JP2002192839A - Thermal transfer sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal transfer sheet, with a single type of which a favorable printing quality is realized without separately using different kinds of thermal transfer sheets to image receiving sheets having a wide range from a low smoothness to a high smoothness and with which no practical problem develops. SOLUTION: This thermal transfer sheet is produced by providing a heat resistant layer on one side of a base material film, on the opposite side of which a colored ink layer is provided through a peel ply on the order named. The colored ink layer includes two kinds of ethylene-vinyl acetate copolymer having melt indices different from one another under the condition that the mixing ratio between the copolymer having the high melt index and that having the low melt index lies in the range of 1:2 to 1:1. At the same time, a pigment includes a dye, a petroleum resin and an inorganic pigment. Since the inclusion of two kinds of or the high and low melt indices means the proper mixing of a resin having a low melt viscosity and a resin having a high melt viscosity, both antipodal performances such as the heat sensitivity at thermal transfer and the blocking resistance at the storage are satisfied well-balancedly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer sheet, and more particularly, to a wide range of image receiving sheets having low smoothness to high smoothness. The present invention relates to a heat transfer sheet having excellent heat resistance.

[0002]

2. Description of the Related Art Conventionally, using a thermal transfer sheet in which a coloring layer in which a coloring agent such as a pigment or a dye is dispersed in a binder such as a hot-melt wax or a resin is supported on a base sheet such as a plastic film. 2. Description of the Related Art There is known a fusion transfer method in which energy corresponding to image information is applied by a heating device such as a thermal head to transfer a colorant together with a binder onto an image receiving sheet such as paper or a plastic sheet.

A print image formed by this fusion transfer method has high density and excellent sharpness, and is suitable for recording binary images such as characters and line drawings. Further, by using a thermal transfer sheet having a colored layer of yellow, magenta, cyan, black, etc., by superimposing and recording each colored layer on an image receiving sheet, it is also possible to form a multi-color or full-color image by subtractive color mixing. is there. Due to its simplicity, such a fusion transfer system can be used for various applications, and for various image receiving sheets such as rough paper having low smoothness to synthetic paper having high smoothness, for characters, numerals, images, etc. And other information are printed by thermal transfer and recorded.

[0004]

However, it has been difficult to record clear thermal transfer prints with only one type of thermal transfer sheet on image receiving sheets having different smoothnesses as described above. For example, a thermal transfer sheet applicable to an image receiving sheet having a relatively low smoothness and a thermal transfer sheet used for an image receiving sheet having a high smoothness have been selectively used. The use of different types of thermal transfer sheets has problems, such as the need to replace the thermal transfer sheets and the cost of purchasing the different types of thermal transfer sheets.

Therefore, in order to solve the above problem, the present invention provides a single type of thermal transfer sheet for a wide range of image receiving sheets from low to high smoothness without using different types of thermal transfer sheets. It is an object of the present invention to provide a thermal transfer sheet having good printing quality and practically causing no problem.

[0006]

In order to achieve the above-mentioned object, the present invention has a heat-resistant layer on one side of a base film and a coloring layer on the opposite side of the base film via a release layer. In a thermal transfer sheet in which ink layers are successively stacked, the colored ink layer contains two types of ethylene-vinyl acetate copolymers having different melt indexes, and the ratio of a high melt index to a low melt index is 1: 2 to 1: 1. And contains a pigment or dye, a petroleum resin, and an inorganic pigment. The melt index is based on JIS
K6730 (Testing method for ethylene-vinyl acetate copolymer)
Alternatively, it is a value measured based on ASTM D 1238 and converted to a condition of a test temperature of 190 ° C. and a test load of 2.16 kgf. The coloring ink layer has a melt index of 1 to 300 of the ethylene-vinyl acetate copolymer.
0 g / 10 min, vinyl acetate content (VA value)
Is preferably in the range of 15 to 35%, and two kinds of ethylene-vinyl acetate copolymers having different melt indices are preferably contained.

The softening point of the petroleum resin is 100 to 100.
170 ° C. and a weight average molecular weight (GPC method) of 100
It is preferably from 0 to 3000. The above weight average molecular weight is an average molecular weight on a mass basis measured by gel permeation (permeation) chromatography (GPC). The average particle size of the inorganic pigment is 0.1 to
Desirably, it is 3 μm. In addition, the release layer contains wax as a main component, and latex as an adhesive component.
The content is preferably 20%, whereby a thermal transfer sheet having excellent thermal sensitivity can be obtained. The above thermal transfer sheet
Printing can be performed on an image receiving sheet having a Beck smoothness in the range of 20 to 4000 sec.

The operation of the present invention is as follows. The heat transfer sheet of the present invention has a heat-resistant layer on one surface of a base film, and a colored ink layer is sequentially provided on the opposite side of the base film via a release layer, and a melt index is applied to the colored ink layer. Ethylene-vinyl acetate copolymers of different
They were mixed at a high melt index and a low melt index in a ratio of 1: 2 to 1: 1 and contained pigments or dyes, petroleum resins, and inorganic pigments. Having two types of ethylene-vinyl acetate copolymers with high melt index and low melt index, the resin with low melt viscosity and the resin with high melt viscosity are appropriately mixed, Satisfies both the thermal sensitivity and the anti-blocking property during storage, which are likely to be contradictory, and provides good print quality on a wide range of image receiving sheets from low to high smoothness. Further, since the colored ink layer contains the petroleum resin and the inorganic particles, it is possible to perform printing having abrasion resistance that does not hinder practical use.

[0009]

Next, embodiments of the present invention will be described in detail. The basic configuration of the thermal transfer sheet of the present invention has a configuration in which a colored ink layer is provided on one side of a base film via a release layer, and a heat-resistant layer is provided on the other side of the base film. If necessary, a layer can be added, for example, by providing an adhesive layer on the colored ink layer.

(Base film) As the base film used in the present invention, the same base film as used in the conventional thermal transfer sheet can be used as it is, and other base films can be used. There is no particular limitation. Specific examples of preferred base film include, for example, polyester, polypropylene, cellophane, polycarbonate, cellulose acetate, polyethylene, polyvinyl chloride, polystyrene, nylon, polyimide, polyvinylidene chloride, polyvinyl alcohol, fluororesin, chlorinated rubber, ionomer, etc. Plastic films, condenser paper, paper such as paraffin paper, non-woven fabric, etc.
Further, a substrate film in which these are combined may be used. A particularly preferred substrate film is a polyethylene terephthalate film. The thickness of the substrate film can be appropriately changed depending on the material so that the strength and the thermal conductivity are appropriate, but the thickness is preferably, for example, 2 to 25 μm.

(Release layer) The release layer formed on one surface of the base film is melted during thermal transfer to improve the releasability of the colored ink layer, and at least a part of the surface of the transferred image is colored after transfer. It is transferred together with the ink layer and acts to improve the abrasion resistance of the transferred image by giving good sliding properties to the protective layer of the colored ink layer, particularly to the transferred image. The release layer of the present invention preferably contains wax as a main component, and contains 1 to 20% by mass of latex as an adhesive component based on the entire release layer. The latex of the adhesive component is an emulsion of a thermoplastic elastomer having rubber elasticity,
For example, synthetic rubbers such as ethylene-vinyl acetate copolymer, butadiene rubber, styrene-butadiene rubber, nitrile rubber, nitrile-butadiene rubber, high styrene rubber, isoprene rubber, and acrylic rubber, and natural rubber latex are exemplified. Among the above thermoplastic elastomers, particularly, ethylene-vinyl acetate copolymer, styrene-
It is preferable to use butadiene rubber or acrylonitrile-butadiene rubber from the viewpoint of printability. When the content of such a latex is small, there is a disadvantage that a sufficient cohesive force cannot be obtained in the release layer and printing defects are likely to occur. On the other hand, if the content of the latex is too large, there is a disadvantage that the release layer is difficult to peel off from the substrate film.

