Laminated piezoelectric element

Abstract

The present application provides a laminated piezoelectric element having excellent suppression effect of characteristic deterioration caused by thermoelectric effect. Inside an element body (10), a first internal electrode (3), a piezoelectric layer (2), and a second internal electrode (4) having polarity different from the first internal electrode (3) are repeatedly laminated in the lamination direction. A first external electrode (5) is formed on a first side surface (10a) of the element body (10). In addition, a second external electrode (6) is formed on a second side surface (10b) of the element body (10). A resistance layer (20) connected to the internal electrodes (3, 4) is formed on at least a part of a third side surface (10c) of the element body (10) exposed by the internal electrodes (3, 4), and an insulating layer (30) is formed on the third side surface (10c) of the element body (10) in a manner to cover the resistance layer (20).

Description

Technical Field

[0001] This invention relates to stacked piezoelectric elements. Background Technology

[0002] Piezoelectric elements are components that utilize the piezoelectric effect and the inverse piezoelectric effect to convert mechanical displacement and electrical displacement into each other. Piezoelectric elements are used in various products, for example, as actuators for applications requiring precise and accurate control. Specifically, examples include applications for lens driving, HDD head driving, inkjet printer head driving, and fuel injection valve driving.

[0003] Furthermore, in order to increase the obtained displacement, when a piezoelectric element is constructed as a stacked type, the ends of the internal electrodes holding the piezoelectric layers sometimes protrude from the surface of the element body. In this case, moisture from the air or other sources may migrate between the internal electrodes with different polarities.

[0004] Furthermore, when such piezoelectric elements are used in applications such as portable electronic devices, they are exposed to temperature changes due to variations in the surrounding environment.

[0005] When exposed to such temperature changes, the polarization caused by the thermoelectric effect becomes problematic. Especially during temperature decreases, the piezoelectric element develops polarization in the opposite direction to the polarization due to the thermoelectric effect, resulting in a decrease in polarizability. This decreased polarizability does not recover even if the temperature rises again. Therefore, the following problem exists: when the temperature decrease process is repeated, the polarizability gradually decreases, the desired displacement is not achieved, and the characteristics deteriorate.

[0006] To address this problem, Patent Document 1 describes a piezoelectric element in which an internal electrode exposed on the side is covered by an anti-migration outer packaging material in a stacked piezoelectric body, thereby dispersing conductive particles in the outer packaging material.

[0007] Furthermore, Patent Document 1 describes a piezoelectric element in which migration is prevented by an anti-migration outer packaging material, and the reduction in polarization caused by the thermoelectric effect is suppressed.

[0008] However, in order to set the resistance value of the outer packaging material to a range that prevents migration and suppresses the decrease in polarization, there are problems such as the need to consider the variation in the resistance value of the resin constituting the outer packaging material and the content of conductive particles, and the difficulty in adjusting the resistance value.

[0009] To address this problem, the applicant developed the stacked piezoelectric element shown in Patent Document 2. However, it was found in the stacked piezoelectric element shown in Patent Document 2 that, without any treatment, the resistance value of the resistive layer may change due to exposure to external gas. Furthermore, it was also found in the stacked piezoelectric element shown in Patent Document 2 that the resistive layer connecting a pair of external electrodes tends to thin at the corners of the element body, resulting in a higher resistance value. This presents the following technical problem: when the resistance of the resistive layer is locally too high, it is difficult to adequately suppress the deterioration of polarization caused by the thermoelectric effect.

[0010] Existing technical documents

[0011] Patent documents

[0012] Patent Document 1: Japanese Patent No. 5040649

[0013] Patent Document 2: Japanese Patent No. 5842635 Summary of the Invention

[0014] The problem that the invention aims to solve

[0015] This invention was developed in view of this actual situation, and its purpose is to provide a stacked piezoelectric element with excellent suppression effect on the characteristic degradation caused by thermoelectric effect.

[0016] Technical means to solve the problem

[0017] To achieve the above objectives, the stacked piezoelectric element of the present invention has the following characteristics:

[0018] The main body of the component has a first internal electrode, a piezoelectric layer, and a second internal electrode with a polarity different from that of the first internal electrode stacked along the stacking direction;

[0019] A first external electrode is electrically connected to the first internal electrode and is formed on a first side of the component body;

[0020] The second external electrode is electrically connected to the second internal electrode and is formed on the second side of the component body;

[0021] A resistive layer is formed on at least a portion of the third side of the component body exposed by the first internal electrode and the second internal electrode to connect the first internal electrode and the second internal electrode.

[0022] An insulating layer is formed on the third side to cover the resistive layer.

[0023] In the stacked piezoelectric element of the present invention, a first internal electrode and a second internal electrode with different polarities exposed on the third side of the element body are connected by a resistive layer. The resistive layer has a higher resistivity than the internal electrodes and a lower resistivity than the insulating layer. Therefore, even if the temperature environment of the stacked piezoelectric element changes, resulting in polarization in the opposite direction to the polarization direction, the generated charge can be reliably discharged through the resistive layer. As a result, the stacked piezoelectric element according to the present invention can suppress the decrease in polarization even when placed in an environment that causes temperature changes.

[0024] Furthermore, in the stacked piezoelectric element of the present invention, the resistive layer is covered by an insulating layer. Therefore, the resistive layer is not exposed to the external gas, and its resistivity is not easily affected. Consequently, the stacked piezoelectric element of the present invention exhibits excellent performance in suppressing characteristic degradation caused by thermoelectric effects. In addition, migration is prevented by the insulating layer, and the reduction in polarization is suppressed by the resistive layer, thereby obtaining a highly reliable stacked piezoelectric element.

[0025] A resistive layer may be formed on the third side of the component body, covering its entire surface. Alternatively, the resistive layer may not be formed on the third side of the component body, leaving the exposed, uncovered portions of the resistive element of the first or second internal electrode. In this case, the insulating layer covers the resistive layer and also covers the uncovered portions of the resistive element. In either case, the first and second internal electrodes with different polarities exposed on the third side of the component body are completely covered by the resistive layer, or completely covered by the insulating layer along with the resistive layer. Therefore, it is possible to prevent moisture from penetrating from the outside and reliably prevent migration between the internal electrodes with different polarities.

[0026] Furthermore, when the third side of the component body has an uncovered portion of the resistive element, the resistive layer does not cover the entire surface of the third side. Therefore, the load on the piezoelectric element is less, allowing the piezoelectric characteristics to be fully utilized. Additionally, having an uncovered portion of the resistive element on the third side of the component body reduces the coverage area of ​​the resistive layer, which also helps to lower costs.

[0027] The resistive layer may also have a longitudinally continuous portion formed along the stacking direction on the third side surface of the element body. Preferably, the longitudinally continuous portion is located near the center in the width direction of the third side surface. With this configuration, it is not necessary for the resistive layer to pass through the corners of the element body, and the thickness of the resistive layer can be easily and uniformly formed. As a result, the resistance value of the resistive layer is easily stabilized, and the reduction in polarization caused by thermoelectric effects can be effectively prevented. In addition, since the resistive layer does not cover the entire surface of the third side surface of the element body, the load relative to the piezoelectric element is small, and the piezoelectric characteristics can be fully utilized.

[0028] The resistive layer may also have island-shaped portions that are intermittently formed on the third side of the element body along the stacking direction. By intermittently forming the resistive layer, the load on the piezoelectric element is less, and the piezoelectric characteristics can be fully utilized.

[0029] The resistive layer may also have an extended portion covering the surface of the first or second external electrode. In the stacked piezoelectric element of the present invention, the resistive layer connects the internal electrodes to each other; therefore, it is not necessary to connect the external electrodes to each other. However, an extended portion covering the surface of the first or second external electrode may be formed when the resistive layer is formed. Thin portions of the resistive layer may occur at the corners of the element body, but since it is not necessary to connect the external electrodes to each other, the possibility of a reduction in the function of the resistive layer is small.

[0030] The insulating layer can also be formed on the component body in a manner that also covers the extended portion. In this case, the extended portion of the resistive layer can also be protected.

[0031] Alternatively, a first lead can be connected to the first external electrode.

[0032] Alternatively, a second lead can be connected to the second external electrode.

[0033] Preferably, these first and second leads are led out in a direction away from the third side.

[0034] By leading these leads away from the third side, the likelihood of the leads coming into contact with the resistive layer is reduced, thus decreasing the possibility of short-circuit defects. Attached Figure Description

[0035] Figure 1 This is a schematic perspective view showing a stacked piezoelectric element according to one embodiment of the present invention.

[0036] Figure 2A It is along Figure 1 The cross-sectional view of the main part of the stacked piezoelectric element shown in the II-II line.

[0037] Figure 2B yes Figure 2A Cross-sectional view of the main part of a modified layered piezoelectric element.

[0038] Figure 3 It is along Figure 1 The cross-sectional view of the main part of the stacked piezoelectric element shown in line III-III.

[0039] Figure 4 This is a schematic perspective view showing a stacked piezoelectric element according to another embodiment of the present invention.

[0040] Figure 5It is along Figure 4 The diagram shows a cross-sectional view of the main part of the stacked piezoelectric element with IV-IV lines.

[0041] Figure 6 This is a schematic perspective view of a stacked piezoelectric element according to another embodiment of the present invention.

[0042] Figure 7 It is along Figure 6 The main cross-sectional view of the stacked piezoelectric element shown in the VII-VII line.

[0043] Figure 8 This is a schematic perspective view of a stacked piezoelectric element according to another embodiment of the present invention.

[0044] Figure 9 It is along Figure 8 The cross-sectional view of the main part of the stacked piezoelectric element with the IX-IX line is shown.

[0045] Figure 10 This is a schematic perspective view of a stacked piezoelectric element according to another embodiment of the present invention.

[0046] Figure 11 It is along Figure 10 The cross-sectional view of the main part of the XI-XI line stacked piezoelectric element is shown.

[0047] Figure 12 This is a schematic perspective view of a stacked piezoelectric element according to another embodiment of the present invention.

[0048] Figure 13 It is along Figure 12 The cross-sectional view of the main part of the stacked piezoelectric element shown in the XIII-XIII line. Detailed Implementation

[0049] The present invention will now be described based on the embodiments shown in the accompanying drawings.

[0050] First Implementation Method

[0051] like Figure 1 As shown, the stacked piezoelectric element 1 of this embodiment has a prism-shaped element body 10. Inside the element body 10, a first internal electrode 3, a piezoelectric layer 2, and a second internal electrode 4 with a polarity different from that of the first internal electrode 3 are repeatedly stacked along the Z-axis direction (stack direction). Furthermore, in the figures, the X-axis, Y-axis, and Z-axis are orthogonal to each other, and the Z-axis is aligned with the stacking direction.

[0052] like Figure 2AAs shown, on the first side 10a of the component body 10, the front end of the first internal electrode 3 in the X-axis direction is exposed, and a first external electrode 5 is formed in such a way as to be electrically connected to these first internal electrodes 3. In addition, on the second side 10b of the component body 10, the front end of the second internal electrode 4 in the X-axis direction is exposed, and a second external electrode 6 is formed in such a way as to be electrically connected to these second internal electrodes 4.

[0053] The rear end of the first internal electrode 3 in the X-axis direction is not exposed on the second side 10b of the component body 10 and is electrically insulated from the second external electrode 6. Similarly, the rear end of the second internal electrode 4 in the X-axis direction is not exposed on the first side 10a of the component body 10 and is electrically insulated from the first external electrode 5.

[0054] like Figure 3 As shown, the portion of the piezoelectric layer 2 that repeats when viewed from the Z-axis direction (which is the stacking direction) with the first internal electrode 3 and the second internal electrode 4 is the portion that produces mechanical displacement when a voltage is applied to the external electrodes 5 and 6 of the piezoelectric element 1 (piezoelectric active portion). The remaining portion is the portion that does not produce mechanical displacement even when a voltage is applied to the external electrodes 5 and 6 of the piezoelectric element 1 (piezoelectric inactive portion). Furthermore, the outer region 2a of the piezoelectric layer 2 that is not held by the first internal electrode 3 and the second internal electrode 4 and corresponds to the two ends of the element body 10 in the Z-axis direction is also called the piezoelectric inactive portion. The piezoelectric active portion corresponds to the portion of the piezoelectric layer 2 held by the first internal electrode 3 and the second internal electrode 4.

[0055] The material of the piezoelectric layer 2 is not particularly limited as long as it exhibits a piezoelectric effect or an inverse piezoelectric effect. Examples include PbZrxTi1-xO3, BaTiO3, PbTiO3, KNbO3, LiNbO3, LiTaO3, NaWO3, BiFeO3, and (KxNa1-x)NbO3. Additionally, it may contain components to improve properties, the content of which can be appropriately determined according to the desired characteristics. The thickness of each piezoelectric layer 2 is not particularly limited, but in this embodiment, it is preferably around 5 to 50 μm.

