JPH041713B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a method for manufacturing a thermal transfer recording medium,
More specifically, the present invention relates to a method for producing a heat-sensitive transfer recording medium that can produce a dye transfer image that has lost its luster.

[Prior Art] A thermal transfer recording medium has been conventionally used as a recording medium for transferring and forming an image on a recording sheet such as plain paper by a thermal printer, a thermal facsimile, or the like. This thermal transfer recording medium has at least one coloring material layer on a support, and the coloring material layer includes, for example, a layer containing a coloring agent made of a dye such as a pigment and a heat-fusible substance. etc. are known. In addition, films with excellent surface smoothness and dimensional stability are used as the support in order to obtain good reproducibility of the dye transfer image obtained from the color material layer coated on the support. There is.

Dye transfer images (printed images) obtained from such conventional thermal transfer recording media have extremely smooth and glossy surfaces, which causes significant eye strain when the records need to be read for a long time. Additionally, there is a drawback that the dye transfer image cannot be seen depending on the condition of the light source. In this regard, JP-A-56-164891 proposes mixing a matting material into the coloring material layer. However, according to this technique, the contamination of the matting agent may affect the coloring material layer, making it difficult to obtain a high-density dye transfer image.
There is a drawback.

Furthermore, Japanese Patent Application Laid-Open No. 16889/1989 discloses a technique for roughening the surface of a support, and cites sandblasting, lapping, and graining as means for roughening the surface.

However, when printing is performed using a recording medium obtained by coating a support surface roughened by this method with an ink layer containing carbon black dispersed in solid paraffin, uneven gloss occurs. There was a drawback.

[Object of the Invention] Therefore, an object of the present invention is to provide a method for producing a thermal transfer recording medium that does not require the use of a matting agent and can obtain a dye transfer image without gloss.

Another object of the present invention is to provide a method for producing a thermal transfer recording medium that can obtain a high-density dye transfer image without causing transfer defects and can significantly remove gloss.

Other objects of the invention will become apparent from the following description of the specification.

[Summary of the Invention] As a result of intensive research, the present inventor has developed a method for producing a heat-sensitive transfer recording medium in which a heat-sensitive transferable color material layer containing a colorant and a heat-melting substance is coated on a support. , low molecular weight polyethylene is used for the heat-sensitive transferable coloring material layer, and the surface of the support in contact with the coloring material layer is embossed to have a centerline average roughness (Ra) of 0.20 to 0.50 μm. discovered that the above purpose could be achieved by forming
This led to the present invention.

[Structure of the invention] The present invention will be explained in more detail below.

The support used as a base material for a thermal transfer recording medium is preferably a support that has heat-resistant strength and high dimensional stability. As for heat resistance strength, it is necessary to have strength and dimensional stability to maintain the toughness as a support without becoming softened or plasticized by the heating temperature of a heat source such as a thermal head. As the material, for example, resin films such as polyester, polycarbonate, polyethylene, polyethylene terephthalate, polystyrene, polypropylene, polyimide, paper-resin film composites, metal sheets such as aluminum foil, etc. are all suitably used. . Note that the thickness of the support is usually about
It is preferably 600 μm or less, particularly 2 to 40 μm.

The support used in the present invention has a centerline average roughness (Ra) of the surface in contact with the heat-melting coloring material layer.
The roughness has a value of 0.20 to 0.50 μm.
If Ra is less than 0.20 μm, it will not be possible to obtain a dye transfer image with no gloss, and conversely, if Ra is less than 0.50 μm, it will not be possible to obtain a dye transfer image with no gloss.
If it exceeds m, transfer defects will occur.
That is, a portion of the coloring material layer components remains in the concave portions of the roughness, and only a low-density dye transfer image can be obtained.

As a technique for imparting the roughness of the present invention to a support, a method of roughening the surface by embossing during film formation of the support is employed. The means for embossing is not particularly limited, and any known method can be employed. Note that a method of stretching (uniaxial or biaxial stretching) after embossing to obtain a uniform film thickness may be added.

The heat-sensitive transferable coloring material layer contains at least a coloring agent and a heat-melting property.

The coloring agent to be contained in the coloring material layer may be appropriately selected from conventionally known dyes, such as direct dyes, acid dyes, basic dyes, disperse dyes, and oil-soluble dyes. The coloring matter used in the coloring material layer of the present invention may be any pigment that can be transferred (transferred) together with the heat-melting substance, and may be a pigment in addition to the above.

The coloring material layer of the present invention contains one or more heat-melting substances. As this heat-fusible substance, conventionally known heat-fusible substances can be used without any particular restrictions.

The thermofusible substance preferably used in the present invention is
Softening point (measured by ring and ball method) or melting point (Yanagimoto
Measured value by MPJ-2 type) is 120℃ or less,
Particularly preferred are those having a melting point of 45 to 120°C.

Specific examples of heat-melting substances preferably used in the present invention include parafin waxes such as paraffin wax, micro wax, and polyethylene wax, beeswax, carnauba wax,
Natural waxes such as wood wax, ester waxes such as Hoechst wax, higher fatty acids such as stearic acid, palmitic acid, bebenic acid, myristic acid, 1,20-eicosandioic acid, stearyl alcohol, palmityl alcohol, etc. Examples include higher alcohols, higher amides such as stearamide, oleamide and palmithiamide, and esters such as butyl stearate, ethyl palmitate and myristyl stearate.

In the manufacturing method of the present invention, low molecular weight polyethylene is used for the coloring material layer.

In addition to the above-mentioned components, the coloring material layer may also contain various additives.

Coating methods suitable for coating a coloring material layer on a support having the roughness of the present invention by solvent coating, hot melt coating, etc. are known in the art, and these techniques are also used in the present invention. be able to. For example, the coating liquid can be applied using a reverse roll coater method, an extrusion coater method, a gravure coater method, a wire bar coating method, etc.
15 μm by solvent coating using any known technique followed by removal of the solvent.
The following color material layers can be applied.

The thermal transfer recording medium produced according to the present invention may have any structure on the back side of the support.

[Effects of the Invention] According to the present invention, the eyes do not get tired even when reading for a long time, and the coloring material layer components remain in the recesses provided on the surface of the support, resulting in a low density dye transfer image. Never.

[Example] Examples are given below, but the embodiments of the present invention are not limited thereto. Note that "parts" used below indicate "parts by weight."

Example 1 One surface of a polyethylene terephthalate film support having a thickness of 6 μm was embossing by pressing with a roughened metal roll to form irregularities to make the surface rough (Ra=0.30 μm). 30 parts of carnauba wax and 40 parts of paraffin wax on this rough surface.
parts, low molecular weight polystyrene (molecular weight 400) 15
A coloring material layer consisting of 15 parts of carbon black and 15 parts of carbon black was coated to a dry film thickness of 3.0 μm to obtain a thermal transfer recording medium sample of the present invention.

On the other hand, for comparison, a comparative thermal transfer recording medium sample was obtained by using the above sample with the only difference being that a coloring material layer was provided on a non-roughened support (Ra=0.15 μm).

This sample was printed on plain paper using a high-sensitivity thermal printer (a prototype equipped with a thin-film line thermal head with a heating element density of 8 dots/mm). As a result, when the sample was used, a clear dye transfer image with no gloss and excellent tamper resistance and storage stability was obtained. This dye transfer image
The glossiness was measured at an angle of 75° C. using the method described in JIS Z 8741 and found to be 7.1%. On the other hand, in the case of the above sample, only a glossy and difficult to see printed image was obtained. The glossiness was measured using the same measuring method as in Example 1 and was found to be 26%.

Example 2 The surface of a polyethylene terephthalate film support with a thickness of 6 μm was embossed by narrow pressure with a roughened metal roll to create a rough surface (Ra=
0.30 μm). Then, on top of this,
A coloring material layer having the same composition as the sample was coated to a thickness of 3 μm to obtain a thermal transfer recording medium sample of the present invention.

On the other hand, for comparison, the surface of the support was Ra=0.60μm.
A comparative thermal transfer recording medium sample was obtained in the same manner as the sample except that the surface was roughened.

Recording was carried out in the same manner as in Example 1 using this sample. As a result, when the thermal transfer recording medium sample of the present invention was used, a dye transfer image with no gloss and high density (optical reflection density 1.4) was recorded, whereas when the sample was used, a dye transfer image with low density (the same With the applied energy, only a dye transfer image with an optical reflection density of 0.9) could be obtained.

Claims (1)

[Claims] 1. A method for producing a heat-sensitive transfer recording medium comprising coating a heat-sensitive transferable coloring material layer containing a colorant and a heat-melting substance on a support, in which a low molecular weight polyethylene is used for the heat-sensitive transferable coloring material layer, A method for producing a thermal transfer recording medium, characterized in that the surface of the support in contact with the coloring material layer is formed by embossing to have a center line average roughness (Ra) of 0.20 to 0.50 μm.