JPH04224987A - Thermal transfer printing method - Google Patents

Abstract

PURPOSE:To obtain a high density in multicolor printing by using a thermal transfer printer and make it possible to set density property with single color. CONSTITUTION:A sublimation ink of a transfer film 5 is transferred to a recording paper 6 by a thermal head 1. Then, the thermal head 1 is heated and reheated by a heating quantity with which smoothness becomes optimum so as to smooth the surface of the recording paper 6. Thereafter, a new ink of the transfer film 5 is transferred to the recording paper 6. Thus, after the surface of the recording paper 6 is smoothed, a next ink is transferred, so that a transference of the transferred ink to the transfer film 5 from the recording paper 6 can be prevented and printing with a high density will be possible.

Description

Detailed Description of the Invention [0001] [Industrial Application Field] The present invention relates to a sublimable or meltable transfer film applied to various recording papers (including cards other than paper) such as OHP recording films. Concerning how to print ink. [0002] Conventionally, when printing on transparent recording sheets such as OHP films, X-ray films, and slides, high-density printing is required. There is a thermal transfer printing method. As a method for this purpose, the present applicant previously proposed patent application No. 1-280185.
or Japanese Patent Application No. 1-285172. The former is a method of controlling the density by correcting the width of the heating pulse applied to the thermal head, and the latter is a method that prevents variations in density from occurring when overprinting is performed. [0003] However, when overlapping recording is performed multiple times to perform high-density printing, the heating temperature by the thermal head becomes high and the surface of the recording paper becomes uneven. As a result, the ink holding power becomes weaker, and when the ink to be printed next is heated, the ink that has already been recorded on the recording paper is transferred again from the recording paper to the transfer film, resulting in high-density printing may not be possible. Means for Solving the Problems In order to solve the above-mentioned problems, the present invention is directed to transfer the ink of the transfer film to the recording paper, and then smoothing the surface of the recording paper by reheating or the like. After smoothing the ink, the next ink was transferred to the recording paper. [0005] Since the recording paper is smoothed to reduce its unevenness, the amount of ink retransferred from the recording paper side to the transfer film side is reduced. In this case, if a transparent member is applied as a smoothing treatment, retransfer of ink can be reliably prevented. Embodiments [0006] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a diagram showing the relationship between the recording density and smoothness of recording paper with respect to the amount of heating, Fig. 2 is a schematic illustration of the printing section of a thermal transfer printer applied to the implementation of the present invention, and Fig. 3 is a diagram showing the relationship between the recording paper and the transfer film. FIG. 4 is a schematic explanatory diagram showing another example of the printing section of a thermal transfer printer to which the present invention is applied, and FIG. 5 shows an example of the film used in the printer of FIG. 4. FIG. 6 is an explanatory diagram showing an example of a film used in the printer of FIG. 1, and FIG. 7 is a diagram for explaining the setting of density characteristics in the present invention. First, in the thermal transfer printer shown in FIG.
Thermal heads 1, drive rollers 2, which are recording paper holding bases, feed rollers 3, and take-up rollers 4 are stretched between yellow (Y), magenta (M), cyan (C), and black (Bk). ) is provided with a transfer film 5 (see FIG. 5(b)) coated with each sublimable ink at a predetermined pitch. In this printer, a transfer film 5 and a recording paper 6 are placed between the thermal head 1 and the drive roller 2.
The thermal head 1 is pressurized by sandwiching the two. Thereafter, by energizing the heating resistor of this thermal head 1 to generate heat, the sublimation ink of the transfer film 5 is transferred to the recording paper 6 to perform printing. By the way, the relationship between the recording density and smoothness of recording paper with respect to the amount of heating is shown in FIG. The maximum concentration was approximately 2.0 as measured using a Maxell densitometer (RD-910), and the heating amount of the thermal head at this time was approximately 0.12 watts per heating resistor. Also,
The smoothness is the result of visual inspection using a microscope. As can be seen from this figure, as the amount of heating increases, the smoothness of the recording paper deteriorates, and once recording (single color)
In this case, the density increases as the heating amount increases even if the smoothness deteriorates; however, in the case of multiple recording (overlapping recording, ie, color), if the smoothness deteriorates, the density does not become sufficiently high. This is because, as shown in FIG. 3(a), if the ink receiving layer of the recording paper is smooth, the ink on the recording paper is difficult to transfer to the transfer film ink layer;
), if the ink-receiving layer of the recording paper has irregularities, the ink on the convex parts is likely to transfer to the transfer film ink layer. Therefore, in this embodiment, after the sublimated ink of the transfer film 5 is transferred to the recording paper 6 by the thermal head 1, the thermal head 1 is heated to reheat it at the heating amount that provides the best smoothness as shown in FIG. After smoothing the surface of the recording paper 6, the sublimation ink of the next transfer film 5 is transferred to the recording paper 6. In this way, by smoothing the surface of the recording paper 6 and then transferring the next ink, it is possible to suppress the transferred ink from being transferred from the recording paper 6 side to the transfer film 5 as described above. This enables high-density printing. Next, in the thermal transfer printer shown in FIG. 4, similar to the thermal transfer printer shown in FIG.
, drive roller 2, feed roller 3, and take-up roller 4
A transfer film 5 as shown in FIG. 5(b) was stretched between the thermal head 11, a drive roller 12, a feed roller 13, and a take-up roller 14 in order to perform a smoothing process. A smoothing film 15 as shown in FIG. 5(a) is provided. In this printer, after the thermal head 1 heats the ink of the first color applied to the transfer film 5 and transfers it to the recording paper 6, the recording paper 5 is sent to the position of the thermal head 11. The surface of the recording paper 6 is smoothed by generating heat and heating the recording paper via the smoothing film 15 at the heating amount that provides the best smoothness as shown in FIG. Thereafter, the recording paper 6 is returned to the thermal head 1 side, the next ink is transferred to the transfer film 5, and high-density printing can be achieved by repeating the same process for a plurality of colors. In this case, heating may be performed directly with the thermal head 11, but since the thermal head 11 becomes easily dirty in this case, a smoothing film 15 made of a thin film similar to the transfer film 5 is interposed. There is. Further, as the smoothing film 15, for example, a transparent member made of a resin mixed with a meltable binder is applied, and this is heated by the thermal head 11 to overcoat the ink surface of the recording paper 6 with the transparent member. In this way, transfer of ink from the recording paper 6 side to the transfer film 5 can be more effectively prevented. In addition, when using a smoothing film in a printer equipped with one thermal head as shown in FIG. 1, as shown in FIG. ), cyan (C), and black (Bk) sublimable inks, a transfer film may be used in which a smoothing film or an overcoat film (OP portion) is formed between each of the sublimable inks of cyan (C) and black (Bk). By the way, conventionally, as shown in FIG. 1, if the recording density is set in a straight line with respect to the heating amount of the thermal head when the recording density is monochrome, then in the case of three-color Y, M, and C overlapping,
As shown by the broken line in the figure, the density of the previously printed ink decreases. Therefore, in order to equalize the color balance in the density characteristics shown by the solid line in FIG. 7, the three colors are set to overlap. As a result, as shown by the broken line in the same figure, the density characteristics shift to a darker direction when using a single color, but by applying smoothing processing, if the density characteristics are set to a straight line when using a single color, almost identical density characteristics can be obtained. . Effects of the Invention As explained above, according to the present invention, after the ink of the transfer film is transferred to the recording paper, smoothing treatment such as reheating is performed to reduce the unevenness of the surface of the recording paper. After smoothing, the next ink is transferred to the recording paper, so the amount of ink transferred from the recording paper side to the transfer film side is reduced, and high density can be achieved when printing multiple colors.
Density characteristics can now be set for a single color, making settings easier.

