JPH0790664B2 - Thermal transfer sheet for color image formation - Google Patents

Description

The present invention relates to a thermal transfer sheet for forming a color image, and more specifically to a wide range of color reproduction similar to various color prints and color photographs that have been widely used in the past. The present invention relates to a thermal transfer sheet for forming a color image having properties.

(Prior Art) Conventionally, a large amount of color printing is performed by offset printing, gravure printing, etc. In such color printing, the original document is used as it is, or another original document, characters, symbols, etc. are combined to perform color separation. Then, a plate of three primary colors of cyan, magenta, and yellow is prepared, a black plate is further added if necessary, and the hue, pattern, etc. of the original are reproduced by each printing ink.

In most cases, pigments are used as color materials for the three primary color inks of cyan, magenta and yellow in such a printing method, and these pigments can reproduce not only the three primary colors but also their intermediate colors in a wide range. The most preferable three primary color pigments have been selected based on many past experiences.

The conventional printing method as described above has a problem that it requires a lot of equipment cost and space because it is always necessary to create a plate of four colors by adding three primary colors or black.
For example, there is a problem that color printing cannot be easily performed in a light factory or office.

On the other hand, in recent years, due to the development of photographic technology, color photographs have been widely used. However, copying these color photographs is not as easy as printing, and the larger the size, the more expensive the reproduction becomes. There is.

One method to solve such problems is to create a thermal transfer sheet of three primary colors from a sublimable (or heat transferable) dye, and use this thermal transfer sheet to transfer the dye with thermal energy to form a color image. A scheme has been proposed. Such a system can easily form a color image without requiring a large printing machine or other various auxiliary equipment, and is expected to develop in the future.

(Problems to be Solved by the Invention) In the above-mentioned thermal transfer method, the material to be transferred and the thermal transfer sheet are superposed, and thermal energy is applied by a thermal head or the like from either example to transfer the dye on the thermal transfer sheet to the material to be transferred. The size of the color dot formed by this transfer is much larger than the dot (halftone dot) in the conventional offset printing. Further, in the case of printing ink, the color density of halftone dots can be freely changed mainly depending on the size of halftone dots, whereas in the case of the thermal transfer method, it is difficult to change the dot size. The difference has to be changed depending on the thermal energy applied, but it is very difficult to change the concentration delicately.

Due to the difference between both methods as described above, when a color image is formed by the thermal transfer method, the range of color reproducibility is significantly inferior to that of a color image by offset printing or the like. Improvement is required.

The present inventor has solved the problems of the prior art as described above, and as a result of earnest research to meet the above-mentioned demand, as a result of conventionally known sublimation (heat transfer dye), a specific three primary color dye is selected. The present inventors have completed the present invention by finding that by producing a thermal transfer sheet, a very excellent wide range of color reproduction can be realized and a color image equivalent to that of conventional color printing or color photography can be obtained.

(Means for Solving Problems) That is, the present invention relates to a thermal transfer sheet for color image formation comprising at least three types of thermal transfer sheets having respective dye carrying layers containing dyes of respective hues of cyan, magenta and yellow. In the above, the cyan dye is CI Solvent Blue 63, and the magenta dye is CI Disperse Red 60 and C.
A thermal transfer sheet for forming a color image, which is a mixture of I. Disperse violet 26 and the yellow dye is a dye represented by the following formula (I).

Next, the present invention will be described in more detail. The main feature of the present invention is that from the dyes for thermal transfer sheets which have been known innumerably in the past, the three primary colors of conventional printing inks, particularly offset printing inks, namely, cyan, magenta and The point is that a dye showing a wide range of color reproducibility closest to the color tone of the yellow printing ink is selected and a thermal transfer sheet of each color tone is prepared.

Most of the three primary colors of conventional offset printing inks are composed of pigments, while the color materials used for the thermal transfer sheet are all sublimable (or heat transferable) dyes, so they both develop their colors. Due to the different mechanism, it was almost impossible to select a heat transferable dye having the same color reproducibility as the wide range of color reproducibility of the three primary colors of the offset printing ink.

For these reasons, the present inventor has conducted earnest research from the viewpoint of color reproducibility without being restricted by the color tone of the dye itself, and as a result, adopted a specific dye for cyan and yellow, and specified a specific dye for magenta. It was discovered that a thermal transfer sheet excellent in a wide range of color reproducibility of not only the three primary colors but also the intermediate colors can be obtained by using the two kinds of dyes in combination.

That is, in the present invention, by adopting CI Solvent Blue 63 as the cyan dye, it is possible to reproduce a wide range of color tones corresponding to the cyan ink of the offset printing ink.

As a magenta dye, CI Disperse Red
To reproduce the color tone corresponding to the magenta ink of the offset printing ink by making 60 and CI Disperse Red 26 into a mixture in which the mixing ratio of the former is 0.3 to 1.0 part by weight per 1 part by weight of the former. You can
If the mixing ratio is out of this range, the object of the present invention cannot be achieved sufficiently.

Further, by using the dye represented by the above formula (I) as the yellow dye, a wide range of color tones corresponding to the yellow color of the offset printing ink can be reproduced.

The most important feature of the present invention is not that the dyes of the three primary colors as described above are simply selected for cyan, magenta, or yellow, respectively, but a color image is formed by these three colors. In this case, it is possible to reproduce the most excellent wide range of intermediate colors. Therefore, as long as it is a simple color, many dyes other than the above dyes that are superior to the above dyes as a single color can be found.However, although these dyes have excellent color reproducibility as a single color, they are not suitable for color image formation. It was insufficient as a primary color and it was difficult to reproduce a wide range of intermediate colors.

Therefore, the main feature of the present invention resides in the three primary colors consisting of the above-mentioned specific combination of dyes.

The above CI Solvent Blue 63 is Kayaset Blue714
(Nippon Kayaku), CI Disperse Red 60 is MS Red
G (manufactured by Mitsui Toatsu Chemicals), CI Disperse Violet 26 are Macrolex Red Violet R (manufactured by Bayer), and the dye represented by the above (I) is Foron Brilliant Yellow S.
−6GL (made by Sand) etc. are available from the market.

The present invention utilizes the combination of specific dyes as described above,
It provides three-color thermal transfer sheets of cyan, magenta, and yellow, respectively.These three-color thermal transfer sheets may be different thermal transfer sheets, or may be provided on a continuous base material sheet in any order. It may be one in which a dye-carrying layer containing three-color dyes is formed, and may further be combined with any of the conventionally known thermal transfer sheets of black color development.

Further, in the case of the above continuous sheet, each of the cyan, magenta, and yellow (and black) dye-carrying layers can be arbitrarily read in correspondence with the three-color (or four-color) portions of the continuous sheet so that the printer can read them. It is also possible to add the detection mark. Examples of these inspection detection marks are shown in the attached drawings.

By using the thermal transfer sheet as described above, it is possible to form a color image having a wide range of color reproducibility, particularly a wide range of intermediate color reproducibility, similar to color printing or color photography obtained by conventional offset printing. , Therefore without the use of traditional printing methods that are expensive and space consuming,
For example, it has become possible to form a very high quality color image even in a small factory, office, home or the like where such a large printing method cannot be adopted.

The thermal transfer sheet of the present invention is characterized by using the above-mentioned specific combination of three color dyes, and other configurations may be the same as the configurations of conventionally known thermal transfer sheets.

The base sheet used for the constitution of the thermal transfer sheet of the present invention containing the above dye may be any one as long as it has a conventionally known degree of heat resistance and strength, for example, 0.5 to 50 μm, preferably Paper having a thickness of about 3 to 10 μm, various types of processed paper, polyester film, polystyrene film, polypropylene film, polysulfone film, polycarbonate film, polyvinyl alcohol film, cellophane, etc., and particularly preferred is polyester film.

The dye carrying layer provided on the surface of the substrate sheet as described above is a layer in which the above dye is carried by any binder resin.

As the binder resin for supporting the dye,
Any of the conventionally known ones can be used, and if preferable examples are shown, ethyl cellulose, hydroxyethyl cellulose, ethyl hydroxycellulose, hydroxypropyl cellulose, methyl cellulose, cellulose acetate, cellulose resins such as cellulose acetate butyrate, polyvinyl alcohol, polyacetic acid. Vinyl-based resins such as vinyl, polyvinyl butyral, polyvinylpyrrolidone, and polyacrylamide, polyesters, and the like are preferable from the viewpoint of heat resistance, dye migration, and the like.

The dye-carrying layer of the thermal transfer sheet of the present invention is basically formed of the above-mentioned materials, but may also contain various additives similar to conventionally known ones, if necessary.

Such a dye-supporting layer is preferably prepared by adding a dye of each of the above-mentioned combinations in a suitable solvent, a binder resin and other optional components to dissolve or disperse each component to prepare a coating liquid or ink for forming a support layer. Then, this is applied onto the above-mentioned substrate sheet and dried to form.

The supporting layer thus formed has a thickness of about 0.2 to 5.0 μm, preferably about 0.4 to 2.0 μm, and the dye in the supporting layer is 5 to 70% by weight, preferably 5 to 70% by weight of the weight of the supporting layer. Is preferably present in an amount of 10 to 60% by weight.

The thermal transfer sheet of the present invention as described above is sufficiently useful as it is for thermal transfer, but an anti-adhesion layer, that is, a release layer may be further provided on the surface of the dye-carrying layer, and such a layer should be provided. This prevents the thermal transfer sheet from sticking to the material to be transferred during thermal transfer, uses a higher thermal transfer temperature, and can form an image with a more excellent density.

The release layer has a considerable effect even by simply adhering an anti-adhesive inorganic powder, and further, from a resin excellent in release property such as a silicone polymer, an acrylic polymer or a fluorinated polymer, 0.01 to 5 μm, preferably
It can be formed by providing a release layer having a thickness of 0.05 to 2 μm.

The inorganic powder or releasable polymer as described above can bring about sufficient effects even when incorporated in the dye carrying layer.

Further, a heat-resistant layer may be provided on the back surface of such a thermal transfer sheet in order to prevent adverse effects due to the heat of the thermal head.

The material to be transferred used for forming an image using the thermal transfer sheet as described above may be any as long as its recording surface has dye acceptability for the dye, and In the case of non-containing paper, metal, glass, synthetic resin, etc., a dye receiving layer may be formed on at least one surface thereof.

Examples of the transferred material that does not need to form a dye receiving layer include polyolefin resins such as polyethylene and polypropylene, halogenated polymers such as polyvinyl chloride and polyvinylidene chloride, polyvinyl alcohol, polyvinyl acetate, and polyacrylic ester. Vinyl polymers such as, polyethylene terephthalate, polyester resins such as polybutylene terephthalate, polystyrene resins, polyamide resins, copolymer resins of olefins such as ethylene and propylene and other vinyl monomers, ionomers,
Cellulose resins such as cellulose diacetate and cellulose triacetate, fibers made of polycarbonate, polysulfone, polyimide and the like, woven fabrics, films, sheets, molded products and the like can be mentioned.

Particularly preferred is a sheet or film made of polyester or a processed paper provided with a polyester layer. Further, even for non-dyeing transfer materials such as paper, metal, glass, etc., a solution or dispersion liquid of the above-mentioned dyeing resin is applied to the recording surface and dried, or those resins are applied. By laminating a film, a material to be transferred can be obtained.

Further, even with the transfer material having the above dyeing property, a dye receiving layer may be formed on the surface of the material having a more dyeing property as in the case of the above paper.

The dye-receptive layer thus formed may be formed of a single material or a plurality of materials, and may naturally contain various additives as long as the intended purpose is not impaired.

Such a dye receiving layer may have any thickness, but is generally 5 to 50 .mu.m thick. Further, although such a dye receiving layer is preferably a continuous coating, it may be formed as a discontinuous coating using a resin emulsion or resin dispersion.

Such a material to be transferred is basically as described above and can be sufficiently used as it is. However, it is possible to include an inorganic powder for preventing adhesion in the material to be transferred or the dye receiving layer thereof. By doing so, even if the temperature at the time of thermal transfer is further increased, the adhesion between the thermal transfer sheet and the transfer target material can be prevented, and further excellent thermal transfer can be performed. Particularly preferred is finely divided silica.

Further, in place of or in combination with the above-mentioned inorganic powder such as silica, the above-mentioned resin having good releasability may be added. Particularly preferable releasing polymer is a cured product of a silicone compound, for example, a cured product of an epoxy-modified silicone oil and an amino-modified silicone oil. Such a release agent is used in an amount of about 0.5 to 3 parts by weight of the dye receiving layer.
A good proportion is 0% by weight.

Further, the transfer-receiving material to be used may have the above-mentioned inorganic powder adhered to the surface of the dye-receiving layer to enhance the anti-adhesion effect, and the release agent having excellent releasability as described above. You may provide the layer which consists of.

When such a release layer has a thickness of about 0.01 to 5 μm, it exerts a sufficient effect to prevent the thermal transfer sheet from sticking to the dye receiving layer and further improve the dye receiving property.

As the means for applying thermal energy used when performing thermal transfer using the thermal transfer sheet of the present invention and the recording material as described above, any conventionally known applying means can be used, for example, a thermal printer (for example, , Toshiba Corporation
5-100 m by controlling the recording time with a recording device such as a thermal printer TN-5400)
By applying thermal energy of about J / mm ² , the intended purpose can be sufficiently achieved.

