Printer and printing method

Abstract

To appropriately perform printing of high quality.SOLUTION: A printer 12 includes an ink jet head 202 and a control part 120. The control part 120 sets, for each nozzle, selectivity for each nozzle, which is a rate of discharge position to be discharged in one main scanning operation, and sets selectivity for each nozzle that becomes gradually smaller as it approaches an end with respect to a plurality of nozzles, out of discharge positions included per unit length on a main scanning direction line to be an arrangement of discharge positions arranged in a main scanning direction at intervals corresponding to printing resolution; and sets selectivity for each nozzle so that a total of the selectivities for nozzle set for line corresponding nozzles becomes a rate other than 100% with respect to at least a part of the main scanning direction line when a nozzle capable of discharging ink in main scanning operation in any session is defined as the line corresponding nozzle with respect to a discharge position included in one main scanning direction line.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a printing apparatus and a printing method. [Background technology]

[0002] Inkjet printers, which are printing devices that use inkjet heads to perform printing, have been widely used in the past. Regarding control of inkjet printers, a method of setting various ejection rates of nozzles (ejection nozzles) in the inkjet head is known (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-184344 A Summary of the Invention [Problem to be solved by the invention]

[0004] When printing is performed using an inkjet head, the nozzles of the inkjet head eject ink to ink ejection positions that are set according to the printing resolution. In this case, the printing operation is usually controlled so that ink can be ejected by any nozzle at any timing to all ejection positions. In addition, when changing the nozzle ejection rate to a value other than a constant value, for example, if the ejection rate of a certain nozzle is reduced, the ejection rates of the other nozzles are increased according to the amount of the decrease. In addition, the ejection rates are usually set so that the relationship between the increase rate and decrease rate of the ejection rate is complementary (complementary) among the multiple nozzles used in printing.

[0005] However, in this case, when the ejection rate of a nozzle at a certain position is changed for a certain purpose, it becomes necessary to change the ejection rates of other nozzles in accordance with the change in the ejection rate of the nozzle. As a result, an unintended change in print quality may occur at the position where ink is ejected by the other nozzles. More specifically, for example, when the ejection rate of a nozzle at a certain position is reduced for a specific purpose, the ejection rate of the other nozzles increases, and a problem may occur in that the amount of ink increases at the position where ink is ejected by the other nozzles. For this reason, a method for more appropriately performing high-quality printing has been desired. Therefore, an object of the present invention is to provide a printing device and a printing method that can solve the above problems. [Means for solving the problem]

[0006] As described above, when printing is performed using an inkjet head, the printing operation is controlled so that ink can be ejected by any nozzle at any timing for all ejection positions set according to the printing resolution. In this case, the ejection rates are usually set so that the relationship between the increase rate and the decrease rate of the ejection rate is complementary (complementary) among the multiple nozzles used in printing. In response to this, the inventor of the present application thought of setting parameters corresponding to the nozzle ejection rates with a higher degree of freedom by not necessarily establishing such a complementary relationship. Then, by actually conducting various experiments, the inventor of the present application found that there are cases where printing with higher quality can be performed by not establishing a complementary relationship. Furthermore, the inventor of the present application further conducted extensive research and found the features necessary to obtain such an effect, and arrived at the present invention.

[0007] In order to solve the above-mentioned problems, the present invention provides a printing device that performs printing by an inkjet system, the printing device comprising: an inkjet head having a nozzle row in which a plurality of nozzles are arranged with their positions shifted in a sub-scanning direction that is set in advance; a main scanning drive unit that causes the inkjet head to perform a main scanning operation in which ink is ejected from the inkjet head while moving in a main scanning direction perpendicular to the sub-scanning direction relative to an ejection target onto which ink is ejected; a sub-scanning drive unit that causes the inkjet head to perform a sub-scanning operation in which ink is moved in the sub-scanning direction relative to the ejection target; and a control unit that controls operations of the inkjet head, the main scanning drive unit, and the sub-scanning drive unit, wherein in the main scanning operation, the inkjet head ejects ink to an ejection position that is set in accordance with a printing resolution, and when an arrangement of the ejection positions that are aligned in the sub-scanning direction and arranged in the main scanning direction at intervals corresponding to the printing resolution is defined as a main scanning direction line, in the main scanning operation, the nozzles in the nozzle row of the inkjet head eject ink to the ejection positions included in any of the main scanning direction lines. and when the number of nozzles in the nozzle row that are capable of ejecting ink to one of the main scanning direction lines in one main scanning operation is one or less, and the control unit causes the inkjet head to perform the main scanning operation and the sub-scanning operation so that the number of times in the main scanning direction at which ink can be ejected from any of the nozzles to one of the main scanning direction lines is a plurality of times, and for each of the nozzles in the nozzle row, a per-nozzle selection rate is set which is a ratio of the ejection positions to be ejected in one main scanning operation among the ejection positions included per unit length in the main scanning direction line, and for the multiple nozzles included in an end region including a plurality of the nozzles at an end of the nozzle row of the inkjet head in the sub-scanning direction, the per-nozzle selection rate is set so as to gradually decrease toward the end in the sub-scanning direction, and when the nozzles that are capable of ejecting ink to the ejection positions included in one of the main scanning operations to be the line-corresponding nozzles,The nozzle selection rate is set so that the sum of the nozzle selection rates set for the line-corresponding nozzles corresponding to the main scanning direction lines is a rate other than 100%.

[0008] In this configuration, for example, by setting the nozzle selection rate for a plurality of nozzles included in the end region so that it gradually decreases toward the end in the sub-scanning direction, it is possible to appropriately prevent the portion corresponding to the end of the inkjet head from being noticeable in the print result. In addition, in this case, by setting the nozzle selection rate so that the sum of the nozzle selection rates set for the line-corresponding nozzles corresponding to at least some of the main scanning direction lines is a ratio other than 100%, it is possible to set the nozzle selection rate with a higher degree of freedom, for example. In addition, this makes it possible to more easily and appropriately set the nozzle selection rate according to the required print quality, for example. Therefore, with this configuration, it is possible to more appropriately perform high-quality printing, for example.

[0009] In this configuration, the object to be ejected is, for example, a medium to be printed. The above operation can be considered to be, for example, an operation focusing on nozzles that eject ink of the same color. Therefore, the nozzles in the nozzle row can be considered to be, for example, nozzles for ink of the same color. The main scanning direction line can be considered to be, for example, an arrangement of ejection positions that eject ink of the same color. The end region can be considered to be, for example, an area including at least the endmost nozzle in the inkjet head. The operation in which ink is ejected from any nozzle multiple times in the main scanning direction for one main scanning direction line can be considered to correspond to, for example, a multi-pass operation. The nozzle selection rate can be considered to be, for example, a parameter corresponding to the nozzle ejection rate. In this configuration, the control unit sets the nozzle selection rate according to, for example, a mask prepared in advance. In this case, the control unit sets the nozzle selection rate individually (independently) for each nozzle. The above-mentioned nozzle selection rate is, for example, a setting for nozzles (normal nozzles) whose ejection characteristics are within a predetermined normal range. In this case, the sum of the per-nozzle selection rates set for the line-corresponding nozzles corresponding to a main scanning direction line may be other than 100%, for example, when all the line-corresponding nozzles corresponding to that main scanning direction line are normal nozzles, and the sum of the per-nozzle selection rates may be other than 100%.

[0010] Also, in this configuration, the printing device includes a plurality of inkjet heads disposed at different positions in the sub-scanning direction. In this case, the control unit, for example, sets a per-nozzle selection rate for nozzles included in the end region for each inkjet head that gradually decreases toward the end in the sub-scanning direction. Also, in this case, the control unit may, for example, set the per-nozzle selection rate for nozzles in the end region of at least some of the inkjet heads differently from the per-nozzle selection rate for nozzles in the end region of the other inkjet heads. With this configuration, for example, it is possible to set the per-nozzle selection rate with a higher degree of freedom. In this case, the control unit, for example, sets the per-nozzle selection rate for nozzles in the end region differently for each inkjet head by using a different mask for setting the per-nozzle selection rate for each inkjet head.

[0011] In addition, the inkjet heads arranged at different positions in the sub-scanning direction can be considered as at least two inkjet heads, for example. In addition, when the ejection positions included in one main scanning direction line are defined as odd-numbered positions, and the ejection positions next to the odd-numbered positions are defined as even-numbered positions, the control unit causes only one of the two inkjet heads to eject ink, for example, to the odd-numbered positions in the main scanning direction line. In addition, in this case, the control unit causes only the other of the two inkjet heads to eject ink, for example, to the even-numbered positions. With this configuration, for example, it is possible to cause the inkjet heads to appropriately eject ink, for example, to the multiple ejection positions in the main scanning direction line. In addition, in this case, the control unit causes one inkjet head to eject ink, for example, to the odd-numbered positions in all main scanning direction lines. In addition, the control unit causes the other inkjet head to eject ink, for example, to the even-numbered positions in all main scanning direction lines.

[0012] Moreover, these two inkjet heads eject, for example, ultraviolet curable ink. When one of the two inkjet heads is designated as the first head and the other is designated as the second head, the control unit causes these inkjet heads to perform main scanning and sub-scanning operations so that, for example, the first head ejects ink first, and then the second head ejects ink, for an ejection position included in a main scanning direction line. In this case, the control unit sets the per-nozzle selection rate so that, for example, the sum of the per-nozzle selection rates set for the nozzles in the first head among the line-corresponding nozzles corresponding to the main scanning direction lines is greater than 50% and the sum of the per-nozzle selection rates set for all the line-corresponding nozzles corresponding to the main scanning direction lines is greater than 100%. In this configuration, for example, by making the sum of the per-nozzle selection rates set for all the line-corresponding nozzles corresponding to the main scanning direction lines greater than 100%, the sum of the per-nozzle selection rates set for the nozzles in the first head can be increased as necessary without worrying about the sum of the per-nozzle selection rates set for the nozzles in the second head. This also makes it possible to easily and appropriately set, for example, a value greater than 50% for the sum of the per-nozzle selection rates set for the nozzles in the first head. In this case, by increasing the sum of the per-nozzle selection rates set for the nozzles in the first head, for example, a large amount of ink can be ejected before ink is ejected by the second head. This also makes it possible, for example, when the per-nozzle selection rate for nozzles in an end region or the like of the second head is reduced, to easily and appropriately eject a required amount of ink for each position of the ejection target object with the sum of the first and second heads without excessively increasing the per-nozzle selection rate for other nozzles in the second head.

[0013] More specifically, in this case, the control unit sets the per-nozzle selection rate so that, for example, among the line-corresponding nozzles corresponding to the main scanning direction lines, the total of the per-nozzle selection rates set for the nozzles in the first head is 90% or more, and the total of the per-nozzle selection rates set for the nozzles in the second head is 20% or more. With this configuration, for example, it is possible to appropriately set the per-nozzle selection rate that is preferable when using ultraviolet curable ink. The total of the per-nozzle selection rates set for the nozzles in the first head may be, for example, about 95 to 100% (for example, 100%). Also, the total of the per-nozzle selection rates set for the nozzles in the second head may be, for example, about 40 to 60% (for example, 50%).

[0014] In this configuration, when the sum of the selection rates per nozzle set for the line-corresponding nozzles corresponding to the main scanning direction line is defined as the total selection rate for the main scanning direction line, the control unit sets the selection rate per nozzle so that the total selection rate for all the main scanning lines is a constant value. In this case, for example, it is possible to divide the nozzles that eject ink to the ejection position on the same main scanning direction line into a plurality of groups, and set the sum of the selection rates per nozzle to a predetermined value for each group. More specifically, for example, when printing under at least some printing conditions, the control unit causes the inkjet head to perform main scanning and sub-scanning operations so that ink is ejected from an even number of nozzles by an even number of main scanning operations on one main scanning direction line. In this case, for example, among the even number of nozzles that eject ink to the ejection position on the same main scanning direction line, half of the nozzles that eject ink in the previous main scanning operation can be defined as the first half nozzles, and the nozzles that eject ink in the main scanning operation after the first half nozzles can be defined as the second half nozzles. In this case, the control unit sets the per-nozzle selection rate so that, for example, for all main scanning direction lines, the sum of the per-nozzle selection rates set for the first half nozzles is a predetermined first value, and the sum of the per-nozzle selection rates set for the second half nozzles is a predetermined second value. With this configuration, for example, the per-nozzle selection rate can be set easily and appropriately. For example, instead of setting the total selection rate to the same constant value for all main scanning direction lines, the total selection rate for some main scanning direction lines may be made different from the total selection rate for other main scanning direction lines.

