JP2694769B2 - Thermal transfer method - Google Patents

Description

Description: TECHNICAL FIELD [0001] The present invention relates to a thermal transfer method, and more specifically, a thermal transfer method in which a transfer speed of a transfer material is set to be higher than a transfer speed of a thermal transfer sheet (hereinafter, simply referred to as an N-fold mode). Law)
The present invention relates to a thermal transfer method capable of high density printing.

(Prior Art and its Problem) Conventionally, when printing an output print of a computer or a word processor by a thermal transfer method, a thermal transfer sheet having a heat-meltable ink layer provided on one surface of a base film is used.

This conventional thermal transfer sheet uses a base film such as 10 to 20 μm thick condenser paper or paraffin paper or 3 to 20 μm thick plastic film such as polyester or cellophane, and wax or pigments or dyes. It is manufactured by providing a heat-meltable ink layer mixed with the colorant of 1. by coating.

In the N-fold mode method using these thermal transfer sheets, when the transfer speed of the material to be transferred is N and the transfer speed of the thermal transfer sheet is N ', and N>N', the printing distance is N, but the transfer distance of the thermal transfer sheet is N. Since the consumption amount is N ', there is an advantage that the consumption amount of the thermal transfer sheet with respect to the printing distance can be saved, but the printing density becomes N' / N, and the printing density is inevitably lowered.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a thermal transfer method capable of providing clear printing with high density even if thermal transfer is performed by the N-fold mode method. .

(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 method in which a transfer speed N of a transfer material is set to be higher than a transfer speed N ′ of a thermal transfer sheet. The pigment concentration P per unit area of the layer is 0.06 to 1 g / m ² × (N / N ′) (however, N / N ′> 1.3)
The thermal transfer method is characterized by using the thermal transfer sheet.

(Function) When performing thermal transfer in the N-fold mode method, the ratio of the transfer speed of the material to be transferred and the transfer speed of the thermal transfer sheet in the printer is taken into consideration, and the heat-melted ink layer having a pigment concentration corresponding to the transfer speed ratio. By using the thermal transfer sheet having the above, high density and clear printing can be provided even when the thermal transfer is performed by the N-fold mode method.

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

The heat transfer sheet used in the present invention has a heat-meltable ink layer on one surface of the base film, and further has a surface layer made of wax formed thereon, if necessary.

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

Specific examples of the preferred base film include, for example,
Polyester, polypropylene, cellophane, polycarbonate, cellulose acetate, polyethylene, polyvinyl chloride, polystyrene, nylon, polyimide, polyvinylidene chloride, polyvinyl alcohol, fluororesin, chlorinated rubber, plastic films such as ionomer, condenser paper, paraffin paper, etc. , Non-woven fabric, etc.
It may be a base film formed by combining these.

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

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

The pigment is preferably an organic or inorganic pigment having good characteristics as a recording material, for example, a pigment having a sufficient coloring density and not fading due to light, heat, temperature or the like.

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 types such as Fischer-Tropsch wax, various low molecular weight polyethylenes, wood wax, beeswax, spermaceti, Ibota wax, wool wax, shellac wax, candelilla wax, petrolactam, polyester wax, partially modified wax, fatty acid ester, fatty acid amide, etc. Is used.

In addition, a heat conductive substance can be added to the heat fusible ink in order to provide the heat fusible ink layer with good heat conductivity and melt transferability. Examples of this substance include carbonaceous substances such as carbon black, aluminum, copper, tin oxide, and molybdenum dioxide.

As a method for directly or indirectly forming a heat-meltable ink layer on a base film, in addition to hot-melt coating, hot lacquer coating, gravure coating, gravure reverse coating, roll coating, and other various coating methods can be used. Examples include a method of applying a liquid.

In the thermal transfer sheet used in the thermal transfer method of the present invention, the pigment concentration of the heat-meltable ink layer is determined in consideration of the transportation speed ratio of the transportation speed N of the material to be transferred and the transportation speed N ′ of the thermal transfer sheet in the printer. To do. That is, when the ink layer as described above is formed, the pigment concentration P of the ink layer is about 0.06 to 1 g / m ² per unit area of the ink layer, whereas the pigment concentration of the conventional thermal transfer sheet is about 0.06 to 1 g / m ² . , In relation to N and N ′ defined above, the pigment concentration per unit area is
0.06 to 1 g / m ² × (N / N ′). For example, if N / N '= 2, a thermal transfer sheet having a pigment concentration of 2P is used.

