JP2010214788A - Image forming apparatus and mist collecting method - Google Patents

Abstract

An image forming apparatus and a mist collecting method are provided that prevent adhesion of mist-like droplets generated during liquid ejection to the vicinity of a nozzle and enable continuous operation for a long period of time.
An ink jet head having a plurality of nozzles arranged in a row direction that forms an angle θ with the paper conveyance direction, and the plurality of nozzle groups arranged in a row direction substantially orthogonal to the paper conveyance direction. A conductive pattern 160 (column direction pattern 160A) is formed on the nozzle surface 150A of 150 in the direction substantially parallel to the direction of the nozzle group (column direction) on the downstream side in the paper conveyance direction of each nozzle group. When the column direction pattern 160A is charged, an electrostatic force C that moves in the direction of the column direction pattern 160A acts on the ink mist separated from the ink (main droplet) after ejection, and the ink mist is applied to the column direction pattern 160A. Since it adheres, it can prevent that ink mist adheres to the vicinity of another nozzle.
[Selection] Figure 6

Description

  The present invention relates to an image forming apparatus and a mist collecting method, and more particularly to a technique for preventing adhesion of mist-like liquid droplets that are generated when liquid is ejected from an inkjet head to a liquid ejection surface.

  An image forming apparatus that forms an image by ejecting ink or a functional material onto a recording medium using an inkjet head is environmentally friendly, and can perform high-speed recording on various recording media. It is difficult to obtain high-definition images, and is used in various fields as a general-purpose image forming apparatus.

  When ink is ejected by the ink jet system, main droplets are generated, satellites that are smaller than the main droplets, and mist that is separated from the main droplets and stalled are generated. When the evaporation of the functional material contained in the ink is negligible, the mist size is about 0.5 μm to 10 μm, and it is particularly difficult to suppress the generation of mist around 1 μm. The mist floats in the apparatus and does not contaminate the inside of the apparatus. In particular, if the mist adheres to the nozzle plate (discharge surface) of the head, it may cause discharge abnormality. In addition, when mist adheres to a detector such as an encoder, an abnormality in conveyance of the recording medium can be induced, and an abnormal drawing due to the abnormality in conveyance can be caused. Such a drawing abnormality adversely affects image formation.

  Patent Document 1 discloses a method in which a conductive coating formed on a nozzle plate is charged to a polarity opposite to the charge charged by the satellite, and the satellite is adsorbed on the conductive coating.

JP 2007-21840 A

  Here, the problems of the prior art will be described in detail with reference to FIGS.

  FIG. 7 is a schematic plan view of a head 250 in which a plurality of nozzles 251 are arranged in a matrix when viewed from the nozzle surface (ink ejection surface) 250A side. A portion surrounded by a solid line in FIG. It is the enlarged view which expanded a part. In FIG. 7, an oblique line segment having a predetermined angle with the paper conveyance direction shown by reference numeral 251 in FIG. 7 represents a plurality of nozzles (nozzle groups) arranged in the same direction.

  As shown in FIG. 7, when ink (not shown) is ejected from the nozzle 251, near the nozzle surface 250 </ b> A, an airflow A that is substantially parallel to the paper conveyance direction and an airflow B that is ejected along the arrangement direction of the nozzles 251 are generated. The generated airflow D, which is a combination of the airflow A and the airflow B, acts on the ink mist (not shown) separated from the ink droplet (main droplet), and the ink mist moves in the direction of the airflow D. In particular, in the head 250 in which the nozzles 251 are arranged in a matrix, the ink mist generated on the upstream side in the paper transport direction (the lower side in FIG. 7) is downstream in the paper transport direction (the upper side in FIG. 7) by the air flow D in FIG. ) And may adhere to the vicinity of the nozzle 251 on the downstream side. If ink mist adheres in the vicinity of the nozzle 251, it may cause a discharge abnormality of the nozzle 251.

  FIG. 8 is a schematic plan view illustrating the nozzle surface 250 </ b> A ′ of the head 250 ′ on which an electrode 260 for collecting mist is formed in a direction substantially orthogonal to the paper transport direction. Further, a part surrounded by a solid line in FIG. 8 is an enlarged view of a part of the nozzle surface 250A ′.

  As shown in FIG. 8, when the electrostatic force C in the direction along the paper conveyance direction generated by charging the electrode 260 acts on the ink mist, the force acting on the ink mist along the direction of the airflow A is increased, and the ink mist is increased. Depending on the speed and volume of the ink, the ink mist may adhere to the vicinity of the adjacent nozzle beyond the electrode 260.

In order to avoid the ink mist from adhering to the nozzles adjacent to the downstream side in the paper transport direction, the nozzle pitch P _ns in the paper transport direction may be increased, but there is a problem that the entire head is increased in size. .

  That is, conventionally, there is no effective means for operating for a long time while preventing ink mist and contamination in an ink jet recording apparatus having a small head capable of performing high resolution image recording.

  The present invention has been made in view of such circumstances. An image forming apparatus and a mist recovery device that prevent mist-like droplets generated during liquid discharge from adhering to the vicinity of a nozzle and enable continuous operation for a long period of time. It aims to provide a method.

  In order to achieve the above object, in the image forming apparatus according to the present invention, a plurality of nozzles that discharge liquid onto a recording medium are two-dimensionally arranged, and a conductive pattern is formed corresponding to the nozzles. An inkjet head including a nozzle plate; a conveyance unit that relatively conveys the inkjet head and the recording medium; and a charging unit that charges the conductive pattern. The plurality of nozzles are arranged along a column direction that forms a predetermined angle θ (0 ° <θ <90 °) with respect to a row direction substantially orthogonal to the transport direction, and the plurality of nozzles along the column direction At least one nozzle group is disposed along the row direction, and the conductive pattern is disposed on the inkjet head of the nozzle group. Wherein the downstream side when conveying the recording medium, characterized by being formed along the column direction substantially parallel direction.

  According to the present invention, a nozzle group in which a plurality of nozzles are arranged in a column direction forming a predetermined angle θ (0 ° <θ <90 °) with respect to a row direction orthogonal to the relative conveyance direction of the inkjet head and the recording medium. Since the conductive pattern is formed along the row direction on the downstream side in the conveyance direction when the recording medium is conveyed to the inkjet head, the conductive pattern is charged and the liquid is discharged from the nozzle. By applying an electrostatic force in the direction of the conductive pattern to the mist-like droplets generated after the mist-like droplets, the mist-like droplets are prevented from moving to other nozzles downstream in the transport direction. The

1 is an overall configuration diagram of an ink jet recording apparatus according to an embodiment of the present invention. Plane perspective view showing a configuration example of the inkjet head shown in FIG. Sectional view showing the three-dimensional configuration of the ink chamber unit The block diagram which shows the structure of the maintenance mechanism of the inkjet head shown in FIG. 1 is a block diagram showing a main part of the system configuration of the ink jet recording apparatus shown in FIG. Explanatory drawing of the mist collection method which concerns on embodiment of this invention The figure explaining the subject which concerns on a prior art The figure explaining the subject which concerns on another prior art

[Overall configuration of inkjet recording apparatus]
Next, the overall configuration of an on-demand ink jet recording apparatus to which the present invention is applied will be described.

  FIG. 1 is a configuration diagram showing the overall configuration of the ink jet recording apparatus according to the present embodiment. An inkjet recording apparatus 10 shown in the figure is a two-liquid aggregation type recording apparatus that forms an image on the recording surface of a recording medium 24 using ink (aqueous ink) and a processing liquid (aggregation processing liquid). The paper unit 12 includes a processing liquid application unit 14, a drawing unit 16, a drying unit 18, a fixing unit 20, and a discharge unit 22. A recording medium 24, which is a sheet, is laminated on the paper supply unit 12, and this recording medium 24 is sent from the paper supply unit 12 to the treatment liquid application unit 14, and the processing liquid application unit 14 processes the recording surface. After the liquid is applied, color ink is applied to the recording surface by the drawing unit 16. The recording medium 24 to which ink has been applied is transported by the discharge unit 22 after the image is fastened by the fixing unit 20.

  In addition, the inkjet recording apparatus 10 includes intermediate conveyance units 26, 28, and 30 between the respective units, and the recording medium 24 is transferred by the intermediate conveyance units 26, 28, and 30. That is, a first intermediate transport unit 26 is provided between the processing liquid application unit 14 and the drawing unit 16, and the recording medium from the processing liquid application unit 14 to the drawing unit 16 by the first intermediate transport unit 26. 24 delivery is performed. Similarly, a second intermediate transport unit 28 is provided between the drawing unit 16 and the drying unit 18. The recording medium 24 is transferred from the drawing unit 16 to the drying unit 18 by the second intermediate transport unit 28. Is done. Further, a third intermediate transport unit 30 is provided between the drying unit 18 and the fixing unit 20, and the third intermediate transport unit 30 transfers the recording medium 24 from the drying unit 18 to the fixing unit 20. Done.

  Hereinafter, each part of the inkjet recording apparatus 10 (the paper feeding unit 12, the processing liquid applying unit 14, the drawing unit 16, the drying unit 18, the fixing unit 20, and the discharging unit 22) will be described.

(Paper Feeder)
The paper feed unit 12 is a mechanism that supplies the recording medium 24 to the treatment liquid application unit 14. The paper feed unit 12 is provided with a paper feed tray 50, and the recording medium 24 is fed from the paper feed tray 50 to the processing liquid application unit 14 one by one.

(Processing liquid application part)
The processing liquid application unit 14 is a mechanism that applies the processing liquid to the recording surface of the recording medium 24. The treatment liquid contains a color material aggregating agent that agglomerates the color material (pigment) in the ink applied by the drawing unit 16, and the ink comes into contact with the color material, the solvent, and the ink by contacting the treatment liquid with the ink. Separation is promoted.

  As shown in FIG. 1, the treatment liquid application unit 14 includes a paper feed drum 52, a treatment liquid drum 54, and a treatment liquid application device 56. The paper feed cylinder 52 is disposed between the paper feed tray 50 of the paper feed unit 12 and the processing liquid drum 54, and the rotation of the paper feed drum 52 is controlled by a motor driver 176 (see FIG. 5) described later. The recording medium 24 fed from the paper feed unit 12 is received by the paper feed drum 52 and transferred to the processing liquid drum 54. In addition, instead of the paper feed cylinder 52, an intermediate conveyance unit described later may be provided.

  The treatment liquid drum 54 is a drum that holds and rotates and conveys the recording medium 24, and its rotation is driven and controlled by a motor driver 176 (see FIG. 5) described later. Further, the processing liquid drum 54 is provided with a claw-shaped holding means on its outer peripheral surface, and the leading end of the recording medium 24 can be held by this holding means. The recording medium 24 is rotated and conveyed by rotating the treatment liquid drum 54 with the tip held by the holding means. At that time, the recording medium 24 is conveyed with its recording surface facing outward. The processing liquid drum 54 may be provided with a suction hole on the outer peripheral surface thereof and connected to a suction unit that performs suction from the suction hole. As a result, the recording medium 24 can be held in close contact with the peripheral surface of the treatment liquid drum 54.

  A processing liquid coating device 56 is provided outside the processing liquid drum 54 so as to face the peripheral surface thereof. The processing liquid coating device 56 is a device that applies the processing liquid to the recording surface of the recording medium 24. The processing liquid container in which the processing liquid to be applied is stored and the processing liquid in the processing liquid container are partially immersed. And an anix roller and a rubber roller that is pressed against the recording medium 24 on the processing liquid drum 54 and transfers the measured processing liquid to the recording medium 24. According to the processing liquid application device 56, the processing liquid can be applied to the recording medium 24 while being measured. The film thickness of the treatment liquid is desirably sufficiently smaller than the droplet diameter of ink ejected from the inkjet heads 72M, 72K, 72C, 72Y of the drawing unit 16. 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 24. 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.

  In the present embodiment, the configuration in which the application method using the roller is applied as the method for applying the treatment liquid to the recording surface of the recording medium 24 is exemplified. However, the present invention is not limited to this. For example, a spray method, an ink jet method, etc. Various methods can also be applied. In addition, a drawing method for fixing the ink to the recording medium by applying energy by heating, pressurization, radiation irradiation, or the like to the ink ejected onto the recording medium from the ink jet heads 72M, 72K, 72C, 72Y of the drawing unit 16 Then, the treatment liquid application unit 14 is omitted.

(Drawing part)
The drawing unit 16 is a mechanism for drawing an image corresponding to an input image by ejecting ink using an ink jet method, and includes a drawing drum 70, a paper holding roller 74, and ink jet heads 72M, 72K, 72C, and 72Y. Yes. The inkjet 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 24 on the outer peripheral surface thereof and rotates and conveys the drum. The rotation of the drawing drum 70 is controlled by a motor driver 176 (see FIG. 5) described later. Further, the drawing drum 70 is provided with a claw-shaped holding means on its outer peripheral surface, and the leading end of the recording medium 24 can be held by this holding means. The recording medium 24 is rotated and conveyed by rotating the drawing drum 70 with the tip held by the holding means. At that time, the recording medium 24 is conveyed so that the recording surface faces outward, and ink is applied to the recording surface from the ink jet heads 72M, 72K, 72C, 72Y.

  The sheet pressing roller 74 is a guide member for bringing the recording medium 24 into close contact with the outer peripheral surface of the drawing drum 70, and is disposed at a position facing the outer peripheral surface of the drawing drum 70. Specifically, it is on the downstream side in the conveyance direction of the recording medium 24 (the rotation direction of the drawing drum 70) from the delivery position of the recording medium 24 from the intermediate conveyance unit 26, and from the inkjet heads 72M, 72K, 72C, 72Y. Is also arranged upstream of the recording medium 24 in the transport direction.

  When the recording medium 24 delivered from the intermediate conveyance unit 26 to the drawing drum 70 is rotated and conveyed in a state where the leading end is held by the holding means described above, the recording medium 24 is pressed by the sheet pressing roller 74 and the outer peripheral surface of the drawing drum 70. It is closely attached to. After the recording medium 24 is brought into close contact with the outer peripheral surface of the drawing drum 70 in this way, the recording medium 24 is sent to the print area immediately below the ink jet heads 72M, 72K, 72C, 72Y without being lifted from the outer peripheral surface of the drawing drum 70. It is done.

  The inkjet heads 72M, 72K, 72C, and 72Y are full-line inkjet recording heads (inkjet heads) each having a length corresponding to the maximum width of the image forming area on the recording medium 24. 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 inkjet head 72M, 72K, 72C, 72Y is fixedly installed so as to extend in a direction orthogonal to the conveyance direction of the recording medium 24 (the rotation direction of the drawing drum 70).

  The inkjet heads 72M, 72K, 72C, and 72Y are horizontal surfaces so that the recording surface of the recording medium 24 held on the outer peripheral surface of the drawing drum 70 and the nozzle surfaces of the inkjet heads 72M, 72K, 72C, and 72Y are substantially parallel. It is arranged incline with respect to.

  Corresponding color ink droplets are ejected from the inkjet heads 72M, 72K, 72C, 72Y configured as described above toward the recording surface of the recording medium 24 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 14, 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 24 is prevented, and an image is formed on the recording surface of the recording medium 24. At that time, since the drawing drum 70 of the drawing unit 16 is structurally separated from the processing liquid drum 54 of the processing liquid applying unit 14, the processing liquid may adhere to the ink jet heads 72M, 72K, 72C, 72Y. In addition, the cause of ink ejection failure can be reduced.

