JP2930309B2 - Thermal transfer image receiving sheet - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a sheet for receiving and recording a thermal transfer ink image. More specifically, the present invention relates to a thermal transfer method that faithfully receives a transferred image and prints a high-resolution halftone image, for example, in a thermal transfer full-color printer using a thermal transfer image forming material such as a melt transfer ink or a sublimable dye. The present invention relates to an image receiving sheet.

[Conventional technology and problems to be solved by the invention]

Recently, color printers that print relatively clear and clear color images, particularly printers of a dye sublimation type and other image thermal transfer systems, have been widely put into practical use.
These color printers print monochromatic yellow, cyan, and magenta image dots in a multi-colored superimposed manner, which enables uniform reproduction of images of red, blue, green, and countless other intermediate hues and densities. It is important to form well.

Among these printers, a dye-sublimation transfer type printer has an image receiving sheet on an ink sheet composed of a base film and a sublimation dye ink layer, and the sublimation dye first-coating layer surface has a sublimation dye ink on the ink sheet. The layers are overlapped so as to be in contact with the surface of the layer, and the heat supplied from the thermal head according to the electric signal causes
An image is formed by transferring a sublimation dye to a required portion and a required density.

Also, in a printer of the heat melting transfer method, by using a special ink sheet, the ink layer on the ink sheet is pressed against the surface of the image receiving layer by a thermal head according to the image, and stepwise. Thus, a predetermined amount of ink is transferred to the surface of the image receiving layer to form an image, and thereby a full-color image having a density gradation can be printed.

It is known to use, as these image-receiving sheets or their base layer sheets (supports), paper containing ordinary wood pulp as a main component or a sheet obtained by subjecting the paper to a surface smoothing treatment. However, in order to obtain good prints and prints on an image receiving sheet by a printer having a thermal head, such as a thermal transfer printer, using paper made mainly of wood pulp improves the surface smoothness. However, there is a problem that the uniformity of the received image is insufficient.

As a technique for imparting excellent image receiving suitability to an image receiving sheet for a hot-melt transfer printer, a conventional 10
The surface of high quality paper having a Beck smoothness of about 50 seconds is further smoothed using a super calender or the like, and this is made 100 seconds or more, and a coating layer mainly containing an oil-absorbing pigment is formed on the paper. (Japanese Patent Application Laid-Open No. Sho 57-182487) has been proposed, and a considerable improvement in the thermal transfer image receptivity of the image receiving sheet has been recognized.

However, these techniques have made it difficult to form images of innumerable intermediate hues and densities with good uniformity and reproducibility by multicolor printing of thermal transfer dots.

In particular, in systems that control the amount of molten ink transferred by pressing and heating the thermal head, and in sublimation dye transfer printers, the uniformity of the ink receiving ability of the image receiving layer has a significant effect on image reproducibility. Therefore, even when the conventional image receiving sheet as described above is used, uneven density of solid portions, unstable transfer of dots, and the like are observed, and thus a satisfactory halftone image cannot be obtained. There is.

In order to solve the above-mentioned problem, a synthetic paper of a multilayer structure film obtained by biaxially stretching a polyolefin containing an inorganic pigment, for example, a resin material containing polypropylene as a main component is used as a base sheet (support). An image receiving sheet provided with an image receiving coating layer thereon has been devised.

In the case of such an image receiving sheet for a dye sublimation transfer printer, an image receiving layer mainly composed of a polyester resin is coated on the base layer sheet. Such an image receiving sheet has advantages such as uniform thickness, flexibility, and low thermal conductivity as compared with paper made of cellulose fiber. It has the advantage that an image can be formed.

However, a resin material containing polypropylene as a main component
When a multilayer structure film obtained by axial stretching is used as a base layer sheet of an image receiving paper for a thermal transfer printer, when the obtained image receiving sheet is subjected to a recording operation using a thermal head, it is held by the multilayer structure film. The stretching stress is relieved by heat, thereby causing the base sheet to thermally shrink, resulting in curling or wrinkling of the image receiving sheet, causing trouble in running the sheet in the printer, and There is a problem that the commercial value of a print to be produced is significantly reduced. In particular, this problem is a serious drawback in a sublimation transfer type printer because the amount of heat required for transfer recording is large.

