JPH0251394B2 - - Google Patents

Description

Detailed Description of the Invention [Summary] The present invention is capable of impairing the function of repeated transfer recording even on recording paper having a relatively rough paper surface by a thermal transfer recording device using a thermal transfer ink sheet that can be repeatedly transferred, a facsimile machine, etc. In order to obtain good printing records without any problems, a wax-like compound having a urethane bond and an ester wax such as carnauba wax are added to the low melting point wax material constituting the heat-melting ink layer of the heat transfer ink sheet that can be repeatedly transferred. By using this method, it is difficult to form a rough surface pattern on the ink layer of the thermal transfer ink sheet after transfer, which causes stains in the form of afterimages to be transferred to the recording paper.
High density on recording paper with a rougher paper surface than before,
Moreover, a homogeneous transferred recorded image can be obtained with good reproducibility.

[Industrial application field]

The present invention relates to the improvement of a thermal transfer ink sheet that can be repeatedly transferred and applied to a thermal transfer recording device or a facsimile machine, etc., and in particular can produce a uniform transfer streak with high density and no afterimage stain even on relatively rough recording paper. This invention relates to the structure of a hot-melt ink layer from which an image can be obtained.

One of the recording methods for thermal printers and facsimiles is the thermal transfer recording method. This is done by pressing a thermal head through a thermal transfer ink sheet with a heat-melting ink layer on plain paper, such as commonly used high-quality paper, which is guided by a platen or the like. A plurality of heat generating parts of a thermal head are selectively made to generate heat based on print information, and heat-melting ink is transferred onto recording paper to perform recording.

The thermal transfer ink sheets mentioned above are widely used as one-time type thermal transfer ink sheets, which cannot be used multiple times because the ink layer used for recording comes off after one transfer recording. Recently, due to the high cost and the problem of disposing of unnecessary thermal transfer ink sheets after recording,
A thermal transfer ink sheet that can be used repeatedly has been developed, and various configurations have been proposed.

Although this thermal transfer recording method has the advantage of being able to use plain paper as the recording paper, in order to obtain good print records, it is necessary to select high-quality plain paper with a smooth surface. . For this reason, there is a demand for thermal transfer ink sheets, ink ribbons, etc. that can perform good printing even on plain paper with a somewhat rough paper surface, especially thermal transfer ink sheets and ink ribbons that can be repeatedly transferred.

[Conventional technology]

As shown in FIG. 3, a conventional thermal transfer ink sheet that can be repeatedly transferred is coated with Kayaset Black (Japanese (manufactured by Kayaku), fatty acid amide wax (manufactured by NOF Corporation) and paraffin wax as low melting point wax materials, and an appropriate amount of fine powder made of carbon black with excellent cohesion as a filler. It has a structure in which a layer 3 of heat-melting ink is melted and dispersed.

Note that the fine powder made of carbon black is not used as a black pigment in this case;
By mixing and dispersing this fine powder, the ink composition material consisting of the colorant and the low melting point wax material on the base material 1 is formed into a porous sponge-like structure, and the ink composition whose clay content has been reduced by heat is removed. , plays the role of a medium that causes the ink layer 3 to seep out little by little from between the dispersed fine powders onto the surface of the ink layer 3.

Then, with the surface of the ink layer 3 of the thermal transfer ink sheet superimposed on the recording paper, the base material 1
By pressing a thermal head against the surface and selectively generating heat from a plurality of heat generating parts of the thermal head based on the printed information, the ink composition material in the ink layer 3 is selectively heated and melted, and the ink layer 3 is heated and melted. 3, and only this exuded ink composition material is transferred to the recording paper, making it possible to repeatedly perform transfer recording with good reproducibility.

[Problem that the invention seeks to solve]

By the way, in thermal transfer recording using a thermal transfer ink sheet, it is generally convenient to use plain paper as the recording paper, but in reality, if plain paper with a rough surface is used, the ink composition of the thermal transfer ink sheet during transfer will be affected. Due to the poor adhesion of the material, the transfer density is low and it is difficult to obtain a homogeneous transferred recorded image. In addition, the heat-melting ink layer 3 after transfer
Due to poor surface coating formation ability (the surface of the transfer afterimage becomes smooth immediately), the rough surface pattern of the transfer afterimage generated on the surface of the ink layer 3 causes transfer stains and background stains on the recording paper. There is a problem that print quality deteriorates. Therefore, in order to obtain good print records, it is necessary to select high-quality plain paper with a smooth surface. However, in thermal transfer recording using the conventional thermal transfer ink sheet that can be repeatedly transferred as described above, it is difficult to obtain good print records on plain paper with a rough surface without impairing the function of repeatedly transferring. There was an extremely difficult drawback.

On the other hand, in order to eliminate blurring of printed characters, a heat-sensitive transfer sheet using urethane wax, which is a compound having an -NHCO- atomic group in its molecules, has already been proposed in Japanese Patent Application Laid-open No. 199195/1983. Proposed.

