JP7131924B2 - Laminated piezoelectric element, piezoelectric vibration device, and electronic equipment - Google Patents

Description

TECHNICAL FIELD The present invention relates to a laminated piezoelectric element, a piezoelectric vibrator, and an electronic device that utilize a piezoelectric transverse effect.

Japanese Laid-Open Patent Publication No. 2002-201001 discloses a multilayer piezoelectric element having a piezoelectric body formed by stacking piezoelectric layers. This laminated piezoelectric element has an elongated shape with a large longitudinal dimension perpendicular to the lamination direction of the piezoelectric body. Since the piezoelectric lateral effect can be effectively obtained in the laminated piezoelectric element having such a shape, it can be greatly expanded and contracted in the longitudinal direction.

Further, Patent Literature 1 discloses a piezoelectric vibration device having a configuration in which a vibration plate is joined to the laminated piezoelectric element. In this piezoelectric vibration device, the laminated piezoelectric element extends in the longitudinal direction along the diaphragm, and the expansion and contraction of the laminated piezoelectric element in the longitudinal direction is transmitted to the diaphragm. Thereby, this piezoelectric vibration device can vibrate the diaphragm.

JP 2016-100760 A International Publication No. 2016/052582

In a laminated piezoelectric element having an elongated shape, external stress due to impact or the like is likely to be applied to both ends in the longitudinal direction. The stress applied to both ends of the laminated piezoelectric element in the longitudinal direction tends to concentrate on the ridges of the piezoelectric body. For this reason, in a laminated piezoelectric element having an elongated shape, cracks tend to occur starting from the ridges of the piezoelectric body.

SUMMARY OF THE INVENTION In view of the circumstances as described above, an object of the present invention is to provide a highly reliable laminated piezoelectric element, a piezoelectric vibration device, and an electronic device.

To achieve the above object, a laminated piezoelectric element according to one aspect of the present invention includes a ceramic body, a pair of external electrodes, a plurality of internal electrodes, and surface electrodes.
The ceramic body is made of piezoelectric ceramics, and has first and second end surfaces facing the longitudinal direction, first and second main surfaces facing the thickness direction orthogonal to the longitudinal direction, and the first and second main surfaces facing the thickness direction perpendicular to the longitudinal direction. and a ridge connecting the second end surface and the first and second main surfaces.
The pair of external electrodes cover the first and second end surfaces, extend from the first and second end surfaces to the first main surface via the ridge, and have the thickness above the first main surface. protrude in the vertical direction.
The plurality of internal electrodes are stacked inside the ceramic body along the thickness direction, and are alternately connected to the pair of external electrodes along the thickness direction.
The surface electrode is provided on at least one of the first and second main surfaces, and is connected to the external electrode different from the internal electrode adjacent in the thickness direction.

A pair of external electrodes of this laminated piezoelectric element are formed with apexes protruding in the thickness direction on the first main surface of the ceramic body. Therefore, external stress is likely to be applied to the top of the pair of external electrodes. However, in the pair of external electrodes, the stress applied to the apex facing the first main surface is dispersed along the first main surface, so that it is difficult to concentrate on the ridges of the ceramic body. Therefore, in this laminated piezoelectric element, the occurrence of cracks originating from the ridges on the first main surface side of the ceramic body is suppressed, and high reliability is obtained.

The pair of external electrodes may extend from the first and second end surfaces to the second main surface via the ridge and protrude in the thickness direction on the second main surface.
In this laminated piezoelectric element, the occurrence of cracks originating from the ridge on the second main surface side of the ceramic body is also suppressed, so that even higher reliability can be obtained.

The ridge may be configured with a curved surface.
In this laminated piezoelectric element, the stress applied to the ridge of the ceramic body is distributed along the curved surface forming the ridge. As a result, in this laminated piezoelectric element, local stress is less likely to be applied to the ridges of the ceramic body, so cracks originating from the ridges of the ceramic body are more effectively suppressed.

A piezoelectric vibration device according to one aspect of the present invention includes the laminated piezoelectric element described above, a diaphragm, and an adhesive layer.
The vibration plate faces the laminated piezoelectric element in the thickness direction.
The adhesive layer is arranged between the laminated piezoelectric element and the diaphragm.
In this piezoelectric vibrating device, the occurrence of cracks originating from the ridges of the ceramic element in the laminated piezoelectric element is suppressed during manufacturing or driving, so that high reliability can be obtained.

