JP2008049569A - Liquid transfer apparatus and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid transfer technique using a piezoelectric actuator, which surely prevents a short circuit or discharge between two kinds of electrodes sandwiching a piezoelectric layer, while suppressing a further increase of an actuator displacement amount, and crosstalk. <P>SOLUTION: A conductive layer 33 is formed in the entire area facing a plurality of pressure chambers on the opposite side to the pressure chamber of a piezoelectric layer, and the conductive layer 33 is partially removed by a first annular groove 40 formed so as to surround an area facing the center of the pressure chamber, so that an discrete electrode 32 is formed inside the first annular groove 40. A second annular groove 41 which penetrates through both the conductive layer 33 and the piezoelectric layer are formed along the circumference of the pressure chamber in the area which faces the circumference of the pressure chamber on the opposite side to the pressure chamber of the piezoelectric layer, and is the outer area than the first annular groove 40. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a liquid transfer device for transferring a liquid and a method for manufacturing the liquid transfer device.

  Conventionally, as an ink jet head that ejects ink droplets, a piezoelectric actuator that applies ejection pressure to ink in an ink flow path by utilizing deformation (piezoelectric strain) of a piezoelectric element when an electric field is applied Some are equipped with.

  For example, a piezoelectric actuator of an ink jet head described in Patent Document 1 includes a plurality of piezoelectric sheets (piezoelectric layers) stacked across a plurality of pressure chambers, and a plurality of pressure chambers on the surface of the uppermost piezoelectric sheet. A plurality of individual electrodes arranged so as to face each other, a common electrode arranged across a plurality of pressure chambers between the uppermost piezoelectric sheet and the piezoelectric sheet therebelow and facing the plurality of individual electrodes; It has. This piezoelectric actuator has other deformation due to deformation (piezoelectric distortion) generated in the active portion of the uppermost piezoelectric sheet when a driving voltage is applied to the individual electrodes from the driving circuit via an FPC (Flexible Printed Circuit). The piezoelectric sheet is configured to bend and apply pressure to the ink in the pressure chamber.

  Incidentally, Patent Document 1 discloses the following process for forming a plurality of individual electrodes of the piezoelectric actuator described above. In this step, first, a conductive film is entirely formed on the surface of the uppermost piezoelectric sheet, and then, in a region facing the pressure chamber, an annular groove is formed in the conductive film by laser processing to form the conductive film. Partially remove. Thereby, the individual electrode insulated from the surrounding electrically conductive film is formed inside a groove part. Further, the groove portion is formed so as to enter the middle portion in the thickness direction of the piezoelectric sheet below the conductive film. Therefore, the deformation of the piezoelectric sheet is difficult to propagate between adjacent pressure chambers, and crosstalk is suppressed.

Japanese Unexamined Patent Publication No. 2004-160966 (FIGS. 21, 22, etc.)

  In the piezoelectric actuator described in Patent Document 1, the effect of suppressing crosstalk increases as the depth at which the groove portion enters the uppermost piezoelectric sheet increases. Further, since the piezoelectric sheet is more easily deformed as the groove is deeper, an effect of efficiently applying pressure to the ink in the pressure chamber with a low driving voltage can be obtained. However, if the groove is made too deep and the groove penetrates the uppermost piezoelectric sheet, the common electrode located on the back surface (lower surface) of the piezoelectric sheet is exposed in the groove, so that the surface of the piezoelectric sheet is exposed. There is a possibility that a short circuit or a discharge may occur between the individual electrode and the common electrode on the back surface. Therefore, in the piezoelectric actuator of Patent Document 1, the groove cannot be made too deep, and the effects of suppressing crosstalk and increasing the deformation amount of the piezoelectric sheet cannot be realized sufficiently.

  An object of the present invention is to provide a liquid transfer technique using a piezoelectric actuator that can reliably prevent a short circuit or discharge between two types of electrodes sandwiching a piezoelectric layer, while realizing further increase in displacement of the actuator and suppression of crosstalk. Is to provide.

  A liquid transfer device according to a first aspect of the present invention includes a flow path unit having a liquid flow path including a plurality of pressure chambers arranged along a plane, and a piezoelectric actuator that selectively applies pressure to the liquid in the plurality of pressure chambers. The piezoelectric actuator includes a diaphragm disposed on one surface of the flow path unit so as to cover the plurality of pressure chambers, and the plurality of pressures on a surface of the diaphragm opposite to the pressure chambers. A piezoelectric layer formed across a region facing the chamber; a first electrode disposed in a region facing the central portion of the pressure chamber on a surface of the piezoelectric layer opposite to the pressure chamber; and the piezoelectric layer A second electrode disposed on a surface of the layer facing the pressure chamber so as to face the first electrode, and facing the plurality of pressure chambers on a surface opposite to the pressure chamber of the piezoelectric layer; A conductive layer is formed in the region, and the inside of the pressure chamber The conductive layer is partially removed by a first annular groove formed so as to surround a region facing the portion, and the first electrode is insulated from the conductive layer outside the first annular groove. Further, on the surface of the piezoelectric layer on the side opposite to the pressure chamber, the conductive layer penetrates into a region facing the peripheral edge of the pressure chamber and outside the first annular groove. Then, at least a concave portion that has entered the middle portion in the thickness direction of the piezoelectric layer is formed along the peripheral edge of the pressure chamber.

  In this liquid transfer device, when a voltage is applied between the first electrode and the second electrode of the piezoelectric actuator corresponding to a certain pressure chamber, the piezoelectric layer is sandwiched between the first electrode and the second electrode. Distortion occurs, and accordingly, the diaphragm is deflected in a region facing the pressure chamber. At this time, since the volume in the pressure chamber changes according to the displacement of the diaphragm, pressure is applied to the liquid in the pressure chamber.

