JPH041717B2 - - 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 inventors have developed 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. The present inventors have discovered that the above object can be achieved by providing a heat-sensitive transfer recording medium in which the resin layer is made of an ethylene-alkyl acrylate copolymer, leading to the present invention.

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

The resin layer of the present invention is made of an ethylene-alkyl acrylate copolymer. The ethylene-alkyl acrylate copolymer of the present invention refers to a copolymer of ethylene and alkyl acrylate, but may also be a terpolymer of ethylene, alkyl acrylate, and a third component. The third component may be any monomer that can be terpolymerized with ethylene and alkyl acrylate.

Among the ethylene-alkyl acrylate copolymers of the present invention, particularly preferred is ethylene-ethyl acrylate, which has a melt index of 10 to 10.
400, with a softening point of 45 to 90 according to Picato's method
℃ is particularly preferred, and an ethylene-ethyl acrylate copolymer having an ethyl acrylate monomer composition ratio of 2 to 50% by weight is particularly preferred. Such ethylene-ethyl acrylate copolymers are commercially available, such as NUC-6170, 6220, and 6570 manufactured by Nippon Unicar Co., Ltd.

The resin layer of the present invention may essentially consist of an ethylene-alkyl acrylate copolymer, and may contain other resin components or appropriate additives. In addition, when using other resin components together, the ethylene-alkyl acrylate copolymer of the present invention accounts for 50% or more (weight%, the same applies hereinafter),
More preferably, the content is 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, stearyl 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 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.

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,
It may be selected from acid dyes, basic dyes, disperse dyes, oil-soluble dyes, etc. 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 yellow pigments, Kayalon Polyester Light Yellow 5G-S (Nippon Kayaku), Oil Yellow S
-7 (white clay), Eisenspiron GRH Special (Hodogaya), Sumiplast Yellow 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 FB (Sumitomo), and 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, cerulean 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. In addition, metal particles or metal oxides may also be used.

It is preferable that the color material layer of the present invention contains a resin. The resin 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 such as polysaccharides such as starch, water-soluble polyvinyl compounds such as polyvinyl alcohol, polyvinylpyrrolidone, and acrylamide polymers. In addition, examples include synthetic water-soluble polymers such as, vinyl-based and polyurethane-based polymer latexes. As hydrophobic polymers, US Pat. No. 3,142,586;
3143386, 3062674, 3220844, 3143386, 3062674, 3220844,
Examples include the synthetic polymers described in No. 3287289 and No. 3411911. Preferred polymers include polyvinyl butyral, polyvinyl formal, polyethylene, polypropylene, polyamide, ethyl cellulose, cellulose acetate, polystyrene, polyethyl acrylate, polyvinyl chloride, polyvinylidene chloride, vinyl chloride-ethyl acrylate copolymer, vinyl chloride-
Examples include ethyl acrylate-maleic acid terpolymers, acrylic resins such as polymethyl methacrylate, polyisobutylene, and rosin derivatives such as ester gum. In the present invention, one or a combination of two or more of these resins may be used.

Although the composition ratio of the coloring material 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 30 parts or less (preferably 5 to 30 parts) of resin.

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 coloring material 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 coloring material layer to a support such as a polymer film via a resin layer are known in the art, and the present invention also includes these techniques. Can be used. For example, the coloring material 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 resistance strength requires strength and dimensional stability to maintain the toughness of the support without becoming softened or plasticized by the heating temperature of a heat source such as a thermal head, and surface smoothness requires heat melting on the support. It is desired that the layer containing a sexual substance has sufficient smoothness to exhibit a good transfer rate. The smoothness is preferably 100 seconds or more in a smoothness test using a Beck tester (JIS P 8119), and when it is 300 seconds or more, images with better transfer rate and reproducibility can be obtained. Materials include, for example, papers such as plain paper, condenser paper, laminated paper, coated paper, resin films such as polyester, polycarbonate, polyethylene, polystyrene, polypropylene, polyimide, paper-resin film composites, aluminum foil, etc. metal sheets etc. are used. The thickness of the support is usually about 60 μm or less, especially 2 to 15 μm in order to obtain good thermal conductivity.
Preferably, it is m. Furthermore, in the thermal transfer recording medium of the present invention, the structure of the back side of the support is arbitrary.

[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 configured to be a layer made of an ethylene-alkyl acrylate copolymer, 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 Ethylene-ethyl acrylate copolymer (NUC-6570 manufactured by Nippon Unicar Co., Ltd.) Softening point 43°C)
A coating solution for a resin layer was obtained by dissolving 100 parts in 1000 parts of methyl ethyl ketone. 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, 10 parts of carnauba wax, ethylene-vinyl acetate resin
A coloring material layer consisting of 10 parts of carbon black and 20 parts of carbon black was coated on the resin layer. 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 sec), and a thermal printer (a prototype equipped with a thin-film line thermal head with a heating element density of 8 dots/mm) was produced. Apply energy to the sample at 0.5 m using
J/dot was given and thermal transfer was performed. This was repeated 1 to 6 times.

Comparative Example 1 A comparative thermal transfer recording medium sample was prepared in the same manner as 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.

Comparative Example 2 According to Example 1 of JP-A No. 54-68253,
10 parts of vinyl chloride/ethyl acrylate copolymer,
Carnauba wax 7 parts, Castor wax 11 parts,
A coating solution consisting of 4 parts of carbon black, 51 parts of ethyl acetate, and 17 parts of toluene was solvent coated onto carbon base paper and treated as described in the publication to obtain a comparative thermal transfer recording medium sample. Also, according to the example of Japanese Patent Application Laid-Open No. 55-105579,
20 parts of vinyl chloride/ethyl acrylate copolymer,
40 parts of common salt, 2 parts of p,p'-oxy-bis(benzenesulfonyl hydrazide), 60 parts of methyl ethyl ketone
A coating solution consisting of 1.5 parts and 40 parts of heptane was applied to a thickness of 12 μm.
A comparative thermal transfer recording medium sample having a microporous ink layer was obtained by solvent coating a polyester film and then processing as described in that example.

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.

Comparative Example 3 A colorant layer composition having the following composition was deposited on a 6 μm thick polyethylene terphthalate film support in a film thickness of 5 μm.
A comparative thermal transfer recording medium sample was obtained.

Coloring material layer composition Microwax 180°F (manufactured by Nippon Oil) (melting point 82°C)
68 parts ethylene-ethyl acrylate copolymer (NUC
-6070, manufactured by Nippon Unicar Co., Ltd.) (polymerization ratio 75/25, softening point 95°C) 17 parts carbon black 15 parts The comparison thermal transfer recording medium sample thus prepared was printed many times in the same manner as in Example 1. I tried.

However, when the energy is 0.50 mJ/dot, which is the same as in Example 1, the first print density is as low as in Example 1.
However, the second print density was almost negligible and was not much different from normal single-use ribbon.

[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 an ethylene-alkyl acrylate copolymer. A multi-time thermal transfer recording medium characterized by having a layer consisting of a combination of layers.