JP6359908B2 - Inkjet head - Google Patents

Description

This specification discloses an ink jet head and a piezoelectric device including a piezoelectric element. The piezoelectric device includes actuators (piezoelectric actuator) and sensors (piezoelectric sensor, pyroelectric sensor). An inkjet head is an example of a piezoelectric actuator.

  An example of an ink jet head provided with a piezoelectric element is disclosed in Patent Document 1. The ink jet head of Patent Document 1 includes a silicon substrate in which a cavity (pressure chamber) as an ink reservoir is formed, a vibration film that forms a ceiling wall of the cavity, and a piezoelectric element that is disposed on the surface of the vibration film. The piezoelectric element includes a lower electrode, an upper electrode, and a piezoelectric film sandwiched between them. When a drive voltage is applied between the upper electrode and the lower electrode, the piezoelectric film is deformed by the inverse piezoelectric effect, and the vibration film is deformed together with the piezoelectric element accordingly. The deformation of the vibrating membrane causes a change in the volume of the cavity, whereby the ink in the cavity is pressurized and ejected.

The lower electrode, the upper electrode, and the piezoelectric film are formed in a substantially rectangular shape on the cavity, and are formed to have a substantially uniform thickness. As the piezoelectric film, a PZT (lead zirconate titanate) film formed by a sol-gel method or a sputtering method is used.
In the cut surface crossing the cavity, the side wall of the cavity and the lower surface of the vibration film each form a straight line, and the straight lines form a corner. That is, the side wall of the cavity and the lower surface of the diaphragm are flat surfaces, and corners are formed where they intersect.

JP 2013-215930 A

One embodiment of the present invention provides an ink jet head excellent in driving performance.
This specification also discloses a piezoelectric device having excellent driving performance or detection performance.

The inkjet head according to the present invention includes a substrate that defines a cavity in which ink is stored, a vibration film that is supported by the substrate and defines the cavity, and is disposed on the vibration film, and displaces the vibration film. A piezoelectric element that changes the volume of the cavity; and a weight that is disposed so as to locally increase an inertial mass in a central portion of the vibration film.
When a driving voltage is applied to the piezoelectric element, the piezoelectric element is deformed by the inverse piezoelectric effect, and the vibration film is displaced accordingly. Thereby, the volume of the cavity is changed, and the ink in the cavity is pressurized and ejected. Since the weight is disposed so as to locally increase the inertial mass at the center of the diaphragm, the displacement of the diaphragm can be increased. Thereby, an ink jet head excellent in driving performance can be realized.

In one embodiment of the present invention, the piezoelectric element includes a lower electrode, a piezoelectric film laminated on the lower electrode, and an upper part laminated on the piezoelectric film and facing the lower electrode with the piezoelectric film interposed therebetween. The piezoelectric film includes a thin film portion and a thicker film portion thicker than the thin film portion, and the thick film portion is the weight.
In this configuration, when a driving voltage is applied between the upper electrode and the lower electrode, the piezoelectric film is deformed, and the piezoelectric element is deformed accordingly. The weight is configured using the thick film portion of the piezoelectric film and is built in the piezoelectric element. Thereby, the weight can be provided with a simple configuration, and an ink jet head excellent in driving performance can be realized.

In one embodiment of the present invention, the piezoelectric element includes a lower electrode, a piezoelectric film laminated on the lower electrode, and an upper part laminated on the piezoelectric film and facing the lower electrode with the piezoelectric film interposed therebetween. The weight is disposed on the upper electrode.
In this configuration, when a driving voltage is applied between the upper electrode and the lower electrode, the piezoelectric film is deformed, and the piezoelectric element is deformed accordingly. Since the weight is arranged on the upper electrode, the arrangement of the upper electrode and the weight can be determined independently. Accordingly, it is possible to effectively apply a driving voltage to the piezoelectric film and determine the weight arrangement for realizing excellent driving performance. Thereby, the inkjet head excellent in drive performance is realizable.

In one embodiment of the present invention, a protective film is disposed between the upper electrode and the weight. Thus, the weight can be disposed on the upper electrode while protecting the upper electrode with the protective film.
In one embodiment of the present invention, the piezoelectric element includes a lower electrode, a piezoelectric film laminated on the lower electrode, and an upper part laminated on the piezoelectric film and facing the lower electrode with the piezoelectric film interposed therebetween. The weight is arranged in the same layer as the upper electrode.

In this configuration, since the weight is arranged in the same layer as the upper electrode, for example, the same material can be used for the upper electrode and the weight, and at least a part of them can be formed at the same time. Thereby, an ink jet head excellent in driving performance can be realized without greatly modifying the manufacturing process.
In one embodiment of the present invention, the piezoelectric element includes a lower electrode, a piezoelectric film laminated on the lower electrode, and an upper part laminated on the piezoelectric film and facing the lower electrode with the piezoelectric film interposed therebetween. The weight is a film made of the same material as the upper electrode and thicker than the upper electrode.

In this configuration, the upper electrode and the weight are made of the same material, and the weight of the weight is made larger than that of the upper electrode, so that the inertial mass at the center of the vibration film is locally increased. Therefore, it is possible to realize an ink jet head having excellent driving performance without greatly modifying the manufacturing process.
In one embodiment of the present invention, the upper electrode has an annular shape surrounding the weight.

In this configuration, since the annular upper electrode surrounds the weight, it is easy to place the weight near the center of the diaphragm. Thereby, the displacement of the vibration film can be increased. Further, since the upper electrode can have an annular shape surrounding the center of the vibration film, the piezoelectric element can be driven efficiently. Thus, an ink jet head with excellent driving performance can be realized. In one embodiment of the present invention, the weight and the upper electrode are set to the same potential.

In this configuration, since the driving voltage can be applied to the piezoelectric film through the weight, the weight also functions as an upper electrode. As a result, a driving voltage can be effectively applied to the piezoelectric film, and the displacement of the vibration film by the weight can be increased, so that an ink jet head having excellent driving performance can be realized.
In one embodiment of the present invention, an extraction electrode is formed from the weight so as to be drawn across the upper electrode, and the upper electrode is formed in a horseshoe shape having both ends spaced apart from each other with the extraction electrode interposed therebetween. Yes.

  In this configuration, since the upper electrode is formed in a horseshoe shape surrounding the weight, it is easy to place the weight near the center of the vibration film, and the upper electrode can effectively apply a driving voltage to the piezoelectric film. An ink jet head excellent in driving performance can be realized. In addition, since the extraction electrode extracted from the weight is not in contact with the upper electrode, a voltage can be applied independently to the weight and the upper electrode. Accordingly, a driving method that further improves the driving performance can be employed.

In one embodiment of the present invention, the cavity is rectangular in plan view, the weight extends along the longitudinal direction of the cavity, and is formed in a band shape having a width that is less than half the length of the cavity in the short direction. The space between the cavity side edge and the weight edge is secured near the center of the cavity in the short direction.
In this configuration, a belt-like weight is disposed at the center of a rectangular cavity in plan view, and a sufficient interval is provided from the cavity side edge to the weight. As a result, the displacement of the vibrating membrane can be effectively increased by the inertial mass of the weight, so that the drive performance of the inkjet head can be improved.

This specification discloses a vibrating membrane, a piezoelectric element disposed on the vibrating membrane, the inertial mass of the central portion of the vibrating membrane and a arranged mass so as to locally increase, the piezoelectric device .
The piezoelectric device can be a piezoelectric actuator or a piezoelectric sensor.
In the piezoelectric actuator, when a driving voltage is applied to the piezoelectric element, the piezoelectric element is deformed by the inverse piezoelectric effect, and the vibration film is displaced accordingly. Since the weight is disposed so as to locally increase the inertial mass near the center of the diaphragm, the displacement of the diaphragm can be increased. Thereby, a piezoelectric actuator excellent in driving performance can be realized.

In the piezoelectric sensor, when the vibration film is displaced, a voltage is generated in the piezoelectric element due to the piezoelectric effect. Since the weight is disposed so as to locally increase the inertial mass near the center of the diaphragm, the displacement of the diaphragm can be increased. Thereby, since a large voltage is generated in the piezoelectric element, a piezoelectric sensor excellent in detection performance (particularly sensitivity) can be realized.
The piezoelectric device can be modified in the same manner as in the case of the above-described ink jet head invention.

FIG. 1 is a schematic cross-sectional view for explaining the configuration of an inkjet head according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view (a cross-sectional view taken along the line II-II in FIG. 3) showing the configuration of the main part of the inkjet head. FIG. 3 is a schematic plan view of the inkjet head. FIG. 4 is a schematic enlarged sectional view taken along line IV-IV in FIG. FIG. 5 is a schematic perspective view of the inkjet head. FIG. 6 is an enlarged plan view showing a configuration example of the operation monitoring electrode provided in the piezoelectric element for driving the inkjet head. FIG. 7 is a schematic cross-sectional view for explaining the operating state of the inkjet head. FIG. 8 is a schematic cross-sectional view showing a configuration example of a piezoelectric film provided in the piezoelectric element. FIG. 9A and FIG. 9B are schematic plan views showing an example of seed layer patterns for forming a piezoelectric film. 10A to 10D show modifications regarding the arrangement of weights provided in the piezoelectric element. FIG. 11A to FIG. 11I show modifications regarding the starting point of displacement of the piezoelectric film. FIG. 12A and FIG. 12B show a modification relating to the feature of providing a piezoelectric element with a third electrode in addition to an upper electrode (first electrode) and a lower electrode (second electrode). 13A to 13D are schematic cross-sectional views showing modifications related to the shape of the cavity provided in the inkjet head. FIG. 14A and FIG. 14B show a modification regarding separation of the diaphragm for each cavity. FIG. 15A to FIG. 15C show a modified example related to the arrangement of the driving IC that drives the piezoelectric element.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic cross-sectional view for explaining the configuration of an inkjet head 1 according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view showing the configuration of the main part of the inkjet head 1.
The inkjet head 1 includes an actuator substrate 2, a nozzle substrate 3, a protective substrate 4, and a drive IC 5.

  The actuator substrate 2 is made of, for example, a silicon substrate and defines a plurality of cavities 6. The plurality of cavities 6 are arranged, for example, in a direction perpendicular to each paper surface of FIGS. 1 and 2. The actuator substrate 2 supports the vibration film 10 on the surface 2a. The vibrating membrane 10 forms the top wall of the cavity 6 and defines the cavity 6. A piezoelectric element 20 is disposed on the vibration film 10.

  The nozzle substrate 3 is bonded to the back surface 2 b of the actuator substrate 2. The nozzle substrate 3 is made of, for example, a silicon substrate, is bonded to the back surface 2 b of the actuator substrate 2, and defines the cavity 6 together with the actuator substrate 2 and the vibration film 10. The nozzle substrate 3 has a recess 33 that faces the cavity 6, and an ink discharge passage 31 is formed on the bottom surface of the recess 33. The ink discharge passage 31 penetrates the nozzle substrate 3 and has a discharge port 32 on the side opposite to the cavity 6. Accordingly, when the volume change of the cavity 6 occurs, the ink stored in the cavity 6 passes through the ink discharge passage 31 and is discharged from the discharge port 32.

  The protective substrate 4 is made of, for example, a silicon substrate. The protective substrate 4 is disposed so as to cover the piezoelectric element 20 and is bonded to the surface 2 a of the actuator substrate 2. The protective substrate 4 has an accommodation recess 42 in a facing surface 41 that faces the surface 2 a of the actuator substrate 2. A plurality of piezoelectric elements 20 respectively corresponding to the plurality of cavities 6 are housed in the housing recesses 42.

The drive IC 5 is mounted on the surface 2 a of the actuator substrate 2. A wiring 15 for connecting the piezoelectric element 20 and the drive IC 5 is formed on the actuator substrate 2. The wiring 15 is drawn out of the protective substrate 4. The driving IC 5 is bonded onto the land 16 of the wiring 15, and thereby the driving IC 5 is mounted on the actuator substrate 2.
The drive IC 5 is a semiconductor integrated circuit, and may have a form of a chip size package, for example. Specifically, the drive IC 5 includes a semiconductor substrate 51, an active region 52 disposed on the front surface 51 a side of the semiconductor substrate 51, and bumps 53 as output terminals disposed on the back surface 51 b of the semiconductor substrate 51. Transistors and other semiconductor devices are formed in the active region 52. A protective resin layer 54 and the like are disposed on the surface of the semiconductor substrate 51 so as to protect the active region 52. A through via 55 is formed in the semiconductor substrate 51. The through via 55 may be made of TSV (Through-Silicon Via). The through via 55 connects the active region 52 and the bump 53, and leads the output terminal of the electronic circuit formed in the active region 52 to the back surface 51 b of the semiconductor substrate 51. The back surface 51 b of the semiconductor substrate 51 is the first surface 5 a of the drive IC 5. The first surface 5 a faces the actuator substrate 2, and a plurality of bumps 53 constituting the output terminal of the drive IC 5 are concentratedly arranged. The number of bumps 53 substantially corresponds to the number of piezoelectric elements 20 provided on the actuator substrate 2. For example, if about 300 piezoelectric elements 20 are provided on the actuator substrate 2, the number of bumps 53 as output terminals is about 300. These bumps 53 are bonded onto the lands 16 of the wiring 15 corresponding to the plurality of piezoelectric elements 20. Thereby, the electrical connection between the driving IC 5 and the piezoelectric element 20 is achieved without using wire bonding or FPC (flexible printed circuit board).

  Input terminals 56 connected to the active region 52 are concentrated on the second surface 5b of the driving IC 5 located on the active region 52 side of the semiconductor substrate 51. The input terminal 56 may have a pad shape exposed from the protective resin layer 54. On the other hand, one end of the FPC 57 is fixed to the actuator substrate 2 in the vicinity of the drive IC 5. A plurality of input terminals 56 are connected to a plurality of core wires of the FPC 57 via bonding wires 58, respectively. The number of input terminals 56 is, for example, about 20, and the number of core wires of the FPC 57 is accordingly about 20. The FPC 57 is connected to a control IC (not shown), for example.

  An ink tank 8 that stores ink is disposed on the protective substrate 4. An ink supply path 43 is formed so as to penetrate the protective substrate 4. The ink supply port 8 a of the ink tank 8 is coupled to the ink supply path 43. The ink supply path 43 of the protective substrate 4 communicates with the ink supply path 44 in the actuator substrate 2. The ink supply path 44 communicates with the cavity 6. Therefore, the ink in the ink tank 8 as an ink supply source is supplied to the cavity 6 through the ink supply paths 43 and 44.

FIG. 3 is a schematic plan view of the inkjet head 1 (particularly, the actuator substrate 2). FIG. 4 is a schematic enlarged sectional view taken along line IV-IV in FIG. FIG. 5 is a schematic perspective view of the inkjet head 1 (particularly the actuator substrate 2). 2 described above is a cross-sectional view taken along the line II-II in FIG.
A vibration film forming layer 11 is formed on the surface 2 a of the actuator substrate 2. In the vibration film forming layer 11, the part constituting the bottom wall of the cavity 6, that is, the part defining the cavity 6 is the vibration film 10.

  In this embodiment, the cavity 6 is formed through the actuator substrate 2. The actuator substrate 2 further has an ink passage 50 communicating with the cavity 6. The ink passage 50 communicates with the cavity 6 and is formed to guide ink supplied from the ink tank 8 through the ink supply path 43 of the protective substrate 4 and the ink supply path 44 of the actuator substrate to the cavity 6. Yes. The ink introduced from the ink passage 50 into the cavity 6 moves along the ink circulation direction 45 parallel to the longitudinal direction of the cavity 6 and reaches the ink discharge passage 31.

  In the actuator substrate 2, a plurality of cavities 6 extend in parallel to each other and are formed in a stripe shape. The plurality of cavities 6 are formed at equal intervals with a minute interval (for example, about 30 μm to 350 μm) in the width direction thereof. Each of the cavities 6 has a rectangular shape elongated in the ink flow direction 45 from the ink passage 50 toward the ink discharge passage 31 in a plan view. The top surface portion of the cavity 6 has two side edges 6 a and 6 b along the ink circulation direction 45 and two end edges 6 c and 6 d along a direction orthogonal to the ink circulation direction 45. The ink passage 50 is divided into two passages at one end of the cavity 6 and communicates with the common ink passage 49. The common ink passage 49 communicates with the ink passages 50 corresponding to the plurality of cavities 6. The ink supply path 44 through which the ink from the ink tank 8 is guided communicates with the common ink path 49. As shown in FIGS. 3 and 5, a plurality of ink supply paths 44 are arranged at intervals along the common ink path 49. The ink supply path 44 is formed so as to penetrate the vibration film 10 (the wiring 15 where the wiring 15 is disposed) and further penetrate the actuator substrate 2 to the common ink path 49.

  Each cavity 6 is partitioned by the vibration film 10, the actuator substrate 2, and the nozzle substrate 3, and in this embodiment, is formed in a substantially rectangular parallelepiped shape. The length of the cavity 6 may be, for example, about 800 μm and the width thereof may be about 55 μm. The ink passage 50 is formed so as to communicate with one end portion in the longitudinal direction of the cavity 6 (in this embodiment, the end portion located on the side opposite to the ejection port 32). In this embodiment, the discharge port 32 of the nozzle substrate 3 is disposed near the other end in the longitudinal direction of the cavity 6.

  The vibration film 10 may be a single film of a silicon oxide film or a laminated film in which a silicon nitride film is laminated on a silicon oxide film. The cavity 6 does not need to penetrate the actuator substrate 2 and may be a recess dug from the lower surface side so as to leave a part on the piezoelectric element 20 side. In this case, the remaining part of the actuator substrate 2 constitutes a part of the vibration film 10. In this specification, the vibration film 10 means a top wall portion defining the cavity 6 in the vibration film forming layer 11.

  The thickness of the vibration film 10 is, for example, 0.4 μm to 2 μm. When the vibration film 10 is composed of a silicon oxide film, the thickness of the silicon oxide film may be about 1.2 μm. When the vibration film 10 is composed of a laminate of a silicon layer, a silicon oxide layer, and a silicon nitride layer, the thicknesses of the silicon layer, the silicon oxide layer, and the silicon nitride layer are about 0.4 μm, respectively. Also good.

  A piezoelectric element 20 is disposed on the vibration film 10. The vibration film 10 and the piezoelectric element 20 constitute a piezoelectric actuator (an example of a piezoelectric device). The piezoelectric element 20 includes a lower electrode 22 formed on the vibration film forming layer 11, a piezoelectric film 24 formed on the lower electrode 22, and an upper electrode 21 formed on the piezoelectric film 24. Yes. In other words, the piezoelectric element 20 is configured by sandwiching the piezoelectric film 24 between the upper electrode 21 and the lower electrode 22.

  The lower electrode 22 may have a two-layer structure in which, for example, a Ti (titanium) layer and a Pt (platinum) layer are sequentially stacked from the vibrating membrane 10 side. In addition, the lower electrode 22 may be formed of a single film such as an Au (gold) film, a Cr (chromium) layer, or a Ni (nickel) layer. The lower electrode 22 includes a main electrode portion 22A that is in contact with the lower surface of the piezoelectric film 24, and an extension 22B (see FIG. 4) that extends to a region outside the piezoelectric film 24.

As the piezoelectric film 24, for example, a PZT (PbZr _x Ti _1-x O ₃ : lead zirconate titanate) film formed by a sol-gel method or a sputtering method can be applied. Such a piezoelectric film 24 is made of a sintered body of metal oxide crystals. The thickness of the piezoelectric film 24 is preferably 1 μm to 5 μm. The total thickness of the vibration film 10 is preferably about the same as the thickness of the piezoelectric film 24 or about 2/3 of the thickness of the piezoelectric film 24.

The upper electrode 21 is formed in substantially the same shape as the piezoelectric film 24 in plan view. The upper electrode 21 may have a stacked structure in which a conductive oxide film (for example, IrO ₂ (iridium oxide) film) and a metal film (for example, Ir (iridium) film) are stacked.
The surface of the vibration film forming layer 11, the surface of the piezoelectric element 20, and the surface of the extension 22 </ b> B of the lower electrode 22 are covered with the hydrogen barrier film 12. The hydrogen barrier film 12 is made of, for example, Al ₂ O ₃ (alumina). Thereby, characteristic deterioration due to hydrogen reduction of the piezoelectric film 24 can be prevented. An insulating film 13 is laminated on the hydrogen barrier film 12. The insulating film 13 is made of, for example, SiO ₂ . A wiring 15 is formed on the insulating film 13. The wiring 15 may be made of a metal material containing Al (aluminum).

  One end of the wiring 15 is disposed above one end of the upper electrode 21. Between the wiring 15 and the upper electrode 21, a through hole (contact hole) 14 that continuously penetrates the hydrogen barrier film 12 and the insulating film 13 is formed. One end of the wiring 15 enters the through hole 14 and is connected to the upper electrode 21 in the through hole 14. One end portion of the wiring 15 is connected to one end portion of the upper electrode 21 (the end portion on one end edge side of the piezoelectric element 20), and is extended and drawn in a direction opposite to the ink circulation direction in a plan view. The land 16 is disposed at the tip of the wiring 15 and is integrated with the wiring 15. In the hydrogen barrier film 12 and the insulating film 13, an opening 17 (see FIG. 2) is formed in a region corresponding to the center of the surface of the upper electrode 21 (the portion surrounded by the peripheral edge on the surface of the upper electrode 21). Yes. The opening 17 is a rectangle that is long in the longitudinal direction of the upper electrode 21.

  As shown in FIG. 2, the extension 22 </ b> B of the lower electrode 22 is routed on the actuator substrate 2 and reaches the mounting area of the drive IC 5. In this mounting region, a land 22C for connecting the lower electrode 22 to the outside is disposed. The bumps 53 of the drive IC 5 are bonded to the land 22C. Thus, the connection between the lower electrode 22 and the driving IC 5 is achieved.

  The piezoelectric element 20 is formed at a position facing the cavity 6 with the vibration film 10 interposed therebetween. That is, the piezoelectric element 20 is formed so as to be in contact with the surface of the vibration film 10 opposite to the cavity 6. A vibration film forming layer 11 is formed on the actuator substrate 2, and the vibration film 10 is supported by a portion around the cavity 6 in the vibration film forming layer 11. Thus, the vibration film 10 is supported on the actuator substrate 2. The vibrating membrane 10 is flexible so that it can be deformed in the direction facing the cavity 6 (in other words, the thickness direction of the vibrating membrane 10).

  The drive IC 5 is connected to the upper electrodes 21 of the plurality of piezoelectric elements 20 via the bumps 53 and the wirings 15, and is connected to the lower electrode 22 common to the plurality of piezoelectric elements 20 via the other bumps 53. ing. Thereby, the drive IC 5 can apply a drive voltage between the upper electrode 21 and the lower electrode 22 of each piezoelectric element 20. When a drive voltage is applied from the drive IC 5 to the piezoelectric element 20, the piezoelectric film 24 is deformed by the inverse piezoelectric effect. Thereby, the vibrating membrane 10 is deformed together with the piezoelectric element 20, thereby causing a volume change of the cavity 6 and pressurizing the ink in the cavity 6. The pressurized ink passes through the ink discharge passage 31 and is discharged as fine droplets from the discharge port 32.

