JP2008155420A - Liquid ejector and liquid ejection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the image quality of a printing image of an upstream end or a downstream end of a medium. <P>SOLUTION: The liquid ejector is equipped with nozzles which form the image to the medium by ejecting the liquid towards the medium on the basis of data on the image while moving relatively to the medium, a conveyance part which conveys the medium in a predetermined direction, and a liquid ejection control part which changes a timing for the liquid to be ejected from the nozzles by using dummy pixel data as data on pixels that constitute the image for the data on the image. When the liquid is ejected from the nozzles towards a region of at least either one of the upstream end and the downstream end of the medium conveyed by the conveyance part, the liquid ejection control part changes the timing by using the dummy pixel data in an arrangement different from that when the liquid is ejected from the nozzles towards another region different from the region. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a liquid discharge apparatus and a liquid discharge method for discharging a liquid toward a medium while a nozzle moves relative to the medium.

  As a liquid ejecting apparatus, an ink jet printer that performs printing by ejecting ink as a liquid toward a medium is known. This ink jet printer performs printing by ejecting ink of each color such as cyan (C), magenta (M), yellow (Y), and black (K) from a nozzle toward a medium as ink. The nozzles that eject these inks are provided on a moving body called a carriage that moves relative to the medium. When printing is performed, the carriage moves relative to the medium, ink is ejected from the nozzles toward the medium, and printing is performed on the medium.

  By the way, in such an ink jet printer, when ink is ejected from the nozzle while the carriage is moving relative to the medium, the ink arrival position is shifted in the nozzle moving direction. Problem occurs. In particular, when printing is performed by ejecting ink while reciprocating the nozzle relative to the medium, the ink arrival position is shifted between the forward path and the backward path, which affects the quality of the printed image.

Therefore, conventionally, in order to make the arrival position of the ink ejected from the nozzle coincide in the forward path and the backward path, the timing of ejecting ink from the nozzle in the forward path and the backward path has been changed (patent). Reference 1). According to such a method, the position at which the ink reaches can be adjusted by changing the timing at which the ink is ejected from the nozzle. Thereby, deterioration of the image quality of the printed image can be suppressed.
JP 2000-318145 A

  However, there is a case where deterioration of the image quality of the printed image cannot be sufficiently prevented at the upstream end or the downstream end of the conveyed medium. This is because the upstream end or the downstream end of the medium slightly floats when printing is performed on the upstream end or the downstream end of the medium. The reason why the upstream end or the downstream end of the medium slightly rises from the printing position in this way is that the upstream end or the downstream end of the medium is separated from the conveyance roller that conveys the medium. . That is, at the initial stage when printing on the medium is started, the downstream end of the medium is not yet in contact with the transport roller and the downstream end of the medium is away from the transport roller. For this reason, when printing is performed on the downstream end portion of the medium, the downstream end portion of the medium may be slightly lifted from the printing position. Further, immediately before the printing on the medium is completed, the upstream end of the medium is separated from the conveying roller or the like. For this reason, when printing is performed on the upstream end portion of the medium, the upstream end portion of the medium may be slightly lifted from the printing position.

  When printing is performed on the upstream end or the downstream end of the medium in a state where the upstream end or the downstream end of the medium is slightly lifted from the printing position in this way, The gap with the nozzle will fluctuate. If the gap between the printing surface of the medium and the nozzles fluctuates in this way, the arrival position of the ink ejected from the nozzles will shift, leading to image quality degradation at the upstream end or downstream end of the medium. There was a case. In particular, recently, the carriage moving speed has been greatly increased in order to improve the printing processing speed. For this reason, image quality deterioration due to a gap variation between the printing surface of the medium and the nozzle cannot be ignored.

  The present invention has been made in view of such circumstances, and an object thereof is to suppress deterioration in image quality of a printed image at an upstream end portion or a downstream end portion of a conveyed medium.

The main invention for achieving the object is as follows:
(A) a nozzle that forms an image on the medium by ejecting liquid toward the medium based on image data while moving relative to the medium;
(B) a transport unit that transports the medium along a predetermined direction;
(C) a liquid ejection control unit that changes the timing at which the liquid is ejected from the nozzle using dummy pixel data as pixel data constituting the image in the image data,
When the liquid is discharged from the nozzle toward at least one of the upstream end and the downstream end of the medium transported by the transport unit, the other is different from the region A liquid discharge control unit that changes the timing by using the dummy pixel data in an arrangement different from the case where the liquid is discharged from the nozzle toward the region;
A liquid ejection apparatus including (D).

  Other features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

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

(A) a nozzle that forms an image on the medium by ejecting liquid toward the medium based on image data while moving relative to the medium;
(B) a transport unit that transports the medium along a predetermined direction;
(C) a liquid ejection control unit that changes the timing at which the liquid is ejected from the nozzle using dummy pixel data as pixel data constituting the image in the image data,
When the liquid is discharged from the nozzle toward at least one of the upstream end and the downstream end of the medium transported by the transport unit, the other is different from the region A liquid discharge control unit that changes the timing by using the dummy pixel data in an arrangement different from the case where the liquid is discharged from the nozzle toward the region;
A liquid discharge apparatus comprising (D).

  In such a liquid ejection device, when the liquid is ejected from the nozzle toward at least one of the upstream end and the downstream end of the medium transported by the transport unit, By changing the timing by using dummy pixel data in a different arrangement from the case where liquid is ejected from the nozzle toward another area different from this area, the upstream end or downstream end of the medium is changed. It is possible to suppress image quality deterioration.

  In such a liquid ejection apparatus, the nozzle is directed toward the medium while moving relative to the medium during the conveyance operation in which the conveyance unit conveys the medium along the predetermined direction. The liquid discharge operation for discharging the liquid may be executed, and the liquid discharge control unit may change the arrangement of the dummy pixel data each time the liquid discharge operation is executed by the nozzle. As described above, the liquid discharge control unit changes the arrangement of the dummy pixel data every time the liquid discharge operation is performed by the nozzle, thereby reducing the image quality of the upstream end or the downstream end of the medium to be conveyed. It can be suppressed more.

  In the liquid discharge apparatus, the nozzle includes a plurality of nozzles arranged along the predetermined direction, and the liquid discharge control unit includes the dummy pixels according to the positions of the plurality of nozzles. The data arrangement may be different. In this way, by changing the arrangement of the dummy pixel data according to the positions of the plurality of nozzles arranged along the predetermined direction, the image quality deterioration at the upstream end or the downstream end of the conveyed medium is further reduced. Can be suppressed.

  Further, in such a liquid ejection device, the nozzle includes a plurality of nozzles arranged along the predetermined direction, the plurality of nozzles are distributed into a plurality of groups, and the liquid ejection control unit includes: The arrangement of the dummy pixel data may be different for each group. In this way, the plurality of nozzles arranged along a predetermined direction are divided into a plurality of groups, and the arrangement of the dummy pixel data is changed for each group, so that the upstream end or the downstream end of the medium to be conveyed It is possible to further suppress the image quality deterioration of the part.

  Further, in such a liquid ejecting apparatus, the dummy pixel data when the liquid is ejected from the nozzle toward at least one of the upstream end and the downstream end of the medium. In order to investigate the arrangement, the adjustment pattern may be formed by the liquid ejected from the nozzle that moves relative to the medium. By forming such an adjustment pattern, it is possible to easily suppress deterioration in image quality at the upstream end or the downstream end of the conveyed medium.

  In the liquid ejecting apparatus, as the adjustment pattern, the first formed on the medium by the liquid ejected from the nozzle when the nozzle is moving in one direction. A pattern and a second pattern formed on the medium by the liquid ejected from the nozzle when the nozzle is moving in a direction opposite to the one direction may be formed. . If such a first pattern and a second pattern are formed as adjustment patterns, it is possible to easily suppress deterioration in image quality at the upstream end or downstream end of the conveyed medium.

  In such a liquid ejecting apparatus, ink may be ejected from the nozzle as the liquid. If ink is ejected from the nozzle as a liquid in this way, image quality deterioration at the upstream end or downstream end of the conveyed medium can be suppressed.

A liquid ejection method for forming an image on the medium by ejecting liquid from the nozzle toward the medium based on image data while moving the nozzle relative to the medium conveyed along a predetermined direction Because
The upstream end of the medium transported by the transport unit when changing the timing at which the liquid is ejected from the nozzle using dummy pixel data as pixel data constituting the image in the image data And when the liquid is discharged from the nozzle toward at least one of the downstream end portions, and the liquid is discharged from the nozzle toward another region different from the region A liquid ejection method, wherein the timing is changed by using the dummy pixel data in an arrangement different from the above.

=== Overview of Liquid Discharge Device ===
Hereinafter, an embodiment of the liquid ejection apparatus according to the present embodiment will be described. Here, as an example of the liquid ejecting apparatus, an ink jet printer 1 which is a printing apparatus that performs printing by ejecting ink toward a medium will be described. 1 to 3 describe the ink jet printer 1. FIG. 1 shows the appearance of the inkjet printer 1. FIG. 2 shows the internal configuration of the inkjet printer 1. FIG. 3 illustrates the configuration of the transport unit of the inkjet printer 1. FIG. 4 shows the nozzles of the ink jet printer 1. FIG. 5 illustrates the system configuration of the inkjet printer 1.

  As shown in FIG. 1, the ink jet printer 1 has a structure for discharging a medium such as printing paper supplied from the back surface from the front surface, and an operation panel 2 and a paper discharge portion 3 are provided on the front surface portion. ing. In addition, a paper feeding unit 4 is provided on the back side. Various operation buttons 5 and display lamps 6 are provided on the operation panel 2. The paper discharge unit 3 is provided with a paper discharge tray 7 that closes the paper discharge port when not in use. The paper feed unit 4 is provided with a paper feed tray 8 for holding a medium such as cut paper.

  Inside the ink jet printer 1, a carriage 41 is provided as shown in FIG. The carriage 41 is provided to be relatively movable along the left-right direction. Around the carriage 41, a carriage motor 42, a pulley 44, a timing belt 45, and a guide rail 46 are provided. The carriage motor 42 is constituted by a DC motor or the like, and is a drive source for relatively moving the carriage 41 in the left-right direction (hereinafter also referred to as the carriage movement direction). The timing belt 45 is connected to the carriage motor 42 via the pulley 44, and a part of the timing belt 45 is connected to the carriage 41. The carriage 41 is moved relative to the carriage 41 in the carriage movement direction (left-right direction) by the rotation of the carriage motor 42. Move. The guide rail 46 guides the carriage 41 along the carriage movement direction (left-right direction).

  In addition, in the periphery of the carriage 41, a linear encoder 51 that detects the position of the carriage 41 and a direction in which the medium S intersects the moving direction of the carriage 41 (the front-rear direction in the figure, hereinafter also referred to as the transport direction). A transport roller 17A for transporting along the transport path 17 and a transport motor 15 for rotationally driving the transport roller 17A are provided.

  On the other hand, the carriage 41 is provided with an ink cartridge 48 that stores various inks, and a head 21 that performs printing on the medium S. The ink cartridge 48 contains, for example, each color ink such as yellow (Y), magenta (M), cyan (C), black (K), and is detachable from a cartridge mounting portion 49 provided on the carriage 41. It is attached to. In the present embodiment, the head 21 performs printing by ejecting ink onto the medium S. For this purpose, the head 21 is provided with a number of nozzles for ejecting ink.

In addition to this, in the inkjet printer 1, printing is performed in order to prevent clogging of the nozzles of the head 21 and the pump device 31 that sucks out ink from the nozzles in order to eliminate clogging of the nozzles of the head 21. A capping device 35 that seals the nozzles of the head 21 when not in use (such as during standby) is provided.
Next, the conveyance unit of the inkjet printer 1 will be described. As shown in FIG. 3, the transport unit includes a paper feed roller 13, a paper detection sensor 53, a transport roller 17A, a paper discharge roller 17B, a platen 14, and free rollers 18A and 18B. Yes.

  The medium S to be printed is set in the paper feed tray 8. The medium S set in the paper feed tray 8 is conveyed along the direction of arrow A in the drawing by the paper feed roller 13 having a substantially D-shaped cross section, and is sent into the ink jet printer 1. The medium S sent to the inside of the ink jet printer 1 comes into contact with the paper detection sensor 53. The paper detection sensor 53 is installed between the paper feed roller 13 and the transport roller 17A, and detects the medium S fed by the paper feed roller 13.

  The medium S detected by the paper detection sensor 53 is sequentially transported to the platen 14 on which printing is performed by the transport roller 17A. A free roller 18A is provided at a position facing the conveying roller 17A. The medium S is smoothly transported by sandwiching the medium S between the free roller 18A and the transport roller 17A.

The medium S sent to the platen 14 is sequentially printed by the ink ejected from the head 21. The platen 14 is provided to face the head 21 and supports the medium S to be printed from below.
The medium S on which printing has been performed is sequentially discharged out of the printer by the paper discharge roller 17B. The paper discharge roller 17B is driven in synchronism with the transport motor 15, and sandwiches the medium S with the free roller 18B provided facing the paper discharge roller 17B, and discharges the medium S to the outside of the printer. To do.

  In the present embodiment, the rear end portion of the medium S is referred to as an “upstream end portion”. The leading end of the medium S is referred to as a “downstream end”.

<Head>
FIG. 4 is a diagram showing an arrangement of ink nozzles provided on the lower surface of the head 21. On the lower surface of the head 21, as shown in the figure, nozzles comprising a plurality of nozzles # 1 to # 90 for each color of yellow (Y), magenta (M), cyan (C), and black (K). A cyan nozzle row 211C, a magenta nozzle row 211M, a yellow nozzle row 211Y, and a black nozzle row 211K are provided.

  The nozzles # 1 to # 90 of each of the nozzle rows 211C, 211M, 211Y, and 211K are linearly arranged in a row at intervals from each other along a predetermined direction (here, the transport direction of the medium S). ing. The nozzle rows 211C, 211M, 211Y, and 211K are arranged in parallel with an interval between each other along the moving direction of the head 21. Each nozzle # 1 to # 90 is provided with a piezo element (not shown) as a drive element for ejecting ink droplets.

  When a voltage having a predetermined time width is applied between the electrodes provided at both ends of the piezoelectric element, the piezoelectric element expands according to the voltage application time and deforms the side wall of the ink flow path. As a result, the volume of the ink flow path contracts in accordance with the expansion and contraction of the piezo element, and the ink corresponding to this contraction becomes ink droplets, and each nozzle # 1 of each color nozzle row 211C, 211M, 211Y, 211K. Discharge from ~ # 90.

<System configuration>
Next, the system configuration of the inkjet printer 1 will be described. As shown in FIG. 5, the inkjet printer 1 includes a buffer memory 122, an image buffer 124, a controller 126, a main memory 127, a communication interface 129, a carriage motor control unit 128, a conveyance control unit 130, A head driving unit 132.

  The communication interface 129 is for the inkjet printer 1 to exchange data with an external computer 140 such as a personal computer. The communication interface 129 is communicably connected to the external computer 140 by wire or wireless, and receives various data such as print data transmitted from the computer 140.

  Various data such as print data received by the communication interface 129 are temporarily stored in the buffer memory 122. The image buffer 124 sequentially stores print data stored in the buffer memory 122. The print data stored in the image buffer 124 is sequentially sent to the head driving unit 132. The main memory 127 is composed of ROM, RAM, EEPROM, and the like. The main memory 127 stores various programs for controlling the inkjet printer 1 and various setting data.

  The controller 126 reads a control program, each setting data, and the like from the main memory 127, and controls the entire inkjet printer 1 according to the control program and various setting data. The controller 126 receives detection signals from various sensors such as the rotary encoder 134, the linear encoder 51, and the paper detection sensor 53.

  When various data such as print data sent from the external computer 140 is received by the communication interface 129 and stored in the buffer memory 122, the controller 126 stores necessary information from the stored data in the buffer memory. Read from 122. Based on the read information, the controller 126 refers to the output from the linear encoder 51 and the rotary encoder 134 and controls the carriage motor control unit 128, the conveyance control unit 130, the head drive unit 132, and the like according to the control program. Control each one.

  The carriage motor control unit 128 drives and controls the rotation direction, number of rotations, torque, and the like of the carriage motor 42 in accordance with instructions from the controller 126. The conveyance control unit 130 controls the conveyance motor 15 that rotationally drives the conveyance roller 17 </ b> A according to a command from the controller 126.

  The head drive unit 132 drives and controls the nozzles of each color provided in the head 21 based on the print data stored in the image buffer 124 in accordance with a command from the controller 126.

=== Conventional problems ===
By the way, in such an ink jet printer 1, the upstream side end portion of the medium S to be conveyed (in this embodiment, it corresponds to the “rear end portion” of the medium S) or the downstream side end portion (note that In the present embodiment, for the “tip portion” of the medium S), there is a case where deterioration of the image quality of the printed image cannot be sufficiently prevented. This is because when the upstream end or downstream end of the medium S is printed, the upstream end or downstream end of the medium S slightly floats. In this way, the upstream end or the downstream end of the medium S is slightly lifted from the printing position because the upstream end or the downstream end of the medium is separated from the transport roller 17A that transports the medium S. Because. That is, at the initial stage when printing on the medium S is started, the downstream end of the medium S is not yet in contact with the transport roller 17A and the downstream end of the medium S is separated from the transport roller 17A and the like. It is in the state. For this reason, when printing is performed on the downstream end portion of the medium S, the downstream end portion of the medium S may be slightly lifted from the printing position. Further, immediately before the printing on the medium S is completed, the upstream end portion of the medium S is separated from the transport roller 17A and the like. For this reason, when printing is performed on the upstream end portion of the medium S, the upstream end portion of the medium S may be slightly lifted from the printing position.

  When printing is performed on the upstream end or the downstream end of the medium S in a state where the upstream end or the downstream end of the medium S is slightly lifted from the printing position in this way, The gap between the printing surface and the nozzle will fluctuate. When the gap between the printing surface of the medium S and the nozzles # 1 to # 90 fluctuates in this way, the arrival position of the ink ejected from the nozzles # 1 to # 90 is shifted, and the upstream end of the medium S Image quality at the edge or downstream side may be deteriorated. In particular, recently, the moving speed of the carriage 41 has been greatly increased in order to improve the printing processing speed. For this reason, image quality deterioration due to a gap variation between the printing surface of the medium S and the nozzles # 1 to # 90 cannot be ignored.

=== Gap between head and printing surface ===
6A to 6C illustrate the gap between the head 21 and the printing surface when the medium S is printed.

  When the medium S is printed, as shown in FIG. 6A, the medium S is sandwiched between the transport roller 17A and the free roller 18A disposed on the upstream side in the transport direction and sent to the platen 14, The paper is sandwiched between a paper discharge roller 17B and a free roller 18B disposed on the downstream side in the transport direction, and sequentially transported to the paper discharge side.

  Then, when printing on the medium S proceeds and the upstream end S1 of the medium S moves away from between the transport roller 17A and the free roller 18A, the upstream end S1 of the medium S is bent as shown in FIG. 6B. It may be in a state of being stuck. The medium S in which the upstream end S1 is bent is sandwiched between the discharge roller 17B and the free roller 18B while being bent, and is conveyed to the discharge side.

  For this reason, even when passing over the platen 14 below the head 21, the upstream end S <b> 1 of the medium S remains in a bent state, and therefore the gap between the head 21 and the printing surface of the medium S. As shown in FIG. 6C, GP1 and GP2 are different between the upstream gap GP2 and the downstream gap GP1 in the transport direction. That is, the gap GP1 from the nozzle # 1 disposed on the downstream side in the transport direction to the printing surface of the medium S is an assumed distance (gap), whereas the nozzle # disposed on the upstream side in the transport direction. The gap GP2 from 90 to the printing surface of the medium S is different from the assumed distance (gap) because the upstream end S1 of the medium S of the medium S is bent and floats from the platen 14. . For this reason, a deviation occurred in the arrival position of the ink ejected from the nozzle # 90.

  In particular, when ink is ejected from the nozzles # 1 to # 90 while the carriage 41 is reciprocally moved relative to the medium S, the carriage 41 is moving in one direction (the carriage 41 Is moving on the forward path), when the position on the medium S where the ink ejected from the nozzles # 1 to # 90 arrives and the carriage 41 is moving in a direction opposite to the one direction ( When the carriage 41 is moving in the return path), the position on the medium S where the ink ejected from the nozzles # 1 to # 90 arrives greatly deviates.

  In FIGS. 6A to 6C, the case where the upstream end S1 of the medium S is bent is described as an example. However, the downstream end (tip) of the medium S is similarly bent. It may be in a state of being stuck.

<Ink arrival position shift>
FIG. 7 illustrates the deviation of the ink arrival position when the carriage 41 is reciprocated.

  When the carriage 41 moves in one direction, that is, in this case, for example, in the right direction (forward path), the position where the ink ejected from the nozzles # 1 to # 90 reaches the medium S, and the carriage 41 The direction opposite to the one direction, that is, here, for example, the position where the ink ejected from the nozzles # 1 to # 90 reaches the medium S when moving leftward (return path) is, for example, Normally, adjustment is performed so that the points coincide with each other by the adjustment method called “Bi-d adjustment”.

  However, as described above, when the upstream end S1 of the medium S is bent and lifted from the platen 14, the gap between the printing surface of the upstream end S1 of the medium S and the head 21 is reduced. From the position where the ink ejected from the nozzles # 1 to # 90 reaches the medium S when the carriage 41 is moving in one direction, that is, in this case, for example, the right direction (outward path), and the carriage 41 is a direction opposite to one direction, that is, here, for example, a position where ink ejected from nozzles # 1 to # 90 reaches the medium S when moving leftward (return path). Are shifted from each other, so that they do not coincide at the point P1.

  That is, as shown in the figure, the position in the height direction of the medium S before the gap change is “H1”. When the position in the height direction of the medium S after the gap change is “H2”, the nozzle # 1 is moved when the carriage 41 moves in one direction, that is, in this case, for example, in the right direction (outward path). The position where the ink ejected from 1 to # 90 reaches the medium S is point P2. On the other hand, the ink ejected from the nozzles # 1 to # 90 reaches the medium S when the carriage 41 moves in the direction opposite to the one direction, that is, here, for example, in the left direction (return path). The position to do is point P3.

  In this way, the position where the ink ejected from the nozzles # 1 to # 90 reaches the medium S when the carriage 41 is moving in one direction, that is, in this case, for example, in the right direction (outward path). (Point P2) and the ink ejected from the nozzles # 1 to # 90 when the carriage 41 is moving in the direction opposite to the one direction, that is, here, for example, when moving in the left direction (return path). Since the position reaching the medium S (point P3) is shifted, the height position “H2” of the medium S needs to be adjusted separately in order to match at the point P1.

=== Adjustment method ===
Therefore, in the present embodiment, when printing is performed on the upstream end portion or the downstream end portion of the conveyed medium, the nozzles are arranged so as not to cause a large shift in the arrival position of the ink ejected from the nozzles. Therefore, it is necessary to adjust the ink arrival position by shifting the timing at which the ink is discharged. In this embodiment, the timing at which ink is ejected from the nozzles is changed by using a technique called “pixel shifting”. This “pixel shift” will be described in detail below.

<Outline of pixel shifting>
FIG. 8 explains the outline of this “pixel shift”. In this “pixel shift”, dummy pixel data is used as the data of the pixels constituting the image as the data of the image to be printed, so that the nozzles # 1 to # 1 of the nozzle rows 211C, 211M, 211Y, and 211K are used. The timing at which ink is ejected from 90 is adjusted. Specifically, as shown in the figure, dummy pixel data is added to pixel data of an image to be printed, and ink is ejected from nozzles # 1 to # 90 using the data created thereby. .

  Here, the dummy pixel data is added to the left and right sides of the pixel data of the image to be printed. As shown in (1) of the figure, when the pixel shift is not performed, for example, the dummy pixel data A1 to A3 and B1 to B3 are respectively provided on the left and right sides of the pixel data of the image to be printed by three pixels. Let's add.

  For example, as shown in (2) of the figure, when it is desired to shift the pixel data of the image to be printed by one pixel in the left direction, 2 on the left side of the pixel data of the image to be printed. While dummy pixel data A1 to A2 for pixels are added, dummy pixel data B1 to B4 for four pixels are added to the right side of the pixel data of the image to be printed. Thereby, the pixel data of the image to be printed can be shifted by one pixel in the left direction. Therefore, when ink is ejected from each nozzle # 1 to # 90 based on the data, the timing at which ink is ejected from the nozzles # 1 to # 90 is shifted.

  Further, for example, as shown in (3) of the figure, when it is desired to shift the pixel data of the image to be printed by one pixel in the right direction, 4 pixels are displayed on the left side of the pixel data of the image to be printed. While dummy pixel data A1 to A4 for pixels are added, dummy pixel data B1 to B2 for two pixels are added to the right side of the pixel data of the image to be printed. As a result, the pixel data of the image to be printed can be shifted rightward by one pixel. Therefore, when ink is ejected from each nozzle # 1 to # 90 based on the data, the timing at which ink is ejected from the nozzles # 1 to # 90 is shifted.

<Actual application examples>
FIGS. 9A to 9D illustrate an arrangement example between the medium S and the head 21. FIG. 9A illustrates a state where the upstream end S1 of the medium S does not reach below the nozzles # 1 to # 90. FIG. 9B illustrates a state in which the upstream end S1 of the medium S is approaching below the nozzles # 61 to # 90. FIG. 9C illustrates a state in which the upstream end S1 of the medium S is approaching below the nozzles # 31 to # 90. FIG. 9D illustrates a state where the upstream end S1 of the medium S is approaching below the nozzles # 1 to # 90.

  FIGS. 10A to 10D illustrate an example of “pixel shifting” in the arrangement examples of FIGS. 9A to 9D. FIG. 10A illustrates an example of “pixel shift” corresponding to FIG. 9A. FIG. 10B illustrates an example of “pixel shift” corresponding to FIG. 9B. FIG. 10C illustrates an example of “pixel shifting” corresponding to FIG. 9C. FIG. 10D illustrates an example of “pixel shift” corresponding to FIG. 9D.

  In the present embodiment, 90 nozzles # 1 to # 90 are divided into three groups when performing “pixel shifting”. That is, the nozzles are divided into three groups: a first group of nozzles # 1 to # 30, a second group of nozzles # 31 to # 60, and a third group of nozzles # 61 to # 90. Then, different shift amounts are set for these three first to third groups.

(1) First Step First, as shown in FIG. 9A, when the upstream end S1 of the medium S does not reach below the nozzles # 1 to # 90, the nozzles # 1 to # 90 of the head 21 Since the gap with the printing surface of the medium S has not changed, “pixel shifting” is not performed for the nozzles # 1 to # 90. That is, for example, as shown in FIG. 10A, the same number of dummy pixel data A1 to A3 and B1 to B3 are added to the left and right sides of the pixel data “1” to “N5” of the image to be printed. Here, dummy pixel data A1 to A3 and B1 to B3 are added to each of the left and right sides of the pixel data “1” to “N5” of the image to be printed.

(2) Second Step Next, as shown in FIG. 9B, the case where the upstream end S1 of the medium S is located below the third group of the nozzles # 61 to # 90 will be described. In this case, although the gaps between the first and second groups of the nozzles # 1 to # 60 of the head 21 and the printing surface of the medium S do not vary greatly, the nozzles # 61 to # 90 of the head 21 and the medium S The gap between the printing surface and the printing surface becomes smaller and fluctuates. Therefore, “pixel shifting” is not performed for nozzles # 1 to # 60, but “pixel shifting” is performed for nozzles # 61 to # 90.

  That is, as shown in (1) of FIG. 10B, since the “pixel shift” is not performed for the nozzles # 1 to # 60, the left and right sides of the pixel data “1” to “N5” of the image to be printed The same number of dummy pixel data A1 to A3 and B1 to B3 are added to both sides. On the other hand, “pixel shift” is performed for the nozzles # 61 to # 90. Here, when the carriage 41 moves in one direction (in the forward path) and when the carriage 41 moves in a direction opposite to the one direction (in the backward path), the arrangement of dummy pixel data, respectively. The method is different.

  That is, as shown in (2) of FIG. 10B, when the carriage 41 moves in one direction (in the forward path), the pixel data “1” to “N5” of the image to be printed are displayed on the left side. Dummy pixel data A1 to A4 for four pixels are added. On the other hand, dummy pixel data B1 to B2 for two pixels are added to the right side of the pixel data “1” to “N5” of the image to be printed. As a result, the pixel data “1” to “N5” of the image to be printed can be shifted rightward by one pixel. Therefore, when ink is ejected from each nozzle # 61 to # 90 based on the data, the timing at which ink is ejected from the nozzles # 61 to # 90 is shifted by one pixel. Thereby, the arrival position of the ink ejected from the nozzles # 61 to # 90 can be adjusted.

  When the carriage 41 moves in the direction opposite to the one direction (in the case of the backward path), a dummy for two pixels is placed on the left side of the pixel data “1” to “N5” of the image to be printed. Pixel data A1 and A2 are added. On the other hand, dummy pixel data B1 to B4 for four pixels are added to the right side of the pixel data “1” to “N5” of the image to be printed. As a result, the pixel data “1” to “N5” of the image to be printed can be shifted leftward by one pixel. Therefore, when ink is ejected from the nozzles # 61 to # 90 based on the data, the timing at which ink is ejected from the nozzles # 61 to # 90 is shifted by one pixel. Thereby, the arrival position of the ink ejected from the nozzles # 61 to # 90 can be adjusted.

(3) Third Step Further, as shown in FIG. 9C, when the upstream end S1 of the medium S reaches below the nozzles # 31 to # 90, the nozzles # 1 to # 30 of the head 21 Although the gap between the printing surface of the medium S does not vary greatly, the gap between the nozzles # 30 to # 90 of the head 21 and the printing surface of the medium S becomes smaller and varies. Therefore, “pixel shifting” is not performed for the nozzles # 1 to # 30, but “pixel shifting” is performed for the nozzles # 31 to # 90.

  That is, as shown in (1) of FIG. 10C, since the “pixel shift” is not performed for the nozzles # 1 to # 30, the left and right sides of the pixel data “1” to “N5” of the image to be printed The same number of dummy pixel data A1 to A3 and B1 to B3 are added to both sides. On the other hand, for the nozzles # 61 to # 90, since “pixel shifting” is performed, the number of dummy pixel data on the left and right sides of the pixel data “1” to “N5” of the image to be printed is adjusted. Here, when the carriage 41 moves in one direction (in the forward path) and when the carriage 41 moves in a direction opposite to the one direction (in the backward path), the arrangement of dummy pixel data, respectively. The method is different. In the present embodiment, the shift amount differs between the second group of nozzles # 31 to # 60 and the third group of nozzles # 61 to # 90.

  That is, in the case of the second group of nozzles # 31 to # 60, as shown in (2) of FIG. 10C, an image to be printed when the carriage 41 moves in one direction (in the forward path). The dummy pixel data A1 to A4 for four pixels are added to the left side of the pixel data “1” to “N5”. On the other hand, dummy pixel data B1 to B2 for two pixels are added to the right side of the pixel data “1” to “N5” of the image to be printed. As a result, the pixel data “1” to “N5” of the image to be printed can be shifted rightward by one pixel. Therefore, when ink is ejected from the nozzles # 31 to # 60 based on the data, the timing at which ink is ejected from the nozzles # 31 to # 60 is shifted by one pixel. Thereby, the arrival position of the ink ejected from the nozzles # 31 to # 60 can be adjusted.

  When the carriage 41 moves in the direction opposite to the one direction (in the case of the backward path), a dummy for two pixels is placed on the left side of the pixel data “1” to “N5” of the image to be printed. Pixel data A1 and A2 are added. On the other hand, dummy pixel data B1 to B4 for four pixels are added to the right side of the pixel data “1” to “N5” of the image to be printed. As a result, the pixel data “1” to “N5” of the image to be printed can be shifted leftward by one pixel. Therefore, when ink is ejected from the nozzles # 31 to # 60 based on the data, the timing at which ink is ejected from the nozzles # 31 to # 60 is shifted by one pixel. Thereby, the arrival position of the ink ejected from the nozzles # 31 to # 60 can be adjusted.

  On the other hand, in the case of the third group of nozzles # 61 to # 90, as shown in (3) of FIG. 10C, an image to be printed when the carriage 41 moves in one direction (in the forward path). The dummy pixel data A1 to A5 for 5 pixels are added to the left side of the pixel data “1” to “N5”. On the other hand, dummy pixel data B1 for one pixel is added to the right side of the pixel data “1” to “N5” of the image to be printed. Accordingly, the pixel data “1” to “N5” of the image to be printed can be shifted by two pixels in the right direction. Therefore, when ink is ejected from the nozzles # 61 to # 90 based on the data, the timing at which ink is ejected from the nozzles # 61 to # 90 is shifted by two pixels. Thereby, the arrival position of the ink ejected from the nozzles # 61 to # 90 can be adjusted.

  When the carriage 41 moves in the direction opposite to the one direction (in the case of the backward path), a dummy for one pixel is placed on the left side of the pixel data “1” to “N5” of the image to be printed. Pixel data A1 is added. On the other hand, dummy pixel data B1 to B5 for five pixels are added to the right side of the pixel data “1” to “N5” of the image to be printed. Thereby, the pixel data “1” to “N5” of the image to be printed can be shifted by two pixels in the left direction. Therefore, when ink is ejected from the nozzles # 61 to # 90 based on the data, the timing at which ink is ejected from the nozzles # 61 to # 90 is shifted by two pixels. Thereby, the arrival position of the ink ejected from the nozzles # 61 to # 90 can be adjusted.

(4) Fourth Step Then, as shown in FIG. 9D, when the upstream end S1 of the medium S reaches below the nozzles # 1 to # 90, all of the nozzles # 1 to # 90 are Since the gap with the printing surface of the medium S is small, “pixel shifting” is performed. Here, different shift amounts are set for the first group of nozzles # 1 to # 30, the second group of nozzles # 31 to # 60, and the third group of nozzles # 61 to # 90.

  That is, for the first group of nozzles # 1 to # 30, as shown in (1) of FIG. 10D, when the carriage 41 moves in one direction (in the forward path), the pixels of the image to be printed Dummy pixel data A1 to A4 for four pixels are added to the left side of the data “1” to “N5”. On the other hand, dummy pixel data B1 to B2 for two pixels are added to the right side of the pixel data “1” to “N5” of the image to be printed. As a result, the pixel data “1” to “N5” of the image to be printed can be shifted rightward by one pixel. Therefore, when ink is ejected from the nozzles # 1 to # 30 based on the data, the timing at which ink is ejected from the nozzles # 1 to # 30 is shifted by one pixel. Thereby, the arrival position of the ink ejected from the nozzles # 1 to # 30 can be adjusted.

  On the other hand, when the carriage 41 moves in the direction opposite to the one direction (in the case of the return path), a dummy for two pixels is placed on the left side of the pixel data “1” to “N5” of the image to be printed. Pixel data A1 and A2 are added. On the other hand, dummy pixel data B1 to B4 for four pixels are added to the right side of the pixel data “1” to “N5” of the image to be printed. As a result, the pixel data “1” to “N5” of the image to be printed can be shifted leftward by one pixel. Therefore, when ink is ejected from the nozzles # 31 to # 60 based on the data, the timing at which ink is ejected from the nozzles # 1 to # 30 is shifted by one pixel. Thereby, the arrival position of the ink ejected from the nozzles # 1 to # 30 can be adjusted.

  For the second group of nozzles # 31 to # 60, as shown in (2) of FIG. 10D, when the carriage 41 moves in one direction (in the forward path), the pixels of the image to be printed Dummy pixel data A1 to A5 for five pixels are added to the left side of the data “1” to “N5”. On the other hand, dummy pixel data B1 for one pixel is added to the right side of the pixel data “1” to “N5” of the image to be printed. Accordingly, the pixel data “1” to “N5” of the image to be printed can be shifted by two pixels in the right direction. Therefore, when ink is ejected from the nozzles # 31 to # 60 based on the data, the timing at which ink is ejected from the nozzles # 31 to # 60 is shifted by two pixels. Thereby, the arrival position of the ink ejected from the nozzles # 31 to # 60 can be adjusted.

  On the other hand, when the carriage 41 moves in the direction opposite to the one direction (in the case of the backward path), a dummy for one pixel is placed on the left side of the pixel data “1” to “N5” of the image to be printed. Pixel data A1 is added. On the other hand, dummy pixel data B1 to B5 for five pixels are added to the right side of the pixel data “1” to “N5” of the image to be printed. Thereby, the pixel data “1” to “N5” of the image to be printed can be shifted by two pixels in the left direction. Therefore, when ink is ejected from the nozzles # 31 to # 60 based on the data, the timing at which ink is ejected from the nozzles # 31 to # 60 is shifted by two pixels. Thereby, the arrival position of the ink ejected from the nozzles # 31 to # 60 can be adjusted.

  For the third group of nozzles # 61 to # 90, as shown in (3) of FIG. 10D, when the carriage 41 moves in one direction (in the forward path), the pixels of the image to be printed Dummy pixel data A1 to A6 for 6 pixels are added to the left side of the data “1” to “N5”. On the other hand, dummy pixel data is not added to the right side of the pixel data “1” to “N5” of the image to be printed. Accordingly, the pixel data “1” to “N5” of the image to be printed can be shifted by three pixels in the right direction. Therefore, when ink is ejected from the nozzles # 61 to # 90 based on the data, the timing at which ink is ejected from the nozzles # 61 to # 90 is shifted by 3 pixels. Thereby, the arrival position of the ink ejected from the nozzles # 61 to # 90 can be adjusted.

  On the other hand, when the carriage 41 moves in the direction opposite to the one direction (in the case of the backward path), dummy pixel data is placed on the left side of the pixel data “1” to “N5” of the image to be printed. Do not add. On the other hand, dummy pixel data B1 to B6 for 6 pixels are added to the right side of the pixel data “1” to “N5” of the image to be printed. As a result, the pixel data “1” to “N5” of the image to be printed can be shifted leftward by three pixels. Therefore, when ink is ejected from the nozzles # 61 to # 90 based on the data, the timing at which ink is ejected from the nozzles # 61 to # 90 is shifted by two pixels. Thereby, the arrival position of the ink ejected from the nozzles # 61 to # 90 can be adjusted.

<Supplement>
9A to 9D, the case where the upstream end S1 of the medium S is bent is described as an example. However, the downstream end (tip) of the medium S is similarly bent. It may be in a state. Thus, even when the downstream end portion (tip portion) of the medium S is bent, it can be handled by the method described with reference to FIGS. 10A to 10D.

