JP2700554B2 - Thermal transfer sheet - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement in a thermal transfer sheet, and more particularly to a thermal transfer sheet useful for forming a color image.

(Conventional technology and its problems) Conventionally, when printing an output print of a computer or a word processor by a thermal transfer method, a thermal transfer sheet provided with a heat-meltable ink layer on one surface of a base film is used. .

This conventional thermal transfer sheet has a thickness as a base film.
Using a 10 to 20 μm thick paper such as condenser paper or paraffin paper or a 3 to 20 μm thick plastic film such as polyester or cellophane, a hot-melt ink layer obtained by mixing a coloring agent such as a pigment or dye with wax is used. It is manufactured by coating.

As these thermal transfer sheets, black, yellow, magenta and cyan thermal transfer sheets are known, and further as a thermal transfer sheet for forming a full-color image from these thermal transfer sheets, a continuous or sheet-like base film yellow, There is known a full-color thermal transfer sheet in which three primary colors of magenta and cyan or four primary colors including black are formed in a plane-sequential manner.

When a color image is formed using these thermal transfer sheets, a three-color or four-color separation image is superimposed and transferred on the same surface of the same material to be transferred, and color reduction is performed by subtractive color mixing on the material to be transferred. Since the synthesis is performed, the three primary colors are required to be as transparent and as high in saturation as possible. The higher the transparency and saturation of each color, the more faithful the image is reproduced in the original, but the saturation of the yellow, magenta and cyan dyes conventionally used is limited, so the reproduced image is reproduced. There were also certain limits on the gender and saturation.

Accordingly, an object of the present invention is to provide a thermal transfer sheet capable of providing a color image with more excellent reproducibility and saturation than ever before.

(Means for Solving the Problems) The above object is achieved by the present invention described below.

That is, the present invention is a thermal transfer sheet in which a three-color heat-meltable ink layer of yellow, magenta, and cyan is formed on one surface of a continuous base film in a plane-sequential manner,
The yellow ink layer contains yellow pigment and yellow fluorescent dye,
A thermal transfer sheet for forming a color image, wherein the magenta ink layer contains a magenta pigment and a red to pink fluorescent dye, and the cyan ink layer contains a cyan pigment and a blue to green fluorescent dye or a fluorescent whitening dye. .

(Function) By adding an appropriate fluorescent dye to the three primary colors of yellow, magenta and cyan to improve their saturation, a thermal transfer sheet that provides a color image with further excellent color reproducibility and saturation is provided. .

(Preferred Embodiment) Next, the present invention will be described in more detail with reference to preferred embodiments.

The thermal transfer sheet of the present invention is obtained by adding a fluorescent dye to three primary colors of yellow, magenta and / or cyan to form a hot-melt ink layer on one surface of the continuous base film.

As the base film used in the present invention, a continuous or single-wafer base film similar to that used in the conventional thermal transfer sheet can be used as it is, and other materials can be used. Not restricted.

Specific examples of preferred base film include, for example, polyester, polypropylene, cellophane, polycarbonate, cellulose acetate, polyethylene, polyvinyl chloride, polystyrene, nylon, polyimide, polyvinylidene chloride, polyvinyl alcohol, fluororesin, chloride rubber, ionomer, etc. Plastic, condenser paper,
There are papers such as paraffin paper, non-woven fabric, and the like, and a base film in which these are combined may be used.

The thickness of the base film can be appropriately changed depending on the material so that its strength and thermal conductivity are appropriate, but the thickness is preferably, for example, 2 to 25 μm.
It is.

When the base film is a continuous film, the yellow, magenta, and cyan heat-meltable ink layers containing a fluorescent dye have, for example, an area corresponding to the A4 plate when a color image of the A4 plate is formed. Then, these color regions may be formed in a plane-sequential manner according to the conventional method.

As the yellow, magenta and cyan dyes, any conventionally known dyes can be used as they are, and as the fluorescent dye, a known fluorescent dye is dissolved in a thermosetting resin and cured.
A variety of pigments such as a fluorescent pigment obtained by pulverizing this into an appropriate particle size and a fluorescent dye as a base thereof are known, such as Epocolor FP3000 (fluorescent yellow), Epocolor FP20 (fluorescent pink), Epocolor FP115 (fluorescent orange), Epocolor FP1007 (fluorescent green), Shinloich color FA48 (fluorescent blue), Fire Orange AX-14-5, glow red powder, and the like are commercially available and can be used in the present invention. As the fluorescent dye, the fluorescent dye used in the fluorescent pigment can be obtained and used.

