JPH0818465B2 - Thermal transfer material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a heat-sensitive transfer member, and more particularly to improvement of an ink layer thereof.

[Conventional technology]

The ink for forming the ink layer of the thermal transfer member is wax,
A colorant such as carbon black is dispersed in a binder such as a thermoplastic resin (see, for example, JP-A-55).
No. 3919), the use of wax as a binder has the advantage that the thermal response of the ink is good, but good transfer cannot be performed on paper with a low Beck smoothness, that is, rough surface paper. There was a drawback.

On the other hand, when a thermoplastic resin is used as the binder, it has the advantage that it can be transferred even to rough surface paper with Beck's smoothness of about 20 seconds, but it has poor thermal responsiveness However, there was a problem in that it could not sufficiently cope with the increase in printing speed.

[Problems to be solved by the invention]

In the present invention, the ink using the conventional thermoplastic resin binder has poor thermal responsiveness and lacks the fidelity of the printed image,
It solves the problem that it was difficult to support high-speed printing, improves the thermal response of the ink without compromising the advantage of being able to transfer to rough surface paper based on thermoplastic resin, and improves the fidelity of the printed image. It is an object of the present invention to provide a heat-sensitive transfer body which is excellent and can be used for high-speed printing.

[Means for solving problems]

INDUSTRIAL APPLICABILITY According to the present invention, an aliphatic polycarbonate is added to a thermoplastic resin, and a mixture of the thermoplastic resin and the aliphatic polycarbonate is used as a binder, so that it can be transferred to rough paper and has good thermal response. It is possible to obtain various inks to improve the fidelity of the printed image and to cope with high-speed printing.

The aliphatic polycarbonate has the following formula (I) As shown by the repeating unit, it has a linear simple structure and has a smaller molecular weight than the thermoplastic resin.
The melt viscosity is low, and the endothermic peak at the melting point of the differential scanning calorimetry curve is sharp. Therefore, by mixing this with another thermoplastic resin, it can be used as an ink binder with good thermal response. In addition, compared with wax, it has a larger molecular weight, so it does not impair the film-forming ability and does not reduce the cohesive strength of the ink. Also, it has a polar group and is compatible with other thermoplastic resins. And the advantages of the thermoplastic resin are not lowered.

Examples of the above aliphatic polycarbonate include compounds represented by the formula (I
I) A polycarbonate having a hexamethylene-based repeating unit represented by is preferably used. As the polycarbonate having the hexamethylene-based repeating unit represented by the above formula (I), those having a number average molecular weight of about 1,000 to 3,000 are particularly preferable.

As the thermoplastic resin, for example, polyamide, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, styrene-butadiene-styrene block copolymer, etc. are used.

In the binder composed of the mixture of these thermoplastic resins and the aliphatic polycarbonate, the content of the aliphatic polycarbonate is preferably 5 to 50% by weight. This is for the following reason. When the content of the aliphatic polycarbonate is less than 5% by weight, the effect of enhancing the thermal response of the ink is small, while when the content of the aliphatic polycarbonate is more than 50% by weight, the bleeding or scumming of the printed characters is caused. Will be caused.

The ink is obtained by adding about 5 to 50 parts by weight of a colorant such as carbon black to 100 parts by weight of the mixture of the thermoplastic resin and the aliphatic polycarbonate, and mixing and dispersing. Additives such as a dispersant, an antioxidant, and an antistatic agent may be appropriately added to this ink. When preparing the ink, the binder may be dissolved in a solvent and the ink may be prepared in the presence of the solvent. Further, as shown in the examples, it is also possible to prepare an ink using a thermoplastic resin as a binder and an ink using an aliphatic polycarbonate as a binder separately, and mix them to prepare an ink.

〔Example〕

Ink A was prepared by mixing 5 kg of polyamide and 1 kg of carbon black in 20 l of n-propyl alcohol and dispersing them for 100 hours using a ball mill.

In addition, aliphatic polycarbonate (S-8200 (trade name),
Asahi Glass Co., Ltd., 5 kg of an aliphatic polycarbonate having a hexamethylene-based repeating unit represented by formula (I) having a number average molecular weight of about 1,500) and 1 kg of carbon black are mixed in 20 l of tetrahydrofuran, and a ball mill is used for 100 hours. Ink B was prepared by dispersion.

Inks A and B prepared as described above were mixed in the proportions shown in Table 1 and dispersed using a ball mill for 8 hours to prepare inks of Sample Nos. 2 to 9 shown in Table 1.

Using polyamide as the thermoplastic resin as described above,
Using a wire bar, the inks of sample Nos. 2 to 8 containing the mixture of this polyamide and the aliphatic polycarbonate as a binder and the inks of sample No. 1 containing only polyamide as a binder were used to form polyethylene terephthalate having a thickness of 3.5 μm. The film thickness after drying on the film is 3μ
It was applied so as to have a thickness of m to prepare a heat-sensitive transfer member. The heat-sensitive transfer member thus produced is shown in FIG. First
In the figure, 1 is a substrate made of polyethylene terephthalate film, and 2 is an ink layer formed by applying the ink prepared as described above on the substrate 1.

The printing evaluation of these heat-sensitive transfer bodies was carried out using a thermal printer with 30 cps and 60 cps on paper with Beck smoothness of 20 seconds, respectively.
ps, 80cps, 120cps and 150cps (1 character is 24 × 2
Printing was performed at a printing speed of 4 dots), and the transfer area ratio was measured. The evaluation results are as shown in Table 1. The transfer area ratio shows the ratio of the size of the printed dot to the size of one dot of the thermal head, and the transfer area ratio of 100% is evaluated as faithfully reproducing the printed image.

As shown in Table 1, the addition of the aliphatic polycarbonate to the polyamide improves the transfer area ratio so that the printed image can be reproduced faithfully. % Range, sample No. 3
As can be seen in ~ 7, the transfer area ratio is almost 10 from low speed printing of 30 ~ 150cps to high speed printing area.
It is in the area close to 0% and can print even on rough surface paper with Beck's smoothness of about 20 seconds, has excellent thermal response, can faithfully reproduce printed images, and supports high-speed printing. A viable ink was obtained.

Further, as described above, by adding the aliphatic polycarbonate, there is an effect that the transfer can be performed even when the applied energy is lower than the conventional one. The proof is as follows.

The applied energy required to print at a printing area rate of almost 100% on a paper with a Beck smoothness of 20 seconds at a printing speed of 80 cps by a thermal transfer body with an ink layer formed from the ink of sample Nos. 1 to 9 The results obtained are shown in Table 2.

As shown in Table 2, when the content of the aliphatic polycarbonate in the binder increases, the transfer area ratio becomes almost 100%.
The energy required to obtain% printing decreases.

From these results, it can be seen that by using the ink containing the aliphatic polycarbonate in the binder, it is possible to transfer at a lower applied energy not only in the high-speed printing but also in the low-speed printing as compared with the conventional product.

〔The invention's effect〕

As described above, in the present invention, by using a binder in which an aliphatic polycarbonate is mixed in a thermoplastic resin, the thermal responsiveness of the ink is enhanced, transfer is possible even to rough surface paper, and printing is possible. It was possible to provide a heat-sensitive transfer member which is excellent in faithful reproducibility of an image and is capable of high-speed printing.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a heat-sensitive transfer member according to the present invention. 1 ... Substrate, 2 ... Ink layer

Claims (3)

[Claims] 1. A heat-sensitive transfer member comprising at least a substrate and an ink layer on one surface thereof which is melted or softened by heat and transferred to another, wherein the ink layer comprises a thermoplastic resin and an aliphatic polycarbonate as binders. A heat-sensitive transfer member, which is formed of an ink using a mixture. 2. An aliphatic polycarbonate has the formula (II) The heat-sensitive transfer member according to claim 1, which is a polycarbonate having a hexamethylene-based repeating unit represented by: 3. The heat-sensitive transfer member according to claim 1, wherein the content of the aliphatic polycarbonate in the binder is 5 to 50% by weight.