JPH0494986A - Composite heat transfer sheet - Google Patents

Abstract

PURPOSE:To obtain a composite heat transfer sheet which is superior for both secret leakage preventive property, bondability and releasability, and eliminate resolving property of printing image and ground staining by forming a masking layer which masks an ink layer on at least one surface of a base film. CONSTITUTION:The title composite heat transfer sheet is a composite heat transfer sheet for which a heat transfer sheet A and a material to be transferred B are separatably adhered by an adhesive layer C, and a masking layer to mask an ink layer is formed on at least one surface of a base film. For the heat transfer sheet A, a ink layer 2 is formed on a base film 1, and a masking layer is formed on one side of the base film 1. Preferably, between the base film 1 and the ink layer 2, a mat layer 3 which is colored with the same hue as the ink layer, or a slip layer 4 which is colored in the same way is formed on the back surface of the base film, and these layers are made to have masking function also. Naturally, a masking layer may be provided separately from a mat layer or slip layer, an aluminum deposited film may be used as the base film, or the base film itself may be colored.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a composite thermal transfer sheet, and more particularly to a novel composite thermal transfer sheet in which a thermal transfer sheet and a transfer material such as paper are temporarily bonded in advance.

(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 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 printing on transfer paper using these conventional thermal transfer sheets, the thermal transfer sheet is supplied from a roll wrapped with the thermal transfer sheet, while a continuous or sheet transfer material is supplied, and both are placed on a platen. In this state, a thermal head applies heat from the back side of the thermal transfer sheet to melt and transfer the ink layer to form a desired image.

However, even if one attempts to use these thermal transfer sheets in a facsimile printer that uses conventional thermal coloring paper, for example, in the above-mentioned facsimile printer, the recording paper itself is thermally colored, so there is no conveyance device for the transfer material ( It cannot be used for other purposes, and this problem also applies to special printers such as large plotters.

As a method to solve the above-mentioned problems, the thermal transfer sheet and the material to be transferred are temporarily bonded in advance and rolled into a roll (or made into a sheet type, so that it can be adapted to facsimile printers, etc.). , methods have been devised to simplify and downsize the device.

When printing using such a composite thermal transfer sheet, white print marks will remain on the printed thermal transfer sheet, and if the printed information is confidential information, secrets may be leaked from the print marks on the used thermal transfer sheet. A problem arises in that

In addition, in the case of the above-mentioned composite thermal transfer sheet, the thermal transfer sheet and the paper firmly adhere to each other, so that no wrinkles or deviations occur on the thermal transfer sheet, and both are easily peeled off after thermal transfer, so that the ink layer does not form in the transfer area. It is required to have the ability to accurately transfer to paper and not to stain the paper by not transferring at all in the transfer area. On the other hand, in the case of conventional composite thermal transfer sheets, there have been no sheets that can fully satisfy these requirements.

Further, in the case of composite thermal transfer sheets, the ink layer is often black, but in these cases, the entire sheet is black, which poses a problem of poor aesthetic appearance.

Therefore, an object of the present invention is to solve the above-mentioned problems and provide a composite thermal transfer sheet that is excellent in both secret leakage prevention properties, adhesion properties, and peelability, and is free from print image resolution and scumming.

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

That is, the present invention provides a composite thermal transfer sheet in which a thermal transfer sheet having a heat-melting ink layer formed on one surface of a base film and a transfer material are releasably adhered by an adhesive layer. This composite thermal transfer sheet is characterized in that a concealing layer that covers an ink layer is formed on at least one surface of the material film.

(Function) By forming a hiding layer that hides the ink layer on at least one surface of the base film of the thermal transfer sheet,
There will be no printing marks on the thermal transfer sheet after printing, and the problem of secret leakage will not occur.

Furthermore, by employing various chromatic colors as the hiding layer, the aesthetic appearance of the composite thermal transfer sheet can be improved.

In addition, in a preferred embodiment, the adhesive layer has a specific configuration, so that the thermal transfer sheet and the paper firmly adhere to each other, preventing wrinkles or misalignment, and providing good conveyance. A composite thermal transfer sheet is provided in which the ink 1 is accurately transferred to the paper in the transfer area, and is not transferred at all in the transferred area, so that the paper is not contaminated.

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

A cross-sectional view of a preferred example of the composite thermal transfer sheet of the present invention is shown in FIG.

The composite thermal transfer sheet of the present invention is a composite thermal transfer sheet in which a thermal transfer sheet A and a transfer material B are releasably adhered to each other by an adhesive layer C, as shown in the figure, and at least one surface of the above-mentioned base film is It is characterized by forming a hiding layer that hides the ink layer.

The thermal transfer sheet A has a heat-melting ink layer 2 formed on a base film 1 as shown in the figure, and a concealing layer formed on either side of the base film 1, but in a preferred embodiment, A matte layer 3 colored in the same hue as the ink layer is formed between the base film l and the ink layer 2, or a slip layer 4 similarly colored is formed on the back side of the base film, and these layers have a concealing effect. Also have. Of course, the hiding layer may be provided separately from the matte layer or the slip layer, an aluminum vapor-deposited film may be used as the base film, or the base film itself may be colored.

An example in which the matte layer is colored will be explained as a representative example. The matte layer 3 is formed by applying a coating liquid containing a suitable binder, colorant (pigment, dye, metal powder, etc.) and organic or inorganic particles to the surface of the base film.

The binder may be any binder such as polyester resin, polyvinyl butyral resin, polyacetal resin, cellulose resin, acrylic resin, polyurethane resin, etc.

In addition to the above-mentioned colorants, the particles used as a matting agent may optionally be inorganic particles such as silica, alumina, clay, or calcium carbonate, or plastic pigments such as acrylic resin particles, epoxy resin particles, melamine resin particles, or benzoguanamine resin particles. used for.

The above matting agent is used in an amount of 30% by weight or less, preferably 5 to 25% by weight, more preferably 10 to 20% by weight of the matte layer.

The matte layer 3 is prepared by dissolving or dispersing the materials described above in a suitable solvent such as acetone, methyl ethyl ketone, toluene, or xylene, and adding a crosslinking agent such as polyisocyanate as necessary to prepare a coating solution. It is formed by applying a coating solution using a conventional coating means such as a gravure coater, roll coater, wire bar, etc. and drying it.

Is the coating amount 2.0g/rr based on solid content? Hereinafter, a colored matte layer having sufficient performance can be formed with a thickness of preferably 0.1 to 1.0 g/r&.

As the base film used in the composite thermal transfer sheet of the present invention, the same base film used in conventional thermal transfer sheets can be used as is, and other materials can also be used, and there are no particular restrictions. .

Specific examples of preferred base films include polyester, polypropylene, cellophane, polycarbonate, cellulose acetate, polyethylene, polyvinyl chloride,
There are plastics such as polystyrene, nylon, polyimide, polyvinylidene chloride, polyvinyl alcohol, fluororesin, chlorinated rubber, ionomer, etc., papers such as capacitor paper and paraffin paper, nonwoven fabrics, etc., and base films made of composites of these. It may be.

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.

The heat-melting ink layer provided on the base film is composed of a colorant and a vehicle, and may further contain various additives as necessary.

As this coloring agent, it is preferable to use organic or inorganic pigments or dyes that have good properties as a recording material, such as those that have sufficient color density and do not turn brown due to light, heat, temperature, etc. .

Of course, carbon black is preferable for black monochrome printing, and chromatic colorants such as cyan, magenta, yellow, etc. are used for multicolor printing. It is generally preferred that the amount of these colorants used is about 5 to 70% by weight in the ink layer.

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. In addition, we have a wide range of products including Fischer-Tropsch wax, various low molecular weight polyethylenes, wood wax, beeswax, spermaceti wax, ipotal wax, wool wax, shellac wax, candelilla wax, petrolactam, polyester wax, custom wax, fatty acid ester, fatty acid amide, etc. wax is used. In the present invention, a thermoplastic resin having a relatively low melting point may be mixed into the wax to improve the adhesion of the ink to the transfer material.

Methods for forming a hot melt ink layer on a base film include hot melt coating, hot lacquer coating,
Examples include gravure coating, gravure reverse coating, roll coating and many other methods. The thickness of these ink layers may be several micrometers as in the conventional case.

The transfer material B preferably has a stiffness of 20 to 2500.
Any sheet or film that can be thermally transferred may be used, such as high-quality paper, plain paper, synthetic paper, tracing paper, plastic film, etc. in the range of gf/cm. If the stiffness is less than the above range, the stiffness of the composite thermal transfer sheet as a whole will be insufficient and it will be weak, and the transfer sheet will peel off or wrinkle due to waving, etc., resulting in serious problems in conveyance. Good printing is not possible. On the other hand, if the stiffness exceeds the above range, the composite thermal transfer sheet becomes uneconomical in terms of thickness, weight, etc.

In a more preferred embodiment, the surface smoothness of the transfer material is in the range of 5 to 500 seconds, and the basis weight of the transfer material is 20 seconds.
By setting it in the range of ~500 g/rrr, good results can be obtained in the -layer. Further, the size of these transfer materials may be sheets of paper such as A-size, B-size, etc. (or may be a continuous sheet of any width.

The adhesive layer C that temporarily adheres the thermal transfer sheet A and the transfer material B can also be achieved by adjusting the adhesive strength of a conventionally known adhesive, but preferably the adhesive has a low glass transition temperature. It consists of adhesive particles, resin particles with a high glass transition temperature, and wax particles.

The glass transition temperature of the above-mentioned adhesive is preferably in the range of -90°C to -60°C, and examples of such adhesives include rubber-based adhesives, acrylic-based adhesives, and silicone-based adhesives. In addition, in terms of form, there are solvent solution type, aqueous solution type, hot melt type, aqueous or oil emulsion type, and any of them can be used in the present invention, but acrylic type is particularly suitable in the present invention. It is an aqueous emulsion type, and its particle size is about 1 to 30 μm, preferably 1 to 6 μm. By using such an emulsion type adhesive, the adhesive 5 of the adhesive layer maintains its particle shape as shown in the third figure.

When the above adhesive is used alone, excellent adhesion can be obtained, but the peelability of the transferred material is insufficient and uneven, and unexpected stress may be applied during manufacturing, storage, transportation, etc. before thermal transfer. If this is added, there is a problem in that the ink layer of the thermal transfer sheet is transferred to the transfer material, resulting in scumming. Furthermore, during thermal transfer, the ink layer is not easily cut, and for example, the ink layer is transferred to the periphery of the area to which heat is applied by the thermal head, resulting in poor resolution of the transferred image.

In the present invention, the above problem can be solved by adding a resin emulsion containing fine resin particles, for example, resin particles 6 with a particle diameter of about 0.01 to 0.5 μm, to the emulsion adhesive, so that the adhesiveness is within a preferable range. By adding emulsion 7 of wax similar to the one used to form the ink layer, foil breakage of the adhesive layer C is improved, and the resolution of the transferred image is improved. was found to be significantly improved.

As the above resin emulsion, for example, ethylene-
Thermoplastic resins such as vinyl acetate copolymer, ethylene-acrylic acid ester copolymer, polyethylene, polystyrene, polypropylene, polybdenum, vinyl chloride resin, vinyl chloride-vinyl acetate copolymer, acrylic resin, and especially acrylic emulsion are suitable. It is. Such resin particles preferably have a glass transition temperature higher than that of the pressure-sensitive adhesive, for example, 60° C. or higher, and may be thermoset resin particles as the case may be.

Further, the wax emulsion is obtained by emulsifying the wax as described above by a known method, and the particle size thereof is not particularly limited, although the finer the better.

The weight ratio of the adhesive, resin particles, and wax is 3 to 5;
A ratio of 1 to 2.5:3 to 5 is preferable, and if the ratio is outside this range, the various problems described above are likely to occur, which is not preferable.

The adhesive layer C made of the above components may be provided on the surface of the transfer material B, but in this case, since the printed matter remains sticky, it is preferably provided on the surface of the ink layer 2 of the thermal transfer sheet. In this case, since the adhesive is used as an aqueous emulsion, the ink layer is not damaged, which is preferable. The emulsion coating method and drying method are not particularly limited, but
Drying is preferably carried out at a low temperature so that the emulsion particles remain.

The adhesive layer preferably has a thickness of 0.1 to 20 um (01 to 5 g/m' in solid coating amount).

The adhesion between the thermal transfer sheet A and the transferred material B is preferably carried out by continuously adhering the transferred material while forming an adhesive layer on the surface of the ink layer of the thermal transfer sheet, and then winding this up into a roll. When winding up, the material to be transferred may be placed on the outside, or the thermal transfer sheet may be placed on the outside (or these may be cut into sheets).

The above is the basic structure of the composite thermal transfer sheet of the present invention. Of course, as shown in the first figure, a slip layer 4 is provided on the back surface of the thermal transfer sheet to prevent adhesion of the thermal head and to improve slipperiness. All well-known techniques in the field of thermal transfer sheets, such as making the print matte by providing a matte layer 3 between the base film and the ink layer, or making the ink layer a hue other than black, can be applied to the present invention. It can be added to the composite thermal transfer sheet.Also, in order to give the matte layer or slip layer a hiding effect, a coloring agent that hides the ink layer can be added to the coating liquid for forming these layers. All you have to do is include it.

The thermal transfer sheet of the present invention described above is set in, for example, a facsimile printer, conveyed as shown by the arrow in FIG. A desired image 9 is formed.

(Example) Next, the present invention will be explained in more detail by giving examples and comparative 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 black ink for forming a heat-resistant slip layer having the following composition was coated on one side of the base film at a rate of 0.7 g/rrr (dry state) using a gravure coating method. A black heat-resistant slip layer was formed by coating and drying.

- Heat slip ink Vinylidene fluoride resin (Kynar SL, manufactured by Pennwalt) 9 parts Teflon powder (Hostaflon TF9205, manufactured by Hoechst)
8 parts acrylic polyol (TP-50
00, manufactured by Denka Polymer Co., Ltd.)
9 parts graft polymer wax (Marked C-11
3. Manufactured by Adeka Argus) 2-part curing agent (Takene 1-D-11ON, manufactured by Takeda Pharmaceutical Company)
1 part carbon black (
Geast S, manufactured by Tokai Electrode) 8 parts methyl ethyl ketone 40 parts toluene
14 parts Next, the following ink composition was applied to the other side of the base film at a rate of 4 g/rd to form an ink layer.

Lie Seiku Carbon Black 15 parts Ethylene/vinyl acetate copolymer 8 parts Paraffin wax 50 parts Carnauba wax
25 parts (4 at 120”C with attritor)
Further, a temporary adhesive having the composition shown below was coated on the above ink layer using a gravure coating method at a dry coating weight of 0.5 g/g, and then plain paper (basis weight 64 g /M, Beck surface smoothness 1
The composite thermal transfer sheet of the present invention was obtained by laminating the sheet for 40 sec, stiffness: 45 gf/cm) and the tube temperature of 50"C, and nip pressure of 500 kg).

Karigumi I Edanui acrylic adhesive particles water-based dispersion (solid content 40
%, glass transition temperature -70"C1 particle size 3-10 μm)
'10 parts acrylic resin particles aqueous dispersion (solid content 20%, glass transition temperature 8
5℃, particle size 0.2-0.5μm) 1
5 parts carnauba wax aqueous dispersion (solids content 4
0%, melting point 83℃) 15 parts water
10 parts Improper tool 30 parts Examples 2 to 4 Using a polyethylene terephthalate film with a thickness of 6.0 μm as a base film, 1 g of silver ink for forming a matte layer having the following composition was coated on one side of the base film by gravure coating method.
It was applied to a thickness of lrd (dry state) and dried to form silver matte eyebrows.

Matte ink aluminum paste (solid content 80%) 12 parts acrylic polyol 14 parts vinyl chloride/vinyl acetate copolymer resin 5 parts polyisocyanate (solid content 50%) 5 parts methyl ethyl ketone 4
0 parts Toluene 30 parts Using the above base film and using the same dispersions as in Example 1, the composition (weight ratio) of the temporary adhesive was changed as shown in Table 1 below, and the rest was the same as in Example 1. A composite thermal transfer sheet of the present invention was obtained.

Comparative Example 1 A composite thermal transfer sheet of a comparative example was obtained in the same manner as in Example 1 except that a base film having an uncolored slip layer was used as the base film in Example 1.

Comparative Example 2 A composite thermal transfer sheet of a comparative example was obtained in the same manner as in Example 1 except that the colored matte layer was not formed in Example 2.

When the composite thermal transfer sheets of the above Examples and Comparative Examples were loaded into a printer and printed, it was found that in the case of the composite thermal transfer sheets of the Examples, no white spots or printing traces were observed on the thermal transfer sheets after printing.On the other hand, In the case of the comparative example, clear print marks were observed, and the content of the printed information could be read from the print marks.

Furthermore, the adhesive strength between the ink layer and paper of the composite thermal transfer sheets of Examples 1 to 4 was measured, and the results are shown in Table 2. If the paper does not peel off easily even when left, it peels off easily with a fingertip after printing, and there is no background smear on the paper, mark it as ○, and if it peels off naturally or causes background smudges when left unused, mark it as ×. expressed. From these results, the adhesive strength is 300 to 1000g, especially 400g.
A range of 800 g was found to be appropriate.

In addition, the adhesive strength (g) is 25mm (width) x 55mm (length)
Cut a sample of
N-14 (manufactured by Shingan Kagaku) at a tensile speed of 1800 mm/min.

(Effect) As described above, according to the present invention, by forming a hiding layer that hides the ink layer on at least one surface of the base film of the thermal transfer sheet, thermal transfer after printing is prevented. There are no printing marks on the sheet, and there is no problem of secret leakage.

Furthermore, by employing various chromatic colors as the hiding layer, the aesthetic appearance of the composite thermal transfer sheet can be improved.

In addition, in a preferred embodiment, the adhesive layer has a specific configuration, so that the thermal transfer sheet and the paper firmly adhere to each other, preventing wrinkles or misalignment, and providing good conveyance. A composite thermal transfer sheet is provided in which the ink layer is accurately transferred to the paper in the transfer area, and the transferred area is not transferred at all and the paper is not contaminated.

[Brief explanation of drawings]

FIGS. 1 and 2 are diagrams schematically explaining the cross section of the composite thermal transfer sheet of the present invention, and FIG. 3 is a diagram schematically explaining the structure of the adhesive layer. A: Thermal transfer sheet C: Adhesive layer 1: Base film 3: Matte layer 5: Adhesive particles 7: Wax particles 9; Image B: Transferred material 2: Ink layer 4 Nislip layer 6: Resin particles 8: To thermal Rad

Claims (3)

[Claims] (1) In a composite thermal transfer sheet formed by releasably adhering a thermal transfer sheet with a heat-melting ink layer formed on one side of a base film and a transfer material using an adhesive layer,
A composite thermal transfer sheet, characterized in that a concealing layer for concealing an ink layer is formed on at least one surface of the base film. (2) The composite thermal transfer sheet according to claim 1, wherein the hiding layer is a colored matte layer. (3) The composite thermal transfer sheet according to claim 1, wherein the hiding layer is a colored back layer.