JPH02277684A - Thermal transfer recording material and preparation thereof - Google Patents

Abstract

PURPOSE:To obtain a recording image excellent in durability by containing a paraffinic compound having a crosslinked structure as the binder of a thermal transfer ink layer. CONSTITUTION:A thermal transfer ink layer contains a paraffinic compound having a crosslinked structure as a binder along with a colorant and is obtained by applying an ink composition to a support and irradiating the coating layer with electron beam to crosslink the paraffinic compound. The above mentioned irradiation with electron beam is a process for increasing the MW of the paraffinic compound and, by this process, the crosslinking structure is generated between the main chains of the paraffinic compound to allow the increase in the MW of the paraffinic compound to advance. When this paraffinic compound is present as the binder, the image formed on a material to be recorded can stably keep its original shape stably even when it is rubbed with an eraser or one's hand.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a thermal transfer recording material, and more particularly to improvement of the thermal transfer ink layer thereof.

[Conventional technology]

The sensitive transfer ink layer of conventional thermal transfer recording materials is made of an ink containing a binder of waxes such as natural wax or synthetic wax and a thermoplastic resin, and a colorant such as carbon black mixed and dispersed therein. (for example,
(Japanese Patent Application Laid-Open No. 63-230392).

As mentioned above, the purpose of using a thermoplastic resin as a component of the binder is to increase the durability of the image formed on the recording medium, but despite the use of such a thermoplastic resin, With conventional methods, the durability of the image is not sufficient, and when rubbed with an eraser or hand, part of the image may be chipped, or stains that look like traces from the image may appear on the surface of the recording medium. There was a problem.

[Problem to be solved by the invention]

As described above, the present invention solves the problem that images formed on a recording medium using conventional thermal transfer recording materials, that is, recorded images lack durability, and provides recorded images with excellent durability. An object of the present invention is to provide a thermal transfer recording material that can obtain the following properties.

[Means to solve the problem]

The present invention provides a heat-sensitive transfer recording material capable of obtaining recorded images with excellent durability by containing a paraffin compound having a crosslinked structure as a binder in the heat-sensitive transfer ink layer.

A thermal transfer recording material having a thermal transfer ink layer containing a paraffinic compound having a crosslinked structure as a binder as described above is produced by applying an ink composition containing a colorant and a paraffinic compound onto a support. It is obtained by crosslinking a paraffinic compound by irradiating it with an electron beam.

Examples of the above paraffinic compounds include paraffin wax and liquid paraffin.

In addition to the above paraffinic compounds, the ink composition also contains silicone compounds such as polyethylene oxide, polyamide, polyester, hexamethylene cyclotrisiloxane, and resins that can be crosslinked by electron beam irradiation, such as polyvinyl compounds represented by the following formula (Il). These resins may be incorporated into the binder and crosslinked together with a paraffinic compound by electron beam irradiation to form a binder.

(CH!-CH)n fII [wherein, R is -Ch Hs, -COOHl CON H
z, CL OH, 0COCHi, CN.

The above polyvinyl compound may be not only a homopolymer in which all R's in the formula are the same, but also a copolymer in which R's are different.

Here, the differences between the thermal transfer ink layer of the thermal transfer recording material of the present invention and the thermal transfer ink layer of a conventional thermal transfer recording material will be explained as follows.

As described above, the thermal transfer ink layer of the present invention contains a paraffin compound having a crosslinked structure as a binder. This thermal transfer ink layer is
It is obtained by applying an ink composition containing a paraffinic compound together with a colorant onto a support, and then irradiating it with an electron beam to crosslink the paraffinic compound.

According to the research of the present inventors, in conventional thermal transfer ink layers, when the image formed on the recording medium is rubbed with an eraser or by hand, chipping and staining occur due to the paraffin-based binder. the compound has a low molecular weight;
This is because the molecular weight does not reach a sufficient molecular weight to stably hold an image on the recording medium. Therefore, in the present invention, the paraffin compound is made to have a high molecular weight so that an image can be stably fixed on the recording medium.

The step of electron beam irradiation described above is a step for increasing the molecular weight of the paraffinic compound, and by passing through this step, crosslinking occurs between the main chains of the paraffinic compound, and the increasing molecular weight progresses.

When this crosslinked structure and high molecular weight paraffin compound is present as a binder, the image formed on the recording medium can stably maintain its original shape even when rubbed with an eraser or by hand. This results in less chipping and staining of images and improved durability compared to conventional ones.

The electron beam irradiation is performed in an atmosphere with a reduced oxygen concentration, preferably in an atmosphere with an oxygen concentration of 500 ppe+ or less, for example, at an accelerating voltage of 150 to 250 kV and an irradiation dose of 1.0 to 250 kV.
This is done so that the amount is about 20 Mrad.

In the thermal transfer recording material of the present invention, the thermal transfer ink layer contains a colorant such as carbon black and a binder as essential components, and may further contain a release agent, a dispersant, etc., if necessary. The amount of colorant such as carbon black in the thermal transfer ink layer is usually 2 to 40% by weight based on the total weight. When the ink layer is formed by a solvent coating method, the ink composition used for forming the thermal transfer ink layer is a coating material in which ink layer constituent components such as colorants and binders are dissolved or dispersed in a solvent. It is prepared to the following condition.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 An ink composition having the following composition was prepared.

Carbon black 25 parts by weight Paraffin wax 50 parts by weight Ethylene-vinyl acetate copolymer 25 parts by weight [Nippon Unicar H
U C-3170 (trade name)] Toluene/methyl ethyl ketone (1/1) 200 parts by weight To prepare the ink composition, each component of the above composition was placed in a ball mill and mixed for 72 hours.
This was done by dispersing.

The above ink composition was applied onto a polyester film (polyethylene terephthalate film) having a thickness of 5 μm to a dry thickness of 2 μm, and dried to obtain a raw fabric. An acceleration voltage of 165k was applied to this original fabric using an electron beam irradiation device.
V, irradiation dose 10 Mrad at oxygen concentration 500 ppm or less
Electron beam irradiation was performed to obtain a heat-sensitive transfer recording material. The thermal transfer recording material thus obtained is shown in FIG.
In FIG. 1, (1) is a support made of a polyester film, and (2) is a thermal transfer ink layer formed on the support (1). This thermal transfer ink layer (2)
The solvent toluene/methyl ethyl ketone (1/l) (a mixture of toluene and methyl ethyl ketone in a weight ratio of 1:1) is evaporated from the ink composition coated on the support (1) by drying, and by electron beam irradiation. A paraffinic compound and an ethylene-vinyl acetate copolymer are crosslinked to form a binder.

Example 2 The ethylene-vinyl acetate copolymer in Example 1 was replaced with polyethylene [151-P (trade name) manufactured by Sanyo Chemical Co., Ltd.
A thermal transfer recording material was obtained in the same manner as in Example 1 except that

Example 3 In place of the ethylene-vinyl acetate copolymer in Example 1, a vinyl chloride-vinyl acetate-vinyl alcohol copolymer (VAGH (trade name) manufactured by CUCC) was used, and the other conditions were the same as in Example 1. A thermal transfer recording material was obtained.

Comparative Example 1 A thermal transfer recording material was obtained in the same manner as in Example 1 except that electron beam irradiation was not performed.

Comparative Example 2 A thermal transfer recording material was obtained in the same manner as in Example 2 except that electron beam irradiation was not performed.

Comparative Example 3 A thermal transfer recording material was obtained in the same manner as in Example 3 except that electron beam irradiation was not performed.

Examples 1 to 3 and Comparative Example 1 manufactured as above
A high-density thermal printer with an 8-dot/11- thermal head was used as the thermal printer, and rough paper (P-3) was used as the recording medium.
PC paper, Beck smoothness 58 seconds) was used, a checkered pattern was selected as the recorded image, and the printing speed was 40 characters/print on rough paper.
A checkered pattern was printed in seconds, and the density of the print recorded on the rough paper (print density) and the durability of the print were examined. The results are shown in Table 1, and the methods for measuring print density and evaluating the durability of prints are as follows.

The reflection density of the printed surface of the square checkered pattern on the raw A leather was measured using a reflection densitometer (RD-915) manufactured by Maches.

The printed area was rubbed with force with a pencil eraser (the eraser was moved back and forth), and the number of times it took for stains to occur (number of back and forth movements) was measured.

Table 1 As shown in Table 1, the thermal transfer recording materials of Examples 1 to 3 in which the paraffin wax or resin as a binder component was crosslinked by electron beam irradiation did not have the paraffin wax or resin crosslinked. The printing durability was excellent compared to the thermal transfer recording materials of Comparative Examples 1 to 3. Furthermore, there was no difference in printing density between the Examples and Comparative Examples, and no deterioration in performance due to crosslinking of the binder constituents was observed.

(Effects of the Invention) As explained above, in the present invention, by incorporating a paraffin compound having a crosslinked structure as a binder in the thermal transfer ink layer, the durability of the recorded image could be improved.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of a thermal transfer recording material according to the present invention. (1)...Support, (2)...Thermal transfer ink layer 1...Support 2...Thermal transfer ink layer

Claims (4)

[Claims] (1) A thermal transfer recording material in which a thermal transfer ink layer consisting of a colorant and a binder is provided on a support, characterized in that the thermal transfer ink layer contains a paraffin compound having a crosslinked structure as a binder. A thermal transfer recording material. (2) The thermal transfer recording material according to claim 1, wherein the binder is made of a mixture of a paraffin compound having a crosslinked structure and a resin having a crosslinked structure. (3) A method for producing a thermal transfer recording material, which comprises applying an ink composition containing a colorant and a paraffin compound onto a support, and then irradiating the support with an electron beam to crosslink the paraffin compound. . (4) The method for producing a thermal transfer recording material according to claim 3, wherein the ink composition contains a colorant, a paraffin compound, and a resin, and the paraffin compound and resin are crosslinked by electron beam irradiation.