JPH0494975A - Thermal transfer sheet - Google Patents

Abstract

PURPOSE:To obtain the title thermal transfer sheet which is excellent in heat resistance and slip property of a rear surface, excellent in both adhesion and peeling off property between the thermal transfer sheet and a material to be transferred and free from resolving property of a printed image and greasing by a method wherein a rear surface layer is formed by using styrene/ acrylonitrile copolymer as a main component of a binder. CONSTITUTION:For a thermal transfer sheet A, a heat fusible ink layer 2 is formed on one side surface of a substrate film 1, a rear surface layer 3 is formed on the other side surface, and a mat layer 4 is formed between the substrate film 1 and the ink layer 2 as occasion demands. The rear surface layer 3 preventing sticking of a thermal head is provided to a rear surface of the thermal transfer sheet. The rear surface layer 3 is that to be provided to the other surface of the substrate film and as the substrate film, that which is comparatively excellent in heat resistance, e.g. a polyethylene terephthalate film, should preferably be used. The rear surface layer is formed by main component, styrene/acrylonitrile copolymer as binder resin and other necessary additive agents.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a thermal transfer sheet, and more particularly to a novel co-wound thermal transfer sheet in which a thermal transfer sheet and a transfer material such as paper are temporarily bonded in advance.

(Prior art and its problems) Conventionally, when printing output prints from computers or word processors using a thermal transfer method, a thermal transfer sheet with a heat-melting ink layer provided on one side of a base film has been used. .

This conventional thermal transfer sheet has a thickness of 1 mm as a base film.
Using paper such as capacitor paper or paraffin paper with a thickness of 0 to 20 μm, or plastic film such as polyester or cellophane with a thickness of 3 to 20 μm, a layer of heat-melting ink made by mixing coloring agents such as pigments and dyes with wax is applied. It is manufactured by coating.

When printing on transfer paper using these conventional thermal transfer sheets, the thermal transfer sheet is supplied from a roll wrapped with the thermal transfer sheet, while a continuous or sheet transfer material is supplied, and both are placed on a platen. In this state, a thermal head applies heat from the back side of the thermal transfer sheet to melt and transfer the ink layer to form a desired image.

However, even if you try to use these thermal transfer sheets for facsimile printers that use conventional thermal coloring paper, for example, the above-mentioned tsukushimiri printers do not have a conveyance device for the transfer material because the recording paper itself is thermally colored. This problem also applies to special printers such as large plotters.

As a method to solve the above-mentioned problems, the thermal transfer sheet and the transfer material are temporarily bonded in advance and rolled up into a roll to make it compatible with facsimile printers, etc., and to simplify and downsize the device. A method has been devised.

The first problem with the above conventional technology is that when a heat-resistant material such as a plastic film is used as the base film of the thermal transfer sheet, the thermal head may stick during printing, resulting in peeling of the thermal head and Problems such as loss of slip properties and tearing of the base film occur.

For this reason, a method of forming a heat-resistant layer made of a thermosetting resin with high heat resistance has been proposed, but this method requires the use of a curing agent such as a crosslinking agent when forming the heat-resistant layer.
Therefore, type 2a is required as the coating liquid, and since the base film is a plastic film, a long heat treatment lasting several tens of hours at a relatively low temperature is required after coating, making the process extremely complicated. Not only that, but there is also the problem of wrinkles occurring during heat treatment unless strict temperature control is carried out.

As a method to solve these problems, methods using various thermoplastic resins with high softening points have been proposed, but these heat-resistant resins are difficult to dissolve in general industrial organic solvents and are thin. It is not easy to form layers. In addition, since the resin used in both cases is a thermoplastic resin, the heat resistance of the formed back layer is limited, and the back layer has poor adhesion to the base film, making it difficult to form a practical back layer. There wasn't.