There are two methods for increasing the pigment concentration of the ink layer, a method of increasing the pigment concentration in the wax ink in advance and a method of increasing the thickness of the ink layer itself, and either method may be used in the present invention. .

If N / N 'is 1.5 or more, it is actually difficult to increase the pigment concentration of the ink corresponding to this value, so increase the ink layer thickness without increasing the pigment concentration too much. Is preferred. According to this method, the value of N / N 'is 2
Even if it is above, it is possible to cope sufficiently. In reality, the value of N / N 'in the N-fold mode method is a value of about 1.4 to 10. Therefore, the pigment concentration of the ink layer in the present invention depends on the type of pigment used (for example, yellow, magenta, cyan and black). ), And is generally 0.06 to 1 g / m ² , so the concentration multiplied by N / N ′, for example, 0.08 to 10 g
/ m ² is common. If the pigment concentration in the ink is made the same as the conventional concentration, the conventional ink layer has a thickness of about 2-5.
Since it is μm, a thickness obtained by multiplying the thickness by N / N ′, for example, a thickness of 2.6 to 20 μm is general.

In the present invention, the surface layer formed on the ink layer is
It forms a part of the transfer film and is formed on the surface in contact with the transfer material to prevent background stain and to improve the adhesion of the ink layer to the transfer material. These surface layers are formed by using the above-mentioned wax as a main component. Further, this surface layer may contain a thermoplastic resin for improving the adhesiveness.

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

Further, while the thermal transfer image is generally glossy and beautiful, the text may be difficult to read, so matte printing may be desirable. In such a case, for example,
As proposed by the applicant (Japanese Patent Application No. 58-208306), a mat layer may be provided on the base film or the base film itself may be mat-processed before use.

Needless to say, the method of the present invention can be applied to a thermal transfer method for color printing.
A method of using a multicolor heat transfer sheet which is separately colored or more is also included in the scope of the present invention. As the thermal transfer printer, either a line type or a serial type can be used.

(Effects) According to the present invention as described above, there is provided a thermal transfer sheet which is free from background stains and tailing at the time of printing even in the N-fold mode method and further has improved printing density and resolution. .

(Examples) Hereinafter, the present invention will be described more specifically with reference to examples. In the 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 a heat-meltable ink and a surface material having the following compositions were prepared on one surface of the base film, and each was coated and dried by the means described in the present invention. A thermal transfer sheet to be used was obtained.

Heat-fusible ink layer Carbon black (Dia Black G, Mitsubishi Kasei) 30 parts Ethylene / vinyl acetate copolymer (EVA Flex 310,
Mitsui Poly Chemicals) 5 parts Paraffin wax (paraffin 150F, manufactured by Nippon Seiro Co., Ltd.) 50 parts Carnauba wax 15 parts Kneading at 120 ° C for 6 hours using an attritor, hot melt roll coating method with ink temperature of 120 ° C Was applied and dried at a rate of 3.5 g / m ² (dry state).

Surface layer 155F Paraffin wax emulsion (WE-70, bond wax company, solid content 40% aqueous emulsion) 20 parts Ionomer resin (Chemipearl S-100, Mitsui Petrochemical, solid content 27%) 10 parts 60% isopropanol aqueous solution 15 Part was applied by a gravure coating method at a rate of 0.8 g / m ² (dry state) and dried at 60 ° C. to form a surface mat-like surface layer.

Thermal transfer printing was carried out using a commercially available thermal head, using the above-mentioned thermal transfer sheets having an ink layer and a surface layer of thicknesses of 3.5 μm and 0.8 μm, respectively, and selecting high quality paper as the transfer target paper. High-speed printing in N times mode (N / N '= 2) with thermal head energy of 0.7 W / dot, transfer paper conveyance speed of 40 cm / sec (N), thermal transfer sheet conveyance speed of 20 cm / sec (N') As a result, it was possible to print with a high density without background stains on the transfer paper, similar to the printing when the pigment concentration was 15 parts and N / N′≈1.

Example 2 Using the same base film as in Example 1, two layers having the following compositions were formed to obtain a thermal transfer sheet used in the present invention.

Heat-meltable ink layer Carbon black (Dia Black G, Mitsubishi Kasei) 15 parts Ethylene / vinyl acetate copolymer (EVA Flex 310,
Mitsui Polychemicals) 8 parts Paraffin wax (paraffin 150F, manufactured by Nippon Seiro Co., Ltd.) 50 parts Carnauba wax 25 parts Kneading at 120 ° C for 6 hours using an attritor, hot melt roll coating method with ink temperature of 120 ° C Was applied and dried at a rate of 7.0 g / m ² (dry state).

Surface layer 155F Paraffin wax emulsion (WE-70, bond wax, solid content 40% aqueous emulsion) 70 parts EVA resin emulsion (bond wax 62-357, bond wax, solid content 40%) 10 parts 50% isopropanol Aqueous solution 50 parts It was applied by a gravure coating method at a rate of 0.5 g / m ² (dry state) and dried at 73 ° C to form a surface layer having a surface smoothness.

This thermal transfer sheet having the thicknesses of the ink layer and the surface layer of 7.0 μm and 0.5 μm, respectively, showed good transfer performance as in Example 1 with N / N ′ = 1.8.

Example 3 Using the same base film as in Example 1, two layers having the following compositions were formed to obtain a thermal transfer sheet used in the present invention.

Heat-meltable ink layer Carbon black (Dia Black G, Mitsubishi Kasei) 15 parts Ethylene / vinyl acetate copolymer (EVA Flex 310,
Mitsui Polychemicals) 8 parts Paraffin wax (paraffin 150F, manufactured by Nippon Seiro Co., Ltd.) 50 parts Carnauba wax 25 parts Kneading at 120 ° C for 6 hours using an attritor, hot melt roll coating method at ink temperature 120 ° C Was applied and dried at a rate of 10 g / m ² (dry state).

Surface layer Carnauba wax 10 parts Ethylene / vinyl acetate copolymer (Eva Flex 31
0, manufactured by Mitsui Polychemicals) After melting 2 parts, emulsified (solid content 20%) is applied by a roll coating method at a rate of 0.3 g / m ² (dry state) and dried at 60 ° C. To form a mat-like surface layer.

The thermal transfer sheet of this example in which the thicknesses of the ink layer and the surface layer were 10 μm and 0.3 μm, respectively, also showed good transfer performance with N / N ′ = 2.2 and no background stain.

Example 4 A polyethylene terephthalate film having a thickness of 6 μm was used as a base film, and each of the yellow (Y), magenta (M), cyan (C), and black (B) heat-melting inks and surface layer inks having the following compositions were used. Then, an ink layer and a surface layer were formed to obtain a thermal transfer sheet used in the present invention.

Heat-fusible ink layer Pigment (yellow, magenta, cyan or black pigment) 12 parts Ethylene / vinyl acetate copolymer (Smitate KC-10,
Sumitomo Chemical Co., Ltd.) 5.5 parts Oxidized paraffin ester-based composite compound (amide polymer T-820, made by Denka Polymer) 10.5 parts Paraffin wax (paraffin SP-0145, made by Nippon Seiro Co., Ltd.) 13 parts Microcrystalline wax (Himic 2065, Nihonsei) Wax) 8 parts Isopropanol 5 parts Xylene 46 parts An ink layer was formed by sequential printing in the order of yellow, magenta, cyan and black by the gravure printing method using the ink composition of the above four colors. The coating weight at that time was 4 g / m ² .

Surface layer Carnauba emulsion (WE-95, manufactured by Bond Wax Co., solid content 40%) 30 parts Ethylene / vinyl acetate copolymer emulsion (Polysol EVAAD-5, Showa High Polymer, solid content 56%) 10 parts 75% Isopropanol Aqueous solution 60 parts By the gravure printing method using the above ink composition, a dry weight of 0.7 g / m ² is applied on the previously printed yellow, magenta, cyan and black heat-meltable ink layers. The surface layer was formed by working. The drying condition at that time was 65 ° C. for 3 seconds.

When a color thermal printer was used to perform printing with N / N '= 1.7 using the thermal transfer sheet produced through the above steps, sufficient printing was possible in the same manner.

Claims (1)

(57) [Claims] 1. A thermal transfer method in which a transfer speed N of a material to be transferred is set to be higher than a transfer speed N'of a thermal transfer sheet, and when the transfer speed of the transfer material is N, the thermal melting property of the heat transfer sheet is The pigment concentration P per unit area of the ink layer is 0.06 to 1 g / m ² × (N / N ′) (however, N / N ′> 1.3)
A thermal transfer method characterized by using the thermal transfer sheet according to claim 1.