Droplet discharge device, droplet discharge method, and droplet discharge program

Abstract

To provide a liquid droplet discharge device, a liquid droplet discharge method, and a liquid droplet discharge program capable of preventing discharge failure of a nozzle.SOLUTION: The droplet discharge device includes a first head and a second head, and the first head and the second head are disposed such that positions of some first nozzles of the plurality of first nozzles and positions of some second nozzles of the plurality of second nozzles overlap in the transport direction in a predetermined joint region, the control device executes a process of acquiring a dense region which is a region where a total volume value which is a total value of a cumulative volume of first droplets discharged from first nozzles arranged in a movement direction and a cumulative volume of second droplets discharged from second nozzles arranged in the movement direction is equal to or more than a threshold value from discharge data, and a process of changing a use number related to discharge of the first nozzles and a use number related to discharge of the second nozzles in a preceding printing pass when a part or all of the joint region does not correspond to the dense region.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a droplet ejection device, a droplet ejection method, and a droplet ejection program used in a printing device such as an inkjet printer. [Background technology]

[0002] Conventionally, there is known a printing device that includes a first nozzle that prints an image on a print medium based on image data using ink of a predetermined base color, and a second nozzle that prints an image on a print medium based on image data using ink of a special color different from the base color (Patent Document 1). Examples of base color inks include cyan ink, yellow ink, magenta ink, and black ink. Furthermore, special color inks are inks of colors different from the base color inks, such as red ink, green ink, or blue ink. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-111540 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when the nozzle ejection frequency is low, ejection defects due to drying are likely to occur. For example, in a configuration in which multiple heads are arranged side by side in the transport direction of the print medium, shingling printing is performed to prevent streaks from occurring at the joints between passes. In this shingling printing, the amount of droplets ejected per pass from the nozzles of each head is reduced, making the nozzles more likely to dry out. As a result, there was a problem of ejection defects being more likely to occur.

[0005] Therefore, an object of the present disclosure is to provide a droplet ejection device, a droplet ejection method, and a droplet ejection program that can make nozzle ejection defects less likely to occur. [Means for solving the problem]

[0006] a conveying device that conveys a print medium in a conveying direction relative to the first head and the second head; a first moving device that moves the first head and the second head in a moving direction that intersects with the conveying direction; and a control device, wherein the first head and the second head are arranged such that positions of some first nozzles among the plurality of first nozzles and positions of some second nozzles among the plurality of second nozzles overlap in the conveying direction in a predetermined seam region, and the control device determines, from ejection data that is data after halftone processing has been performed on the image data, a process for acquiring a dark region, which is a region where a total volume value, which is the sum of the accumulated volume of the first droplets ejected from the first nozzles aligned in the direction of movement and the accumulated volume of the second droplets ejected from the second nozzles aligned in the direction of movement, is equal to or greater than a threshold value; a process for determining whether a part or all of the seam region corresponds to the dark region in a subsequent printing pass, which is a printing pass executed after a preceding printing pass, which is a predetermined printing pass; and a process for changing the number of uses for ejection of the first nozzles and the number of uses for ejection of the second nozzles in the preceding printing pass, the subsequent printing pass, and any one of the preceding and subsequent printing passes, in order to make a part or all of the seam region correspond to the dark region in the subsequent printing pass, if a part or all of the seam region does not correspond to the dark region.

[0007] According to the present disclosure, when a portion or all of a seam region does not correspond to a dark region, the number of first nozzles used for ejection and the number of second nozzles used for ejection in the preceding printing pass, the following printing pass, and one of the preceding and following printing passes are changed. This allows a portion or all of the seam region to correspond to a dark region in the following printing pass, etc. In other words, in the following printing pass, etc., it becomes possible to eject droplets from the first nozzles and the second nozzles whose total volume value is equal to or greater than a threshold. This makes it less likely that ejection defects will occur in the first nozzles and the second nozzles. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide a droplet ejection device, a droplet ejection method, and a droplet ejection program that can make nozzle ejection defects less likely to occur. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a plan view showing the configuration of a printing apparatus equipped with a droplet ejection device according to one embodiment. [Figure 2] FIG. 2 is a diagram showing nozzles in a joint region of each head in FIG. [Figure 3] FIG. 2 is a block diagram showing the configuration of a control system of the printing apparatus of FIG. 1. [Figure 4] FIG. 10 is a diagram showing dark and light regions corresponding to each printing pass in the ejection data, as well as a histogram showing the total volume values ​​of ink droplets corresponding to the dark and light regions. [Figure 5] 10A and 10B are diagrams illustrating examples of dark and light regions corresponding to each printing pass in the ejection data. [Figure 6] 10A and 10B are diagrams illustrating examples of dark and light regions corresponding to each printing pass in the ejection data. [Figure 7] 10A and 10B are diagrams illustrating examples of dark and light regions corresponding to each printing pass in the ejection data. [Figure 8] 2 is a flowchart showing a processing flow in the printing device of FIG. 1. [Figure 9] 9 is a flowchart showing the flow of the pass division process in FIG. 8. [Figure 10] 10 is a flowchart illustrating the flow of the pass division process continued from FIG. 9. [Figure 11] 11A and 11B are diagrams showing a modification of the carriage of FIG. [Figure 12] 10A and 10B are diagrams illustrating examples of dark and light regions corresponding to each printing pass in image data. [Figure 13] FIG. 10 is a diagram showing printing passes in which seam regions correspond to dark regions. [Figure 14] 10 is a flowchart showing a processing flow in the printing device. [Figure 15] 15 is a flowchart showing the flow of the block division and pass division process of FIG. 14. [Figure 16] 16 is a flowchart illustrating the flow of the block division and pass division process continued from FIG. 15. DETAILED DESCRIPTION OF THE INVENTION

[0010] A droplet ejection device according to an embodiment of the present disclosure will be described below with reference to the drawings. The droplet ejection device described below is merely one embodiment of the present disclosure. Therefore, the present disclosure is not limited to the following embodiment, and additions, deletions, and modifications are possible within the scope of the present disclosure. Note that, hereinafter, identical or corresponding elements will be designated by the same reference numerals throughout the drawings, and duplicated descriptions will be omitted unless otherwise noted.

[0011] (First embodiment) FIG. 1 is a plan view showing the configuration of a printing device 100 equipped with a droplet ejection device 101A according to one embodiment. FIG. 2 is a diagram showing nozzles in the joint region Rt of each head 20 in FIG. 1. FIG. 3 is a block diagram showing the configuration of a control system for the printing device 100 in FIG. 1. In FIGS. 1 and 2, mutually perpendicular directions are defined as a first direction Df and a second direction Ds. In this embodiment, for example, the first direction Df is the transport direction of the print medium W, and the second direction Ds is the movement direction of the carriage 41 described below. In the following description, Ds will be referred to as the movement direction, and Df will be referred to as the transport direction. However, the above directions are merely examples and are not limiting.

[0012] The printing device 100 includes an output device 101 and an image processing device 102. The output device 101 and the image processing device 102 are connected to each other so that they can communicate with each other wirelessly or via a wired connection such as a network. The image processing device 102 generates print data from image data of a print image, which is an image to be printed on a print medium W by the output device 101, and transmits the generated print data to the output device 101 wirelessly or via a wired connection. The output device 101 prints the print image on the print medium W based on the print data received from the image processing device 102. Examples of the print medium W include paper, fabric, resin material, metal material, and sheet-fed film.

[0013] The output device 101 is, for example, a serial head type inkjet printer. Based on print data, the output device 101 alternately repeats a pass process in which an inkjet head (hereinafter referred to as a head) 20 is moved in a movement direction Ds to eject ink droplets, and a transport process in which the print medium W is transported in a transport direction Df. This causes a predetermined image to be printed on the print medium W. In FIG. 1, the print medium W is transported in the transport direction Df, from the bottom to the top of the page.

[0014] The output device 101 has a droplet ejection device 101A. The droplet ejection device 101A includes a head unit HU, a platen 11, a plurality of tanks 12, a moving device 30, a transport device 40, and a receiving unit 75. The moving device 30 corresponds to a first moving device.

[0015] The head unit HU has multiple heads 20. The heads 20 print an image on the print medium W using predetermined ink droplets based on print data. Examples of the multiple heads 20 included in the head unit HU include a first inkjet head (hereinafter referred to as the first head) 21, a second inkjet head (hereinafter referred to as the second head) 22, a third inkjet head (hereinafter referred to as the third head) 23, and a fourth inkjet head (hereinafter referred to as the fourth head) 24. Note that, hereinafter, when referring to a head 20, the head 20 is a general term that includes the first head 21, the second head 22, the third head 23, and the fourth head 24.

[0016] For example, the first head 21 has a plurality of first nozzles 121 for ejecting ink droplets of color ink as first droplets onto the print medium W based on image data. A second control device 50, which will be described later, causes the first nozzles 121 in the first head 21 to eject the ink droplets of color ink as first droplets. The second head 22 has a plurality of second nozzles 221 for ejecting ink droplets of color ink as second droplets of the same color as the first droplets onto the print medium W based on image data. The second control device 50, which will be described later, causes the second nozzles 221 in the second head 22 to eject the ink droplets of color ink as second droplets. Examples of color ink include basic colors such as cyan ink, magenta ink, yellow ink, and black ink.

[0017] The third head 23 has a plurality of third nozzles 321 for ejecting ink droplets of the special color ink as third droplets onto the print medium W based on image data. A second control device 50 (described later) causes the third nozzles 321 in the third head 23 to eject ink droplets of the special color ink as third droplets. The fourth head 24 has a plurality of fourth nozzles 421 for ejecting ink droplets of the special color ink as fourth droplets of the same color as the third droplets onto the print medium W based on image data. The second control device 50 (described later) causes the fourth nozzles 421 in the fourth head 24 to eject ink droplets of the special color ink as fourth droplets. Note that the special color ink is an ink of a color different from the above-mentioned basic color inks, and examples thereof include red ink, green ink, and blue ink. However, the above-mentioned colors of ink ejected by each head 20 are merely examples and can be changed as appropriate.

[0018] The first head 21, the second head 22, the third head 23, and the fourth head 24 are arranged in this order from the upstream side in the transport direction Df. For example, the first head 21, the second head 22, the third head 23, and the fourth head 24 are arranged in a staggered pattern.

[0019] 2, the first head 21 and the third head 23 have the same configuration, and the second head 22 and the fourth head 24 have the same configuration. The first head 21 and the second head 22 are arranged such that, in a predetermined seam region Rt, some of the first nozzles 121 among the plurality of first nozzles 121 and some of the second nozzles 221 among the plurality of second nozzles 221 overlap in the transport direction Df. In other words, in the predetermined seam region Rt, some of the first nozzles 121 among the plurality of first nozzles 121 and some of the second nozzles 221 among the plurality of second nozzles 221 are arranged such that, in the predetermined seam region Rt, some of the first nozzles 121 among the plurality of first nozzles 121 and some of the second nozzles 221 among the plurality of second nozzles 221 overlap in the transport direction Df. Furthermore, the third head 23 and the fourth head 24 are arranged such that, in the predetermined seam region Rt, some of the third nozzles 321 among the plurality of third nozzles 321 and some of the fourth nozzles 421 among the plurality of fourth nozzles 421 overlap in the transport direction Df. That is, in a predetermined seam region Rt, the positions of some of the multiple third nozzles 321 and the positions of some of the multiple fourth nozzles 421 are the same in the transport direction Df. Note that the number of nozzles included in a seam region Rt in one nozzle row NL can be set as appropriate.

[0020] The first head 21 has a plurality of nozzle rows NL each configured by arranging a plurality of first nozzles 121 at predetermined intervals in a predetermined nozzle row direction Dn. Each nozzle row NL extends in the nozzle row direction Dn. The nozzle row direction Dn is, for example, parallel to the transport direction Df. Each nozzle row NL is arranged at predetermined intervals in the movement direction Ds. The arrangement of the nozzle rows NL configured by a plurality of second nozzles 221 in the second head 22, the arrangement of the nozzle row NL configured by a plurality of third nozzles 321 in the third head 23, and the arrangement of the nozzle row NL configured by a plurality of fourth nozzles 421 in the fourth head 24 are the same as the arrangement of the nozzle rows NL in the first head 21, for example.

[0021] In this embodiment, the first nozzle 121, the second nozzle 221, the third nozzle 321, and the fourth nozzle 421 are capable of ejecting large, medium, or small ink droplets.

[0022] The platen 11 has a flat upper surface and defines the distance between the print medium W placed on that upper surface and the nozzle surfaces of the heads 20 provided opposite it. The platen 11 moves in the transport direction Df. As a result, the print medium W supported by the platen 11 moves in the transport direction Df.

[0023] Ink is stored in each tank 12. The tanks 12 are connected to the head 20 via a flow path described below to supply ink to the head 20. The tanks 12 are containers that store ink. The number of tanks 12 is equal to or greater than the number of types of ink. For example, the tanks 12 include first tanks 12a that store four types of color ink, one or more second tanks 12b that store spot color inks, and one or more third tanks 12c that store spot color inks of the same color as the spot color inks. However, the number of tanks 12 and the types of ink stored in each tank 12 are examples and are not limited to the above.

[0024] The first tank 12a is connected to the first head 21 and the second head 22 by a first flow path 13a. Color ink is supplied from the first tank 12a to the first head 21 and the second head 22 via the first flow path 13a. The second tank 12b is connected to the third head 23 by a second flow path 13b. Spot color ink is supplied from the second tank 12b to the third head 23 via the second flow path 13b. The third tank 12c is connected to the fourth head 24 by a third flow path 13c. Spot color ink is supplied from the third tank 12c to the fourth head 24 via the third flow path 13c.

[0025] The transport device 40 has a drive unit including, for example, a ball screw or rack and pinion (not shown), and a transport motor 46. The drive unit is connected to the transport motor 46. The transport device 40 transports the print medium W in the transport direction Df relative to the first head 21, the second head 22, the third head 23, and the fourth head 24. More specifically, the platen 11 moves in the transport direction Df due to the rotation of the transport motor 46, thereby transporting the print medium W in the transport direction Df.

[0026] The movement device 30 includes a carriage 41, two guide rails 42, a movement motor 34, and an endless belt 44. The two guide rails 42 extend above the platen 11 in the movement direction Ds, sandwiching the carriage 41 between them in the transport direction Df. The carriage 41 supports the first head 21, the second head 22, the third head 23, and the fourth head 24. The carriage 41 is supported by the two guide rails 42 so as to be movable in the movement direction Ds. The endless belt 44 extends in the movement direction Ds and is attached to the carriage 41 and to the movement motor 34 via a pulley 45. The endless belt 44 operates as the movement motor 34 rotates. As a result, the carriage 41 reciprocates along the guide rails 42 in the movement direction Ds, moving the first head 21, the second head 22, the third head 23, and the fourth head 24 in the movement direction Ds. As a result, the first head 21, the second head 22, the third head 23, and the fourth head 24 move back and forth in the movement direction Ds.

[0027] The receiving unit 75 is disposed at one end of the guide rail 42 in the movement direction Ds so as to overlap with the movement region of the carriage 41 along the movement direction Ds. The receiving unit 75 receives ink droplets ejected from the heads 20 during a flushing process performed when the carriage 41 positions each head 20 above the receiving unit 75. Specifically, the receiving unit 75 receives ink droplets of color ink ejected from the nozzles 121 of the first head 21 and the nozzles 221 of the second head 22, as well as ink droplets of spot color ink ejected from the nozzles 321 of the third head 23 and the nozzles 421 of the fourth head 24. A second control device 50 (described later) causes each of the first head 21, second head 22, third head 23, and fourth head 24 to execute a flushing process before the heads start printing. The ink droplets received by the receiving unit 75 are drained via unillustrated piping connected to the receiving unit 75.

[0028] 3, the first head 21 is provided with a first drive element 27 arranged for each nozzle 121. The second head 22 is provided with a second drive element 28 arranged for each nozzle 221. The third head 23 is provided with a third drive element 29 arranged for each nozzle 321. The fourth head 24 is provided with a fourth drive element 31 arranged for each nozzle 421. The first drive element 27, the second drive element 28, the third drive element 29, and the fourth drive element 31 are piezoelectric elements, heat generating elements, electrostatic actuators, or the like. Each drive element 27, 28, 29, 31 applies pressure to the ink to eject ink droplets from the corresponding nozzle 121, 221, 321, 421.

[0029] The output device 101 includes a second control device 50. The output device 101 also includes a second storage device 51, a second communication interface 52, a first head drive circuit 53, a second head drive circuit 54, a third head drive circuit 57, a fourth head drive circuit 59, a movement drive circuit 55, and a transport drive circuit 56, which are connected to the second control device 50.

[0030] The second storage device 51 is a memory accessible from the second control device 50, and includes, for example, RAM and ROM. The RAM temporarily stores print data and various data used during calculations by the second control device 50. The ROM stores droplet ejection programs and various data for performing various data processing.

[0031] The second control device 50 is configured as a computer and includes a processor such as a CPU. The second control device 50 controls the operation of each part of the output device 101 by executing a droplet ejection program while referring to data stored in a second storage device 51. The second control device 50 receives ejection data from the first control device 61 via a second communication interface 52. The second control device 50 executes pass division processing based on the received ejection data. The pass division processing will be described in detail later. The second control device 50 may be configured as a single device, or may be configured so that multiple independently arranged devices cooperate to perform the operation of the output device 101. The second control device 50 also receives various data such as print data from the image processing device 102 via the second communication interface 52.

[0032] The first head drive circuit 53 controls the operation of the first drive element 27 based on instructions from the second control device 50. In this case, the second control device 50 outputs a control signal to the first head drive circuit 53 to drive the first drive element 27. The first head drive circuit 53 generates a drive signal based on the control signal and outputs the drive signal to the first drive element 27. The first drive element 27 imparts a predetermined ejection energy to the color ink in the first head 21 at a predetermined timing based on the drive signal. This causes ink droplets of the color ink to be ejected from the nozzle 121. Similarly, the second head drive circuit 54 controls the operation of the second drive element 28 based on instructions from the second control device 50. This causes ink droplets of the color ink to be ejected from the nozzle 221. The third head drive circuit 57 controls the operation of the third drive element 29 based on instructions from the second control device 50. This causes ink droplets of the spot color ink to be ejected from the nozzle 321. The fourth head drive circuit 59 controls the operation of the fourth drive element 31 based on instructions from the second control device 50. This causes ink droplets of the special color ink to be ejected from the nozzle 421.

[0033] The movement drive circuit 55 controls the operation of the movement motor 34 of the movement device 30 based on instructions from the second control device 50. The operation of the movement motor 34 causes the carriage 31 to move back and forth in the movement direction Ds. Therefore, the first head 21, the second head 22, the third head 23, and the fourth head 24 move in the movement direction Ds.

[0034] The transport drive circuit 56 controls the operation of the transport motor 46 of the transport device 40 based on instructions from the second control device 50. When the transport motor 46 operates, the platen 11 transports the print medium W intermittently or continuously along the transport direction Df, and also stops the print medium W at a predetermined position in the transport direction Df.

[0035] The image processing device 102 is a device that processes print images to be printed by the output device 101, and is configured, for example, by a personal computer, a tablet, a smartphone, etc. The image processing device 102 includes a first control device 61, and a first storage device 62, a first communication interface 63, a reading device 64, and a display device 65 that are connected to the first control device 61.

[0036] The first storage device 62 is a memory accessible from the first control device 61, and includes, for example, RAM and ROM. The RAM temporarily stores image data and various data used in calculations by the first control device 61. The ROM stores processing programs and various data for various data processing. Examples of the image data include raster data that indicates the image to be printed on the print medium W.

[0037] The first control device 61 is configured as a computer and includes a processor such as a CPU. The first control device 61 controls the operation of the output device 101 and the display device 65 by executing a processing program while referencing data stored in the first storage device 62. The first control device 61 acquires image data. For example, the image data may have 256 RGB values. The first control device 61 performs color conversion processing on the image data to acquire image data expressed as CMYK values, which are color coordinates in a device-dependent CMYK space. The first control device 61 then performs halftone processing on the converted image data to acquire ejection data (dot data). The first control device 61 transmits the ejection data to the second control device 50 via the first communication interface 63. The first control device 61 may be configured as a single device, or may be configured as multiple independently arranged devices working together to perform the operation of the image processing device 102. The first control device 61 transmits various data, such as print data, to the output device 101 via the first communication interface 63. In this embodiment, the first control device 61 cooperates with the second control device 50 of the output device 101 to form the control device 70 of the printing device 100 .

[0038] The reading device 64 reads the droplet ejection program etc. stored in a storage medium KB such as a CD-ROM or a USB flash memory. The read droplet ejection program etc. are stored in the first storage device 62. Alternatively, the droplet ejection program may be downloaded via a predetermined communication network and stored in the first storage device 62. The display device 65 is, for example, a touch panel display, and outputs operation information by the user to the first control device 61. The display device 65 also displays a print image etc. to be printed by the output device 101 based on image data.

[0039] Next, the processing of the second control device 50 in the first embodiment will be described in detail with reference to the drawings. Fig. 4 shows the dark regions Rd and light regions Rf corresponding to each printing pass in the ejection data Dd, and a histogram HG showing the total volume of ink droplets corresponding to the dark regions Rd and light regions Rf. Figs. 5 to 7 show examples of the dark regions Rd and light regions Rf corresponding to each printing pass in the ejection data Dd.

[0040] The second control device 50 executes the following processes as pass division processing. First, the second control device 50 acquires ejection data Dd, which is data obtained after halftone processing has been performed on image data, from the first control device 50. From the acquired ejection data Dd, the second control device 50 acquires a total volume value, which is the sum of the cumulative volume of the color ink droplets ejected from the first nozzles 121 aligned in the movement direction Ds and the cumulative volume of the color ink droplets ejected from the second nozzles 221 aligned in the movement direction Ds. In this case, the second control device 50 acquires the sum of the cumulative volume of ink droplets (ink droplets consisting of any of large droplets, medium droplets, and small droplets) to be ejected from the first nozzles 121 in the first head 21 aligned in the movement direction Ds and the cumulative volume of ink droplets (ink droplets consisting of any of large droplets, medium droplets, and small droplets) to be ejected from the second nozzles 221 in the second head 22 aligned in the movement direction Ds among the first nozzles 121. The second head 22 is disposed at a predetermined distance offset in the transport direction Df from the first head 21. Therefore, the above total volume value obtained for each row of nozzles lined up in the movement direction Ds includes one that is composed only of the cumulative total value of ink droplets ejected from the first nozzle 121, one that is composed of both the cumulative total value of ink droplets ejected from the first nozzle 121 and the cumulative total value of ink droplets ejected from the second nozzle 221, and one that is composed only of the cumulative total value of ink droplets ejected from the second nozzle 221.

[0041] Next, the second control device 50 creates a histogram HG of the acquired volume sum values, as shown in Fig. 4. The histogram HG shows the relationship between the position of the row (i.e., the position in the transport direction Df in the ejection data Dd) and the volume sum value corresponding to that position.

[0042] The second control device 50 then executes a process to acquire a dark region Rd, which is a region where the total volume value is equal to or greater than the threshold value. The dark region Rd is a region that extends in the transport direction Df and the movement direction Ds. In this case, the dimension of the dark region Rd in the transport direction Df may be equal to or greater than the distance from the center of the nozzles on one end of the joint region Rt between the first head 21 and the second head 22 in the transport direction Df to the center of the nozzles on the other end. Furthermore, the dimension of the dark region Rd in the movement direction Ds may be equal to or less than the dimension in the movement direction Ds that can be maximally reproduced by the ejection data Dd. The second control device 50 executes a process to acquire a light region Rf, which is a region where the total volume value is less than the threshold value. In the ejection data Dd1 in FIG. 4, which is an example of the ejection data Dd, the dark region Rd is indicated by a dark gray color, and the light gray region Rf is indicated by a light gray color. In FIG. 4, the first through fifth printing passes, which are examples of printing passes of the first head 21 and the second head 22, are identified by numbers 1 through 5 in open circles. The illustrated identification of the dark regions Rd and light regions Rf in FIGS. 5 to 7, as well as the illustrated identification of each printing pass, are the same as those in FIG.

[0043] The second control device 50 executes a process to determine whether a portion or all of the seam region Rt corresponds to the dark region Rd in a subsequent printing pass, which is a printing pass executed after a preceding printing pass, which is a predetermined printing pass. For example, the preceding printing pass is a printing pass that follows the first printing pass, and the subsequent printing pass is a printing pass that follows the second printing pass. In this case, using the example of FIG. 4 as an example, the second control device 50 determines that a portion or all of the seam region Rt corresponds to the dark region Rd in the second printing pass. Furthermore, if the subsequent printing pass is the third printing pass, the second control device 50 determines that a portion or all of the seam region Rt does not correspond to the dark region Rd in the third printing pass. Furthermore, if the subsequent printing pass is the fourth printing pass, the second control device 50 determines that a portion or all of the seam region Rt corresponds to the dark region Rd in the fourth printing pass.

[0044] 4, in the subsequent printing passes (the second printing pass relative to the first printing pass and the fourth printing pass relative to the third printing pass) following the preceding printing passes (the first printing pass relative to the second printing pass and the third printing pass relative to the fourth printing pass) in which some or all of the seam region Rt does not correspond to the dark region Rd, some or all of the seam region Rt corresponds to the dark region Rd. In such cases, the time interval between non-ejection and ejection is relatively short for the first nozzle 121 and the second nozzle 221 in the seam region Rt, making drying unlikely. For these reasons, when the ejection data Dd is the above-described ejection data Dd1, the second control device 50 does not execute the process described below to change the number of nozzles used for ejection by the first nozzle 121 and the number of nozzles used for ejection by the second nozzle 221.

[0045] In addition to Fig. 4, the discharge data Dd2 shown in Fig. 5 will now be referred to. In Fig. 5, to facilitate understanding, the first head 21 and the second head 22, as well as the printing passes of the first head 21 and the second head 22, before the process described below is executed to change the number of times the first nozzles 121 are used for discharge and the number of times the second nozzles 221 are used for discharge are shown enclosed in rectangular dashed lines.

[0046] With respect to the rectangular dashed lines in FIG. 5, as in the case of FIG. 4, the preceding printing pass is the printing pass after the first printing pass, and the succeeding printing pass is the printing pass after the second printing pass. The second control device 50 determines that part or all of the seam region Rt corresponds to the dark region Rd in the first printing pass. The second control device 50 also determines that part or all of the seam region Rt does not correspond to the dark region Rd in the second and third printing passes. The second control device 50 also determines that part or all of the seam region Rt corresponds to the dark region Rd in the fourth printing pass. Thus, in the example of FIG. 5, part or all of the seam region Rt corresponds to the dark region Rd in the first printing pass, which is a printing pass in which drying of the first nozzle 121 and the second nozzle 221 in the seam region Rt is relatively small due to the flushing process being performed before the execution of the printing pass.

[0047] Therefore, the second control device 50 executes the following process. That is, the second control device 50 changes the number of times the first nozzles 121 and the second nozzles 221 are used for ejection in the preceding printing pass so that part or all of the seam region Rt corresponds to the dark region Rd in the second printing pass, which is the following printing pass. In this case, the second control device 50 reduces the number of times the first nozzles 121 and the second nozzles 221 are used for ejection in the first printing pass, which is the preceding printing pass (i.e., the first printing pass not surrounded by the dashed rectangular line), so that the dark region Rd corresponds to part or all of the seam region Rt in the second printing pass, which is the following printing pass (i.e., the second printing pass not surrounded by the dashed rectangular line). In other words, the region formed by the first nozzles 121 and the second nozzles 221 in the first printing pass becomes the light region Rf, or no region is formed. In conjunction with this, that is, in conjunction with the process of reducing the number of times the first nozzles 121 are used for ejection and the number of times the second nozzles 221 are used for ejection, the second control device 50 changes the transport amount of the print medium W by the transport device 40 in the second printing pass as described above so as to correspond to part or all of the seam region Rt. Note that the second control device 50 may change the number of times the first nozzles 121 are used for ejection and the number of times the second nozzles 221 are used for ejection not only in the preceding printing pass but also in the following printing pass, and in the preceding and following printing passes.

[0048] After acquiring the dark region Rd in the ejection data Dd2 as described above, the second control device 50 executes a process to determine whether there are a predetermined number of subsequent printing passes in which some or all of the seam region Rt do not correspond to the dark region Rd. In the example of FIG. 5, the second control device 50 determines that there are a predetermined number or more consecutive subsequent printing passes in which some or all of the seam region Rt do not correspond to the dark region Rd (e.g., two; in FIG. 5, this corresponds to the third and fourth printing passes). If there are a predetermined number or more subsequent printing passes in which some or all of the seam region Rt do not correspond to the dark region Rd, the second control device 50 executes printing in the predetermined number of subsequent printing passes, and then ejects ink droplets of color ink from the first nozzles 121 and the second nozzles 221 onto the ink receiver 75 during a flushing process.

[0049] Next, let us look at the ejection data Dd3 shown in Fig. 6. The ejection data Dd3 in Fig. 6 differs from the ejection data Dd2 in Fig. 5 in that a blank area Rn exists between the third and fourth printing passes. In this case, the second control device 50 causes the transport device 40 to transport the printing medium W in the transport direction Df in accordance with the blank area Rn, and executes a flushing process between the third and fourth printing passes.

[0050] Next, let's look at the ejection data Dd4 shown in FIG. 7. The ejection data Dd4 in FIG. 7 differs from the ejection data Dd2 in FIG. 5 in that the length of the dark region Rd in the movement direction Ds is shorter than a predetermined value. That is, the ejection data Dd4 includes a partial dark region Rp where the dark region Rd is partially present in the movement direction Ds. In the example of FIG. 7, in the second and third printing passes, which are subsequent printing passes, part or all of the seam region Rt corresponds to the partial dark region Rp. Furthermore, in the printing pass next to the subsequent printing pass where such partial dark regions Rp are continuous (the fourth printing pass in FIG. 7), part or all of the seam region Rt does not correspond to the dark region Rd.

[0051] It is difficult to eject enough ink droplets into such partial-dense regions Rp to prevent the nozzles from drying out. In this way, if a predetermined number (e.g., two) or more partial-dense regions Rp are consecutive in a subsequent printing pass, and if part or all of the seam region Rt does not correspond to a dark region Rd in the printing pass after the subsequent printing pass, the second control device 50 performs a flushing process after printing corresponding to the subsequent printing pass. It is desirable to perform a similar flushing process even if multiple partial-dense regions Rp exist in a single subsequent printing pass and are spaced apart from each other in the movement direction Ds.

[0052] The pass division process for the first head 21 and the second head 22 has been described above, but the pass division process can also be performed similarly for the third head 23 and the fourth head 24. In this case, the second control device 50 may cause the third nozzles 321 and the fourth nozzles 421 to eject ink droplets of the spot color ink in the seam region Rt in the subsequent printing pass, prioritizing the ejection of ink droplets of the color ink from the first nozzles 121 and the second nozzles 221 in the seam region Rt. In this case, the second control device 50 changes the number of nozzles used for ejection by the third nozzles 321 and the number of nozzles used for ejection by the fourth nozzles 421 in the preceding printing pass, in order to cause part or all of the seam region Rt of the third head 23 and the fourth head 24 to correspond to the dark region Rd in the subsequent printing pass. In this example, the above-mentioned "priority" may mean that the first nozzle 121 and the second nozzle 221 in the seam region Rt are not discharged, but the third nozzle 321 and the fourth nozzle 421 in the seam region Rt are discharged.

[0053] Furthermore, the second control device 50 may preferentially cause the first nozzles 121 and second nozzles 221 in the seam region Rt to eject ink in the subsequent printing pass, starting with the nozzle with the least ejection history. Similarly, the second control device 50 may preferentially cause the third nozzles 321 and fourth nozzles 421 in the seam region Rt to eject ink in the subsequent printing pass, starting with the nozzle with the least ejection history. The ejection history may be based on, for example, the ejection data Dd, or on the drive signals generated by each head drive circuit. In this example, the term "priority" may mean that the first nozzles 121 and second nozzles 221 with the most ejection history are not ejected, and only the nozzles with the least ejection history are ejected.

[0054] Next, image processing including pass division processing in the printing device 100 will be described with reference to flowcharts. Fig. 8 is a flowchart showing the flow of processing in the printing device 100 of Fig. 1. Fig. 9 is a flowchart showing the flow of the pass division processing of Fig. 8. Fig. 10 is a flowchart continuing from Fig. 9.

[0055] As shown in FIG. 8, first, the first control device 61 of the image processing device 102 acquires image data consisting of RGB values ​​(step S1). Next, the first control device 61 performs color conversion processing on the image data to acquire image data expressed by CMYK values, which are color coordinates in a device-dependent CMYK space (step S2). Then, the first control device 61 performs halftone processing on the converted image data to acquire ejection data Dd (step S3). The first control device 61 transmits the ejection data Dd to the second control device 50 of the output device 101 via the first communication interface 63. Next, after receiving the ejection data Dd from the first control device 61, the second control device 50 executes the following pass division processing (step S4).

[0056] First, the second control device 50 obtains, from the obtained ejection data Dd, the total volume of the color ink droplets ejected from the first nozzles 121 aligned in the movement direction Ds (hereinafter referred to as the one-side accumulated volume) and the color ink droplets ejected from the second nozzles 221 aligned in the movement direction Ds (hereinafter referred to as the other-side accumulated volume) for each row of nozzles aligned in the movement direction Ds. In this case, as shown in FIG. 9, the second control device 50 sets the leftmost pixel of the first row in the ejection data Dd (e.g., ejection data Dd2 in FIG. 5) as the target pixel (step S11). Next, the second control device 50 determines whether the target pixel has reached the rightmost pixel of the first row (step S12).

[0057] If the target pixel has not yet reached the rightmost pixel of the first row (No in step S12), the second control device 50 adds the volumes of the ink droplets corresponding to the pixel set as the target pixel as the one-side cumulative volume and the other-side cumulative volume (step S13).Then, the second control device 50 sets the target pixel from the leftmost pixel to the pixel adjacent to the leftmost pixel on the right side (step S14), and then returns to the process of step S12 and repeats the subsequent processes.

[0058] On the other hand, when the setting of the target pixel reaches the rightmost pixel of the first row (Yes in step S12), that is, when acquisition of the total volume value, which is the sum of the one-side accumulated volume and the other-side accumulated volume in the first row, is completed, the second control device 50 sets the leftmost pixel of the next row (e.g., the second row) in the discharge data Dd as the target pixel (step S15). Thereafter, the second control device 50 stores the total volume value of the one-side accumulated volume and the other-side accumulated volume in the first row in the second storage device 51, and resets the one-side accumulated volume and the other-side accumulated volume to their initial values ​​(e.g., zero) (step S16).

[0059] Next, the second control device 50 determines whether the setting of the target pixel has reached the right-end pixel of the row related to the next row (for example, the second row) (step S17).

[0060] If the target pixel has not yet reached the rightmost pixel of the first row (No in step S17), the second control device 50 adds the volumes of the ink droplets corresponding to the pixel set as the target pixel as the one-side cumulative volume and the other-side cumulative volume (step S18). The second control device 50 then sets the target pixel from the leftmost pixel to the pixel adjacent to the right of the leftmost pixel (step S19), and then returns to step S15 to repeat the subsequent processes. On the other hand, if the target pixel has reached the rightmost pixel of the next row (e.g., the second row) (Yes in step S17), the second control device 50 stores the total volume of the one-side cumulative volume and the other-side cumulative volume for the next row (e.g., the second row) in the second storage device 51 (step S20).

[0061] Thereafter, the second control device 50 determines whether the setting of the target pixel has reached the final pixel (step S21). If the setting of the target pixel has not reached the final pixel (No in step S21), the second control device 50 returns to the processing of step S15 and repeats the subsequent processing. On the other hand, if the setting of the target pixel has reached the final pixel (Yes in step S21), the second control device 50 creates a histogram HG corresponding to the ejection data Dd as described in FIG. 4 (step S22).

[0062] Next, the second control device 50 acquires the dense region Rd based on the created histogram HG (step S23).Then, the second control device 50 sets a variable K based on the ordinal number of the printing pass for the first head 21 and the second head 22 to 1 (step S24).

[0063] The second control device 50 determines whether a dark region Rd exists in the second K printing pass (for example, the second printing pass when K=1) as the subsequent printing pass (step S25). If a dark region Rd exists in the second K printing pass (Yes in step S25), the second control device 50 determines whether a part or all of the seam region Rt overlaps with the dark region Rd in the second K printing pass (step S26).

[0064] If the seam region Rt partially or entirely overlaps with the dark region Rd in the 2K printing pass (Yes in step S26), the second control device 50 stores the number of active nozzles of the first nozzles 121 and the second nozzles 221 in the 2K-1 printing pass (e.g., the first printing pass when K=1) in the second storage device 51 (step S28). On the other hand, if the seam region Rt partially or entirely does not overlap with the dark region Rd in the 2K printing pass (No in step S26), the second control device 50 changes the number of active nozzles of the first nozzles 121 and the second nozzles 221 in the 2K-1 printing pass (e.g., the first printing pass when K=1), that is, decreases the number of active nozzles (step S27), and then returns to the processing of step S26.

[0065] If no dark region Rd is present in the 2K printing pass (No in step S25), the second control device 50 sets (e.g., turns on a flag) to execute a flushing process after the 2K printing pass (e.g., the second printing pass when K=1) (step S29). The second control device 50 then sets the number of active nozzles of the first nozzles 121 and the second nozzles 221 to the maximum in the 2K-1 printing pass (e.g., the first printing pass when K=1) (step S30). In this case, if each of the first head 21 and the second head 22 has, for example, 210 nozzles arranged in the movement direction Ds, the number of active nozzles of the first nozzles 121 and the second nozzles 221 is set to 210.

[0066] Next, the second control device 50 determines whether the process has been completed up to the final printing pass (step S31). If the process has not been completed up to the final printing pass (No in step S31), the second control device 50 sets the variable K to K+1 (step S32).

[0067] The second control device 50 then determines whether the flushing process flag is on (step S33). If the flushing process flag is on (Yes in step S33), the second control device 50 sets the number of first nozzles 121 and second nozzles 221 to the maximum in use in the 2K-1 printing pass (e.g., the third printing pass) (step S34), and then returns to the processing of step S26 and repeats the subsequent processing.

[0068] On the other hand, if the flushing process flag is not on (No in step S33), the second control device 50 determines whether part or all of the seam region Rt overlaps with the dark region Rd in the second K-1 printing pass (step S35).

[0069] If the seam region Rt does not partially or entirely overlap with the dark region Rd in the 2K-1 printing pass (No in step S35), the second control device 50 reduces the number of first nozzles 121 and second nozzles 221 in use in the 2K-1 printing pass (step S36), and then returns to the processing of step S35. On the other hand, if the seam region Rt partially or entirely overlaps with the dark region Rd in the 2K-1 printing pass (Yes in step S35), the second control device 50 stores the number of first nozzles 121 and second nozzles 221 in use in the 2K-1 printing pass in the second storage device 51 (step S37), and then returns to the processing of step S31 and repeats the subsequent processing.

[0070] On the other hand, if processing has been completed up to the final printing pass (Yes in step S31), the second control device 50 divides the printing passes based on the number of nozzles in use (step S38). In this case, the second control device 50 divides each printing pass for the printing process to be executed based on the number of nozzles in use, and changes the transport amount of the print medium W by the transport device 40.

[0071] 11A and 11B are diagrams showing modified examples of the carriage in FIG. 1. In FIG. 1, the carriage 41 is configured to support the first head 21, the second head 22, the third head 23, and the fourth head 24, but the following configuration may also be adopted. As shown in FIG. 11A, the carriage 41 may support only the first head 21 and the second head 22, and as shown in FIG. 11B, the droplet ejection device 101A may be provided with a second moving device 30A including a carriage 41A that supports the third head 23 and the fourth head 24. The configuration of the second moving device 30A is the same as that of the moving device 30.

[0072] As described above, according to the droplet ejection device 101A, when part or all of the seam region Rt does not correspond to the dark region Rd, the number of first nozzles 121 used for ejection and the number of second nozzles 221 used for ejection are changed in the preceding printing pass, the following printing pass, and one of the preceding and following printing passes. This allows part or all of the seam region Rt to correspond to the dark region Rd in the following printing pass, etc. In other words, in the following printing pass, etc., it becomes possible to eject ink droplets of color ink whose total volume value is equal to or greater than a threshold value from the first nozzles 121 and the second nozzles 221. This prevents the first nozzles 121 and the second nozzles 221 from drying out, making ejection defects less likely to occur.

[0073] Furthermore, in this embodiment, the second control device 50 creates a histogram HG of the acquired volume sum values. This makes it easier to associate the first nozzles 121 and the second nozzles 221 in the seam region Rt in each printing pass with the dense region Rd, which is a region in the histogram HG where the volume sum value is equal to or greater than the threshold value.

[0074] Furthermore, in this embodiment, the second control device 50 may cause the third nozzles 321 and fourth nozzles 421 in the seam region Rt to eject ink in the subsequent printing pass in preference to the first nozzles 121 and second nozzles 221 in the seam region Rt. In this case, it is possible to increase the ejection frequency of the third nozzles 321 and fourth nozzles 421, which eject ink droplets of special color inks that are ejected less frequently than color ink droplets. This can further prevent the third nozzles 321 and fourth nozzles 421 from drying out.

[0075] Furthermore, in this embodiment, the second control device 50 may preferentially eject ink from the first nozzle 121 and the second nozzle 221 in the seam region Rt in the subsequent printing pass, starting with the nozzle with the least ejection history. Similarly, the second control device 50 may preferentially eject ink from the third nozzle 321 and the fourth nozzle 421 in the seam region Rt in the subsequent printing pass, starting with the nozzle with the least ejection history. This can prevent drying from occurring in nozzles that are prone to drying due to their short ejection history.

[0076] In this embodiment, the dark region Rd is a region that extends in the transport direction Df and the movement direction Ds. In this case, it becomes easier to match the first nozzles 121 and second nozzles 221 in the seam region Rt in each printing pass to the dark region Rd.

[0077] Furthermore, in this embodiment, the second control device 50 executes a process to determine whether there are a predetermined number of subsequent printing passes in which some or all of the seam regions Rt do not correspond to the dark regions Rd. If there are a predetermined number or more subsequent printing passes in which some or all of the seam regions Rt do not correspond to the dark regions Rd, the second control device 50 executes a flushing process after printing in the predetermined number of subsequent printing passes. In this case, the flushing process is executed on the first nozzles 121 and the second nozzles 221, which are prone to drying due to the presence of a predetermined number or more subsequent printing passes in which some or all of the seam regions Rt do not correspond to the dark regions Rd. This prevents the first nozzles 121 and the second nozzles 221 from drying out, making ejection defects less likely to occur.

[0078] Furthermore, in this embodiment, the carriage supporting the first head 21 and the second head 22 and the carriage supporting the third head 23 and the fourth head 24 may be configured independently of each other. In this case, it becomes easier to control the ejection of color ink droplets and the ejection of spot color ink droplets.

[0079] (Second embodiment) In the second embodiment, the method of acquiring the dark regions Rd differs from that of the first embodiment. This will be explained in detail below. Fig. 12 is a diagram showing examples of dark regions Rd and light regions Rf corresponding to each printing pass in image data Dp. Fig. 13 is a diagram showing printing passes in which seam regions Rt correspond to dark regions Rd.

[0080] In this embodiment, the first control device 61 acquires image data Dp, as in the first embodiment. The image data Dp may be, for example, data in which each of the RGB values ​​has a value of 256 levels. The first control device 61 executes a process of acquiring a color-related weight value for each pixel from the acquired image data Dp. The weight value is a value based on the RGB value of each pixel, and indicates the magnitude of the reproducibility of a specific color (e.g., red) in each pixel when focusing on the specific color among the colors R (red), G (green), and B (blue). For example, if the weight value is 10 when the RGB value is (255,0,0) when the specific color is red, the weight value is 1 when the RGB value is (32,32,32), for example.

[0081] Next, the first control device 61 divides the image data Dp into blocks Bl each consisting of a plurality of pixels, as shown in Fig. 12. Each block Bl consists of, for example, 60 pixels x 60 pixels.

[0082] Then, the first control device 61 calculates the average value of the weight values ​​of the multiple pixels that make up the block Bl. The first control device 61 obtains the average value of the weight values ​​for each block Bl. The average value of the weight value is calculated by dividing the sum of the weight values ​​of the multiple pixels that make up the block Bl by the number of those multiple pixels.

[0083] Next, the first control device 61 acquires, for each printing pass, a dark region Rd, which is a region where the average value of the weight values ​​is equal to or greater than a threshold value. The first control device 61 also acquires, for each printing pass, a light region Rf, which is a region where the average value of the weight values ​​is less than a threshold value. In the image data Dp of FIG. 12, the dark gray regions are the dark regions Rd, and the light gray regions are the light regions Rf. In addition, in FIGS. 12 and 13, the first and second printing passes, which are examples of printing passes of the first and second heads 21 and 22, are identified by adding the numbers 1 and 2 to open circles.

[0084] Next, as in the first embodiment, the first control device 61 determines whether part or all of the seam region Rt corresponds to the dark region Rd in a subsequent printing pass, which is a printing pass executed after a preceding printing pass, which is a predetermined printing pass. More specifically, in this embodiment, the first control device 61 determines whether part or all of the seam region Rt in the subsequent printing pass corresponds to a predetermined number (e.g., four) or more blocks Bl that are dark regions Rd. In this case, using the example of FIG. 12 as an example, the first control device 61 determines that part or all of the seam region Rt in the second printing pass does not correspond to a predetermined number or more blocks Bl that are dark regions Rd.

[0085] Therefore, the first control device 61 executes the following process. Specifically, the first control device 61 changes the number of times the first nozzles 121 and the second nozzles 221 are used for ejection in the preceding printing pass so that part or all of the seam region Rt corresponds to a predetermined number or more of blocks Bl that are dark regions Rd in the second printing pass, which is the following printing pass. In this case, as shown in FIG. 13 , the first control device 61 reduces the number of times the first nozzles 121 and the second nozzles 221 are used for ejection in the first printing pass, which is the preceding printing pass, so that the predetermined number or more of blocks Bl that are dark regions Rd correspond to part or all of the seam region Rt in the second printing pass, which is the following printing pass. In other words, the region formed by the first nozzles 121 and the second nozzles 221 in the first printing pass becomes a light region Rf, or there is no region formed. In addition, the first control device 61 changes the transport amount of the print medium W by the transport device 40 so that part or all of the seam region Rt corresponds to part or all of the seam region Rt in the second printing pass, as described above. As in the first embodiment, the first control device 61 may change not only the preceding printing pass but also the following printing pass, and the number of first nozzles 121 used for ejection and the number of second nozzles 221 used for ejection in the preceding printing pass and the following printing pass. By the above processing, in the example of Fig. 13, some or all of the seam regions Rt in the second printing pass correspond to six blocks Bl that are dark regions Rd.

[0086] Fig. 14 is a flowchart showing the flow of processing in the printing device 100 of the second embodiment. Fig. 15 is a flowchart showing the flow of the block division / pass division processing of Fig. 14. Fig. 16 is a flowchart showing the flow of the block division / pass division processing continued from Fig. 15.

[0087] As shown in FIG. 14, the first control device 61 first acquires image data consisting of RGB values ​​(step S51). Subsequently, the first control device 61 executes block division and pass division processing (described later) (step S52). Next, the first control device 61 executes color conversion processing on the image data after block division and pass division processing to acquire image data expressed as CMYK values, which are color coordinates in a device-dependent CMYK space (step S53). The first control device 61 then executes halftone processing on the converted image data to acquire ejection data (step S54). Next, the first control device 61 transmits the ejection data, which is the data after halftone processing, to the second control device 50 of the output device 101 via the first communication interface 63 (step S55).

[0088] In the block division / pass division process, as shown in Fig. 15, the first control device 61 first sets the leftmost pixel of the first row in the image data Dp as the target pixel (step S61). Next, the first control device 61 determines whether the target pixel has reached the rightmost pixel of the first row (step S62).

[0089] If the setting of the target pixel has not reached the rightmost pixel of the first row (No in step S62), the first control device 61 acquires a weight value corresponding to the pixel set as the target pixel (step S63).Then, the first control device 61 sets the target pixel from the leftmost pixel to the pixel adjacent to the leftmost pixel on the right side (step S64), and then returns to the processing of step S62 and repeats the subsequent processing.

