Thermal transfer image receiving sheet, printed matter, and method for manufacturing the thermal transfer image receiving sheet

Abstract

To provide a thermal transfer image-receiving sheet excellent in reproducibility and productivity, and capable of forming a fine identification body such as a micro character that provides effects of preventing forgery and alteration also in a gradation image such as a facial photograph, a printed matter, and a production method of the thermal transfer image-receiving sheet.SOLUTION: The thermal transfer image-receiving sheet of the present disclosure is a thermal transfer image-receiving sheet including: a substrate; and a receiving layer provided on one face of the substrate, where the receiving layer has a concave-shaped pattern formed with a resolution of 500 dpi or more and 2,000 dpi or less. The concave-shaped pattern is difficult to be visually deciphered, and is a fine identification body which can be deciphered by enlarging with a loupe and the like.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a thermal transfer image receiving sheet, a printed matter, and a method for manufacturing a thermal transfer image receiving sheet. [Background technology]

[0002] Conventionally, a thermal transfer method has been known as a simple printing method, in which a thermal transfer sheet is used to transfer (also called print) an image onto a thermal transfer image receiving sheet. For example, sublimation thermal transfer is performed using a thermal transfer sheet having a dye layer containing a sublimation dye to form a gradation image such as a face photograph on a thermal transfer image receiving sheet. Also, melting thermal transfer is performed using a thermal transfer sheet having a melting transfer coloring layer containing a colorant such as a pigment to form a monotonous image such as a barcode, letters, or numbers on a thermal transfer image receiving sheet (for example, Patent Document 1).

[0003] Examples of printed materials using this type of thermal transfer method include ID cards such as identification cards, membership cards, and employee ID cards, as well as cards such as credit cards. Cards such as the above-mentioned ID cards contain owner information such as a photograph and card-specific information, and therefore need to be protected from forgery or alteration. One method for preventing this is to form minute identifiers (such as micro-characters) that are difficult to read visually but can be read by magnifying them with a magnifying glass or the like.

[0004] For example, Patent Document 2 proposes a method of printing micro-characters and the like on the surface of a thermal transfer image receiving sheet using ink containing silicone-based components, and then performing melt-type thermal transfer on top of that using a thermal transfer ribbon, thereby obtaining a printed product in which the micro-characters are formed within the ribbon print.

[0005] Furthermore, Patent Document 3 proposes a method of forming micro-characters or the like in the melt-transfer colored layer of a thermal transfer sheet by partially evaporating ink using an infrared laser, and then transferring the image onto a thermal transfer image receiving sheet using the thermal transfer sheet on which the micro-characters or the like have been formed, thereby obtaining a printed product in which the micro-characters or the like have been formed within the image. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 7-290848 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-15310 [Patent Document 3] Japanese Patent Application Laid-Open No. 2011-152652 Summary of the Invention [Problem to be solved by the invention]

[0007] The above-mentioned micro-characters, etc. must be formed with high reproducibility in order to prevent counterfeiting and alteration. Furthermore, since they are provided on cards, etc., the formation of the micro-characters, etc. must also be highly productive. Furthermore, to further enhance security, it is desirable that the micro-characters, etc. be formed within a gradation image such as a facial photograph.

[0008] However, in the method of Patent Document 2, since the micro characters and the like are formed by printing, there is a risk that illegible micro characters and the like may be formed due to printing defects such as faintness or crushing.

[0009] Furthermore, the method of Patent Document 3 uses an infrared laser to evaporate the ink in the melt-transfer colored layer of the thermal transfer sheet to form micro-characters, etc., which takes an enormous amount of time and is not suitable for mass production. Furthermore, the inks that can be used are limited to those that absorb infrared lasers (typically carbon inks). In other words, the method of Patent Document 3 makes it difficult to form micro-characters or the like in gradation images such as facial photographs.

[0010] The present disclosure has been made in consideration of these points, and its main purpose is to provide a thermal transfer image receiving sheet, a printed matter, and a method for manufacturing a thermal transfer image receiving sheet that has excellent reproducibility and productivity and is capable of forming fine identification elements such as microcharacters even in gradation images such as facial photographs. [Means for solving the problem]

[0011] The thermal transfer image receiving sheet of the present disclosure is a thermal transfer image receiving sheet having a substrate and a receiving layer, and the receiving layer has a recessed pattern formed at a resolution of 500 dpi or more and 2000 dpi or less.

[0012] In the thermal transfer image receiving sheet of the present disclosure, the depth of the recessed pattern may be 0.5 μm or more and 1.0 μm or less.

