JPH0333515B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field, etc.] The present invention relates to a thermal transfer recording medium capable of forming a dye image by thermally transferring a sublimable dye. More specifically, it is a heat-sensitive transfer recording medium that can produce a dye image with high sharpness and multi-tone 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. Regarding. [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. As a thermal recording method that solves the above-mentioned drawbacks, for example, a coloring material that is solid or semi-solid at room temperature is coated on a support such as paper or resin film, as described in Japanese Patent Application Laid-open No. 15446/1983. The coloring material on the support is brought into contact with the recording sheet, and the coloring material on the support is heated and selectively transferred to the recording sheet using a heat source controlled according to image information. A thermal transfer method for 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 the color density decreased significantly due to re-sublimation of the dye over time. Therefore, in order to obtain multi-gradation image recording, there is a strong desire to develop a thermal transfer recording medium that uses an advantageous sublimable dye 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 dye image having a high transfer density on plain paper, etc., and having a multi-gradation property with excellent thermal stability and light fastness. The object of the present invention is to provide a thermal transfer recording medium that can obtain the following properties. [Structure of the Invention] The sublimable layer in the present invention is solid at room temperature and can be transferred by sublimation by heating (in the present invention, it is also possible to transfer in a gaseous state by melting with sublimation or vaporizing after melting). , vaporization accompanying this melting or dissolution is also included in the sublimation transfer in the present invention. The sublimation-inhibiting compound is a compound that reacts with a sublimable dye to form a non-sublimable dye, and is a salt or complex containing a polyvalent metal ion. The polyvalent metal ion is preferably copper (), nickel (), zinc (), platinum (), palladium (), cobalt (), aluminum (), or the like. The salts containing polyvalent metal ions include the above-mentioned inorganic salts of polyvalent metals (hydrochlorides, sulfates,
Preferred examples include organic salts such as nitrates, phosphates, etc.), alkyl carboxylic acids, aryl carboxylic acids, alkyl sulfonic acids, arylsulfonic acids, alkyl phosphoric acids, and aryl phosphoric acids, and complexes containing the above-mentioned polyvalent metal ions. In order to carry out a rapid ligand exchange reaction, the coordination bond is not too strong, that is, the stability constant of the complex is 10 ⁶
~ ¹⁰⁸ is preferred. However, the complex used in the present invention may be outside the range of the stability constant. When using a salt or complex containing a polyvalent metal ion as the compound forming the non-sublimable dye,
As dyes that can be sublimated and transferred, the following general formula (1) or
A dye that can form a chelate with a polyvalent metal ion represented by (2) is preferred. General formula (1)

[Formula ^] (wherein,
and at least one adjacent position of the carbon bonded to the azo bond is (a) a nitrogen atom, or (b) a carbon atom substituted with a nitrogen atom, an oxygen atom, or a sulfur atom,
The ring may be further substituted with a substituent, and preferred substituents include an alkyl group, an alkoxy group, a cyano group, a nitro group, a thiol group, a thioalkoxy group, or a halogen atom. X ² represents an aromatic carbocycle or heterocycle in which at least one ring is composed of 5 to 7 atoms, and the ring may be substituted with an appropriate substituent, and preferable rings include: Examples include a benzene ring, a naphthalene ring, a pyridine ring, and a quinoline ring, and preferred substituents include an alkyl group, an alkoxy group, a cyano group, a nitro group, a hydroxyl group, an amino group, and a halogen atom.
G represents a chelating group, and preferred chelating groups include a hydroxyl group, an amino group, a methoxy group, a thiol group, and a thioalkoxy group. ) General formula (2)

[Specific example of Dye]

(1) 1-(2-pyridylazo)-2-naphthol(2) 1-(4-hydroxy-2-pyridylazo)-
2-naphthol (3) 2-(2-hydroxyphenylazo)-5-hydroxypyridine (4) 2-(2-pyridylazo)-4-methoxy-1
-Naphthol(5) 2-(4-nitro-2-pyridylazo)-4-
Methoxy-1-naphthol(6) 1-(2-hydroxyphenylazo)-2-naphthol(7) 1-(2-aminophenylazo)-2-naphthol(8) 2-(2-hydroxyphenyl azo)-5-methoxyphenol (9) 8-(2-hydroxyphenylazo)-quinoline (10) 3-(2-hydroxyphenylazo)-2,
4-pentanedione (11) 1-phenyl-2-(2-hydroxyphenylazo)-1,3-butanedione (12) α-(2-hydroxyphenylazo)-β-
Hydroxycinnamonitrile The heat-melting compound is preferably a low melting point 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 candelilla wax, stearic acid and Examples include higher fatty acids such as behenic acid, alcohols such as xylitol, amides such as acetamide and benzamide, and ureas such as phenyl urea and diethyl urea. As for the method for producing the heat-sensitive transfer recording medium of the present invention, it is preferable that it is 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 an external dye is coated onto a support to form a sublimable layer, and then a heat-melting compound is applied on top of the sublimable layer. A heat-fusible layer may be formed by applying a suitable binder together with a sublimation-inhibiting compound, or by coating the heat-fusible compound itself serving as a binder. 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, etc. 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. The smoothness was determined by the smoothness test using a Beck tester (JIS P
8119), it is sufficient if it is 200 seconds or more, and if it is 300 seconds or more, an image with a good transfer rate and reproducibility can be obtained. 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 above configuration will be described below. That is, when energy is applied to the heat-sensitive transfer recording medium from the support side according to the image information, the heat-fusible layer is transferred to the recording sheet by being given energy above a certain value, and the sublimation layer is transferred to the recording sheet. The dye is sublimated and transferred in accordance with the amount of energy, and a dye image having excellent sublimation resistance and multi-gradation properties that is stable against heat, light, etc. can be obtained on the recording sheet by the action of the sublimation-inhibiting compound. In this case, if a salt or complex of a polyvalent metal ion is used as a non-sublimable dye-forming compound and a chelating dye represented by the general formula (1) or (2) as a sublimable dye, light resistance and sublimation resistance are improved. Excellent images can be obtained. Therefore, the recording sheet may be plain paper, and it is also possible to provide a strong dye image on 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, the means for producing a thermal transfer recording medium will be explained with reference to FIG. First, on a polyethylene terephthalate film base 1 having a thickness of 6μ, the following composition was applied using a wire bar to a wet film thickness of 59.4μ, and dried to form a sublimable layer 2. Cellulose diacetate 0.6g Said sublimable dye Dye(1) 0.3g Acetone 20ml Next, the following composition was applied on the sublimable layer 2 to a wet film thickness of 27.4μ, and dried to form a heat-fusible layer 3. Then, a thermal transfer recording medium A was produced. Permarin PN (manufactured by Sanyo Kasei) 10ml Nickel chloride (non-sublimable pigment-forming compound)
0.15g H ₂ O 10ml 2% anionic activator 0.3ml Next, a thermal transfer recording test using the thermal transfer recording medium A described above will be described. That is, the coated surface of the thermal transfer recording medium A and white plain paper 4 as a recording sheet are stacked facing each other, and a thermal head 5 is used to transfer the sheet from the support 1 side of the thermal transfer recording medium A through a 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 0.8 m).
sec. ), Figure 3 shows the relationship between the application time and the transfer density (at this time, the temperature of the thermal head was set to 150°C).
℃. ). 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. Next, the thermal stability and storage stability test of images will be described. First, thermal transfer recording media B to E were prepared using the same composition as the thermal transfer recording medium A and by the same means except for the following compositional changes. Thermal transfer recording medium B...The sublimable dye was changed to Dye (4). Thermal transfer recording medium C...The sublimable dye was changed to Dye (10). Thermal transfer recording medium D: The non-sublimable dye-forming compound was changed to an acetylacetone copper complex. Thermal transfer recording medium E: The non-sublimable dye-forming compound was changed to a nickel complex of N,N-di(hydroxycarbomethyl)aniline. Further, as a comparative example, the thermal transfer recording medium A,
Thermal transfer recording media F, G, and H were prepared by removing the heat-fusible layer from B and C, respectively. Next, the coated surfaces of the above-mentioned thermal transfer recording media A to H were placed on plain paper, and a thermal plate (4 cm x 1 cm) having a surface temperature of 170° C. was pressed for 1 second to obtain a transferred image on the plain paper. This result is the first
It is shown in the table (see the transfer density section in the same table). As a result of the above, recording media A to E of the present invention provided transferred images with higher density than those of Comparative Examples F to H. Next, the transfer paper was left at a temperature of 80 DEG C. for one week. As a result, no decrease in density was observed in the transferred images using thermal transfer recording media A to C, but the density decreased in F to H. Next, optical density by λmax before and after leaving (before leaving)
D ¹ ₀ and D ¹ after standing were measured, and the thermal stability of the image was tested using D ¹ /D ¹ ₀ ×100 (%) as the residual rate. In addition, the transferred image obtained in the same manner was irradiated with a 6000W xenon lamp for 48 hours (the illuminance on the image surface was
6000 Lux), λmax before and after exposure
Measure the optical density (D ² ₀ before exposure, D ² after exposure) by
Light resistance was tested using D ² /D ² ₀ ×100 (%) as the residual rate. These results are shown in Table 1. As shown in the same table, the thermal transfer recording medium A of the present invention
The thermal transfer recording method using E has improved transfer density, thermal stability (fixing properties), and light resistance compared to the thermal transfer recording method using comparative thermal transfer recording media F to H that do not contain a heat-fusible layer. It can be seen that both properties are 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. carbon dioxide laser,
The heat-sensitive transfer medium may be irradiated with a laser beam such as a YAG laser to generate heat, and the dye may be transferred to form an image.

〔Effect of the invention〕

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

[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 capable of sublimation transfer by heating on a support, and a salt containing a polyvalent metal ion that can react with the dye to form a metal complex of the dye. Alternatively, a heat-sensitive transfer recording medium comprising a heat-fusible layer containing a sublimation-inhibiting compound as a complex and a heat-fusible compound.