JP5542077B2 - Thermal transfer image receiving sheet - Google Patents

Description

  The present invention relates to a thermal transfer image receiving sheet that is used while being superposed on a thermal transfer sheet, and more particularly to a thermal transfer image receiving sheet that is excellent in print image storage stability and capable of forming a high density and high resolution recorded image.

  Various thermal transfer recording systems have been known so far, and among them, there is a sublimation transfer recording system. In the sublimation transfer recording system, a thermal transfer sheet is used in which a sublimation transfer dye is used as a colorant and this is supported on a base material sheet such as a polyester film. Then, using the sublimation transfer recording method, a transfer material that can be dyed with a sublimation dye, for example, a thermal transfer image receiving sheet in which a dye receiving layer is formed on paper or a plastic film, is transferred from the thermal transfer sheet to the base material. A method for thermally transferring a sublimation transfer dye supported on a material to form various full-color images has been proposed.

  In this case, a thermal head that generates heat in response to a recording signal is used, and multicolored dots are transferred to the receiving layer of the thermal transfer image receiving sheet by heating for a very short time to obtain a full color image. According to this recording method, the image formed by the dye is very clear and excellent in transparency, so that the obtained image is excellent in reproducibility of intermediate colors and gradations, and by conventional offset printing or gravure printing. It is possible to form a high-quality image similar to the image and comparable to a silver salt photograph.

  As described above, the thermal transfer image receiving sheet used in the sublimation transfer system has a receiving layer for dyeing a dye on a substrate. Furthermore, an intermediate layer is formed between the base material and the receiving layer in order to provide cushioning properties and flexibility. However, since the interlayer resin generally used has poor barrier properties for preventing diffusion of the dye, the dye image diffuses into the interlayer when the thermal transfer image-receiving sheet is stored at a high temperature for a long period of time. There is a problem that a clear image disappears due to blurring or blurring. Moreover, there exists adhesiveness between a base material and a receiving layer as a required performance with respect to the above-mentioned intermediate | middle layer. This is because it is necessary to prevent the receiving layer from peeling off from the base material when an image is formed in the printer or when a printed image is used.

  For this reason, a material using a polyvinyl alcohol resin, a polyurethane resin, or a mixture thereof excellent in barrier properties (for preventing dye diffusion) has been proposed as a material for forming the intermediate layer. However, these are still insufficient in terms of the barrier effect for preventing the diffusion of the dye image as the intermediate layer and the adhesion to the substrate and the dye receiving layer (see, for example, Patent Documents 1 and 2).

  Furthermore, recently, due to increasing environmental problems, many manufacturers are actively working on this measure, and there is a movement to construct products using materials with excellent environmental conservation, and thermal transfer image receiving sheets are no exception. For example, it is considered that a specific solvent is not selected from organic solvents used when the resin used for the intermediate layer and the dye image-receiving layer (receiving layer) is produced, or a VOC (volatile) is used by using an aqueous resin instead of the organic solvent. Studies are underway to reduce emissions of organic compounds) as much as possible. However, it is still insufficient to meet the current environmental conservation on a global scale.

  As a resin using carbon dioxide as a production raw material, a polyhydroxy polyurethane resin has been known for a long time (see, for example, Patent Documents 3 and 4), but its application development has not progressed. This is because the polyhydroxy polyurethane resin is clearly inferior in terms of its characteristics as compared to the polyurethane resin compared as the same type of polymer compound.

  On the other hand, in recent years, the global warming phenomenon, which is thought to be caused by the ever-increasing amount of carbon dioxide emissions, has become a global problem, and the reduction of carbon dioxide emissions is an important issue worldwide. It has become. Furthermore, from the viewpoint of exhaustible petrochemical resources (petroleum), the shift to renewable resources such as biomass and methane has become a global trend (for example, Non-Patent Documents 1 and 2), and carbon dioxide is used as a raw material for production. The development of technology that can be

  Against the background as described above, the polyhydroxy polyurethane resin has been reviewed again. That is, carbon dioxide, which is a raw material for the 5-membered cyclic carbonate compound constituting this resin, is a readily available and sustainable carbon resource, and a plastic that can use such carbon dioxide as a carbon raw material is This is because it can be an effective means for solving the problems such as global warming and resource depletion.

