Patent Application
20240308234
This invention relates to inkjet technology that controls the amount of ink droplet ejected from nozzles.
There is a known printing apparatus that prints an image on a printing medium by making ink droplet ejected from nozzles of an inkjet printhead land on the printing medium. As shown in Patent Literatures 1 and 2, such a printing apparatus can express the gradation of an image by adjusting the amount of ink droplet ejected from the nozzle in four steps: zero, small (S), medium (M), and large (L), for example.
[Patent Literature 1] JP2008-126453
[Patent Literature 2] JP2012-045836
[Patent Literature 2] JP2001-277484
By the way, at the nozzle that ejects ink by the inkjet method, the ink meniscus formed at the nozzle vibrates as the ink is ejected, as shown in Patent Literature 3. That is, there is a residual vibration in the ink meniscus until a predetermined decay time has elapsed from the ink ejection. Therefore, if the residual vibration caused by the earlier ink droplet ejection affects the ejection of the later ink droplet, the ejection of the later ink droplet cannot be performed well. In particular, as described below, depending on the relationship between the ejection conditions (e.g., ink droplet volume) of the earlier ink droplet and those of the later ink droplet, the effect of residual vibration on the ejection of the later ink droplet may become significant.
The present invention is intended to solve the above-described problem, and it is an object of the present invention to enable good printing by suppressing the effects of residual vibrations of ink caused by ink droplet ejection from nozzles.
A printing apparatus according to the invention, comprises: an ejection head ejecting an ink droplet from a nozzle; and a control unit that controls the ejection of an ink droplet from the nozzle based on ejection data indicating ejection condition for ejecting an ink droplet from the nozzle to a target pixel to which the nozzle faces among pixels arranged at a pitch corresponding to a resolution, wherein the control unit performs a decision process to determine an amount of an ink droplet ejected by the nozzle at a second timing based on a comparison of a first ejection condition, which is the ejection condition when the nozzle ejects a droplet at a first timing, and a second ejection condition, which is the ejection condition when the nozzle ejects a droplet at the second timing after the time corresponding to the resolution has elapsed from the first timing.
A printing method according to the invention, comprises: step of acquiring an ejection data indicating an ejection condition for ejecting an ink droplet from a nozzle to a target pixel facing a nozzle among pixels arranged at a pitch corresponding to a resolution; and step of performing a decision process to determine an amount of an ink droplet ejected by the nozzle at a second timing based on a comparison of a first ejection condition, which is the ejection condition when the nozzle ejects a droplet at a first timing, and a second ejection condition, which is the ejection condition when the nozzle ejects a droplet at the second timing after the time corresponding to the resolution has elapsed from the first timing.
A Printing Program according to the invention causes a computer to execute following: step of acquiring an ejection data indicating an ejection condition for ejecting an ink droplet from a nozzle to a target pixel facing a nozzle among pixels arranged at a pitch corresponding to a resolution; and step of performing a decision process to determine an amount of an ink droplet ejected by the nozzle at a second timing based on a comparison of a first ejection condition, which is the ejection condition when the nozzle ejects a droplet at a first timing, and a second ejection condition, which is the ejection condition when the nozzle ejects a droplet at the second timing after the time corresponding to the resolution has elapsed from the first timing.
A recording medium according to the invention records the above printing program in a computer-readable manner.
That is, if ink solution is ejected continuously at the first and second timings, the residual vibration caused by an ejection of ink droplet at the first timing may affect an ejection of ink droplet at the second timing. In particular, as described below, depending on the relationship between the ejection conditions of the ink solution (first and second ejection conditions) at each of the first and second timings, the effect of such residual vibration could be significant.
In contrast, the invention (printing apparatus, printing method, printing program and recording medium) determines an amount of an ink droplet that is ejected by the nozzle at the second timing based on a comparison (in other words, a combination) of the first ejection condition and the second ejection condition indicated by the ejection data (decision process). Thus, based on the first and second ejection conditions indicated by the ejection data, it is possible to respond to situations where the effect of the residual vibration is judged to be significant. As a result, the effect of residual vibration of ink due to ink droplet ejection from nozzles can be suppressed to enable good printing.
The printing apparatus may be configured so that the control unit stores a reducing criterion for reducing an amount of an ink droplet ejected from the nozzle to the target pixel at the second timing from an amount indicated by the ejection data, and determines to reduce an amount of an ink droplet ejected by the nozzle at the second timing if a result of the comparison between the first ejection condition and the second ejection condition satisfies the reducing criterion in the decision process. In such a configuration, the situation where the effect of the 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 an amount of an ink droplet that is ejected by the nozzle in the second timing. As a result, the effect of the residual vibration of ink due to ink droplet ejection from the nozzle can be suppressed and good printing can be achieved.
The printing apparatus may be configured so that the control unit determines to set an amount of an ink droplet ejected by the nozzle at the second timing to zero if a result of the comparison between the first ejection condition and the second ejection condition satisfies the reducing criterion in the decision process. In such a configuration, the situation where the effect of the residual vibration is determined to be significant based on the first and second ejection conditions indicated by the ejection data can be addressed by setting an amount of an ink droplet that is ejected by the nozzle in the second timing zero. As a result, the effect of the residual vibration of ink due to ink droplet ejection from the nozzle can be suppressed and good printing can be achieved. Here, setting an amount of an ink droplet ejected by the nozzle to zero means that the nozzle does not eject ink droplet.
The printing apparatus may be configured so that in the ejection head, a plurality of nozzles is provided, including the nozzle, and the nozzles eject ink droplets at different positions from each other, if it is decided in the decision process to reduce an amount of an ink droplet that is ejected by the nozzle at the second timing, the control unit increases an amount of an ink droplet ejected from an adjacent nozzle of the plurality of nozzles facing an adjacent pixel, which is a pixel adjacent to the target pixel, to the adjacent pixel from an amount indicated by the ejection data. That is, an amount of an ink droplet that adheres to the area including the target pixel may be insufficient due to a reducing in an amount of an ink droplet that is ejected by the nozzle at the second timing in order to suppress the effect of residual vibration. In contrast, by increasing an amount of an ink droplet ejected from an adjacent nozzle to an adjacent pixel of the target pixel, it is possible to complete the insufficient amount of an ink droplet and print a good image.
Various specific examples of ejection conditions that make the effect of the residual vibration significantly can be envisioned. Therefore, the printing apparatus may be configured so that the ejection condition indicates an amount of an ink droplet ejected from the nozzle to the target pixel.
The printing apparatus may be configured so that in the decision process, the control unit determines an amount of an ink droplet that is ejected by the nozzle at the second timing based on the comparison of the first ejection condition and the second ejection condition and the time interval between the first timing and the second timing. In such a configuration, it is possible to accurately respond to the effects of the residual vibration, which varies depending on the time interval between the first and second timing, and to achieve good printing.
The printing apparatus may be configured so that in the decision process, the control unit determines an amount of an ink droplet that is ejected by the nozzle at the second timing based on the comparison of the first ejection condition and the second ejection condition and an ink temperature. In such a configuration, it is possible to accurately respond to the effects of residual vibrations, which vary with the temperature of the ink, to achieve good printing.
As described above, the present invention enables good printing by suppressing the effects of the residual vibrations of ink caused by ink droplet ejection from the nozzle.
As shown in
Here, the direction in which the printing medium WP is fed and conveyed by the feed unit 1 is the conveyance direction X. The horizontal direction orthogonal to the conveyance direction X is the width direction Y. The feed unit 1 described above is located upstream of the printing apparatus 3 in the conveyance direction X. The above-mentioned discharge unit 4 is located downstream of the printing apparatus 3 in the conveyance direction X.
The printing apparatus 3 has a driven roller 7 on the upstream side to take in the printing medium WP from the fed unit 1. Printing medium WP taken from feed unit 1 by driven roller 7 is sent to conveyance direction X by multiple conveyance rollers 9 and is conveyed downstream toward discharge unit 4. A driven roller 11 is located between the downstream-most conveyance roller 9 and the discharge unit 4. This driven roller 11 feeds the printing medium WP being conveyed on the conveyance roller 9 toward the discharge unit 4.
The printing apparatus 3 comprises a printing unit 13, a drying unit 15, and a line scanner 17 between the driven roller 7 and the driven roller 11, in that order along the conveyance direction X from the upstream. The printing unit 13 prints on printing medium WP. The drying unit 15 dries the printing medium WP printed by printing unit 13. The line scanner 17 inspects the printed area on the printing medium WP for stains, omissions, etc.
The printing unit 13 has an ejection head 5 with multiple nozzles that eject ink onto the printing medium WP. Multiple printing units 13 are generally arranged along the conveyance direction X of the printing medium WP. For example, a total of four printing units 13 of black (K), cyan (C), magenta (M), and yellow (Y) are provided. However, in the following explanation, described is an example in which the printing apparatus 3 is equipped with only one printing unit 13. The printing unit 13 has a length that exceeds the width of the printing medium WP in the width direction Y of the printing medium WP. The printing unit 13 has enough ejection heads 5 to print the print area in the width direction of the printing medium WP without moving in the width direction Y.
For each of the multiple cavities 53, a piezoelectric element 55 is provided. The piezoelectric element 55 deforms in response to the applied electrical signal. The pressure of the ink in the cavity 53 fluctuates in response to the deformation of piezoelectric element 55. As described below, an ejection signal, which is an electrical signal, is applied to this piezoelectric element 55. When the ejection signal is applied to the piezoelectric element 55, the piezoelectric element 55 gives the ink in the cavity 53 the pressure fluctuation (ejection pressure fluctuation) required to eject ink from the nozzle 52.
Furthermore, printing apparatus 3 comprises a control unit 39 that comprehensively controls the entire apparatus. This control unit 39 has an arithmetic unit 391 and a storage unit 392. For example, the arithmetic unit 391 is a processor such as a CPU (Central Processing Unit) or FPGA (Field-Programmable Gate Array), and the storage unit 392 is a storage device such as a HDD (Hard Disk Drive) or SSD (Solid State Drive). The arithmetic unit 391 controls the conveyance motor 341, encoder 342, line scanner 17, and piezoelectric element 55, and the storage unit 392 stores the printing program 393 executed by the arithmetic unit 391. This printing program 393 is provided, for example, by recording medium 399, which is provided separately from control unit 39. This recording medium 399 records the printing program 393 readable by a computer (control unit 39). Such recording media 399 is, for example, USB (Universal Serial Bus) memory, memory cards, or external server computer storage devices. The printing program 393 specifies the contents of the control performed by the control unit 39.
In detail, the arithmetic unit 391 calculates the speed at which the printing medium WP is conveyed based on the conveyance position of the printing medium WP detected by the encoder 342. The arithmetic unit 391 determines the period Cs (i.e., time interval) for outputting the ejection signal Sd to the piezoelectric element 55 based on the conveyance speed of the printing medium WP thus calculated. That is, to make ink land on the printing medium WP at a constant resolution regardless of the conveyance speed of the printing medium WP, it is necessary to adjust the period Cs for outputting ejection signal Sd according to the conveyance speed of the printing medium WP. Specifically, the arithmetic unit 391 shortens the period Cs of the ejection signal Sd as the conveyance speed of the printing medium WP increases and lengthens the period Cs of the ejection signal Sd as the conveyance speed of the printing medium WP decreases. In other words, period Cs is inversely proportional to the conveyance speed.
The arithmetic unit 391 generates multiple ejection signals Sd(s), Sd(m), and Sd(1) by changing the combination of element signals Se(1), Se(2), and Se(3) included in the ejection signal Sd. The ejection signal Sd(s) is an ejection signal Sd including one type of element signal Se(3), the ejection signal Sd(m) is an ejection signal Sd including consecutive two types of element signal Se(2) and Se(3), and the ejection signal Sd(1) is an ejection signal Sd including consecutive three types of element signal Se(1), Se(2) and Se(3). When the ejection signal Sd(s) is applied to the piezoelectric element 55, the piezoelectric element 55 causes the nozzle 52 to eject an S-size ink droplet. When the ejection signal Sd(m) is applied to the piezoelectric element 55, the piezoelectric element 55 causes the nozzle 52 to eject an M size ink droplet, which is larger than S size. When the ejection signal Sd(1) is applied to the piezoelectric element 55, the piezoelectric element 55 causes the nozzle 52 to eject an L-size ink droplet, which is larger than the M-size. That is, the arithmetic unit 391 can change the size (volume) of the ink droplet ejected from the nozzle 52 by switching the ejection signal Sd given to the piezoelectric element 55 among ejection signals Sd(s), S(m) and S(1).
By the way, in the ejection head 5 as described above, residual vibration occurs as the ink is ejected from the nozzle 52. This point is illustrated in
The overall trend is, the larger the size of the preceding ink droplet, the greater the effect of the residual vibration on the subsequent ink droplet's ejection, the larger the size of the subsequent ink droplet, the greater the effect of residual vibration on the subsequent ink droplet's ejection. Factors contributing to the latter tendency could be as follows. That is, as shown in
Therefore, as shown in
In these examples, the ejection signal Sd is applied in each of the consecutive timing T(1) and T(2) (in other words, periods T(1) and T(2) with period Cs). In the example shown in the “LS” column, the ejection signal Sd(1) is applied at the timing T1 and the ejection signal Sd(s) is applied at the timing T2 after the timing T1. In this case, the ejection signal Sd (s) rises at the time Ts3, so there is a time interval Δs between the preceding ejection signal Sd (1) and the rise of the subsequent ejection signal Sd (s). In the example shown in the “LM” column, the ejection signal Sd(1) is applied at the timing T1 and ejection signal Sd(m) is applied at the timing T2 after the timing T1. In this case, the ejection signal Sd (m) rises at the time Ts2, so there is a time interval Δm from the preceding ejection signal Sd (1) to the rise of the subsequent ejection signal Sd (m). In the example shown in the “LL” column, the ejection signal Sd(1) is applied at the timing T1 and ejection signal Sd(L) is applied at the timingT2 after the timingT1. In this case, the ejection signal Sd(1) rises at the timeTs1, so there is a time interval Δ1 from the preceding ejection signal Sd(1) to the rise of the subsequent ejection signal Sd(1).
Thus, when two ejection signals Sd are applied at period Cs, the larger the size of the ink droplet ejected by the subsequent ejection signal Sd, the shorter the time interval Δs, Δm, and Δ1 between the two ejection signals Sd. As the result, the trends described using
In
A plurality of nozzles N1, N2, N3, . . . face a plurality of pixel rows PL1, PL2, PL3, . . . that are adjacent in the Y direction. Each of pixel rows PL1, PL2, PL3, . . . is formed by a plurality of pixel P arranged in one row in the X direction. The nozzles N1, N2, N3, . . . eject the ink droplets synchronously with the conveyance of the printing medium WP in the X direction. Thereby, nozzles N1, N2, N3, . . . eject the ink droplets to multiple pixel P in the opposing pixel rows PL1, PL2, PL3, . . . in order from downstream in the X direction (conveyance direction). In particular, the image data Di indicates the size (S, M, L) of the ink droplet to be ejected to the pixel P for each pixel P, and the nozzles N1, N2, N3, . . . eject the ink droplet having the indicated size to the pixel P.
The flowchart in
When the flowchart in
In step S104, the arithmetic unit 391 checks whether or not there is a preceding pixel P to which the ink droplet is ejected prior to the pixel P (target pixel) of count value Cp. Specifically, the existence of the pixel P (the preceding pixel) adjacent to a target pixel P of count value Cp on the downstream side (arrow side) in the X direction is confirmed. For example, if the target pixel P is located at the edge of the image and there is no corresponding preceding pixel P (“NO” in step S104), return to step S103 and increment the count value Cp of the pixel P by 1.
If the corresponding preceding pixel P exists (if “YES” in step S104), the arithmetic unit 391 determines whether or not the preceding pixel P and the target pixel P satisfy the decimating criterion. That is, whether or not one of the following two decimating criterion is satisfied is determined.
On the other hand, if any of these decimating criteria is satisfied (if “YES” in step S105), then proceed to step S106. Here, specific examples where the decimating criterion is satisfied are explained based on the “Image Data” columns in
If the pixel P surrounded by a solid rectangle in the “Image Data” column in
If the pixel P surrounded by a solid rectangle in the “Image Data” column in
If the pixel P surrounded by a solid rectangle in the “Image Data” column in
In the decimating process of step S106, the size of the ink droplet of the target pixel Pt is set to zero. Here, setting the size of the ink droplet to zero corresponds to not ejecting the ink droplet from the nozzle that was supposed to eject the ink droplet. The following is a specific explanation of this decimating process based on
In step S107, the arithmetic unit 391 stores the pixel Pt to which the decimating process has been executed as a decimated pixel Pd in storage unit 392 for later complementing process. Steps S103 to S107 are repeatedly executed until the count value Cp of pixel P becomes the maximum value Cpx (the total number of pixel P constituting the image data Di) (until “YES” in step S108).
When the count value Cp of the pixel P becomes the maximum value Cpx (“YES” in step S108), the count value Cd (i.e., the value for identifying the decimated pixel Pd) is set to zero (step S109), and the count value Cd of the decimated pixel Pd is incremented by “1” (Step S110).
In step S111, a complementing process is performed to complement the lack of ink volume due to setting zero to the size of the ink droplet to the decimated pixel Pd. In this complementing process, the size of the ink droplet to be ejected to an adjacent pixel Pi is increased, the adjacent pixel Pi being adjacent to the decimated pixel Pd of count value Cd in the Y direction. For example, if the size of the ink droplet to be ejected to the adjacent pixel Pj is size S, it is increased to size M, and if this size is size M, it is increased to size L. If this size is size L, the size is not increased because no larger size exists. This complementing process is specifically illustrated using
In the “complementing process” example in
In the “complementing process” example in
In the “complementing process” example in
Steps S110-S111 are repeatedly executed until the count value Cd of the decimated pixel Pd becomes the maximum value Cdx (the total number of decimated pixel Pd stored in step S107) (until “YES” in step S112).
When the count value Cd of the decimated pixel Pd becomes the maximum value Cdx (“YES” in step S112), the arithmetic unit 391 stores the image data Di for which the decimating and complementing processes have been executed in the storage unit 392 as dot data Dd (step S113). In step S114, the arithmetic unit 391 makes the nozzles N1, N2, N3, . . . eject the ink droplets of the size indicated by the dot data Dd to print the image indicated by the image data Di on the printing medium WP.
In the embodiment described above, the size of the ink droplet to be ejected to each pixel P defined by the image data Di (ejection data) is corrected. Specifically, the size (quantity) of the ink droplet that the nozzle 52 ejects to the target pixel Pt is corrected based on a comparison between the size of the ink droplet that is to be ejected from the nozzle 52 to the preceding pixel Pa (first ejection condition) at timing T1 (first timing) and the size of the ink droplet that is to be ejected from the nozzle 52 to the target pixel Pt at timingT2 (second timing) (second ejection condition) (Steps S105 and S106). Thus, based on the size of the ink droplet to the preceding pixel Pa and target pixel Pt indicated by the image data Di, it is possible to respond to the situation where the effect of residual vibration is judged to be significant. As a result, the effect of residual vibration of ink due to ink droplet ejection from the nozzle 52 can be suppressed and good printing can be achieved.
The control unit 39 stores a decimating criterion (reducing criterion) in storage unit 392, decimating criterion being for reducing the size of the ink droplet to be ejected from nozzle 52 to the target pixel Pt at timing T2 from the size indicated by the image data Di. If the combination of the sizes of the ink droplets to the preceding pixel Pa and target pixel Pt indicated by image data Di (in other words, the comparison result) satisfies the decimating criterion (if “YES” in step S105), it is determined in step S106 that the size of the ink droplet to be ejected by the nozzle 52 at timingT2 is reduced (decimating process). In such a configuration, the situation where the effect of the residual vibration is judged to be significant based on the size of the ink droplet to the preceding pixel Pa and the target pixel Pt indicated by the image data Di can be handled by reducing the size of the ink droplet ejected by the nozzle 52 at timing T2. As a result, the effect of the residual vibration of ink due to the ink droplet ejection from the nozzle 52 can be suppressed and good printing can be achieved.
If the combination of the size of the ink droplet to the preceding pixel Pa and the target pixel Pt indicated by the image data Di satisfies the decimating criterion (if “YES” in step S105), control unit 39 determined that the size of the ink droplet ejected from the nozzle 52 at timingT2 is set to be zero (decimating process). In such a configuration, the situation where the effect of the residual vibration is judged to be significant based on the size of the ink droplet to the preceding pixel Pa and the target pixel Pt indicated by the image data Di can be handled by setting the size of the ink droplet that nozzle 52 ejected at timing T2 to zero. As a result, the effect of the residual vibration of ink due to the ink droplet ejection from the nozzle 52 can be suppressed and good printing can be achieved.
In ejection head 5, a plurality of nozzles N1, N2, N3, . . . are provided, and the plurality of nozzles N1, N2, N3, . . . eject ink droplets at different positions from each other in the Y direction. On the other hand, if it is determined to reduce the size of the ink droplet that nozzle N2 ejects at timing T2 in the decimating process, the control unit 39 increases the size of the ink droplet to be ejected from nozzles N1 and N3 (adjacent nozzles) to adjacent pixels Pj rather than the size indicated by the image data Di (complementing process), the nozzles N1 and N3 facing the adjacent pixels Pj adjacent to the target pixel Pt in the Y direction. That is, the amount of the ink droplet that adheres to the area including the target pixel Pt may be insufficient because the size of the ink droplet that the nozzle N2 ejects at timingT2 has been reduced in order to suppress the effect of the residual vibration. In contrast, by increasing the size of the ink droplet ejected from the nozzles N1 and N3 to adjacent pixel Pj of target pixel Pt, it is possible to complete the insufficient amount of the ink droplet and print a good image.
The first variation of image printing is then described using
Therefore, the effect of the residual vibration when the period Cs is less than a predetermined period (
Therefore, in the first variation of image printing, before step S105 of the flowchart in
In this first variation, one threshold period is provided for period Cs of ejection signal Sd. However, in regions where period Cs is even shorter, it is assumed that the number of combinations of the size of the ink droplet, where the effect of the residual vibration is more significant, may increase. In such a case, a threshold period may be set for the boundary where the number of relevant combinations changes as period Cs changes. The decimating criterion (i.e., the combination of the size of the ink droplet that has a significant effect from the residual vibration) may be changed according to a comparison between period Cs and the threshold period.
Thus, in the first variation, control unit 39 determines the size of the ink droplet to be ejected by nozzle 52 at timing T2 based on the combination of the size of the ink droplet to the preceding pixel Pa and target pixel Pt indicated by image data Di and the period Cs of the ejection signal Sd (in other words, based on the time interval between timing T1 and timing T2) (steps S105 to S107). In such a configuration, it is possible to accurately respond to the effects of the residual vibration, which varies with the period Cs of the ejection signal Sd, and to perform good printing.
Next, the second variation of image printing is explained using
Therefore, the effect of the residual vibration when the ink temperature is higher than or equal to the predetermined temperature (
Therefore, in the second variation of image printing, before step S105 of the flowchart in
In this second variation, one threshold temperature is provided for the temperature of the ink. However, in regions where the ink temperature is even higher, it is assumed that the number of combinations of the size of the ink droplet, where the effect of residual vibration is more significant, may increase. In such cases, a threshold temperature may be set for the boundary where the number of relevant combinations changes in response to changes in ink temperature. The decimating criterion (i.e., the combination of the size of the ink droplet that has a significant effect from the residual vibration) may be changed according to a comparison of the period Cs and the threshold temperature.
Thus, in the second variation, control unit 39 determines the size of the ink droplet that nozzle 52 ejects at timing T2 based on the combination of the size of the ink droplet to the preceding pixel Pa and the target pixel Pt indicated by image data Di and the temperature of the ink (steps S105 to S107). In such a configuration, it is possible to accurately respond to the effects of the residual vibrations, which vary with the temperature of the ink, to achieve good printing.
In the embodiments described above, the printing apparatus 3 corresponds to an example of “printing apparatus” of the present invention, the control unit 39 corresponds to an example of “control unit” or “computer” of the present invention, the printing program 393 corresponds to an example of “printing program” of the present invention, a recording medium 399 corresponds to an example of “recording medium” of the present invention, an ejection head 5 corresponds to an example of “ejection head” of the present invention, the nozzle 52, N1, N2, N3, . . . correspond to an example of “nozzle” of the present invention, the nozzles N1 and N3 correspond to an example of “adjacent nozzle” of the present invention, the image data Di corresponds to an example of “ejection data” of the present invention, the pixel P corresponds to an example of a pixel of the present invention, the target pixel Pt corresponds to an example of “target pixel” of the present invention, the adjacent pixel Pj corresponds to an example of “adjacent pixel” of the present invention, the timing T1 corresponds to an example of “first timing” of the present invention, the timing T2 corresponds to an example of “second timing” of the present invention, steps S105 to S106 correspond to an example of “decision process” of the present invention, the size (amount) of ink droplet corresponds to an example of “ejection condition” of the present invention, the size of ink droplet ejected at timing T1 corresponds to an example of “first ejection condition” of the present invention, the size of ink droplet ejected at timing T2 corresponds to an example of “ejection condition” of the present invention, the size of the link droplet ejected at timing T2 corresponds to an example of “second ejection condition” of the present invention, the decimating criterion corresponds to an example of “reducing criterion” of the present invention, the period Cs corresponds to an example of “time corresponding to the resolution” of the present invention.
Further, the present invention is not limited to the above-described embodiment, but numerous modifications and variations other than those described above can be devised without departing from the scope of the invention. For example, a third variation may be performed by combining the first and second variations of image printing.
In the third variation of image printing, if the period Cs of ejection signal Sd is longer than or equal to the threshold period but the ink temperature is higher than or equal to the threshold temperature, steps S105 to S107 are performed using the combination of ink droplet sizes that has a significant effect from the residual vibration in
The way to combine the first and second variations of image printing is not limited to this example but can also be combined as in the following fourth variation. In this fourth variation, a table quantifying the effect of the residual vibration (small, moderate, and significant) shown in
Alternatively, the configuration shown in
The layout processing part U1 arranges the images indicated by the print data received from an external computer, for example, for the printing medium WP. The print data is data that indicates the gradation value of each pixel that makes up the image in, for example, 256 steps. This layout processing part U1 determines the area of the printing medium WP where the image will be printed, as well as the correspondence between the pixels that make up the image and the nozzle 52. The tone correction part U2 adjusts the color tone of image data Di by gamma correction, for example, for the print data output from the layout processing part U1. The shading correction part U3 performs shading correction on the print data whose color tone has been adjusted by the tone correction part U2.
Thus, the image data Di described above is generated. The vibration influence determination part U4 determines whether the decimating criterion is satisfied by executing step S105 in
Then, for the ink droplet size of pixel P that is determined by the vibration influence judgment part U4 to satisfy the decimating criterion, the decimate complementing process part U5 performs steps S106, S107, S109 to S112. The size of the ink droplet after each processing by the decimate complementing process partU5 is output to the halftone processing partU6. On the other hand, the ink droplet size of pixel P that is judged by the vibration influence judgment part U4 not to satisfy the decimating criterion is output from the vibration influence judgment part U4 to the halftone processing part U6 without going through the decimating complementing process part U5.
Thus, the dot data Dd is input to halftone processing partU6. This halftone processing part U6 performs halftone process on dot data Dd to generate raster data. The arithmetic unit 391 prints images on printing medium WP by controlling the ejection of the ink droplet from the nozzle 52 based on the raster data.
Further, the specific manner of the complementing process in step S111 of
The numerical values of the bars corresponding to adjacent pixelPj1, Pj2, and Pj3 indicate the ratio of distributing the gradation value Vd of the decimated pixel Pd (i.e., the gradation value that was set for the decimated pixel Pd before the decimating process) to the corresponding adjacent pixelsPj1, Pj2, and Pj3. The values of the adjacent pixel Pj1, Pj2 and Pj3, respectively, are 70 (=20+20+10+10+5+5). Therefore, gradation value Vd×20/70 is distributed to adjacent pixel Pj1, gradation value Vd×10/70 is distributed to adjacent pixel Pj2, and gradation value Vd×5/70 is distributed to adjacent pixel Pj3.
“Distribution Value Determination” column in
Variations other than those listed above may be added as appropriate. For example, in the image printing of
The complementing process described above is not mandatory, the complementing process may not be necessary if the ink volume shortage caused by the decimating process is not noticeable.
In the above example, the combination of ink droplet sizes that have a significant effect from the residual vibration is adopted as the decimating criterion. However, specific examples of decimating criterion are not limited to this. That is, a combination of link droplet sizes that have a moderate or significant effect from the residual vibration may be adopted as the decimating criterion.
In the decimating process (step S106), it is not necessary to set the ink size of the decimated pixel Pd to zero, it is sufficient to reduce the ink size. Reducing the ink size can be performed by, for example, reducing the ink size by one step.
Specific examples of “ejection condition” is not limited to the size (amount) of the ink droplet described above. For example, if the effect of residual vibration becomes more pronounced due to the combination of other conditions for ejecting the ink at timingT1 and other condition for ejecting the ink at timingT2, then said other conditions should be adopted instead of the size of the ink droplet.
The specific waveforms of the ejection signals Sd(s), Sd(m), and Sd(s) are not limited to the example in
The method of ejecting the ink is not limited to the method by piezoelectric element 55 described above.
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 conveying the printing medium WP by driven roller 7, multiple conveyance rollers 9 and driven roller 11, ejection head 5 may be moved by a carriage.
The material of the printing medium WP described above was continuous paper, but it is not limited to that. For example, it can be sheet paper. The material of the printing medium is not necessarily limited to paper but can be a film such as OPP (oriented polypropylene) or PET (polyethylene terephthalate), for example.
The invention is applicable to all inkjet technologies that control the amount of ink droplet ejected from the nozzle.
3 . . . printing apparatus
39 . . . control unit (computer)
393 . . . printing program
399 . . . recording medium
5 . . . ejection 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-S106 . . . step (decision process)
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-124972 | Jul 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/027966 | 7/19/2022 | WO |
