JP2015162728A - Piezoelectric actuator, piezoelectric vibration device including the same, portable terminal, acoustic generator, and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric actuator which enables adjustment of piezoelectric characteristics and achieves excellent piezoelectric characteristics, and to provide a piezoelectric vibration device including the piezoelectric actuator, a portable terminal, an acoustic generator, and an electronic apparatus.SOLUTION: In a piezoelectric actuator 1 of the invention, multiple surface electrodes 15 includes: a first surface electrode 151 electrically connected with a first internal electrode 121; a second surface electrode 152 electrically connected with a second internal electrode 122; and a third surface electrode 153 electrically connected with a third internal electrode 123. A flexible substrate 2 includes: a first wiring conductor 221 electrically connected with the first surface electrode 151; a second wiring conductor 222 electrically connected with the second surface electrode 152; and a third wiring conductor 223 electrically connected with the third surface electrode 153.

Description

  The present invention relates to a piezoelectric actuator suitable for a piezoelectric vibration device, a portable terminal, an acoustic generator, and an electronic device, and a piezoelectric vibration device, a portable terminal, an acoustic generator, and an electronic device including the piezoelectric actuator.

  There is known a piezoelectric element including a laminate in which a plurality of internal electrodes and a plurality of piezoelectric layers are laminated, and a plurality of surface electrodes provided on the surface of the laminate (see, for example, Patent Document 1). ). A piezoelectric actuator is known in which a flexible substrate for electrical connection with an external circuit is connected to the surface of a piezoelectric element.

  Here, in a conventional piezoelectric actuator provided with a piezoelectric element having a bimorph structure, a flexible substrate is provided with two wires for applying a voltage to the piezoelectric element.

JP 2007-109754 A

  Here, when the piezoelectric characteristics of the piezoelectric actuator deviate from the target characteristics, it is necessary to adjust the piezoelectric characteristics. However, the characteristics adjustment from the state where the flexible substrate having two wires is connected to the piezoelectric element is required. Was difficult.

  There is a need for a piezoelectric actuator that can adjust piezoelectric characteristics and has excellent piezoelectric characteristics, and a piezoelectric vibration device, a portable terminal, an acoustic generator, and an electronic device having the piezoelectric actuator.

  The present invention has been made in view of the above circumstances, and provides a piezoelectric actuator capable of adjusting piezoelectric characteristics and having excellent piezoelectric characteristics, and a piezoelectric vibration device, a portable terminal, an acoustic generator, and an electronic apparatus having the piezoelectric actuator. With the goal.

  The piezoelectric actuator of the present invention includes a laminate in which a plurality of internal electrodes and a plurality of piezoelectric layers are laminated, a plurality of surface electrodes provided on one main surface of the laminate, the plurality of internal electrodes, and the plurality of A piezoelectric element having a plurality of side electrodes electrically connected to the surface electrode, and a flexible substrate joined to one main surface of the piezoelectric element, wherein the plurality of internal electrodes are: First internal electrodes provided every other layer, second internal electrodes arranged every other layer so as to face the first internal electrode and disposed on one main surface side of the laminate, A third internal electrode that is disposed on the other main surface side of the multilayer body and provided in every other layer so as to face the first internal electrode, and the plurality of surface electrodes include the first internal electrode A first surface electrode electrically connected to A second surface electrode electrically connected to the second internal electrode, and a third surface electrode electrically connected to the third internal electrode, and the flexible substrate includes: A first wiring conductor electrically connected to the first surface electrode, a second wiring conductor electrically connected to the second surface electrode, and an electrical connection to the third surface electrode And a third wiring conductor formed.

  In the piezoelectric actuator of the present invention, in the above configuration, the piezoelectric element is a long plate body, and the first surface electrode extends from one end in the longitudinal direction of the one main surface of the laminate. The second surface electrode and the third surface electrode are disposed in the width direction of the stacked body with a gap provided between the other end portions in the longitudinal direction of the stacked body. The flexible substrate is joined so as to extend in the longitudinal direction from the other end portion of the piezoelectric element, and the first wiring conductor and the second wiring conductor and the third wiring conductor in a plan view. It is arrange | positioned between.

  Moreover, the piezoelectric actuator of the present invention is characterized in that, in the above configuration, the width of the flexible substrate is the same as or narrower than the width of the piezoelectric element.

  In the piezoelectric actuator of the present invention, in the above configuration, the second wiring conductor and the third wiring conductor are led out from the gap between the second surface electrode and the third surface electrode. It is characterized by.

  In the piezoelectric actuator of the present invention, in the above configuration, a constricted portion is provided close to an overlapping region that overlaps the piezoelectric element in the flexible substrate, and the constricted portion from above the overlapping region in the flexible substrate. A reinforcing plate is provided over at least a part of the structure.

  According to another aspect of the present invention, there is provided a piezoelectric vibration device including the above-described piezoelectric actuator and a vibration plate bonded to the other main surface of the piezoelectric element constituting the piezoelectric actuator.

  A portable terminal of the present invention includes the piezoelectric actuator, an electronic circuit, a display, and a housing. The other main surface of the piezoelectric element constituting the piezoelectric actuator is the display or the housing. It is characterized by being joined to the body.

  The portable terminal of the present invention is characterized in that it generates vibrations that convey sound information through at least one of ear cartilage and air conduction.

  The acoustic generator of the present invention is provided with the piezoelectric actuator described above, a diaphragm that is attached to the piezoelectric actuator, vibrates with the piezoelectric actuator by vibration of the piezoelectric actuator, and an outer peripheral portion of the diaphragm. And a frame body.

  According to another aspect of the invention, there is provided an electronic apparatus including the above-described acoustic generator, an electronic circuit connected to the acoustic generator, and a housing that houses the electronic circuit and the acoustic generator. It has a function of generating sound.

  According to the present invention, since the piezoelectric characteristics can be adjusted by applying a voltage while the flexible substrate is connected to the piezoelectric element, a piezoelectric actuator having excellent piezoelectric characteristics can be obtained.

(A) is a schematic perspective view which shows an example of embodiment of the piezoelectric actuator of this invention, (b) is a schematic perspective view of the piezoelectric element shown to (a), (c) is AA of (a). It is sectional drawing cut | disconnected by the line. (A) is sectional drawing cut | disconnected by the BB line shown to Fig.1 (a), (b) is sectional drawing cut | disconnected by the CC line | wire shown to Fig.1 (a). (A) is a schematic perspective view which shows the other example of embodiment of the piezoelectric actuator of this invention, (b) is sectional drawing cut | disconnected by the AA line shown to (a). It is a schematic perspective view which shows the other example of embodiment of the piezoelectric actuator of this invention. It is a schematic perspective view which shows the other example of embodiment of the piezoelectric actuator of this invention. 1 is a schematic perspective view schematically showing a piezoelectric vibration device according to an embodiment of the present invention. It is a schematic perspective view which shows typically the portable terminal of embodiment of this invention. It is the schematic sectional drawing cut | disconnected by the AA line shown in FIG. It is the schematic sectional drawing cut | disconnected by the BB line shown in FIG. (A) is a typical top view which shows schematic structure of embodiment of the acoustic generator of this invention, (b) is a schematic sectional drawing of an example cut | disconnected by the AA line of (a), ( (c) is a schematic sectional drawing of the other example cut | disconnected by the AA line of (a). It is a figure which shows the structure which concerns on embodiment of the electronic device of this invention.

  An example of an embodiment of a piezoelectric actuator of the present invention will be described in detail with reference to the drawings.

  1A is a schematic perspective view showing an example of an embodiment of the piezoelectric actuator of the present invention, FIG. 1B is a schematic perspective view of the piezoelectric element shown in FIG. 1A, and FIG. FIG. 1A is a cross-sectional view taken along line AA in FIG. 1A, and FIG. 1D is a cross-sectional view taken along line BB in FIG. 2A is a cross-sectional view taken along line BB shown in FIG. 1A, and FIG. 2B is a cross-sectional view taken along line CC shown in FIG.

  The piezoelectric actuator 1 of the example shown in FIGS. 1 and 2 includes a laminated body 14 in which a plurality of internal electrodes 12 and a plurality of piezoelectric layers 13 are laminated, and a plurality of surface electrodes provided on one main surface of the laminated body 14. 15, a piezoelectric element 11 having a plurality of internal electrodes 12 and a plurality of side electrodes 16 electrically connected to the plurality of surface electrodes 15, and a flexible substrate 2 joined to one main surface of the piezoelectric element 11. In the piezoelectric actuator 1, the plurality of internal electrodes 12 are arranged on the first main surface side of the multilayer body 14 so as to face the first internal electrodes 121. Second internal electrodes 122 provided in every other layer, and third internal electrodes arranged in every other layer so as to face the first internal electrode 121 and disposed on the other main surface side of the laminate 14 123, The number of surface electrodes 15 includes a first surface electrode 151 electrically connected to the first internal electrode 121, a second surface electrode 152 electrically connected to the second internal electrode 122, The flexible substrate 2 includes a first wiring conductor 221 electrically connected to the first surface electrode 151, a second surface electrode 153 electrically connected to the third internal electrode 123, and a second surface electrode 153 electrically connected to the first surface electrode 151. The second wiring conductor 222 electrically connected to the front surface electrode 152 and the third wiring conductor 223 electrically connected to the third surface electrode 153 are included.

  The piezoelectric actuator 1 of this example has a piezoelectric element 11, and a laminated body 14 constituting the piezoelectric element 11 is formed in a plate shape by laminating a plurality of internal electrodes 12 and a plurality of piezoelectric layers 13. It will be. The piezoelectric actuator 1 has an active portion in which a plurality of internal electrodes 12 overlap in the stacking direction and an inactive portion other than the active portion, and is formed in a long shape, for example. In the case of the piezoelectric actuator 1 attached to a display or casing of a mobile terminal, the length of the laminate 14 is preferably, for example, 18 mm to 28 mm, and more preferably 22 mm to 25 mm. The width of the laminated body 14 is preferably 1 mm to 6 mm, for example, and more preferably 3 mm to 4 mm. The thickness of the laminate 14 is preferably, for example, 0.2 mm to 1.0 mm, and more preferably 0.4 mm to 0.8 mm.

  The plurality of internal electrodes 12 constituting the multilayer body 14 are formed by simultaneous firing with ceramics that form the plurality of piezoelectric layers 13, and are alternately stacked with the piezoelectric layers 13 so that the piezoelectric layers 13 are arranged from above and below. It is sandwiched. Specifically, the first internal electrodes 121 provided every other layer and the second internal electrodes provided every other layer so as to face the first internal electrode 121 are disposed on the one main surface side of the multilayer body 14. Internal electrodes 122 and third internal electrodes 123 disposed on the other main surface side of the laminated body 14 and provided in every other layer so as to face the first internal electrodes 121. By arranging the second internal electrode 122 and the first internal electrode 121 on the upper side of the multilayer body 14 and arranging the third internal electrode 123 and the first internal electrode 121 on the lower side of the multilayer body 14, A drive voltage is applied to the piezoelectric layer 13 sandwiched between them. As this forming material, for example, a conductor mainly composed of silver or silver-palladium alloy having low reactivity with piezoelectric ceramics, or a conductor containing copper, platinum or the like can be used. You may make it contain.

  In the example shown in FIGS. 1 and 2, the end of the first internal electrode 121 is led out to one of a pair of opposing side surfaces of the multilayer body 14, and the end of the second internal electrode 122 and the third An end portion of the internal electrode 123 is led out to the other of the pair of opposing side surfaces of the multilayer body 14. In the case of a piezoelectric actuator attached to a display or casing of a mobile terminal, the length of the internal electrode 12 is preferably, for example, 17 mm to 25 mm, and more preferably 21 mm to 24 mm. For example, the width of the internal electrode 12 is preferably 1 mm to 5 mm, and more preferably 2 mm to 4 mm. The thickness of the internal electrode 12 is preferably 0.1 μm to 5 μm, for example.

The piezoelectric layer 13 constituting the laminated body 14 is formed of ceramics having piezoelectric characteristics. As such ceramics, for example, a perovskite oxide made of lead zirconate titanate (PbZrO ₃ -PbTiO ₃ ), Lithium niobate (LiNbO ₃ ), lithium tantalate (LiTaO ₃ ), or the like can be used. The thickness of one layer of the piezoelectric layer 13 is preferably set to 0.01 to 0.1 mm, for example, so as to be driven at a low voltage. In order to obtain a large bending vibration, it is preferable to have a piezoelectric constant d31 of 200 pm / V or more.

