Thermal transfer recording medium

Abstract

To provide a thermal transfer recording medium that makes it difficult to read the transfer traces on used thermal transfer recording media, thereby preventing the leakage of confidential information such as personal information and confidential documents. [Solution] A thermal transfer recording medium comprising a substrate and a security layer, a release layer, and a colored ink layer laminated in this order on one surface of the substrate, characterized in that the security layer is composed of a die-cut pattern having the same hue as the colored ink layer and the area ratio of the colored portion is 50 to 80%.

Description

Technical Field

[0001] The present invention relates to a thermal transfer recording medium. More specifically, the present invention relates to a thermal transfer recording medium that makes it difficult to read the transfer traces of a used thermal transfer recording medium and can prevent the leakage of confidential information.

Background Art

[0002] Conventionally, thermal transfer recording media have been used to output characters, images, etc. onto a transfer body such as paper or plastic using a thermal transfer printer. As a thermal transfer recording medium, there is a melting type thermal transfer recording medium in which a thermal transfer ink layer is provided on a base material such as a PET (polyethylene terephthalate) film, and the thermal transfer ink layer of the melted portion by the heat of a thermal head is transferred from the base material to the transfer body when using a thermal transfer printer.

[0003] When using the thermal transfer recording medium to transfer characters, images, etc. onto a transfer body, the character or image portion of the thermal transfer ink layer is transferred to the transfer body. Therefore, in the thermal transfer ink layer of the used thermal transfer recording medium after transfer, a transfer trace with the character or image portion missing remains. When creating confidential documents such as contract documents, patent application documents, and know-how documents, since those confidential information are recorded as transfer traces on the used thermal transfer recording medium, there has been a problem that measures to prevent the leakage of confidential information are required at the time of disposal.

[0004] Patent Document 1 proposes a thermal transfer printer equipped with a means for scraping off the used thermal transfer ink from a thermal transfer recording medium by a scraping means provided downstream of the thermal head after a print image has been printed by the thermal head. Patent Document 2 proposes a thermal transfer system in which, after transferring the thermal transfer ink from the thermal transfer ink layer of a thermal transfer recording medium to a transfer target in a first pattern, a heating element is brought into contact with the outermost thermal transfer recording medium wound onto the winding section, thereby transferring a second pattern different from the first pattern to the support layer of the thermal transfer recording medium located inside the thermal transfer recording medium. However, adopting these methods requires modifications to the transport and winding sections of the thermal transfer recording medium, which places a heavy burden on existing systems.

[0005] Patent Document 3 proposes a thermal transfer recording medium for preventing confidential information leakage, in which a matte layer is provided on a substrate, and a thermal transfer ink layer that peels off from the matte layer is provided on the matte layer, and a coloring agent is contained in the matte layer so that it is the same color as the thermal transfer ink layer. However, in this thermal transfer recording medium, because the matte layer generally has a higher light transmittance than the thermal transfer ink layer, the contents of the transfer trace can be confirmed by copying the used thermal transfer recording medium with a copier or by holding it up to light such as a fluorescent lamp. Patent Document 4 proposes a thermal transfer recording medium in which a thermal transfer ink layer is provided on a substrate via a matte layer, characterized in that the matte layer is the same hue as the ink layer and is provided in a pattern. However, the details regarding the pattern provided on the matte layer of this thermal transfer recording medium are not specified, and it was not possible to completely prevent the reading of the transfer trace. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2005-305799 [Patent Document 2] Japanese Patent Publication No. 2014-188731 [Patent Document 3] Japanese Patent Application Publication No. 7-164769 [Patent Document 4] Japanese Patent Application Publication No. 4-197792 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The present invention aims to provide a thermal transfer recording medium that makes it difficult to read the transfer traces on used thermal transfer recording media, thereby preventing the leakage of confidential information such as personal information and confidential documents. [Means for solving the problem]

[0008] The means for achieving the objectives of the present invention will be described in detail below.

[0009] The first invention is a thermal transfer recording medium comprising a substrate and a security layer, a release layer, and a colored ink layer laminated in this order on one surface of the substrate, characterized in that the security layer is composed of a die-cut pattern having the same hue as the colored ink layer and the area ratio of the colored portion is 50 to 80%.

[0010] The second invention is a thermal transfer recording medium according to the first invention, characterized in that the release layer contains polyethylene wax having a melting point of 80°C to 120°C in an amount of 70 to 98% by weight of the solid content of the release layer, and ethylene-vinyl acetate copolymer resin having a vinyl acetate content of 14% to 28% in an amount of 2 to 30% by weight of the solid content of the release layer.

[0011] The third invention is a thermal transfer recording medium according to the first or second invention, characterized in that the thickness of the security layer is 0.3 to 0.7 μm. [Effects of the Invention]

[0012] The configuration of the present invention makes it difficult to decipher the transfer traces on used thermal transfer recording media, thereby providing a thermal transfer recording medium that can prevent the leakage of confidential information such as personal information and confidential documents. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic cross-sectional view showing one embodiment of the thermal transfer recording medium of the present invention. [Figure 2] This is a schematic diagram showing one embodiment of the security layer pattern of the present invention. [Figure 3] This is a schematic diagram showing one embodiment of a pattern in which the characters, symbols, images, etc. described in Comparative Example 1 are colored. [Modes for carrying out the invention]

[0014] The embodiments of the thermal transfer recording medium of the present invention will be described in detail below.

[0015] Figure 1 is a schematic cross-sectional view showing an embodiment of the thermal transfer recording medium of the present invention. The thermal transfer recording medium 10 shown in Figure 1 has a structure in which a security layer 12, a release layer 13, and a colored ink layer 14 are laminated in this order on one surface of a substrate 11, and a heat-resistant slippery layer 15 is provided on the other surface. The security layer 12 of the thermal transfer recording medium 10 of the present invention has the same hue as the colored ink layer 14 and is composed of a die-cut pattern, and the release layer 13 is laminated on the security layer 12 in the colored portion of the die-cut pattern and on the substrate 11 in the uncolored portion. When the thermal transfer recording medium 10 is heat-transferred to the object to be transferred, the security layer 12 is not transferred and remains on the substrate 11, while the release layer 13 and the colored ink layer 14 are transferred to the object to be transferred. In this specification, the die-cut pattern of the thermal transfer recording medium refers to a pattern in which information portions such as characters, symbols, and images are uncolored (transparent) portions without ink, and portions other than information such as characters, symbols, and images are colored.

[0016] (base material) As the base material of the thermal transfer recording medium of the present invention, various plastic films such as polyethylene terephthalate film, polyethylene naphthalate film and other polyester films, polypropylene film, polycarbonate film, polyimide film, aramid film, etc. can be used. Among these, it is preferable to use a polyethylene terephthalate film from the viewpoints of physical properties, processability, cost, etc. The thickness of the base material is usually about 2 to 12 μm, and in order to improve heat transfer, a range of 2 to 6 μm is preferable.

[0017] Also, on the surface on the side where the security layer etc. of the base material is formed, and on the surface on the side where the heat-resistant lubricity layer is formed, a surface treatment may be performed as necessary to improve the adhesion to each layer. Examples of the surface treatment include corona discharge treatment, ultraviolet irradiation treatment, plasma treatment, primer treatment, etc.

[0018] (Security layer) The thermal transfer recording medium of the present invention is provided with a security layer on one surface of the base material. The security layer itself is a layer that is not transferred by thermal transfer, and is provided to make it difficult to read the transfer traces formed in the upper peeling layer and the colored ink layer after thermal transfer. Also, during thermal transfer, the upper peeling layer and the colored ink layer can be easily released, and it is required to hold the upper peeling layer and the colored ink layer so that they do not fall off until thermal transfer.

