JP5593650B2 - Thermal transfer sheet - Google Patents

Description

  The present invention relates to a thermal transfer sheet, and more particularly, to a thermal transfer sheet that can obtain a clear image even when thermally transferred to an aqueous image receiving paper.

  Conventionally, monotonous images such as gradation images, characters, symbols, and the like have been formed on a substrate using a thermal transfer method. As the thermal transfer system, a thermal sublimation transfer system and a thermal melt transfer system are widely used. Among these, the thermal sublimation transfer method uses a thermal transfer sheet in which a dye layer in which a sublimable dye used as a coloring material is melted or dispersed in a binder resin is supported on a base sheet, and this thermal transfer sheet is used as an image receiving sheet (necessary). The sublimation dye contained in the dye layer on the thermal transfer sheet is received by applying energy according to the image information to a heating device such as a thermal printer head over the image receiving sheet provided with a dye receiving layer according to This is a method of forming an image by shifting to a sheet.

  As an image receiving sheet, a solvent-based image receiving sheet having a solvent-based dye-receiving layer and a solvent-based image receiving sheet having a water-based dye-receiving layer are known. According to the solvent-based image-receiving sheet, the image formed on the solvent-based image-receiving sheet is a water-based image-receiving sheet, although it is superior in releasability between the dye layer and the dye-receiving layer as compared with the water-based image-receiving sheet. Since the glossiness of an image formed on a sheet is low, a solvent-based image receiving sheet is not suitable for use when a high glossiness is required. Furthermore, solvent-based image-receiving sheets have a strong irritating odor, which causes health damage when sucked into the human body, and tends to be avoided from use due to problems such as environmental impact due to treatment of waste liquids and the like.

  On the other hand, according to the water-based image receiving sheet, there is no influence on the human body and the environment, and high glossiness can be imparted to the image formed as compared with the solvent-based image receiving sheet. However, as the speed of printers in recent years has increased, the thermal energy applied to thermal printer heads continues to increase, and a combination of a thermal transfer sheet and an image receiving sheet equipped with an aqueous dye-receiving layer (hereinafter referred to as “receiving layer”). When forming an image, the water-based receiving layer and the thermal transfer sheet are thermally fused, and as a result, there is a problem that fine irregularities are formed on the surface of the receiving layer. In particular, heat fusion is likely to occur at the time of printing the second color and the third color (magenta, cyan), and as a result, the density becomes difficult to be generated and the phenomenon that the surface of the receiving layer becomes brown (so-called scorching) occurs.

  In addition, the image receiving sheet provided with an aqueous receiving layer includes an example of using a porous film in order to give the image receiving sheet cushioning properties and heat insulating properties, and an aqueous porous material in which hollow particles and microballoons are dispersed in a binder resin. An example using a layer coated with a layer (Patent Document 1) is well known. However, in the example using the latter aqueous porous layer, the residual moisture during coating has an adverse effect on printing. It was confirmed that the phenomenon that the surface of the above-mentioned receiving layer turns brown was worsened.

  In order to solve these problems, a release agent such as silicone oil or fluororesin has been added to the receiving layer so far, but it is still not sufficient. (Patent Document 1).

JP 2006-264092 A

  The present invention has been made in view of such a situation, and even in high-speed and high-energy printing, a clear image is obtained without causing a decrease in density at which the surface of the receiving layer becomes brown and heat fusion. It is a main problem to provide a thermal transfer sheet that can be used.

The present invention for solving the above problems is a thermal transfer sheet in which a dye layer is formed on one surface of a first substrate and a back layer is formed on the other surface of the first substrate, The thermal transfer sheet is used to form an image by thermal transfer on a thermal transfer image-receiving sheet in which an aqueous receiving layer is formed on a second substrate via an aqueous hollow particle layer, and the dye layer includes at least a dye, 1 to 5 parts by weight (solid content ratio) of a resin binder and 100 parts by weight of the resin binder are contained, and the thermal transfer sheet is in an environment of temperature: 22.5 ° C. and humidity: 50%. After storing for 24 hours, the moisture content is 2.5% or less when measured with an infrared moisture meter.

Further, the present invention for solving the above problems is a combination of a thermal transfer sheet and a thermal transfer image receiving sheet, wherein the thermal transfer sheet has a dye layer formed on one surface of a first substrate, A back layer is formed on the other surface of the base material of 1, and the dye layer is separated by at least 1 to 5 parts by weight (solid content ratio) with respect to 100 parts by weight of the dye, the resin binder, and the resin binder. The thermal transfer sheet containing a mold was stored for 24 hours in an environment of temperature: 22.5 ° C. and humidity: 50%, and the moisture content measured by an infrared moisture meter was 2.5%. The thermal transfer image receiving sheet is characterized in that an aqueous receiving layer is formed on a second substrate via an aqueous hollow particle layer.

  According to the present invention, (1) since the moisture content of the thermal transfer sheet is 2.5% or less, moisture does not move from the dye layer of the thermal transfer sheet to the image receiving paper, and the water volatilizes in the receiving layer of the image receiving paper. And rupture can be prevented. (2) Since the release agent is contained in the dye layer of the thermal transfer sheet at a predetermined ratio, the release property of the thermal transfer sheet (the dye layer of the thermal transfer sheet) and the image receiving paper (the receiving layer of the image receiving paper) It becomes good and can prevent the occurrence of heat fusion (a phenomenon in which the dye layer and the receiving layer are not peeled off). Furthermore, when combined with the above (1) to (2) (due to a synergistic effect), even when applied to water-based image receiving paper having excellent releasability and high water content, the receiving layer is not inhibited and charring occurs. There is nothing.

1 is a schematic cross-sectional view showing a thermal transfer sheet and an image receiving paper according to an embodiment of the present invention. It is a typical sectional view showing the thermal transfer sheet concerning an embodiment of the invention. FIG. 3 is a schematic cross-sectional view showing an aqueous image receiving paper.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view showing a thermal transfer sheet and image receiving paper according to an embodiment of the present invention, FIG. 2 is a schematic cross-sectional view showing a thermal transfer sheet, and FIG. 3 is a schematic view showing an example of an aqueous image receiving paper. It is sectional drawing.