[0090] On the other hand, if the setting of the target pixel has reached the rightmost pixel of the first row (Yes in step S62), that is, if acquisition of weight values ​​for all pixels in the first row has been completed, the first control device 61 sets the leftmost pixel of the next row (e.g., the second row) in the image data Dp as the target pixel (step S65). Thereafter, the first control device 61 determines whether the setting of the target pixel has reached the rightmost pixel of the next row (e.g., the second row) (step S66).

[0091] If the setting of the target pixel has not reached the rightmost pixel of the first row (No in step S66), the first control device 61 acquires a weight value corresponding to the pixel set as the target pixel (step S67). Then, the first control device 61 sets the target pixel from the leftmost pixel to the pixel adjacent to the right of the leftmost pixel (step S68), and then returns to the processing of step S65 and repeats the subsequent processing. On the other hand, if the setting of the target pixel has reached the rightmost pixel of the next row (e.g., the second row) (Yes in step S66), the first control device 61 determines whether the setting of the target pixel has reached the final pixel (step S69).

[0092] If the setting of the target pixel has not reached the final pixel (No in step S69), the first control device 61 returns to the processing of step S65 and repeats the subsequent processing. On the other hand, if the setting of the target pixel has reached the final pixel (Yes in step S69), the first control device 61 divides the image data Dp into blocks Bl each consisting of a plurality of pixels (step S70), as described in FIG.

[0093] Next, the first control device 61 calculates the average value of the weight values ​​for each block Bl (step S71), and then sets a variable K based on the ordinal numbers of the printing passes for the first head 21 and the second head 22 to 1 (step S72).

[0094] The first control device 61 determines whether or not a predetermined number of blocks Bl that are dark regions Rd exist in the second K printing pass (for example, the second printing pass when K=1) as the subsequent printing pass (step S73). If the predetermined number of blocks Bl that are dark regions Rd exist in the second K printing pass (Yes in step S73), the first control device 61 determines whether a part or all of the seam region Rt overlaps with the predetermined number or more of blocks Bl that are dark regions Rd in the second K printing pass (step S74).

[0095] If part or all of the seam region Rt overlaps with a predetermined number or more of blocks Bl that are dark region Rd in the 2K printing pass (Yes in step S74), the first control device 61 stores the number of active nozzles of the first nozzles 121 and the second nozzles 221 in the 2K-1 printing pass (e.g., the first printing pass if K=1) in the second storage device 51 (step S76). On the other hand, if part or all of the seam region Rt does not overlap with a predetermined number or more of blocks Bl that are dark region Rd in the 2K printing pass (No in step S74), the first control device 61 changes the number of active nozzles of the first nozzles 121 and the second nozzles 221 in the 2K-1 printing pass (e.g., the first printing pass if K=1), that is, decreases the number of active nozzles (step S75), and then returns to the processing of step S74.

[0096] If there are not a predetermined number or more blocks Bl that are dark regions Rd in the 2K printing pass (No in step S73), the first control device 61 sets (e.g., turns on a flag) to execute a flushing process after the 2K printing pass (e.g., the second printing pass when K=1) (step S77).Then, the first control device 61 sets the number of first nozzles 121 and second nozzles 221 to the maximum in use in the 2K-1 printing pass (e.g., the first printing pass when K=1) (step S78).

[0097] Next, the first control device 61 determines whether the process has been completed up to the final printing pass (step S79). If the process has not been completed up to the final printing pass (No in step S79), the first control device 61 sets the variable K to K+1 (step S80).

[0098] Then, the first control device 61 determines whether the flushing process flag is on (step S81). If the flushing process flag is on (Yes in step S81), the first control device 61 sets the number of first nozzles 121 and second nozzles 221 to be used in the 2K-1 printing pass (e.g., the third printing pass) to the maximum (step S82), and then returns to the processing of step S74 and repeats the subsequent processing.

[0099] On the other hand, if the flushing process flag is not on (No in step S81), the first control device 61 determines whether part or all of the seam region Rt overlaps with a predetermined number or more of blocks Bl that are dark regions Rd in the second K-1 printing pass (step S83).

[0100] If the seam region Rt, in whole or in part, does not overlap with a predetermined number or more of blocks Bl that are dark regions Rd in the 2K-1 printing pass (No in step S83), the first control device 61 reduces the number of used nozzles of the first nozzles 121 and the second nozzles 221 in the 2K-1 printing pass (step S84), and then returns to the processing of step S83. On the other hand, if the seam region Rt, in whole or in part, overlaps with a predetermined number or more of blocks Bl that are dark regions Rd in the 2K-1 printing pass (Yes in step S83), the first control device 61 stores the number of used nozzles of the first nozzles 121 and the second nozzles 221 in the 2K-1 printing pass in the second storage device 51 (step S85), and returns to the processing of step S79 and repeats the subsequent processing.

[0101] On the other hand, if processing has been completed up to the final printing pass (Yes in step S79), the first control device 61 divides the printing passes based on the number of nozzles in use (step S86). In this case, the first control device 61 divides each printing pass for the printing process to be executed based on the number of nozzles in use, and changes the transport amount of the print medium W by the transport device 40.

[0102] As described above, according to the second embodiment, when part or all of the seam region Rt does not correspond to a predetermined number or more of blocks Bl that are dark regions Rd, the number of first nozzles 121 used for ejection and the number of second nozzles 221 used for ejection are changed in the preceding printing pass, the following printing pass, and one of the preceding and following printing passes. This allows part or all of the seam region Rt to correspond to a predetermined number or more of blocks Bl that are dark regions Rd in the following printing pass, etc. In other words, in the following printing pass, etc., it becomes possible to eject ink droplets of color ink from the first nozzles 121 and the second nozzles 221 that correspond to a predetermined number or more of dark regions Rd (a predetermined number or more of blocks Bl), where the average value of the weight value is equal to or greater than a threshold. This prevents the first nozzles 121 and the second nozzles 221 from drying out, making ejection defects less likely to occur.

[0103] The present disclosure is not limited to the above-described embodiment, and modifications can be made without departing from the spirit of the present disclosure. For example, the following modifications are possible.

[0104] In the second embodiment, the block division / pass division process is performed before the color conversion process, but this is not limited to this, and the block division / pass division process may be performed after the color conversion process.

[0105] In the above embodiment, the first head 21 and the second head 22 that eject ink droplets of color inks, and the third head 23 and the fourth head 24 that eject ink droplets of special color inks are provided on the carriage 41, but this is not limiting. A head that ejects ink droplets of white ink or a head that ejects ink droplets of clear ink may also be provided.

[0106] In the above embodiment, the image processing device 102 and the output device 101 are configured separately and independently, and the concept encompassing these is the printing device (or printing system) 100, but this is not limited to this. A processing unit capable of executing the same processing as that by the image processing device 102 and a processing unit capable of executing the same processing as that by the output device 101 may be provided in a printing device such as a single printer.

[0107] Furthermore, although each head 20 is a serial head in the above embodiment, each head 20 may be a line head. [Explanation of symbols]

[0108] 21 First Head 22 Second Head 23 Third Head 24 4th Head 30 Mobile Device 30A 2nd moving device 40 Conveyor 41,41A Carriage 50 Second control device 61 First control device 70 Control device 75 Receiving part 100 Printing device 101 Output Device 101A Droplet discharge device 102 Image processing device 121 No. 1 nozzle 221 Second Nozzle 321 Third nozzle 421 No. 4 nozzle Bl Block Dd Discharge Data Df Conveying direction Dp image data Ds moving direction HG Histogram Rd dark area Rf thin area Rt Joint area W Printing medium

Claims

1. a first head having a plurality of first nozzles for ejecting first droplets based on image data; a second head having a plurality of second nozzles for ejecting second droplets of the same color as the first droplets based on the image data; a transport device that transports a print medium in a transport direction relative to the first head and the second head; a first moving device that moves the first head and the second head in a moving direction that intersects with the transport direction; a control device; the first head and the second head are arranged such that, in a predetermined seam region, positions of some of the first nozzles among the plurality of first nozzles and positions of some of the second nozzles among the plurality of second nozzles overlap in the transport direction; The control device a process of acquiring, from ejection data that is data after halftone processing has been performed on the image data, a dense region that is a region where a total volume value that is a sum of a cumulative volume of the first droplets ejected from the first nozzles aligned in the movement direction and a cumulative volume of the second droplets ejected from the second nozzles aligned in the movement direction is equal to or greater than a threshold value; a process of determining whether a part or all of the seam region corresponds to the dark region in a subsequent printing pass, which is a printing pass executed after a preceding printing pass, which is a predetermined printing pass; a droplet ejection device that executes a process of changing the number of nozzles used for ejection of the first nozzles and the number of nozzles used for ejection of the second nozzles in the preceding printing pass, the following printing pass, and any one of the preceding printing pass and the following printing pass, in order to make part or all of the seam area correspond to the dark area in the following printing pass when part or all of the seam area does not correspond to the dark area.

