JPH01258984A - Thermal transfer sheet - Google Patents

Abstract

PURPOSE:To eliminate the occurrence of ground staining or stringiness and to obtain a sharp printing, by a method wherein a thermal transfer sheet is formed by laminating a hot-melt ink layer and a surface layer having a heat- resistant network structure on one surface of a substrate film. CONSTITUTION:A hot melt ink layer made of a coloring agent and a vehicle is provided on one surface of a substrate film, such as a plastic film of polyester and polypropyrene and a condenser paper. Furthermore, on the hot melt ink layer, a surface layer made of a heat-resistant resin material, having a melting point higher than that of the ink layer and incompatibility with the ink layer, and having a heat-resistant network structure never melting due to heat during a thermal transfer is laminated to obtain a thermal transfer sheet. By conducting a thermal transfer by a thermal head with the thermal transfer sheet overlapped on a transfer material, a melting ink is oozed out of the network structure to enable a stain-free and clear printing.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to improvements in thermal transfer sheets, and more specifically to a general thermal transfer method and a thermal transfer method in which the conveyance speed of the transfer material is higher than the conveyance speed of the thermal transfer sheet. The present invention relates to a thermal transfer sheet that can prevent background smearing of transfer paper due to a layer of heat-melting ink in a thermal transfer sheet (hereinafter referred to as the N-fold method).

(Prior art and its problems) Conventionally, when printing output prints from computers or word processors using a thermal transfer method, a thermal transfer sheet with a heat-melting ink layer provided on one side of a base film has been used. .

This conventional thermal transfer sheet has a thickness of 1 mm as a base film.
Using paper such as capacitor paper or paraffin paper with a thickness of 0 to 20 μm, or a plastic film such as polyester or cellophane with a thickness of 3 to 20 μm, a layer of heat-melting ink made by mixing coloring agents such as pigments and dyes with wax is applied. It is manufactured by coating.

When a conventional thermal transfer sheet is used to print on a transfer paper, the ink layer comes into direct contact with the transfer paper surface, and the friction between the two often causes scumming in non-print areas.

In addition, in the N-times mode method, if the conveyance speed of the transfer material is N, the conveyance speed of the thermal transfer sheet is N', and NUN', the printing distance is N, but the consumption distance of the thermal transfer 7f sheet is N. ′, there is an advantage in that the amount of thermal transfer sheet consumed relative to the printing distance can be saved, or because the transfer material and the thermal transfer sheet are constantly moving relative to each other and are rubbed, the printed characters are not rubbed. The letters are smudged,
In addition, there are problems in that the print becomes stringy, the print density is low, and the print quality is poor.

The present invention has been made in consideration of the above-mentioned circumstances,
The purpose is to provide a thermal transfer sheet that does not cause scumming or stringiness even when thermal transfer is performed using the N-times mode method, and can provide clear prints.

(Means for solving problems) The above objects are achieved by the present invention as described below.

That is, the present invention provides a thermal transfer sheet in which a heat-melting ink layer and a surface layer are formed on one side of a base film, wherein the surface layer has a heat-resistant network structure. (Function) By forming a heat-resistant net on the heat-melting ink layer, it is possible to solve the problem of background smearing on the rolled material and stringy printing even in the N-time mode method. be done.

(Preferred Embodiments) Next, the present invention will be explained in more detail with reference to preferred embodiments.

The thermal transfer sheet of the present invention has a heat-melting ink layer formed on one surface of a base film, and a network-structured surface layer formed thereon.

As the base film used in the present invention, the same base film used in conventional thermal transfer sheets can be used as is, and other films can also be used, and there are no particular limitations.

Specific examples of preferred base films include polyester, polypropylene, cellophane, polycarbonate, cellulose acetate, polyethylene, polyvinyl chloride,
Polystyrene, nylon, polyimide, polyvinylidene chloride, polyvinyl alcohol, fluororesin, chlorinated rubber,
Examples include plastics such as ionomers, papers such as condenser paper and paraffin paper, nonwoven fabrics, and base films made of composites of these materials.

The thickness of this base film can be changed as appropriate depending on the material so that its strength and thermal conductivity are appropriate, but the thickness is preferably, for example, 2 to 25 μm.
It is.

The heat-melting ink layer formed on the base film comprises a colorant and a vehicle, and may further contain various additives as necessary.

The coloring agent is preferably an organic or inorganic pigment or dye that has good properties as a recording material, for example, one that has sufficient color density and does not discolor or fade due to light, heat, temperature, etc.