[0013] In the thermal transfer image receiving sheet of the present disclosure, the depth of the recessed pattern may be the same as or smaller than the thickness of the receiving layer.

[0014] In the thermal transfer image receiving sheet of the present disclosure, the receiving layer may have a thickness of 2 μm or more and 5 μm or less.

[0015] In the thermal transfer image receiving sheet of the present disclosure, the recessed pattern may have any of the following forms: letters, designs, figures, symbols, lines, dots, and a collection of these.

[0016] The thermal transfer image receiving sheet of the present disclosure may have a plurality of the recessed patterns, and the interval between the plurality of recessed patterns may be 5 mm or more and 10 mm or less.

[0017] In the thermal transfer image receiving sheet of the present disclosure, a plurality of the recessed patterns may be periodically arranged in a plane.

[0018] In the print of the present disclosure, a thermal transfer image is formed on the receptor layer of the thermal transfer image-receiving sheet.

[0019] The method for manufacturing a thermal transfer image receiving sheet of the present disclosure comprises the steps of preparing a thermal transfer image receiving sheet having a substrate and a receiving layer, and pressing an embossing roll or rotary blade against the surface of the receiving layer of the thermal transfer image receiving sheet to form a recessed pattern in the receiving layer, wherein the step of forming the recessed pattern in the receiving layer includes forming the recessed pattern at a resolution of 500 dpi or more and 2000 dpi or less.

[0020] In the method for producing a thermal transfer image receiving sheet of the present disclosure, the embossing roll or rotary blade may have a convex pattern corresponding to the concave pattern, and the height of the convex pattern may be 0.5 μm or more and 1.0 μm or less.

[0021] In the method for producing a thermal transfer image receiving sheet of the present disclosure, the height of the convex pattern may be the same as or smaller than the thickness of the receiving layer. [Effects of the Invention]

[0022] According to the present disclosure, it is possible to obtain a thermal transfer image receiving sheet and a printed matter on which minute identification elements such as micro-characters that are effective in preventing counterfeiting and alteration are formed with good reproducibility and good productivity. It is also possible to obtain a printed matter on which minute identification elements such as micro-characters are formed even in a gradation image such as a face photograph. [Brief explanation of the drawings]

[0023] [Figure 1] Schematic cross-sectional view showing an example of a thermal transfer image-receiving sheet of the present disclosure. [Figure 2] Schematic plan view showing an example of a thermal transfer image receiving sheet of the present disclosure. [Figure 3] Schematic plan view showing an example of a printed matter of the present disclosure. [Figure 4] 1 is a diagram showing an example of a method for producing a thermal transfer image receiving sheet according to the present disclosure; DETAILED DESCRIPTION OF THE INVENTION

[0024] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the embodiments described below are examples of embodiments of the present disclosure, and the present disclosure should not be construed as being limited to these embodiments. In this specification, terms such as "substrate," "board," "sheet," and "film" are not distinguished from one another solely based on differences in name. For example, the concept of "substrate" includes members that may be called sheets or films. "Surface" refers to a surface that coincides with the planar direction of the target plate-like member when viewed holistically and comprehensively. The normal direction used with respect to a plate-like member refers to the normal direction to the surface of the member. As used in this specification, terms such as "parallel" and "orthogonal," as well as length and angle values, that specify shape, geometric conditions, and their degrees, are interpreted without being bound by strict meanings, but rather include a range within which similar functions can be expected.

[0025] In the drawings referred to in this embodiment, the same parts or parts having similar functions are denoted by the same or similar reference numerals, and repeated explanations thereof may be omitted. Furthermore, the dimensional ratios of the drawings may differ from the actual ratios for the convenience of explanation, and some components may be omitted from the drawings.

[0026] [Thermal transfer image receiving sheet] First, the thermal transfer image receiving sheet of the present disclosure will be described with reference to Figures 1 and 2. Here, Figure 1 is a schematic cross-sectional view showing an example of the thermal transfer image receiving sheet of the present disclosure, and Figure 2 is a schematic plan view showing an example of the thermal transfer image receiving sheet of the present disclosure.

[0027] 1, the thermal transfer image receiving sheet 1 has a substrate 11 and a receiving layer 12 provided on one side of the substrate 11. Furthermore, the thermal transfer image receiving sheet 1 has a recessed pattern 13 on the receiving layer 12.

[0028] Note that Figure 1 illustrates a thermal transfer image receiving sheet 1 having a two-layer structure, which has a substrate 11 and a receiving layer 12 provided on one side of the substrate 11, but the thermal transfer image receiving sheet of the present disclosure is not limited to this and may have a multi-layer structure of three or more layers. For example, the thermal transfer image receiving sheet of the present disclosure may have a backside layer on the other side of the substrate 11 (i.e., the side of the substrate 11 opposite to the side on which the receiving layer 12 is provided). Furthermore, although not shown in the example shown in FIG. 1, the thermal transfer image receiving sheet of the present disclosure may have various intermediate layers between the substrate and each layer. For example, a primer layer may be provided between the substrate 11 and the receiving layer 12.

