JPS62278088A - Receiving sheet for thermal transfer - Google Patents

Abstract

PURPOSE:To obtain a receiving sheet for thermal transfer comprising a biaxially strentched polyolefin film and free of heat curling, by providing a surface layer free of heat shrinkable properties on at least one side of a sheet obtained by biaxially stretching a multilayer film comprising an inorganic pigment and a polyolefin as main constituents. CONSTITUTION:A synthetic paper comprising a biaxially stretched polyolefin film of a multilayer structure comprising an inorganic pigment comprises, on at least one side thereof, a coated layer free of heat shrinkable properties, comprising a pigment and an adhesive and functioning to shield the heat generated by a thermal head. The coated layer is provided in a thickness of at least 20 mum, whereby the heat from the thermal head is absorbed and shielded, the polyolefin film as a base is protected, and heat curling is prevented from occurring. Simultaneously, density reproducibility in an image-forming system for reproducing intermediate-gradation images and reproducibility of hues and densities in color superimposition at solid areas can be enhanced, and uniform reproduction of hues and densities of full-color recorded images can be realized. Aragonite, calcined kaolin, satin white or the like, when used as the pigment, has a remarkable effect of forming a surface layer with favorable heat- insulating properties.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a thermal transfer receiving sheet made of synthetic paper, plastic, or paper sheet that has improved suitability for thermal transfer printers, and which is suitable for thermal transfer printers. It retains sharp inks and dyes, has good midtone reproduction of images, clearly accepts single-color or multi-color inks and dyes, and can print characters and images at high resolution. Moreover, it provides a receiving sheet that is free from thermal curling during transfer.

[Prior Art] Recently, the need for color printing and color printers has increased, and in particular, heat-fusion transfer printers using thermal heads and sublimation transfer printers are attracting attention because they can produce clear color images.

Among these, thermal melt transfer type printers use an ink sheet consisting of a base material such as a film or thin paper and a heat melt ink layer. A receiving sheet, such as ordinary high-quality paper, is superimposed on this ink sheet, and heat from a thermal head in response to an image signal transfers hot melt ink to the receiving sheet only in the necessary areas, forming an image. In the case of a color printer, images of different colors such as yellow, magenta, cyan, and black are transferred and layered to create a color image.

In addition, in the case of a sublimation transfer printer, an ink sheet coated with a sublimable dye is used as an ink sheet, and this is combined with a receptor sheet whose surface layer contains polyester that is dyeable to this dye. Transfer and form an image using a thermal head.

[Problems to be solved by the invention] With these thermal transfer printers, the clarity of the transferred image depends on the smoothness of the receiving paper, so it is not possible to print images of the same high quality on any paper. Rather, various technologies have been published regarding receptor sheets that provide resolution and image quality that are appropriate for each printer use.

For example, even with the thermal melt transfer method, it is possible to print half-tone full-color images using the area gradation method, but it is difficult to obtain good prints with a receiving sheet for a thermal transfer printer using such an area gradation method. It is known that a clear transferred image can be obtained by subjecting the receiving sheet to a smoothing process using a supercalender or the like to achieve a Bekk smoothness of 100 seconds or more.

Furthermore, in order to obtain uniform hues and densities of monochrome yellow, cyan, and magenta printed in multiple colors, that is, red, blue, and green, and to obtain high-resolution characters and images with good reproducibility, Beck smoothness of 100 is required. Even if the time is more than a second, it is difficult to use high-quality paper. Furthermore, for high-resolution printers that require high resolutions of 16 dots/II and 32 dots/l, pigment-coated paper and multilayer synthetic paper are preferred over uncoated paper with pulp fibers exposed on the surface. Paper is often used because it exhibits better image reproduction.

In full-color printers that control the amount of sublimable dye transferred by the amount of heat from the thermal head and directly reproduce halftones with density, the uniformity of the ink receiving ability of the receiving layer is critical to image reproducibility. The uniformity of the substrate is strictly required.

When paper containing pulp as a main component is used, even if a coating layer containing pigment as a main component is provided on the surface, density unevenness is observed in solid areas, and a good halftone image cannot be obtained. For this reason, synthetic paper consisting of a biaxially oriented polyolefin film with a multilayer structure containing an inorganic pigment is often used as a receiving sheet because of its excellent homogeneity and compatibility between the sheet surface and the thermal head.

However, biaxially oriented polyolefin sheets do not have heat resistance, and it has been reported that under normal sublimation transfer and melt transfer conditions, the heat from the thermal head often causes the film on the print side to unstretch, resulting in thermal curling. has been done.

An object of the present invention is to provide a thermal transfer receiving sheet made of a biaxially stretched sheet that does not cause thermal curl.

[Means for Solving the Problems] In view of the current situation, the present inventors have developed a method that has heat resistance, reproduces halftone densities evenly, and stably obtains clear recorded images from low to high densities. We have conducted intensive research on thermal transfer receiving sheets used in full-color printers that can be used in full-color printers. As a result, a synthetic paper made of a biaxially oriented polyolefin film with a multilayer structure containing an inorganic pigment is produced, and at least one side is coated with a non-heat-shrinkable coating, preferably made of a pigment and an adhesive, to shield heat generated from the thermal head. By installing a layer, we succeeded in solving the problems of the conventional method. Particularly for sublimation, it is preferable to have this coating layer maintain dye receptivity, or to provide a dye receptive layer thereon.

Coating paint containing pigments on paper to improve oil absorption and general printability has been done in the past, but synthetic paper made of biaxially oriented polyolefin film is the main component. It was discovered for the first time in the present invention that a surface layer that does not shrink due to heat is provided in order to improve heat resistance in a multilayer thermal transfer receiving sheet while maintaining uniform and gradation image reproducibility. It is.

In the present invention, a coating layer of 20 μl for improving heat resistance mainly composed of a pigment and an adhesive is applied to at least one side of a synthetic paper made of a biaxially oriented polyolefin film containing an inorganic pigment with a uniform thickness and a multilayer structure. By providing the above,
Density reproducibility in an image forming method that absorbs and shields heat from the thermal head to protect the multilayered biaxially oriented polyolefin film containing inorganic pigments as a base material, preventing thermal curling, and at the same time reproducing halftone images. To provide a thermal transfer receiving sheet that can improve the reproducibility of the hue and density of overlapping colors in solid areas to an unprecedented degree and achieve uniform reproducibility of the hue and density of full-color recorded images. ′
It has been found that all the problems of conventional receiving sheets can be solved.

Currently, thermal transfer methods, especially sublimation dye transfer methods, are often used in small color printers as the mainstream for small non-impact color printers, and there is a demand for systems and paper that can stably produce clear images with halftone reproduction. ing. By realizing a receiving sheet with high resolution and color reproducibility according to the present invention, it is possible to make homogeneous and stable hard copies of full-color images such as video screens with a compact device, and it is thought that a variety of applications will become possible.

In the present invention, the surface layer coated on at least one side of the synthetic paper made of biaxially oriented polyolefin film is formed of a paint containing pigment and adhesive as main components.

The pigment may be appropriately selected from pigments for pigment coating used in conventional printing paper, such as clay, calcium carbonate, and finely powdered silica, but especially columnar calcium carbonate (aragonite) and calcined kaolin. , Sachin Shiro, etc., form a surface layer with good heat insulation properties, so they are very effective.

Adhesives include styrene-butadiene, methyl methacrylate-styrene-butadiene, vinyl acetate,
Alternatively, acrylic polymers, copolymer emulsions, etc. may be used alone or in combination. Water-soluble polymer adhesives such as polyvinyl alcohol, starch, and casein can also be used alone or in combination, and a coating layer can be formed by solvent coating using adhesives that are soluble in non-aqueous solvents such as toluene. It is also possible to do so.

The ratio of pigment to adhesive in the surface layer is not particularly limited, but considering strength and heat resistance, it is usually preferably 50-90% by weight. Of course, this ratio can be changed as appropriate depending on the type of adhesive and pigment, the use of the sheet, etc. In addition, a non-heat shrinkable surface layer can be formed by various methods such as coating a polymeric substance or the like.

The thickness of the coating layer may be determined depending on the application and image energy by determining the thickness necessary to shield the heat from the thermal transfer printer. Usually, 20 to 50 μl is sufficient. If the amount is less than 10 μl, no significant heat resistance improvement effect is observed.

The biaxially stretched polyolefin sheet with a multilayer structure containing inorganic pigments is used as a sheet base material, and depending on the amount and type of pigment added, it is manufactured from opaque paper to translucent tracing paper-like paper. Also known as paper. Such a multilayer stretched sheet consists of at least a paper-like layer and a base material layer, and the paper-like layer usually contains 8-65% by weight of inorganic fine powder.
It is made of a thermoplastic polymer material with a certain degree of content, and voids are created between it and inorganic fine powder by stretching.

