JP2000108524A - Heat transfer sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an image which is highly heat-sensitive, and is of a high quality and good-looking and further, is reliable in terms of adhesion, scratch resistance and chemical resistance by using a mixture of a specific molecular weight thermoplastic acrylic resin and a vinyl chloride/vinyl acetate copolymer as a binder in a heat transfer ink layer. SOLUTION: A heat transfer ink layer 2 is composed of a coloring agent and a binder, and the content of the coloring agent is 20-70 wt.%. In addition, the coloring agent to be used is such as having good properties as a recording material selected from organic or inorganic pigments or dyes. The binder is composed of a mixture of a thermoplastic acrylic resin and a vinyl chloride/ vinyl acetate copolymer. Further, the thermoplastic acrylic resin is preferably of such a type that has 25,000-100,000 molecular weight. When the molecular weight is 25,000 or below, the scratch resistance is not enhanced and when the molecular weight is 100,000 or more, the heat sensitivity is deteriorated so that the reliable suitableness for printing is not obtained. In addition, the vinyl chloride/vinyl acetate copolymer preferably has 200-400 degree of polymerization.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-sensitivity thermal transfer sheet having excellent durability and chemical resistance.

[0002]

2. Description of the Related Art At present, railway commuter passes are most commonly formed by contacting a resin card as a material to be transferred with a thermal transfer sheet called a resin ribbon and forming an image from the back of the thermal transfer sheet using a thermal head. As the above-mentioned thermal transfer sheet, a heat-melt type thermal transfer in which a heat-meltable thermal transfer ink layer is provided by applying an ink obtained by mixing wax and a pigment on one surface of a base film with a coating device. Sheets are used. The thermal transfer sheet having the thermal transfer ink layer is used to form an image on a material to be transferred by melting the transfer ink by heating the image from the back side using a thermal head and heating the image in an image form. .

[0003]

However, most of the images printed on railway commuter passes by such thermal transfer are plasticizers contained in a vinyl chloride resin used for rubbing by an automatic ticket gate, regular insertion, and the like. Further, the printed ink is often peeled off and stained before the expiration date of the railway commuter pass due to contact with a chemical such as ethanol or the like.

This problem can be solved by using a thermal transfer sheet having a thermal transfer ink layer having excellent durability.
The conventional high-durability thermal transfer sheet has problems that it is difficult to perform high-quality and beautiful printing due to the poor thermal sensitivity of the thermal transfer ink layer, and that a heavy load is imposed on the thermal head. Further, as described above, since the thermal transfer sheet is printed on the resin card as the material to be transferred by thermal transfer, it is also required that the thermal transfer ink layer and the material to be transferred have excellent adhesion during printing. To solve this problem, the binder of the thermal transfer ink layer has a glass transition temperature (Tg) of 5
An acrylic resin having a glass transition temperature (T) of 0 to 105 ° C. and a molecular weight of 60,000 or more
g) of 60 ° C. or more and 90 ° C. or less and use of a vinyl chloride-vinyl acetate copolymer resin having an average molecular weight of 10,000 or more (Japanese Patent Laid-Open No. 7-76178). It was not enough to obtain the property. That is, when only the above acrylic resin is used, the abrasion resistance and the plasticizer resistance are excellent, but the heat sensitivity and the adhesiveness are not sufficient, while only the vinyl chloride-vinyl acetate copolymer resin is used. In this case, there was a problem that the heat sensitivity and the adhesiveness were excellent, but the abrasion resistance and the plasticizer resistance were not sufficient.

In order to solve the above-mentioned disadvantages of the prior art, the present inventors have made intensive studies and have arrived at the present invention. That is, the present invention is a thermal transfer sheet excellent in thermal sensitivity,
It is an object of the present invention to provide a thermal transfer sheet capable of forming a high-quality and beautiful image having excellent adhesiveness, abrasion resistance, and chemical resistance on a railway commuter pass or the like.

[0006]

The thermal transfer sheet of the present invention is a thermal transfer sheet having a thermal transfer ink layer on the surface of a substrate film, wherein the binder of the thermal transfer ink layer has a molecular weight of 25,000 to 100,000. It is characterized by comprising a mixture of a plastic acrylic resin and a vinyl chloride-vinyl acetate copolymer. In the thermal transfer sheet of the present invention, the mixing weight ratio of the thermoplastic acrylic resin and the vinyl chloride-vinyl acetate copolymer in the binder of the thermal transfer ink layer is 1:
It is preferably 0.25 to 1: 1. Further, the thermal transfer sheet of the present invention can be provided with a release layer and / or a protective layer between the base film and the thermal transfer ink layer.
An adhesive layer may be provided on the thermal transfer ink layer.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a thermal transfer sheet of the present invention will be described in detail with reference to the drawings. FIG. 1 is a longitudinal sectional view showing a basic configuration of the thermal transfer sheet of the present invention. In FIG. 1, 1
Denotes a base film, and 2 denotes a thermal transfer ink layer.

