JPH0441075B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field, etc.] The present invention relates to a thermal transfer recording medium and a thermal transfer recording method capable of forming a dye image by thermally transferring a sublimable dye. More specifically, it is a thermal transfer recording medium that can produce a dye image with high sharpness and multi-gradation properties that is stable against heat, light, etc. on a recording sheet such as plain paper through a thermal transfer process using a sublimable dye. and a thermal transfer recording method. [Prior Art] Conventionally, methods have been known in which thermal paper is colored and images are recorded using a thermal head composed of thick-film resistors, thin-film resistors, semiconductor resistors, etc., or a heat source such as a laser or a xenon lamp. Since these methods use thermal paper, there are problems with the stability of the image against heat and light, and there are also disadvantages of high manufacturing costs.Furthermore, for colorization, it is necessary to have multiple coloring layers, so it is necessary to use only two colors. The drawback was that there was a limit. A thermal recording method that solves the above-mentioned drawbacks is, for example, as described in Japanese Patent Application Laid-open No. 15446/1982, in which a coloring material that is solid or semi-solid at room temperature is deposited on a support such as paper or resin film. The coloring material on the support is brought into contact with the recording sheet, and the coloring material on the support is heated by a heat source controlled according to image information to selectively form the recording sheet. A thermal transfer method that performs recording is known. The thermal transfer process in this method uses a coloring material mixed with a dye in a solvent with a low melting point and small heat capacity, and a melt transfer type that thermally transfers the dye together with the solvent, and a melt transfer type that uses a sublimable dye as the coloring material and uses a dye alone. A sublimation transfer type that performs sublimation transfer is known. Among these, the melt transfer type has the disadvantage that if a certain amount of thermal energy or more is applied, all the coloring material is transferred, making it difficult to obtain gradation of the image. On the other hand, in the sublimation transfer type, the dye is transferred depending on the amount of thermal energy applied, so it is a desirable method for obtaining gradation. However, in the sublimation transfer type, sublimable dyes are used for image formation, so there are problems with image fixability and storage stability due to re-sublimation of the dyes, especially when transferring to plain paper.
It had the disadvantage that the color density was low and that the color density decreased significantly due to re-sublimation of the dye over time. Therefore, in order to obtain multi-tone image recording, there is a strong desire to develop a thermal transfer recording medium and a thermal transfer recording method that use advantageous sublimable dyes and can form stable images on plain paper or the like. [Object of the Invention] The present invention has been made to satisfy the above-mentioned requirements, and its purpose is to provide a thermal transfer method capable of obtaining a dye image with high transfer density, high sharpness, and multi-gradation on plain paper, etc. An object of the present invention is to provide a recording medium and a thermal transfer recording method. [Structure of the Invention] In the present invention, the sublimable layer contains a dye that is solid at room temperature and can be sublimated and transferred by heating (hereinafter referred to as sublimable dye), and a heat-fusible layer provided on the sublimable layer. contains a heat-melting compound. Examples of the sublimable dyes include dyes that sublimate at 60° C. to 300° C., such as azo dyes, anthraquinone dyes, xanthene dyes, azomethane dyes, triphenylmethane dyes, nitro dyes, and quinoline dyes. . The heat-melting compound is preferably a low-melting compound, that is, a colorless or white compound having a melting point of 65°C to 130°C, such as waxes such as carnauba wax, beeswax, and canteri wax, and higher fatty acids such as stearic acid and behenic acid. , alcohols such as xylitol, amides such as acetamide and benzamide, ureas such as phenylurea and diethylurea, and the like. In addition, a polymer having excellent dye retention properties such as polyvinylpyrrolidone, polyvinyl butyral, and saturated polyester may be added to the heat-melting layer containing the heat-melting compound. As for the method for producing the thermal transfer recording medium of the present invention, it is preferable that it be produced by coating a sublimable layer and a heat-fusible layer in this order on a support.
Specifically, a sublimation-transferable dye is coated onto a support using a suitable binder, or only the dye is coated onto a support to form a sublimable layer, and a heat-melting compound is applied on top of the sublimable layer. With a suitable binder,
Alternatively, the heat-fusible compound itself may also serve as a binder to form a heat-fusible layer by coating. Note that a suitable intermediate layer may be provided between the sublimable layer and the heat-fusible layer. Furthermore, it is also optional to provide an overcoat layer, an undercoat layer, and the like. As the coating method, the compound of the present invention can be heated and hot-melt coated. As the coating means, wire bar coating, roll coating, gravure roll coating, etc. are used.
It can also be dissolved in a solvent such as toluene or xylene and applied using a similar application method. As the binder, polyvinyl butyral, polyvinyl acetate, polyvinyl alcohol, polystyrene, styrene-butadiene copolymer, cellulose esters such as ethyl cellulose, acrylic resins such as methyl methacrylate, gelatin, etc. can be used. As the support, a support having heat resistance strength and high smoothness is desirable. Heat resistance strength is required to maintain the toughness of the support without softening or plasticization due to the heating temperature of the thermal head, and smoothness is sufficient to ensure that each layer on the support exhibits a good transfer rate. A good level of smoothness is desired. Smoothness was determined by smoothness test using a Beck tester (JIS
P8119), 200 sec or more is sufficient, and 300 sec or more will yield images with good transfer rate and reproducibility. Materials include, for example, paper such as plain paper, synthetic paper, and laminated paper, or polyethylene,
Resin films such as polystyrene, polypropylene, polyimide, and paper-resin film composites are all suitably used. The thickness of the support is preferably about 60 μm or less in order to obtain good thermal conductivity. A condition for obtaining a good image is that each layer of the heat-sensitive transfer recording medium produced as described above has a thickness of about 1 to 20 μm. Preferably one layer
The suitable thickness is 15 μm or less, more preferably about 2 μm to 8 μm. A method for thermal transfer recording using the thermal transfer recording medium of the present invention having the following configuration will be described below. That is, when energy is applied to the heat-sensitive transfer recording medium from the support side in accordance with image information, the heat-fusible layer is transferred to the recording paper by applying energy of a certain value or more. The dye is sublimated and transferred from the sublimable layer according to the amount of energy, and an image made of the sublimable dye is obtained on recording paper (plain paper, etc.) in a form dissolved in the heat-fusible layer. In the present invention, the dye coated on the support is transferred to the recording paper and fixed on the recording sheet as described above because the thermofusible layer containing the thermofusible compound is transferred onto the recording paper by heat. At the same time or later, the sublimable dye is transferred onto the recording paper onto which the heat-fusible compound has been transferred, or after the sublimable dye is transferred to the heat-fusible layer, the sublimable dye is transferred to the heat-fusible layer. This is because the sublimable dye is retained on the recording paper in a state dissolved in the heat-fusible layer by transferring the heat-fusible dye contained therein. Therefore, as described above, the sublimable layer containing a sublimation transferable dye and the heat-fusible layer are preferably coated on the support in this order. The image obtained as described above has a high transfer density, high sharpness and multi-tone property, and is also excellent in fixability. Therefore, plain paper may be used as the recording paper, and dye images can be applied not only to paper but also to various plastic films, cloth, and the like. [Example] Preferred examples of the present invention are shown below, but the present invention is not limited to these examples. First, about the means for producing a thermal transfer recording medium.
This will be explained based on the diagram. First, apply the following composition to a polyethylene terephthalate film base 1 with a thickness of 6 μm.
Apply using a wire bar to give a thickness of 59.4μ.
It was dried to form a sublimable layer 2. Cellulose diacetate Sublimable dye (1) Acetone 0.6g 0.3g 20ml Subsequently, the following composition was coated on the sublimable layer to a wet film thickness of 27.4μ, and dried to form the meltable layer 3.
was formed to produce a thermal transfer recording medium A. Permarin PN (manufactured by Sanyo Kasei) H ₂ O 2% anionic activator 10ml 10ml 0.3ml Next, a thermal transfer recording test using the thermal transfer recording medium A described above will be described. Thermal transfer recording test (1) The coated surface of the thermal transfer recording medium A and white plain paper 4 were stacked facing each other, and the thermal head 5 was used to transfer the paper from the support 1 side of the thermal transfer recording medium A through the heating element 6. A transfer recording test was conducted by heating and transferring Dye 7. In this test, the temperature of the thermal head 5 and the time of voltage application were varied. The situation of the change is shown in Figs. 2 and 3. Figure 2 shows the relationship between temperature and transfer density (at this time, the voltage application time is
It was set to 0.8msec. ), Figure 3 shows the relationship between application time and transfer density (at this time, the temperature of the thermal head is
The temperature was 150℃. ). As shown in the figure, it has been found that according to the present invention, by a simple operation of changing the temperature of the thermal head 5 or the application time, multi-gradation of an image can be obtained corresponding to each change. Thermal transfer recording test (2) The thermal transfer recording medium A and the sublimable dye are as follows.
Thermal transfer recording medium B was prepared using the same composition and method except that Dye (2) was used, and the sublimation dye was changed to Dye (3) below.
A thermal transfer recording medium C was prepared using the same composition and method except that carnauba wax was used as the heat-melting compound, and a thermal transfer recording medium D was prepared using the same composition and method except that carnauba wax was used as the heat-melting compound. Further, as comparative examples, heat-sensitive transfer recording media A to C from which the heat-fusible layer was removed were prepared as heat-sensitive transfer recording media E, F, and G. Next, the coated surfaces of the thermal transfer recording media A to G were placed on plain paper, and a thermal plate (4 cm x 1 cm) having a surface temperature of 150° C. was pressed for 1 second to obtain a transferred image on the plain paper. The results are shown in Table 1 (see the section on transfer density in the same table). As a result of the above, recording media A to D of the present invention provided transferred images with higher density than those of Comparative Examples E to G. Next, as a result of leaving the transfer paper at a temperature of 80°C for one week, only a slight decrease in density was observed in the transferred images using thermal transfer recording media A to C, but F to
In G, the concentration decreased significantly. Next, measure the optical density according to λmax before and after leaving (Do ¹ before leaving, D ¹ after leaving), and calculate D/Do x 100 (%).
The thermal stability of the image was tested using the residual rate. The results are shown in Table 1. As shown in the table, thermal transfer recording medium A of the present invention
In the thermal transfer recording method using ~D, both the transfer density and thermal stability (fixing property) are improved compared to the thermal transfer recording method using comparative example thermal transfer recording media E~G that do not contain a heat-fusible layer. It turns out that it is very good. A preferred embodiment of the present invention has been described above, in which a heating element of a thermal head is applied to heat the dye and the dye is transferred from the heat-sensitive transfer medium. However, the present invention is not limited to this. , carbon dioxide laser,
An image may be formed by irradiating a laser beam such as a YAG laser to generate heat in the heat-sensitive transfer medium to transfer the dye.

〔Effect of the invention〕

As is clear from the above examples, according to the present invention, it is possible to obtain a multi-gradation dye image with high transfer density and excellent thermal stability on plain paper.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the means for producing a thermal transfer recording medium according to the present invention, FIG. 2 is a graph showing the relationship between the temperature of the thermal head and the transfer density, and FIG. 3 is a graph showing the relationship between the voltage application time and the transfer density. This is a graph showing.

Claims (1)

[Claims] 1. A sublimable layer containing a dye that is solid at room temperature and can be sublimated and transferred by heating is provided on a support,
A heat-sensitive transfer recording medium characterized in that a heat-fusible layer containing a heat-fusible compound is provided on the sublimation layer. A heat-sensitive transfer in which a sublimable layer containing a dye that is solid at room temperature and capable of sublimation transfer by heating is provided on a support, and a heat-fusible layer containing a heat-fusible compound is provided on the sublimable layer. 1. A thermal transfer recording method, which comprises overlapping a recording medium and a recording paper, and applying thermal energy according to image information from the thermal transfer recording medium and support side to form a dye image on the recording paper.