JPH0428593A - Heat transfer printer image receiving sheet - Google Patents

Abstract

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

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to printer paper, and in particular, it is used in thermal dye transfer printers to uniformly and sharply accept thermally transferred dyes and produce high-quality full-color images. This invention relates to an image-receiving paper that can be printed and has excellent whiteness.

[Prior Art and Problems to be Solved by the Invention] Recently, compact thermal printers, particularly dye thermal transfer printers capable of printing clear full-color images, have attracted attention. Dye thermal transfer printers overlap an ink sheet with an ink layer made of sublimation dye and a binder over the dye-dyeable resin-coated side of image receiving paper, and then apply heat from a thermal head to the ink sheet. A portion of the image is transferred and dyed onto image-receiving paper in the required density to form an image.

In order to obtain good images with such printers, the image-receiving sheet is made of a film-like base material mainly composed of inorganic pigments and polyolefins or biaxially stretched film, and is coated with polyester, vinyl polymer, etc. It is known that it can be produced by providing a dyeing layer containing a dyeable resin as a main component. These films have uniform thickness, flexibility, and low thermal conductivity, and can produce uniform, high-density prints.

However, for example, when thermally transferred to an image receiving sheet based on a biaxially oriented polypropylene film containing ordinary inorganic pigments, there are differences in the density and uniformity of the image depending on the oriented film, and the image does not necessarily have good commercial value. was not obtained. That is, there were unsatisfactory points such as noise and image unevenness due to the effects of uneven thickness, uneven pigment, and heat conduction of the polyolefin resin, and insufficient sensitivity.

Synthetic paper made of a multilayer biaxially stretched polyolefin film containing inorganic pigments is known for its excellent image homogeneity and good compatibility with thermal heads.
The paper layer, which contains a large amount of pigment on the surface and has voids formed by stretching, has a relatively large roughness, and it was not possible to achieve the expected resolution on the order of 10 μm.

By increasing the suppression of the platen roll against the thermal head, image resolution/reproducibility can be improved to a certain extent, but excessive platen suppression can also cause a loss of transfer fidelity, and due to the rigidity of polyolefin, the micro- However, there are limits to the adhesion of these materials, and improvements to the base sheet are expected. By understanding the causes of these problems, it is possible to design a polymer film that will serve as an ideal image-receiving sheet substrate.
pointed.

It is difficult to obtain a pure white color depending on the type of pigment used in films made with these inorganic pigments, and it is difficult to achieve uniformity, high porosity, and desirable color tone in material design and manufacturing. difficult,
The ultimate challenge for image-receiving paper was to use an inexpensive transparent film.

Furthermore, in the dye thermal transfer method, since the amount of heat applied to the image print sheet is large, there are problems with heat shrinkage, wrinkles, and curling due to heat. By laminating and adhering a stretched film to a core sheet with a low heat shrinkage rate, an image receiving paper with little curl after printing can be obtained. However, the core sheet did not always have the desired color tone, which affected the resulting receiving paper.

Compact full-color printers using the dye thermal transfer method are expected to be widely used for electronic cameras and video printers, so to speak, as ``electronic color prints,'' and they are required to be as ``white'' as conventional color prints. The present invention provides a printing sheet that is suitable for thermal printers that require a large amount of heat, such as thermal dye transfer, and that eliminates the drawbacks associated with the use of multilayer films, and that does not undergo thermal deformation, is clear, and has faithful image information. This is what we provide.

It goes without saying that the present invention is not limited to dye thermal transfer printers, but can be applied to various types of thermal printers including melt ink type printers.

[Means and effects for solving the problem] The present inventors discovered that when used in a dye thermal transfer type thermal printer,
Eliminates or alleviates the above-mentioned drawbacks: there is little density unevenness, clear images can be obtained from low density to high density, there is less curling due to heat during printing, and the "whiteness" is comparable to that of conventional color printing. We conducted extensive research on image-receiving sheets.

The dye thermal transfer print sheet of the present invention has a thickness of 10 to 15
A sheet (core sheet) with a whiteness of 90% or more on at least one side of 0 μm is laminated with a (surface coating film) with an opacity of 90% or less on the surface with a whiteness of 90% or more, and on top This is an image-receiving sheet characterized by having a transparent receptor layer laminated thereon.

The above-mentioned sheet having an opacity of 90% or less preferably has a porosity of 20% or more, particularly preferably 35% or more. This is because the thermal conductivity becomes low and uniform, making it possible to receive uniform images with high sensitivity. In order to have a sufficient effect, the thickness of this film is preferably 20 μm or more. The smaller the specific gravity, the better, and preferably 0.7 or less.

Preferably, a plastic film with a thickness of 10 μm or more is laminated on the opposite side of the core sheet of the image receiving sheet.
Cover.

By using such a printer image-receiving sheet with a specific laminated structure, it is inexpensive, has high sensitivity, has no density unevenness or noise, is clear from low density to high density, has high whiteness, and has a good hue and density. It is possible to produce uniform color prints with stable runnability under a wide range of conditions, and has succeeded in solving the problems of conventional methods.

Printing using heat, such as a thermal head for sublimation dye transfer, forms an image using heat from one side. Conventionally, heat-resistant sheets with low heat shrinkage have been laminated as a core to prevent curling during printing due to heat.

In particular, in image-receiving sheets for dye thermal transfer, a specific type of film is laminated onto a core sheet so that the thermal conductivity is low and uniform. Conventionally, films with high whiteness and opacity have been used, but it has been difficult and expensive to obtain uniformity, high porosity, and desired white color tone. The present invention provides a surface coating film with homogeneity, preferably thermal insulation, and whiteness divided into the underlying substrate, resulting in improved functionality, lower cost, and improved image reception. It was discovered that paper can be obtained.

In the present invention, plastic sheets having a wide range of opacity can be used as such a sheet (surface coating film), and translucent to transparent thermoplastic synthetic resin films can be used.

Such a film can be selected from polyolefins such as high-density polyethylene, low-density polyethylene, and polypropylene, and other thermoplastic synthetic resins selected from many types such as polystyrene and ethylene-vinyl acetate copolymers. The film may be unstretched or stretched, but in order to achieve the stiffness necessary for the runnability of the printer, most films are preferably stretched.

Furthermore, blends and block copolymers of these polymers can also be used. Furthermore, powders such as inorganic pigments can also be used as fillers.

For example, a film whose main component is olefin, especially 30 to 95 parts of polypropylene and 1 part of high density polyethylene.
~40 parts, 0~ of inorganic fine powder such as calcium carbonate
A film having a composition of 50 parts is stretched biaxially to generate voids with a porosity of 10 to 50%, and the film becomes translucent or opaque.

It is preferable that the film of the surface layer (surface coating film) has a small heat shrinkage rate, particularly a heat shrinkage rate of 0.1% or less according to JIS K-6734. The stress during stretching is reduced by heating by contact with a hot roll, and the thermal shrinkage rate is reduced. When a film is used for the back layer, depending on the state of thermal curling, it may be preferable to perform treatment to reduce its thermal shrinkage rate.

In the image-receiving sheet of the present invention, a dye-dyeable coating layer is provided on the front side (and the back side, if necessary). As the dyeing layer, a coating layer is provided whose main component is a resin (for example, polyester resin) that has good dyeability for thermal transfer dyes such as disperse dyes and sublimation dyes. This dyeable coating layer needs to have a thickness of 1 μm or more since it needs to have the capacity to accept and dissolve the dye, but since it usually has good thermal conductivity, it is not preferable to make it too thick because it lowers the sensitivity. The thickness is preferably 10 μm or less.

It is important that the sheet serving as the core to be laminated used in the present invention has a whiteness of 90% or more on one side. For this purpose,
Paper made from pulp with a high degree of whiteness is used, or in the case of film, it is colored by mixing a filler with a high degree of whiteness such as titanium dioxide, or a coating layer containing a pigment with a high degree of whiteness as its main component is provided. I can do it.

The opacity of this sheet is 90% on the side where the whiteness is 90% or more.
By laminating sheets (surface layer coated sheets) of less than 10%, a base material with high whiteness and low cost can be obtained. Further, in order to prevent curling during printing due to heat, the core sheet preferably has a higher elastic modulus and stiffness than the top sheet. The core sheet is preferably a thermoplastic film with good heat resistance, such as polyethylene terephthalate film or paper. The core sheet prevents curling during each process caused by the surface coating film and dyeing layer resin, improving runnability and usability. For this reason, it is necessary to have a thickness of 10 μm or more, but if it is too thick, the texture will be poor and the suitability for use will be impaired, so the thickness is preferably 150 μm or less.

It is preferable to laminate a plastic film on the back side. This prevents curling caused by environmental changes such as humidity. This plastic film preferably has a thickness of 10 μm or more from the viewpoint of coating strength. If necessary, it is preferable to further coat the back side with a layer mainly composed of acrylic resin, surface active polymer, low molecular weight surfactant, etc. for the purpose of improving running properties and preventing static electricity.

In the present invention, various methods can be used to laminate the core sheet, the surface coating sheet, and the back layer, one of which is a dry lamination method using an adhesive. It is preferable to use an adhesive with high heat resistance.

The total thickness of the laminated sheet is selected depending on the final use of the sheet, and is usually preferably 60 to 300 μm.

〔Example〕

Next, the sheet for dye pre-transfer printers of the present invention will be described with reference to Examples. In the following examples, parts are parts by weight (solid content).

Production Example 1 (Production example of core sheet) 95 parts of bleached kraft bulb with a whiteness of 92%, 5 parts of light calcium carbonate, and 0.2 parts of an alkyl ketene dimer sizing agent were mixed, and paper was made using a Fourdrinier paper machine. A high-quality paper with a basis weight of 80 g/m'', an ash content of 3% by weight, a surface Beck smoothness of 400 seconds, and a whiteness of 92% was obtained.

Production Example 2 (Core sheet production example) 50 parts of calcium carbonate, 30 fB of titanium dioxide, 15 parts of styrene-butadiene latex, and starch were added to one side of a biaxially stretched polyethylene terephthalate film (Lumirror 33B, thickness 38 μm, manufactured by Toshi ■). A water-based paint containing 5 parts of the water-based paint was applied and dried to obtain a white coating layer. The Bekk smoothness of the surface of this sheet was 500 seconds, and the whiteness was 94%.

Production Example 3 (Production example of a sheet that becomes a surface coating film) Polypropylene 6 with a melt index (MI) of 0.8
5 parts, 15 parts of low density polyethylene, average particle size 1.5μ
5 parts of heavy calcium carbonate and 3 parts of titanium dioxide were blended, mixed in an extruder set at 270°C, extruded into a sheet, and cooled with a cooling device to obtain a non-stretched sheet. This sheet was heated to 145°C and then stretched 5 times in the machine direction. Next, after heating this to 185°C,
．． The front and back surfaces of the film obtained by stretching 5 times were subjected to corona discharge treatment to obtain a single-layer structure sheet with a wall thickness of 50 μm. This sheet had a porosity of 30%, an ash content of 5% by weight, and a surface Bekk smoothness of 4000 seconds. Also, the opacity is 78
%, and the whiteness was 90%.

Example 1 A multi-layered or biaxially stretched film (YUBO FPG8
A 80 μm thick Oji Yuka Synthetic Paper (manufactured by Oji Yuka Synthetic Paper ■) was used as the back layer and laminated using a dry lamination method using a polyester adhesive to obtain a laminated sheet. A toluene solution of polyester resin (Vylon 200 Toyobo ■) was applied onto the surface layer and dried to form a coating layer of 5 g/m 2 to obtain an image-receiving sheet for dye thermal transfer printing.

Example 2 The sheet of Production Example 2 was used as the core, and the biaxially oriented polypropylene film (Vylon) was used as the surface coating film.
25 μm, opacity 10% or less (manufactured by Toyobo ■) was used to make a laminated sheet, and on the surface layer, a toluene solution of the same polyester resin as in Example 1 was applied and dried to give 5 g/m
A coating layer was formed to obtain a sheet for dye thermal transfer printing.

Comparative Example 1 A multi-layer structured - or biaxially stretched film (
Yubo FPG60 Thickness: 60 μm, Made of egg oil synthetic paper ■ Porosity: 32%, Ash content: 35 parts 1 Surface smoothness: 60
A laminated sheet was obtained in the same manner as in Example 1, except that 0 seconds, opacity was 87%, and whiteness was 91%. Further, in the same manner as in Example 1, a coating layer of 5 g/m'' polyester resin was formed on the surface layer to obtain a sheet for dye thermal transfer printing.

Comparative Example 2 A dye thermal transfer printing sheet was obtained in the same manner as in Example 1 except that a white film without a coating layer was used as the core.

Comparative Example 3 High-quality paper OK as a core (basis weight 64 g/m", whiteness 86)
A sheet for dye thermal transfer printing was obtained in the same manner as in Example 2, except that a dye thermal transfer printing sheet was used.

Comparative Example 4 Instead of the laminate of Example-1, a biaxially stretched polyethylene terephthalate film (whitened by kneading pigment) was used.
Lumirror E20 188μm.

A sheet for dye thermal transfer printing was obtained in the same manner as in Example 1, except that a dye thermal transfer printing sheet (manufactured by Toshi Corporation) was used.

The dye thermal transfer sheets of Examples 1 to 2 and Comparative Examples 1 to 3 were used in a sublimation video printer (UP-5000 manufactured by Sony ■).
We compared the vividness of the colors, whiteness of the white background, cost, etc. The results are shown in the table.

Table [Effects of the Invention] The thermal transfer image-receiving sheet of the present invention has excellent image gradation and homogeneity, as well as excellent print whiteness and clarity, and is suitable for thermal transfer, including sublimation dye transfer. This makes it possible to create a compact full-color printer, which will greatly contribute to industry.

Claims (1)

[Claims] 1. A plastic sheet with a thickness of 10 to 150 μm and a whiteness of at least 90% on one side and a plastic sheet with an opacity of 90% or less is laminated on the side with a whiteness of 90% or more, and a substantially transparent A dye thermal transfer printer image-receiving sheet characterized by laminating a dye-dyeable image-receiving layer.