JP2011178547A - Ink jet recording device and ink jet recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink jet recording device keeping cockling inconspicuous, and to provide an ink jet recording method. <P>SOLUTION: The ink jet recording device 1 includes an ink jet head 72 dropping ink on a recording medium 22 to form an image; a carrier 76 having a carrier carrying the recording medium 22 after dropping the ink thereon, a holder 77 holding the recording medium 22, a plurality of suction holes sucking the recording medium 22 with negative pressure, and a suction means sucking through the suction holes; and heater 78, 80, 82 heating the carrier and the recording medium 22 at their printing surface sides where the image is formed. The suction holes in the suction surface sucking the recording medium 22 have wider pitch intervals and smaller aperture ratios from the center of the suction surface corresponding to the recording medium toward the end. The ink jet recording method is also provided. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus and an ink jet recording method, and more particularly, to an ink jet recording apparatus and an ink jet recording method capable of making a recording medium uncooked after image formation inconspicuous.

  In an ink jet recording method using water-based ink, ink droplets are ejected and landed on a recording medium, so that ink moisture permeates the recording medium such as paper, and the recording medium expands and deforms due to water absorption of the recording medium. ) Has occurred, degrading the recording quality. As inkjet printers have higher resolution and higher recording speed, it has been necessary to improve drying efficiency at high speeds and to suppress cockle.

  For example, Patent Document 1 below proposes an apparatus that includes means for drying while sucking and transporting a recording medium to a rotating drum in order to dry ink on the recording medium after printing in a short time. . However, there is no mention of means for suppressing cockle, and therefore no description has been given regarding the design of the suction portion.

  As a reference to the design of the suction portion, the following Patent Document 2 describes an image forming apparatus that reduces the aperture ratio as it goes downstream in the recording medium conveyance direction. By reducing the aperture ratio toward the downstream side, when the vicinity of the leading end of the recording medium is adsorbed by the opening formed upstream in the transport direction, the negative pressure in the portion blocked by the recording medium is extremely high. It can be suppressed from becoming smaller. However, the suction surface does not move, and the recording medium is transported by being slid on the suction surface while being attracted by the suction holes from the back surface. Therefore, if the suction force is too strong, the recording medium cannot be transported and the paper is torn. There was a problem of jamming. Also. The chucking force after the recording could not be suppressed or corrected with the suction force that can be conveyed by sliding on the suction surface. Further, in a region where the aperture ratio is large, that is, a portion where the suction hole diameter is large, the amount of paper dents due to suction becomes extremely large, and the quality of the recorded matter is impaired. In particular, when the image portion is drawn, the paper becomes stiff due to moisture permeation, so that the dents are more prominent. Furthermore, since the suction hole portion tends to lower the temperature during drying due to suction, the larger the hole diameter, the more likely the drying unevenness occurs. When fixing is performed by pressure heating or UV monomer curing, the residual moisture in the hole portion is reduced. There was a concern that it would be easily lowered.

  Further, in Patent Document 3, by increasing the number of suction holes at positions opposite to the paper edge from the center, it is possible to prevent the edge of the recording medium from easily floating due to a change in wind flow during high-speed conveyance. In addition, it is described that stable conveyance is possible. However, the attracting force at the center of the paper where the image is frequently ejected tends to be insufficient, and the cuckling after recording cannot be sufficiently suppressed. Further, since the attracting force at the end portion is strong, there is a problem that the cockle is easily collected in the central portion of the paper.

JP 2008-179012 A JP 2003-211749 A JP 2007-144848 A

  When the drawn paper is adsorbed, the cockle tends to be concentrated mainly in the center of the paper. Therefore, a large suction force is required at the center of the paper, and the aperture ratio needs to be set large. Here, when trying to achieve this by increasing the diameter of the suction hole, the amount of suction dent in the thin paper becomes large and the quality is impaired. In addition, when paper with a fast progress of cockle, such as matte paper or thin paper, if holes are placed too densely throughout the paper, the ready-made cockle will lose its escape during adsorption, causing abnormal growth of the cockle locally or wrinkles. It may occur.

  The present invention has been made in view of such circumstances, and in the central portion of the paper, the growth of the accumulated cockle is suppressed, and the preformed cockle is dispersed at the end portion, so that abnormalities of the cockle at the time of adsorption are achieved. An object of the present invention is to provide an ink jet recording apparatus and an ink jet recording method capable of preventing growth and generation of wrinkles and making the cockle inconspicuous even after adsorption.

  According to a first aspect of the present invention, in order to achieve the above object, an ink jet head that forms an image by ejecting ink onto a recording medium, a conveyance body that conveys the recording medium after the ink ejection, A holding means for holding the recording medium, a plurality of suction holes for sucking the recording medium under negative pressure, and a suction means for sucking from the suction holes; the transport body; and the recording medium. Heating means for heating from the printing surface side on which the image is formed, and the pitch interval of the suction holes of the suction surface for sucking the recording medium is from the central portion of the suction surface corresponding to the recording medium Provided is an ink jet recording apparatus which is widened toward the end and has a small aperture ratio.

  According to the first aspect of the present invention, the aperture ratio of the suction surface corresponding to the recording medium is decreased from the center to the end, that is, the aperture ratio of the center is increased. Then, it is possible to suppress the growth of aggregated cockle. Further, since the aperture ratio is reduced toward the end portion, the cockle already formed on the end portion of the recording medium can be dispersed. Therefore, the cockle can be made inconspicuous.

  Further, since the aperture ratio is adjusted not by the diameter of the suction holes but by the pitch interval of the suction holes, the amount of dents can be suppressed by the suction holes when the recording medium has low rigidity. Therefore, it is possible to prevent the image quality from deteriorating.

  In the present invention, the “pitch interval” refers to the interval of the endmost distance between adjacent suction holes.

  A second aspect of the present invention is characterized in that in the first aspect, the pitch interval of the suction holes is widened from the central portion of the suction surface corresponding to the recording medium toward the end in the width direction.

  According to the second aspect, since the pitch interval of the suction holes is widened from the center to the end in the width direction of the recording medium, the cockle can be dispersed in the width direction of the recording medium.

  A third aspect of the present invention is characterized in that, in the first aspect, the pitch interval of the suction holes is widened from the central portion of the suction surface corresponding to the recording medium toward the end portion in the transport direction.

  According to the third aspect, since the pitch interval of the suction holes is increased from the central portion toward the end in the recording medium conveyance direction, the cockle can be dispersed in the recording medium conveyance direction.

  A fourth aspect of the present invention is characterized in that, in the second or third aspect, the suction hole has the highest aperture ratio in the central portion of the suction surface corresponding to the recording medium.

  According to the fourth aspect of the present invention, the suction holes are arranged so that the aperture ratio at the center portion of the suction surface is the highest. Can be dispersed at the end.

  A fifth aspect of the present invention is characterized in that, in any one of the first to fourth aspects, the suction holes are arranged in a hexagonal close-packed arrangement, and the suction holes are arranged at a predetermined interval.

  According to the fifth aspect, since the suction holes are arranged in a hexagonal close-packed arrangement, the suction holes can be arranged densely, and further, the aperture ratio is made fine by controlling the interval between the suction holes. Can be controlled.

  A sixth aspect of the present invention is characterized in that, in any one of the first to fifth aspects, the shape of the suction hole is a perfect circle or an ellipse.

  According to the sixth aspect, since the shape of the suction hole is a perfect circle or an ellipse, the visibility of the suction dent generated in the recording medium can be reduced.

  A seventh aspect of the present invention is characterized in that, in any one of the first to sixth aspects, the edge portion of the suction hole is a curved surface.

  According to the seventh aspect, by making the edge portion of the suction hole a curved surface, the suction pressure at the end portion of the suction hole can be suppressed, and the suction dent due to the suction hole in the recording medium can be reduced.

  An eighth aspect of the present invention is characterized in that, in any one of the first to sixth aspects, a groove having a similar shape larger than the suction hole is provided at an edge portion of the suction hole.

  According to the eighth aspect, since the suction pressure at the end of the suction hole can be suppressed by providing the groove at the edge portion of the suction hole, the suction dent due to the suction hole in the recording medium can be reduced.

  According to a ninth aspect of the present invention, in any one of the first to eighth aspects, the apparatus further comprises control means for controlling the suction pressure by the suction means according to the type of the recording medium.

  According to the ninth aspect, since the suction pressure is controlled according to the type of the recording medium, the recording medium can be sucked with a suction pressure setting sufficient to bring the recording medium into close contact with the conveyance body. Can be relaxed.

  A tenth aspect is characterized in that, in any one of the first to ninth aspects, the suction holes are arranged so that an aperture ratio of the suction surface decreases linearly.

  According to the tenth aspect, since the suction holes are arranged so that the aperture ratio of the suction surface decreases linearly, the suction of the recording medium to the conveyance body can be stabilized.

  An eleventh aspect of the present invention is characterized in that, in any one of the first to ninth aspects, the suction surface is divided into a plurality of regions, and the aperture ratio is arranged so as to decrease stepwise for each region.

  According to the eleventh aspect, since the aperture ratio is gradually reduced for each of the divided areas, it is possible to stabilize the adsorption of the recording medium to the conveyance body.

  A twelfth aspect of the present invention is characterized in that, in the eleventh aspect, the aperture ratio decreases linearly between regions where the aperture ratio of the suction surface is constant.

  According to the twelfth aspect, since the area where the aperture ratio decreases linearly is provided between the areas where the aperture ratio is constant, the adsorption of the recording medium to the conveyance body can be stabilized.

  A thirteenth aspect of the present invention is characterized in that, in the tenth to twelfth aspects, the area of 10 to 70% of the central portion of the suction surface has a constant aperture ratio.

  According to the thirteenth aspect, since the aperture ratio in the above-mentioned range at the central portion of the suction surface is constant, the suction force at the central portion of the suction surface can be ensured, and the occurrence of cuckling at the central portion of the recording medium is suppressed. can do.

  In the present invention, the “central portion of the suction surface” is a region similar to the recording medium from the center of the suction surface, and the ratio refers to the ratio to the total area of the recording medium.

  A fourteenth aspect is characterized in that in any one of the first to thirteenth aspects, the recording medium holding means for pressing the recording medium from the print surface side to the surface of the transport body is provided.

  According to the fourteenth aspect, since the recording medium holding means for pressing the recording medium against the surface of the conveyance body is provided, the recording medium can be adsorbed uniformly.

  According to a fifteenth aspect of the present invention, in any one of the first to fourteenth aspects, an aperture ratio of the suction surface corresponding to a rear end of the recording medium in the transport direction is the same as an aperture ratio of a central portion of the suction surface. And

  According to the fifteenth aspect, apart from the configuration in which the aperture ratio decreases from the center portion to the end portion of the suction surface as described above, the aperture ratio of the suction surface corresponding to the rear end in the conveyance direction of the recording medium is set to the center. Since the aperture ratio is the same as that of the recording medium, it is possible to prevent the trailing edge of the recording medium from floating from the conveyance body. In particular, this is effective when the conveyance body is a curved conveyance body and the recording medium has high rigidity.

  A sixteenth aspect is characterized in that, in any one of the first to fourteenth aspects, an aperture ratio of the suction surface corresponding to a leading end of the recording medium in the transport direction is the same as an aperture ratio of a central portion of the suction surface. And

  According to the sixteenth aspect, apart from the configuration in which the aperture ratio decreases from the center to the end of the suction surface as described above, the aperture ratio of the suction surface at the location corresponding to the front end in the conveyance direction of the recording medium is set. Since the aperture ratio is the same as the central portion, it is possible to prevent the slack that occurs at the front end of the recording medium. In particular, this is effective when the conveying body is a curved surface conveying body and the recording medium has low rigidity.

  According to a seventeenth aspect of the present invention, in order to achieve the above object, ink is ejected onto a recording medium to form an image, and the recording medium after the ink is deposited is placed on a carrier and held. While conveying the recording medium by sucking it through the suction holes from the conveyance body, and heating the heating body and the recording medium from the printing surface side on which the image is formed. An ink jet characterized in that the pitch interval of the suction holes of the suction surface for sucking the recording medium increases from the center to the end of the suction surface corresponding to the recording medium, and the aperture ratio decreases. Provide a recording method.

  An eighteenth aspect is characterized in that, in the seventeenth aspect, the pitch interval of the suction holes is widened from the central portion of the suction surface corresponding to the recording medium toward the end in the width direction.

  A nineteenth aspect is the one according to the seventeenth aspect, wherein a pitch interval of the suction holes is widened from a central portion of the suction surface corresponding to the recording medium toward an end portion in a transport direction.

  A twentieth aspect is characterized in that, in any one of the seventeenth to nineteenth aspects, there is a control step of controlling a suction pressure according to the type of the recording medium.

  According to claims 17 to 20, the above-described ink jet recording apparatus is developed as an ink jet recording method. According to claims 17 to 20, the same effects as those of the ink jet recording apparatus can be obtained.

  According to the ink jet recording apparatus and the ink jet recording method of the present invention, by increasing the suction force of the suction surface corresponding to the central portion of the recording medium where an image is highly likely to be ejected and lowering the end portion, Can be made inconspicuous. In addition, since the aperture ratio is controlled not by the diameter of the suction holes but by the pitch interval of the suction holes, it is possible to prevent deterioration in image quality due to the depression of the suction holes and to prevent uneven drying at the suction holes. .

1 is a schematic configuration diagram of an ink jet recording apparatus according to the present invention. It is a figure which shows arrangement | positioning of the suction hole of a suction surface, and a distribution map of an aperture ratio. It is a figure which shows arrangement | positioning of other embodiment of the suction hole of a suction surface, and a distribution map of an aperture ratio. It is a figure which shows the relationship between a suction hole diameter, a hole pitch, and an aperture ratio. It is a distribution map of the aperture ratio of the conveyance direction concerning other embodiment. It is a perspective view which shows schematic structure of a drying drum. It is a disassembled perspective view which shows the internal structure of the drying drum shown in FIG. FIG. 7 is a partially enlarged view of the drying drum shown in FIG. 6. It is sectional drawing which follows the VV line in FIG. It is a perspective view which shows the structure of the intermediate sheet shown in FIG. It is a perspective view which shows the structure of the suction sheet shown in FIG. It is a figure which shows arrangement | positioning of the suction hole of the suction sheet used by this invention. It is a figure which shows arrangement | positioning of the suction hole by hexagonal close-packed arrangement. It is a figure which shows the shape of the edge part of a suction hole. It is a principal block diagram showing the system configuration of the ink jet recording apparatus. 6 is a table showing the results of Test Example 1. FIG. 10 is a table showing the results of Test Example 2. FIG. 10 is a table showing the results of Test Example 3. FIG.

  Preferred embodiments of an ink jet recording apparatus and an ink jet recording method according to the present invention will be described below with reference to the accompanying drawings.

[Overall configuration of inkjet recording apparatus]
First, the overall configuration of the ink jet recording apparatus of the present invention will be described.

  FIG. 1 is a configuration diagram schematically showing an inkjet recording apparatus 1 according to the present embodiment. An inkjet recording apparatus 1 shown in FIG. 1 is an apparatus that forms an image on a recording surface of a recording medium 22, and mainly includes a paper feeding unit 10, a treatment liquid application unit 12, a drawing unit 14, a drying unit 16, an exposure curing unit 18, and a discharge. The unit 20 is configured. A recording medium 22 (sheets) is stacked on the paper supply unit 10, and the recording medium 22 is sent from the paper supply unit 10 to the treatment liquid application unit 12, and the treatment liquid application unit 12 processes the treatment liquid on the recording surface. Is applied to the recording surface by the drawing unit 14. The recording medium 22 to which ink has been applied is dried by the drying unit 16, dried by the exposure curing unit 18, and then transported by the discharge unit 20.

  Intermediate conveyance units (transfer cylinders) 24, 26, and 28 are provided between the respective units, and the recording medium 22 is transferred by the intermediate conveyance units 24, 26, and 28. That is, a first intermediate transport unit 24 is provided between the processing liquid application unit 12 and the drawing unit 14, and the recording medium from the processing liquid application unit 12 to the drawing unit 14 by the first intermediate transport unit 24. 22 delivery is performed. Similarly, a second intermediate transport unit 26 is provided between the drawing unit 14 and the drying unit 16. The recording medium 22 is transferred from the drawing unit 14 to the drying unit 16 by the second intermediate transport unit 26. Is done. Further, a third intermediate conveyance unit 28 is provided between the drying unit 16 and the exposure curing unit 18, and the recording medium 22 from the drying unit 16 to the exposure curing unit 18 is provided by the third intermediate conveyance unit 28. Delivery takes place.

  Hereinafter, each part of the inkjet recording apparatus 1 (the paper feeding unit 10, the treatment liquid application unit 12, the drawing unit 14, the drying unit 16, the exposure curing unit 18, the discharge unit 20, the first to third intermediate conveyance units 24 and 26, 28) will be described.

(Paper Feeder)
The paper feed unit 10 is a mechanism that supplies the recording medium 22 to the drawing unit 14. The paper feed unit 10 is provided with a paper feed tray 50, and the recording medium 22 is fed from the paper feed tray 50 to the processing liquid application unit 12 one by one.

(Processing liquid application part)
The processing liquid application unit 12 is a mechanism that applies the processing liquid to the recording surface of the recording medium 22. The treatment liquid includes a color material aggregating agent that agglomerates or deposits the color material (pigment) in the ink applied by the drawing unit 14, and the ink comes into contact with the color material when the treatment liquid comes into contact with the ink. Separation from the solvent is facilitated. A more detailed description of the treatment liquid will be described later.

  As shown in FIG. 1, the treatment liquid application unit 12 includes a transfer drum 52, a treatment liquid drum 54, a treatment liquid application device 56, an IR heater 58, and a hot air blowing nozzle 60. The transfer drum 52 is disposed between the paper feed tray 50 of the paper feed unit 10 and the processing liquid drum 54 and includes a claw-shaped holding means (such as a gripper) on the outer peripheral surface thereof. Is driven to rotate. The recording medium 22 fed from the paper feed unit 10 is received by the transfer drum 52 and transferred to the processing liquid drum 54.

  The treatment liquid drum 54 is a drum that holds and rotates the recording medium 22 and is driven to rotate. Further, the processing liquid drum 54 includes a claw-shaped holding means 55 on the outer peripheral surface thereof, and the holding means 55 can hold the tip of the recording medium 22. The recording medium 22 is rotated and conveyed by rotating the processing liquid drum 54 with the tip held by the holding means 55. A processing liquid coating device (corresponding to a coating device) 56, an IR heater 58, and a hot air blowing nozzle 60 are provided outside the processing liquid drum 54 so as to face the peripheral surface thereof. The treatment liquid coating device 56, the IR heater 58, and the hot air blowing nozzle 60 are sequentially arranged from the upstream side in the rotation direction of the treatment liquid drum 54 (counterclockwise direction in FIG. 1). The processing liquid is applied to the recording surface by the processing liquid application device 56. The film thickness of the treatment liquid is desirably sufficiently smaller than the droplet diameter of ink ejected from the ink heads 72M, 72K, 72C, 72Y of the drawing unit 14. For example, when the ink droplet ejection amount is 2 pl, the average droplet diameter is 15.6 μm. At this time, when the film thickness of the processing liquid is large, the ink dots float in the processing liquid without contacting the surface of the recording medium 22. Therefore, in order to obtain a landing dot diameter of 30 μm or more when the ink droplet ejection amount is 2 pl, it is desirable that the film thickness of the treatment liquid is 3 μm or less.

The recording medium 22 coated with the treatment liquid by the treatment liquid application device 56 is conveyed to the positions of the IR heater 58 and the hot air blowing nozzle 60. The IR heater 58 is controlled to a high temperature (for example, 180 ° C.), and the hot air blowing nozzle 60 blows the high temperature (for example, 70 ° C.) warm air toward the recording medium 22 at a constant air volume (for example, 9 m ³ / min). Composed. By the heating by the IR heater 58 and the hot air blowing nozzle 60, water in the solvent of the processing liquid is evaporated, and a thin film layer of the processing liquid is formed on the recording surface. By thinning the treatment liquid in this way, the dots of ink that are ejected by the drawing unit 14 come into contact with the recording surface of the recording medium 22 to obtain the required dot diameter, and the thinned treatment liquid component Reacts with the colorant to cause aggregation of the coloring material, and an effect of fixing to the recording surface of the recording medium 22 is easily obtained. The processing liquid drum 54 may be controlled to a predetermined temperature (for example, 50 ° C.).

(Drawing part)
As shown in FIG. 1, the drawing unit 14 includes a drawing drum 70 and ink heads 72M, 72K, 72C, and 72Y that are arranged in close proximity to positions facing the outer peripheral surface of the drawing drum 70. The ink heads 72M, 72K, 72C, and 72Y correspond to inks of four colors, magenta (M), black (K), cyan (C), and yellow (Y), and are upstream in the rotation direction of the drawing drum 70. Arranged in order from the side.