JP-A-8-276669 JP 11-34515 A U.S. Pat. No. 3,072,613 JP 2000-319504 A

N. Kihara, T. Endo, J. Org. Chem., 1993, 58, 6198 N. Kihara, T. Endo, J. Polymer Sci., Part A Polmer Chem., 1993, 31 (11), 2765

  Under such circumstances, the forming material used for the intermediate layer of the thermal transfer image receiving sheet used in the above-described sublimation type transfer system is also excellent in image storability and can form high density and high resolution printed images. In addition, there is a demand for the development of environmentally friendly products with environmental conservation on a global scale.

  Accordingly, an object of the present invention is to provide a conventional product in which an intermediate layer having a barrier effect for preventing the diffusion of a dye image and an adhesive property sufficient to prevent the dye-receiving layer from peeling off from a substrate is formed. It is an object of the present invention to provide a thermal transfer image receiving sheet that is excellent in image storability and capable of forming a high density and high resolution printed image. It is another object of the present invention to provide a thermal transfer image receiving sheet in which an intermediate layer capable of realizing the above excellent characteristics is formed of a material that also contributes to environmental conservation.

  The above object is achieved by the present invention described below. That is, the present invention is a thermal transfer image-receiving sheet in which an intermediate layer and a dye-receiving layer are laminated in this order on at least one surface of a substrate, and the intermediate layer is mainly composed of a polyhydroxy polyurethane resin. A thermal transfer image receiving sheet is provided.

  Furthermore, as a preferred embodiment, the polyhydroxy polyurethane resin has a hydroxyl value of 50 to 350 mg KOH / g; the polyhydroxy polyurethane resin is derived from a reaction between a 5-membered cyclic carbonate compound and an amine compound. It is a resin; the 5-membered cyclic carbonate compound is a reaction product of an epoxy compound and carbon dioxide; the polyhydroxy polyurethane resin contains carbon dioxide in the range of 1 to 25% by mass in the resin structure. Inclusion.

  Moreover, in the said invention, the said polyhydroxy polyurethane resin is bridge | crosslinked with the crosslinking agent which reacts with the hydroxyl group which comprises resin; The said intermediate | middle layer contains a white pigment and / or a fluorescent whitening agent. Is preferred.

  According to the present invention, the intermediate layer of the thermal transfer image-receiving sheet is configured as described above, so that the intermediate layer prevents the dye image from diffusing and the dye-receiving layer peels from the substrate. Exhibits excellent adhesiveness sufficient to prevent damage, especially when used in a sublimation transfer method, superior to existing products, or better than other products, with excellent image storage, high density and high resolution There is provided a thermal transfer image receiving sheet which is a product capable of forming a printed image. At the same time, according to the present invention, since the material in which carbon dioxide is incorporated and fixed in the resin can be used as the intermediate layer forming material, it contributes to the reduction of carbon dioxide, which is regarded as a global problem as a warming gas. It is possible to provide a thermal transfer image-receiving sheet that is also an environmentally friendly product.

Next, the present invention will be described in more detail with reference to preferred embodiments.
The thermal transfer image-receiving sheet of the present invention comprises an intermediate layer and a dye-receiving layer (hereinafter sometimes simply referred to as a receiving layer) laminated in this order on at least one surface of the base material to constitute the intermediate layer. The high molecular compound to be formed is mainly composed of a polyhydroxy polyurethane resin. More preferably, a polyhydroxy polyurethane resin derived from a reaction between a 5-membered cyclic carbonate compound and an amine compound is used as the polyhydroxy polyurethane resin. Further, the resin preferably has a hydroxyl value of 50 to 350 mgKOH / g. Each configuration will be described below.

<Base material>
The base material constituting the thermal transfer image-receiving sheet of the present invention has a role of holding the receiving layer, and heat is applied during thermal transfer, so it is formed using a film having relatively good heat resistance, such as the following. It is preferable. For example, various films such as polyester, polypropylene, PEEK, PEN, PET, polystyrene, polysulfone, aromatic polyamide, polyimide, polycarbonate, triacetylocellulose, synthetic paper (polyolefin, polystyrene), fine paper, art paper, Examples thereof include coated paper and cast coated paper.

