JPH05155057A - Color image recording method - Google Patents

Abstract

PURPOSE:To prevent the change of a hue even when misregistration is generated. CONSTITUTION:A pixel 15 of magenta has length L in a sub-scanning direction and the pixels adjacent to each other in a main scanning directions are shifted by a 1/2 pitch in the sub-scanning direction. Each of pixels 17, 18 of cyan and yellow has length 2L in the sub-scanning direction and the pixels adjacent to each other in the main scanning direction are shifted by a 1/2 pitch in the subscanning direction. When misregistration is generated, the color patterns arranged in the sub-scanning direction change but, since complement relation is held between adjacent color patterns, colors change microscopically but set off macroscopically to generate no hue change.

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 expressing a halftone by changing the length of ink dots in the sub-scanning direction.

[0002]

2. Description of the Related 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. Recently, attention has been paid to a color heat recording method because of the miniaturization of the apparatus and the ease of maintenance. This 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 ink of an ink film is transferred to a recording paper. In the color thermal transfer recording, there are a melt 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.

A color image recording method has been proposed in which a recording head in which a plurality of recording elements are arranged in the main scanning direction is used to express gradation by changing the length of an ink dot in the sub scanning direction in a rectangular pixel. (For example, Japanese Patent Application No. 2-15
886). However, this color image recording method has the following problems. That is, since the ink dots are lines extending in the main scanning direction, color moire is likely to occur. In addition, the pixel size is extremely small (for example, 125
(× 125 μm), and since the recording paper is recorded while moving in the sub-scanning direction, the pixels of each color do not match in the sub-scanning direction, and there is often a slight misalignment. When this pixel position shift (registration shift) occurs, the color tone of the color image changes, resulting in a color different from the original image, or color unevenness occurs.

In order to eliminate the color tone change and the like due to the color moiré and the registration shift, the present applicant changes the length in the sub-scanning direction of pixels between cyan and magenta, which are easily noticeable, and In the recording of No. 2, a recording method has been proposed in which the position of a pixel is shifted by ½ of the length of the pixel in the sub-scanning direction between adjacent pixels in the main scanning direction (for example, Japanese Patent Application No. Hei 2-163726). ).

[0005]

However, in the above-described color image recording method, when a misregistration occurs,
Since the same color pattern is periodically generated between two adjacent columns extending in the sub-scanning direction, color tone change and color unevenness due to misregistration are not significantly improved depending on the content of the original image, and the image quality is improved. It will deteriorate.

It is an object of the present invention to provide a color image recording method which prevents deterioration of image quality due to misregistration.

[0007]

In order to achieve the above object, according to the present invention, a pixel of two colors of yellow, cyan and magenta has a length in the sub-scanning direction twice as long as a pixel of the remaining one color. In addition, for each color, between adjacent pixels in the main scanning direction, the pixel position is shifted in the sub scanning direction by ½ of the length of the pixel in the sub scanning direction.

[0008]

EXAMPLE FIG. 1 shows a recording state of fusion type thermal transfer recording. As shown in (A), the thermal head 10
, A plurality of heating elements 10a, 10b, 10c, ... Are arranged in a line in the main scanning direction. Each heating element has an elongated rectangular shape 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, 1
25 μm, and the length D in the sub-scanning direction is, for example, 3
It is 0 μm.

As shown in FIG. 4, the recording paper 12 and the ink film 13 are moved in the sub-scanning direction relative to the thermal head 10 in a state of being in close contact with each other. Thermal head 10
Heats the back of the ink film 13 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.

As shown in FIG. 1B, the magenta pixel 15 surrounded by a dotted line has a square shape with one side of L.
The length L in the main scanning direction corresponds to the length of the heating element in the main scanning direction, and the length in the sub scanning direction is determined by the energization state of the heating element. Pixels adjacent in the main scanning direction have their recording positions displaced by L / 2 in the sub scanning direction so that moire and parallel lines do not occur. Ink dots 16 having an area ratio of 50% are recorded on each pixel 15, as indicated by hatching.

FIGS. 1C and 1D show cyan and yellow pixels, respectively. Cyan pixel 17
The length of each of the magenta pixels 18 in the main scanning direction is L and the length in the sub scanning direction is 2L. Even for these colors, half of the pixels between adjacent pixels in the main scanning direction
Bitch is being shifted. Incidentally, reference numerals 19 and 20
Represents a cyan ink dot and a yellow ink dot.

