WO2017145649A1

WO2017145649A1 - Acoustic generator and electronic apparatus provided with same

Info

Publication number: WO2017145649A1
Application number: PCT/JP2017/003090
Authority: WO
Inventors: 悟岩崎
Original assignee: 京セラ株式会社
Priority date: 2016-02-25
Filing date: 2017-01-30
Publication date: 2017-08-31
Also published as: JP6585821B2; JPWO2017145649A1

Abstract

Disclosed is an acoustic generator that is provided with: a laminated piezoelectric element 1 having a laminated body 13 in which piezoelectric layers 11 and internal electrode layers 12 are alternately laminated; and a diaphragm 2 having a main surface. The laminated piezoelectric element 1 is disposed such that the lamination direction is along the main surface of the diaphragm 2. Consequently, since displacement in the lamination direction of the laminated piezoelectric element, said displacement being what is called displacement in the d33 mode, is used for the purpose of vibrating the diaphragm, a piezoelectric d constant becomes large compared with that in displacement in the d31 mode, and the displacement quantity and generative force of the laminated piezoelectric element can be improved.

Description

SOUND GENERATOR AND ELECTRONIC DEVICE HAVING THE SAME

The present disclosure relates to an acoustic generator and an electronic device including the same.

Conventionally, there has been known a piezoelectric vibration device including a diaphragm and a laminated piezoelectric element joined to a main surface of the diaphragm via a joining member. Such a piezoelectric vibration device can also be applied to an acoustic generator (see, for example, Patent Document 1).

Here, the piezoelectric vibration device and the sound generator described above join the main surface of the plate-shaped multilayer piezoelectric element to the main surface of the diaphragm so that the direction perpendicular to the main surface of the diaphragm is the stacking direction, A d31 mode displacement is generated in the multilayer piezoelectric element, and bending vibration is generated in the multilayer piezoelectric element and the diaphragm.

International Publication No. 2013/046909

The acoustic generator of the present disclosure includes a laminated piezoelectric element having a laminated body in which piezoelectric layers and internal electrode layers are alternately laminated, and a diaphragm having a main surface, and the laminated piezoelectric element has a laminating direction. Is disposed along the main surface of the diaphragm.

Also, an electronic device of the present disclosure includes the acoustic generator, an electronic circuit connected to the acoustic generator, and a housing that houses the electronic circuit and the acoustic generator.

(A) is a schematic perspective view which shows an example of the sound generator of this embodiment, (b) is a schematic side view of the sound generator shown to (a). It is a schematic side view which shows the other example of the acoustic generator of this embodiment. It is a schematic side view which shows the other example of the acoustic generator of this embodiment. It is a schematic perspective view which shows the other example of the acoustic generator of this embodiment. It is a block diagram which shows an example of the electronic device of this embodiment. It is a figure which shows the sound pressure characteristic of an example of the acoustic generator of this embodiment.

Hereinafter, an example of the sound generator of the present embodiment will be described in detail with reference to the accompanying drawings. In addition, this invention is not limited by embodiment shown below.

FIG. 1A is a schematic perspective view showing an example of the sound generator of the present embodiment, and FIG. 1B is a schematic side view of the sound generator shown in FIG. The acoustic generator 10 of the example shown in FIG. 1 includes a laminated piezoelectric element 1 having a laminated body 13 in which piezoelectric layers 11 and internal electrode layers 12 are alternately laminated, and a diaphragm 2 having a main surface. In the multilayer piezoelectric element 1, the stacking direction is arranged along the main surface of the diaphragm 2.

The multilayer body 13 constituting the multilayer piezoelectric element 1 has active portions in which a plurality of piezoelectric layers 11 and internal electrode layers 12 are alternately stacked, and both ends in the stacking direction of the multilayer body 13 positioned outside the active portion. And an inactive portion made of the piezoelectric layer 11 provided. The laminated body 13 is formed in a rectangular parallelepiped shape, for example, and when disposed on the main surface of the diaphragm 2 described later, the thickness t in the direction perpendicular to the main surface of the diaphragm 2 is, for example, 1.0 to 5.0 mm. The length L in the stacking direction parallel to the main surface of the diaphragm 2 is, for example, 5.0 to 50 mm, and the width W in the direction parallel to the main surface of the diaphragm 2 and perpendicular to the stacking direction is, for example, 1.0 to 10 mm. The dimensions are as follows.