[0029] As described above, the thermal transfer image receiving sheet 1 shown in Fig. 1 has a recessed pattern 13 in the receiving layer 12. This recessed pattern 13 functions as a fine identifier and is effective in preventing counterfeiting and alteration. For example, the planar form of the recessed pattern 13 can be a form representing letters, designs, figures, symbols, lines, dots, or a collection of these.

[0030] For example, in the example shown in Fig. 2, the recessed pattern 13 has the form of a micro character string representing the alphabets ABC. That is, in the example shown in Fig. 2, a micro character string representing the alphabets ABC is provided in a recessed shape on the surface of the receiving layer 12 as the recessed pattern 13. However, the recessed pattern 13 (the micro character string representing ABC) shown in Fig. 2 is a minute identifier that is difficult to read visually and can be read by enlarging it with a magnifying glass or the like. In Fig. 2, the micro character string representing ABC is shown enlarged for ease of explanation.

[0031] Note that the term "microcharacters" used here refers to characters that are difficult to read visually but can be read by enlarging them with a magnifying glass or the like, and is not necessarily limited to characters whose size is in the μm range (for example, characters whose planar size is smaller than 1 mm x 1 mm).

[0032] Furthermore, in the example shown in Figure 2, the concave pattern 13 is composed only of shapes representing letters (i.e., shapes representing the alphabet ABC), but is not limited to this and may be composed of shapes representing patterns, figures, symbols, lines, dots, etc., or may be composed of a mixture of letters and patterns, patterns and symbols, etc.

[0033] The thermal transfer image receiving sheet 1 has the recessed pattern 13, which is a fine identification body, on the surface of the receiving layer 12, and thus effectively prevents counterfeiting and alteration.

[0034] The recessed pattern 13 is preferably formed at a resolution of 500 dpi or higher. This is because the resolution of the thermal head of a typical thermal transfer printer is 300 dpi (approximately 85 μm width / dot), making it difficult to form a fine identifier that is legible at a resolution of 500 dpi or higher using the thermal transfer method. In other words, if the recessed pattern 13 is formed at a resolution of 500 dpi or higher, security against counterfeiting and alteration is increased.

[0035] For example, when calculating the formation of micro characters at a resolution of 500 dpi, if one character is represented by 8 x 8 dots, the width of one dot will be approximately 50 μm, forming a character approximately 0.4 mm x 0.4 mm in size.

[0036] In terms of the anti-counterfeiting effect, the higher the resolution of the recessed pattern 13, the more difficult it is to forge and the greater the security. However, if the resolution is too high, i.e., if the size of the recessed pattern 13 is too small, it becomes difficult to read even when enlarged with a magnifying glass or the like. When enlarging and reading with a magnifying glass or the like, the maximum practical magnification is about 20 times. Furthermore, if the resolution is too high, it becomes difficult to form the recessed pattern 13, which is likely to cause problems in terms of manufacturing and quality. Therefore, it is preferable that the recessed pattern 13 be formed with a resolution of 2000 dpi or less.

[0037] For example, when calculating the width of a micro character at a resolution of 2000 dpi, the width of one dot is approximately 13 μm, and when one character is expressed using 8 x 8 dots, the character formed will be approximately 0.1 mm x 0.1 mm in size. Furthermore, when observed at 20x magnification, a 0.1 mm x 0.1 mm character will appear as a 2 mm x 2 mm character.

[0038] Furthermore, the depth of the concave pattern 13 is preferably 0.5 μm or more for the following reasons.

[0039] An image is transferred to the receiving layer 12 of the thermal transfer image receiving sheet 1 by a thermal transfer method such as sublimation thermal transfer or melting thermal transfer, but during this process, the surface of the receiving layer 12 of the thermal transfer image receiving sheet 1 must be in contact with the surface of the colorant layer of the thermal transfer sheet (the dye layer in sublimation thermal transfer or the melting transfer color layer in melting thermal transfer).

[0040] On the other hand, if the surface of the receptor layer 12 of the thermal transfer image receiving sheet 1 and the surface of the colorant layer of the thermal transfer sheet are separated, the colorant of the colorant layer (sublimation dye in sublimation thermal transfer, or melt-transfer colorant in melt-transfer thermal transfer) is not transferred to the receptor layer 12, resulting in a so-called "blank" state. Therefore, during transfer, pressure is usually applied from the back side of the thermal transfer sheet (the side opposite to the side where the colorant layer is provided) to prevent the surface of the receptor layer 12 of the thermal transfer image receiving sheet 1 and the surface of the colorant layer of the thermal transfer sheet from being separated.

