JPS59229971A - Color thermal transfer recording method - Google Patents

Abstract

PURPOSE:To decrease the consumption of an ink sheet and to realize low-cost printing by performing gradational recording while dividing each gradation representation picture element in a subscanning direction, and using an ink sheet which has the same hue but different in density level. CONSTITUTION:The product of pitch P1 in a main scanning direction and pitch P2 in the subscanning direction is size representing the gradation, and a fine slit- shaped picture element 4 of P1XP2/3 is formed on a thermal transfer medium as normal paper in single-time thermal transfer recording operation. The picture element 24 is formed at P2/3 pitch on an ink sheet with density D0 while shifting in print position in the subscanning direction to obtain a density pattern having one - three gradations. Then, the same density pattern with one - three gradations is formed on an ink sheet with density D1 over the 3rd gradation on the ink sheet with the density D0, obtaining a pattern with four - six gradations. Consequently, gradational picture elements which have seven-gradation representation including the backgroup of a recording medium is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a color thermal transfer recording method used in a color or monochromatic recording device capable of expressing gradation on a pixel-by-pixel basis.

FIG. 1 shows the basic configuration of conventional ink thermal transfer recording.

Here, (1) is a base film such as capacitor paper, (
2) is a solid ink layer consisting of a wax or organic resin binder and a coloring material, and the ink sheet (3) is made up of both. Ink sheet [31 pace paper + 11 side has thermal head (5) All solid ink layer (2) side has plain paper (4) and rubber roller (7
) wo are each arranged. “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) k of the ink sheet (3), and the melted portion (2a ) is transferred onto the plain paper (4).The heating resistor (
6) If either the applied power (W/dot) or the pulse width is changed, the amount of the solid ink layer (2a) to be 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 (μml'
The relationship between applied power and optical reflection density (OD) during recording with a thermal head for high-speed facsimile was measured. The figure also shows the range of variation in data measured at 10 different locations. Note that the heating current pulse width was 2 m5ec.

From the results shown in FIG. 2, it can be seen that when recording at all intermediate densities using the conventional INKSY I-, the variation in OD is extremely large. For this reason, an ink sheet that performs bath-melting transfer has the disadvantage that it is not possible to stably record a type of gradation image that changes the density of pixels.

Figure 8(a) shows that the conventional pixel itself has eight density levels (
This figure shows the structure of an ink sheet that can have 8 values (hereinafter referred to as 8 values). Here, (1) is a base film, on which a high melting point black solid ink layer (8) is completely coated, and then a low melting point gray solid ink layer (9) is coated for 8-value recording. An ink sheet (10) is constructed.

Examples of pixel densities realized by this 8-value recording ink sheet [101] are shown in Figures (b) and (c), respectively. Here, FIG. 8(b) shows the gray solid ink layer (9).
The figure shows a state in which only a portion of the image is thermally transferred onto plain paper (4). This is achieved by selecting the heating temperature by the thermal head at a temperature that melts the gray solid ink layer (9) but does not melt the black solid ink layer (8). 8th
Figure (C) shows a state in which both the black solid ink layer (8) and the gray solid ink/M+91 have been melted and transferred.

This is achieved by heating the thermal head to a temperature at which both the black solid ink layer (8) and the gray solid ink layer (9) melt. As a result, this ink sheet can realize the two densities shown in FIG. 8(b) and FIG. 8(C) and the eight-value pixel density when nothing is transferred. In principle, with this method, it is possible to create ink sheets with 8 or more values by applying multiple layers of solid ink layers with different melting points onto the paste film +1j, but in reality, it is possible to create ink sheets with 8 or more values. In reality, 8-value is the limit for this type of ink sheet because the image fixability is poor and the thermal head has limited durability at high temperatures.

In addition, fluctuations in the heating temperature of the heating element due to environmental temperature or repeated printing may increase instability, such as pixels that should be gray turning black, and because two layers of solid ink are overcoated, the ink sheet may become unstable. The drawback is that it is difficult to manufacture. In addition, in this method, the number of ink layers applied to the ink sheet is equal to the number of density levels N of the pixel itself that can be realized, and when attempting to perform multi-value recording, the recording time increases in proportion to the number of multi-value values. It also has the disadvantage of being long.

This invention was made in order to eliminate the drawbacks of the above-mentioned conventional methods, and is a method of performing gradation recording by dividing and recording one gradation expression pixel in the sub-scanning direction, and with the same color tone. The present invention relates to a color thermal transfer recording method that further increases gradation expressiveness by using ink sheets with different density levels.

FIG. 4 shows the basic configuration of a thermal head Q5) used in the color thermal transfer recording method of the present invention. Note that for convenience of explanation, all parts not directly related to the explanation of the method are omitted here. Here, (n) represents an insulating substrate made of ceramic or the like, and (12) represents a slit-shaped heating resistor whose width is narrower in the sub-scanning direction than in the main-scanning direction. From one side of the slit-shaped heating resistor (14) are individual electrodes (1, 9
However, a common electrode is taken out from the other side. The width of the slit-shaped heating resistor H in the sub-scanning direction is varied by VC4 to an extent that a slit-shaped minute pixel of 1/n (n>2) of the pixel pitch P1 in the sub-scanning direction is formed. Figure 4 shows n
=8 is shown as an example. In the following explanation, unless otherwise specified, only the case where rl-=3 will be explained.

FIG. 5 shows the basic structure of a color ink sheet t231 used in the color thermal transfer recording method of the present invention.

