Printing device, printing method, printing program, and recording medium

Abstract

To perform the excellent printing by suppressing influence due to the residual vibration of ink following discharge of ink droplets from a nozzle.SOLUTION: The size of ink droplets to be discharged to each pixel P predetermined by image data Di (discharge data) is corrected. Concretely, the size (amount) of ink droplets discharged to an object pixel Pt by a nozzle 52 is corrected on the basis of comparison between the size (first discharge condition) of ink droplets to be discharged to a preceding pixel Pa from the nozzle 52 at timing T1 (first timing) and the size (second discharge condition) of ink droplets to be discharged to the object pixel Pt from the nozzle 52 at timing T2 (second timing) (steps S105, S106). With this, such a situation that it is determined that influence of the residual vibration becomes large can be dealt with on the basis of the size of ink droplets to the preceding pixel Pa and the object pixel Pt indicated by the image data Di.SELECTED DRAWING: Figure 10A

Description

[Technical Field]

[0001] The present invention relates to inkjet technology for controlling the amount of ink droplets ejected from a nozzle. [Background technology]

[0002] Printing devices are known that print images on a print medium by ejecting ink droplets from nozzles in an inkjet head and causing them to land on the print medium. As shown in Patent Documents 1 and 2, such printing devices can express the gradation of an image by adjusting the amount of ink droplets ejected from the nozzles in four stages: zero, small (S), medium (M), and large (L). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-126453 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-045836 [Patent Document 3] Japanese Patent Application Laid-Open No. 2001-277484 Summary of the Invention [Problem to be solved by the invention]

[0004] As shown in Patent Document 3, in a nozzle that ejects ink using an inkjet method, the ink meniscus formed in the nozzle vibrates as the ink is ejected. In other words, residual vibrations exist in the ink meniscus until a predetermined decay time has passed since the ink was ejected. Therefore, if the residual vibrations from the ejection of a previous ink droplet affect the ejection of a subsequent ink droplet, the subsequent ink droplet cannot be ejected well. In particular, as will be described later, depending on the relationship between the ejection conditions (e.g., the amount of ink droplet) when ejecting the previous ink droplet and the ejection conditions when ejecting the subsequent ink droplet, the residual vibrations can have a significant effect on the ejection of the subsequent ink droplet.

[0005] The present invention has been made in consideration of the above-mentioned problems, and has an object to suppress the influence of residual vibration of ink that accompanies the ejection of ink droplets from nozzles, thereby enabling good printing. [Means for solving the problem]

[0006] The printing device of the present invention comprises an ejection head that ejects ink droplets from a nozzle, and a control unit that controls the ejection of ink droplets from the nozzle based on ejection data that indicates the ejection conditions when the nozzle ejects ink droplets to a target pixel that the nozzle faces among pixels arranged at a pitch corresponding to the resolution, and the control unit executes a determination process that determines the amount of ink droplets that the nozzle ejects at a second timing based on a comparison between a first ejection condition, which is the ejection condition when the nozzle ejects droplets at a first timing, and a second ejection condition, which is the ejection condition when the nozzle ejects droplets at a second timing after a time corresponding to the resolution has elapsed from the first timing.

[0007] The printing method of the present invention includes a step of acquiring ejection data indicating the ejection conditions when ink droplets are ejected from a nozzle onto a target pixel that the nozzle faces among pixels arranged at a pitch corresponding to the resolution, and a step of executing a determination process to determine the amount of ink droplets that the nozzle will eject at a second timing based on a comparison between a first ejection condition, which is the ejection condition when the nozzle ejects droplets at a first timing, and a second ejection condition, which is the ejection condition when the nozzle ejects droplets at a second timing after a time corresponding to the resolution has elapsed from the first timing.

[0008] The printing program of the present invention causes a computer to execute the following steps: acquiring ejection data indicating the ejection conditions when ink droplets are ejected from a nozzle onto a target pixel that the nozzle faces among pixels arranged at a pitch corresponding to the resolution; and executing a determination process to determine the amount of ink droplets that the nozzle will eject at a second timing based on a comparison between a first ejection condition, which is the ejection condition when the nozzle ejects droplets at a first timing, and a second ejection condition, which is the ejection condition when the nozzle ejects droplets at a second timing after a time corresponding to the resolution has elapsed from the first timing.

[0009] A recording medium according to the present invention records the above-described printing program in a computer-readable manner.

[0010] In other words, when ink liquid is ejected consecutively at the first and second timings, residual vibrations in the ink caused by the ejection of ink droplets at the first timing can affect the ejection of ink droplets at the second timing. In particular, as will be described later, depending on the relationship between the ink liquid ejection conditions at the first and second timings (first and second ejection conditions), the effect of such residual vibrations can become significant.

[0011] In contrast, the present invention (printing device, printing method, printing program, and recording medium) determines the amount of ink droplets to be ejected from the nozzle at the second timing based on a comparison (in other words, a combination) of the first and second ejection conditions indicated by the ejection data (determination process). In this way, it is possible to deal with situations where it is determined that the influence of residual vibrations will be significant based on the first and second ejection conditions indicated by the ejection data. As a result, it is possible to suppress the influence of residual ink vibrations that accompany the ejection of ink droplets from the nozzle, thereby achieving good printing.

[0012] The printing device may also be configured so that the control unit stores a reduction standard for reducing the amount of ink droplets ejected from the nozzles to the target pixel at the second timing from the amount indicated by the ejection data, and if the comparison result between the first and second ejection conditions satisfies the reduction standard, the control unit determines in a determination process to reduce the amount of ink droplets ejected from the nozzles at the second timing. With this configuration, a situation in which it is determined that the influence of residual vibration will be significant based on the first and second ejection conditions indicated by the ejection data can be addressed by reducing the amount of ink droplets ejected from the nozzles at the second timing. As a result, the influence of residual vibration of ink accompanying the ejection of ink droplets from the nozzles is suppressed, enabling good printing.

[0013] The printing device may also be configured such that, if the comparison result between the first and second ejection conditions satisfies a reduction standard, the control unit determines in a determination process to reduce the amount of ink droplets ejected from the nozzle at the second timing to zero. With this configuration, a situation in which the influence of residual vibration is determined to be significant based on the first and second ejection conditions indicated by the ejection data can be addressed by reducing the amount of ink droplets ejected from the nozzle at the second timing to zero. As a result, the influence of residual ink vibration accompanying the ejection of ink droplets from the nozzle is suppressed, enabling good printing. Here, reducing the amount of ink droplets ejected from the nozzle to zero means that no ink droplets are ejected from the nozzle.

[0014] The printing device may also be configured such that the ejection head has a plurality of nozzles, including a nozzle, that eject ink droplets at different positions from each other, and when the control unit determines in the determination process to reduce the amount of ink droplets ejected by the nozzle at the second timing, the control unit increases the amount of ink droplets ejected from an adjacent nozzle facing the adjacent pixel, which is a pixel adjacent to the target pixel, onto the adjacent pixel from among the plurality of nozzles, from the amount indicated by the ejection data. In other words, reducing the amount of ink droplets ejected by the nozzle at the second timing to suppress the effects of residual vibration may result in an insufficient amount of ink droplets adhering to the area including the target pixel. In response to this, by increasing the amount of ink droplets ejected from the adjacent nozzle onto the pixel adjacent to the target pixel, the insufficient amount of ink droplets can be compensated for, making it possible to print a good image.

[0015] There are various possible examples of ejection conditions that will make the effects of residual vibration more pronounced. Therefore, the printing device may be configured so that the ejection conditions indicate the amount of ink droplets ejected from the nozzles onto the target pixel.

[0016] The printing device may also be configured such that, in the determination process, the control unit determines the amount of ink droplets to be ejected from the nozzle at the second timing based on a comparison between the first and second ejection conditions and the time interval between the first and second timings. With this configuration, it is possible to perform good printing by accurately responding to the effects of residual vibrations that change depending on the time interval between the first and second timings.

[0017] The printing device may also be configured so that the control unit, in the determination process, determines the amount of ink droplets to be ejected from the nozzle at the second timing based on a comparison between the first and second ejection conditions and the temperature of the ink. With this configuration, it is possible to perform good printing by accurately responding to the effects of residual vibrations that change depending on the ink temperature. [Effects of the Invention]

[0018] As described above, according to the present invention, it is possible to suppress the influence of residual vibration of ink that accompanies the ejection of ink droplets from the nozzles, thereby enabling good printing. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a front view schematically showing a printing system equipped with an example of a printing device according to the present invention. [Figure 2] FIG. 2 is a partial cross-sectional view schematically illustrating the configuration of a discharge head. [Figure 3] FIG. 2 is a block diagram showing the electrical configuration of the printing apparatus shown in FIG. [Figure 4] FIG. 4 is a diagram schematically showing the waveform of an ejection signal output to a piezoelectric element of the ejection head. [Figure 5] FIG. 4 is a diagram schematically showing details of a discharge signal. [Figure 6] 5A and 5B are diagrams illustrating residual vibrations that occur when ink is ejected in response to an ejection signal. [Figure 7] FIG. 10 is a table showing the relationship between the size of two ink droplets ejected in succession and the effect of residual vibration. [Figure 8] FIG. 10 is a diagram schematically illustrating the relationship between each ejection signal when the size of the leading ink droplet of two ink droplets ejected in succession is L size. [Figure 9] 10 is a flowchart showing an example of image printing executed by a printing device. [Figure 10A] FIG. 10 is a diagram schematically showing an example of image processing executed according to the flowchart of FIG. [Figure 10B] FIG. 10 is a diagram schematically showing an example of image processing executed according to the flowchart of FIG. [Figure 10C] FIG. 10 is a diagram schematically showing an example of image processing executed according to the flowchart of FIG. [Figure 11A] FIG. 10 is a table showing the relationship between the size of two ink droplets ejected in succession and the effect of residual vibration. [Figure 11B] FIG. 10 is a table showing the relationship between the size of two ink droplets ejected in succession and the effect of residual vibration. [Figure 12A] FIG. 10 is a table showing the relationship between the size of two ink droplets ejected in succession and the effect of residual vibration. [Figure 12B] FIG. 10 is a table showing the relationship between the size of two ink droplets ejected in succession and the effect of residual vibration. [Figure 13] FIG. 2 is a block diagram showing an electrical configuration for executing image printing. [Figure 14A] FIG. 10 is a diagram showing a mask used in a first modified example of the interpolation process. [Figure 14B] FIG. 10 is a diagram showing image processing executed in a first modified example of interpolation processing. DETAILED DESCRIPTION OF THE INVENTION

[0020] Figure 1 is a front view showing a printing system 100 equipped with an example of a printing device according to the present invention. In order to clarify the layout of each part of the device, Figure 1 and the following figures appropriately show the X direction, which is the horizontal direction in which the paper feed unit 1, printing device 3, and paper discharge unit 4 that make up the printing system 100 are arranged, and the Y direction, which is the horizontal direction perpendicular to the X direction.

[0021] As shown in FIG. 1, the printing system 100 includes a paper feed unit 1, a printing device 3, and a paper discharge unit 4. The paper feed unit 1 holds a print medium WP, which is a roll of continuous paper, so that it can rotate around a horizontal axis. The paper feed unit 1 unwinds and supplies the print medium WP to the printing device 3. The printing device 3 prints by ejecting ink onto the print medium WP to form an image, and then sends the print medium WP to the paper discharge unit 4. The paper discharge unit 4 takes up the print medium WP that has been printed by the printing device 3 around the horizontal axis.

[0022] Here, the direction in which the printing medium WP is sent out and transported by the paper feed unit 1 is referred to as the transport direction X. The horizontal direction perpendicular to the transport direction X is referred to as the width direction Y. The paper feed unit 1 described above is disposed upstream of the printing device 3 in the transport direction X. The paper discharge unit 4 described above is disposed downstream of the printing device 3 in the transport direction X.

[0023] The printing device 3 has a drive roller 7 on the upstream side for taking in the printing medium WP from the paper feed unit 1. The printing medium WP taken in from the paper feed unit 1 by the drive roller 7 is sent in the transport direction X by a plurality of transport rollers 9 and transported downstream toward the paper discharge unit 4. A drive roller 11 is disposed between the most downstream transport roller 9 and the paper discharge unit 4. This drive roller 11 sends out the printing medium WP being transported on the transport rollers 9 toward the paper discharge unit 4.

[0024] The printing device 3 is provided with a printing unit 13, a drying unit 15, and a line scanner 17, arranged in this order from the upstream side along the transport direction X, between the drive roller 7 and the drive roller 11. The printing unit 13 prints on the print medium WP. The drying unit 15 dries the print medium WP printed by the printing unit 13. The line scanner 17 inspects the printed portion of the print medium WP for stains, omissions, etc.

[0025] The printing unit 13 is equipped with an ejection head 5 having multiple nozzles that eject ink onto the printing medium WP. A plurality of printing units 13 are generally arranged along the transport direction X of the printing medium WP. For example, a total of four printing units 13 are provided, one for black (K), one for cyan (C), one for magenta (M), and one for yellow (Y). However, the following description will be given taking as an example a configuration in which the printing device 3 is provided with only one printing unit 13. Furthermore, the printing unit 13 has a length in the width direction Y of the printing medium WP that exceeds the width of the printing medium WP. The printing unit 13 is equipped with enough ejection heads 5 to print the printing area in the width direction of the printing medium WP without moving in the width direction Y.

[0026] FIG. 2 is a partial cross-sectional view schematically illustrating the configuration of the ejection head. As described above, the printing unit 13 has multiple ejection heads 5, each of which ejects ink using an inkjet system. As shown in FIG. 2, the ejection head 5 has a housing 51 and multiple nozzles 52 arranged in a predetermined direction at the bottom of the housing 51, with each of the multiple nozzles 52 opening downward. Inside the housing 51 are multiple cavities 53 that communicate with the multiple nozzles 52, respectively, and ink supply chambers 54 that communicate with the multiple cavities 53. Furthermore, the housing 51 is provided with an inlet 511 and an outlet 512 that communicate with the ink supply chamber 54. An ink circulation mechanism (not shown) supplies ink from the inlet 511 to the ink supply chamber 54 and collects it from the outlet 512, thereby circulating the ink to the ink supply chamber 54. Ink is then supplied from the ink supply chamber 54 to each cavity 53.

[0027] A piezoelectric element 55 is provided for each of the multiple cavities 53. The piezoelectric element 55 is, for example, a piezo element, and deforms in response to an applied electric signal. The pressure of the ink in the cavity 53 varies in response to the deformation of the piezoelectric element 55. As will be described later, an ejection signal, which is an electric signal, is applied to this piezoelectric element 55. When the ejection signal is applied to the piezoelectric element 55, the piezoelectric element 55 applies a pressure fluctuation (ejection pressure fluctuation) required to eject ink from the nozzle 52 to the ink in the cavity 53.

[0028] Fig. 3 is a block diagram showing the electrical configuration of the printing device of Fig. 1. As shown in Fig. 3, the printing device 3 includes a transport motor 341 that drives a drive roller 7 to transport the printing medium WP, and an encoder 342 that detects the rotational position of the transport motor 341 (in other words, the transport position of the printing medium WP). The transport motor 341 is a servo motor that rotates the drive roller 7. The printing device 3 also includes a line scanner 17 (line camera). This line scanner 17 is disposed perpendicular to the transport direction X of the printing medium WP, and captures an image printed on the recording surface of the printing medium WP as it passes through an imaging position, for example, downstream of the printing unit 13, between the drying unit 15 and the discharge unit 4.

[0029] The printing device 3 further includes a control unit 39 that controls the entire device. The control unit 39 includes a calculation unit 391 and a storage unit 392. The calculation unit 391 is configured, for example, by a processor such as a central processing unit (CPU) or a field-programmable gate array (FPGA), and the storage unit 392 is configured by a storage device such as a hard disk drive (HDD) or a solid state drive (SSD). The calculation unit 391 controls the conveyance motor 341, the encoder 342, the line scanner 17, and the piezoelectric element 55, and the storage unit 392 stores a printing program 393 executed by the calculation unit 391. The printing program 393 is provided, for example, by a recording medium 399 provided separately from the control unit 39. The recording medium 399 records the printing program 393 so that it can be read by a computer (control unit 39). Examples of such a recording medium 399 include a universal serial bus (USB) memory, a memory card, or a storage device of an external server computer. The print program 393 defines the contents of the control to be executed by the control unit 39.

[0030] FIG. 4 is a diagram schematically showing the waveform of the ejection signal output to the piezoelectric element of the ejection head. In FIG. 4, the horizontal axis represents time, and the vertical axis represents voltage. As shown in FIG. 4, the ejection signal Sd is a voltage signal whose voltage changes over time. When the calculation unit 391 outputs the ejection signal Sd to the piezoelectric element 55, the piezoelectric element 55 varies the pressure applied to the ink in the cavity 53 in accordance with the change in voltage indicated by the ejection signal Sd. This pressure variation causes ink to be ejected from the nozzle 52 communicating with the cavity 53. The ejection signal Sd is output periodically in accordance with the transport speed of the printing medium WP.

[0031] More specifically, the calculation unit 391 calculates the speed at which the printing medium WP is transported based on the transport position of the printing medium WP detected by the encoder 342. Based on the transport speed of the printing medium WP calculated in this manner, the calculation unit 391 determines the period Cs (i.e., the time interval) at which the ejection signal Sd is output to the piezoelectric element 55. In other words, to allow ink to land on the printing medium WP at a constant resolution regardless of the transport speed of the printing medium WP, it is necessary to adjust the period Cs at which the ejection signal Sd is output according to the transport speed of the printing medium WP. Specifically, the calculation unit 391 shortens the period Cs of the ejection signal Sd as the transport speed of the printing medium WP increases, and lengthens the period Cs of the ejection signal Sd as the transport speed of the printing medium WP decreases. In other words, the period Cs is inversely proportional to the transport speed.

[0032] FIG. 5 is a diagram schematically illustrating the details of the ejection signal. In FIG. 5, the horizontal axis represents time, and the vertical axis represents voltage. The calculation unit 391 can apply multiple element signals Se(1), Se(2), and Se(3) shown in FIG. 5 to the piezoelectric element 55. Each of the element signals Se(1), Se(2), and Se(3) is a voltage signal whose voltage changes over time. The element signal Se(1) is applied between time Ts1 and time Ts2, the element signal Se(2) is applied between time Ts2 and time Ts3, and the element signal Se(3) is applied between time Ts3 and time Ts4. Here, time Ts1 corresponds to the start time of the cycle Cs, and times Ts1 to Ts4 are set so that the period from time Ts1 to time Ts4 is equal to or shorter than the cycle Cs.

[0033] The calculation unit 391 then generates multiple ejection signals Sd(s), Sd(m), and Sd(l) by changing the combination of the element signals Se(1), Se(2), and Se(3) that make up the ejection signal Sd. The ejection signal Sd(s) is an ejection signal Sd that is made up of one type of element signal Se(3), the ejection signal Sd(m) is an ejection signal Sd that is made up of two consecutive types of element signals Se(2) and Se(3), and the ejection signal Sd(l) is an ejection signal Sd that is made up of three consecutive types of element signals Se(1), Se(2), and Se(3). When the ejection signal Sd(s) is applied to the piezoelectric element 55, the piezoelectric element 55 ejects an S-sized ink droplet from the nozzle 52, when the ejection signal Sd(m) is applied to the piezoelectric element 55, the piezoelectric element 55 ejects an M-sized ink droplet, which is larger than the S size, from the nozzle 52, and when the ejection signal Sd(l) is applied to the piezoelectric element 55, the piezoelectric element 55 ejects an L-sized ink droplet, which is larger than the M size, from the nozzle 52. In other words, the calculation unit 391 can change the size (amount) of the ink droplet ejected from the nozzle 52 by switching the ejection signal Sd to be applied to the piezoelectric element 55 between the ejection signals Sd(s), S(m), and S(l).

[0034] In the ejection head 5 described above, residual vibration occurs as ink is ejected from the nozzles 52. This point will be explained using FIG. 6. FIG. 6 is a diagram schematically showing the residual vibration that occurs as ink is ejected in response to an ejection signal. In FIG. 6, the horizontal axis represents time, and the vertical axis represents the position of the meniscus. When ink is ejected from the nozzles 52, vibration occurs in the ink meniscus formed in the nozzles 52. The residual vibration of the meniscus that occurs as ink is ejected decays over time. Therefore, if the period Cs of the ejection signal Sd is longer than the decay time of the residual vibration, the residual vibration of the meniscus has no effect on the ejection of ink in response to the ejection signal Sd. On the other hand, if the period Cs of the ejection signal Sd is shorter than the decay time of the residual vibration of the meniscus, ink will be ejected in response to the ejection signal Sd while the meniscus is vibrating. In this case, if the residual vibration is in the opposite phase to the ejection signal Sd, the signal Sd is attenuated, the ink ejection speed drops significantly, and the ink landing position on the printing medium WP may be significantly shifted. In particular, the effect of the residual vibration depends on the size of the two ink droplets ejected in succession at the cycle Cs.

[0035] 7 is a table showing the relationship between the size of two ink droplets ejected in succession and the influence of residual vibration. In the figure, the leading ink droplet is the ink droplet that is ejected first of two ink droplets ejected in succession from the same nozzle 52, and the trailing ink droplet is the ink droplet that is ejected after the leading ink droplet. The influence of residual vibration noted here refers to the influence that residual vibration accompanying the ejection of the leading ink droplet has on the ejection of the trailing ink droplet.

[0036] As a general trend, the larger the size of the preceding ink droplet, the greater the impact of residual vibration on the ejection of the following ink droplet, and the larger the size of the following ink droplet, the greater the impact of residual vibration on the ejection of the following ink droplet. The reason for this latter trend is thought to be as follows: That is, as shown in Figure 5, the larger the ink droplet size, the earlier the ejection signal Sd starts. Therefore, the ejection signal Sd for the ejection of the following ink droplet is applied before the residual vibration associated with the ejection of the preceding ink droplet has sufficiently damped, thereby increasing the impact of the residual vibration.

[0037] Therefore, as shown in Figure 7, when the size of the preceding ink drop is small, the influence of residual vibration is small regardless of whether the size of the succeeding ink drop is small, medium, or large. When the size of the preceding ink drop is large and the size of the succeeding ink drop is small, the influence of residual vibration is small. When the size of the preceding ink drop is large and the size of the succeeding ink drop is small or large, the influence of residual vibration is medium. When the size of the preceding ink drop is large and the size of the succeeding ink drop is large or large, the influence of residual vibration is large.

[0038] Figure 8 is a diagram showing the relationship between the ejection signals when the leading ink droplet of two successively ejected ink droplets is an L-size droplet. In Figure 8, the horizontal axis represents time, and the vertical axis represents voltage. In the figure, the "LS" column shows the case where an L-size ink droplet is ejected followed by an S-size ink droplet, the "LM" column shows the case where an L-size ink droplet is ejected followed by an M-size ink droplet, and the "LL" column shows the case where an L-size ink droplet is ejected followed by an L-size ink droplet.

[0039] In these examples, the ejection signal Sd is applied at successive times T(1) and T(2) with a cycle Cs (in other words, periods T(1) and T(2) having a cycle Cs). In the example shown in the "LS" column, the ejection signal Sd(l) is applied at time T1, and the ejection signal Sd(s) is applied at time T2 after time T1. At this time, the ejection signal Sd(s) rises at time Ts3, so there is a time interval Δs between the rising edge of the preceding ejection signal Sd(l) and the rising edge of the following ejection signal Sd(s). In the example shown in the "LM" column, the ejection signal Sd(l) is applied at time T1, and the ejection signal Sd(m) is applied at time T2 after time T1. At this time, the ejection signal Sd(m) rises at time Ts2, so there is a time interval Δm between the rising edge of the preceding ejection signal Sd(l) and the rising edge of the following ejection signal Sd(m). In the example shown in the "LL" column, the ejection signal Sd(l) is applied at timing T1, and the ejection signal Sd(L) is applied at timing T2 after timing T1. In this case, the ejection signal Sd(l) rises at time Ts1, so there is a time interval Δl between the rising edge of the preceding ejection signal Sd(l) and the rising edge of the succeeding ejection signal Sd(l).

[0040] In this way, when two ejection signals Sd are applied with a cycle Cs, the larger the size of the ink droplet ejected by the subsequent ejection signal Sd, the shorter the time intervals Δs, Δm, and Δl between the two ejection signals Sd become, resulting in the tendency described in Figure 7.

[0041] Fig. 9 is a flowchart showing an example of image printing executed by a printing device, and Figs. 10A, 10B, and 10C are diagrams schematically showing an example of image processing executed according to the flowchart of Fig. 9. The flowchart of Fig. 9 is executed by calculation unit 391 based on printing program 393 in order to print a good image while suppressing the effects of the residual vibration described above.

[0042] 10A to 10C, the reference numerals N1, N2, N3, ... are used to indicate the nozzles 52 instead of the reference numeral 52. These nozzles N1, N2, N3, ... are provided at different positions in the Y direction and eject ink droplets based on image data Di. The image data Di is composed of a plurality of pixels P arranged two-dimensionally in the X and Y directions, and an image represented by the image data Di is printed on the printing medium WP by ejecting ink droplets from the nozzles N1, N2, N3, ... onto the pixels P that are virtually set on the printing medium WP. The pitch Ix at which the pixels P are arranged in the X direction corresponds to the resolution of the image data Di and is equivalent to the value obtained by multiplying the transport speed of the printing medium WP by the period Cs of the ejection signal Sd.

[0043] The multiple nozzles N1, N2, N3, ... face multiple pixel columns PL1, PL2, PL3, ... that are adjacent to each other in the Y direction. Each pixel column PL1, PL2, PL3, ... is composed of multiple pixels P arranged in a line in the X direction. The nozzles N1, N2, N3, ... eject ink droplets in synchronization with the transport of the printing medium WP in the X direction. As a result, the nozzles N1, N2, N3, ... eject ink droplets onto the multiple pixels P of the opposing pixel columns PL1, PL2, PL3, ... in order from the downstream side in the X direction (transport direction). In particular, the image data Di indicates, for each pixel P, the size (S, M, L) of the ink droplet to be ejected onto the pixel P, and the nozzles N1, N2, N3, ... eject ink droplets of the indicated size onto the pixel P.

[0044] The flowchart in Figure 9 corrects the image data Di by adjusting the ink droplet size set for each pixel P of the image data Di so as to suppress the effects of the residual vibrations. Specifically, a thinning process is performed to reduce the size of subsequent ink droplets associated with the ink droplet combinations that are significantly affected by the residual vibrations shown in Figure 7 to zero. Note that each of the ink droplet size combinations that are significantly affected by the residual vibrations will be referred to as a "thinning standard" below. This thinning standard is pre-stored in the storage unit 392.

[0045] 9 starts, the calculation unit 391 acquires image data Di (step S101). At this time, the calculation unit 391 may acquire image data Di by receiving image data Di generated by an external computer, or may acquire image data Di by generating image data Di based on print data received from an external computer. In step S102, the calculation unit 391 sets the count value Cp of pixel P (i.e., the value that identifies pixel P) to zero, and in step S103, the calculation unit 391 increments the count value Cp of pixel P by "1".

[0046] In step S104, the calculation unit 391 checks whether there is a preceding pixel P onto which an ink droplet is ejected prior to the pixel P (target pixel) with the count value Cp. Specifically, the calculation unit 391 checks whether there is a pixel P (preceding pixel) adjacent to the target pixel P with the count value Cp downstream in the X direction (toward the arrow). For example, if the target pixel P is located at the edge of the image and no corresponding preceding pixel P exists ("NO" in step S104), the calculation unit 391 returns to step S103 and increments the count value Cp of the pixel P by 1.

[0047] If the corresponding preceding pixel P exists (YES in step S104), the calculation unit 391 determines whether the preceding pixel P and the target pixel P satisfy the thinning criteria. The leading ink droplet size is L and the trailing ink droplet size is M The size of the leading ink droplet is L size, and the size of the trailing ink droplet is L size If none of these thinning criteria are met (NO in step S105), the size of the ink droplet to be ejected onto the target pixel P is not changed and the process returns to step S103.

[0048] On the other hand, if any of these thinning criteria is met (YES in step S105), the process proceeds to step S106. Here, specific examples in which the thinning criteria are met will be described based on the "Image Data" columns in each of Figures 10A to 10C.

[0049] 10A is the target pixel Pt, the pixel P adjacent to the target pixel Pt on the downstream side in the X direction is the preceding pixel Pa. In this example, the size of the ink droplet to be ejected onto the preceding pixel Pa is L, and the size of the ink droplet to be ejected onto the target pixel Pt is M, so the thinning criteria are met.

[0050] 10B, if the pixel P enclosed by the solid-line rectangle is the target pixel Pt, the pixel P adjacent to the target pixel Pt on the downstream side in the X direction is the preceding pixel Pa. In this example, the size of the ink droplet to be ejected onto the preceding pixel Pa is L, and the size of the ink droplet to be ejected onto the target pixel Pt is also L, so the thinning criteria are met.

[0051] 10C, if the pixel P enclosed by the solid-line rectangle is the target pixel Pt, the pixel P adjacent to the target pixel Pt on the downstream side in the X direction is the preceding pixel Pa. In this example, the size of the ink droplet to be ejected onto the preceding pixel Pa is L, and the size of the ink droplet to be ejected onto the target pixel Pt is M, so the thinning criteria are met.

[0052] In the thinning process of step S106, the size of the ink droplets at the target pixel Pt is set to zero. Setting the size of the ink droplets to zero here corresponds to not ejecting ink droplets from the nozzle that was originally scheduled to eject those ink droplets. This thinning process will be described in detail with reference to FIGS. 10A to 10C. In the "thinning process" example of FIG. 10A, the size of the ink droplets to be ejected at the target pixel Pt is changed from medium size to zero. In the "thinning process" example of FIG. 10B, the size of the ink droplets to be ejected at the target pixel Pt is changed from large size to zero. In the "thinning process" example of FIG. 10C, the size of the ink droplets to be ejected at the target pixel Pt is changed from medium size to zero.

[0053] In step S107, for the purpose of subsequent interpolation processing, the calculation unit 391 stores the pixels Pt that have been subjected to the thinning processing as thinned pixels Pd in ​​the storage unit 392. Then, steps S103 to S107 are repeatedly executed until the count value Cp of the pixels P reaches the maximum value Cpx (the total number of pixels P that make up the image data Di) (until step S108 becomes "YES").

[0054] When the count value Cp of pixel P reaches the maximum value Cpx ("YES" in step S108), the count value Cd for counting the thinned pixels Pd (i.e., the value for identifying the thinned pixels Pd) is set to zero (step S109), and the count value Cd for the thinned pixels Pd is incremented by "1" (step S110).

[0055] In step S111, a compensation process is performed to make up for the lack of ink volume caused by setting the ink droplet size for the thinned pixel Pd to zero. This compensation process increases the size of the ink droplet to be ejected for the adjacent pixel Pj that is adjacent in the Y direction to the thinned pixel Pd with the count value Cd. For example, if the size of the ink droplet to be ejected for the adjacent pixel Pj is S size, it is increased to M size, and if that size is M size, it is increased to L size. Note that if the size is L size, there is no larger size, so the size is not increased. This compensation process is specifically shown using Figures 10A to 10C.

[0056] In the example of the "complementation process" in Figure 10A, the size of the ink droplets to be ejected onto the adjacent pixel Pj adjacent to the thinned pixel Pd on one side (right side) of the Y direction is increased from size S to size M, and the size of the ink droplets to be ejected onto the adjacent pixel Pj adjacent to the thinned pixel Pd on the other side (left side) of the Y direction is increased from zero to size S.

[0057] In the example of the "complementation process" in Figure 10B, the size of the ink droplets to be ejected onto the adjacent pixel Pj adjacent to the thinned pixel Pd on one side (right side) of the Y direction is increased from zero to size S, and the size of the ink droplets to be ejected onto the adjacent pixel Pj adjacent to the thinned pixel Pd on the other side (left side) of the Y direction is increased from size M to size L.

[0058] 10C, the size of the ink droplet to be ejected onto the adjacent pixel Pj adjacent to the thinned pixel Pd on one side (right side) in the Y direction is increased from size M to size L. Note that the thinned pixel Pd is located at the end on the other side in the Y direction, so there is no adjacent pixel Pj adjacent to the thinned pixel Pd on the other side (left side) in the Y direction.

[0059] Steps S110 to S111 are then repeated until the count value Cd of the thinned-out pixels Pd reaches the maximum value Cdx (the total number of thinned-out pixels Pd stored in step S107) (until step S112 becomes "YES").

[0060] When the count value Cd of the thinned pixels Pd reaches the maximum value Cdx ("YES" in step S112), the calculation unit 391 stores the image data Di that has been subjected to the thinning process and the interpolation process as dot data Dd in the storage unit 392 (step S113). Then, in step S114, the calculation unit 391 causes the nozzles N1, N2, N3, ... to eject ink droplets of the size indicated in the dot data Dd, thereby printing the image indicated by the image data Di on the printing medium WP.

[0061] In the embodiment described above, the size of the ink droplet to be ejected onto each pixel P, as defined by the image data Di (ejection data), is corrected. Specifically, the size (amount) of the ink droplet to be ejected onto the target pixel Pt from the nozzle 52 is corrected based on a comparison between the size (first ejection condition) of the ink droplet to be ejected from the nozzle 52 onto the preceding pixel Pa at timing T1 (first timing) and the size (second ejection condition) of the ink droplet to be ejected from the nozzle 52 onto the target pixel Pt at timing T2 (second timing) (steps S105 and S106). In this way, it is possible to deal with situations in which it is determined that the influence of residual vibration will be significant, based on the sizes of the ink droplets onto the preceding pixel Pa and the target pixel Pt indicated by the image data Di. As a result, it is possible to suppress the influence of residual ink vibration accompanying the ejection of ink droplets from the nozzle 52, thereby achieving good printing.

[0062] The control unit 39 also stores in the storage unit 392 a thinning criterion (reduction criterion) for reducing the size of the ink droplets ejected from the nozzles 52 to the target pixel Pt at time T2 from the size indicated by the image data Di. If the combination of the ink droplet sizes for the preceding pixel Pa and the target pixel Pt indicated by the image data Di (in other words, the comparison result) satisfies the thinning criterion ("YES" in step S105), the control unit 39 determines in step S106 to reduce the size of the ink droplets ejected from the nozzles 52 at time T2 (thinning process). With this configuration, a situation in which the influence of residual vibration is determined to be significant based on the ink droplet sizes for the preceding pixel Pa and the target pixel Pt indicated by the image data Di can be addressed by reducing the size of the ink droplets ejected from the nozzles 52 at time T2. As a result, the influence of residual vibration of the ink accompanying the ejection of ink droplets from the nozzles 52 is suppressed, enabling good printing.

[0063] Furthermore, if the combination of ink droplet sizes for the preceding pixel Pa and the target pixel Pt indicated by the image data Di satisfies the thinning criteria (if "YES" in step S105), the control unit 39 determines that the size of the ink droplets ejected from the nozzles 52 at timing T2 should be zero (thinning process). With this configuration, a situation in which it is determined that the influence of residual vibrations will be significant based on the sizes of the ink droplets for the preceding pixel Pa and the target pixel Pt indicated by the image data Di is large can be addressed by setting the size of the ink droplets ejected from the nozzles 52 at timing T2 to zero. As a result, it is possible to suppress the influence of residual vibrations in the ink that accompany the ejection of ink droplets from the nozzles 52, thereby achieving good printing.

[0064] The ejection head 5 is provided with multiple nozzles N1, N2, N3, etc., which eject ink droplets at different positions in the Y direction. Meanwhile, if the control unit 39 determines to reduce the size of the ink droplets ejected by nozzle N2 at timing T2 during the thinning process, it increases the size of the ink droplets ejected from nozzles N1 and N3 (adjacent nozzles) facing the adjacent pixel Pj adjacent to the target pixel Pt in the Y direction onto the adjacent pixel Pj (complementary process) from the size indicated by the image data Di. In other words, reducing the size of the ink droplets ejected by nozzle N2 at timing T2 to suppress the effects of residual vibrations may result in an insufficient amount of ink droplets adhering to the area including the target pixel Pt. In response to this, increasing the size of the ink droplets ejected from nozzles N1 and N3 onto the adjacent pixel Pj of the target pixel Pt compensates for the insufficient amount of ink droplets, enabling printing of a good image.

[0065] Next, a first modified example of image printing will be described using Figures 11A and 11B. Figures 11A and 11B are diagrams showing, in table format, the relationship between the size of two successively ejected ink droplets and the effect of residual vibration, and in particular the relationship between the cycle Cs at which the ejection signal Sd is output and the effect of residual vibration. That is, as can be seen from the above explanation using Figure 8, the shorter the cycle Cs of the ejection signal Sd, the shorter the time interval between the ejection signal Sd ejected at timing T1 and the ejection signal Sd ejected at timing T2, and the greater the effect of residual vibration tends to be.

[0066] Therefore, the influence of residual vibration when the period Cs is less than the predetermined period (FIG. 11A) is greater than the influence of residual vibration when the period Cs is equal to or greater than the predetermined period (FIG. 11B). As a result, while the influence of residual vibration shown in FIG. 11A is the same as that in FIG. 7, in FIG. 11B, there is no combination of ink droplet sizes that causes a large influence of residual vibration; in other words, there is no combination of ink droplet sizes that requires thinning processing.

[0067] Therefore, in the first modified example of image printing, before step S105 in the flowchart of Fig. 9, it is determined whether the period Cs of the ejection signal Sd is less than a threshold period corresponding to a predetermined period. If the period Cs is equal to or greater than the threshold period, steps S105 to S107 are not executed and the process proceeds to step S108. On the other hand, if the period Cs is less than the threshold period, steps S105 to S107 are executed.

[0068] In this first modified example, one threshold period is set for the period Cs of the ejection signal Sd. However, it is expected that in areas where the period Cs is even shorter, the number of combinations of ink droplet sizes that are more affected by residual vibrations will increase. In such cases, a threshold period may be set at the boundary where the number of combinations changes as the period Cs changes, and the thinning standard (i.e., the combinations of ink droplet sizes that are more affected by residual vibrations) may be changed based on a comparison between the period Cs and the threshold period.

[0069] In this way, in the first modified example, the control unit 39 determines the size of the ink droplet to be ejected from the nozzle 52 at time T2 based on the combination of ink droplet sizes for the preceding pixel Pa and the target pixel Pt indicated by the image data Di and the period Cs of the ejection signal Sd (in other words, the time interval between times T1 and T2) (steps S105 to S107). This configuration makes it possible to perform good printing by accurately responding to the effects of residual vibrations that change depending on the period Cs of the ejection signal Sd.

[0070] Next, a second variation of image printing will be described using Figures 12A and 12B. Figures 12A and 12B are diagrams showing, in table format, the relationship between the size of two successively ejected ink droplets and the effect of residual vibration, and in particular the relationship between the ink temperature and the effect of residual vibration. In other words, the lower the temperature of the ink inside the ejection head 5, the higher the viscosity of the ink, and therefore the smaller the effect of residual vibration tends to be.

[0071] Therefore, the effect of residual vibration when the ink temperature is equal to or higher than a predetermined temperature (FIG. 12A) is greater than the effect of residual vibration when the ink temperature is lower than the predetermined temperature (FIG. 12B). As a result, while the effect of residual vibration shown in FIG. 12A is the same as that in FIG. 7, in FIG. 12B, there are no combinations of ink droplet sizes that result in a large effect of residual vibration; in other words, there are no combinations of ink droplet sizes that require thinning processing.

[0072] Therefore, in the second modified example of image printing, before step S105 in the flowchart of Fig. 9, it is determined whether the ink temperature is equal to or higher than a threshold temperature corresponding to a predetermined temperature. The calculation unit 391 can confirm the ink temperature by, for example, obtaining a detection value from a thermometer provided in the ink supply chamber 54 of the ejection head 5. If the ink temperature is below the threshold temperature, the process proceeds to step S108 without executing steps S105 to S107. On the other hand, if the ink temperature is equal to or higher than the threshold temperature, steps S105 to S107 are executed.

[0073] In this second modification, one threshold temperature is set for the ink temperature. However, it is expected that in areas where the ink temperature is even higher, the number of combinations of ink droplet sizes that are more affected by residual vibrations will increase. In such cases, a threshold temperature may be set at the boundary where the number of combinations changes depending on the ink temperature, and the thinning standard (i.e., the combinations of ink droplet sizes that are more affected by residual vibrations) may be changed depending on a comparison between the period Cs and the threshold temperature.

[0074] In this way, in the second modified example, the control unit 39 determines the size of the ink droplet to be ejected from the nozzle 52 at timing T2 based on the combination of the ink droplet sizes for the preceding pixel Pa and the target pixel Pt indicated by the image data Di, and the ink temperature (steps S105 to S107). This configuration makes it possible to perform good printing by accurately dealing with the effects of residual vibrations that change depending on the ink temperature.

[0075] In the embodiment described above, the printing device 3 corresponds to an example of the "printing device" of the present invention, the control unit 39 corresponds to an example of the "control unit" or "computer" of the present invention, the printing program 393 corresponds to an example of the "printing program" of the present invention, the recording medium 399 corresponds to an example of the "recording medium" of the present invention, the ejection head 5 corresponds to an example of the "ejection head" of the present invention, the nozzles 52, N1, N2, N3, ... correspond to an example of the "nozzle" of the present invention, the nozzles N1 and N3 correspond to an example of the "adjacent nozzle" of the present invention, the image data Di corresponds to an example of the "ejection data" of the present invention, the pixel P corresponds to an example of the pixel of the present invention, and the target pixel Pt corresponds to an example of the "target pixel" of the present invention. the adjacent pixel Pj corresponds to an example of the "adjacent pixel" of the present invention, timing T1 corresponds to an example of the "first timing" of the present invention, timing T2 corresponds to an example of the "second timing" of the present invention, steps S105 to S106 correspond to an example of the "determination process" of the present invention, the size (amount) of the ink droplets corresponds to an example of the "ejection condition" of the present invention, the size of the ink droplets ejected at timing T1 corresponds to an example of the "first ejection condition" of the present invention, the size of the ink droplets ejected at timing T2 corresponds to an example of the "second ejection condition" of the present invention, the thinning criterion corresponds to an example of the "reduction criterion" of the present invention, and the period Cs corresponds to an example of the "time according to resolution" of the present invention.

[0076] The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention. For example, a third modification may be implemented by combining the first and second modifications of image printing.

[0077] In the third modified example of image printing, even if the period Cs of the ejection signal Sd is equal to or greater than the threshold period, if the ink temperature is equal to or greater than the threshold temperature, steps S105 to S107 are executed using a combination of ink droplet sizes that are significantly affected by residual vibration in Fig. 7 as the thinning criterion. Also, even if the ink temperature is below the threshold temperature, if the period Cs of the ejection signal Sd is less than the threshold period, steps S105 to S107 are executed using a combination of ink droplet sizes that are significantly affected by residual vibration in Fig. 7 as the thinning criterion. Furthermore, if the ink temperature is equal to or greater than the threshold temperature and the period Cs of the ejection signal Sd is less than the threshold period, steps S105 to S107 are executed using a combination of ink droplet sizes that are significantly affected by residual vibration in Fig. 7 as the thinning criterion. Conversely, if the ink temperature is below the threshold temperature and the period Cs of the ejection signal Sd is equal to or greater than the threshold period, steps S105 to S107 are not executed and the process proceeds to step S108.

[0078] Furthermore, the combination of the first and second modified image printing examples is not limited to this example, and can also be combined as in the following fourth modified example. In this fourth modified example, a table that quantifies the degree of influence (small, medium, large) of residual vibration shown in FIGS. 11A, 11B, 12A, and 12B is prepared as a thinning standard. This table is prepared for each of FIGS. 11A, 11B, 12A, and 12B. Then, a numerical value (period reference numerical value) corresponding to the combination of ink droplet sizes and the period Cs of the ejection signal Sd is determined based on the table (the table corresponding to FIG. 11A or 11B). Similarly, a numerical value (temperature reference numerical value) corresponding to the combination of ink droplet sizes and the ink temperature is determined based on the table (the table corresponding to FIG. 12A or 12B). If the product (or sum) of the period reference value and the temperature reference value is less than a predetermined threshold, the process proceeds to step S108 without executing steps S105 to S107, and if the product (or sum) of the period reference value and the temperature reference value is greater than or equal to the predetermined threshold, the process executes steps S105 to S107.

[0079] Alternatively, in order to execute the image printing of Fig. 9, the configuration shown in Fig. 13 may be configured in the calculation unit 391. Fig. 13 is a block diagram showing the electrical configuration for executing image printing. Each of the functional units U1 to U6 in Fig. 13 is configured in the calculation unit 391 as the printing program 393 is executed.