  A plurality of surface electrodes 15 electrically connected to the internal electrode 12 are provided on one main surface of the multilayer body 14. The plurality of surface electrodes 15 in the form shown in FIGS. 1 and 2 are configured by a first surface electrode 151 having a large area, a second surface electrode 152 having a small area, and a third surface electrode 153. For example, the first surface electrode 151 is electrically connected to the first internal electrode 121, and the second surface electrode 152 is a second internal electrode 122 and a third surface electrode 153 arranged on one main surface side. Is electrically connected to a third internal electrode 123 disposed on the other main surface side. In the case of a piezoelectric actuator attached to a display or casing of a portable terminal, the length of the first surface electrode 151 is preferably, for example, 17 mm to 23 mm, and more preferably 19 mm to 21 mm. The width of the first surface electrode 151 is, for example, preferably 1 mm to 5 mm, and more preferably 2 mm to 4 mm. The lengths of the second surface electrode 152 and the third surface electrode 153 are preferably 1 mm to 3 mm, for example. The widths of the second surface electrode 152 and the third surface electrode 153 are preferably 0.5 mm to 1.5 mm, for example.

  The piezoelectric actuator 1 has a flexible substrate 2 bonded to one main surface of the piezoelectric element 11. The flexible substrate 2 is a flexible print in which three wiring conductors 22 (a first wiring conductor 221, a second wiring conductor 222, and a third wiring conductor 223) are provided on the surface of a base film 21 made of resin, for example. It is a wiring board.

A part of the flexible substrate 2 is bonded to one main surface of the piezoelectric element 11 via the conductive bonding material 3, and the wiring conductor 22 is electrically connected to the surface electrode 15 via the conductive bonding material 3. Yes. Specifically, the first wiring conductor 221 is electrically connected to the first surface electrode 151,
The second wiring conductor 222 is electrically connected to the second surface electrode 152, and the third wiring conductor 223 is electrically connected to the third surface electrode 153. For example, the flexible substrate 2 is joined to the piezoelectric element 11 at one end, and joined to an external circuit (connector) at the other end.

  In this example, a cover film 23 is further provided in a region excluding the joint portion with the piezoelectric element 11 and the vicinity thereof. Since the cover film 23 is not provided in the region overlapping with the piezoelectric element 11 and the vicinity thereof, reliable electrical connection can be obtained without being affected by the thickness of the cover film 23.

  As the conductive bonding material 3, a conductive adhesive, solder, or the like is used, but a conductive adhesive is preferable. For example, conductive particles 31 made of, for example, gold, copper, nickel, or gold-plated resin balls are dispersed in a resin adhesive 32 such as acrylic resin, epoxy resin, silicone resin, polyurethane resin, or synthetic rubber. This is because the use of an adhesive can reduce stress caused by vibration compared to solder. More preferably, the conductive adhesive is preferably an anisotropic conductive material. The anisotropic conductive material is composed of conductive particles 31 responsible for electrical bonding and a resin adhesive 32 responsible for adhesion, and one conductive particle 31 is in contact with the surface electrode 15 and the wiring conductor 22. That is, the respective conductive particles 31 between the surface electrode 15 and the wiring conductor 22 are in contact with the surface electrode 15 and the wiring conductor 22. Since this anisotropic conductive material can conduct in the thickness direction and insulate in the in-plane direction, even in a narrow pitch wiring, there is no electrical short between the surface electrodes of different polarities, and a flexible substrate The connection part with 2 can be made compact.

  Further, the conductive bonding material 3 may have a portion extending from the overlapping region of the piezoelectric element 11 and the flexible substrate 2 to the outside of the overlapping region. The extended conductive bonding material 3 is bonded to the piezoelectric element 11 or the flexible substrate 2 in the extended region. The extended distance d1 is set to 0.05 mm to 1.5 mm, for example.

  According to this configuration, the bonding area between the piezoelectric element 11 and the flexible substrate 2 is increased by the extended conductive bonding material 3, so that the bonding strength is enhanced and the effect of absorbing vibration is increased. Moreover, it will become difficult to destroy by moving to the edge part of the electroconductive joining material 3 in which the fracture start point extended. As a result, the flexible substrate 2 can be prevented from peeling from the piezoelectric element 11 even when driven for a long time.

  In addition, as shown in FIG. 3, the piezoelectric actuator 1 of this example may include a reinforcing plate 4 fixed to a region overlapping the piezoelectric element 11 when viewed from above the flexible substrate 2. The reinforcing plate 4 is used to reinforce the bonding region of the flexible substrate 2 with the piezoelectric element 11. For example, glass epoxy (FR-4), composite (CEM-3), polyetherimide, polyimide, polyester, etc. It is a metal such as resin, stainless steel, aluminum and alloys thereof, and has a thickness of 50 to 200 μm, for example.

  Further, the reinforcing plate 4 may be provided with a bent portion 41. The bent portion 41 is a portion where the flexible substrate 2 is bent in the thickness direction of the reinforcing plate 4 (the stacking direction of the piezoelectric elements 11). According to this configuration, the vibration of the flexible substrate 2 is absorbed by the reinforcing plate 4, and when the vibration reaches the bent portion 41 of the reinforcing plate 4, vibration energy is further absorbed by the bent portion 41 and the vibration is attenuated. . As a result, the flexible substrate 2 is difficult to peel off even when driven for a long time.

As described above, the flexible substrate 2 includes the first wiring conductor 221 electrically connected to the first surface electrode 151 and the second wiring conductor 2 electrically connected to the second surface electrode 152.
22 and a third wiring conductor 223 electrically connected to the third surface electrode 153.

  When the piezoelectric element 11 is polarized, the first surface electrode 151, the first surface electrode 151, and the second surface electrode 151 are applied so that the polarization direction is reversed in the upper half region and the lower half region of the laminate 14. Two surface electrodes 152 and a third surface electrode 153 are provided. Then, the piezoelectric element 11 thus polarized is connected to two conventional wiring conductors (a wiring conductor connected to the first surface electrode 151, a second surface electrode 152, and a third surface electrode 153). By joining the flexible substrate 2 provided with the connected wiring conductors), when a voltage is applied to the two wiring conductors, when the upper half region expands, the lower half region contracts, and the upper half When the region is contracted, it is possible to cause a flexural vibration in which the lower half region extends. The piezoelectric actuator 1 is a so-called bimorph type piezoelectric actuator, which receives an electrical signal from the surface electrode 15 and vibrates and vibrates so that one main surface and the other main surface are bent surfaces.

  However, the upper half region and the lower half region of the laminate 14 may have variations in width and length and thickness variations, and even when the same voltage is applied, the amount of displacement may not be exactly the same. In such a case, the flexible substrate 2 having two wiring conductors cannot be adjusted by changing the polarization voltage again and performing polarization later.

  On the other hand, by providing the wiring conductors 22 of the flexible substrate 2 so as to correspond to the respective surface electrodes 15, in the state of the piezoelectric actuator 1 after the flexible substrate 2 is joined to the piezoelectric element 11, Since a polarization voltage can be applied to each of the upper half region and the lower half region, even if there is an individual difference in the deflection amount of the piezoelectric actuator 1, the polarization voltage value is changed and readjusted to make the deflection amount uniform. be able to. Therefore, the piezoelectric actuator 1 having excellent piezoelectric characteristics can be obtained.

  Here, as shown in the figure, the piezoelectric element 11 is a long plate body, and the first surface electrode 151 extends from one end in the longitudinal direction of one main surface of the laminate to the other end direction. The second surface electrode 152 and the third surface electrode 153 are arranged in the width direction of the multilayer body 14 with a gap provided at the other end portion in the longitudinal direction of the multilayer body 14. The flexible substrate 2 is joined so as to extend in the longitudinal direction from the other end of the piezoelectric element 11, and the first wiring conductor 221 is connected to the second wiring conductor 222 and the third wiring conductor 223 in plan view. It is preferable to arrange between them.

  When the piezoelectric element 11 (laminated body 14) is a long plate, the piezoelectric element 11 bends and vibrates in the longitudinal direction. Therefore, when the flexible substrate 2 is extended in a direction (short direction) intersecting the longitudinal direction of the piezoelectric element 11, in other words, when the flexible substrate 2 is extended from the long side of the piezoelectric element 11, the vibration of the piezoelectric element 11 causes There is a possibility that the flexible substrate 2 is easily twisted in the width direction and the flexible substrate 2 is easily peeled off from the piezoelectric element 11. On the other hand, since the flexible substrate 2 is joined so as to extend in the longitudinal direction from the other end portion of the piezoelectric element 11, the flexible substrate 2 is hardly twisted by vibration of the piezoelectric element 11. The possibility of peeling from the piezoelectric element 11 is reduced, and the piezoelectric actuator 1 with high reliability is obtained. At this time, the first wiring conductor 221 connected to the first surface electrode 151 away from the other end of the piezoelectric element 11 includes the second surface electrode 152 provided at the other end of the piezoelectric element 11 and the first surface electrode 152. 3 is arranged between the second wiring conductor 222 and the third wiring conductor 223 respectively connected to the surface electrode 153 of the third, because the arrangement balance of the wiring conductors in the width direction of the flexible substrate 2 is good, The twist of the flexible substrate 2 due to the vibration of the piezoelectric element 11 becomes smaller, and the possibility that the flexible substrate 2 is peeled from the piezoelectric element 11 is further reduced, so that the piezoelectric actuator 1 with higher reliability can be obtained.

Further, as shown in FIGS. 1 and 4, the width of the flexible substrate 2 is preferably the same as or narrower than the width of the piezoelectric element 11. By doing in this way, when mounting the piezoelectric actuator 1 in a portable terminal, an electronic device, etc., a space is saved and it can contribute to size reduction and mounting to a narrow space. Further, since there is no portion where the flexible substrate 2 protrudes in the width direction from the piezoelectric element 11, that is, a portion that is easily twisted by vibration of the piezoelectric element 11, the possibility that the flexible substrate 2 is peeled off from the piezoelectric element 11 is further reduced and more reliable. A high piezoelectric actuator 1 is obtained.

  In addition, as shown in FIG. 4, the second wiring conductor 222 and the third wiring conductor 223 may be drawn from between the second surface electrode 152 and the third surface electrode 153 in plan view. . By doing so, the first wiring conductor 221, the second wiring conductor 222, and the third wiring conductor 223 are arranged in the center of the flexible substrate 2 in the width direction. As a result, the twist of the flexible substrate 2 is reduced, and the possibility that the flexible substrate 2 is peeled off from the piezoelectric element 11 is further reduced, so that the piezoelectric actuator 1 is more reliable.

  In this case, it is preferable that the distal end portion of the second wiring conductor 222 and the distal end portion of the third wiring conductor 223 have a comb shape. In this way, even if the second wiring conductor 222 and the third wiring conductor 223 have a small width, the second wiring at the connection portion with the second surface electrode 152 and the third surface electrode 153 is used. Since the areas of the conductor 222 and the third wiring conductor 223 can be increased, connection reliability can be ensured.

  Further, as shown in FIG. 5, a constricted portion 20 is provided close to the overlapping region of the flexible substrate 2 that overlaps the piezoelectric element 11, and extends from above the overlapping region of the flexible substrate 2 to at least a part of the constricted portion 20. A reinforcing plate 4 is preferably provided. Due to the presence of the constricted portion 20, the deformability at the constricted portion 20 is improved, thereby improving the ease of mounting on a portable terminal, an electronic device, etc. Can be suppressed, and noise caused by unnecessary vibration can be suppressed. In addition, since the reinforcing plate 4 is provided from above the overlapping region of the flexible substrate 2 to at least a part of the constricted portion 20, the flexible substrate 2 is easily bent at a position away from the overlapping region that is the bonding region. Since it becomes difficult to apply stress to the region, the bonding strength against bending of the flexible substrate 2 is increased, and the reliability is improved.

  In addition, by making the other main surface of the piezoelectric element 11 flat, for example, when the other main surface is bonded to an object to be subjected to vibration (for example, a vibration plate described later), it is integrated with the object to be vibrated. As a result, bending vibration is easily generated, and the efficiency of bending vibration can be improved as a whole.

  Next, a method for manufacturing the piezoelectric actuator 1 of the present embodiment will be described.

First, a ceramic green sheet to be the piezoelectric layer 13 is produced. Specifically, a ceramic slurry is prepared by mixing a calcined powder of piezoelectric ceramic, a binder made of an organic polymer such as acrylic or butyral, and a plasticizer. And a ceramic green sheet is produced using this ceramic slurry by using tape molding methods, such as a doctor blade method and a calender roll method. As the piezoelectric ceramic, any material having piezoelectric characteristics may be used. For example, a perovskite oxide made of lead zirconate titanate (PbZrO ₃ —PbTiO ₃ ) can be used. As the plasticizer, dibutyl phthalate (DBP), dioctyl phthalate (DOP), or the like can be used.