The second problem is that in the case of such a co-wound thermal transfer sheet, the thermal transfer sheet and the paper adhere firmly to each other, so that wrinkles and misalignment do not occur in the thermal transfer sheet, and both can be easily separated after thermal transfer. It is required that the ink layer be accurately transferred to the paper in the transfer area and not be transferred at all in the transfer area and that the paper will not be contaminated. On the other hand, in the case of conventional co-wound thermal transfer sheets, none of them could fully satisfy these requirements.

Therefore, an object of the present invention is to solve the above-mentioned problems, to have excellent heat resistance and slip properties on the back side, as well as both adhesion and peelability between the thermal transfer sheet and the transfer material, and to improve the resolution and background of printed images. To provide a co-wound thermal transfer sheet without stains.

(Means for solving problems) The above objects are achieved by the present invention as described below.

That is, the present invention provides a thermal transfer sheet in which a heat-melt ink layer is formed on one surface of a base film and a back layer is provided on the other surface of the base film, and a transfer material is bonded by an adhesive layer. The thermal transfer sheet is a releasably adhesive thermal transfer sheet, characterized in that the back layer is formed using a styrene/acrylonitrile copolymer as a main component of the binder.

(Function) By using a styrene/acrylonitrile copolymer as the resin forming the back layer, a thermal transfer sheet having a back layer with excellent heat resistance can be easily provided without requiring complicated heat treatment. .

In a preferred embodiment, the adhesive layer is made of an adhesive with a specific composition, so that the thermal transfer sheet and the paper firmly adhere to each other, preventing wrinkles or misalignment, and also allowing both to be easily bonded together after thermal transfer. A thermal transfer sheet is provided in which the ink layer is accurately transferred to the paper in the transfer area, and the transferred area is not transferred at all, so that the paper is not contaminated.

(Preferred Embodiments) Next, the present invention will be explained in more detail with reference to preferred embodiments.

A cross-sectional view of a preferred example of the thermal transfer sheet of the present invention is shown in FIG.

The thermal transfer sheet of the present invention is a thermal transfer sheet in which a thermal transfer sheet A and a material to be transferred B are releasably adhered to each other by an adhesive layer C, as shown in the figure, and the back layer 3 formed on the back surface of the thermal transfer sheet is It is characterized by being made of a specific resin.

As shown in the figure, the thermal transfer sheet A has a heat-melting ink layer 2 formed on one side of a base film 1, and a back layer 3 formed on the other surface, and the base film 1 and ink layer are formed as necessary. A matte layer 4 is formed between the two.

As the base film 1 used in the thermal transfer sheet of the present invention, the same base film used in conventional thermal transfer sheets can be used as is, and other materials can also be used, and there are no particular limitations. .

Specific examples of preferable base films include polyester, polypropylene, urethane, cellophane, polycarbonate, cellulose acetate, polyethylene, polyvinyl chloride, polystyrene, nylon, polyimide, polyvinylidene chloride, polyvinyl alcohol, fluororesin, chlorinated rubber, Examples include plastics such as ionomers, papers such as condenser paper and paraffin paper, nonwoven fabrics, and base films made of composites of these materials.

The thickness of this base film can be changed as appropriate depending on the material so that its strength and thermal conductivity are appropriate, but the thickness is preferably, for example, 2 to 25 um.

The heat-melting ink layer 2 provided on the base film is composed of a colorant and a vehicle, and may further contain various additives as necessary.

The colorant is preferably an organic or inorganic pigment or dye that has good properties as a recording material, such as one that has sufficient color density and does not turn brown due to light, heat, temperature, etc.

Of course, carbon black is preferable for black monochrome printing, and chromatic colorants such as cyan, magenta, yellow, etc. are used for multicolor printing. It is generally preferred that the amount of these colorants used is about 5 to 70% by weight in the ink layer.

The vehicle used includes wax as a main component, and mixtures of wax with drying oil, resin, mineral oil, cellulose, rubber derivatives, and the like.

Representative examples of wax include microcrystalline wax, carnauba wax, paraffin wax, and the like. Furthermore, various products such as Fischer-Tropsch wax, various low-molecular-weight polyethylenes, wood wax, beeswax, spermaceti wax, privet wax, wool wax, shellac wax, candelilla wax, petrolactam, polyester wax, assorted waxes, fatty acid esters, fatty acid amides, etc. Wax is used. In the present invention, a thermoplastic resin having a relatively low melting point may be mixed into the wax to improve the adhesion of the ink to the transfer material.

Methods for forming a hot melt ink layer on a base film include hot melt coating, hot lacquer coating,
Examples include gravure coating, gravure reverse coating, roll coating and many other methods. The thickness of these ink layers may be several micrometers as in the conventional case.

On the back surface of the thermal transfer sheet of the present invention described above, a back layer 3 is provided to prevent sticking of the thermal head.

The back layer 3, which primarily characterizes the present invention, is provided on the other surface of the above-mentioned base film, and the base film is made of a material with relatively excellent heat resistance, such as a polyethylene terephthalate film. It is preferable to use

In the present invention, the above-mentioned back layer is formed mainly from a styrene/acrylonitrile copolymer as a binder resin and other necessary additives.

The styrene/acrylonitrile copolymer used in the present invention is obtained by copolymerizing styrene and acrylonitrile, and includes, for example, Cevian AD and Cevian L.
D, Sevian NA (manufactured by Daicel Chemical Company), etc., in various grades are easily available on the market, and any of them can be used in the present invention, and can be easily produced according to conventional methods.

According to the inventor's detailed research, the styrene/acrylonitrile copolymer suitable for the purpose of the present invention has a molecular weight of 100,000 to 200,000, preferably 150,000 to 200,000, among various grades.
190,000, acrylonitrile content is 20 to 40 mol%,
It has been found that a preferable content is 25 to 30 mol %, and a softening temperature of 400° C. or higher as determined by differential thermal analysis gives preferable results in terms of dissolution stability in organic solvents and heat resistance.

The above styrene/acrylonitrile copolymer does not have sufficient adhesion to the base film when a polyethylene terephthalate film is selected as the base film. Therefore, when producing the styrene/acrylonitrile copolymer, it is preferable to copolymerize a small amount, for example, several mol % of a monomer having a functional group (for example, meth (acrylic acid, etc.)).

Alternatively, a method can be used in which a small amount of other adhesive resin is used in combination, or a method in which a primer layer is previously formed on the base film using these adhesive resins.

Preferred adhesive resins are amorphous linear saturated polyester resins with a glass transition point of 50°C or higher, such as products such as Vylon (manufactured by Toyobo), Elitere (manufactured by Unitika), and Polyester (manufactured by Nippon Gosei Kagaku). Various grades are available on the market, and any of them can be used in the present invention.

As a particularly preferable example, Byron RV290 (manufactured by Toyobo ■, epoxy group-introduced product, molecular weight 20,000 to 25,000,
Tg: 77°C, softening point: 180°C, hydroxyl value: 5 to 8).

When forming a primer layer using the above polyester resin, it is preferable to form a layer with a thickness of about 0.05 to 0.5 μm; if it is too thin, adhesiveness will be insufficient;
If it is too thick, the sensitivity and heat resistance of the thermal radar will decrease, which is not preferable.

When mixed with the styrene/acrylonitrile copolymer, it is preferably used at a ratio of 1 to 30 parts by weight per 100 parts by weight of the styrene/acrylonitrile copolymer; if the amount used is too small, adhesion may occur. On the other hand, if the amount is too high, the heat resistance of the back layer will decrease and sticking property will occur, which is not preferable.

Of course, in the present invention, other binder resins such as ethyl cellulose, hydroxyethyl cellulose, ethyl hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, cellulose acetate, cellulose acetate butyrate, nitrified surface, etc. Vinyl resins such as cellulose resins, polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, polyvinyl acetal, polyvinylpyrrolidone, polyacrylamide, acrylonitrile-styrene copolymers,
Polyester resins, polyurethane resins, silicone-modified or fluorine-modified urethanes, etc. can also be used in combination in small amounts.