Inorganic fine powder is selected and used as a spacer for converting a thermoplastic film into paper, and for imparting printing and writing properties to the surface. Usually the average particle size is 20
Calcium carbonate, calcined seaweed, diatomaceous earth, talc, titanium oxide, silica, aluminum sulfate, etc. are used, and can be selected from a wide range.

The thickness of the sheet can be selected depending on its use as a thermal transfer receiving sheet, and a thickness of 40 to 200 μl is usually appropriate.

[Example] Next, the thermal transfer receiving sheet of the present invention will be explained with reference to Examples. In the following, parts represent parts by weight.

Example 1 A multilayer biaxially stretched polypropylene film containing inorganic pigments (thickness: 60 μl, manufactured by Yupo FPG 60 Oji Yuka Synthetic Paper) was used as a base material, and the following paint-1 was applied at 30 g/yi2.
The surface was smoothed by supercalendering to obtain a receiving sheet.

Paint-1 (JSR-0668-day non-synthetic comb) Sodium polyacrylate dispersant 2 parts The produced sheet had a Beck smoothness of 12000 seconds on the coated surface and 550 seconds on the opposite side.The thickness was 84 μl. there were.

Example 2 A biaxially stretched polypropylene film (thickness: 80 μm, manufactured by Oji Yuka Synthetic Paper) with a multilayer structure containing an inorganic pigment was used as a base material, and the following paint-2 was applied at a rate of 20 g/i+2. Then, the surface was smoothed and a receiving sheet was obtained in the same manner as in Example-1.

Paint-2 Calcium carbonate aragonite 100 parts (Okutama Kogyo) Sodium polyacrylate dispersant 2 parts The produced sheet has a Bekk smoothness (Ouken type) of the coated surface of 12,000 seconds, a smoothness of the opposite surface of 550 seconds, and a thickness of 97 μl. Met.

Comparative Example 1 The polyolefin film used as a base material in Example-1 was evaluated as a sheet without being coated with Paint-1. The Bekk smoothness of the surface was 260 seconds, and the smoothness of the back was 250 seconds.

The sheets obtained in Examples and Comparative Examples were evaluated as follows.

1) Melt transfer printer A commercially available thermal transfer color printer is used to heat an ink sheet using wax ink in stages to thermally transfer the dye to each of the receiving sheets of Examples and Comparative Examples to create single-color and multi-color images of each color. I printed it. The image on this receiving sheet was visually evaluated for image clarity, solid area uniformity, and presence or absence of thermal curl.

2) Each receiving sheet of the sublimation transfer printer example and comparative example was coated with polyester resin (Vylon 300) using a toluene solution, and the solid content was 5.
g/m2 surface to obtain a sublimation transfer receiving sheet.

The ink sheet was heated stepwise using a thermal transfer color printer 11=- using a commercially available sublimation dye to thermally transfer the dye to the receiving sheet, thereby printing monochromatic and overlapping images of each color. The image on this receiving sheet was visually evaluated for image clarity, solid area uniformity, and presence or absence of thermal curl.

The results are shown in the table below. Particularly excellent evaluation results were indicated by ◎, good ones by O1, those with some defects by △, and those with significant defects by ×.

Table 1 Melt transfer printer Table 2 Effects of the sublimation transfer printer Both of the uniformities can provide an excellent receiving sheet, and have the effect of making compact full-color thermal transfer printers and hard copies possible, overcoming the drawbacks of conventional methods.

Procedures Amendment Written by the Commissioner of the Japan Patent Office on 8/Q 1986 Black 1) Mr. Akiyu 2. Name of the invention Thermal transfer receiving sheet 3. Relationship with the case of the person making the amendment Patent applicant's address name Oji Paper Co., Ltd. 4 , Agent 6, Contents of amendment 1 Specification box 9 amends the 16th line of "Paper-like layer" to "Paper-like layer".

that's all

Claims (1)

[Scope of Claims] 1. A thermal transfer receiving sheet, characterized in that a non-heat-shrinkable surface layer is provided on at least one side of a biaxially stretched sheet of a multilayered film mainly composed of an inorganic pigment and a polyolefin. 2. The thermal transfer receiving sheet according to claim 1, wherein the non-heat shrinkable surface layer comprises a pigment and a polymeric adhesive as main components. 3. The thermal transfer receiving sheet according to claim 2, wherein the pigment mainly comprises an inorganic pigment selected from the group consisting of aragonite, satin white, and calcined kaolin.