The laminated piezoelectric element may be arranged with the first main surface facing the diaphragm.
In this piezoelectric vibrating device, cracks are less likely to occur starting from the ridges on the first main surface side of the ceramic body due to stress applied from the diaphragm to the laminated piezoelectric element during driving.

A part of the pair of external electrodes of the laminated piezoelectric element may be arranged in the adhesive layer.
The adhesive layer may be filled between the first main surface and the diaphragm.
In these configurations, since the bonding strength between the laminated piezoelectric element and the diaphragm is high, the expansion and contraction of the laminated piezoelectric element in the longitudinal direction is efficiently transmitted to the diaphragm. Therefore, this piezoelectric vibration device can vibrate the diaphragm more greatly.

An electronic device according to one aspect of the present invention includes the laminated piezoelectric element described above, a panel, and a housing.
The panel is bonded with the laminated piezoelectric elements facing each other in the thickness direction.
The housing holds the panel.

ADVANTAGE OF THE INVENTION According to this invention, the laminated piezoelectric element, piezoelectric vibration apparatus, and electronic device which are excellent in reliability can be provided.

1 is a perspective view of a laminated piezoelectric element according to one embodiment of the present invention; FIG. 2 is a cross-sectional view of the laminated piezoelectric element taken along line AA' in FIG. 1; FIG. FIG. 2 is a cross-sectional view of the laminated piezoelectric element taken along line BB′ of FIG. 1; 3 is a partial cross-sectional view showing an enlarged region C of FIG. 2 of the laminated piezoelectric element; FIG. FIG. 4 is a partial cross-sectional view showing Comparative Example 1 of the laminated piezoelectric element. FIG. 5 is a partial cross-sectional view showing Comparative Example 2 of the laminated piezoelectric element. 4 is a flow chart showing a method for manufacturing the laminated piezoelectric element. It is a perspective view which shows the manufacturing process of the said laminated piezoelectric element. It is a perspective view which shows the manufacturing process of the said laminated piezoelectric element. FIG. 2 is a cross-sectional view of a piezoelectric vibration device using the laminated piezoelectric element; It is a flow chart which shows a manufacturing method of the above-mentioned piezoelectric vibration device. It is a perspective view which shows the manufacturing process of the said piezoelectric vibration apparatus. It is a perspective view which shows the manufacturing process of the said piezoelectric vibration apparatus. It is a perspective view which shows the manufacturing process of the said piezoelectric vibration apparatus. FIG. 2 is a plan view of an electronic device using the laminated piezoelectric element; 12B is a cross-sectional view of the electronic device taken along line CC' of FIG. 12A. FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The drawings show mutually orthogonal X, Y and Z axes where appropriate. The X-axis, Y-axis, and Z-axis are common in all drawings.

[Basic Configuration of Laminated Piezoelectric Element 10]
1 to 3 are diagrams schematically showing the basic configuration of a laminated piezoelectric element 10 according to one embodiment of the present invention. FIG. 1 is a perspective view of a laminated piezoelectric element 10. FIG. FIG. 2 is a cross-sectional view of the laminated piezoelectric element 10 taken along line AA' in FIG. FIG. 3 is a cross-sectional view of the laminated piezoelectric element 10 taken along line BB' of FIG.

The laminated piezoelectric element 10 has a longitudinal direction along the X-axis, a width direction along the Y-axis, and a thickness direction along the Z-axis. That is, the laminated piezoelectric element 10 is elongated in the X-axis direction. As a result, in the laminated piezoelectric element 10, deformation in the X-axis direction due to the transverse piezoelectric effect is dominant over deformation in the Z-axis direction due to the longitudinal piezoelectric effect.

The laminated piezoelectric element 10 includes a ceramic body 11 , first external electrodes 14 and second external electrodes 15 . The ceramic body 11 has first and second end faces 11a and 11b facing the X-axis direction, first and second side faces 11c and 11d facing the Y-axis direction, and first and second side faces 11c and 11d facing the Z-axis direction. It has two main surfaces 11e and 11f.

As shown in FIG. 2, the ceramic body 11 is provided with four ridges 11g extending in the X-axis direction and connecting the end faces 11a, 11b and the main faces 11e, 11f. Each ridge 11g is preferably formed of a smooth curved surface. The shape of the ceramic body 11 is not limited to the shapes shown in FIGS.

The first external electrode 14 covers the first end surface 11a of the ceramic body 11 and extends from the first end surface 11a to the main surfaces 11e and 11f via the ridge 11g. The second external electrode 15 covers the second end surface 11b of the ceramic body 11 and extends from the second end surface 11b to the main surfaces 11e and 11f via the ridge portion 11g.

Therefore, both the external electrodes 14 and 15 have a U-shaped cross section along the XZ plane, as shown in FIG. The external electrodes 14 and 15 also extend from the end surfaces 11a and 11b to the side surfaces 11c and 11d. However, in the laminated piezoelectric element 10, the configuration in which the external electrodes 14 and 15 extend to the side surfaces 11c and 11d is not essential.

The external electrodes 14 and 15 are made of a good electrical conductor. Good electrical conductors forming the external electrodes 14 and 15 include, for example, copper (Cu), nickel (Ni), tin (Sn), palladium (Pd), platinum (Pt), silver (Ag), and gold (Au). and the like as a main component.

The ceramic body 11 is made of piezoelectric ceramics having a large absolute value of the piezoelectric constant _d31 . Examples of lead-free materials include lithium niobate (LiNbO ₃ ) and lithium tantalate (LiTaO ₃ ). Examples of lead-based materials include lead zirconate titanate (PbZrO ₃ —PbTiO ₃ ).

A first internal electrode 12 and a second internal electrode 13 are provided inside the ceramic body 11 . The internal electrodes 12 and 13 are sheet-shaped and extend along the XY plane, and are alternately spaced apart along the Z-axis direction. That is, each internal electrode 12, 13 is covered with piezoelectric ceramics.

Therefore, between the internal electrodes 12 and 13, a ceramic layer 18, which is a layer of piezoelectric ceramics, is formed. The first internal electrode 12 is drawn out to the first end surface 11 a of the ceramic body 11 and connected to the first external electrode 14 . The second internal electrode 13 is drawn out to the second end surface 11 b of the ceramic body 11 and connected to the second external electrode 15 .

As shown in FIG. 3, the internal electrodes 12 and 13 are spaced apart from the side surfaces 11c and 11d. That is, the ceramic element body 11 is provided with side margin portions that form spaces between the internal electrodes 12 and 13 and the side surfaces 11c and 11d. This ensures insulation of the internal electrodes 12 and 13 on the side surfaces 11c and 11d.

In the ceramic body 11, a first surface electrode 16 is provided on the first main surface 11e, and a second surface electrode 17 is provided on the second main surface 11f. As a result, between the uppermost second internal electrode 13 and the first surface electrode 16 in the Z-axis direction, and between the lowermost first internal electrode 12 and the second surface electrode 17 in the Z-axis direction. A ceramic layer 18 is formed.

Like the first internal electrode 12 , the first surface electrode 16 is drawn out to the first end surface 11 a of the ceramic body 11 and connected to the first external electrode 14 . Similarly to the second internal electrode 13 , the second surface electrode 17 is drawn out to the second end surface 11 b of the ceramic body 11 and connected to the second external electrode 15 .

The internal electrodes 12, 13 and the surface electrodes 16, 17 are each made of a good electrical conductor. Examples of good electrical conductors forming the internal electrodes 12, 13 and surface electrodes 16, 17 include nickel (Ni), copper (Cu), palladium (Pd), platinum (Pt), silver (Ag), and gold (Au). and the like as a main component.

With the above configuration, in the laminated piezoelectric element 10 , when voltage is applied between the first external electrode 14 and the second external electrode 15 , voltage in the Z-axis direction is applied to all the ceramic layers 18 . As a result, each ceramic layer 18 contracts in the X-axis direction due to the transverse piezoelectric effect, so that the laminated piezoelectric element 10 as a whole contracts in the X-axis direction.

The basic configuration of the laminated piezoelectric element 10 according to this embodiment is not limited to the configurations shown in FIGS. 1 to 3, and can be changed as appropriate. For example, the number of internal electrodes 12 and 13 and the thickness of the ceramic layer 18 can be appropriately determined according to the application of the laminated piezoelectric element 10 or the like. Also, the number of internal electrodes 12 and 13 may be different from each other.

The configuration of surface electrodes 16 and 17 can be changed according to the configuration of internal electrodes 12 and 13 . That is, the surface electrodes 16 and 17 are connected to one of the external electrodes 14 and 15 to which the adjacent internal electrodes 12 and 13 in the Z-axis direction are not connected. Moreover, in the laminated piezoelectric element 10, either one of the surface electrodes 16 and 17 may not be provided.

[Detailed Configuration of External Electrodes 14 and 15]
As shown in FIG. 2, the external electrodes 14 and 15 are provided with top portions 14a and 15a on the main surfaces 11e and 11f of the ceramic body 11, respectively. That is, the external electrodes 14 and 15 protrude downward in the Z-axis direction from the top portions 14a and 15a on the first main surface 11e, and protrude upward in the Z-axis direction from the top portions 14a and 15a on the second main surface 11f.

The apexes 14a and 15a of the external electrodes 14 and 15 on the first main surface 11e form the lowest part of the laminated piezoelectric element 10 in the Z-axis direction, and thus are likely to receive stress from below in the Z-axis direction. In addition, since the apexes 14a and 15a of the external electrodes 14 and 15 on the second main surface 11f form the uppermost part of the laminated piezoelectric element 10 in the Z-axis direction, they are likely to receive stress from above in the Z-axis direction.

FIG. 4 is a partial cross-sectional view showing an enlarged region C surrounded by a dashed line in FIG. 2 of the laminated piezoelectric element 10. As shown in FIG. In the first external electrode 14, the top portion 14a is arranged inside the edge portion 11g of the ceramic body 11 in the X-axis direction. , 11f.

Similarly, since the top portion 15a of the second external electrode 15 is also arranged inside the edge portion 11g of the ceramic body 11 in the X-axis direction, the stress applied to the top portion 15a is concentrated on the edge portion 11g. distributed along the main surfaces 11e and 11f. Thus, in the laminated piezoelectric element 10, the stress is less likely to concentrate on the ridges 11g of the ceramic body 11. FIG.

Further, in the ceramic element body 11, since the edge portion 11g is composed of a curved surface, the stress applied to the edge portion 11g is dispersed along the curved surface forming the edge portion 11g. As a result, in the laminated piezoelectric element 10, application of local stress to the ridges 11g of the ceramic body 11 can be suppressed.

In this manner, the laminated piezoelectric element 10 has a structure in which a large stress is less likely to be applied to the ridges 11g of the ceramic body 11. As shown in FIG. Therefore, in the laminated piezoelectric element 10, it is possible to suppress the occurrence of cracks originating from the ridges 11g of the ceramic body 11. FIG. As a result, the laminated piezoelectric element 10 is highly reliable.

[Comparative example]
FIG. 5A is a partial cross-sectional view of a laminated piezoelectric element 510 according to Comparative Example 1. FIG. The laminated piezoelectric element 510 according to Comparative Example 1 is provided with an external electrode 514 having a configuration different from that of the laminated piezoelectric element 10 according to the present embodiment. The external electrode 514 is provided with a top portion 514a protruding in the Z-axis direction outside the main surfaces 11e and 11f of the ceramic body 11 in the X-axis direction.

In the laminated piezoelectric element 510 according to Comparative Example 1, since the top portion 514a of the external electrode 514 faces the edge portion 11g of the ceramic body 11, the stress applied to the top portion 514a tends to concentrate on the edge portion 11g. For this reason, in the laminated piezoelectric element 510, cracks starting from the ridges 11g of the ceramic body 11 are likely to occur.

5B is a partial cross-sectional view of a laminated piezoelectric element 610 according to Comparative Example 2. FIG. The laminated piezoelectric element 610 according to Comparative Example 2 is provided with an external electrode 614 having a configuration different from that of the laminated piezoelectric element 10 according to the present embodiment. The external electrode 614 is configured such that the upper and lower surfaces in the Z-axis direction are planes along the XY plane.

