JP5648975B2 - Thermal transfer recording medium - Google Patents

Description

  The present invention relates to a thermal transfer recording medium used in a thermal transfer type printer, and a heat-resistant slipping layer is provided on one surface of a substrate, and an undercoat layer and a dye layer are provided on the other surface of the substrate. Regarding the heat-sensitive transfer recording media formed in sequence, more specifically, the transfer sensitivity at high speed printing is high, that is, the dye used in the dye layer can be reduced, and even after storage under high temperature and high humidity for a long time, Abnormal image transfer can be prevented, and image quality defects occurring in high density areas, that is, hue variation occurs when the receiving layer of the transfer target is fused to the thermal transfer recording medium. The present invention relates to a thermal transfer recording medium capable of reducing the phenomenon of so-called “shininess” that is partially matted.

  In general, a thermal transfer recording medium is an ink ribbon called a thermal ribbon, which is used in a thermal transfer type printer, and has a thermal transfer layer on one side of the substrate and heat resistance on the other side of the substrate. A slipping layer (sometimes referred to as a back coat layer) is provided.

  Here, the thermal transfer layer is a layer of ink that is sublimated (sublimation transfer method) or melted (melt transfer method) by the heat generated in the thermal head of the printer and transferred to the transfer target side. It is.

  Currently, among the thermal transfer systems, the sublimation transfer system can easily form full-color images with various functions of the printer, so digital camera self-prints, cards such as identification cards, amusement output, etc. Widely used. Along with the diversification of such applications, there is a growing demand for smaller size, higher speed, lower cost, and durability for the printed material obtained. In recent years, durability has been given to the printed material on the same side of the base sheet. 2. Description of the Related Art Thermal transfer recording media having a plurality of thermal transfer layers provided so as not to overlap protective layers and the like that have been widely used have become quite popular.

  Known image-receiving sheets on the transfer target side include solvent-based image-receiving sheets provided with a dye-receiving layer formed with a solvent-based coating solution, and water-based image-receiving sheets provided with a dye-receiving layer formed with an aqueous coating solution.

  The solvent-based image-receiving sheet is superior to the water-based image-receiving sheet in terms of releasability between the dye layer and the dye-receiving layer, but the glossiness is low. In addition, image-receiving sheets formed with solvent-based coating liquids have a strong irritating odor, which causes health hazards when inhaled by the human body, and has been avoided from use due to problems such as the impact on the environment caused by the treatment of waste liquids. It tends to be.

  Under such circumstances, along with the diversification of applications and the spread of use, there has been a problem that sufficient print density cannot be obtained with the conventional thermal transfer recording medium as the printing speed of the printer further increases.

  In order to increase the transfer sensitivity, attempts have been made to improve the transfer sensitivity in printing by reducing the thickness of the thermal transfer recording medium. However, there is a problem that wrinkles are generated due to heat, pressure or the like during the production of a thermal transfer recording medium or printing, and breakage occurs in some cases.

  In addition, attempts have been made to increase the printing density and transfer sensitivity in printing by increasing the dye / resin (Dye / Binder) ratio in the dye layer of the thermal transfer recording medium. In addition to being up, a part of the dye migrates to the heat-resistant slip layer of the thermal transfer recording medium during the winding state in the manufacturing process (so-called setback), and the dye that has migrated to other colors during subsequent rewinding When the dye layer or the protective layer is re-transferred (so-called back-inside) and the contaminated layer is thermally transferred to the transfer medium, a hue different from the designated color is generated, and so-called background staining occurs.

  Attempts have also been made to increase energy during image formation on the printer side, not on the thermal transfer recording medium side. However, increasing the energy at the time of image formation on the printer side not only increases power consumption, but also shortens the life of the thermal head of the printer, and the dye layer and the transfer target are fused, so-called abnormal transfer is likely to occur. Become. On the other hand, when a large amount of a release agent is added to the dye layer or the transfer target in order to prevent abnormal transfer, blurring of the image or background staining may occur.

  Further, when forming an image by combining an image receiving sheet provided with a dye receiving layer (hereinafter sometimes referred to as “receiving layer”) formed of a thermal transfer recording medium and an aqueous coating liquid, an aqueous coating liquid is used. As a result, the receiving layer and the thermal transfer sheet formed by the above may cause thermal fusion, and as a result, so-called “shine” may occur in which the surface of the printed material is partially matted.

  In order to solve such a demand, several methods have been proposed.

  For example, Patent Document 1 proposes a thermal transfer sheet having an adhesive layer containing a polyvinyl pyrrolidone resin and a modified polyvinyl pyrrolidone resin between a base material and a dye layer.

  Further, for example, Patent Document 2 proposes a thermal transfer sheet having an adhesive layer composed of a polyvinyl pyrrolidone resin or a polyvinyl alcohol resin thermoplastic resin and colloidal inorganic pigment ultrafine particles between a base material and a dye layer. Yes.

JP-A-2005-231354 JP 2006-150956 A

  However, when the thermal transfer recording medium proposed in Patent Document 1 was printed with a recent high-speed printer using a sublimation transfer method, abnormal transfer, including those stored under high temperature and high humidity, Although it was not confirmed, the transfer sensitivity in printing was low, it did not reach a sufficient level, and the shine could not be suppressed sufficiently.

  In addition, when the image was printed on the thermal transfer recording medium proposed in Patent Document 2, the transfer sensitivity in the print was high and reached a sufficient level, but it was abnormal when stored at high temperature and high humidity. Transcription was confirmed, and shine was also confirmed.

  As described above, in the prior art, a thermal transfer recording medium that has high transfer sensitivity in printing and can be used for a high-speed printer that does not cause abnormal transfer even when stored at high temperature and high humidity has not been found.

  In view of the above problems, the present invention has high transfer sensitivity during high-speed printing, that is, can reduce the amount of dye used in the dye layer, and prevents abnormal transfer in printing even after long-term storage at high temperatures and high humidity. In addition, poor image quality occurs in the high density portion, that is, the hue of the transfer material receiving layer is fused to the heat-sensitive transfer recording medium, resulting in partial matting of the surface of the print. An object of the present invention is to provide a thermal transfer recording medium that can reduce the phenomenon of so-called “shine”.

  The present invention employs the following configuration in order to solve the above problems.