The amount of these fluorescent dyes used is from about 0.1 part by weight per 100 parts by weight of conventionally known yellow, magenta and cyan pigments.
It is preferable to use 50 parts by weight, and if the amount is less than the above range, the effect of adding the fluorescent dye is insufficient, while if the amount exceeds the above range, the fluorescent color becomes too strong and the original color becomes too strong. It is not preferable because the color rendering properties of the dye are reduced. It is preferable to use a yellow fluorescent dye for the yellow pigment, a red to pink fluorescent dye for the magenta pigment, and a blue to green fluorescent dye or a fluorescent whitening dye for the cyan pigment. It is generally preferred that the total amount of these dyes be about 2 to 90% by weight of the ink.

As the vehicle, as in the case of the conventional yellow, magenta, and cyan, a mixture containing wax as a main component and other derivatives of wax and drying oil, resin, mineral oil, cellulose, and rubber is used.

Representative examples of the wax include microcrystalline wax, carnauba wax, and paraffin wax. Further, various types of Fischer-Tropsch wax, various low molecular weight polyethylenes, wood wax, beeswax, spermaceti, Ibota wax, wool wax, shellac wax, candelilla wax, petrolactam, polyester wax, partially modified wax, fatty acid ester, fatty acid amide, etc. Wax is used.

In the present invention, the wax may be mixed with a thermoplastic resin having a relatively low melting point to improve the adhesion of the formed ink layer to the material to be transferred. Examples of such a thermoplastic resin include ethylene-vinyl acetate copolymer (EVA), ethylene-acrylate copolymer (EEA), polyethylene, polystyrene, polypropylene, polybutene, petroleum resin, vinyl chloride resin, and chloride resin. Vinyl-vinyl acetate copolymer, polyvinyl alcohol, vinylidene chloride resin, methacrylic resin, polyamide, polycarbonate, fluororesin, polyvinyl formal,
Polyvinyl butyral, acetylcellulose, nitrocellulose, polyvinyl acetate, polyisobutylene, ethylcellulose, polyurethane or polyacetal are used, and in particular, a relatively low softening point conventionally used as a heat-sensitive adhesive, for example, 20 to 80 ° C., preferably Is 50 ~ 80 ℃
Are preferred. The use ratio of the wax to the thermoplastic resin is preferably in the range of 5 to 300 in weight ratio of the thermoplastic resin to 100 of the wax.

For forming the ink layer, a method of melt-liquefying a mixture containing the above components and applying the same, or a method of dissolving and dispersing the above components in an appropriate solvent to form an ink, and applying and drying the ink can be used. Examples of the coating method include hot melt coating, hot lacquer coating, gravure coating, gravure reverse coating, roll coating, and many other means. It is preferable to form the ink layer using a solvent type ink since the hot melt coating may cause thermal degradation of the fluorescent pigment because the fluorescent pigment has insufficient heat resistance.

In the present invention, a surface layer can be formed on the ink layer. This surface layer forms a part of the transfer film at the time of thermal transfer, and is formed mainly of wax as described above.

The surface layer may be formed by hot melt coating or the like in the same manner as the ink layer, but a preferred method is to use an aqueous dispersion containing wax. A particularly preferred method is to apply a water dispersion of wax on the hot melt ink layer and dry it at a temperature equal to or lower than the melting point of the wax. By doing so, the surface layer is formed while maintaining the particle shape of the wax.

The aqueous medium containing the wax is water or a mixture of water and a water-soluble organic solvent, for example, methanol, ethanol, and isopropanol.
By using 5 to 200 parts by weight per 100 parts by weight, the wettability of the aqueous wax dispersion with the hot-melt ink is improved.

Further, the wax aqueous dispersion may contain a small amount of an emulsifier (surfactant) or a known additive such as a leveling agent. The solids content of this dispersion is of the order of 10 to 50% by weight.

In the present invention, the above-mentioned thermoplastic resin having a relatively low melting point can be mixed with the dispersion to improve the adhesion of the surface layer formed to the material to be transferred. The use ratio of the wax to the thermoplastic resin is preferably in the range of 5 to 300 in weight ratio of the thermoplastic resin to 100 of the wax.

The surface layer formed from the wax is formed by applying an ink composition containing a wax by a conventionally known coating method, and drying.If the drying is performed at a temperature equal to or higher than the melting point of the wax, A smooth surface layer is formed,
On the other hand, when the dispersion is dried at a temperature lower than the melting point of the wax, a surface layer having a fine irregular surface with the particle shape of the dispersion remaining is formed.

In the present invention, the surface layer formed as described above has a thickness of preferably 0.1 μm or more and less than 5 μm so that the sensitivity is not insufficient even when the printing energy is low as in a high-speed type printer. . This thickness is 0.1
If it is less than μm, the paper to be transferred and the ink layer may be rubbed to cause background contamination. The surface layer is substantially colorless after thermal transfer, and may be colored white by adding an appropriate amount of extender or white pigment.

