JP2005305695A - Ink jet printer and method for correcting ejection timing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance image quality of print furthermore by contriving correction method of ejection timing in an ink jet printer having a print head H arranged with a plurality of nozzle arrays each ejecting ink of different color. <P>SOLUTION: Test patterns for matching the ink impact position in the main scanning direction between going and returning stroke of scanning are formed of two colors or more of ink, and ejection timing of ink is corrected based on the data being obtained from test patterns formed of two colors or more of ink. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ink jet printing apparatus and an ink ejection timing correction method in the apparatus.

2. Related Art There is known an ink jet printing apparatus that ejects ink onto a print paper from a print head that reciprocates in the main scanning direction (width direction of the print paper). In such a printing apparatus, the printing speed is increased by performing bi-directional printing that ejects ink both during forward scanning and during backward scanning (see, for example, Patent Document 1). In a printing apparatus that performs such bi-directional printing, it is necessary to match the ink landing position during forward scanning with the ink landing position during backward scanning in the main scanning direction in order to improve the print quality. Therefore, in the printing apparatus disclosed in Patent Document 1, a test pattern is created on the print paper, and ink ejection timing is corrected during backward scanning based on the pattern.
JP 2000-296609 A

  By the way, when the ink ejection timing is corrected so as to match the ink landing positions between the reciprocating scans, usually, a test pattern is created with the reference ink (for example, black ink), and the ink ejection of the print head is performed based on the test pattern. The timing is corrected. However, a print head that performs color printing has a plurality of nozzle rows that eject inks of different colors, and the reference ink is caused by the physical properties (for example, viscosity) of the inks of the respective colors being different from each other. Even if the ink ejection timing is corrected based on the test pattern created in step 1, the landing positions of the inks of other colors may be shifted between the reciprocating scans.

  On the other hand, the printing apparatus disclosed in Patent Document 1 uses a correction value based on a test pattern created with reference ink as a reference correction value, and a deviation of the landing position of another ink with respect to the reference ink as a relative correction value. The ink ejection timing is corrected based on the reference correction value and the relative correction value.

  However, even if the ink ejection timing is corrected based on the reference correction value and the relative correction value, the image quality may not be improved much.

  For example, when image data or printing device processing does not require reference ink at the time of printing, for example, in a system that develops black using magenta, cyan, and yellow ink instead of black ink, the black ink is used as the reference. Even if the correction timing is set and the ejection timing is corrected, if the misregistration of the inks of other colors is large, the image quality is deteriorated. Therefore, the discharge timing correction method disclosed in Patent Document 1 has room for improvement in improving image quality.

  The present invention has been made in view of the above points, and an object of the present invention is to provide an ejection timing of an inkjet printing apparatus including a print head having a plurality of nozzle rows that eject inks of different colors. By devising the correction method, the image quality is further improved.

  An ink jet printing apparatus according to the present invention has a plurality of nozzle rows that eject inks of different colors, and ejects ink while reciprocating in the main scanning direction, and the ink ejection timing of the print head. A pattern creating means for creating a test pattern for correction on the print member; and a correcting means for correcting the ink ejection timing of the print head based on data obtained from the test pattern created by the pattern creating means; .

  The pattern creating means creates a test pattern for matching the ink landing position in the main scanning direction between the reciprocating scans with two or more inks, and the correcting means corrects the ink ejection timing with two colors. This is performed based on data obtained from each of the test patterns created with the above inks.

  According to this configuration, the pattern creating unit creates two or more test patterns with two or more colors of ink, and the correcting unit determines the ejection timing based on data obtained from each of the test patterns created with two or more colors of ink. In order to perform correction, variations in ink landing positions due to differences in nozzle arrays, ink physical properties, and the like are smaller than in the case of correcting ejection timing based on a test pattern created with a specific one ink. . In addition, by creating the test pattern itself with two or more colors of ink, it is possible to reliably grasp the deviation of the ink landing position for each color. As a result, the discharge timing correction accuracy can be further improved.

  Further, when the ejection timing is corrected based on a test pattern created with one specific ink, if the tendency of variation in the landing position of each color ink in each print head is different, printing between printing apparatuses Although variations occur in quality, by correcting the ejection timing based on a test pattern created with two or more colors of ink, machine differences between printing apparatuses are reduced, and print quality can be averaged.

  The print head has a plurality of head units arranged side by side in a sub-scanning direction orthogonal to the main scanning direction, and each head unit has a plurality of nozzle rows that discharge inks of different colors, The pattern creating means matches the ink landing position in the main scanning direction between the plurality of head units in the main scanning direction and the ink landing position in the main scanning direction between the reciprocating scans in the head units. The Bi test pattern is created with two or more colors of ink, and the correction means performs two or more colors of ejection timing correction based on the Uni test pattern and ejection timing correction based on the Bi test pattern. Based on the data obtained from each test pattern created with ink Cormorants, it may be.

  In this printing apparatus, since a plurality of head units are arranged in the sub-scanning direction on the print head, the printing speed can be further increased and the image quality can be improved. Needless to match the ink landing positions between the scans, it is necessary to match the ink landing positions between the plurality of head units.

  Therefore, the pattern creating means includes a Uni test pattern for matching the ink landing positions in the main scanning direction between the plurality of head units, and a Bi test pattern for matching the ink landing positions between the reciprocating scans in each head unit. , Create. At this time, each of the Uni and Bi test patterns is created with two or more colors of ink, and the correction unit performs correction of ejection timing based on the Uni test pattern and ejection timing correction based on the Bi test pattern. This is based on data obtained from each test pattern created with ink of a color or higher. As a result, as described above, the variation in the ink landing position for each color due to the difference in the nozzle rows, the difference in the ink physical properties, and the like is reduced, and the print quality is improved.

  The correction unit may set a single color correction value based on a test pattern for each ink color, and may use an average value of the plurality of set single color correction values as a set correction value for the ejection timing of each head unit.

  Further, the correction means may use a weighted average value obtained by weighting a single color correction value of an ink color having a great influence on the print image quality as a setting correction value for the ejection timing of each head unit. Here, the “ink color having a large influence on the print image quality” is determined by the type of ink to be used, image data to be printed, image processing technique, and other factors. For example, if black, magenta, and cyan inks are processed to develop a black color, the magenta and cyan colors have a greater influence on the print image quality than the black ink.

  Then, by setting the set correction value of the ejection timing of each head unit to a weighted average value obtained by weighting the single color correction value of the ink color having a large influence on the print image quality, the landing of the ink color having a large influence on the print image quality is achieved. The positional deviation becomes relatively small. For this reason, print quality further increases. It is also possible to store each single color correction value and set a set correction value optimized according to the image data to be printed each time.

  The printing apparatus further includes a reflective sensor that scans in the main scanning direction integrally with the print head and detects data obtained from the test pattern created by the pattern creation unit, and the pattern creation unit includes: As the test pattern, a variable pitch formed by ejecting ink while shifting the phase with respect to the reference timing to a reference pitch pattern formed by ejecting ink at the reference timing while scanning the print head in the main scanning direction. A gradation pattern in which the patterns are superimposed is created, the reflection type sensor detects a change in shading of the gradation pattern, and the correction means detects ink of each head unit based on the change in shading detected by the reflection type sensor. The ejection timing may be corrected.

  When the pattern creating means creates a gradation pattern, the accuracy of correcting the ink ejection timing of each head unit is further increased. That is, the gradation pattern is formed by ejecting ink while shifting the phase with respect to the reference timing to the reference pitch pattern formed by ejecting ink at the reference timing while scanning the print head in the main scanning direction. This is a superposition of variable pitch patterns, where the portion where the ink landing positions coincide is light and shaded, and the portion where the ink landing position is shifted becomes dark and light. By detecting such a change in gradation of the gradation pattern by a reflective sensor that is scanned in the main scanning direction, it is possible to detect the deviation of the landing position with a resolution higher than the pitch of the test pattern. As a result, the ink discharge timing correction accuracy of each head unit is further increased.

  The ejection timing correction method of the present invention is an ejection timing of an ink jet recording apparatus that ejects ink onto a print member while reciprocally scanning a print head having a plurality of nozzle arrays that eject ink of different colors in the main scanning direction. This is a correction method.

  The ejection timing correction method is based on the test pattern creation step for creating a test pattern for matching the ink landing position in the main scanning direction between reciprocating scans, and the test pattern created in the test pattern creation step. And a correction step of correcting the ink discharge timing of the print head.

  The test pattern creation step is a step of creating a test pattern with two or more colors of ink, and the correction step is data obtained from each of the test patterns created with two or more colors of ink for correcting the ink ejection timing. It is set as the process performed based on.

  Further, according to another ejection timing correction method of the present invention, a print head in which a plurality of head units each having a plurality of nozzle rows that eject inks of different colors are arranged in a sub-scanning direction orthogonal to the main scanning direction, An ejection timing correction method for an ink jet recording apparatus that ejects ink onto a print member while performing reciprocal scanning in the main scanning direction.

  The ejection timing correction method includes a Uni test pattern creation step for creating a Uni test pattern for matching the ink landing positions in the main scanning direction between the plurality of head units, and the reciprocating scanning in each head unit. Based on the Bi test pattern creation process for creating a Bi test pattern for matching the ink landing position with respect to the main scanning direction, and the data obtained from the Uni and Bi test pattern created in the Uni and Bi test pattern creation process, A correction step of correcting the ink discharge timing of each head unit.

  The Uni and Bi test pattern creation step is a step of creating a Uni and Bi test pattern with two or more colors of ink, respectively, and the correction step includes correcting the ejection timing based on the Uni test pattern and the Bi test pattern. Based on the data obtained from each test pattern created with two or more inks, the ejection timing correction based on this is performed.

  According to the ink jet printing apparatus and the ejection timing correction method of the present invention, a test pattern is created with two or more colors of ink, and the ejection timing is determined based on data obtained from each of the test patterns created with the two or more colors of ink. By performing the correction, the variation in the ink landing position for each color due to the difference in the nozzle row, the difference in the ink physical properties, and the like is reduced, and the test pattern itself is created with two or more colors, so that each color Since the deviation amount of the ink landing position is reliably grasped, it is possible to improve the correction accuracy of the ejection timing. It is also possible to average the print quality between the printing apparatuses by absorbing variations in the landing positions for each color in the individual print heads.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[overall structure]
As shown in FIG. 1, an ink jet printing apparatus according to an embodiment of the present invention includes a reception block A that performs image data acquisition and order information acquisition to perform necessary correction processing, and communication from the reception block A. And a print block B that prints image data transmitted via the cable 1 on the print paper P based on the order information.

[Reception block]
The reception block A is provided at an intermediate position in the vertical direction of the frame 5, a reception device 6 provided at the top of the wagon frame 5, a liquid crystal display 8 whose display screen is constituted by the touch panel 7, and the frame 5. And a flatbed scanner FS. On the front surface of the accepting device 6, a semiconductor drive 9 for reading out image data stored in a recording medium Ms composed of a flash memory, and image data stored in a disk-type recording medium Md such as a CD-R or DVD. And a disk drive 10 for reading the data.

  The flat bed scanner FS includes a main body portion 11 having a scanning table 13 made of transparent glass and a scanning head 14 disposed below the scanning table 13, and a platen cover 12 attached to the main body portion 11 so as to be freely opened and closed. And. The scanning head 14 includes a plurality of photoelectric conversion elements (for example, a CCD or the like) disposed in the main scanning direction and a light source, and is placed on the scanning table 13 by moving in the sub scanning direction orthogonal to the main scanning direction. The image of the scanned object is captured as image data that is color-separated into three primary colors of R (red), G (green), and B (blue).

[Print Block]
As shown in FIG. 1 and FIG. 2, the print block B is arranged on the casing 15, two magazine housing portions Ba and Ba arranged at the lower part of the casing 15, and arranged at the upper part of the casing 15 and printed. A printing unit Bb that records image data on the paper P and an ink storage unit Bc disposed on the side of the housing 15 are provided. On the upper surface of the housing 15, a sorting unit 17 that receives the small-size print paper P that is fed by the lateral feed belt 16 and a rack plate 18 that receives the large-size print paper P are disposed.

  The magazine housing portion Ba includes a drawer 20 that slides as the front wall body 15A slides, and is configured to house the roll-shaped print paper P held by the paper magazine 21 in the drawer 20. . The width of the print paper P stored in the lower magazine storage portion Ba is larger than that of the print paper P stored in the upper magazine storage portion Ba (see FIG. 2).

  The print unit Bb includes a print head H that is provided in the wall 15B and that forms an image by spraying ink onto the print paper P.

  The ink reservoir Bc includes seven ink cartridges 23,... That are detachably accommodated in the wall 15C and have different hues. These ink cartridges 23,... Can be replaced with new ink cartridges 23 by being inserted and removed. Each of these ink cartridges 23,... Has black (K), light black (LK), cyan (C), magenta (M), light cyan (LC), light magenta (LM) and yellow (Y) inks. It is enclosed. The wall body 15C is configured to be swingable and openable about an axis extending in the vertical direction.

[Paper transport mechanism]
As shown in FIG. 3, the paper transport mechanism includes a supply unit U1, a print unit U2, a loop forming unit U3, a cutter unit U4, a reversing unit U5, and a discharge unit U6. In the paper transport mechanism, when image data is printed on the print paper P, the print unit P1 stores the print paper P stored in one of the two magazine storage units Ba and Ba by the printing unit. Then, image data is printed by the print head H while the supplied print paper P is conveyed by the print unit U2, and then the printed print paper P is transferred from the loop forming unit U3 to the cutter unit U4. After being cut into print sizes, the paper is fed to the lateral feed belt 16 or the rack plate 18 by the reversing unit U5 and the discharge unit U6.

  More specifically, the supply unit U1 includes a support roller 25 that applies a rotational force to the print paper P accommodated in the paper magazine 21, and a pressure-bonding type for conveying the print paper P from the paper magazine 21 to the print unit U2. A supply roller 26 and a guide member (not shown) for guiding the print paper P conveyed by the supply roller 26 are provided. The support roller 25 and the supply roller 26 are driven by an electric motor for supply and conveyance.

  The print unit U2 includes a guide rail 28 that guides the print head H in the main scanning direction, a drive belt 30 that is wound around a pulley 29 and moves the printer head H back and forth along the guide rail 28, and printer paper P. A paper holding unit D that sucks and holds the head H at a position where printing can be performed, and pressure-type print transport rollers 31 and 31 disposed on the upstream side and the downstream side of the paper holding unit D are provided. Yes. The paper holding unit D includes a guide plate 32 having a plurality of holes formed in the thickness direction, and a fan that is provided in the housing 33 and applies negative pressure to the print paper P through the holes of the guide plate 32. 34. When the print unit U2 (print unit Bb) performs printing on the print paper P, the image is printed at a predetermined interval and a cut mark is formed in an area between the adjacent images. To do.

  As shown in FIG. 3, the loop forming unit U <b> 3 includes a guide plate 36 disposed on the downstream side of the downstream print transport roller 31 and a pressure-bonding mold for transporting the print paper P guided by the guide plate 36. Intermediate roller 37. The guide plate 36 is configured to be switchable between a horizontal posture (dotted line in FIG. 3) extending substantially in the horizontal direction and an open posture (solid line in FIG. 3) extending in the vertical direction. In the loop forming unit U3, when printing a long print paper P, the front end portion of the print paper P is transferred to the intermediate roller 37 through the horizontal guide plate 36 and then printed by the intermediate roller 37. The conveyance of the paper P is stopped, and then the guide plate 36 is switched from the horizontal posture to the open posture, and the print paper P is suspended to form a loop.

  The cutter unit U4 includes a fixed blade 39, a movable blade 40, a cut position sensor 41 having a reflective sensor, and a pressure-feeding type feeding roller 42 for feeding out the print paper P. In the cutter unit U4, when cutting, by removing the region so as to be slightly wider than the interval between adjacent images based on the detection result of the cut position sensor 41, In borderless printing, the cutting operation is performed so as not to leave a margin around the image.

  As shown in FIG. 3, the reversing unit U5 includes a pressure-reversal reversing roller 43 that crimps the printer paper P, a transport drive mechanism (not shown) that rotates the reversing roller 43 forward and backward, and a pair of reversing rollers 43. And a reversing mechanism for rotating the roller 43 by 90 degrees around the axis of the roller. Then, in the reversing unit U5, the print paper P fed from the front end side by the cutter unit U4 is conveyed by the reversing roller 43 so that the rear end portion reaches the position of the reversing roller 43, and is indicated by an arrow in FIG. In this way, the reversing unit U5 is rotated 90 degrees around the axis, and then the reversing roller 43 is rotated in the reverse direction to feed the print paper P from the rear end to the discharge unit U6.

  The discharge unit U6 includes a plurality of pressure-bonding type carry-out rollers 44 for conveying the print paper P, and the print paper P conveyed by the carry-out rollers 44,. A path switching mechanism (not shown) for sending out to one side is provided.

[Print head]
As shown in FIGS. 3 and 4, the print head H is provided with three head units 51 each having a plurality of ink discharge nozzles arranged on the bottom side thereof. For convenience, among the head units 51 provided in three stages, the upper stage (front side in the transport direction of the print paper P) is the first head unit 51a, the middle stage is the second head unit 51b, and the lower stage (the transport direction of the print paper P). The rear side) is referred to as a third head unit 51c.

  In the present embodiment, all the head units 51 have the same configuration. As shown in FIG. 4, each head unit 51 has black (K), light black (LK), cyan (C), magenta (M ), Light cyan (LC), light magenta (LM) and yellow (Y) ink. In each nozzle array 54, ink ejection nozzles are arranged in a row in the sub-scanning direction orthogonal to the main scanning direction that is the scanning direction of the print head H. Thus, each head unit 51 is configured to be able to form a color image by itself.

  A reflective sensor S is attached to the print head H at the front side in the transport direction of the print paper P. The sensor S reciprocates in the main scanning direction together with the print head H, and detects the density of a test pattern (gradation pattern) created on the print paper P as will be described later.

[Control system]
The control system of the printing apparatus is configured as shown in FIG. That is, the receiving device 6 of the receiving block A transmits and receives information between a microprocessor (hereinafter referred to as a CPU) and the CPU via a data bus. The touch panel 7, the display 8, the semiconductor drive 9, and the disk drive 10 A semiconductor memory RAM / ROM, a hard disk HD, and a communication interface 61. The receiving device 6 further includes an operation system 62, an image processing system 63, and a printer driver 64, which are made of software for realizing the processing of the CPU. The accepting device 6 constitutes an input / output system for transmitting / receiving information to / from the flatbed scanner FS, and further constitutes a signal system for transmitting / receiving information to / from the print block via the communication interface 61. Yes.

  The print block B transmits / receives information to / from a microprocessor (hereinafter referred to as “CPU”) and the CPU via a data bus. The transport control unit 66, the head control unit 67, the semiconductor memory RAM / ROM, the reflection A mold sensor S, a cut position sensor 41, an attachment / detachment sensor 65 for determining whether or not the ink cartridge 23 is present in the ink reservoir Bc, and a communication interface 68 are provided. The print block B further includes a print control unit 69, a pattern creation unit 71, and a correction unit 72, which are made of software for realizing the processing of the CPU.

  The transport control unit 66 is for controlling each of the units U1, U2, U3, U4, U5, U6 of the paper transport mechanism. The head controller 67 is for controlling the print head H. The print control means 69 is for performing control when printing the image data on the print paper P based on the image data sent from the receiving block A. The head unit 51 of the third head units 51a to 51c is also assigned for image formation.

  The pattern creating means 71 is for creating a test pattern on the print paper P. The correcting means 72 is for correcting the ink ejection timing of each head unit 51 based on the data obtained from the created test pattern.

[Discharge timing correction]
Next, correction of the ink ejection timing of each head unit 51 will be described. The printing apparatus includes the first to third head units 51a to 51c in the print head H, and performs bi-directional printing that ejects ink both during forward scanning and during backward scanning. For this reason, among the first to third head units 51a to 51c, the third head unit 51c is used as a reference head unit, and the forward and backward scanning ejections of the first and second head units 51a and 51b (adjustment head unit). The correction of the timing and the correction of the ejection timing of the backward scanning of the third head unit 51c are performed. In this printing apparatus, the ejection timing is corrected in units of head units 51, and is not corrected in units of nozzle arrays 54 of each head unit 51.

  The ink ejection timing correction process is performed according to the flowchart shown in FIG. First, if a magazine is selected in step S1, sensitivity calibration of the reflective sensor S is executed (step S2). If the sensitivity calibration of the sensor S is normally completed (step S3), a test pattern is created on the print paper P, and a change in the density of the created test pattern is detected by the reflective sensor S (step S3). S4).

  In step S4, the Uni test pattern for matching the ink landing positions of the first and second head units 51a and 51b with the ink landing positions of the third head unit 51c and the ink landing positions of the third head unit 51c and The Bi test pattern for matching the ink landing positions at the time of backward scanning of the first to third head units 51a to 51c with the ink landing positions at the time of forward scanning of the third head unit 51c. Created.

  Both the Uni test pattern and the Bi test pattern are composed of gradation patterns, and the gradation patterns are created as follows. That is, as shown in FIG. 7, first, the reference pitch pattern 52 is formed by ejecting ink at the reference timing from the third head unit 51 c that is the reference head unit while performing forward scanning of the print head H. The reference pitch pattern 52 is a pattern having substantially the same pitch.

  Then, when creating the Uni test pattern, the phase is changed from + α with respect to the reference timing from the first or second head unit 51a, 51b, which is the adjustment head unit, while scanning the print head H in the same manner. Ink is ejected while continuously (or stepwise) changing to -α. As a result, the variable pitch pattern 53 is superimposed on the reference pitch pattern 52.

  On the other hand, when creating a Bi test pattern, the phase is changed from -α to + α with respect to the reference timing from the first, second, or third head unit 51a, 51b, 51c while backward scanning the print head H. Ink is ejected while changing continuously (or stepwise). As a result, the variable pitch pattern 53 is superimposed on the reference pitch pattern 52.

  In this way, by superimposing the reference pitch pattern 52 and the variable pitch pattern 53, a gradation pattern extending in the main scanning direction is created. In FIG. 7, for ease of understanding, the reference pitch pattern 52 and the variable pitch pattern 53 are shifted in the sub-scanning direction. However, both pitch patterns 52 and 53 may be formed at the same position in the sub-scanning direction. .

  In this gradation pattern, the portion where the ink landing position (printing position) is matched, that is, the center portion of the gradation pattern is light and the portion where the ink landing position (printing position) is shifted, that is, both end portions of the gradation pattern. Becomes darker and darker. Therefore, by detecting the gradation of the gradation pattern in the main scanning direction by the reflective sensor S, a curve of the gradation change with respect to the phase is obtained as shown in the lower diagram of FIG.

  Here, in an ideal case, in other words, when the correction value of the ink ejection timing is 0, the gray level is the lightest at the phase 0 position (the center position in the main scanning direction of the gradation pattern). On the other hand, when the position of the lightest shade in the shade change curve is shifted from the position of phase 0, in order to match the ink landing position, the ejection timing is set by an amount corresponding to the shift amount Δ. It is necessary to correct. In other words, the discharge timing correction value can be obtained by detecting the shift amount Δ from the gradation pattern.

  In step S4, the Uni test pattern and the Bi test pattern are created on the same print paper P at the same time. Specifically, as shown in FIG. 8, a total of 20 test patterns are formed side by side in the sub-scanning direction at each of the right side position and the left side position of the print paper P.

The 20 test patterns include a reference pitch pattern created with black ink during the forward scanning of the third head unit 51c.
(1) A first Uni (K) fine adjustment pattern obtained by superimposing a variable pitch pattern created by black ink during forward scanning of the first head unit 51a. (2) A variable pitch pattern created by black ink during backward scanning. Superposed first Bi (K) fine adjustment pattern (3) Second Uni (K) fine adjustment pattern (4) superposed with a variable pitch pattern created by black ink during the forward scanning of the second head unit 51b. A second Bi (K) fine adjustment pattern obtained by superimposing a variable pitch pattern created by black ink at the time of reverse scanning, and a variable pitch pattern created by black ink at the time of forward scanning of the third head unit 51c. Third Uni (K) fine adjustment pattern (6) Black ink at the time of reverse scanning Accordingly it includes six test patterns of the third Bi (K) fine adjustment pattern obtained by superposing a variable pitch pattern generated.

  In addition, the above six test patterns were created with cyan ink and six test patterns (first to third Uni (M) and Bi (M) fine adjustment patterns) created with magenta ink instead of black ink. Six test patterns (first to third Uni (C) and Bi (C) fine adjustment patterns) are included.

  Furthermore, the first and second Uni (K) coarse adjustment patterns having a coarser pitch than the fine adjustment pattern are included.

  In this way, by creating each Uni and Bi test pattern on the same print paper P at the same time, the conditions for pattern creation match each other. As a result, the ink discharge timing correction accuracy of each head unit 51 can be improved. Further, this contributes to saving of the print paper P and shortens the pattern creation time.

  In step S4, during and / or after the test pattern is created, the reflective sensor S is scanned in the main scanning direction to detect a change in density of each Uni and Bi test pattern in the main scanning direction. At this time, the change in shading of one of the left and right positions of the print paper P may be detected, or the change in shading of both the left and right test patterns may be detected and averaged.

  If a change in shading of each test pattern is detected, as described above, the lightest shade position in each test pattern is specified, and thereby the shift amount Δ is specified for each test pattern. Then, based on the deviation amount Δ of the test pattern, the ink ejection timing at the time of forward scanning and the backward scanning of the first head unit 51a, the ink ejection timing at the time of forward scanning and the backward scanning of the second head unit 51b. And the ink ejection timing during the backward scanning of the third head unit 51c is corrected (step S5).

  Here, the correction value of the ink ejection timing is determined as a correction value (monochromatic correction value) from the deviation amount Δ in each of the test patterns created with black, magenta, and cyan inks, and an average of the plurality of single color correction values. The value is a correction value (setting correction value) of the ink ejection timing of each head unit 51. At this time, a weighted average value obtained by weighting a single color correction value of a color having a large influence on the print image quality may be used as the setting correction value. Colors that have a large effect on print image quality are determined by the type of ink used, image data to be printed, image processing technique, and other factors. For example, a color having a great influence on graininess or a color having a high ratio used for printing can be used. Further, if this apparatus performs a process of developing black with yellow, magenta, and cyan inks, the colors that have a great influence on the print image quality are produced by magenta and cyan.

  The data obtained from the first and second Uni (K) coarse adjustment patterns and the third Uni (K, M, C) fine adjustment pattern are not used for determining the correction value. Therefore, these test patterns may be omitted.

  In this way, by determining the correction value of the ink ejection timing based on the test pattern created with two or more colors of ink, the print quality can be improved.

  That is, even if the landing positions of one specific ink are matched by the tolerance between the nozzle arrays 54 of each head unit 51 or the difference in physical properties between the ink colors, the landing positions of the other color inks are matched. May shift. Therefore, a test pattern is created with two or more colors of ink, and a single color correction value is determined based on data (deviation amount Δ) obtained from each of the created test patterns. Then, by using the average value of the single color correction values as the set correction value of the head unit 51, the deviation of the landing positions of the inks of the respective colors can be reduced. As a result, it is possible to improve the print quality. In particular, by weighting the single color correction values for colors that have a large effect on print image quality and determining the head unit setting correction values, the displacement of the landing positions of colors that have a large effect on print image quality is relatively reduced. Therefore, the print quality can be greatly improved.

  Also, by creating test patterns with two or more inks and storing each single color correction value obtained from each test pattern, setting correction values optimized according to the image data to be printed are set each time. It is also possible to do.

  Further, when the correction value is determined by one specific ink, if the variation tendency of the landing positions of the inks of the respective colors in the individual print heads H (head units 51) is different, the printing apparatuses (head units 51) are different. The print quality varies between the head units 51 and between the printing apparatuses by determining the correction value of each head unit 51 based on the test pattern created with two or more colors of ink. Becomes smaller. That is, the print quality can be averaged by reducing the machine difference of the printing apparatus.

  The Uni and Bi test patterns are not limited to gradation patterns, and may be other patterns.

  In the above embodiment, the test pattern is created by using black, magenta, and cyan inks. However, the present invention is not limited to this, and the ink for creating the test pattern may be other combinations. In that case, it is preferable to select a color having a large influence on the print image quality. Further, the test pattern may be created with all colors (seven colors in the embodiment) ejected by each head unit 51.

  Furthermore, although the reflective sensor S is provided in the print head H in the above embodiment, the reflective sensor S can be omitted. In that case, it is only necessary to separately detect a change in shading of the created test pattern.

  Further, the number of head units 51 provided in the print head H is not limited to three. One print head H may be provided in the print head H.

1 is a perspective view illustrating an entire print system. It is a perspective view of a print block. It is a figure which shows the conveyance system of the print paper of a print block. It is a bottom view of the print unit. 2 is a block diagram illustrating a control system of the print system. FIG. It is a flowchart which concerns on a discharge timing correction process. It is explanatory drawing of a gradation pattern. It is a top view of the printed paper with which the test pattern was created.

Explanation of symbols

51 Head unit 52 Reference pitch pattern 53 Variable pitch pattern 54 Nozzle array (nozzle array)
71 Pattern creation means 72 Correction means H Print head P Print paper (print member)
S reflective sensor

Claims (7)

A print head that has a plurality of nozzle rows that eject ink of different colors and that ejects ink while reciprocating in the main scanning direction;
A pattern creating means for creating a test pattern for correcting the ink ejection timing of the print head on a print member;
Correction means for correcting the ink discharge timing of the print head based on data obtained from the test pattern created by the pattern creation means,
The pattern creating means creates a test pattern for matching ink landing positions in the main scanning direction between reciprocating scans with two or more colors of ink,
The ink jet printing apparatus, wherein the correction unit performs correction of the ink ejection timing based on data obtained from each of test patterns created with two or more colors of ink. The ink jet printing apparatus according to claim 1, wherein
The print head has a plurality of head units arranged side by side in a sub-scanning direction orthogonal to the main scanning direction, and each head unit has a plurality of nozzle rows that discharge inks of different colors,
The pattern creation means matches the Uni test pattern for matching the ink landing positions in the main scanning direction between the plurality of head units with the ink landing positions in the main scanning direction between the reciprocating scans in the head units. Each of the Bi test patterns with two or more colors of ink,
The correction unit performs inkjet correction based on data obtained from each of test patterns created using two or more colors of ink, and correction of ejection timing based on the Uni test pattern and correction of ejection timing based on the Bi test pattern. Type printing device. The ink jet printing apparatus according to claim 1 or 2,
The correction unit sets an monochrome correction value based on a test pattern for each ink color, and uses an average value of the set plurality of monochrome correction values as a setting correction value for the ejection timing of each head unit. . In the ink jet printing apparatus according to claim 3,
The ink jet printing apparatus, wherein the correction unit uses a weighted average value obtained by weighting a single color correction value of an ink color having a large influence on print image quality as a setting correction value for ejection timing of each head unit. The ink jet printing apparatus according to claim 1 or 2,
A reflection type sensor that scans in the main scanning direction integrally with the print head and detects data obtained from the test pattern created by the pattern creating means;
The pattern generation means discharges ink as a test pattern while shifting a phase with respect to the reference timing to a reference pitch pattern formed by discharging ink at a reference timing while scanning the print head in the main scanning direction. Create a gradation pattern that overlays the variable pitch pattern formed
The reflection type sensor detects a change in shading of the gradation pattern,
The correction unit is an ink jet printing apparatus that corrects the ink discharge timing of each head unit on the basis of the light and shade change detected by the reflective sensor. An ejection timing correction method for an ink jet recording apparatus that ejects ink onto a print member while reciprocally scanning a print head having a plurality of nozzle rows that eject inks of different colors in the main scanning direction,
A test pattern creating step for creating a test pattern for matching the ink landing position with respect to the main scanning direction between the reciprocating scans;
A correction step of correcting the ink discharge timing of the print head based on the test pattern created in the test pattern creation step,
The test pattern creation step is a step of creating a test pattern with two or more colors of ink,
The discharge timing correction method, wherein the correction step is a step of performing correction of the ink discharge timing based on data obtained from each test pattern created with two or more colors of ink. A print head in which a plurality of head units each having a plurality of nozzle rows that eject inks of different colors are arranged in a sub-scanning direction orthogonal to the main scanning direction is scanned on the print member while reciprocating in the main scanning direction. An ejection timing correction method for an ink jet recording apparatus that ejects ink,
A Uni test pattern creating step for creating a Uni test pattern for matching ink landing positions in the main scanning direction between the plurality of head units;
A Bi test pattern creating step for creating a Bi test pattern for matching the ink landing positions in the main scanning direction between the reciprocating scans in the head units;
A correction step of correcting the ink ejection timing of each head unit based on the data obtained from the Uni and Bi test patterns created in the Uni and Bi test pattern creation step,
The Uni and Bi test pattern creation step is a step of creating a Uni and Bi test pattern with two or more inks, respectively.
The correction step is a step of performing ejection timing correction based on the Uni test pattern and ejection timing correction based on the Bi test pattern based on data obtained from each of the test patterns created with two or more colors of ink. Discharge timing correction method.

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