However, when transfer recording is performed on recording paper with a relatively rough paper surface using a heat-sensitive transfer sheet using only urethane wax as the binder of such an ink layer, the ink composition has excellent film-forming ability and is stable at room temperature. Because it has high hardness and low adhesiveness, there is no transfer stain on the recording paper due to the surface of the ink layer after transfer, and even if a rough surface like a transfer afterimage occurs on the surface of the ink layer, the transfer stain will not occur on the recording paper. However, since the melt viscosity during transfer recording is too high, homogeneous transfer cannot be obtained, resulting in a low transfer density and a deterioration in recording quality.

In view of these conventional drawbacks, it is an object of the present invention to provide a thermal transfer ink sheet that can be repeatedly transferred and can perform good transfer recording even on plain paper with a somewhat rough paper surface.

[Means for solving problems]

In order to achieve the above object, the present invention has a base material 21 made of polyester film as shown in FIG.
On the top, 1 part by weight of a dye made of Kayaset Black as a coloring agent and a film having good adhesive film forming ability having urethane bond as a low melting point wax material are applied via an intermediate adhesive layer 22 made of a polyester resin and a polyamide resin. 2 parts by weight of a superior urethane wax, 0.1 to 1 part by weight of an ester wax such as carnauba wax, and 1 part by weight of a paraffin wax are mixed, and carbon black, which has excellent cohesive properties, is used as a filler. 0.5 of fine powder
The thermal transfer ink sheet is provided with a heat-melting ink layer 23 in which parts by weight are mixed and dispersed with a solvent such as acetone and can be repeatedly transferred.

[Effect]

For the thermal transfer ink sheet of the present invention, when repeatedly performing transfer recording on recording paper with a rough paper surface, in order to achieve uniform transfer, a low melting point wax material containing a colorant has good adhesion, and the ink sheet is in a molten state. In order for the low melting point wax material to ooze out efficiently from between the fillers onto the surface of the hot melt ink layer, it must have a low melting viscosity, and it must also have a low melting viscosity to prevent the surface of the hot melt ink layer from becoming rough after transfer. In order to eliminate this problem, the low melting point wax material is required to have excellent film forming ability.

Therefore, in the present invention, we developed a wax-like wax that has -NHCO- atomic group of urethane bond in its molecule, which has heat melting properties similar to natural wax and synthetic wax, has good adhesiveness, and has excellent film-forming ability when solidified. compounds, namely isocyanate compounds and alcohols,
A reaction product with any one of amines, thiols, and carboxylic acids, especially those with a molecular weight of 100~
By mixing 1000 urethane wax and carnauba wax whose main component is cerotate ester, which is a type of ester wax, at an appropriate weight ratio, the melting point of the mixed wax material will be the eutectic point. We discovered a phenomenon in which the viscosity of the mixed wax decreases due to the effect of heat transfer, and that the viscosity of the melt viscosity also decreases. Focusing on this phenomenon, we used the above-mentioned mixed wax material as a low melting point material that forms the heat melt ink layer in a heat transfer ink sheet that can be repeatedly transferred, together with a colorant and a filler. Because it is used as a wax material, even if the surface of the transfer trace of the heat-melting ink layer becomes rough during repeated transfer recording on rough recording paper, the surface can be immediately smoothed due to its low melting viscosity and film-forming ability. There is no transfer stain on the recording paper due to the rough surface like an afterimage as in the past, and the heat-melting ink is evenly transferred not only to the convex parts of the uneven paper surface of the recording paper but also to the concave parts.

Therefore, for example, a thermal transfer ink ribbon having the same structure as the thermal transfer ink sheet described above is installed in a serial thermal transfer printer, and a thermal head is printed via the thermal transfer ink ribbon onto recording paper made of plain paper, which has a rougher surface than conventional high-quality paper. By repeating transfer recording in a pressed state, it is possible to obtain a homogeneous transferred recorded image with good transfer density and good reproducibility.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a sectional view of a main part for explaining an embodiment of a thermal transfer ink sheet that can be repeatedly transferred according to the present invention.

In the figure, 21 is a base material made of a polyester film having a thickness of 6 μm, and an intermediate adhesive layer 22 made of a polyester resin and a polyamide resin is provided on the base material 21 to have a thickness of 3 μm.

