JPH01135678A - Electrothermo-transfer medium - Google Patents

Abstract

PURPOSE:To enhance a dot reproducibility in a low-density area to realize a high-quality printing or color reproduction free from a rough feeling in a full-color recording, by a method wherein a surface roughness in a conductive resistant layer is determined to be less than a specific value in difference in irregularities. CONSTITUTION:A conductive head consists of a recording electrode 6 and a return electrode 7. An electric current is passed through the recording electrode 6 to heat a conductive resistant layer 4. The heat is transmitted through a substrate layer 3 to an ink layer 2. Then the ink layer 2 is softened and melted to transfer to a paper to be recorded 5. The conductive resistant layer 4 is obtained by dispersing a carbon black and metal powder in a binder made of an organic thermoplastic or thermosetting resin, an UV-curing resin, or an EV-curing resin, and/or an additive. Additionally, a surface roughness in the conductive resistant layer 4 is determined to be of 30mum or less in the difference in irregularities.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an electrically conductive thermal transfer material for use in electrically thermal transfer pre-printing.

[Conventional technology]

Among thermal transfer recording methods, the method of generating heat in a current-carrying resistive layer with a current-carrying head and transferring ink to the transfer paper for recording is more efficient in terms of recording energy than the conventional method using a thermal head. Recently, it has been attracting more and more attention because it is suitable for full-color recording with halftones.

Here, the difference between the two in terms of heat transfer due to contact with the head is that in the method using a thermal head, contact is made with a support such as a film with a good surface smoothness, whereas in the recording method using energized thermal transfer, the recording method uses energized heat transfer. This was due to contact with the resistance layer. Since the current-carrying resistance layer is composed of conductive carbon black and metal powder (conductive dispersed particles) and a binder for dispersing them, the surface smoothness is poor, and the surface smoothness varies greatly depending on the degree of dispersion.

[Problem that the invention seeks to solve]

However, with the above-mentioned conventional technology, in full-color recording, the seven important factors for achieving high-quality prints with good dot reproducibility are the surface smoothness of the medium that comes into contact with the head; The medium has problems such as poor dot reproducibility, especially at low densities where the recording energy is low, and dot dropout, resulting in problems such as graininess and color unevenness in prints.

The present invention is intended to solve the above problems, and its purpose is to improve dot reproducibility in the low Q degree region and to realize high-quality prints and color reproduction without graininess in full-color recording. .

[Means for solving problems]

The current-carrying thermal transfer medium of the present invention comprises at least a current-carrying resistance layer, a support layer, and an ink layer. The iWi thermal transfer medium is characterized in that the surface roughness of the through-ffi resistance layer is 30 μm or less in terms of difference in unevenness.

[Effect]

According to the present invention, the energizing head and the energizing iI! By improving contact with the resistive layer, heat conduction with little loss is realized, and dot transfer with good reproducibility from low to high concentrations is possible.

〔Example〕

FIG. 1 shows an embodiment of an energized thermal transfer recording method using an energized thermal transfer medium according to the present invention. An 8-current-conducting head is composed of a recording electrode 6 and a return electrode 7. Electricity is applied from the electrode 6 to generate heat in the current-carrying resistance layer 4, and the heat is transmitted through the support layer 3 and then to the ink layer 2, where the ink layer 2 is softened and melted and transferred to the recording paper 5. .

The current-carrying resistance layer 4 is made of carbon black and metal powder (W
ffi dispersion particles) are dispersed.

One Example - Using the binder shown in Table 1, MEK:Toluene=2=
After dissolving in 1, mix with dispersed particles and disperse with an attritor for 7 to 15 hours. Polyethylene terephthalate was used as a support and coated with a gravure coater. Distributed rj! ? By changing the spacing, six types of current-carrying resistance layers with different surface roughness (difference in unevenness) were obtained. Surface roughness was measured using a surface roughness meter.

The coating film thickness was 5 μm.

Table 1 Next, ink with the following composition was manufactured using three rolls. Coating was performed using a gravure coater to obtain an ink layer of three colors of YMC and a thickness of 3 μm.

Oxidized wax 30wt% Paraffin wax 58wt% Ethylene/vinyl acetate copolymer 5wt% Pigment (also known as YMC)
7wt% (coated in the same way as the current-carrying anti-low layer 6N layer) - Comparative example - Current-carrying resistance layer... By changing the dispersion time,
We manufacture current-carrying resistance layers with different surface roughness.

(Other manufacturing conditions are the same) Ink layer: Coated under the same composition and conditions as in the example.

The electrically conductive thermal transfer media of Examples 1 to 6 and Comparative Examples 1 to 3 obtained above were evaluated on the items shown in Table 2, and their transfer properties were compared (1 color transfer - magenta). FIG. 3 shows the gamma characteristic plotting the density of the same gradation obtained from a gray scale print according to the tone (one color transfer - magenta). We also evaluated the color reproducibility of full-color printing.

Table 2 Evaluation of superiority on a scale of 1 to 5 1 Very good (interruption rate 0%) 2 Poor (〃 5% or less) 3 Fair (〃
5-10%) 4 Inferior (〃10-20%)
5. Very poor (20% or more) As shown in the evaluation results, the electrically conductive thermal transfer medium of the present invention exhibits excellent transfer performance, and in particular, dot reproducibility at low density is significantly superior to that of the comparative example. It has achieved extremely unique transferability.

In addition, due to good dot reproducibility and fewer dot omissions, it is possible to transfer full color with good color reproducibility, expressing smooth gradation without any roughness. In contrast, in the comparative example, not only dots were missing at low densities, but the degree of dot omission was not improved even at medium densities, and stable full color reproduction could not be achieved.

〔Effect of the invention〕

As described above, according to the present invention, by setting the surface roughness of the current-carrying resistance layer to 30 μm or less in terms of unevenness, smoothness on the surface of the current-carrying resistance layer is ensured, and the current-carrying head and the current-carrying resistance layer This improves contact with the ink layer and provides efficient heat conduction to the support layer and ink layer, making it possible to transfer from low to high densities with excellent reproducibility without missing any dots, making it extremely effective for full-color recording. This has the effect of realizing high-quality prints.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating an embodiment in which recording is performed by an electrical thermal transfer recording method using the electrical thermal transfer medium of the present invention. FIG. 2 is a sectional view of the electrically conductive thermal transfer medium of the present invention. FIG. 3 is a γ characteristic diagram when grayscale printing is performed on the electrically conductive thermal transfer media of the present invention and a comparative example. 1... Current-carrying thermal transfer medium 2... Ink layer 3... Support layer 4... Current-carrying resistance layer 5... Recording paper 6... J2 Back ≠ ffi Pole 7... Return electrode 21 ... Ink layer (yellow) 22 ... Ink F3 (maze/red) 23 ... Ink layer (cyan) More than +41 people Seiko Epson Corporation Figure 1 Figure 2

Claims (1)

[Claims] An electrically conductive thermal transfer medium comprising at least an electrically conductive resistive layer, a support layer, and an ink layer, wherein the electrically conductive resistive layer has a surface roughness of 30 μm or less in terms of unevenness.