JP2001036990A - Piezoelectric electro-acoustic transducer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a uni-morph type piezoelectric electro-acoustic transducer for easily connecting electrodes arranged between ceramics layers, and for reducing manufacturing costs. SOLUTION: In this electro-acoustic transducer, plural rectangular piezoelectric ceramics layers 2a and 2b are laminated so that a laminated body can be formed, and main face electrodes 4 and 5 are formed on the surface and back main faces of the laminated body, and an inner electrode 6 is formed between each ceramics layer 2a and 2b, and the ceramics layers 2a and 2b are polarized backward in the thickness direction, and a rectangular metallic plate 3 is attached to the back face of the laminated body. In this case, conductive grooves 7a and 7b whose bottom faces deeply reach the inner electrode 6 and the metallic plate 3 are formed on the surface near the opposite two sides of the laminated body in parallel with the sides, and conductive materials 8a and 8b are embedded in the conductive grooves so that the main face electrodes 4 and 5 are conducted, and the inner electrode 6 is led to the surface side.

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 a structure of a unimorph diaphragm.

[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. In the case of a unimorph type diaphragm, 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 to obtain bending vibration.However, since the piezoelectric ceramic plate has a single-layer structure, its displacement is There is a disadvantage that the volume, that is, the sound pressure is small.

Therefore, a unimorph-type diaphragm in which a laminate composed of a plurality of piezoelectric ceramic layers is attached to a metal plate has been proposed (Japanese Patent Laid-Open No. 61-205100). This vibration plate is obtained by laminating a plurality of ceramic green sheets and a plurality of electrodes and affixing a sintered body obtained by simultaneous firing to a metal plate, and is formed at a position where vibration of the vibration plate is not restricted. The through-holes electrically connect the electrodes. In this case, a large displacement amount, that is, a large sound pressure can be obtained as compared with a diaphragm in which a single ceramic layer is attached to a metal plate.

[0004]

By the way, in order to flexurally vibrate a unimorph type diaphragm having a single-layer structure, an alternating voltage may be applied between the main surface electrode on the front surface and the metal plate on the back surface. Connection of external lead wires is easy. However, in the case of a unimorph type diaphragm having a laminated structure, it is necessary to draw out the internal electrodes formed between the thin ceramic layers to the outside, which complicates the drawing structure. For example, there is a method in which an end electrode which is electrically connected to the internal electrode is formed on the end surface of the laminate, and the end electrode is drawn out through the end electrode. In this method, the end electrode is processed for each diaphragm. Since it is necessary, there is a drawback that the number of steps is increased and the cost is increased.

Therefore, in the case of the above publication, the electrodes provided between the ceramic layers are connected to each other every other layer through through holes formed near the vibration node. However, in order to establish mutual connection between the electrodes via the through-holes, it is necessary to perform alignment so that the through-holes exactly coincide with each other when laminating the ceramic layers. Must be done with precision. Therefore, there is a disadvantage that the manufacturing cost is high.

Therefore, an object of the present invention is to easily connect electrodes provided between ceramic layers,
An object of the present invention is to provide a unimorph type piezoelectric electroacoustic transducer capable of reducing the manufacturing cost.

[0007]

In order to achieve the above object, according to the first aspect of the present invention, a laminate is formed by laminating a plurality of piezoelectric ceramic layers, and the laminate has a main surface on both front and back sides. Plane electrodes are formed, internal electrodes are formed between the ceramic layers, and adjacent layers of all the ceramic layers are polarized in the opposite direction in the thickness direction, and a metal plate is attached to the back surface of the laminate. In the piezoelectric-type electroacoustic transducer described above, the laminate and the metal plate are formed in a rectangular shape, and a surface near two opposing sides of the laminate is parallel to the side, and the bottom is an internal electrode and metal. Conducting grooves of a depth reaching the plate are formed, and by embedding a conductive material in the conducting grooves, the electrodes of each layer conduct one by one, and the internal electrodes are drawn out to the surface of the laminate. Characteristic piezoelectric type To provide a gas-acoustic transducer.

