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 increases an ink discharge amount to a correction pixel region adjacent to a defective pixel region corresponding to the defective nozzle in an intersecting direction more than an ink discharge amount to other pixel regions. The control unit decreases the ink discharge amount to the correction pixel region as Oken-type smoothness of a recording medium increases.SELECTED DRAWING: Figure 6

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 degree to which ink droplets penetrate into the recording medium varies depending on the type of recording medium. The amount of movement of ink droplets that move due to impact interference varies depending on the degree to which previously deposited ink droplets penetrate into the recording medium. Therefore, there is a possibility that correction of defective nozzles will not be performed appropriately depending on the type of recording medium, resulting in a deterioration in image quality.

[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 record an input image pattern on the recording medium. The recording head has a plurality of nozzles. The plurality of nozzles are arranged along a cross direction that intersects with the relative movement direction of the recording head with respect to the recording medium, and the order in which ink droplets are ejected differs. When correcting a defective nozzle of the recording head, the control unit increases the amount of ink ejected into a correction pixel area adjacent in the cross direction to the defective pixel area corresponding to the defective nozzle compared to the amount of ink ejected into other pixel areas. The control unit decreases the amount of ink ejected into the correction pixel area as the Oken smoothness of the recording medium increases. [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] 1 is an explanatory diagram showing ink ejection positions of an inkjet recording apparatus 1 according to an embodiment of the present invention. [Figure 7] 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 8] 1 is a table summarizing the evaluation results of examples. 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, a control unit 7, a storage unit 8, a display unit 9, and an operation unit 10.

[0012] The display unit 9 is configured, for example, by a liquid crystal display panel or the like, and can display various information related to the control unit 7, information about processing results, etc. The operation unit 10 is an input device configured, for example, by a keyboard, touch panel, etc., and can input operation information, setting information, etc. to the control unit 7.

[0013] 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 supply unit 3 includes a cassette CA. The cassette CA stores the sheets S. The cassette CA is detachable from the device main body 2. The operation of storing the sheets S in the cassette CA is performed, for example, by the user. When performing the storage operation, the user pulls out the cassette CA from the device main body 2, stores the sheets S in the cassette CA, and then attaches the cassette CA to the device main body 2.

[0014] The paper transport unit 4 transports the paper S sent from the paper supply unit 3 to the recording unit 5 and the drying unit 6, and then discharges the paper S after recording and drying to the paper discharge unit 21. When double-sided recording is performed, the paper transport unit 4 distributes the paper S after recording and drying on the first side to the reversing transport unit 44 by the branching unit 43, and then switches the transport direction to reverse the paper S and transports it again to the recording unit 5 and the drying unit 6.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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).

[0022] 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, which ejects ink onto the paper (recording medium) S, and causes each nozzle 52 to eject an amount of ink toward the paper S that corresponds to the pixel values ​​of the input image pattern. That is, the control unit 7 controls the relative movement of the paper (recording medium) S and the recording head 51 to record the input image pattern on the paper (recording medium) S. In this manner, 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.

[0023] The Oken smoothness of paper S varies depending on the paper type, and as the Oken smoothness increases, ink penetration becomes more difficult and drying speed decreases. In this embodiment, paper S is classified into a first recording medium group, a second recording medium group, and a third recording medium group based on the Oken smoothness. The first recording medium group includes paper S with an Oken smoothness of 2000 seconds or more. The second recording medium group includes paper S with an Oken smoothness of 500 seconds or more and less than 2000 seconds. The third recording medium group includes paper S with an Oken smoothness of less than 500. Oken smoothness is measured in accordance with JIS P 8155:2010.

[0024] The Oken smoothness decreases in the order of the first recording medium group, the second recording medium group, and the third recording medium group. The degree of ink droplet penetration increases in the order of the first recording medium group, the second recording medium group, and the third recording medium group. For example, gloss coated paper belongs to the first recording medium group, which has an Oken smoothness of 2000 seconds or more. Silk coated, satin, and semi-gloss coated paper belong to the second recording medium group, which has an Oken smoothness of 500 seconds or more but less than 2000 seconds. Fine paper, plain paper, and inkjet matte paper belong to the third recording medium group, which has an Oken smoothness of less than 500 seconds.

[0025] The relationship between paper type and Oken smoothness is stored in advance in memory unit 8. As a result, when a user inputs the paper type of paper S stored in cassette CA into operation unit 10, control unit 7 classifies paper S into one of the first recording medium group, second recording medium group, or third recording medium group based on the relationship between paper type and Oken smoothness. Note that in this embodiment, paper S is classified into three groups based on Oken smoothness, but the present invention may also classify paper S into four or more groups, or into two groups.

[0026] 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. Figs. 4 and 5 show ink ejection positions and ink droplet positions on paper S belonging to the third recording medium group. Figs. 4 and 5 show ink ejection positions and ink droplet 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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. 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 other stages, such as five stages. The larger the ink droplet size, the higher the gradation (density) of the pixel.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] The degree to which ink droplets penetrate into the paper S differs depending on the type of paper S. Furthermore, the amount of movement of ink droplets in the correction pixel area Ap2 that move due to landing interference differs depending on the degree to which ink droplets in the previously deposited adjacent pixel area Ap3 penetrate into the paper S.

[0046] Specifically, when the degree to which ink droplets previously deposited on the adjacent pixel region Ap3 penetrate into the paper S is large, the impact of landing interference is reduced. This reduces the movement distance of ink droplets ejected onto the correction pixel region Ap2. This could result in color streaks occurring in the correction pixel region Ap2. On the other hand, when the degree to which ink droplets previously deposited on the adjacent pixel region Ap3 penetrate into the paper S is small, the impact of landing interference is difficult to reduce. This increases the movement distance of ink droplets ejected onto the correction pixel region Ap2. This could result in white streaks remaining in the defective pixel region Ap1.

[0047] In this embodiment, the degree to which ink droplets penetrate into the paper S is determined based on the Oken smoothness of the paper S, and the amount of ink ejected into the correction pixel area Ap2 is changed according to the Oken smoothness of the paper S. Specifically, the amount of ink ejected into the correction pixel area Ap2 is reduced as the Oken smoothness of the paper S increases.

[0048] FIG. 6 is an explanatory diagram showing ink ejection positions. In FIG. 6, ink droplets M1 ejected onto the correction pixel area Ap2 on paper S belonging to the third recording medium group are shown by solid lines. Furthermore, ink droplets M2 ejected onto the correction pixel area Ap2 on paper S belonging to the second recording medium group are shown by dashed lines. Furthermore, ink droplets M3 ejected onto the correction pixel area Ap2 on paper S belonging to the first recording medium group are shown by dashed lines. In this embodiment, the large-sized ink droplets ejected onto the correction pixel area Ap2 can be further changed into three stages: ink droplets M1, ink droplets M2, and ink droplets M3, by increasing or decreasing the ink ejection amount.

[0049] The amount of ink ejected onto the correction pixel area Ap2 decreases in stages in the order of the third recording medium group, in which the Oken-type smoothness of the paper S is less than 500 seconds, the second recording medium group, in which the Oken-type smoothness of the paper S is 500 seconds or more but less than 2000 seconds, and the first recording medium group, in which the Oken-type smoothness of the paper S is 2000 seconds or more.

[0050] When using paper S belonging to the second or third recording medium group, which has a lower Oken smoothness than paper S belonging to the first recording medium group and which has a greater degree of penetration of ink droplets previously deposited into the adjacent pixel region Ap3, the amount of ink droplets moving toward the adjacent pixel region Ap3 decreases. In this case, ejecting ink droplets M2 or M3 onto the correction pixel region Ap2 reduces the amount of ink ejected into the correction pixel region Ap2. This further reduces the occurrence of black streaks (color streaks) in the correction pixel region Ap2.

[0051] On the other hand, when using paper S belonging to the first recording medium group, which has a higher Oken smoothness than paper S belonging to the second or third recording medium group and which has a lower degree of penetration of ink droplets previously deposited into the adjacent pixel region Ap3, the amount of ink droplets moving toward the adjacent pixel region Ap3 increases. In this case, by ejecting ink droplets M1 onto the correction pixel region Ap2 (see FIG. 4), the amount of ink ejected into the correction pixel region Ap2 increases. Therefore, the occurrence of white streaks in the defective pixel region Ap1 can be reduced. This makes it possible to correct defective nozzles according to the type of paper (recording medium) S and suppress degradation of image quality.

[0052] The control unit 7 increases the amount of ink ejected into the correction pixel area AP2 as the Oken smoothness of the paper S increases only when ink droplets have already been ejected into the adjacent pixel area Ap3. In other words, the ink ejection amount does not change for correction pixel area AP2 where there are no ink droplets previously ejected into the adjacent pixel area Ap3, even if the paper type is changed. This makes it possible to prevent image defects from occurring due to changes in the ink ejection amount in correction pixel area AP2, which is not affected by landing interference.

[0053] 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.

[0054] FIG. 7 is a flowchart showing an example of image processing performed by the inkjet recording device 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 being executed. The correction mode is executed, for example, when the user inputs the paper type of the paper S stored in the cassette CA into the operation unit 10. When the correction mode is executed, the control unit 7 classifies the paper S input by the user into one of the first, second, or third recording medium groups based on the relationship between the paper type and the Oken smoothness, and stores the classification in the memory unit 8 (step S1). Next, it is detected whether there is a nozzle 52 that has experienced a defect such as non-ejection (step S2).

[0055] 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 S2), the faulty nozzle 52 is identified and stored in memory unit 8.

[0056] In step S3, 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 S3), the process proceeds to step S4.

[0057] In step S4, the drive conditions of the recording head 51 are corrected. This corrects the amount of ink droplets ejected from the nozzles 52 around the defective nozzle 52. At this time, the amount of ink ejected into the correction pixel area Ap2 is corrected according to the classification of the paper S stored in the memory unit 8. The corrected drive conditions of the recording head 51 are stored in the memory unit 8. As a result, when the normal recording mode is executed, an image is formed based on the corrected drive conditions of the recording head 51. Therefore, when the recording mode is executed, the occurrence of white streaks and black streaks (color streaks) can be reduced. This makes it possible to correct the defective nozzle according to the type of paper (recording medium) S and suppress degradation of image quality.

[0058] Next, an evaluation was made as to whether the occurrence of image defects could be suppressed by correcting the amount of ink droplets ejected from the nozzles 52 around the defective nozzle 52 depending on the type of paper (recording medium) S.

[0059] As an evaluation method, correction of defective nozzles according to Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 was carried out on papers A to F with different Oken-type smoothness. When carrying out correction, ink droplets were ejected onto all of the corresponding correction pixel regions Ap2 for the 41 defective nozzles 52 belonging to the pre-ejection nozzle group. At this time, ink droplets had already been pre-ejected into the adjacent pixel region Ap3.

[0060] Under the corrected driving conditions of the recording head 51, a full-surface solid image was printed on paper sheets A to F. After printing, the number of white streaks and color streaks around the defective nozzle 52 was counted and summarized in the table of FIG. 8. If no white streaks or color streaks occurred, the result was judged as good (◯). If white streaks or color streaks occurred, the result was judged as bad (×). In FIG. 8, the number in parentheses indicates the number of white streaks that occurred, and the number outside the parentheses indicates the total number of white streaks and color streaks that occurred.

[0061] Paper A used fine paper with an Oken smoothness of 90 seconds. Paper B used fine paper with an Oken smoothness of 105 seconds. Paper C used semi-gloss coated paper with an Oken smoothness of 650 seconds. Paper D used semi-gloss coated paper with an Oken smoothness of 1800 seconds. Paper E used gloss coated paper with an Oken smoothness of 3000 seconds. Paper F used gloss coated paper with an Oken smoothness of 5000 seconds.

[0062] In Example 1, papers A to F were classified into a first recording medium group, a second recording medium group, and a third recording medium group based on their Oken smoothness. Paper E and paper F, which have an Oken smoothness of 2000 seconds or more, belong to the first recording medium group. Paper C and paper D, which have an Oken smoothness of 500 seconds or more but less than 2000 seconds, belong to the second recording medium group. Paper A and paper B, which have an Oken smoothness of less than 500 seconds, belong to the third recording medium group.

[0063] In Example 1, the amount of ink ejected onto the correction pixel area Ap2 was gradually reduced in the order of the third recording medium group, the second recording medium group, and the first recording medium group. Specifically, ink droplets of a first size were ejected onto paper E and paper F belonging to the first recording medium group (see ink droplets M3 in FIG. 6). Ink droplets of a second size were ejected onto paper C and paper D belonging to the second recording medium group (see ink droplets M2 in FIG. 6). Ink droplets of a third size were ejected onto paper A and paper B belonging to the third recording medium group (see ink droplets M1 in FIG. 6). The ink droplet size decreases in the order of the third size, the second size, and the first size, and the ink ejection amount also decreases.

[0064] In Comparative Example 1, ink droplets of the third size were ejected onto the correction pixel area Ap2 for all papers belonging to the first, second, and third recording medium groups. In Comparative Example 2, ink droplets of the second size were ejected onto the correction pixel area Ap2 for all papers belonging to the first, second, and third recording medium groups. In Comparative Example 3, ink droplets of the first size were ejected onto the correction pixel area Ap2 for all papers belonging to the first, second, and third recording medium groups.

[0065] 8, it was found that in the evaluation of Example 1, the occurrence of white streaks and color streaks can be suppressed and the occurrence of image defects can be reduced by correcting the defective nozzle 52 according to the paper type. On the other hand, in the evaluation of Comparative Examples 1 to 3, it was found that image defects occur depending on the paper type.

[0066] While 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, the correction of the incorrect nozzles 52 does not need to be changed in all correction pixel areas Ap2 of the image pattern depending on the Oken smoothness of the paper S. In other words, the increase in the amount of ink ejected into some of the correction pixel areas Ap2 of the image pattern may be the same regardless of the Oken smoothness of the paper S. [Industrial Applicability]

[0067] The present invention can be used in inkjet recording apparatuses. [Explanation of symbols]

[0068] 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 9 Display section 10 Control 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 and records an input image pattern 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 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 region as the Oken smoothness of the recording medium increases.

2. 2. The inkjet recording device according to claim 1, wherein the control unit reduces the amount of ink ejected onto the correction pixel area as the Oken smoothness of the recording medium increases only when ink droplets have already been ejected onto an adjacent pixel area that is adjacent to the defective pixel area on the opposite side of the correction pixel area in the cross direction.

3. the control unit is capable of changing the increase / decrease of the ink ejection amount in multiple stages, The recording media are classified into a first recording medium group having an Oken smoothness of 2000 seconds or more, a second recording medium group having an Oken smoothness of 500 seconds or more but less than 2000 seconds, and a third recording medium group having an Oken smoothness of less than 500 seconds, 3. The inkjet recording apparatus according to claim 1, wherein the amount of ink ejected onto the correction pixel region decreases stepwise in the order of the third recording medium group, the second recording medium group, and the first recording medium group.

4. 4. The ink jet recording apparatus according to claim 3, wherein an increase in the amount of ink ejected onto the portion of the correction pixel region of the image pattern is the same regardless of the Oken smoothness of the recording medium.

5. 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.

6. 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.

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