In the external electrode 614, stress is likely to be applied to the ridges 614a on the outer side in the X-axis direction of the upper and lower surfaces in the Z-axis direction. The stress applied to the edge portion 614a of the external electrode 614 tends to concentrate on the edge portion 11g of the ceramic body 11 . Therefore, in the laminated piezoelectric element 610, cracks tend to occur starting from the ridges 11g of the ceramic body 11. As shown in FIG.

[Manufacturing Method of Laminated Piezoelectric Element 10]
FIG. 6 is a flow chart showing a method for manufacturing the laminated piezoelectric element 10. As shown in FIG. 7 and 8 are diagrams showing the manufacturing process of the laminated piezoelectric element 10. FIG. Hereinafter, a method for manufacturing the laminated piezoelectric element 10 will be described along FIG. 6 and with appropriate reference to FIGS.

(Step S01: Fabrication of ceramic body)
In step S01, a ceramic body 11 is produced. In step S01, first, ceramic sheets 101, 102, 103 and 104 shown in FIG. 7 are prepared. The ceramic sheets 101, 102, 103, and 104 are piezoelectric green sheets containing piezoelectric ceramics as a main component.

A piezoelectric green sheet is obtained by molding a ceramic slurry obtained by mixing calcined powder of piezoelectric ceramics, a binder made of an organic polymer material, and a plasticizer into a sheet. A roll coater, a doctor blade, or the like, for example, can be used to form the piezoelectric green sheet.

A conductive paste is applied in a predetermined pattern to each of the ceramic sheets 101, 102, 103, 104, and unfired internal electrodes 12, 13 and surface electrodes 16, 17 are formed. For example, a screen printing method, a gravure printing method, or the like can be used to apply the conductive paste.

Specifically, the first internal electrodes 12 are formed on the ceramic sheet 101 . A second internal electrode 13 is formed on the ceramic sheet 102 . A first surface electrode 16 is formed on the ceramic sheet 103 . A first internal electrode 12 and a second surface electrode 17 are formed on the ceramic sheet 104 .

Then, the ceramic sheets 101, 102, 103 and 104 are laminated in the Z-axis direction in the order shown in FIG. For thermocompression bonding of the ceramic sheets 101, 102, 103, 104, for example, uniaxial pressurization or hydrostatic pressure pressurization can be used.

Subsequently, the unfired ceramic body 11 is heated to, for example, 300 to 500° C. to remove the binder. Then, the ceramic body 11 after the binder removal treatment is sintered by heating to, for example, 900 to 1200.degree. Thereby, the ceramic body 11 shown in FIG. 8 is obtained.

In order to form the ridges 11g of the ceramic body 11 into smooth curved surfaces, the ceramic body 11 can be barrel-polished, for example. In this case, the curvature of the ridge portion 11g of the ceramic body 11 can be adjusted depending on the barrel polishing conditions. The barrel polishing of the ceramic body 11 may be performed before firing or after firing.

(Step S02: External electrode formation)
In step S02, external electrodes 14 and 15 are formed on the ceramic body 11 obtained in step S01, thereby producing the laminated piezoelectric element 10 shown in FIGS. In step S02, for example, the external electrodes 14 and 15 can be formed by baking the conductive paste applied to both ends of the ceramic body 11 in the X-axis direction.

For example, a printing method, a dipping method, or the like can be used to apply the conductive paste. The components and application conditions of the conductive paste can be appropriately determined so that the external electrodes 14 and 15 after baking have the shapes shown in FIGS. Alternatively, the shape of the conductive paste may be adjusted after applying the conductive paste to the ceramic body 11 .

Note that the processing in step S02 can also be performed in step S01. For example, unfired conductive paste may be applied to both ends of the unfired ceramic body 11 in the X-axis direction. Thereby, the firing of the ceramic body 11 and the firing of the external electrodes 14 and 15 can be performed at the same time.

(Step S03: Polarization processing)
In step S03, the laminated piezoelectric element 10 is subjected to a polarization process. Specifically, in the polarization process, by applying a DC high electric field in the Z-axis direction to the laminated piezoelectric element 10, the direction of spontaneous polarization of the piezoelectric ceramics constituting the ceramic layer 18 is aligned. As a result, piezoelectric activity is imparted to the piezoelectric ceramics, and the laminated piezoelectric element 10 can exhibit its function.

[Configuration of Piezoelectric Vibration Device 20]
The laminated piezoelectric element 10 can be widely used as a piezoelectric actuator that operates in the X-axis direction by the piezoelectric lateral effect. An example of the application of the laminated piezoelectric element 10 is a piezoelectric vibration device that generates vibration. A unimorph-type piezoelectric vibration device 20 configured using the laminated piezoelectric element 10 will be described below.

FIG. 9 is a cross-sectional view of the piezoelectric vibration device 20. As shown in FIG. The piezoelectric vibration device 20 includes a laminated piezoelectric element 10 , a vibration plate 21 and an adhesive layer 22 . The vibration plate 21 is configured as a flat plate extending along the XY plane and arranged to face the first main surface 11e of the laminated piezoelectric element 10 . The adhesive layer 22 is arranged between the laminated piezoelectric element 10 and the vibration plate 21 .

The diaphragm 21 is made of, for example, metal or glass, and has flexibility in the Z-axis direction. The adhesive layer 22 is formed of a resin material or the like, and bonds the laminated piezoelectric element 10 and the vibration plate 21 together. The adhesive layer 22 is in close contact with the lower portion of the laminated piezoelectric element 10 in the Z-axis direction and in close contact with the upper surface of the vibration plate 21 in the Z-axis direction.

The adhesive layer 22 is filled between the first main surface 11e of the ceramic body 11 and the diaphragm 21, and bonds the ceramic body 11 and the diaphragm 21 over a wide range. As a result, in the piezoelectric vibration device 20, a high bonding strength can be obtained between the laminated piezoelectric element 10 and the vibration plate 21 via the adhesive layer 22. As shown in FIG.

In the external electrodes 14 and 15 , portions including top portions 14 a and 15 a projecting downward in the Z-axis direction from the first main surface 11 e bite into the adhesive layer 22 . As a result, the bonding area between the external electrodes 14 and 15 and the adhesive layer 22 is increased, and an anchor effect is obtained, so that the bonding strength between the external electrodes 14 and 15 and the diaphragm 21 is increased.

In the piezoelectric vibration device 20, the bonding strength between the external electrodes 14 and 15 arranged at both ends in the X-axis direction of the laminated piezoelectric element 10 where the displacement in the X-axis direction is the largest and the vibration plate 21 is particularly high. The expansion and contraction of 10 in the X-axis direction is easily transmitted to diaphragm 21 . Therefore, in the piezoelectric vibration device 20, the vibration plate 21 can be vibrated more greatly.

In the piezoelectric vibration device 20, since the bonding strength between the external electrodes 14 and 15 and the vibration plate 21 is high, the external electrodes 14 and 15 are greatly displaced in the X-axis direction due to the expansion and contraction of the laminated piezoelectric element 10. Also, the external electrodes 14 and 15 are less likely to peel off from the diaphragm 21 . Therefore, in the piezoelectric vibration device 20, the large vibration of the vibration plate 21 is maintained.

When the piezoelectric vibration device 20 is driven, the expansion and contraction of the laminated piezoelectric element 10 in the X-axis direction is mainly transmitted to the diaphragm 21 from the external electrodes 14 and 15 arranged at both ends in the X-axis direction. Therefore, when the piezoelectric vibrator 20 is driven, a large stress is applied from the diaphragm 21 to the apexes 14a of the external electrodes 14 and 15 that are closest to the diaphragm 21 .

However, as described above, in the laminated piezoelectric element 10, the stress applied to the tops 14a and 15a of the external electrodes 14 and 15 is less likely to concentrate on the edge 11g of the ceramic body 11. FIG. Therefore, in the piezoelectric vibrator 20, failure due to cracks originating from the ridges 11g of the ceramic body 11 in the laminated piezoelectric element 10 is unlikely to occur, and high reliability can be obtained.

[Manufacturing Method of Piezoelectric Vibration Device 20]
FIG. 10 is a flow chart showing a method for manufacturing the piezoelectric vibration device 20. As shown in FIG. First, as shown in FIG. 11A, the adhesive 122 for forming the adhesive layer 22 is placed on the diaphragm 110 (step S11). Next, as shown in FIG. 11B, the laminated piezoelectric element 10 is placed on the adhesive 122 (step S12).

Subsequently, as shown in FIG. 11C, the pressing member P presses the laminated piezoelectric element 10 downward in the Z-axis direction (step S13). As a result, portions of the external electrodes 14 and 15 including the apex 14a protruding downward in the Z-axis direction from the first main surface 11e enter the adhesive 122, and the adhesive 122 spreads along the surface of the laminated piezoelectric element 10. In close contact.

Then, the adhesive 122 is cured (step S14). Thereby, the adhesive layer 22 is formed, and the piezoelectric vibration device 20 shown in FIG. 9 is obtained. Thus, in this manufacturing method, the piezoelectric vibration device 20 can be easily manufactured by bonding the laminated piezoelectric element 10 and the vibration plate 21 using the adhesive 122 .

In step S13 of this manufacturing method, when the laminated piezoelectric element 10 is pressed, stress from the pressing member P is applied to the top portions 14a and 15a projecting upward in the Z-axis direction. Further, in step S13, stress from the adhesive 122 is also applied to the top portions 14a and 15a that enter the adhesive 122 and protrude downward in the Z-axis direction.

However, as described above, in the laminated piezoelectric element 10, the stress applied to the tops 14a and 15a of the external electrodes 14 and 15 is less likely to concentrate on the edge 11g of the ceramic body 11. FIG. Therefore, in this manufacturing method, it is possible to suppress the occurrence of cracks originating from the ridges 11g of the ceramic body 11 in the laminated piezoelectric element 10 .

In addition, in the laminated piezoelectric element 10 of the piezoelectric vibration device 20, the external electrodes 14 and 15 protrude downward in the Z-axis direction from the first main surface 11e of the ceramic body 11. A concave region that is depressed upward in the Z-axis direction is formed. In step S13, the recessed area between the external electrodes 14, 15 is filled with an adhesive 122.

Therefore, in step S13, the thickness of the adhesive 122 between the first main surface 11e of the ceramic body 11 and the diaphragm 21 is larger than the amount of protrusion of the external electrodes 14 and 15 downward in the Z-axis direction. should not be small. Thereby, in the piezoelectric vibrating device 20, a sufficient thickness of the adhesive layer 22 is ensured, so high reliability can be obtained.

[Electronic device 30]
12A and 12B are diagrams schematically showing an electronic device 30 using the laminated piezoelectric element 10. FIG. 12A is a plan view of the electronic device 30. FIG. FIG. 12B is a cross-sectional view of the electronic device 30 taken along line CC' of FIG. 12A. The electronic device 30 is configured as a multifunctional mobile communication terminal generally called a smart phone.

The electronic device 30 has a laminated piezoelectric element 10 , a housing 31 and a panel 32 . The housing 31 has a rectangular bottom plate 31a extending along the XY plane and a frame 31b extending upward in the Z-axis direction from the periphery of the bottom plate 31a, and is formed in a box shape that is open upward in the Z-axis direction. ing. The panel 32 extends rectangularly along the XY plane and closes the housing 31 from above in the Z-axis direction.

The housing 31 accommodates components (not shown) such as circuit boards and electronic components for realizing various functions of the electronic device 30 . The panel 32 is configured as a touch panel. In other words, the panel 32 has both an image display function of displaying an image and an input function of detecting an input operation by a user's finger or the like.

Note that the panel 32 is not limited to a touch panel, and may not have the above configuration. For example, the panel 32 may be a touch pad that has only an input function without an image display function. Also, the panel 32 may be a protection panel that protects a touch panel separately provided on the electronic device 30 .

The laminated piezoelectric element 10 is adhered to the lower surface of the panel 32 in the Z-axis direction and faces the bottom plate 31a inside the housing 31 . The position of the laminated piezoelectric element 10 on the lower surface of the panel 32 in the Z-axis direction can be determined arbitrarily. In the electronic device 30, the panel 32 functions as the diaphragm 21 in the piezoelectric vibration device 20 shown in FIG.

