JPH09277722A - Thermal transfer sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain faithful color reproducibility to original images, sufficient coloring efficiency with low energy heat and high fastness of obtained images, by letting a thermal transfer layer set on a base sheet contain at least two kinds of specific compounds. SOLUTION: A thermal transfer layer 3 is provided on a base sheet 2. The thermal transfer layer 3 contains a dye which is transferred by heat to a body to be transferred, in a binder resin. The dye contained in the thermal transfer layer 3 is at least a mixture of C. I. disperse blue 24 and solvent yellow 93. When a cyan thermal transfer sheet 1 is combined with yellow and magenta thermal transfer sheets 1 to form a full-color image, light and deep colors can be generated in proportion to an applied heat energy, with superior color reproducibility. Moreover, when a full-color image is to be formed, colors can be reproduced in a wide range with a middle color most superiorly reproduced.

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 having a thermal transfer layer for transferring a dye contained in the layer to an object to be transferred by heating, and the thermal transfer layer on the thermal transfer sheet is divided into plural kinds of different materials. The present invention relates to a heat transfer sheet suitable for both a sheet formed by a single type and a sheet formed by a single type. More specifically, it is heated by a heat source such as a thermal head or a laser and printed according to image information. It is a thermal transfer sheet which is particularly suitable for obtaining an image on a transfer body.

[0002]

2. Description of the Related Art In recent years, as a method of outputting an image projected on a display such as a CRT as a hard copy, a thermal transfer sheet is heated by a thermal head or the like whose heat generation is controlled by an electric signal, and a color material layer of the thermal transfer sheet is heated. A thermal transfer system in which an image is formed by transferring a sublimation dye in a (thermal transfer layer) to a thermal transfer sheet is widely used. In this method, a full-color image can be formed (at least in principle) by superimposing and recording three primary colors of yellow, magenta, and cyan. The thermal transfer sheet used in this thermal transfer system is generally one in which a binder resin containing a sublimable dye is applied on a base material to form a color material layer.

[0003] Important problems in the thermal transfer system include color reproducibility, sensitivity, color density, and fastness (heat transfer resistance, light resistance) of a formed image. That is, for the thermal transfer sheet, faithful color reproducibility to the original image, sufficient color development with high heat of low energy (high color development sensitivity) and sufficient color development density (high color development density), and the obtained image It can be said that high robustness is required.

[0004]

However, the thermal transfer sheet according to the prior art was not sufficient to satisfy all of these characteristics. The present invention has been made in view of the problems of the conventional techniques as described above, in an image formed by a thermal transfer method, faithful color reproducibility and high fastness (heat resistance transferability, to the original image, Light resistance), and also has sufficient color developability (high color developability) with low energy heat and high color density, and particularly to provide an excellent thermal transfer sheet for cyan thermal transfer recording. To aim.

[0005]

[Means for Solving the Problems] Means provided by the present invention for solving the above problems are as follows. First, as shown in claim 1, at least a dye and a binder resin are formed on a base sheet. A thermal transfer layer is provided and the thermal transfer layer comprises at least the dye C.I. I. Disperse Blue 24
And dye C. I. A thermal transfer sheet characterized by containing a mixture with Solvent Yellow 93.

Further, preferably, as shown in claim 2,
The thermal transfer sheet according to claim 1, wherein the thermal transfer layer contains a silicon-based release agent.

<Operation> According to the results of intensive studies conducted by the present inventors, as a dye contained in the thermal transfer layer (color material layer), C.I. I. Disperse Blue 24 and C.I. I. By using the mixture with Solvent Yellow 93, faithful color reproducibility to the original image, sufficient color development with low energy heat, high color density, high color development sensitivity, and high fastness of the obtained image We were able to confirm that

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail with reference to preferred embodiments. FIG. 1 shows a thermal transfer sheet 1 of the present invention in which a thermal transfer layer 3 is provided on a base material sheet 2. In this case, it can be said that the thermal transfer sheet according to the present invention has the simplest structure. Examples of the material of the base sheet 2 include paper such as condenser paper, polyester film, polystyrene film, polypropylene film, and cellophane, from the viewpoint of ease of forming the thermal transfer layer, handling, and mechanical strength. Of these, a polyester film (specifically, PET [polyethylene terephthalate], PEN [polyethylene naphthalate], etc.) is particularly preferable because of its high heat resistance.

