JP5194333B2 - Piezoelectric element and piezoelectric device - Google Patents

Description

  The present invention relates to a piezoelectric element and a piezoelectric device including a piezoelectric layer and an electrode.

As a conventional piezoelectric element, for example, a piezoelectric actuator described in Patent Document 1 is known. The piezoelectric actuator described in this document is formed by laminating a piezoelectric sheet having a plurality of drive electrodes, a piezoelectric sheet having a common electrode, and a surface electrode for each drive electrode and an insulating sheet having a surface electrode for the common electrode. ing. Such a piezoelectric actuator is stacked on a cavity plate having a liquid ejection nozzle and a pressure chamber.
JP 2001-260349 A

  However, the following problems exist in the prior art. That is, the liquid in the cavity plate directly touches the end surface (displacement transmission surface) opposite to the surface electrode in the piezoelectric actuator. For this reason, the liquid may be impregnated into the piezoelectric actuator from the displacement transmission surface during use, which may cause deterioration of the characteristics of the piezoelectric actuator such as poor insulation.

  An object of the present invention is to provide a piezoelectric element and a piezoelectric device capable of suppressing deterioration of characteristics when a displacement of a piezoelectric layer is transmitted to a liquid.

  As a result of intensive studies, the inventors of the present invention, as one of the causes of the liquid impregnating in the piezoelectric element, the liquid is charged by static electricity or the like, so that the liquid is drawn toward the electrode inside the element. It was found that there is a so-called electroosmosis phenomenon. Further analysis of the electro-osmosis phenomenon of the liquid revealed that the charge of the liquid is always positive, so that the liquid is attracted toward the negative electrode and impregnated in the piezoelectric element. Therefore, the present inventors considered that if the liquid is prevented from being positively charged, the electroosmosis phenomenon of the liquid will not occur, and further investigation was performed. The present invention has been made based on such knowledge.

That is, the piezoelectric element of the present invention is disposed so as to face the piezoelectric layer with the piezoelectric layer interposed therebetween, and the individual electrode and the common electrode for displacing the piezoelectric layer and the piezoelectric layer are individually provided. A displacement transmission layer that is laminated via an electrode or a common electrode and transmits the displacement of the piezoelectric layer to the liquid, and on the end surface facing the individual electrode and the common electrode on the side opposite to the piezoelectric layer in the displacement transmission layer, A conductive film is formed , the conductive film is electrically connected to the common electrode, the piezoelectric layer and the displacement transmission layer are formed of the same piezoelectric ceramic material, and the piezoelectric layer is subjected to polarization treatment. The displacement transmission layer is not subjected to polarization treatment .

  When liquid is controlled using such a piezoelectric element, for example, a liquid circulation part having a liquid chamber for containing the liquid is arranged on the opposite side of the piezoelectric layer with respect to the displacement transmission layer, and the liquid circulation The liquid chamber of the part is filled with liquid. In this state, when a voltage is applied between the individual electrode and the common electrode, an electric field is generated in a portion (piezoelectric active portion) sandwiched between the individual electrode and the common electrode in the piezoelectric layer, and the piezoelectric active portion Expands and contracts (displaces), and the displacement is transmitted to the liquid via the displacement transmission layer. At this time, by applying the same voltage (ground voltage) as the common electrode to the conductive film formed on the end surface of the displacement transmission layer opposite to the piezoelectric layer, the liquid in contact with the conductive film A negative electric field is applied to. In this case, since the liquid is not positively charged, the occurrence of an electroosmotic phenomenon in which the charged liquid is attracted to the common electrode and impregnated in the piezoelectric element is prevented. Thereby, defective insulation of the piezoelectric element can be suppressed.

Further , the conductive film is electrically connected to the common electrode. For this reason , the same voltage as the common electrode can be applied to the conductive film without attaching a lead wire or the like to the conductive film.

Also, displacement of transfer layer is formed of the same material as the piezoelectric layer. Therefore, the displacement transmission layer can be formed in the same manner as the piezoelectric layer without preparing a material for the displacement transmission layer separately from the material for the piezoelectric layer. Accordingly , the piezoelectric element can be easily manufactured.

