JP7354575B2 - Piezoelectric elements, vibration devices and electronic equipment - Google Patents

Description

The present disclosure relates to piezoelectric elements, vibration devices, and electronic equipment.

Patent Document 1 describes a speaker including a piezoelectric element and a vibration member.

Japanese Patent Application Publication No. 4-70100

When configuring a high-frequency range speaker and a low-frequency range speaker using the above-described speakers, it is conceivable to combine the vibration member of the high-frequency range speaker and the vibration member of the low-frequency range speaker into one. Thereby, the high-frequency range speaker and the low-frequency range speaker are integrated, so that size reduction can be achieved. However, there is a risk that the vibrations of each piezoelectric element will mix together in the vibrating member, resulting in a decrease in sound quality.

The present disclosure provides a piezoelectric element, a vibration device, and an electronic device that can suppress deterioration in sound quality while achieving miniaturization.

A piezoelectric element according to one aspect of the present disclosure includes a piezoelectric element body having a first principal surface and a second principal surface facing each other, and the piezoelectric element body includes a piezoelectrically active first active region and a second piezoelectrically active region. and a piezoelectrically inactive inactive region, and when viewed from the opposing direction of the first principal surface and the second principal surface, the first active region and the second active region are separated by the inactive region. and are spaced apart from each other, and the reproduction frequency band of the first active region is lower than the reproduction frequency band of the second active region.

This piezoelectric element has a first active region, a second active region, and an inactive region. The reproduction frequency band of the first active region is lower than the reproduction frequency band of the second active region. Therefore, the sound quality (sound pressure) in the bass range (low frequency range) can be improved by the first active region, and the sound quality (sound pressure) in the treble range (high frequency range) can be improved by the second active region. . In this way, one piezoelectric element can improve the sound quality in both the high and low ranges. Therefore, compared to the case where two piezoelectric elements are used to improve the sound quality in each sound range, the vibration device can be made smaller. Moreover, the first active region and the second active region are separated from each other with an inactive region interposed therebetween. Therefore, the vibrations of the first active region and the second active region are suppressed from mixing in the piezoelectric element body. Further, the inactive region functions as a restraint body that restrains the vibration of the vibrating member. Therefore, it is also suppressed that the vibrations caused by the first active region and the second active region are mixed in the vibrating member. As a result, deterioration in sound quality in the vibrating device can be suppressed.

The area of the first active region may be larger than the area of the second active region when viewed from the opposing direction. In this case, it is possible to easily realize a configuration in which the reproduction frequency band of the first active region is lower than the reproduction frequency band of the second active region.

The first active region and the second active region may flexurally vibrate in the same direction along opposing directions in synchronization with each other. In this case, the sounds generated by the first active region and the second active region vibrating the vibration member are unlikely to deviate from each other.

A vibrating device according to one aspect of the present disclosure includes a vibrating member having the piezoelectric element, a third principal surface joined to the first principal surface, and a fourth principal surface facing the third principal surface; The vibrating member has a first vibrating portion that overlaps with the first active region and a second vibrating portion that overlaps with the second active region when viewed from the opposing direction, and the vibrating member has a third principal surface. A groove may be provided in at least one of the fourth principal surfaces to separate the first vibrating part and the second vibrating part from each other. In this case, since the vibrating member is provided with the groove, mixing of vibrations in the first vibrating part and the second vibrating part is further suppressed. Therefore, in the vibration device, deterioration in sound quality can be further suppressed.

The groove may pass through the vibrating member so as to connect the third principal surface and the fourth principal surface. In this case, since the first vibrating part and the second vibrating part are reliably separated from each other, mixing of mutual vibrations in the first vibrating part and the second vibrating part is suppressed. Therefore, deterioration in sound quality can be further suppressed.

The vibration device further includes a joining member that joins the first main surface and the third main surface to each other, and the joining member includes a first joining portion that overlaps the first active region and a second active region, when viewed from the opposite direction. and a second joint portion that overlaps with the region, and the first joint portion and the second joint portion may be spaced apart from each other. In this case, since the first joint part and the second joint part are spaced apart from each other, the vibration of the first active region is suppressed from being transmitted to the second vibration part, and the vibration of the second active region is transmitted to the first vibration part. This prevents the information from being transmitted to other parts of the body. Thereby, in the vibrating member, mixing of the vibrations caused by the first active region and the second active region is further suppressed. Therefore, deterioration in sound quality can be further suppressed.

The joining member further includes a third joining part disposed between the first joining part and the second joining part when viewed from the opposite direction, and the first joining part and the second joining part are different from each other in the third joining part. It may be harder than that. In this case, the vibrations of the first active region and the second active region are easily transmitted to the first vibrating part and the second vibrating part via the first joint part and the second joint part.

An electronic device according to one aspect of the present disclosure includes the piezoelectric element or the vibration device.

Since this electronic device includes the piezoelectric element or the vibration device, it is possible to suppress deterioration in sound quality while achieving miniaturization.

According to one aspect of the present disclosure, a piezoelectric element, a vibration device, and an electronic device that can suppress deterioration in sound quality while achieving miniaturization are provided.

FIG. 1 is a perspective view showing a vibration device according to an embodiment. 2 is an exploded perspective view showing the piezoelectric element of FIG. 1. FIG. 2 is a sectional view taken along line III-III in FIG. 1. FIG. It is a perspective view showing a vibrating device concerning a first modification. 5 is an exploded perspective view showing the piezoelectric element of FIG. 4. FIG. FIG. 7 is an enlarged cross-sectional view of a part of a vibrating device according to a second modification. FIG. 7 is an enlarged cross-sectional view of a part of a vibrating device according to a third modification.

Embodiments will be described in detail below with reference to the accompanying drawings. In the description, the same elements or elements having the same function will be denoted by the same reference numerals, and redundant description will be omitted.

FIG. 1 is a perspective view showing a vibration device according to an embodiment. As shown in FIG. 1, a vibration device 100 according to the embodiment includes a piezoelectric element 1 and a vibration member 50. The vibration device 100 drives the piezoelectric element 1 by applying an alternating voltage, and causes the piezoelectric element 1 to vibrate the vibration member 50, thereby generating sound. The vibration device 100 is used, for example, as a speaker or a buzzer. The vibration device 100 is provided, for example, in electronic equipment such as a television and a smartphone.

The piezoelectric element 1 has a piezoelectric element body 2 and external electrodes 11, 12, and 13. Although the piezoelectric element 1 is a bimorph type piezoelectric element in this embodiment, it may be a unimorph type piezoelectric element. The piezoelectric element 1 is a so-called laminated piezoelectric element.

The piezoelectric element body 2 has a rectangular parallelepiped shape. The rectangular parallelepiped shape includes, for example, a rectangular parallelepiped shape with chamfered corners and edge lines, and a rectangular parallelepiped shape with rounded corners and edge lines. The piezoelectric element body 2 has main surfaces 2a and 2b facing each other, side faces 2c and 2d facing each other, and side faces 2e and 2f facing each other. The main surface 2a faces the vibrating member 50 and is joined to the vibrating member 50.

Hereinafter, the opposing direction of the main surfaces 2a and 2b will be referred to as a direction D1, the opposing direction of the side surfaces 2c and 2d will be referred to as a direction D2, and the opposing direction of the side surfaces 2e and 2f will be referred to as a direction D3. The direction D1 is a direction that intersects (perpendicularly intersects here) the main surfaces 2a and 2b. The direction D2 is a direction that intersects (perpendicularly intersects here) the side surfaces 2c and 2d. The direction D3 is a direction that intersects (perpendicularly intersects here) the side surfaces 2e and 2f. The direction D1, the direction D2, and the direction D3 intersect with each other (here, they are orthogonal).

The main surfaces 2a and 2b have a rectangular shape with a pair of long sides and a pair of short sides. That is, the piezoelectric element 1 (piezoelectric element body 2) has a rectangular shape having a pair of long sides and a pair of short sides when viewed from above. The rectangular shape includes, for example, a shape in which each corner is chamfered and a shape in which each corner is rounded. The long side direction of the main surfaces 2a and 2b coincides with the direction D2. The short side direction of the main surfaces 2a and 2b coincides with the direction D3. The length of the piezoelectric element body 2 (the length of the piezoelectric element body 2 in the direction D2) is, for example, 60 mm. The width of the piezoelectric element body 2 (the length of the piezoelectric element body 2 in the direction D3) is, for example, 30 mm. The thickness of the piezoelectric element body 2 (the length of the piezoelectric element body 2 in the direction D3) is, for example, 0.5 mm. Note that the long side direction of the main surfaces 2a, 2b may match the direction D3, and the short side direction of the main surfaces 2a, 2b may match the direction D2.

FIG. 2 is an exploded perspective view showing the piezoelectric element of FIG. 1. FIG. 3 is a sectional view taken along line III-III in FIG. 1. As shown in FIGS. 2 and 3, the piezoelectric element body 2 includes a plurality of stacked piezoelectric layers 20 (here, 10). The stacking direction of the plurality of piezoelectric layers 20 coincides with the direction D1. For example, each piezoelectric layer 20 has the same shape. Equivalence includes the range of manufacturing tolerances. The thickness of each piezoelectric layer 20 is, for example, 30 μm.

Each piezoelectric layer 20 has main surfaces 20a and 20b facing each other. Each main surface 20a faces one side in the stacking direction. The main surface 20a of the piezoelectric layer 20 disposed at one end in the stacking direction is the main surface 2a. Each main surface 20b faces the other side in the stacking direction. The main surface 20b of the piezoelectric layer 20 disposed at the other end in the stacking direction is the main surface 2b.

Each piezoelectric layer 20 is made of piezoelectric material. In this embodiment, each piezoelectric layer 20 is made of piezoelectric ceramic material. Piezoelectric ceramic materials include, for example, PZT[Pb(Zr,Ti)O ₃ ], PT(PbTiO ₃ ), PLZT[(Pb,La)(Zr,Ti)O ₃ ], or barium titanate (BaTiO ₃ ). is used. Each piezoelectric layer 20 is composed of, for example, a sintered body of a ceramic green sheet containing the piezoelectric ceramic material described above. In the actual piezoelectric element body 2, the piezoelectric layers 20 are integrated to such an extent that the boundaries between the piezoelectric layers 20 are unrecognizable.