Next, a conductive paste to be the internal electrode 12 is produced. Specifically, a conductive paste is prepared by adding and mixing a binder and a plasticizer to a silver-palladium alloy metal powder. This conductive paste is applied on the ceramic green sheet in the pattern of the internal electrodes 12 using a screen printing method. Furthermore, after laminating a plurality of ceramic green sheets printed with this conductive paste and performing a binder removal treatment at a predetermined temperature, firing at a temperature of 900 to 1200 ° C., using a surface grinder or the like By performing a grinding process so as to have a shape, a laminated body 14 including the internal electrodes 12 and the piezoelectric body layers 13 that are alternately laminated is manufactured.

  The laminated body 14 is not limited to the one produced by the above manufacturing method, and any production method can be used as long as the laminated body 14 formed by laminating a plurality of internal electrodes 12 and piezoelectric layers 13 can be produced. It may be produced.

  Thereafter, a silver glass-containing conductive paste prepared by adding a binder, a plasticizer, and a solvent to a mixture of conductive particles mainly composed of silver and glass is used as a main electrode of the laminate 14 in a pattern of the surface electrode 15. After printing on the surface and side surfaces by screen printing or the like and drying, baking is performed at a temperature of 650 to 750 ° C. to form the surface electrode 15 and the side electrode 16.

  Then, a voltage is applied to the surface electrode 15 or the side electrode 16 to polarize the piezoelectric layer 13 to produce a piezoelectric element.

  When the surface electrode 15 and the internal electrode 12 are electrically connected, a via that penetrates the piezoelectric layer 13 may be formed or connected, or a side electrode may be formed on the side surface of the multilayer body 14, It may be produced by any manufacturing method.

  Next, the flexible substrate 2 and the reinforcing plate 3 are prepared. For example, a polyimide sheet (multiple sheet for reinforcing plate) having a thickness of, for example, 125 μm that has been processed into a desired shape in advance, and a sheet in which a large number of flexible substrates 2 (base film 21) are arranged (multiple sheet for base film) Is attached to a predetermined position on the surface where the wiring conductor 22 is not provided using a thermosetting adhesive. Here, the reinforcing plate 3 having the bent portion 31 may be processed into a final shape together with the reinforcing plate 3 when the flexible substrate 2 is separated from the sheet using a mold or the like (when it is made into individual pieces). Alternatively, the reinforcing plate 3 processed into a final shape in advance with a mold or the like may be bonded to a predetermined position from the beginning.

  Next, the flexible substrate 2 is connected and fixed (bonded) to the piezoelectric element 11 using a conductive bonding member.

  First, a conductive bonding member paste made of, for example, solder, silver paste, anisotropic conductive material or the like is applied and formed at a predetermined position of the piezoelectric element 11 using a technique such as screen printing. Then, the flexible substrate 2 is connected and fixed to the piezoelectric element 11 by curing the conductive bonding member paste in a state where the flexible substrate 2 is brought into contact therewith. The conductive bonding member paste may be applied and formed on the flexible substrate 2 side.

  When the conductive bonding member is a conductive adhesive and the resin constituting the conductive adhesive is made of a thermoplastic resin, the conductive adhesive is applied to a predetermined position of the piezoelectric element 11 or the flexible substrate 2. After forming, the thermoplastic resin softens and flows by heating and pressurizing in a state where the piezoelectric element 11 and the flexible substrate 2 are in contact with each other via a conductive adhesive, and then returned to room temperature to be thermoplastic again. The resin is cured and the flexible substrate 2 is connected and fixed to the piezoelectric element 11.

In the above description, the method of applying and forming the conductive adhesive on the piezoelectric element 11 or the flexible substrate 2 has been described. However, a sheet of the conductive adhesive formed in a sheet shape in advance between the piezoelectric element 11 and the flexible substrate 2 is used. You may heat-press and join in the state pinched | interposed.

  Further, a flexible substrate 2 (to be described later) is bonded to the piezoelectric element 11 using a mold having a desired shape, and at the same time, the reinforcing plate 3 is fixed to the flexible substrate 2 and the bent portion 31 is formed on the reinforcing plate 3. May be.

  The piezoelectric actuator 1 can be manufactured by the above method.

  If there is a deviation in the capacitance value of the manufactured piezoelectric actuator 1, the capacitance value is readjusted by adjusting the polarization voltage value. Since there is a correlation between the polarization voltage and the capacitance value, the capacitance value can be adjusted by adjusting the polarization voltage value, and the capacitance variation of the piezoelectric actuator 1 can be suppressed.

  Usually, in a piezoelectric actuator in which a flexible substrate is connected to a piezoelectric element, when there are two wiring conductors provided on the flexible substrate, one main surface side led out to the other of a pair of opposing side surfaces of the laminate Since the (upper) internal electrode and the other main surface (lower) internal electrode are electrically connected and voltage is applied at the same time, the displacement of the piezoelectric actuator deviates from the target value due to variations in capacitance values. In some cases, readjustment was impossible.

  On the other hand, the piezoelectric actuator 1 of the present invention has three wiring conductors 22 provided on the flexible substrate 2 and is electrically connected to the internal electrode 12 on one main surface side (upper side) of the piezoelectric element 10. Since the wiring conductor 22 and the wiring conductor 22 electrically connected to the internal electrode 12 on the other main surface side (lower side) exist independently, the internal electrode 12 on the one main surface side (upper side) Since a voltage can be applied independently to the internal electrode 12 on the other main surface side (lower side), when there is a deviation in the capacitance value of the piezoelectric actuator 1, the one main surface side (upper side) and the other main surface side A voltage can be individually applied to the surface side (lower side).

  As shown in FIG. 6, the piezoelectric vibration device of the present embodiment includes a piezoelectric actuator 1 and a vibration plate 81 joined to the other main surface of the piezoelectric element 11 constituting the piezoelectric actuator 1. Note that the flexible substrate 2 bonded to one main surface of the piezoelectric element 11 is omitted in FIG.

  The diaphragm 81 is, for example, a rectangular thin plate. The diaphragm 81 can be preferably formed using a material having high rigidity and elasticity, such as acrylic resin or glass. Moreover, the thickness of the diaphragm 81 is set to 0.4 mm to 1.5 mm, for example.

  The diaphragm 81 is joined to the other main surface of the piezoelectric element 11 via a joining member 82. The entire surface of the other main surface may be bonded to the vibration plate 81 via the bonding member 82, or the substantially entire surface may be bonded.

