JP2012224003A - Piezoelectric actuator, liquid ejecting head and liquid ejecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric actuator that can preferably cause displacement therein and suppress the breakage of a piezoelectric element layer, and to provide a liquid ejecting head and a liquid ejecting device.SOLUTION: In the piezoelectric actuator, the piezoelectric element layer 70 includes: an active part 70a interposed between a first electrode 60 and a second electrode 80; and a non-active part 70b not interposed between the first electrode 60 and the second electrode 80. A porous part 71 having density lower than that of the active part 70a is provided in at least part of the non-active part 70b.

Description

  The present invention relates to a piezoelectric actuator, a liquid ejecting head that ejects liquid droplets from a nozzle by displacing the piezoelectric actuator, and a liquid ejecting apparatus including the liquid ejecting head.

  Conventionally, there has been known a liquid ejecting head that ejects liquid droplets from a nozzle by applying pressure to a liquid in a pressure generating chamber by a pressure generating means. As a typical example, ink droplets are ejected as liquid droplets. There is an ink jet recording head. There are various types of pressure generating means constituting the ink jet recording head. One example is a first electrode (lower electrode film), a piezoelectric layer provided on the first electrode, and a piezoelectric layer. There is a piezoelectric actuator (piezoelectric element) made of a thin film composed of a second electrode (upper electrode film) provided on a body layer (see, for example, Patent Document 1).

  A piezoelectric actuator made of such a thin film has the advantages that it can be arranged at a high density and can be driven at a high speed.

JP 2005-178293 A

  By the way, the end of the active part which is a substantial displacement driving part of the piezoelectric actuator is defined by the end of the first electrode or the end of the second electrode. For example, as shown in FIG. 4A of Patent Document 1, the width of the piezoelectric layer is wider toward the first electrode side, and the side surface of the piezoelectric layer is an inclined surface. Therefore, the end portion of the active portion of the piezoelectric actuator is defined by the end portion of the second electrode, and the portion outside the end portion of the second electrode is an inactive portion that is not substantially driven to be displaced.

  In such a configuration, when the inactive portion becomes large, each time the piezoelectric actuator is displaced, stress concentration occurs at the boundary portion between the inactive portion and the active portion, and cracks occur in the piezoelectric layer. There is a possibility that the problem that the piezoelectric layer and each electrode are peeled off occurs.

  In order to solve such a problem, it is conceivable to reduce the size of the inactive portion by increasing the inclination angle of the side surface of the piezoelectric layer with respect to the first electrode. However, in that case, the length of the side surface of the piezoelectric layer, that is, the distance between the end portion of the first electrode and the end portion of the second electrode is shortened, the leakage current is increased, and the piezoelectric layer may be easily burned out. There is.

  Such a problem is not limited to an ink jet recording head that ejects ink droplets, but also exists in a liquid ejecting head that ejects other droplets. In addition, a piezoelectric actuator mounted on a device other than the liquid ejecting head has the same problem.

  The present invention has been made in view of such circumstances, and provides a piezoelectric actuator, a liquid ejecting head, and a liquid ejecting apparatus that can be favorably displaced and can suppress destruction of a piezoelectric layer. Objective.

  The present invention for solving the above problems is a piezoelectric actuator comprising a first electrode, a piezoelectric layer provided on the first electrode, and a second electrode provided on the piezoelectric layer. The piezoelectric layer includes an active part sandwiched between the first electrode and the second electrode, and an inactive part not sandwiched between the first electrode and the second electrode. The piezoelectric actuator is characterized in that a porous part having a density lower than that of the active part is provided in at least a part of the inactive part.

Here, in the porous portion, the intervals between the crystals are wider than the other portions of the piezoelectric layer. Further, the surface of the porous portion is rougher than other portions of the piezoelectric layer.
In the present invention, the rigidity of the inactive portion is lower than that of the active portion by driving the piezoelectric actuator. For this reason, each piezoelectric actuator can be displaced sufficiently. In addition, since the generation of a leakage current between the first electrode and the second electrode is suppressed, it is possible to suppress the destruction or deterioration of the piezoelectric layer due to the leakage current.

  The porous portion is formed, for example, by dissolving a part of the piezoelectric layer with hydrofluoric acid. Thereby, a porous part can be formed comparatively easily.

  The porous portion preferably includes an organic protective film. As a result, the porous portion substantially functions as a protective film, and the generation of leakage current between the first electrode and the second electrode can be more reliably suppressed.

  The piezoelectric layer is specifically made of a perovskite oxide containing at least lead, zirconium and titanium. In this case, destruction or deterioration due to the leakage current of the piezoelectric layer can be particularly effectively suppressed.

  According to another aspect of the invention, there is provided a liquid ejecting head including such a piezoelectric actuator. Furthermore, the present invention provides a liquid ejecting apparatus including such a liquid ejecting head. According to the present invention, a highly reliable liquid ejecting head or liquid ejecting apparatus can be realized.

2 is a schematic perspective view of a recording head according to Embodiment 1. FIG. 2A and 2B are a plan view and a cross-sectional view taken along line A-A ′ of the recording head according to the first embodiment. 1 is a cross-sectional view showing a piezoelectric actuator according to Embodiment 1. FIG. FIG. 3 is a cross-sectional view illustrating a formation process of the piezoelectric actuator according to the first embodiment. 2 is a cross-sectional photograph showing a piezoelectric actuator according to Embodiment 1. 6 is a cross-sectional view showing a piezoelectric actuator according to Embodiment 2. FIG. 6 is a cross-sectional view showing a piezoelectric actuator according to Embodiment 3. FIG. FIG. 10 is a cross-sectional view illustrating a process for forming a piezoelectric actuator according to a third embodiment. FIG. 6 is a cross-sectional view illustrating a piezoelectric actuator according to a fourth embodiment. FIG. 10 is a cross-sectional view showing a process for forming a piezoelectric actuator according to a fourth embodiment. FIG. 10 is a cross-sectional view illustrating a piezoelectric actuator according to a fifth embodiment. FIG. 10 is a cross-sectional view illustrating a process for forming a piezoelectric actuator according to a fifth embodiment. 1 is a schematic perspective view of a recording apparatus according to an embodiment.

Hereinafter, the present invention will be described in detail based on an embodiment.
(Embodiment 1)
As shown in FIGS. 1 and 2, a pressure generating chamber 12 partitioned by a plurality of partition walls 11 is arranged in parallel in a first direction on a flow path forming substrate 10 made of a silicon single crystal substrate. Further, the flow path forming substrate 10 has a manifold 100 serving as an ink chamber (liquid chamber) common to the pressure generation chambers 12 on the outside of the pressure generation chambers 12 in the second direction orthogonal to the first direction. A communication part 13 constituting a part is formed, and each pressure generating chamber 12 and the communication part 13 are communicated with each other by an ink supply path 14 and a communication path 15. That is, the flow path forming substrate 10 is provided with a liquid flow path including a pressure generation chamber 12, a communication portion 13, an ink supply path 14, and a communication path 15.

  On one surface side of the flow path forming substrate 10, a nozzle plate 20 having a nozzle 21 communicating with the vicinity of the end of each pressure generating chamber 12 on the side opposite to the ink supply path 14 is joined.

  An elastic film 50 and an insulator film 55 constituting a vibration plate are formed on the other surface of the flow path forming substrate 10 opposite to the nozzle plate 20. Furthermore, a piezoelectric actuator 300 composed of the first electrode 60, the piezoelectric layer 70, and the second electrode 80 is provided on the insulator film 55. One of the electrodes of the piezoelectric actuator 300 is a common electrode common to the plurality of piezoelectric actuators 300, and the other electrode is an individual electrode independent for each piezoelectric actuator 300. In the present embodiment, the first electrode 60 is a common electrode, and the second electrode 80 is an individual electrode. In addition, the lead electrode 90 is connected to the second electrode 80 which is an individual electrode of each piezoelectric actuator 300.

  The first electrode 60 and the second electrode 80 are made of, for example, a noble metal such as platinum (Pt) or iridium (Ir), or a conductive oxide such as lanthanum nickelate (LNO).

The piezoelectric layer 70 is made of, for example, a perovskite oxide containing at least lead (Pb), zirconium (Zr), and titanium (Ti). That is, as a material of the piezoelectric layer 70, for example, a ferroelectric piezoelectric material such as lead zirconate titanate (PZT) or a material obtained by adding a metal oxide such as niobium oxide, nickel oxide, or magnesium oxide to the piezoelectric material. Preferably used. Specifically, lead titanate (PbTiO ₃ ), lead zirconate titanate (Pb (Zr, Ti) O ₃ ), lead zirconate (PbZrO ₃ ), lead lanthanum titanate ((Pb, La), TiO ₃ ) ), Lead lanthanum zirconate titanate ((Pb, La) (Zr, Ti) O ₃ ), or lead magnesium niobate zirconium titanate (Pb (Zr, Ti) (Mg, Nb) O ₃ ). . In this embodiment, lead zirconate titanate (PZT) is used as the material of the piezoelectric layer 70. Of course, the material of the piezoelectric layer 70 is not limited to these.

  The lead electrode 90 is made of, for example, gold (Au) or the like. In the present embodiment, the elastic film 50 and the elastic film 50 function as a diaphragm that is deformed as the piezoelectric actuator 300 is driven, but the configuration of the diaphragm is not particularly limited.

  On the flow path forming substrate 10 on which such a piezoelectric actuator 300 is formed, a protective substrate 30 including a holding portion 31 for protecting the piezoelectric actuator 300 is joined. The protective substrate 30 is provided with a manifold portion 32. The manifold portion 32 is connected to the communication portion 13 of the flow path forming substrate 10 and constitutes a manifold 100 that serves as a common ink chamber for the pressure generation chambers 12.

  The protective substrate 30 is provided with a through hole 33 that penetrates the protective substrate 30 in the thickness direction. The vicinity of the end portion of the lead electrode 90 drawn from each piezoelectric actuator 300 is provided so as to be exposed in the through hole 33.

  A drive circuit 120 for driving each piezoelectric actuator 300 is fixed on the protective substrate 30. For example, a circuit board or a semiconductor integrated circuit (IC) can be used as the drive circuit 120. The drive circuit 120 and the lead electrode 90 are electrically connected via a connection wiring 121 made of a conductive wire such as a bonding wire.

  In addition, a compliance substrate 40 including a sealing film 41 and a fixing plate 42 is bonded onto the protective substrate 30. Here, the sealing film 41 is made of a material having low rigidity and flexibility, and one surface of the manifold portion 32 is sealed by the sealing film 41. The fixing plate 42 is made of a hard material such as metal. Since the area of the fixing plate 42 facing the manifold 100 is an opening 43 that is completely removed in the thickness direction, one surface of the manifold 100 is sealed only with a flexible sealing film 41. Has been.

  In such an ink jet recording head of this embodiment, ink is taken in from an ink introduction port connected to an external ink supply means (not shown), and the interior from the manifold 100 to the nozzle 21 is filled with ink, and then from the drive circuit 120. In accordance with the recorded signal, a voltage is applied to each piezoelectric actuator 300 corresponding to the pressure generating chamber 12 to bend and deform the diaphragm composed of the elastic film 50 and the insulator film 55. As a result, the pressure in each pressure generating chamber 12 increases and ink droplets are ejected from the nozzles 21.

  Here, the configuration of the piezoelectric actuator 300 of such an ink jet recording head will be described in more detail.

  As shown in FIG. 3, the piezoelectric actuator 300 includes the first electrode 60 formed on the insulator film 55 as described above, the piezoelectric layer 70 formed on the first electrode 60, and the piezoelectric layer 70. And the second electrode 80 formed thereon. In the present embodiment, the first electrode 60 and the piezoelectric layer 70 are continuously provided on the flow path forming substrate 10 in the direction in which the pressure generation chambers 12 are arranged. The second electrode 80 is provided independently for each piezoelectric actuator 300. Accordingly, the piezoelectric layer 70 includes an active part 70a sandwiched between the first electrode 60 and the second electrode 80, and an inactive part 70b not sandwiched between the first electrode 60 and the second electrode 80. And have.

  As described above, in this embodiment, since the piezoelectric layer 70 is continuously formed between the first electrode 60 and the second electrode 80, the leakage current between the first electrode 60 and the second electrode 80. Occurrence is suppressed. Therefore, the destruction or deterioration of the piezoelectric layer 70 due to the leak current can be suppressed.

  In the present invention, at least a part of the inactive portion 70 b of the piezoelectric layer 70 is provided with a porous portion 71 having a lower density than other portions of the piezoelectric layer 70. In the present embodiment, all of the inactive portions 70 b of the piezoelectric layer 70 are porous portions 71. Specifically, the porous portion 71 has a larger crystal interval than other portions of the piezoelectric layer 70 (portions other than the porous portion 71).

  Thus, since the porous part 71 is formed in the non-active part 70b of the piezoelectric body layer 70, the rigidity of the non-active part 70b becomes significantly lower than the synthesis of the active part 70a by driving the piezoelectric actuator 300. For this reason, even if the piezoelectric layer 70 is continuously formed, each piezoelectric actuator 300 can be sufficiently displaced. In addition, the piezoelectric layer 70 can be prevented from being broken by the repeated driving of the piezoelectric actuator 300. Therefore, a highly reliable ink jet recording head can be realized.

  In the direction intersecting with the direction in which the pressure generating chambers 12 are juxtaposed, the piezoelectric layer 70 is extended to the outside of the first electrode 60, but the porous portion 71 is the first electrode of the piezoelectric layer 70. It is preferable that it is not formed in the part facing 60 edge part vicinity. In the present embodiment, all of the non-active part 70b is the porous part 71. However, the porous part 71 may be provided at least in part of the non-active part 70b, for example, only on the surface layer part of the non-active part 70b. Good.

  The method of forming the porous portion 71 is not particularly limited, but after forming the piezoelectric actuator 300 by a known method, for example, in a state where the resist film 200 is formed on the second electrode 80 as shown in FIG. The inactive portion 70b of the piezoelectric layer 70 is immersed in an etching solution. As a result, a part (part of components) of the inactive portion 70b of the piezoelectric layer 70 is dissolved by the etching solution, and the porous portion 71 having a lower density than the other portions of the piezoelectric layer 70 is formed ( (See FIG. 3). That is, the etching solution used to form the porous portion 71 needs to use a solution that dissolves only a part of the material (element) for forming the piezoelectric layer 70. For example, hydrofluoric acid is used in this embodiment. By using such an etching solution, the piezoelectric layer 70 is not completely removed, but an oxide containing an element that is not dissolved and a reaction product (for example, fluoride) that reacts with a component of the etching solution remains. As a result, for example, as shown in FIG. 5, the inactive portion 70 b of the piezoelectric layer 70 is formed with a porous portion 71 that is a low-density layer composed of these substances and pores. .

(Embodiment 2)
In the first embodiment, the example in which the piezoelectric layers 70 constituting the plurality of piezoelectric actuators 300 arranged in parallel are continuously formed has been described. In contrast, in the present embodiment, as shown in FIG. 6, the piezoelectric layer 70 is provided independently for each piezoelectric actuator 300. The width of the piezoelectric layer 70 constituting each piezoelectric actuator 300 is wider toward the first electrode 60 side. As a result, each of the piezoelectric layers 70 constituting the piezoelectric actuator 300 is sandwiched between the active portion 70a sandwiched between the first electrode 60 and the second electrode 80, and the first electrode 60 and the second electrode 80. Non-active part 70b.

  In the present embodiment, the porous portion 71 </ b> A is formed to part of the active portion 70 a together with the inactive portion 70 b of the piezoelectric layer 70. Of course, the porous portion 71A may be formed only on a part of the inactive portion 70b, for example, only on the surface layer portion.

