 is pulled out from the transfer recipient supply reel 22 and is clamped and fixed by the transport rollers (not shown).

[0068] During printing, the thermal head 23 is lowered by a pressing mechanism (not shown), the thermal transfer sheet 10 and the transfer recipient 30 are pressed against the platen roll 24, and the thermal head 23, which has multiple heating resistors, selectively applies heat in accordance with image information to record an image on the transfer recipient 30. Next, a predetermined portion of the transfer recipient is peeled off by the peel-off layer.

[0069] When printing is completed, the thermal head 23 is raised by a pressing mechanism (not shown), and the pressure contact between the thermal transfer sheet 10 and the transferee 30 is released. The transferee 30 is pulled out by a predetermined length by a transport roller (not shown) and transported to a discharge section (not shown). Meanwhile, the used thermal transfer sheet 40 is taken up by a take-up reel 26 through a transport roller 25. The taken-up sheet is heated by a heating means 27, and the opposing back layer and peel-off layer are fused together. This makes it impossible to view the print marks remaining on the color material layer of the used thermal transfer sheet, preventing information leakage.

[0070] 4 shows an example in which the wound up used thermal transfer sheet 40 is heated, but it is also possible to use a method in which the sheet is heated before being wound up after passing through the transport roller 25, and the back layer and the peel-off layer are fused together while being wound up. Examples of the heating means include a heat roll and a line heater.

[0071] When a used thermal transfer sheet is heated by a heating means, it is preferable to apply energy larger than that applied from a thermal head, in order to sufficiently fuse the peel-off layer and the back layer to make them difficult to peel off.

[0072] In the method according to the present disclosure, the heating temperature when the peel-off layer and the back layer are heat-sealed is preferably 110° C. or higher, more preferably 150° C. or higher, from the viewpoint of adhesion between the peel-off layer and the back layer. On the other hand, the heating temperature when the peel-off layer and the back layer are heat-sealed is, for example, 250° C. or lower, and may be 200° C. or lower.

[0073] An embodiment of the method according to the present disclosure is described below, but the method according to the present disclosure is not limited to these embodiments.

[0074] The present disclosure provides a method for preventing information leakage from a used thermal transfer sheet, comprising: A thermal transfer sheet including a substrate, a color material layer provided on one side of the substrate, a back surface layer provided on the other side of the substrate, and a peel-off layer provided in surface sequence with the color material layer is used to thermally transfer the color material layer onto a transferee, and a predetermined portion of the transferee is peeled off by the peel-off layer, and then This is a method in which the thermal transfer sheet after peel-off is heated before being wound onto a take-up reel, or the thermal transfer sheet after peel-off is wound onto a take-up reel, thereby thermally fusing the opposing peel-off layer and back layer.

[0075] In one embodiment, the heating temperature may be 110° C. or higher.

[0076] In one embodiment, the thermal transfer sheet includes a primer layer between the substrate and the peel-off layer, The primer layer may be adjacent to the substrate and the peel-off layer.

[0077] In one embodiment, the primer layer may be foamed by heating.

[0078] In one embodiment, the logarithmic decay ΔE at 100° C. as measured by rigid pendulum for the peel-off layer may be greater than or equal to 0.25.

[0079] In one embodiment, the peel-off layer may comprise vinyl chloride-vinyl acetate copolymer and polyester.

[0080] In one embodiment, the mass ratio of the vinyl chloride-vinyl acetate copolymer to the polyester may be 0.3 or more and 2 or less.

[0081] In one embodiment, the ten-point average roughness Rz of the surface of the back layer may be 5.0 μm or less. EXAMPLES

[0082] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to these examples. In the following, for materials for which the solid content ratio is written, the content before conversion to solid content is shown.

[0083] [Example 1] As a substrate, a polyethylene terephthalate (PET) film having a thickness of 4.5 μm was prepared. A back layer coating solution A having the following composition was applied onto one surface of the substrate and dried to form a back layer A having a thickness of 0.1 μm. Next, primer layer coating solution A having the following composition was applied to a part of the other surface of the substrate and dried to form a primer layer A having a thickness of 0.3 μm. Next, a primer layer coating solution B having the following composition was applied to the remaining portion on the other surface of the substrate in surface sequence with the primer layer A, and then dried to form a primer layer B having a thickness of 0.3 μm. Next, a coating liquid for a peel-off layer having the following composition was applied onto the primer layer B and dried to form a peel-off layer having a thickness of 0.5 μm. Next, the following coating liquid for yellow colorant layer, coating liquid for magenta colorant layer and coating liquid for cyan colorant layer, each having the following composition, were coated on the primer layer A in the surface order and dried to form a yellow colorant layer, a magenta colorant layer and a cyan colorant layer, each having a thickness of 0.6 μm, to obtain a thermal transfer sheet.

[0084] <Primer layer coating solution A> Alumina (average primary particle size 10 x 100 nm (solid content 10%)) 30 parts by mass (Nissan Chemical Industries, Ltd., Aluminasol 200) Polyvinylpyrrolidone 3 parts by weight (ISP Japan, K-90) ·Water 50 parts by mass Isopropyl alcohol 17 parts by weight

[0085] <Primer layer coating solution B> Polyester 10 parts by weight (Byron (registered trademark) 200, manufactured by Toyobo Co., Ltd.) Methyl ethyl ketone (MEK) 25 parts by weight Toluene 25 parts by weight

[0086] <Yellow colorant layer coating liquid> Solvent Yellow 93 2.5 parts by weight Disperse Yellow 201 2.5 parts by weight Polyvinyl acetal 4 parts by weight (Sekisui Chemical Co., Ltd., S-LEC (registered trademark) KS-5) Polyethylene wax 0.1 parts by weight Toluene 50 parts by weight ·MEK 50 parts by mass

[0087] <Coating liquid for magenta colorant layer> Disperse Red 60 3 parts by weight Disperse Violet 26 3 parts by weight Polyvinyl acetal 5 parts by weight (Sekisui Chemical Co., Ltd., S-LEC (registered trademark) KS-5) Polyethylene wax 0.1 parts by weight Toluene 50 parts by weight ·MEK 50 parts by mass

[0088] <Cyan colorant layer coating liquid> Solvent Blue 63 3 parts by weight Disperse Blue 354 4 parts by weight Polyvinyl acetal 5 parts by weight (Sekisui Chemical Co., Ltd., S-LEC (registered trademark) KS-5) Polyethylene wax 0.1 parts by weight Toluene 50 parts by weight ·MEK 50 parts by mass

[0089] <Coating solution for peel-off layer> Vinyl chloride-vinyl acetate copolymer 3 parts by weight (Manufactured by Nissin Chemical Industry Co., Ltd., Solvine (registered trademark) CNL, glass transition temperature (Tg) 76°C, number average molecular weight (Mn) 16000, shown as "vinyl chloride and acetate" in Table 1) Polyester A 7 parts by weight (Toyobo Co., Ltd., Vylon (registered trademark) GA-6400, Tg -20°C, melting point 96°C, Mn 30000) ·MEK 20 parts by mass Toluene 20 parts by weight

[0090] <Back layer coating solution A> Acrylic modified silicone resin 10 parts by weight (Natoco Co., Ltd., Polyalloy NSA-X55) Silicone isocyanate 2 parts by weight (Dainichi Seika Color & Chemicals Co., Ltd., Dialomer (registered trademark) SP901) ·MEK 20 parts by mass Toluene 20 parts by weight

[0091] [Examples 2 to 9 and Comparative Example 1] A thermal transfer sheet was produced in the same manner as in Example 1, except that the composition of the peel-off layer was changed as shown in Table 1, and the primer layer and the back layer were formed using the coating liquids shown below. When primer layer coating liquid C was used, the thickness of the primer layer C after drying was 5 μm. When back layer coating liquid B was used, the thickness of the back layer B after drying was 1 μm, and when back layer coating liquid C was used, the thickness of the back layer C after drying was 0.5 μm. Polyester B: Vylon (registered trademark) 700, manufactured by Toyobo Co., Ltd., Tg 90°C Polyvinyl butyral: Sekisui Chemical Co., Ltd., S-LEC (registered trademark) KS-5, Tg 113°C, Mn 130000 Urethane-modified silicone resin: Diaromer (registered trademark) SP2105, manufactured by Dainichi Seika Chemicals Mfg. Co., Ltd., described as "silicone" in Table 1

[0092] <Primer layer coating solution C> Polyester 5 parts by weight (Vylonal (registered trademark) MD1930, manufactured by Toyobo Co., Ltd.) Foam particles: 5 parts by weight (Matsumoto Yushi Seiyaku Co., Ltd., Matsumoto Microsphere (registered trademark) HF30D, foaming temperature 115°C) ·Water 23 parts by mass

[0093] <Back layer coating solution B> Polyvinyl butyral resin 1.8 parts by weight (Sekisui Chemical Co., Ltd., S-LEC (registered trademark) BX-1) Polyisocyanate 5.5 parts by weight (DIC Corporation, Burnock (registered trademark) D750) Phosphate ester surfactant 1.6 parts by weight (Manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Plysurf (registered trademark) A208N) Talc 0.35 parts by weight (Microace (registered trademark) P-3, manufactured by Nippon Talc Industries Co., Ltd.) Toluene 18.5 parts by weight ·MEK 18.5 parts by mass

[0094] <Back layer coating solution C> Polyvinyl butyral 36 parts by weight (Sekisui Chemical Co., Ltd., S-LEC (registered trademark) KS-1) Isocyanate compound 25 parts by weight (DIC Corporation, Burnock (registered trademark) D750) Zinc stearyl phosphate 10 parts by weight (Sakai Chemical Industry Co., Ltd., LBT1830 refinement) Zinc stearate 10 parts by weight (Sakai Chemical Industry Co., Ltd., SZ-PF) Polyethylene wax 3 parts by weight (Toyo Adle Co., Ltd., Polywax 3000) Ethoxylated alcohol-modified wax 7 parts by weight (Toyo Adle Co., Ltd., Unitox 750) ·MEK 200 parts by mass Toluene 100 parts by weight

[0095] <<Measurement of logarithmic decrement ΔE>> The thermal transfer sheets obtained in the above examples and comparative examples were cut into a size of 15 mm wide x 50 mm long to prepare test samples. Using these test samples, the logarithmic decrement ΔE was measured when the temperature of the peel-off layer of the test sample reached 100°C according to the above-mentioned method. The measurement results are shown in Table 1. The rigid pendulum physical property tester used was RPT-3000W manufactured by A&D Co., Ltd. The test sample temperature adjustment table used was a cold block CHB-100. The cylindrical cylinder used was a cylindrical cylinder edge RBP-060. The pendulum frame used was FRB-100.

[0096] <<Check the condition of the back>> In the thermal transfer sheets obtained in the above examples and comparative examples, the ten-point average roughness Rz of the surface of the back layer was measured in accordance with JIS B0601:2013. Specifically, the ten-point average roughness Rz was measured using a surface roughness measuring instrument under the following conditions. The surface roughness measuring instrument used was Surfcom 1400 manufactured by Tokyo Seimitsu Co., Ltd. (Measurement conditions) Measurement method: 2D Measurement range: 4mm Measurement pitch: 20μm ·Measurement magnification: 20K λs filter: None Cutoff type: Gaussian Cutoff wavelength: 0.8mm Tilt correction: least squares straight line ·Measurement speed: 0.6mm / s Pickup Type: Standard Pickup

[0097] <<Peel-off test>> First, an intermediate transfer medium was prepared as follows. A release layer coating solution having the following composition was applied onto a polyethylene terephthalate film (substrate) having a thickness of 12 μm, and then dried to form a release layer. Next, a protective layer coating solution having the following composition was applied onto the release layer and dried to form a protective layer. Next, a coating liquid for a receiving layer having the following composition was applied onto the protective layer and dried to form a receiving layer, thereby obtaining an intermediate transfer medium. In the intermediate transfer medium, the release layer, the protective layer and the receiving layer constitute a transfer layer.

[0098] <Coating solution for release layer> Acrylic resin 20 parts by weight (Mitsubishi Rayon Co., Ltd., Dianale (registered trademark) BR-83) Polyester 1 part by weight (Byron (registered trademark) 600, manufactured by Toyobo Co., Ltd.) ·MEK 79 parts by mass

[0099] <Coating solution for protective layer> Polyester 20 parts by weight (Byron (registered trademark) GK-250, manufactured by Toyobo Co., Ltd.) ·MEK 80 parts by mass

[0100] <Coating solution for receiving layer> Vinyl chloride-vinyl acetate copolymer 20 parts by weight (Nissin Chemical Industry Co., Ltd., Solvine (registered trademark) CNL) Silicone oil 1 part by weight (Shin-Etsu Chemical Co., Ltd., X-22-3000T) ·MEK 79 parts by mass

[0101] The yellow colorant layer, magenta colorant layer, and cyan colorant layer of each thermal transfer sheet of the examples and comparative examples prepared above were thermally transferred onto the receiving layer of the intermediate transfer medium prepared above to form an image. Then, the peel-off layer of the thermal transfer sheet and the receiving layer of the intermediate transfer medium were overlapped so that they were in contact with each other, and the rear side of the thermal transfer sheet was heated using the following printer to remove a part of the transfer layer from the intermediate transfer medium. At this time, the occurrence of reverse transfer of the peel-off layer was visually confirmed, and the peel-off property was evaluated based on the following evaluation criteria. The evaluation results are shown in Table 1. In this evaluation, the peel-off property was evaluated at an applied voltage of 21 V as well as at an applied voltage of 15 V, but the peel-off property at an applied voltage of 21 V was evaluated under harsher conditions, and the fact that the peel-off property is good under this condition indicates that the peel-off property is good under a wide range of peel-off conditions.