  As shown in FIGS. 1 and 2, the thermal transfer sheet 1 of the present invention includes a dye layer 3 formed on one surface of a first substrate 2, and a side opposite to the dye layer 3 of the first substrate 2. It is comprised by the back surface layer 4 formed in (back surface), and the easily bonding layer 5 formed between the dye layer 3 and the 1st base material 2. FIG. The present invention is a thermal transfer sheet in which a dye layer 3 is formed on one surface of the first substrate 2 and the first substrate 2, and a back layer 4 is formed on the back surface. 1 to 5 parts by weight (solid content ratio) release agent for 100 parts by weight of dye, resin binder, and resin binder, and the water content of the thermal transfer sheet is 2.5% or less. As long as this requirement is satisfied, the present invention is not limited to this embodiment.

(First base material)
The 1st base material 2 is a base material used for the thermal transfer sheet 1, Comprising: As the 1st base material 2 of the thermal transfer sheet 1 used by this invention, it has a conventionally well-known some heat resistance and intensity | strength. Any film may be used, for example, a polyethylene terephthalate film, a 1,4-polycyclohexylenedimethylene terephthalate film, a polyethylene naphthalate film, a polyphenylene sulfide having a thickness of about 0.5 to 50 μm, preferably about 1 to 10 μm. Film, polystyrene film, polypropylene film, polysulfone film, aramid film, polycarbonate film, polyvinyl alcohol film, cellophane, cellulose derivatives such as cellulose acetate, polyethylene film, polyvinyl chloride film, nylon film, polyimi Film, ionomer film, and the like.

(Easy adhesion treatment)
In order to lower the moisture content of the thermal transfer sheet to 2.5% or less, in the embodiment of the present invention, the first substrate 2 and the dye layer 3 are bonded together by an easy adhesion treatment. For example, as shown in FIG. 1, the easy adhesion treatment forms an easy adhesion layer 5 between the first base material 2 and the dye layer 3 to bond the first base material 2 and the dye layer 3 together. It is processing to do. The easy-adhesion layer 5 formed between the first substrate 2 and the dye layer 3 hardly absorbs water, so that the moisture content of the thermal transfer sheet can be lowered to 2.5% or less. As such an easily bonding layer 5, what consists of water-based acrylic, water-based polyester, and a water-based epoxy compound is preferable, for example. The water-based acrylic is a water-soluble or water-dispersible acrylic resin, preferably having an alkyl acrylate or an alkyl methacrylate as a main component, and the component is 30 to 90 mol% and copolymerized. Those are preferred. The water-based polyester is a water-soluble or water-dispersible polyester resin, and examples of components constituting the polyester resin include polyvalent carboxylic acids and polyvalent hydroxy compounds. An aqueous epoxy compound is a compound containing an epoxy group that is water-soluble or water-dispersible, preferably water-soluble, and contains at least one, preferably two or more epoxy groups in the molecule. is there. Examples of such aqueous epoxy compounds include glycols, polyethers, glycidyl ethers of polyols, glycidyl esters of carboxylic acids, glycidyl-substituted amines, and the like, but glycidyl ethers are preferred. For the easy adhesion treatment, a method of forming an easy adhesion coating film on the surface of the first substrate 2 is preferably used.

  In addition, as a bonding process between the first base material 2 and the dye layer 3, a primer layer may be applied between the first base material 2 and the dye layer 3. The primer layer can be formed from a resin as shown below. Polyester resin, Polyacrylate resin, Polyvinyl acetate resin, Polyurethane resin, Styrene acrylate resin, Polyacrylamide resin, Polyamide resin, Polyether resin, Polystyrene resin, Polyethylene resin, Polypropylene Examples thereof include vinyl resins such as resin, polyvinyl chloride resin, polyvinyl alcohol resin and polyvinyl pyrrolidone, and polyvinyl acetal resins such as polyvinyl acetoacetal and polyvinyl butyral.

The primer layer is prepared by preparing a coating solution prepared by dissolving or dispersing an additive, if necessary, in the resin listed above in water or an aqueous solvent or an organic solvent such as an alcohol. It can be formed using a known coating means such as a screen printing method or a reverse roll coating method using a gravure plate. The primer layer thus formed is about 0.01 to 0.3 g / m ^{2 in} terms of the coating amount when dried.

  The present invention is characterized in that the moisture content of the thermal transfer sheet 1 is 2.5% or less, and the moisture content of the thermal transfer sheet 1 is set to 2.5% or less without performing the easy adhesion treatment. If possible, this processing is unnecessary.

(Dye layer)
A dye layer 3 is formed on one surface of the first substrate 2 (the lower surface of the first substrate 2 in the case shown in FIG. 1). The dye layer 3 is an essential component in the thermal transfer sheet 1 of the present invention, and contains at least a dye, a resin binder, and 1 to 5 parts by weight (solid content ratio) release agent with respect to 100 parts by weight of the resin binder. .

  The dye layer 3 may be composed of a single layer of one color, or a plurality of dye layers containing dyes having different hues may be repeatedly formed on the same surface of the same substrate in the surface order. The dye layer 3 includes a heat transfer dye described below, a binder resin, and a release agent as essential constituent elements, and other various additives as necessary. As the dye to be used, a dye that melts, diffuses or sublimates by heat, and is used in a conventionally known sublimation transfer type thermal transfer sheet can be used in the present invention. The selection is made in consideration of printing sensitivity, light resistance, storage stability, solubility in a binder resin, and the like.

  Examples of the dye include azomethines such as diarylmethane, triarylmethane, thiazole, merocyanine, pyrazolone methine and the like, indoaniline, acetophenone azomethine, pyrazoloazomethine, imidazolazomethine, imidazoazomethine, and pyridone azomethine. , Xanthene, oxazine, dicyanostyrene, cyanomethylene represented by tricyanostyrene, thiazine, azine, acridine, benzeneazo, pyridoneazo, thiophenazo, isothiazoleazo, pyrrolazo, pyralazo, imidazoleazo, Azos such as thiadiazole azo, triazole azo, dizazo, spiropyran, indolinospiropyran, fluoran, rhodamine lactam, naphthoquinone, anne Rakinon system include the quinophthalone like.

  As the binder of the dye layer 3, any conventionally known resin binder can be used, and preferable examples include ethyl cellulose resin, hydroxyethyl cellulose resin, ethyl hydroxy cellulose resin, hydroxypropyl cellulose resin, methyl cellulose resin, cellulose acetate resin, Cellulose resins such as cellulose butyrate resin, polyvinyl alcohol resins, polyvinyl acetate resins, polyvinyl acetal resins such as polyvinyl acetoacetal resins and polyvinyl butyral resins, vinyl resins such as polyvinyl pyrrolidone resins and polyacrylamide resins, polyester resins, phenoxy Resins and the like are listed, and among them, a grade (molecular weight, structure, etc.) satisfying the above numerical definition of the loss modulus is selected. Among these, cellulose resins, acetal resins, polyester resins, phenoxy resins, and the like are particularly preferable from the viewpoints of heat resistance, dye transferability, and the like.

  As a mold release agent contained in the dye layer 3, in addition to a silicon resin such as silicone oil and a fluororesin, the following mold release graft copolymer can be used. This releasable graft copolymer is obtained by graft polymerizing at least one releasable segment selected from a polysiloxane segment, a fluorocarbon segment, a fluorinated hydrocarbon segment, or a long-chain alkyl segment on a polymer main chain. Is. Among these, a graft copolymer obtained by grafting a polysiloxane segment to a main chain made of a polyvinyl acetal resin is particularly preferable.

  The silicon graft polymer is obtained by grafting a polysiloxane chain to a polymer main chain, and a conventionally known silicon graft polymer can be used.

  The silicon graft polymer can be synthesized by various methods. For example, after forming a polymer main chain, a polysiloxane compound having a functional group that reacts with a functional group present in the polymer main chain The method of making this react is mentioned.

  Examples of the polymer constituting the silicon graft polymer include polymers whose main chain is a polyvinyl acetal resin, an acrylic resin, a vinyl resin, a polyester resin, a polyurethane resin, a polyamide resin, and a cellulose resin. Among these, a polymer whose main chain is a polyvinyl acetal resin is particularly preferable from the viewpoint of affinity for a sublimable dye. The term “polyvinyl acetal” in this case should be interpreted in a broad sense, and in the present invention, when the acetal part of the polyvinyl acetal is formaldehyde, it is called polyvinyl formal, and when the acetal part is acetaldehyde, it is called polyvinyl acetal. Furthermore, the case where the acetal part is butyraldehyde is referred to as polyvinyl butyral. Therefore, the term “polyvinyl acetal” is meant to include all these acetals. The above polymer preferably has a degree of polymerization of 500 to 5000, preferably 1000 to 3000.

  In addition, modified silicone oil obtained by modifying or modifying silicone oil with one or more of acrylic, epoxy, acetal, and aralkyl, phosphoric acid ester, and the like can also be suitably used.

  In the thermal transfer sheet of the present invention, the release agent is contained at a ratio of 1 to 5 parts by weight (solid content ratio) with respect to 100 parts by weight of the resin binder, and the moisture content of the thermal transfer sheet is controlled to 2.5% or less. It is characterized by doing.

  When the release agent is 1 part by weight or less with respect to 100 parts by weight of the resin binder, sufficient releasability cannot be obtained when a thermal transfer image is formed in combination with the image receiving sheet described below.

  When 5 parts by weight or more of the release agent is contained with respect to 100 parts by weight of the resin binder, the moisture content of the thermal transfer sheet is 2.5% or more, and a thermal transfer image is formed in combination with the image receiving sheet described below. In this case, there arises a problem that the surface of the receiving layer is brownish and the concentration is lowered.

In addition to the dye, binder resin, and release agent, the dye layer of the present invention may contain various additives similar to those conventionally known as necessary. Examples of the additive include organic fine particles such as polyethylene wax and inorganic fine particles in order to improve releasability from the image receiving sheet and ink coating suitability. Such a dye layer is usually prepared by adding the above-mentioned dye, binder, and additives as necessary in an appropriate solvent, and dissolving or dispersing each component to prepare a coating solution. The liquid can be formed on the first substrate 2 by applying and drying. As this coating method, known means such as a gravure printing method, a screen printing method, a reverse roll coating method using a gravure plate, or the like can be used. The dye layer thus formed has a coating amount at the time of drying of about 0.2 to 6.0 g / m ² , preferably about 0.3 to 3.0 g / m ² .

(Back layer)
The thermal transfer sheet of the present invention has a back layer for preventing adverse effects such as sticking and printing wrinkles due to the heat of the thermal printer head on one side of the first substrate 2 (the back side of the side on which the dye layer is formed). 4) is also provided. The resin for forming the back layer may be any conventionally known resin such as polyvinyl butyral resin, polyvinyl acetoacetal resin, polyester resin, vinyl chloride-vinyl acetate copolymer, polyether resin, polybutadiene resin, Styrene-butadiene copolymer, acrylic polyol, polyurethane acrylate, polyester acrylate, polyether acrylate, epoxy acrylate, urethane or epoxy prepolymer, nitrocellulose resin, cellulose nitrate resin, cellulose acetate propionate resin, cellulose acetate butyrate Resin, cellulose acetate hydrodiene phthalate resin, cellulose acetate resin, aromatic polyamide resin, polyimide resin, polyamideimide resin, polycarbonate Boneto resins, and chlorinated polyolefin resins.

  Examples of the slipperiness-imparting agent added to or overcoating the back layer made of these resins include phosphate ester, silicone oil, graphite powder, silicone-based graft polymer, fluorine-based graft polymer, acrylic silicone graft polymer, acrylic siloxane, aryl siloxane, etc. The silicone polymer is preferably a layer comprising a polyol, for example, a polyalcohol polymer compound, a polyisocyanate compound and a phosphate ester compound, and it is more preferable to add a filler.

The back layer is prepared by dissolving or dispersing the above-described resin, slipperiness-imparting agent, and filler in an appropriate solvent on the first base material 2 to prepare a back layer coating solution. Can be formed by coating with a forming means such as gravure printing, screen printing, reverse roll coating using a gravure plate, and drying. The coating amount of the back layer is a ^{solid, 0.1g / m 2 ~3.0g / m} 2 is preferred.

  Next, the thermal transfer image receiving sheet will be described.

  As shown in FIG. 3, the thermal transfer image-receiving sheet 6 includes an aqueous hollow particle layer 9 containing at least an aqueous binder and hollow particles, an aqueous system mainly composed of an aqueous binder and a release agent, on a second substrate 7. It is a laminate of the receiving layer 8 and, if necessary, a second functional intermediate layer between the second substrate 7 and the aqueous hollow particle layer 9 and between the aqueous hollow particle layer and the aqueous receiving layer. It is also possible to intervene. The thermal transfer image receiving sheet in which the aqueous receiving layer 8 is formed on the second substrate 7 through the hollow particle layer 9 is referred to as an aqueous image receiving paper.

