JP2015098171A - Thermal transfer sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal transfer sheet excellent in various durability of a thermally transferred layer even in a severe service condition, and having excellent film cutting when transferring a transferred layer to a target transfer body.SOLUTION: A thermal transfer sheet 1 provided with a thermally-transferable transfer layer 6 on a substrate 2 has a constitution in which the thickness of an outer marginal part 8 of the transfer layer 6 is reduced stepwise on a part reaching the end y from the center part side x, and the outer marginal part 8 in which the thickness of the transfer layer 6 is reduced stepwise exists in a position of 5-10 mm from the end x of the transfer layer 6.

Description

  The present invention relates to a thermal transfer sheet, and is particularly excellent in various durability of a thermally transferred layer even under severe use conditions, and thermal transfer with good film breakage when transferring the transferred layer to a transfer target. It relates to the sheet.

  Currently, a thermal transfer recording method is widely used as a simple printing method. Since the thermal transfer recording method can easily form various images, printed matter that requires a relatively small number of copies, such as creation of ID cards such as identification cards, business photographs, personal computer printers, video printers, etc. Is used. The thermal transfer recording uses a thermal transfer sheet in which a color material layer containing a sublimable dye is provided on a substrate, and the dye in the color material layer is sublimated and diffused by heat and the dye is transferred to the image receiving sheet. Recording and heat-sensitive fusion transfer recording in which a color material layer is melted and softened by heating and the color material layer itself is transferred to an image receiving sheet using a thermal transfer sheet provided with a color material layer to be thermally fused and transferred onto a substrate. Can be mentioned.

  When using a thermal transfer sheet as described above to produce an identification card, etc., for the purpose of protecting the image, on the image obtained by thermal transfer of the heat-meltable colorant layer or thermal sublimation dye, A method is known in which a protective layer transfer sheet having a resin layer is laminated, the thermal transfer resin layer is transferred using a thermal head, a heating roll, or the like, and a protective layer is formed on the image.

    As a protective layer transfer sheet, for example, as shown in Patent Documents 1 and 2, a release layer is formed on a substrate, an adhesive layer is provided on the release layer, and a release layer is formed on the thermal transfer image-receiving sheet. A configuration in which an adhesive layer is provided for stable transfer is known. Using such a method for forming a transfer of the protective layer, the durability such as chemical resistance and light resistance can be improved to some extent, but when used under severe conditions in practice, the thermal transfer image Durability is not yet perfect.

In contrast, attempts have been made to increase the thickness of the protective layer to be transferred or to increase the molecular weight of the resin constituting the protective layer, but when the protective layer is transferred, it is not a portion to be transferred. Thus, there is a problem that transfer failure such as tailing occurs due to transfer of the protective layer.
In addition to the transfer of the protective layer, if it is a layer that is melted and transferred by heating, it is possible to satisfy both the durability of the transferred portion and the transferability even in the transfer of the heat-meltable color material layer, It is a difficult problem.

JP-A-4-35988 Japanese Patent Laid-Open No. 4-142988

    Therefore, the present invention solves the above-mentioned problems and is excellent in various durability of the thermally transferred layer even under severe use conditions, and when transferring the transferred layer to the transfer target, An object is to provide a thermal transfer sheet having good cutting properties.

In view of the above situation, earnest research and development has been proceeded, and claim 1 of the present invention is directed to a thermal transfer sheet in which a transfer layer capable of thermal transfer is provided on a substrate, and the thickness of the outer edge portion of the transfer layer is the central portion. The outer edge where the thickness of the transfer layer decreases stepwise from the side to the end and the thickness of the transfer layer decreases stepwise exists at a position of 5 to 10 mm from the end of the transfer layer. It is characterized by that. Thereby, the said subject was able to be solved.

According to a second aspect of the present invention, the transfer layer is composed of a release layer and an adhesive layer from the substrate side, and the molecular weight of the resin constituting the adhesive layer is 10,000 to 40,000 on a number average basis. It is characterized by being. Thereby, the durability of the layer transferred by thermal transfer is further improved, and no problem occurs even under severe use conditions.

  In the present invention, the thermal transfer sheet having the above configuration has a noticeable effect even under severe use conditions, for example, even if the surface of the printed material is strongly rubbed with a nail or a plastic eraser is placed on the surface of the printed material for a long time. Various durability, which does not occur, is excellent, and the transfer layer transferred from the thermal transfer sheet to the transfer target has good film breakage.

It is the schematic which shows one embodiment of the thermal transfer sheet of this invention. It is the schematic which shows other embodiment of the thermal transfer sheet of this invention. It is the schematic which shows other embodiment of the thermal transfer sheet of this invention. It is the schematic which shows other embodiment of the thermal transfer sheet of this invention. It is the schematic which shows other embodiment of the thermal transfer sheet of this invention. It is the schematic which shows the example of multiple imposition of the printing plate for forming a transfer layer.

Next, an embodiment of the invention will be described in detail.
FIG. 1 is a schematic view showing one embodiment of the thermal transfer sheet 1 of the present invention, in which a heat-resistant slipping layer 5 is provided on one surface of a substrate 2, and a release layer 3 is provided on the other surface of the substrate 2. 1 is a thermal transfer sheet 1 having an adhesive layer 4. In this case, the combined layer of the release layer 3 and the adhesive layer 4 is transferred to the transfer medium by heating to constitute the transfer layer 6. In the transfer layer 6 shown in FIG. 1, the release layer 3 has a uniform thickness, and the thickness of both ends (outer edge portion 8) of the adhesive layer 4 is a portion extending from the central portion side x to the end portion y. Is decreasing. However, at the end y, the adhesive layer 4 has a smaller thickness than the central part 11, but an adhesive layer exists. As a result, the thickness of the outer edge 8 of the transfer layer 6 is decreased stepwise. The transfer layer 6 can function as a protective layer, function as a receiving layer that receives a sublimable dye, or function as a heat-meltable color material layer. Further, although the transfer layer is shown as two layers in FIG. 1, the transfer layer is not limited to this, and the transfer layer can also be constituted by one layer having both functions of a release layer and an adhesive layer. Further, an intermediate layer may be formed between the release layer and the adhesive layer. In any case, the thickness of the outer edge portion of the transfer layer only needs to be decreased stepwise.

  FIG. 2 is a schematic view showing one embodiment of the thermal transfer sheet 1 of the present invention, in which a heat-resistant slipping layer 5 is provided on one surface of the substrate 2, and a release layer 3 is provided on the other surface of the substrate 2. 1 is a thermal transfer sheet 1 having an adhesive layer 4. In this case, the combined layer of the release layer 3 and the adhesive layer 4 is transferred to the transfer medium by heating to constitute the transfer layer 6. When the transfer layer is heated, a release layer can be provided between the substrate and the release layer in order to improve transferability from the substrate. This release layer can be composed of a conventionally known release resin such as waxes and silicone-modified resins. In the transfer layer 6 shown in FIG. 2, the release layer 3 has a uniform thickness, and the thickness of both ends (outer edge portion 8) of the adhesive layer 4 is a portion extending from the center side x to the end portion y. Is decreasing. In this case, the adhesive layer 4 does not exist at the end y, but the adhesive layer continuously increases from the end y toward the central side x, and a certain thickness is secured at the central part. As a result, the thickness of the outer edge 8 of the transfer layer 6 is decreased stepwise.

  FIG. 3 is a schematic view showing another embodiment of the thermal transfer sheet 1 of the present invention, in which a heat-resistant slipping layer 5 is provided on one surface of the substrate 2, and heat is applied to the other surface of the substrate 2. This is a thermal transfer sheet 1 having a configuration in which a meltable color material layer 7 is provided. In this case, the heat-meltable color material layer 7 is transferred to the transfer medium by heating to constitute the transfer layer 6. The transfer layer 6 shown in FIG. 3 is only the heat-meltable color material layer 7, and the thickness of the outer edge portion 8 of the heat-meltable color material layer 7 is a portion from the central portion side x to the end portion y. , Is decreasing step by step. In FIG. 3, one layer of the heat-meltable color material layer is shown as the transfer layer. However, the present invention is not limited to this, and a release layer may be provided between the substrate and the heat-meltable color material layer, or heat fusion may be performed. An adhesive layer can be provided on the surface of the color material layer. In any case, the thickness of the outer edge portion of the transfer layer only needs to be decreased stepwise.

  1 to 3, the thickness of the outer edge 8 of the transfer layer 6 decreases linearly in proportion to the distance. However, the present invention is not limited to this, and x and y of the outer edge portion 8 may not be connected by a straight line but may be connected by a curved line. The outer edge 8 of the transfer layer 6 shown in FIGS. 1 to 3 is a portion between x and y, and x exists at a position 5 to 10 mm apart from the end y of the transfer layer. Also, as shown in FIG. 4, a structure in which a heat-resistant slipping layer 5 is provided on one surface of the substrate 2, and a heat-meltable color material layer 7 and an adhesive layer 4 are sequentially stacked on the other surface of the substrate 2. In the thermal transfer sheet 1, the coated portion 9 of the heat-meltable color material layer 7 is wide, and the coated portion 10 of the adhesive layer 4 is made longer than the coated portion 9. It can also be formed shorter (with a smaller area). As a result, in the transfer layer 6 having a two-layer structure in which the heat-meltable color material layer 7 and the adhesive layer 4 are sequentially laminated, the thickness of the outer edge portion 8 of the transfer layer 6 is gradually reduced. It will be.

  1 to 4 show a mode in which the thickness of the outer edge portion of the transfer layer is reduced stepwise. In the case of FIG. 4, the thickness is reduced stepwise, but FIG. It is preferable that the thickness as indicated by 3 is continuously reduced because the foil breakage when the transfer layer is transferred to the transfer medium by heating from the thermal transfer sheet is good. In order to reduce the thickness of the outer edge portion of the transfer layer 6 as shown in FIGS. 1 to 3 in a stepwise manner, for example, a gravure printing plate used for forming the transfer layer corresponds to the outer edge portion. The depth of the plate at the position is continuously shallower toward the edge of the transfer layer so as to be inclined, or the density of the halftone dots of the gravure printing plate at the outer edge and the center is changed, As shown in 1 to 3, the thickness of the transfer layer 6 printed on the substrate is gradually reduced in the portion from x on the center side to the end y of the outer edge portion. Can do.

  FIG. 5 is a schematic view showing another embodiment of the thermal transfer sheet 1 of the present invention, in which a heat-resistant slipping layer 5 is provided on one surface of the substrate 2, and the heat melting property is provided on the other surface of the substrate 2. This is a thermal transfer sheet 1 having a color material layer 7. In this case, the heat-meltable color material layer 7 is transferred to the transfer medium by heating to constitute the transfer layer 6. The transfer layer 6 shown in FIG. 5 is only the heat-meltable color material layer 7, and the transfer layer 6 is formed so that the central portion 11 and the outer edge portion 8 are in contact with both ends. The central portion 11 is formed with a constant thickness, and the outer edge portion 8 is formed with a constant thickness under the condition that the thickness is smaller than that of the central portion. In order to form the transfer layer, for example, the density of the halftone dots of the gravure printing plate between the outer edge portion and the central portion is changed, or the depth of the plate at the position corresponding to the outer edge portion corresponds to the central portion. The thickness of the outer edge portion of the transfer layer can be reduced stepwise from the central portion side to the end portion by forming it shallower than the position plate depth.

  In FIGS. 1 to 5, when the thickness of the outer edge 8 of the transfer layer 6 is gradually reduced in the portion from the central side to the end, it is manufactured in the unit pattern shown in the figure, The central portion 11 and the outer edge portion 8 can be formed on four sides by using a multi-faced plate represented by a gravure printing plate as shown in FIG. Thereby, production efficiency can be improved. The figure shows 4 × 4 16-sided imposition, but the number of impositions of multi-sidedness is not limited to this, and is determined from the outer peripheral size and width size of the gravure printing plate and the size of the transfer layer 12 of one unit. be able to. In the illustrated example, the outer edge portions are provided on the four sides of the transfer layer. However, the present invention is not limited thereto, and the outer edge portion is provided only on two sides orthogonal to the printing direction, or one side of the print bottom portion orthogonal to the printing direction. Only the outer edge is provided. This is because the coating liquid tends to accumulate in the print bottom when printing, and as a result, transfer defects such as tailing tend to occur during transfer.

Below, each layer which comprises the thermal transfer sheet of this invention is demonstrated in detail.
(Base material)
As the substrate 2 used in the thermal transfer sheet of the present invention, the same substrate as that used in the conventional thermal transfer sheet can be used as it is, and the surface of the substrate is subjected to an easy adhesion treatment. A thing and others can also be used and there is no restriction | limiting in particular. However, when using a base material that has been subjected to easy adhesion treatment, it is desirable to provide a release layer between the base material and the release layer.

  Specific examples of preferable substrates include, for example, polyesters such as polyethylene terephthalate and polyethylene naphthalate, polycarbonate, polyamide, polyimide, cellulose acetate, polyvinylidene chloride, polyvinyl chloride, polystyrene, fluororesin, polypropylene, polyethylene, and ionomer. Such as plastic films, cellophane, etc., and composite films in which two or more of these are laminated can also be used. Although the thickness of these base materials is suitably changed according to the material so that the strength and heat resistance are appropriate, it is usually preferably about 2.5 to 10 μm.

(Release layer)
On the base material, a release layer that makes the transfer property of the transfer layer formed thereon suitable can be provided. In particular, it is desirable to form a release layer between the substrate and the release layer when the substrate is subjected to an easy adhesion treatment. As the resin for forming the release layer, any conventionally known resin having excellent release properties can be used. For example, waxes, silicone wax, silicone resin, silicone-modified resin, fluorine resin, fluorine-modified resin, polyvinyl alcohol , Acrylic resins, acrylic-styrene resins, heat-crosslinkable epoxy-amino resins, and heat-crosslinkable alkyd-amino resins. These release resins can be used alone or as a mixture.

In the release layer, various fillers can be added to the release resin material as described above. Examples of the filler used include known pigments such as silica, alumina, clay, and talc, and plastic pigments made of thermosetting resins, thermoplastic resins, waxes, and the like. To form a release layer, add a resin as described above and, if necessary, a filler, a crosslinking agent or a catalyst, and prepare a coating solution dissolved or dispersed in a general-purpose solvent such as methyl ethyl ketone, toluene, or isopropyl alcohol. Then, the coating solution is applied and dried on a substrate by a conventionally known method such as gravure coating or gravure reverse coating so as to have a thickness (dry basis) of about 0.5 to 5 g / m ² .

(Peeling layer)
In the thermal transfer sheet of the present invention, an adhesive layer is provided on the substrate via the release layer 3. By having this release layer, the adhesive layer can be reliably and easily transferred from the thermal transfer sheet to the transfer medium. Release layer is, for example, microcrystalline wax, carnauba wax, paraffin wax, Fischer-Tropsch wax, various low molecular weight polyethylene, wood wax, beeswax, whale wax, ibota wax, wool wax, shellac wax, candelilla wax, petrolactam, part Thermoplastics such as modified wax, fatty acid ester, fatty acid amide, etc., silicone wax, silicone resin, fluorine resin, acrylic resin, polyester resin, polyurethane resin, cellulose resin, vinyl chloride-vinyl acetate copolymer, nitrified cotton, etc. It can be formed using a resin.

The release layer can be formed from a binder resin and a releasable material. The binder resin is a thermoplastic resin such as polymethyl methacrylate, polyethyl methacrylate, polybutyl acrylate and other acrylic resins, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, polyvinyl alcohol, polyvinyl butyral, etc. Vinyl resins, cellulose derivatives such as ethyl cellulose, nitrocellulose, and cellulose acetate, unsaturated polyester resins that are thermosetting resins, polyester resins, polyurethane resins, aminoalkyd resins, and the like can be used. In a preferred embodiment of the present invention, the release layer has a molecular weight within the range of 70,000 to 90,000 in terms of number average. When the number average molecular weight is less than 70,000, the plasticizer resistance in the transfer layer is lowered. On the other hand, when the number average molecular weight is larger than 90,000, the viscosity of the release layer coating solution increases and the coating suitability decreases. As the releasable material, waxes, silicone waxes, silicone resins, melamine resins, fluorine resins, fine powders of talc and silica, lubricants such as surfactants and metal soaps, and the like can be used. The release layer was prepared by dissolving or dispersing the above-mentioned necessary materials with an appropriate solvent to prepare a release layer coating solution, and using a gravure printing method, screen printing method or gravure plate on the base sheet. It can be formed by applying and drying by means such as reverse coating. The thickness after the drying is usually 0.1 to 10 g / m ² .

(Adhesive layer)
In the present invention, the thermal transfer sheet can have a configuration in which a release layer and an adhesive layer are sequentially laminated on a substrate. This adhesive layer 4 is provided in order to improve the transfer of the transfer layer (a combination of the release layer and the adhesive layer) in the thermal transfer sheet and the adhesion of the transferred transfer layer to the printed material. As the adhesive layer, any conventionally known heat-sensitive adhesive can be used, but it is more preferably formed from a thermoplastic resin having a glass transition temperature of 50 to 100 ° C., for example, acrylic resin, vinyl chloride-vinyl acetate copolymer A resin having a number average molecular weight of 10,000 to 40,000 is preferably used from a resin having good adhesiveness when heated, such as a coalesced resin, an epoxy resin, a polyester resin, a polycarbonate resin, a butyral resin, a polyamide resin, and a vinyl chloride resin. It is done. When the number average molecular weight is less than 10,000, durability such as plasticizer resistance and scratch resistance in the transfer layer is lowered. Further, when the number average molecular weight is larger than 40,000, the adhesiveness is lowered.

  When the transfer layer is used as a protective layer, by adding an ultraviolet absorber to the adhesive layer, the light resistance, weather resistance, etc. of the transferred image that is transferred and covered by the protective layer after being transferred are further improved. Can do. Examples of the ultraviolet absorber include salicylate-based, benzophenone-based, benzotriazole-based, triazine-based, substituted acrylonitrile-based, nickel chelate-based, hindered amine-based and the like, which are conventionally known organic ultraviolet absorbers. In addition, for example, polymers having addition polymerizable double bonds such as vinyl groups, acryloyl groups, and methacryloyl groups, or alcoholic hydroxyl groups, amino groups, carboxyl groups, epoxy groups, isocyanate groups, etc., are introduced into these ultraviolet absorbers. The material is a UV-absorbing resin, and the adhesive layer can be constituted from this UV-absorbing resin.

In order to form the adhesive layer, the resin as described above is dissolved or dispersed in a general-purpose solvent such as methyl ethyl ketone, toluene, isopropyl alcohol, and, if necessary, an ultraviolet absorber, an antioxidant, a fluorescent brightening agent. Then, an inorganic or organic filler component, a surfactant, a release agent, etc. are added to prepare a coating solution, and the coating solution has a thickness (dry basis) of 0 by a conventionally known method such as gravure coating or gravure reverse coating. It is formed by coating and drying so as to be ⁵ to 10 g / m ² , more preferably 0.7 to 5.0 g / m ² . If the thickness of the adhesive layer is too small, the adhesion of the transfer layer to the printed material will be reduced. On the other hand, if the thickness of the adhesive layer is too large, the thermal sensitivity during transfer of the transfer layer is lowered.

(Hot-melting color material layer)
The heat-meltable color material layer is composed of a colorant and a binder, and may be added with various additives such as a dispersant and an antistatic agent as necessary. As the colorant, each colorant such as yellow, magenta, cyan, and black can be appropriately selected from conventionally known dyes and pigments.

  The binder used for the heat-meltable color material layer is preferably composed mainly of a resin. Specifically, the resin includes a cellulose resin, a melamine resin, a polyester resin, a polyamide resin, a polyolefin resin, an acrylic resin. Examples thereof include thermoplastic elastomers such as resin, styrene resin, ethylene-vinyl acetate copolymer, and styrene-butadiene rubber. In particular, those having a relatively low softening point, for example, a softening point of 50 to 80 ° C., conventionally used as a heat-sensitive adhesive are preferable. Among the resins used as the binder, cellulose resins, melamine resins, and acrylic resins are preferably used particularly in terms of transferability, scratch resistance, heat resistance, and the like. In addition, if necessary, a wax component can be mixed and used to the extent that heat resistance and the like are not impaired.

  Examples of the wax include microcrystalline wax, carnauba wax, and paraffin wax. In addition, Fischer-Tropsch wax, various low molecular weight polyethylene, wood wax, beeswax, whale wax, ibota wax, wool wax, shellac wax, candelilla wax, petrolactam, polyester wax, partially modified wax, fatty acid ester, fatty acid amide, etc. Wax. Among these, those having a melting point of 50 to 85 ° C. are particularly preferable. When the temperature is 50 ° C. or lower, a problem occurs in storage stability, and when the temperature is 85 ° C. or higher, printing sensitivity is insufficient.

It is preferable to use the ink composition mixed in the ratio of 90-20 mass% of colorants and 80-10 mass% of resin for said heat-meltable color material layer. If the colorant is less than the above range, the coating amount must be increased in order to obtain the density, resulting in insufficient printing sensitivity. On the other hand, when the amount of the colorant is larger than the above range, film formability cannot be obtained, and this causes a reduction in scratching after printing. The heat-meltable colored layer is formed by coating the colorant component and the binder component as described above, and further adding a solvent component such as water or an organic solvent as necessary. The working liquid is dried in a thickness of 0.1 to 5 g / m ² , preferably by a conventionally known method such as hot melt coating, hot lacquer coating, gravure direct coating, gravure reverse coating, knife coating, air coating, roll coating, etc. Provides 0.3 to 1.5 g / m ² . When the thickness of the dried coating film is less than 0.1 g / m ² , a uniform color material layer cannot be obtained due to film formation problems, and when the thickness exceeds 5 g / m ² , printing is transferred. In this case, high energy is required, and there is a problem that printing can be performed only with a special thermal transfer printer.

(Receptive layer)
In the present invention, the transfer layer in the thermal transfer sheet can function as a receiving layer for receiving a transfer-type sublimable dye. The receiving layer that can be peeled off from the substrate will be described below. The receiving layer, which is a transfer layer, is for receiving the sublimable dye transferred from the sublimation thermal transfer sheet and maintaining the formed image. Examples of the resin for forming the receiving layer include polyolefin resins such as polypropylene, polyvinyl chloride, vinyl chloride / vinyl acetate copolymers, halogenated polymers such as polyvinylidene chloride, polyvinyl acetate, and polyacrylic esters. Vinyl polymers, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polystyrene resins, polyamide resins, copolymers of olefins such as ethylene and propylene and other vinyl monomers, celluloses such as ionomers and cellulose diacetate Examples thereof include vinyl resins and polycarbonates, with vinyl resins and polyester resins being particularly preferred. Preferable mold release agents used by mixing with the resin include silicone oil, phosphate ester surfactants, fluorine surfactants, etc., but silicone oil is desirable. As the silicone oil, modified silicone oils such as epoxy modification, alkyl modification, amino modification, carboxyl modification, alcohol modification, fluorine modification, alkylaralkyl polyether modification, epoxy / polyether modification, and polyether modification are desirable.

One or more release agents are used. Moreover, the addition amount of this release agent is preferably 0.5 to 30 parts by mass with respect to 100 parts by mass of the receiving layer forming resin. When the range of the addition amount is not satisfied, problems such as fusion between the sublimation thermal transfer sheet and the receiving layer or a decrease in printing sensitivity may occur. By adding such a releasing agent to the receiving layer, the releasing agent bleeds out on the surface of the receiving layer after transfer to form a releasing layer. The receiving layer was prepared by dissolving a resin as described above with a necessary additive such as a mold release agent in one surface of the base material, or dissolving it in a suitable organic solvent or dispersing it in an organic solvent or water. The dispersion is formed by applying and drying the dispersion by a forming means such as a gravure printing method, a screen printing method, or a reverse roll coating method using a gravure plate. The receiving layer formed as described above may have any thickness, but generally has a thickness of 1 to 10 g / m ² . Such a receiving layer is preferably a continuous coating, but may be formed as a discontinuous coating using a resin emulsion or a resin dispersion.

(Heat resistant slipping layer)
In the thermal transfer sheet, it is preferable to provide a heat-resistant slipping layer 5 on the back surface of the substrate, that is, the surface opposite to the surface on which the transfer layer is provided, in order to prevent adverse effects such as sticking and wrinkles due to the heat of the thermal head. The thickness of the heat resistant slipping layer is about 0.1 to ² g / m ² in terms of solid content.

  The protective layer can be transferred onto the image of the printed matter formed by transferring the sublimation dye or the heat-meltable ink using the protective layer transfer sheet which is the thermal transfer sheet of the present invention. The thermal transfer sheet used for the image formation consists of a dye layer containing a sublimable dye on the substrate, a colored pigment or dye colorant, a wax, or a resin binder. An ink layer is formed. In the present invention, the above-mentioned protective layer transfer sheet, and a thermal transfer sheet having a dye layer and a heat-meltable ink layer are separately prepared and used, or on the same substrate, yellow, magenta, cyan, black, etc. Using the same thermal head with a dye layer and / or heat-meltable ink layer having each hue of the above and a protective layer provided in a surface sequential manner, the thermal transfer image and the protective layer are not replaced with the thermal transfer sheet. In addition, it can be used efficiently by continuous thermal transfer.

Next, the present invention will be described more specifically with reference to examples. In the text, “part” or “%” is based on mass unless otherwise specified.
Example 1
As a base material, a heat-resistant slipping layer having a solid content of 1 g / m ² is provided on one surface of a 4.5 μm thick polyethylene terephthalate film (manufactured by Toray Industries, Inc., Lumirror). On the surface, a release layer coating solution having the following composition was used to apply a gravure coat to a thickness of 1.2 g / m ² at the time of drying, followed by drying to form a release layer. . Furthermore, on the release layer, an adhesive layer coating solution having the following composition is used, and it is applied by gravure coating so as to have a thickness of 1.5 g / m ² at the time of drying, and then dried and bonded. The layer was formed, and the thermal transfer sheet which is a protective layer transfer sheet of Example 1 was produced. However, using a gravure printing plate with a constant plate depth such that the size of the release layer is a rectangle of 54 mm × 86 mm (printing direction is 86 mm long), the size of the adhesive layer is the same as that of the release layer. The depth of the plate at the position corresponding to the outer edge is set to x on the center side of the transfer layer so that the outer edge is as shown in FIG. Then, a gravure printing plate having a pattern that was continuously shallow and inclined to a portion reaching the end y of the outer edge portion was used. The thickness of 1.5 g / m ² when the adhesive layer is dried is the thickness at the center, and the thickness of the adhesive layer at the end y of the transfer layer is 0.5 g / m when dried. The condition is ² or less.

(Release layer coating solution)
Acrylic resin (Thermolac LP-45M-30, number average molecular weight 80,000, Tg 105 ° C., manufactured by Soken Chemical Co., Ltd.) 19 parts Polyethylene wax (Slip Agent B, Showa Ink Industries, Ltd.) 0.76 parts Fluorescent whitening agent (CitexOB Double Bond Chemical Ind., Co., Ltd.) 0.14 parts Methyl ethyl ketone 40 parts Toluene 40 parts

(Coating liquid for adhesive layer 1)
Polyester resin (Byron 270, number average molecular weight 23000, Tg 67 ° C., manufactured by Toyobo Co., Ltd.) 17 parts Acrylic copolymer reactively bound with a reactive ultraviolet absorber 6 parts (UVA635L, manufactured by BASF Japan, number average molecular weight 30000) )
Silica manufactured by Fuji Silysia (Silysia P310 1.2 μm) 1 part Methyl ethyl ketone 38 parts Toluene 38 parts

(Example 2)
A thermal transfer sheet of Example 2 was produced in the same manner as in Example 1 except that the adhesive layer coating liquid 1 was changed to one having the following composition under the production conditions of the thermal transfer sheet produced in Example 1. However, the thickness of the adhesive layer in the central portion is 1.5 g / m ² when dried, and the thickness of the adhesive layer at the end y of the transfer layer is 0.8 g / m ² or less when dried. It was.

(Adhesive layer coating solution 2)
Polyester resin (Byron 200, number average molecular weight 17000, Tg 67 ° C., manufactured by Toyobo Co., Ltd.) 17 parts Acrylic copolymer reactively bound with a reactive ultraviolet absorber 6 parts (UVA635L, manufactured by BASF Japan, number average molecular weight 30000) )
Silica manufactured by Fuji Silysia (Silysia P310 1.2 μm) 1 part Methyl ethyl ketone 38 parts Toluene 38 parts

(Example 3)
A thermal transfer sheet of Example 3 was produced in the same manner as in Example 1 except that the adhesive layer coating solution 1 was changed to the following composition under the production conditions of the thermal transfer sheet produced in Example 1. However, the thickness of the adhesive layer in the central portion is 1.5 g / m ² when dried, and the thickness of the adhesive layer at the end y of the transfer layer is 0.5 g / m ² or less when dried. It was.

(Coating liquid 3 for adhesive layer)
Vinyl chloride resin-vinyl acetate copolymer resin (SOLBIN CL, number average molecular weight 25000, Tg 70 ° C., manufactured by Nissin Chemical Industry Co., Ltd.) 17 parts Acrylic copolymer 6 parts reactive UV absorbent (UVA635L) (Manufactured by BASF Japan, number average molecular weight 30000)
Silica manufactured by Fuji Silysia (Silysia P310 1.2 μm) 1 part Methyl ethyl ketone 38 parts Toluene 38 parts

(Comparative Example 1)
Under the production conditions of the thermal transfer sheet produced in Example 1, the adhesive layer coating solution 1 was changed to one having the following composition. The thermal transfer sheet was prepared by applying a gravure printing plate having a constant plate depth to a thickness of 1.5 g / m ² at the time of drying and drying to form an adhesive layer. Coating was carried out using a gravure printing plate having a constant plate depth so that the size of the adhesive layer was a rectangle of 54 mm × 86 mm (printing direction was 86 mm long). As a result, the coating amount did not have an inclination as in the example, but was constant at the center and the end of the adhesive layer.

(Adhesive layer coating solution 4)
Polyester resin (Byron 220, number average molecular weight 3000, Tg 53 ° C., manufactured by Toyobo Co., Ltd.) 17 parts Acrylic copolymer reactively bound with a reactive ultraviolet absorber 6 parts (UVA635L, manufactured by BASF Japan, number average molecular weight 30000) )
Silica manufactured by Fuji Silysia (Silysia P310 1.2 μm) 1 part Methyl ethyl ketone 38 parts Toluene 38 parts

(Comparative Example 2)
A pattern with a constant plate depth such that the adhesive layer coating liquid 1 is a rectangle of 54 mm × 86 mm in size (printing direction is 86 mm long) under the production conditions of the thermal transfer sheet produced in Example 1. Using the gravure printing plate, the coating was applied to a thickness of 1.5 g / m ² at the time of drying and dried to form an adhesive layer. As a result, the coating amount did not have an inclination as in the example, but was constant at the center and the end of the adhesive layer.

(Comparative Example 3)
In the production conditions of the thermal transfer sheet produced in Example 1, the size of the adhesive layer coating solution 2 becomes a rectangle of 54 mm × 86 mm (printing direction is 86 mm long), and the pattern has a constant plate depth. Using a gravure printing plate, it was applied to a thickness of 1.5 g / m ² when dried, and dried to form an adhesive layer. As a result, the coating amount did not have an inclination as in the example, but was constant at the center and the end of the adhesive layer.

(Comparative Example 4)
In the production conditions of the thermal transfer sheet produced in Example 1, the size of the adhesive layer coating solution 3 is a rectangle of 54 mm × 86 mm (printing direction is 86 mm long), and the pattern has a constant plate depth. Using a gravure printing plate, it was applied to a thickness of 1.5 g / m ² when dried, and dried to form an adhesive layer. As a result, the coating amount did not have an inclination as in the example, but was constant at the center and the end of the adhesive layer.

(Comparative Example 5)
A pattern with a constant plate depth such that the adhesive layer coating liquid 1 is a rectangle of 54 mm × 86 mm in size (printing direction is 86 mm long) under the production conditions of the thermal transfer sheet produced in Example 1. Using the gravure printing plate, the coating was applied to a thickness of 0.5 g / m ² at the time of drying and dried to form an adhesive layer. As a result, the coating amount did not have an inclination as in the example, but was constant at the center and the end of the adhesive layer.

  Using the thermal transfer sheets obtained in the above examples and comparative examples, the scuff resistance, plasticizer resistance and foil breakage were evaluated by the following methods.

(Abrasion resistance)
Using a transfer material consisting of a card substrate having the following composition, a dye layer of a DATACARD card printer SP55PLUS standard is provided on the transfer material using a thermal printer for cards (SP55PLUS card printer, manufactured by DATACARD). Using the thermal transfer sheet, each dye was transferred to a transfer medium in accordance with the yellow, magenta, and cyan image information obtained by color separation of the face photograph, thereby forming a full-color photographic image.

<Material composition of card base>
Polyvinyl chloride compound (degree of polymerization 800) 100 parts (contains about 10% of additives such as stabilizers)
White pigment (titanium oxide) 10 parts Plasticizer (DOP) 0.5 parts

  Next, using the thermal transfer sheet obtained in the above examples and comparative examples, the protective layer is transferred in each example and each comparative example using the above thermal printer so as to cover the above photographic image. A solid image was formed on the entire image receiving surface of the body. These prints were subjected to an abrasion test of 500 revolutions on the protective layer with a grinding wheel CS-10F under a load of 500 g using a scratch resistance tester (rotary abrasion tester manufactured by Toyo Seiki Co., Ltd.). The durability was evaluated according to the following criteria.

A: The image is not affected at all.
○: The image starts to be affected by wear, but is hardly noticeable.
Δ: Some wear is confirmed.
×: considerably worn.

(Plasticizer resistance)
A plasticized soft vinyl chloride sheet (Mitsubishi Chemical Co., Ltd. Altron # 480, thickness 400 μm) and the protective layer transfer surface of the printed material are overlapped, and a load of 24 g / cm ² is applied in an 80 ° C. environment for 8 hours. The state of deterioration of the image due to the plasticizer was stored and visually observed, and the plasticizer resistance of the protective layer was evaluated according to the following criteria.
A: There is no migration of the dye.
○: Almost no dye transfer.
Δ: Dye migration can be confirmed to some extent.
X: Dye has been transferred to almost the entire surface.

(Foil cutting property)
The surface of the printed material after the transfer of the protective layer and the transfer edge portion of the thermal transfer sheet were visually observed, and the following criteria were used to evaluate whether the foil breakage was uniform or not.
Evaluation criteria ◎: No tailing and no problem ○: There is a tailing of less than 0.5 mm, but there is no problem in practical use Δ: There is a tailing of 0.5 mm or more and less than 5 mm ×: There is a tailing of 5 mm or more

Table 1 shows the evaluation results of Examples 1 to 3 and Comparative Examples 1 to 5.

  From the above evaluation results, comparing Example 1 and Example 2, when the molecular weight of the adhesive (polyester resin) used in the adhesive layer is low, the plasticizer resistance and scratch resistance in the transfer layer are reduced. . Further, in the thermal transfer sheets prepared in Examples 1 to 3, the thickness of the outer edge portion of the transfer layer was decreased stepwise from the central portion side to the end portion, and all the foil cutting properties were good. And scratch resistance is also good. Comparing Example 1 and Example 3, when the adhesive used in the adhesive layer is changed from a polyester resin to a vinyl chloride-vinyl acetate copolymer resin, the foil breakage and scratch resistance are good and unchanged. Plasticizer resistance is reduced.

In the thermal transfer sheet of Comparative Example 1, the thickness of the outer edge portion of the transfer layer does not decrease stepwise from the central portion side to the end portion, and the thickness of the transfer layer from the central portion to the end portion is The adhesive used in the adhesive layer is a low molecular weight polyester resin, and the plasticizer resistance and scratch resistance in the transfer layer are poor. The thermal transfer sheet of Comparative Example 2 is the same as the thermal transfer sheet of Example 1, but the thickness of the transfer layer is the same at the central portion side, but at the end of the outer edge portion, the central portion side does not decrease compared to the central portion side. Although the thickness is the same, the evaluation of plasticizer resistance and scratch resistance does not change, but the foil breakage is deteriorated. Similarly, in the thermal transfer sheets of Comparative Examples 3 and 4, the thickness of the transfer layer is the same as that of the thermal transfer sheets of Examples 2 and 3, but at the end of the outer edge portion, the thickness is smaller than that of the central portion. Without being changed, the evaluation of the plasticizer resistance and the scratch resistance is not changed, but the foil breakage is deteriorated. Further, in the thermal transfer sheet of Comparative Example 5, like the thermal transfer sheet of Example 1, the thickness of the adhesive layer is gradually decreased at the outer edge portion, from the central portion side to the end portion. Rather, it is a thin film thickness of 0.5 g / m ² , and the foil breakability is good, but the plasticizer resistance and scratch resistance are poor.

DESCRIPTION OF SYMBOLS 1 Thermal transfer sheet 2 Base material 3 Peeling layer 4 Adhesive layer 5 Heat resistant slipping layer 6 Transfer layer 7 Heat-meltable color material layer 8 Outer edge part 9 Coated part of heat-meltable color material layer 10 Application of adhesive layer Part 11 Central part

Claims (2)

In a thermal transfer sheet in which a transfer layer capable of thermal transfer is provided on a substrate, the thickness of the outer edge of the transfer layer decreases stepwise from the center to the end , and the transfer The thermal transfer sheet , wherein the outer edge portion in which the thickness of the layer is gradually reduced exists at a position of 5 to 10 mm from the end portion of the transfer layer . Transfer layer of the can, from the substrate side, the release layer is composed of an adhesive layer, according to claim 1, the molecular weight of the resin constituting the adhesive layer is characterized in that 10,000 to 40,000 on average number The thermal transfer sheet described in 1.

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