Further, on the intermediate adhesive layer 22, for example, 1 part by weight of a dye consisting of Kayaset Black KR (manufactured by Nippon Kayaku Co., Ltd.) as a coloring agent and a reaction product of hexamethylene diisocyanate and ethyl alcohol as a low melting point wax material. Alflo DH-20 (manufactured by NOF Corporation) is a wax-like compound that has a -NHCO- atomic group with a urethane bond in its molecule.
2 parts by weight of urethane wax with good adhesion and excellent film-forming ability, and Carnauba No. 1 (manufactured by Nikko Fine Products), whose main component is cerotate ester, which is a type of ester wax. 0.1 to 1.0 parts by weight of carnauba wax and 1.0 part of paraffin wax (SP0145, manufactured by Nippon Seirosha)
A heat-melting ink made by mixing and dispersing 0.5 parts by weight of finely powdered carbon black made of Toka Black #7550 (manufactured by Tokai Carbon Co., Ltd.), which has excellent cohesion as a filler, with a solvent such as acetone. A thermal transfer ink sheet that can be repeatedly transferred is provided with a layer 23 having a thickness of 10 μm.

Therefore, such a thermal transfer ink sheet is formed into a ribbon and mounted on a recording paper whose paper surface is relatively rougher than the conventional high-quality paper used in a serial thermal transfer printer, such as Xerox paper made of type PA4 manufactured by Kishu Paper Co., Ltd. As a result of repeating transfer recording with a thermal head pressed onto the thermal transfer ink ribbon at a printing energy of 30 mJ/mm ² and a printing pulse width of 1 ms, the low melting point of the ink layer 23 of the thermal transfer ink ribbon was confirmed. Since the melt viscosity of the wax material is reduced by mixing the urethane wax and the ester wax, it oozes out efficiently from between the gaps between the fillers made of carbon black and onto the surface of the ink layer 23, and improves adhesiveness and film-forming ability. As a result, it was possible to repeatedly transfer a homogeneous recorded image with good transfer density and no transfer afterimage stains with good reproducibility.

In addition, Figure 2 shows the type PA4 made by Kishu Paper Co., Ltd.
Transfer results when the weight ratio of carnauba wax to urethane wax in the low melting wax material constituting the ink layer of the thermal transfer ink ribbon according to the above example was varied from 0 to 0.6 onto Xerox paper consisting of Shows the relationship with optical density.

In addition, the Xerox paper (type manufactured by Kishu Paper Co., Ltd.)
PA4) has a ten-point average roughness (Rz) of 19μ.
m, and the commonly used paper surface roughness Rz
This recording paper has a relatively rough surface compared to recording paper whose surface is 10 μm or less.

As is clear from FIG. 2, when carnauba wax is not added to the low melting point wax material that composes the hot melt ink layer together with the colorant and filler, the urethane wax has good adhesion, but the melt viscosity Since the transfer is too high and the transfer is not performed uniformly, the transfer density becomes low, and the original film forming ability is not exhibited, so a rough surface like a transfer afterimage occurs on the surface of the ink layer, resulting in transfer stains, and the transfer record is deteriorated. quality deteriorates. In addition, by changing the blending weight ratio of carnauba wax to urethane wax from 0.1 to 0.5, the adhesion of the urethane wax is optimized, the transfer density increases, and the transfer record is homogeneous without transfer afterimage stains. A clear transferred recorded image with good quality can be obtained.
Furthermore, as the amount of carnauba wax added increases, the melt viscosity increases and the adhesion to recording paper decreases, so the transfer density decreases and the above blended weight ratio increases.
It was confirmed that when the value is 0.6 or more, the homogeneity of the transferred recorded image deteriorates.

〔Effect of the invention〕

As is clear from the above description, according to the repeatable transferable thermal transfer ink sheet of the present invention, the urethane wax with good adhesiveness in the low melting point wax material constituting the ink layer of the thermal transfer ink ribbon By mixing an appropriate amount of ester wax, an excellent advantage is that it is possible to obtain a homogeneous transferred recorded image with high density and no transfer afterimage stains with good reproducibility on recording paper with a rougher paper surface than before. has.

Therefore, by applying the repeatable thermal transfer ink sheet of the present invention to a thermal printer, facsimile, etc., the range of recording paper applications can be widened, and the practical effects are significant.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of essential parts for explaining an embodiment of a thermal transfer ink sheet according to the present invention. FIG. 2 is a diagram showing the relationship between the blending weight ratio of carnauba wax to urethane wax in the low melting point wax material constituting the heat-melting ink layer and the transfer density. FIG. 3 is a sectional view of a main part for explaining a conventional thermal transfer ink sheet. In FIG. 1, 21 is a base material, 22 is an intermediate adhesive layer, and 23 is a heat-melting ink layer.

Claims (1)

[Claims] 1. A thermal transfer ink sheet capable of repeated transfer, comprising a heat-melting ink layer 23 made of a colorant, a low-melting wax material, and a filler provided on a base material 21 via an intermediate adhesive layer 22. A thermal transfer ink sheet, wherein the low melting point wax material constituting the heat-melting ink layer 23 is composed of at least a wax-like compound having a urethane bond and an ester wax. 2. The thermal transfer ink sheet according to claim 1, wherein the mixing ratio of the ester wax to the waxy compound having urethane bonds is 5 to 45% by weight.