Ink jet recording device, image formation method and program

Abstract

To provide an ink jet recording device that can an adjustment image in which defects are ease to appear properly, and an image formation method and a program.SOLUTION: An ink jet recording device comprises an ink discharge part, and a control part which discharges ink droplets from a nozzle to a recording medium and forms an image. The control part forms an adjustment image by the ink discharge part under first image formation condition when forming a prescribed adjustment image, forms a normal image by the ink discharge part under second image formation condition different from the first image formation condition when forming a normal image other than the adjustment image, and the first image formation condition is so determined that defects in the image are easier to appear than the second image formation condition.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an inkjet recording apparatus, an image forming method, and a program. [Background technology]

[0002] Conventionally, there is an inkjet recording apparatus that forms an image on a recording medium by ejecting ink droplets from the nozzles of an inkjet head onto the recording medium to form dots. Also, a technique is known for an inkjet recording apparatus that forms a predetermined adjustment image on the recording medium and analyzes defects that appear in the adjustment image to detect nozzles with ejection defects, misalignment of the recording head, etc. (For example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-138009 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when an adjustment image is formed under the same image forming conditions as when a normal image is formed, depending on the image pattern contained in the formation image, even if the dot position is shifted from the appropriate position, it may not appear as a defect in the adjustment image.

[0005] An object of the present invention is to provide an inkjet recording apparatus, an image forming method, and a program that can appropriately form an adjustment image in which defects are likely to appear. [Means for solving the problem]

[0006] In order to achieve the above object, the inkjet recording apparatus according to claim 1 comprises: an ink ejection unit; a control unit that ejects ink droplets from the nozzles of the ink ejection unit onto a recording medium to form an image; Equipped with The control unit When forming a predetermined adjustment image, the adjustment image is formed by the ink ejection unit under a first image forming condition; When forming a normal image other than the adjustment image, the normal image is formed by the ink ejection unit under second image forming conditions different from the first image forming conditions, The first image forming conditions are determined so that defects are more likely to appear in the image than the second image forming conditions.

[0007] The invention described in claim 2 is the inkjet recording apparatus described in claim 1, The adjustment image includes an image pattern for detecting deviations in the landing positions of the droplets on the recording medium.

[0008] The invention described in claim 3 is the inkjet recording apparatus described in claim 1, the ink ejection unit includes an inkjet head having a plurality of the nozzles, The adjustment image includes an image pattern for detecting the inclination of the inkjet head from a predetermined arrangement direction.

[0009] The invention described in claim 4 is the inkjet recording apparatus described in claim 1, the ink ejection unit includes a plurality of inkjet heads each having a plurality of the nozzles, the plurality of inkjet heads are arranged in a positional relationship having an overlapping region in which the nozzle arrangement ranges in a predetermined direction partially overlap each other, The adjustment image includes an image pattern for detecting density unevenness in a portion of the adjustment image formed by the nozzles that belong to the overlapping region.

[0010] The invention described in claim 5 is the inkjet recording apparatus described in claim 1, The first image forming condition is a condition under which the dot diameter of the ink droplets ejected from the nozzles and landed on the recording medium is smaller than that under the second image forming condition.

[0011] The invention described in claim 6 is the inkjet recording apparatus described in claim 5, an ink heating unit that heats the ink in the ink ejection unit; The control unit controls the ink heating unit so that the temperature of the ink when the adjustment image is formed under the first image forming conditions is lower than the temperature of the ink when the normal image is formed under the second image forming conditions.

[0012] The invention described in claim 7 is the inkjet recording apparatus described in claim 5, the ink ejection unit includes an image forming element that ejects ink droplets from the nozzles in an amount corresponding to the magnitude of a voltage of an input drive signal; The control unit controls the ink ejection unit so that the voltage of the drive signal input to the image forming element when forming the adjustment image under the first image forming conditions is smaller than the voltage of the drive signal input to the image forming element when forming the normal image under the second image forming conditions.

[0013] The invention described in claim 8 is the inkjet recording apparatus described in claim 5, a medium heating unit that heats the recording medium; The control unit controls the medium heating unit so that the temperature of the recording medium when the adjustment image is formed under the first image forming conditions is lower than the temperature of the recording medium when the normal image is formed under the second image forming conditions.

[0014] The invention described in claim 9 is the inkjet recording apparatus described in claim 5, The ink ejection unit ejects droplets of the ink, which changes phase between a sol state and a gel state depending on temperature, from the nozzle.

[0015] In order to achieve the above object, the invention of an image forming method described in claim 10 comprises: An image forming method for forming an image by ejecting ink droplets onto a recording medium from nozzles of an ink ejection unit of an inkjet recording device, comprising: When forming a predetermined adjustment image, the adjustment image is formed by the ink ejection unit under a first image forming condition; When forming a normal image other than the adjustment image, the normal image is formed by the ink ejection unit under second image forming conditions different from the first image forming conditions, The first image forming conditions are determined so that defects are more likely to appear in the image than the second image forming conditions.

[0016] In order to achieve the above object, the invention of the program described in claim 11 is as follows: A computer of an inkjet recording device equipped with an ink ejection unit, the ink ejection unit functions as a control unit for ejecting ink droplets from the nozzles of the ink ejection unit onto a recording medium to form an image; The control means When forming a predetermined adjustment image, the adjustment image is formed by the ink ejection unit under a first image forming condition; When forming a normal image other than the adjustment image, the normal image is formed by the ink ejection unit under second image forming conditions different from the first image forming conditions, The first image forming conditions are determined so that defects are more likely to appear in the image than the second image forming conditions. [Effects of the Invention]

[0017] According to the present invention, it is possible to form an adjustment image that makes defects appear appropriately. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a diagram illustrating a schematic configuration of an inkjet recording apparatus. [Figure 2] FIG. 2 is a schematic diagram illustrating the configuration of a head unit. [Figure 3] FIG. 2 is a block diagram showing the main functional configuration of the inkjet printing apparatus. [Figure 4] FIG. 10 is a diagram showing an example of a conventional adjustment image. [Figure 5] 10A and 10B are diagrams illustrating examples of adjustment images according to the present embodiment using first image forming conditions. [Figure 6] FIG. 3 is a diagram showing the contents of a first image forming condition and a second image forming condition. [Figure 7A] FIG. 10 is a diagram showing another example of an image pattern. [Figure 7B] FIG. 10 is a diagram showing another example of an image pattern. [Figure 7C] FIG. 10 is a diagram showing another example of an image pattern. [Figure 8] 10 is a flowchart showing a control procedure for adjustment processing. DETAILED DESCRIPTION OF THE INVENTION

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an image forming apparatus and an image forming method according to the present invention will be described below with reference to the accompanying drawings.

