JPS638672B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for recording images having monochrome or color gradations using ink thermal transfer recording.

FIG. 1 shows the basic configuration of conventional ink thermal transfer recording. Here, 1 is a base paper such as capacitor paper, 2 is a solid ink layer made of wax or an organic resin binder, and a coloring material, and the ink sheet 3 is constituted by both of them. A thermal head 5 is installed on the base paper 1 side of the ink sheet 3.
A plain paper 4 and a rubber roller 7 are arranged on the solid ink layer 2 side.

Now, when the heating resistor 6 of the thermal head 5 is energized to generate heat, the solid ink layer 2 is heated and melted through the base paper 1 of the ink sheet 3, and the fused portion 2a is transferred onto the plain paper 4. If either the power (W/dot) or the pulse width applied to the heating resistor 6 is changed, the amount of the solid ink layer 2a melted and transferred changes in principle, and it appears that gradation recording is possible.

In Figure 2, the size of the heating resistor is 80 x 200 (μm) ²
The relationship between applied power and optical reflection density OD was measured by recording with a thermal head for high-speed facsimile. In the figure, 10 measurements were taken at different locations.
The range of variation in the data for these locations is also shown.
Note that the heating current pulse width was 2 msec.

From the results shown in Figure 2, it can be seen that when medium densities are recorded using conventional ink sheets, the variation in OD is extremely large. For this reason, an ink sheet that performs melt transfer has the disadvantage that it is not possible to stably record a type of gradation image that changes the density of pixels.

FIG. 3 shows a basic principle diagram for explaining a conventional example in which the above-mentioned drawbacks have been improved. Here 1 is 5
A base paper such as an organic resin film, capacitor paper, glassine paper, etc. with a thickness of ~30 μm, and a solid ink layer 8 having thermal transferability at a low density of approximately 1/n (n≧2) of the desired final image density is formed thereon. It is formed. Now, the case where n=4 will be explained here. A thermal head 5 is placed on the base paper 1 side of the low density ink sheet 9 coated with such a low density solid ink layer 8, and a plain paper 4 is placed on the other side.

Here, the gradation image is recorded as follows. Move the low-density ink sheet 9 and the plain paper 4 in the direction of the solid arrow to remove the first transfer ink layer 8A.
is thermally transferred at the position of the thermal head 5. next,
The plain paper 4 is pulled back in the direction of the dotted arrow to thermally transfer the second transfer ink layer 8B. Thereafter, in the same manner, the third and fourth transfer ink layers 8c and 8D are thermally transferred to complete the recording operation. In this example, the coating density of the low-density solid ink layer 8 is selected to be OD=0.4 so that a maximum saturation density of 1.6 can be obtained in four coats.

Figure 4 shows the number of thermal transfers P obtained using the improved method.
This shows the relationship with OD, 0.4, 0.8, 1.2,
A total of five gradations, 1.6 and white, are recorded.
In the method of the present invention, the low-density solid ink layer 8 is completely transferred from the low-density ink sheet 9 to the low-density solid ink layer 8 each time each layer is formed, and there is no need to control the transfer at an intermediate amount as in the conventional method. It has the advantage of being able to print with extremely stable recording densities and good reproducibility.

The present invention further increases the number of gradations in the conventional method without deteriorating the resolution.

FIG. 5 is a basic principle diagram for explaining the gradation image recording method of the present invention. As shown in the figure, one pixel is represented by a pixel composed of an N×M (N, M≧2) dot matrix, and the number of printed dots that are pixel existing in this dot matrix and/or the printed A predetermined gradation image is recorded by changing the number of times and creating k pixel clusters (k≧2) locally within the dot matrix.
In this example, M=N=4, number of prints P=1,
It has a total of 16 gradations of expressive power. Further, the local pixel cluster k=2. The numbers in parentheses below the dot matrix indicate the gradation number. The method of expressing gradation using this dot matrix is
This has the advantage that gradation can be expressed in a pseudo manner even when using a recording means that cannot change the pixel density itself.

FIG. 6 is an example of a pixel arrangement when the color thermal transfer recording method according to the present invention is applied to an apparatus that can only record the three colors of yellow, magenta, and cyan in binary format.

In the figure, a indicates the pixel arrangement in yellow Y, b indicates cyan C, and c indicates magenta M multi-tone image recording. As shown in the figure, the arrangement of each pixel is characterized in that the order in which the pixel appears is changed for each color of yellow Y, cyan C, and magenta M. The arrangement when the three colors Y, C, and M arranged as shown in a to c are printed in an overlapping manner is shown in d. Note that e is 3 of Y, C, and M.
This is an example of the pixel arrangement of overlapping printing when the appearance order of colors is the same, and as can be seen from the comparison of d and e, the number of pixels in the low density area when expressing the same gradation is d is larger, so there is less deterioration in resolution, and when applied when images and text information are recorded on the same screen, smooth images and clear text can be output. have an effect.

In this example, the number of pixel blocks is k=2, M, N
= 4.

Further, in the above embodiment, a method of expressing gradations by one transfer was shown, but by performing transfer multiple times, more gradations can be expressed.

Furthermore, although the embodiments have been shown in terms of a combination of Y, C, and M, the combination of each color may be orange, green, blue, etc., and is not particularly limited.

Further, the ink material is not limited to a wax type ink material, but may also be one using an organic resin binder. or,
The coloring material may be either a pigment or a dye.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the basic configuration of conventional ink thermal transfer recording, Figure 2 is a diagram showing the relationship between applied power and optical reflection density OD in conventional ink thermal transfer recording, and Figure 3 is the basic principle of the recording method of the present invention. 4 is a diagram showing the relationship between the number of thermal transfers and OD obtained with the configuration of FIG. 3, FIG. 5 is a diagram showing one method for increasing the gradation expressive power of this invention, and FIG. FIG. 3 is a diagram illustrating an example in which the method is expanded and applied to color image recording. 1...Base paper, 2...Solid ink layer, 2a...
Melt-transferred solid ink layer, 3... Ink sheet, 4... Plain paper, 5... Thermal head, 6... Heating resistor, 7... Rubber roller, 8... Low concentration solid ink layer, 8A to 8D... First layer to fourth layer. Transfer ink layer, 9...Low density ink sheet, the same reference numerals in the figures indicate the same or equivalent products.

Claims (1)

[Claims] 1. An ink sheet in which a heat-melting or heat-sublimating ink material is coated on a base film;
a recording paper placed in contact with the ink sheet, and a position on the ink sheet corresponding to a predetermined pixel position of the recording paper is heated to thermally transfer the ink on the ink sheet to the recording paper to create a recorded image. In this method, one pixel expressing a gradation on recording paper is composed of a plurality of pixels arranged in a line or matrix, and a recording pattern of the pixel matrix is determined corresponding to each gradation, and A color thermal transfer recording method characterized by having k (k≧2) local pixel clusters in a recording pattern. 2. The invention according to claim 1, characterized in that the appearance order of pixels of each color in pixels arranged in a line or matrix is made different for at least two or more colors. Color thermal transfer recording method. 3. A patent claim characterized in that the highest value of optical reflection density of an image formed on recording paper is achieved by n times (n≧1) transfers, and gradation is expressed by m times (≧n) transfers. The color thermal transfer recording method according to item 1 or 2.