JPH07100393B2 - Thermal transfer recording material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a heat-sensitive transfer recording material, and more particularly to improvement of a heat-meltable ink constituting the heat-meltable ink layer.

[Conventional technology]

The heat-sensitive transfer recording material is generally constituted by forming a heat-meltable ink layer 2 on a substrate 1 made of a resin film such as a polyester film, as shown in FIG.

For the base material 1, the polyester film (polyethylene terephthalate film) as described above is costly,
It is most often used because it has well-balanced properties such as heat resistance and strength as a base material for a thermal transfer recording material, but in the past, when the thickness was reduced, sufficient strength could not be obtained. A relatively thick polyester film of about 10 μm was used (for example, Trikeps Blue Papers No.1 issued by Trikeps Co., Ltd.)
5, P4-4).

The heat-fusible ink layered on the base material requires a heat of fusion (melting the solid at the melting point) so that the transferable state is quickly reached because the thickness of the base material is large. It was designed to have a relatively small amount of heat. That is, the heat-meltable ink needs to be melted by the heat from the thermal head abutting on the surface of the substrate opposite to the heat-meltable ink layer forming surface and transferred to the transfer target. If the heat of fusion of the fusible ink is large, a large amount of heat must be applied to the base material in order to melt the ink, and the base material may be softened or melted by the heat, which may impair running properties. Therefore, the heat-meltable ink must be melted before the substrate is damaged by heat, and the heat-meltable ink of the commercially available heat-sensitive transfer recording material has a relatively low heat of fusion. According to the measurement, even the large one was designed to be relatively small, about 23 cal / g.

However, various improvements have been made to the base material, and recently, a base material having a thickness of about 3 to 4 μm, which can be sufficiently used as a base material for a thermal transfer recording material, has been developed.

When the base material becomes thinner in this way, compared to conventional products,
The heat conduction to the heat-meltable ink layer is improved. However, as for the heat-meltable ink, the one with a relatively low heat of fusion is used as in the past, so that the applied energy of the thermal head varies to the large side, and the ink is heated to a higher temperature than necessary for transfer. , When printed
Since the thermal transfer recording material moves and the next print is performed before the ink is completely set, the rear part of the print is soiled, which deteriorates the resolution and ink in the part not used for printing is printed by the thermal head. There is a problem in that the surface of the transfer paper is rubbed by sliding and the transfer paper is soiled, that is, so-called background stain occurs.

[Problems to be solved by the invention]

This invention has the "poor resolution" of the above conventional products.
Another object of the present invention is to provide a heat-sensitive transfer recording material that solves the problem of "easiness of scumming" and enables good printing.

[Means for solving problems]

This invention uses a mixture of waxes and a specific thermoplastic resin as a binder of the hot-melt ink to increase the heat of fusion of the hot-melt ink to 30 to 45 cal / g, which is larger than that of the conventional one. The above-mentioned object is achieved by reducing the influence of variations in the applied energy on the printing characteristics, eliminating poor resolution and easiness of scumming.

In order to make it easier to understand the effect of the heat of fusion of the heat-meltable ink on the printing characteristics, description will be given with reference to FIG.

FIG. 2 is a diagram conceptually showing the relationship between the applied energy and the temperature of the ink, with the applied energy on the horizontal axis and the temperature of the ink (heat-melting ink) on the vertical axis.

As energy is applied to the ink, the ink temperature rises to point A accordingly. This point A is a so-called glass transition temperature, and since the ink needs energy to cause the glass transition between points A and B, the temperature of the ink does not rise even if energy is applied during this period. However, when the point B is exceeded, the ink temperature rises as the applied energy increases until the point C is reached. The temperature from the point C to the point D corresponds to the melting point. During this period, the ink temperature does not rise even if energy is applied, the ink is in a semi-molten state, and under normal conditions, when the ink is in this state Is transferred to. The energy (calorific value) required from the point C to the point D corresponds to the heat of fusion, and the longer the distance between the CDs, that is, the larger the heat of fusion, the more the influence of the variation in energy given by the thermal head. Can be absorbed, the ink can be transferred stably,
The printing "blurring" is also eliminated and the resolution is improved. The temperature rises as the applied energy increases from point D toward point E. And if the distance between the CDs is short,
In other words, if the heat of fusion is small, it is more likely to be affected by the variations in the energy provided by the thermal head.If the energy applied to the thermal head varies to the larger side, the ink will not be transferred within the state between the CDs. The transfer is performed after passing the point D, and the rear portion of the print is stained.

As described above, the larger the heat of fusion is, the more stable printing can be performed. However, as described later, even if the heat of fusion is too large, a large amount of energy (heat quantity) is required until the ink can be transferred.
Therefore, the base material is damaged during that time, which is not preferable in some cases.

In the present invention, the heat of fusion of the heat-meltable ink is 30 to 45 cal /
When the heat of fusion of ink is less than 30 cal / g, it is easy to be affected by the variation in energy from the thermal head, and stains occur on the back of the print or background stains. If the heat of fusion of the ink exceeds 45 cal / g, a large amount of energy will be required for proper transfer, and the base material will be damaged by heat deterioration, which will hinder the running performance. is there.

From the viewpoint of the composition of the heat-meltable ink, it is the binder that has the greatest effect on the heat of fusion of the ink,
The heat of fusion of the heat-meltable ink can be adjusted within the range of 30 to 45 cal / g by improving the composition of the binder from the conventional composition.

