JP4373904B2 - Multilayer piezoelectric element - Google Patents

Description

  The present invention relates to a multilayer piezoelectric element.

  The multilayer piezoelectric element is used as a drive source for minute displacement, for example, in a fuel injection device of an internal combustion engine. Conventionally, a multilayer piezoelectric element 501 whose sectional view is shown in FIG. 9 is known. The multilayer piezoelectric element 501 is provided by alternately laminating first internal electrodes 505 and second internal electrodes 507 with a piezoelectric layer 503 interposed therebetween. The multilayer piezoelectric element 501 has a structure in which the first internal electrodes 505 and the second internal electrodes 507 are connected to each other through a through hole in order to prevent migration that occurs through the side surface 517. Is not exposed to the side surface 517.

The first internal electrodes 505 and the second internal electrodes 507 are connected through through holes 509 and 511 provided through the piezoelectric layer 503 in the stacking direction, and connected to terminals 513 and 515, respectively. Has been. Both the first internal electrode 505 and the second internal electrode 507 are provided so that the peripheral edge portion is located on the inner side of the side surface 517 (see, for example, Patent Document 1).
JP 2000-261555 A

  However, the multilayer piezoelectric element 501 has a central region 521 where the internal electrode exists in a plan view and an edge region 523 where the internal electrode does not exist. Since the thermal contraction rate differs between the internal electrode and the piezoelectric layer, a difference in thermal contraction rate occurs between the central region 521 and the edge region 523 when the multilayer piezoelectric element 501 is fired. For this reason, the conventional multilayer piezoelectric element 501 has a problem that deformation occurs during firing due to the difference in thermal shrinkage rate as described above.

  Therefore, an object of the present invention is to provide a multilayer piezoelectric element that can suppress deformation at the time of firing while preventing migration that occurs through a side surface.

  In order to solve the above-described problems, the multilayer piezoelectric element of the present invention includes a first internal electrode and a second internal electrode that are alternately stacked with a piezoelectric layer interposed therebetween. And the second internal electrodes are connected to each other through a through-hole provided through the piezoelectric layer in the stacking direction, and the peripheral edge portion of the first internal electrode is the stacked layer. The second internal electrode is provided so as to be exposed on the side surface of the piezoelectric element, and the peripheral portion is provided on the inner side with respect to the side surface.

  In the multilayer piezoelectric element, the peripheral edge portion of the first internal electrode is exposed on the side surface, while the peripheral edge portion of the second internal electrode is located on the inner side of the side surface. For this reason, it is possible to prevent migration from occurring between the first internal electrode and the second internal electrode via the side surface. In the multilayer piezoelectric element, both the first internal electrode and the second internal electrode exist in the central region in plan view, and the first internal electrode exists in the edge region in plan view. Existing. For this reason, compared with the case where no internal electrode is present in the edge region, the difference in thermal shrinkage between the central region and the edge region is reduced, and deformation during firing can be suppressed. The internal electrode and the piezoelectric layer in the multilayer piezoelectric element shrink as compared with those before firing due to firing in the manufacturing process. The “heat shrinkage rate” in the present invention refers to the shrinkage caused by such firing. It means degree.

  In the multilayer piezoelectric element of the present invention, the first internal electrodes and the second internal electrodes are alternately stacked with the piezoelectric layers interposed therebetween, and the first internal electrodes and the second internal electrodes are stacked. The electrodes are connected to each other via a through-hole provided through the piezoelectric layer in the stacking direction, and the first internal electrode has a peripheral portion on the side surface of the stacked piezoelectric element. The second internal electrode is provided so that the peripheral edge portion is located on the inner side of the side surface, and between the peripheral edge portion and the side surface of the second internal electrode, A spacer layer that is electrically insulated from the second internal electrode is provided so as to surround the second internal electrode.

  In the multilayer piezoelectric element, the peripheral edge portion of the first internal electrode is exposed on the side surface, while the peripheral edge portion of the second internal electrode is located on the inner side of the side surface. For this reason, it is possible to prevent migration from occurring between the first internal electrode and the second internal electrode via the side surface. In the laminated piezoelectric element, both the first internal electrode and the second internal electrode exist in the central region in plan view, and the first internal electrode and the edge region in plan view include And a spacer layer. For this reason, compared with the case where neither an internal electrode nor a spacer layer is present in the edge region, the difference in thermal shrinkage between the central region and the edge region is reduced, and deformation during firing can be suppressed. .

  In the multilayer piezoelectric element, the spacer layer may be formed of a material that has a thermal contraction rate due to firing closer to that of the second internal electrode than the piezoelectric layer. Thus, by making the thermal contraction rate of the spacer layer close to the second internal electrode, the difference in thermal contraction rate between the center region and the edge region is further reduced, and deformation during firing can be further suppressed. .

  The multilayer piezoelectric element may be characterized in that the spacer layer is formed of the same material as that of the second internal electrode. In this way, the thermal contraction rate of the spacer layer becomes equal to that of the second internal electrode, so that the difference in thermal contraction rate between the center region and the edge region is further reduced, and deformation during firing is further suppressed. Can do.

  The multilayer piezoelectric element may be characterized in that the spacer layer has the same thickness as the second internal electrode. In this way, the thermal contraction amount of the spacer layer is close to the thermal contraction amount of the second internal electrode, so that the difference in thermal contraction amount between the central region and the edge region is further reduced, and deformation during firing is reduced. Further suppression can be achieved. Further, if the spacer layer is made of the same material and the same thickness as the second internal electrode, the thermal contraction amount of the spacer layer becomes equal to the thermal contraction amount of the second internal electrode. The difference in the amount of heat shrinkage is further reduced. If the spacer layer is made of the same material and the same thickness as the second internal electrode, the pattern can be formed simultaneously with the second internal electrode.

  In the multilayer piezoelectric element of the present invention, the first internal electrodes and the second internal electrodes are alternately stacked with the piezoelectric layers interposed therebetween, and the first internal electrodes and the second internal electrodes are stacked. A stacked piezoelectric element in which electrodes are connected through a through-hole provided so as to penetrate the piezoelectric layer in the stacking direction, and the first internal electrode and the second internal electrode have peripheral portions It is provided so as to be located on the inner side of the side surface of the multilayer piezoelectric element, insulated from the first internal electrode, and surrounded by the first internal electrode and the side surface so as to surround the first internal electrode A first spacer layer provided therebetween and a second spacer provided between the second internal electrode and the side surface so as to be insulated from the second internal electrode and to surround the second internal electrode And a layer.

  In the multilayer piezoelectric element, the peripheral edge portion of the first internal electrode and the peripheral edge portion of the second internal electrode are located inside the side surface of the multilayer piezoelectric element. For this reason, it is possible to prevent migration from occurring between the first internal electrode and the second internal electrode via the side surface. In the laminated piezoelectric element, both the first internal electrode and the second internal electrode are present in the central region in plan view, and the first spacer layer and the edge region in plan view are A second spacer layer is present. For this reason, compared with the case where neither an internal electrode nor a spacer layer is present in the edge region, the difference in thermal shrinkage between the central region and the edge region is reduced, and deformation during firing can be suppressed. .

  In the multilayer piezoelectric element, the first spacer layer is formed of a material whose thermal contraction rate by firing is closer to the first internal electrode than the piezoelectric layer, and the second spacer layer is You may make it form with the material whose thermal contraction rate by baking is closer to a 2nd internal electrode than a piezoelectric material layer. Thus, by making the thermal contraction rate of the first and second spacer layers close to the first and second internal electrodes, respectively, the difference in thermal contraction rate between the central region and the edge region is further reduced, and the firing is performed. Time deformation can be further suppressed.

  In the multilayer piezoelectric element, the first spacer layer is formed of the same material as the first internal electrode, and the second spacer layer is formed of the same material as the second internal electrode. This may be a feature. In this way, the thermal shrinkage rates of the first and second spacer layers are equal to those of the first and second internal electrodes, respectively, so that the difference in thermal shrinkage rate between the central region and the edge region is further reduced. Further, deformation during firing can be further suppressed.

  In the multilayer piezoelectric element, the first spacer layer has the same thickness as the first internal electrode, and the second spacer layer has the same thickness as the second internal electrode. Also good. In this way, the thermal contraction amount of the first and second spacer layers is close to that of the first and second internal electrodes, respectively, so that the difference in thermal contraction amount between the central region and the edge region is further reduced. Further, deformation during firing can be further suppressed. Further, if the first and second spacer layers are made of the same material and the same thickness as the first and second internal electrodes, respectively, the thermal shrinkage difference between the central region and the edge region is further reduced. Deformation during firing can be further suppressed. Further, if the first and second spacer layers are made of the same material and the same thickness as the first and second internal electrodes, respectively, the first and second spacer layers become the first and second internal layers, respectively. The pattern can be formed simultaneously with the electrode.

  The multilayer piezoelectric element of the present invention is a multilayer piezoelectric element in which a first internal electrode and a second internal electrode are alternately stacked with a piezoelectric layer interposed therebetween. A conductive portion provided on the side surface of the multi-layer piezoelectric element so as to contact the electrode, and the second internal electrode is provided such that the peripheral edge portion is located on the inner side of the side surface; They are connected to each other through a through hole provided through the piezoelectric layer in the stacking direction of the first internal electrode and the second internal electrode.