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

(Drying part)
The drying unit 18 is a mechanism for drying moisture contained in the solvent separated by the color material aggregating action, and includes a drying drum 76 and a solvent drying device 78 as shown in FIG.

  The drying drum 76 is a drum that holds the recording medium 24 on the outer peripheral surface thereof and rotates and conveys the rotation, and the rotation of the drying drum 76 is controlled by a motor driver 176 (see FIG. 5) described later. Further, the drying drum 76 is provided with a claw-shaped holding means on its outer peripheral surface, and the leading end of the recording medium 24 can be held by this holding means. The recording medium 24 is rotated and conveyed by rotating the drying drum 76 with the tip held by the holding means. At that time, the recording medium 24 is conveyed so that the recording surface faces outward, and the recording surface is dried by the solvent drying device 78. The drying drum 76 may be provided with suction holes on the outer peripheral surface thereof, and may be connected to suction means for performing suction from the suction holes. As a result, the recording medium 24 can be held in close contact with the peripheral surface of the drying drum 76.

The solvent drying device 78 is disposed at a position facing the outer peripheral surface of the drying drum 76 and includes a halogen heater 80. The halogen heater 80 is controlled so as to blow warm air at a predetermined temperature (for example, 50 ° C. to 70 ° C.) toward the recording medium 24 at a constant air volume (12 m ³ / min).

  By the solvent drying device 78 configured in this manner, moisture contained in the ink solvent on the recording surface of the recording medium 24 held on the drying drum 76 is evaporated, and a drying process is performed. At that time, since the drying drum 76 of the drying unit 18 is structurally separated from the drawing drum 70 of the drawing unit 16, in the inkjet heads 72M, 72K, 72C, and 72Y, the head meniscus portion is dried by thermal drying. Ink ejection failure can be reduced. Further, there is a degree of freedom in setting the temperature of the drying unit 18, and an optimal drying temperature can be set.

  The curvature of the drying drum 76 is preferably in the range of 0.002 (1 / mm) to 0.0033 (1 / mm). If the curvature of the drying drum 76 is less than 0.002 (1 / mm), the correction effect of the cockling is insufficient even if the recording medium 24 is curved, whereas if it exceeds 0.0033 (1 / mm), This is because the recording medium 24 bends more than necessary and does not return to its original state, and is output in a curved state at the time of stacking.

  The surface temperature of the drying drum 76 is preferably set to 50 ° C. or higher. Drying is accelerated by heating from the back surface of the recording medium 24, and image destruction during fixing can be prevented. At this time, it is more effective to provide means for bringing the recording medium 24 into close contact with the outer peripheral surface of the drying drum 76. As means for bringing the recording medium 24 into close contact, various methods such as vacuum adsorption and electrostatic adsorption can be applied.

  The upper limit of the surface temperature of the drying drum 76 is not particularly limited, but from the viewpoint of safety of maintenance work such as cleaning ink adhering to the surface of the drying drum 76 (preventing burns due to high temperature). It is preferably set to 75 degrees or less (more preferably 60 degrees C or less).

  The recording drum 24 is held on the outer peripheral surface of the drying drum 76 configured in this manner so that the recording surface of the recording medium 24 faces outward (that is, in a state where the recording surface of the recording medium 24 is convex). By drying while rotating and transporting, the recording medium 24 can be prevented from wrinkling and floating, and drying unevenness caused by these can be surely prevented.

(Fixing part)
The fixing unit 20 includes a fixing drum 84, a halogen heater 86, a fixing roller 88, and an inline sensor 90. The halogen heater 86, the fixing roller 88, and the in-line sensor 90 are disposed at positions facing the outer peripheral surface of the fixing drum 84, and are sequentially disposed from the upstream side in the rotation direction of the fixing drum 84 (counterclockwise direction in FIG. 1). The

  The fixing drum 84 is a drum that holds the recording medium 24 on the outer peripheral surface thereof and rotates and conveys the rotation. The rotation of the fixing drum 84 is controlled by a motor driver 176 (see FIG. 5) described later. Further, the fixing drum 84 is provided with a claw-shaped holding unit on the outer peripheral surface thereof, and the leading end of the recording medium 24 can be held by the holding unit. The recording medium 24 is rotated and conveyed by rotating the fixing drum 84 with the tip held by the holding means. At that time, the recording surface of the recording medium 24 is conveyed so that the recording surface faces outward, and the recording surface is subjected to preliminary heating by the halogen heater 86, fixing processing by the fixing roller 88, and inspection by the inline sensor 90. . The fixing drum 84 may be provided with a suction hole on the outer peripheral surface thereof and connected to a suction unit that performs suction from the suction hole. As a result, the recording medium 24 can be held in close contact with the peripheral surface of the fixing drum 84.

  The halogen heater 86 is controlled to a predetermined temperature (for example, 180 ° C.). As a result, the recording medium 24 is preheated.

  The fixing roller 88 is a roller member for heating and pressurizing the dried ink to weld the self-dispersing polymer fine particles in the ink to form a film of the ink, and is configured to heat and press the recording medium 24. The Specifically, the fixing roller 88 is disposed so as to be in pressure contact with the fixing drum 84, and constitutes a nip roller with the fixing drum 84. As a result, the recording medium 24 is sandwiched between the fixing roller 88 and the fixing drum 84 and nipped at a predetermined nip pressure (for example, 0.15 MPa), and a fixing process is performed.

  The fixing roller 88 is configured by a heating roller in which a halogen lamp is incorporated in a metal pipe such as aluminum having good thermal conductivity, and is controlled to a predetermined temperature (for example, 60 to 80 ° C.). By heating the recording medium 24 with this heating roller, thermal energy equal to or higher than the Tg temperature (glass transition temperature) of the latex contained in the ink is applied, and the latex particles are melted. As a result, pressing and fixing are performed on the unevenness of the recording medium 24, and the unevenness of the image surface is leveled to obtain glossiness.

  In the above-described embodiment, only one fixing roller 88 is provided. However, a configuration in which a plurality of fixing rollers 88 are provided in accordance with the image layer thickness and the Tg characteristics of latex particles may be used. Further, the surface of the fixing drum 84 may be controlled to a predetermined temperature (for example, 60 ° C.).

  On the other hand, the in-line sensor 90 is a measuring means for measuring a check pattern, a moisture content, a surface temperature, a glossiness, and the like for an image fixed on the recording medium 24, and a CCD line sensor or the like is applied.

  According to the fixing unit 20 configured as described above, the latex particles in the thin image layer formed by the drying unit 18 are heated and pressurized by the fixing roller 88 and melted, and thus fixed to the recording medium 24. Can be made. Further, according to the fixing unit 20, since the fixing drum 84 is structurally separated from other drums, the temperature setting of the fixing unit 20 is freely set separately from the drawing unit 16 and the drying unit 18. be able to.

  In particular, the fixing drum 84 used in the present embodiment is configured as a rotary conveyance body having a predetermined curvature and a surface temperature set to a predetermined temperature, similar to the drying drum 76 described above, and the curvature of the fixing drum 84 is , 0.002 (1 / mm) or more and 0.0033 (1 / mm) or less is preferable. If the curvature of the fixing drum 84 is less than 0.002 (1 / mm), the correction effect of the cockling is insufficient even if the recording medium 24 is curved, whereas if it exceeds 0.0033 (1 / mm), This is because the recording medium 24 bends more than necessary and does not return to its original state, and is output in a curved state at the time of stacking.

