JPH0622106A - Ink jet recording method - Google Patents

Abstract

PURPOSE:To improve the picture quality by using plural thinned-out patterns in complementary relation of arrangement with each other in the unit of picture element groups and applying main scanning to them for plural number of times so as to record the picture thereby eliminating unevenness due to time difference and unevenness due to color mixture. CONSTITUTION:Separately thinned-out patterns 3001-3004 in the unit of dot groups of prescribed picture elements are formed. Then cartridges are arranged to a carriage so that black, C, M and Y ink sets are overlapped in this order in the forward motion and the ink sets in the opposite order are overlapped in the return motion. A 1st region is printed out according to the pattern 3001 by using Y, C nozzles in a 1st scanning in the forward motion of the carriage and ink is jetted in the order of C Y in regions 3006-3010. Ink is jetted in the order of Y)C to print out the 1st and 2nd regions according to the pattern 3002 in the complementary relation to the pattern 3001 in the 2nd scanning in the return motion. Succeedingly 3rd and 4th regions are printed out in 3rd and 4th scanning in the forward and return motion. Thus, the picture quality is improved by eliminating unevenness due to time difference and unevenness due to color mixture.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording method for recording an image by ejecting ink droplets onto a recording material.

[0002]

BACKGROUND OF THE INVENTION With the widespread use of copiers, word processors, information processing equipment such as computers, and communication equipment, digital image recording is performed by using an ink jet type recording head as one of recording equipments of those equipments. Things to do are rapidly spreading. In such a recording apparatus, a recording head (hereinafter, referred to as a multi-head) in which a plurality of recording elements are integrated and arranged in order to improve a recording speed.
In general, a plurality of ink ejection ports and a plurality of liquid passages are used, and a plurality of the above-mentioned multi-heads are provided for color.

However, unlike a printer that prints only characters as a monochrome printer, various elements such as color developability, gradation and uniformity are required for printing a color image image. With regard to uniformity in particular, slight variations in nozzle units that occur due to differences in the multi-head manufacturing process affect the ink ejection amount and ejection direction of each nozzle when printing, and finally the printed image. As a result, the image quality deteriorates as uneven density.

A specific example will be described with reference to FIGS. 18 and 19. In FIG. 18A, reference numeral 91 denotes a multi-head, which is composed of eight multi-nozzles 92. Reference numeral 93 is an ink droplet ejected by the multi-nozzle 92, and normally, it is ideal that ink is ejected in a uniform direction with a uniform discharge amount as shown in this figure. If such a discharge is performed, the discharge of FIG.
As shown in (b), dots of uniform size are landed on the paper surface, and a uniform image without density unevenness is obtained as a whole (FIG. 18 (c)).

However, in reality, as described above, each nozzle has a variation, and if printing is performed in the same manner as above, as shown in FIG. 19A. The size and direction of the ink drop ejected from each nozzle varies, and the ink drop lands on the paper surface as shown in FIG. 19B. According to this figure, there is a white paper portion that cannot periodically satisfy the area factor 100% with respect to the main scanning direction of the head, and conversely dots are overlapped more than necessary, or as seen in the center of this figure. There are some white streaks. A collection of dots landed in such a state has a density distribution shown in FIG. 19C with respect to the nozzle array direction, and as a result, these phenomena cause a density distribution as far as human eyes can see. Perceived as uneven.

Therefore, the following method has been devised as a countermeasure against this density unevenness. The method will be described with reference to FIGS. 20 and 21. According to this method, the multi-head 91 is scanned three times (main scanning) in order to complete the printing area shown in FIGS. 18 and 19, but the area of a half 4-pixel unit is completed in two passes. . In this case, the 8 nozzles of the multi-head are divided into a group of 4 upper nozzles and 4 lower nozzles, and the dots printed by one nozzle in one scan are specified image data according to a predetermined image data array. It is thinned out to about half. Then, in the second scan, the remaining half of the image data head is embedded,
The printing of the 4-pixel unit area is completed. The recording method as described above is hereinafter referred to as a divided recording method.

When such a recording method is used, even if the same head as the multi-head shown in FIG. 19 is used, the influence on the print image peculiar to each nozzle is halved, so the printed image is shown in FIG. As shown in FIG. 19B, the black streak and the white streak as seen in FIG. 19B become less noticeable. Therefore, as shown in FIG. 20 (c), the density unevenness is different from that in FIG. 19 (c).
Considerably eased.

When performing such recording, the first scan and the second scan
In the scan, the image data is divided and thinned in such a manner as to fill each other according to a certain array, and this image data array (thinning pattern) is usually in a staggered pattern for each vertical and horizontal pixel as shown in FIG. It is most common to use something like Therefore, in the unit printing area (here, in units of 4 pixels), the printing is completed by the first scan for printing the zigzag lattice and the second scan for printing the inverse zigzag lattice.

FIGS. 21 (a), 21 (b) and 21 (c) show how the recording of a fixed area is completed when the zigzag and inverse zigzag patterns are used, respectively, as in FIGS. , A multi-head having 8 nozzles. First, in the first scan, using the lower 4 nozzles, a staggered pattern

[0010]

[Outer 1] Is recorded (FIG. 21A). Next, in the second scan, the paper is fed by 4 pixels (1/2 of the head length) and the reverse zigzag pattern is printed (FIG. 21 (b)). Further, in the third scan, the paper is fed again by 4 pixels (1/2 of the head length), and the staggered pattern is recorded again (FIG. 21).
(C)). In this way, paper feeding in units of 4 pixels and printing of staggered and reverse zigzag patterns are alternately performed, thereby
The recording area in pixel units is completed for each scan.

As described above, printing is completed in the same region by two different types of nozzles, so that it is possible to obtain a high-quality image without density unevenness.

Such a recording method has already been disclosed in JP-A-60-1.
It is disclosed in Japanese Patent Publication No. 07975 and U.S. Pat. No. 4,967,203, and it is stated that its effect on density unevenness and connecting lines is also effective. Regarding the former, "a means for forming paper overlap in each main scan by making the paper feed smaller than the width of the main scan and overlapping two adjacent main scans and a print dot in the overlap two times. It is characterized by having a means for arranging so that they do not overlap during scanning.
Is disclosed. According to the present case, as described above, the thinning mask may be set to "print the odd-numbered steps and the even-numbered steps alternately in every other column", but in addition, the odd-numbered steps and the second-time steps may be performed in the first main scanning. There are cases in which even-numbered stages are printed in the above scanning, or printing is performed randomly in each scanning, and the thinning mask and the paper feed width are not completely limited.

On the other hand, in the latter USP4967203, "a) in the first pass, only the upper half of the first band is printed with alternating pixel positions which are not adjacent in the horizontal and vertical directions, and b) the second pass. At a pixel that was not printed in the first pass in the first swath and in the lower half of the first swath in alternating horizontal and vertical non-adjacent pixels, and c) in the third pass. 1, the pixels in the first swath that were not printed in the second pass are printed, and at the same time, the first pass is made to the swath immediately following. As described above, in this case, the alternating pixel array which is not adjacent in the vertical and horizontal directions is limited as the thinning mask for performing the divided recording.

As a configuration to be added in this case,
A recording method is disclosed in which several pixels are collectively formed as a pseudo pixel (super pixel) for gradation expression and multi-color expression, and alternating thinning printing that is not adjacent in the horizontal and vertical directions in units of pseudo pixel (super pixel) is performed. ing. According to this method, "Once the system for implementing the above method is installed in either the program software or the printer software, the program can be called with the combination of color numbers specified for superpixels. This print quality is achieved without unnecessarily complicating the task of creating a computer program to produce multiple colors. "And simplifies programming for multicolored presentations. As It also states that color bleeding within a superpixel is harmless because each superpixel is intended to be perceived as a single, homogeneous color.

[0015]

By the way, in the above-mentioned divisional recording, there is a problem that the time cost for printing on one sheet is large and the throughput must be reduced. In such a case, a method of reciprocating print scanning of the carriage can be considered in order to perform printing in a shorter time. According to this, since the carriage scanning which has returned to the home position without performing any printing after the conventional one-scan printing is performed, all of the carriage scanning is virtually halved. be able to. In fact, there are not a few monochromatic printing methods that perform the above-mentioned reciprocal printing. However, in the color inkjet device having the configuration as shown in the present invention, due to the following factors,
It has not been realized yet.

FIG. 2 is a cross-sectional view of a landing state of a recording ink which is currently generally used and a medium (paper) for printing the recording ink.
2 shows. Here, the case where two different color inks (dots) are absorbed (recorded) at almost adjacent positions with a time difference is shown. The point to be noted is that in the two-dot overlapping portion, the dots printed later tend to sink in the depth direction of the paper than the dots printed earlier. This is a stage where the dyes such as dyes in the ejected ink are physically and chemically bonded to the recording medium. Since the bond between the recording medium and the dyes is finite, there is a large difference in the bonding force depending on the kind of the dyes. As long as there is no ink, the amount of ink dye ejected earlier remains on the surface of the recording medium because it is prioritized, and the ink dye ejected later does not easily bond on the surface of the recording medium, and It is thought that this is because it sinks in the direction and is dyed.

In this case, even if two types of ink are printed at the same landing point, the priority colors differ depending on the order in which the two types of ink are ejected, and as a result, two different colors are expressed for human visual characteristics. It will be. For example, 4
Each color of the color head from right to black, cyan, magenta,
Arrange in the order of yellow, and head arrangement direction (left and right direction)
The main scanning is performed by reciprocating. In the forward scan, the print data is moved to the right and simultaneously recorded. At this time, since the recording order on the paper surface conforms to the above arrangement order, for example, when a green (cyan + yellow) signal is input to a certain fixed area, ink is absorbed in each pixel in the order of cyan and yellow. It Therefore, as described above, in this scanning, the cyan absorbed first becomes the priority color, and the green dot having a strong cyan tint is formed. On the contrary, in the backward scanning after the paper is fed in the sub-scanning direction, the recording is performed while moving in the direction opposite to the forward scanning. Therefore, the driving order is also reversed, and a green dot having a strong yellow tint is obtained by this scanning. By repeating the above scanning, green dots having a strong cyan tint and green dots having a strong yellow tint are printed according to the forward and backward passes of each print head. If each scan does not use the divided printing method and the paper width is fed by the head width for each reciprocating scan, the green area with a strong cyan color and the green area with a strong yellow color are the heads. The width of the green image is alternately repeated, and the green image, which should be uniform, is significantly deteriorated.

However, this problem can be overcome to some extent by using the divided recording method already shown in the conventional example.
In division printing, as described in FIG. 21, the forward path (a),
In (c), green dots having a strong cyan tint are recorded, and in the returning path (b), green dots having a strong yellow tint are recorded. Therefore, the tint in a certain area is alleviated by the dots of both tints.

This structure and effect are described in US Pat. No. 4,748,453.
It has already been disclosed in. Although the paper feed amount is not limited here, it is possible to perform complementary printing on pixels that are alternately positioned in the horizontal and vertical directions in the same printing area by the first and second (or more) divided printing scans. , Ink beading on a medium such as OHP paper is prevented, and when a color image is formed, the order of ink ejection of mixed color pixels is reversed between the first scan and the second scan (reciprocal recording), thereby achieving color printing. It describes the effect that can prevent banding (color unevenness). In this case, the main purpose is to prevent beading between pixels, so that the pixels printed in one scan are characterized by being alternating in the horizontal and vertical directions (not adjacent to each other). There is.

On the other hand, JP-A-58 of the same applicant as the present invention
In Japanese Patent Laid-Open No. 194541, a plurality of recording element arrays are arranged in parallel, and reciprocatingly travels in a direction orthogonal to the recording element arrays to perform main scanning of dot matrix recording. The number of dots less than the total number of dots to be recorded in each row and each column of the matrix is intermittently recorded, and the remaining dots in each row and each column are intermittently recorded in the return path of the main scanning. There is disclosed a technique in which the overlapping sequence of recording in the overlapping recording dots by the plurality of recording element arrays is made different between the forward pass and the return pass of the main scan by performing the recording on the. In this case as well, there is no limitation to reduce paper feed than usual as in the case of the divided recording described above, and the effect is to prevent image deterioration due to color tone deviation (color unevenness) of the recorded image due to overlapping recording of color inks. I am trying.

In this case, since the main purpose is to prevent this color shift, there is no special limitation on the dot position recorded in each scan, and in the embodiment, in addition to the checkered pattern (staggered, inverted zigzag), Horizontal decimation that records alternately only in the vertical direction,
The vertical thinning is repeated alternately only in the horizontal direction.

Although not limited to a color printer, Japanese Patent Application Laid-Open No. 55-113573 also discloses a structure in which reciprocal recording is performed by using a checkered pattern (staggered or inverted zigzag) pattern. . In this case, it is an object to prevent adjacent dots from being continuously printed, thereby preventing the dot distortion by printing the adjacent dots before the printed dots are dried. Therefore, here, the thinning mask is limited to a twill pattern, as in the case of USP4748453.

By the way, all of the three patents listed here are intended to prevent color unevenness and beading during reciprocal recording. Therefore, unlike the divided recording method described in the present case, the configuration of “making the paper feed amount between each scanning equal to or less than the normal head width” which is performed for the purpose of preventing density unevenness due to nozzle variation is not adopted. .

As described above, if the divided recording is performed in the reciprocal recording, two kinds of recording pixels whose ink colors are ejected in the opposite order can be evenly provided in the recording area, which causes color unevenness. It was possible to easily perform multi-color bidirectional recording.

However, even if the above-described staggered / reverse staggered recording is performed, the problem of color unevenness cannot be completely solved. The reason for this will be explained. Normally, the amount of ink droplets is designed to spread larger than the area given to each pixel on the paper surface. This is because the blank area cannot be seen at all in the area of 100% printing rate data. Therefore, even when the divided recording method is used, only 50% of the recording pixels are printed, but the print medium (recording paper)
As shown in FIG. 23, almost 100% of the area is covered. FIG. 24 shows a sectional view of the paper in this case. Here, a case is shown in which staggered printing is performed on a blank sheet in the first pass (forward scan) and reverse zigzag printing is performed in the second pass (return scan). Reference numeral 2001 shows the state of the ink immediately after the first pass (forward pass) printing, in which the black-painted portion is cyan ink and the shaded portion is yellow ink. Since the yellow ink is ejected at the same position as the cyan ink with a slight time difference, when absorbed by the paper, the cyan ink is in a state with less bleeding and a higher density, and the yellow ink is below the cyan ink. It bleeds so much that it wraps around the periphery, resulting in a print with a low density. At this time, these inks are absorbed up to the adjacent pixels, and the surface of the paper is almost completely filled with the ink as shown in FIG.

Second pass (return pass) performed under these conditions
As shown in 2003, the ink is landed on the adjacent ink which has already been absorbed. Since the second pass is the backward scan, yellow is printed first and cyan is printed later (200
2). If the ink is absorbed as it is, it will eventually reach 20
Both colors such as 03 are in an absorption state that does not appear much on the surface. Then, the density of cyan that is printed first is most strongly emphasized in the final print-completed image, and this print area becomes a green image in which the tint has priority to cyan. On the contrary, in the print area adjacent to the above-mentioned print area where the backward scan is the first pass, the positions of cyan and yellow are reversed, and a green image with a tint of yellow is obtained.

FIG. 25 shows how the above two print areas appear. As can be seen from this figure, the lower half of the head always determines the priority color of each area, and the priority color is reversed by reciprocating scanning. 2 with different priority colors
Since there are two areas alternately, even in division printing, color unevenness still appears and the image is deteriorated, making bidirectional printing impossible.

Further, the adverse effect of ink bleeding on adjacent pixels has been confirmed not only in the above-described color unevenness but also in single-color bidirectional printing. This will be explained below. 26 is shown in FIG.
Similar to 4, the ink absorption states of the first pass and the second pass are shown for a single color. In this figure, 2101 represents the landing state after the first pass printing, 2102 and 2103.
Both show the state after the second pass printing in a cross-sectional view of the paper. Here, 2102 is 2 immediately after the first pass is recorded.
A state in which the second pass is recorded, and 2103 is a state in which the second pass is recorded after a certain time has elapsed after the first pass recording. A difference appears in the state of absorption of the ink recorded in the second pass on the paper surface between them. 2102 is absorbed in the depth direction of the paper surface, whereas in 2103, the ink of the second pass spreads on the paper surface. This is also confirmed from the back side of the paper, and 2103 is 2
The degree of ink leakage to the back side of the paper is larger than that of 102. Then, such a state appears as a density difference on the paper surface between the two (2104, 2105).

The time difference caused by the reciprocating scanning of the carriage is sufficient as compared with the order of the time difference which causes the density difference between the two. Then, this factor appears as a new adverse effect due to the reciprocal printing. This situation will be described with reference to FIG.

In FIG. 27, the head first scans forward from the position 2201 in the direction of the arrow to perform recording with the first scan width. Then, when printing for one line is performed, a paper feed of 1/2 of the scan width is performed, and the backward scan is performed from the position 2202 in the drawing in the reverse direction. Further, after feeding the paper having the same width as the above, the outward scanning is performed again from the position 2203 to perform recording in the direction of the arrow. The following is a comparison of the recording intervals of the two passes for each of the positions 1 to 3 of the printing area completed at this time. That is, in and, after the printing of the first pass is completed and the paper of 1/2 width is fed, the printing of the second pass is performed immediately. On the other hand, in and, after the first pass printing, the second pass is printed after the time for the carriage to make one reciprocating scan. And, the part recorded at the time difference which is exactly in the middle is. Therefore, as described above with reference to FIG. 26, and are the most concentrated portions of these, and and follow,
In and, the ink is deeply absorbed and the surface density is low. Therefore, density unevenness appears in the left side area in which the half width is repeated in the vertical direction and in the right side area in which the half width is repeated, which causes an adverse effect on the image.

As described above, the bleeding to the non-printed pixels in the first pass causes the density to be influenced by the recording interval between the first pass and the second pass. I can understand that it was impossible. Although the above description has been made by taking the single-color recording as an example, this phenomenon appears with the color unevenness already described in the case of the mixed-color recording. In this case, the conspicuousness of the left and right color unevenness or the tint Recognized as a difference.

Also in the one-way recording, the following factors can be cited as adverse factors affecting the recording time difference.
If the printing apparatus performs head recovery scanning in order to maintain its own drive scanning during printing or waits for print data to be transferred, the carriage temporarily suspends. Then, such a pause produces irregular density unevenness in an order of magnitude larger than the time difference unevenness described above. That is, the carriage enters a rest state while the first pass is being printed, and after a lapse of time, the printed print area has a darker density than the other areas. The density unevenness caused by such factors is distinguished from the time difference unevenness and is hereinafter referred to as rest unevenness.

As described above, in the ink jet recording apparatus for forming an image by scanning the recording head in a direction different from the nozzle array direction of one head, divided recording is performed in order to realize high image quality and high speed. In order to realize the bidirectional printing, the image adverse effects such as the color unevenness, the pause unevenness, and the time difference unevenness are still left behind.

The present invention has been made in view of the above points, and an object of the present invention is to provide an ink jet recording method capable of obtaining a high-quality image at high speed by eliminating the density unevenness due to the above-mentioned adverse effects. Especially.

[0035]

In order to achieve the above object, the present invention provides a recording means having a plurality of recording elements for ejecting ink in a direction different from the arrangement direction of the plurality of recording elements. In the ink jet recording method for recording an image on a recording material by moving the recording medium to the main scanning direction and performing the main scanning, and after the main scanning is completed, a predetermined amount of sub-scanning is performed in the direction substantially perpendicular to the main scanning. By dividing all the pixels in the recordable area by a plurality of main scans according to a plurality of divided and thinned arrays having a complementary relationship with each other, and sequentially recording the divided pixels in the area by a plurality of main scans. The area is recorded, and the divided and thinned array is m × n.
The pixel groups of (m and n are positive integers, at least one of which is 2 or more) are arranged as a unit so that the pixel groups are not adjacent to each other.

As a result, the same area is main-scanned a plurality of times in accordance with the divided thinning-out arrangement having a complementary relationship in units of m × n pixel groups, and the image of the area is recorded.

[0037]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a perspective view showing a schematic structure of an ink jet recording apparatus to which the present invention can be applied. In this figure, reference numeral 701 is an ink cartridge. These are 4
It is composed of an ink tank filled with each color ink, black (K), cyan (C), magenta (M), and yellow (Y), and a multi-head 702 corresponding to each color. FIG. 2 shows the state of the multi-nozzles arranged in this multi-head from the z direction.
Reference numeral 01 is a multi-nozzle arranged on the multi-head 702.

Although the multi-nozzles 801 are arranged in parallel along the Y-axis in this figure, they may have some inclination on the XY plane of the figure. In this case, while the head moves in the traveling direction X, each nozzle performs printing while shifting the timing.

Returning to FIG. 1 again. A paper feed roller 703 rotates in the direction of the arrow in the figure while holding the print paper P together with the auxiliary roller 704, and feeds the print paper P in the Y direction at any time. Further, reference numeral 705 denotes a paper feed roller, which not only feeds the printing paper but also holds down the printing paper P like the paper feeding roller 703 and the auxiliary roller 704. A carriage 706 supports the four ink cartridges and moves them together with printing. The carriage 706 is configured to stand by at the home position h at the position shown by the dotted line in the figure when printing is not performed or when multihead recovery work is performed.

In this embodiment, the recording head of each ink jet cartridge ejects ink droplets by causing the ink to change its state using thermal energy.

Here, 4 mounted on the carriage 706.
These ink jet cartridges are used for black ink, cyan ink, magenta ink,
The yellow inks are arranged so that the inks are superposed in this order. Therefore, when the carriage moves backward, the inks are superposed in the reverse order of the forward movement. The intermediate color can be realized by appropriately superimposing ink dots of C, M, and Y colors. That is, red can be realized by overlapping M and Y, blue by overlapping C and M, and green by overlapping C and Y.

Generally, black can be realized by superimposing three colors of C, M, and Y. However, black coloring at this time is bad, and it is difficult to superimpose with high accuracy, so that framing of chromatic colors occurs. Only black is ejected separately because the ink ejection density per unit time becomes too high.

FIG. 3 is a block diagram showing the control section of the ink jet recording apparatus shown in FIG. In the figure, 1201 is a CP
It is a control unit mainly composed of U, ROM, RAM and the like, and controls each unit of the device according to a program stored in the ROM. A driver 1202 drives a carriage motor 1205 for moving (main scanning) the carriage 706 in the x direction based on a signal from the control unit 1201. A reference numeral 1203 indicates a paper feed roller 705 and a paper sheet based on a signal from the control unit 1201. A transport motor 120 for driving the feed roller 703 to transport (sub-scan) the recording material in the y direction.
The driver 1204 drives the multi-heads 1207 to 1 for each color based on the print data from the control unit 1201.
A driver for driving 210 (corresponding to 702 in FIG. 1), 1
Reference numeral 211 denotes an operation display unit for inputting various keys and various displays, and 1212 is a host device for supplying print data to the control unit 1201.

Before the start of printing, the carriage 706 at the position shown in the figure (home position) moves forward in the x direction when the print start command arrives, and moves to n on the multi-head 702.
The individual multi-nozzles 801 perform printing for each recording area divided on the paper surface. When the printing of the data is completed up to the end of the paper and the reversal position is reached, the carriage starts to move back toward the home position, and the data is printed again. From the end of the first printing due to the forward movement of the carriage to the start of the second printing due to the backward movement of the carriage, the paper feed roller 703 rotates in the direction of the arrow so that only the width of the divided recording area is reached. The paper is fed in the y direction. In this way, the printing by the multi-head and the paper feeding (sub-scanning) are repeated for each carriage one scan (main scanning), whereby the data printing on one paper surface is completed.

A specific example of the recording method performed by the ink jet recording apparatus having the above-described structure will be further described.

(First Embodiment) The first embodiment of the present invention will be described below. FIGS. 4 and 5 best show the present invention by comparing with FIG. 23, and similarly to FIG. 23, show the ink landing state after the first scanning within a certain fixed region. Conventionally, dots printed by the same scan have been landed on alternate pixels that are not adjacent to each other (FIG. 23), but in the present invention, all pixels are grouped into 4 × 3 groups in FIG. 4 and 4 × 4 groups in FIG. The pixel groups are arranged so that recording is performed in the same pass, and the groups are recorded in positions that are not adjacent to each other in the same pass. By doing so, as is clear from the figure, the ink overlapping area of the first recording color is reduced by the increase of the overlapping area of the dots in each group, so that the white paper part that can be landed after the second recording color is reduced. To increase. Therefore, even if the ink ejection order is changed by the reciprocal scanning, the area ratio occupied by the priority colors of the first scan is reduced, and the area occupied by the priority colors of the second scan is increased accordingly, so that there is a deviation between the priority colors. Therefore, the difference in color tint in the area where the paper feed width is repeated is reduced.

Below, as the first pattern of this embodiment,
A recording method using the divided thinning pattern in units of 4 × 3 pixel dot groups shown in FIG. 4 will be described. FIG. 6 is a recording state diagram in this embodiment compared with the conventional example of FIG. In this example, a head composed of 16 nozzles is used,
Printing is performed in both directions while feeding paper with 8 nozzles each. The data recorded here is a 100% green image composed of cyan and yellow. In these figures, a case where dots having a diameter of 110 μm are recorded for a pixel density of 360 dpi is shown as an example.

First, the first movement of the carriage 706 in the forward direction
In scanning, the lower thinning nozzles (8 nozzles) of the Y and C multi-heads 702 are used, and the divided thinning pattern 3001
Then, the first area on the recording material is printed. In this first scan, ink is ejected in the order of C → Y onto the areas 3006 to 3010 on the recording material corresponding to the blacked pixel areas in the pattern 3001. After the end of the first scan, the paper is fed (sub-scan) by a distance corresponding to half the length of the multi-head.

Next, in the second scan by the backward movement of the carriage, all the nozzles of the Y and C multi-heads 702 are used to follow the first thinning pattern 3002 on the recording material.
The area and the second area are printed. This pattern 3002
Are patterns complementary to the pattern 3001. In this second scan, Y is applied to the area on the recording material corresponding to the black-painted pixel area in the pattern 3002.
→ Ink is ejected in the order of C. After the second scan is completed, the paper is fed by a distance corresponding to the length of half the multi-head (eight nozzles).

Next, in the third scan by the forward movement of the carriage, all the nozzles of the Y and C multi-heads 702 are used to follow the divided thinning pattern 3003 and the second print on the recording material is performed.
The area and the third area are printed. This pattern 3003
Is a pattern having the same arrangement as the pattern 3001 and is complementary to the pattern 3002. In the third scan, ink is ejected in the order of C → Y onto the area on the recording material corresponding to the black-painted pixel area in the pattern 3003. Then, after the end of the third scan, the paper is fed according to the length of eight nozzles.

Next, the fourth movement of the carriage 706 is performed.
During scanning, printing is performed on the third and fourth areas on the recording material according to the divided thinning pattern 3004 using all nozzles of the Y and C multi-heads 702. This pattern 3
A pattern 004 has the same arrangement as the pattern 3002 and is complementary to the pattern 3003. In this fourth scan, Y is applied to the area on the recording material corresponding to the black-painted pixel area in the pattern 3004.
→ Ink is ejected in the order of C. Then, after the end of the fourth scan, paper feed for 8 nozzles is performed.

After that, the same processing is repeated to complete the recording on one recording material.

In FIG. 25 showing a conventional example, since the print mask is staggered in each scan, each dot having a size of 1 pixel or more greatly bleeds into an adjacent pixel, and a priority color different for each feed width. The density unevenness has been generated.
On the other hand, in FIG. 6 of the present embodiment, since the zigzag mask is used in units of 4 × 3 pixel groups, the ink bleeds into each dot group, and the bleeding into other areas is limited. Therefore, the difference in priority color in each area is considerably suppressed as compared with the conventional example. The arrangement method of this pixel group is
For each color of the color printer, it is sufficient that the pixel groups are formed so as not to bleed out to other areas, so that it is not necessary to record all colors in the same array.
The same color may be used, or different arrangement methods may be used. When different array methods are used, they are described as the second and third embodiments below.

By the way, in the present embodiment, a mask in which a unit of 4 × 3 dot groups is used as a thinning mask, but when grouping m × n pixels as in the present invention, a given pixel density is applied. The appropriate value varies depending on the conditions such as the ink ejection amount or the recording medium. If m or n is too small under the above conditions, the effect of the present invention cannot be obtained, whereas if the dot group is too large to be resolved by human eyes, then the tint between adjacent groups will be increased. Difference is detected, and the image becomes rough and rough.

FIG. 8 shows the protrusion rate and the protrusion rate when division recording is performed with a rectangular thinning mask in units of n × m pixel groups for each size (ratio) of dot diameters with respect to a fixed pixel pitch. It shows the color difference between the recording areas with respect to the ratio. The protrusion rate indicates to what extent the dots printed in the first scan are projected to the non-printing area in which printing should be performed in the second scan. The color difference between the recording areas is the color difference between the adjacent recording areas when the green image composed of cyan and yellow is divided and recorded as shown in FIGS. 6, 7, and 25 with respect to the above-mentioned protrusion rate. Is shown.

According to this figure, the protrusion rate decreases as the number of dots in the dot group increases, and if the number of pixels is the same (the number of dots), the closer to square it is, the smaller. The measured color difference for each protrusion rate is
It is a measured value obtained by actual recording and a color difference meter. Further, the theoretical color difference is obtained by performing calculation for each protrusion rate from the spectral distributions of two types of reference green images.

A method (calculation method) for deriving the theoretical color difference value will be briefly described.

First, the spectral distributions of the green image recorded in the order of cyan and yellow and the green image recorded in the order of yellow and cyan are obtained (measured).

The spectral distribution of the unit area in which the two types of green images complement each other at variable ratios,
The result is used to obtain by additive color mixture.

From the above spectral distribution, tristimulus values of X, Y and Z systems are obtained.

The above tristimulus values are further added to CIE1976 (L
^* a ^* b ^* ).

From the respective values of the green image of each protrusion ratio and the green image in which the protrusion ratio is reversed between cyan and yellow, the color difference between adjacent regions for each protrusion ratio is obtained by the CMC color difference formula.

The CMC color difference used here is one of various color difference formulas that are intended to bring the color difference obtained from the commonly used CIE1976 (L ^* a ^* b ^* ) color difference formula closer to the human visual color difference. The newest method.

Here, the CMC color difference method will be briefly described. First the CMC color difference equation, CIE of L ^* (lightness), a ^*, b ^* representation axis of (chromaticity), L ^* (metric lightness) is intact, a ^* b ^* a C ^* _ab (metric chroma ), H ° _ab (metric hue angle) is expanded to a cylindrical function (L ^* C ^* _ab H ° _ab ) that performs three-dimensional expression.
The expressions metric lightness L ^* , metric saturation C ^* _ab , and metric hue angle H ° _ab are independent of the visual sense in each dimension than the conventional (L ^* a ^* b ^* ) function consisting of lightness and chromaticity. In line with attributes. Therefore, it becomes possible to visually independently evaluate each attribute, and it becomes easy to take measures (weighting) according to each attribute. Then, when the color difference between the two points is calculated thereafter, ΔE = {(ΔL ^* / 1S _L ) by using the three weighting factors 1S _L , cS _C , S _H obtained from experience in the normal color difference formula. ² +
_{^{(ΔC * / cS c) 2}} + it is possible to convert _{^{(ΔH * / S H) 2}} } 1/2. As a formula for obtaining the above-mentioned correction coefficient, the following formula has been obtained as a result of statistical examination.

With respect to the standard color, when L ^* <16, S _L = 0.511 L ^* > = 16, S _L = 0.040975L ₁ ^* / ( ₁ + 0.01765L ₁ ^* ) S _c = 0.0638C1 ^{* _{/(1+0.0131 C1 *) +0.638 S H =}} S C (Tf + 1-f) f = [(C 1 *) 4 / {(C 1 *) 4 +1900}] 1/2 the, h ₁ 164 ° when located between ~345 ° T = 0.56 + | 0.2cos (h1 + 168) | when h ₁ is other than the above, T = 0.36 + | 0.4cos ( h1 + 35) | become (more Yukio Murata Color Technology Handbook (from General Technology Center Co., Ltd.).

By the way, a slight difference is always recognized between the theoretical color difference and the actually measured color difference in FIG. This is because the theoretical color difference is obtained by the complete additive color mixture of two kinds of greens at the stage of the above description. Additive color mixing is the sum of the colors (spectral distributions) of multiple non-overlapping sub-regions that exist in a unit area in proportion to the area ratio of each sub-area, and the resulting spectral distribution is the color of the unit area. It is a method of setting as. In the recording state of the ink jet recording apparatus used in the present invention, as shown in FIG.
In the CY dot and the YC dot of No. 4, it is explained that the dot recorded later always sneaks under the dot recorded earlier, and even in the above theoretical color difference, only the previously recorded dot color is present in the overlapping area. I'm calculating. However, in reality, only the tint of the previously recorded dot does not completely occupy the overlapping portion of both dots. Although it has little influence, dots to be recorded later should be added as a subtractive color mixture to the hue of the overlapping area. Therefore, the theoretical color difference of each area obtained by calculation always appears larger than the measured color difference. However, as shown in FIG. 8, if the difference between the color differences between the two is substantially constant, the appropriate mask size can be estimated by calculation even when the ink or the recording medium is different.

By the way, the limit color difference which can be recognized as an equal color to human eyes is 1.
The result of the panel test is about 0 to 1.8. If two colors with a value larger than this are located next to each other,
A boundary is recognized between them and they are perceived as different areas. In FIG. 8, the limit color difference area is shown by a two-step boundary line. According to this figure, it is understood that the amount of each protrusion corresponding to these limit color differences is about 25 to 33%. That is, it is a condition that the bleeding of the ink to the non-printed area is ⅓, preferably ¼ or less so that the problem of the color unevenness does not occur.

In this embodiment, a dot diameter of 110 μm is used for a pixel density of 360 dpi and a thinning mask of 4 × 3 is used. At this time, the ratio of the dot diameter to the pixel density is about 1.5, the protrusion rate is 21.98%, and the theoretical color difference and the measured color difference are 1.25 and 1.20, respectively, which are sufficiently included in the area that does not cause a color unevenness. Has been.

On the other hand, when the thinning mask as shown in FIG. 23 is used, the ink occupancy rate in the non-printing area of the first scan is 7%.
This is 1.52%, and the color difference is 3.90, which is a value that greatly exceeds the above limit value. As described above, it is understood that increasing the thinning mask is preferable in the direction of improving the color unevenness in each adjacent area.

The present invention is also effective for unevenness in time difference or unevenness in rest, which is confirmed even in a single color. As already described in the conventional example, the time difference unevenness is found when the second pass is printed in the area where the dots of the first pass are protruding and bleeding. Therefore, as in the present invention, if the dots in the first pass are adjacent to each other and the protrusion ratio is small, it is possible to print in two-pass printing under almost the same conditions as in one-pass printing, and the time difference caused by the overlapping of the two can be affected. There will be no factors to be eliminated. FIG. 9 shows a region where unevenness in time difference occurs when divided recording is performed using a mask in which 4 × 3 dot groups are used as a unit.
The above effect is shown by emphasizing the overlapping portion between the first scan and the second scan. By comparing with the case of using the conventional 1-dot-unit zigzag and inverse zigzag masks in FIG. 11, it can be seen that the total area amount of the overlapping portion with respect to the recording area is obviously smaller in this embodiment than in the conventional example. . As described above, the present invention can be said to be more effective with respect to the color unevenness, the time difference unevenness and the pause unevenness that may occur even in single-color recording, as the size of the thinning mask increases.

However, as described above, if the mask is too large, the color difference between the dot groups in the same print area starts to be recognized, and the image becomes rough and deteriorates. Tend. According to empirical judgment, since the size of the mask is about 0.2 mm, a feeling of roughness is perceived to some extent, and it is considered that 0.5 mm or more is regarded as an adverse effect as an image. In this embodiment, 360
Since a dot group of 4 × 3 in dpi is used, the mask has a length of about 0.28 mm and a width of about 0.21 mm, and the above conditions are sufficiently satisfied. From the above, if the recording method shown in FIG. 6 is performed using a 4 × 3 thinning mask under the conditions of the present embodiment, a smooth image can be obtained by bidirectional printing without color unevenness, time difference unevenness, or pause unevenness. You can

Basically, the divided printing method does not exhibit its effect unless the printing pixels in the unit area are printed in two scans substantially equally. In the examples explained so far, all 10
Since a 0% duty image was recorded, an equal number of pixels were always recorded in two passes in both the present embodiment and the conventional example. However, the image data that is actually sent as a signal is the one that is sent after the multi-valued data representing a certain gradation is binarized by a predetermined binarization method and is set in a predetermined pattern. Many. The present embodiment is effective for the dither method which is used particularly often among them. An example thereof is shown in FIG. Among the dither methods, the Bayer type is particularly used as the binarization method. When a duty image in 1/16 (4/64) increments is given within a fixed area of 8 × 9, the conventional divided recording is compared with the divided recording method performed in the present embodiment, and It shows how it is divided into two paths. Reference numerals 1701 and 1702 denote black print pixels allowed in the first scan and print pixels allowed in the second scan, respectively, according to the conventional divided printing method. Similarly, reference numerals 1703 and 1704 denote print pixels by the split printing method of this embodiment. Further, when the binarized image data shown on the left side is input, which pixel is printed by each scan of each printing method is shown on the right side. According to this, it can be seen that in the conventional division printing, the printing is completed by only one scanning up to 8/16, that is, 50% duty. Also, 50
Even if it exceeds%, the deviation of the number of print pixels in each pass is large,
Only when it reaches 100%, the numbers of both are equal. When such a situation occurs, for example, at a low duty of 50% or less, data of one pixel width in the main scanning direction of the head is all printed by the same nozzle, which is the original purpose of the divided printing method described above. The density unevenness due to the nozzle variation is not completely eliminated. Furthermore, the non-uniformity of the print pixels in the first scan and the second scan is 50%.
It is expected that even in the high duty region exceeding (8/16), the image is considerably inferior in the density unevenness as compared with the case of the present embodiment in which the duty is always equalized. This problem is not limited to bidirectional printing, but can occur in unidirectional printing.
In addition, as the same factor, that is, a problem phenomenon caused by unevenness of print pixels in each scan, when printing is performed using two color inks having different duties other than the density unevenness, the ink ejection already described in the conventional example is performed. It also causes color unevenness due to the order. Similar to the density unevenness due to nozzle variations, this problem also occurs in unidirectional printing, and can be solved by making it possible to equally distribute the number of pixels printed in each pass. 4 × of this embodiment
If a thinning mask is used in units of 3 dot groups, the number of dots between both scans is always divided equally.
Therefore, the color unevenness does not occur. Further, since the dots lined up in the same main scanning direction are always printed by two scans, that is, by two kinds of nozzles, this embodiment is effective even in the case of density unevenness due to nozzle variations.

As described above, in the ink jet recording apparatus for recording the dots corresponding to 110 μm in the recording density of 360 dpi, by using the dot group of 4 pixels in the vertical direction and 3 pixels in the horizontal direction as the thinning mask, color unevenness and time difference It is possible to obtain a smooth and high-quality image without unevenness, unevenness of rest, and unevenness of nozzles.

By the way, here, a description will be added to the thinning mask in the unit of 4 × 4 dot groups as the second pattern of the present embodiment. According to FIG. 8, 4 × 4
In the case of using the mask in which each dot group is used as a unit, the protrusion rate is 18.89%, and the color unevenness between the adjacent recording areas is 1.03 in the measured value. It can be seen that the color unevenness is better than when the thinning mask is used. As the number of pixels in the mask increases, the graininess of the image tends to worsen, but since it is about 0.28 mm in both length and width, it is not considered to be an adverse effect on the image. FIG. 7 shows a state in which divided recording is performed using this mask. Since the recording operation in this case is the same as that in the case of FIG. 6, the description thereof will be omitted. It can be seen that the color unevenness due to the dot protrusion is further eliminated as compared with the case of using the mask in which the unit of 4 × 3 dot groups shown in FIG. 6 is used. Further, FIG. 10 shows the time difference unevenness state and the rest unevenness state, which are compared with FIGS. 9 and 11. 4 out of these 3 figures
FIG. 1 using a mask with a dot group of × 4 as a unit.
It can be seen that 0 is the most effective for the unevenness of time difference and the unevenness of rest, since the overlapping portion is the smallest.

Further, when divided recording of binarized data by the dither method is performed using a mask with this 4 × 4 dot group as a unit, the pixels printed by two scans as in FIG. FIG. 13 shows the positions. Also in this figure, the number of dots in the first scan and the number of dots in the second scan are always equally divided. Therefore, regarding the color unevenness due to the deviation of the number of print dots between the scans, the 4 × 3 already explained. This is the same as the effect of the mask for each dot group. However, the effect on the density unevenness caused by the nozzle variation is slightly different. As shown in this figure, when a mask of 4 pixels is used in the horizontal direction, the dots arranged in the same main scanning direction are always equally divided into two scans. On the other hand, in the mask shown in FIG. 10 in which the unit of 4 × 3 dot groups is used, printing is always performed with two types of nozzles (two scans), but the number of dots printed in each scan is somewhat different. There is a bias. Therefore 4x4
The image with the dot group as the unit has a slightly worse image roughness due to the size of the mask than the mask with the unit of 4 × 3 as the unit, but a better image with respect to the nozzle unevenness is obtained. Can be expected.

According to the mask in which 4 × 4 dot groups are used as a unit, it is often effective in this point not only in the Bayer type already shown in FIG. 13 but also in other dither methods. The reason is as follows.

In the binarization method such as the normal dither method, not only the Bayer type, but within a certain area of a 4 × 4 or 8 × 8 square, a unique pixel array corresponds to each duty according to each law. It has been decided. Even in the case of 8 × 8, in many cases, as shown in FIG. 13, two 4 × 4 matrices are arranged side by side as a sub-matrix. This matrix is for realizing area gradation inside the matrix, and if equal data is input, the same pixel arrangement is always output. For example, also in the case of the Bayer type shown in FIG. 13, one pixel arrangement as shown on the left side of the figure is determined for each gradation. Therefore, when image data equal to all matrices is input, as when recording a uniform pattern,
All the matrixes arranged vertically and horizontally on the recorded image record dots of the same pixel arrangement to form a uniform image. The plurality of matrixes to be arranged are all the same and have the same number of dot arrays at all the duties. Also in the sub-matrix, each dot number is not equal in all the duties, but each dot array is distributed so as to have the least deviation.

In this method, all of the above matrix or sub-matrix is included in the 4 × 4 dot group, and adjacent matrixes or sub-matrices are not printed by the same printing scan. . Therefore, the same number of print data of the same arrangement is input into each matrix for image data of any duty, and the difference in dot number between print scans does not appear. Even in the above points, this method has many
It can be said that it is effective for the quantification method.

As the first embodiment, two types of thinning masks have been introduced. When determining these masks, the relationship between the protrusion rate and color unevenness shown in FIG. 8 or the landing of ink on the recording medium is shown. State, and even binary compatible state,
There are a number of factors to consider. The shape of the mask may be a square mask such as 4 × 4 described above, or a rectangular mask such as 4 × 3. It has already been described that the square mask is the most effective against the color unevenness among the mask shapes including the determined number of pixels. It was also stated that a mask having a width of about 4 pixels in the lateral direction is particularly effective for the binarization method.

However, for example, 4 × 3 used in the above embodiment
If the mask has an odd pixel width such as 3 pixels or 5 pixels in the main scanning direction like a mask in which the pixel group is set as a unit, dots having the same main scanning direction have a low duty. However, it means that recording is always performed with two types of nozzles. Like a mask having a width of 4 pixels in the horizontal direction, one cycle of a unit matrix for expressing gradation (see FIG.
The number of pixels in the main scanning direction to be printed in each scan is always equally divided into two scans as long as the number of pixels includes 3 pixels in 3). However, for example, 1 in an 8x8 matrix
At 1/64 duty where only pixels are recorded,
It is obvious that all pixels arranged in one printing scan and one type of nozzle main scanning direction are printed by this thinning mask. On the other hand, in the thinning mask having the width of 3 pixels in the horizontal direction described in the above embodiment, n of 2 is generally used.
It is possible to always print with two kinds of nozzles at any duty, without sharing the cycle with the unit matrix for gradation expression having a power cycle.

There may be various cases of the number of pixels in the vertical direction of the thinning mask. In order to realize the effect of the calculated protrusion ratio in the entire area and to make the state of the joint portion for each scan the same as the other portions, the number of nozzles in the print head must always be divisible by the vertical pixels. Must-have. Further, even when the number of nozzles of the recording head is as small as eight nozzles, the upper limit is set for the number of pixels. 8
The present invention does not work unless at least two pixel groups exist in the nozzle, and in this case, the upper limit is determined to be four pixels.

As described above, the number of pixels in the horizontal direction, the number of pixels in the vertical direction, the total number of pixels in the mask, the shape of the mask, and the like, the thinning mask for realizing the present invention is different in the recording conditions and various conditions. Various patterns can be realized according to various requirements.

By the way, as a matter similar to the present invention, there is USP4967203 already shown in the conventional example.
Also in this case, among the pixels arranged on the paper surface, several pixels (m × n) adjacent to each other are defined as one group (super pixel), and a plurality of groups which are alternately arranged and are not adjacent to each other are recorded in the first scan. , The remaining groups are printed in the second scan. However, this case is a multi-color image image,
Alternatively, the explanation is given using the equal arrangement method for each color in the case of limiting to a multi-gradation image image, and one of the purposes is to represent the gradation and color tone determined in each group as accurately as possible. . Therefore, it is described as an effect that the mixture of colors in each group (super pixel) is encouraged while the bleeding between adjacent groups is prevented.

On the other hand, since the main purpose of the present invention is to eliminate the adverse effects of color unevenness or time difference unevenness in reciprocal recording, it is not necessary to use the same array of recording pixel groups for each color. As will be described later as the second and third embodiments, it is effective that the masks are different from each other in terms of the adverse effect of color unevenness, since the difference between the first recording ink and the second recording ink is smaller. In many cases. However, such a recording method causes bleeding between adjacent different colors, which is an adverse effect in the above patent.

Further, in the above-mentioned patent, it is stated that a special image system for realizing the effect is incorporated with either a program, software or printer / formware. In the above patent, a pixel group consisting of m × n pixels is set as one super pixel, which is a pseudo pixel, and gradation expression and multi-color expression are performed therein. The dot array recorded in each super pixel is selected from one of a plurality of color expression arrays already determined according to the expression color required by a number for one pseudo pixel. Is. Therefore, in the above-mentioned patent, as one of the effects, "the improvement of print quality is achieved without making the work of creating a computer program for creating a large number of colors unnecessarily complicated". ing.

On the other hand, each pixel in m × n according to the present invention has no relation on the image such as forming a pseudo pixel. Other than having the same recording timing during recording, they have no relation to each other and are completely independent of each other. When the mask of 4 × 4 pixels of this embodiment is used, the unit matrix in the binary gradation expression is 4 × 4.
Although the effect of completely including it in the pixel group of the above is described, such an effect can be achieved by using a special image system such as program software or printer formware as shown in the above patent. It's not something you get by being built in. As described above, certainly, in a special case such as the 4 × 4 mask of the present embodiment, a configuration of “recording pixels in the unit matrix of the binarized expression at the same time” is adopted. However, the effect obtained from this is when the recording method (thinning-out mask) of the recording apparatus used in the present invention is adapted to the dither pattern which is already generally known as the binarization method. It is something that happens especially to.

Therefore, in order to realize the effect "adaptability to a binarized signal" of the present embodiment described above, a special image processing system as shown in the above patent is installed on the host side or recording side. There is no requirement for the device body.

Further, the present invention is not particularly limited to multi-color, and is a sufficiently effective invention also in mono-color from the viewpoint of overcoming time difference unevenness and rest unevenness. From the above, it is considered that the present invention is different from the above patent.

As described above, according to this embodiment of the present invention, in the color ink jet recording apparatus, m × n such as a rectangle of 4 × 3 pixels or a square of 4 × 4 pixels is used.
A dot group consisting of pixels is used as a thinning mask unit, and these dot groups are alternately arranged in the vertical and horizontal directions, and by setting the thinning mask in a state where they are not adjacent to each other, bidirectional printing in multi-color and mono-color,
It is possible to obtain a high-quality and smooth image without adverse effects such as color unevenness, time difference unevenness, pause unevenness, and nozzle unevenness in one-way printing.

(Second Embodiment) A second embodiment will be described below.
The present embodiment is characterized in that a thinning mask is used in units of 4 × 4 dot groups and different masks are used for each color. Heretofore, as the image adverse effects to be particularly solved by the present invention, the color unevenness caused by the order in which the colors are printed, and the time difference unevenness and the pause unevenness due to the time difference between the scans have been mentioned. However, what is most noticeable is the former color unevenness.

In this embodiment, with particular emphasis on this color unevenness,
This is an attempt to positively solve this problem. The fundamental cause of the color unevenness is that the four color heads are arranged in the same direction as the scanning direction of the carriage. Since such a configuration is adopted, there is inevitably a difference in the printing order in each scan between the respective colors. Therefore, in the first embodiment, the recording order is alternately reversed so that both are recorded under the same conditions as much as possible in the forward pass and the return pass in which dots of different tints are formed.

On the other hand, in the present embodiment, the aim is to prevent the difference in priority color between each color as much as possible even in each scanning, and in order to realize this, a combination in which color unevenness is easily noticeable The staggered mask is reversed with two colors.
FIG. 14 shows a state in which a thinning mask in which adjacent matrices are thinned in a zigzag manner with a 4 × 4 dot group as a unit matrix is printed while being exchanged for each scan with cyan and yellow. Also in the case of this embodiment, it can be seen that there is no unevenness of tint in each region, as in FIG. If different masks are used for the respective colors as in this embodiment, the first ink to be printed on a blank sheet (cyan for forward scan, yellow for backward scan) is scanned before the same scan is completed. Since other color inks (yellow for forward scan and cyan for backward scan) are printed inside, the printing conditions for each color within each scan are more equalized, and differences in priority colors are less likely to appear. In FIGS. 7 and 14, no expressions that characterize the effects of the present embodiment are particularly shown, but a difference is actually found between them. In particular, in the case of a thinning mask in which 4 × 4 dot groups are used as a unit, if the image is inevitably grainy, the mask itself may be made smaller and the configuration of this embodiment may be adopted.

Of course, in the present embodiment, recording must be completed for each area by two carriage scans.
It is impossible to use a mask in which all four colors do not overlap. However, the number of color combinations in which color unevenness is recognized as an adverse effect on an image is often about one set or two sets. In such a case, the two colors may be set to be printed by different masks. Also,
When the color unevenness is noticeable evenly in the combination of each color, a mask in which each color is shifted by several pixels may be used.

However, in the present embodiment, since the mask is set in the direction in which all pixel areas are printed in the first scan of each area, the time difference between the first scan and the second scan is a detrimental factor. The unevenness in time difference will be somewhat worse. Therefore, the first embodiment is more effective in the case where the time difference unevenness is considerably noticeable, whereas the present embodiment is effective in the case where the particular two colors, especially the color unevenness is noticeable. There is something.

(Third Embodiment) Next, a 4-pass reciprocating recording method will be described as a third embodiment of the present invention. This embodiment is also 4
Although a mask using a unit of × 4 dot groups is used, when printing a fixed area by four scans, a paper feed of 1/4 print width is performed between each scan, and each scan is also performed. The feature is that masks are sequentially changed between the respective colors. FIG. 15 shows this state. Here, it is assumed that one square pattern unit includes 4 × 4 pixel groups, and a 16-nozzle head performs paper feed with a width of 4 nozzles for each scan. In each scan, 4 × 4 masks that do not overlap each other are cyclically passed in each color. By doing so, since two or more colors are not recorded on the same pixel in the same scan, there is no color unevenness due to the head arrangement order specific to reciprocation. As shown in FIG. 15, 4 is recorded in four types of order.
Since the × 4 dot groups are evenly distributed in the recording area, no color unevenness occurs even if a mixed color image is recorded by any combination of colors.

Further, with respect to the time difference unevenness as described above, the present embodiment in which the 4-pass printing is performed is effective. In the two-pass printing, the recording of a certain area is completed by one reciprocating scan of the carriage, and therefore the printing timing is different for each paper feed width, and these appear as time difference unevenness, which is an adverse effect on the image. However, with 4-pass printing as in this embodiment,
Since all areas are printed by four reciprocating scans, a plurality of print pixels printed at different timings are mixed in each area, and therefore each area is not characterized by the printing scan timing.

Further, the present embodiment is more effective than the above-described embodiments not only for the color unevenness and the time difference unevenness but also for the density unevenness caused by the nozzle variation which was the original target of the divided print recording method. is there. This is because the above embodiment is 1
This is because printing is completed with two nozzles for one color in one main scanning direction, whereas in the present embodiment, printing is completed with four nozzles, so a smoother image can be obtained.

As described above, the thinning mask in units of 4 × 4 dot groups is circulated for each color and
By recording by pass, a smooth high-quality image without color unevenness and time difference unevenness can be obtained by reciprocal printing with high throughput.

(Fourth Embodiment) As a fourth embodiment, the case where the divided recording of the present invention is applied to a recording apparatus having a structure in which four color heads are arranged in a vertical direction in a vertical direction will be described. The structure of the main body is the same as that shown in FIG. 1 except for the recording head. As shown in FIG. 16, in the print head of this embodiment, the print nozzles are arranged in the order of black, cyan, magenta, and yellow in the same direction for four colors.

FIG. 17 shows a recording state in which the present invention is incorporated in such a recording apparatus. Paper is fed by half the width of one color nozzle for each scan, and recording is completed in eight scans per unit area. The head performs bidirectional recording with this recording apparatus, but if the head has such a configuration, there will be no adverse effect on the color unevenness due to the ink ejection order in advance. However, even in the recording apparatus having such a configuration, the present invention has the effect of eliminating the time difference unevenness, or the nozzle unevenness by using the thinning mask in the unit of 4 × 4 dot matrix shown in the first embodiment. It is possible to sufficiently demonstrate its effectiveness, such as the effect on.

In this embodiment, for simplification of the description, an example in which the nozzle groups of four colors are formed without a gap is described, but a gap of a predetermined pixel is provided between the nozzle groups for the convenience of the nozzle configuration. The same printing method can be applied to.

In this embodiment, an ink jet type recording apparatus for forming and recording flying droplets by utilizing thermal energy among the ink jet recording methods has been described as an example. And the principle,
For example, U.S. Pat. Nos. 4,723,129 and 47
What is done using the basic principles disclosed in 40796 is preferred. This method can be applied to both the so-called on-demand type and the continuous type. In particular, in the case of the on-demand type, it is arranged corresponding to the sheet or liquid path holding the liquid (ink). By applying at least one drive signal that gives a rapid temperature rise exceeding each boiling to the electrothermal converter being heated, heat energy is generated in the electrothermal converter, and the heat of the recording head is generated. This is effective because film boiling is caused on the working surface, and as a result, bubbles can be formed in the liquid (ink) that correspond one-to-one to this drive signal. Liquid (ink) flows through the ejection openings due to the growth and contraction of these bubbles.
To form at least one drop. When this drive signal is pulsed, the growth and contraction of the bubbles are performed immediately and appropriately, so the liquid (ink) with excellent responsiveness is used.
It is more preferable that the discharge can be achieved.

Suitable pulse-shaped drive signals are those described in US Pat. Nos. 4,463,359 and 4,345,262. The invention relating to the rate of temperature rise on the heat acting surface is disclosed in US Pat. No. 43.
If the conditions described in the specification of No. 13124 are adopted, more excellent recording can be performed.

As the constitution of the recording head, in addition to the combination constitution of the discharge port, the liquid passage and the electrothermal converter (the straight liquid passage or the right-angled liquid passage) as disclosed in the above-mentioned respective specifications, U.S. Pat. No. 4,558,333, US Pat. No. 4,558,333, which discloses a configuration in which the thermal action is arranged in the region of flexion.
A configuration using the specification of No. 59600 may be used.

In addition, Japanese Patent Application Laid-Open No. 59-123670 discloses a structure in which a common slit is used as a discharge portion of an electrothermal converter for a plurality of electrothermal converters, and a pressure wave of thermal energy is absorbed. A configuration based on Japanese Patent Application Laid-Open No. 59-138461, which discloses a configuration in which an opening corresponds to a discharge portion, may be adopted.

Further, as a full line type recording head having a length corresponding to the width of the maximum recording medium that can be recorded by the recording apparatus, the length can be increased by combining a plurality of recording heads as disclosed in the above-mentioned specification. Either of the structure satisfying the requirement or the structure as one recording head integrally formed may be used.

In addition, by being attached to the apparatus main body, it can be electrically connected to the apparatus main body and can be supplied with ink from the apparatus main body by a replaceable chip type recording head or the recording head itself. The present invention is also effective when a cartridge-type recording head provided with an ink tank is used.

Further, it is preferable to add recovery means, preliminary auxiliary means, etc. to the recording head because the effects of the present invention can be further stabilized. Specific examples thereof include capping means, cleaning means, pressurizing or suctioning means for the recording head, an electrothermal converter or a heating element or a preheating means using a combination thereof, and recording separately. It is also effective to perform the stable recording by performing the preliminary discharge mode for discharging.

In the present embodiment described above, the ink is described as a liquid, but it is an ink that solidifies at room temperature or lower and that softens at room temperature, or is a liquid, or the above-mentioned. In the inkjet method, since the temperature of the ink itself is adjusted within a range of 30 ° C. or higher and 70 ° C. or lower to control the temperature of the ink so that the viscosity of the ink is within a stable ejection range, the ink is applied when a use recording signal is applied. May be liquid.

In addition, the temperature rise due to the thermal energy is positively prevented by using it as the energy for changing the state of the ink from the solid state to the liquid state, or the ink is solidified in the standing state for the purpose of preventing evaporation of the ink. In some cases, such as ink that is liquefied by applying heat energy according to a recording signal and ejected as a liquid ink, or one that has already started to solidify when it reaches a recording medium. It is also possible to use an ink that has the property of being liquefied only by heat energy. In this case,
The ink is disclosed in JP-A-54-56847 or JP-A-6-56.
As described in JP-A No. 0-71260, it may be configured to face the electrothermal converter in a state of being held as a liquid or a solid in the concave portion or the through hole of the porous sheet. In the present invention, the most effective method for each of the above-mentioned inks is to execute the above-mentioned film boiling method.

In addition, as a form of the recording apparatus according to the present invention, in addition to one provided integrally or separately as an image output terminal of information processing equipment such as a word processor or a computer, a copying apparatus combined with a reader or the like, May take the form of a facsimile machine having a transmission / reception function.

Further, the present invention is not limited to the ink jet system using heat energy, but the present invention can be applied to the ink jet system using a piezo element or the like.

[0114]

As described above, according to the present invention, m × n (m and n are positive integers, at least one of which is 2 or more) pixel groups are provided in an area which can be recorded by one main scan. As a unit, the pixel groups are arranged so as not to be adjacent to each other, and printing is performed by a plurality of main scans by using a plurality of thinning patterns having complementary array relationships, so time difference unevenness and color mixture unevenness due to variations in printing elements are performed. It becomes possible to obtain a high quality image by eliminating such problems.

[Brief description of drawings]

FIG. 1 is a perspective view showing a schematic configuration of an inkjet recording apparatus to which the present invention can be applied.

FIG. 2 is a diagram showing a recording head.

3 is a block diagram showing a control unit of the inkjet recording apparatus shown in FIG.

FIG. 4 is a diagram showing a thinning-out array of divided recording according to the present invention.

FIG. 5 is a diagram showing another example of a thinning-out array of divided recording according to the present invention.

FIG. 6 is a diagram showing a recording state using the mask of the thinning array shown in FIG.

FIG. 7 is a diagram showing a recording state using the mask of the thinning array shown in FIG.

FIG. 8 is a diagram showing a relationship between an ink dot protrusion rate and a color difference.

9 is a diagram showing an area affected by a round-trip time difference in divided recording using the mask of the thinning array shown in FIG.

10 is a diagram showing a region affected by a round-trip time difference in divided recording using the mask of the thinning array shown in FIG.

FIG. 11 is a diagram showing an area affected by a round-trip time difference in divided recording using a mask of a thinning array in which one pixel is a unit.

FIG. 12 shows how the binarized data by the dither method is used in the case of divided recording using a mask of a thinning array with one pixel as a unit and in the case of divided recording using the mask of a thinning array shown in FIG. It is a figure explaining whether it is recorded.

FIG. 13 shows how the binarized data by the dither method is used in the case of divided recording using a mask of a thinning array with one pixel as a unit and in the case of divided recording using the mask of a thinning array shown in FIG. It is a figure explaining whether it is recorded.

FIG. 14 is a diagram showing a recording state in the second embodiment.

FIG. 15 is a diagram showing a recording state in the third embodiment.

FIG. 16 is a diagram showing a recording head according to a fourth embodiment.

FIG. 17 is a diagram showing a recording state in the fourth embodiment.

FIG. 18 is a diagram showing an ideal printing state of an inkjet printer.

FIG. 19 is a diagram showing a printing state with density unevenness.

FIG. 20 is a diagram illustrating divided recording.

FIG. 21 is a diagram showing a printing state by divided recording.

FIG. 22 is a diagram showing how ink is absorbed on the paper surface.

FIG. 23 is a diagram showing a conventional thinning-out array for divided recording.

FIG. 24 is a cross-sectional view of a paper surface for explaining a state where color unevenness occurs.

FIG. 25 is a diagram illustrating color unevenness due to conventional divided recording.

FIG. 26 is a diagram illustrating a state in which density unevenness occurs due to a time difference.

FIG. 27 is a diagram illustrating a cause of unevenness in time difference.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical display location B41J 2/485 8804-2C B41J 3/12 M (72) Inventor Norifumi Koitabashi Shimomaruko Ota-ku, Tokyo 3-30 2 Canon Inc. (72) Inventor Shigetasu Nagoshi 3-30 30 Shimomaruko Ota-ku, Tokyo Incorporated Canon Inc. (72) Hitoshi Sugimoto 3-30 Shimomaruko, Ota-ku, Tokyo No. 2 within Canon Inc. (72) Inventor Masaya Uetsuki 3-30-2 Shimomaruko, Ota-ku, Tokyo Within Canon Inc.

Claims (8)

[Claims] 1. A main scanning is performed by moving a printing unit having a plurality of printing elements for ejecting ink in a direction different from the arrangement direction of the plurality of printing elements, and after the main scanning is completed, the main scanning is substantially perpendicular to the main scanning. In an inkjet recording method of recording an image on a recording material by performing a predetermined amount of sub-scanning in various directions, all pixels in a recordable area in one main scanning of the recording unit are in a complementary relationship with each other. The divided and thinned array is divided, and the pixels in the divided area are sequentially recorded by a plurality of main scans to record the area, and the divided and thinned array is m × n (where m and n are An ink jet recording method, characterized in that the pixel groups are arranged so as not to be adjacent to each other in the unit of a pixel group of positive integers, at least one of which is 2 or more. 2. The inkjet recording apparatus according to claim 1, wherein the recording unit includes a plurality of recording heads that eject inks of different colors. 3. The ink jet recording apparatus according to claim 2, wherein a divided thinning arrangement used for a predetermined color among a plurality of colors is different from a divided thinning arrangement used for another color in the same main scanning. Recording method. 4. The area is printed by main scanning a number of times corresponding to the number of printing colors, and a plurality of thinning-out arrangements for each color are sequentially performed by different main scanning. The inkjet recording method described in 1. 5. The ink jet recording method according to claim 1, wherein the pixel group is a rectangular pixel group. 6. The ink jet recording method according to claim 1, wherein the pixel group is a square pixel group. 7. The predetermined amount is an amount corresponding to the number of pixels of a quotient value obtained by dividing the number of recording elements by the number of main scans required to complete recording of the area. The ink jet recording method according to claim 1, which is characterized in that. 8. The inkjet recording method according to claim 1, wherein the recording element ejects an ink droplet by causing a state change in the ink by using thermal energy.