  In the multilayer piezoelectric element, the peripheral edge portion of the first internal electrode is exposed on the side surface, while the peripheral edge portion of the second internal electrode is located on the inner side of the side surface. For this reason, it is possible to prevent migration from occurring between the first internal electrode and the second internal electrode via the side surface. In the multilayer piezoelectric element, both the first internal electrode and the second internal electrode exist in the central region in plan view, and the first internal electrode exists in the edge region in plan view. Existing. For this reason, compared with the case where no internal electrode is present in the edge region, the difference in thermal shrinkage between the central region and the edge region is reduced, and deformation during firing can be suppressed. Further, in the multilayer piezoelectric element, the first internal electrodes are connected to each other by the conductive portion via the peripheral portion exposed on the side surface. Therefore, the step of forming a through hole for connecting the first internal electrode is not necessary.

  The multilayer piezoelectric element of the present invention may be characterized in that the second internal electrode is composed of a plurality of individual electrodes arranged in a matrix. In this way, the multilayer piezoelectric element can apply a voltage independently to each of the individual electrodes, so that a plurality of displacement parts can be formed in one element.

  Moreover, the multilayer piezoelectric element of the present invention may further include a terminal electrode provided on the uppermost surface in the stacking direction, and may be supplied with driving power via the terminal electrode.

  ADVANTAGE OF THE INVENTION According to this invention, the multilayer piezoelectric element which can suppress the deformation | transformation at the time of baking can be provided, preventing the migration which arises via a side surface.

  Embodiments of the present invention will be described below. In addition, the same code | symbol is used for the same element and the overlapping description is abbreviate | omitted.

  FIG. 1 is an exploded perspective view showing a multilayer piezoelectric element 100 according to the first embodiment of the present invention. The multilayer piezoelectric element 100 includes a plurality of first internal electrodes 1, a plurality of second internal electrodes 2, a plurality of spacer layers 4, and a plurality of piezoelectric layers 5. The first internal electrodes 1 and the second internal electrodes 2 are alternately stacked with the piezoelectric layers 5 interposed therebetween. The planar view shape of the multilayer piezoelectric element 100 is, for example, a rectangular shape of 10 mm × 15 mm. In the laminated piezoelectric element 100, for example, the first internal electrode 1 and the second internal electrode 2 are laminated in 5 layers each. Hereinafter, the direction in which the first internal electrode 1, the second internal electrode 2, and the piezoelectric layer 5 are stacked is referred to as a “stacking direction”.

  The piezoelectric layer 5 is mainly formed of a ceramic such as lead zirconate titanate, and is formed in a rectangular thin plate shape of, for example, 10 mm × 15 mm and a thickness of 50 μm. The first through hole 11 and the second through hole 21 penetrate the piezoelectric layer 5 in the stacking direction. The first through hole 11 is provided so as to penetrate through the multilayer piezoelectric element 100 over almost the whole of the lamination direction, and the inside of the first through hole 11 is filled with a conductive member 17. The second through-hole 21 is provided so as to penetrate the laminated piezoelectric element 100 over almost the entire lamination direction, and the inside of the second through-hole 21 is filled with a conductive member 27. The second through holes 21 are provided corresponding to the individual electrodes 22 (described later) of the second internal electrode 2, and the individual electrodes 22 corresponding to each other in the stacking direction are electrically connected by the conductive member 27. ing.

  FIG. 2 is a plan view showing the first internal electrode 1. The first internal electrode 1 is made of a material mainly composed of silver and palladium, for example, and is patterned on the piezoelectric layer 5 by screen printing. The first internal electrode 1 is formed in a solid shape over the whole in a plan view, and is formed so that the peripheral edge portion 1a is exposed on the side surface 103 of the multilayer piezoelectric element 100 on all four sides. The first internal electrodes 1 are electrically connected to each other by a conductive member 17 filled in the first through hole 11. An insulating gap 13 is formed at a position corresponding to the second through hole 21 of the first internal electrode 1. Since the second through hole 21 passes through the insulating gap 13 so as not to contact the first internal electrode 1, electrical insulation between the first internal electrode 1 and the second through hole 21 is achieved. .