When L is 125 μm, magenta (M)
The pixel density is 8 dots / pixel in both the main and sub scanning directions.
mm. On the other hand, the pixel densities of cyan (C) and yellow (Y) are 8 dots / mm in the main scanning direction and 4 dots / mm in the sub scanning direction. Therefore, the pixel density in the sub-scanning direction is 1/2 of magenta for cyan and yellow.

On the other hand, since the number of gradations can be increased as the length of the pixel in the sub-scanning direction becomes longer, the number of gradations of magenta is less than half that of yellow and cyan. When the number of gradations is reduced, yellow has the least effect on image quality.
It is possible to express a halftone image such as a photographic image as long as there are gradations. Therefore, the method described in claim 2 is the best.

FIG. 2 shows a state in which gray with an area ratio of 50% is recorded, which is a superposition of pixels of each color shown in FIG. Black (K), green (G), magenta (M), white (W) in any first row extending in the sub-scanning direction.
Color pattern occurs periodically. In the second row adjacent to this, white (W), magenta (M), green (G), black (K)
Color pattern occurs. The two adjacent columns have the reverse color pattern arrangement order, and the adjacent colors have a complementary color relationship.

FIG. 3A shows a state in which the registration shift occurs in yellow and the pixels are shifted upward by 1/4 pitch. In this state, Y, K, G, C,
A color pattern of M, W appears, and B, W,
Color patterns of M, R, G and K appear. These two color patterns also maintain the relationship of complementary colors. For example, in the first row, K in the first column decreases and Y appears, and W in the second column
Decreases and B appears. Since Y and B have a complementary color relationship, they are gray when viewed macroscopically. The same applies to the colors of the other rows.

As described above, when the registration deviation occurs in yellow, the color changes microscopically. However, the human eye does not identify small individual ink dots,
A color is identified from a group of ink dots. Therefore, although the color changes microscopically, since it changes while maintaining the complementary color relationship, the color tone does not change as a whole,
Also, the uneven color is not noticeable.

FIG. 3B shows a state in which cyan is shifted downward by ½ bit of the pixel. When this cyan registration shift occurs, the color pattern changes, but since the complementary color relationship is still maintained, the color tone does not change as a whole. (C) shows a state in which magenta is shifted up by 1/2 bit and yellow is shifted up by 1/4 pitch. Even if this misregistration occurs, the color tone does not change.

FIG. 4 shows a fusion type thermal transfer recording apparatus embodying the present invention. The green image data is converted into magenta print data in the look-up table memory 25. The lookup table memory 25 outputs print data delayed by 1/2 pitch between adjacent pixels in the main scanning direction. Also, this print data is
The signal form is such that the ink dot length is changed in the range of D to L. This print data is the selector S
It is sent to the thermal head 10 via the contact a of W2.

The red image data and the blue image data are
It is selectively taken out by the selector SW1 and sent to the look-up table memory 26. The lookup table memory 26 outputs print data delayed by 1/2 pitch between adjacent pixels in the main scanning direction.
In addition, this print data has the ink dot length of D to 2
The signal form is such that it changes in the range of L. The selector SW2 has two look-up table memories 2
It is connected to either one of 5 and 26 and sends the print data to the thermistor 10.

The thermal head 10 is arranged with an array of heating elements extending in the axial direction of the platen drum 27. The recording paper 12 is mounted on the outer periphery of the platen drum 27, and rotates by a constant bitch in the sub-scanning direction indicated by the arrow. An ink film 13 is arranged between the recording paper 12 and the thermal head 10 and moves in the sub scanning direction together with the recording paper 12 while being guided by the guide rollers 28 and 29. As is well known, cyan, magenta, and yellow ink areas are formed on the ink film 13 at a constant pitch.

FIG. 5 shows a recording procedure. During recording, the platen drum 27 rotates in the sub-scanning direction indicated by the arrow while holding the recording paper 12. With this,
The ink film 13 is fed in the direction of the arrow, 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 in the look-up table memory 26, and the selector SW
It is sent to the thermal head 10 via the second contact point b. The thermal head 10 is driven according to the print data, heats and pressurizes the ink film 13 from behind, and transfers the melted ink to the recording paper 12. As a result, as shown in FIG. 1C, the length in the sub-scanning direction changes according to the recording density, and ink dots that are zigzag in the main scanning direction are recorded in the pixels 17. With the rotation of the platen drum 27, magenta images are recorded on the recording paper 12 line by line.

When the platen drum 27 makes one rotation, the start end of the recording paper 12 returns to the recording start position, and the cyan ink area is set in the ink film 13. The red image data is converted into cyan print data in the look-up table memory 26 via the contact a of the selector SW1. This print data is sent to the thermal head 10 via the contact b of the selector SW2, and a cyan image is recorded line by line as shown in FIG.

In recording a yellow image, the selector SW1
Is connected to the contact b, and the blue image data is converted into yellow print data in the look-up table memory 26. The yellow print data is supplied to the thermal head 10 via the contact b of the selector SW2, and the yellow image is recorded on the recording paper 12 line by line. In the recording of the yellow image, the yellow ink area is set on the thermal head 10.

As is apparent from the above description, the main scanning direction is the array direction of the heating elements, and the sub scanning direction is the direction orthogonal to this. The present invention can also be applied to a serial printer that relatively moves in two dimensions. In this serial printer, the thermal head moves in the sub scanning direction and the recording paper moves in the main scanning direction. .. Further, a black ink area may be provided on the ink film to record a color image with four colors.

Although the above-mentioned embodiment is the fusion 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, the electrophotographic recording and the like.

[0026]

As described above in detail, according to the present invention, the three primary colors are shifted in the sub-scanning direction by about 1/2 bit so that the pixels are not aligned in the main scanning direction.
For one of the primary colors, the pixel density in the sub-scanning direction is halved, so that even if misregistration occurs, the color patterns in two adjacent columns maintain the complementary color relationship. Therefore, according to the present invention, the color tone does not change as a whole and the color unevenness is not noticeable, so that it is possible to prevent the image quality from being deteriorated due to the registration shift.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a recording state of each pixel of yellow, magenta, and cyan.

FIG. 2 is an explanatory diagram showing a color pattern when recording a gray area ratio of 50%.

FIG. 3 is an explanatory diagram showing a color pattern when misregistration occurs.

FIG. 4 is a schematic view showing a fusion type thermal transfer recording apparatus for carrying out the present invention.

FIG. 5 is a flowchart showing a procedure of thermal recording.

[Explanation of symbols]

 10 Thermal Heads 10a, 10b ... Heating Element 12 Recording Paper 13 Ink Film 15, 17, 18 Pixels 16, 19, 20 Ink Dots

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location 8907-2C B41J 3/20 117 C

Claims (3)

[Claims] 1. A recording head in which a plurality of recording elements are arranged in the main scanning direction is used to change the length of an ink dot recorded in a pixel in the sub scanning direction according to the density, and at least yellow, magenta, In a color image recording method of recording a color image on a recording paper with three types of ink dots of cyan, the yellow and cyan pixels have a length in the sub-scanning direction double that of magenta pixels, and all colors are A pixel adjacent to each other in the main scanning direction is shifted by ½ of the length of the pixel in the sub scanning direction in the same direction in the sub scanning direction. 2. A recording head in which a plurality of recording elements are arranged in the main scanning direction is used to change the length of an ink dot recorded in a pixel in the sub scanning direction according to the density, and at least yellow, magenta, In a color image recording method of recording a color image on a recording paper with three types of ink dots of cyan, the cyan and magenta pixels have a length in the sub-scanning direction twice that of a yellow pixel, and all colors are A pixel adjacent to each other in the main scanning direction is shifted by ½ of the length of the pixel in the sub scanning direction in the same direction in the sub scanning direction. 3. A recording head in which a plurality of recording elements are arranged in the main scanning direction is used to change the length of an ink dot recorded in a pixel in the sub scanning direction according to the density, and at least yellow, magenta, In a color image recording method of recording a color image on a recording paper with three types of ink dots of cyan, the yellow and magenta pixels have a length in the sub-scanning direction that is twice that of the cyan pixel, and all colors are A pixel adjacent to each other in the main scanning direction is shifted by ½ of the length of the pixel in the sub scanning direction in the same direction in the sub scanning direction.