  The present invention is a thermal transfer recording medium. The heat-sensitive transfer recording medium includes a substrate, a heat-resistant slipping layer, an undercoat layer, and a dye layer. Further, a heat resistant slipping layer is formed on one surface of the base material, and an undercoat layer is formed on the other surface of the base material. A dye layer is formed on the undercoat layer. The undercoat layer is mainly composed of at least one selected from the group consisting of an alkoxide, a hydrolyzate thereof, and tin chloride, a vinylpyrrolidone-vinylcaprolactam copolymer, a water-soluble polymer, and a urethane resin. It is characterized by including as.

  The urethane resin is preferably polyester urethane. The urethane resin is preferably a polyurethane ionomer.

  The water-soluble polymer is preferably polyvinyl pyrrolidone.

  The alkoxide is preferably tetraethoxysilane or triisopropoxyaluminum, or a mixture thereof.

The coating amount after drying of the undercoat layer, that is, the solid content remaining after applying and drying the coating liquid for forming the undercoat layer on the substrate is 0.10 g / m ^{2 to} 0.30 g / m ^2. It is preferable to be within the range.

  According to the present invention, the undercoat layer is at least one selected from the group consisting of an alkoxide, a hydrolyzate thereof, and tin chloride, a vinylpyrrolidone-vinylcaprolactam copolymer, a water-soluble polymer, and a urethane resin. As a main component, the transfer sensitivity during high-speed printing is high, that is, high-density printing can be obtained without increasing the amount of dye used in the dye layer, and even after storage at high temperature and high humidity for a long time. There is no abnormal transfer in printing, and image quality failure occurs in high density areas, that is, hue variation occurs due to the receiving layer of the transfer target being fused to the thermal transfer recording medium, resulting in partial printing surface Therefore, it is possible to provide a thermal transfer recording medium that can obtain a printed matter with less so-called “shiny” phenomenon that is matted.

  In addition, since the urethane resin is a polyurethane ionomer, a relatively stable coating solution can be obtained. When the water-soluble polymer is polyvinyl alcohol, it is possible to provide a thermal transfer recording medium capable of obtaining a higher density print. Further, since the water-soluble polymer is polyvinyl pyrrolidone, it is possible to provide a heat-sensitive transfer recording medium that can obtain a high-density print and is difficult to stably transfer abnormally.

  Further, since the alkoxide is tetraethoxysilane or triisopropoxyaluminum, a relatively stable coating solution can be obtained.

Furthermore, when the coating amount of the undercoat layer after drying is in the range of 0.10 to 0.30 g / m ² , a high-density print is obtained, abnormal transfer is difficult, and there is little shine. It is possible to provide a thermal transfer recording medium capable of obtaining the above.

  That is, according to the present invention, in the thermal transfer recording medium, the undercoat layer has at least one selected from the group consisting of an alkoxide, a hydrolyzate thereof, and tin chloride, a vinylpyrrolidone-vinylcaprolactam copolymer, Transfer polymer and urethane resin as main components, high transfer sensitivity during high-speed printing, that is, high-density printing can be obtained without increasing the dye used in the dye layer, and high temperature over a long period of time・ There is no abnormal transfer in printing even after storage under high humidity, and the image quality is poor in the high density area, that is, the hue of the transfer layer is fused to the thermal transfer recording medium. As a result, it is possible to obtain a print with less so-called “shine” phenomenon in which the surface of the print is partially matted, and has the following effects:

  The alkoxide of the undercoat layer and / or its hydrolyzate or tin chloride is a highly reactive inorganic component, and is a polymer having a chain or three-dimensional structure by itself undergoing a polycondensation reaction while being dried from an aqueous solution. In addition, it is considered that a vinyl-pyrrolidone-vinylcaprolactam copolymer, a water-soluble polymer and a urethane resin form a complex at the molecular level. Therefore, the alkoxide in the undercoat layer and / or the hydrolyzate thereof or the polycondensate of tin chloride brings about an improvement in transfer sensitivity at the time of high-speed printing, which is insufficient only with the vinylpyrrolidone-vinylcaprolactam copolymer and the water-soluble polymer. it is conceivable that.

  In addition, the composite of the alkoxide of the undercoat layer and / or its hydrolyzate or tin chloride with vinylpyrrolidone-vinylcaprolactam copolymer, urethane resin and water-soluble polymer has a high temperature / It is thought to bring about improvement in abnormal transcription and shine after storage under high humidity.

Further, the water-soluble polymer is polyvinyl alcohol or polyvinyl pyrrolidone, the urethane resin is polyester urethane, particularly polyester urethane ionomer, the alkoxide is tetraethoxysilane or triisopropoxyaluminum, or a mixture thereof, and the undercoat layer By setting the coating amount after drying within the range of 0.10 to 0.30 g / m ² , the transfer sensitivity at the time of high-speed printing is high, higher density printing can be obtained, and storage at high temperature and high humidity. Even afterwards, there is no abnormal transfer in printing, and a printed matter that is more fully satisfactory can be obtained.

1 is a side sectional view of a thermal transfer recording medium according to an embodiment of the present invention.

  Hereinafter, a thermal transfer recording medium according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a side sectional view of a thermal transfer recording medium according to an embodiment of the present invention.

  As shown in FIG. 1, a thermal transfer recording medium according to an embodiment is provided with a heat-resistant slip layer 40 on one surface of a substrate 10, and an undercoat layer 20 and a dye layer on the other surface of the substrate 10. 30 is a thermal transfer recording medium in which 30 is sequentially formed. Specifically, the thermal transfer recording medium according to one embodiment is provided with a heat-resistant slipping layer 40 that imparts slidability with a thermal head on one surface of the substrate 10, and an alkoxide on the other surface of the substrate 10. It is formed by applying and drying a coating solution containing at least one of the hydrolyzate and tin chloride, a vinylpyrrolidone-vinylcaprolactam copolymer, a water-soluble polymer, and a urethane resin as main components. The undercoat layer 20 and the dye layer 30 are sequentially formed.

  First, the undercoat layer 20 is composed of at least one of an alkoxide, a hydrolyzate thereof, and tin chloride, a vinylpyrrolidone-vinylcaprolactam copolymer, a water-soluble polymer, and a urethane resin. It is characterized by including as.

  Here, as long as the effects are not impaired, the main component is at least one of alkoxide, a hydrolyzate thereof, and tin chloride, a vinylpyrrolidone-vinylcaprolactam copolymer, a water-soluble polymer, and a urethane resin. In addition to the above, it represents that other components may be added.

  For example, the main component is the sum of at least one of alkoxide, its hydrolyzate, and tin chloride, vinylpyrrolidone-vinylcaprolactam copolymer, water-soluble polymer, and urethane resin. Although it is meant to be contained in an amount of more than 50% by mass as viewed from the whole when the pulling layer 20 is formed, it is preferably 80% by mass or more.

  Next, since the base material 10 is required to have heat resistance and strength not to be softened and deformed by heat pressure in thermal transfer, for example, polyethylene terephthalate, polyethylene naphthalate, polypropylene, cellophane, acetate, polycarbonate, polysulfone, polyimide, Polyvinyl alcohol, aromatic polyamide, aramid, polystyrene and other synthetic resin films, and condenser paper, paraffin paper, etc. can be used alone or in combination. In view of properties and cost, a polyethylene terephthalate film is preferable.

  In addition, the thickness of the substrate 10 can be in the range of 2 to 50 μm in consideration of operability and workability, but in consideration of handling properties such as transfer suitability and workability, it is 2 to 9 μm. A degree is preferred.

  Moreover, in the said base material 10, it is also possible to perform an adhesion | attachment process to the surface which forms the heat-resistant slipping layer 40 mentioned later and / or the undercoat layer 20. FIG.

  As the adhesion treatment, known techniques such as corona treatment, flame treatment, ozone treatment, ultraviolet treatment, radiation treatment, roughening treatment, plasma treatment, and primer treatment can be applied. More than one species can be used in combination, but it is effective to increase the adhesion between the substrate 10 and the undercoat layer 20, and a primer-treated polyethylene terephthalate film is preferable from the viewpoint of cost.

Next, the heat-resistant slipping layer 40 can be handled by a conventionally known layer. For example, a resin serving as a binder, a functional additive imparting releasability or slipperiness, a filler, a curing agent, a solvent, and the like are blended. And can be formed by coating and drying. The coating amount after drying of the heat resistant slipping layer 40 is suitably about 0.1 to 2.0 g / m ² . Here, the coating amount after drying of the heat resistant slipping layer 40 refers to the amount of solid content remaining after applying and drying the coating solution for forming the heat resistant slipping layer, and drying of the undercoat layer 20 described later. Similarly, the subsequent coating amount and the coating amount after drying of the dye layer 30 also indicate the solid content remaining after the coating liquid is applied and dried.

  Here, as an example of the heat resistant slipping layer 40, the binder resin may be polyvinyl butyral resin, polyvinyl acetoacetal resin, polyester resin, vinyl chloride-vinyl acetate copolymer, polyether resin, polybutadiene resin, acrylic polyol. , Polyurethane acrylate, polyester acrylate, polyether acrylate, epoxy acrylate, nitrocellulose resin, cellulose acetate resin, polyamide resin, polyimide resin, polyamideimide resin, polycarbonate resin and the like.

  In addition, the functional additive is not particularly limited, but includes natural waxes such as animal waxes and plant waxes, synthetic hydrocarbon waxes, aliphatic alcohols and acid waxes, fatty acid esters and glycerite waxes. Synthetic wax such as wax, synthetic ketone wax, amine and amide wax, chlorinated hydrocarbon wax, alpha-olefin wax, higher fatty acid ester such as butyl stearate and ethyl oleate, sodium stearate, zinc stearate, Higher fatty acid metal salts such as calcium stearate, potassium stearate, magnesium stearate, long chain alkyl phosphate ester, polyoxyalkylene alkyl aryl ether phosphate ester or polyoxyalkylene alkyl ether phosphate ester It may be mentioned surfactants of the phosphoric acid esters such as Le.

  The filler is not particularly limited, but talc, silica, magnesium oxide, zinc oxide, calcium carbonate, magnesium carbonate, kaolin, clay, silicone particles, polyethylene resin particles, polypropylene resin particles, polystyrene resin particles. , Polymethyl methacrylate resin particles, polyurethane resin particles, and the like.

  The curing agent is not particularly limited, and examples thereof include isocyanates such as tolylene diisocyanate, triphenylmethane triisocyanate, tetramethylxylene diisocyanate, and derivatives thereof.

  Next, the undercoat layer 20 includes, as essential components, at least one of an alkoxide, a hydrolyzate thereof, and tin chloride, a vinylpyrrolidone-vinylcaprolactam copolymer, a water-soluble polymer, and a urethane resin. And as a main component.

  Examples of the water-soluble polymer include polyvinyl alcohol, polyvinyl pyrrolidone, starch, gelatin, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, and sodium alginate. Among these, polyvinyl alcohol and polyvinyl pyrrolidone are preferable, and polyvinyl alcohol is more preferable.

  The polyvinyl alcohol as used herein is not particularly limited, but is generally obtained by saponifying polyvinyl acetate, and from a so-called partially saponified polyvinyl alcohol in which several tens of percent of acetate groups remain. And so-called completely saponified polyvinyl alcohol in which only a few percent of acetate groups remain.

  The vinylpyrrolidone-vinylcaprolactam copolymer is a copolymer of an N-vinylpyrrolidone monomer and vinylcaprolactam which is a vinyl polymerizable monomer. The copolymerization form is not limited to any of random copolymerization, block copolymerization, and graft copolymerization. Although not particularly limited, the N-vinylpyrrolidone-based monomer refers to N-vinylpyrrolidone (N-vinyl-2-pyrrolidone, N-vinyl-4-pyrrolidone, etc.) and derivatives thereof. The derivatives include pyrrolidone rings such as N-vinyl-3-methylpyrrolidone, N-vinyl-5-methylpyrrolidone, N-vinyl-3-benzylpyrrolidone, and N-vinyl-3,3,5-trimethylpyrrolidone. And those having a substituent.

  Examples of the urethane resins include emulsion polyurethane resins obtained by emulsifying ester polyurethane resins, ether polyurethane resins, carbonate polyurethane resins with emulsifiers, ester polyurethane resins, ether polyurethane resins, carbonate resins. An ionomer-type polyurethane resin in which a metal salt such as a carboxylic acid or a sulfonic acid or an ammonium salt is partially bonded to a polyurethane resin to impart water solubility can be used.

  In view of water resistance, plasticizer resistance, and heat resistance, it is desirable to use an emulsion type polyurethane resin or an ionomer type polyurethane resin obtained by emulsifying an ester polyurethane resin having a carboxyl group, and a polyurethane ionomer resin is preferably used. More desirable.