That is, the electronic device 30 can vibrate the panel 32 by expanding and contracting the laminated piezoelectric element 10 in the X-axis direction. For this reason, it is preferable that the panel 32 is mainly made of glass, acrylic resin, or the like, which can vibrate satisfactorily. Moreover, the adhesive layer that bonds the laminated piezoelectric element 10 and the panel 32 preferably has the same configuration as the adhesive layer 22 of the piezoelectric vibration device 20 .

The electronic device 30 can provide audio information to the user by vibrating the panel 32 and generating sound through air conduction, bone conduction, or the like. Further, the electronic device 30 can present a tactile sensation to a user who performs an input operation on the panel 32, for example, by vibrating the panel 32. FIG.

Although the top surface of the panel 32 in the Z-axis direction is typically flat, it may be curved, for example. Further, the electronic device 30 is not limited to a smart phone, and may be configured as, for example, a tablet terminal, a notebook computer, a mobile phone, a wristwatch, a photo stand, a remote controller or an operation unit of various devices.

[Other embodiments]
Although the embodiments of the present invention have been described above, it is needless to say that the present invention is not limited to the above-described embodiments and can be modified in various ways.

For example, although the external electrodes 14 and 15 of the laminated piezoelectric element 10 extend to both the main surfaces 11e and 11f in the above embodiment, they extend only to the first main surface 11e and extend to the second main surface 11f. You don't have to put it out. Also in this case, the effect of suppressing the occurrence of cracks originating from the ridge portion 11g on the first main surface 11e side of the ceramic body 11 can be obtained.

DESCRIPTION OF SYMBOLS 10... Laminated piezoelectric element 11... Ceramic element body 11a, 11b... End surface 11c, 11d... Side surface 11e, 11f... Main surface 11g... Ridge part 12, 13... Internal electrode 14, 15... External electrode 14a, 15a... Top part 16, 17 ... Surface electrode 18 ... Ceramic layer 20 ... Piezoelectric vibration device 21 ... Diaphragm 22 ... Adhesion layer 30 ... Electronic device 31 ... Case 32 ... Panel

Claims (8)

First and second end surfaces made of piezoelectric ceramics and oriented in the longitudinal direction; a ridge connecting the first and second principal surfaces;
covering the first and second end surfaces, extending from the first and second end surfaces to the first main surface via the ridge, and being longitudinally inward of the ridge on the first main surface; a pair of external electrodes having top portions arranged in the thickness direction and protruding in the thickness direction;
a plurality of internal electrodes stacked along the thickness direction inside the ceramic body and alternately connected to the pair of external electrodes along the thickness direction;
a surface electrode provided on at least one of the first and second main surfaces and connected to the external electrode different from the internal electrode adjacent in the thickness direction;
A laminated piezoelectric element comprising: The laminated piezoelectric element according to claim 1,
The pair of external electrodes extend from the first and second end surfaces to the second main surface via the ridge and are arranged on the second main surface inside the ridge in the longitudinal direction . having a top protruding in the thickness direction
Laminated piezoelectric element. The laminated piezoelectric element according to claim 1 or 2,
The laminated piezoelectric element, wherein the ridge portion is formed of a curved surface. A laminated piezoelectric element according to any one of claims 1 to 3;
a diaphragm facing the laminated piezoelectric element in the thickness direction;
an adhesive layer disposed between the laminated piezoelectric element and the diaphragm;
A piezoelectric vibration device comprising: The piezoelectric vibration device according to claim 4,
The piezoelectric vibration device, wherein the vibration plate is arranged on the first main surface side of the laminated piezoelectric element. The piezoelectric vibration device according to claim 5,
A piezoelectric vibration device, wherein a part of the pair of external electrodes of the laminated piezoelectric element is arranged in the adhesive layer. The piezoelectric vibration device according to claim 5 or 6,
The piezoelectric vibration device, wherein the adhesive layer is filled between the first main surface and the vibration plate. A laminated piezoelectric element according to any one of claims 1 to 3;
a panel to which the laminated piezoelectric elements are bonded while facing each other in the thickness direction;
a housing that holds the panel;
An electronic device comprising

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