  The drawing drum 70 is a drum that holds the recording medium 22 on its outer peripheral surface and rotates and conveys the recording medium 22 and is driven to rotate. Further, the drawing drum 70 includes a claw-shaped holding unit 71 on the outer peripheral surface thereof, and the holding unit 71 can hold the leading end of the recording medium 22. The recording medium 22 is rotated and conveyed by rotating the drawing drum 70 with the leading end held by the holding means 71. At that time, the recording medium 22 is conveyed so that the recording surface faces outward, and ink is applied to the recording surface from the ink heads 72M, 72K, 72C, 72Y.

  Each of the ink heads 72M, 72K, 72C, and 72Y is a full-line ink jet type recording head (ink jet head) having a length corresponding to the maximum width of the image forming area in the recording medium 22, and the ink ejection surface thereof Is formed with a nozzle row in which a plurality of nozzles for ink ejection are arranged over the entire width of the image forming area. Each of the ink heads 72M, 72K, 72C, and 72Y is fixedly installed so as to extend in a direction orthogonal to the conveyance direction of the recording medium 22 (the rotation direction of the drawing drum 70).

  A corresponding color ink cassette is attached to each of the ink heads 72M, 72K, 72C, 72Y. Droplets of each ink are ejected from each ink head 72M, 72K, 72C, 72Y toward the recording surface of the recording medium 22 held on the outer peripheral surface of the drawing drum 70. As a result, the ink comes into contact with the treatment liquid applied to the recording surface in advance by the treatment liquid application unit 12, and the color material (pigment) dispersed in the ink is aggregated to form a color material aggregate. Thereby, the color material flow on the recording medium 22 is prevented, and an image is formed on the recording surface of the recording medium 22. At that time, since the drawing drum 70 of the drawing unit 14 is structurally separated from the processing liquid drum 54 of the processing liquid application unit 12, the processing liquid may adhere to the ink heads 72M, 72K, 72C, 72Y. In addition, the cause of ink ejection failure can be reduced.

  In addition, as an example of the reaction between the ink and the treatment liquid, using a mechanism in which an acid is contained in the treatment liquid and the pigment dispersion is destroyed and aggregated by lowering the pH, the color material bleeds, the color mixture between the inks of each color, and the liquid upon landing of the ink droplet It is conceivable to avoid droplet ejection interference due to coalescence.

  Further, the droplet ejection timings of the ink heads 72M, 72K, 72C, and 72Y are synchronized with an encoder that detects the rotational speed disposed on the drawing drum 70. Thereby, the landing position can be determined with high accuracy. In addition, the fluctuation of the speed due to the deflection of the drawing drum 70 is learned in advance, and the droplet ejection timing obtained by the encoder 91 is corrected to obtain the deflection of the drawing drum 70, the accuracy of the rotation axis, and the speed of the outer peripheral surface of the drawing drum 70. Irregular droplet ejection can be reduced without depending on it.

  Further, maintenance operations such as cleaning the nozzle surfaces of the ink heads 72M, 72K, 72C, and 72Y and discharging the thickened ink may be performed by retracting the head unit from the drawing drum 70.

  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 ink 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.

(Drying part)
The drying unit 16 is a step of drying moisture contained in the solvent separated by the color material aggregating action. The drying drum 76 and a first IR heater disposed at a position facing the outer peripheral surface of the drying drum 76. 78, a hot air jet nozzle 80, and a second IR heater 82. The first IR heater 78 is provided upstream of the hot air jet nozzle 80 in the rotation direction of the drying drum 76 (counterclockwise direction in FIG. 1), and the second IR heater 82 is jetted of hot air. Provided downstream of the nozzle 80.

  The drying drum 76 is a drum that holds and rotates the recording medium 22 on its outer peripheral surface, and the rotation of the drying drum 76 is controlled by a motor driver (not shown). The recording medium 22 is rotated and conveyed by rotating the drying drum 76 with the tip held by the holding unit 77. At that time, the recording surface of the recording medium 22 is conveyed so as to face outward, and the recording surface is dried by the IR heater 78 and the hot air jet nozzle 80.

The hot air jet nozzle 80 is configured to blow hot air controlled at a predetermined temperature (for example, 50 ° C. to 70 ° C.) toward the recording medium 22 with a constant air volume (12 m ³ / min), and an IR heater. Each of 78 is controlled to a predetermined temperature (for example, 180 ° C.). The hot air jet nozzle 80 and the IR heater 78 evaporate moisture contained in the printing surface of the recording medium 22 held on the drying drum 76, and a drying process is performed. At that time, since the drying drum 76 of the drying unit 16 is structurally separated from the drawing drum 70 of the drawing unit 14, the ink menscus 72M, 72K, 72C, 72Y is caused by drying of the head meniscus portion by thermal drying. Ink ejection failure can be reduced. Moreover, there is a degree of freedom in setting the temperature of the drying unit 16, and an optimal drying temperature can be set.

  The evaporated water may be discharged out of the apparatus together with air by a discharge means (not shown). Further, the recovered air may be cooled by a cooler (radiator) or the like and recovered as a liquid.

  The drying drum 76 has suction holes provided on the outer peripheral surface thereof, and has suction means for performing suction from the suction holes. As a result, the recording medium 22 can be held in close contact with the peripheral surface of the drying drum 76. Further, by performing negative pressure suction, the recording medium can be constrained to the conveyance body, so that the recording medium can be prevented from being clogged.

  Moreover, it is preferable that the outer periphery of the drying drum 76 is controlled to a predetermined temperature. Drying is promoted by heating from the back surface of the recording medium 22, and image destruction at the time of fixing can be prevented. The range of the surface temperature of the drying drum 76 is preferably 50 ° C. or higher, more preferably 60 ° C. or higher. Further, the upper limit is not particularly limited, but is preferably 75 ° C. or lower from the viewpoint of safety of maintenance work such as cleaning ink adhering to the surface of the drying drum 76 (preventing burns due to high temperature).

  The adsorption force of the carrier can be expressed by (opening area) × (pressure per unit area). The suction force can be further increased by increasing the area occupied by the suction holes in the recording medium suction holding region, that is, the aperture ratio.

  FIG. 2 is a diagram showing the arrangement of the suction holes on the suction surface, and a distribution diagram of the aperture ratio in the width direction (XX line) and the conveyance direction (YY line) of the recording medium. In the figure, the Y direction is the recording medium conveyance direction, and the X direction is the width direction of the recording medium.

  FIG. 2A is a diagram in which a predetermined area is set at a constant pitch interval from the center to the end of the suction surface, and the aperture ratio is gradually reduced. Similarly, FIG. 2B is a diagram in which the aperture ratio in the conveyance direction of the recording medium is constant and the aperture ratio is gradually reduced in the width direction of the recording medium. FIG. 2C is a diagram in which the aperture ratio in the width direction of the recording medium is constant, and the aperture ratio is gradually reduced from the central portion of the suction surface toward the upstream side and the downstream side in the transport direction.

  Thus, by reducing the aperture ratio from the central part of the suction surface toward the end part, the cockle formed in the central part can be dispersed at the end part, so that the cockle can be made inconspicuous. .

  Moreover, it is preferable that the area | region of 10-70% of center parts of an adsorption | suction surface has the highest aperture ratio, and is constant. By making the central part high, growth of the cockle concentrated in the central part can be suppressed and dispersed at the end part.

  FIG. 3 is a diagram for explaining another embodiment showing the arrangement of suction holes on the suction surface, and a distribution diagram of aperture ratios in the width direction (XX line) and the transport direction (YY line) of the recording medium. It is.

  In FIG. 3A, the pitch interval is gradually widened from the central part to the end part of the suction surface, and the aperture ratio distribution is set to be linearly reduced from the central part to the end part. Yes. In FIG. 3B, the aperture ratio is reduced by making the pitch interval in the transport direction constant and widening the pitch interval in the width direction of the recording medium. 3 (c), contrary to the arrangement of FIG. 3 (b), the pitch interval in the width direction is constant, and the pitch interval is gradually increased from the central portion in the transport direction toward the upstream side and the downstream side. It is a figure which makes the aperture ratio small. Similar to FIG. 2 in which the aperture ratio is decreased stepwise, the same effect can be obtained in FIG. 3 in which the aperture ratio is decreased linearly.

  FIG. 3D shows a case where the central portion in the recording medium width direction has a constant aperture ratio in the arrangement of the suction holes shown in FIG. In this way, by setting the aperture ratio at the central portion to be a constant aperture ratio, it is possible to secure the attracting force at the central portion, and to suppress the occurrence of cockle at the central portion of the recording medium.

The aperture ratio with respect to the unit area per 1 cm ^{2 of the} adsorption surface is preferably 1% or more and 75% or less, and more preferably 1% or more and 50% or less. By setting the aperture ratio within the above range, it is possible to prevent the suppression of cockle and improve the drying performance. If the aperture ratio is less than 1%, expansion deformation of the recording medium due to water absorption after recording cannot be sufficiently suppressed. On the other hand, if it exceeds 75%, the contact area between the back surface of the recording medium and the surface of the conveying member is reduced, so that sufficient drying performance cannot be obtained even in the adsorption holding state. Further, since drying is not promoted, cockle tends to deteriorate.

  More preferably, it is preferably 10% or more and 75% or less, more preferably 20% or more and 75% or less at the center of the adsorption surface. Moreover, it is preferable to set it as 1% or more and 50% or less at the edge part of an adsorption | suction surface, More preferably, they are 1% or more and 30% or less.

The aperture ratio can be controlled by the diameter of the suction holes, the hole pitch, and the shape and arrangement of the holes. The hole diameter is preferably 0.4 mm or more in order to secure the aperture ratio and increase the suction force, and is designed to be 1.5 mm or less so that the recording medium does not have a dent mark (suction mark) due to negative pressure suction. It is preferable to do. By setting the thickness to 0.4 mm or more, it is possible to ensure winding property and rigidity (durability against deformation) around the impression cylinder. In addition, the hole pitch is preferably 0.1 mm or more in order to prevent thermal deformation and rigidity of the surface of the carrier, and if the gap between the holes is too far away, the effect of inhibiting deformation of the recording medium is insufficient. Since wrinkles occur, it is preferable to design to 10 mm or less in order to prevent such wrinkles. FIG. 4 shows the relationship between the suction hole diameter, the hole pitch, and the aperture ratio. It is preferable to set the hole diameter and the hole pitch so that the opening ratio per unit area (1 cm ² ) is within the range of the frame shown in FIG. 4 (opening ratio: 1 to 75%).

  If the shape of the suction hole is a corner (acute angle), stress concentrates on the corner, so that the corner is preferably rounded. Further, in the rotary conveyance body, the deformation amount of the recording medium due to the adsorption pressure is larger in the axial direction (recording medium width direction) than in the circumferential direction (conveyance direction). Therefore, the suction hole may have an elliptical shape or a long hole shape in which the circumferential direction is the major axis direction and the axial direction is the minor axis direction, so that the circumferential deformation and the axial deformation of the recording medium can be made uniform. it can.

  In addition to the numerical range described above, it is preferable to provide a region having an aperture ratio equivalent to the central portion of the suction surface at the position of the suction surface corresponding to the rear end of the recording medium in the conveyance direction. By providing a region having the same opening ratio as the central portion at a position corresponding to the rear end in the transport direction, it is possible to prevent the rear end of the recording medium having high rigidity from being lifted. As a region corresponding to the rear end portion of the recording medium, the entire area in the width direction may have the same aperture ratio as that of the central portion, or a region that partially has the same aperture ratio as that of the central portion may be provided.

  In addition, a region having an aperture ratio equivalent to that of the central portion of the suction surface can be provided at the position of the suction surface corresponding to the front end of the recording medium conveyance direction. By providing a region having an aperture ratio equivalent to that of the central portion at a position corresponding to the leading end in the transport direction, it is possible to prevent the recording medium having low rigidity from being loosened.

  As a specific example, in the distribution diagram of the aperture ratio in the conveyance direction (YY line) of the recording medium shown in FIG. 3C, a distribution diagram having an aperture ratio equivalent to the central portion at a position corresponding to the rear end in the conveyance direction. FIG. 5A shows a distribution diagram having an aperture ratio equivalent to that of the central portion at a position corresponding to the front end in the transport direction.

  Next, the case where the suction sheet having the suction hole arrangement shown in FIGS. 2 and 3 is applied to the drying drum 76 will be described. FIG. 6 is a perspective view showing the overall configuration of the drying drum 76. As shown in the figure, the drying drum 76 is connected to a rotation mechanism (not shown) and is configured to be rotatable around a rotation shaft 212 supported by bearings 211A and 211B by the operation of the rotation mechanism. It is a member.

  The recording medium holding surface (circumferential surface) 213 on which the recording medium 22 of the drying drum 76 is held (fixed) is provided with a recording medium holding area 214 (area shown by a dot hatch), and the recording medium holding area A number of suction holes (openings) are provided in 214. On the other hand, a substantially central portion of the drying drum 76 in the axial direction (parallel to the rotation shaft 212) is a non-opening portion 216 in which no suction hole is provided.

  A vacuum channel communicating with the suction hole is provided inside the drying drum 76 shown in FIG. 6, and the vacuum channel is connected to a vacuum piping system 218 (pipe, joint) provided on the side surface of the drying drum 76. Etc.) and a vacuum pump provided outside the drying drum 76 via a vacuum channel provided inside the rotating shaft 212 of the drying drum 76. When the vacuum pump is operated to generate a vacuum (negative pressure), an adsorption pressure is applied to the recording medium 22 through an adsorption hole and a vacuum channel. That is, the drying drum 76 is configured such that the recording medium 22 is held on the peripheral surface that is the recording medium holding surface 213 by an air adsorption method.

  Next, the structure of the vacuum flow path inside the drying drum 76 will be described.

  FIG. 7 is an exploded perspective view showing the internal structure of the drying drum 76. As shown in the figure, the drying drum 76 has a suction sheet 220 provided with a number of suction holes and a plurality of suction grooves 222 (flow path forming portions having openings) communicating with the suction holes. And a drum suction groove 226 (pressure) that communicates with a throttle portion (not shown in FIG. 3 and indicated by reference numeral 234 in FIG. 10) provided in each suction groove 222. The drum body 230 is provided with a generator.

  Furthermore, a drum suction hole 228 communicating with a vacuum channel (not shown) provided inside the drum body 230 is provided at an end of the drum suction groove 226 provided in the drum body 230.

  As shown in FIG. 7, in the drying drum 76, the drum suction groove 226 of the drum main body 230 and the throttle portion (flow path control unit) of the intermediate sheet 224 are aligned, and the intermediate sheet 224 is placed on the peripheral surface of the drum main body 230. The adsorbing holes 222 of the intermediate sheet 224 and the adsorbing holes of the adsorbing sheet 220 are fixed so that the adsorbing holes provided in the adsorbing sheet 220 communicate with any of the adsorbing grooves 222 of the intermediate sheet 224. The position is aligned, and the suction sheet 220 is wound around the intermediate sheet 224 so as to be in close contact and fixed.

  The arrangement pattern of the suction holes provided in the suction sheet 220 preferably corresponds to the pattern of the suction grooves 222 of the intermediate sheet 224. Note that some of the suction holes may not communicate with the suction groove 222.

  8 and 9 show the arrangement relationship between the suction holes 250, the suction grooves 222, and the drum suction grooves 226. FIG. FIG. 8 is a plan view, and FIG. 9 is a cross-sectional view taken along the line VV in FIG. However, FIG. 9 is enlarged in the depth direction for easy understanding.

  As shown in FIG. 8, the width of the suction groove 222 (the length in the vertical direction in FIG. 8) has a length corresponding to a plurality of suction holes. In FIG. 8, the width of the suction groove 222 is the suction hole. An embodiment in which the diameter (length in the major axis direction) of 250 is approximately four times as large is shown.

  Further, the width of the drum suction groove 226 (in the left-right direction in FIG. 4) is shorter than the length of the throttle portion 234. FIG. 8 shows that the width of the drum suction groove 226 is approximately 1 of the length of the throttle portion 234. The mode which becomes / 2 is shown. Further, the throttle portion 234 has a length that reaches a position beyond the drum suction groove 226.

  As shown in FIGS. 8 and 9, the width of the narrowed portion 234 is narrower than the width of the suction groove 222, and the depths of both are substantially the same. That is, the cross-sectional area of the throttle portion 234 is smaller than the cross-sectional area of the suction groove 222, and the flow rate flowing through the suction groove 222 is limited by the throttle portion 234.

  As shown in FIG. 9, the thickness of the suction sheet 220 is thicker than the thickness of the intermediate sheet 224. In FIG. 10, the thickness of the intermediate sheet 224 with respect to the thickness of the suction sheet 220 is approximately ½. Is illustrated.

  Next, the structure of the intermediate sheet 224 will be described in detail.

  FIG. 10 is a perspective view of the intermediate sheet 224. As shown in FIG. 8, the intermediate sheet 224 has suction grooves 222 along the axial direction of the drying drum 76 and from the substantially central portion of the drying drum 76 toward both ends along the circumferential direction of the drying drum 76. A plurality are provided at equal intervals.

  An end portion of the suction groove 222 on the central portion side of the intermediate sheet 224 has a structure (squeezed structure) in which the groove width is squeezed to ¼ or less than other portions, and a narrowed portion that penetrates the intermediate sheet 224 (Flow path control unit) 234 is formed. The throttle portion 234 has a structure communicating with the drum suction groove 226 shown in FIG. 7 and has a structure in which the opening portion is blocked by the non-opening portion 216 of the suction sheet 220 and is not directly opened to the atmosphere. Yes.

  Further, the suction grooves 222 are preferably arranged as densely as possible, and a mode in which suction grooves corresponding to a recording medium of a predetermined size are arranged at a pitch of 50 mm or less is preferable.

  The suction groove 222 provided in the intermediate sheet 224 has a length corresponding to the size of the recording medium 22 to be used, and the suction grooves 222 having different lengths are provided in order to correspond to a plurality of size recording media. Is provided.

  Next, the suction sheet 220 will be described in detail.

  FIG. 11 is a perspective view of the suction sheet 220.

  A number of suction holes are provided in the recording medium holding area 214 of the suction sheet 220 according to a predetermined arrangement pattern. In addition, a substantially central portion of the suction sheet 220 in the axial direction of the drying drum 76 is a non-opening portion 216 in which the suction hole 250 is not provided. Further, both ends of the suction sheet 220 in the circumferential direction of the drying drum 76 have a folded structure (L-shaped bending structure) for fixing to the drum body 230.

  The suction sheet 220 limits the pressure loss of the throttle portion 234 by limiting the portion corresponding to the throttle portion 234 (see FIG. 10) of the intermediate sheet 224 as a non-opening portion 216, thereby limiting the pressure loss of the throttle portion 234. The function is secured. In addition, by providing a large number of suction holes in portions other than the non-opening portion 216 of the suction sheet 220, it is not necessary to change the suction hole pattern depending on the corresponding paper size, and the suction sheet pattern having the same shape can be obtained.

  FIG. 12 shows a specific example of the suction sheet that can be used in the drying drum.

  In FIG. 12A, the recording medium holding region 214 is divided into two at the center in the width direction parallel to the transport direction by the non-opening portion 216, the opening ratio at the center in the width direction of the suction sheet is increased, and the pitch gradually increases in the width direction. It is an adsorption sheet that widens the interval and reduces the aperture ratio. In FIG. 12B, the method for dividing the recording medium holding area 214 is the same, but the aperture ratio of each recording medium holding area 214 is controlled from the center to the end in the transport direction. In FIG. 12C, the aperture ratio of each recording holding area is gradually reduced from the center in the width direction toward the end.

  12D to 12G are diagrams in which the recording medium holding area 214 is further divided into three or four parts in parallel with the transport direction by the non-opening portion 216. FIG. FIG. 12D is a diagram in which the aperture ratio in the recording medium holding area 214 is made constant, and the aperture ratio is decreased as it goes to the end, and FIG. FIG. 6 is a diagram in which the center of the area 214 is set to a constant aperture ratio, and the aperture ratio of the recording medium holding area 214 at the end is linearly decreased from the center to the end.

  12F and 12G are diagrams in which the recording medium holding area 214 is divided into four in parallel with the transport direction by the non-opening portion 216. FIG. 12F shows the aperture ratio in each recording medium holding area 214. In FIG. 12 (g), the aperture ratio of the central portion and the end portion is constant, and the aperture ratio of the recording medium holding region 214 therebetween is linear. The arrangement is made smaller.

  12H to 12J are diagrams in which the recording medium holding region 214 is divided by the non-opening portion 216 in the direction parallel to the width direction as well as being divided in parallel with the conveyance direction of the drying drum 76. FIG. 12H shows an arrangement in which the aperture ratio decreases linearly from the center of the suction surface in the transport direction and the width direction. FIG. 12I shows that the aperture ratio in the recording medium holding area 214 is constant. Furthermore, it is the figure which arrange | positioned so that a conveyance direction might be fixed and the aperture ratio of the width direction may become small in steps. In FIG. 12J, the recording medium holding area 214 is divided finely by the non-opening part 216, the aperture ratio in the recording medium holding area 214 is made constant, and the opening from the central part to the end part is performed stepwise. It is a figure which makes the rate small.

  Further, FIG. 12 (k) is a view in which the recording medium holding area 214 is divided into a circumferential shape with the suction surface separated from the central part by the non-opening part 216. The aperture ratio in the divided recording medium holding area 214 can be made constant, and the aperture ratio can be decreased stepwise from the center to the end of the suction surface.

  Thus, by adopting various configurations of the suction sheet 220, the cockle formed in the center portion can be released to the end portion.

  Also, the direction in which the aperture ratio is changed is preferably changed according to the grain direction of the recording medium. When the grain direction of the recording medium is perpendicular to the transport direction, the cockle is noticeably generated in the transport direction (circumferential direction). Therefore, it is preferable that the suction surface has an aperture ratio that changes in the circumferential direction as shown in FIG. When the paper grain direction of the recording medium is parallel to the transport direction, the cockle is noticeably generated in the width direction (axial direction). Therefore, as shown in FIG. 12 (b), it is preferable that the suction surface has an aperture ratio that changes in the axial direction.

  Note that the configuration of the suction sheet is not limited to the example illustrated in FIG. 12 and can take various forms as long as the configuration can be such that the aperture ratio of the suction holes decreases from the center toward the end. Further, since the non-opening portion 216 is configured with a very narrow width, even if the center of the suction sheet 220 is a non-opening portion, the non-opening portion 216 is a narrow range, so that a sufficient suction is applied to the surrounding recording medium holding region. If there is pressure, the cockle can be suppressed.

  Further, as described above, since the opening portion is blocked by the non-opening portion 216, it is configured not to be released to the atmosphere. Therefore, when the suction sheet as shown in FIG. 12 is used, the non-opening portion 216 is used. The drum suction groove 226, the drum suction hole 228, and the narrowed portion 234 of the intermediate sheet 224 are arranged at the lower part of the sheet, and the suction groove 222 is arranged below the recording medium holding area 214 of the suction sheet 220. Thus, suction can be performed more effectively.

  Further, the arrangement of the suction holes is not particularly limited, but it is preferable to arrange the suction holes based on the hexagonal close-packed arrangement in order to arrange a large number of suction holes at high density. When the suction holes are arranged in a hexagonal close-packed arrangement, the aperture ratio can be reduced by arranging (thinning out) the suction holes with a predetermined interval between the suction holes arranged in the hexagonal close-packed arrangement. .

  An example of the suction holes of the suction sheet formed by thinning the suction holes is shown in FIG. FIGS. 13A and 13B are diagrams in which the aperture ratio is reduced by gradually increasing the amount of thinning out the suction holes from the center of the suction surface toward the transport direction and the width direction end. It is. Similarly, FIGS. 13C and 13D are diagrams in which the aperture ratio is decreased from the central portion of the suction surface toward the end portion in the transport direction, and FIGS. 13E to 13G are views of the central portion of the suction surface. It is a figure which decreases an aperture ratio toward a width direction edge part. FIG. 13H is a layout diagram in which the aperture ratio is decreased from the central portion of the suction surface to the conveyance direction end portion and the width direction end portion.

  Note that the method of thinning the suction holes in the case of the hexagonal close-packed arrangement is not limited to the example shown in FIG. 13 as long as the aperture ratio can be lowered from the center toward at least one of the end portions. be able to.

  FIG. 14 shows the shape of the suction hole. As the shape of the suction hole, the diameter of the opening portion of the suction sheet surface and the hole diameter of the suction hole shown in FIG. 14A are the same, and the edge portion of the suction hole is not processed. The edge portion of the suction hole shown in b) has an R shape, the edge portion shown in FIG. 14C has a straight line, the edge portion shown in FIG. As shown in e), a groove (step) is provided in the edge portion, which is a two-step process. The shape of the surface of the suction sheet is preferably similar to the shape of the suction holes. The shape of the hole is not particularly limited, and any shape can be used. However, considering the dent of the recording medium due to the suction hole, the shape shown in FIGS. 14B to 14E is preferable. . By adopting such a shape, the suction pressure in the vicinity of the end of the hole on the surface of the suction sheet can be weakened, so that it is difficult to make the dent of the suction hole in the recording medium. In the present invention, the diameter of the suction hole means the length of D1 in FIG.

As shown in FIG. 14, the size of the edge portion of the suction hole is as follows: D1: minimum hole diameter (diameter of suction hole), D2: hole diameter of the suction sheet surface, t: thickness of the suction sheet, h: diameter from D2 When the depth until D1 is a: (D2-D1) / 2,
a ≦ 0.25 × t,
In the case of FIG. 14B, 0 <h ≦ 0.5 × t
In the case of FIG. 14C, 0 <h ≦ 0.35 × t
In the case of FIGS. 14D and 14E, 0 <h ≦ 0.25 × t
It is preferable to provide an edge portion of the suction hole so as to satisfy the above.

  Further, it is preferable to provide a recording medium restraining means 83 for pressing the recording medium 22 against the drying drum 76 on the opposite side of the drying drum 76 across the recording medium 22. By providing the recording medium suppressing means 83, the recording medium can be uniformly adsorbed on the drying drum 76 while suppressing the generation of wrinkles and the like.

  The recording medium holding means 83 can be performed by pressing the recording medium in a non-contact manner by a blowing means as shown in FIG. Further, although it can be performed by contacting and pressing with a roller or the like, since a undried image is formed on the recording medium, it is preferable to use a non-contact type recording medium suppressing means.

(Exposure cured part)
The exposure curing unit 18 includes an ultraviolet light source 88 and an inline sensor 90. The ultraviolet light source 88 and the in-line sensor 90 are disposed at a position facing the peripheral surface of the exposure / curing drum 84, and are sequentially disposed from the upstream side in the rotation direction of the exposure / curing drum 84.

  The exposure curing drum 84 is a drum that holds the recording medium 22 on its outer peripheral surface and rotates and conveys the recording medium 22, and is driven to rotate. Further, the exposure curing drum 84 is provided with a claw-shaped holding means 85 on its outer peripheral surface, and the holding means 85 can hold the leading end of the recording medium 22. The recording medium 22 is rotated and conveyed by rotating the exposure curing drum 84 in a state where the leading end is held by the holding unit 85. At that time, the recording surface of the recording medium 22 is conveyed so that the recording surface faces outward, and the recording surface is subjected to an exposure curing process by the ultraviolet light source 88 and an inspection by the inline sensor 90.

  The ultraviolet light source 88 irradiates the dried ink with UV light, whereby the actinic ray curable resin contained in the ink is cured and the ink is formed into a film. As the ultraviolet light source 88, various ultraviolet light sources such as a metal halide lamp, a high-pressure mercury lamp, a black light, a cold cathode tube, and a UV-LED can be used.

  The peak wavelength of the ultraviolet light irradiated by the ultraviolet light source 88 is preferably 200 to 600 nm, more preferably 300 to 450 nm, and still more preferably 350 to 450 nm, although it depends on the absorption characteristics of the ink composition.

The irradiation energy of the ultraviolet light source 88 is preferably 2000 mJ / cm ² or less, more preferably 10 to 2000 mJ / cm ² , still more preferably ²⁰ to 1000 mJ / cm ² , and particularly preferably 50 to 800 mJ. / Cm ² .

  In the ink jet recording apparatus of the present invention, it is appropriate to irradiate the recording surface of the recording medium with ultraviolet rays for 0.01 to 10 seconds, more preferably for 0.1 to 2 seconds.

  Further, the exposure curing drum 84 may be controlled to a predetermined temperature. Thereby, the curing sensitivity of the ink can be improved, and the ink can be suitably cured and formed into a film with a low irradiation intensity.

  On the other hand, the in-line sensor 90 is a measuring unit for measuring a check pattern, a moisture content, a surface temperature, a glossiness, and the like for an image fixed on the recording medium 22, and a CCD line sensor or the like is applied.

(Discharge part)
As shown in FIG. 1, a discharge unit 20 is provided following the exposure curing unit 18. The discharge unit 20 includes a discharge tray 92. Between the discharge tray 92 and the exposure curing drum 84 of the exposure curing unit 18, a transfer drum 94, a conveyance belt 96, and a stretching roller 98 are in contact with each other. Is provided. The recording medium 22 is sent to the transport belt 96 by the transfer drum 94 and discharged to the discharge tray 92.

(Intermediate transport section)
Next, the structure of the first intermediate transport unit 24 will be described. Note that the second intermediate conveyance unit 26 and the third intermediate conveyance unit 28 have the same configuration as the first intermediate conveyance unit 24, and a description thereof will be omitted.

  The first intermediate transport unit 24 includes an intermediate transport body 30. The intermediate conveyance body 30 is a drum for receiving the recording medium 22 from the preceding drum, rotating and conveying it to the subsequent drum, and is rotatably attached. Further, the intermediate transport body 30 is rotated by a motor (not shown).

  Claw-shaped holding means are provided at 90 ° intervals on the outer peripheral surface of the intermediate conveyance body 30. The holding unit rotates while drawing a circular locus, and the tip of the recording medium 22 is held by the operation of the holding unit. Accordingly, the recording medium 22 can be rotated and conveyed by rotating the intermediate conveyance body 30 with the holding means holding the tip of the recording medium 22. The recording surface of the recording medium may be conveyed in a non-contact manner by providing a plurality of air outlets on the surface of the intermediate carrier 30 and blowing out air from the air outlets.

  The recording medium 22 transported by the first intermediate transport unit 24 is transferred to the subsequent drum (that is, the drawing drum 70). At this time, the recording medium 22 is delivered by synchronizing the holding means of the intermediate transport unit 24 and the holding means of the drawing unit 14. The transferred recording medium 22 is held and drawn by the drawing drum 70.

(Description of control system)
FIG. 15 is a principal block diagram showing the system configuration of the inkjet recording apparatus 1. The ink jet recording apparatus 1 includes a communication interface 120, a system controller 122, a print controller 124, a treatment liquid application controller 126, a first intermediate transport controller 128, a head driver 130, a second intermediate transport controller 132, and a drying controller 134. A third intermediate transport control unit 136, an exposure curing control unit 138, an inline sensor 90, an encoder 91, a motor driver 142, a memory 144, a heater driver 146, an image buffer memory 148, a suction control unit 149, and the like.

  The communication interface 120 is an interface unit that receives image data sent from the host computer 150. As the communication interface 120, a serial interface such as USB (Universal Serial Bus), IEEE 1394, Ethernet (registered trademark), a wireless network, or a parallel interface such as Centronics can be applied. In this part, a buffer memory (not shown) for speeding up communication may be mounted. Image data sent from the host computer 150 is taken into the inkjet recording apparatus 1 via the communication interface 120 and temporarily stored in the memory 144.

  The system controller 122 includes a central processing unit (CPU) and its peripheral circuits, and functions as a control device that controls the entire inkjet recording apparatus 1 according to a predetermined program, and also functions as an arithmetic device that performs various calculations. . That is, the system controller 122 includes the communication interface 120, the treatment liquid application controller 126, the first intermediate transport controller 128, the head driver 130, the second intermediate transport controller 132, the drying controller 134, and the third intermediate transport controller 136. , Exposure curing control unit 138, memory 144, motor driver 142, heater driver 146, suction control unit 149, etc. are controlled to control communication with the host computer 150, read / write control of the memory 144, etc. A control signal for controlling the system motor 152 and the heater 154 is generated.

  The memory 144 is a storage unit that temporarily stores an image input via the communication interface 120, and data is read and written through the system controller 122. The memory 144 is not limited to a memory made of a semiconductor element, and a magnetic medium such as a hard disk may be used.

  The ROM 145 stores programs executed by the CPU of the system controller 122 and various data necessary for control. The ROM 145 may be a non-rewritable storage unit, or may be a rewritable storage unit such as an EEPROM. The memory 144 is used as a temporary storage area for image data, and is also used as a program development area and a calculation work area for the CPU.

  The motor driver 142 is a driver that drives the motor 152 in accordance with an instruction from the system controller 122. In FIG. 15, the motors arranged in the respective units in the apparatus are represented by reference numeral 152 as a representative. For example, the motor 152 shown in FIG. 15 includes a motor for driving rotation of the transfer drum 52, the treatment liquid drum 54, the drawing drum 70, the drying drum 76, the exposure / curing drum 84, the transfer drum 94, and the like. A pump 75 drive motor for sucking negative pressure from the suction holes, a motor for a retraction mechanism of the head units of the ink heads 72C, 72M, 72Y, 72K, and the like are included.

  The heater driver 146 is a driver that drives the heater 154 in accordance with an instruction from the system controller 122. In FIG. 15, a plurality of heaters provided in the inkjet recording apparatus 1 are represented by reference numeral 154 as a representative. For example, the heater 154 shown in FIG. 15 includes a preheater (not shown) for heating the recording medium 22 to an appropriate temperature in the paper supply unit 10 in advance.

  The print control unit 124 has a signal processing function for performing various processes and corrections for generating a print control signal from the image data in the memory 144 under the control of the system controller 122, and the generated print. It is a control unit that supplies data (dot data) to the head driver 130. Necessary signal processing is performed in the print control unit 124, and the ejection amount and ejection timing of the ink droplets of the ink head 100 are controlled via the head driver 130 based on the image data. Thereby, a desired dot size and dot arrangement are realized.

  The print control unit 124 includes an image buffer memory 148, and image data, parameters, and other data are temporarily stored in the image buffer memory 148 when image data is processed in the print control unit 124. In FIG. 15, the image buffer memory 148 is shown in a mode associated with the print control unit 124, but it can also be used as the memory 144. Also possible is an aspect in which the print control unit 124 and the system controller 122 are integrated to form a single processor.

  An outline of the flow of processing from image input to print output is as follows. Image data to be printed is input from the outside via the communication interface 120 and stored in the memory 144. At this stage, for example, RGB image data is stored in the memory 144.

  In the inkjet recording apparatus 1, a pseudo continuous tone image is formed by changing the droplet ejection density and dot size of fine dots with ink (coloring material) to the human eye. It is necessary to convert to a dot pattern that reproduces the gradation (shading of the image) as faithfully as possible. Therefore, the original image (RGB) data stored in the memory 144 is sent to the print control unit 124 via the system controller 122, and the print control unit 124 performs halftoning processing using a threshold matrix, an error diffusion method, or the like. Is converted into dot data for each ink color.

  That is, the print control unit 124 performs a process of converting the input RGB image data into dot data of four colors K, C, M, and Y. Thus, the dot data generated by the print control unit 124 is stored in the image buffer memory 148.

  The head driver 130 is a drive signal for driving the actuator 116 corresponding to each nozzle 102 of the ink head 100 based on print data (that is, dot data stored in the image buffer memory 148) given from the print control unit 124. Is output. The head driver 130 may include a feedback control system for keeping the head driving condition constant.

  When the drive signal output from the head driver 130 is applied to the ink head 100, ink is ejected from the corresponding nozzle 102. An image is formed on the recording medium 22 by controlling the ink ejection from the ink head 100 while conveying the recording medium 22 at a predetermined speed.

  Further, the system controller 122 includes a processing liquid application control unit 126, a first intermediate transfer control unit 128, a second intermediate transfer control unit 132, a drying control unit 134, a third intermediate transfer control unit 136, an exposure / curing control unit 138, and a suction unit. The control unit 149 is controlled.

  The treatment liquid application control unit 126 controls the operation of the treatment liquid application device 56 of the treatment liquid application unit 12 in accordance with an instruction from the system controller 122.

  The first intermediate conveyance control unit 128 controls the operation of the intermediate conveyance body 30 of the first intermediate conveyance unit 24 in accordance with an instruction from the system controller 122. Specifically, in the intermediate transport body 30, the rotational drive of the intermediate transport body 30 itself, the rotation of the holding means provided in the intermediate transport body 30, and the like are controlled. The second intermediate transfer control unit 132 and the third intermediate transfer control unit 136 also perform the same control as the first intermediate transfer control unit 128.

  The suction controller 149 controls suction means provided in the drying drum 76 in order to transport the image-formed recording medium 22 in close contact with the drying drum 76 according to the control of the system controller 122. The suction means controls the suction pressure based on the rigidity of the recording medium 22. By sucking at a suction pressure sufficient to transport the recording medium in close contact, suction dents generated in the recording medium can be controlled. Control can be performed by causing the ROM 145 to record the suction pressure corresponding to the rigidity depending on the type of the recording medium 22 and directly inputting the type of the recording medium 22 to be used by a personal computer (not shown).

[Ink composition]
The ink composition in the present invention contains a pigment, and can be constituted by using a dispersant, a surfactant, and other components as necessary.

(Pigment)
The ink composition in the invention contains at least one pigment as a color material component. There is no restriction | limiting in particular as a pigment, According to the objective, it can select suitably, For example, any of an organic pigment and an inorganic pigment may be sufficient. The pigment is preferably a pigment that is almost insoluble or hardly soluble in water from the viewpoint of ink colorability.

(Dispersant)
The ink composition of the present invention can contain at least one dispersant. The pigment dispersant may be either a polymer dispersant or a low molecular surfactant type dispersant. The polymer dispersant may be either a water-soluble dispersant or a water-insoluble dispersant.

  The weight average molecular weight of the polymer dispersant is preferably 3,000 to 100,000, more preferably 5,000 to 50,000, still more preferably 5,000 to 40,000, and particularly preferably 10,000. 000 to 40,000.

  The acid value of the polymer dispersant is preferably 100 or less mgKOH / g or less from the viewpoint of good aggregation when the treatment liquid comes into contact. Furthermore, the acid value is more preferably from 25 to 100 mgKOH / g, further preferably from 25 to 80, and particularly preferably from 30 to 65. When the acid value of the polymer dispersant is 25 or more, the stability of self-dispersibility is improved.

  The polymer dispersant preferably contains a polymer having a carboxyl group from the viewpoint of self-dispersibility and aggregation rate when the treatment liquid comes into contact. The polymer dispersant has a carboxyl group and an acid value of 25 to 80 mgKOH / g. More preferably.

  In the present invention, from the viewpoint of image light resistance and quality, it is preferable to contain a pigment and a dispersant, more preferably an organic pigment and a polymer dispersant, and a polymer dispersant containing an organic pigment and a carboxyl group. It is particularly preferred that Moreover, it is preferable that a pigment is coat | covered with the polymer dispersing agent which has a carboxyl group from a cohesive viewpoint, and is water-insoluble. Furthermore, from the viewpoint of cohesiveness, it is preferable that the acid value of the self-dispersing polymer particles described later is smaller than the acid value of the polymer dispersant.

  The average particle size of the pigment is preferably 10 to 200 nm, more preferably 10 to 150 nm, and still more preferably 10 to 100 nm. When the average particle size is 200 nm or less, the color reproducibility is good, the droplet ejection characteristics when droplets are ejected by the ink jet method are good, and when it is 10 nm or more, the light resistance is good. Further, the particle size distribution of the color material is not particularly limited, and may be either a wide particle size distribution or a monodisperse particle size distribution. Two or more color materials having a monodisperse particle size distribution may be mixed and used.

  The average particle size and particle size distribution of the pigment particles are determined by measuring the volume average particle size by a dynamic light scattering method using a nanotrack particle size distribution measuring device UPA-EX150 (manufactured by Nikkiso Co., Ltd.). It is what

  You may use a pigment individually by 1 type or in combination of 2 or more types.

  The content of the pigment in the ink composition is preferably 1 to 25% by mass, more preferably 2 to 20% by mass, and more preferably 5 to 20% by mass with respect to the ink composition from the viewpoint of image density. Is more preferable, and 5 to 15% by mass is particularly preferable.

(Polymer particles)
The ink composition in the invention can contain at least one kind of polymer particles. The polymer particles have a function of fixing the ink composition by destabilizing and agglomerating and aggregating the ink to increase the viscosity of the ink when the polymer particles come into contact with a treatment liquid described later or a dried region thereof. The fixing property to the recording medium and the scratch resistance of the image can be further improved.

  In order to react with the aggregating agent, polymer particles having an anionic surface charge are used, and generally known latex is used as long as sufficient reactivity and ejection stability are obtained. It is preferable to use polymer particles.

<Self-dispersing polymer particles>
The ink composition in the invention preferably contains at least one kind of self-dispersing polymer particles as polymer particles. This self-dispersing polymer has a function of fixing the ink composition by destabilizing and agglomerating and aggregating the ink to increase the viscosity of the ink when it comes into contact with a treatment liquid described later or a dried region thereof. Fixability of the composition to a recording medium and image scratch resistance can be further improved. Self-dispersing polymers are also preferred resin particles from the viewpoints of ejection stability and liquid stability (particularly dispersion stability) of the system containing the pigment.

  Self-dispersing polymer particles are water-insoluble polymers that can be dispersed in an aqueous medium by the functional groups (especially acidic groups or salts thereof) of the polymer itself in the absence of other surfactants. Means water-insoluble polymer particles which do not contain free emulsifiers.

  The acid value of the self-dispersing polymer in the present invention is preferably 50 or less KOHmg / g or less from the viewpoint of good cohesiveness when the treatment liquid comes into contact. Furthermore, the acid value is more preferably 25 to 50 KOH mg / g, and still more preferably 30 to 50. When the acid value of the self-dispersing polymer is 25 or more, the stability of the self-dispersing property is improved.

  The self-dispersing polymer particles in the present invention preferably contain a polymer having a carboxyl group from the viewpoint of self-dispersibility and agglomeration speed when the treatment liquid comes into contact, and have a carboxyl group and an acid value of 25 to 25. More preferably, it contains a polymer of 50 KOH mg / g, more preferably a polymer having a carboxyl group and an acid value of 30 to 50 KOH mg / g.

  The molecular weight of the water-insoluble polymer constituting the self-dispersing polymer particles is preferably 3000 to 200,000, more preferably 5000 to 150,000, and more preferably 10,000 to 100,000 in terms of weight average molecular weight. Further preferred. By setting the weight average molecular weight to 3000 or more, the amount of water-soluble components can be effectively suppressed. Moreover, self-dispersion stability can be improved by making a weight average molecular weight into 200,000 or less.

  The weight average molecular weight is measured by gel permeation chromatography (GPC). For GPC, HLC-8220GPC (manufactured by Tosoh Corporation) is used, and as columns, TSKgeL SuperHZM-H, TSKgeL SuperHZ4000, TSKgeL SuperHZ2000 (manufactured by Tosoh Corporation, 4.6 mm ID × 15 cm) are used as eluents. Use THF (tetrahydrofuran). The conditions are as follows: the sample concentration is 0.35 / min, the flow rate is 0.35 ml / min, the sample injection amount is 10 μl, the measurement temperature is 40 ° C., and an IR detector is used. In addition, the calibration curve is “standard sample TSK standard, polystyrene” manufactured by Tosoh Corporation: “F-40”, “F-20”, “F-4”, “F-1”, “A-5000”, It is prepared from 8 samples of “A-2500”, “A-1000”, “n-propylbenzene”.

  The average particle diameter of the self-dispersing polymer particles is preferably in the range of 10 nm to 400 nm, more preferably in the range of 10 to 200 nm, and still more preferably in the range of 10 to 100 nm. When the volume average particle size is 10 nm or more, the production suitability is improved, and when it is 1 μm or less, the storage stability is improved.

  The average particle size and particle size distribution of the self-dispersing polymer particles are measured by the dynamic light scattering method using Nanotrac particle size distribution analyzer UPA-EX150 (manufactured by Nikkiso Co., Ltd.). Is required.

  The self-dispersing polymer particles can be used singly or in combination of two or more. The content of the self-dispersing polymer particles in the ink composition is preferably 1 to 30% by mass with respect to the ink composition from the viewpoint of aggregation rate and image glossiness, and 5 to 15 More preferably, it is mass%.

  In addition, the content ratio of the pigment and the self-dispersing polymer particles in the ink composition (for example, water-insoluble pigment particles / self-dispersing polymer particles) is 1/0 from the viewpoint of image scratch resistance and the like. 5 to 1/10 is preferable, and 1/1 to 1/4 is more preferable.

(Polymerizable compound)
The ink composition in the present invention can contain at least one water-soluble polymerizable compound that is polymerized by active energy rays.

  The term “water-soluble” means that it can be dissolved in water at a certain concentration or higher, and it can be dissolved in water-based ink (preferably uniformly). Further, the solubility may be increased by adding a water-soluble organic solvent to be described later, and it may be dissolved (desirably uniformly) in the ink. Specifically, the solubility in water is preferably 10% by mass or more, and more preferably 15% by mass or more.

  As the polymerizable compound, a nonionic or cationic polymerizable compound is preferable in that it does not interfere with the reaction between the flocculant, the pigment, and the polymer particles, and the solubility in water is 10% by mass or more (more preferably 15% by mass or more). The polymerizable compound is preferable.

  As the polymerizable compound in the present invention, a polyfunctional monomer is preferable from the viewpoint of enhancing scratch resistance, and a bifunctional to hexafunctional monomer is preferable, and from the viewpoint of compatibility between solubility and scratch resistance, bifunctional to tetrafunctional. Are preferred.

  A polymeric compound can be contained individually by 1 type or in combination of 2 or more types.

  The content of the polymerizable compound in the ink composition is preferably 30 to 300% by mass, more preferably 50 to 200% by mass, based on the total solid content of the pigment and the self-dispersing polymer particles. When the content of the polymerizable compound is 30% by mass or more, the image strength is further improved and the image has excellent scratch resistance, and when it is 300% by mass or less, it is advantageous in terms of pile height.

(Initiator)
The ink composition in the present invention may contain at least one initiator that initiates polymerization of the polymerizable compound by active energy rays with or without being contained in a treatment liquid described later. A photoinitiator can be used individually by 1 type or in mixture of 2 or more types or using together with a sensitizer.

  The initiator can contain a compound capable of initiating a polymerization reaction by active energy rays as appropriate. For example, the initiator starts generation of active species (radicals, acids, bases, etc.) by radiation or light, or electron beams. An agent (for example, a photopolymerization initiator) can be used.

  When the initiator is contained, the content of the initiator in the ink composition is preferably 1 to 40% by mass and more preferably 5 to 30% by mass with respect to the polymerizable compound. When the content of the initiator is 1% by mass or more, the scratch resistance of the image is further improved, which is advantageous for high-speed recording, and when it is 40% by mass or less, it is advantageous in terms of ejection stability.

(Water-soluble organic solvent)
The ink composition in the invention can contain at least one water-soluble organic solvent. The water-soluble organic solvent can obtain the effect of preventing drying, wetting or promoting penetration. In order to prevent drying, the ink adheres to and drys at the ink discharge port of the ejection nozzle and is used as an anti-drying agent to prevent clogging. For drying prevention and wetting, the vapor pressure is lower than that of water. A water-soluble organic solvent is preferred. Further, for penetration promotion, it can be used as a penetration enhancer that enhances ink permeability to paper.

  The drying inhibitor is preferably a water-soluble organic solvent having a vapor pressure lower than that of water.

  Anti-drying agents may be used alone or in combination of two or more. The content of the drying inhibitor is preferably in the range of 10 to 50% by mass in the ink composition.

  As a penetration accelerator, it is suitable for the purpose of allowing the ink composition to penetrate better into the recording medium (printing paper or the like). A penetration enhancer may be used individually by 1 type, or may be used together 2 or more types. The content of the penetration enhancer is preferably in the range of 5 to 30% by mass in the ink composition. Moreover, it is preferable to use the penetration enhancer within a range that does not cause image bleeding and paper loss (print-through).

(water)
The ink composition contains water, but the amount of water is not particularly limited. Especially, the preferable content of water is 10 to 99% by mass, more preferably 30 to 80% by mass, and still more preferably 50 to 70% by mass.

(Other additives)
The ink composition in the present invention can be constituted using other additives in addition to the above components. Other additives include, for example, anti-drying agents (wetting agents), anti-fading agents, emulsion stabilizers, penetration enhancers, ultraviolet absorbers, preservatives, anti-fungal agents, pH adjusters, surface tension adjusters, Well-known additives, such as a foaming agent, a viscosity modifier, a dispersing agent, a dispersion stabilizer, a rust preventive agent, a chelating agent, are mentioned.

[Treatment solution]
The treatment liquid contains at least an aggregating agent for aggregating the components in the ink composition described above, and can be constituted using other components as necessary. By using the treatment liquid together with the ink composition, it is possible to increase the speed of ink jet recording, and an image with excellent density and resolution (for example, reproducibility of fine lines and fine portions) can be obtained even at high speed recording.

  The aggregating agent may be a compound capable of changing the pH of the ink composition, a polyvalent metal salt, or polyallylamines. In the present invention, from the viewpoint of cohesiveness of the ink composition, a compound capable of changing the pH of the ink composition is preferable, and a compound capable of lowering the pH of the ink composition is more preferable.

  Among them, as the flocculant in the present invention, an acidic substance having high water solubility is preferable, and an organic acid is preferable, and an organic acid having a valence of 2 or more is more preferable, from the viewpoint of improving the aggregation property and fixing the entire ink. Above-mentioned trivalent or less acidic substances are particularly preferred. The divalent or higher organic acid is preferably an organic acid having a first pKa of 3.5 or less, more preferably an organic acid of 3.0 or less. Specific examples include phosphoric acid, oxalic acid, malonic acid, citric acid and the like.

  A flocculant can be used individually by 1 type or in mixture of 2 or more types.

  The content of the flocculant for aggregating the ink composition in the treatment liquid is preferably 1 to 50% by mass, more preferably 3 to 45% by mass, and still more preferably 5 to 40% by mass.

  The treatment liquid can further contain other additives as other components within a range not impairing the effects of the present invention. Other additives include, for example, anti-drying agents (wetting agents), anti-fading agents, emulsion stabilizers, penetration enhancers, UV absorbers, preservatives, anti-fungal agents, pH adjusters, surface tension adjusters, anti-foaming agents. Well-known additives, such as a foaming agent, a viscosity modifier, a dispersing agent, a dispersion stabilizer, a rust preventive agent, a chelating agent, are mentioned.

<Recording medium>
The inkjet recording method of the present invention records an image on a recording medium.

  The recording medium is not particularly limited, and general printing paper mainly composed of cellulose, such as so-called high-quality paper, coated paper, and art paper, used for general offset printing and the like can be used. General printing paper mainly composed of cellulose is relatively slow in ink absorption and drying in image recording by a general ink jet method using water-based ink, and color material movement is likely to occur after droplet ejection, and image quality is likely to deteriorate. However, according to the ink jet recording method of the present invention, it is possible to record a high-quality image excellent in color density and hue by suppressing the movement of the color material.

  Among the recording media, so-called coated paper used for general offset printing is preferable. The coated paper is obtained by applying a coating material to the surface of high-quality paper, neutral paper, or the like that is mainly surface-treated with cellulose as a main component and is not surface-treated. The coated paper tends to cause quality problems such as image gloss and scratch resistance in image formation by ordinary aqueous inkjet, but in the inkjet recording method of the present invention, gloss unevenness is suppressed and gloss and resistance are reduced. An image having good rubbing properties can be obtained. In particular, a coated paper having a base paper and a coat layer containing an inorganic pigment is preferably used, and a coated paper having a base paper and a coat layer containing kaolin and / or calcium bicarbonate is more preferably used. Specifically, art paper, coated paper, lightweight coated paper, or finely coated paper is more preferable.

[Example]
EXAMPLES Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto.

[Test Example 1] Evaluation by arrangement of holes on the suction surface of the drying drum A solid image was drawn by the ink jet recording apparatus shown in FIG. 1, and the dents of the suction holes, the image strength of the holes, and the occurrence of cockle were confirmed on the formed sample did. The adsorption sheet was tested under the conditions shown in Table 1 for the thickness: 0.4 mm, the aperture ratio, the diameter of the adsorption holes, and the hole pitch. In addition, about the example which changed the aperture ratio by the center part and the edge part, it was set as the average hole diameter: 0.8mm and the average hole pitch 0.8mm. Moreover, the shape of the edge part used the suction hole of the shape shown to Fig.14 (a). The suction pressure was 40 kPa. As the recording medium, an OK top coat 104 gsm and a chrysanthemum half size (636 × 469 mm) were used. In the example, since the recording medium was transported so that the long side of the recording medium was in the width direction and the short side was in the transport direction, Comparative Examples 1 to 3 had a vertical grain (the paper grain was perpendicular to the transport direction), The measurement was performed both in the horizontal direction (the paper pattern was parallel to the transport direction). In Example 1 and Comparative Examples 4 to 6, the test was performed using a recording medium having a horizontal grain, and in Example 2 and Comparative Examples 7 to 9, a vertical recording medium was used. The amount of ink ejected was 5 pl.

  Each evaluation was performed according to the following criteria.

<Suction hole dent>
The visibility of the dent in the suction hole portion of the solid image portion of the output recording medium was visually evaluated.
◎: Not visually recognized ○: Almost not visually recognized ○ △: Partially visually recognized but within tolerance △: Visible ×: Remarkably visually recognized <Image strength of the hole>
Cellophane tape (manufactured by Nichiban Co., Ltd.) was affixed to a region including the suction hole portion of the solid image portion of the output sample to evaluate the adhesion of the image of the suction hole portion.
○: There is no image adhesion on the peeled tape. Δ: Some image adhesion at the suction hole portion on the peeled tape. ×: Image adhesion at the suction hole portion on the peeled tape is remarkable.
The degree of cracking of the solid image portion of the output recording medium was visually evaluated.
○: The cockle is within the allowable range Δ: The cockle may be out of the allowable range Δ ×: The cockle is out of the allowable range X: The cockle is remarkable and is out of the problem As shown in FIG. In the comparative example with a low aperture ratio, the growth of cockle at the central portion could not be suppressed, and in the comparative example with a high aperture ratio, the end portion of the cockle could not be dispersed. In the same manner, Comparative Example 4 and Comparative Example 7 in which the aperture ratio was lowered at the center and the end was raised were confirmed. Further, in Comparative Examples 5, 6, 8, and 9 in which the aperture ratio was changed by changing the hole diameter, a dent was confirmed in the recording medium at the portion where the suction hole had a large hole diameter. In addition, since the hole diameter was 0.8 mm, the influence of the shape of the edge part was not seen.

  In Example 1 and Example 2 in which the hole diameter of the suction holes was made uniform and the aperture ratio was changed by changing the hole pitch, it was possible to form a good image free from dents due to cockle and suction holes.

[Test Example 2] Evaluation of suction dent by basis weight (rigidity) of recording medium Solid images were drawn on three types of recording media by the ink jet recording apparatus shown in FIG. 1, and the suction dent of the image portion was evaluated. The suction sheet is constant at a thickness of 0.4 mm and a hole pitch of 0.8 mm, and the aperture ratio gradually decreases in each region as shown in FIG. 2B or FIG. The hole diameter was changed in the range of 0.2 to 2.0 mm. The aperture ratio in FIG. 17 is the aperture ratio in each region. The ink ejection amount was 5 pl, and the shape of the edge portion of the suction hole was the suction hole having the shape shown in FIG. The suction pressure was 40 kPa.

  As shown in FIG. 17, in the case of a recording medium with high rigidity, even if the hole diameter of the suction hole is increased, it is difficult to dent the suction hole. Therefore, the diameter of the suction hole is controlled according to the rigidity of the recording medium. It is preferable. In order to cope with a recording medium with low rigidity, it is preferable to set the hole diameter to a predetermined value or less. From FIG. 17, if the basis weight corresponds to 104.7 gsm, it is preferable to set the hole diameter to 1.2 mm or less in order to cope with the hole diameter of 1.4 mm or less, and further to 73.3 gsm equivalent.

[Test Example 3] Evaluation of suction dent by edge processing of suction holes A solid image was drawn by the ink jet recording apparatus shown in Fig. 1, and the suction dents were evaluated. The suction sheet is constant at a thickness of 0.4 mm and a hole pitch of 0.8 mm, and the aperture ratio gradually decreases in each region as shown in FIG. 2B or FIG. The hole diameter was changed to 1.2 mm and 1.6 mm. Further, the shape of the edge portion was tested using the suction holes shown in FIGS. 14 (a), 14 (b), and 14 (e), and D1: the diameter of the suction hole, h: the diameter was changed from D2 to D1. The depth until reaching a: (D2-D1) / 2 was performed under the conditions shown in FIG. 18 (in FIG. 14A, both a and h are 0). An OK top coat (basis weight: 73.3 gsm) was used as the recording medium, and the ink droplet ejection amount was 5 pl.

  In Test Example 2, the suction dent was remarkably confirmed in the sample having a suction hole diameter of 1.6 mm. However, by processing the edge portion, as shown in FIG. Improvement was seen and the effect of processing the edge part was confirmed.

  DESCRIPTION OF SYMBOLS 1 ... Inkjet recording apparatus, 10 ... Paper feed part, 12 ... Processing liquid provision part, 14 ... Drawing part, 16 ... Drying part, 18 ... Exposure hardening part, 20 ... Discharge part, 22 ... Recording medium, 24 ... 1st Intermediate transport section, 26 ... second intermediate transport section, 28 ... third intermediate transport section, 30 ... intermediate transport body, 55, 71, 77, 85 ... holding means, 70 ... drawing drum, 72M, 72C, 72Y, 72K ... ink head, 76 ... drying drum, 78 ... first IR heater, 80 ... warm air ejection nozzle, 82 ... second IR heater, 81 ... auxiliary suction means, 83 ... air blowing nozzle (non-contact type recording medium) 84 ... exposure curing drum, 88 ... ultraviolet light source

Claims (20)

An ink jet head that forms an image by ejecting ink onto a recording medium;
A transport body for transporting the recording medium after ink ejection, a holding means for holding the recording medium, a plurality of suction holes for sucking the recording medium under negative pressure, and a suction means for sucking from the suction holes; Conveying means having
Heating means for heating the carrier and the recording medium from the printing surface side on which the image is formed,
Ink jet recording characterized in that the pitch interval of the suction holes of the suction surface for sucking the recording medium increases from the center to the end of the suction surface corresponding to the recording medium, and the aperture ratio decreases. apparatus.   2. The ink jet recording apparatus according to claim 1, wherein a pitch interval of the suction holes is widened from a central portion of the suction surface corresponding to the recording medium toward an end portion in the width direction.   2. The ink jet recording apparatus according to claim 1, wherein a pitch interval of the suction holes is widened from a central portion of the suction surface corresponding to the recording medium toward an end portion in a transport direction.   4. The ink jet recording apparatus according to claim 2, wherein a pitch interval between the suction holes has a highest aperture ratio at a central portion of the suction surface corresponding to the recording medium.   5. The ink jet recording apparatus according to claim 1, wherein the suction holes are arranged in a hexagonal close-packed arrangement, and the suction holes are arranged at a predetermined interval.   The ink jet recording apparatus according to claim 1, wherein the suction hole has a perfect circle shape or an elliptic shape.   The ink jet recording apparatus according to claim 1, wherein an edge portion of the suction hole is a curved surface.   The inkjet recording apparatus according to any one of claims 1 to 6, wherein a groove having a shape similar to that of the suction hole is provided at an edge portion of the suction hole.   The inkjet recording apparatus according to claim 1, further comprising a control unit that controls a suction pressure by the suction unit according to a type of the recording medium.   The ink jet recording apparatus according to claim 1, wherein the suction holes are arranged so that an aperture ratio of the suction surface decreases linearly.   10. The ink jet recording apparatus according to claim 1, wherein the suction surface is divided into a plurality of regions and is arranged so that the aperture ratio decreases step by step for each region.   The ink jet recording apparatus according to claim 11, wherein the aperture ratio decreases linearly between regions where the aperture ratio of the suction surface is constant.   The inkjet recording apparatus according to any one of claims 10 to 12, wherein an aperture ratio is constant in a region of a central portion of the suction surface of 10 to 70%.   14. The inkjet recording apparatus according to claim 1, further comprising a recording medium holding unit that presses the recording medium from the printing surface side to the surface of the conveyance body.   The inkjet according to any one of claims 1 to 14, wherein an aperture ratio of the suction surface corresponding to a rear end in a conveyance direction of the recording medium is the same as an aperture ratio of a central portion of the suction surface. Recording device.   The inkjet recording according to any one of claims 1 to 15, wherein an aperture ratio of the suction surface corresponding to a leading end of the recording medium in a conveyance direction is the same as an aperture ratio of a central portion of the suction surface. apparatus. An ink ejection process for forming an image by ejecting ink onto a recording medium; and
A transporting step of transporting the recording medium by placing the recording medium after the ink droplets on the transporting body and sucking it through the suction holes while holding the recording medium;
A heating step of heating the carrier and the recording medium from the printing surface side on which the image is formed,
Ink jet recording characterized in that the pitch interval of the suction holes of the suction surface for sucking the recording medium increases from the center to the end of the suction surface corresponding to the recording medium, and the aperture ratio decreases. Method.   18. The ink jet recording method according to claim 17, wherein a pitch interval between the suction holes is widened from a center portion of the suction surface corresponding to the recording medium toward an end portion in the width direction.   18. The ink jet recording method according to claim 17, wherein a pitch interval of the suction holes is widened from a central portion of the suction surface corresponding to the recording medium toward an end portion in a conveyance direction.   20. The ink jet recording method according to claim 17, further comprising a control step of controlling a suction pressure depending on a type of the recording medium.