[0056] Furthermore, there are no particular limitations on the conductive materials constituting each internal electrode layer 3 and 4. For example, they can be composed of noble metals such as Ag, Pd, Au, and Pt, and their alloys (Ag-Pd, etc.), or base metals such as Cu and Ni, and their alloys. The thickness of each internal electrode layer 3 and 4 is preferably 1 to 5 μm.

[0057] The material of the external electrodes 5 and 6 is not particularly limited, and the same conductive material as that constituting the internal electrodes can be used. In addition, a plating or sputtering layer of the aforementioned metals can be further formed on the outer side.

[0058] like Figure 1 and Figure 2A As shown, on the third side 10c of the component body 10, one end of the internal electrodes 3 and 4 in the Y-axis direction is exposed, and these exposed ends of the internal electrodes 3 and 4 in the Y-axis direction are covered by the resistive layer 20. That is, the internal electrode layers 3 and 4 are interconnected on the third side 10c of the component body 10 via the resistive layer 20.

[0059] The resistive layer 20 has a longitudinally continuous portion 22 formed along the Z-axis direction on the third side surface 10c of the element body 10, and an extended portion 24 covering one end surface of the first external electrode 5 and the second external electrode 6 in the Y-axis direction. In this embodiment, the longitudinally continuous portion 22 of the resistive layer 20 covers the entire surface of the third side surface 10c of the element body 10.

[0060] Furthermore, the extension 24 is continuously formed with the longitudinal continuous portion 22, continuously covering the corners of the first side surface 10a and the third side surface 10c of the component body 10, and the corners of the second side surface 10b and the third side surface 10c of the component body 10 in the Z-axis direction. Additionally, as... Figure 2B As shown, the resistive layer 20 can be composed solely of the longitudinally continuous portion 22. Figure 2A At least one of the pair of extended portions 24 shown may not be formed in the resistive layer 20.

[0061] in addition, Figure 1 In this process, the extension portion 24 is not formed at both ends of the resistor layer 20 in the Z-axis direction, but the extension portion 24 may be formed at at least one end of the resistor layer 20 in the Z-axis direction.

[0062] In this embodiment, an insulating layer 30 is formed to cover the entire surface of the resistive layer 20. Specifically, the insulating layer 30 is formed to extend from the third side 10c of the element body 10 to a portion of the first side 10a and from the third side 10c to a portion of the second side 10b, such that it covers not only the longitudinally continuous portion 22 of the resistive layer 20 but also the extended portion 24. Furthermore, Figure 1 It can also be seen that the two ends of the resistor layer 20 in the Z-axis direction are not covered by the insulating layer 30, but preferably the two ends of the resistor layer 20 in the Z-axis direction are also covered by the insulating layer 30.

[0063] In this embodiment, by forming a resistive layer 20, as shown below, it is possible to discharge the charge generated in polarization in the opposite direction to the polarization due to the thermoelectric effect.

[0064] Typically, during its manufacturing process, the piezoelectric element 1 is polarized by extending and contracting under applied voltage, and the direction of polarization is determined. When this piezoelectric element 1 is placed in an environment with varying temperatures, especially at decreasing temperatures, polarization occurs in the opposite direction to the polarization due to the thermoelectric effect. The charge generated by this polarization acts to counteract the charge generated in the polarization, thus reducing the degree of polarization.

[0065] To suppress this decrease in polarization, in this embodiment, by forming the resistive layer 20 primarily on the third side surface 10c, the first internal electrode 3 and the second internal electrode 4 exposed on the third side surface 10c can be connected through the resistive layer 20. As a result, the charge generated due to the thermoelectric effect can be discharged.

[0066] The material of the resistive layer 20 is not particularly limited as long as it is a material with a resistivity higher than that of the inner electrode layers 3 and 4, a resistivity lower than that of the insulating layer, and capable of discharging charges generated due to the thermoelectric effect. Specific materials for the resistive layer 20 include: resins with a specified resistivity, insulating resins containing conductive particles such as carbon, and metal oxides. Alternatively, the resistive layer 20 can be formed by winding a thin film with a specified resistivity onto the side of the component body. The resistive layer 20 can also be formed by sputtering a film or the like. Furthermore, the insulating resin or the like used in the insulating layer 30 can be made to contain conductive particles to reduce the resistivity, thus forming the resistive layer 20.

[0067] The resistive layer 20 is preferably composed of a phenolic resin in which conductive particles such as carbon particles are dispersed. Compared with epoxy resin, phenolic resin is preferred from the perspective of being halogen-free and inexpensive, but epoxy resin can also be used.

[0068] The resistivity of the resistive layer 20 can be appropriately determined based on the characteristics of the piezoelectric element, but in this embodiment, it is preferably around 10³ to 10⁶ Ωm. The resistance of the resistive layer 20 can be adjusted by changing the type of material or combining multiple materials, or by changing the shape and thickness of the resistive layer 20. Therefore, in this embodiment, the resistance of the resistive layer can be easily adjusted according to the desired value. In this embodiment, the thickness of the resistive layer 20 is not particularly limited, but is preferably 5 to 20 μm.

[0069] Furthermore, the resistive layer 20 directly covers and connects the Y-axis ends of the internal electrodes 3 and 4 on the third side 10c. However, the resistive layer 20 has a sufficiently high resistance to the internal electrodes 3 and 4, thus preventing short circuits between the internal electrodes 3 and 4 with different polarities. Preferably, the resistivity of the resistive layer 20 is at least 10² Ωm higher than that of the internal electrodes 3 and 4, and at least 10² Ωm lower than that of the insulating layer 30.

[0070] In this embodiment, such as Figure 1 and Figure 2A As shown, on the fourth side 10d, opposite to the third side 10c of the component body 10 along the Y-axis, the other ends of the internal electrodes 3 and 4 in the Y-axis direction are exposed. On the fourth side 10d of the component body 10, the exposed ends of the internal electrodes 3 and 4 in the Y-axis direction are covered by an insulating layer 40. The insulating layer 40 prevents migration.

[0071] The smaller the distance between the internal electrodes 3 and 4 with different polarities, the easier it is for migration to occur. Therefore, by covering the fourth side 10d with the insulating layer 40 to prevent moisture from seeping into the exposed part of the internal electrode, migration can be prevented.

