JPH01281990A - Receiving sheet for thermal transfer recording - Google Patents

Abstract

PURPOSE:To record clear images with high resolution, by forming a receiving sheet for thermal transfer recording by using as a main constituent a pulp to which light calcium carbonate consisting of spindle-shaped calcite crystals having a specified particle diameter and a specified oil absorptivity is internally added. CONSTITUTION:Light calcium carbonate consisting of spindle shaped calcite crystals of which at least 50wt.% is constituted of particles with a particle diameter (major diameter) of at least 2mum and which has an oil absorptivity of at least 10ml/100g is internally added to a wood pulp having a smoothness of at least 100 sec, in an amount of 1-70wt.% based on the pulp. A paper is made by using the wood pulp thus obtained as a main constituent, thereby forming a receiving sheet for thermal transfer recording. As a pigment to be internally added, hexahedral or other precipitated calcium carbonate or the like may be jointly used, in addition to spindle-shaped calcite type precipitated calcium carbonate. The paper is a neutral paper, which preferably has a water extract pH according to JIS-P-8133 of 6-9.5.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a receiving sheet for a thermal transfer printer using a heat bath melting ink sheet, and more specifically, in a color thermal transfer recording system using area gradation and density gradation, The ink density transferred to the sheet surface is uniform, the dot shape is uniform, it gives a clear image of the same degree as a cylinder, and it has the same feel and usability as conventional plain paper. It concerns the seat.

[Prior art]

Recently, hot bath melting transfer printers using thermal heads and dye sublimation transfer printers have become compact devices that can produce clear prints and images for facsimiles, copiers, color computer graphics printers, color video printers, etc. It is attracting attention because it can be displayed in

Thermal transfer type printers combine a receiving sheet such as normal high-quality paper with an ink sheet consisting of a thin substrate such as a film and a layer of thermally fused ink, and transfer the image from a thermal head in response to an image signal. Due to the force of the heat, the thermally molten ink is transferred to the receiving sheet only in the necessary areas, forming the entire image.

In the case of a monochrome printer, it transfers a single color of ink,
In the case of a color printer, all images of different colors such as yellow, magenta, cyan, and black are transferred and combined to obtain a color image. By using area gradation and degree gradation, full color images can be obtained by thermal transfer recording.

However, in such thermal melt transfer printers, the sharpness of the transferred image depends on the smoothness of the receiving sheet, etc., so the high level of printing and image 1f4! Various techniques have been published for imparting image-receiving suitability to a receiving sheet according to each printer.

For receiving sheets for thermal transfer printers such as those using the area gradation method, in order to obtain good transferred images, a smoothing process is performed using ordinary paper with a Beck smoothness of about 10 to 50 seconds, a super calender, etc. However, if it is 100 seconds or more,
It is known that the clarity of transferred images is improved.

Furthermore, in order to improve the transfer characteristics of thermal transfer printers, a proposal has been made to obtain a transferred image with even shading by providing an oil-absorbing pigment on the entire paper base material (1824/1989).
Publication No. 87). This publication lists most of the pigments used in coated printing papers, and claims that a certain degree of improvement in thermal transfer receptivity has been achieved.

Using such a thermal transfer method, halftone full color images can be created.
In order to cover the entire area, the dither method using the area gradation method requires an additional 16~
High snoring of 32 dots/wIL requires precision, and a method has been announced for controlling the size of the transferred dots with an accuracy of less than 9 μm.

Another way to reduce halftone full color 1IIIi images is to
Density gradation printers have also been developed that control the amount of bath-melted ink transferred from a thermal head. In both cases, requirements for answer sheets have become even more stringent.

Being able to see the entire image with good reproducibility is simply a matter of Beck smoothness being 100.
For high-quality paper of seconds or more, it is a rotation axis. In printers that fully control the amount of bath-melted ink transferred from the thermal head, the uniformity of the ink-receiving ability of the receiving paper has a significant impact on the quality of the image. Even when a heat transfer receptor sheet coated with pigment was used, density unevenness or uncertain transfer of halftone dots was observed, making it difficult to obtain images with good intermediate tones (1') and high chromaticity. .

[Problem that the invention seeks to solve]

In view of this current situation, the inventors of the present invention have developed a technology that reproduces the transfer ink without halftone dots and density unevenness, and that can be obtained with a full-color printer, etc., with clear, high-resolution recorded images from low density to high density 1. The object of the present invention is to provide a receiving sheet for thermal transfer recording.

[Means for solving problems]

The inventors of the present invention have conducted intensive research to improve these drawbacks, and as a result, we have found that the receiving sheet for thermal transfer printers has a calcite crystal system, a spindle shape, and a particle size (major axis).
When neutral paper containing 1 to 70% by weight of light calcium carbonate, preferably 10 to 400 to 40% by weight, based on the pulp, is used as a receiving sheet for a thermal transfer printer. It is possible to improve the reliability of dot reproduction, the reproducibility of density, and the reproducibility of hue and density of overlapping colors in a method that reproduces the entire halftone image of density gradation or blood gradation method. I found out everything that could be done to improve the problems.

Calcium carbonate is the preferred filler for acid-free paper, and calcium carbonate can be broadly divided into heavy carbonate and light (precipitated) calcium carbonate. Liangji calcium carbonate is obtained by dry or wet grinding of naturally occurring limestone. Precipitated calcium carbonate can be obtained by dissolving quicklime in water and blowing carbon dioxide gas into the solution to cause a reaction. The particle size of the filler and its distribution are completely controlled by the grinding conditions of calcium carbonate.

The particle shape, particle size, distribution, and crystalline gold of precipitated calcium carbonate can be changed depending on the reaction conditions.

The crystal system of precipitated calcium carbonate is divided into six types: calzite (hexagonal crystal), aragonite (orthorhombic crystal), and vaterite (hexagonal crystal).

Of these, vaterite is rarely used industrially because its crystals are unstable. The preferred calcium carbonate used in the present invention is a spindle-shaped calcite crystal type of precipitated calcium carbonate. Calcite-type crystals also include cubic particles. Aragonite is spindle-shaped and elongated (with a large aspect ratio) and columnar. Moreover, the particle shape of heavy calcium carbonate is naturally irregular.

As a result of a comparative evaluation of these neutral papers filled with calcium carbonate using a thermal transfer printer, the paper filled with spindle-shaped calzite was superior. Although the detailed reason is not clear, it is presumed that the filled filler becomes sloppy, creating an excessive space in the paper layer. Assigonite has thin and small crystals, so the surface is dense and di-ink transfer is poor. Heavy calcium carbonate does not transfer ink well, probably because its particle shape is irregular and its oil absorption is small.

If the particle size is small, oil absorption is generally large and ink transfer is improved, but if the particle size is too small, the yield during filling becomes poor and it cannot be practically used for paper making. Besides that,
It is estimated that transferability, image quality, etc. will deteriorate if there are many particles with small particle sizes. A preferable condition is that particles having a particle diameter (longer axis) of 2 μm or more account for 50% by weight or more.

The larger the oil absorption, the better the adhesion and receptivity of molten ink, and for light calcium carbonate, 10
It has been found that m1 is preferably 79 or more, and particularly desirably 20 m14/, 9 or more.

In addition to the spindle-shaped calcite-type precipitated calcium carbonate, the pigment to be filled may be hexahedral precipitated calcium carbonate, heavy calcium carbonate, etc., as long as the overall image quality does not deteriorate.
Pigments such as clay, calcined tar, titanium dioxide, aluminum hydroxide, talc, calcium silicate, calcium 4A acid, magnesium silicate, and synthetic amorphous silica can also be used in combination.

If the amount of spindle-shaped, calcite-type precipitated calcium carbonate added is less than 1%, there will be no effect, and if it is more than 70%, paper quality, such as strength, will be impaired.

The paper used in the present invention is neutral paper and meets JIS-P-811.
The water extraction pH shown in No. 3 is preferably 6 to 9.5.

Paper produced by a normal papermaking process using neutral bleached wood pulp and pigments is preferred, but synthetic fibers with a whiteness level of 1 and synthetic pulp may all be used in combination. General additives for paper making■
Paper strength agents, retention aids, wet paper strength agents, dyes, and the like can also be used. The basis weight of the sheet is 20-1809
Preferably, it is 7 m2 and has a thickness of 20 to 200 μm.

The paper-made receiving sheet is smoothed to a smoothness of 100 seconds or more using a super calender or the like.

〔Example〕

Next, the present invention will be explained in detail with reference to Examples. Note that the section is the solid content vehicle section.

