JP2002010393A - Piezo-electric electroacoustic transducer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an pieze-electric electroacoustic transducer capable of using a bimolf diaphragm to obtain large sound pressure and attaining a significant improvement against impact. SOLUTION: In the transducer, a laminated unit 1 is formed by laminating double-laminated or triple-laminated piezo-electric ceramics layers 1a, 1b, main surface electrodes 3, 4 are formed on the front and rear main surfaces of the unit 1, an inner electrode 5 is formed between each ceramics layer. At a side surface of the unit 1, a side surface electrode 8 connected mutually to the electrodes 3, 4 a side surface electrode 9 conducted to the electrode 5 are formed. All of the layers 1a, 1b are polarized in the same direction in the thickness direction, an alternating signals is inputted between the electrodes 3, 4 and the electrode 5, so that the unit 1 is processed to make bending vibrations. Almost of whole surfaces of the front and rear surfaces of the unit 1 are covered with resin layers 6, 7, so that the strength is improved against fall down impact.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric electro-acoustic transducer such as a piezoelectric receiver, a piezoelectric sounder, a piezoelectric speaker, and a piezoelectric buzzer, and more particularly to the structure of a diaphragm thereof.

[0002]

2. Description of the Related Art Conventionally, piezoelectric electroacoustic transducers have been widely used for piezoelectric receivers and piezoelectric buzzers. This type of piezoelectric electroacoustic transducer forms a unimorph diaphragm by attaching a circular metal plate to one side of a circular piezoelectric ceramic plate, and supports the periphery of the diaphragm in a circular case. ,
In general, the case has a structure in which the opening of the case is closed with a cover. However, in the case of a unimorph type diaphragm, since a ceramic plate whose outer diameter expands and contracts by applying a voltage is bonded to a metal plate that does not change its dimensions, bending vibration is obtained, so that the displacement amount, that is, the sound pressure is small. is there.

Therefore, a bimorph type diaphragm having a laminated structure composed of a plurality of piezoelectric ceramic layers has been proposed (Japanese Patent Application Laid-Open No. 61-205100). This diaphragm uses a sintered body obtained by laminating a plurality of ceramic green sheets and a plurality of electrodes and firing them at the same time, and has a through hole formed at a position where vibration of the diaphragm is not restricted. And the electrodes are electrically connected. By configuring the first and second vibrating regions arranged in the thickness direction to vibrate in opposite directions to each other, a larger displacement amount, that is, a larger sound pressure can be obtained as compared with the unimorph type.

However, in the case of the above-mentioned bimorph type diaphragm, for example, when a diaphragm composed of three ceramic layers is to be flexibly vibrated, as shown in FIG. And the other internal electrode must be connected to each other through the through-hole, and an alternating voltage must be applied between them. . Therefore, complicated interconnection between the main surface electrode and the internal electrode is required,
The cost could be high.

Accordingly, the applicant of the present application has provided a piezoelectric electroacoustic transducer capable of forming a bimorph-type diaphragm with a simple connection structure by eliminating the interconnection between the main surface electrode and the internal electrode (Japanese Patent Application No. Hei 11-1999). 207198). In this electroacoustic transducer, a laminate is formed by laminating two or three layers of piezoelectric ceramic layers, main surface electrodes are formed on the front and back main surfaces of the laminate, and internal electrodes are provided between the ceramic layers. Formed,
All the ceramic layers are polarized in the same direction in the thickness direction. Then, by applying an alternating signal between the main surface electrode and the internal electrode, the laminate can be flexibly vibrated.

[0006]

Such a bimorph type diaphragm has a feature that a larger sound pressure can be obtained as compared with a unimorph type diaphragm, but has no reinforcement by a metal plate, and thus has a high resistance to noise. The impact strength was low, and sufficient drop strength was not obtained when used for portable terminals and the like.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a piezoelectric electroacoustic transducer which can form a bimorph type diaphragm which can obtain a large sound pressure with a simple connection structure and which can greatly improve the drop strength.

[0008]

In order to achieve the above object, according to the first aspect of the present invention, a laminate is formed by laminating two or three piezoelectric ceramic layers. A main surface electrode is formed on the surface, an internal electrode is formed between the ceramic layers, and all the ceramic layers are polarized in the same direction in the thickness direction, and an alternating signal is provided between the main surface electrode and the internal electrode. A piezoelectric electro-acoustic transducer for bending and vibrating the laminate by applying a pressure, wherein substantially the entire front and back surfaces of the laminate are covered with a resin layer. Provide a container.

In the case of the laminate of the present invention, when an alternating voltage is applied between the main surface electrode and the internal electrode, the direction of the electric field acting on the front and back ceramic layers is reversed in the thickness direction. On the other hand, the polarization direction is such that all the ceramic layers are oriented in the same direction in the thickness direction. Piezoelectric ceramics have the property of contracting in the plane direction when the polarization direction and the electric field direction are the same, and have the property of extending in the plane direction if the polarization direction and the electric field direction are opposite. Therefore,
When the alternating voltage is applied as described above, when the ceramic layer on the front side expands (shrinks), the ceramic layer on the back side shrinks (extends), and the laminated body generates bending vibration as a whole. Since this displacement is larger than that of the unimorph diaphragm, the sound pressure also increases.

[0010] A laminate made of ceramics has a large sound pressure, but is vulnerable to a drop impact. Therefore, in the present invention, the laminate is reinforced by covering substantially the entire front and back surfaces of the laminate with the resin layer, and the drop strength is greatly improved. Since this resin layer does not hinder the bending vibration of the laminate, the sound pressure is hardly impaired, and the resonance frequency is not greatly increased.

The resin layer may be a coating layer obtained by applying a paste-like resin in the form of a film and then hardening the resin, or may be adhered to the laminate as described in claim 3. Resin film may be used. When the resin material constituting the resin layer is a resin material having a low Young's modulus, such as a silicone-based or urethane-based resin, there is almost no reinforcing effect of the laminate, and a sufficient improvement in strength against a drop impact cannot be expected. Epoxy-based, acrylic-based, polyimide-based, polyamide-imide-based resin materials with high Young's modulus,
Impact resistance can be greatly improved.

It is desirable that the laminate be rectangular. In the case of a square laminate, steps such as electrode formation, lamination of ceramic layers, pressure bonding, baking, and formation of a resin layer can be performed at the stage of the mother substrate, thereby improving mass productivity and reducing waste of materials. . Further, when a rectangular diaphragm is formed, there is an advantage that sound conversion efficiency is improved and a low-frequency sound can be generated as compared with a circular diaphragm.

According to a fifth aspect of the present invention, the main surface electrodes on the front and back sides are electrically connected to each other via the first side surface electrodes formed on the side surfaces of the laminate, and the internal electrodes are connected to the side surfaces at positions different from the first side surface electrodes. It is preferable to make conduction with the formed second side surface electrode. In this case, the main surface electrode and the internal electrode are drawn out through the side surface electrode, thereby facilitating the electrical connection with the outside.

It is preferable that the first and second side electrodes are formed so as to extend to the front and back surfaces of the resin layer. For example, when the electroacoustic transducer of the present invention is electrically connected to the outside using a conductive adhesive or the like, the connection is simple and reliable.

According to a seventh aspect of the present invention, the second side surface electrode is formed so as to extend around the front and back surfaces of the laminate, and a cutout portion in which a part of the front and back main surface electrodes is exposed is formed in the resin layer. A notch may be formed to expose a part of the second side surface electrode that goes around the front and back surfaces. In this case, it is not necessary to form an electrode on the surface of the resin layer as in claim 6, and it is only necessary to form an electrode on the laminate, so that not only electrical connection with the outside is facilitated, but also The operation of forming the electrodes is simplified.

[0016]

1 to 4 show a first embodiment of a piezoelectric electro-acoustic transducer according to the present invention. This piezoelectric electro-acoustic transducer includes a rectangular diaphragm (laminated body) 1, a rectangular case 10 containing the diaphragm 1 and a substrate 20, and is configured as a surface mount type.

As shown in FIGS. 5 and 6, the diaphragm 1 of this embodiment is formed by laminating two piezoelectric ceramic layers 1a and 1b made of PZT or the like. Indicates that the main surface electrodes 3 and 4 are formed and the ceramic layer 1
An internal electrode 5 is formed between a and 1b. The two ceramic layers 1a and 1b are polarized in the same direction in the thickness direction as indicated by the thick arrow. In this embodiment, the main surface electrode 3 on the front side and the main surface electrode 4 on the back side extend from one short side of the diaphragm 1 to just before the other short side,
The internal electrode 5 extends symmetrically with the main surface electrodes 3 and 4 from the other short side to immediately before one short side. The front and back surfaces of diaphragm 1 are covered with resin layers 6 and 7. The resin layers 6 and 7
It may be a coating layer obtained by applying a paste-like resin in a film shape and then curing the resin, or may be a resin film adhered thereto. As the resin layers 6 and 7, an epoxy resin,
Young's modulus of 500MPa in cured state of acrylic resin, polyimide resin and polyamideimide resin
Materials of up to 6000 MPa are used.

On one short side surface of the vibration plate 1, a first side electrode 8 is formed which is electrically connected to the main surface electrodes 3, 4. It is formed so as to wrap around. On the other short side surface of the vibration plate 1, a second side surface electrode 9 which is electrically connected to the internal electrode 5 is formed, and the upper and lower portions of the side surface electrode 9 extend to the surfaces of the resin layers 6 and 7. Is formed.

The case 10 is formed of a heat-resistant resin or the like into a box shape having an upper wall and four side walls, a sound emission hole 11 is formed in the upper wall, and a substrate 20 is adhered to the lower opening. ing. Step-shaped support portions 12a and 12b are formed on the inner side surfaces of the two opposing side walls of the case 10. Two short sides of the diaphragm 1 are provided on the support portions 12a and 12b with a support 13a such as an adhesive. , 13b. The gap between the two long sides of the diaphragm 1 and the case 10 is sealed by elastic sealants 14a and 14b such as silicone rubber. In addition, as supporters 13a and 13b,
The same material as the elastic sealants 14a and 14b may be used.

The substrate 20 is made of a heat-resistant resin, glass epoxy, ceramic material, or the like, similarly to the case 10. External connection electrodes 21a and 21b are formed on the front and rear surfaces of both ends, and the electrodes 21a and 21b on the front and back are connected to the substrate 20. Are electrically connected to each other through the inner surfaces of the cutout grooves 22a and 22b formed at the side edges of the both ends. Diaphragm 1 fixed to case 10
The substrate 20 is adhered to the lower opening of the case 10 with the insulating adhesive 24 in a state where the conductive adhesives 23a and 23b are applied in the form of drip on the side electrodes 8 and 9 of The electrode 8 is connected to the external connection electrode 21a by a conductive adhesive 23a, and the side electrode 9 is connected to the external connection electrode 21b by a conductive adhesive 23b.
The insulating adhesive 24 may be applied on the substrate 20 or on the opening of the case 10. Thereafter, the conductive adhesives 23a and 23b and the insulating adhesive 24 are cured to complete the piezoelectric electro-acoustic transducer.

When a predetermined alternating voltage is applied between the external connection electrodes 21a and 21b, the diaphragm 1 bends and vibrates in the length bending mode. That is, the diaphragm 1 vibrates flexibly with the short-side end portions as fulcrums and the central portion in the longitudinal direction as the maximum amplitude point. For example, a negative voltage is applied to the side electrode 8 connected to the external connection electrode 21a, and the external connection electrode 21b
When a positive voltage is applied to the side electrode 9 connected to
An electric field is generated in the direction indicated by the thin arrow in FIG. The ceramic layers 1a and 1b have a property of contracting in the plane direction when the polarization direction and the electric field direction are the same, and have a property of extending in the plane direction if the polarization direction and the electric field direction are opposite. The ceramic layer 1a of this example contracts, and the ceramic layer 1b on the back side expands. Therefore, diaphragm 1 bends so that the central portion is convex downward. If the voltage applied to the external connection electrodes 21a and 21b is an alternating voltage,
The vibration plate 1 periodically generates bending vibration, and can generate a sound with a large sound pressure.

The diaphragm 1 according to the present invention has a ceramic layer 1
Since this is a bimorph diaphragm in which a and 1b are stacked, displacement can be increased as compared with a unimorph diaphragm using a metal plate, and a higher sound pressure can be obtained. Further, since the displacement is not restricted by the metal plate, a low-frequency sound can be generated. In other words, if sound of the same frequency is generated, the size can be reduced. Further, by forming and reinforcing the resin layers 6 and 7 on the front and back surfaces, the drop strength can be improved without damaging the sound pressure and without greatly increasing the resonance frequency.

FIG. 7 shows that the size of the diaphragm 1 is 10 mm × 1.
The sound pressure in the case where each of the resin layers 6 and 7 is coated with an epoxy-based adhesive on the upper and lower surfaces of the diaphragm 1 with a thickness of 20 μm as 0 mm × 0.08 mm is compared with the case where no resin layer is provided. . As is clear from FIG. 7, there is almost no decrease in sound pressure and no change in frequency due to the provision of the resin layers 6 and 7.

Table 1 shows a comparison of the drop strength between the case where the resin layers 6 and 7 are provided on the diaphragm 1 (the present invention) and the case where no resin layer is provided (comparative product) in the same manner as in FIG. It is. In the table, ○ indicates that cracks did not occur, and X indicates that cracks occurred. In the drop test, the diaphragm 1 was housed in a case as shown in FIG. 1, attached to a 100 g jig, and dropped in a horizontal state.

[0025]

[Table 1]

In the above embodiment, the use of the rectangular diaphragm 1 has the following operational effects. First,
The point is that the sound conversion efficiency is improved. In the case of a circular diaphragm, only the central portion has the maximum amplitude point, so that the displacement volume is small and the acoustic conversion efficiency is relatively low. Further, since the periphery of the diaphragm is constrained, the frequency becomes higher, and if a piezoelectric vibrating plate having a lower frequency is to be obtained, the radial dimension becomes larger. On the other hand, in the case of the rectangular diaphragm 1, since the maximum amplitude point exists along the center line in the length direction, the displacement volume is large, and high acoustic conversion efficiency can be obtained. The rectangular diaphragm 1 is fixed at both ends in the longitudinal direction, but the portion between them can be freely displaced by the elastic sealants 14a and 14b, so that a lower frequency can be obtained as compared with a circular diaphragm. it can. Conversely, if the same frequency is obtained, the size can be reduced. Second, productivity is improved.
In the case of a circular vibrating plate, punching punches are punched out of a mother substrate, so that many punching debris are generated. However, in the case of a square diaphragm, a laminated piezoelectric body can be cut out by dicing or the like, so that punching debris is reduced. . Also,
Since the coating of the resin layer and the film can be formed on a large mother substrate, there is an advantage that the mass productivity is improved and the number of steps is reduced.

FIGS. 8 and 9 show a second embodiment of the diaphragm.
The diaphragm 30 has two layers of square ceramic layers 31 and 32 laminated like the diaphragm 1 shown in FIGS. 5 and 6, and has main surface electrodes 33 and 34 formed on the upper and lower surfaces thereof. , 32 are formed with an internal electrode 35. Principal surface electrodes 33, 34 are provided on the upper and lower surfaces of diaphragm 30, respectively.
Are formed. Main surface electrode 3
Reference numerals 3 and 34 denote the first side formed on one side surface of the diaphragm 30.
Are connected to each other through side electrodes 38 of the
Are connected to a second side surface electrode 39 formed on the opposite side surface.

In this embodiment, the side electrodes 38, 39 are formed only on the side surfaces of the ceramic layers 31, 32, and a part of the side electrode 39 extends to the upper and lower surfaces of the ceramic layers 31, 32. At one end of the resin layers 36, 37, a notch 36 exposing a part of the main surface electrodes 33, 34 is exposed.
a, 37a are formed, and cutout portions 36b, 37b are formed on the other end sides of the resin layers 36, 37, and expose part of the side electrodes 39 extending to the upper and lower surfaces of the ceramic layers 31, 32. .

The notches 36a, 37a and 36b,
Since the electrodes 33 and 34 and the side electrodes 39 are exposed on the front and back surfaces of the diaphragm 1 via 37b, when the diaphragm 30 is connected to the outside via a conductive adhesive or the like, the connection operation is easy and I can do it reliably. Further, unlike the diaphragm 1 shown in FIGS. 5 and 6, there is no need to form electrodes on the surfaces of the resin layers 6 and 7, so that there is an advantage that the electrode forming operation is simplified.

FIG. 10 shows a third embodiment of the diaphragm. The diaphragm 40 of this embodiment has three piezoelectric ceramic layers 41.
43, and a main surface electrode 44, a back surface of the ceramics layer 43, and a back surface of the ceramics layer 43.
45 are formed, and internal electrodes 46 and 47 are formed between the ceramic layers 41 to 43. The three ceramic layers 41 to 43 are polarized in the same direction in the thickness direction as indicated by the thick arrows.

On the front and back surfaces of the diaphragm 40, main surface electrodes 44,
Resin layers 48 and 49 covering the surface 45 are formed on the entire surface.
The main surface electrodes 44 and 45 extend from one short side of the diaphragm 40 to just before the other short side, as in FIG. 6, and one end thereof is formed on one short side surface of the diaphragm 40. It is connected to the side electrode 50. Therefore, the front and back main surface electrodes 4
4 and 45 are mutually connected. In addition, the internal electrode 4
Reference numerals 6 and 47 extend symmetrically to the main surface electrodes 44 and 45 from the other short side to immediately before one short side, and one end thereof is provided on a side surface electrode 51 formed on the other short side surface of the diaphragm 40. It is connected to the. Therefore, the internal electrodes 46 and 47 are also connected to each other. The side electrodes 50 and 51 are formed so as to extend around the front and back surfaces of the resin layers 48 and 49.

For example, a negative voltage is applied to the side electrode 50,
When a positive voltage is applied to the side electrode 51, an electric field is generated in the direction shown by the thin arrow in FIG. At this time, the internal electrodes 46 located on both sides of the ceramic layer 42 as the intermediate layer,
Since 47 has the same potential, no electric field is generated. The front side ceramic layer 41 contracts in the plane direction because the polarization direction and the electric field direction are the same direction, and the back side ceramic layer 43 extends in the plane direction because the polarization direction and the electric field direction are opposite. Then, the intermediate layer 42 does not expand and contract. Therefore, the diaphragm 40 is bent so as to be convex downward. When an alternating voltage is applied between the side electrodes 50 and 51, the diaphragm 50
Generates periodic bending vibrations, which can generate a sound with a large sound pressure. In FIG. 10, the side electrodes 50 and 51 are formed so as to extend around the front and back surfaces of the resin layers 48 and 49. However, as shown in FIG. 44, 45 and the side electrode 51 may be exposed.

In the method of manufacturing the diaphragms 1, 30, and 40 of the above embodiment, for example, two or three ceramic green sheets are laminated via an electrode film, and the laminated bodies are simultaneously fired to form a sintered laminated body. After obtaining, the sintered laminate is subjected to a polarization treatment.
After that, a resin layer is formed on the upper and lower surfaces of the polarized laminate,
After the laminate is cut into a predetermined element size, it can be manufactured by forming side electrodes on the side surfaces of the individual elements. Instead of this method, two or three pieces of piezoelectric ceramics plates which have been preliminarily fired and polarized are laminated and bonded, and a resin layer is formed on the upper and lower surfaces of the laminated body. A side electrode may be formed on the side surface of the element. The former manufacturing method of firing after laminating, compared to the latter method of laminating pre-fired ones, can greatly reduce the thickness of the diaphragm and increase the sound pressure, so a diaphragm with excellent acoustic conversion efficiency can be manufactured. It is possible to get. The resin layer also functions as a reinforcing layer that prevents the element from cracking when the mother laminate is cut into the element.

The present invention is not limited to the above embodiment, and various changes can be made without departing from the spirit of the present invention. The shape of the diaphragm (laminated body) according to the present invention is not limited to a square shape as in the embodiment, but may be a circular shape. Even in the case of a circular shape, the sound pressure can be increased as compared with a unimorph diaphragm. FIGS. 1 to 4 show a housing structure for accommodating a diaphragm (laminate).
However, the present invention is not limited to this structure. 1 to 4, the external connection electrodes 21 a and 21 b are formed on the substrate 20.
An electrode for external connection may be formed on the 0 side, or a terminal may be fixed. Therefore, in this case, the substrate and the case are turned upside down. First and second side electrodes 8 of diaphragm 1,
Numeral 9 is not limited to the side surfaces facing each other as shown in FIGS. 5 and 6, and may be formed adjacent to different positions on the same side surface. Note that the piezoelectric electroacoustic transducer of the present invention can be used not only as a sounding body such as a piezoelectric buzzer, a piezoelectric sounder, and a piezoelectric speaker, but also as a sound receiving body such as a piezoelectric receiver.

[0035]

As is apparent from the above description, claim 1
According to the invention described in the above, the main surface electrodes are formed on the front and back surfaces of the laminate composed of two or three piezoelectric ceramic layers, the internal electrodes are formed between the ceramic layers, and all the ceramic layers are When the alternating signal is applied between the main surface electrode and the internal electrode, the ceramic layers on the front side and the back side expand and contract in opposite directions, causing the laminate to generate bending vibration as a whole. Become. Since this displacement is larger than that of the unimorph diaphragm, the sound pressure can also be increased. In addition, since all the ceramic layers are polarized in the same direction in the thickness direction, complicated interconnection between the main surface electrode and the internal electrode as in the related art is unnecessary, and the main surface electrode and the internal electrode are not connected. Only an alternating signal needs to be applied in between, the structure is simple and the manufacturing cost can be reduced. Furthermore, since the front and back surfaces of the laminate are covered with the resin layer, the laminate can be reinforced and the drop strength can be greatly improved. Since the resin layer does not inhibit the bending vibration of the laminate, the sound pressure is hardly impaired, and the resonance frequency is not greatly increased.

[Brief description of the drawings]

FIG. 1 is an external perspective view of a first embodiment of a piezoelectric electro-acoustic transducer according to the present invention.

FIG. 2 is an exploded perspective view of the piezoelectric electro-acoustic transducer shown in FIG.

FIG. 3 is a sectional view taken along line AA of FIG. 1;

FIG. 4 is a sectional view taken along line BB of FIG. 1;

FIG. 5 is a perspective view of a diaphragm used in the piezoelectric electroacoustic transducer of FIG. 1;

FIG. 6 is a sectional view taken along line CC of FIG. 5;

FIG. 7 is a sound pressure comparison diagram of a diaphragm provided with a resin layer and a diaphragm not provided with a resin layer.

FIG. 8 is a perspective view of a second embodiment of the diaphragm according to the present invention.

FIG. 9 is a sectional view taken along line DD of FIG. 8;

FIG. 10 is a perspective view of a third embodiment of the diaphragm according to the present invention.

[Explanation of symbols]

 1, 30, 40 Vibration plate (laminated body) 1a, 1b, 31, 32, 41 to 43 Ceramic layer 3, 4, 33, 34, 44, 45 Main surface electrode 5, 35, 46, 47 Internal electrode 6, 7 , 36,37,48,49 Resin layer 10 Case 20 Substrate

Claims (7)

[Claims] A laminated body is formed by laminating two or three piezoelectric ceramic layers, a main surface electrode is formed on the front and back main surfaces of the laminated body, and an internal electrode is formed between the ceramic layers. All the ceramic layers are polarized in the same direction in the thickness direction. By applying an alternating signal between the main surface electrode and the internal electrode, a piezoelectric electroacoustic transducer that bends and vibrates the laminate is used. A piezoelectric electro-acoustic transducer, wherein substantially the entire front and back surfaces of the laminate are covered with a resin layer. 2. The piezoelectric electroacoustic transducer according to claim 1, wherein the resin layer is a coating layer obtained by applying a paste-like resin in a film shape and then curing the applied resin. 3. The piezoelectric electro-acoustic transducer according to claim 1, wherein the resin layer is a resin film adhered to the laminate. 4. The piezoelectric electro-acoustic transducer according to claim 1, wherein said laminate is formed in a rectangular shape. 5. The front and back main surface electrodes are electrically connected to each other via a first side surface electrode formed on a side surface of the multilayer body, and the internal electrode is formed on a side surface at a position different from that of the first side surface electrode. 5. The piezoelectric electro-acoustic transducer according to claim 1, wherein the piezoelectric electro-acoustic transducer is electrically connected to the second side electrode. 6. The piezoelectric electro-acoustic transducer according to claim 5, wherein the first and second side electrodes are formed so as to extend to the front and back surfaces of the resin layer. 7. The second side surface electrode is formed so as to extend around the front and back surfaces of the laminate, and the resin layer has a cutout portion where a part of the front and back main surface electrodes is exposed, and a cutout portion on the front and back surfaces of the laminate. 6. The piezoelectric electro-acoustic transducer according to claim 5, wherein a cut-out portion that exposes a part of the wrapped second side surface electrode is formed.