[0072] In this embodiment, the insulating layer 40 preferably covers all portions of the first internal electrode 3 and the second internal electrode 4 exposed on the surface of the fourth side surface 10d of the component body 10. This provides more reliable protection against migration. Alternatively, the insulating layer 40 may cover the entire fourth side surface, including the exposed portions of the internal electrodes. Multiple insulating layers 40 may also be provided. The thickness of the insulating layer 40 is not particularly limited, for example, it is about 1 to 20 μm.

[0073] The material of the insulating layer 40 is not particularly limited as long as it is a material with high insulation properties, prevents moisture ingress, and prevents migration between the internal electrodes 3 and 4. Specific materials include resin and glass, but epoxy resin, melamine resin, and DLC (diamond-like carbon) are preferred. Furthermore, the resistivity of the insulating layer 40 is not particularly limited if insulation can be ensured, but in this embodiment, it is preferably 10⁹ Ωm or higher.

[0074] The insulating layer 30, located on the opposite side of the insulating layer 40 in the Y-axis direction, is preferably made of the insulating material constituting the insulating layer 40, but it does not necessarily have to be the same material. In addition, the thickness of the insulating layer 30 is the same as that of the insulating layer 40, but it may be thicker or thinner than the insulating layer 40.

[0075] In addition, such as Figure 1 As shown, a first lead 50 is connected to the upper part of the first external electrode 5 in the Z-axis direction. Additionally, a second lead 52 is connected to the upper part of the second external electrode 6 in the Z-axis direction. These first leads 50 and second leads 52 extend in a direction away from the third side surface 10c (towards the fourth side surface 10d). The insulating layer 40 formed on the fourth side surface 10d preferably does not have an extension covering a portion of the first external electrode 5 and the second external electrode 6. This improves the reliability of the connections of leads 50 and 52 to the external electrodes 5 and 6.

[0076] Next, an example of a method for manufacturing the laminated piezoelectric element 1 according to this embodiment will be described. There are no particular limitations on the method for manufacturing the laminated piezoelectric element 1, but in the following description, the sheet method will be used as an example.

[0077] First, prepare a green sheet with an internal electrode paste film having a predetermined pattern that will become the first internal electrode 3 and the second internal electrode 4 after firing, and a green sheet without an internal electrode paste film.

[0078] The green sheet comprises the material constituting the piezoelectric layer 2 described above. Furthermore, this material may contain unavoidable impurities. Then, using this material, the green sheet is manufactured using known techniques. Specifically, for example, first, the raw materials constituting the piezoelectric layer are uniformly mixed by means of wet mixing, etc., and then dried. Next, pre-firing is performed under appropriately selected firing conditions, and the pre-fired powder is wet-milled. Then, a binder is added to the milled pre-fired powder to form a slurry. Next, the slurry is sheeted using methods such as doctor blade printing or screen printing, and then dried to obtain the green sheet.

[0079] Next, the internal electrode paste containing the aforementioned conductive material is applied onto the green sheet using a printing method or similar means, thereby obtaining a green sheet with an internal electrode paste film forming a predetermined pattern.

[0080] Next, these green sheets are overlapped, pressure is applied to press them together, and after necessary processes such as drying, they are cut to obtain an assembly of green components.

[0081] Next, the assembly is sintered under specified conditions to obtain a sintered body, which is then cut into short pieces using a cutting saw or similar tool. These short sintered pieces are then used as electrodes for the first external electrode 5 and the second external electrode 6. A DC voltage is applied to these electrodes to polarize the piezoelectric material. The polarized short sintered pieces are then cut into individual component bodies 10, resulting in component bodies 10 with the internal electrodes 3 or 4 exposed on their sides. In this embodiment, the obtained component bodies 10 are tumble-ground, and the corners and edges of the component bodies 10 are machined with an R-surface.

[0082] Next, a resistive layer 20 is formed on the third side surface 10c of the component body 10. At this time, the corners and edges of the component body 10 are rounded, so when, for example, the amount of insulating resin containing conductive particles is increased and applied to the third side surface 10c of the component body 10, a portion of the resin becomes the resistive layer 20 and droops down. Therefore, a resistive layer 20 having an extension 24 covering a portion of the first external electrode 5 and the second external electrode 6 is formed on the third side surface 10c. As a result, the resistive layer 20 connects the exposed ends of the internal electrodes 3 and 4 exposed on the third side surface 10c to each other.

[0083] Then, an insulating layer 30 is formed on the third side surface 10c of the component body 10 in such a way that it covers the entire surface of the resistive layer 20, including the extension 24. The insulating layer 30 may also have an extension covering a portion of the surface of the first external electrode 5 and the second external electrode 6 located on the side near the third side surface 10c. Alternatively, the insulating layer 30 may also have an extension covering a portion of the upper and lower surfaces in the Z-axis direction of the component body 10 located on the side near the third side surface 10c. As for the method for forming the insulating layer 30, there is no particular limitation; for example, a method of coating with an insulating resin is exemplified.

[0084] Alternatively, an insulating layer 40 may be formed simultaneously with or before / after the fourth side surface 10d of the component body 10. The insulating layer 40 can be formed in the same manner as the insulating layer 30, or it can be formed using different methods. Then, or before / after, the first lead 50 and the second lead 52 are connected to the respective external electrodes 5 and 6. The connection of each lead 50 and 52 to the respective external electrodes 5 and 6 is performed by, for example, soldering, thermoforming, laser welding, resistance welding, etc., and the connection position is not particularly limited, but the lead-out direction is preferably away from the third side surface 10c. Through the above processes, a... Figure 1 The stacked piezoelectric element 1 is shown.

[0085] In the stacked piezoelectric element 1 of this embodiment, a first internal electrode 3 and a second internal electrode 4 with different polarities exposed on the third side 10c of the element body 10 are connected by a resistive layer 20. The resistance value of the resistive layer 20 is higher than that of the internal electrodes 3 and 4, and lower than that of the insulating layer 30. Therefore, even if the temperature environment of the stacked piezoelectric element 1 changes and polarization occurs in the opposite direction to the polarization direction, the generated charge can be reliably discharged through the resistive layer 20. As a result, the stacked piezoelectric element 1 of this embodiment can suppress the decrease in polarization even when placed in an environment that causes temperature changes.

[0086] Furthermore, in the stacked piezoelectric element 1 of this embodiment, the resistive layer 20 is covered by the insulating layer 30. Therefore, the resistive layer 20 is not exposed to external gas, and its resistance value is not easily affected. Thus, the stacked piezoelectric element 1 of this embodiment exhibits excellent suppression of characteristic degradation caused by the thermoelectric effect. In addition, by preventing migration through the insulating layers 30 and 40 and suppressing the decrease in polarization through the resistive layer 20, a highly reliable stacked piezoelectric element 1 can be obtained.

[0087] Furthermore, in this embodiment, the resistive layer 20 has an extension 24 covering the surface of the first external electrode 5 or the second external electrode 6. In the stacked piezoelectric element 1 of this embodiment, the resistive layer 20 connects the internal electrodes 3 and 4 to each other; therefore, it is not necessary to connect the external electrodes 5 and 6 to each other. However, the extension 24 covering the surface of the first external electrode 5 or the second external electrode 6 can be formed when the resistive layer 20 is formed. Thin portions of the resistive layer 20 may occur at the corners or edges of the element body 10, but since it is not necessary to connect the external electrodes 5 and 6 to each other, the possibility of a reduction in the function of the resistive layer 20 is small.

[0088] In addition, in this embodiment, the insulating layer 30 is formed on the component body 10 such that it also covers the extended portion 24 of the resistive layer 20, thus effectively protecting the extended portion 24 of the resistive layer 20.

[0089] In addition, in this embodiment, by leading the first lead 50 and the second lead 52 outward from the third side 10c, the possibility of the leads 50 and 52 coming into contact with the resistive layer 20 is reduced, thereby reducing the possibility of short-circuit defects.

[0090] Second Implementation Method

[0091] like Figure 4 and Figure 5 As shown, except as described below, the stacked piezoelectric element 1a of this embodiment is the same as the stacked piezoelectric element 1 of the first embodiment described above, with common components marked with common symbols and descriptions of common parts omitted.

[0092] In this embodiment, unlike the first embodiment, the resistive layer is not formed to cover the entire surface of the third side 10c of the element body 10, but rather a resistive layer 20a is formed that only covers the two sides of the third side 10c in the X-axis direction. In this embodiment, the resistive layer 20a formed on the third side 10c has a pair of longitudinally continuous portions 22a, 22a, and an extension portion 24a, 24a is integrally formed on each of the longitudinally continuous portions 22a, 22a.

[0093] A longitudinal continuous portion 22a extends along the Z-axis in a stripe-like pattern, connecting the front end of the first internal electrode 3 exposed in the X-axis direction and the rear end of the second internal electrode 4 exposed in the X-axis direction near the corner of the third side surface 10c and the first side surface 10a. Another longitudinal continuous portion 22a extends along the Z-axis in a stripe-like pattern, connecting the rear end of the first internal electrode 3 exposed in the X-axis direction and the front end of the second internal electrode 4 exposed in the X-axis direction near the corner of the third side surface 10c and the second side surface 10b. These longitudinal continuous portions 22a, 22a are continuous along the entire length of the third side surface 10c in the Z-axis direction and cover both sides of the third side surface 10c in the X-axis direction.

[0094] In this embodiment, a non-covered resistive element portion 23a, not covered by the resistive layer 20a, is formed on the third side surface 10c. The non-covered resistive element portion 23a is formed continuously along the Z-axis at approximately the center of the third side surface 10c in the X-axis direction between a pair of longitudinally continuous portions 22a, 22a. The width of each longitudinally continuous portion 22a, 22a in the X-axis direction is preferably such that the exposed ends of the first internal electrode 3 and the second internal electrode 4 exposed on the third side surface 10c can be reliably connected via the resistive layer 20a. Specifically, the width of each longitudinally continuous portion 22a, 22a in the X-axis direction is preferably determined to be within the range of 1 / 6 to 1 / 2 of the width of the element body 10 in the X-axis direction.

[0095] The other structures (material and thickness, etc.) of the resistive layer 20a are the same as those of the resistive layer 20 in the first embodiment. The structure of the extension portion 24a, which is continuously formed with each longitudinal continuous portion 22a constituting the resistive layer 20, is the same as that of the extension portion 24 in the first embodiment.

[0096] In this embodiment, the insulating layer 30a completely covers the resistive layer 20a, and also covers the uncovered portion 23a of the resistive element remaining on the third side 10c of the component body 10. That is, in this embodiment, a portion of the first internal electrode 3 and the second internal electrode 4 with different polarities exposed on the third side 10c of the component body 10 are covered by the resistive layer 20a, and the other portion is completely covered by the insulating layer 30a.

[0097] Therefore, it is possible to prevent moisture from seeping in from the outside of the element 1a and reliably prevent migration between the internal electrodes 3 and 4 with different polarities. Furthermore, the area of ​​direct contact between the insulating layer 30a and the ceramic surface of the element body 10 is increased, thus improving the connection reliability of the insulating layer 30a with respect to the element body 10. Simultaneously, the connection reliability of the resistive layer 20a with respect to the element body 10 is also improved. Moreover, the other structures of the insulating layer 30a in this embodiment are the same as those of the insulating layer 30 in the first embodiment described above.

[0098] Furthermore, in this embodiment, the third side surface 10c of the component body 10 has a resistive uncovered portion 23a. Therefore, the resistive layer 20a does not cover the entire surface of the third side surface 10c, resulting in a smaller load relative to the piezoelectric element 1a and allowing for full utilization of the piezoelectric characteristics. Additionally, the presence of the resistive uncovered portion 23a on the third side surface 10c of the component body 10 reduces the coverage area of ​​the resistive layer 20a, thus contributing to cost reduction.

[0099] Third Implementation Method

[0100] like Figure 6 and Figure 7 As shown, except as shown below, the stacked piezoelectric element 1b of this embodiment is the same as the stacked piezoelectric element 1a of the second embodiment described above, with common components marked with common symbols and descriptions of common parts omitted.

[0101] In this embodiment, the resistive layer 20b is composed of at least one pair of longitudinally continuous portions 22b and at least one transversely continuous portion 26b. An extension portion 24b may also be formed in each of the longitudinally continuous portions 22b.

[0102] In this embodiment, unlike the second embodiment, the striped longitudinal continuous portions 22b formed on both sides of the third side surface 10c of the component body 10 in the X-axis direction are integrally connected by at least one transverse continuous portion 26b. In this embodiment, the pair of longitudinal continuous portions 22b are connected at both ends in the Z-axis direction by transverse continuous portions 26b. The single opening of the resistive layer 20b surrounded by these pair of longitudinal continuous portions 22b and pair of transverse continuous portions 26b forms a non-covered portion 23b of the resistive body on the third side surface 10c.

[0103] also, Figure 6 In the middle, a single uncovered portion 23b of the resistive element is formed on the third side 10c, but by forming three or more transverse continuous portions 26b on the third side 10c, multiple uncovered portions of the resistive element 23b can also be formed.

[0104] In this embodiment, the insulating layer 30b completely covers the resistive layer 20b and also covers the uncovered portion 23b of the resistive element remaining on the third side 10c of the component body 10. That is, in this embodiment, a portion of the first internal electrode 3 and the second internal electrode 4 with different polarities exposed on the third side 10c of the component body 10 are covered by the resistive layer 20b, while the other portion is completely covered by the insulating layer 30b.

[0105] Therefore, it is possible to prevent moisture from seeping in from the outside of the element 1b and reliably prevent migration between the internal electrodes 3 and 4 with different polarities. Furthermore, the area of ​​direct contact between the insulating layer 30a and the ceramic surface of the element body 10 is increased, thus improving the connection reliability of the insulating layer 30a with respect to the element body 10. Simultaneously, the connection reliability of the resistive layer 20a with respect to the element body 10 is also improved.

[0106] The resistive layer 20b and insulating layer 30b in this embodiment correspond to the resistive layer 20a and insulating layer 30a in the second embodiment, and the description of the common parts is omitted.

[0107] Fourth Implementation Method

[0108] like Figure 8 and Figure 9 As shown, except as shown below, the stacked piezoelectric element 1c of this embodiment is the same as the stacked piezoelectric elements 1, 1a, and 1b of the first to third embodiments described above, with common components marked with common symbols and descriptions of common parts omitted.

[0109] In this embodiment, the resistive layer 20c is composed of a plurality of island-shaped portions 27c that are intermittently formed along the Z-axis direction on the third side surface 10c of the component body 10. Each island-shaped portion 27c connects the first internal electrode 3 and the second internal electrode 4 via the resistive layer 20c near the front end of the first internal electrode 3 or near the front end of the second internal electrode 4 exposed on the third side surface 10c.

[0110] In this embodiment, it is preferable that the extended portions 24, 24a, and 24b of the above-described embodiment are not formed in the resistive layer 20c, but the extended portions 24, 24a, and 24b of the above-described embodiment may also be formed. In this embodiment, the plurality of island-shaped portions 27c constituting the resistive layer 20c are formed in two columns (or one or more columns) in the X-axis direction and intermittently in the Z-axis direction, but they may also be formed continuously in the Z-axis direction.

[0111] In this embodiment, the insulating layer 30c completely covers the resistive layer 20c and also covers the uncovered portion of the resistive element remaining on the third side 10c of the component body 10. That is, in this embodiment, a portion of the first internal electrode 3 and the second internal electrode 4 with different polarities exposed on the third side 10c of the component body 10 are covered by the resistive layer 20c, while the other portion is completely covered by the insulating layer 30c.

[0112] Therefore, it is possible to prevent moisture from seeping in from the outside of the element 1c, and reliably prevent migration between the internal electrodes 3 and 4 with different polarities. Furthermore, the area of ​​direct contact between the insulating layer 30a and the ceramic surface of the element body 10 is increased, thus improving the connection reliability of the insulating layer 30a with respect to the element body 10. Simultaneously, the connection reliability of the resistive layer 20a with respect to the element body 10 is also improved.

[0113] Furthermore, in this embodiment, the resistive layer 20c has island-shaped portions 27c intermittently formed along the Z-axis direction on the third side surface 10c. Therefore, the load relative to the piezoelectric element 1c is small, allowing the piezoelectric characteristics to be fully utilized. Additionally, the area of ​​the uncovered resistive portion formed on the third side surface 10c of the element body 10 is larger than the total area of ​​the resistive layer 20c. Therefore, most of the third side surface 10c is directly covered by the insulating layer 30c, increasing the anti-migration effect. Furthermore, the coating amount of the resistive layer 20c can be kept to the minimum necessary limit, thus contributing to cost reduction.

[0114] Furthermore, in this embodiment, the resistive layer 20c does not cover the surface of the first external electrode 5 or the second external electrode 6. Therefore, the insulating layer 30c does not need to cover the surface of the first external electrode 5 or the second external electrode 6. However, it can also be configured to provide extensions on both sides of the insulating layer 30c in the X-axis direction and cover a portion of these surfaces.

[0115] The resistive layer 20c and insulating layer 30c in this embodiment correspond to the resistive layer 20, 20a or 20b and insulating layer 30, 30a or 30b in the first to third embodiments, respectively, and the description of the common parts is omitted.

[0116] Fifth Implementation Method

[0117] like Figure 10 and Figure 11 As shown, except as shown below, the stacked piezoelectric element 1d of this embodiment is the same as the stacked piezoelectric element 1c of the fourth embodiment described above, with common components marked with common symbols and descriptions of common parts omitted.

[0118] In this embodiment, the resistive layer 20d is composed of a plurality of island-shaped portions 27d that are intermittently formed along the Z-axis direction on the third side surface 10c of the component body 10. At approximately the center of the third side surface 10c in the X-axis direction, each island-shaped portion 27d is connected to the first internal electrode 3 and the second internal electrode 4 exposed on the surface via the resistive layer 20d.

[0119] In this embodiment, it is preferable that the extended portions 24, 24a, and 24b of the above-described embodiment are not formed in the resistive layer 20d, but they may also be formed. In this embodiment, the plurality of island-shaped portions 27d constituting the resistive layer 20d are formed in a single row in the X-axis direction and intermittently in the Z-axis direction, but they may also be formed continuously in the Z-axis direction. The width of the island-shaped portions 27d in the X-axis direction in this embodiment is wider than that of the island-shaped portions 27c in the fourth embodiment.

[0120] In this embodiment, the insulating layer 30d completely covers the resistive layer 20d and also covers the uncovered portion of the resistive element remaining on the third side 10c of the component body 10. That is, in this embodiment, a portion of the first internal electrode 3 and the second internal electrode 4 with different polarities exposed on the third side 10c of the component body 10 are covered by the resistive layer 20d, while the other portion is completely covered by the insulating layer 30d. Therefore, it is possible to prevent moisture from seeping in from the outside of the component 1d and reliably prevent migration between the internal electrodes 3 and 4 with different polarities.

[0121] Furthermore, in this embodiment, the third side 10c of the element body 10 has a non-covered portion of the resistive element. Therefore, the resistive layer 20d does not cover the entire surface of the third side 10c, resulting in a smaller load relative to the piezoelectric element 1d and allowing for full utilization of the piezoelectric characteristics. Additionally, the presence of a non-covered portion of the resistive element on the third side 10c of the element body 10 reduces the coverage area of ​​the resistive layer 20d, thus contributing to cost reduction.