  As described above, in the configuration of this embodiment, since the piezoelectric layer 70 is provided independently for each piezoelectric actuator 300, that is, the piezoelectric layer 70 is not continuously formed, each piezoelectric actuator 300 is sufficiently provided. Can be displaced. In particular, in the present embodiment, since the porous portion 71A is formed in the inactive portion 70b of the piezoelectric layer 70, the piezoelectric actuator 300 can be displaced more favorably and ink droplets can be ejected favorably.

  Further, in the configuration in which the piezoelectric layer 70 is provided for each piezoelectric actuator 300, a leakage current between the first electrode 60 and the second electrode 80 is likely to occur, but the porous portion 71A is provided in the inactive portion 70b of the piezoelectric layer 70. As a result, the occurrence of leakage current can be suppressed. The surface of the porous portion 71A is rougher than the other portions of the piezoelectric layer 70. For this reason, the distance between the first electrode 60 and the second electrode 80 on the surface of the piezoelectric layer 70 is longer than the configuration in which the porous portion 71 </ b> A is not formed on the piezoelectric layer 70. Therefore, the generation of leakage current between the first electrode 60 and the second electrode 80 can be suppressed.

  The porous portion 71A according to the present embodiment is also formed by immersing the inactive portion 70b of the piezoelectric layer 70 in an etching solution after forming the piezoelectric actuator 300 by a known method, as in the first embodiment. ing. Of course, the method for forming the porous portion 71A is not particularly limited.

(Embodiment 3)
In the second embodiment, the porous portion 71 </ b> A is formed across the thickness direction of the piezoelectric layer 70. On the other hand, in the present embodiment, as shown in FIG. 7, the porous portion 71 </ b> B is formed only on a part of the piezoelectric layer 70 on the first electrode 60 side. Although described later in detail, the piezoelectric layer 70 according to the present embodiment includes a first piezoelectric layer 72 and a second piezoelectric layer 73.

  Also in the present embodiment, as in the case of the second embodiment, each piezoelectric actuator 300 can be sufficiently displaced, and the generation of a leakage current between the first electrode 60 and the second electrode 80 is suppressed. can do. Further, in the present embodiment, since the porous portion 71B is not formed at the boundary portion between the piezoelectric layer 70 and the second electrode 80, the adhesion between the piezoelectric layer 70 and the second electrode 80 is also improved.

  Moreover, the formation method of the piezoelectric actuator 300 of this embodiment is not specifically limited, For example, it can form in the following procedures. First, as shown in FIG. 8A, the first electrode 60 is formed in a predetermined pattern on the insulator film 55, and the first piezoelectric layer 72 is formed on the first electrode 60 with a predetermined thickness. Next, as shown in FIG. 8B, a resist film 201 is formed in a region where the active portion 70a of the first piezoelectric layer 72 is formed, and in this state, the first piezoelectric layer 72 is immersed in an etching solution. Thus, the porous portion 71B is formed. Next, as shown in FIG. 8C, a second piezoelectric layer 73 and a second electrode 80 are sequentially formed with a predetermined thickness on the first piezoelectric layer 72 including the porous portion 71B. Thereafter, as shown in FIG. 8D, a resist film 202 is formed on the second electrode 80 so as to oppose each first piezoelectric layer 72 (active portion 70a). Then, by using the resist film 202 as a mask, the second electrode 80, the second piezoelectric layer 73, and the porous portion 71B of the first piezoelectric layer 72 are sequentially patterned to form the piezoelectric actuator 300 of this embodiment. (See FIG. 7).

(Embodiment 4)
The configuration of the present embodiment is basically the same as that of the third embodiment. As shown in FIG. 9, the porous portion 71C is formed only on a part of the piezoelectric layer 70 on the first electrode 60 side. Further, the boundary portion between the piezoelectric layer 70 and the second electrode 80 is covered with a protective film 220. In the present embodiment, the porous portion 71C constituting the inactive portion 70b extends to the outside of the other portions of the inactive portion 70b, and the upper surface 71a of the porous portion 71C is exposed. The protective film 220 is continuously provided from the second electrode 80 to the upper surface 71a of the porous portion 71C.

  Even in such a configuration, each piezoelectric actuator 300 can be sufficiently displaced as in the above-described embodiment, and the occurrence of leakage current between the first electrode 60 and the second electrode 80 can be suppressed. be able to. In particular, since the boundary portion between the piezoelectric layer 70 and the second electrode 80 is covered with the protective film 220, the leakage current can be suppressed more reliably. Furthermore, peeling between the piezoelectric layer 70 and the second electrode 80 can be more reliably suppressed. Further, since the protective film 220 extends to the upper surface 71a of the porous portion 71C, the adhesion of the protective film 220 to the piezoelectric layer 70 can be enhanced.

  The method for forming the piezoelectric actuator 300 of the present embodiment is not particularly limited, but can be formed by the following procedure, for example. First, as shown in FIG. 10A, the piezoelectric layer 70 and the second electrode 80 are sequentially stacked on the first electrode 60, and then the second electrode 80 and the piezoelectric layer 70 are patterned. At this time, only a part of the piezoelectric layer 70 in the thickness direction is removed. Next, as shown in FIG. 10B, a protective film 220 made of, for example, aluminum oxide is formed so as to cover the surfaces of the piezoelectric layer 70 and the second electrode 80. Next, as shown in FIG. 10C, the protective film 220 is patterned into a predetermined shape. Next, as shown in FIG. 10D, a porous portion 71C is formed by immersing the piezoelectric layer 70 exposed through the protective film 220 in an etching solution. Thereafter, by patterning the porous portion 71C, the piezoelectric actuator 300 according to the present embodiment is formed (see FIG. 9).

(Embodiment 5)
This embodiment has basically the same configuration as that of the second embodiment. However, as shown in FIG. 11, for example, a fluorine-based resin or a silicon-based resin (for example, divinyltetramethyl) is formed on the second electrode 80. The second embodiment is different from the second embodiment in that a protective film 221 made of a material such as siloxane benzocyclobutene resin or polyimide is formed. Although details will be described later, the material (component) of the protective film 221 is included in the porous portion 71D.

  Even in such a configuration, as in the second embodiment, each piezoelectric actuator 300 can be sufficiently displaced, and ink droplets can be ejected satisfactorily. In addition, the generation of leakage current between the first electrode 60 and the second electrode 80 can be suppressed. In particular, in the present embodiment, since the second electrode 80 is covered with the protective film 221 and the material of the protective film 221 is included in the porous portion 71D, a leakage current between the first electrode 60 and the second electrode 80 is obtained. Can be more reliably suppressed. That is, the porous portion 71D can function substantially as a protective film, and the generation of a leakage current between the first electrode 60 and the second electrode 80 can be more reliably suppressed. In particular, when an organic protective film (organic material) is used as a material for the protective film 221, the rigidity of the organic protective film is small, so that the rigidity of the porous portion 71D is not significantly increased, and the piezoelectric actuator 300 is sufficiently provided. Can be displaced.

  Such a piezoelectric actuator 300 can be formed by the following procedure, for example. First, as shown in FIG. 12A, the first electrode 60 is formed in a predetermined pattern on the insulator film 55, and then the piezoelectric layer 70 and the second electrode 80 are sequentially formed on the first electrode 60. Next, as shown in FIG. 12B, after patterning the second electrode 80 into a predetermined shape, a resist film 203 is formed to cover each second electrode 80. That is, the resist film 203 is formed in a region where the active portion 70a of the piezoelectric layer 70 is formed. Next, as shown in FIG. 12C, the porous portion 71D is formed by immersing the piezoelectric layer 70 in the etching solution in this state. Next, as shown in FIG. 12D, a protective film 221 made of a fluorine-based resin is formed so as to cover the surfaces of the porous portion 71D (piezoelectric layer 70) and the second electrode 80. At this time, the material of the protective film 221 is included in the porous portion 71D. The material of the protective film 221 enters, for example, the pores of the porous portion 71D. Thereafter, the piezoelectric film 300 of this embodiment is formed by sequentially patterning the protective film 221 and the piezoelectric layer 70 (porous portion 71D) (see FIG. 11).