In the present invention, first, a release layer is formed on one surface of the base film. This release layer is, for example, acrylic resin, silicone resin, fluorine resin,
Various resins modified with silicone or fluorine can be used, but mainly wax components. As such a wax, various kinds of waxes which melt during printing and exhibit releasability are preferable. Suitable waxes include, for example, microcrystalline wax, carnauba wax,
Various waxes such as paraffin wax, Fischer-Tropsch wax, various low-molecular-weight polyethylenes, wood wax, beeswax, spermaceti, Ibota wax, wool wax, shellac wax, candelilla wax, petrolactam, partially modified wax, fatty acid ester, fatty acid amide, etc. Is mentioned. Particularly preferred waxes are microcrystalline wax and carnauba wax which have relatively high melting points and are hardly soluble in solvents. The release layer is preferably a thin layer so as not to lower the sensitivity of the thermal transfer sheet, for example, a thickness of about 0.1 to 2 μm in a dry state.

(Colored Ink Layer) The colored ink layer formed on the base film directly or via a release layer contains two types of ethylene-vinyl acetate copolymers having different melt indices. The ratio of the high index to the low index is in the range of 1: 2 to 1: 1 and the composition contains a pigment or dye, a petroleum resin, and an inorganic pigment. The melt index of the ethylene-vinyl acetate copolymer ranges from two low to high contents and is from 1 to 3000 g / 10 m
in, and the vinyl acetate content (VA value) is 15 to 35%. That is, ethylene-vinyl acetate copolymer having a low melt index is 1 to 10
It is about 00 g / 10 min, and its vinyl acetate content (VA value) is 15 to 35%. The ethylene-vinyl acetate copolymer having a high melt index is about 1000 to 3000 g / 10 min,
The vinyl acetate content (VA value) is 15 to 35%
It is.

The colored ink layer contains two types of ethylene-vinyl acetate copolymers having a high melt index and a low melt index. The ratio of the high melt index to the low melt index is in the range of 1: 2 to 1: 1. By mixing the resin with low melt viscosity and the resin with high melt viscosity appropriately, the thermal sensitivity at the time of thermal transfer and the anti-blocking performance at the time of storage are easily balanced. Satisfaction can be achieved, and good print quality can be obtained for a wide range of image receiving sheets from low to high smoothness. If only a grade having a low melt index of the ethylene-vinyl acetate copolymer is used for the colored ink layer, the adhesiveness between the base film and the colored ink layer is reduced, and during storage of the heat transfer sheet by winding, the colored ink layer is not used. Is transferred to the back side of the thermal transfer sheet in contact with the sheet, that is, blocking tends to occur. In addition, when printing is performed on an image receiving sheet having low smoothness, for example, rough paper or the like, pinhole-shaped transfer omission occurs in a printing solid portion, and so-called voids are generated, which is not preferable.

Further, when only a grade having a high melt index of ethylene-vinyl acetate copolymer is used for the colored ink layer, the ink is not easily cut when printed on an image receiving sheet having a high degree of smoothness. The layer is not sharply transferred, so that the ink layer is removed and transferred even in a portion that should not be transferred to the transfer receiving body, which is unfavorable because a so-called color is generated. Further, if only a grade having an intermediate value of the melt index of the ethylene-vinyl acetate copolymer is used for the colored ink layer, there arises a problem that the thermal transfer sheet sticks to the image receiving sheet at the time of thermal transfer, causing blemishes and the like. Regarding the ethylene-vinyl acetate copolymer contained in the colored ink layer, the vinyl acetate content (VA value) is based on mass, regardless of whether the value of the melt index is high or low, with respect to the entire ethylene-vinyl acetate copolymer. Therefore, it is preferably 15 to 35%. If the vinyl acetate content is too low, the fluidity of the copolymer will decrease, and the printing sensitivity will decrease, which is not preferred. On the other hand, if the vinyl acetate content is larger than the above range, the glass transition temperature of the copolymer becomes low, and during storage and storage of the thermal transfer sheet, for example, blocking occurs on the back side of the thermal transfer sheet where the colored ink layer contacts. It is not preferable because it becomes easy.

