Printer and printing method

Abstract

A printer 10 comprises: an ejection head 100 in which a plurality of ejection rows 102 having a plurality of ejection ports 101 are arranged in a Y direction; and a control device 20. The control device 20 includes: an acquiring unit 23 that acquires image data DT1 which is used during outward printing and which includes a plurality of items of column image data DT2 prepared for each ejection row 102; a data converting unit 25 that adds empty data DT 10 so that ink ejected from the plurality of ejection rows 102 overlaps in return printing, and that creates converted image data DT3 including converted column image data DT4 obtained by inverting the column image data DT2; an outward printing control unit 31 that executes outward printing by ejecting ink sequentially from the ejection row 102 on another side, in the Y direction, among the plurality of ejection rows 102, on the basis of the image data DT1; and a return printing control unit 32 that executes return printing by ejecting ink sequentially from the ejection row 102 on one side, in the Y direction, among the plurality of ejection rows 102, on the basis of the converted image data DT3.

Description

Printers and printing methods

[0001] The present invention relates to a printer and a printing method.

[0002] For example, Patent Document 1 discloses a three-dimensional modeling device equipped with a discharge head that discharges a binder based on image data onto a powder layer made of powder material. In this three-dimensional modeling device, the powder layer is configured to be movable in the X-axis direction relative to the discharge head. The three-dimensional modeling device also includes a rail extending in the Y-axis direction. The discharge head is engaged with the rail and configured to be movable in the Y-axis direction along the rail.

[0003] Japanese Patent Application Laid-Open No. 2017-119363

[0004] For example, the above-described ejection head may eject binder based on image data both on the outward path from one side to the other in the Y-axis direction and on the return path from the other side to one side in the Y-axis direction. Here, if an attempt is made to eject binder while the ejection head is moving in the return path using image data that is used while the ejection head is moving in the outward path, it may not be possible to eject the binder at the desired position.

[0005] The present invention has been made in consideration of these points, and its purpose is to provide a printer and printing method that can eject ink at an appropriate position to perform printing when the ejection head is moving forward and backward in the Y direction.

[0006] The printer disclosed herein includes a table supporting a substrate, a discharge head having a plurality of discharge rows in which discharge ports for discharging ink are aligned in a first direction, the plurality of discharge rows being aligned in a second direction intersecting the first direction, a head movement mechanism for moving the discharge head in the second direction relative to the substrate supported on the table, and a control device. Printing performed when the discharge head moves in a forward pass from one side of the second direction to the other is referred to as forward pass printing, and printing performed when the discharge head moves in a backward pass from the other side of the second direction to the other side is referred to as backward pass printing. The control device includes an acquisition unit, a data conversion unit, a forward pass printing control unit, and a backward pass printing control unit. The acquisition unit acquires image data that indicates whether or not to eject ink toward a position on the substrate corresponding to the forward pass in the second direction, and that includes multiple column image data prepared for each discharge row. The data conversion unit creates converted image data used in the backward pass printing, the converted image data including converted column image data obtained by inverting the column image data based on the image data. In the return pass printing, the data conversion unit begins to reference the converted column image data sequentially, starting with the ejection column on the other side of the second direction among the plurality of ejection columns, and adds null data before the converted column image data so that ink ejected from the plurality of ejection columns overlaps and ink ejection begins sequentially, starting with the ejection column on one side of the second direction. The outward pass printing control unit performs the outward pass printing by beginning to reference the column image data sequentially, starting with the ejection column on the other side of the second direction among the plurality of ejection columns, based on the image data acquired by the acquisition unit, and starting ink ejection, based on the converted image data created by the data conversion unit.

[0007] In this printer, in the return pass printing, as in the forward pass printing, reference to the converted array image data is started sequentially from the ejection array on the other side of the second direction, and the timing of ink ejection is controlled based on the converted array image data so that ink ejected from multiple ejection arrays overlaps, thereby enabling ink to be ejected at appropriate positions in both the forward pass printing and the return pass printing.

[0008] A printing method according to the present invention is a printing method for a printer. The printer includes a table that supports a substrate and a discharge head having a plurality of discharge rows in which discharge ports for discharging ink are aligned in a first direction and arranged in a second direction intersecting the first direction. Printing performed when the discharge head moves in a forward pass from one side to the other in the second direction is referred to as forward pass printing, and printing performed when the discharge head moves in a backward pass from the other side to one side in the second direction is referred to as backward pass printing. The printing method includes an acquisition step, a data conversion step, a forward pass printing control step, and a backward pass printing control step. The acquisition step instructs whether or not to discharge ink toward a position on the substrate corresponding to the forward pass in the second direction, and acquires image data having multiple column image data prepared for each of the discharge rows. The data conversion step creates converted image data used in the backward pass printing, the converted image data having converted column image data obtained by inverting the column image data based on the image data. In the data conversion step, during the return pass printing, reference to the converted column image data is started sequentially, starting with the ejection column on the other side of the second direction among the plurality of ejection columns, and null data is added before the converted column image data so that ink ejected from the plurality of ejection columns overlaps and ink ejection is started sequentially, starting with the ejection column on one side of the second direction. In the outward pass printing control step, reference to the column image data is started sequentially, starting with the ejection column on the other side of the second direction among the plurality of ejection columns, based on the image data acquired in the acquisition step, and ink ejection is started, thereby performing the outward pass printing. In the return pass printing control step, reference to the converted column image data is started sequentially, starting with the ejection column on the other side of the second direction among the plurality of ejection columns, based on the converted image data created in the data conversion step, and ink ejection is started sequentially, starting with the ejection column on one side of the second direction, performing the return pass printing.

[0009] According to the present invention, it is possible to provide a printer and a printing method that can perform printing by ejecting ink at appropriate positions when the ejection head is moving forward and backward in the Y direction.

[0010] FIG. 1 is a perspective view schematically illustrating a printer according to an embodiment. FIG. 2 is a perspective view schematically illustrating an ejection head. FIG. 3 is a block diagram of the printer. FIG. 4 is a right side view schematically illustrating the configuration of forward pass reference marks and backward pass reference marks. FIG. 5 is a conceptual diagram of image data and converted image data. FIG. 6 is a diagram schematically illustrating control according to the position of the ejection head during forward pass printing. FIG. 7A is a diagram schematically illustrating control according to the position of the ejection head during backward pass printing. FIG. 7B is a diagram schematically illustrating control according to the position of the ejection head during backward pass printing. FIG. 8 is a flowchart showing a series of steps in printing by the printer.

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. It should be noted that the embodiment described here is not intended to limit the present invention in any way. Furthermore, the same reference numerals are used to designate components and parts that perform the same functions, and redundant descriptions will be omitted or simplified as appropriate.

[0012] In this specification, the term "printer" includes so-called two-dimensional printers and three-dimensional printers. Two-dimensional printers eject printing ink onto paper, which is an example of a substrate, to print a two-dimensional image on the substrate. In other words, a three-dimensional printer is a three-dimensional modeling device. A three-dimensional printer ejects a hardening liquid such as a binder or water onto a powder material, which is an example of a substrate, to harden the powder material and create a three-dimensional object.

[0013] In addition, in this specification, in the case of a two-dimensional printer, the "printing substrate" includes not only various media made of paper such as plain paper, but also media made of various materials such as resin materials such as polyvinyl chloride (PVC) or polyethylene terephthalate (PET), textiles, cloth, aluminum, iron, or wood. In the case of a three-dimensional printer, the "printing substrate" includes various materials such as powder materials or powder materials that are used as raw materials for three-dimensional objects.

[0014] In this specification, "ink" includes various types of printing ink, such as solvent-based pigment ink, aqueous pigment ink, aqueous dye ink, and ultraviolet-curable pigment ink. "Ink" also includes various liquids, such as curable liquid (e.g., binder) used in forming three-dimensional objects. In addition, the method of ejecting ink in a printer is not particularly limited, and an inkjet method, for example, is used.

[0015] FIG. 1 is a schematic perspective view of a printer 10 according to the present embodiment. In the drawing, the symbols F, Rr, L, R, U, and D represent the front, rear, left, right, top, and bottom of the printer 10, respectively. In this embodiment, the printer 10 is assumed to be disposed in a space defined by an XYZ Cartesian coordinate system with orthogonal X, Y, and Z axes. Here, the symbols X, Y, and Z represent the X direction, which is the direction in which the X axis extends, the Y direction, which is the direction in which the Y axis extends, and the Z direction, which is the direction in which the Z axis extends. For example, the X direction, Y direction, and Z direction are the front-to-back direction, the left-to-right direction, and the up-to-down direction, respectively. Here, the X direction is an example of a first direction. The Y direction is an example of a second direction intersecting the first direction. In this embodiment, the direction from one side of the Y direction to the other is referred to as an outgoing path Y1. The direction from the other side of the Y direction to the other side is referred to as a returning path Y2. One of the Y directions is, for example, the right side. The other of the Y directions is, for example, the left side. The outgoing path Y1 is the direction from right to left, and the returning path Y2 is the direction from left to right. However, these directions are merely defined for the convenience of explanation and do not limit the installation mode of the printer 10 in any way.

