JP2714512B2 - Thermal transfer recording medium - 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 recording medium, and more particularly to a thermal transfer recording medium having high sensitivity and capable of realizing high-resolution printing on rough surface paper such as copy paper.

[0002]

2. Description of the Related Art In a thermal transfer recording system, a thermal transfer recording medium is used in which at least one layer of a thermal fusible ink is applied on a base material on a sheet. This is a recording method in which an ink layer is heated and melted by a heating head from the substrate side of a thermal transfer recording medium to obtain a transfer image on a transfer paper, in such a manner as to be in contact with the substrate. According to this method, the apparatus to be used has been widely used in recent years because the apparatus to be used is low noise, has excellent operability and maintainability, and can use plain paper as a transfer paper.

[0003]

As the performance of a thermal transfer printer has been improved, a complex function such as high-speed printing on rough surface paper has been required. When considering a high-speed printer, high-speed followability (high sensitivity) of the ribbon is a major issue. High sensitivity has been realized by using low-melting wax, but printing with poor coverage and poor chipping on rough surface paper, or printing with poor resolution by penetrating into paper. Was. further,
In order to increase the high-speed followability while keeping the coating of the rough surface paper,
Conventionally, introduction of a resin component into a binder (Japanese Patent Laid-Open No. 54-8723)
No. 5, No. 54-163044, No. 56-98269, No. 62-130887
No.), but none of them could satisfy the complex requirements in a well-balanced manner. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a thermal transfer recording medium capable of performing printing with good resolution (coating) and high-speed followability on rough surface paper.

[0004]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that a hot melt blending of an incyanate polymer of lanolin fatty acid polyhydric alcohol ester having a specific melt viscosity and an ethylene vinyl acetate resin in a specific ratio. Forming a water-soluble ink layer on a substrate via a wax release layer, and providing a coating layer having a cohesive force greater than the cohesive force of the heat-fusible ink layer on the surface of the heat-fusible ink layer. As a result, it has been confirmed that the above object can be achieved, and the present invention has been completed.

That is, the present invention relates to (a) an isocyanate polymer of a lanolin fatty acid polyhydric alcohol ester having a melt viscosity at 100 ° C. of 3,000 to 50,000 cSt, and (b) an ethylene vinyl acetate resin in a binder excluding a coloring component in an amount of 15 to 50%. A heat transfer ink layer comprising 60% by weight and (c) a coloring component as an essential component is formed on a substrate via a wax release layer, and the surface of the heat-fusible ink layer is A cohesive force greater than the cohesive force (F ₁ ) of the hot-melt ink layer
A thermal transfer recording medium provided with a coating layer having (F ₂ ).

The isocyanate polymer of a lanolin fatty acid polyhydric alcohol ester used in the present invention is a lanolin fatty acid obtained by saponifying and decomposing lanolin secreted from the sebaceous line of sheep, and a polyisocyanate such as glycerin, pentaerythritol and trimethylolpropane. It is obtained by crosslinking an esterification reaction product with a polyhydric alcohol with an isocyanate such as tolylene diisocyanate (TDI) or diphenylmethane 4,4′-diisocyanate (MDI). Among them, in the present invention, it is necessary to use a lanolin fatty acid polyhydric alcohol ester isocyanate polymer having a melt viscosity at 100 ° C. of 3,000 to 50,000 cSt. 100 ° C melt viscosity
When a polymer having a viscosity of less than 3000 cSt is used, the cohesive force is weak, as in the case of wax, and the ink becomes poorly coated on the rough surface paper. Conversely, if a lanolin fatty acid polyhydric alcohol ester isocyanate polymer exceeding 50,000 cSt is used, the ink will be poorly cut and the ink will have low resolution in high-speed printing.

Next, the ethylene vinyl acetate resin used in the present invention is a copolymer of ethylene and vinyl acetate, and has a molecular weight,
It can be used regardless of the vinyl acetate ratio. The optimum blending amount of the ethylene vinyl acetate resin is 15 to 60% of the total ink binder excluding the coloring component. If the compounding amount is less than 15%, problems such as background contamination occur, while if it exceeds 60%, sensitivity and ink cut-off are poor, resulting in high-speed printing and low-resolution ink.

The ink binder of the hot-melt ink layer according to the present invention includes waxes such as paraffin wax, carnauba wax, candelilla wax, beeswax, wood wax, low molecular weight polyethylene wax, α-olefin oligomer and montan wax. Ingredient or petroleum resin,
It is also possible to use a resin component such as an ethylene-acrylic acid copolymer, polyethylene, or an acrylic resin in combination. Further, it is also possible to mix optional components such as a dispersant usually mixed in the hot-melt ink.