[Brief explanation of the drawing]

[Figure 1] Diagram showing the relationship between the recording density and smoothness of recording paper with respect to the amount of heating

[Fig. 2] A schematic explanatory diagram of a printing section of a thermal transfer printer applied to the implementation of the present invention.

[Figure 3] An explanatory diagram for explaining the transfer of ink from recording paper to transfer film

FIG. 4 is a schematic explanatory diagram showing another example of a printing section of a thermal transfer printer applied to the implementation of the present invention.

[Fig. 5] An explanatory diagram showing an example of a film used in the printer shown in Fig. 4.

[Fig. 6] An explanatory diagram showing an example of a film used in the printer shown in Fig. 2.

[Fig. 7] Diagram for explaining the setting of concentration characteristics in the present invention

[Explanation of symbols]

1, 11... Thermal head, 2, 12... Drive roller, 5
...Transfer film, 6...Recording paper, 15...Smoothing film.

Claims (3)

[Claims] Claim 1: A transfer film coated with sublimable or meltable ink and a recording paper are sandwiched between a thermal head and a substrate for holding recording paper, and then, after pressurizing the thermal head, the heating resistor of the thermal head is removed. In a thermal transfer printing method in which ink applied to the transfer film is transferred to recording paper by generating heat from a body, the surface of the recording paper is smoothed after the ink applied to the transfer film is transferred to the recording paper. A thermal transfer printing method characterized in that the new ink applied to the transfer film is further transferred to the recording paper. 2. The thermal transfer printing method according to claim 1, wherein the smoothing process involves generating heat in a thermal head to reheat the ink transferred to the recording medium. 3. The thermal transfer printing method according to claim 1, wherein the smoothing process is performed by heating and applying a transparent member onto the ink transferred to the recording paper during reheating by a thermal head. .