[0016] As shown in Figure 1, the printer 10 includes a base 12 and a base member 14. The base 12 is a fixed member whose position is fixed. The base 12 extends in both the X and Y directions. For example, the base 12 has a rectangular shape that is longer in the X direction than in the Y direction.

[0017] The base member 14 is fixed to the base 12. At least a portion of the base member 14 is disposed above the base 12, i.e., at a position overlapping the base 12 in a plan view. In this embodiment, as shown in FIG. 1 , the base member 14 has a main portion 14A, a left support portion 14L, and a right support portion 14R. The main portion 14A is disposed above the base 12 and extends in the Y direction. The main portion 14A is disposed above the base 12 and overlaps the base 12 in a plan view. The left support portion 14L is disposed to the left of the base 12 and extends in the Z direction. The left support portion 14L supports the main portion 14A and is connected to the left end of the main portion 14A. The right support portion 14R is disposed to the right of the base 12 and extends in the Z direction. The right support portion 14R supports the main portion 14A and is connected to the right end of the main portion 14A. The main portion 14A is bridged between the left support portion 14L and the right support portion 14R.

[0018] As shown in FIG. 1 , the printer 10 includes X rails 16 and a table 18. The X rails 16 are provided on the base 12. Here, the X rails 16 are provided on the upper surface of the base 12. The X rails 16 extend in the X direction. There is no particular limitation on the number of X rails 16. Here, there are two X rails 16. The two X rails 16 are arranged side by side in the Y direction.

[0019] The table 18 supports the printing substrate 200. Here, the table 18 extends in the X and Y directions. The printing substrate 200 is placed on the upper surface of the table 18. In this embodiment, the printer 10 prints on the printing substrate 200 supported by the table 18. In the following description, the printing substrate 200 refers to the printing substrate 200 in a state supported by the table 18. In this embodiment, the table 18 is slidably engaged with the X rails 16. The table 18 is configured to be movable in the X direction along the X rails 16. Here, when the table 18 moves in the X direction (e.g., direction B in FIG. 1 ), the table 18 is configured to pass below the main portion 14A of the base member 14.

[0020] The printer 10 includes an ejection head 100. The ejection head 100 ejects ink. FIG. 2 is a perspective view schematically illustrating the ejection head 100. In this embodiment, the ejection head 100 is formed with a plurality of ejection ports 101. The ejection ports 101 eject ink. The ejection ports 101 are formed on the bottom surface of the ejection head 100. The plurality of ejection ports 101 are arranged side by side in the X direction. Here, a row of the plurality of ejection ports 101 arranged side by side in the X direction is referred to as an ejection array 102. Note that the number of ejection ports 101 constituting one ejection array 102 is not particularly limited. In FIG. 2, for convenience of explanation, the number of ejection ports 101 constituting the ejection array 102 is five, but in reality, the ejection array 102 is composed of many more ejection ports 101.

[0021] As shown in FIG. 2 , there are multiple ejection arrays 102. However, the specific number of ejection arrays 102 is not particularly limited. In this embodiment, there are four ejection arrays 102. The ejection arrays 102 include a first ejection array 102A, a second ejection array 102B, a third ejection array 102C, and a fourth ejection array 102D. In this embodiment, the first ejection array 102A, the second ejection array 102B, the third ejection array 102C, and the fourth ejection array 102D are arranged in this order from the other side (left in this case) to one side (right in this case) in the Y direction. Here, the first ejection array 102A to the fourth ejection array 102D are spaced equally apart in the Y direction. For example, the distance between the first ejection array 102A and the second ejection array 102B, the distance between the second ejection array 102B and the third ejection array 102C, and the distance between the third ejection array 102C and the fourth ejection array 102D are all the same reference distance β. The specific value of the reference distance β is not particularly limited, but is, for example, 11 mm.

[0022] In the following description, "ejecting ink from an ejection array 102" means ejecting ink from the multiple ejection ports 101 that make up the ejection array 102. Each ejection array 102 ejects ink of a different color. The ink ejected from the ejection array 102 may be, for example, a process color ink, or may be a special color ink other than a process color ink. In this embodiment, each ejection array 102 ejects a process color ink. Specifically, the first ejection array 102A ejects black ink. The second ejection array 102B ejects cyan ink. The third ejection array 102C ejects magenta ink. The fourth ejection array 102D ejects yellow ink.

[0023] FIG. 3 is a block diagram of the printer 10. As shown in FIG. 3, the printer 10 includes a movement mechanism 50. The movement mechanism 50 moves the printing substrate 200 supported by the table 18 and the ejection head 100 relative to each other. The movement mechanism 50 includes a head movement mechanism 51 and a printing substrate movement mechanism 52. The head movement mechanism 51 moves the ejection head 100 in the Y direction along the base member 14 (more specifically, the main section 14A (see FIG. 1 )). Here, the head movement mechanism 51 moves the ejection head 100 in an outgoing path Y1 and a returning path Y2 in the Y direction. The printing substrate movement mechanism 52 moves the printing substrate 200 supported by the table 18 in the X direction along the X rails 16. Here, the printing substrate movement mechanism 52 moves the table 18 in the X direction along the X rails 16, thereby moving the printing substrate 200 supported by the table 18 in the X direction. There are no particular limitations on the configurations of the head moving mechanism 51 and the printing substrate moving mechanism 52. The head moving mechanism 51 can employ a conventionally known mechanism that moves the ejection head 100 in the Y direction. The printing substrate moving mechanism 52 can employ a conventionally known mechanism that moves the printing substrate 200 supported on the table 18 in the X direction.

[0024] In this embodiment, as shown in FIG. 3 , the printer 10 includes a control device 20. The control device 20 controls printing. The control device 20 comprehensively controls the operation of each unit of the printer 10. The configuration of the control device 20 is not particularly limited. The control device 20 may be, for example, a microcomputer. The hardware configuration of the microcomputer is not particularly limited, but may include, for example, an interface (I / F) that receives image data and the like from an external device such as a host computer, a central processing unit (CPU) that executes instructions from a control program, a read-only memory (ROM) that stores the program executed by the CPU, a random access memory (RAM) used as a working area for expanding the program, and a storage device that stores various data such as the control program. As shown in FIG. 1 , the control device 20 is provided within the base 12, for example. However, the control device 20 does not have to be provided within the base 12. For example, the control device 20 may be realized by a computer or the like installed outside the base 12. In this case, the control device 20 is communicably connected to a control board (not shown) of the printer 10 via a wired or wireless connection.

[0025] In this embodiment, as shown in Fig. 3, the control device 20 is communicatively connected to the ejection head 100 and the movement mechanism 50 (here, a head movement mechanism 51 and a print substrate movement mechanism 52). The control device 20 controls the timing of ink ejection for each ejection row 102 of the ejection head 100. The control device 20 controls the movement of the ejection head 100 in the Y direction (here, an outgoing path Y1 and a returning path Y2) by controlling the drive of the head movement mechanism 51. The control device 20 controls the movement of the table 18 in the X direction by controlling the drive of the print substrate movement mechanism 52.

[0026] 3, the control device 20 includes a storage unit 21, an acquisition unit 23, a data conversion unit 25, a detection unit 27, a forward pass printing control unit 31, and a return pass printing control unit 32. Each of the units 21-32 of the control device 20 may be implemented by hardware or software. Each of the units 21-32 of the control device 20 may also be implemented by one or more processors or by circuits. The control details of the acquisition unit 23, data conversion unit 25, detection unit 27, forward pass printing control unit 31, and return pass printing control unit 32 will be described later.

[0027] In the printer 10 according to this embodiment, when the ejection head 100 moves in the Y direction, ink is ejected from the ejection ports 101 of the ejection head 100 toward the printing substrate 200 supported by the table 18. Printing is performed on the printing substrate 200 by ejecting ink onto the printing substrate 200 in this manner. In this embodiment, printing is performed by ejecting ink from the ejection ports 101 when the ejection head 100 moves on an outward path Y1 in the Y direction, and by ejecting ink from the ejection ports 101 when the ejection head 100 moves on a return path Y2 in the Y direction. Here, printing performed by ejecting ink from the ejection ports 101 when the ejection head 100 moves on the outward path Y1 is referred to as outward path printing. Printing performed by ejecting ink from the ejection ports 101 when the ejection head 100 moves on the return path Y2 is referred to as return path printing.

[0028] In this embodiment, as shown in FIG. 1 , the printer 10 is equipped with an outbound pass reference mark 41, a return pass reference mark 42, and a sensor 306. The outbound pass reference mark 41 indicates a reference position for starting forward printing. Here, the timing for ejecting ink from each ejection array 102 (here, the first ejection array 102A to the fourth ejection array 102D) during forward printing is determined based on the outbound pass reference mark 41. The return pass reference mark 42 indicates a reference position for starting backward printing. Here, the timing for ejecting ink from each ejection array 102 (here, the first ejection array 102A to the fourth ejection array 102D) during backward printing is determined based on the return pass reference mark 42. The sensor 306 detects the outbound pass reference mark 41 and the return pass reference mark 42 (more specifically, the Y-direction positions of the outbound pass reference mark 41 and the return pass reference mark 42).

[0029] The positions at which the outbound path reference mark 41 and the return path reference mark 42 are provided are not particularly limited as long as they can be detected by the sensor 306. Here, the outbound path reference mark 41 and the return path reference mark 42 are arranged side by side in the Y direction. In this embodiment, as shown in FIG. 1 , the outbound path reference mark 41 and the return path reference mark 42 are provided on the base member 14. Here, the outbound path reference mark 41 is provided on the printing start side (here, the right side) of the base member 14 relative to the table 18. The outbound path reference mark 41 is provided on the right end of the main section 14A of the base member 14. The outbound path reference mark 41 is positioned to the right of the table 18 and is provided on the main section 14A to the right of the table 18. The return path reference mark 42 is provided on the printing start side (here, the left side) of the base member 14 relative to the table 18. The return path reference mark 42 is provided on the left end of the main part 14A of the base member 14. The return path reference mark 42 is disposed to the left of the table 18, and is provided on a part of the main part 14A on the left side of the table 18. The return path reference mark 42 is provided to the left of the outgoing path reference mark 41.

[0030] The specific types of the forward path reference mark 41 and the backward path reference mark 42 are not particularly limited. FIG. 4 is a right side view schematically illustrating the configuration of the forward path reference mark 41 and the backward path reference mark 42. In this embodiment, as shown in FIG. 4, the forward path reference mark 41 and the backward path reference mark 42 are formed by light-shielding plates formed in an L-shape. Here, the forward path reference mark 41 and the backward path reference mark 42 have the same configuration. Here, the forward path reference mark 41 and the backward path reference mark 42 each have a support plate 25a extending forward from the base member 14 (here, the main portion 14A) and a detection target plate 25b supported by the support plate 25a. Here, the detection target plate 25b extends downward from the support plate 25a. The detection target plate 25b is disposed spaced apart from the base member 14 (e.g., the main portion 14A). The detection target plate 25b is disposed forward of the base member 14.

[0031] As shown in FIG. 1 , the sensor 306 is provided on the ejection head 100. Therefore, the sensor 306 is configured to be movable in the Y direction together with the ejection head 100. In this embodiment, the sensor 306 is provided at the left end of the ejection head 100. The sensor 306 protrudes upward from the ejection head 100. However, the position of the sensor 306 relative to the ejection head 100 is not particularly limited. For example, the sensor 306 may be provided in the center of the ejection head 100 in the Y direction. The sensor 306 may also be provided so as to protrude in the Y direction (e.g., to the left or right) from the ejection head 100. In this embodiment, as shown in FIG. 3 , the control device 20 is communicatively connected to the sensor 306. The control device 20 can obtain, using the sensor 306, whether or not the forward path reference mark 41 and the backward path reference mark 42 have been detected. Furthermore, the control device 20 can detect, using the sensor 306, the position of the forward path reference mark 41 in the Y direction and the position of the backward path reference mark 42 in the Y direction.

[0032] The type and configuration of the sensor 306 are not particularly limited. In this embodiment, the sensor 306 is a photointerrupter. Here, as shown in FIG. 4 , the sensor 306 has a light-emitting portion 306a that emits light and a light-receiving portion 306b that receives the light. The light-emitting portion 306a and the light-receiving portion 306b are paired. For example, the light-emitting portion 306a and the light-receiving portion 306b are arranged side by side in the X direction so as to be spaced apart. The light-receiving portion 306b receives the light emitted from the light-emitting portion 306a. In this embodiment, when the ejection head 100 moves in the Y direction, the outgoing path reference mark 41 or the returning path reference mark 42 (more specifically, the detection plate 25b of the outgoing path reference mark 41 or the returning path reference mark 42) passes between the light-emitting portion 306a and the light-receiving portion 306b of the sensor 306. Here, when the outbound path reference mark 41 or the inbound path reference mark 42 is positioned between the light-emitting unit 306a and the light-receiving unit 306b, the light emitted from the light-emitting unit 306a is blocked by the detection target plate 25b and does not reach the light-receiving unit 306b. In this way, when the light-receiving unit 306b cannot receive the light emitted from the light-emitting unit 306a, the sensor 306 can detect the outbound path reference mark 41 or the inbound path reference mark 42. At this time, the control device 20 detects the Y-direction position of the outbound path reference mark 41 and the Y-direction position of the inbound path reference mark 42 according to the Y-direction position of the sensor 306.

[0033] In this embodiment, the position of the sensor 306 in the Y direction when the sensor 306 detects the outgoing path reference mark 41 is referred to as the outgoing path detection position P2 (see FIG. 6 ). The position of the sensor 306 in the Y direction when the sensor 306 detects the incoming path reference mark 42 is referred to as the incoming path detection position P4 (see FIG. 7A ).

[0034] FIG. 5 is a conceptual diagram illustrating image data DT1 and converted image data DT3. In this embodiment, the printer 10 controls the timing of ink ejection based on the image data DT1 shown in FIG. 5 to print on the print substrate 200. The prepared image data DT1 is used during forward printing, i.e., printing when the ejection head 100 moves forward in the Y direction (i.e., from right to left) along the Y path Y1. The image data DT1 includes column image data DT2 for each ejection array 102. Here, the image data DT1 includes, as column image data DT2, first column image data DT21 corresponding to the first ejection array 102A, second column image data DT22 corresponding to the second ejection array 102B, third column image data DT23 corresponding to the third ejection array 102C, and fourth column image data DT24 corresponding to the fourth ejection array 102D. For convenience of explanation, it is assumed that the data in each column image data DT2 are arranged in the order 1, 2, 3, 4 from right to left on the paper surface of FIG.

[0035] Each column image data DT2 indicates the presence or absence of ink directed toward a position on the printing substrate 200 corresponding to the outgoing path Y1 in the Y direction. Here, each column image data DT2 has data related to the ejection of ink (e.g., data related to the presence or absence of ejection) toward a portion of the printing substrate 200 corresponding to a position in the Y direction in the ejection array 102. Therefore, the column image data DT2 can be continuous data from right to left in the Y direction. In the example of FIG. 5 , data is processed in the order 1, 2, 3, and 4 in each column image data DT2.

[0036] FIG. 6 is a diagram illustrating control according to the position of the ejection head 100 during forward printing. In this embodiment, as shown in FIG. 6, the first ejection array 102A to the fourth ejection array 102D begin printing based on the column image data DT2 when they pass a predetermined forward pass reference position P1 in the Y direction during forward printing. Here, the forward pass reference position P1 is the same position as the forward pass reference position P6. During forward printing, the first ejection array 102A to the fourth ejection array 102D begin referencing the column image data DT2 when they pass the predetermined forward pass reference position P6 in the Y direction. In other words, during forward printing, the start of printing based on the column image data DT2 and the start of referencing the column image data DT2 occur simultaneously.

[0037] During forward printing, the multiple ejection arrays 102 pass through the forward pass reference position P1 in order, starting with the ejection array 102 located on the other side of the Y direction (here, the left side). Specifically, during forward printing, the first ejection array 102A, the second ejection array 102B, the third ejection array 102C, and the fourth ejection array 102D pass through the forward pass reference position P1 in this order. Therefore, during forward printing, printing (in other words, ink ejection control) begins in the order of the first ejection array 102A, the second ejection array 102B, the third ejection array 102C, and the fourth ejection array 102D. In this embodiment, the forward pass reference position P1 and the forward pass reference position P6 are determined based on the forward pass detection position P2 of the forward pass reference mark 41. Here, the forward pass reference position P1 and the forward pass reference position P6 are located to the left of the forward pass detection position P2.

[0038] Next, the control procedure during forward printing will be described. Forward printing is performed by the forward printing control unit 31 shown in FIG. 3. Forward printing begins with the sensor 306 provided on the ejection head 100 positioned to the right of the forward path reference mark 41. Here, the forward printing control unit 31 first controls the head movement mechanism 51 (see FIG. 3) to move the ejection head 100 to the forward path Y1 in the Y direction. Thereafter, when the ejection head 100 is moving along the forward path Y1, the detection unit 27 shown in FIG. 3 detects the forward path detection position P2 at the forward path reference mark 41 as the sensor 306 passes the forward path reference mark 41, as shown in state S10 in FIG. 6.

[0039] In this embodiment, the forward path reference position P1 is the Y-direction position of the first ejection array 102A when the ejection head 100 is moved a predetermined first movement distance D1 from the forward path detection position P2 to the forward path Y1 as shown in state S11 in FIG. 6 after the sensor 306 detects the forward path reference position 41. Here, the first movement distance D1 is the initial distance α. The specific value of the initial distance α is not particularly limited, but is, for example, 17.6 mm. The forward path printing control unit 31 moves the ejection head 100 from the forward path detection position P2 to the forward path Y1 by the first movement distance D1, as shown in state S11, and when the first ejection array 102A passes the forward path reference position P1, starts printing based on the first array image data DT21 by the first ejection array 102A. Here, the forward printing control unit 31 moves the ejection head 100 from the forward detection position P2 to the forward path Y1 by the first moving distance D1, and then, while moving the ejection head 100 to the forward path Y1, controls the ejection of ink (here, black ink) from the first ejection row 102A onto the printing substrate 200 based on the first row image data DT21.

[0040] In this embodiment, as shown in state S11 in FIG. 6 , after the first ejection array 102A reaches the forward path reference position P1, when the ejection head 100 further moves in the forward path Y1 by the reference distance β, which is the distance between the first ejection array 102A and the second ejection array 102B, the position of the second ejection array 102B in the Y direction becomes the forward path reference position P1, as shown in state S12. Here, the position of the second ejection array 102B in the Y direction when the ejection head 100 moves in the forward path Y1 by a predetermined second movement distance D2 from the forward path detection position P2 becomes the forward path reference position P1. Here, the second movement distance D2 is longer than the first movement distance D1. The second movement distance D2 is, for example, the initial distance α plus the reference distance β. In this embodiment, the forward path printing control unit 31 moves the ejection head 100 a second movement distance D2 from the forward path detection position P2 to the forward path Y1, and when the second ejection array 102B passes the forward path reference position P1, starts printing based on the second array image data DT22 by the second ejection array 102B. Here, the forward path printing control unit 31 moves the ejection head 100 the second movement distance D2 from the forward path detection position P2 to the forward path Y1, and then controls the ejection of ink (cyan ink in this case) from the second ejection array 102B onto the printing substrate 200 based on the second array image data DT22 while moving the ejection head 100 along the forward path Y1. At this time, the cyan ink ejected from the second ejection array 102B is ejected so as to overlap the black ink already ejected onto the printing substrate 200.

[0041] As shown in state S12 of FIG. 6 , after the second ejection array 102B reaches the forward path reference position P1, when the ejection head 100 further moves in the forward path Y1 by the reference distance β, which is the distance between the second ejection array 102B and the third ejection array 102C, the Y-direction position of the third ejection array 102C becomes the forward path reference position P1, as shown in state S13. Here, the Y-direction position of the third ejection array 102C when the ejection head 100 moves in the forward path Y1 by a predetermined third movement distance D3 from the forward path detection position P2 becomes the forward path reference position P1. Here, the third movement distance D3 is longer than the first movement distance D1 and the second movement distance D2. The third movement distance D3 is, for example, the initial distance α + the reference distance β × 2. In this embodiment, the forward path printing control unit 31 moves the ejection head 100 a third movement distance D3 from the forward path detection position P2 to the forward path Y1, and when the third ejection array 102C passes the forward path reference position P1, starts printing based on the third array image data DT23 using the third ejection array 102C. Here, the forward path printing control unit 31 moves the ejection head 100 the third movement distance D3 from the forward path detection position P2 to the forward path Y1, and then controls the ejection of ink (here, magenta ink) from the third ejection array 102C onto the printing substrate 200 based on the third array image data DT23 while moving the ejection head 100 along the forward path Y1. At this time, the magenta ink ejected from the third ejection array 102C is ejected so as to overlap the black ink and cyan ink already ejected onto the printing substrate 200.

[0042] As shown in state S13 in FIG. 6 , after the third ejection array 102C reaches the forward path reference position P1, when the ejection head 100 further moves in the forward path Y1 by the reference distance β, which is the distance between the third ejection array 102C and the fourth ejection array 102D, the Y-direction position of the fourth ejection array 102D becomes the forward path reference position P1, as shown in state S14. Here, the Y-direction position of the fourth ejection array 102D when the ejection head 100 moves in the forward path Y1 by a predetermined fourth movement distance D4 from the forward path detection position P2 becomes the forward path reference position P1. Here, the fourth movement distance D4 is longer than the first movement distance D1 to the third movement distance D3. The fourth movement distance D4 is, for example, the initial distance α + the reference distance β × 3. In this embodiment, the forward path printing control unit 31 moves the ejection head 100 a fourth movement distance D4 from the forward path detection position P2 to the forward path Y1. When the fourth ejection array 102D passes the forward path reference position P1, printing based on the fourth array image data DT24 by the fourth ejection array 102D begins. Here, the forward path printing control unit 31 moves the ejection head 100 the fourth movement distance D4 from the forward path detection position P2 to the forward path Y1, and then controls the ejection of ink (here, yellow ink) from the fourth ejection array 102D onto the printing substrate 200 based on the fourth array image data DT24 while moving the ejection head 100 along the forward path Y1. At this time, the yellow ink ejected from the fourth ejection array 102D is ejected so as to overlap the black ink, cyan ink, and magenta ink already ejected onto the printing substrate 200. In this manner, forward path printing can be performed appropriately based on the image data DT1.

[0043] During backward printing, the ejection head 100 prints while moving from left to right in the Y direction. The column image data DT2 (see FIG. 5 ) of the image data DT1 described above is data for forward printing, and is data that assumes that the ejection head 100 moves from right to left in the Y direction. Therefore, if backward printing is performed based on the image data DT1 in FIG. 5 , there is a risk that an image printed on the printing substrate 200 that is horizontally inverted compared to the image printed during forward printing. Furthermore, when the ejection head 100 moves on the backward path Y2 during backward printing, it passes through an arbitrary Y-direction position in the order of the fourth ejection array 102D, the third ejection array 102C, the second ejection array 102B, and the first ejection array 102A. Here, for example, assume that the same control as for forward printing is performed during return printing, i.e., ink ejection control is initiated in the order of the first ejection array 102A, the second ejection array 102B, the third ejection array 102C, and the fourth ejection array 102D depending on the distance traveled by the ejection head 100 on the return path Y2. In this case, for example, after control of ink ejection of the first ejection array 102A is initiated, control of ink ejection of the second ejection array 102B may be initiated after the ejection head 100 has moved the reference interval β on the return path Y2. Therefore, even though black ink, cyan ink, magenta ink, and yellow ink are ejected so as to overlap each other on a given portion of the printing substrate 200 in the image data DT1, there is a risk that the black ink, cyan ink, magenta ink, and yellow ink may be ejected spaced apart during actual return printing.

[0044] Therefore, in this embodiment, the control device 20 performs control during return printing differently from that during forward printing. Return printing is performed by the return printing control unit 32 shown in FIG. 3 . FIGS. 7A and 7B are diagrams illustrating control according to the position of the ejection head 100 during return printing. In this embodiment, ink ejection control is initiated for the first to fourth ejection arrays 102A to 102D during return printing when they reach a predetermined return reference position P3 in the Y direction (see FIG. 7A ). During return printing, the return reference position P3 is reached sequentially, starting with the ejection array 102 located on one side of the Y direction (here, the right side) among the multiple ejection arrays 102. Specifically, during return printing, the return reference position P3 is passed in the following order: the fourth ejection array 102D, the third ejection array 102C, the second ejection array 102B, and the first ejection array 102A. Therefore, during return printing, printing (in other words, ink ejection control) begins in the order of the fourth ejection array 102D, the third ejection array 102C, the second ejection array 102B, and the first ejection array 102A. In this embodiment, the return pass reference position P3 is determined based on the return pass detection position P4 of the return pass reference mark 42. Here, the return pass reference position P3 is located to the right of the return pass detection position P4.

[0045] In this embodiment, as shown in FIG. 5 , converted image data DT1 for forward printing is converted to create converted image data DT3 for return printing. That is, the converted image data DT3 is created based on the image data DT1. The converted image data DT3 is data used during return printing, that is, data used during printing when the ejection head 100 moves along the return path Y2 in the Y direction (i.e., from left to right). The converted image data DT3 includes converted column image data DT4 for each ejection array 102. Here, the converted image data DT3 includes, as converted column image data DT4, first converted column image data DT41 corresponding to the first ejection array 102A, second converted column image data DT42 corresponding to the second ejection array 102B, third converted column image data DT43 corresponding to the third ejection array 102C, and fourth converted column image data DT44 corresponding to the fourth ejection array 102D.

[0046] In this embodiment, the converted image data DT3 is created by the data conversion unit 25 shown in FIG. 3 . The data conversion unit 25 creates converted column image data DT4 by inverting the column image data DT2 of the image data DT1. Here, the column image data DT2 is data along the Y direction. Inverting the column image data DT2 means inverting the column image data DT2 in the Y direction (here, flipping it horizontally). As shown in FIG. 5 , in each column image data DT2, the data is arranged in the order 1, 2, 3, 4 from right to left. In the converted column image data DT4 obtained by inverting the column image data DT2, the data is arranged in the order 1, 2, 3, 4 from left to right on the page of FIG. 5 .

[0047] Here, the data converter 25 inverts the first column image data DT21 to create first converted column image data DT41 from the first column image data DT21. The data converter 25 inverts the second column image data DT22 to create second converted column image data DT42 from the second column image data DT22. Similarly, the data converter 25 inverts the third column image data DT23 to create third converted column image data DT43 from the third column image data DT23, and inverts the fourth column image data DT24 to create fourth converted column image data DT44 from the fourth column image data DT24.

[0048] In this embodiment, the timing at which reference to the converted image data DT3 begins during backward printing is substantially the same as the timing at which reference to the image data DT1 begins during forward printing. Backward printing begins with the sensor 306 provided on the ejection head 100 positioned to the left of the backward reference mark 42. Here, the backward printing control unit 32 first controls the head movement mechanism 51 (see FIG. 3 ) to move the ejection head 100 to the backward pass Y2 in the Y direction. Then, as the ejection head 100 moves to the backward pass Y2, the detection unit 27 in FIG. 3 detects the backward pass detection position P4 at the backward pass reference mark 42, as the sensor 306 passes the backward pass reference mark 42, as shown in state S20 in FIG. 7A .

[0049] In this embodiment, a return pass reference position P5 (see FIG. 7A ) is predetermined as a reference for starting reference to the converted column image data DT4 during return pass printing. As shown in FIG. 7A , the return pass reference position P5 includes a first return pass reference position P51 where reference to the first converted column image data DT41 starts, a second return pass reference position P52 where reference to the second converted column image data DT42 starts, a third return pass reference position P53 where reference to the third converted column image data DT43 starts, and a fourth return pass reference position P54 where reference to the fourth converted column image data DT44 starts. The return pass reference positions P5 (here, the first return pass reference position P51, second return pass reference position P52, third return pass reference position P53, and fourth return pass reference position P54) are located to the left of the return pass reference position P3 where ink ejection control starts during return pass printing, or are the same position as the return pass reference position P3.

[0050] 7A , the Y-direction position of the first ejection array 102A when the ejection head 100 is moved the first movement distance D1 from the return path detection position P4 to the return path Y2 becomes the first return path reference position P51. As described above, the first movement distance D1 is the initial distance α. As shown in state S21, the return path print control unit 32 moves the ejection head 100 the first movement distance D1 from the return path detection position P4 to the return path Y2, and when the first ejection array 102A passes the first return path reference position P51, begins referencing the first converted array image data DT41. Furthermore, after the first ejection array 102A reaches the first return-pass reference position P51, as shown in state S22 of FIG. 7A , the ejection head 100 further moves in the return pass Y2 by the reference distance β, which is the distance between the first ejection array 102A and the second ejection array 102B. The Y-direction position of the second ejection array 102B becomes the second return-pass reference position P52. Here, the Y-direction position of the second ejection array 102B becomes the second return-pass reference position P52 when the ejection head 100 moves in the return pass Y2 by the second movement distance D2 from the return-pass detection position P4. As shown in state S22, the return-pass print control unit 32 moves the ejection head 100 in the return pass Y2 by the second movement distance D2 from the return-pass detection position P4. When the second ejection array 102B passes the second return-pass reference position P52, the return-pass print control unit 32 begins referencing the second converted array image data DT42. As described above, the second movement distance D2 is the initial distance α plus the reference distance β.

[0051] After the second ejection array 102B reaches the second return-pass reference position P52, as shown in state S23 of FIG. 7A , the ejection head 100 further moves in the return pass Y2 by the reference distance β, which is the distance between the second ejection array 102B and the third ejection array 102C. The Y-direction position of the third ejection array 102C then becomes the third return-pass reference position P53. Here, the Y-direction position of the third ejection array 102C when the ejection head 100 moves the third movement distance D3 in the return pass Y2 from the return pass detection position P4 becomes the third return-pass reference position P53. As shown in state S23, the return-pass printing control unit 32 moves the ejection head 100 the third movement distance D3 in the return pass Y2 from the return pass detection position P4. When the third ejection array 102C passes the third return-pass reference position P53, the return-pass printing control unit 32 begins referencing the third converted array image data DT43. Note that the third movement distance D3 is the initial distance α + the reference distance β × 2, as described above. Furthermore, after the third ejection array 102C reaches the third return-pass reference position P53, as shown in state S24 of FIG. 7A , the ejection head 100 further moves in the return pass Y2 by the reference distance β, which is the distance between the third ejection array 102C and the fourth ejection array 102D. The Y-direction position of the fourth ejection array 102D then becomes the fourth return-pass reference position P54. Here, the Y-direction position of the fourth ejection array 102D when the ejection head 100 moves the fourth movement distance D4 in the return pass Y2 from the return pass detection position P4 becomes the fourth return-pass reference position P54. As shown in state S24, the return-pass print control unit 32 moves the ejection head 100 the fourth movement distance D4 from the return pass detection position P4. When the fourth ejection array 102D passes the fourth return-pass reference position P54, the fourth conversion array image data DT44 is referenced. Note that the fourth movement distance D4 is the initial distance α + reference distance β × 3, as described above.

[0052] In this embodiment, when the return pass printing control unit 32 begins referencing the converted column image data DT4, it controls ink ejection at a timing based on the converted column image data DT4. However, in this embodiment, as shown in FIG. 7A , the first return pass reference position P51, the second return pass reference position P52, and the third return pass reference position P53 are located to the left of the return pass reference position P3, where ink ejection begins during return pass printing. The fourth return pass reference position P54 is located at the same position in the Y direction as the return pass reference position P3. In this embodiment, ink ejection based on the converted column image data DT4 of the converted image data DT3 begins when the first ejection array 102A to the fourth ejection array 102D pass the return pass reference position P3. Therefore, ink ejection from the first ejection array 102A is prevented until the first ejection array 102A moves from the first return pass reference position P51 to the return pass reference position P3. Similarly, the second ejection array 102B is prevented from ejecting ink until it moves from the second backward pass reference position P52 to the backward pass reference position P3. Furthermore, the third ejection array 102C is prevented from ejecting ink until it moves from the third backward pass reference position P53 to the backward pass reference position P3.

[0053] Therefore, in this embodiment, the data conversion unit 25 adds null data DT10 to the converted column image data DT4, as shown in FIG. 7A , so that even when the converted column image data DT4 is referenced, no ink is ejected until the ejection array 102 reaches the return pass reference position P3. During return pass printing, the data conversion unit 25 begins referencing the converted column image data DT4 for each of the multiple ejection arrays 102, starting with the first ejection array 102A on the other side in the Y direction (here, the left side), and adds null data DT10 before the converted column image data DT4 so that the ink ejected from the multiple ejection arrays 102 overlaps. In this embodiment, the data conversion unit 25 adds null data DT10 to the first converted column image data DT41 so that the first ejection array 102A references the null data DT10 while moving from the first return pass reference position P51 to the return pass reference position P3. Here, the null data DT10 added to the first converted row image data DT41 is added before the first converted row image data DT41. The length of the null data DT10 added to the first converted row image data DT41 corresponds to the length taken by the first ejection row 102A to move from the first reverse pass reference position P51 to the reverse pass reference position P3 during reverse pass printing. The length of the null data DT10 added to the first converted row image data DT41 is, for example, the reference interval β x 6.

[0054] The data conversion unit 25 adds null data DT10 to the second converted column image data DT42 so that the second ejection array 102B references the null data DT10 while moving from the second return pass reference position P52 to the return pass reference position P3. The null data DT10 added to the second converted column image data DT42 is added before the second converted column image data DT42. The length of the null data DT10 added to the second converted column image data DT42 corresponds to the length of time it takes for the second ejection array 102B to move from the second return pass reference position P52 to the return pass reference position P3 during return pass printing. The length of the null data DT10 added to the second converted column image data DT42 is, for example, the reference interval β×4. The data conversion unit 25 also assigns null data DT10 to the third converted column image data DT43 so that the third ejection array 102C references the null data DT10 while moving from the third return-pass reference position P53 to the return-pass reference position P3. The null data DT10 is assigned to the third converted column image data DT43 before the third converted column image data DT43. The length of the null data DT10 assigned to the third converted column image data DT43 corresponds to the length of time it takes for the third ejection array 102C to move from the third return-pass reference position P53 to the return-pass reference position P3 during return printing. The length of the null data DT10 assigned to the third converted column image data DT43 is, for example, the reference interval β×2. Note that the null data DT10 assigned to the first to third converted column image data DT41 to DT43 is omitted from FIG. 5 .

[0055] 7A, in this embodiment, as described above, the fourth return pass reference position P54 and the return pass reference position P3 are located at the same position in the Y direction. Therefore, null data DT10 is not added to the fourth converted row image data DT44. As described above, the data conversion unit 25 creates converted image data DT3 having the first converted row image data DT41 to the fourth converted row image data DT44 to which null data DT10 has been added.

[0056] 7A , the sensor 306 detects the return pass reference mark 42. Then, as shown in state S21, the ejection head 100 moves the first movement distance D1 from the return pass detection position P4 on the return pass Y2. Then, as shown in state S21, the return pass print control unit 32 starts referencing the first converted column image data DT41 when the first ejection array 102A passes the first return pass reference position P51. Here, while the first ejection array 102A moves from the first return pass reference position P51 to the return pass reference position P3, the null data DT10 added to the first converted column image data DT41 is referenced. Therefore, control of ink ejection from the first ejection array 102A does not begin until the first ejection array 102A passes the return pass reference position P3. Here, after the first ejection array 102A reaches the first return-pass reference position P51, as the ejection head 100 moves further on the return pass Y2, the second ejection array 102B reaches the second return-pass reference position P52, as shown in state S22 in FIG. 7A . When the second ejection array 102B passes the second return-pass reference position P52, the return-pass print control unit 32 begins referencing the second converted array image data DT42. Here, while the second ejection array 102B moves from the second return-pass reference position P52 to the return-pass reference position P3, the null data DT10 added to the second converted array image data DT42 is referenced. Therefore, control of ink ejection from the second ejection array 102B does not begin until the second ejection array 102B passes the return-pass reference position P3.

[0057] Here, after the second ejection array 102B reaches the second return-pass reference position P52, as the ejection head 100 moves further on the return pass Y2, the third ejection array 102C reaches the third return-pass reference position P53, as shown in state S23 in FIG. 7A . When the third ejection array 102C passes the third return-pass reference position P53, the return-pass print control unit 32 begins referencing the third converted array image data DT43. Here, while the third ejection array 102C moves from the third return-pass reference position P53 to the return-pass reference position P3, the null data DT10 added to the third converted array image data DT43 is referenced. Therefore, control of ink ejection from the third ejection array 102C does not begin until the third ejection array 102C passes the return-pass reference position P3.

[0058] In this embodiment, after the third ejection array 102C reaches the third return pass reference position P53, as the ejection head 100 moves further on the return pass Y2, the fourth ejection array 102D reaches the fourth return pass reference position P54, as shown in state S24 in FIG. 7A . When the fourth ejection array 102D passes the fourth return pass reference position P54, the return pass print control unit 32 begins referencing the fourth converted column image data DT44. In this case, the fourth return pass reference position P54 and the return pass reference position P3 are the same position. Therefore, at the fourth return pass reference position P54, printing based on the fourth converted column image data DT44 by the fourth ejection array 102D begins. Here, as in state S24 of Figure 7B, after the fourth ejection array 102D passes the return path reference position P3, the return path printing control unit 32 moves the ejection head 100 to the return path Y2, while controlling the ejection of ink (here, yellow ink) from the fourth ejection array 102D onto the printing substrate 200 based on the fourth converted array image data DT44.

[0059] Here, as shown in state S24, after the fourth ejection array 102D reaches the return pass reference position P3, the ejection head 100 further moves the reference distance β on the return pass Y2, and the third ejection array 102C reaches the return pass reference position P3, as shown in state S25 in FIG. 7B . After the third ejection array 102C passes the return pass reference position P3, the return pass print control unit 32 controls the ejection of ink (magenta ink in this case) from the third ejection array 102C onto the printing substrate 200 based on the third converted array image data DT43 while moving the ejection head 100 on the return pass Y2. At this time, the magenta ink ejected from the third ejection array 102C is ejected so as to overlap the yellow ink already ejected onto the printing substrate 200.

[0060] After the third ejection array 102C reaches the return pass reference position P3 (as in state S25), the ejection head 100 further moves the reference distance β on the return pass Y2, and the second ejection array 102B reaches the return pass reference position P3 (as in state S26 in FIG. 7B ). After the second ejection array 102B passes the return pass reference position P3, the return pass print control unit 32 controls the ejection of ink (cyan ink in this case) from the second ejection array 102B onto the printing substrate 200 based on the second converted array image data DT42 while moving the ejection head 100 on the return pass Y2. At this time, the cyan ink ejected by the second ejection array 102B is ejected so as to overlap the yellow ink and magenta ink already ejected onto the printing substrate 200.

[0061] Here, after the second ejection array 102B reaches the return pass reference position P3 (as in state S26), the ejection head 100 further moves the reference distance β on the return pass Y2, and the first ejection array 102A reaches the return pass reference position P3 (as in state S27 in FIG. 7B ). After the first ejection array 102A passes the return pass reference position P3, the return pass printing control unit 32 controls the ejection of ink (here, black ink) from the first ejection array 102A onto the printing substrate 200 based on the first converted array image data DT41 while moving the ejection head 100 on the return pass Y2. At this time, the black ink ejected by the first ejection array 102A is ejected so as to overlap the yellow ink, magenta ink, and cyan ink already ejected onto the printing substrate 200. In this way, return pass printing can be performed appropriately based on the converted image data DT3.

[0062] Next, a series of steps for printing by the printer 10 will be briefly described with reference to the flowchart of FIG.

[0063] In this embodiment, first, in step S101 of Fig. 8, the acquisition unit 23 of Fig. 3 acquires image data DT1 based on a target image to be printed on the printing substrate 200. There are no particular limitations on the source from which the acquisition unit 23 acquires the image data DT1. In this embodiment, the image data DT1 is pre-stored in the storage unit 21 of the printer 10. Therefore, the acquisition unit 23 acquires the image data DT1 from the storage unit 21.

[0064] Next, in step S103 of FIG. 8 , the data conversion unit 25 of FIG. 3 creates converted image data DT3 based on the image data DT1 acquired by the acquisition unit 23. In this embodiment, forward printing and backward printing are performed alternately. The image data DT1 may include image data DT1 for forward printing and image data DT1 for backward printing. Therefore, in this embodiment, the data conversion unit 25 creates converted image data DT3 based on the image data DT1 for backward printing. Here, the data conversion unit 25 creates converted column image data DT4 (here, first converted column image data DT41 to fourth converted column image data DT44) by inverting the column image data DT2 (here, first column image data DT21 to fourth column image data DT24) from the image data DT1 for backward printing, as shown in FIG. 5 . In addition, the data conversion unit 25 appropriately adds null data DT10 to the converted column image data DT4, as shown in FIG. 7A . In this way, converted image data DT3 is created from image data DT1 for backward printing. The converted image data DT3 created by data conversion unit 25 is stored in storage unit 21 in FIG.

[0065] Next, in step S105 of FIG. 8, printing is performed on the printing substrate 200. A detailed description has been given above, so a repeated description will be omitted here. Here, the outbound printing control unit 31 of FIG. 3 performs outbound printing based on the image data DT1. After outbound printing, the control device 20 controls the printing substrate movement mechanism 52 (see FIG. 3) to move the printing substrate 200 supported by the table 18 in the X direction. Thereafter, the return printing control unit 32 of FIG. 3 performs return printing based on the converted image data DT3. After return printing, the control device 20 moves the printing substrate 200 supported by the table 18 in the X direction. Thereafter, outbound printing is performed based on the next image data DT1. In this way, printing on the printing substrate 200 can be performed by sequentially repeating the steps of outbound printing, movement of the printing substrate 200 in the X direction, return printing, and movement of the printing substrate 200 in the X direction.

[0066] As described above, in this embodiment, the printer 10 includes a table 18 supporting a printing substrate 200, a discharge head 100, a head movement mechanism 51 (see FIG. 3), and a control device 20, as shown in FIG. 1. As shown in FIG. 2, the discharge head 100 includes a plurality of discharge rows 102 in which ink-discharging nozzles 101 are aligned in the X direction, with the discharge rows 102 aligned in the Y direction intersecting the X direction. The head movement mechanism 51 moves the discharge head 100 in the Y direction relative to the printing substrate 200 supported by the table 18. Here, printing performed when the discharge head 100 moves along a forward path Y1 from one side to the other in the Y direction is referred to as forward printing. Printing performed when the discharge head 100 moves along a backward path Y2 from the other side to one side in the Y direction is referred to as backward printing. As shown in FIG. 3, the control device 20 includes an acquisition unit 23, a data conversion unit 25, a forward path printing control unit 31, and a backward path printing control unit 32. The acquisition unit 23 acquires image data DT1 (see FIG. 5 ) that indicates whether or not ink should be ejected toward a position on the printing substrate 200 corresponding to the outbound pass Y1 in the Y direction, and that includes multiple pieces of column image data DT2 prepared for each ejection array 102. As shown in FIG. 5 , the data conversion unit 25 creates converted image data DT3 to be used in the return pass printing, which includes converted column image data DT4 obtained by inverting the column image data DT2 based on the image data DT1. During the return pass printing, the data conversion unit 25 begins referencing the converted column image data DT4 for each of the multiple ejection arrays 102, starting with the first ejection array 102A on the other side in the Y direction (here, the left side). Null data DT10 is added before the converted column image data DT4 so that the ink ejected from the multiple ejection arrays 102 overlap and ink ejection begins in order, starting with the fourth ejection array 102D on one side in the Y direction (here, the right side). Based on the image data DT1 acquired by the acquisition unit 23, the forward printing control unit 31 performs forward printing by starting to refer to the column image data DT2 and starting to eject ink, starting from the first ejection column 102A on the other side of the Y direction (here, the left side) of the multiple ejection columns 102, as shown in Figure 6.Based on the converted image data DT3 created by the data conversion unit 25, the return pass printing control unit 32 executes return pass printing by sequentially referencing the converted array image data DT4, starting with the first ejection array 102A on the other side of the Y direction among the multiple ejection arrays 102, as shown in FIG. 7B , and sequentially ejecting ink starting with the fourth ejection array 102D on one side of the Y direction (here, the right side). As a result, during return pass printing, just as during forward pass printing, reference to the converted array image data DT4 is sequentially started with the first ejection array 102A on the other side of the Y direction, and the timing of ink ejection is controlled based on the converted array image data DT4 so that the ink ejected from the multiple ejection arrays 102 overlaps. This allows ink to be ejected at appropriate positions during both forward and return passes.

[0067] In this embodiment, the forward pass printing control unit 31 performs forward pass printing by controlling the ejection of ink from the ejection arrays 102 based on the array image data DT2 corresponding to the ejection arrays 102 when the ejection arrays 102 of the ejection heads 100 moving on the forward pass Y1 pass a predetermined forward pass reference position P1 in the Y direction, as shown in FIG. 6 . The backward pass printing control unit 32 performs backward pass printing by controlling the ejection of ink from the ejection arrays 102 based on the converted array image data DT4 corresponding to the ejection arrays 102 when the ejection arrays 102 of the ejection heads 100 moving on the backward pass Y2 pass a predetermined backward pass reference position P3 in the Y direction, as shown in FIG. 7B . In this way, by aligning the timing at which ink ejection control for each ejection array 102 is started when each ejection array 102 passes the forward pass reference position P1 during forward pass printing, ink can be ejected and overlapped at the appropriate positions. Similarly, in the return pass printing, by aligning the timing for starting control of ink ejection for each ejection array 102 when each ejection array 102 passes through the return pass reference position P3, ink can be ejected and overlapped at the appropriate position.

[0068] In this embodiment, as shown in FIG. 1 , the printer 10 includes an outgoing path reference mark 41 located on one side (here, the right side) of the outgoing path reference position P1 in the Y direction, a returning path reference mark 42 located on the other side (here, the left side) of the returning path reference position P3 in the Y direction, and a sensor 306. The sensor 306 is provided in the ejection head 100 and detects the outgoing path reference mark 41 and the returning path reference mark 42. As shown in FIG. 3 , the control device 20 includes a detection unit 27. The detection unit 27 detects an outgoing path detection position P2 (see FIG. 6 ), which is the position of the sensor 306 in the Y direction when the outgoing path reference mark 41 is detected by the sensor 306, or a returning path detection position P4 (see FIG. 7A ), which is the position of the sensor 306 in the Y direction when the returning path reference mark 42 is detected by the sensor 306. As shown in Fig. 6, the outbound printing control unit 31 controls the ejection of ink from the ejection arrays 102 based on the array image data DT2 corresponding to each ejection array 102 when the ejection head 100 moves from the outbound detection position P2 to the outbound path Y1 and passes the outbound reference position P1 for each ejection array 102. As shown in Fig. 7B, the return printing control unit 32 controls the ejection of ink from the ejection arrays 102 based on the converted array image data DT4 corresponding to each ejection array 102 when the ejection head 100 moves from the return path detection position P4 to the return path Y2 and passes the return path reference position P3 for each ejection array 102. In this way, by moving the ejection head 100 to the outbound path Y1 based on the outbound detection position P2 at which the outbound reference mark 41 is detected, it is possible to easily determine that the ejection array 102 has passed the outbound reference position P1. Similarly, by moving the ejection head 100 to the return path Y2 based on the return path detection position P4 where the return path reference mark 42 is detected, it becomes easier to determine that the ejection array 102 has passed the return path reference position P3.

[0069] In this embodiment, as shown in FIG. 7A , the return pass print control unit 32 begins referencing the converted array image data DT4 when the ejection head 100 moves from the return pass detection position P4 to the return pass Y2 and the ejection array 102 passes a predetermined return pass reference position P5. The data conversion unit 25 assigns null data DT10 (see FIG. 7A ) to the converted array image data DT4, which is referenced while the ejection array 102 moves from the return pass reference position P5 to the return pass reference position P3. This prevents ink from being ejected from the ejection array 102 while it moves from the return pass reference position P5 to the return pass reference position P3.

[0070] In this embodiment, as shown in Fig. 2, the ejection array 102 includes a first ejection array 102A and a second ejection array 102B located to one side of the first ejection array 102A in the Y direction (here, the right side). As shown in Fig. 5, the converted array image data DT4 includes first converted array image data DT41 corresponding to the first ejection array 102A and second converted array image data DT42 corresponding to the second ejection array 102B. As shown in Fig. 6, the outbound printing control unit 31 is configured so that the first ejection array 102 reaches the outbound reference position P1 when the ejection head 100 moves a predetermined first movement distance D1 in the outbound path Y1 from the outbound path detection position P2, and the second ejection array 102B reaches the outbound reference position P1 when the ejection head 100 moves a second movement distance D2, which is longer than the first movement distance D1, in the outbound path Y1. 7A , when the ejection head 100 moves a first movement distance D1 on the return path Y2 from the return path detection position P4, the first ejection array 102A passes a first return path reference position P51, and the return path printing control unit 32 begins referencing the first converted array image data DT41. Furthermore, when the ejection head 100 moves a second movement distance D2 on the return path Y2 from the return path detection position P4, the second ejection array 102B passes a second return path reference position P52, and the return path printing control unit 32 begins referencing the second converted array image data DT42. The data conversion unit 25 assigns null data DT10 to the first converted array image data DT41, which is referenced while the first ejection array 102A moves from the first return path reference position P51 to the return path reference position P3. The data conversion unit 25 also assigns null data DT10 to the second converted array image data DT42, which is referenced while the second ejection array 102B moves from the second return-pass reference position P52 to the return-pass reference position P3. In this way, the distance traveled by the first ejection array 102A to reach the return-pass reference position P1 during forward printing can be the same first movement distance D1 as the distance traveled by the first ejection array 102A to reach the return-pass reference position P51 during return printing. The distance traveled by the second ejection array 102B to reach the return-pass reference position P1 during forward printing can be the same second movement distance D2 as the distance traveled by the second ejection array 102B to reach the return-pass reference position P52 during return printing.Therefore, the control up to the start of referencing the row image data DT2 or the converted row image data DT4 can be made common between forward printing and backward printing.

[0071] In this embodiment, as shown in FIG. 2 , the ejection array 102 includes a third ejection array 102C located to one side (here, the right side) of the second ejection array 102B in the Y direction. As shown in FIG. 5 , the converted array image data DT4 includes third converted array image data DT43 corresponding to the third ejection array 102C. As shown in FIG. 6 , the outbound printing control unit 31 is configured so that the third ejection array 102C reaches the outbound reference position P1 when the ejection head 100 moves a third movement distance D3, which is longer than the second movement distance D2, on the outbound path Y1 from the outbound path detection position P2. As shown in FIG. 7A , when the ejection head 100 moves the third movement distance D3 on the inbound path Y2 from the inbound path detection position P4, the third ejection array 102C passes a third inbound path reference position P53, and the inbound printing control unit 32 begins referencing the third converted array image data DT43. The data conversion unit 25 assigns null data DT10 to the third converted array image data DT43, which is referenced while the third ejection array 102C moves from the third return-pass reference position P53 to the return-pass reference position P3. As shown in FIG. 2, the distance between the first ejection array 102A and the second ejection array 102B and the distance between the second ejection array 102B and the third ejection array 102C are the same reference distance β. As shown in FIG. 6, the difference between the first movement distance D1 and the second movement distance D2 and the difference between the second movement distance D2 and the third movement distance D3 are also the reference distance β. As a result, during forward printing, by moving the ejection head 100 by the reference distance β on the forward pass Y1, the first ejection array 102A, the second ejection array 102B, and the third ejection array 102C can be sequentially moved to the forward pass reference position P1. In the return pass printing, the ejection head 100 is moved in the return pass Y2 by the reference interval β, so that the third ejection array 102C, the second ejection array 102B, and the first ejection array 102A can reach the return pass reference position P3 in that order.

[0072] In this embodiment, a printing method is implemented by the printer 10. Here, the printing method includes an acquisition process, a data conversion process, a detection process, a forward pass printing control process, and a return pass printing control process. The acquisition process, data conversion process, detection process, forward pass printing control process, and return pass printing control process are embodied by the acquisition unit 23, data conversion unit 25, detection unit 27, forward pass printing control unit 31, and return pass printing control unit 32, respectively.

[0073] 10 Printer 18 Table 20 Control device 23 Acquisition unit 25 Data conversion unit 27 Detection unit 31 Forward pass printing control unit 32 Return pass printing control unit 41 Forward pass reference mark 42 Return pass reference mark 51 Head movement mechanism 100 Discharge head 101 Discharge orifice 200 Printing substrate 306 Sensor DT1 Image data DT2 Column image data DT3 Converted image data DT4 Converted column image data DT10 Null data P1 Forward pass reference position P2 Forward pass detection position P3 Return pass reference position P4 Return pass detection position P5 Return pass reference position Y1 Forward pass Y2 Return pass

Claims

1. A printing apparatus comprising: a table for supporting a substrate; an ejection head having ejection rows in which ejection ports for ejecting ink are aligned in a first direction, the ejection rows being aligned in a second direction intersecting the first direction; a head moving mechanism for moving the ejection head in the second direction relative to the substrate supported on the table; and a control device; when printing when the ejection head is moving in an outward path from one side to the other in the second direction is defined as outward path printing, and printing when the ejection head is moving in a return path from the other side to one side in the second direction is defined as return path printing, the control device comprises: an acquisition unit for acquiring image data instructing whether or not to eject ink toward a position on the substrate corresponding to the outward path in the second direction, the image data having a plurality of column image data prepared for each of the ejection rows; and a data conversion unit for creating converted image data used for the return path printing, the converted image data having converted column image data obtained by inverting the column image data based on the image data, the data conversion unit, during the return pass printing, begins to refer to the converted column image data starting from the ejection column on the other side of the second direction among the multiple ejection columns, and adds null data before the converted column image data so that ink ejected from the multiple ejection columns overlap and ink ejection begins from the ejection column on one side of the second direction; the control device has an outward pass printing control unit that performs the outward pass printing by starting to refer to the column image data and starting ink ejection from the multiple ejection columns starting from the ejection column on the other side of the second direction among the multiple ejection columns based on the image data acquired by the acquisition unit; and a return pass printing control unit that performs the return pass printing by starting to refer to the converted column image data from the multiple ejection columns starting from the ejection column on the other side of the second direction based on the converted image data created by the data conversion unit, and starting ink ejection from the ejection column on one side of the second direction.

2. The printer described in claim 1, wherein the outbound printing control unit performs the outbound printing by controlling the ejection of ink from the ejection array based on the array image data corresponding to the ejection array when the ejection array of the ejection head moving in the outbound direction passes a predetermined outbound reference position in the second direction, and the return printing control unit performs the return printing by controlling the ejection of ink from the ejection array based on the converted array image data corresponding to the ejection array when the ejection array of the ejection head moving in the return direction passes a predetermined return reference position in the second direction.

3. A printer as described in claim 2, comprising: an outward pass reference mark provided on one side of the outward pass reference position in the second direction; a return pass reference mark provided on the other side of the return pass reference position in the second direction; and a sensor provided on the ejection head for detecting the outward pass reference mark and the return pass reference mark; wherein the control device comprises a detection unit that detects an outward pass detection position, which is the position of the sensor in the second direction when the outward pass reference mark is detected by the sensor, or a return pass detection position, which is the position of the sensor in the second direction when the return pass reference mark is detected by the sensor; wherein the outward pass printing control unit controls the ejection of ink from the ejection array based on the column image data corresponding to the ejection array when the ejection head moves in the outward pass from the outward pass detection position and passes the outward pass reference position for each ejection array; and wherein the return pass printing control unit controls the ejection of ink from the ejection array based on the converted column image data corresponding to the ejection array when the ejection head moves in the return pass from the return pass detection position and passes the return pass reference position for each ejection array.

4. A printer as described in claim 3, wherein the return print control unit begins to refer to the converted row image data when the ejection head moves in the return path from the return path detection position and the ejection row passes a predetermined return path reference position, and the data conversion unit adds the null data to the converted row image data, which is referenced while the ejection row moves from the return path reference position to the return path reference position.

5. The ejection array includes a first ejection array and a second ejection array arranged on one side of the first ejection array in the second direction; the converted array image data includes first converted array image data corresponding to the first ejection array and second converted array image data corresponding to the second ejection array; the outbound printing control unit is configured such that when the ejection head moves a predetermined first movement distance on the outbound path from the outbound detection position, the first ejection array reaches the outbound reference position, and when the ejection head moves a second movement distance longer than the first movement distance on the outbound path from the outbound detection position, the second ejection array reaches the outbound reference position; the return printing control unit is configured such that when the ejection head moves the first movement distance on the return path from the return detection position, the first ejection array passes a first return reference position and starts referring to the first converted array image data; 5. The printer according to claim 4, wherein when the ejection head moves the second movement distance in the return path from the return path detection position, the second ejection array passes a second return path reference position and begins referencing the second converted array image data, and the data conversion unit adds, to the first converted array image data, the null data that is referenced while the first ejection array moves from the first return path reference position to the return path reference position, and adds, to the second converted array image data, the null data that is referenced while the second ejection array moves from the second return path reference position to the return path reference position.

6. The ejection array has a third ejection array arranged on one side of the second ejection array in the second direction, the converted array image data has third converted array image data corresponding to the third ejection array, the outbound print control unit is configured such that the third ejection array reaches the outbound reference position when the ejection head moves a third movement distance longer than the second movement distance in the outbound direction from the outbound detection position, the return print control unit causes the third ejection array to pass a third return reference position and starts referring to the third converted array image data when the ejection head moves the third movement distance in the return direction from the return detection position, the data conversion unit provides the third converted array image data with the null data that is referenced while the third ejection array moves from the third return reference position to the return reference position, the interval between the first ejection array and the second ejection array and the interval between the second ejection array and the third ejection array are the same reference interval, 6. The printer according to claim 5, wherein a difference between the first movement distance and the second movement distance, and a difference between the second movement distance and the third movement distance are each the reference interval.

7. A printing method for a printer, the printer comprising: a table for supporting a substrate; and an ejection head having ejection rows in which ejection ports for ejecting ink are aligned in a first direction, the ejection rows being aligned in a second direction intersecting the first direction; and when printing when the ejection head is moving in an outward path from one side to the other in the second direction is defined as outward printing, and printing when the ejection head is moving in a return path from the other side to one side in the second direction is defined as return printing, the method includes: an acquisition step of acquiring image data having a plurality of row image data in which the presence or absence of ink ejection to a position on the substrate corresponding to the outward path in the second direction is indicated and which is prepared for each of the ejection rows; and a data conversion step of creating converted image data used for the return path printing, the converted image data having converted row image data obtained by inverting the row image data based on the image data, and in which, in the data conversion step, in the return path printing, among the plurality of ejection rows, the ejection rows are sequentially converted from the ejection rows on the other side of the second direction. and adding null data before the converted column image data so that ink ejected from the plurality of ejection columns overlap and ink ejection is started in sequence starting from the ejection columns on one side of the second direction, and performing the forward printing based on the image data acquired in the acquisition step, by starting to refer to the converted column image data and starting to eject ink from among the plurality of ejection columns, starting from the ejection columns on the other side of the second direction, based on the image data acquired in the data conversion step; and performing the return printing based on the converted column image data created in the data conversion step, by starting to refer to the converted column image data from among the plurality of ejection columns, starting from the ejection columns on the other side of the second direction, and starting to eject ink from among the plurality of ejection columns, starting from the ejection columns on the other side of the second direction,

Images