The piezoelectric device of the present invention is disposed so as to face the piezoelectric layer with the piezoelectric layer interposed therebetween, and an individual electrode and a common electrode for moving the piezoelectric layer, and an individual electrode or a common electrode with respect to the piezoelectric layer. A liquid flow having a displacement transmission layer laminated via a common electrode and transmitting the displacement of the piezoelectric layer to the liquid, and a liquid chamber disposed on the opposite side of the piezoelectric transmission layer with respect to the displacement transmission layer and containing the liquid A conductive film is formed on at least a portion corresponding to the liquid chamber on the end surface facing the individual electrode and the common electrode on the liquid flow section side of the displacement transmission layer . It is electrically connected to the common electrode, the piezoelectric layer and the displacement transmission layer are formed of the same piezoelectric ceramic material, the piezoelectric layer is subjected to polarization treatment, and the displacement transmission layer is not subjected to polarization treatment It is what.

  In such a piezoelectric device, when a voltage is applied between the individual electrode and the common electrode in a state where the liquid chamber of the liquid circulation portion is filled with the liquid, the individual electrode and the common electrode in the piezoelectric layer are applied. An electric field is generated in the sandwiched portion (piezoelectric active portion), the piezoelectric active portion expands and contracts (displaces), and the displacement is transmitted to the liquid via the displacement transmission layer. At this time, by applying the same voltage (ground voltage) as that of the common electrode to the conductive film formed on the end surface of the displacement transmitting layer on the liquid circulation part side, the liquid in contact with the conductive film is minus. The electric field is applied. In this case, since the liquid is not positively charged, the occurrence of an electroosmosis phenomenon in which the charged liquid is attracted to the common electrode and impregnated in the piezoelectric layer is prevented. Thereby, the insulation failure of a piezoelectric device, etc. can be suppressed.

  According to the present invention, it is possible to suppress deterioration in characteristics when the displacement of the piezoelectric layer is transmitted to the liquid. Accordingly, it is possible to improve the reliability of the piezoelectric element and the piezoelectric device without providing a partition wall or the like as a separate protective layer between the displacement transmission layer and the liquid.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of a piezoelectric element and a piezoelectric device according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a perspective view showing an embodiment of a piezoelectric device including a piezoelectric element according to the present invention, and FIG. 2 is a partial sectional side view of the piezoelectric device. In each figure, the piezoelectric device 1 of this embodiment is a piezoelectric device for liquid control used in, for example, a micropump unit.

  The piezoelectric device 1 includes a laminated piezoelectric element 2 and a liquid circulation part 3 joined to the bottom surface of the piezoelectric element 2. The piezoelectric element 2 has a rectangular parallelepiped laminated body 4, and the laminated body 4 includes an active region layer 5 and a displacement transmission layer 6 disposed on the liquid circulation part 3 side of the active region layer 5.

  The active region layer 5 is disposed so as to face the piezoelectric layer 7 with the piezoelectric layer 7 interposed therebetween, and a plurality of internal individual electrodes 8 and internal common electrodes for operating the piezoelectric layer 7 to expand and contract (displace). 9 over a plurality of layers. The individual internal electrode layers 8 and the internal common electrodes 9 are alternately stacked via the piezoelectric layers 7. The internal electrode located on the lowermost side of the active region layer 5 is an internal common electrode 9. In the piezoelectric layer 7, a plurality of portions sandwiched between each internal individual electrode 8 and the internal common electrode 9 actually expand and contract when a voltage is applied between each internal individual electrode 8 and the internal common electrode 9. The piezoelectric active portion 7a is configured.

  On the upper surface of the laminate 4, a plurality of individual terminal electrodes 10 electrically connected to the plurality of internal individual electrodes 8 of each layer, and a common terminal electrode 11 electrically connected to the internal common electrode 9 of each layer, Is provided.

  The piezoelectric layer 7 is made of, for example, a piezoelectric ceramic material mainly composed of PZT (lead zirconate titanate). The internal individual electrode 8 and the internal common electrode 9 are made of Ag and Pd, for example, and the individual terminal electrode 10 and the common terminal electrode 11 are made of Ag, Au, or Cu, for example. The thickness of the piezoelectric layer 7 is, for example, about 20 to 50 μm. The thickness of the internal individual electrode 8 and the internal common electrode 9 is, for example, about 0.2 to 5.0 μm.

