JPH0671836B2 - Melt transfer type image receiving sheet for thermal transfer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to an image receiving sheet in a melt transfer type thermal transfer system using a thermal head.

(B) Conventional Technology Conventionally, in a thermal transfer system, a thermal sublimation transfer method in which an ink layer containing a thermally sublimable dye is formed on a support, and the dye is sublimated to the image receiving sheet side by heating to perform recording, and a support A heat-melt transfer method is known in which a heat-meltable ink layer containing colored dyes and pigments is formed on the top (hereinafter referred to as a donor sheet), and is melt-transferred to the image-receiving sheet side by heating for recording.
The thermal sublimation transfer method is promising as a full-color recording method because the image becomes good in gradation because the dye becomes a gas and recording is performed, and an invention of improving the dyeing property of the dye was made as an image receiving sheet of this system. ing. (JP-A-57-9129
6, JP-A-57-107885, JP-A-57-137191, JP-A-59-5
9495, JP-A-59-64393) On the other hand, full-color recording has recently been put to practical use also in the thermal fusion transfer system, and various studies have been made in the past for the purpose of improving transfer efficiency to an image receiving sheet. For example, Japanese Patent Publication No. 59-16950 can be cited.

In this publication, an image-receiving paper (ink thermal transfer recording medium) is formed by applying a water-based coating composed of a water-soluble binder and a pigment to form a smooth surface, and further, a low-melting point additive such as wax is added to the water-based coating. It is also characterized by adding.

(C) Problems to be Solved by the Invention However, the thermal sublimation transfer method has drawbacks that it requires a long heating time and a slow recording speed because the sublimation temperature of the dye is high. It is also possible to use a dye having a low sublimation temperature, but the image storability is poor due to resublimation of the dye,
Furthermore, since it is a dye, the light fastness of the image is not good. For these reasons, various researches have recently been made on a method of producing gradation by a thermal fusion transfer method which has a high recording speed and good image storability.

However, the water-soluble binders and pigments, which are the main constituents of the above publications, are not good at transferring hot-melt ink. That is, any of the materials has a poor affinity with the heat-meltable ink on the surface of the image receiving paper, so that the transfer temperature becomes thin.
This is particularly noticeable in the low energy region of the thermal head.

Also, the adhesiveness between various image-receiving sheets and hot-melt ink is not sufficient, and for example, most of the ink peels off in a scratch test after thermal transfer recording.

Further, in the melt transfer type thermal transfer recording system, recording on a plastic sheet for an overhead projector is easy, and the field of application thereof was wide, but again the compatibility between the plastic sheet and the hot melt ink poses a problem, It was difficult to obtain a plastic sheet having sufficient scratch resistance.

The present invention provides an image-receiving sheet for thermal transfer thermal transfer in which thermal transfer ink has high transfer efficiency in a thermal transfer recording system and the obtained image has good abrasion resistance, scratch resistance and robustness. is there.

(D) Means for Solving the Problems In the present invention, thermal transfer recording is carried out by superposing a coated layer surface of a thermal transfer sheet having a heat-fusible ink layer on a support and an image receiving sheet, and performing thermal fusion transfer by a thermal head. In the system, the image-receiving sheet is one in which a thermoplastic resin layer is provided on a substrate,
And a melting transfer type thermal transfer image-receiving sheet characterized in that the melting point of the thermoplastic resin layer is 135 ℃ or less, containing an inorganic pigment in the thermoplastic resin layer for the purpose of improving the glossiness and whiteness It is an image-receiving sheet for thermal transfer characterized by the above.

Polyethylene is most preferable as the organic polymer that constitutes the thermoplastic resin layer, but the differential scanning calorimetry (DS
If the melting point in C) is 135 ° C. or lower, there is no problem in performance, and even if the thermoplastic resin layer is only the image receiving surface layer on the substrate, or if it is on both the image receiving surface and the back surface. There is no difference in performance.

Conventional image-receiving sheets are commonly called plain paper such as PPC paper and high-quality paper (there may be den powder, polyvinyl alcohol, sizing agent etc. applied by size press, but it is different from coated paper. And coated paper for printing (paper that improves the color of printing ink by applying a white pigment and a coating liquid containing an adhesive as a main component to a base paper such as high-quality paper). It is used.

Polyester films are mainly used for overhead projectors.

The thermoplastic resin coated on the substrate used in the present invention preferably has a good affinity with the hot-melt ink and has a film-forming property.

We performed melt heat transfer recording on thermoplastic resin films of various polyolefins, polyesters, polystyrenes, etc., and tested the scratch resistance of the obtained images, and as a result, the melting point of the thermoplastic resin layer I found that there is a relationship like this. That is, the lower the melting point of the thermoplastic resin layer, the better the scratch resistance of the thermal transfer image formed thereon, and if a thermoplastic resin layer having a melting point of 135 ° C. or less is used, a thermal transfer image having sufficient scratch resistance will be obtained. can get. Probably this effect is that the ink layer melted by the high temperature of the thermal head (250 to 350 ° C.) partially melts the thermoplastic resin layer on the surface of the image receiving sheet, so that the affinity with the ink is improved.

The method of providing the thermoplastic resin layer on the substrate may be a laminating method, a laminating method or the like, in which case white pigment,
It does not matter at all to contain a dye or the like. It is also possible to activate the surface of the image receiving sheet by subjecting it to corona discharge, plasma treatment, flame treatment, or the like.

Examples of the organic polymer that constitutes the thermoplastic resin layer include low-density polyethylene, high-density polyethylene, modified polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer resin, and polybutene.

Examples of the substrate on which the thermoplastic resin layer is provided include plain paper, coated paper, high-quality paper, synthetic paper, glossy paper, and synthetic resin sheets such as polyolefin, polyester, polystyrene, polycarbonate, and cellulose acetate.

(E) Action The melt transfer type image receiving sheet for thermal transfer of the present invention has a thermoplastic resin layer provided on the surface of the support, which enhances affinity and adhesiveness with the hot melt ink and makes the thermal transfer image robust and scratch resistant. Has the effect of improving. At the same time, water resistance and strength are also increased.

(F) Examples The present invention will be described in more detail with reference to Examples. In addition,% and part show weight% and weight part. All melting points are values measured using a differential scanning calorimeter (DSC, manufactured by DuPont 910).

Example 1 Plain paper (grammage 70 g / m ² manufactured by Mitsubishi Paper Mills) was run at a constant speed, and after corona discharge treatment, low density polyethylene (density 0.91
8 g / cm ³ , MI 5, melting point 105 ° C.) was melt extruded with a resin thickness of 30 μm and laminated to obtain an image receiving sheet for thermal transfer. Also, low density polyethylene is melt extruded with a resin thickness of 30 μm and laminated on the back surface of this image receiving sheet in the same manner,
An image receiving sheet for thermal transfer having a thermoplastic resin layer on the image receiving surface and the back surface was obtained.

Example 2 Low density polyethylene density (0.96
5 g / cm ² , MI1.1, melting point 135 ° C.) was laminated with a resin thickness of 30 μm to obtain a thermal transfer image-receiving sheet.

Example 3 Plain paper (basis weight: 70 g / m ² manufactured by Mitsubishi Paper Mills) was run at a constant speed, subjected to corona discharge treatment, and then melted into low density polyethylene (density 0.918 g / m ² , MI 8.5) using a melt extruder. Resin composition consisting of 30 parts by weight of a masterbatch in which titanium oxide is mixed, 45 parts of low-density polyethylene (density 0.918 g / m ² , MI 5.0), 25 parts of high-density polyethylene 0.965 g / m ² , MI 7.0) The product was melt extruded with a resin thickness of 30 μm and laminated to obtain an image receiving sheet for thermal transfer. The melting point of the resin layer by DSC is 1
It was 25 ° C.

Example 4 Polyethylene terephthalate film (made of diamond foil
100 μm) at a constant speed, and after corona discharge treatment,
The low-density polyethylene used in Example 1 was melt-extruded and laminated using a melt extruder to obtain an image-receiving sheet for thermal transfer.

Example 5 Polyethylene terephthalate film (made of diamond foil
100 μm) at a constant speed, a polyacrylic adhesive was applied at a coating amount of ² g / m ² , the solvent was partially dried, and the same resin composition as that used in Example 3 was melt-extruded and laminated. Then, an image receiving sheet for thermal transfer was obtained.

As a comparative example, a polyethylene terephthalate film (100 μm made of diamond foil), a plain paper of 70 g / m ² and a polypropylene of 30 were used.
An image-receiving sheet laminated by fusion extrusion with a thickness of μm,
And 70g / m ² plain paper with a melting point of 60 ° C paraffin wax 5
Each of the image-receiving sheets obtained by hot-melt coating of μm was used to record an image under the same conditions using a commercially available melt-transfer type thermal transfer color copying machine (CX-5000 type manufactured by Sharp Corporation). A scratch test was performed on the captured image.

The results are shown in Table 1.

As a result, in Examples 1 to 5, which are thermoplastic resins having a melting point of 135 ° C. or less, a robust thermal transfer image having good scratch resistance regardless of the presence or absence of an inorganic pigment, the difference in the laminating method, and the difference in the support. was gotten. On the other hand, the polyethylene terephthalate film having a very high melting point had a poor scratch resistance of the thermal transfer image, and the polypropylene transfer sheet obtained a thermal transfer image having a slightly poor scratch resistance. Even if the melting point was low, the effect of scratch resistance was not sufficiently obtained with paraffin wax.

(G) Effect of the Invention In the image-receiving sheet for thermal transfer obtained in the present invention, since the thermoplastic resin layer on the image-receiving surface is brought into close contact with the hot-melt ink during the formation of the thermal transfer image, a robust thermal transfer image having good scratch resistance can be obtained. In addition, a high-quality thermal transfer image with high sharpness can be obtained by containing an inorganic pigment in the thermoplastic resin layer, and the presence of the thermoplastic resin layer on a transparent plastic sheet allows light transmission and scratch resistance. Its industrial significance is extremely high, such as obtaining good and robust thermal transfer images.

Claims (3)

[Claims] 1. A thermal transfer recording system in which a coating layer surface of a thermal transfer sheet having a heat-fusible ink layer coated on a support is superposed on an image-receiving sheet, and thermal fusion transfer is performed by a thermal head. It is provided by laminating a thermoplastic resin layer selected from polyethylene resin, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate, and polybutene, and the melting point of the thermoplastic resin layer is 135 ° C.
An image receiving sheet for thermal transfer type thermal transfer, characterized in that: 2. The melt transfer type image receiving sheet for thermal transfer according to claim 1, wherein the thermoplastic resin layer contains an inorganic pigment. 3. A melt transfer type image receiving sheet for thermal transfer according to claim 1, wherein a thermoplastic resin layer is provided on the back surface of the substrate provided with the thermoplastic resin layer.