JP6065038B2 - Droplet discharge device - Google Patents

Description

  The present invention relates to a droplet discharge device.

  2. Description of the Related Art Conventionally, an ink jet recording apparatus (droplet discharge apparatus) is known as a recording apparatus capable of printing on various recording media represented by plain paper. An ink jet recording apparatus directly applies color ink, which is a color material, and clear ink for undercoat and overcoat, from an ejection port (nozzle) provided on the surface of the recording head (ejection head) facing the recording medium. It is an apparatus that forms an image or the like on a recording medium by discharging to the recording medium, landing on the recording medium, and penetrating or fixing.

  In some cases, such an ink jet recording apparatus is used to record an image or the like on a recording medium made of a material such as resin or metal that does not have ink absorbability. In that case, in order to fix the ink to such a recording medium, for example, a photocurable ink that is cured by ultraviolet irradiation is used. The ink jet recording apparatus using the photocurable ink is provided with an ultraviolet irradiation device for curing the ink. When an image is recorded on the recording medium, the ink is cured immediately after the ink is landed on the recording medium. The ink is cured and fixed by irradiating ultraviolet rays from an ultraviolet irradiation device under possible conditions.

  In a recording apparatus that records on a recording medium with such a photocurable ink, a reflective layer is applied to a platen or the like that supports the recording medium in order to more efficiently use the energy of irradiated ultraviolet rays and improve the printing speed. Have been proposed (see, for example, Patent Document 1).

JP 2008-238454 A

Incidentally, the ink jet recording apparatus has the following problems to be improved.
When recording on a recording medium by the ink jet recording apparatus, the recording medium is held by holding a medium such as a stage for holding the recording medium, but the medium holding unit is scanned while holding the recording medium during recording. The medium holding unit needs to be fixed on the holding surface. Therefore, normally, the medium holding unit is sucked and held on the holding surface by suction grooves and suction holes connected to the negative pressure source.

  However, particularly when the recording medium is a translucent resin or the like, when the ultraviolet rays are irradiated after the ink is ejected onto the recording medium, the irradiated ultraviolet rays pass through the recording medium, and the holding surface of the medium holding unit Reflecting the light and transmitting through the recording medium again affects the curing of the ink on the recording medium. In other words, the ink that has landed on the recording medium begins to cure upon irradiation with ultraviolet rays, but does not cure instantaneously. Accordingly, the ink is further cured by receiving reflected ultraviolet rays.

  However, because there are suction grooves and suction holes in the media holder, and the opening is located on the holding surface, the ultraviolet rays that have passed through the recording medium and entered into the openings of the suction grooves and suction holes are absorbed. Unlike reflection at a portion where there is no opening of the groove or suction hole, for example, scattering or absorption occurs. As a result, there is a difference in reflectance between the portion having the suction groove and the suction hole and the portion having no suction hole, which affects the image quality of the recorded image to be formed. That is, the suction groove and the opening shape of the suction hole are reflected in the recorded image, which may impair the image quality of the recorded image to be formed.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a droplet discharge device that prevents the image quality of a recorded image formed due to suction holes from being impaired. .

A droplet discharge device of the present invention includes a medium holding unit that holds a recording medium, a discharge head that discharges a functional liquid containing an ultraviolet curable component toward the recording medium held by the medium holding unit, An irradiation device that irradiates ultraviolet rays toward the recording medium held by the medium holding unit,
The medium holding portion is provided with a plurality of suction holes for sucking the recording medium on a surface on the side holding the recording medium, and the suction hole has a hole diameter of 0.6 mm or less. Yes.

  According to this droplet discharge device, since the hole diameter of the suction hole is set to 0.6 mm or less, it is possible to suppress the suction hole from affecting the recording image of the recording medium, as is apparent from experimental data described later. It is possible to prevent the recorded image obtained from being deteriorated.

In the droplet discharge device, the medium holding unit includes a table having an adsorption groove connected to a negative pressure source, and a holding plate provided on the table. It is preferable that the suction hole is formed in communication with the suction groove.
If it does in this way, processing of an adsorption hole will become easy by forming an adsorption hole only in a holding plate. In addition, when a problem occurs in the holding plate such as ink or ink mist adhering to the suction hole, it is possible to replace only the holding plate, thereby reducing maintenance costs.

In the droplet discharge device, it is preferable that the suction holes are arranged in a plurality of rows vertically and horizontally on the holding plate.
In this way, the suction holding force with respect to the recording medium is stabilized, so that the recording medium can be stably held on the holding plate.

In the droplet discharge device, it is preferable that a translucent recording medium is used as the recording medium.
Since the translucent recording medium transmits ultraviolet light and reflects it by the holding surface of the medium holding portion, it is easily affected by the suction holes of the holding surface, but as described above, the hole diameter of the suction holes is 0.6 mm or less. Therefore, it is possible to prevent the quality of the recorded image from being deteriorated due to the suction holes.

(A) is a top view of the droplet discharge apparatus which concerns on this invention, (b) is a side view similarly. (A) is a sectional side view of the suction table, (b) is a plan view of the table, and (c) is a plan view of the holding plate. (A)-(c) is a figure for demonstrating schematic structure of an ejection head. It is a bottom view which shows schematic structure of a head unit.

  Hereinafter, embodiments of a droplet discharge device according to the present invention will be described with reference to the drawings. In each drawing used for the following description, the scale of each member is appropriately changed to make each member a recognizable size.