  The thickness of these base materials may be arbitrary, and is usually about 10 to 300 μm. Moreover, when the adhesiveness of these base materials and the layer (after-mentioned intermediate | middle layer) provided on them is scarce, it is preferable to perform various primer processing and corona discharge processing on the surface of a base material. On the surface (back surface) opposite to the side on which the above intermediate layer is provided, a layer for the purpose of imparting releasability or conductivity may be further provided.

<Intermediate layer>
The present invention is characterized in that the intermediate layer laminated on the base material is formed mainly of a polyhydroxy polyurethane resin. The polyhydroxy polyurethane resin characterizing the present invention is preferably a resin derived from the reaction of a 5-membered cyclic carbonate compound and an amine compound. The 5-membered cyclic carbonate compound can be produced, for example, by reacting an epoxy compound and carbon dioxide as shown by the following [Formula-A]. More particularly, the epoxy compound is carbon dioxide in the presence or absence of an organic solvent and in the presence of a catalyst at a temperature of 40 ° C. to 150 ° C. at normal pressure or slightly elevated pressure for 10-20 hours. It can obtain by making it react.

  Examples of the epoxy compound used in the present invention include the following compounds.

  The listed epoxy compounds are preferred compounds used in the present invention, and the present invention is not limited to these exemplified compounds. Accordingly, not only the above-exemplified compounds but also any other compounds that are currently commercially available and can be easily obtained from the market can be used in the present invention.

  The 5-membered cyclic carbonate compound used in the present invention can be obtained by the reaction of the above epoxy compound and carbon dioxide. Examples of catalysts that can be used in this reaction include base catalysts and Lewis acid catalysts.

  Examples of the base catalyst include tertiary amines such as triethylamine and tributylamine, cyclic amines such as diazabicycloundecene, diazabicyclooctane and pyridine, alkalis such as lithium chloride, lithium bromide, lithium fluoride and sodium chloride. Metal salts, alkaline earth metal salts such as calcium chloride, quaternary ammonium salts such as tetrabutylammonium chloride, tetraethylammonium bromide, benzyltrimethylammonium chloride, carbonates such as potassium carbonate and sodium carbonate, zinc acetate, lead acetate, Examples thereof include metal acetates such as copper acetate and iron acetate, metal oxides such as calcium oxide, magnesium oxide and zinc oxide, and phosphonium salts such as tetrabutylphosphonium chloride.

  Examples of the Lewis acid catalyst include tin compounds such as tetrabutyltin, dibutyltin dilaurate, dibutyltin diacetate, and dibutyltin octoate.

  The amount of these catalysts used may be 0.1 to 100 parts by weight, preferably 0.3 to 20 parts by weight, per 50 parts by weight of the epoxy compound. If the amount used is less than 0.1 parts by mass, the effect as a catalyst is small, and if it exceeds 100 parts by mass, various performances of the final resin may be deteriorated. Therefore, when the residual catalyst causes a serious performance deterioration, it may be removed by washing with pure water.

  Examples of the organic solvent that can be used in the reaction between the epoxy compound and carbon dioxide include dimethylformamide, dimethyl sulfoxide, dimethylacetamide, N-methylpyrrolidone, N-ethylpyrrolidone, and tetrahydrofuran. These organic solvents and other poor solvents such as methyl ethyl ketone, xylene, toluene, tetrahydrofuran, diethyl ether, and cyclohexanone may be used in a mixed system.

  As shown by the following [Formula-B], the polyhydroxypolyurethane resin used in the present invention comprises, for example, a 5-membered cyclic carbonate compound obtained by the above reaction and an amine compound in the presence of an organic solvent. It can obtain by making it react under the temperature of 20 to 150 degreeC below.

  As an amine compound used for the said reaction, diamine is preferable, for example, What was conventionally used for manufacture of a polyurethane resin can be used, and it is not specifically limited. For example, aliphatic diamines such as methylenediamine, ethylenediamine, trimethylenediamine, 1,3-diaminopropane, hexamethylenediamine, octamethylenediamine; phenylenediamine, 3,3′-dichloro-4,4′-diaminodiphenylmethane, 4 , 4′-methylenebis (phenylamine), 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylsulfone, metaxylylenediamine, paraxylylenediamine, and the like; 1,4-cyclohexanediamine, 4 , 4'-diaminocyclohexylmethane, 1,4'-diaminomethylcyclohexane, isophoronediamine and other alicyclic diamines; monoethanoldiamine, ethylaminoethanolamine, hydroxyethylaminopropylamine Like alkanol diamine is.

  The amine compounds listed above are preferable compounds used in the present invention, and the present invention is not limited to these exemplified compounds. Accordingly, not only the above-exemplified compounds but also any other compounds that are currently commercially available and can be easily obtained from the market can be used in the present invention.

  The polyhydroxy polyurethane resin used in the present invention preferably has a number average molecular weight (standard polystyrene conversion value measured by GPC) of about 2,000 to 100,000, more preferably 5,000 to About 70,000.

  In addition, the polyhydroxy polyurethane resin used in the present invention can exhibit a barrier property for preventing diffusion of a dye by forming a hydrogen bond between molecules by a hydroxyl group constituting the resin. In order to obtain a barrier effect sufficient to prevent the diffusion of the dye image targeted by the present invention by the intermediate layer characterizing the present invention, the hydroxyl value of the resin is preferably 50 to 350 mgKOH / g. If the hydroxyl group content is less than the above range, not only the barrier property of the formed intermediate layer may be inferior, but also the carbon dioxide reduction effect is insufficient, while if the hydroxyl group content exceeds the above range, the polymer It is not preferable because various physical properties as a compound are insufficient. In particular, in the thermal transfer image receiving sheet used in the sublimation transfer system, in order to ensure a sufficient barrier property against the sublimation dye in the intermediate layer, the polyhydroxy polyurethane resin used in the present invention has its oxygen gas permeability. Is preferably low. This is because it is generally said that there is a correlation between barrier properties for preventing dye diffusion and oxygen gas barrier properties.

  Furthermore, when forming an intermediate | middle layer, it can also be used as a crosslinked film by using the crosslinking agent which reacts with the hydroxyl group which comprises the said polyhydroxy polyurethane resin. By making the intermediate layer a cross-linked film, it is possible to improve the adhesion to the substrate and the adhesion to the receiving layer, and to better prevent the receiving layer from peeling from the substrate. Therefore, it is preferable. As the cross-linking agent, any cross-linking agent capable of reacting with a hydroxyl group in the resin can be used. For example, an alkyl titanate compound and a polyisocyanate compound can be mentioned, but known cross-linking agents conventionally used for crosslinking of polyurethane resins are preferable, but are not particularly limited. Specific examples include adducts of polyisocyanates having the following structural formula with other compounds.

  Moreover, when forming an intermediate | middle layer, you may use a white pigment as an additive with the above-mentioned polyhydroxy polyurethane resin. Examples of white pigments that can be used include titanium oxide, calcium carbonate, magnesium carbonate, and zinc oxide. It is preferable to add the white pigment as described above to the intermediate layer because it can conceal the glare and unevenness of the base material sheet to be laminated, so that the effect of increasing the freedom of selection of the base material is obtained. . The compounding ratio of these white pigments is preferably polyhydroxy polyurethane resin / white pigment = about 0.1 to 6.0 in terms of mass ratio, more preferably in the range of 0.5 to 3.0. Furthermore, a conventionally known fluorescent whitening agent may be used as an additive. The compounding ratio of the optical brightener is preferably polyhydroxypolyurethane resin / fluorescent brightener = 0.001 to 0.50, more preferably in the range of 0.005 to 0.20 in terms of mass ratio.

  In the present invention, it is preferable to use the above-mentioned polyhydroxypolyurethane resin alone as a resin component for forming the intermediate layer. However, for the purpose of imparting functions such as adhesion and film-formation improvement. Various conventionally known binder resins may be mixed and used. The binder resin used in combination is preferably a resin highly compatible with the polyhydroxy polyurethane resin described above. Moreover, the usage-amount should just be a grade which does not impair the effect of polyhydroxy polyurethane resin.

The intermediate layer can be easily formed by applying and drying a composition mainly composed of the polyhydroxy polyurethane resin as described above by a known method such as gravure, screen or reverse roll. The coating amount is preferably about 0.2 to 10.0 g / m ² , more preferably 0.5 to 4.0 g / m ² .

<Dye-receiving layer>
The thermal transfer image receiving sheet of the present invention is obtained by further laminating a dye receiving layer on the intermediate layer formed on the substrate as described above. The receiving layer is for receiving the dye transferred from the thermal transfer sheet when heated and maintaining the formed image. Examples of the resin for forming the receiving layer in the present invention include polyester resins, polyacrylate resins, polyvinyl acetate resins, polyurethane resins, polyolefin resins, polystyrene resins, and polyvinyl chloride resins. , Polyether resin, polyamide resin, polycarbonate resin, polypropylene resin, polyacrylate resin, polyacrylamide resin, polyvinyl butyral resin, polyvinyl acetal resin, vinyl chloride / vinyl acetate / vinyl alcohol copolymer resin, cellulose ester resin, An epoxy resin, a phenol resin, a melamine resin, etc. are mentioned, These are easily available from a market.

  Since the resins listed above generally have a low softening point, depending on the resin used, the receiving layer and the thermal transfer sheet may be fused by the heat of the thermal head generated during image formation. For this reason, for the purpose of obtaining better releasability, a receptive layer is formed by containing various release agents and releasable resins together with the resin, or on the receptive layer formed of the resin. A release layer may be laminated.

For the purpose of improving the whiteness and improving the sharpness of the transferred image or obtaining a matte feeling, the receiving layer is known in the technical field as necessary, for example, pigments, fillers, ultraviolet absorption You may use additives, such as an agent, antioxidant, and a light stabilizer. The dye-receiving layer constituting the thermal transfer image-receiving sheet of the present invention is appropriately used with the above-described resin, if necessary, and dissolved in an appropriate organic solvent or dispersed in an organic solvent or water. Then, it is formed by applying and drying in the same manner as the means for forming the intermediate layer. The thickness of the receiving layer to be formed is arbitrary, but is generally 1.0 to 20.0 g / m ² .

  The thermal transfer image-receiving sheet of the present invention comprises the intermediate layer and the receiving layer as described above, and a release layer is laminated on the receiving layer as necessary. In order to improve durability and prevent curling, a heat insulating layer, a cushion layer, an adhesive layer and an anti-curl layer may be further provided.

  Since the thermal transfer image-receiving sheet of the present invention having the above-described configuration has a specific intermediate layer, the barrier effect for preventing diffusion of the dye image and the substrate and the receiving layer can be sufficiently bonded. When used for thermal transfer, it is possible to effectively prevent the receiving layer from peeling off from the base material, which is comparable to or better than conventional products, and has excellent image storage stability. It can be formed. In addition, since the 5-membered cyclic carbonate compound used for the synthesis of the resin used for the intermediate layer in the present invention can use carbon dioxide as a raw material for production, it can reduce carbon dioxide, which is a cause of global warming. It is possible to provide a thermal transfer image receiving sheet as an environmentally friendly product that is useful from the viewpoint and could not be achieved by conventional products.

  Next, the present invention will be described in more detail with reference to specific production examples, polymerization examples, examples and comparative examples, but the present invention is not limited to these examples. In the following examples, “part” and “%” are based on mass unless otherwise specified.

<Production Example 1> (Production of 5-membered cyclic carbonate compound)
In a reaction vessel equipped with a stirrer, a thermometer, a gas inlet tube and a reflux condenser, a divalent epoxy compound represented by the following formula A (Epicoat 828 (trade name), manufactured by Japan Epoxy Resins Co., Ltd., epoxy equivalent 187 g) / Mol) 100 parts, 100 parts of N-methylpyrrolidone and 1.5 parts of sodium iodide were added and dissolved uniformly.

  Then, carbon dioxide gas was heated and stirred at 80 ° C. for 30 hours while bubbling at a rate of 0.5 liter / min. After completion of the reaction, the obtained solution was gradually added to 300 parts of n-hexane with high-speed stirring at 300 rpm, and the resulting powdery product was filtered through a filter, further washed with methanol, and N-methylpyrrolidone and Sodium iodide was removed. The powder was dried in a drier to obtain 118 parts (yield 95%) of a white powder 5-membered cyclic carbonate compound (1-A).