  Here, the first electrode is insulated from the surrounding conductive layer by the first annular groove. In addition, a concave portion that penetrates through the conductive layer and enters at least a middle portion in the thickness direction of the piezoelectric layer is formed in a region facing the peripheral portion of the pressure chamber of the piezoelectric layer and outside the first annular groove. ing. For this reason, the rigidity of the piezoelectric layer in the region facing the peripheral edge of the pressure chamber is reduced and is easily deformed, and an increase in the displacement of the diaphragm or a reduction in driving voltage can be realized. In addition, since the deformation of the piezoelectric layer in the region facing the pressure chamber is difficult to propagate to the region facing the adjacent pressure chamber, crosstalk can be suppressed. Further, the concave portion is formed so as to enter the piezoelectric layer at a position shifted outward from the first annular groove that divides the first electrode. Therefore, when the recess is formed deeply in order to sufficiently reduce the rigidity of the piezoelectric layer, even if the recess penetrates the piezoelectric layer and the second electrode is exposed, at the position of the first annular groove inside the recess. Compared to the case where the second electrode is exposed, the separation distance between the first electrode and the second electrode becomes longer, so that a short circuit or discharge between the two electrodes is prevented.

  According to a second aspect of the present invention, there is provided the liquid transfer device according to the first aspect, wherein the pressure chamber has a planar shape that is long in one direction, and the concave portion is opposed to at least the central portion of the pressure chamber. And is formed along two edges of the pressure chamber extending in the one direction. In this way, when the pressure chamber has a planar shape that is long in one direction, the diaphragm is particularly formed in the region of the piezoelectric layer facing the vicinity of the two edges extending in the longitudinal direction of the pressure chamber. It is possible to effectively increase the amount of displacement or reduce the driving voltage.

  In the liquid transfer device according to a third aspect of the present invention, in the first or second aspect of the invention, the plurality of recesses surround the first electrode on the surface of the piezoelectric layer opposite to the pressure chamber. The pressure chamber is arranged over substantially the entire circumference of the periphery of the pressure chamber. According to this configuration, the vibration plate and the piezoelectric layer are further easily deformed, and it is possible to further increase the displacement amount of the vibration plate or reduce the driving voltage.

  In the liquid transfer device according to a fourth aspect of the present invention, in the first or second aspect of the invention, the concave portion extends in an annular shape over substantially the entire circumference of the peripheral edge of the pressure chamber so as to surround the first electrode. It is an annular groove. According to this configuration, the vibration plate and the piezoelectric layer are further easily deformed, and it is possible to further increase the displacement amount of the vibration plate or reduce the driving voltage. Further, since the first electrode is doubly surrounded by the first annular groove and the second annular groove, the insulation with respect to the surrounding conductive layer becomes more reliable.

  According to a fifth aspect of the present invention, there is provided the liquid transfer device according to the fourth aspect, wherein at least a surface of the diaphragm opposite to the pressure chamber has electrical insulation, and the second electrode includes the pressure of the diaphragm. The surface opposite to the chamber is formed across the plurality of pressure chambers, and further, the surface of the piezoelectric layer opposite to the pressure chamber is more than the region facing the pressure chamber from the first electrode. A contact portion that is drawn to an outer region and is insulated from the conductive layer on the outer side together with the first electrode by the first annular groove, and the second annular groove is connected to the first electrode. Except for the connection part of the said contact part, it is formed so that the said 1st electrode may be surrounded.

  When the second electrode is provided on the surface of the diaphragm opposite to the pressure chamber (surface on the piezoelectric layer side), if the second annular groove is formed so as to penetrate the piezoelectric layer, The two electrodes may also be annularly separated by the second annular groove. Furthermore, since the second electrode is isolated when the second annular groove is formed so as to completely surround the first electrode and the contact portion, the second electrode corresponding to each of the plurality of pressure chambers, It is necessary to take measures such as connecting the wires individually to establish continuity. However, in the liquid transfer device according to the fifth aspect of the invention, the second annular groove is formed in an annular shape except for the connection portion between the first electrode and the contact portion. In other words, since the state in which the second electrode is electrically connected to the surrounding portion is maintained at least in a region facing the connection portion between the first electrode and the contact portion, the second electrode is not isolated. Therefore, the second electrodes corresponding to the plurality of pressure chambers can be electrically connected to each other, and a common potential can be easily applied.

  In the liquid transfer device according to a sixth aspect, in the fourth aspect, at least a surface of the diaphragm opposite to the pressure chamber has conductivity, and this surface also serves as the second electrode. Furthermore, the surface of the piezoelectric layer opposite to the pressure chamber is drawn from the first electrode to a region outside the region facing the pressure chamber, and the first annular groove allows the first annular groove to be drawn. A contact portion insulated from the conductive layer outside the electrode is formed together with the electrode, and the second annular groove is formed so as to completely surround the first electrode and the contact portion. Is.

  Thus, when the conductive surface of the surface of the diaphragm also serves as the second electrode, the second electrode is isolated even if the second annular groove is formed so as to completely surround the first electrode and the contact portion. There is nothing. Therefore, the first annular electrode and the contact portion are reliably insulated from the surrounding conductive layer by the double annular groove, and the second electrodes corresponding to the plurality of pressure chambers are electrically connected to each other to easily apply a common potential. be able to.

  According to a seventh aspect of the present invention, there is provided the liquid transfer device according to any one of the first to sixth aspects, wherein the recess penetrates the piezoelectric layer and reaches the diaphragm. Since the piezoelectric layer in the portion facing the pressure chamber is separated from the surrounding portion by the recess, the piezoelectric layer is more easily deformed.

  According to an eighth aspect of the present invention, there is provided the liquid transfer device according to any one of the first to seventh aspects, wherein an end of the piezoelectric layer in contact with the recess is in a region facing the pressure chamber. It is. Thus, since the end of the piezoelectric layer in contact with the recess is located in the region facing the pressure chamber, the piezoelectric layer is more easily deformed in the region facing the pressure chamber.

According to a ninth aspect of the invention, there is provided a liquid transfer device manufacturing method comprising: a flow path unit having a liquid flow path including a plurality of pressure chambers arranged along a plane; and the flow path unit so as to cover the plurality of pressure chambers. A diaphragm disposed on one surface; a piezoelectric layer formed on a surface of the diaphragm opposite to the pressure chamber; and a central portion of the pressure chamber on a surface of the piezoelectric layer opposite to the pressure chamber; A first electrode disposed in an opposing region; a second electrode disposed on a surface of the piezoelectric layer facing the pressure chamber so as to face the first electrode; and the liquid in the plurality of pressure chambers A method of manufacturing a liquid transfer device including a piezoelectric actuator that selectively applies pressure,
A piezoelectric layer forming step of forming the piezoelectric layer across a region facing the plurality of pressure chambers on a surface opposite to the pressure chambers of the diaphragm; and a surface of the piezoelectric layer opposite to the pressure chambers A conductive layer forming step for forming a conductive layer without gaps in a region facing the plurality of pressure chambers, and an annular groove surrounding a region facing the central portion of the pressure chamber for each of the plurality of pressure chambers Forming the first electrode insulated from the outer conductive layer inside the annular groove, and forming the first electrode isolated from the pressure chamber of the piezoelectric layer. A concave portion that penetrates the conductive layer and enters at least a middle portion in the thickness direction of the piezoelectric layer into a region facing the peripheral edge of the pressure chamber on the side surface and outside the annular groove. A recess forming step formed along the periphery of the chamber. And it is characterized in that is.

  In this method for manufacturing a liquid transfer device, at least the thickness direction of the piezoelectric layer passes through the conductive layer in a region facing the pressure chamber of the piezoelectric layer and outside the annular groove defining the first electrode. A recess is formed that enters partway. For this reason, it is possible to reduce the rigidity of the piezoelectric layer by this recess and to increase the displacement of the diaphragm or reduce the driving voltage. In addition, since the deformation of the piezoelectric layer in the region facing the pressure chamber is difficult to propagate to the region facing the adjacent pressure chamber, crosstalk can be suppressed. Further, the concave portion is formed so as to enter the piezoelectric layer at a position shifted outward from the annular groove separating the first electrode. For this reason, when the recess is formed deep in order to sufficiently reduce the rigidity of the piezoelectric layer, even if the recess penetrates the piezoelectric layer and the second electrode is exposed, the second electrode is formed in the annular groove inside the recess. Compared with the case where it is exposed, the separation distance between the first electrode and the second electrode becomes longer, so that a short circuit or discharge between the two electrodes is prevented.

  According to a tenth aspect of the present invention, in the ninth aspect of the invention, the annular groove and the recess are both formed by laser processing. In this case, since the process of forming the annular groove and the recess can be continued, the manufacturing cost increases, compared with the case where only the annular groove for forming the electrode is formed, or the annular groove and the recess are formed. The time required for the forming process is not prolonged.

  According to the present invention, the concave portion that penetrates the conductive layer and enters at least the middle portion in the thickness direction of the piezoelectric layer into the region facing the pressure chamber of the piezoelectric layer and outside the annular groove that divides the first electrode. Is formed. For this reason, the recess reduces the rigidity of the piezoelectric layer in the region facing the peripheral edge of the pressure chamber, thereby realizing an increase in the displacement of the diaphragm or a reduction in the driving voltage. Further, the concave portion is formed so as to enter the piezoelectric layer at a position shifted from the annular groove separating the first electrode. Therefore, even when the recess is formed deep in order to further reduce the rigidity of the piezoelectric layer, even if the recess penetrates the piezoelectric layer and the second electrode is exposed, the separation distance between the first electrode and the second electrode Therefore, short circuit and discharge between the electrodes are prevented.

  Embodiments of the present invention will be described. In the present embodiment, an ink jet head (liquid transfer device) that applies pressure to ink and transports it to a nozzle and ejects ink droplets onto the recording paper from the nozzle to record a desired image, character, or the like. It is an example to which the present invention is applied.

  First, an ink jet printer provided with the ink jet head of this embodiment will be briefly described. As shown in FIG. 1, an inkjet printer 100 includes a carriage 2 that can move in the left-right direction in FIG. 1, a serial type inkjet head 1 that is provided on the carriage 2 and that ejects ink onto recording paper P, A transport roller 3 for transporting the recording paper P forward in FIG. 1 is provided. The inkjet head 1 moves in the left-right direction (scanning direction) integrally with the carriage 2 and ejects ink onto the recording paper P from the nozzles 20 (see FIGS. 2 to 6) disposed on the lower surface thereof. Record desired characters and images. The recording paper P on which an image or the like is recorded by the inkjet head 1 is discharged forward (paper feeding direction) by the transport roller 3.

  Next, the inkjet head 1 will be described. 2 is a plan view of the inkjet head 1, FIG. 3 is a partially enlarged view of the inkjet head 1, and FIG. 4 is a partially enlarged view of the inkjet head 1 as viewed from the upper surface of the diaphragm. 5 is a cross-sectional view taken along line VV in FIG. 4, and FIG. 6 is a cross-sectional view taken along line VI-VI in FIG.

  As shown in FIGS. 2 to 6, the inkjet head 1 includes a flow path unit 4 in which an ink flow path (liquid flow path) including a nozzle 20 and a pressure chamber 14 is formed, and jetting pressure to ink in the pressure chamber 14. And a piezoelectric actuator 5 for imparting.

  First, the flow path unit 4 will be described. As shown in FIGS. 5 and 6, the flow path unit 4 includes a cavity plate 10, a base plate 11, a manifold plate 12, and a nozzle plate 13, and these four plates 10 to 13 are joined in a stacked state. Yes. Among these, the cavity plate 10, the base plate 11 and the manifold plate 12 are stainless steel plates, and ink flow paths such as a manifold 17 and a pressure chamber 14 described later can be easily etched in these three plates 10-12. It can be formed. The nozzle plate 13 is formed of, for example, a polymer synthetic resin material such as polyimide, and is bonded to the lower surface of the manifold plate 12. Or this nozzle plate 13 may be formed with metal materials, such as stainless steel, similarly to the three plates 10-12.

  As shown in FIGS. 2 to 6, among the four plates 10 to 13, the cavity plate 10 located at the uppermost position has holes through which a plurality of pressure chambers 14 arranged along a plane penetrate the plate 10. The plurality of pressure chambers 14 are partitioned by the partition wall 10a. The plurality of pressure chambers 14 are respectively covered with a diaphragm 30 and a base plate 11 described later from above and below. The plurality of pressure chambers 14 are arranged in a staggered pattern in two rows in the paper feeding direction (up and down direction in FIG. 2). Further, each pressure chamber 14 is formed in a substantially elliptical shape that is long in the scanning direction (left-right direction in FIG. 2) in plan view.

  As shown in FIGS. 3 to 5, communication holes 15 and 16 are formed at positions where the base plate 11 overlaps both end portions of the pressure chamber 14 in a plan view, respectively. The manifold plate 12 is formed with two manifolds 17 extending in the paper feeding direction so as to overlap with the communication hole 15 side portions of the pressure chambers 14 arranged in two rows in a plan view. These two manifolds 17 communicate with an ink supply port 18 formed in a vibration plate 30 described later, and ink is supplied to the manifold 17 from an ink tank (not shown) via the ink supply port 18. Furthermore, a plurality of communication holes 19 that are continuous with the plurality of communication holes 16 are also formed at positions where the manifold plate 12 overlaps the ends of the plurality of pressure chambers 14 opposite to the manifold 17 in plan view.

  Further, a plurality of nozzles 20 are formed at positions where the nozzle plate 13 respectively overlaps the plurality of communication holes 19 in plan view. As shown in FIG. 2, the plurality of nozzles 20 are arranged so as to overlap the end portions on the opposite side of the manifold 17 of the plurality of pressure chambers 14 arranged in two rows in a staggered manner along the paper feeding direction. Thus, two nozzle rows are configured.

  As shown in FIG. 5, the manifold 17 communicates with the pressure chamber 14 through the communication hole 15, and the pressure chamber 14 communicates with the nozzle 20 through the communication holes 16 and 19. As described above, a plurality of individual ink flow paths 21 extending from the manifold 17 to the nozzles 20 through the pressure chambers 14 are formed in the flow path unit 4.

  Next, the piezoelectric actuator 5 will be described. FIG. 7 is a partially enlarged view of FIG. As shown in FIGS. 3 and 5 to 7, the piezoelectric actuator 5 is continuously formed across the plurality of pressure chambers 14 on the vibration plate 30 covering the plurality of pressure chambers 14 and the upper surface of the vibration plate 30. The piezoelectric layer 31 and a plurality of individual electrodes 32 (first electrodes) disposed on the upper surface of the piezoelectric layer 31 are provided. The piezoelectric actuator 5 is configured to selectively apply pressure to the ink in the plurality of pressure chambers 14.

  The diaphragm 30 is a substantially rectangular metal plate in plan view, and is made of, for example, an iron-based alloy such as stainless steel, a copper-based alloy, a nickel-based alloy, or a titanium-based alloy. The vibration plate 30 is joined to the partition wall 10 a that partitions the plurality of pressure chambers 14 while being disposed on the upper surface of the cavity plate 10 so as to cover the plurality of pressure chambers 14. Further, the upper surface of the diaphragm 30 has conductivity, and is disposed across the plurality of pressure chambers 14 so as to generate an electric field in the thickness direction in the piezoelectric layer 31 between the plurality of individual electrodes 32 (second electrode). Electrode). Therefore, it is not necessary to provide a common electrode separately from the diaphragm 30, and the configuration of the piezoelectric actuator 5 is simplified correspondingly. Further, the diaphragm 30 as the common electrode is always held at the ground potential.

  On the upper surface of the vibration plate 30, a piezoelectric layer 31 made of a piezoelectric material mainly composed of lead zirconate titanate (PZT), which is a solid solution and is a ferroelectric substance, is formed of lead titanate and lead zirconate. Yes. The piezoelectric layer 31 is continuously formed so as to cover the plurality of pressure chambers 14.

  A conductive layer 33 made of a conductive material such as gold, copper, silver, palladium, platinum, or titanium is formed almost entirely on the upper surface of the piezoelectric layer 31 (the surface opposite to the pressure chamber 14). . A plurality of substantially elliptical first annular grooves 40 surrounding the region facing the central portion of the pressure chamber 14 are formed in the region facing the plurality of pressure chambers 14 of the conductive layer 33. Each first annular groove 40 penetrates through the conductive layer 33, and the conductive layer 33 is partially removed in the portion where the first annular groove 40 is formed. Then, on the upper surface of the piezoelectric layer 31, an individual electrode 32 (first electrode) having a substantially elliptical planar shape that is slightly smaller than the pressure chamber 14 in a region facing the central portion of the pressure chamber 14 inside the first annular groove 40. 1 electrode) is formed. A part of the first annular groove 40 protrudes from the longitudinal end portion (end portion on the through hole 15 side) of the pressure chamber 14 to the outer region beyond the peripheral edge of the pressure chamber 14 (protrusion portion 40a). That is, a plurality of contact portions 35 are formed in a substantially circular shape inside the protrusions 40 a of the plurality of first annular grooves 40, respectively, drawn from the plurality of individual electrodes 32 to the outer region beyond the periphery of the pressure chamber 14. Has been.

  As described above, since the first annular groove 40 is formed in an unbroken shape and penetrates the conductive layer 33 over the entire circumference, the individual electrode 32 and the contact point located inside the first annular groove 40 are contacted. The portion 35 is electrically insulated from the outer conductive layer 33 by the first annular groove 40. Note that the first annular groove 40 may not only penetrate the conductive layer 33 but may enter the middle portion in the thickness direction of the piezoelectric layer 31 below, but does not reach the diaphragm 30. Therefore, the upper surface of the diaphragm 30 as a common electrode is not exposed in the first annular groove 40, and a short circuit or a discharge occurs between the individual electrode 32 and the diaphragm 30 in the first annular groove 40. It is prevented.

  Contact points of a flexible wiring member such as a flexible printed circuit (FPC) (not shown) are joined to the plurality of contact portions 35, and the plurality of individual electrodes 32 include the wiring member and the plurality of contact portions. Each is electrically connected to a driver IC (not shown) via 35. When the piezoelectric actuator 5 is driven, a predetermined drive voltage is applied from the driver IC to the individual electrode 32 corresponding to the desired nozzle 20 that ejects ink.

  Further, as shown in FIG. 3 and FIGS. 5 to 7, in a region facing the peripheral edge of the pressure chamber 14 on the upper surface of the piezoelectric layer 31 and outside the first annular groove 40 described above, A second annular groove 41 that penetrates both the conductive layer 33 and the piezoelectric layer 31 and reaches the upper surface of the vibration plate 30 is formed along the periphery of the pressure chamber 14. The second annular groove 41 has a protruding portion 41 a that surrounds the protruding portion 40 a that delimits the contact portion 35. And it is formed without a cut | interruption over the perimeter of the periphery of the pressure chamber 14 so that the whole 1st annular groove 40 including the protrusion part 40a may be surrounded completely. Accordingly, since the piezoelectric layer 31 in the region facing the pressure chamber 14 inside the second annular groove 41 is completely separated from the outer portion, as described later, between the individual electrode 32 and the diaphragm 30. When the drive voltage is applied to the piezoelectric layer 31, the piezoelectric layer 31 is easily deformed.

  Even if the insulation of the individual electrode 32 and the contact portion 35 by the inner first annular groove 40 is insufficient, the outer second annular groove 41 causes the individual electrode 32 and the contact portion 35 to surround the surrounding conductive layer. 33 is reliably insulated from 33.

  In the form in which a common electrode straddling a plurality of pressure chambers is separately provided on the upper surface of the diaphragm 30, when the second annular groove 41 is formed so as to penetrate the piezoelectric layer 31, the common electrode is also in the second annular shape. The portion of the common electrode that is separated by the groove 41 and faces the individual electrode 32 may be isolated. In this case, wiring for applying a ground potential to each of these isolated common electrode portions is required. However, in the present embodiment, as described above, the diaphragm 30 is made of a conductive material (metal), and the upper surface also serves as a common electrode. Therefore, the common electrode portions respectively corresponding to the plurality of individual electrodes 32. Are not divided by the second annular groove 41 and are kept in a conductive state, and a ground potential can be easily applied to them in common.

  Further, the second annular groove 41 is formed at a position shifted outward from the first annular groove 40 that divides the individual electrode 32. Therefore, even if the second annular groove 41 is formed so as to penetrate the piezoelectric layer 31 and the upper surface of the diaphragm 30 as a common electrode is exposed in the second annular groove 41, the individual electrodes 32 and the upper surfaces of the diaphragm 30 A certain separation distance is secured.

  That is, as shown in FIG. 7, when the outer second annular groove 41 penetrates the piezoelectric layer 31, the separation distance between the individual electrode 32 and the upper surface of the diaphragm 30 is This is the sum of the shift amount d of the two annular grooves 40 and 41 in the plane direction and the thickness t of the piezoelectric layer 31. On the other hand, assuming that the inner first annular groove 40 penetrates the piezoelectric layer 31, the separation distance between the individual electrode 32 and the upper surface of the diaphragm 30 at this time is the thickness t of the piezoelectric layer 31. Become. That is, when the piezoelectric layer 31 is separated at the position of the second annular groove 41 on the outer side, the distance between the individual electrode 32 and the upper surface of the diaphragm 30 is larger than when the piezoelectric layer 31 is separated at the position of the first annular groove 41. Is increased by the amount of deviation d between the annular grooves 40 and 41, so that a short circuit or discharge between the individual electrode 32 and the diaphragm 30 is reliably prevented.

  Next, the operation of the piezoelectric actuator 5 during ink ejection will be described. When a driving voltage is selectively applied from the driver IC to the plurality of individual electrodes 32, the individual electrodes 32 on the upper side of the piezoelectric layer 31 to which the driving voltage is applied and the lower side of the piezoelectric layer 31 held at the ground potential. Since the potentials of the diaphragm 30 serving as the common electrode are different from each other, an electric field in the thickness direction is generated in the piezoelectric layer 31 in the drive region sandwiched between the individual electrode 32 and the diaphragm 30. When the polarization direction of the piezoelectric layer 31 and the direction of the electric field are the same, the piezoelectric layer 31 extends in the thickness direction, which is the polarization direction, and contracts in the horizontal direction. A region of the diaphragm 30 facing the pressure chamber 14 is displaced toward the pressure chamber 14, and the diaphragm 30 is deformed so as to be convex toward the pressure chamber 14. At this time, since the volume of the pressure chamber 14 is reduced, pressure is applied to the ink inside the pressure chamber 14, and ink droplets are ejected from the nozzle 20 communicating with the pressure chamber 14.

  Here, as described above, the second annular groove 41 penetrating both the conductive layer 33 and the piezoelectric layer 31 is formed in the region facing the peripheral edge of the pressure chamber 14 on the upper surface of the piezoelectric layer 31. The piezoelectric layer 31 located inside the second annular groove 41 is completely separated from the outer portion. Therefore, since the piezoelectric layer 31 is easily deformed when a driving voltage is applied between the individual electrode 32 and the diaphragm 30, an increase in the amount of displacement of the diaphragm 30 or a reduction in the driving voltage can be realized. . Further, since the deformation of the piezoelectric layer 31 in the region facing the pressure chamber 14 is difficult to propagate to the region facing the adjacent pressure chamber 14, crosstalk can be suppressed. Furthermore, since the individual electrode 32 and the contact portion 35 are doubly surrounded by the two types of annular grooves 40 and 41, the individual electrode 32 and the contact portion 35 are more reliably insulated.

  As shown in FIG. 7, the inner end E of the outer second annular groove 41 (that is, the end of the piezoelectric layer 31 separated by the second annular groove 41 in contact with the second annular groove 41) is the pressure chamber. It is preferable that it is located in the periphery of 14 or the inner side, that is, in the region facing the pressure chamber 14. In this case, when a drive voltage is applied to the individual electrode 32, the portion of the piezoelectric layer 31 cut off by the second annular groove 41 is accommodated in the pressure chamber 14 in plan view, so that the piezoelectric layer 31 is more It becomes easy to deform | transform and the displacement amount of the diaphragm 30 becomes still larger.

Next, the manufacturing method of the inkjet head 1 of this embodiment is demonstrated.
First, among the plates 10 to 13 constituting the flow path unit 4, the ink flow paths such as the pressure chamber 14 and the manifold 17 are formed on the three metal plates of the cavity plate 10, the base plate 11, and the manifold plate 12. Holes are formed by etching. Then, as shown in FIG. 8, a total of four metal plates of the cavity plate 10, the base plate 11, and the manifold plate 12 and the metal diaphragm 30 are joined by an adhesive or metal diffusion bonding.

  Next, as shown in FIG. 9, the piezoelectric layer 31 is continuously formed across the region of the upper surface of the vibration plate 30 facing the plurality of pressure chambers 14 (piezoelectric layer forming step). The piezoelectric layer 31 is formed by depositing piezoelectric material particles on the upper surface of the vibration plate 30. For example, it is possible to use an aerosol deposition method (AD method), a chemical vapor deposition (CVD) method, a sputtering method, or the like in which an aerosol composed of particles and a carrier gas is jetted onto a substrate to deposit the particles. Alternatively, the piezoelectric layer 31 may be formed by attaching a piezoelectric sheet obtained by firing a green sheet to the upper surface of the vibration plate 30 with an adhesive.

  Further, as shown in FIG. 10, the conductive layer 33 is formed without gaps in the region facing the plurality of pressure chambers 14 on the upper surface of the piezoelectric layer 31 (conductive layer forming step). The conductive layer 33 can be formed by a screen printing method, a vapor deposition method, a sputtering method, or the like.

  Next, as shown in FIG. 11, a first annular groove 40 is formed so as to surround a region facing the central portion of the pressure chamber 14 on the upper surface of the piezoelectric layer 31, and the conductive layer 33 is partially removed. The individual electrode 32 and the contact portion 35 insulated from the outer conductive layer 33 are formed inside the first annular groove 40 (individual electrode forming step). Further, a second annular groove 41 (concave portion) that penetrates the piezoelectric layer 31 and reaches the upper surface of the vibration plate 30 is provided along the periphery of the pressure chamber 14 in a region facing the periphery of the pressure chamber 14 on the upper surface of the piezoelectric layer 31. (Recess forming step).

  Here, both types of annular grooves 40 and 41 can be formed by laser processing. However, of the two annular grooves 40 and 41, the inner first annular groove 40 that divides the individual electrode 32 needs to be formed so as not to penetrate the piezoelectric layer 31, whereas the outer second annular groove 41 Since the piezoelectric layer 31 is formed deeper and penetrates the piezoelectric layer 31, the setting of the laser processing when forming the two annular grooves 40 and 41 is slightly different. Specifically, when forming the outer second annular groove 41, the laser intensity is increased, or the laser irradiation time and the number of scans are made longer than when the inner first annular groove 40 is formed. Just do it. It is also possible to form two kinds of annular grooves 40 and 41 having different depths by changing the focal length of the laser. Either of the two types of annular grooves 40 and 41 may be formed first, the inner first annular groove 40 may be formed, and then the outer second annular groove 41 may be formed thereafter. The reverse is also possible.

  As described above, when the two types of annular grooves 40 and 41 are both formed by laser processing, the formation process of these two types of annular grooves 40 and 41 can be performed continuously. Compared with the case where only the first annular groove 40 for forming the electrode 32 is formed (see the above-mentioned Patent Document 1), the manufacturing cost is increased and the time required for forming the annular grooves 40 and 41 is significantly increased. It doesn't get long.

  Finally, as shown in FIG. 12, the nozzle plate 13 made of synthetic resin is joined to the lower surface of the manifold plate 12 with an adhesive or the like to complete the manufacture of the inkjet head 1.

  In the manufacturing process of the inkjet head 1 described above, when the nozzle plate 13 is a metal plate made of stainless steel or the like, the vibration plate 30, the cavity plate 10, the base plate 11, the manifold plate 12, and the nozzle plate 13 are used. These five metal plates may be bonded at once by metal diffusion bonding.

  Next, modified embodiments in which various modifications are made to the embodiment will be described. However, components having the same configuration as in the above embodiment are given the same reference numerals and description thereof is omitted as appropriate.

  1] In the above-described embodiment, the conductive upper surface of the diaphragm also serves as a common electrode (second electrode) that applies a voltage to the piezoelectric layer so as to face a plurality of individual electrodes (first electrodes) ( 5 and FIG. 6), at least the upper surface of the diaphragm has electrical insulation, and a common electrode different from the diaphragm may be provided on the upper surface (Modification 1). As shown in FIGS. 13 and 14, when the diaphragm 30 is a metal plate, the insulating layer 50 is formed on the upper surface of the diaphragm 30 having conductivity, as in the above-described embodiment. It is necessary to insulate the plate 30 from the common electrode 34. The insulating layer 50 can be formed of, for example, an insulating ceramic material such as alumina or zirconia, or a synthetic resin material such as polyimide. On the other hand, when the vibration plate 30 is a plate formed of an insulating material, the above-described insulating layer 50 is unnecessary because the upper surface of the vibration plate 30 itself has electric insulation.

  Also in the first modified embodiment, the upper surface of the piezoelectric layer 31 is formed so as to surround the region facing the central portion of the pressure chamber 14, and the inner first annular groove 40 that divides the individual electrode 32, and this An outer second annular groove 41A surrounding the first annular groove 40 is formed. However, when the outer second annular groove 41A is formed by laser processing or the like so as to penetrate the piezoelectric layer 31 and completely surround the individual electrode 32 and the contact portion 35 as in the above embodiment, the piezoelectric layer It is also possible that the common electrode 34 positioned below 31 is completely separated from the surroundings by the second annular groove 41 and isolated. In such a case, if the isolated portion is always held at the ground potential, it is necessary to reliably establish conduction by individually connecting wirings to these portions, which complicates the structure.

  Therefore, in the first modification, as shown in FIG. 13, the outer second annular groove 41A penetrating the piezoelectric layer 31 is divided at the connection portion between the individual electrode 32 and the contact portion 35 and is substantially in plan view. It is formed in a C shape and surrounds the individual electrode 32 except for this connecting portion. Therefore, even if the second annular groove 41A is formed so as to penetrate the common electrode 34, the inner part of the common electrode 34 from the second annular groove 41A is not isolated, and at least the individual electrode 32 and the contact point Since the state of conduction with the surrounding portions is maintained in the region facing the connection portion with the portion 35, it becomes easy to always keep the portions of the common electrode 34 facing the plurality of individual electrodes 32 at the ground potential. .

  2] In the above embodiment, the second annular groove 41 that separates the piezoelectric layer 31 is formed along the periphery of the pressure chamber 14, but the groove does not necessarily have to be formed over the entire circumference of the pressure chamber 14. A groove may be formed in a part of the region facing the peripheral edge of the pressure chamber 14. For example, as shown in FIG. 15, two peripheral edges of the pressure chamber 14 that are long in one direction are opposed to each other across the central portion of the pressure chamber 14 and extend in the longitudinal direction. Two grooves 41B may be respectively formed along the edge (Modification 2). As described above, the groove 41B is formed particularly in the region facing the vicinity of the two edges extending in the longitudinal direction of the pressure chamber 14, and the rigidity of the piezoelectric layer 31 in this region is reduced, so that the displacement amount of the diaphragm 30 is reduced. Increase or reduction of drive voltage can be effectively realized.

  3] Instead of a continuously extending groove such as the second annular groove 41 of the above embodiment, a plurality of recesses are formed on the upper surface of the piezoelectric layer 31 over almost the entire periphery of the pressure chamber 14 as shown in FIG. 41C may be formed discretely (Modification 3). Further, as shown in FIG. 16, the plurality of recesses 41 </ b> C may be formed over substantially the entire circumference of the pressure chamber 14, but a part of the region facing the peripheral edge of the pressure chamber 14 (for example, the above-described change) Similarly to the second mode, the pressure chamber 14 may be formed in a region along two edges extending in the longitudinal direction. Even in such a configuration, since the rigidity of the piezoelectric layer 31 in the region facing the peripheral edge of the pressure chamber 14 is reduced, an effect of increasing the displacement amount of the diaphragm 30 or reducing the driving voltage can be obtained.

  4] In the embodiment and the modified embodiment thereof, the second annular groove 41 (FIG. 3), the groove 41B (FIG. 15), and the plurality of recesses 41C (FIG. ) Or the like passes through the piezoelectric layer 31 and reaches the upper surface of the vibration plate 30, but may only enter at least partway in the thickness direction of the piezoelectric layer 31. Even with such a configuration, the effect of lowering the rigidity of the piezoelectric layer 31 in the region facing the peripheral edge of the pressure chamber 14 can be obtained, so that the displacement amount of the vibration plate 30 is increased or the driving voltage is reduced. An effect is obtained.

  The above-described embodiment and its modifications are examples in which the present invention is applied to an inkjet head that ejects ink from nozzles. However, targets to which the present invention can be applied are not limited to such an inkjet head. For example, a conductive paste is sprayed to form a fine wiring pattern on the substrate, an organic light emitter is sprayed to the substrate to form a high-definition display, and an optical resin is sprayed to the substrate. The present invention can be applied to various droplet ejecting apparatuses for forming microelectronic devices such as optical waveguides.

  In addition to liquid droplet ejection devices, liquid transfer devices that transfer liquids such as chemicals and biochemical solutions inside the micro total analysis system (μTAS), and liquids that transfer liquids such as solvents and chemical solutions inside the microchemical system The present invention can also be applied to a liquid transfer device that transfers a liquid other than ink, such as a transfer device.

1 is a schematic configuration diagram of an inkjet printer according to an embodiment of the present invention. It is a top view of an inkjet head. FIG. 3 is a partially enlarged view of the inkjet head of FIG. 2. FIG. 4 is a partially enlarged view of the ink jet head viewed from the upper surface of the diaphragm. It is the VV sectional view taken on the line of FIG. It is the VI-VI sectional view taken on the line of FIG. It is an enlarged view of the actuator part of FIG. It is a figure which shows the joining process of a metal plate. It is a figure which shows a piezoelectric layer formation process. It is a figure which shows an individual electrode formation process. It is a figure which shows the process of forming two types of annular grooves in a piezoelectric layer. It is a figure which shows the joining process of a nozzle plate. 6 is a partially enlarged plan view of an ink jet head according to a first modification. FIG. It is the XIV-XIV sectional view taken on the line of FIG. 10 is a partially enlarged plan view of an inkjet head according to a modified embodiment 2. FIG. FIG. 6 is a partially enlarged plan view of an ink jet head according to a third modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet head 4 Flow path unit 5 Piezoelectric actuator 14 Pressure chamber 30 Diaphragm 31 Piezoelectric layer 32 Individual electrode 33 Conductive layer 34 Common electrode 35 Contact part 40 First annular groove 41, 41A Second annular groove 41B Groove 41C Recess

Claims (10)

A flow path unit having a liquid flow path including a plurality of pressure chambers arranged along a plane, and a piezoelectric actuator that selectively applies pressure to the liquid in the plurality of pressure chambers,
The piezoelectric actuator is
A diaphragm disposed on one surface of the flow path unit so as to cover the plurality of pressure chambers;
A piezoelectric layer formed across a region facing the plurality of pressure chambers on the surface of the diaphragm opposite to the pressure chambers;
A first electrode disposed in a region of the surface of the piezoelectric layer opposite to the pressure chamber and facing a central portion of the pressure chamber;
A second electrode disposed on the pressure chamber side surface of the piezoelectric layer so as to face the first electrode;
On the surface of the piezoelectric layer opposite to the pressure chamber, a conductive layer is formed in a region facing the plurality of pressure chambers, and is formed so as to surround a region facing the central portion of the pressure chamber. The conductive layer is partially removed by one annular groove, and the first electrode insulated from the conductive layer outside the first annular groove is formed inside the first annular groove,
Further, on the surface of the piezoelectric layer opposite to the pressure chamber, the region facing the peripheral portion of the pressure chamber and outside the first annular groove penetrates the conductive layer and at least the 2. A liquid transfer apparatus according to claim 1, wherein a concave portion that has entered the middle portion of the piezoelectric layer in the thickness direction is formed along the periphery of the pressure chamber. The pressure chamber has a long planar shape in one direction;
2. The recess according to claim 1, wherein the recess is formed along two edges of the pressure chamber that are opposed to each other with at least a central portion of the pressure chamber and extend in the one direction. The liquid transfer apparatus as described.   The plurality of recesses are arranged over substantially the entire periphery of the pressure chamber so as to surround the first electrode on a surface of the piezoelectric layer opposite to the pressure chamber. 3. The liquid transfer device according to 1 or 2.   3. The liquid transfer device according to claim 1, wherein the concave portion is a second annular groove extending in an annular shape over substantially the entire circumference of the pressure chamber so as to surround the first electrode. . At least the surface of the diaphragm opposite to the pressure chamber has electrical insulation,
The second electrode is formed across the plurality of pressure chambers on the surface of the diaphragm opposite to the pressure chambers,
Furthermore, the surface of the piezoelectric layer opposite to the pressure chamber is drawn from the first electrode to a region outside the region facing the pressure chamber, and the first electrode is formed by the first annular groove. And a contact portion insulated from the conductive layer on the outside thereof is formed,
5. The liquid transfer device according to claim 4, wherein the second annular groove is formed so as to surround the first electrode except for a connection portion between the first electrode and the contact portion. At least the surface of the diaphragm opposite to the pressure chamber has conductivity, and this surface also serves as the second electrode,
Furthermore, the surface of the piezoelectric layer opposite to the pressure chamber is drawn from the first electrode to a region outside the region facing the pressure chamber, and the first electrode is formed by the first annular groove. And a contact portion insulated from the conductive layer on the outside thereof is formed,
The liquid transfer device according to claim 4, wherein the second annular groove is formed so as to completely surround the first electrode and the contact portion.   The liquid transfer device according to claim 1, wherein the recess penetrates the piezoelectric layer and reaches the diaphragm.   The liquid transfer device according to claim 1, wherein an end of the piezoelectric layer in contact with the recess is in a region facing the pressure chamber. A flow path unit having a liquid flow path including a plurality of pressure chambers arranged along a plane;
A diaphragm disposed on one surface of the flow path unit so as to cover the plurality of pressure chambers, a piezoelectric layer formed on a surface of the diaphragm opposite to the pressure chambers, and the pressure of the piezoelectric layer A first electrode disposed in a region facing the central portion of the pressure chamber on the surface opposite to the chamber, and a first electrode disposed on the surface on the pressure chamber side of the piezoelectric layer so as to face the first electrode. A piezoelectric actuator having two electrodes and selectively applying pressure to the liquid in the plurality of pressure chambers;
A method of manufacturing a liquid transfer device comprising:
A piezoelectric layer forming step of forming the piezoelectric layer across a region facing the plurality of pressure chambers on a surface opposite to the pressure chambers of the diaphragm;
A conductive layer forming step of forming a conductive layer without gaps in a region facing the plurality of pressure chambers on the surface of the piezoelectric layer opposite to the pressure chambers;
For each of the plurality of pressure chambers, an annular groove surrounding a region facing the central portion of the pressure chamber is formed to partially remove the conductive layer, and an outer conductive layer is formed inside the annular groove. An electrode forming step of forming the first electrode insulated with
At least the thickness of the piezoelectric layer penetrating the conductive layer in a region opposite to the peripheral portion of the pressure chamber on the surface opposite to the pressure chamber of the piezoelectric layer and outside the annular groove A recess forming step of forming a recess entering the middle of the direction along the periphery of the pressure chamber;
A method for manufacturing a liquid transfer device.   The method for manufacturing a liquid transfer device according to claim 9, wherein both the annular groove and the recess are formed by laser processing.

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