JPS62255189A - Thermal transfer sheet for forming color picture - Google Patents

Abstract

PURPOSE:To enable the formation of the color picture of a good color reproducibility with a small sized apparatus, by using the thermal transfer sheet for forming the color picture having respective dye carrying layers containing specific dyes of cyan, magenta, and yellow. CONSTITUTION:As a cyan dye, C.I. solvent blue 36 and C.I. solvent blue 63 are made the mixture of which the mixing ratio is preferably a range of 0.2-0.5pt.wt. the latter per 1pt.wt. of the former. Further, as a magenta dye, C.I. disperse red 60 and C.I. solvent red 19 are made the mixture of which the mixing ratio is preferably a range of 0.5-1.5pts.wt. the latter per 1pt.wt. of the former. Furthermore, C.I. disperse yellow 141 is used as a yellow dye. Thereby, wide-ranging hue of high density corresponding to respective colors of an offset printing ink can be reproduced. Herein, the base material sheet is one piece of sheet and the dye carrying layer containing dyes of three colors may be preferably formed in a selected order thereon. Further, the thermal transfer sheet of black coloration may be combined therewith.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a thermal transfer sheet for color image formation, and more specifically, it has a wide range of color reproducibility similar to various color printings conventionally widely used commercially. The present invention relates to a thermal transfer sheet for color image formation.

(Prior art) Conventionally, a large amount of color printing has been performed using offset printing, gravure printing, etc. When printing in color, the original is used as it is, or it is color separated by combining other originals, characters, symbols, etc. Then, plates for the three primary colors of cyan, magenta, and yellow are created, and a black plate is added as necessary to reproduce the hue, pattern, etc. of the original using each printing ink.

In most cases, pigments are used as coloring materials for the three primary color inks of cyan, magenta, and yellow in such printing methods, and these pigments are capable of reproducing not only the three primary colors but also all intermediate colors between them. Based on past experience, the most preferred three primary color pigments have been selected.

Conventional printing methods such as those described in 1. always require adding three primary colors or black to create a surrounding plate, which has the problem of requiring a large amount of equipment cost and space. There is a problem in that it is not possible to easily perform color printing.

One method to solve these problems is thermal transfer, in which a thermal transfer sheet of the three primary colors is created from sublimable (or heat transferable) dyes, and this thermal transfer sheet is used to transfer the dye using thermal energy to form a color image. A method has been proposed. Such a method does not require a large printing machine or various other auxiliary equipment, and can easily form color images, and is expected to continue to develop in the future.

(Problems to be Solved by the Invention)'' - The thermal transfer method described above involves superimposing a transfer material and a thermal transfer sheet, and applying thermal energy using a thermal head or the like to coat the dye on the thermal transfer sheet. This is a method in which the color is transferred to a transfer material, and the size of the colored dots formed by this transfer is much larger than the dots (halftone dots) in conventional offset printing. In addition, in the case of printing ink, the color density of halftone dots can be freely changed by changing the size of the halftone dots, whereas in the case of thermal transfer, it is difficult to change the dot size, and the density cannot be changed. The difference has to be changed depending on the heat energy applied.

Therefore, ideally, the amount of thermal energy applied should be proportional to the density of the transferred dots, but in the case of conventional thermal transfer sheets, dye transfer, that is, color density, is poor especially when the thermal energy is small. In addition, it was almost impossible to adjust the transition properties of all three primary colors to the same level, so the color reproducibility of relatively light-colored parts was insufficient and intermediate colors with sufficient gradation could not be formed.

The present inventor solved the problems of the prior art as described above, and
- As a result of intensive research to meet the above-mentioned demands, we have found that by creating a thermal transfer sheet by selecting dyes of three specific primary colors from among conventionally known sublimable (thermally transferable dyes), the thermal energy imparted can be reduced. The present invention was completed based on the discovery that even when the amount is small, it is possible to provide good color density and achieve excellent color reproduction over a wide range.

(Means for Solving the Problems) That is, the present invention provides a thermal transfer sheet for color image formation 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. In "2, the cyan dye is c, r
, Solvent Blue 63 and C.I. I. Solvent Blue 36, and the magenta dye is a mixture of C. I.
Disbirds Red 60 and C1! , and the yellow dye is a mixture of C. I.
This is a thermal transfer sheet for color image formation characterized by being Diverse Yellow 141.

Next, to explain the present invention in more detail, the main feature of the present invention is that it can provide good color density even at low energy using dyes for thermal transfer sheets known in the past, and that it can be used with conventional printing inks, especially offset dyes. The three primary colors of printing ink are cyan.

The dye that exhibits a wide range of color reproducibility that is closest to the tones of magenta and yellow printing inks was selected, and thermal transfer sheets of each tone were prepared.

Most of the three primary colors of conventional offset/printing inks are composed of pigments, while all the coloring materials used in thermal transfer sheets are sublimable (or heat transferable) dyes, so both are different from each other. Because their coloring mechanisms are different,
Based on the color tone of the dye itself, it has been almost impossible to select a desired heat-transferable dye.

For these reasons, the inventor of the present invention has conducted intensive research from the viewpoint of color density and color reproducibility, without being constrained by the color tone of the dye itself, and has adopted a specific dye for yellow, and has adopted a specific dye for cyan and magenta. It was discovered that by using a combination of two specific dyes, it was possible to obtain a thermal transfer sheet that gave good color density even at low energy levels and had excellent color reproducibility not only for the three primary colors but also for their intermediate colors. This is what I did.

That is, in the present invention, C.I. I
．． Truben i Blue 36 and C. I. Solvent Blue 63, preferably at a mixing ratio of 0.2 to 0.5 parts by weight of the latter per 1 part by weight of the former, to reproduce a color tone corresponding to cyan ink of offset printing ink. Can be done. If the mixing ratio falls outside of this range, the object of the present invention will not be fully achieved.

Moreover, as a magenta dye, C. I. Disbirds Red 60 and G, 1. Solvent Red 18, preferably at a mixing ratio of 1 part by weight of the former to 0.5 to 1 part by weight of the latter.
By forming a mixture in the range of 5 troughs, it is possible to reproduce a color tone corresponding to magenta ink of offset printing ink. If the mixing ratio falls outside of this range, the object of the present invention will not be fully achieved.

Furthermore, as a yellow dye, C. I. By using Disverse Yellow 141, it is possible to reproduce a wide range of high density tones corresponding to the yellow color of offset printing ink.

The most important feature of the present invention is not that the three primary color dyes mentioned above are selected simply for cyan, magenta, or yellow, but that a color image is formed using these three colors. It is possible to produce a single shade of color proportional to the thermal energy applied at the time of application, and to reproduce the most excellent and wide range of intermediate colors. Therefore, if it is just a single color, it is possible to find many dyes other than those mentioned above that are better than the dyes mentioned above. It is insufficient as a primary color for color image formation, and it is difficult to reproduce a wide range of intermediate colors.

Therefore, the main feature of the present invention is that a thermal transfer sheet of three primary colors made of the specific combination of dyes listed in -1- is prepared.

In addition, ``2 G, 1. Solvent Blue 36 is Wax
oline Blue AP-FW (manufactured by ICI),
c, i, Solvent Blue 63 are Kayaset
Blue 714 (Nippon Kayaku), G, 1. Disbird's Red 60 is MsRedG (Mitsui Toatsu Chemical), C. I. Solvent Red 19 is 5uda
n Red 7B (manufactured by BASF), C. I. Disbirds Ye 0-141 is commercially available as PTY-52 (manufactured by Mitsubishi Kasei).

The present invention utilizes a combination of specific dyes as described above,
The three-color thermal transfer sheets are provided in cyan, magenta, and yellow, respectively, but these three-color thermal transfer sheets may be separate thermal transfer sheets, or they may be printed in any order on a continuous base sheet. A dye-retaining layer containing dyes of three colors may be formed in the above embodiments, and any conventionally known black-colored thermal transfer sheet may be combined with these embodiments.

By using a thermal transfer sheet such as the one described above, color images with high density and wide color reproducibility, especially relatively light and intermediate colors, can be produced in the same way as color printing obtained by conventional offset printing. can therefore be printed in very high quality without using expensive and space-consuming conventional printing methods, even in small factories, offices or homes, for example, where it is not possible to adopt such large-scale printing methods. It became possible to form color images.

The thermal transfer sheet of the present invention is as follows. The 41F feature is the use of a specific combination of three-color dyes, and the other configurations may be the same as those of conventionally known thermal transfer sheets.

The base sheet used in the construction of the thermal transfer sheet i of the present invention containing the above-mentioned dye may be any conventionally known material having a certain degree of heat resistance and strength, for example, 0.5~ 50ILm, preferably 3-107Lm
paper of a certain thickness, various processed papers, polyester film,
Examples include polystyrene film, polypropylene film, polysulfone film, polycarbonate film, polyvinyl alcohol film, and cellophane, with polyester film being particularly preferred.

The dye-carrying layer provided on the surface of the base sheet as described in -I- is a layer in which the dye described above is supported by an arbitrary binder resin.

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

The dye-supporting layer of the thermal transfer sheet of the present invention is basically formed from the above-mentioned materials, but may also contain various conventionally known additives as required.

Such a dye-carrying layer is preferably prepared by adding the above-mentioned combinations of dyes, binder resin, and other optional components to a suitable solvent and dissolving or dispersing each component to prepare a coating liquid or ink for forming a compatible layer. This is formed by coating and drying this on the above base sheet.

The support layer formed in this way has a concentration of 0.2 to 5,0
JLm, preferably about 0.4 to 2.0 gm, and the dye in the carrier layer is 4r! Suitably it is present in an amount of 5 to 70%, preferably 10 to 60% by weight of the carrier layer.

The thermal transfer sheet of the present invention as described above is sufficiently useful for thermal transfer as it is, but an anti-adhesive layer, that is, a release layer may be further provided on the surface of the dye-supporting layer, and such a layer may be provided. This prevents adhesion between the thermal transfer sheet and the transfer material during thermal transfer, allows use of a higher thermal transfer temperature, and forms images with even better density.

As this mold release layer, even if an inorganic powder with anti-adhesive properties is simply attached, it has a considerable effect. , 01-5 pLm
, preferably by providing a release layer of 0.05 to 2p, m.

Incidentally, the inorganic powders or release polymers described in [2] can exhibit sufficient effects even if they are included in the dye-carrying layer.

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

The transfer material used to form an image using a thermal transfer sheet as described below may be any material as long as its recording surface is receptive to the above-mentioned dyes. In the case of non-receptive materials such as paper, metal, glass, synthetic resin, etc., a dye-receiving layer may be formed on at least one surface thereof.

Examples of transfer materials that do not require the formation of 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 with other vinyl monomers, ionomers,
Examples include fibers, woven fabrics, films, and sheet molded products made of cellulose resins such as cellulose diacetate and cellulose triacetate, polycarbonate, polysulfone, and polyimide.

Particularly preferred are sheets or films made of polyester or processed paper provided with a polyester layer. In addition, even if the transfer material is non-dyeable such as paper, metal, glass, etc., a solution or dispersion of a dyeable resin as described above may be applied and dried on the recording surface, or By laminating the resin film, it can be used as a transfer material.

Furthermore, even if the transfer material has the dyeability described above, a dye-receiving layer may be formed on the surface thereof from a resin having better dyeability, as in the case of the paper described above.

The dye-receiving layer thus formed can be formed from a single material or a plurality of materials, and it goes without saying that it may further contain various additives as long as the intended purpose is not hindered.

Such dye-receiving layers may be of any thickness, but are typically between 5 and 50 pLm thick. Although such a dye-receiving layer is preferably a continuous coating, it may also be formed as a discontinuous coating using a resin emulsion or resin dispersion.

Such a transfer material is basically as described above and can be used as is, but it is possible to incorporate an inorganic powder for anti-adhesion into the transfer material or its dye-receiving layer. In this way, even if the temperature during thermal transfer is increased, adhesion between the thermal transfer sheet and the material to be transferred can be prevented, and even better thermal transfer can be performed. Particularly preferred is finely powdered silica.

Further, in place of or in combination with the above-mentioned starting inorganic powder of silica, the above-mentioned resin having good mold releasability may be added. Particularly preferred release polymers include cured products of silicone compounds, such as cured products of epoxy-modified silicone oil and amine-modified silicone oil. Such a release agent may be used in an amount of about 0.5 to 0.5 to
A ratio that accounts for 30% of the nail amount is good.

In addition, the transfer material to be used may have an inorganic powder as described above sealed on the surface of the dye-receiving layer to enhance the anti-adhesion effect, or a mold release material with excellent mold releasability as described above. A layer consisting of an agent may also be provided.

Such a release layer exhibits a sufficient effect at a thickness of about 0.01 to 5 #Lm, and prevents adhesion to the dye-receiving layer of the thermal transfer sheet, while further improving dye-receptivity. Can be done.

Any conventionally known means for applying thermal energy can be used to perform thermal transfer using the thermal transfer sheet of the present invention as described above and the recording material as described above, such as a thermal printer. (For example, manufactured by Toshiba ■,
By controlling the recording time using a recording device such as a thermal printer TN-5400,
The intended purpose can be fully achieved by applying thermal energy of about 00 mJ/mm'.

(Function/Effect) By using the thermal transfer sheet of the present invention as described above, color printing using various printing methods, especially offset printing method, requires expensive equipment and a large space, but a small and relatively inexpensive device can be used. This makes it possible to form color images with extremely good color reproduction even in small factories, offices, or homes.

Next, the above will be explained in more detail with reference to Examples and Comparative Examples. In the text, parts or % are based on weight unless otherwise specified.

Examples Three types of ink compositions for forming a dye-carrying layer having the following compositions were prepared, and the back surfaces of the ink compositions were heat-resistant treated. 4, 5 Ii,
m-thick polyethylene terephthalate film with a dry coating amount of 1. The coating was coated and dried to obtain three-color thermal transfer sheets of cyan, magenta and yellow according to the present invention.

No. 1 Golden Waxoline Blue AP-FW
8.05 part Kayaset BIue714
1.85 parts polybutyral resin
5.12? B Methyl ethyl ketone
29.44 parts toluene
43.84 parts methyl isobutyl ketone
10.00 copies Micro Fine MF8F
2.08 Part Edan EU MS Red G 2.
40 parts 5udan Red 7B
3.10 parts polybutyral 81 fat
4.80 parts methyl ethyl ketone 4
4.85 parts toluene 44.
85 parts Micro Fine MF8F 2
．． 06 parts Kodama Danji L PTY-525, 50 parts Polybutyral resin 4.80 parts Methyl ethyl ketone 55.00 parts Toluene 34.70 parts Microfine MF8F 2.08 parts Next, as a base sheet, synthetic paper (egg oil Manufactured by Yupo FPG 11
150), a coating liquid having the following composition was applied to one side at a rate of Log/m' when dry, and dried at 100°C for 30 minutes to obtain a transfer material.

Polyester resin (Vylon200, Toyo Dobu) 11
．． 5 parts vinyl chloride-vinyl acetate copolymer (VYHH1u
cc) 5.0 parts Amino-modified silicone oil (KF-393, Shin-Etsu Chemical Division) 1.2 parts Epoxy-modified silicone oil (X-22-343, Shin-Etsu Chemical Division) 1.2 parts Methyl ethyl ketone/toluene /cyclohexanone (weight ratio 4
:4:2) 102 parts The three-color thermal transfer sheet of the present invention described above and the transfer material described in ``-'' are stacked one on top of the other with their respective dye-supporting layers and dye-receiving surfaces facing each other, and from the back side of the thermal transfer sheet. Recording was performed with a thermal head under conditions of a head applied voltage of 1OV, a printing time of 4 sec, and a three-color image. As shown in FIGS. 1 to 3, the densities of these three-color images were much higher than those of the same-color images obtained in Comparative Examples described later.

Example 2 In Example 1, three colors of dye-carrying layer forming inks were used.
Three colors were applied in the same manner as in Example 1, except that cyan, magenta, and yellow were coated and dried in the order of cyan, magenta, and yellow in a fixed area on one continuous sheet (the same base material as in Example 1).
A continuous sheet-like thermal transfer sheet for color image formation of the present invention was obtained, which was arranged one after another.

Using this thermal transfer sheet, thermal transfer was performed successively in the order of cyan, magenta, and yellow in the same manner as in Example 1 to form a color image. The color images thus obtained were of very high density and fully comparable to conventional offset color printed images.

Comparative Example Kayaset B was used instead of cyan dye in Example 1.
Use lue714 and replace magenta dye with MSR
ed GMacrolex Red Violet
Using a mixture with R and replacing the yellow dye, Fo
ron Br1lliantYellows-&G
A three-color image was formed in the same manner as in Example 1 except that L was used. As shown in FIGS. 1 to 3, these images had inferior inventive color density compared to the images of Example 1.

[Brief explanation of drawings]

Figures 1 to 3 show the thermal energy applied and the coloring density due to the energy of the three-color image (A) of the present invention obtained in Example 1 and the three-color image (B) of the comparative example, respectively. The vertical axis shows the concentration and the horizontal axis shows the amount of thermal energy applied. Figure 1 YAN Figure 2 TJ DI (J 15 3rd
figure

Claims (3)

[Claims] (1) A thermal transfer sheet for color image formation comprising at least three types of thermal transfer sheets each having a dye-supporting layer containing a dye of each hue of cyan, magenta, and yellow, wherein the cyan dye is C.I. I. Solvent Blue 63 and C.I. I. Solvent Blue 36, and the magenta dye is a mixture of C. I. Dispersed Red 60 and C.I. I. Solvent Red 19 and the yellow dye is C. I. Disperse Yellow 141
A thermal transfer sheet for color image formation characterized by: (2) Thermal transfer sheet for color image formation according to claim (1), wherein the base sheet is one sheet, and dye-supporting layers of three colors are formed on the surface of the base sheet in any order. . (3) The thermal transfer sheet for color image formation according to claim (1), further comprising a thermal transfer sheet having a black dye-supporting layer.