JPH11245526A - Heat-sensitive transfer recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-sensitive transfer recording material wherein problems such as 'an unfavorable resolution' and 'being easy to generate scumming' owned by conventional products, are eliminated, and by which a favorable printing can be performed, and which is excellent in printing characteristics. SOLUTION: For this heat-sensitive transfer recording material wherein on a base material, a heat-melting ink layer 2 is provided, a binder for the heat-melting ink layer 2 is constituted of a mixture of at least one kind of wax being selected from the group consisting of parapffin waxes and carnauba waxes, and a thermoplastic resin comprising a petroleum resin, or a petroleum resin and an ethylene-vinyl acetate copolymer, and also, the heat of fusion for the heat-melting ink constituting the heat-melting ink layer 2 is made to be 30-45 cal/g.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a thermal transfer recording material.

[0002]

2. Description of the Related Art A thermal transfer recording material is generally formed 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.

As the substrate 1, the polyester film (polyethylene terephthalate film) described above is most often used because it has well-balanced properties as a substrate for a thermal transfer recording material, such as cost, heat resistance, and strength. Conventionally, a relatively thick polyester film having a thickness of about 6 to 10 μm has been used because a sufficient strength was not obtained when the thickness was reduced conventionally [for example, Trikeps Co., Ltd .;・ Blue Papers No. 15, P4-4].

[0004] The heat-meltable ink layered on the base material has a heat of fusion (solids having a melting point is melted) so as to reach a transferable state as soon as the thickness of the base material is large. The heat required for this was designed to be relatively small. That is, the heat-fusible ink needs to be melted by heat from a thermal head that is in contact with the surface of the base material opposite to the surface on which the heat-fusible ink layer is formed 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 heat may soften or melt the base material, impairing runnability. Therefore, the heat-fusible ink must be melted before the base material is damaged by heat, and therefore, the heat of fusion of the heat-fusible ink of a commercially available thermal transfer recording material is relatively small, and the present inventors have found that According to the measurement, even a large one was designed to be relatively small at about 23 cal / g.

However, various improvements have been made to the base material, and recently a 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 thickness of such a base material is reduced, heat conduction to the heat-fusible ink layer is improved as compared with the conventional product. However, as for the heat-meltable inks, those having a relatively small heat of fusion are used as in the past, so that the applied energy of the thermal head fluctuates to the side where the applied energy is large, and the ink is heated to a temperature higher than necessary for transfer. When printing, the thermal transfer recording material moves before the ink is completely solidified, and the next printing is performed, so the rear part of the printing becomes dirty, thereby deteriorating the resolution and the part not used for printing However, there is a problem in that the ink rubs the surface of the paper to be transferred due to the sliding of the thermal head, so that the paper to be transferred is soiled, that is, so-called background soiling occurs.

[0007]

SUMMARY OF THE INVENTION The present invention solves the problems of "poor resolution" and "easiness of background dirt" of the above-mentioned conventional products, and provides a thermal transfer recording capable of performing good printing. The purpose is to provide materials.

[0008]

According to the present invention, there is provided a heat-sensitive transfer recording material having a heat-meltable ink layer provided on a base material, wherein a group of paraffin wax and carnauba wax is used as a binder for the heat-meltable ink layer. And at least one wax selected from the group consisting of a petroleum resin or a mixture of a petroleum resin and a thermoplastic resin composed of an ethylene-vinyl acetate copolymer, and the heat of fusion of the hot-melt ink is 30 to 45 cal / g. The above-mentioned purpose was achieved by reducing the influence on the printing characteristics due to the variation of the applied energy of the thermal head by eliminating the influence of the variation in the applied energy of the thermal head, and eliminating the poor resolution and the easiness of background dirt. is there.

In order to make it easier to understand the influence of the heat of fusion of the hot-melt ink on the printing characteristics, a 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 horizontal axis representing the applied energy and the vertical axis representing the temperature of the ink (heat-meltable ink).

As energy is applied to the ink, the ink temperature rises to point A accordingly. The point A is a so-called glass transition temperature. Between the point A and the point B, the ink requires energy to cause a glass transition. During this time, even if energy is applied, the temperature of the ink does not rise. However, after the point B, the ink temperature increases with an increase in the applied energy until the point C is reached. The temperature from the point C to the point D is the melting point. During this time, even if energy is applied, the ink temperature does not rise, the ink is in a semi-molten state, and under normal conditions, the ink is in this state. The transfer is performed. From this point C to D
The energy (heat amount) required to reach the point corresponds to the heat of fusion. 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 from the thermal head can be absorbed, and Can transfer stably, eliminate "bleeding" of printing, and improve resolution. After the point D and toward the point E, the temperature rises as the applied energy increases. If the distance between the CDs is short, that is, if the heat of fusion is small, the ink tends to be affected by the variation in the energy applied from the thermal head. The transfer is performed after passing the point D without the transfer being performed in the intermediate state, so that the rear portion of the print is stained.

As described above, the larger the heat of fusion, 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) is required until the ink can be transferred. In the meantime, the substrate is damaged during that time, which is not preferable.

In the present invention, the reason why the heat of fusion of the heat-fusible ink is specified in the range of 30 to 45 cal / g is that when the heat of fusion of the ink is less than 30 cal / g, it is affected by the variation in energy from the thermal head. When the ink has a heat of fusion exceeding 45 cal / g, a large amount of energy is required to perform proper transfer, and the base material becomes hot. This is because they are damaged due to deterioration and hinder running performance.

From the viewpoint of the composition of the hot-melt ink, the binder that has the greatest influence on the heat of fusion of the ink is a binder. Heat 30-45
It can be adjusted to the range of cal / g.

The binder is at least one kind of wax selected from the group consisting of paraffin wax and carnauba wax as used in the examples described below, and a thermal resin comprising a petroleum resin or a petroleum resin and an ethylene-vinyl acetate copolymer. It is prepared by using together with a plastic resin. In addition, a fluid such as liquid paraffin or low molecular weight polyethylene glycol, a polystyrene resin, or the like may be optionally added in preparing the binder.

Of these binder materials, those having a large heat of fusion are generally thermoplastic resins such as petroleum resins, and waxes generally have a smaller heat of fusion than thermoplastic resins. Among the waxes, carnauba wax has a lower heat of fusion. It is large and the heat of fusion of paraffin wax etc. is small. Therefore, in preparing the hot-melt ink, appropriate materials are selected and combined in consideration of the heat of fusion of the binder materials. Basically, since 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 small heat of fusion such as paraffin wax is the same as that of the conventional composition. Less.

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

[0018]

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. The ink was prepared using a sand mill, heated to 100 ° C. to melt the binder material, and then charged with carbon black.
Performed by mixing for hours. After preparing the inks, the heat of fusion of each ink was measured with a differential scanning calorimeter. The results are as shown in Tables 1 and 2. In addition, the compounding number of each component in Table 1 is by weight. Also,
Manufacturer names and trade names of the used paraffin wax, petroleum resin, polystyrene resin, mixture of paraffin wax and ethylene-vinyl acetate copolymer, dispersant, carbon black and the like are as shown below.

Paraffin wax: Nippon Seisaku Co., Ltd., H
NP-10 (trade name) Petroleum resin: EXXON, Escorets 1
102 (trade name) Polystyrene resin: Rika Hercules Co., Ltd., picostick (trade name) Mixture of paraffin wax and ethylene-vinyl acetate copolymer: Nippon Seiro Co., Ltd., Pulvacs (trade name) Dispersant : US ICI, Solspers 20000 (trade name) Carbon black: Mitsubishi Kasei Kogyo Co., Ltd., MA-8 (trade name)

[0021]

[Table 1]

A 3.5 μm-thick polyester film (polyethylene terephthalate film) was used as a substrate, and the hot-melt ink was applied on the substrate to a thickness of 3.5 μm by a hot melt coating method. A hot-melt ink layer was formed on the material 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 is a substrate, and 2 is a hot-melt ink layer formed on the substrate 1.

COMPARATIVE EXAMPLE 1 Several commercially available ribbon-shaped thermal transfer recording materials were purchased, and the heats of fusion of the heat-fusible inks were measured by a differential scanning calorimeter. As a result, the one having the largest heat of fusion was 22.8 cal.
/ G. Therefore, the one having the largest heat of fusion was designated as Comparative Example 1. The base material of the commercially available thermal transfer recording material was examined. As a result, a 3.5 μm thick polyester film was used as the base material in the same manner as in the thermal transfer recording material of the above-described embodiment.

Using the heat-sensitive transfer recording materials of Examples 1-3, Comparative Examples 1-2 and Comparative Example 1, an area of 200 μm × 20
An energy of 0.5 mjoul was applied to a thermal head having 0 μm, the image was transferred to plain paper (paper having a Beck smoothness of 175 seconds), and the transfer area ratio was measured. Table 2 shows the results. The transfer area ratio is obtained by actually measuring the area of the transferred ink (measurement is performed by magnifying 100 times with an optical microscope), dividing the area by the head area of the thermal head, and indicating the percentage. .

[0026]

[Table 2]

As shown in Table 2, Examples 1 to 3 of the present invention
The thermal transfer recording material has a transfer area ratio of 97 to 104% and 1
It was close to 00%, and there was no bleeding of printing and the resolution was excellent. In addition, in order to check the occurrence of background dirt due to running, each thermal transfer recording material was 70 m at a printing speed of 40 characters / sec.
Each of the thermal transfer recording materials of Examples 1 to 3 of the present invention had no background stain. In contrast, Comparative Example 1 in which the heat of fusion of the ink was 15.9 cal / g
The thermal transfer recording material of Comparative Example 1 (conventional product) and the thermal transfer recording material of Comparative Example 1 (conventional product) having a heat of fusion of 22.8 cal / g had bleeding on printing at transfer area ratios of 120% and 112%, respectively. As a result, soil stains occurred at eight places and three places, respectively. Further, in the heat-sensitive transfer recording material of Comparative Example 2 in which the heat of fusion was increased to 50.0 cal / g, the melting of the ink was insufficient due to the increase in the heat of fusion, so that the transfer area ratio was 80%. It became smaller, and chipping occurred in printing.

[0028]

As described above, according to the present invention, the binder of the hot-melt ink layer is composed of a mixture of a specific wax and a specific thermoplastic resin, and the heat of fusion of the hot-melt ink is 30%. By setting to ~ 45 cal / g,
It was possible to provide a thermal transfer recording material excellent in printing characteristics, free from rear stains and background stains on printing.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of a thermal transfer recording material.

FIG. 2 is a diagram illustrating a relationship between applied energy and ink temperature.

[Explanation of symbols]

 1 base material 2 heat-meltable ink layer

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Shinji Yamazaki 1-88 Ushitora, Ibaraki-shi, Osaka Inside Hitachi Maxell Co., Ltd.

Claims (1)

[Claims] 1. A thermal transfer recording material comprising a substrate having a heat-fusible ink layer provided thereon, wherein the binder of the heat-fusible ink layer is at least one wax selected from the group consisting of paraffin wax and carnauba wax. And a mixture of a petroleum resin or a thermoplastic resin comprising an ethylene-vinyl acetate copolymer and a petroleum resin, and the heat-fusible ink constituting the heat-fusible ink layer has a heat of fusion of 30 to 45 cal / g. A heat-sensitive transfer recording material, characterized in that: