JPS609798A - Thermal recording medium - Google Patents

Abstract

PURPOSE:To made favorable transferring property and preservability, by replacing a portion of a binder used in an ink by a hydrophilic one. CONSTITUTION:Polyvinyl alcohol and/or a styrene-maleic acid copolymer is used as a hydrophilic binder, in an amount of 10-50%, preferably, 30-40% of the total weight of the ink. Accordingly, the releasability of the ink in a high-humidity condition and its property of penetrating into a transfer sheet are improved, and transferrability and preservability (fixability) can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a thermal recording medium used in a transfer type thermal recording method.

In the conventional transfer type thermal recording method, a thermal recording medium (ink donor film) comprising a support such as paper or a plastic film with a heat-melting or heat-sublimating ink layer on one or both sides, and a transfer sheet are used. The thermal recording medium is overlapped and selectively heated according to the image information, and the ink melted or sublimated by the heat is transferred to the transfer sheet, thereby recording the image information.

The characteristics required for ink used in thermal recording media include being solid at room temperature, having appropriate adhesion between the ink and the support, and having a viscosity that rapidly decreases when heated (60 to 80°C). It may drop or sublimate, and the fixation (storability) of the recording after transfer is good.

A typical conventional thermal transfer recording medium has a support of approximately 13 μm.
Approximately 5 layers of ink having the composition shown in Table 1 are applied to thick capacitor paper.
It is provided with a thickness of μ.

The inks shown in Table 1 are water-repellent depending on the nature of the binder used to impart heat-melting properties;
If the moisture content of the recording paper is high (that is, under high humidity conditions), the peelability between the first ink layer and the support during heating may be poor (or the transferred image may not be sufficiently blended onto the transfer sheet). First, there was a problem in that the recorded image would bleed when rubbed with a finger or the like.

OBJECTS OF THE INVENTION It is an object of the present invention to eliminate the above-mentioned drawbacks and to provide a thermal recording medium with excellent transferability and storage stability.

Structure of the Invention The present invention provides a hydrophilic material for use in a thermal recording medium. In other words, the ink layer of conventional thermal recording media exhibits water repellency because a large amount of carnauba wax or ester wax is used as a binder agent, but in the present invention, the binder agent in the ink is used in a large amount. It is characterized by replacing some parts with hydrophilic ones.

In the present invention, polyvinyl alcohol (PVA) and/or styrene-maleic acid copolymer is used as a hydrophilic binder agent. The amount is 10% of the total weight of ink.
-50%, preferably 30-40%. Usage amount is 1
If it is less than 0%, it will not be effective as a hydrophilic binder,
Moreover, if it exceeds 50 yen, the viscosity properties deteriorate and the storage stability (fixing properties) also decreases.

In the present invention, the components other than the hydrophilic binder in the ink are the same as in inks used for conventional thermal recording media, and carnauba wax and ester wax are also used at the same time to maintain heat-melting properties. Ru. Table 2 shows an example of ink components used in the recording medium of the present invention.

3- The mixture having the composition shown in Table 2 above is coated on a support in a layer of about 15 μm or less by a hot melt coating method or a solvent coating method using water or an organic solvent according to a conventional method.

The thermal recording medium of the present invention will be explained below with reference to Examples and Comparative Examples.

Example 1 An ink having the composition shown in Table 2 above was applied to a thickness of 5μ on a 3μ thick capacitor paper by hot melt coating to obtain a thermal recording medium. As a transfer sheet, use high-quality paper (〆θ
ff/rr? ) at a temperature of 32°C and a humidity of (R,'H,) 8
Printing was carried out using a Zex Printer P6 using paper that had been left for 12 hours under 5% environmental conditions. I rubbed the recorded image between my fingers, but no change was observed in the image.

Comparative Example 1 A thermal recording medium was obtained by applying ink having the composition shown in Table 1 to a thickness of 5μ on a 3μ thick capacitor paper by hot melt coating. Using the same paper as in Example 1 as the transfer sheet, printing was performed using a Xerox □ printer P6, and when the resulting recorded image was rubbed between fingers, smearing occurred in the image.

Effects of the Invention The thermal recording medium of the present invention uses hydrophilic ink as the ink, and improves the releasability of the ink and the permeability to the transfer sheet, which were conventionally observed during thermal recording under high humidity conditions. A thermal recording medium with excellent transferability and storage stability (fixing performance) (3 people)

Claims (1)

[Scope of Claims] 1. A thermal recording medium characterized by having a hot bath meltable ink layer containing a hydrophilic binder agent provided on a support. 2. A thermal recording medium characterized in that the hydrophilic binder agent is made of polyvinyl alcohol or The thermal recording medium according to claim 1, which is a styrene-maleic acid copolymer. 3. The thermal recording medium according to claim 1, wherein the content of the binder agent is 010 to 50% by weight of the ink component.