JP2991374B2 - Thermal transfer method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a thermal transfer method and an image receiving sheet for thermal transfer.
More specifically, it is an object of the present invention to provide a thermal transfer method and a thermal transfer image receiving sheet which can easily provide three or four color images excellent in registration.

(Conventional technology and its problems) Conventionally, a thermal transfer system has been widely used as a simple printing system. This thermal transfer method is roughly classified into a wax type and a sublimation transfer type.

The wax type is provided with a wax ink layer that is softened by heat on a base sheet such as polyester film,
This is a method in which an image is formed by transferring the ink layer to a material to be transferred by heating from the back side with a thermal head.

On the other hand, in the sublimation transfer type, instead of the wax ink layer, a paint that sublimates by heat is carried by a binder, and similarly heated from the back with a thermal head to sublimate only the dye in the dye layer and transfer This is a method of forming an image on a material.

Either of the above methods can form a mono-color image and a full-color image. In particular, in the case of a full-color image, three or four color thermal transfer sheets of yellow, magenta, and cyan (and black) are sequentially polymerized on the surface of one transfer material, that is, the image receiving sheet, and thermal transfer is performed from the back of the thermal transfer sheet each time. In this method, printing is performed by a head, colors are synthesized on an image receiving sheet, and the colors of the document are reproduced.

As a method of superimposing a three-color or four-color heat transfer sheet on an image receiving sheet, a method of fixing the image receiving sheet and sequentially moving and stacking the heat transfer sheets of each color, or a method of fixing the heat transfer sheet of each color and moving the image receiving sheet Although the former method is used, the former method is effective in terms of simplicity of the apparatus.

In any of the methods, it is important that the image receiving sheet and the thermal transfer sheet are accurately superimposed each time, and even if the superimposition position is slightly deviated, the transfer position of each color is disturbed and it becomes difficult to form a desired color image.

Such alignment (registration) can be easily solved mechanically by a technique such as offset printing because the printing press may be very expensive, but in the case of the thermal transfer method, simplicity is strongly required for the printer. It was difficult to solve the problem mechanically.

In particular, the thermal transfer method requires the use of a relatively flexible sheet having good transportability as an image receiving sheet.
Registration is particularly difficult. Of course, the above problem can be solved to some extent by using a relatively hard image receiving sheet. However, in this case, the transportability of the image receiving sheet is deteriorated, and the image receiving sheet becomes thicker by that amount, which is disadvantageous in cost. A surface arises.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a thermal transfer method capable of providing a beautiful full-color image in register even when a relatively soft and thin image-receiving sheet is used, and an image-receiving sheet used for the method.

(Means for Solving the Problems) The above object has been achieved by the present invention described below.

That is, the present invention relates to a thermal transfer method in which a thermal transfer sheet of three or four colors is sequentially polymerized on the surface of a single image receiving sheet, and each time, a thermal image is heated from the back of the thermal transfer sheet by a thermal head to form a color image. A thermal transfer method characterized in that a biaxially stretched plastic film or synthetic paper is used as the image receiving sheet, and the supply direction of the image receiving sheet is made to coincide with the direction in which the stretch ratio of the image receiving sheet is high.

(Function) As a thermal transfer type image receiving sheet, a plastic film or synthetic paper which has been subjected to a biaxial stretching process is used, and is supplied to a printer in a direction in which the stretching ratio is high, so that the image receiving sheet is thin and lightweight. However, it is possible to form a full-color image in register with good transportability in the printer and no misregistration.

Particularly, in an image receiving sheet made of a biaxially stretched plastic film or synthetic paper, the thickness is 60 to 250 μm,
Further, those having a stiffness of at least 30 in at least one stretching direction are most suitable for the purpose of the present invention.

(Preferred Embodiment) Next, the present invention will be described in more detail with reference to preferred embodiments.

The thermal transfer system itself in the present invention may be any of the above-mentioned wax type and sublimation type, and any conventionally known thermal transfer sheets and printers can be used as they are without particular limitation, but a particularly preferred system is a three-color or four-color thermal transfer sheet. (Of course, the thermal transfer sheet is fixed in a roll form, and the thermal transfer sheet is sequentially supplied by rewinding), and the image receiving sheet is conveyed to the thermal transfer sheet at each color, where it is superimposed on the thermal transfer sheet and each color is sequentially polymerized. This is a method in which a full-color image is formed by being transferred onto the image receiving sheet surface, and the image receiving sheet is supplied in a single-wafer manner like a B plate and an A plate.

The present invention is characterized by an image receiving sheet used in the above-described general thermal transfer system and a method of feeding the image receiving sheet to a printer.

The image receiving sheet used in the present invention is a polyester film such as polyethylene terephthalate, a polyolefin film such as polypropylene, a polyhalogenated vinyl film such as polyvinyl chloride, a cellulosic film such as cellulose acetate, a polystyrene film and the like. Various synthetic papers made of the above materials can be used, and biaxially stretched films and synthetic papers are particularly suitable.

Biaxially stretched films and synthetic papers are stretched in the machine direction and in the transverse direction during or after the formation of the film or the synthetic paper, and the stretch ratio in the machine direction is generally larger than the stretch ratio in the transverse direction. Has become.

Such a biaxially stretched film or synthetic paper generally has a large stretching ratio in the longitudinal direction, and thus has a greater rigidity in the longitudinal direction than in the lateral direction.

Conventionally, when the above-mentioned film or synthetic paper is used as a thermal transfer sheet in a sheet-fed type, the cutting direction is set so that the direction in which the paper is fed to the printer is the same as the horizontal stretching direction. The transfer and thermal transfer sheets were misaligned during polymerization.

The present inventor, even if the same film or synthetic paper, when used in a sheet-fed type, by matching the longitudinal stretching direction, that is, the direction of high rigidity, with the paper feeding direction of the printer,
It has been found that the registration becomes good and an excellent full-color image can be obtained.

According to a detailed study of the present inventors, in order for these films and synthetic papers to be optimally adapted to the thermal transfer method,
It is necessary that the thickness be 60 to 250 μm, and
乃至 150 μm was found to be optimal. If the thickness is less than the above range, even if the paper feeding direction matches the longitudinal stretching direction, the rigidity is insufficient and registration is out of order.On the other hand, if the thickness exceeds the above range, sufficient rigidity is obtained, It is not preferable in terms of cost.

Further, the rigidity of the image receiving sheet capable of sufficiently registering in the thermal transfer system is 30 or more, preferably 40 or more.
If the stiffness is less than 30, it becomes difficult to convey and study. This stiffness is not necessary for both the vertical and horizontal directions.If either one has a stiffness of 30 or more, even if the stiffness is less than 30 in the other direction, the direction with the higher stiffness is By matching, the object of the present invention is achieved.

Various types of plastic films and synthetic paper satisfying the above conditions can be obtained from the market.
Specifically, it is supplied by Oji Yuka Co., Ltd. under the Yupo trade name.

FPG # 80 (80 μm thick, 41 in the vertical direction, 2 in the horizontal direction)
2), FPG # 95 (thickness 95μm, longitudinal rigidity 60, lateral rigidity 3)
2), FPG # 110 (thickness 110μm, vertical stiffness 76, horizontal stiffness 3)
9), FPG # 130 (Thickness 130μm, vertical stiffness 108, horizontal stiffness 5
1), FPG # 150 (Thickness 150μm, vertical stiffness 149, horizontal stiffness 7
0), FPG # 200 (thickness 200μm, vertical stiffness 260, horizontal stiffness 13
0), SGG # 80 (thickness 80μm, longitudinal rigidity 40, lateral rigidity 2)
4), SGG # 110 (thickness 110μm, vertical stiffness 85, horizontal stiffness 3
9), TPG # 90 (thickness 90μm, vertical stiffness 47, horizontal stiffness 3
7), KPG # 80 (thickness 80 μm, longitudinal stiffness 30, lateral stiffness 22). The stiffness referred to in the present invention is JIS P
This is the value measured by -8143.

The image receiving sheet of the present invention as described above may, of course, contain a filler such as a white pigment, or may have been subjected to any surface treatment as long as the above conditions are satisfied. Further, when these image receiving sheets are used in a sublimation type thermal transfer system, a paint receiving layer can be provided on the surface thereof as required.

(Effects) According to the present invention as described above, a biaxially stretched plastic film or synthetic paper is used as an image receiving sheet of a thermal transfer system, and the image is supplied to a printer in a direction in which the stretching ratio is high. Even if the image receiving sheet is thin and lightweight, it is possible to form a registerable full-color image with good transportability in the printer and no displacement.

Particularly, in an image receiving sheet made of a biaxially stretched plastic film or synthetic paper, the thickness is 60 to 250 μm,
Further, those having a stiffness of at least 30 in at least one stretching direction are most suitable for the purpose of the present invention.

Next, the present invention will be described more specifically with reference to examples.
In the description, parts or% are based on weight.

Examples 1 to 10 As the image receiving sheet, the following synthetic paper was cut into the size of A4 size, and the direction of high rigidity was set to the vertical direction, and the image receiving sheet of the present invention was obtained.

Example 1 FPG # 80 (thickness: 80 μm, vertical stiffness: 41, horizontal stiffness: 2
2), Example 2 FPG # 95 (thickness 95 μm, vertical stiffness 60, horizontal stiffness 3
2), Example 3 FPG # 110 (thickness 110 μm, vertical stiffness 76, horizontal stiffness 3
9), Example 4 FPG # 130 (thickness 130 μm, vertical stiffness 108, horizontal stiffness 5
1), Example 5 FPG # 150 (thickness 150 μm, stiffness 149 in the vertical direction, stiffness 7 in the horizontal direction)
0), Example 6 FPG # 200 (thickness: 200 μm, vertical stiffness: 260, horizontal stiffness: 13)
0), Example 7 SGG # 80 (80 μm thick, 40 stiffness in the vertical direction, 2 stiffness in the horizontal direction)
4), Example 8 SGG # 110 (thickness 110 μm, vertical stiffness 85, horizontal stiffness 3
9), Example 9 TPG # 90 (thickness 90 μm, vertical stiffness 47, horizontal stiffness 3
7), Example 10 KPG # 80 (80 μm thick, vertical stiffness 30, horizontal stiffness 2)
2), using the image receiving sheet of the present invention as a material to be transferred, using Fantasia (manufactured by Toshiba) as a printer, and using a wax type of four colors of yellow, magenta, cyan and black as a thermal transfer sheet; And heated at a thermal head output of 1 mJ / dot, a pulse width of 0.4 mm / sec., And a dot density of 3 dots / mm to form a full-color image.

Comparative Examples 1 to 3 The following synthetic paper was cut into an A4 size as an image receiving sheet, and the direction having lower rigidity was defined as the vertical direction.

Comparative Example 1 FPG # 80 (80 μm thick, 41 stiffness in the vertical direction, 2 stiffness in the horizontal direction)
2), Comparative Example 2 SGG # 60 (thickness 60 μm, vertical stiffness 26, horizontal stiffness 1
4), Comparative Example 3 TPG # 60 (thickness: 60 μm, vertical stiffness: 15, horizontal stiffness: 1)
2) Using the image receiving sheet, sheet feeding was performed in the direction of low rigidity, and a full-color image was formed in the same manner as in the example.

Example 11 Using synthetic paper FPG # 95 (thickness: 95 μm, vertical stiffness: 60, horizontal stiffness: 32), a coating liquid having the following composition was applied to one surface of the coated paper at a rate of 10.0 g / m ² when dried. It was applied, dried at 100 ° C. for 30 minutes, cut into A4 plates, and the direction having high rigidity was set as the longitudinal direction to obtain an image receiving sheet of the present invention.

Polyester resin (Vylon200, manufactured by Toyobo) 11.5 parts Vinyl chloride-vinyl acrylate copolymer (VYHH, manufactured by UCC) 5.0 parts Amino-modified silicone (KF-393, manufactured by Shin-Etsu Chemical Co., Ltd.)
1.2 parts Epoxy-modified silicone (X-22-343, manufactured by Shin-Etsu Chemical Co., Ltd.) 1.2 parts Methyl ethyl ketone / toluene / cyclohexanone (weight ratio 4: 4: 2) 102.0 parts The above image-receiving sheet is fed vertically to a printer, and yellow, magenta . Using a cyan and black sublimation type thermal transfer sheet, recording was performed from the back surface of the thermal transfer sheet with a thermal head under the conditions of a head applied voltage of 10 V and a printing time of 4.0 msec. To obtain a full-color image.

Comparative Example 4 A dye receiving layer was formed in the same manner as in Example 11 except that synthetic paper FPG # 80 (thickness: 80 μm, longitudinal stiffness: 41, transverse stiffness: 22) was used. The image receiving sheet of the comparative example was taken as the vertical direction.

Using the image receiving sheet, a full-color image was formed in the same manner as in the example.

When the dot shift, resolution, and color reproducibility of each color of the full-color images of the above Examples and Comparative Examples were visually evaluated, the results shown in Table 1 below were obtained.

The evaluation criteria are as follows.

Dot displacement: The displacement of the four color dots in each color matching area is 0 mm
The following were rated as ○, and those exceeding 0.5 mm were rated as x.

Resolution: も の indicates that the black dot pattern and the fine character pattern were sufficiently expressed, and × indicates that it was not.

Color reproducibility: も の indicates that the superimposed color pattern faithfully reproduced the color of the original pattern, and x indicates that it did not.

Claims (1)

(57) [Claims] 1. A thermal transfer method in which a thermal transfer sheet of three or four colors is sequentially superimposed on the surface of a single image receiving sheet, and each time, a thermal image is heated from the back side of the thermal transfer sheet by a thermal head to form a color image. A thermal transfer method, wherein a biaxially stretched plastic film or synthetic paper is used as the image receiving sheet, and a supply direction of the image receiving sheet is made to coincide with a direction in which the stretching ratio of the image receiving sheet is high.