JPH02108581A - thermal transfer recording medium - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thermal transfer recording medium used in a printer that obtains a record by heating and melting a heat-melting ink and transferring it to a transfer target.

[Prior art]

Recording using the thermal transfer method can be performed on plain paper, the equipment used is compact and noiseless, and high-speed printing is possible.
It has the characteristics of low initial cost and has been widely used recently.

On the other hand, in addition to conventional printing in a single color (for example, black or blue) using the thermal transfer method, there is a strong desire to put into practical use full-color printing similar to that of a photograph.

Currently, research and development on recording media for high-quality full-color printing is actively progressing, but conventionally, the appropriate thickness of the ink layer of the recording medium is 3 μm to 6 μm from the perspective of superimposition and coating technology. It was thought that

[Problem to be solved by the invention]

However, the above-mentioned technique has a problem in that when a color image is created by overlapping three or four color inks, the image becomes grainy due to the disturbance of dots in the halftone region.

The present invention is an attempt to solve this problem.The purpose of the present invention is to provide a clear photographic image with stable registration, no roughness, and good dot reproducibility when overlapping color inks. The object of the present invention is to provide a thermal transfer recording medium that produces ordinary color images.

[Means to solve the problem]

The structure of the thermal transfer recording medium to solve the above problems is as follows:
In a thermal transfer recording medium to be used in a printer that transfers the ink to a transfer target using a heat-generating means provided with a heat-melt ink on at least one surface of the base material and obtains a record, the film thickness of the heat-melt ink is 2 μm. It is characterized by being coated with:

[Effect]

In the thermal transfer recording medium of the present invention, the film thickness of the heat-melting ink is 2
By coating with a thickness of .mu.m or less, it is possible to produce an image with excellent gradation and to prevent holes in the halftone region when overlapping color inks.

The ink layer components used in the present invention have a melting point or softening point of 50 to 150"C, preferably 70 to 100"C.
It consists of a binder made of thermoplastic material, coloring material, and various additives.

The binder is a resin, wax, or a mixture thereof.The waxes include natural waxes such as paraffin wax, microcrystalline wax, carnauba wax, polyethylene wax, beeswax, ceresin wax, spermaceti wax, low molecular weight polyethylene wax, oxidized wax, and ester wax. Ethylene and ethylene copolymers, styrene resins, acrylic resins, etc. are used as the synthetic waxes and resins.

The coloring material used is various pigments, dyes, or mixtures thereof, and the additives used include antioxidants, plasticizers, adhesion promoters, and the like.

The production method is to dissolve or disperse in a solvent such as organic solution ttX (tetrahydrofuran, 1-2 dichloroethane, methyl ethyl ketone, toluene, ethyl acetate) using an attritor, etc., and apply solvent coating, or to hot coat the dispersion using a three-roll mill, etc. It can be obtained by melt coating or by solvent coating a product dissolved or dispersed in the above organic solvent.

〔Example〕

The present invention will be explained in detail below.

Table 1 shows the ink composition. The numbers in the table indicate parts by weight.

Table 1 Example 1 The mixture shown in Table 1 was preliminarily dispersed using a planetary mixer, cooled and solidified (160° C. for 30 minutes), pulverized, and then main dispersed using a three-roll mill. (The rear roll and middle roll were cooled at 100°C, and the front roll was water-cooled and passed through 10 times.) The three colors of dispersed ink (magenta, yellow, and cyan) were transferred to a polyethylene terephthalate film (4μ
A recording medium was obtained by applying hot-melt coating to a thickness of 2 .mu.m in repeating units along the length direction as shown in FIG.

Comparative Example 1 A recording medium was obtained in the same manner as in Example 1 except that the ink in Example 1 was coated to a thickness of 3 μm.

Example 2 The dispersion ink of Example 1 was dissolved and dispersed in toluene by heating with a paint shaker so that the solid content concentration was 10%, and the ink was coated on a polyethylene terephthalate film (4 μm) with a thickness of 2 μm while maintaining the ink temperature at 50°C to 80″C. A recording medium was obtained by applying solvent hot-melt coating in repeating units along the length as shown in FIG.

Comparative Example 2 A recording medium was obtained in the same manner as in Example 2 except that the ink in Example 1 was coated to a thickness of 3 μm.

