JPH0651431B2 - Thermal transfer ink sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a thermal transfer used in a printing apparatus that activates a thermoplastic ink that forms a solid phase at room temperature by heat energy and transfers it to a recording medium. Regarding the ink sheet.

(Prior Art) In a printing apparatus of the type in which a thermoplastic ink that forms a solid phase at room temperature is activated by heat energy to transfer this ink to a recording medium, an ink layer is usually applied uniformly on one surface of a base layer. Ink sheets are used.

For this type of ink sheet, it is necessary to use an ink having a large condensation power in order to enhance transfer reproducibility, and the adhesive force between the ink and the recording medium is made larger than the adhesive force between the ink and the base layer. Although it is necessary to reduce the shearing force at the boundary surface between the heated part and the non-heated part, increasing the cohesive force of the ink and decreasing the shearing force are actually contradictory to each other. It was not possible to realize a sharp transfer.

On the other hand, in order to solve such a problem, JP-A-53-9
Japanese Patent No. 3042 proposes a method in which solid ink is dispersedly formed in a dot shape on a base layer, and only the dot ink that is heated and melted is transferred onto a recording medium. In this case, the size of the ink spot is 120 μm, which means that one ink spot corresponds to each pixel. Therefore, when dots are reproduced on a recording paper with large and small dot diameters, the ink spots peeled from the film are not well cut off, and the reproducibility of the dot diameter is reduced, resulting in the inconvenience of clear printing. .

(Problems to be Solved by the Invention) The present invention has been made in view of such problems, and an object of the present invention is to provide a new thermal transfer ink sheet having good ink shortage and high dot diameter reproducibility. To provide.

(Means for Solving the Problems) That is, according to the present invention, as a thermal transfer ink sheet for achieving such a problem, several dot-shaped inks are formed on one surface of a base layer in one pixel region formed by a heating element. Is formed so that innumerable dot-like inks are dispersed and formed in a dot shape with a density such that they exist at intervals.

(Operation) With this configuration, only the dot-shaped ink melted by the thermal energy applied to the base layer is transferred onto the recording medium while being separated from the non-melted ink,
It forms images with good ink reproducibility and faithful dot diameter reproducibility.

(Example) Then, the Example illustrated below is described.

FIG. 1 shows a thermal transfer ink sheet which is an embodiment of the present invention.

In the figure, reference numeral 201 indicates a thickness of 1 μm, which has high thermal and mechanical strength like PET film or condenser paper.
Reference numeral 202 denotes a base layer having a thickness of 20 μm, and 202 denotes a colored thermoplastic ink layer which is applied to the base layer and forms a solid phase at room temperature.

The ink layer 202 has a region of one pixel size formed by a thermal printer, that is, a size of 60 to 240 μm formed when a voltage of one pulse is applied to each heating element of the thermal head. Innumerable dot-shaped solid inks are dispersed and formed in a dot shape with a density such that a plurality of dot-shaped solid inks are present in one pixel formation region with a gap therebetween.

As an example, a PET film having a thickness of 4 μm is used for the base layer 201, and 20 wt% of oxidation wax, 20 wt% of paraffin wax, 20 wt% of EVA, and 20 w of pigment are provided on the PET film.
An ink having a composition of t% and a melting point of 70 ° C. is dispersed by a hot-melt gravure method in a dot shape so that the dot diameter is 10 μm, the dot pitch is 15 μm, and the ink application amount is 4 g / m ^2. Print.

On the thermal transfer ink sheet formed in this way, for example,
6dot / mm, that is, the size of one pixel to be formed is 4μ
When printing is performed using a thermal head that can be about m, the base layer 201 is heated from the center of the contact portion of the head toward the outer peripheral edge, and The heated area is increased / decreased in proportion to the applied pulse width, and a plurality of fine solid inks present in the area are individually melted, transferred to the recording medium, and pulsed on the recording medium. Large and small dots that are proportional to the width are formed, and a clear image is formed by the aggregation of these dots.

The ink sheet shown in FIG. 2 constitutes a second embodiment of the present invention, in which a base layer carrying an ink layer 303 made of fine dot-shaped solid ink has a surface resistance value of 10 kΩ. It is composed of a conductive resin layer 301 containing conductive carbon black of about 1 / port, and a PET film 302 having a thickness of about 6 μm.

Then, as shown in FIG. 3B, when the bin electrode 306 and the return electrode 307 are brought into contact with the conductive resin layer 301 of this sheet and a voltage of, for example, 40 V is applied between them,
Similar to the first embodiment, a plurality of fine solid inks in the heated region, which change in comparison with the pulse width, are individually melted and transferred to the recording medium, and the diameters of the dots formed there are changed. Depending on the size, a sharp and excellent image can be formed.

(Effect) As described above, according to the present invention, when the ink is transferred to the recording medium, the dot-shaped ink peeled off from the base layer is well cut, and the dot diameter can be faithfully reproduced. With printers and high-resolution printers, clear printing and printing can be realized. For example, it is particularly effective when a full-color printer is used to reproduce an original print using the thermal transfer ink sheet. That is, since the ink sheet is dispersed and formed with a density such that a plurality of dot-shaped inks exist in one pixel area, the number of dot-shaped inks to be melt-transferred can be controlled according to the amount of energization. This allows faithful reproduction of dots on the recording paper so that even the light and shade of the image displayed on the monitor can be clearly expressed.

[Brief description of drawings]

1 (a) and 1 (b) are cross-sectional views and partial plan views of a thermal transfer ink sheet showing an embodiment of the present invention, and FIG. 2 is a sectional view of a thermal transfer ink sheet showing another embodiment of the present invention. FIGS. 3 (a) and 3 (b) are diagrams showing the relationship between the thermal energy applied and the melted ink in each of the above-mentioned examples. 201 ... Base layer 202 ... Ink layer 301 ... Conductive resin layer 302 ... PET film 303 ... Ink layer 306 ... Bottle electrode 307 ... Return electrode

Claims (1)

[Claims] 1. An infinite number of dot-shaped inks having a density such that several dot-shaped inks are spaced apart from each other in one pixel region formed by a heating element on one surface of a base layer. A thermal transfer ink sheet characterized in that it is dispersed and formed into a shape.