The thickness of the base sheet 2 is 2 to 50 μm because of its mechanical strength, easy handling or easy availability.
However, in order to expect higher effects of the present invention (because it is also related to thermal characteristics such as heat conductivity, heat transfer coefficient, and heat storage performance), 2 to 16 μm is more preferable.

The thermal transfer layer 3 is composed of a binder resin containing a dye which is transferred by heating and transferred to a transfer target. The dye contained in the thermal transfer layer 3 is at least
C. I. Use either mixture of Disperse Blue 24 and Solvent Yellow 93.

The thermal transfer sheet of the present invention is applied not only for a cyan single color but also when a yellow and magenta thermal transfer sheet is used in combination with the cyan thermal transfer sheet to form a full-color image. It is possible to develop light and shade in proportion to heat energy and to have excellent color reproducibility. Furthermore, in the case of full-color image formation, it is possible to reproduce a wide range of intermediate colors that are the best. Further, in addition to the cyan thermal transfer layer according to the present invention, it is also preferable to separately form each of the yellow and magenta thermal transfer layers on one thermal transfer sheet.

When the cyan thermal transfer sheet of the present invention is used for full-color image formation, the magenta dye used in the yellow thermal transfer sheet in combination with the yellow thermal transfer sheet is, for example, C.I. I.
Disperse Yellow 201, C.I. I. Disperse Yellow 231 and the like.

When the cyan thermal transfer sheet of the present invention is used for full-color image formation, the cyan dye used for the magenta thermal transfer sheet in combination with the magenta thermal transfer sheet is, for example, C.I.
I. Disperse Red 60, C.I. I. Disperse Violet 26, C.I. I. Solvent Red 27 or C.I. I. Solvent Red 19, and the like.

Examples of the binder resin contained in the thermal transfer layer 3 include cellulose resins such as ethyl cellulose, hydroxyethyl cellulose, ethyl hydroxy cellulose, hydroxypropyl cellulose, methyl cellulose and cellulose acetate, butyral resin, acetal resin, phenoxy resin, polycarbonate resin, Examples include polyester resins.

The ratio of the dye to the binder resin in the thermal transfer layer 3 is dye / resin = 10/100 to 300 /
100 is preferred. This has a dye / resin ratio of 10
If it is less than / 100, the amount of dye is too small and the color development sensitivity is insufficient to obtain a good thermal transfer image.
If it exceeds 00/100, the solubility of the dye in the binder resin is extremely lowered, and the storage stability of the thermal transfer layer in a thermal transfer sheet is deteriorated (dye tends to be deposited). Further, in order to expect a higher effect in the present invention, dye / resin = 40/100 to 200/1
00 is more preferable.

The thermal transfer layer 3 of the thermal transfer sheet of the present invention is basically formed of the above materials, but in order to prevent fusion of the thermal transfer sheet and the transferred material during thermal transfer,
It is preferable to add a release agent to the thermal transfer layer 3 if necessary after examining compatibility with the transfer target. As such a release agent, silicone oil, silicone resin, or the like is suitable, but in particular, when it is desired to impart high preservability to the thermal transfer sheet, a silicone-modified resin in which the main chain is silicon-modified is preferable.

The main chain used in such a release agent may be an acrylic resin, a cellulose resin, a vinyl resin, a polyester resin, or the like, with an acrylic resin or a polyester resin being particularly preferable. desirable. When such a release agent is added to the ink for the thermal transfer layer to form a film, the silicon portion bleeds to the surface (because of low compatibility with the ink for the thermal transfer layer), and a good release property upon heating is obtained. It is possible to demonstrate. The amount of the release agent added is 0.0% based on the solid content of the thermal transfer layer ink.
About 1% to 10% is desirable. This addition amount is 0.01
If it is less than%, the releasability cannot be fully exerted, and 1
If it exceeds 0%, it becomes difficult to form the thermal transfer layer on the substrate sheet by coating, or the amount of bleeding on the surface of the thermal transfer layer increases too much, and the transferred material is apt to be contaminated. This is because various problems will occur.