For example, in the case of a diaphragm having a structure in which a rectangular laminate composed of two ceramic layers is adhered to a rectangular metal plate, it is necessary to apply an alternating voltage between the front and rear main surface electrodes and the internal electrodes. There is. Therefore, the conductive groove provided near one side is defined as a depth reaching the internal electrode, and the conductive groove provided near the other side is defined as a depth reaching the metal plate. By embedding a conductive material such as a conductive adhesive or solder in these conductive grooves, the main surface electrode on the front surface and the metal plate (main surface electrode on the back surface) can be connected to each other and the internal electrode can be connected. To the surface of the laminate. Therefore, the electrode can be drawn out from the front side without providing the end face electrode. Since the conductive groove can be easily processed by half-cutting using a dicer or the like, it is not necessary to perform through hole positioning and accurate electrode pattern positioning work as in the related art, thereby reducing manufacturing costs.

When the main surface electrode on the front surface is a full-surface electrode, the main surface electrode on the front surface and the internal electrode are electrically connected via a conductive groove having a depth reaching the internal electrode. Therefore, as in claim 2, a separation groove parallel to the conduction groove and having a depth not reaching the internal electrode is formed inside the conduction groove having a depth reaching the internal electrode. It is desirable to separate the surface electrodes. In this case, by additionally processing the separation groove, the main surface electrode on the surface and the internal electrode can be easily separated.

When the internal electrodes are full-surface electrodes, the main surface electrodes on the front and back and the internal electrodes are electrically connected via the conductive grooves having a depth reaching the metal plate. In such a case, a separation groove parallel to the conduction groove and having a depth reaching the internal electrode is formed inside the conduction groove having a depth reaching the metal plate. It is desirable to split the electrodes. Also in this case, similarly to the second aspect, the front and back main surface electrodes and the internal electrodes can be easily separated by the groove processing.

It is desirable that the laminated body be a sintered body obtained by laminating a plurality of ceramic green sheets via an electrode film and firing them simultaneously. That is,
Although it is possible to obtain a laminate by laminating and bonding a plurality of ceramic plates that have been preliminarily fired and subjected to polarization processing, the thickness of the laminate cannot be reduced, and the sound pressure is low. On the other hand, if the ceramic green sheets are laminated with the electrode film therebetween and are fired at the same time, a very thin laminate can be obtained and a high sound pressure can be obtained.

In the case of a conventional 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 a rectangular diaphragm as in the present invention, 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. According to a fifth aspect of the present invention, the vibration plate is accommodated in the housing, the two sides of the vibration plate provided with the conductive grooves are supported by the housing with the support, and the elastic sealant is provided between the other two sides and the housing. To form an acoustic space on the front and back of the diaphragm. That is, two opposing sides of the rectangular diaphragm are constrained, but the portion between them can be freely displaced by the elastic sealant, so that a lower frequency can be obtained as compared with a circular diaphragm. Conversely, if you want to get the same frequency,
The size can be reduced.

[0013]

1 and 2 show a first embodiment of a piezoelectric electro-acoustic transducer according to the present invention. The piezoelectric electro-acoustic transducer includes a rectangular diaphragm 1, a square case 10 containing the diaphragm 1, and a back cover 11 (housing).
It is composed of A sound emission hole 10 is provided on the upper surface of the case 10.
a is formed, and the back cover 11 is adhered to the lower surface opening. Step-shaped support portions 12a and 12b are formed on inner surfaces of two opposite sides of the case 10, and these support portions 12a and 12b are formed.
The two short sides of the diaphragm 1 are supported on the support 12b by supports 13a and 13b such as an insulating adhesive. 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. Thereby, acoustic spaces 15 and 16 are formed on the front and back of the diaphragm 1. External connection electrodes 17a and 17b are formed on the front and back surfaces of both ends of the back cover 11, and the front and back electrodes 17a and 17b are formed on the inner surfaces of through-hole grooves 18a and 18b formed on both side edges of the back cover 11. Through each other.

