JPH06270442A - Heat recording method of color - Google Patents

Abstract

PURPOSE:To make an interlinear gap or stripe inconspicuous, by a method wherein parts where colors each are piled upon each other are shifted so that the parts do not become coincident with each other and at the parts where the same colors are piled upon each other, recording is performed so that the more it goes to the end, the lower a gradation level becomes. CONSTITUTION:One line comprised, for example, of 128 pieces of sublines is recorded by one time scanning of a thermal head 10. After one yellow line is recorded, recording paper is conveyed by amount, for example, of seven pieces of sublines and one magenta line is recorded. Then the recording paper is conveyed by amount of seven pieces of the sublines and one cyanogen line is recorded. Then the recording paper is conveyed by amount of 111 [128-(3+7X2)] pieces of sublines and recording is performed so that the sublines are piled upon the previous line by three lines. Thereby, an overlapped part OLY1 is formed. Overlapped parts OLM1, OLC1 are formed by piling up sublines of every color by three colors each, which are recorded under a state wherein they are separated four sublines by four sublines from each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a color thermal recording method for a serial printer in which a thermal head moves in a sub scanning direction and a recording paper moves in a main scanning direction.

[0002]

2. Description of the Related Art Thermal recording methods include thermal recording in which an image is directly recorded on a thermal recording paper and thermal transfer recording in which ink of an ink film is transferred onto the recording paper. This thermal transfer recording is classified into a melting type in which a melted ink is transferred to a recording paper and a sublimation type in which the amount of the ink transferred to the recording paper changes according to thermal energy. For thermal transfer recording, in order to reduce the size and weight of the apparatus, a recording head in which a plurality of recording elements are arranged in the main scanning direction is used, and while moving this in the sub scanning direction, one line consisting of a plurality of sub lines is formed. A serial printer of the type in which after printing, the paper is fed in the main scanning direction to print the next line is often used.

However, in a serial printer, unevenness in paper feeding is likely to occur, so that the edges of adjacent rows in the main scanning direction overlap each other, the density of that portion increases, and streaks occur in the sub scanning direction. On the contrary, there is a defect that a gap is formed between the lines and the background of the recording paper appears in a stripe shape in the sub-scanning direction. As a method for improving this, for example, JP-A-63-2
As described in Japanese Patent No. 76565, it is known that the end of the nth row and the end of the (n + 1) th row are overlapped by one dot for each color, and the overlapping portion is slightly shifted depending on the color.

Further, in Japanese Laid-Open Patent Publication No. 3-146363, in order to prevent the recording density at both ends of the thermal head from being lowered due to the thermal storage phenomenon of the thermal head, the ends of each line are overlapped and recorded by 7 dots. A thermal recording method is described in which a density gradient is provided so that the recording density of this portion becomes zero toward the end of the thermal head.

[0005]

In the former thermal recording method described in the above publication, the overlapping width for each color is as small as 1 dot, but since these are adjacent to each other, the density is thin but the stripes are wide. Then, after all, it stands out.
Further, in the latter case, since three colors overlap in the same portion, when the overlapping width is 7 dots or more, the increased dot portion becomes a dark streak.

The present invention is intended to solve the above problems, and an object of the present invention is to provide a color thermal recording method for a serial printer in which gaps and lines between lines are inconspicuous.

[0007]

In order to achieve the above object, in the color thermal recording method of the present invention, lines of the same color are recorded with their edges overlapping each other, and the overlapping portions of each color are The shift is made so that they do not coincide with each other, and in the overlapping portion of the same color, the gradation level is recorded so as to decrease toward the edge.

[0008]

Since lines of the same color are recorded with their edges overlapping each other, there is no gap between the lines. Further, since the overlapped portions are separated for each color and the gradation level of the portions is recorded so as to be lowered toward the edge, the overlapped portions are not conspicuous.

[0009]

2 shows a serial printer to which the thermal recording method of the present invention is applied, the thermal head 10 is reciprocated in the horizontal direction (sub-scanning direction (S)) by a head moving mechanism 11, and the recording paper 12 is a platen. The roller 13 and the conveying roller 14 convey the recording position in the vertical direction (main scanning direction (M)). The ink ribbon 15 for melt heat transfer is supplied by a well-known ribbon cassette 16. The ribbon cassette 16 is mounted behind the thermal head 10,
The ink ribbon 15 is slightly pulled out from the ribbon cassette 16 and passed between the thermal head 10 and the recording paper 12. As is well known, yellow, magenta, and cyan ink areas are formed on the ink ribbon 15 at a constant pitch. The pulse motor 17 is controlled by the driver 18 and drives the platen roller 13 and the transport roller 14. Reference numeral 19 is a head drive unit that drives the thermal head 10, and reference numeral 20 is a head moving mechanism 1.
1, a controller that controls the driver 18 and the head drive unit 19.

During recording, the ink ribbon 15 is brought into close contact with the recording paper 12 from behind by the thermal head 10, and the ribbon cassette 16 is moved together with the thermal head 10 in the sub-scanning direction by the head moving mechanism 11. The thermal head 10 heats the back of the ink ribbon 15 and transfers the melted or softened ink to the recording paper 12. This ink adheres to the virtually represented pixel to form an ink dot. When the recording of one line is completed, the thermal head 10 and the ribbon cassette 16 are returned to the initial positions, and the ink ribbon 15 is sent to set the ink area of the next color at the recording position. When the three-color frame sequential recording is completed, the recording paper 12 is conveyed.

In FIG. 1, the thermal head 10 includes:
A plurality of, for example, 128 heating elements 10a, 10b, 10
are arranged along the main scanning direction. One row of 128 sub-lines is printed by one scanning of the thermal head 10. After recording one line of yellow, the recording paper 12 is conveyed by, for example, seven sub lines, and one line of magenta is recorded. Next, the recording paper 12 is conveyed by the amount of seven sub lines to record one line of cyan. After this, the recording paper 12 is moved to the sub line 111 (128- (3 + 7
X2)) Convey only the number of lines and record so as to overlap the previous line by three sublines. As a result, the overlap portion OL _Y1 as shown in the figure is formed. Thereafter, by repeating this, three sublines for each color are overlapped to form the overlap portions OL _M1 and OL _C1 , and these are recorded in a state of being separated by four sublines.

In this embodiment, as shown in FIG.
The pixel 21a in the non-overlap portion has 64 gradations,
As shown in (B), the pixel 21b in the overlapping portion has 16 gradations. The reason why the overlapping part has 16 gradations is that the number of pixels to be overlapped is 2 or more, preferably 2 to 5, and the gradation level is lowered toward the edge of the row within this range. This is because even if the number of gradations is increased, the number of gradations is not sufficiently reflected as gradation expression. In this embodiment, since the number of pixels to be overlapped is three, 16 gradations are sufficient for the overlapping portion, but 32 gradations or more may be used.

The pixel 21a in the non-overlap portion has 64 pixels.
Are virtually divided into individual micro areas 22a, 22b, ... When the thermal head 10 is conveyed by one pixel (for example, 160 μm) in the sub-scanning direction, each micro area 22a corresponds to a gradation level. , 22b, ..., Ink dots are recorded. FIG. 3A is an example in which the gradation level is “6”. The pixel 21b in the overlap portion is
Virtually divided into 16 micro areas 23a to 23p, and each micro area 23 is divided according to the gradation level of the image.
Ink dots are recorded on a to 23p. FIG. 3 (B) shows
This is an example in which the gradation level is “2” in 16 gradations.

FIGS. 4A and 4B show n in the same color.
The lower edge of the row and the upper edge of the (n + 1) th row are shown,
FIG. 6C shows a state in which they are superposed. The lower edge and the upper edge of each row are arranged so that the gradation level becomes lower toward the edge of the row and the recording positions are opposite to each other. As a result, as shown in FIG. 4C, the recording area ratio becomes 50% (the gradation level is “8”) in the overlapping portion OL, similarly to the non-overlapping portion OL. Further, according to such a recording method, even if the paper feed amount fluctuates to some extent to cause misregistration, the overlap portion OL
There is an advantage that there is little change in concentration.

The gradation level D _n (X) of the nth row and the gradation level D of the (n + 1) th row of the overlap part OL.
_{The n + 1} (X) is calculated by using the following equations (1) and (2), respectively, and is obtained by truncating the decimal point of each calculated value. D _n (X) = (1/16) · K _n (X) · D _X +0.5 (1) D _{n + 1} (X) = (1/16) · K _{n + 1} (X) D _X +0.49 (2) However, X: a number indicating the position of the sub-line in the overlap portion K _n (X): a coefficient K _n indicating the distribution of the gradation level of the nth row in the overlap portion ₊₁ (X): Coefficient indicating the distribution of the gradation level of the (n + 1) th row in the overlap portion D _X / 16: Recording area ratio The result calculated based on these equations (1) and (2) is 5
And the gradation levels D _n (X), D _{n + 1}
(X) becomes 6, 4, and 2 as it goes to each edge.

