JP5371796B2 - Inkjet recording apparatus and ejection detection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink-jet recorder and an ejection detecting method achieving desirable ejection abnormality detection and image recording by reducing an invalid region caused by switching a driving waveform when driving an ink-jet head having nozzles arranged in a two-dimensional matrix while switching a plurality of kinds of driving waveforms. <P>SOLUTION: A multi-head (100) structured to connect sub-heads 102 with a structure of arranging the nozzles 108 in matrix shape is used to form one stage of nozzle checking patterns having multiple stages of vertical line groups (230). At this time, all the nozzles belonging to one or more lines of nozzles are used, and at least all the nozzles belonging to the nozzle line 110F on the uppermost reaches when moving a recording medium relative to the head are included in the nozzles forming the final stage of the nozzle check patterns. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an inkjet recording apparatus and a discharge detection method, and more particularly to a discharge detection technique for an inkjet head in which a plurality of nozzles are arranged in a matrix.

  2. Related Art An ink jet recording apparatus that forms a desired image on a recording medium by an ink jet method is known. Sub-heads with a two-dimensional nozzle array are arranged in the paper width direction, and equipped with a full-line inkjet head corresponding to the full width of the paper, and the full-line head and the paper are scanned only once to form an image on the entire paper. High productivity is realized by the single pass image recording.

  In an inkjet recording apparatus, unstable discharge nozzles (abnormal nozzles) in which the ink discharge state is unstable cause various problems. Therefore, it is necessary to detect unstable discharge nozzles and perform non-discharge (mask) processing. There is. In order to increase detection sensitivity when detecting unstable discharge nozzles, a method of drawing a detection pattern by discharging with a special discharge waveform not used in normal drawing is known (Patent Document 1).

  The detection pattern for detecting the unstable ejection nozzle is drawn on an area such as an edge of the paper that is not a user drawing area, and an unstable drawing state is detected using a reading device such as an inline scanner. With regard to detection of such ejection abnormalities, a “1 on N off” (N is a natural number) vertical nozzle check pattern is drawn in order to determine “nozzle leakage of the head”, and the nozzle check pattern is generated using a scanner or the like. A technique for reading and determining the presence or absence of unstable ejection nozzles or non-ejection nozzles is known (Patent Document 2).

  Note that the nozzle check pattern of the vertical line “1 ON N OFF” (N is a natural number) in Patent Document 2 is a pattern illustrated by adding reference numeral 4 in FIG. , Off is not printed. That is, ink is ejected from nozzles separated by an interval of N + 1 nozzles to form a vertical line for one stage having a predetermined length, and then separated from nozzles not ejecting ink by an interval of N + 1 nozzles. This is a nozzle check pattern formed by selecting nozzles and ejecting ink from them to form the next vertical line, and repeating this ejection operation to eject ink from all nozzles.

JP 2003-205623 A JP 2004-9474 A

  However, when the technology for switching between the detection driving waveform and the drawing driving waveform described in Patent Document 1 is applied to the configuration in which the driving waveform is set in units of sub-heads having a two-dimensional nozzle arrangement, the nozzle An invalid area due to the two-dimensional arrangement (matrix arrangement) occurs.

  For example, as in the paper (recording medium) 400 illustrated in FIG. 21, a vertical line group of 1 on 10 off using a dedicated drive waveform in a check pattern formation area 406 between the front end 402 and the user layout area 404. Consider the case of forming an 11-stage nozzle check pattern having

  Further, the configuration shown in FIG. 22A is applied to the head for drawing on the paper 400. FIG. 22A shows a head having a plurality of nozzles 420 arranged in a row direction V that forms an angle β with respect to the main scanning direction X and a column direction W that forms an angle α with respect to the sub-scanning direction Y. (Sub head) 422 is a perspective plan view (a diagram showing a nozzle arrangement when the recording medium is viewed from the head 422), and is an enlarged view of a part of the head 422. FIG. FIG. 22B is an enlarged view of FIG. 22A in the X direction. The nozzle check pattern 426 and the head 422 formed using the head 422 having the nozzle arrangement shown in FIG. FIG. 6 is a diagram illustrating a relationship with a nozzle 420.

  A vertical line group 426 in which vertical lines 424 are arranged at equal intervals at an 11-pixel pitch shown in FIG. 22B constitutes one stage of a 1 on N off nozzle check pattern. The line 424 is formed by the nozzles 420 (shown with “ON”) belonging to a plurality of nozzle rows arranged over almost the entire area in the head 422.

  Next, a procedure for forming the vertical line group 426 for one stage will be described in chronological order with reference to FIGS. In FIGS. 23A to 23E, illustration of a part of the nozzles provided in the head 422 is omitted, and the omitted nozzles are indicated by dotted lines or wavy lines.

  23A to 23E illustrate that the nozzle check pattern 426 is formed on the fixed sheet 400 while the head 422 moves from the top to the bottom in the figure.

  FIG. 23A shows a state in which the vertical line 424A is formed. The nozzles forming the vertical line 424A belong to the lowermost nozzle row 421A in the drawing. FIG. 23B shows a state in which the vertical line 424B is formed by moving the head 422 downward by one stage in the drawing. The nozzles forming the vertical line 424B belong to the second nozzle row 421B from the bottom in the figure.

  FIG. 23 (c) shows a state in which the vertical line 424C is formed by further moving the head 422 downward in the figure, and FIG. 23 (d) shows the state in which the head 422 is further moved downward in the figure. A state in which a vertical line 424D is formed is shown. In this way, the nozzles to be driven are switched while the head 422 and the paper 400 are moved relatively, and the nozzles belonging to all the nozzle rows are used, and a vertical line group for one stage along the main scanning direction. 426 is formed.

  FIG. 23E shows a state in which the vertical line group 426 at the final stage (the lowest stage in the figure) of the nozzle check pattern 428 is formed. In this state, the distance in the sub-scanning direction between the nozzle 420F positioned at the lowermost end of the head 422 in the drawing and the nozzle 420G positioned at the uppermost end of the head 422 in the drawing becomes the distance in the sub-scanning direction of the invalid region 430. .

  That is, in order to form the vertical line group 426 for one stage, the nozzle at the beginning of writing located at the lowest stage in the figure (for example, the nozzle 420F that first reaches a position facing a predetermined recording position on the paper 400). Up to the end-of-writing nozzle located at the uppermost stage (for example, the nozzle 420G that finally reaches a position facing a predetermined recording position on the paper 400) is used. Then, until the vertical line group at the last stage (end stage of writing) of the nozzle check pattern is formed, it is not possible to switch to a recording waveform for performing image recording in the user layout area 404. A large invalid area 430 corresponding to the number of all nozzle rows is generated.

  If an attempt is made to secure the predetermined user layout area 404, the substantial check pattern formation area 406 becomes narrow. As a result, in order to form a nozzle check pattern using all nozzles, the nozzle check pattern is divided into a plurality of pages (paper). A large number of printed materials).

  The problem is that when driving an inkjet head having nozzles arranged in a two-dimensional matrix, drawing is performed while switching between a plurality of types of drive waveforms (for example, a drive waveform for recording and a drive waveform for drawing a nozzle check pattern). It is a newly discovered problem that arises when performing. Note that this problem is not unique to the two-dimensional matrix array shown in FIG. 22A, but other two-dimensional matrix arrays (for example, the row direction along the main scanning direction and the column direction oblique to the main scanning direction). This is a problem common to nozzles arranged along the nozzles).

  In view of the above problems, the present invention reduces the ineffective area caused by switching the drive waveform when driving an inkjet head having nozzles arranged in a two-dimensional matrix while switching a plurality of types of drive waveforms, and preferable discharge abnormality An object of the present invention is to provide an ink jet recording apparatus and an ejection detection method in which detection and image recording are realized.

In order to achieve the above object, an ink jet recording apparatus according to the present invention includes an ink jet head having a structure in which a plurality of nozzles for ejecting liquid droplets onto a recording medium are two-dimensionally arranged, and the ink jet head and the recording medium. Moving means for relatively moving along the moving direction of the drive, and drive control means for performing drive control so that nozzles driven at the same drive timing are driven using the same drive waveform or the same drive waveform group Recording waveform used when recording an image on the image forming area of the recording medium, and used for forming a nozzle check pattern in a margin area on the front end side or rear end side adjacent to the outside of the image forming area. Drive waveform switching means for switching between the abnormal nozzle detection waveform and the inkjet nozzle, wherein the inkjet head is a main scan orthogonal to the moving direction. Rows oblique direction with respect to the main scanning direction in the structure of the row direction and two-dimensional array of nozzles which are arranged a plurality of nozzles along the column direction oblique to the row direction, or the nozzle arrangement of the direction The drive control means has a vertical line group for one stage in which vertical lines extending in the sub-scanning direction are arranged at predetermined intervals in the main scanning direction; In addition, a nozzle check pattern formed so that a plurality of vertical line groups whose phases in the main scanning direction are shifted are arranged along the sub-scanning direction is provided for all nozzles used for image recording of the inkjet head. It used to form, or using all the nozzles belonging to the nozzle row of one line in forming a vertical line group for one stage, or to use all the nozzles belonging to a plurality of nozzles rows not adjacent, each nozzle control the drive of the And, and performs driving control of each nozzle so that the interval in the main scanning direction of the vertical line to form a nozzle check pattern to be unequal intervals corresponding to the nozzle arrangement.

  According to the present invention, there is an invalid area when switching between a recording waveform used when recording an image in the image recording area and an abnormal nozzle detection waveform used when forming a nozzle check pattern in the blank area. It is reduced, and an area for forming a nozzle check pattern is secured. Accordingly, since a sufficient nozzle check pattern can be formed in one recording medium, the frequency of detection of unstable nozzles is improved, and the detection accuracy is improved.

  Also, since the area for forming the nozzle check pattern can be made smaller, the image forming area can be made larger if the overall size of the recording medium is constant, while the size of the image forming area Is constant, the overall size of the recording medium can be reduced.

1 is an overall configuration diagram of an ink jet recording apparatus according to an embodiment of the present invention. The top view which shows the structure of the inkjet head mounted in the inkjet recording device shown in FIG. Enlarged view of FIG. The figure explaining the nozzle arrangement of the sub head shown in FIG. Sectional drawing which shows the three-dimensional structure of the subhead shown in FIG. 1 is a block diagram showing the configuration of a control system of the ink jet recording apparatus shown in FIG. Enlarged view of the nozzle section showing the cause of abnormal discharge Waveform diagram showing an example of drive waveform of recording waveform (recording waveform group) Waveform diagram showing an example of abnormal nozzle detection waveform suitable for detection of nozzle internal factors Waveform diagram showing an example of abnormal nozzle detection waveform suitable for detection of nozzle internal factors Waveform diagram showing an example of abnormal nozzle detection waveform suitable for detection of nozzle internal factors Waveform diagram showing an example of abnormal nozzle detection waveform suitable for detection of nozzle internal factors Waveform diagram showing an example of abnormal nozzle detection waveform suitable for detection of nozzle internal factors Waveform diagram showing an example of abnormal nozzle detection waveform suitable for detection of nozzle internal factors Waveform diagram showing an example of abnormal nozzle detection waveform suitable for detection of nozzle internal factors Waveform diagram showing an example of abnormal nozzle detection waveform suitable for detection of nozzle internal factors The figure explaining the relationship between the nozzle arrangement of the subhead shown in FIG. 2, and the nozzle check pattern The figure explaining the formation procedure of the pattern for nozzle checks in the inkjet recording device shown in FIG. Configuration diagram of inline detector Flowchart showing a sequence of unevenness correction in the ink jet recording apparatus shown in FIG. Top view showing layout on paper The figure explaining the relationship between the nozzles arranged in matrix and the nozzle check pattern according to the prior art The figure explaining the formation procedure of the pattern for nozzle check concerning a prior art

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

[Description of overall configuration of inkjet recording apparatus]
FIG. 1 is a configuration diagram showing the overall configuration of the ink jet recording apparatus according to the present embodiment. The ink jet recording apparatus 10 shown in the figure forms an image on the recording surface of the recording medium 14 based on predetermined image data using an ink containing a color material and an aggregating treatment liquid having a function of aggregating the ink. This is a two-liquid aggregation type recording apparatus.

  The ink jet recording apparatus 10 mainly includes a paper supply unit 20, a treatment liquid application unit 30, a drawing unit 40, a drying processing unit 50, a fixing processing unit 60, and a discharge unit 70. Transfer cylinders 32, 42, 52, and 62 are provided as means for delivering the recording medium 14 conveyed upstream of the treatment liquid application unit 30, the drawing unit 40, the drying processing unit 50, and the fixing processing unit 60, and the treatment liquid. As means for conveying the recording medium 14 while holding the recording medium 14 in each of the coating unit 30, the drawing unit 40, the drying processing unit 50, and the fixing processing unit 60, impression cylinders 34, 44, 54, and 64 having a drum shape are provided. .

  The transfer cylinders 32, 42, 52, 62 and the impression cylinders 34, 44, 54, 64 are provided with grippers 80 </ b> A, 80 </ b> B that hold the front end portion (or rear end portion) of the recording medium 14 at predetermined positions on the outer peripheral surface. It has been. The structure in which the gripper 80A and the gripper 80B sandwich and hold the leading end portion of the recording medium 14 and the structure in which the recording medium 14 is transferred between the gripper provided in another impression cylinder or the transfer cylinder are the same, and The gripper 80 </ b> A and the gripper 80 </ b> B are arranged at symmetrical positions that are moved 180 ° in the rotation direction of the pressure drum 34 on the outer peripheral surface of the pressure drum 34.

  When the transfer cylinders 32, 42, 52, 62 and the impression cylinders 34, 44, 54, 64 are rotated in a predetermined direction with the gripper 80A, 80B holding the tip of the recording medium 14, the transfer cylinders 32, 42 are rotated. , 52, 62 and the outer circumference of the impression cylinders 34, 44, 54, 64, the recording medium 14 is rotated and conveyed.

  In FIG. 1, only the grippers 80 </ b> A and 80 </ b> B provided in the impression cylinder 34 are denoted by reference numerals, and the reference numerals of the other impression cylinders and the transfer cylinder grippers are omitted.

  When the recording medium (sheet) 14 accommodated in the paper supply unit 20 is fed to the treatment liquid application unit 30, the aggregation process is performed on the recording surface of the recording medium 14 held on the outer peripheral surface of the impression cylinder 34. A liquid (hereinafter simply referred to as “treatment liquid”) is applied. The “recording surface of the recording medium 14” is an outer surface in a state where the impression cylinders 34, 44, 54, 64 are held, and is a surface opposite to the surface held by the impression cylinders 34, 44, 54, 64. It is.

  Thereafter, the recording medium 14 to which the aggregation treatment liquid has been applied is sent to the drawing unit 40, and color ink is applied to the area of the recording surface to which the aggregation treatment liquid has been applied, thereby forming a desired image.

  Further, the recording medium 14 on which the image of the color ink is formed is sent to the drying processing unit 50, where the drying processing unit 50 performs the drying processing, and after the drying processing, the recording medium 14 is sent to the fixing processing unit 60 to perform the fixing processing. Applied. By performing the drying process and the fixing process, the image formed on the recording medium 14 is hardened. In this way, a desired image is formed on the recording surface of the recording medium 14, and after the image is fixed on the recording surface of the recording medium 14, it is conveyed from the discharge unit 70 to the outside of the apparatus.

  Hereinafter, each unit (the paper feeding unit 20, the processing liquid coating unit 30, the drawing unit 40, the drying processing unit 50, the fixing processing unit 60, and the discharging unit 70) of the inkjet recording apparatus 10 will be described in detail.

(Paper Feeder)
The paper feeding unit 20 is provided with a paper feeding tray 22 and a feeding mechanism (not shown), and the recording medium 14 is configured to be fed one by one from the paper feeding tray 22. The recording medium 14 sent out from the paper feed tray 22 is positioned by a guide member (not shown) so that its tip is positioned at a gripper (not shown) of the transfer drum (paper feed drum) 32 and temporarily stops.

(Processing liquid application part)
The processing liquid application unit 30 includes a pressure drum (processing liquid drum) 34 that holds the recording medium 14 delivered from the paper feeding cylinder 32 on the outer peripheral surface and conveys the recording medium 14 in a predetermined conveying direction, and a processing liquid drum. And a processing liquid coating device 36 for applying a processing liquid to the recording surface of the recording medium 14 held on the outer peripheral surface 34 of the recording medium 14. When the processing liquid drum 34 is rotated counterclockwise in FIG. 1, the recording medium 14 is rotated and conveyed in the counterclockwise direction along the outer peripheral surface of the processing liquid drum 34.

  The processing liquid coating apparatus 36 shown in FIG. 1 is provided at a position facing the outer peripheral surface (recording medium holding surface) of the processing liquid drum 34. As a configuration example of the processing liquid coating device 36, a processing liquid container in which the processing liquid is stored, a pumping roller that is partially immersed in the processing liquid in the processing liquid container, and pumps up the processing liquid in the processing liquid container, and a pumping roller An embodiment including an application roller (rubber roller) that moves the pumped processing liquid onto the recording medium 14 is exemplified.

  In addition, there is provided an application roller moving mechanism that moves the application roller in the vertical direction (the normal direction of the outer peripheral surface of the treatment liquid drum 34), and an aspect in which collision between the application roller and the grippers 80A and 80B can be avoided. preferable.

  The treatment liquid applied to the recording medium 14 by the treatment liquid application unit 30 contains a color material aggregating agent that aggregates the color material (pigment) in the ink applied by the drawing unit 40, and the treatment liquid is applied on the recording medium 14. And the ink come into contact with each other, the separation of the color material and the solvent in the ink is promoted.

  The treatment liquid application device 36 is preferably applied while measuring the amount of the treatment liquid to be applied to the recording medium 14, and the film thickness of the treatment liquid on the recording medium 14 is an ink droplet ejected from the drawing unit 40. It is preferable to make it sufficiently smaller than the diameter.

(Drawing part)
The drawing unit 40 holds an impression cylinder (drawing drum) 44 that holds and transports the recording medium 14, a sheet pressing roller 46 for bringing the recording medium 14 into close contact with the drawing drum 44, and an inkjet that applies ink to the recording medium 14. Heads 48M, 48K, 48C, and 48Y are provided. The basic structure of the drawing drum 44 is the same as that of the processing liquid drum 34 described above, and a description thereof is omitted here.

  The sheet pressing roller 46 is a guide member for bringing the recording medium 14 into close contact with the outer peripheral surface of the drawing drum 44, faces the outer peripheral surface of the drawing drum 44, and delivers the recording medium 14 between the transfer drum 42 and the drawing drum 44. It is disposed downstream of the position in the transport direction of the recording medium 14 and upstream of the ink jet heads 48M, 48K, 48C, and 48Y in the transport direction of the recording medium 14.

  The recording medium 14 transferred from the transfer drum 42 to the drawing drum 44 is pressed by the sheet pressing roller 46 when being rotated and conveyed with the leading end held by a gripper (reference numeral omitted), and the outer periphery of the drawing drum 44. Adhere to the surface. After the recording medium 14 is brought into close contact with the outer peripheral surface of the drawing drum 44 in this way, the recording medium 14 is sent to the print area immediately below the ink jet heads 48M, 48K, 48C, 48Y without being lifted from the outer peripheral surface of the drawing drum 44. It is done.

  The inkjet heads 48M, 48K, 48C, and 48Y correspond to inks of four colors, magenta (M), black (K), cyan (C), and yellow (Y), respectively, and the rotation direction of the drawing drum 44 (see FIG. 1 are arranged in order from the upstream side in the counterclockwise direction in FIG. 1, and the ink discharge surfaces (nozzle surfaces, denoted by reference numeral 114A in FIG. 5) of the ink jet heads 48M, 48K, 48C, 48Y are drawn drums. The recording medium 14 is held so as to face the recording surface of the recording medium 14. Note that the “ink ejection surface (nozzle surface)” is a surface of the inkjet heads 48M, 48K, 48C, and 48Y that faces the recording surface of the recording medium 14, and is a nozzle that ejects ink described later (reference numeral in FIG. 4). This is a surface on which is formed.

  Further, in the inkjet heads 48M, 48K, 48C, 48Y shown in FIG. 1, the recording surface of the recording medium 14 held on the outer peripheral surface of the drawing drum 44 and the nozzle surfaces of the inkjet heads 48M, 48K, 48C, 48Y are substantially parallel. In such a manner, it is arranged to be inclined with respect to the horizontal plane.

  The inkjet heads 48M, 48K, 48C, and 48Y are full-line heads having a length corresponding to the maximum width of the image forming area in the recording medium 14 (the length in the direction orthogonal to the conveyance direction of the recording medium 14). The recording medium 14 is fixedly installed so as to extend in a direction orthogonal to the conveyance direction of the recording medium 14.

  On the nozzle surfaces of the inkjet heads 48M, 48K, 48C, and 48Y, nozzles for ejecting ink are formed in a matrix arrangement over the entire width of the image forming area of the recording medium 14.

  When the recording medium 14 is conveyed to the printing area immediately below the ink jet heads 48M, 48K, 48C, 48Y, the image data is converted into the area where the aggregation processing liquid of the recording medium 14 is applied from the ink jet heads 48M, 48K, 48C, 48Y. Based on this, ink of each color is ejected (droplet ejection).

  When droplets of the corresponding color ink are ejected from the inkjet heads 48M, 48K, 48C, and 48Y toward the recording surface of the recording medium 14 held on the outer peripheral surface of the drawing drum 44, processing is performed on the recording medium 14. The liquid and the ink come into contact with each other, and an aggregation reaction of the color material (pigment-based color material) dispersed in the ink or the color material (dye-based color material) to be insolubilized appears, and a color material aggregate is formed. As a result, movement of the color material in the image formed on the recording medium 14 (dot misalignment, dot color unevenness) is prevented.

  In addition, since the drawing drum 44 of the drawing unit 40 is structurally separated from the processing liquid drum 34 of the processing liquid application unit 30, the processing liquid does not adhere to the ink jet heads 48M, 48K, 48C, and 48Y. In addition, the cause of abnormal ink ejection can be reduced.

  In this example, the configuration of CMYK standard colors (four colors) is illustrated, but the combination of ink colors and the number of colors is not limited to this embodiment, and light ink, dark ink, and special colors are used as necessary. Ink may be added. For example, it is possible to add an inkjet head that discharges light-colored ink such as light cyan and light magenta, and the arrangement order of the color heads is not particularly limited.

(Dry processing part)
The drying processing unit 50 holds an impression cylinder (drying drum) 54 that holds and conveys the recording medium 14 after image formation, and a solvent drying device 56 that performs a drying process for evaporating moisture (liquid component) on the recording medium 14. It has. The basic structure of the drying drum 54 is the same as that of the processing liquid drum 34 and the drawing drum 44 described above, and a description thereof is omitted here.

  The solvent drying device 56 is a processing unit that is disposed at a position facing the outer peripheral surface of the drying drum 54 and evaporates moisture present in the recording medium 14. When ink is applied to the recording medium 14 by the drawing unit 40, the liquid component (solvent component) of the ink and the liquid component (solvent component) of the processing liquid separated by the aggregation reaction between the processing liquid and the ink are placed on the recording medium 14. Since it remains, it is necessary to remove such a liquid component.

  The solvent drying device 56 performs a drying process for evaporating the liquid component existing on the recording medium 14 by heating with a heater, blowing with a fan, or a combination thereof, and removing the liquid component on the recording medium 14. Part. The amount of heating and the amount of air supplied to the recording medium 14 are appropriately set according to parameters such as the amount of moisture remaining on the recording medium 14, the type of the recording medium 14, and the conveyance speed (interference processing time) of the recording medium 14. Is done.

  When the drying process is performed by the solvent drying device 56, the drying drum 54 of the drying processing unit 50 is structurally separated from the drawing drum 44 of the drawing unit 40, and therefore, the inkjet heads 48M, 48K, 48C, and 48Y. In this case, it is possible to reduce the cause of abnormal ink ejection due to drying of the head meniscus by heat or air blowing.

  In order to exhibit the cockling correction effect of the recording medium 14, the curvature of the drying drum 54 is preferably 0.002 (1 / mm) or more. Further, in order to prevent the recording medium from being curved (curled) after the drying process, the curvature of the drying drum 54 is preferably 0.0033 (1 / mm) or less.

  In addition, a means (for example, a built-in heater) for adjusting the surface temperature of the drying drum 54 may be provided, and the surface temperature may be adjusted to 50 ° C. or higher. By applying heat treatment from the back surface of the recording medium 14, drying is promoted and image destruction during the subsequent fixing process is prevented. In this embodiment, it is more effective to provide means for bringing the recording medium 14 into close contact with the outer peripheral surface of the drying drum 54. Examples of the means for bringing the recording medium 14 into close contact include vacuum suction and electrostatic suction.

  The upper limit of the surface temperature of the drying drum 54 is not particularly limited, but from the viewpoint of safety of maintenance work such as cleaning ink adhering to the surface of the drying drum 54 (preventing burns due to high temperature). It is preferably set to 75 ° C. or lower (more preferably 60 ° C. or lower).

  The recording drum 14 is held on the outer peripheral surface of the drying drum 54 configured in this manner so that the recording surface of the recording medium 14 faces outward (that is, in a state in which the recording surface of the recording medium 14 is convex). By performing the drying process while rotating and transporting, drying unevenness due to wrinkling and floating of the recording medium 14 is surely prevented.

(Fixing processing part)
The fixing processing unit 60 includes a pressure drum (fixing drum) 64 that holds and conveys the recording medium 14, a heater 66 that heats the recording medium 14 on which an image is formed and liquid is removed, and the recording And a fixing roller 68 that presses the medium 14 from the recording surface side. Since the basic structure of the fixing drum 64 is common to the processing liquid drum 34, the drawing drum 44, and the drying drum 54, description thereof is omitted here. The heater 66 and the fixing roller 68 are disposed at a position facing the outer peripheral surface of the fixing drum 64, and are sequentially disposed from the upstream side in the rotation direction of the fixing drum 64 (counterclockwise direction in FIG. 1).

  In the fixing processing unit 60, the recording surface of the recording medium 14 is subjected to a preheating process by the heater 66 and a fixing process by the fixing roller 68. The heating temperature of the heater 66 is appropriately set according to the type of recording medium, the type of ink (the type of polymer fine particles contained in the ink), and the like. For example, a mode in which the glass transition temperature and the minimum film forming temperature of the polymer fine particles contained in the ink are considered.

  The fixing roller 68 is a roller member for heating and pressurizing the dried ink to weld the self-dispersing polymer fine particles in the ink to form a film of the ink, and is configured to heat and press the recording medium 14. The Specifically, the fixing roller 68 is disposed so as to be in pressure contact with the fixing drum 64, and constitutes a nip roller with the fixing drum 64. As a result, the recording medium 14 is sandwiched between the fixing roller 68 and the fixing drum 64 and nipped at a predetermined nip pressure, and a fixing process is performed.

  As an example of the configuration of the fixing roller 68, there is an embodiment in which the fixing roller 68 is configured by a heating roller in which a halogen lamp is incorporated in a metal pipe such as aluminum having good thermal conductivity. By heating the recording medium 14 with such a heating roller, when thermal energy equal to or higher than the glass transition temperature of the polymer fine particles contained in the ink is applied, the polymer fine particles are melted to form a transparent film on the surface of the image. Is done.

  When pressure is applied to the recording surface of the recording medium 14 in this state, the polymer fine particles melted into the unevenness of the recording medium 14 are pressed and fixed, and the unevenness of the image surface is leveled, so that preferable glossiness can be obtained. A configuration in which a plurality of fixing rollers 68 are provided in accordance with the thickness of the image layer and the glass transition temperature characteristics of the polymer particles is also preferable.

  The surface hardness of the fixing roller 68 is preferably 71 ° or less. By making the surface of the fixing roller 68 softer, a follow-up effect can be expected for the unevenness of the recording medium 14 caused by cockling, and fixing unevenness due to the unevenness of the recording medium 14 can be more effectively prevented. .

  In the ink jet recording apparatus 10 shown in FIG. 1, an inline sensor 82 is provided at a subsequent stage (downstream in the recording medium conveyance direction) of the processing area of the fixing processing unit 60. The in-line sensor 82 is a sensor for reading an image formed on the recording medium 14 (or a check pattern formed in a blank area of the recording medium 14), and a CCD line sensor is preferably used.

  In the ink jet recording apparatus 10 shown in this example, the presence or absence of ejection abnormality of the ink jet heads 48M, 48K, 48C, and 48Y is determined based on the reading result of the inline sensor 82. Further, the in-line sensor 82 may include a measuring unit for measuring the moisture content, the surface temperature, the glossiness, and the like. In such an embodiment, parameters such as the processing temperature of the drying processing unit 50, the heating temperature of the fixing processing unit 60, and the pressure pressure are appropriately adjusted based on the moisture content, surface temperature, and gloss reading result, and the temperature inside the apparatus. The control parameter is adjusted as appropriate in accordance with the change and the temperature change of each part.

(Discharge part)
As shown in FIG. 1, a discharge unit 70 is provided following the fixing processing unit 60. The discharge unit 70 includes an endless conveyance belt 74 wound around the stretching rollers 72A and 72B, and a discharge tray 76 that stores the recording medium 14 after image formation.

  The recording medium 14 after the fixing process sent out from the fixing processing unit 60 is transported by the transport belt 74 and discharged to the discharge tray 76.

[Description of structure of inkjet head]
FIG. 2 is a schematic configuration diagram of an ink jet head applied to the present invention. FIG. 2 is a diagram (a plan perspective view of the head) of the recording surface of the recording medium viewed from the ink jet head. In addition, since the inkjet heads 48M, 48K, 48C, and 48Y shown in FIG. 1 have the same structure, in the following description, when it is not necessary to distinguish the inkjet heads 48M, 48K, 48C, and 48Y, these are used. Collectively, they are described as “inkjet head 100” or simply “head 100”.

  The head 100 shown in the figure forms a multi-head by connecting n sub-heads 102-i (i is an integer from 1 to n) in a line. Each sub head 102-i is supported by head covers 104 and 106 from both sides of the head 100 in the short direction. It is also possible to configure a multi-head by arranging the sub-heads 102 in a staggered manner.

  As an application example of a multi-head configured by a plurality of sub-heads, a full-line head corresponding to the entire width of a recording medium can be given. The full-line head has a plurality of nozzles (corresponding to the length (width) in the main scanning direction of the recording medium along the direction (main scanning direction) orthogonal to the moving direction (sub-scanning direction) of the recording medium. 4 is illustrated with reference numeral 108.) is arranged. An image can be formed on the entire surface of the recording medium by a so-called single-pass image recording method in which image recording is performed by scanning the head 100 having such a structure and the recording medium only once relatively.

  FIG. 3 is a partially enlarged view of the head 100. As shown in the figure, the sub head 102 has a substantially parallelogram-shaped planar shape, and an overlap portion is provided between adjacent sub heads. The overlap portion is a connecting portion of the sub heads, and is formed by nozzles in which dots adjacent to the sub heads 102-i are arranged in different sub heads in the arrangement direction of the sub heads 102-i (the horizontal direction in FIG. 2, the main scanning direction X shown in FIG. 3). The

  FIG. 4 is a plan view showing the nozzle arrangement of the sub head 102-i. As shown in the figure, each sub head 102-i has a structure in which nozzles 108 are arranged two-dimensionally, and a head including such a sub head 102-i is a so-called matrix head.

  In the sub-head 102-i shown in FIG. 4, a large number of nozzles 108 are arranged along a row direction W that forms an angle α with respect to the sub-scanning direction Y and a row direction V that forms an angle β with respect to the main scanning direction X. The substantial nozzle arrangement density in the main scanning direction X is increased. In FIG. 4, nozzle groups (nozzle rows) arranged along the row direction V are illustrated with reference numeral 110, and nozzle groups (nozzle arrays) arranged along the column direction W are illustrated with reference numeral 112. Is shown.

  FIG. 5 is a cross-sectional view showing a three-dimensional configuration of one channel of droplet discharge elements (ink chamber units corresponding to one nozzle 108) serving as a recording element unit. As shown in the figure, in the head 100 of this example, a nozzle plate 114 formed with nozzles 108 and a flow path plate 120 formed with flow paths such as a pressure chamber 116 and a common flow path 118 are laminated and joined. Consists of structure. The nozzle plate 114 forms a nozzle surface 114A of the head 100, and a plurality of nozzles 108 communicating with the pressure chambers 116 are two-dimensionally formed.

  The flow path plate 120 constitutes a side wall portion of the pressure chamber 116 and a flow path forming a supply port 122 as a throttle portion (most narrowed portion) of an individual supply path that guides ink from the common flow path 118 to the pressure chamber 116. It is a forming member. For convenience of explanation, the flow path plate 120 has a structure in which one or a plurality of substrates are stacked, although it is illustrated schematically in FIG.

  The nozzle plate 114 and the flow path plate 120 can be processed into a required shape by a semiconductor manufacturing process using silicon as a material.

  The common flow path 118 communicates with an ink tank (not shown) serving as an ink supply source, and ink supplied from the ink tank is supplied to each pressure chamber 116 via the common flow path 118.

  A diaphragm 124 constituting a part of the pressure chamber 116 (the top surface in FIG. 5) includes an individual electrode 126 and a lower electrode 128, and the piezoelectric body 130 is interposed between the individual electrode 126 and the lower electrode 128. A piezo actuator 132 having a sandwiched structure is joined. When the diaphragm 124 is formed of a metal thin film or a metal oxide film, it functions as a common electrode corresponding to the lower electrode 128 of the piezoelectric actuator 132. In the aspect in which the diaphragm is formed of a non-conductive material such as resin, a lower electrode layer made of a conductive material such as metal is formed on the surface of the diaphragm member.

  By applying a driving voltage to the individual electrode 126, the piezo actuator 132 is deformed to change the volume of the pressure chamber 116, and ink is ejected from the nozzle 108 due to a pressure change accompanying this. When the piezo actuator 132 returns to its original state after ink ejection, new ink is refilled into the pressure chamber 116 from the common flow path 118 through the supply port 122.

As shown in FIG. 4, the ink chamber unit having such a structure is latticed in a fixed arrangement pattern along a row direction V that forms an angle β with the main scanning direction X and a column direction W that forms an angle α with respect to the sub-scanning direction Y. The high-density nozzle head of this example is realized by arranging a large number in the shape. In such matrix arrangement, when the adjacent nozzle spacing in the sub-scanning direction and L _s, the main scanning direction that substantially each nozzle 108 are arranged linearly at a fixed pitch P = L s _/ tanθ equivalent Can be handled.

  The nozzle arrangement applicable to the present invention is not limited to the nozzle arrangement shown in FIG. 4. For example, a plurality of nozzles along the row direction along the main scanning direction and the column direction oblique to the main scanning direction are used. Is also applicable to a matrix array.

[Explanation of control system]
FIG. 6 is a block diagram showing a system configuration of the inkjet recording apparatus 10. As shown in FIG. 6, the inkjet recording apparatus 10 includes a communication interface 170, a system controller 172, an image memory 174, a ROM 175, a motor driver 176, a heater driver 178, a print control unit 180, an image buffer memory 182 and a head driver 184. I have.

  The communication interface 170 is an interface unit (image input means) that receives image data sent from the host computer 186. As the communication interface 170, a serial interface such as USB (Universal Serial Bus), IEEE 1394, Ethernet (registered trademark), a wireless network, or a parallel interface such as Centronics can be applied. In this part, a buffer memory (not shown) for speeding up communication may be mounted.

  Image data sent from the host computer 186 is taken into the inkjet recording apparatus 10 via the communication interface 170 and temporarily stored in the image memory 174. The image memory 174 is a storage unit that stores an image input via the communication interface 170, and data is read and written through the system controller 172. The image memory 174 is not limited to a memory composed of semiconductor elements, and a magnetic medium such as a hard disk may be used.

  The system controller 172 includes a central processing unit (CPU) and its peripheral circuits, and functions as a control device that controls the entire inkjet recording apparatus 10 according to a predetermined program, and also functions as an arithmetic device that performs various calculations. . That is, the system controller 172 controls the communication interface 170, the image memory 174, the motor driver 176, the heater driver 178, and the like, and performs communication control with the host computer 186, read / write control of the image memory 174 and ROM 175, and the like. At the same time, a control signal for controlling the motor 188 and the heater 189 of the transport system is generated.

  In addition, the system controller 172 determines whether or not there is a discharge abnormal nozzle from a test chart read from the inline detection unit 144 or reading data of a nozzle check pattern to be described later, and identifies a position of the discharge abnormal nozzle. 172A is included. The processing function of the ejection abnormal nozzle determination unit 172A can be realized by ASIC, software, or an appropriate combination.

  The abnormal discharge nozzle information (data) obtained by the abnormal discharge nozzle determination unit 172A is stored in the abnormal discharge nozzle information storage unit 190.

  The ROM 175 stores programs executed by the CPU of the system controller 172 and various data necessary for control (data for ejecting test charts, waveform data for detecting abnormal nozzles, waveform data for drawing and recording, abnormal nozzle information, etc.) Is stored). The ROM 175 may be a non-rewritable storage unit or a rewritable storage unit such as an EEPROM. Further, by utilizing the storage area of the ROM 175, a configuration in which the ROM 175 is also used as the ejection abnormal nozzle information storage unit 190 is possible.

  The image memory 174 is used as a temporary storage area for image data, and is also used as a program development area and a calculation work area for the CPU.

The motor driver 176 is a driver (driving circuit) that drives the conveyance motor 188 in accordance with an instruction from the system controller 172. The heater driver 178 is a driver that drives the Heater 189 according to an instruction from the system controller 172.

  In accordance with the control of the system controller 172, the print control unit 180 performs various processes, corrections, and the like for generating a droplet ejection control signal from image data (multi-value input image data) in the image memory 174. In addition to functioning as signal processing means, it also functions as drive control means for controlling the ejection drive of the head 100 by supplying the generated ink ejection data to the head driver 184.

  That is, the print control unit 180 includes a density data generation unit 180A, a correction processing unit 180B, an ink ejection data generation unit 180C, and a drive waveform generation unit 180D. Each of these functional blocks (180A to 180D) can be realized by ASIC, software, or an appropriate combination.

  The density data generation unit 180A is a signal processing unit that generates initial density data for each ink color from input image data, and performs density conversion processing (including UCR processing and color conversion) and, if necessary, pixel number conversion. Process.

  The correction processing unit 180 </ b> B is a processing unit that performs correction calculation based on the information of the ejection abnormality nozzle stored in the ejection abnormality nozzle information storage unit 190. As a processing example of the correction processing unit 180B, there is an undischarge processing (mask processing) in which the data value of the pixel corresponding to the ejection abnormal nozzle is zero.

  The ink ejection data generation unit 180C is a signal processing unit including a halftoning processing unit that converts the corrected image data (density data) generated by the correction processing unit 180B into binary or multivalued dot data. Value (multi-value) conversion processing is performed. Various known means such as an error diffusion method, a dither method, a threshold matrix method, and a density pattern method can be applied as the halftone processing means. In the halftone process, generally, gradation image data having an M value (M ≧ 3) is converted into gradation image data having an N value (N <M). In the simplest example, the image data is converted into binary (dot on / off) dot image data. However, in the halftone process, the dot size type (for example, three types such as a large dot, a medium dot, and a small dot) is converted. It is also possible to perform corresponding multi-level quantization.

  The ink discharge data generated by the ink discharge data generation unit 180C is given to the head driver 184, and the ink discharge operation of the head 100 is controlled.

  The drive waveform generation unit 180D drives a drive waveform for driving an actuator (shown with reference numeral 132 in FIG. 4) corresponding to each nozzle 108 of the head 100, or a drive waveform group including a plurality of drive waveforms. And a drive signal for switching on / off for each nozzle. The signals (drive waveform and drive signal) generated by the drive waveform generator 180D are supplied to the head driver 184. The signal output from the drive waveform generator 180D may be digital waveform data or an analog voltage signal.

  Note that the terms “recording waveform” and “abnormal nozzle detection waveform” in the following description represent a concept that encompasses not only a single waveform but also a group of waveforms including a plurality of waveform elements. That is, the “recording waveform” may represent not only a single recording waveform but also a recording waveform group in which a plurality of recording waveforms are continuous.

  The drive waveform generation unit 180D generates a recording waveform and an abnormal nozzle detection waveform. Various waveform data are stored in the ROM 175 in advance, and waveform data to be used is selectively output as necessary.

  The head driver 184 supplies the same (common) driving waveform for each head module, and supplies a driving signal for switching on / off of each nozzle for each head module. That is, the same drive waveform and the drive signal for each nozzle are supplied to the piezo actuator 132 corresponding to each nozzle belonging to one head module. Further, switching between the recording waveform and the abnormal nozzle detection waveform is performed for each head module.

  The head driver 184 may be provided for each head, or may be provided for each head module that constitutes the head.

  The print control unit 180 includes an image buffer memory 182, and image data, parameters, and other data are temporarily stored in the image buffer memory 182 when image data is processed in the print control unit 180. In FIG. 6, the image buffer memory 182 is shown in a form associated with the print control unit 180, but it can also be used as the image memory 174. Also possible is an aspect in which the print controller 180 and the system controller 172 are integrated and configured with one processor.

  An outline of the flow of processing from image input to print output is as follows. Image data to be printed is input from the outside via the communication interface 170 and stored in the image memory 174. At this stage, for example, RGB multivalued image data is stored in the image memory 174.

  In the inkjet recording apparatus 10, a pseudo continuous tone image is formed by human eyes by changing the droplet ejection density and dot size of fine dots by ink (coloring material). It is necessary to convert to a dot pattern that reproduces the gradation (shading of the image) as faithfully as possible. Therefore, the original image (RGB) data stored in the image memory 174 is sent to the print control unit 180 via the system controller 172, and the density data generation unit 180A, the correction processing unit 180B of the print control unit 180, the ink It is converted into dot data for each ink color via the ejection data generation unit 180C.

  In other words, the print control unit 180 performs processing for converting the input RGB image data into dot data of four colors of M, K, C, and Y. Thus, the dot data generated by the print control unit 180 is stored in the image buffer memory 182. This dot data for each color is converted into MKCY droplet ejection data for ejecting ink from the nozzles of the head 100, and ink ejection data to be printed is determined.

  The head driver 184 outputs a drive waveform for driving the piezo actuator 132 corresponding to each nozzle 108 of the head 100 in accordance with the print contents based on the ink ejection data and the drive waveform given from the print control unit 180. The head driver 184 may include a feedback control system for keeping the head driving condition constant.

  In this way, the drive waveform output from the head driver 184 is applied to the head 100, whereby ink is ejected from the corresponding nozzle 108. An image is formed on the recording medium 14 by controlling ink ejection from the head 100 in synchronization with the conveyance speed of the recording medium 14.

  As described above, the ejection amount and ejection timing of the ink droplets from each nozzle are controlled via the head driver 184 based on the ink ejection data and the drive waveform generated through the required signal processing in the print control unit 180. Done. Thereby, a desired dot size and dot arrangement are realized.

  As described with reference to FIG. 1, the in-line detection unit 144 is a block including an image sensor, reads an image printed on the recording medium 14, performs necessary signal processing, and the like to perform a printing situation (whether ejection is performed, droplet ejection Variation, optical density, etc.) and the detection result is provided to the print controller 180 and the system controller 172.

  The print control unit 180 performs various corrections on the head 100 based on information obtained from the inline detection unit 144 as necessary, and performs cleaning operations (nozzle recovery operation) such as preliminary ejection, suction, and wiping as necessary. Perform the controls to be implemented.

  The maintenance mechanism 194 in the drawing includes members necessary for head maintenance, such as an ink receiver, a suction cap, a suction pump, and a wiper blade.

  The operation unit 196 as a user interface includes an input device 197 and a display unit (display) 198 for an operator (user) to make various inputs. The input device 197 may employ various forms such as a keyboard, a mouse, a touch panel, and buttons. By operating the input device 197, an operator can input printing conditions, select an image quality mode, input / edit attached information, search information, and the like. This can be confirmed through the display on the display unit 198. The display unit 198 also functions as means for displaying a warning such as an error message.

  The ink jet recording apparatus 10 of the present embodiment has a plurality of image quality modes, and the image quality mode is set by a user's selection operation or by automatic selection by a program. The criterion for determining an abnormal nozzle is changed according to the output image quality level required in the set image quality mode. The higher the required quality, the more severe the criteria.

  Information regarding the printing conditions and abnormal nozzle determination criteria for each image quality mode is stored in the ROM 175.

  A mode in which all or part of the processing functions performed by the ejection abnormality nozzle determination unit 172A, the density data generation unit 180A, and the correction processing unit 180B described with reference to FIG. 6 is also possible is possible.

[Cause of abnormal discharge]
Next, the cause of the ejection abnormality will be described. FIG. 7 is an enlarged view of the nozzle portion schematically showing the cause of the ejection abnormality. In FIG. 7, reference numeral 108 denotes a nozzle, 200 denotes ink filled in the nozzle 108, and 202 denotes a meniscus (gas-liquid interface). FIG. 5A shows a state where bubbles 204 are mixed in the ink 200 in the nozzle 108. The nozzle 108 communicates with a pressure chamber (not shown) (shown with reference numeral 116 in FIG. 5). The pressure chamber has a piezoelectric element (piezo actuator, reference numeral 132 in FIG. 5) as pressure generating means. Is shown). By driving the piezoelectric element to change the volume of the pressure chamber, droplets are ejected from the nozzle 108. At this time, if the bubble 204 exists in the nozzle 108, the pressure is absorbed by the bubble 204 or the flow of the liquid is hindered, resulting in a discharge abnormality.

  FIG. 7B shows a state in which the foreign matter 206 is attached to the inner wall surface of the nozzle 108. When foreign matter 206 adheres to the inside of the nozzle, the foreign matter 206 impedes the flow of the liquid, causing discharge abnormalities such as flying bends.

  FIG. 7C shows a case where foreign matter 208 is attached near the nozzle hole outside the nozzle 108. When foreign matter 208 adheres to the vicinity of the nozzle outside the nozzle, the liquid comes into contact with the foreign matter 208 and the axial symmetry of the meniscus is lost, causing ejection abnormalities such as flying bends.

  In the case of a partial decrease in liquid repellency in the vicinity of the nozzle on the nozzle surface 114A (for example, peeling of the liquid repellent film) instead of the adhesion of the foreign matter 208, this is the same as in FIG. 7C. The foreign matters 206 and 208 include, for example, agglomerates of ink components, dry matter, paper powder, dust, ink mist, and residues that remain unintentionally in the head manufacturing process.

[Abnormal nozzle detection method]
As shown in FIG. 7, the cause of the ejection abnormality is roughly classified into the nozzle internal factors described in (a) and (b) and the nozzle external factors described in (c). In the case where bubbles 204 or foreign matter 206 are present in the nozzle (abnormal nozzle due to nozzle internal factor), when the ejection force is reduced, ejection abnormality due to the nozzle internal factor is promoted. That is, the influence of the bubbles 204 and the foreign matter 206 is exerted by driving to reduce the ejection speed by reducing the displacement amount of the piezoelectric element or applying pressure fluctuation at a frequency shifted from the head resonance frequency. This is more remarkably reflected in the discharge result. As a result, undischarge is promoted or the amount of bending of the flying curve is amplified.

  On the other hand, when there is a foreign matter 208 or poor liquid repellency outside the nozzle, the ink overflows from the hole of the nozzle 108 (pumps the ink), and the ink contacts the foreign matter 208 or poor liquid repellency outside the nozzle. By doing so, ejection abnormalities due to external factors of the nozzle are promoted.

  In this embodiment, when an ejection abnormality is detected, drawing of a nozzle check pattern (also referred to as a test chart or a test pattern) is performed using a waveform that promotes the ejection abnormality in addition to the drive waveform for drawing recording. And print the result. That is, even when the piezoelectric element is driven using the ejection driving waveform at the time of normal drawing, even if there is a state of bubbles 204, foreign matters 206, 208, etc. that do not appear (cannot be detected) as ejection abnormalities. By using a waveform for detection that promotes and amplifies discharge abnormality, it can be expressed as a detectable defect. As a result, it is possible to detect an early stage discharge abnormality that cannot be recognized as a discharge abnormality in the drawing recording drive waveform at an early stage.

  A specific waveform example will be described below.

(About drive waveforms during drawing and recording)
FIG. 8 is an example of a drive waveform for ejection during normal drawing and recording (hereinafter referred to as “recording waveform”). Here, in order to simplify the description, a so-called pull-push type drive waveform is illustrated. However, in the implementation of the present invention, the form of the drive waveform is not particularly limited, and a pull-push-pull waveform and other various drive waveforms can be used.

  The recording waveform 210 shown in FIG. 8 includes a first signal element 210a that outputs a reference potential for maintaining the volume of the pressure chamber in a steady state, and a second signal that drives the piezoelectric element in the direction of expanding the pressure chamber from the steady state. A signal element (pulling waveform section) 210b, a third signal element 210c that maintains the pressure chamber in an expanded state, a fourth signal element (push waveform section) 210d that drives the piezoelectric element in a direction to compress and compress the pressure chamber, have.

  That is, the first signal element 210a is a waveform part that maintains the reference potential, and the second signal element 210b is a falling waveform part that lowers the potential from the reference potential. The third signal element 210c is a waveform part that maintains the potential lowered by the second signal element 210b, and the fourth signal element 210d is a rising waveform part that raises the potential of the third signal element 210c to the reference potential.

The pulse interval of this pulling waveform is preferably made to coincide with the head resonance period (Helmholtz natural vibration period) T, and the pulse width T _p is set to a natural number of the head resonance period (Helmholtz natural vibration period) _Tc. It is desirable. The head resonance period refers to the natural period of the entire vibration system determined from the ink flow path system, ink (acoustic element), dimensions, material, physical property values, and the like of the piezoelectric element.

(Example of abnormal nozzle detection waveform suitable for detecting defects in nozzle internal factors)
When detecting an abnormal nozzle, a special waveform (referred to as “abnormal nozzle detection waveform”) different from the recording waveform described in FIG. 8 is used to promote and amplify the discharge abnormality, thereby detecting sensitivity and accuracy. To improve.

  Examples of abnormal nozzle detection waveforms suitable for detecting abnormal nozzles caused by internal nozzle factors are shown in FIGS.

  In FIG. 9, the potential difference Vpp (difference between the maximum value and the minimum value of the voltage waveform) is smaller than that of the recording waveform of FIG. It is preferable to reduce the potential difference of the recording waveform by 10% or more, and more preferable to decrease in the range of 15% to 25%.

In FIG. 10, the pulse width T _p is changed as compared with the recording waveform of FIG. It is preferably increased or decreased by 10% or more with respect to the pulse width of the recording waveform, and more preferably increased or decreased in the range of 20% to 50%.

  The ink jet head has a pulse width that can be stably discharged due to the flow path structure and the physical properties of the liquid used. The pulse width of the recording waveform is determined to be a pulse width that enables stable ejection. On the other hand, in the abnormal nozzle detection waveform, in order to weaken the ejection force, a waveform with a changed pulse width is used.

  In FIG. 11, the slope of the pulse waveform (the slope of the rise of the fourth signal element 210d) is changed as compared to the recording waveform of FIG. It is preferable to increase or decrease the slope by 20% or more with respect to the slope of the recording waveform, and more preferably to increase or decrease within the range of 50% to 200%.

FIG. 12 shows an example in which a waveform signal (pre-pulse) that weakens the ejection force is applied before the ejection pulse 212. When the head resonance frequency is 1 / _Tc , a pulse with a small potential difference ( _Tc / 2) × n before the ejection pulse 212 (a weak pulse that cannot be ejected from the nozzle only by applying this pulse) (Where n is a natural number).

  The pre-pulse 214 includes a waveform portion (fifth signal element 214a) that lowers the potential from the reference potential, a sixth signal element 214b that maintains the potential lowered by the fifth signal element 214a, and the potential of the sixth signal element 214b. A seventh signal element that raises to a reference potential. The vibration wave generated by the application of the pre-pulse 214 inhibits the subsequent drawing of the ejection pulse 212 (the drawing operation by the first signal element 210a), and the ejection force by the ejection pulse 212 is reduced. That is, by applying the pre-pulse 214, the meniscus in the nozzle is once drawn into the nozzle and then pushed out so as to rise out of the nozzle. At the timing when this vibration remains and the meniscus is drawn again and pushed out, the drawing signal element (210a) of the next ejection pulse 212 is added. For this reason, the pulling operation of the pull-in signal element (210a) overlapping the swell operation of the residual vibration of the prepulse 214 is hindered, and the discharge force is weakened. In addition, the structure demonstrated in FIGS. 9-12 can also be combined suitably.

(Example of abnormal nozzle detection waveform suitable for detecting defects of nozzle external factors)
Next, examples of abnormal nozzle detection waveforms suitable for detecting abnormal nozzles caused by nozzle external factors are shown in FIGS.

  In FIG. 13, the potential difference Vpp (difference between the maximum value and the minimum value of the voltage waveform) is larger than that of the recording waveform of FIG. It is preferable to increase the potential difference of the recording waveform by 10% or more.

  FIG. 14 shows that a signal element (reference numeral 210e) for contracting the pressure chamber and raising ink from the nozzle (expanding ink) and its potential are maintained before the drawing signal element (reference numeral 210b) of the ejection pulse 220. This is an example in which a signal element 210f is added.

  By these signal elements 210e and 210f, the ink rises from the nozzle before ejection, and the ink can come into contact with the foreign matter 208 or the like outside the nozzle.

In addition to the waveform of FIG. 14, FIG. 15 further applies the ejection pulse 220 at a time interval n × T _c . According to the configuration of FIG. 15, ink can be further raised from the nozzle by the pressure chamber contraction signal element (210 e) before the next ejection by the residual vibration generated by the application of the previous ejection pulse 220. By adding an extrusion operation at a timing that is an integral multiple of the vibration period _Tc , vibration can be amplified.

In FIG. 16, a pre-pulse 222 having a small potential difference is applied before the ejection pulse 220. The pre-pulse 222 is applied at a timing “n × T _c ” before the ejection pulse 220. The pre-pulse 222 includes a pushing signal element (eighth signal element) 222a that raises the potential from the reference potential to contract the pressure chamber, a ninth signal element 222b that maintains the potential raised by the eighth signal element 222a, And a tenth signal element 222c for returning the potential of the ninth signal element 222b to the reference potential. The ink cannot be ejected from the nozzle only by applying the pre-pulse 222 alone.

  The swell from the nozzle can be amplified by causing the vibration wave generated by the application of the pre-pulse 222 to resonate with the vibration caused by the subsequent ejection pulse 220.

  As described with reference to FIGS. 9 to 16, the nozzle check pattern is ejected using a special waveform (abnormal nozzle detection waveform) different from the drawing and recording drive waveform, and the print result of the nozzle check pattern is printed. To detect the presence of abnormal nozzles.

  This abnormal nozzle detection waveform can amplify the degree of abnormality in the nozzle as compared with the recording waveform. Therefore, it is possible to detect an abnormality at an early stage before a recording failure occurs during drawing / recording using the recording waveform. In addition, detection with a low-resolution detector is possible, and high-speed detection and high-sensitivity detection are possible.

  In addition, by detecting abnormal nozzles using multiple types of abnormal nozzle detection waveforms corresponding to both internal and external nozzle failure causes, it is possible to detect abnormal discharges due to each failure cause with high sensitivity. It is possible.

  Furthermore, during drawing and recording of the target image, a nozzle check pattern is formed on the non-image area (margin portion) of the recording medium using the abnormal nozzle detection waveform, and abnormal nozzle detection is performed from the print result of the nozzle check pattern. It can be performed. When an abnormal nozzle is detected, the use of the abnormal nozzle is stopped and the image data is corrected so that a good image can be output only with the remaining normal nozzles. Based on the corrected image data, the target image is corrected. Printing can be continued. In this way, an abnormal nozzle is discovered and dealt with early before a problem occurs in the drawing and recording of the image portion using the recording waveform, thereby enabling continuous recording (continuous printing). In other words, before an actual malfunction occurs in the drawing of the image area, abnormal nozzles that are likely to become ejection abnormalities are detected at an early stage, and this is treated as an ejection failure, and the effects of the ejection failure are compensated by the remaining nozzles. The image data is corrected as follows. For this reason, it is possible to continue printing while avoiding the occurrence of lost paper and a decrease in throughput with respect to problems occurring during continuous recording.

[Description of nozzle check pattern]
Next, a method for forming a nozzle check pattern formed using the above-described abnormal nozzle detection waveform will be described.

  FIG. 17 is a diagram showing the relationship between the nozzle check pattern and the nozzle arrangement. In this figure, a part of the sub head 102 constituting the head (shown with reference numeral 100 in FIG. 2) is enlarged. A part of the vertical line group 230 for one stage constituting the nozzle check pattern is also illustrated.

  As shown in the figure, vertical lines 232 (232A, 232B) constituting the vertical line group 230 have a pattern corresponding to nozzles arranged in a matrix. That is, the vertical line group 230 is formed by vertical lines 232A formed by all the nozzles 108A belonging to the lowermost nozzle row 110A in the drawing and all nozzles 108B belonging to the fifth nozzle row 110B from the lower side in the drawing. Vertical lines 232B. In other words, the vertical line group for one stage constituting the nozzle check pattern is formed by all nozzles belonging to one nozzle row or all nozzles belonging to two or more nozzle rows.

  When the vertical line group 230 is formed by using the nozzles 108A and 108B belonging to the two nozzle rows 110A and 110B shown in FIG. 17, the vertical line 232A formed by the nozzle 108A belonging to the nozzle row 110A and the nozzle The vertical lines 232B formed by the nozzles 108B belonging to the row 110B are alternately arranged. In addition, the vertical lines 232A and 232B constituting the vertical line group 230 shown in FIG. 17 are not corresponding to the nozzle arrangement, such as 14 pixels, 16 pixels, 15 pixels, 16 pixels,. Arranged at equal intervals.

  That is, the nozzles 108A belonging to the nozzle row 110A are arranged at unequal intervals in the main scanning direction. For example, the rightmost nozzle 108A (1) and the left adjacent nozzle 108A (2) in the figure are 30 nozzles (pixels) apart, and the nozzle 108A (2) and the left adjacent nozzle 108A (3) are 31. Nozzle spacing. That is, in the nozzle row along the main scanning direction, a plurality of nozzles belonging to the nozzle row are arranged at unequal intervals. Similarly, the nozzles 108B belonging to the nozzle row 110B are also arranged at unequal intervals.

  That is, in order to achieve a higher recording resolution in the main scanning direction, the nozzles in the main scanning direction are reduced as much as possible as a result of closing the nozzle rows as much as possible with the intention of reducing the substantial nozzle arrangement interval in the main scanning direction. The arrangement interval is unequal.

  Other vertical line groups (not shown) constituting the nozzle check pattern use all the nozzles of the nozzle row to which the nozzles used when forming the vertical line group belong, similarly to the vertical line group 230. It is formed. In this way, a nozzle check pattern including a plurality of vertical line groups arranged by shifting the position in the sub-scanning direction while sequentially switching the nozzle rows to be used is formed.

  When the number of nozzle rows is q and the number of nozzle rows forming one line of vertical line groups is r, the nozzle check pattern is composed of q / r stages of vertical line groups. If r is not a divisor of q, the number of nozzle rows forming one line of vertical line groups may be smaller than r.

  The ink jet recording apparatus 10 shown in FIG. 1 has four heads 48M, 48K, 48C, and 48Y corresponding to four colors, so that a nozzle check pattern for four heads is formed. If it is possible to fit the nozzle check patterns for four heads in the margin area of one sheet, the nozzle check patterns for four heads are formed in the margin area of one sheet. When the nozzle check pattern for the head cannot be accommodated in the margin area of one sheet, it is preferable that the nozzle check pattern for at least one head is formed in the margin area of one sheet. When it cannot fit on one sheet, it may be divided into a plurality of sheets.

  FIGS. 18A to 18E are explanatory diagrams illustrating a state in which nozzle check patterns for one head are formed in chronological order. 18A to 18E show image recording by moving the head (sub head 102) from the upper side to the lower side in the drawing with respect to a fixed sheet 240 (equivalent to the recording medium 14 in FIG. 1). Illustrated as what to do. That is, FIG. 18A shows the state closest to the beginning of writing, and FIG. 18E shows the state closest to the end of writing.

  In other words, “the downstream side of the relative movement direction of the head (the end of writing)” is the lower side in the drawing with reference to the paper 240, and the “most downstream nozzle row in the movement direction of the head” is the lowermost row in the drawing. Nozzle row (nozzle row 110E including the nozzle 108E in FIG. 18C), which is the nozzle row that first reaches a predetermined recording position on the paper 240. Further, “upstream side in the relative movement direction of the head (writing start side)” is the upper side in the drawing, and “uppermost nozzle row in the relative movement direction of the head” is the uppermost nozzle row in the drawing (FIG. 18). (B) Nozzle row 110 </ b> D including nozzle 108 </ b> D), which is a nozzle row that finally reaches a predetermined recording position on paper 240.

  In FIGS. 18A to 18E, some nozzles of the sub head 102 and some vertical lines of the vertical line group are omitted.

18A shows a vertical line formed by all the nozzles 108C belonging to the nozzle row 110C at the start position 244 of the nozzle check pattern formation area 231 (for example, a position 3 mm away from the leading edge 242 of the paper 240 in the sub-scanning direction). A state in which 232C (vertical line group at the beginning of writing) is formed is illustrated.

  The nozzles 108C in the nozzle row 110C are driven in order from the left end to the right in the drawing, and a group of vertical lines 232C is formed. Since the vertical line 232C has a length corresponding to several dots in the sub-scanning direction Y, the nozzle 108C is continuously driven several times corresponding to the length of the vertical line 232C in the sub-scanning direction Y. The

  In the state shown in FIG. 18A, vertical line groups are formed at other positions by the nozzle row driven at the same drive timing as the nozzle row 110C, but these other vertical line groups are illustrated. Is omitted.

  FIG. 18B illustrates a state in which the vertical lines 232D constituting the same vertical line group as the vertical lines 232C are formed. In this way, all the nozzles 108C belonging to the nozzle row 110C and all the nozzles 108D belonging to the nozzle row 110D are sequentially driven, and the vertical line 232C and the vertical line 232D are formed at the start position 246 of the nozzle check pattern formation area 244. A one-stage vertical line group 230 </ b> C is formed.

  FIG. 18C shows a vertical line group (shown with reference numeral 230F in FIG. 18E) of the last stage of the nozzle check pattern (the stage closest to the user layout area 264 at the lowest stage in the figure). The state in which the vertical line 232E that constitutes is formed is shown. The vertical line 232E belongs to the nozzle row 110E on the most downstream side in the head movement direction (which first reaches the position facing the paper 240 when the head at the lower end in the figure and the paper 240 are relatively moved). The nozzle 108E is used.

  FIG. 18D shows a state in which the vertical lines 232F constituting the same vertical line group as the vertical lines 232E are formed. When the driving of the nozzle 108F at the right end in the drawing of the nozzle row 110F forming the vertical line 232F is completed, the nozzle check pattern is completed. When the formation of the nozzle check pattern is completed, the drive waveform is switched from the abnormal nozzle detection waveform to the recording waveform, and image recording in the user layout area 264 is started.

  FIG. 18E shows a state where image recording in the user layout area 264 is started. In this state, the leftmost nozzle 108E (see FIG. 18C) of the lowermost nozzle row 110E in the drawing is located in the user layout area 264.

Here, the distance in the sub-scanning direction between the nozzle 108E at the left end of the nozzle row 110E and the nozzle 108F at the right end of the nozzle row 110F when the drive waveform shown in FIG. This is obtained by adding the distance corresponding to the inclination of the nozzle row to the distance corresponding to the number of rows from the row 110E to the nozzle row 110F. The distance obtained in this manner is the distance in the sub-scanning direction of the invalid area. For example, the number of rows from the nozzle row 110E to the nozzle row 110F is p, the distance in the sub-scanning direction for one nozzle row is ΔY, and the nozzle If the distance in the sub-scanning direction corresponding to the inclination of the row is Y _a , the distance in the sub-scanning direction of the invalid area is p × ΔY + Y _a .

  That is, by appropriately selecting the arrangement interval of the vertical lines 232 in the main scanning direction corresponding to the matrix arrangement of the nozzles 108, the difference in the number of nozzle rows forming the vertical line group for one stage of the nozzle check pattern can be reduced. The distance in the sheet movement direction from the nozzle check pattern formation end position to the image recording start position due to the difference in the number of rows can be minimized, and this occurs due to switching of drive waveforms. The invalid area can be reduced.

  For example, when considering the case where 2048 nozzles are arranged in 32 rows and 64 columns at a nozzle density of 1200 nozzles per inch, the invalid area of the nozzle check pattern formed by the procedure according to the prior art is the row loss amount. Is about 9.2mm (for 31 steps), and the nozzle tilt loss is about 1.3mm, which results in an invalid area of about 10.5mm, but the invalid area of the nozzle check pattern formed by the procedure according to the present invention is The row loss can be reduced to about 1.2 mm (4 stages) or less, and the combined loss of the nozzle inclination can be reduced to about 2.5 mm or less. Therefore, a significant reduction of the invalid area is realized as compared with the conventional case.

  In the above-described embodiment, the case where the nozzle check pattern is formed in the margin area on the leading end side of the sheet 240 has been described. However, the case where the nozzle check pattern is formed in the margin area on the trailing end side of the sheet 240 is also described. The present invention can be applied.

  When a nozzle check pattern is formed in a margin area on the rear end side of the paper 240, the top and bottom of FIGS. 18 (a) to 18 (e) are reversed, and FIG. 18 (e), FIG. 18 (d), FIG. The nozzle check pattern may be formed in the order of (c), FIG. 18 (b), and FIG. 18 (a). In this aspect, the first-stage pattern 230F closest to the user layout area 264 belongs to all the nozzle rows 110E that finally reach the position facing the paper 240 when the head and the paper 240 are relatively moved. The nozzle 108E is used.

[Configuration example of inline detection unit]
FIG. 19 is a configuration diagram of the inline detection unit 144. The in-line detection unit 144 includes a read sensor unit 274 in which a line CCD 270, a lens 272 that forms an image on the light receiving surface of the line CCD 270, and a mirror 273 that bends the optical path are arranged in parallel. Read each image. The line CCD 270 has a photocell (pixel) array for each color provided with RGB color filters, and a color image can be read by RGB color separation. For example, a CCD analog shift register for separately transferring the charges of even-numbered pixels and odd-numbered pixels in one line is provided next to the photocell array for each of RGB3 lines.

  Specifically, a line CCD “μPD8827A” (trade name) manufactured by NEC Electronics Corporation having a pixel pitch of 9.325 μm, 7600 pixels × RGB, and an element length (sensor width in the photocell arrangement direction) of 70.87 mm can be used.

  The line CCD 270 is fixed so that the arrangement direction of the photocells and the axis of the drum on which the recording medium is conveyed are parallel to each other.

  The lens 272 is a lens of a reduction optical system that forms an image on a recording medium wound on a conveyance drum (an impression cylinder 64 in FIG. 1) at a predetermined reduction ratio. For example, when a lens that reduces an image by 0.19 times is employed, a 373 mm width on the recording medium is imaged on the line CCD 270. At this time, the reading resolution on the recording medium is 518 dpi.

  As shown in FIG. 19, the reading sensor unit 274 in which the line CCD 270, the lens 272, and the mirror 273 are integrated can be moved and adjusted in parallel with the axis of the transport drum, and the positions of the two reading sensor units 274 are adjusted, respectively. The image read by the reading sensor unit 274 is slightly overlapped. Although not shown in FIG. 19, as an illuminating means for detection, for example, a xenon fluorescent lamp is disposed on the back surface of the bracket 75 and on the recording medium side, and a white reference plate is periodically placed between the image and the illumination. To measure the white reference. In this state, the lamp is turned off and the black reference level is measured.

  The reading width of the line CCD 270 (the range that can be inspected at one time) can be designed in various ways in relation to the width of the image recording area on the recording medium. From the viewpoint of lens performance and resolution, for example, the reading width of the line CCD 270 is about ½ of the width of the image recording area (the maximum width that can be inspected).

  Image data obtained by the line CCD 270 is converted into digital data by an A / D converter or the like, stored in a temporary memory, processed through the system controller 172, and stored in the image memory 174.

[Discharge abnormality correction sequence flowchart]
FIG. 20 is a flowchart showing a discharge abnormality correction sequence in the inkjet recording apparatus according to the embodiment of the present invention. In this example, the ejection abnormality correction includes a pre-correction (offline correction) process (steps S12 to S16) in which a test chart is measured offline to obtain correction data before starting continuous printing by a print job (steps S12 to S16), and continuous printing is in progress. In addition, by measuring the nozzle check pattern with the sensor (in-line detection unit 144) in the apparatus, the in-line correction process (step S20) performs adaptive correction while performing continuous printing (without interrupting printing). To S36).

  First, a test chart for offline measurement is output (step S12), and the print result is measured in detail by an offline scanner (not shown) (step S14). The test chart here includes a line pattern suitable for specifying the presence / absence of an abnormal discharge nozzle and the position of the abnormal discharge nozzle. Of course, a density pattern suitable for measuring density unevenness or the like may be included to achieve other purposes. In the case of off-line measurement, a test pattern can be formed on the entire recording surface (image forming area and non-image area) of the recording medium 14.

  These test patterns may be combined and printed on one recording medium, or the elements of each test pattern may be divided and printed on a plurality of recording media. The print result of the test chart output in this way is read using an image reading device such as a flatbed scanner, and various data necessary for processing such as discharge correction nozzle data that specifies the position of the discharge failure nozzle is generated. To do. Note that it is desirable to use an offline scanner having a higher resolution (higher resolution) than the inline detection unit 144 in the apparatus.

  Various data thus obtained is input to the inkjet recording apparatus 10 via a communication interface, an external storage medium (removable medium), or the like.

  Correction data is created using this offline measurement result (step S16). The correction data is stored in a predetermined storage unit as a system parameter. When correction data is created in step S16, a print job for performing continuous printing of a large number of sheets at an appropriate timing is started (step S20). After printing starts, inline correction is performed.

  That is, when printing is started, an inline nozzle check pattern is formed on the non-image portion at the leading edge of the paper with an abnormal nozzle detection waveform (step S22), and the normal drawing drive waveform (recording) is recorded for the image portion. The target image is drawn and recorded by the waveform (step S24).

  Note that the nozzle check pattern formed in step S22 may be formed in the non-image portion at the rear end of the sheet. The 1 on N off pattern shown in FIGS. 17 and 18 is applied to the nozzle check pattern, and the method described with reference to FIGS. 18A to 18E is applied to the nozzle check pattern forming method. Is done.

  The recording medium 14 in which the drawing and recording of the nozzle check pattern and the image portion has been completed is transported by the transport means, and the print result of the nozzle check pattern is read by the inline detection unit 144 (step S26). Based on this read information, the presence or absence of an abnormal discharge nozzle is determined (step S28).

  Information relating to the criterion for determining an abnormal ejection nozzle is stored in advance in the ROM 175 or the like, and a criterion value corresponding to the image quality mode is set. For example, reference values relating to one or a plurality of evaluation items such as an allowable value of landing error due to a flying curve, an allowable value of line width (allowable value of discharge amount), and a density value are defined. The presence or absence of an abnormal nozzle is determined according to this reference value, and the abnormal nozzle is specified.

  If there is no ejection abnormality (non-ejection or flying curve) nozzle in step S28, the process proceeds to step S34.

  On the other hand, if there is a discharge abnormal nozzle in step S28, the position of the discharge abnormal nozzle is specified, and the discharge abnormal nozzle is treated as a non-discharge nozzle that is not used when drawing the image portion. The non-ejection nozzle data indicating the nozzle is updated (step S30).

  Then, the image data is corrected based on the measurement result, and corrected image data is generated (step S32). The “image data” here is image data before quantization processing (image data having multivalued pixel values). That is, the corrected image data is subjected to a quantization process to generate dot data. On the other hand, it is also possible to change the dot data so that a substitute dot by the adjacent nozzle of the abnormal ejection nozzle is added to the vicinity of the dot that should be originally formed by the abnormal ejection nozzle with respect to the quantized dot data. is there.

  In step S34, the number of drawn images is counted, and it is determined whether or not the number of drawn images has reached the designated number. If the number of drawn images has not reached the designated number (No determination), the print job is continued and each of the steps S22 to S32 is repeatedly executed. On the other hand, if the number of drawn images reaches the designated number in step S34 (Yes determination), the process proceeds to step S36, and the print job is terminated.

(Action to be taken when many abnormal discharge nozzles are detected)
In the steps described in steps S28 to S30 in FIG. 20, when the number of nozzles detected as ejection abnormal nozzles exceeds a predetermined specified value, it is preferable to warn the user (user). For example, a warning message is displayed on the display unit 198 to alert the user about the necessity of head maintenance.

  Alternatively, a mode in which the head maintenance is automatically executed instead of or in combination with the above warning is also preferable. In this case, since it is necessary to move the head to the maintenance position, printing is interrupted, and maintenance operations such as pressure purge, ink suction, idle ejection, and nozzle surface wiping are performed in the maintenance unit.

(Other methods for correcting ejection abnormal nozzles)
As the correction of the ejection abnormal nozzle, correction (substitute droplet ejection) by changing the nozzle drive is also possible. For example, it is possible to perform substitute droplet ejection using a nozzle located in the vicinity of an abnormal ejection nozzle. That is, the drive signal of the ejection abnormal nozzle is always turned off, and the non-driving nozzle among the nozzles located around the ejection abnormal nozzle is driven at the timing when the ejection abnormal nozzle is driven. By substituting droplets for such ejection abnormal nozzles, surrogate dots are formed in the vicinity of the dots originally formed by the ejection abnormal nozzles, and the visibility of missing dots due to the ejection abnormal nozzles can be reduced.

  According to the method for forming a nozzle check pattern configured as described above, when forming a nozzle check pattern having a 1 on N off pattern formed on a non-image portion of a sheet in order to detect ejection abnormality, Using all the nozzles belonging to at least one nozzle row arranged along the row direction V that forms an angle β with the main scanning direction, a vertical line group (dot group) for one stage of the nozzle check pattern is formed. Therefore, the invalid area generated when switching between the nozzle detection waveform applied when forming the nozzle check pattern and the drawing recording waveform for drawing on the image portion of the paper is reduced, and the nozzle check A non-image portion for forming a pattern can be used effectively.

[Example of application to other devices]
In the above embodiment, application to an inkjet recording apparatus for graphic printing has been described as an example, but the scope of application of the present invention is not limited to this example. For example, a wiring drawing device that draws a wiring pattern of an electronic circuit, a manufacturing device for various devices, a resist printing device that uses a resin liquid as a functional liquid for ejection, a color filter manufacturing device, and a material deposition material. The present invention can be widely applied to inkjet systems that obtain various shapes and patterns using a liquid functional material, such as a fine structure forming apparatus for forming a structure.

[Appendix]
As can be understood from the description of the embodiment described in detail above, the present specification includes disclosure of various technical ideas including the invention described below.

  (Invention 1): An inkjet head having a structure in which a plurality of nozzles for discharging droplets to a recording medium are two-dimensionally arranged, and a movement for relatively moving the inkjet head and the recording medium along a predetermined movement direction And a drive control means for performing drive control so that the nozzles driven at the same drive timing are driven using the same drive waveform or the same drive waveform group, and recording an image on an image forming area of the recording medium Drive for switching between a recording waveform used at the time of printing and an abnormal nozzle detection waveform used when a nozzle check pattern is formed in a margin area on the front end side or rear end side adjacent to the outside of the image forming area Waveform switching means, wherein the ink jet head is arranged in a main scanning direction orthogonal to the moving direction or in a diagonal direction forming a predetermined angle with the main scanning direction. A plurality of nozzles arranged along a direction and a sub-scanning direction parallel to the moving direction or an oblique row direction forming a predetermined angle with the sub-scanning direction, and the drive control means The vertical lines extending in the sub-scanning direction have a group of vertical lines arranged at a predetermined interval in the main scanning direction and have a plurality of vertical lines that are shifted in phase in the main scanning direction. When a nozzle check pattern formed so as to be arranged in the sub-scanning direction is formed using all the nozzles used for image recording of the inkjet head, and a vertical line group for one stage is formed An ink jet recording apparatus, wherein driving of each nozzle is controlled so that all nozzles belonging to one nozzle row are used, or all nozzles belonging to a plurality of non-adjacent nozzle rows are used.

  According to the present invention, there is an invalid area when switching between a recording waveform used when recording an image in the image recording area and an abnormal nozzle detection waveform used when forming a nozzle check pattern in the blank area. It is reduced, and an area for forming a nozzle check pattern is secured. Accordingly, since a sufficient nozzle check pattern can be formed in one recording medium, the frequency of detection of unstable nozzles is improved, and the detection accuracy is improved.

  Also, since the area for forming the nozzle check pattern can be made smaller, the image forming area can be made larger if the overall size of the recording medium is constant, while the size of the image forming area Is constant, the overall size of the recording medium can be reduced.

  The inkjet head includes a plurality of liquid chambers provided corresponding to the plurality of nozzles, and a plurality of discharge elements provided corresponding to the plurality of liquid chambers, and the liquid chambers and discharge elements corresponding to the arrangement of the nozzles There is a mode in which the is arranged.

  In addition to the form in which the color ink is ejected from the nozzle, the ink jet head has a form in which a desired pattern is formed by ejecting a liquid such as a resist liquid or a resin liquid from the nozzle.

  The abnormal nozzle detection waveform is preferably a drive waveform that is generated with the intention that a phenomenon caused by ejection abnormality is likely to occur.

  The arrangement interval of the vertical lines constituting the vertical line group for one stage in the main scanning direction is determined according to the reading resolution of the reading unit that reads the nozzle check pattern. That is, when a nozzle check pattern is formed using all nozzles belonging to a plurality of nozzle rows, the number of rows between nozzle rows forming the same vertical line group is (head recording resolution) / (reading). The reading resolution of the means) or more.

  (Invention 2): In the ink jet recording apparatus according to Invention 1, the drive control unit forms a nozzle check pattern in which the vertical lines have an unequal interval corresponding to the nozzle arrangement in the main scanning direction. In addition, the drive control of each nozzle is performed.

  That is, for the purpose of increasing the recording density in the main scanning direction, all the heads belonging to one nozzle row are arranged using a head in which the arrangement pitch between nozzle rows is made smaller and the nozzle arrangement intervals in the row direction are unequal. When one stage of the nozzle check pattern is formed using the nozzles, the vertical line intervals of the vertical line row for the one stage are unequal.

(Invention 3): In the ink jet recording apparatus according to the first or second aspect, before Symbol drive control means, the nearest stage to the image forming region of the nozzle check pattern to the distal end side of the blank area of the image forming region When forming, when the inkjet head and the recording medium are relatively moved, the drive control of each nozzle is performed so that all the nozzles belonging to the nozzle row that first reaches the position facing the recording medium are used. It is characterized by performing.

  According to this aspect, after the nozzle row that first reaches the position facing the recording medium when the recording head and the recording medium are relatively moved passes through the invalid area, Image recording can be started.

(Invention 4): In the ink jet recording apparatus according to Invention 1 or 2, when forming a step closest to the image formation area of the nozzle check pattern in a margin area on the rear end side of the image formation area, The drive control of each nozzle is performed so that all nozzles belonging to the nozzle row that finally reaches the position facing the recording medium when the inkjet head and the recording medium are relatively moved are used. .

  According to this aspect, immediately after the nozzle row that finally reaches the position facing the recording medium passes through the image forming area when the recording head and the recording medium are relatively moved, the image forming area Formation of the nozzle check pattern can be started in the margin area at the end of writing.

  (Invention 5): In the ink jet recording apparatus according to any one of the inventions 1 to 4, the ink jet head has a structure in which sub heads having a structure in which a plurality of nozzles are two-dimensionally arranged are connected, and the drive control is performed. The means controls the driving of each nozzle provided in the sub head using a predetermined driving waveform or a group of driving waveforms for each sub head.

  In such an aspect, the drive control is performed for each sub head, so that the control load of the drive control means can be distributed as compared with the aspect in which the entire head is collectively controlled.

  (Invention 6): In the inkjet recording apparatus according to Invention 5, the inkjet head has a structure in which a plurality of sub-heads are arranged in a line along the main scanning direction.

  In such an embodiment, it is preferable that the plane shape of each sub head is a substantially parallelogram and an overlap portion is provided at the joint between the sub heads.

  (Invention 7): In the ink jet recording apparatus according to any one of Inventions 1 to 6, the waveform generation means for generating the recording waveform and the abnormal nozzle detection waveform, and the waveform generated by the waveform generation means. A drive waveform generation unit that generates a drive waveform or a drive waveform group and a drive signal generation unit that generates a drive signal for selectively turning on and off each nozzle based on image data are provided.

  In such an aspect, an aspect in which the means for generating the recording waveform and the means for generating the abnormal nozzle detection waveform are separately provided is also possible.

  (Invention 8): In the ink jet recording apparatus according to any one of Inventions 1 to 7, an abnormal nozzle that determines an abnormal nozzle having an ejection abnormality based on reading information obtained from a reading device that reads the nozzle check pattern. It is characterized by comprising determination means and processing means for performing predetermined processing on the nozzles determined to be abnormal nozzles.

  As a form of the processing means in such an aspect, a correction process for performing recalculation with the data value of the nozzle determined to be an abnormal nozzle as a minimum value (or maximum value), or using a nozzle adjacent to the nozzle determined to be an abnormal nozzle is used instead. A process of performing droplet ejection is possible. That is, the processing unit according to the eighth aspect can be configured to function as a correction unit that performs correction processing such as correction of image data.

  (Invention 9): In the ink jet recording apparatus described in Invention 8, the processing means performs processing corresponding to the abnormal nozzle so as not to use the nozzle determined to be an abnormal nozzle.

  In such an aspect, when correcting the image data, it is conceivable that the pixel value corresponding to the abnormal nozzle is set to zero and the quantization process is performed based on the corrected pixel value. Further, when correcting by changing the drive of the abnormal nozzle, it is conceivable to stop the drive of the abnormal nozzle (no drive signal is applied).

  As an example of the correction process in such an embodiment, a masking process (an undischarge process) is given.

  (Invention 10): The ink jet recording apparatus according to the invention 8 or 9, wherein the reading device is an in-line sensor provided in the ink jet recording apparatus.

  According to such an aspect, it is possible to correct the sequential ejection abnormal nozzles by in-line inspection.

(Invention 11): Same as the moving step of relatively moving an inkjet head having a structure in which a plurality of nozzles for discharging droplets to the recording medium are two-dimensionally arranged and the recording medium along a predetermined moving direction. A drive control process for performing drive control so that the nozzles driven at the drive timing are driven using the same drive waveform or the same drive waveform group, and recording used when recording an image on the image forming area of the recording medium A drive waveform switching step for switching between a waveform for use and a waveform for detecting an abnormal nozzle used when forming a nozzle check pattern in a margin area on the front end side or rear end side adjacent to the outside of the image forming area; anda detection step of detecting abnormal discharge nozzle by using the patterns for the nozzle check, the ink-jet head in the main scanning direction perpendicular to the moving direction Is a plurality of rows along an oblique row direction that forms a predetermined angle with the main scanning direction and a sub-scanning direction that is parallel to the moving direction or an oblique column direction that forms a predetermined angle with the sub-scanning direction. Nozzles are arranged, and in the drive control step, the vertical lines extending in the sub-scanning direction have a group of vertical lines arranged at a predetermined interval in the main scanning direction, and A nozzle check pattern formed such that a plurality of vertical line groups whose phases in the main scanning direction are shifted are arranged along the sub-scanning direction, using all the nozzles used for image recording of the inkjet head. Each nozzle is driven so that all nozzles belonging to one nozzle row are used or all nozzles belonging to a plurality of non-adjacent nozzle rows are used when forming a vertical line group for one stage. To be controlled Discharge detection method and butterflies.

  DESCRIPTION OF SYMBOLS 10 ... Inkjet recording device, 48M, 48K, 48C, 48Y, 100 ... Head, 82 ... In-line sensor, 102 ... Sub head, 108 ... Nozzle, 110 ... Nozzle row, 144 ... In-line detection unit, 172 ... System controller, 172A ... Discharge Abnormal nozzle determination unit, 180 ... print control unit, 180B ... correction processing unit, 180C ... ink ejection data generation unit, 180D ... drive waveform generation unit, 184 ... head driver

Claims (10)

An inkjet head having a structure in which a plurality of nozzles for discharging droplets to a recording medium are two-dimensionally arranged;
Moving means for relatively moving the inkjet head and the recording medium along a predetermined moving direction;
Drive control means for performing drive control so that nozzles driven at the same drive timing are driven using the same drive waveform or the same drive waveform group;
Recording waveform used when recording an image on an image forming area of a recording medium, and used for forming a nozzle check pattern in a margin area on the leading end side or the trailing end side adjacent to the outside of the image forming area. Drive waveform switching means for switching to the abnormal nozzle detection waveform;
With
The inkjet head includes a two-dimensional array of nozzles in which a plurality of nozzles are arranged along a row direction in a main scanning direction orthogonal to the moving direction and a column direction oblique to the row direction, or the nozzle arrangement described above. In the structure, having a two-dimensional array of nozzles with the diagonal direction with respect to the main scanning direction as the row direction ,
The drive control means includes a plurality of stages in which the vertical lines extending in the sub-scanning direction have a group of vertical lines arranged at predetermined intervals in the main scanning direction, and the phases in the main scanning direction are shifted. Forming a nozzle check pattern formed so that minute vertical line groups are arranged in the sub-scanning direction using all the nozzles used for image recording of the inkjet head, or using all the nozzles belonging to the nozzle row of one line in forming, or to use all the nozzles belonging to a plurality of nozzles rows not adjacent, to control the drive of each nozzle, and the vertical lines An ink jet recording apparatus , wherein drive control of each nozzle is performed so as to form a nozzle check pattern in which an interval in a main scanning direction is an unequal interval corresponding to the nozzle arrangement . The inkjet recording apparatus according to claim 1, wherein
The drive control unit relatively moves the inkjet head and the recording medium when forming a step closest to the image forming area of the nozzle check pattern in a blank area on the leading end side of the image forming area. An ink jet recording apparatus, wherein drive control of each nozzle is performed so that all nozzles belonging to a nozzle row that first reaches a position facing a recording medium when used. The inkjet recording apparatus according to claim 1, wherein
When forming the step closest to the image forming area of the nozzle check pattern in the blank area on the rear end side of the image forming area, the recording medium is moved when the inkjet head and the recording medium are relatively moved. An ink jet recording apparatus, wherein drive control of each nozzle is performed so that all nozzles belonging to the nozzle row that finally arrives at a position opposite to are used. In the ink jet recording apparatus according to any one of claims 1 to 3,
The inkjet head has a structure in which sub-heads having a structure in which a plurality of nozzles are two-dimensionally arranged based on the two-dimensional arrangement of the nozzles are connected,
The ink jet recording apparatus, wherein the drive control unit controls driving of each nozzle provided in the sub head using a predetermined drive waveform or a drive waveform group for each sub head. The inkjet recording apparatus according to claim 4 , wherein
The ink jet recording apparatus according to claim 1, wherein the ink jet head has a structure in which a plurality of sub heads are arranged in a line along a main scanning direction. In the ink jet recording apparatus according to any one of claims 1 to 5,
Waveform generating means for generating the recording waveform and the abnormal nozzle detection waveform;
Drive waveform generation means for generating a drive waveform or a drive waveform group having the waveform generated by the waveform generation means;
Drive signal generating means for generating a drive signal for selectively turning on and off each nozzle based on image data;
An ink jet recording apparatus comprising: In the ink jet recording apparatus according to any one of claims 1 to 6,
An abnormal nozzle determining means for determining an abnormal nozzle that is abnormal in ejection based on reading information obtained from a reading device that reads the nozzle check pattern;
Processing means for performing predetermined processing on the nozzle determined to be an abnormal nozzle;
An ink jet recording apparatus comprising: The inkjet recording apparatus according to claim 7 , wherein
The ink jet recording apparatus, wherein the processing unit performs processing corresponding to the abnormal nozzle so as not to use a nozzle determined to be an abnormal nozzle. In the ink jet recording apparatus according to claim 7 or 8 ,
The ink jet recording apparatus, wherein the reading device is an in-line sensor included in the ink jet recording apparatus. A moving step of relatively moving an ink jet head having a structure in which a plurality of nozzles for discharging droplets to the recording medium are two-dimensionally arranged and the recording medium along a predetermined moving direction;
A drive control step for performing drive control so that nozzles driven at the same drive timing are driven using the same drive waveform or the same drive waveform group;
Recording waveform used when recording an image on an image forming area of a recording medium, and used for forming a nozzle check pattern in a margin area on the leading end side or the trailing end side adjacent to the outside of the image forming area. A drive waveform switching step for switching to the abnormal nozzle detection waveform;
A detection step of detecting a nozzle with abnormal discharge using the nozzle check pattern;
Including
The inkjet head includes a two-dimensional array of nozzles in which a plurality of nozzles are arranged along a row direction in a main scanning direction orthogonal to the moving direction and a column direction oblique to the row direction, or the nozzle arrangement described above. In the structure, having a two-dimensional array of nozzles with the diagonal direction with respect to the main scanning direction as the row direction ,
In the drive control step, a plurality of stages in which the vertical lines extending in the sub-scanning direction have a group of vertical lines arranged in the main scanning direction at a predetermined interval and the phases in the main scanning direction are shifted. Forming a nozzle check pattern formed so that minute vertical line groups are arranged in the sub-scanning direction using all the nozzles used for image recording of the inkjet head, or using all the nozzles belonging to the nozzle row of one line in forming, or to use all the nozzles belonging to a plurality of nozzles rows not adjacent, to control the drive of each nozzle, and the vertical lines An ejection detection method, wherein drive control of each nozzle is performed so as to form a nozzle check pattern in which intervals in the main scanning direction are unequal intervals corresponding to the nozzle arrangement .

Images