[0102] <Printer> Thermal head: KEE-57-12GAN2-STA (Kyocera Corporation) Heating element average resistance: 3303 (Ω) Print density in the main scanning direction: 300 dpi Sub-scanning direction print density: 300 dpi 1 line period: 2.0 (msec.) Printing start temperature: 35(℃) Pulse duty ratio: 85% Applied voltage: low energy 15 (V), high energy 21 (V)

[0103] (Evaluation Criteria) A: It was confirmed that the transfer layer in the removal area of ​​the intermediate transfer medium was accurately removed. B: A small part of the transfer layer remained in the removed area of ​​the intermediate transfer medium. C: Part of the transfer layer remained in the removed area of ​​the intermediate transfer medium, but this does not cause any practical problem. NG: A large amount of the transfer layer remains in the removed area of ​​the intermediate transfer medium, which is problematic for practical use.

[0104] <<Adhesion evaluation>> After each used thermal transfer sheet in the peel-off property test was wound on a take-up reel, the used thermal transfer sheet was heated by a heated roll at 90°C and a processing speed of 1 m / min. The adhesion was evaluated based on the following evaluation criteria. The evaluation results are shown in Table 1. The heating temperature was changed to 110° C. and 130° C., and the same evaluation was carried out. The evaluation results are shown in Table 1.

[0105] (Evaluation Criteria) A: The peel-off layer and back layer do not peel off completely, and the thermal transfer sheet tears when you try to peel them off. B: There are some areas where the peel-off layer and the back layer peel off slightly, but if you try to peel it off completely, the thermal transfer sheet will tear. C: The peel-off layer and the back layer are partially peeled off, but if you try to peel them off completely, the thermal transfer sheet will tear. NG: The thermal transfer sheet peels off without tearing.

[0106] [Table 1] [Explanation of symbols]

[0107] 10: thermal transfer sheet, 11: substrate, 12: color material layer, 13: back layer, 14: peel-off layer, 15: primer layer, 21: thermal transfer sheet supply reel, 22: transferee supply reel, 23: thermal head, 24: platen roll, 25: transport roller, 26: take-up reel, 27: heating means, 30: transferee, 40: used thermal transfer sheet, A: rigid pendulum physical property tester, B: test sample temperature adjustment table, C: cylindrical cylinder, D: pendulum frame, E: vibration displacement detector, S: test sample

Claims

1. A method for preventing information leakage from a used thermal transfer sheet, comprising the steps of: A thermal transfer sheet including a substrate, a color material layer provided on one side of the substrate, a back surface layer provided on the other side of the substrate, a peel-off layer provided in surface sequence with the color material layer, and a primer layer located between the substrate and the peel-off layer and adjacent to the substrate and the peel-off layer, is used to thermally transfer the color material layer to a transfer recipient, and a predetermined portion of the transfer recipient is peeled off by the peel-off layer, The thermal transfer sheet after peeling off is heated before being wound on a take-up reel, or the thermal transfer sheet after being wound on a take-up reel is heated to thermally fuse the opposing peel-off layer and back layer, and The method wherein said primer layer is foamed by said heating.

2. A method for preventing information leakage from a used thermal transfer sheet, comprising the steps of: a thermal transfer sheet including a substrate, a color material layer provided on one surface of the substrate, a back layer provided on the other surface of the substrate, and a peel-off layer provided in surface sequence with the color material layer, the peel-off layer having a logarithmic decrement ΔE of 0.25 or more at 100° C. as determined by a rigid pendulum measurement, the color material layer is thermally transferred to a transferee, and a predetermined portion of the transferee is peeled off by the peel-off layer; The peel-off thermal transfer sheet is heated before being wound on a take-up reel, or heated after being wound on a take-up reel, thereby thermally fusing the opposing peel-off layer and back surface layer.

3. A method for preventing information leakage from a used thermal transfer sheet, comprising the steps of: A thermal transfer sheet is provided which comprises a substrate, a color material layer provided on one side of the substrate, a back layer provided on the other side of the substrate, and a peel-off layer provided in surface sequence with the color material layer, and the back layer has a ten-point average roughness Rz of 5.0 μm or less. The thermal transfer sheet is used to thermally transfer the color material layer to a transferee, and a predetermined portion of the transferee is peeled off by the peel-off layer. The peel-off thermal transfer sheet is heated before being wound on a take-up reel, or heated after being wound on a take-up reel, thereby thermally fusing the opposing peel-off layer and back surface layer.

4. The method according to any one of claims 1 to 3, wherein the heating temperature is 110°C or higher.

5. The method of any one of claims 1 to 4, wherein the peel-off layer comprises vinyl chloride-vinyl acetate copolymer and polyester.

6. The method according to claim 5, wherein a mass ratio of the vinyl chloride-vinyl acetate copolymer to the polyester is 0.3 or more and 2 or less.

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