JP7071172B2 - Laminated piezoelectric elements, piezoelectric vibration devices, and electronic devices - Google Patents

Description

The present invention relates to a laminated piezoelectric element in which piezoelectric bodies and electrodes are alternately laminated, a piezoelectric vibration device, and an electronic device.

A laminated piezoelectric element is known in which a large number of piezoelectric bodies are alternately laminated with internal electrodes and have end face electrodes (external electrodes) connected to these internal electrodes (see Patent Document 1). The laminated piezoelectric element expands and contracts due to the adverse effect of piezoelectricity when a voltage is applied to a plurality of piezoelectric bodies via an external electrode and an internal electrode. Since such a laminated piezoelectric element is small and can obtain a large displacement, it is widely used for actuator parts that require a large generated force and high-speed response.

As the vibration modes that can be adopted by the laminated piezoelectric element, there are known a vibration mode in which the piezoelectric constant that expands and contracts in the thickness direction (stacking direction) is d33 and a vibration mode in which the piezoelectric constant that expands and contracts in the direction along the internal electrode surface is d31. There is. The vibration mode of the laminated piezoelectric element can be controlled by controlling its shape and the like. For example, in the laminated piezoelectric element, the vibration mode of d31 can be made dominant by setting the direction along the internal electrode surface as the longitudinal direction.

Japanese Unexamined Patent Publication No. 2016-100760 International Publication No. 2016/052582

The laminated piezoelectric element has a plurality of electrodes that do not function as a piezoelectric body as described above. Therefore, in order to improve the displacement performance, an optimum structural design according to the vibration mode is required.

In view of the above circumstances, an object of the present invention is to provide a laminated piezoelectric element, a piezoelectric vibration device, and an electronic device having high displacement performance.

In order to achieve the above object, the laminated piezoelectric element according to one embodiment of the present invention includes a laminated piezoelectric body and a plurality of internal electrodes.
The laminated piezoelectric body has a pair of main surfaces facing in the first axial direction, a pair of end faces facing in the second axial direction orthogonal to the first axial direction, and the first axial direction and the above. It has a pair of side surfaces facing in the third axis direction orthogonal to the second axis direction.
The plurality of internal electrodes are arranged inside the laminated piezoelectric body and are laminated in the first axial direction.
Of the plurality of internal electrodes, the first cross section of the central internal electrode arranged in the central portion of the laminated piezoelectric body as viewed from the third axis direction is the first cross section of the central internal electrode as viewed from the second axis direction. It has more undulations than two cross sections.

According to the above configuration, since the undulations of the internal electrodes arranged in the central portion along the longitudinal direction are large, the displacement performance along the longitudinal direction can be improved.

Specifically, it connects the first traveling line running along the center of the first cross section in the first axial direction and having a length of 100 μm in the second axial direction and the end points of the first traveling line. The maximum deviation dimension in the first axial direction from the first reference line is a second traveling line that runs along the center of the second cross section in the first axial direction and has a length of 100 μm in the third axial direction. And the second reference line connecting the end points of the second traveling line may be larger than the maximum deviation dimension in the first axis direction.

As described above, the centrally arranged internal electrode can be configured to have minute undulations along the longitudinal direction.

For example, the maximum deviation dimension between the first traveling line and the first reference line may be 2 μm or more.

Further, among the plurality of internal electrodes, a third cross section of the peripheral internal electrode arranged at a position closest to the main surface of one of the pair of main surfaces of the laminated piezoelectric body as viewed from the third axial direction. Rather, the first cross section may have a large undulation.

As a result, the internal electrode arranged in the center can have a larger undulation than the internal electrode arranged in the peripheral edge.

The piezoelectric vibration device according to one embodiment of the present invention includes the laminated piezoelectric element, a diaphragm, and an adhesive layer.
The diaphragm faces the laminated piezoelectric element in the first axial direction.
The adhesive layer is arranged between the laminated piezoelectric element and the diaphragm.

The electronic device according to one embodiment of the present invention includes the laminated piezoelectric element, a panel, and a housing.
The panel is adhered in a state where the laminated piezoelectric element faces the first axial direction.
The housing holds the panel.

As described above, according to the present invention, it is possible to provide a laminated piezoelectric element, a piezoelectric vibration device, and an electronic device having high displacement performance.

It is a perspective view of the laminated piezoelectric element which concerns on one Embodiment of this invention. It is sectional drawing which follows the AA' line of FIG. 1 of the laminated piezoelectric element. It is sectional drawing along the BB'line of FIG. 1 of the laminated piezoelectric element. FIG. 2 is an enlarged view of FIG. 2 and is a diagram showing a fine structure of a cross section of the laminated piezoelectric element. It is an enlarged view of FIG. 3, and is the figure which shows the fine structure of the cross section of the laminated piezoelectric element. It is a graph which shows the experimental result of the displacement amount with respect to a voltage value. It is a flowchart which shows the manufacturing method of the said laminated piezoelectric element. It is a perspective view which shows the manufacturing process of the said laminated piezoelectric element. It is a perspective view which shows the manufacturing process of the said laminated piezoelectric element. It is sectional drawing corresponding to FIG. 2 of the laminated piezoelectric element which concerns on the modification of the said embodiment. It is sectional drawing corresponding to FIG. 3 of the said laminated piezoelectric element. It is an enlarged view of FIG. 10, and is the figure which shows the fine structure of the cross section of the laminated piezoelectric element. It is an enlarged view of the other part of FIG. 10, and is the figure which shows the fine structure of the cross section of the laminated piezoelectric element. It is sectional drawing of the piezoelectric vibration apparatus using the said laminated piezoelectric element. It is a top view of the electronic device using the laminated piezoelectric element. FIG. 3 is a cross-sectional view taken along the line CC'of FIG. 15A of the electronic device.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The drawings show X-axis, Y-axis, and Z-axis that are orthogonal to each other as appropriate. The X-axis direction corresponds to the "second axis direction", the Y-axis direction corresponds to the "third axis direction", and the Z-axis direction corresponds to the "first axis direction". The X-axis, Y-axis, and Z-axis are common to all drawings.

[Basic configuration of laminated piezoelectric element]
1 to 3 are views showing a laminated piezoelectric element 10 according to an embodiment of the present invention. FIG. 1 is a perspective view of the laminated piezoelectric element 10. FIG. 2 is a cross-sectional view of the laminated piezoelectric element 10 along the AA'line of FIG. FIG. 3 is a cross-sectional view of the laminated piezoelectric element 10 along the line BB'of FIG.

The laminated piezoelectric element 10 includes a laminated piezoelectric body 11, a first external electrode 14, a second external electrode 15, a plurality of first internal electrodes 12, a plurality of second internal electrodes 13, and a first surface electrode 16. , A second surface electrode 17 and the like.

As will be described later, the laminated piezoelectric body 11 is formed by laminating a plurality of piezoelectric layer 20s. The laminated piezoelectric body 11 has two end faces 11a and 11b facing the X-axis direction, two side surfaces 11c and 11d facing the Y-axis direction, and two main surfaces 11e and 11f facing the Z-axis direction. Have. Typically, each surface is configured to be substantially rectangular.
The laminated piezoelectric body 11 has a longitudinal direction along the X-axis direction. As a result, expansion and contraction along the X-axis direction becomes dominant, and the laminated piezoelectric element 10 having a piezoelectric constant of d31 can be configured.

The shape of the laminated piezoelectric body 11 does not have to be a rectangular parallelepiped shape as shown in FIGS. 1 to 3. For example, the ridge portion connecting each surface of the laminated piezoelectric body 11 may be chamfered. Further, each surface of the laminated piezoelectric body 11 may be a curved surface, and the laminated piezoelectric body 11 may have a rounded shape as a whole.

A plurality of electrodes for supplying a driving voltage are arranged on the laminated piezoelectric body 11. External electrodes 14 and 15 are arranged on the end faces 11a and 11b of the laminated piezoelectric body 11. A plurality of internal electrodes 12 and 13 are arranged inside the laminated piezoelectric body 11, and surface electrodes 16 and 17 are arranged on the main surfaces 11e and 11f, respectively. The first internal electrode 12 and the first surface electrode 16 are connected to the first external electrode 14, and the second internal electrode 13 and the second surface electrode 17 are connected to the second external electrode 15.

The laminated piezoelectric body 11 has a piezoelectric active portion 18 and a side margin portion 19. The side margin portion 19 covers the entire region of both side surfaces of the piezoelectric active portion 18 facing the Y-axis direction. Further, the laminated piezoelectric body 11 may have a joining portion for joining the piezoelectric active portion 18 and the side margin portion 19, if necessary.

The piezoelectric active portion 18 has a plurality of piezoelectric layers 20, and the piezoelectric layers 20 and the plurality of internal electrodes 12 and 13 are alternately laminated in the Z-axis direction. A first surface electrode 16 and a second surface electrode 17 are arranged on the outermost piezoelectric layer 20.
Strictly speaking, the region of the laminated piezoelectric body 11 having piezoelectric activity is a region where the internal electrodes 12 and 13 and the surface electrodes 16 and 17 adjacent to each other in the Z-axis direction face each other, but here, the internal electrodes 12 and 13 are opposed to each other. The region up to the end faces 11a and 11b from which the surface electrodes 16 and 17 are drawn out is referred to as the piezoelectric active portion 18.

The piezoelectric layer 20 is made of ceramics having piezoelectric properties. Examples of such ceramics include perovskite-type oxides containing lead zirconate titanate (PbZrO ₃ -PbTIO ₃ ) as a main component, and oxidation containing lithium niobate (LiNbO ₃ ) and lithium tantalate (LiTaO ₃ ) as main components. Things can be used.

The side margin portion 19 is a region that does not have the internal electrodes 12 and 13 and the surface electrodes 16 and 17 and does not have piezoelectric activity. The side margin portion 19 has a function of protecting the piezoelectric active portion 18 and ensuring the insulating properties of the internal electrodes 12 and 13 and the surface electrodes 16 and 17. The side margin portion 19 may be formed of insulating ceramics, but by using ceramics having the same piezoelectric characteristics as the piezoelectric layer 20, the internal stress in the laminated piezoelectric body 11 can be relaxed.

The internal electrodes 12 and 13 are alternately arranged along the Z-axis direction between the plurality of piezoelectric layers 20 stacked in the Z-axis direction. The first internal electrode 12 is connected to the first external electrode 14 and is separated from the second external electrode 15. The second internal electrode 13 is connected to the second external electrode 15 and is separated from the first external electrode 14. As a result, the internal electrodes 12 and 13 adjacent to each other in the Z-axis direction can apply a driving voltage to the piezoelectric layer 20 between them. The internal electrodes 12 and 13 are formed in a rectangular shape, for example.
The internal electrodes 12 and 13 are formed of a conductor containing silver (Ag) or silver-palladium (Pd) as a main component, which has low reactivity with piezoelectric ceramics, or a conductor containing copper (Cu), platinum (Pt), or the like. be able to. Alternatively, these materials may contain a ceramic component or a glass component.

The surface electrodes 16 and 17 are arranged on the outermost piezoelectric layer 20, respectively, the first surface electrode 16 is arranged on the main surface 11e, and the second surface electrode 17 is arranged on the main surface 11f. The first surface electrode 16 is connected to the first external electrode 14 and is separated from the second external electrode 15. The second surface electrode 17 is connected to the second external electrode 15 and is separated from the first external electrode 14.
The first surface electrode 16 can apply a driving voltage to the piezoelectric layer 20 between the first surface electrode 16 and the second internal electrode 13 closest to the main surface 11e. The second surface electrode 17 can apply a driving voltage to the piezoelectric layer 20 between the second surface electrode 17 and the first internal electrode 12 closest to the main surface 11f. The piezoelectric layer 20 between the surface electrodes 16 and 17 and the innermost electrodes 12 and 13 of the outermost layer may be a single layer or a plurality of layers.
With the surface electrodes 16 and 17, the piezoelectric active region of the laminated piezoelectric body 11 can be increased, and the entire laminated piezoelectric body 11 can be expanded and contracted.
The surface electrodes 16 and 17 may be formed in the same rectangular shape as the internal electrodes 12 and 13, respectively, but may have a predetermined pattern.
The surface electrodes 16 and 17 can be formed of silver (Ag), a silver compound containing silver containing glass containing silica (Si) as a main component, nickel (Ni), or the like.

The external electrodes 14 and 15 cover the end faces 11a and 11b of the laminated piezoelectric body 11 and extend to four surfaces (two side surfaces 11c and 11d and two main surfaces 11e and 11f) connected to the end faces 11a and 11b. .. As a result, in each of the external electrodes 14 and 15, the shape of the cross section parallel to the XY plane and the cross section parallel to the XY plane is U-shaped. The external electrodes 14 and 15 may be formed only on the end faces 11a and 11b.
The external electrodes 14 and 15 are composed of, for example, silver, a silver compound containing silver containing glass or the like containing silica as a main component, nickel, or the like.

With the above configuration, in the laminated piezoelectric element 10, when a voltage is applied between the first external electrode 14 and the second external electrode 15, a plurality of plurality of layers between the first internal electrode 12 and the second internal electrode 13 are applied. A voltage is applied to the piezoelectric layer 20. As a result, the plurality of piezoelectric layers 20 expand and contract in the X-axis direction. Further, since the voltage is applied to the outermost piezoelectric layer 20 by the surface electrodes 16 and 17, the entire piezoelectric active portion 18 can be expanded and contracted in the X-axis direction.

The basic configuration of the laminated piezoelectric element 10 according to the present embodiment is not limited to the configurations shown in FIGS. 1 to 3, and can be appropriately changed. For example, the number of internal electrodes 12 and 13 and the thickness of the piezoelectric layer 20 can be appropriately determined according to the size and performance required for the laminated piezoelectric element 10.

[Detailed configuration of internal electrodes]
The laminated piezoelectric element 10 is characterized in that the internal electrodes 12 and 13 have a plurality of undulations along the X-axis direction which is the longitudinal direction.
As shown in FIGS. 2 and 3, the internal electrodes 12 and 13 have a plurality of undulations observed in a cross section parallel to the X-axis direction and not in a cross section parallel to the Y-axis direction. Here, among the plurality of internal electrodes 12 and 13, the internal electrode arranged in the central portion of the laminated piezoelectric body 11 is referred to as the central internal electrode 21, and the central internal electrode 21 is taken as an example to explain the undulating configuration.
The central internal electrode 21 may be either the first internal electrode 12 or the second internal electrode 13.

As shown in FIG. 2, the cross section of the central internal electrode 21 seen from the Y-axis direction (that is, a cross section parallel to the X-axis direction and orthogonal to the Y-axis direction) is defined as the first cross section 22. On the other hand, as shown in FIG. 3, the cross section of the central internal electrode 21 seen from the X-axis direction (that is, the cross section parallel to the Y-axis direction and orthogonal to the X-axis direction) is referred to as the second cross section 23. As shown in these figures, the first cross section 22 has a plurality of undulations protruding or depressed in the Z-axis direction, but the second cross section 23 is configured to be substantially flat. That is, the first cross section 22 has a larger undulation than the second cross section 23. From this, it can be said that the electrode surface of the central internal electrode 21 is formed with wavy undulations having a ridgeline along the Y-axis direction and traveling in the X-axis direction.

Such undulations may be possessed by at least the central internal electrode 21, but may be possessed by all the internal electrodes 12 and 13 as shown in FIG. Alternatively, only one or more internal electrodes 12, 13 including the central internal electrode 21 may have. The shape of the undulations may be substantially the same or different between the internal electrodes 12 and 13.

The microscopic shape of the central internal electrode 21 will be further described.
FIGS. 4 and 5 are views showing a cross section of the laminated piezoelectric body 11 observed with a scanning electron microscope in a field of view of 50 μm in length × 250 μm in width. FIG. 4 corresponds to an enlarged view of FIG. 2 and shows a cross section of the laminated piezoelectric body 11 orthogonal to the Y-axis direction of the central portion in the X-axis direction and the Z-axis direction. FIG. 5 corresponds to an enlarged view of FIG. 3 and shows a cross section of the laminated piezoelectric body 11 orthogonal to the X-axis direction of the central portion in the Y-axis direction and the Z-axis direction. 4 and 5 both show the central internal electrode 21, a part of the first cross section 22 is shown in FIG. 4, and a part of the second cross section 23 is shown in FIG. 5, respectively. There is.

As shown in FIG. 4, a virtual line traveling along the center of the first cross section 22 in the Z-axis direction and having a length of 100 μm (L) in the X-axis direction is defined as the first traveling line 22a. Further, a virtual straight line connecting the end points of the first traveling line 22a is defined as the first reference line 22b. In the first cross section 22, the first traveling line 22a deviates from the first reference line 22b in the Z-axis direction. The maximum deviation dimension T1 along the Z-axis direction of the first traveling line 22a with respect to the first reference line 22b is, for example, 2 μm or more.

On the other hand, as shown in FIG. 5, a traveling line and a reference line are defined for the second cross section 23 as well as the first cross section 22. That is, a virtual line traveling along the center of the second cross section 23 in the Z-axis direction and having a length of 100 μm (L) in the Y-axis direction is defined as the second traveling line 23a. Further, a virtual straight line connecting the end points of the second traveling line 23a is defined as the second reference line 23b. As shown in the figure, in the second cross section 23, the first traveling line 22a does not deviate from the first reference line 22b in the Z-axis direction, and the second traveling line 23a with respect to the second reference line 23b. The maximum dissociation dimension T2 along the Z-axis direction is about 0 μm. That is, the maximum dissociation dimension T1 is larger than the maximum dissociation dimension T2.

As described above, the central internal electrode 21 has a plurality of minute undulations observed in the first cross section 22 and not in the second cross section 23. From the experiment, it was clarified that the amount of displacement in the X-axis direction increases when a voltage is applied to the laminated piezoelectric body 11 having the above configuration. The results of the experiment will be described below.

FIG. 6 is a graph showing the relationship between the voltage value applied to the external electrode of the laminated piezoelectric element and the displacement amount, and the horizontal axis shows the voltage value [V] and the vertical axis shows the displacement amount [nm] in the X-axis direction. .. Further, the solid line shows the result of the piezoelectric laminated element according to the embodiment of the present embodiment in which the central internal electrode 21 has undulations. The broken line shows the result of the piezoelectric laminated element according to the comparative example of this embodiment having an overall flat internal electrode.

As shown in the figure, it was confirmed that the piezoelectric laminated element according to the embodiment has a displacement amount of about 20% in the X-axis direction when the same voltage is applied as compared with the piezoelectric laminated element according to the comparative example. Was done. There are several possible reasons for this, but one is that the surface area of the internal electrodes 12 and 13 increases due to the undulations, and the drive current when the same voltage is applied increases. It is also considered that there are multiple factors such as the contribution of the electric field distribution and the decrease of the binding force on the piezoelectric body by the internal electrodes.

[Basic manufacturing method of laminated piezoelectric element 10]
FIG. 7 is a flowchart showing a method of manufacturing the laminated piezoelectric element 10. 8 to 9 are views showing a manufacturing process of the laminated piezoelectric element 10. Hereinafter, a basic manufacturing method of the laminated piezoelectric element 10 will be described with reference to FIGS. 8 to 9 with reference to FIGS. 7.

(Step S01: Laminating ceramic sheets)
In step S01, as shown in FIG. 8, the first ceramic sheet 101, the second ceramic sheet 102, the third ceramic sheet 103, and the fourth ceramic sheet 104 for forming the laminated piezoelectric body 11 are laminated, and the ceramic laminate is formed. 105 is made. In this step, the first ceramic sheet 101 and the second ceramic sheet 102 are alternately laminated in the Z-axis direction, and the third ceramic sheet 103 and the fourth ceramic sheet 104 are laminated on the upper and lower surfaces of the laminated body, respectively. The number of laminated ceramic sheets is not limited to the example shown in FIG.

The ceramic sheets 101, 102, 103, 104 are configured as unfired piezoelectric green sheets containing piezoelectric ceramics as a main component. The piezoelectric green sheet is prepared by mixing a calcined powder of piezoelectric ceramics, a binder made of an organic polymer, and a plasticizer to prepare a ceramic slurry, which is molded into a sheet using, for example, a roll coater or a doctor blade. Will be done.

As shown in FIG. 8, the first ceramic sheet 101 is formed with an unfired first internal electrode 112 corresponding to the first internal electrode 12, and the second ceramic sheet 102 is not corresponding to the second internal electrode 13. The second internal electrode 113 for firing is formed. Further, the unfired first surface electrode 114 corresponding to the first surface electrode 16 is formed on the third ceramic sheet 103. An unfired first internal electrode 112 corresponding to the first internal electrode 12 is formed on one surface of the fourth ceramic sheet 104, and an unfired second surface corresponding to the second surface electrode 17 is formed on the other surface. The electrode 115 is formed.

The internal electrodes 112, 113 and the surface electrodes 114, 115 can be formed by applying an arbitrary conductive paste to the ceramic sheets 101, 102, 103, 104. The method for applying the conductive paste can be arbitrarily selected from known techniques, and for example, a screen printing method or a gravure printing method can be used.

It is also possible to arrange one or more ceramic sheets to which the conductive paste is not applied between each of the ceramic sheets 103 and 104 and the laminated structure of the ceramic sheets 101 and 102. Thereby, the thickness of the piezoelectric layer 20 between the surface electrodes 16 and 17 and the internal electrodes 12 and 13 can be adjusted. In this case, the internal electrode is not formed on the fourth ceramic sheet 104, and only the second surface electrode 115 is formed.

(Step S02: crimping)
In step S02, the ceramic laminate 105 is crimped. As a result, the ceramic sheets 101, 102, 103, 104 are integrated to form the unfired laminated chip 111 shown in FIG. The laminated chip 111 corresponds to the laminated piezoelectric body 11 before firing and before the polarization treatment. For crimping of the ceramic laminate 105, for example, uniaxial pressurization or hydrostatic pressure pressurization is preferably used. This makes it possible to increase the density of the laminated chip 111.

FIG. 9 is a perspective view of the laminated chip 111 obtained in step S02. The laminated chip 111 is formed with a piezoelectric active portion 116 and a side margin portion 117. A ceramic layer 118 is formed between the internal electrodes 112 and 113, and surface electrodes 114 and 115 are formed on the uppermost surface and the lowermost surface, respectively.

The laminated sheet in which a plurality of regions corresponding to the laminated chips 111 are formed may be crimped and then cut to individualize the laminated chips 111. In this case, the ceramic sheet constituting the laminated sheet has an electrode pattern corresponding to a plurality of internal electrodes and surface electrodes. This makes it possible to produce a plurality of laminated chips from one laminated sheet.
Further, after forming a laminated body consisting of only the piezoelectric active portion 116, side margin portions 117 may be formed on both side surfaces of the laminated body.

(Step S03: Firing)
In step S03, the unfired laminated chip 111 obtained in step S02 is sintered to produce a laminated chip corresponding to the laminated piezoelectric body 11. The laminated chip obtained by this step corresponds to the laminated piezoelectric body 11 before the polarization treatment, and has the same configuration as the laminated piezoelectric body 11 shown in FIGS. 1 to 3.

The firing method in step S03 can be determined based on the composition of the laminated chip 111 and the sintering temperature. For example, after performing a binder removal treatment at 300 to 500 ° C., it can be fired at about 900 to 1200 ° C. Further, the calcination can be performed, for example, in a reducing atmosphere, an atmospheric atmosphere, or a low oxygen partial pressure atmosphere.

(Step S04: External electrode formation)
In step S04, a ceramic element corresponding to the laminated piezoelectric element 10 is manufactured by forming the external electrodes 14 and 15 on the laminated chip obtained in step S03. The ceramic element obtained by this step corresponds to the laminated piezoelectric element 10 before the polarization treatment, and has the same configuration as the laminated piezoelectric element 10 shown in FIGS. 1 to 3.

In step S04, for example, an unfired electrode material is applied so as to cover both end faces in the X-axis direction of the fired laminated chips. The electrode material may be, for example, a conductive paste containing silver (Ag) or the like as a main component. External electrodes 14 and 15 are formed by baking the applied unfired electrode material, for example, in a reducing atmosphere, an air atmosphere, or a low oxygen partial pressure atmosphere. As the method for forming the external electrodes 14 and 15, any method may be used as long as the adhesion is good and the internal electrode and the surface electrode are well energized, and a sputtering method, a vacuum vapor deposition method, or the like may be used.

A part of the process in step S04 may be performed before step S03. For example, the unfired electrode material may be applied to both end faces in the X-axis direction of the unfired laminated chip 111 before step S03. As a result, in step S03, the unbaked laminated chip 111 can be fired and the electrode material can be fired at the same time.

(Step S05: Polarization treatment)
In step S05, the laminated chips after firing are subjected to polarization treatment to impart piezoelectric activity. For the polarization treatment, a voltage may be applied to the laminated piezoelectric body 11 using the external electrodes 14 and 15, or a voltage is applied by connecting other feeding members to the internal electrodes 12 and 13 and the surface electrodes 16 and 17. You may.
As a result, the laminated piezoelectric element 10 is manufactured.

In addition, step S05 may be performed before step S04. In this case, the feeding member is connected to the internal electrodes 12 and 13 and the surface electrodes 16 and 17, and a voltage is applied. This also enables the polarization treatment of the laminated piezoelectric body 11 after firing.

[Manufacturing method of internal electrodes]
The internal electrodes 12 and 13 of the laminated piezoelectric element 10 according to the present embodiment can be manufactured as follows.

For example, in the crimping step of step S02, uniaxial pressurization can be performed using a press device having a rubber sheet made of elastically deformable rubber. Specifically, rubber sheets are attached to both the upper plate and the lower plate of the press device, and the ceramic laminate 105 is arranged between these rubber sheets to apply uniaxial pressure. The rubber sheet is elastically deformed at the time of pressurization due to a slight difference in thickness of the ceramic laminate 105 or the like. By being crimped by the deformed rubber sheet, the internal electrodes 112 and 113 having undulations can be formed.

Alternatively, the composition of the green sheet or the internal electrode may be adjusted to form the internal electrodes 12 and 13 by the difference in the shrinkage ratio between the green sheet and the conductive paste at the time of firing. Alternatively, a rubber sheet may be used at the time of crimping while adjusting the composition of the material.

[Modification example]
10 and 11 are views showing the configuration of the laminated piezoelectric element 30 according to the modified example of the present embodiment. FIG. 10 is a cross-sectional view orthogonal to the Y-axis direction and corresponds to FIG. FIG. 11 is a cross-sectional view orthogonal to the X-axis direction and corresponds to FIG. The laminated piezoelectric element 30 includes a laminated piezoelectric body 11, a first external electrode 14, a second external electrode 15, a plurality of first internal electrodes 32, a plurality of second internal electrodes 33, and a first surface electrode 16. The second surface electrode 17 is provided, and the configurations of the internal electrodes 32 and 33 are different from those of the laminated piezoelectric element 10. Hereinafter, the same reference numerals will be given to the same configurations, and the description thereof will be omitted.

In this modification, of the internal electrodes 32 and 33, the same undulations as the central internal electrode 21 are formed on the electrode surface of the central internal electrode 41 arranged in the central portion of the laminated piezoelectric body 11. On the other hand, of the internal electrodes 32 and 33, the peripheral internal electrode 44 arranged at the position closest to the main surface 11e is formed flat as a whole. The central internal electrode 41 and the peripheral internal electrode 44 may be either the first internal electrode 32 or the second internal electrode 33. Further, the peripheral peripheral internal electrode 44 may be one arranged at a position closest to the main surface 11f among the internal electrodes 32 and 33.

As shown in FIG. 10, the cross section of the central internal electrode 41 seen from the Y-axis direction (that is, the cross section parallel to the X-axis direction and orthogonal to the Y-axis direction) is defined as the first cross section 42. Further, as shown in FIG. 11, the cross section of the central internal electrode 41 seen from the X-axis direction (that is, the cross section parallel to the Y-axis direction and orthogonal to the X-axis direction) is referred to as the second cross section 43. As shown in these figures, the first cross section 42 has a plurality of undulations protruding or depressed in the Z-axis direction, while the second cross section 43 is configured to be substantially flat. From this, it can be said that the electrode surface of the central internal electrode 41 also has ridges along the Y-axis direction and has wavy undulations traveling in the X-axis direction.

On the other hand, as shown in FIG. 10, the cross section of the peripheral internal electrode 44 seen from the Y-axis direction (that is, the cross section parallel to the X-axis direction and orthogonal to the Y-axis direction) is defined as the third cross section 45, and as shown in FIG. The cross section of the peripheral internal electrode 44 seen from the X-axis direction (that is, a cross section parallel to the Y-axis direction and orthogonal to the X-axis direction) is referred to as a fourth cross section 46. As shown in these figures, both the third cross section 45 and the fourth cross section 46 are configured to be substantially flat. From this, it can be said that the peripheral internal electrode 44 is configured to be flat as a whole.

The microscopic shapes of the central internal electrode 41 and the peripheral internal electrode 44 will be further described.
12 and 13 are both views showing a cross section of the laminated piezoelectric body 11 observed with a scanning electron microscope in a field of view of 50 μm in length × 250 μm in width. FIG. 12 corresponds to an enlarged view of FIG. 10 and shows a cross section of the laminated piezoelectric body 11 orthogonal to the Y-axis direction of the central portion in the X-axis direction and the Z-axis direction. FIG. 13 also corresponds to an enlarged view of FIG. 10, and is a view showing a cross section of the laminated piezoelectric body 11 at the center in the Y-axis direction and near the main surface 11e. FIG. 12 shows a part of the first cross section 42 of the central internal electrode 41, and FIG. 13 shows a part of the third cross section 45 of the peripheral internal electrode 44.

As shown in FIG. 12, a virtual line traveling along the center of the first cross section 42 in the Z-axis direction and having a length of 100 μm (L) in the X-axis direction is defined as the first traveling line 42a. Further, a virtual straight line connecting the end points of the first traveling line 42a is defined as the first reference line 42b. In the first cross section 42, the first traveling line 42a deviates from the first reference line 42b in the Z-axis direction. The maximum deviation dimension T1'along the Z-axis direction of the first traveling line 42a with respect to the first reference line 42b is, for example, 2 μm or more.

On the other hand, as shown in FIG. 13, a traveling line and a reference line are also defined for the third cross section 45. That is, a virtual line traveling along the center of the third cross section 45 in the Z-axis direction and having a length of 100 μm (L) in the X-axis direction is defined as the third traveling line 45a. Further, a virtual straight line connecting the end points of the third traveling line 45a is defined as the third reference line 45b. As shown in the figure, in the third cross section 45, the third traveling line 45a does not deviate from the third reference line 45b in the Z-axis direction, and the third traveling line 45a with respect to the third reference line 45b. The maximum dissociation dimension T3 along the Z-axis direction is about 0 μm. That is, the maximum dissociation dimension T1'is larger than the maximum dissociation dimension T3.

As described above, if the central internal electrode 41 arranged in the central portion has undulations, the peripheral internal electrodes 44 near the main surfaces 11e and 11f may not have undulations. It was confirmed that the displacement amount of the laminated piezoelectric body 11 can be increased by the same experiment as the experiment described with reference to FIG. 6 even with this configuration.

It should be noted that only one or a plurality of internal electrodes 32, 33 arranged in the central portion of the laminated piezoelectric body 11 may have undulations, or from the central portion to the internal electrodes 32, 33 near the main surfaces 11e, 11f. It may be configured so that the undulations gradually become smaller as it approaches.

[Piezoelectric vibrating device]
The laminated piezoelectric element 10 can be widely used as a piezoelectric actuator that operates in the X-axis direction due to the piezoelectric lateral effect. An example of an application of the laminated piezoelectric element 10 is a piezoelectric vibration device that generates vibration. Hereinafter, a unimorph type piezoelectric vibration device 50 configured by using the laminated piezoelectric element 10 will be described.

FIG. 14 is a cross-sectional view of the piezoelectric vibration device 50. The piezoelectric vibration device 50 includes a laminated piezoelectric element 10, a diaphragm 51, and an adhesive layer 52. The diaphragm 51 is configured as a flat plate extending along the XY plane, and is arranged so as to face the first main surface 11e of the laminated piezoelectric element 10. The adhesive layer 52 is arranged between the laminated piezoelectric element 10 and the diaphragm 51.

The diaphragm 51 is made of, for example, metal or glass, and has flexibility in the Z-axis direction. The adhesive layer 52 is formed of a resin material or the like, and joins the laminated piezoelectric element 10 and the diaphragm 51. The adhesive layer 52 is in close contact with the lower portion of the laminated piezoelectric element 10 in the Z-axis direction and is in close contact with the upper surface of the diaphragm 51 in the Z-axis direction.

The adhesive layer 52 is filled between the first main surface 11e of the laminated piezoelectric body 11 and the diaphragm 51, and the laminated piezoelectric body 11 and the diaphragm 51 are joined in a wide range. As a result, in the piezoelectric vibration device 50, high bonding strength can be obtained via the adhesive layer 52 between the laminated piezoelectric element 10 and the diaphragm 51.

In the piezoelectric vibration device 50, since the bonding strength between the laminated piezoelectric element 10 and the diaphragm 51 due to the adhesive layer 52 is high, the laminated piezoelectric element 10 is connected to the diaphragm 51 even when the laminated piezoelectric element 10 is greatly expanded and contracted. Hard to peel off. Therefore, in the piezoelectric vibration device 50, the large vibration of the diaphragm 51 is maintained.

[Electronics]
15A and 15B are diagrams schematically showing an electronic device 60 using the laminated piezoelectric element 10. FIG. 15A is a plan view of the electronic device 60. FIG. 15B is a cross-sectional view taken along the line CC'of FIG. 15A of the electronic device 60. The electronic device 60 is configured as a multifunctional mobile communication terminal generally called a smartphone.

The electronic device 60 includes a laminated piezoelectric element 10, a housing 61, and a panel 62. The housing 61 has a bottom plate 61a extending rectangularly along the XY plane and a frame body 61b extending upward in the Z-axis direction from the peripheral edge of the bottom plate 61a, and is formed in a box shape open upward in the Z-axis direction. ing. The panel 62 extends rectangularly along the XY plane and closes the housing 61 from above in the Z-axis direction.

The housing 61 accommodates each configuration (not shown) such as a circuit board and electronic components for realizing various functions of the electronic device 60. The panel 62 is configured as a touch panel. That is, the panel 62 has both an image display function for displaying an image and an input function for detecting an input operation by a user's finger or the like.

The panel 62 is not limited to the touch panel, and may not have the above-mentioned configuration. For example, the panel 62 may be a touch pad that does not have an image display function but has only an input function. Further, the panel 62 may be a protective panel for protecting the touch panel separately provided in the electronic device 60.

The laminated piezoelectric element 10 is adhered to the lower surface of the panel 62 in the Z-axis direction and faces the bottom plate 61a in the housing 61. The position of the laminated piezoelectric element 10 on the lower surface of the panel 62 in the Z-axis direction can be arbitrarily determined. In the electronic device 60, the panel 62 functions as the diaphragm 51 in the piezoelectric vibration device 50 shown in FIG.

That is, the electronic device 60 can vibrate the panel 62 by expanding and contracting the laminated piezoelectric element 10 in the X-axis direction. Therefore, it is preferable that the panel 62 is mainly made of glass, acrylic resin, or the like that can vibrate well. Further, it is preferable that the adhesive layer for adhering the laminated piezoelectric element 10 and the panel 62 has the same configuration as the adhesive layer 52 of the piezoelectric vibrating device 50.

The electronic device 60 can provide voice information to the user by vibrating the panel 62 to generate sound by air conduction, bone conduction, or the like. Further, the electronic device 60 can also present a tactile sensation to, for example, a user who performs an input operation on the panel 62 by vibrating the panel 62.

The upper surface of the panel 62 in the Z-axis direction is typically a flat surface, but may be, for example, a curved surface. Further, the electronic device 60 is not limited to a smartphone, and may be configured as, for example, a tablet terminal, a notebook computer, a mobile phone, a wristwatch, a photo stand, a remote controller or an operation unit of various devices.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made.

For example, although it has been described that the laminated piezoelectric element 10 has the surface electrodes 16 and 17, it is not necessary to have the surface electrodes. In this case, a cover portion made of insulating ceramics is formed in the vicinity of the main surfaces 11e and 11f of the laminated piezoelectric body 11. As a result, the cover portion can protect the piezoelectric laminate in the Z-axis direction as well.

10, 30 ... Laminated piezoelectric element 11 ... Laminated piezoelectric body 12, 13, 32, 33 ... Internal electrode 21, 41 ... Central internal electrode 22, 42 ... First cross section 23, 43 ... Second cross section 44 ... Peripheral internal electrode 45 ... Third section 50 ... Piezoelectric vibrating device 51 ... Vibrating plate 52 ... Adhesive layer 60 ... Electronic equipment 61 ... Housing 62 ... Panel

Claims (6)

A pair of main surfaces facing in the first axial direction, a pair of end faces orthogonal to the first axial direction and facing the second axial direction in the longitudinal direction, and orthogonal to the first axial direction and the second axial direction. A laminated piezoelectric body having a pair of side surfaces facing each other in the third axis direction,
A plurality of internal electrodes arranged inside the laminated piezoelectric body and laminated in the first axial direction ,
With the pair of external electrodes covering the pair of end faces and having the plurality of internal electrodes drawn out alternately along the first axial direction.
Equipped with
Of the plurality of internal electrodes, the first cross section of the central internal electrode arranged in the central portion of the laminated piezoelectric body as viewed from the third axis direction is the entire area thereof from the second axis direction of the central internal electrode. A laminated piezoelectric element having a larger undulation than the second cross section seen. The laminated piezoelectric element according to claim 1.
A first straight line that runs along the center of the first cross section in the first axial direction and connects the first traveling line having a length of 100 μm in the second axial direction and the end points of the first traveling line. The maximum deviation dimension in the first axial direction from the reference line is a second traveling line traveling along the center of the second cross section in the first axial direction and having a length of 100 μm in the third axial direction. A laminated piezoelectric element larger than the maximum deviation dimension in the first axial direction from the second reference line, which is a straight line connecting the end points of the second traveling line. The laminated piezoelectric element according to claim 2.
A laminated piezoelectric element having a maximum dissociation dimension of 2 μm or more between the first traveling line and the first reference line. The laminated piezoelectric element according to any one of claims 1 to 3.
Of the plurality of internal electrodes, the peripheral internal electrodes arranged at positions closest to the main surface of one of the pair of main surfaces of the laminated piezoelectric material, as compared with the third cross section seen from the third axial direction. , The first cross section is a laminated piezoelectric element having large undulations. The laminated piezoelectric element according to any one of claims 1 to 4,
A diaphragm facing the laminated piezoelectric element in the first axial direction,
An adhesive layer arranged between the laminated piezoelectric element and the diaphragm,
A piezoelectric vibration device equipped with. The laminated piezoelectric element according to any one of claims 1 to 4,
A panel to which the laminated piezoelectric element is bonded in a state of facing the first axial direction,
The housing that holds the panel and
An electronic device equipped with.

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