JP3168371B2 - Thermal transfer sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer sheet used in a thermal transfer printer.

[0002]

2. Description of the Related Art A thermal transfer recording system using a thermal printer has been widely put to practical use because of its compactness and excellent operability and maintainability. As the field of use of barcode management systems in factory automation for industrial applications has expanded, higher-performance characteristics have been demanded, and conventional thermal transfer sheets have become unable to respond. For example, methyl ethyl ketone as a solvent,
There is a demand for a label that can withstand a strong solvent such as toluene, but there is no thermal transfer sheet that can cope with this.

[0003]

The thermal transfer sheet of the present invention is superimposed on a label to be printed, and printed by a thermal printer, thereby exhibiting excellent solvent resistance to withstand strong solvents such as methyl ethyl ketone and toluene. An object of the present invention is to provide a thermal transfer sheet on which a label can be made.

[0004] The lower the softening point of the heat-sensitive ink in the thermal transfer recording system using a thermal head is, the smaller the load applied to the head is preferably reduced. Therefore, the present invention uses a polyethylene resin having a low softening point and excellent solvent resistance as a binder component of the thermal transfer ink. However, simply using a polyethylene resin as the binder for the ink layer does not mean that a thermal transfer sheet excellent in solvent resistance can be obtained. In order to manufacture a thermal transfer film sheet, it is necessary to apply a thin thermal transfer ink layer to a base film.

[0005] As a coating method for producing a thermal transfer sheet, there are a hot-melt coating method in which a heated ink is coated without using a solvent, which is a general coating method of wax ink, and a resin-type ink coating method. There is a method of applying a paint dissolved or dispersed by using a solvent as described above. However, in the hot-melt coating method, it is difficult to coat a thin film because the melt viscosity is too high even with an ink comprising a polyethylene resin having a molecular weight of 2,000 which is the minimum molecular weight of the present invention. In the solvent coating method, which is another method, there is no solvent that can be made into a solution due to the fact that polyethylene resin has excellent solvent resistance, and a dispersion liquid in which fine particles of polyethylene resin are dispersed is used as a paint. Is the most appropriate method. However, even if this dispersion liquid is simply applied, a dot having good dot reproducibility, and a thermal transfer sheet which provides a label having good printing quality and sufficient solvent resistance that does not stain the surface of the label to be printed is obtained. I can't do things.

[0006]

Means for Solving the Problems As the base film of the thermal transfer sheet, a conventionally known polyester film such as polyethylene terephthalate, a polyether ether ketone film, a polyimide film, etc.
A 12 μm film can be mentioned, but a polyester film is particularly preferable in view of economy. The thermal transfer ink layer constituting the thermal transfer sheet of the present invention, which resists a strong solvent such as methyl ethyl ketone and toluene, is composed of a polyethylene resin and a colorant. Polyethylene resin has no solvent that dissolves at room temperature, and dissolves only when heated like hot toluene and hot xylene. And it has the property that it does not melt unless the dissolution temperature is raised as the molecular weight increases. Due to this property, considering polyethylene resin alone, the solvent resistance improves as the molecular weight increases,
In the case of the thermal transfer ink layer, it does not mean that the molecular weight should be large, and the molecular weight of the polyethylene resin is 2,000.
Those which are 0 or more and are soluble in xylene at 100 ° C. are preferred. When the molecular weight is 2,000 or less, the molecular weight is too small and sufficient solvent resistance is not obtained. Conversely, if the molecular weight is too large, it will not completely dissolve in hot toluene or hot xylene, and undesirably forms insolubles.

More importantly, the paint for forming the thermal transfer ink layer of the present invention is a dispersion in which fine particles of a polyethylene resin and a pigment as a colorant are dispersed in a solvent such as toluene or xylene. The anti-stick layer is coated on the transfer control layer of the base film provided with the transfer control layer on the other side, and the fine particles of polyethylene resin and the colorant By binding and integrating the particles, it is possible to obtain a thermal transfer ink layer which is excellent in solvent resistance and does not cause the so-called "ground stain" which stains the surface of the label as the printing object. Although the thermal transfer ink layer is melted when printing with a thermal printer, this alone does not exhibit sufficient solvent resistance, and it is essential that the thermal transfer ink layer is already bonded and integrated in the thermal transfer sheet state Requirements. Therefore, xylene is more preferable than toluene as a solvent for the paint for forming the thermal transfer ink layer. This is because toluene has a boiling point of 110 ° C., xylene has a boiling point of 144 ° C., and xylene has a higher boiling point. This is because polyethylene particles are less likely to evaporate than toluene during the drying process, and the polyethylene fine particles can be dissolved by heat to promote binding and integration. Density of polyethylene resin (JIS
K6760) is very important, and a thermal transfer sheet having good solvent resistance cannot be obtained unless the polyethylene has a density of 0.95 or more. Any colorant can be used without particular limitation as long as it does not bleed into the solvent.

The transfer adjusting layer is for controlling the adhesive force between the base film and the thermal transfer ink layer to obtain good printing quality. If the adhesive force is too strong, the ink will not be transferred to the printing medium, whereas if the adhesive force is too weak, the ink will be transferred to unnecessary portions and the print quality will be degraded. As the transfer adjustment layer, an ethylene vinyl acetate resin, an acrylic resin, a polyamide resin, or a polyurethane resin can be used. When the base film is a polyester film, printing quality excellent in dot reproducibility can be obtained by using a solvent-soluble polyester resin.

[0009] As a label material to be printed, a polypropylene sheet, a synthetic paper, a polyethylene sheet, a rigid PVC sheet or the like is suitable, but of course, a polyethylene sheet is most suitable. Hereinafter, the present invention will be described in more detail with reference to Examples. In the examples, "parts" and "%" indicate parts by weight and% by weight, respectively, unless otherwise specified.

[0010]

Example 1 A 6 μm polyester film having a stick prevention layer provided on one surface as a base film was coated with a coating for a transfer adjusting layer having the following composition on the other surface using a 100 μm wire wound wire bar. To obtain a transfer control layer having a dry coating of 0.5 μm. Hereinafter this is referred to as base film A. [Transfer Adjustment Coating Composition] Polyester resin (Toyobo Byron 200) 10 parts Toluene 70 parts Methyl ethyl ketone 20 parts As a coating material for a thermal transfer ink layer, 15 parts of polyethylene having a molecular weight of 2,000 and a density of 0.95 was added to 85 parts of xylene. This was heated to 100 ° C. to dissolve it, and then cooled to precipitate polyethylene fine particles. To this, 5 parts of carbon raben 1255 (manufactured by Columbia Carbon) and 95 parts of xylene were added and uniformly stirred and mixed, and then dispersed with a sand mill for 30 minutes to obtain a 10% concentration paint. This paint was applied on the transfer adjustment layer of the base film A with a Mayer bar wound with an 800 μm wire and dried at 130 ° C. for 2 minutes to obtain a thermal transfer sheet having a thermal transfer ink layer with a dry thickness of 4 μm. .
The thermal transfer sheet and the polyethylene sheet were superimposed and printed with an energy of 0.5 mj / dot using a thermal printer having a resolution of 8 dots / mm to obtain a label. Then, methyl ethyl ketone (hereinafter referred to as MEK)
And toluene (hereinafter referred to as TOL) to evaluate the solvent resistance. The evaluation was performed by impregnating a cotton swab with a solvent,
The print surface was rubbed with a load of g, and the number of evaluations until the print disappeared was evaluated. As a result, no more than 51 reciprocations were observed in MEK, but damage was observed in 35 reciprocations in TOL.

[0011]

Example 2 As a paint for the thermal transfer ink layer, a molecular weight of 4,
15 parts of polyethylene having a density of 0.98 at 000 are added to 85 parts of xylene, and this is heated to 100 ° C. to dissolve it,
Then, the mixture was cooled to precipitate polyethylene fine particles. In addition, carbon raben 1255 is used as a colorant.
(Colombia Carbon) (5 parts) and xylene (95 parts) were added and uniformly stirred and mixed, and then dispersed by a sand mill for 30 minutes to obtain a 10% concentration paint. This paint was applied on the transfer adjustment layer of the base film A with a Mayer bar wound with an 800 μm wire, and dried at 130 ° C. for 2 minutes to obtain a thermal transfer sheet having a thermal transfer ink layer with a dry thickness of 4 μm. . The thermal transfer sheet and the polyethylene sheet are overlapped and printed with a thermal printer having a resolution of 8 dots / mm at an energy of 0.5 mj / dot.
Got the label. Next, the solvent resistance was evaluated in the same manner as in Example 1. The result is 51 for both MEK and TOL.
No damage was found on the round trip.

[0012]

Example 3 As a paint for the thermal transfer ink layer, a molecular weight of 8,
15 parts of polyethylene having a density of 0.97 at 000 are added to 85 parts of xylene, and this is heated to 100 ° C. to dissolve it.
Then, the mixture was cooled to precipitate polyethylene fine particles. In addition, carbon raben 1255 is used as a colorant.
(Colombia Carbon) (5 parts) and xylene (95 parts) were added and uniformly stirred and mixed, and then dispersed by a sand mill for 30 minutes to obtain a 10% concentration paint. This paint was applied on the transfer adjustment layer of the base film A with a Mayer bar wound with an 800 μm wire and dried at 130 ° C. for 2 minutes to obtain a thermal transfer sheet having a thermal transfer ink layer with a dry thickness of 4 μm. . The thermal transfer sheet and the polyethylene sheet are overlapped and printed with a thermal printer having a resolution of 8 dots / mm at an energy of 0.5 mj / dot.
Got the label. Next, the solvent resistance was evaluated in the same manner as in Example 1. The result is 51 for both MEK and TOL.
No damage was found on the round trip.

[0013]

Example 4 As a paint for a thermal transfer ink layer, a molecular weight of 1 was used.
15 parts of 1,000 polyethylene having a density of 0.96 was added to 85 parts of xylene, which was dissolved by heating to 100 ° C., and then cooled to precipitate polyethylene fine particles. Carbon raben 125 as a coloring agent
5 (manufactured by Columbia Carbon) and 95 parts of xylene were added, uniformly stirred and mixed, and then dispersed by a sand mill for 30 minutes to obtain a 10% concentration paint. This paint was applied on the transfer adjustment layer of the base film A with a Mayer bar wound with an 800 μm wire and dried at 130 ° C. for 2 minutes to obtain a thermal transfer sheet having a thermal transfer ink layer with a dry thickness of 4 μm. . The thermal transfer sheet and the polyethylene sheet were overlapped and printed with a thermal printer having a resolution of 8 dots / mm at an energy of 0.5 mj / dot to obtain a label. Next, the solvent resistance was evaluated in the same manner as in Example 1. The result is 51 for both MEK and TOL.
No damage was found on the round trip.

[0014]

Comparative Example 1 The thermal transfer ink layer had a molecular weight of 1,
15 parts of polyethylene having a density of 0.95 at 000 are added to 85 parts of xylene, and this is heated to 100 ° C. to dissolve it,
Then, the mixture was cooled to precipitate polyethylene fine particles. In addition, carbon raben 1255 is used as a colorant.
(Colombia Carbon) (5 parts) and xylene (95 parts) were added and uniformly stirred and mixed, and then dispersed by a sand mill for 30 minutes to obtain a 10% concentration paint. This paint was applied on the transfer adjustment layer of the base film A with a Mayer bar wound with an 800 μm wire and dried at 130 ° C. for 2 minutes to obtain a thermal transfer sheet having a thermal transfer ink layer with a dry thickness of 4 μm. . The thermal transfer sheet and the polyethylene sheet are overlapped and printed with a thermal printer having a resolution of 8 dots / mm at an energy of 0.5 mj / dot.
Got the label. Next, the solvent resistance was evaluated in the same manner as in Example 1. The result is 35 round trips for MEK,
In the TOL, significant damage was observed in eight round trips.

[0015]

Comparative Example 2 As a coating material for the thermal transfer ink layer, a molecular weight of 2,
15 parts of polyethylene having a density of 0.92 and a density of 2,000 are added to 85 parts of xylene, and the mixture is heated to 100 ° C. and dissolved.
Then, the mixture was cooled to precipitate polyethylene fine particles. In addition, carbon raben 1255 is used as a colorant.
(Colombia Carbon) (5 parts) and xylene (95 parts) were added and uniformly stirred and mixed, and then dispersed by a sand mill for 30 minutes to obtain a 10% concentration paint. This paint was applied on the transfer adjustment layer of the base film A with a Mayer bar wound with an 800 μm wire, and dried at 130 ° C. for 2 minutes to obtain a thermal transfer sheet having a thermal transfer ink layer with a dry thickness of 4 μm. . The thermal transfer sheet and the polyethylene sheet are superimposed and printed with an energy of 0.5 mj / dot using a thermal printer having a resolution of 8 dots / mm.
Got the label. Next, the solvent resistance was evaluated in the same manner as in Example 1. The result is 20 round trips for MEK,
In the TOL, significant damage was observed in 6 round trips.

[0016]

Comparative Example 3 As a paint for the thermal transfer ink layer, a molecular weight of 7,
15 parts of polyethylene having a density of 0.92 and a density of 2,000 are added to 85 parts of xylene, and the mixture is heated to 100 ° C. and dissolved.
Then, the mixture was cooled to precipitate polyethylene fine particles. In addition, carbon raben 1255 is used as a colorant.
(Colombia Carbon) (5 parts) and xylene (95 parts) were added and uniformly stirred and mixed, and then dispersed by a sand mill for 30 minutes to obtain a 10% concentration paint. This paint was applied on the transfer adjustment layer of the base film A with a Mayer bar wound with an 800 μm wire, and dried at 130 ° C. for 2 minutes to obtain a thermal transfer sheet having a thermal transfer ink layer with a dry thickness of 4 μm. . The thermal transfer sheet and the polyethylene sheet are superimposed and printed with an energy of 0.5 mj / dot using a thermal printer having a resolution of 8 dots / mm.
Got the label. Next, the solvent resistance was evaluated in the same manner as in Example 1. The result is 20 round trips for MEK,
In the case of TOL, significant damage was observed in five round trips.

[0017]

[Comparative Example 4] White PE with resin type thermal transfer sheet available from Company A
Printing was performed on T (manufactured by Toray E-20), and the solvent resistance was evaluated in the same manner as in Example 1. As a result, remarkable damage was observed in 1 round trip for MEK and 5 round trips for TOL.

[0018]

Comparative Example 5 Commercially available resin-type thermal transfer sheet of Company B with white PE
Printing was performed on T (manufactured by Toray E-20), and the solvent resistance was evaluated in the same manner as in Example 1. As a result, remarkable damage was observed in one round trip for MEK and one round trip for TOL.

[0019]

Comparative Example 5 Comparative Example 6 A commercially available resin-type thermal transfer sheet of Company C was used for white PET (E made by Toray).
-20), and the solvent resistance was evaluated in the same manner as in Example 1. The result is one round trip for MEK, TOL
However, significant damage was observed in one round trip.

[0020]

The solvent resistance of the examples and comparative examples obtained as described above was evaluated on a five-point scale as shown below, and the results are shown in Table 1. Table 1 Molecular weight Density Solvent resistance g / cm3 MEK TOL Example 1 2,000 0.95 ○ 〃 24,000 0.98 〃 〃 3 8.000 0.97 ◎ １１ 4 11.000 0.96 ◎ ◎ Comparative Example 1 1.000 0.95 ○ × 〃 22,000 0.92 △ × ３ 37,000 0.92 △ × ４ 4 Company A resin type thermal transfer sheet ×× × ５ 5 Company B Resin-type thermal transfer sheet ×× ×× ６ 6C Company resin-type thermal transfer sheet ×× ×× However, the meanings of the symbols are as follows. ◎: 51 reciprocations or more ：: 31 to 50 reciprocations △: 11 to 30 〃 ×: 2 to 10 〃 XX: 1 reciprocal or less As described above, the image of the label printed with the thermal transfer sheet of the present invention is very excellent. Solvent resistance.

Continuation of front page (56) References JP-A-1-301286 (JP, A) JP-A-2-241790 (JP, A) JP-A-62-158093 (JP, A) JP-A-4-327989 (JP, A) JP-A-1-301286 (JP, A) JP-A-2-241790 (JP, A) JP-A-6-328867 (JP, A) JP-A-62-37189 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) B41M 5/38-5/40

Claims (1)

(57) [Claims] 1. A thermal transfer sheet comprising a base film provided with a stick prevention layer on one surface and a transfer adjustment layer and a thermal transfer ink layer on the other surface, wherein the resin component of the thermal transfer ink layer has a molecular weight of 2,000 or more. A polyethylene resin having a density of 0.95 or more and dispersed in a xylene solvent together with a colorant component, and is a thermal transfer ink layer formed by dissolving in hot xylene during the drying process of the solvent xylene and binding and integrating with the colorant particles. A thermal transfer sheet that is unique.