[0015] In addition, in this configuration, the control unit causes the inkjet head to eject ink multiple times to at least some of the ejection positions by setting the selection rate per nozzle so that the sum of the selection rates per nozzle set for the line-corresponding nozzles corresponding to the main scanning direction lines for at least some of the main scanning direction lines is greater than 100%. As described above, the printing device may include multiple inkjet heads. In this case, causing the inkjet head to eject ink multiple times to at least some of the ejection positions may be, for example, causing the inkjet head to eject ink multiple times by the multiple inkjet heads. In addition, the inkjet head may be capable of changing the volume of ink to be ejected in multiple stages. In this case, the control unit may cause the inkjet head to eject ink multiple times to the same ejection position only at a portion of the ink volumes excluding at least the smallest volume among the multiple ink volumes. With this configuration, for example, it is possible to cause the inkjet head to appropriately eject ink multiple times to the same ejection position.

[0016] In addition, it is also conceivable to use ink other than ultraviolet curable ink in the printing device. In this case, the inkjet head discharges, for example, an evaporative drying type ink that is fixed to the discharged object by evaporating the solvent. In this case, it is also conceivable to set the selection rate for each nozzle, for example, suitable for the case of using the evaporative drying type ink. In this regard, for example, when an evaporative drying type ink such as a solvent ink is used, the ink that has been fixed to the discharged object in the previous main scanning operation may be re-dissolved in the subsequent main scanning operation. As a result, for example, when the selection rate for each nozzle is set to be gradually smaller toward the end in the sub-scanning direction for the nozzles in the end region of the inkjet head, the color may become lighter in the printed result at a location corresponding to the middle part of the end region. In this case, it is conceivable to increase the selection rate for each nozzle set for the nozzles that discharge ink to the part where the color becomes lighter. More specifically, in this case, the control unit, for example, makes the total selection rate for some main scanning direction lines different from the total selection rate for other main scanning direction lines. In this case, the control unit may, for example, set the total selection rate for a main scanning direction line for ejecting ink from nozzles located in at least a portion of the middle in the sub-scanning direction among the nozzles included in the end region to be greater than the total selection rate for other main scanning direction lines. With this configuration, for example, more ink can be ejected onto a portion where the color becomes lighter due to the effect of re-dissolving the ink. This also makes it possible to more appropriately perform high-quality printing, for example, when using evaporative drying ink.

[0017] Furthermore, the features of the present invention can be considered from a different perspective than that described above, for example.In this case, the present invention relates to, for example, a printing device that performs printing by an inkjet method, the printing device including an inkjet head having a nozzle row in which a plurality of nozzles are arranged with their positions shifted in a sub-scanning direction set in advance, a main scanning drive unit that causes the inkjet head to perform a main scanning operation in which ink is ejected from the inkjet head while moving in a main scanning direction perpendicular to the sub-scanning direction relative to an ejection target onto which ink is ejected, the sub-scanning drive unit that causes the inkjet head to perform a sub-scanning operation in which ink is moved in the sub-scanning direction relative to the ejection target, and a control unit that controls operations of the inkjet head, the main scanning drive unit, and the sub-scanning drive unit, wherein, in the main scanning operation, the inkjet head ejects ink to an ejection position that is set in accordance with a printing resolution, and when an arrangement of the ejection positions that are aligned in the sub-scanning direction and arranged in the main scanning direction at an interval corresponding to the printing resolution is defined as a main scanning direction line, in the main scanning operation, the nozzles in the nozzle row of the inkjet head are included in any of the main scanning direction lines. and among the nozzles in the nozzle array, there is one or less nozzles capable of ejecting ink to one of the main scanning direction lines in one main scanning operation, and the control unit causes the inkjet head to perform the main scanning operation and the sub-scanning operation so that the number of times in the main scanning direction at which ink can be ejected from any of the nozzles to one of the main scanning direction lines is multiple, and for each of the nozzles in the nozzle array, a per-nozzle selection rate is set which is the proportion of the ejection positions that are to be ejected in one main scanning operation among the ejection positions included per unit length in the main scanning direction line, and when the nozzles that are capable of ejecting ink in any of the main scanning operations to the ejection positions included in one of the main scanning direction lines are defined as line-corresponding nozzles, the per-nozzle selection rate is set so that, for at least some of the main scanning direction lines, the sum of the per-nozzle selection rates set for the line-corresponding nozzles that correspond to the main scanning direction lines is a proportion other than 100%.As a configuration of the present invention, for example, it is also possible to use a printing method or the like having the same characteristics as those described above. Effect of the Invention

[0018] According to the present invention, for example, high quality printing can be more appropriately performed. [Brief description of the drawings]

[0019] [Figure 1] Fig. 1 is a diagram illustrating a printing system 10 according to an embodiment of the present invention. Fig. 1(a) shows an example of the configuration of the printing system 10. Fig. 1(b) shows an example of the configuration of a printing device 12 in the printing system 10. Fig. 1(c) shows an example of the configuration of a head unit 102 in the printing device 12. [Diagram 2] 2A and 2B are diagrams illustrating the printing operation executed in the printing device 12. Fig. 2(a) shows a simplified configuration of the head unit 102 in the printing device 12. Fig. 2(b) shows an example of ink dots 302 formed on the medium 50 by ink ejected from the inkjet head 202. Fig. 2(c) shows an example of how ink is ejected for one main scanning direction line 312. [Diagram 3] This is a diagram for explaining typical duty settings. Fig. 3(a) shows an example of duty settings when printing is performed using a multi-pass method with the number of passes set to the minimum number. Fig. 3(b) shows an example of duty settings when printing is performed using a multi-pass method with a number of passes greater than the minimum number. [Figure 4] FIG. 11 is a diagram illustrating a typical duty setting. [Diagram 5] 5A and 5B are diagrams for explaining the duty settings used in this example, in which Fig. 5A shows an example of the duty settings used when ultraviolet curable ink is used, and Fig. 5B shows another example of the duty settings. [Figure 6] 6(a) and 6(b) are diagrams for explaining modified examples of duty settings, showing various modified examples of duty settings. [Figure 7] 7A and 7B are diagrams illustrating modified examples of the operation of the printing device 12. Fig. 7A shows an example of a typical duty setting when a two-peak setting is used as the duty setting. Fig. 7B shows an example of the ejection positions where the inkjet heads 202a and 202b eject ink. [Figure 8] 8A and 8B are diagrams illustrating modified examples of the operation of the printing device 12. Fig. 8A shows an example of an operation in normal scan corresponding to the operation shown in Fig. 5A when a two-peak setting is used as the duty setting. Fig. 8B shows an example of the ejection positions where the inkjet heads 202a and 202b eject ink. [Figure 9] FIG. 13 is a diagram showing a further modified example of the duty setting. [Figure 10] 10A and 10B are diagrams showing further modified examples of duty settings. [Figure 11] 11A and 11B are diagrams illustrating the setting of a duty that takes into consideration the influence of variations in ejection characteristics, and show examples of duty settings and print results. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram for explaining a printing system 10 according to an embodiment of the present invention. FIG. 1(a) shows an example of the configuration of the printing system 10. FIG. 1(b) shows an example of the configuration of a printing device 12 in the printing system 10. FIG. 1(c) shows an example of the configuration of a head unit 102 in the printing device 12. Except for the points described below, the printing system 10 and each part thereof in this example may have the same or similar features as a known printing system and each part thereof. In this example, the printing system 10 is a system that prints on a medium 50 to be printed, and includes a printing device 12 and a control PC 14. The printing device 12 is an inkjet printer that prints on the medium 50 by an inkjet method, and executes a printing operation according to the control of the control PC 14. In this example, the medium 50 is an example of a target object onto which ink is ejected from an inkjet head. For example, known paper, film, etc. can be suitably used as the medium 50.

[0021] In this example, the printing device 12 includes a head unit 102, a platen 104, a Y bar unit 106, a main scanning drive unit 108, a sub-scanning drive unit 110, a setting storage unit 112, and a control unit 120. The head unit 102 is a unit that ejects ink onto the medium 50, and includes a plurality of inkjet heads 202 and a plurality of ultraviolet ray irradiation units 204, as shown in FIG. 1(c), for example. The head unit 102 includes two inkjet heads 202 that are arranged at different positions in a sub-scanning direction (X direction in the figure) that is set in advance in the printing device 12, as distinguished by the reference characters 202a and b in the figure. The head unit 102 may include more inkjet heads 202. In this case, the head unit 102 can be considered to include at least two inkjet heads 202 that are arranged at different positions in the sub-scanning direction, for example. The inkjet head 202 also has a nozzle row 212 in which a plurality of nozzles are arranged at different positions in a predetermined nozzle row direction, and ink is discharged from the nozzles in the nozzle row 212 onto the medium 50. In this example, the nozzle row direction is parallel to the sub-scanning direction, and the inkjet head 202 discharges ultraviolet-curable ink (UV ink) that is cured in response to irradiation of ultraviolet light from the nozzles in the nozzle row 212. The inkjet head 202 also has a plurality of nozzle rows 212 formed at different positions in a main scanning direction (Y direction in the figure) perpendicular to the sub-scanning direction. In this case, the inkjet head 202 discharges ink of a plurality of colors from the plurality of nozzle rows 212, for example. In this example, the nozzle row 212 has eight nozzle rows 212, and by discharging ink of a different color from each nozzle row 212, a maximum of eight colors of ink are discharged from one inkjet head 202. More specifically, in the illustrated example, the inkjet head 202 ejects magenta (M), cyan (C), yellow (Y), black (K), light cyan (Lc), and light magenta (Lm) inks from six of the eight nozzle rows 212. The inkjet head 202 also ejects spot color inks from the remaining two nozzle rows 212. In this case, the colors MCYK are examples of process colors.Process colors can be considered, for example, as basic colors in color expression. Furthermore, Lc and Lm inks are light versions of C and M. Therefore, Lc and Lm can be considered, for example, as light versions of some of the process colors. Furthermore, special colors can be considered, for example, as colors that are different from the individual process colors.

[0022] Also, depending on the contents of printing to be performed in the printing device 12, printing conditions, and the like, the inkjet head 202 may eject ink of a different color from the above. For example, the inkjet head 202 may eject ink of the same color from a plurality of nozzle rows 212. Also, in this case, in the inkjet head 202, for example, it is conceivable to eject ink of each color of MCYK from two nozzle rows 212. Also, it is conceivable to eject ink for process colors from six nozzle rows 212 by ejecting ink for only some colors of MCYK (for example, M color and C color) from two nozzle rows 212, and to eject ink for special colors from the remaining two nozzle rows 212. Also, it is conceivable to eject ink for special colors from the nozzle rows 212 for Lc color and Lm color in FIG. 1(c). Also, in the head unit 102, the ultraviolet ray irradiation unit 204 is a light source that irradiates ultraviolet rays that cure ultraviolet curable ink. In this example, the head unit 102 has ultraviolet ray irradiation units 204 on one side and the other side in the main scanning direction for a plurality of inkjet heads 202 .

[0023] The platen 104 is a platform member that supports the medium 50 at a position facing the head unit 102. The Y bar unit 106 is a member that holds the head unit 102 at a position facing the medium 50. In this example, the Y bar unit 106 is a member that extends in the main scanning direction and holds the head unit 102 so that it can move in the main scanning direction. The main scanning drive unit 108 is a drive unit that causes the multiple inkjet heads 202 in the head unit 102 to perform a main scanning operation (scan). The main scanning operation can be considered to be, for example, an operation of ejecting ink from a nozzle while moving in the main scanning direction relative to the medium 50. In this example, the main scanning drive unit 108 moves the head unit 102 along the Y bar unit 106 and causes the multiple inkjet heads 202 to eject ink, thereby causing the multiple inkjet heads 202 to perform a main scanning operation. The sub-scan drive unit 110 is a drive unit that causes the multiple inkjet heads 202 to perform a sub-scan operation. The sub-scanning operation can be considered, for example, as an operation of moving in the sub-scanning direction relative to the medium 50. The sub-scanning operation can also be considered, for example, as a feed operation of changing the position of the inkjet head 202 facing the medium 50. The sub-scanning drive unit 110 moves the inkjet heads 202 relative to the medium 50, for example, by conveying the medium 50. The sub-scanning drive unit 110 may also move the inkjet heads 202 relative to the medium 50 by moving the head unit 102 together with the Y bar unit 106. The setting storage unit 112 is configured to store parameters used to control the operation of the printing device 12. In this example, the setting storage unit 112 stores, for example, the printing resolution and the number of passes. The control unit 120 is configured to include, for example, a CPU of the printing device 12, and controls the operation of each unit of the printing device 12. In this example, the control unit 120 controls the operation of each unit of the printing device 12 based on the printing conditions stored in the setting storage unit 112. More specifically, with regard to control of the sub-scanning operation, the control unit 120 sets a feed amount, which is the amount of movement of the inkjet head 202 relative to the medium 50 in one sub-scanning operation, based on, for example, the printing resolution and the number of passes.Furthermore, with regard to the control of the main scanning operation, the control unit 120 causes the inkjet head 202 to eject ink onto an ejection position selected according to, for example, the print resolution and the number of passes.

[0024] Furthermore, in the printing system 10, the control PC 14 is a computer that controls the operation of the printing device 12. In this example, the control PC 14 controls the operation of the printing device 12 by supplying print data indicating an image to be printed by the printing device 12 to the printing device 12. Furthermore, the control PC 14 sets the conditions for printing to be executed by the printing device 12, for example, based on an instruction from a user. As the printing conditions, for example, it is possible to set the printing resolution, the number of passes, etc. According to this example, for example, the printing operation on the medium 50 can be appropriately performed.

[0025] Next, the printing operation performed by the printing device 12 of this example will be described in more detail. FIG. 2 is a diagram for explaining the printing operation performed by the printing device 12. FIG. 2(a) shows a simplified configuration of the head unit 102 in the printing device 12. As described above, in the head unit 102 of this example, the inkjet head 202 ejects ink of multiple colors. In addition, the printing device 12 performs, for example, color printing on the medium 50 (see FIG. 1). In this case, the control unit 120 (see FIG. 1) of the printing device 12 expresses various colors at each position on the medium 50 by, for example, changing the color of ink ejected at each position on the medium 50 based on the print data. In addition, in this example, the control unit 120 sets the color of ink ejected at each position on the medium 50 by determining for each ink color whether or not to eject ink at the ink ejection position set according to the print resolution. In this case, the control unit 120 controls the inkjet head 202 and the like, for example, for each ink color. Therefore, in the following, an example of control performed by the control unit 120 on the inkjet head 202 etc. will be described, focusing on one color of ink among the multiple colors of ink ejected from the inkjet head 202 of this example. In this case, the configuration of the head unit 102 can be simplified to a configuration having multiple inkjet heads 202, each having one nozzle row 212 for one color, as shown in FIG. 2(a).

[0026] More specifically, in FIG. 2(a), two inkjet heads 202 indicated by reference numerals 202a and 202b in FIG. 1(c) are simplified to have a nozzle row 212 for one color. In this case, the nozzle row 212 in the inkjet head 202a and the nozzle row 212 in the inkjet head 202b eject ink of the same color. In this example, the nozzle row 212 in the inkjet head 202a and the nozzle row 212 in the inkjet head 202b can be considered as a single virtual nozzle row in which multiple nozzles ejecting ink of the same color are arranged. In this case, the nozzle row length of this virtual nozzle row, which is the width in the nozzle row direction (sub-scanning direction), can be considered to be twice the nozzle row length of the nozzle row 212 in one inkjet head 202. In addition, the operation of the control unit 120 that controls the ejection of ink from the nozzle rows 212 in the multiple inkjet heads 202 can be considered to correspond to the operation of controlling the ejection of ink from such a virtual nozzle row. In this example, the inkjet head 202 ejects ink from the nozzles in the nozzle row 212 under the control of the control unit 120, thereby forming an array of ink dots 302 on the medium 50, as shown in Fig. 2(b), for example. Fig. 2(b) is a diagram showing an example of ink dots 302 formed on the medium 50 by ink ejected from the inkjet head 202, and shows a simplified array of dots 302 when ink dots 302 are formed at all ejection positions set according to the printing resolution for one color of ink.

[0027] Here, during actual printing, the control unit 120 causes the inkjet head 202 to eject ink to ejection positions selected according to, for example, an image to be printed. In this case, ink dots 302 are usually formed only at some of the ejection positions on the medium 50. Therefore, for example, FIG. 2(b) can be considered to show ink dots 302 that can be formed on the medium 50 as necessary. Also, for example, FIG. 2(b) can be considered to show an example of an arrangement of ejection positions by showing an arrangement of the dots 302. Also, as shown in the figure, FIG. 2(b) shows an example of an arrangement of the nozzles 222 in the nozzle row 212 together with the arrangement of the dots 302. In this case, for example, FIG. 2(b) can be considered to show the relationship between the positions of the nozzles 222 in the nozzle row 212 and the ejection positions set according to the print resolution, focusing on the timing of performing any one main scanning operation.

[0028] In this example, the printing device 12 performs printing on the medium 50 using a multi-pass method. The multi-pass method can be considered, for example, as a method in which the number of main scanning operations in which the inkjet head 202 passes a position facing a position on at least a part of the medium 50 is multiple. The multi-pass method can also be considered, for example, as a method in which the feed amount in the sub-scanning operation is made shorter than the nozzle row length in the head unit 102. The nozzle row length in the head unit 102 can be considered, for example, as the nozzle row length of a virtual nozzle row corresponding to the nozzle rows 212 of the multiple inkjet heads 202 in the head unit 102. In this example, the control unit 120 makes the feed amount in the sub-scanning operation shorter than the nozzle row length of the nozzle row 212 in one inkjet head 202. In addition, the control unit 120 increases the print resolution in the sub-scanning direction by having the inkjet head 202 perform a sub-scanning operation with a feed amount that is shifted from an integer multiple of the nozzle pitch, which is the interval between the nozzles 222 in the nozzle row 212, in the sub-scanning operation. In addition, the control unit 120 increases the printing resolution in the main scanning direction by causing the inkjet head 202 to perform multiple main scanning operations to eject ink corresponding to multiple dots 302 at the same position in the sub-scanning direction.

[0029] More specifically, in the main scanning operation of this example, the inkjet head 202 ejects ink to an ejection position set according to the printing resolution. Then, for example, when focusing on the main scanning direction line 312, the position of the nozzle 222 in the nozzle row 212 in the sub-scanning direction corresponds to the position of one of the main scanning direction lines 312. In this case, the main scanning direction line 312 can be considered as an arrangement of ejection positions aligned in the main scanning direction at intervals corresponding to the printing resolution, such as the part shown by the dashed line in FIG. 2B. Also, in this case, it can be considered that the nozzle 222 in the nozzle row 212 of the inkjet head 202 is capable of ejecting ink to an ejection position included in one of the main scanning direction lines 312, for example, in the main scanning operation. Also, in the illustrated example, the nozzle 222 does not exist at the position of some of the main scanning direction lines 312. In this case, the control unit 120 causes the inkjet head 202 to eject ink in another main scanning operation to eject positions in the main scanning direction line 312 for which no corresponding nozzle 222 exists in the figure. With this configuration, for example, it is possible to increase the print resolution in the sub-scanning direction to be higher than the resolution facing the nozzle pitch. As can be understood from the above explanation, in this example, the main scanning direction line 312 can be considered as, for example, an array of ejection positions for ejecting ink of the same color. In the multi-pass operation in this example, the number of times in the main scanning direction for ejecting ink from any of the nozzles 222 to one main scanning direction line 312 is set to multiple times, as shown in FIG. 2(c).

[0030] FIG. 2C is a diagram showing an example of how ink is ejected onto one main scanning direction line 312, and indicates by the presence or absence of a hatched pattern that dots 302 corresponding to a plurality of ejection positions on one main scanning direction line 312 are formed by different main scanning operations. More specifically, as can be understood from the configuration shown in FIG. 2B, when considering ink of one color, the number of nozzles 222 in the nozzle row 212 of the inkjet head 202 that can eject ink onto one main scanning direction line 312 in one main scanning operation is one or less (one or zero). In this case, if the main scanning direction line 312 is aligned with any of the nozzles 222 in the sub-scanning direction, there is one nozzle 222 that can eject ink onto that main scanning direction line 312, and if the main scanning direction line 312 is not aligned with any of the nozzles 222 in the sub-scanning direction, there is zero nozzles 222 that can eject ink onto that main scanning direction line 312. In this example, the control unit 120 causes the inkjet head 202 to perform main scanning and sub-scanning operations so that the number of times in the main scanning direction in which ink can be ejected from any of the nozzles 222 onto one main scanning direction line 312 is multiple by the multi-pass operation. For example, in the example shown in FIG. 2C, the control unit 120 causes any of the nozzles 222 in the nozzle rows 212 of the multiple inkjet heads 202 to eject ink onto ejection positions corresponding to the dots 302 with a crosshatched pattern among the ejection positions on the main scanning direction line 312 during one main scanning operation. Then, the control unit 120 causes the other nozzles 222 in the nozzle rows 212 of the multiple inkjet heads 202 to eject ink onto ejection positions corresponding to the dots 302 without a crosshatched pattern among the ejection positions on the main scanning direction line 312 during another main scanning operation. Such an operation can be thought of as, for example, different main scanning operations for ejecting ink to ejection positions at odd-numbered positions on the main scanning direction line 312 from main scanning operations for ejecting ink to ejection positions at even-numbered positions.The odd-numbered positions can be considered, for example, as ejection positions that are arranged every other ejection position from one side in the main scanning direction among the ejection positions included in one main scanning direction line 312. The even-numbered positions can be considered, for example, as ejection positions adjacent to the odd-numbered positions in the main scanning direction line 312. Such an operation can be considered, for example, as a so-called high scan (Hi scan) operation.

[0031] In addition, in regard to making the main scanning operation for discharging ink to odd-numbered positions on the main scanning direction line 312 different from the main scanning operation for discharging ink to even-numbered positions, the control unit 120 of this example causes only one of the two inkjet heads 202 in the head unit 102 to discharge ink to odd-numbered positions on the main scanning direction line 312. Also, the control unit 120 causes only the other of the two inkjet heads 202 to discharge ink to even-numbered positions. With this configuration, for example, it is possible to cause the inkjet heads 202 to appropriately discharge ink to multiple discharge positions on the main scanning direction line 312. Also, in this case, the control unit 120 causes, for example, one inkjet head 202 to discharge ink to odd-numbered positions on all the main scanning direction lines 312. Also, the control unit 120 causes, for example, the other inkjet head 202 to discharge ink to even-numbered positions on all the main scanning direction lines 312.