  The displacement transmitting layer 6 laminated on the lower side with respect to the active region layer 5 is a layer that transmits the displacement of the piezoelectric active portion 7a of the piezoelectric body 7 to the liquid flowing through the liquid flowing portion 3, It has a function of protecting the lowermost internal common electrode 9 of the layer 5. The displacement transmission layer 6 is preferably made of the same ceramic material as the piezoelectric layer 7. Thereby, since the displacement transmission layer 6 can be made in the same process as the piezoelectric layer 7 as described later, the laminate 4 can be easily manufactured. The thickness of the displacement transmission layer 6 is, for example, about 20 to 40 μm. At this time, if the displacement transmission layer 6 is made thinner than the piezoelectric layer 7, the displacement of the piezoelectric layer 7 is easily transmitted, which is effective.

  Unlike the active region layer 5, the displacement transmission layer 6 is a layer that is not subjected to polarization processing (described later). When the polarization treatment is performed on the element, the element may be distorted and a gap may be formed at the grain boundary. However, if the displacement transmission layer 6 is an unpolarized layer, such a gap may be formed in the displacement transmission layer 6. Since it is not formed, the displacement transmission layer 6 has a structure in which the liquid is difficult to penetrate. Further, the end surface (displacement transmission surface) 6a on the liquid flow section 3 side of the displacement transmission layer 6 is a firing surface (natural surface) in a state where mechanical surface processing such as polishing is not performed after firing (described later). Is desirable. In this case, since there is no minute defect due to the mechanical surface processing on the displacement transmission surface 6a, the liquid hardly penetrates into the displacement transmission layer 6 as described above.

  On the displacement transmission surface 6 a of the displacement transmission layer 6, a conductive film 12 (hereinafter simply referred to as a conductive film) 12 for applying a negative electric field to the liquid flowing through the liquid circulation portion 3 is formed. The conductive film 12 covers substantially the entire displacement transmission surface 6a of the displacement transmission layer 6 (see FIG. 8). The conductive film 12 is formed of a metal such as Au, Ag, or Cu, or a polymer organic material having conductivity (such as a carbon-dispersed organic material). The thickness of the conductive film 12 is preferably about 0.1 to 2.0 μm, for example, from the viewpoint of preventing the penetration of liquid and not inhibiting the displacement of the active region layer 5.

  Specifically, as shown in FIG. 3, the piezoelectric element 2 has a structure in which a plurality of types (here, five types) of sheet-like electrode-attached ceramic layers 13 to 17 are stacked by a predetermined number (here, 10). have. The individual internal electrodes 8 of each layer in the piezoelectric element 2 are two-dimensionally arranged on the upper surface of the rectangular piezoelectric layer 7. At this time, the internal individual electrodes 8 adjacent to each other in the short direction of the piezoelectric layer 7 are arranged so as to be shifted in the longitudinal direction of the piezoelectric layer 7. Thereby, in order to cope with the miniaturization and high integration of the piezoelectric element 2, it is possible to secure the area of each piezoelectric active portion 7a of the piezoelectric layer 7 even when a large number of internal individual electrodes 8 are arranged at high density. it can.

  As shown in FIG. 4, the electrode-attached ceramic layer 13 has a plurality of individual electrode patterns 18 corresponding to the internal individual electrodes 8 and a common electrode relay pattern 19 on the upper surface of the piezoelectric layer 7. The common electrode relay pattern 19 is formed at one end of the upper surface of the piezoelectric layer 7. The ceramic layer with electrodes 13 is provided with a plurality of through holes 20 electrically connected to the internal individual electrodes 8 and through holes 21 electrically connected to the common electrode relay pattern 19. . The through holes 20 and 21 are filled with a conductive material made of, for example, Ag and Pd.

  As shown in FIG. 5, the electrode-attached ceramic layer 14 has a plurality of individual electrode patterns 18 and a common electrode relay pattern 19 on the upper surface of the piezoelectric layer 7 in the same manner as the above-described electrode-attached ceramic layer 13. Yes. The ceramic layer 14 with an electrode is provided with the same through hole 21 as the ceramic layer 13 with an electrode, but the through hole 20 is not provided.

  As shown in FIG. 6, the electrode-attached ceramic layer 15 has a common electrode pattern 22 corresponding to the internal common electrode 9 and a plurality of individual electrode relay patterns 23 on the upper surface of the piezoelectric layer 7. The common electrode pattern 22 includes a plurality of electrode pattern portions 22 a formed at positions corresponding to the individual electrode patterns 18, and an electrode pattern portion 22 b formed at positions corresponding to the common electrode relay pattern 19. The individual electrode relay pattern 23 is formed adjacent to the electrode pattern portion 22 a at a position corresponding to the individual electrode pattern 18. The ceramic layer with electrodes 15 is provided with a plurality of through holes 24 electrically connected to the individual electrode relay patterns 23 and through holes 25 electrically connected to the common electrode pattern 22. . The through holes 24 and 25 are filled with a conductive material.

  As shown in FIG. 7, the electrode-attached ceramic layer 16 has a common electrode pattern 26 corresponding to the internal common electrode 9 on the upper surface of the displacement transmission layer 6. The common electrode pattern 26 includes a connection electrode pattern portion 26a in addition to the same electrode pattern portions 22a and 22b as those of the ceramic layer with electrode 15 described above. The connection electrode pattern portion 26 a is formed at the corner on the same side as the electrode pattern portion 22 b on the upper surface of the displacement transmission layer 6. The connection electrode pattern portion 26a may be formed on the opposite side of the upper surface of the displacement transmission layer 6 from the electrode pattern portion 22b. In addition, a through-hole 27 that is electrically connected to the common electrode pattern 26 is formed in the ceramic layer 16 with an electrode. The through hole 27 is formed in a region corresponding to the connection electrode pattern portion 26 a in the displacement transmission layer 6. The through hole 27 is filled with a conductive material.

  As shown in FIG. 8, the conductive film 12 is formed on the lower surface of the electrode-attached ceramic layer 16 so as to cover substantially the entire surface of the displacement transmission layer 6. The conductive film 12 is electrically connected to the common electrode pattern 26 through the through hole 27.

  As shown in FIG. 9, the electrode-attached ceramic layer 17 has the plurality of individual terminal electrodes 10 and the common terminal electrode 11 on the upper surface of the piezoelectric layer 7. The individual terminal electrode 10 is formed at a position corresponding to the individual electrode relay pattern 23 of the electrode-attached ceramic layer 15. The common terminal electrode 11 is formed at a position corresponding to the common electrode relay pattern 19 of the electrode-attached ceramic layer 13. The ceramic layer 17 with electrodes is provided with a plurality of through holes 28 electrically connected to the individual terminal electrodes 10 and through holes 29 electrically connected to the common terminal electrodes 11. The through holes 28 and 29 are filled with a conductive material.

  In addition, as the common electrode pattern 22 of the ceramic layer 15 with an electrode, as shown in FIG. 6, it may be a solid structure without being separated into a plurality of electrode pattern portions 22a and electrode pattern portions 22b. The same applies to the common electrode pattern 26 of the electrode-attached ceramic layer 16.

  As shown in FIG. 3, the piezoelectric element 2 has a structure in which a ceramic layer 17, a ceramic layer 15, a ceramic layer 13, a ceramic layer 15,..., A ceramic layer 13, a ceramic layer 15, a ceramic layer 14, and a ceramic layer 16 are stacked in order from the top. I am doing. The individual terminal electrode 10 has two layers from the bottom through the through hole 28 of the ceramic layer 17, the individual electrode relay pattern 23 and the through hole 24 of the ceramic layer 15, and the individual electrode pattern 18 and the through hole 20 of the ceramic layer 13. The individual electrode pattern 18 of the ceramic layer 14 of the eye is electrically connected. The common terminal electrode pattern 11 includes a through hole 29 in the ceramic layer 17, a common electrode pattern 22 and a through hole 25 in the ceramic layer 15, a common electrode relay pattern 19 and a through hole 21 in the ceramic layer 13, and a common electrode in the ceramic layer 14. The relay electrode 19 and the through hole 21 are electrically connected to the common electrode pattern 26 of the lowermost ceramic layer 16.

  Returning to FIG. 1 and FIG. 2, a voltage application lead wire 30 is joined to each individual terminal electrode 10 and common terminal electrode 11 by soldering or the like. The lead wire 30 is made of, for example, a flexible printed wiring board (FPC).

  The liquid circulation part 3 located on the back surface side of the piezoelectric element 2, that is, the displacement transmission surface 6 a side, has a plurality of liquid chambers 31 for containing the liquid to which the displacement of the piezoelectric layer 7 is transmitted. . Each liquid chamber 31 is formed at a position corresponding to each internal individual electrode 10. A liquid inlet 32 for introducing a liquid into each liquid chamber 31 is provided on one end side of the liquid circulation part 3. In addition, a plurality of liquid outlets 33 through which liquid flows out from the liquid chamber 31 when the displacement of the piezoelectric layer 7 is transmitted to the liquid are provided at the bottom of the liquid circulation part 3. The liquid circulation part 3 is formed of a metal material such as nickel alloy steel or chromium alloy steel, resin, ceramic, or the like.

  Next, a procedure for manufacturing the above-described piezoelectric device 1 will be described. First, the piezoelectric element 2 is manufactured as follows.

  That is, for example, a piezoelectric ceramic mainly composed of PZT is prepared, and a paste in which an organic binder, an organic solvent, and the like are mixed is prepared. Then, a ceramic green sheet that becomes the piezoelectric layer 7 and the displacement transmission layer 6 is formed by forming a paste sheet using the PET film as a carrier film.

  Subsequently, for example, a through hole is formed in the green sheet by irradiating a predetermined position of the green sheet with a third harmonic laser beam of YAG, for example. At this time, the through hole is processed so that the hole diameter becomes, for example, 40 to 50 μm after firing described later. Then, for example, a conductive paste in which a conductive material configured in a ratio of Ag: Pd = 7: 3 is mixed with an organic binder, an organic solvent, and the like is manufactured, and the conductive paste is filled into the through holes by, for example, a screen printing method.

  Subsequently, for example, using the same conductive paste, an internal electrode pattern is formed on one surface of the green sheet by, for example, a screen printing method. Subsequently, a predetermined number of green sheets on which internal electrode patterns are printed are stacked in a predetermined order. Then, the green laminate is pressed at a pressure of about 100 MPa while applying heat of about 60 ° C., for example, and the green sheets of the respective layers are pressure-bonded. Thereafter, the green laminate is cut into a predetermined dimension.

  Subsequently, the green laminated body is placed on a setter, and degreasing (debinding) of the green laminated body is performed at a temperature of about 400 ° C. for about 10 hours, for example. Thereafter, the setter on which the green laminate is placed is put in a closed mortar, and the green laminate is fired at a temperature of, for example, about 1100 ° C. for about 2 hours to obtain the laminate 4 as a sintered body.

  Subsequently, the individual terminal electrode 10 and the common terminal electrode 11 made of, for example, Ag are formed on the upper surface of the fired laminate 4. As a method for forming the terminal electrodes 10 and 11, baking, sputtering, electroless plating, or the like is used. Subsequently, a conductive film 12 made of, for example, Au is formed on the lower surface (displacement transmission surface) 6 a of the stacked body 4. As a method for forming the conductive film 12, sputtering, baking, vapor deposition, electroless plating, or the like is used.

  Subsequently, the lead wires 30 are connected to the terminal electrodes 10 and 11 by solder or the like. Then, for example, under a temperature of 120 ° C., a polarization process is performed by applying a predetermined voltage, for example, for 3 minutes so that the electric field strength with respect to the thickness of the piezoelectric layer 7 becomes 3 kV / mm. Thereby, the piezoelectric element 2 as a piezoelectric ceramic actuator is completed.

  Then, the piezoelectric device 1 is obtained by sticking the separately prepared liquid circulation part 3 to the bottom surface (displacement transmission surface) 6a of the piezoelectric element 2 with an adhesive.