As an example of the alkoxide, the following general formulas such as tetraethoxysilane [Si (OC ₂ H ₅ ) ₄ ] and triisopropoxyaluminum [Al (O-2′-C ₃ H ₇ ) ₃ ] are used. It can be expressed. Among these, tetraethoxysilane or triisopropoxyaluminum is preferable because it is relatively stable even in an aqueous solvent.

M (OR) _n (1)
(In the above formula 1, M represents a metal such as Si, Ti, Al, or Zr, and R represents an alkyl group such as CH ₃ or C ₂ H ₅ )

The tin chloride may be stannous chloride (SnCl ₂ ), stannic chloride (SnCl ₃ ), or a mixture thereof, and may be an anhydride or a hydrate.

Moreover, the coating amount after drying of the undercoat layer 20 is not generally limited, but is preferably in the range of 0.10 to 0.30 g / m ² . If it is less than 0.10 g / m ² , the transfer sensitivity at the time of high-speed printing is insufficient due to the deterioration at the time of laminating the dye layer 30, and there is a concern that the adhesiveness with the substrate 10 or the dye layer 30 has a problem. On the other hand, if it exceeds 0.30 g / m ² , the sensitivity of the thermal transfer recording medium itself is affected, and there is a concern that the transfer sensitivity at the time of high-speed printing is insufficient.

Next, the dye layer 30 can be handled by a conventionally known one, for example, a dye layer forming coating solution is prepared by blending a heat transferable dye, a binder, a solvent, and the like, and formed by coating and drying. About 1.0 g / m ² is appropriate.

  The dye layer 30 can be formed of a single layer of one color, or a plurality of dye layers 30 containing dyes having different hues can be repeatedly formed on the same surface of the same base material in the surface order.

  The heat transferable dye of the dye layer 30 is not particularly limited as long as it is a dye that melts, diffuses or sublimates and transfers by heat. For example, as yellow components, solvent yellow 56, 16, 30 93, 33, Disperse Yellow 201, 231, 33, and the like. Examples of the magenta component include C.I. I. Disperse thread 60, C.I. I. Disperse violet 26, C.I. I. Solvent Red 27, or C.I. I. Solvent Red 19 etc. can be mentioned. As the cyan component, C.I. I. Disperse Blue 354, C.I. I. Solvent Blue 63, C.I. I. Solvent Blue 36, or C.I. I. Disperse Blue 24 and the like. As the ink dye, it is common to perform color matching by combining the above dyes.

  In addition, as the binder in the dye layer 30, any conventionally known resin binder can be used, and is not particularly limited, but cellulose such as ethyl cellulose, hydroxyethyl cellulose, ethyl hydroxy cellulose, hydroxypropyl cellulose, methyl cellulose, cellulose acetate and the like. Examples thereof include vinyl resins such as resin, polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, polyvinyl acetal, polyvinyl pyrrolidone, and polyacrylamide, polyester resins, styrene-acrylonitrile copolymer resins, and phenoxy resins.

  Here, the ratio of the dye and the binder in the dye layer 30 is preferably dye / binder = 10/100 to 300/100. This is because when the dye / binder ratio is less than 10/100, the amount of dye is too small and the color development sensitivity becomes insufficient, and a good thermal transfer image may not be obtained. On the other hand, when this ratio exceeds 300/100, the solubility of the dye in the binder is extremely lowered, so that when it becomes a thermal transfer recording medium, the storage stability is deteriorated and the dye is likely to precipitate. Because.

  Further, known additives such as isocyanate compounds, silane coupling agents, dispersants, viscosity modifiers and stabilizers can be used in the dye layer 30 or the dye layer forming coating solution as long as the performance is not impaired. .

  The heat-resistant slip layer 40, the undercoat layer 20, and the dye layer 30 described above can be formed by applying and drying by a conventionally known coating method. An example of a coating method is gravure. Examples thereof include a coating method, a screen printing method, a spray coating method, and a reverse roll coating method.

  Next, an image-receiving sheet on the transfer target side, specifically, an aqueous thermal transfer image-receiving sheet is formed on the substrate 10 with an aqueous hollow particle layer containing at least an aqueous binder and hollow particles, an aqueous binder and a release agent. A water-based receptive layer containing as a main component is laminated.

  The aqueous thermal transfer image-receiving sheet is an aqueous coating mainly comprising a hollow particle layer formed of an aqueous coating liquid containing at least an aqueous binder and hollow particles, an aqueous binder, and a release agent on a substrate. A receiving layer formed of a liquid is laminated.

  In addition, there is no restriction | limiting in particular about the base material used for a water-system thermal transfer image receiving sheet, According to the intended purpose etc., the thing of various materials, layer structure, and a size can be selected and used suitably. Examples thereof include various papers such as paper, coated paper, and synthetic paper (polypropylene, polystyrene, or a composite material obtained by bonding them with paper).

(Hollow particle layer)
The thermal transfer printing is performed by heating from a thermal head, and it is required that the thermal head and the image receiving paper base have good adhesion. Since the thermal transfer image-receiving sheet having a hollow particle layer has a cushioning property, the adhesion to the thermal head is improved, and a more uniform image can be obtained at the time of printing.

  As a material for forming the walls of the hollow particles, acrylonitrile, vinylidene chloride, a styrene acrylate polymer, or the like is preferably used. In addition, as a manufacturing method of a hollow particle, the system which encloses foaming agents, such as butane gas, in a resin particle, heat-foams, an emulsion polymerization system, etc. are mentioned. As a method of heating and foaming, when using pre-foamed hollow particles obtained by pre-foaming hollow particles by preheat treatment, and after forming a layer containing unfoamed particles by coating or the like, by heat treatment such as a drying step In some cases, a hollow structure is formed. From the viewpoint of easily controlling the hollow ratio and particle diameter of the hollow particles, it is generally preferable to use the already-expanded particles.

(Receptive layer)
As the dyeing resin used in the receiving layer of the thermal transfer image-receiving sheet, it is preferable to use a thermoplastic resin having high affinity for the dye and good dye dyeing property. And as said resin, for example, vinyl chloride resin, urethane resin, polyester resin, polycarbonate resin, polyvinyl acetal resin, polyvinyl butyral resin, polystyrene resin, polyacrylate resin, acrylic resin, cellulose resin, Examples thereof include thermoplastic resins such as polyamide resins, copolymers of vinyl compound monomers and monomers having a benzotriazole skeleton and / or benzophenone skeleton, and these thermoplastic resins may be used alone or in combination of two kinds. The above may be used in combination.