[0032] Here, when printing is performed using a multi-pass method, for example, the minimum number of passes (resolution pass number) that is the minimum number of passes required in the multi-pass method is determined depending on the print resolution, etc. For example, as shown in Figs. 2(b) and (c), when the print resolution in the sub-scanning direction is set to twice the resolution corresponding to the nozzle pitch, and ink is ejected in two main scanning operations for one main scanning direction line 312, the minimum number of passes can be considered to be four. Also, when printing using a multi-pass method, the quality can usually be improved by increasing the number of passes. Therefore, it is also possible to consider increasing the number of passes beyond the minimum number of passes. Also, when the number of passes is increased, for example, the feed amount in the sub-scanning operation changes depending on the number of passes. In this case, the feed amount can be considered to be, for example, the distance obtained by dividing the nozzle row length of a virtual nozzle row that combines the nozzle rows 212 of the multiple inkjet heads 202 by the number of passes. In this case, the feed amount is the distance obtained by dividing the nozzle row length by the number of passes, and this can be considered to be equal to the feed amount obtained by appropriately adjusting the distance less than the nozzle pitch in order to increase the printing resolution in the sub-scanning direction, for example, for the distance obtained by dividing the nozzle row length by the number of passes. In addition, when printing using a multi-pass method, it is considered to diffuse the ends of the passes in order to prevent banding, which makes the boundaries of the passes noticeable in the print result. In this case, it is considered to make the boundaries of the passes gradational, for example. As for the number of passes, it can be considered that the number of passes may be a non-integer depending on the feed amount in the sub-scanning operation, for example.

[0033] Furthermore, when printing is performed with a pass number larger than the minimum pass number, it is usually necessary to adjust the number of ejection positions from one nozzle 222 in one main scanning operation according to the pass number. More specifically, when focusing on a plurality of ejection positions arranged in the main scanning direction line 312 at the print resolution, in this example, the control unit 120 selects a portion of ejection positions at a ratio determined according to the pass number from among the plurality of ejection positions arranged in the print resolution as ejection positions to be ejected by the nozzle 222 corresponding to that main scanning direction line 312 in one main scanning operation. In addition, hereinafter, this ratio is referred to as a duty. The duty can be considered, for example, as the ratio of ejection positions selected as ejection targets in the main scanning operation for the nozzle 222 corresponding to the main scanning direction line 312. The duty can also be considered, for example, as a parameter corresponding to the operation rate of the nozzle. In addition, in this example, the duty is a parameter corresponding to the selection rate for each nozzle. The nozzle selection rate can be considered to be, for example, a ratio of ejection positions that are ejection targets in one main scanning operation among the ejection positions included per unit length in the main scanning direction line 312. In this case, the nozzle selection rate can be considered to be, for example, a parameter corresponding to the ejection rate of the nozzle. Furthermore, regarding the operation of the control unit 120, causing the nozzle 222 to eject ink to an ejection position selected according to the duty can be considered to be, for example, an example of an operation of setting a nozzle selection rate for each nozzle for the nozzles 222 in the nozzle row 212 of the inkjet head 202. Furthermore, in this example, the control unit 120 determines the ejection positions that are ejection targets of the nozzles 222 according to, for example, a mask prepared in advance. In this case, the operation of determining the ejection position according to the mask can be considered to correspond to, for example, an operation of setting a nozzle selection rate according to the mask.

[0034] Next, the setting of the duty and the like in relation to the printing operation executed by the printing device 12 will be described in more detail. FIG. 3 and FIG. 4 are diagrams for explaining the setting of a general duty, and show examples of known duty settings. In these diagrams, the two inkjet heads 202 shown on the left side of the diagram with the reference numerals 202a and b are associated with each other, and the duties corresponding to each nozzle in the nozzle row of the two inkjet heads 202 are shown in a simplified manner by the graph on the right side of the diagram. Also, in the diagrams described below, examples of duty settings are shown as appropriate, similar to FIG. 3 and FIG. 4. FIG. 3(a) is a diagram showing an example of the duty setting when printing is performed by a multi-pass method with the number of passes set to the minimum number of passes, and shows an example of the duty corresponding to each nozzle when the minimum number of passes is 4. Also, in the illustrated example, when printing is performed with the minimum number of passes, the ejection position to be ejected by the nozzle is determined without selection according to a mask. In this case, the duty corresponding to each nozzle is constant at a predetermined maximum value (hereinafter referred to as the maximum duty value) indicated as Full Duty in the figure. More specifically, as described above, the operation in which the minimum number of passes is 4 corresponds to, for example, an operation in which the printing resolution in the sub-scanning direction is twice the resolution corresponding to the nozzle pitch, and ink is ejected in two main scanning operations on one main scanning direction line 312 (see FIG. 2). In this case, the duty corresponding to the maximum duty value can be considered to be, for example, a ratio in which half of the ejection positions on the main scanning direction line 312 are selected as ejection targets. In addition, in this case, the operation of selecting half of the ejection positions on the main scanning direction line 312 can be considered to correspond to, for example, selecting all ejection positions that can be ejected in one main scanning operation. Therefore, such a selection method can be considered, for example, as selection without using a mask. In addition, such a selection method can be considered, for example, as selection using a mask (100%) that selects all ejection positions.

[0035] Here, when printing is performed with the minimum number of passes, the number of passes is reduced, which allows for example high-speed printing. However, in this case, the amount of ink ejected per unit area in one main scanning operation increases, which may cause problems such as unintended striped patterns in the printed result. In this case, the occurrence of unintended striped patterns can be considered to be, for example, unintended striped patterns that affect the quality of the print when a human visually checks the printed result from at least one direction. Furthermore, as in the example shown in FIG. 3(a), when printing is performed using a multi-pass method with a constant duty, for example, the boundaries of passes become more noticeable in the printed result. In this case, the boundaries of passes become more noticeable, especially at the boundaries of passes corresponding to the ends of the inkjet head 202. In response to this, in order to prevent the boundaries of passes from becoming more noticeable, for example, the ends of passes can be diffused, as described above. In this case, for example, as shown in FIG. 3(b), it is possible to gradually reduce the duty near the ends of the inkjet head 202 toward the ends.

[0036] FIG. 3B is a diagram showing an example of duty setting when printing is performed using a multi-pass method with a pass number larger than the minimum pass number, and shows an example of the duty corresponding to each nozzle when the minimum pass number is 4 and the pass number is 6. In this case, as shown in the figure, the duty gradually decreases in a gradational manner toward the end of the inkjet head 202. In addition, in this case, for example, for each inkjet head 202, it can be considered that the duty for the nozzles included in the end area gradually decreases toward the end in the sub-scanning direction. The end area can be considered, for example, as an area including multiple nozzles at the end of the nozzle row of the inkjet head 202 in the sub-scanning direction. In addition, the end area can be considered, for example, as an area including at least the endmost nozzle of the inkjet head 202. In addition, the control unit 120 (see FIG. 1) of the printing device 12 determines the ejection position to be ejected by the nozzle at a ratio corresponding to such a duty by, for example, selecting the ejection position according to a mask. Such a duty setting can be considered to correspond to, for example, setting the nozzle selection rate for a plurality of nozzles included in the end region of the inkjet head 202 so that it gradually decreases toward the end in the sub-scanning direction. By using such a duty setting, for example, it is possible to appropriately prevent the boundary between passes corresponding to the end of the inkjet head 202 from being conspicuous in the printed result. In addition, the manner in which the duty for the nozzles in the end region is changed can be made different from that shown in FIG. 3B, for example, by changing the mask used. More specifically, FIG. 3B shows an example in which the duty for the nozzles in the end region is changed linearly. In contrast, the duty for the nozzles in the end region can be changed nonlinearly, for example, as shown in FIG. 4. FIG. 4 shows an example in which the manner in which the duty for the nozzles included in the end region is changed is different from the duty setting shown in FIG. 3B. When such a duty setting is used, for example, it is possible to appropriately prevent the boundary between passes corresponding to the end of the inkjet head 202 from being conspicuous in the printed result.

[0037] Here, when the duty setting in the end region is set to a gradational form as in the example shown in FIG. 3(b) and FIG. 4, it is possible to appropriately prevent the boundary between the passes corresponding to the ends of the inkjet head 202 from being conspicuous, as described above. However, even in this case, when printing is performed with a small number of passes, the duty corresponding to some nozzles may become the maximum duty value, as in the example shown in FIG. 3(b) and FIG. 4. As a result, for example, there may be a position where the amount of ink ejected per unit area in one main scanning operation is large, and problems such as the occurrence of striped patterns are likely to occur. In this regard, for example, if the number of passes is made sufficiently large, it is possible to reduce the amount of ink ejected per unit area in one main scanning operation at all positions. This also makes it possible to appropriately prevent problems such as the occurrence of striped patterns. However, in this case, there is a risk that the printing speed will be significantly reduced due to the excessive number of passes. In contrast, in this example, for example, by using a duty setting different from that of the conventional configuration, the occurrence of problems that occur in the conventional configuration is prevented. More specifically, in this example, for example, the duty setting shown in FIG. 5(a) is used to appropriately prevent the occurrence of unintended striped patterns.

[0038] FIG. 5 is a diagram for explaining the setting of the duty used in this example. FIG. 5(a) shows an example of the duty setting used when using ultraviolet curable ink. As described above, when printing is performed using the inkjet head 202, ink is discharged from the nozzles in the nozzle row of the inkjet head 202 to the discharge positions set according to the print resolution. In this case, in order to discharge ink to all discharge positions, the duty needs to be set so that ink can be discharged by any nozzle at any timing to all discharge positions. Therefore, when the duty for any nozzle is changed, it is usually necessary to change the duty for the other nozzles so that the duty is in a complementary relationship (complementary relationship) with respect to the change. However, in this case, changing the duty for the other nozzles may cause an unintended change in print quality at the position where the nozzle discharges ink. As a result, for example, when trying to change the duty of any nozzle, it may be difficult to flexibly change the duty because it is necessary to consider the influence of the change in duty that occurs in the other nozzles. In this case, for example, the degree of freedom in selecting a mask to be used for duty setting may be reduced, making it difficult to set an optimal duty, etc. In response to this, the inventors of the present application have found through various experiments, etc. that by changing the duty without establishing the above-mentioned complementary relationship, it may be possible to perform printing with higher quality by using a duty setting different from that of the conventional configuration described with reference to Figures 3 and 4, etc.

[0039] Here, as described above, in this example, the duty can be considered to correspond to the nozzle selection rate, which is the ratio of ejection positions that are ejection targets in one main scanning operation with respect to the main scanning direction line 312 (see FIG. 2). In this case, the complementary relationship regarding the duty can also be considered, for example, by focusing on the nozzle selection rate corresponding to one main scanning direction line. More specifically, when a nozzle that can eject ink to an ejection position included in one main scanning direction line 312 in one main scanning operation is defined as a line corresponding nozzle, the complementary relationship regarding the duty can be considered to be established, for example, when the sum of the nozzle selection rates set for the line corresponding nozzles corresponding to the main scanning direction line 312 is 100%. In this case, the ratio of 100% can be considered, for example, as the ratio corresponding to the ejection of ink in one main scanning operation with respect to one ejection position. In this example, as described above, the duty is set as necessary without establishing the complementary relationship. Setting such a duty can be considered to correspond to setting the per-nozzle selection rate so that the sum of the per-nozzle selection rates set for the line-corresponding nozzles corresponding to at least some of the main scanning direction lines 312 is a rate other than 100%. When configured in this way, for example, the duty can be set with a higher degree of freedom. This also makes it possible, for example, to more easily and appropriately set the duty in accordance with the required printing quality. Therefore, according to this example, for example, high-quality printing can be more appropriately performed.

[0040] In this case, the duty may be set for each nozzle, for example, independently of the duties of the other nozzles. In this case, the operation of the control unit 120 (see FIG. 1) may be considered to set the duty for each nozzle individually (independently). In this example, the duty can be set with a high degree of freedom, and it is easy to set different duties for each of the inkjet heads 202. In this case, for example, a gradation-like duty for the end region of the inkjet head 202 may be set differently for each inkjet head 202. In this case, when the operation of the control unit 120 is taken into consideration, the duty for the nozzles in the end region of at least some of the inkjet heads 202 may be set differently from the duty for the nozzles in the end region of the other inkjet heads 202. With this configuration, for example, the duty can be set with a higher degree of freedom. In this case, the control unit 120 may, for example, set different masks for each inkjet head 202 to be used for setting the duty, thereby setting different duties for the nozzles in the end regions for each inkjet head 202 .

[0041] More specifically, in this case, it is possible to set different duties for the inkjet heads 202, as shown in FIG. 5(a), for example. In this case, the control unit 120 controls the inkjet heads 202a and 202b, which are distinguished by the reference characters 202a and 202b, to perform main scanning and sub-scanning operations so that the inkjet head 202a first ejects ink, and then the inkjet head 202b ejects ink, to ejection positions included in the main scanning direction line 312. As a result, the inkjet head 202a ejects ink before the inkjet head 202b ejects ink to each position on the medium 50. In this example, the inkjet head 202a is an example of a first head. The inkjet head 202a can be considered, for example, as an inkjet head that performs the first half of the main scanning operation of the main scanning operation performed to each position on the medium 50. The inkjet head 202b is an example of a second head. The inkjet head 202b can be considered, for example, as an inkjet head that performs the latter main scanning operation. The inkjet head 202b can also be considered, for example, as an inkjet head that performs the final main scanning operation for each position on the medium 50. In addition, when focusing on the line-corresponding nozzles and the selection rate per nozzle described above, in this example, the control unit 120 sets the duties corresponding to the inkjet heads 202a and 202b so that the sum of the selection rates per nozzle set for the nozzles in the inkjet head 202a among the line-corresponding nozzles corresponding to one main scanning direction line 312 is 100%. In this case, by adding the sum of the selection rates per nozzle set for the nozzles in the inkjet head 202b, the sum of the selection rates per nozzle set for all the line-corresponding nozzles corresponding to one main scanning direction line 312 exceeds 100%.

[0042] In this case, if one focuses only on the total amount of ink ejected onto the medium 50, it may seem that printing will be performed in an excessively dark color. However, in this example, as can be understood from the duty settings shown in the figure, the total amount of ink ejected from the inkjet head 202b that ejects ink after the inkjet head 202a to each position on the medium 50 is set to be smaller than the total amount of ink ejected from the inkjet head 202a. In this case, the duty setting for the inkjet head 202b is set to be less than the maximum duty value for each nozzle. In this configuration, by reducing the duty set for the inkjet head 202b that performs the second half main scanning operation to each position on the medium 50, it is possible to appropriately prevent, for example, the occurrence of unintended striped patterns. In this case, by ejecting a large amount of ink from the inkjet head 202a that performs the first half main scanning operation, it is possible to appropriately prevent, for example, the color from becoming lighter in the printed result. Furthermore, in this case, by reducing the duty set for the inkjet head 202b, even if a large amount of ink is ejected by the inkjet head 202a, it is possible to appropriately prevent the actual appearance of the image from appearing as if it were printed in an excessively dark color. Therefore, according to this example, it is possible to appropriately prevent deterioration in print quality due to the occurrence of unintended striped patterns, for example. This also makes it possible to more appropriately perform high-quality printing, for example.

[0043] In this example, the duty setting for the inkjet head 202a can be considered to be a setting that increases the print density of the print result obtained by using the multiple inkjet heads 202a and 202b. In this case, increasing the print density can be considered to be, for example, increasing the total amount of ink ejected per unit area. In addition, in this case, the duty setting for the inkjet head 202a can be considered to be, for example, setting the maximum duty value for at least some of the nozzles. In contrast, the duty setting for the inkjet head 202b can be considered to be, for example, setting the amount of ink ejected to improve the surface condition of the print result. By configuring in this way, for example, a portion where ink is ejected at the maximum duty value by the nozzles of the inkjet head 202a (full duty surface) can be made less noticeable. In addition, the duty setting for the inkjet head 202a can be considered to be, for example, set to be about twice the total amount of ink ejected compared to the case of using the duty setting in the conventional configuration shown in FIG. 3(b) (during normal printing). In this case, it is preferable to set the total amount of ink ejected by the inkjet heads 202a and 202b to about 1.5 times that of normal printing. With this configuration, for example, when using ultraviolet curable ink, high quality printing can be performed more appropriately. Also, the printing operation performed with such a duty setting can be considered as, for example, an operation of drawing a light color image by the inkjet head 202b on top of a dark color image by the inkjet head 202a. Also, as described above, the control unit 120 of this example causes only one of the inkjet heads 202a and 202b to eject ink to odd positions on the main scanning direction line 312. Also, the control unit 120 causes only the other of the inkjet heads 202a and 202b to eject ink to even positions.Therefore, a dark color image drawn by inkjet head 202a can be considered to be, for example, an image drawn only with ink ejected to one of the odd-numbered and even-numbered positions. A light color image drawn by inkjet head 202b can be considered to be, for example, an image drawn only with ink ejected to the other of the odd-numbered and even-numbered positions. In this case, a dark color image and a light color image can be considered to be, for example, a relatively dark image and a relatively light image.

[0044] As described above, in this example, the control unit 120 determines the ejection position of the nozzle according to, for example, a mask. In this case, the nozzle to which the maximum duty value is set can be considered to be, for example, a nozzle to which a mask is not applied. Therefore, when the duty is set as shown in FIG. 5(a), for example, the inkjet head 202a can be considered to have a mask not applied to at least some of the nozzles. Also, for the inkjet head 202b, for example, the mask can be considered to have been applied to the nozzles at all positions. Also, in this example, the number of passes of printing can be considered to be the number of passes corresponding to the duty setting. For example, in the case of the duty setting shown in FIG. 5(a), the number of passes can be considered to be 10 passes. In this case, the number of passes is larger than, for example, 6 passes, which is the number of passes in the cases shown in FIG. 3(b) and FIG. 4, but is not excessively large. Therefore, according to this example, for example, it is possible to appropriately perform high-quality printing while preventing the printing speed from decreasing excessively. Also, when printing with the inkjet method, in order to print at a high resolution, it is usually necessary to reduce the size of the ink dots formed on the medium 50. Also, as a result, when printing at a high resolution, the print density is likely to be insufficient in the print result. However, in this case, for example, simply increasing the duty setting and increasing the amount of ink ejected is likely to cause problems such as the occurrence of unintended striped patterns. Also, if one tries to prevent such problems by simply increasing the number of passes, the number of passes will increase significantly and the printing speed will decrease significantly. In contrast, according to this example, for example, it is possible to appropriately increase the amount of ink ejected per unit area while appropriately preventing the occurrence of unintended striped patterns, etc., without excessively increasing the number of passes. Therefore, according to this example, for example, it is possible to more appropriately perform printing at a high resolution.

[0045] The duty setting in this example can also be considered by focusing on the nozzle selection rate corresponding to the duty. In this case, the control unit 120 can be considered to set the nozzle selection rate so that the sum of the nozzle selection rates set for the nozzles in the inkjet head 202a among the line-corresponding nozzles corresponding to the main scanning direction line 312 is greater than 50% and the sum of the nozzle selection rates set for all the line-corresponding nozzles corresponding to the main scanning direction line 312 is greater than 100%. With this configuration, for example, the sum of the nozzle selection rates set for the nozzles in the inkjet head 202a can be appropriately increased as necessary without worrying about the sum of the nozzle selection rates set for the nozzles in the inkjet head 202b. This also makes it possible to easily and appropriately set the sum of the nozzle selection rates set for the nozzles in the inkjet head 202a to a value greater than 50%. In this case, by increasing the sum of the nozzle selection rates set for the nozzles in the inkjet head 202a, for example, a large amount of ink can be appropriately ejected before ink is ejected by the inkjet head 202b. This also allows the ink jet heads 202a, b to easily and appropriately eject a required amount of ink for each position on the medium 50 in a total of two or more positions, for example, when the nozzle selection rate for nozzles in an end region of the ink jet head 202b is reduced, without excessively increasing the nozzle selection rate for other nozzles in the ink jet head 202b. The control unit 120 may set the total of the nozzle selection rates set for the nozzles in the ink jet head 202a to 100% or a value close to 100%. More specifically, in this case, the control unit 120 sets the nozzle selection rate such that, for example, among the line-corresponding nozzles corresponding to the main scanning direction line 312, the total of the nozzle selection rates set for the nozzles in the ink jet head 202a is 90% or more, and the total of the nozzle selection rates set for the nozzles in the ink jet head 202b is 20% or more.With this configuration, it is possible to appropriately set the nozzle selection rate, which is preferable when using ultraviolet curable ink, for example. The total of the nozzle selection rates set for the nozzles in the inkjet head 202a may be set to, for example, about 95 to 100% (e.g., 100%). The total of the nozzle selection rates set for the nozzles in the inkjet head 202b may be set to, for example, about 40 to 60% (e.g., 50%).

[0046] As described above, in this example, the control unit 120 causes only one of the two inkjet heads 202a, b in the head unit 102 to eject ink to odd-numbered positions on the main scanning direction line 312. Also, the control unit 120 causes only the other of the two inkjet heads 202 to eject ink to even-numbered positions. In this case, when focusing on the ink ejection positions determined according to the image to be printed, if the sum of the per-nozzle selection rates set for the nozzles in the inkjet head 202a is greater than 50%, the inkjet head 202a ejects ink at least twice to any of the ejection positions. Also, if the sum of the per-nozzle selection rates set for the nozzles in the inkjet head 202b is 50% or less, the inkjet head 202b ejects ink once or less (one time or zero times) to any of the ejection positions. More specifically, for example, when the sum of the nozzle selection rates set for the nozzles in the inkjet head 202a is 100% and the sum of the nozzle selection rates set for the nozzles in the inkjet head 202b is 50%, the inkjet head 202a ejects ink twice to all ejection positions determined according to the image to be printed. In this case, for the inkjet head 202a, all ejection positions determined according to the image to be printed can be considered to be, for example, ejection positions (either odd-numbered positions or even-numbered positions) at which the inkjet head 202a can eject ink among the ejection positions determined according to the image to be printed. In addition, the inkjet head 202b ejects ink once to all ejection positions determined according to the image to be printed. For the inkjet head 202b, all ejection positions determined according to the image to be printed can be considered to be, for example, ejection positions (the other of odd-numbered positions or even-numbered positions) at which the inkjet head 202b can eject ink among the ejection positions determined according to the image to be printed.Furthermore, when the sum of the nozzle selection rates set for the nozzles in the inkjet head 202a is greater than 50% and less than 100%, the inkjet head 202a ejects ink twice to some of the ejection positions determined according to the image to be printed, and ejects ink once to the other ejection positions. Furthermore, when the sum of the nozzle selection rates set for the nozzles in the inkjet head 202b is less than 50%, the inkjet head 202b ejects ink once to some of the ejection positions determined according to the image to be printed, and does not eject ink to the other ejection positions. Furthermore, the specific settings of the duty are not limited to those specifically shown in FIG. 5, and can be changed in various ways.

[0047] Furthermore, if the sum of the per-nozzle selection rates set for the line-corresponding nozzles corresponding to the main scanning direction line 312 is defined as the total selection rate for the main scanning direction line 312, in this example, the control unit 120 sets the per-nozzle selection rate so that the total selection rate for all the main scanning direction lines 312 is a constant value. In this case, for example, it is conceivable to divide a plurality of nozzles that eject ink to an ejection position on the same main scanning direction line 312 into a plurality of groups, and set the sum of the per-nozzle selection rate for each group to a predetermined value. In this case, the control unit 120 sets the per-nozzle selection rate so that, for example, among the line-corresponding nozzles corresponding to one main scanning direction line 312, the sum of the per-nozzle selection rates set for the nozzles in the inkjet head 202a is a predetermined first value, and the sum of the per-nozzle selection rates set for the nozzles in the inkjet head 202b is a predetermined second value. With this configuration, for example, the per-nozzle selection rate can be easily and appropriately set. More specifically, when printing under at least some printing conditions, the control unit 120 causes the inkjet heads 202a and 202b to perform main scanning and sub-scanning operations so that ink is ejected from an even number of nozzles by an even number of main scanning operations on one main scanning direction line 312. In this case, the nozzles in the inkjet head 202a can be considered as, for example, first half nozzles, which are half of the nozzles that eject ink in the previous main scanning operation among the even number of nozzles that eject ink to the ejection position on the same main scanning direction line 312. Furthermore, the nozzles in the inkjet head 202b can be considered as, for example, second half nozzles, which are nozzles that eject ink in a main scanning operation after the first half nozzles. In this case, the control unit 120 sets the per-nozzle selection rate so that the sum of the per-nozzle selection rates set for the first half nozzles for all the main scanning direction lines 312 becomes a predetermined first value, and the sum of the per-nozzle selection rates set for the second half nozzles becomes a predetermined second value.With this configuration, for example, a plurality of nozzles that eject ink to ejection positions on the same main scanning direction line 312 can be divided into a plurality of groups, and the sum of the per-nozzle selection rates for each group can be appropriately set to a predetermined value. Also, depending on the printing conditions, it is conceivable that the number of main scanning operations that eject ink onto one main scanning direction line 312 will be an odd number in at least a part of the medium 50. In this case as well, for a plurality of main scanning direction lines 312 that eject ink with the same odd number of main scanning operations, the control unit 120 sets the per-nozzle selection rate so that the sum of the per-nozzle selection rates set for the nozzles in the inkjet head 202a becomes a predetermined first value, and the sum of the per-nozzle selection rates set for the nozzles in the inkjet head 202b becomes a predetermined second value. With this configuration, for example, even if the number of main scanning operations for ejecting ink onto at least some of the main scanning direction lines 312 is an odd number, multiple nozzles that eject ink onto ejection positions on the same main scanning direction line 312 can be divided into multiple groups, and the sum of the nozzle selection rates for each group can be appropriately set to a predetermined value.

