JP3055800B2 - Thermal transfer sheet - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a thermal transfer sheet, and more particularly, to a novel thermal transfer sheet that does not cause leakage of confidential information from a used thermal transfer sheet.

(Prior Art) Conventionally, when an output print of a computer or a word processor is printed by a thermal transfer method, a thermal transfer sheet provided with a heat-fusible ink layer on one surface of a base film has been used.

This conventional thermal transfer sheet has a thickness as a base film.
Using a 10-20 μm thick paper such as condenser paper or paraffin paper or a 3-20 μm thick plastic film such as polyester or cellophane, a wax is mixed with a coloring agent such as a pigment or dye to form a hot-melt ink layer. It is manufactured by coating.

When output printing is performed on a transfer paper using a conventional thermal transfer sheet, the ink layer is transferred to the transfer paper surface, and the used thermal transfer sheet is discarded in a white character state.

(Problems to be Solved by the Invention) In the above-described conventional method, there is no problem of confidential leakage in the creation of a document having no confidentiality such as a general document.
For example, when creating highly confidential documents such as contract documents, patent documents, know-how documents, etc., since the contents of those documents are recorded as white characters on the used thermal transfer sheet, they must be discarded. Has the problem that sufficient attention is required.

As a method of solving the above-mentioned problems, there is a method of coloring the base film, etc., but the ink-drained characters can still be read due to the density difference between the portion where the ink has been removed and the portion which has not been removed, and sufficient confidentiality is maintained. Sex is not obtained.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a thermal transfer sheet which is free from leakage of confidential information from a used thermal transfer sheet.

(Means for Solving the Problems) The above object is achieved by the present invention described below. That is,
The present invention relates to a thermal transfer sheet having a heat-fusible ink layer provided on one surface of a base film via a mat layer, wherein the mat layer has the same hue as the ink layer and is provided in a pattern. A thermal transfer sheet characterized by the following.

(Function) By providing the mat layer in the same hue as the ink layer and in a pattern, even if the ink layer is transferred, the white characters of the used thermal transfer sheet cannot be read, and the used thermal transfer sheet There is no risk of leaking secrets.

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

As the substrate film used in the present invention, the same substrate film as used in the conventional thermal transfer sheet can be used as it is, and other materials can be used without any particular limitation.

Specific examples of preferred base film include, for example, polyester, polypropylene, cellophane, polycarbonate, cellulose acetate, polyethylene, polyvinyl chloride, polystyrene, nylon, polyimide, polyvinylidene chloride, polyvinyl alcohol, fluororesin, chloride rubber, ionomer, etc. Plastic, condenser paper,
There are papers such as paraffin paper, non-woven fabric, and the like, and a base film in which these are combined may be used.

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

In the present invention, a colored mat layer is formed in a pattern on one surface of the base film. This mat layer is, for example, a color pigment having the same hue as the ink layer on the base film, an inorganic pigment as a matting agent, for example, silica,
It is obtained by printing and forming a pattern by, for example, a gravure printing method using a mat layer forming ink in which calcium carbonate or the like is dispersed in an appropriate resin solution. The pattern may be any pattern such as a character, a symbol, a tint block, a straight line, and a curve. Further, the image may be an image (negative) in which the above pattern is inverted in black and white. The thickness of such a mat layer is preferably, for example, about 0.05 to 1.0 μm.

Further, as an example of the pattern, a large number of oblique lines having a certain width may be provided by the mat layer ink. In this case, unevenness occurs in the printed matter, or the gloss of the printed matter is partially changed. Therefore, a clear matte ink may be applied to the entire surface including the pattern to fill the irregularities. Further, these patterns may be provided on the surface of the base film opposite to the mat layer (on the heat-resistant layer side).

In the present invention, a hot-melt ink layer is formed on the surface of the mat layer. The hot-melt ink comprises a colorant and a vehicle, and may further contain various additives as necessary.

The hot-melt ink used in the present invention comprises a colorant and a vehicle, and may further contain various additives as necessary.

As the coloring agent, among organic or inorganic pigments or dyes, those having good characteristics as a recording material, for example, those having a sufficient coloring density and not discoloring by light, heat, temperature or the like are preferable. In addition, a substance which is colorless when not heated but develops a color when heated, or a substance which develops a color when it comes into contact with a substance applied to a transfer target body may be used. In addition to the colorants that form cyan, magenta, yellow, and black, other various colorants can also be used.

As the vehicle, a mixture of wax as a main component, and other components such as a wax and a derivative of a drying oil, a resin, a mineral oil, cellulose, and rubber is used.

Representative examples of the wax include microcrystalline wax, carnauba wax, and paraffin wax. Furthermore, various waxes such as Fischer-Tropsch wax, various low molecular weight polyethylene, wood wax, beeswax, spermaceti, Ibota wax, wool wax, shellac wax, candelilla wax, petrolactam, partially modified wax, fatty acid ester, fatty acid amide, etc. Used.
Further, a heat conductive substance can be added to the heat fusible ink in order to give the heat fusible ink layer good heat conductivity and melt transferability. Examples of this substance include carbonaceous substances such as carbon black, aluminum, copper, tin oxide, and molybdenum dioxide.

Examples of a method for forming an ink layer on the mat layer include a method of applying the ink by hot lacquer coating, gravure coating, gravure reverse coating, roll coating, and other various means, in addition to hot melt coating.

The thickness of the ink layer to be formed should be determined so that the required density and thermal sensitivity can be harmonized, and 0.1 to 30 μm
, Preferably in the range of 1 to 20 μm.

In the present invention, a surface layer can be further formed on the ink layer. The surface layer forms part of a transfer film,
It forms a surface in contact with the paper to be transferred, has a function of stopping the printed portion of the paper at the time of transfer, preventing background stains, and improving the adhesiveness of the ink layer to the paper to be transferred. The wax used to form the surface layer is the same as the wax used in the above-described hot-melt ink layer.

Also, when using a material weak to heat as the base film,
It is preferable to provide a heat-resistant lubricating layer on the surface in contact with the thermal head to improve the slipperiness of the thermal head and prevent sticking. The heat-resistant lubricating layer has a heat-resistant resin and a substance acting as a heat releasing agent or a lubricant as basic constituent components. By providing such a heat-resistant lubricating layer, thermal printing is possible without sticking even on a thermal transfer sheet based on a heat-sensitive plastic film. Advantages such as ease can be used.

Needless to say, the present invention can be applied to a thermal transfer sheet for color printing, and a multicolor thermal transfer sheet is also included in the scope of the present invention. Further, as a thermal transfer printer, it can be applied to either a line or a serial type.

(Examples) Hereinafter, the present invention will be described more specifically with reference to examples. In the following description, parts and% are based on weight unless otherwise specified.

Example 1 A polyethylene terephthalate film having a thickness of 3.5 μm was used as a base film, and on one surface thereof, a gravure roll engraved with a fine copy-forgery-inhibited pattern with an ink for forming a mat layer having the following composition was used. g / m
Printing ( ² ) (dry state) and drying were performed to form a patterned mat layer. Next, a heat-fusible ink material having the following composition was applied and cooled at a rate of 3.5 g / m ² (dry state) to obtain a thermal transfer sheet of the present invention.

Ink composition for mat layer formation CAP (482-05, manufactured by Kodak) 4.0 parts PET (UE3200, Tg65 ° C, manufactured by Unitika) 3.0 parts Colored carbon (Seast S, 66mμ, manufactured by Tokai Electrode) 8.0 parts Soybean lecithin (lecithin, Ajinomoto) 0.2 parts Crystalline cellulose (KC Floc W400, manufactured by Sanyo Kokusaku Pulp) 3.0 parts Solvent (MEK / toluene = 1/1) 81.8 parts Heat-meltable ink layer Carbon black (Diablack G, manufactured by Mitsubishi Kasei) 15 parts Ethylene / Vinyl acetate copolymer (EVA Flex 310,
8 parts Paraffin wax (Paraffin 150F, manufactured by Nippon Seiro) 50 parts Carnauba wax 25 parts Next, using the above thermal transfer sheet, using high quality paper as the paper to be transferred, and using a commercially available thermal head When thermal transfer printing was performed, it was difficult to read out white characters from the thermal transfer sheet after printing.

Example 2 A gravure printing method using a 3.5 μm-thick polyethylene terephthalate film as a substrate film, and using a gravure roll having fine wavy curves parallel to one side thereof with a mat layer forming ink having the following composition on one surface thereof By 0.
Printing and drying were performed at a rate of 3 g / m ² (dry state) to form a patterned mat layer. Next, a heat-fusible ink material having the following composition was applied and cooled at a rate of 3.5% g / m ² (dry state) to obtain a thermal transfer sheet of the present invention.

Ink composition for mat layer formation SAN (Sebian AD, manufactured by Daicel Chemical) 10.0 parts PET (TP220, Tg70 ° C, manufactured by Nippon Synthetic Chemical) 2.0 parts Potassium titanate (Tismo D, manufactured by Otsuka Chemical) 6.0 parts Conductive carbon (Ketjen) Black EC, manufactured by Lion Akzo) 1.0 part Release agent (Mold Vitz F57, manufactured by Axel Plastic) 1.0 part Solvent (MEK / toluene = 1/1) 80.0 parts Hot-melt ink layer Carbon black (Diablack G, manufactured by Mitsubishi Chemical) )
15 parts Ethylene / vinyl acetate copolymer (EVA Flex 310,
8 parts paraffin wax (paraffin 150F, manufactured by Nippon Seisaku)
50 parts Carnauba wax 25 parts Next, using the above thermal transfer sheet, high-quality paper as the paper to be transferred, and performing thermal transfer printing using a commercially available thermal head, the white characters on the thermal transfer sheet after printing are It was difficult to read.

Example 3 A 3.5 μm-thick polymethylene terephthalate film was used as a base film, and on one side thereof, 10 “DI” s per inch width were formed with a mat layer forming ink having the following composition.
Using a gravure roll having the letter “P”, printing and drying were performed at a rate of 4.0 g / m ² (dry state) by a gravure printing method to form a patterned mat layer. Next, a heat-fusible ink material having the following composition was applied and cooled at a rate of 3.5 g / m ² (dry state) to obtain a thermal transfer sheet of the present invention.

Ink composition for mat layer formation SAN (Sebian AD, manufactured by Daicel Chemical) 8.0 parts Potassium titanate (Tismo D, manufactured by Otsuka Chemical) 6.0 parts Carbon (Seast SO, 43 μm, manufactured by Tokai Electrode) 10.0 parts Soybean lecithin (lecithin, Ajinomoto) 0.2 parts Release agent (Mike FC 113, manufactured by Adeka Argus) 1.5 parts Solvent (MEK / toluene = 1/1) 74.3 parts Heat-meltable ink layer Carbon black (Diablack G, manufactured by Mitsubishi Kasei)
15 parts Ethylene / vinyl acetate copolymer (EVA Flex 310,
8 parts paraffin wax (paraffin 150F, manufactured by Nippon Seisaku)
50 parts Carnauba wax 25 parts Next, using the above thermal transfer sheet, high-quality paper as the paper to be transferred, and performing thermal transfer printing using a commercially available thermal head, the white characters on the thermal transfer sheet after printing are It was difficult to read.

(Effects) According to the present invention as described above, by providing the same hue as the ink layer and in a pattern, even if the ink layer is transferred, the white characters of the used thermal transfer sheet cannot be read, There is no danger of secrets leaking from the used thermal transfer sheet.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B41M 5/38-5/40

Claims (2)

(57) [Claims] 1. A thermal transfer sheet having a heat-fusible ink layer provided on one side of a base film via a mat layer, wherein the mat layer has the same hue as the ink layer and is provided in a pattern. A thermal transfer sheet characterized by the above-mentioned. 2. The thermal transfer sheet according to claim 1, wherein the ink layer and the mat layer are black.