Further, it may be a substance that is colorless when not heated but develops color when heated, or a substance that develops color when it comes into contact with something coated on the transfer target. In addition to the colorants forming cyan, magenta, yellow, and black, colorants of various other colors can also be used. It is generally preferred that these colorants be used in an amount of about 2 to 90% by weight in the ink.

The vehicle used includes wax as a main component, and mixtures of wax with drying oil, resin, mineral oil, cellulose, rubber derivatives, and the like.

Representative examples of wax include microcrystalline wax, carnauba wax, paraffin wax, and the like. Furthermore, Fischer-Tropsch wax, various low-molecular L1 polyethylenes, wood wax, beeswax, spermaceti wax, ipotal wax, wool wax, shellac wax, candelilla wax, petrolactam, polyester wax, partially modified waxes, fatty acid esters, fatty acid amides, etc. Various waxes are used.

Methods for forming the ink layer on the base film include hot melt coating, hot lacquer coating, gravure coating, gravure reverse coating, roll coating, and many other methods.

In the present invention, a thermoplastic resin having a relatively low melting point may be further mixed into the ink layer to improve the adhesion of the formed ink layer to the transfer material. Examples of such thermoplastic resins include ethylene-vinyl acetate copolymer (EVA), ethylene-acrylic acid ester copolymer (EE8), polyethylene, polystyrene, polypropylene, polybutene, petroleum resin, vinyl chloride resin, Vinyl chloride-vinyl acetate copolymer, polyvinyl alcohol,
Vinylidene chloride resin, methacrylic resin, polyamide, polycarbonate, fluororesin, polyvinyl formal, polyvinyl butyral, acetyl cellulose, nitrocellulose, polyvinyl acetate, polyisobutylene, ethyl cellulose, polyurethane or polyacetal are used, especially as conventional heat-sensitive adhesives. It is preferred that those used have a relatively low softening point, for example a softening point of 50 to 80°C. The ratio of wax and thermoplastic resin used is 5 to 30 parts thermoplastic resin to 100 parts wax.
A weight ratio range of 0 is preferred.

The heat-resistant network structure formed on the surface of the ink layer is a network structure that does not melt due to heat during thermal transfer, and is formed from a heat-resistant resin material that has a higher melting point than the ink layer and is incompatible with the ink layer. Examples of such heat-resistant resins include water-soluble or hydrophilic resins, such as polyvinyl alcohol, partially saponified polyvinyl acetate, polyvinylpyrrolidone, polyacrylic acid, hydroxyethylcellulose, carboxymethylcellulose, water-soluble polyester, and water-soluble Examples include water-soluble polyamide and water-soluble polyurethane. Since these resins are water-soluble or hydrophilic, they are not crosslinked (of course crosslinking is also preferred) and are not compatible with highly hydrophobic waxes.

Another example of the heat resistant resin includes a crosslinkable or thermosetting heat resistant resin. For example, various heat resistant resins can be used, such as those conventionally used in the paint and printing ink fields. These heat-resistant resins can be cured by adding a crosslinking agent or by heating to make them sufficiently incompatible with wax during or after forming the porous layer. As the crosslinking agent, polyisocyanate, methylol compound, epoxy compound, polyamine, melamine resin, glyoxal resin, etc. are used.

A network structure can be formed by preparing a suitable ink using the above-mentioned resin, printing it in a network shape by gravure printing or the like on the heat-melting ink layer, and drying it.

Another preferred method is to form a layer by using the above resin as a binder and adding appropriate particles or short fibers therein, such as silica, alumina, talc, clay, diatomaceous earth, calcium carbonate, sulfuric acid, etc. Various inorganic pigments such as barium, plastic pigments made of resins such as epoxy resins, acrylic resins, urea resins, melamine resins, polyethylene and polypropylene, or J11 short fibers made of inorganic and organic materials such as those mentioned above, polyester, polyamide, This method uses ink containing fillers such as polyacrylonitrile and short fibers such as cotton.

When forming a layer from the above-mentioned filler and binder, if a large amount of binder is used, a network structure cannot be formed, but by reducing the amount of binder, a network structure with various porosity can be formed. I can do it. For example, although this varies to some extent depending on the particle size of the filler, network structures with various porosity can be created by adding 10 to 400 parts by volume, preferably 100 to 200 parts by volume, of the binder per 100 parts by volume of the particles. is formed. Of course, the ink containing the filler may be printed in a mesh shape by gravure printing or the like to form a network structure.

