JP6102998B2 - Thermal transfer sheet - Google Patents

Description

  The present invention relates to a thermal transfer sheet.

  As a method of forming images using thermal transfer, a thermal transfer sheet in which a sublimation dye as a recording material is carried on a substrate such as a plastic film, and a dye receiving layer are provided on another substrate such as paper or plastic film. There is known a sublimation thermal transfer system in which a full color image is formed by superimposing the thermal transfer image receiving sheets on each other. Since this method uses sublimation dyes as color materials, it is excellent in halftone reproducibility and gradation, and a full color image as it is on the original can be clearly displayed on the image receiving sheet. It is applied to color image formation for computers. The image is of a high quality comparable to a silver salt photograph.

  Known thermal transfer image-receiving sheets used in the sublimation thermal transfer system include solvent-based thermal transfer image-receiving sheets provided with solvent-based dye-receiving layers and water-based thermal transfer image-receiving sheets provided with aqueous dye-receiving layers. The solvent-based thermal transfer image-receiving sheet is superior in releasability from the thermal transfer sheet compared to the water-based thermal transfer image-receiving sheet, but has a lower gloss than the image formed on the water-based thermal transfer image-receiving sheet. For this reason, in a field where a high glossiness is required for an image to be formed, an aqueous thermal transfer image-receiving sheet tends to be preferred. Also, the use of water-based thermal transfer image-receiving sheets tends to increase due to problems such as environmental impact due to treatment of waste liquids and the like.

  The water-based thermal transfer image-receiving sheet has the advantage that a high glossiness can be imparted to an image formed as compared with a solvent-based thermal transfer image-receiving sheet without affecting the human body and the environment. On the other hand, the water-based dye-receiving layer contains an aqueous resin that can be dispersed or dissolved in an aqueous solvent, and has a property of easily absorbing water in the environment during printing in a high-humidity environment and the like, and making it soft. The aqueous dye-receiving layer is susceptible to damage during printing due to softening due to water absorption, and when it is damaged during printing, the glossiness that is an advantage of the aqueous thermal transfer image-receiving sheet is significantly reduced.

  In order to prevent a decrease in glossiness, which is an advantage of an aqueous thermal transfer image-receiving sheet, it is possible to prevent the aqueous dye-receiving layer from being softened, or to reduce damage to the aqueous dye-receiving layer during printing. Conceivable. However, in the former case, it is not realistic to prevent the dye receiving layer from becoming soft as long as an aqueous dye receiving layer containing an aqueous resin is used. As a result of diligent investigation focusing on the latter damage received by the water-based dye-receiving layer, the inventors of the present application mainly caused the decrease in the slipperiness between the thermal transfer sheet and the thermal head during printing. And found that it can occur. Specifically, if the thermal transfer sheet and the thermal head have low lubricity, the dye layer of the thermal transfer sheet is damaged, and this damage adversely affects the water-based dye-receiving layer, resulting in a decrease in glossiness of the printed material. I found out.

  As a thermal transfer sheet that improves the lubricity with the thermal head, a thermal transfer sheet in which a back layer is provided on a surface different from the surface on which the dye layer of the base material is provided is known. Discloses a silicone-modified urethane resin, a silicone-modified acrylic resin, and a coating solution prepared by dissolving and dispersing a polyisocyanate curing agent in a suitable solvent on a substrate and drying. Further, Patent Document 2 discloses a thermal transfer sheet in which a binder resin having a reactive group such as a hydroxyl group and a polyisocyanate are used in combination to form a cross-linked back layer on a substrate. The back layers disclosed in Patent Documents 1 and 2 impart heat resistance to the back layer by curing the binder resin with a curing agent. Further, these patent documents disclose that it is preferable to contain a lubricant component such as phosphate ester, silicone oil, zinc stearate in order to impart slipperiness to the back layer.

  However, the thermal transfer sheet disclosed in Patent Documents 1 and 2 and the conventionally known thermal transfer sheet having a back layer are printed in combination with a thermal transfer image receiving sheet having an aqueous dye-receiving layer in a high-temperature and high-humidity environment. There is a problem that the gloss is lowered when performing. In addition, there is a problem that printing wrinkles occur during low-temperature and low-humidity printing. In order to solve these problems, it is necessary that the thermal transfer sheet and the thermal head have sufficient sliding properties and high heat resistance. As a method for improving the slipperiness, increasing the lubricant in the back layer can be mentioned. However, if the lubricant is increased, debris may adhere to the thermal head during printing, and scratches or streaks may occur in the printed matter.

  Patent Document 3 discloses a cellulose acetate butyrate resin (A1), an acrylic resin, and a polyvinyl acetal resin for the purpose of preventing the transfer of dye to the back layer and the retransfer of the transferred dye. A thermal transfer sheet provided with a back layer containing at least one resin (A2) selected from the group and a lubricant is disclosed. In this patent document, the content of the cellulose acetate butyrate resin is defined within a range of 60 to 90% by mass of the total weight of the cellulose acetate butyrate resins (A1) and (A2).

  However, when image formation is performed in a high-temperature and high-humidity environment using the thermal transfer sheet disclosed in Patent Document 3, the dye layer of the thermal transfer sheet is damaged, and the gloss of the printed matter is lowered. When printing at low temperature and low humidity, printing wrinkles occur.

Japanese Patent Laid-Open No. 9-11647 JP-A-6-99670 JP 2008-105371 A

  The present invention has been made in such a situation, and is excellent in glossiness in both high temperature and high humidity environments and low temperature and low humidity environments, and an image having no print wrinkles or few wrinkles is generated in an aqueous system. The main object is to provide an image forming method that can be formed on a dye receiving layer and a combination of a thermal transfer sheet and a thermal transfer image receiving sheet that can form this image.

The present invention for solving the above problems is a thermal transfer sheet in which a back layer is provided on one side of a substrate and a dye layer is provided on the other side of the substrate, wherein the back layer comprises (A) polyvinyl It contains an acetal resin or polyvinyl butyral resin, (B) a cellulose resin, and (C) a lubricant component, and the (B) cellulose resin is 3% by mass with respect to the total solid content of the back layer. It is contained within the range of 40% by mass or less, and the (B) cellulose resin is a cellulose acetate butyrate resin or a cellulose acetate propionate resin.
The invention of one embodiment is a thermal transfer sheet in which a back layer is provided on one side of a substrate and a dye layer is provided on the other side of the substrate, wherein the back layer comprises (A) a polyvinyl acetal resin Or a polyvinyl butyral resin, (B) a cellulose-based resin, and (C) a lubricant component, and the (B) cellulose-based resin is 3% by mass or more and 40% by mass based on the total solid content of the back layer. It is contained within the range of mass% or less.
The invention of one embodiment includes a thermal transfer sheet in which a back layer is provided on one side of a substrate and a dye layer is provided on the other side of the substrate, and a dye receiving layer is provided on one side of the other substrate. An image forming method for forming an image on a thermal transfer image receiving sheet using a combination of the obtained thermal transfer image receiving sheet, wherein the back layer comprises (A) polyvinyl acetal resin or polyvinyl butyral resin, and (B) cellulose And (C) a lubricant component, and the (B) cellulose resin is contained within a range of 3% by mass to 40% by mass with respect to the total solid content of the back layer, The dye receiving layer is an aqueous dye receiving layer.

  The (B) cellulose resin may be a cellulose acetate butyrate resin or a cellulose acetate propionate resin.

  The (A) polyvinyl acetal resin or polyvinyl butyral resin may be a polyvinyl acetal resin having a crosslinked structure or a polyvinyl butyral resin having a crosslinked structure.

  The invention of one embodiment is a combination of a thermal transfer sheet and a thermal transfer image-receiving sheet, wherein the thermal transfer sheet has (A) a polyvinyl acetal resin or polyvinyl butyral resin on one side of the substrate, and (B) cellulose. A back layer containing a base resin and (C) a lubricant component, a dye layer on the other side of the substrate is provided, and the total amount of solids in the back layer is based on the (B) cellulosic resin. It is a thermal transfer sheet contained in the range of 3% by mass or more and 40% by mass or less, and the thermal transfer image receiving sheet is a thermal transfer image receiving sheet in which an aqueous dye-receiving layer is provided on another substrate. And

  According to the image forming method of the present invention and the combination of the thermal transfer sheet and the thermal transfer image-receiving sheet, the gloss is excellent in any environment of high temperature and high humidity and low temperature and low humidity, and there is no print wrinkle or no wrinkle. An image with less generation can be formed on an aqueous dye-receiving layer.

It is a schematic sectional drawing which shows an example of the thermal transfer sheet used for this invention. It is a schematic sectional drawing which shows an example of the thermal transfer image receiving sheet used for this invention.

  The image forming method of the present invention and the combination of a thermal transfer sheet and a thermal transfer image receiving sheet will be described in detail below. The image forming method of the present invention includes a thermal transfer sheet 10 having a back layer 3 provided on one side of a substrate 1 and a dye layer 2 provided on the other side of the substrate, as shown in FIG. An image forming method for forming an image on a thermal transfer image receiving sheet by using in combination with a thermal transfer image receiving sheet 30 provided with a dye receiving layer 22 on one side of the other substrate 21, (A) A polyvinyl acetal resin or polyvinyl butyral resin, (B) a cellulose resin, and (C) a lubricant component. The dye receiving layer 22 is an aqueous dye receiving layer. Hereinafter, the thermal transfer sheet 10 and the thermal transfer image receiving sheet 30 used in the present invention will be specifically described. FIG. 1 is a schematic cross-sectional view showing an example of a thermal transfer sheet used in combination with the image forming method of the present invention and a thermal transfer image receiving sheet, and FIG. 2 shows the image forming method of the present invention and the thermal transfer sheet. It is a schematic sectional drawing which shows an example of the thermal transfer image receiving sheet used for this combination.

<< Thermal transfer sheet >>
As shown in FIG. 1, a thermal transfer sheet 10 used in combination with the image forming method of the present invention and a thermal transfer image receiving sheet is provided with a back layer 3 on one side of a substrate 1, and the other side of the substrate 1. The dye layer 2 is provided on the top. In the present invention, the back layer 3 contains (A) a polyvinyl acetal resin or polyvinyl butyral resin, (B) a cellulose-based resin, and (C) a lubricant component, and is based on the total solid content of the back layer. (B) Cellulosic resin is contained in the range of 3 mass% or more and 40 mass% or less. Hereinafter, each configuration of the thermal transfer sheet 10 will be specifically described.

(Base material)
The substrate 1 used in the thermal transfer sheet 10 of the present invention is not particularly limited as long as it has transparency in addition to a certain degree of heat resistance and strength, and a conventionally known material is appropriately selected and used. be able to. Examples of such a substrate 1 include polyethylene terephthalate film, 1,4-polycyclohexylenedimethylene terephthalate film, polyethylene naphthalate film, polyphenylene sulfide having a thickness of about 0.5 to 50 μm, preferably about 1 to 10 μm. Film, polystyrene film, polypropylene film, polysulfone film, aramid film, polycarbonate film, polyvinyl alcohol film, cellophane, cellulose derivatives such as cellulose acetate, polyethylene film, polyvinyl chloride film, nylon film, polyimide film, ionomer film, etc. . Furthermore, each of these materials can be used alone, but may be used as a laminate in combination with other materials.

(Back layer)
In the case shown in FIG. 1 on one surface of the substrate 1, a back layer 3 is provided on the lower surface of the substrate 1. The back surface layer 3 contains at least three kinds of components (A) polyvinyl acetal resin or polyvinyl butyral resin, (B) a cellulose-based resin, and (C) a lubricant component.

(A) polyvinyl acetal resin, polyvinyl butyral resin;
The back layer 3 contains polyvinyl acetal resin or polyvinyl butyral resin. Hereinafter, the polyvinyl acetal resin or the polyvinyl butyral resin may be simply referred to as the component (A).

  By containing the component (A) in the back layer 3, high heat resistance is imparted to the back layer 3, so that damage to the dye layer during image formation can be reduced. As a result, it is possible to form a high-quality image that is excellent in glossiness, has no printing wrinkles, and has few wrinkles without damaging the dye-receiving layer of the thermal transfer image-receiving sheet. Further, it is possible to prevent the back layer 3 and the thermal head from being thermally fused.

  The polyvinyl acetal resin and the polyvinyl butyral resin preferably have a hydroxyl value of 9% by mass or more and 25% by mass or less. By setting it within the range, the heat resistance can be further improved and can be easily dissolved in a solvent such as methyl ethyl ketone, ethyl acetate, or toluene used for preparing the coating liquid. Examples of such a polyvinyl acetal resin having a hydroxyl value include BX-L, BX-1, BX-5, KS-1, KS-3, KS-5, and KS-10 manufactured by Sekisui Chemical Co., Ltd. Examples of such a polyvinyl butyral resin include BM-5, BM-S, BH-3, and BH-S. In the present specification, “hydroxyl value” means the ratio of the monomer component having a hydroxyl group in the resin polymer, and the ratio of the mass of the monomer component having a hydroxyl group to the mass of the entire resin polymer (mass). %).

  In addition, other binder resins can be added to the back surface layer coating liquid within a range not impeding the gist of the present invention. Examples of the other binder resin include acrylic resin, polyester resin, styrene-maleic acid copolymer, polyimide resin, polyamide resin, polyamideimide resin, vinylidene fluoride resin, and nylon.

  Moreover, it is preferable that the polyvinyl acetal resin and polyvinyl butyral resin which are (A) components have a crosslinked structure. By making the resin of the component (A) a resin having a cross-linked structure, higher heat resistance can be imparted to the back layer 3.

  The polyvinyl acetal resin having a crosslinked structure and the polyvinyl butyral resin having a crosslinked structure can be formed by crosslinking a polyvinyl acetal resin or a polyvinyl butyral resin with a crosslinking agent. Examples of the crosslinking agent include isocyanate-based crosslinking agents such as polyisocyanate resins, oxazoline-based crosslinking agents, and carbodiimide-based crosslinking agents. Various polyisocyanate resins are conventionally known, and among them, it is desirable to use an adduct of aromatic isocyanate. As the aromatic polyisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, or a mixture of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate, 1,5-naphthalene diisocyanate, tolidine diisocyanate, Examples include p-phenylene diisocyanate, trans-cyclohexane, 1,4-diisocyanate, xylylene diisocyanate, triphenylmethane triisocyanate, and tris (isocyanatephenyl) thiophosphate, especially 2,4-toluene diisocyanate and 2,6-toluene diisocyanate. Or, a mixture of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate is preferable.

  When the polyvinyl acetal resin or polyvinyl butyral resin having a crosslinked structure is formed by an isocyanate crosslinking agent, the equivalent ratio of the hydroxyl group of the polyvinyl butyral resin or polyvinyl acetal resin and the isocyanate group of the isocyanate curing agent (-NCO /- OH) is preferably 0.1 or more and 3 or less.

  The component (A) is preferably contained in the range of 5% by mass to 60% by mass with respect to the total solid content of the back layer 3, and preferably in the range of 10% by mass to 40% by mass. Is particularly preferred. When the content of the component (A) is less than 5% by mass, the heat resistance of the back layer 3 tends to decrease, whereas when it exceeds 60% by mass, the lubricity of the back layer 3 tends to decrease. It becomes.

(B) Cellulosic resin;
The back layer 3 contains (B) a cellulose resin. Hereinafter, the (B) cellulosic resin may be simply referred to as the component (B). In the present invention, by containing the component (B) in the back layer 3, damage to the aqueous dye-receiving layer during image formation is prevented, and glossiness and print wrinkles are prevented from occurring. Specifically, the component (B) plays a role of extracting the function of the (C) lubricant component, and the performance of the (C) lubricant component is sufficiently exhibited by including the component (B) in the back layer 3. Thereby, extremely high slipperiness is imparted to the back layer 3.

  Examples of the cellulose resin include cellulose acetate resin, cellulose acetate butyrate resin, cellulose acetate propionate resin, and nitrocellulose. Among these, cellulose acetate butyrate having good solubility in solvents. Rate resin and cellulose acetate propionate resin can be particularly preferably used as the cellulose resin.

  Moreover, the cellulose resin which is (B) component is contained within the range of 3 mass% or more and 40 mass% or less with respect to the total solid content of the back surface layer 3. When the amount is less than 3% by mass, the performance of the lubricant component cannot be sufficiently exhibited, and the slipperiness of the back layer 3 is low, causing a decrease in glossiness of an image and occurrence of printing wrinkles. On the other hand, when it exceeds 40 mass%, the content of the component (A) is reduced correspondingly, and the heat resistance of the back layer 3 is lowered.

  The molecular weight of the cellulosic resin is preferably a mass average molecular weight (Mw) of 15000 or less. By containing the cellulosic resin having a molecular weight within this range in the back surface layer 3, the performance of the lubricant component can be expressed more effectively, and excellent slipperiness can be imparted to the back surface layer 3. On the other hand, when the molecular weight (Mw) of the cellulosic resin exceeds 15000, particularly when the molecular weight (Mw) exceeds 40000, the heat resistance of the back layer 3 is improved, but the performance of the lubricant component can be sufficiently brought out. It can be difficult.

  The cellulose resin may be a cellulose resin having a crosslinked structure. By containing the cellulosic resin having a crosslinked structure in the back layer 3, the heat resistance of the back layer 3 can be improved by a synergistic effect with the component (A).

(C) a lubricant component;
The back layer 3 contains a lubricant component in order to improve the sliding property with the thermal head. There is no particular limitation on the lubricant component, and conventionally known lubricants such as phosphate ester, metal soap, graphite powder, fluorine-based graft polymer, silicone oil, silicone-based graft polymer, acrylic silicone graft polymer, acrylic siloxane, aryl siloxane, etc. A silicone polymer or the like can be appropriately selected and used. Among the above-mentioned lubricant components, phosphate esters and metal soaps can be particularly preferably used in the present invention.

  Examples of the metal soap include polyvalent metal salts of alkyl phosphates and metal salts of alkyl carboxylic acids. As the polyvalent metal salt of the alkyl phosphate, those known as additives for plastics can be used. The polyvalent metal salt of the alkyl phosphate ester is generally obtained by substituting the alkali metal salt of the alkyl phosphate ester with a polyvalent metal, and various grades are available.

  Examples of the phosphate ester include (1) a phosphoric acid monoester or diester of a saturated or unsaturated higher alcohol having 6 to 20 carbon atoms, and (2) a phosphoric acid monoester of a polyoxyalkylene alkyl ether or polyoxyalkylene alkyl allyl ether. Ester or diester, (3) phosphoric acid monoester or diester of the above-mentioned saturated or unsaturated higher alcohol alkylene oxide adduct (average number of added moles of 1 to 8), (4) alkylphenol having an alkyl group of 8 to 12 carbon atoms Alternatively, phosphoric acid monoester or diester of alkyl naphthol can be used. Examples of the saturated or unsaturated higher alcohol in the above (1) and (3) include cetyl alcohol, stearyl alcohol, oleyl alcohol and the like. Examples of the alkylphenol in the above (3) include nonylphenol, dodecylphenol, diphenylphenol and the like.

  Although there is no limitation in particular about content of a lubricant component, when content of a lubricant component is less than 5 mass% with respect to the solid content total amount of the back surface layer 3, it is a case where (B) component is contained. However, the slipperiness of the back surface layer 3 becomes insufficient, the glossiness of the formed image is lowered, and the occurrence of printing wrinkles may occur. On the other hand, when the content of the lubricant component exceeds 40% by mass, scraped scraps of the lubricant are liable to adhere to the thermal head, which may cause poor printing. Considering such points, the content of the lubricant component is preferably in the range of 5% by mass to 40% by mass with respect to the total solid content of the back layer 3, and is preferably 10% by mass to 30% by mass. It is particularly preferable that the value falls within the range.

  Normally, in order to impart sufficient lubricity to the back surface layer 3, the amount of the lubricant component is increased, and as described above, the adhesion of shavings and the content of the binder resin are reduced accordingly. However, in the present invention, by containing the component (B) in the back layer 3, the performance of the lubricant component is sufficiently exhibited while suppressing the content of the lubricant component. be able to. Therefore, the slipperiness of the back surface layer 3 can be improved without causing the adhesion of shavings that may be caused by containing a large amount of the lubricant component and the decrease in heat resistance.

  Although there is no limitation in particular about the thickness of the back surface layer 3, when the thickness of a back surface layer is too thin, sufficient heat resistance may not be provided to the back surface layer 3. On the other hand, if the thickness of the back layer 3 is too thick, heat from the thermal head may not be efficiently transferred to the dye layer side. Therefore, the thickness of the back layer 3 needs to be determined in consideration of these points, and is preferably about 0.1 to 5 μm, more preferably about 0.2 to 2 μm.

  Although there is no limitation in particular about the formation method of the back layer 3 which comprises the thermal transfer sheet 10 used with the image forming method of this invention, (A) component, (B) component, (C) component demonstrated above, as needed The known coating means such as gravure printing method, screen printing method, reverse roll coating method using gravure plate, etc. prepared by dissolving or dispersing other components added in a suitable solvent It can be formed by coating on a substrate using and drying. Examples of the solvent used for preparing the coating liquid include water, toluene, methyl ethyl ketone, ethanol, isopropyl alcohol, cyclohexane, dimethylformamide, and ethyl acetate.

(Dye layer)
As shown in FIG. 1, a dye layer 2 is provided on at least a part of one surface of the substrate 1. In the embodiment shown in FIG. 1, the dye layer 2 and the transferable protective layer 5 are provided in the surface order, but the dye layer 2 is provided on the entire surface of the substrate 1. You can also. In addition to this, a dye layer containing a sublimable dye and a dye layer containing a heat-meltable ink comprising a heat-melt composition containing a colorant are sequentially arranged on a single substrate. It may be provided. The dye layer 2 is an essential component in the thermal transfer sheet 10 used in the image forming method of the present invention.

  This dye layer 2 is a dye layer containing a sublimable dye when the thermal transfer sheet of the present invention is a sublimation type thermal transfer sheet, and in the case of a hot melt type thermal transfer sheet, a thermal melt composition containing a colorant. It becomes a dye layer containing a heat-meltable ink made of a material. Hereinafter, although the case of a sublimation type thermal transfer sheet will be described as a representative example, the present invention is not limited to only a sublimation type thermal transfer sheet.

  As the material of the dye layer, conventionally known dyes can be used, but those having good characteristics as printing materials, for example, those having a sufficient coloring density and not discolored by light, heat, temperature, etc. Preferably, diarylmethane dyes, triarylmethane dyes, thiazole dyes, merocyanine dyes, pyrazolone dyes, methine dyes, indoaniline dyes, acetophenone azomethine, pyrazoloazomethine, imidazolazomethine, imidazoazomethine, pyridone azomethine, etc. Azomethine dyes, xanthene dyes, oxazine dyes, cyanostyrene dyes such as dicyanostyrene and tricyanostyrene, thiazine dyes, azine dyes, acridine dyes, benzeneazo dyes, pyridoneazo, thiophenazo, isothiazole azo, Pyrroleazo Azo dyes such as pyrazole azo, imidazole azo, thiadiazole azo, triazole azo, and disazo, spiropyran dyes, indolinospiropyran dyes, fluorane dyes, rhodamine lactam dyes, naphthoquinone dyes, anthraquinone dyes, quinophthalone dyes, etc. Is mentioned. Specifically, red dyes such as MSRedG (manufactured by Mitsui Toatsu Chemical Co., Ltd.), Macrolex Red Violet R (manufactured by Bayer), CeresRed 7B (manufactured by Bayer), Samalon Red F3BS (manufactured by Mitsubishi Chemical), and holon brilliant yellow Yellow dyes such as 6GL (manufactured by Clariant), PTY-52 (manufactured by Mitsubishi Kasei), Macrolex Yellow 6G (manufactured by Bayer), Kayaset Blue 714 (manufactured by Nippon Kayaku Co., Ltd.), Waxoline Blue AP-FW ( ICI), Holon Brilliant Blue SR (Sand), MS Blue 100 (Mitsui Toatsu Chemical), C.I. I. Blue dyes such as Solvent Blue 22 are listed.

  Examples of the binder resin for supporting the dye include cellulose resins such as ethyl cellulose resin, hydroxyethyl cellulose resin, ethyl hydroxy cellulose resin, methyl cellulose resin, and cellulose acetate resin, polyvinyl alcohol resin, polyvinyl acetate resin, and polyvinyl butyral resin. And vinyl resins such as polyvinyl acetal resin and polyvinyl pyrrolidone, acrylic resins such as poly (meth) acrylate and poly (meth) acrylamide, polyurethane resins, polyamide resins and polyester resins. Among these, cellulose-based, vinyl-based, acrylic-based, polyurethane-based, and polyester-based resins are preferable in terms of heat resistance, dye transferability, and the like.

  The dye layer 2 may contain additives such as inorganic fine particles and organic fine particles. Examples of the inorganic fine particles include carbon black, aluminum, and molybdenum disulfide. Examples of the organic fine particles include polyethylene wax. The dye layer 2 may contain a release agent. Examples of the mold release agent include silicone oil and phosphate ester.

  As a method for forming the dye layer 2, an additive such as a release agent and a filler is added to the dye and the binder resin as necessary, and an appropriate solvent such as toluene, methyl ethyl ketone, ethanol, isopropyl alcohol, cyclohexane, dimethylformamide or the like. Formed by applying the coating liquid dispersed or dissolved in, for example, on a substrate by a gravure printing method, a reverse roll coating method using a gravure plate, a roll coater, a bar coater or the like and drying it. can do.

(Transferable protective layer)
As shown in FIG. 1, in the thermal transfer sheet 10 used in the image forming method of the present invention, the dye layer 2 and the transferable protective layer 5 described above can be provided on the substrate 1 in the surface order. The transferable protective layer 5 may have a multilayer structure or a single layer structure. In the case of a multi-layer structure, in addition to the main protective layer which is a main component for imparting various durability to the image, transferability protection is provided to enhance the adhesion between the transferable protective layer 5 and the image receiving surface of the printed material. The adhesion layer arrange | positioned on the outermost surface of the layer 5, an auxiliary | assistant protective layer, the layer for adding functions other than the function of a protective layer main body, etc. may be contained. The order of the main protective layer and other layers is arbitrary, but usually other layers are placed between the adhesive layer and the main protective layer so that the main protective layer becomes the outermost surface layer of the image receiving surface after transfer. To do.

  The main protective layer or the single-layered transferable protective layer 5 constituting the multi-layered transferable protective layer 5 can be formed of various resins conventionally known as protective layer forming resins. Examples of the resin for forming the protective layer include polyester resins, polystyrene resins, acrylic resins, polyurethane resins, acrylic urethane resins, resins obtained by silicone-modifying these resins, mixtures of these resins, ionizing radiation curable resins, An ultraviolet blocking resin can be exemplified.

  The protective layer containing the ionizing radiation curable resin is particularly excellent in plasticizer resistance and scratch resistance. As the ionizing radiation curable resin, known ones can be used. For example, a radical polymerizable polymer or oligomer is crosslinked and cured by ionizing radiation irradiation, and a photopolymerization initiator is added if necessary, and an electron beam Those obtained by polymerization and crosslinking with ultraviolet rays can be used.

  The main purpose of the protective layer containing the ultraviolet blocking resin is to impart light resistance to the printed material. As the ultraviolet blocking resin, for example, a resin obtained by reacting and bonding a reactive ultraviolet absorber with a thermoplastic resin or the above ionizing radiation curable resin can be used. More specifically, addition-polymerizable double-reactive organic UV absorbers such as salicylates, benzophenones, benzotriazoles, substituted acrylonitriles, nickel chelates, hindered amines, etc. Examples thereof include those in which a reactive group such as a bond (for example, a vinyl group, an acryloyl group, a methacryloyl group), an alcoholic hydroxyl group, an amino group, a carboxyl group, an epoxy group, or an isocyanate group is introduced.

  The main protective layer provided in the single layer structure transferable protective layer 5 or the multilayer structure transferable protective layer 5 usually has a thickness of about 0.5 to 10 μm, although it depends on the type of the protective layer forming resin. It is preferable.

  An adhesive layer may be formed on the outermost surface of the transferable protective layer 5. The adhesive layer should be formed of a resin having good adhesiveness when heated, such as acrylic resin, vinyl chloride resin, vinyl acetate resin, vinyl chloride / vinyl acetate copolymer resin, polyester resin, polyamide resin. Can do. The thickness of the adhesive layer is usually about 0.1 to 5 μm. Moreover, you may provide a release layer between the transferable protective layer 5 and a base material.

(Underlayer)
In the present invention, an undercoat layer 6 is preferably provided between the substrate 1 and the dye layer 2. By providing the undercoat layer 6, adhesion between the substrate 1 and the dye layer 2 can be improved, and abnormal transfer of the dye layer 2 to the thermal transfer image receiving sheet can be prevented during thermal transfer. The undercoat layer has an arbitrary configuration in the thermal transfer sheet 10.

  Examples of the resin constituting the undercoat layer 6 include polyester resins, polyacrylate resins, polyvinyl acetate resins, polyurethane resins, styrene acrylate resins, polyacrylamide resins, polyamide resins, and polyether resins. And polystyrene resins, polyethylene resins, polypropylene resins, vinyl resins such as polyvinyl chloride resins and polyvinyl alcohol resins, and polyvinyl acetal resins such as polyvinyl acetoacetal and polyvinyl butyral.

  Further, the undercoat layer 6 can also be composed of colloidal inorganic pigment ultrafine particles. This not only prevents abnormal transfer of the dye layer 2 during image formation, but also prevents dye transfer from the dye layer 2 to the undercoat layer 6 and effectively diffuses the dye to the dye receiving layer side of the thermal transfer image receiving sheet. Printing density can be increased.

  As the colloidal inorganic pigment ultrafine particles, conventionally known compounds can be used. For example, silica (colloidal silica), alumina or alumina hydrate (alumina sol, colloidal alumina, cationic aluminum oxide or hydrate, pseudoboehmite, etc.), aluminum silicate, magnesium silicate, magnesium carbonate, magnesium oxide, oxidation Examples include titanium. In particular, colloidal silica and alumina sol are preferably used. These colloidal inorganic pigment ultrafine particles have a primary average particle size of 100 nm or less, preferably 50 nm or less, and particularly preferably 3 to 30 nm.

  The undercoat layer 6 is a gravure coating method, a roll coating method, a screen printing method, a gravure plate, and a coating solution for the undercoat layer in which the resin exemplified above or colloidal inorganic pigment ultrafine particles are dissolved or dispersed in an appropriate solvent. It can be formed by coating and drying by a conventionally known forming means such as a reverse roll coating method using sapphire. The coating amount of the undercoat layer coating solution is preferably about 0.02 to 1.0 g / m2.

(Back primer layer)
Further, a back primer layer (not shown) may be provided between the substrate 1 and the back layer 3. The back primer layer is a layer provided in order to improve the adhesion between the substrate 1 and the back layer 3 and is an arbitrary layer. Examples of the back primer layer include polyester resin, polyurethane resin, acrylic resin, polycarbonate resin, vinyl chloride / vinyl acetate copolymer, and polyvinyl butyral resin.

<< Thermal transfer image-receiving sheet >>
Next, the image forming method of the present invention and the thermal transfer image receiving sheet used in combination with the thermal transfer sheet will be described. As shown in FIG. 2, the thermal transfer image receiving sheet 30 used in the present invention has a configuration in which a dye receiving layer 22 is provided on one surface of another base material 21. The present invention is characterized in that the dye receiving layer 22 is an aqueous dye receiving layer. In FIG. 2, the heat insulating layer 25 is provided between the other base material 21 and the dye receiving layer 22, but the heat insulating layer 25 has an arbitrary configuration in the thermal transfer image receiving sheet 30 used in the present invention. is there. Hereinafter, each configuration of the thermal transfer image receiving sheet 30 will be specifically described.

(Other base materials)
The other substrate 21 is an essential component in the thermal transfer image-receiving sheet 30 used in the present invention, and is provided to hold the dye-receiving layer 22 or the heat insulating layer 25 having an arbitrary configuration. There is no limitation in particular about the other base material 21, and stretched or unstretched plastics such as polyolefin, polyester, polypropylene, polycarbonate, cellulose acetate, polyethylene derivatives, polyamide, polymethylpentene and the like having high heat resistance such as polyethylene terephthalate and polyethylene naphthalate Films and white opaque films formed by adding white pigments and fillers to these synthetic resins can also be used. In addition, materials such as high-quality paper, coated paper, art paper, cast coated paper, and paperboard can also be used. Moreover, the composite film which laminated | stacked 2 or more types of these materials can also be used. Examples of typical laminates include cellulose fiber paper and synthetic paper or cellulose synthetic paper, plastic film, and synthetic paper. In the present invention, a commercially available base material can be used, for example, RC paper paper ( Mitsubishi Paper Industries, Ltd., trade name: STF-150) and the like are preferable. In the present specification, the base material constituting the thermal transfer image receiving sheet 30 is referred to as another base material 21 in order to distinguish it from the base material 1 constituting the thermal transfer sheet. 1 and the other substrate 21 constituting the thermal transfer image receiving sheet 30 may be the same or different.

  The thickness of the other base material 21 can be appropriately selected depending on the material so that its strength, heat resistance and the like are appropriate, but is usually about 50 μm to 1000 μm, preferably about 60 μm to 300 μm.

(Dye-receiving layer)
A dye receiving layer 22 is provided on another substrate 21. The dye receiving layer 22 is an essential component in the thermal transfer image receiving sheet 30 used in the present invention.

  In the present invention, the dye receiving layer 22 is an aqueous dye receiving layer 22. By forming an image using a thermal transfer image-receiving sheet having an aqueous dye-receiving layer 22, an image having a high glossiness can be formed. The water-based dye receiving layer 22 is a receiving layer that is easily softened by water absorption and easily damaged during printing. In the present invention, an image is formed in combination with the thermal transfer sheet 10 described above. The receiving layer 22 can be prevented from being damaged, and an image can be formed without reducing the glossiness that is an advantage of the water-based dye receiving layer 22.

  In the present invention, the aqueous dye-receiving layer is an aqueous coating solution obtained by dissolving or dispersing a resin that can be dissolved or dispersed in an aqueous solvent, such as a water-soluble resin, a water-soluble polymer, or an aqueous resin, in an aqueous solvent. This means a dye-receiving layer formed using Water-soluble resins, water-soluble polymers such as polyvinyl pyrrolidone, polyvinyl alcohol, hydroethyl cellulose, carboxymethyl cellulose, phenol resin, polyacrylic acid, polyacrylic acid ester, polyacrylic acid ester copolymer, polymethacrylic acid Acryl resin, gelatin, starch, casein, and modified products thereof. Water-based resins are vinyl chloride resin emulsions, vinyl chloride-vinyl acetate resin emulsions, vinyl chloride resin emulsions such as vinyl chloride-acrylic resin emulsions, acrylic resin emulsions, urethane resin emulsions, PVC resin dispersions, and acrylic resin dispersions. Examples include a solvent in which a part of the solvent is composed of water, such as John and urethane resin dispersions. The water-based resin can be formed, for example, by dispersing and preparing a solution containing a solvent-based resin with a homogenizer.

  The water-soluble resin, water-soluble polymer, or water-based resin is preferably contained in the range of 50% by mass or more and 95% by mass or less with respect to the total solid content of the dye receiving layer 22. By setting it as the dye receiving layer 22 containing the aqueous resin in the said range, a high glossiness can be provided with the image formed.

  It is preferable that a release agent for enhancing the releasability of the thermal transfer sheet 10 with the dye layer 2 is added to the dye receiving layer 22.

  Release agents used in combination with water-soluble resins, water-soluble polymers, or water-based resins include silicone oils (including those called silicone resins); solids such as polyethylene wax, amide wax, and Teflon (registered trademark) powder. Waxes: fluorine-based and phosphate-based surfactants and the like. Among them, silicone oil is preferable.

  The dye receiving layer 22 is a water-soluble resin, a water-soluble polymer, a water-based resin, or other additives that are added as necessary. It is formed by coating and drying using a bar coat, gravure coat, slide coat, roll coating method or the like. When preparing an aqueous coating solution, it is desirable to dissolve or disperse the resin in water according to the solubility or dispersibility of the water-soluble resin, water-soluble polymer, or water-based resin in water. Although there is no limitation in particular about the thickness of the dye receiving layer 22, the range of 0.5-10 micrometers is common.

(Sealing layer)
Since the dye receiving layer 22 is formed using an aqueous coating solution, for example, when coated paper is used as the other substrate 21, the coated paper absorbs water, and as a result, the thermal transfer image receiving sheet 30 is used. There is a possibility that curling may occur. Therefore, when the other base material 21 is a base material with high water absorption, it is preferable to provide a sealing layer (not shown) between the base material 1 and the dye receiving layer 22. In addition, when another arbitrary layer is provided between the other base material 21 and the dye receiving layer 22, and the said layer is formed without using a water-system coating liquid, a sealing layer is unnecessary. On the other hand, when another arbitrary layer, for example, a heat insulating layer 25 described later is directly formed on the other base material 21 by using an aqueous coating solution, a sealing layer is provided for the same reason as described above. It is preferable.

  The sealing layer is not particularly limited as long as it has a function of being waterproof, and examples thereof include polyester resins, acrylic resins, acrylic-urethane resins, vinyl chloride resins, and the like. , (Meth) acrylic acid alkyl ester homopolymer emulsion, (meth) acrylic acid alkyl ester-styrene copolymer emulsion, (meth) acrylic acid alkyl ester-vinyl acetate copolymer emulsion, cement filler emulsion, etc. Things can be mentioned.

  The thickness of the sealing layer is not particularly limited, but is preferably about 0.2 g / m @ 2 to 10.0 g / m @ 2.

(Insulation layer)
A heat insulating layer 25 may be provided between the other base material 21 and the dye receiving layer 22. By providing the heat insulating layer 25, it is possible to prevent the heat applied from the thermal head to the dye receiving layer 22 from being transferred to the other base material 21 and the like, thereby preventing the print density from being lowered. Hereinafter, an example of the heat insulating layer will be described, but any other conventionally known materials referred to as “heat insulating layer”, “hollow (particle) layer”, and “heat insulating layer” can be appropriately selected and used. .

  The heat insulating layer 25 generally contains hollow particles having a function of imparting heat insulating properties and cushioning properties. The hollow particles may be expanded particles or non-expanded particles. Further, the expanded particles may be independent expanded particles or continuous expanded particles. Furthermore, the hollow particles may be organic hollow particles composed of resin or the like, or inorganic hollow particles composed of glass or the like. The hollow particles may be cross-linked hollow particles.

  Examples of the resin constituting the hollow particles include styrene resins such as crosslinked styrene-acrylic resins, (meth) acrylic resins such as acrylonitrile-acrylic resins, phenolic resins, fluorine resins, polyamide resins, and polyimide resins. And polycarbonate resins and polyether resins. The average particle diameter of the hollow particles is not particularly limited as long as the desired heat insulating property and cushioning property can be imparted to the heat insulating layer depending on the type of resin constituting the hollow particles, but is usually 0. It is preferably within the range of 1 μm to 15 μm, and particularly preferably within the range of 0.1 μm to 10 μm. This is because if the average particle size is too small, the amount of hollow particles used increases and the cost increases, and if the average particle size is too large, it becomes difficult to form a smooth heat insulating layer.

  In the present invention, the amount of the hollow particles contained in the heat insulating layer 25 is not particularly limited as long as a heat insulating layer having desired heat insulating properties and cushioning properties can be obtained, for example, 30% by mass to 90% by mass. It is preferable to be within the range of 50% by mass to 80% by mass. This is because if the content is too small, the gaps in the heat insulating layer are reduced, and sufficient heat insulating properties and cushioning properties may not be obtained. If the content is too large, the adhesiveness is inferior.

  The thermal transfer image receiving sheet 30 may have various functional layers. Examples of the various functional layers include a primer layer for improving adhesion between the other substrate 21 and the dye receiving layer 22 or the heat insulating layer 25, a barrier layer for imparting solvent resistance, and the like. be able to. In addition, a back surface layer having a function of improving the transferability of the thermal transfer image receiving sheet and a function of preventing curling can be provided on a surface different from the surface on which the dye receiving layer 22 of the other substrate 21 is provided. As described above, the thermal transfer image-receiving sheet 30 used in the present invention only needs to have the dye-receiving layer 22 containing an aqueous resin that can be dispersed or dissolved in an aqueous solvent as an essential component. There are no limitations on the various functional layers.

(Image formation)
In the present invention, the dye layer 2 of the thermal transfer sheet 10 described above and the dye receiving layer 22 of the thermal transfer image receiving sheet 30 are overlapped, and heat is applied from the back side of the thermal transfer sheet 10 by a thermal head, thereby the dye layer 22. The dye can be transferred to the dye receiving layer 22 to form an image.

  Hereinafter, the present invention will be described with reference to examples and comparative examples. “Parts” in the text are based on mass unless otherwise noted.

(Preparation of thermal transfer sheet 1)
Using a polyethylene terephthalate film with a thickness of 4.5 μm as the base material, a back layer coating liquid 1 having the following composition was applied to the back layer at a dryness of 0.8 g / m 2. Formed. Next, a primer layer coating solution having the following composition is applied to a part of the surface of the substrate opposite to the side where the back layer is provided, and dried so that the dry coating amount is 0.10 g / m 2. Thus, a primer layer was formed. Subsequently, a yellow dye layer coating liquid (Y), a magenta dye layer coating liquid (M), and a cyan dye layer coating liquid (C) having the following composition are applied to the primer layer by dry coating. The coating was applied so that the amount was 0.6 g / m @ 2, dried, and repeated in this order in order. In addition, a protective layer coating liquid having the following composition is applied to the other part of the surface opposite to the side on which the back layer of the substrate is provided, and dried at a rate of 1.5 g / m @ 2 in terms of solid content. Formed. Thus, a back surface layer is provided on one surface of the base material, and a primer layer and a dye layer (Y, M, C) are stacked in this order on a part of the other surface of the base material, A thermal transfer sheet 1 having a protective layer provided on the other part of the other surface of the material was obtained.

<Back layer coating liquid 1>
・ 35 parts of polyvinyl acetal resin (SREC BX-1 manufactured by Sekisui Chemical Co., Ltd.)
・ Polyisocyanate (solid content 100% NCO = 17.3 mass%) 30 parts (Bernock D750-45, manufactured by Dainippon Ink & Chemicals, Inc.)
Cellulose acetate butyrate resin (molecular weight 6000) 10 parts (Solus 2100 manufactured by Eastman Chemical Company)
-Zinc stearyl phosphate 10 parts (LBT-1830 refining Sakai Chemical Industry Co., Ltd.)
・ 10 parts of zinc stearate (SZ-PF manufactured by Sakai Chemical Industry Co., Ltd.)
・ 5 parts of talc (Microace P-3 manufactured by Nippon Talc Industry Co., Ltd.)
・ Methyl ethyl ketone 450 parts ・ Toluene 450 parts

<Primer layer coating solution>
Colloidal silica (particle diameter 4-6 nm, solid content 10%) 30 parts (Snowtex OXS, manufactured by Nissan Chemical Industries, Ltd.)
・ Polyvinylpyrrolidone resin (K-90, manufactured by ISP) 3 parts ・ Water 50 parts ・ Isopropyl alcohol 17 parts

<Yellow dye layer coating liquid (Y)>
-Dye represented by the following general formula (1) 2.0 parts-Polyvinylacetoacetal resin 4.5 parts (KS-5, manufactured by Sekisui Chemical Co., Ltd.)
・ Polyethylene wax 0.1 part ・ Methyl ethyl ketone 45.0 parts ・ Toluene 45.0 parts

<Magenta dye layer coating solution (M)>
-Dye represented by the following general formula (2) 2.0 parts-Polyvinylacetoacetal resin 4.5 parts (KS-5, manufactured by Sekisui Chemical Co., Ltd.)
・ Polyethylene wax 0.1 part ・ Methyl ethyl ketone 45.0 parts ・ Toluene 45.0 parts

<Cyan dye layer coating solution (C)>
-Dye represented by the following general formula (3) 2.0 parts-Polyvinylacetoacetal resin 4.5 parts (KS-5, manufactured by Sekisui Chemical Co., Ltd.)
・ Polyethylene wax 0.1 part ・ Methyl ethyl ketone 45.0 parts ・ Toluene 45.0 parts

<Coating liquid for protective layer>
・ Acrylic resin 69.6 parts
(Dianar BR-83, manufactured by Mitsubishi Rayon Co., Ltd.)
17.4 parts of an acrylic copolymer reactively bonded with a reactive ultraviolet absorber (UVA635L, manufactured by BASF Japan)
・ Silica 25 parts (Silicia 310, manufactured by Fuji Silysia)
・ Methyl ethyl ketone 100 parts ・ Toluene 100 parts

(Preparation of thermal transfer sheet 2)
A thermal transfer sheet 2 was obtained in the same manner as the thermal transfer sheet 1 except that the back layer coating solution 1 was changed to the back layer coating solution 2 having the following composition.

<Back layer coating liquid 2>
・ 35 parts of polyvinyl acetal resin (SREC KS-3 manufactured by Sekisui Chemical Co., Ltd.)
・ Polyisocyanate (solid content 100% NCO = 17.3 mass%) 30 parts (Bernock D750-45, manufactured by Dainippon Ink & Chemicals, Inc.)
Cellulose acetate butyrate resin (molecular weight 6000) 10 parts (Solus 2100 manufactured by Eastman Chemical Company)
-Zinc stearyl phosphate 10 parts (LBT-1830 refining Sakai Chemical Industry Co., Ltd.)
・ 10 parts of zinc stearate (SZ-PF manufactured by Sakai Chemical Industry Co., Ltd.)
・ 5 parts of talc (Microace P-3 manufactured by Nippon Talc Industry Co., Ltd.)
・ Methyl ethyl ketone 450 parts ・ Toluene 450 parts

(Preparation of thermal transfer sheet 3)
A thermal transfer sheet 3 was obtained in the same manner as the thermal transfer sheet 1 except that the back layer coating solution 1 was changed to the back layer coating solution 3 having the following composition.

<Back layer coating liquid 3>
・ 24.2 parts of polyvinyl acetal resin (manufactured by SREC BX-1 by Sekisui Chemical Co., Ltd.)
Polyisocyanate (solid content: 100% NCO = 17.3 mass%) 20.8 parts (Bernock D750-45, Dainippon Ink & Chemicals, Inc.)
Cellulose acetate butyrate resin (molecular weight 6000) 30 parts (Solus 2100 manufactured by Eastman Chemical Company)
-Zinc stearyl phosphate 10 parts (LBT-1830 refining Sakai Chemical Industry Co., Ltd.)
・ 10 parts of zinc stearate (SZ-PF manufactured by Sakai Chemical Industry Co., Ltd.)
・ 5 parts of talc (Microace P-3 manufactured by Nippon Talc Industry Co., Ltd.)
・ Methyl ethyl ketone 450 parts ・ Toluene 450 parts

(Preparation of thermal transfer sheet 4)
A thermal transfer sheet 4 was obtained in the same manner as the thermal transfer sheet 1 except that the back layer coating solution 1 was changed to the back layer coating solution 4 having the following composition.

<Back layer coating liquid 4>
・ 18.8 parts of polyvinyl acetal resin (SREC BX-1 manufactured by Sekisui Chemical Co., Ltd.)
Polyisocyanate (solid content 100% NCO = 17.3 mass%) 16.2 parts (Bernock D750-45, manufactured by Dainippon Ink & Chemicals, Inc.)
Cellulose acetate butyrate resin (molecular weight 6000) 40 parts (Solus 2100 manufactured by Eastman Chemical Company)
-Zinc stearyl phosphate 10 parts (LBT-1830 refining Sakai Chemical Industry Co., Ltd.)
・ 10 parts of zinc stearate (SZ-PF manufactured by Sakai Chemical Industry Co., Ltd.)
・ 5 parts of talc (Microace P-3 manufactured by Nippon Talc Industry Co., Ltd.)
・ Methyl ethyl ketone 450 parts ・ Toluene 450 parts

(Preparation of thermal transfer sheet 5)
A thermal transfer sheet 5 was obtained in the same manner as the thermal transfer sheet 1 except that the back layer coating solution 1 was changed to the back layer coating solution 5 having the following composition.

<Back layer coating liquid 5>
・ 38.8 parts of polyvinyl acetal resin (SREC BX-1 manufactured by Sekisui Chemical Co., Ltd.)
Polyisocyanate (solid content: 100% NCO = 17.3 mass%) 33.2 parts (Bernock D750-45 manufactured by Dainippon Ink & Chemicals, Inc.)
Cellulose acetate butyrate resin (molecular weight 6000) 3 parts (Solus 2100 manufactured by Eastman Chemical Company)
-Zinc stearyl phosphate 10 parts (LBT-1830 refining Sakai Chemical Industry Co., Ltd.)
・ 10 parts of zinc stearate (SZ-PF manufactured by Sakai Chemical Industry Co., Ltd.)
・ 5 parts of talc (Microace P-3 manufactured by Nippon Talc Industry Co., Ltd.)
・ Methyl ethyl ketone 450 parts ・ Toluene 450 parts

(Preparation of thermal transfer sheet 6)
A thermal transfer sheet 6 was obtained in the same manner as the thermal transfer sheet 1 except that the back layer coating solution 1 was changed to the back layer coating solution 6 having the following composition.

<Back layer coating liquid 6>
・ 45 parts of polyvinyl acetal resin (SREC BX-1 manufactured by Sekisui Chemical Co., Ltd.)
Cellulose acetate butyrate resin (molecular weight 6000) 30 parts (Solus 2100 manufactured by Eastman Chemical Company)
-Zinc stearyl phosphate 10 parts (LBT-1830 refining Sakai Chemical Industry Co., Ltd.)
・ 10 parts of zinc stearate (SZ-PF manufactured by Sakai Chemical Industry Co., Ltd.)
・ 5 parts of talc (Microace P-3 manufactured by Nippon Talc Industry Co., Ltd.)
・ Methyl ethyl ketone 450 parts ・ Toluene 450 parts

(Preparation of thermal transfer sheet 7)
A thermal transfer sheet 7 was obtained in the same manner as the thermal transfer sheet 1 except that the back layer coating solution 1 was changed to the back layer coating solution 7 having the following composition.

<Back layer coating liquid 7>
・ 35 parts of polyvinyl acetal resin (SREC BX-1 manufactured by Sekisui Chemical Co., Ltd.)
・ Polyisocyanate (solid content 100% NCO = 17.3 mass%) 30 parts (Bernock D750-45, manufactured by Dainippon Ink & Chemicals, Inc.)
Cellulose acetate butyrate resin (molecular weight 16000) 10 parts (CAB551-0.01 manufactured by Eastman Chemical Company)
-Zinc stearyl phosphate 10 parts (LBT-1830 refining Sakai Chemical Industry Co., Ltd.)
・ 10 parts of zinc stearate (SZ-PF manufactured by Sakai Chemical Industry Co., Ltd.)
・ 5 parts of talc (Microace P-3 manufactured by Nippon Talc Industry Co., Ltd.)
・ Methyl ethyl ketone 450 parts ・ Toluene 450 parts

(Preparation of thermal transfer sheet 8)
A thermal transfer sheet 8 was obtained in the same manner as the thermal transfer sheet 1 except that the back layer coating solution 1 was changed to the back layer coating solution 8 having the following composition.

<Back layer coating liquid 8>
・ 35 parts of polyvinyl acetal resin (SREC BX-1 manufactured by Sekisui Chemical Co., Ltd.)
・ Polyisocyanate (solid content 100% NCO = 17.3 mass%) 30 parts (Bernock D750-45, manufactured by Dainippon Ink & Chemicals, Inc.)
Cellulose acetate butyrate resin (molecular weight 40000) 10 parts (CAB531-1 manufactured by Eastman Chemical Company)
-Zinc stearyl phosphate 10 parts (LBT-1830 refining Sakai Chemical Industry Co., Ltd.)
・ 10 parts of zinc stearate (SZ-PF manufactured by Sakai Chemical Industry Co., Ltd.)
・ 5 parts of talc (Microace P-3 manufactured by Nippon Talc Industry Co., Ltd.)
・ Methyl ethyl ketone 450 parts ・ Toluene 450 parts

(Preparation of thermal transfer sheet 9)
A thermal transfer sheet 9 was obtained in the same manner as the thermal transfer sheet 1 except that the back layer coating solution 1 was changed to the back layer coating solution 9 having the following composition.

<Back layer coating liquid 9>
・ 35 parts of polyvinyl acetal resin (SREC BX-1 manufactured by Sekisui Chemical Co., Ltd.)
・ Polyisocyanate (solid content 100% NCO = 17.3 mass%) 30 parts (Bernock D750-45, manufactured by Dainippon Ink & Chemicals, Inc.)
Cellulose acetate propionate resin (molecular weight 15000) 10 parts (CAP504-0.2 manufactured by Eastman Chemical Company)
-Zinc stearyl phosphate 10 parts (LBT-1830 refining Sakai Chemical Industry Co., Ltd.)
・ 10 parts of zinc stearate (SZ-PF manufactured by Sakai Chemical Industry Co., Ltd.)
・ 5 parts of talc (Microace P-3 manufactured by Nippon Talc Industry Co., Ltd.)
・ Methyl ethyl ketone 450 parts ・ Toluene 450 parts

(Preparation of thermal transfer sheet 10)
A thermal transfer sheet 10 was obtained in the same manner as the thermal transfer sheet 1 except that the back layer coating solution 1 was changed to the back layer coating solution 10 having the following composition.

<Back layer coating liquid 10>
・ 35 parts of polyvinyl acetal resin (SREC BX-1 manufactured by Sekisui Chemical Co., Ltd.)
・ Polyisocyanate (solid content 100% NCO = 17.3 mass%) 30 parts (Bernock D750-45, manufactured by Dainippon Ink & Chemicals, Inc.)
Cellulose acetate propionate resin (molecular weight 25000) 10 parts (CAP482-0.5 manufactured by Eastman Chemical Company)
-Zinc stearyl phosphate 10 parts (LBT-1830 refining Sakai Chemical Industry Co., Ltd.)
・ 10 parts of zinc stearate (SZ-PF manufactured by Sakai Chemical Industry Co., Ltd.)
・ 5 parts of talc (Microace P-3 manufactured by Nippon Talc Industry Co., Ltd.)
・ Methyl ethyl ketone 450 parts ・ Toluene 450 parts

(Preparation of thermal transfer sheet 11)
A thermal transfer sheet 11 was obtained in the same manner as the thermal transfer sheet 1 except that the back layer coating solution 1 was changed to the back layer coating solution 11 having the following composition.

<Back surface layer coating solution 11>
・ 35 parts of polyvinyl acetal resin (SREC BX-1 manufactured by Sekisui Chemical Co., Ltd.)
・ Polyisocyanate (solid content 100% NCO = 17.3 mass%) 30 parts (Bernock D750-45, manufactured by Dainippon Ink & Chemicals, Inc.)
Cellulose acetate propionate resin (molecular weight 25,000) 10 parts (CAP482-0.5 manufactured by Eastman Chemical Company)
-Zinc stearyl phosphate 6.6 parts (LBT-1830 purification, Sakai Chemical Industry Co., Ltd.)
・ Zinc stearate 6.6 parts (SZ-PF Sakai Chemical Industry Co., Ltd.)
・ Phosphate 6.6 parts (Pricesurf A-208N Daiichi Kogyo Seiyaku Co., Ltd.)
・ 5 parts of talc (Microace P-3 manufactured by Nippon Talc Industry Co., Ltd.)
・ Methyl ethyl ketone 450 parts ・ Toluene 450 parts

(Preparation of thermal transfer sheet A)
A thermal transfer sheet A was obtained in the same manner as the thermal transfer sheet 1 except that the back layer coating solution 1 was changed to the back layer coating solution A having the following composition.

<Back layer coating liquid A>
・ 45 parts of polyvinyl acetal resin (SREC BX-1 manufactured by Sekisui Chemical Co., Ltd.)
・ Polyisocyanate (solid content 100% NCO = 17.3 mass%) 30 parts (Bernock D750-45, manufactured by Dainippon Ink & Chemicals, Inc.)
-Zinc stearyl phosphate 10 parts (LBT-1830 refining Sakai Chemical Industry Co., Ltd.)
・ 10 parts of zinc stearate (SZ-PF manufactured by Sakai Chemical Industry Co., Ltd.)
・ 5 parts of talc (Microace P-3 manufactured by Nippon Talc Industry Co., Ltd.)
・ Methyl ethyl ketone 450 parts ・ Toluene 450 parts

(Preparation of thermal transfer sheet B)
A thermal transfer sheet B was obtained in the same manner as the thermal transfer sheet 1 except that the back layer coating liquid 1 was changed to the back layer coating liquid B having the following composition.

<Back layer coating liquid B>
・ 13.5 parts of polyvinyl acetal resin (SREC BX-1 manufactured by Sekisui Chemical Co., Ltd.)
・ Polyisocyanate (solid content 100% NCO = 17.3 mass%) 11.5 parts (Bernock D750-45, Dainippon Ink & Chemicals, Inc.)
Cellulose acetate butyrate resin (molecular weight 6,000) 50 parts (Solus 2100 manufactured by Eastman Chemical Company)
-Zinc stearyl phosphate 10 parts (LBT-1830 refining Sakai Chemical Industry Co., Ltd.)
・ 10 parts of zinc stearate (SZ-PF manufactured by Sakai Chemical Industry Co., Ltd.)
・ 5 parts of talc (Microace P-3 manufactured by Nippon Talc Industry Co., Ltd.)
・ Methyl ethyl ketone 450 parts ・ Toluene 450 parts

(Preparation of thermal transfer sheet C)
A thermal transfer sheet C was obtained in the same manner as the thermal transfer sheet 1 except that the back layer coating solution 1 was changed to the back layer coating solution C having the following composition.

<Back layer coating liquid C>
・ 13.5 parts of polyvinyl acetal resin (SREC BX-1 manufactured by Sekisui Chemical Co., Ltd.)
・ Polyisocyanate (solid content 100% NCO = 17.3 mass%) 11.5 parts (Bernock D750-45, Dainippon Ink & Chemicals, Inc.)
Cellulose acetate propionate resin (molecular weight 40,000) 50 parts (CAP482-0.5 manufactured by Eastman Chemical Company)
-Zinc stearyl phosphate 10 parts (LBT-1830 refining Sakai Chemical Industry Co., Ltd.)
・ 10 parts of zinc stearate (SZ-PF manufactured by Sakai Chemical Industry Co., Ltd.)
・ 5 parts of talc (Microace P-3 manufactured by Nippon Talc Industry Co., Ltd.)
・ Methyl ethyl ketone 450 parts ・ Toluene 450 parts

(Preparation of thermal transfer sheet D)
A thermal transfer sheet D was obtained in the same manner as the thermal transfer sheet 1 except that the back layer coating liquid 1 was changed to the back layer coating liquid D having the following composition.

<Back layer coating liquid D>
・ 35 parts of polyvinyl acetal resin (SREC BX-1 manufactured by Sekisui Chemical Co., Ltd.)
・ Polyisocyanate (solid content 100% NCO = 17.3 mass%) 30 parts (Bernock D750-45, manufactured by Dainippon Ink & Chemicals, Inc.)
-Acrylic resin (Molecular weight (Mw) 25000) 10 parts Dianal BR-87 manufactured by Mitsubishi Rayon Co., Ltd.
-Zinc stearyl phosphate 10 parts (LBT-1830 refining Sakai Chemical Industry Co., Ltd.)
・ 10 parts of zinc stearate (SZ-PF manufactured by Sakai Chemical Industry Co., Ltd.)
・ 5 parts of talc (Microace P-3 manufactured by Nippon Talc Industry Co., Ltd.)
・ Methyl ethyl ketone 450 parts ・ Toluene 450 parts

(Preparation of thermal transfer sheet E)
A thermal transfer sheet E was obtained in the same manner as the thermal transfer sheet 1 except that the back layer coating liquid 1 was changed to the back layer coating liquid E having the following composition.

<Back layer coating liquid E>
・ 35 parts of polyvinyl acetal resin (SREC BX-1 manufactured by Sekisui Chemical Co., Ltd.)
・ Polyisocyanate (solid content 100% NCO = 17.3 mass%) 30 parts (Bernock D750-45, manufactured by Dainippon Ink & Chemicals, Inc.)
・ Polyvinyl butyral resin (Molecular weight (Mw) = 40000) 10 parts ESREC BM-1 Sekisui Chemical Co., Ltd.)
-Zinc stearyl phosphate 10 parts (LBT-1830 refining Sakai Chemical Industry Co., Ltd.)
・ 10 parts of zinc stearate (SZ-PF manufactured by Sakai Chemical Industry Co., Ltd.)
・ 5 parts of talc (Microace P-3 manufactured by Nippon Talc Industry Co., Ltd.)
・ Methyl ethyl ketone 450 parts ・ Toluene 450 parts

(Preparation of thermal transfer sheet F)
A thermal transfer sheet F was obtained in the same manner as the thermal transfer sheet 1 except that the back layer coating solution 1 was changed to the back layer coating solution F having the following composition.

<Back layer coating liquid F>
・ 35 parts of polyvinyl acetal resin (SREC BX-1 manufactured by Sekisui Chemical Co., Ltd.)
Polyvinyl acetal resin (Molecular weight (Mw) = 27000) 10 parts (ESREC KS-1 Sekisui Chemical Co., Ltd.)
・ Polyisocyanate (solid content 100% NCO = 17.3 mass%) 30 parts (Bernock D750-45, manufactured by Dainippon Ink & Chemicals, Inc.)
-Zinc stearyl phosphate 10 parts (LBT-1830 refining Sakai Chemical Industry Co., Ltd.)
・ 10 parts of zinc stearate (SZ-PF manufactured by Sakai Chemical Industry Co., Ltd.)
・ 5 parts of talc (Microace P-3 manufactured by Nippon Talc Industry Co., Ltd.)
・ Methyl ethyl ketone 450 parts ・ Toluene 450 parts

(Preparation of thermal transfer sheet G)
A thermal transfer sheet G was obtained in the same manner as the thermal transfer sheet 1 except that the back layer coating solution 1 was changed to the back layer coating solution G having the following composition.

<Back layer coating liquid G>
・ 40 parts of polyvinyl acetal resin (S-REC BX-1 manufactured by Sekisui Chemical Co., Ltd.)
Cellulose acetate butyrate resin (molecular weight 16000) 60 parts (CAB551-0.01 manufactured by Eastman Chemical Company)
・ Zinc stearate 5 parts (SZ-PF Sakai Chemical Industry Co., Ltd.)
・ Silicone-modified acrylic resin 16.7 parts (Symac US-380, solid content 30 wt%, manufactured by Toagosei Co., Ltd.)
・ 5 parts of talc (Microace P-3 manufactured by Nippon Talc Industry Co., Ltd.)
・ Methyl ethyl ketone 484.5 parts ・ Toluene 484.5 parts

(Preparation of thermal transfer image-receiving sheet 1)
Using RC paper (manufactured by Mitsubishi Paper Industries Co., Ltd.) as the base sheet, heat-treating coating solution for heat-insulating layer and dye-receiving layer coating solution 1 having the following compositions were each heated to 40 ° C., and using slide coating, The film was applied to a thickness of 12 μm and 3 μm when dried, cooled at 5 ° C. for 30 seconds, and then dried at 50 ° C. for 2 minutes to obtain a thermal transfer image receiving sheet 1. In addition, all the coating liquids of the following composition are diluted with pure water so that the total solid content is 15 to 30%.

<Coating liquid for heat insulation layer>
・ Hollow particles (volume average particle size: 0.5 μm) 70 parts (MH5055 manufactured by Nippon Zeon Co., Ltd.)
・ Gelatin 25 parts (RR Nitta Gelatin Co., Ltd.)
・ Water-based polyurethane resin 5 parts (AP40 manufactured by DIC Corporation)

<Receptive layer coating solution 1>
・ Vinyl chloride-based emulsion (PVC / Vinyl acetate = 97.5 / 2.5): solid content 36%) 411 parts ・ Aqueous dispersion of release agent (solid content: 17%) 98 parts ・ Epoxy crosslinking agent 7 .6 parts (manufactured by Nagase ChemteX Corporation, trade name EX-512: solid content 100%)
・ Pure water (for epoxy crosslinker dispersion) 11.4 parts ・ Thickener (solid content 30%) 45 parts (Adecanol UH-526, manufactured by ADEKA Corporation)
・ Pure water (for thickener dispersion) 230 parts ・ Surfactant (sodium dioctylsulfosuccinate aqueous solution: solid content 20%) 23 parts The above-mentioned vinyl chloride emulsion and the aqueous dispersion of the release agent are as follows: It was prepared as described above.

(Synthesis of vinyl chloride-based emulsion)
In a 2.5 L autoclave, 600 g of deionized water, 438.8 g of vinyl chloride monomer (97.5% by weight based on the total charged monomer) and 11.2 g of vinyl acetate (2% based on the total charged monomer) 0.5 wt.%) Was charged with 2.25 g of potassium persulfate. The reaction mixture was stirred with a stirring blade so as to maintain a rotation speed of 120 rpm, and the temperature of the reaction mixture was raised to 60 ° C. to initiate polymerization. 180 g of 5% by weight aqueous sodium dodecylbenzenesulfonate solution (2% by weight based on the total amount of charged monomers) was continuously added from the start of polymerization to 4 hours later, and the saturated vapor pressure of the vinyl chloride monomer at a polymerization pressure of 60 ° C. The polymerization was stopped when the pressure dropped from 0.6 MPa to a residual monomer, and a vinyl acetate emulsion was obtained.

(Creation of aqueous dispersion of release agent)
16 g of epoxy-modified silicone (trade name X-22-3000T, manufactured by Shin-Etsu Chemical Co., Ltd.) and 8 g of aralkyl-modified silicone (trade name X-24-510, manufactured by Shin-Etsu Chemical Co., Ltd.) were dissolved in 85 g of ethyl acetate. . Next, 14 g of sodium triisopropyl naphthalene sulfonate (solid content: 10%) was dissolved in 110 g of pure water. The two liquids were mixed and stirred, and then dispersed using a homogenizer to prepare a dispersion. Thereafter, ethyl acetate was removed under reduced pressure while heating the dispersion to 30 to 60 ° C. to obtain an aqueous dispersion of silicone.

(Preparation of thermal transfer image receiving sheet 2)
A thermal transfer image receiving sheet 2 was obtained in the same manner as the thermal transfer image receiving sheet 1 except that the receiving layer coating liquid 1 was changed to the receiving layer coating liquid 2 having the following composition.

<Receptive layer coating solution 2>
・ 80 parts of vinyl chloride resin (Viniblanc 900 manufactured by Nissin Chemical Industry Co., Ltd.)
-10 parts of polyether-modified silicone (KF615A manufactured by Shin-Etsu Chemical Co., Ltd.)
・ Gelatin 20 parts (G-0637K Nitta Gelatin Co., Ltd.)
・ Surfactant 0.5 part (Surfinol 440 manufactured by Nissin Chemical Industry Co., Ltd.)
・ 400 parts of water

(Preparation of thermal transfer image receiving sheet 3)
A thermal transfer image-receiving sheet 3 was obtained in the same manner as the thermal transfer image-receiving sheet 1 except that the receiving-layer coating liquid 1 was changed to a receiving-layer coating liquid 3 having the following composition.

<Receptive layer coating solution 3>
・ Emulsion (as solids) 90 parts ・ Gelatin (as solids) 10 parts (RR Nitta Gelatin Co., Ltd.)
-10 parts of polyether-modified silicone (KF615A manufactured by Shin-Etsu Chemical Co., Ltd.)
・ Surfactant 1 part (Surfinol 440 manufactured by Nissin Chemical Industry Co., Ltd.)
-333 parts of water The above emulsion was prepared as follows.
Synthesis of emulsion In a 500 mL (liter) Erlenmeyer flask, 121 g of styrene, 77 g of ethyl acrylate and 2 g of acrylic acid as copolymer forming monomers and 1.9 g of Aqualon HS-10 (Daiichi Kogyo Seiyaku Co., Ltd.) as an emulsifier are placed. The mixture was stirred and mixed (hereinafter referred to as monomer A). In a 1 L three-necked flask, 200 g of distilled water was added and heated to 80 ° C., and about 20% of the total amount of the monomer A was added and stirred for 10 minutes. Thereafter, 0.4 g of ammonium persulfate dissolved in 20 g of pure water was added and stirred for 10 minutes, and then the remaining 80% of the monomer A was dropped with a dropping funnel over 3 hours and further stirred for 3 hours. Thereafter, the mixture was cooled to room temperature and filtered through # 150 mesh (Japanese fabric) to obtain an emulsion (molecular weight 240000, Tg 50 ° C.). Further, from the molecular weight of styrene and ethyl acrylate and the amount used for the reaction, the respective molar ratios are 60% and 40%.

(Combination of thermal transfer sheet and thermal transfer image receiving sheet in Examples and Comparative Examples)
In the print wrinkle evaluation and the gloss evaluation, the combinations of the thermal transfer sheet and the thermal transfer image receiving sheet shown in Table 1 below are the combinations of the thermal transfer sheet and the thermal transfer image receiving sheet of Examples 1 to 13 and Comparative Examples 1 to 7, respectively.

(Print wrinkle evaluation)
A thermal transfer sheet 1 based on the combination of Example 1 is attached to each of the Y area, M area, and C area of a media set CW-MS46 of a sublimation type thermal transfer printer (manufactured by ALTECH ADS Co., Ltd .; model: CW-01). In addition, after the thermal transfer image receiving sheet 1 based on the combination of the printer and Example 1 is left in a low temperature and low humidity environment (5 ° C., 20%) for 3 hours, (1) a solid black image, (2) Right black image (left white), (3) Left black image (right white), and (4) Middle black image (left and right white), each 5 sheets (20 sheets in total) are printed and based on the following evaluation criteria The print wrinkles were evaluated. This printing was carried out for all combinations of the examples and comparative examples described in Table 1 above. The black image is an image formed with (255/255 gradation), and the white image is an image formed with (0/255 gradation). Table 2 shows the evaluation results of the printing wrinkles in the combination of each example and the comparative example.
"Evaluation criteria"
A: Wrinkles are not generated in all images ((1) to (4)).
○: Wrinkles occur in one image of any one of (1) to (4).
(Triangle | delta): A wrinkle generate | occur | produces in 2-3 types of images among the images of (1)-(4).
X: Wrinkles occur in all images (1) to (4).

(Gloss evaluation)
Thermal transfer sheet 1 based on the combination of Example 1 in the Y region, M region, C region, and OP region of the media set CW-MS46 of a sublimation type thermal transfer printer (manufactured by ALTECH ADS Co., Ltd .; model: CW-01) The thermal transfer image-receiving sheet 1 based on the combination of the printer and Example 1 was left in a high-temperature and high-humidity environment (40 ° C., 85%) for 3 hours so as not to cause condensation. A black solid image (255/255 gradations) was printed on the sheet 1, and the glossiness was measured. This printing and the measurement of glossiness were carried out in the same manner for all combinations of Examples and Comparative Examples described in Table 1 above. The glossiness was measured by a gloss meter (Nippon Denshoku Co., Ltd., model: VG2000) 45 ° measurement, and gloss evaluation was performed based on the following evaluation criteria. The evaluation results are also shown in Table 2.
"Evaluation criteria"
A: When the glossiness of an image formed by the combination of Comparative Example 1 is 100, the glossiness is 110 or more.
A: When the glossiness of an image formed by the combination of Comparative Example 1 is 100, the glossiness is 105 or more and less than 110.
X: When the glossiness of an image formed by the combination of Comparative Example 1 is 100, the glossiness is less than 105.

  According to Examples 1 to 13 that satisfy all the invention specific matters of the thermal transfer sheet and thermal transfer image-receiving sheet used in the image forming method of the present invention and the combination of the present invention, there is no generation of printing wrinkles and no reduction in glossiness, and gloss An image having excellent feeling and no print wrinkles or few wrinkles could be formed. On the other hand, all the comparative examples which do not contain a cellulosic resin in the back layer or the content of the cellulosic resin contained in the back layer is out of the scope of the present invention have a lower gloss than the examples. became. Moreover, the evaluation of printing wrinkles was low except for Comparative Example 2 containing a cellulose resin. From the above results, the superiority of the image forming method of the present invention and the combination of the present invention became clear.

DESCRIPTION OF SYMBOLS 10 ... Thermal transfer sheet 30 ... Thermal transfer image receiving sheet 1 ... Base material 2 ... Dye layer 3 ... Back layer 21 ... Other base materials 22 ... Dye receiving layer

Claims (2)

A thermal transfer sheet provided with a back layer on one side of the substrate and a dye layer on the other side of the substrate,
The back layer contains (A) a polyvinyl acetal resin or polyvinyl butyral resin, (B) a cellulose-based resin, and (C) a lubricant component.
The (B) cellulosic resin is contained within a range of 3% by mass to 40% by mass with respect to the total solid content of the back layer ,
The thermal transfer sheet, wherein the (B) cellulose resin is a cellulose acetate butyrate resin or a cellulose acetate propionate resin .   The thermal transfer sheet according to claim 1, wherein the (A) polyvinyl acetal resin or polyvinyl butyral resin is a polyvinyl acetal resin having a crosslinked structure or a polyvinyl butyral resin having a crosslinked structure.

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