Inkjet recording apparatus

Abstract

To provide an inkjet recording device capable of suppressing deterioration of image quality.SOLUTION: In the inkjet recording device, when correcting the defective nozzle of the recording head, the control part increases an ink discharge amount to a correction pixel region adjacent to a defective pixel region corresponding to the defective nozzle in the crossing direction more than an ink discharge amount to other pixel regions. The control unit reduces the ink discharge amount to the correction pixel region of the recording head arranged on the downstream side in the moving direction of the recording medium to be smaller than the ink discharge amount to the correction pixel region of the recording head arranged on the upstream side in the moving direction of the recording medium.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an inkjet recording apparatus. [Background technology]

[0002] A conventional inkjet recording device includes a recording head, a driving unit, a drying unit, and a control unit. The recording head ejects ink onto a recording medium. The driving unit moves the recording medium relatively to the recording head. The drying unit is located downstream of the recording head in the direction of recording medium movement and dries the recording medium. The control unit controls the recording head, driving unit, and drying unit to perform recording on the recording medium. Multiple recording heads are arranged in the direction of recording medium movement. Each recording head is arranged along a direction intersecting the direction of relative movement of the recording head with respect to the recording medium, and has multiple nozzles that eject ink droplets in different orders.

[0003] When correcting a defective nozzle of the recording head, the control unit reduces the amount of ink ejected to an adjacent pixel area adjacent in the cross direction to a correction pixel area adjacent in the cross direction to the defective pixel area into which the defective nozzle is scheduled to eject ink droplets.

[0004] This reduces the risk of ink droplets ejected onto the correction pixel region moving toward the ink droplets of the adjacent pixel region due to impact interference when ink is ejected onto the correction pixel region after ink is ejected onto the adjacent pixel region, thereby suppressing the occurrence of white streaks in the defective pixel region. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-055497 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in conventional inkjet recording devices, ink droplets ejected onto a correction pixel area are affected by landing interference and gradually move toward the ink droplets of adjacent pixel areas until they dry. Furthermore, ink droplets ejected from a recording head downstream in the recording medium's movement direction take less time to reach the drying area than ink droplets ejected from a recording head upstream in the recording medium's movement direction, and are therefore less susceptible to landing interference. This reduces the movement of ink droplets ejected onto the correction pixel area from the recording head downstream in the recording medium's movement direction, potentially resulting in color streaks in the correction pixel area. Therefore, image quality can be degraded by correcting a defective nozzle.

[0007] The present invention has been made in view of the above points, and has as its object to provide an inkjet recording apparatus that can suppress deterioration in image quality. [Means for solving the problem]

[0008] In order to solve the above problems, the inkjet recording apparatus of the present invention includes a recording head, a driving unit, a drying unit, and a control unit. The recording head ejects ink onto a recording medium. The driving unit moves the recording medium relative to the recording head. The drying unit is located downstream of the recording head in the direction of recording medium movement and dries the recording medium. The control unit controls the recording head, the driving unit, and the drying unit to record an input image pattern on the recording medium. A plurality of recording heads are arranged in the direction of recording medium movement. Each recording head is arranged along an intersecting direction intersecting the direction of recording medium movement and has a plurality of nozzles that eject ink droplets in different orders. When correcting a defective nozzle of a recording head, the control unit increases the ink ejection amount to a defective pixel region corresponding to the defective nozzle and a correction pixel region adjacent to the intersecting direction compared to the ink ejection amount to other pixel regions. The control unit reduces the ink ejection amount to a correction pixel region of a recording head located downstream in the direction of recording medium movement compared to the ink ejection amount to a correction pixel region of a recording head located upstream in the direction of recording medium movement. [Effects of the Invention]

[0009] According to the configuration of the present invention, it is possible to provide an inkjet recording apparatus that can suppress deterioration in image quality. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view showing a schematic configuration of an inkjet recording apparatus 1 according to an embodiment of the present invention. [Figure 2] FIG. 2 is a plan view of the recording unit 5 of the inkjet recording apparatus 1 of FIG. [Figure 3] FIG. 2 is a block diagram showing a schematic configuration of the inkjet recording apparatus 1 of FIG. [Figure 4] 1 is an explanatory diagram showing ink ejection positions of an inkjet recording apparatus 1 according to an embodiment of the present invention. [Figure 5] 1 is an explanatory diagram showing ink droplet positions on a paper surface in an inkjet recording apparatus 1 according to an embodiment of the present invention. [Figure 6] 10 is a flowchart showing an example of execution of a correction mode in the inkjet recording apparatus 100 according to an embodiment of the present invention. [Figure 7] 1 is a table summarizing the evaluation results of Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0011] <1. Configuration of Inkjet Recording Apparatus> Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a schematic configuration of an inkjet recording apparatus 1 according to an embodiment. FIG. 2 is a plan view of a recording unit 5 of the inkjet recording apparatus 1 of FIG. 1. FIG. 3 is a block diagram showing a schematic configuration of the inkjet recording apparatus 1 of FIG. 1. The right side of FIG. 2 is the upstream side in the paper transport direction Dc, and the upper left side is the downstream side in the paper transport direction Dc. The inkjet recording apparatus 1 is, for example, an inkjet recording printer. As shown in FIGS. 1, 2, and 3, the inkjet recording apparatus 1 includes a device main body 2, a paper supply unit 3, a paper transport unit 4, a recording unit 5, a drying unit 6, and a control unit 7.

[0012] The paper supply unit 3 stores multiple sheets of paper (recording media) S, and separates and sends out the sheets S one by one during image formation. The paper transport unit 4 transports the sheets S sent out from the paper supply unit 3 to the recording unit 5 and drying unit 6, and then discharges the sheets S after image formation and drying to the paper discharge unit 21. When double-sided recording is performed, the paper transport unit 4 distributes the dried sheets S after image formation on the first side to the reversing transport unit 44 using the branching unit 43, and then switches the transport direction to reverse the sheets S and transport them again to the recording unit 5 and drying unit 6.

[0013] The paper transport unit 4 has a first belt transport unit 41 and a second belt transport unit 42. The first belt transport unit 41 and the second belt transport unit 42 adsorb and hold the paper S on the upper surface of an endless belt and transport it. In other words, the paper transport unit 4 is a drive unit that moves the paper (recording medium) S relative to the recording unit 5.

[0014] The recording unit 5 is disposed above the first belt transport unit 41 at a predetermined distance, facing the paper S, which is held by suction on the upper surface of the first belt transport unit 41 and transported. The recording unit 5 has line-type inkjet recording heads 51. As shown in FIG. 2, the recording heads 51 include recording heads 51B, 51C, 51M, and 51Y corresponding to four colors: black, cyan, magenta, and yellow. A plurality of recording heads 51 for each color are arranged in the paper transport direction Dc. A plurality of (for example, three) recording heads 51 for each color are arranged in a staggered pattern along the paper width direction Dw, which is perpendicular to the paper transport direction Dc.

[0015] In this embodiment, three recording heads 51 for each color are arranged, but the present invention is not limited to this. For example, one recording head 51 for each color may be arranged, or four or more recording heads 51 for each color may be arranged.

[0016] The multiple nozzles 52 can eject ink droplets over the entire recording area on the paper S. Specifically, the recording head 51 has multiple nozzles 52 that eject ink droplets in different orders. The multiple nozzles 52 are arranged along a cross direction (paper width direction) Dw that intersects with the movement direction (paper transport direction) Dc of the paper (recording medium) S.

[0017] The recording unit 5 sequentially ejects ink from four color recording heads 51B, 51C, 51M, and 51Y toward the paper S transported by the first belt transport unit 41, and records a full-color image or a monochrome image on the paper S. The recording heads 51B, 51C, 51M, and 51Y are arranged in order from the upstream side to the downstream side in the paper transport direction DC.

[0018] The drying unit 6 is disposed downstream of the recording unit 5 in the paper transport direction, and is provided with a second belt transport unit 42. The paper S, on which an ink image has been recorded in the recording unit 5, is adsorbed and held by the second belt transport unit 42 in the drying unit 6, and the ink is dried while being transported. That is, the drying unit 6 is disposed downstream of the recording head 51 in the movement direction (paper transport direction) Dc of the paper (recording medium) S, and dries the paper S.

[0019] The control unit 7 includes a CPU and other electronic circuits and electronic components (not shown). Based on control programs and data stored in the memory unit 8, the CPU controls the operation of each component provided in the inkjet recording device 1 to perform processing related to the functions of the inkjet recording device 1. The paper supply unit 3, paper transport unit 4, recording unit 5, and drying unit 6 each receive commands individually from the control unit 7 and perform recording on the paper S in cooperation with each other.

[0020] The storage unit 8 is configured by combining a non-volatile storage device such as a program ROM (Read Only Memory) or a data ROM (not shown) with a volatile storage device such as a RAM (Random Access Memory).

[0021] The control unit 7 controls the relative movement of the paper S and the recording head 51 to perform recording on the paper S. More specifically, the control unit 7 controls the recording head 51 to cause each nozzle 52 to eject ink of a volume corresponding to the pixel value of the image data onto the paper S. In this way, an image is formed on the paper S. In this embodiment, the direction of movement of the recording head 51 relative to the paper S is the paper transport direction Dc.

[0022] Fig. 4 is an explanatory diagram showing ink ejection positions, and Fig. 5 is an explanatory diagram showing ink droplet positions on the paper surface. Specifically, Fig. 4 and Fig. 5 show ink ejection positions when recording 14 pixels Px in 25 pixel areas Ap from the first row, column A to the fifth row, column E. The paper transport direction Dc is the direction from bottom to top in Figs. 4 and 5, with the bottom side in Figs. 4 and 5 being the upstream side of the paper transport direction Dc and the top side being the downstream side of the paper transport direction Dc.

[0023] 4 and 5, each pixel area Ap represents a virtual area obtained by dividing the image recording area of ​​the paper S by resolution. In FIGS. 4 and 5, the pixel areas are represented by dashed rectangles, but these dashed rectangles are not actually recorded on the paper S. The control unit 7 sends an ink ejection control signal to the recording head 51 each time the paper S moves by the resolution in the paper transport direction Dc. This causes the recording head 51 to eject ink toward the pixel area on the paper S. A pixel Px is an element of an image recorded by ink droplets ejected corresponding to each image area, and is the smallest unit component of an image.

[0024] 4, the ink droplets M1 ejected onto the correction pixel area Ap2 by the recording heads 51B and 51C are indicated by solid lines, and the ink droplets M2 ejected onto the correction pixel area Ap2 by the recording heads 51M and 51Y are indicated by dashed lines.

[0025] Furthermore, in this embodiment, the nozzles 52 that eject ink onto rows A, C, and E of the pixel region Ap belong to the first-deposit nozzle group, and the nozzles 52 that eject ink onto rows B and D of the pixel region Ap belong to the second-deposit nozzle group. The nozzles 52 that belong to the first-deposit nozzle group and the nozzles 52 that belong to the second-deposit nozzle group are arranged alternately in the paper width direction (intersecting direction) Dw.

[0026] The nozzles 52 belonging to the first-deposit nozzle group eject ink droplets before the nozzles 52 belonging to the second-deposit nozzle group. In other words, after ink droplets are ejected from the nozzles 52 belonging to the first-deposit nozzle group, ink droplets are ejected from the nozzles 52 belonging to the second-deposit nozzle group at the timing when the paper S moves between the nozzles 52 belonging to the first-deposit nozzle group and the nozzles 52 belonging to the second-deposit nozzle group.

[0027] Recording heads 51B, 51C, 51M, and 51Y each eject ink droplets corresponding to one of four colors, black (B), cyan (C), magenta (M), and yellow (Y), from nozzles 52 onto paper S. By moving paper S and recording head 51 relative to each other, an image made up of ink droplets can be formed on paper S.

[0028] In addition, the ink droplets M2 ejected from the recording heads 51M and 51Y arranged downstream in the movement direction (paper transport direction) Dc of the paper (recording medium) S take less time to reach the drying section 6 than the ink droplets M1 ejected from the recording heads 51B and 51C arranged upstream in the movement direction (paper transport direction) Dc of the paper (recording medium) S, and are less susceptible to impact interference.

[0029] In the inkjet recording device 1 according to this embodiment, when a defect such as non-ejection occurs in a nozzle 52 belonging to the first nozzle group, the control unit 7 corrects the defect by changing the amount of ink droplets ejected from the nozzles 52 surrounding the defective nozzle 52.

[0030] Specifically, for example, if a defect such as a non-ejection occurs in the nozzle 52 corresponding to the defective pixel area Ap1 of row C, the control unit 7 changes the amount of ink ejected into each correction pixel area Ap2 of rows B and D that are adjacent in the paper width direction (intersecting direction) Dw to each defective pixel area Ap1 of row C onto which ink droplets are to be ejected. Furthermore, the amount of ink ejected into each correction pixel area Ap2 of rows B and D is changed depending on whether ink droplets have already been ejected and pre-deposited into each adjacent pixel area Ap3 of rows A and E. Note that each adjacent pixel area Ap3 of rows A and E is adjacent to the opposite side of each defective pixel area Ap1 of row C across the correction pixel areas Ap2 of rows B and D in the paper width direction (intersecting direction) Dw.

[0031] More specifically, when ink droplets have already been ejected and pre-deposited into each adjacent pixel area Ap3 of rows A and E, the amount of ink ejected into each correction pixel area Ap2 of rows B and D is greater than the amount of ink ejected into each correction pixel area Ap2 of rows B and D when ink droplets have not yet been ejected into each adjacent pixel area Ap3 of rows A and E.

[0032] In this embodiment, the ink ejection amount can be increased or decreased in multiple stages. The ink ejection amount is determined by the size of the ink droplets (pixels). That is, pixels Px recorded with large-sized ink droplets have the largest ink ejection amount, followed by medium-sized and small-sized droplets. The ink ejection amount can also be in a state where there are no ink droplets.

[0033] Furthermore, in this embodiment, the large-sized ink droplets ejected into the correction pixel area Ap2 can be further changed to two levels, ink droplet M1 and ink droplet M2, by increasing or decreasing the ink ejection amount. Therefore, the ink ejection amount is recorded in five levels, including a state where there are no ink droplets. Also, the size of the ink droplets (pixels) is not limited to four levels, and may be set to other multiple levels, such as six levels. Note that the larger the ink droplet size, the higher the gradation (density) of the pixel.

[0034] The ink ejection positions and ink droplet sizes for the multiple pixel regions Ap are determined based on image data to be recorded on the paper S. In this embodiment, ink is ejected onto the second row, column A, the third row, column A, the fifth row, column B, the first row, column B, the third row, column B, the fifth row, column B, the first row, column D, the second row, column D, the third row, column D, the fourth row, column E, the first row, column E, the third row, and column E. Note that the ink ejection pattern in this embodiment is an example, and the present invention is not limited to this.

[0035] Furthermore, if the nozzle 52 corresponding to each defective pixel area Ap1 in column C is defective, such as non-ejecting, no ink droplets are ejected into each defective pixel area Ap1 in column C. Large ink droplets M1 and M2 are ejected into the correction pixel areas Ap2 of the second row B, the third row B, the fifth row B, the first row D, the third row D, and the fourth row D. Medium ink droplets M3 are ejected into the correction pixel areas Ap2 of the first row B and the second row D. Small ink droplets M4 are ejected into the adjacent pixel areas Ap3 of the second row A, the third row A, the fifth row A, the first row E, the third row E, and the fourth row E.

[0036] When ink is ejected based on the ink ejection positions and ink droplet sizes for the multiple pixel areas Ap determined as described above (see FIG. 4), pixels Px are actually recorded as shown in the ink droplet positions on the paper surface in FIG.

[0037] The pixels Px in the second row, column B, the third row, column B, the fifth row, column B, the first row, column D, the third row, column D, and the fourth row, column D are recorded closer to the pixels Px in the second row, column A, the third row, column A, the fifth row, column A, the first row, column E, the third row, column E, and the fourth row, column E, which are adjacent in the paper width direction Dw. This is because the ink droplets in the correction pixel area Ap2 are attracted to the ink droplets in the adjacent pixel area Ap3 that were previously ejected onto the paper S due to landing interference.

[0038] On the other hand, the pixels Px in the first row, column B and the second row, column D are not recorded near the adjacent pixel areas Ap3 in the first row, column A and the second row, column E, which are adjacent in the paper width direction Dw. In other words, the ink droplets in the correction pixel area Ap2 are not easily attracted toward the adjacent pixel area Ap3 where no ink droplets have been ejected.

[0039] In this embodiment, the amount of ink ejected onto each correction pixel area Ap2 of rows B and D that is subsequently ejected is changed depending on whether ink droplets have already been ejected onto each adjacent pixel area Ap3 of rows A and E that is previously ejected.

[0040] Specifically, large ink droplets M1 and M2 are ejected onto the correction pixel areas Ap2 of the second row, column B, the third row, column B, the fifth row, column B, the first row, column D, the third row, column D, and the fourth row, column D. On the other hand, medium ink droplets M3 are ejected onto the correction pixel areas Ap2 of the first row, column B, and the second row, column D.

[0041] That is, the amount of ink discharged into the correction pixel region Ap2 is different from the amount of ink discharged into the adjacent pixel region Ap3. Furthermore, when ink droplets have already been discharged into the adjacent pixel region Ap3 adjacent to the correction pixel region Ap2 in the intersecting direction Dw, the amount of ink discharged into the correction pixel region Ap2 is two or three levels higher than the amount of ink discharged into the adjacent pixel region Ap3, and when ink droplets have not yet been discharged into the adjacent pixel region Ap3 adjacent to the intersecting direction Dw, the amount of ink discharged into the correction pixel region Ap2 is one level higher than the amount of ink discharged into the adjacent pixel region Ap3.

[0042] As a result, by ejecting large ink droplets M1 and M2 in the correction pixel area Ap2, which is susceptible to the effects of landing interference, even if ink droplets move toward the adjacent pixel area Ap3, the large ink droplets record the pixel Px, which has a large droplet diameter. As a result, part of the pixel Px protrudes from the correction pixel area Ap2 and covers part of the defective pixel area Ap1. This reduces the occurrence of white streaks in the defective pixel area Ap1.

[0043] On the other hand, by ejecting medium-sized ink droplets in the correction pixel area Ap2, which is less susceptible to impact interference, it is possible to reduce the occurrence of black streaks (color streaks) in the correction pixel area Ap2 and also reduce ink consumption.

[0044] Ink ejected from recording heads 51M and 51Y arranged downstream in the movement direction (paper transport direction) Dc of paper (recording medium) S takes less time to reach the drying unit 6 than ink ejected from recording heads 51B and 51C arranged upstream in the movement direction (paper transport direction) Dc of paper (recording medium) S, and is less susceptible to impact interference. As a result, the movement amount of ink droplets M2 ejected from recording heads 51M and 51Y onto correction pixel area Ap2 is smaller than the movement amount of ink droplets M1 ejected from recording heads 51B and 51C onto correction pixel area Ap2.

[0045] Therefore, when ink droplets M1 and M2 have the same ink ejection volume and correction is performed to suppress the occurrence of white streaks in defective pixel area Ap1, color streaks may occur in corrected pixel area Ap2 where ink droplets M2 are ejected from recording heads 51M and 51Y. Therefore, there is a possibility that image quality may deteriorate due to correction of the defective nozzle.

[0046] In this embodiment, the ink ejection volume of ink droplet M2 is smaller than the ink ejection volume of ink droplet M1. As a result, the ink ejection volume of recording heads 51M and 51Y arranged downstream in the movement direction (paper transport direction) Dc of paper (recording medium) S onto correction pixel area Ap2 is smaller than the ink ejection volume of recording heads 51B and 51C arranged upstream in the movement direction (paper transport direction) Dc of paper (recording medium) S onto correction pixel area Ap2.

[0047] Therefore, by reducing the amount of ink ejected onto the correction pixel area Ap2 from the print heads 51M and 51Y, which are less affected by landing interference, it is possible to reduce the occurrence of black streaks (color streaks) in the correction pixel area Ap2.

[0048] In this embodiment, medium-sized ink droplets M3 are ejected onto the correction pixel areas Ap2 in the first row, column B and the second row, column D, but small-sized ink droplets M4 may also be ejected onto the correction pixel areas Ap2 in the first row, column B and the second row, column D. In other words, only when ink droplets have already been ejected onto the adjacent pixel area Ap3 may the amount of ink ejected onto the correction pixel area Ap2 be increased compared to the amount of ink ejected onto other pixel areas. The ink ejection amount is not changed in correction pixel areas Ap2 where no ink droplets previously ejected onto the adjacent pixel area Ap3 exist. This makes it possible to prevent image defects caused by changes in the ink ejection amount in correction pixel areas Ap2 that are not affected by landing interference.

[0049] Furthermore, the ink ejection pattern for the correction pixel region Ap2 is different from the ink ejection pattern for other pixel regions, including the adjacent pixel region Ap3. The ink ejection pattern refers to, for example, the waveform or gradation of the ink ejection. By changing the ink ejection pattern for the correction pixel region Ap2 from the ink ejection pattern for other pixel regions, such as the adjacent pixel region Ap3, correction of the defective nozzle 52 can be performed more accurately, and degradation of image quality can be further suppressed.

[0050] 6 is a flowchart showing an example of image processing execution in the inkjet recording apparatus 1. In this embodiment, a correction mode can be executed to correct the drive conditions of the recording head 51 when the normal recording mode is executed. When the correction mode is executed, it is detected whether or not there is a nozzle 52 that has experienced a defect such as non-ejection (step S1).

[0051] Specifically, a check chart (not shown) for detecting faulty nozzles 52 is recorded on paper S, and the check chart recorded on paper S is optically read by an image reading unit (not shown). Next, recording data corresponding to the read image is generated, and faulty nozzles 52 are detected based on the recording data. If a faulty nozzle 52 is detected (YES in step S1), the faulty nozzle 52 is identified and stored in memory unit 8.

[0052] In step S2, it is determined whether the identified defective nozzle 52 belongs to the first-deposit nozzle group. If the defective nozzle 52 belongs to the first-deposit nozzle group (YES in step S2), the process proceeds to step S3.

[0053] In step S3, the drive conditions of the print head 51 are corrected. This corrects the amount of ink droplets ejected from the nozzles 52 around the defective nozzle 52. The corrected drive conditions of the print head 51 are stored in the memory unit 8. As a result, when the normal print mode is executed, an image is formed based on the corrected drive conditions of the print head 51. Therefore, when the print mode is executed, the occurrence of white streaks and black streaks (color streaks) can be reduced.

[0054] It is preferable that the control unit 7 sets the increase in the ink ejection amount to the maximum value for all correction pixel areas Ap2 when the gradation value of the image pattern recorded during execution of the recording mode becomes equal to or greater than a predetermined value as a result of correction, thereby further suppressing degradation of image quality.

[0055] Next, an evaluation was made as to whether the occurrence of image defects could be suppressed by correcting the ejection amount of ink droplets ejected from the nozzles 52 surrounding the defective nozzle 52.

[0056] As an evaluation method, in the evaluations of Example 1, Comparative Example 1, and Comparative Example 2, for a defective nozzle 52 belonging to the first-deposit nozzle group, the ink ejection amount into the correction pixel area Ap2 of recording heads 51M and 51Y located downstream in the movement direction (paper transport direction) Dc of paper (recording medium) S, and the ink ejection amount into the correction pixel area Ap2 of recording heads 51B and 51C located upstream in the movement direction (paper transport direction) Dc of paper (recording medium) S. The number of white streaks and color streaks that occurred were counted and summarized in the table of FIG.

[0057] It should be noted that recording head 51B had 55 faulty nozzles 52, recording head 51C had 30 faulty nozzles 52, recording head 51M had 51 faulty nozzles 52, and recording head 51Y had 22 faulty nozzles 52. All of these faulty nozzles 52 were arranged in positions where landing interference occurred. Furthermore, in the evaluations of Example 1, Comparative Example 1, and Comparative Example 2, ink droplets had already been ejected and pre-deposited into adjacent pixel region Ap3.

[0058] Furthermore, recording heads 51B, 51C, 51M, and 51Y were arranged in order from upstream to downstream in the paper transport direction DC, and it took 156.25 ms for ink droplets ejected from recording head 51B to reach the drying unit 6. It took 125 ms for ink droplets ejected from recording head 51C to reach the drying unit 6. It took 93.75 ms for ink droplets ejected from recording head 51M to reach the drying unit 6. It took 62.5 ms for ink droplets ejected from recording head 51Y to reach the drying unit 6.

[0059] In the evaluations of Example 1, Comparative Example 1, and Comparative Example 2, large ink droplets M1 or M2 were ejected onto each correction pixel area Ap2. The ink droplets M1 had a larger ejection volume than the ink droplets M2 (see FIG. 4).

[0060] In the evaluation of Example 1, the recording heads 51M and 51Y ejected ink droplets M2 onto the correction pixel area Ap2, while the recording heads 51B and 51C ejected ink droplets M1 onto the correction pixel area Ap2.

[0061] In the evaluation of Comparative Example 1, the recording heads 51B, 51C, 51M, and 51Y ejected ink droplets M2 onto the correction pixel area Ap2.

[0062] In the evaluation of Comparative Example 2, the recording heads 51B, 51C, 51M, and 51Y ejected ink droplets M1 onto the correction pixel area Ap2.

[0063] In addition, in the evaluation of whether the occurrence of image defects could be suppressed, image data was recorded under the driving conditions of each recording head 51, and the image data after recording was observed to see whether there were any white or colored streaks. If no white or colored streaks occurred, it was judged as good "O". If white or colored streaks occurred, it was judged as poor "X".

[0064] 7, it was found that in the evaluation of Example 1, the occurrence of white streaks and color streaks could be suppressed by ink droplets ejected from recording heads 51B, 51C, 51M, and 51Y, thereby reducing the occurrence of image defects. On the other hand, in the evaluation of Comparative Example 1, it was found that white streaks were likely to occur due to ink droplets ejected from recording heads 51B and 51C, which are significantly affected by landing interference. Furthermore, in the evaluation of Comparative Example 2, it was found that color streaks were likely to occur due to ink droplets ejected from recording heads 51M and 51Y, which are less affected by landing interference.

[0065] Although the embodiments of the present invention have been described above, the scope of the present invention is not limited to these, and various modifications can be made without departing from the spirit of the invention. For example, in correcting the incorrect nozzle 52, the amount of ink ejected into the correction pixel area Ap2 by the recording heads 51M and 51Y located downstream in the movement direction (paper transport direction) Dc of the paper (recording medium) S may be the same as the amount of ink ejected into the correction pixel area Ap2 by the recording heads 51B and 51C located upstream in the movement direction (paper transport direction) Dc of the paper (recording medium) S.

[0066] Furthermore, in this embodiment, the ink ejection amount into the correction pixel area Ap2 of the recording heads 51M and 51Y arranged downstream in the movement direction (paper transport direction) Dc of the paper (recording medium) S is reduced compared to the ink ejection amount into the correction pixel area Ap2 of the recording heads 51B and 51C arranged upstream in the movement direction (paper transport direction) Dc of the paper (recording medium) S. However, this is not limited to this. For example, the ink ejection amount into the correction pixel area Ap2 of the recording head 51Y arranged downstream in the movement direction (paper transport direction) Dc of the paper (recording medium) S may be reduced compared to the ink ejection amount into the correction pixel area Ap2 of the recording heads 51B, 51C, and 51M arranged upstream in the movement direction (paper transport direction) Dc of the paper (recording medium) S.

[0067] Alternatively, the ink ejection amount to the correction pixel area Ap2 may be decreased in the order of the recording heads 51B, 51C, 51M, and 51Y. [Industrial Applicability]

[0068] The present invention can be used in inkjet recording apparatuses. [Explanation of symbols]

[0069] 1. Inkjet recording device 2. Device body 3 Paper supply unit 4 Paper transport section 5 Recording section 6 Drying section 7 Control Unit 8 Memory section 21 Paper output section 41 First belt conveyor 42 Second belt conveyor 43 Branch 44 Reversing conveying section 51, 51B, 51C, 51M, 51Y recording head 52 nozzles Ap pixel area Ap1 Bad pixel area Ap2 Correction pixel area Ap3 Adjacent pixel area Dc Paper transport direction (relative movement direction) Dw Paper width direction (cross direction) Px pixels S Paper (recording medium) M1, M2, M3, M4 ink droplets

Claims

1. a recording head that ejects ink onto a recording medium; a drive unit that moves the recording medium relative to the recording head; a drying unit that is disposed downstream of the recording head in a direction in which the recording medium moves and that dries the recording medium; a control unit that controls the recording head, the driving unit, and the drying unit, and records an input image pattern on the recording medium, a plurality of the recording heads are arranged in the moving direction of the recording medium; Each of the recording heads is a plurality of nozzles arranged along a direction intersecting the direction of movement of the recording medium, the nozzles ejecting ink droplets in different orders; when correcting a defective nozzle of the recording head, the control unit increases the amount of ink ejected to a defective pixel area corresponding to the defective nozzle and a correction pixel area adjacent to the intersection direction compared to the amount of ink ejected to other pixel areas; The control unit reduces the amount of ink ejected onto the correction pixel area by the recording head located downstream in the direction of movement of the recording medium to less than the amount of ink ejected onto the correction pixel area by the recording head located upstream in the direction of movement of the recording medium.

2. 2. The inkjet recording device according to claim 1, wherein, when correcting a defective nozzle of the recording head, the control unit increases the amount of ink ejected into the correction pixel area compared to the amount of ink ejected into other pixel areas only if ink droplets have already been ejected into an adjacent pixel area that is adjacent to the defective pixel area on the opposite side of the correction pixel area in the intersecting direction.

3. 3. The inkjet recording apparatus according to claim 1, wherein, in a portion of the image pattern, the amount of ink ejected onto the correction pixel area by the recording head arranged downstream in the direction of movement of the recording medium is the same as the amount of ink ejected onto the correction pixel area by the recording head arranged upstream in the direction of movement of the recording medium.

4. 3. The inkjet recording apparatus according to claim 1, wherein the ink ejection pattern for the correction pixel region is different from the ink ejection pattern for other pixel regions.

5. 3. The inkjet recording device according to claim 1, wherein the control unit sets an increase in the amount of ink ejected into all of the correction pixel areas to a maximum value when the gradation value of the image pattern to be recorded after correction becomes equal to or greater than a predetermined value.

Images