  The piezoelectric element 20 has a length in the ink distribution direction 45 (the same direction as the longitudinal direction of the vibration film 10) shorter than the length in the longitudinal direction of the vibration film 10, and has a rectangular shape in plan view. . As shown in FIG. 3, both end edges 20 d and 20 c in the longitudinal direction of the piezoelectric element 20 are corresponding to both corresponding end edges of the vibration film 10 (matching both end edges 6 c and 6 d of the cavity 6 in plan view). They are arranged inside with a predetermined distance d1 (for example, 5 μm). In addition, the piezoelectric element 20 has a width in the short direction perpendicular to the longitudinal direction of the vibration film 10 (direction parallel to the main surface of the actuator substrate 2) in the short direction of the vibration film 10 (the top surface portion of the cavity 6). It is formed narrower than the width of. Then, both side edges 20a and 20b along the longitudinal direction of the piezoelectric element 20 are set to a predetermined distance d2 (for example, with the side edges 6a and 6b of the cavity 6 in plan view) corresponding to the corresponding side edges of the diaphragm 10 (for example, in plan view). 5 μm) is opened and arranged inside.

  As shown in FIG. 3, the lower electrode 22 has a predetermined width in the ink circulation direction 45 and extends across the plurality of cavities 6 in a direction orthogonal to the ink circulation direction 45 in a plan view. It is a common electrode shared for the piezoelectric element 20. The first side 22a along the direction orthogonal to the ink flow direction 45 of the lower electrode 22 is aligned with a line connecting one end edge of the plurality of piezoelectric elements 20 in plan view. A second side 22b opposite to the first side 22a of the lower electrode 22 is outside the edge 6d of the cavity 6 corresponding to the other edge of the plurality of piezoelectric elements 20 (the edge of the vibration film 10) ( It is disposed on the downstream side of the ink distribution direction 45.

  The lower electrode 22 is pulled out in a direction along the surface of the vibration film forming layer 11 from the main electrode part 22A having a rectangular shape in plan view and constituting the piezoelectric element 20, and the top surface part of the cavity 6 (the vibration film 10). ) And an extension 22B extending outward from the periphery of the top surface of the cavity 6. The shape, size, and arrangement of the main electrode portion 22A in plan view are the same as those of the piezoelectric element 20.

  The extension 22B extends outward from the side edge of the top surface portion of the cavity 6 across the corresponding side edge of the top surface portion of the cavity 6 from each side edge of the main electrode portion 22A in plan view. The extension portion 22B is a region excluding the main electrode portion 22A in the entire region of the lower electrode 22. In the extension portion 22B, a cut-out portion 22D having a rectangular shape in plan view that penetrates the lower electrode 22 is formed on the downstream side in the ink circulation direction 45 of each piezoelectric element 20. Each cut portion 22D has two side edges (short sides) along the ink circulation direction 45 and two end edges (long sides) along a direction orthogonal to the ink circulation direction in plan view. One edge of the cut portion 22D is disposed at a position aligned with the edge of the piezoelectric element 20 (the edge on the downstream side of the main electrode portion 22A) in the ink flow direction, and the other edge is the edge of the vibrating membrane 10 It is arranged on the outer side (downstream side in the ink circulation direction 45). One side edge of the excision part 22D is arranged outside the one side edge of the vibration film 10, and the other side edge of the excision part 22D is arranged outside the other side edge of the vibration film 10. Therefore, in plan view, the end portion on the edge side of the vibrating membrane 10 is disposed inside the cut portion 22D.

The upper electrode 21 is formed in a rectangular shape having the same pattern as the main electrode portion 22A of the lower electrode 22 in plan view. That is, the shape, size, and arrangement of the upper electrode 21 in plan view are the same as those of the piezoelectric element 20.
The piezoelectric film 24 is formed in a rectangular shape having the same pattern as the upper electrode 21 in plan view, that is, the same pattern as the piezoelectric element 20. The lower surface of the piezoelectric film 24 is in contact with the upper surface of the main electrode portion 22 A of the lower electrode 22, and the upper surface of the piezoelectric film 24 is in contact with the lower surface of the upper electrode 21.

  A separation groove 60 is formed between adjacent cavities 6 in the extension 22B of the lower electrode 22. In this embodiment, the separation groove 60 extends linearly along the longitudinal direction of the cavity 6, and separates the lower electrode 22 into portions corresponding to the cavities 6. In this embodiment, both ends of the separation groove 60 are located outside in the longitudinal direction from both ends of the cavity 6. Therefore, the separation groove 60 is formed over a range from one end to the other end of the partition wall 61 (see FIG. 4) that partitions the adjacent cavity 6. As shown in FIG. 4, the separation groove 60 passes through the lower electrode 22 and the vibrating membrane 10 and reaches a partition wall 61 that partitions the adjacent cavities 6. The portion formed in the partition wall 61 of the separation groove 60 has a depth that exceeds one half of the height of the partition wall 61 (equal to the height of the cavity 6).

  Thus, the separation groove 60 separates the vibrating membrane 10 and the lower electrode 22 corresponding to the adjacent cavities 6 from each other. Thereby, the vibration film 10 of each cavity 6 can be displaced independently from the vibration film 10 of the adjacent cavity 6. Furthermore, since the separation groove 60 is formed to a depth reaching the partition wall 61 between the adjacent cavities 6, the partition wall 61 can be displaced with the displacement of the vibrating membrane 10.

  As shown in FIG. 4, the piezoelectric film 24 has a thick film portion 25 at the center in the short direction and thin film portions 26 at both sides in the short direction in a cross section along the short direction. . Each of the thick film portion 25 and the thin film portion 26 extends in a straight strip shape along the longitudinal direction of the cavity 6. The width of the thick film portion 25 is, for example, half or less of the length of the cavity 6 in the short direction. As shown in FIGS. 2 and 3, in the thick film portion 25, the length of the cavity 6 in the longitudinal direction is shorter than the length of the piezoelectric film 24 in the same direction. Thin film portions 26 are formed at both ends of the piezoelectric film 24. That is, the thin film portion 26 is formed in a band shape along the periphery of the piezoelectric film 24 so as to surround the thick film portion 25 in an annular shape. The thick film portion 25 functions as a weight that contributes to an increase in inertial mass in the vicinity of the center of the movable part including the piezoelectric element 20 and the vibration film 10. The upper electrode 21 is in contact with the thick film portion 25 and the thin film portion 26.

  At the boundary portion between the thick film portion 25 and the thin film portion 26, a step surface 28 (see FIGS. 2 and 4) corresponding to the difference in film thickness between the thick film portion 25 and the thin film portion 26 occurs. And the surface of the thick film part 25 and the level | step difference surface 28 cross | intersect at substantially right angle, and the bending part 27 is formed by it. As described above, since the thin film portion 26 is formed in an annular shape, the bent portion 27 is also formed in an annular shape. That is, the bent portion 27 has both side portions that extend along the longitudinal direction of the cavity 6 and both end portions that connect the both side portions at both ends in the longitudinal direction of the cavity 6. The bending portion 27 functions as a starting point where the displacement starts when the vibration film 10 is displaced together with the piezoelectric element 20 when a driving voltage is applied between the upper electrode 21 and the lower electrode 22.

  As shown in FIGS. 2 and 4, the inner wall surface 62 of the cavity 6 has a curved surface portion 62 </ b> A at a location in contact with the vibrating membrane 10. The curved surface portion 62 </ b> A preferably extends over the entire circumference of the peripheral edge where the vibrating membrane 10 and the inner wall surface 62 are in contact. The curved surface portion 62A is in contact with the vibration film 10 at the upper edge thereof and is continuous with the flat surface portion 62B at the lower edge thereof. The curved surface portion 62 </ b> A forms a concave curved surface that recedes toward the outside of the cavity 6 and toward the nozzle substrate 3 from the edge in contact with the vibration film 10. The flat surface portion 62 </ b> B is a part of the inner wall surface 62 of the cavity 6. The lower edge of the flat surface portion 62B is in contact with the nozzle substrate 3. The flat surface portion 62 </ b> B may be along the normal direction of the vibration film 10 or may be inclined with respect to the normal direction of the vibration film 10. For example, the flat surface portion 62 </ b> B is preferably inclined from the edge continuous with the curved surface portion 62 </ b> A toward the outside of the cavity 6 and toward the nozzle substrate 3 with respect to the normal direction of the vibration film 10.

  As shown in the enlarged plan view of FIG. 6, the upper electrode 21 is formed with a notch 35 that is inward from the periphery. In this embodiment, the notch portion 35 is arranged at one corner of the upper electrode 21 and extends linearly from the one end of the upper electrode 21 along the longitudinal direction of the cavity 6 by a predetermined length. The operation monitoring electrode 23 is disposed in the notch portion 35. The operation monitoring electrode 23 is in contact with the upper surface of the piezoelectric film 24. The operation monitoring electrode 23 is arranged in a region overlapping with the cavity 6 (in the notch portion 35) in plan view. Therefore, the operation monitoring electrode 23 faces the main electrode portion 22A of the lower electrode 22 with the piezoelectric film 24 interposed therebetween. The operation monitoring electrode 23 is formed in a U shape within the notch portion 35. A pair of terminal portions 23 a and 23 b are provided at both ends of the operation monitoring electrode 23. The pair of terminal portions 23 a and 23 b are outside the notch portion 35. In this embodiment, the pair of terminal portions 23 a and 23 b are disposed on the actuator substrate 2 in a region outside the cavity 6, more specifically in a region outside the protective substrate 4.

  The pair of terminal portions 23 a and 23 b are connected to the drive state monitoring circuit 36. The drive state monitoring circuit 36 includes a temperature detection circuit that measures the electrical resistance between the terminal portions 23 a and 23 b, that is, the electrical resistance of the operation monitoring electrode 23, thereby detecting the temperature of the piezoelectric film 24. When the piezoelectric film 24 expands and contracts due to the inverse piezoelectric effect, the temperature of the piezoelectric film 24 rises accordingly. The drive state monitoring circuit 36 detects the operation state of the piezoelectric element 20 by measuring the temperature of the piezoelectric film 24. If the temperature rise of the piezoelectric film 24 is not detected despite the drive voltage being applied to the piezoelectric element 20, there is a possibility that an abnormality has occurred in the piezoelectric element 20. Thus, in this embodiment, the operation monitoring electrode 23 is a temperature detection electrode used to detect the temperature of the piezoelectric film 24.

  The drive IC 5 drives the piezoelectric element 20 by applying a drive voltage between the upper electrode 21 and the lower electrode 22. Thereby, the piezoelectric film 24 is deformed by the inverse piezoelectric effect, and the vibration film 10 is displaced accordingly. As a result, the volume of the cavity 6 changes and the internal pressure increases, so that ink droplets are ejected from the ejection ports 32 formed in the nozzle substrate 3. On the other hand, ink from the ink tank 8 is supplied to the cavity 6 through the ink supply paths 43 and 44, the common ink path 49 and the ink path 50.

  In this embodiment, the piezoelectric film 24 has a thick film portion 25 disposed so as to correspond to the vicinity of the center of the vibration film 10. The thick film portion 25 has a function as a weight that locally increases the inertial mass near the center of the vibration film 10. The thick film portion 25 as the weight amplifies the displacement of the vibration film 10 by its inertial mass when the vibration film 10 is displaced by applying a driving voltage. Thereby, since the volume of the cavity 6 can be changed greatly, the inkjet head 1 excellent in drive performance is realizable.