[0122] Furthermore, in this embodiment, the resistive layer 20d does not cover the surface of the first external electrode 5 or the second external electrode 6. Therefore, the insulating layer 30d does not need to cover the surface of the first external electrode 5 or the second external electrode 6. However, it may be configured such that an extension portion is provided on both sides of the insulating layer 30d in the X-axis direction and covers a portion of these surfaces.

[0123] The resistive layer 20d and insulating layer 30d in this embodiment correspond to the resistive layer 20c and insulating layer 30c in the fourth embodiment, and the description of the common parts is omitted.

[0124] Sixth Implementation Method

[0125] like Figure 12 and Figure 13 As shown, except as shown below, the stacked piezoelectric element 1e of this embodiment is the same as the stacked piezoelectric element 1d of the fifth embodiment described above, with common components marked with common symbols and descriptions of common parts omitted.

[0126] In this embodiment, the resistive layer 20e is composed of a longitudinally continuous portion 22e formed continuously along the Z-axis direction on the third side surface 10c of the component body 10. The longitudinally continuous portion 27e is located approximately at the center of the third side surface 10c in the X-axis direction, where the first internal electrode 3 and the second internal electrode 4 exposed on the surface are connected via the resistive layer 20e.

[0127] In this embodiment, the extended portions 24, 24a, and 24b of the above-described embodiment are not formed in the resistive layer 20e. In this embodiment, the longitudinally continuous portion 22e constituting the resistive layer 20e is preferably formed in a single column in the X-axis direction and continuously in the Z-axis direction, but it may also be formed intermittently in the Z-axis direction. In this embodiment, the width of the resistive layer 20e in the X-axis direction is preferably about 1 / 16 to 4 / 5 of the width of the element body 10 in the X-axis direction.

[0128] In this embodiment, the insulating layer 30e completely covers the resistive layer 20d and also covers the uncovered portion of the resistive element remaining on the third side 10c of the component body 10. That is, in this embodiment, a portion of the first internal electrode 3 and the second internal electrode 4 with different polarities exposed on the third side 10c of the component body 10 are covered by the resistive layer 20e, while the other portion is completely covered by the insulating layer 30e. Therefore, it is possible to prevent moisture from seeping in from the outside of the component 1e and reliably prevent migration between the internal electrodes 3 and 4 with different polarities.

[0129] Furthermore, in this embodiment, the third side 10c of the element body 10 has a non-covered portion of the resistive element. Therefore, the resistive layer 20e does not cover the entire surface of the third side 10c, resulting in a smaller load relative to the piezoelectric element 1e and allowing full utilization of the piezoelectric characteristics. Additionally, the presence of a non-covered portion of the resistive element on the third side 10c of the element body 10 reduces the coverage area of ​​the resistive layer 20d, thus contributing to cost reduction.

[0130] Furthermore, in this embodiment, the resistive layer 20e does not cover the surface of the first external electrode 5 or the second external electrode 6. Therefore, the insulating layer 30e does not need to cover the surface of the first external electrode 5 or the second external electrode 6. However, it can also be configured to provide extensions on both sides of the insulating layer 30e in the X-axis direction and cover a portion of these surfaces.

[0131] In this embodiment, the longitudinal continuous portion 22e is located near the center of the third side surface 10c in the X-axis width direction. With this configuration, it is not necessary for the resistive layer 20e to pass through the corners of the component body 10, making it easy to uniformly form the thickness of the resistive layer 20e. As a result, the resistance value of the resistive layer 20e is easily stabilized, effectively preventing a decrease in polarization caused by thermoelectric effects.

[0132] Furthermore, in this embodiment, by reducing the width of the resistive layer 20e in the X-axis direction, the area of ​​the uncovered portion of the resistive element formed on the third side 10c of the component body 10 can be increased compared to the total area of ​​the resistive layer 20e. In this case, most of the third side 10c is directly covered by the insulating layer 30c, thus increasing the anti-migration effect. In addition, the coating amount of the resistive layer 20c can be kept to the minimum necessary limit, thereby increasing the cost reduction effect.

[0133] Furthermore, in this embodiment, by increasing the width of the resistive layer 20e in the X-axis direction, the area of ​​the uncovered portion of the resistive element formed on the third side 10c of the component body 10 can be reduced compared to the total area of ​​the resistive layer 20e. In this case, the connection reliability of the first internal electrode 3 and the second internal electrode 4 through the resistive layer 20e is improved.

[0134] The resistive layer 20e and insulating layer 30e in this embodiment correspond to the resistive layer 20d and insulating layer 30d in the fifth embodiment, and the description of the common parts is omitted.

[0135] Furthermore, the present invention is not limited to the embodiments described above, and various modifications can be made within the scope of the present invention.

[0136] For example, in the above embodiment, the component body 10 is shaped as a quadrangular prism, but there are no particular limitations. For example, the shape of the component body 10 can be a polygonal prism, a cylinder, or an elliptical cylinder. In addition, in the above embodiment, the first to fourth side surfaces 10a to 10d are all planar, but any one of them can also be a convex or concave curved surface.

[0137] Furthermore, if the external electrodes are electrically connected to the internal electrodes, there are no particular restrictions on where they can be formed; they can be formed on adjacent surfaces of the component body. Additionally, multiple external electrodes of the same polarity or multiple external electrodes of different polarities can be formed on the same surface.

[0138] Example

[0139] The present invention will be further described below based on detailed embodiments, but the present invention is not limited to these embodiments.

[0140] Examples 1 and 2

[0141] Production Figure 1 and Figure 12 The sample of the stacked piezoelectric element shown is illustrated. The resistive layers 20 and 20e are made of phenolic resin containing carbon black as conductive particles. The resin constituting the insulating layers 30 and 30e is epoxy resin, which does not contain conductive particles.

[0142] In all samples, internal electrodes 3 and 4 are composed of a metal with Pd / Ag as the main component, and their stack number is 90. External electrodes 5 and 6 are composed of Ag as the main component. Additionally, the piezoelectric layer 2 is made of a piezoelectric material composed of Pb(ZrxTi1-x)O3, with an average thickness of 20–22 μm. The average thickness of internal electrodes 3 and 4 is 2–3 μm.

[0143] In these samples, after heating at 160℃ for 1 hour and then cooling to room temperature, the improvement effect on polarization degradation caused by thermoelectric degradation due to temperature change was confirmed. The average, maximum, minimum, and standard deviation of the piezoelectric k-constant for each sample are shown in Table 1. The standard deviation of the piezoelectric k-constant before and after heat treatment was used as an indicator of polarization degradation.

[0144] Regarding the samples before and after heat treatment, samples that maintain 100%–105% of the piezoelectric k-constant relative to the design value (50%) are designated as Evaluation A; samples that maintain 95%–100% of the piezoelectric k-constant are designated as Evaluation B; samples that maintain 90%–95% of the piezoelectric k-constant are designated as Evaluation C; and samples that maintain less than 90% of the piezoelectric k-constant are designated as Evaluation D. The proportion of samples that meet each evaluation is shown in Table 1. Evaluations A–D correspond to the characteristic degradation caused by the thermoelectric effect. Within evaluations A–D, the characteristic deterioration is indicated by the order of A–D.

[0145] Furthermore, in the samples where polarization degradation improvement evaluation was conducted, the natural logarithm of the resistance values ​​before and after heating was calculated, and the standard deviation was compared to confirm the improvement effect on the difference in resistance values ​​caused by the thinning of the corners of the component body, and the improvement effect on the change in resistance values ​​of the resistive layer caused by exposure to external gases. The average, maximum, minimum, and standard deviation values ​​of the samples before and after heating are shown in Table 1. Additionally, the natural logarithm of the resistance value means, for example, that in the case of a resistance value of 1 × 10⁵ Ω, its natural logarithm is 5.

[0146] [Table 1]

[0147]

[0148]

[0149] * Insulation resistance is calculated using the natural logarithm.

[0150] Reference Example 1

[0151] Production of Japanese Patent No. 5842635 (Patent Document 2) Figure 1The sample shown was tested under the same conditions as in Example 1, and the results are presented in Table 1. That is, unlike the sample in Example 1, the stacking order of the resistive layer 20 and the insulating layer 30 was reversed, a portion of the insulating layer 30 was covered by the resistive layer 20, and the two ends of the resistive layer 20 in the X-axis direction were connected to the first external electrode 5 and the second external electrode 6, respectively, and the sample of Reference Example 1 was made in the above manner.

[0152] evaluate

[0153] Table 1 confirms that in the sample of Reference Example 1, the standard deviation of the piezoelectric k-constant increased after heat treatment, and the proportion of evaluations B to D increased, thus causing thermoelectric degradation due to temperature change. Furthermore, it was confirmed that in the samples of Examples 1 and 2, the standard deviation of the piezoelectric k-constant did not change after heat treatment, and the proportion of evaluations B to D did not increase compared to the sample of Reference Example 1; therefore, thermoelectric degradation caused by temperature change could be suppressed.

[0154] Table 1 confirms that the standard deviation of the natural logarithm of the insulation resistance of the samples in Examples 1 and 2 is smaller than that of the sample in Reference Example 1. Therefore, it is possible to manufacture components with more stable resistance values. Furthermore, Table 1 confirms that the standard deviation of the insulation resistance of the sample in Reference Example 1 after heat treatment increases. Therefore, fluctuations in the resistance value of the resistance layer due to exposure to external gas occur. Additionally, it is confirmed that in the samples of Examples 1 and 2, the standard deviation of the insulation resistance does not change before and after heat treatment. Therefore, fluctuations in the resistance value of the resistance layer due to exposure to external gas can be suppressed.

[0155] Explanation of symbols

[0156] 1. 1a~1e…Layered piezoelectric elements

[0157] 2…Piezoelectric layer

[0158] 2a…Exterior Area

[0159] 3…First internal electrode

[0160] 4…Second internal electrode

[0161] 5…First external electrode

[0162] 6…Second external electrode

[0163] 10…Component Body

[0164] 10a…First side view

[0165] 10b…Second side

[0166] 10c…Third side

[0167] 10d…Fourth side view

[0168] 20, 20a~20e…resistive layer

[0169] 22, 22a, 22b, 22e… Longitudinal continuous section

[0170] 23a, 23b... Uncovered parts of the resistor

[0171] 24, 24a, 22b… Extended sections

[0172] 26b… Horizontal continuous portion

[0173] 27c, 27d… Island-shaped parts

[0174] Insulation layers 30, 30a~30e, 40…

[0175] 50, 52... lead wires.

Claims

1. A stacked piezoelectric element, wherein, have: The main body of the component has a first internal electrode, a piezoelectric layer, and a second internal electrode with a polarity different from that of the first internal electrode stacked along the stacking direction. A first external electrode is electrically connected to the first internal electrode and is formed on a first side of the component body; The second external electrode is electrically connected to the second internal electrode and is formed on the second side of the component body; A resistive layer is formed on at least a portion of the third side of the component body in such a way that the first internal electrode and the second internal electrode are connected; and An insulating layer is formed on the third side surface in a manner that covers the resistive layer. The third side is the side where the first internal electrode and the second internal electrode are exposed and parallel to the stacking direction. The first external electrode and the second external electrode are not formed on the third side. The resistive layer covers at least a portion of the third side surface and is stacked on the third side surface in a direction perpendicular to the third side surface. At least a portion of the insulating layer is stacked on the resistive layer stacked on the third side surface in a direction perpendicular to the third side surface.

2. The stacked piezoelectric element according to claim 1, wherein, On the third side of the component body, the resistive layer is not formed, leaving the uncovered portion of the resistive element where the first or second internal electrode is exposed. The insulating layer covers the resistive layer and also covers the uncovered portion of the resistive element.

3. The stacked piezoelectric element according to claim 1 or 2, wherein, The resistive layer has a longitudinally continuous portion that is continuous along the stacking direction and formed on the third side of the element body.

4. The stacked piezoelectric element according to claim 1 or 2, wherein, The resistive layer has island-shaped portions that are intermittently formed on the third side of the element body along the stacking direction.

5. The stacked piezoelectric element according to claim 1 or 2, wherein, The resistive layer has an extended portion that covers the surface of the first external electrode or the second external electrode.

6. The stacked piezoelectric element according to claim 5, wherein, The insulating layer is formed on the element body in such a way that it also covers the extended portion.

7. The stacked piezoelectric element according to claim 1 or 2, wherein, A first lead is connected to the first external electrode. A second lead is connected to the second external electrode. These first and second leads extend away from the third side.

8. The stacked piezoelectric element according to claim 1 or 2, wherein, The resistive layer comprises resin.

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