In the colored ink layer, conventionally known pigments or dyes can be appropriately selected as a colorant in an arbitrary hue such as yellow, magenta, cyan, black, and white. The colored ink layer has a softening point of 10%.
0 to 170 ° C. and a weight average molecular weight (GPC method) of 1
It is desirable to contain 000-3000 petroleum resins. Examples of the petroleum resin include aromatic resins such as "N-Polymer" manufactured by Nippon Petrochemical Co., Ltd., "Hi-Resin" manufactured by Toho Chemical Co., Ltd., and "Clinton" manufactured by Nippon Zeon Co., Ltd., which are acid-modified polyolefin resins. Petroleum resins.

The coloring ink layer includes silica, talc, calcium carbonate, precipitated barium sulfate, alumina,
Add inorganic pigments such as titanium white, clay, magnesium carbonate, tin oxide. The inorganic pigment preferably has an average particle size of about 0.1 to 3 μm as a size, and when added to the coloring ink layer together with the above-mentioned petroleum resin, the resulting printed matter has excellent scratch resistance. Further, it has an effect of preventing blocking of the colored ink layer from contacting with the back side of the thermal transfer sheet. Various waxes can be added to the colored ink layer of the present invention in order to improve transferability during thermal transfer printing. For example, microcrystalline wax, carnauba wax, paraffin wax, Fischer-Tropsch wax, various low molecular weight polyethylene, wood wax, beeswax, whale wax, ibota wax, wool wax, shellac wax, candelilla wax, petrolactam, partially modified wax, fatty acid ester , Fatty acid amides and the like.

As described above, the colored ink layer of the thermal transfer sheet of the present invention has ethylene-
It contains two types of vinyl acetate copolymers, and the ratio of a high melt index to a low melt index is in the range of 1: 2 to 1: 1 and contains a pigment or dye, a petroleum resin, and an inorganic pigment. The ethylene-vinyl acetate copolymer has a high melt index.
More than one kind may be used, and the ethylene-vinyl acetate copolymer having a low melt index may be used not only one kind but also two or more kinds. In any case,
At least one high melt index ethylene-
It is sufficient to use a vinyl acetate copolymer and at least one ethylene-vinyl acetate copolymer having a low melt index. For the colored ink layer, a thermoplastic resin other than those mentioned above can be appropriately used as long as it does not hinder the purpose of the thermal transfer sheet of the present invention.

Such a colored ink layer may have a different melt index, that is, an ethylene-vinyl acetate copolymer having a high or low melt index, a pigment or dye, a petroleum resin, or an inorganic pigment, if necessary. It is formed from a coating solution to which various additives such as other binders, dispersants, and antistatic agents are added. The colored ink layer is formed by coating a coating liquid for forming a colored ink layer obtained by mixing a solvent component such as an organic solvent with the above-described material with a conventionally known gravure coat,
The coating can be performed by gravure reverse coating, roll coating, air knife coating, die coating, or hot lacquer coating. The thickness of the colored ink layer is preferably about 0.5 to 6 g / m ² in a dry state.
If it is less than 0.5 g / m ² , sufficient coloring properties cannot be obtained, and
If it exceeds g / m ² , a large amount of printing energy is required, which is not preferable.

(Adhesive Layer) In the thermal transfer sheet of the present invention, an adhesive layer can be provided on the colored ink layer. The adhesive layer can improve the adhesiveness between the image receiving sheet and the transferred colored ink layer. This adhesive layer is mainly made of a thermoplastic resin which exhibits an adhesive property by being softened by heating with a thermal head, a laser or the like, and waxes for preventing blocking when the obtained thermal transfer sheet is wound into a roll. An anti-blocking agent such as amides, esters and salts of higher fatty acids, powders of fluororesins and inorganic substances can be added.