The thermal transfer layer 3 is preferably prepared by adding the above-mentioned dye, binder resin and other additives in a suitable solvent to dissolve or disperse the respective components to prepare an ink for the thermal transfer layer. It is applied and dried on the surface to form (coating). The thermal transfer layer (that is, the dye carrying layer) thus formed has a thickness of 0.2 to 5 μm, preferably about 0.4 to 3 μm. Here, with respect to the thickness of the thermal transfer layer, if the thickness is less than 0.2 μm, sufficient coloring sensitivity cannot be obtained, and if it exceeds 5 μm, the coloring sensitivity is deteriorated.

In order to improve the heat resistance and slipperiness of the thermal transfer sheet 1, it is also preferable to provide the back coat layer 4 on the surface of the base sheet 2 on which the thermal transfer layer 3 is not provided. When the requirements for thermal transfer become stricter (for example, a requirement for high-speed thermal transfer), a back coat layer made of a suitable material compatible with the material of the base sheet is combined with the basic structure of the thermal transfer sheet. This makes it easier to respond to more stringent requirements.

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 acceptability for the dye. That is, the recording surface may be a dye receptor. Examples of the resin having dye acceptability include, for example, polyolefin resins such as polyethylene and polypropylene,
Examples thereof include acetal resin, polyvinyl chloride resin, vinyl chloride-vinyl acetate copolymer resin, polyester resin, polystyrene resin, copolymer resin of olefin and other vinyl monomer, ionomer, cellulose resin, and polycarbonate resin.

In the dye receiving layer, in order to prevent fusion of the thermal transfer sheet and the transferred material during thermal transfer,
It is also preferable to consider the compatibility between the thermal transfer sheet and the object to be transferred, and to add a release agent such as silicone oil if necessary. If the thickness of the dye receiving layer is too thin, there is usually a problem that sufficient coloring sensitivity cannot be obtained.

When the recording surface has no dye receptivity (for example, paper, metal, glass, resin having no dye receptivity), a dye receptive layer (comprising a dye receptor) Layer) is prepared separately, and a dye receiving layer is formed on the recording surface that does not have dye receptivity, and then an image is formed using a thermal transfer sheet, or thermal transfer is performed in advance on a separately prepared dye receiving layer. This can be dealt with by forming an image using a sheet and then forming a dye receiving layer on the recording surface having no dye receiving property.

As the means for applying the thermal energy used when performing the thermal transfer on the transfer target as described above using the thermal transfer sheet of the present invention as described above, a known application means is, for example, a thermal head or a laser. Can also be used, and by controlling the energy applied thereby, it is possible to obtain a gradation image.

[0024]

EXAMPLES The present invention will be described more specifically below with reference to examples. In the description of the present specification, "part" means part by weight, and "%" means% by weight.

Example 1 An ink composition for a thermal transfer layer having the following composition was prepared and heat-treated on the back side to a thickness of 5.4 μm.
m of a polyethylene terephthalate film having a dry film thickness of 1.5 μm and dried to obtain a thermal transfer sheet of the present invention. [Ink for thermal transfer layer] C.I. I. Disperse Blue 24 3.5 parts C.I. I. Solvent Yellow 93 0.5 parts Butyral resin 5.0 parts Methyl ethyl ketone 60.0 parts Toluene 31.0 parts

Next, a foamed polypropylene film (thickness: 50 μm) / adhesive resin layer / coated paper (108 g / m ² ) / adhesive resin layer / foamed polypropylene film (thickness: 50 μm) was used as a base sheet. The following dye-receiving layer ink was applied to the surface so as to have a dry film thickness of 4 μm, dried, and then aged at 45 ° C. for one week to obtain a transfer-receiving body. [Ink for dye receiving layer] Acetal resin 10.0 parts Vinyl chloride-vinyl acetate copolymer resin 10.0 parts Silicon oil 2.0 parts Isocyanate resin 3.0 parts Methyl ethyl ketone 50.0 parts Toluene 25.0 parts

