JP2019010752A - Printer - Google Patents

Abstract

To provide a printer capable of determining the existence/absence of color shift of a printed image while avoiding the complication of a device configuration.SOLUTION: A printer control part 25 controls ejection timing of ink in each ink jet head 52 of printing parts 22A, 22B on the basis of a pulse signal outputted by an encoder 45, and controls timing of printing an image of each page of a rear face of a web W by the printing part 22B on the basis of timing obtained by reading a mark by a reading part 23. Also, the printer control part 25 determines whether color shift exists in the mark in the conveyance direction of the web W on the basis of read data of the mark read by the reading part 23, and determines that color shift occurs in a printed image of the page in the case of determining that the color shift exists in the mark read by the reading part 23 in the conveyance direction of the web W.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a printing apparatus for printing on a web.

  2. Description of the Related Art There is known a printing apparatus that prints an image by ejecting ink from an inkjet head onto a web while conveying a long web as a printing medium.

  In such a printing apparatus, the ink ejection timing in the ink jet head is controlled based on a pulse signal output from an encoder connected to a roller driven and rotated by a web being conveyed (see, for example, Patent Document 1).

JP 2008-126516 A

  In the printing apparatus as described above, when the web slides with respect to the roller to which the encoder is connected, a deviation may occur between the web conveyance amount obtained from the encoder pulse signal and the actual web conveyance amount. is there. As a result, the ink landing positions may deviate between the inkjet heads that eject the inks of the respective colors, and the color deviation may occur in the printed image.

  When color misregistration occurs in the printed image, it is desirable to take measures such as issuing a warning to the user. For this purpose, it is necessary to determine the presence or absence of color misregistration in the print image. However, if a dedicated sensor or the like is provided to determine the presence or absence of color misregistration in the printed image, the apparatus configuration becomes complicated.

  The present invention has been made in view of the above, and an object of the present invention is to provide a printing apparatus capable of determining the presence or absence of color misregistration of a printed image while avoiding complication of the apparatus configuration.

  In order to achieve the above object, the printing apparatus of the present invention is arranged in parallel in the web conveyance direction, and prints an image of each page by ejecting different colors of ink onto the first surface of the web being conveyed. A first printing unit having a plurality of inkjet heads and printing a mark corresponding to each page by at least some of the plurality of inkjet heads; and the first printing unit in the transport direction A reading unit that reads the mark, and is arranged in parallel in the transport direction on the downstream side of the reading unit, and ejects ink of different colors to the second surface of the web to A second printing unit having a plurality of inkjet heads for printing an image; a driven roller that is driven to rotate by a web being conveyed; and a rotation angle of the driven roller In response, an encoder that outputs a pulse signal, and based on the pulse signal output from the encoder, controls the ink ejection timing in each of the inkjet heads of the first and second printing units, and the reading unit detects the mark. A control unit that controls the timing of printing the image of the page of the second surface of the web by the second printing unit based on the read timing, and the control unit reads the mark read by the reading unit. If it is determined whether or not the mark has a color shift in the transport direction based on the data, and it is determined that the mark has a color shift in the transport direction, a color shift has occurred in the printed image of the page. It is characterized by determining.

  According to the printing apparatus of the present invention, it is possible to determine the presence / absence of color misregistration of a print image while avoiding the complexity of the apparatus configuration.

1 is a schematic configuration diagram of a printing system including a printing apparatus according to an embodiment. FIG. 2 is a control block diagram of the printing system shown in FIG. 1. It is a figure which shows typically a mode that the image and mark of each page are printed on the surface of the web conveyed. 5 is a flowchart of color misregistration determination processing. It is a figure which shows an example of the printing image of the mark with a color shift area.

  Embodiments of the present invention will be described below with reference to the drawings. Throughout the drawings, the same or equivalent parts and components are denoted by the same or equivalent reference numerals.

  The following embodiments exemplify devices for embodying the technical idea of the present invention, and the technical idea of the present invention is the material, shape, structure, arrangement, etc. of each component. Is not specified as follows. The technical idea of the present invention can be variously modified within the scope of the claims.

  FIG. 1 is a schematic configuration diagram of a printing system including a printing apparatus according to an embodiment of the present invention. FIG. 2 is a control block diagram of the printing system shown in FIG. In the following description, the direction orthogonal to the paper surface of FIG. 1 is the front-rear direction, and the front surface direction is the front. Also, the top, bottom, left, and right of the paper surface in FIG.

  As shown in FIGS. 1 and 2, the printing system 1 according to the present embodiment includes an unwinding device 2, a printing device 3, and a winding device 4. In the following description, upstream and downstream mean upstream and downstream in the conveyance direction of the web W conveyed from the unwinding device 2 toward the winding device 4.

  The unwinding device 2 unwinds the web W, which is a long print medium made of film, paper, or the like, to the printing device 3. The unwinding device 2 includes a web roll support shaft 11, a brake 12, and an unwinding device control unit 13.

  The web roll support shaft 11 rotatably supports the web roll 16. The web roll support shaft 11 is formed in a long shape extending in the front-rear direction. The web roll 16 is obtained by winding a web W in a roll shape.

  The brake 12 brakes the web roll support shaft 11. Thereby, tension | tensile_strength is provided to the web W between the web roll 16 and the conveyance roller 43 of the printing apparatus 3 mentioned later.

  The unwinding device control unit 13 controls the brake 12. The unwinding device control unit 13 includes a CPU, a memory, a hard disk, and the like.

  The printing device 3 prints an image on the web W while conveying the web W unwound from the unwinding device 2. The printing apparatus 3 includes a transport unit 21, printing units 22 </ b> A and 22 </ b> B, a reading unit 23, an operation panel 24, and a printing device control unit 25.

  The transport unit 21 transports the web W unwound from the unwinding device 2. The transport unit 21 includes guide rollers 31 to 40, 20 head lower support members 41, a meandering control unit 42, a pair of transport rollers 43, a transport motor 44, and an encoder 45.

  The guide rollers 31 to 40 guide the web W conveyed in the printing apparatus 3. The guide rollers 31 to 40 are driven to rotate by the web W being conveyed. The guide rollers 31 to 40 are formed in a long shape extending in the front-rear direction.

  The guide rollers 31 and 32 guide the web W between the unwinding device 2 and the meandering control unit 42. The guide roller 31 is disposed below the left end portion of the printing apparatus 3. The guide roller 32 is disposed between the guide roller 31 and a meandering control roller 46 of a meandering control unit 42 described later.

  The guide rollers 33 to 39 guide the web W between the meandering control unit 42 and the conveying roller 43. The guide roller 33 is disposed slightly above the left side of the meandering control roller 47 of the meandering control unit 42 described later. The guide roller 34 is disposed above the guide roller 33. The guide roller 35 has the same height as the guide roller 34 and is disposed on the right side of the guide roller 34. The guide roller 36 is disposed below the guide roller 35 and at a position higher than the guide roller 33. The guide roller 37 is disposed on the left side of the guide roller 36, in the vicinity of the right side of the web W between the guide rollers 33 and 34, and at the same height as the guide roller 36. The guide roller 38 is disposed on the lower right side of the guide roller 37. The guide roller 39 is disposed slightly below the right side of the guide roller 38. The guide roller 34 corresponds to a driven roller in claims.

  The guide roller 40 guides the web W between the conveyance roller 43 and the winding device 4. The guide roller 40 is disposed at the lower part of the right end portion of the printing apparatus 3.

  The head lower support member 41 supports the web W below the head unit 51 described later between the guide rollers 34 and 35 and between the guide rollers 36 and 37. The head lower support member 41 is formed in a long shape extending in the front-rear direction. Ten head support members 41 are arranged between the guide rollers 34 and 35 and between the guide rollers 36 and 37, respectively. Two head lower support members 41 are arranged immediately below each head unit 51.

  The meandering control unit 42 corrects the meandering of the web W. The meandering control unit 42 includes meandering control rollers 46 and 47, a meandering control motor 48, and an edge sensor 49.

  The meandering control rollers 46 and 47 are rollers for guiding the web W and correcting the meandering of the web W. The meandering control rollers 46 and 47 are formed in a long cylindrical shape extending in the front-rear direction. The meandering control rollers 46 and 47 are driven to rotate by the web W being conveyed. The meandering control roller 46 is disposed on the right side of the guide roller 32. The meandering control roller 47 is disposed above the meandering control roller 46. The meandering control rollers 46 and 47 correct the meandering by moving the web W in the width direction by rotating so as to be inclined with respect to the width direction (front-rear direction) of the web W when viewed from the left-right direction. is there.

  The meander control motor 48 rotates the meander control rollers 46 and 47 around a rotation axis parallel to the left-right direction.

  The edge sensor 49 detects an edge in the width direction (front-rear direction) of the web W. The edge sensor 49 is disposed in the vicinity of the downstream side of the meandering control roller 47.

  The pair of transport rollers 43 transport the web W toward the winding device 4 while nipping the web W. The conveyance roller 43 is formed in a long shape extending in the front-rear direction. The transport roller 43 is disposed between the guide rollers 39 and 40.

  The transport motor 44 drives the transport roller 43 to rotate.

  The encoder 45 is connected to the guide roller 34 and outputs a pulse signal according to the rotation angle of the guide roller 34.

  The printing unit 22A prints an image of each page on the surface of the web W (corresponding to the first surface of the claims). Further, the printing unit 22A prints a mark 71 described later. The printing unit 22 </ b> A is disposed in the vicinity of the upper portion of the web W between the guide rollers 34 and 35. The printing unit 22A includes head units 51K, 51C, 51M, 51Y, and 51P arranged in parallel in the web W conveyance direction. In some cases, alphabetical suffixes are omitted from the symbols of the head units 51K, 51C, 51M, 51Y, 51P, etc. The printing unit 22A corresponds to a first printing unit in the claims.

  The head units 51K, 51C, 51M, 51Y, 51P are arranged in this order from the upstream side in the left-right direction (sub-scanning direction). The head units 51K, 51C, 51M, 51Y, and 51P have inkjet heads 52K, 52C, 52M, 52Y, and 52P, respectively.

  The inkjet head 52 has a plurality of nozzles (not shown) arranged along the front-rear direction, and prints an image by ejecting ink from the nozzles to the web W. The inkjet heads 52K, 52C, 52M, 52Y, and 52P eject black (K), cyan (C), magenta (M), yellow (Y), and preliminary ink colors, respectively. Red, light cyan or the like is used as the preliminary ink color. The inkjet heads 52K, 52C, 52M, and 52Y correspond to a black head, a cyan head, a magenta head, and a yellow head, respectively.

  The printing unit 22B prints an image of each page on the back surface of the web W (corresponding to the second surface of the claims). The printing unit 22 </ b> B is disposed in the vicinity of the upper portion of the web W between the guide rollers 36 and 37. Similar to the printing unit 22A, the printing unit 22B includes head units 51K, 51C, 51M, 51Y, and 51P arranged in parallel in the conveyance direction of the web W. The printing unit 22B corresponds to a second printing unit in the claims.

  The reading unit 23 optically reads a later-described mark 71 in color, and generates read data in RGB format. The reading unit 23 includes a light source that irradiates light toward the web W, and a plurality of reading elements (all of which are not shown) that read reflected light from the web W.

  The reading unit 23 is disposed in the vicinity of the upstream side of the printing unit 22B on the downstream side of the printing unit 22A. More specifically, the reading unit 23 is disposed on the front surface side (lower side) of the web W between the guide roller 36 and the uppermost head unit 51 of the printing unit 22B.

  The operation panel 24 displays various screens and accepts input operations by the user. The operation panel 24 includes a display unit having a liquid crystal display panel and the like, and an input unit (all not shown) having various operation keys, a touch panel, and the like.

  The printing device control unit 25 controls the operation of each unit of the printing device 3. The printing apparatus control unit 25 includes a CPU, a RAM, a ROM, a hard disk, and the like. The printing device control unit 25 corresponds to a control unit in claims.

  When performing printing, the printing apparatus control unit 25 controls the printing units 22 </ b> A and 22 </ b> B to print an image on the web W while rotating the conveyance roller 43 by the conveyance motor 44 to convey the web W. At this time, the printing apparatus control unit 25 controls the ink ejection timing in each of the inkjet heads 52 of the printing units 22A and 22B based on the pulse signal output from the encoder 45.

  In addition, when printing the front surface, the printing apparatus control unit 25 causes the printing unit 22A to print a later-described mark 71 corresponding to each page together with the image of each page. Here, the printing apparatus control unit 25 causes the marks 71 to be printed by a plurality of inkjet heads 52 among the five inkjet heads 52 of the printing unit 22A. Then, the printing apparatus control unit 25 controls the timing for printing the image of each page on the back side of the web W by the printing unit 22B based on the timing when the reading unit 23 reads the mark 71.

  Further, the printing apparatus control unit 25 determines whether or not the mark 71 has a color shift in the web W conveyance direction based on the read data of the mark 71 read by the reading unit 23. If the printing device control unit 25 determines that the mark 71 read by the reading unit 23 has a color shift in the web W conveyance direction, the printing apparatus control unit 25 determines that a color shift has occurred in the printed image of the page.

  The winding device 4 winds the web W printed by the printing device 3. The winding device 4 includes a winding shaft 61, a winding motor 62, and a winding device control unit 63.

  The winding shaft 61 winds and holds the web W. The winding shaft 61 is formed in a long shape extending in the front-rear direction.

  The winding motor 62 rotates the winding shaft 61 in the clockwise direction in FIG. The web W is wound around the winding shaft 61 by the rotation of the winding shaft 61.

  The winding device control unit 63 controls driving of the winding motor 62. The winding device control unit 63 includes a CPU, a memory, a hard disk, and the like.

  Next, the printing operation of the printing system 1 will be described.

  When printing is performed by the printing system 1, when a print job is input, the printing apparatus control unit 25 starts driving the conveyance motor 44, and the winding apparatus control unit 63 starts driving the winding motor 62. Thereby, the conveyance of the web W is started from the unwinding device 2 toward the winding device 4. When the conveyance speed of the web W reaches a predetermined print conveyance speed after the conveyance of the web W starts, the unwinding device control unit 13 starts driving the brake 12. When the web roll support shaft 11 is braked by the brake 12, the web W is conveyed while tension is applied to the web W between the web roll 16 and the conveyance roller 43. Moreover, after the conveyance speed of the web W reaches the printing conveyance speed, the printing apparatus control unit 25 controls the conveyance motor 44 so as to maintain the printing conveyance speed.

  In the printing apparatus 3, during the conveyance of the web W, the meandering of the web W is corrected by the meandering control unit 42. Specifically, the printing apparatus control unit 25 controls the meandering control motor 48 to meander the meandering control rollers 46 and 47 so that the edge position in the width direction of the web W detected by the edge sensor 49 is maintained at a predetermined position. Adjust the angle.

  After starting the constant-speed conveyance of the web W at the printing conveyance speed, the printing apparatus control unit 25 controls each inkjet head 52 of the printing unit 22A to print the image of each page on the surface of the web W based on the print job. To start.

  Here, as illustrated in FIG. 3, the printing apparatus control unit 25 controls the printing unit 22 </ b> A to print the mark 71 in association with each page P together with the image of each page P.

  The mark 71 is used for alignment between the image on the front page and the image on the back page. The mark 71 is also used to determine whether or not color misregistration has occurred in the image of the page printed on the web W.

  The mark 71 is printed with ink ejected from a plurality of inkjet heads 52 of the five inkjet heads 52 of the printing unit 22A. In the present embodiment, the mark 71 is printed in composite black with black, cyan, magenta, and yellow ink respectively ejected from the inkjet heads 52K, 52C, 52M, and 52Y of the printing unit 22A. The mark 71 is composed of, for example, a solid image having a rectangular shape in plan view. The mark 71 is printed at a predetermined position outside the print area of the image of the page P.

  The mark 71 is read by the reading unit 23 after being printed by the printing unit 22A. When the reading unit 23 reads the mark 71, the control unit 5 controls the printing unit 22B to print the image of the back page at a timing according to the timing. Specifically, the control unit 5 prints the image of the back page corresponding to the front page corresponding to the mark 71 based on the number of output pulses of the encoder 45 after the reading unit 23 reads the mark 71. The timing for printing on 22B is controlled. Thereby, the image of each page on the back surface of the web W is printed in alignment with each page on the front surface.

  When printing of the image of each page based on the print job is completed, the unwinding device control unit 13 stops the brake 12, the printing device control unit 25 stops the transport motor 44, and the winding device control unit 63 uses the winding motor. 62 is stopped. As a result, the conveyance of the web is finished, and a series of printing operations is finished.

  Next, the color misregistration determination process performed during the above-described printing operation will be described.

  The color misregistration determination process is a process for determining whether or not a color misregistration has occurred in the printed image of the page due to the conveyance misalignment of the web W. The conveyance deviation of the web W is a phenomenon in which a deviation occurs between the conveyance amount of the web W obtained from the pulse signal of the encoder 45 and the actual conveyance amount of the web W when the web W slides with respect to the guide roller 34. is there.

  When the conveyance deviation of the web W occurs, the ejection timing of the ink from each inkjet head 52 is delayed with respect to the timing according to the actual movement of the web W. For this reason, when the landing positions of the inks of the respective colors ejected from the respective inkjet heads 52 to the same pixel are shifted, a color shift occurs in the printed image. In the printing system 1, color misregistration determination processing is performed in order to determine the presence or absence of such color misregistration in the print image.

  FIG. 4 is a flowchart of the color misregistration determination process. The process of the flowchart in FIG. 4 starts when printing based on the print job is started.

  In step S <b> 1 of FIG. 4, the printing apparatus control unit 25 determines whether the reading unit 23 has read the mark 71.

  When it is determined that the reading unit 23 has read the mark 71 (step S1: YES), in step S2, the printing apparatus control unit 25 is based on the read data of the mark 71 read by the reading unit 23 in the conveyance direction of the web W. It is determined whether or not there is a color shift area at the end of the mark 71.

  The color misregistration area is a print color area different from the mark print color. The mark print color is a color set as the print color of the mark 71. The mark printing color is a color that is realized by overlapping and printing a plurality of colors of ink used for printing the mark 71 from the plurality of inkjet heads 52. In the present embodiment, the mark 71 is printed in composite black with black, cyan, magenta, and yellow ink as described above, and therefore the mark print color is black.

  The printing apparatus control unit 25 detects a mark print color area that is an area composed of the mark print color based on the RGB value of each pixel in the read data of the mark 71 that is RGB format data. Then, the printing apparatus control unit 25 adjoins the mark print color area in the web W conveyance direction based on the RGB value of each pixel in the read data, and has a color area different from the mark print color and the background color of the web W. Judge whether there is.

  Here, the printing apparatus control unit 25 determines that the color having at least one of the RGB values different from the RGB value of the mark print color is different from the mark print color. To do. Similarly, the printing apparatus control unit 25 determines that a color having a difference of at least one of RGB values that is equal to or greater than a threshold value with respect to the RGB value of the ground color of the web W is the ground color of the web W. Judged to be a different color.

  When the printing apparatus control unit 25 determines that there is an area of a color different from the mark printing color and the background color of the web W adjacent to the mark printing color area in the web W conveyance direction, It is determined that there is a color shift area.

  Here, the printing apparatus control unit 25 stores in advance the RGB values of the mark printing color. As the RGB value of the mark printing color, for example, the reading unit 23 reads an image printed in the mark printing color on the web W used for printing by the printing system 1 before starting execution of the print job. The obtained RGB values are stored.

  In addition, for example, the RGB value obtained by reading the image printed on the standard paper in the mark printing color by the reading unit 23 using the printing system 1 as the RGB value of the mark printing color is given to the printing apparatus control unit 25 in advance. It may be memorized.

  Here, FIG. 5 shows an example of a print image of the mark 71 having the color misregistration region at the end in the conveyance direction of the web W.

  In FIG. 5, a mark print color area 71 a is an area printed in the mark print color, and is an area where inks of all colors used for printing the mark 71 are applied in an overlapping manner. The color misregistration areas 71b and 71c are areas formed respectively on the upstream side and the downstream side of the mark print color area 71a in the web W conveyance direction. The color misregistration areas 71b and 71c are areas where some of the colors of ink used for printing the mark 71 are not applied. Due to the occurrence of the conveyance deviation of the web W described above, the color deviation areas 71b and 71c are formed.

  However, as described above, in the present embodiment, since the black ink ejected from the most upstream inkjet head 52K is used for printing the mark 71, the color misregistration area 71c is also determined as a black area that is the mark printing color. Is done. That is, when the web W conveyance deviation occurs, as described above, the ejection timing of the ink from each inkjet head 52 is delayed with respect to the timing according to the actual movement of the web W. In addition, since the inkjet head 52K that discharges black ink is arranged in the uppermost stream, when the print image by the ink other than black deviates from the print image by the black ink due to the influence of the conveyance deviation of the web W. , Shift upstream. For this reason, even if there is an area where any one of cyan, magenta, and yellow ink is not applied to the downstream end of the mark 71, the print color is almost black because the black ink is applied. become. For this reason, the color misregistration area 71c is also determined to be a black print area.

  On the other hand, the color misregistration area 71b at the end on the upstream side of the mark 71 is an area where black ink is not applied, and thus is detected as an area having a printing color other than black. For this reason, it is determined that there is a color misregistration region at the end of the mark 71 in the conveyance direction of the web W.

  Returning to FIG. 4, when it is determined in step S2 that there is a color misregistration region at the end of the mark 71 read by the reading unit 23 (step S2: YES), in step S3, the printing apparatus control unit 25 displays the page. It is determined that color misregistration has occurred in the printed image. Thereafter, the printing apparatus control unit 25 returns to Step S1.

  When it is determined that there is no color misregistration area at the end of the mark 71 read by the reading unit 23 (step S2: NO), in step S4, the printing apparatus control unit 25 causes color misregistration in the printed image of the page. Judge that there is no. Thereafter, the printing apparatus control unit 25 returns to Step S1.

  If it is determined in step S1 that the reading unit 23 has not read the mark 71 (step S1: NO), in step S5, the printing apparatus control unit 25 determines whether printing based on the print job is finished. . If it is determined that printing based on the print job has not ended (step S5: NO), the printing apparatus control unit 25 returns to step S1.

  When the printing apparatus control unit 25 determines that printing based on the print job has ended (step S5: YES), the color misregistration determination process ends.

  When it is determined by the above-described color misregistration determination processing that there is a color misregistration in the printed image of the page when any of the marks 71 is read, the printing apparatus control unit 25 displays the operation panel 24 after the printing operation is completed. Display a warning screen (not shown). This warning screen is a screen for notifying the user that color misregistration has occurred in the print image due to the aforementioned transport misalignment. The user who has confirmed this warning screen can take measures for preventing conveyance deviation, such as decreasing the printing conveyance speed, in the next and subsequent printing.

  In the color misregistration determination process, if it is determined that there is a color misregistration in the printed image of the page, the printing operation may be stopped at that time and a warning screen may be displayed on the display unit of the operation panel 24. .

  As described above, in the printing apparatus 3, the printing apparatus control unit 25 performs color misregistration in the conveyance direction of the web W on the mark 71 based on the read data of the mark 71 read by the reading unit 23 in the color misregistration determination process. It is determined whether or not there is. If the printing device control unit 25 determines that the mark 71 read by the reading unit 23 has a color shift in the web W conveyance direction, the printing apparatus control unit 25 determines that a color shift has occurred in the printed image of the page. Thereby, according to the printing apparatus 3, the presence or absence of the color shift of the print image by the conveyance shift of the web W can be determined.

  In the printing apparatus 3, since the color misregistration determination process is performed using the mark 71 and the reading unit 23 used for alignment between the image on the front page and the image on the back page, the apparatus configuration is complicated. It is possible to determine the presence or absence of color misregistration in the printed image while avoiding it.

  Specifically, in the printing apparatus 3, the printing unit 22A prints the mark 71 with composite black using black, cyan, magenta, and yellow ink. When the printing device control unit 25 detects an area having a print color other than black adjacent to the area in which the print color is black in the read data of the mark 71 in the web W conveyance direction, 71, it is determined that there is a color shift in the conveyance direction of the web W. Thereby, since the mark print color is black and the presence / absence of color misregistration is determined based on the presence / absence of an area having a print color other than black, the accuracy of color misregistration determination can be improved.

  In the above-described embodiment, the mark 71 is printed with composite black using black, cyan, magenta, and yellow inks. However, the combination of ink colors used for printing the mark 71 is not limited to this. In addition, a combination of ink colors used for printing the mark 71 may be selected from a plurality of combinations.