Example 1 20 parts of light calcium carbonate (manufactured by PC Shiraishi Kogyo Co., Ltd.), which is made of spiny calcite crystals with an average particle size of 6.2 μm and 75% of which is 2 μm or more, was added as a persimmon material to a dispersant and water. After rapid dispersion mixing, all 100 parts of bleached kraft pulp beaten in a beater for 20 minutes were added. At this time, as additives, sizing agent (Filan 81 Tamago National Co., Ltd. 1) o, os part, kaotin starch (C
A, 1 part of TO-F (manufactured by Tamago National Co., Ltd.) and 0.02 parts of polyacrylamide as a retention aid were added and diluted with water to a total concentration of 0.06% to obtain a papermaking raw material. This raw material was made into a high-quality paper of 65 I//m2 and a whiteness of 90% using a Fourdrinier multi-tube paper machine and smoothed with a supercalender to obtain a receiving sheet with a Bekk smoothness of 350 seconds. The ash content (calcium carbonate) was 15.5%.

Example 2 Light calcium carbonate (manufactured by PC Shiraishi Kogyo (Isu) 16 parts as 94th grade, particle content of 1.5 μm average particle size 1 particle size 2 μm or more 33%, oil absorption 1d32vte/100
9.4 parts of light calcium carbonate (Albafil, manufactured by Pfizer MSP (closed)) consisting of six-part calzite crystals were used, and 0.04 parts of polyacrylamide was used as a retention aid.
High-quality paper was made entirely in the same manner as in Example 1 except that
It was smoothed with a supercalender to obtain a receiving sheet with a Beck smoothness of 600 seconds. Ash content (calcium carbonate) is 17.0
%Met.

Comparative Example 1 Paper was made in the same manner as in Example 1, except that 20 parts of the light calcium carbonate (Albafil, manufactured by Pfizer MSP Co., Ltd.) of Example 2 was used as a filler, and the paper was smoothed with a super calender to a Beck smoothness of 300 seconds. The acceptance of

The ash content (calcium carbonate) was 17.1%.

Comparative Example 2 The answer sheet of Example 1 was machine-calented to give a total smoothness of 8.
It was set to 0 seconds.

Comparative Example 6 Receiving sheet of Example 2 Purple machine calendered with smoothness of 9 in total
It was set to 0 seconds.

Comparative Example 4 Pigment: average particle size 2.0 μm 1 oil absorption 26 ml t/
100,! i1.2 The content of particles larger than 5 μm
Paper was made in the same manner as in Example 1 except that 5% heavy calcium carbonate (Whiten P-10 manufactured by Toyo Fine Chemicals) was used, and it was smoothed with a super calender to obtain a receiving sheet with a Beck smoothness of 200 seconds. Ta. The ash content (calcium carbonate was 15.5%).

Comparison 1 Tari 5 20 parts of fine particle silicic acid (Fine Seal, manufactured by Tokuyama Todatsu) with an average particle diameter of 2.6 pm and an oil absorption of 280 mm/10°9 was added as a filler in place of the carbonated calcium in Example 1, and the paper was made into paper. The paper was made into a paper and smoothed using a super calender to obtain a receiving sheet having a Beck smoothness of 150 seconds. The ash content was 15%.

Using a commercially available bath-fusion thermal transfer color printer, ink sheets were placed on a polyester substrate with a thickness of 6 μm, and the ink sheets of each of the three colors yellow, magenta, and cyan were thermally transferred to the receiving sheet of the above Examples/Comparative Examples to produce a single color. And print the aperture with overlapping colors/ζ. This image was visually evaluated for image clarity, uniformity of dot shape and foundation degree, and uniformity of monochromatic and heavy color solidification.
It was a song.

The results are shown in Table 1 below. The evaluation results were particularly excellent (5), good (4), general properties (3), slightly defective (2), and significant defects'f! :1.

〔Effect of the invention〕

The thermal transfer receiving sheet of the present invention has excellent ink transferability, uniformity, dot diameter, and shape, and eliminates the drawbacks of conventional methods, making it possible to use high-resolution thermal transfer printers, and is suitable for use in the industry. Dogs contribute to this.

Claims (1)

[Claims] 1. Light calcium carbonate consisting of cone-shaped calcite crystals with a particle diameter (major axis) of 2 μm or more and a particle content of 50% by weight or more and an oil absorption of 10 ml/100 g or more based on the absolute dry weight of the pulp. A receiving sheet for thermal transfer recording, characterized in that it is made of paper whose main component is wood pulp containing 70% by weight and having a smoothness of 100 seconds or more.