JPH01263081A - Image-receiving sheet for thermal transfer - Google Patents

Abstract

PURPOSE:To provide the title sheet capable of being used on a color printer with high resolution and record clear images stably, from lower to higher densities, by providing a base comprising a paper, a surface coat layer comprising a polyolefin resin and a white pigment as main constituents, and a back coat layer comprising a polyolefin resin as a main constituent. CONSTITUTION:A receiving sheet 1 comprises a paper base 2 comprising a pulp as a main constituent, a surface coat layer 3 provided on the face side of the paper base 2 and comprising a mixture of a polyolefin resin and a white pigment as a main constituent, and a back coat layer 4 provided on the back side of the base 2 and comprising a polyolefin resin as a main constituent. The surface coat layer 3 comprises 5-20wt.% of the white pigment dispersed therein. If the pigment content exceeds 20wt.%, the polyolefin resin layer with which the base 2 is laminated may be cracked. If the pigment content is less than 5wt.%, the surface coat layer obtained may be unsatisfactory in transparency or brightness. The polyolefin resin enhances the flatness and brightness of the surface of the receiving layer, enabling the formation of excellent images with high fineness, sensitivity and gradation properties.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image receiving sheet used in a thermal transfer printer for documents and images. More specifically, the present invention provides a thermal transfer printer using hot-melt or hot-adhesive ink that sharply accepts single-color or multi-color ink images, has good microreproducibility of characters and images, and is therefore capable of printing characters and images easily. The present invention relates to a thermal transfer image-receiving sheet capable of printing with high resolution.

[Prior art]

Recently, the demand for color printing and color printers has increased, and in particular, wax ink heat-melting type and dye sublimation type transfer printers using thermal heads have made it possible to print clear color images, so their use has increased. Attention has been paid. A heat-melt transfer printer overlays a receptor sheet on an ink sheet consisting of a film-like base material and a heat-melt ink layer, and applies heat-melt ink to the required areas on the receptor sheet by heating in response to image signals from a thermal head. to form an image. In the case of a color printer, images of different colors such as yellow, magenta, cyan, and black are transferred to an image-receiving sheet and then superimposed to form a Kalani image.

Thermal transfer method, which uses heat-melting or heat-adhesive ink, is the mainstream for small non-impact printers, and is often used for kanji printers and color printers. There was a demand for a system that could be used to print documents and paper. If paper that can accept images with high resolution and good color reproducibility is realized, it will be possible to make hard copies of color images such as videos and computer graphics using compact equipment.
A wide variety of applications are expected.

The sharpness of images transferred by a thermal melt transfer printer depends on the performance of the receiving sheet. In other words, it is not possible to print images of the same high quality on all types of paper, and various techniques have been developed to impart receptivity to paper that meets the needs of each printer. For example, regular high-quality paper with a Beck smoothness of about 10 to 50 seconds is smoothed using a super calendar, etc., and the Beck smoothness is 1
It is known that when the time is set to 00 seconds or more, the sharpness of the image is improved.

In the thermal transfer method, the density of the image is usually binary, but
It is now possible to print halftone color images using an area gradation type thermal transfer printer.

For receiving paper for area-gradation type thermal transfer printers,
In order to use the dither method, a resolution of 16 to 3 pixels, which is higher than the pixel
The printer is required to transfer images such as 2 dots)/mm. Furthermore, recently, the requirement for high resolution changes has become even stricter, such as the announcement of an area gradation method that controls the size of transferred dots with an accuracy of 10 μm or less. It is clear that image-receiving sheets using high-quality paper have their limits.

In order to improve the transfer characteristics of a thermal transfer printer, a method has been proposed (Japanese Patent Laid-Open No. 182487/1987) that provides an oil-absorbing pigment on a paper base material to obtain a transferred image with even shading. Most of the pigments used in coated papers for printing are listed as usable in this image-receiving sheet, and a considerable improvement is obtained in the thermal transfer receptivity of the receiving sheet.

However, in high-resolution printers, the uniformity of the ink-receiving ability of the image-receiving layer of the receiving sheet has a significant impact on image reproducibility, and traditional coated or non-coated thermal transfer When using a receptor sheet, uneven density in solid areas,
Unstable transfer of dots was observed, and a good halftone image could not be obtained.

Furthermore, forming an image with good reproducibility in the hue and density of red, blue, and green by overlapping the single colors yellow, cyan, and magenta is simply Beck smoothing. It was difficult to use only high-quality paper or coated paper.

[Problem to be solved by the invention]

In view of the above-mentioned current situation, the present invention can also be used in color printers with high resolution, and the dots and solid areas made of transfer ink are evenly reproduced, stably and clearly from low density to high density. An object of the present invention is to provide a thermal transfer image-receiving sheet capable of recording a good image.

By using such a receptor sheet, it is possible to realize an image with a high resolution and high color reproducibility never seen before, even if an area gradation method is used.

[Means and effects for solving the problem of bad luck] The present inventors have developed a color printer that can reproduce halftone dots made of transfer ink and solid areas evenly and obtain stable and clear recorded images, and We conducted extensive research on the thermal transfer receiving sheet used for this purpose, and as a result, we completed the present invention.

The thermal transfer image-receiving sheet of the present invention includes a base made of paper mainly containing bulbs, a polyolefin resin formed on the surface side of the base, and 5 to 20% by weight of polyolefin resin dispersed therein.
The present invention is characterized by having a surface coating layer containing a white pigment as a main component, and a back coating layer formed on the back side of the substrate and containing a polyolefin resin as a main component.

In an example of the thermal transfer image receiving sheet of the present invention shown in FIG. 1, the receiving sheet 1 includes a paper base 2 mainly composed of pulp, and is formed on the surface side (image receiving surface side) of the paper base 2. It consists of a surface coating layer 3 whose main component is a mixture of a polyolefin resin and a white pigment, and a back coating layer 4 which is formed on the back side of the paper substrate 2 and whose main component is a polyolefin resin.

5 to 20% by weight of white pigment is dispersed in this surface coating N3.

In the receiving sheet of the present invention, the type of paper substrate is not particularly limited, but high-quality paper is generally used. The thickness, stiffness, etc. of the sheet can be set arbitrarily depending on the purpose of the receiving sheet, but generally 20 to 200 g/
A material having a basis weight of m2 is used.

Since the surface flatness of the receptor sheet of the present invention is influenced by the formation, surface properties and flatness of the low base paper, the low base paper
It is preferable that the material has good texture, surface properties, and flatness.

As the polyolefin resin used for the polyolefin resin coating layer on both the front and back surfaces of the paper base, it is preferable to use polyethylene, copolymers thereof, and mixtures thereof, but polypropylene, polybutene, polypentene, copolymers thereof, and mixtures thereof are preferably used. Mixtures thereof can also be used. Generally, the weight of the surface coating layer is between 2 and 8
It is preferable that it is 0 g/...2, and 10 to 30 g/m2
It is more preferable that

White pigments used in the surface coating layer include titanium dioxide, zinc sulfide, zinc oxide, calcium sulfate, calcium sulfite, barium sulfate, clay, talc, kaolin, light or heavy calcium carbonate, silica, calcium silicate, etc. You can play with the materials that have been conventionally used as white pigments for mixing in polyolefin resins. The white pigment used in the surface coating layer must have high whiteness, be usable in a coating process using a melt-extrusion laminator, and not impair the flatness of the resulting surface coating layer or the adhesion between the paper substrate and the resin layer. It is preferable that it satisfies the following requirements.

Generally, the content of white pigment in the surface coating layer is 5 to 20
It is preferably within the range of % (weight).

If this content is higher than 20%, cracks may occur in the laminated polyolefin resin layer. Moreover, when this content is lower than 5%, the opacity and whiteness of the resulting surface coating layer may become insufficient.

The polyolefin resin, with or without white pigment, is coated onto the paper substrate, preferably using a melt extrusion laminator. The surface is highly flat and has a high degree of whiteness if it contains white pigment. Such a resin layer naturally makes the surface of the receptor layer highly flat and has a high degree of whiteness.
Therefore, an image with excellent high definition, high sensitivity, and high gradation can be formed.

In the thermal transfer image-receiving sheet of the present invention, a polyolefin resin coating layer is preferably formed on the back side of the paper substrate by an extrusion lamination method.

If necessary, the surface may be matted. To achieve this matting, for example, when extruding and laminating a polyolefin resin onto a paper base, a cooling roll whose surface has been matted in a desired pattern is pressed onto the surface of the resin layer. The matte surface may be embossed on the surface of the resin layer. Generally, the weight of the back coating layer is preferably 2 to 50 g/m2, and 5 to 20 g/m2.
More preferably, it is g/m2.

By laminating polyolefin resin coating layers on both the front and back sides of the paper, it is possible to prevent the receiving sheet from curling, and it is also possible to impart water resistance and weather resistance to the receiving sheet.

In the image-receiving sheet of the present invention, the front and back coating layers may contain conductive agents, anti-slip agents, etc., depending on the needs of thermal transfer operations.

〔Example〕

The invention will be further illustrated by the following examples.

On one side of 170 g/m2 high-quality paper as a substrate, 10
A polyethylene resin layer containing 30% by weight of titanium dioxide
Melt-extrusion lamination was carried out at a weight of 112 g/l, and a polyethylene resin layer having a weight of 25 g/m2 was melt-extruded and laminated on the opposite side, and the surface was subjected to a matting treatment.

Bekk smoothness of the surface side of the obtained receiving sheet (Oken method)
is 20000 seconds, and the Bekk smoothness of the opposite side is 250
It was seconds.

An ink sheet with three sides of yellow, magenta, and cyan, which is made of polyester with an evaluation thickness of 6 μm as a base material and has an ink layer containing wax and pigment as its main components, is inserted into the thermal head of a commercially available printer. The image was heated in stages to thermally transfer it to a receiving sheet, and a single color image and a color superimposed image of each color were printed. The image on this receiving sheet was visually evaluated for image clarity, dot uniformity, solid area uniformity, and thermal curl.

The evaluation results are shown in Table 1 on a 5-grade scale. On a five-point scale, 5 is for products with excellent performance, 4 is for products with good performance, 3 is for products with average performance, 2 is for products with slightly inferior performance, and 1 is for products with defects that pose problems in use. represent.

Fire 1 Salmon A high-quality paper weighing 64 g/m2 was used as the base material, and polyethylene resin was laminated on both sides with a coating amount of 20 g/m2. The Bekk smoothness (Oken method) of the surface of the obtained sheet was 600 seconds, and the Bekk smoothness of the opposite surface was 600 seconds.
It was seconds.

The evaluation results are shown in Table 1.

The high-quality paper described in Example 2 was used as a textured base material, and its surface was smoothed by supercalendering to prepare a receiving sheet.

The Bekk smoothness (Oken method) of the image receiving surface of the generated receiving sheet was 300 seconds, and the Bekk smoothness of the opposite surface was 250 seconds.
It was seconds.

The evaluation results are shown in Table 1.

A synthetic paper with a multi-N structure containing an inorganic pigment, Yubo FPGIIO (thickness: 110 μm, egg oil synthetic paper) was used as the base material.

The evaluation results are shown in Table 1.

Margin Table 1 below [Effects of the Invention] The thermal transfer image receiving sheet of the present invention has good uniformity of the image transferred thereon, high color density of the image, less thermal curling after printing, and sharpness of the image. It has excellent texture and natural feel, overcomes the drawbacks of conventional receptor sheets, and can be used in high-resolution melt transfer printers.

[Brief explanation of the drawing]

FIG. 1 is an explanatory cross-sectional view showing the structure of an example of the thermal transfer image receiving sheet of the present invention. DESCRIPTION OF SYMBOLS 1... Sheet, 2... Paper base, 3... Surface coating layer, 4... Back coating layer.

Claims (1)

[Claims] 1. A substrate made of paper mainly made of pulp, and a surface coating formed on the surface side of this substrate and consisting mainly of a polyolefin resin and 5 to 20% by weight of a white pigment dispersed therein. layer, and a back coating layer formed on the back side of the base and containing a polyolefin resin as a main component,
Thermal transfer image receiving sheet.