[0080] The layout processing unit U1 places an image represented by print data received from, for example, an external computer on the print medium WP. The print data is data that indicates the gradation value of each pixel that makes up the image, for example, in 256 stages. This layout processing unit U1 determines the area of ​​the print medium WP on which the image is to be printed and also determines the correspondence between the pixels that make up the image and the nozzles 52. The tone correction unit U2 adjusts the color tone of the image data Di for the print data output from the layout processing unit U1, for example, by gamma correction, and the shading correction unit U3 performs shading correction on the print data whose color tone has been adjusted by the tone correction unit U2.

[0081] In this way, the image data Di described above is generated. The vibration influence determination unit U4 executes step S105 in Fig. 9 to determine whether the thinning criteria are met. In this example, the image data Di is data indicating the gradation values ​​of each pixel P that constitutes the image, and is not data that directly indicates the size of the ink droplets to be ejected onto each pixel P. In contrast, the vibration influence determination unit U4 has a table that indicates the correspondence between gradation values ​​and ink droplet sizes, and checks the size of the ink droplets to be ejected onto each pixel P based on this table.

[0082] Then, for the ink droplet size of a pixel P that the vibration influence determination unit U4 determines satisfies the thinning criterion, the thinning complement processing unit U5 executes steps S106, S107, and S109 to S112. The ink droplet sizes that have undergone each process by the thinning complement processing unit U5 are output to the shading processing unit U6. On the other hand, the ink droplet sizes of a pixel P that the vibration influence determination unit U4 determines does not satisfy the thinning criterion are output from the vibration influence determination unit U4 to the shading processing unit U6 without going through the thinning complement processing unit U5.

[0083] In this way, the dot data Dd is input to the shader processor U6. This shader processor U6 performs shader processing on the dot data Dd to generate raster data. The calculation unit 391 then controls the ejection of ink droplets from the nozzles 52 based on the raster data, thereby printing an image on the print medium WP.

[0084] Furthermore, the specific aspect of the interpolation processing in step S111 of Fig. 9 may be modified as follows. Fig. 14A is a diagram showing a mask used in a first modified example of the interpolation processing, and Fig. 14B is a diagram showing image processing executed in the first modified example of the interpolation processing. The mask in Fig. 14A distributes the gradation value of a thinned-out pixel Pd to pixels Pj1, Pj2, and Pj3 adjacent to the thinned-out pixel Pd in ​​the Y direction. Here, with respect to a pitch Iy at which the pixels P are arranged in the Y direction, the adjacent pixel Pj1 (primary adjacent pixel) and the thinned-out pixel Pd are arranged at one pitch Iy, the adjacent pixel Pj2 (secondary adjacent pixel) and the thinned-out pixel Pd are arranged at twice the pitch Iy, and the adjacent pixel Pj3 (tertiary adjacent pixel) and the thinned-out pixel Pd are arranged at three times the pitch Iy.

[0085] The numerical values ​​in the bar graphs corresponding to adjacent pixels Pj1, Pj2, and Pj3 indicate the ratio of the gradation value Vd of the thinned pixel Pd (i.e., the gradation value set for the thinned pixel Pd before the thinning process) to be distributed to the adjacent pixels Pj1, Pj2, and Pj3. The numerical value of each of the adjacent pixels Pj1, Pj2, and Pj3 is 70 (=20+20+10+10+5+5). Therefore, the gradation value Vd×20 / 70 is distributed to adjacent pixel Pj1, the gradation value Vd×10 / 70 is distributed to adjacent pixel Pj2, and the gradation value Vd×5 / 70 is distributed to adjacent pixel Pj3.

[0086] As shown in the "Image Data" column of FIG. 14B, the results of determining the gradation values ​​to be distributed based on the mask of FIG. 14A for image data Di with a gradation value Vd of 48 are shown in the "Determined Distribution Value" column of FIG. 14B. As shown in this column, 14, 7, and 3 are distributed as additional values ​​to adjacent pixels Pj1, Pj2, and Pj3, respectively. The "Distribution Result" column of FIG. 14B shows the results of adding the additional value to each gradation value for adjacent pixels Pj1, Pj2, and Pj3. In this column, the values ​​shown in the open bars are the gradation values ​​of adjacent pixels Pj1, Pj2, and Pj3, and the values ​​shown in the hatched bars are the distributed and added values. Note that, as in the above-described embodiment, the gradation value of the thinned pixel Pd is set to zero.

[0087] Furthermore, modifications other than those described above can be made as appropriate. For example, in printing the image in Figure 9, steps S102 to S112 (thinning and interpolation processes) do not need to be performed on all pixels P that make up the image data Di. For example, the distribution of dots (ink droplets) in the image data Di may be confirmed, and steps S102 to S112 may be performed only in an area where the dots are concentrated.

[0088] Furthermore, the above-described supplementary processing is not essential, and if the shortage of ink amount due to the thinning processing is not significant, the supplementary processing does not have to be performed.

[0089] Furthermore, in the above embodiment, a combination of ink droplet sizes that is significantly affected by residual vibration is used as the thinning criterion. However, specific examples of the thinning criterion are not limited to this. In other words, a combination of ink droplet sizes that is significantly affected by residual vibration may be used as the thinning criterion.

[0090] Furthermore, in the thinning process (step S106), it is not necessary to set the ink size of the thinned pixels Pd to zero, but it is sufficient to reduce the ink size. The ink size can be reduced by, for example, reducing the ink size by one level.

[0091] Furthermore, specific examples of the "ejection conditions" of the present invention are not limited to the size (amount) of ink droplets. For example, if the influence of residual vibration becomes significant due to a combination of other conditions for ejecting ink at timing T1 and other conditions for ejecting ink at timing T2, the other conditions may be used instead of the size of the ink droplets.

[0092] Furthermore, the specific waveforms of the ejection signals Sd(s), Sd(m), and Sd(s) are not limited to the example in Figure 5. Furthermore, the types of ejection signals Sd are not limited to three types. For example, if the ink size is changed in four or more stages, the corresponding types of ejection signals Sd may be used.

[0093] Furthermore, the method of ejecting ink is not limited to the method using the piezoelectric element 55 described above.

[0094] Furthermore, the specific mechanism for moving the printing medium WP relative to the ejection head 5 is not limited to the above example. That is, instead of transporting the printing medium WP by the drive roller 7, the plurality of transport rollers 9, and the drive roller 11, the ejection head 5 may be moved by a carriage.

[0095] Furthermore, although the material of the printing medium WP described above is continuous paper, it is not limited to this and may be, for example, sheet paper. Furthermore, the material of the printing medium is not necessarily limited to paper and may be, for example, OPP (oriented polypropylene) or PET (polyethylene A film of acrylic acid terephthalate or the like may also be used. [Industrial Applicability]

[0096] The present invention is applicable to all inkjet technologies that control the amount of ink droplets ejected from a nozzle. [Explanation of symbols]

[0097] 3...Printing device 39...Control unit (computer) 393...Printing Program 399...Recording media 5...Discharge head 52...Nozzle N1...Nozzle (adjacent nozzle) N2…Nozzle N3...Nozzle (adjacent nozzle) Di...Image data (ejection data) P...pixel Pt: Target pixel Pj: adjacent pixel T1...Timing (first timing) T2...Timing (second timing) S105 to S106: Steps (decision processing)

Claims

1. an ejection head that ejects ink droplets from nozzles; a control unit that controls the ejection of ink droplets from the nozzles based on ejection data that indicates ejection conditions when the ink droplets are ejected from the nozzles onto target pixels that the nozzles face among pixels that are arranged at a pitch corresponding to the resolution; Equipped with the control unit executes a determination process to determine the amount of ink droplets to be ejected from the nozzle at the second timing based on a comparison between a first ejection condition, which is the ejection condition when the nozzle ejects droplets at the first timing, and a second ejection condition, which is the ejection condition when the nozzle ejects droplets at the second timing after a time corresponding to the resolution has elapsed since the first timing; the control unit stores a first reduction standard and a second reduction standard for reducing the amount of ink droplets ejected from the nozzle to the target pixel at the second timing from the amount indicated by the ejection data, and when a comparison result between the first ejection condition and the second ejection condition satisfies one of the first reduction standard and the second reduction standard, determines in the determination process to reduce the amount of ink droplets ejected from the nozzle at the second timing; the ejection data indicates, as the ejection condition, an ink droplet size selected from an S size, an M size larger than the S size, and an L size larger than the M size; the first reduction criterion is that the size of the ink droplets ejected at the first timing is L size and the size of the ink droplets ejected at the second timing is M size; A printing apparatus in which the second reduction criterion is a criterion that the size of the ink droplets ejected at the first timing is L size and the size of the ink droplets ejected at the second timing is L size.

2. 2. A printing device as described in claim 1, wherein the control unit determines in the determination process that if the result of comparing the first ejection condition with the second ejection condition satisfies one of the first reduction criterion and the second reduction criterion, the amount of ink droplets ejected by the nozzle at the second timing will be set to zero.

3. An ejection head that ejects ink droplets from nozzles; a control unit that controls the ejection of ink droplets from the nozzles based on ejection data that indicates ejection conditions when the ink droplets are ejected from the nozzles onto target pixels that the nozzles face among pixels that are arranged at a pitch corresponding to the resolution; Equipped with the control unit executes a determination process to determine the amount of ink droplets to be ejected from the nozzle at the second timing based on a comparison between a first ejection condition, which is the ejection condition when the nozzle ejects droplets at the first timing, and a second ejection condition, which is the ejection condition when the nozzle ejects droplets at the second timing after a time corresponding to the resolution has elapsed since the first timing; the control unit stores a reduction standard for reducing the amount of ink droplets ejected from the nozzles to the target pixels at the second timing from the amount indicated by the ejection data, and when a comparison result between the first ejection condition and the second ejection condition satisfies the reduction standard, determines in the determination process to reduce the amount of ink droplets ejected from the nozzles at the second timing; the ejection head is provided with a plurality of nozzles including the nozzle, and the plurality of nozzles eject ink droplets at different positions from each other; When the control unit determines in the determination process to reduce the amount of ink droplets ejected by the nozzle at the second timing, the control unit increases the amount of ink droplets ejected from an adjacent nozzle among the plurality of nozzles that faces the adjacent pixel, which is the pixel adjacent to the target pixel, onto the adjacent pixel from the amount indicated by the ejection data.

4. 4. The printing apparatus according to claim 1, wherein the ejection condition indicates an amount of ink droplets to be ejected from the nozzle onto the target pixel.

5. An ejection head that ejects ink droplets from nozzles; a control unit that controls the ejection of ink droplets from the nozzles based on ejection data that indicates ejection conditions when the ink droplets are ejected from the nozzles onto target pixels that the nozzles face among pixels that are arranged at a pitch corresponding to the resolution; Equipped with the control unit executes a determination process to determine the amount of ink droplets to be ejected from the nozzle at the second timing based on a comparison between a first ejection condition, which is the ejection condition when the nozzle ejects droplets at the first timing, and a second ejection condition, which is the ejection condition when the nozzle ejects droplets at the second timing after a time corresponding to the resolution has elapsed since the first timing; In the determination process, the control unit determines the amount of ink droplets to be ejected from the nozzle at the second timing based on a comparison between the first ejection condition and the second ejection condition and the time interval between the first timing and the second timing.

6. A printing device as described in Claim 5, wherein the shorter the time interval between the first timing and the second timing, the smaller the amount of ink droplets ejected by the nozzle at the second timing.

7. An ejection head that ejects ink droplets from a nozzle; a control unit that controls the ejection of ink droplets from the nozzles based on ejection data that indicates ejection conditions when the ink droplets are ejected from the nozzles onto target pixels that the nozzles face among pixels that are arranged at a pitch corresponding to the resolution; Equipped with the control unit executes a determination process to determine the amount of ink droplets to be ejected from the nozzle at the second timing based on a comparison between a first ejection condition, which is the ejection condition when the nozzle ejects droplets at the first timing, and a second ejection condition, which is the ejection condition when the nozzle ejects droplets at the second timing after a time corresponding to the resolution has elapsed since the first timing; A printing device in which the control unit, in the determination process, determines the amount of ink droplets to be ejected by the nozzle at the second timing based on a comparison between the first ejection condition and the second ejection condition and the temperature of the ink.

8. a step of acquiring ejection data indicating ejection conditions when an ink droplet is ejected from a nozzle onto a target pixel that faces the nozzle among pixels arranged at a pitch corresponding to the resolution; a step of executing a determination process for determining the amount of ink droplets to be ejected from the nozzle at the second timing based on a comparison between a first ejection condition, which is the ejection condition when the nozzle ejects droplets at the first timing, and a second ejection condition, which is the ejection condition when the nozzle ejects droplets at the second timing after a time corresponding to the resolution has elapsed since the first timing; Equipped with the control unit stores a first reduction standard and a second reduction standard for reducing the amount of ink droplets ejected from the nozzle to the target pixel at the second timing from the amount indicated by the ejection data, and when a comparison result between the first ejection condition and the second ejection condition satisfies one of the first reduction standard and the second reduction standard, determines in the determination process to reduce the amount of ink droplets ejected from the nozzle at the second timing; the ejection data indicates, as the ejection condition, an ink droplet size selected from an S size, an M size larger than the S size, and an L size larger than the M size; the first reduction criterion is that the size of the ink droplets ejected at the first timing is L size and the size of the ink droplets ejected at the second timing is M size; The printing method, wherein the second reduction criterion is that the size of the ink droplets ejected at the first timing is L size, and the size of the ink droplets ejected at the second timing is L size.

9. a step of acquiring ejection data indicating ejection conditions when an ink droplet is ejected from a nozzle onto a target pixel that faces the nozzle among pixels arranged at a pitch corresponding to the resolution; a step of executing a determination process for determining the amount of ink droplets to be ejected from the nozzle at the second timing based on a comparison between a first ejection condition, which is the ejection condition when the nozzle ejects droplets at the first timing, and a second ejection condition, which is the ejection condition when the nozzle ejects droplets at the second timing after a time corresponding to the resolution has elapsed since the first timing; The computer executes the following. the computer stores a first reduction standard and a second reduction standard for reducing the amount of ink droplets ejected from the nozzle to the target pixel at the second timing from the amount indicated by the ejection data, and when a comparison result between the first ejection condition and the second ejection condition satisfies one of the first reduction standard and the second reduction standard, determines in the determination process to reduce the amount of ink droplets ejected from the nozzle at the second timing; the ejection data indicates, as the ejection condition, an ink droplet size selected from an S size, an M size larger than the S size, and an L size larger than the M size; the first reduction criterion is that the size of the ink droplets ejected at the first timing is L size and the size of the ink droplets ejected at the second timing is M size; The second reduction criterion is a criterion that the size of the ink droplets ejected at the first timing is L size, and the size of the ink droplets ejected at the second timing is L size.

10. 10. A recording medium for recording the printing program according to claim 9 in a computer-readable manner.

Images