The surface of the thermal transfer layer of the obtained thermal transfer sheet was superimposed on the surface of the dye receiving layer of the transfer object, and the dye was transferred under the following conditions using a thermal head to form an image. [Printing conditions] Printing machine: SIP company simulator (300
dot / mm head used) Printing pattern: 16 gradation patterns Printing energy: 0.6 mJ / dot at 16th gradation

The following evaluation was performed on the obtained images. [Evaluation items] Color density: Reflection density at 16th gradation was measured by Macbeth RD-918 Heat resistance transferability: Density reduction rate at 16th gradation after 70 hours at 70 ° C Light resistance: After 80 hours irradiation with xenon fade meter 16th gradation density reduction rate

As a result of evaluating the above items, the following good results were obtained. Further, the color reproducibility of cyan was also good. [Evaluation results] Color density: 2.2 Heat transfer resistance: 5% or less Light resistance: 3% or less

<Example 2> A thermal transfer sheet was obtained in the same manner as in Example 1 except that the ink composition for the thermal transfer layer was changed to the following composition. [Ink for thermal transfer layer] C.I. I. Disperse Blue 24 3.5 parts C.I. I. Solvent Yellow 93 0.5 parts Phenoxy resin 3.0 parts Butyral resin 2.0 parts Methyl ethyl ketone 60.0 parts Toluene 31.0 parts

The transferred object obtained in the same manner as in Example 1 was overlaid on the thermal transfer sheet, and the image formation and evaluation were performed in the same manner as in Example 1. The evaluation results are as follows. [Evaluation results] Color density: 2.1 Heat resistance transferability: 5% or less Light resistance: 3% or less Further, color reproducibility as a cyan color was also good.

Example 3 A thermal transfer sheet was obtained in the same manner as in Example 1, except that the ink composition for the thermal transfer layer was changed to the following composition. [Ink for thermal transfer layer] C.I. I. Disperse Blue 24 3.5 parts C.I. I. Solvent Yellow 93 0.5 parts Butyral resin 5.0 parts Silicon modified resin 0.05 parts Methyl ethyl ketone 60.0 parts Toluene 31.0 parts

The material to be transferred obtained in the same manner as in Example 1 and the thermal transfer sheet were overlaid, and image formation and evaluation were carried out in the same manner as in Example 1. The evaluation results are as follows. [Evaluation results] Color density: 2.2 Heat transfer resistance: 5% or less Light resistance: 3% or less Further, color reproducibility as a cyan color was also good.

[0034]

As described above in detail, according to the present invention, by using a specific dye, an image formed by a thermal transfer system can be faithfully reproduced with respect to the original image and high color fastness. And heat resistance (heat resistance and light resistance), and also has sufficient color development (high color development sensitivity) and color density with heat of low energy, and provides an excellent thermal transfer sheet especially for cyan color. I was able to do it.

[Brief description of drawings]

FIG. 1 is an explanatory view schematically showing an outline of a thermal transfer sheet according to an embodiment of the present invention using a cross-sectional view.

FIG. 2 is an explanatory view schematically showing the outline of another embodiment of the thermal transfer sheet of the present invention by using a sectional view.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Thermal transfer sheet 2 ... Base sheet 3 ... Thermal transfer layer 4 ... Back coat layer

Claims (2)

[Claims] 1. A thermal transfer layer comprising at least a dye and a binder resin is provided on a substrate sheet, and the thermal transfer layer comprises at least a dye C.I. I. Disperse Blue 24 and dye C.I. I. A thermal transfer sheet containing a mixture with Solvent Yellow 93. 2. The thermal transfer sheet according to claim 1, wherein the thermal transfer layer contains a silicon-based release agent.