JPH0461798B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a thermal transfer recording medium that can be used multiple times. More specifically, the present invention relates to a thermal transfer recording medium that exhibits a small decrease in density with the number of uses, can be printed with low energy, and provides printing quality with high density and excellent resolution.

[Prior Art] As a thermal transfer recording medium intended for multiple uses, there is, for example, an invention described in Japanese Patent Application Laid-Open No. 54-68253. This invention is a technique in which a microporous layer is formed using a resin, and the pores are impregnated with hot-melt ink, but the density of the dye transfer image is low, and it is difficult to obtain a high density dye transfer image. This requires high energy, and even if a high-density dye transfer image is obtained by applying high energy, the edges of the printed image lack sharpness. Japanese Unexamined Patent Publication 1973-
105579 also discloses a technique similar to the above, but it has the same drawbacks.

In addition to the above, heat-sensitive transfer recording media that can be used many times using various techniques are being considered. for example,
As shown in JP-A-57-185195, a method of grafting a vinyl monomer onto carbon black, JP-A No. 57-36698, JP-A No. 57-138984, JP-A No. 58
As shown in Japanese Patent No. 116193 and No. 58-155995, there are known ones in which an intermediate layer for adhesion is provided between the base material and the ink layer (heat-melting color material layer).
These prevent all of the colorant from being transferred at once when heated with a thermal head, and although each of them is effective to some extent, it is still insufficient.

[Objective of the Invention] The object of the present invention is to enable low-energy printing, and to reduce the decrease in density with respect to the number of times of use.
It is an object of the present invention to provide a heat-sensitive transfer recording medium capable of obtaining high-density dye transfer images many times.

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 discovered that in a thermal transfer recording medium in which a heat-fusible coloring material layer is laminated on a support, a It has been discovered that the above object can be achieved by interposing an intermediate layer containing a highly thermally conductive fine powder and an ethylene-ethyl acrylate resin, leading to the present invention.

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

In the thermal transfer recording medium of the present invention, an intermediate layer consisting of a resin layer in which highly thermally conductive fine powder is dispersed is interposed between the support and the heat-melting coloring material layer.

Ethylene-ethyl acrylate resin is used as the resin to be kneaded with the highly thermally conductive fine powder used in the thermal transfer recording medium of the present invention to form the intermediate layer. As a highly thermally conductive fine powder, it has a higher thermal conductivity than the aforementioned resin (for example, thermal conductivity 6.0×
10 ^-4 ~25.0×10 ^-4 cal/sec・cm・℃) and has a high melting point. Many metals such as aluminum and copper are possible, and tin oxide, aluminum oxide, magnesium oxide, etc. Oxides of titanium and nitrides such as titanium nitride can also be used. The particle size of the high thermal conductivity fine powder of the present invention is preferably 3 μm or less, more preferably 1 μm or less. The mixing ratio of the aforementioned resin and fine powder is preferably 10 to 90% by volume of fine powder.
More preferably it is 20-60%. This is because if the volume fraction of the fine powder is smaller than this, no effect on thermal conductivity will be exhibited, whereas if it is larger than this, the adhesive strength with the support and the coloring layer will be reduced, and the multi-printability will be reduced.

The highly thermally conductive fine powder may be dispersed and contained in at least the intermediate layer.
Alternatively, it may be contained in the colorant layer. The particle size of the highly conductive fine powder used in the present invention may be larger than the thickness of the intermediate layer. In this case, a portion of the fine powder protrudes into the colorant layer, but this does not impede the effects of the present invention.

The heat-melting color material layer in the present invention mainly consists of a low-melting point substance, a colorant, and a softener.The low-melting point substance is a solid or It is a semi-solid substance, and specific examples include carnauba wax,
Plant waxes such as tree wax, auricilla wax, and esparto wax, beeswax, insect wax, serat's wax,
Animal wax such as whale wax, paraffin wax, microcrystalline wax, S.L. wax,
In addition to waxes such as petroleum waxes such as oxidized waxes, mineral waxes such as montan wax, ozokerite, and ceresin; higher fatty acids such as palmitic acid, stearic acid, margaric acid, and behenic acid; palmityl alcohol, stearyl alcohol, behenyl alcohol, and marga Higher alcohols such as nyl alcohol, myricyl alcohol, and eicosanol; higher fatty acid esters such as cetyl palmitate, myricyl palmitate, cetyl stearate, and myricyl stearate; acetamide, propionic acid amide, palmitic acid amide, stearic acid amide,
Amides such as amide wax; rosin derivatives such as ester gum, rosin maleic acid resin, rosin phenol resin, hydrogenated rosin; high softening point of 50 to 120℃ such as phenol resin, terpene resin, cyclopentadiene resin, aromatic resin, etc. Molecular compounds; Higher amines such as stearylamine, behenylamine, palmitinamine; polyethylene glycol
4000, polyethylene oxide such as polyethylene glycol 6000, etc., and these may be used alone or in combination. Among these,
Higher amides such as palmitic acid amide, stearic acid amide, oleic acid amide, and amide wax are particularly preferred. Furthermore, the "thermofusible solid component that is solid at room temperature" described in JP-A-54-68253 and the "vehicle" described in JP-A-55-105579 can also be used. good.

The coloring agent used in the present invention may be appropriately selected from conventionally known pigments, such as direct dyes, acid dyes, basic dyes, disperse dyes, and oil-soluble dyes (including metal-containing oil-soluble dyes). You can choose from. 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. In addition, specifically, the following can be mentioned. In other words, the yellow pigment is Kayalon Polyester Light Yellow.
5G-S (Nippon Kayaku), Oil Yellow S-7 (white clay), Eisenspiron Yellow GRH Special (Hodogaya), Sumiplast Yellow FG (Sumitomo), Eisenspiron Yellow GRH (Hodogaya), etc. are suitable. used for. As red pigments, Diaceriton Fastret R (Mitsubishi Kasei), Dianix Primer Lead BS-E (Mitsubishi Kasei), Sumiplast Stret FB (Sumitomo), Sumiplast Stret
HFG (Sumitomo), Kayalon Polyester Pink RCL
-E (Nippon Kayaku), Eisen Spiron Red GEH
Special (Hodogaya), etc. are preferably used.
Blue pigments include Diaceritone Fast Brilliant Blue R (Mitsubishi Kasei), Dianics Blue EB-E (Mitsubishi Kasei), Kayalon Polyester Blue B-SF Conc (Nippon Kayaku), and Sumiplast Blue 3R (Sumitomo). , Sumiplast Blue G (Sumitomo)
etc. are preferably used. In addition, as yellow pigments, Hansa Yellow 3G, Tartrazine Lake, etc. are used, as red pigments, brilliant carmine FB-Pure (Sanyo Dyes), brilliant carmine 6B (Sanyo Dyes), Alizarin Lake, etc. are used, and as blue pigments, As for, Serillian Blue,
Sumika print cyanine blue GN-O (Sumitomo),
Phthalocyanine blue or the like is used, and carbon black, oil black or the like is used as the black pigment.

Examples of the softener used in the present invention include low softening point polymers selected from ethylene-ethyl acrylate copolymers, ethylene-vinyl acetate copolymers, and the like.

Note that the support used in the thermal transfer recording medium of the present invention is preferably a support that has heat-resistant strength, high dimensional stability, and high surface smoothness. Materials include, for example, papers such as plain paper, condenser paper, laminated paper, coated paper, resin films such as polyethylene, polyethylene terephthalate, polystyrene, polypropylene, polyimide, paper-resin film composites, aluminum foil, etc. Metal sheets and the like are preferably used. The thickness of the support is normal for good thermal conductivity.
It is preferably 60 μm or less, particularly 2 to 20 μm.
Furthermore, in the thermal transfer recording medium of the present invention, the structure on the back side of the support may be optional, and a backing layer such as a sticking prevention layer may be provided.

In the heat-sensitive transfer recording medium of the present invention, techniques suitable for coating the intermediate layer on a support such as a polymer film and techniques suitable for coating the heat-melting coloring material layer on the intermediate layer are as described above. Japanese Patent Publication No. 54-68253,
These techniques are described in Japanese Patent No. 55-105579 and are known in the art, and these techniques can also be used in the present invention. For example, the intermediate layer (and the heat-melting color material layer) is a layer formed by hot-melt coating the composition, or by solvent coating a coating solution obtained by dissolving or dispersing the composition in an appropriate solvent. It is. The method for applying the intermediate layer (and heat-melting coloring material layer) of the present invention is as follows:
Any known technique can be employed, such as a reverse roll coater method, an extrusion coater method, a gravure coater method, and a wire bar coating method. The heat-melting coloring material layer of the present invention may have a thickness of 20 μm or less, more preferably 1 to 15 μm. Further, the intermediate layer of the present invention may have a thickness of 3 μm or less, more preferably 1 μm or less.

[Effects of the Invention] According to the present invention, in a heat-sensitive transfer recording medium in which a heat-fusible coloring material layer is laminated on a support, highly thermally conductive fine powder and Since the structure includes an intermediate layer containing a resin, the above-mentioned object of the present invention can be achieved.

[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 Using a wire bar on a 5.3 μm thick polyethylene terephthalate film, the dry film thickness was 0.6 μm.
An intermediate layer was obtained by applying an ethylene-ethyl acrylate resin solution having the following composition.

Ethylene-ethyl acrylate resin 10 parts (NUC-6070 manufactured by Nippon Unicar Co., Ltd.) Copper powder (particle size 3 μm or less) 10 parts Toluene 100 parts After drying, apply the following coloring layer coating solution using a wire bar until the dry film thickness is 12 μm. After applying it to 100%
A sample of the thermal transfer recording medium of the present invention was obtained by heating in a dryer at .degree. C. for 20 minutes.

Carbon black 10 parts Microcrystalline wax 40 parts (Micro UHF BARECO Co., Ltd.) Ethylene-ethyl acrylate resin 2 parts (NUC-6070 Nippon Unicar Co., Ltd.) Toluene 120 parts This thermal transfer recording medium sample was printed on a thermal printer (heating element density 8 dots) A prototype machine equipped with a /mm thin-film line thermal head) was used to record (print) energy on plain paper with an applied power of 0.6 W per heating element and an application time of 1 millisecond. This was repeated 1 to 5 times. Note that commercially available high-quality paper (60 g/m ² ) was used as the plain paper.

As a result, as shown in FIG. 1, printing with sufficient density was obtained even after more than 5 printings. The print quality was also good.

Comparative Example 1 An intermediate layer was coated on a 5.3 μm thick polyethylene terephthalate film in the same manner as in Example 1, but no highly thermally conductive fine powder was added to this intermediate layer.
After drying, a colorant layer having the same composition as in Example 1 was applied to give a dry film thickness of 12 μm, and then heated in a dryer at 100° C. for 20 minutes to obtain a comparative thermal transfer recording medium sample. Using this thermal transfer recording medium sample, printing was performed using a thermal printer in the same manner as in Example 1. As a result, as shown in FIG. 1, the density (Dmax) was low and the print quality was also poor.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the number of printing times and the density of a dye transfer image for a thermal transfer recording medium sample of the present invention and a comparative thermal transfer recording medium sample.

Claims (1)

[Claims] 1. In a thermal transfer recording medium in which a heat-melting coloring material layer is laminated on a support, an intermediate layer containing a highly thermally conductive fine powder and an ethylene-ethyl acrylate resin is provided between the support and the heat-melting coloring material layer. A thermal transfer recording medium characterized by interposing.