  The surface temperature of the fixing drum 84 is preferably set to 50 ° C. or higher. By heating the recording medium 24 held on the outer peripheral surface of the fixing drum 84 from the back surface, drying is promoted, image destruction at the time of fixing can be prevented, and the image strength is increased by the effect of increasing the image temperature. Can do.

  The upper limit of the surface temperature of the fixing drum 84 is not particularly limited, but is preferably set to 75 ° C. or less (more preferably 60 ° C. or less) from the viewpoint of maintainability.

  The fixing roller 88 used in this embodiment preferably has a surface hardness of 71 ° or less. By making the surface of the fixing roller 88, which is a heating and pressing member, softer, a tracking effect can be expected with respect to the unevenness of the recording medium 24 caused by cockling, and uneven fixing can be more effectively prevented.

  In addition, the moisture in the image is volatilized and the high boiling point organic solvent is concentrated in the image in an appropriate amount (specifically, the high boiling point organic solvent remains in the image at 4% or more of the ink droplet amount). ) Is preferable because the surface of the fixing roller (heating and pressing member) 88 is easily deformed at the time of fixing while having a strength that does not cause image destruction. Further, in the case where the image contains a binder component, the followability of the image can be expected on the surface of the fixing roller 88 as in the case where the image is heated in advance, and fixing unevenness can be prevented more effectively.

  Here, “the state where the high-boiling organic solvent remains in the image at 4% or more of the ink droplet ejection amount” means that the image present on the surface of the recording medium with respect to the ink droplet ejection amount at the timing of the fixing process. The state where the ratio of the residual amount of the high boiling point organic solvent is 4% or more.

  The recording drum 24 is held on the outer peripheral surface of the fixing drum 84 configured in this manner so that the recording surface of the recording medium 24 faces outward (that is, in a state where the recording surface of the recording medium 24 is convex). By fixing by heating and pressurizing while rotating and transporting, the cockling can be corrected even in a state where moisture cannot be completely dried and some cockling can occur.

  In addition, the surface of the recording medium 24 is stretched against the force for generating irregularities on the surface (recording surface) of the recording medium 24 due to swelling of the pulp fibers, and the irregularities generated by cockling are relaxed and smoothed. Thus, fixing can be performed by the fixing roller 88, so that occurrence of uneven fixing due to cockling can be prevented.

(Discharge part)
As shown in FIG. 1, a discharge unit 22 is provided following the fixing unit 20. The discharge unit 22 includes a discharge tray 92, and a transfer drum 94, a conveyance belt 96, and a tension roller 98 are provided between the discharge tray 92 and the fixing drum 84 of the fixing unit 20 so as to be in contact therewith. It has been. The recording medium 24 is sent to the conveying 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 26 will be described. Note that the second intermediate conveyance unit 28 and the third intermediate conveyance unit 30 have the same configuration as the first intermediate conveyance unit 26, and a description thereof will be omitted.

  The intermediate conveyance body 32 of the first intermediate conveyance unit 26 is a drum for receiving the recording medium 24 from the preceding drum, rotating and conveying it to the subsequent drum, and is rotatably attached. Further, the intermediate transport body 32 is rotated by a motor (not shown in FIG. 1; indicated by reference numeral 188 in FIG. 5), and is rotated by a motor driver 176 (see FIG. 5) described later. Drive controlled. The intermediate transport body 32 includes a claw-shaped holding unit on the outer peripheral surface thereof, and the leading end of the recording medium 24 can be held by the holding unit. The recording medium 24 is rotated and conveyed by rotating the intermediate conveyance body 32 in a state where the tip is held by the holding means. At this time, the recording medium 24 is rotated and conveyed so that the recording surface faces inward and the non-recording surface faces outward.

  The recording medium 24 transported by the first intermediate transport unit 26 is transferred to the subsequent drum (that is, the drawing drum 70). At this time, the recording medium 24 is delivered by synchronizing the holding means of the intermediate transport unit 26 and the holding means of the drawing unit 16. The delivered recording medium 24 is held by the drawing drum 70 and rotated and conveyed.

[Inkjet head structure]
Next, the structure of each inkjet head will be described. Since the structures of the inkjet heads 72M, 72K, 72C, 72Y corresponding to the respective colors are common, the inkjet head (hereinafter also simply referred to as “head”) is denoted by reference numeral 150 in the following. And

  2A is a plan perspective view showing a structural example of the head 150, FIG. 2B is an enlarged view of a part thereof, and FIG. 2C is a plan view showing another structural example of the head 150. FIG. FIG. FIG. 3 is a cross-sectional view (a cross-sectional view taken along line 3-3 in FIGS. 2A and 2B) showing a three-dimensional configuration of the ink chamber unit.

  In order to increase the dot pitch formed on the recording medium 24, it is necessary to increase the nozzle pitch in the head 150. As shown in FIGS. 2A and 2B, the head 150 of this example is a nozzle plate (not shown in FIG. 2 and provided with reference numeral 151A in FIG. 3) provided with nozzles 151 serving as ink discharge ports. And a plurality of ink chamber units (droplet discharge elements as recording element units) 153 corresponding to each nozzle 151 are arranged in a staggered matrix (two-dimensionally). Thus, the substantial nozzle interval (projection nozzle pitch) projected so as to be aligned along the longitudinal direction of the head (direction perpendicular to the conveyance direction (paper conveyance direction) of the recording medium 24; main scanning direction) is increased. Densification has been achieved.

  The configuration in which one or more nozzle rows are formed in a direction corresponding to the entire width of the recording medium 24 in a direction (main scanning direction) substantially orthogonal to the conveyance direction (sub-scanning direction) of the recording medium 24 is not limited to this example. For example, instead of the configuration of FIG. 2A, as shown in FIG. 2C, short head blocks 150 ′ in which a plurality of nozzles 151 are two-dimensionally arranged are arranged in a staggered manner and connected. The line head having a nozzle row having a length corresponding to the entire width of the recording medium 24 as a whole may be configured by increasing the length of the head. Although not shown, a line head may be configured by arranging short heads in a line.

  Further, the short head block 150 ′ may include only one nozzle group, and a line head may be configured by connecting the head blocks 150 ′ by the number of necessary nozzle groups.

  The pressure chamber 152 provided corresponding to each nozzle 151 has a substantially square planar shape, the nozzle 151 is provided at one of the diagonal corners, and the supply port 154 is provided at the other. ing. The shape of the pressure chamber 152 is not limited to this example, and the planar shape may have various forms such as a quadrangle (rhombus, rectangle, etc.), a pentagon, a hexagon, other polygons, a circle, and an ellipse.

  Each pressure chamber 152 communicates with a common flow path 155 through a supply port 154. The common flow path 155 communicates with an ink tank (not shown) as an ink supply source, and ink supplied from the ink tank is supplied to each pressure chamber 152 via the common flow path 155.

  A piezoelectric element 158 having an individual electrode 157 is joined to a diaphragm 156 that constitutes a part of the pressure chamber 152 (the top surface in FIG. 3) and also serves as a common electrode. By applying a driving voltage to the individual electrode 157, the piezoelectric element 158 is deformed to change the volume of the pressure chamber 152, and ink is ejected from the nozzle 151 due to the pressure change accompanying this. When the piezoelectric element 158 returns to its original state after ink ejection, new ink is refilled into the pressure chamber 152 from the common flow path 155 through the supply port 154.

  In this example, the piezoelectric element 158 is applied as a means for generating ink ejection force to be ejected from the nozzles 151 provided in the head 150. However, a heater is provided in the pressure chamber 152 and the pressure of film boiling caused by heating of the heater is used. It is also possible to apply a thermal method that ejects ink.

  As shown in FIG. 2B, the ink chamber unit 153 having such a structure has a row angle along the main scanning direction and an oblique angle θ (0 ° <θ <90 °) that is not orthogonal to the main scanning direction. The high-density nozzle head of this example is realized by arranging a large number in a lattice pattern with a constant arrangement pattern along the column direction.

  That is, with a structure in which a plurality of ink chamber units 153 are arranged at a constant pitch d along a direction that forms an angle θ with respect to the main scanning direction, the pitch P of the nozzles projected in the main scanning direction is d ×. cos θ, and in the main scanning direction, each nozzle 151 can be handled equivalently as a linear arrangement with a constant pitch P. With such a configuration, it is possible to realize a high-density nozzle configuration in which 2400 nozzle rows are projected per inch (2400 nozzles / inch) so as to be aligned in the main scanning direction.

  In the implementation of the present invention, the nozzle arrangement structure is not limited to the illustrated example, and various nozzle arrangement structures such as an arrangement structure having one nozzle row in the sub-scanning direction can be applied. The nozzle arrangement applied to this example is a nozzle arrangement in which the dot density in the main scanning direction is 450 dpi or more when dots are formed using all nozzles.

  In the head 150 applied to this example, a conductive pattern 160 is formed on a nozzle surface 150A of a nozzle plate (shown with reference numeral 151A in FIG. 3) on which nozzles 151 are provided. The conductive pattern 160 is formed along the main scanning direction and the column direction pattern 160A formed along the column direction that forms an angle θ (0 ° <θ <90 °) with respect to the sub-scanning direction. A row direction pattern 160B is provided which is electrically connected to each of the plurality of column direction patterns 160A arranged along the direction. In addition, one end (the left end in FIG. 2A) of the row direction pattern 160B is connected to a power supply device (not shown in FIGS. 2A to 2C) via a wiring not shown in FIG. Reference numeral 199 is attached to the figure).

  The row direction pattern 160A is formed on the downstream side of each nozzle group in the paper conveyance direction, and has the same length as the length of each nozzle group in the row direction or a length exceeding the length of each nozzle group in the row direction. ing.

  When the conductive pattern 160 is charged in response to the start of the operation of the head 150, an electrostatic force (see FIG. 5) is formed in a direction connecting each nozzle 151 and the row direction pattern 160A with the shortest distance with respect to ink mist generated during ink ejection. 6 (b) is attached with a symbol C, and the movement of the ink mist in the paper transport direction is suppressed.

  The shortest distance between each nozzle 151 (each nozzle group) and the column direction pattern 160A is preferably about several μm to several tens of mm, and more preferably about 5 μm to 30 μm. If the preferable range of the shortest distance between each nozzle 151 and the conductive pattern is maintained, the column direction pattern 160A may be formed obliquely with respect to the nozzle arrangement direction of the nozzle group.

  2A to 2C illustrate the linear conductive pattern 160 having a uniform width, the shape of the conductive pattern is not limited to a linear shape. For example, the width may be partially different, and various forms such as a combination of a curve and a straight line are applicable.

  The row direction pattern 160B is preferably formed on the most downstream side in the paper conveyance direction. That is, even if the ink mist moves beyond the row direction pattern 160B to the downstream side in the paper conveyance direction of the row direction pattern 160B by forming the row direction pattern on the downstream side in the paper conveyance direction for all the nozzles 151, The nozzle 151 does not exist at the movement destination of the ink mist, and the ink mist does not adhere to the vicinity of the nozzle 151. It is preferable that the distance between the row direction pattern 160B and the nozzle on the most downstream side in the paper transport direction exceeds 1 mm.

  Further, the row direction pattern may be formed on the surface opposite to the nozzle surface 150A. In such a mode, a mode in which the row direction pattern 160B and the column direction pattern 160A are electrically connected using a wiring pattern penetrating the nozzle plate 151A is preferable.

  For the conductive pattern 160, a metal material having high electrical conductivity such as gold or platinum is preferably used. The charge amount of the conductive pattern 160 is preferably about 500 V to 5000 V, more preferably about 1000 V with respect to the ground potential (reference potential). The charge amount of the conductive pattern 160 may be appropriately set within the above preferable range depending on the physical properties, volume, etc. of the ink mist.

  The conductive pattern 160 illustrated in FIGS. 2A to 2C is covered with a protective film (not illustrated) having electrical insulation performance. The protective film may be patterned corresponding to the conductive pattern 160, or may be formed over the entire surface of the nozzle surface 150A while avoiding the opening of the nozzle 151.

  The nozzle plate 151A is preferably made of silicon or a metal material that can be processed with high accuracy and is easy to process. When a metal material is applied to the nozzle plate 151A, an insulating film may be formed between the nozzle plate 151A and the conductive pattern 160.

[Configuration of ink supply system and maintenance processing section]
FIG. 4 is a block diagram illustrating a schematic configuration of an ink supply system and a maintenance processing unit in the inkjet recording apparatus 10. The ink supply tank 161 is a base tank that supplies ink to the head 150. The ink supply tank 161 includes a method of replenishing ink from a replenishment port (not shown) when the remaining amount of ink is low, and a cartridge method of replacing the entire tank. A cartridge system is suitable for changing the ink type according to the intended use. In this case, it is preferable that the ink type information is identified by a barcode or the like, and ejection control is performed according to the ink type.

  A filter 162 is provided between the ink supply tank 161 and the head 150 in order to remove foreign matters and bubbles. The filter mesh size is preferably equal to or smaller than the nozzle diameter (generally about 20 μm).

  Although not shown in FIG. 4, a configuration in which a sub tank is provided in the vicinity of the head 150 or integrally with the head 150 is also preferable. The sub-tank has a function of improving a damper effect and refill that prevents fluctuations in the internal pressure of the head.

  Further, the inkjet recording apparatus 10 is provided with a cap 164 as a means for preventing the nozzle 151 from drying or preventing an increase in ink viscosity near the nozzle, and a cleaning blade 166 as a cleaning means for the nozzle surface 150A of the head 150. Yes.

  A maintenance unit (maintenance means) including the cap 164 and the cleaning blade 166 can be moved relative to the head 150 by a moving mechanism (not shown), and is moved from a predetermined retracted position to a maintenance position below the head 150 as necessary. Moved.

  The cap 164 is displaced up and down relatively with respect to the head 150 by an elevator mechanism (not shown). The cap 164 is raised to a predetermined raised position when the power is turned off or during printing standby, and is brought into close contact with the head 150, thereby covering the nozzle surface 150A with the cap 164.

  During printing or standby, the frequency of use of a specific nozzle 151 (see FIG. 3) decreases, and if ink is not ejected for a certain period of time, the ink solvent near the nozzle evaporates and the ink viscosity increases. End up. In such a state, ink cannot be ejected from the nozzle 151 even if the piezoelectric element 158 (see FIG. 3) operates.

  Before this state is reached, the piezoelectric element 158 is operated within the range of viscosity that can be discharged by the operation of the piezoelectric element 158, and a preliminary operation is performed toward the cap 164 in order to discharge the deteriorated ink near the nozzle whose viscosity has increased. Discharging is performed. “Preliminary discharge” includes processes called purge, idle discharge, spit discharge, dummy discharge, and the like.

  Further, when air bubbles are mixed in the ink in the head 150 or the pressure chamber 152 (see FIG. 3), the ink cannot be ejected from the nozzle even if the piezoelectric element 158 operates. In such a case, the cap 164 is applied to the head 150, the ink mixed with the bubbles in the pressure chamber 152 is removed by suction with the suction pump 167, and the suctioned and removed ink is sent to the recovery tank 168.

  In this suction operation, the deteriorated ink with increased viscosity (solidified) is sucked out when the initial ink is loaded into the head 150 or when the ink is used after being stopped for a long time. Since the suction operation is performed on the entire ink in the pressure chamber 152, the amount of ink consumption increases. Therefore, it is preferable to perform preliminary ejection when the increase in ink viscosity is small.

  The cleaning blade 166 is made of rubber at a portion that contacts the nozzle surface 150A of the head 150, and can slide on the nozzle surface 150A of the head 150 by a blade moving mechanism (not shown). When ink droplets or foreign matters adhere to the nozzle surface 150A, the nozzle surface 150A is wiped by sliding the cleaning blade 166 on the nozzle surface 150A, and the nozzle surface 150A is cleaned.

[Explanation of control system]
FIG. 5 is a principal block diagram showing the system configuration of the inkjet recording apparatus 10. The inkjet recording apparatus 10 includes a communication interface 170, a system controller 172, a memory 174, a motor driver 176, a heater driver 178, a print control unit 180, an image buffer memory 182, a head driver 184, and the like.

  The communication interface 170 is an interface unit that receives image data sent from the host computer 186. As the communication interface 170, a serial interface such as USB (Universal Serial Bus), IEEE 1394, Ethernet (registered trademark), a wireless network, or a parallel interface such as Centronics can be applied. In this part, a buffer memory (not shown) for speeding up communication may be mounted. Image data sent from the host computer 186 is taken into the inkjet recording apparatus 10 via the communication interface 170 and temporarily stored in the memory 174.

  The memory 174 is a storage unit that temporarily stores an image input via the communication interface 170, and data is read and written through the system controller 172. The memory 174 is not limited to a memory made of a semiconductor element, and a magnetic medium such as a hard disk may be used.

  The system controller 172 includes a central processing unit (CPU) and its peripheral circuits, and functions as a control device that controls the entire inkjet recording apparatus 10 according to a predetermined program, and also functions as an arithmetic device that performs various calculations. . That is, the system controller 172 controls each part such as the communication interface 170, the memory 174, the motor driver 176, the heater driver 178, the treatment liquid application control unit 196, the drying control unit 197, the fixing control unit 198, etc. In addition to performing communication control between them, read / write control of the memory 174, etc., control signals for controlling the above-described units are generated.

  The memory 174 stores programs executed by the CPU of the system controller 172 and various data necessary for control. Note that the memory 174 may be a non-rewritable storage means, or may be a rewritable storage means such as an EEPROM. The memory 174 is used as a temporary storage area for image data, and is also used as a program development area and a calculation work area for the CPU.

  Various control programs are stored in the program storage unit 190, and the control programs are read and executed in accordance with instructions from the system controller 172. The program storage unit 190 may use a semiconductor memory such as a ROM or an EEPROM, or may use a magnetic disk or the like. An external interface may be provided and a memory card or PC card may be used. Of course, you may provide several recording media among these recording media. The program storage unit 190 may also be used as a recording unit (not shown) for operating parameters.

  The motor driver 176 is a driver that drives the motor 188 in accordance with an instruction from the system controller 172. In FIG. 5, the motors arranged in the respective units in the apparatus are represented by reference numeral 188. For example, the motor 188 shown in FIG. 5 includes a motor that drives the rotation of the paper feed drum 52, the processing liquid drum 54, the drawing drum 70, the drying drum 76, the fixing drum 84, the transfer drum 94, and the like shown in FIG. A motor for driving the rotation of the intermediate conveyance body 32 of the third intermediate conveyance units 26, 28, and 30 is included.

  The heater driver 178 is a driver that drives the heater 189 in accordance with an instruction from the system controller 172. In FIG. 5, the heaters arranged in the respective units in the apparatus are represented by reference numeral 189. For example, the heater 189 shown in FIG. 5 includes the halogen heater 80 of the solvent drying device 78 provided in the drying unit 18 shown in FIG. 1, the halogen heater of the drying unit 38 provided inside the intermediate transport body 32, and the like. Yes. Further, a heater for heating the surfaces of the drying drum 76 and the fixing drum 84 shown in FIG. 1 is also included.

  Further, the inkjet recording apparatus 10 includes a processing liquid application control unit 196, a drying control unit 197, and a fixing control unit 198, and in accordance with instructions from the system controller 172, the processing liquid coating device 56 and the solvent drying unit, respectively. The operation of each unit of the device 78 and the fixing roller 88 is controlled.

  The print control unit 180 has a signal processing function for performing various processes and corrections for generating a print control signal from the image data in the memory 174 in accordance with the control of the system controller 172. The generated print data This is a control unit that supplies (dot data) to the head driver 184. Necessary signal processing is performed in the print control unit 180, and the ejection droplet amount (droplet ejection amount) and ejection timing of the head 150 are controlled via the head driver 184 based on the image data. Thereby, a desired dot size and dot arrangement are realized.

  The print control unit 180 is provided with an image buffer memory 182, and image data, parameters, and other data are temporarily stored in the image buffer memory 182 when image data is processed in the print control unit 180. Also possible is an aspect in which the print controller 180 and the system controller 172 are integrated and configured with one processor.

  The head driver 184 generates a drive signal to be applied to the piezoelectric element 158 (see FIG. 3) of the head 150 based on the image data given from the print control unit 180, and applies the drive signal to the piezoelectric element 158. A drive circuit for driving the piezoelectric element 158 is included. The head driver 184 shown in FIG. 5 may include a feedback control system for keeping the driving conditions of the head 150 constant.

  The sensor 185 is a variety of sensors provided in each part in the apparatus, and includes a temperature sensor, a position detection sensor, a pressure sensor, a linear encoder provided in the transport system, etc. in addition to the inline sensor 90 shown in FIG. Yes. The output signal of the sensor 185 is sent to the system controller 172, and the system controller 172 sends a control signal to each part of the apparatus based on the output signal, and each part of the apparatus is controlled.

  The maintenance control unit 191 controls the operation of the maintenance processing unit including the cap 164 and the cleaning blade 166 illustrated in FIG. That is, the maintenance control unit 191 moves the head 150 to a predetermined maintenance position in accordance with a command from the system controller 172, and operates the cap 164, the cleaning blade 166, the suction pump 167, and the like during the maintenance process at the maintenance position. Control.

  The power supply unit 199 functions as a charging unit for the conductive pattern 160 that applies a voltage between the conductive pattern 160 and the ground potential (reference potential) in accordance with a command from the system controller 172. During operation of the head 150, the power supply unit 199 is controlled so that the conductive pattern 160 is always charged. The power supply unit 199 preferably has a function of changing the voltage applied to the conductive pattern 160.

[Explanation of ink mist collection method]
Next, the function of collecting the ink mist floating near the nozzle surface 150A of the head 150 will be described in detail with reference to FIG.

  FIG. 6 is an explanatory diagram showing a simplified structure of the nozzle surface 150A of the head 150 at the top. A portion surrounded by a solid line at the bottom of the figure is an enlarged view of a part of the nozzle surface 150A. FIG. 6 shows a nozzle group in which a plurality of nozzles 151 are arranged along the row direction by broken lines, and shows a row direction pattern 160A formed along a direction substantially parallel to the nozzle group and the main scanning direction (FIG. The conductive pattern 160 including the row direction pattern 160 </ b> B formed along the line) is indicated by a solid line. In addition, a power supply unit 199 that applies a predetermined voltage to the conductive pattern 160 via a predetermined wiring is shown with a symbol V.

  In the enlarged view of FIG. 6, an arrow line with a symbol A represents an air flow generated in a direction substantially parallel to the paper conveyance direction, and an arrow line with a symbol B represents an air flow due to discharge generated in the nozzle group arrangement direction. ing. Moreover, the arrow line which attached | subjected and showed the code | symbol C represents the electrostatic force generated with the electroconductive pattern 160 (column direction pattern 160A).

  Due to the action of the electrostatic force C, the ink mist (not shown) floating in the vicinity of the lowermost nozzle 151 in FIG. 6 moves toward the column direction pattern 160A shown by the thick arrow curve, and the column direction pattern It adheres to 160A. Therefore, it is possible to avoid the ink mist from moving to the vicinity of a neighboring nozzle (for example, the central nozzle 151 in the lower part of FIG. 6) and to prevent the ink mist from adhering to an adjacent nozzle in the paper transport direction.

  In the matrix arrangement of the nozzles 151 shown in this example, the arrangement interval in the paper feeding direction between the adjacent nozzle groups is separated, so that the ink mist is prevented from adhering to the other nozzles 151 beyond the column direction pattern 160A. Is done.

  Since the nozzle groups adjacent to each other in the direction orthogonal to the paper transport direction are sufficiently separated from each other, even if the row direction pattern 160A is formed for each nozzle group, the increase in the size of the head 150 can be avoided.

  For example, when the projected nozzle pitch projected so as to be aligned in the main scanning direction is arranged at 450 npi, it is adjacent to the arrangement direction of the nozzles forming an angle θ (0 ° <θ <90 °) with respect to the paper transport direction. The pitch between nozzles is 821 μm, the pitch between adjacent nozzles in the direction orthogonal to the paper transport direction is 1694 μm, and a column direction pattern 160A having a width of about 10 to 1690 μm can be formed.

  If silicon is used for the nozzle plate 151A (see FIG. 3), the nozzle plate 151A tends to be negatively charged due to the friction between the ink and the nozzle 151 at the time of discharge, so that the ink after discharge is charged positively. The ink mist separated from the (main droplet) is also positively charged. In order to generate an electrostatic force that moves the ink mist charged to the positive polarity toward the conductive pattern 160, the conductive pattern 160 is preferably charged to the negative polarity.

  That is, the voltage applied from the power supply unit 199 to the conductive pattern 160 is controlled so that the charging polarity of the conductive pattern 160 is opposite to the charging polarity of the ink mist.

  In addition, a mode in which the ink in the nozzle 151 is charged to a polarity opposite to the charging polarity of the conductive pattern 160 is also preferable. In such an embodiment, an embodiment in which the absolute value of the electric potential of the conductive pattern 160 exceeds the absolute value of the electric potential of the ink is preferable.

  A known technique (for example, a means for applying a predetermined voltage to the ink in the head 150) can be applied to the means for charging the ink in the head 150.

  According to the inkjet recording apparatus 10 configured as described above, a row direction that forms an angle θ (0 ° <θ <90 °) with the paper conveyance direction on the nozzle surface 150A of the head 150 in which a plurality of nozzles 151 are arranged in a matrix. A conductive pattern 160 (column direction pattern) is formed along the direction parallel to the nozzle group on the downstream side in the paper conveyance direction of the nozzle groups arranged in the nozzle group, and the conductive pattern 160 is charged when ink is ejected. An electrostatic force acting on the generated ink mist toward the row direction pattern 160A acts to attach the ink mist to the row direction pattern 160A, and the ink mist toward the nozzles adjacent to the paper transport direction Movement is prevented.

  Further, since the distance between the adjacent nozzle groups is large, the nozzle 151 of the nozzle group adjacent to the downstream side in the paper transport direction beyond the row direction pattern 160A formed on the downstream side in the paper transport direction of each nozzle group. Ink mist does not adhere to the vicinity of.

[Modification]
Next, a modification according to the above-described embodiment will be described.

  As shown in FIG. 3 with reference numeral 160 ', the conductive pattern may be formed on the surface opposite to the nozzle surface 150A of the nozzle plate 151A. According to this aspect, the insulating protective film formed on the nozzle surface 150A can be omitted.

  Further, the cleaning blade 166 shown in FIG. 4 can be used as a means for charging the conductive pattern 160 (see FIGS. 2A to 2C) formed on the nozzle surface 150A. That is, since metal has a property of being easily charged to negative polarity by friction, when the cleaning blade 166 is slid on the nozzle surface 150A, the conductive pattern 160 is charged to negative polarity by frictional charging.

  Rubber may be applied to the portion of the cleaning blade 166 that contacts the nozzle surface 150A. Also. When the cleaning blade 166 is used as a means for charging the conductive pattern 160, the conductive pattern can be charged during the maintenance of the nozzle surface 150 </ b> A by the cleaning blade 166.

  In this example, an ink jet recording apparatus that records color images by discharging color ink onto a recording medium is illustrated as an example of an image forming apparatus. However, a resin pattern or the like is used for a substrate such as mask pattern formation or wiring drawing on a printed wiring board. The present invention is also applicable to an image forming apparatus that forms a predetermined pattern shape.

  The image forming apparatus according to the present invention has been described in detail above. However, the present invention is not limited to the above examples, and various improvements and modifications may be made without departing from the gist of the present invention. Of course.

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

  (Invention 1): An inkjet head comprising a nozzle plate in which a plurality of nozzles for discharging liquid onto a recording medium are two-dimensionally arranged and a conductive pattern is formed corresponding to the nozzle, and the inkjet head Conveying means for relatively conveying the recording medium and charging means for charging the conductive pattern, and the nozzle plate is predetermined in a row direction substantially perpendicular to the conveying direction of the conveying means. The plurality of nozzles are arranged along a column direction forming an angle θ (0 ° <θ <90 °), and a nozzle group in which a plurality of nozzles are arranged along the column direction is along the row direction. At least one structure, and the conductive pattern is located in a lower direction of conveyance when the recording medium is conveyed to the inkjet head of the nozzle group. Image forming apparatus characterized by the side, is formed along the column direction substantially parallel direction.

  According to the present invention, a nozzle group in which a plurality of nozzles are arranged in a column direction forming a predetermined angle θ (0 ° <θ <90 °) with respect to a row direction orthogonal to the relative conveyance direction of the inkjet head and the recording medium. Since the conductive pattern is formed along the row direction on the downstream side in the conveyance direction when the recording medium is conveyed to the inkjet head, the conductive pattern is charged and the liquid is discharged from the nozzle. By applying an electrostatic force in the direction of the conductive pattern to the mist-like droplets generated after the mist-like droplets, the mist-like droplets are prevented from moving near other nozzles downstream in the transport direction. Is done.

  An ink jet head is a liquid discharge head that discharges liquid from nozzles provided on a nozzle plate using an ink jet method. As an example of the configuration, a liquid chamber that communicates with the nozzle and pressurization that pressurizes liquid in the liquid chamber Means. The liquid ejected from the inkjet head includes various liquids such as a color ink for forming (recording) an image on a recording medium and a resin liquid for forming a predetermined pattern on the substrate.

  In addition, an aspect in which a plurality of modules are connected to form one ink jet head is also possible. The concept of “inkjet head” in such an embodiment includes one module included in the inkjet head.

  The mist-like droplet is a concept including a minute droplet having a smaller volume than the main droplet separated from the main droplet discharged from the nozzle. Mist droplets include what are called “satellite”, “contamination” and the like.

  An inkjet head in which nozzles are arranged at a high density so that the dot density in the direction orthogonal to the recording medium conveyance direction is 450 dpi or more has a smaller pitch between adjacent nozzles, and a mist shape in the vicinity of adjacent nozzles. Therefore, it is possible to effectively prevent the mist-like droplets from adhering to the vicinity of the nozzle.

  (Invention 2): In the image forming apparatus according to Invention 1, the nozzle plate has a structure in which a plurality of the nozzle groups are arranged along the row direction, and the conductive for each of the plurality of nozzle groups. A characteristic pattern is formed.

  According to this aspect, the interval between adjacent nozzle groups can be separated, and mist-like droplets are prevented from adhering to other nozzles beyond the conductive pattern.

  A wiring pattern that is electrically connected to each of the conductive patterns formed for each nozzle group may be formed. As an example of forming the wiring pattern, there is an aspect in which the wiring pattern is formed along the direction orthogonal to the transport direction on the most downstream side in the transport direction when transporting the recording medium to the ink jet head.

  (Invention 3): In the image forming apparatus according to Invention 1 or 2, the conductive pattern is formed on a side surface of a liquid ejection surface from which the liquid of the nozzle plate is ejected, and is covered with an insulating film having an insulation performance. It is characterized by being.

  According to this aspect, the electrostatic force by the conductive pattern can be effectively applied to the mist-like droplets floating in the vicinity of the liquid ejection surface.

  (Invention 4): In the image forming apparatus according to Invention 1 or 2, the conductive pattern is formed on a side surface opposite to a liquid ejection surface from which the liquid of the nozzle plate is ejected.

  According to this aspect, it is not necessary to form an insulating coating on the liquid discharge surface, and the nozzle plate manufacturing process can be simplified.

  (Invention 5): In the image forming apparatus according to any one of Inventions 1 to 4, the material of the nozzle plate includes silicon, and the charging unit charges the conductive pattern negatively. .

  In such an aspect, in the aspect in which the nozzle plate is formed of silicon, the nozzle plate is easily charged to a negative polarity due to friction between the nozzle and the liquid when passing through the nozzle, whereas the liquid is easily charged to a positive polarity. Therefore, by charging the conductive pattern to the negative polarity, the mist-shaped droplet separated from the positively charged liquid (main droplet) is also charged to the positive polarity. On the other hand, electrostatic force can be applied.

  (Invention 6): In the image forming apparatus according to any one of Inventions 1 to 5, the charging unit includes a blade including rubber in a portion sliding on the liquid discharge surface, and the blade during maintenance of the inkjet head. And control means for controlling the operation of the blade so as to charge the conductive pattern by sliding on the liquid discharge surface.

  According to this aspect, it is possible to charge the conductive pattern using an existing configuration having other uses without providing a power supply device that applies a predetermined voltage to the conductive pattern.

  (Invention 7): The image forming apparatus according to any one of Inventions 1 to 6, further comprising a liquid charging unit that charges the liquid to a polarity opposite to that of the conductive pattern.

  In such an embodiment, the liquid charging means may be configured to charge the ink in the inkjet head.

  (Invention 8): In the image forming apparatus according to Invention 7, the absolute value of the potential of the conductive pattern exceeds the absolute value of the potential of the liquid.

  According to this aspect, since silicon is easily charged to a negative polarity, the liquid can be easily charged to a positive charge, and the electrostatic adsorption effect can be improved.

  (Invention 9): In the image forming apparatus according to any one of Inventions 1 to 8, the shortest distance between the nozzle group and the conductive pattern is 5 μm or more and 30 μm or less.

  According to such an aspect, the electrostatic force due to the conductive pattern can be reliably applied to the ink mist generated after ink ejection.

  (Invention 9): In the image forming apparatus according to any one of Inventions 1 to 9, the nozzle plate is substantially orthogonal to the recording medium conveyance direction when dots are formed using all of the plurality of nozzles. It has a structure in which the plurality of nozzles are arranged so as to have a dot density of 450 dots or more per inch in the direction.

  According to this aspect, the present invention is particularly effective in image formation in which the dot density in the direction orthogonal to the recording medium conveyance direction is 450 dpi or more.

  (Invention 11): When the liquid is ejected from the plurality of nozzles to the recording medium while relatively transporting the inkjet head in which the plurality of nozzles are two-dimensionally arranged and the recording medium, On the downstream side in the transport direction when the recording medium is transported to the ink jet head of the nozzle group in which a plurality of nozzles are arranged in a row direction that forms a predetermined angle θ (0 ° <θ <90 °). The conductive pattern formed along a direction substantially parallel to the nozzle group is charged, and after the liquid is discharged from each nozzle, the mist-like liquid droplet separated from the liquid is moved toward the conductive pattern. The mist collection method characterized by this.

  In the present invention, an embodiment in which the conductive pattern is always charged during operation of the ink jet head is preferable.

  DESCRIPTION OF SYMBOLS 10 ... Inkjet recording device, 72M, 72K, 72C, 72Y, 150 ... Inkjet head, 150A ... Nozzle surface, 151A ... Nozzle plate, 160 ... Conductive pattern, 166 ... Cleaning blade, 199 ... Power supply unit

Claims (11)

An inkjet head comprising a nozzle plate in which a plurality of nozzles for discharging liquid onto a recording medium are two-dimensionally arranged and a conductive pattern is formed corresponding to the nozzles;
Conveying means for relatively conveying the inkjet head and the recording medium;
Charging means for charging the conductive pattern;
With
In the nozzle plate, the plurality of nozzles are arranged along a row direction that forms a predetermined angle θ (0 ° <θ <90 °) with respect to a row direction substantially orthogonal to the transfer direction of the transfer means, Having a structure in which at least one nozzle group in which a plurality of nozzles are arranged along the column direction is arranged along the row direction;
The conductive pattern is formed along a direction substantially parallel to the row direction on the downstream side in the transport direction when the recording medium is transported to the inkjet head of the nozzle group. apparatus. The image forming apparatus according to claim 1,
The nozzle plate has a structure in which a plurality of nozzle groups are arranged along the row direction, and the conductive pattern is formed for each of the plurality of nozzle groups. The image forming apparatus according to claim 1, wherein
2. The image forming apparatus according to claim 1, wherein the conductive pattern is formed on a liquid ejection surface from which the liquid of the nozzle plate is ejected and is covered with an insulating film having an insulating performance. The image forming apparatus according to claim 1, wherein
The image forming apparatus according to claim 1, wherein the conductive pattern is formed on a side surface opposite to a liquid ejection surface from which the liquid of the nozzle plate is ejected. The image forming apparatus according to claim 1,
The material of the nozzle plate includes silicon,
The image forming apparatus, wherein the charging unit charges the conductive pattern to a negative polarity. The image forming apparatus according to claim 1,
The charging means includes a blade including rubber in a portion sliding on the liquid discharge surface;
Control means for controlling the operation of the blade so as to charge the conductive pattern by sliding the blade on the liquid ejection surface during maintenance of the inkjet head;
An image forming apparatus comprising: The image forming apparatus according to claim 1,
An image forming apparatus comprising: a liquid charging unit that charges the liquid with a polarity opposite to that of the conductive pattern. The image forming apparatus according to claim 7.
The image forming apparatus, wherein an absolute value of the electric potential of the conductive pattern exceeds an absolute value of the electric potential of the liquid. The image forming apparatus according to claim 1,
The shortest distance between the nozzle group and the conductive pattern is 5 μm or more and 30 μm or less. The image forming apparatus according to claim 1,
The nozzle plate includes a plurality of nozzles having a dot density of 450 dots or more per inch in a direction substantially orthogonal to a recording medium conveyance direction when dots are formed using all of the plurality of nozzles. An image forming apparatus characterized by having a structure in which is arranged.   A predetermined angle with respect to the row direction when liquid is ejected from the plurality of nozzles to the recording medium while relatively transporting the inkjet head in which the plurality of nozzles are two-dimensionally arranged and the recording medium. Substantially parallel to the nozzle group on the downstream side in the transport direction when the recording medium is transported to the ink jet head of the nozzle group in which a plurality of nozzles are arranged in the row direction forming θ (0 ° <θ <90 °). A mist is formed by charging a conductive pattern formed along a direction and moving a mist-like droplet separated from the liquid toward the conductive pattern after the liquid is discharged from each nozzle. Collection method.

Images