JPH0313386A - Thermal transfer recording medium - Google Patents

Abstract

PURPOSE:To release a sublimable transfer ribbon without generating adhesion even when direct transfer is performed to a vinyl chloride resin card base material by forming a color ink layer consisting of a polyvinyl acetal resin, isocyanate and a sublimable or heat-meltable transfer dye to the surface of a polyester film whose rear is subjected to heat-resistant treatment and further forming a heat-resistant surfactant layer thereon. CONSTITUTION:A heat-resistant layer 2 is provided in order to prevent the fusion of a polyester film 1 by high temp. and high pressure applied by a thermal head and, as the material of said layer 2, a cellulosic or silicone tape heat- resistant resin is used. In a color ink layer 3, a dye is used as a colorant and, as the dye, one sublimed or melted and transferred by the heat from the thermal head is pref. As the binder of ink, a reaction product obtained by reacting isocyanate with the hydroxyl group of polyvinyl acetal to generate an urethane bond is used. Further, in order to make heat resistance and releasability sufficient, a surfactant layer 4 having heat resistance and releasability is provided on the color ink layer. Especially, an alkyl phosphoric ester type surfactant is optimum.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention provides a thermal transfer recording medium that can perform transfer painting with sublimation dye on a base material such as a PVC card using a thermal recording member such as a thermal head. Regarding.

<Prior Art> Recently, the usage of cards such as cash cards and credit cards has been rapidly increasing, and in particular, cards made of hard polyvinyl chloride resin have become mainstream. When using this card, it is required to have a face photo and name printed on the surface to prevent counterfeiting. Fill it in the groove, and then apply a film over it so as to cover the groove. ■A photosensitive material is partially applied to the surface of the card, and an image such as a photograph of a face is printed on the applied surface. ■The first method of engraving the card surface physically and mechanically using electrical signals is used, but the process is complicated, the incidence of defective products is high, the cost is high, and there are practical problems. There was a desire to develop an efficient and low-cost method.

One method is a thermal transfer method (sublimation dye type) using a thermal head, but in order to perform sublimation transfer, it is necessary to provide a polyester resin layer as a dye image-receiving layer on the vinyl chloride base material. . However,
Vinyl chloride resin and polyester resin originally have weak adhesion to each other, and there have been drawbacks such as the polyester resin layer peeling off due to wear or bending during use of the card.

On the other hand, direct sublimation transfer to vinyl chloride resin has been attempted, but the heat resistance of the vinyl chloride resin base material is low, and the ink binder of the sublimation transfer ribbon and the heat-softened vinyl chloride base material tend to adhere, making it difficult to remove. In many cases, it has been difficult to put it into practical use.

<Problems to be Solved by the Invention> The present invention has been made in view of the above-mentioned circumstances, and even if sublimation transfer is performed directly using a thermal gelatin plate without providing an image-receiving layer on a vinyl chloride resin card, The object of the present invention is to provide a color heat-sensitive sublimation transfer recording medium in which only the dye sublimes or heat-melts and diffuses to the surface of the base material, without the drawback that a vinyl chloride card base material and a sublimation transfer ribbon adhere to each other and become difficult to separate. shall be.

<Means for solving the problem> In order to achieve the above objectives, we mainly investigated peeling improvement during transfer, and found that polyvinyl setter resin, isocyanate, etc. and a dye having sublimation property or thermal melt transfer property, and a heat-resistant surfactant layer for preventing adhesion is further formed on the colored ink layer. By using this, a remarkable effect was obtained in that the sublimation transfer ribbon could be peeled off without adhesion even when directly transferred to a vinyl chloride resin card base material.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a sectional view showing the structure of the thermal transfer recording medium of the present invention.

(1) is a biaxially stretched polyester film as a base material, with 4μ
Thicknesses of m to 9 μm can be used.

(2) is a heat-resistant layer that prevents the polyester film from fusing due to the high temperature and high pressure applied by the thermal head, and the material used can be heat-resistant resin such as cellulose or silicone. can.

(3) is a colored ink layer, in which a dye is used as a coloring agent. The dye is preferably one that sublimes or melts and transfers due to the heat from the thermal head, and oil-soluble dyes or disperse dyes with a molecular weight of about 150 to 700 can be used. As an ink binder, it tightly encloses the dye at room temperature, but during transfer, the resin structure loosens slightly due to the high temperature and pressure applied at that time, and it is necessary to release only the dye. . Moreover, it must not adhere to the vinyl chloride resin card that is the object to be transferred, and no binder must remain on the polyester film that is the base material of the transfer ribbon.

Resins that meet these characteristics to some extent include cellulose, polyester, urethane, polyamide, and polyvinyl acetal (including vinyl alcohol), but they have releasability to vinyl chloride resin, Moreover, none of these products have excellent adhesion to the polyester film base material, so as a result of intensive research, we found that
When polyvinyl acetal (vinyl alcohol) is reacted with isocyanate to form a urethane bond as a binder, it improves adhesion to polyester film and also improves heat resistance as crosslinking of the resin progresses. The releasability of vinyl chloride resin cards can also be slightly improved. Furthermore, in order to ensure sufficient heat resistance and releasability, a surfactant layer (4) having heat resistance and releasability is provided on the colored ink layer, as shown in FIG. The performance required for heat resistance is 200
“C30 seconds or more, dynamic wear coefficient at 20°C is 0.
Any surfactant having a concentration of 3 or less satisfies this condition, but among them, alkyl phosphate esters were the most suitable.

<Example> Stretched polyester film with a thickness of 5.7 μm
An indigo dye ink containing polyvinyl acetal resin, isocycinate, and an indigo dye as shown in the following formulation (A) was printed on the surface of Nilmirror 60F53) with a plate depth of 40 μm using a gravure solid plate to a thickness of approximately 1 μm. An ink layer was formed thereon, and a surfactant solution shown in the following formulation (B) was printed thereon using a gravure solid plate with a plate depth of 20J1 m to form a layer with a thickness of about 0.2 μm. On the other hand, the back side of the film was coated with a heat-resistant backcoat liquid shown in the following formulation (C) using a gravure solid plate to form a heat-resistant layer with a thickness of 0.4 μm, thereby obtaining an indigo sublimation heat transfer recording medium. Ta.

Next, the above thermal transfer recording medium was layered on the surface of a hard vinyl chloride resin card for cash cards (thickness: 0.75cm), and a transfer print was made using a video printer (Visual Card Printer V C-Ploo, manufactured by Sharp ■). When this process was carried out, a blue print was obtained which was easy to release from the mold, had a clear hue, and had good photographic gradation reproducibility.

Prescription (＾) Blue dye ink prescription (B) Prescription (C) Surfactant solution heat-resistant back coating liquid <Effects of the invention> Since the thermal transfer recording medium of the present invention has the above-mentioned structure, Even when used on a substrate, it has good transferability and release properties, and can be transferred without forming an image-receiving layer on the substrate, simplifying the transfer process.

Furthermore, since the transferred dye is fixed in the vinyl chloride resin, the image has a high shelf life.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure of the thermal transfer recording medium of the present invention. (1) ...Polyester film (2)
...Heat-resistant layer (3) ...Colored ink layer (4) ...Heat-resistant surfactant layer Figure 1 Patent application Hitotoppan Printing Co., Ltd. Representative Suzuki Kazuo

Claims (3)

[Claims] (1) Polyvinyl acetal resin, isocyanate,
and a dye having sublimation property or thermal melt transfer property, and a heat-resistant surfactant layer is further formed thereon. (2) The thermal transfer recording medium according to claim (1), wherein the polyvinyl acetal resin has a molecular weight of 200,000 or more and a hydroxyl group content of 30% by weight. (3) The thermal transfer recording medium according to claim (1), wherein the surfactant is an alkyl phosphate ester having resistance to heating at 200° C. for 30 seconds or more.