Note that the laminated body 13 in which the piezoelectric layers 11 and the internal electrode layers 12 are alternately laminated may include an active portion in which the piezoelectric layers 11 and the internal electrode layers 12 are alternately laminated. It does not exclude the configuration in which inactive portions are present at both ends in the stacking direction as described above.

The piezoelectric layer 11 constituting the multilayer body 13 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 11 is preferably set to, for example, 0.01 to 0.1 mm in order to drive at a low voltage.

The internal electrode layer 12 constituting the laminate 13 is fired at the same time as the ceramic forming the piezoelectric layer 11. The internal electrode layer 12 includes a first internal electrode layer 121 and a second internal electrode layer 122 which are different poles, and applies a driving voltage to the piezoelectric layer 11 sandwiched therebetween. As a material for the internal electrode layer 12, for example, a conductor mainly composed of silver or a silver-palladium alloy that can be fired at a low temperature, or a conductor containing copper, platinum, or the like can be used. You may make it contain. The thickness of one layer of the internal electrode layer 12 is, for example, 0.1 to 5 μm.

The stacked body 13 has two end faces located at one end and the other end in the stacking direction, and four side faces. The first internal electrode layer 121 or the second internal electrode layer 122 (one of the first internal electrode layer 121 and the second internal electrode layer 122) is formed on a pair of side surfaces facing each other among the four side surfaces. Has been derived. Further, the end surfaces of both the first internal electrode layer 121 and the second internal electrode layer 122 are exposed on the other pair of side surfaces facing each other among the four side surfaces.

The external electrode layer 14 is provided on each of a pair of opposing side surfaces from which the first internal electrode layer 121 or the second internal electrode layer 122 is derived in the stacked body 13. The pair of external electrode layers 14 are made of, for example, a conductive paste containing a metal metal such as Ag or Cu, and are provided on opposite side surfaces of the laminate 13 from the active portion to the inactive portion. . Here, when the external electrode layer 14 is viewed in a cross section perpendicular to the side surface of the multilayer body 13, the thickness of the external electrode layer 14 is set to, for example, 5 to 70 μm.

Although not shown, a coating layer may be provided so as to surround a part or the whole of the side surface of the laminated body 13. This covering layer is provided in order to suppress migration or discharge that occurs through the end portion of the internal electrode layer 12 provided so as to reach the side surface of the multilayer body 13 and be exposed. If necessary, an external electrode plate may be provided on the external electrode layer 14 via a conductive adhesive or the like.

The diaphragm 2 has a main surface (upper surface) having a relatively large area, and the laminated piezoelectric element 1 is disposed on the main surface (upper surface) of the diaphragm 2 and bonded by a bonding material 3. Yes.

The diaphragm 2 is, for example, a rectangular thin plate, and has a rectangular shape in plan view in the example shown in the figure. There is no restriction | limiting in particular in the shape of the diaphragm 2, In addition to polygonal plate shapes, such as a rectangular shape like the example shown to a figure, circular plate shape and elliptical plate shape may be sufficient. As the material of the diaphragm 2, metals such as brass, phosphor bronze, and stainless steel, glass, resins such as acrylic and polycarbonate, and resin films such as polyethylene and polyimide can be preferably used. For example, the diaphragm 2 is made of tempered glass having a thickness of 0.4 to 1.0 mm, and the main surface has a rectangular shape with a longitudinal (short direction) of 30 to 80 mm and a lateral (longitudinal direction) of 80 to 150 mm. Can do. Further, a diaphragm 2 made of a resin film such as polyethylene or polyimide having a thickness of 10 to 200 μm and having a main surface of a rectangular shape with a length (short direction) of 8 to 28 mm and a width (long direction) of 28 to 60 mm is provided. It can also be used.

As the bonding material 3, use may be made of a resin adhesive, a viscoelastic material molded into a sheet, or a structure in which a base material layer and a layer made of a viscoelastic material are laminated (double-sided tape). it can. As these materials, acrylic-based, epoxy-based, silicone-based adhesives, and rubber-based, acrylic-based, silicone-based, urethane-based adhesives are used. As the base material layer, acetate foam, acrylic foam, cellophane, polyethylene foam, paper, and nonwoven fabric are used. In particular, since at least a part of the bonding material 3 is formed of a viscoelastic body, strong vibration from the multilayer piezoelectric element 1 is transmitted to the vibration plate 2, while weak vibration reflected from the vibration plate 2 is transmitted to the bonding material. 3 can absorb. The thickness of the bonding material 3 can be set to 0.1 mm to 2 mm, for example. However, the material of the bonding material 3 is not limited, and the bonding material 3 may be formed of a material that is harder than the diaphragm 2 and hardly deformed. In some cases, the bonding material 3 does not include the bonding material 3. It doesn't matter.

Here, the lamination type piezoelectric element 1 is arranged along the main surface (upper surface) of the diaphragm 2 in the lamination direction. Specifically, the multilayer piezoelectric element 1 is configured such that one of a plurality of side surfaces of the multilayer piezoelectric element 1 is the diaphragm 2 so that a direction parallel to the main surface (upper surface) of the diaphragm 2 is a lamination direction. Are joined to the main surface (upper surface).

In FIG. 1, of the four side surfaces of the multilayer body 13 constituting the multilayer piezoelectric element 1, the surface where both end surfaces of the first internal electrode layer 121 and the second internal electrode layer 122 are exposed is vibrated. The main surface (upper surface) of the plate 2 is opposed and joined. Of the four side surfaces of the multilayer body 13 constituting the multilayer piezoelectric element 1, one end surface of either the first internal electrode layer 121 or the second internal electrode layer 122 is led out to provide the external electrode layer 14. The side surfaces are arranged at positions perpendicular to the main surface of the diaphragm 2. Although not shown, a lead member is joined to the end of the external electrode layer 14 and is electrically connected to an external circuit via the lead member.

Then, the laminated piezoelectric element 1 is driven by receiving a voltage to vibrate the diaphragm 2. Specifically, the multilayer piezoelectric element 1 is bonded to the main surface (upper surface) of the diaphragm 2 by the bonding material 3, and the multilayer piezoelectric element 1 and the diaphragm 2 are restrained by the bonding material 3. The multilayer piezoelectric element 1 and the diaphragm 2 are flexibly vibrated when the multilayer piezoelectric element 1 tries to expand and contract in the stacking direction.

With such a configuration, a displacement in the stacking direction of the multilayer piezoelectric element 1 (a direction perpendicular to the electrode surface of the internal electrode layer 12), that is, a so-called d33 mode displacement is used for the vibration of the diaphragm 2. Therefore, the piezoelectric d constant becomes larger than the displacement in the direction along the electrode surface of the internal electrode layer 12, that is, the displacement in the so-called d31 mode, and the displacement amount and the generated force of the multilayer piezoelectric element 1 can be improved. Due to this effect, the bending vibration of the diaphragm 2 can be increased, so that the sound pressure of the sound generator 10 can be improved.

In the example shown in FIG. 1, the entire region of the side surface of the multilayer piezoelectric element 1 that faces the main surface of the diaphragm 2 is bonded by the bonding material 3, but as shown in FIG. 2. Only both end portions in the stacking direction of the multilayer piezoelectric element 1 may be bonded to the diaphragm 2 by the bonding material 3. In other words, the bonding material 3 may be disposed only at both ends of the region between the multilayer piezoelectric element 1 and the diaphragm 2. Here, both end portions (one end portion and the other end portion) mean portions within the range of the distance from the end of the stacked body 13 to one third of the length in the stacking direction.

By making the constrained region of the multilayer piezoelectric element 1 by the bonding material 3 only at both ends, the displacement of the multilayer piezoelectric element 1 can be increased and the flexural vibration of the diaphragm 2 can be increased. When used as the sound pressure of the sound generator 10 can be improved.

Further, as shown in FIG. 3, the laminated piezoelectric element 1 has both end portions joined to the diaphragm 2 by the first joining material 31, and a region other than both end portions is joined to the diaphragm 2 by the second joining material 32. The first bonding material 31 and the second bonding material 32 may have different elastic moduli.

With such a configuration, spurious vibrations are induced, and the resonance of each region of the multilayer piezoelectric element 1 in contact with each of the first bonding material 31 and the second bonding material 32 is divided and can be damped. With this effect, the sound pressure level peak in the vicinity of the resonance frequency in the sound generator 10 is divided and damped, and the peak and dip can be flattened, so that the sound quality of the sound generator 10 can be improved.

Here, it is preferable that the elastic modulus of the first bonding material 31 is larger than the elastic modulus of the second bonding material 32. As the combination, for example, the second bonding material 32 includes a silicone-based adhesive, and the first bonding material 31 includes an acrylic-based or epoxy-based adhesive.

With such a configuration, the peak dip can be flattened while amplifying the displacement of the multilayer piezoelectric element 1 without greatly hindering expansion and contraction of the active portion of the multilayer piezoelectric element 1. Therefore, the sound pressure of the sound generator 10 can be improved and the sound quality can be improved.

Further, in the multilayer piezoelectric element 1, the thickness t in the direction perpendicular to the main surface of the diaphragm 2 has a length L in the stacking direction parallel to the main surface of the diaphragm 2 and a width W in the direction perpendicular to the stacking direction. It should be thin. With such a configuration, flexural vibration is likely to occur, and the entire diaphragm 2 can be vibrated. Therefore, the resonance frequency can be shifted to the low frequency side because the region where the fundamental vibration is generated is wide. Since the sound pressure peak accompanying the fundamental vibration in the sound generator 10 can be shifted to the low frequency side, the sound pressure in the low frequency region can be improved.

Further, in FIG. 1, of the four side surfaces of the multilayer body 13 constituting the multilayer piezoelectric element 1, the surface where both end surfaces of the first internal electrode layer 121 and the second internal electrode layer 122 are exposed. Is bonded to the main surface (upper surface) of the diaphragm 2. As shown in FIG. 4, among the four side surfaces of the multilayer body 13 constituting the multilayer piezoelectric element 1, the first internal electrode Either the end surface of the layer 121 or the second internal electrode layer 122 may be led out and the side surface on which the external electrode layer 14 is provided may be opposed to the main surface of the diaphragm. At this time, for example, a bonding material 3 for bonding the multilayer piezoelectric element 1 and the diaphragm 2 is used as a conductive adhesive, and the conductive adhesive protrudes between the multilayer piezoelectric element 1 and the diaphragm 2. The lead member may be bonded to the conductive adhesive. Alternatively, the diaphragm 2 may be made of metal, and a lead member may be joined thereto.

Next, an example of a method for manufacturing the sound generator 10 of the present embodiment will be described.

First, a ceramic green sheet to be the piezoelectric layer 11 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 layer 12 (the first internal electrode layer 121 and the second internal electrode layer 122) is prepared. Specifically, a conductive paste is prepared by adding and mixing a binder and a plasticizer to a metal powder of a silver-palladium alloy. This conductive paste is applied on the ceramic green sheet in the pattern of the internal electrode layer 12 using a screen printing method. Further, a plurality of ceramic green sheets on which the conductive paste is printed are laminated, subjected to binder removal treatment at a predetermined temperature, fired at a temperature of 900 to 1200 ° C., and then subjected to a predetermined grinding using a surface grinder or the like. By applying a grinding process so as to form a shape, an active portion including the piezoelectric layers 11 and the internal electrode layers 12 that are alternately stacked is manufactured. The inactive part is produced by laminating ceramic green sheets that are not coated with the conductive paste to be the internal electrode layer 12. The laminated body 13 is manufactured by combining the active part and the inactive part.

The laminated body 13 is not limited to the one produced by the above manufacturing method, and any laminated body 13 may be produced as long as the laminated body 13 formed by laminating a plurality of piezoelectric layers 11 and internal electrode layers 12 can be produced. It may be produced by a manufacturing method.

Next, the external electrode layer 14 is provided on the side surface of the laminate 13. For the external electrode layer 14, for example, a paste obtained by mixing glass powder or lead zirconate titanate powder with Ag powder is applied using screen printing, and baked on the laminate 13 at a temperature of 550 to 650 ° C., for example.

If necessary, a conductive adhesive made of an epoxy resin or a polyimide resin containing a metal powder having good conductivity such as Ag powder or Cu powder on the external electrode layer 14, or a solder made of tin, silver, copper or the like. The external electrode plate which consists of metal flat plates, such as copper, iron, stainless steel, phosphor bronze, is joined via. For example, in order to form the external electrode plate with a slit in the width direction or a mesh shape, a punching die or laser processing may be used.

The lead member is used for electrical connection with the outside, and is preferably a copper wire, and is preferably silver-plated for soldering. When covering the portion excluding the joint with the external electrode layer 14, it may be covered with a resin such as polytetrafluoroethylene, polyvinyl chloride, or polyurethane.

Thereafter, a DC electric field of 0.1 to 3 kV / mm is applied to the external electrode layer 14 to polarize the piezoelectric layer 11 constituting the multilayer body 13, thereby completing the multilayer piezoelectric element 1.

Then, the acoustic generator 10 is obtained by bonding and fixing the laminated piezoelectric element 1 to the main surface of the diaphragm 2 using the bonding material 3. Here, for example, when an anaerobic resin adhesive is used as the bonding material 3, an anaerobic adhesive paste is applied and formed at a predetermined position of the diaphragm 2 using a technique such as screen printing. Thereafter, the multilayer piezoelectric element 1 is bonded and fixed to the diaphragm 2 by applying pressure while the multilayer piezoelectric element 1 is in contact with the paste and curing the anaerobic adhesive paste. The anaerobic adhesive paste may be applied and formed on the laminated piezoelectric element 1 side. As the other bonding material 3, for example, an adhesive such as a thermosetting epoxy adhesive can be used.

In addition, when the bonding material 3 is composed of two types of adhesives having different elastic moduli, it is only necessary to apply adhesives having different elastic moduli to respective desired regions. Further, one adhesive is applied to a predetermined position of the multilayer piezoelectric element 1 by screen printing or the like, and the other adhesive is applied to a predetermined position of the diaphragm 2 by screen printing or the like, and then laminated on the diaphragm 2. The type piezoelectric element 1 may be mounted and cured.

Next, an example of an electronic device equipped with the sound generator 10 will be described with reference to FIG. FIG. 5 is a block diagram illustrating a configuration of the electronic device 50. Note that FIG. 5 shows an example in which the electronic device 50 is a mobile terminal, and only the components necessary for the description are shown, and descriptions of general components are omitted.

As shown in FIG. 5, 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. In addition, as the electronic device 50 of this embodiment, not only the sound generator 10 accommodated in the housing 70 but also a part of the housing 70 may be the diaphragm 2 constituting the sound generator 10. Good.

The electronic device 50 includes an electronic circuit 60. Examples of the electronic circuit 60 include a circuit that processes image information displayed on a display and audio information transmitted by a portable 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 element 1 are connected by a connection wiring (not shown).

The electronic circuit 60 shown in the figure includes, for example, a controller 60a, a transmission / reception unit 60b, a key input unit 60c, and a microphone input unit 60d. 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.

In addition, the electronic device 50 includes a display unit 50a, an antenna 50b, and the sound generator 10. Further, the electronic device 50 includes a housing 70 that accommodates these devices. Although FIG. 5 shows a state in which each device including the controller 60a 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 60 a is a control unit of the electronic device 50. The transmission / reception unit 60b transmits / receives data via the antenna 50b based on the control of the controller 60a. The key input unit 60c is an input device of the electronic device 50 and accepts a key input operation by an operator. The key input unit 60c may be a button-like key or a touch panel integrated with the display unit 50a. The microphone input unit 60d is also an input device of the electronic device 50, and receives a voice input operation by an operator. The display unit 50a is a display output device of the electronic device 50, outputs display information based on the control of the controller 60a, and corresponds to a display. In addition, as a display, known displays, such as a liquid crystal display and an organic EL display, can be used suitably, for example.

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

In addition, although the portable terminal which has a communication means which transmits / receives data via an antenna etc. was demonstrated as the electronic device 50, it does not ask | require the classification of the electronic device 50, but has various functions which emit a sound. It may be applied to consumer equipment. 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.

Next, a specific example of the sound generator of this embodiment will be described.

A multilayer piezoelectric element was produced as follows. First, by a doctor blade method using a ceramic slurry in which a calcined powder of a piezoelectric ceramic mainly composed of lead zirconate titanate (PbZrO ₃ -PbTiO ₃ ) having an average particle diameter of 0.4 μm, a binder and a plasticizer are mixed. A ceramic green sheet to be a piezoelectric layer having a thickness of 50 μm was produced.

Next, a binder was added to silver-palladium to produce a conductive paste to be an internal electrode layer.

Next, a conductive paste serving as an internal electrode layer was printed on one side of the ceramic green sheet by a screen printing method, and 200 ceramic green sheets printed with the conductive paste were laminated. Further, a total of 15 ceramic green sheets not printed with the conductive paste serving as the internal electrode layer were laminated on the top and bottom of the 200 ceramic green sheets printed with the conductive paste serving as the internal electrode layer. . Then, it was fired at 980 to 1100 ° C. and ground to a predetermined shape using a surface grinder to obtain a laminate.

Next, a paste containing Ag powder and a glass component was applied to the surface of the laminate by screen printing and baked at about 600 ° C. to form an external electrode layer having a width of 1.5 mm and a thickness of 30 μm.

The obtained multilayer piezoelectric element was a long plate having a length in the stacking direction of 15 mm, a width of 2 mm, and a thickness in the direction perpendicular to the diaphragm of 2 mm. This laminated piezoelectric element was joined with a double-sided tape on a diaphragm made of tempered glass and having a thickness of 0.7 mm, a length of 120 mm, and a width of 50 mm, to produce an acoustic generator as shown in FIG. At this time, the stacking direction of the multilayer piezoelectric element is parallel to the glass surface.

A frequency sweep test from 200 Hz to 10 kHz was performed on the sound pressure characteristics of the sound generator according to the example produced as described above, and the frequency characteristics were measured. The result is shown in FIG.

On the other hand, the following sound generator was produced as a comparative example.

The laminated piezoelectric element is made of the same material as in the example, and has a plate shape with a length of 23 mm along the diaphragm, a width of 3.3 mm, and a thickness perpendicular to the diaphragm of 0.8 mm. Was made. The lamination direction of the multilayer piezoelectric element is a direction perpendicular to the main surface of the diaphragm, and 40 ceramic green sheets on which a conductive paste serving as an internal electrode layer is printed, and a conductive paste disposed on the uppermost layer are provided. A laminated body is made from an unprinted ceramic green sheet, and a surface electrode is baked on the top surface of the uppermost layer, and an external electrode layer that electrically connects the surface electrode and the internal electrode layer is baked on the side surface. To be formed.

The sound generator was manufactured by bonding the multilayer piezoelectric element on the same diaphragm as the example with double-sided tape. At this time, the stacking direction of the multilayer piezoelectric element is perpendicular to the glass surface.

The sound pressure characteristics of this acoustic generator were measured in the same manner as in the above example. The result is shown in FIG.

According to the results shown in FIG. 6, it is apparent that the displacement characteristics of the example A are improved compared to the comparison example B.

From the above, it was confirmed that the displacement can be improved by adopting the structure of this example.

DESCRIPTION OF SYMBOLS 1 Multilayer piezoelectric element 11 Piezoelectric layer 12 Internal electrode layer 13 Laminated body 14 External electrode layer 2 Diaphragm 3 Bonding material 31 First bonding material 32 Second bonding material

Claims

A laminated piezoelectric element having a laminated body in which piezoelectric layers and internal electrode layers are alternately laminated; and a diaphragm having a main surface, wherein the laminated piezoelectric element has a laminating direction on the main surface of the diaphragm. Sound generators placed along.
The acoustic generator according to claim 1, wherein only both end portions in the stacking direction of the stacked piezoelectric element are bonded to the diaphragm by a bonding material.
The laminated piezoelectric element has both ends bonded to the diaphragm by a first bonding material, and a region other than both ends bonded to the diaphragm by a second bonding material. The acoustic generator according to claim 1, wherein the elastic modulus is different between the second bonding material and the second bonding material.
The acoustic generator according to claim 3, wherein the elastic modulus of the first bonding material is larger than the elastic modulus of the second bonding material.
The laminated piezoelectric element has a thickness in a direction perpendicular to the main surface of the diaphragm that is thinner than a length in the lamination direction parallel to the main surface of the diaphragm and a width in a direction perpendicular to the lamination direction. The sound generator according to any one of claims 1 to 4.
A sound generator according to any one of claims 1 to 5, an electronic circuit connected to the sound generator, and a housing that houses the electronic circuit and the sound generator. Electronics.