JP3065844B2 - Color image recording method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a color image 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. Related Background Art As a color image recording method, a color thermal recording method, a color ink jet recording method, a color electrophotographic recording method and the like are known. In recent years, attention has been paid to a color thermal recording method due to miniaturization of the apparatus and simplicity of maintenance. The color thermal recording method includes color thermal recording in which a color image is directly recorded on a thermal recording sheet, and color thermal transfer recording in which the ink of an ink film is transferred to recording paper. The color thermal transfer recording includes a fusion type in which the molten ink is transferred to recording paper, and a sublimation type in which the amount of ink transferred to the recording paper changes according to thermal energy.

For example, in color thermal transfer recording, a recording head having a plurality of recording elements arranged in the main scanning direction is used. One line is printed while moving this in the sub-scanning direction, and then the paper is fed in the main scanning direction. A serial printer of a type that prints the next one line is often used.

[0004]

However, in the above-described serial printer, since the paper feed tends to be uneven, the edges of the rows adjacent to each other in the main scanning direction overlap with each other (the overlap portion). There is a drawback in that the density is increased and streaks are formed in the sub-scanning direction, and conversely, there is a gap between rows, and the recording paper is streaked in the sub-scanning direction.

An object of the present invention is to provide a color image recording method for a serial printer which eliminates streaks and gaps between lines caused by uneven paper feeding.

[0006]

In order to achieve the above-mentioned object, the present invention provides a printing system comprising : M printing elements arranged in a main scanning direction;
Using the recording head, the ink dots recorded in the pixels
When the length in the sub-scanning direction is changed according to the density
It consists of M sub-lines extending in the sub-scanning direction.
Each line is printed on the recording paper with ink dots of multiple colors.
ー Color image of a serial printer that records images sequentially
In the recording method, for at least one color pixel,
For every other pixel in the main scanning direction, the pixels are shifted in the sub-scanning direction by a predetermined pitch, and for the other color pixels, in the main scanning direction, the pixels are shifted in the sub-scanning direction by a predetermined pitch every two pixels, The first eye and the (n + 1) th line are overlapped by M ₁ sub-lines, and the pixels in the M ₁ sub-lines are divided into first and second groups. was printed, it is also to you printing the (n + 1) pixel of the second group during the recording of the line. Also before
The multiple colors are at least yellow, magenta, and cyan.
There are three types.

[0007]

Since adjacent rows are always printed so as to overlap each other by a predetermined width, it is possible to prevent a gap between rows from being opened to form a streak-shaped gap. In the overlap portion, since each row is shared and recorded, there is no possibility that a stripe is formed due to a high density in this portion.
Further, even if the pixels of each color are shifted due to uneven paper feeding, the color is changed while maintaining the complementary color relationship, so that even if the color changes microscopically, the color tone does not change as a whole.

[0008]

FIG. 2 shows a recording state of a fusion type thermal transfer recording. As shown in FIG.
Represents a plurality of, for example, 64 heating elements 10a, 10b,
Are arranged in a line in the main scanning direction, and print 64 sub-lines constituting one row. Each heating element has an elongated rectangle having a length L in the main scanning direction and a length D in the sub-scanning direction. The length L in the main scanning direction is, for example, 125 μm, and the length D in the sub-scanning direction is, for example, 25 μm.

As shown in FIG. 3, the ink ribbon 11 is supplied by a known ribbon cassette 12. The ribbon cassette 12 is mounted behind the thermal head 10, and the ink ribbon 11 is slightly pulled out of the ribbon cassette 12 and passed between the thermal head 10 and the recording paper 13. As is well known, cyan, magenta, and yellow ink areas are formed on the ink ribbon 11 at a constant pitch.

At the time of recording, the ink ribbon 11 is brought into close contact with the recording paper 13 from behind by the thermal head 10, and the ribbon cassette 12 is moved in the sub-scanning direction by the head moving mechanism 14 together with the thermal head 10. The thermal head 10 heats the back of the ink ribbon 11 and transfers the melted or softened ink to the recording paper 13. This ink adheres to the pixel represented virtually, and forms an ink dot. When the recording of one line is completed, the thermal head 10 and the ribbon cassette 12 are returned to the initial positions, and the recording paper 13 is conveyed slightly less than the width of one line in the main scanning direction. Rows are overlapped. Reference numeral 15 denotes a platen roller, and reference numeral 16 denotes a transport roller.

As shown in FIG. 2B, a magenta pixel 17 surrounded by a dashed line has a rectangular shape with one side L and the other side 2L. The length L in the main scanning direction corresponds to the length of the heating element in the main scanning direction, and the length 2L in the sub-scanning direction is determined by the energization state of the heating element. In this embodiment, 1
Each pixel has ten gradations, and one pixel is composed of ten micro lines. For example, in the case of one gradation, one micro line is recorded, and in the case of two gradations, two micro lines are recorded. Pixels adjacent in the main scanning direction have recording positions shifted by a predetermined distance, for example, 2L / 2 (= L) in the sub-scanning direction so that moire and parallel lines do not occur. Each pixel 17 shown in FIG. 2B has an ink dot 18 having an area ratio of 50%, as indicated by hatching.
Is recorded.

FIGS. 2C and 2D show cyan and yellow pixels, respectively. Like the magenta pixel 17, the cyan pixel 19 and the yellow pixel 20 have a length L in the main scanning direction and a length 2 in the sub-scanning direction.
L is determined by the energized state of the heating element. Pixels adjacent in the main scanning direction are grouped every two pixels, and for each of these groups, the recording position is set to a predetermined distance, for example, L in the sub-scanning direction.
It is only shifted. Reference numerals 21 and 22 represent a cyan ink dot and a yellow ink dot having an area ratio of 50%.

FIG. 4 shows a state in which gray with an area ratio of 50% is recorded, in which pixels of respective colors shown in FIG. 2 are superimposed. In an arbitrary first column extending in the main scanning direction, color patterns of black (BK), green (G), magenta (M), and white (W) are periodically generated at a rate of one cycle of four pixels. In the second row adjacent to this, color patterns of white (W), magenta (M), green (G), and black (BK) are generated. The arrangement order of the color patterns in the two adjacent rows is reversed, and the adjacent colors have a complementary color relationship. Hereinafter, the eight pixels shown in FIG. 4 are referred to as complementary color compensation units.

FIG. 5 shows a state in which gray is recorded on the n-th row with an area ratio of 50%. This shows a state in which six sub-lines overlapping the (n + 1) -th line to be recorded next are recorded at 50% of the compensation unit of the complementary color, that is, only three of the six colors excluding W are recorded. This overlap part OVL
In the example, the color pattern of only BK appears in the first column, the color patterns of M and G appear in the second column, and these are repeated.

FIG. 6 shows that the area ratio of the (n + 1) th row is 50%.
Shows a state in which the gray of the image is recorded. The six sub-lines overlapping the previous n-th row are the compensation units 50 of the complementary color.
%, That is, a state in which only three of the six colors excluding W are recorded. In this state, the M and G color patterns appear in the first column, the BK only color pattern appears in the second column,
These are repeated. Reference numeral 10 'indicates a thermal head on which the n-th row is recorded.

When both the n-th row and the (n + 1) -th row are recorded, the overlap portion OVL is recorded in the same pattern and the same density as the non-overlapping row, as shown in FIG. . Here, the paper feed is uneven,
For example, when the n-th line and the (n + 1) -th line are shifted in the main scanning direction, the BK and W color patterns appear as shown in FIG. Becomes gray and the overall color tone remains unchanged. Also, n
Even when the row and the (n + 1) th row are shifted in the sub-scanning direction,
As shown in FIG. 8, BK and W color patterns appear, which also become gray when viewed macroscopically.

FIG. 3 shows a fusion-type thermal transfer recording apparatus embodying the present invention. The green image data is converted into magenta print data by a look-up table memory (hereinafter referred to as LUT) 25. The LUT 25 outputs print data delayed by ピ ッ チ pitch between pixels adjacent in the main scanning direction. This print data is
The signal form is such that the length of the ink dot is changed in the range of D to 2L. Also, the overlap portion OV
In the print data forming L, two pixels are grouped in the main scanning direction so as to be 50% of the compensation unit of the complementary color, and the data is thinned out every other group and output. This print data is sent to the thermal head 10 via the contact point a of the selector SW2. Note that only the first recorded line and the last recorded line have the overlap portion OVL only on the lower side or only on the upper side.
The print data is created so that a portion where VL does not occur is recorded as usual without skipping.

The red image data and the blue image data are
It is selectively taken out by the selector SW1, and the LUT2
Sent to 6. The LUT 26 is grouped every two pixels in the main scanning direction.
Print data delayed by two pitches in the sub-scanning direction is output. In addition, this print data indicates that the length of the ink dot is D
The signal form is such that it is changed in the range of ２2L. The print data forming the overlap portion OVL is thinned out every other pixel in the main scanning direction and output. The selector SW2 is connected to one of the two LUTs 25 and 26, and transfers print data to the thermal head 10.
Send to

Next, the recording procedure of the fusion type thermal transfer recording apparatus will be described with reference to FIG. During recording, the platen roller 15 and the transport roller 16 rotate in the direction of the arrow to
The leading end of the recording area 3 is fed to the position of the thermal head 10. Thermal head 10 and ribbon cassette 1
2 is moved to the initial position at the left end in the sub-scanning direction, the ink ribbon 11 is fed, and the start end of the magenta ink area is set below the thermal head 10.

The green image data is converted into magenta print data by the LUT 25 and sent to the thermal head 10 via the contact a of the selector SW2. The thermal head 10 is driven in accordance with the print data, and the thermal head 10 heats and presses the ink ribbon 11 from behind while the thermal head 10 and the ribbon cassette 12 move rightward in the sub-scanning direction to melt the ink ribbon 11. Apply the ink to recording paper 13
Transfer to Thereby, as shown in FIG. 2B, the length in the sub-scanning direction changes according to the recording density, and
The zigzag ink dots in the main scanning direction are assigned to pixel 1
Record in 7. In a portion overlapping with the next row, two pixels are thinned out every two pixels in the main scanning direction and recorded.

When the thermal head 10 moves to the right end of the recording area and one line of the magenta image is recorded on the recording paper 12, the heating and pressurizing of the ink ribbon 11 are stopped, and the thermal head 10 and the ribbon cassette 12 are stopped. Is moved to the left in the sub-scanning direction. During this movement, the platen roller 1
5 rotates and the recording paper 13 is conveyed, and the next line is conveyed to the position of the thermal head 10. This transport amount is 64
The row length L ₀ (= 6) of the heating elements 10a, 10b,.
4L) is less by 6L, and adjacent rows overlap by this amount. Hereinafter, this operation is repeated, and the entire magenta image is recorded on the recording paper 13.

When the recording of the magenta image is completed, the platen roller 15 and the transport roller 16 are rotated in the reverse direction, and the starting end of the recording paper 12 returns to the recording start position. Further, a cyan ink area is set on the ink ribbon 11. The red image data is sent to the LUT2 via the contact a of the selector SW1.
In step 6, the data is converted into cyan print data. This print data is transferred to the thermal head 1 via the contact b of the selector SW2.
0, and as shown in FIG.
Recorded sequentially line by line. In the case of this cyan image,
As in the case of recording a magenta image, paper is fed so that adjacent lines overlap by 6 L, and in the overlap portion OVL, data is recorded by thinning out every other pixel in the main scanning direction. You.

In recording a yellow image, a yellow ink area is set on the thermal head 10 and
The selector SW1 is connected to the contact b, and the blue image data is converted into yellow print data by the LUT 26. This yellow print data is supplied to the thermal head 10 via the contact b of the selector SW2, and the yellow image is line by line so that adjacent lines overlap by 6L, similarly to the recording of the cyan image. It is recorded on recording paper 12.

When the recording of all three colors is completed, the platen roller 15 and the conveying roller 16 are continuously rotated in the direction of the arrow, and the recording paper 13 is discharged. Overlap part OVL
Is finished to the same hue and density as the non-overlapping part, and a high quality print without streaks in the sub-scanning direction can be obtained.

In the embodiment described above, at the time of recording the overlap portion OVL, 50% of the compensation unit of the complementary color, that is, only three pixels are recorded for six pixels excluding W. FIG.
In the embodiment shown in FIG. 0, the overlap portion OVL is divided into three lines, and the closer to the end the line, the lower the recording area ratio. In this embodiment, one for six pixels, three for six pixels, and five for six pixels are recorded from a line near the end. Although each of the above embodiments is a fusion type thermal transfer recording, the present invention can be applied to a sublimation type thermal transfer recording, a thermal recording, an ink jet recording, and the like.

[0026]

As described above, according to the present invention,
Adjacent lines are overlapped and printed, and the print of this overlap part is shared by the upper line and the lower line, so that the line gap is open and a streak-like gap is created, It is possible to prevent the overlap portion from having a high density to form a streak. Further, even if pixels of each color are shifted in the overlapped portion due to uneven paper feeding, the color is changed while maintaining the complementary color relationship, so that a print having a good color tone can be obtained macroscopically.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a state in which an n-th line and an (n + 1) -th line are overlapped and recorded in gray with an area ratio of 50%.

FIG. 2 is an explanatory diagram illustrating a recording state of each pixel of yellow, magenta, and cyan.

FIG. 3 is a schematic view showing a fusion-type thermal transfer recording apparatus embodying the present invention.

FIG. 4 is an explanatory diagram showing a color pattern when gray having an area ratio of 50% is recorded.

FIG. 5 is an explanatory diagram showing a state where an n-th row is recorded in gray with an area ratio of 50%.

FIG. 6 is an explanatory diagram showing a state where the (n + 1) -th row is recorded in gray with an area ratio of 50%.

FIG. 7 is an explanatory diagram illustrating a color pattern when a registration shift occurs in the main scanning direction.

FIG. 8 is an explanatory diagram illustrating a color pattern when a registration shift occurs in the sub-scanning direction.

FIG. 9 is a flowchart showing a procedure of thermal recording.

FIG. 10 is an explanatory diagram showing another example of a recording method of an overlap portion.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Thermal head 10a, 10b ... Heating element 11 Ink ribbon 12 Ribbon cassette 13 Recording paper 17, 19, 20 Pixel 18, 21, 22 Ink dot OVL Overlap part

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) B41J 2/325 B41J 2/355-2/36

Claims (2)

(57) [Claims] [Claim 1] using a recording head having an array of M number of recording elements in the main scanning direction, a control system which changes according to the concentration of the length in the sub-scanning direction of the ink dots recorded in the pixel, the sub-scanning direction In a color image recording method of a serial printer for sequentially recording a color image on recording paper with ink dots of a plurality of colors in each row composed of the extended M sub-lines, at least one color pixel is provided in a main scanning direction. To shift the pixel by a predetermined pitch in the sub-scanning direction every other pixel,
For color pixels, the main with shifted in the sub-scanning direction by a predetermined pitch in every two pixels in the scanning direction, n-th row and (n + 1) and row by overlapping only _one sub-line M, M ₁ The pixels in the sub-lines are divided into first and second groups, and the pixels in the first group are printed when printing n rows, and the pixels in the second group are printed when printing (n + 1) rows. A color image recording method, comprising: 2. The method according to claim 1, wherein the plurality of colors are at least yellow,
3. The method according to claim 1, wherein the three types are zenta and cyan.
2. The color image recording method according to item 1.