JP2532532B2 - Thermal transfer recording sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a thermal transfer recording sheet. More specifically, the present invention relates to a thermal transfer recording sheet capable of recording a good transfer recording image on a recording medium having low surface smoothness.

(B) Prior Art In recent years, thermal transfer recording for forming a transfer image on plain paper using a thermal printer, a thermal facsimile or the like has been actively developed. This thermal transfer recording is easy to maintain because the mechanism of the device is simple, and the cost and maintenance cost are low. Also, clear and robust recording can be performed with low energy. It has been widely used recently because it can easily perform color recording.

In particular, the use amount of monochrome type thermal transfer recording sheets is increasing due to the spread of thermal printers.

When a conventional thermal transfer recording sheet is used, the recording medium to be used, that is, the paper usually called plain paper, is preferably one having high surface smoothness. The surface smoothness of paper is usually JIS
It is expressed by the Beck's (BEKK) smoothness (seconds) defined in P8119. If this smoothness is expressed, a paper of about 200 seconds is suitable.

However, when using paper with low surface smoothness, such as PPC paper or foam paper for 20 to 30 seconds and bond paper for 10 seconds or less, conventional thermal transfer recording sheets produce clear transfer images with high print quality. I can't get it.

There are various known techniques for the thermal transfer recording sheet corresponding to the paper having such low surface smoothness.

For example, there is a method of improving the fluidity of the heat-meltable ink during heating so that the heat-meltable ink flows into the concave portion of the rough surface of the plain paper. That is, a method of adding a high-boiling point hydrocarbon solvent or a high-boiling point halogenated hydrocarbon solvent to a hot-melt ink as disclosed in JP-A-60-161196 is disclosed.

Further, there is a method in which a thermally decomposable foaming agent is added to the heat fusible ink so that the ink adheres to or penetrates into the concave portion of the rough surface portion of the plain paper by the pressing force of the gas generated at the time of transfer. That is,
JP-A-59-201893 discloses a method of adding an inorganic compound such as bicarbonate, carbonate, nitrite, or a nitroso-based or sulfonylhydrazide-based organic compound to a substance that decomposes upon heating. .

Further, the transfer layer has a two-layer structure, and an intermediate layer containing no colorant is provided on the surface close to the base material, and a heat-meltable ink is provided on the intermediate layer to transfer the projections after heating to the rough surface. There is a way to bridge it. That is, JP-A-62-1
Japanese Patent Laid-Open No. 9991 discloses a method in which a material having a supercooling property such as dicyclohexyl phthalate, benzotriazole and acetanilide is used as an intermediate layer.

(C) Problems to be Solved by the Invention The patent publications cited in the above-mentioned prior art have various problems.

For example, a hot-melt ink that improves fluidity improves transferability, but causes a problem that a transferred image is contaminated by friction and rubbing during handling. Further, it is difficult to find a suitable transfer condition by the method of adding the heat-decomposable foaming agent, and the gas generated during transfer is small. In particular, it is not preferable when a hot-melt type heat-meltable ink is applied to a device.

Further, the method of forming the transfer layer into a two-layer structure is suitable for transferring to a target recording medium having a low surface smoothness, but is limited to a material having an official melting point and supercooling property. is there.

(D) Means for Solving the Problems The present invention provides a thermal transfer recording sheet that solves the conventional drawbacks and is capable of recording a clear transfer image with high printing quality even on a recording medium having low surface smoothness. It is provided.

That is, the thermal transfer recording sheet provided by the present invention is a thermal transfer recording sheet obtained by sequentially coating a release layer and a heat-meltable ink layer on a substrate, wherein the release layer is composed of a heat-meltable substance, Critical surface tension γc of the heat-meltable substance
The value (20 ° C.) is lower than the critical surface tension γc value (20 ° C.) of the base material.

When the substrate is a polyester film, the critical surface tension γc value of the present invention is 40 dyne / cm or less.

Furthermore, when the substrate is a polyethylene film,
The critical surface tension γc value of the present invention is 30 dyne / cm or less.

 Hereinafter, the present invention will be specifically described.