  Among these, acrylic resins, copolymer resins of vinyl compound monomers and monomers having a benzotriazole skeleton and / or a benzophenone skeleton, and urethane resins are preferable because of excellent light resistance of printed images. This is because the urethane-based resin has a crystalline region in the molecule, and thus abnormal transfer hardly occurs.

  Further, the dyeing resin is more preferably composed of a water-soluble or water-dispersed so-called aqueous system from the viewpoint of environmental load.

  In thermal transfer printing, the receiving layer on the image receiving paper substrate and the dye layer 30 of the ink ribbon are superposed and heated with a thermal head, and then the ink ribbon is peeled off from the receiving layer. Is required to be releasable from the ink ribbon. For this reason, it is preferable to add a release agent to the receiving layer for the purpose of preventing fusion with the ink ribbon and improving printing runnability. Examples of the release agent to be added include silicone oil, polysiloxane graft acrylic resin, waxes, and fluorine compounds.

  It is preferable to add a crosslinking agent to the receiving layer to improve heat resistance. As a crosslinking agent, a carbodiimide compound, an isocyanate compound, an oxazoline compound, and an organic titanium chelate compound are preferable. Among these cross-linking agents, carbodiimide-based cross-linking agents are preferable because they are highly effective in improving heat resistance, are less likely to cause running problems such as ribbon fusion during printing, and are stable in aqueous paints. .

  In addition, it is preferable that the addition amount of a carbodiimide type crosslinking agent makes it 1-30 parts of carbodiimide type crosslinking agents with respect to 100 parts of resin contained in a receiving layer, and 3-25 parts is more preferable. If it is less than 1 part, sufficient crosslinking effect cannot be obtained, and printing running failure may occur. If it exceeds 30 parts, the curing property of the resin may inhibit the density of the printed image.

The coating amount of the receptor layer is preferably from 0.5 to 5 g / m ^2, more preferably 0.5-4 g / m ^2. If it is less than 0.5 g / m ² , the light resistance of the image may be inferior. If it exceeds 5 g / m ² , the dye may diffuse in the receiving layer, and image bleeding may occur.

(Coating method)
Various auxiliary agents such as wetting agents, dispersants, thickeners, antifoaming agents, colorants, antistatic agents, preservatives and the like used in the production of general coated papers are appropriately added to the above coating layers. . Each coating layer uses a known coater such as a bar coater, gravure coater, comma coater, blade coater, air knife coater, gate roll coater, die coater, curtain coater, and slide bead coater, and a predetermined coating solution. Can be formed by coating and drying each layer or two or more layers simultaneously. Drying is performed by a drying furnace or the like attached to the coater. Examples of the drying method generally include hot air drying and heat drying. The drying temperature can be appropriately selected within the range of 70 to 130 ° C., but is not particularly limited as long as the solvent contained in the coating liquid evaporates after coating.

  EXAMPLES Hereinafter, although this invention is further demonstrated based on an Example and a comparative example, this invention is not restrict | limited by the following example. In the following, “part” is based on mass unless otherwise specified.

<Preparation of substrate with heat-resistant slip layer>
As a base material 10, a polyethylene terephthalate film with a single-sided easy-adhesion treatment of 4.5 μm is used. After coating and drying so that the coating amount was 1.0 g / m ² , the substrate with the heat resistant slipping layer 40 was obtained by aging in a 40 ° C. environment for 1 week.

<Heat resistant slipping layer coating solution>
Acrylic polyol resin 12.5 parts Polyoxyalkylene alkyl ether / phosphate ester 2.5 parts Talc 6.0 parts 2,6-tolylene diisocyanate prepolymer 4.0 parts Toluene 50.0 parts Methyl ethyl ketone 20.0 parts Ethyl acetate 5.0 parts

Example 1
In Example 1, the coating amount after drying of the undercoat layer coating solution-1 having the composition shown below on the easy-adhesion treated surface of the substrate with the heat-resistant slip layer 40 is 0 by the gravure coating method. The undercoat layer 20 was formed by coating at ² g / m ² and drying at 100 ° C. for 2 minutes. Subsequently, on the undercoat layer 20, a dye layer coating solution having the composition shown below was applied by a gravure coating method so that the coating amount after drying was 0.7 g / m ² , By drying in 1 minute, the dye layer 30 was formed, and the thermal transfer recording medium of Example 1 was obtained.

<Undercoat layer coating solution-1>
Tetraethoxysilane 6.2 parts Polyvinyl alcohol 2.2 parts Vinylpyrrolidone-vinylcaprolactam copolymer 2.2 parts Ionomer-type polyester urethane 2.2 parts 0.1N hydrochloric acid 53.8 parts Pure water 33.9 parts Isopropyl alcohol 3 .9 parts

<Dye layer coating solution>
C. I. Solvent Blue 63 6.0 parts Polyvinyl acetal resin 4.0 parts Toluene 45.0 parts Methyl ethyl ketone 45.0 parts

(Example 2)
In Example 2, in the heat-sensitive transfer recording medium produced in Example 1, the same applies as in Example 1 except that the undercoat layer 20 was changed to the undercoat layer coating solution-2 having the composition shown below. A thermal recording transfer medium of Example 2 was obtained.

<Undercoat layer coating solution-2>
Tetraethoxysilane 6.2 parts Polyvinylpyrrolidone 2.2 parts Vinylpyrrolidone-vinylcaprolactam copolymer 2.2 parts Ionomer type polyester urethane 2.2 parts 0.1N hydrochloric acid 53.8 parts Pure water 33.9 parts Isopropyl alcohol 3 .9 parts

Example 3
In Example 3, in the heat-sensitive transfer recording medium produced in Example 1, the same applies as in Example 1 except that the undercoat layer 20 was changed to the undercoat layer coating solution-3 of the composition shown below. A thermal recording transfer medium of Example 3 was obtained.

<Undercoat layer coating liquid-3>
Stannous chloride 1.8 parts Polyvinyl alcohol 1.2 parts Vinylpyrrolidone-vinylcaprolactam copolymer 2.2 parts Ionomer-type polyester urethane 2.2 parts Pure water 64.0 parts Ethyl alcohol 29.1 parts Isopropyl alcohol 9 copies

Example 4
In Example 4, in the heat-sensitive transfer recording medium produced in Example 1, the same applies as in Example 1 except that the undercoat layer 20 was changed to the undercoat layer coating solution-4 of the composition shown below. Thus, a thermal recording transfer medium of Example 4 was obtained.

<Undercoat layer coating solution-4>
Tetraethoxysilane 6.2 parts Polyvinyl alcohol 2.2 parts Vinylpyrrolidone-vinylcaprolactam copolymer 2.2 parts Ionomer type ether urethane 2.2 parts 0.1N hydrochloric acid 53.8 parts Pure water 33.9 parts Isopropyl alcohol 3 .9 parts

(Example 5)
In Example 5, in the heat-sensitive transfer recording medium produced in Example 1, the same applies as in Example 1 except that the undercoat layer 20 was changed to the undercoat layer coating solution-5 of the composition shown below. A thermal recording transfer medium of Example 5 was obtained.

<Undercoat layer coating solution-5>
Tetraethoxysilane 6.2 parts Polyvinyl alcohol 2.2 parts Vinylpyrrolidone-vinylcaprolactam copolymer 2.2 parts Emulsion-type polyester urethane 2.2 parts 0.1N hydrochloric acid 53.8 parts Pure water 33.9 parts Isopropyl alcohol 3 .9 parts

(Example 6)
In Example 6, the heat-sensitive transfer recording medium produced in Example 1 was prepared in the same manner as in Example 1 except that the undercoat layer 20 was changed to the undercoat layer coating solution-6 having the composition shown below. A thermal recording transfer medium of Example 6 was obtained.

<Undercoat layer coating solution-6>
Tetraethoxysilane 6.2 parts Polyvinyl alcohol 2.2 parts Vinylpyrrolidone-vinylcaprolactam copolymer 2.2 parts Ionomer type ether urethane 0.3 part 0.1N hydrochloric acid 53.8 parts Pure water 33.9 parts Isopropyl alcohol 3 .9 parts

(Example 7)
Example 7 was the same as Example 1 except that the undercoat layer 20 in the heat-sensitive transfer recording medium produced in Example 1 was changed to the undercoat layer coating solution 7 having the composition shown below. Thus, a thermal recording transfer medium of Example 7 was obtained.

<Undercoat layer coating solution-7>
Tetraethoxysilane 6.2 parts Polyvinyl alcohol 2.2 parts Vinylpyrrolidone-vinylcaprolactam copolymer 2.2 parts Ionomer type ether urethane 0.12 parts 0.1N hydrochloric acid 53.8 parts Pure water 33.9 parts Isopropyl alcohol 3 .9 parts

(Example 8)
In Example 8, in the heat-sensitive transfer recording medium produced in Example 1, the same applies as in Example 1 except that the undercoat layer 20 was changed to the undercoat layer coating solution-8 having the composition shown below. A thermal recording transfer medium of Example 8 was obtained.

<Undercoat layer coating solution-8>
Tetraethoxysilane 6.2 parts Polyvinyl alcohol 0.3 parts Vinyl pyrrolidone-vinyl caprolactam copolymer 2.2 parts Ionomer type ether urethane 2.2 parts 0.1N hydrochloric acid 53.8 parts Pure water 33.9 parts Isopropyl alcohol 3 .9 parts

Example 9
In Example 9, in the thermal transfer recording medium produced in Example 1, the same applies as in Example 1 except that the undercoat layer 20 was changed to the undercoat layer coating solution-9 of the composition shown below. A thermal recording transfer medium of Example 9 was obtained.

<Undercoat layer coating solution-9>
Tetraethoxysilane 6.2 parts Polyvinyl alcohol 0.12 parts Vinylpyrrolidone-vinylcaprolactam copolymer 2.2 parts Ionomer type ether urethane 2.2 parts 0.1 N hydrochloric acid 53.8 parts Pure water 33.9 parts Isopropyl alcohol 3 .9 parts

(Example 10)
In Example 10, the thermal transfer recording medium produced in Example 1 was used except that the undercoat layer 20 was applied and dried so that the coating amount after drying was 0.05 g / m ^2. In the same manner as in Example 1, the thermal recording transfer medium of Example 10 was obtained.

(Example 11)
In Example 11, the thermal transfer recording medium produced in Example 1 was used except that the undercoat layer 20 was applied and dried so that the coating amount after drying was 0.35 g / m ^2. In the same manner as in Example 1, the thermal recording transfer medium of Example 11 was obtained.

(Example 12)
In Example 12, the coating amount of the undercoat layer coating liquid-10 having the composition shown below is 0 on the easy-adhesion treated surface of the substrate with the heat resistant slipping layer 40 by the gravure coating method. The undercoat layer 20 was formed by coating and drying so as to be ² g / m ² . Subsequently, on the undercoat layer 20, the same dye layer coating solution as in Example 1 is applied and dried by the gravure coating method so that the applied amount after drying is 0.7 g / m ^2. Thus, the dye layer 30 was formed, and the thermal transfer recording medium of Example 12 was obtained.

<Undercoat layer coating solution-10>
Tetraethoxysilane 6.2 parts Polyester 2.2 parts Ionomer-type polyester urethane 2.2 parts 0.1N hydrochloric acid 53.8 parts Pure water 33.9 parts Isopropyl alcohol 3.9 parts

(Comparative Example 1)
In Comparative Example 1, the same dye layer coating as in Example 1 was applied on the easy adhesion treated surface without forming the undercoat layer 20 on the easy adhesion treated surface of the substrate with the heat resistant slipping layer 40. By applying and drying the working solution by a gravure coating method so that the coating amount after drying was 0.7 g / m ² , a dye layer was formed, and the thermal transfer recording medium of Comparative Example 1 was obtained.

(Comparative Example 2)
In Comparative Example 2, the undercoat layer coating liquid 11 having the composition shown below was applied to the surface of the base material with the heat resistant slipping layer 40 by a gravure coating method, and the coating amount after drying was 0. The undercoat layer 20 was formed by coating and drying so as to be ² g / m ² . Subsequently, on the undercoat layer 20, the same dye layer coating solution as in Example 1 is applied and dried by the gravure coating method so that the applied amount after drying is 0.7 g / m ^2. Then, the dye layer 30 was formed, and the thermal transfer recording medium of Comparative Example 2 was obtained.