Here, (16) is polyestes, capacitor paper, etc. σ)
Base film shown. On the base film θ6), there is a first yellow layer (171) and a second yellow layer (172).
, first magenta layer (181), second magenta layer (18
2), first cyan layer (191), second cyan layer (19)
2), a first black layer (201), and a second black layer (202) are applied in sequence. Further, a reference mark υ for detecting the reference position and a color order mark 4 for color sequential counting are provided. The color ink sheet of the present invention is coated with a plurality of ink layers of the same color but different densities for at least one of the colors. Here are some examples: Take a po.

Between, D+ = (1,1~2.5)・D,
Both densities are selected so that the relationship f1+ holds.

Generally, a color ink sheet coated with k types (k≧2) of ink layers with different densities is used, and the kth density D
The density D of the ink layer of the 1st@th ink layer (k-1
) 1 Dk = (1,1~2,5)・D(k-1)
(It is better to make sure that the relationship ``1'' holds true.

FIG. 6 shows an embodiment of the gradation expression method according to the present invention. In this example, (main scanning direction pitch P,) x (sub scanning direction pitch 2 - P,) is the pixel (hereinafter referred to as gradation pixel) f size expressing the gradation, and the thermal head shown in Fig. 4 05
) with one thermal transfer recording operation, PBX%”
Slit-shaped minute pixels are formed on a thermal transfer recording medium such as plain paper.

By shifting the print position in the sub-scanning direction and forming these micropixels every three pitches using an ink sheet with a density of Pa, a density pattern of 1 to 8 gradations as shown in FIG. 6 is obtained. Next, using an ink sheet with a density of D+, a density pattern that is the same as the 1st to 3rd gradations is formed on the 8th gradation pattern of the Do ink sheet to obtain a pattern of 4th to 6th gradations,
It is possible to form gradation pixels having the expressive power of seven gradations including zero (background of the recording medium). In this example, pixels in the two states of combination Do and po + D are used, and if an ink sheet with the density of the ridge is used by general ICN division printing, a combination of +11 gradation micropixels will be obtained. The gradation expressive power of (n x k+ 1 f3) is obtained.

In addition, D,, D, and D-+D+ are combinations of 8 states, and a combination of minute pixels with 2 gradations, nX
A gradation expressive power of (2 to -1)+1 f41 can be obtained.

In the above explanation, the ink layer of each color has the same type of density, but the density type and the degree difference can be selected in many ways, and only for at least one color. As long as two or more types of ink layers having density differences are formed and a gradation pixel is obtained by combining minute pixels that are recorded separately in the sub-scanning direction, the combination is not limited to a specific one.

In addition, here we have explained the gradation expressive power of the pixel body, but it is also possible to simulate the gradation expressive power by configuring a matrix of gradation pixels such as the conventionally known multi-value dither method or multi-value a degree pattern method. Of course, it is also possible to use a method of increasing the number of pixels in combination, and many changes are possible in the arrangement of the gradation pixels (b), which are minute pixels.

Further, the shape of the heating resistor of the thermal head used in the present invention may be one in which the long axis of the slit-shaped heating resistor forms an angle with the main scanning direction in the range of 0° to 45°.

As detailed above, using thermal transfer recording, which could only record binary states using conventional methods, n-divided recording enables recording of a maximum of nX (2"1) + 11 gradation multi-value states. Halftone recording can be performed using only a small number of ink sheets, and this has the effect of enabling low-cost printing by reducing the amount of ink sheets used.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the basic configuration of conventional ink thermal transfer recording.
Fig. 2 is a diagram showing the relationship between applied power and optical reflection density in conventional ink thermal transfer recording, Fig. 8 is a structural diagram of a conventional ink sheet designed to be able to express eight dark/reverse levels in the pixel itself, FIG. 4 is a diagram showing the basic configuration of a thermal head used in the color thermal transfer recording method of the present invention, and FIG.
This figure shows the basic structure of a color ink sheet (b) used in the color thermal transfer recording method of the present invention, and FIG. 6 is a diagram showing an embodiment of the gradation expression method according to the method of the present invention. In the figure, (2) is an ink layer, (3) is an ink layer, (5105) is a thermal head. Agent Masuo Oiwa Figure 1 Figure 2 Figure 1. θ ----- 0θl 02 θ3 ri4
t7f O, d'' Rudder force (WA, sword) No. 314 (b) (C) Fig. 4-Fig.

Claims (1)

[Claims] A row of a plurality of heat generating resistors is provided on an insulating substrate at a pitch ps in the main scanning direction, and the long axis of the heat generating resistors is arranged at an angle of 0 to 456 degrees from the main scanning direction. A thermally transferable ink layer was applied to the formed thermal head on the base film at a density level of 70% lower than the saturation density of the final recorded image (k>1) including Do or D. The base film side of the ink sheet is pressed against the ink layer side of the ink sheet, and micropixels consisting of slit-shaped thermally transferred images of the ink layer are formed on the transfer medium that is pressed against the ink layer side of the ink sheet by energizing the heating resistor. Using a device that forms gradation images by combining pixels,
If the pip P in the sub-scanning direction of a gradation pixel, which is a unit pixel consisting of a collection of minute pixels expressing a gradation, is approximately Pg/n pitch per movement of the ink sheet and transfer medium in the sub-scanning direction, Recording of minute pixels having an area of p IX p m/H is performed, and the first
After the process of obtaining pixels using an ink sheet with a density level of
A color thermal transfer recording method that obtains a color image consisting of a single color or a combination of predetermined colors having gradation by obtaining gradation pixels consisting of a combination of minute pixels of gradation.