=== Adjustment pattern ===
In the present embodiment, an adjustment pattern is formed on the medium in order to obtain an appropriate adjustment value for “pixel shift”. FIG. 11 illustrates an example of this adjustment pattern.

  Here, as shown in the figure, the adjustment pattern has first patterns 80A, 80B, 80C, 80D, 80E, 80F and second patterns 82A, 82B, 82C, 82D, 82E, 82F. Yes. The first patterns 80A, 80B, 80C, 80D, 80E, and 80F are formed by ink ejected from all or part of the nozzles # 1 to # 90 when the carriage 41 moves in one direction. The The second patterns 82A, 82B, 82C, 82D, 82E, and 82F are ejected from all or a part of the nozzles # 1 to # 90 when the carriage 41 moves in the direction opposite to the one direction. Formed by ink.

  Here, six first patterns 80A, 80B, 80C, 80D, 80E, and 80F are formed as the first patterns. In addition, six second patterns 82A, 82B, 82C, 82D, 82E, and 82F are formed as the second patterns. The six first patterns 80A, 80B, 80C, 80D, 80E, and 80F formed as the first pattern are different in the “pixel shift” method. That is, specifically, for example, the first pattern 80A that is the first from the left indicates a pattern in a case where “pixel shifting” is not performed. The second first pattern 80B from the left shows a pattern when “pixel shifting” for one pixel is performed in the right direction. The third first pattern 80 </ b> C from the left shows a pattern in a case where “pixel shift” for two pixels is performed in the right direction. The fourth first pattern 80D from the left shows a pattern when “pixel shifting” for three pixels is performed in the right direction. The fifth first pattern 80E from the left shows a pattern in the case of performing “pixel shift” for four pixels in the right direction. The first pattern 80F on the rightmost side shows a pattern when “pixel shifting” for five pixels is performed in the right direction.

  Similarly, the six second patterns 82A, 82B, 82C, 82D, 82E, and 82F formed as the second patterns have different pixel shift methods. That is, specifically, for example, the first second pattern 82A from the left indicates a pattern when “pixel shifting” is not performed. The second pattern 82B, which is the second from the left, indicates a pattern when “pixel shifting” for one pixel is performed in the left direction. The third second pattern 82C from the left shows a pattern in the case of performing “pixel shift” for two pixels in the left direction. The fourth second pattern 82D from the left shows a pattern when “pixel shifting” for three pixels is performed in the left direction. The fifth second pattern 82E from the left shows a pattern in the case of performing “pixel shift” for four pixels in the left direction. The second pattern 82F on the rightmost side shows a pattern when “pixel shifting” for five pixels is performed in the left direction.

  Here, the first pattern 80A and the second pattern 82A, which are the first from the left, are formed by performing “pixel shift” with the same shift amount. The first pattern 80B and the second pattern 82B, which are the second from the left, are formed by performing “pixel shift” with the same shift amount. In addition, the first pattern 80C and the second pattern 82C, which are the third from the left, are formed by performing “pixel shift” with the same shift amount. The fourth pattern from the left, the first pattern 80D and the second pattern 82D, are formed by performing “pixel shift” with the same shift amount. Further, the first pattern 80E and the second pattern 82E that are fifth from the left are formed by performing “pixel shift” with the same shift amount. In addition, the first pattern 80F and the second pattern 82F, which are the sixth from the left, are formed by performing “pixel shift” with the same shift amount.

  The first pattern 80A and the second pattern 82A that are the first from the left constitute a set of patterns 84A. Further, the first pattern 80B and the second pattern 82B that are second from the left form a set of patterns 84B. Further, the first pattern 80C and the second pattern 82C that are third from the left form a set of patterns 84C. The fourth pattern from the left, the first pattern 80D and the second pattern 82D, is a set of patterns 84D. The fifth first pattern 80E and the second pattern 82E from the left are a set of patterns 84E. Further, the first pattern 80F and the second pattern 82F which are the sixth from the left are a set of patterns 84F.

  When an appropriate adjustment value for “pixel shifting” is acquired, the most appropriate set of patterns is selected from these six sets of patterns 84A, 84B, 84C, 84D, 84E, and 84F. Here, when the carriage 41 is moving in one direction, the first pattern formed by the ink ejected from all or part of the nozzles # 1 to # 90 and the carriage 41 in one direction. When moving in the opposite direction, a set of patterns is selected such that the second patterns formed by the ink ejected from all or part of the nozzles # 1 to # 90 overlap each other. That is, the pattern of the group to be selected here is the fourth pattern 84D from the left.

  In the present embodiment, codes (A) to (F) are assigned to the six sets of patterns 84A, 84B, 84C, 84D, 84E, and 84F, respectively. When an appropriate adjustment value for “pixel shift” is set, a code corresponding to the most appropriate set of patterns is input. That is, here, the code (D) corresponding to the fourth set of patterns 84D from the left is set as the most appropriate adjustment value.

=== Method of Forming Actual Adjustment Patterns ===
FIG. 12 illustrates an example of an actual method for forming an adjustment pattern. Here, twelve adjustment patterns, that is, first to twelfth adjustment patterns 86A, 86B, 86C, 86D, 86E, 86F, 86G, 86H, 86I, 86J, 86K, and 86L are formed on the medium S. The first to twelfth adjustment patterns 86A, 86B, 86C, 86D, 86E, 86F, 86G, 86H, 86I, 86J, 86K, and 86L are formed in the vicinity of the upstream end S1 of the medium S. Here, an example of adjustment when the upstream end S1 of the medium S is bent will be described, but the same adjustment pattern is also used when the downstream end (tip) of the medium S is bent. Can be adjusted.

  The first to twelfth adjustment patterns 86A, 86B, 86C, 86D, 86E, 86F, 86G, 86H, 86I, 86J, 86K, and 86L are, for example, as described in FIG. One pattern and a second pattern are included.

  In the drawing, the first adjustment pattern 86A is shown in detail. The first adjustment pattern 86A includes, for example, six first patterns 80A, 80B, 80C, 80D, 80E, and 80F, and six second patterns 82A, 82B, 82C, 82D, 82E, and 82F. Yes. The first patterns 80A, 80B, 80C, 80D, 80E, and 80F are patterns formed by ink ejected when the carriage 41 is moving in one direction. The first patterns 80A, 80B, 80C, 80D, 80E, and 80F are different from each other in the “pixel shift”. The second patterns 82A, 82B, 82C, 82D, 82E, and 82F are patterns formed by ink ejected when the carriage 41 is moving in the direction opposite to the one direction. These second patterns 82A, 82B, 82C, 82D, 82E, and 82F have different pixel shift methods.

  The first pattern 80 </ b> A and the second pattern 82 </ b> A are formed by performing “pixel shift” with the same shift amount, and constitute a set of patterns 84 </ b> A. Further, the first pattern 80B and the second pattern 82B are formed by performing “pixel shift” with the same shift amount, and constitute a set of patterns 84B. Further, the first pattern 80C and the second pattern 82C are formed by performing “pixel shift” with the same shift amount, and constitute a set of patterns 84C. Further, the first pattern 80D and the second pattern 82D are formed by performing “pixel shift” with the same shift amount, and constitute a set of patterns 84D. Further, the first pattern 80E and the second pattern 82E are formed by performing “pixel shift” with the same shift amount, and constitute a set of patterns 84E. Further, the first pattern 80F and the second pattern 82F are formed by performing “pixel shift” with the same shift amount, and constitute a set of patterns 84F.

  Then, the most appropriate set of patterns is selected from the six sets of patterns 84A, 84B, 84C, 84D, 84E, and 84F. As a set of patterns to be selected here, for example, the first pattern formed by ink ejected when the carriage 41 is moving in one direction and the carriage 41 opposite to the one direction are used. A set of patterns is selected such that the second pattern formed by the ink ejected while moving in the direction overlaps each other.

  The other adjustment patterns, that is, the second to twelfth adjustment patterns 86B, 86C, 86D, 86E, 86F, 86G, 86H, 86I, 86J, 86K, and 86L are also the same as the first adjustment pattern 86A. A pattern and a second pattern. Then, an appropriate set of patterns is selected for each of the adjustment patterns 86B, 86C, 86D, 86E, 86F, 86G, 86H, 86I, 86J, 86K, and 86L.

<Method for forming each adjustment pattern>
Here, a method of forming each of the adjustment patterns (first to twelfth adjustment patterns) 86A, 86B, 86C, 86D, 86E, 86F, 86G, 86H, 86I, 86J, 86K, and 86L will be described.

  Here, the first adjustment pattern 86A, the fourth adjustment pattern 86D, the seventh adjustment pattern 86G, and the tenth adjustment pattern 86J are formed by ink ejected from the nozzles # 61 to # 90. Further, the second adjustment pattern 86B, the fifth adjustment pattern 86E, the eighth adjustment pattern 86H, and the eleventh adjustment pattern 86K are formed by ink ejected from the nozzles # 31 to # 60. The third adjustment pattern 86C, the sixth adjustment pattern 86F, the ninth adjustment pattern 86I, and the twelfth adjustment pattern 86L are formed by ink ejected from the nozzles # 1 to # 30.

  The first adjustment pattern 86A is the ink ejected from the nozzles # 61 to # 90 when the nozzles # 1 to # 90 are arranged with respect to the medium S at positions corresponding to “pass 1” in FIG. Formed by.

  After the first adjustment pattern 86A is thus formed, next, the medium S is conveyed by a predetermined amount. Here, the predetermined amount by which the medium S is conveyed is set to a distance corresponding to 30 nozzles. After the medium S is transported, the nozzles # 1 to # 90 are arranged at positions corresponding to “pass 2” in FIG. At this time, ink is ejected from the nozzles # 31 to # 60 to form the second adjustment pattern 86B. At this time, ink is ejected from the nozzles # 61 to # 90, and the fourth adjustment pattern 86D is formed.

  After the second adjustment pattern 86B and the fourth adjustment pattern 86D are thus formed, the medium S is again conveyed by the distance of 30 nozzles, and the nozzles # 1 to # 90 are moved relative to the medium S in the same figure. It is arranged at a position corresponding to “pass 3” in the middle. At this time, ink is ejected from the nozzles # 1 to # 30, and a third adjustment pattern 86C is formed. At this time, ink is ejected from the nozzles # 31 to # 60 to form the fifth adjustment pattern 86E. At this time, ink is ejected from the nozzles # 61 to # 90 to form the seventh adjustment pattern 86G.

  After the third adjustment pattern 86C, the fifth adjustment pattern 86E, and the seventh adjustment pattern 86G are thus formed, the medium S is again conveyed by a distance of 30 nozzles, and the nozzle # 1 ˜ # 90 are arranged at positions corresponding to “pass 4” in FIG. At this time, ink is ejected from the nozzles # 1 to # 30, and a sixth adjustment pattern 86F is formed. At this time, the eighth adjustment pattern 86H is formed by ejecting ink from the nozzles # 31 to # 60. At this time, ink is ejected from the nozzles # 61 to # 90 to form the tenth adjustment pattern 86J.

  After the sixth adjustment pattern 86F, the eighth adjustment pattern 86H, and the tenth adjustment pattern 86J are formed in this way, the medium S is again conveyed by a distance of 30 nozzles, and the nozzles # 1 to # 1 are conveyed. # 90 is arranged at a position corresponding to “pass 5” in FIG. At this time, ink is ejected from the nozzles # 1 to # 30 to form a ninth adjustment pattern 86I. At this time, the eleventh adjustment pattern 86K is formed by ejecting ink from the nozzles # 31 to # 60.

  Then, after the ninth adjustment pattern 86I and the eleventh adjustment pattern 86K are formed, the medium S is again conveyed by the distance of 30 nozzles, and the nozzles # 1 to # 90 are made the same with respect to the medium S. It is arranged at a position corresponding to “path 6” in the figure. At this time, ink is ejected from the nozzles # 1 to # 30, and the twelfth adjustment pattern 86L is formed.

  Through the above procedure, twelve adjustment patterns, that is, first to twelfth adjustment patterns 86A, 86B, 86C, 86D, 86E, 86F, 86G, 86H, 86I, 86J, 86K, and 86L are mediums. S is formed.

  In this way, twelve adjustment patterns, that is, the first to twelfth adjustment patterns 86A, 86B, 86C, 86D, 86E, 86F, 86G, 86H, 86I, 86J, 86K, and 86L are formed on the medium S. In this way, the adjustment value for performing “pixel shifting” can be acquired every time the operation of ejecting ink is performed between the operations of transporting the medium S, that is, for each pass.

<Adjustment value setting>
Such an adjustment value may be acquired for a print process that is executed after the upstream end S1 of the medium S is separated from the paper detection sensor 53 (see FIG. 3). That is, for the printing process to be executed after the upstream end S1 of the medium S is separated from the paper detection sensor 53 (see FIG. 3), that is, after the medium S is no longer detected by the paper detection sensor 53, the medium S The adjustment pattern is obtained by forming an adjustment pattern every time an operation for ejecting ink is performed between the operations in which the ink is conveyed, that is, for each pass.

  FIG. 13 illustrates an example of the adjustment value acquired in this way. After the medium S is no longer detected by the paper detection sensor 53, the adjustment is performed by forming an adjustment pattern for each pass, that is, every time ink is ejected between the operations of transporting the medium S. Get the value. In pass “1” immediately after the medium S is no longer detected by the paper detection sensor 53, the nozzles # 1 to # 30, the nozzles # 31 to # 60, and the nozzles # 61 to # 90 all have the adjustment value “0”. There is no need to change the timing at which ink is ejected by “pixel shifting”.

  Then, when the medium S is sequentially conveyed and the nozzles # 61 to # 90 out of the nozzles # 1 to # 90 reach the upstream end S1 of the medium S in the pass “N”, the nozzles located on the upstream side For # 61 to # 90, the adjustment value is set to “1” as the shift amount of “pixel shift”.

  Further, in the next pass “N + 1”, the nozzles # 31 to # 60 also approach the upstream end S1 of the medium S, and the adjustment values for the nozzles # 31 to # 60 are “pixel shift”. 1 ”, and for nozzles # 61 to # 90, the adjustment value is set to“ 2 ”as the shift amount of“ pixel shift ”.

  Furthermore, in the next pass “N + 2”, all the nozzles # 1 to # 90 reach the upstream end S1 of the medium S. Therefore, for nozzles # 1 to # 30, the adjustment value is set to “1” as the shift amount of “pixel shift”, and for nozzles # 31 to # 60, the shift amount of “pixel shift” is adjusted. The value is set to “2”, and for nozzles # 61 to # 90, the adjustment value is set to “3” as the shift amount of “pixel shift”.

  Then, in the next pass “N + 3”, the nozzles # 61 to # 90 are detached from the upstream end S 1 of the medium S. As a result, for nozzles # 61 to # 90, the adjustment value is set to “0” as the shift amount of “pixel shift”. On the other hand, for nozzles # 1 to # 60, the upstream end S1 of the medium S is approached, and for nozzles # 1 to # 30, the adjustment value is set to “2” as the shift amount of “pixel shift”. For nozzles # 31 to # 60, the adjustment value is set to “3” as the shift amount of “pixel shift”.

  Further, in the next pass “N + 4”, only the nozzles # 1 to # 30 reach the upstream end S1 of the medium S, and the nozzles # 1 to # 30 have a shift amount of “pixel shift”. The adjustment value is set to “3”. For the other nozzles, that is, the nozzles # 31 to # 60 and the nozzles # 61 to # 90, the adjustment value is set to “0” as the shift amount of “pixel shift”.

  Thereafter, all the nozzles # 1 to # 90 are disengaged from the upstream end S1 of the medium S, and the adjustment values are set to “0” as the shift amount of “pixel shift” for all the nozzles # 1 to # 90. .

=== Summary ===
As described above, in the present embodiment, when ink is ejected from the nozzles # 1 to # 90 to the upstream end S1 in the transport direction of the medium S, the pixels constituting the image are included in the image data to be printed. The dummy pixel data is added as the data and the data generated thereby is used to eject ink from the nozzles # 1 to # 90, thereby ejecting ink from the nozzles # 1 to # 90. Can be shifted. As a result, even if the gap between the nozzles # 1 to # 90 and the printing surface of the medium S fluctuates, the arrival positions of the inks ejected from the nozzles # 1 to # 90 in the forward path and the return path of the carriage 41 are mutually different. Adjustments can be made to match.

=== Other Embodiments ===
As described above, the embodiment has been described. However, the above-described embodiment is for facilitating the understanding of the present invention, and is not intended to limit the present invention. The present invention can be changed or improved without departing from the gist thereof, and needless to say, the present invention includes equivalents thereof. In particular, the embodiments described below are also included in the present invention.

<About media>
In the above-described embodiment, the “medium” includes plain paper, matte paper, cut paper, glossy paper, roll paper, paper, photographic paper, roll-type photographic paper, etc. In addition to these, OHP film and glossy film It may be a film material, cloth material, metal plate material, or the like. That is, any medium can be used as long as it can be a printing target.

<About liquid>
In the embodiment described above, ink such as cyan (C), magenta (M), yellow (Y), and black (K) is ejected from the nozzles as the “liquid”. In this case, the ink is not necessarily limited to such an ink.

<About liquid ejection device>
In the above-described embodiment, the case where the “liquid ejecting apparatus” is a printing apparatus such as the ink jet printer 1 has been described as an example. However, the “liquid ejecting apparatus” described here is not necessarily limited to such an ink jet printer 1. Need not be. That is, any type of liquid ejecting apparatus may be used as long as the liquid ejecting apparatus includes a nozzle that ejects liquid.

1 is a perspective view of a liquid ejection device (printing device) according to an embodiment. The perspective view explaining the internal structure of the liquid discharge apparatus (printing apparatus). Sectional drawing which shows the conveyance part of a liquid discharge apparatus (printing apparatus). Explanatory drawing which shows the arrangement | sequence of the nozzle of a head. The block block diagram which shows the system configuration | structure of a liquid discharge apparatus (printing apparatus). Explanatory drawing of the gap between the head and printing surface at the time of medium printing. FIG. 6 is an explanatory diagram when the medium end is separated from the conveyance roller. FIG. 6 is an explanatory diagram when a medium end away from a conveyance roller is printed. Explanatory drawing of the shift | offset | difference of the ink arrival position. Explanatory drawing of "pixel shift". Explanatory drawing of the state which the upstream edge part of the medium has not reached under nozzle # 1- # 90. Explanatory drawing of the state in which the upstream edge part of the medium is approaching below nozzles # 61 to # 90. Explanatory drawing of the state in which the upstream edge part of the medium is approaching below nozzles # 31 to # 90. Explanatory drawing of the state in which the upstream edge part of the medium is approaching below nozzles # 1 to # 90. FIG. 9B is an explanatory diagram of an example of “pixel shift” corresponding to FIG. 9A. FIG. 9B is an explanatory diagram of an example of “pixel shift” corresponding to FIG. 9B. FIG. 9D is an explanatory diagram of an example of “pixel shift” corresponding to FIG. 9C. FIG. 9D is an explanatory diagram of an example of “pixel shift” corresponding to FIG. 9D. Explanatory drawing explaining an example of the pattern for adjustment. Explanatory drawing of an example of the formation method of the actual adjustment pattern. Explanatory drawing of the example of a setting of the adjustment value acquired by the pattern for adjustment.

Explanation of symbols

1 Inkjet printer, 2 operation panel, 3 paper discharge unit, 4 paper supply unit,
5 operation buttons, 6 indicator lamps, 7 paper discharge tray, 8 paper feed tray,
13 paper feed roller, 14 platen, 15 transport motor, 17A transport roller,
17B paper discharge roller, 18A free roller, 18B free roller,
21 head, 41 carriage, 42 carriage motor, 44 pulley,
45 timing belt, 46 guide rail, 48 ink cartridge,
49 cartridge mounting part, 51 linear encoder, 53 paper detection sensor,
80A first pattern, 80B first pattern, 80C first pattern,
80D first pattern, 80E first pattern, 80F first pattern,
82A second pattern, 82B second pattern, 82C second pattern,
82D second pattern, 82E second pattern, 82F second pattern,
84A pattern, 84B pattern, 84C pattern,
84D pattern, 84E pattern, 84F pattern,
86A First adjustment pattern, 86B Second adjustment pattern,
86C third adjustment pattern, 86D fourth adjustment pattern,
86E 5th adjustment pattern, 86F 6th adjustment pattern,
86G seventh adjustment pattern, 86H eighth adjustment pattern,
86I 9th adjustment pattern, 86J 10th adjustment pattern,
86K 11th adjustment pattern, 86L 12th adjustment pattern,
211Y yellow nozzle row, 211M magenta nozzle row,
211C cyan nozzle row, 211K black nozzle row

Claims (8)

(A) a nozzle that forms an image on the medium by ejecting liquid toward the medium based on image data while moving relative to the medium;
(B) a transport unit that transports the medium along a predetermined direction;
(C) a liquid ejection control unit that changes the timing at which the liquid is ejected from the nozzle using dummy pixel data as pixel data constituting the image in the image data,
When the liquid is discharged from the nozzle toward at least one of the upstream end and the downstream end of the medium transported by the transport unit, the other is different from the region A liquid discharge control unit that changes the timing by using the dummy pixel data in an arrangement different from the case where the liquid is discharged from the nozzle toward the region;
A liquid discharge apparatus comprising (D). The nozzle ejects the liquid toward the medium while moving relative to the medium between the transport operations in which the transport unit transports the medium along the predetermined direction. Run
The liquid ejection apparatus according to claim 1, wherein the liquid ejection control unit changes the arrangement of the dummy pixel data every time the liquid ejection operation is executed by the nozzle. As the nozzle, comprising a plurality of nozzles arranged along the predetermined direction,
The liquid ejection apparatus according to claim 1, wherein the liquid ejection control unit varies the arrangement of the dummy pixel data according to the positions of the plurality of nozzles. As the nozzle, comprising a plurality of nozzles arranged along the predetermined direction,
The plurality of nozzles are divided into a plurality of groups,
The liquid ejection apparatus according to claim 1, wherein the liquid ejection control unit varies the arrangement of the dummy pixel data for each group.   In order to investigate the arrangement of the dummy pixel data when the liquid is ejected from the nozzle toward at least one of the upstream end and the downstream end of the medium, 5. The liquid ejection apparatus according to claim 1, wherein an adjustment pattern is formed by the liquid ejected from the relatively moving nozzle.   As the adjustment pattern, a first pattern formed on the medium by the liquid ejected from the nozzle when the nozzle is moving in the one direction, and the nozzle is in the one direction. The liquid ejection according to claim 5, wherein the second pattern formed on the medium is formed by the liquid ejected from the nozzle when moving in the opposite direction. apparatus.   The liquid ejecting apparatus according to claim 1, wherein ink is ejected from the nozzle as the liquid. A liquid ejection method for forming an image on the medium by ejecting liquid from the nozzle toward the medium based on image data while moving the nozzle relative to the medium conveyed along a predetermined direction Because
The upstream end of the medium transported by the transport unit when changing the timing at which the liquid is ejected from the nozzle using dummy pixel data as pixel data constituting the image in the image data And when the liquid is discharged from the nozzle toward at least one of the downstream end portions, and the liquid is discharged from the nozzle toward another region different from the region A liquid ejection method, wherein the timing is changed by using the dummy pixel data in an arrangement different from the above.