JPH01218885A - Thermal transfer sheet - Google Patents

Abstract

PURPOSE:To ensure that open face characters are not left on a used thermal transfer sheet after transfer of an ink layer and confidential information is not leaked from the used thermal transfer sheet, by providing a non-transferable colored layer, in a thermal transfer sheet comprising a heat fusible ink layer on one side of a base film. CONSTITUTION:A non-transferable colored layer (a) is provided, in a thermal transfer sheet comprising a heat fusible ink layer 2 on one side of a base film 1. The colored layer (a) must not be transferred onto a transfer recording material together with the ink layer 2 at the time of transferring. The hue of the colored layer (a) is preferably the same as that of the ink layer. Since the ink layers of thermal transfer sheets are black in most cases, the colored layer (a) is generally black.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a thermal transfer sheet, and more specifically, to a new thermal transfer sheet that is free from the risk of leaking confidential information from a used thermal transfer sheet.

(Prior Art) Conventionally, when printing output prints from computers or word processors by a thermal transfer method, a thermal transfer sheet having 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 for output printing on transfer paper, the ink layer is transferred to the transfer paper surface, and the used thermal transfer sheet is discarded in the form of white characters.

(Problem to be solved by the invention) In the above conventional method, there is no problem of confidentiality leakage when creating documents that are not particularly confidential, such as general documents, but for example, contract documents, patent documents δ, know-how documents, etc. When creating highly confidential documents such as documents, the content of those documents is recorded as white characters on used thermal transfer sheets, so great care must be taken when disposing of them. be.

The present invention was made against the background of two circumstances, and its purpose is to provide a thermal transfer sheet that is free from the risk of leaking confidential information from a used thermal transfer sheet.

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

That is, the present invention is a thermal transfer sheet having a heat-fusible ink layer provided on one side of a base film, which is characterized in that a non-transferable colored layer is provided.

(Function) By providing a non-transferable colored layer on the thermal transfer sheet, white characters will not appear on the used thermal transfer sheet even if the ink layer is transferred, and there is a risk that confidential information will be leaked from the used thermal transfer sheet. does not occur.

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

1 to 4 are diagrams schematically showing a cross section of a part of the thermal transfer sheet of the present invention.

The thermal transfer sheet of the present invention has a base film l as shown in the figure.
The thermal transfer sheet is characterized in that a non-transferable colored layer a is provided on one side of the thermal transfer sheet, in which a heat-melting ink layer 2 is provided.
This is an example in which the film itself is colored, and the example in FIG. 2 is an example in which the heat-resistant layer 3 formed on the surface of the base film 1 is colored,
The example in FIG. 3 is an example in which the matte layer 4 provided at the interface between the base film 1 and the ink layer 2 is colored, and the example in FIG. Colored layer a between
was formed.

In the above, the formed colored layer a must not be transferred to the transfer material together with the ink layer 2 during thermal transfer, and the hue of the colored layer a is different from that when the ink layer is black. If the ink layer is black, it is preferably the same hue as the ink layer, such as red.Since the ink layer of a thermal transfer sheet is often black, it is preferable that the colored layer a is black. is more common.

As the base film 1 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 1 to 25 μm, for example.
It is.

The base film used in the example shown in Figure 1 may be a base film as described above that has been colored by printing, coating, dyeing, undiluted solution coloring, etc. The density of the coloring is determined by the transfer of the ink layer. Preferably, the density is such that the transferred portion is unreadable to the naked eye after being applied.

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

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.

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, various waxes are used, such as Fischer-Tropsch wax, various low molecular weight polyethylenes, wood wax, beeswax, spermaceti wax, privet wax, wool wax, shellac wax, candelilla wax, petrolatum, assorted waxes, fatty acid esters, and fatty acid amides. It will be done.

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

In addition to hot melt coating, methods for forming a hot melt ink layer directly or indirectly on a base film include:
Examples include hot lacquer coating, gravure coating, gravure reverse coating, roll coating, and many other methods of applying the ink. The thickness of the ink layer formed should be determined to balance the required density and thermal sensitivity, and should be in the range of 0.1 to 3.0 μm,
Preferably it is in the range of 1 to 20 tim.

In the present invention, a surface layer can be further formed on the ink layer. The speaker layer forms a part of the transfer film and forms the surface in contact with the transfer paper, sealing the printed area of the transfer paper during transfer, preventing background smearing, and preventing the ink layer from forming. It has the function of improving adhesion to the transfer paper.

The wax used to form the surface layer is the same as the wax used in the hot-melt ink layer described above.

The surface layer made of the wax is formed by coating and cooling a wax melt, coating and drying an organic solvent solution containing the wax, coating and drying an aqueous dispersion containing particles of the wax, and the like.

The coating of the surface layer, as well as the formation of the ink layer, can also be done by various techniques. In the present invention, the thickness of this layer is preferably 0.5 mm to prevent insufficient sensitivity even when printing energy is low as in high-speed printers.
It is 1 μm or more and less than 5 μm.

It is recommended that an appropriate amount of extender pigment be added to the surface layer. This is because bleeding and trailing of printed characters can be better prevented.

Excessively large particle sizes of extender pigments are inappropriate.

Suitable as extender pigments are inorganic fillers such as silica, talc, calcium carbonate, precipitated barium sulphate, alumina, titanium white, clay, magnesium carbonate, carbon black or tin oxide.

If the amount of extender pigment is small, the effect will be poor.
Since the coated material may easily fall off from the base film, it is preferable to add it in a range of 0.1 to 60% by weight.

As described above, the surface layer may or may not contain a colorant, if necessary. If a coloring agent is used, it overlaps with the coloring agent in the hot-fusible ink layer, giving a record of 1-minute density; if only a colorless vehicle is used, the receiving paper and the hot-fusible ink layer rub against each other, resulting in a dark background. Prevents stains from forming.

When a heat-sensitive material is used for the base film, it is preferable to provide a heat-resistant layer on the surface in contact with the thermal head to prevent sticking of the thermal head.

The basic components of the heat-resistant layer are a heat-resistant resin and a substance that functions as a thermal mold release agent or a lubricant. As a heat-resistant resin, a compound having two or more amino groups or a diisocyanate or triisocyanate is added to a synthetic resin having a glass transition point of 60° C. or higher or a thermoplastic resin having a hydroxyl group or a carboxyl group to form a single crosslinker. Those that have been cured are preferred. 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 remain solid, such as fluororesin and inorganic substance powders. There is.

By providing such a heat-resistant layer, thermal printing is possible without sticking even on thermal transfer sheets made of heat-sensitive plastic films as a base material. You can take advantage of advantages such as

In the present invention, the heat transfer sheet of the present invention can be obtained by coloring the heat-resistant layer when forming the heat-resistant layer. The coloring of the heat-resistant layer is done when forming the heat-resistant layer.
A coloring agent of an appropriate hue may be added.

Thermal transfer images generally have glossy and beautiful prints, but the documents may become difficult to read, so matte prints are sometimes desirable. In such a case, for example, as proposed by the applicant (Japanese Patent Application No. 58-208306),
The base film is coated with an inorganic pigment such as silica, calcium carbonate, etc. dispersed in a suitable solvent to form a matte layer, and then a heat-melting ink layer is coated to form a thermal transfer sheet. It's good to do that. Alternatively, the base film itself may be matted and used (this is also the technique of Japanese Patent Application No. 1983-208307 proposed by the applicant).

In the present invention, the thermal transfer sheet of the present invention can be obtained by coloring the matte layer when forming the matte layer. The matte layer may be colored by adding a coloring agent of an appropriate hue when forming the matte layer.

The above is a conventionally known thermal transfer sheet in which the base film, heat-resistant layer, or matte layer is colored, but it is sufficient that at least one of these layers is colored; Good too. Furthermore, the present invention is not limited to the coloring of the above layer, and for example, another colored layer a may be formed as shown in FIG.

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.

(Effects) According to the present invention as described above, by providing a non-transferable colored layer on a thermal transfer sheet, even if an ink layer is transferred, white characters will not appear on a used thermal transfer sheet, making it easy to use. There is no risk that confidential information will be leaked from the already used thermal transfer sheet.

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

In addition, unless otherwise specified, parts or % in the text are ff.
1ffi standard.

Example 1 A 3.5 μm thick polyethylene terephthalate film colored with a black stock solution was used as a base film, and 3.5 g/rn” ( The thermal transfer sheet of the present invention was obtained by coating and cooling on a base in a dry state.

"Sad Enemy Enoma" Carbon Black (Dia Black G, manufactured by Sanro Kasei)
15 parts ethylene/vinyl acetate copolymer (EVA Flex 310, manufactured by Mitsui Polychemicals) 8 parts paraffin wax (paraffin 1
50F, made by Nippon Seiro) 50
Part: Carnauba wax: 25 parts Using the above thermal transfer sheet, high-quality paper was used as the transfer paper, and thermal transfer printing was performed using a commercially available thermal head. When I looked at the used thermal transfer sheet, I couldn't find any white characters.

Example 2 A polyethylene terephthalate film with a thickness of 3.5 μm was used as a base film, and 0.7 g of a black ink for forming a heat-resistant layer having the following composition was applied to one side of the base film by gravure coating.
A black heat-resistant layer was formed by coating and drying to a thickness of /m'' (dry state).Next, a heat-melt ink having the following composition was coated at a rate of 3.5g/rn' by a hot melt coating method and cooled. A thermal transfer sheet of the present invention was obtained.

Salmon shin ■Goshikii 2 ma Vinylidene fluoride resin (Kynar SL, manufactured by Pennwalt) 9 parts Teflon powder (
Hostaflon TF9205, manufactured by Hoechst)
8 parts acrylic polyol (TP-500
0, manufactured by Denka Polymer Co., Ltd.)
9 parts grafted polymer wax (Marked C-113,
Manufactured by Adeka Argus Co., Ltd.) Two-part hardening agent (
Takenate D-11ON, manufactured by Narita Pharmaceutical Industries)
10 parts Carbon black (Geast S, Tokai Electrode Source) 8 parts Methyl ethyl ketone 40 parts Toluene
Part 14 Easy concealment Enoma eyebrow carbon black (Diablack G, manufactured by Mitsubishi Kasei)
15 parts ethylene/vinyl acetate copolymer (EV^Flex 31O1 manufactured by Mitsui Polychemicals) 8 parts paraffin wax (paraffin 1
5 leaves, made by Japanese wax) SO
Part: Carnauba wax: 25 parts Using the above thermal transfer sheet, high-quality paper was used as the transfer paper, and thermal transfer printing was performed using a commercially available thermal head. When the used thermal transfer sheet was observed, no white characters were observed.

Example 3 A polyethylene terephthalate film with a thickness of 3.5 μm was used as a base film, and a matte layer was formed on one side of the base film using a black ink having the following composition by a gravure coating method.
/rn'' (dry state) and dried to form a black matte layer.Next, hot-melt ink having the following composition was applied at a rate of 3.5 g/rn' by hot melt coating and cooled. A thermal transfer sheet of the present invention was obtained.

Benzoguanamine resin (Epostor S, Nippon Shokubai Kajigen) 10 parts fluorinated carbon (Mold Vic F-57, manufactured by Accel Plastic Co., Ltd.)
8 parts carbon black (GEST S, Tokai Electrode Gen) 10 parts acrylic polyol (TP-5000, manufactured by Denka Polymer Co., Ltd.) 8 parts curing agent (Takenate D-11ON, manufactured by Narita Pharmaceutical Co., Ltd.)
10 parts methyl ethyl ketone
30 parts toluene, 24 parts, carbon black (Diablack G, manufactured by Mitsubishi Kasei)
15 parts ethylene/vinyl acetate copolymer (EVA Flex 310, manufactured by Mitsui Polychemicals) 8 parts paraffin wax (paraffin 15
50 parts carnauba wax 25 parts Thermal transfer printing was carried out using the above thermal transfer sheet and a commercially available thermal head using high quality paper as the transfer paper. When the used thermal transfer sheet was observed, the text could not be easily read from the print marks. .

Example 4 A polyethylene terephthalate film with a thickness of 6 μm was used as a base film, and yellow, red, blue, and black paints having the following composition were sequentially applied side by side to a dry film thickness of approximately 3 g/rn” (when dry). Colored layers of four colors were formed.Additionally, yellow (Y) having the following composition was added to match the hue of these colored layers.
), magenta (M), cyan (C) and black (B)
An ink layer was formed by sequential printing using a hot-melt ink composition of each color using a gravure printing method.

The coating weight at that time was 1.5 g/rn” (dry)
Met.

Goshiki Ego coloring pigment 10 parts Acrylic polyol (Thermolac V-230, manufactured by Soken Chemical Co., Ltd.)
20 parts methyl methacrylate resin (Thermolact 116^, manufactured by Soken Chemical)
10 parts isocyanate (Takenate D-11ON
, manufactured by Narita Pharmaceutical Industries) 10 parts methyl ethyl ketone 30 parts toluene
20 parts Yushin female ennoe notification pigment (yellow, magenta, cyan, or black pigment), 4 parts ethylene/vinyl acetate copolymer (G-10 in Sumitate, manufactured by Takuhō Kagaku Kogyo)
7.5 parts oxidized paraffin ester complex compound (
Amide Polymer T-820, manufactured by Denka Polymer) 12.
5 parts Paraffin wax (Paraffin 5P-0145, manufactured by Nippon Seiro) 15 parts Using the above thermal transfer sheet and high-quality paper as the transfer paper, full-color thermal transfer printing was performed using a commercially available thermal head. . When the used thermal transfer sheet was observed, no white characters were observed in any hue.

[Brief explanation of the drawing]

1 to 4 are diagrams schematically showing a cross section of a part of the thermal transfer sheet of the present invention. 1: Base film 2: Hot-melt ink layer 3: Heat-resistant layer 4: Matte layer a: Colored layer Patent applicant Dai Nippon Printing Co., Ltd.

Claims (6)

[Claims] (1) A thermal transfer sheet comprising a heat-melting ink layer provided on one side of a base film, characterized in that a non-transferable colored layer is provided. (2) The thermal transfer sheet according to claim (1), wherein the non-transferable colored layer has the same hue as the ink layer. (3) The non-transferable colored layer is black (
The thermal transfer sheet described in item 1). (4) The thermal transfer sheet according to claim (1), wherein the non-transferable colored layer is a colored base film. (5) The thermal transfer sheet according to claim (1), wherein the non-transferable colored layer is a heat-resistant layer provided on the surface of the base film. (6) The thermal transfer sheet according to claim (1), wherein the non-transferable colored layer is a matte layer provided between the base film and the ink layer.