JP2011005422A - Liquid coating head and liquid coating device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid coating head which can coat a target distant from the liquid coating head with a liquid, and a liquid coating device using the same.SOLUTION: The liquid coating head 2 has a plurality of liquid compressing chambers 10, a plurality of compressing parts pressurizing each liquid in a plurality of liquid compressing chambers 10, a plurality of liquid discharge holes 8 connecting respectively with a plurality of liquid compressing chambers 10, and a plurality of gas ejection holes 88 to jet a gas. A plurality of gas ejection holes 88 are opened at the same direction side as a plurality of liquid discharge holes 8 so as to jet the gas to separate the liquid discharged from a plurality of liquid discharge holes 8 from a plurality of liquid discharge holes 8.

Description

  The present invention relates to an apparatus for applying a liquid using an inkjet head.

  In recent years, printing apparatuses using inkjet recording methods such as inkjet printers and inkjet plotters are not only printers for general consumers, but also, for example, formation of electronic circuits, manufacture of color filters for liquid crystal displays, manufacture of organic EL displays It is also widely used for industrial applications.

  In such an ink jet printing apparatus, a liquid discharge head for discharging liquid is mounted as a print head. This type of print head includes a heater as a pressurizing unit in an ink flow path filled with ink, heats and boiles the ink with the heater, pressurizes the ink with bubbles generated in the ink flow path, A thermal system that ejects droplets from the ink ejection holes, and a part of the walls of the ink channel filled with ink is bent and displaced by a displacement element, and the ink in the ink channel is mechanically pressurized to eject ink. A piezoelectric method for discharging liquid droplets from holes is generally known.

  In addition, in such a liquid discharge head, a serial type that performs recording while moving the liquid discharge head in a direction orthogonal to the conveyance direction of the recording medium, and a state in which the liquid discharge head that is longer in the main scanning direction than the recording medium is fixed Alternatively, there is a line type in which recording is performed on a recording medium conveyed in the sub-scanning direction in a state where a plurality of liquid ejection heads are arranged and fixed so that the recording range is wider than the recording medium. The line type has the advantage that high-speed recording is possible because there is no need to move the liquid discharge head as in the serial type.

  In order to print droplets at a high density in any of the serial type and line type liquid discharge heads, the density of the liquid discharge holes for discharging the droplets formed in the liquid discharge head must be increased. There is a need to.

  Therefore, the liquid discharge head includes a manifold, a flow path member having an individual flow path connected to the liquid discharge hole via the common flow path, the squeezing, the liquid pressurization chamber and the communication path in order from the manifold, and the liquid pressurization chamber. Is formed by laminating an actuator unit having a plurality of displacement elements provided so as to cover each of them (see, for example, Patent Document 1). In this liquid discharge head, the liquid pressurization chambers connected to the plurality of liquid discharge holes are arranged in a matrix, and the displacement elements of the actuator unit provided so as to cover the liquid pressurization chambers are displaced, whereby each liquid pressurization chamber is A liquid droplet is ejected from each of the liquid ejection holes, and printing is possible at a resolution of dpi in the main scanning direction.

JP 2003-305852 A

  However, in the liquid ejection head described in Patent Document 1, since the flying distance of the droplet is short, even if the distance to the target on which the droplet is landed is large, even if the droplet does not reach or reaches the target There was a problem that unevenness occurred in the application state.

  Accordingly, an object of the present invention is to provide a liquid application head capable of applying a liquid to an object at a distance from the liquid application head, and a liquid application apparatus using the liquid application head.

  The liquid application head includes a plurality of liquid pressurizing chambers, a plurality of pressurizing units that apply pressure to the liquids in the plurality of liquid pressurizing chambers, and a plurality of liquid ejection units connected to the plurality of liquid pressurizing chambers, respectively. And a plurality of gas ejection holes for ejecting gas, wherein the plurality of gas ejection holes are on the same direction side as the plurality of liquid ejection holes, and the liquid ejected from the plurality of liquid ejection holes An opening is provided so as to eject gas so as to be separated from the plurality of liquid discharge holes.

  Further, when viewed from the opening side of the plurality of liquid ejection holes, a liquid ejection hole group including the plurality of liquid ejection holes extends in one direction, and the plurality of gas ejection holes sandwich the liquid ejection hole group. It is preferable that it is provided along the said one direction on the both sides.

  Furthermore, it is preferable that the plurality of gas ejection holes are provided so as to surround a liquid ejection hole group including the plurality of liquid ejection holes when viewed from the opening side of the plurality of liquid ejection holes.

  Furthermore, when viewed from the opening side of the plurality of liquid ejection holes, the plurality of gas ejection holes are on the circumference of a circle centered on one liquid ejection hole for each of the plurality of liquid ejection holes. It is preferable that a plurality are provided at equal intervals.

  Furthermore, it is preferable that the axes of the plurality of gas ejection holes provided on the circumference of the circle are inclined toward the center of the circle.

  The liquid coating apparatus of the present invention includes the liquid coating head and a control unit that controls driving of the liquid coating head.

  According to the liquid application head of the present invention, the plurality of liquid pressurizing chambers, the plurality of pressurizing units that respectively apply pressure to the liquid in the plurality of liquid pressurizing chambers, and the plurality of liquid pressurizing chambers, respectively. A plurality of liquid ejection holes and a plurality of gas ejection holes for ejecting gas, wherein the plurality of gas ejection holes are on the same direction side as the plurality of liquid ejection holes and from the plurality of liquid ejection holes The liquid ejected from the opening of the liquid ejection hole is formed by ejecting gas so as to eject the liquid to be ejected from the plurality of liquid ejection holes, so that the gas ejected from the gas ejection hole As a result, the flying distance increases, so that the liquid can be applied even if the distance to the application object is long.

  Further, when viewed from the opening side of the plurality of liquid ejection holes, a liquid ejection hole group including the plurality of liquid ejection holes extends in one direction, and the plurality of gas ejection holes sandwich the liquid ejection hole group. When provided on the both sides along the one direction, the gas ejected from the gas ejection holes on both sides of the liquid ejection hole group allows a stable gas flow to the tip of the liquid ejection hole group, A stable liquid can be applied.

  Further, when the plurality of gas ejection holes are provided so as to surround the liquid ejection hole group composed of the plurality of liquid ejection holes when viewed from the opening side of the plurality of liquid ejection holes, The gas ejected from the surrounding gas ejection holes allows a stable gas flow at the tip of the liquid ejection hole group, and a stable liquid can be applied.

  Furthermore, when viewed from the opening side of the plurality of liquid ejection holes, the plurality of gas ejection holes are on the circumference of a circle centered on one liquid ejection hole for each of the plurality of liquid ejection holes. When the plurality of liquid discharge holes at the center are provided at equal intervals, the liquid discharge holes at the center of the liquid discharge holes are symmetrically ejected from the gas discharge holes provided on the circumference of the circumference. A stable gas flow can be achieved, and a stable liquid can be applied.

  Furthermore, when the axes of the plurality of gas ejection holes provided on the circumference of the circle are inclined toward the center of the circle, the liquid discharge hole at the center is located on the circumference of the circumference. The gas ejected symmetrically from the gas ejection holes provided in the can make a stable gas flow at the tip of the liquid ejection holes, and more stable liquid can be applied.

  According to the liquid application apparatus of the present invention, the liquid application head and the control unit that controls driving of the liquid application head are provided, so that the liquid can be applied even when the distance to the application target is long. .

It is a perspective view which shows an example of the liquid application apparatus of this invention. It is a top view which shows an example of the head main body which comprises the liquid application head of this invention. FIG. 3 is an enlarged view of a region surrounded by an alternate long and short dash line in FIG. 2. It is a longitudinal cross-sectional view of the part along the VV line of FIG. 3, and a part of gas flow path member. (A), (b) is a longitudinal cross-sectional view which shows an example of the other liquid application head of this invention. (A), (b) is a longitudinal cross-sectional view which shows an example of the other liquid application head of this invention. (A) is a top view which shows an example of the other liquid application head of this invention, (b) is the side view, (c) is a top view which shows an example of the other liquid application head of this invention (D) is a side view thereof, (e) is a plan view showing an example of another liquid application head of the present invention, and (f) is a side view thereof. (A) is a top view which shows an example of the other liquid application head of this invention, (b) is a top view which shows arrangement | positioning of a liquid discharge hole and a gas ejection hole, (c) is this invention. It is a top view which shows an example of the other liquid application head, (d) is the sectional view on the AA line of (c).

  FIG. 1 is a perspective view of an example of a liquid application apparatus 1 according to the present invention. FIG. 2 is a plan view showing the liquid application head 2 shown in FIG. FIG. 3 is an enlarged view of a region surrounded by a one-dot chain line in FIG. 2 and is a part of the liquid application head 2. In FIG. 3, for easy understanding of the drawing, the liquid pressurizing chamber 10 (liquid pressurizing chamber group 9), the squeezing 12 and the liquid discharge hole 8 which are to be drawn by broken lines below the piezoelectric actuator unit 21 are shown by solid lines. It is drawn in. FIG. 4 is a longitudinal sectional view of a portion along the line VV in FIG. 3 and a part of the gas flow path member 80.

  The liquid coating apparatus 1 includes a liquid coating head 2, a liquid distribution channel member 70, a housing 90, and a control unit (not shown) that controls the discharge of liquid droplets from the liquid coating head 2. The housing 90 is made of metal, and a hole 91 through which a signal cable for transmitting a driving signal is partially opened. In the example of FIG. 1, a hole 91 is opened in a part of the upper surface, and a signal cable (not shown) through which a drive signal connected to the control unit housed in the housing 90 is transmitted passes through the hole 91. It is covered with a resin lid.

  The liquid application head 2 includes a liquid flow path member 4, a piezoelectric actuator unit 21, and a gas flow path member 80, and a lower surface (gas) of the flow path member that combines the liquid flow path member 4 and the gas flow path member 80. A plurality of gas ejection holes 88 for blowing out gas are opened on the same direction side as the plurality of liquid ejection holes 8 for ejecting liquid. The liquid flow path member 4 has a plurality of manifold openings 5 b for allowing liquid to enter the liquid flow path member 4.

  The liquid distribution channel member 70 is stacked on the liquid channel member 4, and the piezoelectric actuator unit 21 is accommodated in a recess provided in the liquid distribution channel member 70. The liquid distribution channel member 70 has a liquid introduction hole 71b, and the liquid introduced from the outside through the liquid introduction hole 71b is distributed in the liquid distribution channel member 70 and flows into the openings 5b of a plurality of manifolds. It has become. When a liquid reservoir provided with a damper is provided in the liquid distribution flow path member 70, and the supply of liquid from the outside is not in time, the damper is deformed to reduce the volume of the liquid reservoir, and the liquid corresponding to the liquid reservoir is reduced. The liquid channel member 4 may be supplied to the liquid channel member 4. Further, a heater may be provided in the liquid distribution channel member 70, and the temperature may be controlled so as to keep the viscosity of the liquid constant in order to stabilize the liquid discharge state.

  A gas introduction hole 81b is opened in the gas flow path member 80, and gas sent from an external pump or the like enters the gas flow path 81 of the gas flow path member 80 through the gas introduction hole 81b and is blown out from the gas ejection hole 88. The

  The liquid application device 1 places an object to which a liquid is applied at the tip of the gas ejection hole surface on the lower surface, ejects liquid droplets from the liquid ejection holes 8, and ejects gas from the gas ejection holes 88. The liquid droplets are transported by the air current generated by the blown gas, and the liquid can be applied to the object. Since the ejected droplets are carried by the airflow, even if there are irregularities on the object and there is a difference in the flight distance until the droplets ejected from the plurality of liquid ejection holes 8 land, Can land on an object.

  When the object has a more complicated shape, the liquid application apparatus 1 is attached to a robot arm having a joint, and the robot arm is controlled so that the distance from the object is controlled to a certain degree. The liquid can be applied to an object having a more complicated shape.

  Next, the liquid application head 2 constituting the liquid application apparatus 1 of the present invention will be described.

  The liquid application head 2 includes a flat liquid flow path member 4 constituting a flow path member, a gas flow path member 80, and a displacement element 50, which will be described later, which is a pressurizing portion disposed on the liquid flow path member 4. Are provided with a plurality of piezoelectric actuator units 21. The piezoelectric actuator unit 21 has a trapezoidal shape, and is disposed on the upper surface of the liquid flow path member 4 so that a pair of parallel opposing sides of the trapezoidal shape is parallel to the longitudinal direction of the liquid flow path member 4. .

  In addition, two piezoelectric actuator units 21 are arranged along the two virtual straight lines parallel to the longitudinal direction of the liquid flow path member 4, that is, a total of four piezoelectric actuator units 21 are arranged on the liquid flow path member 4 as a whole. Has been. The oblique sides of the piezoelectric actuator units 21 adjacent on the liquid flow path member 4 partially overlap when the short direction of the liquid flow path member 4 is viewed. When the longitudinal direction of the liquid coating apparatus 1 is viewed, by driving the piezoelectric actuator unit 21 in this overlapping portion, the density of the ejected droplets is averaged in the longitudinal direction. When the liquid application head 2 is moved in the short direction, the liquid can be applied at a constant concentration.

  A manifold 5 which is a part of the liquid flow path is formed inside the liquid flow path member 4. The manifold 5 has an elongated shape extending along the longitudinal direction of the liquid flow path member 4, and an opening 5 b of the manifold 5 is formed on the upper surface of the liquid flow path member 4. A total of ten openings 5 b are formed along each of two straight lines (imaginary lines) parallel to the longitudinal direction of the liquid flow path member 4. The opening 5b is formed at a position that avoids a region where the four piezoelectric actuator units 21 are disposed. The manifold 5 is supplied with a liquid from a liquid tank (not shown) through a liquid channel in the liquid distribution channel member 70 and the opening 5b.

  The manifold 5 formed in the liquid flow path member 4 is branched into a plurality of branches (the manifold 5 at the branched portion may be referred to as a sub-manifold 5a). The manifold 5 connected to the opening 5 b extends along the oblique side of the piezoelectric actuator unit 21, and is disposed so as to intersect with the longitudinal direction of the liquid flow path member 4. In a region sandwiched between two piezoelectric actuator units 21, one manifold 5 is shared by adjacent piezoelectric actuator units 21, and the sub-manifold 5 a branches off from both sides of the manifold 5. These sub-manifolds 5 a extend in the longitudinal direction of the liquid application head 2 adjacent to each other in regions facing the piezoelectric actuator units 21 inside the liquid flow path member 4.

  The liquid flow path member 4 has four liquid pressurizing chamber groups 9 in which a plurality of liquid pressurizing chambers 10 are formed in a matrix (that is, two-dimensionally and regularly). The liquid pressurizing chamber 10 is a hollow region having a substantially rhombic planar shape with rounded corners. The liquid pressurizing chamber 10 is formed so as to open on the upper surface of the liquid flow path member 4. These liquid pressurizing chambers 10 are arranged over almost the entire area of the upper surface of the liquid flow path member 4 facing the piezoelectric actuator unit 21. Accordingly, each liquid pressurizing chamber group 9 formed by these liquid pressurizing chambers 10 occupies a region having almost the same size and shape as the piezoelectric actuator unit 21. Further, the opening of each liquid pressurizing chamber 10 is closed by adhering the piezoelectric actuator unit 21 to the upper surface of the liquid flow path member 4.

  In the present embodiment, as shown in FIG. 3, the manifold 5 branches into four rows of E1-E4 sub-manifolds 5a arranged in parallel to each other in the short direction of the liquid flow path member 4, and The liquid pressurizing chambers 10 connected to the manifold 5a constitute a row of the liquid pressurizing chambers 10 arranged in the longitudinal direction of the liquid flow path member 4 at equal intervals, and the rows are arranged in four rows parallel to each other in the short direction. Has been. Two rows of liquid pressurizing chambers 10 connected to the sub-manifold 5a are arranged on both sides of the sub-manifold 5a.

  As a whole, the liquid pressurizing chambers 10 connected from the manifold 5 constitute a row of liquid pressurizing chambers 10 arranged in the longitudinal direction of the liquid flow path member 4 at equal intervals, and the rows are parallel to each other in the short direction. It is arranged in a column. The number of liquid pressurizing chambers 10 included in each liquid pressurizing chamber row is arranged so as to gradually decrease from the long side toward the short side, corresponding to the outer shape of the displacement element 50 that is an actuator. ing. The liquid discharge holes 8 are also arranged in the same manner.

  In the gas flow path member 80, a plurality of gas ejection holes 88 are opened on the gas ejection hole surface corresponding to the lower surface of the liquid application head 2, and the gas fed from the gas introduction hole opening 81 b is gas from the gas ejection hole 88. Blowing is performed in a direction substantially orthogonal to the ejection hole surface. The liquid droplets ejected from the liquid ejection holes 8 are ejected and ejected in a direction substantially orthogonal to the liquid and the ejection hole surface, which are flush with the gas ejection hole surface.

  Individual electrodes 35 to be described later are formed at positions facing the liquid pressurizing chambers 10 on the upper surface of the piezoelectric actuator unit 21. The individual electrode 35 is slightly smaller than the liquid pressurizing chamber 10, has a shape substantially similar to the liquid pressurizing chamber 10, and fits in a region facing the liquid pressurizing chamber 10 on the upper surface of the piezoelectric actuator unit 21. Is arranged.

  A large number of liquid discharge holes 8 are formed on the liquid discharge surface on the lower surface of the liquid flow path member 4. These liquid discharge holes 8 are disposed at positions avoiding a region facing the sub-manifold 5 a disposed on the lower surface side of the liquid flow path member 4. Further, these liquid discharge holes 8 are disposed in a region facing the piezoelectric actuator unit 21 on the lower surface side of the liquid flow path member 4. These liquid discharge hole groups occupy an area having almost the same size and shape as the piezoelectric actuator unit 21, and by displacing the displacement element 50 of the corresponding piezoelectric actuator unit 21, a droplet is discharged from the liquid discharge hole 8. Can be discharged. The arrangement of the liquid discharge holes 8 and the air ejection holes 88 will be described in detail later. The liquid discharge holes 8 in each region are arranged at equal intervals along a plurality of straight lines parallel to the longitudinal direction of the liquid flow path member 4.

  The liquid flow path member 4 constituting the liquid application head 2 has a laminated structure in which a plurality of plates are laminated. These plates are, in order from the upper surface of the liquid flow path member 4, a cavity plate 22, a base plate 23, an aperture (squeezing) plate 24, a supply plate 25, manifold plates 26, 27, 28, 29, a cover plate 30 and a nozzle plate 31. It is. A number of holes are formed in these plates. Each plate is aligned and laminated so that these holes communicate with each other to form the individual flow path 32 and the sub-manifold 5a. As shown in FIG. 4, the liquid application head 2 has a liquid pressurizing chamber 10 on the upper surface of the liquid flow path member 4, a sub manifold 5a on the inner lower surface side, and a liquid discharge hole 8 on the lower surface. Each part constituting the individual flow path 32 is disposed close to each other at different positions, and the sub-manifold 5 a and the liquid discharge hole 8 are connected via the liquid pressurizing chamber 10.

  The holes formed in each plate will be described. These holes include the following. First, the liquid pressurizing chamber 10 formed in the cavity plate 22. Second, there is a communication hole that forms a flow path that connects from one end of the liquid pressurizing chamber 10 to the sub-manifold 5a. This communication hole is formed in each plate from the base plate 23 (specifically, the inlet of the liquid pressurizing chamber 10) to the supply plate 25 (specifically, the outlet of the sub manifold 5a). Note that the communication hole includes the aperture 12 formed in the aperture plate 24 and the individual supply flow path 6 formed in the supply plate 25.

  Third, there is a communication hole that constitutes a communication path that communicates from the other end of the liquid pressurizing chamber 10 to the liquid discharge hole 8, and this communication path is a descender (partial flow channel) in the liquid discharge hole 8 and the following description. ) It consists of a part called 7. The liquid discharge hole 8 is formed in the nozzle plate 31. The descender 7 is formed on each plate from the base plate 23 (specifically, the outlet of the liquid pressurizing chamber 10) to the cover plate 30 (specifically, the connection end with the liquid discharge hole 8).

  Fourthly, there is a communication hole constituting the sub-manifold 5a. The communication holes are formed in the manifold plates 25-29.

  Such communication holes are connected to each other to form an individual flow path 32 from the liquid inflow port (the outlet of the submanifold 5a) from the submanifold 5a to the liquid discharge hole 8. The liquid supplied to the sub manifold 5a is discharged from the liquid discharge hole 8 through the following path. First, from the sub-manifold 5a, it passes through the individual supply flow path 6 and reaches one end of the aperture 12. Next, it proceeds horizontally along the extending direction of the aperture 12 and reaches the other end of the aperture 12. From there, it reaches one end of the liquid pressurizing chamber 10 upward. Further, the liquid pressurizing chamber 10 proceeds horizontally along the extending direction of the liquid pressurizing chamber 10 and reaches the other end of the liquid pressurizing chamber 10. From there, moving in the descender 7 little by little in the horizontal direction, it proceeds mainly downward and to the liquid discharge hole 8 opened on the lower surface.

  As shown in FIG. 4, the piezoelectric actuator unit 21 has a laminated structure including two piezoelectric ceramic layers 21a and 21b. Each of these piezoelectric ceramic layers 21a and 21b has a thickness of about 20 μm. The total thickness of the piezoelectric actuator unit 21 is about 40 μm. Each of the piezoelectric ceramic layers 21a and 21b extends so as to straddle the plurality of liquid pressurizing chambers 10 (see FIG. 3). The piezoelectric ceramic layers 21a and 21b are made of a lead zirconate titanate (PZT) ceramic material having ferroelectricity.

  Adhesion between the piezoelectric actuator unit 21 and the liquid flow path member 4 is performed through an adhesive layer, for example. The adhesive layer is at least one selected from the group consisting of epoxy resin, phenol resin, and polyphenylene ether resin having a thermosetting temperature of 100 to 150 ° C. so as not to affect the piezoelectric actuator unit 21 and the liquid flow path member 4. A thermosetting resin adhesive is used. The reason why the thermosetting resin adhesive is used is that the room temperature curing adhesive may not ensure sufficient ink resistance. For this reason, the piezoelectric actuator unit 21 is in a state in which a stress generated by a difference in thermal expansion coefficient between the liquid flow path member 4 and the piezoelectric actuator unit 21 is applied by being cooled from the thermosetting temperature to room temperature. When the stress is large, the piezoelectric actuator unit 21 may be broken, and even if the stress is not so high that the piezoelectric actuator unit 21 is broken, the characteristics of the piezoelectric actuator unit 21 vary depending on the applied stress. Specifically, in a state where compressive stress is applied, the piezoelectric constant is lowered, but the influence of the phenomenon of drive deterioration in which the amount of displacement is reduced when the drive is repeated for a very long time is reduced. Conversely, in a state where tensile stress is applied, the piezoelectric constant increases, but the influence of drive deterioration increases. In any case, the difference in thermal expansion coefficient between the liquid flow path member 4 and the piezoelectric actuator unit 21 needs to be reduced, and the influence of drive deterioration does not increase the fluctuation of the discharge characteristics even when used for a long time. It is preferable that a small compressive stress is applied. Therefore, when a PZT ceramic is used for the piezoelectric actuator unit 21, it is preferable to use 42 alloy as the material of the liquid flow path member 4.

  The gas flow path member 80 constituting the liquid application head 2 has a laminated structure in which a plurality of plates 85 to 87 are laminated. A number of holes are formed in these plates. Each plate is aligned and laminated so that these holes communicate with each other to form a communication hole from the gas introduction hole 81 b to the gas ejection hole 88 through the gas flow path 81. The plate 85 has an opening 81 b of the gas flow path 81. The holes of the plate 81 are connected to a plurality of gas ejection holes 88. The plates 85 to 87 are bonded through an adhesive layer, for example. Further, the gas flow path member 80 and the liquid flow path member 4 are also bonded through, for example, an adhesive layer. As the adhesive layer, an adhesive of at least one thermosetting resin selected from the group of epoxy resin, phenol resin, and polyphenylene ether resin having a thermosetting temperature of 100 to 150 ° C. is used.

  The piezoelectric actuator unit 21 includes a common electrode 34 made of a metal material such as Ag—Pd and an individual electrode 35 made of a metal material such as Au. As described above, the individual electrode 35 is disposed at a position facing the liquid pressurizing chamber 10 on the upper surface of the piezoelectric actuator unit 21. One end of the individual electrode 35 is drawn out of a region facing the liquid pressurizing chamber 10 to form a connection electrode 36. The connection electrode 36 is made of, for example, gold containing glass frit, and has a convex shape with a thickness of about 15 μm. The connection electrode 36 is electrically joined to an electrode provided in an FPC (Flexible Printed Circuit) (not shown). Although details will be described later, a drive signal is supplied to the individual electrode 35 from the control unit through the FPC. The drive signal is supplied at a constant period in synchronization with the conveyance speed of the recording paper P.

  The common electrode 34 is formed over almost the entire surface in the area between the piezoelectric ceramic layer 21a and the piezoelectric ceramic layer 21b. That is, the common electrode 34 extends so as to cover all the liquid pressurizing chambers 10 in the region facing the piezoelectric actuator unit 21. The thickness of the common electrode 34 is about 2 μm. The common electrode 34 is grounded in a region not shown, and is held at the ground potential. In the present embodiment, a surface electrode (not shown) different from the individual electrode 35 is formed on the piezoelectric ceramic layer 21b at a position avoiding the electrode group composed of the individual electrodes 35. The surface electrode is electrically connected to the common electrode 34 through a through-hole formed in the piezoelectric ceramic layer 21b, and is connected to another electrode on the FPC in the same manner as many individual electrodes 35. ing.

  As shown in FIG. 4, the common electrode 34 and the individual electrode 35 are arranged so as to sandwich only the uppermost piezoelectric ceramic layer 21b. A region sandwiched between the individual electrode 35 and the common electrode 34 in the piezoelectric ceramic layer 21b is referred to as an active portion, and the piezoelectric ceramic in that portion is polarized. In the piezoelectric actuator unit 21 of the present embodiment, only the uppermost piezoelectric ceramic layer 21b includes an active portion, and the piezoelectric ceramic 21 layer a does not include an active portion and functions as a diaphragm. The piezoelectric actuator unit 21 has a so-called unimorph type configuration.

  As will be described later, when a predetermined drive signal is selectively supplied to the individual electrode 35, pressure is applied to the liquid in the liquid pressurizing chamber 10 corresponding to the individual electrode 35. As a result, droplets are discharged from the corresponding liquid discharge ports 8 through the individual flow paths 32. That is, the portion of the piezoelectric actuator unit 21 that faces each liquid pressurizing chamber 10 corresponds to an individual displacement element 50 (actuator, pressurizing unit) corresponding to each liquid pressurizing chamber 10 and the liquid discharge port 8. That is, in the laminate composed of the two piezoelectric ceramic layers 21a and 21b, the displacement element 50 having the unit structure as shown in FIG. The piezoelectric actuator unit 21 includes a plurality of displacement elements 50. The piezoelectric actuator unit 21 includes a plurality of displacement elements 50. The piezoelectric actuator unit 21 includes a plurality of displacement elements 50. In the present embodiment, the amount of liquid ejected from the liquid ejection port 8 by one ejection operation is about 5 to 7 pL (picoliter). Further, since the ejection speed of the ejected droplet is about 5 to 8 m / s, when there is no gas ejection from the gas ejection hole 88, it stops at a distance of about 3 cm from the liquid ejection hole surface and floats in the air. In this state, the liquid droplet cannot be landed further away. In addition, if the distance from the liquid discharge hole surface is 1 cm or more, the flying speed becomes slow and stable landing is not achieved.

The gas to be ejected is preferably temperature-adjusted in advance by a heating means or a cooling means before entering the gas flow path member 80 in order to stabilize the temperature of the liquid in the liquid application head. In the temperature adjustment, for example, the control unit controls the heating unit or the cooling unit so that the temperature measured by the sensor provided in the gas flow path member 80 is kept constant. If the gas flow path member 80 is cooled by the gas passing through the gas flow path member 80, it is preferable to heat the gas in advance, and the gas passing through the gas flow path member 80 due to friction or the like causes the gas flow path member 80 to be heated. If the temperature is high, it is preferable to heat the gas in advance. In addition, since the ejected north may expedite the drying of the liquid applied to the droplets or the object, the drying state of the liquid can be adjusted by controlling the temperature of the ejected gas. The individual electrodes 35 are individually electrically connected to the actuator control means via contacts and wirings on the FPC so that the potential can be individually controlled.

  In the piezoelectric actuator unit 21 in the present embodiment, when an electric field is applied in the polarization direction to the piezoelectric ceramic layer 21b by setting the individual electrode 35 to a potential different from that of the common electrode 34, the portion to which this electric field is applied is piezoelectric. It works as an active part that is distorted by the effect. At this time, the piezoelectric ceramic layer 21b expands or contracts in the thickness direction, that is, the stacking direction, and tends to contract or extend in the direction perpendicular to the stacking direction, that is, the surface direction, due to the piezoelectric lateral effect. On the other hand, since the remaining piezoelectric ceramic layer 21a is an inactive layer that does not have a region sandwiched between the individual electrode 35 and the common electrode 34, it does not spontaneously deform. In other words, the piezoelectric actuator unit 21 uses the upper piezoelectric ceramic layer 21b (that is, the side away from the liquid pressurizing chamber 10) as a layer including the active portion and the lower side (that is, close to the liquid pressurizing chamber 10). This is a so-called unimorph type configuration in which the piezoelectric ceramic layer 21a on the side) is an inactive layer.

  In this configuration, when the individual electrode 35 is set to a predetermined positive or negative potential with respect to the common electrode 34 by the actuator controller so that the electric field and the polarization are in the same direction, a portion sandwiched between the electrodes of the piezoelectric ceramic layer 21b. (Active part) contracts in the surface direction. On the other hand, the piezoelectric ceramic layer 21a, which is an inactive layer, is not affected by an electric field, so that it does not spontaneously shrink and tries to restrict deformation of the active portion. As a result, there is a difference in strain in the polarization direction between the piezoelectric ceramic layer 21b and the piezoelectric ceramic layer 21a, and the piezoelectric ceramic layer 21b is deformed so as to protrude toward the liquid pressurizing chamber 10 (unimorph deformation). .

  In an actual driving procedure in the present embodiment, the individual electrode 35 is set to a potential higher than the common electrode 34 (hereinafter referred to as a high potential) in advance, and the individual electrode 35 is temporarily set to the same potential as the common electrode 34 every time an ejection request is made ( Hereinafter, this is referred to as a low potential), and then the potential is set again at a predetermined timing. Thereby, the piezoelectric ceramic layers 21a and 21b return to their original shapes at the timing when the individual electrode 35 becomes low potential, and the volume of the liquid pressurizing chamber 10 is compared with the initial state (the state where the potentials of both electrodes are different). To increase. At this time, a negative pressure is applied to the liquid pressurizing chamber 10 and the liquid is sucked into the liquid pressurizing chamber 10 from the manifold 5 side. Thereafter, at the timing when the individual electrode 35 is set to a high potential again, the piezoelectric ceramic layers 21 a and 21 b are deformed so as to protrude toward the liquid pressurizing chamber 10. Becomes a positive pressure, the pressure on the liquid rises, and droplets are ejected. That is, a drive signal including a pulse based on a high potential is supplied to the individual electrode 35 in order to eject a droplet. The ideal pulse width is AL (Acoustic Length), which is the length of time during which the pressure wave propagates from the manifold 5 to the liquid discharge hole 8 in the liquid pressurizing chamber 10. According to this, when the inside of the liquid pressurizing chamber 10 is reversed from the negative pressure state to the positive pressure state, both pressures are combined, and the liquid droplet can be ejected with a stronger pressure.

  When the liquid application head 2 as described above is used, a liquid droplet ejection head provided with an air flow ejection hole that generates an air flow in the same direction as the liquid droplet ejection in the vicinity of the liquid droplet ejection hole is created and used. The structure having irregularities on the surface was painted.

  In this embodiment, by keeping the distance from the surface to be coated in the range of 2 to 7 cm and continuously discharging the droplets along with the air current, the fine mist that occurs accidentally with the droplets can reach the substrate. It was possible to paint by.

In particular, in this embodiment, it is possible to arbitrarily control the flying speed and discharge amount of the droplets by adjusting the airflow speed and the number of discharge nozzles, and the conventional linear spraying can be applied uniformly. Even on complex uneven surfaces that were difficult to control, it was possible to control the discharge amount according to the wraparound of the ink and the uneven shape, and it became possible to uniformly coat the entire surface.
Furthermore, conventionally, when droplets are continuously ejected by an inkjet head that does not have an airflow generating means, the mist drifting in the air adheres to the nozzle surface and gradually becomes large droplets. In some cases, the mist is blown toward the object by generating an air current, so that the droplets can be prevented from adhering to the nozzle plate, and the coating can be performed efficiently. I was able to.

  In addition, such a liquid application head 2 as a whole can form an image with a resolution of 600 dpi in the longitudinal direction. That is, the individual flow paths 32 are connected to each sub-manifold 5a at intervals corresponding to 150 dpi on average. This is because the individual flow paths 32 connected to the sub-manifolds 5a are not necessarily connected at equal intervals when the liquid ejection holes 8 for 600 dpi are divided and connected to the four sub-manifolds 5a. That is, the individual flow paths 32 are formed in the extending direction of 5a at intervals of an average of 170 μm or less (25.4 mm / 150 = 169 μm intervals if 150 dpi).

  As a result, when ejecting droplets, air is ejected from the airflow ejection nozzle around the liquid spray nozzle at a speed substantially equal to the droplet ejection speed, so that the relative velocity with the airflow around the droplet is reduced. By lowering, deceleration due to air resistance can be mitigated. As a result, the control unit controls the discharge of the liquid droplets from each liquid discharge hole 8, so that even when the distance from the object is about 1 cm to 3 cm, compared to a conventional inkjet head without airflow jetting. Since the straightness of the liquid droplets is not easily lost, it is possible to print an image with high liquid accuracy. Further, as in Example 1, since mist-like droplets are less likely to adhere to the nozzle surface due to the air current, stable printing is possible without the droplets blocking the nozzles.

Further, since it is possible to select whether or not to discharge from each liquid discharge hole 8 when the distance is long, even when 600 dpi printing cannot be performed, a gradation that continuously changes the concentration of the liquid can be added, The application amount to the place where the concentration of application becomes thin can be increased depending on the shape, etc., and the application amount to the object can be made close to homogeneity. Further, the arrangement of the liquid discharge holes and the gas discharge holes will be described in detail. . As viewed from the opening side of the plurality of liquid ejection holes, the plurality of liquid ejection holes constitute a liquid ejection hole group in which the plurality of liquid ejection holes are long in one direction, and the plurality of gas ejection holes are the liquid ejection holes. The liquid application head according to claim 1, wherein the liquid application head is provided on both sides in the longitudinal direction of the group.

  5 (a), 5 (b), 6 (a), and 6 (b) are longitudinal sectional views showing an example of another liquid application head of the present invention.

  The flow path members 103, 203, 303, and 403 constituting the liquid application heads 102, 202, 302, and 402 have a laminated structure in which a plurality of plates are laminated. In these plates, plates 122, 222, 322, 422 to 131, 231, 331, 431 are laminated in order from the upper surface of the flow path members 103, 203, 303, 403. Similarly to the liquid application head 2, the liquid application heads 102, 202, 302, and 402 are supplied from the manifolds 105, 205, 305, and 206 through the liquid pressurization chambers 110, 210, 310, and 410, and the liquid discharge holes 108, 208, Individual flow paths 131, 231, 331, and 431 connected to 308 and 408 are provided. Similarly to the liquid application head 2, the liquid application heads 102, 202, 302, and 402 pass the gas sent from the outside through the gas flow path 181 and the openings of the liquid discharge holes 108, 208, 308, and 408. The gas is ejected from gas ejection holes 188, 288, 388, and 488 opened in the same direction.

  In the liquid application head 304, the plates 322 to 329 are plates constituting a liquid flow path, constitute a liquid flow path member 304, and the plates 329 to 331 are plates constituting a gas flow path 381. The gas flow path member 380 is configured.

  In the liquid application head 404, the plates 422 to 429 are plates constituting a liquid flow path, constitute a liquid flow path member 404, and the plates 429 to 431 are plates constituting a gas flow path 481. The gas flow path member 480 is configured.

  Similarly to the case of the liquid application head 2, piezoelectric actuator units 121, 221, 321, 421 are stacked on the flow path members 103, 203, 303, 403, and the piezoelectric actuator units 121, 221, 321, 421 are stacked. Liquid droplets are ejected from the liquid ejection holes 108, 208, 308, and 408 by the pressure applied by the displacement elements 150, 250, 350, and 450 provided.

  Fig.7 (a) is a top view which shows an example of the other liquid application head of this invention, (b) is the side view. 7A and 7B includes a liquid channel member 504 and a gas channel member 580. When viewed from the opening side of the liquid discharge hole 508, the opening of the gas ejection hole 588 is provided so as to surround an opening group of a plurality of liquid discharge holes formed by the openings of the liquid discharge holes 580.

  The gas flow path member 580 is stacked on the liquid flow path member 504. The flow path of such a flow path member can take the cross-sectional structure shown to FIG. 4 (a), (b), for example. By providing the gas flow path only in the gas flow path member 580, the liquid flow path member 580 can be stacked on the liquid flow path member 504 designed for printing or the like to obtain a liquid application head.

  FIG.7 (c) is a top view which shows an example of the other liquid application head of this invention, (d) is the side view. 7C and 7D includes a liquid channel member 604 and a gas channel member 680. When viewed from the opening side of the liquid discharge hole 608, the opening of the liquid discharge hole 608 constitutes a liquid discharge hole group that is long in one direction, and the gas discharge holes 688 are provided on both sides in the longitudinal direction of the opening group of liquid discharge holes. Yes. That is, the openings of the plurality of gas ejection holes 688 are provided along the one direction on both sides of the opening group of the liquid ejection holes.

  FIG.7 (e) is a top view which shows an example of the other liquid application head of this invention, (f) is the side view. 7 (e) and 7 (f) includes a liquid channel member 704 and a gas channel member 780. When viewed from the opening side of the liquid ejection hole 708, the opening of the gas ejection hole 788 is provided so as to surround an opening group of liquid ejection holes including the opening of the liquid ejection hole 780.

  The liquid discharge holes 508, 608, and 708 shown in FIGS. 7A, 7C, and 7E are fewer than the liquid discharge holes 8 connected to the liquid pressurizing chamber 10 shown in FIG. 3, but are shown in FIG. More liquid discharge holes 508, 608, and 708 may be arranged as the liquid discharge holes 8 connected to the liquid pressurizing chamber 10.

  FIG. 8A is a plan view showing an example of another liquid application head of the present invention. In the flow path member 803, a plurality of liquid discharge holes 808 and a plurality of gas ejection holes 888 are opened in the same direction. Four gas ejection holes 888 are provided centering on one liquid ejection hole 808, and the four gas ejection holes 888 are provided at equal intervals on the circumference of a circle centering on one liquid ejection hole 808. It has been.

  The number of gas ejection holes arranged for one liquid ejection hole may be other than four, and two or more liquid gas ejection holes may be provided at equal intervals on the circumference of a circle centered on the liquid ejection hole. . FIG. 8B is a plan view showing the arrangement of the liquid ejection holes 808-1 and the gas ejection holes 880-1, and three gas ejection holes 888-1 are provided for one liquid ejection hole 808-1. It is provided at equal intervals on the circumference of a circle C centered on the liquid discharge hole 808-1.

  FIG. 8C is a plan view showing an example of another liquid application head of the present invention, and FIG. 8D is a partial sectional view taken along line A in FIG. In the flow path member 903, a plurality of liquid discharge holes 908 and a plurality of gas ejection holes 988 are opened in the same direction. Four gas ejection holes 988 are provided around one liquid ejection hole 908, and the four gas ejection holes 988 are provided at equal intervals on the circumference of a circle centered on one liquid ejection hole 808. It has been.

  Although the embodiment has been described above, the present invention is not limited to this, and can be applied to modifications and improvements without departing from the gist of the present invention. For example, in the above-described embodiment, by first reducing the volume of the liquid pressurizing chamber 10, the volume of the liquid pressurizing chamber 10 is adjusted according to the reflected pressure after drawing the meniscus in the vicinity of the liquid discharge hole 8. Although the so-called “pulling discharge method” in which droplets are discharged in a large size has been described, first, the volume of the liquid pressurizing chamber 10 is increased, and a meniscus in the vicinity of the liquid discharge hole 8 is used as a liquid column from the liquid discharge hole 8. A so-called push-out ejection method in which the rear end of the liquid column is cut by reducing the volume of the liquid pressurizing chamber 10 in accordance with the pressure that has been extruded and reflected may be used.

DESCRIPTION OF SYMBOLS 1 ... Liquid application apparatus 2 ... Liquid application head 4 ... Liquid flow path member 5 ... Manifold 5a ... Sub manifold 5b ... (manifold) opening 6 ... Individual supply flow path DESCRIPTION OF SYMBOLS 7 ... Decender 8 ... Liquid discharge hole 9 ... Liquid pressurization chamber group 10 ... Liquid pressurization chamber 11a, b, c, d ... Liquid pressurization chamber row | line | column 12 ... Squeezing 15a , B, c, d: liquid discharge hole array 21: piezoelectric actuator unit 21a: piezoelectric ceramic layer (vibrating plate)
21b ... Piezoelectric ceramic layer 22-31 ... Plate 32 ... Individual flow path 34 ... Common electrode 35 ... Individual electrode 36 ... Connection electrode 50 ... Displacement element 70 ... Liquid Distributing flow path member 71b ... liquid introduction hole 80 ... gas flow path member 81 ... gas flow path 81b ... (gas flow path) opening 85, 86, 87 ... plate 88 ... Gas ejection hole 90 ... Case 91 ... Hole

Claims (6)

  A plurality of liquid pressurizing chambers, a plurality of pressurizing units that apply pressure to the liquids in the plurality of liquid pressurizing chambers, a plurality of liquid discharge holes respectively connected to the plurality of liquid pressurizing chambers, and a gas A plurality of gas ejection holes for ejecting, the plurality of gas ejection holes being on the same direction side as the plurality of liquid ejection holes, and the liquid ejected from the plurality of liquid ejection holes being the plurality of liquid ejection A liquid application head characterized by being opened so as to eject gas so as to be separated from the hole.   When viewed from the opening side of the plurality of liquid discharge holes, a liquid discharge hole group consisting of the plurality of liquid discharge holes extends in one direction, and the plurality of gas discharge holes sandwiches the liquid discharge hole group on both sides thereof. The liquid application head according to claim 1, wherein the liquid application head is provided along the one direction.   The plurality of gas ejection holes are provided so as to surround a liquid ejection hole group including the plurality of liquid ejection holes when viewed from the opening side of the plurality of liquid ejection holes. Liquid application head.   As viewed from the opening side of the plurality of liquid ejection holes, the plurality of gas ejection holes are equally spaced on the circumference of a circle centering on the one liquid ejection hole with respect to each of the plurality of liquid ejection holes. The liquid application head according to claim 1, wherein a plurality of the liquid application heads are provided.   5. The liquid application head according to claim 4, wherein axes of the plurality of gas ejection holes provided on a circumference of the circle are inclined toward a center side of the circle.   A liquid coating apparatus comprising: the liquid coating head according to claim 1; and a control unit that controls driving of the liquid coating head.

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