In the present invention, when forming the back layer from the above-mentioned materials, waxes, higher fatty acid amides, esters, surfactants, fatty acid metal soaps, alkyl phosphate metal salts, etc. Thermal release agents and lubricants can be included.

In addition, in order to improve the heat resistance of the back layer, as a heat resistant agent,
Hydrotalcite DHT-4A (manufactured by Kyowa Chemical Industry)
, Talc Micro Ace L-1 (manufactured by Nippon Talc), Teflon LeBron Shi-2 (manufactured by Daikin Industries), Graphite Fluoride 5CP-10 (manufactured by Royal Chemical Industries), Graphite AT40S
(manufactured by Oriental Sangyo) or silica, calcium carbonate, precipitated barium, urea resin crosslinked powder, styrene/acrylic resin crosslinked powder, amino resin crosslinked powder, silicone powder, wood flour,
Fine particles of molybdenum disulfide, boron nitride, etc. can be included.

Further, a conductive agent such as carbon black can also be added for the purpose of imparting antistatic properties to the back layer.

To form the back layer, prepare a coating solution by dissolving or dispersing the above materials in a suitable solvent such as acetone, methyl ethyl ketone, toluene, xylene, etc., and apply this coating solution to a gravure coater, roll coater, etc. It is formed by coating with a conventional coating means such as , wire bar, etc. and drying.

The coating amount, that is, the thickness of the back layer is also important, and in the present invention, the coating amount is 0.5 g/rd or less, preferably 0.5 g/rd or less on a solid content basis.
A back layer having sufficient performance can be formed with a thickness of 1 to 0.5 g/rrr. If the back layer is too thick, the sensitivity during transfer will decrease, which is not preferable.

It is also effective to form a primer layer made of polyester resin, polyurethane resin, etc. on the base film before forming the above-mentioned back layer.

Transfer material B may be any sheet or film that can be thermally transferred, such as normal high-quality paper, plain paper, synthetic paper, tracing paper, plastic film, etc., and is not a sheet or film that is used as a conventional transfer material for thermal transfer. Good to have. Further, the size of the transfer material may be a sheet of paper such as an A version or a B version, but preferably a continuous sheet of any width.

The composition of the adhesive layer C for temporarily adhering the thermal transfer sheet A and the transfer material B may be the same as that of the prior art, but in a preferred embodiment of the present invention, the adhesive is made of adhesive particles having a low glass transition temperature. It consists of resin particles with a high glass transition temperature and wax particles.

The glass transition temperature of the above-mentioned adhesive is preferably in the range of -90°C to -60°C, and examples of such adhesives include rubber-based adhesives, acrylic-based adhesives, and silicone-based adhesives. In addition, in terms of form, there are solvent solution type, aqueous solution type, hot melt type, aqueous or oil emulsion type, and any of them can be used in the present invention, but acrylic type is particularly suitable in the present invention. It is an aqueous emulsion type, and its particle size is about 1 to 30 μm, preferably 5 to 20 μm. By using such an emulsion type adhesive, the adhesive 5 of the adhesive layer maintains its particle shape as shown in the third figure.

When using the above-mentioned adhesive alone, excellent adhesion can be obtained, but the removability of the transfer material is insufficient and uneven, and unexpected damage may occur during manufacturing, storage, transportation, etc. before thermal transfer. When this force is applied, there is a problem in that the ink layer of the thermal transfer sheet is transferred to the transfer material, resulting in scumming. Furthermore, during thermal transfer, the ink layer is not easily cut, and for example, the ink layer is transferred to the periphery of the area where the thermal head prints, resulting in poor resolution of the transferred image.

In the present invention, the above problem can be solved by adding a resin emulsion containing fine resin particles, for example, resin particles 6 with a particle diameter of about 0.01 to 0.5 μm, to the emulsion adhesive, so that the adhesiveness is within a preferable range. By adding emulsion 7 of wax similar to the one used to form the ink layer, foil breakage of the adhesive layer C is improved, and the resolution of the transferred image is improved. was found to be significantly improved.