The thermal transfer recording sheet of the present invention has a two-layer structure in which a release layer is coated on one surface of a substrate, and a heat-meltable ink layer is further coated thereon. When the heat-meltable ink layer side of the base material and the plain paper are superposed and heat printing is performed from the opposite surface of the base material using a thermal head, a printed image can be obtained by transfer on the plain paper surface. In this case, the printed image is in a state in which the release layer and the heat-meltable ink are both transferred from the base material. That is, the adhesiveness of the release layer is higher with the heat-fusible ink layer than with the base material, and therefore, the release layer is separated from the base material. In the thermal transfer recording sheet of the present invention, both the release layer and the heat-fusible ink layer are peeled off from the base material as described above and transferred to plain paper to print on plain paper, particularly paper with low surface smoothness. It has the purpose and effect of obtaining a clear transferred image of high quality.

That is, the object of the present invention is to peel off both the release layer and the heat-meltable ink layer from the substrate.

The release layer in contact with the base material is easily transferred to the plain paper together with the hot-melt ink by the heat from the thermal head.

As a result, a clear transferred image can be obtained even on paper having low surface smoothness.

The thermal transfer recording sheet of the present invention forms a transfer image on plain paper together with a release layer which is heat-printed by a thermal head by being overlapped with plain paper, but the heat-meltable ink is melted by heating and penetrates into the rough surface of plain paper. Alternatively, it adheres and the associated release layer transfers with the ink. At this time, it is considered that the release layer imparts sharpness to the print by causing a bridge over the valleys in the uneven portion of the rough surface. However, it is considered that the release layer basically has a low adhesiveness with the base material, and therefore is easily separated from the base material by heating printing with a thermal head.

As described above, in the present invention, the peeling between the base material and the release layer has a unique critical surface tension γc value (20
It was expressed as (° C.) and was found to depend on the γc value. That is, the object of the present invention is achieved by making the critical surface tension γc value of the release layer smaller than the critical surface tension γc value of the substrate. The larger the difference in the critical surface tension γc value is, the smaller the critical surface tension γc value of the release layer is. This also means that the surface energy of the release layer is smaller. From the viewpoint of adhesiveness, the smaller the surface energy, the smaller the adhesiveness. In other words, if the critical surface tension γc value of the release layer is smaller than the critical surface tension γc value of the substrate, the adhesiveness with the substrate becomes weak.

On the contrary, the low adhesiveness is nothing but the improvement of the transferability of the present invention. Based on the above reasons, the thermal transfer recording sheet of the present invention can obtain a clear transfer image with high printing quality on the target paper having low surface smoothness.

Next, the materials used will be described more specifically.

As the base material, condenser paper, typewriter paper,
Thin paper such as tracing paper, synthetic paper, cellophane paper,
Further, a synthetic resin film such as a polyester film, a polyimide film, a polyethylene film, a polycarbonate film and a Teflon film is used as it is or after being subjected to a heat treatment so as not to stick to a thermal head. Among these examples, for the purpose of the present invention,
Polyester film (critical surface tension γc = 43 dyne / c
m) and polyethylene film (the same, 31 dyne / cm) are preferred.

Examples of the material used for the release layer of the present invention include synthetic resins. For example, polyvinylidene chloride (critical surface tension γc = 40dyne / cm), polystyrene (the same, 33-43dyn
e / cm), polyvinyl chloride (39dyne / cm), polyethylene (31dyne / cm), polyisobutylene (30dyne / cm)
cm) Polyvinyl alcohol (the same, 37 dyne / cm), etc., and polymethyl methacrylate (the same, 36 dyne / cm), polyethyl methacrylate (the same, 31.5 dyne / cm), polybutyl acrylate (the same, 29 dyne / cm), Polyhexyl acrylate (the same, 27.5dyne / cm) Polyoctyl acrylate (the same, 23.5dyne / cm), polylauryl acrylate (the same, 21.3dyne / cm), polystearyl acrylate (the same, 20.8dyne / cm), polyoctadecyl acrylate (Same as above, 20 dyne / cm) and the like. Further, within the scope of the present invention, for example, a heat-melting substance such as wax may be used. or,
There is no limitation on the use alone or in combination.

The release layer of the present invention is formed by coating the above-mentioned various materials on the substrate as an aqueous system, a solvent system or a hot melt system, but any method may be used for coating or printing. The coating thickness of the release layer is 0.25 to 10 μm, preferably 0.5 to 5 μm, more preferably 1 to 3 μm.

The ink used in the heat-fusible ink layer of the present invention is composed of a heat-melting substance, a colorant, a binder, a softening agent, etc., and may be used depending on the need.

Typical examples of the heat-melting substance are shown below, but the heat-melting substance is not limited to these.

Examples of the waxes include plant waxes such as rice wax, wood wax, candeli wax, and carnauba wax, animal waxes such as lanolin, beeswax, whale wax, shellac wax, montan wax, ozokerite, ceresin, etc. Mineral wax, paraffin wax, petroleum wax such as microcrystalline wax, oxidized paraffin wax, synthetic hydrocarbon wax such as low molecular weight polyethylene, ricinoleic acid amide, lauric acid amide, erucic acid amide, palmitic acid amide, oleic acid amide And fatty acid amide waxes such as stearic acid amide and ethylenebisstearic acid amide.

Examples of the metal soap include metal salts of higher fatty acids such as sodium stearate, sodium palmitate, potassium laurate, potassium myristate, calcium stearate, zinc stearate, aluminum stearate and magnesium stearate.

As the resins, polyamide resin, polyester resin, epoxy resin, polyurethane resin, polyacrylic resin, polyvinyl resin, polyvinyl chloride resin,
Examples thereof include cellulose resins, polyvinyl alcohol resins, petroleum resins, terpene resins, polystyrene resins, polyolefin resins, and elastomers.

Coloring agents include water-soluble dyes, oil-soluble dyes, disperse dyes, and facial cleansers such as colored pigments, and they are used as needed. Specific examples will be given below, but the present invention is not limited to these, and two or more types may be used in combination.

As the water-soluble dye, nitroso dye, azo dye (mono, bis, tris, tetrakisazo dye), stilbene azo dye, ketoimine (diphenylmethane) dye, triphenylmethane dye, xanthene dye, acridine dye, quinoline dye, methine dye, Examples thereof include polymethine dyes, thiazole dyes, indamine dyes, azine dyes, thiazine dyes, oxyketone dyes, anthraquinone dyes and phthalocyanine dyes.

Oil-soluble dyes include azo dyes, azo metal complex salt dyes,
Anthraquinone dyes and phthalocyanine dyes can be mentioned. More specifically, as an azo dye, Solvent Yellow 2 (CI11020, the numbers in parentheses below indicate CI No.) Solvent Orange 1 (11920),
Solvent Red 24 (26105), Solvent Brown 3
(11360), etc., as the azo metal complex salt dye, Solvent Yellow 19 (13900A), Solvent Orange 5 (1874
5A), Solvent Red 8 (12715), Solvent Brown 37, Solvent Black 123 (12195), etc. are anthraquinone dyes such as Solvent Violet 13
(60725), Solvent Bull-11 (61525), Solvent Green 3 (61565) and the like, and phthalocyanine dyes include Solvent Blue 25 (74350) and the like.

Examples of disperse dyes include aminoazo or aminoanthraquinone dyes and nitroarylamine dyes. More specifically, examples of aminoazo dyes include Disperse Yellow 3 (CI11855; hereinafter, the numbers in parentheses indicate CI No.), Disperse Orange 3 (100
5), Disperse Red 1 (11110), Disperse Violet 24 (11200), Disperse Blue 44, etc. Disperse Orange 11 (60700) and Disperse Red 4 (6075 as aminoanthraquinone dyes
5), Disperse Violet 1 (61100), Disperse Blue 3 (61505), etc.

Nitroarylamine dyes include Disperse Yellow 1 (10345) and 42 (10338).

Colored pigments include azo pigments (monoazo, bisazo,
Condensed azo pigment), Dyeing lake pigment (acid dye lake, basic dye lake, mordant dye lake pigment), nitro pigment,
Examples thereof include nitroso pigments, phthalocyanine pigments, and higher pigments (vat dye pigments, metal complex salt pigments, perylene pigments, isoindolinone pigments, quinacridone pigments). More specifically, examples of azo pigments include Hansa Yellow G (CI11680, hereinafter, CI No. is shown in parentheses), Hansa Yellow R (12710), and pyrazolone red B
(21120), permanent red R (12085), lake red C (15585), brilliant carmine 6B (15850),
Permanent Carmine FB (12490) (above monoazo pigment), Benzidine Yellow G (21090), Benzidine Yellow GR (21100), Permanent Yellow NCR (20040) (above Bisazo pigment), Chromophthal Yellow, Chromophthal Red (above condensed azo pigment) )and so on. Dyeing lake pigments include quinoline yellow lake (47005), eosin lake (45380), and alkaline blue lake (42750).
A, 42770A) (or more acid dye lake pigment), Rhodamine lake B (45170), Methyl violet lake (4253
5), Victoria Blue Lake (44045), Malachite Green Lake (42000) (above basic dye lake pigment), Alizarin Lake (58000) (mordanting dye lake pigment), etc. Naphthol Yellow S as nitro pigment
(10316), Pigment Green B as nitroso pigment
(10006), naphthol green B (10020), as a phthalocyanine pigment, metal-free phthalocyanine blue (74
100), phthalocyanine blue (74160) and phthalocyanine green (74260). As a high-quality pigment,
Anthrapyrimidine yellow (68420), indanthrene brilliant orange GK (59305), indanthrene blue RS (69800), thioindigo red B (73300) (above vat dye pigment), nickel azo yellow (1775) metal complex salt pigment ), Perylene red (71140), perylene scarlet (71137) (above perylene pigment), isoindolinone yellow (isoindolinone pigment), quinacridone red Y (46500), quinacridone magenta (73915) and the like.

As a black pigment, carbon block (CI7726
There is 5).

As the binder, either a water-soluble binder or a water-insoluble binder can be used.

Specific examples of such a binder are illustrated below or not limited to these, and two or more kinds may be used in combination.

Examples of the binder include polyvinyl alcohol, methyl cellulose, gelatin, hydroxyethyl cellulose, carboxymethyl cellulose, gum arabic, starch and its derivatives, casein, polyvinyl pyrrolidone, butyral resin, ethylene ethyl acrylate, styrene-butadiene copolymer, vinyl acetate resin,
Examples thereof include vinyl acetate-based copolymers, acrylic resins, mail methacrylic resins, styrene-acrylonitrile resins, ethylene-vinyl acetate copolymers, polyester resins and petroleum resins.

Examples of the softening agent include mineral oil, dibutyl phthalate, dioctyl phthalate, mineral spirits and liquid paraffin.

In addition to the heat-melting substances, colorants, binders and softeners mentioned above, additives such as surfactants, dispersants, antistatic agents, antioxidants, and ultraviolet absorbers may be added.

A coating machine used for coating the release layer and the heat-meltable ink layer of the present invention on a substrate is a known coater such as a hot melt coater, an air knife coater, a roll coater, a blade coater, and a bar coater. Further, a known printing machine such as a flexographic method or a gravure method may be used.

It should be noted that the solvent coating can be performed with a general solvent, but for example, methanol, ethanol, isopropyl alcohol, toluene, methyl ethyl ketone, acetone, ethyl acetate or the like can be appropriately used.

(E) Action The thermal transfer recording sheet of the present invention comprises a release layer and a heat-meltable ink layer, which are sequentially coated on one surface of a substrate. The release layer is composed of a heat-meltable substance, and the critical surface tension γc value (20 ° C) of the heat-meltable substance is lower than the critical surface tension γc value (20 ° C) of the base material. It is a feature.

The thermal transfer recording sheet of the present invention having such characteristics is
It has an effect that a clear transfer image with high printing quality can be obtained on a recording medium having low surface smoothness.

Further, in the thermal transfer recording sheet of the present invention, the release layer and the heat-meltable ink layer are transferred together in the thermal printing with the thermal head, and therefore, the heat-meltable ink release layer transferred onto the recording medium is covered. As a result, a transfer image having abrasion resistance can be obtained.

Hereinafter, the present invention will be specifically described with reference to examples. In addition, "part" in an Example shows a weight part.

(F) Example Example 1 A non-coated surface (critical surface tension γc = 43 dyne / cm) of a 6 μm-thick polyester film coated with a heat-resistant treatment layer was coated with a release layer made of a heat-fusible substance to a coating thickness of 2 μm. Was coated using a roll coater. An aqueous emulsion of polymethylmethacrylate having a critical surface tension γc = 36 dyne / cm was used as the heat-meltable substance. Subsequently, a heat-meltable ink layer having a coating thickness of 4 μm was coated on the release layer with a hot-melt coater using a heat-meltable ink having the following composition to obtain a thermal transfer recording sheet.

Carbon black 15 parts Ethylene-vinyl acetate copolymer 10 parts Carnauba wax 30 parts 150 ° F paraffin wax 40 parts Petroleum resin (m.p85 ° C) 5 parts The thermal transfer recording sheet thus obtained is formed into a ribbon. When a commercially available thermal transfer printer (Canon, type star 5) was used to print on bond paper (Mitsubishi Paper, Spicabond paper) with a surface smoothness of 10 seconds, a clear and abrasion-resistant transfer image was obtained on the bond paper. I was able to get it.

Comparative Example 1 The release layer in Example 1 was peeled off, and only the heat-meltable ink layer was applied to obtain a thermal transfer recording sheet, which was printed in the same manner as in Example 1. As a result, the recessed portion of the rough surface of the transferred image was white and unprinted portions remained, and a fine transferred image could not be obtained. Further, when the transferred image was rubbed with a finger, stains were generated and the abrasion resistance was insufficient.

Example 2 Instead of the polymethylmethacrylate used in Example 1, polyvinyl alcohol (critical surface tension γc = 37 dyne / c
A thermal transfer recording sheet was obtained in the same manner as in Example 1 except that m) was used.

When printing was performed in the same manner as in Example 1, a clear and abrasion-resistant transferred image could be obtained.

Example 3 Polyethylene film having a thickness of 10 μm (critical surface tension γ
c = 31 dyne / cm) and a release layer material consisting of polyoctadecyl acrylate (critical surface tension γc = 20 dyne / cm) as a heat-melting substance coated with a hot melt coater 1
It was coated so as to have a thickness of μm. Subsequently, the hot-melt ink used in Example 1 was applied onto the release layer by a hot-melt coater so that the coating thickness was 4 μm, to obtain a thermal transfer recording sheet.

The thermal transfer recording sheet thus obtained was printed on a bond paper (made by Mitsubishi Paper Mills, Spicabond paper) with a surface smoothness of 10 seconds using a commercially available facsimile (Oki Electric Co., OF-101), and it was clear and abrasion resistant. A transfer image having a property was obtained.

Comparative Example 2 A thermal transfer recording sheet was obtained in the same manner as in Example 3 except that the release layer was removed.

Further, when printing was performed in the same manner as in Example 3, the transferred image was left unprinted, was white, and lacked in clarity.
In addition, the transfer image had insufficient abrasion resistance and was contaminated.

(G) Effects of the Invention As described above, the thermal transfer recording sheet of the present invention can obtain a clear transfer image with high printing quality and a transfer image having abrasion resistance on paper having low surface smoothness. An image can be obtained, and the thermal transfer recording sheet of the present invention has extremely high industrial significance.

[Brief description of drawings]

1 and 2 are views showing the structure of a thermal transfer recording sheet according to the present invention. Note that FIG. 1 is a configuration diagram in which the heat-resistant treatment layer is provided on the surface opposite to the heat-meltable ink layer, and FIG. 2 is a configuration diagram in which the heat-resistant treatment layer is not provided.

Continuation of the front page (56) Reference JP-A 63-251289 (JP, A) JP-A 60-189492 (JP, A) JP-A 60-40294 (JP, A) JP-A 61-286195 (JP , A) "Chemical Dictionary" published by Kyoritsu Shuppan Co., Ltd. in 1976.

Claims (3)

(57) [Claims] 1. A thermal transfer recording sheet comprising a release layer and a heat-fusible ink layer sequentially coated on a substrate, wherein the release layer comprises a heat-fusible substance, and the heat-fusible substance has a criticality. A thermal transfer recording sheet having a surface tension γc value (20 ° C.) lower than the critical surface tension γc value (20 ° C.) of the substrate. 2. When the substrate is a polyester film,
The thermal transfer recording sheet according to claim 1, wherein the critical surface tension γc value of the heat-fusible substance is 40 dyn / cm or less. 3. When the substrate is a polyethylene film,
The thermal transfer recording sheet according to claim 1, wherein the critical surface tension γc of the heat fusible substance is 30 dyne / cm or less.