KR910007068B1 - Ink sheet for thermal transfer recording - Google Patents

Abstract

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Description

[Name of invention]

Thermal transfer recording ink sheet

Detailed description of the invention

The present invention relates to an ink sheet for thermal transfer recording. In particular, the present invention relates to an ink composition for forming a colorant layer of such an ink sheet.

The thermal transfer recording ink sheet is composed of a support such as paper or plastic film and a colorant layer applied thereon, and prints by melting the solid ink and transferring the melted ink onto the recording paper.

The heating is carried out by using a heating element from the surface to which the colorant of the sheet is applied or other surface (that is, the surface to which the colorant is not applied) through the recording paper. Or by passing a current through a resistive layer formed in the ink sheet. A colorant layer is a composition which consists of a pigment, dye, and a heat meltable material as a coloring colorant.

For example, carnauba wax or paraffin wax is usually used as a Young Melt material, while a polyethylene terephthalate film or a polycarbonate film having excellent surface smoothness and dimensional stability is commonly used as a support.

The transfer of images from the thermal transfer recording ink sheet to paper is performed by a thermal transfer printer provided with a thermal head, and the thermal energy required for printing in this transfer is preferably as low as possible. This reduces the heat energy required to print, which shortens the heat-cool cycle time of the head, thereby accelerating the print and protecting the head from thermal degradation, as well as miniaturizing the power supply of the line printer. to be. Furthermore, this reduction can compensate for the lack of heat resistance of the base film. However, when an ink sheet containing a low melting point ink component is used to print on paper for the purpose of improving the transfer sensitivity, the non-image portion of the paper is contaminated with the low melting point component of the wax contained in the ink and the fixation and firmness of the print Is degraded. Furthermore, when the ambient temperature rises during the storage of the ink sheet, the sheet causes a so-called blocking phenomenon. So in fact it is difficult to reduce the thermal energy required to print.

In order to solve the above problem, various thermoplastic polymers have been added to the ink composition. For example, polyethylene wax (Japanese Patent Publication No. 101094/1983), ethylene-alkyl acrylate copolymer (Japanese Patent Publication No. 120092/1985) and 1,2-polybutadiene (Japanese Patent Publication No. 127193/1985) are added. Methods have been known that are capable of low energy printing without contaminating the non-image portion. All these methods are characterized by using a composition consisting of a low melting wax as a main component and a thermoplastic resin as an additive and aiming at improving film strength and preventing contamination of non-image parts by the network of resin. do. Therefore, the performance of the sheet obtained by this process is limited.

The inventors have studied to solve the above problems and the ink composition capable of forming a solid coating film exhibits a high transfer strength capable of sufficiently performing low energy printing, and has a specific melting point and specific molecular weight as a main component of the heat meltable material of the ink composition. It has been found that it can be obtained by using an ester oligomer having.

The present invention consists of a base layer, a colorant and / or an inorganic or organic fine powder, and a heat-melt material containing at least 40% by weight of an ester oligomer having a melting point of 60 to 110 ° C. having a number average molecular weight of 500 to 6,000 on the base layer. An ink sheet for thermal transfer recording comprising a coated colorant layer is provided.

The above object according to the invention is achieved by using ester oligomers having a melting point of 60 to 110 ° C. and a number average molecular weight of 500 to 6,000. Therefore, the present invention is advantageous in that a small amount of high melting point, such as wax, as a main component having a low melting point, which enables low energy printing, and a non-image portion, which serves to prevent contamination of the low melting material. It is different from the prior art method characterized by using a composition composed of a molten thermoplastic resin.

An ink sheet according to the present invention comprises a colorant layer containing a support and a heat-melt material applied thereon, wherein the heat-melt material contains at least 40% by weight of the ester oligomer to achieve the above object. If the ester oligomer content is less than 40% by weight, the obtained ink sheet does not exhibit high transfer sensitivity inherent in the ester oligomer.

The thermal transfer recording ink sheet according to the present invention is composed of a base film and at least one colorant layer applied thereon as a support, the colorant layer comprising at least one ester oligomer. The colorant layer further contains at least one colorant and / or inorganic or organic fine powder. The colorant is not particularly limited and may be any conventional dyes or pigments such as yellow, red and black. For example, carbon black or oil black may be used as the black pigment. The fine powder used in the present invention may be selected according to the purpose, and magnetic powder, other metal powder or conductive fine powder is preferable.

The ester oligomers used in the present invention are formed by axial polymerization of polyhydric alcohols with polyacids, particularly preferably with dihydroxy compounds and diacids or their anhydrides, and have a lower degree of polymerization than that of the prior art polyethylene terephthalates. Has Therefore, ester oligomers melt at relatively low temperatures and in a narrow temperature range, and are therefore suitable as heat-melt materials for thermal transfer inks. The number average molecular weight and the melting point of the ester oligomers are respectively 300 to 10,000 (calculated by terminal analysis) and 40 to 120 ° C., preferably 500 to 6,000 and 60 to 110 ° C., respectively (ring-and-ball). Measured by law).

The axial polymerization may be carried out by a conventional process. Examples of diacids include adipic acid, azelaic acid, sebacic acid, succinic acid and dodecane acid, and examples of dihydroxy compounds include ethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1, 6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol and neopentylglycol.

According to the invention, one of these ester oligomers may be used or a mixture of two or more thereof may be used. In addition, ester oligomers can be used with conventional oxis (e.g. paraffin or carnauba wax), rosin derivatives (e.g. hydrogenated rosin or ester gum), polyethylene waxes, methylene-alkylacrylates. Further, the ink sheet according to the present invention comprises a base film and at least one layer of colorant applied thereon and other layers such as a top coating layer or a resistive layer for electrical heating, if necessary.

The support used in the ink sheet according to the present invention is preferably heat resistant and excellent in dimensional stability and surface smoothness. In particular, the polyethylene terephthalate film and polycarbonate, polyethylene, polystyrene, polypropylene, and polyimide, which have been used as a base film, can be preferably used.

As described above, the thermal transfer recording ink sheet according to the present invention contains an ester oligomer having a low melting point of 60 to 110 ° C. as a heat meltable material, so that the ink sheet exhibits high transfer sensitivity and enables low energy printing. It is suitable for high speed printing. Furthermore, this ink sheet can print with uniformity without deteriorating its robustness and there is no risk of causing blocking. This is because this ink sheet contains only a very small amount of low melting point component having a melting point of less than 55 占 폚.

EXAMPLE

The present invention is explained in more detail by the following examples, but is not limited to these examples.

Example 1

Polydecamethylene adipate (number average molecular weight; 1600, melting point: 73 ° C.) 80 copies

Rosin ester HS (Arakawake Ikal Co., Ltd.) Part 5

Carbon black… Part 15

The mixture consisting of the above components is stirred with 200 parts of toluene in a ball mill for 12 hours to obtain a uniform coating liquid. This coating solution was applied to a polyethylene terephthalate film (Lumirror, manufactured by Toray Industries) having a thickness of 6 μ with a wire bar, and after drying, a colorant layer having a thickness of 3.5 μ was formed on the film. Thus, an ink sheet for thermal transfer recording is manufactured. Printing on paper is carried out by using the obtained ink sheet and line type thermal transfer printer, and the density of the transferred image is measured. To investigate the print energy and the density of the transferred image, change the pulse width of the applied voltage between 0.65 to 0.85 seconds and operate the density control lever at each pulse width with a Macbeth densitometer (RD 514 type). The density of the transferred image is measured. As a result of this investigation, it was found that the pulse width of the applied voltage required to form the transfer image having a concentration of 1.2 was 0.66 seconds. No contamination was found in the non-image section. Five sheets of thermal transfer ink sheets are stacked and stored under a pressure of 500 g / cm 2 for one week. The paper was taken out and examined for blocking, which was not found at all.

Example 2

Polyhexamethylene sebacate (number average molecular weight: 3200, melting point: 75 캜). 80 copies

Rosin Ester HS (Arakawa Chemical Co., Ltd.) 5

Carbon black… 15

The same procedure as described in Example 1 was repeated except that the mixture consisting of the above components was used in place of the mixture used in Example 1 to prepare and print the ink sheet.

The concentration of the transferred image is measured with a McGabed densitometer (RD 514 type). The pulse width of the voltage applied to form the transfer image having a concentration of 1.2 is 0.66 seconds.

Comparative Example

Paraffin wax… 60 copies

Carnauba Wax… 25

Carbon black… 15

The mixture consisting of the components is dispersed for 4 hours with 100 ° C. attritor to obtain ink.

This ink is applied to a polyethylene terephthalate film having a thickness of 6 mu to apply hot melt coating to prepare an ink sheet having an ink layer having a thickness of 3.5 mu.

Printing is done by using this ink sheet in a similar manner to that described in Example 1. If the pulse width of the popular voltage is 0.65 seconds, the transferred image has a concentration of only 0.20.

The pulse width of the voltage applied to form a transferred image with a concentration of 1.2 is 0.85 seconds.

Claims (3)

A colorant layer comprising a base layer, a colorant and / or an inorganic or organic fine powder, and a heat-melt material containing 40 wt% or more of an ester oligomer having a number average molecular weight of 500 to 6,000 and a melting point of 60 to 110 ° C. An ink sheet for thermal transfer recording, comprising: a. The ink sheet as claimed in claim 1, wherein the ester oligomer is a axial polymer of a polyhydric alcohol and a polycarboxylic acid. The ink sheet as claimed in claim 1, wherein the ester oligomer is a axial polymer of a dihydroxy compound and a diacid or a diacid anhydride.