2. The droplet ejection device of claim 1 , wherein the control device creates a histogram of the volume sum values.

3. a third head having a plurality of third nozzles for ejecting third droplets based on the image data; a fourth head having a plurality of fourth nozzles for ejecting fourth droplets of the same color as the third droplets based on the image data, the transport device transports the print medium in the transport direction relative to the third head and the fourth head; the first moving device moves the third head and the fourth head in the movement direction; The control device ejecting color ink droplets as the first droplets from the first nozzles of the first head, and ejecting color ink droplets as the second droplets from the second nozzles of the second head; ejecting ink droplets of a special color as the third droplets from the third nozzles of the third head, and ejecting ink droplets of a special color as the fourth droplets from the fourth nozzles of the fourth head; the third head and the fourth head are arranged such that, in a predetermined seam region, positions of some of the third nozzles among the plurality of third nozzles and positions of some of the fourth nozzles among the plurality of fourth nozzles overlap in the transport direction; The droplet ejection device according to claim 1 , wherein the control device further causes ejection from the third and fourth nozzles in the seam region in priority over the first and second nozzles in the seam region in the subsequent printing pass.

4. The droplet ejection device according to claim 1 , wherein the control device causes the nozzles with the least ejection history to be ejected preferentially from among the first nozzles and the second nozzles in the seam region in the subsequent printing pass.

5. The droplet ejection device according to claim 1 , wherein the dense region is a region that extends in the transport direction and the movement direction.

6. a receiving section for receiving the first droplets ejected from the first nozzles and the second droplets ejected from the second nozzles, The control device a process of determining whether or not there are a predetermined number or more of the subsequent printing passes in which the seam region does not correspond to the dark region after acquiring the dark region; 2. The droplet ejection device according to claim 1, further comprising: a flushing process for ejecting the first droplets from the first nozzles and the second droplets from the second nozzles onto the receiving portion after printing in the predetermined number of subsequent printing passes is performed when there are a predetermined number or more of the subsequent printing passes.

7. a third head having a plurality of third nozzles for ejecting third droplets based on the image data; a fourth head having a plurality of fourth nozzles for ejecting fourth droplets of the same color as the third droplets based on the image data; a second moving device that moves the third head and the fourth head in the movement direction, the transport device transports the print medium in the transport direction relative to the third head and the fourth head; ejecting color ink droplets as the first droplets from the first nozzles of the first head, and ejecting color ink droplets as the second droplets from the second nozzles of the second head; ejecting ink droplets of a special color as the third droplets from the third nozzles of the third head, and ejecting ink droplets of a special color as the fourth droplets from the fourth nozzles of the fourth head; the third head and the fourth head are arranged such that, in a predetermined seam region, positions of some of the third nozzles among the plurality of third nozzles and positions of some of the fourth nozzles among the plurality of fourth nozzles overlap in the transport direction; 2. The droplet ejection device according to claim 1, wherein the control device ejects the third droplet and the fourth droplet from the third nozzle and the fourth nozzle in the seam region in priority to ejecting the first droplet and the second droplet from the first nozzle and the second nozzle in the seam region in the subsequent printing pass.

8. a first head having a plurality of first nozzles for ejecting first droplets based on image data; a second head having a plurality of second nozzles for ejecting second droplets of the same color as the first droplets based on the image data; a transport device that transports a print medium in a transport direction relative to the first head and the second head; a moving device that moves the first head and the second head in a moving direction that intersects with the transport direction; a control device; the first head and the second head are arranged such that, in a predetermined seam region, positions of some of the first nozzles among the plurality of first nozzles and positions of some of the second nozzles among the plurality of second nozzles overlap in the transport direction; The control device A process of obtaining a weight value relating to color for each pixel from the image data; Dividing the image data into blocks each consisting of a plurality of pixels; a process of calculating an average value of the weight values ​​of the plurality of pixels constituting the block for each of the blocks; A process of acquiring, for each printing pass, a dark region where the average value of the weight values ​​is equal to or greater than a threshold value; a process of determining whether a part or all of the seam region corresponds to the dark region in a subsequent printing pass, which is a printing pass executed after a preceding printing pass, which is a predetermined printing pass; a droplet ejection device that executes a process of changing the number of nozzles used for ejection of the first nozzles and the number of nozzles used for ejection of the second nozzles in the preceding printing pass, the following printing pass, and any one of the preceding printing pass and the following printing pass, in order to make part or all of the seam area correspond to the dark area in the following printing pass when part or all of the seam area does not correspond to the dark area.

9. a receiving section for receiving the first droplets ejected from the first nozzles and the second droplets ejected from the second nozzles, The control device a process of determining whether or not there are a predetermined number of subsequent printing passes in which the seam region does not correspond to the dark region after acquiring the dark region; 9. The droplet ejection device according to claim 8, further comprising: a flushing process for ejecting the first droplets from the first nozzles and the second droplets from the second nozzles onto the receiving portion after printing in the predetermined number of subsequent printing passes is performed when there is a predetermined number of subsequent printing passes.

10. A droplet ejection method using a droplet ejection device including: a first head having a plurality of first nozzles for ejecting first droplets based on image data; a second head having a plurality of second nozzles for ejecting second droplets of the same color as the first droplets based on the image data; and a control device, the first head and the second head are arranged such that, in a predetermined seam region, positions of some of the first nozzles among the plurality of first nozzles and positions of some of the second nozzles among the plurality of second nozzles overlap in a transport direction of the print medium; From the ejection data, which is data after halftone processing has been performed on the image data, a dense region is obtained, which is a region where a total volume value, which is a sum of a cumulative volume of the first droplets ejected from the first nozzles aligned in a movement direction intersecting the transport direction and a cumulative volume of the second droplets ejected from the second nozzles aligned in the movement direction, is equal to or greater than a threshold value; determining whether a part or all of the seam region corresponds to the dark region in a subsequent printing pass, which is a printing pass executed after a preceding printing pass, which is a predetermined printing pass; A droplet ejection method in which, when part or all of the seam area does not correspond to the dark area, the number of times the first nozzle is used for ejection and the number of times the second nozzle is used for ejection are changed in the preceding printing pass, the following printing pass, and any one of the preceding printing pass and the following printing pass, in order to make part or all of the seam area correspond to the dark area in the following printing pass.

11. A droplet ejection program executed by a computer in a droplet ejection device including: a first head having a plurality of first nozzles for ejecting first droplets based on image data; a second head having a plurality of second nozzles for ejecting second droplets of the same color as the first droplets based on the image data; and a control device, the first head and the second head are arranged such that, in a predetermined seam region, positions of some of the first nozzles among the plurality of first nozzles and positions of some of the second nozzles among the plurality of second nozzles overlap in a transport direction of the print medium; The computer an acquisition means for acquiring, from ejection data that is data after halftone processing has been performed on the image data, a dense region that is a region where a total volume value that is a sum of a cumulative volume of the first droplets ejected from the first nozzles aligned in a movement direction intersecting the transport direction and a cumulative volume of the second droplets ejected from the second nozzles aligned in the movement direction is equal to or greater than a threshold value; a determining means for determining whether a part or all of the seam region corresponds to the dark region in a subsequent printing pass, which is a printing pass executed after a preceding printing pass, which is a predetermined printing pass; and A droplet ejection program that functions as a modification means for modifying the preceding printing pass, the following printing pass, and the number of times the first nozzle is used for ejection and the number of times the second nozzle is used for ejection in any one of the preceding printing pass and the following printing pass, in order to make part or all of the seam area correspond to the dark area in the following printing pass when part or all of the seam area does not correspond to the dark area.

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