JP5332764B2 - Printing apparatus and printing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the irregularity of density. <P>SOLUTION: The printing apparatus includes: a nozzle array in which a plurality of nozzles for delivering inks on mediums are arranged in a predetermined direction; a moving mechanism which moves the nozzle array to the medium in a direction that intersects the predetermined direction; a conveying mechanism which conveys the medium to the nozzle array in the predetermined direction; and a control part which alternately repeats delivering operations by which an ink is delivered from the nozzle array while the nozzle array is moved by the moving mechanism in the intersection direction, and the conveying operation by which the medium is conveyed by the conveying mechanism in the predetermined direction. The control part makes the medium conveyed by the conveying operation so that an end of a first image formed by the earlier delivering operation and an end of a second image formed by the later delivering operation overlap each other, and makes ink amounts delivered from the nozzles for forming the end of the first image and ink amounts delivered from the nozzles for forming the end of the second image different from each other. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a printing apparatus and a printing method.

An example of a printing apparatus is an ink jet printer (hereinafter referred to as a printer) that ejects ink from nozzles. A nozzle array in which a plurality of nozzles are arranged in a predetermined direction moves ink in a direction that intersects the predetermined direction with respect to the medium. There is known a serial printer that alternately repeats an operation (hereinafter referred to as a pass) and an operation of conveying a medium in a predetermined direction with respect to a nozzle row.
A printing method for a serial printer is a printing method (so-called band) in which an image having a predetermined width is printed in a certain pass, a medium is conveyed by a predetermined width, and an image having a predetermined width is printed again in the next pass. Printing).
However, when a medium transport error occurs, a gap is generated between images having a predetermined width, or ends of images having a predetermined width are overlapped, and streaks appear on the image. Therefore, a printing method in which a joint portion of an image having a predetermined width is divided into two passes, and, for example, printing is performed so that dots formed in the first pass and dots formed in the subsequent pass are alternately arranged. (So-called partial overlap printing) has been proposed.

JP-A-6-47925

By the way, when a large amount of ink is ejected onto a medium (particularly plain paper) at once, a large amount of color material sinks into the medium (inside the fiber), and the density decreases. In partial overlap printing, ink is ejected in two passes at a joint portion of an image, but ink is ejected in one pass in a region other than the joint. Therefore, the color material hardly sinks in the joint portion and the density is relatively high, but the color material easily sinks in a region other than the joint, and the density is relatively low. As a result, uneven density occurs in the image.
Accordingly, an object of the present invention is to reduce density unevenness.

The main invention for solving the above problems is (1) a nozzle row in which a plurality of nozzles for ejecting ink on a medium are arranged in a predetermined direction, and (2) the nozzle row with respect to the medium in the predetermined direction. A moving mechanism that moves in the intersecting direction; (3) a transport mechanism that transports the medium in the predetermined direction with respect to the nozzle row; and (4) the nozzle row is moved in the intersecting direction by the moving mechanism. A control unit that alternately repeats an ejection operation for ejecting ink from the nozzle row and a transportation operation for transporting the medium in the predetermined direction by the transport mechanism, and is formed by the previous ejection operation. The medium is transported by the transport operation so that the end of the first image to be performed and the end of the second image formed by the subsequent ejection operation overlap, and the first image To form the end of And (5) a control unit that makes the amount of ink ejected from the nozzle different from the amount of ink ejected from the nozzle to form the end of the second image. Device.
Other features of the present invention will become apparent from the description of this specification and the accompanying drawings.

FIG. 1A is an overall configuration block diagram of the printer, and FIG. 1B is a perspective view of a part of the printer. It is a figure which shows the nozzle arrangement | sequence in the lower surface of a head. FIG. 3A is a diagram illustrating a state of band printing, and FIG. 3B is a diagram illustrating a state of dot formation when a transport error occurs. FIG. 4A is a diagram illustrating a state of partial overlap printing of a comparative example, and FIG. 4B is a diagram illustrating a state of dot formation when a transport error occurs. 5A and 5B are diagrams illustrating a state in which pigment ink is discharged onto a sheet. It is a figure which shows the partial overlap printing of a comparative example. It is a table | surface which shows the measurement result of the luminance value of the image which performed the partial overlap printing of this embodiment. It is the figure which made the measurement result of FIG. 7A a graph. It is a figure which shows the mode of the partial overlap printing of this embodiment. It is a figure which shows the preparation procedure of print data. FIG. 10 is a diagram illustrating a procedure for creating print data in a print example 2; 11A and 11B are diagrams illustrating how dots are formed in the printing example 3. FIG.

=== Summary of disclosure ===
At least the following will become apparent from the description of the present specification and the accompanying drawings.

That is, (1) a nozzle row in which a plurality of nozzles that eject ink to a medium are arranged in a predetermined direction, and (2) a moving mechanism that moves the nozzle row in a direction intersecting the predetermined direction with respect to the medium. (3) a transport mechanism for transporting the medium in the predetermined direction with respect to the nozzle array; and (4) ejecting ink from the nozzle array while moving the nozzle array in the intersecting direction by the moving mechanism. A control unit that alternately repeats a discharge operation to be performed and a transport operation to transport the medium in the predetermined direction by the transport mechanism, and an end portion of the first image formed by the previous discharge operation In order to form the end portion of the first image by transporting the medium in the transport operation so that the end portion of the second image formed in the subsequent ejection operation overlaps the end portion of the first image. Ejected from nozzle Click amount and an ink amount to be ejected from the nozzle to form the end portion of the second image, and a control unit for varying the, (5) to realize a printing apparatus characterized by having a.
According to such a printing apparatus, it is possible to reduce a difference in sinking amount of the ink colorant between the region where the edge of the image overlaps and the other region, and the overlapping region and the other region Concentration unevenness can be reduced.

In this printing apparatus, the amount of ink ejected from the nozzle to form the end portion of the second image is more than the amount of ink ejected from the nozzle to form the end portion of the first image. Do more.
According to such a printing apparatus, it is possible to further reduce the density unevenness between the region where the edge of the image overlaps and the other region.

In this printing apparatus, the ink ejected from the nozzle is a pigment ink.
According to such a printing apparatus, it is possible to reduce density unevenness between a region where the edges of the image overlap and a region other than the region.

In this printing apparatus, a correction value for a region where the end portion of the first image and the end portion of the second image overlap is stored, and the control unit corresponds to the overlapping region in print data. The gradation value indicated by the pixel to be corrected is corrected with the correction value.
According to such a printing apparatus, it is possible to further reduce the density unevenness between the region where the edge of the image overlaps and the other region.

In this printing apparatus, when the plain paper is selected as the medium, the control unit includes an amount of ink ejected from the nozzle to form an end of the first image, and the second Different ink amounts are ejected from the nozzles to form the edge of the image.
According to such a printing apparatus, when printing on plain paper, it is possible to reduce density unevenness between a region where the edges of the image overlap and other regions, and printing on a medium other than plain paper. In this case, it is possible to further suppress image quality deterioration such as when a conveyance error occurs.

In this printing apparatus, in an area where the end of the first image and the end of the second image overlap, a plurality of dot rows in which dots are arranged in the intersecting direction are arranged in the predetermined direction. In order to form each dot row, the control unit makes the ink amount ejected in the previous ejection operation different from the ink amount ejected in the subsequent ejection operation.
According to such a printing apparatus, it is possible to suppress image quality deterioration such as when a conveyance error occurs.

In this printing apparatus, the control unit may be configured to form dots formed by the discharge operation with the smaller amount of ink discharged from the previous discharge operation and the subsequent discharge operation in the plurality of dot rows. Different positions of the intersecting directions.
According to such a printing apparatus, it is possible to suppress image quality deterioration such as when a conveyance error occurs.

Also, a discharge operation for discharging ink from the nozzle row while moving a nozzle row in which a plurality of nozzles for discharging ink to the medium are arranged in a predetermined direction in a direction intersecting the predetermined direction, and the medium to the nozzle row In contrast, a printing method in which a conveying operation for conveying in the predetermined direction is alternately repeated, and a second image formed by the end portion of the first image formed by the preceding ejection operation and the subsequent ejection operation. The medium is transported so as to overlap the edge of the first image, and the amount of ink ejected from the nozzle to form the edge of the first image and the edge of the second image are formed. In order to achieve this, the printing method is characterized in that the amount of ink ejected from the nozzle is different.
According to such a printing method, it is possible to reduce the difference in sinking amount of the ink colorant between the region where the edge of the image overlaps and the other region, and the overlapping region and the other region Concentration unevenness can be reduced.

=== Configuration of inkjet printer ===
Hereinafter, an embodiment will be described by taking a printing apparatus as an ink jet printer and taking a serial printer (printer 1) in the ink jet printer as an example.

  FIG. 1A is a block diagram of the overall configuration of the printer 1 according to the present embodiment, and FIG. 1B is a perspective view of a part of the printer 1. The printer 1 that has received the print data from the computer 60 that is an external device controls each unit (conveyance unit 20, carriage unit 30, head unit 40) by the controller 10, and forms an image on the paper S (medium). Further, the detector group 50 monitors the situation in the printer 1, and the controller 10 controls each unit based on the detection result.

  The controller 10 is a control unit for controlling the printer 1. The interface unit 11 is for transmitting and receiving data between the computer 60 as an external device and the printer 1. The CPU 12 is an arithmetic processing unit for controlling the entire printer 1. The memory 13 is for securing an area for storing a program of the CPU 12, a work area, and the like. The CPU 12 controls each unit by the unit control circuit 14.

The transport unit 20 (corresponding to a transport mechanism) is for feeding the paper S to a printable position and transporting the paper S by a predetermined transport amount in the transport direction (corresponding to a predetermined direction) during printing.
The carriage unit 30 (corresponding to a moving mechanism) is for moving the head 41 in a direction crossing the transport direction (hereinafter referred to as a moving direction).

  The head unit 40 is for ejecting ink onto the paper S, and has a head 41. A plurality of nozzles that are ink ejecting portions are provided on the lower surface of the head 41. In addition, ink is ejected from the nozzles by driving the piezoelectric elements associated with each nozzle.

  FIG. 2 is a diagram showing the nozzle arrangement on the lower surface of the head 41. A nozzle row in which 360 nozzles (# 1 to # 360) are arranged in the transport direction at a predetermined nozzle pitch (360 dpi) is formed. Four nozzle rows are formed in the head 41, and each ejects ink of a different color. The head 41 of this embodiment includes a yellow nozzle row Y that discharges yellow ink, a magenta nozzle row M that discharges magenta ink, a cyan nozzle row C that discharges cyan ink, and a black nozzle row K that discharges black ink. And having.

  In the serial printer 1 having such a configuration, a dot forming operation in which ink is intermittently ejected from the head 41 moving in the moving direction by the carriage unit 30 to form dots on the paper S, and the paper by the transport unit 20. The carrying operation of carrying S in the carrying direction is repeated alternately. As a result, dots can be formed at positions different from the positions of the dots formed by the previous dot forming operation, and a two-dimensional image can be formed on the paper.

=== Regarding Partial Overlap Printing of Comparative Example ===
FIG. 3A is a diagram illustrating a state of band printing. For simplicity of explanation, the number of nozzles in one nozzle row is 12. Originally, in the printer 1, the medium is transported in the transport direction with respect to the head 41, but in the drawing, the head 41 is drawn in the transport direction. In band printing, an image forming operation for printing a band image by a single movement in the moving direction of the head 41 (hereinafter also referred to as a pass), and an interval between dots positioned at the end of the band image is a nozzle pitch (360 dpi). ) In which the sheet is conveyed by a predetermined conveyance amount F1 alternately and repeatedly.

  In FIG. 3A, a band image composed of white circles (◯) is formed in the first pass (hereinafter referred to as the preceding pass), and black dots (●) are formed in the subsequent pass (hereinafter referred to as the subsequent pass). A configured band image is formed. One band image is configured such that a dot row (hereinafter referred to as a raster line) in which a plurality of dots are arranged in the movement direction is arranged in the transport direction by the number of nozzles every nozzle pitch (360 dpi). Further, the transport amount of the paper so that the interval between the most upstream raster line in the preceding pass band image (◯) and the most downstream raster line in the succeeding pass band image (●) is the nozzle pitch 360 dpi. F1 is determined. As described above, in band printing, raster lines (or dots) in the subsequent pass are not formed between raster lines (or dots) printed in the preceding pass.

  FIG. 3B is a diagram illustrating how dots are formed when a transport error occurs in a transport operation in band printing. Assume that after the band image (◯) is printed in the preceding pass, the sheet is transported by a transport amount F1 + α that is larger than the predetermined transport amount F1. Then, the interval between the raster line on the most upstream side in the preceding pass and the raster line on the most downstream side in the succeeding pass becomes larger than the nozzle pitch (360 dpi + α), and white stripes along the moving direction appear on the image. . Conversely, when the paper is transported with a transport amount smaller than the predetermined transport amount F1 (not shown), the end of the band image of the preceding pass and the end of the band image of the subsequent pass overlap, and the image is over the image. Dark streaks appear along the direction of movement. In this way, when a transport error or the like occurs in band printing, streaks appear on the image and the image quality deteriorates.