[0048] Also, regarding the total selection rate, for example, it is possible to set the total selection rate for some of the main scanning direction lines 312 different from the total selection rate for the other main scanning direction lines 312, rather than setting the same constant value for all the main scanning direction lines 312. In this case, for example, the duty setting shown in FIG. 5(b) can be used. FIG. 5(b) is a diagram showing another example of the duty setting. The duty setting shown in FIG. 5(b) can be suitably used, for example, when the inkjet heads 202a and 202b eject ink other than ultraviolet curable ink. More specifically, in a modified example of the configuration of the printing device 12 (see FIG. 1), it is also possible to use ink other than ultraviolet curable ink. In this case, the inkjet heads 202a and 202b eject, for example, an evaporative drying type ink that is fixed on the medium 50 by evaporating the solvent. As the evaporative drying type ink, for example, a known solvent ink can be suitably used.

[0049] When such an evaporative drying type ink is used, when printing is performed by the multi-pass method, the ink fixed on the medium 50 in the previous main scanning operation may be re-melted in the subsequent main scanning operation among the multiple main scanning operations that eject ink to the same position on the medium 50. The effect of such re-melting may be particularly noticeable, for example, in the middle part of the range in which the duty is changed. As a result, for example, when the duty is set to gradually decrease toward the end in the sub-scanning direction for the nozzles in the end region of the inkjet head 202, the color may become lighter in the part corresponding to the middle part of the end region in the print result. Therefore, in order to set the duty appropriately when an evaporative drying type ink is used, for example, it is considered to increase the duty set for the nozzles that eject ink to the part where the color becomes lighter due to the effect of re-melting. In addition, it is considered to use, for example, the setting shown in FIG. 5(b) as such a duty setting.

[0050] Also, in this case, when considering the total selection rate, the operation of the control unit 120 can be considered to, for example, make the total selection rate for some main scanning direction lines 312 different from the total selection rate for other main scanning direction lines 312. More specifically, in FIG. 5B, the dashed lines shown together with the solid lines showing the duty settings show the duty settings when the total selection rate for all main scanning direction lines 312 is constant. Therefore, the duty setting shown by the solid lines in FIG. 5B can be considered to be larger than the duty shown by the dashed lines, for example, for nozzles included in the end regions of the inkjet heads 202a and 202b that are located at least in a part of the middle in the sub-scanning direction. Also, in this case, the control unit 120 makes the total selection rate for the main scanning direction lines 312 that eject ink from nozzles included in the end regions that are located at least in a part of the middle in the sub-scanning direction is larger than the total selection rate for the other main scanning direction lines 312. In this configuration, for example, more ink can be ejected to a portion where the color becomes lighter due to the effect of re-dissolving the ink. This also makes it possible to more appropriately perform high-quality printing when using, for example, an evaporative drying type ink. In this case, for example, the total of the nozzle selection rates set for at least some of the line-corresponding nozzles corresponding to the main scanning direction line 312 that ejects ink from at least some of the nozzles in the end region exceeds 100%. Therefore, the duty setting shown in FIG. 5(b) can also be considered as a setting that is realized by allowing a ratio other than 100% as the total of the nozzle selection rates.

[0051] Next, supplementary explanations regarding each of the configurations described above and further modified examples will be given. In the following, for convenience of explanation, the modified examples described above or below may be referred to as the present example. As described above, in this example, the duty can be set with a high degree of freedom by setting the duty without necessarily establishing a complementary relationship. However, when the duty is set without establishing a complementary relationship, for example, the amount of ink ejected per unit area (ejection amount) is different from the case where the complementary relationship is established. Therefore, when the print result is viewed in detail in pixel units, for example, it is considered that there are parts where the image is not completed, parts where the color is locally dark, etc. In addition, as a result, for example, there is a possibility that the color of the print result changes. And, in the conventional configuration, it can be said that the duty is usually set so that the complementary relationship is established, taking such points into consideration. In contrast, in the actual experimental results, it is also possible to improve the quality of the print by not establishing the complementary relationship as described above. Therefore, the configuration of this example can be considered, for example, as a configuration in which the duty is set without establishing the complementary relationship to perform printing with higher quality. As described above, in this example, the amount of ink ejected per unit area can be considered to be determined, for example, according to the duty setting. In this case, it can be considered that the greater the amount of ink ejected per unit area, the darker the color will be. However, the color density recognized in the print result is not necessarily proportional to the amount of ink ejected per unit area. For example, even if the amount of ink ejected per unit area is doubled, the color density in the printed image does not simply double.

[0052] In this embodiment, the inkjet head 202 may be an inkjet head capable of changing the volume of ink to be ejected in multiple stages. In this case, the ink volume may be variable in three stages corresponding to ink dots of large size (L dot), medium size (M dot), and small size (S dot). When multiple types of ink volumes are used, the control unit 120 may cause the inkjet head 202 to eject ink multiple times (twice) to the same ejection position only at a portion of the volumes. More specifically, in this case, the control unit 120 causes the inkjet head 202 to eject ink multiple times (overlap) to at least some of the ejection positions by setting a duty such that the sum of the nozzle selection rates set for the nozzles (line-corresponding nozzles) corresponding to the main scanning direction lines 312 is greater than 100% for at least some of the main scanning direction lines 312. In this case, making the inkjet head 202 eject ink multiple times onto at least some of the ejection positions may be, for example, making the inkjet head 202 included in the printing device 12 eject ink multiple times. In this case, the control unit 120 makes the inkjet head 202 eject ink multiple times onto the same ejection position, for example, with only a portion of the ink volumes excluding at least the smallest volume among the multiple ink volumes. In addition, in this regard, when multiple types of ink volumes are used, the smallest ink dots such as S dots are used, for example, for printing highlights. In this case, if the ink volume corresponding to S dots or the like is ejected multiple times onto the same ejection position, there is a risk of image quality defects in which the graininess increases in the printed result. Therefore, in a configuration using the inkjet head 202 that can change the ink volume in multiple stages, when using a duty setting for ejecting ink multiple times onto the same ejection position, it is preferable to eject ink multiple times onto the same ejection position, for example, as described above, with only a portion of the ink volumes excluding at least the smallest volume.In this case, the control unit 120, for example, causes the inkjet head 202 to perform overlapping ejection only for the L dots and M dots among the L dots, M dots, and S dots. With this configuration, for example, it is possible to cause the inkjet head 202 to appropriately eject ink multiple times onto the same ejection position. This also makes it possible, for example, to more appropriately increase the amount of ink ejected per unit area.

[0053] As described above, in this embodiment, for example, two inkjet heads 202a and 202b are used, which are arranged at different positions in the sub-scanning direction. For example, a duty that gradually decreases toward the end in the end region is set for each inkjet head 202. Such a duty setting can be considered, for example, as a setting in which the duty setting for each inkjet head 202 changes in a mountain shape. In addition, the duty setting for a virtual nozzle row combining the nozzle rows of the two inkjet heads 202a and 202b can be considered, for example, as a two-peak setting that has two peaks corresponding to the two inkjet heads 202a and 202b. As described above, in this embodiment, different duties can be easily and appropriately set for the multiple inkjet heads 202a and 202b. In this case, for example, as shown in FIG. 5(a), the duty setting that gradually changes in the end region of the inkjet heads 202a and 202b can be considered to be different for each inkjet head 202. With this configuration, for example, the setting for diffusing the ends of the paths to prevent the boundaries between paths from being conspicuous in the print result can be easily and appropriately set to different values ​​for each inkjet head 202. In this case, it is also possible to set the duty of the central portion, which is the portion other than the end regions of the inkjet heads 202a and 202b, to different values ​​for each inkjet head 202. With this configuration, for example, the amount of ink ejected from the multiple inkjet heads 202a and 202b can be appropriately set to different values ​​for each inkjet head 202. In this case, it is also possible to set the duty of each inkjet head 202 to different values, for example, as shown in FIG. 6.

[0054] FIG. 6 is a diagram for explaining modified duty settings. FIGS. 6(a) and 6(b) show various modified duty settings. The duty settings shown in FIG. 6(a) are examples in which the rate of change of the duty is made different for the inkjet heads 202a and 202b. More specifically, in the example shown in FIG. 6(a), the duty is made the largest at the center in the sub-scanning direction for each inkjet head 202, and the duty is made gradually smaller toward the end. In this case, the duty is changed linearly, and the duty at the center and end in the sub-scanning direction is made different for each inkjet head 202, so that the rate of change of the duty is made different for each inkjet head 202. In this case, the case in which the difference in duty between the center and end in the sub-scanning direction is made relatively small, as in the duty setting for the inkjet head 202a, can be considered as, for example, a setting with low smoothing. Then, as in the duty setting for the inkjet head 202b, when the difference in duty between the center and the end in the sub-scanning direction is relatively large, it can be considered to set the smoothing to a high level, for example. Furthermore, when ultraviolet curable ink is used, the occurrence of unintended striped patterns, for example, can be appropriately prevented by setting the smoothing to a low level. Furthermore, the boundary between passes can be made less noticeable, for example. In this case, the duty setting shown in FIG. 6(a) can be used to appropriately prevent the occurrence of striped patterns, for example, and reduce banding. Therefore, even when the duty setting shown in FIG. 6(a) is used, for example, high quality printing can be appropriately performed.

[0055] Moreover, the duty setting shown in FIG. 6(b) shows an example in which different masks are used for the inkjet heads 202a and 202b. More specifically, in the example shown in FIG. 6(b), a mask that linearly decreases the duty toward the end in the sub-scanning direction is used for the inkjet head 202a. Also, a mask that non-linearly decreases the duty toward the end in the sub-scanning direction is used for the inkjet head 202b. When ultraviolet-curable ink is used, the above mask can be used for the inkjet head 202a to make the surface of the base portion formed by the ink ejected from the inkjet head 202a uniform, for example. Also, the above mask can be used for the inkjet head 202b to make it difficult for unintended striped patterns to occur, for example. Therefore, even when the duty setting shown in FIG. 6(b) is used, for example, high-quality printing can be appropriately performed. Also, various settings other than the above can be used for the duty setting method. In this case, too, according to this example, by selecting the smoothing level and mask with a high degree of freedom, the duty can be set more appropriately according to the required print quality. In addition, in this case, in a printing operation performed using a multi-pass method, the control method can be appropriately changed according to the ejection timing (the timing when ink dots fall) that changes depending on which main scanning operation is used to eject ink. In addition, the freedom in mask selection is increased, and the options for setting the duty are increased, so that the duty can be set more appropriately according to, for example, the printing conditions and the type of ink used.

[0056] In the above, the configuration of the printing device 12 has been described mainly in terms of the case where the number of inkjet heads 202 that eject ink onto ejection positions included in one main scanning direction line 312 is two. In contrast, in a modified configuration of the printing device 12, the head unit 102 (see FIG. 1) may have a number of inkjet heads 202 other than two. In this case, the control unit 120 also causes some of the inkjet heads 202 to eject ink onto odd-numbered positions among the ejection positions on the main scanning direction line 312, and causes other inkjet heads 202 to eject ink onto even-numbered positions. In the above, the operation of so-called high scan (Hi scan) has been described mainly in terms of the method of ejecting ink onto a plurality of ejection positions on the main scanning direction line 312. In contrast, in a modified operation of the printing device 12, the control unit 120 may cause one inkjet head 202 to eject ink onto both odd-numbered positions and even-numbered positions on the main scanning direction line 312. Such an operation can be considered as, for example, a so-called normal scan operation, etc. In this case, the control unit 120 causes the inkjet head 202 to eject ink to an ejection position on a main scanning direction line 312, as will be described below with reference to, for example, Figs. 7 and 8.

[0057] 7 and 8 are diagrams for explaining modified examples of the operation of the printing device 12, and show examples of duty settings for normal scan operation. FIG. 7(a) shows an example of a general duty setting in the case where a two-peak setting that forms two peaks corresponding to two inkjet heads 202a and b is used as the duty setting. FIG. 7(b) shows an example of the ejection positions where the inkjet heads 202a and b eject ink according to the duty setting shown in FIG. 7(a). When normal scan is performed, the inkjet heads 202a and b are able to eject ink to both the odd-numbered positions and the even-numbered positions. Therefore, in this case, the maximum duty value (Full Duty) can be considered as, for example, a duty value for ejecting ink to all odd-numbered positions and all even-numbered positions that are ejectable from one nozzle during main scan operation. In this case, in order to make the sum of the nozzle selection rates set for the line-corresponding nozzles corresponding to the main scanning direction line 312 100%, a mask division filter is used to separate the ejection positions where the inkjet head 202a ejects ink from the ejection positions where the inkjet head 202b ejects ink, as shown in Fig. 7(b), for example. In this case, the positions indicated by the hatched circles in Fig. 7(b) are the ejection positions where ink is ejected. With this configuration, for example, it is possible to cause any of the nozzles in the inkjet heads 202a and 202b to eject ink in any one of the main scanning operations for all the ejection positions set according to the printing resolution.

[0058] The operation shown in FIG. 7 can be considered as, for example, an operation in which the inkjet head 202a ejects ink onto half of all the ejection positions, and the inkjet head 202b ejects ink onto the remaining half of the ejection positions. In addition, in such an operation, the mask division filter can be considered as, for example, a filter that sets the ratio of the ejection positions to which ink is ejected for each inkjet head 202. In this case, the ejection positions for which a predetermined value is set in the corresponding mask division filter for the inkjet heads 202a and 202b become the ejection positions selected according to the mask division filter. In addition, in this case, it can be considered that the inkjet heads 202a and 202b eject ink onto the positions that are ON in the mask division filter. It can also be considered that the inkjet heads 202a and 202b eject ink onto (are used) the same positions as the ejection positions set according to the resolution, for example, if the mask division filter is ON in the mask division filter. As such a division filter, for example, a filter of the same size as the mask used to set the duty can be used. Regarding the mask and the mask division filter, the fact that they are the same size can be considered as, for example, that the range of the ejection positions to which they are applied is the same size.

[0059] More specifically, in the case of the operation shown in FIG. 7, the mask division filter used can be considered to be, for example, a mask (50% mask) that assigns half of the ejection positions to each inkjet head. The operation shown in FIG. 7 can also be considered to be, for example, an operation in normal scan corresponding to the operation shown in FIG. 4 with respect to the high scan operation. On the other hand, for example, an operation in normal scan corresponding to the operation shown in FIG. 5(a) with respect to the high scan operation can be, for example, an operation shown in FIG. 8. FIG. 8(a) shows an example of an operation in normal scan corresponding to the operation shown in FIG. 5(a) in the case where a two-peak setting is used as the duty setting. FIG. 8(b) shows an example of an ejection position where the inkjet heads 202a and 202b eject ink according to the duty setting shown in FIG. 8(a).

[0060] When the ratio of the ejection positions for ejecting ink from the inkjet heads 202a and 202b is specified using a mask division filter, the ejection amount per unit area from the inkjet heads 202a and 202b can be changed by increasing or decreasing the ejection positions (the positions where the mask division filter is used) selected by the mask division filter. In this case, for example, a mask division filter (100% mask) that assigns all the ejection positions is used for the inkjet head 202a, and a mask division filter (50% mask) that assigns half the ejection positions is used for the inkjet head 202b, so that the ink can be ejected from the inkjet heads 202a and 202b as shown in FIG. 8(b). With this configuration, for example, it is possible to appropriately perform the operation in normal scan corresponding to the operation shown in FIG. 5(a). This also makes it possible to appropriately prevent the occurrence of unintended striped patterns, for example, in the same way as in the case of performing the operation shown in FIG. 5(a).

[0061] Also, in this case, for example, ink can be ejected to all ejection positions corresponding to the printing resolution only by the inkjet head 202a. Therefore, in this case, it can be considered that an image at the printing resolution is once completed at each position of the medium 50 (see FIG. 1) when, for example, the inkjet head 202a has completed ejecting ink. Also, in this case, by further ejecting ink by the inkjet head 202b to some of the ejection positions to which the inkjet head 202a has ejected ink, for example, it is possible to appropriately increase the amount of ink ejected per unit area while adjusting the surface condition of the printed result. Also, in a modified example of the printing operation, it is possible to use a mask division filter for the inkjet head 202a that assigns some of the ejection positions. In this case, the inkjet head 202b may eject ink to ejection positions including ejection positions to which the inkjet head 202a has not ejected ink.

[0062] As described above, in this example, for example, the duty can be set individually for each nozzle. In this case, for a virtual nozzle row that combines the nozzle rows of all the inkjet heads 202 in the head unit 102, it is also possible to set the duty as shown in Figs. 9 and 10. Figs. 9, 10(a) and (b) show further modified examples of the duty setting. More specifically, Fig. 9 shows an example of the duty setting when adjusting the ink ejection amount. In Fig. 9, the duty setting shown on the left side shows an example of the duty setting before the adjustment. Also, the duty setting shown on the right side shows an example of the duty setting after the adjustment. As described above, when the duty is set without necessarily establishing a complementary relationship, the duty can be set with a high degree of freedom. In this case, for example, in contrast to the duty setting that gradually decreases toward the end as shown on the left side of Fig. 9, it is possible to reduce some of the duties to reduce the ink ejection amount as shown on the right side of Fig. 9. Such an adjustment can be considered to be, for example, an adjustment to change the shape of smoothing to reduce the amount of ink applied at one time, etc. Also, by using the duty setting after such an adjustment, for example, it is possible to make it difficult for unintended streaks or bleeding to occur in the printed result.

[0063] In addition, in a further modified example of the duty setting, for example, the setting shown in FIG. 10(a) may be used to increase the print density. In FIG. 10(a), the duty setting shown by the dashed line is an example of the setting before the print density is increased (setting before the density is increased). In addition, the duty setting shown by the solid line is an example of the setting after the print density is increased (setting after the density is increased). In this case, the setting before the density is increased may be considered to be, for example, a setting in which the sum of the nozzle selection rates set for the line-corresponding nozzles corresponding to the main scanning direction lines 312 is 100% for all the main scanning direction lines 312. In addition, the setting after the density is increased may be considered to be, for example, a setting in which the sum of the nozzle selection rates set for the line-corresponding nozzles corresponding to the main scanning direction lines 312 is greater than 100% for at least some of the main scanning direction lines 312. The duty setting shown in FIG. 10(a) may be considered to be, for example, a one-mountain setting in which the duty changes to one mountain shape for virtual nozzles corresponding to a plurality of inkjet heads 202. In this case, the two peaks corresponding to the first and second nozzles are not created as in the case of a two-peak setting, so it can be thought of as increasing the overall ejection amount. Even with this configuration, it is possible to appropriately increase the print density as needed, for example.

[0064] In addition, when using an inkjet head 202 capable of ejecting special color inks in addition to color printing inks, such as the inkjet heads 202a and 202b shown in FIG. 1(b), a multi-layer printing can be performed by overlapping an ink layer formed with a special color ink of a predetermined color, such as white, and an ink layer formed with a process color ink (color ink). For example, when a white layer formed with white ink and a color layer formed with a process color ink are formed, multi-layer printing can be performed as shown in FIG. 10(b). In this case, the density of the print can be increased for each layer by setting the duty for the nozzle arrangement used to form one ink layer, for example, as in FIG. 10(a). More specifically, the left diagram in FIG. 10(b) shows an example in which a white layer is formed with the inkjet head 202a and a color layer is formed with the inkjet head 202b in the case of performing two-layer printing. In this case, the density of the print of the white layer and the color layer can be increased by setting the duty for the inkjet heads 202a and 202b as shown in the figure. 10(b) shows an example of three-layer printing in which the first color layer and part of the white layer are formed by the inkjet head 202a, and the remaining part of the white layer and the second color layer are formed by the inkjet head 202b. In this case, too, the print density of the white layer and the color layers can be increased by setting the duties for the inkjet heads 202a and 202b as shown in the figure.

[0065] In addition, in the above, an example of duty setting has been described mainly in the case where the influence of the variation in the ejection characteristics of each nozzle is not taken into consideration. In this case, the duty setting described above can be considered as an example of setting for a normal nozzle, for example. A normal nozzle can be considered as a nozzle whose ejection characteristics are within a predetermined normal range. In this case, the sum of the nozzle selection rates set for the line-corresponding nozzles corresponding to the main scanning direction line 312 can be considered to be a percentage other than 100%, for example, when all the line-corresponding nozzles corresponding to the main scanning direction line 312 are normal nozzles, the sum of the nozzle selection rates can be considered to be a percentage other than 100%. The duty setting for a normal nozzle can be considered to be, for example, a setting that is performed without taking into consideration the difference in the ejection characteristics of each nozzle. In contrast, in a modified example of the method of setting the duty, the duty may be set by taking into consideration the influence of the variation in the ejection characteristics of each nozzle. In this case, for example, it is considered that the ejection characteristics of the nozzles are compensated for by setting the duty individually for each nozzle according to the ejection characteristics of each nozzle. More specifically, in this case, it is possible to compensate for the nozzle ejection characteristics by setting a different duty for abnormal nozzles other than normal nozzles compared to normal nozzles. With this configuration, it is possible to more appropriately perform high-quality printing, for example, even when there is a large variation in the ejection characteristics of each nozzle. In this case, it is also possible to set the duty as shown in FIG.

[0066] FIG. 11 is a diagram for explaining the setting of the duty while considering the influence of the variation in the ejection characteristics of each nozzle. FIGS. 11(a) and (b) show an example of the duty setting and the print result. In FIG. 11, as in FIG. 9, an example of the duty setting for the virtual nozzle row corresponding to the nozzle row 212 of the multiple inkjet heads 202 is shown. In FIGS. 11(a) and (b), the diagram on the left shows an example of the duty setting. The diagram on the right shows a simplified result of the printing performed using the duty setting. More specifically, FIG. 11(a) shows an example of the duty setting and the print result in the case where the duty is set without considering the influence of the variation in the ejection characteristics of each nozzle. The duty setting shown in FIG. 11(a) can be considered to be, for example, the same duty setting as when all the nozzles are normal nozzles. In this case, the print result may be affected by the deviation in the amount of ink ejected per unit area in the part where the ink is ejected by the abnormal nozzle. For example, in this case, it is considered that the position corresponding to the abnormal nozzle stands out in the print result, as shown by the portion with a different hatched pattern in the figure. In contrast, FIG. 11(b) shows an example of duty setting and print result when the duty is set taking into consideration the influence of the variation in the ejection characteristics of each nozzle. The duty setting shown in FIG. 11(b) can be considered as, for example, a setting in which the duty setting for the abnormal nozzle is made different from that shown in FIG. 11(a). More specifically, in the example shown in FIG. 11(b), the duty for the abnormal nozzle is changed to a larger value than that shown in FIG. 11(a). With this configuration, for example, the amount of ink ejected from the abnormal nozzle can be appropriately adjusted. This also makes it possible to appropriately prevent, for example, the position corresponding to the abnormal nozzle from standing out in the print result.

[0067] Here, FIG. 11(b) shows an example of duty setting in the case where there is an abnormal nozzle that ejects a small amount of ink. In addition, in the abnormal nozzle, for example, the amount of ink ejected may be large. Therefore, it is preferable to set the duty for the abnormal nozzle according to the characteristics of the abnormal nozzle. More specifically, for example, it is possible to adjust the duty to be larger for an abnormal nozzle that ejects a small amount of ink. In addition, it is possible to adjust the duty to be smaller for an abnormal nozzle that ejects a large amount of ink. With this configuration, for example, it is possible to appropriately compensate for the ejection characteristics of the abnormal nozzle. In addition, it is possible to adjust such a duty in combination with the duty setting described using FIG. 5 to FIG. 10, etc. In this case, it is possible to adjust the duty for each nozzle according to the ejection characteristics of each nozzle after setting the duty described using FIG. 5 to FIG. 10, etc. In addition, the duty adjustment shown in FIG. 11(b) can be considered to be, for example, an adjustment to increase or decrease the duty in a part of the duty setting that changes in a gradational manner.

[0068] In addition, when the duty for the abnormal nozzle is adjusted, the adjustment may affect the print result. More specifically, for example, when the duty for the abnormal nozzle is reduced, the amount of ink ejected may be reduced, which may cause the image to be printed to be incomplete, or the color of the print result to change. In addition, when the duty for the abnormal nozzle is increased, the position corresponding to the abnormal nozzle may stand out due to the ink ejection performed multiple times at the ejection position where the abnormal nozzle ejects ink. Therefore, when setting (adjusting) the duty while taking into account the effect of the variation in the ejection characteristics of each nozzle, in order to print with higher quality, for example, the duty may be changed for at least a part of the normal nozzles other than the abnormal nozzle. In this case, for example, it is possible to change the duty of any normal nozzle that ejects ink to an ejection position around the ejection position where the abnormal nozzle ejects ink, in accordance with the change in the duty performed for the abnormal nozzle. With this configuration, for example, it is possible to more appropriately perform printing with higher quality.

[0069] In addition, it is also possible to change the duty for all nozzles arbitrarily according to the quality required for printing. In this case, for example, it is also possible to consider the duty setting for all nozzles to be a setting that changes in an arbitrary manner. In addition, such a duty setting with a high degree of freedom can be suitably used, for example, when performing glossy coating with clear ink. In this case, the clear ink can be considered to be, for example, a colorless and transparent ink. The inkjet head 202 ejects clear ink as, for example, a special color ink. In addition, performing glossy coating with clear ink can be considered to be, for example, forming a layer of glossy clear ink on an ink layer formed with color ink. The layer of glossy clear ink can be considered, for example, a layer of clear ink that has been fixed on a medium after ink dots have been sufficiently flattened after landing. In this case, by setting the duty with a high degree of freedom, for example, adjustments to excess or deficiency of clear ink can be easily and appropriately performed. In addition, this also makes it possible to more appropriately perform glossy coating with clear ink, for example. In the above, the configuration of the printing device 12 (see FIG. 1) has been mainly described in terms of the case where ink is ejected onto a medium. In this case, the printing device 12 can be considered to be, for example, an inkjet printer that draws a two-dimensional image on a medium. In contrast, in a modified example of the printing device 12, a 3D printer (3D printing device) that forms a three-dimensional object can be used as the printing device 12. In this case, for example, a modeling table that supports the object being modeled, or the object being modeled can be considered to be an object onto which ink is ejected. [Industrial Applicability]

[0070] The present invention can be suitably used in, for example, a printing device. [Explanation of symbols]

[0071] 10 printing system, 102 head section, 104 platen, 106 Y-bar section, 108 main scanning drive section, 110 sub-scanning drive section, 112 setting storage section, 12 printing device, 120 control section, 14 control PC, 202 inkjet head, 204 ultraviolet irradiation section, 212 nozzle row, 222 nozzle, 302 dot, 312 main scanning direction line, 50 medium

Claims

1. A printing apparatus that performs printing using an inkjet method, An inkjet head having a nozzle row in which multiple nozzles are arranged in the sub-scanning direction, A control unit that controls the operation of the inkjet head, the main scanning operation in the main scanning direction perpendicular to the sub-scanning direction, and the sub-scanning operation. Equipped with, The inkjet head ejects ink to an ejection position set according to the print resolution, In a main scanning direction line, which is a sequence of ejection positions arranged in the main scanning direction at intervals corresponding to the printing resolution, the nozzles are capable of ejecting ink to any of the ejection positions included in the main scanning direction line. The control unit, For each nozzle, a nozzle-specific selectivity ratio is set, which is the ratio of the discharge positions to be discharged in one main scanning operation, and the nozzle-specific selectivity ratio is set so that it gradually decreases toward the end in the sub-scanning direction. A printing apparatus characterized in that, for at least some of the main scanning lines, the selectivity of each nozzle is set such that the sum of the selectivity of each nozzle is not 100% for the line-corresponding nozzles, which are nozzles that can eject ink in any of the main scanning operations for the ejection position included in one of the main scanning lines.

2. The printing apparatus according to Claim 1, characterized in that the control unit sets the nozzle selectivity for at least a portion of the nozzles at the end in the sub-scanning direction of the inkjet head to be different from the nozzle selectivity setting for the nozzles at the end of the other inkjet heads.

3. The system comprises at least two inkjet heads arranged at different positions in the aforementioned sub-scanning direction, The printing apparatus according to claim 1, wherein, among the ejection positions included in one main scanning direction line, the ejection positions that are arranged alternately from one side in the main scanning direction are defined as odd-numbered positions, and the ejection position adjacent to the odd-numbered position is defined as an even-numbered position, the control unit ejects ink from only one of the two inkjet heads for the odd-numbered positions in the main scanning direction line, and ejects ink from only the other of the two inkjet heads for the even-numbered positions.

4. The system comprises at least two inkjet heads arranged at different positions in the aforementioned sub-scanning direction, The two inkjet heads mentioned above eject ultraviolet-curable ink. The control unit, The inkjet heads are made to perform the main scanning operation and the sub-scanning operation such that, with respect to the ejection position included in the main scanning direction line, the first head, which is one of the two inkjet heads, ejects ink first, and then the second head, which is the other of the two inkjet heads, ejects ink. The printing apparatus according to claim 1, further characterized in that the nozzle selectivity is set such that, among the line-corresponding nozzles corresponding to the main scanning direction lines, the sum of the nozzle selectivity set for the nozzles in the first head is greater than 50%, and the sum of the nozzle selectivity set for all the line-corresponding nozzles corresponding to the main scanning direction lines is greater than 100%.

5. The printing apparatus according to claim 4, characterized in that the control unit sets the nozzle selectivity such that, among the line-corresponding nozzles corresponding to the main scanning direction line, the sum of the nozzle selectivity settings for the nozzles in the first head is 90% or more, and the sum of the nozzle selectivity settings for the nozzles in the second head is 20% or more.

6. The aforementioned inkjet head ejects an evaporative-drying ink that adheres to the material to be ejected by evaporating the solvent. If the sum of the selectivity rates set for each nozzle corresponding to the main scanning direction line is defined as the total selectivity rate for the main scanning direction line, the control unit shall, The total selectivity for some of the main scanning direction lines is made different from the total selectivity for other main scanning direction lines. The printing apparatus according to claim 1, further characterized in that the total selectivity for the main scanning direction line that ejects ink from nozzles located in at least a portion of the nozzles in the middle of the sub-scanning direction among the nozzles included in the end region is greater than the total selectivity for the other main scanning direction lines.

7. The aforementioned main scanning direction line is a sequence of ejection positions that eject ink of the same color. During printing under at least some printing conditions, the control unit causes the inkjet head to perform the main scanning operation and the sub-scanning operation such that ink is ejected from an even number of nozzles by an even number of main scanning operations for one main scanning direction line. The printing apparatus according to claim 1, characterized in that, among the even number of nozzles that eject ink to the ejection position in the same main scanning direction line, half of the nozzles that eject ink in the previous main scanning operation are defined as first-half nozzles, and the nozzles that eject ink in the main scanning operation after the first-half nozzles are defined as second-half nozzles, the sum of the nozzle selectivity rates set for the first-half nozzles for all main scanning direction lines becomes a predetermined first value, and the sum of the nozzle selectivity rates set for the second-half nozzles becomes a predetermined second value.

8. The aforementioned inkjet head can change the amount of ink ejected in multiple stages. The control unit sets the nozzle selectivity for at least some of the main scanning direction lines such that the sum of the nozzle selectivity settings for the line-corresponding nozzles corresponding to the main scanning direction lines is greater than 100%, thereby causing the inkjet head to eject ink multiple times for at least some of the ejection positions. The printing apparatus according to claim 1, further characterized in that the inkjet head is made to eject ink multiple times to the same ejection position using only a portion of the ink capacities of the multiple stages of ink, excluding at least the smallest capacity.

9. A printing method that uses an inkjet method, An inkjet head having a nozzle row in which multiple nozzles are arranged in the sub-scanning direction is made to perform a main scanning operation in the main scanning direction perpendicular to the sub-scanning direction, and a sub-scanning operation. The inkjet head ejects ink to an ejection position set according to the print resolution. In a main scanning direction line, which is a sequence of ejection positions arranged in the main scanning direction at intervals corresponding to the printing resolution, the nozzles are made capable of ejecting ink to any of the ejection positions included in the main scanning direction line. For each nozzle, a nozzle-specific selectivity ratio is set, which is the ratio of the discharge positions to be discharged in one main scanning operation, and the nozzle-specific selectivity ratio is set so that it gradually decreases toward the end in the sub-scanning direction. A printing method characterized in that, for at least some of the main scanning lines, the selectivity of each nozzle is set such that the sum of the selectivity of each nozzle is not 100% for the line-corresponding nozzles, which are nozzles that can eject ink in any of the main scanning operations for the ejection position included in one of the main scanning lines.

10. A printing apparatus that performs printing using an inkjet method, An inkjet head having a nozzle row in which multiple nozzles are arranged in the sub-scanning direction, A control unit that controls the operation of the inkjet head, the main scanning operation in the main scanning direction perpendicular to the sub-scanning direction, and the sub-scanning operation. Equipped with, The inkjet head ejects ink to an ejection position set according to the print resolution, In a main scanning direction line, which is a sequence of ejection positions arranged in the main scanning direction at intervals corresponding to the printing resolution, the nozzles are capable of ejecting ink to any of the ejection positions included in the main scanning direction line. The control unit, For each nozzle, a nozzle-specific selectivity ratio is set, which is the ratio of the discharge positions to be discharged in one main scanning operation. A printing apparatus characterized in that, for at least some of the main scanning lines, the selectivity of each nozzle is set such that the sum of the selectivity of each nozzle is not 100% for the line-corresponding nozzles, which are nozzles that can eject ink in any of the main scanning operations for the ejection position included in one of the main scanning lines.

11. A printing method that uses an inkjet method, An inkjet head having a nozzle row in which multiple nozzles are arranged in the sub-scanning direction is made to perform a main scanning operation in the main scanning direction perpendicular to the sub-scanning direction, and a sub-scanning operation. The inkjet head ejects ink to an ejection position set according to the print resolution. In a main scanning direction line, which is a sequence of ejection positions arranged in the main scanning direction at intervals corresponding to the printing resolution, the nozzles are made capable of ejecting ink to any of the ejection positions included in the main scanning direction line. For each nozzle, a nozzle-specific selectivity ratio is set, which is the ratio of the discharge positions to be discharged in one main scanning operation. A printing method characterized in that, for at least some of the main scanning lines, the selectivity of each nozzle is set such that the sum of the selectivity of each nozzle is not 100% for the line-corresponding nozzles, which are nozzles that can eject ink in any of the main scanning operations for the ejection position included in one of the main scanning lines.

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