[0041] However, if the depth of the recessed pattern 13 of the thermal transfer image receiving sheet 1 is 0.5 μm or more, it is difficult for the bottom of the recessed pattern 13 to come into contact with the surface of the color material layer of the thermal transfer sheet, even when the pressure described above is applied. As a result, the color material of the color material layer is not transferred to the areas where the recessed pattern 13 is provided, resulting in a so-called blank area. Therefore, it is preferable that the depth of the recessed pattern 13 be 0.5 μm or more.

[0042] On the other hand, the upper limit of the depth of the recessed pattern 13 can be any size that does not impede the purpose of preventing counterfeiting or alteration and allows the recessed pattern 13 to be formed from the viewpoint of reproducibility and productivity.

[0043] Here, even if the depth of the recessed pattern 13 is excessively deep, exceeding the thickness of the receiving layer 12 of the thermal transfer image receiving sheet 1, the effect of the above-mentioned blank spaces will not be improved, and rather, it will be more likely to cause problems in reproducibility and productivity. For example, when processing a concave pattern 13, the larger the aspect ratio, i.e., the larger the depth (D shown in Figure 1) of the concave pattern 13 relative to the width (W shown in Figure 1) of the opening of the concave pattern 13, the more difficult the processing typically becomes.

[0044] Embossing is one method for forming the recessed pattern 13, but in cards such as ID cards, a hard material is used for the base material 11 to prevent deformation, so if one were to attempt to form a recessed pattern 13 that is dug deep enough to reach the base material 11 beyond the thickness of the receiving layer 12, it would be difficult to form this by embossing.

[0045] Therefore, it is preferable that the depth of recessed pattern 13 is the same as or smaller than the thickness of receiving layer 12. This is because such a size allows recessed pattern 13 to be easily formed by embossing even when used for an ID card or the like.

[0046] Although it depends on the application, the thickness of the receiving layer of a thermal transfer image receiving sheet is generally in the range of 2 μm to 5 μm. Therefore, the depth of the recessed pattern 13 is preferably 5 μm or less, more preferably 2 μm or less, and even more preferably 1.0 μm or less. If the depth of the recessed pattern 13 is 1.0 μm or less, it can be made smaller than the thickness of the receiving layer 12 regardless of the application of the thermal transfer image receiving sheet 1.

[0047] As mentioned above, when calculating the width of one dot when forming micro characters at a resolution of 2000 dpi, if the depth of the concave pattern 13 is 1.0 μm or less, the aspect ratio does not pose any particular difficulty in embossing, and a thermal transfer image receiving sheet 1 having a concave pattern 13 can be easily manufactured using an embossing roll, for example.

[0048] Furthermore, when forming micro characters at a resolution of 2000 dpi or less (for example, a resolution of 500 dpi), the aspect ratio is not as strict as when forming micro characters at a resolution of 2000 dpi, so there is no particular difficulty in embossing, and for example, a thermal transfer image receiving sheet 1 having a concave pattern 13 can be easily manufactured using an embossing roll.

[0049] 2, a plurality of micro character strings representing the alphabet ABC are provided on the receiving layer 12 of the thermal transfer image receiving sheet 1. That is, the thermal transfer image receiving sheet 1 has a plurality of recessed patterns 13 on the receiving layer 12. Furthermore, in the example shown in FIG. 2, a plurality of micro character strings are periodically arranged in a plane. That is, the thermal transfer image receiving sheet 1 has a plurality of recessed patterns 13 on the receiving layer 12, and the plurality of recessed patterns 13 are periodically arranged in a plane.

[0050] As described above, the recessed pattern 13 is a minute identifier that is difficult to read visually, but can be read by magnifying it with a magnifying glass or the like. Therefore, if the recessed pattern 13 is provided alone, it will be difficult to find the recessed pattern 13, and it will also be difficult to determine whether it is genuine or a counterfeit. Therefore, it is preferable that the thermal transfer image receiving sheet 1 has a plurality of recessed patterns 13, and further, it is preferable that the plurality of recessed patterns 13 be periodically arranged in a plane so that the recessed patterns 13 can be easily found.

[0051] However, if the recessed patterns 13 are arranged too closely together, the quality of the image formed thereon may be reduced. As described above, this is because the color material of the color material layer is not transferred to the recessed patterns 13, resulting in blank areas. Therefore, although this depends on the size of the recessed patterns 13 and the image to be transferred, it is preferable that the spacing between the recessed patterns 13 be 5 mm or more.