When a material weak to heat is used for the base film, it is preferable to provide a layer for preventing sticking of the thermal head on the surface in contact with the thermal head. The sticking prevention layer has a heat-resistant resin and a substance acting as a heat release agent or a lubricant as basic constituent components. As the heat-resistant resin, a compound having two or more amino groups or a diisocyanate or triisocyanate is added to a synthetic resin having a glass transition point of 60 ° C. or higher or a thermoplastic resin having an OH group or a COOH group, and the resin is slightly cross-linked and cured. Are preferred. Thermal release agents or lubricants that act by melting when heated, such as amides, esters and salts of waxes and higher fatty acids, and those that remain solid, such as powders of fluororesins and inorganic substances There is.

By providing such an anti-sticking layer, thermal printing can be performed without sticking even on a thermal transfer sheet based on a plastic film that is weak to heat, and the plastic film is difficult to cut and easy to process. You can take advantage of such advantages.

A matte print may be desirable because a thermal transfer image generally has a glossy print and is beautiful, but may make the document difficult to read. In such a case, for example, as proposed by the applicant (Japanese Patent Application No. 58-208306), an inorganic pigment such as silica, calcium carbonate or the like dispersed in a suitable solvent is dispersed on a base film. It is preferable to form a thermal transfer sheet by coating and providing a mat layer, and then coating a hot-melt ink layer. Alternatively, the base film itself may be used after mat processing (the technique of Japanese Patent Application No. 58-208307 also proposed by the applicant).

The thermal transfer sheet of the present invention as described above can be applied to a general thermal transfer printer, for example, any commercial line or serial type printer.

(Effects) According to the present invention as described above, by adding an appropriate fluorescent dye to the three primary colors of yellow, magenta, and cyan to improve the saturation thereof, a color having more excellent color reproducibility and saturation can be obtained. A thermal transfer sheet for providing an image is provided.

(Examples) Hereinafter, the present invention will be described more specifically with reference to examples. In the description, parts and% are based on weight unless otherwise specified.

Example 1 A continuous film of polyethylene terephthalate having a thickness of 3.5 μm was used as a base film, and one surface thereof was coated with a three-color hot-melt ink having the following composition and dried, and further coated and dried with a surface layer material. The thermal transfer sheet of the present invention was obtained.

Hot-melt ink layer Dye x part Ethylene / vinyl acetate copolymer (Evaflex 420,
Mitsui Polychemicals) 24 parts Paraffin wax (Paraffin HNP-10, manufactured by Nippon Seiro) 42 parts Carnauba wax 14 parts Xylol 153.8 parts Isopropyl alcohol 31 parts Yellow color yellow pigment 8 parts Fluorescent yellow (Epocolor FP3000) 16 parts Magenta red Pigment 8 parts Fluorescent pink pigment (Epocolor FP20) 16 parts Cyan blue pigment 8 parts Fluorescent green pigment (Epocolor FP1007 16 parts 3 g / m ² (approx. (Dried state) at a rate of yellow, magenta, and cyan in order of A4, respectively, and dried.

Surface layer 155F Paraffin wax emulsion (WE-75, manufactured by Bond Wax Co., 40% solids aqueous emulsion) 20 parts Ionomer resin (Chemipearl S-100, manufactured by Mitsui Petrochemical, solids 27%) 10 parts 60% isopropanol aqueous solution 15 Part The composition was applied to the surface of the ink layer at a rate of 0.8 g / m ² (dry state) by a gravure coating method, and dried at 60 ° C. to form a surface mat-like surface layer.

Using the above thermal transfer sheet, using high-quality paper as the paper to be transferred, and using a commercially available thermal head to reproduce a full-color image, compared with the case of the following comparative example,
The saturation and color reproducibility of the entire image were excellent.

Comparative Example 1 A thermal transfer sheet of the present invention was obtained in the same manner as in Example 1 except that no fluorescent dye was used in Example 1.

A full-color image was reproduced using the above thermal transfer sheet, a high-quality paper as a transfer paper, and a commercially available thermal head.

Claims (1)

(57) [Claims] 1. A thermal transfer sheet comprising a continuous base film and heat-fusible ink layers of three colors of yellow, magenta and cyan formed on one surface of the continuous base film in a face-sequential manner, wherein the yellow ink layer is a yellow pigment. And a yellow fluorescent dye, the magenta ink layer contains a magenta pigment and a red to pink fluorescent dye,
A thermal transfer sheet for forming a color image, wherein the cyan ink layer contains a cyan pigment and a blue or green fluorescent dye or a fluorescent whitening dye.