[0019] In the colored ink layer after transfer of a normal thermal transfer recording medium, the ink in the portion where characters, symbols, images, etc. have been transferred to the transfer target has a missing pattern state, and it is easily legible. However, considering that the colored ink layer after transfer is in a missing pattern state, a security layer is formed under the colored ink layer having the same hue as the colored ink layer and in the form of a missing pattern in which any characters, symbols, images, etc. as shown in Fig. 2 are non-colored. When provided, compared to the case where the lower layer has the same hue as the colored ink layer and is composed of a pattern in which any characters, symbols, images, etc. as shown in Fig. 3 are colored, or when a matte layer having the same hue as the colored ink layer is provided as the lower layer over the entire surface, it becomes more difficult to read the transfer trace. In particular, when the area ratio of the colored portion of the missing pattern formed in the security layer is 50 to 80%, it becomes difficult to read the transfer trace, and more preferably, when it is in the range of 55 to 70%, it becomes even more difficult to read the transfer trace. When the area ratio of the colored portion is less than 50%, there are more portions where the portions where the ink of the colored ink layer has come off can be seen as they are, so it becomes easier to read. When it is more than 80%, there are more portions where the remaining portions of the colored ink layer exist on the colored portions of the security layer. Therefore, when light such as fluorescent light is transmitted or reflected due to the influence of density difference or gloss difference, the transfer trace becomes easier to read. Note that the colored portion of the missing pattern formed in the security layer refers to the portion where the security layer ink is applied, and the area ratio is the ratio of the area where the security layer ink is actually applied to the application area when the security layer ink is applied over the entire surface.

[0020] The missing pattern formed in the uncoated portion of the security layer ink may be any of various characters such as hiragana, katakana, kanji, numbers, alphabet, symbols, images, etc., and there are no particular restrictions on the size, orientation, etc. They can be configured in a state where those with different sizes and different orientations are randomly arranged.

[0021] The security layer of the present invention is a layer that is not transferred by thermal transfer, and can be configured in the same way as those conventionally used in transfer control layers and mat layers of thermal transfer recording media, and mainly consists of a thermoplastic resin and a colorant.

[0022] As the thermoplastic resin, any resin that exhibits good adhesion to the substrate and the upper release layer is acceptable. Polyester resins, polyurethane resins, olefin copolymer resins such as ethylene-vinyl acetate copolymers and ethylene-acrylic acid ester copolymers are preferably used. Furthermore, to ensure adhesion to the substrate, the resin may be crosslinked and cured with a crosslinking agent such as isocyanate. The content of the thermoplastic resin in the security layer solids is preferably 10 to 90% by weight. If it is less than 10% by weight, the security layer will not have sufficient adhesion, and the adhesion to the substrate and the upper release layer will decrease. On the other hand, if it exceeds 90% by weight, the adhesion of the security layer will become too strong, which may cause transfer failures during heat transfer.

[0023] The coloring agent can be either a pigment or a dye, for example, carbon black, acetylene black, lamp black, black soot, iron black, aniline black, silica, calcium carbonate, titanium dioxide, cadmium red, cadmopon red, chrome red, vermilion, red iron oxide, azo pigments, alizarin lake, quinacridone, cochineal lake perylene, yellow ochre, aureolin, cadmium yellow, cadmium orange, chrome yellow, zinc yellow, Naples yellow, nickel yellow, azo pigments, greenish yellow, ultramarine, cobalt, phthalocyanine, anthraquinone, and phosphate. Examples of pigments include dicoids, cinnabar green, cadmium green, chromium green, phthalocyanine, azomethine, perylene, and aluminum pigments, as well as dyes such as diarylmethane dyes, triarylmethane dyes, thiazole dyes, merocyanine dyes, pyrazolone dyes, methine dyes, indoaniline dyes, acetophenoneazomethine dyes, pyrazoloazomethine dyes, xanthene dyes, oxazine dyes, thiazine dyes, azine dyes, acridine dyes, azo dyes, spiropyran dyes, indolinospiropyran dyes, fluorane dyes, naphthoquinone dyes, anthraquinone dyes, and quinophthalone dyes. It is preferable to use the same colorant as that used in the colored ink layer in order to achieve the same hue. The content of the colorant in the security layer solids is preferably in the range of 10 to 90% by weight, but can be adjusted as appropriate according to the hue of the colored ink layer.

[0024] The security layer of the present invention may contain a silicone-modified resin as a release component, such as a silicone-modified urethane resin, a silicone-modified acrylic resin, or a silicone-modified polyester resin. By including the release component, the upper release layer and colored ink layer are firmly held except during heat transfer, while during heat transfer, the force holding the upper layer is reduced, enabling highly sensitive transfer of the upper layer. The content of the release component in the solid content of the security layer is preferably 4 to 20% by weight. If the content of the release component is less than 4% by weight, the effect of enabling highly sensitive transfer during heat transfer cannot be obtained. On the other hand, if it exceeds 20% by weight, the force holding the upper layer is reduced too much, and transfer defects such as surface peeling may occur during heat transfer.

[0025] The thickness of the security layer in this invention (thickness after drying, hereinafter the same) is preferably 0.3 to 0.7 μm. If the thickness of the security layer is less than 0.3 μm, the density becomes low, and the effect of preventing the readability of the transfer trace after thermal transfer decreases. On the other hand, if it exceeds 0.7 μm, the retention force on the upper layer becomes too strong, or the thermal responsiveness of the thermal transfer recording medium decreases, which may result in poor transfer of the upper layer during thermal transfer. Note that the thickness of the security layer in this invention is the measured layer thickness of the portion to which the security layer ink constituting the die-cut pattern is applied.

[0026] When the thermal transfer recording medium of the present invention has a black hue, it is preferable that the transmittance density of the security layer be 1.70 or higher. If the transmittance density of the security layer is less than 1.70, the transfer trace after thermal transfer may become easily readable due to the density difference. The above transmittance density is the value measured using an X-Rite 361T(V) monochrome transmittance densitometer, with the ink constituting the security layer applied to the entire surface with the same thickness as the security layer.

[0027] The surface of the security layer of the present invention is preferably a smooth surface with a surface roughness (arithmetic mean roughness Ra) of 0.25 μm or less, rather than a matte surface with irregularities. If the surface of the security layer is a matte surface, during thermal transfer, the upper release layer and colored ink layer may not peel off completely, leaving some of them on the security layer, or conversely, some of the security layer may peel off together with the upper release layer, which may make the transfer marks after thermal transfer easier to read. The surface roughness (Ra) is a value measured using a surface roughness measuring instrument (Surfcoder ET200A manufactured by Kosaka Research Institute Co., Ltd.) based on JIS-B0601-1994, with the ink constituting the security layer applied to the entire surface with the same thickness as the security layer.

[0028] Furthermore, the security layer may contain various components such as dispersants, leveling agents, fillers, and antistatic agents as needed, within the limits that do not impair the effects of the present invention.

[0029] The security layer of the present invention is obtained by dissolving and dispersing the thermoplastic resin, colorant, etc., in a solvent to prepare a coating liquid, and then applying and drying this coating liquid onto a substrate, for example, using a gravure coater, to form a desired pattern.

[0030] (Exfoliation layer) A release layer is provided between the security layer and the colored ink layer described later. Because the security layer is formed in a pattern, if the colored ink layer is applied directly on the security layer, variations in shade and gloss will occur on the surface of the printed material transferred to the transfer target due to the unevenness of the security layer's pattern. However, by providing a release layer, these variations in shade and gloss are eliminated to the point where they are not discernible.

[0031] As the release layer, one that has been conventionally used as a release layer for thermal transfer recording media can be applied. As the constituent material of this release layer, conventionally known heat-meltable waxes, thermoplastic resins, etc., can be used.

[0032] Examples of heat-meltable waxes include plant-based waxes such as candelilla wax, carnauba wax, rice wax, wood wax, and jojoba oil; animal-based waxes such as beeswax, lanolin, and whale wax; mineral-based waxes such as montane wax, ozokerite, and ceresin; petroleum-based waxes such as paraffin wax, microcrystalline wax, and petrolatum; synthetic hydrocarbon waxes such as Fischer-Tropsch wax and polyethylene wax; modified waxes such as montane wax derivatives, paraffin wax derivatives, and microcrystalline wax derivatives; hydrogenated waxes such as hydrogenated castor oil and hydrogenated castor oil derivatives; fatty acids such as lauric acid, palmitic acid, myristic acid, stearic acid, and 1,2-hydroxystearic acid; and fatty acid amides.

[0033] Examples of thermoplastic resins include vinyl resins such as polyvinyl chloride, polyvinyl acetate, and ethylene-vinyl acetate copolymers, polyester resins, (meth)acrylic resins, polyurethane resins, cellulose resins, melamine resins, polyamide resins, polyolefin resins, and styrene resins.

[0034] The release layer of the present invention has a portion that is directly laminated on the substrate and a portion that is laminated on the security layer ink. Since the release force during thermal transfer differs in each portion, problems such as ink residue may occur during transfer. For this reason, among the constituent materials, it is preferable to have a configuration in which polyethylene wax with a melting point of 80°C to 120°C accounts for 70 to 98% by weight of the solid content of the release layer, and ethylene-vinyl acetate copolymer resin with a vinyl acetate content of 14% to 28% accounts for 2 to 30% by weight of the solid content of the release layer. If the melting point or content of polyethylene wax is outside the above range, problems such as blurring of printed characters, trailing, surface peeling, etc., deterioration of the cut quality, and transfer failure due to decreased thermal responsiveness are likely to occur. If the vinyl acetate content of the ethylene-vinyl acetate copolymer resin is less than 14% or if the content of the ethylene-vinyl acetate copolymer resin in the solid content of the release layer is less than 2% by weight, the same deterioration of printed character cut quality and so-called powdering, where some of the ink falls off in powder form when not in use, are likely to occur. If the vinyl acetate content is higher than 28% or if the content of ethylene-vinyl acetate copolymer resin in the release layer solids is higher than 30% by weight, the security layer and the release layer may not separate cleanly, and a portion of the security layer may peel off together with the release layer, or a portion of the release layer may not be completely transferred to the substrate, leaving some residue on the substrate.

[0035] The release layer may contain various known additives as needed, such as dispersants, leveling agents, fillers, and antistatic agents.

[0036] The thickness of the release layer (thickness after drying, the same applies hereinafter) can be appropriately determined to balance the adhesion to the substrate and security layer with the sensitivity during thermal transfer, and is usually preferably in the range of 0.5 to 3.0 μm.

[0037] The release layer can be formed by conventionally known methods. For example, it can be formed by dissolving and dispersing the constituent materials of the release layer in a solvent such as toluene or MEK, and then applying and drying the resulting coating solution onto the surface on which the security layer is formed using a known coating method such as a gravure coater.

[0038] (Colored ink layer) The colored ink layer of the thermal transfer recording medium of the present invention, which is provided on the release layer, is not particularly limited, and conventional colored ink layers commonly used for thermal transfer recording media can be applied. Conventional known heat-meltable waxes, thermoplastic resins, and colorants can be used as constituent materials for this colored ink layer.

[0039] Examples of heat-meltable waxes and thermoplastic resins are the same as those used in the release layer. Examples of colorants are the same as those used in the security layer.

[0040] Furthermore, the colored ink layer may contain various known additives as needed, such as particles, lubricants, dispersants, leveling agents, fillers, and antistatic agents.

[0041] The thickness of the colored ink layer (thickness after drying, the same applies hereinafter) can be appropriately determined to balance the required print density and the sensitivity during thermal transfer, and is usually preferably in the range of 0.5 to 5.0 μm.

[0042] The colored ink layer can be formed by conventionally known methods. For example, it can be formed by dissolving and dispersing the constituent materials of the colored ink layer in a solvent such as toluene or MEK, and then applying and drying the resulting coating solution onto the surface on which the release layer is formed using a known coating method such as a gravure coater.

[0043] Furthermore, if necessary, an adhesive layer having the function of improving adhesion to the transfer target may be formed on the heat-meltable colored ink layer. The constituent materials of the adhesive layer can also be conventionally known heat-meltable waxes, thermoplastic resins, various additives, etc.

[0044] (Heat-resistant slip layer) In the thermal transfer recording medium of the present invention, it is preferable to provide a heat-resistant slip layer on the side of the substrate opposite to the side on which the security layer or the like is provided. By providing a heat-resistant slip layer, damage to the substrate of the thermal transfer recording medium by the thermal head of the printer during printing on the transfer target can be reduced. If the substrate is damaged, the thermal head may stick to the substrate during printing, preventing it from moving smoothly, a phenomenon known as "sticking." By providing a heat-resistant slip layer, such sticking can be prevented.

[0045] As for the material of the heat-resistant lubricating layer, those conventionally used in thermal transfer recording media can be used without any particular limitations. Considering the heat resistance to the thermal head, the reduction of the coefficient of dynamic friction at high temperatures, and cost, among these, silicone-modified urethane resin, silicone-modified acrylic resin, silicone resin, or mixtures thereof are particularly preferred as materials for the heat-resistant lubricating layer.

[0046] The heat-resistant lubricating layer may contain other additives as appropriate, such as particles, lubricants, and antistatic agents.

[0047] The thickness of the heat-resistant lubricating layer (thickness after drying, the same applies hereinafter) is preferably 0.05 to 0.80 μm, in order to achieve a good stick prevention effect and prevent deterioration of thermal conductivity. If the thickness of the heat-resistant lubricating layer is less than 0.05 μm, the heat resistance is insufficient, which may cause sticking during printing or the substrate to melt, making printing impossible. If it exceeds 0.80 μm, thermal conductivity deteriorates, which may interfere with printing.

[0048] The heat-resistant slippery layer can be formed by conventionally known methods. For example, it can be formed by dissolving and dispersing the constituent materials of the heat-resistant slippery layer in a solvent such as toluene or MEK, and then applying and drying the resulting coating solution on the surface opposite to the surface on which the security layer or the like is formed, using a known coating method such as a gravure coater. [Examples]

[0049] The thermal transfer recording medium of the present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. Hereinafter, when the amount of each material is indicated as "parts," it refers to parts by weight unless otherwise specified.

[0050] (Example 1) <Fabrication of thermal transfer recording media> (Heat-resistant slip layer) A heat-resistant lubricating layer coating liquid was prepared by mixing the materials according to the following formulation. This liquid was then coated onto a 4.5 μm PET film used as a substrate, to a dry thickness of 0.20 μm, and dried to form a heat-resistant lubricating layer. (Heat-resistant lubricating coating liquid) Silicone-modified urethane resin (20% solids content) 12.50 parts Isocyanate (50% solids) 3.00 parts MEK 72.00 copies Toluene 12.50 parts

[0051] (Security layer) A security layer coating liquid 1 was prepared by mixing the materials according to the following formulation. A security layer was formed by coating the substrate surface opposite to the surface coated with the heat-resistant slippery layer using a gravure roll 1 that had a die-cut pattern formed so that the area ratio of the colored portion was 65%, and then drying it to a thickness of 0.50 μm after drying. (Security layer coating liquid 1) Urethane-modified copolymer polyester resin (30% solids content) 8.23 ​​parts Silicone-modified urethane resin (30% solids content) 6.67 parts Isocyanate (75% solids) 2.13 parts Carbon black (100% solids) 12.00 parts Pigment dispersant (100% solids) 1.92 parts MEK 55.25 parts Toluene 13.80 units

[0052] (Exfoliation layer) A release layer ink 1 was prepared by mixing the materials according to the following formulation, and a release layer was formed on the security layer by hot-melt coating to a thickness of 1.1 μm. (Release layer ink 1) Polyethylene wax (melting point 99°C, solids content 100%) 90.00 parts Ethylene-vinyl acetate copolymer resin 10.00 parts (Vinyl acetate content 19%, solids content 100%)

[0053] (Colored ink layer) A colored ink layer coating liquid 1 was prepared by kneading the materials according to the following formulation, and this was coated onto the release layer to a thickness of 1.3 μm after drying. The liquid was then dried to form a colored ink layer, thereby obtaining a thermal transfer recording medium having the following configuration: heat-resistant slippery layer / PET film / security layer / release layer / colored ink layer. (Colored ink layer coating solution 1) Carnauba wax (100% solids) 12.40 parts Carbon black (100% solids) 5.80 parts Pigment dispersant (100% solids) 1.80 parts IPA 80.00 copies

[0054] (Example 2) The thermal transfer recording medium of Example 2 was obtained in the same manner as in Example 1, except that the security layer was fabricated using a gravure roll 2 in which a die-cut pattern was formed so that the area ratio of the colored portion was 50%.

[0055] (Example 3) The thermal transfer recording medium of Example 3 was obtained in the same manner as in Example 1, except that the security layer was fabricated using a gravure roll 3 in which a die-cut pattern was formed so that the area ratio of the colored portion was 80%.

[0056] (Example 4) A thermal transfer recording medium of Example 4 was obtained in the same manner as in Example 1, except that the security layer coating liquid was changed to security layer coating liquid 2 prepared by kneading materials according to the following formulation, the release layer ink was changed to release layer ink 2 prepared by kneading materials according to the following formulation, and the colored ink layer coating liquid was changed to colored ink layer coating liquid 2 prepared by kneading materials according to the following formulation. (Security layer coating liquid 2) Urethane-modified copolymer polyester resin (30% solids content) 18.58 parts Silicone-modified urethane resin (30% solids content) 6.67 parts Isocyanate (75% solids) 3.37 parts Phthalocyanine blue (100% solids) 9.00 parts Pigment dispersant (100% solids) 0.90 parts MEK 49.18 parts Toluene 12.30 parts (Release layer ink 2) Polyethylene wax (melting point 99°C, solids content 100%) 70.00 parts Ethylene-vinyl acetate copolymer resin 30.00 parts (Vinyl acetate content 19%, solids content 100%) (Colored ink layer coating liquid 2) Polyester resin (Mn 15000, Tg 67℃, solids content 100%) 2.00 parts Ketone-aldehyde condensation resin (100% solids) 11.60 parts Polyethylene oxide wax (10% solids content) 20.00 parts Phthalocyanine blue (100% solids) 4.00 parts Pigment dispersant (100% solids) 0.40 parts Toluene 46.00 units MEK 16.00 copies

[0057] (Example 5) A thermal transfer recording medium of Example 5 was obtained in the same manner as in Example 1, except that the security layer coating liquid was changed to a security layer coating liquid 3 prepared by kneading the materials according to the following formulation, the release layer ink was changed to a release layer ink 3 prepared by kneading the materials according to the following formulation, and the colored ink layer coating liquid was changed to a colored ink layer coating liquid 3 prepared by kneading the materials according to the following formulation. (Security layer coating liquid 3) Urethane-modified copolymer polyester resin (30% solids content) 16.33 parts Silicone-modified urethane resin (30% solids content) 6.67 parts Isocyanate (75% solids) 3.07 parts Quinacridone Red (100% solids) 9.00 parts Pigment dispersant (100% solids) 1.80 parts MEK 50.50 copies Toluene 12.63 parts (Release layer ink 3) Polyethylene wax (melting point 99°C, solids content 100%) 98.00 parts Ethylene-vinyl acetate copolymer resin 2.00 parts (Vinyl acetate content 19%, solids content 100%) (Colored ink layer coating liquid 3) Polyester resin (Mn 15000, Tg 67℃, solids content 100%) 2.00 parts Ketone-aldehyde condensation resin (100% solids) 11.20 parts Polyethylene oxide wax (10% solids content) 20.00 parts Quinacridone Red (100% solids) 4.00 parts Pigment dispersant (100% solids) 0.80 parts Toluene 46.00 units MEK 16.00 copies

[0058] (Example 6) A thermal transfer recording medium of Example 6 was obtained in the same manner as in Example 1, except that the release layer ink was changed to release layer ink 4, which was prepared by kneading the materials of the following formulation. (Release layer ink 4) Polyethylene wax (melting point 118°C, solids content 100%) 90.00 parts Ethylene-vinyl acetate copolymer resin 10.00 parts (Vinyl acetate content 14%, solids content 100%)

[0059] (Example 7) The thermal transfer recording medium of Example 7 was obtained in the same manner as in Example 1, except that the release layer ink was changed to release layer ink 5, which was prepared by kneading the materials of the following formulation. (Release layer ink 5) Polyethylene wax (melting point 81°C, solids content 100%) 90.00 parts Ethylene-vinyl acetate copolymer resin 10.00 parts (Vinyl acetate content 28%, solids content 100%)

[0060] (Example 8) The thermal transfer recording medium of Example 8 was obtained in the same manner as in Example 1, except that the security layer coating liquid 4, which was prepared by kneading the materials according to the following formulation, had the thickness of the security layer changed to 0.3 μm. (Security layer coating liquid 4) Urethane-modified copolymer polyester resin (30% solids content) 6.67 parts Silicone-modified urethane resin (30% solids content) 10.27 parts Isocyanate (75% solids) 1.33 parts Carbon black (100% solids) 12.00 parts Pigment dispersant (100% solids) 1.92 parts MEK 54.25 parts Toluene 13.56 parts

[0061] (Example 9) The thermal transfer recording medium of Example 9 was obtained in the same manner as in Example 1, except that the security layer coating liquid 5, which was prepared by kneading the materials according to the following formulation, had the thickness of the security layer changed to 0.7 μm. (Security layer coating liquid 5) Urethane-modified copolymer polyester resin (30% solids content) 12.23 parts Silicone-modified urethane resin (30% solids content) 2.67 parts Isocyanate (75% solids) 2.13 parts Carbon black (100% solids) 12.00 parts Pigment dispersant (100% solids) 1.92 parts MEK 55.25 parts Toluene 13.80 units

[0062] (Comparative Example 1) A thermal transfer recording medium for Comparative Example 1 was obtained in the same manner as in Example 1, except that the security layer was fabricated using a gravure roll 4 in which the area ratio of the colored portion was 50% and the pattern consisted of colored characters, symbols, and images.

[0063] (Comparative Example 2) A thermal transfer recording medium for Comparative Example 2 was obtained in the same manner as in Example 1, except that the security layer was fabricated using a gravure roll 5 in which a die-cut pattern was formed so that the area ratio of the colored portion was 35%.

[0064] (Comparative Example 3) A thermal transfer recording medium of Comparative Example 3 was obtained in the same manner as in Example 1, except that the security layer was prepared using a gravure roll 6 for full-surface coating, which had no characters, symbols, or images and whose colored area ratio was 100%.

[0065] (Comparative Example 4) A thermal transfer recording medium of Comparative Example 4 was obtained in the same manner as in Example 1, except that a colored ink layer was directly formed on the security layer without forming a release layer.

[0066] (evaluation) <Print evaluation conditions> Using the thermal transfer recording media prepared in each example and comparative example, predetermined patterns consisting of characters, symbols, barcodes, etc., were printed under the following conditions to produce used thermal transfer recording media and printed materials. (Printing conditions) Thermal transfer printer: Printer for Takazono Corporation's drug packaging system (Crestage-Lite3) Print speed: 180 Printing energy: 20 Transfer target: Polyethylene laminated cellophane (printing should be done on the cellophane side)

[0067] (1) Difficulty in deciphering the transcription traces The used thermal transfer recording medium was unrolled, the transfer traces were visually inspected, and an evaluation was performed according to the evaluation criteria below. The evaluation results are shown in Table 1. (○ or higher indicates the practical application area.) (Evaluation Criteria) ◎: The copied pattern is illegible. ○: Some parts of the copied pattern are legible, but the content of the pattern cannot be deciphered. ×: The content of the copied pattern is legible.

[0068] (2) Transferability of the release layer and / or colored ink layer The transfer marks on the used thermal transfer recording medium and the printed materials produced using the thermal transfer recording medium were visually inspected and evaluated according to the evaluation criteria below. The evaluation results are shown in Table 1. (○ or higher indicates the practical application area.) (Evaluation Criteria) ◎: The release layer peels cleanly from the security layer and substrate, resulting in good print quality. ○: There is a very slight printing defect, or a small portion of the security layer ink is adhering to the release layer. ×: Print smudging and transfer defects such as security layer ink being absorbed onto the release layer are observed.

[0069] (3) Print quality The printed materials produced using the aforementioned thermal transfer recording medium were visually inspected, and their crispness, such as trailing or surface peeling, was evaluated according to the evaluation criteria below. The evaluation results are shown in Table 1. (○ or higher indicates a practical application.) (Evaluation Criteria) ◎: Excellent sharpness. ○: The sharpness is slightly poor, but there are no problems with reading text, etc. ×: The writing is not sharp enough, and some parts of the text are illegible.

[0070] [Table 1] [Explanation of Symbols]

[0071] 10: Thermal transfer recording media 11: Base material 12: Security Layer 13: Exfoliation layer 14: Colored ink layer 15: Heat-resistant slippery layer

Claims

1. A thermal transfer recording medium comprising a substrate and a security layer, a release layer, and a colored ink layer laminated in this order on one surface of the substrate, characterized in that the security layer is composed of a die-cut pattern having the same hue as the colored ink layer and the area ratio of the colored portion being 50 to 80%.

2. The thermal transfer recording medium according to claim 1, characterized in that the release layer contains 70 to 98% by weight of polyethylene wax having a melting point of 80°C to 120°C in the solid content of the release layer, and 2 to 30% by weight of ethylene-vinyl acetate copolymer resin having a vinyl acetate content of 14% to 28% in the solid content of the release layer.

3. The thermal transfer recording medium according to claim 1 or 2, characterized in that the thickness of the security layer is 0.3 to 0.7 μm.

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