Since the weight is formed by using the thick film portion 25 of the piezoelectric film 24, the piezoelectric element 20 incorporating the weight can be configured with a simple configuration.
The thick film portion 25 as a weight extends along the longitudinal direction of the cavity 6 having a rectangular shape in plan view, and is formed in a strip shape that is less than half of the length in the short direction of the cavity 6. Located near the center. Thereby, a sufficient interval from the side edge of the cavity 6 to the edge of the thick film portion 25 is secured. As a result, the displacement of the vibration film 10 can be effectively increased by the inertial mass of the thick film portion 25 as a weight, so that the drive performance of the inkjet head 1 can be improved.

  In this embodiment, a bent portion 27 is formed at the boundary between the thick film portion 25 and the thin film portion 26 of the piezoelectric film 24. The bent portion 27 is a unique shape portion in the piezoelectric film 24 and provides a starting point portion that is a starting point of displacement of the piezoelectric film 24. Therefore, when the piezoelectric film 24 is deformed (displaced), it can be guaranteed that the deformation (displacement) starts from the bent portion 27 as the starting point portion. Therefore, the deformation (displacement) of the piezoelectric film 24 is similarly caused in the plurality of piezoelectric elements 20 and the plurality of times of driving. Thereby, operation control is easy and highly accurate operation becomes possible. Therefore, the piezoelectric element 20 with high operation controllability can be realized, and the inkjet head 1 with high operation controllability can be provided accordingly. That is, it is possible to provide the inkjet head 1 capable of stable and accurate operation control.

  The bent portion 27 is provided with a convex portion (thick film portion 25) and a concave portion (thin film portion 26) projecting in the stacking direction of the upper electrode 21, the piezoelectric film 24 and the lower electrode 22 on the surface of the piezoelectric film 24. , Formed in the meantime. More specifically, assuming a rectangular outer contour line that encompasses the cross section of the piezoelectric film 24, a step is interposed at an intermediate position of the upper side of the rectangular outer contour line. As a result, a bent portion 27 is formed as a unique shape point, and the outer contour line is interrupted by the bent portion 27. As a result, the piezoelectric film 24 can be displaced from the bent portion 27 as a starting point.

The bent portion 27 is a kind of a hollow shape that is recessed along the stacking direction. The bent portion 27 is a fragile portion that is weaker than other portions in the piezoelectric element 20. Therefore, the bent portion 27 can surely give a starting point of displacement of the piezoelectric film 24.
Further, the bent portion 27 is in contact with the periphery of the piezoelectric element 20 and reaches an inner region than the periphery of the piezoelectric element 20. Thereby, the displacement of the piezoelectric film 24 is likely to start, and the displacement of the piezoelectric film 24 is easily propagated to the whole. Therefore, the piezoelectric element 20 with high responsiveness can be provided, and accordingly, the inkjet head 1 including the piezoelectric element 20 with high operation controllability can be realized.

Further, since the bent portion 27 is continuous with the periphery of the piezoelectric film 24, it can be formed simultaneously when the periphery of the piezoelectric film 24 is processed. Therefore, the inkjet head 1 including the piezoelectric element 20 with high operation controllability can be realized without increasing the number of manufacturing steps.
In addition, since the bending portion 27 serving as a starting point of the displacement is provided in the piezoelectric film 24, the displacement of the piezoelectric film 24 can be surely generated from the bending portion 27. The ink jet head 1 including the high piezoelectric element 20 can be realized.

Further, since the bent portion 27 has a shape extending along the peripheral edge of the piezoelectric element 20, the displacement of the piezoelectric film 24 can be reliably started in a wide range, and the operation controllability is accordingly improved. Ink jet head 1 having high piezoelectric element 20 can be realized.
Further, since the bent portion 27 is also located in the vicinity of both ends in the longitudinal direction of the cavity 6, the displacement of the piezoelectric film 24 can be started from the vicinity of both ends of the cavity 6. Thereby, it is possible to provide the inkjet head 1 that is excellent not only in operation controllability but also in response to drive voltage.

Further, since the bent portion 27 extends along the side along the longitudinal direction of the cavity 6, the displacement of the piezoelectric film 24 starts in a wide range in response to the drive voltage application. Thereby, it is possible to provide the inkjet head 1 that is excellent not only in operation controllability but also in response to drive voltage.
In this embodiment, the piezoelectric element 20 includes an operation monitoring electrode 23 as a third electrode in addition to an upper electrode 21 as a first electrode and a lower electrode 22 as a second electrode. Is in contact with the piezoelectric film 24. The state of the piezoelectric film 24 can be detected by the operation monitoring electrode 23. In this embodiment, the operation monitoring electrode 23 is a temperature detection electrode that detects the temperature of the piezoelectric film 24. That is, when the piezoelectric element 20 is operated by applying a driving voltage from the driving IC 5 to the upper electrode 21 and the lower electrode 22, the temperature of the piezoelectric film 24 is increased. Therefore, the operation of the piezoelectric element 20 can be confirmed by detecting the temperature of the piezoelectric film 24 by the operation monitoring electrode 23.

In this embodiment, since the operation monitoring electrode 23 is disposed in the same layer as the upper electrode 21, it can be formed in the same process as the upper electrode 21 when the piezoelectric element 20 is manufactured. Therefore, the inkjet head 1 provided with the piezoelectric element 20 having a state monitoring function can be provided without increasing the number of steps.
Further, in this embodiment, the upper electrode 21 has a notch portion 35 that is inward from the peripheral edge, and the operation monitoring electrode 23 is disposed so as to enter the notch portion 35. That is, the operation monitoring electrode 23 is disposed so as to enter the region where the upper electrode 21 and the piezoelectric film 24 are in contact with each other. Therefore, since the operation monitoring electrode 23 is in contact with the piezoelectric film 24 in a region where deformation for operation occurs, the state of the piezoelectric film 24 can be monitored more accurately. More specifically, the temperature in the operation region (deformation region) of the piezoelectric film 24 can be detected.

In this embodiment, the operation monitoring electrode 23 faces the lower electrode 22 with the piezoelectric film 24 interposed therebetween. Therefore, the operation monitoring electrode 23 is in contact with the piezoelectric film 24 in the operation region when the drive voltage is applied. Thereby, the state of the piezoelectric film 24 can be monitored more accurately. More specifically, the temperature in the operating region of the piezoelectric film 24 can be detected.
In this embodiment, the operation monitoring electrode 23 is disposed at a position facing the cavity 6. Therefore, the state of the piezoelectric film 24 can be detected in the operation region that is deformed for ink ejection. Thereby, the state of the piezoelectric film 24 can be detected more accurately.

  In this embodiment, the operation monitoring electrode 23 has two terminal portions 23a and 23b arranged at both ends. The driving state monitoring circuit 36 detects the electrical resistance between the two terminal portions 23a and 23b. The electrical resistance detected by the drive state monitoring circuit 36 corresponds to the temperature of the piezoelectric film 24. That is, the drive state monitoring circuit 36 includes a temperature detection circuit that detects the temperature of the piezoelectric film 24 in this embodiment. By detecting the temperature of the piezoelectric film 24, particularly the temperature of the operating region, the operating state of the piezoelectric film 24 can be monitored. Thereby, the operation state of the inkjet head 1 can be monitored.

When the piezoelectric film 24 is deformed when a driving voltage is applied between the upper electrode 21 and the lower electrode 22, an electromotive force generated by the deformation is generated between the operation monitoring electrode 23 and the lower electrode 22. Therefore, the operation state of the piezoelectric film 24 can be monitored by providing a detection circuit that detects a potential difference between the operation monitoring electrode 23 and the lower electrode 22.
In this embodiment, the inner wall surface 62 that defines the cavity 6 of the actuator substrate 2 has a curved surface portion 62 </ b> A that is continuous with the surface of the vibrating membrane 10 on the cavity 6 side. Therefore, even if air bubbles are included in the ink supplied from the ink tank 8, the air bubbles are not easily captured in the cavity 6, and are quickly discharged from the ejection port 32 together with the ink before forming a bubble reservoir. . Thereby, it is possible to suppress or prevent the occurrence of bubble accumulation in the cavity 6. As a result, since the volume change of the cavity 6 can be suppressed or prevented from being absorbed by the contraction of the bubbles, the ink discharge amount corresponding to the drive voltage applied to the piezoelectric element 20 can be realized with high accuracy. Thus, the ink jet head 1 with improved ink discharge controllability can be provided.

  In this embodiment, the curved surface portion 62 </ b> A formed on the inner wall surface 62 of the actuator substrate 2 is connected to the contact point with the vibration film 10 in a cross section intersecting the surface of the vibration film 10. A curved portion toward the contact is formed. In other words, the curved surface portion 62 </ b> A has a shape that recedes from the position in contact with the vibrating membrane 10 to the outside of the cavity 6. As a result, no corners are formed between the inner wall surface 62 of the actuator substrate 2 and the vibration film 10, so that bubble accumulation is unlikely to occur. Thereby, it is possible to provide the inkjet head 1 with improved ink discharge controllability.

In this embodiment, the inner wall surface 62 of the actuator substrate 2 has a flat surface portion 62B that is continuous with the curved surface portion 62A (on the nozzle substrate 3 side). Therefore, it is possible to suppress or prevent air bubbles in the ink from being captured by the inner wall surface 62 of the actuator substrate 2.
Furthermore, in this embodiment, the curved surface portion 62 </ b> A extends over the entire circumference of the boundary between the inner wall surface 62 that defines the cavity 6 of the actuator substrate 2 and the vibrating membrane 10. Thereby, bubble accumulation at the intersection of the inner wall surface 62 and the vibrating membrane 10 can be more effectively suppressed or prevented, and ink ejection control performance can be improved accordingly.

  In this embodiment, the separation groove 60 is formed between the adjacent cavities 6, and the separation groove 60 passes through the vibration film 10 and reaches the partition wall 61 that partitions the adjacent cavities 6. ing. As a result, the vibration film 10 of each cavity 6 is unconstrained from the other part of the vibration film 10 at the separation groove 60, so that the amount of displacement increases. Furthermore, since the separation groove 60 reaches the partition wall 61, the partition wall 61 is also displaced in accordance with the displacement of the vibrating membrane 10. That is, as shown in FIG. 7, when the vibration film 10 is deformed so as to protrude toward the ink cavity 6, the upper end portion of the partition wall 61 is pulled inside the cavity 6 by the vibration film 10 and deforms. Thereby, the volume of the cavity 6 largely changes between the state before deformation indicated by the two-dot chain line and the state after deformation indicated by the solid line. Accordingly, the ink discharge amount can be increased. From another viewpoint, since the volume change rate of the cavity 6 can be increased, the size of the cavity 6 for realizing a constant ink discharge amount can be reduced, and the inkjet head 1 can be downsized accordingly. Can be planned.

  In this embodiment, the separation groove 60 is continuously formed over a range from one end to the other end of the partition wall 61 that partitions the pair of adjacent cavities 6 (see FIG. 3). That is, a continuous separation groove 60 is formed over the entire boundary between adjacent cavities 6. Therefore, there are few restrictions from the periphery with respect to the vibration film 10 corresponding to each cavity 6. FIG. Further, the wide range of the partition wall 61 can be largely displaced with the displacement of the vibrating membrane 10. As a result, the ink discharge amount can be increased or the inkjet head 1 can be downsized.