  1A and 1B are schematic views showing a schematic configuration of an embodiment of a droplet discharge device according to the present invention, in which FIG. 1A is a plan view of the droplet discharge device, and FIG. It is a side view of a droplet discharge device. 1A and 1B show a case where the liquid droplet ejection apparatus of the present invention is applied to a printing apparatus that performs printing on a continuous long recording medium. In FIGS. 1A and 1B, reference numeral 1 denotes a droplet discharge device. The droplet discharge device 1 includes a discharge head 20 that discharges ultraviolet curable ink as a functional liquid, and a discharge head 20. Irradiation device (not shown) for irradiating the discharged ultraviolet curable ink with ultraviolet rays, a head mechanism unit 2 having an ejection head 20, a supply / discharge mechanism unit 3, an ink supply unit (not shown), and maintenance Part 5.

  The discharge head 20 is an ink jet type discharge head, and becomes a recording location of a continuous long band-shaped recording medium 10 using ink containing an ultraviolet curable component, that is, ultraviolet curable ink as droplets. It is discharged toward the surface. Here, as the recording medium 10, in this embodiment, a translucent medium capable of recording with ultraviolet curable ink is used. Specifically, polyethylene terephthalate (PET), polyethylene (PE), polycarbonate (PC) is used. ) Or the like is used.

  The supply / discharge mechanism 3 supplies the recording medium 10 to a recording position by the ejection head 20 and discharges the recording medium 10 from the recording position. The ink supply unit supplies ink stored in a storage tank (not shown) to the ejection head 20. The maintenance unit 5 performs maintenance of the ejection head 20. Further, the droplet discharge device 1 is provided with a control unit (not shown) that comprehensively controls these mechanism units and the like.

The supply / discharge mechanism unit 3 includes a supply reel 31, a take-up reel 32, a suction unit 33, an idler roller 37, an idler roller 38, and a Y-axis scanning mechanism 42.
The Y-axis scanning mechanism 42 includes two sets of Y-axis guide rails 42a and Y-axis sliders 42b. The suction unit 33 includes a suction table 33a serving as a medium holding unit in the present invention, a table base 43, a table lifting mechanism 44, a supply roller 34, a driven roller 34a, a medium feeding roller 36, a driven roller 36a, It is configured with. Each reel and each roller are rotatable around a rotation axis, and the respective rotation axes are substantially parallel to each other.
The direction in which the recording medium 10 is fed is a direction substantially orthogonal to the rotation axes of the reels and rollers that are substantially parallel to each other. A direction parallel to the axial direction of the rotation axis of each reel and each roller is expressed as an X-axis direction, and a feeding direction of the recording medium 10 is expressed as a Y-axis direction.

  One Y-axis guide rail 42a of the Y-axis scanning mechanism 42 is disposed on each side in the X-axis direction with the suction table 33a interposed therebetween, and extends in the Y-axis direction. The Y-axis slider 42b is provided on the bottom surface of the table base 43 and is disposed on the Y-axis guide rail 42a in that state. The Y-axis slider 42b is moved on the Y-axis guide rail 42a by a Y-axis drive motor (not shown). It is configured to slide in the extending direction.

  The suction table (medium holding unit) 33 a of the suction unit 33 is fixed to a table lifting mechanism 44 fixed on the table base 43. As shown in FIG. 2A, which is a side sectional view in the present embodiment, the suction table (medium holding unit) 33a is fixed to the table lifting mechanism 44, and is placed on the table 60 and screwed. A holding plate 61 that is detachably fixed by a stopper or the like, and is configured to hold the recording medium 10 on the upper surface of the holding plate 61.

  As shown in FIG. 2B, which is a plan view of the table 60, the table 60 has a rectangular shape in plan view. A small rectangular frame-shaped suction groove 62a is formed in the center of the upper surface of the table 60, and a large rectangular frame is formed outside the table 60. In this configuration, a suction groove 62b is formed. That is, the openings of the suction grooves 62 a and 62 b are arranged on the upper surface of the table 60. These suction grooves 62a, 62b are connected to a suction pump (negative pressure source) (not shown) disposed outside the table 60 via a pipe (not shown) passing through the table 60, and from this opening. Suction is performed at a predetermined pressure (for example, a suction pressure of -70 kPa).

  The holding plate 61 is a rectangular plate made of a metal such as SUS, and has a thickness of about 0.3 mm to 1.0 mm, for example. As shown in FIG. 2C, which is a plan view of the holding plate 61, a large number of suction holes 63 penetrating from the front surface (upper surface) to the rear surface (lower surface) are formed. In the present embodiment, nine rows of suction holes 63 are formed and arranged vertically and horizontally, and a total of 81 through holes are formed. These suction holes 63 are formed and arranged with a pitch of 10 mm both vertically and horizontally, and each hole diameter is formed to be 0.6 mm or less.

  The holding plate 61 in which the suction holes 63 are formed is placed on the upper surface of the table 60 and is fixed to the upper surface with a slight gap so that the suction groove is interposed with the gap. It communicates with 62a and 62b. That is, for example, when the upper surface of the table 60 is a rough surface or the back surface (lower surface) of the holding plate 61 is a rough surface, there is a gap between the upper surface of the table 60 and the back surface of the holding plate 61. Is to be formed. In order to form such a gap more reliably, for example, a rectangular frame-shaped convex portion (not shown) is formed on the outer surface of the upper surface of the table 60 or the rear surface of the holding plate 61, and the convex By interposing the section between the upper surface of the table 60 and the back surface of the holding plate 61, an airtight gap may be formed between the upper surface of the table 60 and the back surface of the holding plate 61.

By forming the gaps in this way, the suction holes 63 of the holding plate 61 communicate with the suction grooves 62a and 62b through the gaps. Therefore, when the suction grooves 62a and 62b are sucked by the suction pump, the suction holes 63 communicating with the suction grooves 62a and 62b are also sucked from the openings formed on the surfaces thereof.
Note that, unlike the back surface (lower surface), the front surface (upper surface) of the holding plate 61 is preferably polished. In this way, at the portion other than the opening of the suction hole 63, the polishing plate 63 is polished. Almost the entire area has the same reflectance.

  Based on such a configuration, the surface (upper surface) of the holding plate 61 is a holding surface for holding the recording medium 10, and the recording medium 10 is sucked and held on the holding surface by suction by the suction holes 63. It has become. That is, the recording medium 10 is held and fixed on the holding surface by being sucked and sucked by the suction holes 63 in a state where the predetermined portion is positioned on the holding surface. In this state of being held and fixed on the holding surface, the ultraviolet curable ink is discharged from the discharge head 20, and the droplets of the ink land on the recording medium 10.

  As shown in FIGS. 1A and 1B, the table elevating mechanism 44 elevates and lowers the suction table 33a in the Z-axis direction, and the holding surface (suction surface) of the suction table 33a is set in a predetermined direction in the Z-axis direction. It is moved up and down between a suction position that is a position and a retracted position closer to the table base 43 than the suction position, and is held and fixed at each position. The position of the holding surface of the suction table 33a when in the suction position substantially coincides with the positions of the upper ends of the outer periphery of the supply roller 34 and the outer periphery of the medium feed roller 36, which will be described later.

  On both sides of the suction table 33a in the Y-axis direction, a supply roller 34 and a driven roller 34a, and a medium feeding roller 36 and a driven roller 36a are disposed. The supply roller 34 and the driven roller 34a, and the medium feeding roller 36 and the driven roller 36a are fixed to the table base 43 via a support member (not shown), and in that state, the suction table 33a is sandwiched on both sides thereof. It is arranged. The supply roller 34 and the driven roller 34a are disposed on the upstream side of the suction table 33a, that is, on the supply reel 31 side, and the medium feed roller 36 and the driven roller 36a are on the downstream side of the suction table 33a, that is, the take-up reel 32. It is arranged on the side.

  The table base 43 can be moved in the Y-axis direction by the Y-axis scanning mechanism 42 and can be held at an arbitrary position in the Y-axis direction. The suction table 33a, the supply roller 34 and the driven roller 34a, the medium feeding roller 36 and the driven roller 36a arranged on the table base 43 are also movable in the Y-axis direction by the Y-axis scanning mechanism 42. And it can hold | maintain in the arbitrary positions in a Y-axis direction.

  The supply reel 31, the idler roller 37, the suction unit 33, the idler roller 38, and the take-up reel 32 included in the supply / discharge mechanism unit 3 are arranged in this order in the Y-axis direction, which is the supply direction of the recording medium 10. The supply reel 31 side is the upstream side in the supply direction of the recording medium 10, and the take-up reel 32 side is the downstream side.

  In the suction unit 33, the supply roller 34 and the driven roller 34a, the suction table 33a, the medium feeding roller 36, and the driven roller 36a are arranged in this order in the Y-axis direction. Therefore, in the supply / discharge mechanism 3, the supply reel 31, the idler roller 37, the supply roller 34 and the driven roller 34a, the suction table 33a, the medium feeding roller 36 and the driven roller 36a, the idler roller 38, and the winding roller The reels 32 are arranged in this order in the Y-axis direction.

  A belt-shaped recording medium 10 is wound around the supply reel 31, and the recording medium 10 is fed out by rotating the supply reel 31 by a supply motor (not shown). The outer periphery of the driven roller 34a is disposed in contact with the outer periphery of the supply roller 34 and is pressed against the supply roller 34 by an urging device (not shown). The supply roller 34 is rotated by a supply motor (not shown), and the driven roller 34a that is in direct or indirect contact with the supply roller 34 is rotated by the rotation of the supply roller 34. It has become. Under such a configuration, the recording medium 10 sandwiched between the supply roller 34 and the driven roller 34 a is fed by the rotation of the supply roller 34.

  The idler roller 37 has a rotating shaft that can swing in the Z-axis direction and is biased to one of the swing directions (downward in the present embodiment). The idler roller 37 is brought into contact with the portion of the recording medium 10 between the supply reel 31, the supply roller 34, and the driven roller 34a by the urging force. Under such a configuration, the recording medium 10 is urged by the idler roller 37, so that it is between the supply reel 31 and the idler roller 37, and between the idler roller 37, the supply roller 34, and the driven roller 34a. The part of is stretched without slack.

  Therefore, the state when the recording medium 10 is supplied and sandwiched between the supply roller 34 and the driven roller 34a is easily maintained substantially flat. Note that the amount of slack in the portion between the supply reel 31, the supply roller 34, and the driven roller 34a varies depending on the difference between the supply speed of the recording medium 10 in the supply roller 34 and the feeding speed of the recording medium 10 in the supply reel 31. To do. However, by changing the position of the idler roller 37 following the fluctuation of the slack amount, the tensioned state is maintained without slack. Similarly, the fluctuation of the slack amount of the recording medium 10 between the supply reel 31, the supply roller 34, and the driven roller 34a due to the movement of the suction unit 33 is also maintained in a tensioned state without any slack. It has become.