As shown in FIG. 1, each external electrode 11, 12, 13 is arranged on the main surface 2b. The external electrodes 11, 12, and 13 are provided closer to the side surface 2d than the center in the long side direction of the main surface 2b, and are lined up along the short side direction of the main surface 2b. The external electrodes 11, 12, and 13 are arranged in this order from the side surface 2e toward the side surface 2f. The external electrodes 11, 12, and 13 are spaced apart from each other in the short side direction of the main surface 2b. The external electrodes 11, 12, and 13 are spaced apart from all edges (four sides) of the main surface 2b when viewed from the direction D1.

Each of the external electrodes 11, 12, 13 has, for example, a rectangular shape when viewed from the direction D1. Each of the external electrodes 11, 12, and 13 may have a square shape, a circular shape, or the like when viewed from the direction D1. The rectangular shape and square shape include, for example, a shape in which each corner is chamfered and a shape in which each corner is rounded. Each external electrode 11, 12, 13 is made of a conductive material. For example, Ag, Pd, Pt, or Ag-Pd alloy is used as the conductive material. Each of the external electrodes 11, 12, and 13 is configured, for example, as a sintered body of conductive paste containing the above-mentioned conductive material.

External electrodes 11, 12, and 13 are connected to a control circuit (not shown) that controls vibration device 100. The control circuit includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). In this case, the control circuit performs various processes by loading a program stored in the ROM into the RAM and executing it on the CPU.

The control circuit inputs a drive signal for driving the piezoelectric element 1 to the external electrodes 12 and 13. External electrodes 12 and 13 receive drive signals for driving active regions R1 and R2, which will be described later, from a control circuit. External electrode 11 is a ground terminal. The external electrodes 11, 12, and 13 are connected to a control circuit by, for example, a wiring member (not shown) such as a flexible printed circuit board (FPC) or a flexible flat cable (FFC).

The vibrating member 50 is, for example, a rectangular plate member. The vibrating member 50 has flexibility. The vibrating member 50 is made of resin, glass, or metal, for example. The vibrating member 50 has main surfaces 50a and 50b facing each other. The main surfaces 50a and 50b have a rectangular shape with a pair of long sides and a pair of short sides. The main surface 50a faces the main surface 2a and is joined to the piezoelectric element 1. The piezoelectric element 1 is arranged, for example, at the center of the main surface 50a. The vibrating member 50 is arranged, for example, so that the long side direction of the main surface 50a coincides with the long side direction of the main surface 2a. The length of the long side of the main surfaces 50a and 50b is, for example, 200 mm. The length of the short side of the main surfaces 50a and 50b is, for example, 150 mm. The thickness of the vibrating member 50 is, for example, 1 mm.

As shown in FIGS. 2 and 3, the piezoelectric element 1 includes internal electrodes 31, 32, 33, 34, 35, 41, 42, 43 and through-hole conductors T1, T2, T3. .

Each internal electrode is arranged on the main surface 20b of each piezoelectric layer 20 located at a location other than the other end in the stacking direction. On these main surfaces 20b, the internal electrodes 31, 32, 33 are arranged so as to overlap the external electrodes 11, 12, 13 when viewed from the stacking direction. The arrangement and shape of the internal electrodes 31, 32, 33 on the main surface 20b match, for example, the arrangement and shape of the external electrodes 11, 12, 13 on the main surface 2b. The internal electrodes 31, 32, and 33 are provided closer to the side surface 2d than the center in the long side direction of the main surface 20b, and are lined up along the short side direction of the main surface 2b.

In these main surfaces 20b, an internal electrode 34 is arranged on the side surface 2c side of the internal electrodes 31, 32, 33, and an internal electrode 35 is arranged on the side surface 2d side of the internal electrodes 31, 32, 33. . The internal electrodes 34 and 35 have, for example, a rectangular shape when viewed from the stacking direction. The internal electrodes 34 and 35 have, for example, the same shape and overlap each other when viewed from the stacking direction. All edges (four sides) of the internal electrodes 34 and 35 overlap each other, for example, when viewed from the stacking direction. The internal electrodes 34 and 35 are spaced apart from, for example, all edges (four sides) of the main surface 20b when viewed from the stacking direction.

The internal electrodes 34, 35 are connected to one of the internal electrodes 31, 32, 33 by a pair of internal electrodes 41, 42, 43, and are spaced apart from the other internal electrodes. The internal electrodes connected to the internal electrodes 34 and 35 differ depending on the stacking position.

If the piezoelectric layer 20 disposed at one end in the stacking direction is the first piezoelectric layer 20, the pair of internal electrodes 41 are the first, third, fifth, seventh, and ninth layers. It is provided on each main surface 20b of the piezoelectric layer 20 of the eye. One internal electrode 41 is arranged between internal electrode 34 and internal electrode 31, and connects internal electrode 34 and internal electrode 31 to each other. The other internal electrode 41 is arranged between the internal electrode 35 and the internal electrode 31, and connects the internal electrode 35 and the internal electrode 31 to each other. Therefore, on each main surface 20b of the first, third, fifth, seventh, and ninth piezoelectric layers 20, the internal electrodes 34 and 35 are connected to the pair of internal electrodes 41 and the internal electrode 31. are connected to each other by.

A pair of internal electrodes 42 are provided on each main surface 20b of the second and fourth piezoelectric layers 20. One internal electrode 42 is arranged between internal electrode 34 and internal electrode 32, and connects internal electrode 34 and internal electrode 32 to each other. The other internal electrode 42 is arranged between the internal electrode 35 and the internal electrode 32, and connects the internal electrode 35 and the internal electrode 32 to each other. Therefore, on each main surface 20b of the second and fourth piezoelectric layers 20, the internal electrodes 34 and 35 are connected to each other by the pair of internal electrodes 42 and the internal electrode 32.

A pair of internal electrodes 43 are provided on each main surface 20b of the sixth and eighth piezoelectric layers 20. One internal electrode 43 is arranged between internal electrode 34 and internal electrode 33, and connects internal electrode 34 and internal electrode 33 to each other. The other internal electrode 43 is arranged between the internal electrode 35 and the internal electrode 33, and connects the internal electrode 35 and the internal electrode 33 to each other. Therefore, on each main surface 20b of the sixth and eighth piezoelectric layers 20, the internal electrodes 34 and 35 are connected to each other by the pair of internal electrodes 43 and the internal electrode 33.

Each internal electrode is made of conductive material. For example, Ag, Pd, Pt, or Ag-Pd alloy is used as the conductive material. Each internal electrode is configured, for example, as a sintered body of conductive paste containing the above-mentioned conductive material.

The through-hole conductors T1, T2, T3 penetrate through positions corresponding to the external electrodes 11, 12, 13 and the internal electrodes 31, 32, 33 in each piezoelectric layer 20 arranged other than one end in the stacking direction. It is arranged in a through hole (not shown). The external electrodes 11, 12, 13 and each internal electrode 31, 32, 33 are electrically connected to each other by through-hole conductors T1, T2, T3.

Through-hole conductors T1, T2, T3 include conductive material. The conductive material is made of, for example, one or more metals selected from the group consisting of Pd, Ag, Cu, W, Mo, Sn, and Ni, or an alloy containing one or more of the above metals. The diameters of the through-hole conductors T1, T2, and T3 are, for example, 20 μm or more and 100 μm or less.

As shown in FIG. 3, the vibration device 100 includes a joining member 51. The joining member 51 joins the piezoelectric element 1 and the vibration member 50. The joining member 51 includes, for example, a base material made of a nonwoven fabric and adhesive layers arranged on both sides of the base material. When the bonding member 51 includes a nonwoven fabric, the bonding member 51 can easily follow the undulations and small irregularities on the bonding surface of the piezoelectric element 1 and the bonding member 51, and the influence of the surface condition can be reduced. Vibrations can be efficiently transmitted to the vibrating member 50. When viewed from the stacking direction, the outer edge of the joining member 51 is located slightly inside the outer edge of the main surface 20a. This prevents foreign matter from adhering to the adhesive layer of the bonding member 51. The joining member 51 may be a resin layer made of epoxy resin or acrylic resin, for example. In this case, since the joining member 51 does not have an adhesive layer, the outer edge of the joining member 51 may be located outside the outer edges of the main surfaces 2a and 2b when viewed from the direction D1.

Next, each region of the piezoelectric element body 2 will be explained. As shown in FIG. 3, the piezoelectric element body 2 has piezoelectrically active active regions R1 and R2 and a piezoelectrically inactive inactive region R3. The active region R1 includes an internal electrode 34 (among the plurality of internal electrodes 34, the internal electrode 34 located closest to the main surface 2a) arranged on the main surface 20b (see FIG. 2) of the first piezoelectric layer 20. and the internal electrode 34 disposed on the principal surface 20b of the ninth piezoelectric layer 20 (the internal electrode 34 disposed closest to the principal surface 2b among the plurality of internal electrodes 34). . The active region R2 includes an internal electrode 35 disposed on the principal surface 20b of the first piezoelectric layer 20 (the internal electrode 35 disposed closest to the principal surface 2a among the plurality of internal electrodes 35), and an internal electrode 35 disposed on the principal surface 20b of the first piezoelectric layer 20; This is a region between the inner electrode 35 (among the plurality of internal electrodes 35, the inner electrode 35 disposed closest to the main surface 2b) arranged on the main surface 20b of the piezoelectric layer 20.

The inactive region R3 is a region of the piezoelectric element body 2 other than the active regions R1 and R2. Specifically, the inactive region R3 includes a region located between the active regions R1 and R2 and the main surfaces 2a and 2b, a region located between the active region R1 and the active region R2 when viewed from the direction D1, and an active region located between the active region R1 and the active region R2. It includes regions located between R1 and R2 and side surfaces 2e and 2f, between active region R1 and side surface 2c, and between active region R2 and side surface 2d.

Active regions R1, R2 and inactive region R3 are integrally formed. Active regions R1 and R2 are spaced apart from each other via inactive region R3 when viewed from direction D1. The reproduction frequency band of active region R1 is lower than the reproduction frequency band of active region R2. The reproduction frequency band of the piezo sounding body changes depending on the shape, material, density, structure, stress, etc. of the active regions R1 and R2. Density varies not only depending on the material but also on the manufacturing method.

When viewed from direction D1, the area of active region R1 is larger than the area of active region R2. As mentioned above, there are multiple parameters for changing the reproduction frequency band, but when changing the reproduction frequency band by area, the active regions R1 and R2 can be manufactured using the same material and the same manufacturing method except for different areas. , the manufacturing method is prevented from becoming complicated. Here, since the active regions R1 and R2 have the same thickness, the volume of the active region R1 is larger than the volume of the active region R2. When viewed from direction D1, the maximum length of active region R1 is longer than the maximum length of active region R2. In this embodiment, since the active regions R1 and R2 have a rectangular shape when viewed from the direction D1, the maximum length of the active regions R1 and R2 is the length of the diagonal line of the active regions R1 and R2.

The active region R1 includes an active region R11 and an active region R12 stacked in the direction D1. Active region R11 and active region R12 are arranged side by side in direction D1. Active region R11 is arranged on the main surface 2a side. Active region R12 is arranged on the main surface 2b side. Specifically, the active region R11 includes an internal electrode 34 arranged on the main surface 20b of the first piezoelectric layer 20 and an internal electrode 34 arranged on the main surface 20b of the fifth piezoelectric layer 20. This is the area between. Specifically, the active region R12 includes an internal electrode 34 arranged on the main surface 20b of the fifth piezoelectric layer 20 and an internal electrode 34 arranged on the main surface 20b of the ninth piezoelectric layer 20. This is the area between.

The active region R2 includes an active region R21 and an active region R22 stacked in the direction D1. Active region R21 and active region R22 are arranged side by side in direction D1. Active region R21 is arranged on the main surface 2a side. Active region R22 is arranged on the main surface 2b side. Specifically, the active region R21 includes an internal electrode 35 arranged on the main surface 20b of the first piezoelectric layer 20 and an internal electrode 35 arranged on the main surface 20b of the fifth piezoelectric layer 20. This is the area between. Specifically, the active region R22 includes an internal electrode 35 arranged on the main surface 20b of the fifth piezoelectric layer 20 and an internal electrode 35 arranged on the main surface 20b of the ninth piezoelectric layer 20. This is the area between.

The active regions R1 and R2 are polarized, for example, by applying voltages of different polarities to the external electrodes 12 and 13 while the external electrode 11 is connected to the ground. When the piezoelectric element 1 is driven, voltages of the same polarity are applied to the external electrodes 12 and 13 while the external electrode 11 is connected to the ground. As a result, one of the pair of active regions R11 and R21 and the pair of active regions R12 and R22 is applied with a voltage in the same direction as the polarization direction (forward direction) and expands, and the other pair is polarized. A voltage in the opposite direction (opposite direction) is applied to cause contraction. As a result, the active regions R1 and R2 flexurally vibrate in synchronization with each other in the same direction along the stacking direction.

Specifically, for example, when a forward voltage is applied to the active regions R11, R21 and a reverse voltage is applied to the active regions R12, R22, the active regions R11, R21 expand, and the active regions R12, R21 expand. R22 contracts. As a result, the active regions R1 and R2 are bent so that the main surface 2a is convex and the main surface 2b is concave. At this time, main surface 2a has a convex shape on both sides of active regions R1 and R2, and main surface 2b has a concave shape on both sides of active regions R1 and R2.

Further, for example, if a voltage in the opposite direction is applied to the active regions R11, R21 and a voltage in the forward direction is applied to the active regions R12, R22, the active regions R11, R21 contract, and the active regions R12, R22 expand. do. As a result, the active regions R1 and R2 are bent so that the main surface 2a is concave and the main surface 2b is convex. At this time, the main surface 2a has a concave shape on both active region R1 and R2 sides, and the main surface 2b has a convex shape on both active region R1 and R2 sides.

The vibrating member 50 thus bends and vibrates in accordance with the bending vibrations of the active regions R1 and R2, and generates sound. The vibration member 50 generates a sound due to the bending vibration of the active region R1 and a sound due to the bending vibration of the active region R2. As mentioned above, the reproduction frequency band of active region R1 is lower than the reproduction frequency band of active region R2. Therefore, the vibrating member 50 generates sound with improved sound quality in the low range due to the vibration of the active region R1, and generates sound with improved sound quality in the high range due to the vibration of the active region R2.

As explained above, the piezoelectric element 1 has active regions R1, R2 and an inactive region R3. The reproduction frequency band of active region R1 is lower than the reproduction frequency band of active region R2. Therefore, the active region R1 can improve the sound quality in the bass range, and the active region R2 can improve the sound quality in the treble range. In this way, the piezoelectric element 1 can improve sound quality in both the high and low ranges. Therefore, the size of the vibration device 100 can be reduced compared to the case where two piezoelectric elements are used to improve sound quality in the high or low range.

In the piezoelectric element 1, active regions R1 and R2 are separated from each other with an inactive region R3 interposed therebetween. Therefore, the vibrations of the active regions R1 and R2 are suppressed from mixing in the piezoelectric element body 2. Further, the inactive region R3 functions as a restraining body that restrains the vibrating member 50. Therefore, mixing of the vibrations caused by the active regions R1 and R2 in the vibrating member 50 is also suppressed. As a result, deterioration in sound quality in the vibrating device 100 can be suppressed. Since the through-hole conductors T1, T2, and T3 are provided in the inactive region R3, piezoelectric The space of the element body 2 can be effectively utilized.

In the piezoelectric element 1, the area of the active region R1 is larger than the area of the active region R2 when viewed from the direction D1. A configuration in which the reproduction frequency band of the active region R1 is lower than the reproduction frequency band of the active region R2 can be easily realized.

The piezoelectric element disclosed in Japanese Unexamined Patent Publication No. 2015-27154 has two active regions when viewed from the stacking direction. These two active regions flexurally vibrate in mutually opposite directions along the stacking direction in synchronization with each other. Therefore, in this piezoelectric element, the sounds generated by the two active regions vibrating the vibrating member tend to deviate from each other. In contrast, in the piezoelectric element 1, the active regions R1 and R2 bend and vibrate in synchronization with each other in the same direction along the stacking direction. Therefore, the sounds generated by the active regions R1 and R2 vibrating the vibration member 50 are unlikely to deviate from each other.

In the piezoelectric element 1, the external electrodes 11, 12, 13 are arranged together in the center of the main surface 2b, so that the external electrodes 11, 12, 13 and the control circuit can be easily connected with one wiring member. can. Therefore, the wiring member can be easily attached to the piezoelectric element 1.

(First variation)
FIG. 4 is a perspective view showing a vibration device according to a first modification. FIG. 5 is an exploded perspective view showing the piezoelectric element of FIG. 4. As shown in FIGS. 4 and 5, the vibrating device 100A according to the first modification is different from the vibrating device 100 (see FIG. 1) in that it includes a piezoelectric element 1A instead of the piezoelectric element 1 (see FIG. 1). They are different. Below, the piezoelectric element 1A will be explained focusing on the differences from the piezoelectric element 1.

In the piezoelectric element 1A, each external electrode 11, 12, 13 is provided continuously on the main surface 2b and the side surface 2e. That is, each external electrode 11, 12, 13 has a main surface electrode portion provided on the main surface 2b and a side electrode portion provided on the side surface 2e. The main surface electrode portion and the side surface electrode portion of each external electrode 11, 12, 13 are integrally formed with each other.

The external electrodes 11, 12, and 13 are arranged on the main surface 2b and the side surface 2e closer to the side surface 2d than the center in the long side direction of the main surface 2b. The external electrodes 11, 12, and 13 are spaced apart from each other in the long side direction of the main surface 2b. The external electrodes 11, 12, and 13 are arranged along the long side direction of the main surface 2b. The external electrodes 11, 12, and 13 are arranged in this order from the side surface 2c side toward the side surface 2d side. The side electrode portions of the external electrodes 11, 12, 13 extend from the edge on the main surface 2a side of the side surface 2e to the edge on the main surface 2b side, and are connected to the main surface electrode portions of the external electrodes 11, 12, 13. There is. The main surface electrode portions of the external electrodes 11, 12, and 13 are arranged at the edge of the main surface 2b on the side surface 2e side.

The piezoelectric element 1A does not have the internal electrodes 31, 32, 33 and the through-hole conductors T1, T2, T3 shown in FIG. The piezoelectric element 1A has an internal electrode 36 in addition to internal electrodes 34 and 35. The internal electrode 36 is made of the same conductive material as the internal electrodes 34 and 35, for example.

The internal electrode 36 is connected to the internal electrode 34 on the main surface 20b of each piezoelectric layer 20 (that is, each piezoelectric layer 20 from the first layer to the ninth layer) located other than the other end in the stacking direction. 35, and connects the internal electrode 34 and the internal electrode 35. The internal electrode 36 is provided on the side surface 2e side of the main surface 20b. The internal electrode 36 is spaced apart from the side surface 2e when viewed from the stacking direction.

The internal electrodes 41, 42, 43 are arranged so as to overlap the external electrodes 11, 12, 13 when viewed from the direction D3. In this embodiment, the internal electrodes 41, 42, 43 are exposed on the side surface 2e. One internal electrode 41 is provided on each main surface 20b of the first, third, fifth, seventh, and ninth piezoelectric layers 20. In each of these main surfaces 20b, the internal electrode 41 is arranged between the internal electrode 34 and the side electrode part of the external electrode 11, and connects the internal electrode 34 and the side electrode part of the external electrode 11 to each other. In each of these main surfaces 20b, the internal electrodes 34, 35, and 36 are electrically connected to each other, so the internal electrodes 34, 35, and 36 are all electrically connected to the external electrode 11.

One internal electrode 42 is provided on each main surface 20b of the second and fourth piezoelectric layers 20. In each of these main surfaces 20b, the internal electrode 42 is arranged between the internal electrode 36 and the side electrode part of the external electrode 12, and connects the internal electrode 36 and the side electrode part of the external electrode 12 to each other. In each of these main surfaces 20b, the internal electrodes 34, 35, and 36 are electrically connected to each other, so the internal electrodes 34, 35, and 36 are all electrically connected to the external electrode 12.

One internal electrode 43 is provided on each main surface 20b of the sixth and eighth piezoelectric layers 20. In each of these main surfaces 20b, the internal electrode 43 is arranged between the internal electrode 35 and the side electrode part of the external electrode 13, and connects the internal electrode 35 and the side electrode part of the external electrode 13 to each other. In each of these main surfaces 20b, the internal electrodes 34, 35, and 36 are electrically connected to each other, so the internal electrodes 34, 35, and 36 are all electrically connected to the external electrode 13.

Also in the piezoelectric element 1A, the reproduction frequency band of the active region R1 is lower than the reproduction frequency band of the active region R2. Therefore, the piezoelectric element 1A can also improve sound quality in both the high and low ranges. Therefore, it is possible to downsize the vibration device 100A. Furthermore, the active regions R1 and R2 are separated from each other with an inactive region R3 interposed therebetween. Therefore, this piezoelectric element 1A can also suppress deterioration in sound quality in the vibration device 100A.

(Second modification)
FIG. 6 is an enlarged cross-sectional view of a part of the vibration device according to the second modification. As shown in FIG. 6, the vibration device 100B according to the second modification includes a vibration member 50B instead of the vibration member 50 (see FIG. 3), and a joining member instead of the joining member 51 (see FIG. 3). It differs from the vibration device 100 (see FIG. 3) in that it includes a vibration device 51B. Below, the vibrating member 50B and the joining member 51B will be explained, focusing on the differences from the vibrating member 50 and the joining member 51.

The vibrating member 50B has vibrating parts V1 and V2. The vibrating portion V1 overlaps the active region R1 when viewed from the direction D1. The vibrating portion V2 overlaps the active region R2 when viewed from the direction D1. The vibrating member 50B is provided with a groove 50c on at least one of the main surfaces 50a and 50b to separate the vibrating parts V1 and V2 from each other. In this embodiment, two grooves 50c are provided in the main surface 50a. Each groove 50c extends along the short side direction of the main surface 2b, and is continuously provided from one end of the main surface 50a to the other end in the short side direction of the main surface 2b. The two grooves 50c are arranged between the active region R1 and the active region R2 when viewed from the direction D1, and are spaced apart from each other in the long side direction of the main surface 2b.

The joining member 51B has joining parts 51a, 51b, and 51c spaced apart from each other. The joint portion 51a overlaps the active region R1 when viewed from the direction D1. The joint portion 51b overlaps the active region R2 when viewed from the direction D1. The joint portions 51a and 51b do not overlap the groove 50c when viewed from the direction D1. The joint portion 51c is arranged between the joint portion 51a and the joint portion 51b when viewed from the direction D1. The joint portion 51c overlaps with a region between the active region R1 and the active region R2 in the inactive region R3 when viewed from the direction D1. The joint portion 51c is arranged between the two grooves 50c when viewed from the direction D1, and does not overlap with the two grooves 50c.

Joint parts 51a and 51b are harder than joint part 51c.

The vibration device 100B includes a piezoelectric element 1. Therefore, the vibration device 100B can also be made smaller. Further, deterioration in sound quality can be suppressed.

The vibrating member 50B has a vibrating portion V1 that overlaps with the active region R1, and a vibrating portion V2 that overlaps with the active region R2. The vibrating member 50B is provided with a groove 50c on the main surface 50a to separate the vibrating parts V1 and V2 from each other. The presence of the groove 50c in this way suppresses the vibrations from mixing with each other in the vibrating parts V1 and V2. Therefore, in the vibration device 100B, deterioration in sound quality can be further suppressed. Furthermore, since the vibrating member 50B is provided with two grooves 50c, deterioration in sound quality can be further suppressed compared to the case where one groove 50c is provided.

The bonding member 51B has a bonding portion 51a that overlaps with the active region R1, and a bonding portion 51b that overlaps with the active region R2. Since the joint portions 51a and 51b are spaced apart from each other, the vibrations of the active region R1 are suppressed from being transmitted to the vibrating portion V2, and the vibrations of the active region R2 are also suppressed from being transmitted to the vibrating portion V1. Thereby, in the vibrating member 50B, mixing of the vibrations caused by the active regions R1 and R2 is further suppressed. Therefore, in the vibration device 100B, deterioration in sound quality can be further suppressed.

Joint parts 51a and 51b are harder than joint part 51c. The higher the hardness, the easier vibration is transmitted. Therefore, the vibrations of the active regions R1, R2 are easily transmitted to the vibrating parts V1, V2 via the joint parts 51a, 51b.

(Third variation)
FIG. 7 is an enlarged cross-sectional view of a part of the vibration device according to the third modification. As shown in FIG. 7, the vibration device 100C according to the third modification includes a vibration member 50C instead of the vibration member 50 (see FIG. 3), and a joining member instead of the joining member 51 (see FIG. 3). It differs from the vibration device 100 (see FIG. 3) in that it includes the vibration device 51C. Since the joining member 51C has the same configuration as the joining member 51B (see FIG. 6), the description thereof will be omitted. The vibrating member 50C differs from the vibrating member 50B in that a groove 50c passes through the vibrating member 50C to connect the main surface 50a and the main surface 50b, and has the same configuration as the vibrating member 50B in other respects. have. In the vibrating device 100C, since the vibrating parts V1 and V2 are reliably separated from each other by the groove 50c, mixing of vibrations in the vibrating parts V1 and V2 is further suppressed. Therefore, deterioration in sound quality can be further suppressed. Since the vibration device 100C includes the piezoelectric element 1, it is possible to suppress deterioration in sound quality while achieving miniaturization.

The present invention is not necessarily limited to the embodiments and modified examples described above, and various changes can be made without departing from the gist thereof.

In the vibration devices 100B and 100C, two grooves 50c are provided, but one groove 50c may be provided, or three or more grooves 50c may be provided. In the vibration device 100B, the groove 50c is provided only on the main surface 50a, but may be provided on the main surface 50b. The grooves 50c may be provided on the main surfaces 50a and 50b, respectively. In this case, compared to the case where the groove 50c is provided only on the main surface 50a or only on the main surface 50b, mixing of vibrations between the vibrating portions V1 and V2 is further suppressed. Therefore, deterioration in sound quality can be further suppressed.

In the vibration devices 100B and 100C, the groove 50c is continuously provided from one end of the main surface 50a to the other end in the short side direction of the main surface 2b, but the groove 50c is provided continuously from one end of the main surface 50a in the short side direction of the main surface 2b. It may be provided in the section. The grooves 50c may be provided intermittently along the short side direction of the main surface 2b.

In the vibration devices 100B and 100C, the hardness of the joints 51a and 51b may be equal to the hardness of the joint 51c. In this case, the joint portions 51a, 51b, and 51c can be easily formed of the same material. In the vibration devices 100B and 100C, the joint portions 51a, 51b, and 51c do not need to be spaced apart from each other.

The vibrating devices 100 and 100A may include vibrating members 50B and 50C instead of the vibrating member 50. In the vibration devices 100 and 100A, a joining member 51B may be provided instead of the joining member 51. In the vibration devices 100B and 100C, a piezoelectric element 1A may be provided instead of the piezoelectric element 1.

DESCRIPTION OF SYMBOLS 1, 1A... Piezoelectric element, 2... Piezoelectric element body, 2a... Principal surface (first principal surface), 2b... Principal surface (second principal surface), 50, 50B, 50C... Vibration member, 50a... Principal surface (second principal surface) 3 principal surfaces), 50b...Main surface (fourth principal surface), 50c...Groove, 51, 51B, 51C...Joint member, 51a...Joint part (first joint part), 51b...Joint part (second joint part) , 51c... Junction (third junction), 100, 100A, 100B, 100C... Vibration device, R1... Active region (first active region), R2... Active region (second active region), R3... Inactive region .

Claims (8)

comprising a piezoelectric element body having a first principal surface and a second principal surface facing each other,
The piezoelectric element has a piezoelectrically active first active region and a second piezoelectrically active region, and a piezoelectrically inactive inactive region,
When viewed from the opposing direction of the first main surface and the second main surface, the first active region and the second active region are separated from each other via the inactive region provided with a through-hole conductor,
A piezoelectric element, wherein a reproduction frequency band of the first active region is lower than a reproduction frequency band of the second active region. The piezoelectric element according to claim 1 , wherein the area of the first active region is larger than the area of the second active region when viewed from the opposing direction. The piezoelectric element according to claim 1 or 2 , wherein the first active region and the second active region flexurally vibrate in the same direction along the opposing direction in synchronization with each other. a piezoelectric element including a piezoelectric element body having a first principal surface and a second principal surface facing each other;
a vibrating member having a third main surface joined to the first main surface, and a fourth main surface facing the third main surface,
The piezoelectric element has a piezoelectrically active first active region and a second piezoelectrically active region, and a piezoelectrically inactive inactive region,
When viewed from the opposing direction of the first main surface and the second main surface, the first active region and the second active region are separated from each other via the inactive region,
The reproduction frequency band of the first active region is lower than the reproduction frequency band of the second active region,
The vibrating member includes a first vibrating part that overlaps with the first active region and a second vibrating part that overlaps with the second active region, when viewed from the opposing direction,
The vibrating device, wherein the vibrating member is provided with a groove that separates the first vibrating part and the second vibrating part from each other on at least one of the third principal surface and the fourth principal surface. The vibration device according to claim 4 , wherein the groove passes through the vibration member so as to connect the third main surface and the fourth main surface. further comprising a joining member that joins the first main surface and the third main surface to each other,
The bonding member has a first bonding portion that overlaps with the first active region and a second bonding portion that overlaps with the second active region, when viewed from the opposing direction,
The vibrating device according to claim 4 or 5 , wherein the first joint part and the second joint part are spaced apart from each other. The bonding member further includes a third bonding portion disposed between the first bonding portion and the second bonding portion when viewed from the opposing direction,
The vibrating device according to claim 6 , wherein the first joint and the second joint are harder than the third joint. An electronic device comprising the piezoelectric element according to any one of claims 1 to 3 or the vibration device according to any one of claims 4 to 7 .

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