  In the above-described embodiment, the configuration in which the unwinding device and the winding device are connected to the printing device as separate devices has been described. However, a configuration in which the unwinding unit and the winding unit are incorporated in the printing device may be used.

  The present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiments. For example, some components may be deleted from all the components shown in the embodiment.

[Appendix]
The present application discloses the following inventions.

(Appendix 1)
A plurality of inkjet heads that are arranged in parallel in the web conveyance direction and that eject images of different colors onto the first surface of the web to be conveyed and print images of each page; A first printing unit that prints a mark corresponding to each page by at least some of the plurality of inkjet heads;
A reading unit disposed on the downstream side of the first printing unit in the transport direction and reading the mark;
A second printing unit that is arranged in parallel in the transport direction on the downstream side of the reading unit, and has a plurality of inkjet heads that eject ink of different colors onto the second surface of the web and print images of each page; ,
A driven roller that rotates following the web being conveyed;
An encoder that outputs a pulse signal according to the rotation angle of the driven roller;
Based on the pulse signal output from the encoder, the ink ejection timing in each inkjet head of the first and second printing units is controlled, and the second printing is performed based on the timing when the reading unit reads the mark. A control unit that controls the timing of printing the image of the second page of the web by the unit,
The control unit determines whether the mark has a color shift in the transport direction based on reading data of the mark read by the reading unit, and determines that the mark has a color shift in the transport direction. In this case, the printing apparatus determines that color misregistration has occurred in the printed image of the page.

(Appendix 2)
The first printing unit includes:
Each has a black head, a cyan head, a magenta head, and a yellow head, which are the inkjet heads that discharge black, cyan, magenta, and yellow ink,
The mark is printed in composite black by ejecting ink from the black head, the cyan head, the magenta head, and the yellow head,
The controller is
In the read data of the mark read by the reading unit, when an area having a print color other than black adjacent to the area in which the print color of the mark is black is detected in the conveyance direction, The printing apparatus according to appendix 1, wherein it is determined that there is a color shift in the transport direction.

DESCRIPTION OF SYMBOLS 1 Printing system 2 Unwinding device 3 Printing device 4 Winding device 21 Conveyance part 22A, 22B Printing part 23 Reading part 24 Operation panel 25 Printing apparatus control part 31-40 Guide roller 41 Head lower support member 42 Meander control part 43 Conveyance roller 44 Conveyance motor 45 Encoder 51, 51K, 51C, 51M, 51Y, 51P Head unit 52, 52K, 52C, 52M, 52Y, 52P Inkjet head 71 Mark

Claims (2)

A plurality of inkjet heads that are arranged in parallel in the web conveyance direction and that eject images of different colors onto the first surface of the web to be conveyed and print images of each page; A first printing unit that prints a mark corresponding to each page by at least some of the plurality of inkjet heads;
A reading unit disposed on the downstream side of the first printing unit in the transport direction and reading the mark;
A second printing unit that is arranged in parallel in the transport direction on the downstream side of the reading unit, and has a plurality of inkjet heads that eject ink of different colors onto the second surface of the web and print images of each page; ,
A driven roller that rotates following the web being conveyed;
An encoder that outputs a pulse signal according to the rotation angle of the driven roller;
Based on the pulse signal output from the encoder, the ink ejection timing in each inkjet head of the first and second printing units is controlled, and the second printing is performed based on the timing when the reading unit reads the mark. A control unit that controls the timing of printing the image of the second page of the web by the unit,
The control unit determines whether the mark has a color shift in the transport direction based on reading data of the mark read by the reading unit, and determines that the mark has a color shift in the transport direction. In this case, the printing apparatus determines that color misregistration has occurred in the printed image of the page. The first printing unit includes:
Each has a black head, a cyan head, a magenta head, and a yellow head, which are the inkjet heads that discharge black, cyan, magenta, and yellow ink,
The mark is printed in composite black by ejecting ink from the black head, the cyan head, the magenta head, and the yellow head,
The controller is
In the read data of the mark read by the reading unit, when an area having a print color other than black adjacent to the area in which the print color of the mark is black is detected in the conveyance direction, The printing apparatus according to claim 1, wherein it is determined that there is a color shift in the transport direction.