The heat-fusible ink layer according to the present invention comprises the above-mentioned ink binder component and coloring component as essential components. As the coloring component, any coloring component having coloring ability can be used. For example, black dyes and pigments such as carbon black, oil black, and graphite, CI Pigment Yellow 1, 3, 74, 97, and 98
Acetoacetate arylamide type monoazo yellow pigment (fast yellow), CI Pigment Yellow 12, 13, and 14 etc.
yellow pigments such as ent Yellow 19, 77, 79, CI Disperse Yellow 164, CI Pigment Red 48, 49: 1, 53: 1, 5
7: 1, 81, 122, 5 etc.red or red pigment, CIS
olvent Red 52, 58, 8 etc., red pigments, CI Pigment
Blue dyes and pigments such as copper phthalocyanine and derivatives thereof such as Blue 15: 3 and modified products can be used. Further, dyes and pigments known in the related art for printing inks and other coloring purposes, such as colored or colorless sublimable dyes, can be used. The amount is not particularly limited, but 10 to 60% is optimal.

In the thermal transfer recording medium of the present invention, a coating layer is formed on the surface of the above-mentioned heat-meltable ink layer.
The cohesive force (F ₂ ) of the coating layer must be greater than the cohesive force (F ₁ ) of the hot-melt ink layer. In the present invention, the cohesive force between the hot-melt ink layer and the coating layer is measured as follows. First, the cohesive force (F ₁ ) of the heat-meltable ink layer is measured by bonding a pressure-sensitive adhesive tape to the ink layer formed on the base material and using a tensile strength tester (Tensilon RTM-100 manufactured by Toyo Baldwin Co., Ltd.). The force when the support and the adhesive tape were peeled off at 25 ° C. at a peeling angle of 180 ° and a peeling speed of 300 mm / min was converted to a width per 1 cm. The cohesive force (F ₂ ) of the coating layer is measured in the same manner as the cohesive force of the ink using a tensile strength tester with an adhesive tape adhered to the coating layer formed on the surface of the heat-meltable ink layer. The coating layer provided on the surface of the hot-melt ink of the present invention, polyethylene, ethylene vinyl acetate copolymer resin and its modified, ethylene acrylate copolymer, ionomer resin, polyamide resin, nylon resin, polyester resin, polypropylene A resin or the like is used. The above resins may be used alone or in combination of two or more. Further, in order to improve the wettability of the transfer material, rosin, rosin derivative, terpene, modified terpene resin, aliphatic petroleum resin, aromatic petroleum resin, water-added and copolymerized petroleum resin, dicyclopentadiene-based Petroleum resins, cumarone-indene resins, styrene resins, and isoprene resins may be added. In addition, in order to improve the cut of printing, paraffin wax, microcrystalline wax, Fischer-Tropsch wax,
Various low molecular weight polyethylene waxes, modified waxes, waxes such as atactic polypropylene may be added.

In the thermal transfer recording medium of the present invention, it is essential to provide a wax-based release layer between the substrate and the heat-meltable ink layer. As the wax used for the wax-based release layer, microcrystalline wax, carnauba wax,
One or more selected from the group consisting of candelilla wax, rice bran wax and oxidized polyethylene wax are preferred. In addition to the waxes, resins such as an ethylene-vinyl acetate copolymer, an ethylene-acrylic acid copolymer, polyethylene, and a petroleum resin may be added to improve the strength of the coating film. By providing a wax-based release layer between the substrate and the heat-fusible ink layer, a high-sensitivity, high-quality transfer image can be obtained.

The base material of the thermal transfer recording medium of the present invention includes
Paper sheets such as condenser paper and glassine paper, thin sheets and films of polyester such as polyethylene terephthalate, and plastics such as polyimide, polycarbonate, polyamide, polyethylene, and polypropylene are used. The thickness of the substrate is preferably in the range of about 2 to 20 μm. When recording is performed using a thermal head or the like, a silicone-based or fluorine-based compound, a resin layer, a cross-linked polymer layer, or a metal layer is provided on the side of the substrate in contact with the thermal head to improve heat resistance and runnability. May be provided. In particular, in order to sufficiently exhibit the performance of the lanolin fatty acid polyhydric alcohol ester isocyanate polymer ink of the present invention, it is more preferable to use a silicone-modified acrylic resin or a silicone-modified ester resin.

[0013]

According to the present invention, there is provided a well-balanced thermal transfer recording medium having a film-forming property capable of covering a rough surface paper and ensuring transferability and resolution. The thermal transfer recording medium of the present invention can provide high-sensitivity and high-resolution printing on paper with a rough surface such as copy paper even when printing is performed with a high-speed printer of, for example, about 100 characters / second. Shows good performance.

[0014]

The following examples illustrate the effectiveness of the present invention, but of course the present invention is not limited to these examples.

Example 1 Rice bran wax is blended in toluene at a composition ratio shown in column B of the blending table 1 so as to have a solid concentration of 10%. This is dispersed using a ball mill for 12 hours to form a paint. This paint was treated with a silicone back coat using a wire bar coater to a 3.5 μm thick PET.
Coated to a dry weight of 0.7 g / m ² on a film,
A wax release layer is formed. Next, the melt viscosity at 100 ° C 4
A 000 cSt lanolin fatty acid polyhydric alcohol ester isocyanate polymer is blended in toluene at a composition ratio shown in column D of the blending table 2 so that the solid content concentration becomes 18%. This is dispersed for 12 hours using a ball mill to form an ink. This paint is applied to the wax release layer side of the PET film coated with the wax release layer using a wire bar coater so as to have a dry weight of 2.5 g / m ² to form an ink layer. Finally, using the ethylene-vinyl acetate copolymer, the solid content concentration was determined by the composition ratio shown in the F column of the formulation table 3.
Mix in toluene to 10%. This is dispersed using a ball mill for 12 hours to form a paint. Using a wire bar coater, apply this paint to the PE coated with the ink layer.
A thermal transfer ink ribbon is obtained by applying a dry weight of 0.7 g / m ² on the side of the ink layer of the T film and slitting it to a predetermined width. Using this ribbon, printing was performed with a commercially available Sharp personal word processor WD-A561 (100 characters / second), and the results shown in Table 4 were obtained.

Example 2 Carnauba wax was blended in toluene at a composition ratio shown in column A of Formulation Table 1 so as to have a solid content of 10%, and dispersed in a ball mill for 12 hours to form a paint. I do. This paint is applied on a 3.5 μm PET film treated with a silicone back coat using a wire bar coater so as to have a dry weight of 0.7 g / m ² to form a wax release layer. Next, a lanolin fatty acid polyhydric alcohol ester isocyanate polymer having a melt viscosity of 5500 cSt at 100 ° C. is blended in toluene at a composition ratio shown in column E of the blending table 2 so as to have a solid concentration of 18%. This is dispersed for 12 hours using a ball mill to form an ink. This paint is applied to the wax release layer side of the PET film coated with the wax release layer using a wire bar coater so as to have a dry weight of 2.5 g / m ² to form an ink layer. Finally, a polyamide resin is blended in toluene at a composition ratio shown in column G of the blending table 3 so that the solid content concentration becomes 5%. This is dispersed using a ball mill for 12 hours to form a paint. This paint is applied to the ink layer side of the PET film on which the ink layer has been applied using a wire bar coater so as to have a dry weight of 0.7 g / m ² , and slit into a predetermined width to obtain a thermal transfer ink ribbon. Using this ribbon, a commercially available Sharp personal word processor WD-A56
When printing was performed at 1 (100 characters / second), the results shown in Table 4 were obtained.

Comparative Example 1 Carnauba wax was blended in toluene at a composition ratio shown in column A of formulation table 1 so as to have a solid concentration of 10%, and dispersed in a ball mill for 12 hours to form a paint. I do. This paint is applied using a wire bar coater to a dry weight of 0.7 g / m ² on a 3.5 μm PET film treated with a silicone back coat to form a wax release layer. Next, a lanolin fatty acid polyhydric alcohol ester isocyanate polymer having a melt viscosity of 4,000 cSt at 100 ° C. is blended in toluene at a composition ratio shown in column D of blending table 2 so that the solid content concentration becomes 18%. This is dispersed for 12 hours using a ball mill to form an ink. This paint is applied to the wax release layer side of the PET film coated with the wax release layer using a wire bar coater so as to have a dry weight of 2.5 g / m ² to form an ink layer. Finally, using paraffin wax,
It is blended in toluene so that the solid content concentration becomes 5% at the composition ratio shown in the column. This is dispersed using a ball mill for 12 hours to form a paint. This paint is applied to the ink layer side of the PET film on which the ink layer has been applied using a wire bar coater so as to have a dry weight of 0.7 g / m ² , and slit into a predetermined width to obtain a thermal transfer ink ribbon. Using this ribbon, a commercially available Sharp personal word processor WD-
When printing was performed at A561 (100 characters / second), the results shown in Table 4 were obtained.

Comparative Example 2 A lanolin fatty acid polyhydric alcohol ester isocyanate polymer having a melt viscosity of 5500 cSt at 100 ° C. was used and dissolved in toluene so as to have a solid content of 18% at a composition ratio shown in column E of formulation table 2. Mix. This is dispersed for 12 hours using a ball mill to form an ink. Using a wire bar coater, this paint was applied on a 3.5 μm-thick PET film provided with a silicone-based back coat, to a dry weight of 2.5 g / m ^2.
To form an ink layer. Next, an ethylene-vinyl acetate copolymer is blended in toluene at a composition ratio shown in the F column of the blending table 3 so that the solid content concentration becomes 10%. This is dispersed using a ball mill for 12 hours to form a paint. This paint is applied to the ink layer side of the PET film on which the ink layer has been applied using a wire bar coater so as to have a dry weight of 0.7 g / m ² , and slit into a predetermined width to obtain a thermal transfer ink ribbon. Using this ribbon, a commercially available Sharp personal word processor WD-A561
(100 characters / second), the results shown in Table 4 were obtained.

Comparative Example 3 A microcrystalline wax was blended in toluene at a composition ratio shown in column C of Formulation Table 1 so as to have a solid content of 10%, and dispersed in a ball mill for 12 hours. Become Using a wire bar coater, this paint
3.5μm PET treated with silicone back coat
Coated to a dry weight of 0.7 g / m ² on a film,
A wax release layer is formed. Next, the melt viscosity at 100 ° C 5
A lanolin fatty acid polyhydric alcohol ester isocyanate polymer of 500 cSt is used and blended in toluene at a composition ratio shown in column E of blending table 2 so that the solid content concentration becomes 18%. This is dispersed for 12 hours using a ball mill to form an ink. Using a wire bar coater, apply this coating material to the wax release layer side of the PET film coated with the wax release layer so as to have a dry weight of 2.5 g / m ^2. Get the ribbon. Using this ribbon, a commercially available Sharp personal word processor WD-A
Printing at 561 (100 characters / sec) gave the results shown in Table 4.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

[Table 3]

[0023]

[Table 4]

Here, each evaluation in Table 4 was performed by the following method. (1) Sensitivity: Judgment of dot pattern reproducibility visually ○: Almost perfect reproducibility △: Insufficient reproducibility ×: Poor reproducibility (2) Resolution: Reproducibility of one dot fine line visually judged ○: Reproduction Poor reproducibility ×: Insufficient reproducibility ×: Poor reproducibility (3) Coating: Reproducibility of solid black printing visually judged ○: Reproducibility almost perfect △: Insufficient reproducibility ×: Poor reproducibility (4) Transferability: The state of removal of the ink layer of the ink ribbon after printing is visually determined. ；: Complete or almost complete removal △: Careful observation indicates that only a small part but not removed is present. A part which has not been removed is clearly recognized. (5) Robustness: After printing on solid black, place paper on it and apply a pressure of about 150 g with a pencil (hardness H) on the paper and scratch it to print solid black. The scratched state of the print was visually judged. ；: No scratches were observed. △: Partially scratched. ×: The presence of a scratch is recognized over the entire surface.

As shown in Table 4, the thermal transfer recording medium of the present invention has a very good print quality in terms of sensitivity, resolution, coating, etc., and sufficiently fulfills the original purpose.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-126379 (JP, A) JP-A-62-108089 (JP, A)

Claims (2)

(57) [Claims] (1) The melt viscosity at 100 ° C. is 3000 to 50.
(B) ethylene vinyl acetate resin to the isocyanate polymer of lanolin fatty acid polyhydric alcohol ester of 000 cSt,
15 to 60% by weight in the binder excluding the coloring component, and (c)
A heat transfer ink layer containing a coloring component as an essential component is formed on a substrate via a wax release layer, and the aggregation of the heat-fusible ink layer on the surface of the heat-fusible ink layer A thermal transfer recording medium comprising a coating layer having a cohesive force (F ₂ ) greater than a force (F ₁ ). 2. The wax component according to claim 1, wherein the wax component of the wax release layer is at least one selected from the group consisting of microcrystalline wax, carnauba wax, candelilla wax, rice bran wax and polyethylene oxide wax. Thermal transfer recording medium.