  FIG. 3 is a plan view showing the second internal electrode 2 and the spacer layer 4. Similar to the first internal electrode 1, the second internal electrode 2 is made of a material mainly composed of silver and palladium, and is patterned on the piezoelectric layer 5 by screen printing. The second internal electrode 2 is composed of a plurality of individual electrodes 22 arranged in a matrix. In the present embodiment, 16 individual electrodes 22 are arranged in 2 columns and 8 rows. The peripheral edge 2 a of the second internal electrode 2 is located on the inner side of the side surface 103 of the multilayer piezoelectric element 100 and is formed so that the peripheral edge 2 a is not exposed to the side surface 103. Here, the edge of the rectangular area in which the individual electrodes 22 are arranged is defined as the peripheral edge 2 a of the second internal electrode 2. Each individual electrode 22 is formed in a rectangular shape and is arranged so that its longitudinal direction is orthogonal to the longitudinal direction of the piezoelectric layer 5. Since the individual electrodes 22 adjacent to each other are arranged with a predetermined gap, they are electrically insulated from each other and are prevented from being affected by vibration. The second through-hole 21 passes through the outer end of each individual electrode 22 in the longitudinal direction. Each individual electrode 22 is electrically connected to a conductive member 27 filled inside the second through hole 21 penetrating the individual electrode 22. The individual electrodes 22 stacked in the stacking direction are connected by the conductive member 27. They are electrically connected to each other.

  The spacer layer 4 is formed in a rectangular ring shape and is provided so as to surround the second internal electrode 2. The peripheral edge 4 a of the spacer layer 4 is exposed on the side surface 103. The spacer layer 4 is provided with a predetermined gap between each individual electrode 22 and is electrically insulated from the second internal electrode 2. The peripheral edge 4 a of the spacer layer 4 is formed so as to be exposed on the side surface 103 on all four sides, but may be formed so that the peripheral edge 4 a is located on the inner side of the side surface 103. An insulating gap 43 is formed at a position corresponding to the first through hole 11 in the spacer layer 4. Since the first through hole 11 passes through the insulating gap 43 so as not to contact the spacer layer 4, electrical insulation between the spacer layer 4 and the first through hole 11 is achieved. The insulating gap 43 may not be provided, and the spacer layer 4 and the first internal electrode 1 may be electrically connected. In this case, the electrical resistance on the first internal electrode 1 side can be reduced. The spacer layer 4 is made of a material mainly composed of silver and palladium, which are the same material as the second internal electrode 2. That is, the spacer layer 4 has a material having a thermal contraction rate higher than that of the piezoelectric layer 5 and is closer to the second internal electrode 2 than the piezoelectric layer 5 (in this embodiment, the same as the second internal electrode). Material). The spacer layer 4 is formed to have the same thickness as the second internal electrode 2. Accordingly, the spacer layer 4 may be patterned on the piezoelectric layer 5 by screen printing simultaneously with the second internal electrode 2.

  Refer to FIG. 1 again. The stacked piezoelectric element 100 has a first terminal electrode 15 and a second terminal electrode 25 provided on the uppermost surface 105 in the stacking direction. The multilayer piezoelectric element 100 is driven by receiving driving power from the outside via the first terminal electrode 15 and the second terminal electrode 25. The first terminal electrode 15 is electrically connected to the conductive member 17 filled in the first through hole 11, and is electrically connected to the first internal electrode 1 via the conductive member 17. Each second terminal electrode 25 is electrically connected to a conductive member 27 filled in each second through hole 21, and each individual electrode of the second internal electrode 2 is connected via the conductive member 27. 22 is electrically connected. When the multilayer piezoelectric element 100 is driven, a potential difference is generated between the first terminal electrode 15 and each second terminal electrode 25 by an external power supply means (not shown), and the first internal electrode 1 An electric field is generated between the second internal electrode 2 and the piezoelectric layer 5 sandwiched between the two electrodes. Since it is possible to generate an electric field between each of the second terminal electrodes 25 and the first terminal electrode 15 independently, a displacement occurs in the portion of the piezoelectric layer 5 corresponding to each second terminal electrode 25. It is also possible to make it.

  Next, a manufacturing procedure of the multilayer piezoelectric element 100 will be described. First, a base paste is prepared by mixing a piezoelectric ceramic material mainly composed of lead zirconate titanate and the like with an organic binder, an organic solvent, and the like, and a green sheet to be the piezoelectric layer 5 is formed using the base paste. . The thickness of the green sheet is 50 micrometers. Moreover, an organic binder, an organic solvent, etc. are mixed with the metal material which consists of silver and palladium of a predetermined ratio, and an electrically conductive paste is produced.

  Subsequently, the first through hole 11 and the second through hole 21 are formed by irradiating a predetermined position of the green sheet to be the piezoelectric layer 5 with a laser beam. The laser used at this time is a YAG third-order long-wave laser, and the hole diameter of the through hole is 40 to 50 micrometers. Then, filling screen printing is performed on the inside of the first through hole 11 and the second through hole 21 using a conductive paste to form conductive members 17 and 27, respectively. The conductive paste used is a mixture of a metal powder of Ag: Pd = 7: 3 with an organic binder, an organic material, or the like.

  Thereafter, the green sheet to be the piezoelectric layer 5 is screen-printed with the pattern of the first internal electrode 1 using a conductive paste to form the first internal electrode 1. Similarly, screen printing is performed on the green sheet with a pattern including both the second internal electrode 2 and the spacer layer 4 to simultaneously form the second internal electrode 2 and the spacer layer 4. That is, here, two types of green sheets are produced: a green sheet on which the pattern of the first internal electrode 1 is printed and a green sheet on which the pattern of the second internal electrode 2 and the spacer layer 4 are printed simultaneously. In addition, the green sheet to be the piezoelectric layer 5 on the uppermost surface 105 is screen-printed using a conductive paste to form the first terminal electrode 15 and the second terminal electrode 25. The conductive paste used here is the same as that used in the above filling screen printing.

  Subsequently, the above two types of green sheets on which electrode patterns are formed are alternately laminated, and pressed in the laminating direction at a pressure of 100 MPa while applying heat at 60 ° C. to produce a laminate green. The produced laminate green is cut into 10 mm × 15 mm. This laminate green is degreased at around 400 ° C. and fired at 1100 ° C. for 2 hours in a sealed mortar to obtain a sintered body.

  Next, a silver baking electrode is applied to the terminal electrodes 15 and 25 on the sintered sheet to be the piezoelectric layer 5 to form terminals for lead connection. Thereafter, a polarization process for 3 minutes is performed at a temperature of 120 ° C. so that the electric field strength is 3 kV / mm, and the multilayer piezoelectric element 100 is obtained. As the material for the terminal electrodes 15 and 25, gold or copper may be used instead of silver. Further, as a method of forming the terminal electrodes 15 and 25, sputtering, vapor deposition, electroless plating, or the like may be employed instead of baking.

  In the multilayer piezoelectric element 100, the peripheral edge portion 1 a of the first internal electrode 1 is exposed on the side surface 103, while the peripheral edge portion 2 a of the second internal electrode 2 is located on the inner side of the side surface 103. The spacer layer 4 has a peripheral edge 4a exposed at the side surface 103, but is electrically insulated from the second internal electrode 2. For this reason, it is possible to prevent migration from occurring between the first internal electrode 1 and the second internal electrode 2 via the side surface 103. Further, the multilayer piezoelectric element 100 includes both the first internal electrode 1 and the second internal electrode 2 in the central region 111 (see FIG. 1) on the inner side of the peripheral edge 2a of the second internal electrode 2 in plan view. The first internal electrode 1 and the spacer layer 4 are present in the edge region 113 (see FIG. 1) outside the peripheral edge 2a of the second internal electrode 2 in plan view. For this reason, the difference in thermal shrinkage between the central region 111 and the edge region 113 is smaller than in the case where neither the internal electrode nor the spacer exists in the edge region 113, and deformation, distortion, cracks during firing are reduced. Occurrence can be suppressed.

  In the multilayer piezoelectric element 100, the spacer layer 4 is formed of the same material as that of the second internal electrode 2. For this reason, the thermal contraction rate of the spacer layer 4 becomes equal to that of the second internal electrode, the difference in thermal contraction rate between the central region 111 and the edge region 113 is further reduced, and the generation of deformation, distortion, and cracks during firing is further reduced. Can be suppressed. From the viewpoint of suppressing such deformation due to firing, it is preferable to form the spacer layer 4 with the same material as that of the second internal electrode 2 and equalize the thermal contraction rate. It is not limited to. That is, if the spacer layer 4 is formed of a material whose thermal contraction rate is closer to the second internal electrode 2 than the piezoelectric layer 5, an effect of suppressing deformation due to firing can be obtained.

  In the multilayer piezoelectric element 100, the spacer layer 4 is provided with the same thickness as that of the second internal electrode 2. For this reason, the thermal contraction amount of the spacer layer 4 becomes equal to the thermal contraction amount of the second internal electrode 2, the difference in thermal contraction amount between the central region 111 and the edge region 113 is further reduced, and deformation and distortion during firing are reduced. Further, the generation of cracks can be further suppressed. Moreover, since the spacer layer 4 is the same material and thickness as the 2nd internal electrode 2, it can pattern-form by screen printing simultaneously with a 2nd internal electrode.

  In the multilayer piezoelectric element 100, the first internal electrodes 1 are electrically connected to each other through the first through holes 11, and the second internal electrodes 2 are electrically connected to each other through the second through holes 21. . For this reason, it is not necessary to connect these two electrodes via the side surface 103, and an insulating treatment step for insulating the electrodes exposed to the side surface 103 is unnecessary. Further, since it is not necessary to connect both electrodes via the side surface 103, a step of polishing the side surface 103 (barrel polishing step) is not required in order to completely expose the both electrodes after baking to the side surface 103.

  In the multilayer piezoelectric element 100, the second internal electrode 2 is composed of a plurality of individual electrodes 22 arranged in a matrix. For this reason, in the multilayer piezoelectric element 100, it is possible to cause a smaller displacement by applying a voltage to each of the individual electrodes 22 independently.

  In the multilayer piezoelectric element 100 according to the above-described embodiment, it is preferable to provide the spacer layer 4 so as to surround the second internal electrode 2 because the difference in thermal contraction rate between the central region 111 and the edge region 113 is further reduced. However, the spacer layer 4 may not be provided. FIG. 4 shows the second internal electrode 2 in the multilayer piezoelectric element having such a configuration. Even when the spacer layer 4 is not provided, the multilayer piezoelectric element 100 has both the first internal electrode 1 and the second internal electrode 2 in the central region 111 in plan view, and the edge in plan view. In the region 113, the first internal electrode 1 is present. For this reason, compared with the case where no electrode is present in the edge region 113, the difference in thermal contraction rate between the central region 111 and the edge region 113 is reduced, thereby suppressing deformation, distortion, and crack generation during firing. Can do.

  Next, with reference to FIG. 5, a multilayer piezoelectric element 200 according to the second embodiment of the present invention will be described. The laminated piezoelectric element 200 is different from the laminated piezoelectric element 100 in the configuration of the first internal electrode 201. Since other configurations are the same as those of the multilayer piezoelectric element 100, description thereof is omitted.

  FIG. 5 is a plan view showing the first internal electrode 201 of the multilayer piezoelectric element 200. In the multilayer piezoelectric element 200, the peripheral edge portion 201 a of the first internal electrode 201 is located on the inner side of the side surface 103, and the peripheral edge portion 201 a is not exposed to the side surface 103.

  The multilayer piezoelectric element 200 includes another spacer layer 3 (first spacer layer) in addition to the spacer layer 4 (second spacer layer; see FIG. 3). The spacer layer 3 is provided in a region sandwiched between the first internal electrode 201 and the side surface 103 and is provided so as to surround the first internal electrode 201. The spacer layer 3 is provided with a predetermined gap between the spacer layer 3 and the first internal electrode 201 so as to be electrically insulated from the first internal electrode 201. The peripheral edge portion 3 a of the spacer layer 3 is formed so as to be exposed on the side surface 103 on all four sides, but may be formed so that the peripheral edge portion 3 a is positioned inside the side surface 103. The spacer layer 3 is made of a material mainly composed of silver and palladium, which are the same materials as the first internal electrode 201, and is formed to have the same thickness as the first internal electrode 201. Therefore, the spacer layer 3 may be patterned on the piezoelectric layer 5 by screen printing simultaneously with the first internal electrode 201.

  In the multilayer piezoelectric element 200, the peripheral edge portion 201 a of the first internal electrode 201 and the peripheral edge portion 2 a of the second internal electrode 2 are located inside the side surface 103. In addition, the spacer layer 3 has the peripheral edge 3a exposed at the side surface 103, but is electrically insulated from the first internal electrode 201. The spacer layer 4 has a peripheral edge 4a exposed at the side surface 103, but is electrically insulated from the second internal electrode 2. For this reason, migration can be prevented from occurring between the first internal electrode 201 and the second internal electrode 2 via the side surface 103. In the multilayer piezoelectric element 200, both the first internal electrode 201 and the second internal electrode 2 exist in the central region 111 (see FIG. 1) in plan view, and the edge region 113 (in plan view) In FIG. 1), the spacer layer 3 and the spacer layer 4 exist. For this reason, compared with the case where neither the internal electrode nor the spacer layer is present in the edge region 113, the difference in thermal contraction rate between the central region 111 and the edge region 113 is reduced, and deformation, distortion during firing, Crack generation can be suppressed.

  In the multilayer piezoelectric element 200, the spacer layer 3 is formed of the same material as the first internal electrode 201, and the spacer layer 4 is formed of the same material as the second internal electrode 2. For this reason, since the thermal contraction rates of the spacer layers 3 and 4 are equal to those of the first internal electrode 201 and the second internal electrode 2, respectively, the difference in thermal contraction rate between the central region 111 and the edge region 113 is further reduced. Deformation, distortion, and crack generation during firing can be further suppressed. From the viewpoint of suppressing deformation due to firing, the spacer layer 3 is formed of the same material as the first internal electrode 201 as in the present embodiment, and the spacer layer 4 is formed of the same material as the second internal electrode 2. It is preferable that the heat shrinkage rates are equal to each other, but the present invention is not limited to this form. That is, the spacer layer 3 is formed of a material that has a thermal contraction rate closer to the first internal electrode 201 than the piezoelectric layer 5, and the spacer layer 4 has a thermal contraction rate that is closer to the second internal electrode 2 than the piezoelectric layer 5. By forming with a close material, the effect which suppresses the deformation | transformation by baking is acquired.