  In the piezoelectric device 1 as described above, each liquid chamber 31 of the liquid circulation part 3 contains liquid in advance, and the liquid is in contact with the bottom surface 6 a of the piezoelectric element 2. In this state, when a predetermined voltage is applied via the lead wire 30 between any of the individual terminal electrodes 10 and the common terminal electrode 11 so that the common terminal electrode 11 is at the GND potential, the selected individual terminal electrode is selected. A voltage is applied between the internal individual electrode 8 corresponding to 10 and the internal common electrode 9. As a result, an electric field is generated in a portion (piezoelectric active portion 7 a) between the internal individual electrode 8 and the internal common electrode 9 in the piezoelectric layer 7 of each layer, and the piezoelectric active portion 7 a is displaced in the stacking direction of the stacked body 4. To come. Then, the displacement of the piezoelectric active portion 7 a is transmitted to the liquid in the corresponding liquid chamber 31 through the displacement transmission layer 6. As a result, the volume of the liquid chamber 31 is reduced, and an amount of liquid corresponding to the volume reduction is discharged from the liquid outlet 33.

  At this time, since the conductive film 12 provided on the bottom surface 6 a of the piezoelectric element 2 is electrically connected to the internal common electrode 9 through the through hole 27, the conductive film 12 is the same as the internal common electrode 9. A GND voltage is applied. For this reason, a negative electric field is applied to the conductive film 12, and accordingly, a negative electric field is also applied to the liquid in contact with the conductive film 12. This prevents the liquid in the liquid chamber 31 from being positively charged due to static electricity or the like, so that the charged liquid is prevented from being drawn into the internal common electrode 9 due to the electroosmosis phenomenon and penetrating into the piezoelectric element 2. Is done. Accordingly, a decrease in the insulation resistance of the piezoelectric element 2 due to the permeation of the liquid can be suppressed, so that the deterioration of the characteristics of the piezoelectric element 2 can be suppressed. As a result, the reliability of the piezoelectric element 2 can be improved.

  Therefore, it is not necessary to provide a partition wall having a predetermined thickness between the piezoelectric element 2 and the liquid circulation part 3 in order to avoid an insulation failure or the like of the piezoelectric element 2. For this reason, the displacement transmission of the piezoelectric layer 7 with respect to the liquid is not hindered by the partition walls, so that it is not necessary to increase the number of layers of the stacked body 4 more than necessary to compensate for the loss of the transmission displacement amount by the partition walls. As a result, the piezoelectric element 2 and thus the piezoelectric device 1 can be reduced in size, and an increase in manufacturing cost thereof can be suppressed.

  The piezoelectric element and the piezoelectric device according to the present invention are not limited to the above embodiment. For example, in the piezoelectric element 2 of the above embodiment, the through hole 27 for electrically connecting the conductive film 12 and the internal common electrode 9 is provided in the displacement transmission layer 6, but as shown in FIG. The through hole 27 is not necessarily provided. In this case, a lead wire or the like is provided on the conductive film 12 and the same voltage may be applied to the internal common electrode 9 and the conductive film 12.

  Moreover, in the said embodiment, although the electrically conductive film 12 was formed in the substantially whole surface of the displacement transmission surface 6a of the displacement transmission layer 6, the electrically conductive film 12 respond | corresponds to the liquid chamber 31 of the liquid distribution part 3 in the displacement transmission surface 6a. What is necessary is just to form in a site | part.

  Moreover, in the said embodiment, although it was set as the structure which laminated | stacked the several piezoelectric material layer 7, if the big displacement amount is not especially required, the piezoelectric material layer 7 may be a single layer. Further, the number and arrangement of the internal individual electrodes 8 in each layer are not particularly limited to those in the above embodiment. Further, the internal electrode located on the lowermost side of the active region layer 5 is not limited to the internal common electrode 9 as in the above embodiment, and may be the internal individual electrode 8.

  Furthermore, in the above embodiment, the displacement transmission layer 6 is formed of the same ceramic material as that of the piezoelectric layer 7. However, the displacement transmission layer 6 may be formed of a ceramic material or resin different from the piezoelectric layer 7.

  In addition, the electrical connection means between the internal individual electrodes 8 of each layer and the internal common electrodes 9 of each layer is not limited to the through-hole as in the above-described embodiment. For example, as an external electrode formed on the side surface of the laminate 4 Also good.

(1) Example First, 30 piezoelectric elements according to the present invention were prepared, and a liquid circulation part was bonded to these to form a piezoelectric device. Then, a lead wire was attached to each piezoelectric element so that a voltage could be applied to the terminal electrode. Subsequently, the liquid circulation part of the piezoelectric device was filled with a liquid and sealed. As the liquid, pure water was used as a main component, and a mixture of glycerin and a nonionic surfactant was used. Subsequently, a DC voltage of 1 kV / mm per piezoelectric layer thickness was simultaneously applied to all the individual terminal electrodes. Then, static electricity was periodically applied to the piezoelectric device.

  Thus, the piezoelectric device was continuously driven for 500 hours, and the state before and after the driving of the piezoelectric element was confirmed. Specifically, after 500 hours from the start of driving of the piezoelectric device, the liquid was discharged from the liquid circulation portion, and the insulation resistance of the piezoelectric element was examined. As a result, there was no piezoelectric element having a reduced insulation resistance value.

(2) Comparative Example Thirty piezoelectric elements having no conductive film formed on the bottom surface (displacement transmission surface) were prepared as piezoelectric elements of the comparative example, and a piezoelectric device was formed. Then, the piezoelectric device was continuously driven for 500 hours in the same manner as in the above example. As a result, the insulation resistance value decreased by 2 to 3 digits in 17 piezoelectric elements. Thus, it was judged that the effect of the present invention was obtained.

It is a perspective view showing one embodiment of a piezoelectric device provided with a piezoelectric element concerning the present invention. It is a partial sectional side view of the piezoelectric device shown in FIG. FIG. 3 is an exploded perspective view of the piezoelectric element shown in FIG. 2. It is a top view which shows one of the ceramic layers with an electrode shown in FIG. It is a top view which shows another one of the ceramic layers with an electrode shown in FIG. It is a top view which shows another one of the ceramic layers with an electrode shown in FIG. It is a top view which shows another one of the ceramic layers with an electrode shown in FIG. It is a bottom view of the ceramic layer with an electrode shown in FIG. It is a top view which shows another one of the ceramic layers with an electrode shown in FIG. It is a top view which shows the modification of the ceramic layer with an electrode shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Piezoelectric device, 2 ... Piezoelectric element, 3 ... Liquid distribution part, 6 ... Displacement transmission layer, 6a ... Displacement transmission surface (end surface), 7 ... Piezoelectric layer, 8 ... Internal individual electrode, 9 ... Internal common electrode, 12 ... conductive film (film having conductivity), 27 ... through hole, 31 ... liquid chamber.

Claims (2)

A piezoelectric layer;
An individual electrode and a common electrode that are arranged so as to face each other with the piezoelectric layer interposed therebetween, and for displacing the piezoelectric layer,
A displacement transmission layer that is laminated to the piezoelectric layer via the individual electrode or the common electrode, and transmits a displacement of the piezoelectric layer to a liquid;
A conductive film is formed on an end surface of the displacement transmission layer opposite to the piezoelectric layer and facing the individual electrode and the common electrode .
The conductive film is electrically connected to the common electrode,
The piezoelectric element is characterized in that the piezoelectric layer and the displacement transmission layer are formed of the same piezoelectric ceramic material, the piezoelectric layer is subjected to polarization treatment, and the displacement transmission layer is not subjected to polarization treatment . A piezoelectric layer;
An individual electrode and a common electrode that are arranged so as to face each other with the piezoelectric layer interposed therebetween, and for displacing the piezoelectric layer,
A displacement transmission layer that is laminated to the piezoelectric layer via the individual electrode or the common electrode, and transmits the displacement of the piezoelectric layer to a liquid;
A liquid circulation part disposed on the opposite side of the piezoelectric layer with respect to the displacement transmission layer and having a liquid chamber for containing the liquid;
A conductive film is formed on at least a portion corresponding to the liquid chamber on the end surface facing the individual electrode and the common electrode on the liquid flow portion side of the displacement transmission layer ,
The conductive film is electrically connected to the common electrode,
The piezoelectric device, wherein the piezoelectric layer and the displacement transmission layer are formed of the same piezoelectric ceramic material, the piezoelectric layer is subjected to polarization treatment, and the displacement transmission layer is not subjected to polarization treatment .

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