JP5915719B2 - Fluid ejecting apparatus and fluid ejecting method - Google Patents

Description

  The present invention relates to a fluid ejecting apparatus and a fluid ejecting method.

As one of fluid ejecting apparatuses, there is an ink jet printer (hereinafter referred to as a printer) that ejects ink (fluid) from a head and prints an image on a medium. In some printers, the operation of ejecting ink while moving the head in the movement direction and the operation of conveying the medium in the conveyance direction intersecting the movement direction with respect to the head are performed two-dimensionally on the medium. There is a printer that prints images.
Among printers, there are printers that use white ink in addition to color inks such as cyan, magenta, and yellow (see, for example, Patent Document 1). In such a printer, an image with good color development can be printed without being affected by the ground color of the medium by printing the background image with white ink and the main image with color ink in an overlapping manner.

JP 2002-38063 A

In addition, there is a printer that performs control to change the moving distance of the head according to the position of the end (end) in the moving direction of the image. In such a printer, when a small image is printed, the moving distance of the head is shortened, and the printing time can be shortened.
However, when the background image and the main image are printed in an overlapping manner, if the head movement distance is shortened, the time interval for printing the background image and the main image is shortened, and blurring or color mixing occurs in the image. The image quality of the image deteriorates.
Therefore, an object of the present invention is to suppress image quality deterioration of an image.

A main invention for solving the above problems is that a first nozzle row in which nozzles for ejecting a first fluid are arranged in a predetermined direction, and a second nozzle row in which nozzles for injecting a second fluid are arranged in the predetermined direction. An ejection operation of ejecting fluid from the nozzles while moving the first nozzle row and the second nozzle row in a moving direction intersecting the predetermined direction with respect to the medium, and the first nozzle row and A control unit that executes a transport operation for relatively moving the second nozzle row and the medium in the predetermined direction, and the control unit is configured to perform the operation according to a position of an end of the image in the moving direction. It is possible to control the movement distance of the first nozzle row and the second nozzle row in the moving direction, and a main image formed by the first fluid and a background formed by the second fluid Different images When the recording medium is formed to overlap with the medium by the ejection operation, the movement distance of the first nozzle row and the second nozzle row in the movement direction varies according to the position of the end of the image in the movement direction. It is a fluid ejecting apparatus characterized by not performing control to perform.
The fluid ejection device of the present invention includes a first nozzle row in which nozzles that eject the first fluid are arranged in a predetermined direction, and a second nozzle row in which nozzles that eject the second fluid are arranged in the predetermined direction. A control unit that performs an ejection operation of ejecting fluid by moving the first nozzle row and the second nozzle row in a movement direction that intersects the predetermined direction, and the control unit includes an image. It is possible to control the movement distance of the first nozzle row and the second nozzle row in the movement direction in accordance with the position of the end of the first nozzle row in the movement direction, and the first fluid is formed by the first fluid. When the main image and the background image formed by the second fluid are formed on the medium by the different ejection operations , the first nozzle row and the second nozzle are bidirectional in the moving direction. Flow when moving columns Even in bidirectional printing for ejecting, in the unidirectional printing for ejecting fluid when moving the first nozzle row and the second nozzle array in one direction of the moving direction, the main image and the background Performing an ejection operation of moving the first nozzle row and the second nozzle row in the moving direction not only in an image printing range but also in a range in which the main image and the background image are not printed. It may be a fluid ejecting apparatus.
Other features of the present invention will become apparent from the description of this specification and the accompanying drawings.

1 is an overall configuration block diagram of a printer. 2A is a perspective view of the printer, and FIG. 2B is a diagram illustrating an arrangement of nozzles provided on the lower surface of the head. It is a figure explaining the printing mode which a printer has. 4A is a diagram for explaining a printing method in the white usage mode / front printing mode, and FIG. 4B is a diagram for explaining a printing method in the white usage mode / back printing mode. It is a figure explaining shortest printing control. It is a figure explaining the printing method of a comparative example. FIG. 7A is a flowchart for setting the printing method in the first embodiment, and FIG. 7B is a diagram for explaining the printing method in the first embodiment. FIG. 8A is a flowchart for setting the printing method in the second embodiment, and FIG. 8B is a diagram for explaining the printing method in the second embodiment. FIG. 9A is a flowchart for setting the printing method in the third embodiment, and FIG. 9B is a diagram for explaining the printing method in the third embodiment. It is a figure explaining the shortest distance from the image edge part in another image to the medium edge part. It is a setting flow of the printing method in 4th Example. It is a figure explaining the printing method of 4th Example. It is a setting flow of the printing method in 5th Example. 14A and 14B are diagrams illustrating a printing method according to the fifth embodiment. It is a setting flow of the printing method in 7th Example.

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

(A) a first nozzle row in which nozzles for ejecting a first fluid are arranged in a predetermined direction; (B) a second nozzle row in which nozzles for injecting a second fluid are arranged in the predetermined direction; C) an ejection operation of ejecting fluid from the nozzles while moving the first nozzle row and the second nozzle row in a moving direction intersecting the predetermined direction with respect to the medium; the first nozzle row; A control unit that repeatedly executes a transport operation for relatively moving the second squeeze row and the medium in the predetermined direction, and formed by the main image formed by the first fluid and the second fluid. When the background image to be formed is superimposed on the medium by the different ejection operations, the first nozzle row and the second nozzle row are moved in the moving direction according to the position of the edge in the moving direction of the image. The moving distance of The control of a control unit is not performed, a fluid jet apparatus characterized by having (D).
According to such a fluid ejecting apparatus, even when the main image and the background image are formed to overlap each other, it is possible to prevent blurring and color mixing of the image, and to suppress image quality deterioration of the image.

In the fluid ejecting apparatus, the control unit may form the first nozzle row according to a position of an end of the image in the moving direction when the main image is formed on the medium without overlapping the background image. And control for changing the moving distance of the second nozzle row in the moving direction.
According to such a fluid ejecting apparatus, the image forming time can be shortened.

In the fluid ejecting apparatus, the control unit may form the first image when forming the first image on the predetermined area of the medium when the main image and the background image are formed to overlap each other. When the distance from the end of the image on the side assumed to move the nozzle row and the second nozzle row in the moving direction to the assumed side end in the moving direction of the medium is less than a threshold value, When the first nozzle row and the second nozzle row are moved to the same side in the moving direction of the jetting operation, fluid is jetted from the nozzle, and when the distance is equal to or greater than the threshold, the previous jetting is performed. When the first nozzle row and the second nozzle row are moved to the opposite side in the movement direction, the fluid is ejected from the nozzle.
According to such a fluid ejecting apparatus, it is possible to shorten the image forming time while suppressing image quality deterioration of the image.

In the fluid ejecting apparatus, the control unit may move the first nozzle row and the second nozzle row to one side in the moving direction when the main image and the background image are formed to overlap each other. From an end on the one side in the moving direction of an image to be formed first with respect to a predetermined region of the medium during the certain ejection operation to move, to an end on the one side in the moving direction of the medium When the distance is less than the threshold value, during the injection operation next to the certain injection operation, when moving the first nozzle row and the second nozzle row to the one side in the movement direction, When the fluid is ejected and the distance is equal to or greater than the threshold value, the first nozzle row and the second nozzle row are moved to the other side in the movement direction at the time of the ejection operation following the certain ejection operation. When letting the nozzle Thereby ejecting a fluid.
According to such a fluid ejecting apparatus, it is possible to shorten the image forming time while suppressing image quality deterioration of the image.

In the fluid ejecting apparatus, the control unit may move the first nozzle row and the second nozzle row to one side in the moving direction when the main image and the background image are formed to overlap each other. The moving direction of the medium from the end on the one side in the moving direction of an area that overlaps an image to be formed later, among images that are formed first with respect to a predetermined area of the medium during the ejecting operation to be moved When the distance to the one-side end of the nozzle is less than a threshold value, the first nozzle row and the second nozzle row are moved in the moving direction at the time of the injection operation following the certain injection operation. When the fluid is ejected from the nozzle, the fluid is ejected from the nozzle. When the distance is equal to or greater than the threshold value, the first nozzle row and the second nozzle row at the time of the ejection operation following the certain ejection operation. The moving direction When moving to the other side, thereby ejecting fluid from the nozzles.
According to such a fluid ejecting apparatus, it is possible to shorten the image forming time while suppressing image quality deterioration of the image.

In this fluid ejecting apparatus, the control unit moves the first nozzle row and the second nozzle row in both directions in the moving direction when the main image and the background image are formed to overlap each other. Control is performed to eject the fluid from the nozzles when the first nozzle row and the second nozzle row are moved in the moving direction when an image to be formed first on a predetermined area of the medium is formed. When the distance from the edge of the image on the moving side to the edge on the moving side in the moving direction of the medium is less than the threshold, the ejection operation is performed as compared with the case where the distance is equal to or more than the threshold. Increase the time interval.
According to such a fluid ejecting apparatus, it is possible to shorten the image forming time while suppressing image quality deterioration of the image.

In the fluid ejecting apparatus, the control unit may move the first nozzle row and the second nozzle row to one side in the moving direction when the main image and the background image are formed to overlap each other. Implement control to eject fluid from the nozzle only when it is moved.
According to such a fluid ejecting apparatus, when the main image and the background image are formed so as to overlap each other, it is possible to more reliably prevent image blurring and color mixing.

Further, a first nozzle row in which nozzles for ejecting the first fluid are arranged in a predetermined direction, and a second nozzle row in which nozzles for ejecting the second fluid are arranged in the predetermined direction intersect with the predetermined direction. A fluid ejection method for performing an ejection operation of ejecting a fluid from the nozzle while moving in a moving direction, wherein a main image formed by the first fluid is different from a background image formed by the second fluid When the image is formed so as to overlap with the medium in the ejection operation, the movement distance of the first nozzle row and the second nozzle row in the movement direction is changed according to the position of the end of the image in the movement direction. Without performing the jetting operation, and carrying out a transporting operation in which the first nozzle row, the second nozzle row, and the medium move relative to each other in the predetermined direction. Fluid injection It is the law.
According to such a fluid ejection method, even when the main image and the background image are formed to overlap each other, it is possible to prevent blurring and color mixing of the image, and it is possible to suppress image quality deterioration of the image.

=== About the printing system ===
Hereinafter, an embodiment will be described by taking as an example a printing system in which an inkjet printer (hereinafter referred to as a printer) and a computer are connected.

  FIG. 1 is a block diagram of the overall configuration of the printer 1. FIG. 2A is a perspective view of the printer 1, and FIG. 2B is a diagram illustrating an arrangement of nozzles provided on the lower surface of the head 41. FIG. 2B is a diagram in which the nozzle is virtually seen from the upper surface of the head 41. The computer 60 is communicably connected to the printer 1 and outputs print data for causing the printer 1 to print an image to the printer 1. The computer 60 is installed with a program (printer driver) for converting image data output from the application program into print data. The printer driver is stored in a storage medium such as a CD-ROM or can be downloaded to a computer via the Internet.

  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 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 detector group 50 monitors the situation in the printer 1, and the controller 10 controls each unit based on the detection result.

The transport unit 20 feeds the medium S to a printable position, and transports the medium S by a predetermined transport amount in the transport direction during printing.
The carriage unit 30 is for moving the head 41 in a movement direction that intersects the conveyance direction, and includes a carriage 31.

  The head unit 40 is for ejecting ink onto the medium S and has a head 41. The head 41 is moved in the movement direction by the carriage 31. A plurality of nozzles that are ink ejecting units are provided on the lower surface of the head 41, and each nozzle is provided with an ink chamber (not shown) filled with ink.

  As shown in FIG. 2B, on the lower surface of the head 41, five nozzle rows are formed in which 180 nozzles are arranged at a predetermined interval D (eg, 180 dpi) in the transport direction. Black nozzle row K for jetting black ink, cyan nozzle row C for jetting cyan ink, magenta nozzle row M for jetting magenta ink, yellow nozzle row Y for jetting yellow ink, and white ink jetted from the left side in the moving direction The white nozzle rows W to be arranged are arranged in order. The black nozzle row K, the cyan nozzle row C, the magenta nozzle row M, and the yellow nozzle row Y correspond to the “first nozzle row”, and the white nozzle row W corresponds to the “second nozzle row”. Also, the 180 nozzles in each nozzle row are numbered in order from the nozzle on the downstream side in the transport direction (# 1 to # 180).

  In such a printer 1, the controller 10 performs an ejection operation for ejecting ink from the nozzles while moving the head 41 in the movement direction with respect to the medium, and a transport operation for transporting the medium in the transport direction with respect to the head. Let it run repeatedly. By doing so, dots can be formed by a subsequent ejection operation at a position on the medium different from the dot positions formed by the previous ejection operation, and a two-dimensional image can be printed on the medium. it can.

  For the following description, an operation in which the head 41 moves in the movement direction is referred to as a “pass”, and a path (ejection operation) in which ink is ejected from the nozzles when the head 41 moves in the movement direction is referred to as a “printing pass”. A path in which ink is not ejected from the nozzles when the head 41 moves in the movement direction is referred to as a “return path”. And, in order from the first pass for one page (one medium), it is called “pass 1, pass 2, pass 3...” In order from the first print pass for one page, “print pass 1, print pass 2. Called “Print pass 3...”.

=== About print mode ===
FIG. 3 is a diagram for explaining a print mode included in the printer 1 of the present embodiment. The printer 1 has a “color mode” in which only a main image with four colors of ink (YMCK, corresponding to the first fluid) is printed on the medium, and a background image with white ink (corresponding to the second fluid) on the main image. It has a “white use mode” for printing on a medium in an overlapping manner. By superimposing and printing the main image and the background image as in the white usage mode, it is possible to print an image with good color development, particularly when the medium is not white. In addition, when the medium is transparent, it is possible to prevent the opposite side of the printed material from being seen through by printing the main image and the background image in an overlapping manner.

  Further, the printer 1 has a “front printing mode” for printing the main image so as to be viewed from the printing surface side, and a “back printing mode” for printing so that the main image is viewed through the medium. Therefore, when the white usage mode / front printing mode is set, the background image is printed on the medium first, and the main image is printed over the background image. On the other hand, when the white use mode / back printing mode is set, the main image is printed on the medium first, and the background image is printed over the main image. In addition, when the medium has transparency, the back printing mode can be performed.

  For the following explanation, an image that is printed first with respect to a predetermined area of the medium among the main image and the background image is referred to as a “lower layer image (previous image)”, and is an image that is printed with respect to the predetermined area of the medium Is called “upper layer image (subsequent image)”.

=== About the printing method in the white use mode ===
4A is a diagram for explaining a printing method in the white usage mode / front printing mode, and FIG. 4B is a diagram for explaining a printing method in the white usage mode / back printing mode. In the figure, the number of nozzles belonging to one nozzle row is reduced to 14 for simplicity of explanation. In addition, the nozzle row that ejects each of the four color inks (YMCK) is collectively referred to as “color nozzle row Co”. The printing method shown in FIG. 4 is band printing. Band printing is a printing method in which band images formed in one pass are arranged in the transport direction, and a raster line of another pass is formed between raster lines (dot rows along the moving direction) formed in a certain pass. Is a printing method in which is not formed.

  In the printing method of the white usage mode / front printing mode (FIG. 4A), the nozzles # 8 to # 14 (Δ) on the upstream side in the transport direction of the white nozzle row W are used as nozzles for printing the background image. The half nozzles # 1 to # 7 (●) on the downstream side in the conveyance direction of the color nozzle row Co are used nozzles for printing the main image. The half nozzles # 1 to # 7 on the downstream side in the transport direction of the white nozzle row W and the half nozzle on the upstream side in the transport direction of the color nozzle row Co are unused nozzles. Then, the medium conveyance amount at one time is set as the width length in the conveyance direction of the background image or the main image formed in one pass (here, the length is 7D, which is half the nozzle row).

  By doing so, the predetermined area of the medium first opposes the used nozzle (Δ) on the upstream side in the transport direction of the white nozzle row W in a certain printing pass, and a background image is printed in the predetermined area of the medium. The Thereafter, when the medium is transported downstream in the transport direction, the predetermined area of the medium faces the use nozzle (●) on the downstream side in the transport direction of the color nozzle row Co in the next printing pass, and the background of the predetermined area of the medium The main image is printed over the image.

  On the other hand, in the printing method in the white usage mode / back printing mode (FIG. 4B), the nozzles # 1 to # 7 (Δ) on the downstream side in the transport direction of the white nozzle row W are used nozzles for printing the background image. The nozzles # 8 to # 14 (●) on the upstream side in the transport direction of the color nozzle row Co are used nozzles for printing the main image. A single medium conveyance amount is set to the width (7D) in the conveyance direction of the background image or the main image formed in one pass.

  By doing so, the predetermined area of the medium first faces the use nozzle (●) on the upstream side in the transport direction of the color nozzle row Co in a certain printing pass, and the main image is printed in the predetermined area of the medium. The Thereafter, when the medium is transported downstream in the transport direction, the predetermined area of the medium faces the use nozzle (Δ) on the downstream side in the transport direction of the white nozzle row W in the next printing pass, and the main area of the predetermined area of the medium A background image is printed over the image.

  As described above, in the white use mode, the main image and the background image are printed in different print passes on a predetermined area of the medium. For this purpose, the use nozzle for printing the lower layer image is set to the nozzle upstream of the use direction for printing the upper layer image. By doing so, the time interval for printing the background image and the main image in an overlapping manner can be made relatively long, and bleeding and color mixing of the image can be suppressed.

  However, the present invention is not limited to this, and all nozzles belonging to the color nozzle row Co and the white nozzle row W may be used even in the white use mode. In this case, for example, in the case of the surface printing mode, after printing the background image using all the nozzles of the white nozzle row W, it belongs to the color nozzle row Co in the next printing pass without transporting the medium. Print the main image on the background image using all nozzles. By doing so, it is possible to print the main image and the background image in different printing passes on a predetermined area of the medium.

  In the color mode printing method, all the nozzles belonging to the color nozzle row Co may be used, or only half of the nozzles belonging to the color nozzle row Co may be used as in the white use mode.

  In addition to band printing, for example, interlaced printing (a printing method in which raster lines are printed in another printing pass between raster lines printed in a certain printing pass) or overlap printing may be performed. (Printing method in which one raster line is printed by a plurality of nozzles in different printing passes) may be performed.

=== About the shortest printing control ===
FIG. 5 is a diagram for explaining the shortest printing control. For the following description, the left end of the moving direction in the range in which the head 41 can move in the moving direction is referred to as “left return position LP (corresponding to the home position HP)”, and the right end in the moving direction is referred to as “right return position RP. " The left diagram of FIG. 5 shows the case where the shortest print control is not performed, and the right diagram of FIG. 5 shows the case where the shortest print control is implemented.

  If the shortest printing control is set not to be performed, the controller 10 moves the head 41 to the left return position LP and the right side even when an image is printed only at the center in the moving direction of the medium as shown in the left diagram of FIG. Ink is ejected from the head 41 while reciprocating between the return positions RP. That is, the head 41 moves not only to the image printing range but also to the range where no image is printed.

  On the other hand, if the shortest print control is set to be executed, the controller 10 ejects ink from the head 41 while reciprocating the head 41 between the left end and the right end of the image as shown in the right diagram of FIG. That is, the head 41 moves only in the image printing range. However, when a cleaning operation of the head 41 is necessary, the head 41 moves to the home position HP.

  That is, the shortest printing control is control for changing the moving distance of the head 41 according to the position of the end (end) in the moving direction of the image to be printed. By performing the shortest printing control, the printing time can be shortened.

=== Printing Method of Comparative Example ===
FIG. 6 is a diagram illustrating a printing method of a comparative example. In the printing method of the comparative example, the controller 10 performs the shortest printing control when the white usage mode in which the background image and the main image are overprinted is set. The drawing shows a printing method in which ink is ejected from the nozzles (hereinafter referred to as “bidirectional printing”) both when the head 41 moves to the right and to the left in the direction of movement. The case where is implemented is shown.

  A specific printing method will be described. First, in pass 1 (print pass 1), the head 41 prints a background image while moving to the right in the moving direction. When the printing of the right end portion of the background image is completed, the head 41 stops at the point where the printing of the right end portion of the background image is completed without moving to the right return position RP. Next, after the medium is transported downstream in the transport direction, in pass 2 (print pass 2), the head 41 moves to the left in the moving direction from the point where printing of the right end of the background image is completed. The main image is printed on the background image printed in pass 1.

  Therefore, especially at the point P1 on the medium on the side where the head 41 moves (right side in the moving direction) in pass 1, the time from when the background image is printed until the main image is printed is shortened. Specifically, when the shortest print control is performed as in this comparative example, the head 41 reciprocates between the right edge of the background image and the right return position RP, compared to the case where the shortest print control is not performed. The time interval (drying time) at which the background image and the main image are overlaid is shortened by the amount of time to be printed.

That is, when the shortest printing control is performed in the white use mode, the moving distance of the head 41 is shortened, and the time interval for printing the background image and the main image is shortened. As a result, the image is blurred or mixed and the image quality of the image is deteriorated.
Therefore, an object of the present embodiment is to suppress image quality deterioration of an image.

=== First Embodiment ===
FIG. 7A is a flowchart for setting the printing method in the first embodiment, and FIG. 7B is a diagram for explaining the printing method in the first embodiment. FIG. 7B shows a case where the bidirectional printing / front printing mode is performed. In the first embodiment, when the controller 10 receives the print data in the white use mode (S001 → Y), the controller 10 sets that the shortest print control is not performed (S002).

  That is, when the controller 10 forms the main image formed with the four colors of ink (YMCK) and the background image formed with the white ink (W) on the medium in different printing passes, the end in the moving direction of the image. Control for changing the moving distance of the head 41 in the moving direction according to the position of the part (end) is not performed.

  Specifically, referring to FIG. 7B, first, in pass 1 (print pass 1), the head 41 prints a background image while moving to the right in the moving direction. When printing of the right end portion of the background image is completed, the head 41 moves to the right return position RP without stopping at that point. Then, after the medium is transported downstream in the transport direction, in pass 2 (printing pass 2), the head 41 is printed in pass 1 while moving from the right return position RP to the left in the moving direction. Print the main image on the image.

  Therefore, in the first embodiment, compared to the printing method of the comparative example (FIG. 6), the head 41 is between the printing of the background image at a certain point P1 on the medium and the printing of the main image. It moves long by a distance twice as long as the distance from the right end of the background image to the right return position RP. Therefore, in the first embodiment, compared with the printing method of the comparative example, the background image and the main image are overlapped and printed for the time required for the head 41 to reciprocate between the right edge of the background image and the right return position RP. It is possible to lengthen the time interval.

  That is, by not performing the shortest printing control in the white use mode, the time interval for the head 41 to pass through a certain point P1 on the medium becomes long, and the time interval for printing the background image and the main image in an overlapping manner is lengthened. can do. As a result, blurring and color mixing of the image can be prevented, and image quality deterioration of the image can be suppressed.

  Furthermore, in the first embodiment, when color mode print data is received (S001 → N), the controller 10 sets to perform the shortest print control (S003).

  That is, the controller 10 controls the movement distance of the head 41 in the moving direction according to the position of the end (end) in the moving direction of the image when the main image is formed on the medium without overlapping the background image. Is carried out.

  Even when the shortest printing control is performed and the time interval for the head 41 to pass through a certain point on the medium becomes short, only the main image is printed at a certain point on the medium in the color mode. Therefore, there is no problem of image bleeding or color mixing. That is, by performing the shortest print control in the color mode, it is possible to shorten the printing time without degrading the image quality.

  In the case of the color mode, the controller 10 is not limited to determining that the shortest print control is to be performed, and for example, the user may be allowed to determine whether or not to perform the shortest print control. Also in the color mode, the shortest printing control may not be performed as in the white usage mode.

=== Second Embodiment ===
FIG. 8A is a printing method setting flow in the second embodiment, and FIG. 8B is a diagram illustrating the printing method in the second embodiment. FIG. 8B shows a case where the front printing mode is performed. In the second embodiment, when the print data in the white use mode is received (S101 → Y), the controller 10 sets that the shortest print control is not performed, and further performs the “unidirectional printing”. (S103). Unidirectional printing is a printing method in which ink is ejected only when the head 41 moves to one side in the movement direction, and ink is not ejected when the head 41 moves to the other side in the movement direction.

  That is, the controller 10 performs control to eject ink from the nozzles only when the head 41 is moved to one side in the movement direction when the main image and the background image are formed to overlap each other.

  Specifically, referring to FIG. 8B, first, in pass 1 (print pass 1), the head 41 prints a background image while moving to the right in the moving direction. When printing of the right end portion of the background image is completed, the head 41 moves to the right return position RP without stopping at that point. In pass 2 (return pass), the head 41 moves from the right return position RP to the left return position LP without ejecting ink. Thereafter, after the medium is transported downstream in the transport direction, in pass 3 (printing pass 2), the head 41 moves from the left return position LP to the right in the moving direction, and the background image printed in pass 1 is printed. Print the main image on top.

  Therefore, in the second embodiment, as compared with the printing method of the comparative example (FIG. 6), the head 41 does not move between the time when the background image is printed at a certain point P1 on the medium and the time when the main image is printed. In addition to the reciprocating distance from the right end of the background image to the right return position RP, the distance from the right return position RP to the left return position LP also moves long. Therefore, the time interval for printing the background image and the main image in an overlapping manner can be made longer.

  In other words, in the second embodiment, in the white use mode, unidirectional printing is performed, and a return path is provided between the printing passes, thereby extending the time interval for printing the background image and the main image in an overlapping manner. As a result, blurring and color mixing of the image can be more reliably prevented, and image quality deterioration of the image can be suppressed.

  On the other hand, when receiving the color mode print data (S101 → N), the controller 10 allows the user to determine whether or not to perform bidirectional printing (S102). When the user determines not to perform bidirectional printing (S102 → N), the controller 10 sets to perform unidirectional printing (S103), and when the user determines to perform bidirectional printing (S102 → Y). Then, it is set to execute bidirectional printing (S104).

  However, the user is not limited to determining whether or not to perform bidirectional printing. When bi-directional printing is performed, the printing time can be shortened, and when uni-directional printing is performed, image quality deterioration due to reciprocal characteristic differences can be prevented. Therefore, for example, bidirectional printing may be performed when “fast mode” is set, and unidirectional printing may be performed when “clean mode” is set.

  In the printer 1 of the present embodiment, it is assumed that the medium transport operation is not performed simultaneously with the return path. This is because if the medium transport operation is performed simultaneously with the return path, the transport accuracy is lowered due to the influence of mechanical vibrations, noise on the drive signal, and the like, and the control becomes complicated. By not performing the medium transport operation at the same time as the return pass, the time interval between the print passes becomes longer, and the time interval for overlapping the background image and the main image for printing can be made longer. Therefore, it is possible to more reliably prevent image bleeding and color mixing.

  The moving speed of the head 41 during the printing pass is fixed according to the ink ejection interval, but the moving speed of the head 41 during the return pass can be changed. Therefore, the time interval for printing the background image and the main image may be extended by slowing down the moving speed of the head 41 during the return pass so as to surely prevent blurring and color mixing of the image. On the other hand, when the time interval for printing the background image and the main image in an overlapping manner is longer than the time necessary for preventing blurring and color mixing of the image, the moving speed of the head 41 during the return pass is increased. Printing time may be shortened.

=== Third embodiment ===
In the present embodiment, since the shortest print control is not performed in the white use mode, the comparative example (for the time required for the head 41 to reciprocate between the image end portion and the right return position RP or the left return position LP is shown. The time interval for printing the background image and the main image in an overlapping manner can be made longer than in FIG.

  However, if the distance from the image end to the medium end on the side on which the head 41 moves when printing the lower layer image (the previous image), the medium end after the head 41 finishes printing the lower layer image. This means that the distance traveled to is short. Therefore, the distance that the head 41 reciprocates from the end of the lower layer image to the right return position RP or the left return position LP is also shortened. Therefore, if bidirectional printing is performed in this case, the time interval from when the head 41 finishes printing the edge of the lower layer image to when printing of the upper layer image is shortened, the background image and the main image Since the time interval for printing the two images is shortened, there is a possibility that image blurring or color mixing may occur.

  On the other hand, when the lower end image is printed, if the distance from the image end to the medium end on the side on which the head 41 moves is long, the head 41 finishes printing the end of the lower layer image and then reaches the end of the medium. This means that the distance traveled is long. Therefore, the distance that the head 41 reciprocates from the end of the lower layer image to the right return position RP or the left return position LP also increases. Therefore, even if bidirectional printing is performed in this case, the time interval from when the head 41 finishes printing the edge of the lower layer image to when the upper layer image starts printing is long, that is, the background image and the main image Since the time interval for overlapping and printing is long, there is no possibility of image blurring or color mixing.

  Therefore, unidirectional printing is performed according to the distance (distance along the moving direction) from the image edge to the medium edge on the side on which the head 41 moves when the lower layer image is printed, or bidirectional printing is performed. It is good to set whether to implement.

  That is, it is assumed that the controller 10 moves the head 41 in the movement direction when forming a lower layer image (an image formed first with respect to a predetermined area of the medium) when the main image and the background image are formed in an overlapping manner. If the distance from the edge of the image (edge of the image) to the edge of the medium (edge of the medium) is less than the threshold, ink is ejected from the nozzles when moving the head 41 to the same side as the previous printing pass and moving direction. If the distance is equal to or greater than the threshold value, ink is ejected from the nozzles when the head 41 is moved in the direction opposite to the movement direction from the previous printing pass (bidirectional printing is performed). .

  If the distance from the image edge to the medium edge on the side on which the head 41 moves when printing the lower layer image is greater than or equal to the threshold value, blurring or color mixing of the image occurs even if bidirectional printing is performed. The threshold is set so as not to occur.

  FIG. 9A is a flowchart for setting the printing method in the third embodiment, and FIG. 9B is a diagram for explaining the printing method in the third embodiment. FIG. 9B shows a case where the front printing mode is performed. In the third embodiment, the controller 10 sets whether to perform unidirectional printing or bidirectional printing for each page (each image to be printed on one medium).

  For this purpose, the controller 10 sets that the shortest print control is not performed when the print data in the white use mode is received, and further, based on the print data, from the edge of the image on one page to the edge of the medium. The shortest distance among the distances is calculated, and the shortest distance is compared with a threshold value (S201 in FIG. 9A). When the calculated shortest distance is less than the threshold (S201 → Y), the controller 10 sets to perform unidirectional printing (S202). When the calculated shortest distance is equal to or greater than the threshold (S201 → N), the controller 10 is bidirectional. It is set to execute printing (S203).

  Note that, when unidirectional printing is set and when bidirectional printing is set, the side on which the head 41 moves when printing the lower layer image is different, and when bidirectional printing is set, the print path The side on which the head 41 moves when printing the lower layer image is different for each. Therefore, assuming that the head 41 moves to the left side and the right side when printing the lower layer image, the distance from the right end portion of the image to the right end portion of the medium in the entire image area, and the left end portion of the image The shortest distance in the distance from the left edge of the medium is calculated.

  Further, the distance from the edge of the main image to the edge of the medium may be calculated, or the distance from the edge of the background image to the edge of the medium may be calculated. Also, the distance from the edge of the larger image of the two images to the edge of the medium may be calculated, or the distance from the edge of the smaller image to the edge of the medium may be calculated. .

  This will be specifically described with reference to FIG. 9B. Here, a case where the background image is larger than the main image and the distance from the edge of the main image to the medium edge is calculated is taken as an example. In the image shown on the left side of FIG. 9B, since the image is printed largely on the medium, it is assumed that the shortest distance d1 from the main image end on the same side to the medium end in the moving direction is shorter than the threshold. In this case, the controller 10 sets the image on the left side of FIG. 9B to be printed by unidirectional printing (that is, a return path is provided between the printing passes, and the head 41 is placed on the same side as the previous printing pass in the moving direction. Ink is ejected from the nozzles when moving).

  By doing so, the distance d1 from the right edge of the main image to the right edge of the medium is short, and the head 41 moves to the right in the moving direction in pass 1 while the background image is placed at a certain point P1 on the medium. Since the main image is not printed in pass 2 even if the time from printing until the head 41 moves to the left in the moving direction and passes a certain point P1 on the medium in pass 2 is short, Bleeding and color mixing can be prevented.

  On the other hand, in the image shown on the right side of FIG. 9B, an image having a narrow width in the moving direction is printed at the center of the medium, so that the shortest distance d2 from the main image end on the same side to the medium end in the moving direction is long. Suppose that the threshold is exceeded. In this case, the controller 10 sets the image on the right side of FIG. 9B to be printed by bidirectional printing (that is, no return path is provided between the printing passes, and the head 41 is placed on the opposite side of the previous printing pass and the moving direction. Ink is ejected from the nozzle when moving the ink).

  By doing so, the background image is printed at a certain point P1 on the medium while the head 41 moves to the right side in the movement direction in pass 1, and the head 41 moves to the left side in the movement direction in pass 2. Even if the main image is printed on the background image at a certain point P1 on the medium, the distance d2 from the right end of the main image to the right end of the medium is long, and the head 41 is at a certain point P1 on the medium. Since the time interval of passing through is long, it is possible to prevent bleeding and color mixing of the image.

  In other words, a time interval for printing the background image and the main image in an overlapping manner is required by providing a return pass between the print passes even though the time interval for the head 41 to pass a certain point P1 on the medium is long. It is possible to prevent the length from becoming longer. That is, it is possible to prevent the printing time from being unnecessarily prolonged.

  FIG. 10 is a diagram for explaining the shortest distance from the image edge to the medium edge in another image. In the image shown in FIG. 9B, since the side in the movement direction is along the conveyance direction, the distance from the image edge to the medium edge is equal throughout the conveyance direction. Further, since the image shown in FIG. 9B is printed at the center in the moving direction of the medium, the distance from the left end of the image to the left end of the medium and the right end of the image to the right end of the medium. Are equal in distance. However, the image shown in FIG. 9B is not limited to being printed.

For example, there is an image whose width in the moving direction increases from the top to the bottom of the image, such as the image on the left side of FIG. In this case, the distance d1 from the image edge to the medium edge at the bottom of the image is the shortest distance. When the shortest distance d1 is less than the threshold value, in the third embodiment, the upper and lower parts of the image are printed by unidirectional printing.
In addition, like the image on the right side of FIG. 10, even if the width in the moving direction of the image is narrow, the image may be printed on one side of the moving direction with respect to the medium (left side in the figure). In this case, if the distance d1 from the image edge on the side where the image is close to the medium edge is short and less than the threshold value, the image is printed by unidirectional printing.

Further, it is not limited to calculating the shortest distance among the distance from the right edge of the image to the right edge of the medium and the distance from the left edge of the image to the left edge of the medium in the entire image. Assuming that an image is printed by bidirectional printing, for each area where the image is printed in a single printing pass, the medium from the image end on the side where the head 41 moves when printing a lower layer image in each area The shortest distance to the end may be calculated.
For example, when the lower layer image is printed in a certain area on the medium while the head 41 moves to the right in the movement direction in the printing pass 1, the right side of the medium is printed from the right edge of the image printed in the certain area on the medium. When the shortest distance to the edge is calculated and the lower layer image is printed in another area on the medium while the head 41 moves to the left in the moving direction in the printing pass 2, the image printed in another area on the medium The shortest distance from the left end of the medium to the left end of the medium is calculated.
Then, the shortest distance among the shortest distances of each region may be compared with a threshold value to set whether to perform unidirectional printing or bidirectional printing.

=== Fourth Embodiment ===
FIG. 11 is a flowchart for setting the printing method in the fourth embodiment, and FIG. 12 is a diagram for explaining the printing method in the fourth embodiment. FIG. 12 shows a case where the front printing mode is performed. In the fourth embodiment, the direction in which the head 41 moves is determined for each printing pass (that is, which side in the moving direction the ink is ejected from the nozzles is determined). Then, based on the distance from the end on one side of the moving direction of the lower layer image to be printed while moving the head 41 to one side of the moving direction in a certain printing pass, the next The direction in which the head 41 moves in the printing pass is determined.

  Therefore, when receiving the print data in the white use mode, the controller 10 sets not to perform the shortest print control, and further determines the direction in which the head 41 moves in each print pass. As shown in FIG. 11, the controller 10 first confirms the presence or absence of image data in the next printing pass n + 1 of a certain printing pass n (S301). When there is image data of the next printing pass n + 1 (S301 → Y), the controller 10 acquires image data of a lower layer image printed in a certain printing pass n (S302). Based on the acquired image data, the controller 10 calculates the distance from the edge of the lower layer image to the edge of the medium on the side where the head 41 moves in a certain printing pass n, and compares the calculated distance with the threshold value. (S303).

  When the calculated distance is less than the threshold (S303 → Y), the controller 10 provides a return path between a certain printing pass n and the next printing pass n + 1, and sets the direction in which the head moves in the next printing pass n + 1. The direction is set in the same direction as the head 41 moves in a printing pass n (S304). On the other hand, if the calculated distance is equal to or greater than the threshold (S303 → N), the controller 10 does not provide a return path between a certain print pass n and the next print pass n + 1, and the head is printed in the next print pass n + 1. The direction in which the head 41 moves is set to a direction opposite to the direction in which the head 41 moves in a certain printing pass n (S305). The controller 10 repeatedly executes this process until there is no more data for the next print pass.

  That is, when the main image and the background image are formed in an overlapping manner, the controller 10 first forms a lower layer image (first with respect to a predetermined area of the medium) formed during a certain printing pass in which the head 41 is moved to one side in the moving direction. When the distance from the edge (edge) on one side in the moving direction of the image to be formed to the edge (edge) on one side in the moving direction of the medium is less than the threshold, the next printing in a certain printing pass During a pass, ink is ejected from the nozzles when moving the head 41 to one side (same side) of the moving direction, and when the distance is greater than or equal to the threshold, the head 41 is moved during the next printing pass of a certain printing pass. Ink is ejected from the nozzle when moving to the other side (reverse side) of the direction.

  By doing so, the distance that the head 41 moves to the edge of the medium after completing the printing of the lower layer image in a certain printing pass is short, that is, the head 41 returns to the edge of the lower layer image and the right return position RP or the left return. When the distance reciprocating between the position LP and the head 41 is short and the time interval for the head 41 to pass a certain point on the image printing area is short, a return path is provided between the printing passes (the head 41 in the preceding and following printing passes). Are moving in the same direction, that is, the same movement as in the unidirectional printing). Therefore, it is possible to lengthen the time interval for printing the background image and the main image in an overlapping manner, to prevent image blurring and color mixing, and to suppress image quality deterioration of the image.

  On the other hand, the distance that the head 41 moves to the edge of the medium after completing the printing of the lower layer image in a certain printing pass is long, that is, the head 41 moves from the end of the lower layer image to the right return position RP or the left return position LP. When the distance between the head 41 and the head 41 passes through a certain point on the image printing area is long, the return path is not provided between the printing passes (the head 41 in the preceding and following printing passes). The direction of movement is the opposite direction, that is, the same movement as bidirectional printing). Therefore, it is possible to prevent the time interval for printing the background image and the main image from being overlapped more than necessary, and to shorten the printing time while preventing image bleeding and color mixing.

  Specifically, referring to FIG. 12, first, in pass 1 (print pass 1), the head 41 prints a background image (lower layer image) while moving to the right in the moving direction. The distance d3 from the right edge of the background image printed in pass 1 to the right edge of the medium is short and less than the threshold. In this case, in the next printing pass 2, the controller 10 ejects ink from the nozzles when moving the head 41 to the same side (right side) as the printing pass 1. Therefore, path 2 becomes a return path.

  After the medium is transported downstream in the transport direction after pass 2, the head 41 prints the background image and the main image while moving to the right in the travel direction in pass 3 (print pass 2). The distance d4 from the right edge of the background image printed in pass 3 to the right edge of the medium is long and is greater than or equal to the threshold value. In this case, in the next printing pass 3, the controller 10 ejects ink from the nozzles when moving the head 41 to the opposite side (left side) of the printing pass 2. Therefore, no return path is provided between pass 3 and pass 4, and after the medium is transported downstream in the transport direction after pass 3, the head 41 is moved to the left in the movement direction in pass 4 (print pass 3). The background image and the main image are printed while moving.

  In FIG. 12, since the front printing mode is taken as an example, the background image is a lower layer image, and the distance from the edge of the background image to the edge of the medium is compared with a threshold value. On the other hand, in the reverse printing mode (not shown), the main image is a lower layer image, and the distance from the edge of the main image to the edge of the medium is compared with a threshold value. Therefore, when the main image and the background image are different in size, the distance compared with the threshold value is slightly different.

=== Fifth embodiment ===
FIG. 13 is a flowchart for setting the printing method in the fifth embodiment, and FIGS. 14A and 14B are diagrams for explaining the printing method in the fifth embodiment. FIG. 14 shows a case where the front printing mode is performed. In the fifth embodiment, the direction in which the head 41 moves is determined for each printing pass. Then, in one printing pass, the head 41 moves to one side of the moving direction, and the lower side image to be printed and the upper layer image that overlaps the upper layer image overlap from one end in the moving direction to one side of the moving direction of the medium. The direction in which the head 41 moves in the next printing pass is determined on the basis of the distance to the end portion.

  Therefore, the controller 10 sets that the shortest print control is not to be performed when receiving the print data in the white use mode, and further determines the direction in which the head 41 moves in each print pass. As shown in FIG. 13, the controller 10 first checks the presence / absence of image data in the next printing pass n + 1 of a certain printing pass n (S401). When there is image data of the next print pass n + 1 (S401 → Y), the controller 10 obtains image data of a lower layer image printed in a certain print pass n and image data of an upper layer image printed thereon. (S402). Hereinafter, an area where a lower layer image printed in a certain printing pass n and an upper layer image overlapping therewith are referred to as an “overlapping area”. Based on the acquired image data, the controller 10 calculates the distance from the edge of the overlap area to the edge of the medium on the side where the head 41 moves in a certain printing pass n, and compares the calculated distance with the threshold value. (S403).

  When the calculated distance is less than the threshold (S403 → Y), the controller 10 provides a return path between a certain printing pass n and the next printing pass n + 1, and sets the direction in which the head moves in the next printing pass n + 1. The direction is set in the same direction as the head 41 moves in a certain printing pass n (S404). On the other hand, if the calculated distance is equal to or greater than the threshold (S403 → N), the controller 10 does not provide a return path between a certain print pass n and the next print pass n + 1, and the head is printed in the next print pass n + 1. The direction in which the head 41 moves is set to a direction opposite to the direction in which the head 41 moves in a certain printing pass n (S405). The controller 10 repeatedly executes this process until there is no more data for the next print pass.

  That is, when the controller 10 overlaps the main image and the background image, the controller 10 first forms an image on a predetermined area of the medium during a certain printing pass in which the head 41 is moved to one side in the moving direction. When the distance from one side end (edge) in the moving direction of an area overlapping an image to be formed later to one side end (end) in the medium moving direction is less than a threshold value, a certain printing is performed. In the next printing pass of the pass, ink is ejected from the nozzles when the head 41 is moved to one side (same side) in the moving direction. When the distance is equal to or greater than the threshold value, in the next printing pass of a certain printing pass When the head 41 is moved to the other side (reverse side), ink is ejected from the nozzles.

  Therefore, when the head 41 finishes printing the lower layer image while moving to one side in the moving direction in a certain printing pass, the head 41 passes through the end on one side in the moving direction of the medium and returns to the right return position RP or left side. When returning from the position LP, when the time until the end of the overlapping region of the lower layer image and the upper layer image passes through one end (the printing point) is short, the upper layer image is Does not print. Therefore, the time interval for printing the background image and the main image in an overlapping manner becomes long, preventing blurring and color mixing of the image, and suppressing image quality deterioration of the image.

  On the other hand, when the head 41 finishes printing the lower layer image while moving to one side in the moving direction in a certain printing pass, the head 41 passes through the end on one side in the moving direction of the medium and returns to the right return position RP or left side. When returning from the position LP, when the time is long until the end of one side in the moving direction of the overlapping region of the lower layer image and the upper layer image (the point where printing is performed), the upper layer image is displayed when the head 41 is folded back. Printed. Therefore, it is possible to prevent the time interval for overlapping the background image and the main image from being printed more than necessary, and it is possible to reduce the printing time while preventing image bleeding and color mixing.

  Specifically, referring to FIG. 14, first, as shown in the left diagram of FIG. 14A, the head 41 moves the right side of the moving direction in the pass 1 (printing pass 1) and displays the background image (lower layer image). Print. On the background image printed in the printing pass 1, the main image is overlaid and printed as shown in the right figure of FIG. 14A. It is assumed that the distance d5 from the right end of the overlapping area (thick frame) of the background image and the main image to the right end of the medium is short and less than the threshold. In this case, in the next printing pass 2, the controller 10 ejects ink from the nozzles when moving the head 41 to the same side (right side) as the printing pass 1. Therefore, path 2 (not shown) is a return path.

  Then, after the medium is transported downstream in the transport direction after pass 2, as shown in the left diagram of FIG. 14B, the head 41 moves to the right in the travel direction in pass 3 (printing pass 2), and the background image And print the main image. On the background image printed in the printing pass 2, as shown in the right figure of FIG. 14B, the main image is overlaid and printed. The distance d6 from the right end of the overlapping area (thick frame) of the background image and main image printed in pass 3 to the right end of the medium is long and is greater than or equal to the threshold value. In this case, in the next printing pass 3, the controller 10 ejects ink from the nozzles when moving the head 41 to the opposite side (left side) of the printing pass 2. Therefore, no return path is provided between the path 3 and the path 4.

=== Sixth embodiment ===
In the fourth and fifth embodiments described above, the direction in which the head 41 moves is determined for each print pass. Therefore, in the fourth embodiment, the head 41 moves from one end of the lower layer image to be printed while moving to one side of the moving direction in a certain printing pass to the end of one side of the moving direction of the medium. And the threshold are compared. Further, in the fifth embodiment, the head 41 moves while moving to one side of the moving direction in a certain printing pass from the end on one side in the moving direction of the region where the lower layer image printed and the upper layer image overlapping therewith overlap. The distance to the end on one side in the moving direction of the medium is compared with the threshold value.

  Also in the sixth embodiment, the direction in which the head 41 moves is determined for each printing pass. Then, in a certain printing pass, the head 41 moves in one direction of the medium from an end (edge) on one side in the moving direction of the upper layer image to be printed over the lower layer image to be printed while moving to one side in the moving direction. The distance to the side edge (end) is compared with the threshold value. If the distance is less than the threshold, the controller 10 provides a return path between a certain printing pass and the next printing pass, and the head 41 moves in a certain printing pass in the direction in which the head moves in the next printing pass. If the distance is equal to or greater than the threshold value, the return path is not provided between a certain print pass and the next print pass, and the direction in which the head 41 moves in the next print pass is set. A direction opposite to the direction in which the head 41 moves in a certain printing pass is set.

  By doing so, when the head 41 moves back to one side of the moving direction in a certain printing pass and then returns from the right return position RP or the left return position LP after the lower layer image is printed, In the case where the time from when passing through one end in the moving direction to when passing through one end in the moving direction of the upper layer image (a point where printing is performed) is short, when the head 41 is folded back, The image is not printed. Therefore, the time interval for printing the background image and the main image in an overlapping manner can be lengthened, and bleeding and color mixing of the image can be prevented.

  On the other hand, when the head 41 returns from the right return position RP or the left return position LP after printing the lower layer image while the head 41 moves to one side of the movement direction in a certain printing pass, the head 41 moves in one direction of the medium movement. When the time from passing through the end on the side to passing through the end on one side in the moving direction of the upper layer image is long, the upper layer image is printed when the head 41 is folded back. Therefore, it is possible to prevent the time interval for printing the background image and the main image from being overlapped more than necessary, and to shorten the printing time without degrading the image quality of the image.

=== Seventh embodiment ===
FIG. 15 is a flowchart for setting a printing method according to the seventh embodiment. In the above-described third to sixth embodiments, whether a return path is provided between the print paths according to the distance from the image edge to the medium edge on the side on which the head 41 moves when the lower layer image is printed. (Whether or not to perform unidirectional printing is determined).

  In contrast, in the seventh embodiment, bidirectional printing is always performed in the white use mode. When the lower layer image is printed, if the distance from the image edge to the medium edge on the side on which the head 41 moves is short, a pause time is provided between the printing passes. That is, the head 41 is stopped for a predetermined time at the right return position RP or the left return position LP. Therefore, when the distance from the image edge to the medium edge on the side on which the head 41 moves when printing the lower layer image is shorter than in the case of performing normal bidirectional printing, The time interval becomes longer. For this purpose, for example, a counter that counts downtime may be provided in the controller 10. Further, when the lower layer image is printed, the pause time may be increased as the distance from the image end to the medium end on the side where the head 41 moves is shorter.

  That is, when the controller 10 forms the main image and the background image so as to overlap each other, the controller 10 performs control to eject the fluid from the nozzle when moving the head 41 in both directions of the moving direction, and prints the lower layer image. When the distance from the image edge (edge) to the medium edge (edge) on the side of moving 41 in the movement direction is less than the threshold, the time interval of the printing pass is set as compared with the case where the distance is greater than or equal to the threshold. Lengthen.

  By doing so, when the lower layer image is printed, the distance from the image end to the medium end on the side where the head 41 moves is short, and the time interval for the head 41 to pass a certain point on the image print region is short. In this case, a pause time is provided, and the time interval for printing the background image and the main image in an overlapping manner can be increased. Conversely, when the lower layer image is printed, when the distance from the image edge to the medium edge on the side on which the head 41 moves is long and the time interval for the head 41 to pass a certain point on the image printing area is long. In this case, no pause time is provided, and the time interval for printing the background image and the main image in an overlapping manner can be prevented from becoming unnecessarily long. As a result, it is possible to shorten the printing time while preventing bleeding and color mixing of the image.

  Therefore, for example, as shown in the flow of FIG. 15, the controller 10 may set whether or not to provide a pause time for each page (each image to be printed on one medium). Specifically, when the controller 10 receives the print data in the white usage mode (S501), the controller 10 determines the shortest distance among the distances from the edge of the image to the edge of the medium on one page based on the print data. Calculate (similar to the third embodiment) and compare the shortest distance with the threshold (S502). When the calculated shortest distance is less than the threshold (S502 → Y), the controller 10 provides a pause time between the print passes (S503). When the calculated shortest distance is equal to or greater than the threshold (S502 → N), the print path No pause time is provided (S504).

Further, the present invention is not limited to this, and it may be determined whether or not a pause time is provided for each print pass. Therefore, as in the fourth embodiment, the head 41 moves to one side in the moving direction in a certain printing pass, and moves from one end of the lower layer image to the one end in the moving direction of the medium. When the distance to the copy is calculated and the distance is less than the threshold, a pause time may be provided between a certain print pass and the next print pass.
Further, as in the fifth embodiment, an end portion on one side in the moving direction of a region where the lower layer image printed while moving the head 41 to one side in the moving direction and an upper layer image overlapping therewith in a certain printing pass. From this, the distance to one end in the moving direction of the medium is calculated, and when the distance is less than the threshold value, a pause time may be provided between a certain printing pass and the next printing pass.
Further, as in the sixth embodiment, from the end on one side in the moving direction of the upper layer image to be printed over the lower layer image to be printed while the head 41 moves to one side in the moving direction in a certain printing pass, A distance to one end in the moving direction of the medium may be calculated, and when the distance is less than a threshold value, a pause time may be provided between a certain printing pass and the next printing pass.

=== Other Embodiments ===
Although this embodiment mainly describes the fluid ejecting apparatus, disclosure of a fluid ejecting method and the like is also included. Further, the present embodiment is intended to facilitate understanding of the present invention and is 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 the control unit>
In the above-described embodiment, the controller 10 in the printer 1 is set to perform the shortest print control when receiving print data in the white use mode. Therefore, the controller 10 corresponds to a control unit, and the printer 1 alone corresponds to a fluid ejecting apparatus. However, the present invention is not limited to this. When a printer driver (program) installed in the computer 60 connected to the printer 1 uses the hardware resources of the computer 60 to create print data in the white usage mode, The print data may be set to be printed without performing the shortest print control. In this case, the computer 60 in which the printer driver is installed and the controller of the printer 1 correspond to the control unit, and the printing system in which the printer 1 and the computer 60 are connected corresponds to the fluid ejecting apparatus.

<About background images>
In the above-described embodiment, the background image is printed with white ink. However, the present invention is not limited to this, and the background image may be printed with a color ink other than white (for example, metallic ink).
When a background image is printed using only white ink, the color of the white ink itself that prints the background image becomes the color of the background image. Similarly, even if the ink is called white ink, the white color is slightly different depending on the ink material. A background image having some chromatic color rather than simple white may be desired. Therefore, a desired white background image may be printed by appropriately using a small amount of other color ink (YMCK) together with the white ink. In this case, for example, the half nozzles (# 8 to # 14) on the upstream side in the transport direction of the color nozzle row Co in the head 41 shown in FIG. On the contrary, when the white ink has a slight color, the color can be canceled by printing the background image with the white ink and the color ink.

<Nozzle array configuration>
In the above-described embodiment (FIG. 2), in one head 41, the four-color nozzle row (YMCK) for printing the main image and the white nozzle row (W) for printing the background image It is lined up in the moving direction, but is not limited to this. For example, the four-color nozzle row (YMCK) and the white nozzle row (W) may be displaced in the nozzle row direction. In order to realize both the front printing mode and the back printing mode, the white nozzle row W may be provided on both ends in the nozzle row direction with respect to the four-color nozzle row. Further, the four-color nozzle row (YMCK) and the white nozzle row (W) may be provided in different heads 41.

<About white>
Although the background image is white, the term “white” in this specification is not limited to white in the strict sense that is the surface color of an object that reflects 100% of all wavelengths of visible light. It is assumed that a color called “white” is included in the common sense, such as “color”. “White” means, for example, (1) color measurement mode: spot color measurement, light source: D50, backing: Black, printing medium: transparent film using x-rite colorimeter eye-onePro When colored, the mark in the L ^* a ^* b ^* color space is on the a ^* b ^* plane and within the circumference of the radius 20 and within the hue range represented by an L ^* value of 70 or more. (2) When the color is measured with Minolta colorimeter CM2022 in the measurement mode D502 ° field of view, SCF mode, and white background, the label in the L ^* a ^* b ^* color space is a ^* b ^*. Whether the color is within the circumference of the circle having a radius of 20 on the plane and the inside thereof, and the color is in the hue range represented by an L ^* value of 70 or more. (3) As described in Japanese Patent Application Laid-Open No. 2004-306591 The color of the ink used as the background of the image. If it is used as the background, it is pure white. It is not.

<About ink and media>
In the present embodiment, an ink and a medium having an ink absorptivity that absorbs the ink are used. The ink may be any ink that is absorbed by the absorbent medium, but preferably contains an evaporable solvent in order to ensure absorbability to the ink absorbent medium. Further, “water-based ink” containing at least water as a solvent is particularly preferable. As other components constituting the ink, there are dyes and pigments as color materials. In addition, it may contain a water-soluble organic solvent for ejection stability from an inkjet head, and if necessary, contains a moisturizing agent, a penetration enhancer, a ph regulator, an insect repellent, an ultraviolet absorber and the like. It may be. As such a color ink, for example, inks described in JP-A-2008-81693, JP-A-2005-105135, and JP-A-2003-292934 can be used.
The white ink contains a white pigment such as a hollow resin or titanium oxide as a color material, and components other than the color material may be the same as those of the color ink. As such white ink, for example, inks described in JP-A-2009-138078 and JP-A-2009-137124 can be used.
The medium fixes the color material of the ink composition by absorbing the solvent of the ink composition. For example, a medium using a base material that absorbs ink such as paper or cloth may be used, or a base material that absorbs ink or a base material that does not absorb ink may be provided with an ink absorption layer that absorbs ink. When a transparent medium is used, for example, media described in JP-A-2009-925, JP-A-9-99634, and JP-A-9-208870 can be used.
If the ink and medium used in the present embodiment are those described above, it is possible to provide a longer ink drying time by providing a longer time interval for printing the background image and the main image superimposed as in the previous embodiment. Image blur and color mixing can be prevented. However, the ink and medium used in this embodiment are not limited to those described above, and any ink or medium may be used as long as it is necessary to provide time for the components in the ink to adhere to the medium.

<About the printer>
In the above-described embodiment, a printer that repeats the operation of printing an image on a cut sheet while moving the head 41 in the moving direction and the operation of conveying the cut sheet to the head in a conveying direction that intersects the moving direction. However, the present invention is not limited to this. For example, for continuous paper transported to the print area, the image is printed by repeating the operation of printing the image while moving the head in the direction in which the paper continues and the operation of moving the head in the width direction of the paper. Thereafter, the printer may be a printer that conveys a portion of continuous paper on which an image has not yet been printed to a printing area.

<About fluid ejection device>
In the above-described embodiment, the ink jet printer is exemplified as the fluid ejecting apparatus, but the present invention is not limited thereto. If it is a fluid ejecting apparatus, it can be applied to various industrial apparatuses, not a printer (printing apparatus). For example, a textile printing apparatus for applying a pattern to a fabric, a display manufacturing apparatus such as a color filter manufacturing apparatus or an organic EL display, a DNA chip manufacturing apparatus for manufacturing a DNA chip by applying a solution in which DNA is dissolved to a chip, and the like. Also, the present invention can be applied.
Further, the fluid ejection method from the nozzle may be a piezo method in which a fluid is ejected by applying a voltage to the driving element (piezo element) to expand and contract the pressure chamber, or bubbles are generated in the nozzle using a heating element. A thermal method may be used in which the liquid is generated and the liquid is ejected by the bubbles.
The ink ejected from the head 41 may be ultraviolet curable ink that cures when irradiated with ultraviolet rays.

  1 printer, 10 controller, 11 interface unit, 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)

A first nozzle row in which nozzles for ejecting the first fluid are arranged in a predetermined direction;
A second nozzle row in which nozzles for ejecting the second fluid are arranged in the predetermined direction;
A controller that performs an ejection operation of ejecting fluid by moving the first nozzle row and the second nozzle row in a moving direction that intersects the predetermined direction;
The controller is
Control can be performed to vary the movement distance of the first nozzle row and the second nozzle row in the movement direction according to the position of the end of the image in the movement direction,
When the main image formed by the first fluid and the background image formed by the second fluid are formed to overlap the medium by the different ejection operations , the first direction is bidirectional in the moving direction. Even in bidirectional printing in which fluid is ejected when moving the nozzle row and the second nozzle row, fluid is moved when the first nozzle row and the second nozzle row are moved in one direction of the moving directions. Even in the unidirectional printing to be ejected, the first nozzle row and the second nozzle row are not limited to the print range of the main image and the background image, but the range where the main image and the background image are not printed. A fluid ejecting apparatus that performs an ejecting operation of moving in a moving direction. The fluid ejection device according to claim 1,
The control unit is configured to move the first nozzle row and the second nozzle row only in a printing range of the main image when the main image is formed on the medium without overlapping the background image. A fluid ejecting apparatus that performs an operation. The fluid ejection device according to claim 1,
When the main image is formed on the medium without overlapping the background image, the control unit includes not only the print range of the main image but also the range in which the main image is not printed, A fluid ejecting apparatus that performs an ejecting operation of moving the second nozzle row. The fluid ejection device according to any one of claims 1 to 3,
When the control unit forms the image to be formed first with respect to the predetermined area of the medium when the main image and the background image are formed to overlap each other, the first nozzle row and the second nozzle If the distance from the edge of the image on the side assumed to move the column in the movement direction to the edge on the assumed side in the movement direction of the medium is less than a threshold, the previous ejection operation and the movement A fluid ejecting apparatus that ejects fluid when moving the first nozzle row and the second nozzle row to the same side in a direction. The fluid ejection device according to any one of claims 1 to 3,
When the control unit forms the image to be formed first with respect to the predetermined area of the medium when the main image and the background image are formed to overlap each other, the first nozzle row and the second nozzle If the distance from the edge of the image on the side assumed to move the column in the movement direction to the edge on the assumed side in the movement direction of the medium is equal to or greater than a threshold, the previous ejection operation and the movement A fluid ejecting apparatus that ejects fluid when moving the first nozzle row and the second nozzle row to opposite sides in a direction. The first nozzle row in which the nozzles that eject the first fluid are arranged in a predetermined direction and the second nozzle row in which the nozzles that eject the second fluid are arranged in the predetermined direction move in a moving direction that intersects the predetermined direction. A fluid ejection method for performing an ejection operation of ejecting fluid.
The movement distance of the first nozzle row and the second nozzle row in the movement direction can be varied according to the position of the end of the image in the movement direction, and is formed by the first fluid. When the main image and the background image formed by the second fluid are formed on the medium by the different ejection operations , the first nozzle row and the second nozzle are bidirectional in the moving direction. Even in bidirectional printing in which fluid is ejected when moving a row, even in unidirectional printing in which fluid is ejected when moving the first nozzle row and the second nozzle row in one direction of the moving direction, The first nozzle row and the second nozzle row are moved in the movement direction not only to the print range of the main image and the background image but also to the range where the main image and the background image are not printed. Fluid ejection method characterized by performing an injection operation to.

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