The material of the base film 1 is not particularly limited, and may be, for example, polyethylene terephthalate, polyester, polypropylene, cellophane, polycarbonate, cellulose acetate, polyethylene, polyvinyl chloride, polystyrene, nylon, polyimide, polyvinylidene chloride, Plastic films such as polyvinyl alcohol, fluororesin, chlorinated rubber, and ionomer, papers such as condenser paper and paraffin paper, nonwoven fabrics, and the like, and a base film in which these are combined may be used. The thickness of the substrate film can be variously selected so that strength and thermal conductivity are appropriate.
〜１０10 μm.

The thermal transfer ink layer 2 comprises a colorant and a binder, and the content of the colorant is 20 to 70% by weight.

The colorant of the thermal transfer ink layer 2 is an organic or inorganic pigment or dye having good properties as a recording material, for example, having a sufficient coloring density,
Those which do not discolor by heat, temperature, etc. are preferred. Further, it may be a substance that develops a color by heating or a substance that develops a color when it comes into contact with a component applied to the surface of the transfer object. Further, as the color of the colorant, cyan, magenta,
The colorants are not limited to yellow and black, and various colorants can be used.

The binder of the thermal transfer ink layer 2 is composed of a mixture of a thermoplastic acrylic resin and a vinyl chloride-vinyl acetate copolymer. The thermoplastic acrylic resin constituting the binder preferably has a molecular weight of 25,000 to 100,000. If it is less than 25,000, the abrasion resistance will not be improved, and if it exceeds 100,000, the thermal sensitivity will be poor and good printability will not be obtained.

The vinyl chloride-vinyl acetate copolymer constituting the binder preferably has a degree of polymerization of 200 to 450.

The above thermoplastic acrylic resin and vinyl chloride
The mixing weight ratio of the vinyl acetate copolymer is 1: 0.25 to 1:
It is preferably 1. The mixing weight ratio of the vinyl chloride-vinyl acetate copolymer to the thermoplastic acrylic resin is 0.
If it is less than 25, it is excellent in abrasion resistance and plasticizer resistance, but sufficient thermal sensitivity and adhesiveness cannot be obtained. When the mixing weight ratio exceeds 1, heat sensitivity and adhesiveness are excellent, but scratch resistance and plasticizer resistance deteriorate.

The thickness of the thermal transfer ink layer 2, that is, the coating amount,
It is necessary to determine so that the density required for printing and the thermal sensitivity can be harmonized, but for example, about 0.2 to 1.0 g / m ² is preferable.

FIG. 2 is a longitudinal sectional view showing a specific configuration example of the present invention. FIG. 2 shows the base film 1 and the thermal transfer ink layer 2
A release layer 3 and a protective layer 4 are provided in that order, an adhesive layer 5 is provided on the transfer ink layer, and a heat-resistant lubricating layer 6 is provided on the back surface of the base film 1.

The material of the release layer 3 is preferably various waxes which exhibit a releasability by melting at the time of printing. Various waxes such as molecular weight polyethylene, wood wax, beeswax, spermaceti, Ibota wax, wool wax, shellac wax, candelilla wax, partially modified wax, fatty acid ester, fatty acid amide and the like can be mentioned. In addition, for example, acrylic resin, silicone resin, fluorine resin, silicone, or various resins modified with fluorine, which are excellent in peelability, can also be used. The thickness of the release layer, that is, the coating amount, is preferably a thin layer, for example, about 0.1 to 1.0 g / m ² so as not to lower the sensitivity of the entire heat-sensitive recording sheet.

