JP7653906B2 - Printing device - Google Patents

Description

The present invention relates to a printing device capable of layered printing.

Conventionally, in a printing device that prints images, etc. by ejecting ink from a print head onto dot formation positions on a recording medium, a method for suppressing misalignment of dot formation positions formed with different ejection timings has been known (see, for example, Patent Document 1). In this method, dots are formed by the print head moving forward in the main scanning direction, moving in the sub-scanning direction by a feed amount of half the nozzle pitch, and forming dots by the print head moving backward in the main scanning direction. In this way, a test pattern is printed in which rows of dots formed by the back and forth movement are arranged alternately in the sub-scanning direction. The ejection timing is adjusted based on the linearity of this test pattern.

JP 2001-130112 A

In the printing device of the prior art disclosed in Patent Document 1, it is possible to adjust the misalignment of the dot formation position in the dot formation layer within the plane of a single printing pass, but in multi-layer printing (laminate printing) in which ink is printed on a recording medium multiple times and multiple layers are printed on top of each other, no consideration is given to adjusting the printing position for each layer that is printed multiple times, and it is not possible to address misalignment of the printing position.

The present invention has been made in consideration of the above circumstances, and aims to provide a printing device capable of interlayer printing that can easily and accurately align the interlayer printing position in laminate printing, which involves printing multiple times on top of each other.

A printing device according to one aspect of the present invention includes a print head having nozzles for ejecting ink, and a control unit that executes an mth layer printing process that prints the mth printing layer on the recording medium based on the mth printing condition (m is an integer equal to or greater than 1) by moving the print head relative to the recording medium in the main scanning direction and the sub-scanning direction intersecting the main scanning direction, and an nth layer printing process that prints the nth printing layer on the recording medium on which the mth printing layer has been printed based on the nth printing condition (n is an integer other than m). In this printing device, the control unit executes an adjustment pattern printing process that prints an adjustment pattern for checking and adjusting the relative misalignment of the printing position between the mth printing layer and the nth printing layer, and a print position adjustment process that adjusts the relative misalignment of the printing position between the mth printing layer and the nth printing layer based on a set adjustment value.

In one embodiment of the present invention, the mth printing condition and the nth printing condition each include at least one of the drive waveform supplied to the print head and the movement speed of the print head, and are different from each other.

In another embodiment of the present invention, the adjustment pattern includes a first adjustment pattern in which the mth printed layer and the nth printed layer do not overlap in printed locations.

In yet another embodiment of the present invention, the adjustment pattern includes a second adjustment pattern in which the printing areas of the mth printing layer and the nth printing layer overlap.

In yet another embodiment of the present invention, the adjustment pattern includes a first adjustment pattern and a second adjustment pattern, the first adjustment pattern includes a reference line formed on one of the mth printing layer and the nth printing layer and an adjustment line formed on the other, the second adjustment pattern includes a reference block formed on one of the mth printing layer and the nth printing layer and an adjustment block formed on the other, the reference line and the adjustment line do not overlap, and the reference block and the adjustment block overlap.

In yet another embodiment of the present invention, the first adjustment pattern is a pattern that is repeatedly formed in the main scanning direction, and the position of the adjustment line relative to the reference line gradually shifts from one side of the main scanning direction to the other.

In yet another embodiment of the present invention, the second adjustment pattern is a pattern that is repeatedly formed in the main scanning direction, and the position of the adjustment block relative to the reference block gradually shifts from one side to the other side of the main scanning direction.

In yet another embodiment of the present invention, the print position adjustment process is at least one of a process of shifting the output timing of a drive waveform supplied to the print head in either the mth layer printing process or the nth layer printing process, a process of shifting the print data of either the mth printing layer or the nth printing layer in the main scanning direction, and a process of shifting a table on which the recording medium is placed in the main scanning direction.

In yet another embodiment of the present invention, the ink is a reactive curing ink.

According to the present invention, alignment of interlayer printing positions in laminate printing can be performed easily and with high accuracy.

1 is a diagram showing a schematic configuration of a printing apparatus according to a first embodiment of the present invention. FIG. 2 is a block diagram illustrating a schematic functional configuration of the printing apparatus. FIG. 2 is a diagram illustrating a print head of the printing device. FIG. 2 is a diagram illustrating a hardware configuration of the printing apparatus. 1 is an explanatory diagram showing the dot formation positions and the distance between the head and the landing position in layered printing. 13 is a diagram showing a first adjustment pattern for adjusting a misalignment of printing positions between printing layers based on differences in printing conditions for each printing layer. FIG. 11A and 11B are diagrams for explaining waveforms in a print position adjustment method. 11A and 11B are diagrams for explaining waveforms in an unadjusted state in the adjustment method. 13A and 13B are diagrams for explaining adjustments for delaying the ejection timing of a waveform. 13A and 13B are diagrams for explaining adjustment to advance the ejection timing of a waveform. 13A to 13C are diagrams showing other examples of the first adjustment pattern for adjusting the misalignment of printing positions between printing layers based on differences in printing conditions for each printing layer. 13 is a diagram for explaining a first example of a second adjustment pattern used in a method for adjusting the printing position between each printed layer during multi-layer printing according to a second embodiment of the present invention. FIG. 13A and 13B are diagrams for explaining an image of dot formation positions before and after adjustment in the first example. 13A and 13B are diagrams for explaining a second example of a method for adjusting a print position using a second adjustment pattern. 13A and 13B are diagrams for explaining an image of dot formation positions before and after adjustment in the second example. 13A to 13C are diagrams for explaining a third adjustment pattern used in a method for adjusting the printing position between each printed layer during multi-layer printing according to a third embodiment of the present invention. 11A and 11B are diagrams for explaining an image of pattern reference in the adjustment method. 10 is a flowchart showing an adjustment process procedure for implementing a specific adjustment method for selecting an optimal adjustment value. FIG. 11 is a diagram for explaining a coarse adjustment pattern. FIG. 11 is a diagram for explaining a fine adjustment pattern. FIG. 4 is a diagram showing a display example of a display. FIG. 4 is a diagram showing a display example of a display. 11A and 11B are diagrams for explaining the relationship between adjustment values of a coarse adjustment pattern and a fine adjustment pattern; FIG. 13 is a diagram for explaining a confirmation pattern. FIG. 13 is a diagram for explaining a layered image of layered printing. FIG. 13 is a diagram for explaining a layered image of layered printing. FIG. 4 is a diagram showing a display example of a display.

Below, a printing device according to an embodiment of the present invention will be described in detail with reference to the attached drawings. However, the following embodiments do not limit the invention according to each claim, and not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention. In the following embodiments, identical or corresponding components are given the same reference numerals and duplicated descriptions are omitted. In the embodiments, the arrangement, scale, dimensions, etc. of each component may be exaggerated or minimized and may not match the actual ones, and descriptions of some components may be omitted.

[First embodiment]
[Printing Device Configuration]
Fig. 1 is a diagram showing a schematic configuration of a printing device according to a first embodiment of the present invention. Fig. 2 is a block diagram showing a schematic functional configuration of the printing device. Fig. 3 is a diagram showing a schematic print head of the printing device. Fig. 4 is a diagram showing a schematic hardware configuration of the printing device.

As shown in FIG. 1, the printing device 10 of this embodiment is a device capable of multi-layer printing (lamination printing) in which multiple print layers are stacked on top of each other by ejecting, for example, ultraviolet-curable ink (UV ink) onto a recording medium (paper, transparent plate, etc.) 4 placed on a table 1. The printing device 10 includes the table 1, a control unit 20, and a print head 30.

The print head 30 is configured to be movable in the main scanning direction (CR direction) indicated by the arrow in the figure by the carriage drive mechanism 2. The table 1 is configured to be movable in the sub-scanning direction (PF direction) indicated by the arrow in the figure by the table drive mechanism 3. As a result, the print head 30 is configured to be movable relative to the recording medium 4 in the CR direction and the PF direction. When performing multi-layer printing, the printing device 10 is configured to, for example, print the mth (m is an integer of 1 or more) layer (e.g., the first layer), and then return the table 1 to the sub-scanning direction by the table drive mechanism 3, and print the nth (n is an integer other than m) layer (e.g., the second layer) and subsequent layers thereon. In the following, unless otherwise specified, the mth layer and the mth print layer will be described as the first layer and the first print layer, and the nth layer and the nth print layer will be described as the second layer and the second print layer. The printing device 10 of this embodiment will be described as having a structure in which the table moves, but it is also possible to use a structure in which the table is fixed and the print head 30 moves in the PF direction relative to the recording medium 4, or a structure in which the recording medium 4 is conveyed by being sandwiched between a belt conveyor or a pressure roller, etc.

The printing device 10 of this embodiment will be described using the above-mentioned UV ink as an example of multi-layer printing (laminate printing), but the ink used is not limited to this, and reactive curing inks that utilize light, heat, chemical reactions, etc., such as electromagnetic wave curing inks (EB inks) that use electron beams, etc., and inks that cure using other chemical reactions, can also be used.

As shown in FIG. 2, in addition to the print head 30 and the control unit 20, the printing device 10 also includes a print data input unit 11 that inputs print data including various printing conditions and image data, a display 12 as a display device, and an operation unit 13. The display 12 may be included in the operation unit 13 of the printing device 10.

The printing device 10 further includes a carriage drive unit 14 that drives the carriage drive mechanism 2, a table drive unit 15 that drives the table drive mechanism 3, a head drive unit 16 that drives the print head 30, and a memory unit 17. The print head 30 is provided with an ultraviolet (UV) irradiation device 32 that includes a UV-LED lamp or the like.

The print data input unit 11 inputs print data from the outside, which includes image data including lines, characters, figures, photographs, etc. in formats such as PDF (Portable Document Format) and PS (PostScript: registered trademark), and print conditions including information about the head drive voltage waveform ("drive waveform", hereinafter sometimes simply referred to as "waveform") of the print head 30.

The print data may be configured with different printing conditions for each layer, for example, when performing layered printing. The printing conditions of the print data may further include at least one of the following information: the carriage speed of the print head 30, the viscosity of the UV ink, and the heating temperature of the UV ink.

The print data input by the print data input unit 11 includes image data consisting of, for example, vector data. This image data is converted by the control unit 20, which has, for example, a RIP (Raster Image Processor) function, into raster image data (CMYK data) such as a TIFF image consisting of raster data. The image data included in the print data may have been converted into raster image data in advance externally.

The control unit 20 performs various conversion processes on the image data (raster image data), such as color conversion and halftone processing, to generate image data for printing. This image data can be composed of six-color data consisting of four colors, cyan (C), magenta (M), yellow (Y), and black (K), plus white (W) and varnish (V). The control unit 20 also executes an adjustment pattern printing process and a print position adjustment process, which will be described later.

The display 12 has a display screen that displays various information. The operation unit 13 accepts operation input by a user of the printing device 10, for example, via the input device 28 (see FIG. 4). The carriage drive unit 14, table drive unit 15, and head drive unit 16 operate the carriage drive mechanism 2, table drive mechanism 3, and print head 30 in response to control commands from the control unit 20 to print image data based on printing conditions.

The storage unit 17 stores various information such as data on various print profiles and processing tables, data on display drivers and printer drivers, data on programs that execute print position adjustment processes and various control programs, and print data having various image data as described above.

[Print head configuration]
As shown in FIG. 3, the print head 30 includes an inkjet recording head unit 31 and an ultraviolet (UV) irradiation device 32. The inkjet recording head unit 31 includes, for example, six recording heads 33 each having the same width of printing range. If the main scanning direction toward the left in the figure is the printing direction, the inkjet recording head unit 31 is arranged so that the recording heads 33 ejecting white (W), white (W), yellow (Y), cyan (C), magenta (M), black (K), varnish (V), and varnish (V) UV inks are arranged in the order of WWYCMKVV from the leading side in the printing direction. Note that, although an example in which two white (W) and two varnish (V) recording heads 33 are provided has been described here, one white (W) and one varnish (V) recording head 33 may be arranged.

Each recording head 33 has a number of ink ejection nozzles driven by, for example, piezoelectric elements arranged at a constant nozzle pitch in the PF direction, and these numerous ink ejection nozzles form a nozzle array extending in the PF direction. The nozzle array of each recording head 33 may be configured in a single row or multiple rows.

The ultraviolet (UV) irradiation device 32 is mounted on the rear side of the inkjet recording head unit 31 in the printing direction, and irradiates ultraviolet (UV) rays onto the UV ink ejected onto the recording medium 4 under the control of the control unit 20. When performing bidirectional printing, this ultraviolet (UV) irradiation device 32 may be provided on both sides of the inkjet recording head unit 31 in the main scanning direction.

[Hardware configuration of the printing device]
4 shows the hardware configuration of the printing device 10. Like a computer, the printing device 10 includes a CPU 21, a RAM 22, a ROM 23, a HDD (hard disk drive) 24, and an SSD (solid state drive) 25. The printing device 10 also includes an input/output I/F (interface) 26 and a communication I/F (interface) 27. The components 21 to 27 of the printing device 10 are connected to each other via a bus 9 so as to be able to communicate with each other.

The CPU 21 controls the entire printing device 10 by executing various programs stored in the RAM 22, ROM 23, HDD 24, SSD 25, etc., and also realizes a position adjustment function for the interlayer printing position during stacking printing by executing an adjustment processing program. The RAM 22 can be used as a working area for the CPU 21, for example, for drawing and expanding various image data, and for arithmetic and calculation processing based on various printing conditions.

The ROM 23 stores the various programs described above in a readable manner, for example. The HDD 24 and SSD 25 store various data in a readable and writable manner, and realize the function of the storage unit 17 of the printing device 10. In addition to the HDD 24 and SSD 25, the printing device 10 may be provided with a card slot unit to which a removable and portable storage medium (such as a memory card) can be connected.

An input device 28, such as a keyboard, mouse, and touch panel (not shown), which functions as the operation unit 13, is connected to the input/output I/F 26. The input device 28 receives information associated with operation input from the user. In addition, for example, a display 12 is connected to the input/output I/F 26. The display 12 displays various information including information related to the operation of the printing device 10. Note that when a touch panel is used as the input device 28, the touch panel may be provided on the display 12.

An external device 29 can be connected to the communication I/F 27 via a network 18 such as the Internet. The external device 29 includes, for example, other printing devices in remote locations, other control devices such as computers and workstations, and portable information terminal devices such as tablet terminals. In this way, the printing device 10 is configured to be able to communicate with the external device 29 via the communication I/F 27. Although not shown in the figure, the printing device 10 may further be equipped with various sensors such as a color sensor and a distance sensor.

[Problem of misalignment of printing position when printing multiple layers]
For example, when performing thick printing with UV (curable) ink on a transparent smartphone case, multi-layer printing may be performed, such as printing the entire surface of W (white) ink as a base layer, printing an image with CMYK ink on it, and then performing thick printing using V (varnish) ink on it. In such a case of multi-layer printing, since the types and viscosities of the inks used in different printing layers are different, the printing conditions such as the driving voltage waveform applied to the print head 30 and the moving speed of the print head 30 may differ for each printing layer. For example, when the first printing layer is printed using CMYK ink, a first driving voltage waveform suitable for CMYK ink is used. Also, when the second printing layer is printed using V (varnish) ink, a second driving voltage waveform suitable for V ink is used. Also, the driving speed of the print head 30 may be different between the printing of the first printing layer and the printing of the second printing layer. In this way, if printing conditions such as the drive voltage waveform, drive speed, ink viscosity, heating temperature, etc. applied to the print head 30 differ depending on the printing layer, the formation positions of the print dots may be slightly misaligned between the printing layers.

Furthermore, regardless of whether the printing conditions are different, when dots of each printing layer are formed, if dots of an upper printing layer are formed overlapping positions where dots of a lower printing layer are formed, the distance between the nozzles of the print head 30 and the ink landing position changes.
FIG. 5 is an explanatory diagram showing the dot formation positions and the distance between the head and the landing position in layered printing.
5, when UV ink is ejected while the print head 30 is driven in the printing direction, the UV ink flies at an inclination angle determined by the movement speed of the print head 30 in the movement direction and the ejection speed of the ink toward the recording medium 4. Here, when performing two-layer laminate printing, for example, the print head 30 is driven in the printing direction to eject UV ink, form dots 6 of a first layer on the recording medium 4 and harden it, and then the print head 30 is driven again in the printing direction to eject UV ink on the dots 6 of the first layer, form dots 7 of a second layer and harden it.

In this case, the paper gap (PG) H2 when printing the second layer is shorter by the thickness of the dots 6 than the paper-to-paper distance (hereafter referred to as the "paper gap (PG)") H1, which is the distance between the nozzle face of the print head 30 and the surface (paper surface) of the recording medium 4 when printing the first layer. This tendency continues in printing the third layer and beyond.

As a result, the landing position of the UV ink will shift as shown by the amount of deviation d, for example, between the formation of the first layer and the formation of the third layer (or later). As such, the landing distance changes for each layer, causing gradual deviation, so if the layer thickness, landing position and landing distance of the UV ink on the recording medium 4 are not taken into consideration when forming the dots 6 and 7 for each layer, the printing precision and print quality will end up being significantly degraded.

Taking the above points into consideration, the printing device 10 of this embodiment is configured to enable adjustment of the printing position between each printing layer during multi-layer printing.

Note that "one printing layer" here means a printing layer obtained as a result of printing by the print head 30 from the printing start position (home position) in the CR direction and PF direction to the printing end position. Therefore, even if there is a multi-layer structure in which, for example, white (W) UV ink, color (CMYK) UV ink, and varnish (V) UV ink are layered, if they are a printing layer completed by one movement from the printing start position to the printing end position, they are included in "one printing layer". For example, even in the case of multi-layer printing in which the white (W), color (CMYK), and varnish (V) UV inks are ejected simultaneously while shifting the print head 30 little by little in the sub-scanning direction, and the white (W) UV ink, color (CMYK) UV ink, and varnish (V) UV ink are layered in sequence, if the printing layer is completed by moving the print head 30 from the printing start position to the printing end position, it is considered to be one printing layer. In addition, since "one printing layer" does not necessarily print on the entire surface, there may be some parts where ink is not ejected.

[How to adjust the print position]
The following describes a method for adjusting the print position between layers, which is realized by the adjustment pattern printing process and the print position adjustment process executed by the control unit 20.
6 is a diagram showing a first adjustment pattern 60 for adjusting the misalignment of the printing positions between the printing layers due to differences in the printing conditions of each printing layer. The first adjustment pattern 60 is printed by the adjustment pattern printing process of the control unit 20.

In this first adjustment pattern 60, the effects of misalignment due to overlapping of ink layers between printing layers are eliminated, and only the effects due to differences in printing conditions are confirmed. First, from all types of driving voltage waveforms of the print head 30 equipped in the printing device 10, for example, a waveform (reference waveform) "waveform A" that serves as the adjustment standard for the landing position of UV ink included in the first printing conditions (print data 1) is determined. Then, the landing position is corrected by adjusting the waveform (adjustment waveform) "waveform B" that is the adjustment target for the landing position of UV ink included in the second printing conditions that are different from the first printing conditions.

As shown in FIG. 6(a), first, in the first printing layer, which is the first scan, the print head 30 is moved in the printing direction based on the first printing conditions to eject a specified UV ink in "waveform A," and a reference line 61 consisting of multiple linear patterns, for example, inverted T-shapes and T-shapes spaced apart vertically, is printed on the recording medium 4 (mth layer printing process).

Next, as shown in FIG. 6(b), the recording medium 4 is controlled by the table driving mechanism 3 to keep the same position in the PF direction without being fed, and then in the second printing layer, which is the second scan, the print head 30 is moved in the printing direction (head scanning direction) based on the second printing conditions to eject a predetermined UV ink in "waveform B" and print adjustment lines 62 consisting of a plurality of I-shaped linear patterns, for example, between the reference lines 61 on the recording medium 4 (nth layer printing process). These reference lines 61 and adjustment lines 62 constitute the first adjustment pattern 60 (printing pattern). The printing positions of the reference lines 61 and adjustment lines 62 do not overlap.

Then, the landing positions of the UV ink on the reference line 61 and the adjustment line 62 in the print result (first adjustment pattern 60) thus printed are checked. It can be seen that in the first adjustment pattern 60, the adjustment line 62 is printed with a position shift to the left of the reference line 61, and therefore it can be seen that the output timing (hereinafter also referred to as the "ejection timing") of "waveform B" is delayed.

Therefore, in the case of such a print result, for example, using an adjustment value corresponding to the amount of misalignment input by the user via the operation unit 13, under the control of the control unit 20, a correction is made to "advance" the ejection timing of waveform B of the second printing condition so that the printing position of the adjustment line 62 coincides with the printing position of the reference line 61, as shown in Figure 6 (c), and the landing position of the UV ink is adjusted.

In the example shown in FIG. 6, the landing position of the UV ink on the adjustment line 62 is moved backward in the printing direction by "advancing" the ejection timing of "waveform B," thereby matching the landing positions of the reference waveform (waveform A) and the adjustment waveform (waveform B). However, if the position of the adjustment line 62 is misaligned in the opposite direction, this can be adjusted by "slowing" the ejection timing of "waveform B." In this way, according to the adjustment method of this embodiment, the landing position of the UV ink between the waveforms is adjusted by correcting the waveform, thereby adjusting the printing position.

Figure 7 is a diagram for explaining the waveform in the print position adjustment method. Figure 8 is a diagram for explaining the waveform in an unadjusted state in the adjustment method. Also, Figure 9 is a diagram for explaining an adjustment to delay the ejection timing of the waveform, and Figure 10 is a diagram for explaining an adjustment to advance the ejection timing of the waveform.

Here, a specific description will be given of how the print position is adjusted by changing the adjustment waveform "waveform B" relative to the reference waveform "waveform A."
The waveforms A and B used by the print head 30 to eject UV ink can be expressed as shown in Figures 7(a) and 7(b), for example, by taking the elapsed time on the horizontal axis and the drive voltage value applied to the piezoelectric element of the recording head 33 on the vertical axis.

These waveforms A and B correspond to the waveforms that eject one dot of UV ink from the ink ejection nozzle of the recording head 33. When the print head 30 is actually driven in the CR direction to perform one print scan, the head drive unit 16 repeatedly outputs waveforms A and B as shown in the figure for the number of dots to be printed.

The ejection timing of each of the waveforms A and B when the waveform B has not been adjusted relative to the waveform A (unadjusted state) is as shown in FIG. 8. The output start timing of the waveforms A and B in this unadjusted state is managed in ejection coordinate units by the control unit 20 and the head driving unit 16, so that both start output from exactly the same start position.

In this case, in the first adjustment method, the impact timing of the UV ink is adjusted by delaying or advancing the output start timing of the adjustment waveform, waveform B, as described above. Note that the following relationship must be satisfied for one cycle (ejection cycle) of waveforms A and B to eject one dot.
・Discharge cycle (sec) ≦discharge resolution (m)/carriage speed (m/sec)
Therefore, for example, when the ejection resolution is 360 (dpi) = 70.6 (μm) and the carriage speed is 0.5 (m/sec), the ejection cycle must be 70.6 (μm)/0.5 (m/sec) = 141 (μsec) or less.

Under these assumptions, as shown in Figure 9 (b), if the adjustment line 62 by waveform B in the first adjustment pattern 60 is printed with a position shift to the right of the reference line 61 (UV ink lands on the front side in the printing direction), the output start timing of waveform B will be earlier than the output start timing of waveform A.

For this reason, as shown in FIG. 9(a), the output start timing of the reference waveform, waveform A, is not changed, and the output start timing of the pre-adjustment waveform B is delayed by a small time ΔT (adjustment value) to be corrected to become the output start timing of the adjusted waveform B'.

As a result, at the output start timing of waveform B', the start of UV ink ejection is delayed by a small time ΔT from waveform A, so the impact position can be moved so that the adjustment line 62 is shifted to the left relative to the reference line 61 (so that the UV ink lands on the far side in the printing direction). This aligns the adjustment line 62 with the reference line 61, and adjusts the printing position.

On the other hand, as shown in FIG. 10(b), if the adjustment line 62 by waveform B in the first adjustment pattern 60 is printed with a position shift to the left of the reference line 61 (UV ink lands on the far side in the printing direction), the output start timing of waveform B will be later than the output start timing of waveform A.

For this reason, as shown in FIG. 10(a), the output start timing of waveform A, which is the reference waveform, is not changed as described above, but the output start timing of waveform B before adjustment is advanced by a small time ΔT (adjustment value) to correct it to become the output start timing of waveform B' after adjustment.

As a result, at the output start timing of waveform B', the start of UV ink ejection is advanced by a small time ΔT relative to waveform A, so the landing position can be moved so that the adjustment line 62 is shifted to the right relative to the reference line 61 (so that the UV ink lands on the near side in the printing direction). This aligns the adjustment line 62 with the reference line 61, and adjusts the printing position.

In this way, in the adjustment method according to this embodiment, for example, after checking the landing position of the UV ink in the first adjustment pattern 60 of the printed result, the timing of ejection of waveform B is advanced or delayed so as to minimize the positional deviation of the adjustment line 62 relative to the reference line 61, thereby correcting the landing position of the UV ink between each printed layer and adjusting the printing position. This makes it possible to easily and precisely align the printing positions between each printed layer during multi-layer printing.

FIG. 11 is a diagram showing another example of the first adjustment pattern for adjusting the misalignment of the printing positions between the printing layers based on the difference in the printing conditions of each printing layer.
In another example of the first adjustment pattern 60, first, a waveform (reference waveform) "waveform A" that serves as a reference for adjusting the landing position of UV ink included in, for example, the first printing condition (print data 1) is determined from all types of drive voltage waveforms of the print head 30 provided in the printing device 10. Then, the landing position is corrected by adjusting a waveform (adjustment waveform) "waveform C" that is the adjustment target for the landing position of UV ink included in a third printing condition that is different from the first and second printing conditions.

As shown in FIG. 11(a), first, in the first printing layer, which is the first scan, the print head 30 is moved in the printing direction based on the first printing conditions, and a specified UV ink is ejected in "waveform A" to print a reference line 61 on the recording medium 4 (mth layer printing process).

Next, as shown in FIG. 11 (b), after controlling so as not to feed the recording medium 4, in the second printing layer, which is the second scan, the print head 30 is moved in the printing direction based on the third printing conditions, and a specified UV ink is ejected in "waveform C " to print the adjustment lines 62 of the first adjustment pattern 60 between the reference lines 61 on the recording medium 4 (nth layer printing process).

Then, the landing positions of the UV ink on the reference line 61 and the adjustment line 62 in the print result (first adjustment pattern 60) thus printed are checked. It can be seen that in the first adjustment pattern 60, the adjustment line 62 is printed with a position shift to the left of the reference line 61, and therefore it can be seen that the output timing (hereinafter also referred to as the "ejection timing") of "waveform C" is delayed.

Therefore, in the case of such a print result, for example, the adjustment value corresponding to the amount of misalignment input by the user via the operation unit 13 is used to "advance" the ejection timing of waveform C under the control of the control unit 20 so that the printing position of the adjustment line 62 matches the printing position of the reference line 61, as shown in FIG. 11(c), and the landing position of the UV ink is adjusted. The above explanation was about two-layer stacked printing, but if the number of layers is increased (for example, when printing under the third printing condition is performed from the third layer onwards), the printing conditions can be set to the optimum ones for each printing layer.

Second Embodiment
[First example of printing position adjustment method]
Fig. 12 is a diagram for explaining a first example of a second adjustment pattern used in a method for adjusting the printing position between each printing layer during multi-layer printing according to a second embodiment of the present invention. Fig. 13 is a diagram for explaining an image of the dot formation position before and after the adjustment of the first example. In the following description including Fig. 12 and Fig. 13, the same components as those in the first embodiment and its modified examples are given the same reference numerals, so that duplicated descriptions will be omitted below.

Here, we use the first example adjustment pattern 70A from the second adjustment pattern 70, which takes into account not only misalignment due to differences in printing conditions between printed layers, but also misalignment due to overlapping ink between printed layers. This adjustment pattern 70A is a pattern in which the recording medium 4 is undercoated with the reference waveform "waveform A" included in the first printing conditions (print data 1) among the driving voltage waveforms of the print head 30 provided in the printing device 10, and overcoated with the adjustment waveform "waveform B" included in the second printing conditions (print data 2). This adjustment pattern 70A is printed by the adjustment pattern printing process of the control unit 20.

As shown in FIG. 12(a), first, in the first printing layer, which is the first scan, the print head 30 is moved in the printing direction based on the first printing conditions, and a specific UV ink is ejected in "waveform A" to print a reference block 71 consisting of, for example, a rectangular block pattern on the recording medium 4 (mth layer printing process).

Next, as described above, without feeding the recording medium 4, in the second printing layer, which is the second scan, the print head 30 is moved in the printing direction based on the second printing conditions, and a specified UV ink is ejected in "waveform B" to print an adjustment block 72 consisting of a block-shaped pattern similar to the reference block 71 on top of the reference block 71 (nth layer printing process). The reference block 71 and adjustment block 72 constitute the adjustment pattern 70A.

Then, check the UV ink landing positions of the reference block 71 and adjustment block 72 in the print result (adjustment pattern 70A) printed in this way. In the adjustment pattern 70A of the above example, it can be seen that the adjustment block 72 is printed with a position shift to the right of the reference block 71, and therefore it can be seen that the output start timing of "waveform B" is advanced.

Therefore, in the case of such a print result, for example, a correction is performed under the control of the control unit 20 by an adjustment value corresponding to the amount of misalignment input by the user via the operation unit 13, so that the print position of the adjustment block 72 overlaps directly above the print position of the reference block 71, as shown in Fig. 12(b), to "delay" the output start timing of the waveform B of the second print condition, and the landing position of the UV ink is adjusted in response to the change in the landing distance in PG. Note that in the second adjustment pattern 70, for example, when focusing on the adjustment pattern 70A of the first example, if the reference color constituting the reference block 71 and the adjustment color constituting the adjustment block 72 are the same color or similar colors, it may be difficult to confirm them. For this reason, taking into consideration that when performing layered printing, an undercoat (or a topcoat in the case of the second example adjustment pattern 70B described below) is often done with white (W) UV ink, it is easier to check if the reference block 71 is printed with white (W) UV ink and the adjustment block 72 is printed with a colored UV ink (for example, a standard color for adjustment such as magenta (M)).

That is, as shown in FIG. 13, after the print head 30, whose nozzle alignment has been adjusted in advance, is moved in the printing direction to cause the dots 6 of the first printing layer to land on the recording medium 4, in the unadjusted state shown in FIG. 13(a), the landing positions of the dots 7 of the second printing layer are misaligned with respect to the dots 6 of the first printing layer, whereas in the adjusted state shown in FIG. 13(b) (waveform B has been corrected with the adjustment value), it is possible for the landing positions of the dots 7' of the second printing layer to be directly above the dots 6 of the first printing layer, and the printing positions of each layer between each printing layer during multi-layer printing (laminated printing) can be aligned.

[Second Example of Print Position Adjustment Method]
FIG. 14 is a diagram for explaining a second example of the method of adjusting the print position using the second adjustment pattern.
Since the method of laminating UV ink in laminate printing can be changed as appropriate, in addition to the adjustment according to the first example using the adjustment pattern 70A, it is also possible to adjust according to the second example using the following adjustment pattern 70B. In this adjustment method, the landing position is corrected when undercoating the recording medium 4 with the adjustment waveform "waveform B" included in the second printing condition (print data 2) among the driving voltage waveforms of the print head 30 provided in the printing device 10, and overcoating with the reference waveform "waveform A" included in the first printing condition (print data 1).

As shown in FIG. 14, first, in the first printing layer, which is the first scan, the print head 30 is moved in the printing direction based on the second printing conditions, the specified UV ink is ejected in "waveform B", and the adjustment block 72 is printed on the recording medium 4. Next, without feeding the recording medium 4, in the second printing layer, which is the second scan, the print head 30 is moved in the printing direction based on the first printing conditions, the specified UV ink is ejected in "waveform A", and the adjustment block 72 is printed superimposed on the reference block 71, forming the adjustment pattern 70B.

Then, check the UV ink landing positions of the reference block 71 and adjustment block 72 in this print result (adjustment pattern 70B). In the example adjustment pattern 70B in Figure 14, it can be seen that the adjustment block 72 has been printed with a position shift to the right of the reference block 71, and similar to the position shift described above, it can be seen that the output start timing of "waveform B" has been advanced.

Even in such a print result, the adjustment value is used to "delay" the output start timing of waveform B under the second printing condition so that the printing position of adjustment block 72 overlaps directly below the printing position of reference block 71, and the landing position of the UV ink is adjusted in response to the change in landing distance in PG.

That is, as shown in FIG. 15, after the print head 30, whose nozzle alignment has been adjusted in advance, is moved in the printing direction to cause the dots 6 of the first printing layer to land on the recording medium 4, in the unadjusted state shown in FIG. 15(a), the dots 6 of the first printing layer are misaligned with respect to the landing positions of the dots 7 of the second printing layer, whereas in the adjusted state shown in FIG. 15(b) (waveform B has been corrected with the adjustment value), it is possible for the landing positions of the dots 6' of the first printing layer to be directly below the dots 7 of the second printing layer, and the printing positions of each layer between each printing layer during multi-layer printing (laminated printing) can be aligned.

In this way, even with the adjustment method according to this embodiment, for example, after checking the landing position of the UV ink in each of the printed adjustment patterns 70A, 70B, the ejection timing of waveform B can be advanced or delayed so that the printing position of adjustment block 72 overlaps with reference block 71, thereby correcting the landing position of the UV ink between layers during stack printing to adjust the printing position. This makes it possible to precisely and easily align the interlayer printing position during stack printing.

[Third embodiment]
[How to adjust the print position]
Fig. 16 is a diagram for explaining a third adjustment pattern used in a method for adjusting the printing position between each printing layer during multi-layer printing according to a third embodiment of the present invention. Fig. 17 is a diagram for explaining an image of pattern reference in the adjustment method. Here, a third adjustment pattern 80 that combines the above-mentioned adjustment pattern 60 and the second adjustment patterns 70A and 70B will be explained.

That is, as shown in FIG. 16, the print head 30 is moved in the printing direction based on the first and second printing conditions, and for the adjustment patterns 60 and 70A, a predetermined UV ink is ejected in "waveform A" to print the reference line 61 and reference block 71, and for the adjustment pattern 70B, a predetermined UV ink is ejected in "waveform B" to print the adjustment block 72, each as a first printing layer on the recording medium 4.

Next, the print head 30 is moved again in the printing direction based on the first printing conditions and the second printing conditions, and the adjustment lines 62 and adjustment blocks 72 are printed as a second printing layer on the recording medium 4 by ejecting the specified UV ink in "waveform B" for the adjustment patterns 60 and 70A, and the reference blocks 71 are printed as a second printing layer on the recording medium 4 by ejecting the specified UV ink in "waveform A" for the adjustment pattern 70B. The adjustment patterns 60, 70A, and 70B thus formed constitute the adjustment pattern 80 of this embodiment.

In this embodiment, the landing positions of the UV ink for adjustment patterns 60, 70A, and 70B in this print result (adjustment pattern 80) are checked, and those that can be recognized as having a small amount of misalignment on average are determined to be correct for the adjustment of the print position, and an adjustment value based on the judgment result is obtained to correct the "waveform B" of the second printing condition, thereby adjusting the landing positions of the UV ink.

In addition, if the tendency for misalignment between adjustment patterns 60 and 70 in adjustment pattern 80 is different (for example, adjustment pattern 60 is considered to be correct, but adjustment patterns 70A and 70B printed based on different adjustment values are considered to have less misalignment), it is possible to select adjustment patterns 60, 70A, and 70B to be referenced based on the printing tendency of the image data contained in the print data printed by the user, using the following criteria.

That is, as shown in FIG. 17(a), when there are no or few overlapping portions in the image data, the first adjustment pattern 60 of the adjustment pattern 80 is used as the reference pattern 81. Also, as shown in FIG. 17(b), when there are many portions that are undercoated with the reference waveform "waveform A," such as when a solid coat is applied with white (W) UV ink and then a top coat is applied with color (CMYK) UV ink, the second adjustment pattern 70A of the adjustment pattern 80 is used as the reference pattern 81.

Furthermore, as shown in FIG. 17(c), in cases where there are many areas that are overcoated with the reference waveform "waveform A," such as when a recording medium 4, such as a transparent acrylic plate, is undercoated with color (CMYK) UV ink and then thickly printed with varnish (V) UV ink, the second adjustment pattern 70B of the adjustment patterns 80 is used as the reference pattern 81.

[Print position adjustment process]
Fig. 18 is a flow chart showing the procedure of the adjustment pattern printing process and the print position adjustment process executed by the control unit 20 to realize a specific adjustment method for selecting the optimum adjustment value. Fig. 19 is a diagram for explaining the coarse adjustment pattern. Fig. 20 is a diagram for explaining the fine adjustment pattern. Figs. 21 and 22 are diagrams showing examples of display on the display.

Next, the print position adjustment process procedure according to this embodiment will be described. Note that, for the sake of convenience, the following adjustment process includes several steps that involve operation input by the user via the operation unit 13, but all of these can also be automated by the processing of various sensors and the control unit 20 provided in the printing device 10.

As shown in Figure 18, first, in order to check the misalignment of the print position with the adjustment values currently set in the printing device 10 (current adjustment values), a confirmation pattern 30A (see Figure 24) is printed (step S100) based on operation input from the user via the operation unit 13 (hereinafter, description will be omitted unless otherwise specified). As shown in Figure 24, this confirmation pattern 30A is a pattern in which multiple adjustment patterns 80 are repeatedly printed at a predetermined interval in the CR direction across the entire width of the printing area of the recording medium 4.

Next, the user visually checks the printed confirmation pattern, paying particular attention to the reference pattern 81, to check the occurrence of misalignment between the printing layers based on the printing status with the current adjustment values (current values) (step S101). As a result, it is determined whether the alignment of the printing positions for each printing layer has been completed (step S102), and if it is determined that it has not been completed (No in step S102), the amount of misalignment is selected (step S103). On the other hand, if it is determined that it has been completed (Yes in step S102), the series of processes according to this flowchart is terminated.

If the amount of misalignment is judged to be clearly large or if the amount of misalignment cannot be determined ("Large" in step S103), a coarse adjustment pattern 40 as shown in FIG. 19 is printed (step S104). On the other hand, if the amount of misalignment is judged to be clearly small ("Small" in step S103), a fine adjustment pattern 50 as shown in FIG. 20 is printed (step S106).

Here, the coarse adjustment pattern 40 will be described.
With regard to the adjustment of the print position, the adjustment resolution of the printing device 10 is sufficiently small compared to the ejection resolution of the print head 30. For this reason, if the print position is adjusted with the original fine adjustment resolution from the beginning of the adjustment, the adjustment efficiency will actually deteriorate if the amount of deviation is large.

As shown in FIG. 19, in the coarse adjustment pattern 40, a plurality of adjustment patterns 41 based on the adjustment values in the adjustment pattern 80 in which the deviation amount is selected are printed with a sufficiently large resolution (coarse adjustment resolution) that is, for example, several times the resolution of the original adjustment resolution as described above, while changing the adjustment value of the deviation amount. This improves the adjustment efficiency.

The coarse adjustment pattern 40 shown in FIG. 19 is composed of a number of adjustment patterns 41 that are printed with adjustment values that are changed to vary the amount of deviation based on the coarse adjustment resolutions, for example numbers "1" to "11." Note that adjustment pattern 41 numbered "6" is a pattern printed based on the adjustment value in adjustment pattern 80 for which the amount of deviation has been selected.

In addition, as the numbers decrease from "5" to "4", the adjustment values are changed so that the landing position of the printed result of the adjusted waveform "waveform B" under the second printing conditions is shifted in the direction opposite to the origin (to the left as you face it). Conversely, as the numbers increase from "7" to "8", the adjustment values are changed so that the landing position of the printed result of the adjusted waveform "waveform B" under the second printing conditions is shifted in the direction toward the origin (to the right as you face it).

Then, in the thus formed coarse adjustment pattern 40, the selection of the adjustment pattern (adjustment value) with the smallest amount of misalignment of the adjustment line 62 of the adjustment pattern 60 and the adjustment block 72 of the adjustment patterns 70A and 70B is accepted (step S105). In the illustrated example, of the printed adjustment patterns 41 numbered "1" to "11", the adjustment pattern 41 numbered "9" has the smallest amount of misalignment, so this adjustment pattern 41 numbered "9" is selected.

The adjustment pattern 41 in the coarse adjustment pattern 40 is selected by the user selecting the number "9" in the above example, in accordance with the operation message "Select adjustment pattern: (1-11)" displayed on the display 12, as shown in FIG. 21.

Next, the fine adjustment pattern 50 will be described.
The above-mentioned coarse adjustment pattern 40 is composed of a plurality of adjustment patterns 41 in which the adjustment value of the deviation amount is changed based on the coarse adjustment resolution, but as shown in FIG. 20, the fine adjustment pattern 50 is formed by printing a plurality of adjustment patterns 51 based on the adjustment value in the adjustment pattern 80 (or the adjustment pattern 41 selected in the coarse adjustment pattern 40) in which the deviation amount is selected, while changing the adjustment value of the deviation amount, using the original adjustment resolution (narrowed high fine adjustment resolution) of the printing device 10.

The fine adjustment pattern 50 shown in FIG. 20 is composed of a number of adjustment patterns 51 that are printed with adjustment values that are changed to vary the amount of deviation based on the fine adjustment resolutions, for example, numbers "1" to "7." Note that the adjustment pattern 51 numbered "4" is a pattern printed based on the adjustment value in the adjustment pattern 80 (or the adjustment pattern 41 selected in the coarse adjustment pattern 40) for which the amount of deviation has been selected.

In addition, as the number decreases to "3" and "2", the adjustment value is changed so that the landing position of the printed result of the adjusted waveform "waveform B" under the second printing conditions is shifted in the direction opposite to the origin (to the left as you face it). Conversely, as the number increases to "5" and "6", the adjustment value is changed so that the landing position of the printed result of the adjusted waveform "waveform B" under the second printing conditions is shifted in the direction toward the origin (to the right as you face it).

Then, in the fine adjustment pattern 50 thus formed, the selection of the adjustment pattern (adjustment value) with the smallest amount of misalignment of the adjustment line 62 of the adjustment pattern 60 and the adjustment block 72 of the adjustment pattern 70 is accepted (step S107). In the illustrated example, of the printed adjustment patterns 51 numbered "1" to "7", the adjustment pattern 51 numbered "2" has the smallest amount of misalignment, so this adjustment pattern 51 numbered "2" is selected.

The selection of adjustment pattern 51 in fine adjustment pattern 50 is performed by the user selecting number "2" in the above example in accordance with the operation message "Select fine adjustment pattern: (1-7)" displayed on display 12, as shown in FIG. 22, for example.

23 is a diagram for explaining the relationship between the adjustment values of the coarse adjustment pattern and the fine adjustment pattern. As shown in FIG. 23, the relationship between the coarse adjustment pattern 40 and the fine adjustment pattern 50 is as follows.
Coarse adjustment: "Number" + 1 > Fine adjustment: "Number" 7 > Current value > Fine adjustment: "Number" 1 > Coarse adjustment: "Number" - 1

In other words, if the adjustment values of adjustment patterns 41 and 51 numbered "4" in coarse adjustment pattern 40 and fine adjustment pattern 50 are assumed to be the current reference values, the adjustment value of adjustment pattern 41 numbered "5" in coarse adjustment pattern 40 and the adjustment value of adjustment pattern 51 numbered "7" in fine adjustment pattern 50 are set so as not to overlap with each other.

The adjustment value of adjustment pattern 41 numbered "3" in coarse adjustment pattern 40 and the adjustment value of adjustment pattern 51 numbered "1" in fine adjustment pattern 50 are set so as not to overlap. This further improves the efficiency of adjusting the print position using coarse adjustment pattern 40 and fine adjustment pattern 50.

Then, for example, the adjustment value (current value) selected and accepted in step S107 for the printed coarse adjustment pattern 40 or fine adjustment pattern 50 is stored in the memory unit 17 (step S108).

Based on the adjustment values thus stored, the second printing conditions are corrected so that the landing positions of the adjustment lines 62 and adjustment blocks 72 of the adjustment patterns 41 and 51 are aligned with the landing positions of the reference lines 61 and reference blocks 71 of the adjustment patterns 41 and 51 (step S109), and the process proceeds to step S100 above to print the confirmation pattern 30A again (step S100).

FIG. 24 is a diagram for explaining the confirmation pattern.
Using the first printing conditions together with the second printing conditions corrected in step S109, a confirmation pattern 30A is printed in which a plurality of adjustment patterns 80 are pattern-printed, as shown in Fig. 24 (step S100). The illustrated confirmation pattern 30A is one in which the adjustment waveform "waveform B" is corrected based on the adjustment value of adjustment pattern 51 numbered "2" of fine adjustment pattern 50, which has the smallest amount of misalignment, for example, and therefore the misalignment is almost unnoticeable by visual inspection. In such a case, it is determined that the printing position alignment for each printing layer has been performed (completed) (Yes in step S102).

In the above example, the printing position is adjusted by successively printing the fine adjustment pattern 50 and selecting the adjustment value after printing the coarse adjustment pattern 40 and selecting the adjustment value, but it is also possible to select either the printing of the coarse adjustment pattern 40 (step S104) or the printing of the fine adjustment pattern 50 (step S106) based on the amount of deviation.

The print position may be adjusted based not only on the drive voltage waveform for the print head 30 described above, but also on other information included in the printing conditions (information on the carriage speed of the print head 30, the viscosity of the UV ink, the heating temperature of the UV ink, etc.). For example, if the waveform types included in the first and second printing conditions are three types, "waveform A", "waveform B", and "waveform C", and the carriage speed types of the print head 30 are two types, "speed L (Low)" and "speed H (High)", then all of these combinations will be as follows:

[Standard layer] [Adjustment layer]
・Waveform A - Speed L; Waveform B - Speed L
・Waveform A-Speed L; Waveform B-Speed H
・Waveform A-Speed H; Waveform B-Speed L
・Waveform A-Speed H; Waveform B-Speed H
・Waveform A - Speed L; Waveform C - Speed L
・Waveform A-Speed L; Waveform C-Speed H
・Waveform A-Speed H; Waveform C-Speed L
・Waveform A-Speed H; Waveform C-Speed H
・Waveform B-Speed L; Waveform C-Speed L
・Waveform B-Speed L; Waveform C-Speed H
・Waveform B-Speed H; Waveform C-Speed L
・Waveform B-Speed H; Waveform C-Speed H

For all of the above combinations, the waveform is corrected as described above to adjust the ejection timing, and the adjustment values are stored and used for each layered printing in which printing is performed multiple times. In this way, the interlayer printing position for each printing layer in layered printing with the printing device 10 can be aligned accurately and easily, improving print quality.

[Other embodiments]
25 and 26 are diagrams for explaining a layered image of layered printing, and Fig. 27 is a diagram showing a display example of a display.
In addition to the method of adjusting the print position by correcting the landing position of the UV ink described in each of the above embodiments, the printing device 10 can also employ the following adjustment method. That is, in layered printing, when printing is repeatedly performed on the same print target on the recording medium 4, the thickness of the ink layer of the UV ink increases. This change in the ink layer thickness changes the PG, landing distance, and landing position, so it is necessary to consider a method of adjusting the ink layer.

That is, the first correction method in the ink layer adjustment method is landing position correction based on the number of layer printings. In this first correction method, the number of layer printings is counted in the control unit 20, and the landing position adjustment value for each UV ink layer is automatically linearly corrected according to the number of printings to obtain a correction value. The linear correction coefficient is determined in advance by repeating experiments and measurements for each driving voltage waveform as described above, for example, and stored in the storage unit 17. This allows the user of the printing device 10 to print at the optimal UV ink landing position according to the number of layer printings, without being aware of the number of layer printings.

The second correction method in the ink layer adjustment method is PG correction by lowering table 1. In this second correction method, the thickness of the ink layer increased by the ink layer is absorbed by lowering table 1 (work stage (the surface on which recording medium 4 is placed)), and the distance (paper gap: PG) from the nozzle surface of recording head 33 of print head 30 to the landing surface of the UV ink is controlled to be constant. In this case, the printing device 10 is provided with a lifting mechanism for table 1, and the height of table 1 is controlled by controlling the lifting mechanism based on firmware stored in memory unit 17 by control unit 20.

In the ink layer adjustment method, the first and second correction methods may be combined to calculate an optimal correction value. For example, the first correction method is implemented while the PG that changes due to the ink layer is within the recommended range of the product specifications of the print head 30. On the other hand, if the ink layer continues and the PG exceeds the recommended range of the product specifications of the print head 30, the second correction method is implemented to lower the table 1 so that the PG becomes an appropriate value, and the correction value obtained by the first correction method is recalculated according to the change in PG caused by this lowering and applied as the correction value. In addition, in the ink layer adjustment method, for example, a lifting mechanism (not shown) may be provided in the print head 30, and the height of the print head 30 itself may be controlled by the control unit 20 controlling the lifting mechanism based on the firmware stored in the memory unit 17.

In addition, in ink layering, the thickness of the ink layer on the recording medium 4 due to the number of layers will be significantly different between image data (1) included in the print data in which different colored UV inks are deposited as dots 6 in the first layer, dots 7 in the second layer, and dots 8 in the third layer over the entire print area on the recording medium 4 as shown in FIG. 25, and image data (2) included in the print data in which the print area on the recording medium 4 is divided by color of UV ink and UV inks are deposited as dots 6 in the first layer, dots 7 in the second layer, and dots 8 in the third layer as shown in FIG. 26.

In other words, in the image data (1) contained in the former print data, the layer thickness h1 of the ink layer on the recording medium 4 is the thickness of three layers, but in the image data (2) contained in the latter print data, the printing areas of the layers do not overlap, so the layer thickness h2 of the ink layer on the recording medium 4 is only the thickness of one layer.

Therefore, when layer printing is performed by making heavy use of image data (2) contained in the latter print data, the above-mentioned ink layer adjustment method may actually be counterproductive, and in such a case disabling the ink layer adjustment method will result in less degradation of print image quality. For this reason, the ink layer adjustment method is configured so that the adjustment can be selected to be enabled or disabled as appropriate.

In other words, in the ink layer adjustment method, the correction strength (correction level) of the layer correction can be selected from the following three levels + OFF depending on the tendency of the image data to be printed, for example, by following the operation message "Correction level: (OFF, 1-3)" displayed on the display 12 as shown in FIG. 27.

Layer correction level setting:
・3: Strong ・2: Standard ・1: Weak ・OFF: Correction function disabled

The correction level setting criteria is, for example, "2: Normal" or "3: Strong" when the UV ink lands across the entire printing area of each layer, as in image data (1), and "OFF: Correction function disabled" when the UV ink lands on each layer and does not overlap, as in image data (2). When using print data that contains a mixture of image data (1) and image data (2), select "1: Weak" which performs weak correction so that the areas where the UV ink is layered and the areas where it is not layered are good on average, and when printing with the so-called overlay setting turned on, select "3: Strong" since the amount of ink layered per layer is large.

Another adjustment method is, for example, automatic adjustment of the print position using a color sensor. In this automatic adjustment, the control unit 20 automatically changes the adjustment values as described above to prepare a dedicated adjustment pattern that can express so-called shading, and the color sensor reads the printing state of this adjustment pattern to automatically determine and reflect the correction value.

In addition, as a process for shifting the printing layer to be adjusted in the CR direction relative to the reference printing layer, in addition to adjusting the output start timing of the drive voltage waveform as described above, the following method may be executed.

For example, an adjustment method in which the table 1 is driven in the CR direction can be mentioned. The table 1 on which the recording medium 4 is placed is usually configured to be driven only in the PF direction and cannot be driven in the CR direction, but for example, the lifting mechanism for the table 1 can be provided with a movement mechanism in the CR direction, and the table 1 can be shifted in the CR direction under the control of the control unit 20. By shifting the table 1 in the CR direction by a small shift that is sufficiently small compared to the ejection resolution of the print head 30, it becomes possible to adjust the landing position of the UV ink for each waveform on the table 1 side, instead of adjusting the ejection timing on the print head 30 side. In this case, for example, the position change control of the table 1 in the CR direction is performed every time the drive voltage waveform changes.

In addition, for example, an adjustment method of performing data shifting can be mentioned. In this data shifting, the amount of shift for each driving voltage waveform is measured in advance, and dummy data corresponding to the amount of shift measured when creating the print data is added in the CR direction to adjust the landing position of the UV ink in print resolution units. Note that it is possible to realize data shifting in the direction opposite to the origin, which is premised on the addition of dummy data in the CR direction. Therefore, among the landing positions of the UV ink of all the driving voltage waveforms provided in the printing device 10, for example, the waveform printed closest to the origin is set as the reference waveform to which dummy data is not added. This data shifting is suitable for correcting the landing position of the UV ink between each ink color within the same driving voltage waveform, for example. As described above, according to the method for adjusting the printing position between each printing layer during multilayer printing according to each of the above embodiments, it is possible to easily and accurately align the interlayer printing position during stacked printing.

Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the scope of the invention and its equivalents described in the claims.

REFERENCE SIGNS LIST 1 table 2 carriage drive mechanism 3 table drive mechanism 4 recording medium 10 printing device 11 print data input section 12 display 13 operation section 14 carriage drive section 15 table drive section 16 head drive section 17 storage section 20 control section 30 print head 32 ultraviolet (UV) irradiation device

Claims (8)

A print head having nozzles for ejecting reactive curable ink;
a control unit that executes an mth layer printing process in which the print head is moved relatively to a recording medium in a main scanning direction and a sub-scanning direction intersecting the main scanning direction to form and harden dots of the reactive curable ink on the recording medium based on mth printing conditions (m is an integer equal to or greater than 1) and print the mth printing layer; and an nth layer printing process in which the print head is moved relatively to the recording medium in the main scanning direction and the sub-scanning direction to form and harden dots of the reactive curable ink on the recording medium on which the mth printing layer has been printed based on nth printing conditions (n is an integer other than m), and print the nth printing layer,
The control unit is
an adjustment pattern printing process for printing an adjustment pattern for checking and adjusting a deviation in a relative printing position due to a layer thickness, a landing position, and a landing distance of the cured reactive curable ink on the recording medium between the mth printing layer and the nth printing layer;
and a print position adjustment process that adjusts the relative print position deviation taking into consideration the layer thickness, landing position, and landing distance of the cured reactive curable ink on the recording medium between each printing layer between the mth printing layer and the nth printing layer based on the set adjustment value. 2 . The printing device according to claim 1 , wherein the mth printing condition and the nth printing condition each include at least one of a drive waveform supplied to the print head and a movement speed of the print head, and are different from each other. The printing device according to claim 1 or 2, wherein the adjustment patterns include a first adjustment pattern in which the mth printed layer and the nth printed layer do not overlap each other. The printing device according to claim 1 or 2, wherein the adjustment patterns include a second adjustment pattern in which the mth printed layer and the nth printed layer have overlapping printed portions. the adjustment pattern includes a first adjustment pattern and a second adjustment pattern,
the first adjustment pattern includes a reference line formed on one of the mth printed layer and the nth printed layer and an adjustment line formed on the other of the mth printed layer and the nth printed layer;
the second adjustment pattern includes a reference block formed on one of the mth printing layer and the nth printing layer and an adjustment block formed on the other of the mth printing layer and the nth printing layer,
The reference line and the adjustment line do not overlap,
The printing device according to claim 1 or 2, wherein the reference block and the adjustment block overlap each other. The printing device according to claim 5 , wherein the first adjustment pattern is repeatedly formed in the main scanning direction, and the position of the adjustment line relative to the reference line gradually shifts from one side to the other side in the main scanning direction. 6. The printing apparatus according to claim 5, wherein the second adjustment pattern is repeatedly formed in the main scanning direction, and the position of the adjustment block relative to the reference block gradually shifts from one side to the other side in the main scanning direction. A printing device as described in any one of claims 1 to 7, wherein the printing position adjustment process is at least one of a process of shifting the output timing of a drive waveform supplied to the print head in either the mth layer printing process or the nth layer printing process, a process of shifting the printing data of either the mth printing layer or the nth printing layer in the main scanning direction, and a process of shifting a table on which the recording medium is placed in the main scanning direction.

Images