Printer, control method thereof and program

Abstract

To provide a printer capable of suppressing discharge failure of ink.SOLUTION: In a printer, a control device executes second acquisition processing to acquire a mask pattern for a mask applied to image data of a duplicate image, based on information related to drying risk. The mask applied to the duplicate image includes a mask pattern that prevents ink discharge from nozzles corresponding to the duplicate image. This mask pattern includes: a first mask pattern, and a second mask pattern in which a masked portion is smaller than that of the first mask pattern, applied to an end of the duplicate image that is positioned away from a non-duplicate image in a conveying direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a printing apparatus, a control method thereof, and a program. [Background technology]

[0002] A known example of a conventional printing device is the printing device disclosed in Patent Document 1. This printing device has first nozzles that eject ink of a base color and second nozzles that eject ink of a special color that is different from the base colors. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-111540 Summary of the Invention [Problem to be solved by the invention]

[0004] In the printing device described above, an image is printed by ejecting a base color ink from a first nozzle and a special color ink from a second nozzle. However, because some images do not use a lot of special color ink, the ejection frequency of the special color ink may be lower than the ejection frequency of the base color ink. In this case, the special color ink in the second nozzle dries more easily than the base color ink in the first nozzle, which can lead to problems with ink ejection from the second nozzle.

[0005] In view of the above, an object of the present invention is to provide a printing apparatus that can suppress ink ejection defects, a control method thereof, and a program. [Means for solving the problem]

[0006] A printing device according to one aspect of the present invention comprises a head having nozzles, a movement device that moves the head in a movement direction, a transport device that transports a print medium in a transport direction that intersects with the movement direction, and a control device, wherein the control device performs a first acquisition process that acquires information regarding the risk of ink drying in the nozzles, a pass operation that ejects ink from the nozzles onto the print medium while moving the head based on image data of a partial image of a print image, and a transport operation that transports the print medium, and executes a printing process in which an overlapping image of the partial image that is the target of the current pass operation is overlapped with an overlapping image of the partial image that is the target of the previous pass operation, and the partial image is overlapped with other adjacent partial images. and a non-overlapping image that is a region that overlaps with the partial image of the printing head, and a non-overlapping image that is a region different from the overlapping image and does not overlap with other partial images, the mask is applied to image data of the overlapping image and has a mask pattern including a mask portion that prevents ink from being ejected from the nozzles corresponding to the overlapping image in the pass operation, the mask having a first mask pattern and a second mask pattern in which the mask portion is smaller than that of the first mask pattern at an end of the overlapping image that is farther from the non-overlapping image in the transport direction, and the control device executes a second acquisition process to acquire the mask pattern of the mask to be applied to image data of the overlapping image based on information about the drying risk.

[0007] A control method for a printing device according to one aspect of the present invention is a control method for a printing device that includes a head having nozzles, a movement device that moves the head in a movement direction, and a transport device that transports a print medium in a transport direction that intersects with the movement direction, and the control method includes: a first acquisition process that acquires information about the risk of ink drying in the nozzles; a pass operation that ejects ink from the nozzles onto the print medium while moving the head based on image data of a partial image of a print image; and a transport operation that transports the print medium, and a printing process that overlaps an overlapping image of the partial image that is the target of the current pass operation with an overlapping image of the partial image that is the target of the previous pass operation, and includes an overlapping image, which is an area that overlaps with another adjacent partial image, and a non-overlapping image, which is an area different from the overlapping image and does not overlap with the other partial image, the mask is applied to image data of the overlapping image and has a mask pattern including a mask portion that prevents ink from being ejected from the nozzles corresponding to the overlapping image in the pass operation, and a second mask pattern, the mask portion of which is smaller than that of the first mask pattern, at an end of the overlapping image that is away from the non-overlapping image in the transport direction, and a second acquisition process is executed to acquire the mask pattern of the mask to be applied to the image data of the overlapping image based on information related to the drying risk.

[0008] A program according to one aspect of the present invention causes a printing device including a head having nozzles, a movement device that moves the head in a movement direction, and a transport device that transports a print medium in a transport direction that intersects with the movement direction to perform a first acquisition process that acquires information regarding the risk of ink drying in the nozzles, a pass operation that ejects ink from the nozzles onto the print medium while moving the head based on image data of a partial image of a print image, and a transport operation that transports the print medium, and executes a printing process in which an overlapping image of the partial image that is the target of the current pass operation is overlapped with an overlapping image of the partial image that is the target of the previous pass operation, and the partial image is overlapped with an overlapping image of the partial image that is the target of the previous pass operation, The mask includes an overlapping image, which is an area that overlaps with other partial images, and a non-overlapping image, which is an area different from the overlapping image and does not overlap with other partial images, and the mask is applied to image data of the overlapping image and has a mask pattern including a mask portion that prevents ink from being ejected from the nozzles corresponding to the overlapping image in the pass operation, and a second mask pattern, the mask portion of which is smaller than that of the first mask pattern, at an end of the overlapping image that is away from the non-overlapping image in the transport direction, and a second acquisition process is executed to acquire the mask pattern of the mask to be applied to the image data of the overlapping image based on information about the drying risk. [Effects of the Invention]

[0009] According to the present invention, during printing processing, an overlapping image of a partial image targeted by a current pass operation overlaps an overlapping image of a partial image targeted by a previous pass operation. A mask that prevents some nozzles from ejecting ink during a pass operation is applied to the image data of this overlapping image. This reduces the frequency of ink ejection from the nozzles, which increases the risk of ink drying in the nozzles. In response to this, a mask with a mask pattern that minimizes the masked portion is used during the pass operation based on information regarding the risk of drying, thereby increasing the ink ejection frequency and suppressing ink ejection defects.

[0010] The above and other objects, features, and advantages of the present invention will become apparent from the following detailed description of preferred embodiments, which proceeds with reference to the accompanying drawings. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram showing a printing apparatus according to the present invention as viewed from above. [Figure 2] FIG. 2 is a functional block diagram showing the configuration of the printing apparatus of FIG. [Figure 3] FIG. 3 is a schematic view of the head of FIG. 1 as seen from below. [Figure 4] FIG. 4 is a diagram showing a partial image, an overlapping image, and a non-overlapping image. [Figure 5] 5A is a diagram showing a mask of a first mask pattern and the kth partial image, and FIG. 5B is a diagram showing a mask of the first mask pattern and the k+1th partial image. [Figure 6] 6A is a diagram showing the mask of the second mask pattern a and the kth partial image, and FIG. 6B is a diagram showing the mask of the second mask pattern a and the k+1th partial image. [Figure 7] 7A is a diagram showing the mask of the second mask pattern b and the kth partial image, and FIG. 7B is a diagram showing the mask of the second mask pattern b and the k+1th partial image. [Figure 8] Fig. 8A is a graph showing the proportion of the mask portion of the first mask pattern in each of the mutually overlapping upstream k-th overlap region and downstream k+1-th overlap region, Fig. 8B is a graph showing the proportion of the mask portion of the second mask pattern a in each of the mutually overlapping upstream k-th overlap region and downstream k+1-th overlap region, Fig. 8C is a graph showing the proportion of the mask portion of the second mask pattern b in each of the mutually overlapping upstream k-th overlap region and downstream k+1-th overlap region. [Figure 9] FIG. 9 is a flowchart showing an example of a control method for a printing device. [Figure 10] FIG. 10 is a flowchart showing an example of the masking process. [Figure 11]Fig. 11A is a diagram showing the mask and kth partial image of the second mask pattern a of the printing device according to Modification 1. Fig. 11B is a diagram showing the mask and k+1th partial image of the second mask pattern a of Fig. 11A. [Figure 12] Fig. 12A is a diagram showing the mask and kth partial image of the second mask pattern b of the printing device according to Modification 1. Fig. 12B is a diagram showing the mask and k+1th partial image of the second mask pattern b of Fig. 11A. [Figure 13] FIG. 13 is a flowchart showing an example of mask processing in the control method of the printing device according to the first modification. DETAILED DESCRIPTION OF THE INVENTION

[0012] <Printing device configuration> 1, a printing device 10 according to an embodiment of the present disclosure is a device that prints an image on a print medium A using a head 20. The print medium A is, for example, a sheet of paper, fabric, or the like.