  The joining member 82 has a film shape. Further, the joining member 82 is formed of a material that is softer and more easily deformed than the vibration plate 81, and has a smaller elastic modulus and rigidity such as Young's modulus, rigidity, and bulk elastic modulus than the vibration plate 81. That is, the joining member 82 can be deformed when the diaphragm 81 is vibrated by driving the piezoelectric actuator 1 (piezoelectric element 11), and deforms more greatly than the diaphragm 81 when the same force is applied. is there. Then, the other main surface (main surface on the −z direction side in the drawing) of the multilayer body 11 is fixed to one main surface (main surface on the + z direction side in the drawing) of the bonding member 82, so A part of one main surface (main surface on the + z direction side in the drawing) of the diaphragm 81 is fixed to the other main surface (main surface on the −z direction side in the drawing).

  When the vibration is transmitted from the piezoelectric actuator 1 by joining the piezoelectric element 11 and the diaphragm 81 with the joining member 82 that is deformable than the diaphragm 81, the deformable joining member 82 is larger than the diaphragm 81. Deform.

  At this time, the anti-phase vibration reflected from the vibration plate 81 can be mitigated by the deformable joining member 82, so that the piezoelectric actuator 1 (piezoelectric element 11) is not affected by the surrounding vibration and the vibration plate 81. Strong vibrations can be transmitted.

  In particular, since at least a part of the joining member 82 is made of a viscoelastic body, strong vibration from the piezoelectric actuator 1 (piezoelectric element 11) is transmitted to the vibration plate 81, while weak vibration reflected from the vibration plate 81. Is preferable in that the bonding member 82 can absorb. For example, it is possible to use a double-sided tape in which an adhesive is attached to both surfaces of a base material made of nonwoven fabric or the like, or a joining member including an adhesive having elasticity, and the thickness thereof is, for example, 10 μm to 2000 μm. Can be used.

  The joining member 82 may be a single member or a composite made up of several members. As such a joining member 82, for example, a double-sided tape in which a pressure-sensitive adhesive is attached to both surfaces of a base material made of a nonwoven fabric or the like, various elastic adhesives that are adhesives having elasticity, and the like can be suitably used. Further, the thickness of the bonding member 82 is preferably larger than the amplitude of the bending vibration of the piezoelectric actuator 1 (piezoelectric element 11). However, if the thickness is too thick, the vibration is attenuated. Is set. However, in the piezoelectric vibration device of the present invention, the material of the bonding member 82 is not limited, and the bonding member 82 may be formed of a material that is harder and more difficult to deform than the vibration plate 81. Moreover, depending on the case, the structure which does not have the joining member 82 may be sufficient.

  The piezoelectric vibration device of this example having such a configuration functions as a piezoelectric vibration device that flexibly vibrates the piezoelectric actuator 1 (piezoelectric element 11) by applying an electric signal, thereby vibrating the vibration plate 81. The other end in the length direction of the diaphragm 81 (the end in the −y direction in the figure, the peripheral edge of the diaphragm 81, etc. may be supported by a support member not shown).

  In the piezoelectric vibration device of this example, a diaphragm 81 is joined to the other flat main surface of the piezoelectric element 11. Thereby, a piezoelectric vibration device in which the piezoelectric element 11 and the vibration plate 81 are firmly bonded can be obtained.

  Moreover, since the piezoelectric vibration device of this example is configured using the piezoelectric actuator 1 having excellent piezoelectric characteristics, it can be a high-performance piezoelectric vibration device.

  As shown in FIGS. 7 to 9, the mobile terminal of the present embodiment includes the piezoelectric actuator 1, an electronic circuit (not shown), a display 91, and a housing 92. The other main surface of the constituting piezoelectric element 11 is bonded to a display 91 or a casing 92. 6 is a schematic perspective view schematically showing the portable terminal of the present invention, FIG. 8 is a schematic cross-sectional view taken along line AA shown in FIG. 7, and FIG. 9 is a line BB shown in FIG. It is the schematic sectional drawing cut | disconnected by. A flexible substrate bonded to one main surface of the piezoelectric element 11 is omitted in FIGS.

  In this example, the piezoelectric actuator 1 is attached to a part of a casing 92 that serves as a cover for the display 91, and a part of the casing 92 functions as the diaphragm 922.

The housing 92 includes a box-shaped housing main body 921 having one surface opened, and a diaphragm 922 that closes the opening of the housing main body 921. The casing 92 (the casing main body 921 and the diaphragm 922) can be formed preferably using a material such as a synthetic resin having high rigidity and elastic modulus.

  A peripheral edge portion of the vibration plate 922 is attached to the housing main body 921 via a bonding material 93 so as to vibrate. The bonding material 93 is formed of a material that is softer and easier to deform than the diaphragm 922, and has a smaller elastic modulus and rigidity such as Young's modulus, rigidity, and bulk modulus than the diaphragm 922. That is, the bonding material 93 can be deformed, and deforms more greatly than the diaphragm 922 when the same force is applied.

  The bonding material 93 may be a single material or a composite material composed of several members. As such a bonding material 93, for example, a double-sided tape in which an adhesive is attached to both surfaces of a base material made of a nonwoven fabric or the like can be suitably used. The thickness of the bonding material 93 is set so that vibration is not attenuated due to being too thick, and is set to, for example, 0.1 mm to 0.6 mm. However, in the mobile terminal of the present invention, the material of the bonding material 93 is not limited, and the bonding material 93 may be formed of a material that is harder than the vibration plate 922 and hardly deforms. Moreover, depending on the case, the structure which does not have the joining material 93 may be sufficient.

  Examples of the electronic circuit (not shown) include a circuit that processes image information displayed on the display 91 and audio information transmitted by the mobile terminal, a communication circuit, and the like. At least one of these circuits may be included, or all the circuits may be included. Further, it may be a circuit having other functions. Furthermore, you may have a some electronic circuit. The electronic circuit and the piezoelectric actuator 1 are connected by a connection wiring (not shown).

  The display 91 is a display device having a function of displaying image information. For example, a known display such as a liquid crystal display or an organic EL display can be suitably used. The display 91 may have an input device such as a touch panel. Moreover, the cover (diaphragm 922) of the display 91 may have an input device such as a touch panel. Further, the entire display 91 or a part of the display 91 may function as a diaphragm.

  The portable terminal has a communication means (communication unit) that transmits and receives data via an antenna or the like. For example, mobile phones such as smartphones, mobile devices such as tablet PCs and notebook PCs, game machines, and the like can be given.

  Here, it is preferable that the piezoelectric actuator 1 and the housing 92 (the vibration plate 922) are joined by using a joining member that can be deformed more than the housing 92 (the vibration plate 922). That is, in FIG. 8 and FIG. 9, the joining member 82 is a deformable joining member.

  By joining the piezoelectric actuator 1 and the housing 92 with a joining member 82 that can be deformed more than the housing 92, the deformable joining member 82 is larger than the housing 92 when vibration is transmitted from the piezoelectric actuator 1. Deform. The joining member 82 can be deformed when the housing 92 is vibrated by driving the piezoelectric actuator 1, and is deformed to be larger than the housing 92 when the same force is applied. Such a joining member 82 has, for example, a film shape. The housing 92 is made of a material that is softer and more easily deformed, and has a smaller elastic modulus and rigidity such as Young's modulus, rigidity, and bulk modulus than the housing 92.

  At this time, the anti-phase vibration reflected from the casing 92 can be mitigated by the deformable joining member 82, so that the piezoelectric actuator 1 transmits strong vibration to the casing 92 without being affected by the surrounding vibration. Can be made.

In particular, since at least a part of the joining member 82 is made of a viscoelastic body, strong vibration from the piezoelectric actuator 1 is transmitted to the housing 92, while the joining member 82 transmits weak vibration reflected from the housing 92. It is preferable in that it can be absorbed. For example, it is possible to use a double-sided tape in which an adhesive is attached to both surfaces of a base material made of nonwoven fabric or the like, or a joining member including an adhesive having elasticity, and the thickness thereof is, for example, 10 μm to 2000 μm. Can be used.

  In this example, the piezoelectric actuator 1 is bonded to the housing 92. However, the piezoelectric actuator 1 may be bonded to the display 91. In this case, the piezoelectric actuator 1 and the display 91 are more than the display 91. It is preferable to join using a deformable joining member.

  In addition, the mobile terminal according to the present embodiment is characterized in that the display 91 or the casing 92 generates vibration that transmits sound information through the ear cartilage or air conduction. The portable terminal of this example can transmit sound information by transmitting a vibration to the cartilage of the ear by bringing the diaphragm (display 91 or housing 92) into contact with the ear directly or via another object. That is, sound information can be transmitted by bringing a vibration plate (display 91 or housing 92) into direct or indirect contact with the ear and transmitting vibration to the cartilage of the ear. Thereby, for example, sound information can be transmitted clearly even when the surroundings are noisy, and a mobile terminal can be obtained in which sound can be heard clearly even under noise, and even a hearing-impaired person can recognize the sound. Note that the object interposed between the diaphragm (display 91 or housing 92) and the ear may be, for example, a cover of a mobile terminal, a headphone or an earphone, and any object that can transmit vibration. Anything can be used. Further, it may be a portable terminal that transmits sound information by propagating sound generated from the diaphragm (display 91 or housing 92) in the air. Furthermore, it may be a portable terminal that transmits sound information via a plurality of routes.

  According to the portable terminal of this example, since it is configured using the piezoelectric actuator 1 having excellent piezoelectric characteristics, a high-quality portable terminal can be obtained.

  Further, as shown in FIG. 10, the acoustic generator 10 of the present embodiment has the piezoelectric actuator 1 described above and the piezoelectric actuator 1 attached thereto, and a diaphragm 20 that vibrates together with the piezoelectric actuator 1 due to the vibration of the piezoelectric actuator 1. And a frame body 30 provided on the outer peripheral portion of the diaphragm 20.

  The piezoelectric actuator 1 is an exciter that excites the diaphragm 20 by vibrating under application of a voltage. The main surface of the piezoelectric actuator 1 and the main surface of the vibration plate 20 are joined by an adhesive such as an epoxy resin, and the piezoelectric actuator 1 bends and vibrates, so that the piezoelectric actuator 1 gives a certain vibration to the vibration plate 20. Sound can be generated.

  The periphery of the diaphragm 20 is fixed to the frame 30 in a state where tension is applied, and the diaphragm 20 vibrates with the piezoelectric actuator 1 by the vibration of the piezoelectric element actuator 1. The diaphragm 20 can be formed using various materials such as resin and metal. For example, the diaphragm 20 can be formed of a resin film such as polyethylene, polyimide, or polypropylene having a thickness of 10 to 200 μm. Since the resin film is a material having a lower elastic modulus and mechanical Q value than a metal plate or the like, the diaphragm 20 is made of a resin film, so that the diaphragm 20 bends and vibrates with a large amplitude, thereby reducing the sound pressure. It is possible to reduce the difference between the resonance peak and the dip by widening the width of the resonance peak and reducing the height in the frequency characteristics.

The frame body 30 functions as a support body that supports the diaphragm 20 at the periphery of the diaphragm 20, and can be formed using various materials such as metals such as stainless steel and resins. This frame 3
May be composed of one frame member (upper frame member 301) as shown in FIG. 10B, and two frame members (upper frame member 301 and lower frame member 302 as shown in FIG. 10C). ). In this case, the tension of the diaphragm 2 can be stabilized by sandwiching the diaphragm 20 between the two frame members. The upper frame member 301 and the lower frame member 302 have a thickness of, for example, 100 to 5000 μm.

  In the acoustic generator 10 of this example, as shown in FIGS. 10B and 10C, the acoustic generator 10 is provided so as to cover from the piezoelectric actuator 1 to at least the periphery of the piezoelectric actuator 1 on the surface of the diaphragm 20. It is preferable to further have a resin layer 40. As the resin layer 40, for example, an acrylic resin can be used. By embedding the piezoelectric actuator 1 (piezoelectric element 11) in the resin layer 40, an appropriate damper effect can be induced, so that the resonance phenomenon is suppressed and the peak or dip in the frequency characteristic of the sound pressure is suppressed to be small. Can do. 10B and 10C, the resin layer 40 may be formed to have the same height as the upper frame member 301.

  Since such a sound generator 10 is configured using the piezoelectric actuator 1 having excellent piezoelectric characteristics, it can emit high-quality sound.

  Next, an electronic device equipped with an acoustic generator will be described with reference to FIG. FIG. 11 is a diagram illustrating a configuration of the electronic device 50 according to the embodiment. In the figure, only components necessary for explanation are shown, and descriptions of general components are omitted.

  As shown in FIG. 11, the electronic device 50 of this example includes an acoustic generator 10, an electronic circuit 60 connected to the acoustic generator 10, and a housing 70 that houses the electronic circuit 60 and the acoustic generator 10. And having a function of generating sound from the sound generator 10.

  The electronic device 50 includes an electronic circuit 60. The electronic circuit 60 includes, for example, a controller 50a, a transmission / reception unit 50b, a key input unit 50c, and a microphone input unit 50d. The electronic circuit 60 is connected to the sound generator 10 and has a function of outputting an audio signal to the sound generator 10. The sound generator 10 generates sound based on the sound signal input from the electronic circuit 60.

  The electronic device 50 includes a display unit 50e, an antenna 50f, and the sound generator 10. Further, the electronic device 50 includes a housing 70 that accommodates these devices. Although FIG. 11 shows a state in which each device including the controller 50a is accommodated in one casing 70, the accommodation form of each device is not limited. In the present embodiment, it is only necessary that at least the electronic circuit 60 and the sound generator 10 are accommodated in one housing 70.

  The controller 50 a is a control unit of the electronic device 50. The transmission / reception unit 50b transmits / receives data via the antenna 50f based on the control of the controller 50a. The key input unit 50c is an input device of the electronic device 50 and accepts a key input operation by an operator. The microphone input unit 50d is also an input device of the electronic device 50, and accepts a voice input operation by an operator. The display unit 50e is a display output device of the electronic device 50, and outputs display information based on the control of the controller 50a.

  The sound generator 10 operates as a sound output device in the electronic device 50. The sound generator 10 is connected to the controller 50a of the electronic circuit 60, and emits sound upon application of a voltage controlled by the controller 50a.

  In FIG. 11, the electronic device 50 has been described as a portable terminal device. However, the electronic device 50 is not limited to the type of the electronic device 50, and may be applied to various consumer devices having a function of generating sound. For example, flat-screen televisions and car audio devices can of course be used for products having a function of generating sound, for example, various products such as vacuum cleaners, washing machines, refrigerators, microwave ovens, and the like.

  According to the electronic device 50 of this example, since the sound generator 1 with improved sound quality is used, a high sound quality electronic device can be obtained. In addition, by providing the housing 70, it is possible to increase the low-frequency sound pressure.

1: piezoelectric actuator 11: piezoelectric element 12: internal electrode 121: first internal electrode 122: second internal electrode 123: third internal electrode 13: piezoelectric layer 14: laminate 15: surface electrode 151: first Surface electrode 152: second surface electrode 153: third surface electrode 16: side electrode 2: flexible substrate 21: base film 22: wiring conductor 221: first wiring conductor 222: second wiring conductor 223: second 3 wiring conductor 23: cover film 3: conductive bonding material 31: conductive particles 32: resin adhesive 4: reinforcing plate 41: bending portion 81: vibration plate 82: bonding member 91: display 92: housing 921: housing Main body 922: Diaphragm 93: Bonding material 10: Sound generator 20: Diaphragm 30: Frame body 301: Upper frame member 302: Lower frame member 40: Resin layer 50: Electronic device 60: Electronic circuit 70: Housing 50a Controller 50b: transceiver 50c: key input unit 50d: microphone input unit 50e: Display unit 50f: Antenna

Claims (10)

  A laminate in which a plurality of internal electrodes and a plurality of piezoelectric layers are laminated, a plurality of surface electrodes provided on one main surface of the laminate, and the plurality of internal electrodes and the plurality of surface electrodes are electrically connected A piezoelectric actuator comprising a piezoelectric element having a plurality of side electrodes connected to the piezoelectric element and a flexible substrate bonded to one main surface of the piezoelectric element, wherein the plurality of internal electrodes are provided every other layer. A first internal electrode; a second internal electrode disposed on every other layer so as to face the first internal electrode and disposed on one main surface side of the laminate; and the other main surface of the laminate And a plurality of third internal electrodes provided on every other side so as to face the first internal electrode, and the plurality of surface electrodes are electrically connected to the first internal electrode. The first surface electrode and the second internal electrode electrically A second surface electrode connected and a third surface electrode electrically connected to the third internal electrode, wherein the flexible substrate is electrically connected to the first surface electrode; A first wiring conductor; a second wiring conductor electrically connected to the second surface electrode; and a third wiring conductor electrically connected to the third surface electrode. A piezoelectric actuator characterized by that.   The piezoelectric element is a long plate body, and the first surface electrode extends from one end to the other end in the longitudinal direction of the one main surface of the laminate, and the second surface electrode and The third surface electrode is disposed in the width direction of the multilayer body with a gap provided between the other end portions in the longitudinal direction of the multilayer body, and the flexible substrate is disposed on the other end portion of the piezoelectric element. And the first wiring conductor is disposed between the second wiring conductor and the third wiring conductor in a plan view. The piezoelectric actuator according to 1.   The piezoelectric actuator according to claim 2, wherein a width of the flexible substrate is equal to or smaller than a width of the piezoelectric element.   2. The plan view of claim 2, wherein the second wiring conductor and the third wiring conductor are led out from the gap between the second surface electrode and the third surface electrode. The piezoelectric actuator according to claim 3.   A constricted portion is provided close to an overlapping region of the flexible substrate that overlaps the piezoelectric element, and a reinforcing plate is provided from above the overlapping region of the flexible substrate to at least a part of the constricted portion. The piezoelectric actuator according to any one of claims 1 to 4, wherein the piezoelectric actuator is characterized.   6. A piezoelectric vibration device comprising: the piezoelectric actuator according to claim 1; and a vibration plate joined to the other main surface of the piezoelectric element constituting the piezoelectric actuator. The piezoelectric actuator according to any one of claims 1 to 5, an electronic circuit, a display, and a housing,
A portable terminal, wherein the other main surface of the piezoelectric element constituting the piezoelectric actuator is joined to the display or the casing.   8. The portable terminal according to claim 7, wherein the display or the casing generates vibration that transmits sound information through at least one of ear cartilage and air conduction. A piezoelectric actuator according to any one of claims 1 to 5, a diaphragm to which the piezoelectric actuator is attached, which vibrates with the piezoelectric actuator by vibration of the piezoelectric actuator, and an outer peripheral portion of the diaphragm A sound generator comprising: a frame body provided on the sound generator.   A function of generating sound from the sound generator, comprising: the sound generator according to claim 9; an electronic circuit connected to the sound generator; and a housing that houses the electronic circuit and the sound generator. An electronic device comprising:

Images