JPH08267945A - Thermal transfer sheet - Google Patents

Abstract

PURPOSE: To provide a thermal transfer sheet capable of well laminating respective colors and capable of obtaining a sharp color image free from a color mixture in process color printing performing printing by overlapapping at least two or more colors. CONSTITUTION: In a thermal transfer sheet wherein a hot-melt ink layer and a surface layer are laminated to at least one surface of a base material sheet, the surface layer is formed from a wax emulsion based on wax particles with an average particle size of 0.1-5μm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer sheet used in a thermal transfer printer using heating means such as a thermal head and a laser, and more specifically, a process color print for printing at least two or more colors. Thermal transfer sheet.

[0002]

2. Description of the Related Art Conventionally, a hot-melt ink layer in which a coloring material such as a pigment is dispersed in a hot-melt wax or a binder such as a resin,
Using a thermal transfer sheet supported on a base material sheet such as a plastic film, energy according to image information is applied to a heating device such as a thermal head, and the coloring material is transferred together with a binder onto a transfer target paper such as paper or a plastic sheet. A melt transfer method is known (Japanese Patent Application Laid-Open No. 57-1053).
No. 95). The image formed by the melt transfer method has high density and excellent sharpness, and is suitable for recording binary images such as characters and line drawings. Further, it is possible to form a multicolor or color image by using a thermal transfer sheet of yellow, magenta, cyan, black or the like and recording it on the transfer paper in an overlapping manner. As such a thermal transfer sheet for forming a color image, there is JP-A-58-138684.

[0003]

However, in the case of the thermal transfer sheet described in JP-A-58-138684, when the overprinting of each color is performed, the previously transferred ink is melted and the colors are different. Since the hot-melt inks are mixed with each other, there is a problem that clear printing cannot be performed. The present invention is intended to solve the above problems, and in a process color print in which at least two or more colors are overlapped and printed, it is possible to favorably stack the respective colors, and there is no color mixture. An object of the present invention is to provide a thermal transfer sheet capable of obtaining a clear color image.

[0004]

In order to achieve the above object, the present invention is a thermal transfer sheet comprising a base sheet and a heat-fusible ink layer and a surface layer laminated on at least one side of the base sheet. The surface layer was composed of a wax emulsion containing wax particles having an average particle diameter of 0.1 to 5 μm as a main component, thereby forming a thermal transfer sheet.

[0005]

The present invention provides a surface layer on a heat-meltable ink layer, so that when printing is performed by overlapping at least two colors, the respective heat-meltable inks can be laminated neatly without being mixed with each other. It will be transferred to the paper in the state of being put, and clear printing can be obtained. The surface layer has an average particle size of 0.1 to 5 μm.
When the surface layer is formed, the wax emulsion containing the above wax particles as a main component does not attack the previously prepared heat-meltable ink layer, and has a good color mixing prevention function even if it is thin.

[0006]

[Preferred Embodiment] As the base sheet 1, a base sheet used in a conventional thermal transfer sheet can be used as it is, and specifically, a polyester film, polypropylene, cellophane, polycarbonate, cellulose acetate, polyethylene, Polyvinyl chloride polystyrene,
There are plastics such as nylon, polyimide, polyvinylidene chloride, polyvinyl alcohol, fluororesin, chlorinated rubber, and ionomer, papers such as condenser paper and paraffin paper, non-woven fabrics, and the like, or a combination thereof. The thickness of the base sheet can be changed depending on the material so that the strength and thermal conductivity thereof are appropriate, but it is preferably 2 to 25 μm. A heat-resistant slip layer may be provided on the side of the substrate sheet opposite to the side where the transfer layer is provided, for the purpose of preventing fusion with the thermal head and improving slipperiness.

The heat-fusible ink layer provided on the above-mentioned substrate sheet is an ink layer composed of any one color of yellow, magenta, cyan and black, but at least two colors of yellow, magenta, cyan and black are used. It is also possible to use a multicolor ink layer in which the ink layer is applied separately in the width direction or the flow direction of the base sheet, but in each case, each ink layer consists of a colorant and a binder,
Further, various additives may be added if necessary.

Here, the colorant can be appropriately selected from known organic or inorganic cyan, magenta, yellow pigments or dyes. For example, the colorant has a sufficient coloring density, light, heat, etc. Therefore, those that do not discolor or fade are preferable. As the wax used as a binder, microcrystalline wax, carnauba wax, paraffin wax, Fischer-Tropsch wax, various low molecular weight polyethylenes, waxes, beeswax,
Examples thereof include various waxes such as whale wax, ivorot wax, wool wax, shellac wax, candelilla wax, petrolactam, partially modified wax, fatty acid ester, and fatty acid amide. As the resin, polyester resin, polyamide resin, polyolefin resin, acrylic resin, styrene resin, ethylene-vinyl acetate copolymer,
Examples thereof include thermoplastic elastomers such as styrene-butadiene rubber.

The above heat-fusible ink layer composition contains a colorant 5
-40% by weight, resin 5-20% by weight, wax 60-8
It is preferable to mix at a ratio of 0% by weight. If the colorant is less than the above range, the desired print density cannot be obtained.
When the amount is more than the above range, good ink fluidity cannot be obtained. When the amount of the resin is less than the above range, it is not preferable in that the film strength is lowered. If the amount exceeds the above range, the viscosity of the ink increases and the transferability deteriorates, which is not preferable. When the amount of wax is less than the above range, the printing sensitivity is lowered.
When the amount is more than the above range, good ink fluidity cannot be obtained. The heat-meltable ink layer is formed using the above-mentioned heat-meltable ink layer composition by hot melt coating, hot lacquer coating, gravure direct coating, gravure reverse coating, knife coating, air coating and roll coating methods. 0.5 to 7 μm, preferably 2 to 4 μm
To form a heat-meltable ink layer. When the thickness is 0.5 μm or less, the print density is low and there are many voids. When the thickness is 7 μm or more, the printing sensitivity decreases.

In addition, a release layer may be formed between the base sheet and the hot-melt ink layer, if necessary. Since the release layer is mainly composed of wax and improves the adhesion to the substrate sheet, it is possible to add a part of the above-mentioned thermoplastic elastomer, polyolefin resin, polyester resin or the like. The release layer is formed by using the above-mentioned release layer composition by a hot melt coating, a hot lacquer coating, a gravure direct coating, a gravure reverse coating, a knife coating, an air coating or a roll coating method, and a release layer having a thickness of 0.05 to 5 μm. To form. When the thickness is 0.05 μm or less, the adhesiveness between the base sheet and the thermal transfer ink layer is improved, and a good peeling effect cannot be obtained. When the thickness is 5 μm or more, the transfer sensitivity at the time of printing decreases, which is not preferable.

The thermal transfer sheet of the present invention has at least two colors or more by forming a surface layer composed of a wax emulsion mainly containing wax particles having an average particle diameter of 0.1 to 5 μm on the above heat-meltable ink layer. When process color printing is performed by superposing colors, the respective colors are favorably stacked, and a clear color image without color mixture can be obtained. By forming the surface layer with the wax emulsion, the previously formed heat-meltable ink layer is not damaged when the surface layer is formed. Further, since the wax maintains the particle shape in the surface layer, the cut between the printed portion and the non-printed portion becomes better at the time of transfer, as compared with the film-forming state.

As the wax particles, polyethylene wax, paraffin wax, carnauba wax, microcrystalline wax, wood wax, beeswax, whale wax,
Among various waxes such as ivory wax, wool wax, candelilla wax, partially modified wax and fatty acid amide, those having a melting point of 60 to 90 ° C. are used. When the melting point is 60 ° C. or lower, it causes blocking, and when the melting point is 90 ° C. or higher, printing sensitivity becomes insufficient. It is preferable to select a material whose melting point of the surface layer is higher than that of the hot-melt ink layer. The average particle size of the wax particles is preferably 0.1 to 5 μm, and when the average particle size is 0.1 μm or less, the function as the color mixing prevention layer is not fulfilled, and when the average particle size is 5 μm or more, the printing sensitivity decreases, which is not preferable.

In addition, by containing silica, microsilica, talc, urea resin, melamine resin, calcium carbonate or the like in an amount of 5 to 45% of the total weight of the surface layer, an effect of preventing blocking can be obtained.

By forming the surface layer from the above-mentioned materials, the surface layer has a high responsiveness to heat, and at the time of transfer, the surface layer quickly solidifies after coming into contact with the image receiving sheet. Good transfer without seeping into the paper. In addition, even when overprinting is performed, the newly transferred ink layer surface quickly solidifies after contacting the previously transferred ink layer, so the newly transferred ink is transferred to the previously transferred ink layer. Good transfer without color mixing with layers. The surface layer is formed by coating the emulsion coating liquid in which the wax particles are dispersed in water as described above on the heat-meltable ink layer at a rate of 0.3 to ² g / m ² and drying. Formed by. Thickness 0.3g / m ²
In the following cases, it does not function as a color mixing prevention layer, and 2
When it is more than g / m ^2, the printing sensitivity is lowered, which is not preferable.

[0015]

EXAMPLES Next, the present invention will be described more specifically with reference to Examples and Comparative Examples. In the text, parts and% are based on weight unless otherwise specified. Example 1 A 3.5 μm-thick polyester film (Lumirror manufactured by Toray) having a heat-resistant slip layer formed on the back side was coated with the following coating liquid for a heat-meltable ink layer using a bar coater and dried at 80 ° C. A heat-fusible ink layer is formed, and a surface layer coating solution is applied on it with a bar coater so that the solid coating amount becomes 0.5 g / m ² , and dried at 80 ° C. to form a surface layer. A thermal transfer sheet of the present invention was obtained. Thermal transfer sheet 1 of the present invention Coating liquid for hot melt ink layer Magenta pigment 10 parts EVA 10 parts Carnauba wax 7 parts Candelilla wax 14 parts Paraffin wax 30 parts Xylene 80 parts Surface layer coating liquid carnauba wax emulsion (particle size 0.3 μm) 40 parts IPA / water (3/1) 60 parts The thermal transfer sheet 2 of the present invention 2 coating liquid yellow pigment for heat-fusible ink layer 10 parts EVA 10 parts carnauba wax 7 parts candelilla wax 14 parts paraffin wax 30 Parts xylene 80 parts surface layer coating liquid carnauba wax emulsion (particle size 0.3 μm) 40 parts IPA / water (3/1) 60 parts thermal transfer sheet 3 of the present invention coating liquid cyan pigment for heat fusible ink layer 10 Part EVA 10 parts carnauba wax 7 parts candelilla wax 14 parts paraffin wax 30 parts Xylene 80 parts Surface layer coating liquid Carnauba wax emulsion (particle size 0.3 μm) 40 parts IPA / water (3/1) 60 parts

Example 2 A thermal transfer sheet of the present invention was obtained in the same manner as in Example 1 except that the surface layer coating liquid was changed to the following surface layer coating liquid. Coating liquid for surface layer Melamine particles (particle size 0.5 μm) 5 parts Carnauba wax emulsion (particle size 0.3 μm) 40 parts IPA / water (3/1) 60 parts

Comparative Example 1 A comparative thermal transfer sheet was prepared in the same manner as in Example 1 except that the surface layer coating liquid was changed to the following surface layer coating liquid.
Three types of thermal transfer sheets each having a yellow, magenta, and cyan ink layer were obtained. Carnauba wax emulsion for surface layer coating (particle size 0.05 μm) 40 parts IPA / water (3/1) 60 parts

Comparative Example 2 A comparative thermal transfer sheet was prepared in the same manner as in Example 1 except that the surface layer coating solution was changed to the following surface layer coating solution (as in Example 1 above).
Three types of thermal transfer sheets each having a yellow, magenta, and cyan ink layer were obtained. Carnauba wax emulsion for surface layer (particle size 6 μm) 40 parts IPA / water (3/1) 60 parts

Comparative Example 3 A comparative thermal transfer sheet was obtained in the same manner as in Example 1 except that the surface layer coating liquid was not formed.

Printing conditions Printer In-house printing tester Printing speed 2 inch / sec Printing paper Beck smoothness 200 seconds paper

[0021]

[Table 1]

Sensitivity Evaluation Method The ink transfer property of the printed matter by the test pattern prepared in-house was visually evaluated. Overprinting Suitability Evaluation Method Overprinting was performed using each of the yellow, magenta, and cyan thermal transfer sheets, and the print quality of the obtained printed matter was visually evaluated.

[0023]

According to the thermal transfer sheet of the present invention, in a process color print in which at least two or more colors are overlapped and printed, the respective colors can be favorably laminated, and a clear color image without color mixture is obtained. Can be obtained.

Claims (1)

[Claims] 1. A thermal transfer sheet comprising a base sheet and a heat-fusible ink layer and a surface layer laminated on at least one surface of the base sheet, the surface layer containing wax particles having an average particle size of 0.1 to 5 μm. A thermal transfer sheet comprising a wax emulsion as a main component.