After the back cover 11 is bonded to the opening on the lower surface of the case 10, as shown in FIG.
By pouring the conductive adhesives 19a and 19b from b,
The external connection electrodes 17a, 17b and the electrodes of the diaphragm 1 are connected to each other, and the through-hole grooves 18a, 18
b is closed. Thereby, the piezoelectric electroacoustic transducer is completed.

As shown in FIGS. 3 and 4, the diaphragm 1 of this embodiment has two piezoelectric ceramic layers 2 such as PZT.
A metal plate 3 is attached to a laminate composed of a and 2b, and the two ceramic layers 2a and 2b are polarized in opposite directions in the thickness direction as indicated by arrows in FIG. Main surface electrodes 4 and 5 are formed on the entire front and back main surfaces of the diaphragm 1, and the main surface electrode 5 on the back side is electrically connected to the metal plate 3.
An internal electrode 6 is partially formed between the ceramic layers 2a and 2b.
b extends from one side edge to just before the other side edge. 3 and FIG. 4 are exaggerated in thickness for easy understanding of the structure of the diaphragm 1.

At both ends of the diaphragm 1 in the longitudinal direction, conductive grooves 7 a and 7 whose bottoms reach the internal electrodes 6 and the metal plate 3 are provided.
b are formed in parallel with the short sides. In the vicinity of the inside of the conduction groove 7a, a separation groove 7c is formed in a depth not to reach the internal electrode 6 in parallel with the conduction groove 7a, and the terminal electrode 4a is formed by the separation groove 7c.
Separated from By embedding a conductive material 8a, 8b such as a conductive adhesive in the conductive grooves 7a, 7b, the internal electrode 6 and the terminal electrode 4a are connected via the conductive material 8a, and the front main surface electrode 4 And the metal plate 3 (the back-side main surface electrode 5) are connected to each other via the conductive material 8b.

The vibration plate 1 is attached to the case 10 with the metal plate 3 side facing the support portions 12a and 12b of the case 10. In particular, the supports 13a and 13b have a role of insulatingly covering the metal plate 3 corresponding to at least the through-hole grooves 18a and 18b so as not to be exposed. After fixing the diaphragm 1 to the case 10, the terminal electrode 4a of the diaphragm 1 is connected to the external connection electrode 17a by a conductive adhesive 19a as shown in FIG. 2, and the main surface electrode 4 is connected to the conductive adhesive 19b. Is connected to the external connection electrode 17b. By applying a predetermined alternating voltage between the external connection electrodes 17a and 17b, the diaphragm 1 can be flexibly vibrated in the length bending mode. That is, bending vibration can be performed with both ends in the length direction of the diaphragm 1 as fulcrums and the center part in the length direction as the maximum amplitude point.

For example, when a negative voltage is applied to one external connection electrode 17a and a positive voltage is applied to the other external connection electrode 17b, an electric field is generated in a direction indicated by an arrow in FIG. The ceramic layers 2a and 2b 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 layers 2a and 2b are simultaneously extended. Therefore, diaphragm 1 is bent so that the center portion is convex upward. External connection electrode 17
Assuming that the voltage applied to a and 17b is an alternating voltage, the diaphragm 1 periodically generates bending vibration, whereby a sound having a large sound pressure can be generated.

The diaphragm 1 having the above-described structure is, for example, shown in FIG.
It is manufactured by the method shown in FIG. First, as shown in FIG. 5A, a ceramic green sheet 2A in a mother substrate state is prepared, and another ceramic green sheet 2B is prepared.
An electrode film 6A serving as an internal electrode is formed in a predetermined pattern on the surface of the substrate by printing or the like, and the ceramic green sheets 2A and 2B are laminated and pressed. After lamination and crimping,
The sintered body 2 is obtained by firing (see FIG. 5B). next,
After the main surface electrodes 4A and 5A are formed on the entire front and back surfaces of the sintered body 2, a DC voltage is applied between the main surface electrodes 4 and 5 and the internal electrode 6 to perform polarization. In other words, the two ceramic layers 2A and 2B are polarized in opposite directions (see FIG. 5C). Next, the polarized sintered body 2 is bonded to the metal plate 3A using a conductive adhesive or the like (see FIG. 5D). Next, conductive grooves 7a and 7b and a separation groove 7c are continuously formed on the surface of the sintered body 2 to which the metal plate 3A is attached by using a dicer or the like (see FIG. 5E). Next, the conductive groove 7
By embedding the conductive material 8a at a plurality of locations a, the internal electrode 6A and the terminal electrode 4a are electrically connected, and the conductive material 8b is embedded at a plurality of locations in the conduction groove 7b. 5 are connected to each other (see FIG. 5F).
Next, the sintered body 2 and the metal plate 3A are simultaneously cut into individual elements along a cut line CL using a dicer or the like (see FIG. 5G). In this way, the diaphragm 1 is obtained (see FIG. 5H). As described above, the processing of the grooves 7a to 7c and the application of the conductive materials 8a and 8b can be performed at the stage of the mother substrate, so that the diaphragm 1 with good productivity and stable quality can be manufactured. Also, grooves 7a to 7c
Is performed after the sintered body 2 is attached to the metal plate 3A, there is an advantage that cracking of the sintered body 2 can be prevented.

FIG. 6 shows a second embodiment of the diaphragm according to the present invention. The diaphragm 20 of this embodiment uses a full-surface electrode as the internal electrode 6. In this case, the conductive groove 7
Since the internal electrode 6 and the main surface electrodes 4 and 5 are electrically connected by the conductive material 8b embedded in b, a separating groove 7d for dividing the internal electrode 6 is added inside the conductive groove 7b.
In this case, when manufacturing as in FIG. 5, the internal electrode 6 can be used as the whole surface electrode, so that the electrode formation is facilitated and the alignment with the internal electrode is performed at the time of groove processing or cutting. There is no need to make it easy to manufacture.

FIG. 7 shows a third embodiment of the diaphragm according to the present invention. In the diaphragm 30 of this embodiment, the internal electrode 6 is used as a partial electrode, and the main surface electrode 4 on the front side is also used as a partial electrode. Therefore, the main surface electrode 4 on the front side and the terminal electrode 4a are separated in advance, and the dividing groove 7c in FIG. 4 can be omitted.

FIG. 8 shows a fourth embodiment of the diaphragm according to the present invention. The diaphragm 40 of this embodiment is formed by laminating three ceramic layers 2a, 2b, 2c, and two layers of internal electrodes 6a, 6b are provided between these ceramic layers. These internal electrodes 6a, 6b are partial electrodes, and one internal electrode 6a is a ceramic layer 2a, 2b,
2c extends from one side edge to the vicinity of the other side edge, and the other internal electrode 6b extends from the other side edge of the ceramic layers 2a, 2b, 2c to the vicinity of one side edge. At one end in the length direction of the vibration plate 40, the bottom portion penetrates the internal electrode 6a and the metal plate 3
A conduction groove 7e having a depth reaching the internal electrode 6b is formed parallel to the short side at the other end in the longitudinal direction. In the vicinity of the inside of the conduction groove 7e, a separation groove 7g is formed in parallel with the conduction groove 7e and having a depth such that the separation groove 7g does not reach the internal electrode 6a. The electrode 4a is separated. By embedding a conductive material 8a, 8b such as a conductive adhesive in the conductive grooves 7e, 7f, the terminal electrode 4a, the internal electrode 6a, and the metal plate 3 (the back surface main surface electrode 5) are connected to the conductive material 8a. , And the main surface electrode 4 on the front side and the internal electrode 6b are connected to each other via the conductive material 8b.

Also in the case of the vibration plate 40, the ceramic layers 2a, 2b and 2c are polarized in opposite directions as indicated by arrows in FIG. 8, and an alternating voltage is applied between the main surface electrode 4 and the terminal electrode 4a. Is applied, the main surface electrode 4 and the internal electrode 6b have the same potential, the internal electrode 6a and the main surface electrode 5 have the same potential, and the vibration plate 40 can be caused to vibrate flexibly. This makes it possible to generate a sound having a higher sound pressure than a unimorph diaphragm having a single-layer structure.

FIG. 9 shows a fourth embodiment of the diaphragm according to the present invention. The diaphragm 50 of this embodiment is formed by laminating four ceramic layers 2a, 2b, 2c and 2d, and three internal electrodes 6a, 6b,
6c is provided. Each of the internal electrodes 6a, 6b, 6c is a partial electrode, and an intermediate internal electrode 6b extends from one side edge of the ceramic layer 2a, 2b, 2c to the vicinity of the other side edge, and the other internal electrodes 6a, 6c are Ceramic layer 2
a, 2b, 2c extend from the other side edge to the vicinity of one side edge. At one end in the longitudinal direction of the vibration plate 50, a conduction groove 7h whose bottom extends to the metal plate 3 through the internal electrode 6b is formed in parallel with the short side, and at the other end in the longitudinal direction, a bottom is formed. Is a conductive groove 7i having a depth reaching the internal electrode 6c through the internal electrode 6a.
Are formed in parallel with the short sides. In the vicinity of the inside of the conductive groove 7i, the internal electrode 6a is parallel to the conductive groove 7i.
Is formed, and the terminal electrode 4b is separated from the main surface electrode 4 by this groove 7j. By embedding conductive materials 8a and 8b such as a conductive adhesive in the conductive grooves 7h and 7i, the main surface electrodes 4 and 5 are formed.
And the internal electrode 6b are connected via the conductive material 8a,
The terminal electrode 4b and the internal electrodes 6a and 6c are made of a conductive material 8b.
And are connected to each other.

In the case of the diaphragm 50, the ceramic layers 2a, 2b, 2c and 2d are polarized in opposite directions as shown by arrows in FIG. By applying a voltage, the main surface electrodes 4, 5
And the internal electrode 6b have the same potential, and the internal electrodes 6a and 6b have the same potential, so that the diaphragm 40 can be flexibly vibrated. Thereby, a sound with a large sound pressure can be generated.

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 housing structure for accommodating the diaphragm according to the present invention is not limited to FIGS. For example,
In FIG. 1, electrodes 17 a and 17 b for external connection are formed on the back cover 11, but electrodes or terminals for external connection may be fixed to the case 10 side. Further, in order to lead the electrodes of the vibrator 1 to the outside, lead wires may be used instead of the conductive adhesive. In this case, solder may be used as the conductive material embedded in the conductive grooves 7a and 7b, and the lead wires may be connected using the solder. The diaphragms 1, 20, and
Each of 30, 40 and 50 shows the case where the ceramic laminate and the metal plate 3 have the same shape, but the metal plate 3 may be larger than the laminate.

The diaphragms 1, 20, 30, 4 of the above embodiment
The method of manufacturing a ceramic green sheet is performed by laminating a plurality of ceramic green sheets via an electrode film, firing the laminated body at the same time to obtain a sintered body, polarizing the sintered body, and forming a metal plate. However, a polarization process may be performed after attaching to a metal plate. Further, a plurality of piezoelectric ceramics plates and metal plates which have been preliminarily fired and polarized may be laminated and bonded. However, the former manufacturing method of firing after laminating can greatly reduce the thickness of the diaphragm and increase the sound pressure, compared to the latter method of laminating previously fired ones. It is possible to obtain a diaphragm excellent in sound conversion efficiency. The polarization direction of the laminate is not limited to the facing direction as shown in FIG. 3 as long as the layer adjacent to the ceramic layer is in the thickness direction, and may be the reciprocal direction. 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.