Example 3 The mixture shown in Table 1 was adjusted to a solid content concentration of 10% in toluene, and dispersed using an attritor while maintaining the ink temperature at 50°C to 80°C using a circulation pump and a heat exchanger. Polyethylene terephthalate film (
A recording medium was obtained by applying solvent hot-melt coating to a 2-μm-thick film (4 μm) in repeating units along the length direction as shown in FIG.

Comparative Example 3 A recording medium was obtained in the same manner as in Example 3 except that the ink in Example 3 was coated to a thickness of 3 μm.

Example 4 A current-carrying resistance layer made of the components shown in Table 2 was formed on the opposite side of the ink layer via the base material of Example 3 by solvent coating to a film thickness of 3 μm (surface resistance value 1 Ω/hole). A recording medium was created in the same manner except for the following.

Comparative Example 4 A recording medium was obtained in the same manner as in Example 3, except that the ink in Example 4 was coated to a thickness of 3 μm.

Table 2 Evaluation of the transferability of the ink by weight was carried out using two methods: thermal transfer using a thermal head for Examples 1 to 3 and Comparative Examples 1 to 3, and transfer using an electrical thermal transfer method for Example 4 and Comparative Example 4. .

The above two types of evaluation methods and evaluation results are shown below.

(1) Evaluation using a thermal head Cyan was transferred onto the transfer target and onto the magenta full peta on the transfer target. At this time, a thermal head with a resolution of 180 dpi and a heating element resistance of 200 Ω was used, and a printing pulse width of 0.
At 48m5ec, the magenta full density is 0.487 for cyan.
Increase the pulse width linearly in 16 m5ec steps,
16 gradation transfer was performed. The evaluation is based on the cyan optical density (0-D
values) were compared. The O-D value measuring device is k011omo
Macbeth TR-927 (manufactured by Rgan) was used.

Also, three-color superimposed gray scale (0,48/16
The dot reproducibility of m sec ) was observed using a microscope. As the transfer target, TTR manufactured by Mitsubishi Paper Mills Co., Ltd. was used. The results are shown in FIGS. 2 to 7.

Each graph shows the printing energy on the horizontal axis and the 0.D value of the transferred ink on the vertical axis.

In Examples 1 to 3, as shown in FIGS. 2 to 4, the gradation properties and the density of the second color in the entire gradation area are good.

In addition, the dot reproducibility was also good from the gray scale micrograph.

In Comparative Examples 1 to 3, as shown in FIGS. 5 to 7, the transferability of the low density region was poor, and the transferability of the second color was particularly poor. Furthermore, there is a rapid increase in density from the medium to high density region, and the gradation is poor. Furthermore, the dot reproducibility of the three-color superimposed gray scale was also very poor.

(2) Evaluation using energized thermal transfer method The energized thermal transfer test uses an energized head (electrode density: 5.6 electrodes/mm) that has a recording electrode and a return electrode, and uses a color silver halide photograph as the original, and after color separation using a color scanner. , converted to various signals of 32 gradations, and printed in full color.

As a result, in Example 4, compared to Comparative Example 4, a beautiful color image with good gradation that was extremely close to the original image was obtained.

〔Effect of the invention〕

As explained above, the thermal transfer recording medium of the present invention improves the dot reproducibility in medium to high density areas, and can create clear, photograph-like full-color images without roughness.

[Brief explanation of drawings]

FIG. 1 is a schematic plan view showing an embodiment of the thermal transfer recording medium of the present invention. FIGS. 2 to 7 are correlation diagrams between transfer energy and transfer density of trial recording media of Examples 1 to 3 and Comparative Examples 1 to 3. IY...Yellow ink 1M...Magenta ink IC...Cyan ink...Base material or more Applicant Seiko Epson Corporation Attorney Kizo Suzuki (1 other person) Fig. 1 Fig. 2 Example = 2 Fig. Comparative example - 1 Fig. Armor example - 3 Fig. Comparative example - 2 Fig.

Claims (3)

[Claims] (1) In a thermal transfer recording medium that is used in a printer that obtains a record by transferring the ink to an object to be transferred using a heat-generating means provided with a heat-melting ink on at least one surface of the base material, a film of the heat-melting ink is used. A thermal transfer recording medium characterized by being coated with a thickness of 2 μm or less. (2) The thermal transfer recording medium according to claim 1, wherein the heat-melting ink consists of at least three types: yellow, magenta, and cyan. (3) The thermal transfer recording medium according to claim 1, further comprising a current-carrying resistance layer on the opposite side of the ink layer via the base material.