The binder is selected from the group consisting of at least one wax selected from the group consisting of paraffin wax and carnauba wax as used in Examples described later, and a group consisting of petroleum resin, polystyrene resin and ethylene-vinyl acetate copolymer. It is prepared by using together with at least one kind of thermoplastic resin. Fluids such as liquid paraffin and low molecular weight polyethylene glycol are also optionally used for preparing the binder.

Thermoplastic resins such as petroleum resins generally have the highest heat of fusion among these binder materials, and waxes generally have lower heat of fusion than thermoplastic resins. Among waxes, carnauba wax has higher heat of fusion and paraffin Wax has a small heat of fusion. Therefore, when preparing the heat-meltable ink, the heat of fusion of the binder materials is taken into consideration, and appropriate materials are selected and combined. Basically, because the heat of fusion is higher than that of the conventional composition, the blending amount of thermoplastic resin such as petroleum resin is larger than that of the conventional composition, and the blending amount of wax having a low heat of fusion such as paraffin wax is the conventional composition. To be less.

A polyester film (polyethylene terephthalate film) is generally used as the base material, but other resin films such as a polyimide film, a polycarbonate film and a nylon film can be used instead.

EXAMPLES Next, the present invention will be described in more detail with reference to examples.

Examples 1 to 3 and Comparative Examples 1 to 2 Hot melt inks having the compositions shown in Table 1 were prepared. To prepare the ink, use a sand mill, heat to 100 ° C to melt the binder material, and then add carbon black.
This was done by mixing for hours. After the ink was prepared, the heat of fusion of each ink was measured with a differential scanning calorimeter. The results are shown in Tables 1 and 2. In addition, the compounding number of each component in Table 1 is based on the weight part.
In Table 1, the manufacturer name and trade name of paraffin wax, petroleum resin, polystyrene resin, carbon black, etc. used are shown in parentheses.

A 3.5 μm-thick polyester film (polyethylene terephthalate film) is used as the base material, and the above heat-meltable ink is applied onto this base material by the hot melt coating method to a thickness of 3.5 μm and heat-melted onto the base material. A conductive ink layer was formed and cut into a ribbon having a width of 6.3 mm.

The structure of the thermal transfer recording material produced as described above is as shown in FIG. In FIG. 1, reference numeral 1 is a base material, and 2 is a hot-melt ink layer formed on the base material 1.

Comparative Example 1 Several commercially available ribbon-shaped thermal transfer recording materials were purchased, and the heat of fusion of these heat-meltable inks was measured by a differential scanning calorimeter. The highest heat of fusion was 22.8 cal / g. Therefore, the one having the largest heat of fusion was set as Comparative Example 1. In addition, when the base material of this commercially available heat-sensitive transfer recording material was examined, a polyester film having a thickness of 3.5 μm was used for the base material, as in the heat-sensitive transfer recording material of the above-mentioned example.

Using the thermal transfer recording materials of Examples 1 to 3, Control Examples 1 and 2 and Comparative Example 1, 0.5 mjoul of energy was applied to a thermal head having an area of 200 μm × 200 μm, and plain paper (paper having a Beck smoothness of 175 seconds was used. ), And the transfer area ratio was measured. The results are shown in Table 2. The transfer area ratio is
Measure the area of the transferred ink (measurement with an optical microscope
The measurement is carried out by magnifying 100 times), and it is divided by the head area of the thermal head, and is shown as a percentage.

As shown in Table 2, the thermal transfer recording materials of Examples 1 to 3 of the present invention had a transfer area ratio of 97 to 104%, which was close to 100%.
There was no print bleeding and the resolution was excellent. Further, in order to investigate the occurrence of scumming due to running, each thermal transfer recording material was run by 70 m at a printing speed of 40 characters / second, but the thermal transfer recording materials of Examples 1 to 3 of the present invention were all There was no dirt. In contrast, the heat of fusion of the ink
The thermal transfer recording material of Comparative Example 1 of 15.9 cal / g and the heat of fusion is 22.8 c
The thermal transfer recording material of Comparative Example 1 (conventional product) of al / g has a transfer area ratio of 120% and 112%, respectively, and print bleeding occurs, and running causes scumming at 8 and 3 places, respectively. did. Further, in the thermal transfer recording material of Comparative Example 2 in which the heat of fusion was increased to 50.0 cal / g, the ink was insufficiently melted as the heat of fusion was increased, so that the transfer area ratio was as small as 80%. Then, there was a chip in the print.

〔The invention's effect〕

As described above, in the present invention, the heat of fusion of the heat-meltable ink is set to 30 to 45 cal / g, thereby providing a thermal transfer recording material having excellent printing characteristics, which is free from back stains and background stains of printing. I was able to.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a thermal transfer recording material, and FIG. 2 is a view showing a relationship between applied energy and ink temperature. 1 ... Substrate, 2 ... Hot-melt ink layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Shinji Yamazaki Inventor Shinji Yamazaki 1-88 No. 1 Tora, Ibaraki-shi, Osaka Inside Hitachi Maxell Co., Ltd. (56) Reference JP-A-61-84288 (JP, A) JP-A-SHO 60-198292 (JP, A)

Claims (1)

[Claims] 1. A heat-sensitive transfer recording material comprising a base material and a heat-meltable ink layer, wherein the binder of the heat-meltable ink layer is at least one wax selected from the group consisting of paraffin wax and carnauba wax. Kind,
The heat of fusion of the heat-meltable ink, which is composed of a mixture with at least one thermoplastic resin selected from the group consisting of petroleum resin, polystyrene resin and ethylene-vinyl acetate copolymer, and has a heat of fusion of the heat-meltable ink constituting the heat-meltable ink layer is 30-45cal / g
A heat-sensitive transfer recording material characterized by: