JP2015063050A - Thermal transfer recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal transfer recording material made of a combination of a thermal transfer sheet and a thermal transfer image receiving sheet, the thermal transfer recording material capable of preventing a defective thermally transferred image due to wrinkles in a thermal transfer sheet at thermal transfer.SOLUTION: A thermal transfer image receiving sheet includes a substrate sheet, a porous layer and a reception layer sequentially laminated. The basis weight of the substrate sheet is 190-205 g/m. The total thickness of the substrate sheet and the porous layer is 190-240 μm. A thermostable lubricant layer of the thermal transfer sheet is formed of a binder resin including a hydroxy group-containing thermoplastic resin and a polyisocyanate. A molar equivalent ratio (-NCO/-OH) of a hydroxy group included in the hydroxy group-containing thermoplastic resin and an isocyanate group of the polyisocyanate is 0.01-3.0.

Description

  The present invention includes a thermal transfer image-receiving sheet obtained by laminating at least a base sheet, a porous layer and a receiving layer in this order, and at least a color material layer on one surface of the base, and the other of the bases The present invention relates to a thermal transfer recording material comprising a combination with at least a thermal transfer sheet having a heat-resistant slip layer.

  Conventionally, a thermal transfer sheet in which a dye layer, which is a color material layer carrying a sublimation dye with an appropriate binder, is provided on one surface of a substrate such as a polyester film, and a thermal transfer image-receiving sheet as a transfer target are superimposed, There is known a sublimation transfer method in which a sublimation dye is transferred to a transfer medium by performing heat treatment with a thermal head while bringing the other surface side of the substrate into contact with the thermal head. According to this sublimation transfer method, the transfer amount of sublimable dye can be controlled in dot units by the amount of energy applied to the thermal transfer sheet, so that density gradation is possible, the image is very clear, and transparency In addition, it is excellent in halftone color reproducibility and gradation, and can form a high-quality image comparable to a full-color photographic image.

  By the way, in a thermal transfer sheet, if printing is performed with a thermal head directly in contact with the substrate, sticking occurs during scanning due to the frictional force generated between the substrate and the thermal head, resulting in poor printing. There is. Further, the base material is fused to the thermal head by heat at the time of printing, which prevents the thermal transfer sheet from running and causes sticking, and in some cases, may cause sheet breakage. Therefore, in the field of thermal transfer sheets, a back layer (also referred to as a heat-resistant slipping layer) is usually provided on the other surface of the base material for the purpose of improving heat resistance and running stability by imparting slipperiness. Yes.

  As shown in Patent Document 1, the above-described thermal transfer sheet uses a binder resin having a reactive group such as a hydroxyl group and a polyisocyanate in combination, and a heat resistant slipping layer having a crosslinked structure on a substrate. Is forming. In Patent Document 1, in order to improve the heat resistance of such a thermal transfer sheet, the amount of polyisocyanate added to the heat resistant slipping layer is set to the molar equivalent ratio (-NCO) between the isocyanate group and the hydroxyl group of the binder resin. / -OH) is in the range of 0.01 to 3.00. On the other hand, as in Patent Document 2, the total thickness of the porous film and the base sheet of the thermal transfer image receiving sheet, which is the transfer target, is about 180 to 230 μm, and the thickness is the same as that of silver salt photographic printing paper. It is known to form a high-quality thermal transfer image by suppressing curling of photographic paper.

  However, when a printed product is produced by using a heat transfer sheet having heat resistance prepared by adding the above-mentioned polyisocyanate in a predetermined amount, and securing the total thickness of the heat transfer image receiving sheet to about 180 to 230 μm, At the time of thermal transfer, wrinkles are generated on the thermal transfer sheet, and a problem that defects in the printed image tend to occur.

JP-A-6-99670 JP 2012-158121 A

  As described above, a heat transfer sheet and a heat transfer image which are formed on the heat transfer image receiving sheet having the same thickness as a silver salt photographic printing paper and having an anti-curl property using a heat transfer sheet having heat resistance. The main object of the present invention is to provide a thermal transfer recording material that can prevent thermal transfer image defects caused by wrinkles occurring in the thermal transfer sheet during thermal transfer.

The above object is achieved by the present invention described below. That is, the present invention is a thermal transfer image-receiving sheet in which at least a base sheet coated with a resin on both sides of a middle paper, a porous layer, and a receiving layer are laminated in this order;
A thermal transfer recording material comprising a combination of thermal transfer sheets having at least a color material layer on one surface of a substrate and at least a heat-resistant slipping layer on the other surface of the substrate,
The basis weight of the base sheet of the thermal transfer image-receiving sheet is 190 g / m ² or more and 205 g / m ² or less, and the combined thickness of the base sheet and the porous layer is 190 μm or more and 240 μm or less,
The heat-resistant slip layer of the thermal transfer sheet contains at least a binder resin,
The binder resin comprises a hydroxyl group-containing thermoplastic resin and a polyisocyanate;
A thermal transfer recording material characterized in that a molar equivalent ratio (-NCO / -OH) between a hydroxyl group of the hydroxyl group-containing thermoplastic resin and an isocyanate group of the polyisocyanate is 0.01 or more and 3.0 or less. The configuration.

  According to the thermal transfer recording material of the present invention, it is possible to prevent the thermal transfer sheet from being wrinkled during thermal transfer, causing thermal transfer image defects on the printed matter, and suppressing curling of the printed matter. A print having a thermal transfer image of can be obtained.

It is a schematic sectional drawing which shows one embodiment of the thermal transfer recording material of this invention. It is a schematic sectional drawing which shows other embodiment of the thermal transfer recording material of this invention.

Next, an embodiment of the invention will be described in detail.
FIG. 1 shows one embodiment of the thermal transfer recording material of the present invention. The illustrated thermal transfer recording material 1 includes a thermal transfer sheet 20 having a color material layer 22 on one surface of a substrate 21 and a heat-resistant slipping layer 23 on the other surface of the substrate 21, and It is composed of a combination with a thermal transfer image receiving sheet on which a porous layer 12 and a receiving layer 13 are laminated. The base sheet 11 of the thermal transfer image receiving sheet 10 is preferably a resin-coated paper in which both sides of an intermediate paper 14 serving as a core material are coated with polyethylene or polypropylene. That is, in this case, the base sheet 11 is provided with the resin coat layers 15 and 16 on both sides of the inner paper 14 as illustrated.

  2 shows another embodiment of the thermal transfer recording material of the present invention. Compared with the thermal transfer recording material of FIG. 1, the thermal transfer image-receiving sheet 10 has a back surface on the side opposite to the side having the receiving layer 13 of the base sheet 11. The layer 17 is added. In addition, as compared with the thermal transfer recording material of FIG. 1, the thermal transfer sheet 20 has a color material layer 22 on the opposite side to the side having the heat-resistant slip layer 23 of the base material 21, yellow (Y), magenta (M), cyan (C ) Each color material layer is repeatedly provided in the surface order.

  Although not shown, a primer layer is provided between the base material 21 and the heat-resistant slip layer 23 of the thermal transfer sheet, a color material primer layer is provided between the base material 21 and the color material layer 22, and the like. A new layer can be provided as long as the function of the thermal transfer sheet is not impaired. Although not shown, the thermal transfer image receiving sheet is provided with an adhesive layer between the base material sheet 11 and the porous layer 12, and is provided with an adhesive layer between the base material sheet 11 and the back surface layer 17. A new layer can be provided as long as the function of the image receiving sheet is not impaired.

<< Thermal transfer image-receiving sheet >>
Below, each layer which comprises the thermal transfer image receiving sheet of the thermal transfer recording material of this invention is explained in full detail.
(Base material sheet)
The base sheet 11 of the thermal transfer image receiving sheet is preferably formed of resin-coated paper (also referred to as RC paper) in which both sides of the inner paper 14 are coated with a thermoplastic resin such as polyethylene or polypropylene.
The inner paper 14 can include, for example, natural pulp, synthetic pulp, pulp paper made from a mixture thereof, and the like. Among them, a piece of wood from which the bark has been removed is made into a small piece (chip), Papers mainly composed of chemical pulp (sulfate pulp or sulfite pulp) produced by semi-chemical and chemical treatment can be used. For example, sizing agents such as higher fatty acids and alkyl ketene dimers; paper strength enhancing agents such as starch; white pigments such as calcium carbonate and titanium oxide; fluorescent whitening agents, softening agents, moisture retention agents, and dispersions An agent or the like can be appropriately added. Moreover, whiteness can also be improved by performing a bleaching process. Further, the medium paper is not limited to high-quality paper and medium-quality paper, and a photographic printing paper support (medium paper for RC paper) can be used. In addition to coated paper, art paper, cast coated paper, etc., on which a functional layer is applied on the surface to improve printing suitability and appearance, white board paper or high-grade white board paper called ivory or coat ivory can also be used.

The inner paper can be produced by a known method, but the inner paper is preferably calendered. Since the resin coated paper obtained by calendering the inner paper has improved surface smoothness, the glossiness of the thermal transfer image receiving sheet obtained from the resin coated paper subjected to such treatment is improved. Medium paper weighing, 180~240g / m ² is preferred.

A base sheet may be prepared by coating (coating) polyethylene or polypropylene, which is a thermoplastic resin, on both sides of the inner paper to form the resin coating layers 15 and 16. By providing the polyolefin resin layer, the smoothness on the side of the dye receiving layer is increased, and the formation of the printed material can be maintained. Among the polyethylene or polypropylene constituting the resin coat layer, high density polyethylene (HDPE), low density polyethylene (LDPE) are considered in consideration of heat resistance of the inner paper, molding processability when the inner paper is coated, resin cost, and the like. ), Linear low density polyethylene (LLDPE), or a mixture thereof, and more preferably a mixture of high density polyethylene and low density polyethylene.
When used as the mixture, the mixing ratio of the high density polyethylene and the low density polyethylene can be used, for example, as 1/9 to 9/1 in terms of mass ratio. 1 is preferred.
The molecular weight of polyethylene or polypropylene is particularly suitable as long as the melt flow rate (MFR) under the coating temperature condition is about 2.0 to 50 g / 10 min (measurement condition: JIS K 7210). Can be used without restriction.

  Titanium oxide can be added to the resin coat layer in order to improve whiteness. The addition amount of titanium oxide is 1 to 15% by mass, preferably 2 to 10% by mass in polyethylene or polypropylene. In addition, in order to adjust the white background, a color pigment such as ultramarine, bitumen, and phthalocyanine blue, and a fluorescent whitening agent such as bisdimethylaminostilbene and bismethylaminostilbene can be added to the resin coat layer.

  The resin-coated paper is coated with the polyethylene or polypropylene on the front and back surfaces of the inner paper to form a resin-coated layer. The coating method can be applied by a known method such as extrusion coating, blade coating, wire bar coating, roll coating, spray coating, cast coating method, etc. Considering the adverse effect of the extrusion coating method is preferable. The resin coat layer can be appropriately subjected to primer treatment or corona discharge treatment on the surface of the inner paper for the purpose of improving interlayer adhesion.

The thickness of the front and back resin coat layers covering both sides of the inner paper is selected considering the curl properties due to changes in film thickness, humidity, and temperature conditions. Generally, the thickness of the coat resin layer is the front side (porous The thickness ratio of the resin coating layer on the front and back sides changes depending on the thickness of the inner paper, etc., so as to adjust the curl, in the range of 10 to 40 μm on the side where the layer is formed) and 10 to 30 μm on the back side (back layer side) The thickness ratio of the front / back resin coat layer is usually about 3/1 to 1/3.
In addition, as the resin constituting the front and back resin coat layers of the resin-coated paper, either one of polyethylene and polypropylene is selected and used, or the resin used in the front and back resin coat layers is formed from different resins. It is also possible.

The thickness of the resin-coated paper is preferably 120 to 220 μm. When the thickness is 120 μm or more, sufficient stiffness and rigidity can be obtained. On the other hand, if it exceeds 220 μm, wrinkles are generated in the thermal transfer sheet during thermal transfer, and defects in the printed image tend to occur. On the other hand, if the thickness is less than 120 μm, curling of the printed matter is not sufficiently suppressed.
In the present invention, a resin-coated paper having a basis weight of 190 g / m ² or more and 205 g / m ² or less is used in the thermal transfer image receiving sheet. This means, for example, that the weight of the inner paper is about 180 to 240 g / m ² and the density of the polyethylene or polypropylene used for the resin coating layer provided on both sides of the inner paper is adjusted so that the basis weight of the entire resin coated paper is It is preferable to be 190 g / m ² or more and 205 g / m ² or less. When the basis weight of the resin-coated paper is less than 190 g / m ² , curling in the thermal transfer image-receiving sheet or printed matter is likely to occur, and it becomes difficult to ensure the total thickness of the photographic paper. On the other hand, if the basis weight of the resin-coated paper exceeds 205 g / m ² , the thermal transfer sheet is likely to be wrinkled during thermal transfer, and the printed image tends to be defective.

(Porous layer)
The porous layer 12 in the thermal transfer image-receiving sheet used in the present invention can be composed of a layer containing hollow particles and a binder resin as described in JP 2010-149286 A, or a porous film. It is preferable to form the porous layer with a porous film so that functions such as cushioning properties and heat insulating properties of the porous layer can be stably exhibited. The porous film has a thickness of less than 50 μm, preferably 15 μm or more and less than 50 μm, more preferably 20 μm or more and 25 μm or less. Further, the porous film is preferably a porous film containing a polypropylene resin as a base resin and having fine voids inside. By providing a porous layer made of a porous film having a thickness of less than 50 μm and containing a polypropylene resin, the amount of curl change due to environmental changes (particularly humidity changes) of the printed matter of the thermal transfer image-receiving sheet is reduced. Thus, the quality after storage in each environment can be improved.

In the thermal transfer image receiving sheet of the present invention, the combined thickness of the base material sheet and the porous layer is specified to be 190 μm or more and 240 μm or less. Thereby, it is excellent in the curl prevention property of a thermal transfer image receiving sheet.
As described above, the thickness of the intermediate paper and the resin coat layer constituting the base sheet and the thickness of the porous layer are set so that the respective functions can be exhibited. It is necessary to make the combined thickness fall within the above range.

  In a porous film, as a method for producing fine voids in the film, a method of producing by using a compound in which organic fine particles or inorganic fine particles (one kind or plural kinds) are incompatible with the resin serving as a base of the film is kneaded. Can be adopted. When this compound is viewed microscopically, the base resin and fine particles incompatible with the base resin form a fine sea-island structure. The fine voids as described above are generated by separation of the interface or large deformation of the region forming the island.

  As a method for forming the fine voids, for example, a method in which polypropylene is mainly used and polyester or acrylic resin having a melting point higher than that of polypropylene is added thereto. In this case, polyester or acrylic resin serves as a nucleating agent that forms fine voids. It is preferable that content of the polyester and acrylic resin is 2-10 mass parts with respect to 100 mass parts of polypropylene in any case. When the content is 2 parts by mass or more, fine voids can be sufficiently generated, and the printing sensitivity can be further improved. Moreover, when content is 10 mass parts or less, the heat resistance of a porous film can fully be ensured.

  Moreover, when producing the porous film which uses polypropylene as the base resin, it is preferable to add polyisoprene in order to generate more fine and dense voids. Thereby, higher printing sensitivity can be obtained. For example, a porous film having high printing sensitivity can be obtained by preparing a compound mainly composed of polypropylene, blended with acrylic resin or polyester, and polyisoprene, forming a compound, and stretching.

(Receptive layer)
The receiving layer 13 in the thermal transfer image receiving sheet used in the present invention is for receiving a sublimation dye transferred from the thermal transfer sheet and maintaining the formed image. As the resin for forming the receiving layer, polycarbonate resin, polyester resin, polyamide resin, acrylic resin, cellulose resin, polysulfone resin, polyvinyl chloride resin, polyvinyl acetate resin, vinyl chloride-acetic acid Examples include vinyl copolymer resins, polyvinyl acetal resins, polyvinyl butyral resins, polyurethane resins, polystyrene resins, polypropylene resins, polyethylene resins, ethylene-vinyl acetate copolymer resins, and epoxy resins.

  The thermal transfer image-receiving sheet can have a release agent in the receiving layer in order to improve releasability from the thermal transfer sheet. Various release agents such as polyethylene wax, amide wax, solid wax such as Teflon (registered trademark), fluorine or phosphate ester surfactant, silicone oil, reactive silicone oil, curable silicone oil, etc. Silicone oil and various silicone resins can be mentioned, and silicone oil is preferable. An oily oil can be used as the silicone oil, but a curable oil is preferred. Examples of the curable silicone oil include a reaction curable type, a photo curable type, and a catalyst curable type, and a reaction curable type and a catalyst curable type silicone oil are particularly preferable.

  As the reactive silicone oil, those obtained by reaction-curing amino-modified silicone oil and epoxy-modified silicone oil are preferable. As amino-modified silicone oil, KF-393, KF-857, KF-858, X-22-3680 are used. X-22-3801C (manufactured by Shin-Etsu Chemical Co., Ltd.) and the like, and epoxy-modified silicone oils such as KF-100T, KF-101, KF-60-164, and KF-103 (above, Shin-Etsu Chemical Co., Ltd.). Examples of the catalyst curable silicone oil include KS-705, FKS-770, and X-22-1212 (manufactured by Shin-Etsu Chemical Co., Ltd.). The addition amount of these curable silicone oils is preferably 0.5 to 30% by mass of the resin constituting the receiving layer.

  In the formation of the receiving layer, pigments and fillers such as titanium oxide, zinc oxide, kaolin, clay, calcium carbonate, and fine powder silica are used for the purpose of improving the whiteness of the receiving layer and further enhancing the sharpness of the transferred image. Can be added. Moreover, you may add plasticizers, such as a phthalic acid ester compound, a sebacic acid ester compound, and a phosphoric acid ester compound.

The thickness of the receiving layer is not particularly limited as long as it is within a range capable of expressing a desired image density, at a coat weight of solids, ^{usually, 1g / m 2 ~20g / m} 2, preferably is ^{1g / m 2 ~15g / m 2} . The receiving layer can be formed by using a commonly used coating means, such as a gravure printing method, a screen printing method, a reverse roll coating method using a gravure plate, and the like. By doing so, it can be formed.

(Back layer)
Further, as shown in FIG. 2, on the surface of the base sheet 11 opposite to the side on which the receiving layer 13 is formed, a back surface layer for the purpose of improving the mechanical transportability of the sheet, preventing curling, writing properties, preventing charging, etc. 17 may be provided. The back layer may be composed of only one layer, or may be composed of two or more layers having different compositions and the like.

  The back layer is, for example, polyurethane resin, polyester resin, polybutadiene resin, poly (meth) acrylate resin, epoxy resin, polyamide resin, rosin-modified phenol resin, terpene phenol resin, ethylene-vinyl acetate copolymer resin, polyolefin series It can be formed from resins such as resin, cellulose resin, gelatin, and casein. Further, the back layer may be a layer to which a water-soluble polymer is added, for example. Examples of the water-soluble polymer include cellulose resin, polysaccharides such as starch and agar, proteins such as casein and gelatin, polyvinyl alcohol, ethylene-vinyl acetate copolymer, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer. , Vinyl acetate- (meth) acrylic copolymer, vinyl acetate-veova copolymer, (meth) acrylic resin, styrene- (meth) acrylic copolymer, vinyl resin such as styrene resin, melamine resin, urea resin, Examples thereof include polyamide resins such as benzoguanamine resin, polyester, polyurethane and the like. In the present invention, the water-soluble polymer is completely dissolved in an aqueous solvent (particle size 0.01 μm or less), colloidal dispersion (particle size 0.01 to 0.1 μm), emulsion (particle size 0.1 to 1 μm). Or the polymer which will be in the state of a slurry (particle size of 1 micrometer or more) is meant.

When forming the back layer, for example, (1) In addition to the above-exemplified resins and the like, an appropriate amount of organic filler or inorganic filler is added, or (2) a resin having high lubricity such as a polyolefin resin or a cellulose resin. When used, a thermal transfer image receiving sheet with improved transportability can be obtained.
Further, when the back layer is formed, curling of the resulting thermal transfer image-receiving sheet can be prevented when a water-holding resin such as polyvinyl alcohol or polyethylene glycol is used as a main component. In addition, when the back layer is formed, when the pigments, fillers and the like exemplified as the additive in the above-described receiving layer are blended, the writing property can be imparted to the obtained thermal transfer image receiving sheet.
The back layer may contain a conductive resin such as an acrylic resin and / or various antistatic agents such as fatty acid ester, sulfate ester, phosphate ester, and ethylene oxide adduct in order to obtain an antistatic function. Good.

The thickness of the back layer is not particularly limited, but the coating amount of solid content, of the order of ^{0.1g / m 2 ~3.0g / m 2} . For the formation of the back layer, generally used coating means can be used, for example, by a gravure printing method, a screen printing method, a reverse roll coating method using a gravure plate, and the like. By doing so, it can be formed.

(Adhesive layer)
Although not shown, an adhesive layer can be provided between the base material sheet 11 and the porous layer 12, and an adhesive layer can be provided between the base material sheet 11 and the back surface layer 17. The adhesive layer is made of an adhesive. Examples of the adhesive include polyolefin resins such as urethane resins and α-olefin-maleic anhydride resins, polyester resins, acrylic resins, epoxy resins, urea resins, Melamine resins, phenol resins, vinyl acetate resins, cyanoacrylate resins and the like can be used. Among them, a reactive type of acrylic resin or a modified one can be preferably used.

Further, it is preferable to cure the adhesive using a curing agent because the adhesive force is improved and the heat resistance is also increased. As the curing agent, an isocyanate compound is generally used, but aliphatic amines, cycloaliphatic amines, aromatic amines, acid anhydrides and the like can be used. The thickness of the adhesive layer is in a coating amount of solid content is ^{usually, 0.5g / m 2 ~10g / m} 2 approximately. For the formation of the adhesive layer, commonly used coating means can be used, for example, by means of gravure printing, screen printing, reverse roll coating using a gravure plate, etc. By doing so, it can be formed. Further, EC sand lamination using a polyolefin material or the like may be performed.

<< Thermal transfer sheet >>
Each layer constituting the thermal transfer sheet used in the present invention will be described in detail.
(Base material)
The substrate 21 is provided to hold the heat-resistant slip layer 23 and the color material layer 22 in the thermal transfer sheet 20. The material of the base material is not particularly limited, but it is desirable to have mechanical characteristics that can withstand the heat applied by the thermal head when the dye of the color material layer is transferred onto the transfer target and does not hinder handling. Examples of such base materials include polyesters such as polyethylene terephthalate, polyarylate, polycarbonate, polyurethane, polyimide, polyetherimide, cellulose derivatives, polyethylene, ethylene / vinyl acetate copolymer, polypropylene, polystyrene, acrylic, and polyvinyl chloride. , Polyvinylidene chloride, polyvinyl alcohol, polyvinyl butyral, nylon, polyether ether ketone, polysulfone, polyether sulfone, tetrafluoroethylene / perfluoroalkyl vinyl ether, polyvinyl fluoride, tetrafluoroethylene / ethylene, tetrafluoroethylene / hexafluoro Various plastic fills such as propylene, polychlorotrifluoroethylene, and polyvinylidene fluoride Or it can be given a seat. Moreover, the thickness of a base material can be suitably set according to a material so that the intensity | strength and heat resistance may become suitable, About 2.5-100 micrometers is common, Preferably it is 1-10 micrometers.

(Heat resistant slipping layer)
The heat-resistant slip layer 23 in the thermal transfer sheet contains at least a binder resin,
The binder resin comprises a hydroxyl group-containing thermoplastic resin and a polyisocyanate;
The molar equivalent ratio (-NCO / -OH) between the hydroxyl group of the hydroxyl group-containing thermoplastic resin and the isocyanate group of the polyisocyanate was 0.01 or more and 3.0 or less.

  The hydroxyl group-containing thermoplastic resin preferably has a hydroxyl value of 9% by mass to 25% by mass. By setting it within this range, the heat resistance can be further improved, and it can be easily dissolved in a solvent such as ethyl acetate or toluene used for preparing the coating solution for the heat resistant slipping layer. For example, as such a polyvinyl acetal resin having a hydroxyl value, as a commercial product, S-LEC BX-L, BX-1, BX-5, KS-1, KS-3, KS-5, KS- manufactured by Sekisui Chemical Co., Ltd. 10 etc. are mentioned. Examples of such polyvinyl butyral resin include ESREC BM-5, BM-S, BH-3, and BH-S. In the present specification, “hydroxyl value” means the ratio of the monomer component having a hydroxyl group in the resin polymer, and the ratio of the mass of the monomer component having a hydroxyl group to the mass of the entire resin polymer (mass). %).

  In addition, other binder resins can be added to the heat-resistant slipping layer coating liquid as long as the gist of the present invention is not impaired. Examples of other binder resins include acrylic resin, polyester resin, styrene-maleic acid copolymer, polyimide resin, polyamide resin, polyamideimide resin, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate, and vinylidene fluoride. Resins, nylon, polyvinyl carbazole, chlorinated rubber, cyclized rubber and polyvinyl alcohol can be mentioned.

  Said polyisocyanate can bridge | crosslink above-described polyvinyl butyral resin and polyvinyl acetal resin using the hydroxyl group, and can improve the coating-film intensity | strength or heat resistance of a heat-resistant slipping layer. Various polyisocyanate resins are conventionally known, and among them, it is desirable to use an adduct of aromatic isocyanate. As the aromatic polyisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, or a mixture of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate, 1,5-naphthalene diisocyanate, tolidine diisocyanate, Examples include p-phenylene diisocyanate, trans-cyclohexane, 1,4-diisocyanate, xylylene diisocyanate, triphenylmethane triisocyanate, and tris (isocyanatephenyl) thiophosphate, especially 2,4-toluene diisocyanate and 2,6-toluene diisocyanate. Or, a mixture of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate is preferable.

  In the coating solution for the heat resistant slipping layer, the polyisocyanate has a molar equivalent ratio (-NCO / -OH) of the hydroxyl group of the hydroxyl group-containing thermoplastic resin described above to the isocyanate group of the polyisocyanate is 0.00. The molar equivalent ratio (—NCO / —OH) is particularly preferably from 0.1 to 2.5. When the molar equivalent ratio (-NCO / -OH) is less than 0.01, the amount of polyisocyanate used is too small, the crosslinking density is low, the heat resistance is insufficient, and the heat resistant slipping layer is formed on the thermal head. This is not preferable because a part thereof easily adheres as debris and a print portion is easily damaged. On the other hand, when the molar equivalent ratio (-NCO / -OH) is larger than 3.0, the amount of polyisocyanate used increases, and the frictional force between the heat-resistant slipping layer and the thermal head increases, resulting in streaks and unevenness in the printed portion. Etc. are likely to occur, which is not preferable.

  The filler which may be contained in the heat resistant slipping layer can clean the residue attached to the thermal head and change the slipperiness of the heat resistant slipping layer. Moreover, blocking with the color material layer coating surface and color material migration during storage of the thermal transfer sheet in a wound form can be reduced. Examples of the filler include ores such as talc, kaolin, mica and graphite, fluorides such as calcium fluoride, barium fluoride and graphite fluoride, sulfides such as molybdenum disulfide, tungsten disulfide and iron sulfide, and oxidation. Inorganic fillers such as oxides such as lead, alumina, and molybdenum oxide can be used. Further, a metal soap which is a fine powdery solid of a fatty acid such as stearic acid or lauric acid and a metal salt such as lithium, magnesium, calcium, barium or zinc can also be used as a filler. Furthermore, organic fillers such as phthalocyanine, fluororesin, silicone resin, polyethylene wax, and nylon (registered trademark) wax can also be used. Of these, fillers of ores such as talc, metal soaps such as zinc stearate, and fillers of silicone resin are preferable, and the slipperiness of the thermal transfer sheet is good, and the winding deviation when winding the thermal transfer sheet, the winding The function to prevent blocking of the wound winding is high. The average particle size of the filler is preferably in the range of 0.05 to 10 μm. The filler is solid at room temperature (20 ° C. ± 15 ° C.). In addition, the above metal soap and organic filler are solid at room temperature. However, when heated, for example, at 200 ° C. or higher, if it liquefies, the lubricity with a heating device such as a thermal head is further improved, which is preferable. .

The filler added to the heat-resistant slipping layer can sufficiently exhibit the functions such as the above-described slipperiness as the filler by being about 5 to 40% by mass with respect to the total solid content of the heat-resistant slipping layer. .
The heat resistant slipping layer is prepared by adding the resin and filler described above and other additives as necessary, and dissolving or dispersing them in an appropriate solvent to prepare a heat resistant slipping layer forming ink. It can be formed by coating on the back surface of the substrate sheet by a forming means such as a gravure printing method, a screen printing method, a reverse coating method using a gravure plate, and drying. Its heat-resistant lubricating layer is 0.1g / m ² ~2g / m ² approximately at a coat weight of solids.

(Color material layer)
In the present invention, the color material layer 22 is provided on the surface opposite to the surface provided with the heat-resistant slip layer in the base material of the thermal transfer sheet. The color material layer is a heat transferable color material layer, and the following dye layer or heat-meltable ink layer can be applied. When the thermal transfer sheet is a sublimation type thermal transfer sheet, a layer containing a sublimable dye (dye layer) is formed as the thermal transfer color material layer. In the case of a heat melting type thermal transfer sheet, a layer containing a heat melting ink (hot melting ink layer) made of a heat melting composition containing a colorant is formed. Note that a layer region containing a sublimable dye and a layer region containing a heat-meltable ink composed of a heat-melting composition containing a colorant may be provided in a surface sequence on a continuous substrate. Good.

  Hereinafter, a dye layer will be described as an example of the color material layer, but the color material layer is not limited thereto, and the color material layer may be a hot-melt ink layer. As the material of the heat transferable color material layer, conventionally known dyes can be used, but those having good characteristics as a printing material, for example, having a sufficient coloring density and changing color due to light, heat, temperature, etc. Those that do not are preferred. For example, as a red dye, MS Red G (manufactured by Mitsui Toatsu Chemical Co., Ltd.), Macrolex Red Violet R (manufactured by Bayer), CeresRed 7B (manufactured by Bayer), Samalon Red F3BS (manufactured by Mitsubishi Chemical), etc. are yellow. Examples of the dye include Holon Brilliant Yellow 6GL (manufactured by Clariant), PTY-52 (manufactured by Mitsubishi Chemical), Macrolex Yellow 6G (manufactured by Bayer), and the like, and Kayaset Blue 714 (Nippon Kayaku Co., Ltd.) as the blue dye. Manufactured), Waxoline Blue AP-FW (manufactured by ICI), Holon Brilliant Blue SR (manufactured by Sand), MS Blue 100 (manufactured by Mitsui Toatsu Chemicals) and the like. In addition, a dye contained in a thermal transfer sheet used in a commercially available sublimation thermal transfer method can also be used.

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

Examples of the method for forming the heat transferable color material layer include the following methods. For the heat-transferable colorant layer obtained by adding additives such as a release agent to the above dyes and binder resin, if necessary, dissolved in an appropriate organic solvent such as toluene or methyl ethyl ketone, or dispersed in water. A coating solution (dissolved solution or dispersion) is applied to one surface of a substrate by, for example, a gravure printing method, a reverse roll coating method using a gravure plate, a roll coater, a bar coater or the like, and dried. Can be formed. It is preferable to form the heat transferable color material layer at a coating amount of about 0.2 to 5.0 g / m ² in terms of solid content. The content of the sublimable dye in the heat transferable colorant layer is preferably 5 to 90% by mass, and more preferably 5 to 70% by mass.

(Primer layer)
A primer layer can be provided between the heat-resistant slip layer of the thermal transfer sheet and the substrate, and the adhesion between the heat-resistant slip layer and the substrate can be improved. A binder resin having good adhesion can be formed mainly on both the heat-resistant slip layer and the substrate.

(Color material primer layer)
In the thermal transfer sheet used in the present invention, a color material primer layer can be provided between the color material layer and the substrate, and adhesion between the color material layer and the substrate can be improved. A binder resin having good adhesion can be formed mainly on both the color material layer and the base material.

(Protective layer)
The thermal transfer sheet used in the present invention may be provided with a protective layer in the surface order on the same side as the color material layer. After the color material is transferred to the thermal transfer image-receiving sheet, the protective layer is transferred to cover the image, whereby the image can be protected from light, gas, liquid, abrasion and the like. Other layers such as an adhesive layer, a release layer, or an undercoat layer may be provided as a protective layer.
(Image forming method)
In the image forming method using the thermal transfer recording material of the present invention, the thermal transfer sheet and the thermal transfer image-receiving sheet are superposed and heated according to the recording signal, whereby the sublimation dye or colorant contained in the thermal transfer sheet is contained. An image can be formed by transferring a heat-meltable ink layer containing the toner to a thermal transfer image-receiving sheet. In the case of a sublimation type thermal transfer sheet, the image forming surface of the thermal transfer image receiving sheet has a dyeing property.
As a thermal transfer recording apparatus that can be used in such an image forming method, a known apparatus can be used and is not particularly limited.

Next, the present invention will be described more specifically with reference to examples and comparative examples. “Parts” in the text are based on mass unless otherwise noted.
Example 1
(Preparation of thermal transfer sheet)
A polyethylene terephthalate film having a thickness of 4.5 μm is used as a base material, and a primer layer coating solution having the following composition is applied to one surface of the base material by a gravure coating method at a solid content of 0.2 g / m ² . Coating is performed to form a primer layer, and then the heat-resistant slipping layer coating liquid 1 having the following composition is applied onto the primer layer by a gravure coating method at a solid content of 0.5 g / m ² , A slipping layer was formed.

<Primer layer coating solution>
-Polyester resin 16.67 parts (Brand name Polyester WR-961, Nippon Synthetic Chemical Co., Ltd. solid content 30%)
・ Water 41.67 parts ・ Isopropyl alcohol 41.67 parts

<Coating liquid 1 for heat resistant slipping layer>
Molar equivalent ratio (-NCO / -OH); 2.5
・ Polyvinyl butyral resin (hydroxyl value 16% by mass) 2.0 parts (SREC BX-1 manufactured by Sekisui Chemical Co., Ltd.)
Polyisocyanate (NCO = 17.3 mass%) 4.4 parts (Bernock D750, manufactured by Dainippon Ink & Chemicals, Inc.)
・ Phosphate surfactant 1.3 parts (Pricesurf A208N, manufactured by Daiichi Pharmaceutical Co., Ltd.)
・ Filler (talc, Microace P-3 manufactured by Nippon Talc Kogyo Co., Ltd.) 0.3 part ・ Methyl ethyl ketone 43.6 parts ・ Toluene 43.6 parts

On a part of the surface of the substrate opposite to the side on which the heat-resistant slip layer is provided, a colorant primer layer coating solution having the following composition is applied by a gravure coating method to a dry coating amount of 0.10 g / m ^2. Coating and drying were performed to form a color material primer layer.
<Colorant primer layer coating solution>
Alumina sol (average primary particle size 10 × 100 nm, solid content 10%) 30 parts (alumina sol 200 manufactured by Nissan Chemical Industries, Ltd.)
・ Polyvinylpyrrolidone resin (K-90, manufactured by ISP) 3 parts ・ Water 50 parts ・ Isopropyl alcohol 17 parts

Subsequently, a yellow dye layer coating liquid (Y), a magenta dye layer coating liquid (M), and a cyan dye layer coating liquid (C) having the following composition are gravure-coated on the color material primer layer. The layers were coated and dried by a printing machine so that the dry coating amount of each layer was 0.6 g / m ² , and the layers were repeatedly formed in this order.

<Yellow dye layer coating liquid (Y)>
Disperse dye (yellow dye represented by the following chemical formula (I)) 2.0 parts Binder resin 4.5 parts (polyvinylacetoacetal resin KS-5, manufactured by Sekisui Chemical Co., Ltd.)
・ 0.045 parts of silicone oil (KF-354L, manufactured by Shin-Etsu Chemical Co., Ltd.)
・ Polyethylene wax 0.1 part ・ Methyl ethyl ketone 45.0 parts ・ Toluene 45.0 parts

<Magenta dye layer coating solution (M)>
Disperse dye (magenta dye represented by the following chemical formula (II)) 2.0 parts Binder resin 4.5 parts (polyvinylacetoacetal resin KS-5, manufactured by Sekisui Chemical Co., Ltd.)
・ 0.045 parts of silicone oil (KF-354L, manufactured by Shin-Etsu Chemical Co., Ltd.)
・ Polyethylene wax 0.1 part ・ Methyl ethyl ketone 45.0 parts ・ Toluene 45.0 parts

<Cyan dye layer coating solution (C)>
Disperse dye (cyan dye represented by the following chemical formula (III)) 2.0 parts Binder resin 4.5 parts (polyvinyl acetoacetal resin KS-5, manufactured by Sekisui Chemical Co., Ltd.)
・ 0.045 parts of silicone oil (KF-354L, manufactured by Shin-Etsu Chemical Co., Ltd.)
・ Polyethylene wax 0.1 part ・ Methyl ethyl ketone 45.0 parts ・ Toluene 45.0 parts

A release layer coating solution having the following composition was applied to the remaining part of the base material on which each of the above dye layers was formed (coating amount 1.0 g / m ² (when dried)) and dried to form a release layer. .
<Coating liquid for release layer>
・ 20 parts of polymethyl methacrylate resin (Dianar BR-87, manufactured by Mitsubishi Rayon Co., Ltd.)
・ Toluene 40 parts ・ Methyl ethyl ketone 40 parts

Further, a protective layer coating solution having the following composition is applied on the release layer (coating amount 2.0 g / m ² (during drying)) and dried to form a protective layer on the substrate. Then, a thermal transferable protective layer composed of a release layer and a protective layer was formed to produce the thermal transfer sheet of Example 1. (See Figure 2)

<Protective layer forming coating solution>
・ 100 parts of vinyl chloride-vinyl acetate copolymer (Solvine CNL Nissin Chemical Industry Co., Ltd.)
・ Toluene 200 parts ・ Methyl ethyl ketone 200 parts

(Preparation of thermal transfer image receiving sheet)
On the porous layer made of a porous polyethylene film (thickness 39 μm), the intermediate layer coating solution and the receiving layer coating solution having the following composition are sequentially applied and dried by the gravure reverse coating method, and then the intermediate layer A receptor layer was formed. The adhesive layer is applied to the porous polyethylene film on the opposite side of the surface provided with the intermediate layer and the receiving layer, using a coating liquid for an adhesive layer having the following composition, and dried by a gravure reverse roll coating method. The heat transfer image receiving sheet of Example 1 was prepared by pasting together with an RC base paper (basis weight 195 g / m ² , thickness 190 μm) as a base sheet. (See FIG. 1) Each of the above coating amounts was a solid content, the intermediate layer was 1.5 g / m ² , the receiving layer was 5.0 g / m ² , and the adhesive layer was 5 g / m ² .
The combined thickness of the base material sheet and the porous layer of the thermal transfer image receiving sheet of Example 1 is 229 μm.

<Intermediate layer coating solution>
・ Polyester resin 50 parts (Polyester WR-905 Nippon Synthetic Chemical Industry Co., Ltd.)
・ Titanium oxide 20 parts (TCA888 Tochem Products)
・ Fluorescent brightener 1.2 parts (Ubitex BAC Ciba Specialty Chemicals Co., Ltd.)
・ Water / isopropyl alcohol = 1/1 (mass ratio) 28.8 parts

<Coating solution composition for receiving layer>
・ 60 parts of vinyl chloride-vinyl acetate copolymer (Solvine C Nissin Chemical Industry Co., Ltd.)
・ Epoxy-modified silicone 1.2 parts (X-22-3000T Shin-Etsu Chemical Co., Ltd.)
・ Methylstil modified silicone 0.6 parts (X-24-510, Shin-Etsu Chemical Co., Ltd.)
・ Methyl ethyl ketone / toluene (mass ratio 1/1) 5 parts

<Coating liquid for adhesive layer>
・ Urethane resin 30 parts (Takelac A-969V Mitsui Takeda Chemical Co., Ltd.)
・ Isocyanate 10 parts (Takenate A-5 Mitsui Takeda Chemical Co., Ltd.)
・ 100 parts of ethyl acetate

(Example 2)
(Preparation of thermal transfer sheet)
A thermal transfer sheet was produced in the same manner as in Example 1 except that the heat-resistant slipping layer coating liquid 1 in the thermal transfer sheet produced in Example 1 was replaced with the heat-resistant slipping layer coating liquid 2 having the following composition.
<Coating fluid 2 for heat resistant slipping layer>
Molar equivalent ratio (-NCO / -OH); 1.0
・ Polyvinyl acetal resin (hydroxyl value: 12% by mass) 60.8 parts (ESREC KS-1 Sekisui Chemical Co., Ltd.)
・ Polyisocyanate (NCO = 17.3 mass%) 42 parts (Bernock D750 Dainippon Ink & Chemicals, Inc.)
・ Filler (zinc stearyl phosphate) 10 parts (LBT1830 purification, manufactured by Sakai Chemical Industry Co., Ltd.)
・ Filler (zinc stearate) 10 parts (SZ-PF manufactured by Sakai Chemical Industry Co., Ltd.)
・ 3 parts of filler (polyethylene wax)
・ 7 parts of filler (ethoxylated alcohol-modified wax) (Unitox 750, manufactured by Toyo Adre Co., Ltd.)
・ Methyl ethyl ketone 200 parts ・ Toluene 100 parts

(Preparation of thermal transfer image receiving sheet)
A thermal transfer image-receiving sheet was prepared in the same manner as in Example 1 except that the porous layer in the thermal transfer image-receiving sheet prepared in Example 1 was replaced with a porous polyethylene film (thickness 30 μm).
The combined thickness of the base material sheet and the porous layer of the thermal transfer image receiving sheet of Example 2 is 220 μm.

(Example 3)
(Preparation of thermal transfer sheet)
A thermal transfer sheet was produced in the same manner as in Example 1 except that the heat-resistant slipping layer coating liquid 1 in the thermal transfer sheet produced in Example 1 was replaced with the heat-resistant slipping layer coating liquid 3 having the following composition.
<Coating fluid 3 for heat resistant slipping layer>
Molar equivalent ratio (-NCO / -OH); 0.1
-Polyvinyl acetal resin (hydroxyl value: 12% by mass) 60.8 parts (S-REC KS-1 Sekisui Chemical Co., Ltd.)
・ Polyisocyanate (NCO = 17.3 mass%) 4.2 parts (Bernock D750 Dainippon Ink & Chemicals, Inc.)
・ Filler (zinc stearyl phosphate) 10 parts (LBT1830 purification, manufactured by Sakai Chemical Industry Co., Ltd.)
・ Filler (zinc stearate) 10 parts (SZ-PF manufactured by Sakai Chemical Industry Co., Ltd.)
・ 3 parts of filler (polyethylene wax)
・ 7 parts of filler (ethoxylated alcohol-modified wax) (Unitox 750, manufactured by Toyo Adre Co., Ltd.)
・ Toluene 200 parts ・ Methyl ethyl ketone 100 parts

(Preparation of thermal transfer image receiving sheet)
The thermal transfer image receiving sheet produced in Example 2 was used as the thermal transfer image receiving sheet of Example 3.

(Comparative Example 1)
(Preparation of thermal transfer sheet)
The thermal transfer sheet produced in Example 1 was used as the thermal transfer sheet of Comparative Example 1.
(Preparation of thermal transfer image receiving sheet)
A thermal transfer image receiving sheet was prepared in the same manner as in Example 2 except that the RC base paper, which is the base sheet in the thermal transfer image receiving sheet prepared in Example 2, was replaced with a basis weight of 211 g / m ² and a thickness of 190 μm.
The combined thickness of the base material sheet and the porous layer of the thermal transfer image receiving sheet of Comparative Example 1 is 220 μm.

(Comparative Example 2)
(Preparation of thermal transfer sheet)
The thermal transfer sheet produced in Example 2 was used as the thermal transfer sheet of Comparative Example 2.
(Preparation of thermal transfer image receiving sheet)
A thermal transfer image receiving sheet was prepared in the same manner as in Example 1 except that the RC base paper, which is a base sheet in the thermal transfer image receiving sheet prepared in Example 1, was replaced with a basis weight of 211 g / m ² and a thickness of 190 μm.
The combined thickness of the base material sheet and the porous layer of the thermal transfer image receiving sheet of Comparative Example 2 is 229 μm.

(Comparative Example 3)
(Preparation of thermal transfer sheet)
The thermal transfer sheet produced in Example 2 was used as the thermal transfer sheet of Comparative Example 3.
(Preparation of thermal transfer image receiving sheet)
The RC base paper as the base sheet in the thermal transfer image-receiving sheet produced in Example 1 was replaced with a basis weight of 211 g / m ² and a thickness of 210 μm, and the porous layer was replaced with a porous polyethylene film (thickness of 20 μm). Other than that was carried out similarly to Example 1, and produced the thermal transfer image receiving sheet.
The combined thickness of the base material sheet and the porous layer of the thermal transfer image receiving sheet of Comparative Example 3 is 230 μm.

(Comparative Example 4)
(Preparation of thermal transfer sheet)
A thermal transfer sheet was produced in the same manner as in Example 1 except that the heat-resistant slip layer coating liquid 1 in the thermal transfer sheet produced in Example 1 was replaced with the heat-resistant slip layer coating liquid 4 having the following composition.
<Coating fluid 4 for heat resistant slipping layer>
Molar equivalent ratio (-NCO / -OH); 0
Polyvinyl acetal resin (hydroxyl value: 12% by mass) 90.3 parts (SREC KS-1 manufactured by Sekisui Chemical Co., Ltd.)
・ Methyl ethyl ketone 200 parts ・ Toluene 100 parts

(Preparation of thermal transfer image receiving sheet)
The thermal transfer image receiving sheet prepared in Example 1 was used as the thermal transfer image receiving sheet of Comparative Example 4.

(Comparative Example 5)
(Preparation of thermal transfer sheet)
A thermal transfer sheet was produced in the same manner as in Example 1 except that the heat-resistant slipping layer coating liquid 1 in the thermal transfer sheet produced in Example 1 was replaced with the heat-resistant slipping layer coating liquid 5 having the following composition.
<Coating fluid 5 for heat resistant slipping layer>
Molar equivalent ratio (-NCO / -OH); 1
Polyvinyl acetal resin (hydroxyl value: 12% by mass) 90.3 parts (SREC KS-1 manufactured by Sekisui Chemical Co., Ltd.)
-Polyisocyanate (NCO = 17.3 mass%) 62.7 parts (Bernock D750, manufactured by Dainippon Ink & Chemicals, Inc.)
・ Methyl ethyl ketone 200 parts ・ Toluene 100 parts

(Preparation of thermal transfer image receiving sheet)
The RC base paper, which is a base sheet in the thermal transfer image-receiving sheet produced in Example 1, was replaced with a basis weight of 186 g / m ² and a thickness of 151 μm, and the porous layer was replaced with a porous polyethylene film (thickness of 35 μm). Other than that was carried out similarly to Example 1, and produced the thermal transfer image receiving sheet.
The combined thickness of the base material sheet and the porous layer of the thermal transfer image receiving sheet of Comparative Example 5 is 186 μm.

  Using the thermal transfer recording material produced by the combination of each thermal transfer sheet and thermal transfer image-receiving sheet prepared in the above Examples and Comparative Examples, back friction, printing wrinkles, heat resistance and curl resistance were evaluated as follows.

(Evaluation of back friction)
In combination with each of the thermal transfer sheets obtained above and each of the thermal transfer image receiving sheets, the frictional force during printing was measured under the following conditions. In addition, the thermal transfer printer with a frictional force measurement function described in Japanese Patent Application Laid-Open No. 2003-300338 was used for measurement of printing and frictional force.
"Printing conditions"
Thermal head: Toshiba Hokuto Electronics thermal head, head resistance 5020Ω resolution 300 dpi (dots per inch)
Line speed: 1 ms / Line (Resolution in the paper transport direction is 300 lpi (line per inch))
Pulse duty: 90%
Applied voltage: 30.0V
Printing pressure: 40N
Print image: gradation image with a width of 1388 pixels x length of 945 pixels and gradations of 0 to 255 (one pixel corresponds to one dot)

Under the above printing conditions, print a solid pattern (high density area) with the highest printing gradation value and a solid pattern (intermediate density area) with 128/255 gradation (gray), and measure the dynamic friction coefficient at that time. The evaluation was performed according to the following evaluation criteria.
"Evaluation criteria"
A: The coefficient of dynamic friction is less than 0.3, and the slipperiness due to contact with the thermal head during printing is very good.
A: The dynamic friction coefficient is 0.3 or more and less than 0.4, and the slipperiness due to contact with the thermal head during printing is good.
(Triangle | delta): A dynamic friction coefficient is 0.4 or more and less than 0.5, and the slipperiness by contact with the thermal head at the time of printing is a little inferior.
X: The coefficient of dynamic friction is 0.5 or more, and the slipperiness due to contact with the thermal head during printing is poor.

(Evaluation of printing wrinkles)
By combining the thermal transfer sheets of the above-mentioned examples and comparative examples and the thermal transfer image-receiving sheet, an image of 255 gradations (maximum applied energy) is printed under the following printing conditions, and an image such as wrinkles is printed on the printed material image. The presence or absence of defects was examined visually. The evaluation was performed according to the following evaluation criteria.

"Printing conditions"
-Thermal head; head resistance value 5020Ω, resolution 300 dpi (dots per inch) (manufactured by Toshiba Hokuto Electronics)
Line speed: 1 ms / Line, (The resolution in the paper transport direction is 300 lpi (line
per inch))
・ Pulse duty: 90%
・ Applied power: 32V
・ Printing pressure: 40N
・ Print image; gradation image with a width of 1600 pixels × length of 1090 pixels and a gradation of 255 (one pixel corresponds to one dot)

"Evaluation criteria"
◎ ・ ・ ・ No image defects such as printing wrinkles.
O: Some image defects such as printing wrinkles occur, but there is no practical problem.
Δ: Image defects such as printing wrinkles occur and are noticeable.
X: Many image defects such as printing wrinkles occur and are very conspicuous.
When the evaluation is ◯, there is almost no risk of image defects such as print wrinkles on the print, and a good print can be obtained.

(Evaluation of heat resistance)
The above printing conditions for the evaluation of the back friction are changed to a gradation value of 5 increments, and a solid pattern is printed. This causes a problem such as wrinkles, sticking, scratches of the heat-resistant sliding layer, etc. The heat resistance of each thermal transfer sheet was evaluated using the weakest energy as the maximum print gradation value. It is assumed that the gradation value of the print data corresponds to 100% solid of 255 gradation, and the ratio of the gradation value at the time of printing divided by 255 is the applied energy of the pattern with respect to the maximum applied energy (for example, If the gradation value at the time of printing is 210 gradations, 210/255 = 0.823, that is, 82% solid). Therefore, it can be said that the higher the maximum print gradation value, the higher the applied energy, that is, the higher the heat resistance.

"Evaluation criteria"
A: The maximum printing gradation value is 255 gradations, and the heat resistance is very high.
O: The maximum printing gradation value is 250 gradations, and the heat resistance is high.
Δ: The maximum print gradation value is 245 gradation, and the heat resistance is not good.
X: The maximum printing gradation value is 240 gradations or less, and the heat resistance is low.

(Evaluation of curl resistance)
A solid pattern was printed on the receiving layer of each thermal transfer image receiving sheet of Examples and Comparative Examples using the corresponding thermal transfer sheets under the printing conditions shown below. After printing, the curl amounts at the four corners were measured, and the maximum value was measured. It should be noted that “+” indicates a convex curl with the stamp screen facing upward, and “−” indicates a concave curl. The smaller the absolute value in both the convex and concave curl directions, the better the evaluation. The following evaluation criteria were used.

"Evaluation criteria"
O: The maximum curl value is within -10 mm and within +10 mm.
Δ: The maximum curl value exceeds ± 10 mm. (The maximum curl value is smaller than −10 mm or larger than +10 mm.)

The evaluation results of the above-mentioned back friction, printing wrinkles, heat resistance and curl resistance are shown in Table 1 below.

As shown in the above results, the thermal transfer recording materials of Examples 1 to 3 showed good results in all of the evaluations of back friction, printing wrinkles, heat resistance and curl resistance.
In the thermal transfer recording material of Comparative Example 1, the basis weight of the resin-coated paper of the thermal transfer image receiving sheet is out of the range of 190 g / m ² or more and 205 g / m ² or less, and 211 g / m ^2. Occurred, and the printed image was defective.
In the thermal transfer recording material of Comparative Example 2, the basis weight of the resin-coated paper of the thermal transfer image-receiving sheet is 211 g / m ² , and the basis weight is out of the range of 190 g / m ² or more and 205 g / m ² or less. Wrinkles are likely to occur.

In the thermal transfer recording material of Comparative Example 3, the basis weight of the resin-coated paper of the thermal transfer image-receiving sheet is 211 g / m ² , and the basis weight is out of the range of 190 g / m ^{2 to} 205 g / m ^2. The combined thickness of the quality layers is larger than 240 μm, the frictional force between the thermal head and the thermal transfer sheet during printing is large, and the slipperiness is not good.
The thermal transfer recording material of Comparative Example 4 does not use an isocyanate-based curing agent in the heat resistant slipping layer of the thermal transfer sheet, and the heat resistance is poorly evaluated.
In the thermal transfer recording material of Comparative Example 5, the combined thickness of the base sheet and the porous layer of the thermal transfer image receiving sheet is 187 μm, and the thermal transfer image receiving sheet curls.

DESCRIPTION OF SYMBOLS 1 Thermal transfer recording material 10 Thermal transfer image receiving sheet 11 Base material sheet 12 Porous layer 13 Receiving layer 14 Middle paper 15, 16 Resin coat layer 17 Back surface layer 20 Thermal transfer sheet 21 Base material 22 Color material layer 23 Heat resistant slipping layer 24 Peeling layer 25 Protective layer

Claims (1)

At least a base sheet, a porous layer, and a receiving layer, a thermal transfer image receiving sheet formed by laminating in this order;
A thermal transfer recording material comprising a combination of thermal transfer sheets having at least a color material layer on one surface of a substrate and at least a heat-resistant slipping layer on the other surface of the substrate,
The basis weight of the base sheet of the thermal transfer image-receiving sheet is 190 g / m ² or more and 205 g / m ² or less, and the combined thickness of the base sheet and the porous layer is 190 μm or more and 240 μm or less,
The heat-resistant slip layer of the thermal transfer sheet contains at least a binder resin,
The binder resin comprises a hydroxyl group-containing thermoplastic resin and a polyisocyanate;
A thermal transfer recording material, wherein a molar equivalent ratio (-NCO / -OH) between a hydroxyl group of the hydroxyl group-containing thermoplastic resin and an isocyanate group of the polyisocyanate is 0.01 or more and 3.0 or less.

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