(Other embodiments)
As mentioned above, although embodiment of this invention was described, of course, this invention is not limited to these embodiment.

  Further, the ink jet recording head having such a configuration constitutes a part of a recording head unit including an ink flow path communicating with an ink cartridge or the like, and is mounted on the ink jet recording apparatus. In the ink jet recording apparatus shown in FIG. 13, a recording head unit 1 having an ink jet recording head is detachably equipped with a cartridge 2 constituting an ink supply means. A carriage 3 on which the recording head unit 1 is mounted is provided on a carriage shaft 5 attached to the apparatus main body 4 so as to be movable in the axial direction. For example, the recording head unit 1 ejects a black ink composition and a color ink composition, respectively.

  Then, the driving force of the driving motor 6 is transmitted to the carriage 3 via a plurality of gears and a timing belt 7 (not shown), so that the carriage 3 on which the recording head unit 1 is mounted is moved along the carriage shaft 5. On the other hand, the apparatus main body 4 is provided with a platen 8 along the carriage shaft 5, and a recording sheet S, which is a recording medium such as paper fed by a not-shown paper feed roller, is conveyed on the platen 8. It is like that.

  Although the ink jet recording apparatus I has been exemplified in which the recording head unit 1 is mounted on the carriage 3 and moves in the main scanning direction, the configuration of the ink jet recording apparatus I is not limited to this. The ink jet recording apparatus I may be, for example, a so-called line type in which an ink jet recording head is fixed and printing is performed by moving a recording sheet such as paper in the sub-scanning direction.

  In the above-described example, the ink jet recording head has been described as an example of the liquid ejecting head. However, the present invention is widely intended for all liquid ejecting heads, and is a liquid ejecting head that ejects liquid other than ink. Of course, it can also be applied. Examples of the liquid ejecting head include various recording heads used in image recording apparatuses such as printers, color material ejecting heads used for manufacturing color filters such as liquid crystal displays, organic EL displays, and FEDs (field emission displays). Examples thereof include an electrode material ejection head used for electrode formation, a bioorganic matter ejection head used for biochip production, and the like.

  The present invention is not limited to a piezoelectric actuator mounted on a liquid ejecting head typified by an ink jet recording head, and can also be applied to piezoelectric actuators mounted on other devices.

  DESCRIPTION OF SYMBOLS 10 Flow path formation board | substrate, 12 Pressure generating chamber, 20 Nozzle plate, 21 Nozzle, 30 Protection board | substrate, 40 Compliance board | substrate, 41 Sealing film, 42 Fixing board, 50 Elastic film, 55 Insulator film, 60 1st electrode, 70 Piezoelectric layer, 70a Active part, 70b Inactive part, 71 Porous part, 80 Second electrode, 90 Lead electrode, 100 Manifold, 200-203 Resist film, 220, 221 Protective film, 300 Piezoelectric actuator

Claims (8)

A piezoelectric actuator comprising a first electrode, a piezoelectric layer provided on the first electrode, and a second electrode provided on the piezoelectric layer,
The piezoelectric layer has an active part sandwiched between the first electrode and the second electrode, and an inactive part not sandwiched between the first electrode and the second electrode. And
A piezoelectric actuator, wherein a porous portion having a density lower than that of the active portion is provided on at least a part of the inactive portion.   2. The piezoelectric actuator according to claim 1, wherein the porous portion has a larger interval between crystals than the other portion of the piezoelectric layer.   3. The piezoelectric actuator according to claim 1, wherein the porous portion has a rougher surface than other portions of the piezoelectric layer.   The piezoelectric actuator according to any one of claims 1 to 3, wherein the porous portion is formed by dissolving a part of the piezoelectric layer with hydrofluoric acid.   The piezoelectric actuator according to claim 4, wherein the porous portion includes an organic protective film.   The piezoelectric actuator according to claim 1, wherein the piezoelectric layer is made of a perovskite oxide containing at least lead, zirconium, and titanium.   A liquid ejecting head comprising the piezoelectric actuator according to claim 1.   A liquid ejecting apparatus comprising the liquid ejecting head according to claim 7.