JPH0811467B2 - Thermal transfer sheet - 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,
More specifically, it is an object of the present invention to provide a thermal transfer sheet which can easily provide a transferred image with a recorded image excellent in color density, sharpness and various fastnesses.

[0002]

2. Description of the Related Art Conventionally, various thermal transfer methods have been known. Among them, a sublimable dye is used as a recording agent, which is supported on a base material sheet such as paper to form a thermal transfer sheet, which is dyed with the sublimable dye. There is a sublimation transfer method in which a sublimable dye is transferred to a transfer target material by superimposing it on a transferable material such as a woven polyester cloth and applying heat energy in a pattern from the back surface of the thermal transfer sheet.

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In the sublimation transfer method described above, in the sublimation printing method in which the material to be transferred is, for example, a polyester woven cloth, the transfer of the heat energy takes a relatively long time, and therefore the material to be transferred itself. Also as a result of being heated with the applied thermal energy, a relatively good dye transfer is achieved. However, due to the progress of recording methods, a thermal head or the like is used at a high speed, for example, a transfer material having a dye receiving layer provided on a polyester sheet or paper is used, and delicate characters or figures are formed on the transfer material. Alternatively, when a photographic image is formed, the application of heat energy is required to be performed in an extremely short time of seconds or less. Therefore, the sublimable dye and the material to be transferred are not sufficiently heated in such a short time. Therefore, an image with sufficient density cannot be formed.

Therefore, in order to cope with such high speed recording, a sublimable dye having an excellent sublimation property has been developed. However, since a dye having an excellent sublimation property generally has a small molecular weight, a dye after transfer is transferred. There is a problem that an image formed at a corner is disturbed, becomes unclear, or contaminates surrounding articles because the dye migrates with time in the transfer material or bleeds out on the surface. In order to avoid such a problem, when a sublimable dye having a relatively large molecular weight is used, the sublimation speed of the dye is inferior in the above high-speed recording method, so that an image having a satisfactory density as described above can be formed. It was not there. Therefore, an object of the present invention is to provide a sufficiently dense and clear image by applying thermal energy for an extremely short time as described above in a thermal transfer method using a sublimable dye, and the formed image is excellent. It is to provide a thermal transfer sheet showing various toughness.

[0005]

The above object can be achieved by the present invention described below. That is, the present invention comprises a base material sheet and a dye carrying layer formed on one surface of the base material sheet, and the dye contained in the dye carrying layer is a dye represented by the following formula (I): At least 1 represented by the following formulas 1 to 15
It is a thermal transfer sheet characterized by being a mixture with a sublimable dye of one kind.

[0006]

Embedded image

[0007]

[Chemical 6]

[0008]

[Chemical 7]

[0009]

Embedded image

[0010]

The dye of the formula (I) as a dye for a thermal transfer sheet shows a clear cyan color tone and an excellent heat transfer property and forms a high density and clear image. However, after transfer, in the image receiving layer of the transferred material. The dye has a bleeding property, causes image bleeding during long-term storage, and lacks fastness such as light resistance. On the other hand, other cyan dyes having a high molecular weight or having a polar group such as a hydroxyl group form an image with excellent bleeding resistance and light resistance after transfer, but are crystallized or granularly precipitated in the dye-carrying layer, and heat transfer occurs. It is inferior in properties and cannot form high density and clear images.

On the other hand, by using a mixture of the dye represented by the formula (I) and the sublimable dyes represented by the formulas 1 to 15, one of the mixture dyes is an impurity in the dye carrying layer. It has less tendency to crystallize or precipitate as a result of the above, and therefore exhibits a good heat transfer property and gives an image excellent in color density and sharpness. On the other hand, in the image-receiving layer, the dyes of formulas 1 to 15 having a large molecular weight and the dyes of formula (I) associate with each other to suppress the bleeding property of the dye of formula (I), and to prevent bleeding resistance and storage stability. The image has excellent fastness.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in more detail with reference to preferred embodiments. The dye of formula (I) and the above formula 1
The preferable mixing ratio with the dye of 15 to 15 is 85:85 to 85 :.
It is a weight ratio of 15. If either one is too small or too much, any one of high density, sharpness and fastness becomes insufficient, which is not preferable. Further, the above dye mixture has good solubility in general-purpose organic solvents such as methyl ethyl ketone, toluene, ethanol, isopropyl alcohol, cyclohexanone, ethyl acetate and the like or a mixed solvent thereof used in preparing the thermal transfer sheet, In the dye-carrying layer formed in the above, the dye can exist without or in a crystalline state, and the dye is coated with a significantly smaller amount of applied heat as compared with the existing state with high crystallinity as in the case of the conventional dye. The heat could easily be transferred to the transfer material.

The thermal transfer sheet of the present invention is characterized by using the above-mentioned specific dye mixture, and other configurations may be the same as those of the conventionally known thermal transfer sheets.
The base sheet used for the thermal transfer sheet of the present invention containing the above-mentioned dye mixture 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 Is a paper having a thickness of about 3 to 10 μm, various processed papers, polyester film, polystyrene film, polypropylene film, polysulfone film, polycarbonate film, aramid film, polyvinyl alcohol film, cellophane, etc., and particularly preferred is polyester film. . The dye-carrying layer provided on the surface of the base sheet as described above is a layer in which the dye mixture is carried by an arbitrary binder resin.

As the binder resin for supporting the above-mentioned dye mixture, any conventionally known binder resin can be used,
Preferred examples include ethylcellulose, hydroxyethylcellulose, ethylhydroxycellulose,
Specific examples include cellulose-based resins such as hydroxypropyl cellulose, methyl cellulose, cellulose acetate, and cellulose acetate butyrate, polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, polyvinyl acetoacetal, polyvinylpyrrolidone, and vinyl-based resins such as polyacrylamide. In particular, polyvinyl butyral and polyvinyl acetal are preferable from the viewpoint of heat resistance and dye migration. The dye-carrying layer of the thermal transfer sheet of the present invention is basically formed from the above materials,
In addition, various additives similar to conventionally known additives can be included as necessary.

Such a dye-supporting layer is preferably prepared by adding the above-mentioned dye mixture, 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 a support layer. Then, this is applied and dried on the above-mentioned substrate sheet to form. The carrier layer thus formed has a thickness of 0.2 to 5.0 μm, preferably 0.4 to 5.0 μm.
Suitably, it is about 2.0 μm thick and the dye mixture in the carrier layer is present in an amount of 5 to 70% by weight, preferably 10 to 60% by weight of the weight of the carrier layer. .

Although the thermal transfer sheet of the present invention as described above is sufficiently useful as it is 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. Is provided, it is possible to prevent sticking between the thermal transfer sheet and the material to be transferred at the time of thermal transfer, to use a higher thermal transfer temperature, and to form an image with even better density. As the release layer, even if only an inorganic powder having anti-adhesion property is adhered, a considerable effect is exhibited. Further, for example, a resin having excellent release properties such as a silicone polymer, an acrylic polymer, and a fluorinated polymer can be used. .01-5
It can be formed by providing a release layer of 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 using the thermal transfer sheet as described above 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 the transfer material that does not need to form a dye receiving layer include, for example, polyolefin resins such as polypropylene, polyvinyl chloride, halogenated polymers such as polyvinylidene chloride, polyvinyl acetate, vinyl polymers such as polyacrylester, Polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polystyrene resins, polyamide resins, copolymer resins of olefins such as ethylene and propylene with other vinyl monomers, ionomers,
Cellulosic resins such as cellulose diacetate, fibers made of polycarbonate, etc., woven fabrics, films, sheets,
Examples include molded products.

Particularly preferred is a polyester sheet or film 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 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 receiving layer formed in this manner may be formed from a single material, or may be formed from a plurality of materials, and may further contain various additives as long as the intended purpose is not hindered. Is natural.

Such a dye receiving layer may have any thickness, but is generally 3 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. Such a material to be transferred is basically as described above and can be used satisfactorily as it is. However, the above-mentioned material to be transferred or its dye receiving layer contains an inorganic powder for preventing adhesion. In this way, even if the temperature at the time of thermal transfer is further increased, adhesion between the thermal transfer sheet and the material to be transferred 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 used in an amount of about 0.5 to about 0.5% by weight of the dye receiving layer.
A ratio occupying 30% by weight is good.

The material to be used for transfer may have the above-mentioned inorganic powder adhered to the surface of the dye-receiving layer to enhance the anti-adhesion effect, and it has excellent releasability as described above. A layer made of a releasing agent 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, , Hitachi, Video Printer VY-1
By controlling the recording time with a recording device such as 00), the intended purpose can be sufficiently achieved by applying thermal energy of about 5 to 100 mJ / mm ² .

[0021]

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 A dye-carrying layer-forming ink composition having the following composition was prepared, and applied to a 6 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. Thus, the thermal transfer sheet of the present invention shown in Table 1 below was obtained. The dye (I) and the dyes (II) of the formulas 1 to 15 in total 3.0 parts Polyvinyl butyral resin 4.5 parts Methyl ethyl ketone 46.25 parts Toluene 46.25 parts

However, when the dye mixture in the above composition is insoluble in the above solvent, DMF, dioxane, chloroform or the like was appropriately used as the solvent. 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 dried on one surface of the synthetic paper 10.
The transfer material was applied at a rate of 0 g / m ² 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 (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

The above-mentioned thermal transfer sheet of the present invention and the above-mentioned material to be transferred are superposed with their dye carrying layers and dye receiving surfaces facing each other, and the head applied voltage 1 is applied from the back surface of the thermal transfer sheet.
0 V, printing time 4.0 msec. Recording was performed with a thermal head under the conditions of, and the results shown in Table 1 below were obtained.

[0024]

[Table 1] The mixing ratio in Table 1 above is based on weight. Further, the hues of the mixed dyes are all cyan.

Comparative Example The dyes shown in Table 2 below were used in place of the dyes in the examples,
Others were the same as in the example, and the results shown in Table 2 below were obtained.

[Table 2]

[0026]

[Chemical 9] The color density in the above is a value measured by a densitometer RD-918 manufactured by Macbeth Co., USA. The fastness is ◎ when the recorded image is left in an atmosphere of 50 ° C. for a long time and the sharpness of the image does not change, and the white paper is not colored even if the surface is rubbed with a white paper. Was marked and the white paper was slightly colored, and the sharpness was lost and the white paper was colored, and the image was unclear, and the white paper was marked significantly.

[0027]

[Effects] According to the present invention as described above, by using a specific dye mixture as a dye of a thermal transfer sheet, a clear image with high density can be formed, and particularly these images have excellent bleeding resistance and stain resistance. Therefore, the sharpness of the image is not deteriorated even if the image is stored for a long period of time, and even if it comes into contact with other articles, they are not contaminated, and various problems of the prior art have been solved.

Claims (2)

[Claims] 1. 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 a dye represented by the following formula (I) Formula 1
A thermal transfer sheet characterized by being a mixture with at least one sublimable dye represented by Embedded image Embedded image Embedded image [Chemical 4] 2. The mixing ratio of the dye of the formula (I) and at least one sublimable dye of the formulas 1 to 15 is 15:85.
The thermal transfer sheet according to claim 1, having a weight ratio of 85:15.