[0013] In the following, the direction in which the head 20 moves will be referred to as the left-right direction. A direction that intersects (for example, is perpendicular to) this direction of movement and in which the print medium A is transported will be referred to as the front-rear direction. Furthermore, a direction that intersects (for example, is perpendicular to) the direction in which the head 20 moves and the transport direction of the print medium A will be referred to as the up-down direction. However, the directions related to the printing device 10 are not limited to these.

[0014] The printing device 10 also includes a first device 10a and a second device 10b that can communicate with each other. The first device 10a is a device that processes image data, such as a personal computer. The second device 10b is a device that prints an image on a printing medium A based on the image data processed by the first device 10a, such as a serial head inkjet printer.

[0015] The second device 10b has a plurality of heads 20. Each of the plurality of heads 20 has a chip 21 (FIG. 3), a plurality of nozzles 22 (FIG. 3), and a plurality of drive elements 23 (FIG. 2). The nozzles 22 open on the underside of the chip 21. The drive elements 23 are piezoelectric elements, heat generating elements, electrostatic actuators, etc., and are provided for each nozzle 22. They apply pressure to the ink inside the head 20 to eject ink from the nozzles 22, causing the ink to be ejected from the nozzles 22 onto the print medium A. Details of the head 20 will be described later.

[0016] Furthermore, the second device 10b is equipped with a moving device 11 that moves the head 20 in the left-right direction. The moving device 11 has a carriage 11a and a moving motor 11b (FIG. 2). The carriage 11a is box-shaped, carries a plurality of heads 20, and is connected to the moving motor 11b. Therefore, when the moving motor 11b is driven to rotate, the moving device 11 moves the carriage 11a and the head 20 in the left-right direction.

[0017] Furthermore, the second device 10b is equipped with a transport device 12 that transports the print medium A in the front-to-back direction. The transport device 12 has, for example, a platen 12a and a transport motor 12b (Figure 2). The platen 12a is located a predetermined distance below the head 20. The flat upper surface of the platen 12a is disposed opposite the lower surface of the chip 21 and supports the print medium A from below. The transport motor 12b is connected to the platen 12a. When the transport motor 12b is driven to rotate, the transport device 12 transports the platen 12a and the print medium A in the front-to-back direction.

[0018] 2, the second device 10b includes a second control device 13b, and a head drive circuit 14a, a movement drive circuit 14b, and a transport drive circuit 14c electrically connected to the second control device 13b. The second control device 13b is configured by, for example, a computer, and includes a second calculation unit 13b1, a second storage unit 13b2, and a second communication interface 13b3.

[0019] The second communication interface 13b3 is a connection device that connects to an external device that exists independently of the printing device 10. The second storage unit 13b2 is a memory that can be accessed by the second calculation unit 13b1, and includes, for example, RAM and ROM. The second storage unit 13b2 stores data input from the second communication interface 13b3, as well as programs and various data used in data processing by the second calculation unit 13b1.

[0020] The second calculation unit 13b1 includes a circuit such as a processor such as a CPU, an integrated circuit such as an ASIC, or both. The second calculation unit 13b1 executes a program while referencing the data stored in the second storage unit 13b2, and the second control device 13b controls the operation of each unit of the second device 10b. As a result, the second device 10b executes various processes such as pass division processing, mask processing, and printing processing.

[0021] The second control device 13b is electrically connected to the drive element 23 of the head 20 via the head drive circuit 14a, and controls the drive of the drive element 23 based on the image data of the print image B. The second control device 13b is also electrically connected to the movement motor 11b of the movement device 11 via the movement drive circuit 14b, and controls the drive of the movement motor 11b. The second control device 13b is also electrically connected to the transport motor 12b of the transport device 12 via the transport drive circuit 14c, and controls the drive of the transport motor 12b.

[0022] The first device 10a also includes a first control device 13a. The first control device 13a is configured, for example, by a computer, and includes a first calculation unit 13a1, a first storage unit 13a2, and a first communication interface 13a3. The first storage unit 13a2 is a memory accessible from the first calculation unit 13a1, and includes at least one of, for example, RAM and ROM, and stores data input from the first communication interface 13a3, as well as programs and various data used in data processing by the first calculation unit 13a1.

[0023] First calculation unit 13a1 includes a processor such as a CPU. First calculation unit 13a1 executes a program while referring to data stored in first storage unit 13a2, causing first device 10a to perform various processes such as color conversion and halftone processing.

[0024] The first communication interface 13a3 is connected to the second communication interface 13b3 and an external device so as to be able to communicate with them. The first control device 13a and the second control device 13b can communicate with each other via the first communication interface 13a3 and the second communication interface 13b3, so the first control device 13a and the second control device 13b cooperate to control the printing device 10. The first control device 13a also acquires data such as image data of a print image B from the external device via the first communication interface 13a3. The image data is data representing the image to be printed, such as raster data.

[0025] <head> 3, the multiple heads 20 include, for example, a first head 20a, a second head 20b, and a third head 20c. The number of types of heads 20 is not limited to three, and the number of types of heads 20 may be two, or four or more.

[0026] The first head 20a has one or more first chips 21a1 and 21a2 and a plurality of first nozzles 22a. The first nozzles 22a eject ink of predetermined primary colors, such as process colors, including cyan, magenta, yellow, and black.

[0027] The first nozzles 22a are aligned in rows at equal intervals in the front-to-rear direction. The row of first nozzles 22a ejecting cyan ink, the row of first nozzles 22a ejecting magenta ink, the row of first nozzles 22a ejecting yellow ink, and the row of first nozzles 22a ejecting black ink are aligned in the left-to-right direction.

[0028] First nozzles 22a open on the undersides of the first chips 21a1 and 21a2. The first chip 21a1 is disposed diagonally forward and to the left of the first chip 21a2. The first chips 21a1 and 21a2 are disposed with a shift in the front-to-rear direction so that the rear of the first chip 21a1 overlaps the front of the first chip 21a2 when viewed left-to-right. This arrangement of the first chips 21a1 and 21a2 allows the length of the row of first nozzles 22a to be increased in the front-to-rear direction. In this row, the multiple first nozzles 22a in the first chip 21a1 and the multiple first nozzles 22a in the first chip 21a2 are arranged at equal intervals in the front-to-rear direction.

[0029] The second head 20b has one or more second chips 21b1, 21b2 and multiple second nozzles 22b. The second nozzles 22b eject, for example, spot color ink. Spot colors are colors different from the basic colors and include, for example, metallic colors such as gold, silver, and copper, pearlescent colors, and fluorescent colors. The multiple second nozzles 22b are aligned at equal intervals in the front-to-rear direction to form a row.

[0030] The second nozzles 22b open on the undersides of the second chips 21b1 and 21b2. The second chip 21b1 is disposed diagonally forward and to the left of the second chip 21b2. The second chips 21b1 and 21b2 are disposed with a shift in the front-to-rear direction so that the rear of the second chip 21b1 overlaps the front of the second chip 21b2 when viewed left-to-right. This arrangement of the second chips 21b1 and 21b2 allows the length of the row of the second nozzles 22b to be increased in the front-to-rear direction. In this row, the multiple second nozzles 22b in the second chip 21b1 and the multiple second nozzles 22b in the second chip 21b2 are arranged at equal intervals in the front-to-rear direction.

[0031] The third head 20c has one or more third chips 21c1 and 21c2 and multiple third nozzles 22c. The third nozzles 22c eject, for example, ink of a base color. The base color is a color different from the base color and the spot color, and includes, for example, white. The multiple third nozzles 22c are aligned at equal intervals in the front-to-rear direction to form a row.

[0032] Third nozzles 22c open on the undersides of the third tips 21c1 and 21c2. The third tip 21c1 is disposed diagonally forward and to the left of the third tip 21c2. Furthermore, the third tips 21c1 and 21c2 are disposed with a shift in the front-to-rear direction so that the rear of the third tip 21c1 overlaps the front of the third tip 21c2 when viewed left-to-right. This arrangement of the third tips 21c1 and 21c2 allows the length of the row of third nozzles 22c to be increased in the front-to-rear direction. In this row, the multiple third nozzles 22c in the third tip 21c1 and the multiple third nozzles 22c in the third tip 21c2 are arranged at equal intervals in the front-to-rear direction.

[0033] <Printing process> As shown in FIG. 4, the second control device 13b executes a printing process on the print medium A based on the image data of the print image B, and performs a pass operation and a transport operation during the printing process. During the pass operation, the second control device 13b ejects ink from the nozzles 22 of the head 20 onto a partial area A1 of the print medium A based on the partial image data of the partial image B1 while moving the head 20 left and right. This causes dots to be formed in the partial area A1, and a partial image B1 composed of the dots is formed. During the transport operation, the second control device 13b transports the print medium A backward by a transport amount such that the overlapping area A1a of the partial area A1 targeted by the current pass operation overlaps with the overlapping area A1a of the partial area A1 targeted by the previous pass operation. This forms a print image B composed of multiple partial images B1.

[0034] This partial area A1 is a portion of the print medium A and has an overlapping area A1a and a non-overlapping area A1b. The overlapping area A1a is a portion of the partial area A1 and overlaps with another overlapping area A1a. The non-overlapping area A1b is an area of ​​the partial area A1 other than the overlapping area A1a and does not overlap with another partial area A1. The overlapping area A1a and the non-overlapping area A1b are adjacent to each other in the front-to-back direction in the partial area A1.

[0035] The partial image data is a portion of the image data and represents the partial image B1. The partial image B1 is a portion of the print image B and is formed in the partial area A1 of the print medium A by a pass operation. The partial image B1 has an overlapping image B1a and a non-overlapping image B1b. The overlapping image B1a is a portion of the partial image B1 and is formed in the overlapping area A1a of the partial area A1 by a pass operation, and overlaps with another adjacent overlapping image B1a. The non-overlapping image B1b is a portion of the partial image B1 and is a different area from the overlapping image B1a. It is formed in the non-overlapping area A1b of the partial area A1 by a pass operation, and does not overlap with the other partial images B1.

[0036] As shown in FIG. 5A, partial image B1 is made up of a plurality of pixels B0. The pixels B0 include pixels B0 with dots and pixels B0 without dots. The plurality of pixels B0 are arranged in a checkerboard pattern in the front-to-back and left-to-right directions. A pixel row, which is a row of pixels B0 arranged in the left-to-right direction, corresponds to one nozzle 22 in the pass operation. This pixel B0 corresponds to pixel area A0 in partial area A1. Therefore, ink is ejected from the nozzle 22 moving left-to-right for each pixel area A0 in the row of pixel areas A0, and a dot is formed for each pixel B0 in the pixel row.

[0037] In the following, the partial area A1 targeted by the kth (natural number) pass operation, which is the current pass operation, and the partial image B1 formed in this partial area A1 may be referred to as "kth." The partial area A1 targeted by the k+1th pass operation, which is the next pass operation, and the partial image B1 formed in this partial area A1 may be referred to as "k+1th."

[0038] Furthermore, in the printing process, base color ink is ejected from the third nozzles 22c of the third head 20c onto the print medium A, and a base made of the base color ink is printed on the print medium A. Then, base color ink is ejected onto the base from the first nozzles 22a of the first head 20a, and special color ink is ejected onto the base from the second nozzles 22b of the second head 20b. A print image B is formed on the base using these base color inks and special color inks. The method for printing the base is the same as the method for printing the print image B. Alternatively, the print image B may be printed on the print medium A without printing the base.

[0039] 4, this pass operation of the first head 20a causes basic color ink to be ejected from the first nozzles 22a of the first chips 21a1 and 21a2 of the first head 20a, forming a partial image B1 in the partial region A1. Here, the kth overlapping region A1a of the kth partial region A1 targeted by the kth pass operation overlaps the k+1st overlapping region A1a of the k+1st partial region A1 targeted by the k+1st pass operation. Therefore, the kth overlapping image B1a of the kth partial image B1 is overlapped by the k+1st overlapping image B1a of the k+1st partial image B1. When the print medium A is transported backward, the kth overlapping image B1a is the front portion of the kth partial image B1, which is upstream in the transport direction, and the k+1st overlapping image B1a is the rear portion of the k+1st partial image B1, which is downstream in the transport direction.

[0040] Furthermore, when the first chip 21a1 is disposed forward of the first chip 21a2, the k-th overlapping image B1a is formed by ink ejected from the first chip 21a1, and the k+1-th overlapping image B1a is formed by ink ejected from the first chip 21a2. Similarly to the first head 20a, the second head 20b also has the k-th overlapping image B1a formed by ink from the second chips 21b1 and 21b2 and the k+1-th overlapping image B1a formed by ink from the second chips 21b1 and 21b2 overlapping with each other. Similarly to the first head 20a, the third head 20c also has the k-th overlapping image B1a formed by ink from the third chips 21c1 and 21c2 and the k+1-th overlapping image B1a formed by ink from the third chips 21c1 and 21c2 overlapping with each other.

[0041] <Mask> In this way, in the printing process, the k-th overlapping image B1a, which is located upstream in the transport direction in the k-th partial image B1 targeted by the k-th pass operation in the example of Fig. 5A, is overlapped with the k+1-th overlapping image B1a, which is located downstream in the transport direction in the k+1-th partial image B1 targeted by the k+1-th pass operation in the example of Fig. 5B. A mask is applied to the image data of the partial image B1 so that ink is ejected in one of the k-th pass operation and the k+1-th pass operation, but not in the other, into pixel regions A0 of the printing medium A corresponding to overlapping pixels B0 in the k-th overlapping image B1a and the k+1-th overlapping image B1a. As a result, masked portions are positioned complementary to the overlapping k-th overlapping image B1a and the k+1-th overlapping image B1a.

[0042] The mask is applied to partial image data of the overlapping image B1a so as to prevent some of the multiple nozzles 22 from ejecting ink during pass operations. The mask includes mask portions that prevent ink from being ejected from the nozzles 22 corresponding to the overlapping image B1a during pass operations. Because dots are formed by ejecting ink for each pixel B0 of the overlapping image B1a, the mask portions are applied to each pixel B0. The mask portions prevent ink from being ejected from the nozzles 22 corresponding to the shaded pixels B0.

[0043] In the kth partial image B1 in Figure 5A, the kth overlapping image B1a is located upstream of the kth non-overlapping image B1b in the transport direction. In the k+1th partial image B1 in Figure 5B, the k+1th overlapping image B1a is located downstream of the kth non-overlapping image B1b in the transport direction. When the print medium A is transported backward, the kth overlapping image B1a is a front portion of the kth partial image B1 that includes the front end of the kth partial image B1, and includes, for example, a pixel row of seven pixels B0 rearward from the front end of the kth partial image B1. The k+1st overlapping image B1a is a rear portion of the k+1th partial image B1 that includes the rear end of the k+1st partial image B1, and includes, for example, a pixel row of seven pixels B0 forward from the rear end of the k+1st partial image B1. In this case, the ejection in the pass operation of the nozzles 22 corresponding to the seven pixel columns of the kth overlapping image B1a and the seven pixel columns of the k+1th overlapping image B1a is restricted by the mask portion.

[0044] Furthermore, the mask portions are arranged complementarily for the kth overlapping image B1a and the k+1th overlapping image B1a. Therefore, as shown in Fig. 8A, the sum of the ratio Rk of the mask portion for the kth overlapping image B1a and the ratio Rk+1 of the mask portion for the k+1th overlapping image B1a is 100%. The ratio R of the mask portion for the overlapping image B1a is the number of pixels B0 to which the mask portion is applied relative to the number of pixels B0 in the pixel row of the overlapping image B1a.

[0045] Furthermore, since the non-overlapping image B1b does not overlap with other partial images B1, no mask is applied to the image data of the non-overlapping image B1b. Therefore, the ratio R of the masked portion to the non-overlapping image B1b is the ratio of the number of pixels B0 to which the masked portion is applied to the number of pixels B0 in the pixel row of the non-overlapping image B1b, which is 0%.

[0046] <Mask type> The mask has a varying type mask pattern and a fixed type mask pattern depending on whether the proportion R of the masked portion changes or not.

[0047] In a variation-type mask pattern, as shown in the examples of FIGS. 5A and 5B, the number of masked portions (shaded pixels B0) in the overlapping image B1a increases as the overlapping image B1a moves away from the non-overlapping image B1b in the transport direction. In other words, in a variation-type mask pattern, the proportion R of masked portions changes along the transport direction. In the example of FIG. 5A, the kth overlapping image B1a is located forward, upstream of the kth non-overlapping image B1b in the transport direction, and the number of masked portions for the kth overlapping image B1a increases toward the front. In the example of FIG. 5B, the k+1st overlapping image B1a is located backward, downstream of the k+1st non-overlapping image B1b in the transport direction, and the number of masked portions for the k+1st overlapping image B1a increases toward the rear. As shown in FIG. 8A, the proportion Rk of masked portions for the kth overlapping image B1a increases toward the front. The proportion Rk+1 of masked portions for the k+1st overlapping image B1a increases toward the rear.

[0048] In this way, an upstream mask pattern of a variation type in which the number of masked portions increases toward the front is applied to the upstream k-th overlapping image B1a, and a downstream mask pattern of a variation type in which the number of masked portions increases toward the back is applied to the downstream k+1-th overlapping image B1a. In the upstream mask pattern and downstream mask pattern, the masked portions are arranged complementarily.

[0049] In a fixed type mask pattern, as shown in the examples of Figures 7A and 7B, the number of masked portions in the overlapping image B1a remains constant along the transport direction. In other words, in a fixed type mask pattern, the ratio R of the masked portions along the transport direction is constant. Therefore, as shown in Figure 8C, the ratio Rk of the masked portions to the kth overlapping image B1a and the ratio Rk+1 of the masked portions to the k+1th overlapping image B1a are constant along the transport direction, for example, 50%.

[0050] In this case, a certain type of upstream mask pattern is applied to the upstream k-th overlapping image B1a, and a certain type of downstream mask pattern is applied to the downstream k+1-th overlapping image B1a, with the mask portions of the upstream mask pattern and the downstream mask pattern being arranged complementarily.

[0051] When such a variable-type mask pattern is applied to the image data of partial image B1, banding such as color unevenness is less likely to occur than when a fixed-type mask pattern is applied to the image data of partial image B1. However, the number of mask portions for the far end B1aa, which is the end (pixel row) of overlapping image B1a that is farther from non-overlapping image B1b, is greater with a variable-type mask pattern than with a fixed-type mask pattern. As a result, the ejection frequency of nozzles 22 for the far end B1aa is lower with a variable-type mask pattern than with a fixed-type mask pattern. The lower the ejection frequency, the greater the risk of ink drying in the nozzles 22.

[0052] Furthermore, the frequency of ejection of spot color ink from the second nozzle 22b tends to be lower than the frequency of ejection of base color ink from the first nozzle 22a. Therefore, a mask pattern in which the mask portion for the far end B1aa of the overlapping image B1a has a different ratio R is applied to the pass operation according to information related to the risk of ink drying in the second nozzle 22b.

[0053] <Mask pattern types> The mask patterns include a first mask pattern in the example of Fig. 5A and a second mask pattern in the example of Fig. 6A. The second mask pattern has a smaller mask portion for the far end B1aa of the overlapping image B1a that is farther from the non-overlapping image B1b in the transport direction than the first mask pattern.

[0054] The first mask pattern is a variable type as shown in the examples of FIGS. 5A and 5B. The second mask pattern includes a variable type second mask pattern a as shown in the examples of FIGS. 6A and 6B, and a fixed type second mask pattern b as shown in the examples of FIGS. 7A and 7B. However, it is sufficient for the second mask pattern to be at least one of a variable type and a fixed type. These mask patterns are pre-stored in the second storage unit 13b2.

[0055] The first mask pattern and second mask pattern a of the variable type have a greater banding suppression effect than the second mask pattern b of the fixed type. Furthermore, the masked portion of the far end B1aa of the overlapping image B1a is larger in the first mask pattern than in the second mask pattern a. For this reason, as shown in FIGS. 8A and 8B, the rate of change in the proportion R of the masked portion of the overlapping image B1a along the transport direction (the slope of the proportion lines Lk and Lk+1, which are lines indicating the proportion R) is smaller in the first mask pattern than in the second mask pattern a. As a result, the first mask pattern has a greater banding suppression effect than the second mask pattern a. For this reason, the banding suppression effect increases in the order of the second mask pattern b, the second mask pattern a, and the first mask pattern.

[0056] Furthermore, the ratio R of the mask portion to the far end B1aa of the overlapping image B1a decreases in the order of the first mask pattern, the second mask pattern a, and the second mask pattern b. As a result, the ink drying suppression effect increases in the order of the first mask pattern, the second mask pattern a, and the second mask pattern b. In this way, masks with mask patterns that have different ink drying suppression effects and banding suppression effects are applied to the image data of the overlapping image B1a according to information regarding the risk of ink drying in the second nozzle 22b.

[0057] <Information about the risk of dryness> The information regarding the risk of drying is based on the frequency of ink ejection from the nozzles 22. With regard to this ejection frequency, there are cases where the ejection frequency of the second nozzles 22b ejecting the special color ink is lower than that of the first nozzles 22a ejecting the base color ink. In this case, the ejection frequency of the second nozzles 22b of the nozzles 22 is used for the information regarding the risk of drying.

[0058] Furthermore, by applying a mask to the overlapping image B1a, the nozzles 22 tend to eject ink less frequently onto the overlapping image B1a than onto the non-overlapping image B1b in the partial image B1. For this reason, the ejection frequency of the second nozzles 22b corresponding to the overlapping image B1a is used for information relating to the drying risk.

[0059] Furthermore, the kth overlapping image B1a downstream of the current kth pass operation overlaps with the k+1th overlapping image B1a upstream of the next k+1th pass operation. The same mask pattern is applied to the kth overlapping image B1a and the k+1th overlapping image B1a. Therefore, the ejection frequency of the second nozzle 22b corresponding to the kth overlapping image B1a and the k+1th overlapping image B1a is used as information regarding the drying risk.

[0060] 4, the second nozzles 22b corresponding to the kth overlapping image B1a are the seven second nozzles 22b arranged from the front end to the rear on the second chip 21b1. The second nozzles 22b corresponding to the k+1th overlapping image B1a are the seven second nozzles 22b arranged from the rear end to the front on the second chip 21b2. In this case, for example, the average value of the discharge frequencies of the 14 second nozzles 22b may be used as information related to the drying risk.

[0061] The ink ejection frequency from the second nozzle 22b is, for example, the number of times ink is ejected from the second nozzle 22b per unit time. This ejection frequency is the quotient (d / e) obtained by dividing the number of times d that ink is ejected from the second nozzle 22b in a predetermined time e by the predetermined time e. This predetermined time e is, for example, a predetermined time until the previous pass operation of the current printing process, such as the time from a predetermined time until the previous pass operation, or a certain time going back from the previous pass operation.

[0062] The number of ejections d of the second nozzle 22b is, for example, the sum of the number of ejections d1 up to the previous printing process and the number of ejections d2 up to the previous pass operation of the current printing process. The second nozzle 22b has already ejected ink up to the previous printing process. Therefore, every time ink is ejected from the second nozzle 22b, the number of ejections of that second nozzle 22b is stored in the second storage unit 13b2. Therefore, the number of ejections d1 of the second nozzle 22b up to the previous printing process is obtained from the second storage unit 13b2.

[0063] In contrast, there are cases where ink ejection from the second nozzles 22b up to the previous pass operation of the current printing process has not yet been performed. In this case, the number of ejections d2 by the second nozzles 22b up to the previous pass operation is obtained based on the image data of the partial image B1 used in the pass operation. Here, if the image data is expressed as the presence or absence of dots, ink is ejected onto pixels B0 with dots, and ink is not ejected onto pixels B0 without dots. Therefore, the number of pixels B0 with dots corresponds to the number of ejections.

[0064] The relationship between the ink ejection frequency from the second nozzles 22b and information about the risk of drying is stored in advance in the second storage unit 13b2. For example, the information about the risk of drying is "medium" for an ejection frequency equal to or greater than a first predetermined value and less than a second predetermined value that is greater than the first predetermined value, "high" for an ejection frequency less than the first predetermined value, and "low" for an ejection frequency equal to or greater than the second predetermined value, indicating a lower than medium risk of drying.

[0065] In the above description, information regarding the risk of drying was acquired based on the ejection frequency of the second nozzles 22b corresponding to the kth overlapping image B1a and the k+1th overlapping image B1a, which overlap each other. However, ink is more likely to dry out in the second nozzles 22b corresponding to the far end B1aa of the overlapping image B1a. Therefore, information regarding the risk of drying may be acquired based on the ejection frequency of the second nozzles 22b for the far end B1aa of the kth overlapping image B1a and the far end B1aa of the k+1st overlapping image B1a. Information regarding the risk of drying may also be acquired based on the ejection frequency of the first nozzles 22a and the second nozzles 22b corresponding to the kth overlapping image B1a and the k+1st overlapping image B1a, which overlap each other.

[0066] <Printing device control method> The printing device 10 is controlled by the first control device 13a and the second control device 13b in accordance with the flowchart shown in the example of Fig. 9. First, the first control device 13a of the first device 10a acquires image data of the print image B from the first communication interface 13a3 or the first storage unit 13a2 (step S10).

[0067] Next, the first control device 13a performs color conversion processing on the image data of the print image B (step S11). In the color conversion processing, the first control device 13a converts the RGB image data into image data for each color that can be printed by the printing device 10 (for example, the basic colors CMYK and spot colors).

[0068] Next, the first control device 13a performs halftone processing on the image data for each color (step S12). In the halftone processing, the first control device 13a acquires image data converted into the presence or absence of dots according to the density of pixel B0 of the print image B, and transmits the image data to the second device 10b. This image data expressed by the presence or absence of dots may be, for example, binary data, or may also be quaternary data that further includes the size of the dots.

[0069] Next, the second control device 13b of the second device 10b acquires the halftone-processed image data from the first control device 13a and performs pass division processing on the image data (step S13). In the pass division processing, the second control device 13b divides the image data of the print image B for each pass operation and stores the partial image data of multiple partial images B1 in the second storage unit 13b2. Here, the partial images B1 are assigned to pass operations so that the kth overlapping image B1a upstream in the transport direction of the kth partial image B1 of the kth pass operation and the k+1th overlapping image B1a downstream in the transport direction of the k+1th partial image B1 of the k+1th pass operation overlap.

[0070] Furthermore, with this division of the image data, the print medium A is divided into partial areas A1 that are targets of pass operations. Here, the partial areas A1 are assigned to pass operations so that the k-th overlapping area A1a upstream in the transport direction of the k-th partial area A1 that is the target of the k-th pass operation and the k+1-th overlapping area A1a downstream in the transport direction of the k+1-th partial area A1 that is the target of the k+1-th pass operation overlap.

[0071] Next, the second control device 13b executes a masking process to apply a mask to the partial image data of the partial image B1 (step S14). The masking process is executed by the second control device 13b according to the flowchart shown in the example of Fig. 10. In this masking process, the second control device 13b resets k to 1 (step S20), and acquires the partial image data of the kth pass operation and the partial image data of the k+1th pass operation from the second storage unit 13b2 (step S21).

[0072] Next, the second control device 13b executes a first acquisition process to acquire information regarding the risk of ink drying in the nozzle 22 (step S22). In this first acquisition process, the second control device 13b acquires the second nozzle 22b corresponding to the overlapping upstream kth overlapping image B1a and downstream k+1th overlapping image B1a. The second control device 13b then acquires the number of ejections d1 of the second nozzle 22b up to the previous printing process from the second storage unit 13b2. The second control device 13b also acquires the number of ejections d2 of the second nozzle 22b in the first to previous pass operations of the current printing process based on the partial image data of these pass operations. The second control device 13b then acquires the quotient obtained by dividing the sum d of the number of ejections d1 up to the previous printing process and the number of ejections d2 up to the previous pass operation by a predetermined time e, as the ejection frequency of the second nozzle 22b. Then, the second control device 13b acquires information about the risk of drying corresponding to the ejection frequency of the second nozzle 22b from the second storage unit 13b2.

[0073] Next, the second control device 13b determines whether the information regarding the risk of dryness is "low" (step S23). Here, if the information regarding the risk of dryness is not "low" (step S23: NO), the second control device 13b determines whether the information regarding the risk of dryness is "medium" (step S26). Based on the determination results of steps S23 and S26, the second control device 13b executes a second acquisition process to acquire a mask pattern of a mask to be applied to the image data of the kth partial image B1 and the k+1th partial image B1 based on the information regarding the risk of dryness.

[0074] That is, in the second acquisition process, if the information on the drying risk is "low" (step S23: YES), the second control device 13b acquires the first mask pattern as a mask to be applied to the image data of the kth partial image B1 and the (k+1)th partial image B1 (step S24). In this way, if the ink in the second nozzles 22b is difficult to dry, the first mask pattern, which has a small effect of suppressing the drying of the ink, is used.

[0075] The second control device 13b then applies a mask of the first mask pattern to the upstream kth overlapping image B1a and the downstream k+1th overlapping image B1a. Here, if a masked portion of the mask corresponds to a pixel B0 with a dot among the pixels B0 of these overlapping images B1a, the pixel B0 is converted from dot-presence to dot-absence. This masked portion prevents ink from being ejected to the pixel region A0 of the printing medium A corresponding to the pixel B0 in the kth pass operation and the k+1th pass operation. The second control device 13b then acquires the partial image data of the kth partial image B1 and the k+1st partial image B1 to which the mask of the first mask pattern has been applied, and stores the partial image data in the second storage unit 13b2 (step S25).

[0076] Furthermore, in the second acquisition process, if the information on the risk of drying is "medium" (step S23: NO, S26: YES), the second control device 13b acquires the second mask pattern a as a mask to be applied to the image data of the kth partial image B1 and the k+1th partial image B1 (step S27). In this way, if the degree of dryness of the second nozzle 22b is medium, the second mask pattern a, which has a medium effect of suppressing ink drying, is used.

[0077] The second control device 13b then applies the mask of the second mask pattern a to the mutually overlapping upstream k-th overlapping image B1a and downstream k+1-th overlapping image B1a. The second control device 13b then acquires the partial image data of the k-th partial image B1 and the k+1-th partial image B1 to which the mask of the second mask pattern a has been applied, and stores the partial image data in the second storage unit 13b2 (step S28).

[0078] Furthermore, in the second acquisition process, if the information regarding the drying risk is "high" (step S23: NO, S26: NO), the second control device 13b acquires the second mask pattern b as a mask to be applied to the image data of the kth partial image B1 and the k+1th partial image B1 (step S29). In this way, if the ink in the second nozzles 22b is prone to drying, the second mask pattern b, which has a large effect of suppressing the drying of the ink, is used. This reduces the drying of the ink in the second nozzles 22b, and makes it possible to suppress poor ink ejection from the second nozzles 22b.

[0079] The second control device 13b then applies a mask of the second mask pattern b to the mutually overlapping upstream k-th overlapping image B1a and downstream k+1-th overlapping image B1a. The second control device 13b then acquires partial image data of the k-th partial image B1 and the k+1-th partial image B1 to which the mask of the second mask pattern b has been applied, and stores the partial image data in the second storage unit 13b2 (step S30).

[0080] Next, the second control device 13b determines whether all partial image data of the second head 20b has been acquired (step S31). If the second control device 13b has not acquired all partial image data of partial image B1 (step S31: NO), it increments k by 1 (step S32) and returns to step S21 to execute subsequent processes. If the second control device 13b has acquired all partial image data of partial image B1 (step S31: YES), it ends the masking process of step S14 in FIG. 9.

[0081] Next, the second control device 13b executes a printing process based on the partial image data that has been subjected to masking (step S15). In the printing process, the second control device 13b executes a pass operation based on the partial image data to which the masking has been applied, and forms a partial image B1 in the partial area A1 of the print medium A. Then, the second control device 13b executes a transport operation, and transports the print medium A a predetermined transport distance. As a result, the overlapping area A1a of the partial area A1 that is the target of the current pass operation overlaps with the overlapping area A1a of the partial area A1 that is the target of the previous pass operation. Accordingly, the overlapping image B1a of the partial image B1 from the current pass operation overlaps with the overlapping image B1a of the partial image B1 from the previous pass operation.

[0082] Thus, in the printing device 10, the second control device 13b executes a second acquisition process to acquire a mask pattern to be applied to the image data of the overlapping image B1a based on information regarding the risk of drying. For example, if there is a high risk of ink drying in the nozzles 22 corresponding to the overlapping image B1a, the second mask pattern, which has a smaller masked portion than the first mask pattern, is used for the pass operation. This tends to increase the frequency of ink ejection from the nozzles 22 corresponding to the overlapping image B1a, thereby reducing ink drying in the nozzles 22 and suppressing ink ejection defects.

[0083] Furthermore, in the printing device 10, information regarding the risk of drying is based on the frequency of ink ejection from the nozzles 22 in the passes executed up to the previous pass. As a result, the mask pattern applied to the current pass changes depending on the ejection frequency up to the previous pass. Therefore, ink drying in the nozzles 22 is more appropriately reduced depending on the risk of drying of the nozzles 22 up to the previous pass, and ink ejection defects are suppressed.

[0084] Furthermore, in the printing device 10, information regarding the risk of drying is based on the ejection frequency of spot color ink from the second nozzles 22b. The ejection frequency of ink from the second nozzles 22b may be lower than the ejection frequency of ink from the first nozzles 22a. In such cases, the drying of ink in the second nozzles 22b is more appropriately reduced in accordance with the risk of drying based on the ejection frequency of spot color ink from the second nozzles 22b, thereby suppressing ink ejection defects.

[0085] Furthermore, in the printing device 10, the mask pattern applied to the image data of the overlapping image B1a in a pass operation increases the ratio R of the masked portion to the overlapping image B1a as the overlapping image B1a moves away from the non-overlapping image B1b along the transport direction. The rate of change in the ratio R of the masked portion along the transport direction (the slope of the ratio lines Lk and Lk+1 indicating the ratio R) is smaller for the first mask pattern than for the second mask pattern a.

[0086] As a result, the ratio R of the masked portion at the near end B1ab, which is the end (pixel row) of the overlapping image B1a that is closest to the non-overlapping image B1b in the transport direction, is smaller for the first mask pattern than for the second mask pattern. Therefore, the difference in the ratio R of the masked portion between the non-overlapping image B1b, to which no mask is applied, and the near end B1ab of the overlapping image B1a is smaller for the first mask pattern than for the second mask pattern. As a result, the banding suppression effect is greater for the first mask pattern than for the second mask pattern. By applying such a mask of the first mask pattern to the image data of the partial image B1 of the pass operation, banding in the overlapping image B1a can be suppressed.

[0087] On the other hand, the ratio R of the masked portion at the far end B1aa of the overlapping image B1a, which is farther from the non-overlapping image B1b in the transport direction, is smaller for the second mask pattern than for the first mask pattern. As a result, the drying suppression effect is greater for the second mask pattern than for the first mask pattern. By applying such a mask of the second mask pattern to the image data of the partial image B1 of the pass operation, it is possible to suppress drying of the ink in the nozzles 22 corresponding to the overlapping image B1a.

[0088] Furthermore, in the printing device 10, the first mask pattern has a varying type in which the proportion R of the masked portion changes along the transport direction. The second mask pattern has at least one of a varying type and a fixed type in which the proportion R of the masked portion is constant along the transport direction. The varying type has a greater banding suppression effect than the fixed type, and the fixed type has a greater drying suppression effect than the varying type. By applying these various types of mask patterns to the image data of the partial image B1, it is possible to achieve both drying suppression and banding suppression.

[0089] <Variation 1> In the printing device 10 according to the first modification, the mask of the second mask pattern has a smaller dimension in the transport direction than the mask of the first mask pattern. The transport amount of the print medium A in the transport operation executed between the current pass operation and the next pass operation is larger when the mask of the second mask pattern is applied to the image data of the overlapping image B1a targeted for the current pass operation and the overlapping image B1a targeted for the next pass operation, which overlap each other, than when the mask of the first mask pattern is applied.

[0090] Specifically, the mask size of a mask pattern in the transport direction corresponds to the size of the overlapping image B1a to which the mask of that mask pattern is applied. This overlapping image B1a includes a pixel row of multiple pixels B0 aligned in the left-right direction, and the size of one pixel row in the transport direction is M. As shown in the examples of FIGS. 5A and 5B, the mask size of the first mask pattern in the transport direction corresponds to the size of seven pixel rows of the overlapping image B1a, which is 7×M. As shown in the examples of FIGS. 11A and 11B, the mask size of the second mask pattern a in the transport direction corresponds to the size of six pixel rows of the overlapping image B1a, which is 6×M. Furthermore, as shown in the examples of FIGS. 12A and 12B, the mask size of the second mask pattern b in the transport direction corresponds to the size of five pixel rows of the overlapping image B1a, which is 5×M.

[0091] In this case, the transport amount of the print medium A in the transport operation between the kth pass operation and the k+1th pass operation is determined so that the upstream kth overlapping image B1a and the downstream k+1th overlapping image B1a overlap each other. Therefore, the transport amount of the print medium A corresponds to the difference between the transport amount N and the mask dimensions of the mask pattern applied to the overlapping kth overlapping image B1a and the k+1st overlapping image B1a. This transport amount N is the transport amount of the print medium A when the kth partial image B1 and the k+1th partial image B1 do not overlap each other.

[0092] Therefore, the carry amount when the first mask pattern is used for the kth overlapping image B1a and the k+1th overlapping image B1a is the first carry amount (N-7×M). The carry amount when the second mask pattern a is used for the kth overlapping image B1a and the k+1th overlapping image B1a is the second carry amount (N-6×M). The carry amount when the second mask pattern b is used for the kth overlapping image B1a and the k+1th overlapping image B1a is the third carry amount (N-5×M).

[0093] In this way, the mask dimensions in the transport direction decrease in the order of the first mask pattern, the second mask pattern a, and the second mask pattern b. In contrast, the transport amounts of the printing medium A increase in the order of the first transport amount, the second transport amount, and the third transport amount. This relationship between the mask patterns and the transport amounts is pre-stored in the second storage unit 13b2.

[0094] The masking process of the printing device 10 according to the first modification is executed according to the flowchart shown in Fig. 13. In the flowchart of Fig. 13, the operations for determining the transport amount of the print medium A in steps S40 to S42 are executed after steps S25, S28, and S30 in Fig. 10.

[0095] That is, if the information regarding the drying risk is "low" (step S23: YES), the second control device 13b acquires a first mask pattern as a mask to be applied to the image data of the mutually overlapping kth overlapping image B1a and the k+1th overlapping image B1a (step S24).The second control device 13b then acquires partial image data of the kth partial image B1 and the k+1th partial image B1 obtained by applying the first mask pattern to these overlapping images B1a, and stores the partial image data in the second storage unit 13b2 (step S25).The second control device 13b then determines the transport amount of the printing medium A in the transport operation between the kth pass operation and the k+1th pass operation as the first transport amount, and stores the first transport amount in the second storage unit 13b2 (step S40).

[0096] Furthermore, if the information regarding the drying risk is "medium" (step S23: NO, S26: YES), the second control device 13b acquires a second mask pattern a as a mask to be applied to the image data of the mutually overlapping kth overlapping image B1a and the k+1th overlapping image B1a (step S27).The second control device 13b then acquires partial image data of the kth partial image B1 and the k+1th partial image B1 obtained by applying the second mask pattern a to these overlapping images B1a, and stores the partial image data in the second storage unit 13b2 (step S28).The second control device 13b then determines the transport amount of the printing medium A in the transport operation between the kth pass operation and the k+1th pass operation as the second transport amount, and stores the second transport amount in the second storage unit 13b2 (step S41).

[0097] Furthermore, if the information regarding the drying risk is "high" (steps S23: NO, S26: NO), the second control device 13b acquires a second mask pattern b as a mask to be applied to the image data of the mutually overlapping kth overlapping image B1a and the k+1th overlapping image B1a (step S29). Then, the second control device 13b acquires partial image data of the kth partial image B1 and the k+1th partial image B1 obtained by applying the second mask pattern b to these overlapping images B1a, and stores the partial image data in the second storage unit 13b2 (step S30). Then, the second control device 13b determines the transport amount of the printing medium A in the transport operation between the kth pass operation and the k+1th pass operation to be a third transport amount, and stores the third transport amount in the second storage unit 13b2 (step S42).

[0098] 9, the second control device 13b acquires the partial image data of the kth partial image B1 from the second storage unit 13b2, executes the kth pass operation based on this partial image data, and forms the kth partial image B1 in the kth partial region A1. The second control device 13b then acquires the transport amount for the transport operation between the kth pass operation and the k+1th pass operation from the second storage unit 13b2, and transports the print medium A by this transport amount. The second control device 13b then acquires the partial image data of the k+1th partial image B1 from the second storage unit 13b2, executes the k+1th pass operation based on this partial image data, and forms the k+1st partial image B1 in the k+1st partial region A1. The k+1st overlapping region A1a downstream of the k+1st partial region A1 and the kth overlapping region A1a of the kth partial region A1 overlap each other. Accordingly, the k+1th overlapping image B1a downstream of the k+1th partial image B1 and the kth overlapping image B1a of the kth partial image B1 overlap each other.

[0099] In this printing device 10, the pass operations include a first pass operation in which the first head 20a is moved while ejecting a base color ink from the first nozzles 22a, and a second pass operation in which the second head 20b is moved while ejecting a spot color ink from the second nozzles 22b. The transport amount of the print medium A in the transport operation performed between the current first pass operation and the previous first pass operation is the same as the transport amount of the print medium A in the transport operation performed between the current second pass operation and the previous second pass operation.

[0100] That is, in the color conversion process of step S11 in Fig. 9, the second control device 13b converts the image data into image data for base colors and image data for spot colors. Then, in the masking process of step S14, the second control device 13b applies a mask with a mask pattern based on information about the drying risk to the overlapping image B1a of the partial image B1 that is the target of each of the first pass operation based on the image data for base colors and the second pass operation based on the image data for spot colors. This information about the drying risk corresponds to the ejection frequency of the second nozzle 22b. Therefore, the kth overlapping image B1a and the k+1th overlapping image B1a that overlap each other have the same mask pattern applied to the image data for base colors and the image data for spot colors.

[0101] 9, the second control device 13b executes the current k-th pass operation and the next k+1-th pass operation as first pass operations based on the image data of the base colors. The second control device 13b also executes the current k-th pass operation and the next k+1-th pass operation as second pass operations based on the image data of the special colors. The transport distance of the print medium A in the transport operation between the k-th pass operation and the k+1-th pass operation corresponds to the mask dimensions of the mask patterns applied to the overlapping k-th overlapping image B1a and the k+1-th overlapping image B1a.

[0102] The same mask pattern is applied to the kth overlapping image B1a and the k+1th overlapping image B1a based on the image data of the base colors and the image data of the special colors. Therefore, the transport amount of the print medium A in the transport operation between the kth pass operation, which is the first pass operation based on the image data of the base colors, and the transport amount of the print medium A in the transport operation between the kth pass operation and the k+1th pass operation, which is the second pass operation based on the image data of the special colors, are equal to each other.

[0103] Note that different mask patterns may be applied to the overlapping image B1a based on the image data of the base colors and the overlapping image B1a based on the image data of the special colors. For example, a mask pattern based on the ejection frequency of the ink of the base colors from the first nozzles 22a may be applied to the overlapping image B1a based on the image data of the base colors. Also, a mask pattern based on the ejection frequency of the ink of the special colors from the second nozzles 22b may be applied to the overlapping image B1a based on the image data of the special colors.

[0104] As a result, masks with different mask patterns may be applied to the overlapping image B1a based on the image data of the base colors and the image data of the spot colors. Even if the dimensions of these mask patterns in the transport direction are different, the second control device 13b may make the transport amount of the print medium A in the transport operation between the kth pass operation, which is the first pass operation based on the image data of the base colors, and the k+1th pass operation equal to the transport amount of the print medium A in the transport operation between the kth pass operation and the k+1th pass operation, which is the second pass operation based on the image data of the spot colors.

[0105] <Other variations> In all of the above embodiments and modifications, as shown in Figures 8A and 8B, the mask pattern of the mask applied to the kth overlapping image B1a has a mask proportion line Lk in which the proportion Rk of the masked portion decreases from the upstream end to the downstream end in the transport direction. Furthermore, the mask pattern of the mask applied to the k+1th overlapping image B1a has a mask proportion line Lk+1 in which the proportion Rk+1 of the masked portion decreases from the downstream end to the upstream end in the transport direction. The proportion R of the masked portion at the intersection L of the mask proportion line Lk and the mask proportion line Lk+1 is equal for the first mask pattern and the second mask pattern a. Note that the proportion R of the masked portion at the intersection L of the mask proportion line Lk and the mask proportion line Lk+1 may be smaller for the second mask pattern a than for the first mask pattern a.

[0106] In all of the above-described embodiments and modifications, the printing device 10 is configured by the first device 10a and the second device 10b that are provided separately from each other. However, the printing device 10 may be configured by a device in which the first device 10a and the second device 10b are provided integrally.

[0107] In all of the above embodiments and modifications, the first head 20a, the second head 20b, and the third head 20c are mounted on the same carriage 11a and moved together by the moving device 11. However, the moving device 11 may include a first moving device having the first head 20a, a second moving device that moves the second head 20b, and a second moving device that moves the third head 20c. The first head 20a, the second head 20b, and the third head 20c may be moved by the first to third moving devices, respectively.

[0108] Different mask patterns may be applied to the image data of the base colors of the first head 20a and the image data of the spot colors of the second head 20b. The dimensions of the masks of these mask patterns in the transport direction may differ from each other. In this case, the transport amount of the print medium A in the transport operation between the kth pass operation and the k+1th pass operation may be determined based on the dimensions in the transport direction of the masks applied to the overlapping kth overlapping image B1a and the k+1st overlapping image B1a. As a result, the transport amount between pass operations based on the image data of the base colors of the first head 20a and the transport amount between pass operations based on the image data of the spot colors of the second head 20b may differ from each other.

[0109] It should be noted that all of the above embodiments may be combined with one another as long as they do not exclude one another. Furthermore, many improvements and other embodiments of the present invention will be apparent to those skilled in the art from the above description. Therefore, the above description should be construed as merely illustrative and is provided for the purpose of teaching those skilled in the art the best mode for carrying out the present invention. Details of the structure and / or function of the present invention may be substantially changed without departing from the spirit of the present invention. [Explanation of symbols]

[0110] 10:Printing device 11: Mobile device 12:Transportation device 13a: First control device (control device) 13b: Second control device (control device) 20: Head 20a: 1st head 20b: 2nd head

Claims

1. a head having a nozzle; a moving device that moves the head in a moving direction; a conveying device that conveys the print medium in a conveying direction that intersects with the movement direction; a control device; The control device a first acquisition process for acquiring information regarding a risk of ink drying in the nozzles; a pass operation in which ink is ejected from the nozzles onto the print medium while moving the head, and a transport operation in which the print medium is transported, based on image data of a partial image that is a part of the print image, and a printing process in which an overlapping image of the partial image that is the target of the current pass operation is superimposed on an overlapping image of the partial image that is the target of the previous pass operation, The partial image is an overlapping image, which is an area overlapping with another adjacent partial image; a non-overlapping image that is a region different from the overlapping image and does not overlap with other partial images, The mask is applied to the image data of the overlapping image, and is a mask pattern including a mask portion that prevents ink from being ejected from the nozzles corresponding to the overlapping image in the pass operation, a first mask pattern; a second mask pattern in which the mask portion is smaller than the first mask pattern at an end of the overlapping image that is farther from the non-overlapping image in the transport direction, The control device and executing a second acquisition process of acquiring a mask pattern of the mask to be applied to the image data of the overlapping image based on the information about the dryness risk. Printing device.

2. the information regarding the drying risk is based on the frequency of ink ejection from the nozzles in the pass operations executed up to the previous pass operation; The printing device of claim 1 .

3. The nozzle is a first nozzle that ejects ink of a predetermined basic color; a second nozzle that ejects ink of a special color different from the basic color; the information about the drying risk is based on a frequency of ejection of the spot color ink from the second nozzles; The printing device of claim 1 .

4. a mask of the second mask pattern has a smaller dimension in the transport direction than a mask of the first mask pattern; a transport amount of the printing medium in the transport operation executed between the current pass operation and the next pass operation is larger when the mask of the second mask pattern is applied to the image data of the overlapping image of the target of the current pass operation and the overlapping image of the target of the next pass operation, which overlap each other, than when the mask of the first mask pattern is applied; The printing device of claim 1 .

5. The head a first head including first nozzles that eject ink of a predetermined basic color; a second head that is disposed offset from the first head in the transport direction and includes second nozzles that eject ink of a special color different from the basic colors, The pass operation is a first pass operation in which ink of a basic color is ejected from the first nozzles while the first head is moved; a second pass operation in which the second head is moved while ejecting ink of the special color from the second nozzles, a transport amount of the print medium in the transport operation performed between the current first pass operation and the previous first pass operation is equal to a transport amount of the print medium in the transport operation performed between the current second pass operation and the previous second pass operation; The printing device according to claim 4 .

6. the mask pattern applied to the image data of the overlapping image of the pass operation is such that the ratio of the mask portion to the overlapping image increases as the overlapping image moves away from the non-overlapping image along the transport direction, a rate of change in the proportion of the mask portion along the transport direction is smaller for the first mask pattern than for the second mask pattern; The printing device of claim 1 .

7. The first mask pattern is a variation type in which the proportion of the mask portion varies along the conveying direction, The second mask pattern is The mask has at least one of the varying type and a constant type in which the proportion of the mask portion is constant along the conveying direction. The printing device of claim 1 .

8. a head having a nozzle; a moving device that moves the head in a moving direction; a conveying device that conveys the print medium in a conveying direction that intersects with the movement direction; A control method for a printing device comprising: a first acquisition process for acquiring information regarding a risk of ink drying in the nozzles; a pass operation in which ink is ejected from the nozzles onto the print medium while moving the head, and a transport operation in which the print medium is transported, based on image data of a partial image that is a part of the print image, and a printing process in which an overlapping image of the partial image that is the target of the current pass operation is overlapped with an overlapping image of the partial image that is the target of the previous pass operation, The partial image is an overlapping image, which is an area overlapping with another adjacent partial image; a non-overlapping image that is a region different from the overlapping image and does not overlap with other partial images, The mask is applied to the image data of the overlapping image, and is a mask pattern including a mask portion that prevents ink from being ejected from the nozzles corresponding to the overlapping image in the pass operation, a first mask pattern; a second mask pattern in which the mask portion is smaller than the first mask pattern at an end of the overlapping image that is farther from the non-overlapping image in the transport direction, a second acquisition process for acquiring a mask pattern of the mask to be applied to the image data of the overlapping image based on the information about the risk of drying; A method for controlling a printing device.

9. a head having a nozzle; a moving device that moves the head in a moving direction; a conveying device that conveys the print medium in a conveying direction that intersects with the movement direction; A printing device comprising: a first acquisition process for acquiring information regarding a risk of ink drying in the nozzles; a pass operation in which ink is ejected from the nozzles onto the print medium while moving the head, and a transport operation in which the print medium is transported, based on image data of a partial image that is a part of the print image, and a printing process in which an overlapping image of the partial image that is the target of the current pass operation is overlapped with an overlapping image of the partial image that is the target of the previous pass operation, The partial image is an overlapping image, which is an area overlapping with another adjacent partial image; a non-overlapping image that is a region different from the overlapping image and does not overlap with other partial images, The mask is applied to the image data of the overlapping image, and is a mask pattern including a mask portion that prevents ink from being ejected from the nozzles corresponding to the overlapping image in the pass operation, a first mask pattern; a second mask pattern in which the mask portion is smaller than the first mask pattern at an end of the overlapping image that is farther from the non-overlapping image in the transport direction, a second acquisition process for acquiring a mask pattern of the mask to be applied to the image data of the overlapping image based on the information about the risk of drying; program.

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