As the thermoplastic resin, for example, ethylene-
Vinyl acetate copolymer (EVA), ethylene-acrylate copolymer (EEA), polyester resin, polyethylene, polystyrene, polypropylene, polybutene, petroleum resin, vinyl chloride resin, vinyl chloride-vinyl acetate copolymer, polyvinyl alcohol , Vinylidene chloride resin, methacrylic resin, polyamide, polycarbonate,
Polyvinyl formal, polyvinyl butyral, acetylcellulose, nitrocellulose, polyvinyl acetate,
Examples thereof include polyisobutylene, ethyl cellulose, and polyacetal, and particularly those having a relatively low softening point conventionally used as a heat-sensitive adhesive, for example, a softening point of 50 to 150 ° C.

The adhesive layer is formed by hot-melt coating the above-mentioned thermoplastic resin and additives or a coating liquid for forming an adhesive layer in which an appropriate organic solvent or water is dissolved or dispersed in a conventionally known hot-melt coat. Lacquer coat, gravure direct coat, gravure reverse coat, knife coat, air coat, roll coat, etc.
In the dry state, a thickness of 0.05 to 5 g / m ² is provided. When the thickness of the dried coating film is less than 0.05 g / m ² ,
Adhesiveness between the image receiving sheet and the colored ink layer is poor, resulting in poor transfer during printing. On the other hand, when the thickness exceeds 5 g / m ² , the transfer sensitivity at the time of printing decreases, and satisfactory printing quality cannot be obtained.

(Heat-Resistant Layer) In the present invention, a heat-resistant layer is provided on the substrate film on the surface in contact with the thermal head in order to improve the slipperiness of the thermal head and prevent sticking. Is preferred. The heat-resistant layer has a heat-resistant resin and a substance acting as a heat releasing agent or a lubricant as basic components. By providing such a heat-resistant layer, thermal printing can be performed without sticking even on a thermal transfer sheet made of a plastic film that is weak to heat, making it difficult to cut the plastic film and making it easy to process. You can take advantage of such advantages.

This heat-resistant layer is composed of a binder resin, a slip agent,
It is suitably used and formed by adding a surfactant, inorganic particles, organic particles, a pigment and the like. Binder resin used for the heat-resistant layer, for example, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose resin such as nitrified cotton, polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, polyvinyl acetal And vinyl resins such as polyvinylpyrrolidone, acrylic resin, polyacrylamide, acrylonitrile-styrene copolymer, polyester resin, polyurethane resin, silicone-modified or fluorine-modified urethane resin.

Among them, those having several reactive groups, for example, those having a hydroxyl group are used, and as a crosslinking agent,
It is preferable to use a crosslinked resin in combination with a polyisocyanate or the like. The means for forming the heat-resistant layer may be prepared by dissolving or dispersing a material obtained by adding a slipping agent, a surfactant, inorganic particles, organic particles, a pigment, etc. to a binder resin in an appropriate solvent as described above, Is prepared, and the coating liquid is applied by a conventional coating means such as a gravure coater, a roll coater, and a wire bar, and dried. The thickness of the heat-resistant layer is 0.1 to 3 g / m ² in a dry state.
The degree is preferred.

(Image Receiving Sheet) The thermal transfer sheet of the present invention comprises:
Printing can be performed on an image receiving sheet having a Beck smoothness in the range of 20 to 4000 sec. That is, rough paper such as Kent paper having a Beck smoothness of nearly 20 seconds, medium quality paper, high quality paper, art paper, lightweight coated paper, lightly coated paper, coated paper, cast coated paper, synthetic resin or emulsion impregnated paper,
An image receiving sheet such as a synthetic rubber latex impregnated paper, a synthetic resin internal paper, or a synthetic paper having a Beck smoothness of about 4000 sec can be used. That is, Beck smoothness is 20 to 400
Any material can be used for the image receiving sheet within a range of 0 sec. In addition, Beck smoothness is JIS
It is measured according to P8119. In the present invention, an image receiving sheet having a thickness of about 40 to 300 μm can be used.

[0027]

The present invention will be described more specifically with reference to examples and comparative examples. In the text, "part" or "%" means
Unless otherwise specified, it is based on mass. (Example 1) As a substrate film, a coating liquid for a release layer having the following composition was applied to one surface of a polyethylene terephthalate film having a thickness of 4.0 µm by gravure coating.
The coating is applied so that the dry coating amount is 1.0 g / m ² , and dried to form a release layer. Further, on the release layer, a coating liquid for a colored ink layer having the following composition was applied by gravure coating so that the dry coating amount was 1.0 g / m ² .
After drying to form a colored ink layer, the thermal transfer sheet of Example 1 is prepared. In addition, on the other surface of the above substrate film,
A heat-resistant layer coating solution having the following composition is applied in advance by gravure coating to a dry coating amount of 0.3 m ² and dried to form a heat-resistant layer.

[Coating liquid for release layer] Carnauba wax 84 parts Oxidized microcrystalline wax 12 parts Styrene-butadiene copolymer rubber 3 parts Leveling agent 1 part

[Coating Liquid for Colored Ink Layer] Carbon black (Mitsubishi Chemical Corporation, # 44) 3 parts Ethylene-vinyl acetate copolymer 4 parts (Mitsui Dupont Chemical Co., Ltd., Elvacs 200W, melt index 25) Petroleum resin (Nippon Petrochemical (00 g / 10 min, VA = 28%) Ethylene-vinyl acetate copolymer 7 parts (Sumitomo Chemical Co., Ltd., Sumitate KC-10, melt index 150 g / 10 min, VA = 28%) 4 parts (softening point 160 ° C., average molecular weight 2700) Fine powder polyethylene wax 3 parts (melting point 101-109 ° C., average molecular weight 700, average particle size 50 μm) Synthetic silica (Fuji Silysia, Sylysia) 350) 0.1 part (average particle size 1.8 μm) Dispersant 0.1 part Cyclohexane 40 parts Toluene 40 parts

[Coating liquid for heat-resistant layer] Silicon urethane resin 15 parts Curing agent 4 parts Methyl ethyl ketone 60 parts Cyclohexane 19 parts Ethyl acetate 4 parts

Example 2 The same composition as the base film with a heat-resistant layer used in Example 1 was used except that the colored ink layer used in Example 1 was changed to the following composition, and dried and applied by gravure coating. The coating was applied so that the amount became 1.0 g / m ² , and dried to form a colored ink layer. Other than that, the thermal transfer sheet of Example 2 was produced in the same manner as in Example 1. [Coating Liquid for Colored Ink Layer] Carbon Black (Mitsubishi Chemical Co., Ltd., # 44) 40 parts Ethylene-vinyl acetate copolymer 2 parts (Mitsui DuPont Polychemicals Co., Ltd., Elvacs 200W, melt index 2500g / 10min, VA = 28%) Ethylene-vinyl acetate copolymer 2 parts (manufactured by DuPont-Mitsui Polychemicals, Evaflex 460, melt index 2.5 g / 10 min, VA = 19%) Petroleum resin (manufactured by Nippon Petrochemical Co., Ltd.) Neopolymer 170S) 4 parts (softening point 160 ° C, average molecular weight 2700) Fine powder polyethylene wax 3 parts (melting point 101 to 109 ° C, average molecular weight 700, average particle size 50 µm) Synthetic silica (Fuji Silysia, Sylysia 350) 0. 1 part (average particle size 1.8 μm) Dispersant 0.1 part Cyclohexane 40 Toluene 40 parts

