JPH05238158A - Thermal transfer medium and production thereof - Google Patents

Abstract

PURPOSE:To obtain a thermal transfer medium good in preservability without bringing about the lowering of sensitivity. CONSTITUTION:In a thermal transfer medium having a thermal transfer dye layer based on a thermal transfer dye and an org. binder is provided on a base sheet, the concn. of the dye in the dye layer is set to 80% or less and the amount of the residual solvent in the layer is set to 60mug/10cm<1> or less. The solvent used in the dye layer has the relation, (solvent hard to remain in dye layer)/(solvent easy to remain in dye layer) >1. Further, respective dye layers of yellow, magneta and cyan are successively applied using coating solutions in the order from the coating containing more solvents the hardest to remain in the dye layers to the one containing the same less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer medium using a heat transferable dye and a method for producing the same.

[0002]

2. Description of the Related Art Generally, an organic solvent is used as an ink solvent used in an ink layer (dye layer) of a thermal transfer recording medium of this kind. However, if the solvent remains in the ink layer after production, dye crystallization occurs. , Reduce the image quality during storage. Therefore, the storability of the dye in the ink layer largely depends on the amount of residual solvent after the ink layer is formed. This storability is also affected by the dye concentration in the ink layer.

On the other hand, the ink layer of a sublimation type thermal transfer recording medium is usually formed by coating each dye on a support using a gravure printing method in the order of yellow, magenta and cyan. The coating speed is generally set high in order to improve productivity. Therefore, it is desirable to raise the drying temperature, but raising the drying temperature too much is limited in terms of thermal properties of the dye and uniform coating of the ink layer.

The sensitivity of the sublimation type thermal transfer recording medium depends on the concentration of the dye in the ink layer. That is, if the dye concentration is too low, practical sensitivity cannot be maintained.

As described above, in order to improve the storage stability of the dye in the ink layer, it is necessary to reduce the residual solvent in the ink layer and to reduce the dye concentration in the ink layer as much as possible. There is a limit to reducing the residual solvent only by the temperature, and the dye concentration cannot be extremely lowered from the viewpoint of sensitivity.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermal transfer medium having good storage stability.

[0007]

That is, the present invention relates to a thermal transfer medium having a heat transferable dye layer mainly composed of a heat transferable dye and an organic binder on a base sheet, and a dye concentration in the dye layer. Is 80% or less and the residual solvent is 60
The thermal transfer medium is characterized in that it is not more than 10 μg / 10 cm ² .

Further, in the method for producing a thermal transfer medium, the organic solvent contained in the coating liquid for forming the heat transferable dye layer is a mixed solvent having the following relationship. Solvent that does not easily remain in the dye layer / solvent that easily remains in the dye layer> 1 (weight ratio)

Further, when the yellow, magenta, and cyan heat-transferable dye layers are applied to the support in a face-sequential manner, the dye layer-forming coating liquid, which tends to remain in the dye layer, contains less solvent. A method of manufacturing a thermal transfer medium, characterized in that the coating liquids are applied in this order.

The upper limit of the amount of residual solvent in the heat transferable dye layer is set to 60 μg / 10 cm ^{2 as} described above, because if the amount is less than this, the image quality is less likely to deteriorate due to crystallization of the dye during storage.

Further, the solvent which does not easily remain in the heat transferable dye layer is not used, but the solvent which tends to remain is mixed. Since the solubility is good, by mixing a solvent that easily remains with a solvent that does not easily remain, and by increasing the amount of the solvent that does not easily remain than the solvent that easily remains, it is possible to achieve both image density and storage stability. ..

Further, in the surface sequential coating of the heat transferable dye layer, it was decided to apply in order from the coating solution containing a large amount of the solvent that tends to remain in the dye layer to the coating solution containing a small amount of the solvent. Because it can be removed. That is, in the sequential coating of each color of yellow, magenta and cyan, the heat transferable dye layer is coated and dried for each color. Therefore, the heat transferable dye layer applied first is dried three times, the second is dried twice and the third is dried once. Therefore, the residual solvent is effectively removed by applying the solvent in the order of the amount of the solvent that tends to remain.

The base sheet used in the present invention includes:
Any known material having a certain degree of heat resistance and strength may be used, and the thickness thereof is 0.5 μm to 50 μm, preferably 3 μm to 10 μm.
About μm paper, various processed papers, polyester film, polystyrene film, polypropylene film, polysulfone film, polycarbonate film, etc., particularly preferred is a polyester film, which is further provided with a heat resistant slipping layer on the back surface. More preferable.

The binder resin for the heat transferable dye layer may be any conventionally known binder resin, and examples thereof include cellulosic resins such as ethyl cellulose, hydroxyethyl cellulose, ethyl vidoxy cellulose, methyl cellulose and cellulose acetate, polyvinyl alcohol, Examples thereof include vinyl resins such as polyvinyl acetate, polyvinyl butyral, polyvinyl acetal, polyvinyl pyrrolidone, and polyacrylamide. Among them, polyvinyl butyral is preferable in terms of heat resistance and migration of dyes.

The heat transferable dye is a dye that sublimes or vaporizes at 60 ° C. or higher, and may be a dye mainly used in thermal transfer printing such as a disperse dye or an oil-soluble dye.
I Desperce Yellow 1,3,8,9,16,41,54,6
0,77,116 etc. CI Desper Red 1,4,6
11,15,17,55,59,60,73,83, CI Desperse Blue 3,14,19,26,56,60,64,72,99,108, CI Solvent Yellow 77,116 Examples include CI Solvent Red 23, 25, 27 and the like, CI Solvent Blue 36, 83, 105, and the like, and one of these dyes can be used, but several kinds may be mixed.

As an ink solvent for dissolving or dispersing a dye and a binder resin, a conventional ink solvent can be freely selected. As an alcohol solvent, methanol, ethanol, isopropyl alcohol, butanol, isobutanol, etc., and as a ketone solvent, methyl ethyl ketone. , Methyl isobutyl ketone, cyclohexanone and the like, aromatic compounds such as toluene and xylene, and halogen compounds such as dichloromethane, trichloroethane and the like, dioxane, tetrahydrofuran and the like, formamide, dimethylformamide, dimethylsulfoxide or the above-mentioned kobubutsu. Table 1 shows examples of the solvent that hardly remains in the heat transferable dye layer and the solvent that easily remains in the present invention.

[0017]

[Table 1] Table 1

The dye concentration is 5 to 80% by weight,
It is preferably about 10 to 60% by weight. The ink layer thickness is 0.1 μm to 30 μm, preferably 0.5 μm to 2.0 μm.
It is in the range of m.

The coating method of the heat transferable dye layer may be any conventionally known method, but the preferred method is the gravure printing method.

The heat transferable dye layer in the present invention is basically formed of the above-mentioned materials, but may optionally contain various conventionally known additives.

[Examples] [0021] Specific examples will be described below. The amounts (parts) of each component in the examples are all parts by weight.

Example 1 (Dye layer formulation) Organic binder: Polyvinyl butyral BX-1 (Sekisui Chemical Co., Ltd.) 10 parts Heat transfer dye: HM-1450 / Macrolex Red Violet R = 6/4 15 parts Solvent : Dioxane 114 parts Toluene 38 parts Methyl ethyl ketone 38 parts

After dissolving the composition of the above formulation, 1 μm on the back surface
A 6 μm-thick polyethylene terephthalate film having a thick silicone resin heat-resistant layer formed thereon was coated with a wire bar and dried at a drying temperature of 80 ° C. for 2 minutes to prepare a heat transferable dye layer of about 1 μm.

Example 2 All were the same as in Example 1 except that the solvent for the dye layer was 95 parts of dioxane and 95 parts of methyl ethyl ketone and the drying time was 1 minute.

Example 3 (Dye layer formulation) Organic binder: Polyvinyl butyral BX-1 (Sekisui Chemical Co., Ltd.) 10 parts Heat transfer dye: Y Foron Brillant Yellow S 6GL / MS Yellow VP = 6/4 7 Part M HM-1450 / Macrolex Red Violet R = 6/4 15 parts C HSO-16 / HSO-144 13 parts Solvent: Dioxane 114 parts Toluene 38 parts Methyl ethyl ketone 38 parts

After the composition of the above formulation was dissolved, the number of lines of the gravure roll and the plate depth were adjusted by using a gravure coater, and the following ink liquid amount for each color was previously heat-treated at 6 μm on the back surface.
50m / min while coating yellow, cyan and magenta on a polyethylene terephthalate film of m thickness,
Drying was carried out at 80 ° C. in a length of each drying box of 3 m to obtain a thermal transfer recording medium. Yellow ink deposit 18g / m ² Magenta ink deposit 9g / m ² Cyan ink deposit 15g / m ²

Comparative Example 1 All were the same except that the drying time of the dye layer in Example 1 was 30 seconds.

Comparative Example 2 In Example 2, the solvent for the heat transferable dye layer was changed to dioxane 17
All were the same except 1 part and 19 parts of methyl ethyl ketone.

Comparative Example 3 All were the same except that the coating order in Example 3 was yellow, magenta, and cyan.

The recording media prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were stored at 60 ° C. for 100 hours in a state where the heat transferable dye layer and the heat resistant layer were in contact with each other, and then both were peeled off to form the dye layer. Table 2 shows the results of the evaluation.

[0031]

[Table 2]

(Note) 1) O ... No change in heat transferable layer. X ... Change in heat transferable layer. 2) Measurement of residual solvent in the ink layer by thermal decomposition gas chromatography.

From Table 2, the amount of residual solvent in Example 1 was limited, and in Example 2 the amount of the solvent in the coating liquid for forming the heat transferable dye layer was such that the solvent was liable to remain / the amount of the solvent was less likely to remain> 1. It is clear that the mixed solvent having the above relation was used, and further, in Example 3, the amount of the residual solvent was decreased and the storage stability was improved by coating the solvent in the order of the solvent that easily remains.

[0034]

As described above, according to the present invention, it is possible to obtain a thermal transfer medium having good storability without causing thermal damage to the dye or lowering the sensitivity.

Claims (3)

[Claims] 1. A thermal transfer medium having a heat transferable dye layer mainly composed of a heat transferable dye and an organic binder on a base sheet, wherein the dye concentration in the dye layer is 80% or less, and the residual solvent is used. Is 60 μg / 10 cm ² or less, a thermal transfer medium. 2. A thermal transfer method for forming a heat transferable dye layer by applying a heat transferable dye layer-forming coating liquid mainly composed of a heat transferable dye, an organic binder and an organic solvent onto a base sheet and drying it. The method for producing a medium, wherein the organic solvent is a mixed solvent having the following relationship. Solvent that does not easily remain in the dye layer / solvent that easily remains in the dye layer> 1 (weight ratio) 3. Yellow, magenta, and
In the method for producing a thermal transfer medium in which the heat transferable dye layers of respective colors containing cyan heat transferable dyes are formed in a frame-sequential manner, coating is performed in order from a coating solution containing a large amount of a solvent that tends to remain in the dye layer to a coating solution containing a small amount thereof A method of manufacturing a thermal transfer medium, comprising: