JP2013022730A - Inkjet recorder and inkjet recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely detect and correct a variation in ink application due to a deviation between a top end of a sheet of paper and a start position for ink application and between a rear end of the sheet of paper and a finish position for ink application.SOLUTION: This inkjet recorder includes a recording medium transporting means, an applying roller for applying a treatment liquid for aggregating ink on a recording medium transported by the transporting means, a measuring roller which measures an amount of the treatment liquid and supplies it to the applying roller, and a measuring roller separation/contact means which brings the measuring roller into contact with the applying roller at a predetermined contact timing and separates the measuring roller from the applying roller at a predetermined separation timing. The inkjet recorder further includes an image recording means which records an image on the recording medium applied with the treatment liquid by depositing ink droplets thereon, an image capturing means which captures the image recorded on the recording medium, a detecting means which detects a density distribution in the transporting direction of the captured image, a determining means which determines the presence or absence of a region on the recording medium in which the treatment liquid is excessive or insufficient on the basis of the detected result, and a correcting means which corrects the contact timing or separation timing of the measuring roller separation/contact means on the basis of the result of the determining means.

Description

  The present invention relates to an ink jet recording apparatus and a recording method therefor, and more particularly to a coating technique for applying a liquid to a sheet-type medium such as cut paper.

  2. Description of the Related Art Conventionally, as a general-purpose image forming apparatus, an ink jet recording apparatus that forms a desired image on a recording medium by discharging color ink from a nozzle of an ink jet head is known.

  In an inkjet recording apparatus, a technique for forming a high-definition image by applying a treatment liquid for aggregating or insolubilizing ink to a recording medium in advance and then ejecting the ink is known. According to this two-component aggregation method, even when non- (hard) penetrable media such as a resin sheet and a metal sheet are used as well as a paper medium, a preferable image formation that does not cause blurring or color misregistration is generated. Realization is possible.

  In this two-liquid aggregation method, a roller coating method using a coating roller is preferably used in order to uniformly apply the processing liquid over the entire surface of the recording medium (a relatively wide area of the recording medium). The roller coating method can apply a large amount of coating liquid onto a recording medium without depending on the physical properties of the coating liquid (here, the processing liquid), and a coating liquid layer having a uniform thickness. It can be formed on a recording medium.

  When applying the processing liquid to the paper using the application roller, if an excess of the processing liquid remains on the application roller, it affects the application of the processing liquid on the next paper and causes uneven application. Therefore, in order to make the rear end of the sheet coincide with the application end position, it is necessary to stop the supply of the processing liquid to the application roller in accordance with the passage timing of the rear end of the sheet.

  In Patent Document 1, an anilox roller that supplies liquid to the application roller is separated from the application roller in accordance with the timing at which the rear edge of the paper passes based on the input paper size information. Techniques for matching are disclosed.

  Here, the problem relating to the on-demand application of a sheet using a conventional application roller will be described with reference to FIG. 22A to 22F illustrate a roller coating method in which the coating liquid 306 is applied to a plurality of sheets (recording media) 304 held on the peripheral surface 302A of the impression cylinder 302 using the coating roller 300. It is a conceptual diagram for doing.

  FIG. 22A shows a state in which the coating liquid 306 is applied to the first recording medium 304-1.

  The recording medium 304-1 is conveyed while being held on the peripheral surface 302A of the impression cylinder 302. A predetermined amount of the coating liquid 306 stored in the coating tray 308 is measured by a measuring roller (anilox roller) 310 and continuously supplied to the coating roller 300. The coating liquid 306 held on the surface of the coating roller 300 is applied to the recording medium 304-1 that moves as the impression cylinder 302 rotates.

  FIG. 22B shows a state in which the measuring roller 310 is separated from the application roller 300 in accordance with the rear end of the first recording medium 304-1, and the supply of the application liquid 306 to the application roller 300 is stopped. ing. The timing at which the rear end of the recording medium 304-1 passes can be estimated from the paper size input by the user.

  FIG. 22C shows a state in which the coating liquid 306 is applied up to the rear end of the first recording medium 304-1. FIG. 22D is an enlarged view of the contact surface between the application roller 300 and the impression cylinder 302 in the state of FIG. Here, the case where the separation timing of the measuring roller 310 shown in FIG. 22B is later than the desired timing is shown, and the application liquid 306 supplied to the rear end of the recording medium 304-1 and the application roller 300 is shown. The rear ends of the liquid films do not coincide with each other, and the liquid film of the coating liquid 306 is shifted after a distance a.

  Accordingly, the coating liquid 306 in the liquid film portion is not supplied to the recording medium 304-1 and remains on the surface of the coating roller 300. The remaining coating liquid 306 comes into contact with the peripheral surface 302A of the impression cylinder 302, but the peripheral surface 302A of the impression cylinder 302 does not have absorbency, and therefore remains on the surface of the application roller 300.

  FIG. 22E shows a state where the first recording medium 304-1 has passed through the application roller 300. As shown in the drawing, the coating liquid 306 </ b> Z remaining on the surface of the coating roller 300 moves as the coating roller 300 rotates.

  FIG. 22F shows a state where the coating liquid 306 is applied to the second recording medium 304-2. The coating liquid 306 is supplied from the measuring roller 300 so as to overlap the coating liquid 306Z remaining on the surface of the coating roller 300. Accordingly, the portion where the previous coating liquid 306Z remained is in the state where the coating liquid 306 is excessive, and is directly applied to the recording medium 304-2 by the coating roller 300.

  As described above, when the separation timing of the measuring roller 310 is delayed from a desired timing, a thick coating portion of the coating liquid 306 is generated on the recording medium 304 to be conveyed next.

  FIG. 23A is a top view showing the recording medium 304-2 coated with the coating liquid 306 in FIG. As shown in the drawing, a thick coating portion 312 of the coating liquid 306 having a length a with respect to the transport direction is generated on the recording medium 304-2.

  Conversely, when the timing of separation of the measuring roller 310 is early, a lightly coated portion is generated on the recording medium 304-2 to which the coating liquid 306 is applied next.

  A small amount of the liquid film of the coating liquid 306 remains on the surface of the coating roller 300 after the coating liquid 306 is applied to the recording medium 304-1 (reference numeral 306a shown in FIG. 22D). When the separation timing of the metering roller 310 is early, a region where the coating liquid 306 is not supplied from the metering roller 310 is generated on the surface of the coating roller 300. In this region, the coating liquid 306 is recorded on the recording medium 304 by the liquid film 306a. To be supplied. Therefore, a thin coating portion of the coating liquid 306 is generated at the rear end of the recording medium 304-1 (reference numeral 314 in FIG. 23B).

  Furthermore, since only the liquid film 306a of the coating liquid 306 is not excessively absorbed by the recording medium 304 and remains on this portion of the surface of the coating roller 300, the coating liquid 306 is supplied from the measuring roller 310 next. Sometimes, the coating liquid is insufficient in this portion by the amount of the liquid film 306a. As a result, a thin coating portion of the coating liquid 306 is generated on the next transported recording medium 304-2 (reference numeral 316 in FIG. 23C).

  As described above, in the on-demand application of a sheet by the roller method shown in FIG. 22, there is a problem that uneven application occurs when the application end position does not coincide with the rear end of the paper. Although the application end position has been described here, there is a similar problem with respect to the application start position.

  However, since the application roller is an elastic body, an error corresponding to the elastic deformation of the roller occurs between the separation timing of the anilox roller (theoretical application end position) and the actual application end position. Similarly, the theoretical position and position are also determined by mechanical factors such as the gear used for the mechanism for contacting and separating the anilox roller and the backlash of the gear for transmitting the rotational force to the anilox roller and the application roller. Error occurs. In addition, an error occurs at the application end position due to a time lag caused by control of the processing time of the software or the like, or a difference between the nominal size of the paper and the actual size (paper cutting error). As described above, it is difficult to precisely match the application end position and the rear end of the sheet.

  A method of measuring these errors in advance and canceling the errors by offsetting the separation timing is also conceivable, but for this purpose, the test application is repeated in advance, and the operator of the printing press removes the unevenness generated in the printed image. It is necessary to visually observe and obtain an appropriate offset value so as to minimize unevenness. Even if the offset value is obtained once, if the elasticity of the application roller or the nip force of the anilox roller fluctuates due to changes in application conditions or changes over time, it will be corrected each time, and it will take time and correction accuracy will be increased. There is a limit. In addition, these errors have a greater effect as the conveyance speed is increased, and unevenness is more likely to occur, so that there is a problem that correction becomes more difficult.

  For such a problem, Patent Document 2 describes a technique for measuring the application length of an object to be applied by directly imaging the application state of a liquid applied to an application surface by a CCD camera. . According to Patent Document 2, it is possible to correct a necessary operation parameter so as to approach the reference value based on the length measurement result.

JP 2011-67984 A JP 2004-77436 A

  However, the technique of Patent Document 2 has the following problems.

  First, since the application state of the coating liquid applied on the substrate is directly imaged, when the coating liquid is transparent, when the coating thickness is extremely thin, when the glossiness of the substrate and the coating liquid is close (for example, In the case of applying a gloss liquid to glossy paper such as gloss coated paper, the difference in reflectance becomes small, and edge detection becomes difficult.

  Further, since the technique of Patent Document 2 is a technique that assumes continuous paper as an object to be coated, an edge can be easily detected regardless of whether the coating position is shifted upstream or downstream in the transport direction. However, when this technology is applied to a sheet, when the application start position is greatly shifted upstream in the transport direction or the application end position is greatly shifted downstream in the transport direction, that is, when the paper is caught, The end edge cannot be detected. However, there has been a problem that such deviation also causes uneven coating.

  The present invention has been made in view of such circumstances, and reliably detects and corrects coating unevenness (image unevenness) caused by a deviation between the leading and trailing ends of the sheet and the coating start and end positions. An ink jet recording apparatus and an ink jet recording method are proposed.

  In order to achieve the above object, an ink jet recording apparatus according to the present invention includes a transport unit that transports a sheet-like recording medium in a predetermined transport direction, and a processing liquid that agglomerates ink on the recording medium transported by the transport unit. A coating roller for coating; a metering roller for measuring and supplying the treatment liquid to the coating roller; and the metering roller being brought into contact with the coating roller at a predetermined contact timing; and from the coating roller at a predetermined separation timing. Measuring roller separating / contacting means for separating, image recording means for recording an image by ejecting ink droplets onto a recording medium coated with the treatment liquid by an ink jet head, and imaging an image recorded on the recording medium Imaging means for detecting, detecting means for detecting a gradation distribution in the transport direction in the captured image, and processing liquid on the recording medium from the detection result Judgment means for judging whether or not there is an excess area or insufficient area, and correction means for correcting the contact timing or separation timing of the metering roller separation means based on the judgment result of the judgment means. Features.

  According to the present invention, an image recorded on a recording medium is picked up, a gradation distribution in the transport direction in the picked-up image is detected, and an excess area or a shortage area of the processing liquid on the recording medium is detected from the detection result. The presence / absence is determined and the contact timing or separation timing of the measuring roller separation / contact means is corrected based on the determination result, so that the difference between the leading and trailing edges of the sheet and the coating start and end positions is caused. It is possible to reliably detect and correct the coating unevenness.

  According to the present invention, it is possible to reliably detect and correct coating unevenness (image unevenness) caused by a shift between the leading edge and the trailing edge of the sheet, and the coating start position and the coating end position.

Configuration diagram showing overall configuration of inkjet recording apparatus Plane perspective view showing structural example of head Enlarged view of a part of the head The figure which shows the line head which connected the short head module The figure which shows the line head which arranged the short head module in a line. Sectional view showing the three-dimensional structure of the head Block diagram showing schematic configuration of control system of inkjet recording apparatus Schematic diagram showing enlarged treatment liquid application Conceptual diagram schematically showing the contact timing of the anilox roller Conceptual diagram schematically showing the timing of anilox roller separation Flow chart showing separation timing correction processing The figure which shows the generation | occurrence | production position of the image nonuniformity which generate | occur | produces by a separation timing error Diagram for explaining an image read by an inline sensor The figure for demonstrating the relationship between the sum of the gradation value of a pixel, and separation timing The figure which shows the chart image printed on the margin part of the recording medium The figure which shows the generation | occurrence | production position of the image nonuniformity which generate | occur | produces by a contact timing error Flow chart showing contact timing correction processing The figure which shows the area | region of the thin coating nonuniformity on the recording medium resulting from a contact timing error or a separation timing error The figure which shows an example of the histogram of an image gradation Diagram for explaining measurement of ink dot diameter The figure which shows an example of the histogram of an ink dot diameter A diagram for explaining on-demand application of a sheet using a conventional application roller Top view showing recording medium coated with coating liquid

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

[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 leading end portion of the recording medium 14 at predetermined positions on the outer peripheral surface. The structure for holding the front end portion of the recording medium 14 in the gripper 80A and the gripper 80B and the structure for delivering the recording medium 14 to and from the gripper provided in another impression cylinder or 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 32-62 and the impression cylinders 34, 44, 54, 64 are rotated in a predetermined direction with the gripper 80A, 80B holding the leading end of the recording medium 14, the transfer cylinders 32-62 and the impression cylinder 34 are rotated. , 44, 54, 64, the recording medium 14 is rotated and conveyed along the outer peripheral surface.

  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 part (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 an example of the configuration of the processing liquid coating device 36, a processing liquid container (a liquid receiving tray denoted by reference numeral 220 in FIG. 8) in which the processing liquid is stored and a part of the processing liquid in the processing liquid container are immersed in the processing liquid. A pumping roller for pumping up the processing liquid in the liquid container (anilox roller shown with reference numeral 222 in FIG. 8) and a coating roller for moving the processing liquid pumped up by the pumping roller onto the recording medium 14 (reference numeral in FIG. 8). 210).

  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 processing liquid applied to the recording medium 14 by the processing liquid coating apparatus 36 contains a color material flocculant that aggregates the color material (pigment) in the ink applied by the drawing unit 40, and the processing 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 unit 30 is preferably applied while measuring the amount of the treatment liquid applied to the recording medium 14, and the film thickness of the treatment liquid on the recording medium 14 is determined by the ink droplets 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 100A in FIG. 2) of the ink jet heads 48M, 48K, 48C, and 48Y are illustrated in the drawing drum. The recording medium 14 is held so as to face the recording surface of the recording medium 14. 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 (not shown in FIG. This is the surface on which the reference numeral 102 is shown in FIG.

  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 (liquid ejection surfaces) of the inkjet heads 48M, 48K, 48C, and 48Y, ink ejection nozzles 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 drying processing 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 drying processing 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 drying processing device 56 performs a drying process for evaporating a liquid component existing on the recording medium 14 by heating with a heater, blowing with a fan, or a combination thereof, and a process for 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 processing by the drying processing device 56 is performed, 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, 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. .

  The ink jet recording apparatus 10 shown in FIG. 1 is provided with an inline sensor (ILS) 82 (corresponding to an image pickup unit) at the subsequent stage (downstream in the recording medium conveyance direction) of the processing region of the fixing processing unit 60. The ILS 82 is a sensor for reading an image formed on the surface of the recording medium 14 (or a check pattern formed in a blank area of the recording medium 14).

  As the ILS 82, a CCD line sensor is preferably used. For example, a sensor having a resolution of 125 dpi can be used. In this case, the pixel pitch is about 0.2 mm, and when the conveyance speed of the recording medium 14 is 500 mm / sec, the readout time is 0.4 msec.

  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 ILS 82. In addition, the ILS 82 may include a measurement 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 96 and discharged to the discharge tray 92.

[Inkjet head structure]
Next, the structure of the inkjet heads 48M, 48K, 48C, 48Y provided in the drawing unit 40 will be described. Since the structures of the ink jet heads 48M, 48K, 48C, and 48Y corresponding to the respective colors are common, the ink jet head (hereinafter also simply referred to as “head”) is denoted by reference numeral 100 in the following. And

  FIG. 2 is a perspective plan view showing a structural example of the head 100. Hereinafter, in this specification, the same or similar parts as those described above are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIG. 2, the head 100 is a full-line head having a structure in which a plurality of nozzles 102 are arranged on a nozzle surface 100A over a length corresponding to the entire width Wm of the recording medium 14. The conveyance direction S of the recording medium 14 is sometimes referred to as a sub-scanning direction, and the direction M orthogonal to the conveyance direction S of the recording medium 14 is sometimes referred to as a main scanning direction.

  In order to increase the dot pitch formed on the recording medium 14, it is necessary to increase the nozzle pitch in the head 100. As shown in FIG. 2, the head 100 of this example includes a nozzle 102 that is an ink discharge port, a pressure chamber 104 that communicates with each nozzle 102, a common channel that is not shown, and a supply that communicates with each pressure chamber 104. It has a structure in which a plurality of ink chamber units (droplet discharge elements as recording element units) 108 including ports 106 and the like are arranged in a matrix, so that they are arranged along the main scanning direction which is the longitudinal direction of the head 100. A substantial increase in the density of the projected nozzles (projection nozzle pitch indicated by Pn in FIG. 3) is achieved.

  The pressure chamber 104 communicating with the nozzle 102 has a substantially square planar shape, the nozzle 102 is provided at one of the diagonal corners, and the supply port 106 is provided at the other. The shape of the pressure chamber 104 is not limited to this example, and the planar shape may have various forms such as a quadrangle (rhombus, rectangle, etc.), a pentagon, a hexagon and other polygons, a circle, and an ellipse.

  FIG. 3 is an enlarged view of a part of the head 100 shown in FIG. As shown in the figure, the ink chamber unit 108 composed of the nozzles 102, the pressure chambers 104, and the like is arranged at a certain angle that is not orthogonal to the row direction and the main scanning direction along the main scanning direction (shown with reference numeral M). The high-density nozzle head of this example is arranged in a matrix with a fixed arrangement pattern along an oblique column direction (shown with reference numeral S ′) having θ (0 ° <θ <90 °). It has been realized.

  In other words, the projected nozzle pitch Pn of the nozzles projected in the main scanning direction by the structure in which a plurality of ink chamber units 108 are arranged at a constant pitch g along a direction that forms an angle θ with respect to the main scanning direction is g × cos θ, and in the main scanning direction, each nozzle 102 can be handled equivalently as a linear array with a constant pitch Pn. With such a configuration, it is possible to realize a high-density arrangement of 1200 nozzle arrays per inch (1200 nozzles / inch) that are projected so as to be aligned in the main scanning direction.

  In addition, the form which comprises one or more nozzle rows over the length corresponding to the full width Wm of the recording medium 14 is not limited to this example. For example, instead of the configuration of FIG. 2, as shown in FIG. 4, a short head module 100 ′ in which a plurality of nozzles 102 are two-dimensionally arranged is arranged in a staggered manner and connected to be elongated. Thus, a line head having a nozzle row having a length corresponding to the entire width of the recording medium 14 as a whole may be configured.

  Further, as shown in FIG. 5, a line head may be configured by arranging short head modules 100 ″ that are less than the full width of the recording medium 14 in a line. In the figure, along the line direction (see FIG. 2). The arranged nozzles 102 are shown by oblique solid lines.

  6 is a cross-sectional view (a cross-sectional view taken along the line AA in FIG. 2) showing a three-dimensional structure of the head 100 (ink chamber unit 108) shown in FIG.

  The pressure chamber 104 communicating with the nozzle 102 communicates with the common flow path 110 via the supply port 106. The common channel 110 communicates with an ink tank (not shown) as an ink supply source, and the ink supplied from the ink tank is supplied to each pressure chamber 104 via the common channel 110.

  The vibration plate 112 constituting the upper surface of the pressure chamber 104 includes an individual electrode 114 and a common electrode 116, and a piezoelectric element having a structure in which a piezoelectric body 118 is sandwiched between the individual electrode 114 and the common electrode 116. 120 is joined. Further, the head 100 shown in FIG. 6 includes a nozzle plate 124 in which an opening 122 of the nozzle 102 is formed in a structure in which a flow channel structure such as the pressure chamber 104, the supply port 106, and the common flow channel 110 is formed. It has a joined structure.

  By applying a predetermined drive voltage between the individual electrode 114 and the common electrode 116, the piezoelectric element 120 and the diaphragm 112 are deformed, and the volume of the pressure chamber 104 changes accordingly. A pressure change occurs in the ink inside the pressure chamber 104 due to the volume change of the pressure chamber 104, and a volume of ink corresponding to the volume change of the pressure chamber 104 is ejected from the nozzle 102. After the ink is ejected, the pressure chamber 104 is filled with new ink from the common flow path 110 through the supply port 106 when the piezoelectric element 120 and the vibration plate 112 return to the original state.

  In this example, the piezoelectric element 120 is used as a means for generating ink ejection force to be ejected from the nozzles 102 provided in the head 100. However, a heater is provided in the pressure chamber 104 and the pressure of film boiling caused by heating of the heater is used. It is also possible to apply a thermal method that ejects ink.

[Explanation of control system]
FIG. 7 is a block diagram illustrating a schematic configuration of a control system of the inkjet recording apparatus 10. The inkjet recording apparatus 10 includes a communication interface 140, a system control unit 142, a conveyance control unit 144, an image processing unit 146, a head driving unit 148, and a storage unit (memory) 150 and a temporary storage unit 152.

  The communication interface 140 is an interface unit that receives image data sent from the host computer 154. The communication interface 140 may be a serial interface such as USB (Universal Serial Bus) or a parallel interface such as Centronics. The communication interface 140 may include a buffer memory (not shown) for speeding up communication.

  The system control unit 142 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. Further, it functions as a memory controller for the storage unit 150 and the temporary storage unit 152. That is, the system control unit 142 controls each unit such as the communication interface 140 and the transport control unit 144, performs communication control with the host computer 154, read / write control of the storage unit 150 and the temporary storage unit 152, and the like. A control signal is generated to control each part.

  Image data sent from the host computer 154 is taken into the ink jet recording apparatus 10 via the communication interface 140, and predetermined image processing is performed by the image processing unit 146.

  The image processing unit 146 has a signal (image) processing function for performing various processing and correction processes for generating a print control signal from the image data, and supplies the generated print data to the head drive unit 148. It is a control unit. Necessary signal processing is performed in the image processing unit 146, and the ejection droplet amount (droplet ejection amount) and ejection timing of the head 100 are controlled via the head driving unit 148 based on the image data. Thereby, a desired dot size and dot arrangement are realized. Note that the head driving unit 148 shown in FIG. 7 may include a feedback control system for keeping the driving conditions of the head 100 constant.

  Further, the conveyance control unit 144 controls the conveyance timing and conveyance speed of the recording medium 14 (see FIG. 1) based on the print control signal generated by the image processing unit 146. 7 includes a motor that rotates the impression cylinders 34, 44, 54, and 64 in FIG. 1, a motor that rotates the transfer cylinders 32 to 62, and a motor for the feeding mechanism of the recording medium 14 in the sheet feeding unit 20. In addition, a motor for driving the stretching roller 72A (72B) of the discharge unit 70 is included, and the conveyance control unit 144 functions as a driver for the motor.

  The storage unit 150 stores a program executed by the CPU of the system control unit 142, various data necessary for control of each unit of the apparatus, control parameters, and the like, and data is read and written through the system control unit 142. The storage unit 150 is not limited to a memory made of a semiconductor element, and a magnetic medium such as a hard disk may be used. Alternatively, a removable storage medium that includes an external interface may be used.

  The temporary storage unit (temporary storage memory) 152 functions as a temporary storage unit that temporarily stores image data input via the communication interface 140, a development area for various programs stored in the storage unit 150, and a CPU. It has a function as a calculation work area (for example, a work area of the image processing unit 146). As the temporary storage unit 152, a volatile memory (RAM) capable of sequential reading and writing is used.

  Further, the inkjet recording apparatus 10 includes a processing liquid application control unit 160, a drying processing control unit 162, and a fixing processing control unit 164, and in accordance with instructions from the system control unit 142, the processing liquid application unit 30 is provided. The operation of each part of the fixing processing unit 60 including the drying processing unit 50, the heater 66, and the fixing roller 68 (see FIG. 1) is controlled.

  The treatment liquid application controller 160 controls the timing of application of the treatment liquid and also controls the application amount of the treatment liquid. The treatment liquid application device 36 provided in the treatment liquid application unit 30 is an anilox roller (FIG. 8) that measures the amount of treatment liquid supplied to the application roller with respect to the application roller (indicated by reference numeral 210 in FIG. 8). An anilox roller moving mechanism for moving the anilox roller is provided so that the contact (contact) and separation of the reference numeral 222 can be performed.

  7 controls the contact timing and separation timing between the anilox roller and the application roller.

  The drying process control unit 162 controls the timing of the drying process and also controls the processing temperature, the air flow rate, and the like, and the fixing process control unit 164 controls the temperature of the heater 66 and the pressing of the fixing roller 68. .

  The detection unit 166 is a processing block including a signal processing unit that performs predetermined signal processing such as nozzle removal, amplification, and waveform shaping on the read signal output from the ILS 82 illustrated in FIG. 1. Based on the detection signal obtained by the detection unit 166, the system control unit 142 determines whether there is an ejection abnormality of the head 100.

  The encoder 168 is attached to a motor serving as a drive source for rotating the impression cylinders 34, 44, 54, and 64, and a pulse signal corresponding to the rotation of the motor is output. By counting the pulse signals output from the encoder 168, the amount of rotation of the impression cylinders 34, 44, 54, 64 can be grasped. Further, the rotation unevenness of the impression cylinders 34, 44, 54, 64 can be grasped based on the frequency fluctuation of the pulse signal output from the encoder 168.

  That is, the pulse train output from the encoder 168 is subjected to predetermined signal processing such as waveform shaping and noise removal, and is sent to the system control unit 142. Based on the pulse train acquired from the encoder 168, the system control unit 142 sends a command signal for controlling the contact timing and separation timing of the anilox roller to the processing liquid application control unit 160.

  The paper sensor 170 is a sensor provided in the conveyance path of the recording medium 14 and can grasp the position of the recording medium 14 on the conveyance path based on the detection result of the paper sensor 170. For example, when the paper sensor 170 provided in the vicinity of the gripper 80 of the impression cylinder 34 (44, 54, 64) detects the recording medium 14, the gripper 80 is operated to sandwich the leading end of the recording medium 14, and the impression cylinder 34 is operated. The adsorption control and temperature control are switched to the recording medium holding state.

  In FIG. 7, a plurality of paper sensors provided on the recording medium conveyance path are represented by reference numeral 170.

  In this example, the ink jet recording apparatus 10 to which the impression cylinder conveyance method is applied is illustrated, but the conveyance method of the recording medium 14 is not limited to the impression cylinder conveyance method, and the recording medium is sucked and held on the conveyance belt. It is also possible to appropriately select a belt conveyance method for conveying the ink and other conveyance methods.

[Description of treatment liquid application equipment]
Next, the processing liquid coating apparatus 36 applied to the processing liquid coating unit 30 illustrated in FIG. 1 will be described in detail. FIG. 8 is an enlarged schematic view of the treatment liquid application unit 30 of FIG. In addition, the same code | symbol is attached | subjected to the part which is the same as that already demonstrated, or is the same, and the description is abbreviate | omitted.

  The processing liquid coating device 36 shown in FIG. 8 is stored in a liquid receiving tray 220 while rotating at a predetermined rotational speed and an application roller 210 that applies a processing liquid while contacting a recording medium while rotating at a predetermined rotational speed. An anilox roller (measuring roller) 222 that measures the amount of the processing liquid that is being supplied and supplies the measured processing liquid to the application roller 210, a blade 224 that scrapes off excess processing liquid adhering to the anilox roller 222, and the application roller 210 and anilox An anilox roller moving mechanism (not shown) that varies the distance between the shaft and the roller 222 is configured.

  The application roller 210 is disposed so as to contact the impression cylinder 34 at a position closer to the transfer cylinder 32 (upstream in the recording medium conveyance direction) than the highest position of the impression cylinder 34. The application roller 210 has a length in the longitudinal direction corresponding to the length of the impression cylinder 34 in the axial direction (the direction passing through the paper surface in FIG. 8), and moves the recording medium 14 only once with respect to the application roller 210. Thus, it is possible to apply the treatment liquid over the entire surface of the recording medium 14.

  As the application roller 210, a rubber material having acid resistance and a hardness of 40 to 70 ° is preferable. Examples thereof include EPDM (ethylene-propylene-diene rubber) and silicon rubber.

  The liquid receiving tray 220 has a length in the longitudinal direction corresponding to the length of the application roller 210 in the axial direction, and stores the processing liquid inside.

  The anilox roller 222 has a length in the longitudinal direction corresponding to the length of the application roller 210 in the axial direction, and a large number of cells (concave shape for measuring the treatment liquid) are formed on the surface thereof.

  The anilox roller 222 is rotatably held with the lower half immersed in the processing liquid stored in the liquid receiving tray 220.

  The anilox roller moving mechanism moves the anilox roller 222 to vary the distance between the axes of the application roller 210 and the anilox roller 222, and supplies the processing liquid from the anilox roller 222 to the application roller 210 (FIG. 8A). )) And a separation position (FIG. 8B) where the processing liquid is not supplied from the anilox roller 222 to the application roller 210 can be switched.

  In the supply position, the surface of the anilox roller 222 is in contact with the surface of the application roller 210. When the anilox roller 222 is rotated, the processing liquid in the liquid receiving tray 220 is drawn up, and excess processing liquid adhering to the surface is scraped off by the blade 224. A certain amount of the processing liquid held in the cell of the anilox roller 222 is supplied to the application roller 210 at a position where it is in contact with the application roller 210.

  In the separation position, even if the anilox roller 222 is rotated, the treatment liquid is not supplied to the application roller 210.

  As the anilox roller 222, a structure in which a surface of a stainless steel roller is engraved or a structure in which a laser is applied to the surface of a ceramic roller can be applied. The rotational speed of the anilox roller 222 is set to 70 to 150% with respect to the rotational speed of the application roller 210, so that the surface state of the liquid surface is improved and the application amount can be adjusted according to the rotational speed.

  The blade 224 is a thin plate having a length in the longitudinal direction corresponding to the length of the anilox roller 222 in the axial direction, and one end thereof is urged and held so as to be pressed against the cylindrical surface of the anilox roller 222.

  The blade 224 is made of a material having acid resistance and wear resistance such as a resin material or a rubber material, or a material such as stainless steel (a metal material or metal alloy having acid resistance).

  FIG. 8A illustrates the state of the application period in which the anilox roller 222 is in contact with the application roller 210. That is, during the application period, the anilox roller 222 is urged toward the application roller 210 by an anilox roller moving mechanism (not shown), and the anilox roller 222 is in contact with the application roller 210. As a result, the processing liquid is supplied to the application roller 210.

  On the other hand, FIG. 8B shows the state of the non-application period. In the non-application period, the anilox roller 222 is separated from the application roller 210 by an anilox roller moving mechanism (not shown), and the supply of the processing liquid is stopped. Even after the anilox roller 222 is separated from the application roller 210, the anilox roller 222 is maintained in a state of rotating at a predetermined rotation speed.

  The treatment liquid coating apparatus 36 shown in this example is coated from the anilox roller 222 in accordance with the transport timing of the recording medium 14 and the length in the transport direction of the recording medium 14 (hereinafter referred to as “the length of the recording medium”). The supply start and stop of the processing liquid to the roller 210 are controlled. Hereinafter, contact control and separation control between the application roller 210 and the anilox roller 222 will be described in detail.

[Description of Anilox Roller Contact Control]
First, the contact control (contact timing) of the anilox roller 222 will be described. FIG. 9 is a conceptual diagram schematically showing the timing at which the anilox roller 222 is brought into contact with the application roller 210.

  A position where the application roller 210 and the anilox roller 222 come into contact with each other when the processing liquid is supplied from the anilox roller 222 to the application roller 210 is referred to as a “supply processing position”, and is indicated by reference numeral 240. Further, a position where the application roller 210 and the recording medium 14 (the impression cylinder 34) come into contact when the processing liquid is applied from the application roller 210 to the recording medium 14 is referred to as an “application processing position”, and is denoted by reference numeral 242. . In the drawing, an anilox roller that is separated from the application roller 210 is indicated by a broken line with a reference numeral 222A. The direction indicated by the outlined arrow line is the moving (contacting) direction of the anilox roller 222.

  The timing at which the anilox roller 220 and the application roller 210 are brought into contact with each other is the timing at which the front end portion 14A of the recording medium 14 reaches the application processing position 242 and the processing liquid supply start position on the application roller 210 reaches the application processing position 242. It is determined so that the timing to do matches.

That is, the conveyance distance (movement distance of the peripheral surface of the impression cylinder 34) between the position of the leading end portion 14A of the recording medium 14 and the application processing position 242 when the anilox roller 222 is brought into contact with the application roller 210. L ₁ , the movement distance of the peripheral surface of the application roller 210 between the supply processing position 240 and the application processing position 242 is L ₂ , the conveyance speed of the recording medium 14 (the peripheral speed of the impression cylinder 34) is V ₁ , and the peripheral speed of the application roller 210. When the _{V 2, that,} to satisfy the relationship of _{L 1 / V 1 = L 2} / V 2, timing for abutting the anilox roller 216 to the application roller 210 is determined.

  In this way, the supply of the processing liquid from the anilox roller 222 to the coating roller 210 is started, and the coating roller 210 is brought into contact with the recording medium 14 at the timing when the front end portion 14A of the recording medium 14 reaches the coating processing position 242. Thus, the processing liquid is applied to the recording medium 14.

  Further, the application roller 210 and the anilox roller 222 are applied so that the treatment liquid is applied from the rear side by the amount of the gripper (shown with reference numeral 80A in FIG. 8) from the front end portion 14A of the recording medium 14. Correction of the contact timing is also possible.

[Explanation of anilox roller separation control]
Next, the separation control (separation timing) of the anilox roller 222 will be described. FIG. 10 is a conceptual diagram schematically illustrating the timing at which the anilox roller 222 is separated from the application roller 210. In the figure, the anilox roller in contact with the application roller 210 is indicated by a dashed line with reference numeral 222B. The direction indicated by the white arrow line is the movement (separation) direction of the anilox roller 222.

  The timing at which the anilox roller 220 and the application roller 210 are separated is the timing at which the rear end portion 14B of the recording medium 14 reaches the application processing position 242 and the processing liquid supply end position on the application roller 210 reaches the application processing position 242. It is determined so that the timing to do matches.

That is, when a distance on the conveyance between the position of the rear end portion 14B and the coating processing position 242 of the recording medium 14 obtained while separating the anilox roller 222 from the application roller 210 and _{L 3, L 3 / V 1} = The timing for separating the anilox roller 222 from the application roller 210 is determined so as to satisfy the relationship of L ₂ / V ₂ .

When there is no change in the conveyance speed of the recording medium 14 (the peripheral speed of the impression cylinder 34) and the peripheral speed of the application roller 210, the relationship L ₁ = L ₃ is established.

  In order to grasp the position of the rear end portion 14B of the recording medium 14, it is necessary to grasp the size of the recording medium 14. As an example of grasping the size of the recording medium 14, the type and standard (minimum length) of the recording medium 14 are stored in a data table in advance, and the acquired type information of the recording medium 14 is referred to. Can be mentioned. The type information of the recording medium 14 is read from an information storage medium such as an IC tag attached to the recording medium 14 when the recording medium 14 is loaded in the paper feeding unit 20, or is input by an operator via a user interface. A method of actually measuring the size of the recording medium 14 can be applied.

  In this example, a mode in which the conveyance speed of the recording medium 14 and the position on the conveyance path are grasped based on the information obtained from the pressure drum 34 or an encoder (rotary detector) attached to the motor that drives the pressure drum 34 is illustrated. However, it is also possible to grasp based on information obtained from a linear scale (linear detector) provided in the vicinity of the conveyance path instead of the encoder.

[First Embodiment]
Thus, according to the treatment liquid application device 36, the application roller 210 starts application of the treatment liquid from the front end portion 14A of the recording medium 14, and ends application of the treatment liquid at the rear end portion 14B of the recording medium 14.

  However, as described above, an error occurs in the application start position and the paper front end portion or the application end position and the paper rear end portion due to various factors, and application unevenness occurs due to the error. In the present embodiment, an image is read by the ILS 82, and color density unevenness caused by the contact / separation timing error of the anilox roller 222 is determined based on the read image, so that the contact / separation of the anilox roller 222 is performed. Correct the timing.

  FIG. 11 is a flowchart showing separation timing correction processing according to the present embodiment.

First, the inkjet recording apparatus 10 starts printing on the recording medium 14. At this time, the treatment liquid application control unit 160 initializes the variable n to 1 (step S1). In addition, as an initial value of the separation timing T _0, a time obtained by dividing the conveyance direction length of the recording medium 14 by the conveyance speed (the peripheral speed of the impression cylinder 34) is set. An initial value is set as ΔD ₀ .

  When printing is started, the paper supply unit 20 supplies the recording medium 14 accommodated in the paper supply tray 22 to the treatment liquid application unit 30. The treatment liquid application device 36 of the treatment liquid application unit 30 applies the treatment liquid to the entire surface of the conveyed recording medium 14.

  The recording medium 14 to which the processing 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 processing liquid has been applied, thereby forming a desired image.

  The recording medium 14 on which the color ink image is formed is sent to the drying processing unit 50, where the drying processing unit 50 performs drying processing, and after the drying processing, the recording medium 14 is sent to the fixing processing unit 60, where fixing processing is performed. .

  Next, the image formed on the recording medium 14 is read by the ILS 82 (step S2). In the present embodiment, since the occurrence of image unevenness cannot be detected on the first recording medium 14 at the start of printing, this is performed on the second and subsequent recording media 14.

  Here, the occurrence position of the image unevenness due to the error in the separation timing is the size of the recording medium 14 in the conveyance direction, the roller diameter (circumferential length) of the impression cylinder 34, the peripheral speed of the impression cylinder 34, and the roller of the application roller 210. It can be predicted from the diameter and peripheral speed.

That is, assuming that the peripheral speed of the impression cylinder 34 is V ₁ , the peripheral speed of the application roller 210 is V ₂ , and the diameter of the application roller 210 is b ₁ , the position of occurrence of image unevenness is determined by the recording medium 14 (processing liquid by the application roller 210. Is applied from the rear end of the recording medium 14) conveyed to the downstream side M × π × b ₁ × V ₁ / V ₂ (Equation 1)
Only the position shifted upstream along the conveying surface of the impression cylinder 34 is predicted. M is a positive integer.

  Therefore, image unevenness may occur in the recording medium 14 conveyed on the position of the rear impression cylinder 34.

The impression cylinder 34 of this embodiment conveys the Nth recording medium 14 and the (N + 1) th recording medium 14 at a symmetrical position obtained by moving the Nth recording medium 14 by 180 ° in the rotation direction of the impression cylinder 34. Thus, the generation position of the image unevenness, as shown in FIG. 12, the diameter of the impression cylinder 34 b ₂ that occurs N + 1 sheet of recording medium 14 by the separation timing error in the N-th recording medium _14, recording medium 14 (L × π × b ₁ × V ₁ / V ₂ ) − (π × b ₂ −L) (Equation 2) from the leading end portion 14A of the (N + 1) th recording medium 14. )
Only the upstream position 250 is obtained.

  Therefore, the ILS 82 reads only the image around the predicted image unevenness occurrence position 250 (step S2).

  FIG. 13A is a schematic diagram illustrating an image unevenness occurrence position 250 of the recording medium 14 and a detection area 252 that is read by the ILS 82. The detection area 252 only needs to include the image unevenness occurrence position 250, and the range can be determined as appropriate. Here, the detection area 252 is an area of a normal print image.

FIG. 13B is a schematic diagram showing a scan image 254 when the detection area 252 is read by the ILS 82. Here, the gradation value of the pixel in the i-th row and j-th column of the scanned image 254 is assumed to be _dij .

The system control unit 142 calculates the sum of the gradation values of the pixels for each row for all rows from the scan image 254 in the conveyance direction of the recording medium 14. That is, the sum of d _{11 to} d _1j, the sum of d _{21 to} d _2j , the sum of d _{31 to} d _3j ,..., The sum of d _{i1 to} d _ij is calculated. FIG. 13C is a graph showing the sum of the gradation values of the pixels for each row. The bottom value Db and the peak value Dp are extracted from the sum of the gradation values of the pixels for each row.

  A difference ΔDn between the bottom value Db and the peak value Dp is calculated (step S3), and the calculated ΔDn is stored in the primary storage unit 152 (step S4).

  Here, the relationship between the sum of the gradation values of the pixels for each row in the transport direction and the separation timing of the anilox roller 222 will be described with reference to FIG. In FIG. 14, the peak value of the sum or valley of the gradation values of the pixels for each row in the transport direction is Dp, and the bottom value is Db.

  When ΔD = Dp−Db> 0 (in the case of FIG. 14A), it can be understood that thick coating unevenness occurs because the treatment liquid is dark and the ink is excessively aggregated. This occurs because the separation timing of the anilox roller 222 at the rear end of the previous recording medium 14 is late. Therefore, when ΔD> 0, the separation timing needs to be advanced.

  On the other hand, when ΔD = Dp−Db <0 (in the case of FIG. 14B), it can be seen that thin coating unevenness occurs because the processing liquid is thin and ink aggregation is insufficient. This occurs because the separation timing of the anilox roller 222 at the rear end of the previous recording medium 14 is early. Therefore, when ΔD <0, it is necessary to delay the separation timing.

  Since the ILS 82 reads an image around the predicted image unevenness occurrence position 250, the gradation value of the area of the image unevenness occurrence position 250 in the scan image 254 is determined from the peak value Dp and the image unevenness occurrence position 250. It is possible to extract the gradation value of the distant area as the bottom value Db.

Returning to the description of the flowchart of FIG. 11, the absolute value of ΔD _n in the Nth recording medium 14 stored in step S4 and the absolute value of ΔD _{n−1 in} the N−1 recording medium 14 already stored. The values are compared (step S5).

If towards the absolute value of [Delta] D _n is small, and migration is determined that there is not enough correction of the separation timing in step S6, it is determined whether [Delta] D _n is greater than 0.

If ΔD _n is greater than 0, the process proceeds to step S7. As described above, when ΔD _n > 0, it is thick coating unevenness, and the separation timing needs to be advanced. Therefore, in step S7, the shorter predetermined amount Δt than the separation timing _{T n-1} of the previous the separation timing _{T n} of the anilox roller _{222 (T n = T n-} 1 -Δt).

If ΔDn is not greater than 0, the process proceeds to step S8, and determines whether or not [Delta] D _n is less than zero.

If ΔD _n is smaller than 0, the process proceeds to step S9. As described above, when ΔD _n <0, it is a thin coating unevenness and it is necessary to delay the separation timing. Therefore, in step S9, the longer by a predetermined amount Delta] t than the separation timing _{T n-1} of the previous one the separation timing _{T n} of the anilox roller _{222 (T n = T n-} 1 + Δt).

In step S8, if [Delta] D _n is not less than 0, a [Delta] D _n = 0. Therefore, in this case, since no unevenness has occurred, the separation timing is set to _Tn , and the process is terminated.

When the separation timing _Tn is corrected in step S7 and step S9, n is incremented, and the process returns to step S2 to perform the same processing.

In step S5, when towards the absolute value of [Delta] D _n is large, it is determined that the correction of the separation timing is overcorrection, to set the separation timing T _n to the previous T _n-1 (step S11) The process is terminated.

  According to this embodiment, since the density of the inkjet image drawn in the treatment liquid is detected instead of directly detecting the application surface of the treatment liquid, it is affected by the gloss of the treatment liquid surface and the substrate (paper). Therefore, the coating unevenness can be detected. Further, since unevenness of the inkjet image that finally occurs is targeted for detection, there is no error factor, and application unevenness can be reliably detected. As a result, coating unevenness can be reliably eliminated.

  Further, even when the application position is shifted upstream or downstream in the transport direction, the shift direction can be determined and corrected by detecting the density of unevenness.

  Furthermore, since the existing in-line sensor is used as it is, it is not necessary to newly add an optical sensor, a CCD camera or the like, and the cost can be reduced. Further, by predicting the occurrence position of image unevenness and reading only the image of that portion, it is possible to reduce the load of image processing.

  When the contact / separation timing is corrected using the position of the recording medium as a reference, the deviation (density unevenness) due to the timing error increases as the conveyance speed of the recording medium increases. It is not affected by the transport speed.

  In this embodiment, the sum of the gradation values of the pixels for each row is calculated from the scanned image 254, and the separation timing is controlled using the difference ΔD between the maximum value and the minimum value. It is also possible to control using an average value in the column direction or an integral value.

  Moreover, in order to increase the detection accuracy of unevenness, unevenness detection may be performed using a chart image. For example, unevenness can be detected with higher accuracy by printing a chart image suitable for unevenness detection in the detection area 252 during test printing before normal printing.

  Further, the detection area 252 may be a chart image printed on the margin of the recording medium 14 instead of the normal print area. For example, as shown in FIG. 15, CMY three-color gray halftone is printed in an area outside the print area (image area) 256 on the recording medium 14 and including the unevenness occurrence position 250. By using the three-color gray halftone as the detection area 258, it becomes possible to detect coating unevenness with higher accuracy. Further, since the blank portion is used, it is possible to always detect unevenness during normal printing, and to correct the contact / separation timing in real time during printing.

[Second Embodiment]
In the first embodiment, the separation timing of the anilox roller 222 is corrected, but the contact timing of the anilox roller 222 can also be corrected in the same manner.

As shown in FIG. 16, it is possible to predict the occurrence position of image unevenness caused by the error in the contact timing of the anilox roller 222. That is, if the peripheral speed of the impression cylinder 34 is V ₁ , the peripheral speed of the application roller 210 is V ₂ , and the diameter of the application roller 210 is b ₁ , the image is caused by an error in the contact timing of the Nth recording medium 14. The occurrence position of the unevenness is predicted to be a position 260 shifted from the front end of the Nth recording medium 14 to the upstream side along the conveying surface of the impression cylinder 34 by M × π × b ₁ × V ₁ / V _2. The M is a positive integer.

  Therefore, image unevenness may occur in the recording medium 14 conveyed on the position of the impression cylinder 34. In the example of FIG. 16, image unevenness occurs on the Nth recording medium 14.

  FIG. 17 is a flowchart showing the contact timing correction process. In addition, the same code | symbol is attached | subjected to the part which is common in the flowchart shown in FIG. 11, and the detailed description is abbreviate | omitted. The contact timing of the anilox roller 222 is opposite to the separation timing, and thick coating unevenness occurs when it is early, and thin coating unevenness occurs when it is late.

Therefore, when the ΔDn is determined that [Delta] D _n greater than 0 in S6, in step S21, contact timing _{T n} the previous contact timing _{T n-1} predetermined amount Δt than the anilox roller 222 (T _n = T _n-1 + Δt).

Further, when the ΔDn is determined that [Delta] D _n less than 0 at S8, in step S22, contact timing _{T n} the previous contact timing _{T n-1} predetermined amount Δt than the anilox roller 222 (T _n = T _n−1 −Δt).

By performing this process until | ΔD _n |> | ΔD _n-1 | is satisfied (step S5), the contact timing can be corrected to the appropriate timing.

[Third Embodiment]
FIG. 18 is a diagram illustrating an image unevenness occurrence position on the recording medium 14 that is generated due to the contact timing error or the separation timing error of the anilox roller 222.

  When the contact timing of the Nth recording medium 14 is later than the desired timing, the region including the tip portion 14A of the Nth recording medium 14 becomes the image unevenness occurrence position 262, and thin coating unevenness occurs. . Similarly, when the separation timing of the Nth recording medium 14 is earlier than the desired timing, the region including the rear end portion 14B of the Nth recording medium 14 becomes the image unevenness occurrence position 266, and the thin coating unevenness. Will occur.

  Therefore, the detection areas 264 and 268 are provided in the vicinity of the front end portion 14A and the rear end portion 14B, the ink image in the detection area is read by the ILS 82, and the density distribution in the transport direction is examined from the captured ink image, so that thin coating unevenness is obtained. The occurrence can be detected.

  In this case, when the occurrence of thin coating unevenness is detected in the detection area 264, the contact timing of the anilox roller 222 may be advanced by a predetermined time Δt. Conversely, when the occurrence of thin coating unevenness is detected in the detection area 268, the separation timing of the anilox roller 222 may be delayed by a predetermined time Δt.

  Further, by printing CMY three-color gray halftone in the detection areas 264 and 268, it becomes possible to detect coating unevenness more appropriately.

[Fourth Embodiment]
In the first to third embodiments, the occurrence of thick coating unevenness or thin coating unevenness is determined using the difference ΔDn between the bottom value Db of the sum of the gradation values of the pixels for each row and the peak value Dp. The occurrence of thick coating unevenness or thin coating unevenness may be determined using a tone histogram.

  For example, an image gradation histogram (horizontal axis: gradation, vertical axis: number of pixels) is calculated for all pixels of the scanned image 254, and the gradation value at the maximum peak and the gradation value at the second peak of the histogram are calculated. Correction is made so that the difference between and is minimized. FIG. 19 is a diagram illustrating an example of a histogram of calculated image gradations.

In FIG. 19, the gradation value at the peak where the number of pixels is maximum is D ₁ , and the gradation value at the second peak is D ₂ . Since the ILS 82 reads a sufficiently wide range in the conveyance direction with respect to the predicted image unevenness occurrence position, the gradation values of each pixel of the scan image 254 are majority other than the image unevenness occurrence portion. It becomes. That D ₁ is the gradation value representative of the entire image except the uneven portion, D ₂ shows a tone value of uneven portions.

Here, by setting ΔDn = D ₂ −D ₁ , the flowchart of FIG. 11 can be applied to the separation timing correction process, and the flowchart of FIG. 17 can be applied to the contact timing correction process.

That is, when ΔDn = D ₂ −D ₁ > 0 (in the case of FIG. 19A), it can be seen that thick coating unevenness occurs because the treatment liquid is dark and the ink is excessively aggregated. . This occurs because the separation timing of the anilox roller 222 is late or the contact timing is early. Therefore, when ΔDn> 0, the separation timing is corrected earlier or the contact timing is delayed.

On the other hand, when ΔDn = D ₂ −D ₁ <0 (in the case of FIG. 19B), since the processing liquid is thin and ink aggregation is insufficient, thin coating unevenness may occur. Recognize. This occurs because the separation timing of the anilox roller 222 is early or the contact timing is late. Therefore, when ΔDn <0, correction is made so that the separation timing is delayed or the contact timing is advanced.

  As described above, it is possible to appropriately correct the separation timing and the contact timing by determining the occurrence of thick coating unevenness and thin coating unevenness using the histogram of the image gradation.

[Fifth Embodiment]
Further, the occurrence of thick coating unevenness or thin coating unevenness may be determined using a histogram of ink dot diameters.

  For example, the ink dot diameter is measured for an arbitrary region of the scan image 254 (for example, in a measurement area randomly selected from the scan image), and a histogram for all areas (horizontal axis: dot diameter, vertical axis: number of dots). Is corrected so that the difference between the dot diameter at the maximum peak of the histogram and the dot diameter at the second peak is minimized.

  First, the detection area 252 is read by the ILS 82 in the vicinity of the image unevenness occurrence position 250 of the recording medium 14 shown in FIG. FIG. 20B is a schematic diagram showing the scan image 254 at this time.

  Next, the system control unit 142 measures the ink dot diameter for an arbitrary region of the scan image 254. Here, as an example, the dot diameters of the five dot diameter measurement areas 270-1 to 270-5 are measured. FIG. 20C is an enlarged schematic diagram of the regions 270-1 and 270-4. The ILS 82 in the present embodiment has a resolution capable of measuring the dot diameter.

FIG. 21 is a diagram showing an example of a histogram of ink dot diameters calculated in this way. In FIG. 21, the dot diameter at the peak where the number of pixels is maximum is D ₁ , and the dot diameter at the second peak is D ₂ . That D ₁ is the dot diameter representing the entire image except the uneven portion, D ₂ shows a dot diameter of unevenness portion.

Here, by setting ΔDn = D ₁ −D ₂ , the flowchart of FIG. 11 can be applied to the separation timing correction process, and the flowchart of FIG. 17 can be applied to the contact timing correction process.

That is, when ΔD = D ₁ −D ₂ <0 (in the case of FIG. 21A), the processing liquid is thin and the ink is insufficiently aggregated. Recognize. This occurs because the separation timing of the anilox roller 222 is early or the contact timing is late. Therefore, when ΔDn <0, correction is made so that the separation timing is delayed or the contact timing is advanced.

On the other hand, when ΔDn = D ₁ −D ₂ > 0 (in the case of FIG. 21B), it can be seen that thick coating unevenness occurs because the treatment liquid is dark and the ink is excessively aggregated. . This occurs because the separation timing of the anilox roller 222 is late or the contact timing is early. Therefore, when ΔDn> 0, the separation timing is corrected earlier or the contact timing is delayed.

  As described above, it is possible to appropriately correct the separation timing and the contact timing by determining the occurrence of thick coating unevenness and thin coating unevenness using the histogram of the ink dot diameter.

  In the present embodiment, when a chart image is recorded in the detection area, K, M, and C single color halftones are desirable.

<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): Conveying means for conveying a sheet-like recording medium in a predetermined conveying direction, an application roller for applying a processing liquid for aggregating ink on the recording medium conveyed by the conveying means, and measuring the processing liquid A metering roller for supplying to the coating roller, a metering roller separating / contacting means for bringing the metering roller into contact with the coating roller at a predetermined contact timing, and separating from the coating roller at a predetermined separation timing; An image recording unit that records an image by ejecting ink droplets onto a recording medium coated with a liquid by an ink jet head, an imaging unit that captures an image recorded on the recording medium, and the image in the captured image A detecting means for detecting a gradation distribution in the transport direction, and a determination means for determining the presence or absence of an excessive or insufficient area of the processing liquid on the recording medium from the detection result; When ink-jet recording apparatus characterized by comprising a correction means for correcting the timing of contact or separation timing of the metering roller disjunction means based on the determination result of said determining means.

(Invention 2): In the ink jet recording apparatus of Invention 1, the imaging means captures an image of a predetermined area of the recording medium, and the predetermined area has a transport speed V _{1 of the} transport means and an outer periphery of the coating roller. When the surface speed is V ₂ and the diameter of the coating roller is b, L = M × π × b × from the leading edge or the trailing edge of the recording medium or the recording medium conveyed downstream from the recording medium. This is a region separated upstream by a transport distance L represented by V ₁ / V ₂ (where M is an integer) along the transport surface of the transport means.

  Thereby, the load of image processing can be reduced.

  (Invention 3): In the ink jet recording apparatus of Invention 2, the predetermined area is an area separated from the recording medium or a leading edge of a recording medium conveyed downstream from the recording medium by the conveyance distance L, When the determination means determines that there is an area where the processing liquid is insufficient, the correction means advances the contact timing of the metering roller separation means by a predetermined time, and determines that there is an area where the processing liquid is excessive. If so, the contact timing of the metering roller separating / contacting means is delayed by a predetermined time.

  Thereby, the contact timing can be appropriately corrected.

  (Invention 4): In the ink jet recording apparatus of Invention 2 or 3, the predetermined area is an area separated from the rear end of the recording medium conveyed downstream of the recording medium by the distance L, and the correcting means When the determination means determines that there is an area where the processing liquid is insufficient, the separation timing of the measuring roller separation means is delayed by a predetermined time, and when it is determined that there is an area where the processing liquid is excessive Increases the separation timing of the measuring roller separation means by a predetermined time.

  Thereby, the separation timing can be appropriately corrected.

  (Invention 5): In the ink jet recording apparatus of Invention 1, the imaging means captures an image of a predetermined area of the recording medium, and the predetermined area is an area near the front end or the rear end of the recording medium. is there.

  Thereby, the load of image processing can be reduced.

  (Invention 6): In the ink jet recording apparatus of Invention 5, the predetermined area is an area in the vicinity of the tip of the recording medium, and the correction means determines that there is an area where the processing liquid is insufficient by the determination means. In this case, the contact timing of the measuring roller separating / contacting means is advanced by a predetermined time.

  Thereby, the contact timing can be appropriately corrected.

  (Invention 7): In the ink jet recording apparatus of Invention 5 or 6, the predetermined area is an area in the vicinity of the rear end of the recording medium, and the correction means includes an area where the processing liquid is insufficient by the determination means. If it is determined, the separation timing of the measuring roller separation / contact means is delayed by a predetermined time.

  Thereby, the separation timing can be appropriately corrected.

  (Invention 8): In the ink jet recording apparatus according to any one of Inventions 1 to 7, the detection unit is configured to calculate a sum, an average value, or an integral value of gradation values of pixels for each row in the transport direction of the captured image. The difference between the bottom value and the peak value is detected as a gradation distribution, and when the detected difference exceeds 0, the determination unit determines that there is an area where the processing liquid is excessive, and the detected difference is 0. If it is less than that, it is determined that there is a region where the processing liquid is insufficient.

  Thereby, the presence or absence of the application | coating nonuniformity of a process liquid can be judged appropriately.

  (Invention 9): In the ink jet recording apparatus according to any one of Inventions 1 to 7, the detection means includes a gradation value at the maximum peak and a gradation value at the second peak of the gradation histogram of the captured image. Is detected as a gradation distribution.

  Thereby, the presence or absence of the application | coating nonuniformity of a process liquid can be judged appropriately.

  (Invention 10): In the inkjet recording apparatus of Invention 8 or 9, the image recording means records a chart image in the predetermined area, and the imaging means images a chart image in the predetermined area.

  Thereby, the presence or absence of the application | coating nonuniformity of a process liquid can be judged appropriately.

  (Invention 11): In the ink jet recording apparatus according to invention 10, the image recording means is an ink jet head for the plurality of colors corresponding to at least each of cyan (C), magenta (M), and yellow (Y) as the ink jet head. The chart image is a CMY 3-color gray halftone image.

  Thereby, the presence or absence of the application | coating nonuniformity of a process liquid can be judged appropriately.

  (Invention 12): In the ink jet recording apparatus according to any one of Inventions 1 to 7, the detection unit is configured to calculate a dot diameter at a maximum peak and a dot diameter at a second peak of a histogram of ink dot diameters of the captured image. The difference is detected as a gradation distribution.

  Thereby, the presence or absence of the application | coating nonuniformity of a process liquid can be judged appropriately.

  (Invention 13): In the ink jet recording apparatus of Invention 12, the image recording means records a chart image in the predetermined area, and the imaging means images a chart image in the predetermined area.

  Thereby, the presence or absence of the application | coating nonuniformity of a process liquid can be judged appropriately.

  (Invention 14): In the ink jet recording apparatus of invention 13, the image recording means, as the ink jet head, uses a plurality of color ink jets corresponding to at least black (K), cyan (C), and magenta (M) colors. The chart image is a monochrome halftone image of K, M, and C.

  Thereby, the presence or absence of the application | coating nonuniformity of a process liquid can be judged appropriately.

  (Invention 15): a transporting process for transporting a sheet-like recording medium in a predetermined transporting direction, a coating process for applying a treatment liquid for aggregating ink on the recording medium transported in the transporting process by a coating roller, and a metering roller Supplying the measurement liquid to the application roller and supplying the application liquid to the application roller; a measurement roller abutting step for bringing the measurement roller into contact with the application roller at a predetermined contact timing; and the measurement roller at a predetermined separation timing A measuring roller separating step of separating the coating liquid from the coating roller, an image recording step of recording an image by ejecting ink droplets onto the recording medium coated with the treatment liquid by an inkjet head, and recording on the recording medium An imaging step of capturing a captured image, a detection step of detecting a gradation distribution in the transport direction in the captured image, and from the detection result, A determination step for determining whether there is an excess region or a shortage region of the processing liquid on the recording medium, and a contact timing of the measuring roller contact step or a separation of the measurement roller separation step based on a determination result of the determination step An inkjet recording method comprising: a correction step of correcting timing.

  Note that the technical idea of the present specification includes a program for causing a computer to execute the above steps.

  DESCRIPTION OF SYMBOLS 10 ... Inkjet recording device, 14 ... Recording medium, 14A ... Front-end | tip part, 14B ... Rear-end part, 30 ... Treatment liquid application part, 32 ... Transfer cylinder, 34 ... Impression cylinder, 36 ... Treatment liquid application apparatus, 82 ... Inline sensor , 142, system controller, 166, detector, 210, application roller, 220, liquid tray, 222, anilox roller (metering roller), 250, 262, 266, image unevenness occurrence position, 252, 258, 264, 268,. Detection area, 254 ... Scanned image, 256 ... Print area (image area), 270 ... Dot diameter measurement area

Claims (15)

Conveying means for conveying a sheet-like recording medium in a predetermined conveying direction;
An application roller for applying a treatment liquid for aggregating ink on the recording medium conveyed by the conveying means;
A measuring roller for measuring the treatment liquid and supplying it to the application roller;
A metering roller separating / contacting means for bringing the metering roller into contact with the application roller at a predetermined contact timing and separating the metering roller from the application roller at a predetermined separation timing;
Image recording means for recording an image by ejecting ink droplets onto a recording medium coated with the treatment liquid by an ink jet head;
Imaging means for imaging an image recorded on the recording medium;
Detecting means for detecting a gradation distribution in the transport direction in the captured image;
Judgment means for judging the presence or absence of an excess area or a lack area of the processing liquid on the recording medium from the detection result;
Correction means for correcting the contact timing or separation timing of the measuring roller separation means based on the judgment result of the judgment means;
An ink jet recording apparatus comprising: The imaging means captures an image of a predetermined area of the recording medium,
The predetermined area is the recording medium or the downstream side of the recording medium when the conveying speed of the conveying means is V ₁ , the speed of the outer peripheral surface of the applying roller is V ₂ , and the diameter of the applying roller is b. L = M × π × b × V ₁ / V ₂ (where M is an integer)
The inkjet recording apparatus according to claim 1, wherein the inkjet recording apparatus is a region separated upstream by a conveyance distance L represented by: The predetermined area is an area separated from the leading edge of the recording medium or a recording medium conveyed downstream from the recording medium by the conveyance distance L;
When the determination means determines that there is an area where the processing liquid is insufficient, the correction means advances the contact timing of the metering roller separation means by a predetermined time, and if there is an area where the processing liquid is excessive 3. The ink jet recording apparatus according to claim 2, wherein when the determination is made, the contact timing of the measuring roller separating / contacting means is delayed by a predetermined time. The predetermined area is an area separated from the rear end of the recording medium conveyed downstream of the recording medium by the distance L;
When the determination means determines that there is an area where the processing liquid is insufficient, the correction means delays the separation timing of the measuring roller separation means by a predetermined time, and determines that there is an area where the processing liquid is excessive. 4. The ink jet recording apparatus according to claim 2, wherein, in the case of being performed, the separation timing of the measuring roller separation / contact means is advanced by a predetermined time. The imaging means captures an image of a predetermined area of the recording medium,
The inkjet recording apparatus according to claim 1, wherein the predetermined area is an area in the vicinity of a front end or an area in the vicinity of a rear end of the recording medium. The predetermined area is an area near the tip of the recording medium,
6. The correction unit according to claim 5, wherein when the determination unit determines that there is a region where the processing liquid is insufficient, the correction unit advances the contact timing of the metering roller separation unit by a predetermined time. Inkjet recording apparatus. The predetermined area is an area near the rear end of the recording medium,
7. The correction unit according to claim 5, wherein when the determination unit determines that there is an area where the processing liquid is insufficient, the correction unit delays the separation timing of the metering roller separation unit by a predetermined time. The ink jet recording apparatus described. The detection means detects the difference between the sum, the average value, or the bottom value and the peak value of the integration value of the pixels for each row in the transport direction of the captured image as a gradation distribution,
The determination means determines that there is an area where the processing liquid is excessive when the detected difference exceeds 0, and determines that there is an area where the processing liquid is insufficient when the detected difference is less than 0. The ink jet recording apparatus according to claim 1, wherein the ink jet recording apparatus is an ink jet recording apparatus.   The detection unit detects a difference between a gradation value at a maximum peak and a gradation value at a second peak of a gradation histogram of the captured image as a gradation distribution. 8. The ink jet recording apparatus according to any one of 7 above. The image recording means records a chart image in the predetermined area;
The inkjet recording apparatus according to claim 8, wherein the imaging unit captures a chart image of the predetermined area. The image recording means includes, as the ink jet head, a plurality of color ink jet heads corresponding to at least cyan (C), magenta (M), and yellow (Y) colors,
11. The inkjet recording apparatus according to claim 10, wherein the chart image is a CMY three-color gray halftone image.   The detection means detects a difference between a dot diameter at a maximum peak and a dot diameter at a second peak of the histogram of ink dot diameters of the captured image as a gradation distribution. The inkjet recording apparatus according to any one of the above. The image recording means records a chart image in the predetermined area;
The inkjet recording apparatus according to claim 12, wherein the imaging unit captures a chart image of the predetermined area. The image recording means includes, as the ink jet head, a plurality of color ink jet heads corresponding to at least black (K), cyan (C), and magenta (M) colors,
The inkjet recording apparatus according to claim 13, wherein the chart image is a monochrome halftone image of K, M, and C. A transporting process for transporting a sheet-like recording medium in a predetermined transporting direction;
An application step of applying a treatment liquid for aggregating the ink on the recording medium conveyed by the conveyance step with an application roller;
A supply step of measuring the processing liquid by a measuring roller and supplying the processing liquid to the application roller;
A metering roller abutting step for abutting the metering roller with the application roller at a predetermined abutting timing;
A metering roller separating step of separating the metering roller from the application roller at a predetermined spacing timing;
An image recording step of recording an image by ejecting ink droplets onto the recording medium coated with the treatment liquid by an inkjet head; and
An imaging step of imaging an image recorded on the recording medium;
A detection step of detecting a gradation distribution in the transport direction in the captured image;
A determination step of determining the presence or absence of an excess area or an insufficient area of the processing liquid on the recording medium from the detection result;
A correction step of correcting the contact timing of the measuring roller contact step or the separation timing of the measurement roller separation step based on the determination result of the determination step;
An ink jet recording method comprising: