Liquid ejection device, control method thereof, and program

Abstract

To suppress dot-missing due to a defective nozzle even when a deviation in a conveyance amount and an impact position occurs, and suppress the degradation in the image quality and complication in processing.SOLUTION: Discharge processing includes a plurality of discharge steps E1a, E1b that are executed with a time interval to a unit region of a sheet. The plurality of discharge steps E1a, E1b selectively discharge ink from a nozzle on the basis of the data obtained by decomposing image data into a complementary pattern. In at least one of the plurality of discharge steps E1a, E1b, a function of a discharge duty of a nozzle to a position of the nozzle in the conveyance direction has a rising part H that gradually rises from the upstream to the downstream in the conveyance direction or a falling part I that gradually falls. In the plurality of unit regions adjacent to each other in the conveyance direction, the function is constituted by at least the rising part H and the falling part I. A control unit of the printer executes detection processing for detecting a defective nozzle before executing the discharge processing and changes the function when the defective nozzle is detected.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a liquid ejection device that executes a conveying process in which a conveying mechanism conveys a recording medium based on image data, and an ejection process in which liquid is ejected from a plurality of nozzles onto the recording medium, as well as a control method and program therefor. [Background technology]

[0002] Patent Document 1 discloses a printer (liquid ejection device) that prints an image by repeatedly executing a formation process (ejection process) in which ink is ejected onto a recording medium to form dots according to image data, and a transport process in which the recording medium is transported. Patent Document 1 also discloses that at least a portion of a first scanning range on the recording medium scanned by a print head in a first formation process overlaps with at least a portion of a second scanning range on the recording medium scanned by a print head in a second formation process. The function of the nozzle recording rate (ejection duty) relative to the nozzle position in the transport direction is composed of a flat central portion, a portion located upstream of the central portion in the transport direction that linearly decreases from 50% to 0% in the -Y direction as the nozzle position in the transport direction changes (an ascending portion that gradually increases from upstream to downstream in the transport direction), and a portion located downstream of the central portion in the transport direction that linearly decreases from 50% to 0% in the +Y direction as the nozzle position in the transport direction changes (a descending portion that gradually decreases from upstream to downstream in the transport direction). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-52051 A Summary of the Invention [Problem to be solved by the invention]

[0004] In a liquid ejection device, if any of the nozzles is a "faulty nozzle," the defective nozzle will be unable to properly land the liquid in the area where it is supposed to be ejected, which can result in missing dots. A "faulty nozzle" is a nozzle that becomes clogged and is unable to eject liquid, or the amount of liquid ejected is less than the specified amount, or the landing position of the ejected liquid is shifted due to an increase in the viscosity of the liquid or the like.

[0005] When a discharge process such as that described in Patent Document 1 is performed, one possible way to prevent missing dots caused by defective nozzles is to increase the discharge duty of a nozzle corresponding to the position of the defective nozzle in a discharge step other than the discharge step to which the defective nozzle belongs, among the multiple discharge steps corresponding to a unit area, to complement the image. However, with this method, if the carry amount or landing position is shifted, the image cannot be complemented by the other nozzle, and missing dots (and therefore banding) occur.

[0006] Therefore, when a defective nozzle is detected, rather than simply increasing the ejection duty of another nozzle corresponding to the defective nozzle, it is possible to change the above function. However, if the function is changed uniformly regardless of whether the defective nozzle belongs to the peak or base of the function, this could result in a deterioration in image quality and complicate processing.

[0007] The object of the present invention is to provide a liquid ejection device, a control method and a program for the same, which can suppress missing dots caused by defective nozzles even if there is a deviation in the transport amount or landing position, and can suppress deterioration of image quality and complexity of processing. [Means for solving the problem]

[0008] According to a first aspect of the present invention, there is provided a recording medium printing apparatus comprising a head having a plurality of nozzles, a transport mechanism that transports a recording medium in a transport direction, and a control unit, wherein the plurality of nozzles are spaced apart from one another in the transport direction, and the control unit executes, based on image data, a transport process that causes the transport mechanism to transport the recording medium in the transport direction, and a discharge process that causes the plurality of nozzles to discharge liquid onto the recording medium, the discharge process comprising a plurality of discharge steps that are executed at time intervals for a unit area of ​​the recording medium, the discharge steps including a plurality of discharge steps that selectively discharge liquid from the plurality of nozzles based on data obtained by breaking down the image data into complementary patterns, and at least one of the plurality of discharge steps corresponding to the unit area a liquid ejection device in which a function of the ejection duty of the nozzle relative to the position of the nozzle in the transport direction has an ascending portion that gradually increases or a descending portion that gradually decreases from upstream to downstream in the transport direction, and in a plurality of unit areas that are adjacent to each other in the transport direction, the function is composed of at least the ascending portion and the descending portion, and the control unit executes a detection process to detect a faulty nozzle among the plurality of nozzles before executing the ejection process, and a modification process to modify the function if a faulty nozzle is detected in the detection process, and in the modification process, the function is changed depending on whether the faulty nozzle belongs to the peak or base of the function.

[0009] According to a second aspect of the present invention, there is provided a control method for controlling a liquid ejection device comprising a head having a plurality of nozzles and a transport mechanism that transports a recording medium in a transport direction, the plurality of nozzles being spaced apart from one another in the transport direction, the method comprising: performing a transport process that transports the recording medium in the transport direction by the transport mechanism based on image data; and a discharge process that discharges liquid from the plurality of nozzles onto the recording medium, the discharge process comprising a plurality of discharge steps that are performed at time intervals for a unit area of ​​the recording medium, the discharge steps including a plurality of discharge steps that selectively discharge liquid from the plurality of nozzles based on data obtained by breaking down the image data into complementary patterns; and In at least one of the control methods, a function of the ejection duty of the nozzle relative to the position of the nozzle in the transport direction has an ascending portion that gradually increases or a descending portion that gradually decreases from upstream to downstream in the transport direction, and in a plurality of the unit areas that are adjacent to each other in the transport direction, the function is made up of at least the ascending portion and the descending portion, and before executing the ejection process, a detection process is executed to detect a faulty nozzle among the plurality of nozzles, and if a faulty nozzle is detected in the detection process, a modification process is executed to modify the function, and in the modification process, the function is changed depending on whether the faulty nozzle belongs to a peak or a base of the function.

[0010] According to a third aspect of the present invention, there is provided a program that causes a liquid ejection device, which is provided with a head having a plurality of nozzles and a transport mechanism that transports a recording medium in a transport direction, the plurality of nozzles being spaced apart from one another in the transport direction, to function as means for executing a transport process that transports the recording medium in the transport direction by the transport mechanism based on image data, and a discharge process that discharges liquid from the plurality of nozzles onto the recording medium, the discharge process comprising a plurality of discharge steps that are executed at time intervals for a unit area of ​​the recording medium, the discharge steps including a plurality of discharge steps that selectively discharge liquid from the plurality of nozzles based on data obtained by breaking down the image data into complementary patterns, and at least one of the plurality of discharge steps that corresponds to the unit area. In one of the above, a function of the ejection duty of the nozzle with respect to the position of the nozzle in the transport direction has an ascending portion that gradually increases or a descending portion that gradually decreases from upstream to downstream in the transport direction, and in a plurality of the unit areas that are adjacent to each other in the transport direction, the function is made up of at least the ascending portion and the descending portion, and the program functions as a means for executing a detection process that detects faulty nozzles among the plurality of nozzles before executing the ejection process, and a modification process that modifies the function if a faulty nozzle is detected in the detection process, and in the modification process, the function is changed depending on whether the faulty nozzle belongs to a peak or a base of the function. [Effects of the Invention]

[0011] According to this invention, when a faulty nozzle is detected, rather than simply increasing the ejection duty of another nozzle corresponding to the position of the faulty nozzle, by changing the function, it is possible to suppress missing dots caused by the faulty nozzle even if there is a deviation in the carry amount or landing position. Furthermore, by changing the function depending on whether the faulty nozzle belongs to the peak or base of the function in the change process, it is possible to suppress deterioration of image quality and complicated processing. [Brief explanation of the drawings]

[0012] [Figure 1]1 is a plan view of a printer according to an embodiment of the present invention; [Figure 2] FIG. 2 is a block diagram showing the electrical configuration of the printer in FIG. [Figure 3] 2 is a flow chart showing a program executed by a control unit of the printer of FIG. 1. [Figure 4] 4A and 4B are graphs showing the function of nozzle ejection duty versus nozzle position in the transport direction when recording is performed using two movement operations on a unit area of ​​paper, where (a) is a graph showing a situation in which a faulty nozzle belongs to the peak of the function, and (b) is a graph showing a modified version of the function of Figure 4A. [Figure 5] 5A and 5B are graphs showing the function of nozzle ejection duty versus nozzle position in the transport direction when recording is performed using two movement operations on a unit area of ​​paper, where (a) is a graph showing a situation in which a faulty nozzle belongs to the base of the function, and (b) is a graph showing a modified version of the function of Figure 5A. [Figure 6] 6(a) and 6(b) are graphs showing the function of nozzle ejection duty versus nozzle position in the transport direction when recording is performed using two movement operations on a unit area of ​​paper, where (a) is a graph showing a situation where two faulty nozzles belong to the base of the function, and (b) is a graph showing a modified version of the function of Figure 6(a). [Figure 7] 7A and 7B are graphs showing the function of nozzle ejection duty versus nozzle position in the transport direction when recording is performed using two movement operations on a unit area of ​​paper, where (a) is a graph showing a situation in which defective nozzles belong to both the peak and base of the function, and (b) is a graph showing a modified version of the function of Figure 7A. [Figure 8] 8(a) and 8(b) are graphs showing the function of nozzle ejection duty versus nozzle position in the transport direction when recording is performed using three movement operations on a unit area of ​​paper, where (a) is a graph showing a situation in which a faulty nozzle belongs to the peak of the function, and (b) is a graph showing a modified version of the function of Figure 8(a). [Figure 9]9(a) and 9(b) are graphs showing the function of nozzle ejection duty versus nozzle position in the transport direction when recording is performed using three movement operations on a unit area of ​​paper, where (a) is a graph showing a situation in which a faulty nozzle belongs to the base of the function, and (b) is a graph showing a modified version of the function of Figure 9(a). [Figure 10] 10(a) and 10(b) are graphs showing the function of nozzle ejection duty versus nozzle position in the transport direction when recording is performed using three movement operations on a unit area of ​​paper, where (a) is a graph showing a situation where two faulty nozzles belong to the base of the function, and (b) is a graph showing a modified version of the function in Figure 10(a). [Figure 11] 11(a) and 11(b) are graphs showing the function of nozzle ejection duty versus nozzle position in the transport direction when recording is performed using three movement operations on a unit area of ​​paper, where (a) is a graph showing a situation in which defective nozzles belong to both the peak and base of the function, and (b) is a graph showing a modified version of the function of Figure 11(a). [Figure 12] 4A and 4B are diagrams showing a reference example of the present invention, in which (a) is a graph showing the function of nozzle ejection duty versus nozzle position in the transport direction when recording is performed by two movement operations on a unit area of ​​paper, similar to FIG. 4A, and is a graph showing a situation in which a defective nozzle belongs to the peak of the function, and (b) is a graph in which the ejection duty of another nozzle corresponding to the position of the defective nozzle is increased. DETAILED DESCRIPTION OF THE INVENTION

[0013] As shown in Figure 1, a printer (liquid ejection device) 10 according to one embodiment of the present invention has a head 1 having a plurality of nozzles 11 on its underside, a carriage 2 that holds the head 1, a movement mechanism 3 that moves the carriage 2 in a movement direction (a direction perpendicular to the vertical direction), a platen 4 that supports paper (recording medium) P from below, a transport mechanism 5 that transports paper P in a transport direction (a direction perpendicular to the movement direction and the vertical direction), and a control unit 9.

[0014] The head 1 ejects ink from the nozzles 11 when the driver IC1x (see Figure 2) is driven under the control of the control unit 9. The nozzles 11 form four nozzle rows aligned in the movement direction. Each nozzle row is made up of multiple nozzles 11 spaced apart from each other in the transport direction.

[0015] The movement mechanism 3 includes a pair of guides 3a and 3b that support the carriage 2, and a belt 3c connected to the carriage 2. The guides 3a and 3b and the belt 3c extend in the movement direction. When the carriage motor 3x (see FIG. 2) is driven under the control of the control unit 9, the belt 3c runs, and the carriage 2 moves in the movement direction along the guides 3a and 3b.

[0016] The platen 4 is disposed below the carriage 2 and the head 1. A paper sheet P is placed on the upper surface of the platen 4.

[0017] The transport mechanism 5 has two rollers 5a and 5b. The head 1, carriage 2, and platen 4 are arranged between the rollers 5a and 5b in the transport direction. When the transport motor 5x (see FIG. 2) is driven under the control of the control unit 9, the rollers 5a and 5b rotate while sandwiching the paper P, and the paper P is transported in the transport direction.

[0018] As shown in Fig. 2, the control unit 9 has a ROM (Read Only Memory) 9a, a RAM (Random Access Memory) 9b, and an ASIC (Application Specific Integrated Circuit) 9c. The ROM 9a stores programs and data for the ASIC 9c to control various operations. The RAM 9b temporarily stores data used by the ASIC 9c when executing the programs. The ASIC 9c executes recording processing in accordance with the programs and data stored in the ROM 9a and RAM 9b, based on a recording command (including image data) received from an external device (such as the PC 20 shown in Fig. 2).

[0019] The recording process includes a transport process in which the transport mechanism 5 transports the paper P in the transport direction, and a discharge process in which ink is discharged from the multiple nozzles 11 onto the paper P. The discharge process includes a movement operation in which the movement mechanism 3 moves the head 1 in the movement direction and discharges ink from the nozzles 11 onto the paper P multiple times. An operation from one side of the movement direction to the other (forward movement) and an operation from the other side of the movement direction to one side (return movement) are each referred to as one movement operation. In the recording process, the control unit 9 controls the driver IC 1x, carriage motor 3x, and transport motor 5x to alternately perform a transport process in which the transport mechanism 5 transports the paper P a predetermined distance in the transport direction and a movement operation. As a result, ink dots are formed on the paper P, and an image is recorded.

[0020] Next, the processing executed by the control unit 9 will be described in detail with reference to FIG.

[0021] The control unit 9 first determines whether or not a recording command has been received from the PC 20 etc. (S1). If it is determined that a recording command has not been received (S1: NO), the control unit 9 repeats the process of S1.

[0022] If the control unit 9 determines that a recording command has been received (S1: YES), it executes a discharge test (S2). The discharge test corresponds to the "detection process" of the present invention and is a process for detecting "faulty nozzles" among the multiple nozzles 11. A "faulty nozzle" refers to a nozzle 11 that is clogged and unable to discharge ink, or that discharges less than the specified amount, or that the landing position of the discharged ink is shifted due to an increase in ink viscosity or other reasons. In S2, for example, an optical sensor having a light-emitting element and a light-receiving element is used. Ink is discharged from each nozzle 11 in turn, and the light-receiving element receives light generated when the light emitted from the light-emitting element intersects with the ink droplets. The presence and location of faulty nozzles are detected based on the intensity of the light received by the light-receiving element. Alternatively, in S2, ink may be discharged from each nozzle 11 onto a test sheet P to form a test pattern, and the presence and location of faulty nozzles may be detected visually by a user.

[0023] After S2, the control unit 9 determines whether or not a faulty nozzle has been detected based on the results of S2 (S3). If it determines that a faulty nozzle has been detected (S3: YES), the control unit 9 changes (S4) the function used in the ejection process included in the recording process (S5) (a function of the ejection duty of the nozzle 11 relative to the position of the nozzle 11 in the transport direction). S4 corresponds to the "changing process" of the present invention. The ejection duty refers to the ratio of the ejection amount of the nozzle 11 to the required ejection amount of the nozzle 11 based on the image data included in the recording command received in S1. The function before the change is determined based on the image data at any timing after S1 and before S3.

[0024] The ejection process includes a plurality of ejection steps (steps corresponding to movement operations) that are executed at time intervals for a unit area of ​​the paper P. The unit area of ​​the paper P is an area that corresponds to a transport amount (predetermined amount) in the transport process.

[0025] FIG. 4(a) is a graph showing the above function before modification when recording is performed on a unit area of ​​paper P by two movement operations. For example, each nozzle row includes 30 nozzles 11, and the unit area of ​​paper P corresponds to 15 nozzles 11 in the transport direction. Movement operations 1 to 4 are performed sequentially, and a transport process is performed between movement operations to transport paper P a predetermined distance in the transport direction. Within the range of each of movement operations 1 to 4, the horizontal axis indicates the position of the multiple nozzles 11 in the transport direction, and the vertical axis indicates the ejection duty of each nozzle 11. In each of movement operations 1 to 4, the ejection duty of the nozzle 11 located at the upstream end in the transport direction and the nozzle 11 located at the downstream end in the transport direction is 0%. In each of movement operations 1 to 4, the ejection duty of the nozzle 11 located in the center in the transport direction is the maximum value (100%).

[0026] In successive movement operations (for example, movement operations 1 and 2, movement operations 2 and 3, and movement operations 3 and 4 in Figure 4(a)), the ink ejection areas onto the paper P have overlapping portions (the overlapping portions correspond to unit areas). Each of the successive movement operations constitutes an ejection step onto the unit area of ​​the paper P. In Figure 4(a), movement operations 1 and 2 constitute ejection steps E1a and E1b onto the unit area of ​​the paper P. In Figure 4(a), two ejection steps are executed for each unit area.

[0027] In the multiple ejection steps for a unit area of ​​the paper P, ink is selectively ejected from the multiple nozzles 11 based on data obtained by breaking down image data into complementary patterns. In other words, image data that can normally be printed in a single movement operation is divided using a mask, and ejection is performed using a different nozzle 11 in each ejection step (shingling method). Then, in the multiple ejection steps, the ejection duty of each nozzle 11 is configured to be 100% (i.e., the sum of the ejection duty values ​​for each ejection step for each nozzle 11 is 100%). Note that in the multiple ejection steps for a unit area of ​​the paper P, there may be nozzles 11 that are not used for ejection.

[0028] In at least one of the multiple discharge steps corresponding to a unit area of ​​the paper P, the function has an ascending portion H that gradually increases or a descending portion I that gradually decreases from upstream to downstream in the transport direction. In FIG. 4(a), the function for the discharge step E1a has a descending portion I that gradually decreases from upstream to downstream in the transport direction. The function for the discharge step E1b has an ascending portion H that gradually increases from upstream to downstream in the transport direction. The absolute values ​​of the slopes of the descending portion I and the ascending portion H are the same.

[0029] Furthermore, in a plurality of unit areas adjacent to each other in the conveying direction, the function is made up of at least an ascending portion H and a descending portion I. In FIG. 4(a), movement motion 1 corresponds to two unit areas adjacent to each other in the conveying direction, and the function of movement motion 1 is made up of an ascending portion H and a descending portion I. In other words, in two unit areas adjacent to each other in the conveying direction, the function is in the shape of a mountain, with the highest value (100%) at the center of the conveying direction at its peak and descending from 100% to 0% from the peak toward both the upstream and downstream sides of the conveying direction.

[0030] In S4, the control unit 9 determines whether the defective nozzle N is located at the peak A or the base B of the mountain-shaped function. x The function is different depending on which category it belongs to.

[0031] The peak portion A is a certain range including the peak of the function (the center in the conveying direction). For example, the peak portion A is a range from the peak to a distance half the length of the ascending portion H or the descending portion I in the conveying direction, both upstream and downstream in the conveying direction.

[0032] The base portion B is a certain range including the base end of the function (the upstream end or downstream end in the conveying direction). For example, the base portion B on the upstream side in the conveying direction is a range from the base end (the upstream end in the conveying direction) to a distance that is half the length of the ascending portion H in the conveying direction, toward the downstream side in the conveying direction. For example, the base portion B on the downstream side in the conveying direction is a range from the base end (the downstream end in the conveying direction) to a distance that is half the length of the descending portion I in the conveying direction, toward the upstream side in the conveying direction.

[0033] As shown in Figure 4(a), defective nozzle N x belongs to the peak A, the control unit 9 determines in the function that the defective nozzle N x Peaks T are set on the upstream and downstream sides of the transport direction with respect to the nozzle 11 located at the upstream end in the transport direction and the defective nozzle N (see FIG. 4(b)). In other words, the function determined based on the image data (see FIG. 4(a)) is changed to a different function (see FIG. 4(b)). Specifically, the nozzle 11 located at the upstream end in the transport direction and the defective nozzle N are changed to a different function (see FIG. 4(b)). xThe nozzle 11 between the first peak T and the defective nozzle N x The nozzle 11 located between the nozzle 11 located at the downstream end and the nozzle 11 located at the downstream end (the nozzle 11 located at the center in the transport direction with a discharge duty of 100% in the function before the change shown in FIG. 4(a)) is associated with the second peak T. Then, the section from the nozzle 11 located at the upstream end in the transport direction to the first peak T is defined as an ascending section H, and the section from the first peak T to the defective nozzle N is defined as an ascending section H. x The descending section I is up to the defective nozzle N. x The rising section H is from the second peak T to the first predetermined discharge duty, the falling section I is from the second peak T to the first predetermined discharge duty, the rising section H is from the first predetermined discharge duty to 100% discharge duty, and the falling section I is from 100% discharge duty to the nozzle 11 located at the downstream end in the conveying direction. The changed function (see FIG. 4(b)) includes, in the discharge step E1a, the falling section I from the second peak T to the first predetermined discharge duty, the rising section H from the first predetermined discharge duty to 100% discharge duty, and the falling section I from 100% discharge duty to the nozzle 11 located at the downstream end in the conveying direction, and in the discharge step E1b, the rising section H from the nozzle 11 located at the upstream end in the conveying direction to the first peak T, and the falling section I from the first peak T to the defective nozzle N. x Downward section I and defective nozzle N x It includes an ascending portion H from the first peak T to the second peak T. In the discharge steps E1a and E1b for the unit area of ​​the paper P, the discharge duty of each nozzle 11 is configured to be 100% (i.e., for each nozzle 11, the sum of the discharge duty values ​​of the discharge steps E1a and E1b is 100%), and the discharge steps E1a and E1b maintain a complementary relationship. In other words, the sum of the discharge duty at the first peak T and the first predetermined discharge duty is 100%.

[0034] As shown in Figure 5(a), the defective nozzle N x belongs to the base B, the control unit 9 calculates the number of nozzles from the nozzle N0 belonging to the base end (the upstream end in the conveying direction) to the defective nozzle N xThe area from nozzle N0 belonging to the base end (upstream end in the transport direction) to defective nozzle N is flattened (see FIG. 5(b)). In other words, the function determined based on the image data (see FIG. 5(a)) is changed to a different function (see FIG. 5(b)). Specifically, the area from nozzle N0 belonging to the base end (upstream end in the transport direction) to defective nozzle N x The area up to is the flat area F with 0% discharge duty, and the defective nozzle N x The ascending section H is the area from the top of the ascending section H to the nozzle 11 with a 100% discharge duty (the nozzle 11 located in the center in the transport direction with a 100% discharge duty in the function before the change shown in FIG. 5(a)), the area from the top of the ascending section H to the same number of nozzles 11 as the flat section F with a 0% discharge duty is the flat section F with a 100% discharge duty, and the area from the downstream end of the flat section F in the transport direction to the nozzle 11 located at the downstream end in the transport direction in the movement operation is the descending section I. The changed function (see FIG. 5(b)) includes, in the discharge step E1a, the flat section F with a 100% discharge duty and the descending section I from the downstream end in the transport direction of the flat section F to the nozzle 11 located at the downstream end in the transport direction in the movement operation, and in the discharge step E1b, x The flat area F with 0% ejection duty in the area up to and including the defective nozzle N x It includes an ascending portion H from the nozzle 11 with a discharge duty of 100% to the nozzle 11 with a discharge duty of 100%. In the discharge steps E1a and E1b for the unit area of ​​the paper P, the discharge duty of each nozzle 11 is 100% (i.e., for each nozzle 11, the sum of the discharge duty values ​​of the discharge steps E1a and E1b is 100%), and the discharge steps E1a and E1b maintain a complementary relationship.

[0035] As shown in Figure 6(a), two defective nozzles N x ,N x If the nozzle N belongs to the base B, the control unit 9 calculates the number of nozzles in the function from the nozzle N0 belonging to the base end (the upstream end in the conveying direction) to the two defective nozzles N x ,N x The defective nozzle N closest to the peak x' is flattened (see FIG. 6(b)). In other words, the function determined based on the image data (see FIG. 6(a)) is changed to a different function (see FIG. 6(b)). Specifically, the nozzles from the nozzle N0 belonging to the base end (the upstream end in the transport direction) to the two defective nozzles N x ,N x The defective nozzle N closest to the peak x The area up to ' is the flat area F with 0% discharge duty, and the defective nozzle N x The ascending section H is the area from the top of the ascending section H to the nozzle 11 with a discharge duty of 100% (the nozzle 11 located in the center in the conveying direction with a discharge duty of 100% in the function before the change shown in FIG. 6(a)), the area from the top of the ascending section H to the same number of nozzles 11 as the flat section F with a discharge duty of 0% is the flat section F with a discharge duty of 100%, and the area from the downstream end of the flat section F in the conveying direction to the nozzle 11 located at the downstream end in the conveying direction in the movement operation is the descending section I. The changed function (see FIG. 6(b)) includes, in the discharge step E1a, the flat section F with a discharge duty of 100% and the descending section I from the downstream end in the conveying direction of the flat section F to the nozzle 11 located at the downstream end in the conveying direction in the movement operation, and in the discharge step E1b, x The flat area F with 0% ejection duty in the area up to ', and the defective nozzle N x It includes an ascending section H from ' to the nozzle 11 with a discharge duty of 100%. In the discharge steps E1a and E1b for the unit area of ​​the paper P, the discharge duty of each nozzle 11 is 100% (i.e., for each nozzle 11, the sum of the discharge duty values ​​of each discharge step E1a and E1b is 100%), and the discharge steps E1a and E1b maintain a complementary relationship.

[0036] As shown in Figure 7(a), there are two defective nozzles N at the peak A and base B of the function. x ',N x belongs to the peak portion A, the control unit 9 determines in the function that the defective nozzle N x', a peak T is provided on each of the upstream and downstream sides of the conveying direction, and the nozzles N0 belonging to the base end (upstream end in the conveying direction) to the defective nozzles N belonging to the base B are x (See FIG. 7(b)). In other words, the function determined based on the image data (See FIG. 7(a)) is changed to a different function (See FIG. 7(b)). Specifically, the area up to the defective nozzle N in the transport direction is flattened. x and defective nozzle N x The nozzle 11 between the first peak T and the second peak T is associated with the defective nozzle N x The nozzle 11 between the nozzle 11 at the downstream end and the nozzle 11 at the downstream end (the nozzle 11 at the center in the transport direction with a discharge duty of 100% in the function before the change shown in FIG. 7(a)) is associated with the second peak T. Then, the nozzles N0 belonging to the base end (the upstream end in the transport direction) to the defective nozzle N belonging to the base B are x The area up to is the flat area F with 0% discharge duty, and the defective nozzle N x The rising part H is from the first peak T to the defective nozzle N. x ' is the descending part I, and the defective nozzle N x The section from the first peak to the second peak T is defined as the ascending section H, and the area from the top of the ascending section H to the same number of nozzles 11 as the flat section F with a discharge duty of 0% is defined as the flat section F with a discharge duty of 100%, and the section from the downstream end of the flat section F in the conveying direction to the second specified discharge duty is defined as the descending section I, and the section from the second specified discharge duty to the nozzle 11 with a discharge duty of 100% is defined as the ascending section H, and the section from the nozzle 11 with a discharge duty of 100% to the nozzle 11 located at the downstream end in the conveying direction is defined as the descending section I. The changed function (see FIG. 7(b)) includes, in the discharge step E1a, a flat portion F of 100% discharge duty, a descending portion I from the downstream end of the flat portion F in the transport direction to a second predetermined discharge duty, an ascending portion H from the second predetermined discharge duty to the nozzle 11 whose discharge duty is 100%, and a descending portion I from the nozzle 11 whose discharge duty is 100% to the nozzle 11 located at the downstream end in the transport direction, and in the discharge step E1b, a descending portion I from the nozzle N0 belonging to the base end (upstream end in the transport direction) to the defective nozzle N belonging to the base B. xFlat area F with 0% discharge duty, defective nozzle N x The rising part H from the first peak T to the faulty nozzle N x Downward section I up to ' and defective nozzle N x It includes the rising portion H from ' to the second peak T. In the discharge steps E1a and E1b for the unit area of ​​the paper P, the discharge duty of each nozzle 11 is configured to be 100% (i.e., for each nozzle 11, the sum of the discharge duty values ​​of each discharge step E1a and E1b is 100%), and the discharge steps E1a and E1b maintain a complementary relationship. In other words, the sum of the discharge duty at the first peak T and the second specified discharge duty is a discharge duty of 100%.

[0037] FIG. 8(a) is a graph showing the above function before modification when recording is performed on a unit area of ​​paper P using three movement operations. For example, each nozzle row includes 30 nozzles 11, and the unit area of ​​paper P corresponds to 10 nozzles 11 in the transport direction. Movement operations 1 to 6 are performed sequentially, and a transport process is performed between movement operations to transport paper P a predetermined distance in the transport direction. Within the range of each of movement operations 1 to 6, the horizontal axis indicates the position of the multiple nozzles 11 in the transport direction, and the vertical axis indicates the ejection duty of each nozzle 11. In each of movement operations 1 to 6, the ejection duty of the nozzle 11 located at the upstream end in the transport direction and the nozzle 11 located at the downstream end in the transport direction is 0%. In each of movement operations 1 to 6, the ejection duty of the nozzle 11 located in the center in the transport direction is the maximum value (50%).

[0038] In successive movement operations (for example, movement operations 1 to 3, movement operations 2 to 4, movement operations 3 to 5, and movement operations 4 to 6 in FIG. 8(a)), the ink ejection areas onto the paper P have overlapping portions (the overlapping portions correspond to unit areas). Each of the successive movement operations constitutes an ejection step onto the unit area of ​​the paper P. In FIG. 8(a), movement operations 1 to 3 constitute ejection steps E1a, E1b, and E1c onto the unit area of ​​the paper P. In FIG. 8(a), three ejection steps are executed onto each unit area.

[0039] In at least one of the multiple discharge steps corresponding to a unit area of ​​the paper P, the function has an ascending portion H that gradually increases or a descending portion I that gradually decreases from upstream to downstream in the transport direction. In FIG. 8(a), the function for the discharge step E1a has a descending portion I that gradually decreases from upstream to downstream in the transport direction. The function for the discharge step E1b has a flat portion F where the discharge duty is constant (50%). The function for the discharge step E1c has an ascending portion H that gradually increases from upstream to downstream in the transport direction. The absolute values ​​of the slopes of the descending portion I and the ascending portion H are the same.

[0040] Furthermore, in a plurality of unit areas adjacent to each other in the conveying direction, the function is made up of at least an ascending portion H and a descending portion I. In FIG. 8(a), movement motion 1 corresponds to three unit areas adjacent to each other in the conveying direction, and the function of movement motion 1 is made up of an ascending portion H, a flat portion F, and a descending portion I. In other words, in the three unit areas adjacent to each other in the conveying direction, the function is in a mountain shape, with the highest value (50%) at the center of the conveying direction as its peak and descending from 50% to 0% from the peak toward both the upstream and downstream sides of the conveying direction.

[0041] In FIG. 8(a), peak portion A is a certain range including the top of the function (flat portion F), and is a range from the top (flat portion F) to a distance half the length of the ascending portion H or descending portion I in the conveying direction, respectively, upstream and downstream in the conveying direction. In other words, peak portion A occupies two-thirds of the area in the conveying direction of movement operation 1. On the other hand, base portion B occupies one-third of the area in the conveying direction of movement operation 1.

[0042] When recording is performed on a unit area of ​​paper P by three movement operations (see Figures 8 to 11), the function change process is performed in the same way as when recording is performed on a unit area of ​​paper P by three movement operations (see Figures 4 to 7).

[0043] As shown in Figure 8(a), the defective nozzle N xbelongs to the peak A, the control unit 9 determines in the function that the defective nozzle N x Peaks T are set on the upstream and downstream sides of the transport direction with respect to the nozzle 11 located at the upstream end in the transport direction and the defective nozzle N (see FIG. 8(b)). In other words, the function determined based on the image data (see FIG. 8(a)) is changed to a different function (see FIG. 8(b)). Specifically, the nozzle 11 located at the upstream end in the transport direction and the defective nozzle N are changed to a different function (see FIG. 8(b)). x The nozzle 11 between the peaks A and the flat portion F in the conveying direction (the nozzle 11 located at the upstream end of the flat portion F in the convex portion A in the function before the change shown in FIG. 8(a)) is associated with the first peak T, and the nozzle 11 between the peaks A and the flat portion F in the conveying direction is associated with the first peak T. x and the nozzle 11 located at the downstream end (the defective nozzle N among the peaks A in the function before the change shown in FIG. 8(a)). x The nozzles 11 that form the flat portion F and are located downstream in the transport direction from the nozzle 11 with a 50% discharge duty are associated with the second peak T. Then, the section from the nozzle 11 located at the upstream end in the transport direction to the nozzle 11 with a 50% discharge duty is designated as an ascending section H, the section from the nozzle 11 with a 50% discharge duty to the nozzle 11 with a third predetermined discharge duty is designated as a descending section I, the section from the nozzle 11 with the third predetermined discharge duty to the first peak T is designated as an ascending section H, and the section from the first peak T to the defective nozzle N is designated as a descending section I. x The descending section I is up to the defective nozzle N. x The region from the second peak T to the second peak T is defined as an ascending portion H, the region from the second peak T to the nozzle 11 located at the downstream end in the transport direction of the flat portion F of the crest A in the function before the change shown in FIG. 8(a) is defined as a flat portion F with a discharge duty of 50%, the region from the downstream end in the transport direction of the flat portion F to the nozzle 11 with the fourth predetermined duty is defined as a descending portion I, and the region from the fourth predetermined discharge duty to the nozzle 11 located at the downstream end in the transport direction is defined as a descending portion I. The changed function (see FIG. 8(b)) includes, in the discharge step E1a, the flat portion F with a discharge duty of 50%, the descending portion I from the downstream end in the transport direction of the flat portion F to the nozzle 11 with the fourth predetermined duty, and the descending portion I from the fourth predetermined discharge duty to the nozzle 11 located at the downstream end in the transport direction, and the region from the first peak T to the defective nozzle N x Downward section I, defective nozzle Nx The discharge step E1c includes an ascending portion H from the nozzle 11 located at the upstream end in the transport direction to the nozzle 11 with a 50% discharge duty, a descending portion I from the nozzle 11 with a 50% discharge duty to the nozzle 11 with a third predetermined discharge duty, and an ascending portion H from the nozzle 11 with the third predetermined discharge duty to the first peak T. In the discharge steps E1a to E1c for a unit area of ​​the paper P, the discharge duty of each nozzle 11 is 100% (i.e., for each nozzle 11, the sum of the discharge duty values ​​of the discharge steps E1a to E1c is 100%), and the discharge steps E1a to E1c maintain a complementary relationship. In other words, the sum of the third predetermined discharge duty and the fourth predetermined discharge duty is a discharge duty of 50%.

[0044] The reason why the changed function is as shown in Figure 8(b) will be explained below. The changed function has a portion of the peak A where the discharge duty is maintained at 50% at the top of the function (flat portion F), so the discharge duty totals 100% using the rising portion H and falling portion I in Figure 8(a). On the other hand, there is a portion of the peak A where the discharge duty is not maintained at 50% at the top of the function (flat portion F), that is, the defective nozzle N. xTherefore, if the ascending portion H and descending portion I of FIG. 8(a) are used, there will be portions where the ejection duty does not total 100%. Therefore, the modified function has a descending portion I from the nozzle 11 with a 50% ejection duty to the nozzle 11 with a fourth predetermined ejection duty at the peak (flat portion F) of the function in the ejection step E1a, and a descending portion I from the nozzle 11 with a 50% ejection duty to the nozzle 11 with a third predetermined ejection duty that is not 0% at the peak (flat portion F) of the function in the ejection step E1c. The descending portion I from the nozzle 11 with a 50% ejection duty to the nozzle 11 with the fourth predetermined ejection duty at the peak (flat portion F) of the function in the ejection step A and the descending portion I from the nozzle 11 with a 50% ejection duty to the nozzle 11 with a third predetermined ejection duty that is not 0% have different inclination angles from the ascending portion H and descending portion I of FIG. 8(a) so that the ejection duty totals 100%.