As the above resin emulsion, for example, ethylene-
Thermoplastic resins such as vinyl acetate copolymer, ethylene-acrylic acid ester copolymer, polyethylene, polystyrene, polypropylene, polybdenum, vinyl chloride resin, vinyl chloride-vinyl acetate copolymer, acrylic resin, and especially acrylic emulsion are preferred. be. Such resin particles preferably have a glass transition temperature higher than that of the pressure-sensitive adhesive, for example, 60° C. or higher, and may be thermoset resin particles as the case may be.

Further, the wax emulsion is obtained by emulsifying the wax as described above by a known method, and the particle size thereof is not particularly limited, although the finer the better.

The weight ratio of the adhesive, resin particles, and wax is 3 to 5:
It is preferably 1 to 2.5 + 3 to 5. If the ratio is outside this range, the various problems described above are likely to occur, which is not preferable.

The adhesive layer C made of the above components may be provided on the surface of the transfer material B, but in this case, since the printed matter remains sticky, it is preferably provided on the surface of the ink layer 2 of the thermal transfer sheet. In this case, since the adhesive is used as an aqueous emulsion, the ink layer will not be damaged (preferably. The emulsion coating method and drying method are not particularly limited, but
Drying is preferably carried out at a low temperature so that the emulsion particles remain.

The adhesive layer preferably has a thickness of 0.1 to 20 μm (0.1 to 5 g/rrf as solid coating amount).

The adhesion between the thermal transfer sheet A and the transferred material B is preferably carried out by continuously adhering the transferred material while forming an adhesive layer on the surface of the ink layer of the thermal transfer sheet, and then winding this up into a roll. When winding up, the material to be transferred may be placed on the outside, or the thermal transfer sheet may be placed on the outside (or these may be cut into sheets).

The above is the basic structure of the co-wound thermal transfer sheet of the present invention, but of course, as shown in the first diagram, a matte layer 4 is provided between the base film and the ink layer to make the printing matte.
Any technique well known in the field of thermal transfer sheets can be added to the thermal transfer sheet of the present invention, such as making the ink layer a color other than black.

The thermal transfer sheet of the present invention described above is set in, for example, a facsimile printer, conveyed as shown by the arrow in FIG. A desired image 9 is formed.

(Example) Next, the present invention will be described in more detail with reference to reference examples, examples, and comparative examples. In the text, parts or percentages are based on weight unless otherwise specified.

Reference Examples 1 to 3 Ink 1 Styrene/acrylonitrile copolymer (Sevian AD,
Daicel Chemical ■) 6.0 parts linear saturated polyester resin (Eliteir UE3200, Unitika ■) 0.3 parts zinc stearyl phosphate (LBT 1830, Sakai Chemical ■)
3.0 parts urea resin crosslinked powder (organic filler, manufactured by Nippon Kasei ■) 3.0 parts melamine crosslinked resin powder (Eposter S, manufactured by Nippon Kasei ■)
1.5 parts melting point 11 (M
EK/) Luene = 1/l)
86. 2-part ink (2 Styrene/acrylonitrile copolymer (Sevian LD,
6.0 parts linear saturated polyester resin (Vylon 200, manufactured by Toyobo ■)
0.3 parts Aluminum stearate (SA 1000, manufactured by Sakai Chemical ■) 4.5 parts Polyethylene wax (Mark FC113, manufactured by Adeka Argus ■) 1.0 parts Fluorocarbon (Mold Vuit F57, manufactured by Accel Plastic ■) 1.0 parts Solvent ( MEK/) Luen=l/I) 87.
Part 2 1 Ink (3) Styrene/acrylonitrile copolymer (Sevian NA,
Daicel Chemical (manufactured by Kiki) 6.0 parts Linear saturated polyester resin (Elitaire UE3201, manufactured by Unitika Co., Ltd.) 0.3 parts Zinc stearate (SZ 2
000, manufactured by Sakai Kagaku ■) 4.5 parts Urea resin powder (organic filler, manufactured by Nippon Kasei ■) 3.0 parts Conductive carbon (Ketchen Black EC600JD, manufactured by Lion Akzo ■) 0.8 parts Solvent 1 (M
EK/) Ruen 1/11
85.4 parts After stirring and mixing the above composition, it was dispersed in a paint shaker for 3 hours, and diluted with a diluting solvent (MEK/toluene=
1/1) was added to prepare ink for each back layer.

Each of the above inks was applied to a polyester film (thickness 6 μm).
m, Lumirror F-53, manufactured by Toshi ■) with a wire bar coater to coat one side with solid content of 0.2 g/r and 0.5 g/r.
After coating at a ratio of r1', it was dried with hot air to form a back layer.

Reference example 4 (combined with primer paint) Epoxy-modified linear saturated polyester resin (Vylon RV
290.7g77℃, mp 180℃, manufactured by Toyobo ■) 5
1 part was dissolved in 95 parts of an equivalent MEK/toluene mixed solvent.

This primer paint was applied to a 6 μm thick polyethylene terephthalate raw film using a wire bar coater at a rate of 0.2 g/rr. (solid content) and dried to form a primer layer.

Next, an ink composition obtained by removing the linear saturated polyester resin from the composition (1) of Reference Example 1 was applied at a rate of 0.3 g/rrr (solid content) and dried to form a back layer.

The contents of the styrene/acrylonitrile copolymer used above are as listed in Table 1 below.

(Margin below) Table 1 Example 1 The following ink composition was applied to the other side of the base film provided with the back layer of Example 1 at a rate of 4 g/d to form an ink layer.

Soil composition Cocarbon black 15 parts Ethylene/vinyl acetate copolymer 8 parts Paraffin wax 50 parts Carnauba wax
25 parts (4 at 120”C with attritor)
Further, a temporary adhesive having the composition shown below was coated on the above ink layer using a gravure coating method at a dry coating weight of 0.5 g/I, and then plain paper (basis weight 64 g / Go, Beck surface smoothness 1
The thermal transfer sheet of the present invention was obtained by laminating the film with a nip temperature of 50° C. and a nip thickness of 500 kg).

Temporarily placed acrylic adhesive particles water-based dispersion (solid content 40
%, glass transition temperature -70°C, particle size 3-10 μm)
10 parts acrylic resin particles aqueous dispersion (solid content 20%, glass transition temperature 85°C
, particle size 0.2-0.5 μm) 15 parts carnauba wax aqueous dispersion (solid content 40%,
Melting point 83℃) 15 parts water
10 parts Improper tool 30 parts Examples 2 to 4 The same dispersion as in Example 1 was used on the other side of the base film of Reference Examples 2 to 4, and the composition (weight ratio) of the temporary adhesive was adjusted as shown below. A thermal transfer sheet of the present invention was obtained in the same manner as in Example 1 except for the changes shown in Table 2.

Comparative Example 1 A thermal transfer sheet of a comparative example was obtained in the same manner as in Example 1 except that only the adhesive particle dispersion in Example 1 was used as a temporary adhesive.

Comparative Example 2 A thermal transfer sheet of a comparative example was prepared in the same manner as in Example 1 except that adhesive particles and resin particles were used in a weight ratio of 1:1 as the temporary adhesive in Example 1, and wax was not used. I got it.

Comparative example 3 A temporary adhesive layer was formed from polyvinyl alcohol.

Comparative Example 4 A temporary adhesive layer was formed using a polyurethane adhesive. (The temporary adhesive layers in the above comparative examples all have a thickness of 0.5g1rd) The adhesive strength between the ink layer and paper of the thermal transfer sheets of the above examples and comparative examples was measured, and the results are shown in Table 3. Ta. If the paper does not peel off easily even when left, it peels off easily with a fingertip after printing, and there is no background smudge on the paper, mark it as ○, and if it peels off naturally or causes background smudges when left unused, mark it as X. expressed. From these results, the adhesive strength is 300 to 1000g, especially 400g.
A range of 800 g was found to be appropriate.

In addition, the adhesive strength (g) is 25mm (width) x 50mm (length)
Cut a sample of
N-14 (manufactured by Shingengakugaku) at a tensile speed of 1800 mm/min.

(The following is a margin) Table 3 A thermal transfer sheet of a comparative example was obtained in the same manner as in Example 1. When a printing test was conducted in the same manner as in Example 1, the sticking phenomenon was severe and printing was impossible.

Further, the thermal transfer sheets of Examples 1 to 4 and Comparative Example 5 were measured for friction coefficient, staking resistance, and stain resistance, and the results shown in Table 4 below were obtained.

*l: Adhesive force was not measured.

Comparative Example 5 As the binder resin for the back layer in Reference Example 1, a partially saponified vinyl chloride/vinyl acetate copolymer resin (manufactured by UCC, Vinyrite VAGH) was used, and the others were min.

○: No problem △ Some problems ×: Difficult to use Friction coefficient; The friction coefficient between the back layers was measured (load 100g/c
m, speed 100mm/ Stakes resistance: (1) Test machine Thin film head 6d/mm 17V2m
s=1.66mJ/d peta printing (2) Practical machine Partially braced thin film head 8d/m
m Solid print storage stability: The ink-coated surface and back layer surface of a test piece (50 x 50 mm) were placed one on top of the other, and a constant load was applied using a blocking tester to compare performance under the following conditions.

+1) 55℃ 15Kg/crt? /48 hours (2) 60
℃/2Kg/crd/24 hours

[Brief explanation of drawings]

FIGS. 1 and 2 are diagrams schematically illustrating the cross section of the thermal transfer sheet of the present invention, and FIG. 3 is a diagram schematically illustrating the structure of the adhesive layer. A: Thermal transfer sheet B: Transfer material C: Adhesive layer and base film 3: Back layer 5: Adhesive particles 7: Wax particles 9: Image 2: Ink layer 4: Matte layer 6: Resin particles 8: Thermal head Figure 1 Figure 2

Claims (10)

[Claims] (1) A thermal transfer sheet in which a heat-melting ink layer is formed on one side of the base film and a back layer is provided on the other side of the base film and the transfer material can be separated by an adhesive layer. 1. A thermal transfer sheet formed by adhesion, wherein the back layer is formed using a styrene/acrylonitrile copolymer as a main component of a binder. (2) The thermal transfer sheet according to claim 1, wherein the styrene/acrylonitrile copolymer has an acrylonitrile copolymerization ratio of 20 to 40 mol%. (3) The thermal transfer sheet according to claim 1, wherein the styrene/acrylonitrile copolymer has a molecular weight of 100,000 to 200,000. (4) The thermal transfer sheet according to claim 1, wherein the back layer contains a linear polyester resin mixed as an adhesive resin. (5) The thermal transfer sheet according to claim 1, wherein the back layer has a two-layer structure including a primer layer made of a linear polyester resin and a back layer made of a styrene/acrylonitrile copolymer. (6) The thermal transfer sheet according to claim 1, wherein the adhesive layer comprises adhesive particles having a low glass transition temperature, resin particles having a high glass transition temperature, and wax particles. (7) The glass transition temperature of the adhesive is -90°C to -60°C
The thermal transfer sheet according to claim 1, wherein the resin particles have a glass transition temperature of 60° C. or higher. (8) The weight ratio of adhesive: resin particles: wax is 3 to 5:
The thermal transfer sheet according to claim 1, wherein the ratio is 1 to 2.5:3 to 5. (9) The thermal transfer sheet according to claim 1, wherein the adhesive layer has a thickness of 0.2 to 20 μm. (10) The thermal transfer sheet according to claim 1, wherein the adhesive layer is formed from a dispersion containing adhesive particles, resin particles, and wax particles.