JP7496549B2 - Printing method and printing device - Google Patents

Description

This disclosure relates to a printing method and a printing device.

Conventionally, when forming an image using an inkjet printing device, the image is formed by ejecting ink from a large number of nozzles formed in a print head. In such a configuration, due to processing variations in each nozzle of the print head, the amount and direction of ink ejected from the nozzles may not be stable, or ink may not be ejected from certain nozzles due to nozzle clogging, etc., resulting in a deterioration in the image quality formed. Therefore, a multi-pass method is adopted as a method for improving the deterioration in image quality as described above.

When forming an image using the multi-pass method, the print head is scanned over the target object (recording medium) while ejecting ink from the print head to form the image. At this time, a nozzle row consisting of multiple nozzles is divided into multiple sections for the number of passes, and ink is ejected for each divided area (hereinafter sometimes referred to as a "print nozzle row"). An image is formed in stages by sequentially ejecting ink from the multiple print nozzle rows onto an area of a band width on the target object. Hereinafter, the printing portion of the band width may be referred to as a "band". With this configuration, even if the amount or direction of ink ejection from a specific nozzle is unstable, or ink is not ejected from a specific nozzle, ink ejected from a nozzle that is not experiencing such defects is applied in layers, so an image with reduced degradation in image quality can be obtained.

However, in the multi-pass method, when the print head is scanned to eject ink onto the target object while moving the target object in band width units, the positioning repeatability and positioning accuracy of the print head can cause the ink to land misaligned on the target object. This misalignment of the ink landing position has a significant effect on image quality, particularly at the boundaries of the bands, causing streaks in these areas and degrading image quality. Therefore, configurations to prevent such problems from occurring are being considered (see, for example, Patent Document 1).

In the technology of Patent Document 1, in a multi-pass method, skip columns that do not eject ink are set between adjacent print nozzle columns. With this configuration, blank rows (non-recorded areas) are formed on the bands formed in the previous scan. In addition, the ends of the bands formed in the current scan are shifted from the ends of the lower bands formed in the previous scan. As a result, the boundaries of the bands do not overlap in the stacking direction, reducing the effects of misalignment of landing positions due to positioning repeatability and positioning accuracy at the boundaries of the bands, and improving streaking at the boundaries of the bands.

JP 2012-121317 A

The technology described in Patent Document 1 is considered to be effective to a certain extent in improving streaks at the boundaries of bands. However, with the technology described in Patent Document 1, although the boundaries of bands do not overlap in the stacking direction of the bands, multiple boundaries are formed, and therefore many fine streaks may occur near the boundaries of bands. In addition, since other bands are stacked on top of the boundaries of bands, density unevenness may occur at the boundaries of bands.

The present disclosure aims to provide a printing method and printing device that can form an image on an object with reduced degradation in image quality.

The printing method disclosed herein is a multi-pass printing method that forms an image on an object by ejecting ink from a nozzle array composed of a plurality of nozzles aligned in a direction intersecting the main scanning direction, and includes the steps of: determining the number of passes; determining the length of the object in a sub-scanning direction perpendicular to the main scanning direction as a bandwidth; setting, for the nozzle array, a plurality of print nozzle arrays that can print the bandwidth in one pass based on the number of passes and the bandwidth; and forming the image by performing a scan in which one of the plurality of print nozzle arrays is moved relative to the object in the main scanning direction while ejecting ink from the nozzle array, and the nozzle array is moved relative to the object in the sub-scanning direction to perform the scan for the number of passes, while changing the print nozzle array that performs the scan.

The printing device disclosed herein includes a print head having a nozzle row composed of a plurality of nozzles arranged in a direction intersecting the main scanning direction, and a control unit that performs multi-pass printing to form an image on an object using the print head. The control unit includes a pass number determination unit that determines the number of passes, a bandwidth determination unit that determines the length of the object in a sub-scanning direction perpendicular to the main scanning direction as a bandwidth, a print nozzle row setting unit that sets a plurality of print nozzle rows that can print the bandwidth in one pass based on the number of passes and the bandwidth, and a print control unit that performs a scan in which one of the plurality of print nozzle rows is moved relative to the object in the main scanning direction while ejecting ink from the nozzle row, and moves the nozzle row relative to the object in the sub-scanning direction to perform the scan for the number of passes to form the image.

The printing method and printing device disclosed herein can form an image on a target object with reduced degradation in image quality.

FIG. 1 is a perspective view showing a main configuration of an inkjet printing apparatus according to a first embodiment and a second embodiment of the present disclosure; FIG. 1 is a schematic diagram showing a print nozzle row when the number of passes is set to four in a typical multi-pass printing method; FIG. 1 is a schematic diagram showing the printing state for each scan of a print head when the number of passes is set to four in a typical multi-pass printing method. FIG. 1 is a schematic diagram showing a print nozzle row when the number of passes is set to four passes in a multi-pass printing method according to a first embodiment of the present disclosure; FIG. 13 is a schematic diagram showing the printing state for each scan of the print head when the number of passes is set to four in the multi-pass printing method according to the first embodiment of the present disclosure; 1A to 1D are schematic diagrams showing the mask patterns of each pass during four-pass printing in the first embodiment of the present disclosure, where (A) shows the mask pattern of the first pass, (B) shows the mask pattern of the second pass, (C) shows the mask pattern of the third pass, and (D) shows the mask pattern of the fourth pass. FIG. 13 is a schematic diagram showing the relationship between the print nozzle row and the width of the target object in the multi-pass printing method according to the second embodiment of the present disclosure; 13A and 13B are schematic diagrams showing print nozzle rows and non-print nozzle rows in a multi-pass printing method according to a second embodiment of the present disclosure, where FIG. 13A shows a first setting example and FIG. 13B shows a second setting example.

[First embodiment]
A first embodiment of the present disclosure will be described with reference to the drawings.

<Configuration of Inkjet Printing Apparatus>
1 is a perspective view showing the main configuration of an inkjet printing device according to the first and second embodiments of the present disclosure. The inkjet printing device 1 is an example of a printing device. The inkjet printing device 1 includes a stand 2, a movable stage 3, a gantry (gatepost) 4, a guide unit 5, a carriage 6, a print head 7, and a control unit 8.

The stand 2 is configured to be able to move up and down. The stand 2 has a highly rigid structure.

The movable stage 3 is placed on the stand 2. A fixing jig 31 for fixing the object T is placed on the movable stage 3. The movable stage 3 is configured to be movable in the main scanning direction H1 and the sub-scanning direction H2 perpendicular to the main scanning direction H1. Ball screws (not shown) extending in the main scanning direction H1 and the sub-scanning direction H2 are connected to the movable stage 3. Motors (not shown) for rotating the ball screws are connected to each ball screw. A control unit 8 is connected to each motor. The rotation of each motor is controlled by commands from the control unit 8, so that the movable stage 3 moves to any position at any speed.

The gantry 4 is made of a highly rigid frame and has a structure that is resistant to external disturbances such as vibrations. The gantry 4 is installed so as to straddle the movable stage 3. The gantry 4 is installed so as to have a guide section 5 extending in the main scanning direction H1.

A ball screw (not shown) extending in the primary scanning direction H1 is installed inside the guide section 5. The carriage 6 is connected to the ball screw installed in the guide section 5. A motor (not shown) for rotating the ball screw is also connected to the end of the ball screw installed in the guide section 5. The motor is connected to the control section 8. The rotation of the motor is controlled by commands from the control section 8, so that the carriage 6 moves back and forth in the primary scanning direction H1 at any speed.

The carriage 6 is equipped with multiple print heads 7 and ink tanks corresponding to each print head 7. The carriage 6 is equipped with an encoder (a sensor for reading using a laser sensor or the like) (not shown). The encoder is installed in a position facing the guide section 5. A linear scale (not shown) extending in the main scanning direction H1 is installed near the guide section 5. When the carriage 6 is moved in the main scanning direction H1, the linear scale is read by the encoder installed on the carriage 6. The encoder outputs the reading result of the linear scale to the control section 8. Based on the pulse signal generated by the control section 8 based on this reading result, ink is ejected from the print head 7 so as to form a specified image at a specified timing.

Each print head 7 has a plurality of nozzles 70 (see FIG. 2, for example) for ejecting ink arranged in a row along the sub-scanning direction H2. The plurality of nozzles 70 arranged in a row in the sub-scanning direction H2 constitute a nozzle row 71 (see FIG. 2, for example). The print head 7 ejects ink from the nozzles when an ejection signal is input at a predetermined timing. Since a plurality of print heads 7 are installed, a full-color image can be formed by ejecting ink of different colors (C (cyan), Y (yellow), M (magenta), K (black), etc.) from each print head 7. The number of print heads 7 installed may be increased depending on the image to be formed. When applying a single color, the number of print heads 7 installed may be one. A control unit 8 is connected to each print head 7 for ejecting ink from each nozzle 70 at a predetermined timing in order to form an image on the target object T.

In the printing operation, the object T is fixed on the movable stage 3, and the movable stage 3 is moved so that the object T is located directly below the print head 7. The height of the stand 2 is set so that the distance between the object T and the print head 7 is an appropriate distance (approximately 2 mm). The print head 7 is caused to scan the object T in the main scanning direction H1, while ink is ejected from the print head 7 onto the object T. After ink is ejected from the print head 7 onto the object T for one scan, the movable stage 3 is moved a predetermined distance in the sub-scanning direction H2, and the print head 7 is again caused to scan the object T in the main scanning direction H1, while ink is ejected from the print head 7 onto the object T. This is repeated to form an image on the object T.

The above is the main configuration of the inkjet printing device for printing in the first and second embodiments of the present disclosure, but the main configuration is an example of the equipment configuration. An inkjet printing device may be used in which the movable stage 3 moves in the main scanning direction H1 relative to the print head 7, ink is ejected from the print head 7 as the movable stage 3 moves, and an image is formed while the print head 7 moves in the sub-scanning direction H2 for each scan of the movable stage 3. Also, an inkjet printing device may be used in which the print head 7 remains fixed and only the movable stage 3 moves in the main scanning direction H1 relative to the print head 7 and in the sub-scanning direction H2 for each scan. Furthermore, an inkjet printing device may be used in which both the print head 7 and the movable stage 3 move in the main scanning direction H1 and both the print head 7 and the movable stage 3 move in the sub-scanning direction H2 for each scan.

The ink used to form the image can be any type, including water-based ink, solvent-based ink, UV ink, etc. Depending on the ink, it may be necessary to introduce a component that dries or hardens the ink, so such a component can be introduced into the inkjet printing device as appropriate.

<General multi-pass printing method>
Next, a description will be given of a typical multi-pass printing method using the inkjet printing device 1. In a typical multi-pass method, printing is performed by dividing the nozzle row arranged on the print head 7 of the inkjet printing device 1 into equal intervals based on the number of passes. At this time, the length of the print nozzle row, which is set by dividing the nozzle row by the number of passes, is the same as the bandwidth.

Figure 2 is a schematic diagram showing a print nozzle row when the number of passes is set to four in a typical multi-pass printing method. As shown in Figure 2, the nozzle row 71 of the print head 7 is divided into four equal parts to set a first print nozzle row 711, a second print nozzle row 712, a third print nozzle row 713, and a fourth print nozzle row 714. If the length of the nozzle row is L, the length of the first to fourth print nozzle rows 711 to 714 is L/4. An image is formed on the object T by ejecting ink from the print head 7 while scanning the print head 7 in the main scanning direction H1 and moving the object T in the sub-scanning direction H2 in band width units.

Figure 3 is a schematic diagram showing the printing state for each scan of the print head when the number of passes is set to four in a typical multi-pass printing method. In Figure 3, the first to fourth print nozzle rows 711 to 714 are shown diagrammatically as rectangles. Here, the width (length in the sub-scanning direction H2) of the object T on which the image is formed is taken as D.

In the first scan, since the fourth print nozzle row 714 is shorter than the width D of the target object T, ink is ejected from the fourth print nozzle row 714 only onto area A whose length is the same as the band width, and no ink is ejected onto the remaining area B.

In the second scan, the object T is moved the same length as one print nozzle row, and then ink is ejected. At this time, ink is ejected from the third print nozzle row 713 into area A, and ink is ejected from a part of the fourth print nozzle row 714 into area B.

After that, in the third, fourth, and fifth scans, the print head 7 is scanned while the object T is moved and ink is ejected onto the object T. In this way, ink is repeatedly ejected from the first to fourth print nozzle rows 711 to 714, which are different from each other, of the print head 7, and an image is formed on the object T by overlapping the ejection of ink four times each onto areas A and B.

At this time, because the length of the first to fourth print nozzle rows 711 to 714 is shorter than the width D of the target object T, streaks occur at the boundary between area A and area B (band boundary).

Furthermore, when the ink ejection during the scan of the print head 7 is not ejected only in one direction, but is ejected in a reciprocating scan to form an image on the target object T (for example, when the first, third, and fifth scans in FIG. 3 are the forward pass, and the second and fourth scans are the return pass, and ink is ejected on each of the forward and return passes), if ink of different colors is ejected from each print head 7, the order of overlapping colors will be different in area A and area B. If the order of overlapping colors is different in this way, when the image is completed, images with different color shades will be formed in area A and area B. Furthermore, this difference in color shade will make the streaks at the boundaries of the bands even more noticeable.

As mentioned above, when an image is formed using a typical multi-pass method, streaks occur at the boundaries between bands, degrading the image quality of the formed image.

<Multi-pass printing method according to the first embodiment>
Next, a multi-pass printing method in the first embodiment will be described. The multi-pass printing method in the first embodiment includes the following first to fourth steps. The first step is a step of determining the number of passes when forming an image in stages on the object T by the multi-pass method. The second step is a step of determining the bandwidth. The third step is a step of setting a plurality of print nozzle rows for printing the bandwidth for the nozzle row 71 based on the number of passes and the bandwidth. The fourth step is a step of performing a scan for printing the bandwidth by the number of passes by ejecting ink from any one of the plurality of print nozzle rows while moving the object T and the nozzle row 71 (print head 7) relatively in the main scanning direction H1, and completing the image by changing the print nozzle row for printing the bandwidth by moving the object T and the nozzle row 71 relatively in the sub-scanning direction H2. The first to fourth steps will be described in detail below.

[First step]
The first step is performed by the pass number determination unit of the control unit 8. When printing using the multi-pass method, in the third step, print nozzle rows into which the nozzle row 71 is divided are set according to the number of passes, and ink ejection is repeatedly performed for each print nozzle row. At this time, the greater the number of passes, the greater the number of times a band width is printed using nozzles 70 in different regions, reducing the effect of ejection variations due to the nozzles 70, making it possible to form a high-quality image.

However, in the first embodiment, if the number of passes is P, the width of the object is D, and the length of the nozzle row 71 of the print head 7 is L, the pass number determination unit sets the number of passes to satisfy L/D<P≦1.5×L/D. The reason is as follows. When the number of passes is set to satisfy L/D<P, the print nozzle rows are set so that adjacent print nozzle rows overlap in part, as described below. In such a situation, if the number of passes P is made larger than 1.5×L/D, the area of the print nozzle rows that overlaps between passes becomes large, and the effects of variations in the ejection of the nozzles 70 and non-ejection of ink are duplicated, which may lead to a deterioration in image quality even when the multi-pass method is used.

[Second step]
The second step is performed by a bandwidth determination unit of the control unit 8. The bandwidth determination unit determines the width of the target object T as the bandwidth. In other words, the bandwidth determination unit sets the width of the band printed by one print nozzle row to be the same size as the width of the target object T.

[Third step]
The third step is performed by the print nozzle array setting unit of the control unit 8. The print nozzle array setting unit sets the same number of print nozzle arrays as the number of passes for the nozzle array 71. The print nozzle array setting unit also sets a print nozzle array with the same width as the width of the target object T. At this time, since the width of the target object T is larger than L/P (D>L/P), the nozzle array 71 cannot be divided evenly by the band width (the width of the target object T). Therefore, the print nozzle array setting unit sets the print nozzle arrays so that adjacent print nozzle arrays partially overlap.

Figure 4 is a schematic diagram showing the print nozzle array when the number of passes is set to four in the multi-pass printing method of the first embodiment. As shown in Figure 4, when the nozzle array 71 of the print head 7 is divided into four equal parts, the widths (band widths) of the first, second, third, and fourth print nozzle arrays 711, 712, 713, and 714 are W11, W12, W13, and W14, respectively. On the other hand, in the first embodiment, the width of the target object T is larger than the widths (W11 to W14) of the first to fourth print nozzle arrays 711 to 714 obtained by dividing the nozzle array 71 into four equal parts. Therefore, when the print nozzle array setting unit sets a print nozzle array with the same width as the width of the target object T for the nozzle array 71, it overlaps a part of the adjacent print nozzle array.

Specifically, the print nozzle row setting unit sets a nozzle row obtained by adding a portion of the second print nozzle row 712 to the first print nozzle row 711 as the first print nozzle row 721. The print nozzle row setting unit sets a nozzle row obtained by adding a portion of the third print nozzle row 713 to the second print nozzle row 712 as the second print nozzle row 722. The print nozzle row setting unit sets a nozzle row obtained by adding a portion of the fourth print nozzle row 714 to the third print nozzle row 713 as the third print nozzle row 723. The print nozzle row setting unit sets a nozzle row obtained by adding a portion of the third print nozzle row 713 to the fourth print nozzle row 714 as the fourth print nozzle row 724. The widths (band widths) of the first, second, third and fourth print nozzle rows 721, 722, 723 and 724 are W21, W22, W23 and W24, which are greater than W11, W12, W13 and W14, respectively. In this manner, the print nozzle row setting unit sets the first, second, third and fourth print nozzle rows 721, 722, 723 and 724 to the same width as the width of the target object T by overlapping a portion of the adjacent print nozzle rows. The print nozzle row setting unit sets the first, second, third and fourth print nozzle rows 721, 722, 723 and 724 to satisfy the relationship W21=W22=W23=W24=D. The overlap width of adjacent print nozzle rows is
They may be the same or different in each overlapping portion.

[Step 4]
The fourth step is performed by the print control unit of the control unit 8. The print control unit ejects ink onto the object T from each of the first to fourth print nozzle rows 721 to 724 set in the third step. The print control unit scans the print head 7 in the main scanning direction H1, ejects ink from the first print nozzle row 721 in the first pass, and then moves the object T in the sub-scanning direction H2 before the next scan to a position facing the second print nozzle row 722 in the second pass. Next, the print control unit scans the print head 7 in the main scanning direction H1, ejects ink from the second print nozzle row 722. The print control unit repeats such scanning of the print head 7 and movement of the object T for the number of passes to form an image on the object T.

Figure 5 is a schematic diagram showing the printing state for each scan of the print head when the number of passes is set to four in the multi-pass printing method of the first embodiment. In Figure 5, the first to fourth print nozzle rows 721 to 724 are shown as rectangles, similar to Figure 3.

In the first scan, the width of the fourth print nozzle row 724 is the same as the width D of the object T, so ink is ejected over the entire width of the object T in one scan.

In the second scan, the print control unit moves the object T to a position facing the third print nozzle row 723 in the second pass, and scans the print head 7 to eject ink from the third print nozzle row 723.

Thereafter, in the third and fourth scans, the print control unit moves the object T to a position facing the second print nozzle row 722 in the third pass and the first print nozzle row 721 in the fourth pass, in the same manner as in the first and second scans, and forms an image on the object T by ejecting ink from the second print nozzle row 722 and the first print nozzle row 721.

Ink is ejected from the first to fourth print nozzle rows 721 to 724, which have the same width as the width of the object T, so the width of the object T matches the band width. This eliminates the boundaries between bands, making it possible to form an image on the object T without streaks. In addition, when reciprocating printing is performed using multiple print heads 7, the width of the object T matches the band width, so the order in which each color is overlaid on the object T is the same, and color unevenness does not occur.

In the fourth step, ink is ejected in the order of the fourth, third, second, and first print nozzle rows 724, 723, 722, and 721, but the order in which ink is ejected may be an order that is unrelated to the order in which the first through fourth print nozzle rows 721-724 are arranged.

For example, ink may be ejected in the order of the third, first, fourth, and second print nozzle rows 723, 721, 724, and 722. In this case, it is more preferable to use an order that improves image quality. For example, if there are nozzles 70 that do not eject ink in the first and second print nozzle rows 721 and 722, and there are no nozzles 70 that do not eject ink in the third and fourth print nozzle rows 723 and 724, it is more preferable to eject ink in the order of the first, third, second, and fourth print nozzle rows 721, 723, 722, and 724. In other words, it is more preferable to use an order that does not allow the print nozzle rows in which there are nozzles 70 that do not eject ink to be consecutive.

In addition, in the fourth step, if the variation in ink ejection from the first to fourth print nozzle rows 721-724 is relatively small, but the ink ejection state from a very small number of nozzles 70 is poor and adversely affects the formed image quality, the deterioration of the image quality can be prevented by stopping the ejection of ink from the print nozzle row including the nozzle 70 with the poor ejection state. In this case, an image is formed by ejecting ink multiple times only from the print nozzle row that does not include the nozzle 70 with the poor ejection state. However, if ink is ejected from the same print nozzle row continuously, the effect of the variation in the landing of the ink ejected from this print nozzle row becomes noticeable, and there is a possibility that the image quality will deteriorate. For this reason, it is preferable not to eject ink from the same print nozzle row continuously.

For example, if the ink ejection condition from the second print nozzle row 722 is so poor that it affects image quality, ink is not ejected from this second print nozzle row 722. Instead, ink is ejected from the first print nozzle row 721 multiple times, and ink is ejected in the order of the fourth, first, third, and first print nozzle rows 724, 721, 723, and 721.

In addition, in the fourth step, ink may be ejected using a different mask pattern in each pass. The mask pattern is a pattern for thinning out the images so that the images formed in each pass are complementary to each other.

Figures 6(A) to 6(D) are schematic diagrams showing mask patterns for each pass during four-pass printing shown in Figures 4 and 5. Figure 6(A) shows a mask pattern 91 for the first pass. Figure 6(B) shows a mask pattern 92 for the second pass. Figure 6(C) shows a mask pattern 93 for the third pass. Figure 6(D) shows a mask pattern 94 for the fourth pass. Each mask pattern 91 to 94 corresponds to 8 x 8 pixels. When image data exists in the black rectangular pixel portion in Figures 6(A) to 6(D), ink is ejected corresponding to that pixel portion. The mask patterns 91 to 94 are staggered patterns, and each is complementary. Therefore, a predetermined image is formed by ejecting ink from each of the first to fourth print nozzle rows 721 to 724 for each pass and overlapping the images formed for each pass. However, this mask pattern is just an example, and an appropriate mask pattern can be used as appropriate.

[Second embodiment]
Next, a second embodiment of the present disclosure will be described with reference to the drawings. In the second embodiment, an image is formed by using an inkjet printing apparatus 1 shown in FIG. 1 and a multi-pass printing method different from that of the first embodiment.

<Multi-pass printing method according to the second embodiment>
In the multi-pass printing method in the second embodiment, printing is performed by setting the width of the print nozzle row obtained by dividing the nozzle row 71 at equal intervals by the number of passes to be longer than the width of the target object T. Each process constituting the multi-pass printing method will be described below.

[First step]
The first step is performed by a pass number determination unit of the control unit 8. If the number of passes is P, the width of the target object is D, and the length of the nozzle row 71 of the print head 7 is L, the pass number determination unit sets the number of passes so as to satisfy P<L/D.

[Second step]
The second step is performed by a bandwidth determination section of the control section 8. The bandwidth determination section determines the width of the object T as the bandwidth, similarly to the first embodiment.

[Third step]
The third step is performed by the print nozzle array setting unit of the control unit 8. The print nozzle array setting unit sets the same number of print nozzle arrays as the number of passes for the nozzle array 71. The print nozzle array setting unit also sets a print nozzle array with the same width as the width of the target object T. At this time, because the width of the target object T is less than L/P (D<L/P), there will be nozzles 70 that are not included in the print nozzle array.

Figure 7 is a schematic diagram showing the relationship between the print nozzle array and the width of the target object in the multi-pass printing method of the second embodiment. As shown in Figure 7, if the same number of print nozzle arrays 730 as the number of passes are set for the nozzle array 71, the width of each print nozzle array 730 will be W30. On the other hand, the width (D) of the target object T will be shorter than the width (W30) of each print nozzle array 730. As described above, in the second embodiment, the width of each print nozzle array 740 is set to the same as the width of the target object T, so there is no need to eject ink from the nozzle arrays corresponding to each print nozzle array 730 that have a length of W31 (=W30-D).

The print nozzle array setting unit may set adjacent print nozzle arrays equal in number to the number of passes, and may set the surplus nozzle arrays as non-print nozzle arrays (first setting example). The non-print nozzle arrays are composed of nozzles 70 that do not eject ink in any scan. The print nozzle array setting unit may also set split nozzle arrays by dividing the nozzle array 71 at equal intervals by the number of passes, set print nozzle arrays centered on the center of each split nozzle array, and set the surplus nozzle arrays as non-print nozzle arrays (second setting example). The first and second setting examples are described in detail below.

FIG. 8(A) is a schematic diagram showing a first example of the settings of print nozzle rows and non-print nozzle rows in a multi-pass printing method according to a second embodiment. FIG. 8(B) is a schematic diagram showing a second example of the settings of print nozzle rows and non-print nozzle rows in a multi-pass printing method according to a second embodiment.

In a first setting example shown in Fig. 8 (A), when the number of passes is 4, the print nozzle array setting unit sets the first, second, third, and fourth print nozzle arrays 751, 752, 753, and 754 adjacent to each other and having the same width as the width of the target object T, and sets the surplus nozzle array as a non-print nozzle array 759. In a second setting example shown in Fig. 8 (B), when the number of passes is 4, the print nozzle array setting unit first sets the first, second, third, and fourth divided nozzle arrays 791, 792, 793, and 794 by dividing the nozzle array 71 at equal intervals by the number of passes. Next, the print nozzle array setting unit sets the first, second, third, and fourth print nozzle arrays 761, 762, 763, and 764 centered on the centers of the first, second, third, and fourth divided nozzle arrays 791, 792, 793, and 794, and sets the surplus nozzle array as a non-print nozzle array 769.

[Step 4]
The fourth step is performed by the print control unit of the control unit 8. As in the first embodiment, the print control unit forms an image on the target object T by ejecting ink from the first, second, third and fourth print nozzle rows 751, 752, 753 and 754 (761, 762, 763 and 764) and not ejecting ink from the non-print nozzle row 759 (769) in the first, second, third and fourth scans.

The inkjet printing method and printing device disclosed herein can form high-quality images without streaks, and can be used for a wide range of consumer and industrial purposes, including not only image formation but also the manufacture of various devices and 3D printer printing methods using the inkjet method.

REFERENCE SIGNS LIST 1 Inkjet printing device 2 Stand 3 Movable stage 4 Gantry 5 Guide section 6 Carriage 7 Print head 8 Control section 31 Fixture 70 Nozzle 71 Nozzle row 91, 92, 93, 94 Mask pattern 711, 721, 751, 761 First print nozzle row 712, 722, 752, 762 Second print nozzle row 713, 723, 753, 763 Third print nozzle row 714, 724, 754, 764 Fourth print nozzle row 730, 740 Print nozzle row 759, 769 Non-print nozzle row A, B Area D Width H1 Main scanning direction H2 Sub-scanning direction T Target object

Claims (7)

A multi-pass printing method for forming an image on an object by ejecting ink from a nozzle row composed of a plurality of nozzles aligned in a direction intersecting a main scanning direction, comprising:
determining the number of passes;
determining a length of the object in a sub-scanning direction perpendicular to the main scanning direction as a bandwidth;
setting a plurality of print nozzle rows for the nozzle rows that can print the bandwidth in one pass based on the number of passes and the bandwidth;
and forming the image by performing a scan in which ink is ejected from any one of the plurality of print nozzle arrays and the nozzle array is moved relatively to the object in the main scanning direction, while moving the nozzle array relatively to the object in the sub-scanning direction, for the number of passes, while changing the print nozzle array that performs the scan. determining the number of passes includes determining the number of passes so as to satisfy P>L/D, where P is the number of passes, D is a length of the object in the sub-scanning direction, and L is a length of the nozzle row in the sub-scanning direction;
The printing method of claim 1 , wherein setting the plurality of print nozzle rows relative to the nozzle row includes setting the print nozzle rows such that adjacent print nozzle rows partially overlap. The printing method according to claim 2, wherein the step of determining the number of passes includes a step of determining the number of passes so as to satisfy P≦1.5×L/D, where P is the number of passes, D is the length of the object in the sub-scanning direction, and L is the length of the nozzle row in the sub-scanning direction. determining the number of passes includes determining the number of passes so as to satisfy P<L/D, where P is the number of passes, D is a length of the object in the sub-scanning direction, and L is a length of the nozzle row in the sub-scanning direction;
2. The printing method according to claim 1, wherein the step of setting the plurality of print nozzle rows for the nozzle row includes a step of setting the plurality of print nozzle rows and a non-print nozzle row that does not eject the ink in the step of forming the image for the nozzle row. The printing method according to any one of claims 1 to 4, wherein the step of forming the image includes a step of ejecting ink from the same print nozzle row in multiple scans among the scans of the number of passes. The printing method according to any one of claims 1 to 5, wherein the step of forming the image includes a step of changing the print nozzle row that faces the object in an order that is unrelated to the order in which the multiple print nozzle rows are arranged. a print head having a nozzle row made up of a plurality of nozzles aligned in a direction intersecting the main scanning direction;
a control unit that performs multi-pass printing to form an image on an object using the print head,
The control unit is
a number of paths determination unit for determining the number of paths;
a bandwidth determination unit that determines a length of the object in a sub-scanning direction perpendicular to the main scanning direction as a bandwidth;
a print nozzle array setting unit that sets, for the nozzle array, a plurality of print nozzle arrays that can print the bandwidth in one pass based on the number of passes and the bandwidth;
a print control unit that forms the image by performing a scan in which one of the plurality of print nozzle arrays is moved relative to the object in the main scanning direction while ejecting ink from the nozzle array, and performing the scan for the number of passes while changing the print nozzle array that performs the scan by moving the nozzle array relative to the object in the sub-scanning direction.

Images