Method for removing residual images from thermal transfer sheets

Abstract

To prevent information leakage from a used thermal transfer sheet.SOLUTION: A thermal transfer sheet includes a base material, and a transfer layer provided on one surface of the base material, and includes an adhesive layer between the base material and the transfer layer. The transfer layer has a peeling layer provided on the adhesive layer, and an adhesive layer or a molten ink layer provided on the peeling layer. A back face layer may be provided on the other surface of the base material. The transfer layer is transferred, then a used thermal transfer sheet to which the surface of the adhesive layer is exposed is wound, and the adhesive layer and a back face side of the thermal transfer sheet positioned on an inner peripheral side or an outer peripheral side are bonded to each other.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a thermal transfer sheet, a method for treating an afterimage on a thermal transfer sheet, and a thermal transfer printing device. [Background technology]

[0002] 2. Description of the Related Art There is known a thermal transfer printing device in which a thermal transfer sheet and a receiver paper are sandwiched between a thermal head and a platen roll, and heat is applied from the thermal head to the thermal transfer sheet to transfer the dye of the thermal transfer sheet to the receiver paper to form an image.

[0003] Used thermal transfer sheets retain an afterimage of the print, which may lead to information leakage. For example, in commercial printers, used thermal transfer sheets used by users are left stored inside the printer in the store. The used thermal transfer sheets are simply set inside the printer, so they can be easily accessed by the printer manager. If these used thermal transfer sheets are simply discarded, there is a possibility that the printed information may be leaked to a third party. For this reason, it is necessary to implement some kind of information leakage prevention measures for used thermal transfer sheets. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2008-049663 A Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present disclosure is to provide a thermal transfer sheet capable of preventing information leakage from a used thermal transfer sheet, a method for processing an afterimage on a thermal transfer sheet, and a thermal transfer printing device. [Means for solving the problem]

[0006] The thermal transfer sheet according to the present disclosure comprises a substrate and a transfer layer provided on one surface of the substrate, with an adhesive layer provided between the substrate and the transfer layer.

[0007] The thermal transfer printing device according to the present disclosure comprises a supply unit that supplies the thermal transfer sheet of the present disclosure, a thermal head that heats the thermal transfer sheet supplied from the supply unit and transfers the transfer layer onto an image receiving sheet, and a recovery unit that rolls up and recovers the thermal transfer sheet with the surface of the adhesive layer exposed after the transfer layer has been transferred.

[0008] The method for processing an afterimage of a thermal transfer sheet according to the present disclosure comprises the steps of heating the thermal transfer sheet with a thermal head and transferring the transfer layer onto an image receiving sheet, and after transferring the transfer layer, rolling up the used thermal transfer sheet with the surface of the adhesive layer exposed, and adhering the adhesive layer to the back side of the thermal transfer sheet located on the inner or outer circumference side. Effect of the Invention

[0009] According to the present disclosure, it is possible to prevent information leakage from used thermal transfer sheets. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic configuration diagram of a thermal transfer printing device according to an embodiment of the present disclosure. [Diagram 2] FIG. [Diagram 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. [Figure 4] FIG. 4 is a plan view of the protective layer after printing processing. [Diagram 5] 5 is a cross-sectional view taken along line VV in FIG. 4. [Figure 6] FIG. 2 is a schematic diagram showing a method for recovering a used thermal transfer sheet. [Figure 7] 7a and 7b are diagrams for explaining the operation of the buffer unit. [Figure 8] FIG. 2 is a cross-sectional view of a thermal transfer sheet. [Figure 9] FIG. 2 is a plan view of the melt transfer layer after printing processing. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the present disclosure can be implemented in many different forms, and should not be interpreted as being limited to the description of the embodiments exemplified below. In addition, in order to clarify the explanation, the drawings may show the width, thickness, etc. of each part in a schematic manner compared to the actual form, but these are merely examples and do not limit the interpretation of the present disclosure.

[0012] Fig. 1 is a schematic diagram of a thermal transfer printing device according to an embodiment of the present disclosure, Fig. 2 is a plan view of a thermal transfer sheet 5 (ink ribbon) used in the thermal transfer printing device, and Fig. 3 is a cross-sectional view taken along line III-III in Fig. 2. The thermal transfer printing device prints an image by sublimation-transferring yellow, magenta, and cyan dyes onto an image-receiving sheet 7. The image to be printed is, for example, a human image such as a face image, or text such as an address or name.