In FIG. 6 showing an example of the head drive section 19, blue, green, and red image data are stored in lookup table memories (hereinafter referred to as LUTs) 31, 32, and 33.
Are converted into yellow, magenta, and cyan image data, and then written in the Y frame memory 34, the M frame memory 35, and the C frame memory 36, respectively.

As shown in FIGS. 1 and 7, the data width of the yellow image initially read from the Y frame memory 34 is set to 114 (128-7 × 2) sublines. The controller 20 reads out the image data on the 114 sub lines from the Y frame memory 34 for each column and writes the image data in the line memory 37. The image data for one column written in the line memory 37 is transferred to the OL converter 41 and then sent to the LUT 44.

The OL converter 41 converts the gradation levels of the pixels on each of the three sub-lines that are overlapped with the preceding and following rows based on the above equations (1) and (2). L
The UT 44 generates drive data for recording a dot pattern by the area gradation method, and ink dots on the right side (see FIG. 4B) for pixels on three sublines that overlap with the previous row. Is generated, and drive data is generated so that ink dots are recorded on the left side (see FIG. 4A) for the three sub-lines overlapping the next row. For pixels on sub-lines that are not overlapped, drive data is generated so as to record at the original gradation level and with ink dots depending on the left side.

The drive data generated from the LUT 44 is
It is transferred to the thermal head 10 via the contact a of the selector SW. The recording of the first line of the yellow image is performed by 114 excluding the upper 14 elements of the heating element array. Reading of the second and subsequent rows of the yellow image is performed column by column.

Similarly, for the magenta and cyan image data, the line memories 38 and 39 and the OL converters 42 and 4 are also used.
3, the respective drive data are transferred to the thermal head 10 via the LUTs 45, 46 and the contacts b, c of the selector SW. The data width of the magenta image read from the M frame memory 35 on the first line is subline 121.
The data width is set to (128-7) lines, and the second and subsequent rows are read one column at a time, and the data width read at the time of recording the last line is set to 121 sublines. Further, from the C frame memory 36, the cyan image is read column by column from the time of recording the first row, and the data width read at the time of recording the last row is 114 sublines.

When recording the 121 sub-lines of the first row of the magenta image, the 12 sub-lines below the heating element array are recorded.
One is used, and when recording 121 sub-lines of the last row, the upper 121 of the heating element row is used. Further, when printing the last 114 sub-lines of the cyan image, the 114 upper heating element rows are used.

A recording procedure of the serial printer thus configured will be described. During recording, platen roller 1
3, the transport roller 14 rotates in the direction of the arrow, and the recording paper 12
Is fed to the position of the thermal head 10. Thermal head 10 and ribbon cassette 16
Is moved to the initial position at the left end in the sub-scanning direction, the ink ribbon 15 is fed, and the start end of the yellow ink area is set below the thermal head 10.

The image data of the pixels belonging to the first row is read from the frame memory 34 for each column, and the OL conversion unit 4
1, converted into drive data by the LUT 44. Selector S
W is set at the contact a, and the driving data of the yellow image in the first column is transferred to the thermal head 10. The driving data drives 114 lower heater elements, and the thermal head 10 heats and presses the ink ribbon 15 from behind. The melted yellow ink is the recording paper 12
And the first row of yellow images on the 114 sub-lines is recorded on the recording paper 12. The second row is recorded while moving the thermal head 10 and the ribbon cassette 16 in the sub-scanning direction during or after the recording of the first row.

When the thermal head 10 moves to the right end of the recording area, heating / pressurization of the ink ribbon 15 is stopped, and the thermal head 10 and the ribbon cassette 16 are moved to the left in the sub scanning direction. During this movement, the platen roller 13 and the transport roller 14 are rotated by the pulse motor 17, the recording paper 12 is transported by the amount of seven sublines, and the ink ribbon 15 is fed so that the start end of the magenta ink area is the thermal head. Set under 10.

Then, the selector SW is set to the contact b. The magenta image data of the first row is read from the frame memory 35 for each column, converted into drive data, and then sent to the thermal head 10. The drive data drives the lower 121 heating element rows, and the sub-line 121
The magenta images for the number of lines are recorded on the recording paper 12 for each column.
As a result, as shown in FIG. 7, the upper end of the previously recorded yellow and the upper end of this magenta are recorded so as to coincide with each other. Next, the thermal head 10 and the ribbon cassette 16
While the recording paper 12 is returned to the initial position,
The ink ribbon 15 is conveyed by this amount, the ink ribbon 15 is fed, and the starting end of the cyan ink area is set below the thermal head 10.

The selector SW is set at the contact c. The cyan image data in the first row is stored in the frame memory 36 for each column.
Is read out, converted into drive data, and then sent to the thermal head 10. One of the heating element rows is generated by this drive data.
All 28 are driven and one row of cyan image is recorded on the recording paper 12 for each column. As a result, as shown in FIG. 7, the upper end of the first line of the previously recorded yellow and magenta and the upper end of the first line of cyan are recorded in coincidence. In addition,
Reference numeral K indicates a recording area.

Further, the thermal head 10 and the ribbon cover
While the set 16 is returned to the initial position, the recording paper 12 is supported.
Only 111 brines are transported. Ink ribbon 15
Is fed and the yellow ink area is in the thermal head 1.
It is set below 0 and one row of yellow image is recorded for each column.
To be done. As shown in FIG. 1, this yellow line is
Yellow line and 3 sub-lines overlap and over
Lap part OL_Y1Is formed. This overlap part O
L_Y1Now, as shown in Figure 4, the edge of each yellow row
The lower the gradation level
And is it recorded at a different position in the pixel?
And complement each other, non-overlapping part OL ₀Same gradation as
Is reproduced.

Similarly, each image of magenta and cyan is recorded one line at a time, and as shown in FIG.
L _M1 and OL _C1 are formed at intervals of four sub lines. Then, after 108 non-overlap portions, overlap portions OL _Y2 , OL _M2 , and OL _C2 are formed at intervals of four sub-lines. These steps are repeated thereafter, and the last yellow image, magenta image, and cyan image have 128 sublines (1 line) and 12 sublines, respectively.
It is recorded on 1 sub-line and 114 sub-lines. When the recording of all three colors is completed, the platen roller 13 and the transport roller 14 are continuously rotated in the arrow direction, and the recording paper 12 is ejected.

In the embodiment described above, the number of superposed pixels is 3 and the interval is 4 pixels, but the present invention is not limited to these numerical values. In addition, there are three types of colors for color recording: yellow, magenta, and cyan.
Although the color is used, the present invention is not limited to this, and for example, black may be added to this to provide four colors. In addition, although the above-mentioned embodiment is the melting type thermal transfer recording, the present invention can be applied to the sublimation type thermal transfer recording, the heat sensitive recording, the ink jet recording and the like.

[0030]

As described above, according to the color thermal recording method of the present invention, lines of the same color are overlapped with each other at their edges, and the overlapping parts are shifted so that they do not coincide with each other. Since the gradation level is recorded so as to be lowered toward the edge of the line, the gap between the lines and the overlapped portion are prevented from becoming conspicuous, and a high-quality color image can be recorded.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a recording state by a color thermal recording method of the present invention.

FIG. 2 is a schematic diagram showing a serial printer embodying the present invention.

FIG. 3 is an explanatory diagram showing a difference in gradation number between a non-overlap portion and an overlap portion.

FIG. 4 is an explanatory diagram showing a recording state of an overlap portion.

FIG. 5 is an explanatory diagram showing a relationship between an overlap portion recorded in gray with a recording area ratio of 50%, a gradation level of each sub-line forming the overlap portion, and distribution thereof.

FIG. 6 is a block diagram showing a configuration of a head drive unit.

FIG. 7 is an explanatory diagram showing a recording state of each color.

[Explanation of symbols]

10 Thermal Heads 10a, 10b, ... Heating Element 12 Recording Paper 15 Ink Ribbon 19 Head Drive Units OL, OL _Y1 , OL _M1 , OL _C1 , OL _Y2 , OL _M2 , OL
_C2 overlap section

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location B41J 3/20 115 D 9305-2C 117 A

Claims (1)

[Claims] 1. A recording head in which a plurality of heating elements are arranged in the main scanning direction is used, and the recording head is moved in the sub scanning direction to record one line consisting of a plurality of sub lines, and at the same time a main recording paper is used. In a color thermal recording method of a serial printer that moves a predetermined width in the scanning direction and records a color image on recording paper with ink dots of the number N of colors, lines of the same color are recorded with their edges overlapping each other. A color heat recording method, wherein the overlapping portions of the respective colors are shifted so that they do not coincide with each other, and in the overlapping portions of the same color, the gradation level is lowered toward the edge.