  In the multilayer piezoelectric element 200, the spacer layers 3 and 4 are provided with the same thickness as the first internal electrode 201 and the second internal electrode 2, respectively. For this reason, the thermal contraction amounts of the spacer layers 3 and 4 are equal to the thermal contraction amounts of the first internal electrode 201 and the second internal electrode 2, respectively, and the difference in thermal contraction amount between the central region 111 and the edge region 113 is further increased. Since it becomes small, the deformation | transformation at the time of baking, distortion, and a crack generation can be suppressed further. The first spacer layer 3 and the second spacer layer 4 have the same material and thickness as the first internal electrode 201 and the second internal electrode 2, respectively. Each pattern can be simultaneously formed by screen printing.

  In the multilayer piezoelectric element 200, the first internal electrodes 201 are electrically connected to each other through the first through holes 11, and the second internal electrodes 2 are electrically connected to each other through the second through holes 21. . For this reason, it is not necessary to connect these two electrodes via the side surface 103, and an insulating treatment step for insulating the electrodes exposed to the side surface 103 is unnecessary. Further, since it is not necessary to connect both electrodes via the side surface 103, a step of polishing the side surface 103 (barrel polishing step) is not required in order to completely expose the both electrodes after baking to the side surface 103.

  Subsequently, a multilayer piezoelectric element 300 according to a third embodiment of the present invention will be described with reference to FIGS. The multilayer piezoelectric element 300 is different from the multilayer piezoelectric element 100 in the electrical connection between the first internal electrodes 301.

  FIG. 6 is a longitudinal sectional view of the vicinity of the side surface 103 in the multilayer piezoelectric element 300. FIG. 7A is a plan view of the first internal electrode 301, and FIG. 7B is a plan view of the second internal electrode 2. The peripheral edge 301 a of the first internal electrode 301 is exposed on the side surface 103. A conductive part 109 made of a conductive material is formed on the side surface 103. The conductive portion 109 is formed so as to cover the side surface 103 while being in contact with the exposed peripheral edge portion 301a. The conductive portion 109 does not need to cover the entire side surface 103 as long as it is in contact with each peripheral portion 301a. For example, the conductive portion 109 may be formed so as to cover a part of the side surface 103 in a strip shape in the stacking direction. The first internal electrodes 301 are electrically connected to each other through the conductive portion 109 that is in contact with the peripheral edge portion 301a. Since other configurations are the same as those of the multilayer piezoelectric element 100, description thereof is omitted.

  In the multilayer piezoelectric element 300, the peripheral edge portion 301 a of the first internal electrode 301 is exposed on the side surface 103, while the peripheral edge portion 2 a of the second internal electrode 2 is positioned on the inner side of the side surface 103. For this reason, it is possible to prevent migration from occurring between the first internal electrode 301 and the second internal electrode 2 via the side surface 103. In the multilayer piezoelectric element 300, both the first internal electrode 301 and the second internal electrode 2 exist in the central region 111 (see FIG. 1) in plan view, and the edge region 113 (in plan view) In FIG. 1, the first internal electrode 301 and the spacer layer 4 are present. For this reason, compared with the case where neither the internal electrode nor the spacer layer is present in the edge region 113, the difference in thermal contraction rate between the central region 111 and the edge region 113 is reduced, and deformation, distortion during firing, Crack generation can be suppressed. In the multilayer piezoelectric element 300, the first internal electrodes 301 are connected to each other by the conductive portion 109 through the peripheral portion 301 a exposed from the side surface 103. Therefore, a step of forming a through hole for connecting the first internal electrode 301 is not necessary. As described above, since a through hole forming process that generally requires high accuracy is not required, the yield of the multilayer piezoelectric element 300 can be increased.

  In the multilayer piezoelectric element 300, it is preferable to provide the spacer layer 4 so as to surround the second internal electrode 2 because the difference in thermal contraction rate between the central region 111 and the edge region 113 is further reduced. In this case, it is not essential to provide the spacer layer 4. Even when the spacer layer 4 is not provided, the multilayer piezoelectric element 300 includes both the first internal electrode 301 and the second internal electrode 2 in the central region 111 in plan view, and the edge portion in plan view. In the region 113, the first internal electrode 1 is present. For this reason, compared with the case where no electrode is present in the edge region 113, the difference in thermal contraction rate between the central region 111 and the edge region 113 is reduced, thereby suppressing deformation, distortion, and crack generation during firing. Can do. Note that the peripheral edge 301 a of the first internal electrode 301 and the peripheral edge of the spacer layer 4 do not necessarily have to be on the same plane as the side surface 103, and may be located, for example, several microns inside the side surface 103. This is based on the fact that, for example, a slight difference occurs between the thermal contraction rate of the internal electrode and the spacer layer and the thermal contraction rate of the piezoelectric layer. Even in such a configuration, the effect of the present embodiment can be obtained.