(Second base material)
There is no restriction | limiting in particular about the 2nd base material 7 used for the thermal transfer image receiving sheet 6, According to the intended purpose etc., the thing of a various material, a layer structure, and a size can be selected and used suitably. For example, various papers such as paper, coated paper, and synthetic paper (polypropylene, polystyrene, or a composite material obtained by bonding them with paper), vinyl chloride resin sheet, ABS resin sheet, polyethylene terephthalate (PET) base film , Polybutylene terephthalate base film, polyethylene naphthalate (PEN) base film, polyarylate base film, polycarbonate base film, polyether ether ketone base film, polysulfone base film, polyether sulfone base film, polyetherimide base film, polyimide base A single layer such as a film, or various plastic films or sheets laminated with two or more layers, films or sheets formed of various metals, various types Can be given the appropriate combination laminated composite materials from La mixes such in formed film or sheet, or of the described ones.

(Water-based hollow particle layer)
Examples of the hollow particles contained in the aqueous hollow particle layer 9 formed on the second substrate 7 include thermally expandable hollow particles and capsule-shaped hollow polymers. The heat-expandable hollow particles are hollow particles having a thermoplastic material such as vinylidene chloride-acrylonitrile copolymer as a wall material, and a material containing a heat-expandable gas such as propane, n-butane and isobutane inside the particle. It is. The capsule-like hollow polymer is a hollow polymer having a wall material made of a resin such as styrene-acrylic resin or melamine resin. The hollow particles as described above generally have a particle size of about 0.1 to 100 μm, but in the present invention, hollow particles having a particle size of about 0.1 to 50 μm are preferably used. If the thickness is less than 0.1 μm, a sufficient heat insulating effect as a hollow particle cannot be obtained, and if it exceeds 50 μm, the smoothness is significantly lowered.

  Examples of the aqueous binder used in the aqueous hollow particle layer 9 include polyester resin, polyacrylate resin, polycarbonate resin, polyvinyl acetate resin, styrene acrylate resin, etc .; and those having urethane bonds, polyurethane resins; amide bonds Polyamide resin (nylon); urea resin having urea bond; and other highly polar bonds having polycaprolactone resin, polystyrene resin, polyvinyl chloride, polyacrylonitrile Resin etc. can be used, or it can be used as a copolymer mainly composed of one or more of the above structural units of the resin, for example, vinyl chloride-vinyl acetate copolymer, styrene-butadiene copolymer, etc. In addition, the above resins can be used alone or in combination of two or more. It can be used.

  In addition, vinyl polymers such as water-soluble polyvinyl alcohol, polyvinyl pyrrolidone, cation-modified polyvinyl alcohol and derivatives thereof, polyacrylamide, polydimethylacrylamide, polydimethylaminoacrylate, polyacrylic acid or salts thereof, acrylic acid-methacrylic acid copolymer Acrylic group-containing polymers such as coalesced or salt thereof, polymethacrylic acid or salt thereof, acrylic acid-vinyl alcohol copolymer or salt thereof, starch, oxidized starch, starch acetate, carboxyl starch, dialdehyde starch, cationic starch, dextrin Natural polymers such as sodium alginate, gum arabic, casein, pullulan, dextran, etc. or derivatives thereof, maleic acid-vinyl acetate copolymer, maleic acid-N-vinyl pyro Don copolymer, maleic acid - alkyl vinyl copolymers, synthetic polymers such as polyethylene imine, can be also used.

  Colored pigments, white pigments and the like can be used for the water-based hollow particle layer 9 as necessary. Specific examples of white pigments include barium sulfate, titanium dioxide (rutile type and anatase type), zinc sulfide, and carbonic acid. Examples include calcium, magnesium oxide, various silicates, aluminum oxide, titanium phosphate, satin white, talc, and clay. In particular, from the viewpoint of high whiteness, barium sulfate, titanium dioxide, calcium carbonate and the like are preferably used. Further, an antistatic agent, a fluorescent brightening agent, a wetting agent, an antifoaming agent, a dispersing agent, an ultraviolet absorber, a light stabilizer and the like may be added as necessary.

  The aqueous hollow particle layer 9 is prepared by dispersing or dissolving an aqueous binder, hollow particles, and other additives to be added in water or an aqueous solution to prepare an aqueous coating liquid. It can be produced by a coating method that is applied to the surface and dried.

  When preparing an aqueous coating solution, it is desirable to dissolve or disperse the resin in water according to the solubility or dispersibility of the aqueous binder in water. Moreover, depending on the case, you may use together the alcohol solvent which mixes with water, acetone, a dioxane, etc. in the ratio of 20 weight% or less with respect to 100 weight% of water.

  The aqueous hollow particle layer-forming coating solution prepared as described above is applied onto the second substrate 7 using a known coating method, such as an extrusion coating method, a wire bar coating method, or a roll coating method. Dried.

  The thickness of the aqueous hollow particle layer composed of the above components can be appropriately set in the range of 20 to 80 μm.

(Water receptive layer)
The aqueous receiving layer binder used for the aqueous receiving layer 8 mainly composed of an aqueous binder and a release agent has a dyeing property with respect to a heat-diffusible dye and a coating solution for forming an aqueous receiving layer, which will be described later. Therefore, those having good solubility or dispersibility in water are preferable.

  Examples of such binders include polyvinyl chloride resins, copolymer resins of vinyl chloride and other monomers (isobutyl vinyl ether, vinyl propionate, etc.), polyester resins, poly (meth) acrylic acid, poly (meth) acrylic acid. Esters, polyvinyl pyrrolidone, polyvinyl acetal resins, polyvinyl alcohol, polycarbonate, cellulose triacetate, polystyrene, copolymers of styrene and other monomers (acrylic ester, acrylonitrile, ethylene chloride, etc.), ethylene and other monomers (acetic acid Vinyl, acrylate ester, etc.), vinyl toluene acrylate resin, polyurethane resin, polyamide resin, urea resin, epoxy resin, phenoxy resin, polycaprolactone resin, polyacrylonitrile resin, methyl Cellulose resins such as cellulose, may be mentioned gelatin, starch, casein, and their modified products.

  Among the above-mentioned resins, polyvinyl chloride resin, copolymers of vinyl chloride and other monomers, polyvinyl acetal resins, copolymers of styrene and other monomers, polyester resins, and epoxy resins are preferable.

  These resins can be used alone or in combination of two or more.

  The release agent used in combination with the binder includes silicone oil (including those called silicone resins); solid waxes such as polyethylene wax, amide wax, Teflon (registered trademark) powder; fluorine-based, phosphate ester-based In particular, silicone oil is preferable. This silicone oil is classified into a type that is simply added and a type that is cured or reacted.

  As a type that is simply added, modified silicone oil (polyester-modified silicone oil, urethane-modified silicone oil, acrylic-modified silicone oil, alcohol-modified silicone oil, amide-modified silicone oil, etc.) in order to improve compatibility with the above-mentioned resin Is preferably used.