The porosity of the network structure as described above ranges from about 1% to 9% in terms of area ratio.
Although it can be formed arbitrarily up to about 9%, in the present invention, l
It is preferable to have a porosity of about 0 to 80%. If the porosity is less than the above range, the amount of ink discharged during thermal transfer will be small, while if the porosity exceeds the above range, the net
The structure itself lacks strength and may break during thermal transfer, which is undesirable.

In the present invention, the thickness of this layer is set so that the net structure formed as described above does not lack sensitivity even when the printing energy is low as in a high-speed printer.
Preferably it is 0.1 μm or more and less than 5 μm. If the thickness is less than 0.1 μm, there is a risk that the transfer paper and the ink layer will rub against each other, resulting in scumming. The network structure is substantially uncolored, and may be colored white by adding an extender pigment of Am or a white pigment.

When a heat-resistant material is used for the base film, it is preferable to provide a layer on the surface in contact with the thermal head to prevent sticking of the thermal head. The basic components of the anti-sticking +h layer include a heat-resistant resin and a substance that functions as a heat release agent or a lubricant. Heat-resistant resins include synthetic resins with a glass transition point of 60°C or higher, thermoplastic resins having OH groups or COOH groups, and compounds containing two or more amino groups, or diisocyanates, or diisocyanates added to 1 and a little. It is preferable to use a material that undergoes crosslinking and curing. Thermal mold release agents or lubricants include those that melt when heated, such as waxes, amides, esters, and salts of higher fatty acids, and those that remain solid, such as fluororesin and inorganic substance powders. role) γ
There is always something.

By providing such a sticking layer, it is possible to perform thermal printing without causing sticking even on thermal transfer sheets based on heat-sensitive plastic films, and it is possible to print thermally without sticking, and to reduce the difficulty of cutting and processing of plastic films. Benefits such as ease of use can be taken advantage of.

Since it goes without saying that the present invention can be applied to thermal transfer sheets for color printing, multicolor thermal transfer sheets are also included within the scope of the present invention. Further, as a thermal transfer printer, it can be applied to either a line or serial type.

(Effects) According to the present invention as described above, by forming a network structure on the heat-fusible ink layer, the background smudge on the transfer material and the stringy print phenomenon can be solved even in the N-times mote method. Ta.

That is, due to the presence of the network structure on the ink layer, even if the transfer material and the thermal transfer sheet are rubbed during thermal transfer, the transfer material will not be contaminated because the network structure is colorless or white.

Then, when sufficient heat is supplied from the thermal head (
Since molten ink is ejected from the network structure only during printing, clear printing without background smearing is possible. Furthermore, by increasing the porosity of the porous layer, the print density will not decrease even if thermal transfer is performed in the N-fold mode.

(Example) Hereinafter, the present invention will be explained in more detail with reference to Examples.

In the text, parts or percentages are based on weight unless otherwise specified.

Example I A polyethylene terephthalate film with a height of 3.5 μm was used as a base film, and on one side thereof, a heat-melting ink layer and a net with the following composition and a “structural material” were coated and dried by the means indicated respectively. A thermal transfer sheet of the present invention was obtained.

Kaikou adaptation Enoma Yu Carbon Black (Diablack G, manufactured by Mitsubishi Kasei)
15 parts ethylene/vinyl acetate copolymer (V, V Eighturex 31O1 manufactured by Mitsui Polychemicals) 8 parts paraffin wax (paraffin 1
(5 leaves, 11 pieces made of rust wax) 50 parts carnauba wax 25 parts Attritor was kneaded at 120°C for 6 hours, and 5g was mixed by hot melt roll coating at an ink temperature of 120°C.
/rn'' (dry state).

Thermosetting acrylic resin 50 parts Crosslinking agent
1 part catalyst
0.1 part solvent
Mesh printing was performed at a ratio of Ig/m'' using a 160-part gravure method, dried at 60° C. for 1 hour, and further aged at 50° C. for 24 hours. The porosity of this layer was 76% in terms of area ratio.

Thermal transfer printing was performed using the thermal transfer sheet described in 1- above, using high-quality paper as the transfer paper, and using a commercially available thermal head. When the energy of the thermal head is 0.7 W/dot, the conveying speed of the transfer paper (N) is 400 m/sec, and the conveying speed of the thermal transfer sheet (N') is 20 cm/sec, N/N'=
When high-speed printing was performed at N times mode of 2, high-quality printing was achieved without background smearing or stringy printing.

Example 2 A thermal transfer sheet of the present invention was obtained in the same manner as in Example 1 except that the same base film as in Example 1 was used and the materials having the following composition were used.

42 minute carbon black (dia black G, manufactured by Mitsubishi Kasei)
15 parts ethylene/vinyl acetate copolymer (14V Hachiflex 31O1 manufactured by Mitsui Polychemicals) EBIS paraffin wax (paraffin 15 leaves, manufactured by Nippon Seiro) 5
0 parts carnauba wax 25 parts Using an attritor, the mixture was kneaded at 120°C for 6 hours, and then mixed with an ink temperature of 120°C using a hot melt roll coating method.
．． 11i L/m was applied at a rate of 5 g/m'' (dry state).

Shindankaku L Plastic pigment (particle size: approx. 3.5 μm, epoxy resin particles) 50 parts Reactive polyester resin 15 parts Crosslinking agent
1 part catalyst 0.1 part solvent 160 parts Coated to a dry thickness of 4 μm using a gravure coater, dried at 60° C. for 1 hour, and further aged at 50° C. for 24 hours. The porosity of this layer was 68% in area ratio.

This transfer sheet also showed good transfer performance as in Example 1.

Example 3 A thermal transfer sheet of the present invention was obtained in the same manner as in Example 1 except that the same base film as in Example 1 was used and the materials having the following composition were used.

Easy-to-use carbon black (dia black G, manufactured by Mitsubishi Kasei)
15 parts ethylene/vinyl acetate copolymer (EVA Flex 31O1 manufactured by Mitsui Polychemicals) 8 parts paraffin wax (paraffin 15
0F, manufactured by Nippon Seiro) 50 parts carnauba wax 25 parts Attritor was kneaded at 120°C for 6 hours, and the ink temperature was 8.0° by hot melt roll coating at 120°C.
g/m'' (dry state).

Aim and Structure L Polyester short fiber (diameter 0.5 μm, length 10 μm)
50 parts epoxy resin
20 parts crosslinking agent
1 part catalyst 0.1 part solvent 160 parts It was coated using a gravure coater to a dry thickness of 2 μm, dried at 60° C. for 1 hour, and further aged at 50° C. for 24 hours. The porosity of this layer was 70% in area ratio.

The transfer sheet of this example also exhibited good transfer performance without background stains.

Example 4 A polyethylene terephthalate film with a thickness of 6 μm was used as a base film, and hot-melt inks and network structure inks of each color of yellow (Y), magenta (M), cyan (C), and black (B) were used. In the same manner as in Example 1, a thermal transfer sheet of the present invention was prepared as IB7.

Yukyo Yuryu E2A light pigment (yellow, magenta, cyan or black pigment). 4 parts ethylene/vinyl acetate conjugate sumitate K (Nie 10, produced by Sumitomo Chemical Co., Ltd.) 7.5 parts oxidized paraffin ester composite compound (amide polymer T-820, produced by Denka Polymer) 12
．． 5 parts paraffin wax (paraffin 5P-0145, "1
Made of genuine wax) 15 parts Microcrystalline wax (HIMIC 2065, Nihon Kei! l
manufactured by fi) 10 parts isopropanol
5 parts xylene
46 parts Yellow, magenta, cyan, and black were printed in the order of surface sequentially by a gravure printing method using the above four-color ink compositions. The coating weight at that time was 6g/m
' (when dry).

The acrylic ultraviolet curable paint was printed with a mesh at a rate of Ig/m'' using a gravure printing method and photocured.The porosity of this layer was 60% in terms of area ratio.

When the thermal transfer sheet of the present invention prepared by the above process was used to print with a color thermal printer in N-times mode with N/N' = 1.7, there was no background smear caused by rubbing the paper and film. There wasn't.

Patent applicant: Dai Nippon Printing Co., Ltd.

Claims (3)

[Claims] (1) A thermal transfer sheet comprising a heat-melting ink layer and a surface layer formed on one side of a base film, wherein the surface layer has a heat-resistant network structure. (2) Thermal transfer according to claim 1, which is used in a thermal transfer method in which the conveying speed of the transferred material is higher than the conveying speed of the thermal transfer sheet when the thermal transfer sheet and the transferred material are overlapped and thermal transfer is performed with a thermal head. sheet. (3) The thermal transfer sheet according to claim 1, wherein the network structure is formed from a crosslinkable resin.