[0045] As shown in Figure 9(a), the defective nozzle N x belongs to the base B, the control unit 9 calculates the number of nozzles from the nozzle N0 belonging to the base end (the upstream end in the conveying direction) to the defective nozzle N x The area from nozzle N0 belonging to the base end (upstream end in the transport direction) to defective nozzle N is flattened (see FIG. 9(b)). In other words, the function determined based on the image data (see FIG. 9(a)) is changed to a different function (see FIG. 9(b)). Specifically, the area from nozzle N0 belonging to the base end (upstream end in the transport direction) to defective nozzle N x The area up to is the flat area F with 0% discharge duty, and the defective nozzle N xThe area from the downstream end of the flat portion F in the function before the change shown in FIG. 9(a) to the nozzle 11 with a 50% discharge duty (the nozzle 11 located at the upstream end in the transport direction of the flat portion F in the function before the change shown in FIG. 9(a)) is defined as an ascending portion H, the area of ​​the flat portion F in the function before the change shown in FIG. 9(a) is defined as a flat portion F with a 50% discharge duty, and the area from the downstream end of the flat portion F in the transport direction to the nozzle 11 located at the downstream end in the transport direction of the movement operation is defined as a descending portion I. The changed function (see FIG. 9(b)) includes, in the discharge step E1a, the flat portion F with a 50% discharge duty and the descending portion I from the downstream end in the transport direction of the flat portion F to the nozzle 11 located at the downstream end in the transport direction of the movement operation, includes, in the discharge step E1b, the flat portion F with a 50% discharge duty, and in the discharge step E1c, x The flat area F with 0% discharge duty and the defective nozzle N x It includes an ascending portion H from nozzle 11 at the base end (upstream end in the transport direction) to nozzle 11 at a discharge duty of 50%. In the discharge steps E1a to E1c for the unit area of ​​the paper P, the discharge duty of each nozzle 11 is configured to be 100% (that is, for each nozzle 11, the sum of the discharge duty values ​​of each discharge step E1a and E1b is 100%), and the discharge steps E1a to E1c maintain a complementary relationship. More specifically, the changed function is x The area from nozzle N0 belonging to the base end (upstream end in the transport direction) to defective nozzle N is flat, so that the total ejection duty is 100%. x The discharge step E1a and the discharge step E1b are set so that the discharge duty is 50% in the area corresponding to the area up to the discharge step E1a. Therefore, the discharge step E1a includes the area where the discharge duty is 50% and the descending part I from the top of the function (flat part F) to the nozzle 11 located at the downstream end in the transport direction. Note that the discharge step E1c is set so that the discharge duty is 50% in the area corresponding to the area up to the discharge step E1a. x It includes an ascending portion H from the peak (flat portion F) of the function to the nozzle 11 where the ejection duty is 50%.

[0046] As shown in Figure 10(a), two defective nozzles Nx ,N x If the nozzle N belongs to the base B, the control unit 9 calculates the number of nozzles in the function from the nozzle N0 belonging to the base end (the upstream end in the conveying direction) to the two defective nozzles N x ,N x The defective nozzle N closest to the peak x ' is flattened (see FIG. 10(b)). In other words, the function determined based on the image data (see FIG. 10(a)) is changed to a different function (see FIG. 10(b)). Specifically, the nozzles from the nozzle N0 belonging to the base end (the upstream end in the transport direction) to the two defective nozzles N x ,N x The defective nozzle N closest to the peak x The area up to ' is the flat area F with 0% discharge duty, and the defective nozzle N x The area from peak A to nozzle 11 with a 50% discharge duty (nozzle 11 located at the upstream end in the conveying direction of flat portion F of peak A in the function before the change shown in FIG. 10(a)) is defined as an ascending portion H, the area of ​​flat portion F in the function before the change shown in FIG. 10(a) is defined as flat portion F with a 50% discharge duty, and the area from the downstream end in the conveying direction of flat portion F to nozzle 11 located at the downstream end in the conveying direction of the movement operation is defined as descending portion I. The changed function (see FIG. 10(b)) includes, in the discharge step E1a, the flat portion F with a 50% discharge duty and the descending portion I from the downstream end in the conveying direction of flat portion F to nozzle 11 located at the downstream end in the conveying direction of the movement operation, includes the flat portion F with a 50% discharge duty in the discharge step E1b, and in the discharge step E1c, x ,N x The defective nozzle N closest to the peak x ', the flat area F with 0% discharge duty, and the defective nozzle N xIt includes an ascending portion H from ' to the nozzle 11 with a discharge duty of 50%. In the discharge steps E1a to E1c for the unit area of ​​the paper P, the discharge duty of each nozzle 11 is 100% (that is, for each nozzle 11, the sum of the discharge duty values ​​of each discharge step E1a and E1b is 100%), and the discharge steps E1a to E1c maintain a complementary relationship. More specifically, the changed function is x Since the area from nozzle N0 to defective nozzle N' becomes flat, the ejection duty is adjusted so that the total ejection duty is 100%. x The discharge step E1a and the discharge step E1b are set so that the discharge duty is 50% in the portion corresponding to the flat portion F up to '. Therefore, the discharge step E1a includes a portion where the discharge duty is 50% and a descending portion I from the top of the function (flat portion F) to the nozzle 11 located at the downstream end in the transport direction. Note that the discharge step E1c is set so that the discharge duty is 50% in the portion corresponding to the flat portion F up to '. x 1 includes an ascending portion H from the peak (flat portion F) of the function to the nozzle 11 where the ejection duty is 50%.

[0047] As shown in Figure 11(a), there are two defective nozzles N at the peak A and base B of the function. x ',N x belongs to the peak portion A, the control unit 9 determines in the function that the defective nozzle N x ', a peak T is provided on each of the upstream and downstream sides of the conveying direction, and the nozzles N0 belonging to the base end (upstream end in the conveying direction) to the defective nozzles N belonging to the base B are x (See FIG. 11(b)). In other words, the function determined based on the image data (See FIG. 11(a)) is changed to a different function (See FIG. 11(b)). Specifically, the area up to the defective nozzle N in the transport direction is flattened. x and defective nozzle N x The nozzle 11 between the first peak T and the second peak T is associated with the defective nozzle N xThe nozzle 11 between the nozzle 11 at the downstream end and the nozzle 11 at the downstream end (the nozzle 11 at the upstream end of the flat portion F of the peak portion A in the conveying direction in the function before the change shown in FIG. 11(a)) is associated with the second peak T. Then, the nozzles 11 at the base end (upstream end in the conveying direction) to the defective nozzles N at the base B are associated with the nozzles N at the upstream end of the flat portion F of the peak portion A in the conveying direction. x The area up to is the flat area F with 0% discharge duty, and the defective nozzle N x The rising part H is from the first peak T to the defective nozzle N. x ' is the descending part I, and the defective nozzle N x The section from ' to the second peak T is defined as the ascending section H, the area of ​​the flat section F in the function before the change shown in Figure 11(a) is defined as the flat section F with an ejection duty of 50%, the section from the downstream end of the flat section F in the transport direction to the nozzle 11 with the fifth specified duty is defined as the descending section I, the section from the nozzle 11 with the fifth specified duty to the nozzle 11 with an ejection duty of 50% is defined as the ascending section H, and the section from the nozzle 11 with an ejection duty of 50% to the nozzle 11 located at the downstream end in the transport direction is defined as the descending section I. The changed function (see FIG. 11(b)) includes, in the discharge step E1a, a flat portion F of 50% discharge duty, a descending portion I from the downstream end of the flat portion F in the transport direction to the nozzle 11 of the fifth predetermined duty, an ascending portion H from the nozzle 11 of the fifth predetermined duty to the nozzle 11 of the 50% discharge duty, and a descending portion I from the nozzle 11 of the 50% discharge duty to the nozzle 11 located at the downstream end in the transport direction, and includes, in the discharge step E1b, a flat portion F of 50% discharge duty, and in the discharge step E1c, a descending portion I from the nozzle N0 belonging to the base end (upstream end in the transport direction) to the defective nozzle N0 belonging to the base B. x Flat area F with 0% discharge duty, defective nozzle N x The rising part H from the first peak T to the faulty nozzle N x Downward section I up to ' and defective nozzle N xIt includes an ascending portion H from the peak T to the second peak T. In the discharge steps E1a to E1c for the unit area of ​​the paper P, the discharge duty of each nozzle 11 is 100% (that is, for each nozzle 11, the sum of the discharge duty values ​​of the discharge steps E1a and E1b is 100%), and the discharge steps E1a to E1c maintain a complementary relationship. More specifically, the changed function is x Since the area from nozzle N0 to defective nozzle N' becomes flat, the ejection duty is adjusted so that the total ejection duty is 100%. x The discharge duty of the portion corresponding to the region up to ' is set to 50% in the discharge steps E1a and E1b. Also, since the discharge duty of the changed function is 50% in the discharge step E1b, the descending portion I from the top (flat portion F) of the function to the nozzle 11 with the fifth predetermined duty in the discharge step E1a and the defective nozzle N in the discharge step E1c are x The discharge duty of the changed function is 50% in the discharge step E1b, so the discharge duty of the rising portion H from the nozzle 11 with the fifth predetermined duty to the nozzle 11 with a discharge duty of 50% in the discharge step E1a, and the discharge duty of the rising portion H from the first peak T to the defective nozzle N in the discharge step E1c are 50%. x In addition, since the discharge duty of the changed function is 50% in the discharge step E1b, the discharge duty of the discharge step E1a is 50% in the discharge step E1b, and the discharge duty of the discharge step E1c is 50% in the discharge step E1b. x The sum of the ejection duties from the rising portion H to the top (flat portion F) of the function is set to 50%.

[0048] 3, after S4, or if it is determined that no faulty nozzles have been detected (S3: NO), the control unit 9 executes the recording process (transport process and ejection process) (S5). When S5 is executed after S4, the control unit 9 executes the transport process and the ejection process based on the function changed in S4. When S5 is executed without detecting a faulty nozzle (S3: NO), the control unit 9 executes the transport process and the ejection process based on the function before the change.

[0049] After S5, the control unit 9 ends the routine.

[0050] As described above, according to this embodiment, the control unit 9 determines whether the defective nozzle N x Detecting the defective nozzle N x If it is detected (S3: YES), the function is changed (S4). Figure 12 shows a reference example of the present invention, where (a) is a graph showing the function before change when recording is performed by two movement operations on a unit area of ​​paper P, similar to Figure 4(a), and (b) is a graph showing the function before change when recording is performed by two movement operations on a unit area of ​​paper P, similar to Figure 4(a), and x Another nozzle N corresponding to the position y This is a graph showing the discharge duty of the defective nozzle N. x Another nozzle N corresponding to the position y When the ejection duty of the nozzle N is increased to complement the image, if the transport amount or landing position is shifted, y In this regard, in this embodiment, the defective nozzle N x If a defective nozzle N is detected, x Another nozzle N corresponding to the position y Instead of increasing the ejection duty of the nozzles, the function is changed (see Figures 4 to 11). This allows the nozzles to be identified as defective even if deviations in the transport amount or landing position occur. x This can reduce missing dots caused by this.

[0051] Furthermore, the control unit 9 changes the defective nozzle N xThe function is changed depending on whether the nozzle belongs to the peak A or the base B of the function (see FIGS. 4, 5, 8, and 9). x belongs to the peak A of the function, the nozzles from the base end (upstream end in the conveying direction) to the defective nozzle N x If the area up to the defective nozzle N is made flat, the flat area will become longer, and the effect of providing a slope in suppressing deterioration of image quality will be reduced. x belongs to base B, the defective nozzle N x If peaks T are provided on both the upstream and downstream sides of the transport direction, it becomes necessary to provide peaks T in areas that should be flat, which complicates the process. x By changing the function depending on whether the function belongs to the peak A or the base B, it is possible to prevent the above-mentioned deterioration of image quality and the complexity of processing.

[0052] In the change process (S4), the control unit 9 determines whether the defective nozzle N x belongs to the peak A, the function is x In this case, a slope is provided on both the upstream and downstream sides of the transport direction, sandwiching the peak T, thereby suppressing deterioration of image quality due to the slope.

[0053] In the change process (S4), the control unit 9 determines whether the defective nozzle N x belongs to the base B, in the function, the nozzles N0 to N0 belonging to the base end (upstream end in the conveying direction) x The region up to is flattened (see FIG. 5(b) and FIG. 9(b)). In this case, compared to the case where a peak T is provided, it is possible to suppress the processing from becoming complicated.

[0054] In the change process (S4), the control unit 9 changes the two defective nozzles N x ,N xWhen the nozzle N belongs to the base B, the function is x ,N x The defective nozzle N closest to the peak x ' is flattened (see FIG. 6(b) and FIG. 10(b)). In this case, the defective nozzles N x ,N x Even when ' is present, the processing can be prevented from becoming complicated.

[0055] In the change process (S4), the control unit 9 determines whether the defective nozzles N are located at the peaks A and bases B of the function as shown in FIG. 7(a) and FIG. 11(a). x ',N x belongs to the peak A in the function, x ', a peak T is provided on each of the upstream and downstream sides of the conveying direction, and the nozzles N0 belonging to the base end (upstream end in the conveying direction) to the defective nozzles N belonging to the base B are x The area up to the defective nozzle N is flattened (see FIG. 7(b) and FIG. 11(b)). x ,N x When each of the peaks A and the bases B is included in the image, the deterioration of image quality and the complexity of processing can be suppressed by combining the above methods.

[0056] The ejection process includes a movement operation multiple times in which the head 1 is moved in the movement direction by the movement mechanism 3 while ink is ejected from the nozzles 11 onto the paper P. In such serial type heads, the shingling method is often used, and the effects of the present invention are demonstrated.

[0057] <Modification> Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various design modifications are possible within the scope of the claims.

[0058] For example, the number of ejection steps for a unit area on the recording medium is two in FIGS. 4 to 7 and three in FIGS. 8 to 11, but it may be four or more.

[0059] The rising portion H, the falling portion I, and the flat portion F are linear in FIGS. 4 to 11, but may have some undulations.

[0060] The ejection process may be performed during a "bidirectional" (forward and backward) movement operation, or may be performed during a "unidirectional" (either forward or backward) movement operation.

[0061] In the above-described embodiment, the head is a serial type, but may be a line type. Furthermore, in the above-described embodiment, the liquid ejection device includes one head with nozzles regularly arranged, but is not limited to this. The liquid ejection device may include multiple heads with nozzles regularly arranged. For example, the multiple heads may be arranged in a staggered pattern along an orthogonal direction (the movement direction in FIG. 1) perpendicular to the transport direction, and the nozzles of two heads adjacent in the orthogonal direction may partially overlap in the transport direction. In this configuration, when a defective nozzle is detected, the ejection duty of the nozzles in one of the two heads in an area overlapping with the other may be set to the ejection duty of the ejection step E1a in FIG. 4(b), and the ejection duty of the nozzles in the other of the two heads in an area overlapping with the first may be set to the ejection duty of the ejection step E1b in FIG. 4(b).

[0062] The liquid ejected from the nozzles is not limited to ink, and may be a liquid other than ink (for example, a treatment liquid that aggregates or precipitates components in the ink).

[0063] The recording medium is not limited to paper, but may be, for example, cloth, a resin member, or the like.

[0064] The present invention is not limited to printers, but can also be applied to facsimiles, copiers, multifunction machines, etc. The present invention can also be applied to liquid ejection devices used for purposes other than image recording (for example, liquid ejection devices that eject conductive liquid onto a substrate to form a conductive pattern).

[0065] The program according to the present invention can be distributed by recording it on a removable recording medium such as a flexible disk or a fixed recording medium such as a hard disk, or can be distributed via a communication line. [Explanation of symbols]

[0066] 1 head 11 nozzles 3 Moving mechanism 5. Transport mechanism 9 Control Unit 10 Printer (liquid ejection device) A Yamabe B base E1a, E1b, E1c Discharge steps F flat area H rising part I descending section N x ,N x ' Bad nozzle P Paper (recording medium) T-peak

Claims

1. a head having a plurality of nozzles; a conveying mechanism that conveys the recording medium in a conveying direction; a control unit, the plurality of nozzles are spaced apart from one another in the transport direction; the control unit executes a conveying process for conveying the recording medium in the conveying direction by the conveying mechanism based on image data, and a discharging process for discharging liquid from the plurality of nozzles onto the recording medium; the ejection process includes a plurality of ejection steps that are executed at time intervals for a unit area of ​​a recording medium, and that selectively eject liquid from the plurality of nozzles based on data obtained by decomposing the image data into complementary patterns; in at least one of the plurality of ejection steps corresponding to the unit area, a function of the ejection duty of the nozzle with respect to the position of the nozzle in the transport direction has an ascending portion that gradually increases or a descending portion that gradually decreases from upstream to downstream in the transport direction, In the plurality of unit areas adjacent to each other in the transport direction, the function is made up of at least the ascending portion and the descending portion, Before executing the ejection process, the control unit a detection process for detecting a defective nozzle among the plurality of nozzles; If the defective nozzle is detected in the detection process, a change process is performed to change the function; In the change process, The function is varied depending on whether the defective nozzle belongs to a peak or a base of the function; A liquid ejection device, characterized in that, when the defective nozzle belongs to the peak portion, the function has peaks on both the upstream side and downstream side in the transport direction relative to the defective nozzle.

2. a head having a plurality of nozzles; a conveying mechanism that conveys the recording medium in a conveying direction; a control unit, the plurality of nozzles are spaced apart from one another in the transport direction; the control unit executes a conveying process for conveying the recording medium in the conveying direction by the conveying mechanism based on image data, and a discharging process for discharging liquid from the plurality of nozzles onto the recording medium; the ejection process includes a plurality of ejection steps that are executed at time intervals for a unit area of ​​a recording medium, and that selectively eject liquid from the plurality of nozzles based on data obtained by decomposing the image data into complementary patterns; in at least one of the plurality of ejection steps corresponding to the unit area, a function of the ejection duty of the nozzle with respect to the position of the nozzle in the transport direction has an ascending portion that gradually increases or a descending portion that gradually decreases from upstream to downstream in the transport direction, In the plurality of unit areas adjacent to each other in the transport direction, the function is made up of at least the ascending portion and the descending portion, Before executing the ejection process, the control unit a detection process for detecting a defective nozzle among the plurality of nozzles; If the defective nozzle is detected in the detection process, a change process is performed to change the function; In the change process, The function is varied depending on whether the defective nozzle belongs to a peak or a base of the function; A liquid ejection device characterized in that, when the defective nozzle belongs to the base end, the region from the nozzle belonging to the base end to the defective nozzle is flattened in the function.

3. In the change processing, the control unit 3. The liquid ejection device according to claim 2, wherein, when a plurality of the faulty nozzles belong to the base, the function flattens the area from the nozzle belonging to the base end to the faulty nozzle that is closest to the peak among the plurality of faulty nozzles.

4. a head having a plurality of nozzles; a conveying mechanism that conveys the recording medium in a conveying direction; a control unit, the plurality of nozzles are spaced apart from one another in the transport direction; the control unit executes a conveying process for conveying the recording medium in the conveying direction by the conveying mechanism based on image data, and a discharging process for discharging liquid from the plurality of nozzles onto the recording medium; the ejection process includes a plurality of ejection steps that are executed at time intervals for a unit area of ​​a recording medium, and that selectively eject liquid from the plurality of nozzles based on data obtained by decomposing the image data into complementary patterns; in at least one of the plurality of ejection steps corresponding to the unit area, a function of the ejection duty of the nozzle with respect to the position of the nozzle in the transport direction has an ascending portion that gradually increases or a descending portion that gradually decreases from upstream to downstream in the transport direction, In the plurality of unit areas adjacent to each other in the transport direction, the function is made up of at least the ascending portion and the descending portion, Before executing the ejection process, the control unit a detection process for detecting a defective nozzle among the plurality of nozzles; If the defective nozzle is detected in the detection process, a change process is performed to change the function; In the change process, The function is varied depending on whether the defective nozzle belongs to a peak or a base of the function; A liquid ejection device characterized in that, when the defective nozzle belongs to each of the peak portion and the base portion, the function has peaks on both the upstream and downstream sides of the transport direction for the defective nozzle belonging to the peak portion, and the area from the nozzle belonging to the base end to the defective nozzle belonging to the base portion is flattened.

5. a movement mechanism that moves the head in a movement direction perpendicular to the transport direction, the ejection process includes a moving operation of ejecting liquid from the plurality of nozzles onto a recording medium while moving the head in the movement direction by the movement mechanism a plurality of times; the control unit alternately executes the conveying process, which causes the conveying mechanism to convey the recording medium a predetermined distance in the conveying direction, and the moving operation, based on the image data; 5. The liquid ejection device according to claim 1, wherein the movement operation corresponds to the ejection step.

6. A control method for controlling a liquid ejection device that includes a head having a plurality of nozzles and a transport mechanism that transports a recording medium in a transport direction, the plurality of nozzles being spaced apart from one another in the transport direction, the method comprising: a conveying process for conveying the recording medium in the conveying direction by the conveying mechanism based on image data, and a discharging process for discharging liquid from the plurality of nozzles onto the recording medium; the ejection process includes a plurality of ejection steps that are executed at time intervals for a unit area of ​​a recording medium, and that selectively eject liquid from the plurality of nozzles based on data obtained by decomposing the image data into complementary patterns; in at least one of the plurality of ejection steps corresponding to the unit area, a function of the ejection duty of the nozzle with respect to the position of the nozzle in the transport direction has an ascending portion that gradually increases or a descending portion that gradually decreases from upstream to downstream in the transport direction, In the plurality of unit areas adjacent to each other in the transport direction, the function is made up of at least the ascending portion and the descending portion, Before performing the ejection process, a detection process for detecting a defective nozzle among the plurality of nozzles; If the defective nozzle is detected in the detection process, a change process is performed to change the function; In the change process, The function is varied depending on whether the defective nozzle belongs to a peak or a base of the function; a control method, characterized in that, when the defective nozzle belongs to the peak portion, a peak is set in the function on both the upstream side and the downstream side in the transport direction relative to the defective nozzle.

7. a liquid ejection device including a head having a plurality of nozzles and a transport mechanism that transports a recording medium in a transport direction, the plurality of nozzles being spaced apart from one another in the transport direction; a program that functions as a means for executing a conveying process for conveying a recording medium in the conveying direction by the conveying mechanism based on image data, and a discharging process for discharging liquid from the plurality of nozzles onto the recording medium, the ejection process includes a plurality of ejection steps that are executed at time intervals for a unit area of ​​a recording medium, and that selectively eject liquid from the plurality of nozzles based on data obtained by decomposing the image data into complementary patterns; in at least one of the plurality of ejection steps corresponding to the unit area, a function of the ejection duty of the nozzle with respect to the position of the nozzle in the transport direction has an ascending portion that gradually increases or a descending portion that gradually decreases from upstream to downstream in the transport direction, In the plurality of unit areas adjacent to each other in the transport direction, the function is made up of at least the ascending portion and the descending portion, Before performing the ejection process, a detection process for detecting a defective nozzle among the plurality of nozzles; and when the defective nozzle is detected in the detection process, a modification process for modifying the function; In the change process, The function is varied depending on whether the defective nozzle belongs to a peak or a base of the function; a peak provided in the function on both the upstream side and the downstream side of the transport direction relative to the defective nozzle when the defective nozzle belongs to the peak portion;

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