  The amount of these silicone oils to be added varies depending on the type and cannot be determined uniformly, but is generally 0.1 to 50% by weight based on the binder for the receiving layer. It is preferably 0.5 to 20% by weight.

  Examples of the curing reaction type silicone oil include reaction curing type (such as those obtained by reaction curing of amino-modified silicone oil and epoxy-modified silicone oil), photo-curing type, and catalyst-curing type.

  The addition amount of these curable silicone oils is preferably 0.5 to 30% by weight of the receptor layer binder.

  The aqueous receiving layer is prepared by dispersing or dissolving a resin, a release agent, and other additives that are added as necessary in water or an aqueous solution to prepare an aqueous coating solution. When preparing an aqueous coating solution, it is desirable to dissolve or disperse the resin in water according to the solubility or dispersibility of the receptor layer binder in water. Moreover, depending on the case, you may use together the alcohol solvent which mixes with water, acetone, a dioxane, etc. in the ratio of 20 weight% or less with respect to 100 weight% of water.

  That is, in order to prepare this aqueous coating solution, a water-soluble resin in which the binder is well dissolved in water (water-soluble polyvinyl acetal resin, water-soluble polyester, polyvinyl alcohol, starch, casein, gelatin, polyacrylic acid, etc.) If it is an emulsion resin (polyvinyl chloride resin, styrene-butadiene copolymer, etc.) formed by solution polymerization in water or an aqueous solution or a binder using water as a solvent, it is appropriately Suspension resin (epoxy resin, copolymer of vinyl chloride and other monomers, etc.) that is dispersed in water by suspending in water or aqueous solution with a surfactant or by using a dispersant as the binder If this is the case, use a dispersing agent with a known dispersing machine such as an attritor, ball mill, sand grinder or the like. It is desirable to disperse in the solution.

  These coating liquids can be used together as appropriate, and emulsion resins and dispersion resins are commercially available suspensions (vinyl chloride latex, styrene-butadiene latex, ethylene-vinyl acetate latex from the beginning). , Water-dispersed polymer polyester, etc.) or a dispersion.

  The aqueous receptive layer-forming coating solution prepared as described above is coated and dried on the aqueous hollow particle layer using a known coating method, such as an extrusion coating method, a wire bar coating method, or a roll coating method. The

  The thickness of the water-based receiving layer comprising the above components can be appropriately provided in the range of 0.5 to 10 μm.

(Water content of thermal transfer image-receiving sheet)
The moisture content of the thermal transfer image-receiving sheet (aqueous image-receiving paper) used in combination with the thermal transfer sheet 1 of the present invention is not particularly limited, but the thermal transfer sheet 1 of the present invention has a moisture content of 3 to 10%, preferably a moisture content. It can be used particularly suitably in combination with a 4 to 6% thermal transfer image receiving sheet (water-based image receiving sheet). By using the thermal transfer sheet 1 of the present invention in combination with the thermal transfer image-receiving sheet having a moisture content in the above range, a high gloss feeling can be imparted to the printed matter after transfer. In addition, according to the thermal transfer sheet 1 of the present invention characterized by the content of the release agent contained in the dye layer and the water content, when printing is performed on a thermal transfer image-receiving sheet having a high water content as in the above range Even so, there is no occurrence of scorching that the surface of the receiving layer becomes brownish brown or thermal fusion that prevents the receiving layer and the dye layer from separating.

  Reference numeral 10 shown in FIG. 1 denotes a thermal printer head. The thermal transfer sheet and water-based image receiving paper contain moisture, and when heat is sent from the upper side of the thermal transfer sheet, the moisture of the thermal transfer sheet moves to the image receiving paper side, and when the water in the receiving layer reaches the boiling point and volatilizes and bursts. When doing so, the surface of the receiving layer is obstructed, and the density of that portion becomes lighter, and the color becomes lighter. In the present invention, the moisture content of the thermal transfer sheet is lowered due to the knowledge that moisture in the thermal transfer sheet is a cause of scorching. Specifically, the moisture content of the thermal transfer sheet should be 2.5% or less with respect to 100 parts by weight of the resin binder. By setting the water content to 2.5% or less, the volatilization and rupture of water are eliminated and the occurrence of scorching is prevented. The moisture content should be small, and 2.5% or less includes 0%.

  Next, an Example is given and this invention is demonstrated further more concretely. Hereinafter, unless otherwise specified, parts or% is based on weight.

Example 1
As the first substrate, a 6 μm-thick single-sided easy-adhesion-treated polyethylene terephthalate (PET) film (manufactured by Mitsubishi Chemical Polyester Film Co., Ltd., Diafoil K203E) is used. Then, a dye layer coating solution having the following composition was applied by gravure coating so that the dry coating amount was 1.0 g / m ² and dried to form a dye layer to prepare a thermal transfer sheet of the example. In addition, the primer layer coating liquid for the back layer having the following composition was applied and dried in advance on the other surface of the first base material so as to have a coating amount of 0.2 g / m ² when dried. After coating and drying the following back layer coating solution on the surface of 1.0 g / m ² when dried, heat treatment is performed at 60 ° C. for 5 days to form a back layer (heat resistant slipping layer). I kept it.

<Dye layer coating solution>
Solvent Blue 63 (cyan dye) 7.0 parts Polyvinyl acetoacetal resin 3.0 parts (# 6000-AS, manufactured by Denki Kagaku Kogyo Co., Ltd.)
0.6 parts of silicone-modified acrylic resin (Modiper FS710 (solid content 15 wt%), manufactured by NOF Corporation)
Methyl ethyl ketone 44.7 parts Toluene 44.7 parts

<Primer layer coating solution for back layer>
10.0 parts of polyester resin (Nichigo Polyester LP-035; manufactured by Nippon Synthetic Chemical Industry Co., Ltd.)
Methyl ethyl ketone 90.0 parts

<Back layer coating solution>
13.6 parts of polyvinyl butyral resin (manufactured by SREC BX-1 by Sekisui Chemical Co., Ltd.)
0.6 parts of polyisocyanate curing agent (Takenate D218, Takeda Pharmaceutical Company Limited)
Phosphate 0.8 parts (Pricesurf A208N, Daiichi Kogyo Seiyaku Co., Ltd.)
Methyl ethyl ketone 42.5 parts Toluene 42.5 parts

  A thermal transfer sheet of Example 2 was prepared in the same manner as Example 1 except that the dye layer coating solution was changed to the following composition.

<Dye layer coating solution>
Solvent Blue 63 (cyan dye) 7.0 parts Polyvinyl acetoacetal resin 3.0 parts (# 6000-AS, manufactured by Denki Kagaku Kogyo Co., Ltd.)
0.6 parts of silicone-modified acetal resin (Diaroma SP755 (solid content 12.5 wt%), manufactured by Dainichi Seika Co., Ltd.)
Methyl ethyl ketone 44.7 parts Toluene 44.7 parts

  A thermal transfer sheet of Example 3 was prepared in the same manner as in Example 1 except that the dye layer coating solution was changed to the following composition.

<Dye layer coating solution>
Solvent Blue 63 (cyan dye) 7.0 parts Polyvinyl acetoacetal resin 3.0 parts (# 6000-AS, manufactured by Denki Kagaku Kogyo Co., Ltd.)
Epoxy-modified silicone 0.6 parts (KF-1001 manufactured by Shin-Etsu Chemical Co., Ltd.)
Methyl ethyl ketone 44.7 parts Toluene 44.7 parts

  A thermal transfer sheet of Example 4 was prepared in the same manner as in Example 1 except that the dye layer coating solution was changed to the following composition.

<Dye layer coating solution>
Solvent Blue 63 (cyan dye) 7.0 parts Polyvinyl acetoacetal resin 3.0 parts (# 6000-AS, manufactured by Denki Kagaku Kogyo Co., Ltd.)
Epoxy, 0.6 parts of aralkyl-modified silicone (X22-3000T manufactured by Shin-Etsu Chemical Co., Ltd.)
Methyl ethyl ketone 44.7 parts Toluene 44.7 parts

  A thermal transfer sheet of Example 5 was prepared in the same manner as in Example 1 except that the dye layer coating solution was changed to the following composition.

<Dye layer coating solution>
Solvent Blue 63 (cyan dye) 7.0 parts Polyvinyl acetoacetal resin 3.0 parts (# 6000-AS, manufactured by Denki Kagaku Kogyo Co., Ltd.)
Phosphate ester 0.6 parts (Plysurf A208N, Daiichi Kogyo Seiyaku Co., Ltd.)
Methyl ethyl ketone 44.7 parts Toluene 44.7 parts

(Comparative Example 1)
For comparison, a thermal transfer sheet of Comparative Example 1 was prepared in the same manner as in Example 1 except that the dye layer coating solution was changed to the following composition.

<Dye layer coating solution>
Solvent Blue 63 (cyan dye) 7.0 parts Polyvinyl acetoacetal resin 3.0 parts (# 6000-AS, manufactured by Denki Kagaku Kogyo Co., Ltd.)
Methyl ethyl ketone 45.0 parts Toluene 45.0 parts

(Comparative Example 2)
A thermal transfer sheet of Comparative Example 2 was prepared in the same manner as in Example 1 except that the dye layer coating solution was changed to the following composition.

<Dye layer coating solution>
Solvent Blue 63 (cyan dye) 7.0 parts Polyvinyl acetoacetal resin 3.0 parts (# 6000-AS, manufactured by Denki Kagaku Kogyo Co., Ltd.)
0.10 parts of silicone-modified acrylic resin (Modiper FS710 (solid content 15 w%), manufactured by NOF Corporation)
Methyl ethyl ketone 44.95 parts Toluene 44.95 parts

(Comparative Example 3)
A thermal transfer sheet of Comparative Example 3 was prepared in the same manner as in Example 1 except that the dye layer coating solution was changed to the following composition.

<Dye layer coating solution>
Solvent Blue 63 (cyan dye) 7.0 parts Polyvinyl acetoacetal resin 3.0 parts (# 6000-AS, manufactured by Denki Kagaku Kogyo Co., Ltd.)
1.2 parts of silicone-modified acrylic resin (Modiper FS710 (solid content 15 w%), manufactured by NOF Corporation)
Methyl ethyl ketone 44.4 parts Toluene 44.4 parts

(Comparative Example 4)
As a first base material, on a polyethylene terephthalate film (PET) having a thickness of 6.0 μm, an undercoat layer coating solution having the following composition is subjected to gravure coating so that the dry coating amount becomes 0.06 g / m ^2. Application and drying were performed to form an undercoat layer (referred to as “undercoat layer A”). A thermal transfer sheet of Comparative Example 4 was prepared in the same manner as in Example 1 except that a dye layer was formed on the undercoat layer A.

<Undercoat layer coating solution>
Alumina sol (Alumina sol 200, feather shape, manufactured by Nissan Chemical Industries, Ltd.) 50 parts Water 25 parts Isopropyl alcohol 25 parts

(Comparative Example 5)
As a first base material, on a polyethylene terephthalate film (PET) having a thickness of 6.0 μm, an undercoat layer coating solution having the following composition is subjected to gravure coating so that the dry coating amount becomes 0.06 g / m ^2. Application and drying were performed to form an undercoat layer (“undercoat layer A”). On the undercoat layer A, a dye layer coating solution having the following composition was applied by gravure coating to a dry coating amount of 1.0 g / m ² and dried to form a dye layer. Comparative Example 5 A thermal transfer sheet was prepared.

<Undercoat layer coating solution>
Alumina sol (Alumina sol 200, feather shape, manufactured by Nissan Chemical Industries, Ltd.) 50 parts Water 25 parts Isopropyl alcohol 25 parts

<Dye layer coating solution>
Solvent Blue 63 (cyan dye) 7.0 parts Polyvinyl acetoacetal resin 3.0 parts (# 6000-AS, manufactured by Denki Kagaku Kogyo Co., Ltd.)
Methyl ethyl ketone 45.0 parts Toluene 45.0 parts

(Comparative Example 6)
As a first base material, on a polyethylene terephthalate film (PET) having a thickness of 6.0 μm, an undercoat layer coating solution having the following composition is subjected to gravure coating so that the dry coating amount becomes 0.06 g / m ^2. Application and drying were performed to form an undercoat layer (referred to as “undercoat layer B”). On the undercoat layer B, a dye layer coating solution having the following composition was applied by gravure coating to a dry coating amount of 1.0 g / m ² and dried to form a dye layer. Comparative Example 6 A thermal transfer sheet was prepared.

<Undercoat layer coating solution>
Polyvinylpyrrolidone resin (K-90, manufactured by ISP) 10 parts Water 100 parts Isopropyl alcohol 100 parts

<Dye layer coating solution>
Solvent Blue 63 (cyan dye) 7.0 parts Polyvinyl acetoacetal resin 3.0 parts (# 6000-AS, manufactured by Denki Kagaku Kogyo Co., Ltd.)
Methyl ethyl ketone 45.0 parts Toluene 45.0 parts

(Reference example)
A thermal transfer sheet of a reference example was prepared in the same manner as in Example 1.