Comparative Example 1 A thermal transfer sheet of Comparative Example 1 was prepared in the same manner as in Example 1 except that the coating composition for the colored ink layer was changed to the following composition. did. [Coating Liquid for Colored Ink Layer] Carbon Black (Mitsubishi Chemical Co., Ltd., # 44) 19 parts EVA (Sumitomo Chemical Co., Ltd., Sumitate KC-10) 70 parts (Melt Index 150 g / 10 min, VA = 19) %) Petroleum resin (Neopolymer 170S, manufactured by Nippon Petrochemical Co., Ltd.) 10 parts Synthetic silica (Silicia 350, manufactured by Fuji Silysia) 1 part Dispersant 0.5 part Toluene 150 parts Methyl ethyl ketone 150 parts

Using the thermal transfer sheets of Examples and Comparative Examples described above, printing is performed under the following printing conditions, and the printed matter is evaluated for print quality by the following evaluation method. (Printing conditions) Smapro540 manufactured by ALPS Electric Co., Ltd.
N, using a thermal transfer printer, the image receiving sheet is composed of synthetic paper (Beck smoothness: 3610 sec), coated paper (Beck smoothness: 348 sec), rough paper (Kent paper, Beck smoothness: 23).
Then, test patterns were printed using the thermal transfer sheets of Examples and Comparative Examples, and evaluation samples were prepared.

(Evaluation method of print quality) Under the above printing conditions, the obtained printed matter is visually inspected for transferability, particularly for the presence of blemishes at the edge of the printed part and the presence of voids in the printed solid part. Checked the quality.

(Evaluation Results) Examples 1 and 2 above
The printed matter obtained from the above, from rough paper having a low Beck smoothness to synthetic paper having a high Beck smoothness, was excellent in print quality without any blemishes or voids, regardless of the level of smoothness. On the other hand, the printed matter of Comparative Example 1 was poor in that rough voids with low Beck smoothness had significant voids.

[0036]

As described above, the thermal transfer sheet of the present invention has a heat-resistant layer on one side of a base film, and a colored ink layer on the opposite side of the base film via a release layer. The coloring ink layer contains two types of ethylene-vinyl acetate copolymers having different melt indices.
A mixture of a high melt index and a low melt index in a range of 1: 2 to 1: 1 and a pigment or dye,
It contains petroleum resin and inorganic pigment. Melt index is high, and it contains two kinds of low ethylene-vinyl acetate copolymer, because the resin with low melt viscosity and the resin with high melt viscosity are appropriately mixed,
The thermal sensitivity at the time of thermal transfer and the anti-blocking property at the time of preservation are satisfied in a well-balanced manner, and the printing quality is good for a wide range of image receiving sheets from low to high smoothness. can get.

Claims (6)

[Claims] 1. A thermal transfer sheet comprising a heat-resistant layer on one side of a substrate film and a colored ink layer successively laminated via a release layer on the opposite side of the substrate film, wherein the colored ink layer is melted. It contains two kinds of ethylene-vinyl acetate copolymers having different indices, and the ratio of a high melt index to a low melt index is in the range of 1: 2 to 1: 1, and a pigment or dye, a petroleum resin, or an inorganic pigment is used. A thermal transfer sheet characterized by containing. 2. The colored ink layer according to claim 1, wherein the ethylene-vinyl acetate copolymer has a melt index of 1 to 3000.
2. The thermal transfer sheet according to claim 1, wherein the thermal transfer sheet contains two kinds of resins each having a g / 10 min and a vinyl acetate content (VA value) of 15 to 35%. 3. The softening point of the petroleum resin is 100-17.
0 ° C. and a weight average molecular weight (GPC method) of 1,000 to
2. The thermal transfer sheet according to claim 1, wherein the thermal transfer sheet is 3,000. 4. The inorganic pigment has an average particle size of 0.1 to 0.1.
The thermal transfer sheet according to claim 1, wherein the thickness is 3 µm. 5. The release layer contains wax as a main component,
2. The thermal transfer sheet according to claim 1, wherein the thermal transfer sheet contains 1 to 20% of latex as an adhesive component. 6. The thermal transfer sheet according to claim 1, wherein printing is possible on an image receiving sheet having a Beck smoothness in the range of 20 to 4000 sec.