Image forming device, image forming method, and image forming program

Abstract

This image forming device comprises a head unit, and a control unit that performs a first operation and a second operation. When the number of the first operation is n (an integer equal to or greater than 2) times and the second operation of m × n times, moving in one direction to one side in a second direction, with respect to each pixel row formation region obtained by dividing a nozzle pitch corresponding region into m (an integer equal to or greater than 1) regions in the second direction, is performed, the control unit prohibits the discharge of the ink in at least one nozzle from an end portion side of the head unit in at least one first operation.

Description

Image forming apparatus, image forming method, and image forming program

[0001] The present invention relates to an image forming apparatus, an image forming method, and an image forming program.

[0002] Inkjet printing devices (image forming devices) are used for industrial printing. For example, inkjet printing devices are used to print wiring patterns and the like on printed circuit boards (PCBs), which serve as recording media. In inkjet printing devices, there is some variation in print length between inkjet heads (hereinafter referred to as heads), and such variation can cause ink droplets to land misaligned, resulting in defects such as gaps and streaks in the printed wiring patterns.

[0003] To prevent wiring defects caused by misaligned ink droplets, a printing method known as block printing, a type of multi-pass printing, is generally used (see, for example, Patent Document 1). In block printing, adjacent pixels adjacent to a printed pixel are printed using the same nozzle or nearby nozzles on the head, thereby reducing the amount of movement of the recording medium or head carriage in the nozzle row direction. This reduces ink droplet landing misalignment caused by variations in print length between heads. When printing an image width greater than the print length of the heads, block printing advances the recording medium or carriage by the number of heads multiplied by the print length.

[0004] Japanese Patent Application Laid-Open No. 2022-72456

[0005] In combination with the block printing described above, there is a method called feathering or interleaving, in which the pixel rows of the target area are not printed in a single pass, but are printed over multiple passes. In this method, the pixel rows of the target area are printed over multiple passes, so it is necessary to reverse the direction of movement of the recording medium or carriage. When reversing the direction of movement of the recording medium or carriage, the accuracy of the recording medium or carriage movement during reversal can be reduced due to structural play in the movement mechanism.

[0006] An object of the present invention is to provide an image forming apparatus, an image forming method, and an image forming program that can prevent deterioration in the movement accuracy of a recording medium or a carriage.

[0007] An image forming apparatus according to the present invention comprises: a head unit that ejects ink from a plurality of nozzles arranged in a row at a nozzle pitch along a second direction perpendicular to the first direction; and a control unit that controls the formation of an image using the ink in a nozzle pitch corresponding area of ​​the recording medium that corresponds to the nozzle pitch by repeating a first operation of ejecting the ink while moving the recording medium and the head unit relatively in the first direction, and a second operation of moving the recording medium and the head unit relatively in the second direction, wherein when the number of first operations is n (an integer of 2 or more) for each of pixel row formation areas obtained by dividing the nozzle pitch corresponding area in the second direction, the control unit prohibits the ejection of ink from at least one of the nozzles from the end side of the head unit in at least one of the first operations when performing the second operations m x n times by moving in one direction on one side of the second direction, when the number of first operations is n (an integer of 2 or more) for each of pixel row formation areas obtained by dividing the nozzle pitch corresponding area in the second direction.

[0008] The image forming method according to the present invention is an image forming device having a head unit that ejects ink from a plurality of nozzles arranged in a row at a nozzle pitch along a second direction perpendicular to a first direction, the image forming method forming an image using the ink in a nozzle pitch corresponding area of ​​the recording medium that corresponds to the nozzle pitch by repeating a first operation of ejecting the ink while moving the recording medium and the head unit relatively in the first direction, and a second operation of moving the recording medium and the head unit relatively in the second direction, wherein when the number of first operations is n (an integer of 2 or more) for each of pixel row formation areas obtained by dividing the nozzle pitch corresponding area in the second direction into m (an integer of 1 or more), when performing m x n second operations moving in one direction on one side of the second direction, the ejection of ink from at least one nozzle from the end side of the head unit is prohibited in at least one of the first operations.

[0009] The image forming program of the present invention is an image forming device having a head unit that ejects ink from a plurality of nozzles arranged in a row at a nozzle pitch along a second direction orthogonal to a first direction, the image forming program causing a computer to execute a process of forming an image using the ink in a nozzle pitch corresponding area of ​​the recording medium that corresponds to the nozzle pitch by repeating a first operation of ejecting the ink while moving a recording medium and the head unit relatively in the first direction, and a second operation of moving the recording medium and the head unit relatively in the second direction, the image forming program causing the computer to execute a process of prohibiting the ejection of ink from at least one nozzle from an end side of the head unit in at least one first operation when the number of first operations is n (an integer of 2 or more) for each pixel row formation area obtained by dividing the nozzle pitch corresponding area into m (an integer of 1 or more) in the second direction.

[0010] According to the present invention, it is possible to prevent deterioration in the movement accuracy of the recording medium or the carriage.

[0011] FIG. 1 is a top view showing the main configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2A is a diagram showing an example of the configuration of an inkjet head. FIG. 2B is a diagram showing an example of the configuration of a carriage having the inkjet head shown in FIG. 2A. FIG. 3A is a diagram showing another example of the configuration of an inkjet head. FIG. 3B is a diagram showing another example of the configuration of an inkjet head. FIG. 3C is a diagram showing another example of the configuration of an inkjet head. FIG. 4A is a diagram explaining a conventional image forming method, illustrating the first to fourth passes. FIG. 4B is a diagram explaining a conventional image forming method, illustrating the fifth to eighth passes. FIG. 5A is a diagram explaining an image forming method according to an embodiment of the present invention, illustrating the first to fourth passes. FIG. 5B is a diagram explaining an image forming method according to an embodiment of the present invention, illustrating the fifth to eighth passes. FIG. 6 is a diagram explaining a state in which the spacing between pixel rows becomes uneven when there is variation in print length between inkjet heads in general multi-pass printing. FIG. 7A is a diagram illustrating a modified example (Modification 1) of the image forming method according to the embodiment of the present invention, illustrating the first to fourth passes. FIG. 7B is a diagram illustrating a modified example (Modification 1) of the image forming method according to the embodiment of the present invention, illustrating the fifth to eighth passes. FIG. 8A is a diagram illustrating another modified example (Modification 2) of the image forming method according to the embodiment of the present invention, illustrating the first to third passes. FIG. 8B is a diagram illustrating another modified example (Modification 2) of the image forming method according to the embodiment of the present invention, illustrating the fourth to sixth passes. FIG. 9A is a diagram illustrating another modified example (Modification 3) of the image forming method according to the embodiment of the present invention, illustrating the first to fourth passes. FIG. 9B is a diagram illustrating another modified example (Modification 3) of the image forming method according to the embodiment of the present invention, illustrating the fifth to eighth passes. FIG. 10A is a diagram illustrating another modified example (Modification 4) of the image forming method according to the embodiment of the present invention, illustrating the first to fourth passes. FIG. 10B is a diagram for explaining another modified example (modified example 4) of the image forming method according to the embodiment of the present invention, and is a diagram for explaining the fifth to eighth passes.11A is a diagram showing how ink is ejected from each nozzle of the inkjet head so as to narrow inward, and FIG. 11B is a diagram showing how ink is ejected from each nozzle of the inkjet head so as to widen outward.

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0013] [Image Forming Apparatus] FIG. 1 is a top view showing the main configuration of an image forming apparatus 1 according to this embodiment.

[0014] The image forming apparatus 1 includes a mounting table 11 on which a recording medium B is placed, a carriage 12 (head unit in the present invention) having an inkjet head (hereinafter referred to as a head) 13, a drive unit 20, and a control unit 30. The control unit 30 is a so-called computer. FIG. 1 is a schematic diagram, and the size of each component has been appropriately changed for the sake of explanation and differs from the actual size. In the following description, the front side of the paper in FIG. 1 is vertically upward, and the back side of the paper is vertically downward.

[0015] The drive unit 20 includes a motor 21 including a rotating shaft, a coil, and an electromagnet, a drive mechanism (not shown) that drives at least one of the mounting table 11 and the carriage 12 using the motor 21, and is controlled by the control unit 30. For example, the drive unit 20 is controlled by the control unit 30 based on a relative position read by a position sensor described later.

[0016] In this embodiment, the drive unit 20 is configured to be able to move the mounting table 11 and the carriage 12 relatively in a first direction D1, and is also configured to be able to move the mounting table 11 and the carriage 12 relatively in a second direction D2, which is a direction perpendicular to the first direction.

[0017] The drive unit 20 may be configured, for example, such that when the position of the mounting table 11 is fixed, the carriage 12 is independently movable in the first direction D1 and the second direction D2. Alternatively, when the position of the carriage 12 is fixed, the mounting table 11 may be independently movable in the first direction D1 and the second direction D2. Alternatively, the mounting table 11 may be configured to be movable in either the first direction D1 or the second direction D2, and the carriage 12 may be configured to be movable in the other of the first direction D1 or the second direction D2. Alternatively, the mounting table 11 may be configured to be movable in both the first direction D1 and the second direction D2, and the carriage 12 may be configured to be movable in both the first direction D1 and the second direction D2.

[0018] The recording medium B is a target for image formation by the image forming apparatus 1, and is, for example, a substrate used in a printed circuit board (PCB). The printed circuit board includes an insulating substrate and wiring conductors arranged on the insulating substrate.

[0019] Preferred examples of such recording medium B include paper phenol, paper epoxy, glass cloth epoxy, glass polyimide, glass cloth / non-woven cloth epoxy, glass cloth / paper epoxy, synthetic fiber epoxy, etc. Also preferred examples of such recording medium B include copper-clad laminates, polyimide films, PET films, glass substrates, ceramic substrates, wafer plates, stainless steel plates, etc.

[0020] The carriage 12 has at least one head 13, a tank (not shown) that stores ink and supplies it to the head 13, etc. The carriage 12 also has a position sensor (not shown) that reads the relative position with respect to the recording medium B. The operations of the head 13, the tank, etc. are controlled by the control unit 30. The carriage 12 may also have a head control unit that operates under the control of the control unit 30 and controls the operations of the head 13, the tank, etc.

[0021] The carriage 12 having such a configuration is positioned above the mounting table 11 and the recording medium B (toward the front of the paper in Figure 1) so that the nozzles 40 of the head 13 (see Figures 2A and 2B described below) face the recording medium B.

[0022] Fig. 2A is a diagram showing an example of the configuration of the head 13. Fig. 2B is a diagram showing an example of the configuration of the carriage 12 having the head 13 shown in Fig. 2A. In Fig. 2B, for the convenience of the following explanation, the two heads 13 are denoted by the reference numerals 13A and 13B. Fig. 2A is a diagram showing the head 13 as viewed from below, i.e., from the mounting table 11 (recording medium B) side, and Fig. 2B is also a diagram showing the carriage 12 as viewed from below, i.e., from the mounting table 11 (recording medium B) side.

[0023] As shown in Fig. 2A, the head 13 has a plurality of nozzles 40 that eject ink (ink droplets). In Fig. 2A, the plurality of nozzles 40 are arranged in rows at a nozzle pitch along the second direction D2 to form a single nozzle row 41.

[0024] As shown in Figure 2B, the carriage 12 has two heads 13A and 13B. The heads 13A and 13B are arranged offset from each other in the first direction D1 and extend in the second direction D2. In each of the heads 13A and 13B, the multiple nozzles 40 (nozzle rows 41) are arranged along the second direction D2. This arrangement makes it possible to increase the printing length of one carriage 12.

[0025] The carriage 12 may also be configured to have an image forming area where the end of the nozzle row 41 of the head 13A overlaps with the nozzle row 41 of the adjacent head 13B. This allows the joints between the heads 13A and 13B and between passes (described later) to overlap, preventing gaps, streaks, and the like, and making the joints less noticeable.

[0026] 2A and 2B are configured to have one nozzle row 41, but the head 13 may be configured to have, for example, multiple nozzle rows 41. FIG. 3A is a diagram showing another configuration example of the head 13. For example, as shown in FIG. 3A, one head 13 may be configured to have two nozzle rows 41. In the example shown in FIG. 3A, the two nozzle rows 41 are arranged offset from each other in the first direction D1 and the second direction D2, thereby improving printing resolution.

[0027] 3B and 3C are also diagrams showing other configuration examples of head 13. As shown in Figures 3B and 3C, a configuration may be used in which head chip module 42 is used in which multiple nozzles and multiple ink ejection mechanisms are configured as chip modules, and one head 13 has two head chip modules 42 (two nozzle rows).

[0028] In the example shown in Fig. 3B, two head chip modules 42 are arranged offset from each other in the first direction D1 and the second direction D2 to improve printing resolution. In the example shown in Fig. 3C, two head chip modules 42 are arranged offset from each other in the first direction D1 and extend in the second direction D2 to increase the printing length of one head 13.

[0029] In this embodiment, it is preferable to use a single type of ink. When multiple types of ink are used to form pixel rows in the same region, multiple heads filled with different inks are used in the first operation described below. In this case, the print length of each head may vary, which may cause misalignment of the pixel rows. Therefore, it is preferable to use a single ink in the region where pixel rows are formed in at least one first operation.

[0030] In addition, in this embodiment, the ink is preferably, for example, an ink containing a coating agent or insulating material for manufacturing printed wiring, or a solder resist ink for forming circuits on PCB substrates. To prevent ink droplets from shifting, ink that hardens when irradiated with energy rays, such as a UV-curable ink that hardens when irradiated with ultraviolet light or a thermosetting ink that hardens when heated, can be used. UV-curable ink and thermosetting ink may contain a gelling agent. Such ink is stored in a tank in the carriage 12, supplied to the nozzles 40 of the head 13, and ejected.

[0031] 1, when UV-curable ink, heat-curable ink, or the like is used as the ink, the image forming apparatus 1 may include an irradiation unit 50 that irradiates the recording medium B with energy rays such as ultraviolet rays or infrared rays (heat rays). After the image is formed on the recording medium B, for example, the mounting table 11 or the irradiation unit 50 moves in the second direction D2, thereby irradiating the image formed on the recording medium B with energy rays and curing the image (ink).

[0032] The image forming apparatus 1 has the above-described configuration, and the control unit 30 controls the above-described configuration to form an image on the recording medium B. Specifically, the control unit 30 performs a first operation of ejecting ink from the head 13 while moving the recording medium B on the mounting table 11 and the carriage 12 relatively in a first direction D1, and a second operation of moving the recording medium B and the carriage 12 relatively in a second direction D2. The control unit 30 then repeats the first operation and the second operation to form an image using ink in a nozzle pitch corresponding area of ​​the recording medium B that corresponds to the nozzle pitch (see FIG. 2A ).

[0033] In the image forming method described below, as an example, the explanation will be given on the assumption that the drive unit 20 moves the mounting table 11 (recording medium B) in a first direction D1 and moves the carriage 12 (heads 13A and 13B described later) in a second direction D2.

[0034] [Conventional Image Forming Method - Block Printing + Feathering] Figure 4A is a diagram illustrating an image forming method in a conventional image forming apparatus, illustrating the first to fourth passes. Figure 4B is a diagram illustrating an image forming method in a conventional image forming apparatus, illustrating the fifth to eighth passes. Here, a method that combines block printing and feathering will be described.

[0035] Block printing is described, for example, in International Publication No. 2022 / 190367 (particularly FIG. 7 and its description), a prior application of the present inventors, and is summarized as follows: In block printing, a nozzle pitch corresponding area on a recording medium corresponding to the nozzle pitch of the head is divided into multiple pixel array formation areas in which pixel arrays are formed. Then, pixel arrays are formed in the pixel array formation areas, and pixel arrays are formed in pixel array formation areas adjacent to the formed pixel arrays using the same nozzles of the same head, thereby filling the nozzle pitch corresponding area and forming an image. By forming an image in this manner, the image area formed by one head consists of pixels formed by that head, and pixels formed by other heads are not mixed in. Therefore, within the image areas formed by multiple heads, misregistration due to different print lengths of the multiple heads can be reduced.

[0036] Feathering is a method of using mutually complementary random patterns when forming pixel rows by performing the first operation multiple times on one pixel row formation region. Interleaving is a method of using mutually complementary regular patterns when forming pixel rows by performing the first operation multiple times on one pixel row formation region. Since feathering and interleaving differ only in whether the pattern used is random or regular, the following explanation will use feathering as an example.

[0037] 4A and 4B, the right side of each figure shows a schematic diagram illustrating the relative movement of the two heads 13A, 13B and the recording medium B (the formed image area) in time series. The left side of each figure shows an enlarged view of the area enclosed by the dashed line in the image area shown on the right side. In addition, in Figures 4A and 4B, the reference numeral "1-1" indicates the first nozzle 40 of the first head 13A, the reference numeral "1-2" indicates the second nozzle 40 of the first head 13A, and the reference numeral "1-3" indicates the third nozzle 40 of the first head 13A. Furthermore, the number of nozzles in each head 13A, 13B is denoted as p.

[0038] 2B will be described. Specifically, the description will be made of a case where an image is formed using the carriage 12 shown in Fig. 2B. Specifically, the description will be made of a case where an image with a print resolution of 1440 dpi is formed by performing four-pass block printing using heads 13A and 13B with a nozzle density of 360 dpi (dots per inch).

[0039] In the following, the number of passes refers to the number of pixel array formation areas obtained by dividing the nozzle pitch corresponding area in the second direction. Also, the first pass refers to the first operation since the start of printing, and the same applies to the second pass and onwards.

[0040] First, the control unit 30 performs the first operation of the first pass. For example, while keeping the recording medium B stationary, the control unit 30 ejects ink using the nozzles 40 of the heads 13A and 13B while moving the heads 13A and 13B along the first direction D1 to form pixel arrays in the pixel array formation regions of the first pass. At this time, the control unit 30 forms pixel arrays in part of the pixel array formation regions of the first pass without ejecting ink into them.

[0041] As a result, 2 x p pixel rows are formed on the recording medium B, spaced apart by the nozzle pitch. In each pixel row, only some of the pixels are formed, rather than all of them. If p = 1024, that is, if each of the heads 13A and 13B has 1024 nozzles, then an image area consisting of 2 x 1024 = 2048 pixel rows is formed.

[0042] After forming the pixel row in the first pass, the control unit 30 performs a second operation, for example, moving the recording medium B a predetermined amount along the second direction D2. Here, because four-pass block printing is performed, the predetermined amount is the distance between the nozzle pitch divided by four. For example, if the printing length of each of the heads 13A and 13B is 72.1 mm and the number of nozzles is 1,024, the distance between the nozzle pitch is 70.4 μm, and the predetermined amount is 17.6 μm. This predetermined amount corresponds to the width of one pixel in the second direction D2.

[0043] Next, the control unit 30 sequentially performs the first and second operations of the second and third passes, which are the same as the first and second operations of the first pass. As a result, on the recording medium B, a pixel row of the second pass is formed adjacent to the pixel row formed in the first pass, and a pixel row of the third pass is formed adjacent to the pixel row formed in the second pass.

[0044] Next, the control unit 30 performs the first operation of the fourth pass. The first operation of the fourth pass is basically the same as the first operations of the first to third passes. The first operation of the fourth pass completes image formation of pixel rows between the nozzle pitch. In other words, by performing the first and second operations of the first to fourth passes, four adjacent pixel rows are formed using the same nozzle 40.

[0045] After forming the pixel array in the fourth pass, the control unit 30 performs a second operation, for example, moving the recording medium B along the second direction D2. However, because images are formed using the same nozzles in the same pixel array formation region, the direction of movement in the second direction D2 is opposite to that of the first to third passes. The amount of movement in this case is 52.8 μm, since the total movement in the first to third passes is 52.8 μm. Because the direction of movement in the second direction D2 in the fourth pass is opposite to that of the first to third passes, this is shown as -52.8 μm in FIG. 4A.

[0046] Next, the control unit 30 sequentially performs the first and second operations for the fifth to eighth passes. The first and second operations for the fifth to eighth passes are basically the same as the first and second operations for the first to fourth passes.

[0047] 4A and 4B, images are formed using the same nozzles in the same pixel array formation region. Specifically, in the fifth pass, ink is ejected to parts of the pixel array formation region where no pixels were formed in the first pass. As a result, pixels are formed in the fifth pass in parts of the pixel array formation region where no pixels were formed in the first pass, completing the pixel array.

[0048] The sixth to eighth passes are similar to the fifth pass, and each ejects ink onto parts of the pixel array formation region where no pixels were formed in the second to fourth passes. As a result, pixels are formed in the sixth to eighth passes in the parts of the pixel array formation region where no pixels were formed in the pixel arrays in the second to fourth passes, completing the pixel array. By performing the first and second operations in the fifth to eighth passes, four adjacent pixel arrays are formed using the same nozzles 40, and image formation of the pixel arrays between the nozzle pitch is completed.

[0049] By performing the first and second operations of the first to eighth passes described above, an image area is formed in a predetermined area, as shown in the eighth pass in FIG. 4B.

[0050] After forming the pixel row in the eighth pass, when forming the next pixel row in the ninth pass or later, the control unit 30, for example, moves the recording medium B. For example, when forming the next image area in an area adjacent in the second direction D2 to the image area formed in the first to eighth passes, the control unit 30 moves the recording medium B a predetermined amount along the second direction D2. The predetermined amount W here is the printing length for the two heads 13A, 13B ± the distance between the nozzle pitch, and changes depending on which side of the image area formed in the first to eighth passes the next image area is adjacent to in the second direction D2.

[0051] When moving from the position of the pixel row for the eighth pass to the position where the pixel row for the next ninth pass is formed, the predetermined amount W may be set to a movement amount that is smaller than the distance between the print length ± the nozzle pitch. This allows the joint between the pixel row for the eighth pass and the pixel row for the ninth pass to overlap, reducing the impact of the joint.

[0052] By repeating the above-described operations, a desired image, such as a wiring pattern, is formed on the recording medium B.

[0053] Through the operation described above, adjacent four pixel rows are formed in two passes using the same nozzle 40. Therefore, even if the print lengths of heads 13A and 13B are different or the landing positions are different due to the ink ejection angles of the nozzles 40, the effects of these can be minimized, and gaps, streaks, etc. can be prevented from occurring between adjacent pixel rows.

[0054] However, among the first to eighth passes described above, the movement direction in the second direction D2 in the fourth pass is opposite to that in the first to third passes. Furthermore, in some cases, the movement direction in the second direction D2 in the eighth pass may also be opposite to that in the first to third passes and the fifth to seventh passes. When the movement direction is reversed, structural play (also known as backlash) in the movement mechanism of the drive unit 20 can degrade the movement accuracy upon reversal. In this case, as shown in FIG. 4B , the ink will be ejected at a position offset from the target ejection position (see the dotted line) (see the black circle that is offset from the dotted line), which may result in defects such as gaps or streaks.

[0055] Therefore, in this embodiment, by performing the image forming method shown in Figures 5A and 5B, movement is performed in only one direction in the second direction D2, preventing deterioration of movement accuracy and preventing defects such as gaps and streaks from occurring.

[0056] [Image Forming Method of the Present Embodiment - Block Printing + Feathering] Figure 5A is a diagram illustrating the image forming method of the present embodiment, illustrating the first to fourth passes. Figure 5B is a diagram illustrating the image forming method of the present embodiment, illustrating the fifth to eighth passes. Here again, a method combining block printing and feathering will be described.

[0057] 5A and 5B, the figures shown on the left and right are the same as those in Figures 4A and 4B, and the reference numerals "1-1" and the like are the same as those explained in Figures 4A and 4B. The number of nozzles in each of the heads 13A and 13B is also p.

[0058] Here, we will also explain the case where an image with a printing resolution of 1440 dpi is formed by performing four-pass block printing using the carriage 12 shown in Figure 2B, specifically using heads 13A and 13B with a nozzle density of 360 dpi.

[0059] Therefore, in this embodiment, the number of divisions into which the nozzle pitch corresponding area of ​​the recording medium B, which corresponds to the nozzle pitch (see FIG. 2A ), is divided in the second direction is m = 4. In other words, the number of pixel array formation areas (pixel arrays) in the nozzle pitch corresponding area is m = 4. In this embodiment, the area is divided into m = 4 pixel array formation areas in the second direction, and for each of these pixel array formation areas, the number of first operations performed by the n = 2 nozzles 40 is n = 2.

[0060] First, the control unit 30 performs the first operation of the first pass. For example, while keeping the recording medium B stationary, the control unit 30 ejects ink using the nozzles 40 of the heads 13A and 13B while moving the heads 13A and 13B along the first direction D1 to form pixel arrays in the pixel array formation regions of the first pass. At this time, the control unit 30 forms pixel arrays without ejecting ink into part of the pixel array formation regions of the first pass. Furthermore, in this embodiment, nozzle 1-1, which is the nozzle 40 at one end, is prohibited from ejecting ink, and pixel arrays are not formed.

[0061] As a result, 2×p-1 pixel rows are formed on recording medium B, spaced apart by the nozzle pitch, excluding the pixel row formation region corresponding to nozzle 1-1. In each pixel row, only some of the pixels are formed, rather than all of them. If p=1024, that is, if each of heads 13A and 13B has 1024 nozzles, then an image area consisting of 2×1024-1=2047 pixel rows is formed.

[0062] After forming the pixel row in the first pass, the control unit 30 performs a second operation, for example, moving the recording medium B a predetermined amount along the second direction D2. Here, too, because four-pass block printing is performed, the predetermined amount is the distance between the nozzle pitch divided by four, for example, 17.6 μm.

[0063] Next, the control unit 30 sequentially performs the first and second operations of the second and third passes, which are the same as the first and second operations of the first pass. As a result, on the recording medium B, except for the pixel array formation region corresponding to nozzle 1-1, a pixel array of the second pass is formed adjacent to the pixel array formed in the first pass, and a pixel array of the third pass is formed adjacent to the pixel array formed in the second pass.

[0064] Next, the control unit 30 performs the first and second operations of the fourth pass. In this embodiment, the first and second operations of the fourth pass are the same as the first and second operations of the first to third passes. After the pixel row is formed in the fourth pass, the control unit 30 performs the second operation, and moves the recording medium B by the above-mentioned predetermined amount in the second direction D2, which is the same direction as the first to third passes. Then, the first operation of the fourth pass completes image formation of the pixel row between the nozzle pitches, except for the pixel row formation region corresponding to nozzle 1-1.

[0065] Next, the control unit 30 sequentially performs the first and second operations of the fifth to eighth passes. The first and second operations of the fifth to eighth passes are basically the same as the first and second operations of the first to fourth passes, but ink is also ejected from nozzle 1-1, and pixels of a pixel row are formed by different nozzles 40 adjacent to the same pixel row formation region.

[0066] For example, as can be seen from a comparison between the first and fifth passes, in the pixel row formed by nozzle 1-2 in the first pass, pixels are formed in the portion of the pixel row formation region where no pixels were formed by ejecting ink from nozzle 1-1 in the fifth pass. The same is true for the other pixel rows; for example, in the pixel row formed by nozzle 1-3 in the first pass, pixels are formed in the portion of the pixel row formation region where no pixels were formed by ejecting ink from nozzle 1-2 in the fifth pass. In this way, pixels are formed in the fifth pass in the portion of the pixel row formation region where no pixels were formed in the pixel row in the first pass, completing the pixel row.

[0067] The sixth to eighth passes are similar to the fifth pass. That is, in the pixel row formed in the second to fourth passes, pixels are formed in the sixth to eighth passes by ejecting ink from adjacent nozzles different from those in the second to fourth passes in the portions of the pixel row formation region where pixels were not formed in the second to fourth passes. In this way, pixels are formed in the sixth to eighth passes in the portions of the pixel row formation region where pixels were not formed in the pixel row in the second to fourth passes, and the pixel row is completed.

[0068] In addition, in the last four passes (passes 5 to 8), the nozzle 40 (nozzle 2-1024 when p = 1024) at the end opposite to the side where the above-mentioned nozzle 1-1 is located is prohibited from ejecting ink, and pixel rows do not need to be formed.

[0069] By performing the first and second operations of the first to eighth passes described above, an image area is formed in a predetermined area, as shown in the eighth pass in FIG. 5B.

[0070] After forming the pixel row in the eighth pass, when forming the pixel row in the next ninth pass or later, the control unit 30 moves the recording medium B, but here too, it moves the recording medium B in the second direction D2, which is the same direction as the first to seventh passes.

[0071] At this time, the amount of movement in the second direction D2 may be set to be smaller than the distance between the printing length ± the nozzle pitch, so that the joint between the 8th and 9th passes overlaps, thereby reducing the effect of the joint.

[0072] By repeating the above-described operations, a desired image, such as a wiring pattern, is formed on the recording medium B.

[0073] Through the operation described above, adjacent four pixel rows are formed in two passes using two adjacent nozzles 40. Therefore, even if the print lengths of heads 13A and 13B are different, the effect of this can be suppressed, and gaps, streaks, etc. can be prevented from occurring between adjacent pixel rows.

[0074] Additionally, in this embodiment, when moving in the second direction D2, the control unit 30 moves in the same direction for all passes, so there is no reversal of the movement direction. Therefore, there is no deterioration in movement accuracy due to structural play (backlash) in the movement mechanism of the drive unit 20, and it is possible to prevent deterioration of movement accuracy. In particular, when the motor 21 is used as the drive source of the drive unit 20, by eliminating reversals in the movement direction and moving only in one direction, it is possible to prevent deterioration of movement accuracy. As a result, it is possible to prevent gaps, streaks, etc. from occurring between adjacent pixel columns.

[0075] [Summary] As described above, the image forming apparatus 1 of this embodiment includes the carriage 12 and the control unit 30 that performs the first operation and the second operation.

[0076] When the number of first operations is n (an integer of 2 or more) for each of the pixel array formation regions obtained by dividing the nozzle pitch corresponding region of the recording medium B corresponding to the nozzle pitch into m (an integer of 1 or more) regions in the second direction D2, the control unit 30 performs the following: Specifically, when performing m×n second operations moving in one direction on one side of the second direction D2, the control unit 30 inhibits ink ejection from at least one nozzle 40 from the end side of the carriage 12 in at least one first operation.

[0077] In the example shown in FIGS. 5A and 5B , m = 4 and n = 2. Therefore, the number of first operations and second operations is 8 (m × n = 8). When the number of first operations performed by two (n = 2) nozzles 40 for each of the pixel array formation regions obtained by dividing the nozzle pitch corresponding area into four (m = 4) areas in the second direction D2 is 2 (n = 2), the control unit 30 performs the following. Specifically, when performing eight second operations moving in one direction on one side of the second direction D2, the control unit 30 prohibits ink ejection from one (n-1 = 1) nozzle 1-1 from the end on the other side of the second direction D2 in each of the first four (m = 4) first operations. Note that ink ejection from one (n-1 = 1) nozzle 40 (nozzle 2-1024 when p = 1024) from the end on one side of the second direction D2 may also be prohibited in each of the last four (m = 4) first operations. This also applies to Modifications 1 to 4 described below.

[0078] This embodiment can also be applied, for example, to a case where n = 3, i.e., a case where the first operation is performed three times using different nozzles 40 for the same pixel array formation region on the recording medium B. In this case, if m = 4, the number of first operations and second operations is 12 (m × n = 12). When performing 12 second operations moving in one direction on one side of the second direction D2, the control unit 30 simply prohibits ink ejection from 2 (n - 1 = 2) nozzles 1-1 and 1-2 from the end on the other side of the second direction D2 during each of the first four (m = 4) first operations. In this way, in this embodiment, n is variable, and m is also variable, as shown in Modification 2 described below.

[0079] According to the image forming apparatus 1 of this embodiment configured as described above, when moving in the second direction D2, the movement is made in the same direction for all passes, and therefore the movement direction is not reversed. Therefore, there is no deterioration in movement accuracy due to structural play (backlash) in the movement mechanism of the drive unit 20, and deterioration in movement accuracy can be prevented. As a result, gaps, streaks, etc. can be prevented from occurring between adjacent pixel columns.

[0080] In typical multi-pass printing, if the print length varies from head to head, the nozzle position relative to the recording medium will be shifted from its original position for each head. Therefore, when adjacent pixel rows are formed using different heads, as shown in FIG. 6 , there may be areas Aw where the spacing between pixel rows becomes wider and areas An where the spacing becomes narrower, as shown in FIG. 6 . Here, FIG. 6 is a diagram illustrating a state in which the spacing between pixel rows becomes uneven when the print length varies from head to head in typical multi-pass printing. FIG. 6 exaggerates the misalignment of pixel rows. When using an image forming apparatus to print wiring portions of a PCB (e.g., solder resist ink for forming circuits on a PCB substrate), such misalignment of pixel rows can result in serious defects.

[0081] In contrast to this, in the present embodiment, the image forming method described above can suppress misalignment of pixel rows even when the print lengths of the multiple heads 13 are different, for example, in applications such as printing solder resist ink for forming circuits on PCB substrates. This makes it possible to prevent defects caused by misalignment of pixel rows when forming circuits on PCB substrates.

[0082] <Variation 1> Fig. 7A is a diagram illustrating a variation of the image forming method according to the present embodiment, illustrating the first to fourth passes. Fig. 7B is a diagram illustrating a variation of the image forming method according to the present embodiment, illustrating the fifth to eighth passes. Here, too, a method that combines block printing and feathering will be described.

[0083] 7A and 7B, the diagrams shown on the left and right are the same as those in FIGS. 4A and 4B, and the reference numerals "1-1" and the like are as explained in FIGS. 4A and 4B. The number of nozzles in each of the heads 13A and 13B is also p. However, in this modified example, as an example, it is assumed that nozzle 1-3 is in an unusable state due to non-ejection, deflected ejection, or the like. The state of the nozzle 40 (whether it is usable or unusable) is confirmed in advance using, for example, a device for inspecting the heads 13A and 13B, or an inspection device for reading and inspecting images formed by the heads 13A and 13B.

[0084] Here, we will also explain the case where an image with a printing resolution of 1440 dpi is formed by performing four-pass block printing using the carriage 12 shown in Figure 2B, specifically using heads 13A and 13B with a nozzle density of 360 dpi.

[0085] First, the control unit 30 performs the first operation of the first pass. For example, while keeping the recording medium B stationary, the control unit 30 moves the heads 13A and 13B along the first direction D1, ejecting ink using the nozzles 40 of the heads 13A and 13B to form pixel arrays in the pixel array formation regions of the first pass. At this time, the control unit 30 forms pixel arrays without ejecting ink into a portion of the pixel array formation region of the first pass. Furthermore, in this embodiment, nozzle 1-1, which is the nozzle 40 at one end, is prohibited from ejecting ink and does not form a pixel array, and nozzle 1-3 also does not form a pixel array. In addition, the pixel array formed by nozzle 1-4 is located at the position to which nozzle 1-3 moves in the fifth pass, so ink is ejected from all pixels in the pixel array.

[0086] As a result, 2×p−2 pixel rows are formed on the recording medium B, excluding the pixel row formation regions corresponding to nozzles 1-1 and 1-3. Of the 2×p−2 pixel rows, all pixels are formed in one pixel row, and in the 2×p−3 pixel rows, only some, but not all, of the pixels are formed.

[0087] After forming the pixel row in the first pass, the control unit 30 performs a second operation, for example, moving the recording medium B a predetermined amount along the second direction D2. Here, too, because four-pass block printing is performed, the predetermined amount is the distance between the nozzle pitch divided by four, for example, 17.6 μm.

[0088] Next, the control unit 30 sequentially performs the first and second operations of the second and third passes, which are the same as the first and second operations of the first pass. As a result, on the recording medium B, except for the pixel array formation regions corresponding to nozzles 1-1 and 1-3, pixel arrays of the second pass are formed adjacent to the pixel arrays formed in the first pass, and pixel arrays of the third pass are formed adjacent to the pixel arrays formed in the second pass.

[0089] Next, the control unit 30 performs the first and second operations of the fourth pass. In this modified example, the first and second operations of the fourth pass are the same as the first and second operations of the first to third passes. After the pixel array is formed in the fourth pass, the control unit 30 performs the second operation, moving the recording medium B by the above-mentioned predetermined amount in the second direction D2, which is the same direction as the first to third passes. Then, the first operation of the fourth pass completes image formation of the pixel array between the nozzle pitches, except for the pixel array formation regions corresponding to nozzles 1-1 and 1-3.

[0090] Next, the control unit 30 sequentially performs the first and second operations of the fifth to eighth passes. The first and second operations of the fifth to eighth passes are basically the same as the first and second operations of the first to fourth passes, but ink is also ejected from nozzle 1-1, and pixels of a pixel row are formed by different nozzles 40 adjacent to the same pixel row formation region.

[0091] For example, as can be seen from a comparison between the first and fifth passes, in the pixel row formed by nozzle 1-2 in the first pass, in the part of the pixel row formation area where no pixels were formed, ink is ejected from nozzle 1-1 to form pixels in the fifth pass.

[0092] The same is true for the other pixel rows, but in the fifth pass, nozzles 1-2 and 1-3 are operated as follows. As can be seen from a comparison of the first and fifth passes, no pixel row was formed in the pixel row formation region corresponding to nozzle 1-3 in the first pass, so in the fifth pass, nozzle 1-2 ejects ink onto all pixels in the pixel row into the same pixel row formation region. Also, since all pixels in the pixel row were formed by nozzle 1-4 in the first pass, no pixel row is formed by nozzle 1-3 in the fifth pass for the pixel row formed by nozzle 1-4 in the first pass.

[0093] As a result, pixels are formed in the fifth pass in the pixel row formation region where no pixels were formed in the pixel row of the first pass, completing the pixel row.

[0094] The sixth to eighth passes are similar to the fifth pass. That is, in the pixel row formed in the second to fourth passes, pixels are formed in the sixth to eighth passes by ejecting ink from adjacent nozzles different from those in the second to fourth passes in the portions of the pixel row formation region where pixels were not formed in the second to fourth passes. In this way, pixels are formed in the sixth to eighth passes in the portions of the pixel row formation region where pixels were not formed in the pixel row in the second to fourth passes, respectively, and the pixel row is completed.

[0095] By performing the first and second operations of the first to eighth passes described above, an image area is formed in a predetermined area, as shown in the eighth pass in FIG. 7B.

[0096] After forming the pixel row in the eighth pass, when forming the pixel row in the next ninth pass or later, the control unit 30 moves the recording medium B, but here too, it moves the recording medium B in the second direction D2, which is the same direction as the first to seventh passes.

[0097] By repeating the above-described operations, a desired image, such as a wiring pattern, is formed on the recording medium B.

[0098] Through the operation described above, in pixel row formation regions excluding the pixel row formation region corresponding to the unusable nozzle 1-3, four adjacent pixel rows are formed in two separate runs by two adjacent nozzles 40. Furthermore, in the pixel row formation region corresponding to the unusable nozzle 1-3, four adjacent pixel rows are formed by nozzles other than nozzle 1-3, for example, adjacent nozzles 1-2 and 1-4. Therefore, even if the print lengths of heads 13A and 13B differ, the effect of this can be suppressed, and gaps, streaks, and the like can be prevented from occurring between adjacent pixel rows.

[0099] Additionally, in this modification, when moving in the second direction D2, the control unit 30 moves in the same direction for all passes, so there is no reversal of the movement direction. Therefore, there is no deterioration in movement accuracy due to structural play (backlash) in the movement mechanism of the drive unit 20, and it is possible to prevent deterioration in movement accuracy. As a result, it is possible to prevent gaps, streaks, etc. from occurring between adjacent pixel columns.

[0100] Furthermore, even if there is an unusable nozzle 40, if nozzles 40 other than that nozzle 40 are usable, the control unit 30 controls the usable nozzles 40 to eject ink into the nozzle pitch corresponding area of ​​the recording medium B that corresponds to the unusable nozzle 40. This makes it possible to prevent gaps, streaks, etc. from occurring between adjacent pixel rows even if there is an unusable nozzle 40.

[0101] <Variation 2> Fig. 8A is a diagram illustrating another variation of the image forming method according to the present embodiment, illustrating the first to third passes. Fig. 8B is a diagram illustrating another variation of the image forming method according to the present embodiment, illustrating the fourth to sixth passes. Here, too, a method combining block printing and feathering is described.

[0102] 8A and 8B, the figures shown on the left and right are the same as those in Figures 4A and 4B, and the reference numerals "1-1" and the like are the same as those explained in Figures 4A and 4B. The number of nozzles in each of the heads 13A and 13B is also p.

[0103] Here, too, we will explain the case where the carriage 12 shown in Figure 2B is used, specifically, heads 13A and 13B with a nozzle density of 360 dpi are used, and an image with a printing resolution of 1080 dpi is formed by performing three-pass block printing.

[0104] First, the control unit 30 performs the first operation of the first pass. For example, while keeping the recording medium B stationary, the control unit 30 ejects ink using the nozzles 40 of the heads 13A and 13B while moving the heads 13A and 13B along the first direction D1 to form pixel arrays in the pixel array formation regions of the first pass. At this time, the control unit 30 forms pixel arrays without ejecting ink into part of the pixel array formation regions of the first pass. Furthermore, in this modified example, nozzle 1-1, which is the nozzle 40 at one end, is prohibited from ejecting ink, and pixel arrays are not formed.

[0105] As a result, 2×p-1 pixel rows are formed on recording medium B, spaced apart by the nozzle pitch, excluding the pixel row formation region corresponding to nozzle 1-1. In each pixel row, only some of the pixels are formed, rather than all of them. If p=1024, that is, if each of heads 13A and 13B has 1024 nozzles, then an image area consisting of 2×1024-1=2047 pixel rows is formed.

[0106] After forming the pixel row in the first pass, the control unit 30 performs a second operation, for example, moving the recording medium B a predetermined amount along the second direction D2. Here, because three-pass block printing is performed, the predetermined amount is the distance between the nozzle pitch divided by three, for example, 23.5 μm.

[0107] Next, the control unit 30 performs the first and second operations of the second pass. The first and second operations of the second pass are the same as the first and second operations of the first pass, except for the direction of movement in the first direction D1. In the second pass, the direction of movement in the first direction D1 is opposite to that in the first pass. As a result, a pixel row in the second pass is formed on the recording medium B adjacent to the pixel row formed in the first pass, except for the pixel row formation region corresponding to nozzle 1-1.

[0108] Next, the control unit 30 performs the first and second operations of the third pass. The first and second operations of the third pass are the same as the first and second operations of the first pass, including the direction of movement in the first direction D1. As a result, a pixel row of the third pass is formed on the recording medium B adjacent to the pixel row formed in the second pass, except for the pixel row formation region corresponding to nozzle 1-1. The first operation of the third pass completes image formation of the pixel row between the nozzle pitches, except for the pixel row formation region corresponding to nozzle 1-1.

[0109] In the above-described embodiment and variant 1, the movement direction in the first direction D1 was the same for all passes, but here, the movement direction in the first direction D1 is alternately reversed in the first to third passes.

[0110] Next, the control unit 30 performs the first and second operations of the fourth pass. However, if the first and second operations of the fourth pass are performed in this state, the direction of movement in the first direction D1 in the fourth pass will be opposite to the direction of movement in the first direction D1 in the first pass for the same pixel array formation region. As a result, there is a possibility that the ink will land misaligned in the same pixel array formation region.

[0111] Therefore, in this modified example, in the third pass, the control unit 30 moves the recording medium B a predetermined amount along the second direction D2, and then moves the recording medium B along the first direction D1 in the opposite direction to the third pass. At this time, ink is not ejected, but only moved. As a result, the direction of movement in the first direction D1 in the fourth pass is the same as the direction of movement in the first direction D1 in the first pass, making it possible to suppress deviations in the impact of ink on the same pixel array formation region.

[0112] As described above, after the third pass, the control unit 30 moves the recording medium B in the first direction D1, which is the opposite direction to the third pass. Therefore, the control unit 30 performs the same movement operations for the fourth to sixth passes as for the first to third passes, respectively.

[0113] Next, the control unit 30 sequentially performs the first and second operations of the fourth to sixth passes. The first and second operations of the fourth to sixth passes are the same as the first and second operations of the first to third passes, respectively. However, nozzle 1-1 also ejects ink, and pixels of a pixel row are formed by different adjacent nozzles 40 in the same pixel row formation region. As a result, pixels are formed in the fourth to sixth passes in the parts of the pixel row formation region where pixels were not formed in the pixel rows in the first to third passes, completing the pixel row.

[0114] By performing the first and second operations of the first to sixth passes described above, an image area is formed in a predetermined area, as shown in the sixth pass in FIG. 8B.

[0115] After forming the pixel row in the sixth pass, when forming the pixel row in the next seventh pass or later, the control unit 30 moves the recording medium B, but here too, it moves the recording medium B in the second direction D2, which is the same direction as the first to sixth passes.

[0116] By repeating the above-described operations, a desired image, such as a wiring pattern, is formed on the recording medium B.

[0117] Through the operation described above, adjacent three pixel rows are formed in two passes using two adjacent nozzles 40. Therefore, even if the print lengths of heads 13A and 13B are different, the effect of this can be suppressed, and gaps, streaks, etc. can be prevented from occurring between adjacent pixel rows.

[0118] Additionally, in this modification, when moving in the second direction D2, the control unit 30 moves in the same direction for all passes, so there is no reversal of the movement direction. Therefore, there is no deterioration in movement accuracy due to structural play (backlash) in the movement mechanism of the drive unit 20, and it is possible to prevent deterioration in movement accuracy. As a result, it is possible to prevent gaps, streaks, etc. from occurring between adjacent pixel columns.

[0119] Furthermore, even if the number of passes between nozzles is odd, by only performing movement, the movement direction in the first direction D1 for the same pixel row formation region is made the same (aligned), so that deviation in the landing of ink for the same pixel row formation region can be suppressed.

[0120] <Variation 3> Fig. 9A is a diagram illustrating another variation of the image forming method according to the present embodiment, illustrating the first to fourth passes. Fig. 9B is a diagram illustrating another variation of the image forming method according to the present embodiment, illustrating the fifth to eighth passes. Here again, a method combining block printing and feathering is described.

[0121] 9A and 9B, the figures shown on the left and right are the same as those in Figures 4A and 4B, and the reference numerals "1-1" and the like are the same as those explained in Figures 4A and 4B. The number of nozzles in each of the heads 13A and 13B is also p.

[0122] Here, we will also explain the case where an image with a printing resolution of 1440 dpi is formed by performing four-pass block printing using the carriage 12 shown in Figure 2B, specifically using heads 13A and 13B with a nozzle density of 360 dpi.

[0123] First, the control unit 30 performs the first operation of the first pass. For example, while keeping the recording medium B stationary, the control unit 30 ejects ink using the nozzles 40 of the heads 13A and 13B while moving the heads 13A and 13B along the first direction D1 to form pixel arrays in the pixel array formation regions of the first pass. At this time, the control unit 30 forms pixel arrays without ejecting ink into part of the pixel array formation regions of the first pass. Furthermore, in this modified example, nozzle 1-1, which is the nozzle 40 at one end, is prohibited from ejecting ink, and pixel arrays are not formed.

[0124] As a result, 2×p-1 pixel rows are formed on recording medium B, spaced apart by the nozzle pitch, excluding the pixel row formation region corresponding to nozzle 1-1. In each pixel row, only some of the pixels are formed, rather than all of them. If p=1024, that is, if each of heads 13A and 13B has 1024 nozzles, then an image area consisting of 2×1024-1=2047 pixel rows is formed.

[0125] After forming the pixel row in the first pass, the control unit 30 performs a second operation, for example, moving the recording medium B a predetermined amount along the second direction D2. Here, because four-pass block printing is performed, the predetermined amount is the distance between the nozzle pitch divided by four, for example, 17.6 μm.

[0126] Next, the control unit 30 performs the first and second operations of the second pass. The first and second operations of the second pass are the same as the first and second operations of the first pass, except for the direction of movement in the first direction D1. In the second pass, the direction of movement in the first direction D1 is opposite to that in the first pass. As a result, a pixel row in the second pass is formed on the recording medium B adjacent to the pixel row formed in the first pass, except for the pixel row formation region corresponding to nozzle 1-1.

[0127] Next, the control unit 30 performs the first and second operations of the third pass. The first and second operations of the third pass are the same as the first and second operations of the first pass, including the direction of movement in the first direction D1. As a result, a pixel row of the third pass is formed on the recording medium B adjacent to the pixel row formed in the second pass, except for the pixel row formation region corresponding to nozzle 1-1.

[0128] Next, the control unit 30 performs the first and second operations of the fourth pass. The first and second operations of the fourth pass are the same as the first and second operations of the second pass, including the direction of movement in the first direction D1. As a result, a pixel row of the fourth pass is formed on the recording medium B adjacent to the pixel row formed in the third pass, except for the pixel row formation region corresponding to nozzle 1-1. The first operation of the fourth pass completes image formation of the pixel row between the nozzle pitches, except for the pixel row formation region corresponding to nozzle 1-1.

[0129] In the above-described embodiment and variant 1, the movement direction in the first direction D1 was the same for all passes, but here, the movement direction in the first direction D1 is alternately reversed in the first to fourth passes.

[0130] In Modification 3, the number of passes between nozzles was odd, so there was an operation that only involved movement, but here, the number of passes between nozzles is even, so the direction of movement in the first direction D1 in the fourth pass is the same as the direction of movement in the first direction D1 in the first pass, so an operation that only involves movement is not necessary.

[0131] Next, the control unit 30 sequentially performs the first and second operations of the fifth to eighth passes. The first and second operations of the fifth to eighth passes are the same as the first and second operations of the first to fourth passes, respectively, but nozzle 1-1 also ejects ink, and pixels of a pixel row are formed by different adjacent nozzles 40 in the same pixel row formation region. As a result, pixels of the fifth to eighth passes are formed in the parts of the pixel row formation region where pixels were not formed in the pixel rows of the first to fourth passes, and the pixel row is completed.

[0132] By performing the first and second operations of the first to eighth passes described above, an image area is formed in a predetermined area, as shown in the eighth pass in FIG. 9B.

[0133] After forming the pixel row in the eighth pass, when forming the pixel row in the next ninth pass or later, the control unit 30 moves the recording medium B, but here too, it moves the recording medium B in the second direction D2, which is the same direction as the first pass to the eighth pass.

[0134] By repeating the above-described operations, a desired image, such as a wiring pattern, is formed on the recording medium B.

[0135] Through the operation described above, adjacent four pixel rows are formed in two passes using two adjacent nozzles 40. Therefore, even if the print lengths of heads 13A and 13B are different, the effect of this can be suppressed, and gaps, streaks, etc. can be prevented from occurring between adjacent pixel rows.

[0136] Additionally, in this modification, when moving in the second direction D2, the control unit 30 moves in the same direction for all passes, so there is no reversal of the movement direction. Therefore, there is no deterioration in movement accuracy due to structural play (backlash) in the movement mechanism of the drive unit 20, and it is possible to prevent deterioration in movement accuracy. As a result, it is possible to prevent gaps, streaks, etc. from occurring between adjacent pixel columns.

[0137] Furthermore, because the number of passes between nozzles is an even number, the movement direction in the first direction D1 for the same pixel array formation region is the same, making it possible to suppress deviation in the landing of ink for the same pixel array formation region.

[0138] <Variation 4> Fig. 10A is a diagram illustrating another variation of the image forming method according to the present embodiment, illustrating the first to fourth passes. Fig. 10B is a diagram illustrating another variation of the image forming method according to the present embodiment, illustrating the fifth to eighth passes. Here again, a method combining block printing and feathering is described.

[0139] 10A and 10B, the figures shown on the left and right are the same as those in Figures 4A and 4B, and the reference numerals "1-1" and the like are the same as those explained in Figures 4A and 4B. The number of nozzles in each of the heads 13A and 13B is also p.

[0140] Here, we will also explain the case where an image with a printing resolution of 1440 dpi is formed by performing four-pass block printing using the carriage 12 shown in Figure 2B, specifically using heads 13A and 13B with a nozzle density of 360 dpi.

[0141] First, the control unit 30 performs the first operation of the first pass. For example, while keeping the recording medium B stationary, the control unit 30 ejects ink using the nozzles 40 of the heads 13A and 13B while moving the heads 13A and 13B along the first direction D1 to form pixel arrays in the pixel array formation regions of the first pass. At this time, the control unit 30 forms pixel arrays in some of the pixel array formation regions of the first pass without ejecting ink. Furthermore, in this modified example, nozzle 1-1, which is the nozzle 40 at one end, is prohibited from ejecting ink, and pixel arrays are not formed.

[0142] As a result, 2×p-1 pixel rows are formed on recording medium B, spaced apart by the nozzle pitch, excluding the pixel row formation region corresponding to nozzle 1-1. In each pixel row, only some of the pixels are formed, rather than all of them. If p=1024, that is, if each of heads 13A and 13B has 1024 nozzles, then an image area consisting of 2×1024-1=2047 pixel rows is formed.

[0143] After forming the pixel row in the first pass, the control unit 30 performs a second operation, for example, moving the recording medium B a predetermined amount along the second direction D2. Here, because four-pass block printing is performed, the predetermined amount is the distance between the nozzle pitch divided by four, for example, 17.6 μm.

[0144] Next, the control unit 30 sequentially performs the first and second operations of the second to fourth passes. The first and second operations of the second to fourth passes are the same as the first and second operations of the first pass, including the direction of movement in the first direction D1. As a result, a pixel row of the second pass is formed adjacent to the pixel row formed in the first pass on the recording medium B, except for the pixel row formation region corresponding to nozzle 1-1. Similarly, a pixel row of the third pass is formed adjacent to the pixel row formed in the second pass, and a pixel row of the fourth pass is formed adjacent to the pixel row formed in the third pass. The first operation of the fourth pass completes image formation of the pixel row between the nozzle pitch, except for the pixel row formation region corresponding to nozzle 1-1.

[0145] Next, the control unit 30 sequentially performs the first and second operations of the fifth through eighth passes. The first and second operations of the fifth through eighth passes are basically the same as the first and second operations of the first pass, including the direction of movement in the first direction D1. However, nozzle 1-1 also ejects ink, and pixels of the pixel row are formed by different adjacent nozzles 40 in the same pixel row formation region. In addition, the droplet volume of the ink droplets ejected in the fifth through eighth passes is different from that in the first through fourth passes. As a result, pixels are formed in the fifth through eighth passes in the portions of the pixel row formation region where pixels were not formed in the pixel row in the first through fourth passes, completing the pixel row.

[0146] By performing the first and second operations of the first to eighth passes described above, an image area is formed in a predetermined area, as shown in the eighth pass in FIG. 10B.

[0147] In this modified example, as an example, of the eight (m x n = 8) first operations, the ink droplet volume is changed to a different amount in the first four first operations and the last four first operations. However, the present invention is not limited to this, and the ink droplet volume may be changed to a different amount in at least one or more of the multiple first operations.

[0148] After forming the pixel row in the eighth pass, when forming the pixel row in the next ninth pass or later, the control unit 30 moves the recording medium B, but here too, it moves the recording medium B in the second direction D2, which is the same direction as the first pass to the eighth pass.

[0149] By repeating the above-described operations, a desired image, such as a wiring pattern, is formed on the recording medium B.

[0150] Through the operation described above, adjacent four pixel rows are formed in two passes using two adjacent nozzles 40. Therefore, even if the print lengths of heads 13A and 13B are different, the effect of this can be suppressed, and gaps, streaks, etc. can be prevented from occurring between adjacent pixel rows.

[0151] Additionally, in this modification, when moving in the second direction D2, the control unit 30 moves in the same direction for all passes, so there is no reversal of the movement direction. Therefore, there is no deterioration in movement accuracy due to structural play (backlash) in the movement mechanism of the drive unit 20, and it is possible to prevent deterioration in movement accuracy. As a result, it is possible to prevent gaps, streaks, etc. from occurring between adjacent pixel columns.

[0152] In addition, in this modified example, the ink droplet volume is changed between passes, so the film thickness of the image formed can be adjusted without changing the ink droplet volume within a pass. Also, because the ink droplet volume is not changed within a pass, the drive waveform for ejecting ink is not switched to a different drive waveform within a pass, so fluctuations in droplet speed, etc. due to drive waveform switching can be suppressed, and as a result, impact deviation can be suppressed.

[0153] The above-described embodiments and modifications are merely examples of specific embodiments of the present invention, and the technical scope of the present invention should not be construed as being limited by these. In other words, the present invention can be embodied in various forms without departing from the gist or main characteristics thereof.

[0154] For example, Fig. 11A is a diagram showing how ink is ejected from each nozzle of the head 13 so as to narrow inward. Fig. 11B is a diagram showing how ink is ejected from each nozzle of the head 13 so as to widen outward. In Fig. 11A and Fig. 11B, the dashed lines indicate the direction of the ejected ink.

[0155] 11A and 11B, when ink is ejected from the nozzles of the head 13 as a whole at an angle, the landing position of the ink will deviate from the target position depending on the distance between the nozzles and the recording medium B. This deviation becomes greater the greater the distance between the nozzle ejection opening and the recording medium B.

[0156] For this reason, the control unit 30 adopts the printing operation of the above embodiment or modification when the angle of ink ejected from the nozzles of the head 13 as a whole is greater than a predetermined angle, or when the distance between the recording medium B and the nozzle outlet is greater than a predetermined distance. This is because, since the same nozzles form adjacent pixels within an image area formed by the same head 13, even if the ink ejection angle from the nozzles is biased, the deviation will be smaller.

[0157] The disclosures of the specification, drawings and abstract contained in Japanese Patent Application No. 2023-143541, filed on September 5, 2023, are incorporated herein by reference in their entirety.

[0158] REFERENCE SIGNS LIST 1 image forming apparatus 11 mounting table 12 carriage 13, 13A, 13B inkjet head 20 driving unit 21 motor 30 control unit 40 nozzle 41 nozzle row 42 head chip module 50 irradiation unit

Claims

1. An image forming device comprising: a head unit which ejects ink from a plurality of nozzles arranged in a row at each nozzle pitch along a second direction perpendicular to a first direction; and a control unit which controls the formation of an image using the ink in a nozzle pitch corresponding area of ​​the recording medium which corresponds to the nozzle pitch by repeating a first operation of ejecting the ink while moving a recording medium and the head unit relatively in the first direction, and a second operation of moving the recording medium and the head unit relatively in the second direction, wherein the control unit prohibits the ejection of the ink from at least one of the nozzles from the end side of the head unit in at least one of the first operations when the number of first operations is n (an integer of 2 or more) for each pixel row formation area obtained by dividing the nozzle pitch corresponding area into m (an integer of 1 or more) in the second direction.

2. The image forming apparatus according to claim 1, wherein the control unit prohibits the ejection of ink from n-1 nozzles from the end of the head unit on the other side in the second direction during each of the first m operations.

3. The image forming apparatus according to claim 2, wherein the control unit prohibits the ejection of ink from n-1 nozzles from the end of the head unit on one side in the second direction during each of the last m first operations.

4. The image forming apparatus according to claim 1, wherein, when the head unit has a nozzle that cannot be used, the control unit controls the nozzles other than the unusable nozzle to eject the ink into the pixel array formation region.

5. The image forming apparatus according to claim 1, wherein the head portion has a plurality of nozzle rows.

6. The image forming apparatus according to claim 1, wherein the ink is a single type of ink.

7. The image forming apparatus according to claim 1, wherein the recording medium is a wiring board.

8. The image forming device according to claim 1, wherein when the control unit alternately reverses the movement direction in the first operation and m is an odd number, the control unit performs the first operation without ejecting the ink, thereby aligning the movement direction in the first operation for the same pixel row formation region.

9. The image forming apparatus according to claim 1, wherein the head unit changes the amount of ink droplets to be ejected at least once during the m×n number of first operations.

10. The image forming apparatus according to claim 1, wherein the head unit has a plurality of heads each having one nozzle row.

11. The image forming apparatus according to claim 10, wherein an end of the nozzle row of the head has an image forming area that overlaps with the nozzle row of an adjacent head.

12. The image forming apparatus according to claim 1, further comprising a drive unit for executing the first operation and the second operation, the drive unit having a motor including a rotating shaft, a coil, and an electromagnet.

13. The image forming apparatus according to claim 1, wherein the ink is an ink that is cured by irradiation with energy rays.

14. The image forming apparatus according to claim 13, wherein the energy rays are ultraviolet rays.

15. The image forming apparatus according to claim 1, wherein the ink contains a gelling agent.

16. The image forming apparatus according to claim 7, wherein the wiring board includes an insulating substrate and a wiring conductor disposed on the insulating substrate, and the ink is a solder resist ink.

17. The image forming apparatus according to claim 1, wherein the ink is a thermosetting ink.

18. An image forming method in an image forming apparatus having a head unit that ejects ink from a plurality of nozzles arranged in a row at each nozzle pitch along a second direction perpendicular to a first direction, the image forming method forming an image using the ink in a nozzle pitch corresponding area of ​​the recording medium that corresponds to the nozzle pitch by repeating a first operation of ejecting the ink while moving a recording medium and the head unit relatively in the first direction, and a second operation of moving the recording medium and the head unit relatively in the second direction, wherein when the number of first operations is n (an integer of 2 or more) for each pixel row formation area obtained by dividing the nozzle pitch corresponding area in the second direction into m (an integer of 1 or more), the image forming method inhibits the ejection of ink from at least one nozzle from the end side of the head unit in at least one first operation when performing the second operation m x n times to move in one direction on one side of the second direction.

19. In an image forming device having a head unit that ejects ink from a plurality of nozzles arranged in a row at each nozzle pitch along a second direction perpendicular to a first direction, an image forming program that causes a computer to execute a process of forming an image using the ink in a nozzle pitch corresponding area of ​​the recording medium that corresponds to the nozzle pitch by repeating a first operation of ejecting the ink while moving a recording medium and the head unit relatively in the first direction, and a second operation of moving the recording medium and the head unit relatively in the second direction, wherein the image forming program causes the computer to execute a process of prohibiting the ejection of the ink from at least one of the nozzles from the end side of the head unit in at least one of the first operations when the number of times of the first operation is n (an integer of 2 or more) for each pixel row formation area obtained by dividing the nozzle pitch corresponding area into m (an integer of 1 or more) in the second direction.