[0013] The image receiving sheet 7 is wound around the image receiving paper roll 6 and is unwound from the image receiving paper roll 6. A known image receiving sheet can be used for the image receiving sheet 7. The image receiving sheet 7 is unwound and wound by a drive unit 12 including the image receiving paper roll 6, a capstan roller 9a, and a pinch roller 9b.

[0014] A thermal transfer sheet 5 used in a thermal transfer printing device has a dye layer 5A and a protective layer 5B, which are provided in frame sequence on a substrate 51 (see FIG. 3). The dye layer 5A has a Y layer containing a yellow dye, an M layer containing a magenta dye, and a C layer containing a cyan dye, which are provided in frame sequence.

[0015] 3, in the region where the protective layer 5B is provided, the thermal transfer sheet 5 has a substrate 51, an adhesive layer 52 and a protective layer 5B laminated in this order on one surface side of the substrate 51, and a back layer 55 provided on the other surface side of the substrate 51. The protective layer 5B includes a release layer 53 located on the adhesive layer 52 and an adhesive layer 54 provided on the release layer 53, and is a transfer layer to be transferred to the image-receiving sheet 7.

[0016] In addition, in the region where the above-mentioned dye layer 5A is formed, the back layer 55 is provided, but the adhesive layer 52 is not provided.

[0017] The thermal transfer printing device includes a thermal head 1 that heats a thermal transfer sheet 5. The thermal transfer sheet 5 is fed from a supply section 3, passes through the thermal head 1, and is collected in a collection section 4. The collection section 4 winds up the thermal transfer sheet 5 so that the dye layer 5A (and protective layer 5B) is on the inside and the back layer 55 is on the outside.

[0018] A rotatable platen roll 2 is provided below the thermal head 1. A printing unit 10 including the thermal head 1 and the platen roll 2 sandwiches an image-receiving sheet 7 and a thermal transfer sheet 5, and the thermal head 1 heats the thermal transfer sheet 5 from the back layer 55 side to perform printing processing.

[0019] The control device 14 controls the driving of each part of the thermal transfer printing device to perform the printing process. In the printing process, first, the yellow dye layer, the magenta dye layer, and the cyan dye layer of the dye layer 5A are heated in order to transfer the dye from the thermal transfer sheet 5 to the image receiving sheet 7 to form an image.

[0020] Next, the protective layer 5B is transferred from the thermal transfer sheet 5 so as to cover the image formed on the image-receiving sheet 7. The image-receiving sheet 7 to which the protective layer 5B has been transferred is cut out as a print sheet 7a by a cutter 8 on the downstream side. The print sheet 7a is discharged from a discharge port (not shown).

[0021] After transfer of the protective layer 5B, in the protective layer transfer area of ​​the thermal transfer sheet 5 (the area where the transferred protective layer 5B was provided), the surface of the adhesive layer 52 located below the protective layer 5B is exposed, as shown in Figures 4 and 5.

[0022] The used thermal transfer sheet 5 after the protective layer has been transferred passes through the buffer section 20 and is taken up in the recovery section 4. As shown in Fig. 6, the adhesive layer 52 with its exposed surface adheres to the back layer 55 of the thermal transfer sheet 5 on the inner periphery side. The used thermal transfer sheet 5 that has been integrated by being adhered with the adhesive layer 52 is extremely difficult to peel off, and if an attempt is made to peel it off forcefully, the thermal transfer sheet 5 will break. This prevents the leakage of printed information.

[0023] A buffer section 20 for adjusting the transport amount of the used thermal transfer sheet 5 after thermal transfer is provided between the thermal head 1 and the recovery section 4. The buffer section 20 has a roller 21 that contacts the back layer 55 side of the thermal transfer sheet 5, and the roller 21 is movable in the thickness direction of the thermal transfer sheet 5.

[0024] 7a shows the position of the roller 21 when the thermal transfer sheet 5 is transported in the forward direction, and FIG. 7b shows the position of the roller 21 when the thermal transfer sheet 5 is transported in the reverse direction. Here, the forward direction is the direction in which the thermal transfer sheet 5 proceeds to the recovery section 4, and the thermal transfer sheet 5 is taken up in the recovery section 4. The reverse direction is the direction in which the supply section 3 rotates in the reverse direction to rewind the thermal transfer sheet 5, and the thermal transfer sheet 5 proceeds (returns) to the supply section 3.

[0025] As shown in FIGS. 7a and 7b, during forward transport, the transport path between the thermal head 1 and the recovery unit 4 is longer than during reverse transport.

[0026] Depending on the printing process method, the thermal transfer sheet 5 transported in the forward direction may be transported in the reverse direction by a specified amount. When transporting the thermal transfer sheet 5 in the reverse direction, the roller 21 is moved so that the thermal transfer sheet 5 that was on the transport path between the thermal head 1 and the recovery unit 4 is transported. This allows the thermal transfer sheet 5 to be transported in the reverse direction without peeling off the thermal transfer sheet 5 that was adhered in the recovery unit 4.

[0027] 8, the thermal transfer sheet 5 may include a melt transfer layer 5C provided on an adhesive layer 52. The melt transfer layer 5C has a release layer 53 located on the adhesive layer 52, and a melt ink layer 56 provided on the release layer 53. The melt ink layer 56 is formed by dispersing a pigment such as carbon black in a binder resin.

[0028] The melt transfer layer 5C is transferred in a pattern such as letters onto the image receiving sheet 7. After the transfer of the melt transfer layer 5C, the surface of the adhesive layer 52 located below the melt transfer layer 5C is exposed in the melt transfer layer transfer area of ​​the thermal transfer sheet 5 (the area where the transferred melt transfer layer 5C was provided), as shown in FIG.

[0029] The used thermal transfer sheet 5 after the melt transfer layer has been transferred is taken up in the recovery section 4, and the exposed surface of the adhesive layer 52 adheres to the back layer 55 of the thermal transfer sheet 5 on the inner periphery side. The used thermal transfer sheet 5 is integrated by adhesion with the adhesive layer 52, so that leakage of printed information can be prevented. The thermal transfer sheet 5 has at least one of a protective layer 5B and a melt transfer layer 5C.

[0030] A roller may be provided near the recovery unit 4 to press the back layer 55 of the thermal transfer sheet 5 wound up and recovered in the recovery unit 4 toward the inner periphery. This allows the adhesive layer 52 and the back layer 55 to adhere more firmly.

[0031] In the above embodiment, an example has been described in which the recovery unit 4 recovers the thermal transfer sheet 5 by winding it inward so that the adhesive layer 52 with its exposed surface adheres to the back layer 55 of the thermal transfer sheet 5 on the inner periphery side, but the recovery unit 4 may recover the thermal transfer sheet 5 by winding it outward so that the adhesive layer 52 with its exposed surface adheres to the back layer 55 of the thermal transfer sheet 5 on the outer periphery side. In this case, it is preferable to provide a pressing roller having a releasable surface near the recovery unit 4 and press the wound up thermal transfer sheet 5 towards the inner periphery side.

[0032] Next, the material constituting the thermal transfer sheet 5 will be described.

[0033] (base material) The substrate 51 of the thermal transfer sheet 5 may be any of those known in the art that have a certain degree of heat resistance and strength, such as polyethylene terephthalate film, 1,4-polycyclohexylene dimethylene terephthalate film, polyethylene naphthalate film, polyphenylene sulfide film, polystyrene film, polypropylene film, polysulfone film, aramid film, polycarbonate film, polyvinyl alcohol film, cellophane, cellulose derivatives such as cellulose acetate, polyethylene film, polyvinyl chloride film, nylon film, polyimide film, resin films such as ionomer film, as well as papers such as condenser paper and paraffin paper, nonwoven fabrics, and the like, or composites of paper or nonwoven fabric with resin.

[0034] The thickness of the substrate is not particularly limited, but is preferably about 0.5 μm or more and 50 μm or less.

[0035] (dye layer) The dye layer 5A is formed as a layer containing a sublimable dye. As the dye, any dye used in known thermal transfer sheets can be used, and there is no particular limitation. Examples of these dyes include methine dyes such as diarylmethane dyes, triarylmethane dyes, thiazole dyes, and merocyanine dyes, azomethine dyes such as indoaniline dyes, acetophenone azomethine, pyrazoloazomethine, imidazole azomethine, and pyridone azomethine, xanthene dyes, oxazine dyes, cyanomethylene dyes such as dicyanostyrene and tricyanostyrene, thiazine dyes, azine dyes, acridine dyes, benzene azo dyes, pyridone azo dyes, thiophene azo dyes, isothiazole azo dyes, pyrrole azo dyes, pyrazole azo dyes, imidazole azo dyes, thiadiazole azo dyes, triazole azo dyes, and disazo dyes, spiropyran dyes, indolinospiropyran dyes, fluorans, rhodamine lactam dyes, naphthoquinone dyes, anthraquinone dyes, and quinophthalone dyes.

[0036] The dye layer can be formed by adding at least one of the dyes and binder resin, and optionally a pigment and a conductive agent, to one side of the substrate, dissolving them in a suitable organic solvent such as toluene, methyl ethyl ketone, ethanol, isopropyl alcohol, cyclohexanone, DMF, etc., or dispersing them in an organic solvent, water, etc., and applying and drying them by means of, for example, gravure printing, screen printing, reverse roll coating printing, etc. The thickness of the dye layer after drying is about 0.2 μm or more and 6.0 μm or less.

[0037] (Adhesive layer) There are no particular limitations on the adhesive that forms the adhesive layer 52, and any conventionally known solvent-based or water-based adhesive can be used. Examples of adhesives include vinyl acetate resin, acrylic resin, vinyl acetate-acrylic copolymer, vinyl acetate-vinyl chloride copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer, polyurethane, natural rubber, chloroprene rubber, and nitrile rubber.

[0038] The thickness of the adhesive layer is approximately 1 μm or more and 20 μm or less.

[0039] Considering the adhesive strength with the back layer 55 on the inner circumference side when taken up in the recovery section 4, the adhesive strength of the adhesive layer is preferably such that the peel strength when a release paper is attached to the surface of the adhesive layer exposed after the protective layer is transferred and then peeled off is 20 gf / cm or more. If the adhesive layer and the back layer are attached and then peeled off, the peel strength is too large and the thermal transfer sheet breaks.

[0040] (protective layer) The protective layer 5B has a release layer 53 and an adhesive layer 54.

[0041] The adhesive layer 54 improves the transferability of the protective layer 5B and the adhesion of the protective layer 5B to the image surface after transfer. Any conventionally known heat-sensitive adhesive can be used for this adhesive layer, but it is more preferable to form it from a thermoplastic resin having a glass transition temperature of 50° C. or more and 100° C. or less, and it is preferable to select one having an appropriate glass transition temperature from resins having good adhesiveness when heated, such as ultraviolet absorbing resins, acrylic resins, vinyl chloride-vinyl acetate copolymers, epoxy resins, polyesters, polycarbonates, butyral resins, polyamides, and polyvinyl chloride.

[0042] The adhesive layer can be formed by preparing a coating liquid for the adhesive layer by adding one or more resin materials selected from the above-mentioned materials, and further adding additives as necessary, dissolving or dispersing them in an appropriate solvent such as an organic solvent, and applying and drying this by means of gravure printing, screen printing, reverse coating using a gravure plate, etc. The thickness of the adhesive layer is not particularly limited, but is usually about 0.3 μm to 10 μm in the dry state.

[0043] The peeling layer 53 facilitates peeling of the protective layer 5B from the adhesive layer 52 during thermal transfer, and is a layer that is transferred onto a transfer-receiving body during thermal transfer.

[0044] The release layer is composed of, for example, various waxes such as silicone wax, various resins such as silicone resin, fluororesin, acrylic resin, water-soluble resin, cellulose derivative resin, polyurethane, acetate-based polyvinyl, acrylic vinyl ether resin, maleic anhydride resin, and mixtures thereof.

[0045] The release layer can be formed by applying a coating liquid containing at least one selected from the group consisting of the waxes and resins on the adhesive layer according to a conventionally known coating method, and drying the coating liquid. The thickness of the release layer after drying is about 0.5 μm to 5 μm.

[0046] (back layer) The back layer 55 is provided on the surface (back surface) of the substrate 51 opposite to the surface on which the dye layer 5A and protective layer 5B are provided, and prevents thermal fusion between a heating device such as a thermal head and the substrate, thereby making the substrate run smoothly.

[0047] Examples of resins that may form the back layer 55 include polyvinyl butyral, polyvinyl acetoacetal, polyester, vinyl chloride-vinyl acetate copolymer, polyether, polybutadiene, styrene-butadiene copolymer, acrylic polyol, polyurethane acrylate, polyester acrylate, polyether acrylate, epoxy acrylate, urethane or epoxy prepolymer, nitrocellulose resin, cellulose nitrate resin, cellulose acetopropionate resin, cellulose acetate butyrate resin, cellulose acetate hydrodiene phthalate resin, cellulose acetate resin, polyamide, polyimide, polyamideimide, polycarbonate, chlorinated polyolefin, and the like.

[0048] As described above, in the recovery section 4, the exposed surface portion of the adhesive layer 52 and the back layer 55 of the thermal transfer sheet 5 on the inner circumferential side are adhered to each other. In order to increase the adhesion area with the adhesive layer 52 and improve adhesion, it is preferable that the back layer 55 has a small solid filler content and a smooth surface.

[0049] The ten-point average roughness Rz of the surface of the back layer 55 is preferably 5.0 μm or less, more preferably 4.0 μm or less, and even more preferably 3.0 μm or less. For example, the surface roughness can be measured using a surface roughness measuring device (Surfcom 1400 3DF, manufactured by Tokyo Seimitsu Co., Ltd.) under the following measurement conditions. <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

[0050] The back layer 55 can be formed by dissolving or dispersing the above-mentioned resin in an appropriate solvent to prepare a back layer coating liquid, applying this to the back surface of the substrate 51 by a forming means such as gravure printing, screen printing, or reverse coating using a gravure plate, and drying. The thickness of the back layer 55 after drying is about 0.1 μm or more and 2 μm or less. EXAMPLES

[0051] The present disclosure will now be described in more detail with reference to examples, but the present disclosure is not limited to these examples. In the text, "parts" are by mass unless otherwise specified.

[0052] [Example 1] A PET film having a thickness of 5 μm was used as the substrate, and a coating liquid for adhesive layer having the following composition was applied to one side of the substrate and dried to form an adhesive layer having a thickness of 2 μm. A coating liquid for peeling layer having the following composition was applied to this adhesive layer and dried to form a peeling layer having a thickness of 0.5 μm. A coating liquid for adhesive layer having the following composition was applied to this peeling layer and dried to form an adhesive layer having a thickness of 0.5 μm, and a protective layer having a laminated peeling layer and adhesive layer was obtained. A coating liquid 1 for back layer having the following composition was applied to the other side of the substrate and dried to form a back layer having a thickness of 1 μm, and a thermal transfer sheet of Example 1 in which the back layer, substrate, adhesive layer, and protective layer (peeling layer and adhesive layer) were laminated in this order was produced.

[0053] <Coating fluid for adhesive layer> Acrylic copolymer 15 parts (SK Dyne 1251 Soken Chemical Industries, Ltd.) Hardener 0.33 parts (L-45 Soken Chemical Co., Ltd.) Hardener 0.1 parts (E-AX Soken Chemical Co., Ltd.) Ethyl acetate 16.14 parts

[0054] <Coating solution for release layer> ·10 parts silicone release agent (KS-847H Shin-Etsu Chemical Co., Ltd.) Methyl ethyl ketone 40 parts Toluene 40 parts

[0055] <Coating liquid for adhesive layer> Polyester resin 20 parts (Byron 200 Toyobo Co., Ltd.) UV absorber copolymer resin 10 parts (UVA-635L manufactured by BASF Japan) Methyl ethyl ketone 80 parts

[0056] <Back layer coating solution 1> Polyvinyl acetal resin 60 parts (S-LEC KS-1 Sekisui Chemical Co., Ltd.) Polyisocyanate 4 parts (Burnoc D750 Dainippon Ink and Chemicals, Inc.) Filler (zinc stearyl phosphate) 10 parts (LBT1830 Refined by Sakai Chemical Industry Co., Ltd.) Filler (zinc stearate) 10 parts (SZ-PF Sakai Chemical Industry Co., Ltd.) Filler (polyethylene wax) 3 parts (Polywax 3000 Toyo Adle Co., Ltd.) Filler (ethoxylated alcohol modified wax) 7 parts (Unitox 750 Toyo Adle Co., Ltd.) Toluene 200 parts Methyl ethyl ketone 100 parts

[0057] <Transfer of protective layer> Using the prepared thermal transfer sheet, the protective layer was transferred onto image receiving paper for a thermal transfer printer (DS620) manufactured by Dai Nippon Printing Co., Ltd., using the following test printer.

[0058] <<Test Printer>> Thermal head: F3598 (Toshiba Hokuto Electronics Co., Ltd.) Heating element average resistance: 5015(Ω) - Print density in the main scanning direction: 300 (dpi) Sub-scanning direction print density: 300 (dpi) Applied voltage: 20(V) Line period: 2.0 (msec. / line) Pulse Duty: 85%

[0059] <Peel force measurement> A release layer coating liquid having the same composition as the release layer coating liquid was applied to one side of a coated paper (thickness 80 μm), dried, and a release layer having a thickness of 0.3 μm was formed to obtain a release paper. This release paper was attached to the surface of the adhesive layer exposed by the protective layer transfer, and a peeling device (HEIDON-14DR Shinto Scientific Co., Ltd.) was used to perform 180° peeling at a pulling speed of 2000 mm / min, and the peeling force at that time was measured. The results are shown in Table 1.

[0060] <Information concealment evaluation> After laminating the back layer of the thermal transfer sheet to the surface of the adhesive layer exposed by the protective layer transfer, it was confirmed whether the back layer could be peeled off from the adhesive layer, and the peel resistance was evaluated according to the following criteria. The results are shown in Table 1.

[0061] "Evaluation Criteria" A: It doesn't peel off at all. B: It peels off slightly, but if you try to peel it off further the ribbon breaks. C: Part of the ribbon peels off, but if you try to peel it off further the ribbon breaks. D: The ribbon can be peeled off but there is resistance and if you try to peel it off further the ribbon breaks. E: Easily peeled off

[0062] [Examples 2 to 6, Comparative Examples 1 to 2] A thermal transfer sheet was prepared in the same manner as in Example 1, except that at least one of the composition of the coating liquid for the back layer, the thickness of the adhesive layer, and the voltage applied during the transfer of the protective layer was changed, and the protective layer was transferred and evaluated. The results are shown in Table 1.

[0063] <Back layer coating liquid 2> Polyvinyl butyral resin 1.8 parts (S-LEC (registered trademark) BX-1 Sekisui Chemical Co., Ltd.) Polyisocyanate 5.5 parts (Burnoc (registered trademark) D750 DIC Corporation) Phosphate ester surfactant 1.6 parts (Prysurf (registered trademark) A208N Daiichi Kogyo Seiyaku Co., Ltd.) Talc 0.35 parts (Microace (registered trademark) P-3 Nippon Talc Industrial Co., Ltd.) Toluene 18.5 parts Methyl ethyl ketone 18.5 parts

[0064] [Table 1]

[0065] For the thermal transfer sheets of each Example, the ten-point average roughness Rz of the surface of the back layer was measured under the above-mentioned measurement conditions using a surface roughness measuring instrument (Surfcom 1400 3DF, manufactured by Tokyo Seimitsu Co., Ltd.) The ten-point average roughness Rz of the surface of the back layer of the thermal transfer sheets of Examples 1, 3, and 5 was 4.8 μm, and the ten-point average roughness Rz of the surface of the back layer of the thermal transfer sheets of Examples 2, 4, and 6 was 2.0 μm or less. [Explanation of symbols]

[0066] 1 Thermal head 2 Platen Roll 3 Supply section 4. Collection Section 5. Thermal transfer sheet 5A dye layer 5B Protective layer 7 Receiving sheet 10 Printing Department 14 Control device 20 Buffer section 51 Base material 52 Adhesive layer 53 Peeling layer 54 Next layer 55 Back layer

Claims

1. A method for treating residual images of a thermal transfer sheet having a substrate, a dye layer and a transfer layer provided in surface sequence on one surface of the substrate, and a back layer provided on the other surface of the substrate, the method comprising the steps of: a step of heating the thermal transfer sheet with a thermal head, transferring a dye to an image receiving sheet to form an image, and transferring the transfer layer onto the image receiving sheet after the image is formed; a step of inwardly winding the thermal transfer sheet after the transfer layer has been transferred by a recovery unit so that the adhesive layer having an exposed surface is adhered to the back surface layer of the thermal transfer sheet on the inner peripheral side; a step of pressing the back surface layer of the thermal transfer sheet wound and collected in the collection section toward an inner periphery side with a roller; A method for treating an afterimage on a thermal transfer sheet comprising:

2. A method for treating residual images of a thermal transfer sheet having a substrate, a dye layer and a transfer layer provided in surface sequence on one surface of the substrate, and a back layer provided on the other surface of the substrate, the method comprising the steps of: a step of heating the thermal transfer sheet with a thermal head, transferring a dye to an image receiving sheet to form an image, and transferring the transfer layer onto the image receiving sheet after the image is formed; a step of winding the thermal transfer sheet after the transfer layer has been transferred outwardly by a recovery section so that the adhesive layer on the exposed surface is adhered to the back layer of the thermal transfer sheet on the outer periphery; a step of pressing the thermal transfer sheet, which has been wound up and collected in the collection section, toward an inner periphery with a roller having a releasable surface; A method for treating an afterimage on a thermal transfer sheet comprising:

Images