JPH0416389A - Multiple times printing thermal transfer sheet - Google Patents

Abstract

PURPOSE:To prevent printing density from decreasing in multiple times printing by a method wherein a printing transfer sheet is formed by laminating a porous surface layer consisting of ionizing radiation setting resin on a thermal fusible ink layer provided to one face of a substrate film. CONSTITUTION:Thermal fusible ink layer forming ink is prepared by having a coloring agent and a vehicle as main components and by mixing heat conductive substance and others therein, and this ink is applied to one face of a substrate film by a hot melt coat method to form a thermal fusible ink layer. Separately, monomer or the like having an addition polymerizing double bond is added to polyurethane resin or the like, which are dissolved or dispersed in an organic solvent to prepare ionizing radiation setting resin solution. This resin solution is applied onto abovementioned thermal fusible ink layer, and the coated layer is dried to form a required porous layer. Thereafter, the porous layer is irradiated by ionizing radiations of electron beams or the like, and is hardened by crosslinking to obtain the subject many times printing thermal transfer sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to improvements in thermal transfer sheets, and more particularly to a novel thermal transfer sheet capable of printing multiple times with the same thermal transfer sheet.

(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/
A heat-melting ink layer made by mixing wax with colorants such as pigments and dyes, using paper such as capacitor paper or paraffin paper with a thickness of 0 to 20 μm, or plastic film such as polyester or cellophane with a thickness of 3 to 20 μm. It is manufactured by applying a coating.

When printing on transfer paper using these conventional thermal transfer sheets, the entire ink layer of the printed area is transferred in one printing, so it is impossible to print on the same spot on the thermal transfer sheet again. Therefore, there is a problem in that a thermal transfer sheet that is approximately the same length as the length of printing is consumed, and the base film for that amount cannot be reused, making it extremely uneconomical.

As a method to solve such problems, a method is known in which a porous layer is formed on the base material and the porous layer is impregnated with hot-melt ink. There is a limit to the amount of ink that can be impregnated into the ink, and there is a problem that the printing a degree rapidly decreases as the number of printings increases. or,
Another method is to form a porous surface layer on the surface of the fusible ink layer, but in this method, the porous surface layer must be formed extremely thin, and the porous surface layer It lacks strength and cannot withstand repeated printing.Additionally, one possible way to increase the strength is to use thermosetting resin, but in reality, the ink layer melts due to thermosetting. It is difficult to hire.

Therefore, it is an object of the present invention to provide a highly practical multi-printing thermal transfer sheet that can be printed many times and the print density does not drop sharply with the number of printings.

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

That is, the present invention provides a multi-print thermal transfer sheet, characterized in that a heat-melting ink layer is provided on one side of a base film, and a porous surface layer made of an ionizing radiation-curable resin is formed thereon. It is.

(Function) By forming a porous surface layer from an electronic hardening resin on the surface of the meltable ink layer, an extremely strong and thin layer can be formed without requiring high temperatures to form the layer.
High-quality printing is possible without destroying the surface layer even after printing is repeated many times.

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

The base film used in the present invention is not particularly limited, and the same base film used in conventional thermal transfer sheets can be used as is, and other films can also be used.

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.

In the present invention, a heat-melting ink layer is formed on the surface of the base film using an ink containing necessary materials.

The ink for forming the hot-melt ink layer used in the present invention consists of a colorant and a vehicle as main components, and may further contain various additives as necessary. The colorant is preferably an organic or inorganic pigment or dye that has good properties as a recording material, such as one that has sufficient color density and does not discolor due to light, heat, temperature, etc. . Alternatively, 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 colorants that form cyan, magenta, yellow, and black,
Colorants of various other colors can also be used.

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 microcrystanone wax, carnauba wax, paraffin wax, and the like. In addition, various waxes such as Fischer-Tropsch wax, various low molecular weight polyethylenes, wood wax, beeswax, spermaceti wax, privet wax, wool wax, shellac wax, candelilla wax, petrolactam, assorted waxes, fatty acid esters, fatty acid amides, etc. used.

Further, in order to provide the hot-melt ink layer with good thermal conductivity and melt transferability, a thermally conductive substance can be blended into the hot-melt ink. Examples of such substances include carbonaceous substances such as carbon black, aluminum, copper, tin oxide, and molybdenum disulfide.

As a method for forming an ink layer made of the above-mentioned components on the base film, conventionally known methods such as hot melt coating, hot lacquer coating, gravure coating, gravure reverse coating, roll coating, and many others may be used.

The thickness of the ink layer formed as described above is approximately 2 μm to 30 μm.
The thickness of the ink layer varies depending on the number of printings required, but for example, for printing 3 to 5 times, the thickness of the ink layer is approximately 6μm.
A range of ~20 um is preferred.

The porous layer formed on one surface of the base film is formed from an ionizing radiation-curable resin. A particularly preferred ionizing radiation-curable resin is an ionizing radiation-curable polyurethane resin, which is a polyurethane resin or its prepolymer combined with or added with a monomer, oligomer, or polymer having an addition-polymerizable double bond. It is.

Polyurethane resin itself is well known and can be obtained from the market and used easily. Further, the above-mentioned monomers, oligomers, polymers, etc. are known as constituent components of ionizing radiation-curable resins, and can be similarly obtained and used from the market.

If a coating film is formed by a conventional method using the above-mentioned ionizing radiation-curable polyurethane resin, a non-porous film is normally formed, but in the present invention, the ionizing radiation-curable polyurethane resin is submerged in oil. Used as a water (Wlo) emulsion to form a porous surface layer.

Such an emulsion is produced by dissolving or dispersing the ionizing radiation-curable polyurethane resin in an organic solvent with a relatively low boiling point and limited mutual solubility with water, and adding an appropriate surfactant to this solution or dispersion. This is made by emulsifying an appropriate amount of water using an emulsifying agent. This is applied to the surface of the ink layer to an appropriate thickness, and this coating layer is dried at an appropriate temperature to first evaporate the organic solvent. The ionizing radiation-curable polyurethane resin is gelatinized, water is then evaporated to form a desired porous layer, and then ionizing radiation such as electron beams or ultraviolet rays is irradiated to crosslink and cure.

In addition, when forming a porous layer, a suitable crosslinking agent such as polyisocyanate, methylol compound, epoxy compound,
By using a known crosslinking agent such as polyamine, melamine resin, cryoxal resin, etc., a porous layer that is incompatible with heat-melting ink and has excellent heat resistance is formed. In addition, one or more suitable additives may be added depending on the purpose.

A porous layer is formed by coating the emulsion as described above on the surface of the ink layer and performing a drying gelation treatment and a crosslinking hardening treatment, but the porosity of such a porous layer ranges from about /0% to It can be formed arbitrarily up to about 95%, and in the present invention, it can be formed up to 30%.
A layer with a porosity of about 80% is good, especially a layer with a porosity of 40 to 7
0% is optimal. If the porosity is less than 30%, the amount of ink passing through the porous layer will be small, resulting in insufficient print density. On the other hand, if the porosity exceeds 80%, the strength of the porous layer itself will be insufficient, which is not preferable. Also, the thickness of the porous layer is 0.5
The thickness is preferably about 5 μm, and is determined based on the porosity, the required print density, the number of times of printing, and the printing energy of the printer.

When a heat-sensitive 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 anti-sticking layer basically includes 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, or thermoplastic resins having OH or COOH groups, and a compound having two or more amino groups, or diisocyanate or triisocyanate added to slightly crosslink and cure. Preferably, those that cause

Thermal mold release agents or lubricants include those that melt when heated, such as waxes and amides, esters, and salts of higher fatty acids, and those that act as solids, such as fluororesin and inorganic substance powders. There is. By providing such an anti-sticking layer, it is possible to perform thermal printing without causing sticking even on thermal transfer sheets made of heat-sensitive plastic films as a base material. You can take advantage of the advantages 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.

(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 1 A polyethylene terephthalate film with a thickness of 6.0 μm was used as a base film, and a heat-melting ink consisting of the following components was kneaded on one side at 120 ° C. for 6 hours.
7g/rr? by hot melt roll coating method with ink temperature of 120℃. (dry state) to form an ink layer.

Fake Carbon Black (Diamond Black G, manufactured by Mitsubishi Kasei)
15 parts ethylene/vinyl acetate copolymer (EVA Flex 3/O, manufactured by Mitsui Polychemicals) 8 parts paraffin wax (paraffin 15
0F, manufactured by Hiki Seiro) 50 parts Carnauba wax 25 parts Next, apply the following emulsion at a rate of 3 μm in thickness when rolled, and heat at 50°C.
The gel was dried for 5 minutes at 75° C. and for 0 minutes at 75° C., and then cross-linked and cured by irradiation with ultraviolet rays to form a porous layer with a porosity of about 70%, thereby producing a multiple thermal transfer sheet of the present invention.

Methyl ethyl ketone containing 20% polyether polyurethane resin and 5% neopentyl glycol diacrylate M/0 parts sensitizer (Irgakinia 65)
1) 3 parts W/O type emulsifier
5 parts methyl ethyl ketone
20 parts toluene 20 parts water 8
0 copies Using the above thermal transfer sheet, using high-quality paper as the transfer paper, and using a commercially available thermal head to perform thermal transfer on the same thermal transfer sheet 5 times, the print density from the second time onwards was the same as the first time. If it is /O0, /O0 (second time)
, 98 (third time), 90 (fourth time), and 87 (fifth time), and there was only a slight decrease in print density.

Example 2 A thermal transfer sheet of the present invention was obtained using the same base film as in Example 1, using the following ink composition and emulsion, and curing with an electron beam, and in the same manner as in Example 1. Ta.

LZE” Yisheng Carbon Black (Diablack G, manufactured by Mitsubishi Kasei)
15 parts ethylene/vinyl acetate copolymer (EVA Flex 31O1 manufactured by Mitsui Polychemicals) 8 parts paraffin wax (paraffin 150
F, manufactured by Hiki Seiro) 50 parts Carnauba wax 25 parts Coating amount 8g/
Methyl ethyl ketone solution containing 30% polyester polyurethane resin and 3% pentaerythritol triacrylate / 0 parts W/O type emulsifier
5 part dioxane
/O part toluene /O part xylene 20 parts water
60 parts Thickness 0.5μm Porosity 70% Number of prints 12345 Print density /O0 97 95 89 8g (
Effect) According to this hardening method as described above, by forming a porous surface layer from ionizing radiation curable resin on the surface of the fusible ink layer, an extremely strong and thin layer can be created without requiring high temperatures for layer formation. Therefore, even if printing is repeated many times, the surface layer is not destroyed and high quality printing is possible.

1 other person

Claims (3)

[Claims] (1) A multi-print thermal transfer sheet, characterized in that a heat-melt ink layer is provided on one side of a base film, and a porous surface layer made of an ionizing radiation-curable resin is formed thereon. (2) The multi-print thermal transfer sheet according to claim 1, wherein the porous layer has a porosity of 30 to 80%. (3) The multiple printing thermal transfer sheet according to claim 1, wherein the porous surface layer is formed from a W/O type ionizing radiation curable resin polyurethane resin emulsion.