JPH07102748B2 - Thermal transfer sheet for color image formation - Google Patents

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 for forming a color image, and more particularly to a thermal transfer sheet for forming a color image having a wide range of color reproducibility similar to various color printing widely used in the past. .

[0002]

2. Description of the Related Art Conventionally, a large amount of color printing is carried out by offset printing, gravure printing, etc. In such color printing, the original document is used as it is, or other original document,
Characters, symbols, etc. are combined and color-separated to create a plate of the three primary colors of cyan, magenta, and yellow. If necessary, a black plate is added, and the hue and pattern of the original document 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 system, and these pigments reproduce not only the three primary colors but also their intermediate colors in a wide range. As can be seen, the most preferable three primary color pigments have been selected from many past experiences. In the conventional printing method as described above, since it is indispensable to always add four primary colors or black to create a four-color plate, there is a problem that it requires a lot of equipment cost and space. However, there is a problem that color printing cannot be performed easily.

As one method for solving such a problem, a thermal transfer sheet of three primary colors is prepared from a sublimable (or heat transferable) dye, and the dye is transferred by thermal energy using this thermal transfer sheet to transfer a color image. A thermal transfer method for forming a film has been proposed. Such a method 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.

[0005]

SUMMARY OF THE INVENTION In the above-mentioned thermal transfer system, 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 side to transfer the dye on the thermal transfer sheet. This is a method of transferring to a material, and the size of the color dot formed by this transfer is much larger than the dot (halftone dot) in conventional offset printing. 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 it is difficult to change the dot size in the case of thermal transfer method. There is no choice but to change the difference by the thermal energy applied.

Therefore, it is ideal that the magnitude of the applied thermal energy is proportional to the density of the transferred dots.
In the case of the conventional thermal transfer sheet, especially when the thermal energy is small, the migration of the dye, that is, the color density is inferior, and it is almost impossible to adjust the migration property to the same level for all three primary colors. There is a problem in that the color reproducibility of the light-colored portion is insufficient and an intermediate color with sufficient gradation cannot be formed.

As a result of earnest research to solve the above-mentioned problems of the prior art and meet the above-mentioned demands, the present inventor found that among the conventionally known sublimable (heat transferable dye) dyes, a specific magenta By selecting a dye and creating a single color or full color thermal transfer sheet, it is possible to give a good color density even when the applied thermal energy is small and to achieve a very wide range of color reproduction. Found out.

[0007]

That is, the present invention relates to a thermal transfer sheet for forming a color image, which comprises a base material sheet and a dye carrying layer formed on one surface of the base material sheet, wherein the dye carrying layer is used. The dye contained is at least C.I. I. A thermal transfer sheet for forming a color image, which contains Solvent Red 19.

[0008]

[Function] At least C.I. I. By using Solvent Red 19, it is possible to provide a thermal transfer sheet for forming a color image, which can provide a good color density even when applied with a small amount of heat energy and can realize a very wide range of color reproduction. I can.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in more detail with reference to preferred embodiments. The main feature of the present invention is that it gives a good color density even at low energy from magenta dyes known in the past, and is most suitable for the color tone of conventional printing inks, especially magenta printing inks among the three primary colors of offset printing inks. The point is that the thermal transfer sheet was constructed by selecting a specific dye exhibiting close color reproducibility.

Magenta of the conventional offset printing ink,
Most of the three primary colors of cyan and yellow are composed of pigments, while the color materials used in the thermal transfer sheet are all sublimable (or heat transferable) dyes, so they both have their coloring mechanism. However, it was almost impossible to select the desired heat transferable dye based on the color tone of the dye itself.

For these reasons, the present inventor has conducted diligent research from the viewpoint of color density and color reproducibility without being restricted by the color tone of the dye itself, and as a result, by adopting a specific dye for magenta color, It was found that a thermal transfer sheet having excellent color reproducibility which gives good color density even with low energy can be obtained.

That is, in the present invention, as the magenta dye, C.I. I. Solvent Red 19 may be used alone or may be a C.I. I. Disperse Red 60 and C.I. I. By using the mixture with Solvent Red 19, it is possible to reproduce the color tone corresponding to the magenta ink of the offset printing ink. Incidentally, C.I. I. Disperse Red 60 and C.I. I. When a mixture with Solvent Red 19 is used, the mixing ratio is preferably C.I. I. C. per 1 part by weight of Disperse Red 60 I. By setting the solvent red 19 in the range of 0.5 to 1.5 parts by weight, the intended purpose is sufficiently exhibited. The above C. I.
Solvent Red 19 is Sudan Red 7B
(Manufactured by BASF), C.I. I. Disperse Red 6
0 can be easily obtained from the market as MS Red G (manufactured by Mitsui Toatsu Chemical) and the like, and is preferably used in the present invention.

When the magenta heat transfer sheet of the present invention is used for forming a full-color image, the cyan heat transfer sheet used in combination with the magenta heat transfer sheet may be a cyan dye such as C.I. I. Solvent Blue 36 and C.I. I. Solvent Blue 63
Preferably, the mixing ratio of the latter is 0.2 per 1 part by weight of the latter.
By using the mixture in the range of 0.5 to 0.5 parts by weight, it is possible to reproduce the color tone corresponding to the cyan ink of the offset printing ink. Further, as the dye used for the yellow thermal transfer sheet used in combination, C.I. I. By using Disperse Yellow 141, it is possible to reproduce a wide range of high-density color tones corresponding to the yellow color of the offset printing ink.

In the present invention, C.I. which is a cyan dye used together with the above magenta dye is used. I. Solvent Blue 36 is Waxoline Blue AP-FW
(Made by ICI), C.I. I. Solvent Blue 63 is a dye such as Kayaset Blue 714 (manufactured by Nippon Kayaku Co., Ltd.) and C.I. I. Disperse Yellow 141 is easily obtained from the market as PTY-52 (manufactured by Mitsubishi Kasei) and the like, and is preferably used in the present invention.

The thermal transfer sheet of the present invention can be used not only for a magenta single color but also for the thermal energy applied when a full-color image is formed by using a combination of cyan and yellow thermal transfer sheets with the magenta thermal transfer sheet. Proportion of shades of color is possible and color reproducibility is excellent, and in the case of full-color image formation, it is possible to reproduce a wide range of intermediate colors that are the best.

By using the thermal transfer sheet of the present invention as described above in combination with the above-mentioned cyan and yellow thermal transfer sheets, high density and wide range of color reproducibility similar to full color printing obtained by conventional offset printing. In particular, it is possible to form a full-color image having a wide range of color reproducibility of a relatively pale intermediate color. Therefore, it is possible to form a very high-quality full-color image without using an expensive and space-consuming conventional printing method, for example, even in a small factory, an office, or a home where a large-scale printing method cannot be adopted. It will be possible. The thermal transfer sheet of the present invention is characterized by using the specific magenta dye as described above, and other configurations may be the same as those of conventionally known thermal transfer sheets.

The base sheet used for the thermal transfer sheet of the present invention may be any one as long as it has conventionally known heat resistance and strength to some extent. For example, 0.
5 to 50 μm, preferably about 3 to 10 μm thick paper, various processed papers, polyester film, polystyrene film, polypropylene film, polysulfone film, polycarbonate film, polyvinyl alcohol film, cellophane, etc. are particularly preferable. Is a polyester film. The dye carrying layer provided on the surface of the substrate sheet as described above is C.I.
I. Solvent Red 19, or C.I. I. Disperse Red 60 and C.I. I. It is a layer in which a mixture with Solvent Red 19 is supported by an arbitrary binder resin.

As the binder resin for supporting the dye, any conventionally known binder resin can be used, and preferred examples include ethyl cellulose, hydroxyethyl cellulose, ethyl hydroxycellulose, hydroxypropyl cellulose, methyl cellulose, cellulose acetate and vinegar. Cellulose resins such as cellulose butyrate, polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, polyvinyl pyrrolidone, vinyl resins such as polyacrylamide, and polyester resins are preferable from the viewpoints of heat resistance and dye migration.

The dye-carrying layer of the thermal transfer sheet of the present invention is basically formed of the above-mentioned materials, but may optionally contain various additives similar to those conventionally known. Such a dye-carrying layer is preferably prepared by adding the above-mentioned dye, a binder resin and other optional components to a suitable solvent to dissolve or disperse each component to prepare a coating liquid or ink for forming the carrier layer. Is applied and dried on the above-mentioned substrate sheet to form. The dye-supporting layer thus formed has a density of 0.
It has a thickness of about 2 to 5.0 μm, preferably about 0.4 to 2.0 μm, and the dye in the carrier layer is 5 to 70% by weight, preferably 10 to 60% by weight of the weight of the carrier layer. Is preferably present in an amount of.

Although the thermal transfer sheet of the present invention as described above is sufficiently useful for thermal transfer as it is, an anti-adhesion layer, that is, a release layer may be further provided on the surface of the dye carrying layer. By providing the above, it is possible to prevent the thermal transfer sheet from sticking to the material to be transferred at the time of thermal transfer, use a higher thermal transfer temperature, and form an image with a more excellent density.

As the release layer, even if only the adhesion-preventing inorganic powder is adhered, a considerable effect is exhibited.
For example, from a resin having excellent releasability such as a silicone polymer, an acrylic polymer, or a fluorinated polymer, 0.01 to
It can be formed by providing a release layer having a thickness of 5 μm, preferably 0.05 to 2 μm. Incidentally, the inorganic powder or the releasing polymer as described above has a sufficient effect 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 by using the above-mentioned thermal transfer sheet may be any material as long as its recording surface has dye receptivity to the above dye, or In the case of paper, metal, glass, synthetic resin or the like having no dye-receptive property, the dye-receptive layer may be formed on at least one surface thereof.

Examples of materials to be transferred without forming a dye receiving layer include polyolefin resins such as polyethylene and polypropylene, halogenated polymers such as polyvinyl chloride and polyvinylidene chloride, 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 diacetate, cellulose Fibers, woven fabrics, films, sheets, molded products and the like made of cellulosic resins such as triacetate, polycarbonate, polysulfone, polyimide 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. Even for non-dyeing transfer materials such as paper, metal, glass, etc., a solution or dispersion of the dyeing resin as described above is applied to the recording surface and dried, or those resins are used. By laminating the film, a material to be transferred can be obtained.

Further, even in the case of 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 is
Further, it may be formed of a plurality of materials, and may further contain various additives within a range not impairing the intended purpose.

The dye receiving layer as described above may have any thickness, but it is generally 5 to 50 .mu.m thick. Further, such a dye receiving layer is preferably a continuous coating, but it may be formed as a discontinuous coating by using a resin emulsion or a resin dispersion. The material to be transferred is basically as described above and can be used as it is. However, the material to be transferred or the dye receiving layer thereof can contain inorganic powder for preventing adhesion. By doing so, even if the temperature at the time of thermal transfer is further raised, the adhesion between the thermal transfer sheet and the transfer material can be prevented, and more 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 preferably contained in an amount of about 0.5 to 30% by weight based on the weight of the dye receiving layer. In addition, the surface of the dye receiving layer of the material to be transferred used may have the above-mentioned inorganic powder adhered to enhance the anti-adhesion effect, or the release agent having excellent releasability as described above. May be provided.
Such a release layer exerts a sufficient effect with a thickness of about 0.01 to 5 μm, and can prevent the adhesion of the thermal transfer sheet 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 as described above and the recording material as described above, any conventionally known applying means can be used. For example, a thermal printer (for example, thermal printer TN-540 manufactured by Toshiba
By controlling the recording time with a recording device such as 0), it is possible to sufficiently achieve the intended purpose by applying thermal energy of about 5 to 100 mJ / mm ² .

[0029]

EXAMPLES Next, the present invention will be described more specifically with reference to Examples, Reference Examples and Comparative Examples. In the text, parts and% are based on weight unless otherwise specified. Example 1 An ink composition for forming a dye carrying layer having the following composition was prepared and applied to a 9 μm-thick polyethylene terephthalate film having a heat-treated back surface so that the dry coating amount was 1.0 g / m ² and dried. Then, a thermal transfer sheet of the present invention was obtained.