In the infrared absorption spectrum (Horiba FT-720) of the obtained product (1-A), the peak derived from the epoxy group of the raw material in the vicinity of 910 cm ⁻¹ almost disappeared in the product, and 1,800 cm ^−1. Absorption of a carbonyl group of a cyclic carbonate group not present in the raw material was confirmed in the vicinity. Moreover, the number average molecular weight of the product was 414 (polystyrene conversion, Tosoh; GPC-8220). In the obtained 5-membered cyclic carbonate compound (1-A), 19% of carbon dioxide was immobilized.

<Polymerization Examples 1-3> (Production of polyhydroxypolyurethane resin)
A reaction vessel equipped with a stirrer, a thermometer, a gas inlet tube and a reflux condenser was replaced with nitrogen, and the 5-membered cyclic carbonate compound (1-A) obtained in Production Example 1 had a solid content of 35%. Propylene glycol monomethyl ether acetate (PGM) was added and dissolved uniformly. Next, a predetermined equivalent amount of each amine compound shown in Table 1 was added, and the mixture was stirred at a temperature of 90 ° C. for 10 hours until the amine compound could not be confirmed. Table 1 shows properties of the obtained three types of polyhydroxypolyurethane resins.

<Comparative Production Example 1> (Polyester urethane resin)
The polyester urethane resin used in the comparative example was synthesized as follows. A reaction vessel equipped with a stirrer, a thermometer, a gas introduction pipe and a reflux condenser was replaced with nitrogen, and 150 parts of polybutylene adipate having an average molecular weight of about 2,000 and 15 parts of 1,4-butanediol were mixed with 200 parts. Dissolved in a mixed organic solvent consisting of methyl ethyl ketone (MEK) and 50 parts of dimethylformamide. Thereafter, 62 parts of water-added MDI (methylenebis (1,4-cyclohexane) -diisocyanate) dissolved in 171 parts of dimethylformamide was gradually added dropwise while stirring well at 60 ° C. For 6 hours. This solution had a solid content of 35%, a viscosity of 3.2 MPa · s (25 ° C.), and a hydroxyl value of zero. The oxygen gas permeability was 4,380 cm ³ / m ² · 24 h · atm (25 ° C., 65% RH, thickness 25 μm).

  In the above, for the purpose of evaluating the barrier property with respect to the dye (sublimation dye), “oxygen gas permeability” which is considered to be correlated with the barrier property was measured. That is, it can be evaluated that a material having a smaller oxygen gas permeability value can form an intermediate layer excellent in preventing dye diffusion. As will be described later, there is a correlation between the oxygen gas permeability value of each material and the occurrence of bleeding in the image. The “oxygen gas permeability” was measured by the following method. First, the resin solution obtained above was molded at 210 ° C. using a cast film molding machine to obtain a film having a thickness of 25 μm. The oxygen gas permeability of the obtained film was measured using a gas permeability meter (MOCON OXTRAN-10 / 50A manufactured by Modern Controller) under the conditions of 25 ° C. and 65% RH.

<Comparative Production Example 2> (Polyvinyl alcohol)
As the polyvinyl alcohol used in the comparative example, NM-11 (trade name, Nippon Synthetic Chemical Industry Co., Ltd., saponification degree 99.0 mol% or more) was used. This NM-11 was dissolved in warm water to obtain a polyvinyl alcohol solution having a solid content of 5%. The oxygen gas permeability was 0.5 cm ³ / m ² · 24 h · atm (25 ° C., 65% RH, thickness 25 μm).

<Comparative Production Example 3> (Cellulose acetate)
L-20 ((trade name), Daicel Chemical Industries, Ltd.) was used as the cellulose acetate used in the comparative example. L-20 was dissolved in a solvent (acetone / anone = 1/1) to obtain a cellulose acetate solution having a solid content of 10%. The oxygen gas permeability was 1,820 cm ³ / m ² · 24 h · atm (25 ° C., 65% RH, thickness 25 μm).

<Examples 1-3, Comparative Examples 1-3>
(Middle layer creation)
A synthetic paper (manufactured by YUPO Corporation) having a thickness of 150 μm is used as a base material, and each coating liquid having the composition shown in Table 2 is used on one surface, and the coating amount after drying is 3.0 g / m. After coating so as to be ² , it was dried at 130 ° C. for 4 minutes to prepare each intermediate layer.

