Piezoelectric element

Abstract

To provide a piezoelectric element capable of mitigating a stress which acts in a piezoelectric element assembly.SOLUTION: A piezoelectric element 10 comprises: a piezoelectric element assembly 11 including principal surfaces 11a and 11b which are opposed to each other and a side face which connects the principal surfaces 11a and 11b and including a region R1 including the principal surface 11a and a region R2 including the principal surface 11b; an internal electrode group 20 which is disposed in the region R1 and includes a plurality of internal electrodes 21 and 25 opposed to each other in a direction in which the principal surfaces 11a and 11b are opposed; and an internal electrode group 22 which is disposed in the region R2 and includes a plurality of internal electrodes 23 and 25 opposed to each other in the direction in which the principal surfaces 11a and 11b are opposed. The internal electrode 25 which is closest to the region R2 in the plurality of internal electrodes 21 and 25 included in the internal electrode group 20 and the internal electrode 25 which is closest to the region R1 in the plurality of internal electrodes 23 and 25 included in the internal electrode group 22 are electrically connected with each other.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a piezoelectric element. [Background technology]

[0002] A known piezoelectric element includes one electrode and two piezoelectric elements arranged on either side of the electrode (see, for example, Patent Document 1). Each of the two piezoelectric elements is displaced by application of a voltage. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-318725 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of one aspect of the present invention is to provide a piezoelectric element capable of alleviating stress acting within the piezoelectric element.An object of another aspect of the present invention is to provide a piezoelectric element capable of alleviating stress acting within the piezoelectric element. [Means for solving the problem]

[0005] A piezoelectric element according to one aspect of the present invention comprises: a piezoelectric element including a first region including the first main surface and a second main surface facing each other and a side surface connecting the first main surface and the second main surface, and including a second region including the second main surface; a first internal electrode group including a plurality of internal electrodes arranged in the first region and facing each other in the direction in which the first main surface and the second main surface face each other; and a second internal electrode group including a plurality of internal electrodes arranged in the second region and facing each other in the direction in which the first main surface and the second main surface face each other. Of the plurality of internal electrodes included in the first internal electrode group, an internal electrode closest to the second region and an internal electrode closest to the first region among the plurality of internal electrodes included in the second internal electrode group are electrically connected to each other.

[0006] In one aspect of the present invention, the first internal electrode group includes a plurality of internal electrodes facing each other in a first region, the first region including a region located between the plurality of facing internal electrodes. The second internal electrode group includes a plurality of internal electrodes facing each other in a second region, the second region including a region located between the plurality of facing internal electrodes. Hereinafter, the region located between the plurality of facing internal electrodes may be referred to as an "inter-electrode region." When a voltage is applied, an electric field is generated in the inter-electrode region included in each of the first and second regions, and the inter-electrode region included in each of the first and second regions may be displaced. In the above-described aspect, the internal electrode closest to the second region and the internal electrode closest to the first region are electrically connected. Therefore, when a voltage is applied, an electric field is unlikely to be generated in the region located between the internal electrode closest to the second region and the internal electrode closest to the first region, i.e., the region located between the first and second regions, and the region located between the first and second regions is unlikely to be displaced. When the inter-electrode region included in each of the first and second regions is displaced, the region located between the first and second regions relieves the stress acting on the second region due to the displacement in the first region, and relieves the stress acting on the first region due to the displacement in the second region. The above-described aspect can relieve stress acting within the piezoelectric element.

[0007] A piezoelectric element according to another aspect of the present invention comprises: a piezoelectric body including a first main surface and a second main surface facing each other, and a side surface connecting the first main surface and the second main surface, and including a first region including the first main surface and a second region including the second main surface; a first internal electrode group arranged in the first region and including a plurality of internal electrodes facing each other in the direction in which the first main surface and the second main surface face each other; a second internal electrode group arranged in the second region and including a plurality of internal electrodes facing each other in the direction in which the first main surface and the second main surface face each other; and an internal conductor arranged between an internal electrode of the plurality of internal electrodes included in the first internal electrode group that is closest to the second region and an internal electrode of the plurality of internal electrodes included in the second internal electrode group that is closest to the first region, and that is not electrically connected to the plurality of internal electrodes included in the first internal electrode group and the plurality of internal electrodes included in the second internal electrode group.

[0008] In another aspect of the invention, the piezoelectric element includes a region between an internal electrode of the plurality of internal electrodes included in the first internal electrode group that is closest to the second region and an internal electrode of the plurality of internal electrodes included in the second internal electrode group that is closest to the first region, i.e., a region located between the first and second regions. In another aspect of the invention, the internal conductor is disposed in the region located between the first and second regions and is not electrically connected to the plurality of internal electrodes included in the first internal electrode group and the plurality of internal electrodes included in the second internal electrode group. Therefore, when a voltage is applied, an electric field is unlikely to be generated in the region located between the first and second regions. The region located between the first and second regions is unlikely to be displaced. The region located between the first and second regions relieves stress acting on the second region due to displacement in the first region, and relieves stress acting on the first region due to displacement in the second region. This another aspect of the invention can relieve stress acting within the piezoelectric element. [Effects of the Invention]

[0009] One aspect of the present invention provides a piezoelectric element capable of alleviating stress acting within a piezoelectric element. Another aspect of the present invention provides a piezoelectric element capable of alleviating stress acting within a piezoelectric element. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view showing a vibration device including a piezoelectric element according to a first embodiment. [Figure 2] FIG. 2 is a diagram showing a cross-sectional configuration of the piezoelectric element according to the first embodiment. [Figure 3] FIG. 3 is an exploded perspective view of the piezoelectric element according to the first embodiment. [Figure 4] FIG. 4 is an exploded perspective view of the piezoelectric element according to the first embodiment. [Figure 5] FIG. 5 is an exploded perspective view of the piezoelectric element according to the first embodiment. [Figure 6] FIG. 6 is a diagram showing a cross-sectional configuration of a piezoelectric element according to a modified example of the first embodiment. [Figure 7] FIG. 7 is an exploded perspective view of a piezoelectric element according to a modified example of the first embodiment. [Figure 8] FIG. 8 is a diagram showing a cross-sectional configuration of a piezoelectric element according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments and modifications of the present invention will be described in detail with reference to the accompanying drawings. In the description, the same elements or elements having the same functions will be denoted by the same reference numerals, and redundant description will be omitted.

[0012] (First embodiment) The piezoelectric element according to the first embodiment will be described with reference to Figs. 1 to 5. Fig. 1 is a perspective view showing a vibration device including the piezoelectric element according to the first embodiment. Fig. 2 is a view showing the cross-sectional configuration of the piezoelectric element according to the first embodiment. Figs. 3, 4, and 5 are exploded perspective views of the piezoelectric element according to the first embodiment. Fig. 3 shows the cross-sectional configuration of the first region, and Fig. 4 shows the cross-sectional configuration of the third region. Fig. 5 shows the cross-sectional configuration of the second region.

[0013] 1, the vibration device 1 includes a piezoelectric element 10, a vibration member 50, and a wiring member 60. In order to clearly show the piezoelectric element 10 in FIG. 1, the wiring member 60 is shown by a two-dot chain line. First, the piezoelectric element 10 will be described. The piezoelectric element 10 includes a piezoelectric body 11, a plurality of external electrodes 13, 14, and 15, and a plurality of connecting conductors 30, 31, and 32. In the first embodiment, the piezoelectric element 10 includes three external electrodes 13, 14, and 15, and three connecting conductors 30, 31, and 32. The connecting conductor 30 is connected to the external electrode 13. The connecting conductor 31 is connected to the external electrode 14. The connecting conductor 32 is connected to the external electrode 15. The piezoelectric element 10 includes a bimorph element.

[0014] The piezoelectric element 11 has a rectangular parallelepiped shape. In this specification, the rectangular parallelepiped shape includes a rectangular parallelepiped shape with chamfered corners and ridges, and a rectangular parallelepiped shape with rounded corners and ridges. The piezoelectric element 11 includes two opposing main surfaces 11a and 11b, a pair of opposing side surfaces 11c, and a pair of opposing side surfaces 11e.

[0015] The principal surfaces 11a, 11b face each other in the first direction D1. The principal surface 11a is perpendicular to the first direction D1. The pair of side surfaces 11c face each other in the second direction D2. The pair of side surfaces 11e face each other in the third direction D3. The pair of side surfaces 11c and the pair of side surfaces 11e extend in the first direction D1 so as to connect the pair of principal surfaces 11a, 11b. The pair of side surfaces 11c and the pair of side surfaces 11e are adjacent to each other. In the first embodiment, the surface of the piezoelectric element 11 includes the principal surfaces 11a, 11b and the side surfaces 11c, 11e. Each of the main surfaces 11a and 11b, the pair of side surfaces 11c, and the pair of side surfaces 11e has a rectangular shape. In this specification, a rectangular shape includes a shape in which each corner is chamfered or a shape in which each corner is rounded. For example, when the main surface 11a includes a first main surface, the main surface 11b includes a second main surface.

[0016] The length of the piezoelectric element 11 in the first direction D1 is, for example, 0.3 to 2 mm. The length of the piezoelectric element 11 in the second direction D2 is, for example, 5 to 70 mm. The length of the piezoelectric element 11 in the third direction D3 is, for example, 5 to 70 mm. In the piezoelectric element 11, the second direction D2 is, for example, the long side direction. The second direction D2 intersects the first direction D1. The third direction D3 intersects the first direction D1 and the second direction D2. In the first embodiment, the first direction D1, the second direction D2, and the third direction D3 are perpendicular to one another.

[0017] The external electrodes 13, 14, and 15 are arranged on the main surface 11a. The external electrodes 13, 14, and 15 are lined up in the second direction D2 in the order of external electrode 13, external electrode 14, and external electrode 15. The external electrodes 13 and 14 are adjacent to each other in the second direction D2. The external electrodes 14 and 15 are adjacent to each other in the second direction D2. In the second direction D2, the shortest distance between the external electrodes 14 and 15 is longer than, for example, the shortest distance between the external electrodes 13 and 14. The external electrodes 13, 14, and 15 are spaced apart from the side surfaces 11c and 11e when viewed from the first direction D1.

[0018] The external electrodes 13, 14, and 15 are rectangular. In the first embodiment, each corner of the rectangle is rounded. The external electrodes 13, 14, and 15 may be square. The external electrodes 13, 14, and 15 include a conductive material. The conductive material includes, for example, Ag, Pd, Pt, or an Ag-Pd alloy. The external electrodes 13, 14, and 15 are formed, for example, as a sintered body of a conductive paste including the conductive material.

[0019] As shown in FIGS. 2 to 5, the piezoelectric element 11 includes a region R1 and a region R2. The region R1 includes the main surface 11a, and the region R2 includes the main surface 11b. The region R1 is located closer to the main surface 11a, and the region R2 is located closer to the main surface 11b. The regions R1 and R2 are spaced apart in the first direction D1. In the first embodiment, the piezoelectric element 11 includes a region R3. The region R3 is located between the regions R1 and R2 in the first direction D1. The region R3 does not include the main surfaces 11a and 11b. For example, if the region R1 includes the first region, the region R2 includes the second region.

[0020] The piezoelectric element 11 includes a plurality of piezoelectric layers 17. The plurality of piezoelectric layers 17 are stacked in the first direction D1. Each of the regions R1 and R2 includes a plurality of piezoelectric layers 17. The region R1 includes, for example, seven piezoelectric layers 17. The region R2 includes, for example, seven piezoelectric layers 17. Of the piezoelectric layers 17 included in the region R1, the piezoelectric layer 17 closest to the main surface 11a includes the main surface 11a. Of the piezoelectric layers 17 included in the region R2, the piezoelectric layer 17 closest to the main surface 11b includes the main surface 11b. In the regions R1 and R2, the piezoelectric layers 17 are polarized. Piezoelectric layers 17 with opposite polarization directions are alternately arranged in the first direction D1. In the first embodiment, the thicknesses of the plurality of piezoelectric layers 17 are the same. In this specification, "same" may refer to values ​​that include not only equality but also slight differences or manufacturing errors within a predetermined range. For example, if multiple values ​​are within a range of ±10% of the average value of the multiple values, the multiple values ​​are defined as being "the same" as each other.

[0021] The piezoelectric element 10 includes an internal electrode group 20 and an internal electrode group 22. The internal electrode group 20 and the internal electrode group 22 are spaced apart from each other in a first direction D1. The internal electrode group 20 is arranged in the region R1. The internal electrode group 20 includes a plurality of internal electrodes 21, 25. The internal electrode 25 faces the internal electrode 21. The plurality of internal electrodes 21, 25 face each other in the first direction D1. The internal electrodes 21, 25 are arranged at different positions (layers) in the first direction D1. In the first embodiment, the internal electrode group 20 includes three internal electrodes 21 and four internal electrodes 25. The internal electrodes 21 and the internal electrodes 25 are alternately arranged, and the internal electrodes 21 and the internal electrodes 25 face each other at a distance L1, with a corresponding piezoelectric layer 17 sandwiched between them. The size of the distance L1 between the plurality of opposing internal electrodes 21, 25 is the same. The internal electrode group 20 includes the internal electrode 25 that is closest to the region R2 among the multiple internal electrodes 21, 25 included in the internal electrode group 20. The internal electrode group 20 includes the internal electrode 25 that is closest to the main surface 11a among the multiple internal electrodes 21, 25 included in the internal electrode group 20.

[0022] The internal electrode group 22 is arranged in the region R2. The internal electrode group 22 includes a plurality of internal electrodes 23, 25. The internal electrode 23 is not electrically connected to the plurality of internal electrodes 21, 25 included in the internal electrode group 20. The internal electrode 25 faces the internal electrode 23. The plurality of internal electrodes 23, 25 face each other in the first direction D1. The internal electrode 25 included in the internal electrode group 22 is electrically connected to the internal electrode 25 included in the internal electrode group 20. The internal electrodes 23, 25 are arranged at different positions (layers) in the first direction D1. In the first embodiment, the internal electrode group 22 includes three internal electrodes 23 and four internal electrodes 25. In the internal electrode group 22, the internal electrodes 23 and the internal electrodes 25 are alternately arranged, and the internal electrodes 23 and the internal electrodes 25 face each other at a distance L2, with a corresponding one of the piezoelectric layers 17 sandwiched between them. The size of the gaps L2 between the plurality of internal electrodes 23 and 25 facing each other is the same.

[0023] The internal electrode group 22 includes the internal electrode 25 that is closest to the region R1 among the multiple internal electrodes 23, 25 included in the internal electrode group 22. The internal electrode group 22 includes the internal electrode 25 that is closest to the main surface 11b among the multiple internal electrodes 23, 25 included in the internal electrode group 22.

[0024] Of the multiple internal electrodes 23, 25 included in the internal electrode group 22, the internal electrode 25 closest to the region R1 and the internal electrode 25 closest to the region R2 of the multiple internal electrodes 21, 25 included in the internal electrode group 20 are electrically connected to each other. For example, when the internal electrode group 20 includes the first internal electrode group, the internal electrode group 22 includes the second internal electrode group. For example, when the internal electrode 21 includes the first internal electrode, the internal electrode 25 included in the internal electrode group 20 includes the second internal electrode. For example, when the internal electrode 23 includes the third internal electrode, the internal electrode 25 included in the internal electrode group 22 includes the fourth internal electrode.

[0025] In the internal electrode groups 20 and 22, the internal electrodes 21, 23, and 25 are not exposed on the surface of the piezoelectric element 11. The internal electrodes 21, 23, and 25 are not exposed on the principal surface 11a, the principal surface 11b, and the side surfaces 11c and 11e. The internal electrodes 21, 23, and 25 are spaced apart from the principal surface 11a, the principal surface 11b, and the side surfaces 11c and 11e.

[0026] Region R3 is located between the internal electrode 25 of the internal electrode group 20 that is closest to region R2 and the internal electrode 25 of the internal electrode group 22 that is closest to region R1. Region R3 includes a plurality of piezoelectric layers 19. Region R3 includes, for example, two piezoelectric layers 19. The piezoelectric layer 19 is located between the piezoelectric layer 17 included in region R1 and the piezoelectric layer 17 included in region R2. In the piezoelectric element 11, the plurality of piezoelectric layers 17, 19 are stacked in the first direction D1. The thicknesses of the piezoelectric layers 19 are the same as each other. The piezoelectric layers 19 are substantially not polarized.

[0027] The piezoelectric element 10 includes an internal conductor 27. The piezoelectric element 10 includes, for example, one internal conductor 27. The internal conductor 27 is not electrically connected to the multiple internal electrodes 21, 25 included in the internal electrode group 20 and the multiple internal electrodes 23, 25 included in the internal electrode group 22. The internal conductor 27 is not exposed on the surface of the piezoelectric body 11. The internal conductor 27 is not exposed on the side surfaces 11c, 11e. The internal conductor 27 is spaced apart from the side surfaces 11c, 11e.

[0028] The internal conductor 27 is disposed between the internal electrode 25 of the internal electrode group 20 that is closest to region R2 and the internal electrode 25 of the internal electrode group 22 that is closest to region R1. The internal conductor 27 is disposed in region R3. The internal electrode 25 closest to region R2 and the internal electrode 25 closest to region R1 form a distance L3 in the first direction D1 between them, and the distance L3 corresponds to the length of region R3 in the first direction D1. The distance L3 is greater than the distances L1 and L2. The piezoelectric element 10 may not include the internal conductor 27. Even when the piezoelectric element 10 does not include the internal conductor 27, the distance L3 is greater than the distances L1 and L2.

[0029] The piezoelectric layers 17 and 19 include a piezoelectric material. The piezoelectric layers 17 and 19 include, for example, a piezoelectric ceramic material. The piezoelectric ceramic material includes, for example, PZT [Pb(Zr,Ti)O3], PT(PbTiO3), PLZT [(Pb,La)(Zr,Ti)O3], or barium titanate (BaTiO3). The piezoelectric layers 17 and 19 are formed, for example, from a sintered ceramic green sheet containing the above-mentioned piezoelectric ceramic material. In an actual piezoelectric element 11, the piezoelectric layers 17 and 19 are integrated to the extent that the boundaries between the piezoelectric layers are indistinguishable.

[0030] The internal electrodes 21 arranged in the region R1 are electrically connected to the external electrodes 14 via the connecting conductors 31. The connecting conductors 31 include a plurality of conductors 34 and a plurality of through-hole conductors 44. In the region R1, each of the multiple conductors 34 is located in the same layer as the corresponding internal electrode 25. Each of the multiple conductors 34 is located in an opening formed in the corresponding internal electrode 25. Each of the openings is formed at a position corresponding to the external electrode 14 when viewed from the first direction D1. Each of the multiple conductors 34 is surrounded by the internal electrode 25 when viewed from the first direction D1. Each of the multiple conductors 34 is spaced apart from the internal electrode 25. Each of the multiple conductors 34 faces the external electrode 14 in the first direction D1 and is arranged at a position overlapping with the external electrode 14 when viewed from the first direction D1. Each of the multiple conductors 34 faces the corresponding internal electrode 21 in the first direction D1 and is arranged at a position overlapping with the internal electrode 21 when viewed from the first direction D1.

[0031] In region R2, each of the multiple conductors 34 is located on the same layer as the corresponding internal electrodes 23, 25. Each of the multiple conductors 34 is located in an opening formed in the corresponding internal electrode 23, 25. Each of the openings is formed at a position corresponding to the external electrode 14 when viewed from the first direction D1. Each of the multiple conductors 34 is surrounded by the internal electrodes 23, 25 when viewed from the first direction D1. Each of the multiple conductors 34 is spaced apart from the internal electrodes 23, 25. Each of the multiple conductors 34 faces the external electrode 14 in the first direction D1 and is positioned so as to overlap with the external electrode 14 when viewed from the first direction D1.

[0032] In region R3, the conductor 34 is located on the same layer as the internal conductor 27. The conductor 34 is located in an opening formed in the internal conductor 27. The opening is formed at a position corresponding to the external electrode 14 when viewed from the first direction D1. The conductor 34 is surrounded by the internal conductor 27 when viewed from the first direction D1. The conductor 34 is spaced apart from the internal conductor 27. The conductor 34 faces the external electrode 14 in the first direction D1 and is positioned so as to overlap with the external electrode 14 when viewed from the first direction D1.

[0033] In region R1, each of the multiple through-hole conductors 44 is located between the external electrode 14 and the internal electrode 25 closest to the main surface 11a, between the multiple internal electrodes 21 and the corresponding multiple internal electrodes 25, and between the internal electrode 25 closest to region R2 and the corresponding internal electrode 21. Each of the multiple through-hole conductors 44 is arranged at a position overlapping with the external electrode 14 when viewed from the first direction D1, and penetrates the corresponding piezoelectric layer 17 in the first direction D1.

[0034] In region R2, each of the multiple through-hole conductors 44 is located between the internal electrode 25 closest to region R1 and the corresponding multiple internal electrodes 23, between the multiple internal electrodes 23 and the corresponding multiple internal electrodes 25, and between the internal electrode 25 closest to the main surface 11b and the corresponding internal electrode 23. Each of the multiple through-hole conductors 44 is arranged at a position overlapping with the external electrode 14 when viewed from the first direction D1, and penetrates the corresponding piezoelectric layer 17 in the first direction D1.

[0035] In region R3, each of the multiple through-hole conductors 44 is located between the internal electrode 25 and the internal conductor 27 of the internal electrode group 20 that is closest to region R2, and between the internal electrode 25 and the internal conductor 27 of the internal electrode group 22 that is closest to region R1. Each of the multiple through-hole conductors 44 is located at a position overlapping with the external electrode 14 when viewed from the first direction D1, and penetrates the corresponding piezoelectric layer 19 in the first direction D1. The internal electrode 23 located in region R2 is electrically connected to the external electrode 13 via a connecting conductor 30. The connecting conductor 30 includes multiple conductors 33 and multiple through-hole conductors 43.