[0052] On the other hand, if the multiple recessed patterns 13 are provided too sparsely, it becomes difficult to find the recessed pattern 13, just as it is when a single recessed pattern 13 is provided. Therefore, although it depends on the size of the recessed pattern 13 and the image to be transferred, it is preferable that the interval between the multiple recessed patterns 13 be 10 mm or less.

[0053] Here, when the recessed pattern 13 is in a form representing a collection of letters, designs, etc., the above-mentioned interval refers to the interval between the collections. For example, in the example shown in Fig. 2, the recessed pattern 13 is in a form representing a collection of letters (a micro-character string representing the alphabet ABC), and multiple recessed patterns 13 are periodically arranged in a plane in the X direction and the Y direction. In this case, the interval between multiple recessed patterns 13 refers to PX and PY shown in Fig. 2.

[0054] Hereinafter, each of the components constituting the thermal transfer image receiving sheet of the present disclosure will be described in more detail.

[0055] <Base material> The substrate may be, for example, a paper substrate or a film made of a resin material (hereinafter simply referred to as a "resin film"). Examples of paper substrates include fine paper, art paper, coated paper, resin-coated paper, cast-coated paper, paperboard, synthetic paper, and impregnated paper.

[0056] Examples of resin materials that can be used to form the resin film include polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), 1,4-polycyclohexylene dimethylene terephthalate, and terephthalic acid-cyclohexanedimethanol-ethylene glycol copolymer; polyamides such as nylon 6 and nylon 6,6; polyolefins such as polyethylene (PE), polypropylene (PP), and polymethylpentene; vinyl resins such as polyvinyl chloride, polyvinyl alcohol (PVA), polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, polyvinyl butyral, and polyvinylpyrrolidone (PVP); (meth)acrylic resins such as polyacrylate and polymethacrylate; imide resins such as polyimide and polyetherimide; cellophane, cellulose acetate, nitrocellulose, cellulose acetate propionate (CAP), and cellulose acetate butyrate (CAB); styrene resins such as polystyrene (PS); polycarbonate; and ionomer resins. The resin film may be a stretched film or an unstretched film.

[0057] In the present disclosure, "(meth)acrylic" is intended to encompass both "acrylic" and "methacrylic," and "(meth)acrylate" is intended to encompass both "acrylate" and "methacrylate."

[0058] The substrate may also be a laminate of two or more paper substrates, a laminate of two or more resin films, or a laminate of a paper substrate and a resin film. These laminates can be produced by dry lamination, wet lamination, extrusion, or the like.

[0059] The thickness of the substrate is preferably 100 μm or more and 200 μm or less, and more preferably 120 μm or more and 170 μm or less, which can further improve the curl suppression property.

[0060] <Receptor layer> The receiving layer receives the sublimation dye transferred from the thermal transfer sheet by dye sublimation thermal transfer and maintains the formed image. It also fixes the melt-transfer color layer transferred from the thermal transfer sheet by melt-transfer thermal transfer and maintains the formed image. The receiving layer is also called the image-receiving layer. The receiving layer contains at least one resin material. Examples include polyolefin, vinyl resin, (meth)acrylic resin, cellulose resin, polyester, polyamide, polycarbonate, polystyrene, urethane resin, and ionomer resin. The content of the resin material in the receiving layer is preferably 80% by mass to 98% by mass, more preferably 90% by mass to 98% by mass.

[0061] The receiving layer may contain at least one release agent. This improves the releasability from the thermal transfer sheet during image formation. Examples of release agents include solid waxes, surfactants, silicone oils, and silicone resins. Examples of solid waxes include polyethylene wax, amide wax, and Teflon (registered trademark) powder. Examples of surfactants include fluorine-based surfactants and phosphate ester surfactants. Examples of silicone oils include amino-modified silicone, epoxy-modified silicone, aralkyl-modified silicone, epoxy-aralkyl-modified silicone, alcohol-modified silicone, vinyl-modified silicone, and urethane-modified silicone.

[0062] The thickness of the receiving layer is preferably 2 μm or more and 5 μm or less, which can improve the density of the image formed on the receiving layer.

[0063] The receiving layer can be formed by dispersing or dissolving the above-mentioned materials in an appropriate solvent to prepare a coating solution, applying this to the substrate (or to the primer layer, if one is provided as an intermediate layer) to form a coating film, and drying the coating film. Usable coating methods include known methods such as roll coating, reverse roll coating, gravure coating, reverse gravure coating, bar coating, and rod coating.

[0064] <Primer layer> The thermal transfer image receiving sheet of the present disclosure may have a primer layer between the substrate and the receiving layer. This can improve adhesion between the layers. The primer layer contains at least one resin material. Examples include polyester, urethane resin, polycarbonate, (meth)acrylic resin, styrene resin, vinyl resin, and cellulose resin. The thickness of the primer layer is, for example, 0.1 μm or more and 3 μm or less. The primer layer can be formed by dispersing or dissolving the above materials in an appropriate solvent to prepare a coating liquid, applying this to the substrate using the above-mentioned coating means to form a coating film, and drying this.

[0065] <Backing layer> The thermal transfer image receiving sheet of the present disclosure may have a backing layer on the back side of the substrate (i.e., the side opposite to the side on which the receiving layer is provided) for the purpose of improving the transportability of the thermal transfer image receiving sheet and suppressing curling, etc. The back surface layer may be made of a resin such as an acrylic resin, a cellulose-based resin, a polycarbonate resin, a polyvinyl acetal resin, a polyvinyl alcohol resin, a polyamide resin, a polystyrene-based resin, a polyester-based resin, or a halogenated polymer. The back surface layer is preferably made of a resin cured with a curing agent.

[0066] [Prints] Next, the printed matter of the present disclosure will be described with reference to Fig. 3. Here, Fig. 3 is a schematic plan view showing an example of the printed matter of the present disclosure.

[0067] The printed matter of the present disclosure is produced using the thermal transfer image receiving sheet of the present disclosure, and as shown in Fig. 3, in the printed matter 20, a thermal transfer image 21 is formed on the receiving layer 12 of the thermal transfer image receiving sheet 1. The thermal transfer image 21 may be a photograph, a letter, a pattern, a figure, a symbol, a line, a dot, a symbol, or a combination thereof, but is not particularly limited thereto. The thermal transfer image 21 can be formed by a conventionally known thermal transfer method such as sublimation thermal transfer or melting thermal transfer.

[0068] As described above, the thermal transfer image receiving sheet 1 has the recessed pattern 13, which is a fine identifier, on the surface of the receiving layer 12. This recessed pattern 13 is a fine identifier that is difficult to read visually and can be read only by enlarging it with a magnifying glass, etc. As described above, the color material of the color material layer is not transferred to the areas where the recessed pattern 13 is provided, resulting in blank areas. Therefore, as shown in Figure 3, the printed matter 20 has a thermally transferred image 21 containing minute white-out identifiers (recessed pattern 13) that are difficult to read visually but can be read by enlarging with a magnifying glass or the like, thereby effectively preventing counterfeiting and alteration.

[0069] In the method of Patent Document 2, the micro characters and the like are formed by printing, so there is a risk that illegible micro characters and the like may be formed due to printing defects such as faintness or crushing.

[0070] On the other hand, according to the present disclosure, since the micro characters and the like are configured as recessed patterns, the formation of illegible micro characters and the like due to printing defects does not occur. This recessed pattern can be formed by embossing or the like, and recessed patterns such as micro characters and the like can be formed on the thermal transfer image receiving sheet with good reproducibility.

[0071] Furthermore, the method of Patent Document 3 described above has the drawback of taking a huge amount of time to form micro-characters, etc., because it uses an infrared laser to evaporate the ink in the melt-transfer colored layer of the thermal transfer sheet, making it unsuitable for mass production. Furthermore, there was a problem in that the inks that could be used were limited to those that absorb infrared lasers (typically carbon inks). In other words, the method of Patent Document 3 made it difficult to form micro-characters or the like in gradation images such as facial photographs.

[0072] On the other hand, according to the present disclosure, the micro characters and the like provided on the surface of the receiving layer of the thermal transfer image receiving sheet are configured as a recessed pattern, and this recessed pattern can be formed by embossing, etc. For example, by using an embossing roll as in the manufacturing method of the thermal transfer image receiving sheet described below, recessed patterns such as micro characters can be formed on the thermal transfer image receiving sheet with good reproducibility and productivity.

[0073] Furthermore, according to the present disclosure, the ink used for thermal transfer is not limited to ink that absorbs infrared laser (typically carbon ink). For example, dye-sublimation thermal transfer can be used to form minute identifiers such as micro-characters in a gradation image such as a face photograph. This can further enhance security against counterfeiting and alteration. For example, in the printed matter 20 shown in FIG. 3, a micro-character string representing the letters ABC is formed in a gradation image such as a face photograph.

