Piezoelectric element

Abstract

This piezoelectric element is provided with a multilayer body, a conductor layer, an electrode plate and a cover layer. With respect to the multilayer body, a plurality of piezoelectric bodies and a plurality of internal electrodes are stacked upon each other. The conductor layer is connected to the internal electrodes and is positioned along the stacking direction of the multilayer body. The electrode plate is bonded to the conductor layer with a conductive bonding material being interposed therebetween, and is positioned along the stacking direction of the multilayer body. The cover layer covers the conductor layer and the electrode plate. The electrode plate has a plurality of slits which extend in a direction that intersects with the stacking direction. This piezoelectric element has a first void among the electrode plate, the conductor layer and the bonding material.

Description

Piezoelectric element

[0001] The disclosed embodiments relate to a piezoelectric element.

[0002] A piezoelectric element is known that includes a laminate in which a plurality of piezoelectric bodies and internal electrodes are stacked, a conductor layer located on the side of the laminate and connected to the internal electrodes, and an electrode plate having a portion in the width direction joined to the conductor layer via a conductive bonding material (see, for example, Patent Document 1). Also, a structure has been proposed in which the conductor layer and the electrode plate are covered by a covering layer located on the side of the laminate (see, for example, Patent Document 2).

[0003] JP 2008-211054 A JP 2006-41279 A

[0004] A piezoelectric element according to one aspect of the embodiment includes a laminate, a conductor layer, an electrode plate, and a covering layer. The laminate is formed by stacking a plurality of piezoelectric bodies and internal electrodes. The conductor layer is connected to the internal electrodes and is positioned along the stacking direction of the laminate. The electrode plate is bonded to the conductor layer via a conductive bonding material and is positioned along the stacking direction of the laminate. The covering layer covers the conductor layer and the electrode plate. The electrode plate has a plurality of slits extending in a direction intersecting the stacking direction. The piezoelectric element has a first gap between the electrode plate, the conductor layer, and the bonding material.

[0005] According to one aspect of the embodiment, it is possible to reduce the possibility of peeling off of the electrode plate covered with the covering layer.

[0006] FIG. 1 is a perspective view showing the overall configuration of a piezoelectric element according to an embodiment. FIG. 2 is an enlarged plan view showing an example of an electrode plate and its surrounding configuration according to an embodiment. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 2. FIG. 5 is a cross-sectional view showing an example of an electrode plate and its surrounding configuration according to Alternative Embodiment 1. FIG. 6 is a cross-sectional view showing an example of an electrode plate and its surrounding configuration according to Alternative Embodiment 1. FIG. 7 is a cross-sectional view showing an example of an electrode plate and its surrounding configuration according to Alternative Embodiment 2. FIG. 8 is a cross-sectional view showing an example of an electrode plate and its surrounding configuration according to Alternative Embodiment 2. FIG. 9 is an enlarged plan view showing an example of an electrode plate according to Alternative Embodiment 3. FIG. 10 is an enlarged plan view showing an example of an electrode plate according to Alternative Embodiment 4. FIG. 11 is an enlarged plan view showing an example of an electrode plate and its surrounding configuration according to Alternative Embodiment 5. FIG. 12 is a cross-sectional view taken along line XII-XII in FIG. 11. FIG. 13 is a cross-sectional view taken along line XIII-XIII in FIG. 11. FIG. 14 is a cross-sectional view showing an example of an electrode plate and its surrounding configuration according to Alternative Embodiment 6. FIG. 15 is a cross-sectional view showing an example of the configuration of an electrode plate and its periphery according to Alternative Embodiment 6. FIG. 16 is an enlarged plan view showing an example of the configuration of an electrode plate and its periphery according to Alternative Embodiment 7. FIG. 17 is a cross-sectional view taken along the arrows XVII-XVII shown in FIG. 16. FIG. 18 is a cross-sectional view showing an example of the configuration of an electrode plate and its periphery according to Alternative Embodiment 8. FIG. 19 is an enlarged plan view showing an example of the configuration of an electrode plate and its periphery according to Alternative Embodiment 9. FIG. 20 is a cross-sectional view taken along the arrows XX-XX shown in FIG. 19. FIG. 21 is a cross-sectional view showing an example of the configuration of an electrode plate and its periphery according to Alternative Embodiment 10. FIG. 22 is an enlarged plan view showing an example of the configuration of an electrode plate and its periphery according to Alternative Embodiment 11. FIG. 23 is a cross-sectional view showing an example of the configuration of an electrode plate and its periphery according to Alternative Embodiment 12.

[0007] Hereinafter, embodiments of the piezoelectric element disclosed in the present application will be described with reference to the accompanying drawings. Note that the present disclosure is not limited to the embodiments shown below. It should be noted that the drawings are schematic, and the dimensional relationships and ratios of elements may differ from reality. Furthermore, the drawings may include portions in which the dimensional relationships and ratios differ from one another.

[0008] <Overall Configuration of Piezoelectric Element> First, the overall configuration of a piezoelectric element 1 according to the embodiment will be described with reference to Fig. 1. Fig. 1 is a perspective view showing the overall configuration of a piezoelectric element 1 according to the embodiment.

[0009] As shown in Fig. 1, the piezoelectric element 1 according to the embodiment includes a laminate 10, a pair of conductor layers 20, a pair of electrode plates 40, and a covering layer 50 (see Figs. 3 and 4). The pair of conductor layers 20 include a conductor layer 20A and a conductor layer 20B, and the pair of electrode plates 40 include an electrode plate 40A and an electrode plate 40B. For ease of explanation, the covering layer 50, the conductor layer 20B, and the electrode plate 40B are not shown in Fig. 1.

[0010] The laminate 10 has a columnar shape. The laminate 10 is, for example, a square pillar (rectangular parallelepiped) having a length of 0.5 mm to 10 mm, a width of 0.5 mm to 10 mm, and a height of 1 mm to 100 mm. The shape of the laminate 10 is not limited to a square pillar, and may be a hexagonal pillar, an octagonal pillar, a cylindrical pillar, or the like.

[0011] The laminate 10 has a piezoelectric body 11, an internal electrode 12, and a planned fracture layer 13. The laminate 10 is configured by stacking the piezoelectric body 11, the internal electrode 12, and the planned fracture layer 13 in a predetermined order along a stacking direction D. In the present disclosure, the stacking direction D of the laminate 10 coincides with the longitudinal direction of the laminate 10.

[0012] The piezoelectric body 11 is made of a piezoelectric material having piezoelectric properties, such as piezoelectric ceramics. Examples of the material of such piezoelectric ceramics include lead zirconate titanate (PbZrO ３ -PbTiO ３ ), a perovskite oxide consisting of lithium niobate (LiNbO ３) or lithium tantalate (LiTaO ３ ) etc.

[0013] The average particle size of such piezoelectric ceramics is, for example, 1.6 μm to 2.8 μm, and the thickness of the piezoelectric body 11 is, for example, 3 μm to 250 μm.

[0014] The internal electrodes 12 are made of a conductive material and include a plurality of first electrodes 12a and a plurality of second electrodes 12b. The first electrodes 12a are electrically connected to a conductor layer 20A disposed on one side surface 10a of the laminate 10. A predetermined positive voltage is applied to the first electrodes 12a via the conductor layer 20A.

[0015] The second electrode 12b is electrically connected to a conductor layer 20B disposed on the side surface 10b opposite to the side surface 10a of the laminate 10. A predetermined negative voltage (or ground voltage) is applied to the second electrode 12b via the conductor layer 20B.

[0016] Inside the laminate 10, the first electrode 12a, the second electrode 12b, and the piezoelectric body 11 are laminated so that the piezoelectric body 11 is disposed between the first electrode 12a and the second electrode 12b. This allows the laminate 10 to apply a drive voltage to the piezoelectric body 11 by the first electrode 12a and the second electrode 12b.

[0017] The laminate 10 according to the embodiment is composed of an active portion formed by alternately stacking multiple piezoelectric bodies 11 and internal electrodes 12, and an inactive portion having a piezoelectric body 11 and arranged on both ends of the active portion in the stacking direction D.

[0018] The active portion is a portion that expands or contracts (hereinafter also referred to as expansion and contraction) in the stacking direction D when a drive voltage is applied to the laminate 10 from the outside. On the other hand, the inactive portion is a portion that does not expand or contract even when a drive voltage is applied to the laminate 10 from the outside.

[0019] In the present disclosure, the lower end in FIG. 1 is referred to as a base end 10e of the laminate 10, and the upper end in FIG.

[0020] In the piezoelectric element 1 according to the embodiment, the base end 10e of the laminate 10 is fixed, and the tip end 10f of the laminate 10 is displaceable along the lamination direction D.

[0021] The material of the internal electrodes 12 is, for example, a metal whose main component is silver, silver-palladium, silver-platinum, or copper. The internal electrodes 12 can be formed, for example, by co-firing with the piezoelectric body 11. The thickness of the internal electrodes 12 is, for example, 0.1 μm to 5 μm.

[0022] The planned rupture layer 13 is a layer for alleviating stress caused by driving the laminate 10. Examples of the planned rupture layer 13 include a porous metal layer that does not function as the internal electrode 12, or a metal layer that has cracks in it. Note that the planned rupture layer 13 may be omitted in the laminate 10 according to the embodiment.

[0023] As described above, the pair of conductor layers 20 includes a conductor layer 20A located on the side surface 10a of the laminate 10 and a conductor layer 20B located on the side surface 10b of the laminate 10. The conductor layer 20 is disposed across the entire active portion of the laminate 10. The conductor layer 20 is positioned along the stacking direction D.

[0024] The material of the conductor layer 20 is, for example, a metal containing silver or copper as a main component. For example, a metallized layer made of a sintered body of the above metal and glass can be used for the conductor layer 20. The thickness of the conductor layer 20 is, for example, 5 μm to 500 μm.

[0025] The pair of electrode plates 40 includes electrode plate 40A and electrode plate 40B, which are electrically connected to the pair of conductor layers 20. Specifically, electrode plate 40A is electrically connected to conductor layer 20A, and electrode plate 40B is electrically connected to conductor layer 20B.

[0026] The electrode plate 40 is positioned along the stacking direction D of the laminate 10. A portion of the electrode plate 40 in the width direction intersecting with the stacking direction D is joined to the conductor layer 20 via a conductive bonding material 30. As such bonding material 30, for example, an epoxy resin or polyimide resin containing a metal powder having high conductivity, such as Ag powder or Cu powder, is used.

[0027] The electrode plate 40 is made of a metal such as copper, iron, stainless steel, or phosphor bronze. The width of the electrode plate 40 is, for example, 0.5 mm to 10 mm, and the thickness of the electrode plate 40 is, for example, 0.01 mm to 1.0 mm. The surface of the electrode plate 40 may be plated with a plating film such as tin or silver to improve electrical conductivity and thermal conductivity.

[0028] The covering layer 50 is positioned around the entire periphery of the side surfaces, including the side surfaces 10a and 10b, of the laminate 10, and covers the conductor layer 20 and the electrode plate 40. By providing the covering layer 50 on the side surfaces 10a and 10b, it is possible to reduce creeping discharge that occurs between the electrodes when a high voltage is applied during operation.

[0029] The covering layer 50 is made of, for example, an insulator, such as a fluorine-based resin, a silicone resin, an epoxy resin, or a nylon resin.

[0030] The covering layer 50 does not necessarily have to be disposed around the entire periphery of the side surfaces, as long as it is positioned at least on the side surfaces 10a and 10b of the laminate 10 so as to cover the conductor layer 20 and the electrode plate 40. For example, the covering layer 50 may not be disposed on the side surfaces 10c and 10d of the laminate 10, but may be disposed only on the side surfaces 10a and 10b.

[0031] <Configuration of Electrode Plate and Covering Layer> Next, the detailed configuration of the electrode plate 40 and covering layer 50 according to the embodiment will be described with reference to FIGS. 2 to 4. FIG. 2 is an enlarged plan view showing an example of the configuration of the electrode plate 40 and its surroundings according to the embodiment. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 2. For ease of explanation, the covering layer 50 is omitted from FIG. 2.

[0032] As described above, the electrode plate 40 is a plate-shaped member extending in the stacking direction D of the laminate 10, and a portion of the width direction intersecting the stacking direction D is joined to the conductor layer 20 via a conductive bonding material 30.

[0033] 2, in this embodiment, the electrode plate 40 has a plurality of slits S. The slits S are cut out so as to extend, for example, along the width direction of the electrode plate 40 (i.e., the direction intersecting with the stacking direction D).

[0034] The slits S are alternately cut out from the end faces of both ends of the electrode plate 40 that are located outside the bonding material 30 in the width direction in a plan view, and are arranged side by side at approximately equal intervals along the stacking direction D. The slits S all have approximately the same length. The length of the slits S refers to the length in the cutout direction of the slits S (i.e., the width direction of the electrode plate 40).

[0035] Furthermore, the lengths of the multiple slits S are set so that the tips of the slits S overlap when viewed in the stacking direction D. Here, overlapping means that adjacent slits S have regions where they face each other when viewed in the stacking direction D.

[0036] In the embodiment, by arranging a plurality of slits S in the electrode plate 40, the electrode plate 40 can expand and contract in the stacking direction D in accordance with the expansion and contraction of the laminate 10 in the stacking direction D. Therefore, according to the embodiment, the possibility of the electrode plate 40 peeling off from the laminate 10 or the conductor layer 20 can be reduced.

[0037] On the other hand, the electrode plate 40 is covered together with the conductor layer 20 by a covering layer 50 (see FIGS. 3 and 4) located on the side surface of the laminate 10 .

[0038] If the periphery of the electrode plate 40 and the conductor layer 20 were completely covered with the covering layer 50, when the laminate 10 expanded or contracted, a large stress that limits the deformation of the electrode plate 40 would be generated in the electrode plate 40. In particular, the stress that limits the torsional deformation would be concentrated on the end portion of the electrode plate 40 that is located outside the bonding material 30 in the width direction in a plan view. Then, as the laminate 10 expands or contracts, stress that limits the deformation would be generated in the electrode plate 40, which could cause the electrode plate 40 to peel off from the laminate 10 or the conductor layer 20.

[0039] Therefore, in the embodiment, as shown in Figures 3 and 4, the conductor layer 20 and the electrode plate 40 are covered with the covering layer 50, with a gap G remaining between the conductor layer 20 and the end of the electrode plate 40 located outside the bonding material 30 in the width direction in a planar view. In other words, in the embodiment, the piezoelectric element 1 has a gap G between the electrode plate 40, the conductor layer 20, and the bonding material 30. A plurality of such gaps G are formed in positions that do not overlap with the plurality of slits S in the electrode plate 40 in a planar view (see Figure 2). The end of the electrode plate 40 located outside the bonding material 30 in the width direction in a planar view and the conductor layer 20 are positioned opposite each other with each gap G sandwiched between them. The gap G is an example of a first gap.

[0040] In the embodiment, by covering the conductor layer 20 and the electrode plate 40 with the covering layer 50 while leaving such gap G, twisting deformation occurs at the end of the electrode plate 40 in the width direction in accordance with expansion and contraction of the laminate 10 in the stacking direction D, making it possible to easily deform the electrode plate 40. Therefore, according to the embodiment, it is possible to alleviate stress generated in the electrode plate 40 due to expansion and contraction of the laminate 10, thereby reducing the possibility of the electrode plate 40 peeling off from the laminate 10 or the conductor layer 20.

[0041] 2 and 3 , in the embodiment, the gap G between one end of the electrode plate 40 located outside the bonding material 30 in a plan view in the width direction and the conductor layer 20 is separated from the gap G between the other end of the electrode plate 40 and the conductor layer 20. That is, the gap G between one end of the electrode plate 40 and the conductor layer 20 and the gap G between the other end of the electrode plate 40 and the conductor layer 20 are not connected, but are individually closed with the bonding material 30 as a boundary. By separating the gap G on one end side of the electrode plate 40 from the gap G on the other end side, torsional deformation can be more easily generated at both ends of the electrode plate 40 in the width direction in accordance with expansion and contraction of the laminate 10 in the stacking direction D. Therefore, according to the embodiment, stress generated in the electrode plate 40 due to expansion and contraction of the laminate 10 can be further alleviated, thereby further reducing the possibility of the electrode plate 40 peeling off from the laminate 10 or the conductor layer 20.

[0042] 2 , in the embodiment, the gap G between one end of the electrode plate 40 and the conductor layer 20 and the gap G between the other end of the electrode plate 40 and the conductor layer 20 are positioned at positions offset from each other in the stacking direction D of the laminate 10. This makes it easier for torsional deformation to occur at both ends in the width direction of the electrode plate 40 in accordance with expansion and contraction of the laminate 10 in the stacking direction D. Therefore, according to the embodiment, the stress generated in the electrode plate 40 due to expansion and contraction of the laminate 10 can be further alleviated, thereby further reducing the possibility of the electrode plate 40 peeling off from the laminate 10 or the conductor layer 20.

[0043] 2 , the bonding material 30 may be positioned so as to overlap the central portion of the electrode plate 40 in a plan view. This allows the gap G on one end side of the electrode plate 40 separated by the bonding material 30 and the gap G on the other end side to be approximately the same size, and torsional deformation occurs evenly at both widthwise ends of the electrode plate 40 in accordance with expansion and contraction of the laminate 10 in the stacking direction D. Therefore, according to the embodiment, stress generated in the electrode plate 40 due to expansion and contraction of the laminate 10 can be alleviated evenly at both widthwise ends of the electrode plate 40, further reducing the possibility of the electrode plate 40 peeling off from the laminate 10 or the conductor layer 20.

[0044] 2 , the bonding material 30 may have an area that overlaps with the slit S of the electrode plate 40 in a plan view. This makes it difficult for the electrode plate 40 to peel off from the bonding material 30 in the vicinity of the slit S of the electrode plate 40.

[0045] In addition, in the embodiment, the length of the slit S in the electrode plate 40 is greater than half the width of the electrode plate 40. As a result, the position of the tip of the slit S in the cutout direction, which is the starting point of twisting generated at the end of the electrode plate 40 in the width direction, is misaligned with the position of the bonding material 30 located in the central part of the electrode plate 40, making it difficult for the electrode plate 40 to peel off from the bonding material 30.

[0046] <Another embodiment 1> Next, various other embodiments will be described with reference to Figures 5 to 23. Note that in the various other embodiments described below, the same components as those in the embodiment will be assigned the same reference numerals, and redundant description may be omitted.

[0047] 5 and 6 are cross-sectional views showing an example of the configuration of the electrode plate 40 and its surroundings according to Alternative Embodiment 1. Fig. 5 corresponds to the cross-sectional view taken along line III-III in Fig. 2, and Fig. 6 corresponds to the cross-sectional view taken along line IV-IV in Fig. 2.

[0048] In another embodiment 1 shown in Figures 5 and 6, the configuration of the covering layer 50 differs from that of the above-described embodiment. Specifically, in another embodiment 1, as shown in Figure 5, the covering layer 50 has a protruding portion 51. The protruding portion 51 is positioned to protrude inward from the end of the electrode plate 40 in a direction intersecting the stacking direction D (i.e., the width direction), and is in contact with the conductor layer 20. Here, "inward" means the side toward the center of the electrode plate 40. The protruding portion 51 is an example of a first protruding portion.

[0049] In Alternative Embodiment 1, by providing the overhanging portion 51 on the covering layer 50, the adhesion between the covering layer 50 and the conductor layer 20 is improved compared to when the overhanging portion 51 is not provided, and therefore the adhesion between the electrode plate 40 covered with the covering layer 50 and the conductor layer 20 is improved. Therefore, according to Alternative Embodiment 1, it is possible to reduce the possibility that the electrode plate 40 covered with the covering layer 50 will peel off from the conductor layer 20.

[0050] In another embodiment 1, as shown in Fig. 6, the covering layer 50 may have a protruding portion 52. The protruding portion 52 is located protruding inward from the inner wall surface of the slit S in the electrode plate 40 and is in contact with the conductor layer 20. Here, "inward" refers to the side closer to the center of each electrode plate. The protruding portion 52 is an example of a second protruding portion.

[0051] By providing the overhanging portion 52 on the covering layer 50, the adhesion between the covering layer 50 and the conductor layer 20 is improved compared to when the overhanging portion 52 is not provided, and therefore the adhesion between the electrode plate 40 covered by the covering layer 50 and the conductor layer 20 is improved. Therefore, according to the alternative embodiment 1, it is possible to reduce the possibility that the electrode plate 40 covered by the covering layer 50 will peel off from the conductor layer 20.

[0052] 7 and 8 are cross-sectional views showing an example of the configuration of an electrode plate 40 and its surroundings according to another embodiment 2. Fig. 7 corresponds to the cross-sectional view taken along line III-III in Fig. 2, and Fig. 8 corresponds to the cross-sectional view taken along line IV-IV in Fig. 2.

[0053] 7 and 8, the configuration of the electrode plate 40 differs from that of the above-described alternative embodiment 2. Specifically, in alternative embodiment 2, as shown in Fig. 7, the electrode plate 40 has a protrusion 41 that protrudes in the thickness direction of the electrode plate 40 on the periphery of the end of the electrode plate 40 in a direction intersecting the stacking direction D (i.e., the width direction). The protrusion 41 is an example of a first protrusion.

[0054] In Alternative Embodiment 2, by providing the protrusions 41 on the electrode plate 40, the strength of both ends of the electrode plate 40 is increased compared to when the protrusions 41 are not provided, and therefore damage to both ends of the electrode plate 40 due to repeated deformation is less likely to occur. Therefore, Alternative Embodiment 2 can improve the durability of the electrode plate 40. Note that, although the protrusions 41 are located on both the laminate 10 side and the opposite side of the laminate 10 in the structure shown in FIG. 7, they may be located only on the laminate 10 side.

[0055] Furthermore, in Alternative Embodiment 2, the thickness of the protruding portion 51 of the covering layer 50 located near the protruding portion 41 is reduced by the thickness of the protruding portion 41, which makes it easier for the electrode plate 40 to deform in accordance with the expansion and contraction of the laminate 10 in the stacking direction D. Therefore, according to Alternative Embodiment 2, the stress generated in the electrode plate 40 due to the expansion and contraction of the laminate 10 can be further alleviated, which further reduces the possibility of the electrode plate 40 peeling off from the laminate 10 or the conductor layer 20.

[0056] In another embodiment 2, the protrusions 41 may extend along the stacking direction D of the laminate 10. This further increases the strength of both ends of the electrode plate 40, making it less likely that damage to both ends of the electrode plate 40 will occur due to repeated deformation. Therefore, according to the second embodiment, the durability of the electrode plate 40 can be further improved.

[0057] 8 , the electrode plate 40 may have a protrusion 42 that protrudes in the thickness direction of the electrode plate 40 around the periphery of the slit S in the electrode plate 40. The protrusion 42 is an example of a second protrusion.

[0058] By providing the protrusions 42 on the electrode plate 40, the strength of the edges of the slits S in the electrode plate 40 is increased compared to when the protrusions 42 are not provided, and therefore the edges of the slits S in the electrode plate 40 are less likely to be damaged due to repeated deformation. Therefore, according to Alternative Embodiment 2, the durability of the electrode plate 40 can be improved. Note that, although the protrusions 42 are located on both the laminate 10 side and the opposite side of the laminate 10 in the structure shown in FIG. 8, they may be located only on the laminate 10 side.

[0059] Furthermore, in Alternative Embodiment 2, the thickness of the protruding portion 52 of the covering layer 50 located near the protruding portion 42 is reduced by the thickness of the protruding portion 42, which makes it easier for the electrode plate 40 to deform in accordance with the expansion and contraction of the laminate 10 in the stacking direction D. Therefore, according to Alternative Embodiment 2, the stress generated in the electrode plate 40 due to the expansion and contraction of the laminate 10 can be further alleviated, which further reduces the possibility of the electrode plate 40 peeling off from the laminate 10 or the conductor layer 20.

[0060] In another embodiment 2, the protrusions 42 may extend along the longitudinal direction of the slits S. This further increases the strength of the edges of the slits S in the electrode plate 40, making it less likely that damage to the edges of the slits S in the electrode plate 40 will occur due to repeated deformation. Therefore, according to the second embodiment, the durability of the electrode plate 40 can be further improved.

[0061] The formation of the protrusions 41 and 42 can be achieved by etching the side surface of the metal plate 40a (see Figure 7) that serves as the base material of the electrode plate 40 to form a recess, and then plating the corners located on the periphery of the recess more thickly than other parts.

[0062] <Other Embodiment 3> Fig. 9 is an enlarged plan view showing an example of the configuration of an electrode plate 40 according to Other Embodiment 3. In Other Embodiment 3 shown in Fig. 9, the shape of the electrode plate 40 differs from that of the above-described embodiments. Specifically, in Other Embodiment 3, the electrode plate 40 has a plurality of slits S and a plurality of through holes H.

[0063] The slits S are formed, for example, so as to extend along the width direction of the electrode plate 40 (i.e., the direction intersecting with the stacking direction D) to the end face of one of the ends of the electrode plate 40. Furthermore, the through holes H are formed so as to extend along the same direction as the slits S, but do not extend to the end faces of either end of the electrode plate 40.

[0064] The multiple slits S are cut out alternately from the end face of both ends in the width direction of the electrode plate 40, and are arranged side by side at approximately equal intervals along the stacking direction D. The multiple slits S all have approximately the same length. The lengths of the multiple slits S are set so that the tips of the slits S overlap each other when viewed in the stacking direction D.

[0065] In alternative embodiment 3, by arranging a plurality of slits S in the electrode plate 40, the electrode plate 40 can expand and contract in the stacking direction D in accordance with the expansion and contraction of the laminate 10 in the stacking direction D. Therefore, according to alternative embodiment 3, the possibility of the electrode plate 40 peeling off from the laminate 10 or the conductor layer 20 can be reduced.

[0066] Furthermore, in Alternative Embodiment 3, through holes H are located between slits S that are alternately cut out from the end face on both ends in the width direction of the electrode plate 40. The through holes H are arranged at positions that are equidistant from both adjacent slits S, and have lengths that are approximately equal to the lengths of the slits S.

[0067] That is, in another embodiment 3, as shown in Figure 9, in the electrode plate 40, slits S and through holes H extending from the end face of one end, and slits S and through holes H extending from the end face of the other end are arranged in this order at approximately equal intervals along the stacking direction D.

[0068] In another embodiment 3, a through hole H is arranged at a location where the tips of a slit S extending from the end face of one end and a slit S extending from the end face of the other end overlap.

[0069] This makes it possible to disperse stress generated between the slit S extending from the end face of one end and the slit S extending from the end face of the other end, thereby alleviating stress generated in the electrode plate 40 due to expansion and contraction of the laminate 10. Therefore, according to alternative embodiment 3, the possibility of the electrode plate 40 peeling off from the laminate 10 or the conductor layer 20 can be further reduced.

[0070] Alternative Embodiment 4 Fig. 10 is an enlarged plan view showing an example of the configuration of an electrode plate 40 according to Alternative Embodiment 4. In Alternative Embodiment 4 shown in Fig. 10, the arrangement of the through holes H differs from that in Alternative Embodiment 3 described above.

[0071] Specifically, in alternative embodiment 4, two or more through holes H are positioned adjacent to each other between slits S cut alternately from the end face of the electrode plate 40 at both ends in the width direction.

[0072] For example, as shown in Figure 10, in the electrode plate 40, a slit S extending from the end face of one end, a through hole H, a through hole H, and a slit S extending from the end face of the other end are arranged in this order at approximately equal intervals along the stacking direction D.

[0073] In this way, by arranging two or more through holes H adjacent to each other between the slits S cut alternately from the end face of both ends in the width direction of the electrode plate 40, it is possible to further alleviate the stress generated in the electrode plate 40 due to expansion and contraction of the laminate 10. Therefore, according to the fourth alternative embodiment, it is possible to further reduce the possibility that the electrode plate 40 will peel off from the laminate 10 or the conductor layer 20.

[0074] Alternative Embodiment 5 Fig. 11 is an enlarged plan view showing an example of the configuration of an electrode plate 40 and its surroundings according to Alternative Embodiment 5. Fig. 12 is a cross-sectional view taken along line XII-XII in Fig. 11. Fig. 13 is a cross-sectional view taken along line XIII-XIII in Fig. 11. For ease of explanation, the coating layer 50 is omitted from Figs. 11 to 13.

[0075] 11 to 13 differs from the above-described embodiments in the configuration of the electrode plate 40 and in the addition of a fixing material 60. Specifically, in Alternative Embodiment 5, as shown in Fig. 11 , the electrode plate 40 is a plate-like member extending in the stacking direction D of the laminate 10, and has a main body portion 43 joined to the conductor layer 20 via a conductive bonding material 30, and a protruding portion 44 protruding from one end 43a of the main body portion 43 in the stacking direction D and facing the laminate 10.

[0076] The main body portion 43 has a first portion 431 that contacts the bonding material 30, and a second portion 432 that is located on both sides of the first portion 431 in the width direction (i.e., the direction intersecting the stacking direction D) and faces the conductor layer 20 without contacting the bonding material 30.

[0077] 11 , in Alternative Embodiment 5, the main body 43 of the electrode plate 40 has a plurality of slits S. The slits S are cut out so as to extend, for example, along the width direction of the main body 43 (i.e., the direction intersecting with the stacking direction D).

[0078] The slits S are cut alternately from both sides of the main body 43 (i.e., from the sides of the pair of second portions 432) and are arranged side by side at approximately equal intervals along the stacking direction D. The slits S all have approximately the same length. The length of the slits S refers to the length in the cutout direction of the slits S (i.e., the width direction of the main body 43).

[0079] Furthermore, the lengths of the multiple slits S are set so that the tips of the slits S overlap when viewed in the stacking direction D. Here, overlapping means that adjacent slits S have regions where they face each other when viewed in the stacking direction D.

[0080] In another embodiment 5, by arranging a plurality of slits S in the main body portion 43 of the electrode plate 40, the main body portion 43 can expand and contract in the stacking direction D in accordance with the expansion and contraction of the laminate 10 in the stacking direction D. Therefore, according to another embodiment 5, the possibility of the electrode plate 40 peeling off from the laminate 10 or the conductor layer 20 can be reduced.

[0081] The protrusion 44 of the electrode plate 40 is located in the first gap G １ 1. The laminate 10 is opposed to the laminate 10 with the gap therebetween.

[0082] Furthermore, the piezoelectric element 1 according to Alternative Embodiment 5 includes a fixing member 60. The fixing member 60 fixes the electrode plate 40 and the laminate 10. For example, the fixing member 60 fixes at least the protruding portion 44 of the electrode plate 40 to the laminate 10.

[0083] The fixing material 60 according to the fifth alternative embodiment does not necessarily need to fix the entire periphery of the protruding portion 44 to the laminate 10. In short, it is sufficient that the fixing material 60 fixes at least a portion of the periphery of the protruding portion 44 to the laminate 10.

[0084] Furthermore, the fixing material 60 according to Alternative Embodiment 5 may fix the entire periphery of the protruding portion 44 to the laminate 10, with a predetermined region surrounded by the periphery of the protruding portion 44 remaining on the protruding portion 44. This allows the predetermined region remaining on the protruding portion 44 to be used as a region for joining a lead terminal that supplies power to the electrode plate 40.

[0085] The fixing material 60 is made of, for example, a heat-resistant and flexible insulating material. Examples of insulating materials that can be used for the fixing material 60 include epoxy resin, glass, ceramics, and composite materials of epoxy resin and ceramics. When ceramics or composite materials of epoxy resin and ceramics are used as the insulating material for the fixing material 60, the ceramic material may be the same as the piezoelectric ceramic material that will form the piezoelectric body 11.

[0086] As shown in FIGS. 12 and 13, in another embodiment 5, the fixing material 60 fixes at least the protruding portion 44 of the electrode plate 40 to the first gap G between the protruding portion 44 and the laminate 10. １In other words, in the fifth embodiment, the piezoelectric element 1 is fixed to the laminate 10 while the first gap G is formed between the fixing material 60, the protrusion 44, and the laminate 10. １ It has the following characteristics.

[0087] As a result, the first gap G １ The upper protrusion 44 expands and contracts along the stacking direction D, and stress generated at the end (near one end 43 a) of the joint between the electrode plate 40 and the conductor layer 20 can be released to the interface between the fixing material 60 and the laminate 10. Therefore, according to the fifth alternative embodiment, stress generated at the end (near one end 43 a) of the joint between the electrode plate 40 and the conductor layer 20 due to expansion and contraction of the laminate 10 in the stacking direction D can be dispersed, and the possibility of the electrode plate 40 peeling off from the conductor layer 20 can be reduced.

[0088] Alternative Embodiment 6 Figures 14 and 15 are cross-sectional views showing an example of the configuration of an electrode plate 40 and its surroundings according to Alternative Embodiment 6. Figure 14 corresponds to the cross-sectional view taken along line XII-XII in Figure 11, and Figure 15 corresponds to the cross-sectional view taken along line XIII-XIII in Figure 11. For ease of explanation, the coating layer 50 is omitted from Figures 14 and 15.

[0089] In Alternative Embodiment 6 shown in Figures 14 and 15, the configuration of the fixing member 60 differs from that of Alternative Embodiment 5 described above. Specifically, in Alternative Embodiment 6, the fixing member 60 has an overhanging portion 61. The overhanging portion 61 is positioned to overhang inward from the periphery of the protruding portion 44 and is in contact with the laminate 10. Here, "inward from the periphery of the protruding portion 44" can also be rephrased as "inward from the periphery of the protruding portion 44" as a direction approaching the central axis of the protruding portion 44 (electrode plate 40). The overhanging portion 61 is an example of a first overhanging portion.

[0090] In alternative embodiment 6, by providing a protruding portion 61 on the fixing material 60, stress generated at the end (near one end 43 a) of the joint portion between the electrode plate 40 and the conductor layer 20 can be efficiently released from the interface between the fixing material 60 and the laminate 10 in accordance with expansion and contraction of the laminate 10 in the stacking direction D. Therefore, according to alternative embodiment 6, stress generated at the end of the joint portion between the electrode plate 40 and the conductor layer 20 due to expansion and contraction of the laminate 10 in the stacking direction D can be more efficiently dispersed, and the possibility of the electrode plate 40 peeling off from the conductor layer 20 can be further reduced.

[0091] Alternative Embodiment 7 Fig. 16 is an enlarged plan view showing an example of the configuration of an electrode plate 40 and its surroundings according to alternative embodiment 7. Fig. 17 is a cross-sectional view taken along line XVII-XVII shown in Fig. 16 .

[0092] As shown in Figures 16 and 17, in another embodiment 7, the fixing material 60 fixes the main body portion 43 and the conductor layer 20 to the laminate 10 at one end of the conductor layer 20 located on the one end 43a side of the main body portion 43.

[0093] As a result, in Alternative Embodiment 7, in accordance with expansion and contraction of the laminate 10 in the stacking direction D, stress generated at the end (near one end 43 a) of the joint portion between the electrode plate 40 and the conductor layer 20 can be more efficiently released at the interface between the fixing material 60 and the laminate 10. Therefore, according to Alternative Embodiment 7, stress generated at the end of the joint portion between the electrode plate 40 and the conductor layer 20 due to expansion and contraction of the laminate 10 in the stacking direction D can be more efficiently dispersed, and the possibility of the electrode plate 40 peeling off from the conductor layer 20 can be further reduced.

[0094] Alternative Embodiment 8 Fig. 18 is a cross-sectional view showing an example of the configuration of an electrode plate 40 and its surroundings according to alternative embodiment 8. Fig. 18 corresponds to the cross-sectional view taken along line XVII-XVII shown in Fig. 16 .

[0095] As described above, the main body 43 has a first portion 431 that contacts the bonding material 30, and second portions 432 that are located on both sides of the first portion 431 in the width direction (i.e., the direction intersecting the stacking direction D) and that face the conductor layer 20 without contacting the bonding material 30. The second portions 432 are spaced apart from each other by the second gap G. ２The conductive layer 20 faces the conductive layer 20 with the insulating layer 21 therebetween.

[0096] In Alternative Embodiment 8 shown in Fig. 18 , the configuration of the fixing material 60 differs from that of Alternative Embodiment 7 described above. Specifically, in Alternative Embodiment 8, the fixing material 60 has an overhanging portion 62. The overhanging portion 62 is positioned to overhang more inward than the side portion of the second portion 432 and is in contact with the conductor layer 20. Here, "more inward than the side portion of the second portion 432" can also be rephrased as a direction approaching the central axis of the protrusion 44 (electrode plate 40). The overhanging portion 62 is an example of a second overhanging portion.

[0097] In alternative embodiment 8, by providing the fixing material 60 with the protruding portion 62, the adhesive strength between the fixing material 60 and the conductor layer 20 is improved compared to when the protruding portion 62 is not provided, and therefore the adhesive strength between the fixing material 60 and the laminate 10 is improved. Therefore, according to alternative embodiment 8, the possibility that the conductor layer 20 will peel off from the laminate 10 can be reduced.

[0098] Alternative Embodiment 9 Fig. 19 is an enlarged plan view showing an example of the configuration of an electrode plate 40 and its surroundings according to alternative embodiment 9. Fig. 20 is a cross-sectional view taken along line XX-XX shown in Fig. 19 .

[0099] 19 , in Alternative Embodiment 9, a covering layer 50 that covers the main body portion 43 and the conductor layer 20 is located on a side surface 10a (an example of a surface located along the stacking direction D of the laminate 10) of the laminate 10. Although not shown in FIG. 19 , a covering layer 50 that covers the main body portion 43 and the conductor layer 20 is also located on a side surface 10b (an example of a surface located along the stacking direction D of the laminate 10) of the laminate 10. By arranging such covering layers 50 on the side surfaces 10a and 10b, the main body portion 43 and the conductor layer 20 can be protected.

[0100] The covering layer 50 is made of, for example, an insulator, such as a fluorine-based resin, a silicone resin, an epoxy resin, or a nylon resin.

[0101] In the ninth alternative embodiment, as shown in FIGS. 19 and 20, the end of the covering layer 50 covers the end of the fixing material 60 located on the one end 43 a side of the main body 43 .

[0102] As a result, in alternative embodiment 9, stress generated at the end (near one end 43 a) of the joint between the electrode plate 40 and the conductor layer 20 can be released to the interface between the fixing material 60 and the laminate 10 and the interface between the covering layer 50 and the laminate 10 in accordance with expansion and contraction of the laminate 10 in the stacking direction D. Therefore, according to alternative embodiment 9, stress generated at the end of the joint between the electrode plate 40 and the conductor layer 20 due to expansion and contraction of the laminate 10 in the stacking direction D can be more efficiently dispersed, and the possibility of the electrode plate 40 peeling off from the conductor layer 20 can be further reduced.

[0103] Alternative Embodiment 10 Fig. 21 is a cross-sectional view showing an example of the configuration of an electrode plate 40 and its surroundings according to alternative embodiment 10. Fig. 21 corresponds to the cross-sectional view taken along line XXI-XXI in Fig. 19 .

[0104] 21 , the configuration of the coating layer 50 differs from that of the above-described alternative embodiment 9. Specifically, in alternative embodiment 10, the coating layer 50 is located around the entire periphery of the side surfaces, including the side surface 10a, of the laminate 10. That is, the coating layer 50 is located not only on the side surfaces 10a and 10b of the laminate 10, but also on the side surfaces 10c (see FIG. 1 ) and 10d (see FIG. 1 ) located between the side surfaces 10a and 10b.

[0105] As a result, in another embodiment 10, the stress generated in the coating layer 50 can be dispersed over the entire periphery of the side surface of the laminate 10 in accordance with expansion and contraction of the laminate 10 in the stacking direction D.

[0106] 22 is an enlarged plan view showing an example of the configuration of an electrode plate 40 and its surrounding area according to another embodiment 11. As described above, the laminate 10 is composed of an active portion 10A formed by alternately laminating a plurality of piezoelectric bodies 11 and internal electrodes 12, and an inactive portion 10B disposed on both ends of the active portion in the lamination direction D, which has the piezoelectric bodies 11 but does not have the internal electrodes 12.

[0107] 22 , in another embodiment 11, the electrode plate 40 has a wide portion 45 that is wider than the other portions at least in a position of the protruding portion 44 that overlaps with the inactive portion 10B in a plan view. In another embodiment 11, a fixing material 60 may fix the wide portion 45 to the laminate 10.

[0108] As a result, in another embodiment 11, stress generated at the end (near one end 43 a) of the joint between the electrode plate 40 and the conductor layer 20 can be efficiently released at the interface between the fixing material 60 and the laminate 10 in accordance with expansion and contraction of the laminate 10 in the stacking direction D. Therefore, according to another embodiment 11, stress generated at the end of the joint between the electrode plate 40 and the conductor layer 20 due to expansion and contraction of the laminate 10 in the stacking direction D can be more efficiently dispersed, and the possibility of the electrode plate 40 peeling off from the conductor layer 20 can be further reduced.

[0109] Alternative Embodiment 12 Fig. 23 is a cross-sectional view showing an example of the configuration of an electrode plate 40 and its surroundings according to alternative embodiment 12. Fig. 23 corresponds to the cross-sectional view taken along line XXI-XXI in Fig. 19 .

[0110] 23 , the protrusion 44 is inclined so that the distance between the protrusion 44 and the laminate 10 narrows toward the tip 44a of the protrusion 44. In other words, the protrusion 44 is inclined downward toward the tip 44a of the protrusion 44.

[0111] As a result, in another embodiment 12, a portion of the unhardened fixing material 60 is appropriately filled into the gap between the tip 44a of the protrusion 44 and the laminate 10, thereby improving the adhesion strength between the tip 44a of the protrusion 44 and the laminate 10 after the fixing material 60 has hardened.

[0112] 9 and 10, the shape of the through hole H is rectangular in plan view, but it may be rounded near the end in the width direction of the electrode plate 40. In this case, stress is concentrated at the corners during expansion and contraction, which reduces the risk of cracks occurring.

[0113] <Method for Manufacturing Piezoelectric Element> Next, an example of a method for manufacturing the piezoelectric element 1 of this embodiment will be described. First, a ceramic green sheet that will become the piezoelectric layer (piezoelectric element 11) is prepared. Specifically, a calcined powder of piezoelectric ceramic is mixed with a binder containing an organic polymer such as an acrylic or butyral-based polymer, and a plasticizer to prepare a ceramic slurry. Then, a ceramic green sheet is prepared from this ceramic slurry using a tape molding method such as a well-known doctor blade method or calendar roll method. The piezoelectric ceramic may be any material that has piezoelectric properties, and examples thereof include perovskite-type oxides having PbZrO3-PbTiO3. Furthermore, examples of the plasticizer that can be used include dibutyl phthalate (DBP) and dioctyl phthalate (DOP).

[0114] Next, a conductive paste that will become the internal electrodes 12 is prepared. Specifically, the conductive paste is prepared by adding a binder and a plasticizer to a metal powder of a silver-palladium alloy and mixing them. This conductive paste is printed on the ceramic green sheets using a screen printing method. Next, a plurality of ceramic green sheets on which the conductive paste has been printed are stacked together with a plurality of ceramic green sheets on both ends in the stacking direction on which the conductive paste has not been printed, to obtain a laminated compact. This laminated compact is subjected to a binder removal treatment at a predetermined temperature, and then fired at 900 to 1200°C to obtain the laminate 10.

[0115] Thereafter, a conductive paste made of silver and glass is applied to the side surface of the laminate 10 and baked to form the conductor layer 20. The conductive paste is made by adding and mixing a binder, a plasticizer, glass powder, etc. to a metal powder made mainly of silver, and the conductor layer 20 can be formed by printing the conductive paste on the side surface of the laminate 10 by a screen printing method or the like and baking it at 600 to 800°C.

[0116] Next, a bonding material 30 is applied to the upper surface of the conductor layer 20, and an electrode plate 40 is attached thereon. The bonding material 30 is then dried at a temperature of 100 to 140°C, and then hardened at a temperature of 180 to 220°C to fix the electrode plate 40.

[0117] Thereafter, when the coating layer 50 is applied to the laminate 10 by a general application method such as dipping, and then degassed and cured, minute voids of 0.1 μm or less may be dispersed in the coating layer 50, but the voids G will not be formed. Therefore, the voids G can also be formed by using a highly viscous resin as the coating layer 50 and applying it to predetermined positions by screen printing. Note that the voids G can also be formed, for example, by the following method as another method.

[0118] A photosensitive coating layer 50 is applied to the laminate 10. Thereafter, a gap G is provided between the electrode plate 40 and the conductor layer 20, and the coating layer 50 is cured by irradiating it with light before it flows into the gap G. By the above method, the piezoelectric element 1 of this example is produced.

[0119] There is also a method in which the coating layer 50 is applied twice. Specifically, the coating layer 50 is applied before the bonding material 30 and the electrode plate 40 are fixed. Then, plasma etching or blasting is performed on the area where the electrode plate 40 is to be fixed to expose the conductor layer 20, and then the bonding material 30 and the electrode plate 40 are fixed. Furthermore, the coating layer 50 is applied again on the electrode plate 40 to form the gap G.

[0120] 7 and 8 is fixed to the laminate 10, the gap between the protrusions 41 (42) and the conductor layer 20 is reduced, and the coating layer 50 is applied by screen printing. This makes it difficult for the coating layer 50 to flow into the protrusions 41 (42), and by curing the coating layer 50 in this state, voids G are formed. The piezoelectric element 1 of this example is produced by the above method.

[0121] As described above, a piezoelectric element (e.g., piezoelectric element 1) according to an embodiment includes a laminate (e.g., laminate 10), a conductor layer (e.g., conductor layer 20), an electrode plate (e.g., electrode plate 40), and a covering layer (e.g., covering layer 50). The laminate includes a plurality of stacked piezoelectric bodies (e.g., piezoelectric bodies 11) and internal electrodes (e.g., internal electrodes 12). The conductor layers are connected to the internal electrodes and are positioned along the stacking direction (e.g., stacking direction D) of the laminate. The electrode plate is bonded to the conductor layer via a conductive bonding material (e.g., bonding material 30) and is positioned along the stacking direction of the laminate. The covering layer covers the conductor layer and the electrode plate. The electrode plate has a plurality of slits (e.g., slits S) extending in a direction intersecting the stacking direction (e.g., width direction). The piezoelectric element includes a first gap (e.g., gap G) between the electrode plate, the conductor layer, and the bonding material. This reduces the possibility of peeling of the electrode plate covered with the covering layer.

[0122] In addition, the following supplementary notes are disclosed regarding the above-described embodiment.

[0123] (Supplementary Note 1) A piezoelectric element comprising: a laminate formed by laminating a plurality of piezoelectric bodies and internal electrodes; conductor layers connected to the internal electrodes and positioned along the stacking direction of the laminate; an electrode plate joined to the conductor layers via a conductive bonding material and positioned along the stacking direction of the laminate; and a covering layer covering the conductor layers and the electrode plate, wherein the electrode plate has a plurality of slits extending in a direction intersecting the stacking direction, and a first gap is present between the electrode plate, the conductor layer, and the bonding material.

[0124] (Supplementary Note 2) The piezoelectric element according to Supplementary Note 1, wherein the covering layer has a first protruding portion that is positioned to protrude inward beyond an end of the electrode plate in a direction intersecting the stacking direction and that contacts the conductor layer.

[0125] (Supplementary Note 3) The piezoelectric element according to Supplementary Note 1 or 2, wherein the electrode plate has a first convex portion that protrudes in a thickness direction of the electrode plate on a peripheral edge of an end of the electrode plate in a direction intersecting the stacking direction.

[0126] (Supplementary Note 4) The piezoelectric element according to Supplementary Note 3, wherein the first protrusion extends along the stacking direction of the stack.

[0127] (Appendix 5) The piezoelectric element according to any one of Appendices 1 to 4, wherein the covering layer has a second protruding portion that is positioned protruding inward from an inner wall surface of the slit in the electrode plate and that is in contact with the conductor layer.

[0128] (Supplementary Note 6) The piezoelectric element according to any one of Supplementary Notes 1 to 5, wherein the electrode plate has a second convex portion that protrudes in a thickness direction of the electrode plate on a periphery of the slit.

[0129] (Supplementary Note 7) The piezoelectric element according to Supplementary Note 6, wherein the second convex portion extends along the longitudinal direction of the slit.

[0130] (Appendix 8) A piezoelectric element according to any one of Appendices 1 to 7, wherein a gap between one end of the electrode plate located outside the bonding material in a planar view in the width direction and the conductor layer and a gap between the other end of the electrode plate and the conductor layer are separated.

[0131] (Supplementary Note 9) The piezoelectric element according to any one of Supplementary Notes 1 to 8, wherein the electrode plate has a through hole located between the adjacent slits.

[0132] Further advantages and other embodiments may readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

[0133] REFERENCE SIGNS LIST 1 Piezoelectric element 10 Laminated body 10a to 10d Side surface 10e Base end portion 10f Tip portion 11 Piezoelectric body 12 Internal electrode 12a First electrode 12b Second electrode 13 Planned fracture layer 20, 20A, 20B Conductor layer 30 Bonding material 40, 40A, 40B Electrode plate 41, 42 Convex portion 50 Covering layer 51, 52 Protruding portion D Lamination direction G Gap H Through hole S Slit

Claims

1. a laminate in which a plurality of piezoelectric bodies and internal electrodes are laminated; a conductor layer connected to the internal electrode and positioned along a lamination direction of the laminate; an electrode plate joined to the conductor layer via a conductive bonding material and positioned along the stacking direction of the laminate; a covering layer that covers the conductor layer and the electrode plate; Equipped with The electrode plate has a plurality of slits extending in a direction intersecting the stacking direction, A piezoelectric element having a first gap between the electrode plate, the conductor layer, and the bonding material.

2. The piezoelectric element according to claim 1 , wherein the covering layer has a first protruding portion that is positioned to protrude inward beyond an end of the electrode plate in a direction intersecting with the stacking direction and that is in contact with the conductor layer.

3. The piezoelectric element according to claim 1 , wherein the electrode plate has a first protrusion that protrudes in a thickness direction of the electrode plate on a peripheral edge of an end of the electrode plate in a direction intersecting with the stacking direction.

4. The piezoelectric element according to claim 3 , wherein the first protrusion extends along a stacking direction of the laminate.

5. The piezoelectric element according to claim 1 , wherein the covering layer has a second protruding portion that is positioned to protrude inward from an inner wall surface of the slit in the electrode plate and that is in contact with the conductor layer.

6. The piezoelectric element according to claim 1 , wherein the electrode plate has a second protrusion on a periphery of the slit, the second protrusion protruding in a thickness direction of the electrode plate.

7. The piezoelectric element according to claim 6 , wherein the second convex portion extends along a longitudinal direction of the slit.

8. 2. The piezoelectric element according to claim 1, wherein a gap between one end of the electrode plate located outside the bonding material in a planar view in the width direction and the conductor layer and a gap between the other end of the electrode plate and the conductor layer are separated.

9. 9. The piezoelectric element according to claim 1, wherein the electrode plate has through holes positioned between adjacent ones of the slits.