[0028]

As is apparent from the above description, claim 1
According to the invention described in the above, conductive grooves having a depth parallel to the sides and having a depth reaching the internal electrode and the metal plate are formed on the surface near the two opposing sides of the multilayer body including the plurality of ceramic layers, respectively. By forming and burying a conductive material in these conductive grooves, the electrodes of each layer are electrically connected one by one, so that the electrodes provided between the ceramic layers can be easily connected to each other. In addition, since the internal electrodes are drawn out to the surface side of the stacked body through the conductive grooves in order to pull out the internal electrodes, groove processing and burying of the conductive material can be performed at the mother substrate stage, and the number of steps can be reduced. Cost can be reduced. Moreover, unlike the method of conducting through the through-hole, a strict alignment work is not required, so that the productivity is improved and a vibrator with stable quality can be manufactured. Furthermore, since the laminate and the metal plate are rectangular, multi-processing including groove processing can be performed, and there is an advantage that the material can be manufactured at low cost with little waste.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a first embodiment of a piezoelectric electro-acoustic transducer according to the present invention as viewed from the back side.

FIG. 2 is a longitudinal sectional view of the assembled state of the piezoelectric electroacoustic transducer of FIG. 1;

FIG. 3 is a perspective view of a diaphragm used in the piezoelectric electroacoustic transducer of FIG.

FIG. 4 is a longitudinal sectional view of the diaphragm shown in FIG. 3;

FIG. 5 is a process chart showing a method for manufacturing the diaphragm of FIG. 3;

FIG. 6 is a longitudinal sectional view of a second embodiment of the diaphragm.

FIG. 7 is a longitudinal sectional view of a third embodiment of the diaphragm.

FIG. 8 is a longitudinal sectional view of a fourth embodiment of the diaphragm.

FIG. 9 is a longitudinal sectional view of a fifth embodiment of the diaphragm.

[Explanation of symbols]

 1, 20, 30, 40, 50 Vibration plate 2a, 2b, 2c, 2d Ceramic layer 3 Metal plate 4,5 Main surface electrode 6 Internal electrode 10 Case 11 Back cover

Claims (5)

[Claims] A laminated body is formed by laminating a plurality of piezoelectric ceramic layers, main surface electrodes are formed on the front and back main surfaces of the laminated body, and internal electrodes are formed between the ceramic layers. In the piezoelectric electroacoustic transducer in which the adjacent layers of the ceramic layers are polarized in the opposite direction in the thickness direction, and the metal plate is attached to the back surface of the laminate, the laminate and the metal plate have a rectangular shape. On the surface near the two opposing sides of the stacked body, conductive grooves are formed in parallel with the sides and have a bottom portion having a depth reaching the internal electrode and the metal plate, and a conductive material is formed in the conductive grooves. The piezoelectric type electro-acoustic transducer is characterized in that the electrodes of each layer are electrically connected to each other by embedding, and the internal electrodes are drawn out to the surface of the laminate. 2. A main surface electrode on the surface of the laminated body is a full-surface electrode, and a separation groove having a depth parallel to the conduction groove and not reaching the internal electrode inside a conduction groove having a depth reaching the internal electrode. 2. The piezoelectric electro-acoustic transducer according to claim 1, wherein a main surface electrode on the surface is divided by the separation groove. 3. The internal electrode of the laminate is a full-surface electrode,
Inside the conduction groove having a depth reaching the metal plate, a separation groove having a depth parallel to the conduction groove and reaching the internal electrode is formed,
3. The piezoelectric electro-acoustic transducer according to claim 1, wherein the internal electrode is divided by the separation groove. 4. The laminate according to claim 1, wherein the laminate comprises a sintered body obtained by laminating a plurality of ceramic green sheets via an electrode film and firing them simultaneously. Piezoelectric acoustic transducer. 5. The vibrating plate is housed in a housing, two sides of the vibrating plate provided with conductive grooves are supported by a housing by a support, and a space between the other two sides and the housing is provided by an elastic sealant. The piezoelectric electroacoustic transducer according to any one of claims 1 to 4, wherein the transducer is sealed, and an acoustic space is formed on both sides of the diaphragm.