[0074] That is, according to the present disclosure, it is possible to obtain a printed matter on which minute identification elements such as micro-characters that are effective in preventing counterfeiting and alteration are formed with good reproducibility and high productivity. It is also possible to obtain a printed matter on which minute identification elements such as micro-characters are formed even in a gradation image such as a face photograph.

[0075] 3, the printed matter of the present disclosure may have a protective layer on the thermally transferred image 21. For example, by having a protective layer on the thermally transferred image 21 of the printed matter 20, the abrasion resistance and storage stability of the thermally transferred image 21 can be significantly improved.

[0076] [Method of manufacturing thermal transfer image receiving sheet] Next, a method for producing a thermal transfer image-receiving sheet according to the present disclosure will be described with reference to Fig. 4. Here, Fig. 4 is a diagram showing an example of the method for producing a thermal transfer image-receiving sheet according to the present disclosure. As an example, a manufacturing method for a thermal transfer image receiving sheet of the present disclosure includes a step of preparing a thermal transfer image receiving sheet having a substrate and a receiving layer, and a step of pressing an embossing roll against the surface of the receiving layer of the thermal transfer image receiving sheet to form a recessed pattern in the receiving layer.

[0077] In the method for manufacturing a thermal transfer image receiving sheet according to the present disclosure, first, a thermal transfer image receiving sheet 100 having a substrate and a receiving layer is prepared. This thermal transfer image receiving sheet 100 is the thermal transfer image receiving sheet 1 shown in FIG. 1 before the recessed pattern 13 is formed. The substrate of the thermal transfer image receiving sheet 100 is the same as the substrate 11 of the thermal transfer image receiving sheet 1 shown in FIG. 1. On the other hand, the receiving layer of the thermal transfer image receiving sheet 100 is made of the same material as the receiving layer 12 of the thermal transfer image receiving sheet 1 shown in FIG. 1 and has the same thickness as the receiving layer 12, but the recessed pattern 13 is not formed.

[0078] The method for manufacturing a thermal transfer image receiving sheet according to the present disclosure also includes a step of pressing an embossing roll against the surface of the receiving layer of the thermal transfer image receiving sheet prepared above to form a recessed pattern in the receiving layer. This step of forming a recessed pattern in the receiving layer can be performed using, for example, a thermal transfer image receiving sheet manufacturing apparatus 30 shown in Fig. 4. As shown in Fig. 4, the thermal transfer image receiving sheet manufacturing apparatus 30 has an unwinding section 31, a winding section 32, and an embossing roll 40.

[0079] For example, in the thermal transfer image receiving sheet manufacturing apparatus 30 shown in Fig. 4, the thermal transfer image receiving sheet 100 is unwound from the unwinding section 31, and then an embossing roll is pressed against the surface of the receiving layer of the thermal transfer image receiving sheet 100, forming a recessed pattern in the receiving layer. That is, a thermal transfer image receiving sheet 1 having a recessed pattern 13 in the receiving layer 12 is manufactured. The thermal transfer image receiving sheet 1 is then taken up by the winding section 32.

[0080] The embossing roll 40 has a convex pattern corresponding to the concave pattern 13. As described above, the concave pattern 13 formed in the receiving layer 12 is preferably formed with a resolution of 500 dpi or more. Therefore, the convex pattern of the embossing roll 40 is also preferably formed with a resolution of 500 dpi or more.

[0081] Furthermore, the effect of preventing counterfeiting and alteration is such that the higher the resolution of the recessed pattern 13, the more difficult it becomes to counterfeit and the greater the security. However, if the resolution is too high, i.e., if the size of the recessed pattern 13 becomes too small, it becomes difficult to read even when enlarged with a magnifying glass or the like. When enlarging and reading with a magnifying glass or the like, the maximum practical magnification is about 20 times. Furthermore, if the resolution is too high, it becomes difficult to form the recessed pattern 13, which is likely to cause problems in terms of manufacturing and quality. Therefore, it is preferable that the recessed pattern 13 be formed at a resolution of 2000 dpi or less. Therefore, it is preferable that the convex pattern of the embossing roll 40 be formed at a resolution of 2000 dpi or less.

[0082] As described above, the depth of the concave pattern 13 is preferably 0.5 μm or more. Therefore, the height of the convex pattern of the embossing roll 40 is also preferably 0.5 μm or more.

[0083] As described above, the depth of recessed pattern 13 is preferably the same as or smaller than the thickness of receiving layer 12. This is because such a size allows recessed pattern 13 to be easily formed by embossing even when used for cards such as ID cards. Therefore, it is preferable that the height of the convex pattern on the embossing roll 40 is the same as or smaller than the thickness of the receiving layer 12 .