  The outer periphery of the driven roller 36a is disposed in contact with the outer periphery of the supply roller 36, and is pressed against the medium feeding roller 36 by an urging device (not shown). The medium feed roller 36 is rotated by a medium feed motor (not shown), and a driven roller 36a that directly or indirectly contacts the medium feed roller 36 is driven by the rotation of the medium feed roller 36. To rotate. Under such a configuration, the recording medium 10 sandwiched between the medium feeding roller 36 and the driven roller 36 a is fed by the rotation of the medium feeding roller 36.

  Here, the feed amount by the medium feed roller 36 is set to be larger than the feed amount by the supply roller 34. Further, a torque control mechanism (not shown) is incorporated in the power transmission mechanism from the medium feed motor to the medium feed roller 36. Under such a configuration, the recording medium 10 that is fed faster than the supply roller 34 by the medium feed roller 36 has a torque controlled by the torque control mechanism at a portion between the supply roller 34 and the medium feed roller 36. It is designed to be tensioned according to the tension.

  The holding surface of the suction table 33a (the surface of the holding plate 61) faces the stretched portion. That is, the portion of the recording medium 10 located on the holding surface of the suction table 33a is stretched with a tension according to the torque controlled by the torque control mechanism. Here, the position of the holding surface of the suction table 33 a located at the above-described suction position substantially coincides with the position of the surface formed by the outer peripheral upper end of the medium feeding roller 36 and the outer peripheral upper end of the supply roller 34. Therefore, the holding surface of the suction table 33a located at the suction position is in contact with and holds the recording medium 10 stretched between the supply roller 34 and the medium feed roller 36.

The take-up reel 32 is rotated by a take-up motor (not shown), so that the recording medium 10 fed from the medium feed roller 36 is taken up by the take-up reel 32. It has become.
The idler roller 38 has a rotating shaft that can swing in the Z-axis direction and is biased in one of the swing directions. The idler roller 38 is brought into contact with the portion of the recording medium 10 between the medium feeding roller 36 and the driven roller 36 a and the take-up reel 31 by the urging force. Under such a configuration, the recording medium 10 is urged by the idler roller 38, so that the medium feeding roller 36, the driven roller 36 a and the take-up reel 31, and the idler roller 38 and the take-up reel 32. The part between is stretched without slack.

  Therefore, the recording medium 10 is easily maintained in a substantially flat state when being wound on the take-up reel 32. The amount of slack in the portion between the medium feed roller 36 and the take-up reel 32 depends on the difference between the feed speed of the recording medium 10 at the medium feed roller 36 and the take-up speed of the recording medium 10 at the take-up reel 32. fluctuate. However, by changing the position of the idler roller 38 following the fluctuation of the slack amount, the tensioned state is maintained without slack. Similarly, the fluctuation of the slack amount of the recording medium 10 between the medium feeding roller 36 and the take-up reel 32 due to the movement of the suction unit 33 is also maintained in a tensioned state without slack. ing.

  Under such a state, the recording medium 10 is fed from the supply reel 31 to the take-up reel 32, and recorded (printed) on a portion held on the holding surface 33b of the suction table (medium holding portion) 33a in the middle. ) Is made.

The head mechanism unit 2 includes a head carriage 22 and an X-axis scanning mechanism 11.
The X-axis scanning mechanism 11 includes two sets of an X-axis guide 11a, an X-axis slider 11b, and a support base 11d, and further includes four guide rail support columns 11c. The support column base 11d is disposed on each side of the suction table 33a in the X-axis direction of the suction table 33a, and sandwiches the pair of Y-axis guide rails 42a and 42a. Arranged in position. A maintenance unit 5 is disposed between one Y-axis guide rail 42a and the support column base 11d.

  On each of the two support column bases 11d and 11d, two guide rail support columns 11c are erected on each end in the Y-axis direction, one in total. One of the two X-axis guide rails 11a is bridged between the guide rail support columns 11c erected at the end of the support column base 11d on the supply reel 31 side and above the suction table 33a. And arranged in a state extending in the X-axis direction. Further, the other of the pair of X-axis guide rails 11a is bridged between the guide rail support pillars 11c erected on the end of the support pillar base 11d on the take-up reel 32 side, and the suction table 33a. It is arranged in a state extending in the X-axis direction above.

  The X-axis slider 11b is disposed on the X-axis guide rail 11a, and is configured to slide on the X-axis guide rail 11a in the extending direction by an X-axis drive motor (not shown). Is. Both ends of the bridge plate 27 of the head carriage 22 are fixed to the X-axis slider 11b supported on each of the two X-axis guide rails 11a. The bridge plate 27 having both ends fixed to the X-axis slider 11b is suspended between the two X-axis guide rails 11a while being supported by the X-axis slider 11b. Based on such a configuration, the bridge plate 27 is slid in the extending direction on the X-axis guide rail 11a by the X-axis drive motor, and at an arbitrary position in the X-axis direction. It is supposed to be retained.

  The head carriage 22 includes a bridge plate 27, a sub-carriage 28, and a head unit 21. The sub-carriage 28 is provided at substantially the center of the lower surface of the bridge plate 27, and the head unit 21 is fixed to the lower surface side of the sub-carriage 28. A discharge head 20 is provided on the lower surface side of the head unit 21, and a nozzle substrate 25 on which discharge nozzles 24 are formed is disposed on the bottom side of the discharge head 20, as shown in FIG. Yes. Under such a configuration, the ejection head 20 is positioned on the holding surface 33b of the suction table 33a. At this time, the nozzle substrate 25 is opposed to the holding surface 33b. Yes.

Here, the suction unit 33 is movable in the Y-axis direction by the Y-axis scanning mechanism 42, and therefore the holding surface 33b of the suction table 33a is movable in the Y-axis direction. That is, the portion of the recording medium 10 that is sucked and held on the holding surface 33b of the suction table 33a can be scanned in the Y-axis direction.
On the other hand, the ejection head 20 of the head unit 21 fixed to the sub-carriage 28 is scanned in the X-axis direction when the bridge plate 27 provided with the sub-carriage 28 is moved in the X-axis direction by the X-axis scanning mechanism 11. It is supposed to be made.

  Under such a configuration, the X-axis scanning mechanism 11 causes the ejection head 20 of the head unit 21 to scan in the X-axis direction, and the Y-axis scanning mechanism 42 sucks and holds the holding surface 33b of the suction table 33a in the recording medium 10. The scanned part can be scanned in the Y-axis direction. That is, the discharge nozzles 24 of the discharge head 20 can be made to face almost the entire surface of the portion of the recording medium 10 that is sucked and held by the holding surface 33b of the suction table 33a.

  Therefore, the recording portion of the recording medium 10 sucked and held on the holding surface 33b of the suction table 33a is moved to the discharge position in the Y-axis direction and stopped, and synchronized with the movement of the head unit 21 in the X-axis direction. By ejecting the ultraviolet curable ink as droplets from the ejection head 20, the droplets (dots) of the ultraviolet curable ink can be arranged at desired positions on the recording medium 10. Therefore, by controlling the main scanning for moving the head unit 21 in the X-axis direction and the sub-scanning (line feed) for moving the recording medium 10 sucked and held on the holding surface 33b of the suction table 33a in the Y-axis direction, The discharge head 20 of the head unit 21 can be opposed to an arbitrary position on the recording medium 10 held on the holding surface 33b of the suction table 33a, and in this state, the ultraviolet curable ink can be discharged as droplets. As a result, a desired image can be formed (recorded) on the recording medium 10.

  Next, the ejection head will be described with reference to FIGS. 3A to 3C are diagrams illustrating a schematic configuration of the ejection head, FIG. 3A is an external perspective view illustrating a schematic configuration of the ejection head 20, and FIG. 3B illustrates an internal structure of the ejection head 20. FIG. 3C is a main part perspective view showing a discharge nozzle portion of the discharge head 20. Note that the X axis, Y axis, and Z axis shown in FIG. 3 indicate the state in which the ejection head 20 is incorporated in the droplet ejection apparatus 1. It coincides with the Z axis.

As shown in FIG. 3A, the ejection head 20 includes a nozzle substrate 25, and the nozzle substrate 25 has two nozzle rows 24A in which a large number of ejection nozzles 24 are linearly arranged. Is formed. Then, the ultraviolet curable ink can be disposed at a desired position on the recording medium 10 by ejecting the ultraviolet curable ink as droplets from the ejection nozzle 24 and landing on the surface of the opposing recording medium 10. It has become.
The nozzle row 24A is formed along the Y-axis direction, and the discharge nozzles 24 are arranged at equal intervals. It should be noted that between the two rows of nozzles 24A, the positions of the discharge nozzles 24 are staggered with a half pitch shift.

  As shown in FIGS. 3B and 3C, the ejection head 20 has a pressure chamber plate 51 stacked on a nozzle substrate 25 and a vibration plate 52 stacked on the pressure chamber plate 51. The pressure chamber plate 51 is formed with a liquid pool 55 that is always filled with ultraviolet curable ink supplied to the ejection head 20. The liquid pool 55 is composed of the diaphragm 52, the nozzle substrate 25, and a wall (see FIG. (Not shown). The ultraviolet curable ink is supplied to the liquid pool 55 via the liquid supply hole 53 of the vibration plate 52. The pressure chamber plate 51 is formed with a pressure chamber 58 partitioned by a plurality of head partition walls 57.

  The pressure chambers 58 are provided corresponding to the respective discharge nozzles 24, and the number of the pressure chambers 58 and the number of the discharge nozzles 24 are the same. A functional liquid is supplied to the pressure chamber 58 from a liquid pool 55 through a supply port 56 positioned between the two head partition walls 57. A set of the pressure chamber 58, the discharge nozzle 24, and the supply port 56 of the head partition wall 57 is arranged in a line along the liquid pool 55, and the discharge nozzles 24 arranged in a line form a nozzle line 24A. . Although not shown in FIG. 3B, another nozzle row 24A is formed on the side of the nozzle row 24A including the discharge nozzle 24A.

  As shown in FIG. 3C, piezoelectric elements 59 are arranged on the diaphragm 52 so as to correspond to the respective pressure chambers 58. The piezoelectric element 59 is formed by sandwiching a piezoelectric layer between a lower electrode and an upper electrode. When a driving voltage is applied between the electrodes, the ultraviolet curable ink is ejected from the corresponding ejection nozzle 24. It has become.

Next, a schematic configuration of the head unit 21 provided in the head mechanism unit 2 will be described with reference to FIG. FIG. 4 is a bottom view showing a schematic configuration of the head unit. Note that the X axis and Y axis shown in FIG. 4 coincide with the X axis and Y axis shown in FIG.
As shown in FIG. 4, the head unit 21 includes a unit plate 23 attached to the lower surface of the sub-carriage 28, and nine discharge heads 20 mounted on the lower surface side of the unit plate 23. Irradiation devices 80 for irradiating ultraviolet rays are respectively disposed on both sides of the discharge head 20 in the X-axis direction.

  The discharge head 20 is fixed to the unit plate 23 by a holding member (not shown) with the nozzle substrate 25 facing downward. The nine ejection heads 20 are divided in the Y-axis direction to form three head sets 20A each including three ejection heads 20 each. The nozzle row 24A of each ejection head 20 is arranged along the Y-axis direction with the head unit 21 attached to the droplet ejection device 1.

  The three ejection heads 20 constituting one head set 20A are arranged in the other ejection head 20 with respect to the ejection nozzle 24 at the end of one ejection head 20 of the ejection heads 20 adjacent to each other in the Y-axis direction. The discharge nozzles 24 at the ends of the nozzles are arranged with a half nozzle pitch shift. In the three ejection heads 20 included in the head set 20A under such a configuration, if the positions of all the ejection nozzles 24 in the X-axis direction are the same, all the ejection nozzles 24 have a half-nozzle pitch in the Y-axis direction. Are arranged at regular intervals. In other words, at the same position in the X-axis direction, the droplets discharged from the discharge nozzles 24 constituting the respective nozzle rows 24A of the respective discharge heads 20 are arranged in a straight line at equal intervals in the Y-axis direction by design. To land on. Accordingly, the six nozzle rows 24A included in the three ejection heads 20 included in one head set 20A can be handled as one nozzle row. The nozzle row has 1080 discharge nozzles 24, which is six times 180, for example, the nozzle pitch in the Y-axis direction is 70 μm, and the distance between the centers of the discharge nozzles 24 at both ends in the Y-axis direction (nozzle row) Length) is about 75.5 mm. Since the ejection heads 20 overlap each other in the Y-axis direction, the head set 20A is configured side by side in a step shape in the X-axis direction.

  Further, in the three head sets 20A included in the head unit 21, when the positions of all the discharge nozzles 24 in the X-axis direction are the same, all the discharge nozzles 24 are arranged at equal intervals of a half nozzle pitch in the Y-axis direction. It has become. In other words, at the same position in the X-axis direction, the droplets discharged from the discharge nozzles 24 constituting the respective nozzle rows 24A of the respective discharge heads 20 are arranged in a straight line at equal intervals in the Y-axis direction by design. It is supposed to land on. Accordingly, the 18 nozzle rows 24A included in the nine ejection heads 20 in the three head sets 20A included in the head unit 21 can be handled as one nozzle row. When the nozzle row is expressed as “unit nozzle row 240A”, this unit nozzle row 240A has, for example, 3240 ejection nozzles 24 that is 18 times 180, and the nozzle pitch in the Y-axis direction is 70 μm. The distance between the centers of the discharge nozzles 24 at both ends in the Y-axis direction (nozzle row length) is about 226.7 mm. That is, when one droplet is ejected from the ejection nozzle 24 of one head unit 21 and landed so that the X-axis direction is at the same position, a straight line in which 3240 dots are connected at a pitch interval of 70 μm is formed. Become.

  The irradiation device 80 includes an ultraviolet light source (not shown), and is fixed to the sub-carriage 28 or the unit plate 23 with the ultraviolet light source facing downward. As described above, the irradiation device 80 is disposed on each side of the ejection head 20 in the X-axis direction. As a result, immediately after the ultraviolet curable ink is ejected from the ejection head 20 toward the recording medium 10. The ultraviolet curable ink landed on the recording medium 10 can be irradiated with ultraviolet rays. That is, the ejection head 20 ejects ultraviolet curable ink while scanning in the X-axis direction. Therefore, when the unit plate 23 is scanned in the X-axis direction, it irradiates the recording medium 10 by irradiating the recording medium 10 with ultraviolet rays from the irradiation device 80 located on the rear side with respect to the scanning direction. It is possible to irradiate ultraviolet rays to the existing ultraviolet curable ink.

  Here, as the ultraviolet light source, a metal halide lamp, a xenon lamp, a carbon arc lamp, a chemical lamp, a low-pressure mercury lamp, a high-pressure mercury lamp, or the like can be used. An LED that emits light in the ultraviolet band can also be used.

  The ultraviolet curable ink that is cured by ultraviolet rays irradiated from such an ultraviolet light source was prepared by adding an auxiliary agent such as an antifoaming agent or a polymerization inhibitor to a mixture of a vehicle, a photopolymerization initiator and a pigment. Things. The vehicle is prepared by adjusting the viscosity of an oligomer, monomer or the like having photopolymerization curability with a reactive diluent. Therefore, the solvent is not volatilized for the purpose of curing the ink.

  As the vehicle, monofunctional or polyfunctional polymerizable compounds can be used. More specifically, oligomers (prepolymers) such as polyester acrylate, epoxy acrylate, and urethane acrylate can be exemplified, and these materials can also be used as a reactive diluent for adjusting the viscosity as an ink.

  As the photopolymerization initiator, benzophenone series, benzoin series, acetophenone series, and thioxanthone series are widely used. More specifically, 4-benzoyl-N, N, N-trimethyl benzene methanenannium chloride, 2-hydroxy 3- (4-benzoyl-phenoxy) -N, N, N-trimethyl 1-propylene, -N, N-dimethyl N- [2- (1-oxo-2-propenyloxy) ethyl] A quaternary ammonium salt type water-soluble organic substance such as benzene methanol bromide can be used. This type of photopolymerization initiator has different ultraviolet absorption characteristics, reaction initiation efficiency, yellowing, and the like depending on its composition, so that it is properly used depending on the color of the ink.

  As the polymerization inhibitor, any compound that has radical scavenging ability and inhibits radical polymerization can be used. However, in consideration of ejection suitability and the like in the ink jet recording apparatus, at least one compound selected from hydroquinones, catechols, hindered amines, phenols, phenothiazines, and condensed aromatic ring quinones is preferable.

  Examples of hydroquinones include hydroquinone, hydroquinone monomethyl ether, 1-o-2,3,5-trimethylhydroquinone, 2-tert-butylhydroquinone and the like. Examples of catechols include catechol, 4-methylcatechol, 4-tert-butylcatechol and the like. Examples of hindered amines include compounds having a tetramethylpiperidinyl group.

  Examples of phenols include phenol, butylhydroxytoluene, butylhydroxyanisole, pyrogallol, gallic acid, gallic acid alkyl ester, and the like. Examples of phenothiazines include phenothiazine. Examples of the condensed aromatic ring quinones include naphthoquinone and the like.

  Furthermore, the polymerization inhibitor may be carbon black or inorganic / organic fine particles having a polymerization-inhibiting functional group introduced on the surface. Examples of the polymerization-preventing functional group include a hydroxyphenyl group, a dihydroxyphenyl group, a tetramethylpiperidinyl group, and a condensed aromatic ring.

  Examples of such ultraviolet curable inks include color inks as color materials containing color components such as pigments and dyes, but also clear inks for undercoat and overcoat. That is, in the present invention, both the color ink and the clear ink are included as a functional liquid containing an ultraviolet curable ink, that is, an ultraviolet curable component.

  In order to print (record) an image on the recording medium 10 by the droplet discharge device 1 having such a configuration, a holding plate 61 is previously placed and fixed on the table 60 as shown in FIG. The suction table 33a is set. Next, the suction pump is operated and sucked by the suction holes 63 through the suction grooves 62a and 62b to hold and fix a predetermined portion of the recording medium 10 on the surface (holding surface) of the holding plate 61.

  Then, as shown in FIGS. 1A and 1B, the ejection head 20 of the head unit 21 is scanned in the X-axis direction by the X-axis scanning mechanism 11, and the suction on the recording medium 10 is performed by the Y-axis scanning mechanism 42. While the part held by suction on the holding surface of the table 33a is scanned in the Y-axis direction, the ultraviolet curable ink is ejected from the ejection head 20 toward the recording medium 10 and landed.

  After the ultraviolet curable ink is landed on the recording medium 10 in this manner, the ultraviolet light is irradiated from the ultraviolet light source of the irradiation device 80 toward the recording medium 10. Then, a part of the ultraviolet rays from the ultraviolet light source is directly irradiated with the ultraviolet curable ink that has landed on the recording medium 10, and the curing thereof proceeds. Further, the remainder of the ultraviolet light from the ultraviolet light source passes through the translucent recording medium 10 and is reflected by the holding surface 33b of the suction table 33a.

At this time, although a large number of suction holes 63 are formed on the surface of the holding plate 61 that serves as a holding surface of the recording medium 10, the suction holes 63 have a diameter of 0.6 mm or less. As is apparent from experimental data to be described later, the suction holes 63 are prevented from affecting the recorded image formed on the recording medium 10.
That is, since the hole diameter of the suction hole 63 is sufficiently small as 0.6 mm or less, the reflected light reflected from the surface of the holding plate 61 is hardly affected by the opening of the suction hole 63. Therefore, the reflected light is again transmitted to the recording medium. When the ultraviolet curable ink 10 is irradiated, the curing of the ultraviolet curable ink further proceeds, but the opening of the suction holes 63 hardly affects the curing.

Therefore, in the droplet discharge device 1 of the present embodiment, it is possible to prevent the quality of the recorded image formed due to the suction holes 63 from being impaired.
Further, since the suction table 33a serving as the medium holding portion is composed of the table 60 having the suction grooves 62a and 62b and the holding plate 61 having the suction holes 63, the suction holes 63 are formed only in the holding plate 61. By doing so, the processing of the suction holes 63 can be facilitated. Further, when a problem occurs in the holding plate 61, such as ink or ink mist adhering to the suction hole 63, only the holding plate 61 needs to be replaced, so that maintenance costs can be reduced.

  Further, since the suction holes 63 are formed and arranged in a plurality of rows in the vertical and horizontal directions on the holding plate 61, the suction holding force with respect to the recording medium 10 is stabilized, and therefore the recording medium 10 is stably held on the holding plate 61. be able to.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention.
For example, in the above-described embodiment, the droplet discharge device of the present invention is applied to a printing device that performs printing on a continuous long recording medium. However, the present invention is not limited to this, for example, The recording medium to be used is not long and can be a rectangular light-transmitting substrate. Moreover, as such a translucent board | substrate, a glass substrate can also be made into object besides the translucent resin mentioned above.
In the embodiment, the irradiation device 80 is fixed to the sub-carriage 28 or the unit plate 23 and applied to a serial type printing device that scans the head unit 21 in the X-axis direction by the X-axis scanning mechanism 11. The invention is not limited to this, and a head carriage in which the length of the head carriage is equal to or greater than the length in the width direction of the printing area of the recording medium 10, a so-called line head, may be employed. Further, an irradiation device having a length equal to or greater than the length in the width direction of the printing area of the recording medium 10, a so-called line irradiation device may be employed.
In the above-described embodiment, the case where the present invention is applied mainly to a droplet discharge apparatus for industrial use has been described. However, the present invention can also be applied to a printer for consumer use.

[Experiment 1]
First, as the suction table 33a, only the SUS (stainless steel) table 60 having the suction grooves 62a and 62b as shown in FIG. 2B was used, and the recording medium was directly placed thereon. The suction grooves 62a and 62b have a groove width of 5 mm and a depth of 2 mm. Further, as the recording medium, a translucent medium in which a PET film was attached to a polycarbonate sheet having a thickness of 0.5 mm was used. In this state, suction was performed by a suction pump, and the recording medium was held and fixed on the upper surface of the table 60 by suction grooves 62a and 62b. Thereafter, in the same manner as in the above embodiment, ultraviolet curable ink was ejected from the ejection head 20 to the entire surface of the recording medium, and the landed ink was irradiated with ultraviolet rays from the irradiation device 80 to cure the ink.

  When the recording medium on which the ink was cured was magnified 100 times with a microscope, it was recognized that there was a gap between the inks at locations corresponding to the openings of the suction grooves 62a and 62b. On the other hand, no gap was observed between the inks on the surface of the table 60 different from the openings of the suction grooves 62a and 62b. Further, when the recording medium was viewed from above with the naked eye, the portions corresponding to the openings of the suction grooves 62a and 62b were thinned and the groove marks were visually recognized.

[Experiment 2]
As the suction table 33a, a total of 81 suction holes 63 are formed on the table 60 used in Experimental Example 1 as shown in FIG. A recording medium was placed directly on the holding plate 61 made of (stainless steel). The suction holes 63 were formed by punching by laser irradiation with a laser aperture (beam diameter) of 0.2 mm. With respect to all the suction holes 63, the hole diameters on the surface (upper surface) side of the holding plate 61, that is, the side holding the recording medium 10 were measured. The obtained measurement results are shown in Table 1 corresponding to the positions of the suction holes 63 shown in FIG.

  As shown in Table 1, although punching was performed with a laser aperture (beam diameter) of 0.2 mm, the formed holes expanded during processing, resulting in an average hole diameter of 526 μm. The maximum diameter was 627 μm, and the minimum diameter was 526 μm. In addition, as a result of measuring the hole diameter on the back surface (lower surface) side of the holding plate 61 as a reference, it was about 300 μm.

  The recording medium was placed on the holding plate 61 and sucked by the suction pump in this state, and the recording medium was held and fixed on the upper surface of the holding plate 61 by the suction holes 63 via the suction grooves 62a and 62b. Note that the same recording medium as in Example 1 was used. Thereafter, in the same manner as in Experimental Example 1, ultraviolet curable ink was ejected from the ejection head 20 to the entire surface of the recording medium, and the landed ink was irradiated with ultraviolet rays from the irradiation device 80 to cure the ink.

When the recording medium on which the ink was cured was magnified 100 times with a microscope, no gap was observed between the inks even at locations corresponding to the openings of the suction holes 63. Further, even when the recording medium was viewed from above with the naked eye, the hole trace corresponding to the opening of the suction hole 63 was not visually recognized.
Therefore, by setting the diameter of the suction hole 63 to 0.6 mm (600 μm) or less, it is possible to suppress the suction hole 63 from affecting the recorded image of the recording medium and to prevent the image quality of the obtained recorded image from being impaired. I found out that I can do it.

  DESCRIPTION OF SYMBOLS 1 ... Droplet discharge apparatus, 10 ... Recording medium, 20 ... Discharge head, 33a ... Suction table (medium holding part), 33b ... Holding surface, 60 ... Table, 61 ... Holding plate, 62a, 62b ... Suction groove, 63 ... Adsorption hole, 80 ... irradiation device.

Claims (4)

A medium holding unit for holding a recording medium; a discharge head for discharging a functional liquid containing an ultraviolet curable component toward the recording medium held by the medium holding unit; and the holding unit held by the medium holding unit A droplet discharge device comprising: an irradiation device that irradiates ultraviolet rays toward a recording medium;
The medium holding unit is a rectangular holding plate made of a metal having a suction groove connected to a negative pressure source and a metal mounted on the upper surface of the table and fixed between the upper surface via a gap. When,
With
The holding plate is provided with a plurality of suction holes for sucking the recording medium on the surface holding the recording medium,
The side of the holding plate that holds the recording medium is polished .
The upper surface of the table or the lower surface of the holding plate is a rough surface,
The gap is formed by placing the holding plate on the table,
The liquid droplet ejection apparatus, wherein the suction groove and the suction hole communicate with each other through the gap .   The droplet discharge device according to claim 1, wherein the suction hole has a hole diameter of 627 μm or less.   3. The droplet discharge device according to claim 1, wherein the suction holes are arranged in a plurality of rows vertically and horizontally on the holding plate. 4.   The liquid droplet ejection apparatus according to claim 1, wherein a translucent recording medium is used as the recording medium.

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