JP2023159533A - Piezoelectric element - Google Patents

Abstract

To provide a piezoelectric element enabling the deviation thereof to be equalized.SOLUTION: A piezoelectric device 2 comprises: an element assembly 10 which includes main surfaces 10a and 10b opposite each other in a direction D1 and side surfaces 10c and 10d opposite each other in a direction D2; internal electrodes 15, 16, and 17 which are provided in the element assembly 10 and which are laminated in the direction D1; and external electrodes 11, 12, and 13 which have electrode portions 11c, 12c, and 13c provided on the side surface 10c, respectively, and electrode portions 11a, 12a, and 13a provided on the main surface 10a. The element assembly 10 includes active regions R11 and R12 which are piezoelectricity active and arranged between the plurality of internal electrodes 15, 16, and 17. The electrode portions 11a, 12a, and 13a include overlapping regions 11d, 12d, and 13d overlapped to the activation regions R11 and R12 in view of the direction D1. An area of each of the overlapping regions 11d, 12d, and 13d is 50% of each area of the electrode portions 11a, 12a, and 13a.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to piezoelectric elements.

Patent Document 1 describes a piezoelectric element including an element body, a plurality of internal electrodes, and a plurality of external electrodes. In this piezoelectric element, the element body has an active region and a plurality of inactive regions, and the inactive region surrounds the active region. As a result, the resonance point of the piezoelectric element is moved to the bass side, so that high sound pressure can be obtained.

JP2019-121664A

In the piezoelectric element described above, the displacement is greatest at the center of the element body. In speaker applications, it is difficult to obtain uniform sound quality due to resonance in the center of the element.

One aspect of the present disclosure provides a piezoelectric element that can uniformize displacement.

A piezoelectric element according to one aspect of the present disclosure has a first main surface and a second main surface facing each other in a first direction, and a first main surface and a second main surface facing each other in a second direction perpendicular to the first direction. an element body having a first side surface and a second side surface connecting the second main surface; a plurality of internal electrodes provided in the element body and laminated in the first direction; and a first side surface, respectively. A plurality of external electrodes having a first electrode portion provided on the top and connected to the corresponding internal electrode, and a second electrode portion provided on the first main surface and connected to the first electrode portion. and, the element body includes a piezoelectrically active active region disposed between the plurality of internal electrodes, and the second electrode portion includes an overlapping region that overlaps the active region when viewed from the first direction. , the area of the overlapping region is 50% or more of the area of the second electrode portion.

In the piezoelectric element, each of the plurality of external electrodes has a second electrode portion provided on the first main surface of the element body. The second electrode portion includes an overlapping region overlapping the active region of the element body. Since the area of the overlapping region is more than half the area of the second electrode portion, the active region is suppressed by the overlapping region of the second electrode portion, and displacement of the central portion of the element body is suppressed. Thereby, displacement can be made uniform.

The length of the second electrode portion in the second direction may be 50% or more of the length of the first principal surface in the second direction. In this case, displacement of the central portion of the element body is further suppressed. Thereby, the displacement can be made more uniform.

The active region may be spaced apart from the outer edge of the element body when viewed from the first direction. In this case, the active region is surrounded by the inactive region, and the resonance point of the piezoelectric element moves toward the bass side. As a result, when the piezoelectric element is applied to an acoustic device, a sound pressure that is sufficiently high for practical purposes can be obtained.

The overlapping region may include a joining region joined to the wiring member. In this case, the junction region is located above the active region. Since the wiring member is displaced following the displacement of the active region, it is more difficult to bond the wiring member than when the wiring member is not located on the active region.

The overlapping region may include an exposed region exposed from the wiring member. In this case, displacement of the active region formed between the exposed region and the internal electrode disposed closest to the first principal surface is difficult to be suppressed.

The entire overlapping region may be covered by the wiring member. In this case, corrosion in the overlapping region can be suppressed.

According to one aspect of the present invention, a piezoelectric element capable of uniformizing displacement is provided.

FIG. 1 is a perspective view showing a vibration device according to a first embodiment. FIG. 2 is a plan view showing the piezoelectric element of FIG. 1. FIG. 3 is an exploded perspective view of the piezoelectric element of FIG. 1. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. FIG. 5 is a cross-sectional view taken along line V-V in FIG. FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. FIG. 7 is a perspective view showing a vibration device including a piezoelectric element according to a second embodiment.

Embodiments will be described in detail below with reference to the accompanying drawings. In the description of the drawings, the same or equivalent elements are given the same reference numerals, and redundant description will be omitted.

[First embodiment]
The vibration device 1 according to the first embodiment shown in FIGS. 1 to 6 is, for example, an acoustic device used for a speaker. The vibration device 1 includes a piezoelectric element 2, a wiring member 3, and bonding members 4 and 5. The piezoelectric element 2 includes an element body 10 and external electrodes 11, 12, and 13 provided on the surface of the element body 10. In FIG. 2, illustration of the external electrodes 11, 12, and 13 is omitted. The piezoelectric element 2 is a laminated piezoelectric element, and the element body 10 includes a plurality of laminated element body layers 14. The element layer 14 is made of a piezoelectric material such as a piezoelectric ceramic material. The piezoelectric element 2 is, for example, a bimorph type.

The element body 10 has a rectangular flat outer shape. The element body 10 has main surfaces 10a and 10b and four side surfaces 10c to 10f. The four side surfaces 10c to 10f connect the main surface 10a and the main surface 10b. The main surfaces 10a and 10b face each other in the stacking direction of the plurality of element layers 14. The side surfaces 10c and 10d face each other in the short side direction of the main surfaces 10a and 10b. The side surfaces 10e and 10f face each other in the long side direction of the main surfaces 10a and 10b. Hereinafter, the stacking direction of the plurality of element layers 14 will be referred to as direction D1, the short side direction of major surfaces 10a and 10b will be referred to as direction D2, and the long side direction of major surfaces 10a and 10b will be referred to as direction D3.

The external electrodes 11, 12, and 13 are made of, for example, Ag or an Ag alloy. The external electrodes 11, 12, and 13 are arranged on the element body 10 at a distance from each other. The external electrodes 11, 12, and 13 are arranged in this order in the direction D3. The external electrode 11 is arranged closest to the side surface 10e. The external electrode 13 is arranged closest to the side surface 10f. External electrode 12 is arranged between external electrode 11 and external electrode 13.

The width L1 of the external electrode 11 in the direction D3 is wider than the width L2 of the external electrode 12 in the direction D3 and the width L3 of the external electrode 13 in the direction D3. The width L2 is, for example, equivalent to the width L3. A distance L4 between the external electrodes 11 and 12 in the direction D3 is longer than the width L2. A distance L5 between the external electrodes 12 and 13 in the direction D3 is shorter than the width L2 and shorter than the width L3.

The external electrode 11 has electrode portions 11a, 11b, and 11c. The electrode portion 11a is provided on the main surface 10a and extends in the direction D2. The electrode portion 11b is provided on the main surface 10b. The electrode portion 11c is provided on the side surface 10c. Electrode portion 11c is connected to electrode portion 11a and electrode portion 11b.

The external electrode 12 has electrode portions 12a, 12b, and 12c. The electrode portion 12a is provided on the main surface 10a and extends in the direction D2. Electrode portion 12b is provided on main surface 10b. The electrode portion 12c is provided on the side surface 10c. Electrode portion 12c is connected to electrode portion 12a and electrode portion 12b.

The external electrode 13 has electrode portions 13a, 13b, and 13c. The electrode portion 13a is provided on the main surface 10a and extends in the direction D2. Electrode portion 13b is provided on main surface 10b. The electrode portion 13c is provided on the side surface 10c. Electrode portion 13c is connected to electrode portion 13a and electrode portion 13b.

The length L6 of the electrode portion 11a in the direction D2, the length L7 of the electrode portion 12a in the direction D2, and the length L8 of the electrode portion 13a in the direction D2 are each 50% of the length L9 of the main surface 10a in the direction D2. % or more, and more preferably 60% or more. In this embodiment, it is 60%. For example, the lengths L6, L7, and L8 are equal to each other.

The piezoelectric element 2 includes a plurality of internal electrodes 15 , 16 , 17 provided within the element body 10 . The internal electrodes 15, 16, and 17 are made of, for example, Ag or an Ag alloy. The internal electrodes 15, 16, and 17 are stacked together with the plurality of element layers 14 in the direction D1.

Internal electrode 15 includes a main electrode part 15a and a connection part 15b. The main electrode portion 15a is spaced apart from the four side surfaces 10c, 10d, 10e, and 10f. The connecting portion 15b extends from the main electrode portion 15a in the direction D2 and is exposed on the side surface 2c. The connecting portion 15b is connected to the electrode portion 11c. The width of the connecting portion 15b in the direction D3 is equal to the width L1.

The internal electrode 16 includes a main electrode part 16a and a connecting part 16b. The main electrode portion 16a is spaced apart from the four side surfaces 10c, 10d, 10e, and 10f. The connecting portion 16b extends from the main electrode portion 16a in the direction D2 and is exposed on the side surface 2c. The connecting portion 16b is connected to the electrode portion 12c. The width of the connecting portion 16b in the direction D3 is equal to the width L2.

Internal electrode 17 includes a main electrode part 17a and a connection part 17b. The main electrode portion 17a is spaced apart from the four side surfaces 10c, 10d, 10e, and 10f. The connecting portion 17b extends from the main electrode portion 17a in the direction D2 and is exposed on the side surface 2c. The connecting portion 17b is connected to the electrode portion 13c. The width of the connecting portion 17b in the direction D3 is equal to the width L3.

The main electrode parts 15a, 16a, and 17a have the same shape and overlap when viewed from the direction D1. The connecting portion 15b overlaps the electrode portion 11a when viewed from the direction D1. The connecting portion 16b overlaps the electrode portion 12a when viewed from the direction D1. The connecting portion 17b overlaps the electrode portion 13a when viewed from the direction D1. The connecting portions 15b, 16b, and 17b are spaced apart from each other in the direction D3.

The stacking order of the plurality of internal electrodes 15, 16, and 17 will be described with reference to FIG. If the element body layer 14 including the principal surface 10a is the first element body layer 14, then the internal electrodes 15 are arranged on the second element body layer 14. Internal electrodes 17 are arranged on the third element body layer 14 . Internal electrodes 15 are arranged on the fourth element layer 14 . Internal electrodes 17 are arranged on the fifth element body layer 14 . Internal electrodes 15 are arranged on the sixth element body layer 14 . An internal electrode 16 is arranged on the seventh element body layer 14. Internal electrodes 15 are arranged on the eighth element body layer 14 . Internal electrodes 16 are arranged on the ninth element body layer 14 . Internal electrodes 15 are arranged on the tenth element body layer 14 .

That is, on the upper side (principal surface 10a side) of the element body 10, internal electrodes 15, 17 are alternately laminated, and on the lower side (principal surface 10b side) of the element body 10, internal electrodes 15, 16 are alternately laminated. ing. The internal electrode 15 disposed on the second element body layer 14 is disposed closest to the principal surface 10a among the plurality of internal electrodes 15, 16, and 17. The internal electrode 15 disposed on the tenth element body layer 14 is disposed closest to the main surface 10b among the plurality of internal electrodes 15, 16, and 17.

As shown in FIGS. 4 to 6, the element body 10 has a piezoelectrically active active region R1 and a piezoelectrically inactive inactive region R2. Active region R1 includes active regions R11, R12, R13, and R14. Active regions R11 and R12 are regions arranged between internal electrodes 15, 16, and 17. More specifically, active region R11 is a region sandwiched between internal electrodes 15 and 16. Active region R12 is a region sandwiched between internal electrodes 15 and 17.

In FIG. 2, active regions R11 and R12 are shown transparently. As shown in FIG. 2, the active regions R11 and R12 are spaced apart from the outer edge of the element body 10 when viewed from the direction D1. When viewed from direction D1, active regions R11 and R12 are surrounded all around by inactive region R2 (FIGS. 4 to 6).

As shown in FIG. 5, the active region R13 is a region sandwiched between the external electrode 12 and the internal electrode 15 disposed on the second element body layer 14 (see FIG. 3). As shown in FIG. 6, the active region R14 is a region sandwiched between the external electrode 13 and the internal electrode 15 disposed on the second element body layer 14 (see FIG. 3). The inactive region R2 is a region of the element body 10 other than the active region R1.

When a voltage is applied between the external electrodes 11 and 12, the electric field generated between the internal electrodes 15 and 16 causes the active region R11 to expand and contract, and the electric field generated between the external electrode 12 and the internal electrode 15 causes the active region R13 to expand and contract. Expand and contract. When a voltage is applied between the external electrodes 11 and 13, the electric field generated between the internal electrodes 15 and 17 causes the active region R12 to expand and contract, and the electric field generated between the external electrode 13 and the internal electrode 15 causes the active region R14 to expand and contract. Expand and contract.

Active regions R11 and R13 are polarized in the same direction. Active regions R12 and R14 are polarized in the same direction. The direction of polarization of active regions R11 and R13 is opposite to the direction of polarization of active regions R12 and R14. Therefore, by applying a first voltage to the external electrode 11 and applying a second voltage different from the first voltage to both the external electrodes 12 and 13, the active regions R11 and R13 and the active regions R12 and R14 are They can be expanded and contracted in opposite directions.

As shown in FIGS. 2 and 4, the electrode portion 11a includes an overlapping region 11d that overlaps the active regions R11 and R12 when viewed from the direction D1. The area of the overlapping region 11d is 50% or more of the area of the electrode portion 11a when viewed from the direction D1.

As shown in FIGS. 2 and 5, the electrode portion 12a includes an overlapping region 12d that overlaps the active regions R11 and R12 when viewed from the direction D1. The area of the overlapping region 12d is 50% or more of the area of the electrode portion 12a when viewed from the direction D1.

As shown in FIGS. 2 and 6, the electrode portion 13a includes an overlapping region 13d that overlaps the active regions R11 and R12 when viewed from the direction D1. The area of the overlapping region 13d is 50% or more of the area of the electrode portion 13a when viewed from the direction D1.

As shown in FIGS. 1, 4 to 6, the wiring member 3 electrically connects the piezoelectric element 2 and an external control circuit (not shown), and applies a voltage to the piezoelectric element 2. The wiring member 3 is, for example, a flexible printed circuit board (FPC) or a flexible flat cable (FFC). The wiring member 3 is arranged on the main surface 10a and is joined to the main surface 10a by the joining members 4 and 5. The wiring member 3 is drawn out along the direction D2 from the side surface 10d side of the main surface 10a. The wiring member 3 is plate-shaped, sheet-shaped, or band-shaped.

The joining member 4 is a resin layer that does not contain conductive particles and has electrical insulation properties. The joining member 4 is, for example, a hot melt resin whose main components are a reactive phenol resin and nitrile rubber. The joining member 4 is arranged along the long side of the main surface 10a on the side surface 10d side. The joining member 4 joins the entire width direction (direction D3) of the wiring member 3 to the main surface 10a. The joining member 4 is spaced apart from the joining member 5 in the direction D2.

The joining member 5 is a resin layer containing a plurality of conductive particles (not shown). The conductive particles are, for example, metal particles or gold-plated particles. The joining member 5 contains, for example, a thermosetting elastomer. The joining member 5 is formed, for example, by curing an anisotropic conductive paste or an anisotropic conductive film. The joining member 5 is electrically connected to the wiring member 3 and the electrode portions 11a, 12a, and 13a.

The electrode portion 11a includes a bonding region 11e that is bonded to the wiring member 3 by the bonding member 5. The electrode portion 12a includes a bonding region 12e that is bonded to the wiring member 3 by the bonding member 5. The electrode portion 13a includes a bonding region 13e that is bonded to the wiring member 3 by the bonding member 5.

In this embodiment, the overlapping region 11d includes the entire joining region 11e. The overlapping region 12d includes the entire joining region 12e. The overlapping region 13d includes the entire joining region 13e. The overlapping region 11d further includes an exposed region 11f exposed from the wiring member 3. The overlapping region 12d further includes an exposed region 12f exposed from the wiring member 3. The overlapping region 13d further includes an exposed region 13f exposed from the wiring member 3.

The wiring member 3 includes conductor layers 31 and 32, a base 33, and a cover 34. The conductor layers 31 and 32 are made of, for example, Cu. The base 33 and the cover 34 are resin layers made of polyimide resin, for example. The conductor layers 31 and 32 are arranged between the base 33 and the cover 34. The conductor layers 31 and 32 are bonded to the base 33 and the cover 34 by, for example, an adhesive layer (not shown).

The conductor layers 31 and 32 extend in the direction D2 on the main surface 10a and are spaced apart from each other in the direction D3. One end portion of the conductor layers 31 and 32 in the direction D2 is exposed from the cover 34. One end portion of the conductor layer 31 exposed from the cover 34 faces the bonding region 11e in the direction D1, and is electrically connected to the bonding region 11e by the bonding member 5. One end portion of the conductor layer 32 exposed from the cover 34 faces the bonding regions 12e, 13e in the direction D1, and is electrically connected to the bonding regions 12e, 13e by the bonding member 5.

In the piezoelectric element 2, the largest displacement occurs at the center of the element body 10, more specifically, at the portion that overlaps with the vicinity of the center of gravity of the main surface 10a when viewed from the direction D1. If resonance occurs in a portion where the displacement becomes large in this way, the sound will become louder at a specific frequency, and uniform sound quality may not be obtained. In the piezoelectric element 2, the area of the overlapping regions 11d, 12d, 13d is more than half the area of the electrode portions 11a, 12a, 13a. That is, when viewed from direction D1, more electrode portions 11a, 12a, 13a are arranged on active regions R11, R12 than in regions where active regions R11, R12 are not arranged. Therefore, the active regions R11 and R12 are suppressed by the overlapping regions 11d, 12d, and 13d, and displacement of the central portion of the element body 10 is suppressed. Thereby, the displacement of the piezoelectric element 2 can be made uniform, and uniform sound quality can be obtained.

The lengths L6, L7, and L8 of the electrode portions 11a, 12a, and 13a in the direction D2 are 50% or more of the length L9 of the main surface 10a in the direction D2. Therefore, displacement of the central portion of the element body 10 is further suppressed. Thereby, the displacement of the piezoelectric element 2 can be made more uniform, and even more uniform sound quality can be obtained.

When viewed from direction D1, active regions R11 and R12 are spaced apart from the outer edge of element body 10. Therefore, the active regions R11 and R12 are surrounded by the inactive region R2, and the resonance point of the piezoelectric element 2 moves toward the bass side. Thereby, when the piezoelectric element 2 is applied to an acoustic device, a sound pressure that is sufficiently high for practical purposes can be obtained.

The overlapping regions 11d, 12d, and 13d include bonding regions 11e, 12e, and 13e that are bonded to the wiring member 3. Junction regions 11e, 12e, 13e are located on active regions R11, R12. Since the wiring member 3 is displaced following the displacement of the active regions R11 and R12, it is more difficult to connect the wiring member 3 than when the wiring member 3 is not located on the active regions R11 and R12.

The overlapping regions 11d, 12d, and 13d also include exposed regions 11f, 12f, and 13f exposed from the wiring member 3. Therefore, among the plurality of internal electrodes 15, 16, 17, the active regions R13, R14 formed between the internal electrode 15 disposed closest to the main surface 10a and the exposed regions 12f, 13f are displaced. Hard to suppress. Therefore, the displacement of the piezoelectric element 2 can be improved.

The regions sandwiched between the internal electrode 15 located closest to the main surface 10a and the external electrodes 12 and 13 become active regions R13 and R14, whereas the internal electrodes located closest to the main surface 10a The region sandwiched between the electrode 15 and the external electrode 11 becomes an inactive region R2. As a result, the internal electrodes 15 and 16 are not affected by electrical influences from the outside, and reliability is improved.

[Second embodiment]
The vibration device 1A according to the second embodiment shown in FIG. 7 differs from the vibration device 1 mainly in that the wiring member 3 is drawn out along the direction D2 from the side surface 10c side of the main surface 10a. . In this embodiment, the entire electrode portions 11a, 11b, and 11c are covered with the wiring member 3. That is, the overlapping regions 11d, 12d, and 13d do not include the exposed regions 11f, 12f, and 13f, respectively. In this way, since the overlapping regions 11d, 12d, and 13d are not exposed, corrosion of the overlapping regions 11d, 12d, and 13d can be suppressed. Moreover, since the wiring member 3 suppresses the displacement of the active regions R13 and R14, the piezoelectric element 2 can be displaced in a well-balanced manner between the side surface 10c side and the side surface 10d side.

Although the embodiments of the present invention have been described above, the present invention is not necessarily limited to the embodiments described above, and various changes can be made without departing from the gist thereof.

The piezoelectric element 2 may be of a monomorph type. The wiring member 3 may be drawn out from the side surface 10e side or the side surface 10f side of the main surface 10a. The piezoelectric element 2 may be used, for example, in a haptic device.

The above embodiments and modifications may be combined as appropriate.

As understood from the descriptions of the embodiments and modifications described above, this specification includes the disclosure of the following aspects.
(Additional note 1)
A first main surface and a second main surface facing each other in a first direction, and a second main surface facing each other in a second direction perpendicular to the first direction and connecting the first main surface and the second main surface. an element body having a first side and a second side,
a plurality of internal electrodes provided within the element body and stacked in the first direction;
A first electrode portion provided on the first side surface and connected to the corresponding internal electrode, and a second electrode provided on the first main surface and connected to the first electrode portion. a plurality of external electrodes,
The element body includes a piezoelectrically active active region disposed between the plurality of internal electrodes,
The second electrode portion includes an overlapping region that overlaps the active region when viewed from the first direction,
The area of the overlapping region is 50% or more of the area of the second electrode portion,
Piezoelectric element.
(Additional note 2)
The length of the second electrode portion in the second direction is 50% or more of the length of the first principal surface in the second direction.
The piezoelectric element according to Supplementary Note 1.
(Additional note 3)
When viewed from the first direction, the active region is spaced apart from an outer edge of the element body.
The piezoelectric element according to supplementary note 1 or 2.
(Additional note 4)
The overlapping area includes a bonding area to be bonded to a wiring member.
The piezoelectric element according to any one of Supplementary Notes 1 to 3.
(Appendix 5)
The overlapping region includes an exposed region exposed from the wiring member,
The piezoelectric element according to appendix 4.
(Appendix 6)
the entire overlap region is covered with the wiring member;
The piezoelectric element according to appendix 4.

2... Piezoelectric element, 10... Element body, 3... Wiring member, 11, 12, 13... External electrode, 15, 16, 17... Internal electrode, 11d, 12d, 13d... Overlapping region, 11e, 12e, 13e... Bonding region , 11f, 12f, 13f... exposed region, R1, R11, R12, R13, R14... active region.

Claims (6)

A first main surface and a second main surface facing each other in a first direction, and a second main surface facing each other in a second direction perpendicular to the first direction and connecting the first main surface and the second main surface. an element body having a first side and a second side,
a plurality of internal electrodes provided within the element body and stacked in the first direction;
A first electrode portion provided on the first side surface and connected to the corresponding internal electrode, and a second electrode provided on the first main surface and connected to the first electrode portion. a plurality of external electrodes,
The element body includes a piezoelectrically active active region disposed between the plurality of internal electrodes,
The second electrode portion includes an overlapping region that overlaps the active region when viewed from the first direction,
The area of the overlapping region is 50% or more of the area of the second electrode portion,
Piezoelectric element. The length of the second electrode portion in the second direction is 50% or more of the length of the first principal surface in the second direction.
The piezoelectric element according to claim 1. When viewed from the first direction, the active region is spaced apart from an outer edge of the element body.
The piezoelectric element according to claim 1 or 2. The overlapping area includes a bonding area to be bonded to a wiring member.
The piezoelectric element according to claim 1 or 2. The overlapping region includes an exposed region exposed from the wiring member,
The piezoelectric element according to claim 4. the entire overlap region is covered with the wiring member;
The piezoelectric element according to claim 4.

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