Inkjet recording apparatus

Abstract

To provide an inkjet recording apparatus capable of suppressing deterioration in image quality.SOLUTION: In an inkjet recording apparatus, when correcting a defective nozzle of a recording head, a control unit changes an ink discharge amount to a correction pixel region adjacent to a defective pixel region corresponding to the defective nozzle in an intersecting direction. The ink discharge amount to the correction pixel region in a case where ink droplets have already been discharged to an adjacent pixel region adjacent to the defective pixel region on the side opposite to the defective pixel region with the correction pixel region interposed therebetween in the intersecting direction is larger than the ink discharge amount to the correction pixel region in a case where ink droplets have not been discharged to the adjacent pixel region.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 drive unit, and a control unit. The recording head ejects ink onto a recording medium. The drive unit moves at least one of the recording medium and the recording head. The control unit controls the relative movement of the recording medium and the recording head to perform recording on the recording medium. The recording head has multiple nozzles arranged along a direction intersecting the direction of relative movement of the recording head with respect to the recording medium, and each nozzle ejects ink droplets in a different order.

[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, the amount of ink ejected into the correction pixel area is constant, which can cause color streaks in the correction pixel area, potentially resulting in a deterioration in image quality due to the correction of defective nozzles.

[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 drive unit, and a control unit. The recording head ejects ink onto a recording medium. The drive unit moves at least one of the recording medium and the recording head. The control unit controls the relative movement of the recording medium and the recording head to perform recording on the recording medium. The recording head has a plurality of nozzles. The plurality of nozzles are arranged along an intersecting direction that intersects the relative movement direction of the recording head with respect to the recording medium, and the order in which ink droplets are ejected varies. When correcting a defective nozzle of the recording head, the control unit changes the amount of ink ejected onto a correction pixel area that is adjacent in the intersecting direction to a defective pixel area corresponding to the defective nozzle. The amount of ink ejected onto a correction pixel area when ink droplets have already been ejected onto an adjacent pixel area that is adjacent to the opposite side of the correction pixel area in the intersecting direction, with the correction pixel area in between, is greater than the amount of ink ejected onto a correction pixel area when ink droplets have not yet been ejected onto the adjacent pixel area. [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 the positions of ink droplets on a paper surface in an inkjet recording apparatus 1 according to an embodiment of the present invention. [Figure 6] 5 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 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 recording. 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 recording and drying to the paper discharge unit 21. When double-sided recording is performed, the paper transport unit 4 distributes the sheets S after recording on the first side and drying to the reversing transport unit 44 using the branch 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 that 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 (for example, three) are arranged in a staggered pattern along the paper width direction Dw, which is perpendicular to the paper transport direction Dc.

[0015] 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 a relative movement direction (paper transport direction) Dc of the recording head 51 with respect to the paper (recording medium) S.

[0016] The recording unit 5 sequentially ejects ink from four color recording heads 51B, 51C, 51M, and 51Y onto 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.

[0017] 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.

[0018] 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.

[0019] 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).

[0020] 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 relative movement of the recording head 51 with respect to the paper S is the paper transport direction Dc.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] Specifically, for example, if a defect such as a non-ejection occurs in a nozzle 52 corresponding to a defective pixel area Ap1 in row C, the control unit 7 changes the amount of ink ejected into each correction pixel area Ap2 in rows B and D that are adjacent in the paper width direction (intersecting direction) Dw to each defective pixel area Ap1 in row C onto which ink droplets are to be ejected. Furthermore, the amount of ink ejected into each correction pixel area Ap2 in rows B and D is changed depending on whether ink droplets have already been ejected and pre-deposited into each adjacent pixel area Ap3 in rows A and E. Each adjacent pixel area Ap3 in rows A and E is adjacent to the opposite side of each defective pixel area Ap1 in row C across the correction pixel areas Ap2 in rows B and D in the paper width direction (intersecting direction) Dw.

[0028] 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.

[0029] In this embodiment, the ink ejection amount can be increased or decreased in four 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 a state where there are no ink droplets. Therefore, the ink ejection amount is recorded in four stages, including a state where there are no ink droplets. The size of the ink droplets (pixels) is not limited to three stages, and may be set to multiple stages, such as five stages. The larger the ink droplet size, the higher the pixel density.

[0030] 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.

[0031] Furthermore, if the nozzle 52 corresponding to each defective pixel area Ap1 in column C is defective, such as non-ejecting, no ink is ejected into each defective pixel area Ap1 in column C. Large droplets of ink 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 droplets of ink are ejected into the correction pixel areas Ap2 of the first row B and the second row D. Small droplets of ink 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.

[0032] 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.

[0033] 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.

[0034] On the other hand, the pixels Px in the first row, column B and the second row, column D are not recorded close to 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 to the adjacent pixel area Ap3 where no ink droplets have been ejected.

[0035] 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.

[0036] Specifically, large ink droplets 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 are ejected onto the correction pixel areas Ap2 of the first row, column B, and the second row, column D.

[0037] 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, the amount of ink discharged into the correction pixel region Ap2 when ink droplets have already been discharged into the adjacent pixel region Ap3 adjacent to it in the intersecting direction Dw is two levels higher than the amount of ink discharged into the adjacent pixel region Ap3, and the amount of ink discharged into the correction pixel region Ap2 when ink droplets have not yet been discharged into the adjacent pixel region Ap3 adjacent to it in the intersecting direction Dw is one level higher than the amount of ink discharged into the adjacent pixel region Ap3.

[0038] As a result, by ejecting large ink droplets 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 pixels Px with large droplet diameters. As a result, part of the pixels 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.

[0039] On the other hand, by ejecting medium-sized ink droplets in the correction pixel area Ap2, which is less susceptible to the impact of landing interference, it is possible to reduce the occurrence of black streaks in the correction pixel area Ap2 and also reduce ink consumption.

[0040] 5 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).

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] As an evaluation method, the ink ejection amount in the correction pixel area Ap2 was changed for the 85 defective nozzles 52 belonging to the first-ejection nozzle group in the evaluations of Example 1, Comparative Example 1, and Comparative Example 2. The number of white streaks and color streaks that occurred was counted and summarized in the table of FIG.

[0046] In the evaluation of Example 1, when ink droplets had already been ejected onto the adjacent pixel area Ap3 and had been pre-ejected, large droplets of ink were ejected onto each correction pixel area Ap2. Furthermore, when ink droplets had not yet been ejected onto the adjacent pixel area Ap3, medium droplets of ink were ejected onto each correction pixel area Ap2 adjacent in the paper width direction Dw.

[0047] Furthermore, in the evaluation of Comparative Example 1, when ink droplets had already been ejected onto the adjacent pixel region Ap3 and had been pre-ejected, or when ink droplets had not yet been ejected onto the adjacent pixel region Ap3, medium-sized ink droplets were ejected onto each correction pixel region Ap2 adjacent in the paper width direction Dw. In this case, the size of the ink droplets ejected onto each correction pixel region Ap2 was medium-sized, regardless of whether ink droplets had already been ejected onto the adjacent pixel region Ap3.

[0048] Furthermore, in the evaluation of Comparative Example 2, when ink droplets had already been ejected onto the adjacent pixel region Ap3 and had been pre-ejected, or when ink droplets had not yet been ejected onto the adjacent pixel region Ap3, large droplet-sized ink was ejected onto each correction pixel region Ap2 adjacent in the paper width direction Dw. In this case, the size of the ink droplets ejected onto each correction pixel region Ap2 was large, regardless of whether ink droplets had already been ejected onto the adjacent pixel region Ap3.

[0049] 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".

[0050] 7, it was found that the evaluation of Example 1 could suppress the occurrence of white streaks and color streaks and reduce the occurrence of image defects regardless of the presence or absence of the influence of landing interference. On the other hand, the evaluation of Comparative Example 1 found that white streaks were likely to occur when the influence of landing interference was present.

[0051] 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. [Industrial Applicability]

[0052] The present invention can be used in inkjet recording apparatuses. [Explanation of symbols]

[0053] 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)

Claims

1. a recording head that ejects ink onto a recording medium; a drive unit that moves at least one of the recording medium and the recording head; a control unit that controls relative movement of the recording medium and the recording head to perform recording on the recording medium, The recording head includes: a plurality of nozzles arranged along a direction intersecting a direction of relative movement of the recording head with respect to the recording medium, the nozzles ejecting ink droplets in different orders; when correcting a defective nozzle of the recording head, the control unit changes the amount of ink ejected to a defective pixel area corresponding to the defective nozzle and a correction pixel area adjacent to the defective pixel area in the intersecting direction; an inkjet recording device, wherein when ink droplets have already been ejected onto an adjacent pixel region adjacent to the defective pixel region on the opposite side of the correction pixel region in the intersecting direction, the amount of ink ejected onto the correction pixel region is greater than the amount of ink ejected onto the adjacent pixel region when ink droplets have not yet been ejected onto the correction pixel region.

2. 2. The inkjet recording apparatus according to claim 1, wherein the amount of ink ejected to the correction pixel region is different from the amount of ink ejected to the adjacent pixel region.

3. the control unit is capable of changing the increase / decrease of the ink ejection amount in three or more stages, an amount of ink ejected onto the correction pixel region when ink droplets have already been ejected onto the adjacent pixel region adjacent to the correction pixel region in the crossing direction is two levels higher than the amount of ink ejected onto the adjacent pixel region; 3. The inkjet recording apparatus according to claim 2, wherein the amount of ink ejected into the correction pixel area when ink droplets have not been ejected into the adjacent pixel area adjacent to the correction pixel area in the crossing direction is one level higher than the amount of ink ejected into the adjacent pixel area.

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