The protective layer 4 formed on the release layer 3 comprises:
When the protective layer 4 is transferred together with the thermal transfer ink layer 2 during thermal transfer and covers the surface of the transferred image, and the protective layer 4 itself has good releasability from the substrate film 1, the protective layer 4 It may also serve as the layer 3. The protective layer 4 is formed of a resin which forms a tough film such as heat resistance and friction resistance, such as an acrylic resin, a polyurethane resin, a copolymer resin of an acrylic monomer and another monomer, a polyester resin, a polyamide resin and the like. Therefore, tough coatings made of these resins are not easily cut off during printing. Therefore, in the present invention, the protective layer 4 is formed so that the film is sufficiently cut.
Is preferably formed to a thickness of, for example, about 0.1 to 1.5 μm. In order to further improve the film breakage, it is preferable to form a protective layer by adding a fine pigment such as silica, alumina, clay, or calcium carbonate.
The release layer and the protective layer as described above are not indispensable requirements of the present invention, and are not always necessary when, for example, the substrate film has good releasability.

In the present invention, as shown in FIG. 2, an adhesive layer 5 is provided on the thermal transfer ink layer 2 to further improve the thermal sensitivity when printing on a material to be transferred such as a resin card using a thermal head. Is preferred.

The material of the adhesive layer 5 can be arbitrarily selected according to the type of the image receiving paper, and various thermoplastic resins, for example, polyester resin, ethylene-vinyl acetate copolymer (EV)
A), ethylene-acrylate (EEA), polyethylene, polypropylene, polybutene, petroleum resin, vinyl chloride resin, vinyl chloride-vinyl acetate copolymer, polyvinyl alcohol, vinylidene chloride resin, methacrylic resin, polyamide, polycarbonate, fluorine resin Polyvinyl formal, polyvinyl butyral, acetylcellulose, nitrocellulose, polyvinyl acetate, polyisobutylene, ethylcellulose, polyurethane or polyacetal may be used, and a mixture of these thermoplastic resins and waxes may be used.

A colorant can be mixed in the adhesive layer 5 for the purpose of performing higher quality and beautiful printing. There is no particular limitation on the coloring agent to be mixed in the adhesive layer 5,
It may be the same as or different from the colorant compounded in the thermal transfer ink layer 2. The preferred coating amount of the adhesive layer 5 is
It is about 0.1 to 1.0 g / m ² .

In the present invention, when a material that is weak to heat is used as the base film 1, the thermal head has good slipperiness on the surface in contact with the thermal head, that is, the back surface of the base film, and sticking is performed. It is preferable to provide a heat-resistant lubricating layer 6 for preventing the occurrence of heat. The heat-resistant lubricating layer 6 has a heat-resistant resin and a substance that functions as a heat release agent or a lubricant as basic components. Materials for the heat-resistant lubricating layer 6 include:
Uses thermoplastic resins with high heat resistance such as fluororesin and polyimide resin, thermosetting resins such as silicone resin, polyimide resin, epoxy resin, phenol resin and melamine resin, as well as ultraviolet curable resin and electron beam curable resin. it can. By providing such a heat-resistant lubricating layer 6, thermal printing can be performed without sticking even on a thermal transfer sheet using a plastic film that is weak to heat, making it difficult to cut the plastic film. Advantages such as ease of use can be utilized.

In the present invention, a method of sequentially providing a release layer, a protective layer, a thermal transfer ink layer, and an adhesive layer on the surface of a substrate film and forming a heat-resistant lubricating layer on the back surface of the substrate film includes gravure coating. , Gravure reverse coating, roll coating, and many other means, and a method using a wire bar may be used. The present invention can be applied to a thermal transfer sheet for color printing, and a multicolor thermal transfer sheet is also included in the scope of the present invention. Further, as a thermal transfer printer, it can be applied to either a line or serial printer.

The image formation in the present invention is performed by the image forming method of the present invention in which the thermal transfer sheet is overlaid on a material to be transferred and heat is applied from the back of the thermal transfer sheet. The material to be transferred is not particularly limited, and may be, for example, a synthetic resin film such as an acrylic resin.Paper, synthetic paper, various synthetic resin films, sheets, a surface of a card, etc. May be provided with an ink receiving layer.

[0024]

Next, the present invention will be described in more detail with reference to specific examples. Example 1 A polyethylene terephthalate film having a thickness of 4.5 μm was used as a base material, and 60 parts of an aqueous solution of isopropyl alcohol (a mixture weight ratio of water and isopropyl alcohol was 1: 3) was added to 40 parts of carnauba wax on one surface. The mixed solvent was applied with a wire bar so that the carnauba wax became 0.7 g / m ² when dried, and then dried at 70 ° C. to form a release layer.

Next, a mixture having the following composition was applied on the upper surface of the release layer using a wire bar so that the solid content was 0.7 g / m ² when dried, and then dried at 70 ° C. to form a thermal transfer ink. A layer was formed to obtain a thermal transfer sheet.

Composition of thermal transfer ink layer Acrylic resin (BR87, manufactured by Mitsubishi Rayon Co., Ltd., molecular weight 25,000) 9 parts by weight Vinyl chloride-vinyl acetate copolymer (degree of polymerization 420) 9 parts by weight Carbon black 9 parts by weight Methyl ethyl ketone / toluene (Mixing weight ratio 1/1) 73 parts by weight

Example 2 Example 1 was repeated except that the composition of the thermal transfer ink layer was as follows.
A thermal transfer sheet was prepared in the same manner as described above.

Composition of thermal transfer ink layer Acrylic resin (BR80, manufactured by Mitsubishi Rayon Co., Ltd., molecular weight 95,000) 14.4 parts by weight Vinyl chloride-vinyl acetate copolymer (degree of polymerization 420) 3.6 parts by weight Carbon black 9 parts by weight Parts: methyl ethyl ketone / toluene (mixing weight ratio 1/1) 73 parts by weight

Example 3 A release layer and a thermal transfer ink layer were formed on a substrate film in the same manner as in Example 1. Next, an adhesive layer having the following composition is applied on the upper surface of the thermal transfer ink layer using a wire bar so that the solid content upon drying is 0.2 g / m ² , and then dried at 70 ° C. Was formed.

Composition of Adhesive Layer Polyester resin (Vinaroll MD-1500 manufactured by Toyobo Co., Ltd.) 30 parts Water / isopropanol (mixing weight ratio 1/2) 70 parts

Example 4 Example 1 except that the composition of the thermal transfer ink layer was as follows:
A thermal transfer sheet was prepared in the same manner as described above.

Composition of Thermal Transfer Ink Layer Acrylic resin (BR83, manufactured by Mitsubishi Rayon Co., Ltd., molecular weight 40,000) 8 parts by weight Vinyl chloride-vinyl acetate copolymer (degree of polymerization 420) 10 parts by weight Carbon black 9 parts by weight Methyl ethyl ketone / toluene (Component weight ratio 1/1) 73 parts by weight

Comparative Example 1 A thermal transfer sheet was prepared in the same manner as in Example 1 except that the composition of the thermal transfer ink layer was as follows using an acrylic resin having a molecular weight of 150,000.

Composition of Thermal Transfer Ink Layer Acrylic resin (BR82, manufactured by Mitsubishi Rayon Co., Ltd., molecular weight: 150,000) 9 parts by weight Vinyl chloride-vinyl acetate copolymer (degree of polymerization 420) 9 parts by weight Carbon black 9 parts by weight Methyl ethyl ketone / toluene (Mixing weight ratio 1/1) 73 parts by weight

Comparative Example 2 A thermal transfer sheet was prepared in the same manner as in Example 1, except that the composition of the thermal transfer ink layer was as follows using an acrylic resin having a molecular weight of 15,000.

Composition of thermal transfer ink layer Acrylic resin (molecular weight 15,000) 9 parts by weight Vinyl chloride-vinyl acetate copolymer (degree of polymerization 420) 9 parts by weight Carbon black 9 parts by weight Methyl ethyl ketone / toluene (component weight ratio 1/1) ) 73 parts by weight

Comparative Example 3 Example 1 was repeated except that the composition of the thermal transfer ink layer was as follows.
A thermal transfer sheet was prepared in the same manner as described above.

Composition of Thermal Transfer Ink Layer Acrylic resin (BR87, manufactured by Mitsubishi Rayon Co., Ltd., molecular weight 25,000) 18 parts by weight Carbon black 9 parts by weight Methyl ethyl ketone / toluene (mixing weight ratio 1/1) 73 parts by weight

Comparative Example 4 Example 1 was repeated except that the composition of the thermal transfer ink layer was as follows.
A thermal transfer sheet was prepared in the same manner as described above.

Composition of thermal transfer ink layer Vinyl chloride-vinyl acetate copolymer (degree of polymerization 420) 18 parts by weight Carbon black 9 parts by weight Methyl ethyl ketone / toluene (component weight ratio 1/1) 73 parts by weight

The thermal transfer sheets obtained in Examples 1 to 4 and Comparative Examples 1 to 4 were evaluated for thermal sensitivity, plasticizer resistance,
Tests for ethanol resistance, gasoline resistance, abrasion resistance, and adhesion were performed. The test method is as follows.

The thermal sensitivity test was conducted by using a partial grace thin film head type thermal head and applying an energy of 0.7.
After printing on white polyethylene terephthalate receiving paper under the conditions of mJ / dot and a printing speed of 40 msec / line, the appearance was observed. Evaluation criteria are
It is as follows. : The image edge is sharp without voids, blurring, and blemishes. ○: Almost no voids, blurring, and rust. Δ: There are voids, blurs, and lumps. ×: No transfer at all.

The plasticizer resistance was evaluated by placing an eraser (dragonfly) on a printed material for 48 hours, removing the eraser, scratching with a nail, and observing the appearance of the printed surface. The evaluation criteria are as follows. A: The image is not destroyed at all. : The image is hardly destroyed. Δ: Image is slightly destroyed. ×: The image is completely destroyed.

The ethanol resistance was evaluated by impregnating a cotton swab with ethanol and then observing the appearance of the swab after rubbing the printed surface. The evaluation criteria are as follows. A: The image is not destroyed at all. : The image is hardly destroyed. Δ: Image is slightly destroyed. ×: The image is completely destroyed.

The gasoline resistance was evaluated by impregnating a cotton swab with gasoline and then observing the appearance after rubbing the printed surface with the cotton swab. The evaluation criteria are as follows. A: The image is not destroyed at all. : The image is hardly destroyed. Δ: Image is slightly destroyed. ×: The image is completely destroyed.

The abrasion resistance was evaluated by observing the appearance after performing a gate pass test 3000 times using a gate tester. The evaluation criteria are as follows. A: The image is not destroyed at all. : The image is hardly destroyed. Δ: Image is slightly destroyed. ×: The image is completely destroyed.

The adhesion test was performed by attaching a cellophane tape to the surface on which the image was formed, and then evaluating the appearance after removing the cellophane tape. The evaluation criteria are as follows. A: The image does not peel at all. : The image hardly peels off. Δ: Image peels slightly. ×: The image is completely peeled.

Table 1 shows the results of the above tests.

[0049]

[Table 1]

[0050]

As described above, according to the present invention, in a thermal transfer sheet having a thermal transfer ink layer on the surface of a substrate film, a thermoplastic acrylic having a molecular weight of 25,000 to 100,000 is used as a binder of the thermal transfer ink layer. By using a mixture of resin and vinyl chloride-vinyl acetate copolymer, excellent heat sensitivity and adhesiveness can be achieved, high quality beautiful printing can be performed, and chemical resistance such as abrasion resistance and plasticizer resistance can be obtained. It is possible to obtain a thermal transfer sheet having excellent properties. In the present invention, if the mixing weight ratio of the thermoplastic acrylic resin and the vinyl chloride-vinyl acetate copolymer as the binder of the thermal transfer ink layer is within the range of 1: 0.25 to 1: 1, the thermal sensitivity and the adhesiveness are improved. And a thermal transfer sheet having particularly excellent balance between scratch resistance and plasticizer resistance.

In the present invention, by providing an adhesive layer containing a coloring agent on the upper surface of the thermal transfer ink layer, it is possible to perform higher quality and beautiful printing, and to provide a thermal transfer excellent in durability and adhesiveness. Sheets can be provided.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a basic configuration of a heat-sensitive transfer recording sheet of the present invention.

FIG. 2 is a longitudinal sectional view showing a specific configuration of the heat-sensitive transfer recording sheet of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base film 2 Thermal transfer ink layer 3 Release layer 4 Protective layer 5 Adhesive layer 6 Heat resistant slip layer

Claims (4)

[Claims] 1. A thermal transfer sheet having a thermal transfer ink layer on the surface of a substrate film, wherein the binder of the thermal transfer ink layer is a thermoplastic acrylic resin having a molecular weight of 25,000 to 100,000 and a vinyl chloride-vinyl acetate copolymer. A thermal transfer sheet comprising a mixture of coalescing. 2. The method according to claim 1, wherein the mixing weight ratio of the thermoplastic acrylic resin and the vinyl chloride-vinyl acetate copolymer in the binder of the thermal transfer ink layer is 1: 0.25 to 1: 1. Thermal transfer sheet. 3. The thermal transfer sheet according to claim 1, wherein a release layer and / or a protective layer is provided between the base film and the thermal transfer ink layer. 4. The thermal transfer sheet according to claim 1, wherein an adhesive layer is provided on the thermal transfer ink layer.