JPH0421599B2 - - 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, has high sensitivity, and has 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 resin and the pores are impregnated with heat-sensitive ink, but the density of the dye transfer image is low, and in order to obtain a high density dye transfer image, it is necessary to , high energy is required, and even if a high density dye transfer image is obtained by applying high energy, the edges of the printed image lack sharpness. JP-A-55-105579 also discloses a technique similar to the above,
The same drawbacks can be seen.

As a thermal transfer recording medium that overcomes these drawbacks, Japanese Patent Application Laid-Open No. 57-36698 discloses a technique in which a resin layer made of polyvinyl butyral is interposed between the ink layer (coloring material layer) and the support. has been done. This technology improves the adhesion between the ink layer and the support, and it is true that high-density printing is possible with relatively low energy; however, the density of the dye transfer image increases with the number of times it is used. This thermal transfer recording medium had the disadvantage of a significant decrease, and was not practical.

[Objective of the Invention] The object of the present invention is to enable low-energy printing, to have high sensitivity, and to have little loss of density with respect to the number of uses, so that high-density dye transfer images can be obtained many times. An object of the present invention is to provide a thermal transfer recording medium.

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 colorant layer containing a heat-fusible substance on a support, and a resin layer interposed between the colorant layer and the support. The present inventors have discovered that the above object can be achieved in a thermal transfer recording medium when the resin layer contains a polycaprolactone-based polymer compound as a main component, leading to the present invention.

[Structure of the invention] The present invention will be described in further detail below.

A typical example of the polycaprolactone-based polymer compound of the present invention is a caprolactone-based thermoplastic polymer represented by the following structural formula.

(In the formula, n represents an integer of 50 to 1000.) Among the thermoplastic polymers of the caprolactone-based polymer of the present invention, the molecular weight is 10,000 to 100,000, and the softening point by the Picato method is 45 to 85 degrees. Particularly preferred are those. Such caprolactone-based thermoplastic polymers can be obtained from commercial products.
For example, PLACCEL H- manufactured by Daicel Chemical Industries, Ltd.
1, H-4, H-7, etc.

The resin layer of the present invention may be substantially made of a caprolactone-based thermoplastic polymer,
It may contain other resin components or appropriate additives. In addition, when using other resin components together, the thermoplastic polymer of the caprolactone-based polymer of the present invention accounts for 50% (weight%, the same applies hereinafter).
The content is more preferably 70% or more.

Techniques for coating a resin layer on a support are known, and these known techniques such as solvent coating can also be used for coating the resin layer of the present invention.

Although the thickness of the resin layer of the present invention is not limited,
It may be 0.1 to 4 μm.

In the present invention, the coloring material layer is a layer containing a heat-fusible substance. The heat-melting substance used here may be any conventionally known heat-melting substance, but the melting point (as measured by Yanagimoto MPJ-2 type) is 40 to 120°C.
A solid or semi-solid substance is preferable, and specific examples include vegetable waxes such as carnauba wax, wood wax, auricilla wax, and espar wax; animal waxes such as beeswax, insect wax, serrata wax, spermaceti wax; In addition to waxes such as petroleum waxes such as paraffin waxes, microcrystalline waxes, ester waxes, and oxidized waxes, and mineral waxes such as montan wax, ozokerite, and ceresin; Higher fatty acids; higher alcohols such as palmityl alcohol, stearic alcohol, behenyl alcohol, marganyl alcohol, myricyl alcohol, eicosanol; higher fatty acid esters such as cetyl palmitate, myricyl palmitate, cetyl stearate, myricyl stearate; acetamide, propion Acid amide, palmitic acid amide, stearic acid amide,
Amides such as amide wax; rosin derivatives such as ester gum, rosin maleic acid resin, rosin phenolic resin, and hydrogenated rosin; high softening points of 50 to 120°C such as phenolic 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,
Particularly preferred are higher amides such as palmitic acid amide, stearic acid amide, oleic acid amide, and amide wax.

The dye to be contained in the color material layer of the present invention may be appropriately selected from conventionally known dyes, including direct dyes,
The dye may be selected from acid dyes, basic dyes, disperse dyes, oil-soluble dyes (including oil-soluble metal complex dyes), and the like. The dye used in the present invention may be any pigment that can be transferred (migrated) together with the heat-melting substance, and thus may be a pigment in addition to the above. Specifically, the following can be mentioned. That is, as the yellow pigment, Kayalon Polyester Light Yellow 5G-
S (Nippon Kayaku), Oil Re Yellow S-7 (white clay),
Eisenspiron Yellow GRH Special (Hodogaya), Sumiplast Yeto FG (Sumitomo), Eisenspiron Yellow GRH (Hodogaya), etc. are preferably used. Red pigments include Diaceriton Fastred R (Mitsubishi Kasei), Dianics Brilliant Red BS-E (Mitsubishi Kasei), Sumiplast Stretch FB (Sumitomo), and Sumiplast Stret HFG.
(Sumitomo), Kayalon Polyester Pink RCL-E
(Nippon Kayaku), Eizenspiron Red GEH Special (Hodogaya), etc. are preferably used. As blue pigments, Diaceritone Fast Brilliant Blue R (Mitsubishi Kasei), Dianics Blue
EB-E (Mitsubishi Kasei), Kayalon Polyester Blue B-SF Conc (Nippon Kayaku), Sumiplast Blue 3R (Sumitomo), Sumiplast Blue G (Sumitomo), etc. are preferably used. In addition, Hansa Yellow 3G, Tartrazine Lake, etc. are used as yellow pigments, and brilliant carmine is used as red pigments.
FB-Piure (Sanyo Color), Prilliant Carmine 6B (Sanyo Color), Alizarin Lake, etc. are used, and as blue pigments, Cerulean Blue, Sumikaprint Cyanine Blue GN-O (Sumitomo), Phthalocyanine Blue, etc. are used. As the black pigment, carbon black, oil black, etc. are used. In addition, metal particles or metal oxides may also be used.

It is preferable that the coloring material layer of the present invention contains a binder. The binder used in the present invention preferably has a softening point (measured by the ring and ball method) of 40 to 200°C, and either a hydrophilic polymer or a hydrophobic polymer can be used. Examples of hydrophilic polymers include gelatin, gelatin derivatives, cellulose derivatives, proteins such as casein, natural products and natural product derivatives of polysaccharide sugars such as starch, and water-soluble polyvinyl compounds such as polyvinyl alcohol, polyvinylpyrrolidone, and acrylamide polymers. Examples include synthetic water-soluble polymers such as, vinyl-based and polyurethane-based polymer latexes. As a hydrophobic polymer, U.S. Patent No.
No. 3142586, No. 3143386, No. 3062674, No. 3142586, No. 3143386, No. 3062674, No.
Examples include the synthetic polymers described in No. 3220844, No. 3287289, and No. 3411911. Preferred polymers include polyvinyl butyral, polyvinyl formal, polyethylene, polypropylene, polyamide, ethyl cellulose, cellulose acetate, polystyrene, polyvinyl acetate, polyvinyl chloride, polyvinylidene chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-
Examples include vinyl acetate-maleic acid terpolymers, acrylic resins such as polymethyl methacrylate, polyisobutylene, and rosin derivatives such as ester gum. In the present invention, one kind or a combination of two or more kinds of these resins are used.

Although the composition ratio of the colorant layer of the present invention is not limited,
For the total amount of color material layer 100 parts (parts by weight, the same applies hereinafter),
50 to 90 parts of hot melt material, 5 to 20 parts of colorant, and up to 30 parts (preferably 5 to 30 parts) of binder.

The color material layer of the present invention may contain known additives. For example, examples of the thermally conductive substance include metals with good thermal conductivity such as aluminum, copper, and zinc. Such a thermally conductive substance promotes the heat conduction effect of melting, softening, or sublimating the colorant layer by heat. Also, softeners such as oleic acid, castor oil, and dioctyl phthalate may be added.

In the thermal transfer recording medium of the present invention, techniques suitable for applying the colorant layer to a support such as a polymer film via a resin layer are known in the art, and these techniques are also applicable to the present invention. Can be used. For example, the colorant layer is a layer formed by hot melt coating the composition or by solvent coating a coating solution prepared by dissolving or dispersing the composition in an appropriate solvent. As a method for applying the coloring material layer of the present invention, 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-sensitive transfer recording medium of the present invention may have other constituent layers such as an overcoat layer (for example, a layer made of a heat-fusible substance).

Note that the support used as a base material for 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.
Heat-resistant strength requires strength and dimensional stability to maintain toughness as a support that does not soften or plasticize due to the heating temperature of a heat source such as a thermal head, and surface smoothness requires a heat-fusible material on the support. Sufficient smoothness is desired for the containing layer to exhibit good transfer rates. The smoothness should be 100 seconds or more in a smoothness test using a Beck testing machine (JIS P 8119).
When the time is 300 seconds or more, images with better transfer rate and reproducibility can be obtained. Examples of materials include:
Uses paper such as plain paper, condenser paper, laminated paper, coated paper, resin films such as polyester, polycarbonate, polyethylene, polystyrene, polypropylene, polyimide, paper-resin film composites, metal sheets such as aluminum foil, etc. be done. The thickness of the support is preferably about 60 .mu.m or less, particularly 2 to 15 .mu.m, in order to obtain good thermal conductivity.

In the thermal transfer recording medium of the present invention, the structure on the back side of the support is arbitrary, but it is preferable to provide a backing layer on the back side of the support in order to prevent the sticking phenomenon. For example, JP-A-55-
Silicone resin layer in No. 7467, JP-A-57-
No. 129789, resin containing a surfactant or organic salt that is solid or semi-solid at room temperature, patent application No. 1982-
There are combinations of heat-melting substances and resins as described in No. 189295.

[Effects of the Invention] According to the present invention, in a heat-sensitive transfer recording medium having a coloring material layer containing a heat-fusible substance on a support, and a resin layer interposed between the coloring material layer and the support, Since the resin layer is made of a caprolactone-based thermoplastic polymer, 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 1 100 parts of a caprolactone-based thermoplastic polymer (PLACCEL H-7 manufactured by Daicel Chemical Industries, Ltd.) (softening point: 60°C) was dissolved in 1000 parts of toluene to obtain a resin layer coating liquid. This coating solution was applied onto a polyethylene terephthalate film support with a thickness of 5 μm using a wire bar, and dried to a thickness of 5 μm.
A resin layer of 2 μm was formed.

Next, 60 parts of microcrystalline wax,
A coloring material layer consisting of 10 parts of carnauba wax, 10 parts of ethylene-ethyl acrylate resin, and 20 parts of carbon black was coated on the resin. This coloring material layer has a dry film thickness of 3 μm.

The heat-sensitive transfer recording medium sample of the present invention thus obtained was layered on plain paper (white paper with a Beck smoothness of 200 seconds), and a thermal printer (equipped with a thin-film line thermal head with a heating element density of 8 dots/mm) was used. Apply energy to the sample using a prototype device.
Thermal transfer was performed by applying 0.5 mJ/dot. This is 1~
I was able to repeat it 6 times.

Comparative Example 1 A comparative thermal transfer recording medium sample was prepared in the same manner as in the sample of the present invention, except that the resin layer was replaced with a layer made of polyvinyl butyral (Eslec BL-1, manufactured by Sekisui Chemical Co., Ltd.) (softening point: 120°C). was created and printed many times in the same way as above.

As a result, as shown in Fig. 1, in contrast to the comparison sample, where a significant decrease in the density of the dye transfer image was observed with respect to the number of times of printing, in the sample of the present invention, the decrease in the density of the dye transfer image with respect to the number of times of printing was suppressed. Ta.

Example 2 A mixture of vinylidene chloride resin and fluorine surfactant was applied to the back surface of the support of an ink ribbon prepared in the same manner as in Example 1.

When printing was repeated many times in the same manner as in Example 1, the decrease in the density of the dye transfer image with respect to the number of printings was suppressed, as was the case with the sample, and at the same time, there was no show-through of the ink ribbon, and staining of the thermal head was prevented. .

Comparative Example 2 According to Example 1 of JP-A No. 54-68253,
A coating solution consisting of 10 parts of vinyl chloride/vinyl acetate copolymer, 7 parts of carnauba wax, 11 parts of castor wax, 4 parts of carbon black, 51 parts of ethyl acetate, and 17 parts of toluene was solvent-coated onto carbon base paper. Comparative thermal transfer recording media samples were obtained by processing as described in . Also, Tokukai Akira
55-105579, 20 parts of vinyl chloride/vinyl acetate copolymer, 40 parts of common salt, p, p
-oxy-bis(benzenesulfonylhydrazide) 2 parts, methyl ethyl ketone 60 parts, heptane 40 parts
Solvent coating a 12 μm thick polyester film with the coating solution consisting of
Comparative thermal transfer recording media samples having microporous ink layers were obtained by processing as described in the examples.

For these comparison samples, repeated printing was attempted on plain paper in the same manner as in Example 1 above. However, in both samples, only dye transfer images with a density too low to be of practical use were obtained from the first printing. Furthermore, in order to obtain the same transfer density using both of these samples as in the dye transfer image obtained using the sample of the present invention, approximately 2.5 times as much applied power was required. Moreover, the sharpness of the edges of the dye transfer image obtained was several orders of magnitude worse than that of the sample of the present invention.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the number of times of printing and the density of the dye transfer image for thermal transfer recording medium samples, where the x mark indicates the case of the sample of the present invention, and the o mark indicates the case of the comparative sample.

Claims (1)

[Claims] 1. A thermal transfer recording medium having a coloring material layer containing a heat-fusible substance on a support, and a resin layer interposed between the coloring material layer and the support, in which the resin layer is made of a polycaprolactone-based polymer compound. A thermal transfer recording medium characterized by containing as a main component.