  In the first, second, and third embodiments, the present invention is applied to a laminated piezoelectric element in which the second internal electrode 2 is composed of a plurality of individual electrodes 22, but the present invention is not limited to this, and is solid. It is also possible to apply to the laminated piezoelectric element 400 provided with the provided second internal electrode. FIG. 8A shows a plan view of the first internal electrode 401 of the multilayer piezoelectric element 400, and FIG. 8B shows a plan view of the second internal electrode 402. The peripheral edge 401 a of the first internal electrode 401 is exposed on the side surface 103, and the peripheral edge 402 a of the second internal electrode 402 is located on the inner side than the side surface 103.

1 is an exploded perspective view showing a multilayer piezoelectric element according to a first embodiment. It is a top view which shows a 1st internal electrode. It is a top view which shows a 2nd internal electrode and a spacer layer. It is a top view which shows the 2nd internal electrode of the multilayer piezoelectric element which concerns on a modification. It is a top view which shows the 1st internal electrode of the multilayer piezoelectric element which concerns on 2nd Embodiment. It is a longitudinal cross-sectional view near the side surface of the multilayer piezoelectric element according to the third embodiment. (A) is a top view of the 1st internal electrode of the lamination type piezoelectric element concerning a 3rd embodiment, and (b) is a top view of the 2nd internal electrode. (A) is a top view of the 1st internal electrode of the lamination type piezoelectric element concerning a modification, (b) is a top view of the 2nd internal electrode. It is sectional drawing which shows the conventional lamination type piezoelectric element.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... 1st internal electrode, 1a ... peripheral part, 2 ... 2nd internal electrode, 2a ... peripheral part, 3 ... spacer layer, 3a ... peripheral part, 4 ... spacer layer, 4a ... peripheral part, 5 ... piezoelectric material layer, DESCRIPTION OF SYMBOLS 11 ... 1st through hole, 13 ... Insulation cap, 15 ... 1st terminal electrode, 17 ... Conductive member, 21 ... 2nd through hole, 22 ... Individual electrode, 25 ... 2nd terminal electrode, 27 ... Conductive member, 43 ... Insulation cap, 100 ... multilayer piezoelectric element, 103 ... side surface, 105 ... top surface, 109 ... conductive portion, 200 ... multilayer piezoelectric element, 201a ... peripheral portion, 201 ... first internal electrode, 300 ... multilayer piezoelectric element, DESCRIPTION OF SYMBOLS 301 ... 1st internal electrode, 301a ... Peripheral part, 400 ... Multilayer piezoelectric element, 401 ... 1st internal electrode, 401a ... Peripheral part, 402 ... 2nd internal electrode, 402a ... Peripheral part.

Claims (5)

The first internal electrodes and the second internal electrodes are alternately stacked with the piezoelectric layer interposed therebetween, and the first internal electrodes and the second internal electrodes form the piezoelectric layer. A laminated piezoelectric element having a rectangular shape in plan view connected through a through hole provided penetrating in the direction of the lamination,
The first internal electrode is
It is formed in a solid shape over the whole in a plan view, and the peripheral part is provided so that all four sides are exposed on the side surface of the multilayer piezoelectric element,
The second internal electrode is
The peripheral edge is provided so as to be located on the inner side of the side surface,
Between the peripheral portion of the second internal electrode and the side surface, a spacer layer electrically insulated from the second internal electrode is provided so as to surround the second internal electrode ,
The spacer layer is formed in a square ring shape with a material whose thermal shrinkage ratio due to firing is closer to that of the second internal electrode than the piezoelectric layer, and all the four edges are exposed to the side surface of the multilayer piezoelectric element. A laminated piezoelectric element, characterized in that it is provided . The spacer layer is laminated piezoelectric element according to claim 1, characterized in that it is formed by the second of the same material as the internal electrodes. The spacer layer is laminated piezoelectric element according to claim 1 or claim 2, characterized in that said second same thickness as the internal electrode. The second internal electrode is
The multi-layer piezoelectric element according to any one of claim 1 to 3, characterized in that it is composed of a plurality of individual electrodes arranged in a matrix. A terminal electrode provided on the uppermost surface in the stacking direction;
The multi-layer piezoelectric element according to any one of claims 1-4, characterized in that to receive the supply of the drive power via the terminal electrode.

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