JPH02199181A - Heat transfer ink - Google Patents

Abstract

PURPOSE:To improve environmental resistance and clarity of a printed image and to widen color reproducibility by incorporating two or more specified waxes and a was and/or polymer without a well-difined m.p. CONSTITUTION:A coloring material is added to a soln. wherein a wax (A) with the lowest melting temp. of 45 deg.C or higher (e.g. paraffin wax.), a wax (B) with a difference in m.p. from the component A of 20 deg.C or larger (e.g. an oxidized PE wax) and a wax exhibiting no well-defined m.p. (e.g. carnauba wax) and/or a polymer (e.g. polyester) are homogeneously dissolved or dispersed in a solvent and the mixture is homogeneously dispersed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a thermal transfer ink used in a recording apparatus using a thermal transfer method.

[Prior Art] Thermal transfer ink used in conventional thermal transfer printers is
It is necessary to form a uniform ink layer in order to transfer the ink to the transfer object sensitively and with good reproducibility during thermal transfer. Therefore, in order to meet the above ink performance, we selected a binder that melts in the same temperature range and has good compatibility, added coloring materials such as pigments and dyes, and then heat-kneaded, hot-melt coated, or dispersed in a solvent. -Most of the thermal transfer inks were obtained using solvent coating or emulsion.

[Problem to be solved by the invention M1 However, the thermal transfer ink of the above-mentioned prior art has poor environmental resistance under high temperature conditions when made into an ink film, and it is difficult to create inks of three colors: yellow, magenta, and cyan. However, when a full-color image is printed using three-color sequential thermal transfer, the gradation characteristics of the ink are poor, resulting in density jumps and insufficient density, resulting in a narrow color expression range and an unclear image. was.

Therefore, the purpose of the present invention is to improve the gradation characteristics of ink with excellent environmental resistance, and to obtain clear images with a wide color reproduction range when printing color images using the multicolor plane sequential method. An object of the present invention is to provide a thermal transfer ink that can be used as a thermal transfer ink.

Means for Solving Section E U] The thermal transfer ink of the present invention contains at least the following in the ink layer:
Two or more types of waxes with a melting temperature difference of 20°C or more,
Contains waxes and/or polymers that do not exhibit a clear melting point, and among multiple waxes that exhibit different melting temperatures, the wax that exhibits the lowest melting temperature has a melting temperature of 45 ° C
It is characterized by the above.

[Function] According to the thermal transfer ink of the present invention having the above characteristics, the ink layer contains a mixture of a plurality of materials having different melting temperatures and a material that does not have a clear melting temperature, so that high temperature It has excellent environmental resistance under high temperature conditions, provides excellent gradation characteristics from low density to high density, and provides clear images with a wide color reproduction range.

rExample 1 The present invention will be specifically explained below using Examples and Comparative Examples.

Tables 1 to 4 show examples of thermal transfer inks of the present invention, and Tables 5 to 7 show ink composition examples of three colors of yellow, magenta, and cyan as comparative examples. However, the numbers in the table indicate parts by weight.

In addition, the component with the lowest melting temperature (45°C or higher) among the ink components excluding the coloring material is A, the melting temperature of A + 20°
Components exhibiting a melting temperature of C or higher are B and E's melting temperature +
Components showing a melting temperature of 20° C. or higher are shown as C1. Components that do not show a clear melting temperature are shown with an X attached to each component.

The thermal transfer ink was prepared using the following procedure.

First, the above ink composition is added to a solvent in which the above composition can be dissolved or uniformly dispersed, and mixed by stirring.

Next, a coloring material was added and dispersed in a ball mill for 18 hours.
Uniform dispersion of each binder and coloring material was confirmed and the ink was prepared.

The method for producing the thermal transfer ink of the present invention is not limited to the above-mentioned solvent method, but can also be produced by a hot melt method, an emulsion method, or the like.

The ink prepared as described above is shown in Figure 1.
The ink layer 1 (thickness: 1 to 3 μm) was formed by coating and drying to obtain an ink film for thermal transfer. Thereafter, the manufacturing method and coating method of the thermal transfer ink were performed in the same manner.

Tables 5 to 7 show yellow magenta of comparative examples of the present invention,
Examples of ink compositions for three cyan colors are shown.

Comparative Example 1 of the thermal transfer ink of the present invention shown in Table 5 is a yellow color in which all components other than the coloring material have similar melting temperatures.
Examples of ink compositions for three colors, magenta and cyan, are shown.

Comparative Example 2 of the thermal transfer ink of the present invention shown in Table 6 shows an example of an ink composition of three colors, yellow, magenta, and cyan, in which none of the contained components exhibits a clear melting temperature.

Comparative Example 3 of the thermal transfer ink of the present invention shown in Table 7 shows an example of an ink composition of three colors, yellow, magenta, and cyan, containing a component having a melting temperature of less than 45"C.

Table 1 (Example 1) EVA: Ethylene vinyl acetate copolymer EEA: Ethylene ethyl acrylate copolymer Table 3 (Example 3) Table 2 (Example 2) Table 4 (Example 4) Table 5 (Comparison) Example 1 Table 6 (Comparative Example 2 Table 7 (Comparative Example 3) In the examples of the present invention, toluene was used as a solvent, but the present invention is not limited thereto. Methyl ethyl ketone, tetrahydrofuran, acetone, methyl isobutyl ketone, , cyclohexanone, butyl acetate, ethyl acetate,
Organic solvents such as ethanol, methanol, carbon tetrachloride, etc. or water may be used alone or in combination.

Polymers that can be used in the thermal transfer ink of the present invention include, in addition to the above, acrylic resin, polyurethane, polyvinyl acetal, polyamide, nylon, rosin resin, polyethylene, polycarbonate, vinylidene chloride resin, polyvinyl alcohol, cellulose resin, epoxy resin, Examples include vinyl acetate resin and vinyl chloride resin.

In addition to the above waxes, waxes that can be used in the present invention include montan wax, alcohol wax, synthetic oxidized wax, α-olefin-maleic anhydride copolymer, animal and vegetable waxes, and lanolin.

In addition to the above-mentioned organic pigments, coloring materials that can be used in the present invention include inorganic pigments, dyes, carbon black, and the like.

Next, a printing test was conducted using the above thermal transfer ink. The print test was conducted using a three-color superimposed print using a thermal head. FIG. 2 schematically shows a printing mechanism using a thermal head using the present thermal transfer ink film.

Thermal transfer ink film 2 created by the above method
The surface not coated with the thermal transfer ink 1 contacts the heating element 3 of the thermal head, and the surface coated with the thermal transfer ink contacts the printing paper 4. In this state, the heating element 3 of the thermal head generates heat according to the printing information, and the thermal energy is transmitted to the thermal transfer ink layer 1 via the base material 5, the ink is melted, and the dots 6 are transferred to the printing paper 4, forming an image. It is formed.

The print pattern was a density gradation pattern of 16 horizontal stripes on smooth paper. Adjust the printing energy so that the 14th gradation is at full density when the first color is transferred,
A constant value was set so that excess energy was applied to gradations of 15 and above. Next, to evaluate the transferability, the transfer density for each gradation was measured using Mac b
The reflection OD value was measured using eth-TR-927 using a complementary color filter.

The evaluation results of gradation of the present example and comparative example are shown below.

FIG. 3 shows the gradation of magenta, the first color, in the example.

FIG. 4 shows the gradation of the second color cyan in this example.

FIG. 5 shows the gradation of the third color yellow in the example.

FIG. 6 shows the gradation of magenta, the first color, in a comparative example.

FIG. 7 shows the gradation of cyan, the second color, in a comparative example.

FIG. 8 shows the gradation of the third color yellow in a comparative example.

As shown in Figures 3 to 5, the thermal transfer inks of Examples 1 to 4 have excellent gradation from the low printing energy range to the high printing energy range, are free from background smear, and have high No ink flow phenomenon occurred even in the high density region where printing energy was applied.

On the other hand, as shown in FIGS. 6 to 8, Comparative Example 1
．． Ink No. 2 not only had poor ink transferability in the low density range, but also had a rapid increase in density from medium density to high density. Furthermore, the ink of Comparative Example 2 had poor ink transfer efficiency and did not provide sufficient density. Furthermore, with the ink of Comparative Example 1.3, scumming occurred on the entire print surface, and an ink flow phenomenon occurred in the high density region.

Next, using the above six types of thermal transfer inks, 64
As a result of printing a full-color image by superimposing three-color gradation transfer, the images using the inks of Examples 1 to 4 had a wide range of color expression, and a clear and vivid image was obtained.

In addition, the images using the inks of Comparative Examples 1 to 3 had a narrow color expression range, and image quality deterioration phenomena such as roughness due to density jumps, ink flow, scumming, and insufficient density were observed.

Next, an environmental resistance test was conducted on the seven types of ink films of the above Examples and Comparative Examples.

The test method was as shown in Figure 1, each ink film was wound around a core with a diameter of 20 mm, and the temperature was 50°C and the humidity was 90°C.
The sample was left in a 0% environment for one week, and then the amount of ink transferred was observed using a microscope.

As a result, no ink set-off phenomenon was observed for the inks of Examples 1 and 4 and the inks of Comparative Example 2, whereas ink set-off was observed for the ink films of Comparative Examples 1 and 3, and especially In the ink of Comparative Example 3, a large amount of ink was set off.

From the above results, when used as an ink film, it has excellent environmental resistance, and when printing full-color images, there is no image quality deterioration such as roughness, ink flow, background smearing, lack of density, etc., and there is no gradation. In order to have high image quality with excellent clarity and a wide range of color expression, the ink layer must contain at least two or more types of wax that exhibit a difference in melting temperature of 20°C or more, and a wax that does not exhibit a clear melting point and/or Among a plurality of waxes containing polymers and exhibiting different melting temperatures, a thermal transfer ink in which the melting temperature of the wax exhibiting the lowest melting temperature is 45° C. or higher is effective.

Furthermore, although this embodiment has been described with respect to a three-color superimposed image using a thermal head, the present invention is not limited thereto, and can also be applied to an electric thermal transfer method or other thermal transfer methods.

Furthermore, in this embodiment, three colors of yellow, magenta, and cyan are used.
Although a color image composed of colors has been described, the present invention is not limited to this, and the present invention is not limited to this.
It is also possible to apply the present invention to color printers, monochrome printers, and two-color printers.

[Effect of the invention 1 As explained above, if the thermal transfer ink of the present invention is used, it has excellent environmental resistance under high temperature conditions, and when printing full-color images, etc., it can produce good gradations in all density ranges. This has the effect that it is possible to obtain high image quality with clear and wide color expression range.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure of a thermal transfer ink film using the thermal transfer ink of the present invention. FIG. 2 is a schematic diagram showing a mechanism for transferring dots onto photographic paper by heat generation from a thermal head using the thermal transfer ink of the present invention. FIG. 3 is a correlation diagram between printing energy and transfer density showing the gradation of magenta ink, the first color of the ink of the example of the present invention. FIG. 4 is a correlation diagram between printing energy and transfer density showing the gradation of cyan ink, the second color of the ink of the example of the present invention. FIG. 5 is a correlation diagram between printing energy and transfer density showing the gradation of the third color yellow of the ink of the example of the present invention. FIG. 6 is a correlation diagram between printing energy and transfer density showing the gradation of magenta ink, the first color of ink of a comparative example of the present invention. FIG. 7 is a correlation diagram between printing energy and transfer density showing the gradation of cyan ink, the second color of ink of a comparative example of the present invention. FIG. 8 is a correlation diagram between printing energy and transfer density showing the gradation of the third color yellow of an ink of a comparative example of the present invention. Thermal transfer ink Thermal transfer ink film Heat-generating element Photographic paper support Heat-melted ink Figure 1 and above Applicant: Seiko Epson Co., Ltd. Representative Patent Attorney: Kizobu Bensue (and 1 other person) Figure 2 Figure 3 Figure 5

Claims (2)

[Claims] (1) A thermal transfer ink characterized in that the ink layer contains at least two or more types of waxes with a melting temperature difference of 20° C. or more, and a wax and/or polymer that does not have a clear melting point. (2) The thermal transfer ink according to claim 1, wherein among the plurality of waxes having different melting temperatures contained in the ink layer, the wax exhibiting the lowest melting temperature has a melting temperature of 45° C. or higher.