JP2595311B2 - Method for producing base layer sheet for thermal transfer image receiving sheet - Google Patents

Description

The present invention relates to a base sheet for a thermal transfer image receiving sheet and a method for producing the same. More specifically, the present invention is a method of transferring a full-color print image sharply with a thermal transfer ink such as a sublimated dye without curling due to heat in a printer using large thermal energy, such as a dye heating sublimation type printer. The present invention relates to a base sheet useful for a thermal transfer image receiving sheet capable of receiving a high resolution halftone image with high fidelity and a method for producing the same.

[Problems to be solved by the prior art and the invention]

In recent years, color printers capable of printing clear color images with a relatively compact device, particularly color printers of a thermal transfer system such as a dye sublimation type, have attracted attention.

Among these color printers, a dye sublimation transfer type printer is an image receiving sheet containing a sublimation dye-dyeing polyester resin of an image receiving sheet in an ink sheet composed of a substrate such as a film or thin paper and a sublimation ink layer. The surface of the layers are superposed, and the sublimation ink is transferred to the image receiving sheet by a required portion and a required density to form an image by the heat supplied from the thermal head according to the electric signal. However, in such a sublimation type thermal transfer system, the uniformity of the base material of the image receiving sheet affects the uniformity and sharpness of the obtained transfer image. The same high-level printing is not possible with a receiving sheet.

Good printing on image receiving sheet for thermal transfer printer,
In order to obtain a print, it is known to form a base sheet by laminating and laminating a biaxially stretched multi-layer film containing a polyolefin containing an inorganic pigment as a main component on a support. In the image receiving sheet for a sublimation transfer printer, an image receiving layer containing a polyester resin is formed on the base sheet. Such a base layer sheet has a uniform thickness,
Due to its advantages such as flexibility and lower thermal conductivity than paper made of cellulose fiber, there is an advantage that a uniform and high-density transfer image can be obtained.

However, when a biaxially stretched multilayer film containing polypropylene as a main component is used as a base layer sheet of an image receiving sheet for a thermal transfer printer, when an image receiving sheet obtained therefrom is subjected to a thermal transfer operation, a base sheet is formed. The axially stretched multi-layer polypropylene film has drawbacks such as heat shrinkage, resulting in curling or wrinkling of the film, which causes trouble in running of the sheet and significantly reduces the commercial value of the print. In particular, in the sublimation transfer system, since the amount of heat applied to the image receiving sheet is large, this problem has occurred remarkably. The sublimation type thermal transfer method is often used for small electronic camera printers and video printers as the mainstream of small full-color non-impact printers, and is also used for thermal transfer printers with a large heating amount such as the sublimation transfer method. However, it has been desired to provide an image receiving sheet capable of obtaining a clear print without thermal deformation.

The present invention provides a base layer sheet useful for a thermal transfer image receiving sheet which has good printing adequacy for other thermal transfer printers including a sublimation method, and which has solved the above-mentioned drawbacks caused when the multilayer structure film is used, and a method for producing the same. It is intended to provide.

[Means and actions for solving the problem]

The method for producing a base layer sheet for a thermal transfer image receiving sheet according to the present invention comprises the steps of: comprising a polyolefin resin as a main component on the surface (image receiving layer forming surface) and the back surface of a sheet support having a thickness of 20 to 300 μm; When forming the front side resin coating layer and the back side resin coating layer by laminating and applying the axially stretched multilayer structure film under tension, the tension (T ₁ )
The ratio T ₁ / T ₂ to the tension (T ₂ ) applied to the resin film for forming the backside resin coating layer is controlled to be 1/2 or less.

Therefore, the base layer sheet for a thermal transfer image receiving sheet produced by the method of the present invention is formed on a sheet-like support having a thickness of 20 to 300 μm, on the front surface (the image receiving layer forming surface side) and the back surface of the support. Each comprising a polyolefin resin as a main component, and a front side resin coating layer comprising a multilayer resin film formed by a biaxial stretching method, and a back side resin coating layer; The resin coating layer is formed by controlling the ratio T ₁ / T ₂ to 1: 2 or less by applying tensions T ₁ and T ₂ to the front side and the back side resin films forming the respective layers. Therefore, the backside resin coating layer retains a larger residual shrinkage stress than the frontside resin coating layer.

The present inventors, for example, such as a dye sublimation method, when used in a thermal transfer printer, without density unevenness, can obtain a clear image recording from low density to high density, less curl due to heating The inventors have intensively studied an image receiving sheet which has solved or reduced the above-mentioned disadvantages. As a result, as shown in FIG. 1, the front side resin coating layer 2 and the back side resin coating layer 3 are laminated and adhered on the support layer 1 to form the base layer sheet 4, As shown in the figure, an image receiving layer 5 is formed on the front side resin coating layer 2 to obtain a thermal transfer image receiving sheet. Such front and back side resin coating layers are each formed by laminating and laminating a biaxially stretched multilayered polyolefin resin film to a support under tension, each of which contains a polyolefin resin as a main component. is there.

In the method of the present invention, the ratio T _{1 of the} tension (T ₁ ) applied to the resin film for forming the resin coating layer on the front side to the tension (T ₂ ) applied to the resin film for forming the resin coating layer on the back side.
/ T ₂ is 1/2 or less, preferably 1/3 or less. Ratio T ₁ /
When T ₂ is greater than 1/2, of the image-receiving sheet produced from substrate obtained sheet, it is impossible to sufficiently prevent curling occurring during image transfer. This lamination is preferably performed using an adhesive, but may be performed by heat bonding.

Further, it is preferable that the resin film extends 0.1 to 0.5% due to the tension applied to the resin film for the surface side resin coating layer. Further, the resin film for forming the resin coating layer on the front side and the back side may both contain an inorganic pigment, and the support layer has a heat shrinkage according to JIS K-6732 of 0.1% or less at 100 ° C., that is, It is preferable that the image receiving sheet obtained from the base layer sheet has substantially no density unevenness in an image formed thereon and has a wide density range from low density to high density. Thus, a clear image record can be obtained. Furthermore, when the base layer sheet of the present invention is used, during thermal printing or a processing process using a thermal head, etc.,
It is possible to obtain an image receiving sheet for a thermal transfer printer, in which curling is small. Such an image receiving sheet,
When used in a dye sublimation transfer type printer, a color image having a uniform hue and density can be obtained. The sheet-like support used in the method of the present invention has a thickness of 20 to 300 μm, preferably 50 to 300 μm. If the thickness is less than 20 μm, the resulting sheet-like support may have insufficient hardness and rebound (weakness of the stiffness) and may not be sufficiently prevented from curling during image thermal transfer. When the thickness exceeds 300 μm, the thickness of the obtained receiving sheet becomes excessively large, and the volume of the color printer required for mounting the desired number of receiving sheets becomes large, which makes it difficult to make the color printer compact. There are inconveniences.

The sheet-like support used in the method of the present invention may be a sheet substrate composed of a biaxially stretched multi-layer film mainly composed of polyolefin containing an inorganic pigment. Such sheets are known as synthetic papers and are used for applications such as printing, writing, and printers. In order to solve the drawbacks of this synthetic paper, such as weakness and heat shrinkage, it is also known that this sheet is laminated with a film of polyester or the like, a multilayer film, or a synthetic paper / paper / synthetic paper. Have been.

On the other hand, it is also known that the synthetic paper can be used as an image receiving sheet for thermal transfer such as a sublimation transfer system to improve the quality of a transferred image. However, there is a problem that curling is generated due to heat shrinkage during processing or printing at the time of poor heat resistance.

In order to prevent the curl due to the heat shrinkage, a multi-layer laminated image receiving sheet in which a core material such as paper, polyester (PET), film or the like is laminated between synthetic papers is also known.

However, in a thermal transfer type printer, heat is applied to only one surface of an image receiving sheet from a thermal head or the like, and particularly in a sublimation transfer type, a receiving layer for dyeing a sublimation dye image has a heat shrinkable property. In the case where the laminated body is formed of a polyester resin having the above-mentioned property, the occurrence of thermal curl cannot be sufficiently prevented even with the above-described three-layer laminated body.

Therefore, in the method of the present invention, a film having a multilayer structure containing a polyolefin resin as a main component and produced by a biaxial stretching method, that is, a synthetic paper, is laminated and stuck under tension on the front and back sides of the sheet-like support. At this time, the ratio T ₁ / T ₂ of the tension (T ₁ ) applied to the front side film to the tension (T ₂ ) applied to the back side film is set to 1/2 or less, thereby forming the back side The side resin coating layer holds a residual shrinkage stress larger than the residual shrinkage stress of the front side resin coating layer. The residual shrinkage stress on the back side cancels out the heat shrinkage stress generated on the front side of the image receiving sheet during thermal transfer, thereby preventing curling due to the heat shrinkage stress.

The support used in the present invention has a small heat shrinkage, and preferably has a heat shrinkage at 100 ° C. of 0.1 according to JIS K-6734.
% Or less. Examples of such a support include high quality paper, medium quality paper, Japanese paper, thin paper, coated paper (including finely coated paper, lightweight coated paper, art paper, etc.), and non- or non-polyester, polyolefin, and nylon. A low heat shrinkable synthetic resin film or the like can be used. Here, coated paper refers to kaolin, clay,
Pigment such as calcium carbonate, aluminum hydroxide, plastic pigment, etc. and water-soluble adhesive such as starch, and / or coating layer mainly composed of synthetic polymer emulsion adhesive such as styrene and butadiene. is there. Basis weight of the coated paper in the 50~200g / m ^2, the coating weight is 5 to 2
It is preferably about 0 g / m ² .

The resin film used for forming the front and rear resin coating layers of the present invention is preferably a stretched synthetic paper having a multilayer structure of a polyolefin containing a well-known inorganic pigment (for example, calcium carbonate), It is a synthetic paper with a three-layer structure in which a paper-like layer made of a uniaxial or biaxially stretched film is bound to the front and back surfaces of the base material layer, or four or more layers in which a layer other than the paper-like layer and the base material layer exists. Synthetic paper may be used. Further, a film mainly composed of other thermoplastic resins such as polyethylene and polypropylene may be used.

Further, in the method of the present invention, as the adhesive used for bonding the support and the resin coating layer on the front surface and the back surface, a polyether-based adhesive, a polyester-based adhesive, or the like can be used. It is preferred to be selected from high adhesives for dry lamination.

〔Example〕

Next, the receiving sheet for a thermal transfer printer of the present invention will be described with reference to examples.

Example 1 A film having a multilayer structure biaxially stretched with polyolefin (polypropylene) containing an inorganic pigment as a main component (trademark:
Yupo FPG80, thickness 80 μm, manufactured by Oji Yuka Synthetic Paper) is used as a resin film for forming a resin coating layer on the front side and the back side, and these are made of high-quality paper (OK foam paper manufactured by Oji Paper Co., Ltd .; m ² , heat shrinkage rate, 0.1%), a polyester-based adhesive (trade name: S-391)
1, and these three layers were laminated by dry lamination via a Toa Gosei Chemical Industry Co., Ltd.). At that time, a tension of T ₁ = 1.0 kgf and a tension of T ₂ = 3.0 kgf were applied to the front-side film and the back-side film, respectively. The ratio T ₁ / T ₂ = 1/3. A 5 g / m ² image-receiving layer was formed by applying a toluene solution of a polyester resin (Vylon 200, manufactured by Toyobo Co., Ltd.) on the surface-side resin coating layer of the base layer sheet thus obtained, followed by sublimation. An image receiving sheet for a mold transfer printer was manufactured.

The image receiving sheet was subjected to thermal transfer printing using a commercial thermal transfer printer (trademark: CHC-35, manufactured by Shinko Electric Co., Ltd.). The quality of the image of the obtained print and the state of curl were observed, and evaluated according to the following five grades. Further, the image receiving sheet was heated at 120 ° C. for 10 minutes, the occurrence of thermal curl was observed, and this was evaluated on a five-point scale. Class evaluation contents 5 Excellent 4 Good 3 Normal 2 Slightly poor 1 Bad Evaluation results are shown in Table 1.

Further, the image receiving sheet was subjected to a print test by using a commercially available sublimation dye transfer video printer (trade name: VY-50, manufactured by Hitachi, Ltd.). The results were evaluated on a five-point scale in the same manner as above, and the results are shown in Table 2.

Example 2 The same operation as in Example 1 was performed. However, the tension applied to the film for forming the resin coating layer on the front side and the back side was T ₁ = 1.0 kgf T ₂ = 4.0 kgf T ₁ / T ₂ = 1/4.

The test results of the obtained image receiving sheet are shown in Tables 1 and 2.

Example 3 The same operation as in Example 1 was performed. However, the tension applied to the front and back side resin coating layer forming films was as follows.

T ₁ = 1.0 kgf T ₂ = 2.0 kgf T ₁ / T ₂ = 1/2 Test results of the obtained image receiving sheet are shown in Tables 1 and 2.

Example 4 The same operation as in Example 1 was performed. However, a polyethylene terephthalate film having a thickness of 18 μm was used as the support layer. The test results of the obtained image receiving sheet are shown in Tables 1 and 2.

Comparative Example 1 A multi-layered film (trade name: YUPO FPG150, thickness 150 μm, manufactured by Oji Oil Chemicals, Inc.) biaxially stretched with a polyolefin (polypropylene) containing an inorganic pigment (calcium carbonate) as a main component was directly image-received. Used as a sheet. The test results are shown in Tables 1 and 2.

Comparative Example 2 The same operation as in Example 1 was performed. However, T _{1 was set to} T ₂ . The test results of the obtained image receiving sheet are shown in Tables 1 and 2.

[Effect of the Invention] The thermal transfer image receiving sheet of the present invention is excellent in all of the sharpness, gradation, and homogeneity of an image received by the sheet, and generates curl after printing or during heating. Significantly reduces the use of a compact full-color printer for thermal transfer such as a sublimation transfer system, and greatly contributes to the industry.

[Brief description of the drawings]

FIG. 1 is an explanatory cross-sectional view showing a configuration of an embodiment of a base layer sheet for a thermal transfer image receiving sheet according to the present invention, and FIG. 2 is a thermal transfer image receiving sheet obtained using the base layer sheet of the present invention. FIG. 2 is an explanatory cross-sectional view illustrating a configuration of one embodiment. DESCRIPTION OF SYMBOLS 1 ... Support layer, 2 ... Front side resin coating layer, 3 ... Back side resin coating layer, 4 ... Base layer sheet, 5 ... Image receiving layer.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location B29L 9:00

Claims (1)

(57) [Claims] 1. A biaxially stretched multilayer resin film containing a polyolefin resin as a main component and being stretched on the front surface (image receiving layer forming surface side) and the back surface of a sheet-like support having a thickness of 20 to 300 μm. Laminated and adhered under tension, when forming the front side resin coating layer and the back side resin coating layer,
The ratio T ₁ / T ₂ of the tension (T ₁ ) applied to the resin film for forming the front-side resin coating layer to the tension (T ₂ ) applied to the resin film for forming the rear-side resin coating layer is 1/2 or less. A method for producing a base sheet for a thermal transfer image receiving sheet.