[0084] Although it depends on the application, the thickness of the receiving layer of a thermal transfer image receiving sheet is generally in the range of 2 μm to 5 μm. Therefore, the height of the convex pattern is preferably 5 μm or less, more preferably 2 μm or less, and even more preferably 1.0 μm or less. If the height of the convex pattern is 1.0 μm or less, it can be made smaller than the thickness of the receiving layer 12 regardless of the application of the thermal transfer image receiving sheet 1.

[0085] As mentioned above, when calculating the width of one dot when forming micro characters at a resolution of 2000 dpi, if the height of the convex pattern is 1.0 μm or less, the aspect ratio does not pose any particular difficulty to embossing, and a thermal transfer image receiving sheet 1 having a concave pattern 13 can be easily manufactured using an embossing roll 40, for example.

[0086] Furthermore, Figure 4 shows a manufacturing method for forming a recessed pattern 13 using an embossing roll 40 as an example of a manufacturing method for a thermal transfer image receiving sheet of the present disclosure, but the manufacturing method for a thermal transfer image receiving sheet of the present disclosure is not limited to this, and for example, a recessed pattern may be formed using a rotary blade instead of the embossing roll 40. In this case, the recessed patterns formed in the receiving layer each have a long and narrow rectangular planar shape, and the multiple recessed patterns are linearly arranged in a planar configuration, but even when forming the recessed patterns using a rotary blade, the protruding patterns of the rotary blade are preferably formed with a resolution of 500 dpi or higher, as in the case of using the embossing roll 40. This is because, as described above, recessed patterns 13 formed in receiving layer 12 are preferably formed with a resolution of 500 dpi or higher. Similarly, since the concave pattern 13 is preferably formed at a resolution of 2000 dpi or less, the convex pattern of the rotary blade is also preferably formed at a resolution of 2000 dpi or less.

[0087] Similarly, when a rotary blade is used instead of an embossing roll 40 to form a concave pattern, the height of the convex pattern on the rotary blade is preferably 0.5 μm or more, and is preferably the same as or smaller than the thickness of the receiving layer 12.

[0088] Although it depends on the application, the thickness of the receiving layer of a thermal transfer image receiving sheet is generally in the range of 2 μm to 5 μm. Therefore, the height of the convex pattern of the rotary blade is also preferably 5 μm or less, more preferably 2 μm or less, and even more preferably 1.0 μm or less. If the height of the convex pattern of the rotary blade is 1.0 μm or less, the depth of the formed concave pattern can be made smaller than the thickness of the receiving layer 12, regardless of the application of the thermal transfer image receiving sheet 1.

[0089] Although the embodiments of the thermal transfer image receiving sheet, the print, and the method for manufacturing the thermal transfer image receiving sheet according to the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea of ​​the present disclosure and exhibits similar effects is included within the technical scope of the present disclosure in any case. [Explanation of symbols]

[0090] 1 Thermal transfer image receiving sheet 11 Base material 12 Receptor 13 Concave pattern 20 Printed matter 21 Thermal Transfer Image 30 Thermal transfer image receiving sheet manufacturing equipment 31 Unwinding section 32 Winding section 40 Embossing Roll 100 Thermal transfer image receiving sheet

Claims

1. A step of preparing a thermal transfer image receiving sheet having a substrate and a receiving layer; a step of pressing an embossing roll or a rotary blade against the surface of the receptor layer of the thermal transfer image receptor sheet to form a recessed pattern in the receptor layer; Equipped with The method for producing a thermal transfer image receiving sheet, wherein the step of forming a recessed pattern in the receiving layer includes a step of forming the recessed pattern at a resolution of 500 dpi or more and 2000 dpi or less.

2. the embossing roll or rotary blade has a convex pattern corresponding to the concave pattern, 2. The method for producing a thermal transfer image receiving sheet according to claim 1, wherein the height of the convex pattern is 0.5 [mu]m or more and 1.0 [mu]m or less.

3. The method for producing a thermal transfer image receiving sheet according to claim 2, wherein the height of the convex pattern is equal to or smaller than the thickness of the receiving layer.

4. A method of manufacturing a thermal transfer image receiving sheet comprising: preparing a thermal transfer image receiving sheet having a substrate and a receiving layer; a step of pressing an embossing roll or a rotary blade against the surface of the receptor layer of the thermal transfer image receptor sheet to form a recessed pattern in the receptor layer; forming a thermal transfer image on the surface of the receiving layer on which the recessed pattern is formed; Equipped with The method for producing a printed matter, wherein the step of forming a recessed pattern in the receiving layer includes a step of forming the recessed pattern at a resolution of 500 dpi or more and 2000 dpi or less.

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