<Undercoat layer coating solution-11>
Polyvinyl alcohol 3.0 parts Pure water 87.3 parts Isopropyl alcohol 9.7 parts

(Comparative Example 3)
In Comparative Example 3, the coating amount after drying of the undercoat layer coating liquid-12 having the composition shown below on the easy-adhesion treated surface of the substrate with the heat-resistant slip layer 40 was 0 by the gravure coating method. The undercoat layer 20 was formed by coating and drying so as to be ² g / m ² . Subsequently, on the undercoat layer 20, the same dye layer coating solution as in Example 1 is applied and dried by the gravure coating method so that the applied amount after drying is 0.7 g / m ^2. Then, the dye layer 30 was formed, and the thermal transfer recording medium of Comparative Example 3 was obtained.

<Undercoat layer coating solution-12>
Polyvinylpyrrolidone 3.0 parts Pure water 87.3 parts Isopropyl alcohol 9.7 parts

(Comparative Example 4)
In Comparative Example 4, the coating amount of the undercoat layer coating liquid-13 having the composition shown below on the easy-adhesion treated surface of the substrate with the heat resistant slipping layer 40 was 0 by the gravure coating method. The undercoat layer 20 was formed by coating and drying so as to be ² g / m ² . Subsequently, on the undercoat layer 20, the same dye layer coating solution as in Example 1 is applied and dried by the gravure coating method so that the applied amount after drying is 0.7 g / m ^2. Thus, the dye layer 30 was formed, and the thermal transfer recording medium of Comparative Example 4 was obtained.

<Undercoat layer coating solution-13>
Tetraethoxysilane 6.2 parts Polyvinyl alcohol 2.2 parts 0.1N hydrochloric acid 53.8 parts Pure water 33.9 parts Isopropyl alcohol 3.9 parts

(Comparative Example 5)
In Comparative Example 5, the coating amount after drying of the undercoat layer coating solution-14 having the composition shown below on the easy-adhesion treated surface of the base material with the heat-resistant slip layer 40 was 0 by the gravure coating method. The undercoat layer 20 was formed by coating and drying so as to be ² g / m ² . Subsequently, on the undercoat layer 20, the same dye layer coating solution as in Example 1 is applied and dried by the gravure coating method so that the applied amount after drying is 0.7 g / m ^2. Then, the dye layer 30 was formed, and the thermal transfer recording medium of Comparative Example 5 was obtained.

<Undercoat layer coating solution-14>
Tetraethoxysilane 6.2 parts Polyvinylpyrrolidone 2.2 parts 0.1N hydrochloric acid 53.8 parts Pure water 33.9 parts Isopropyl alcohol 3.9 parts

(Comparative Example 6)
In Comparative Example 6, an undercoat layer coating solution-15 having the composition shown below was applied to the surface of the substrate with the heat-resistant slip layer 40 by a gravure coating method so that the coating amount after drying was 0. The undercoat layer 20 was formed by coating and drying so as to be ² g / m ² . Subsequently, on the undercoat layer 20, the same dye layer coating solution as in Example 1 is applied and dried by the gravure coating method so that the applied amount after drying is 0.7 g / m ^2. Thus, the dye layer 30 was formed, and the thermal transfer recording medium of Comparative Example 6 was obtained.

<Undercoat layer coating solution-15>
Tetraethoxysilane 6.2 parts Polyvinyl alcohol 2.2 parts Ionomer-type polyester urethane 2.2 parts 0.1N hydrochloric acid 53.8 parts Pure water 33.9 parts Isopropyl alcohol 3.9 parts

(Comparative Example 7)
In Comparative Example 7, the coating amount of the undercoat layer coating liquid-16 having the composition shown below was applied to the surface of the easy-adhesion treated surface of the substrate with the heat resistant slipping layer 40 by the gravure coating method, and the coating amount after drying was 0. The undercoat layer 20 was formed by coating and drying so as to be ² g / m ² . Subsequently, on the undercoat layer 20, the same dye layer coating solution as in Example 1 is applied and dried by the gravure coating method so that the applied amount after drying is 0.7 g / m ^2. Then, the dye layer 30 was formed, and the thermal transfer recording medium of Comparative Example 7 was obtained.

<Undercoat layer coating solution-16>
Tetraethoxysilane 6.2 parts Polyvinylpyrrolidone 2.2 parts Ionomer-type polyester urethane 2.2 parts 0.1N hydrochloric acid 53.8 parts Pure water 33.9 parts Isopropyl alcohol 3.9 parts

  Next, a thermal transfer image receiving sheet was prepared. The manufacturing method is as follows.

<Formation of hollow particle layer>
After applying and drying a hollow particle layer coating liquid having the composition shown below on the image receiving paper substrate so that the coating amount after drying becomes 10 g / m ² by gravure coating method, The image receiving paper with a hollow particle layer was obtained by aging for 1 week.

<Hollow particle layer coating solution>
45 parts of pre-expanded hollow particles made of a copolymer mainly composed of acrylonitrile and methacrylonitrile (average particle size 3.2 μm, volumetric hollowness 85%)
Polyvinyl alcohol 10 parts Vinyl chloride vinyl acetate copolymer resin dispersion 45 parts (vinyl chloride / vinyl acetate = 70/30, Tg 64 ° C.)
200 parts of water

<Formation of receiving layer>
On the hollow particle layer, a receiving layer coating solution having the composition shown below is applied and dried by a gravure coating method so that the coating amount after drying is 4 g / m ² , and then 1 in a 40 ° C. environment. A receiving layer was obtained by aging for a week.

<Receptive layer coating solution>
97 parts of urethane resin (glass transition temperature: -20 ° C)
Associative urethane thickener 1 part Sulfonic acid surfactant 2 parts Water 200 parts

<Evaluation of adhesion of dye layer at room temperature>
With respect to the thermal transfer recording media of Examples 1 to 12 and Comparative Examples 1 to 7, a cellophane tape having a width of 18 mm and a length of 150 mm was applied on the dye layer 30 of the thermal transfer recording medium stored at room temperature, and immediately thereafter. Table 1 shows the results of evaluation by examining the presence or absence of adhesion of the dye layer 30 to the cellophane tape when peeled off.

The evaluation was performed according to the following criteria.
○: Adhesion of the dye layer is not recognized Δ: Adhesion of the dye layer is recognized very slightly ×: Adhesion of the dye layer is observed on the entire surface

<Evaluation of adhesion of dye layer after storage at high temperature and high humidity>
With respect to the thermal transfer recording media of Examples 1 to 12 and Comparative Examples 1 to 7, the dye layer 30 of the thermal transfer recording media stored for 72 hours at 40 ° C. and 90% RH and then further stored for 24 hours at room temperature. Table 1 shows the results of evaluation by examining the presence or absence of the dye layer 30 adhering to the cellophane tape side when a cellophane tape having a width of 18 mm and a length of 150 mm was applied to the top and peeled immediately thereafter. The evaluation was performed according to the same standard as the above evaluation at normal temperature.

<Print evaluation>
Regarding the thermal transfer recording media of Examples 1 to 12 and Comparative Examples 1 to 7, the thermal transfer recording media stored at room temperature, and after being stored in a 40 ° C. 90% RH environment for 72 hours, further 24 at normal temperature. Table 1 shows the results of evaluating the maximum reflection density, the presence / absence of abnormal transfer, and the shine by performing solid printing with a thermal simulator using a heat-sensitive transfer recording medium and a transfer medium that have been stored for a long time. Note that the maximum reflection density is a value obtained by measuring a printed portion where no shine is confirmed with X-Rite 528.

<Printing conditions>
Printing environment: 23 ° C, 50% RH
Applied voltage: 29V
Line cycle: 0.7msec
Print density: main scanning 300 dpi sub-scanning 300 dpi

<Abnormal transcription evaluation>
Also, abnormal transcription was evaluated according to the following criteria.
○: Abnormal transfer to the transfer object is not observed Δ: Abnormal transfer to the transfer object is very slight ×: Abnormal transfer to the transfer object is observed on the entire surface

<Electricity evaluation>
Moreover, the evaluation of shine was performed according to the following criteria.
○: shine is not recognized △: shine is partially recognized ×: shine is clearly recognized

  From the results shown in Tables 1 and 2, in the thermal transfer recording medium, the heat-resistant slip layer 40 is provided on one surface of the substrate 10, and the undercoat layer 20 and the dye layer 30 are sequentially formed on the other surface of the substrate 10. The undercoat layer 20 includes, as main components, at least one of an alkoxide, a hydrolyzate thereof, and tin chloride, a vinylpyrrolidone-vinylcaprolactam copolymer, a water-soluble polymer, and a urethane resin. The thermal transfer recording media of Examples 1 to 12 provided with the undercoat layer 20 included clearly transferred at the time of high-speed printing as compared with the thermal transfer recording medium of Comparative Example 1 provided with no undercoat layer 20. It was found that the sensitivity was high.

  It was also found that the adhesion of the dye layer 30 during normal temperature storage and high temperature / high humidity storage and abnormal transfer in printing are not problematic in practice.

  It was also found that there was almost no problem with shine. Among them, the water-soluble polymer is polyvinyl pyrrolidone or polyvinyl from the highest reflection density of the normal temperature storage product and the high temperature / high humidity storage product of Examples 1, 2, 3, 4, 5, 6, 7, 8, and 12. It turned out that alcohol is preferable and especially polyvinyl alcohol is preferable.

  From the adhesion of the dye layer 30 after storage at high temperature and high humidity in Example 1, it was found that tetraethoxysilane was more preferable.

In the thermal transfer recording medium of Example 8, the coating amount of the undercoat layer 20 is less than 0.10 g / m ² , so that the adhesion after storage at high temperature and high humidity is somewhat lowered, and the transfer sensitivity is also somewhat different. It turned out that the minute effect has fallen.

In the thermal transfer recording medium of Example 9, it was found that the effect of the transfer sensitivity was lowered because the coating amount of the undercoat layer 20 exceeded 0.30 g / m ² .

  On the other hand, in the thermal transfer recording medium of Comparative Example 2, as compared with the thermal transfer recording medium of Example 1, as a result of providing the undercoat layer 20 only with polyvinyl alcohol which is a water-soluble polymer, Although the transfer sensitivity was high, it was found that there was a problem with the adhesion of the dye layer 30 during high temperature and high humidity storage. I also found that there was a problem with shine.

  Similarly, the thermal transfer recording medium of Comparative Example 3 has the same problem as Comparative Example 2 as a result of providing the undercoat layer 20 only with polyvinylpyrrolidone, which is a water-soluble polymer, as compared with the thermal transfer recording medium of Example 2. I understood that I have it.

  Further, it was found that the thermal transfer recording media of Comparative Examples 4 and 5 had a problem in the adhesion of the dye layer 30 in the long-term storage at a high temperature and high humidity as compared with the thermal transfer recording medium of Example 1. I also found that there was a problem with shine.

  The heat-sensitive transfer recording media of Comparative Examples 6 and 7 have high transfer sensitivity at room temperature storage and good adhesion to the dye layer 30 at high temperature and high humidity storage, but it has been found that there is a problem with respect to gloss.

  Thermal transfer for forming an image by thermal transfer on a thermal transfer image-receiving sheet on which a receiving layer formed with an aqueous coating liquid is formed via a hollow particle layer formed with an aqueous coating liquid on a substrate obtained by the present invention The recording medium is an ink ribbon used in sublimation transfer printers. In addition to high-speed and high-performance printers, various types of images can be easily formed in full color. Cards such as, amusement output, etc. can be widely used.

10: Base material 20: Undercoat layer 30: Dye layer 40: Heat-resistant slip layer

Claims (7)

A thermal transfer recording medium,
A substrate;
A heat resistant slipping layer;
An undercoat layer,
A dye layer,
The heat resistant slipping layer is formed on one surface of the base material,
The undercoat layer is formed on the other surface of the substrate,
A dye layer is formed on the undercoat layer,
The undercoat layer is mainly composed of at least one selected from the group consisting of an alkoxide, a hydrolyzate thereof, and tin chloride, a vinylpyrrolidone-vinylcaprolactam copolymer, a water-soluble polymer, and a urethane resin. A thermal transfer recording medium comprising:   The thermal transfer recording medium according to claim 1, wherein the urethane resin is polyester urethane.   The thermal transfer recording medium according to claim 1, wherein the urethane resin is a polyurethane ionomer.   The thermal transfer recording medium according to claim 1, wherein the water-soluble polymer is polyvinyl alcohol.   The thermal transfer recording medium according to any one of claims 1 to 3, wherein the water-soluble polymer is polyvinylpyrrolidone.   6. The thermal transfer recording medium according to claim 1, wherein the alkoxide is tetraethoxysilane, triisopropoxyaluminum, or a mixture thereof. The remaining solid content after coating and drying the coating liquid for forming an undercoat layer on the substrate is characterized in that it is in the range of ^{0.10g / m 2 ~0.30g / m 2} , The thermal transfer recording medium according to any one of claims 1 to 6.

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