A method of providing an organic polymer barrier layer on a paper base layer without using a heat-deformable base layer sheet as described above and for solving problems such as non-uniformity of an image is disclosed in Japanese Patent Application Laid-Open Publication No. HEI 9-163191. 62-21590. However, in order to improve image quality by this method, the surface of the image receiving sheet is required to be highly smooth. That is, if the smoothness of the image receiving surface is insufficient, the uniformity of transfer of the image forming material such as ink becomes insufficient, and this appears as density unevenness.

[Means for solving the problem and operation]

The thermal transfer image receiving sheet of the present invention is a sheet-like support containing pulp as a main component, and is formed on the surface or both front and back surfaces of the support, and contains a mixture of a pigment and a water-soluble polymer adhesive as a main component. And, by super calendering, an undercoat layer having a surface smoothness of 1000 seconds or more according to the test method of JIS P8119, and formed on the surface undercoat layer, containing a polyolefin resin as a main component, and JIS P8119 5000 depending on test method
A surface-side coating layer having a surface smoothness of not less than seconds, an image-receiving layer formed on the surface-side coating layer, and made of a thermal transfer image-receiving resin material, and formed on the back side of the support, and And a backside coating layer containing a polyolefin resin as a main component.

In the image receiving sheet of the present invention, the surface-side polyolefin-based resin coating layer formed on the surface-side undercoat layer has 5 to 5 coating layers.
It is preferable to contain 20% (weight) of a white pigment, and the polyolefin resin contained in the front-side and back-side coating layers is polyethylene, polypropylene, polybutene,
It is preferable to be selected from polypentene, a copolymer of the above-mentioned olefins, or a mixture of the above-mentioned polyolefins.

The thermal transfer image receiving sheet of the present invention contains a mixture of a pigment and an adhesive as a main component, an undercoat layer having a Beck surface smoothness of 1000 seconds or more, and a sheet-like support having both heat resistance and uniformity. This is characterized in that a base layer sheet containing a combination of the above is formed, whereby the uniformity of absorption and reception of the thermal transfer ink or dye is improved, and the conventional problems are solved.

The smoothness of the image receiving surface of the image receiving sheet of the present invention,
It is not an exaggeration to say that it is determined by the smoothness of the surface of the base sheet.If the surface properties including the surface smoothness of the base sheet can be improved, paper made of wood pulp having excellent heat resistance as a main raw material can be used. Thus, the base sheet used as the sheet-like support can be obtained. The surface of the sheet-shaped support made of base paper can be considerably smoothed by the type of raw pulp, the pulp treatment method, the type of added chemicals, the papermaking conditions, the post-treatment conditions, etc., and the uniformity of the transferred image is improved. Can be improved. However, at least one surface (referred to as surface) of such a sheet-like support made of base paper is coated with an undercoat layer containing a mixture of a pigment and an adhesive as a main component, thereby greatly improving the surface smoothness. Then, by further coating the undercoat layer with a thermoplastic resin, an image receiving sheet with further improved surface smoothness can be obtained.

The configuration of the image receiving sheet of the present invention will be described with reference to the accompanying drawings.

In the thermal transfer image receiving sheet of the embodiment shown in FIG. 1, a base layer sheet 5 is formed and bound on a sheet-like support (paper) 1 and one surface (surface) thereof, and contains a mixture of a pigment and an adhesive. An undercoat layer 4 containing as a main component a surface-side coating layer 2 formed and bound on the undercoat layer 4 and preferably containing a polyolefin resin containing preferably a white pigment as a main component
And a backside coating layer 3 formed and bound on the other surface (backside) of the support 1 and containing a polyolefin resin as a main component.

A thermal transfer image receiving layer 6 is formed and bound on the surface of the surface side coating layer 2 of the base layer sheet 5.

In another embodiment of the thermal transfer image receiving sheet of the present invention,
Between the back surface of the sheet-like support 1 and the back surface side coating layer 3,
A back side undercoat layer may be formed.

The thickness and rigidity of the image receiving sheet of the present invention are appropriately set depending on the use, that is, color printing, computer graphics, labels, cards, etc.
It preferably has a thickness of about μm.

The type of paper used for the support 1 is not particularly limited, but generally, high-quality paper is preferably used. On the support, although an undercoat layer containing a pigment and an adhesive as main components and a surface-side coating layer containing a polyolefin resin as a main component are provided thereon, the surface flatness of the image receiving sheet is, It depends on the formation of support (paper) and surface flatness, etc.
It is preferable to use paper having good formation and good surface properties on the support.

Examples of the pigment used in the undercoat layer of the present invention include white pigments used in ordinary coated paper for printing and art paper, such as various clays such as kaolin, calcium carbonate, titanium dioxide, aluminum hydroxide, satin white, talc, and sulfurous acid. Calcium, calcined clay, finely divided silica, and other white pigments can be used alone or as a mixture.

As the adhesive used for the undercoat layer, a water-soluble polymer adhesive is used. For example, a water-soluble polymer adhesive such as polyvinyl alcohol, starch, and casein is used alone or in combination.

In addition, an antifoaming agent, a dispersing agent, a conductive agent, a wetting agent, and the like may be contained in the undercoat layer as required for the formation of the undercoat layer, that is, for coating or printing.

The undercoat layer may be formed by applying a mixture (dispersion, emulsion) containing a pigment and an adhesive to one surface (surface) of a sheet-like support by a conventional method and solidifying the mixture.

After forming the undercoat layer, the surface is smoothed by a super calender treatment, and the smoothness of the surface is adjusted to a certain value or more, thereby improving the surface properties of the base layer sheet, and thereby making the transferred image of the image receiving sheet uniform. It is effective for improving sex. The surface of the undercoat layer treated with super calender is JIS P8119
It is necessary to have a surface smoothness of 1000 seconds or more in a surface smoothness test according to.

The surface side coating layer may contain a white pigment. Examples of the polyolefin resin contained in the surface-side coating layer include polyethylene, polypropylene, polybutene, polypentene, a copolymer of two or more of these olefins, and a mixture of these polyolefins.

The white pigment contained in the surface side coating layer is titanium dioxide, zinc sulfide, zinc oxide, calcium sulfate, calcium sulfite, barium sulfate, clay, calcined clay, talc,
It can be suitably selected from those conventionally known for kneading and blending with polyolefin resins, such as kaolin, calcium carbonate, silica, calcium silicate and the like.

Polyolefin resin, and white pigment, respectively,
It is preferable that the resin coating layer can be used for a melt extrusion laminator, and that the obtained resin coating layer has good surface flatness and good adhesion to a sheet-like support or an undercoat layer. JIS P8 of this surface side coating layer
In the smoothness test according to 119, the surface smoothness needs to be 5000 seconds or more.

Generally, the content of white pigment in the surface side coating layer is 20%
(Weight) or less. This content is 20%
When the value exceeds, the mechanical strength of the surface-side coating layer formed by the laminating method is insufficient, so that the film is easily cracked.

The polyolefin resin coating layer on the back side is formed on the back surface of the sheet-like support, preferably using a melt extrusion laminator, and the surface is preferably highly flat, and the back surface side coating layer contains white pigment. If included, it indicates high whiteness. Such a backside-side coating layer naturally makes the surface of the image receiving layer highly flat, and thus has excellent high definition, high sensitivity,
It enables a high gradation image to be formed on the image receiving layer.

The back surface side coating layer is effective for preventing curling of the image receiving paper, and enables printing and writing on the back surface of the image receiving sheet by matting the back surface.

[Examples] The present invention will be further described by the following examples.

Example 1 Using a high-quality paper of 64 g / m ² as a support, the surface thereof was coated with paint-1 having the following composition at a solid content of 20 g / m ² and dried.
The surface was smoothed by a super calender treatment to form an undercoat layer. The smoothness of the undercoat layer surface according to JIS P8119 is 1
200 seconds. A polyethylene resin was laminated on the undercoat layer and on the back surface of the support at a coating amount of 15 g / m ^{2 by} a melt extrusion method. The smoothness according to JIS P8119 of the obtained surface side coating layer surface was 7,000 seconds.

On the surface-side coating layer, paint-2 having the following composition was added with a solid content of 10
Coating was carried out to a coating amount of g / m ² , followed by drying to form a sublimation dye image receiving layer.

JIS P8 on the surface of the image receiving sheet obtained above
The smoothness of 119 was 8000 seconds, and the smoothness of the backside coating layer surface was 800 seconds.

Comparative Example 1 The high-quality paper described in Example 1 was used as a support, and the surface thereof was coated with Paint-3 having the following composition at an application amount of 35 g / m ² to form an undercoat layer. The surface was super-calendered to smooth the surface The smoothness of this surface according to JIS P8119 was 2000 seconds.
On this undercoat layer, the coating-2 described in Example 1 was directly applied at a coating amount of 10 g / m ² of solid content without applying a polyethylene laminate, and dried to form a sublimation dye image receiving layer.
The smoothness of the image receiving layer surface of the obtained image receiving sheet is 85.
00 seconds, and the smoothness of the back surface was 400 seconds.

Comparative Example 2 Synthetic paper YUPO FP having a multilayer structure containing an inorganic pigment as a support
Using G110 (110 μm thick, Oji Oil Chemical Synthetic Paper), the surface was coated with the paint-2 described in Example 1 at a coating amount of 10 g / m ² of solid content, and dried to form an image receiving layer. . The smoothness of the obtained image receiving layer surface according to JIS P8119 was 15,000 seconds, and the smoothness on the opposite side was 400 seconds.

Thermal Transfer Test The image receiving performance of the image receiving sheets prepared in Example 1 and Comparative Examples 1 and 2 was evaluated as follows.

An ink layer containing a sublimable dye together with a binder was provided on a polyester film having a thickness of 6 μm to prepare ink sheets of three colors, yellow, magenta, and cyan. This ink sheet was heated stepwise by a thermal head of a commercially available thermal transfer printer to thermally transfer an image to each image receiving sheet, and printed a halftone single color and color superimposed image of each color. The images on each image receiving sheet were visually evaluated for image clarity, dot uniformity, solid portion uniformity, and curl due to heat.

The results are evaluated in five grades of excellent, good, normal, poor and extremely poor, and are shown in Table 1.

[Effects of the Invention] The thermal transfer image receiving sheet of the present invention is excellent in image gradation, low density, and high density uniformity. It is excellent in both vividness and natural feeling, eliminates the drawbacks of the conventional thermal transfer image receiving sheet, and enables high quality thermal transfer printing.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view of one embodiment of the thermal transfer image receiving sheet of the present invention. DESCRIPTION OF SYMBOLS 1 ... Support, 2 ... Front side coating layer, 3 ... Back side coating layer, 4 ... Undercoat layer, 5 ... Base layer sheet, 6 ... Image receiving layer.

Continuation of the front page (56) References JP-A-1-283186 (JP, A) JP-A-1-1666991 (JP, A) JP-A-64-45687 (JP, A) JP-A-1-267090 (JP) , A) (58) Field surveyed (Int.Cl. ⁶ , DB name) B41M 5/38

Claims (1)

(57) [Claims] 1. A sheet-like support containing pulp as a main component, and a mixture of a pigment and a water-soluble polymer adhesive formed on the surface or on both front and back surfaces of the support as a main component. By a calendering treatment, an undercoat layer having a surface smoothness of 1000 seconds or more according to the test method of JIS P8119, formed on the surface side undercoat layer, containing a polyolefin resin as a main component, and a test method of JIS P8119 By 500
A surface-side coating layer having a surface smoothness of 0 second or more, an image-receiving layer formed on the surface-side coating layer, and made of a thermal transfer image-receiving resin material, and formed on the back side of the support, And a thermal transfer image receiving sheet comprising a backside coating layer containing a polyolefin resin as a main component.