(Operation / Effect) By using the thermal transfer sheet of the present invention as described above, color printing by various printing methods, particularly offset printing method requires expensive equipment and a large space. While copying a large plate was expensive, a small-sized and relatively inexpensive device can form a color image with excellent color reproduction even in a small factory, office, or home.

Next, the above will be described more specifically with reference to examples. still,
In the text, "part" or "%" is based on weight unless otherwise specified.

Example Three types of ink compositions for forming a dye carrying layer having the following compositions were prepared. The yellow ink composition was prepared by dissolving the components and then filtering to remove the insoluble matter. Each of these was applied to a polyethylene terephthalate film having a thickness of 4.5 μm and heat-treated on the back surface so that the dry coating amount was 1.0 g / m ² , and dried to obtain the three colors of cyan, magenta and yellow of the present invention. Each thermal transfer sheet was obtained.

Cyan Kayaset Blue 714 5.00 parts Polybutyral resin 3.92 parts Methyl ethyl ketone 22.54 parts Toluene 50.18 parts Methyl isobutyl ketone 13.00 parts Xylene 5.00 parts Magenta MS Red G 2.60 parts Macrolex Red Violet R 1.40 parts Polybutyral resin 4.32 parts Methyl ethyl ketone 43.34 parts Toluene 43.34 parts n -Propanol 5.00 parts Yellow color Foron Brilliant Yellow S-6GL (containing dispersant) 5.50 parts Polybutyral resin 4.52 parts Methyl ethyl ketone 48.49 parts Toluene 41.49 parts
# 150), a coating solution having the following composition was applied to one surface of the surface at a rate of 10 g / m ² when dried, and dried at 100 ° C. for 30 minutes to obtain a transfer material.

Polyester resin (Vylon200, Toyobo) 11.5 parts Vinyl chloride-vinyl acetate copolymer (VYHH, UCC) 5.0 parts Amino-modified silicone oil (KF-393, Shin-Etsu Chemical Co., Ltd.) 1.2 parts Epoxy-modified silicone oil (X-22 -343, manufactured by Shin-Etsu Chemical Co., Ltd.) 1.2 parts Methyl ethyl ketone / toluene / cyclohexanone (weight ratio 4: 4: 2) 102 parts The above-mentioned three-color thermal transfer sheet of the present invention and the above-mentioned transferred material are respectively used as dye carrying layers. And the dye receiving surface are opposed to each other and overlapped, and recording is performed from the back surface of the thermal transfer sheet with a thermal head under the conditions of a head applied voltage of 10 V and a printing time of 4.0 msec.
Three color images were obtained. When the color reproducibility of these three color images was compared with the print image of the standard color of the offset printing ink, an image with a wide range of color reproducibility was obtained.

Example 2 In Example 1, three color dye carrying layer forming ink
Three colors were sequentially arranged on the continuous sheet in the same manner as in Example 1 except that cyan, magenta, and yellow were applied and dried on one continuous sheet (the same base material as in Example 1) in order. A continuous sheet-like color image forming thermal transfer sheet of the present invention was obtained.

Using this thermal transfer sheet, continuous thermal transfer was performed in the order of cyan, magenta, and yellow in the same manner as in Example 1 to form a color image. On the other hand, for comparison, a standard offset ink (G set ink, made by Moroboshi Ink) was used to form a color image from the same original, and when compared with the above color image, it was indistinguishable to the naked eye. The color reproducibility of the two types of color images was as shown in FIG.

[Brief description of drawings]

FIG. 1 is a color image (A) according to the present invention obtained in Example 2 and a color image (B) using a standard offset ink.
FIG. 6 is an xy chromaticity diagram of a CIE XYZ display system in which each of the above is measured using a color difference meter CR100 manufactured by Minolta. 2 to 5 show examples of detection marks that can be applied to the continuous sheet-shaped thermal transfer sheet of the present invention. In the figure, C is cyan, M is magenta, and Y is
The yellow color, Bk indicates the black color, and T indicates the detection mark.

Claims (3)

[Claims] 1. A thermal transfer sheet for color image forming comprising at least three types of thermal transfer sheets each having a dye carrying layer containing a dye of each hue of cyan, magenta and yellow, wherein the cyan dye is CI Solvent Blue 63. The magenta dye is CI Disperse Red 60 and C.
I. Disperse violet 26 mixture, and the yellow dye is a dye represented by the following formula (I), a thermal transfer sheet for color image forming. 2. A color image forming apparatus according to claim 1, wherein the base material sheet is a single sheet, and the dye carrying layers of three colors are formed on the surface in an arbitrary order. Thermal transfer sheet. 3. The thermal transfer sheet for color image molding according to claim 1, further comprising a thermal transfer sheet having a black dye carrying layer.