JPH01262188A - Thermal transfer recording medium - Google Patents

Abstract

PURPOSE:To prevent the release of an ink layer from the surface of a substrate, by providing an intermediate adhesive layer containing at least one of an ethylene/vinyl acetate copolymer resin EVA and an ethylene/ethyl acrylate copolymer resin EEA between the substrate and a heat-meltable ink layer. CONSTITUTION:When an intermediate adhesive layer 5 containing either one of EVA and EEA having comonomer content (NUC method) of 3-45%, a melt index (ASTM, D1238) of 0.5-2,500g/10min density (ASTM, D1505) of 0.92-0.97g/ml and a softening point (ring and ball method) of 80-190 deg.C is provided between an ink layer 6 and a substrate 4, the bonding strength between the ink layer and the substrate is enhanced and the release of the ink layer from the surface of the substrate is not generated and this recording medium is stably cut and released on the surface of the release layer of a thermal receiving recording medium. Even if the bonding strength of the ink layer itself with the substrate is weak, the release on the surface of the release layer of the thermal transfer receiving medium is stably performed and the material of the ink layer is selected widely.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thermal transfer recording medium, and particularly to a thermal transfer recording medium that is excellent in gradation expression.

[Prior Art] Currently, facsimile machines, printers, copying machines, etc. are rapidly becoming popular, but among the recording methods used in these devices, thermal transfer recording methods using thermal heads have problems such as low noise and equipment complexity. It is attracting attention because it is relatively inexpensive, compact, easy to maintain, and highly reliable.

This thermal transfer recording method that uses a thermal head to transfer and form an image includes a sublimation method that records by forming an ink layer containing a sublimable dye on a substrate such as paper or a plastic sheet and sublimating the dye by heating. There is also a melting method in which a heat-melting ink layer is provided on a substrate and the ink layer is melted by heating for transfer recording. With the former, it is possible to control the amount of dye transferred by changing the amount of heat applied from the thermal head and obtain a photographic image with gradations, but because it uses sublimable dye, the storage stability of the recorded image is poor. Moreover, since high energy is required for recording, there are problems such as slow recording speed and short life of the thermal head. Since the latter uses a heat-fusible substance and a colorant such as a pigment in the transfer layer, a recorded image can be obtained with lower energy than the former, and the recorded image has excellent storage stability.

However, in this method, the amount of transferred ink layer is controlled according to changes in the amount of heat applied from the thermal head.
It is difficult to obtain images with gradation, and basically binary recording is required.

Various studies are being carried out to enable good gradation recording in such thermal melt transfer recording methods, but one of them is to ink ink on a substrate that has an absorption and retention area on its surface that can absorb and retain ink. By using a layer containing a substance that has virtually no adhesion to the surface, it has the same sensitivity, storage stability, simplicity, and stability of recorded images as the conventional thermal melt transfer recording method. There is a thermal transfer gradation recording method that allows gradation recording. (Unexamined Japanese Patent Publication No. 61-280991).

In this method, the amount of ink that permeates into the thermal transfer recording medium is controlled by changing the amount of heat applied to the thermal head, and after recording, the ink layer is separated and peeled off on the peeling layer surface of the thermal transfer recording medium. For this reason, in the thermal transfer recording medium used, if the heat-fusible ink layer does not have strong adhesion to the substrate, peeling will occur on the surface of the substrate, resulting in binary recording and gradation recording.

However, it is difficult to select a heat-melting ink that can control the amount of coloring material permeated into the thermal transfer recording medium by changing the amount of heat applied and has strong adhesion to the substrate, making it difficult to obtain a good iJ image. could not.

[Problems to be Solved by the Invention] The present invention provides a substrate having an absorbing and retaining portion on its surface capable of absorbing and retaining heat-melting type thermal transfer recording ink, which is substantially attached to the thermal transfer recording ink. A thermal transfer recording medium used for a thermal transfer recording medium provided with a peeling layer that does not have adhesive strength, which prevents peeling of an ink layer from a substrate surface and enables good gradation recording. The purpose is to provide

[Means for Solving the Problems] The thermal transfer recording medium of the present invention has a substrate (
4) and the intermediate adhesive layer (5) between the hot-melt ink layer (6)
It has been established.

As a material for the intermediate adhesive layer, after considering adhesiveness, flexibility, thermal conductivity, coatability, etc., the comonomer content (NU
C method: Nippon Unicar ■ measurement method) is 3-45%, melt index is 0.5-2500g/10m1n
(457M, 01238) Density (ASTM, 015
Ethylene-vinyl acetate copolymer resin (hereinafter referred to as EVA), or ethylene-ethyl acrylate, which has a softening point (ring and ball method) of 0.29 to 0.97 g/-1 and a softening point (ring and ball method) of 80 to 190°C. Copolymer resin (hereinafter referred to as EEA)
It is called. ) is a resin layer containing at least one of the following.

Figure 2 shows a thermal transfer recording method using a thermal transfer recording medium without an intermediate adhesive layer. When a thermal transfer recording medium (2) without an intermediate adhesive layer is used, the thermal head (9) The heat-melting ink melts and permeates into the transfer recording medium (3) according to the amount of heat applied, and is then cooled and solidified. Thereafter, when the ink layer (6) of the thermal transfer recording medium (2) is separated and peeled off on the surface of the release layer (7) of the transfer recording medium (3), only the permeated hot melt ink is removed from the transfer recording medium (3). ) to obtain floor 11 images. However, when performing this peeling, if the adhesive force between the ink layer (6) of the thermal transfer recording medium (2) and the substrate (4) is low,
The ink layer (6) peels off on the surface of the substrate (4), and as shown by the broken line circle, the entire ink layer is transferred to that area, resulting in binary recording. Therefore, the material for the ink layer is required to have high adhesiveness to the substrate. Also,
In order to obtain good gradation images, the ink layer must have excellent properties such as melt viscosity, fluidity, and thermal properties, as well as excellent adhesion to the substrate. It is difficult to find such a hot melt ink.

Therefore, as shown in Fig. 3, the ink layer (6) and the substrate (
4) Conomer content (NUC method) 3 to 45%,
Melt index (ASTM, 01238) 0.
5~2500g/10m1n, density (^ST?!,
01505) Intermediate adhesive N containing at least either EVA or EEA having a softening point (ring and ball method) of 80 to 190'C in the range of 0.92 to 0.97 g/-1
By providing (5), the adhesive force between the ink layer and the substrate is improved, and the ink layer does not peel off on the substrate surface, but is stably separated and peeled off on the surface of the peeling layer of the thermal transfer recording medium. Become. In addition, even if the ink layer itself has weak adhesive strength with the base material, the peeling layer of the thermal transfer recording medium can be stably peeled off on the surface of the peeling layer, and the range of choices for the ink layer material is widened. .

The intermediate adhesive layer is required to exhibit strong adhesive force even if it is a thin film, and is also required to have thermal conductivity, flexibility, film stability, etc. If so, each of the above required physical properties can be satisfied.

The substrate used in the thermal transfer recording medium of the present invention includes paper and plastic films used in ordinary thermal transfer recording media, such as condenser paper, polyester film, polyamide film, polyimide film, aramid film, cellophane film, etc. Melting inks include waxes such as carnauba wax, polyethylene wax, paraffin wax, microcrystalline wax, ethyl wax, candelilla wax, hydrocarbon synthetic wax, ethylene-vinyl acetate copolymer resin, butyral resin, It is possible to use a material in which thermoplastic resins such as polyester resin, urethane resin, polyethylene resin, polystyrene resin, etc. are appropriately blended, colored with various pigments and dyes, and necessary additives are added.

In the thermal transfer recording medium of the present invention, an intermediate adhesive layer is provided on the substrate, and an ink layer is provided thereon. When providing the ink layer, it is preferable to use a method that does not attack the intermediate adhesive layer.

In addition, when recording full-color images with gradations such as color photographs, it is necessary to use heat-melting inks of three primary colors in a subtractive color mixture having hues of yellow, magenta, and cyan. After the intermediate adhesive layer is applied over the entire surface, it is also possible to appropriately apply hot-melt inks of three colors, yellow, magenta, and cyan, on the intermediate adhesive layer.

[Effects of the Invention] By using the thermal transfer recording medium of the present invention, the thermal melt ink can be stably separated and peeled off on the surface of the peeling layer of the thermal transfer recording medium, regardless of the adhesive strength of the thermal melt ink layer. This enables good gradation recording.

[Example 1] A coating liquid having the following composition was applied to a 6 μm thick polyester film (230 manufactured by Diafoil ■) using a wire bar so that the coating amount was 0.5 g/rrr in terms of non-volatile content, Dry. .

After that, a coating liquid containing a wax emulsion and a coloring agent having the composition shown below was applied on top of this using a wire bar so that the coating amount was 2.5 g/rrf in terms of non-volatile content.
A thermal transfer recording medium was obtained by drying.

Next, silicone oil was applied to the film whose surface was coated with a resin containing a matting agent in an amount of 0.2 g/rd in terms of non-volatile content, and dried to obtain a thermal transfer recording medium. . Using this thermal transfer recording medium and the above-mentioned thermal transfer recording medium, recording is performed by changing the transfer energy stepwise to form a density step scale using thermal rad, and then the thermal transfer recording medium is transferred to the thermal transfer recording medium. When the ink layer is peeled off from the recording medium, no peeling occurs on the substrate surface of the thermal transfer recording medium, and the ink layer is separated and peeled off on the surface of the peeling layer of the thermal transfer recording medium, resulting in a stable gradation image with stepped density. Obtained.

[Comparative example] A coating liquid containing the same wax emulsion and colorant as in the example was applied to a 6 μm thick polyester film (manufactured by Guyafoil ■, K230) at a coating amount of 2.5 g/rrf in terms of non-volatile content weight. The mixture was coated and dried to obtain a thermal transfer recording medium having no intermediate adhesive layer. Using this thermal transfer recording medium and the same thermal transfer recording medium as in the example, recording was performed by changing the transfer energy stepwise with a thermal head in the same manner as in the example, and then in the same manner as in the example. When the thermal transfer recording medium was peeled off from the thermal transfer recording medium, the ink layer partially peeled off on the substrate surface of the thermal transfer recording medium, making it impossible to obtain a stable gradation image.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure of the thermal transfer recording medium of the present invention;
FIG. 2 is an explanatory diagram of a thermal transfer recording method using a conventional thermal transfer recording medium without an intermediate adhesive layer, and FIG. 3 is an explanatory diagram of a thermal transfer recording method using a thermal transfer recording medium of the present invention. It is. (1)...Thermal transfer recording medium of the present invention (2)...
... Conventional thermal transfer recording medium (3) ... Heat transfer recording medium (4) ... Base (5) ... Intermediate adhesive layer (6) ... ... Ink layer (7) ... Peeling layer (8) ... Substrate having absorption and retention layer (9) ...
...Thermal head patent application Kazuo Suzuki, Representative of Toppan Printing Co., Ltd.

Claims (2)

[Claims] (1) A thermal transfer recording medium having a heat-fusible ink layer on a base material, and a heat-fusible ink layer on a base material having at least an absorbing and retaining portion on its surface capable of absorbing and retaining the heat-fusible thermal transfer recording ink. A thermal transfer recording medium for use in thermal transfer recording using a thermal transfer recording medium provided with a release layer having substantially no adhesion to the substrate, the thermal transfer recording medium comprising a substrate of the thermal transfer recording medium and a heat-fusible ink layer. 1. A thermal transfer recording medium comprising an intermediate adhesive layer containing at least one of an ethylene-vinyl acetate copolymer resin and an ethylene-ethyl acrylate copolymer resin. (2) The ethylene-vinyl acetate copolymer resin or ethylene-ethyl acrylate copolymer resin used for the intermediate adhesive layer has a comonomer content of 3 to 45%, a melt index of 0.5 to 2500 g/10 min, and a density of 0.92.
The thermal transfer recording medium according to claim 1, characterized in that it has a softening point of 80 to 190°C.