[0036] In region R1, each of the multiple conductors 33 is located on the same layer as the corresponding internal electrodes 21, 25. Each of the multiple conductors 33 is located in an opening formed in the corresponding internal electrode 21, 25. Each of the openings is formed at a position corresponding to the external electrode 13 when viewed from the first direction D1. Each of the multiple conductors 33 is surrounded by the internal electrodes 21, 25 when viewed from the first direction D1. Each of the multiple conductors 33 is spaced apart from the internal electrodes 21, 25. Each of the multiple conductors 33 faces the external electrode 13 in the first direction D1 and is positioned so as to overlap with the external electrode 13 when viewed from the first direction D1.

[0037] In region R2, each of the multiple conductors 33 is located in the same layer as the corresponding internal electrode 25. Each of the multiple conductors 33 is located in an opening formed in the corresponding internal electrode 25. Each of the openings is formed at a position corresponding to the external electrode 13 when viewed from the first direction D1. Each of the multiple conductors 33 is surrounded by the internal electrode 25 when viewed from the first direction D1. Each of the multiple conductors 33 is spaced apart from the internal electrode 25. Each of the multiple conductors 33 faces the external electrode 13 in the first direction D1 and is arranged at a position overlapping with the external electrode 13 when viewed from the first direction D1. Each of the multiple conductors 33 faces the corresponding internal electrode 23 in the first direction D1 and is arranged at a position overlapping with the internal electrode 23 when viewed from the first direction D1.

[0038] In region R3, the conductor 33 is located on the same layer as the internal conductor 27. The conductor 33 is located in an opening formed in the internal conductor 27. The opening is formed at a position corresponding to the external electrode 13 when viewed from the first direction D1. The conductor 33 is surrounded by the internal conductor 27 when viewed from the first direction D1. The conductor 33 is spaced apart from the internal conductor 27. The conductor 33 faces the external electrode 13 in the first direction D1 and is positioned so as to overlap with the external electrode 13 when viewed from the first direction D1. The conductor 33 and conductor 34, which are located on the same layer as the internal electrode 25, are located adjacent to each other in the same opening.

[0039] In region R1, each of the multiple through-hole conductors 43 is located between the external electrode 13 and the internal electrode 25 closest to the main surface 11a, between the multiple internal electrodes 21 and the corresponding multiple internal electrodes 25, and between the internal electrode 25 closest to region R2 and the corresponding internal electrode 21. Each of the multiple through-hole conductors 43 is arranged at a position overlapping with the external electrode 13 when viewed from the first direction D1, and penetrates the corresponding piezoelectric layer 17 in the first direction D1.

[0040] In region R2, each of the multiple through-hole conductors 43 is located between the internal electrode 25 closest to region R1 and the corresponding multiple internal electrodes 23, between the multiple internal electrodes 23 and the corresponding multiple internal electrodes 25, and between the internal electrode 25 closest to the main surface 11b and the corresponding internal electrode 23. Each of the multiple through-hole conductors 43 is arranged at a position overlapping with the external electrode 13 when viewed from the first direction D1, and penetrates the corresponding piezoelectric layer 17 in the first direction D1.

[0041] In region R3, each of the multiple through-hole conductors 43 is located between the internal electrode 25 and internal conductor 27 of the internal electrode group 20 that is closest to region R2, and between the internal electrode 25 and internal conductor 27 of the internal electrode group 22 that is closest to region R1. Each of the multiple through-hole conductors 43 is located at a position overlapping with the external electrode 13 when viewed from the first direction D1, and penetrates the corresponding piezoelectric layer 19 in the first direction D1. The internal electrodes 25 located in region R1 are electrically connected to the external electrode 15 via connecting conductors 32. The connecting conductors 32 include multiple conductors 35 and multiple through-hole conductors 45.

[0042] Each of the multiple conductors 35 is located on the same layer as the internal electrodes 21, 23. Each of the multiple conductors 35 is located in an opening formed in the internal electrodes 21, 23. Each of the openings is formed at a position corresponding to the external electrode 15 when viewed from the first direction D1. Each of the multiple conductors 35 is surrounded by the internal electrodes 21, 23 when viewed from the first direction D1. Each of the multiple conductors 35 is spaced apart from the internal electrodes 21, 23. Each of the multiple conductors 35 faces the external electrode 15 in the first direction D1 and is arranged at a position overlapping with the external electrode 15 when viewed from the first direction D1. Each of the multiple conductors 35 faces the internal electrode 25 in the first direction D1 and is arranged at a position overlapping with the internal electrode 25 when viewed from the first direction D1.

[0043] In region R1, each of the multiple conductors 35 is located in the same layer as the corresponding internal electrode 21. Each of the multiple conductors 35 is located in an opening formed in the corresponding internal electrode 21. Each of the openings is formed at a position corresponding to the external electrode 15 when viewed from the first direction D1. Each of the multiple conductors 35 is surrounded by the internal electrode 21 when viewed from the first direction D1. Each of the multiple conductors 35 is spaced apart from the internal electrode 21. Each of the multiple conductors 35 faces the external electrode 15 in the first direction D1 and is positioned so as to overlap with the external electrode 15 when viewed from the first direction D1.

[0044] In region R2, each of the multiple conductors 35 is located in the same layer as the corresponding internal electrode 23. Each of the multiple conductors 35 is located in an opening formed in the corresponding internal electrode 23. Each of the openings is formed at a position corresponding to the external electrode 15 when viewed from the first direction D1. Each of the multiple conductors 35 is surrounded by the internal electrode 23 when viewed from the first direction D1. Each of the multiple conductors 35 is spaced apart from the internal electrode 23. Each of the conductors 35 faces the external electrode 15 in the first direction D1 and is arranged at a position overlapping with the external electrode 15 when viewed from the first direction D1. Each of the multiple conductors 35 faces the corresponding internal electrode 25 in the first direction D1 and is arranged at a position overlapping with the internal electrode 25 when viewed from the first direction D1.

[0045] In region R3, the conductor 35 is located on the same layer as the internal conductor 27. The conductor 35 is located in an opening formed in the internal conductor 27. The opening is formed at a position corresponding to the external electrode 15 when viewed from the first direction D1. The conductor 35 is surrounded by the internal conductor 27 when viewed from the first direction D1. The conductor 35 is spaced apart from the internal conductor 27. The conductor 35 faces the external electrode 15 in the first direction D1 and is positioned so as to overlap with the external electrode 15 when viewed from the first direction D1.

[0046] In region R1, each of the multiple through-hole conductors 45 is located between the external electrode 15 and the internal electrode 25 closest to the main surface 11a, between the multiple internal electrodes 21 and the corresponding multiple internal electrodes 25, and between the internal electrode 25 closest to region R2 and the corresponding internal electrode 21. Each of the multiple through-hole conductors 45 is arranged at a position overlapping with the external electrode 15 when viewed from the first direction D1, and penetrates the corresponding piezoelectric layer 17 in the first direction D1.

[0047] In region R2, each of the multiple through-hole conductors 45 is located between the internal electrode 25 closest to region R1 and the corresponding multiple internal electrodes 23, between the multiple internal electrodes 23 and the corresponding multiple internal electrodes 25, and between the internal electrode 25 closest to the main surface 1b and the corresponding internal electrode 23. Each of the multiple through-hole conductors 45 is arranged at a position overlapping with the external electrode 15 when viewed from the first direction D1, and penetrates the corresponding piezoelectric layer 17 in the first direction D1.

[0048] In region R3, each of the multiple through-hole conductors 45 is located between the internal electrode 25 and the internal conductor 27 that is closest to region R2 among the internal electrode group 20, and between the internal electrode 25 and the internal conductor 27 that is closest to region R1 among the internal electrode group 22. Each of the multiple through-hole conductors 45 is disposed at a position overlapping with the external electrode 15 when viewed from the first direction D1, and penetrates the corresponding piezoelectric layer 19 in the first direction D1.

[0049] Each of the connecting conductors 30, 31, and 32 has a rectangular shape when viewed from the first direction D1. In the first embodiment, each corner of the rectangular shape is rounded. Each of the connecting conductors 30, 31, and 32 may have a square shape. The connecting conductors 30, 31, and 32 contain a conductive material. The conductive material includes, for example, Ag, Pd, Pt, or an Ag-Pd alloy. The connecting conductors 30, 31, and 32 are configured, for example, as a sintered body of a conductive paste containing the conductive material. The through-hole conductors 43, 44, and 45 are formed by sintering the conductive paste that is filled in through holes formed in ceramic green sheets for forming the corresponding piezoelectric layers 17 and 19.

[0050] Region R1 includes a region located between the multiple opposing internal electrodes 21, 25. Region R2 includes a region located between the multiple opposing internal electrodes 23, 25. Hereinafter, the region located between the multiple opposing internal electrodes may be referred to as the "inter-electrode region." The inter-electrode regions included in region R1 include regions sandwiched between the plurality of internal electrodes 21 and the corresponding plurality of internal electrodes 25 in the plurality of piezoelectric layers 17 included in region R1. The inter-electrode regions included in region R1 include piezoelectrically active regions. The inter-electrode regions included in region R2 include regions sandwiched between the plurality of internal electrodes 23 and the corresponding plurality of internal electrodes 25 in the plurality of piezoelectric layers 17 included in region R2. The inter-electrode regions included in region R2 include piezoelectrically active regions. The active region included in region R1 and the active region included in region R2 are located between main surface 11a and main surface 11b. The active region included in region R1 and the active region included in region R2 are configured by at least one piezoelectric layer 17. The active region included in region R1 is located closer to main surface 11a than the active region included in region R2. The active region included in region R2 is located closer to main surface 11b than the active region included in region R1. Region R3 is located between the active region included in region R1 and the active region included in region R2. In the first embodiment, region R3 includes an inactive region that is piezoelectrically inactive. In the first embodiment, the active regions included in regions R1 and R2 are positioned, as viewed from the first direction D1, to surround the multiple external electrodes 13, 14, and 15. The active regions included in regions R1 and R2 include a region positioned between external electrode 14 and external electrode 15, as viewed from the first direction D1, and a region outside the region where the external electrodes 13, 14, and 15 are located, as viewed from the first direction D1.

[0051] When operating the piezoelectric element 10, voltages of opposite polarities are applied to the external electrodes 13 and 14. The voltage applied to the external electrodes 13 and 14 is not applied to the external electrode 15. The external electrode 15 includes a ground electrode. When a voltage is applied to the external electrode 14, an electric field is generated between the internal electrode 21 and the corresponding internal electrode 25. An electric field is generated in the region R1, and the active region included in the region R1 is displaced in response to the electric field. When a voltage is applied to the external electrode 13, an electric field is generated between the internal electrode 23 and the corresponding internal electrode 25. An electric field is generated in the region R2, and the active region included in the region R2 is displaced in response to the electric field. The regions R1 and R2, for example, displace in opposite directions. When the regions R1 and R2 are displaced in opposite directions, the active region included in the region R1 and the active region included in the region R2 are displaced in opposite directions to each other in the first direction D1. When a voltage is applied to the external electrodes 13 and 14, a deflection occurs in the piezoelectric element 10.

[0052] The vibrating member 50 will be described with reference to FIG. 1. The vibrating member 50 is bonded to the main surface 11b of the piezoelectric element 11. The vibrating member 50 includes main surfaces 50a and 50b facing each other. The piezoelectric element 10 is disposed on the main surface 50a. In the first embodiment, the vibrating member 50 includes a plate-shaped member. The vibrating member 50 includes, for example, a metal. The vibrating member 50 includes, for example, a Ni-Fe alloy, glass, resin, or stainless steel. The vibrating member 50 has a rectangular shape when viewed from the first direction D1. The length of the vibrating member 50 in the first direction D1 is, for example, 0.1 to 2 mm. The length of the vibrating member 50 in the second direction D2 is, for example, 10 to 75 mm. The length of the vibrating member 50 in the third direction D3 is, for example, 10 to 75 mm. For example, the second direction D2 of the vibrating member 50 is the long side direction.

[0053] The vibration member 50 is bonded to the piezoelectric element 10 by, for example, a resin layer. The main surface 11b of the piezoelectric body 11 and the main surface 50a of the vibration member 50 face each other. The resin layer is located between the main surfaces 11b and 50a. The main surfaces 11b and 50a are bonded by the resin layer. When the piezoelectric element 10 is bonded to the vibration member 50, the main surfaces 50a and 50b face each other in the first direction D1. When viewed from the first direction D1, the piezoelectric element 10 is disposed, for example, in the central region of the main surface 50a. The resin layer contains, for example, an epoxy resin or an acrylic resin. The resin layer does not contain, for example, a conductive filler and is electrically insulating.

[0054] When an AC voltage is applied to the external electrodes 13 and 14, the active region included in region R1 and the active region included in region R2 of the piezoelectric element 10 repeatedly expand and contract in accordance with the frequency of the applied AC voltage. The active region included in region R1 and the active region included in region R2 expand and contract in opposite directions, causing flexural vibration of the piezoelectric element 10. In response to the flexural vibration of the piezoelectric element 10, flexural vibration occurs in the vibrating member 50 integrally with the piezoelectric element 10.

[0055] Next, the wiring member 60 will be described. The wiring member 60 electrically connects the piezoelectric element 10 and the electronic device. The wiring member 60 includes one end, which is bonded to the piezoelectric element 10. The wiring member 60 includes a base material 61 and a reinforcing member 62. A plurality of conductors are arranged on the base material 61, and the plurality of conductors are electrically connected at one end to the external electrodes 13, 14, and 15 of the piezoelectric element 10. The wiring member 60 includes, for example, a flexible printed circuit (FPC) or a flexible flat cable (FFC). The wiring member 60 has a plate-like, sheet-like, or strip-like shape. The wiring member 60 includes another end on the opposite side of the one end in the third direction D3, and the other end is bonded to the reinforcing member 62. The reinforcing member 62 includes an electrically insulating plate-like member. The reinforcing member 62 includes, for example, a polyimide resin. The electronic device includes, for example, a circuit board or another electronic component.

[0056] A piezoelectric element 10 according to a modification of the first embodiment will be described with reference to Fig. 6 and Fig. 7. Fig. 6 is a diagram showing the cross-sectional configuration of the piezoelectric element according to the modification of the first embodiment. Fig. 7 is an exploded perspective view of the piezoelectric element according to the modification of the first embodiment. Fig. 7 shows the cross-sectional configuration of region R3. The piezoelectric element 10 according to the modified example is generally similar to or the same as the piezoelectric element 10 according to the first embodiment described above, but the piezoelectric element 10 according to the modified example differs from the piezoelectric element 10 according to the first embodiment in terms of the configuration of region R3. The following mainly describes the differences from the piezoelectric element 10 according to the first embodiment.

[0057] Region R1 according to the modification has the same configuration as region R1 according to the first embodiment. Region R2 according to the modification has the same configuration as region R2 according to the first embodiment. Region R3 according to the modification differs from the first embodiment and includes, for example, four piezoelectric layers 19. The internal electrode group 20 includes a plurality of internal electrodes 21 and 25. The region R2 according to the modified example has the same configuration as the region R2 according to the first embodiment. The plurality of internal electrodes 21 and the corresponding plurality of internal electrodes 25 face each other at a distance L1, with one corresponding piezoelectric layer 17 sandwiched between them. The internal electrode group 22 includes a plurality of internal electrodes 23 and 25. The plurality of internal electrodes 23 and the corresponding plurality of internal electrodes 25 face each other at a distance L2, with one corresponding piezoelectric layer 17 sandwiched between them. Region R3 is located between the internal electrode 25 of the internal electrode group 20 that is closest to region R2 and the internal electrode 25 of the internal electrode group 22 that is closest to region R1. Region R3 includes a plurality of piezoelectric layers 19. Region R3 includes, for example, four piezoelectric layers 19. The piezoelectric layer 19 is located between the piezoelectric layer 17 included in region R1 and the piezoelectric layer 17 included in region R2. In the piezoelectric element 11, the plurality of piezoelectric layers 17, 19 are stacked in the first direction D1. The piezoelectric layers 19 have the same thickness.

[0058] In this modification, the piezoelectric element 10 includes a plurality of internal conductors 27 in the region R3. Unlike the first embodiment, the piezoelectric element 10 includes two internal conductors 27. The piezoelectric element 10 includes an internal electrode 25 disposed between the two internal conductors 27. The two internal conductors 27 and the internal electrode 25 disposed between the two internal conductors 27 are disposed between the internal electrode 25 of the internal electrode group 20 that is closest to the region R2 and the internal electrode 25 of the internal electrode group 22 that is closest to the region R1. The two internal conductors 27 are disposed in the region R3. The internal electrode 25 closest to the region R2 and the internal electrode 25 closest to the region R1 form a distance L3 in the first direction D1. In this modification, the distance L3 is greater than the distances L1 and L2. The two internal conductors 27 are not electrically connected to the plurality of internal electrodes 21 and 25 included in the internal electrode group 20 and the plurality of internal electrodes 23 and 25 included in the internal electrode group 22. The two internal conductors 27 and the internal electrode 25 disposed between the two internal conductors 27 are not exposed to the side surfaces 11c and 11e. The internal conductors 27 are spaced apart from the side surfaces 11c and 11e. In region R3, the piezoelectric element 10 may not include two internal conductors 27. When the piezoelectric element 10 does not include two internal conductors 27, the interval L3 is greater than intervals L1 and L2. In region R3, the piezoelectric element 10 may include an internal electrode 25 while not including two internal conductors 27. When the piezoelectric element 10 includes an internal electrode 25 while not including two internal conductors 27, the interval L3 is greater than intervals L1 and L2.

[0059] As described above, in the piezoelectric element 10, the internal electrode group 20 includes multiple internal electrodes 21 and 25 facing each other in region R1, and region R1 includes an interelectrode region. The internal electrode group 22 includes multiple internal electrodes 23 and 25 facing each other in region R2, and region R2 includes an interelectrode region. When a voltage is applied, an electric field is generated in the interelectrode region included in each of regions R1 and R2, and the interelectrode region included in each of regions R1 and R2 may be displaced. In the piezoelectric element 10, the internal electrode 25 closest to region R2 and the internal electrode 25 closest to region R1 are electrically connected. Therefore, when a voltage is applied, an electric field is unlikely to be generated in the region located between the internal electrode 25 closest to region R2 and the internal electrode 25 closest to region R1, i.e., region R3, and region R3 is unlikely to be displaced. When the inter-electrode regions included in regions R1 and R2 are displaced, region R3 relieves the stress acting on region R2 due to the displacement in region R1, and relieves the stress acting on region R1 due to the displacement in region R2. Piezoelectric element 10 can relieve the stress acting within piezoelectric body 11.

[0060] In the piezoelectric element 10, the multiple internal electrodes 21, 25 included in the internal electrode group 20 include the internal electrode 21 and an internal electrode 25 facing the internal electrode 21. The multiple internal electrodes 23, 25 included in the internal electrode group 22 include the internal electrode 23 that is not electrically connected to the internal electrode 21 and the internal electrode 25, and the internal electrode 25 that faces the internal electrode 23 and is electrically connected to the internal electrode 25 included in the internal electrode group 20. The internal electrode closest to region R2 includes the internal electrode 25, and the internal electrode closest to region R1 includes the internal electrode 25. In the piezoelectric element 10, the internal electrode group 20 includes an internal electrode 21 and an internal electrode 25 opposite the internal electrode 21. The internal electrode group 22 includes an internal electrode 23 that is not electrically connected to the internal electrodes 21 and 25, and an internal electrode 25 opposite the internal electrode 23. Even if the internal electrode closest to region R2 includes the internal electrode 25 opposite the internal electrode 21 and the internal electrode closest to region R1 includes the internal electrode 25 opposite the internal electrode 23, the internal electrode 25 closest to region R2 is electrically connected to the internal electrode 25 closest to region R1. Therefore, when a voltage is applied, an electric field is unlikely to be generated in region R3, and region R3 is unlikely to be displaced. Region R3 relieves stress acting on region R2 due to displacement in region R1, and relieves stress acting on region R1 due to displacement in region R2. As a result, the piezoelectric element 10 can relieve stress acting within the piezoelectric body 11.

[0061] The piezoelectric element 10 is arranged between the internal electrode 25 closest to region R2 and the internal electrode 25 closest to region R1, and has an internal conductor 27 that is not electrically connected to the multiple internal electrodes 21, 25 included in the internal electrode group 20 and the multiple internal electrodes 23, 25 included in the internal electrode group 22. The internal conductor 27 is disposed between the internal electrode 25 closest to region R2 and the internal electrode 25 closest to region R1, i.e., in region R3, and is not electrically connected to the multiple internal electrodes 21, 23, and 25. Therefore, when a voltage is applied, an electric field is unlikely to be generated in region R3, and region R3 is unlikely to be displaced. Region R3 relieves stress acting on region R2 due to displacement in region R1, and relieves stress acting on region R1 due to displacement in region R2. As a result, the piezoelectric element 10 can relieve stress acting within the piezoelectric body 11.

[0062] In the piezoelectric element 10, the internal conductor 27 is not exposed on the side surfaces 11c and 11e. In the piezoelectric element 10, the internal conductor 27 is covered by the piezoelectric body 11 and is disposed within the piezoelectric body 11. Therefore, in the piezoelectric element 10, electrical short circuits are unlikely to occur.

[0063] In the piezoelectric element 10, the distance L3 is greater than the distance L1 and the distance L2. In the piezoelectric element 10, the distance between the region R1 and the region R2 is reliably large. The greater the distance between the region R1 and the region R2, the greater the attenuation of the stress acting on the region R2 due to the displacement in the region R1 and the stress acting on the region R1 due to the displacement in the region R2. As a result, the piezoelectric element 10 can reliably relieve the stress acting within the piezoelectric body 11.

[0064] In the piezoelectric element 10, the plurality of internal electrodes 21 and 25 included in the internal electrode group 20 and the plurality of internal electrodes 23 and 25 included in the internal electrode group 22 are not exposed on the side surfaces 11c and 11e. In the piezoelectric element 10, the multiple internal electrodes 21, 23, 25 are covered by the piezoelectric body 11 and are disposed within the piezoelectric body 11. Therefore, in the piezoelectric element 10, electrical short circuits are unlikely to occur.

[0065] In the piezoelectric element 10, the regions R1 and R2 are displaced in opposite directions. The piezoelectric element 10 is arranged on the main surface 11a and has a plurality of external electrodes 13, 14, 15 that are electrically connected to corresponding internal electrodes 21, 23, 25 among the plurality of internal electrodes 21, 25 included in the internal electrode group 20 and the plurality of internal electrodes 23, 25 included in the internal electrode group 22.

[0066] (Second embodiment) A piezoelectric element 10 according to the second embodiment will be described with reference to Fig. 8. Fig. 8 is a diagram showing the cross-sectional structure of the piezoelectric element according to the second embodiment. The piezoelectric element 10 according to the second embodiment is generally similar to or the same as the piezoelectric element 10 according to the first embodiment described above, but the piezoelectric element 10 according to the second embodiment differs from the piezoelectric element 10 according to the first embodiment with respect to the relationship between region R1 and region R3, and between region R3 and region R2. The following mainly describes the differences from the piezoelectric element 10 according to the first embodiment.

[0067] The piezoelectric element 10 according to the second embodiment includes an internal electrode group 20 and an internal electrode group 22. The internal electrode group 20 is arranged in the region R1. The internal electrode group 20 includes a plurality of internal electrodes 21 and 25. The internal electrode 25 faces the internal electrode 21. The internal electrode group 20 includes four internal electrodes 21 and four internal electrodes 25. The internal electrodes 21 and 25 are alternately arranged, and the internal electrodes 21 and 25 face each other at a distance L1, with a corresponding piezoelectric layer 17 sandwiched between them. The size of the distance L1 between the plurality of facing internal electrodes 21 and 25 is the same. Of the plurality of internal electrodes 21 and 25, the internal electrode group 20 includes the internal electrode 21 closest to the region R2 and the internal electrode 25 closest to the main surface 11a.

[0068] The internal electrode group 22 is arranged in region R2. The internal electrode group 22 includes a plurality of internal electrodes 23 and 25. The internal electrode 23 is not electrically connected to the plurality of internal electrodes 21 and 25 included in the internal electrode group 20. The internal electrode 25 faces the internal electrode 23. The internal electrodes 25 included in the internal electrode group 22 are electrically connected to the internal electrodes 25 included in the internal electrode group 20. In the second embodiment, the internal electrode group 22 includes four internal electrodes 23 and four internal electrodes 25. In the internal electrode group 22, the internal electrodes 23 and the internal electrodes 25 are alternately arranged, and the internal electrodes 23 and the internal electrodes 25 face each other at a distance L2, with a corresponding piezoelectric layer 17 sandwiched between them. The size of the distance L2 between the plurality of facing internal electrodes 23 and 25 is the same. The internal electrode group 22 includes the internal electrode 23 closest to the region R1 among the multiple internal electrodes 23, 25 included in the internal electrode group 22. The internal electrode 23 closest to the region R1 and the internal electrode 21 closest to the region R2 are not electrically connected to each other. The internal electrode group 22 includes the internal electrode 25 closest to the main surface 11b among the multiple internal electrodes 23, 25 included in the internal electrode group 22.

[0069] Region R3 is located between the internal electrode 21 closest to region R2 and the internal electrode 23 closest to region R1. Region R3 includes multiple piezoelectric layers 19. Region R3 includes, for example, three piezoelectric layers 19. The piezoelectric layers 19 are located between the piezoelectric layer 17 included in region R1 and the piezoelectric layer 17 included in region R2. In the piezoelectric element 11, the multiple piezoelectric layers 17, 19 are stacked in the first direction D1. The piezoelectric layers 19 have the same thickness.

[0070] The piezoelectric element 10 according to the second embodiment includes a plurality of internal conductors 27. The piezoelectric element 10 may include, for example, two internal conductors 27. The two internal conductors 27 face each other and are disposed between the internal electrode 21 closest to the region R2 and the internal electrode 23 closest to the region R1. The two internal conductors 27 are disposed in the region R3. The internal electrode 21 closest to the region R2 and the internal electrode 23 closest to the region R1 are spaced apart by a distance L3 in the first direction D1. The distance L3 is greater than the distances L1 and L2. The two internal conductors 27 are not electrically connected to the plurality of internal electrodes 21, 25 included in the internal electrode group 20 and the plurality of internal electrodes 23, 25 included in the internal electrode group 22. The two internal conductors 27 are not exposed on the side surfaces 11c, 11e. The piezoelectric element 10 according to the second embodiment may include a single internal conductor 27. When the piezoelectric element 10 includes a single internal conductor 27, the distance L3 is greater than the distances L1 and L2.

[0071] As described above, the piezoelectric element 10 includes the piezoelectric element 11, which includes the principal surfaces 11a and 11b facing each other and the side surfaces 11c and 11e connecting the principal surfaces 11a and 11b, and also includes a region R1 including the principal surface 11a and a region R2 including the principal surface 11b; the internal electrode group 20, which is arranged in the region R1 and includes a plurality of internal electrodes 21 and 25 facing each other in the direction in which the principal surfaces 11a and 11b face each other; and the internal electrode group 20, which is arranged in the region R2 and includes a plurality of internal electrodes 21 and 25 facing each other in the direction in which the principal surfaces 11a and 11b face each other. and an internal conductor 27 that is arranged between the internal electrode 21, 25 included in the internal electrode group 20, which is closest to the region R2, and the internal electrode 23, 25 included in the internal electrode group 22, which is closest to the region R1, and that is not electrically connected to the internal electrodes 21, 25 included in the internal electrode group 20 and the internal electrodes 23, 25 included in the internal electrode group 22.

[0072] In the piezoelectric element 10, the piezoelectric body 11 includes a region R3 between the internal electrode 21, 25 included in the internal electrode group 20, which is closest to the region R2, and the internal electrode 23, 25 included in the internal electrode group 22, which is closest to the region R1. The internal conductor 27 is disposed in the region R3 and is not electrically connected to the internal electrodes 21, 25 included in the internal electrode group 20 or the internal electrodes 23, 25 included in the internal electrode group 22. Therefore, when a voltage is applied, an electric field is unlikely to be generated in the region R3. The region R3 is unlikely to be displaced. The region R3 relieves stress acting on the region R2 due to displacement in the region R1, and relieves stress acting on the region R1 due to displacement in the region R2. The piezoelectric element 10 can relieve stress acting within the piezoelectric body 11.

[0073] The above describes embodiments and modifications of the present invention, but the present invention is not necessarily limited to the above-described embodiments and modifications, and various modifications are possible without departing from the spirit of the present invention.

[0074] The internal conductor 27 may be exposed on either the side surface 11c or 11e. In a configuration in which the internal conductor 27 is not exposed on the side surface 11c or 11e, as described above, an electrical short circuit is less likely to occur. The distance L3 may be smaller than the distance L1 and the distance L2. A configuration in which the distance L3 is larger than the distance L1 and the distance L2 can more reliably relieve stress acting within the piezoelectric element 11, as described above. The internal electrodes 21, 23, 25 may be exposed on either the side surfaces 11c, 11e. In a configuration in which the internal electrodes 21, 23, 25 are not exposed on the side surfaces 11c, 11e, as described above, electrical short circuits are less likely to occur.

[0075] As can be understood from the above description of the embodiments and modifications, the present specification includes disclosure of the following aspects. (Appendix 1) a piezoelectric element including a first main surface and a second main surface facing each other, and a side surface connecting the first main surface and the second main surface, and including a first region including the first main surface and a second region including the second main surface; a first internal electrode group including a plurality of internal electrodes disposed in the first region and facing each other in a direction in which the first main surface and the second main surface face each other; a second internal electrode group including a plurality of internal electrodes that are arranged in the second region and face each other in the direction in which the first main surface and the second main surface face each other, A piezoelectric element, wherein an internal electrode of the plurality of internal electrodes included in the first internal electrode group that is closest to the second region and an internal electrode of the plurality of internal electrodes included in the second internal electrode group that is closest to the first region are electrically connected to each other. (Appendix 2) The plurality of internal electrodes included in the first internal electrode group are A first internal electrode; a second internal electrode facing the first internal electrode, The plurality of internal electrodes included in the second internal electrode group are a third internal electrode that is not electrically connected to the first internal electrode and the second internal electrode; a fourth internal electrode facing the third internal electrode and electrically connected to the second internal electrode, the internal electrode closest to the second region includes the second internal electrode, 2. The piezoelectric element of claim 1, wherein the internal electrode closest to the first region includes the fourth internal electrode. (Appendix 3) 3. The piezoelectric element according to claim 1, further comprising an internal conductor that is disposed between the internal electrode closest to the second region and the internal electrode closest to the first region, and that is not electrically connected to the plurality of internal electrodes included in the first internal electrode group and the plurality of internal electrodes included in the second internal electrode group. (Appendix 4) 4. The piezoelectric element according to claim 3, wherein the internal conductor is not exposed on the side surface. (Appendix 5) a piezoelectric element including a first main surface and a second main surface facing each other, and a side surface connecting the first main surface and the second main surface, and including a first region including the first main surface and a second region including the second main surface; a first internal electrode group including a plurality of internal electrodes disposed in the first region and facing each other in a direction in which the first main surface and the second main surface face each other; a second internal electrode group including a plurality of internal electrodes disposed in the second region and facing each other in a direction in which the first main surface and the second main surface face each other; a piezoelectric element comprising: an internal conductor that is disposed between an internal electrode of the plurality of internal electrodes included in the first internal electrode group that is closest to the second region and an internal electrode of the plurality of internal electrodes included in the second internal electrode group that is closest to the first region, and that is not electrically connected to the plurality of internal electrodes included in the first internal electrode group and the plurality of internal electrodes included in the second internal electrode group. (Appendix 6) 6. The piezoelectric element according to claim 5, wherein the internal conductor is not exposed on the side surface. (Appendix 7) 7. The piezoelectric element according to any one of claims 1 to 6, wherein the distance between the internal electrode closest to the second region and the internal electrode closest to the first region is greater than the distance between the internal electrodes included in the first internal electrode group and the distance between the internal electrodes included in the second internal electrode group. (Appendix 8) The piezoelectric element according to any one of appendices 1 to 7, wherein the plurality of internal electrodes included in the first internal electrode group and the plurality of internal electrodes included in the second internal electrode group are not exposed on the side surface. (Appendix 9) 9. The piezoelectric element according to any one of claims 1 to 8, wherein the first region and the second region are displaced in opposite directions. (Appendix 10) The piezoelectric element according to any one of appendices 1 to 9, further comprising a plurality of external electrodes arranged on the first main surface and electrically connected to corresponding internal electrodes among the plurality of internal electrodes included in the first internal electrode group and the plurality of internal electrodes included in the second internal electrode group. [Explanation of symbols]

[0076] 10...piezoelectric element, 11...piezoelectric body, 11a, 11b...main surfaces, 11c, 11e...side surfaces, 20...internal electrode group, 21...internal electrode, 22...internal electrode group, 23...internal electrode, 25...internal electrode, 27...internal conductor, L1, L2, L3...spacing, R1, R2...area.

Claims

1. a piezoelectric element including a first main surface and a second main surface facing each other, and a side surface connecting the first main surface and the second main surface, and including a first region including the first main surface and a second region including the second main surface; a first internal electrode group including a plurality of internal electrodes disposed in the first region and facing each other in a direction in which the first main surface and the second main surface face each other; a second internal electrode group including a plurality of internal electrodes that are arranged in the second region and face each other in the direction in which the first main surface and the second main surface face each other, A piezoelectric element, wherein an internal electrode of the plurality of internal electrodes included in the first internal electrode group that is closest to the second region and an internal electrode of the plurality of internal electrodes included in the second internal electrode group that is closest to the first region are electrically connected to each other.

2. The plurality of internal electrodes included in the first internal electrode group are A first internal electrode; a second internal electrode facing the first internal electrode, The plurality of internal electrodes included in the second internal electrode group are a third internal electrode that is not electrically connected to the first internal electrode and the second internal electrode; a fourth internal electrode facing the third internal electrode and electrically connected to the second internal electrode, the internal electrode closest to the second region includes the second internal electrode, The piezoelectric element according to claim 1 , wherein the internal electrode closest to the first region includes the fourth internal electrode.

3. 3. The piezoelectric element according to claim 1, further comprising an internal conductor that is arranged between the internal electrode closest to the second region and the internal electrode closest to the first region, and that is not electrically connected to the plurality of internal electrodes included in the first internal electrode group and the plurality of internal electrodes included in the second internal electrode group.

4. The piezoelectric element according to claim 3 , wherein the internal conductor is not exposed at the side surface.

5. a piezoelectric element including a first main surface and a second main surface facing each other, and a side surface connecting the first main surface and the second main surface, and including a first region including the first main surface and a second region including the second main surface; a first internal electrode group including a plurality of internal electrodes disposed in the first region and facing each other in a direction in which the first main surface and the second main surface face each other; a second internal electrode group including a plurality of internal electrodes disposed in the second region and facing each other in a direction in which the first main surface and the second main surface face each other; a piezoelectric element comprising: an internal conductor that is disposed between an internal electrode of the plurality of internal electrodes included in the first internal electrode group that is closest to the second region and an internal electrode of the plurality of internal electrodes included in the second internal electrode group that is closest to the first region, and that is not electrically connected to the plurality of internal electrodes included in the first internal electrode group and the plurality of internal electrodes included in the second internal electrode group.

6. The piezoelectric element according to claim 5 , wherein the internal conductor is not exposed at the side surface.

7. 6. The piezoelectric element according to claim 1, wherein the distance between the internal electrode closest to the second region and the internal electrode closest to the first region is greater than the distance between the plurality of internal electrodes included in the first internal electrode group and the distance between the plurality of internal electrodes included in the second internal electrode group.

8. The piezoelectric element according to claim 1 , wherein the plurality of internal electrodes included in the first internal electrode group and the plurality of internal electrodes included in the second internal electrode group are not exposed on the side surface.

9. The piezoelectric element according to claim 1 , wherein the first region and the second region are displaced in opposite directions.

10. 6. The piezoelectric element according to claim 1, further comprising a plurality of external electrodes arranged on the first main surface and electrically connected to corresponding internal electrodes among the plurality of internal electrodes included in the first internal electrode group and the plurality of internal electrodes included in the second internal electrode group.

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