(Creation of thermal transfer image receiving sheet)
100 parts of vinyl chloride-vinyl acetate copolymer (A type manufactured by Nissin Chemical), 5 parts of silicone oil SF8417 (manufactured by Toray Silicone), 10 parts of polyisocyanate (manufactured by Nippon Polyurethane, Coronate L), methyl ethyl ketone / toluene (= 1 / 1) was added to adjust the solid content to 20% to obtain a coating for the receiving layer. This receiving layer coating composition was applied at 5 μm on each of the intermediate layers obtained above to obtain thermal transfer image receiving sheets of Examples and Comparative Examples.

<Evaluation>
Using the thermal transfer image receiving sheets obtained above, image density, bleeding, adhesion, and environmental compatibility were evaluated by the following methods.

(Image density)
32-tone gradation printing was performed on each thermal transfer image-receiving sheet of Examples and Comparative Examples using a Sony sublimation thermal transfer printer CVP-G7. And about each of the obtained printed matter, the printing density of the high density gradation part was measured with the reflection type Macbeth densitometer (Macbeth company make, RD918), and the following reference | standard evaluated. The results are shown in Table 3.
○: 1.8 or more Δ; 1.5 or more and less than 1.8 ×; less than 1.5

(Smear)
The image quality was obtained in the same manner as that for evaluation of density. Each print was allowed to stand in an environment of 50 ° C. for 1 week, and the presence or absence of blurring of the image was observed with a magnifying glass (10 times) and evaluated according to the following criteria. The results are shown in Table 3.
○: No bleed is observed at all. △: There is a bleed, but it is a level that is not observed visually. ×: There is a bleed, and bleed is recognized visually.

(Adhesiveness)
A cellophane tape was applied to the surface (dye receiving layer surface) on which the intermediate layer and the receiving layer of each thermal transfer image receiving sheet of Examples and Comparative Examples were coated, and the film was peeled off after 1 minute. The dye receiving layer surface and the cellophane tape surface were visually observed and evaluated according to the following criteria. The results are shown in Table 3.
○: There is no peeling part in the dye receiving layer. Δ: Part of the dye receiving layer is peeled. ×: The dye receiving layer is peeled off.

(Environmental compatibility)
It evaluated by (circle) x by the presence or absence of fixation of the carbon dioxide in each thermal transfer image receiving sheet. The results are shown in Table 3.

  According to the present invention described above, it is particularly useful as a thermal transfer image receiving sheet used in a sublimation type transfer system, and an intermediate layer and a receiving layer are laminated in this order on one side, By comprising a polyhydroxypolyurethane resin, there is provided a thermal transfer image-receiving sheet that is excellent in a barrier effect for preventing diffusion of a dye image and excellent in adhesion to a substrate and a dye-receiving layer. At the same time, carbon dioxide, which is considered to be a global warming gas, can be used as a raw material for the intermediate layer, so it is possible to provide thermal transfer image-receiving sheets as environmentally friendly products that could not be achieved with conventional products from the viewpoint of global environmental conservation. become.

Claims (7)

  A thermal transfer image-receiving sheet in which an intermediate layer and a dye-receiving layer are laminated in this order on at least one surface of a base material, wherein the intermediate layer comprises a polyhydroxy polyurethane resin as a main component. Sheet.   2. The thermal transfer image receiving sheet according to claim 1, wherein the polyhydroxy polyurethane resin has a hydroxyl value of 50 to 350 mg KOH / g.   The thermal transfer image receiving sheet according to claim 1, wherein the polyhydroxy polyurethane resin is a resin derived from a reaction between a 5-membered cyclic carbonate compound and an amine compound.   The thermal transfer image receiving sheet according to claim 3, wherein the five-membered cyclic carbonate compound is a reaction product of an epoxy compound and carbon dioxide.   The thermal transfer image receiving sheet according to any one of claims 1 to 4, wherein the polyhydroxypolyurethane resin contains carbon dioxide in a range of 1 to 25 mass% in the resin structure.   The thermal transfer image receiving sheet according to any one of claims 1 to 5, wherein the polyhydroxypolyurethane resin is crosslinked with a crosslinking agent that reacts with a hydroxyl group constituting the resin.   The thermal transfer image receiving sheet according to any one of claims 1 to 6, wherein the intermediate layer contains a white pigment and / or a fluorescent brightening agent.