  FIG. 4A is a diagram illustrating a state of partial overlap printing of a comparative example. In the partial overlap printing of the comparative example, the dots (◯) formed by the upstream end nozzles (# 9 to # 12 in the drawing) in the preceding pass and the nozzle row in the subsequent pass The dots (●) formed by the downstream end nozzles (# 1 to # 4) are printed so as to be alternately arranged in the transport direction and the movement direction. That is, in partial overlap printing, printing is performed so that the edge of the image formed in the preceding pass overlaps the edge of the image formed in the subsequent pass. Therefore, the downstream end nozzles (# 1 to # 4) are opposed to the area on the sheet facing the upstream end nozzles (# 9 to # 12) in the preceding pass. Then, the sheet is transported in the transport direction by a transport amount F2 (corresponding to a transport operation). For the following description, a joint portion of images printed in two passes is referred to as an “overlapping region”, and an image portion printed in one other pass is referred to as a “normal region”.

  FIG. 4B is a diagram illustrating a state in which a conveyance error occurs in the partial overlap printing of the comparative example. In the drawing, the case where the sheet is conveyed more than the predetermined conveyance amount F2 is shown, and the dots (●) formed in the subsequent pass are formed shifted to the upstream side in the conveyance direction by the conveyance error α. Yes. However, in partial overlap printing, the overlapping area, which is the joint of the image, is divided into two passes for printing, so even if the dots in the subsequent pass are formed in a shifted manner, the dots in the preceding pass are predetermined in the transport direction. Formed at intervals. Therefore, in the band printing (FIG. 3B), a streak occurs on the image when a conveyance error occurs, but in the partial overlap printing (FIG. 4B) of the comparative example, the streak can be prevented from occurring on the image. . As described above, in the partial overlap printing, the overlapping area, which is a joint of images, is printed in two passes, so that it is possible to reduce image quality degradation due to a transport error.

  In partial overlap printing, a raster line is formed by one nozzle in the normal region, and a raster line is formed by two nozzles in the overlapping region. In the overlap line raster line in the partial overlap printing of the comparative example (FIG. 4A), the dot formed in the preceding pass (◯) and the dot formed in the succeeding pass (●) move and move. They are arranged alternately in the direction.

  Therefore, in the overlapping area of the comparative example, the number of dots in the preceding pass and the number of dots in the succeeding pass are equal, and the amount of ink ejected from the nozzle to the overlapping area in the preceding pass and the nozzle in the overlapping area in the following pass The amount of ink ejected from the ink is equal. In other words, in the partial overlap printing of the comparative example, 50% of the pixels corresponding to the overlapping area are assigned to the nozzles of the preceding pass and the succeeding pass on the print data.

=== About sinking of ink coloring material ===
5A and 5B are diagrams illustrating a state in which pigment ink is ejected onto the paper S. FIG. It is assumed that “pigment ink” in which the colorant is a pigment is ejected from the head 41 of the printer 1 of the present embodiment. Since the pigment does not dissolve in the solvent (for example, moisture), the pigment is indicated by “black square (■)” in the figure. The paper S is plain paper.

  In FIG. 5A, first, a predetermined amount of pigment ink is ejected to one of the two pixel areas on the paper corresponding to the two pixels on the print data. When the pigment ink droplets ejected from the nozzles land on the paper S, the solvent component of the pigment ink penetrates into the fibers of the paper S. At this time, most of the pigment components do not penetrate into the fibers of the paper S and remain on the surface of the paper S. Thus, dots are formed by the pigment component on the paper S, and the person recognizes the color on the paper by the pigment component on the paper S.

  In FIG. 5A, after the pigment ink is ejected to one pixel region, the pigment ink is ejected to the other pixel region after a predetermined time has elapsed. At this time, the solvent component of the pigment ink ejected to one pixel region has already penetrated into the sheet S, and the pigment component remains on the sheet S and is fixed. For this reason, the pigment component in one pixel area remains on the paper S even if the pigment ink droplet is ejected to the other pixel area. Similarly, the pigment ink ejected to the other pixel region penetrates into the fibers of the paper S, but the pigment component remains on the surface of the paper S. In this way, in the two pixel regions of FIG. 5A, a relatively large amount of pigment component remains on the paper S, has good color development, and is visually perceived deeply by humans.

  In FIG. 5B, a predetermined amount of pigment ink is simultaneously ejected to two pixel regions on the paper. When ink droplets are simultaneously ejected to adjacent pixel regions, the two pigment ink droplets that have landed on the paper S affect each other. Therefore, the amount of pigment ink droplets on the pixel region is larger than when pigment ink droplets are ejected in two steps as shown in FIG. 5A. Then, when the solvent component of the pigment ink penetrates into the fiber of the paper S, the pigment component located below the landed pigment ink droplet sinks into the fiber of the paper S due to the weight of the other pigment component. End up. Eventually, some pigment components stay on the surface of the paper S, but some pigment components sink into the fibers of the paper S. For this reason, in the two pixel regions in FIG. 5B, the amount of the pigment component remaining on the paper S is reduced, the color developability is poor, and it is visually perceived lightly by humans.

  As described above, in FIGS. 5A and 5B, the surface of the sheet S is the surface of the paper S in which the pigment ink is ejected in two times even though the same amount of the pigment ink is ejected to the two pixel regions. In FIG. 5B in which the pigment ink is discharged at the same time, there are fewer pigment components remaining on the surface of the paper S. When the pigment component sinks into the fiber of the paper, the color developability deteriorates. Therefore, the image in which the pigment ink is ejected twice as shown in FIG. 5A is darker than the image in which the pigment ink is ejected once as in FIG. 5B.

  When the ink is ejected in two times as shown in FIG. 5A, the amount of ink ejected simultaneously with respect to the unit area (for two pixel areas in FIG. 5) is small, and the ink is 1 as shown in FIG. 5B. “Discharging at a time” means that a large amount of ink is simultaneously discharged to the unit area. Therefore, the smaller the amount of ink ejected simultaneously to the unit area, the more difficult the pigment component sinks into the fibers of the paper S, the better the color development, and the greater the amount of ink ejected simultaneously to the unit area. It can be said that the pigment component easily sinks into the fibers of the paper S and has poor color development.

  FIG. 5B shows a phenomenon in which pigment ink droplets are simultaneously ejected to two pixel regions, but immediately after a pigment ink droplet is ejected to one pixel region, adjacent pixel regions It is considered that the same phenomenon as in FIG. 5B also occurs when pigment ink droplets are discharged. That is, when a pigment ink droplet is ejected to an adjacent pixel region in a short period of time after the pigment ink droplet lands on one pixel region and before the pigment ink droplet penetrates into the inside of the paper S, In this case, some pigment components sink into the inside of the paper S due to influences on each other. That is, when ink is ejected at a short time interval with respect to the unit area, the pigment component easily sinks into the fibers of the paper S, and the color developability deteriorates.

  In addition, when a special paper (for example, coated paper, glossy paper) or a film (for example, an OHP sheet) whose surface is coated is used as a medium, such a phenomenon is caused because the pigment component does not easily sink into the medium. Is unlikely to occur. In addition, not only when plain paper is used as a medium, but when a pigment component sinks inside the medium, such a phenomenon occurs.

  The same phenomenon occurs not only in the pigment ink but also in the dye ink whose colorant is a dye. Therefore, even the printer 1 that uses dye ink may perform the printing method described below. However, it is considered that the phenomenon shown in FIGS. 5A and 5B is more likely to occur in the pigment ink because the dye is easily dissolved in the solvent but the pigment is not dissolved in the solvent.

  FIG. 6 is a diagram illustrating density unevenness that occurs when partial overlap printing of a comparative example is performed using pigment ink. The shaded portion in the figure corresponds to the normal region, and the cross portion corresponds to the overlapping region. As described above, in the partial overlap printing of the comparative example, the printing is performed so that the joint portions (edge portions) of the image formed in one pass overlap. For this reason, printing is performed in two passes for the overlapping region, which is a joint between images, and printing is performed in one pass for the other normal regions.

  As shown in FIG. 4A, in the partial overlap printing of the comparative example, one raster line (dot row along the moving direction) in the normal area is formed in one pass, whereas 1 in the overlapping area. In one raster line, after half dots are formed in the preceding pass, the remaining half dots are formed in the subsequent pass. In the raster line of the overlapping area, the dots in the preceding pass and the dots in the succeeding pass are alternately formed in the moving direction and the carrying direction.

  That is, in the partial overlap printing of the comparative example, the amount of ink ejected to the unit area simultaneously or at a short time interval is larger in the normal area than in the overlapping area. Therefore, in the normal region, the pigment component easily sinks inside the medium and the density is visually recognized as low, and in the overlap area, the pigment component hardly sinks inside the medium, the density is visually recognized as high, and density unevenness occurs in the entire image. In FIG. 4A, since the number of nozzles is reduced, the difference in the width in the transport direction between the normal area and the overlapping area is small, but the width of the overlapping area is actually smaller than the width of the normal area. For this reason, the overlapping region appears as a dark streak on the image due to the difference in sinking of the pigment component, and the image quality is deteriorated.

  In view of this, an object of the present embodiment is to reduce density unevenness between the normal region and the overlapping region, which is generated due to the difference in sinking of the colorant (pigment component) when partial overlap printing is performed.

=== Regarding Partial Overlap Printing of this Embodiment ===
In this embodiment, in order to eliminate the density unevenness between the normal region and the overlapping region due to the difference in the subtraction of the pigment component, the subsidence of the pigment component in the overlapping region is increased to be equivalent to the subsidence of the pigment component in the normal region. To. As described above, the greater the amount of ink ejected simultaneously or at short time intervals in the unit area, the more easily the pigment component sinks. Therefore, in the partial overlap printing of the comparative example, the amount of ink ejected in the preceding pass and the amount of ink ejected in the subsequent pass are made the same for the overlapping region, whereas the partial overprinting of this embodiment is performed. In wrap printing, the amount of ink ejected in the preceding pass (previous ejection operation) and the subsequent pass (following) for the overlapping region (the region where the edge of the first image overlaps the edge of the second image) The amount of ink discharged in the discharge operation) is made different.

  That is, the amount of ink ejected simultaneously (or at a short time interval) in the overlapping area in either the preceding pass or the subsequent pass is increased. By doing so, in the path where a large amount of ink is ejected to the overlapping area, the pigment component sinks a lot inside the paper, so that the sinking of the pigment component in the overlapping area becomes closer to the sinking of the pigment component in the normal area. I can do it. As a result, the density difference between the overlap region and the normal region can be reduced.

  FIG. 7A shows a luminance value (L value: indicates brightness per unit area) of an image on which partial overlap printing was performed by changing the ink ejection amount with respect to the overlapping region in the preceding pass and the subsequent pass. It is a table | surface which shows a result, FIG. 7B is the figure which made the measurement result of FIG. 7A a graph. The image whose luminance value is measured is an image printed on plain paper with pigment ink, and the print resolution in the conveyance direction and the movement direction is “360 dpi × 360 dpi”. Further, the ratios of ink discharge amounts of cyan C, magenta M, yellow Y, and black K are 28%, 17%, 5%, and 64%. The normal area is printed in one pass, and the overlapping area is printed in two passes. It is a printed image.

  Since the pigment component sinks into the inside of the paper in the normal region, when the normal region is viewed from the back side (the side opposite to the printing surface) of the paper, the image is easily visible due to the sinked pigment component. On the contrary, since the pigment component stays on the surface of the paper in the overlapping area, it is difficult to see the image when the overlapping area is viewed from the back side of the paper. The paper used when performing the measurement result of FIG. 7A is white, and as the pigment component sinks into the paper, the brightness value measured from the back side of the paper becomes lower (looks darker). That is, since the pigment component sinks in the normal area compared to the overlap area, the brightness value in the normal area is lower than the brightness value in the overlap area.

  The measurement result in FIG. 7A shows the difference between the luminance value in the normal region and the luminance value in the overlapping region. For example, in the result of No. 1 in FIG. 7A, among the amount of ink ejected to the overlapping area, the ink ejection amount in the preceding pass is set to 6.25%, and the ink ejection amount in the subsequent pass is set to 93.75%. The difference in luminance value between the normal area and the overlapping area (on the back side) is “0.233”.

  The small difference in luminance value between the overlapping region and the normal region means that the subsidence amount of the pigment component in the overlapping region has approached the subsidence amount of the pigment component in the normal region. For this reason, the smaller the difference in luminance value between the normal area and the overlap area, the smaller the density difference between the overlap area and the normal area when the paper is viewed from the front surface, and density unevenness can be eliminated.

  From the results of FIGS. 7A and 7B, when the ratio of the ink discharge amount of the preceding pass and the ink discharge amount of the subsequent pass is set to 50% (No. 8 result), the difference in luminance value between the normal region and the overlap region (2. 328) is the largest. From this result, when the ink amount ejected from the preceding pass and the ink amount ejected from the subsequent pass are made the same for the overlapping region as in the partial overlap printing of the comparative example (FIG. 4A), the normal region and the overlapping region It can be seen that the density difference of the image becomes the largest and the image quality is most deteriorated.

  As the ink discharge amount in the preceding pass is made larger than the ink discharge amount in the subsequent pass (as a result of a larger number), the difference in luminance value between the normal region and the overlap region becomes smaller, and density unevenness is eliminated. Further, as the ink discharge amount in the subsequent pass is made larger than the ink discharge amount in the previous pass (as the result of a smaller number), the difference in luminance value between the normal region and the overlap region becomes smaller, and density unevenness is eliminated.

  That is, density unevenness is eliminated as the amount of ink ejected to the overlapping region is increased in either one of the preceding pass and the subsequent pass. This is because, as the amount of ink ejected to the overlapping area in one pass increases, the amount of ink ejected simultaneously (or at a short time interval) to the unit area increases, and in the same way as in the normal area, the pigment inside the paper This is because the amount of sinking of the component increases.

  Further, when the ratio of the amount of ink ejected to the overlapping area in the subsequent pass is maximized (the first result), the difference in luminance value between the normal area and the overlapping area (0.233) overlaps in the preceding pass. When the ratio of the amount of ink ejected to the area is maximized (the 15th result), it is smaller than the difference (0.502) in the luminance value between the normal area and the overlapping area, and density unevenness is further eliminated. In other results (for example, the comparison between the second result and the 14th result), the amount of ink ejected in the overlapping area in the subsequent pass is made larger than the amount of ink ejected in the overlapping area in the preceding pass (the second result) By making the amount of ink ejected to form the edge of the image larger than the amount of ink ejected to form the edge of the first image), the difference in luminance value between the normal region and the overlapping region is further increased. Can be small.

  That is, by increasing the ink discharge amount of the subsequent pass relative to the ink discharge amount of the preceding pass, the density unevenness between the normal region and the overlap region can be further improved. Specifically, among the ink amounts to be ejected in the overlapping area, 94% of the ink amount is ejected in the subsequent pass, and the remaining 6% of the ink amount is ejected in the preceding pass. Improved.

  In summary, in the partial overlap printing of the present embodiment, the amount of ink ejected to the overlapping area in the preceding pass and the amount of ink ejected to the overlapping area in the subsequent pass are made different from each other in the same manner as in the normal area. The amount of subsidence of the pigment component in the overlapping region is increased, and the density unevenness in the normal region and the overlapping region is reduced. Further, the density unevenness can be further improved by increasing the amount of ink ejected to the overlapping area in the subsequent pass as compared to the amount of ink ejected to the overlapping area in the preceding pass.

<Printing example 1>
FIG. 8 is a diagram illustrating dots formed by partial overlap printing according to the present embodiment, and FIG. 9 is a diagram illustrating a print data creation procedure in the first printing example. In the printing example 1, it is assumed that 6% of the amount of ink discharged to the overlapping region is discharged in the preceding pass, and the remaining 94% of the ink amount is discharged in the subsequent pass. However, the present invention is not limited to this, and an ink amount of 94% may be ejected in the preceding pass, and an ink amount of 6% may be ejected in the subsequent pass. In FIG. 8, it is assumed that ink droplets are ejected from all nozzles at predetermined intervals (that is, all pixels indicate dot formation), and dots formed in pass 1 and pass 3 are white circles (◯ ), And dots formed in pass 2 are indicated by black circles (●).

  In FIG. 8, one raster line is composed of 16 dots, and four raster lines (dot rows along the moving direction) belonging to the overlapping region of pass 1 and pass 2 are each of the preceding pass 1. It is composed of one dot (◯) and fifteen dots (●) in the second pass. In this way, by setting the ink discharge amount (number of dots to be formed) in the subsequent pass to be larger than the ink discharge amount (number of dots to be formed) in the preceding pass with respect to the overlapping region, the sinking of the pigment component in the overlapping region The amount of entrainment is brought close to the amount of subsidence of the pigment component in the normal region. Thus, density unevenness between the overlapping region and the normal region is reduced. Even if a transport error occurs, the overlap area, which is a joint between the image of the preceding pass and the succeeding pass, is printed in two passes, so that there is a gap at the joint of the image as in band printing shown in FIG. 3B. Can be prevented.

  Next, a print data creation procedure (FIG. 9) for the printer 1 to perform printing as shown in FIG. 8 will be described. In the printing system of this embodiment, it is assumed that the computer 60 performs print data to be printed by the printer 1 according to a printer driver stored in the memory of the computer 60. The print data created in the computer 60 is transmitted to the printer 1, and the controller 10 of the printer 1 controls the printing operation according to the print data. Therefore, in this embodiment, the printing system in which the computer 60 and the printer 1 are connected corresponds to a “printing apparatus”, and the computer 60 in which the printer driver is installed and the controller 10 of the printer 1 correspond to a “control unit”.

  Further, the print data is not limited to being generated by the computer 60 connected to the printer. For example, the controller 10 of the printer 1 generates the print data, and the ink amount and the subsequent pass that are ejected to the overlapping area in the preceding pass. The amount of ink ejected to the overlapping area may be varied. In this case, the printer 1 alone corresponds to the printing apparatus, and the controller 10 of the printer 1 corresponds to the control unit.

  First, in the resolution conversion process (S001), image data output from various application programs of the computer 60 is converted into a resolution for printing on paper. The image data after the resolution conversion process is multi-gradation data (RGB data) represented by an RGB color space. In the next color conversion process (S002), the RGB data is converted into CMYK data represented by the CMYK color space corresponding to the ink of the printer 1.

  Then, in the halftone process (S003), the multi-gradation data is converted into the gradation data that can be formed by the printer 1. Assume that the printer 1 of this embodiment forms dots of one type of size. In this case, one pixel is expressed by two gradations of “form a dot” and “do not form a dot”.

  Thereafter, the computer 60 determines whether printing based on the image data is performed on “plain paper”. If “plain paper” is selected by the user (S004 → YES), print data is created so as to perform partial overlap printing (FIG. 8) of this embodiment. If the user selects a paper other than plain paper (S004 → NO), print data is created so as to perform partial overlap printing (FIG. 4A) of the comparative example.

  As described above, the ease of sinking of the pigment component (colorant) varies depending on the type of medium. When using a medium that causes the pigment component to sink when a large amount of ink is ejected at once, such as plain paper, the amount of ink ejected to the overlapping area in the preceding pass and the ejecting to the overlapping area in the subsequent pass The amount of ink to be changed is changed (that is, the partial overlap printing of the present embodiment in FIG. 8 is performed). By doing so, the difference between the subsidence amount of the pigment component in the normal region and the subsidence amount of the pigment component in the overlapping region can be reduced, and uneven density can be eliminated. In the flow of FIG. 9, plain paper is used as a criterion for determination in S004. However, the present invention is not limited to this, and when a medium in which the pigment component easily sinks is used, the partial overlap printing of this embodiment is performed. It is good to do.

  When a paper other than plain paper is selected, the amount of ink ejected to the overlapping area in the preceding pass and the amount of ink ejected to the overlapping area in the subsequent pass, as in the partial overlap printing of the comparative example (FIG. 4A) Are equal (the number of pixels assigned to the nozzles in the preceding pass is equal to the number of pixels assigned to the nozzles in the subsequent pass). By doing so, it is possible to further suppress image quality deterioration when a conveyance error occurs. For example, as shown in FIG. 4B, when the transport error is larger than the predetermined transport amount F2, even if the dots in the subsequent pass are formed shifted to the upstream side in the transport direction, the preceding pass is formed at the joint portion of the image. Since a relatively large number of dots (half of the dots that should be originally formed) are formed, image quality deterioration due to transport errors can be further suppressed. Also, if the medium other than plain paper and the pigment component is difficult to sink inside, the pigment component sinks even if the amount of ink ejected to the overlapping area is 50% in the preceding pass and the subsequent pass. Concentration unevenness due to the difference in density does not occur.

  If plain paper is selected (S004 → YES), whether or not the pixels (hereinafter referred to as ejection pixels) that form dots among the pixels corresponding to the overlapping area are assigned to the nozzles of the preceding pass or after It is determined whether the nozzle is assigned to the row pass (S005). Here, of the ejection pixels corresponding to the overlapping region, 94% of the pixels are assigned to the nozzles in the subsequent pass, and 6% of the pixels are assigned to the nozzles in the preceding pass. By doing so, the ratio of “the amount of ink ejected to the overlapping area in the subsequent pass and the ink amount ejected to the overlapping area in the preceding pass” can be set to “94: 6”, and the difference in sinking of the pigment component It is possible to reduce the density unevenness due to.

  In the overlapping area raster line shown in FIG. 8, 15 dots (16 in pass 2) out of 16 dots arranged in the movement direction are formed by nozzles in the subsequent pass, and one dot (pass 1). Of ○) is formed by the nozzle of the preceding pass. That is, the ink amount (16 dots) for forming one raster line belonging to the overlapping area is 6% (1 dot) of the ink amount ejected from the nozzle of the preceding pass, and the subsequent pass The amount of ink ejected from these nozzles occupies 94% (15 dots).

  As described above, when the overlapping region is composed of a plurality of raster lines, a predetermined ratio (here, 6% and 94) is set for each raster line (for each of a plurality of dot rows in which dots are arranged in the intersecting direction). %), The number of dots formed in the preceding pass may be different from the number of dots formed in the subsequent pass. For this purpose, the computer 60 converts the ejection pixels in a plurality of pixels (hereinafter referred to as pixel columns) arranged in a direction corresponding to the moving direction on the image data at a predetermined ratio to the nozzles in the preceding pass and the nozzles in the subsequent pass. Assign to. By doing so, even if the amount of ink ejected to the overlapping area in one pass is reduced, there is a dot in one pass in each raster line. Therefore, even if a transport error occurs, it is possible to prevent white streaks from occurring on the image as in the band printing in FIG. 3B.

  In FIG. 8, since one raster line is composed of 16 dots, the number of dots formed by the nozzles in the preceding pass is one. However, in practice, since one raster line is composed of a large number of dots, the number of dots formed by the nozzles in the preceding pass is also plural. At this time, in one raster line in the overlapping region, it is preferable that the dots (◯) in pass 1 that reduce the ink amount are arranged at predetermined intervals in the movement direction. In other words, the dots in pass 1 should be arranged in a balanced manner in the movement direction without being biased. Specifically, in FIG. 8, since the dots of pass 1 are formed at a ratio of 1 to 16, it is preferable to arrange the dots of pass 1 every 16 dots. By doing so, it is possible to further suppress image quality deterioration when a conveyance error occurs.

  In addition, in the plurality of raster lines belonging to one overlapping region, the positions of the dots in the movement direction of the path that reduces the ink discharge amount are made different. Specifically, as shown in FIG. 8, in the overlapping region of pass 1 and pass 2, a second digit dot is formed by the nozzle of pass 1 in the most downstream raster line, and then the downstream raster line. In, the 6th digit dot is formed by the pass 1 nozzle, the 10th digit dot is formed by the pass 1 nozzle in the downstream raster line, and the 14th digit dot is passed in the most upstream raster line. 1 nozzle.

  As described above, when there are a plurality of raster lines belonging to the overlapping region, it is preferable to disperse the dots in the pass that reduces the ink discharge amount in different raster lines in the moving direction. For this purpose, the computer 60 sets, for each pixel column, the position (digit number) in the moving direction of the ejection pixel assigned to the nozzle of the pass that reduces the ink ejection amount in each pixel column corresponding to the plurality of raster lines in the overlapping region. To be different. Furthermore, in each pixel row corresponding to a plurality of raster lines in the overlapping area, it is preferable that the ejection pixels assigned to the nozzles in the path for reducing the ink ejection amount are arranged in a balanced manner in the movement direction without being biased. In FIG. 8, every fourth dot (◯) in pass 1 is formed in the moving direction in a plurality of raster lines in the overlapping area.

  By doing so, even if the amount of ink ejected to the overlapping region in one pass is reduced, the dots in one pass are dispersed in the moving direction in the entire overlapping region, so that even if a transport error occurs It is possible to prevent white streaks from occurring on the image as in the band printing in FIG. 3B.

  Then, after the ejection pixels corresponding to the overlap area are allocated to the nozzles in the preceding pass and the nozzles in the subsequent pass, the computer 60 transfers the matrix pixel data to the printer 1 as rasterization processing (S006). Sort in order of data to be used. The print data generated through these processes is transmitted to the printer 1 together with command data (such as a conveyance amount) corresponding to the printing method.

  Summarizing the above, in printing example 1, in order to make the amount of ink ejected to the overlapping area in the preceding pass different from the amount of ink ejected to the overlapping area in the subsequent pass, among the pixels corresponding to the overlapping area on the print data, Are assigned to the nozzles in the preceding pass and the nozzles in the subsequent pass at a predetermined ratio (for example, 6% and 94%) for each raster line (for each pixel column). By doing so, the density unevenness of the normal region and the overlapping region can be reduced. Further, the ejection pixels allocated to the nozzles in the pass that reduces the amount of ink ejected to the overlapping area are dispersed in the movement direction. By doing so, image quality deterioration can be suppressed even if a transport error occurs.

  Further, as in the print data creation flow shown in FIG. 9, after the halftone process, the ejection pixels of the pixels corresponding to the overlapping area are set at a predetermined ratio (for example, 6% and 94%) in the nozzles of the preceding pass. It is not limited to assigning to the nozzles in the subsequent pass. Regardless of whether the pixels corresponding to the overlapping region are ejection pixels or non-ejection pixels on the print data, the nozzles in the preceding pass and the nozzles in the subsequent pass may be assigned at a predetermined ratio.

  By doing so, for example, if the number of pixels allocated to the nozzles of the preceding pass is reduced, the amount of ink ejected from the nozzles of the preceding pass to the overlapping region can be reduced, and the pixels allocated to the nozzles of the subsequent pass If the number is increased, the amount of ink ejected from the nozzles in the subsequent pass to the overlapping region can be increased. As a result, the amount of ink ejected to the overlapping area in the preceding pass and the succeeding pass can be made different, density unevenness in the normal area and the overlapping area can be reduced, and compared with the print data creation flow of FIG. Thus, the process of creating print data by the computer 60 can be facilitated.

  However, as shown in the print data creation flow in FIG. 9, it is more likely that the ejection pixels among the pixels corresponding to the overlapping area are assigned to the nozzles in the preceding pass and the nozzles in the succeeding pass at a predetermined ratio in the preceding pass. The amount of ink ejected to the region and the amount of ink ejected to the overlapping region in the subsequent pass can be reliably set to a predetermined ratio.

  Also, the more pixels in the overlapping area are ejection pixels (for example, solid printing), the higher the probability that dots will be formed in the neighboring pixel area of a certain pixel area. It is necessary to adjust the amount of ink ejected simultaneously to the unit area (a certain pixel area and a neighboring pixel area) by adjusting the ink ejection quantity in the subsequent pass (adjusting the sinking amount of the pigment component). . However, when the number of ejected pixels in the overlapping region is small, the probability of forming dots in the neighboring pixel region of a certain pixel region is low, so that the ink that is ejected simultaneously to the unit region (a certain pixel region and the neighboring pixel region) The necessity of adjusting the amount is low, and the necessity of deliberately changing the ink discharge amount of the preceding pass and the ink discharge amount of the subsequent pass is reduced. Therefore, the computer 60 may perform the partial overlap printing according to the present embodiment when the number of dots (the number of ejection pixels) formed in the overlapping region is larger than, for example, a threshold value.

<Printing example 2>
FIG. 10 is a diagram illustrating print data creation processing in the second printing example. In the printing example 2, density unevenness that cannot be improved only by making the amount of ink ejected to the overlapping area in the preceding pass different from the amount of ink ejected to the overlapping area in the subsequent pass is corrected by the correction value H. Here, even if the amount of ink ejected to the overlap area is different between the preceding pass and the subsequent pass, if the density of the overlap area is still higher than that of the normal area, the pixel corresponding to the overlap area is determined by the correction value H. Is corrected to a gradation value with a lighter density.

  In order to calculate such a correction value H, it is preferable to cause the printer 1 to actually perform the partial overlap printing (FIG. 8) of the present embodiment in the manufacturing process of the printer 1 to form a test pattern. . As a test pattern, one or a plurality of images having uniform predetermined gradation values may be printed by the partial overlap printing (FIG. 8) of the present embodiment. The test pattern is read by a scanner or the like, and the reading gradation value of the normal area and the reading gradation value of the overlapping area in an image having a uniform predetermined gradation value are acquired.

  The difference between the reading gradation value of the normal area and the reading gradation value of the overlapping area is uneven density that cannot be improved only by changing the amount of ink ejected to the overlapping area between the preceding pass and the subsequent pass. Therefore, the ratio of the read gradation value St of the normal area to the read gradation value Sc of the overlap area is calculated as a correction value H for reducing the density of the overlap area (H = St / Sc). The calculated correction value H may be stored in the memory 13 of the printer 1 or the like. With this correction value H, the gradation value indicated by the pixel corresponding to the overlapping region is corrected to a gradation value with a light density.

  Specifically, as shown in the flow of FIG. 10, after the color conversion process (S102), the multi-gradation data indicated by the pixels corresponding to the overlapping area is subjected to density correction processing using the correction value H. By correcting the gradation value of the pixel corresponding to the overlap area to a light gradation value using the correction value H, the amount of ink ejected to the overlap area is more than the amount of ink ejected to the normal area even with the same gradation value. And the overlapping area can be prevented from being viewed darker than the normal area.

  In addition, when one image having a uniform predetermined gradation value is formed as a test pattern and one correction value H is calculated based on the image, regardless of the gradation value indicated by the pixel corresponding to the overlapping region, A common correction value H is used. On the other hand, when a plurality of images having a uniform predetermined gradation value are formed as a test pattern and a plurality of correction values H are calculated based on the images, correction according to each gradation value indicated by the pixel corresponding to the overlapping region is performed. The value H may be calculated by linear interpolation of a plurality of correction values H calculated from the test pattern, and density correction processing may be performed.

  In this way, when performing partial overlap printing, if the density unevenness of the normal region and the overlapping region cannot be improved by merely making the amount of ink ejected to the overlapping region different between the preceding pass and the subsequent pass, Furthermore, the gradation value indicated by the pixel corresponding to the overlapping region may be corrected to a gradation value with a light density. By doing so, it is possible to further improve the density unevenness caused by the difference in sinking of the pigment component.

  It should be noted that density unevenness that cannot be improved only by changing the amount of ink ejected to the overlap area between the preceding pass and the subsequent pass is not limited to correcting the gradation value indicated by the pixel corresponding to the overlap area. The gradation value indicated by the pixel corresponding to the normal area may be corrected to a dark gradation value by the correction value H. However, since the number of pixels corresponding to the overlapping area is smaller than the number of pixels corresponding to the normal area, it is easier for the computer 60 to correct the gradation value indicated by the pixels corresponding to the overlapping area.

<Printing example 3>
FIG. 11A is a diagram illustrating how dots are formed when the ratio of the amount of ink ejected to the overlapping area in the preceding pass and the amount of ink ejected to the overlapping area in the subsequent pass is different for each raster line. In the printing example 1 described above (FIG. 8), the ratio between the ink amount of the preceding pass and the ink amount of the subsequent pass in the lath line of the overlapping region is 6% and 94% in all the raster lines. However, the present invention is not limited to this, and the ratio of the ink amount ejected in the preceding pass and the ink amount ejected in the subsequent pass may be made different for each raster line in the overlapping region.

  For example, in FIG. 11A, although the amount of ink ejected to the overlapping area in the preceding pass (pass 1) is smaller than the amount of ink ejected to the overlapping area in the subsequent pass (pass 2), In the raster line close to the downstream side in the direction, the ratio of the amount of ink ejected in the preceding pass is increased.

  Specifically, among the raster lines belonging to the overlapping area of pass 1 and pass 2, the raster line on the most downstream side in the transport direction (normal area side of pass 1) has the ink ejection amount of the preceding pass and the subsequent pass. The ratio is “19% and 81%”, and in the next downstream raster line, the ratio of the ink discharge amount between the preceding pass and the subsequent pass is “13% and 87%”. Of the raster lines belonging to the overlapping area of pass 1 and pass 2, the two raster lines located on the normal area side of the pass 2 (upstream side in the transport direction) have ink ejection amounts of the preceding pass and the subsequent pass. The ratio becomes “6% and 94%”.

  In this way, the ratio of the ink discharge amount of the preceding pass and the subsequent pass is made different for each raster line belonging to the overlapping area, and the ink discharge amount of one pass (pass 1) is changed to that of the other pass (pass 2). Even if the ink discharge amount is smaller than the ink discharge amount, the ratio of the ink discharge amount in one pass is higher in the raster line on the image side in one pass than in the other raster line (dots in one pass). Increase the number). By doing so, the transition from the image of one pass to the image of the other pass can be made smooth, and the joint (overlapping region) between the image of pass 1 and the image of pass 2 can be made less noticeable. I can do it.

  FIG. 11B is a diagram illustrating a state in which raster lines that increase the amount of ink ejected to the overlapping area in the preceding pass and raster lines that increase the amount of ink ejected to the overlapping area in the subsequent pass are mixed in the same overlapping area. . In the above-described printing example 1 (FIG. 8), the ink amount in the subsequent pass is made larger than the ink amount in the preceding pass in all the lath lines in the overlapping region, but this is not restrictive. As shown in FIGS. 7A and 7B, even when the ink amount in the preceding pass is increased or the ink amount in the subsequent pass is increased, the density unevenness between the normal region and the overlapping region can be reduced. An effect is obtained.

  Therefore, among the raster lines in the overlapping area, the raster line close to the normal area side (downstream in the transport direction) of the preceding pass, the ink amount of the preceding path is made larger than the ink amount of the succeeding path, In a raster line close to the region side (upstream side in the transport direction), the ink amount in the subsequent pass may be larger than the ink amount in the preceding pass. By doing so, the transition from the image of the preceding path to the image of the succeeding path can be made smooth, and the joint (overlapping area) between the image of the preceding path and the image of the succeeding path can be made less noticeable. I can do it.

=== Other Embodiments ===
Each of the above embodiments has been described mainly for a printing system having an ink jet printer, but includes disclosure of a density unevenness correction method and the like. The above-described embodiments are for facilitating understanding of the present invention, and are not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and it is needless to say that the present invention includes equivalents thereof. In particular, the embodiments described below are also included in the present invention.

<About printing devices>
The ink ejection method may be a piezo method in which ink is ejected by applying a voltage to the driving element (piezo element) to expand and contract the ink chamber, or by generating bubbles in the nozzle using a heating element, A thermal method in which ink is ejected by the bubbles may be used.

1 Printer, 10 Controller, 11 Interface section, 12 CPU, 13 Memory, 14 Unit control circuit, 20 Transport unit, 30 Carriage unit, 31 Carriage, 40 Head unit, 41 Head, 50 Detector group, 60 Computer

Claims (6)

(1) a nozzle row in which a plurality of nozzles that discharge pigment ink onto a medium are arranged in a predetermined direction;
(2) a moving mechanism that moves the nozzle row with respect to the medium in a direction crossing the predetermined direction;
(3) a transport mechanism that transports the medium in the predetermined direction with respect to the nozzle row;
(4) A discharge operation for discharging pigment ink from the nozzle row while moving the nozzle row in the intersecting direction by the moving mechanism, and a transport operation for transporting the medium in the predetermined direction by the transport mechanism. It is a control unit that repeats alternately,
When plain paper is selected as the medium, the end of the first image formed by the previous ejection operation overlaps the end of the second image formed by the subsequent ejection operation. In order to form the edge of the first image by transporting the medium in the transport operation , the positions of dots formed by ejecting ink from the nozzles, and the second image Different positions of dots formed by ejecting ink from the nozzles to form end portions, and ink amounts ejected from the nozzles to form end portions of the first image; A control unit that varies the amount of ink ejected from the nozzles to form the edge of the second image;
A printing apparatus comprising (5).
The printing apparatus according to claim 1,
Making the amount of ink ejected from the nozzles to form the end of the second image larger than the amount of ink ejected from the nozzles to form the end of the first image;
Printing device.
The printing apparatus according to claim 1 or 2 , wherein
Storing a correction value for a region where an end of the first image and an end of the second image overlap;
The control unit corrects the gradation value indicated by the pixel corresponding to the overlapping region in the print data with the correction value;
Printing device.
The printing apparatus according to any one of claims 1 to 3 ,
In a region where the end of the first image and the end of the second image overlap, a plurality of dot rows in which dots are arranged in the intersecting direction are arranged in the predetermined direction,
The control unit varies the amount of ink ejected in the previous ejection operation and the amount of ink ejected in the subsequent ejection operation to form each dot row,
Printing device.
The printing apparatus according to claim 4 ,
In the plurality of dot rows, the control unit is configured to determine the positions of the intersecting directions of dots formed by the ejection operation with the smaller amount of ink to be ejected of the previous ejection operation and the subsequent ejection operation. Make it different,
Printing device.
A discharge operation for discharging pigment ink from the nozzle row while moving a nozzle row in which a plurality of nozzles for discharging pigment ink are arranged in a predetermined direction in a direction intersecting the predetermined direction, and the medium to the nozzle row In contrast, a printing method in which the conveyance operation of conveying in the predetermined direction is repeated alternately,
When plain paper is selected as the medium, the edge of the first image formed by the previous ejection operation overlaps the edge of the second image formed by the subsequent ejection operation. In order to form the edge of the second image and the position of the dot formed by ejecting ink from the nozzle to form the edge of the first image The positions of dots formed by ejecting ink from the nozzles are different , and the amount of ink ejected from the nozzles to form the end of the first image, and the end of the second image The printing method is characterized in that the amount of ink ejected from the nozzle in order to form the ink is made different.

Images