Magenta color MS Red G 2.40 parts Sudan Red 7B 3.10 parts Polyvinyl butyral resin 4.80 parts Methyl ethyl ketone 44.85 parts Toluene 44.85 parts Microfine MF8F 2.06 parts

Next, a synthetic paper (Yupo FPG # 150, manufactured by Oji Yuka) was used as a base sheet, and a coating solution having the following composition was applied to one surface of the synthetic paper at a rate of 10.0 g / m ² when dried. And then 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 (KF-393, Shin-Etsu Chemical Co., Ltd.) 1.2 parts Epoxy-modified Silly Corn (X-22-343, manufactured by Shin-Etsu Chemical Co., Ltd.) 1.2 parts Methyl ethyl ketone / toluene / cyclohexanone (weight ratio 4: 4: 2) 102.0 parts

Reference Example 1 An ink composition for forming a dye carrying layer having the following composition was prepared, and a 9 μm-thick polyethylene terephthalate film having a heat-treated back surface was coated so that the dry coating amount was 1.0 g / m ² . After coating and drying, a cyan and yellow thermal transfer sheet was obtained. Cyan color Waxline Blue AP-FW (manufactured by ICI) 6.05 parts Kayase Blue 714 1.65 parts Polyvinyl butyral resin 5.12 parts Methyl ethyl ketone 29.44 parts Toluene 43.84 parts Methyl isobutyl ketone 10.00 parts Microfine MF8F 2 .06 copy

Yellow PTY-52 5.50 parts Polyvinyl butyral resin 4.80 parts Methyl ethyl ketone 55.00 parts Toluene 34.70 parts Microfine MF8F 2.06 parts The above-mentioned magenta heat transfer sheet of the present invention and cyan of the reference example and The yellow thermal transfer sheet and the transfer material,
The dye-carrying layer and the dye-receiving surface are opposed to each other and overlapped,
From the back surface of the thermal transfer sheet, a head applied voltage of 10 V and a printing time of 4.0 msec. Recording was carried out with a thermal head under the conditions described above, and three-color images were obtained. The density of these three color images is
As shown in FIGS. 1 to 3, the images were very high as compared with the images of the same color in each of Comparative Examples described later.

Comparative Example 1 In place of the magenta dye in Example 1, MS-Red
G and Macrolex Red Violet R
, Instead of the cyan dye, Kayase Bl
ue 714 and replacing the yellow dye with F
oron Brilliant Yellow S-6
A three-color image was formed in the same manner as in Reference Example 1 except that GL was used. These color images were inferior in color density as shown in FIGS. 1 to 3 as compared with the image according to Reference Example 1.

[0035]

[Effect] As described above, by using the thermal transfer sheet of the present invention, it is possible to form a magenta image having excellent color reproducibility and capable of developing a magenta color of light and shade that is proportional to the applied heat energy. I can. Further, by using the thermal transfer sheet of the present invention in combination with the cyan and yellow thermal transfer sheets, it becomes possible to reproduce a wide range of excellent intermediate colors when a full color image is formed.

[0036]

[Brief description of drawings]

FIG. 1 shows applied thermal energy of each of a cyan image (A) obtained in Reference Example 1 and a cyan image (B) obtained in a comparative example, and a coloring density by the energy, and the vertical axis represents the density. The horizontal axis represents the amount of applied heat energy.

FIG. 2 shows applied thermal energy of each of a magenta image (A) obtained in Reference Example 1 and a magenta image (B) obtained in a comparative example, and a color development density due to the energy, and the vertical axis represents the density. The horizontal axis represents the amount of applied heat energy.

FIG. 3 shows applied thermal energy of each of a yellow image (A) obtained in Reference Example 1 and a yellow image (B) obtained in a comparative example, and a color development density due to the energy, and the vertical axis represents the density. The horizontal axis represents the amount of applied heat energy.

Claims (2)

[Claims] 1. A thermal transfer sheet for color image formation comprising a base sheet and a dye carrying layer formed on one surface of the base sheet, wherein the dye contained in the dye carrying layer is at least C.I. I. A thermal transfer sheet for color image formation, which contains Solvent Red 19. 2. The dye contained in the dye carrying layer is C.I. I.
Solvent Red 19 and C.I. I. The thermal transfer sheet for color image formation according to claim (1), which is a mixture of Disperse Red 60.