(Moisture content measurement)
And the moisture content of the thermal transfer sheet in Examples 1-5, Comparative Examples 1-6, and a reference example prepared in this way was measured. Table 1 shows the measurement results of the moisture content. The measuring method of the moisture content was as follows.

Measuring instrument: Infrared moisture meter (AD-4715)
Measurement conditions: Stored at a temperature of 130 ° C. for 4 minutes. And it measured within 10 minutes after completion | finish of storage.
Measurement method: Each transfer sheet sample cut to a size of 50 mm × 100 mm was stored in a 22.5 ° C. 50% oven for about 24 hours for humidity control.

  The samples for measuring the moisture content of the thermal transfer sheet were 9 sheets of 50 mm × 100 mm, and the breakdown was yellow, magenta, and cyan. Each sample was cut into a size of 25 mm × 50 mm and measured. The measurement was performed 3 times and the average value was used. Table 1 shows the measurement results of the moisture content of the thermal transfer sheet. In addition, the measurement was performed after the measuring device was sufficiently cooled during the repeated measurement.

  Moreover, the water content measurement sample of the water-based image receiving paper shown below was cut into a size of 50 mm × 100 mm, and the measurement was performed three times as in the case of the thermal transfer sheet, and the average value was used.

  Next, the thermal transfer sheets of Examples 1 to 5 and Comparative Examples 1 to 6 were printed on a water-based image receiving paper prepared as described below with a thermal printer head under the printing conditions described below to form images. Further, a thermal transfer sheet of a reference example was printed on a solvent-based image receiving paper prepared as follows under the same printing conditions by a thermal printer head to form an image.

(Water-based image receiving paper)
The production method of the water-based image receiving paper (thermal transfer image receiving sheet) was as follows.

  Using RC paper (STF-150, manufactured by Mitsubishi Paper Industries Co., Ltd.) as the second base material, the coating liquid for forming a porous layer and the coating liquid for forming a receiving layer having the following compositions were heated to 50 ° C., respectively, and slide coating was performed. Was applied to the thickness of 30 μm and 5 μm when dried, cooled and gelled at 5 ° C. for 1 minute, and dried at 50 ° C. for 5 minutes to obtain an aqueous thermal transfer image-receiving sheet. The moisture content of the image receiving paper thus obtained was 5%.

<Porous layer forming coating solution>
Hollow particles (Rohm and Haas, trade name: HP-91) (as solids)
70 parts by weight Gelatin (Nitta Gelatin Co., Ltd., trade name: RR) (as solid content) 30 parts by weight Surfactant (Nissin Chemical Industry Co., Ltd., trade name: Surfynol 440) 0.15 weight Part

<Coating liquid for forming receiving layer>
Emulsion (as solids) 70 parts by weight Resin filler (VB900) (as solids) 15 parts by weight Gelatin (made by Nitta Gelatin Co., Ltd., trade name: RR) (as solids) 15 parts by weight Silicone release agent (Shin-Etsu Chemical Co., Ltd., trade name: Surfinol 440)
10 parts by weight Surfactant (manufactured by Nissin Chemical Industry Co., Ltd., trade name: Surfynol 440) 1 part by weight

  The synthesis of the above emulsion was as follows. In a 500 mL Erlenmeyer flask, 103 g of styrene, 54 g of ethyl acrylate, 41 g of lauryl acrylate, 2 g of acrylic acid, and 1.9 g of an emulsifier (Daiichi Kogyo Seiyaku Co., Ltd., trade name: Aqualon HS-10) were added and stirred and mixed ( This is hereinafter referred to as monomer A). In a 1 L three-necked flask, 200 g of distilled water was added and heated to 80 ° C., and about 20% of the total amount of monomer A was added and stirred for 10 minutes. Thereafter, 0.2 g of ammonium persulfate dissolved in 20 g of pure water was added and stirred for 10 minutes, and then the remaining 80% of the monomer A was dropped with a dropping funnel over 3 hours and further stirred for 3 hours. Thereafter, the mixture was cooled to room temperature and filtered through # 150 mesh (Japanese fabric) to obtain an emulsion of the example. Molecular weight 242273, Tg 50 ° C. Further, from the molecular weight of styrene, ethyl acrylate and lauryl acrylate and the amount used for the reaction, the respective molar ratios are 58%, 32% and 10%.

  Also, as a resin filler, vinyl chloride-ethyl acrylate copolymer (monomer blending ratio is 90% vinyl chloride, 10% ethyl acrylate), Tg 70 ° C. (trade name: VB900 manufactured by Nissin Chemical Industry Co., Ltd.) It was used.

(Solvent-based image-receiving paper)
As the second substrate, an adhesive layer coating solution having the following composition was applied to the surface opposite to the surface on which the dye-receiving layer described later of the 39 μm-thick microvoided film of the fine void layer was formed, and dried. The coated paper (186.1 g / m ² ), which is a support provided with a back layer on one side, was attached to the side where the back layer was not laminated. A primer layer coating solution having the following composition was applied to the surface to be coated with the receiving layer by wire bar coating so that the dry coating amount was 2.0 g / m ² and dried to form a primer layer. On the primer layer, a receiving layer forming coating solution having the following composition was applied by wire bar coating so that the dry coating amount was 4.0 g / m ² and dried (110 ° C., 1 minute), A dye-receiving layer was formed to obtain a solvent-based thermal transfer image-receiving sheet.

<Adhesive layer coating solution>
30 parts of polyfunctional polyol (Takelac A-969V, manufactured by Mitsui Chemicals Polyurethane Co., Ltd.)
Isocyanate 10 parts (Takenate A-5, manufactured by Mitsui Chemicals Polyurethanes)
60 parts of ethyl acetate

<Back layer formation conditions>
Using a coated paper with a basis weight of 157 g / m ² , after applying corona discharge treatment on one side, high-density polyethylene was applied as an underside grip layer on that side by a coating method (basis weight 29.1 g / m ² ). By doing so, a back layer was provided on the coated paper.

<Primer layer coating solution>
Polyester polyol 15.0 parts (manufactured by Toyo Morton Co., Ltd., Adcoat)
Methyl ethyl ketone / toluene (mass ratio 2: 1) 85.0 parts

<Coating liquid for forming receiving layer>
20.0 parts of vinyl chloride-vinyl acetate copolymer resin (Solvain C, manufactured by Nissin Chemical Industry Co., Ltd., vinyl chloride / vinyl acetate = 87/13, number average molecular weight 31000, Tg 70 ° C.)
Carboxyl-modified silicone 1.0 part (Shin-Etsu Chemical Co., Ltd., X-22-3701E)
Methyl ethyl ketone / toluene (mass ratio 1: 1) 79.0 parts

Printing conditions Thermal printer head; KGT-217-12MPL20 (manufactured by Kyocera Corporation)
Heating element average resistance value: 2994 (Ω)
Main scanning direction printing density; 300 dpi
Sub-scanning direction print density; 300 dpi
Applied power: 0.10 (w / dot)
1 line cycle: 5 (msec.)
Printing start temperature; 40 (° C)
Applied pulse (gradation control method): Using a multi-pulse test printer that can vary the number of divided pulses from 0 to 255 in one line period and having a pulse length obtained by equally dividing one line period into 256 The duty ratio of the divided pulses was fixed to 70%, and the number of pulses per line period was divided into 15 from 0 to 255. Thereby, different energy can be given to 15 steps. This time, only the largest energy of 15 different energy levels was used for printing.
Print pattern: Solid black

(Burn level, releasability evaluation)
Burning level and releasability after transferring the thermal transfer sheets of Examples 1 to 5 and Comparative Examples 1 to 6 to aqueous image receiving paper, and scoring level and releasability after transferring the thermal transfer sheet of the reference example to solvent based image receiving paper Evaluated. The results are also shown in Table 1. In Table 1, the scoring level and the evaluation criteria for releasability were as follows.

Burning level evaluation criteria A: There is no surface roughness or unevenness of the receiving layer.
○: Roughness and unevenness of the surface of the receiving layer occur when the screen area is 1/10 or less.
Δ: Roughness or irregularities on the surface of the receiving layer occurs at 1/4 or less of the screen area.
X: Roughness of the surface of the receiving layer and unevenness occur at 1/4 to less than half of the screen area.
XX: Roughness and unevenness of the surface of the receiving layer occur in more than half of the screen area.

Criteria for releasability ○: No heat fusion occurs.
X: Thermal fusion occurred.
Thermal fusion: A phenomenon in which a dye layer and a receiving layer cannot be peeled after printing because the releasability between the dye layer and the receiving layer is poor.

(Glossiness measurement)
The glossiness of the image after transferring the thermal transfer sheets of Examples 1 to 5 and Comparative Examples 1 to 6 to the aqueous image receiving paper and the glossiness of the image after transferring the thermal transfer sheet of the reference example to the oil based image receiving paper were measured. The measurement results of glossiness are also shown in Table 1. The glossiness was measured under the following conditions.

Glossiness measurement condition Measuring instrument: Nippon Denshoku Co., Ltd. gloss meter Gloss meter VG2000
Measurement incident angle: 45 °
Measurement direction: Sub-scanning direction

  As shown in Table 1, an embodiment of the present invention containing 1 to 5 parts by weight (solid content ratio) of a release agent with respect to 100 parts by weight of the resin binder, and having a moisture content of the thermal transfer sheet of 2.5% or less. For Nos. 1 to 5, the scoring level and the releasability were good even when water-based image-receiving paper having a high water content of 5% was used. Moreover, the glossiness was 70 or more, and a high glossiness could be imparted.

  On the other hand, Comparative Example 1 had a moisture content within the range of the present invention, but was inferior in releasability because the release agent was not contained in the dye layer.

  In Comparative Example 2, the water content was within the range of the present invention, but the content of the release agent was low outside the range of the present invention, and the release property was inferior.

  In Comparative Example 3, since the content of the release agent was high outside the range of the present invention, the moisture content was high outside the range of the present invention, and the burn level was inferior.

  In Comparative Example 4, since the easy adhesion treatment was not performed, the moisture content was high outside the range of the present invention, and the burn level was inferior.

  In Comparative Example 5, the release agent was not contained in the dye layer and the easy adhesion treatment was not performed, so that the moisture content was high outside the range of the present invention, and the releasability and scoring level were inferior.

  In Comparative Example 6, since the release agent was not contained in the dye layer and no easy adhesion treatment was performed, the moisture content was high outside the range of the present invention, and the releasability and burn level were inferior.

  Moreover, in Comparative Examples 3-6 in which a moisture content is higher than 2.5%, glossiness is less than 70, and glossiness is inferior compared with Examples 1-5. Further, in the reference example in which the image is formed on the solvent-based image receiving sheet, the glossiness is remarkably inferior as compared with the image formed on the water-based image receiving sheet.

  As a result, it can be seen that the thermal transfer sheet of the present invention is excellent in releasability and does not cause burning even when applied to water-based image receiving paper. Furthermore, high glossiness can be imparted to the formed image.

DESCRIPTION OF SYMBOLS 1 Thermal transfer sheet 2 1st base material 3 Dye layer 4 Back surface layer 5 Adhesive layer 6 Aqueous image receiving paper 7 Second base material 8 Aqueous receiving layer 9 Aqueous hollow particle layer 10 Thermal printer head

Claims (2)

A thermal transfer sheet in which a dye layer is formed on one surface of a first substrate and a back layer is formed on the other surface of the first substrate,
The thermal transfer sheet is used for forming an image by thermal transfer on a thermal transfer image-receiving sheet in which an aqueous receiving layer is formed on the second substrate via an aqueous hollow particle layer,
The dye layer contains at least a dye, a resin binder, and a release agent of 1 to 5 parts by weight (solid content ratio) with respect to 100 parts by weight of the resin binder,
The thermal transfer sheet has a value of 2.5% or less when its moisture content is measured with an infrared moisture meter after being stored in an environment of temperature: 22.5 ° C. and humidity: 50% for 24 hours. Thermal transfer sheet. A combination of a thermal transfer sheet and a thermal transfer image receiving sheet,
The thermal transfer sheet has a dye layer formed on one surface of a first substrate and a back layer formed on the other surface of the first substrate. The dye layer includes at least a dye and a resin binder. And 1 to 5 parts by weight (solid content ratio) of a release agent with respect to 100 parts by weight of the resin binder, and the thermal transfer sheet is 24 under an environment of temperature: 22.5 ° C. and humidity: 50%. After storing for a time, the value when the moisture content is measured with an infrared moisture meter is 2.5% or less,
The thermal transfer image-receiving sheet is a combination of a thermal transfer sheet and a thermal transfer image-receiving sheet, wherein a water-based receptor layer is formed on a second substrate via an aqueous hollow particle layer.

Images