In this embodiment, since the separation groove 60 penetrates the lower electrode 22, the restraint by the lower electrode 22 is also small. Accordingly, the displacement amount of the vibration film 10 is increased and the displacement amount of the partition wall 61 is also increased, so that the ink discharge amount can be increased or the ink jet head 1 can be downsized.
Furthermore, in this embodiment, the lower end of the separation groove 60 is located at a position lower than half the height of the partition wall 61, and the depth of the separation groove 60 is less than half the height of the partition wall 61. Also deep. Accordingly, the partition wall 61 can be greatly deformed along with the deformation of the vibrating membrane 10, and accordingly, the volume of the cavity 6 can be greatly changed. As a result, the ink discharge amount can be increased or the inkjet head 1 can be downsized.

  In this embodiment, the driving IC 5 for driving the piezoelectric element 20 is mounted on the actuator substrate 2, and the bumps 53 as output terminals of the driving IC are opposed to the first surface 5 a (facing surface) facing the actuator substrate 2. ) Is concentrated. These bumps 53 are bonded to lands 16 and 22C provided on the wiring on the actuator substrate 2. Thereby, a cable (for example, FPC) and a bonding wire for connecting the actuator substrate 2 and the output terminal of the drive IC 5 are not required. Thereby, the inkjet head 1 can be reduced in size.

In general, the drive IC 5 for driving the inkjet head 1 has more output terminals than input terminals. Therefore, a significant space saving can be achieved by eliminating the cables and bonding wires connected to the output terminals.
The centralized arrangement means that most output terminals (preferably all output terminals) included in the drive IC 5 are arranged on the first surface 5a. However, the input terminal is not prevented from being arranged on the first surface 5a.

  In this embodiment, an active region 52 is disposed on the semiconductor substrate 51 of the drive IC 5 on the opposite side to the actuator substrate 2, and the active region 52 and the output terminal (bump 53) are connected to the through via 55 (TSV). ). Thereby, the output terminals can be concentrated on the first surface 5a of the drive IC 5 on the actuator substrate 2 side. Since the driving IC 5 having the through via 55 does not need to route wiring from the active region 52 to the non-active surface side outside the semiconductor substrate 51, the driving IC 5 can be made small in size. Thereby, it can contribute to size reduction of the inkjet head 1.

  Further, the drive IC 5 includes a plurality of input terminals 56 disposed on the second surface 5b opposite to the first surface 5a. The plurality of input terminals 56 are connected to the FPC 57 via bonding wires 58. The FPC 57 is connected to a control IC, for example. Since the number of input terminals 56 of the drive IC 5 is not so large, the inkjet head 1 is not so large even if the connection between the input terminal 56 and the FPC 57 is performed by wire bonding.

FIG. 8 is a schematic cross-sectional view showing a configuration example of the piezoelectric film 24. A lower electrode 22 is formed on the vibration film 10, a piezoelectric film 24 is formed on the lower electrode 22, and an upper electrode 21 is formed on the piezoelectric film 24. The lower electrode 22 is made of, for example, a Pt / Ti laminated film having a Ti film as a lower layer and a Pt film as an upper layer. The upper electrode 21 is made of, for example, an Ir / IrO ₂ laminated film having an IrO ₂ film as a lower layer and an Ir film as an upper layer.

The piezoelectric film 24 includes an adhesion layer 71 formed on the surface of the lower electrode 22, a seed layer 72 formed on the adhesion layer 71, and a plurality of main firing unit PZT layers stacked on the seed layer 72. 73.
“The PZT layer of the main firing unit” is a main firing step in which one or a plurality of gelled films formed by gelating a coating film of a precursor solution containing PZT is laminated and then heat-fired by heat treatment. This is a PZT layer formed. The gelled film forming step for forming the gelled film includes a coating step for applying a precursor solution containing PZT to form a coated film, a drying step for drying the coated film, and a gel after the drying step. And a preliminary firing step. By performing the main baking after performing the gelled film forming step one or more times, the PZT layer 73 of the main baking unit is formed. That is, the PZT layer 73 of the main firing unit is formed by a sol-gel method.

  The precursor solution contains a solvent in addition to PZT. In the application process, for example, the precursor solution is spin-coated. The drying process is performed in a temperature environment of 140 ° C., for example. The drying process may be natural drying. In the temporary firing step, for example, a heat treatment at a temperature (for example, 300 ° C.) lower than the melting point (327.5 ° C.) of lead may be performed on the coating film after the drying step. In the main baking step, for example, heat treatment at 700 ° C. is performed on the gelled coating film. The main firing step may be performed by RTA (Rapid Thermal Annealing).

The adhesion layer 71 is a layer provided to improve adhesion between the piezoelectric film 24 and the lower electrode 22. The adhesion layer 71 is made of, for example, a TiO layer. The TiO layer can be formed by, for example, a sol-gel method or a sputtering method.
The seed layer 72 is a layer provided in order to improve the crystallinity and adhesion of PZT, and is composed of, for example, a PZT seed layer made of PZT or a TiO seed layer made of TiO. The seed layer 72 is preferably formed by sputtering, but may be formed by sol-gel method. When formed by sputtering, an electric field is generated in the vicinity of the lower electrode 22 at the time of formation, so that crystals grow in a polarized state and a seed layer 72 having a uniform orientation direction is obtained. In this case, the seed layer 72 is a columnar texture layer composed of crystal grains grown in a columnar shape in the normal direction of the lower electrode 22. In the case of the sol-gel method, the precursor solution is applied, the coating film is dried, and the coating film after drying is gelated in order to form a single gelled coating film. A seed layer 72 is formed. The thickness of the seed layer 72 is, for example, about 5 nm to 500 nm.

In this embodiment, a seed layer 72 (for example, a PZT seed layer) is formed by sputtering, and a plurality of PZT layers 73 of a main firing unit are sequentially stacked on the seed layer 72 by repeating the sol-gel method a plurality of times. Is done. The seed layer formed by the sputtering method forms a columnar structure layer 75, and the PZT layer 73 of the main firing unit formed by the sol-gel method forms an amorphous structure layer 76.
The piezoelectric film 24 thus formed is laminated in contact with the seed layer 72 composed of the columnar structure layer 75 and the seed layer 72, and a plurality of main firings constituting the amorphous structure layer 76 of the piezoelectric material. Unit PZT layer 73. The columnar texture layer 75 has a uniform crystal orientation. The amorphous structure layer 76 has a dense film quality and is excellent in pressure resistance. Since the amorphous structure layer 76 is laminated in contact with the columnar structure layer 75, it follows the orientation of the columnar structure layer 75. Therefore, the piezoelectric film 24 in which the columnar structure layer 75 and the amorphous structure layer 76 are laminated is excellent in both orientation and pressure resistance. Thereby, the inkjet head 1 driven by the piezoelectric element 20 having the piezoelectric film 24 excellent in orientation and pressure resistance can be provided.

  When the columnar texture layer 75 has a <100> orientation, the amorphous texture layer 76 also has a strong tendency to be oriented. In this case, the piezoelectric film 24 has a property that the displacement due to the inverse piezoelectric effect at the time of voltage application is large and the electromotive force due to the piezoelectric effect at the time of deformation is large. On the other hand, when the columnar structure layer 75 has the <111> orientation, the amorphous structure layer 76 also has a strong tendency to be oriented. In this case, the piezoelectric film 24 has a property that it is easy to control the magnitude of displacement due to the piezoelectric effect when a voltage is applied, and the electromotive force due to the piezoelectric effect during deformation is stable.

  Therefore, by controlling the orientation of the columnar structure layer 75 according to the required characteristics, the ink jet head 1 having excellent characteristics can be realized. For example, when the columnar tissue layer 75 is in the <100> orientation, the displacement of the vibration film 10 can be increased, so that the inkjet head 1 having excellent driving performance can be provided. In addition, when the columnar tissue layer is in the <111> orientation, the magnitude of displacement due to the piezoelectric effect at the time of voltage application can be easily controlled, so that the inkjet head 1 having excellent controllability can be provided.

  As described above, the columnar structure layer 75 can be formed by a sputtering method, whereby the columnar structure layer 75 with high orientation controllability can be formed. Then, by forming the piezoelectric material in a polarized state, the columnar structure layer 75 with high orientation control can be formed. More specifically, the columnar tissue layer 75 with uniform orientation can be formed by depositing a piezoelectric material by sputtering with an electric field applied. As described above, the amorphous structure layer 76 can be formed by a sol-gel method, whereby the dense and high withstand pressure amorphous structure layer 76 can be formed.

If the columnar structure layer 75 and the amorphous structure layer 76 are made of the same kind of piezoelectric material (for example, PZT), the orientation of the amorphous structure layer 76 can be more strictly controlled, and thus the orientation and pressure resistance are excellent. Further, the piezoelectric film 24 can be provided.
Such a piezoelectric film 24 can also be applied to piezoelectric actuators other than the inkjet head 1, and piezoelectric sensors represented by microphones and ultrasonic sensors. That is, in the piezoelectric actuator, by applying a driving voltage between the upper electrode 21 and the lower electrode 22, the piezoelectric film 24 can be deformed by the inverse piezoelectric effect. In the piezoelectric sensor, a voltage can be generated between the upper electrode 21 and the lower electrode 22 by the piezoelectric effect by deforming the piezoelectric film 24 by an external force. By controlling the orientation of the columnar tissue layer 75 in accordance with the required characteristics, a piezoelectric actuator or piezoelectric sensor having excellent characteristics can be realized. For example, when the columnar tissue layer 75 is in the <100> orientation, the piezoelectric film 24 has a property that the displacement due to the inverse piezoelectric effect at the time of voltage application is large and the electromotive force due to the piezoelectric effect at the time of deformation is large. Therefore, it is possible to realize a piezoelectric actuator with excellent driving performance and a highly sensitive piezoelectric sensor. In addition, when the columnar tissue layer 75 is in the <111> orientation, the piezoelectric film 24 can easily control the magnitude of displacement due to the piezoelectric effect during voltage application, and can stabilize the electromotive force due to the piezoelectric effect during deformation. Have Therefore, a piezoelectric actuator with excellent controllability and a piezoelectric sensor with stable output can be realized.

  9A and 9B are schematic plan views for explaining the characteristics of the pattern of the seed layer 72. FIG. Although the seed layer 72 may be formed over the entire surface of the lower electrode 22, as shown in FIGS. 9A and 9B, the seed layer 72 is locally shown (hatched for clarity). May be formed. That is, the seed layer 72 is formed in the seed formation region 81 set on the lower electrode 22 (particularly the main electrode portion 22A) as the underlayer, and the seed layer 72 is formed in the seed non-formation region 82 set on the lower electrode 22. It may not be formed. The piezoelectric material layer may be formed across the seed formation region 81 and the seed non-formation region 82.

  The piezoelectric material formed in contact with the seed layer 72 and the piezoelectric material formed in contact with the base layer (lower electrode 22) without contacting the seed layer 72 have different orientations and different characteristics accordingly. Therefore, when a seed formation region 81 in which the seed layer 72 is formed and a seed non-formation region 82 in which the seed layer 72 is not formed and a piezoelectric material layer is formed so as to straddle these regions, A piezoelectric film 24 having various properties can be obtained. Therefore, the piezoelectric film 24 having various properties can be obtained by variously determining the area ratio between the seed formation region 81 and the seed non-formation region 82 and the arrangement pattern. Therefore, it is possible to provide the piezoelectric film 24 whose characteristics are controlled according to the application.

  The piezoelectric film 24 includes a first alignment region formed in the seed formation region 81 and oriented in the first direction, and a second alignment region formed in the seed non-formation region 82 and oriented in the second direction. The first alignment region and the second alignment region have different properties according to their alignment directions. Therefore, the piezoelectric film 24 having various properties can be provided according to the area ratio, arrangement pattern, and the like of the seed formation region 81 and the seed non-formation region 82.

  The orientation direction (first direction) of the piezoelectric material layer in the seed formation region 81 is, for example, <100>. The orientation direction (second direction) of the piezoelectric material layer in the seed non-formation region 82 is, for example, <111>. More specifically, if there is a Pt layer on the surface of the lower electrode 22, a <111> oriented piezoelectric material layer is formed under the influence of the orientation. The <100> oriented piezoelectric material layer has a large reverse piezoelectric effect. Therefore, when applied to the piezoelectric element 20, a large displacement characteristic can be obtained, and the discharge amount of the inkjet head 1 can be increased. On the other hand, the piezoelectric performance of the <111> oriented piezoelectric material layer is stable. Accordingly, when applied to the piezoelectric element 20, stable driving performance can be obtained, so that the ejection amount of the inkjet head 1 can be controlled with high accuracy and stability. Therefore, by mixing the regions of the piezoelectric material layers of those orientations, it is possible to achieve both stability and strength of the piezoelectric performance according to required characteristics. That is, by setting the area ratio and arrangement pattern of the first alignment region and the second alignment region in accordance with the required control accuracy and the required displacement, it is possible to provide the inkjet head 1 having the required drive performance.

  In the example of FIGS. 9A and 9B, the seed formation region 81 and the non-seed formation region 82 include a total of three or more separated regions. The seed formation regions 81 and the seed non-formation regions 82 are alternately arranged on the lower electrode 22 (main electrode portion 22A). As described above, since the seed formation regions 81 and the non-seed formation regions 82 are alternately arranged, the piezoelectric material layer easily has an intermediate property. Thereby, the piezoelectric film 24 with high characteristic controllability can be provided.

In the example of FIG. 9A, seed formation regions 81 and non-seed formation regions 82 are alternately arranged in stripes. As a result, the degree of mixing of the orientation increases, so that it is possible to provide the piezoelectric film 24 with higher characteristic controllability.
More specifically, in the example of FIG. 9A, the seed formation regions 81 and the seed non-formation regions 82 are each formed in a rectangular shape, and are arranged alternately by overlapping one side of adjacent rectangles. The plurality of seed formation regions 81 and the plurality of seed non-formation regions 82 form a rectangular region corresponding to the main electrode portion 22A of the lower electrode 22 as a whole. As described above, the rectangular seed formation regions 81 and the rectangular seed non-formation regions 82 are alternately arranged to provide a rectangular piezoelectric film 24 with high characteristic controllability.

  In the example of FIG. 9B, an annular seed formation region 81 and an annular seed non-formation region 82 disposed inside or outside the annular seed formation region 81 are provided. By disposing the annular seed formation region 81 and the annular seed non-formation region 82 on the inner side or the outer side, it is easy to obtain intermediate characteristics according to the respective orientations. Thereby, the piezoelectric film 24 with high characteristic controllability can be provided.

In addition, by having the annular seed formation region 81, the influence of the characteristics according to the orientation affected by the seed layer 72 can be exerted on a wide range of the piezoelectric film 24, thereby having high characteristic controllability. The piezoelectric film 24 can be provided.
Similarly, by having the annular seed non-formation region 82, the influence of the characteristics according to the orientation directly affected by the underlayer (lower electrode 22) can be exerted on a wide range of the piezoelectric film 24. Thereby, the piezoelectric film 24 with high characteristic controllability can be provided.

The seed layer of each pattern in FIGS. 9A and 9B may be formed by a sputtering method or a sol-gel method. The seed layer 72 is preferably formed of a piezoelectric material (for example, PZT).
10A, FIG. 10B, FIG. 10C, and FIG. 10D show modified examples related to the arrangement of the weights.
In the configuration of FIG. 10A, the upper electrode 21 is covered with the protective film 19, and the weight 65 is disposed on the protective film 19. In this example, the protective film 19 is a laminated film of the hydrogen barrier film 12 and the insulating film 13. The weight 65 may be made of a metal film. The weight 65 is disposed at a position near the middle with respect to the lateral direction of the cavity 6 and extends along the longitudinal direction of the cavity 6. The weight 65 is formed in a strip shape having a width shorter than the width of the cavity 6 in the short direction (preferably about a half of the width of the cavity 6). Therefore, a sufficient interval is secured between the weight 65 and the side edge of the vibration film 10 so as not to inhibit the displacement of the vibration film 10. Further, the weight 65 is shorter than the length of the cavity 6 with respect to the longitudinal direction of the cavity 6, and a sufficient interval is secured between both ends of the weight 65 and both ends of the cavity 6 so as not to disturb the displacement of the vibration film 10. Has been. Therefore, there is no possibility that the displacement of the vibration film 10 is largely restrained by the weight 65.

  In this configuration, since the weight 65 is arranged on the upper electrode 21, the arrangement of the upper electrode 21 and the weight 65 can be determined independently. Thereby, the driving voltage can be effectively applied to the piezoelectric film 24, and the arrangement of the weights 65 for realizing excellent driving performance can be determined. Thereby, the inkjet head 1 excellent in drive performance is realizable. In addition, since the protective film 19 is disposed between the upper electrode 21 and the weight 65, the weight 65 can be disposed thereon while protecting the upper electrode 21 with the protective film 19.

  In the configuration of FIG. 10B, the weight 65 is arranged in the same layer as the upper electrode 21. The weight 65 is made of the same material (metal material) as the upper electrode 21 and is formed of a film that is thicker than the upper electrode 21. The weight 65 is arranged in the vicinity of the center of the cavity 6 in plan view, and the upper electrode 21 has an annular (square annular) shape surrounding the weight 65. There is a gap between the upper electrode 21 and the weight 65, which are separated from each other.

In this configuration, since the weight 65 is disposed in the same layer as the upper electrode 21, the same material can be used for the upper electrode 21 and the weight 65, and at least a part of them can be formed simultaneously. Then, by making the film thickness of the weight 65 larger than that of the upper electrode 21, the inertial mass near the center of the vibration film 10 is locally increased. Thereby, the inkjet head 1 excellent in driving performance can be realized without greatly modifying the manufacturing process. Further, since the annular upper electrode 21 surrounds the weight 65, the weight 65 can be easily disposed near the center of the vibration film 10. Thereby, the displacement of the vibrating membrane 10 can be increased. Further, since the upper electrode 21 has an annular shape surrounding the center of the vibration film 10, the piezoelectric element 20 can be driven efficiently. In this way, the inkjet head 1 having excellent driving performance can be realized. FIG. 10B shows a structure in which the upper electrode 21 and the weight 65 are separated from each other. However, as shown in FIG. They may be connected and integrated. In this case, the upper electrode 21 and the weight 65 have the same potential, and a driving voltage can be applied to the piezoelectric film 24 via the weight 65. That is, the weight 65 also has a function as the upper electrode 21. Thereby, a driving voltage can be applied to a wide range of the piezoelectric film 24 and the displacement of the vibration film 10 by the weight 65 can be increased, so that the inkjet head 1 having excellent driving performance can be realized.

  In the configuration shown in FIG. 10D, a lead electrode 66 that crosses the upper electrode 21 is formed from a weight 65 formed in the same layer as the upper electrode 21. The upper electrode 21 is formed in a horseshoe shape having both ends spaced from each other with the extraction electrode 66 interposed therebetween. Gaps are formed between the upper electrode 21 and the weight 65, and between the upper electrode 21 and the extraction electrode 66, and they are separated from each other.

  In this configuration, since the weight 65 can be easily disposed near the center of the vibration film 10 and the upper electrode 21 can effectively apply a driving voltage to the piezoelectric film 24, the inkjet head 1 having excellent driving performance is realized. it can. Further, since the extraction electrode 66 extracted from the weight 65 is not in contact with the upper electrode 21, a voltage can be applied to the weight 65 and the upper electrode 21 independently. Accordingly, a driving method that further improves the driving performance can be employed.

  The piezoelectric device using the weight is not limited to the inkjet head. That is, the piezoelectric device can include a vibration film, a piezoelectric element disposed on the vibration film, and a weight disposed so as to locally increase an inertial mass near the center of the vibration film. Such a piezoelectric device may be a piezoelectric actuator or a piezoelectric sensor. An ink jet head is a kind of piezoelectric actuator.

In the piezoelectric actuator, when a driving voltage is applied to the piezoelectric element, the piezoelectric element is deformed by the inverse piezoelectric effect, and the vibration film is displaced accordingly. Since the weight is disposed so as to locally increase the inertial mass at the center of the diaphragm, the displacement of the diaphragm can be increased. Thereby, a piezoelectric actuator excellent in driving performance can be realized.
In the piezoelectric sensor, when the vibration film is displaced, a voltage is generated in the piezoelectric element due to the piezoelectric effect. Since the weight is disposed so as to locally increase the inertial mass at the center of the diaphragm, the displacement of the diaphragm can be increased. Thereby, since a large voltage is generated in the piezoelectric element, a piezoelectric sensor excellent in detection performance (particularly sensitivity) can be realized. Examples of the piezoelectric sensor include a microphone and an ultrasonic sensor.

FIG. 11A to FIG. 11I show modifications regarding the starting point of displacement of the piezoelectric film 24.
In the configuration of FIG. 11A, a pair of dot-like recesses 85 as starting points are formed in the vicinity of both ends of the upper electrode 21. The recess 85 may penetrate the upper electrode 21 or may not penetrate. The concave portion 85 is an example of a bent portion, and has a concave shape in the stacking direction of the upper electrode 21, the lower electrode 22, and the piezoelectric film 24. In addition, since at least a part of the upper electrode 21 is removed in the recess 85, the recess 85 is a fragile portion that is weaker than other portions of the piezoelectric element 20. The recess 85 is disposed in a region inward of the periphery of the piezoelectric element 20 and is separated from the periphery of the piezoelectric element 20. In this example, the recess 85 has a rectangular dot shape, but may have a dot shape of other shapes such as other polygons, circles, ellipses and the like.

  According to this configuration, the concave portion 85 as the starting point portion is disposed in a region inward of the periphery of the piezoelectric element 20 and is separated from the periphery of the piezoelectric element 20, so that the displacement of the piezoelectric film 24 is entirely Easy to propagate. Therefore, the inkjet head 1 with high responsiveness can be provided, and the inkjet head 1 with high operation controllability can be realized accordingly. Further, since the concave portion 85 as the starting point portion can be provided by processing the upper electrode 21, the inkjet head 1 having high operation controllability can be realized by an easy manufacturing process. Then, since the displacement of the piezoelectric film 24 starts from the recess 85 as the starting point, a stable response and a stable displacement corresponding to the drive voltage can be obtained. Thereby, the inkjet head 1 which can perform stable and accurate operation control can be provided. In addition, since the displacement of the piezoelectric film 24 can be started from the vicinity of both ends of the cavity 6, it is possible to provide the inkjet head 1 that is excellent not only in operation controllability but also in response to drive voltage.

  In the configuration of FIG. 11B, the starting point portion is constituted by a groove 86 that is a concave portion formed in the upper electrode 21. The groove 86 may or may not penetrate the upper electrode 21 in the film thickness direction. The groove 86 is provided in the vicinity of both ends in the longitudinal direction of the cavity 6, has a hollow shape in the stacking direction, and provides a fragile portion that is weaker than other portions of the piezoelectric element 20. The groove 86 extends along the short direction of the cavity 6, that is, along the peripheral edge of the piezoelectric element 20, and reaches the entire width of the upper electrode 21. Accordingly, the groove 86 extends from the inner region of the piezoelectric element 20 toward the periphery of the piezoelectric element 20 and is in contact with the periphery of the piezoelectric element 20. Therefore, the groove 86 is formed by processing a region continuous with the periphery of the piezoelectric element 20. In this example, the groove 86 is formed in a straight line shape, but may be formed in a polygonal line shape or a curved line shape.

  According to this configuration, the groove 86 as the starting point extends from the inner region of the piezoelectric element 20 toward the peripheral edge of the piezoelectric element 20 and is in contact with the peripheral edge of the piezoelectric element 20. Since the groove 86 as the starting point is in contact with the periphery of the piezoelectric element 20, the displacement of the piezoelectric film 24 is likely to start. Thereby, the piezoelectric element 20 with high responsiveness can be provided, and accordingly, the inkjet head 1 with high operation controllability can be realized. Further, since the groove 86 as the starting point extends along the periphery of the piezoelectric element 20, the displacement of the piezoelectric film 24 can be reliably started in a wide range, and accordingly, an inkjet with high operation controllability can be obtained. The head 1 can be realized.

  In the configuration of FIG. 11C, notches 87 are formed in positions near both ends of the cavity 6 on both side edges along the longitudinal direction of the upper electrode 21. The notch 87 has a bent shape that is bent in plan view, and is an example of a hollow shape that is recessed inward of the upper electrode 21. Specifically, the notch 87 has a hollow shape along a direction (orthogonal direction) intersecting the stacking direction of the upper electrode 21 and the piezoelectric film 24. The notch 87 may or may not penetrate the upper electrode 21 in the film thickness direction. The notch 87 provides a weakened portion that is weaker than other portions of the piezoelectric element 20. The notch 87 is in contact with the periphery of the piezoelectric element 20, and is formed by processing a region continuous with the periphery of the piezoelectric element 20.

  The notch 87 provides a starting point where displacement starts when a drive voltage is applied to the piezoelectric element 20. Therefore, it is possible to provide the ink jet head 1 which can be easily controlled and can be operated with high accuracy. Further, since the notch 87 as the starting point is in contact with the peripheral edge of the piezoelectric element 20, the displacement of the piezoelectric film 24 is likely to start. Thereby, the piezoelectric element 20 with high responsiveness can be provided, and the inkjet head 1 with high operation controllability can be provided accordingly. And since the notch 87 can be formed simultaneously when processing the periphery of the piezoelectric element 20 (more specifically, the periphery of the upper electrode 21), the piezoelectric element 20 with high operation controllability can be realized without increasing the number of manufacturing steps. . In addition, since the displacement of the piezoelectric film 24 can be started from the vicinity of both ends of the cavity 6, it is possible to provide the inkjet head 1 that is excellent not only in operation controllability but also in response to the drive voltage.

  In the configuration of FIG. 11D, the starting point portion is constituted by a pair of grooves 88 that are concave portions formed in the upper electrode 21. The groove 88 may or may not penetrate through the upper electrode 21 in the film thickness direction. The grooves 88 are provided in the vicinity of both side edges along both side edges along the longitudinal direction of the cavity 6, that is, along the peripheral edge of the piezoelectric element 20. The groove 88 has a hollow shape in the stacking direction of the upper electrode 21 and the piezoelectric film 24, and provides a fragile portion that is weaker than other portions of the piezoelectric element 20. The groove 88 is arranged along the short direction of the cavity 6 with a gap from the side edge of the upper electrode 21. The groove 88 continuously extends linearly from the vicinity of one end in the longitudinal direction of the upper electrode 21 to the vicinity of the other end. Both ends of the upper electrode 21 are spaced from both ends. Therefore, the groove 88 is separated from the peripheral edge of the piezoelectric element 20. Since the groove 88 extends along the longitudinal direction of the cavity 6, the displacement of the piezoelectric film 24 starts in a wide range in response to the application of the driving voltage. Thereby, it is possible to provide the inkjet head 1 that is excellent not only in operation controllability but also in response to drive voltage. The groove 88 may have a polygonal line shape or a curved shape in addition to the linear shape.

The configuration of FIG. 11E is similar to the configuration of FIG. 11D, except that a groove 89 extending linearly along the longitudinal direction of the cavity 6 is discontinuous. With this configuration, the same effect as the configuration of FIG. 11D can be obtained.
11D and 11E, the grooves 88 and 89 may extend from one end of the upper electrode 21 to the other end, and may be in contact with the periphery of the piezoelectric element 20. However, in this case, it is preferable to leave the upper electrode 21 at least partially at the bottom of the continuous groove 88 shown in FIG. 11D so that the upper electrode 21 is not separated between the inside and the outside of the groove 88.

  In the configuration of FIG. 11F, an annular groove 90 extending along the periphery of the piezoelectric element 20 is formed in the upper electrode 21. In this example, since the upper electrode 21 has a rectangular shape, a rectangular annular groove 90 is formed. The groove 90 includes a pair of long side portions 91 extending along the longitudinal direction of the cavity 6 and a pair of short side portions 92 extending along the short side direction of the cavity 6. The long side portion 91 is disposed in the vicinity of the side edge of the upper electrode 21 (that is, the peripheral edge of the piezoelectric element 20) with a gap from the side edge. The short side portion 92 is disposed in the vicinity of both end edges of the upper electrode 21 (that is, the peripheral edge of the piezoelectric element 20) with a gap from the end edge. Therefore, the annular groove 90 is not in contact with the peripheral edge of the piezoelectric element 20. It is preferable to leave the upper electrode 21 at least partially on the bottom of the groove 90 so that the upper electrode 21 is not separated inside and outside the annular groove 90.

The configuration of FIG. 11G is similar to the configuration of FIG. 11F, except that the annular groove 93 is discontinuous. In the case of this configuration, the groove 93 may penetrate the upper electrode 21 in all portions.
In the configuration of FIG. 11H, substantially arc-shaped recesses 94 are formed at the four corners of the rectangular upper electrode 21. The recess may or may not penetrate through the upper electrode 21. The recess has an arc shape that swells toward the corner of the upper electrode 21. The recesses are arranged in the vicinity of both ends in the longitudinal direction of the cavity 6 and in the vicinity of both ends in the short direction of the cavity 6. The recess is formed separately from the periphery of the piezoelectric element 20. Also with this configuration, when a driving voltage is applied to the piezoelectric element 20, the deformation of the piezoelectric film 24 and the vibration film 10 starts with the recess as a starting point of displacement. Thereby, the inkjet head 1 which is stable and highly responsive can be realized.

  The configuration in FIG. 11I is similar to the configuration shown in FIGS. 2 to 5, an annular thin film portion 26 is provided on the peripheral edge portion of the piezoelectric film 24. In contrast, in the configuration of FIG. 11I, a pair of thin film portions 96 are provided along both side portions along the longitudinal direction of the piezoelectric film 24. The thin film portion 96 is formed over the entire length of the piezoelectric film 24 from one end to the other end in the longitudinal direction. The thin film portions 96 are formed only at both ends in the lateral direction at both ends in the longitudinal direction of the piezoelectric film 24, and a thick film portion 95 exists between them. The thin film portion 96 is in contact with the peripheral edge of the piezoelectric element 20.

  The feature of providing a starting point of a specific shape (for example, a bent shape) as a starting point of displacement in the piezoelectric element can be applied not only to the ink jet head 1 but also to other forms of piezoelectric actuators such as a piezoelectric speaker. Is also applicable. In the piezoelectric sensor, when an external force is applied to the piezoelectric film, a voltage is generated between the upper electrode and the lower electrode due to the piezoelectric effect. When an external force is applied, it can be ensured that the deformation (displacement) of the piezoelectric film starts from the starting point, so that the deformation (displacement) of the piezoelectric film similarly occurs for a plurality of piezoelectric elements and a plurality of external forces. . As a result, the detection sensitivity becomes stable and a highly accurate operation becomes possible. Examples of the piezoelectric sensor include a microphone and an ultrasonic sensor.

FIG. 12A and FIG. 12B show a modification regarding the feature of providing the third electrode in addition to the upper electrode 21 (first electrode) and the lower electrode 22 (second electrode).
In the configuration of FIG. 12A, the operation monitoring electrode 100 is disposed in the same layer as the upper electrode 21. The operation monitoring electrode 100 enters the notch 101 formed in the upper electrode 21 and faces the lower electrode 22 with the piezoelectric film 24 interposed therebetween. Further, the operation monitoring electrode 100 faces the cavity 6. The operation monitoring electrode 100 is formed in a straight line and has only one terminal portion 102. The terminal part 102 is disposed outside the notch part 101. In this example, the notch 101 has a shape that is elongated in a straight line from the middle position of the edge of the upper electrode 21 in the longitudinal direction of the cavity 6. The motion monitoring electrode 100 extends linearly at least within the notch 101 so as to correspond to the shape of the notch 101. The operation monitoring electrode 100 is disposed at a distance from the periphery of the notch 101 and is therefore electrically separated from the upper electrode 21.

When the piezoelectric film 24 is deformed when a driving voltage is applied between the upper electrode 21 and the lower electrode 22, an electromotive force generated by the deformation is generated between the operation monitoring electrode 100 and the lower electrode 22. Therefore, the operation state of the piezoelectric film 24 can be monitored by providing a detection circuit that detects a potential difference between the operation monitoring electrode 100 and the lower electrode 22.
In the configuration of FIG. 12B, the intermediate electrode 103 as the third electrode is in contact with the piezoelectric film 24 between the upper electrode 21 and the lower electrode 22. More specifically, the intermediate electrode 103 is disposed at the middle position of the film thickness of the piezoelectric film 24. The intermediate electrode 103 is parallel to the upper electrode 21 and the lower electrode 22 and faces the upper electrode 21 and the lower electrode 22 with the piezoelectric film 24 interposed therebetween. Since the intermediate electrode 103 is thus embedded in the piezoelectric film 24, the state of the piezoelectric film 24 can be monitored more accurately by using the intermediate electrode 103.

  In addition, since the piezoelectric film 24 is interposed between the intermediate electrode 103 and the lower electrode 22, and between the intermediate electrode 103 and the upper electrode 21, respectively, between the intermediate electrode 103 and the upper electrode 21, and By applying a drive voltage between / or the intermediate electrode 103 and the lower electrode 22, the piezoelectric film 24 can be deformed. Accordingly, it is possible to provide the inkjet head 1 that can operate in a number of operation modes. For example, the piezoelectric element 20 may be driven by setting the upper electrode 21 and the lower electrode 22 to the ground potential and applying a driving voltage to the intermediate electrode 103.

  The feature of having the third electrode in addition to the upper electrode (first electrode) and the lower electrode (second electrode) is applicable not only to piezoelectric actuators such as inkjet heads, but also to piezoelectric sensors such as microphones and ultrasonic sensors. it can. For example, if the configuration shown in FIGS. 6 and 12A is applied to a piezoelectric sensor, the third electrode in addition to the detection output signals from the upper electrode 21 and the lower electrode 22 when an external force is generated in the piezoelectric film 24. By detecting a detection signal from 23 (operation monitoring electrode), the external force applied to the piezoelectric film 24 can be detected in more detail. In other words, a piezoelectric sensor having a large number of detection modes can be provided. Also. If the configuration shown in FIG. 12B is applied to a piezoelectric sensor, an electromotive force is generated between the upper electrode 21 or the lower electrode 22 and the intermediate electrode 103 when an external force is applied to the piezoelectric film 24. A piezoelectric sensor having a mode can be provided.

13A to 13D show a modification related to the shape of the cavity 6.
In the configuration shown in FIG. 13A, the inner wall surface 62 of the actuator substrate 2 has a recessed portion 62 </ b> C that is recessed outward from the cavity 6. The recessed portion 62 </ b> C forms a trough that forms an obtuse angle in a cross section that intersects the surface of the vibrating membrane 10 on the cavity 6 side. The lower edge of the first flat surface portion 62D is continuous with the upper side (the actuator substrate 2 side) of the recessed portion 62C. The first flat surface portion 62D is inclined with respect to both the direction parallel to the vibration film 10 and the normal direction of the vibration film 10. The upper edge of the first flat surface portion 62D is continuous with the curved surface portion 62A. On the lower side (the nozzle substrate 3 side) of the recessed portion 62C, the second flat surface portion 62E is connected to the recessed portion 62C. The second flat surface portion 62E is inclined with respect to both the direction parallel to the vibration film 10 and the normal direction of the vibration film 10. The first flat surface portion 62D is inclined toward the outside of the cavity 6 from the curved surface portion 62A toward the recessed portion 62C. The second flat surface portion 62E is inclined toward the outside of the cavity 6 from the nozzle substrate 3 toward the recessed portion 62C. The plane including the first flat surface portion 62D and the plane including the second flat surface portion 62E form an obtuse angle in a cross section intersecting the surface of the vibration film 10 on the cavity 6 side. That is, the recess 62C forms an obtuse angle in the cross section.

  In this configuration, since the hollow portion 62C forms an obtuse valley, trapping of bubbles in the hollow portion 62C can be suppressed or prevented. Thereby, the ink ejection control performance can be improved. In addition, the inner wall surface 62 having the first flat surface portion 62D and the second flat surface portion 62E can be easily formed, and the intersecting portions (indented portions) form obtuse angles, so that air bubbles at the intersecting portions are formed. The accumulation can be suppressed or prevented. As a result, it is possible to provide the ink jet head 1 that has a simple manufacturing process and improved ink ejection control performance.

The configuration shown in FIG. 13B is similar to the configuration shown in FIG. 13A, except that the recess 62C has no corners and its inner surface is a curved surface. Since the recessed part 62C forms a curved surface, the trapping of bubbles in the recessed part 62C can be more effectively suppressed or prevented. Thereby, the ink ejection control performance can be improved.
In the configuration shown in FIG. 13C, the curved surface portion 62 </ b> A that is in contact with the lower surface of the vibrating membrane 10 is continuous from one surface of the actuator substrate 2 to the other surface. Thereby, it is possible to suppress or prevent bubble accumulation on the inner wall surface of the cavity 6. In addition, since the curved surface portion 62 </ b> A is also in contact with the nozzle substrate 3, it is difficult for air bubbles to be captured at the boundary portion between the inner wall surface 62 of the cavity 6 and the nozzle substrate 3. Accordingly, it is possible to realize the ink jet head 1 with further improved ink discharge control performance. The curved surface portion 62 </ b> A preferably extends over the entire circumference of the boundary between the inner wall surface 62 of the cavity 6 and the nozzle substrate 3. Thereby, bubble accumulation can be suppressed more reliably.

  In the configuration shown in FIG. 13D, the inner wall surface 62 of the cavity 6 has a curved surface portion 62F that curves and spreads outward on the nozzle substrate 3 side. The lower edge of the curved surface portion 62F is in contact with the nozzle substrate 3. According to this configuration, since the inner wall surface 62 of the cavity 6 has the curved surface portion 62F on the nozzle substrate 3 side, it is possible to suppress or prevent bubble accumulation at the intersection between the nozzle substrate 3 and the inner wall surface 62. Thereby, the ink jet head 1 with improved ink ejection control performance can be provided. The curved surface portion 62 </ b> F preferably extends over the entire circumference of the boundary between the inner wall surface 62 of the cavity 6 and the nozzle substrate 3. Thereby, bubble accumulation at the intersection between the inner wall surface of the cavity 6 and the nozzle substrate 3 can be more effectively suppressed or prevented, and ink ejection control performance can be improved accordingly. When the vibrating membrane 10 is disposed above the nozzle substrate 3, since bubble accumulation occurs on the vibrating membrane 10 side, trapping of bubbles on the nozzle substrate 3 side need not be considered much.

FIG. 14A and FIG. 14B show a modification regarding the separation characteristics of the vibrating membrane 10 for each cavity 6.
As shown in FIG. 14A, the separation groove 60 that separates the vibrating membranes 10 between the cavities 6 may be a discontinuous pattern groove. Even with such a discontinuous pattern of grooves, it is possible to reduce the constraint on the vibrating membrane 10 corresponding to each cavity 6 from the periphery.

  As shown in FIG. 14B, the separation groove 60 may be formed in a pattern that further extends from a partition wall 61 that partitions a pair of adjacent cavities 6 and surrounds the cavities 6. Thereby, since the restraint from the circumference | surroundings with respect to the vibration film 10 can be decreased further, the displacement of the vibration film 10 and a partition wall can be enlarged more. In the example of FIG. 14B, the separation groove 60 includes a side edge separation groove 60 a extending along the side edge of the cavity 6 and an edge separation groove 60 b extending along the edge of the cavity 6. An edge separation groove 60b is connected to both ends of the side edge separation groove 60a. The side edge separation groove 60a and / or the edge separation groove 60b may be a discontinuous pattern groove.

15A, FIG. 15B, and FIG. 15C show a modified example related to the feature of the arrangement of the drive IC 5.
In the configuration of FIG. 15A, the drive IC 5 is mounted on the surface of the actuator substrate 2 so as to cover the piezoelectric element 20. Therefore, the drive IC 5 also serves as a protective substrate for protecting the piezoelectric element 20. Thereby, it is not necessary to separately arrange a protective substrate for protecting the piezoelectric element 20. In addition, since the drive IC 5 can be mounted on the actuator substrate 2 so as to overlap the piezoelectric element 20, the ink jet head 1 can be further reduced in size.

  The drive IC 5 has a recess 5 c formed on a first surface 5 a (opposing surface) facing the surface of the actuator substrate 2. The piezoelectric element 20 is accommodated in the recess 5c. As a result, an operation space for operating the piezoelectric element 20 can be secured, and the height of the upper surface (second surface 5b, the surface opposite to the actuator substrate 2) of the drive IC 5 can be reduced. Thereby, the small-sized inkjet head 1 can be realized while ensuring the working space of the piezoelectric element 20.

  The configuration shown in FIG. 15B is similar to the configuration shown in FIG. 15A, but the FPC 57 is directly joined to the input terminal 56 disposed on the upper surface (second surface 5 b) of the drive IC 5. As a result, wire bonding between the input terminal 56 of the drive IC 5 and the FPC 57 is not necessary, so that it is not necessary to provide a space for wire bonding on the actuator substrate 2. Thereby, the inkjet head 1 can be further reduced in size.

In the configuration shown in FIG. 15C, the drive IC 5 has a flat facing surface that faces the surface of the actuator substrate 2 as the first surface 5a, and bumps 53 that form output terminals are formed on the first surface 5a. ing. The driving IC 5 is disposed on the actuator substrate 2 so as to cover the piezoelectric element 20.
A gap 53 is formed between the surface of the actuator substrate 2 and the first surface 5 a of the drive IC 5 by the bump 53, and the piezoelectric element 20 is disposed in the gap 7, so that the flat first surface 5 a of the drive IC 5 is formed. Opposite. Thus, the space formed by the bumps 53 is used as a space for arranging and operating the piezoelectric element 20. Thereby, since it is not necessary to form a recess in the first surface 5a of the drive IC 5, the manufacturing process is simplified.

As mentioned above, although embodiment of this invention was described, this invention can also be implemented with another form. For example, the features related to piezoelectric elements are applicable not only to inkjet heads but also to microphones, pressure sensors, acceleration sensors, angular velocity sensors, ultrasonic sensors, speakers, IR sensors (thermal sensors), etc. Can do.
In addition, various design changes can be made within the scope of matters described in the claims.

DESCRIPTION OF SYMBOLS 1 Inkjet head 2 Actuator substrate 3 Nozzle substrate 4 Protection substrate 6 Cavity 8 Ink tank 10 Vibration film 11 Vibration film formation layer 12 Hydrogen barrier film 13 Insulation film 15 Wiring 16 Land 19 Protection film 20 Piezoelectric element 21 Upper electrode 22 Lower electrode 22A Main Electrode portion 22B Extension portion 22C Land 23 Operation monitoring electrodes 23a, 23b Terminal portion 24 Piezoelectric film 25 Thick film portion 26 Thin film portion 27 Bending portion 28 Step surface 31 Ink discharge passage 32 Discharge port 35 Notch portion 36 Drive state monitoring circuit 41 Opposite Surface 42 Housing recess 43 Ink supply path 44 Ink supply path 45 Ink flow direction 49 Common ink path 50 Ink path 51 Semiconductor substrate 52 Active area 53 Bump (output terminal)
54 Protective resin layer 55 Through-via 56 Input terminal 57 FPC
58 Bonding wire 60 Separating groove 60a Side edge separating groove 60b End edge separating groove 61 Partition wall 62 Inner wall surface 62A Curved surface portion 62B Flat surface portion 62C Depressed portion 62D First flat surface portion 62E Second flat surface portion 62F Curved portion 65 Weight 66 Drawer Electrode 71 Adhesion layer 72 Seed layer 73 PZT layer 75 of main firing unit Columnar structure layer 76 Amorphous structure layer 81 Seed formation region 82 Seed non-formation region 85 Recess 86 Groove 87 Notch 88 Groove 89 Groove 90 Groove 93 Groove 94 Recess 95 Thick film part 96 Thin film part 100 Operation monitoring electrode 101 Notch part 102 Terminal part 103 Intermediate electrode

Claims (7)

A substrate that defines a cavity in which ink is stored;
A vibrating membrane supported by the substrate and defining the cavity;
A piezoelectric element disposed on the vibrating membrane and changing a volume of the cavity by displacing the vibrating membrane;
A weight arranged to locally increase the inertial mass of the central portion of the vibrating membrane,
The piezoelectric element includes a lower electrode, a piezoelectric film laminated on the lower electrode, and an upper electrode laminated on the piezoelectric film and facing the lower electrode across the piezoelectric film,
The weight is the is disposed on the upper electrode, Lee inkjet head. A substrate that defines a cavity in which ink is stored;
A vibrating membrane supported by the substrate and defining the cavity;
A piezoelectric element disposed on the vibrating membrane and changing a volume of the cavity by displacing the vibrating membrane;
A weight arranged to locally increase the inertial mass of the central portion of the vibrating membrane,
The piezoelectric element includes a lower electrode, a piezoelectric film laminated on the lower electrode, and an upper electrode laminated on the piezoelectric film and facing the lower electrode across the piezoelectric film,
The weight is the are located on the same layer as the upper electrode, Lee inkjet head. The inkjet head according to claim 2 , wherein the weight is a film made of the same material as the upper electrode and thicker than the upper electrode. Wherein the upper electrode has an annular form surrounding the weight, the ink-jet head according to claim 2 or 3. The inkjet head according to any one of claims 2 to 4 , wherein the weight and the upper electrode have the same potential. From the weight, a lead electrode is formed that is drawn across the upper electrode,
The inkjet head according to any one of claims 2 to 5 , wherein the upper electrode is formed in a horseshoe shape having both ends spaced from each other with the lead electrode interposed therebetween. The cavity is rectangular in plan view;
The weight extends along the longitudinal direction of the cavity, and is formed in a band shape having a width less than half of the length of the cavity in the short direction, and is arranged near the center of the cavity in the short direction. edge spacing to the edge of the weight is secured from ink jet head according to any one of claims 1-6.

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