[0020] FIG. 1 is a diagram showing a schematic configuration of an inkjet recording apparatus 1 according to an embodiment of the present invention. The inkjet recording apparatus 1 includes a paper feed unit 10, an image forming unit 20, a paper discharge unit 30, and a control unit 40 (see FIG. 3) (control means, computer). Under the control of the control unit 40, the inkjet recording apparatus 1 transports a recording medium M stored in the paper feed unit 10 to the image forming unit 20, forms an image on the recording medium M in the image forming unit 20, and transports the recording medium M with the image formed thereon to the paper discharge unit 30. The recording medium M may be paper such as plain paper or coated paper, or various media such as fabric or sheet-like resin, on whose surface the ink can be fixed.

[0021] The paper feed unit 10 has a paper feed tray 11 that stores the recording medium M, and a medium supply unit 12 that transports and supplies the recording medium M from the paper feed tray 11 to the image forming unit 20. The medium supply unit 12 has a ring-shaped belt supported on the inside by two rollers, and transports the recording medium M from the paper feed tray 11 to the image forming unit 20 by rotating the rollers with the recording medium M placed on this belt.

[0022] The image forming section 20 includes a transport section 21, a delivery unit 22, a medium heating section 23, a head unit 24 (ink ejection section), a fixing section 25, an imaging section 26, a delivery section 27, and the like.

[0023] The conveying section 21 holds the recording medium M placed on the conveying surface (loading surface) of the cylindrical conveying drum 211, and performs a conveying operation to convey the recording medium M in the direction of the circular movement of the conveying drum 211 (hereinafter referred to as the conveying direction) by the conveying drum 211 rotating and moving in a circular motion around a rotation axis (cylindrical axis) extending in the width direction perpendicular to the drawing in Figure 1.

[0024] The transport drum 211 has claws and an air intake section (not shown) for holding the recording medium M on its transport surface. The recording medium M is held on the transport surface by having its edges pressed down by the claws and being drawn to the transport surface by the air intake section. The transport section 21 is connected to a transport drum motor (not shown) for rotating the transport drum 211. The transport drum 211 rotates by an angle proportional to the amount of rotation of the transport drum motor.

[0025] The transfer unit 22 transfers the recording medium M transported by the medium supply unit 12 of the paper feed unit 10 to the transport unit 21. The transfer unit 22 is provided at a position between the medium supply unit 12 of the paper feed unit 10 and the transport unit 21, and holds and picks up one end of the recording medium M transported from the medium supply unit 12 with a swing arm unit 221, and transfers it to the transport unit 21 via a transfer drum 222.

[0026] The medium heating unit 23 is provided between the position where the delivery drum 222 is disposed and the position where the head unit 24 is disposed, and heats the recording medium M conveyed by the conveyance unit 21 so that the temperature of the recording medium M falls within a predetermined temperature range. The medium heating unit 23 has, for example, an infrared heater or the like, and energizes the infrared heater based on a control signal supplied from the control unit 40 to cause the infrared heater to generate heat.

[0027] The head unit 24 forms an image by ejecting ink onto the recording medium M from nozzles N (see FIG. 2) provided on a nozzle surface (ink ejection surface) facing the transport surface of the transport drum 211 at appropriate timing according to the rotation of the transport drum 211 on which the recording medium M is held. The head unit 24 is arranged so that the nozzle surface and the transport surface are separated by a predetermined distance. In this embodiment, four head units 24 corresponding respectively to four ink colors, yellow (Y), magenta (M), cyan (C), and black (K), are arranged at predetermined intervals from the upstream side in the transport direction of the recording medium M in the order of Y, M, C, and K.

[0028] FIG. 2 is a schematic diagram showing the configuration of the head unit 24. The nozzle surface of the head unit 24 facing the transport surface of the transport drum 211 is shown here. The head unit 24 includes eight inkjet heads 242 attached to a mounting member 244. However, the number of inkjet heads 242 included in the head unit 24 is not limited to eight, and may be seven or fewer, or nine or more. Each inkjet head 242 includes a plurality of nozzles N and a plurality of image-forming elements 2421 (see FIG. 3) provided corresponding to the plurality of nozzles N. The image-forming elements 2421 include a pressure chamber communicating with the nozzle N and storing ink, a piezoelectric element provided on the wall of the pressure chamber and deforming in response to an applied drive signal, and an electrode for applying a voltage to the piezoelectric element. When a drive signal is input to the electrode of the image-forming element 2421, the pressure chamber is deformed due to the deformation of the piezoelectric element, changing the pressure within the pressure chamber, and ink droplets are ejected from the nozzle N communicating with the pressure chamber. The image forming element 2421 ejects ink droplets from the nozzle N with a volume corresponding to the magnitude of the voltage of the input drive signal, in other words, the magnitude of the voltage amplitude of the drive signal. In this embodiment, the image forming element 2421 ejects ink droplets with a volume m1 from the nozzle N in response to a drive signal of voltage V1, and ejects ink droplets with a volume m2 greater than the volume m1 from the nozzle N in response to a drive signal of voltage V2, which is greater than the voltage V1. The image forming element 2421 can also eject large droplets and small droplets with a smaller volume than the large droplets in response to the waveform of the drive signal. The volume of ink in large droplets ejected in response to a large droplet drive signal of voltage V2 is greater than the volume of ink in large droplets ejected in response to a large droplet drive signal of voltage V1. The volume of ink in small droplets ejected in response to a small droplet drive signal of voltage V2 is greater than the volume of ink in small droplets ejected in response to a small droplet drive signal of voltage V1. The image forming element 2421 may be capable of ejecting medium-sized droplets in an amount intermediate between the large droplets and the small droplets.

[0029] The inkjet head 242 is formed with two nozzle rows each consisting of nozzles N arranged at equal intervals in the width direction. These two nozzle rows are arranged so that the arrangement positions of the nozzles N are shifted from each other in the width direction by half the arrangement interval of the nozzles N in each nozzle row. The arrangement direction of the nozzle rows may be inclined with respect to the width direction. Furthermore, the number of nozzle rows arranged in one inkjet head 242 is not limited to two rows, and may be one row or three or more rows.

[0030] The eight inkjet heads 242 are arranged so that the arrangement ranges of the nozzle rows are continuous in the width direction. More specifically, the eight inkjet heads 242 are arranged in a staggered positional relationship with an overlapping region R where the arrangement ranges of the nozzles N in the width direction (predetermined direction) partially overlap. The arrangement range in the width direction of the nozzles N included in the head unit 24 covers the width of the area in the width direction where an image is formed on the recording medium M transported by the transport unit 21. The head unit 24 is used in a state where its position is fixed with respect to the rotation axis of the transport drum 211 during image formation. In other words, the head unit 24 has a line head that can eject ink across the image formable width in the width direction of the recording medium M. Therefore, the inkjet recording device 1 forms images in a single pass format.

[0031] The ink used in this embodiment contains a gelling agent in addition to a coloring material such as a pigment, and changes phase between a sol state and a gel state depending on the temperature. This ink is in a gel state at room temperature and becomes a sol state when heated above its phase transition temperature. The ink used in this embodiment also has the property of hardening when irradiated with energy rays such as ultraviolet light. The head unit 24 includes an ink heating unit 243 (see FIG. 3) that heats the ink stored in the head unit 24. The ink heating unit 243 operates under the control of the control unit 40 and heats the ink to a temperature at which the ink becomes a sol. The inkjet head 242 ejects the heated, sol-state ink. When this sol-state ink is ejected onto the recording medium M, the ink droplets land on the recording medium M, and then rapidly become a gel state due to natural cooling, and solidify on the recording medium M.

[0032] The fixing unit 25 has a light-emitting unit arranged across the width of the conveying unit 21 in the width direction, and irradiates the recording medium M placed on the conveying unit 21 with energy rays such as ultraviolet rays from the light-emitting unit to harden and fix the ink (gel ink) ejected onto the recording medium M. The light-emitting unit of the fixing unit 25 is arranged opposite the conveying surface between the position where the head unit 24 is arranged and the position where the delivery drum 271 of the delivery unit 27 is arranged in the conveying direction.

[0033] The imaging unit 26 is disposed at a position in the conveyance direction between the position where the ink is fixed by the fixing unit 25 and the position where the transfer drum 271 is disposed. The imaging unit 26 has, for example, a line sensor provided across the width of the conveyance drum 211 in the width direction. The imaging unit 26 reads the surface of the recording medium M on the conveyance surface to generate imaging data, and outputs the imaging data to the control unit 40.

[0034] The delivery unit 27 includes a cylindrical delivery drum 271 and a belt loop 272. The delivery drum 271 delivers the recording medium M from the conveyance unit 21 to the belt loop 272. The belt loop 272 has a circular belt supported by two rollers on the inside. The delivery unit 27 transports the recording medium M delivered from the conveyance unit 21 onto the belt loop 272 by the delivery drum 271, using the belt loop 272, and sends it to the paper discharge unit 30.

[0035] The paper discharge unit 30 has a plate-shaped paper discharge tray 31 on which the recording medium M sent out from the image forming unit 20 by the delivery unit 27 is placed.

[0036] 3 is a block diagram showing the main functional configuration of the inkjet recording apparatus 1. The inkjet recording apparatus 1 includes a medium heating section 23, a head control section 241, a head unit 24 having an inkjet head 242 and an ink heating section 243, a fixing section 25, an imaging section 26, a control section 40, a transport drive section 51, an operation display section 52, and a communication section 53. The various sections of the inkjet recording apparatus 1 are connected via a signal transmission path such as a bus. In the following, a description of the configuration already described in FIG. 1 will be omitted.

[0037] The head control unit 241 outputs various control signals and image data to a head drive unit (not shown) in the inkjet head 242 at a timing corresponding to the control signal input from the control unit 40, thereby causing the head drive unit to supply a drive signal to the image forming element 2421 to deform the piezoelectric element, thereby causing ink droplets to be ejected from the nozzle N.

[0038] The control unit 40 is a hardware processor having a CPU 41 (Central Processing Unit), RAM 42 (Random Access Memory), and a storage unit 43. The CPU 41 reads out a program 431 and setting data stored in the storage unit 43, stores them in the RAM 42, and executes the program 431 to perform various arithmetic processing. In this way, the CPU 41 comprehensively controls the overall operation of the inkjet recording apparatus 1. The RAM 42 provides a working memory space for the CPU 41 and stores temporary data.

[0039] The storage unit 43 stores the program 431 executed by the CPU 41, setting data, etc. For example, a hard disk drive (HDD), flash memory, or read-only memory (ROM) is used as the storage unit 43. The storage unit 43 stores print jobs (image recording commands) input from external devices via the communication unit 53, image data related to the print jobs, image data for adjustment images (described later), and image data generated by the imaging unit 26, etc.

[0040] The transport drive unit 51 supplies a drive signal to the transport drum motor of the transport drum 211 based on a control signal supplied from the control unit 40, thereby rotating the transport drum 211 at a predetermined speed and timing. In addition, the transport drive unit 51 operates the medium supply unit 12, the delivery unit 22, and the delivery unit 27 based on a control signal supplied from the control unit 40, and causes the recording medium M to be supplied to the transport unit 21 and discharged from the transport unit 21.

[0041] The operation display unit 52 includes a display device such as a liquid crystal display or an organic EL display, and an input device such as operation keys and a touch panel overlaid on the screen of the display device. The operation display unit 52 displays various information on the display device, and converts user input operations on the input device into operation signals and outputs them to the control unit 40.

[0042] The communication unit 53 is a communication interface that controls communication operations with external devices. The communication unit 53 acquires data related to print jobs from external devices under the control of the control unit 40, and also transmits status information and the like to the external devices.

[0043] Next, a method for adjusting the landing position of ink from the nozzles N in the inkjet recording apparatus 1 will be described. When forming an image using the head unit 24, if ink droplets ejected from each nozzle N land at a position that is different from the desired position, defects will occur in the image. Defects include "streaks," in which unintended lines are visible in the transport direction, and "unevenness," in which an unintended density distribution occurs in the image. These are examples, and defects are not limited to these. Misalignment of the landing position of ink droplets can occur when there is an abnormality in the ink ejection operation from the nozzles N by the image forming elements 2421, or when the inkjet heads 242 are not properly attached to the head unit 24. Abnormal ejection operation can be caused, for example, by foreign matter adhering to the nozzles N or malfunctioning of the image forming elements 2421. Furthermore, the attachment state of the head unit 24 can be affected by factors such as the attachment position, the tilt from a predetermined arrangement direction, and the spacing between adjacent inkjet heads 242 in the width direction or transport direction.

[0044] To detect misalignment of ink droplets and adjust the inkjet recording apparatus 1 to prevent image defects, the inkjet recording apparatus 1 forms a predetermined adjustment image 70 on the recording medium M before forming a normal image. The adjustment image 70 is also called a test image or test chart. FIG. 4 shows an example of a conventional adjustment image 70. This adjustment image 70 is a monochromatic image formed by ejecting ink from one of the head units 24. The adjustment image 70 includes an image pattern P for detecting misalignment of ink droplets. The image pattern P includes dot rows L1 and L2 each consisting of a plurality of dots D arranged one-dimensionally in the width direction. Each dot D is formed by a large droplet ejected from one nozzle N landing on the recording medium M. The dot row L1 is formed by a nozzle N belonging to one of the nozzle rows of the inkjet head 242. The dot row L2 is formed by a nozzle N belonging to the other nozzle row of the inkjet head 242. The dot rows L1 and L2 are alternately formed in the transport direction. In the image pattern P of FIG. 4, when each dot D is formed at an appropriate position, the arrangement pitch of the dots D in the width direction is constant, and the arrangement pitch of the dot rows L1 and L2 in the transport direction is constant.

[0045] In the example shown in Fig. 4, the adjustment image 70 is formed under the same image forming conditions (hereinafter referred to as "second image forming conditions") as the image forming conditions when forming a normal image other than the adjustment image 70. In the example shown in Fig. 4, when the adjustment image 70 is formed under the second image forming conditions, if each dot D is formed in an appropriate position in the image pattern P, adjacent dots D will partially overlap each other, resulting in a state in which the surface of the recording medium M is covered with ink with almost no gaps.

[0046] In the example shown in FIG. 4, a landing position shift has occurred in one dot De belonging to dot row L2. Specifically, the landing position of dot De has shifted in the negative width direction from the correct landing position. However, when the adjustment image 70 is formed under the second image formation conditions, even if the landing position of dot De is shifted, there is almost no gap between dots D that would make the position shift visible. Therefore, the landing position shift of dot De is unlikely to appear as a defect in the adjustment image 70.

[0047] Therefore, in the inkjet recording apparatus 1 of this embodiment, the control unit 40 causes the head unit 24 to form the adjustment image 70 under first image forming conditions that are different from the second image forming conditions. The first image forming conditions are determined so that defects in the adjustment image 70 are more likely to appear than under the second image forming conditions. More specifically, the first image forming conditions are conditions under which the dot diameter (diameter) of ink droplets ejected from the nozzles N using a common drive signal and landed on the recording medium M is smaller than under the second image forming conditions. Here, the common drive signal is a signal that has a common drive waveform except for the voltage magnitude. Note that the common drive signal may also be a signal that has the same drive waveform, including the voltage magnitude.

[0048] FIG. 5 is a diagram showing an example of an adjustment image 70 of this embodiment using the first image forming conditions. In this adjustment image 70, each dot D is formed by a large droplet ejected from one nozzle N landing on the recording medium M. However, under the first image forming conditions, the amount of liquid ejected from each nozzle N is smaller than under the second image forming conditions, or the droplets that land are less likely to wet and spread on the surface of the recording medium M than under the second image forming conditions. As a result, in the adjustment image 70 of FIG. 5, the dot diameter d1 of the dots D is smaller than the dot diameter d2 in FIG. 4. Therefore, even when each dot D is formed in the correct position, a gap will be formed between adjacent dots D.

[0049] In Figure 5, the landing position of the dot De corresponding to Figure 4 is also shifted in the negative direction in the width direction. This landing position shift creates a large gap G to the left of the dot De, and an overlapping portion O with the adjacent dot D on the right. The presence of this gap G and overlapping portion O makes it easy to detect the landing position shift. In other words, defects caused by the landing position shift are more likely to appear.

[0050] The adjustment image 70 is captured by the imaging unit 26. The control unit 40 performs predetermined image processing on the captured data of the adjustment image 70 to detect defects caused by misalignment of ink droplets. The content of the image processing is determined appropriately depending on the content of the adjustment image 70 and the defect to be detected. For example, the image processing includes processing to detect the positions of dots, the spacing between dots, and density distribution in the adjustment image 70 based on pixel values ​​of the captured data of the adjustment image 70, and processing to identify the presence or absence of defects and their locations based on these detection results. The control unit 40 identifies defective nozzles that have misaligned ink droplets based on the locations of the defects. The control unit 40 performs predetermined adjustment processing to eliminate the misalignment of ink droplets, i.e., to eliminate the image defects. For example, the control unit 40 compensates for defective ink droplet ejection caused by defective nozzles. Specifically, the control unit 40 sets the defective nozzles so that ink droplets are not ejected, and adjusts the amount and timing of ink ejection from surrounding normal nozzles so that the amount of ink not ejected from the defective nozzles is compensated for by ink ejection from surrounding normal nozzles. For example, the failure of a large droplet from a faulty nozzle may be compensated for by a number of small droplets from surrounding normal nozzles.

[0051] FIG. 6 is a diagram showing the contents of the first image forming conditions and the second image forming conditions. Here, conditions a to g are shown as examples of the first image forming conditions. In the second image forming conditions, the temperature of the ink when ejected from the nozzle N (hereinafter referred to as "ink temperature") is set to T2, the voltage of the drive signal (hereinafter referred to as "drive voltage") is set to V2, and the temperature of the recording medium M when the ink lands (hereinafter referred to as "medium temperature") is set to t2. In FIG. 6, the parts of the first image forming conditions that differ from the second image forming conditions are shown in color.

[0052] Under condition a of the first image formation conditions, the ink temperature is set to T1, which is lower than T2, and the drive voltage and medium temperature are set to the same as those of the second image formation conditions. By reducing the ink temperature in this manner, the viscosity of the ink increases, reducing the amount of ink droplets ejected from the nozzle N using the same drive signal. This reduces the dot diameter. The control unit 40 adjusts the ink temperature. To adjust the ink temperature, the control unit 40 changes the amount of electricity applied to the ink heating unit 243 to adjust the heating temperature of the ink stored in the head unit 24. The ink temperature is adjusted within a range in which the ink is maintained in a sol state. For example, a first operation setting of the ink heating unit 243, which sets the ink temperature in the head unit 24 to T1, and a second operation setting of the ink heating unit 243, which sets the ink temperature to T2, may be predetermined. In this case, the control unit 40 selects the operation setting of the ink heating unit 243 from the first operation setting and the second operation setting according to the image formation conditions, and operates the ink heating unit 243 using the selected operation setting.

[0053] Under the first image formation conditions, the drive voltage is set to V1, which is lower than V2, and the ink temperature and medium temperature are set to the same as those under the second image formation conditions. By reducing the drive voltage in this way, the amount of deformation of the piezoelectric element decreases, which weakens the pressure pushing ink out of the nozzle N and reduces the amount of ink ejected from the nozzle N. This allows the dot diameter to be reduced. The drive voltage is adjusted by the control unit 40. To adjust the drive voltage, the control unit 40 sends a control signal to the head control unit instructing it to change the drive voltage.

[0054] Under condition c of the first image formation conditions, the medium temperature is set to t1, which is lower than t2, and the ink temperature and drive voltage are set to the same as those of the second image formation conditions. By lowering the medium temperature in this manner, ink droplets that land on the recording medium M are less likely to wet and spread. This allows for smaller dot diameters. The control unit 40 adjusts the medium temperature. To adjust the medium temperature, the control unit 40 changes the amount of current supplied to the medium heating unit 23 to adjust the heating temperature of the recording medium M. For example, a first operation setting of the medium heating unit 23, which brings the temperature of the recording medium M to t1, and a second operation setting of the medium heating unit 23, which brings the temperature of the recording medium M to t2, may be determined in advance. In this case, the control unit 40 selects the operation setting of the medium heating unit 23 from the first operation setting and the second operation setting according to the image formation conditions, and operates the medium heating unit 23 using the selected operation setting.

[0055] The first image formation conditions may be obtained by changing two of the ink temperature, driving voltage, and medium temperature from the second image formation conditions. For example, condition d is obtained by changing the ink temperature from T2 to T1 and the driving voltage from V2 to V1. Condition e is obtained by changing the driving voltage from V2 to V1 and the medium temperature from t2 to t1. Condition f is obtained by changing the ink temperature from T2 to T1 and the medium temperature from t2 to t1. By changing two of the ink temperature, driving voltage, and medium temperature from the second image formation conditions in a direction that reduces the dot diameter, as in conditions d, e, and f, it is possible to achieve an even smaller dot diameter than conditions a, b, and c.

[0056] The first image forming conditions may be conditions in which all of the ink temperature, driving voltage, and medium temperature are changed from the second image forming conditions. That is, as in condition g, the ink temperature may be changed from T2 to T1, the driving voltage may be changed from V2 to V1, and the medium temperature may be changed from t2 to t1. Condition g allows for an even smaller dot diameter than conditions d, e, and f.

[0057] The image pattern P in the adjustment image 70 is not limited to that shown in FIG. 5. FIGS. 7A to 7C are diagrams showing other examples of the image pattern P. The image pattern P shown in FIG. 7A is made up of multiple line segments extending in the transport direction. One line segment is formed by ink ejected from one nozzle N. The image pattern P in FIG. 7A can be used to detect faulty nozzles (missing nozzles) that do not eject ink, abnormalities in the amount of ink ejected, and deviations in the ink landing position in the width direction. By reducing the dot diameter using the first image formation condition, the position of the line segments can be detected with higher accuracy.

[0058] The image pattern P shown in FIG. 7B consists of multiple line segments extending in the width direction. Each line segment is formed by ink ejected simultaneously from nozzles N belonging to one nozzle row. The tilt of the line segments in the image pattern P in FIG. 7B from the width direction can be used to detect an abnormality in the mounting angle of the inkjet head 242, i.e., tilt of the inkjet head 242 from a predetermined orientation. Here, the tilt of the inkjet head 242 can also be expressed as the angle of the inkjet head 242 in the rotation direction about an axis perpendicular to the conveyance surface. When tilt of the inkjet head 242 is detected, the control unit 40 displays on the operation / display unit 52 the inkjet head 242 for which tilt has been detected and the amount of tilt. Based on this display, the user can adjust the mounting angle of the inkjet head 242. Alternatively, the head unit 24 may be provided with a position adjustment mechanism for adjusting the mounting position and angle of the inkjet head 242, and the position adjustment mechanism may change the position or angle of the inkjet head 242 under control of the control unit 40. By reducing the dot diameter using the first image formation condition, the position and tilt of the line segments can be detected with higher accuracy.

[0059] Furthermore, according to the image pattern P in FIG. 7B, it is possible to detect a deviation in the landing position in the transport direction from the jaggedness of the line segments. The deviation in the landing position in the transport direction occurs when there is an abnormality in the flight speed of the ejected ink. In this case, the control unit 40, for example, adjusts the setting of the ink ejection timing from the nozzle N where the deviation in the landing position occurs, or performs compensation for the defective nozzle as described above. By reducing the dot diameter using the first image formation condition, it is possible to detect the jaggedness of the line segments, i.e., the deviation in the landing position, with higher accuracy.

[0060] The image pattern P shown in FIG. 7C includes a halftone solid pattern. This image pattern P allows for the detection of density unevenness in the portion formed by the nozzles N belonging to the overlap region R of the inkjet heads 242. Normally, the seam between two adjacent inkjet heads 242 in the width direction is invisible due to complementary ink ejection in the overlap region R. However, if the inkjet heads 242 are misaligned in the width direction or if the ejection / non-ejection settings of the nozzles N in the overlap region R for complementary ink ejection are inappropriate, density unevenness occurs in the halftone solid pattern. The density unevenness may be a density higher than the normal region or a density lower than the normal region (whiteout). If density unevenness is detected in the image pattern P, the control unit 40 displays on the operation display unit 52 the inkjet heads 242 that require seam correction, the required adjustment direction, and the amount of adjustment. Based on this display, the user can adjust the seam between the inkjet heads 242 to a proper state. The control unit 40 may operate the position adjustment mechanism to change the position of the inkjet head 242 and perform seam correction. Also, by reducing the dot diameter using the first image forming condition, density unevenness can be detected with higher accuracy.

[0061] Next, the adjustment process executed by the control unit 40 to cause the inkjet recording apparatus 1 to perform the above operations will be described.

[0062] 8 is a flowchart showing the control procedure for the adjustment process. This adjustment process is executed, for example, when the inkjet recording apparatus 1 is started or at a predetermined timing for maintenance. When the adjustment process is started, the control unit 40 sets the operating conditions of the inkjet recording apparatus 1 to the first image formation conditions, i.e., any of the conditions a to g in FIG. 6 (step S1). Which of the conditions a to g is to be used is set in advance based on a user operation or the like. In step S1, the control unit 40 adjusts the operations by sending control signals to the ink heating unit 243, the head control unit 241, and the medium heating unit 23 so that the ink temperature, driving voltage, and medium temperature each match the first image formation conditions.

[0063] The control unit 40 forms the adjustment image 70 on the recording medium M (step S2). Here, the control unit 40 causes the head control unit 241 to supply image data of the adjustment image 70 stored in the storage unit 43 to the inkjet head 242 at appropriate timing according to the rotation of the conveyance drum 211. As a result, the control unit 40 causes ink to be ejected from the nozzles N of the head unit 24 onto the recording medium M, forming the adjustment image 70 on the recording medium M. The control unit 40 also causes the fixing unit 25 to irradiate ultraviolet light onto the recording medium M to which the ink has been applied, thereby fixing the ink to the recording medium M.

[0064] The control unit 40 causes the imaging unit 26 to capture an image of the adjustment image 70 on the recording medium M (step S3). Here, the control unit 40 causes the line sensor of the imaging unit 26 to repeatedly capture images of the adjustment image 70 on the recording medium M at appropriate timing according to the rotation of the conveying drum 211, acquires imaging data of the adjustment image 70 consisting of multiple line imaging data, and stores it in the memory unit 43.

[0065] The control unit 40 performs predetermined image processing on the captured data of the adjustment image 70 and determines whether the adjustment image 70 has a defect (step S4). The type of defect to be detected from the adjustment image 70 is predetermined depending on the image pattern P included in the adjustment image 70. If it is determined that the adjustment image 70 has a defect ("YES" in step S4), the control unit 40 performs predetermined adjustment processing to eliminate the defect (step S5). For example, when the image pattern P shown in FIG. 5 or 7A is used, the control unit 40 performs settings related to the repair of the defective nozzles described above. Furthermore, when the image pattern P shown in FIG. 7B is used, the control unit 40 causes the operation display unit 52 to display information related to the inkjet head 242 for which tilt has been detected and the amount of tilt. Alternatively, the control unit 40 adjusts the settings of the ink ejection timing from the nozzle N where the landing position is shifted in the transport direction. Furthermore, when the image pattern P shown in FIG. 7C is used, the control unit 40 causes the operation display unit 52 to display the inkjet heads 242 that require seam correction, the required adjustment direction, the amount of adjustment, and the like.

[0066] Upon completion of step S5, the control unit 40 returns the process to step S2 and executes steps S2 to S4 again to determine whether the defect has been resolved. If the defect has not been resolved ("YES" in step S4), adjustment is performed again in step S5. Note that the content of the first image formation conditions may be changed so that the dot diameter becomes smaller when forming the adjustment image 70 in step S2 for the second or subsequent times. For example, if any of conditions a to c is used when forming the first adjustment image 70, any of conditions d to f that result in a smaller dot diameter may be used when forming the second adjustment image 70. Furthermore, if any of conditions d to f is used when forming the second adjustment image 70, any of conditions g that result in a smaller dot diameter may be used when forming the third adjustment image 70. Furthermore, if the adjustment can be performed appropriately by executing step S5 once, the control unit 40 may proceed to step S6 after completing step S5 without returning the process to step S2.

[0067] If it is determined in step S4 that there are no defects in the adjustment image 70 ("NO" in step S4), the control unit 40 sets the operating conditions of the inkjet recording apparatus 1 to second image forming conditions (step S6). The second image forming conditions are set in advance for each of the colors C, M, Y, and K and stored in the storage unit 43 so as to enable reproduction of a desired color tone. Here, the control unit 40 adjusts the operations by sending control signals to the ink heating unit 243, the head control unit 241, and the medium heating unit 23 so that the ink temperature is T2, the driving voltage is V2, and the medium temperature is t2. Thereafter, the control unit 40 forms a normal image according to the input print job (step S7). When step S7 is completed, the control unit 40 ends the adjustment process.

[0068] As described above, the inkjet recording apparatus 1 of this embodiment includes the head unit 24 and the control unit 40, which ejects ink droplets from the nozzles N of the head unit 24 onto the recording medium M to form an image. When forming the adjustment image 70, the control unit 40 causes the head unit 24 to form the adjustment image 70 under first image forming conditions. When forming a normal image other than the adjustment image 70, the control unit 40 causes the head unit 24 to form the normal image under second image forming conditions different from the first image forming conditions. The first image forming conditions are determined so that defects in the image are more likely to appear than under the second image forming conditions. This allows the adjustment image 70 to be formed in a way that makes defects more likely to appear. In other words, defects can be detected from the adjustment image 70 with higher accuracy and sensitivity. Therefore, by adjusting the inkjet recording apparatus 1 to eliminate detected defects, the image can be adjusted appropriately to make image results such as streaks and unevenness less noticeable.

[0069] The adjustment image 70 also includes an image pattern P for detecting deviations in the landing positions of droplets on the recording medium M. This makes it possible to detect deviations in the landing positions with high sensitivity and accuracy.

[0070] The head unit 24 also includes an inkjet head 242 having a plurality of nozzles N. In this case, the adjustment image 70 may include an image pattern P for detecting the inclination of the inkjet head 242 from a predetermined arrangement direction. This makes it possible to detect an abnormality in the installation angle of the inkjet head 242 with high sensitivity and accuracy.

[0071] The inkjet heads 242 are arranged in a positional relationship that provides an overlapping region R where the nozzle N arrangement ranges in a predetermined direction partially overlap. In this case, the adjustment image 70 may include an image pattern P for detecting density unevenness in a portion of the adjustment image 70 formed by the nozzles N that belong to the overlapping region R. If the positions of the inkjet heads 242 are misaligned in the width direction or if the settings for ejecting or not ejecting the nozzles N in the overlapping region R for complementary ink ejection are inappropriate, density unevenness will occur in the image pattern P. Therefore, the image pattern P makes it possible to detect with high sensitivity and accuracy whether the joints between the inkjet heads 242 are inappropriate.

[0072] Furthermore, the first image formation conditions are conditions under which the dot diameter of ink droplets ejected from the nozzles N and landing on the recording medium M is smaller than that under the second image formation conditions. As a result, gaps G and overlapping portions O are more likely to occur between dots D depending on the landing position deviation, so it is possible to detect landing position deviation and the like with higher sensitivity and accuracy. Furthermore, since the positions of line segments and the like in the image pattern P can be identified more accurately, the amount of deviation in landing position can be detected more accurately.

[0073] The inkjet recording apparatus 1 also includes an ink heating unit 243 that heats the ink in the head unit 24. The control unit 40 controls the ink heating unit 243 so that the temperature of the ink when forming the adjustment image 70 under the first image forming conditions is lower than the temperature of the ink when forming a normal image under the second image forming conditions. This increases the viscosity of the ink ejected under the first image forming conditions, and therefore reduces the amount of ink when ink droplets are ejected from the nozzles N using the same drive signal. This allows the dot diameter to be reduced.

[0074] The head unit 24 also includes an image forming element 2421 that ejects ink droplets from the nozzles N in a volume that corresponds to the magnitude of the voltage of the input drive signal, and the control unit 40 controls the head unit 24 so that the voltage of the drive signal input to the image forming element 2421 when forming the adjustment image 70 under the first image forming conditions is smaller than the voltage of the drive signal input to the image forming element 2421 when forming a normal image under the second image forming conditions. This weakens the pressure that pushes the ink out of the nozzles N when ejecting ink under the first image forming conditions, reducing the volume of ink ejected from the nozzles N. This allows the dot diameter to be reduced.

[0075] The inkjet recording apparatus 1 also includes a medium heating unit 23 that heats the recording medium M, and the control unit 40 controls the medium heating unit 23 so that the temperature of the recording medium M when forming the adjustment image 70 under the first image forming conditions is lower than the temperature of the recording medium M when forming a normal image under the second image forming conditions. This makes it difficult for ink droplets that land on the recording medium M to wet and spread when ink is ejected under the first image forming conditions. This allows the dot diameter to be reduced.

[0076] The head unit 24 also ejects droplets of ink that changes phase between sol and gel depending on the temperature from the nozzles N. This increases the viscosity of the ink by lowering the ink temperature, thereby reducing the dot diameter. Furthermore, since the viscosity of droplets that land on the low-temperature recording medium M increases rapidly, lowering the medium temperature can suppress the droplets from wetting and spreading, thereby reducing the dot diameter.

[0077] Furthermore, in the image forming method of this embodiment, when forming a predetermined adjustment image 70, the control unit 40 causes the head unit 24 to form the adjustment image 70 under first image forming conditions. When forming a normal image other than the adjustment image 70, the control unit 40 causes the head unit 24 to form the normal image under second image forming conditions that are different from the first image forming conditions. The first image forming conditions are determined so that defects in the image are more likely to appear than under the second image forming conditions. This makes it possible to form an adjustment image 70 in which defects are more likely to appear appropriately.

[0078] Furthermore, the program 431 of this embodiment causes the control unit 40 to function as a control unit that ejects ink droplets from the nozzles N of the head unit 24 onto the recording medium M to form an image. When forming a predetermined adjustment image 70, the control unit causes the head unit 24 to form the adjustment image 70 under first image forming conditions. When forming a normal image other than the adjustment image 70, the control unit causes the head unit 24 to form the normal image under second image forming conditions that are different from the first image forming conditions. The first image forming conditions are determined so that defects in the image are more likely to appear than under the second image forming conditions. By operating the inkjet recording apparatus 1 in accordance with this program 431, it is possible to appropriately form an adjustment image 70 in which defects are more likely to appear.

[0079] The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, the image pattern P included in the adjustment image 70 is not limited to the one exemplified in the above embodiment. The image pattern P may be any pattern that can reflect an abnormality in the ink ejection operation or an abnormality in the arrangement of the inkjet head 242.

[0080] Furthermore, the first image forming conditions are not limited to the conditions a to g exemplified in the above embodiment, and may be any conditions under which the dot diameter on the recording medium M is smaller than that under the second image forming conditions.

[0081] In the above embodiment, the recording medium M is transported by the transport drum 211, but this is not intended to be limiting. For example, the recording medium M may be transported by a transport belt that is supported by two or more rollers and moves in accordance with the rotation of the rollers.

[0082] Furthermore, in the above embodiment, the inkjet recording apparatus 1 of a single pass type has been described as an example, but the present invention may also be applied to an inkjet recording apparatus that records an image while scanning the recording head.

[0083] In the above embodiment, the inkjet recording apparatus 1 is described as an example in which ink that is in a gel state at room temperature and turns into a sol state when heated is heated to a sol state and then ejected, but the present invention is not limited to this, and ink that is in a sol state or liquid state at room temperature may also be used. Ink that does not have the property of being cured by energy rays such as ultraviolet rays may also be used.

[0084] Furthermore, in the above embodiment, an example has been described in which the inkjet recording apparatus 1 is equipped with the imaging unit 26. However, instead of this, the adjustment image 70 may be captured by an imaging device provided separately outside the inkjet recording apparatus 1. Furthermore, analysis of the captured data of the adjustment image 70 may be performed by an analysis device provided outside the inkjet recording apparatus 1. Furthermore, defects in the adjustment image 70 may be detected visually by the user.

[0085] In the above embodiment, the inkjet recording device 1 is a piezoelectric type that uses a piezoelectric element, but the present invention is not limited to this. For example, a thermal type inkjet recording device that generates bubbles in ink by heating and ejects the ink may be used.

[0086] Although several embodiments of the present invention have been described, the scope of the present invention is not limited to the above-described embodiments, but includes the scope of the invention described in the claims and its equivalents. [Explanation of symbols]

[0087] 1. Inkjet recording device 10 Paper feed section 20 Image forming unit 211 Transport drum 23 Medium heating section 24 Head unit (ink ejection unit) 26 Imaging unit 30 Paper output section 40 Control unit (control means, computer) 70 Adjustment Images 242 Inkjet head 2421 Image forming element 243 Ink heating unit D, De Dot d1, d2 dot diameter M Recording medium N nozzle P Image Pattern R overlap region

Claims

1. an ink ejection unit; a control unit that ejects ink droplets from the nozzles of the ink ejection unit onto a recording medium to form an image; Equipped with The control unit When forming a predetermined adjustment image, the adjustment image is formed by the ink ejection unit under a first image forming condition; When forming a normal image other than the adjustment image, the normal image is formed by the ink ejection unit under second image forming conditions different from the first image forming conditions, An inkjet recording apparatus, wherein the first image forming conditions are determined so that defects in the image are more likely to appear than under the second image forming conditions.

2. the adjustment image includes an image pattern for detecting deviations in landing positions of the droplets on the recording medium. The inkjet recording apparatus according to claim 1 .

3. the ink ejection unit includes an inkjet head having a plurality of the nozzles, the adjustment image includes an image pattern for detecting an inclination of the inkjet head from a predetermined arrangement direction; The inkjet recording apparatus according to claim 1 .

4. the ink ejection unit includes a plurality of inkjet heads each having a plurality of the nozzles, the plurality of inkjet heads are arranged in a positional relationship having an overlapping region in which the nozzle arrangement ranges in a predetermined direction partially overlap each other, the adjustment image includes an image pattern for detecting density unevenness in a portion of the adjustment image formed by the nozzles belonging to the overlapping region, The inkjet recording apparatus according to claim 1 .

5. the first image forming condition is a condition under which the dot diameter of the ink droplets ejected from the nozzles and landed on the recording medium is smaller than that under the second image forming condition; The inkjet recording apparatus according to claim 1 .

6. an ink heating unit that heats the ink in the ink ejection unit; the control unit controls the ink heating unit so that a temperature of the ink when the adjustment image is formed under the first image forming condition is lower than a temperature of the ink when the normal image is formed under the second image forming condition. The inkjet recording apparatus according to claim 5 .

7. the ink ejection unit includes an image forming element that ejects ink droplets from the nozzles in an amount corresponding to the magnitude of a voltage of an input drive signal; the control unit controls the ink ejection unit so that a voltage of the drive signal input to the image forming element when forming the adjustment image under the first image forming condition is smaller than a voltage of the drive signal input to the image forming element when forming the normal image under the second image forming condition. The inkjet recording apparatus according to claim 5 .

8. a medium heating unit that heats the recording medium; the control unit controls the medium heating unit so that a temperature of the recording medium when the adjustment image is formed under the first image forming condition is lower than a temperature of the recording medium when the normal image is formed under the second image forming condition. The inkjet recording apparatus according to claim 5 .

9. the ink ejection unit ejects droplets of the ink, which undergoes a phase change between a sol state and a gel state depending on temperature, from the nozzle; The inkjet recording apparatus according to claim 5 .

10. An image forming method for forming an image by ejecting ink droplets onto a recording medium from nozzles of an ink ejection unit of an inkjet recording device, comprising: When forming a predetermined adjustment image, the adjustment image is formed by the ink ejection unit under a first image forming condition; When forming a normal image other than the adjustment image, the normal image is formed by the ink ejection unit under second image forming conditions different from the first image forming conditions, An image forming method, wherein the first image forming conditions are determined so that defects in the image are more likely to appear than under the second image forming conditions.

11. A computer of an inkjet recording device equipped with an ink ejection unit, the ink ejection unit functions as a control unit for ejecting ink droplets from the nozzles of the ink ejection unit onto a recording medium to form an image; The control means When forming a predetermined adjustment image, the adjustment image is formed by the ink ejection unit under a first image forming condition; When forming a normal image other than the adjustment image, the normal image is formed by the ink ejection unit under second image forming conditions different from the first image forming conditions, The first image forming condition is determined so that defects are more likely to appear in the image than the second image forming condition.

Images